2,315 research outputs found

    On the number of particles which a curved quantum waveguide can bind

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    We discuss the discrete spectrum of N particles in a curved planar waveguide. If they are neutral fermions, the maximum number of particles which the waveguide can bind is given by a one-particle Birman-Schwinger bound in combination with the Pauli principle. On the other hand, if they are charged, e.g., electrons in a bent quantum wire, the Coulomb repulsion plays a crucial role. We prove a sufficient condition under which the discrete spectrum of such a system is empty.Comment: a LateX file, 12 page

    On the origin of the deflection of light

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    Action at distance in Newtonian physics is replaced by finite propagation speeds in classical post--Newtonian physics. As a result, the differential equations of motion in Newtonian physics are replaced by functional differential equations, where the delay associated with the finite propagation speed is taken into account. Newtonian equations of motion, with post--Newtonian corrections, are often used to approximate the functional differential equations. In ``On the origin of quantum mechanics'', preprint, physics/0505181, May 2005, a simple atomic model based on a functional differential equation which reproduces the quantized Bohr atomic model was presented. The unique assumption was that the electrodynamic interaction has a finite propagation speed. In ``On the origin of the gravitational quantization: The Titius--Bode Law'', preprint, physics/0507072, Jul 2005, a simple gravitational model based on a functional differential equation which gives a gravitational quantification and an explanation of the modified Titius--Bode law is described. In ``On the origin of the anomalous precession of Mercury's perihelion'', preprint, physics/0510086, Oct 2005, an explanation of the anomalous precession of Mercury's perihelion is given in terms of a simple retarded potential, which, at first order, coincides with Gerber's potential of 1898, and which agrees with the author's previous works. In this paper, it is shown how the simple retarded potential presented in physics/0510086 also gives the correct value of the gravitational deflection of fast particles of General Relativity.Comment: 10 pages, 2 figure

    The marine plastic litter issue: a social-economic analysis

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    The issue of marine plastic litter pollution is multifaceted, cross-sectoral, and ongoing in the absence of appropriate management measures. This study analysed the issue of marine plastic litter pollution in the context of the Descriptor 10 of the Marine Strategy Framework Directive and Good Environmental Status of the oceans and seas. The Driver-Pressure-State-Impact-Response (DPSIR) framework was used to assess the causes, e ects, and management measures to changes in the marine environment resulting from marine plastics pollution. We noted that less than 10 peer-reviewed publications have applied the Driver-Pressure-State-Impact-Response (DPSIR) model to the issue of marine plastics pollution. Some basic needs such as food security, movement of goods and services, and shelter are also some of the major drivers of marine plastic pollution. The use of plastics is linked to multiple economic sectors (fisheries, agriculture, transport, packaging, construction) and other human activities. A significant amount of the resulting pressures came from the economic sectors for packaging and construction. State changes occurred at the environmental (contamination and bioaccumulation), ecosystem (ingestion of plastics, ghost fishing) and ecosystem service levels (supply of sea food, salt and cultural benefits), with possible loss of jobs and income being some of the observed impacts on human welfare. Responses as management measures, which are tailored to meet each component of the DPSIR framework, were identified. These included policies, regulations, technological advancement and behavioural change. The research acknowledges the issue of marine plastics pollution as a global environmental problem and recommends a trans-disciplinary approach, involving all types of stakeholders. Future research and analysis applying the DPSIR framework will be useful to provide the information necessary for the e ective, adaptive management of litter pollution by marine plastics.PLASTICSEA- Impact of Microplastics in the Ocean, Sea Salt and Aquaculture FA-06-2017-0046; FCT: UI/MAR/00350/2020:info:eu-repo/semantics/publishedVersio

    Natural Two-Higgs-Doublet Model

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    We show that the Two-Higgs-Doublet Model (2HDM) constrained by the two-loop-order requirement of cancellation of quadratic divergences is consistent with the existing experimental constraints. The model allows to ameliorate the little hierarchy problem by suppressing the quadratic corrections to scalar masses and lifting the mass of the lightest Higgs boson. A strong source of CP violation emerges from the scalar potential. The cutoff originating from the naturality arguments is shifted from 0.6 TeV in the Standard Model to >6 TeV in the 2HDM, depending on the mass of the lightest scalar.Comment: 2 figures, submitted to Fortschritte der Physik, presented at the 10th Hellenic School on Elementary Particle Physics and Gravity, Corfu 201

    Fatty acid profiles of the main lipid classes of green seaweeds from fish pond aquaculture

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    The lipid composition of five species of green seaweeds (Chaetomorpha linum, Rhizoclonium riparium, Ulva intestinalis, Ulva lactuca, and Ulva prolifera) grown in fish pond aquaculture systems was studied. In particular, the overall fatty acid (FA) profile and the FA profile of each main lipid class found in these seaweed species were thoroughly analyzed. It was found that every seaweed had a specific FA profile, whose specificities were rendered more obvious with the study of the FA profile per lipid class. However, between U.lactuca and U.intestinalis, there were only minor differences. Nonetheless, it was possible to identify significant differences between the palmitic acid content in the phospholipid (PL) and glycolipid (GL) classes of each seaweed. A clear distinction between the FA profiles of R.riparium and C.linum, which belong to the Cladophorales order, and those of Ulva genus, Ulvales order, was also determined. Moreover, there were also differences among lipid classes, yielding large contrasts between PLs+GLs and triacylglycerols (TAGs) as well as between monoacylglycerols (MAGs) and free fatty acids (FFAs). This study also found evidence supporting the location of particular FAs in specific TAG positions. FA profiles have the potential to be used as a chemotaxonomic tool in green seaweeds, providing a simple method to check authenticity of seaweed used as food.Fundacao para a Ciencia e a Tecnologiainfo:eu-repo/semantics/publishedVersio

    Social-environmental analysis for the management of coastal lagoons in North Africa

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    This study provides an overview of 11 lagoons in North Africa, from the Atlantic to the Eastern Mediterranean. Lagoons are complex, transitional, coastal zones providing valuable ecosystem services that contribute to the welfare of the human population. The main economic sectors in the lagoons included fishing, shellfish harvesting, and salt and sand extraction, as well as maritime transport. Economic sectors in the areas around the lagoons and in the watershed included agriculture, tourism, recreation, industrial, and urban development. Changes were also identified in land use from reclamation, changes in hydrology, changes in sedimentology from damming, inlet modifications, and coastal engineering. The human activities in and around the lagoons exert multiple pressures on these ecosystems and result in changes in the environment, affecting salinity, dissolved oxygen, and erosion; changes in the ecology, such as loss of biodiversity; and changes in the delivery of valuable ecosystem services. Loss of ecosystem services such as coastal protection and seafood affect human populations that live around the lagoons and depend on them for their livelihood. Adaptive management frameworks for social–ecological systems provide options that support decision makers with sciencebased knowledge to deliver sustainable development for ecosystems. The framework used to support the decision makers for environmental management of these 11 lagoons is Drivers–Activities–Pressures–State Change–Impact (on Welfare)–Responses (as Measures).info:eu-repo/semantics/publishedVersio

    Contribution of remote sensing technologies to a holistic coastal and marine environmental management framework: a review

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    Coastal and marine management require the evaluation of multiple environmental threats and issues. However, there are gaps in the necessary data and poor access or dissemination of existing data in many countries around the world. This research identifies how remote sensing can contribute to filling these gaps so that environmental agencies, such as the United Nations Environmental Programme, European Environmental Agency, and International Union for Conservation of Nature, can better implement environmental directives in a cost-e ective manner. Remote sensing (RS) techniques generally allow for uniform data collection, with common acquisition and reporting methods, across large areas. Furthermore, these datasets are sometimes open-source, mainly when governments finance satellite missions. Some of these data can be used in holistic, coastal and marine environmental management frameworks, such as the DAPSI(W)R(M) framework (Drivers–Activities–Pressures–State changes–Impacts (on Welfare)–Responses (as Measures), an updated version of Drivers–Pressures–State–Impact–Responses. The framework is a useful and holistic problem-structuring framework that can be used to assess the causes, consequences, and responses to change in the marine environment. Six broad classifications of remote data collection technologies are reviewed for their potential contribution to integrated marine management, including Satellite-based Remote Sensing, Aerial Remote Sensing, Unmanned Aerial Vehicles, Unmanned Surface Vehicles, Unmanned Underwater Vehicles, and Static Sensors. A significant outcome of this study is practical inputs into each component of the DAPSI(W)R(M) framework. The RS applications are not expected to be all-inclusive; rather, they provide insight into the current use of the framework as a foundation for developing further holistic resource technologies for management strategies in the future. A significant outcome of this research will deliver practical insights for integrated coastal and marine management and demonstrate the usefulness of RS to support the implementation of environmental goals, descriptors, targets, and policies, such as theWater Framework Directive, Marine Strategy Framework Directive, Ocean Health Index, and United Nations Sustainable Development Goals. Additionally, the opportunities and challenges of these technologies are discussed.Murray Foundation: 25.26022020info:eu-repo/semantics/publishedVersio

    Loss of survivin in intestinal epithelial progenitor cells leads to mitotic catastrophe and breakdown of gut immune homeostasis

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    A tightly regulated balance of proliferation and cell death of intestinal epithelial cells (IECs) is essential for maintenance of gut homeostasis. Survivin is highly expressed during embryogenesis and in several cancer types, but little is known about its role in adult gut tissue. Here, we show that Survivin is specifically expressed in transit-amplifying cells and Lgr5(+) stem cells. Genetic loss of Survivin in IECs resulted in destruction of intestinal integrity, mucosal inflammation, and death of the animals. Survivin deletion was associated with decreased epithelial proliferation due to defective chromosomal segregation. Moreover, Survivin-deficient animals showed induced phosphorylation of p53 and H2AX and increased levels of cell-intrinsic apoptosis in IECs. Consequently, induced deletion of Survivin in Lgr5(+) stem cells led to cell death. In summary, Survivin is a key regulator of gut tissue integrity by regulating epithelial homeostasis in the stem cell niche

    Introduction: anthropology's queer sensibilities

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    This special issue addresses vital epistemological, methodological, ethical and political issues at the intersections of queer theory and anthropology as they speak to the study of sexual and gender diversity in the contemporary world. The special issue centres on explorations of anthropology’s queer sensibilities, that is, experimental thinking in ethnographically informed investigations of gender and sexual difference, and related connections, disjunctures and tensions in their situated and abstract dimensions. The articles consider the possibilities and challenges of anthropology’s queer sensibilities that anthropologise queer theory whilst queering anthropology in ethnographically informed analyses. Contributors focus on anthropologising queer theory in research on same-sex desire in the Congo; LGBT migrant and asylum experience in the UK and France; same-sex intimacies within opposite gender oriented sexualities in Kenya and Ghana; secret and ambiguous intimacies and sensibilities beyond an identifiable ‘queer subject’ of rights and recognition in India; migrant imaginings of home in Indonesian lesbian relationships in Hong Kong; and cross-generational perspectives on ‘coming out’ in Taiwan and their implications for theories of kinship and relatedness. An extensive interview with Esther Newton, the prominent figure in gay and lesbian and queer anthropology concludes the collection

    Growth performance, feed utilisation and body composition of advanced nursing Nile tilapia (Oreochromis niloticus) fed diets containing Black Soldier Fly (Hermetia illucens) larvae meal

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    A 32-day experiment was conducted to evaluate the effects on the performance, feed utilisation efficiency and body composition of a strategic inclusion of Black Soldier Fly larvae meal (MM) in a commercially formulated diet for advance nursing Nile tilapia (Oreochromis niloticus). Four isonitrogenous and isoenergetic diets were commercially formulated and manufactured as a control and 3 test diets with strategic inclusions of MM inclusions (0, 30, 50 and 80 g kg-1) and poultry byproduct meal substituting gradually three conventional expensive feedstuffs: fish meal, fish oil and soybean meal. Fish (5.7±0.5 g fish-1) were nursed in a cage-in-lake system (Volta Lake, Ghana), under conditions similar to commercial farming practices. Control and experimental diets were fed to triplicate cages by hand to visual satiety, 6 times day-1. Growth performance (final weight; weight gain and SGR); feed utilisation efficiency indices (FCR and PER) and feed intake were not significantly different (P≥0.05) between treatments. Survival was significantly different (P<0.05) but more likely explained by the stress related to frequent handling on the smaller fish. Fish whole body composition (dry matter, crude protein, lipid, ash and fibre) was unaffected by the treatment (P≥0.05), except for the fatty acid compositions which mirrored that of the diets
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