Flow Injection Analysis of Nitrite Nitrogen in Seawater Introducing Standard Addition Method

A flow injection analysis of nitrite nitrogen (N-NO2-) in the samples which contain relatively high degrees of salt is described. The N-NO2- was optically detected by use of Griess method. Five pseudo-seawater samples containing 40 μg L-1 N-NO2- with 0, 1, 2, 3, or 4% sodium chloride (NaCl) were tested using two quantitative analysis approaches. In an absolute calibration method, approximately 30% of positive errors were found in the presence of NaCl. On the other hand, the errors fell within the range of −2.6 to +7.3% by introducing a standard addition method. The latter method has successfully been applied to the determination of nitrite nitrogen in real seawater and estuary water

Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor

We refined crystal structures of newly found members of the Fe-1111 superconductor family, CaFe\_{1-x}Co\_{x}AsF and SrFe\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12) by powder synchrotron X-ray diffraction analysis. The tetragonal to orthorhombic phase transitions were observed at ~120 K for unsubstituted CaFeAsF and at ~180 K for unsubstituted SrFeAsF, the transition temperatures agreeing with kinks observed in temperature-dependent resistivity curves. Although the transition temperature decreases, the structural phase transitions were observed below 100 K in both samples of x = 0.06, and finally they were suppressed in the doping level of x = 0.12. The refined structures reveal that distortions of the FeAs4 tetrahedron from the regular tetrahedron likely originate from mismatches in atomic radii among the constituent elements. In this system, the enlarged FeAs4 tetrahedron resulting from larger radius of Sr than that of Ca is flattened along a-b plane, whereas the smaller radius of Ca makes the tetrahedron closer to regular one, and their characteristic shapes are further enhanced by Co substitution. These results suggest that the CaFeAsF compound is a promising candidate for higher-Tc superconductor.Comment: 17 pages, 8 figures, 2 tables, Supplementary information is included at the end of the documen

First mesopause temperature measurements using sodium lidar observations in the Antarctic region

The mesopause temperature structure was observed using a sodium temperature lidar system at Syowa Station (69°00\u27 S, 39°35\u27 E), beginning in February 2000. The laser transmitter was newly developed and included two injection-seeded Nd: YAG lasers. Regular observations were performed using the two-frequency technique as demonstrated by C.Y. She et al. (Geophys. Res. Lett., 17, 929, 1990), with a spatial resolution of about 1 km and a temporal resolution of 6 min. The temperature structures of the 85km to 105km region of the upper atmosphere were measured by Na D_2 Doppler profile-fitting as well as the two-frequency technique. Temperatures derived from the two techniques agreed well and were consistent with the MSIS 90 model temperature structure. Night-time temperature variations over a 15-hour period were measured in May 2000. A large temperature fluctuation with an interval of about 4 hours, and an amplitude of 60 K (probably caused by gravity waves) was observed. From the average night temperature profile, the mesopause was determined to be located at 102km, and have a temperature of 180K. These values are similar to winter values observed in the northern hemisphere

Electronic and Magnetic Phase Diagram of a Superconductor, SmFeAsO1-xFx

A crystallographic and magnetic phase diagram of SmFeAsO1-xFx is determined as a function of x in terms of temperature based on electrical transport and magnetization, synchrotron powder x-ray diffraction, 57Fe Mossbauer spectra (MS), and 149Sm nuclear resonant forward scattering (NRFS) measurements. MS revealed that the magnetic moments of Fe were aligned antiferromagnetically at ~144 K (TN(Fe)). The magnetic moment of Fe (MFe) is estimated to be 0.34 myuB/Fe at 4.2 K for undoped SmFeAsO; MFe is quenched in superconducting F-doped SmFeAsO. 149Sm NRFS spectra revealed that the magnetic moments of Sm start to order antiferromagnetically at 5.6 K (undoped) and 4.4 K (TN(Sm)) (x = 0.069). Results clearly indicate that the antiferromagnetic Sm sublattice coexists with the superconducting phase in SmFeAsO1-xFx below TN(Sm), while antiferromagnetic Fe sublattice does not coexist with the superconducting phase.Comment: Accepted in New Journal of Physic