1,682 research outputs found
Application of multispectral radar and LANDSAT imagery to geologic mapping in death valley
Side-Looking Airborne Radar (SLAR) images, acquired by JPL and Strategic Air Command Systems, and visible and near-infrared LANDSAT imagery were applied to studies of the Quaternary alluvial and evaporite deposits in Death Valley, California. Unprocessed radar imagery revealed considerable variation in microwave backscatter, generally correlated with surface roughness. For Death Valley, LANDSAT imagery is of limited value in discriminating the Quaternary units except for alluvial units distinguishable by presence or absence of desert varnish or evaporite units whose extremely rough surfaces are strongly shadowed. In contrast, radar returns are most strongly dependent on surface roughness, a property more strongly correlated with surficial geology than is surface chemistry
Countryside biogeography of neotropical herbaceous and shrubby plants
As human impacts on the environment intensify, the future of plant and animal biodiversity will depend increasingly on the floras surviving in human-dominated "countryside" habitats. To begin to characterize these floras for the Neotropics, we investigated the richness and composition of herbaceous and shrubby plant communities in six forested and deforested habitats, in three replicated study areas (7.5-km in diameter), of southern Costa Rica. We chose habitat types that are common throughout the tropics, to begin building a general understanding of both the habitats of origin and the diversity of countryside floras. Focal forest habitats were understory, 1- to 2-year-old tree-fall gaps, and riverbanks, all in primary forest. Focal deforested habitats were ungrazed road verges, grazed pasture, and riverbanks in grazed pasture. Non-riverbank habitats were sampled both near and far from. forest edge. In total, we sampled 772 species from 79 families, similar to 40% of the non-tree plant diversity of the region. Only 6% of identified species are known to be exotic. In each study area, understory and pasture plots were consistently species poor, while tree-fall gaps and road verges near forest were consistently the most species-rich habitats. In each study area, we found the same proportion of species restricted to forested habitats (similar to 45%) and deforested habitats (similar to 37%), and the same proportion of "countryside-habitat generalists" ( similar to 18%) occurring in both forested and deforested habitats. However, different forested habitats supported different proportions of country side-habitat generalists in each study area, although understory plots consistently 'supported the fewest generalists. Among forested habitats, riverbanks were the most similar floristically to deforested habitats. Pasture riverbanks and road verges near forest supported plant communities most similar to those in forested habitats. The uniqueness and richness of each habitat suggests that countrysides with diverse land uses can support many native herbaceous and shrubby plant species. As it becomes increasingly difficult to protect large tracts of undisturbed tropical forest, we suggest that conservation goals expand to encompass maintenance of heterogeneity in countryside landscapes
A Policy Makerâs Guide to Designing Payments for Ecosystem Services
Over the past five years, there has been increasing interest around the globe in payment schemes for the provision of ecosystem services, such as water purification, carbon sequestration, flood control, etc. Written for an Asian Development Bank project in China, this report provides a user-friendly guide to designing payments for the provision of ecosystem services. Part I explains the different types of ecosystem services, different ways of assessing their value, and why they are traditionally under-protected by law and policy. This is followed by an analysis of when payments for services are a preferable approach to other policy instruments. Part II explains the design issues underlying payments for services. These include identification of the service as well as potential buyers and sellers, the level of service needed, payment timing, payment type, and risk allocation. Part II contains a detailed analysis of the different types of payment mechanisms, ranging from general subsidy and certification to mitigation and offset payments. Part III explores the challenges to designing a payment scheme. These include the ability to monitor service provision, secure property rights, perverse incentives, supporting institutions, and poverty alleviation
Species and functional diversity of native and human-dominated plant communities
Despite growing attention to how human activities alter plant communities, little is known about the ecosystem consequences of these changes. We explore the relationship between species and functional diversity of herbaceous and shrubby plant communities in forested and deforested habitats in three Neotropical landscapes. We focus on six traits: pollination mechanism, dispersal mechanism, growth form, fruit type, fruit size, and seed size. We ask: (1) What is the relationship between species richness and functional diversity (trait state richness)? (2) Do species/functional diversity relationships differ between forested and deforested habitats? and (3) Are observed species/functional diversity patterns more consistent with ecological filtering or differentiation-based assembly processes? We show that species richness is often a weak surrogate for functional diversity, depending on the trait. Species/functional diversity relationships differ significantly between forested and deforested habitats, but the nature of-differences is trait dependent. Dispersal mechanism and fruit type number increased more rapidly in deforested than forested habitats, but the opposite was true for most other traits. Using a null model, we found evidence of ecological filtering for most traits in both habitats. Results demonstrate that deforested habitats do not necessarily contain lower functional diversity than forest but that the ecological assembly processes influencing community function in deforested communities differ dramatically from forest
Ignition and Combustion Characteristics of Pure Bulk Metals: Normal-Gravity Test Results
An experimental apparatus has been designed for the study of bulk metal ignition under elevated, normal and reduced gravity environments. The present work describes the technical characteristics of the system, the analytical techniques employed, the results obtained from the ignition of a variety of metals subjected to normal gravity conditions and the first results obtained from experiments under elevated gravity. A 1000 W xenon short-arc lamp is used to irradiate the top surface of a cylindrical metal specimen 4 mm in diameter and 4 mm high in a quiescent pure-oxygen environment at 0.1 MPa. Iron, titanium, zirconium, magnesium, zinc, tin, and copper specimens are investigated. All these metals exhibit ignition and combustion behavior varying in strength and speed. Values of ignition temperatures below, above or in the range of the metal melting point are obtained from the temperature records. The emission spectra from the magnesium-oxygen gas-phase reaction reveals the dynamic evolution of the ignition event. Scanning electron microscope and x-ray spectroscopic analysis provide the sequence of oxide formation on the burning of copper samples. Preliminary results on the effect of higher-than-normal gravity levels on the ignition of titanium specimens is presented
The Paradox of Power in CSR: A Case Study on Implementation
Purpose Although current literature assumes positive outcomes for stakeholders resulting from an increase in power associated with CSR, this research suggests that this increase can lead to conflict within organizations, resulting in almost complete inactivity on CSR.
Methods A single in-depth case study, focusing on power as an embedded concept.
Results Empirical evidence is used to demonstrate how some actors use CSR to improve their own positions within an organization. Resource dependence theory is used to highlight why this may be a more significant concern for CSR.
Conclusions Increasing power for CSR has the potential to offer actors associated with it increased personal power, and thus can attract opportunistic actors with little interest in realizing the benefits of CSR for the company and its stakeholders. Thus power can be an impediment to furthering CSR strategy and activities at the individual and organizational level
Challenges in the Quest for Keystones
Identifying keystone species is difficult-but essential to understanding bow loss of species will affect ecosystems
Foundational stigma: placeâbased stigma in the age before advanced marginality.
This paper joins the debate on the formation of territorial stigma by uncovering the existence of a form of âfoundational stigmaâ that preceded place-based stigma of the era of advanced marginality. I show that not only were the traces of stigma present prior to the era of advanced marginality but that these early traces facilitate later forms of stigma by providing the necessary foundations upon which adhesive and detrimental stigma was operationalized. Following a critical discourse analysis approach, this paper examines coverage in the British press of Toxteth, Liverpool between 1900 and 1981 as a paradigmatic case study to show that this primitive stigma existed in three key ways: relating to inter-community strife, to crime, and to substandard housing conditions. These traces of stigma laid the foundations for later forms of stigma based on the presence of the poor, violent, deviant other that would be operationalized by dominant voices during the era of advanced marginality
Specialized dynamical properties of promiscuous residues revealed by simulated conformational ensembles
The ability to interact with different partners is one of the most important features in proteins. Proteins that bind a large number of partners (hubs) have been often associated with intrinsic disorder. However, many examples exist of hubs with an ordered structure, and evidence of a general mechanism promoting promiscuity in ordered proteins is still elusive. An intriguing hypothesis is that promiscuous binding sites have specific dynamical properties, distinct from the rest of the interface and pre-existing in the protein isolated state. Here, we present the first comprehensive study of the intrinsic dynamics of promiscuous residues in a large protein data set. Different computational methods, from coarse-grained elastic models to geometry-based sampling methods and to full-atom Molecular Dynamics simulations, were used to generate conformational ensembles for the isolated proteins. The flexibility and dynamic correlations of interface residues with a different degree of binding promiscuity were calculated and compared considering side chain and backbone motions, the latter both on a local and on a global scale. The study revealed that (a) promiscuous residues tend to be more flexible than nonpromiscuous ones, (b) this additional flexibility has a higher degree of organization, and (c) evolutionary conservation and binding promiscuity have opposite effects on intrinsic dynamics. Findings on simulated ensembles were also validated on ensembles of experimental structures extracted from the Protein Data Bank (PDB). Additionally, the low occurrence of single nucleotide polymorphisms observed for promiscuous residues indicated a tendency to preserve binding diversity at these positions. A case study on two ubiquitin-like proteins exemplifies how binding promiscuity in evolutionary related proteins can be modulated by the fine-tuning of the interface dynamics. The interplay between promiscuity and flexibility highlighted here can inspire new directions in protein-protein interaction prediction and design methods. © 2013 American Chemical Society
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