The biogeochemical influence of nitrate, dissolved oxygen, and dissolved organic carbon on stream nitrate uptake

Streams are potential hotspots for retention and removal of NO3−, and understanding the mechanisms that enhance NO3− reactivity in stream systems is critical for predicting and preventing eutrophication. Both dissolved organic C (DOC) and dissolved O2 (DO) influence NO3− removal processes. Assessing the individual impacts of NO3−, DO, and DOC concentrations on stream NO3− removal is difficult because these factors covary and are coupled through the C and N cycles. We used an experimental approach to quantify the influences of NO3−, DOC, and DO on NO3− transport in headwater streams of the Ipswich and Parker River watersheds (Massachusetts, USA) with contrasting levels of DOC and DO. In a 1st set of experiments, we added NO3− to address how uptake kinetics differed between a low-DO/high-DOC stream (Cedar Swamp Creek) and a high-DO/low-DOC stream (Cart Creek). In a 2nd set of experiments, we manipulated, for the first time at the reach scale, both DO and DOC in a factorial experiment. DO was added to the low-DO stream by injecting O2 and was removed from the high-DO stream by adding sodium sulfite. DOC was added both alone and in combination with the DO manipulations. NO3− concentration was an important control of NO3− uptake velocity in our study streams, consistent with previous findings. The results of the DOC and DO manipulations suggested that DO determines whether a stream has net NO3− uptake or production and that the presence of DOC magnifies the DO response processes. Addition of DOC by itself did not lead to increased NO3− uptake. In addition, we observed organic matter priming effects, wherein the addition of labile organic matter resulted in accelerated metabolism of naturally occurring DOC in the water column. Priming effects have not been reported previously in stream systems. Results from our experiments suggest that NO3− uptake in streams might arise from complex interactions among DOC, DO, and NO3−, and ultimately, from the influence of DO on dominant stream processes

IT Outsourcing in Finnish Business

This paper reviews the characteristics and magnitude of information technology (IT) outsourcing as well as studies its labor productivity effects with a representative sample of Finnish businesses. Depending on the IT task in question, on average from one-third to two-thirds of IT has been outsourced; of the ten categories considered, the development of non-Internet business-to-business applications (e.g., EDI) is the leading activity in this respect. The various dimensions of IT outsourcing are all highly positively correlated. After controlling for industry and regional effects as well as characteristics of firms and their employees, it is found that an externally-supported computer user is about 20% more productive than an otherwise similar worker without a computer, which corresponds to about 5% output elasticity of outsourced IT; the effect of internally-supported computer use is not statistically significantly different for zero, and it is also several times smaller in magnitude. While the issues of causality, timing, self-selection, and unobserved firm heterogeneity are not fully addressed, the findings nevertheless suggest that IT outsourcing may have significant economic consequences

Concentrations of potentially toxic elements and soil environmental quality evaluation of a typical Prosecco vineyard of the Veneto region (NE Italy)

Purpose The aim of this work was to assess the concentrations of potentially toxic elements and to evaluate the soil quality of a typical Prosecco Denomination of Controlled and Guaranteed Origin vineyard of the Veneto region, NE Italy. Materials and methods Soil samples and leaves of Taraxacum officinale and Vitis vinifera were collected during spring–summer 2014. Element determination (Al, Cd, Cr, Cu, Fe, Mg, Mn, Ni, P, Pb, V, and Zn) were performed with ICP-OES after microwave digestion of samples. Soil quality was assessed via the biological soil quality (BSQ-ar) index. Lipid peroxidation test was performed to evaluate the vegetation oxidative stress, based on malondialdehyde (MDA) content via spectrophotometer. Results and discussion High concentrations of Al,Mg, and P were identified in soil, while high contents of Al, Cu, Fe, and Zn were found in V. vinifera leaves. The high concentrations in soil are probably due to agricultural activities, whereas those in leaves are probably due to atmospheric deposition and repeated use of foliar sprays in viticulture. The bioconcentration factor showed an effective transport of Cu, P, and Zn, from soil to leaf. The BSQ-ar values registered were similar to those obtained in preserved soils; hence, the biological class (VI) of these soils is high. The MDA content in T. officinale and V. vinifera leaves was below the reference value for T. officinale (2.9 ± 0.2 μM), suggesting that the metal content did not stress the vegetation in the investigated site. Conclusions The MDA value for V. vinifera (1.1 ± 0.7 μM) could be adopted as another control value for soil quality, which in our case is of Bgood quality.^ Moreover, our results suggest that high concentrations of elements detected in the analyzed samples do not influence negatively the quality of soil, but a better agronomic management could improve soil quality in the studied area

OPTIMAL ACTUATION STRATEGIES FOR SENSOR/ACTUATOR NETWORKS

Sensor networks have been successfully deployed for passively monitoring environments, for example [1], but there has been much less progress towards developing networks that interact with the environment. Wireless sensor and actuator networks (SANETs) represent an important extension, allowing nodes to perform actions (actuation) in response to sensor measurements and shared information. The potentia

Caractérisation Expérimentale d'un Arc Electrique Impulsionnel dans l'Eau

International audienceLes applications des décharges d'arc impulsionnelles dans l'eau sont nombreuses : fracturation de roches, formage électrohydraulique de pièces métalliques ou encore traitement de l'eau [1-3]. Ces applications requièrent, pour beaucoup, des ondes de pression intenses. Dès lors les contraintes et verrous technologiques sont nombreux. Par exemple, les problématiques électriques et mécaniques liées aux vibrations des réacteurs, l'usure et la durée de vie des électrodes sont autant de points limitants pour l'industrialisation des procédés utilisant ce type de décharge [4]. Il semble, dans ce contexte, que la caractérisation de l'arc électrique impulsionnel dans l'eau et des mécanismes associés soit essentielle à l'optimisation de ces dispositifs

Survey and comparative analysis of entropy and relative entropy thresholding techniques

Entropy-based image thresholding has received considerable interest in recent years. Two types of entropy are generally used as thresholding criteria: Shannon's entropy and relative entropy, also known as Kullback-Leibler information distance, where the former measures uncertainty in an information source with an optimal threshold obtained by maximising Shannon's entropy, whereas the latter measures the information discrepancy between two different sources with an optimal threshold obtained by minimising relative entropy. Many thresholding methods have been developed for both criteria and reported in the literature. These two entropy-based thresholding criteria have been investigated and the relationship among entropy and relative entropy thresholding methods has been explored. In particular, a survey and comparative analysis is conducted among several widely used methods that include Pun and Kapur's maximum entropy, Kittler and Illingworth's minimum error thresholding, Pal and Pal's entropy thresholding and Chang et al.'s relative entropy thresholding methods. In order to objectively assess these methods, two measures, uniformity and shape, are used for performance evaluation