Investigation on the structural and magnetic properties of sputtered TbFe2/Fe3Ga heterostructures

We have analyzed the structural and magnetic properties of as-grown and annealed [TbFe2/Fe3Ga]n heterostructures grown by sputtering. Evidence of the bcc structure in the Fe3Ga layers has been found. The diffraction peak related to this structure shifts to high angles with the annealing temperature. Also, we have observed a change in the microstructure of the Tb-Fe layers when the thickness layer is reduced in the as-grown heterostructures. Moreover, the Tb content is lower than 33% of the TbFe2 Laves phase and it depends on the layer thickness. The thermal treatments promote the increase of the Tb content, but only in the heterostructures with thick layers. The strong lattice mismatch between the Tb-Fe and Fe-Ga layers seems to prevent a complete Tb diffusion upon the annealing process. Thus, the crystallization of the TbFe2 Laves phase is inhibited in the heterostructures with thin layers, although our experimental results indicate the presence of potential magnetostrictive TbFeGa alloy

Choques externos y políticas de protección social en América Latina

Las crisis recientes han demostrado que América Latina sigue siendo altamente vulnerable a los choques externos. A pesar de la recuperación económica que desde fines del año 2009, la vulnerabilidad externa prevalece debido a la alta volatilidad de los mercados mundiales. Las opciones de un crecimiento sostenible y de reducción de la pobreza dependerán en alto grado de las capacidades de los países para mitigar esa volatilidad y su impacto sobre el bienestar de la población. Diversas simulaciones generadas para siete países de la región mediante el modelo de equilibrio general computable denominado MACEPES, demuestran que choques externos típicos de un contexto de crisis mundial (deterioro en los términos de intercambio, salida de capitales y reducción de las remesas) contraen la demanda agregada y el empleo, generando “desprotección” social y más pobreza en ausencia de políticas anti-cíclicas. Ante la eventualidad de choques externos, las transferencias directas a los hogares son altamente efectivas en términos de reducir la pobreza, incluso una vez considerado el impacto contractivo de su financiamiento sobre la inversión. Este instrumento podría implementarse en el marco de programas de transferencias condicionadas a la educación o de pensiones no contributivas, pero se plantea como reto la movilización de recursos para su financiamiento.

The moderating role of gender on entrepreneurial intentions: a TPB perspective

Purpose: To disentangle the ways in which social norms shape entrepreneurial intentions of university students and to analyse the moderating effect of gender that may arise. Design/methodology/approach: We have used the entrepreneurial intention model based on Theory of Planned Behaviour (TPB) literature and moderated by students’ gender affecting this intention. We tested some hypotheses using data from undergraduate business students in Spain and their entrepreneurial intentions. Findings: Our results suggest that perceived behavioural control and attitudes affect the entrepreneurial intentions of university students towards entrepreneurship while subjective norms do not. Furthermore, our findings reveal that the moderating effect of gender has a positive influence for women in the relationship between those subjective norms and the perceived behavioural control. However, as to some research done so far, the moderating role of gender does not seem to have a particular effect on predicting entrepreneurial intentions when moderating TPB dimensions. Practical implications: Given the socio-economic benefits attributed to entrepreneurship, the results allow the design of more effective education initiatives and policies. Originality/value: This research provides support for the application of the TPB, allowing for a better understanding of gender differences in entrepreneurial intentions

Local and average fields inside surface-disordered waveguides: Resonances in the one-dimensional Anderson localization regime

We investigate the one-dimensional propagation of waves in the Anderson localization regime, for a single-mode, surface disordered waveguide. We make use of both an analytical formulation and rigorous numerical simulation calculations. The occurrence of anomalously large transmission coefficients for given realizations and/or frequencies is studied, revealing huge field intensity concentration inside the disordered waveguide. The analytically predicted s-like dependence of the average intensity, being in good agreement with the numerical results for moderately long systems, fails to explain the intensity distribution observed deep in the localized regime. The average contribution to the field intensity from the resonances that are above a threshold transmission coefficient $T_{c}$ is a broad distribution with a large maximum at/near mid-waveguide, depending universally (for given $T_{c}$) on the ratio of the length of the disorder segment to the localization length, $L/\xi$. The same universality is observed in the spatial distribution of the intensity inside typical (non-resonant with respect to the transmission coefficient) realizations, presenting a s-like shape similar to that of the total average intensity for $T_{c}$ close to 1, which decays faster the lower is $T_{c}$. Evidence is given of the self-averaging nature of the random quantity $\log[I(x)]/x\simeq -1/\xi$. Higher-order moments of the intensity are also shown.Comment: 9 pages, 9 figure

Magnetic Field Effects on the Transport Properties of One-sided Rough Wires

We present a detailed numerical analysis of the effect of a magnetic field on the transport properties of a `small-$N$' one-sided surface disordered wire. When time reversal symmetry is broken due to a magnetic field $B$, we find a strong increase with $B$ not only of the localization length $\xi$ but also of the mean free path $\ell$ caused by boundary states. Despite this, the universal relationship between $\ell$ and $\xi$ does hold. We also analyze the conductance distribution at the metal-insulator crossover, finding a very good agreement with Random Matrix Theory with two fluctuating channels within the Circular Orthogonal(Unitary) Ensemble in absence(presence) of $B$Comment: 5 pages, 4 figures, to appear in Phys. Rev.

Optimal allocation of agriculture’s public budget can improve transformation and healthy diets access in Ethiopia

Agriculture is under transformation in sub-Saharan Africa where millions still do not have access to a healthy diet. Policy makers in this region should find ways to accelerate agricultural transformation while increasing access to healthy diets. Optimizing agriculture’s public budget stands out as a handy option. By combining a dynamic computable general equilibrium model and a multi-criteria decision-making technique, and applying them in the context of Ethiopia, this paper points to an important trade-off that policy makers should keep in mind. An optimal allocation of agriculture’s public budget aimed at increasing agri-food output, creating off- farm jobs and reducing rural poverty, which are agricultural transformation objectives, will help to reduce the cost of a healthy diet, allowing around 2 million more Ethiopians to afford it. This number could even be higher should policy makers allocate the budget optimally aiming at only lowering the cost of a healthy diet, but at the cost of reducing household income and slowing down transformation.Facultad de Ciencias Económica

Choques externos y políticas de protección social en América Latina

Las crisis recientes han demostrado que América Latina sigue siendo altamente vulnerable a los choques externos. A pesar de la recuperación económica que desde fines del año 2009, la vulnerabilidad externa prevalece debido a la alta volatilidad de los mercados mundiales. Las opciones de un crecimiento sostenible y de reducción de la pobreza dependerán en alto grado de las capacidades de los países para mitigar esa volatilidad y su impacto sobre el bienestar de la población. Diversas simulaciones generadas para siete países de la región mediante el modelo de equilibrio general computable denominado MACEPES, demuestran que choques externos típicos de un contexto de crisis mundial (deterioro en los términos de intercambio, salida de capitales y reducción de las remesas) contraen la demanda agregada y el empleo, generando "desproteccion" social y mas pobreza en ausencia de políticas anti-cíclicas. Ante la eventualidad de choques externos, las transferencias directas a los hogares son altamente efectivas en términos de reducir la pobreza, incluso una vez considerado el impacto contractivo de su financiamiento sobre la inversión. Este instrumento podría implementarse en el marco de programas de transferencias condicionadas a la educación o de pensiones no contributivas, pero se plantea como reto la movilización de recursos para su financiamiento.Centro de Estudios Distributivos, Laborales y Sociales (CEDLAS

Singular sources in the Demianski-Newman spacetimes

The analysis of singular regions in the NUT solutions carried out in the recent paper (Manko and Ruiz, 2005 Class. Quantum Grav. 22, p.3555) is now extended to the Demianski-Newman vacuum and electrovacuum spacetimes. We show that the effect which produces the NUT parameter in a more general situation remains essentially the same as in the purely NUT solutions: it introduces the semi-infinite singularities of infinite angular momenta and positive or negative masses depending on the interrelations between the parameters; the presence of the electromagnetic field additionally endows the singularities with electric and magnetic charges. The exact formulae describing the mass, charges and angular momentum distributions in the Demianski-Newman solutions are obtained and concise general expressions P_n=(m+i\nu)(ia)^n, Q_n=(q+ib)(ia)^n for the entire set of the respective Beig-Simon multipole moments are derived. These moments correspond to a unique choice of the integration constant in the expression of the metric function \omega which is different from the original choice made by Demianski and Newman.Comment: 22 pages, 5 figures; submitted to Classical and Quantum Gravit

Reflection and transmission of waves in surface-disordered waveguides

The reflection and transmission amplitudes of waves in disordered multimode waveguides are studied by means of numerical simulations based on the invariant embedding equations. In particular, we analyze the influence of surface-type disorder on the behavior of the ensemble average and fluctuations of the reflection and transmission coefficients, reflectance, transmittance, and conductance. Our results show anomalous effects stemming from the combination of mode dispersion and rough surface scattering: For a given waveguide length, the larger the mode transverse momentum is, the more strongly is the mode scattered. These effects manifest themselves in the mode selectivity of the transmission coefficients, anomalous backscattering enhancement, and speckle pattern both in reflection and transmission, reflectance and transmittance, and also in the conductance and its universal fluctuations. It is shown that, in contrast to volume impurities, surface scattering in quasi-one-dimensional structures (waveguides) gives rise to the coexistence of the ballistic, diffusive, and localized regimes within the same sample.Comment: LaTeX (REVTeX), 12 pages with 14 EPS figures (epsf macro), minor change

Universal Conductance Distributions in the Crossover between Diffusive and Localization Regimes

The full distribution of the conductance $P(G)$ in quasi-one-dimensional wires with rough surfaces is analyzed from the diffusive to the localization regime. In the crossover region, where the statistics is dominated by only one or two eigenchannels, the numerically obtained P(G) is found to be independent of the details of the system with the average conductance as the only scaling parameter. For < e^2/h, P(G) is given by an essentially ``one-sided'' log-normal distribution. In contrast, for e^2/h <= 2e^2/h, the shape of P(G) remarkable agrees with those predicted by random matrix theory for two fluctuating transmission eigenchannels.Comment: Accepted for publication in Phys. Rev. Let