Spectral functions and optical conductivity of spinless fermions on a checkerboard lattice

We study the dynamical properties of spinless fermions on the checkerboard lattice. Our main interest is the limit of large nearest-neighbor repulsion $V$ as compared with hopping $|t|$. The spectral functions show broad low-energy excitation which are due to the dynamics of fractionally charged excitations. Furthermore, it is shown that the fractional charges contribute to the electrical current density.Comment: 9 Pages, 9 Figure

The thermal conductivity reduction in HgTe/CdTe superlattices

The techniques used previously to calculate the three-fold thermal conductivity reduction due to phonon dispersion in GaAs/AlAs superlattices (SLs) are applied to HgTe/CdTe SLs. The reduction factor is approximately the same, indicating that this SL may be applicable both as a photodetector and a thermoelectric cooler.Comment: 5 pages, 2 figures; to be published in Journal of Applied Physic

Improved Method for Detecting Local Discontinuities in CMB data by Finite Differencing

An unexpected distribution of temperatures in the CMB could be a sign of new physics. In particular, the existence of cosmic defects could be indicated by temperature discontinuities via the Kaiser-Stebbins effect. In this paper, we show how performing finite differences on a CMB map, with the noise regularized in harmonic space, may expose such discontinuities, and we report the results of this process on the 7-year Wilkinson Microwave Anisotropy Probe data.Comment: 5 pages, 6 figures; Text has been edited, in line with the PRD articl

Ending hunger in Africa prospects for the small farmer

"In contrast to widely held uncertainties about Sub-Saharan Africa's ability to meet the Millennium Development Goals (MDGs), recent successes in African smallholder farming show that agriculture could play a key role in helping the region reach those goals. African governments and the donor community have recognized this potential and have pledged to help generate agricultural progress. This policy brief considers recent trends in poverty, malnutrition, and growth; outlines some of the challenges to boosting agricultural growth; and highlights cases of agricultural success in specific countries. By learning from case studies of smallholder success and building on the new enthusiasm of African governments, donors and their African partners can ensure that agriculture's role in meeting the MDGs is fully realized." from TextMillenium Development Goals ,

Telomere Formation Systems in Budding and Fission Yeasts

Telomeres are specialized structures essential for genomic stability in eukaryotic cells. Inducible systems causing telomere shortening or telomere formation from short tracts of telomere repeats were developed in the late 1990s in Saccharomyces cerevisiae and have been adapted to investigate multiple aspects of telomere biology. In the formation system, an internal tract of telomere repeats is placed next to an inducible double-strand break. Inducing the break converts the telomere tract into a functional telomere whose fate can be followed kinetically and allows one to assay elongation, protein recruitment, and the DNA damage checkpoint activation. This work was extended to Schizosaccharomyces pombe, as it shares some features of telomeric chromatin with mammalian cells that are missing in S. cerevisiae. The S. pombe system has revealed novel aspects of telomeric chromatin formation and similarities with S. cerevisiae. This chapter will review these past discoveries in different yeast model organisms, and what they reveal about telomere physiology that may well be conserved in mammals

Ending hunger by 2050

"To end hunger and prevent the recurrence of famine and starvation, we need to take the following steps: invest in public health, child nutrition, education, women's and girls' social status, and other components of human capital; reform public institutions and create innovative funding and partnership arrangements; change government policies at all levels to be both pro-poor and pro-growth; increase funding for scientific and technological research to boost agricultural production and efficiency; and develop specific policies and institutions to deal with environmental degradation caused by population growth. The international community, national governments, nongovernmental organizations (NGOs), and the private sector must cooperate to bring about these changes, which reach beyond redistribution programs, narrowly focused market-oriented solutions, or campaigns based solely on local self-reliance." from text

Electron-phonon coupling in the C60 fullerene within the many-body GW approach

We study the electron-phonon coupling in the C60 fullerene within the first-principles GW approach, focusing on the lowest unoccupied t1u three-fold electronic state which is relevant for the superconducting transition in electron doped fullerides. It is shown that the strength of the coupling is significantly enhanced as compared to standard density functional theory calculations with (semi)local functionals, with a 48% increase of the electron-phonon potential Vep. The calculated GW value for the contribution from the Hg modes of 93 meV comes within 4% of the most recent experimental values. The present results call for a reinvestigation of previous density functional based calculations of electron-phonon coupling in covalent systems in general.Comment: 4 pages, 0 figur