Effect of conversion of natural grassland to cropland on nitric oxide emissions from Venezuelan savanna soils. A four-year monitoring study

Conversion of “natural” savanna to agricultural soil is proceeding at a very fast rate. In this work, nitric oxide (NO) emissions were measured immediately after conversion of a “natural” grassland to fertilized agricultural fields (corn, sorghum and cultivated pasture), and also during the second and fourth year after conversion. Large fluxes were observed after plowing grassland soil, and almost no difference was observed between ammonium-fertilized and unfertilized plowed grassland soils. Soil water content and pH related negatively to NO emissions. NO emissions were positively correlated with soil nitrate concentrations and carbon content (corn only) whereas little or no correlation was found with ammonium concentrations. This suggests that in these savanna soils, the NO emitted from soil is mainly denitrification-derived. The disturbed soils emitted on average ∼7 times more NO than the original grassland. During the second and fourth year of cultivation the emissions from corn and sorghum fields (plowed every year) were around 10 times higher than from the control grassland soils. The fertilizer-induced emission (FEI) values for NO emission estimated in this work show that similar agricultural practices could lead to dramatically different FEI values depending on the water content of the soils. These FEI results corroborates that modeling approaches to determine the global agriculture-derived NO emissions should take into consideration the main factors that regulate the NO emission at the scale of functional units with similar climate, soil and management conditions instead of expressing it as a percentage of the fertilizer applied. In our sandy loam savanna soils these factors are inorganic nitrogen content, pH and WFPS.     

Effect of the method of preparation on the surface area and porosity of titanium(IV) phenylphosphonate

By using three synthetic procedures we have prepared layered -titanium phenylphosphonate samples with different degrees of crystallinity and distinct textural parameters. The solids were prepared by reacting phenylphosphonic acid with different titanium compounds used as precursors. The materials obtained have a high thermal stability as shown by TGA measurements.An analysis of nitrogen adsorption-desorption isotherms on the resulting materials allowed determination of the corresponding specific surface area and porous texture. The N₂-isotherms correspond to type IV of the BDDT classification with hysteresis loops of the type H-1. The materials are essentially mesoporous and it was not detected any mensurable microporosity. Crystallinity, BET surface areas and porosity are markedly dependent on the preparation procedure.     

Studies on chemically precipitated Mn(IV) oxides—II

The discharge characteristics of manganese dioxides prepared by chlorate oxidation of Mn(II) salts [Electrochim. Acta28, 309 (1983)] have been evaluated in 9 M KOH solution. The results would seem to indicate that some of the manganese dioxides prepared in this work have a comparatively better discharge performance than the I.C. MnO₂ samples in alkaline electrolyte.     

Rethinking universal accessibility: a broader approach considering the digital gap

The universal accessibility concept is usually formulated in terms that ignore the socioeconomic and sociopolitical contexts. Therefore, it has impact only on a small fraction of the global population of people with disabilities. This issue raises the need for a comprehensive approach that takes into account issues related to literacy, availability of technology, digital literacy, the use of minority languages, etc.     

Cryptanalysis of an EPC Class-1 Generation-2 standard compliant authentication protocol

Recently, Chen and Deng (2009) proposed an interesting new mutual authentication protocol. Their scheme is based on a cyclic redundancy code (CRC) and a pseudo-random number generator in accordance with the EPC Class-1 Generation-2 specification. The authors claimed that the proposed protocol is secure against all classical attacks against RFID systems, and that it has better security and performance than its predecessors. However, in this paper we show that the protocol fails short of its security objectives, and in fact offers the same security level than the EPC standard it tried to correct. An attacker, following our suggested approach, will be able to impersonate readers and tags. Untraceability is also not guaranteed, since it is easy to link a tag to its future broadcast responses with a very high probability. Furthermore, readers are vulnerable to denial of service attacks (DoS), by obtaining an incorrect EPC identifier after a successful authentication of the tag. Moreover, from the implementation point of view, the length of the variables is not compatible with those proposed in the standard, thus further discouraging the wide deployment of the analyzed protocol. Finally, we propose a new EPC-friendly protocol, named Azumi, which may be considered a significant step toward the security of Gen-2 compliant tags.     

Adopting television as a new channel for e-commerce. The influence of interactive technologies on consumer behavior

The aim of this research is twofold. Firstly, it analyzes how the two main features of Internet Protocol Television (IPTV), interactivity and personalization, influence both customers’ perceived performance and involvement with a web-based information service. Secondly, it studies whether personalization and interactivity improve customer purchase intentions of this service through IPTV. We developed a 2×2 between-subjects factorial design and applied MANOVA analyses. Findings verify that interactivity and personalization foster customer involvement with the service, perceived performance of IPTV and purchase intentions. Moreover, interactivity promotes the effect of personalization on perceived performance and customer involvement. This research concludes that customers’ involvement and purchase behavior are not derived exclusively from their relationship with the firm, but also from connections established in the channel with other customers. Customers also appreciate participating in the service provision process, so firms should promote personalization activities during the purchase in order to improve customers’ performance evaluation.     

Generating certified code from formal proofs: a case study in homological algebra

We apply current theorem proving technology to certified code in the domain of abstract algebra. More concretely, based on a formal proof of the Basic Perturbation Lemma (a central result in homological algebra) in the prover Isabelle/HOL, we apply various code generation techniques, which lead to certified implementations of the associated algorithm in ML. In the formal proof, algebraic structures occurring in the Basic Perturbation Lemma are represented in a way, which is not directly amenable to code generation with the available tools. Interestingly, this representation is required in the proof, while for the algorithm simpler data structures are sufficient. Our approach is to establish a link between the non-executable setting of the proof and the executable representation in the algorithm, which is to be generated. This correspondence is established within the logical framework of Isabelle/HOL—that is, it is formally proved correct. The generated code is applied to and illustrated with a number of examples.     

SAR image processing using adaptive stack filter

Stack filters are a special case of non-linear filters. They have a good performance for filtering images with different types of noise while preserving edges and details. A stack filter decomposes an input image into several binary images according to a set of thresholds. Each binary image is filtered by a Boolean function. The Boolean function that characterizes an adaptive stack filter is optimal and is computed from a pair of images consisting of an ideal noiseless image and its noisy version. In this work the behavior of adaptive stack filters on synthetic aperture radar (SAR) data is evaluated. With this aim, the equivalent number of looks for stack filtered data are calculated to assess the speckle noise reduction capability of this filter. Then a classification of simulated and real SAR images is carried out on data filtered with a stack filter trained with selected samples. The results of a maximum likelihood classification of these data are evaluated and compared with the results of classifying images previously filtered using the Lee and the Frost filters.     

Quantitative assessment of mobile web guidelines conformance

Conformance metrics for the mobile web can play a crucial role as far as engineering mobile websites are concerned, especially if they are automatically obtained. In this way, developers can have an idea in numeric terms of how suitable their developments are for mobile devices. However, there are a plethora of devices with their own particular features (screen size, formats support, etc.) that restrict a unified automatic assessment process. This paper proposes a tool-supported method for device-tailored assessment in terms of conformance with Mobile Web Best Practices 1.0, including the definition of five quantitative metrics for automatically measuring mobile web conformance: Navigability, Page layout, Page definition, User input and Overall score. The behaviour of these metrics was analysed for different devices and different web paradigms, both mobile web pages and their equivalent desktop pages. As expected, the results show that mobile web pages on more capable devices score higher. In addition, 20 users took part in an experiment aimed at discovering how conformance-based scores relate to usability dimensions. The results demonstrate that automatic scoring approaches strongly correlate with usability scores obtained by direct observation, such as task completion time and user satisfaction. This correlation is even stronger for the device-tailored assessment than the one that assumes a general profile for all devices. For instance, results show a strong negative correlation between Overall score and task completion time: ρ (9) = −0.81, (p < 0.05) for the generalist approach and ρ (9) = −0.88 for the device-tailored one, entailing that mobile web guidelines and the metrics based on their conformance capture usability aspects. This result challenges the widely accepted belief that conformance to guidelines does not imply more usable web pages, at least for web accessibility conformance.