Synthesis of terminally substituted stilbene-tolane liquid crystals

Methods for synthesizing substituted alkyl and fluoro stilbene-tolane (PTPDP) liquid crystal materials are presented. These compounds show a slightly higher birefringence than the analogous bistolanes, but higher melting points and heats of fusion. Potential applications of these compounds for optical communications and displays are discussed.     

PhotochemCAD‡: A Computer-Aided Design and Research Tool in Photochemistry

A database of absorption and fluorescence spectra, including molar absorption coefficients and fluorescence quantum yields, has been compiled for 125 photochemically relevant compounds. An accompanying program enables calculation of oscillator strengths, natural radiative lifetimes, transition dipole moments, Forster energy-transfer rates, multicomponent analysis, simulations of fluorescence spectra upon energy transfer among linear arrays of pigments, calculations of blackbody radiator curves at different temperatures and Lorentzian and Gaussian peak distributions. The program runs under Windows 95 and is equipped with extensive literature references and help features.     

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Reference materials for PCDD and PCDF analysis: production and verification of the contents of twelve congeners in iso-octane reference solutions

Summary The Community Bureau of Reference (BCR) of the Commission of the European Communities has produced standard solutions of PCDDs and PCDFs (dirty dozen) to guarantee proper calibration and traceability of results in the certification of these compounds in matrix materials. The purity of each individual isomer has been evaluated on the initial crystals using several analytical methods. Solvents have been checked for impurities. The entire procedure of preparation of the twelve solutions has been performed under strict metrological conditions and will be published elsewhere. All results and the preparation procedure followed are described. The solutions are not certified, but may be obtained from BCR together with an analytical report.     

Accuracy and precision of a laser-spectroscopy approach to the analysis of δ2H and δ18O in human urine

The isotope ratio analysis of body water often involves large sample numbers and lengthy sample processing. Here we demonstrate the ability of isotope ratio infrared spectroscopy (IRIS) to rapidly and accurately analyse the isotope ratios of water in urine. We analysed water extracted from human urine using traditional isotope ratio mass spectrometry (IRMS) and compared those values with IRIS-analysed extracted water and un-extracted urine. Regression analyses for δ²H and δ¹⁸O values between (1) extracted water analysed via IRMS and IRIS and (2) urine and extracted water analysed via IRIS were significant (R ²=0.99). These results indicate that cryogenic distillation of urine was not required for an accurate estimate of the isotopic composition of urine when using IRIS.     

Convergence of Adaptive Compression Methods for Hartree-Fock-Like Equations

The adaptively compressed exchange (ACE) method provides an efficient way to solve Hartree-Fock-like equations in quantum physics, chemistry, and materials science. The key step of the ACE method is to adaptively compress an operator that is possibly dense and full-rank. In this paper, we present a detailed study of the adaptive compression operation and establish rigorous convergence properties of the adaptive compression method in the context of solving linear eigenvalue problems. Our analysis also elucidates the potential use of the adaptive compression method in a wide range of problems. © 2018 Wiley Periodicals, Inc.