Magnetic excitation spectra of Sr2IrO4 probed by resonant inelastic x-ray scattering: establishing links to cuprate superconductors

We used resonant inelastic x-ray scattering to reveal the nature of magnetic interactions in Sr2IrO4, a 5d transition-metal oxide with a spin-orbit entangled ground state and J(eff)=1/2 magnetic moments. The magnon dispersion in Sr2IrO4 is well-described by an antiferromagnetic Heisenberg model with an effective spin one-half on a square lattice, which renders the low-energy effective physics of Sr2IrO4 much akin to that in superconducting cuprates. This point is further supported by the observation of exciton modes in Sr2IrO4, whose dispersion is strongly renormalized by magnons, which can be understood by analogy to hole propagation in the background of antiferromagnetically ordered spins in the cuprates.     

Single-molecule surface-enhanced Raman scattering: Current status and future perspective

The single-molecule surface-enhanced Raman scattering （smSERS） has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application.     

Performance of a collimating L‐shaped laterally graded multilayer mirror for the IXS analyzer system at NSLS‐II

The L‐shaped laterally graded multilayer mirror is a vital part of the ultrahigh‐energy and momentum‐resolution inelastic X‐ray scattering spectrometer at the National Synchrotron Light Source II. This mirror was designed and implemented as a two‐dimensional collimating optic for the analyzer system. Its performance was characterized using a secondary large‐divergence source at the 30‐ID beamline of the Advanced Photon Source, which yielded an integrated reflectivity of 47% and a collimated beam divergence of 78 µrad with a source size of 10 µm. Numerical simulations of the mirror performance in tandem with the analyzer crystal optics provided details on the acceptance sample volume in forward scattering and defined the technical requirements on the mirror stability and positioning precision. It was shown that the mirror spatial and angular stability must be in the range <8.4 µm and <21.4 µrad, respectively, for reliable operation of the analyzer.     

Magnetic resonance imaging features in melanoma

T1 and T2 relaxation time shortening secondary to paramagnetic compounds has been described in melanoma. The purpose of this paper is to evaluate the signal behavior of melanoma involved in various body areas using short TR, TE and long TR, TE sequences. Twenty-seven sites of melanoma were evaluated with MR using T1 weighted and T2-weighted techniques. Using fat and muscle signal intensities as references tissues, lesions were graded into high, low or intermediate intensity categories for each of the sequences. Four signal patterns emerged. The typical pattern characterized by high signal on T1-weighted images and low signal on T2-weighted images reflected T1 and T2 shortening. The other pattern categories comprised of lesions demonstrating low signal T1-weighted images and high signal on T2-weighted images, high signal on both T1- and T2-weighted images and lesions showing intermediate signal on either T1- or T2-weighted images. We observed a tendency away from the typical signal pattern in extraocular melanoma cases with only one of 14 demonstrating this pattern. Moreover, only seven of thirteen ocular melanomas exhibited such behavior. Possible explanations for this findings as well as the existence of a variety of MR appearances to melanoma are offered. We conclude that while signal patterns showing T1 and T2 shortening are typical of melanoma, the absence of these does not exclude the diagnosis.     

The Synthesis of (±)-α-Vetispirene Via the Dieckmann Condensation of Ethyl 4-(2,6-Dimethyl-1-Carbethoxycyclohex-2-Enyl)-Butyrate

A new process for the synthesis of (±)-α-vetispirene ( 1 ) starting from 2,4-dimethyl-3-carbethaxycyclohexene ( 2 ) is described. The key steps include the stereoselective alkylation of 2 with ethyl 4-bromo-butyrate to yield ethyl 4-(2,6-dimethyl-1-carbethoxycyctohex-2-enyl)-bytyrate ( 3 ) and spiroannulation of 3 by Dieckmann condensation to give 2-carbethoxy-6,10-dimethyl spiro[4,5] deca-6-en-1-one ( 4 ).     

Fragmentation of α-Acetoximino Ketoesters in Polyphosphoric Acid

Fragmentations of various α-acetoximino ketoesters in neat polyphosphoric acid medium to form acylium ions were studied. The resulting acylium ions were trapped by benzene rings either intermolecularly or intramolecularly.     

Analysis of pipecolic acid in biological fluids using capillary gas chromatography with electron-capture detection and [2H11]pipecolic acid as internal standard.

A sensitive and accurate stable isotope dilution assay was developed for the measurement of pipecolic acid in body fluids using capillary gas chromatography with electron-capture detection. The method utilizes [2H11]pipecolic acid as the internal standard. Sample preparation consisted of derivatization in aqueous solution (pH 11.5) of the amine moiety with methyl chloroformate to the N-methylcarbamate, followed by acidic ethyl acetate extraction at pH less than or equal to 2 and further derivatization of the carboxyl moiety with pentafluorobenzyl bromide, the excess of which was removed by solid-phase extraction. Control values have been determined in the plasma of at-term infants, age greater than 1 week (n = 21, mean = 1.36 microM, range = 0.47-3.27 microM). The utility of the method was demonstrated by quantitating pipecolic acid in biological fluids derived from patients with peroxisomal disorders. The method was validated against an established electron-capture negative ion mass fragmentographic technique.     

The Decarboxylation and Dimerization Product of 1-Methylindole-3-Fumaric Acid-2,4-Bis-(1-Methylindol-3-YL)-2-Methyl-γ-Butyrolactone-4-Carboxylic Acid

The decarboxylation and dimerization product of 1-methylindole-3-fumaric acid was elucidated as 2, 4-bis-(1-methylindol-3-yl)-2-methyl-γ-butyrolactone-4-carboxylic acid. Some of its derivatives were also prepared.     

Preparation of 3,4,5,3′-Tetramethoxy-4′,5′-Methylenedioxybenzophenone and Bis-(3-Methoxy-4,5-Methylenedioxy)-Benzophenone

The preparation of 3,4,5,3′-tetramethoxy-4′,5′-methylenedioxybenzophenone (I) and bis-(3-methoxy-4,5-methylenedioxy)-benzophenone(II) were reported. The synthesis of these compounds were accomplished using two separate synthetic routes starting from gallic add and its derivatives to the corresponding benzils. Both compound I and II were obtained by benzilic acid rearrangement of the benzils and followed by an oxidative decarboxylation.