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71.
In this paper we show how to establish a reliable and efficient high level communication system in a randomly deployed network of sensors equipped with directional antennas. This high level communication system enables the programming of the sensor network using high level communication functionalities without the burden of taking care of their physical capacities (low range, unidirectional links, single frequency, presence of collisions, etc.). The high level communication functionalities we offer include point-to-point communication, point-to-area communication, and one-to-all communication. The basic idea to implement this system is to simulate a virtual network that emerges from the ad-hoc network using self-organization, self-discovery and collaborative methods. We also analyse the efficiency, scalability and robustness of the proposed protocols. 相似文献
72.
Marcos Hernández Suárez Jordi Rull Pallarés Domingo Ríos Mesa Elena Rodríguez Rodríguez Carlos Díaz Romero 《Journal of the science of food and agriculture》2008,88(11):1882-1891
BACKGROUND: Tomato producers are looking for alternatives to protect their crops against the tomato yellow leaf curl virus (TYLCV), including replacement of cultivars with other more resistant ones. Major chemical components, sugars, mineral composition, organic acids, lycopene, total phenols and hydroxycinnamic acids were determined in six tomato cultivars, three of them (Boludo, Dorothy and Tyna) resistant, and the other three (Daniela, Dominique and Thomas), non‐resistant against TYLCV. RESULTS: The Daniela cultivar showed the greatest difference with respect to the others, mostly due to the higher content of soluble solids. The major significant differences between the mean values according to the cultivar and resistance against the TYLCV were observed for total soluble solids, pH, ascorbic acid, total phenols and hydroxycinnamic acids. High coefficients of correlation were found between glucose and fructose, and among ferulic, caffeic and p‐coumaric acids. CONCLUSION: Linear discriminant analysis made it possible to differentiate tomato samples according to the cultivar. A clear varietal influence on the chemical composition was observed; however, resistance or non‐resistance against TYLCV does not seem to influence the chemical composition. Copyright © 2008 Society of Chemical Industry 相似文献
73.
Design,Synthesis, and Biological Evaluation of Unconventional Aminopyrimidine,Aminopurine, and Amino‐1,3,5‐triazine Methyloxynucleosides
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Gloria Fernández‐Cureses Sonia de Castro María‐Luisa Jimeno Jan Balzarini Prof. María‐José Camarasa 《ChemMedChem》2015,10(2):321-335
Herein we describe a class of unconventional nucleosides (methyloxynucleosides) that combine unconventional nucleobases such as substituted aminopyrimidines, aminopurines, or aminotriazines with unusual sugars in their structures. The allitollyl or altritollyl derivatives were pursued as ribonucleoside mimics, whereas the tetrahydrofuran analogues were pursued as their dideoxynucleoside analogues. The compounds showed poor, if any, activity against a broad range of RNA and DNA viruses, including human immunodeficiency virus (HIV). This inactivity may be due to lack of an efficient metabolic conversion into their corresponding 5′‐triphosphates and poor affinity for their target enzymes (DNA/RNA polymerases). Several compounds showed cytostatic activity against proliferating human CD4+ T‐lymphocyte CEM cells and against several other tumor cell lines, including murine leukemia L1210 and human prostate PC3, kidney CAKI‐1, and cervical carcinoma HeLa cells. A few compounds were inhibitory to Moloney murine sarcoma virus (MSV) in C3H/3T3 cell cultures, with the 2,6‐diaminotri‐O‐benzyl‐D ‐allitolyl‐ and ‐D ‐altritolyl pyrimidine analogues being the most potent among them. This series of unconventional nucleosides may represent a novel family of potential antiproliferative agents. 相似文献
74.
Originally, Wireless Local Area Networks served only small indoor areas. Nevertheless, the idea of employing IEEE 802.11 networks in large outdoor environments is
a very attractive possibility. IEEE 802.11 technology offers several advantages: the low cost of equipment, its operation
in the unlicensed spectrum and its higher data rates. Since the advent of the first IEEE 802.11 standard, a great deal of
research has been carried out. So-called Wifi-based Long Distance networks are currently being deployed. In this paper, we study the suitability of employing IEEE 802.11 networks in large
outdoor environments without modifying the standard working procedure. In such scenarios, IEEE 802.11 networks should offer
coverage ranges of several kilometer, which leads to high propagation delay values. Thus, we analyze the influence of increasing
propagation delay in the IEEE 802.11 MAC protocol. To carry out our analysis we present a mathematical model and simulation
results. We provide an operating range in which IEEE 802.11 performance is feasible and establish a throughput threshold according
to the propagation delay. 相似文献
75.
Víctor Falguera Jordi PagánSalvador Garza Alfonso GarvínAlbert Ibarz 《Food research international (Ottawa, Ont.)》2011,44(6):1580-1588
The effectiveness of ultraviolet irradiation in inactivating microorganisms has been known for decades. Nevertheless, in the processing of foodstuff other important issues must be considered, such as organoleptic or nutritional properties preservation. Ultraviolet irradiation constitutes an alternative to thermal treatment that is being studied and developed to obtain a better final product sensory quality, but without neglecting microbial safety. Moreover, it has been proved that this technology can be useful to decompose some toxins that are not affected by thermal processing. In this piece of work, the effect of UV irradiation on all of these contaminants and components of liquid food has been reviewed. 相似文献
76.
Factors influencing the soil-air partitioning and the strength of soils as a secondary source of polychlorinated biphenyls to the atmosphere 总被引:2,自引:0,他引:2
Cabrerizo A Dachs J Moeckel C Ojeda MJ Caballero G Barceló D Jones KC 《Environmental science & technology》2011,45(11):4785-4792
Soils are a major reservoir of persistent organic pollutants, and soil-air partitioning and exchange are key processes controlling the atmospheric concentrations and regional fate of pollutants. Here, we report and discuss the concentrations of polychlorinated biphenyls (PCBs) in soils, their measured fugacities in soil, the soil-air partition coefficients (K(SA)) and soil-air fugacity gradients in rural background areas of N-NE Spain and N-NW England. Four sampling campaigns were carried out to assess seasonal and daily variability and differences between sampling sites. K(SA) values were significantly dependent on soil temperature and soil organic matter quantity, and to a minor extent organic matter type. All the PCB congeners in the soil are close to equilibrium with the atmosphere at rural Ebro sites, but soil fugacities tend to be higher than ambient air fugacities in early and late summer, consistent with the influence of temperature on soil-air partitioning. Therefore, during warm periods, soils increment their strength as secondary sources to the atmosphere. The mixture of PCBs found in the atmosphere is clearly strongly influenced by the mixture of PCBs which escape from soil, with significant correlations between them (R(2) ranging between 0.35 and 0.74 and p-level <0.001 for the Ebro sampling sites). Conversely, the close-to-equilibrium to net sink status of rural UK sites, suggest a close coupling of air and soil concentrations, but it is not possible to elucidate the importance of these soils as secondary sources yet, and presumably there are still significant primary sources to the regional/global environment. 相似文献
77.
78.
Devis Tuia Jordi Muñoz-Marí Mikhail Kanevski Gustavo Camps-Valls 《Journal of Signal Processing Systems》2011,65(3):301-310
Traditional kernel classifiers assume independence among the classification outputs. As a consequence, each misclassification
receives the same weight in the loss function. Moreover, the kernel function only takes into account the similarity between
input values and ignores possible relationships between the classes to be predicted. These assumptions are not consistent
for most of real-life problems. In the particular case of remote sensing data, this is not a good assumption either. Segmentation
of images acquired by airborne or satellite sensors is a very active field of research in which one tries to classify a pixel
into a predefined set of classes of interest (e.g. water, grass, trees, etc.). In this situation, the classes share strong
relationships, e.g. a tree is naturally (and spectrally) more similar to grass than to water. In this paper, we propose a
first approach to remote sensing image classification using structured output learning. In our approach, the output space
structure is encoded using a hierarchical tree, and these relations are added to the model in both the kernel and the loss
function. The methodology gives rise to a set of new tools for structured classification, and generalizes the traditional
non-structured classification methods. Comparison to standard SVM is done numerically, statistically and by visual inspection
of the obtained classification maps. Good results are obtained in the challenging case of a multispectral image of very high
spatial resolution acquired with QuickBird over a urban area. 相似文献
79.
Jordi Cabana Laure Monconduit Dominique Larcher M. Rosa Palacín 《Advanced materials (Deerfield Beach, Fla.)》2010,22(35):E170-E192
Despite the imminent commercial introduction of Li‐ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li‐ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two‐to‐five times larger than those attained with currently used materials, such as graphite and LiCoO2, can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report. 相似文献
80.
Víctor Falguera Oriol Miarnau Jordi Pagán Albert Ibarz 《European Food Research and Technology》2011,233(6):1075-1079
In recent years, some beneficial effects on health of melanins that are formed as a result of polyphenol oxidase action have
been discovered. However, it is also known that similar polymers have a detrimental effect on proteases activity. Thus, the
aim of this work was to assay whether melanins from two different substrates act as carboxypeptidase A and carboxypeptidase
B inhibitors. It was found that melanin synthesized from l-tyrosine decreases both the apparent affinity between carboxypeptidases and their substrates and the maximum reaction rate.
Consequently, it is possible to conclude that these melanins inhibit CPA and CPB activity in a mixed way. On the contrary,
no inhibition was found in the case of melanin synthesized from 4-methylcatechol. 相似文献