178 research outputs found
Who wants to conserve remaining forest fragments in the Manompana Corridor?
Contiguous forests in Madagascar are continuously converted into forest fragments due to deforestation, and dispersed into landscape mosaics dominated by agriculture. These fragments are of increasing importance for biodiversity conservation as well as for the well being of rural inhabitants, providing a high diversity of timber and non- timber forest products. An increasing number of international projects are therefore trying to preserve remaining forests and to transfer the management of these forests to local communities. However, it is not known how important the preservation of forest fragments is to local people. We therefore explore the importance of forest fragments as a source of cash income to different groups separated by wealth level and access to forest resources. A multi-method research approach was taken, based on score application exercises as well as interviews with individual households and focus groups. Our study site was located at the east coast of Madagascar in the Manompana corridor. Results show that some groups are significantly more interested in the preservation of forest fragments than others. Interest is significantly related to the wealth of local inhabitants as well as to the walking distance between villages and forest resources. Nevertheless, interest in resource preservation does not depend on how important fragments are to local people, but rather on the awareness about resource scarcity. RĂ©sumĂ© En raison dâune forte dĂ©forestation sur la cĂŽte est de Madagascar, de nombreux massifs forestiers dâun seul tenant et de vastes Ă©cosystĂšmes interconnectĂ©s ont Ă©tĂ© dĂ©truits, laissant des fragments de forĂȘts qui sâintĂšgrent dans une mosaĂŻque paysagĂšre dominĂ©e par lâagriculture. Ces fragments gagnent en importance. Ils jouent un rĂŽle de premier plan dans les rĂ©seaux de biodiversitĂ© en assurant un certain niveau de connectivitĂ©. Mais les fragments sont essentiels au bien - ĂȘtre de la population locale, fournissant produits et services pour la consommation quotidienne ou donnant accĂšs Ă un revenu monĂ©taire. Sur un plan global, aussi bien les organisations de protection de la nature que les milieux scientifiques essayent dâendiguer la dĂ©forestation. Depuis les annĂ©es 1996 la politique nationale Ă Madagascar a gĂ©nĂ©rĂ© lois et processus visant Ă transfĂ©rer la gestion des ressources forestiĂšres de lâEtat aux communautĂ©s locales. Cependant, il nâa pas Ă©tĂ© possible, jusquâĂ ce jour, dâattĂ©nuer lâampleur de la destruction et de la fragmentation des forĂȘts pluviales de lâĂźle. Plus encore, Ă lâheure actuelle la perception de lâimportance des fragments de forĂȘts nâest pas connue par la population. Un projet de recherche a Ă©tĂ© lancĂ© pour contribuer Ă combler cette lacune, dans le corridor de Manompana, sur la cĂŽte. Les buts de ce projet Ă©taient (i) dâexplorer lâimportance des fragments de forĂȘts pour les revenus monĂ©taires de la population locale et (ii) dâanalyser la perception de lâimportance des fragments de forĂȘts par la population locale. Les recherches se sont dĂ©roulĂ©es dans quatre villages situĂ©s Ă des distances diffĂ©rentes du grand massif forestier. La population locale a Ă©tĂ© rĂ©partie en diffĂ©rentes catĂ©gories de niveau de vie et en fonction de la distance Ă parcourir entre les villages et la forĂȘt. Cette approche a permis dâĂ©tudier le rĂŽle de la forĂȘt quant aux revenus monĂ©taires des diffĂ©rents groupes de la population. Nous avons Ă©galement cherchĂ© Ă Ă©tablir un lien entre lâampleur des revenus monĂ©taires et un intĂ©rĂȘt Ă conserver les fragments de forĂȘts qui subsistent. Nos mĂ©thodes de recherche font recours Ă des exercices de « scoring », Ă des discussions avec des groupes ciblĂ©s et Ă des enquĂȘtes de mĂ©nages. Il ressort des analyses que certains groupes ont un intĂ©rĂȘt Ă conserver les fragments forestiers. Cet intĂ©rĂȘt est significativement liĂ©, dâune part, au niveau de vie de la population, dâautre part, Ă la distance entre le village et le massif forestier. Cependant, lâintĂ©rĂȘt Ă conserver les fragments de forĂȘts est plus fortement liĂ© Ă la conscience de la finitude des ressources forestiĂšres quâau montant des revenus monĂ©taires que la population peut tirer des produits forestiers.
On the Corrections to Dashen's Theorem
The electromagnetic corrections to the masses of the pseudoscalar mesons
and are considered. We calculate in chiral perturbation theory the
contributions which arise from resonances within a photon loop at order . Within this approach we find rather moderate deviations to Dashen's
theorem.Comment: 14 pages, sligthly enlarged version; a numerical error is corrected
and the embedding of the figures is improved. The complete paper, including
figures, is also available via anonymous ftp at
ftp://www-ttp.physik.uni-karlsruhe.de/ , or via www at
http://www-ttp.physik.uni-karlsruhe.de/cgi-bin/preprints/; to be published in
Phys.Rev.
Boltzmann Equations for Spin and Charge Relaxations in Superconductors
In a superconductor coupled with a ferromagnetic metal, spin and charge
imbalances can be induced by injecting spin-polarized electron current from the
ferromagnetic metal. We theoretically study a nonequilibrium distribution of
quasiparticles in the presence of spin and charge imbalances. We show that four
distribution functions are needed to characterize such a nonequilibrium
situation, and derive a set of linearized Boltzmann equations for them by
extending the argument by Schmid and Sch\"{o}n based on the quasiclassical
Green's function method. Using the Boltzmann equations, we analyze the spin
imbalance in a thin superconducting wire weakly coupled with a ferromagnetic
electrode. The spin imbalance induces a shift () of
the chemical potential for up-spin (down-spin) quasiparticles. We discuss how
is relaxed by spin-orbit impurity scattering.Comment: 16 pages, 2 figure
Sequential vector and axial-vector meson exchange and chiral loops in radiative phi decay
We study the radiative decay into and taking into account mechanisms in which there are two sequential
vector-vector-pseudoscalar or axial-vector--vector--pseudoscalar steps followed
by the coupling of a vector meson to the photon, considering the final state
interaction of the two mesons. There are other mechanisms in which two kaons
are produced through the same sequential mechanisms or from decay into
two kaons and then undergo final state interaction leading to the final pair of
pions or , this latter mechanism being the leading one. The results
of the parameter free theory, together with the theoretical uncertainties, are
compared with the latest experimental results of KLOE at Frascati.Comment: 28 pages, 20 figure
Shape modeling technique KOALA validated by ESA Rosetta at (21) Lutetia
We present a comparison of our results from ground-based observations of
asteroid (21) Lutetia with imaging data acquired during the flyby of the
asteroid by the ESA Rosetta mission. This flyby provided a unique opportunity
to evaluate and calibrate our method of determination of size, 3-D shape, and
spin of an asteroid from ground-based observations. We present our 3-D
shape-modeling technique KOALA which is based on multi-dataset inversion. We
compare the results we obtained with KOALA, prior to the flyby, on asteroid
(21) Lutetia with the high-spatial resolution images of the asteroid taken with
the OSIRIS camera on-board the ESA Rosetta spacecraft, during its encounter
with Lutetia. The spin axis determined with KOALA was found to be accurate to
within two degrees, while the KOALA diameter determinations were within 2% of
the Rosetta-derived values. The 3-D shape of the KOALA model is also confirmed
by the spectacular visual agreement between both 3-D shape models (KOALA pre-
and OSIRIS post-flyby). We found a typical deviation of only 2 km at local
scales between the profiles from KOALA predictions and OSIRIS images, resulting
in a volume uncertainty provided by KOALA better than 10%. Radiometric
techniques for the interpretation of thermal infrared data also benefit greatly
from the KOALA shape model: the absolute size and geometric albedo can be
derived with high accuracy, and thermal properties, for example the thermal
inertia, can be determined unambiguously. We consider this to be a validation
of the KOALA method. Because space exploration will remain limited to only a
few objects, KOALA stands as a powerful technique to study a much larger set of
small bodies using Earth-based observations.Comment: 15 pages, 8 figures, 2 tables, accepted for publication in P&S
Non-Perturbative Study of the Light Pseudoscalar Masses in Chiral Dynamics
We perform a non-perturbative chiral study of the masses of the lightest
pseudoscalar mesons. In the calculation of the self-energies we employ the
S-wave meson-meson amplitudes taken from Unitary Chiral Perturbation Theory
(UCHPT) that include the lightest nonet of scalar resonances. Values for the
bare masses of pions and kaons are obtained, as well as an estimate of the mass
of the \eta_8. The former are found to dominate the physical pseudoscalar
masses. We then match to the self-energies from Chiral Perturbation Theory
(CHPT) to O(p^4), and a robust relation between several O(p^4) CHPT
counterterms is obtained. We also resum higher orders from our calculated
self-energies. By taking into account values determined from previous chiral
phenomenological studies of m_s/\hat{m} and 3L_7+L^r_8, we determine a tighter
region of favoured values for the O(p^4) CHPT counterterms 2L^r_6-L^r_4 and
2L^r_8-L^r_5. This determination perfectly overlaps with the recent
determinations to O(p^6) in CHPT. We warn about a likely reduction in the value
of m_s/\hat{m} by higher loop diagrams and that this is not systematically
accounted for by present lattice extrapolations. We also provide a favoured
interval of values for m_s/\hat{m} and 3L_7+L^r_8.Comment: 26 pages, 9 figures. Original new material is included. Major
rewriting when comparing with lattice QC
The Electromagnetic Mass Differences of Pions and Kaons
We use the Cottingham method to calculate the pion and kaon electromagnetic
mass differences with as few model dependent inputs as possible. The
constraints of chiral symmetry at low energy, QCD at high energy and
experimental data in between are used in the dispersion relation. We find
excellent agreement with experiment for the pion mass difference. The kaon mass
difference exhibits a strong violation of the lowest order prediction of
Dashen's theorem, in qualitative agreement with several other recent
calculations.Comment: 40 pages, Latex, needs axodraw. and psfig. macros, 4 figure
Hadronic light-by-light scattering contribution to the muon g-2: an effective field theory approach
The hadronic light-by-light contribution to a_{mu}, the anomalous magnetic
moment of the muon, is discussed from the point of view of an effective
low-energy theory. As an application, the coefficient of the leading logarithm
arising from the two-loop graphs involving two anomalous vertices is computed,
and found to be positive. This corresponds to a positive sign for the pion-pole
contribution to the hadronic light-by-light correction to a_{mu}, and to a
sizeable reduction of the discrepancy between the present experimental value of
a_{mu} and its theoretical counterpart in the standard model.Comment: 4 pages, 1 figure. v2: published versio
Isospin Breaking and -> Decay
We study decay up to including all orders of the chiral
expansion and one-loop level of mesons in formlism of chiral constituent quark
model. This G-parity forbidden decay is caused by and
electromagnetic interaction of mesons. We illustrate that in the formlism both
nonresonant contact interaction and resonance exchange contribute to
this process, and the contribution from resonance exchange is dominant.
We obtain that transition matrix element is
MeV, and
isospin breaking parameter is MeV at energy scale .Comment: Revtex file, 16 pages, four eps figur
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