Electronic and magnetic properties of the kagome systems YBaCo4O7 and YBaCo3MO7 (M=Al, Fe)

We present a combined experimental and theoretical x-ray absorption spectroscopy (XAS) study of the new class of cobaltates YBaCo4O7 and YBaCo3MO7 (M= Al, Fe). The focus is on the local electronic and magnetic properties of the transition metal ions in these geometrically frustrated kagome compounds. For the mixed valence cobaltate YBaCo4O7, both the Co2+ and Co3+ are found to be in the high spin state. The stability of these high spin states in tetrahedral coordination is compared with those in the more studied case of octahedral coordination. For the new compound YBaCo3FeO7, we find exclusively Co2+ and Fe3+ as charge states

Regional Disparities in Ghana: Policy Options and Public Investment Implications

Ghana has achieved sustained growth and poverty reduction during the 1990s, but such growth did not benefit the three poor northern regions and the development gap has increased between the south and north. One of the most important reasons is that much of the growth has been generated by export agriculture in which northern Ghana has little contribution if any. This paper sets out to identify avenues for pro-poor growth in Ghana, focussing on agricultural opportunities, particularly in northern Ghana. Using an economywide, multimarket model and based on time series production data between 1991 and 2000 and Ghana Living Standards Survey data of 1991/92 and 1998/99, this paper analyzes the possible poverty reduction trends up to 2015 by assuming different patterns of growth. The results show that agriculture-led growth has a larger poverty reducing effect than nonagriculture-led growth. Within agriculture, growth in staple crop production reduces poverty more than export crops. In northern Ghana, the staple crops whose growth exerts the largest effect on poverty reduction are groundnut, cassava and cowpea. However, despite the large effects of the agriculture-led growth, the projections of poverty rates in the regions, particularly Upper East are still high implying a need for complementary avenues for poverty reduction. A review of the literature shows that while the north generally is a net migration area, the rewards of migration have been limited because people who migrate have no skills and are, therefore, limited to entering the informal job market where wages are low. The implication is to enhance this labour with education and skills. Ultimately, the regions must attract production investment to boost economic activity and generate local growth. The state must play a leading role in investing in productive and social infrastructure as a way of facilitating the environment for private sector operators

SUCCEEDING WITH TRANSFORMATIONAL INITIATIVES: PRACTICAL APPROACHES FOR MANAGING CHANGE PROGRAMS

According to exiting literature, most change programs fail to manage and/or meet the expectations of stakeholders; leading to the failure of larger strategic organisational and transformational initiatives. Undoubtedly, change management necessitates introspective planning and responsive implementation but a failure to acknowledge and manage the external stakeholder environment will undermine these efforts. This article presents some practical frameworks for managing the delivery of change that were used collectively in different situations and contributed to the successful implementation of change programs. It does not recommend any specific approach to yield successful outcomes, but it considers a range of approaches for practitioners to take into account to assure seamless integration of programs with the formulation of overall strategy and implementation planning. Understanding the components of each program is asserted to support organisations to better understand the people and non-technology dimensions of their projects and the need to ensure effective, consultative communications to gain and maintain support for the program of change.people Management, change Management tactics

Electronic state and superconductivity of YBa2Cu3-xO7-y (M=Al,Zn and Sn) systems

A series of YBa2Cu(3-x)MxO(7-y) (M=Al,Zn and Sn) single phase samples were prepared, and the measurements of the crystal structure, oxygen content, electric resistivity, thermoelectric power, Mossbauer spectrum, XPS and superconductivity were performed. The experimental results of X ray powder diffraction, Mossbauer spectrum and oxygen content show that the Zn(2+) and the Al(3+) occupy the Cu(2) site in Cu-O planes and the Cu(1) site in Cu-O chains respectively, but the Sn(4+) occupies both the Cu(1) sites. As regards the properties in superconducting state, both the Zn(2+) and the Al(3+) depress T(sub c) strongly, but the Sn(4+) does not. As for the electronic transport properties in normal state, the system doped by Al(3+) displays a rapid increase of resistivity and some electron localization-like effects, and the thermoelectric power enhances obviously; the series contained Zn(2+) almost shows no changes of electric resistivity but the sign of the thermoelectric power is reversed. Other results are given and briefly discussed

Curvature estimates for Weingarten hypersurfaces in Riemannian manifolds

We prove curvature estimates for general curvature functions. As an application we show the existence of closed, strictly convex hypersurfaces with prescribed curvature $F$, where the defining cone of $F$ is \C_+. $F$ is only assumed to be monotone, symmetric, homogeneous of degree 1, concave and of class C^{m,\al}, $m\ge4$.Comment: 9 pages, v2:final version, to be publishe

Selective dilution and magnetic properties of La_{0.7}Sr_{0.3}Mn_{1-x}M'_xO_3 (M' = Al, Ti)

The magnetic lattice of mixed-valence Mn ions in La$_{0.7}$Sr$_{0.3}$MnO$_3$ is selectively diluted by partial substitution of Mn by Al or Ti. The ferromagnetic transition temperature and the saturation moment decreases with substitution in both series. The volume fraction of the non-ferromagnetic phases evolves non-linearly with the substitution concentration and faster than theoretically expected. By presenting the data in terms of selective dilutions, the reduction of $T_\mathrm{c}$ is found to be scaled by the relative ionic concentrations and is consistent with a prediction derived from molecular-field theory.Comment: 6 pages, 5 figures, REVTex4.0. Submitted to PR