Molecular and crystal structure of 4,4,4-trifluoro-3,3-dihydroxy-1-thiophene-2-yl-butane-1-one

An X-ray diffraction analysis and quantum chemical calculations of hydrated 2-thenoyltrifluoroacetone show that the planar diketone, form of TTA found in its metal complexes, does not occur in the free ligand. Hydrated TTA with two geminal hydroxo groups has a non-planar structure stabilized by an intramolecular hydrogen bond.     

Preconcentration of albumin on silica with attached groups of polyoxyethylated isooctyl phenol

The potencies of silica with attached groups of polyoxyethylated isooctyl phenol (SiO ₂ -TX) as an adsorbent for the solid phase extraction (SPE) preconcentration of bovine serum albumin (BSA) in urine are examined. SiO₂-TX is shown to effectively extract BSA (up to 96%) as an ion associate with cationic (at pH 8) and anionic (at pH 1.5) surfactants. The maximal capacity of SiO₂-TX to BSA makes 33 mg/g in the presence of octylpyridinium bromide, 27 mg/g in the presence of cetyltrymethylammonium bromide or sodium dodecylsulfate with the linearity range in Henri’s area up to 23 and 20 mg/g of SiO₂-TX, respectively; the distribution coefficients attain 1.8 × 10³ mL/g. BSA is eluted quantitatively with 1–4 mL of acetonitrile containing NaOH, which makes possible the use of adsorbent for the reaction of protein with trifluoroethanol (TFE) before its photometric determination by the Lowry method. The influence of accompanying urine components is studied, i.e., urea, glucose, Na⁺, K⁺, Mg²⁺, chlorides, and phosphates, on the efficiency BSA extraction from model aqueous solutions on SiO₂-TX. The detection limit for BSA makes 4 mg/L and the analytical range, from 12 to 140 mg/L.     

Does a Form Factor in Smith–Purcell Radiation Exist Always?

JETP Letters - In the theory of radiation emitted by bunches of charged particles, the effects of coherence are commonly taken into account by multiplying the intensity of radiation generated by a...     

New fast and memory-sparing method for rigorous electromagnetic analysis of 2D periodic dielectric structures

A method is presented that performs the exact electromagnetic analysis of 2D periodic dielectric structures of arbitrary profile or index distribution and possibly large period. The generalized source method is used to formulate the problem of light diffraction in the form of a volume integral equation reduced to a linear equation system, which is solvable by known fast algorithms. The calculation time and required memory are linearly proportional to the total number N_o of considered diffraction orders instead of N_o³ typical for conventional methods. Numerical examples are provided to demonstrate the potential of the method for the analysis of complex periodic structures.     

Magnetic structure of low-dimensional LiCu2O2 multiferroic according to 63,65Cu and 7Li NMR studies

The complex NMR study of the magnetic structure of LiCu₂O₂ multiferroic has been performed. It has been shown that the spin spirals in LiCu₂O₂ are beyond the ab, bc, and ac crystallographic planes. The external magnetic field applied along the c axis of the crystal does not change the spatial orientation of spirals in Cu²⁺ chains. A magnetic field of H ₀ = 94 kOe applied along the a and b axes rotates the planes of spin spirals in chains, tending to orient the normal n of spirals along the external magnetic field. The rotation angle of the planes of the magnetic moments are maximal at H ₀ ?? b.     

Computer emulation of the method for comparing the isotopic composition of CO<Subscript>2</Subscript> in gas mixtures based on laser spectral analysis at the 2.05-<Emphasis Type="Italic">µ</Emphasis>m line

An algorithm for processing spectral data in order to determine the isotopic composition of gas mixtures is proposed and simulated using emulated transmission spectra of CO₂ in exhaled air tests. It is shown that the ratio of the optical-density spectra of the analyzed and reference gas mixtures is a contrast spectrum with resonant features and a fixed depth of their amplitude modulation. Based on the simulation results several spectral ranges are found to be optimal for analyzing the relative ¹²CO₂ and ¹³CO₂ contents in exhaled air. The effect of random noise on the isotopic analysis result is estimated, and the correlation between the optical density of analyzed gas media, level of random noise, and sensitivity of isotopic analysis is determined. The use of the algorithm proposed reduces the effect of such noises as interference at optical elements, absorption in open atmosphere, drift of the laser pulse envelope, and disbalance of spectral channels. This algorithm is valid for comparative isotopic analysis of any other gas molecules with similar spectral properties.     

Magnetic structure of the quasi-one-dimensional frustrated antiferromagnet LiCu<Subscript>2</Subscript>O<Subscript>2</Subscript> with Spin <Emphasis Type="Italic">S</Emphasis> = 1/2

The magnetic properties of LiCu₂O₂ single-crystal samples without twinning are investigated using electron spin resonance and nuclear magnetic resonance spectroscopy. The experimental results obtained are described in terms of the model of a planar spiral antiferromagnet for the orientation of the magnetic field H ‖ b or H ‖ c and the model of a collinear spin-modulated antiferromagnet for the orientation of the static magnetic field H ‖ a.