1,361 research outputs found
Rural poverty in Ecuador : a qualitative assessment
A complement to recent in-depth quantitative analyses of rural poverty in Ecuador, this is a report on the results of the Rural Qualitative Assessment in living conditions in rural communities in all three Ecuador's diverse regions. Using a variety of qualitative techniques, the research aimed to assess what poverty means to marginalized rural families, what kind of survival strategies families use in times of hardship, and what these families believe is needed to alleviate poverty. Several key messages emerge: 1) rural communities with the same characteristics (such as area, soil quality, and ethnic background) are actually very heterogeneous in their command of land resources, definition of well-being, range of economic activities, and recommendations for what is needed to overcome poverty; 2) in times of hardship, families have complemented income for traditional sources with earnings from new activities. In addition to migration, which plays a pivotal role in all communities, piecework and weaving are important to income generation in the Sierra, small businesses are important in the Costa, and increased production of cash crops is important in the Oriente. Families have also reduced expenditures on clothing, fiestas, and food. Spending less on food is alarming as malnutrition rates in rural Ecuador are already very high; and 3) poor rural families express very practical solutions to overcoming poverty. They don't demand sweeping changes. Overwhelmingly, they suggest measures that will make available land and human resources more productive. Almost half the suggestions from poor rural families have to do with infrastructure. Many families also want training courses (both agricultural and nonagricultural).Public Health Promotion,Environmental Economics&Policies,Agricultural Knowledge&Information Systems,Health Monitoring&Evaluation,Water Conservation,Environmental Economics&Policies,Agricultural Knowledge&Information Systems,Crops&Crop Management Systems,Health Monitoring&Evaluation,Housing&Human Habitats
Anisotropic Diffusion Limited Aggregation
Using stochastic conformal mappings we study the effects of anisotropic
perturbations on diffusion limited aggregation (DLA) in two dimensions. The
harmonic measure of the growth probability for DLA can be conformally mapped
onto a constant measure on a unit circle. Here we map preferred directions
for growth of angular width to a distribution on the unit circle which
is a periodic function with peaks in such that the width
of each peak scales as , where defines the
``strength'' of anisotropy along any of the chosen directions. The two
parameters map out a parameter space of perturbations that allows a
continuous transition from DLA (for or ) to needle-like fingers
as . We show that at fixed the effective fractal dimension of
the clusters obtained from mass-radius scaling decreases with
increasing from to a value bounded from below by
. Scaling arguments suggest a specific form for the dependence
of the fractal dimension on for large , form which compares
favorably with numerical results.Comment: 6 pages, 4 figures, submitted to Phys. Rev.
Residual disorder and diffusion in thin Heusler alloy films
Co2FeSi/GaAs(110) and Co2FeSi/GaAs(111)B hybrid structures were grown by
molecular-beam epitaxy and characterized by transmission electron microscopy
(TEM) and X-ray diffraction. The films contained inhomogeneous distributions of
ordered L2_1 and B2 phases. The average stoichiometry was controlled by lattice
parameter measurements, however diffusion processes lead to inhomogeneities of
the atomic concentrations and the degradation of the interface, influencing
long-range order. An average long-range order of 30-60% was measured by
grazing-incidence X-ray diffraction, i.e. the as-grown Co2FeSi films were
highly but not fully ordered. Lateral inhomogeneities of the spatial
distribution of long-range order in Co2FeSi were found using dark-field TEM
images taken with superlattice reflections
New Algorithm for Parallel Laplacian Growth by Iterated Conformal Maps
We report a new algorithm to generate Laplacian Growth Patterns using
iterated conformal maps. The difficulty of growing a complete layer with local
width proportional to the gradient of the Laplacian field is overcome. The
resulting growth patterns are compared to those obtained by the best algorithms
of direct numerical solutions. The fractal dimension of the patterns is
discussed.Comment: Sumitted to Phys. Rev. Lett. Further details at
http://www.pik-potsdam.de/~ander
Deformation of feldspar at greenschist facies conditions – the record of mylonitic pegmatites from the Pfunderer Mountains, Eastern Alps
Deformation microstructures of albitic plagioclase and K-feldspar were investigated in
mylonitic pegmatites from the Austroalpine basement south of the western
Tauern Window by polarized light microscopy, electron microscopy and electron
backscatter diffraction to evaluate feldspar deformation mechanisms at
greenschist facies conditions. The main mylonitic characteristics are
alternating almost monophase quartz and albite layers, surrounding
porphyroclasts of deformed feldspar and tourmaline. The dominant deformation
microstructures of K-feldspar porphyroclasts are intragranular fractures at a
high angle to the stretching lineation. The fractures are healed or sealed by
polyphase aggregates of albite, K-feldspar, quartz and mica, which also occur
along intragranular fractures of tourmaline and strain shadows around other
porphyroclasts. These polyphase aggregates indicate dissolution–precipitation
creep. K-feldspar porphyroclasts are partly replaced by albite characterized
by a cuspate interface. This replacement is interpreted to take place by
interface-coupled dissolution–precipitation driven by a solubility difference
between K-feldspar and albite. Albite porphyroclasts are replaced at
boundaries parallel to the foliation by fine-grained monophase albite
aggregates of small strain-free new grains mixed with deformed fragments.
Dislocation glide is indicated by bent and twinned albite porphyroclasts with
internal misorientation. An indication of effective dislocation climb with
dynamic recovery, for example, by the presence of subgrains, is systematically
missing. We interpret the grain size reduction of albite to be the result of
coupled dislocation glide and fracturing (low-temperature plasticity).
Subsequent growth is by a combination of strain-induced grain boundary
migration and formation of growth rims, resulting in an aspect ratio of albite
with the long axis within the foliation. This strain-induced replacement by
nucleation (associated dislocation glide and microfracturing) and subsequent
growth is suggested to result in the observed monophase albite layers,
probably together with granular flow. The associated quartz layers show
characteristics of dislocation creep by the presence of subgrains, undulatory
extinction and sutured grain boundaries. We identified two endmember matrix
microstructures: (i) alternating layers of a few hundred micrometres' width,
with isometric, fine-grained feldspar (on average 15 µm in diameter)
and coarse-grained quartz (a few hundred micrometres in diameter),
representing lower strain compared to (ii) alternating thin layers of some
tens of micrometres' width composed of fine-grained quartz (<20 µm in diameter)
and coarse elongated albite grains (long axis of a few tens of
micrometres) defining the foliation, respectively. Our observations indicate
that grain size reduction by strain-induced replacement of albite (associated
dislocation glide and microfracturing) followed by growth and granular flow
simultaneous with dislocation creep of quartz are playing the dominating role
in formation of the mylonitic microstructure.</p
Nonlinear anomalous diffusion equation and fractal dimension: Exact generalized gaussian solution
In this work we incorporate, in a unified way, two anomalous behaviors, the
power law and stretched exponential ones, by considering the radial dependence
of the -dimensional nonlinear diffusion equation where , ,
, and are real parameters and is a time-dependent
source. This equation unifies the O'Shaugnessy-Procaccia anomalous diffusion
equation on fractals () and the spherical anomalous diffusion for
porous media (). An exact spherical symmetric solution of this
nonlinear Fokker-Planck equation is obtained, leading to a large class of
anomalous behaviors. Stationary solutions for this Fokker-Planck-like equation
are also discussed by introducing an effective potential.Comment: Latex, 6 pages. To appear in Phys. Rev.
Statistical Mechanics of Glass Formation in Molecular Liquids with OTP as an Example
We extend our statistical mechanical theory of the glass transition from
examples consisting of point particles to molecular liquids with internal
degrees of freedom. As before, the fundamental assertion is that super-cooled
liquids are ergodic, although becoming very viscous at lower temperatures, and
are therefore describable in principle by statistical mechanics. The theory is
based on analyzing the local neighborhoods of each molecule, and a statistical
mechanical weight is assigned to every possible local organization. This
results in an approximate theory that is in very good agreement with
simulations regarding both thermodynamical and dynamical properties
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