Stripe antiferromagnetic correlations in LaFeAsO1-xFx probed by 75As NMR

The anisotropy of the nuclear spin-lattice relaxation rate $1/T_{1}$ of $^{75}$As was investigated in the iron-based superconductor LaFeAs(O$_{1-x}$F$_{x}$) ($x = 0.07, 0.11$ and 0.14) as well as LaFeAsO. While the temperature dependence of the normal-state $1/T_1T$ in the superconducting (SC) $x = 0.07$ is different from that in the SC $x = 0.11$, their anisotropy of $1/T_1$, $R \equiv (1/T_{1})_{H \parallel ab}/(1/T_{1})_{H \parallel c}$ in the normal state is almost the same ($\simeq$ 1.5). The observed anisotropy is ascribable to the presence of the local stripe correlations with $Q = (\pi, 0)$ or $(0, \pi)$. In contrast, $1/T_1$ is isotropic and $R$ is approximately 1 in the overdoped $x = 0.14$ sample, where superconductivity is almost suppressed. These results suggest that the presence of the local stripe correlations originating from the nesting between hole and electron Fermi surfaces is linked to high-$T_c$ superconductivity in iron pnictides.Comment: 4 pages, 3 figures, Accepted for publication in Phys. Rev.

^{31}P and ^{75}As NMR evidence for a residual density of states at zero energy in superconducting BaFe_2(As_{0.67}P_{0.33})_2

^{31}P and ^{75}As NMR measurements were performed in superconducting BaFe_2(As_{0.67}P_{0.33})_2 with T_c = 30 K. The nuclear-spin-lattice relaxation rate T_1^{-1} and the Knight shift in the normal state indicate the development of antiferromagnetic fluctuations, and T_1^{-1} in the superconducting (SC) state decreases without a coherence peak just below T_c, as observed in (Ba_{1-x}K_{x})Fe_2As_2. In contrast to other iron arsenide superconductors, the T_1^{-1} \propto T behavior is observed below 4K, indicating the presence of a residual density of states at zero energy. Our results suggest that strikingly different SC gaps appear in BaFe_2(As_{1-x}P_{x})_2 despite a comparable T_c value, an analogous phase diagram, and similar Fermi surfaces to (Ba_{1-x}K_{x})Fe_2As_2.Comment: 4 pages, 5 figure

Implementation of a new composting technology, serial self-turning reactor system, for municipal solid waste management in a small community in Thailand

“Serial Self-turning Reactors” (STR) is an innovative technology, which was developed to be an alternative organicwaste treatment for small communities in Thailand. It is a vertical-flow composting system which consists of a set of aerobicreactors sandwiched with a set of self-turning units. Combination of those components results to a high performance compostingwith capacity flexible. The pilot-scaled prototype of the new technology has been tested to ensure its effectiveness.This paper focuses on the implementation of STR technology. The study consisted of four parts: 1) selection of a targetcommunity and investigation of its current MSW practice, 2) preparation of a proposal which STR incorporated would andsubmit to the university’s administration for approval, 3) establishment of a demonstration plant and trial on actual practice,and 4) discussion and evaluation of the new technology in general and economical aspects. Thammasat University Rangsitcampus was selected to be the target community to approach the new technology. An improvement program, namely“Recycling and Composting Pretreatment Program” (RCPP) was proposed and implemented. Trial operation on plant-scaleperformed effectively with low running costs. An economic evaluation of STR was carried out to generalize the system