2,454 research outputs found
Inequality of opportunity and growth
Theoretical and empirical studies exploring the effects of income inequality upon growth reach a disappointing inconclusive result. This paper postulates that one reason for this ambiguity is that income inequality is actually a composite measure of at least two different sorts of inequality: inequality of opportunity and inequality of returns to effort. These two types of inequality affect growth through opposite channels, so the relationship between income inequality and growth is positive or negative depending on which component is larger. We test this proposal using inequality-of-opportunity measures computed from the PSID database for 23 states of the U.S. in 1980 and 1990. We find robust support for a negative relationship between inequality of opportunity and growth, and a positive relationship between inequality of returns to effort and growth.income inequality; inequality of opportunity; economic growth.
Inequality of opportunity in Europe: Economic and policy facts
In this paper we consider the main factors that have influenced inequality of opportunity (IO) in Europe. Based on the EU-SILC database, we find that the various levels of development, education and social protection expenditure in 23 European countries significantly affect IO. Dropping out from school, reaching at least secondary levels of education, social spending to promote social integration and child care are the most important variables of those analyzed. The functioning of the labor market and the tax structure, on the other hand, do not have a significant bearing on IO. Lastly, we note that IO and total inequality exhibit differentiated explanatory patterns, which signifies that means of redistribution that serve to reduce overall inequality do not necessarily reduce IO.inequality of opportunity; growth; education; public expenditure; labor market.
Polyradical character and spin frustration in fullerene molecules: An ab initio non-collinear Hartree--Fock study
Most {\em ab initio} calculations on fullerene molecules have been carried
out based on the paradigm of the H\"uckel model. This is consistent with the
restricted nature of the independent-particle model underlying such
calculations, even in single-reference-based correlated approaches. On the
other hand, previous works on some of these molecules using model Hamiltonians
have clearly indicated the importance of short-range inter-atomic spin-spin
correlations. In this work, we consider {\em ab initio} non-collinear
Hartree--Fock (HF) solutions for representative fullerene systems: the bowl,
cage, ring, and pentagon isomers of C, and the larger C,
C, C, C, and C fullerene cages. In all cases but
the ring we find that the HF minimum corresponds to a truly non-collinear
solution with a torsional spin density wave. Optimized geometries at the
generalized HF (GHF) level lead to fully symmetric structures, even in those
cases where Jahn-Teller distortions have been previously considered. The nature
of the GHF solutions is consistent with the -electron space becoming
polyradical in nature: each -orbital remains effectively singly occupied.
The spin frustration, induced by the pentagon rings in an otherwise
anti-ferromagnetic background, is minimized at the HF level by aligning the
spins in non-collinear arrangements. The long-range magnetic ordering observed
is reminiscent of the character of broken symmetry HF solutions in polyacene
systems.Comment: 16 figure
Multi-reference symmetry-projected variational approximation for the ground state of the doped one-dimensional Hubbard model
A multi-reference configuration mixing scheme is used to describe the ground
state, characterized by well defined spin and space group symmetry quantum
numbers as well as doping fractions , of one dimensional
Hubbard lattices with nearest-neighbor hopping and periodic boundary
conditions. Within this scheme, each ground state is expanded in a given number
of nonorthogonal and variationally determined symmetry-projected
configurations. The results obtained for the ground state and correlation
energies of half-filled and doped lattices with 30, 34 and 50 sites, compare
well with the exact Lieb-Wu solutions as well as with the ones obtained with
other state-of-the-art approximations. The structure of the intrinsic
symmetry-broken determinants resulting from the variational procedure is
interpreted in terms of solitons whose translational and breathing motions can
be regarded as basic units of quantum fluctuations. It is also shown that in
the case of doped 1D lattices, a part of such fluctuations can also be
interpreted in terms of polarons. In addition to momentum distributions, both
spin-spin and density-density correlation functions are studied as functions of
doping. The spectral functions and density of states, computed with an ansatz
whose quality can be well-controlled by the number of symmetry-projected
configurations used to approximate the electron systems, display
features beyond a simple quasiparticle distribution, as well as spin-charge
separation trends.Comment: 16 pages, 11 figure
Inequality of Opportunity and Inequality of Effort: a Canonical Growth Model
Theoretical and empirical studies exploring the effects of income inequality upon growth reach a disappointing inconclusive result. Some recent empirical papers have emphasized that one reason for this ambiguity could be that income inequality is actually a composite measure of inequality of opportunity (IO) and inequality of effort (IE). These types of inequality would affect growth through opposite channels, so the relationship between inequality and growth would depend on which component is larger. Based on this preliminary empirical result, we build an intergenerational model with human capital of inequality and development. The existence of a trap in the process of human capital accumulation generates multiplicity of equilibria and permits the inclusion of social mobility in the analysis. The model is able to explain how IO and IE affect human capital accumulation and hence ongoing long-run growth. The existence of social mobility in society makes the relationship between income inequality and growth to be non-linear, and the final sign of the in fluence of inequality on growth to be dependent on the degree of development and overall inequality of the economy. We find that IE is generally benefi cial to human capital accumulation and, therefore, to ongoing
growth, while IO positively affects human capital (income) only for less developed economies
Caza, recolecciĂłn y pesca como estrategia de explotaciĂłn de recursos en forestas tropicales lluviosas: los nukak de la AmazonĂa colombiana.
Sin resume
Change in Educational Models for Facing Challenges to Lead Students into a New Way of Learning
Contemporary societies face challenges that come from competition, dynamism, and change, where people and students, in particular, embrace attitudes and practices that are different from those that their parents and teachers share. Change in educational models for facing those challenges implies a different know-how and also different abilities that teachers have to develop, in order for them to lead students into new way for learning. What kind of transformational and integrative leadership is needed for professors to create conditions and abilities that will help their students to face the challenges for the future in a developing country? In this chapter, we aim to provide proof of how the most important private university in Mexico, the TecnolĂłgico de Monterrey, has changed not only an educational model but also an inspiring and transforming leadership-oriented model for teachers for change. Projects and new teaching abilities are needed, but also a sense where the professor gets a more flexible role, contributing for creating and working with scientific knowledge
Multi-component symmetry-projected approach for molecular ground state correlations
The symmetry-projected Hartree--Fock ansatz for the electronic structure
problem can efficiently account for static correlation in molecules, yet it is
often unable to describe dynamic correlation in a balanced manner. Here, we
consider a multi-component, systematically-improvable approach, that accounts
for all ground state correlations. Our approach is based on linear combinations
of symmetry-projected configurations built out of a set of non-orthogonal,
variationally optimized determinants. The resulting wavefunction preserves the
symmetries of the original Hamiltonian even though it is written as a
superposition of deformed (broken-symmetry) determinants. We show how short
expansions of this kind can provide a very accurate description of the
electronic structure of simple chemical systems such as the nitrogen and the
water molecules, along the entire dissociation profile. In addition, we apply
this multi-component symmetry-projected approach to provide an accurate
interconversion profile among the peroxo and bis(-oxo) forms of
[CuO], comparable to other state-of-the-art quantum chemical
methods
Condiciones limnolĂłgicas en el embalse La Plata en Puerto Rico: 2008 a 2009
Water column profiles of important limnological indicators (temperature, pH, dissolved oxygen, reduction potential, nutrients) were collected at the center section of La Plata reservoir in north-central Puerto Rico during 2008 and 2009. Temperatures at the surface ranged from values close to 25° C during the hemisphere winter months (December-February) to approximately 30° C during summer (June-August). Total nitrogen and phosphorus concentrations at the epilimnion (≤ 3-m depth) averaged 1.06 mg/L and 50 µg/L, respectively. Chlorophyll a values averaged 32.4 µg/L, which altogether with its nutrient status, would place this reservoir within the eutrophic-hypereutrophic categories. The annual average volume-weighed dissolved oxygen concentration for the reservoir was 3.02 mg/L, a reflection of the delicate ecological condition of this reservoir. The reservoir remains stratified during a large portion of the year (≥ eight months), inducing prevailing anoxic conditions at the hypolimnion. However, mixing because of incoming flow associated with intense rain events can be common. As a result, the mixing regime of this reservoir is best classified as discontinuous warm polymictic. Runoff associated with intense rainfall is probably the major contributor of hypolimnion dissolved oxygen and nutrient recharge at this reservoir. The distribution of iron (Fe) and manganese (Mn) is strongly influenced by the redox status of the system. Solid phases containing these metals exert a dominant role in the cycling of phosphate in the system. Durante los años 2008 y 2009 se obtuvieron perfiles de la columna de agua de importantes indicadores limnolĂłgicos (e.g., temperatura, pH, oxĂgeno disuelto, potencial de reducciĂłn, nutrientes) en la secciĂłn central del embalse La Plata, localizado en el norte-central de Puerto Rico. Las temperaturas en la superficie oscilaron entre valores cercanos a 25° C durante los meses de nuestro invierno hemisfĂ©rico (diciembre a febrero) hasta unos 30° C durante el verano (junio a agosto). Las concentraciones promedio de nitrĂłgeno total y fĂłsforo total en el epilimion (s 3 m de profundidad) fueron 1.06 mg/L y 50 µg/L, respectivamente. La concentraciĂłn promedio de clorofila a, 32.4 µg/L. en conjunto con su estado nutricional, colocarĂa a este embalse dentro de las categorĂas eutrĂłfico-hipereutrĂłfico. La concentraciĂłn promedio anual de oxĂgeno disuelto, ponderado por volumen, para el embalse fue de 3.02 mg/L, lo cual refleja la delicada situaciĂłn ecolĂłgica del mismo. El embalse permanece estratificado durante una gran parte del año (a ocho meses), lo cual induce condiciones prevalecientemente anĂłxicas en el hipolimio. Sin embargo, la mezcla de la columna de agua debido al flujo de entrada asociado con eventos de lluvia intensa puede ser comĂşn. Como resultado, el rĂ©gimen de mezcla de este embalse es mejor clasificado como polimĂctico cálido discontinuo. La escorrentĂa asociada con las intensas lluvias es probablemente el mayor contribuyente de oxĂgeno disuelto y de recarga de nutrientes en el hipolimio de este embalse. La distribuciĂłn del hierro (Fe) y manganeso (Mn) está fuertemente influenciada por el estado redox del sistema. Las fases sĂłlidas que contienen estos metales ejercen un papel dominante en el ciclo del fĂłsforo en el sistema
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