841 resultados para Shearing layers of change


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The CGIAR Strategy and Results Framework sets out four system level outcomes (SLOs), namely: reducing rural poverty, improving food security, improving nutrition and health and sustainable management of natural resources. In pursuit of these objectives the CGIAR has developed a set of sixteen CGIAR Research Programs (CRPs), each of which is expected to make specific contributions to a range of intermediate development outcomes (IDOs) linked to the SLOs. As part of this work the CRPs are developing impact pathways and theories of change designed to explain how the programs will achieve IDOs. The purpose of the present paper is to explain the approach that the CRP on Aquatic Agricultural Systems (AAS) is taking to using these programmatic tools to help achieve impact.

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Based on a talk given before a meeting of the Society of Fisheries Technologists, India.

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Environmental mechanism of change in cyanobacterial species composition in the northeastern part of Lake Dianchi (also called Macun Bay and Haidong Bay) was studied using canonical correlation analysis (CCA), but also bottom-up control and top-down control were fully discussed. Results from CCA suggest: (1) the abundance and dominance of Microcystis aeruginosa in Macun Bay and Haidong Bay are influenced by total phosphorus (TP), nitrate (NO3--N), nitrite (NO2--N), dissolved oxygen (DO) and water temperature (WT); (2) water temperature has a positive correlation with the abundance of M. aeruginosa and it also has negative correlations with the abundances of Anabaena flos-aquae and Aphanizomenonon flos-aquae; and (3) abundances of both Anabaena flos-aquae and Aphanizomenon flos-aquae have positive correlations with ammonia-N (NH4+-N). Furthermore, cyanobacterial species composition has no significant correlations with light and size-fractioned iron in this study. Grazers, cyanophages and viruses were able to control cyanobacterial blooms and change the composition of cyanobacterial species. Though we studied physical and chemical factors intensely enough, we still are not able to predict the change in the composition of cyanobacterial blooms, because of plankton system in a chaotic behavior.

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We studied the charge transport in organic heterojunction films consisting of copper phthalocyanine (CuPc) and copper hexadecafluorophthalocyanine (F16CuPc). The heterojunction effect between CuPc and F16CuPc induced high-density carriers at both sides of heterojunction. The Hall effect was observed at room temperature, which demonstrated the existence of free carriers and their delocalized transport under heterojunction effect. The Hall mobility of 1.2 cm(2)/V s for holes and 2.4 cm(2)/V s for electrons indicated that the transport capability of the heterojunction films is comparable to single crystals. The transport process was further explained by the multiple trap-and-release model according to the temperature dependence of conduction.

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An unusual polyoxometalate [H2N(C2H4)(2)NH2](4)(H3O)[(PMO2Mo6V4O40)-Mo-V-V-VI-O-IV((VO)-O-IV)(2)].H2O is hydrothermally synthesized and characterized by IR, UV-VIS, elemental analyses, X-ray photoelectron spectrum, ESR, TG and Single crystal X-ray diffraction. The title compound crystallizes in the orthorhombic space group Pbca with a = 15-227(5), b = 19.491(4), c = 18.737(3) Angstrom, V = 5123(2) Angstrom(3), Z = 4, and R-1 (wR(2)) = 0.0726(0.1416). The compound contains an unusual highly reduced pseudo-Keggin type polyoxoanion and exhibits an interesting phosphorus-centered alternate arrangement of layers of molybdenum and vanadium oxides.

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The community structure and vertical distribution of prokaryotes in a deep-sea (ca. 3,191 m) cold sediment sample (ca. 43 cm long) collected at the East Pacific Rise (EPR) similar to 13 degrees N were studied with 16SrDNA-based molecular analyses. Total community DNA was extracted from each of four discrete layers EPRDS-1, -2, -3 and -4 (from top to bottom) and 16S rDNA were amplified by PCR. Cluster analysis of DGGE profiles revealed that the bacterial communities shifted sharply between EPRDS-1 and EPRDS-2 in similarity coefficient at merely 49%. Twenty-three sequences retrieved from DGGE bands fell into 11 groups based on BLAST and bootstrap analysis. The dominant groups in the bacterial communities were Chloroflexi, Gamma proteobacteria, Actinobacterium and unidentified bacteria, with their corresponding percentages varying along discrete layers. Pairwise Fst (F-statistics) values between the archaeal clone libraries indicated that the archaeal communities changed distinctly between EPRDS-2 and EPRDS-3. Sequences from the archaeal libraries were divided to eight groups. Crenarchaea Marine Group I (MGI) was prevalent in EPRDS-1 at 83%, while Uncultured Crenarchaea group II B (UCII B) abounded in EPRDS-4 at 61%. Our results revealed that the vertically stratified distribution of prokaryotic communities might be in response to the geochemical settings and suggested that the sampling area was influenced by hydrothermalism. The copresence of members related to hydrothermalism and cold deep-sea environments in the microbial community indicated that the area might be a transitional region from hydrothermal vents to cold deep-sea sediments.

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In the present study, a method based on transmission-line mode for a porous electrode was used to measure the ionic resistance of the anode catalyst layer under in situ fuel cell operation condition. The influence of Nafion content and catalyst loading in the anode catalyst layer on the methanol electro-oxidation and direct methanol fuel cell (DMFC) performance based on unsupported Pt-Ru black was investigated by using the AC impedance method. The optimal Nafion content was found to be 15 wt% at 75 degrees C. The optimal Pt-Ru loading is related to the operating temperature, for example, about 2.0 mg/cm(2) for 75-90 degrees C, 3.0 mg/cm2 for 50 degrees C. Over these values, the cell performance decreased due to the increases in ohmic and mass transfer resistances. It was found that the peak power density obtained was 217 mW/cm(2) with optimal catalyst and Nafion loading at 75 degrees C using oxygen. (c) 2005 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

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Although Iran borders with many states and has direct access to the Caspian Sea as well as the Indian Ocean, the Persian Gulf region seems to be the most vital area to its security and prosperity. Yet since the 70’s Iran’s relations with the Arab states in the region have been rather strained and complex. The main reason for that had been the success of the Islamic revolution in 1979 which later resulted in a new dimension of Sunni-Shia rivalry. Moreover, post-revolutionary Iranian authorities also intended to maintain the regional hegemony from the Imperial State of Iran period. As a result, successive Iranian governments competed for hegemony in the Persian Gulf with the littoral Arab states which consolidated their regional positions due to close links and intensive cooperation with the West especially with the United States. Despite some political and economic initiatives which were undertaken by President Mahmoud Ahmadinejad, this rivalry was also evident between 2005–2013. The main aim of this article is to find out whether Iranian foreign policy towards the Arab states in the Persian Gulf region has undergone any significant changes since Hassan Rouhani became the President of the Islamic Republic of Iran in August 2013. According to Mohammad Reza Deshiri, the Iranian foreign policy after 1979 can be divided into so-called waves of idealism and realism. During dominance of idealism values and spirituality are more important than pragmatism while during the realistic waves political as well as economic interests prevail over spirituality. Iranian idealism is connected with export of revolutionary ideas, Shia dominance as well as the restoration of unity among all muslims (ummah). On this basis both presidential terms of Mahmoud Ahmadinejad can be classified as ‘waves of idealism’, albeit some of his ideas were very pragmatic. The question is if Hassan Rouhani’s foreign policy represents a continuity or a change. Is the current Iran’s foreign policy towards the Persian Gulf region idealistic or rather realistic? The main assumption is that there will be no Arab-Iranian rapprochement in the Persian Gulf without a prior normalization of political relations between Iran and the West especially the United States.

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http://www.archive.org/details/challengeofchang028207mbp

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Transformation optics (TO) is a powerful tool for the design of electromagnetic and optical devices with novel functionality derived from the unusual properties of the transformation media. In general, the fabrication of TO media is challenging, requiring spatially varying material properties with both anisotropic electric and magnetic responses. Though metamaterials have been proposed as a path for achieving such complex media, the required properties arising from the most general transformations remain elusive, and cannot implemented by state-of-the-art fabrication techniques. Here, we propose faceted approximations of TO media of arbitrary shape in which the volume of the TO device is divided into flat metamaterial layers. These layers can be readily implemented by standard fabrication and stacking techniques. We illustrate our approximation approach for the specific example of a two-dimensional, omnidirectional "invisibility cloak", and quantify its performance using the total scattering cross section as a practical figure of merit. © 2012 American Institute of Physics.

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The size, shape, and connectivity of water bodies (lakes, ponds, and wetlands) can have important effects on ecological communities and ecosystem processes, but how these characteristics are influenced by land use and land cover change over broad spatial scales is not known. Intensive alteration of water bodies during urban development, including construction, burial, drainage, and reshaping, may select for certain morphometric characteristics and influence the types of water bodies present in cities. We used a database of over one million water bodies in 100 cities across the conterminous United States to compare the size distributions, connectivity (as intersection with surface flow lines), and shape (as measured by shoreline development factor) of water bodies in different land cover classes. Water bodies in all urban land covers were dominated by lakes and ponds, while reservoirs and wetlands comprised only a small fraction of the sample. In urban land covers, as compared to surrounding undeveloped land, water body size distributions converged on moderate sizes, shapes toward less tortuous shorelines, and the number and area of water bodies that intersected surface flow lines (i.e., streams and rivers) decreased. Potential mechanisms responsible for changing the characteristics of urban water bodies include: preferential removal, physical reshaping or addition of water bodies, and selection of locations for development. The relative contributions of each mechanism likely change as cities grow. The larger size and reduced surface connectivity of urban water bodies may affect the role of internal dynamics and sensitivity to catchment processes. More broadly, these results illustrate the complex nature of urban watersheds and highlight the need to develop a conceptual framework for urban water bodies.