2,315 research outputs found
On the number of particles which a curved quantum waveguide can bind
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
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
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
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
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
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
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
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
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
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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