Interplay between electron-electron and electron-vibration interactions on the thermoelectric properties of molecular junctions

The linear thermoelectric properties of molecular junctions are theoretically studied close to room temperature within a model including electron-electron and electron-vibration interactions on the molecule. A nonequilibrium adiabatic approach is generalized to include large Coulomb repulsion through a self-consistent procedure and applied to the investigation of large molecules, such as fullerenes, within the Coulomb blockade regime. The focus is on the phonon thermal conductance which is quite sensitive to the effects of strong electron-electron interactions within the intermediate electron-vibration coupling regime. The electron-vibration interaction enhances the phonon and electron thermal conductance, and it reduces the charge conductance and the thermopower inducing a decrease of the thermoelectric figure of merit. For realistic values of junction parameters, the peak values of the thermoelectric figure of merit are still of the order of unity since the phonon thermal conductance can be even smaller than the electron counterpart.Comment: 8 pages, 1 Appendix, 12 pages. arXiv admin note: substantial text overlap with arXiv:1406.377

Electron-vibration effects on the thermoelectric efficiency of molecular junctions

The thermoelectric properties of a molecular junction model, appropriate for large molecules such as fullerenes, are studied within a non-equilibrium adiabatic approach in the linear regime at room temperature. A self-consistent calculation is implemented for electron and phonon thermal conductance showing that both increase with the inclusion of the electron-vibration coupling. Moreover, we show that the deviations from the Wiedemann-Franz law are progressively reduced upon increasing the interaction between electronic and vibrational degrees of freedom. Consequently, the junction thermoelectric efficiency is substantially reduced by the electron-vibration coupling. Even so, for realistic parameters values, the thermoelectric figure of merit can still have peaks of the order of unity. Finally, in the off-resonant electronic regime, our results are compared with those of an approach which is exact for low molecular electron densities. We give evidence that in this case additional quantum effects, not included in the first part of this work, do not affect significantly the junction thermoelectric properties in any temperature regime.Comment: 15 pages, 11 figures, 2 Appendice

In-kind transfers and household food consumption

This paper examines the impact of wheat transfers and cash incomes on wheat consumption and wheat markets. Using propensity score- matching techniques, the total marginal propensity to consume (MPC) for wheat is, on average, 0.33, ranging from essentially zero for Food For Work (a program with large transfers) to 0.51 for Food For Education. Econometric estimates indicate that the MPC for small wheat transfers to poor households is approximately 0.25, while the MPC for wheat out of cash income is near zero. This increase in demand for wheat reduces the potential price effect of three major targeted programs involving small rations (Food For Education, Vulnerable Group Development, and Vulnerable Group Feeding) by about one-third.Transfer payments. ,Incomes. ,Wheat. ,Wheat Economic aspects Bangladesh. ,Food consumption. ,Cereal crops. ,Education. ,Labor. ,Access to education. ,

In-kind transfers and household food consumption

This paper examines the impact of wheat transfers and cash incomes on wheat consumption and wheat markets. Using propensity score- matching techniques, the total marginal propensity to consume (MPC) for wheat is, on average, 0.33, ranging from essentially zero for Food For Work (a program with large transfers) to 0.51 for Food For Education. Econometric estimates indicate that the MPC for small wheat transfers to poor households is approximately 0.25, while the MPC for wheat out of cash income is near zero. This increase in demand for wheat reduces the potential price effect of three major targeted programs involving small rations (Food For Education, Vulnerable Group Development, and Vulnerable Group Feeding) by about one-third.Transfer payments. ,Incomes. ,Wheat. ,Wheat Economic aspects Bangladesh. ,Food consumption. ,Cereal crops. ,Education. ,Labor. ,Access to education. ,

The 1998 floods in Bangladesh: disaster impacts, household coping strategies, and responses

This report combines a careful analysis of government policy and private foodgrain markets with a detailed survey of 757 households in rural Bangladesh in November and December 1998, about two months after the floodwaters receded. The report describes short- and medium-term government policy measures taken to encourage private trade, including an earlier trade liberalization that permitted private-sector imports of rice from India that stabilized private markets and largely offset the decline in production. The impact of the floods on household assets, employment, consumption, and nutritional outcomes is analyzed using the micro-level survey data. The study finds that flood-exposed households were, in general, able to avoid severe declines in food consumption and nutritional status through a combination of private-sector borrowing... and targeted government and NGO transfers.Food relief Bangladesh., Food supply Bangladesh., Disasters Asia., Households Bangladesh.,

Effect of ELF e.m. fields on metalloprotein redox-active sites

The peculiarity of the distribution and geometry of metallic ions in enzymes pushed us to set the hypothesis that metallic ions in active-site act like tiny antennas able to pick up very feeble e.m. signals. Enzymatic activity of Cu2+, Zn2+ Superoxide Dismutase (SOD1) and Fe2+ Xanthine Oxidase (XO) has been studied, following in vitro generation and removal of free radicals. We observed that Superoxide radicals generation by XO is increased by a weak field having the Larmor frequency fL of Fe2+ while the SOD1 kinetics is sensibly reduced by exposure to a weak field having the frequency fL of Cu2+ ion.Comment: 18 pages, 4 figure

Orbital-dependent electron dynamics in Fe-pnictide superconductors

We report on orbital-dependent quasiparticle dynamics in EuFe$_2$As$_2$, a parent compound of Fe-based superconductors and a novel way to experimentally identify this behavior, using time- and angle-resolved photoelectron spectroscopy across the spin density wave transition. We observe two different relaxation time scales for photo-excited d$_x$$_z$/d$_y$$_z$ and d$_x$$_y$ electrons. While d$_x$$_z$/d$_y$$_z$ electrons relax faster through the electron-electron scattering channel, showing an itinerant character, d$_x$$_y$ electrons form a quasi-equilibrium state with the lattice due to their localized character, and the state decays slowly. Our findings suggest that electron correlation in Fe-pnictides is an important property, which should be taken into careful account when describing the electronic properties of both parent and electron-doped compounds, and therefore establish a strong connection with cuprates