1,260 research outputs found
Valuing Africa's inland fisheries: overview of current methodologies with an emphasis on livelihood analysis
While Africa’s inland fisheries are widely recognized to be of great importance to local people, accurate and up-to-date information on their value is sparse and its absence is a serious constraint to the formulation of effective fisheries policies and management practices. As a contribution to current efforts to address this constraint, this paper reviews the different methods that are potentially applicable to the valuation of inland fisheries and discusses their respective rationales and limitations within a multi-sectoral, multi-user context. The livelihood analysis approach is given special emphasis. The complementarity of this recently developed approach with the other, more conventional, environmental economics methods is illustrated
Theoretical study of charge exchange dynamics in He + NO collisions
We investigate the charge transfer mechanism in the collisions of helium ions
on nitric oxide using a molecular description framework with consideration of
the orientation of the projectile toward the target. The anisotropy of the
collision process has been analysed in detail in connection with the
non-adiabatic interactions around avoided crossings. Potential energy curves,
radial and rotational coupling matrix elements have been determined by means of
ab initio quantum chemical methods. The collision dynamics is performed in the
[1.-25.] keV collision energy range using a semiclassical approach, and the
total electron transfer cross sections are analysed with regard to available
experimental data.Comment: 16 pages, 3 tables, 6 figure
Tropical river fisheries valuation: a global synthesis and critical review
River fisheries / Inland fisheries / Economic impact / Cost benefit analysis / Developing countries / River basin management / Wetlands / Valuation
Groupoid Extensions of Mapping Class Representations for Bordered Surfaces
The mapping class group of a surface with one boundary component admits
numerous interesting representations including as a group of automorphisms of a
free group and as a group of symplectic transformations. Insofar as the mapping
class group can be identified with the fundamental group of Riemann's moduli
space, it is furthermore identified with a subgroup of the fundamental path
groupoid upon choosing a basepoint. A combinatorial model for this, the mapping
class groupoid, arises from the invariant cell decomposition of Teichm\"uller
space, whose fundamental path groupoid is called the Ptolemy groupoid. It is
natural to try to extend representations of the mapping class group to the
mapping class groupoid, i.e., construct a homomorphism from the mapping class
groupoid to the same target that extends the given representations arising from
various choices of basepoint.
Among others, we extend both aforementioned representations to the groupoid
level in this sense, where the symplectic representation is lifted both
rationally and integrally. The techniques of proof include several algorithms
involving fatgraphs and chord diagrams. The former extension is given by
explicit formulae depending upon six essential cases, and the kernel and image
of the groupoid representation are computed. Furthermore, this provides
groupoid extensions of any representation of the mapping class group that
factors through its action on the fundamental group of the surface including,
for instance, the Magnus representation and representations on the moduli
spaces of flat connections.Comment: 24 pages, 4 figures Theorem 3.6 has been strengthened, and Theorems
8.1 and 8.2 have been adde
Finite type invariants and fatgraphs
We define an invariant of pairs M,G, where M is a 3-manifold
obtained by surgery on some framed link in the cylinder , S is a
connected surface with at least one boundary component, and G is a fatgraph
spine of S. In effect, is the composition with the maps of
Le-Murakami-Ohtsuki of the link invariant of Andersen-Mattes-Reshetikhin
computed relative to choices determined by the fatgraph G; this provides a
basic connection between 2d geometry and 3d quantum topology. For each fixed G,
this invariant is shown to be universal for homology cylinders, i.e.,
establishes an isomorphism from an appropriate vector space
of homology cylinders to a certain algebra of Jacobi diagrams. Via
composition for any pair of fatgraph spines
G,G' of S, we derive a representation of the Ptolemy groupoid, i.e., the
combinatorial model for the fundamental path groupoid of Teichmuller space, as
a group of automorphisms of this algebra. The space comes equipped
with a geometrically natural product induced by stacking cylinders on top of
one another and furthermore supports related operations which arise by gluing a
homology handlebody to one end of a cylinder or to another homology handlebody.
We compute how interacts with all three operations explicitly in
terms of natural products on Jacobi diagrams and certain diagrammatic
constants. Our main result gives an explicit extension of the LMO invariant of
3-manifolds to the Ptolemy groupoid in terms of these operations, and this
groupoid extension nearly fits the paradigm of a TQFT. We finally re-derive the
Morita-Penner cocycle representing the first Johnson homomorphism using a
variant/generalization of .Comment: 39 page
Conventional and manipulated growth of Cu-Cu(111)
Molecular beam epitaxy of Cu on Cu(111) was studied using thermal energy He scattering, in the temperature range between 100 and 450 K. Three-dimensional growth was observed in the whole temperature range. To determine the onset of various diffusion processes, submonolayer films formed by deposition at low temperature were annealed. Annealing proceeds in two steps. The first step is interpreted as a change in island shape, the second as Ostwald-ripening. A comparison with homoepitaxy on Pt(111) and Ag(111) is made. Growth manipulation was carried out by artificially increasing the island number density via intervention in the nucleation stage of each layer. The procedures applied were temperature reduction during nucleation as well as pulsed ion bombardment. These techniques enabled the convenient growth of good quality films consisting of a large number of monolayers. Finally, the use of oxygen as a surfactant modifying the growth mode was investigated. Under some growth conditions, pre-exposure of the surface to oxygen was found to induce weak He-intensity oscillations during deposition. The quality of the films grown in this way was, however, low
Répertoire et contextes sociaux des cris unitaires du colobe vert (procolobus verus) dans le Parc National de Taï (PNT), Côte d\'Ivoire
Pour caractériser l\'environnement social et écologique du Colobe Vert (Procolobus verus), des observations régulières par tranche de 15 minutes d\'animaux focaux dans trois groupes ont été méné. Les observations et les enregistrements de cris occasionnels (Ad libitum) ont permis de répertorier huit (8) types de cris unitaires émis par différentes classes
de sexes et d\'âges. Ces cris peuvent être regroupés en quatre catégories selon les contextes sociaux dans lesquels ils interviennent : les cris a, b et c en cas de prédation et de trouble (présence de prédateur, cris d\'alarme d\'autres espèces), les cris f et g en situation de conflit (combat entre individus), les cris b, c et e en contexte de stabilité (calme
apparent), et les cris b, c et e pour signaler des rencontres inter-groupes (rencontre avec d\'autres groupes de singes).In order to knod how Olive Colobus monkeys (Procolobus verus) interact with their social and ecological environment, we carried out regular observations by 15 minutes old section of focal animals in three groups. These observations
associated with the recordings of occasional calls (Ad libitum) enabled us to index eight (8) types of unit calls emitted by various sex and age classes. These calls can be gathered into four types according to social contexts in which they happened : the calls a, b and c in context of predation and disturbance (presence of predator, alarm calls from other monkey species), the calls f and g in a situation of conflict (fights between individual), the calls b, c and e as a signal of stability (peaceful context), and the calls b, c and e in case of intergroup encounters (encounter with other monkey groups). Keywords: Colobe Vert, vocalisation, cri unitaire, contexte social, communication, Parc National de Taï, Côte d'Ivoire.Olive Colobus, vocalization, unit call, social context, communication, Taï National Park, Ivory Coast.Sciences & Nature Vol. 4 (2) 2007: pp. 137-14
Exploring Set-Theoretic Practices of Youth Engagement in Connective Journalism: What We Lose in School-Mathematical Descriptions
Analyzing youth video submissions regarding COVID-19 to KQED’s ‘Let’s Talk About the Election’ website, we explore the mathematics these youth engaged in through their submissions without creating any explicit connection to school mathematical concepts or standards. Our focus is the students’ construction of sets (e.g. sets of nurses, doctors, American workers), as a means of creating connection with voters and other media authors through Marchi and Clark’s (2021) construct of connective journalism. We observe these youth constructing sets of varying sizes and reflecting on how these sets are contextualized within a larger political dialogue. We also attempt to rewrite part of one student composition using school mathematical symbolic logic, reviewing what in the student’s message is no longer present in the school mathematical analogue and why. We conclude by encouraging practitioners to explore with their students other instances in which they can challenge numerical or school mathematical symbolic writing as a superior means of communicating ideas
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