Analysis of organ weight in toxicology studies is an important endpoint for identification of potentially harmful effects of chemicals. Differences in organ weight between treatment groups are often accompanied by differences in body weight between these groups, making interpretation of organ weight differences more difficult. Using data from control rats that were part of 26 toxicity studies conducted under similar conditions, we have evaluated the relationship between organ weight and body/brain weight to determine which endpoint (organ weight, organ-to-body weight ratio, or organ-to-brain weight ratio) is likely to accurately detect target organ toxicity. This evaluation has shown that analysis of organ-to-body weight ratios is predictive for evaluating liver and thyroid gland weights, and organ-to-brain weight ratios is predictive for evaluating ovary and adrenal gland weights. Brain, heart, kidney, pituitary gland, and testes weights are not modeled well by any of the choices, and alternative analysis methods such as analysis of covariance should be utilized.

The magnetic structure and electronic ground state of the layered perovskite Ba(2)IrO(4) have been investigated using x-ray resonant magnetic scattering. Our results are compared with those for Sr(2)IrO(4), for which we provide supplementary data on its magnetic structure. We find that the dominant, long-range antiferromagnetic order is remarkably similar in the two compounds and that the electronic ground state in Ba(2)IrO(4), deduced from an investigation of the x-ray resonant magnetic scattering L(3)/L(2) intensity ratio, is consistent with a J(eff)=1/2 description. The robustness of these two key electronic properties to the considerable structural differences between the Ba and Sr analogues is discussed in terms of the enhanced role of the spin-orbit interaction in 5d transition metal oxides.

Sr2IrO4 is a prototype of the class of Mott insulators in the strong spin-orbit interaction (SOI) limit described by a Jeff = 1/2 ground state. In Sr2IrO4, the strong SOI is predicted to manifest itself in the locking of the canting of the magnetic moments to the correlated rotation by 11.8(1)° of the oxygen octahedra that characterizes its distorted layered perovskite structure. Using x-ray resonant scattering at the Ir L3 edge we have measured accurately the intensities of Bragg peaks arising from different components of the magnetic structure. From a careful comparison of integrated intensities of peaks due to basal-plane antiferromagnetism, with those due to b-axis ferromagnetism, we deduce a canting of the magnetic moments of 12.2(8)°. We thus confirm that in Sr2IrO4 the magnetic moments rigidly follow the rotation of the oxygen octahedra, indicating that, even in the presence of significant non-cubic structural distortions, it is a close realization of the Jeff = 1/2 state.

Sample characterizationIn this section we show resistivity data measured on the samples we studied. The sample growth technique is described in the Methods section of the main text. Fig. S1 shows the resistivity curves for different dopant concentrations. Note that the rough La concentrations reported in the graph are determined by energy dispersive x--ray spectroscopy (EDX), and this method averages over variations of the doping concentration. We estimate these variations to occur on a length--scale of hundreds of micrometers, and the magnitude to be of the order of a few percentage points. These variations in doping concentrations have to be considered when interpreting resistivity ( Figure S1) and magnetization data of the iridate samples. SUPPLEMENTARY INFORMATION Set--up effect in topographs

We report the first observation of two-dimensional incommensurate magnetic fluctuations in the layered metallic perovskite Sr3Ru2O7. The wavevectors where the magnetic fluctuations are strongest are different from those observed in the superconducting single layer ruthenate Sr2RuO4 and appear to be determined by Fermi surface nesting. No antiferromagnetic ordering is observed for temperatures down to 1.5 K. For temperatures T > ∼ 20 K, the fluctuations become predominately ferromagnetic. Our inelastic neutron scattering measurements provide concrete evidence of the coexistence of competing interactions in Sr3Ru2O7 and of the low energy scale of the fluctuations.78.70. Nx, 75.40.Gb, 74.20.Mn, 75.30.Kz

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We characterize the electron doping evolution of ðSr 1−x La x Þ 3 Ir 2 O 7 by means of angle-resolved photoemission. Concomitant with the metal insulator transition around x ≈ 0.05 we find the emergence of coherent quasiparticle states forming a closed small Fermi surface of volume 3x=2, where x is the independently measured La concentration. The quasiparticle weight Z remains large along the entire Fermi surface, consistent with the moderate renormalization of the low-energy dispersion, and no pseudogap is observed. This indicates a conventional, weakly correlated Fermi liquid state with a momentum independent residue Z ≈ 0. The 5d transition metal iridium oxides may host exotic quantum phases emerging from the interplay of correlations and strong spin-orbit coupling [1,2]. Iridates of the Ruddlesden-Popper series Sr nþ1 Ir n O 3nþ1 share key structural and electronic properties with the parent compounds of copper oxide superconductors [3][4][5] and are thus of particular interest as candidate materials for engineering unconventional superconductivity [6,7]. Despite their partially filled 5d shell with a single hole per Ir in the t 2g manifold, the layered n ¼ 1; 2 members are antiferromagnetic insulators. This has been attributed to a reduced orbital degeneracy and one-electron bandwidth resulting from strong spin-orbit coupling and structural distortions leading to a single, narrow j eff ¼ 1=2 band that is susceptible to the moderate electron correlations in the Ir t 2g shell [3,8,9]. This picture is supported by band structure calculations for single layer Sr 2 IrO 4 . Its low-energy electronic structure can indeed be approximated by a single j eff ¼ 1=2 band, which opens a gap in the presence of electron correlations [10,11]. The resulting insulating state shows in-plane ordered moments and the characteristic spin dynamics of a Heisenberg antiferromagnet with a gapless excitation spectrum [4,5,12,13]