Parity violation in the 17/2−–17/2+ doublet in93Tc

The parity-violating mixing of the 17/2^– and 17/2⁺ levels in⁹³Tc nuclei, polarized by the tilted multifoil interaction, was measured by the observation of the forward-backward-ray asymmetry. The nuclear polarization, induced by the tilted multifoils, was measured directly for the neighboring^88,90Zr isomers. The forward to backward asymmetry was determined to be A=(2.5±2.1) 10^–3 which implies a parity violating matrix element ¦H _PV )¦=(4.0±3.7)meV.     

Solid-phase extraction and HPLC determination of 4-vinyl guaiacol and its precursor, ferulic acid, in orange juice.

This study is undertaken to develop a simplified, rapid method to determine both immediate and potential off odors due to 4-vinyl guaiacol and its odorless precursor, ferulic acid, from a single sample preparation and chromatographic analysis. Orange juice sample preparation consists of a simple, C18 solid phase extraction. Utilizing a 5-microns, 25-cm, C18 column, both compounds can be separated within 40 min using a one-step, linear gradient beginning with an aqueous 12% tetrahydrofuran (THF)-5% acetonitrile mixture and ending with 35% aqueous THF. Hesperidin and nariutin have been identified as the compounds that interfered with the ultraviolet (UV) determination of sinapic and caffeic acids. Fluorescence detection with wavelength programming offers optimal sensitivity and selectivity. Recoveries of 4-vinyl guaiacol and ferulic acid range from 90 to 103%. Detection limits are 1 ppm and 5 ppm for ferulic acid and 4-vinyl guaiacol, respectively. Other hydroxycinnamic acids such as coumaric, sinapic, and caffeic acids may also be determined from the same chromatogram.     

The structure of pediculidine

Summary A new alkaloid pediculidine, C₁₀H₉NO, mp 74–75°C, has been isolated from the ethereal fraction of the combined alkaloids ofP. olgae. Structure (I) has been proposed for the new alkaloid on the basis of its UV, IR, NMR, and mass spectra.Order of the Red Banner of Labor Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 304–306, May–June, 1971.     

Exceptionally Plastic/Elastic Organic Crystals of a Naphthalidenimine-Boron Complex Show Flexible Optical Waveguide Properties

The design of molecular compounds that exhibit flexibility is an emerging area of research. Although a fair amount of success has been achieved in the design of plastic or elastic crystals, realizing multidimensional plastic and elastic bending remains challenging. We report herein a naphthalidenimine–boron complex that showed size-dependent dual mechanical bending behavior whereas its parent Schiff base was brittle. Detailed crystallographic and spectroscopic analysis revealed the importance of boron in imparting the interesting mechanical properties. Furthermore, the luminescence of the molecule was turned-on subsequent to boron complexation, thereby allowing it to be explored for multimode optical waveguide applications. Our in-depth study of the size-dependent plastic and elastic bending of the crystals thus provides important insights in molecular engineering and could act as a platform for the development of future smart flexible materials for optoelectronic applications.     

Numerical comparison of methods for solving second-order ordinary initial value problems

In this paper, we apply Adomian decomposition method (shortly, ADM) to develop a fast and accurate algorithm of a special second-order ordinary initial value problems. The ADM does not require discretization and consequently of massive computations. This paper is particularly concerned with the ADM and the results obtained are compared with previously known results using the Quintic C²-spline integration methods. The numerical results demonstrate that the ADM is relatively accurate and easily implemented.     

Influence of fullerene C60 on the structure and mechanical properties of polyethylene

Influence of fullerene C₆₀ on the structure and mechanical properties of low-density polyethylene samples cast from a melt and a solution was studied.     

Structure,mechanical, and tribological characteristics of polyurethane modified with nanodiamonds

The effect of modifying additives based on detonation nanodiamonds on the tribological characteristics of polyurethane rubber is studied. Introduction of modifying additives based on detonation nanodiamonds (0.5 wt %) leads to a marked improvement in the antifriction and wear-resistance characteristics under conditions of boundary sliding friction for steel and for lubrication with water. The attained tribological characteristics (total energy loss for friction, weight loss of polymer during tribological contact, maximum admissible working pressure) are well (∼300%) above the corresponding characteristics of foreign analogs. Changes in the tribological characteristics of the formed nanocomposite material are observed, but the elastic and strength characteristics remain unchanged.     

Inverse problem of determining the kernel in an integro-differential equation of parabolic type

We study the inverse problem of determining the multidimensional kernel of the integral term in a parabolic equation of second order. As additional information, the solution of the direct problem is given on the hyperplane x _n = 0. We prove a local existence and uniqueness theorem for the inverse problem.     

Synthesis of a C-2 Stapled Bis-Lexitropsin

Summary. A convenient synthesis method was developed for the preparation of C-stapled homodimeric bis-lexitropsins connected through the nitrogen atoms of the central pyrrole ring with a bis-methylene linker. This lexitropsin is designed as a standard for other bis-lexitropsins with longer chains in biological evaluation and NMR studies. The key step in this method is the treatment of ethyl 4-nitropyrrole-2-carboxylate with flame-dried potassium carbonate in DMF followed by the addition of 1,2-dibromoethane to form the 1,2-dipyrroloethane derivative.     

Detection of incipient gear failures using statistical techniques

Gears are important components in most power transmission mechanisms.Failures of gears can cause heavy losses in industry. Conditionmonitoring and fault diagnosis of gears is therefore importantto improve safety and reliability of gearbox operations andreduce losses caused by gear failures. This research proposesa new diagnostic approach based on the statistical analysisof data. It investigates the use of Principal Components Analysis(PCA) to detect growing local faults in a two-stage industrialhelical gearbox. In this research, the vibration signal is usedto monitor fault conditions and a broken tooth is simulatedas a local fault. Since the early detection of faults is a challenge,small fault conditions were tested first as well as severe faultconditions. In order to examine the ability of the PCA to detectfault conditions, first the PCA-based model was created fornormal operating conditions. Any unexpected event such as afault condition causes a significant deviation from the PCAmodel, which is obtained from the normal condition data of thegearbox. The Square Prediction Error (SPE) was calculated todetect the fault conditions. When the vibration signal fromthe gearbox is representative of normal operation, the valueof the SPE shows very little fluctuation and remains under acertain threshold value. However, in the presence of the faultthe SPE fluctuates considerably beyond the threshold value.It is shown that the PCA-based statistical approach cannot onlybe used to detect severe fault conditions, but that it alsoreveals small growing fault conditions at very early stage.The technique also provides information about the state of thefault such as the location of the fault as well as its severity. Received 5 March 2001. Revised 12 December 2001. Accepted 17 January 2002.