413 research outputs found

    Interplay between topography, fog and vegetation in the central South Arabian mountains revealed using a novel Landsat fog detection technique

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    In the central South Arabian mountains of Yemen and Oman, monsoon fog interception by the endemic cloud forest is essential for ecosystem functions and services. Yet, we know little about the local factors affecting fog distributions and their cumulative effects on vegetation. To examine these relationships, we developed a novel method of high-resolution fog detection using Landsat data, and validated the results using occurrence records of eight moisture-sensitive plant species. Regression tree analysis was then used to examine the topographic factors influencing fog distributions and the topoclimatic factors influencing satellite-derived vegetation greenness. We find that topography affects fog distributions. Specifically, steep windward slopes obstruct the inland movement of fog, resulting in heterogenous fog densities and hotspots of fog interception. We find that fog distributions explain patterns of vegetation greenness, and overall, that greenness increases with fog density. The layer of fog density describes patterns of vegetation greenness more accurately than topographic variables alone, and thus, we propose that regional vegetation patterns more closely follow a fog gradient, than an altitudinal gradient as previously supposed. The layer of fog density will enable an improved understanding of how species and communities, many of which are endemic, range-restricted, and in decline, respond to local variability in topoclimatic conditions

    A rehabilitation program for lung cancer patients during postthoracotomy chemotherapy

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    Objective: The objective of this pilot study was to describe the effects of a 16-week home-based rehabilitative exercise program on cancer-related fatigue (CRF), other symptoms, functional status, and quality of life (QOL) for patients with non-small cell lung cancer (NSCLC) after thoracotomy starting within days after hospital discharge and continuing through the initiation and completion of chemotherapy. Materials and methods: Five patients with NSCLC completed the Brief Fatigue Inventory (measuring CRF severity) and the MD Anderson Symptom Inventory (measuring symptom severity) before and after thoractomy, and at the end of each week of the 16-week exercise program. Additionally, the Medical Outcomes Study Short Form-36 (measuring physical and mental functional status) and the Quality of Life Index (measuring QOL) were completed before and after thoracotomy, after weeks 3, 6, 12, and 16 (the end of the exercise program). Further, the 6-minute walk test (measuring functional capacity) was administered before thoracotomy, prior to the initiation of chemotherapy and/or radiation therapy, and at the end of the 16-week exercise program, after completion of chemotherapy. Results: Participants had a mean age of 63 years and a mean of five comorbid conditions; the exercise program was initiated within 4 days after hospital discharge. Participants\u27 CRF severity scores were reduced to mild levels, while the mean number of symptoms decreased from 9 postthoracotomy to 6 after the exercise program, with mean levels of severity and interference decreasing to below prethoracotomy levels. Likewise, participants\u27 functional status and QOL after completing the exercise program improved to near or above prethoracotomy levels. Conclusion: The home-based, light-intensity exercise program for NSCLC patients receiving and completing adjuvant chemotherapy postthoracotomy showed promising trends in improving CRF severity, other symptom severity, functional status, and QOL. Further testing via a two-arm randomized controlled trial is being conducted

    A scale-dependent model to represent changing aerodynamic roughness of ablating glacier ice based on repeat topographic surveys

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    Turbulent fluxes make a substantial and growing contribution to the energy balance of ice surfaces globally, but are poorly constrained owing to challenges in estimating the aerodynamic roughness length (z0). Here, we used structure from motion (SfM) photogrammetry and terrestrial laser scanning (TLS) surveys to make plot-scale 2-D and 3-D microtopographic estimations of z0 and upscale these to map z0 across an ablating mountain glacier. At plot scales, we found spatial variability in z0 estimates of over two orders of magnitude with unpredictable z0 trajectories, even when classified into ice surface types. TLS-derived surface roughness exhibited strong relationships with plot-scale SfM z0 estimates. At the glacier scale, a consistent increase in z0 of ∌0.1 mm d−1 was observed. Space-for-time substitution based on time since surface ice was exposed by snow melt confirmed this gradual increase in z0 over 60 d. These measurements permit us to propose a scale-dependent temporal z0 evolution model where unpredictable variability at the plot scale gives way to more predictable changes of z0 at the glacier scale. This model provides a critical step towards deriving spatially and temporally distributed representations of z0 that are currently lacking in the parameterisation of distributed glacier surface energy balance models

    Possible Cosmological Implications of the Quark-Hadron Phase Transition

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    We study the quark-hadron phase transition within an effective model of QCD, and find that in a reasonable range of the main parameters of the model, bodies with quark content between 10−210^{-2} and 10 solar masses can have been formed in the early universe. In addition, we show that a significant amount of entropy is released during the transition. This may imply the existence of a higher baryon number density than what is usually expected at temperatures above the QCD scale. The cosmological QCD transition may then provide a natural way for decreasing the high baryon asymmetry created by an Affleck-Dine like mechanism down to the value required by primordial nucleosynthesis.Comment: 19 pages, LaTeX, 5 Postscript figures included. Submitted to Journal of Physics

    Dynamics of hydration water in deuterated purple membranes explored by neutron scattering

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    The function and dynamics of proteins depend on their direct environment, and much evidence has pointed to a strong coupling between water and protein motions. Recently however, neutron scattering measurements on deuterated and natural-abundance purple membrane (PM), hydrated in H2O and D2O, respectively, revealed that membrane and water motions on the ns–ps time scale are not directly coupled below 260 K (Wood et al. in Proc Natl Acad Sci USA 104:18049–18054, 2007). In the initial study, samples with a high level of hydration were measured. Here, we have measured the dynamics of PM and water separately, at a low-hydration level corresponding to the first layer of hydration water only. As in the case of the higher hydration samples previously studied, the dynamics of PM and water display different temperature dependencies, with a transition in the hydration water at 200 K not triggering a transition in the membrane at the same temperature. Furthermore, neutron diffraction experiments were carried out to monitor the lamellar spacing of a flash-cooled deuterated PM stack hydrated in H2O as a function of temperature. At 200 K, a sudden decrease in lamellar spacing indicated the onset of long-range translational water diffusion in the second hydration layer as has already been observed on flash-cooled natural-abundance PM stacks hydrated in D2O (Weik et al. in J Mol Biol 275:632–634, 2005), excluding thus a notable isotope effect. Our results reinforce the notion that membrane-protein dynamics may be less strongly coupled to hydration water motions than the dynamics of soluble proteins

    Naturalized alien flora of the world: species diversity, taxonomic and phylogenetic patterns, geographic distribution and global hotspots of plant invasion

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    Using the recently built Global Naturalized Alien Flora (GloNAF) database, containing data on the distribution of naturalized alien plants in 483 mainland and 361 island regions of the world, we describe patterns in diversity and geographic distribution of naturalized and invasive plant species, taxonomic, phylogenetic and life-history structure of the global naturalized flora as well as levels of naturalization and their determinants. The mainland regions with the highest numbers of naturalized aliens are some Australian states (with New South Wales being the richest on this continent) and several North American regions (of which California with 1753 naturalized plant species represents the world's richest region in terms of naturalized alien vascular plants). England, Japan, New Zealand and the Hawaiian archipelago harbour most naturalized plants among islands or island groups. These regions also form the main hotspots of the regional levels of naturalization, measured as the percentage of naturalized aliens in the total flora of the region. Such hotspots of relative naturalized species richness appear on both the western and eastern coasts of North America, in north-western Europe, South Africa, south-eastern Australia, New Zealand, and India. High levels of island invasions by naturalized plants are concentrated in the Pacific, but also occur on individual islands across all oceans. The numbers of naturalized species are closely correlated with those of native species, with a stronger correlation and steeper increase for islands than mainland regions, indicating a greater vulnerability of islands to invasion by species that become successfully naturalized. South Africa, India, California, Cuba, Florida, Queensland and Japan have the highest numbers of invasive species. Regions in temperate and tropical zonobiomes harbour in total 9036 and 6774 naturalized species, respectively, followed by 3280 species naturalized in the Mediterranean zonobiome, 3057 in the subtropical zonobiome and 321 in the Arctic. The New World is richer in naturalized alien plants, with 9905 species compared to 7923 recorded in the Old World. While isolation is the key factor driving the level of naturalization on islands, zonobiomes differing in climatic regimes, and socioeconomy represented by per capita GDP, are central for mainland regions. The 11 most widely distributed species each occur in regions covering about one third of the globe or more in terms of the number of regions where they are naturalized and at least 35% of the Earth's land surface in terms of those regions' areas, with the most widely distributed species Sonchus oleraceus occuring in 48% of the regions that cover 42% of the world area. Other widely distributed species are Ricinus communis, Oxalis corniculata, Portulaca oleracea, Eleusine indica, Chenopodium album, Capsella bursa-pastoris, Stellaria media, Bidens pilosa, Datura stramonium and Echinochloa crus-galli. Using the occurrence as invasive rather than only naturalized yields a different ranking, with Lantana camara (120 regions out of 349 for which data on invasive status are known), Calotropis procera (118), Eichhornia crassipes (113), Sonchus oleraceus (108) and Leucaena leucocephala (103) on top. As to the life-history spectra, islands harbour more naturalized woody species (34.4%) than mainland regions (29.5%), and fewer annual herbs (18.7% compared to 22.3%). Ranking families by their absolute numbers of naturalized species reveals that Compositae (1343 species), Poaceae (1267) and Leguminosae (1189) contribute most to the global naturalized alien flora. Some families are disproportionally represented by naturalized aliens on islands (Arecaceae, Araceae, Acanthaceae, Amaryllidaceae, Asparagaceae, Convolvulaceae, Rubiaceae, Malvaceae), and much fewer so on mainland (e.g. Brassicaceae, Caryophyllaceae, Boraginaceae). Relating the numbers of naturalized species in a family to its total global richness shows that some of the large species-rich families are over-represented among naturalized aliens (e.g. Poaceae, Leguminosae, Rosaceae, Amaranthaceae, Pinaceae), some under-represented (e.g. Euphorbiaceae, Rubiaceae), whereas the one richest in naturalized species, Compositae, reaches a value expected from its global species richness. Significant phylogenetic signal indicates that families with an increased potential of their species to naturalize are not distributed randomly on the evolutionary tree. Solanum (112 species), Euphorbia (108) and Carex (106) are the genera richest in terms of naturalized species; over-represented on islands are Cotoneaster, Juncus, Eucalyptus, Salix, Hypericum, Geranium and Persicaria, while those relatively richer in naturalized species on the mainland are Atriplex, Opuntia, Oenothera, Artemisia, Vicia, Galium and Rosa. The data presented in this paper also point to where information is lacking and set priorities for future data collection. The GloNAF database has potential for designing concerted action to fill such data gaps, and provide a basis for allocating resources most efficiently towards better understanding and management of plant invasions worldwide

    The global naturalized Alien Flora (GloNAF) database

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    This dataset provides the Global Naturalized Alien Flora (GloNAF) database, ver-sion 1.2. Glo NAF represents a data compendium on th e occurrence and identit y of naturalizedalien vascular plant taxa across geographic regions (e.g. countries, states, provinces, districts,islands) around the globe. The dataset includes 13,939 taxa and covers 1,029 regions (including381 islands). The dataset is based on 210 data sources. For each ta x on-b y-region combination, wepr ovide information on whether the tax on is consider ed to be naturalized in the specific region(i.e. has established self-sustaining popula tions in the wild). Non-native taxa are marked as“alien”, when it is not clear whether they are naturalized. To facilitate alignment with other plantdatabases, we pro v ide f or each taxon the name as given in the original data source and the stan-dardized taxon and family names used by The Plant List Version 1.1 (http://www.theplantlist.org/). We pro vide an ESRI shapefile including polygons f or each region and informa tion on whetherit is an island or a mainland region, the country and the Taxonomic Databases Working Group(TDWG) regions it is part of (TDWG levels 1–4). We also provide several variables that can beused to filter the data according to quality and completeness of alien taxon lists, which varyamong the combinations of regions and da ta sources. A pre vious version of the GloNAF dataset(version 1.1) has already been used in several studies on, for example, historical spatial flows oftaxa between continents and geographical patterns and determinants of naturalization across dif-ferent taxonomic groups. We intend the updated and expanded GloNAF version presented hereto be a global resource useful for studying plant inv asions and changes in biodiversity from regio-nal to global scales. We release these data into the public domain under a Crea ti ve CommonsZer o license waiver (https://creati v ecommons.org/share-y our -work/public-domain/cc0/). Wheny ou use the da ta in your publication, we request that y ou cite this da ta paper. If GloN AF is amajor part of the data analyzed in your study, you should consider inviting the GloNAF coreteam (see Metadata S1: Originators in the Overall project description) as collaborators. If youplan to use the GloNAF dataset, we encourage y ou to contact the GloNAF core team to checkwhether there have been recent updates of the dataset, and whether similar analyses are already ongoing

    Entrepreneurs’ mental health and well-being:A review and research agenda

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    Interest in entrepreneurs’ mental health and well-being (MWB) is growing in recognition of the role of MWB in entrepreneurs’ decision making, motivation, and action. Yet relevant knowledge is dispersed across disciplines, which makes what we currently understand about entrepreneurs’ MWB unclear. In this systematic review I integrate insights from 144 empirical studies. These studies show that research is focused on three research questions: (1) Do different types of entrepreneurs differ in their MWB? What are the (2) antecedents and (3) consequences of entrepreneurs’ MWB? The review systematizes evidence on known antecedents and consequences of entrepreneurs’ MWB but also reveals overlooked and undertheorized sources and outcomes of entrepreneurs’ MWB. The review provides a mapping and framework that advance research on entrepreneurs’ MWB and help to position entrepreneurs’ MWB more centrally in management and entrepreneurship research. It calls for researchers to go beyond applying models developed for employees to understand entrepreneurs. Instead, the findings point the way to developing a dedicated theory of entrepreneurial work and MWB that is dynamic, socialized, and open to considering context and acknowledges variability and fluidity across entrepreneurs’ life domains, as well as the centrality of work for entrepreneurs’ identity
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