Hydrous Manganese Oxide Doped Gel Probe Sampler for Measuring In Situ Reductive Dissolution Rates. 2. Field Deployment

In situ rates of reductive dissolution in submerged shoreline sediments at Lake Tegel (Berlin, Germany) were measured with a novel hydrous manganese (Mn) oxide-doped gel probe sampler in concert with equilibrium gel probe and sequential extraction measurements. Rates were low in the top 8 cm, then showed a peak from 8 to 14 cm, with a maximum at 12 cm depth. This rate corresponded with a peak in dissolved porewater iron (Fe) at 11 cm depth. Below 14 cm, the reductive dissolution rate reached an intermediate steady value. Lower rates at depth corresponded with increases in operationally defined fractions of carbonate-bound and organic- and sulfide-bound Mn and Fe as detected by sequential extraction. Observed rates of reductive dissolution, which reflect a capacity for Mn reduction rather than actual rates under ambient conditions, appear to correlate with porewater chemistry and sequential extraction fractions as expected in early sediment diagenesis, and are consistent with previous measurements of in situ reductive dissolution rates. Significant downward advection in this bank filtration setting depletes the Mn and Fe oxides in the sediments and enhances the transport of dissolved Fe and Mn into the infiltrating water

Convolutional RNN: an Enhanced Model for Extracting Features from Sequential Data

Traditional convolutional layers extract features from patches of data by applying a non-linearity on an affine function of the input. We propose a model that enhances this feature extraction process for the case of sequential data, by feeding patches of the data into a recurrent neural network and using the outputs or hidden states of the recurrent units to compute the extracted features. By doing so, we exploit the fact that a window containing a few frames of the sequential data is a sequence itself and this additional structure might encapsulate valuable information. In addition, we allow for more steps of computation in the feature extraction process, which is potentially beneficial as an affine function followed by a non-linearity can result in too simple features. Using our convolutional recurrent layers we obtain an improvement in performance in two audio classification tasks, compared to traditional convolutional layers. Tensorflow code for the convolutional recurrent layers is publicly available in https://github.com/cruvadom/Convolutional-RNN

Testing sequential quantum measurements: how can maximal knowledge be extracted?

The extraction of information from a quantum system unavoidably implies a modification of the measured system itself. It has been demonstrated recently that partial measurements can be carried out in order to extract only a portion of the information encoded in a quantum system, at the cost of inducing a limited amount of disturbance. Here we analyze experimentally the dynamics of sequential partial measurements carried out on a quantum system, focusing on the trade-off between the maximal information extractable and the disturbance. In particular we consider two different regimes of measurement, demonstrating that, by exploiting an adaptive strategy, an optimal trade-off between the two quantities can be found, as observed in a single measurement process. Such experimental result, achieved for two sequential measurements, can be extended to N measurement processes.Comment: 5 pages, 3 figure

Manganese and zinc in acidic agricultural soils from Central Spain: Distribution and phytoavailability prediction with chemical extraction tests

The extractability and distribution of manganese (Mn) and zinc (Zn) were evaluated in acidic agricultural soils from Central Spain. Both single (0.1 M hydrochloride [HCl] and 0.05 M ethylenediaminetetraacetate [EDTA]) and sequential extraction procedures (SEP) (modified Tessier procedure and Community Bureau of Reference [BCR] protocol) were applied to 29 representative soils that belong to the Alfisol, Inceptisol, and Entisol orders. Average relative Mn extractabilities with respect to the total content (16.6% for HCl and 31.9% for EDTA) were higher than those of Zn (7.7% for HCl and 6.5% for EDTA). Manganese was mainly released in the oxide-bound phase of both SEP (33.1% for modified Tessier and 48.9% for BCR), whereas Zn was predominantly found in the residual fraction (49.1% for modified Tessier and 31.4% for BCR). Significant correlations were only found between the amounts of extractable Zn and the oxide-bound fraction in both SEP. Few relationships were established between Zn fractions extracted by the BCR procedure and those obtained with the Tessier method. Both metal concentrations in spring barley (Hordeum vulgare L., cv Beka) grown in 11 selected soils and the calculated soil/plant transfer coefficients (soil/plant concentration factor (CF), mean values of 31.2 for Mn and 196 for Zn) were poorly (or not at all) correlated with the different extracted soil fractions (single and sequential). A number of empirical equations have been obtained by regression analyses to predict the Mn and Zn uptake by barley, with soil metal forms and some soil characteristics as components (pH for Mn and organic matter for Zn). Values of R2 in the equations were relatively low (<68%). Single-extraction techniques produced worse results than SEP for the evaluation of Mn phytoavailability. The modified Tessier procedure provided better predictions of Zn uptake by plants than BCR, but not better than those obtained with the HCl extraction method

Heavy metal contamination in some soils of the McMurdo Sound region, Antarctica

Soil samples from eight sites at Marble Point and Pram Point, McMurdo Sound region, contaminated by human activities were examined for heavy metal content, using sequential extraction methods. The redistribution of lead, zinc and copper arising from point sources of these metals was demonstrated. The levels found are not considered to represent serious pollution but do indicate that human activities can change the chemistry of the Antarctic environment in localized areas