EXAFS study of nickel tetracarbonyl and nickel clusters in zeolite Y

Adsorption and thermal decomposition of Ni(CO)4 in the cage system of zeolite Y have been studied with EXAFS, electron microscopy and IR spectroscopy , Ni(CO)4 is adsorbed as an intact molecule in both cation - free zeolite Y and NaY. Symmetry changes of the molecule in NaY are assigned to the formation of Na—OC-IMi bridges. Thermal treatment of the Ni(CO)4/NaY adduct leads to loss of CO concomitant with the formation of a binodal Ni phase. A major part of the forms clusters with diameter between 0.5 and about 1.5 nm, in addition to larger crystallites (5-30 nm), sticking at the outer surface of the zeolite matrix., The Ni-Ni scattering amplitude indicates increasing average particle size with increasing temperature

Information mobility in complex networks

The concept of information mobility in complex networks is introduced on the basis of a stochastic process taking place in the network. The transition matrix for this process represents the probability that the information arising at a given node is transferred to a target one. We use the fractional powers of this transition matrix to investigate the stochastic process at fractional time intervals. The mobility coefficient is then introduced on the basis of the trace of these fractional powers of the stochastic matrix. The fractional time at which a network diffuses 50% of the information contained in its nodes (1/ k50 ) is also introduced. We then show that the scale-free random networks display better spread of information than the non scale-free ones. We study 38 real-world networks and analyze their performance in spreading information from their nodes. We find that some real-world networks perform even better than the scale-free networks with the same average degree and we point out some of the structural parameters that make this possible

Visual 3-D SLAM from UAVs

The aim of the paper is to present, test and discuss the implementation of Visual SLAM techniques to images taken from Unmanned Aerial Vehicles (UAVs) outdoors, in partially structured environments. Every issue of the whole process is discussed in order to obtain more accurate localization and mapping from UAVs flights. Firstly, the issues related to the visual features of objects in the scene, their distance to the UAV, and the related image acquisition system and their calibration are evaluated for improving the whole process. Other important, considered issues are related to the image processing techniques, such as interest point detection, the matching procedure and the scaling factor. The whole system has been tested using the COLIBRI mini UAV in partially structured environments. The results that have been obtained for localization, tested against the GPS information of the flights, show that Visual SLAM delivers reliable localization and mapping that makes it suitable for some outdoors applications when flying UAVs

Distribution and Origin of Amino Acids in Lunar Regolith Samples

The existence of organic compounds on the lunar surface has been a question of interest from the Apollo era to the present. Investigations of amino acids immediately after collection of lunar samples yielded inconclusive identifications, in part due to analytical limitations including insensitivity to certain compounds, an inability to separate enantiomers, and lack of compound-specific isotopic measurements. It was not possible to determine if the detected amino acids were indigenous to the lunar samples or the result of terrestrial contamination. Recently, we presented initial data from the analysis of amino acid abundances in 12 lunar regolith samples and discussed those results in the context of four potential amino acid sources [5]. Here, we expand on our previous work, focusing on amino acid abundances and distributions in seven regolith samples and presenting the first compound-specific carbon isotopic ratios measured for amino acids in a lunar sample

Communicability in complex networks

Many topological and dynamical properties of complex networks are defined by assuming that most of the transport on the network flows along the shortest paths. However, there are different scenarios in which non-shortest paths are used to reach the network destination. Thus the consideration of the shortest paths only does not account for the global communicability of a complex network. Here we propose a new measure of the communicability of a complex network, which is a broad generalization of the concept of the shortest path. According to the new measure, most of real-world networks display the largest communicability between the most connected (popular) nodes of the network (assortative communicability). There are also several networks with the disassortative communicability, where the most "popular" nodes communicate very poorly to each other. Using this information we classify a diverse set of real-world complex systems into a small number of universality classes based on their structure-dynamic correlation. In addition, the new communicability measure is able to distinguish finer structures of networks, such as communities into which a network is divided. A community is unambiguously defined here as a set of nodes displaying larger communicability among them than to the rest of nodes in the network.Comment: 20 pages, 5 figure

Gathering in the City: An Annotated Bibliography and Review of the Literature About Human-Plant Interactions in Urban Ecosystems

The past decade has seen resurgence in interest in gathering wild plants and fungi in cities. In addition to gathering by individuals, dozens of groups have emerged in U.S., Canadian, and European cities to facilitate access to nontimber forest products (NTFPs), particularly fruits and nuts, in public and private spaces. Recent efforts within cities to encourage public orchards and food forests, and to incorporate more fruit and nut trees into street tree planting programs indicate a growing recognition among planners that gathering is an important urban activity. Yet the academic literature has little to say about urban gathering practices or the people who engage in them. This annotated bibliography and literature review is a step toward filling the gap in knowledge about the socioecological roles of NTFPs in urban ecosystems in the United States. Our objectives are to demonstrate that gathering—the collecting of food and raw materials—is a type of human-plant interaction that warrants greater attention in urban green space management, and to provide an overview of the literature on human-plant interactions—including gathering—in urban environments. Our review found that very few studies of urban gathering have been done. Consequently, we included gathering field guides, Web sites, and articles from the popular media in our search. These sources, together with the small number of scientific studies of urban gathering, indicated that people derive numerous benefits from gathering plants and fungi in U.S. cities. Gathering provides useful products, encourages physical activity, offers opportunities to connect with and learn about nature, helps strengthen social ties and cultural identities, and, in some contexts, can serve as a strategic tool for ecological restoration. These benefits parallel those identified in environmental psychology and cultural ecology studies of the effects of gardening and being in nature. The literature on human-plant interactions also emphasizes that humans need to be treated as endogenous factors in dynamic, socially and spatially heterogeneous urban ecosystems. Spatially explicit analyses of human-plant interactions show that the distribution of wealth and power within societies affects the composition, species distribution, and structure of urban ecologies. Our review also indicates that tensions exist between NTFP gatherers and land managers, as well as between gatherers and other citizens over gathering, particularly in public spaces. This tension likely is related to perceptions about the impact these practices have on cherished species and spaces. We conclude that gathering is an important urban activity and deserves a greater role in urban management given its social and potential ecological benefits. Research on urban gathering will require sensitivity to existing power imbalances and the use of theoretical frameworks and methodologies that assume humans are integral and not always negative components of ecosystems