Trace levels of metallic corrosion in water determined by emission spectrography

Emission spectrographic method determines trace amounts of inorganic impurities in potable water. The capability of this innovation should arouse considerable interest among plant biologists, chemists working in organic synthesis, and pathologists

A program of research in environmental modeling

A theoretical framework for the interpretation of satellite measurements of stratospheric temperature and trace gases is provided. This problem is quite complicated since the distributions of trace gases are dependent on dynamics and photochemistry. Therefore, the problem was attacked with models employing varying degrees of photochemical and dynamical complexity. The relationship between dynamics and trace gas transport and wave transience, dissipation and critical levels and the net (permanent) transport of trace gases, the role of photochemistry in trace gas transport, photochemistry and dynamics and altering the mean-zonal distribution of stratospheric ozone, and approximations to simplify the interpretation of observations and General Circulation Models are discussed

Management of trace elements and vitamins in organic ruminant livestock nutrition in the context of the whole farm system

There is a wealth of information on the vital role of trace minerals in ruminant health. This information gives some reasonable indications of the levels required by dairy and beef animals to maintain good health though there is much less information available for sheep. There is also a wealth of information available on the role played by trace elements in the major diseases of ruminants, particularly mastitis and the problem of high somatic cell counts. There is also information available on the effects of trace mineral supplementation on fertility and production. This information should be used by organic farmers and their advisors to assess trace mineral status of animals under their care and to design strategies to help ensure that the trace element requirements of the ruminant are met and that good health status can be established and maintained. This should enable them to better resist the every day challenges by pathogenic organisms responsible for many of the current infections such as mastitis. However, currently we only have enough information to be able to do this with any degree of certainty by using dietary supplementation with appropriate trace elements which is a conventional approach and does not sit well with organic philosophy. There are indications from a very small number of studies that there may be a more “sustainable, organic” way to achieve the same objective by increasing the diversity of the pastures used as the major food source for ruminant livestock. However, much more information is needed on the levels of trace elements present in these plants, how the level varies with soil trace element content and health status of the soil and how the level varies with stage of growth through the season. Only when we have this more detailed information can we design pastures that provide for the animal’s requirements. An additional benefit of such pastures is that they may result in a much greater diversity of wildlife. Attention also needs to be paid to the management and nutrition of the livestock in order to reduce both physical and nutritional stress to a minimum

Measurement of Trace I-129 Concentrations in CsI Powder and Organic Liquid Scintillator with Accelerator Mass Spectrometry

Levels of trace radiopurity in active detector materials is a subject of major concern in low-background experiments. Procedures were devised to measure trace concentrations of I-129 in the inorganic salt CsI as well as in organic liquid scintillator with Accelerator Mass Spectrometry (AMS) which leads to improvement in sensitivities by several orders of magnitude over other methods. No evidence of their existence in these materials were observed. Limits of < 6 X 10^{-13} g/g and < 2.6 X 10^{-17} g/g on the contaminations of I-129 in CsI and liquid scintillator, respectively, were derived.These are the first results in a research program whose goals are to develop techniques to measure trace radioactivity in detector materials by AMS.Comment: Proceedings of 10th International Conference on Accelerator Mass Spectrometr

Metals in the shell of Bathymodiolus azoricus from a hydrothermal vent site on the Mid-Atlantic Ridge

Specimens of the mussel Bathymodiolus azoricus were collected from Menez Gwen, a relatively shallow (850 m) hydrothermal vent field on the Mid-Atlantic Ridge. Each bivalve shell (n = 21) was individually cleaned by selective chemical. The residual crystal matrix of each shell was individually analysed for the concentrations of the minor elements magnesium and strontium and the trace elements iron, manganese, copper and zinc. The chemical composition of the crystal matrix is unusual. B. azoricus is identified as a species having one of the most strontium impoverished shells amongst the marine molluscs. For a bimineral species the magnesium concentration is also extraordinary low. Despite originating from a trace metal rich environment; the metal concentrations in the shells were exceptionally low. Mean concentrations of iron, manganese, copper and zinc were 20.6, 3.7, 0.6 and 9.4 microg g(-1) respectively. Minor and trace element concentrations exhibited a marked intra-population variability. Copper concentrations increased and iron and zinc concentrations decreased with increasing shell weight. Due to its insensitivity to the high environmental levels of trace elements and the variability in intra-population concentrations induced by shell weight the crystal matrix of the shell of B. azoricus has little potential for use in environmental trace metal monitoring in areas contiguous to deep-sea hydrothermal vents.info:eu-repo/semantics/publishedVersio

Active Learning for Accurate Estimation of Linear Models

We explore the sequential decision making problem where the goal is to estimate uniformly well a number of linear models, given a shared budget of random contexts independently sampled from a known distribution. The decision maker must query one of the linear models for each incoming context, and receives an observation corrupted by noise levels that are unknown, and depend on the model instance. We present Trace-UCB, an adaptive allocation algorithm that learns the noise levels while balancing contexts accordingly across the different linear functions, and derive guarantees for simple regret in both expectation and high-probability. Finally, we extend the algorithm and its guarantees to high dimensional settings, where the number of linear models times the dimension of the contextual space is higher than the total budget of samples. Simulations with real data suggest that Trace-UCB is remarkably robust, outperforming a number of baselines even when its assumptions are violated.Comment: 37 pages, 8 figures, International Conference on Machine Learning, ICML 201

Design evolution of a low shock release nut

Design improvements and detailed functional analyses are reviewed to trace the development of a pyroactuated release device with segmented thread design from its intermediate design into one that reduces the levels of shock spectra generated during its operation by 50%. Comparisons of shock output and internal load distribution are presented, along with descriptions of mechanical operation for both designs. Results also show the potential areas where design development activity can gain further progress in lowering actuation shock levels

Spatial variations of nitrogen trace gas emissions from tropical mountain forests in Nyungwe, Rwanda

Globally, tropical forest soils represent the second largest source of N2O and NO. However, there is still considerable uncertainty on the spatial variability and soil properties controlling N trace gas emission. Therefore, we carried out an incubation experiment with soils from 31 locations in the Nyungwe tropical mountain forest in southwestern Rwanda. All soils were incubated at three different moisture levels (50, 70 and 90 % water filled pore space (WFPS)) at 17 °C. Nitrous oxide emission varied between 4.5 and 400 μg N m−2 h−1, while NO emission varied from 6.6 to 265 μg N m−2 h−1. Mean N2O emission at different moisture levels was 46.5 ± 11.1 (50 %WFPS), 71.7 ± 11.5 (70 %WFPS) and 98.8 ± 16.4 (90 %WFPS) μg N m−2 h−1, while mean NO emission was 69.3 ± 9.3 (50 %WFPS), 47.1 ± 5.8 (70 %WFPS) and 36.1 ± 4.2 (90 %WFPS) μg N m−2 h−1. The latter suggests that climate (i.e. dry vs. wet season) controls N2O and NO emissions. Positive correlations with soil carbon and nitrogen indicate a biological control over N2O and NO production. But interestingly N2O and NO emissions also showed a positive correlation with free iron and a negative correlation with soil pH (only N2O). The latter suggest that chemo-denitrification might, at least for N2O, be an important production pathway. In conclusion improved understanding and process based modeling of N trace gas emission from tropical forests will benefit from spatially explicit trace gas emission estimates linked to basic soil property data and differentiating between biological and chemical pathways for N trace gas formation

Assessment of trace element pollution and its environmental risk to freshwater sediments influenced by anthropogenic contributions: The case study of Alqueva reservoir (Guadiana Basin)

The Guadiana Basin.(SW Iberian Peninsula) is affected by acid mine drainage (AMD), a consequence of ancient mining activities in the Iberian Pyrite Belt (IPB). Consequently, the sedimerits at the Alqueva reservoir (SE Portugal) in the Guadiana Basin are potentially contaminated by trace elements, which make important: (i) to characterize the status of trace element pollution of the sediments; (ii) to evaluate the mobility and the bioavailability of As, Cd, Cu, Cr, Pb and Zn; and (iii) to assess the environmental risk associated with the total and bioavailable concentrations of trace elements, using the sediment quality guidelines (SQGs) and the risk assessment code (RAC). Metal enrichment factors (EF) and geoaccumulation indexes (I-geo), determined taking into account the regional background levels, revealed that, among the metals analyzed, Cd contributed the highest to pollution levels followed by Pb and As. Despite the trace element contamination of the Alqueva sediments, the sequential extraction showed that Most of them are found in the oxidizable and residual fractions, which indicates that they are sparingly bioavailable, with exception of Cd (acid-labile fraction) and Pb (reducible fraction). Based on the RAC, Cd was the only metal that presented a high risk, while Pb, As and Zn showed a medium risk. Moreover, the SQGs revealed the existence of certain areas of extremely high risk, particularly related to high concentrations of total As and, in less extent, of Pb and Cd, associated with AMD, wastewater discharges and runoff of plant protection products from agricultural fields located near the reservoir. (C) 2015 Elsevier By. All rights reserved.FCT (Fundacao para a Ciencia e Tecnologia) [PTDC/AAC-AMB/103547/2008]; FEDER, through POFC (Eixo I - Programa Operacional Fatores de Competitividade) from QREN [COMPETE Re: FCOMP-01-0124-FEDER-008582]info:eu-repo/semantics/publishedVersio