Synthesis and structural characterization of 2Dioxane.2H2O.CuCl2: metal-organic compound with Heisenberg antiferromagnetic S=1/2 chains

A novel organometallic compound 2Dioxane.CuCl2.2H2O has been synthesized and structurally characterized by X-ray crystallography. Magnetic susceptibility and zero-field inelastic neutron scattering have also been used to study its magnetic properties. It turns out that this material is a weakly coupled one-dimensional S=1/2 Heisenberg antiferromagnetic chain system with chain direction along the crystallographic c axis and the nearest-neighbor intra-chain exchange constant J=0.85(4) meV. The next-nearest-neighbor inter-chain exchange constant J' is also estimated to be 0.05 meV. The observed magnetic excitation spectrum from inelastic neutron scattering is in excellent agreement with numerical calculations based on the Muller ansatz.Comment: 4 pages; 5 figure

Genomic variations associated with attenuation in Mycobacterium avium subsp paratuberculosis vaccine strains

BACKGROUND: Mycobacterium avium subspecies paratuberculosis (MAP) whole cell vaccines have been widely used tools in the control of Johne's disease in animals despite being unable to provide complete protection. Current vaccine strains derive from stocks created many decades ago; however their genotypes, underlying mechanisms and relative degree of their attenuation are largely unknown. RESULTS: Using mouse virulence studies we confirm that MAP vaccine strains 316 F, II and 2e have diverse but clearly attenuated survival and persistence characteristics compared with wild type strains. Using a pan genomic microarray we characterise the genomic variations in a panel of vaccine strains sourced from stocks spanning over 40 years of maintenance. We describe multiple genomic variations specific for individual vaccine stocks in both deletion (26-32 Kbp) and tandem duplicated (11-40 Kbp) large variable genomic islands and insertion sequence copy numbers. We show individual differences suitable for diagnostic differentiation between vaccine and wild type genotypes and provide evidence for functionality of some of the deleted MAP-specific genes and their possible relation to attenuation. CONCLUSIONS: This study shows how culture environments have influenced MAP genome diversity resulting in large tandem genomic duplications, deletions and transposable element activity. In combination with classical selective systematic subculture this has led to fixation of specific MAP genomic alterations in some vaccine strain lineages which link the resulting attenuated phenotypes with deficiencies in high reactive oxygen species handling

Coupling Between An Optical Phonon and the Kondo Effect

We explore the ultra-fast optical response of Yb_{14}MnSb_{11}, providing further evidence that this Zintl compound is the first ferromagnetic, under-screened Kondo lattice. These experiments also provide the first demonstration of coupling between an optical phonon mode and the Kondo effect.Comment: 4 Pages, 3 Figures, submitted to Phys. Rev. Let

Low-lying optical phonon modes in the filled skutterudite CeRu4Sb12

The phonon dynamics of filled skutterudite CeRu4Sb12 have been studied at room temperature by inelastic neutron scattering. Optical phonons associated with a large vibration of Ce atoms are observed at a relatively low energy of E = 6 meV, and show anticrossing behavior with acoustic phonons. We propose that the origin of the low lattice thermal conductivity in filled skutterudites can be attributed to intensive Umklapp scattering originating from low-lying optical phonons. By an analysis based on a Born-von Karman force model, the longitudinal force constants of the nearest Ce-Sb and Ce-Ru pairs are estimated to be 0.025 mdyn/A, while that of the nearest Ru-Sb pair is estimated to be 1.4 mdyn/A, indicating that the Ce atoms are bound very weakly to the surrounding rigid RuSb6-octahedron cages.Comment: 4pages, 5 figures, J. Phys. Soc. Jpn. (2006) in pres

Possible Spin-triplet Superconductivity in NaxCoO2yH2O - 59Co NMR Study

We report 59Co NMR studies on the magnetically oriented powder samples of Co-oxide superconductors NaxCoO2yH2O with Tc ~ 4.7 K. From two-dimensional powder pattern in the NMR spectrum, the ab-plane Knight shift in the normal state was estimated by the magnetic field dependence of second-order quadrupole shifts at various temperatures. Below 50 K, the Knight shift shows a Curie-Weiss-like temperature dependence, similarly to the bulk magnetic susceptibility chi. From the analysis of so-called K-chi plot, the spin and the orbital components of K and the positive hyperfine coupling constant were estimated. The onset temperature of superconducting transition in the Knight shift does not change so much in an applied magnetic field up to 7 T, which is consistent with the reported high upper critical field Hc2. The Knight shift at 7 T shows an invariant behavior below Tc. No coherence peak just below Tc was observed in the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1 in both cases of NMR and NQR. We conclude that the invariant behavior of the Knight shift below Tc and unconventional behaviors of 1/T possibly indicate the spin-triplet superconductivity with p- or f-wave symmetry.Comment: 17 pages, 10 figures. Extended versio

Comparisons of reproductive function and fatty acid fillet quality between triploid and diploid farm Atlantic salmon (Salmo salar)

Triploidy could prevent escaped farm salmon breeding in the wild, while also improving nutrient quality within farmed fillets. Despite these potential advantages, triploid Atlantic salmon have not been widely used in aquaculture, and their reproductive function has yet to be fully evaluated. Here, we compare reproductive function and fillet composition between triploid and diploid farm salmon under standard aquaculture rearing conditions. We show that female triploids are sterile and do not develop gonads. By contrast, males produce large numbers of motile spermatozoa capable of fertilizing wild salmon eggs. However, compared with diploids, reproductive development and survival rates of eggs fertilized by triploid males were significantly reduced, with less than 1% of eggs sired by triploid males reaching late-eyed stages of development. Analyses of fillets showed that total lipid and fatty acid quantities were significantly lower in triploid than in diploid Atlantic salmon fillets. However, when fatty acids were normalized to total lipid content, triploid fillets had significantly higher relative levels of important omega-3 long-chain polyunsaturated fatty acids. Our results show that: (i) escaped triploid farm salmon are very unlikely to reproduce in the wild and (ii) if able to match diploid fillet lipid content, triploid farm salmon could achieve better fillet quality in terms of essential fatty acids

Static and Dynamic Magnetism in Underdoped Superconductor BaFe1.92_{1.92}Co0.08_{0.08}As2_2

We report neutron scattering measurements on single crystals of BaFe$_{1.92}$Co$_{0.08}$As$_2$. The magnetic Bragg peak intensity is reduced by 6 % upon cooling through T$_C$. The spin dynamics exhibit a gap of 8 meV with anisotropic three-dimensional (3d) interactions. Below T$_C$ additional intensity appears at an energy of $\sim$4.5(0.5) meV similar to previous observations of a spin resonance in other Fe-based superconductors. No further gapping of the spin excitations is observed below T$_C$ for energies down to 2 meV. These observations suggest the redistribution of spectral weight from the magnetic Bragg position to a spin resonance demonstrating the direct competition between static magnetic order and superconductivity.Comment: 4 pages, 4 figure

Sowing date, transplanting, plant density and nitrogen fertilization affect indigo production from Isatis species in a Mediterranean region of Spain

The increasing interest in natural products from a renewable source has encouraged growers to reintroduce indigo-producing crops into the European agriculture. We studied agronomic conditions (sowing date, plant density, nitrogen fertilization, irrigation rate, seedling transplanting) influencing production of the blue pigment indigo, from Isatis tinctoria and I. indigotica crops in a Mediterranean region of Spain (Valencia). I. tinctoria was more suitable for cultivation in our climate conditions than I. indigotica. Indigo yield from Spanish I. tinctoria trials was greater than in Northern and Central Europe. Furthermore, indigo production was maintained when water and nitrogen supplies were significantly restricted, showing that I. tinctoria is not a high-demanding crop. © 2005 Elsevier B.V. All rights reserved

Fermi surface of the filled-skutterudite superconductor LaRu4P12: A clue to the origin of the metal-insulator transition in PrRu4P12

We report the de Haas-van Alphen (dHvA) effect and magnetoresistance in the filled-skutterudite superconductor LaRu4P12, which is a reference material of PrRu4P12 that exhibits a metal-insulator (M-I) transition at T_MI~60 K. The observed dHvA branches for the main Fermi surface (FS) are well explained by the band-structure calculation, using the full potential linearized augmented-plane-wave method with the local-density approximation, suggesting a nesting instability with q =(1,0,0) in the main multiply connected FS as expected also in PrRu4P12. Observed cyclotron effective masses of (2.6-11.8)m_0, which are roughly twice the calculated masses, indicate the large mass enhancement even in the La-skutterudites. Comparing the FS between LaRu4P12 and PrRu4P12, an essential role of c-f hybridization cooperating with the FS nesting in driving the the M-I transition in PrRu4P12 has been clarified.Comment: Appeared in Physical Review