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Pure Material (pure + material)
Selected AbstractsSynthesis of Enantiopure Tricarbonyl(indan-1,2-dione)chromiumEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2005Dirk Leinweber Abstract A multistep synthesis of the planar chiral tricarbonyl(,6 -indan-1,2-dione)chromium, based on acetal protection of the keto groups, is presented. Since common deacetalization procedures failed, an oxidative deprotection with triphenylcarbenium tetrafluoroborate was used. Tricarbonyl(,6 -indan-1,2-dione)chromium is regarded as a potential precursor for dianionic oxy-Cope rearrangements upon alkenyllithium diaddition. As an unexpected side product in the synthesis, an indan-1,2-dione complex with a triphenylmethyl substituent at C-3 was obtained. Attempts directed towards the formation of enantiomerically pure material include the first reported investigation into an enantioselective ketone reduction with two methoxy substituents present in the , position. Although enantiomeric excesses of up to 84.5,% were achieved, the chemical yields decreased with increasing ee. A classical resolution was therefore undertaken, giving access to the enantiomerically pure title compound (99.4,% ee). The absolute configuration was verified by an X-ray structure analysis of an intermediate. First experiments concerning the alkenyllithium addition showed that a single addition is possible while a second one does not occur, presumably due to enolate formation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Beneficial Effects of AlN as Sintering Aid on Microstructure and Mechanical Properties of Hot-pressed ZrB2,ADVANCED ENGINEERING MATERIALS, Issue 7 2003F. Monteverde Higher density of ZrB2 ceramics than with the pure material is achieved when 4.6,% of aluminum nitride are added before hot-pressing as a sintering aid. AlN supports densification and prevents grain coarsening, mainly by virtue of its ability to remove the boron oxide layer that otherwise covers ZrB2 particles. The new material (see Figure for an SEM image of a polished section) has outstanding mechanical properties, e.g. strength values of 600 and 200 MPa at 25 and 1500,°C. [source] Mechanical behavior of recycled reinforced polyamide railway fastenersPOLYMER COMPOSITES, Issue 7 2010José Antonio Casado Modern railway tracks use short-fiber glass reinforced polyamide to inject insulating and mechanically resistant fasteners to connect the rails to the sleepers. Some of this material is later withdrawn, due either to defective production or to breakage in service. The recovery of the material for its later re-use would lead to a great saving, from both an environmental and an economic viewpoint. Mechanical recycling is a simple, economic process that only requires the crushing of the material and its subsequent molding, without the need for any chemical treatments. However, it has some drawbacks; as with any kind of recycling, there is a certain loss of material quality with some degradation of its properties. In this work, the physical and mechanical results for fasteners injected with recycled material are compared to others injected with pure material. The results show that the use of recycled fasteners is limited in-service by working conditions that increase the thermoplastic material temperature above its critical glass transition temperature, Tg. POLYM. COMPOS., 31:1142,1149, 2010. © 2009 Society of Plastics Engineers [source] Chemical study of triterpenoid resinous materials in archaeological findings by means of direct exposure electron ionisation mass spectrometry and gas chromatography/mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 11 2006Francesca Modugno A systematic study of standard triterpenes (, -amyrine, oleanolic acid, betulin, lupeol, betulinic acid and lupenone) and of raw resinous materials (frankincense resin, mastic resin and birch bark pitch) was performed using direct exposure electron ionisation mass spectrometry (DE-MS) and gas chromatography/mass spectrometry (GC/MS). DE-MS provides a mass spectral fingerprint of organic materials in a few minutes which highlights the compounds that are the main components in the sample. The application of principal component analysis (PCA) on DE-MS data in the mass ranges m/z 181,260 and m/z 331,500, corresponding to the fragmentation of triterpenoid molecules, enabled us to distinguish between different triterpenoid materials such as mastic resin, frankincense resin and birch bark pitch, and to graphically plot the resinous substances in three separate clusters, retaining 89% of the total variance. GC/MS analysis of the same materials has permitted us to elucidate in detail the molecular composition and to identify minor components and species that act as markers of the degradation undergone by the materials. The paper also reports the results for the organic residues contained in an Egyptian censer (5th,7th century AD) which was recovered in the excavation of the Necropolis of Antinoe (Egypt), and for the hafting material found on a Palaeolithic tool recovered at the site of Campitello (Arezzo, Tuscany), dating back to the Mid-Pleistocene period. Although DE-MS was found to be a fast analytical tool, it failed to give any information on the presence of less abundant compounds when applied to mixtures of different materials: only mastic resin was found in the residues from the Roman censer, whereas GC/MS analysis identified the presence of a vegetable oil from Brassicaceae seeds and Pinaceae resin. Birch bark pitch as a pure material was identified in the sample from the Palaeolithic flint flake using both procedures. Copyright © 2006 John Wiley & Sons, Ltd. [source] Effect of Volume Fraction of Material on Separation by Density Difference in a Liquid-Fluidized Bed of Inert ParticlesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2010Y. Tatemoto Abstract A liquid-fluidized bed was used to separate a pure material from a mixture. A quantity of relatively large sized material was immersed in an inert-particle fluidized bed and the behavior of materials was examined for different liquid velocities. In particular, the volume fraction of the material was varied and its effect on the separation characteristics was examined. The material floats on the inert-particle fluidized bed when the density of the material is lower than the apparent density of the bed, regardless of the volume fraction of the material. The apparent density of the bed can be adjusted by changing the liquid velocity. The materials in the upper portion of the bed affect the properties of the bed below them, i.e., the void fraction decreases and the apparent density increases in the inert-particle suspension when materials are present in the upper portion of the bed. Therefore, the materials float on the bed although the apparent density of the inert-particle suspension obtained from the case without material is less than the density of the material at a relatively high volume fraction of material. This phenomenon occurs more easily for lighter and smaller materials. This means that small inert particles and low liquid velocities are the optimum operating conditions for the separation. [source] Multi-Input/Multi-Output Molecular Response System Based on the Dynamic Redox Behavior of 3,3,4,4-Tetraaryldihydro[5]helicene Derivatives: Reversible Formation/Destruction of Chiral Fluorophore and Modulation of Chiroptical Properties by Solvent PolarityCHEMISTRY - A EUROPEAN JOURNAL, Issue 37 2009Takanori Suzuki Prof. Abstract 3,3,4,4-Tetaaryldihydro[5]helicenes (1) and 1,1,-binaphthyl-2,2,-diylbis(diarylcarbenium)s (22+) can be reversibly interconverted upon electron transfer, which is accompanied by a vivid color change (electrochromism) as well as by the formation/cleavage of a CC bond ("dynamic redox behavior"). Because only the neutral donor 1 exhibits strong fluorescence, electrochemical input can further modify the fluorescent properties of the pair. Due to the configurational stability of the helicity in 1 and axial chirality in 22+, the redox reaction of optically pure material proceeds stereospecifically, which induces a chiroptical change such as circular dichroism (CD) as an additional output. The CD spectra of dications 22+ exhibit solvent dependency (chiro-solvatochromism), which is accompanied by solvatochromic behavior based on the ,,, interaction of the two cationic chromophores as well as coordinative interaction of the Lewis basic solvent to the Lewis acidic triarylcarbenium moieties. Thus, the present system is endowed with multi-input functionality for modifying multiple output signals. [source] A simple method for compressible multiphase mixtures and interfacesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 2 2003Nikolai Andrianov Abstract We develop a Godunov-type scheme for a non-conservative, unconditional hyperbolic multiphase model. It involves a set of seven partial differential equations and has the ability to solve interface problems between pure materials as well as compressible multiphase mixtures with two velocities and non-equilibrium thermodynamics (two pressures, two temperatures, two densities, etc.).Its numerical resolution poses several difficulties. The model possesses a large number of acoustic and convective waves (seven waves) and it is not easy to upwind all these waves accurately and simply. Also, the system is non-conservative, and the numerical approximations of the corresponding terms need to be provided. In this paper, we focus on a method, based on a characteristic decomposition which solves these problems in a simple way and with good accuracy. The robustness, accuracy and versatility of the method is clearly demonstrated on several test problems with exact solutions. Copyright © 2003 John Wiley & Sons, Ltd. [source] 31P Solid state NMR study of structure and chemical stability of dichlorotriphenylphosphoraneMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2009Nina C. Gonnella Abstract Solid state 31P NMR spectroscopy was used to examine, monitor and quantify the compound integrity of the chemical reagent dichlorotriphenylphosphorane. Comparison was also made with solution 31P NMR spectra which showed that this highly reactive species could be observed in dry benzene prior to conversion to the hydrolyzed product. This is the first reported solid state NMR study of the stability and reactivity of dichlorotriphenylphosphorane and the first account of its observation and comparison in the solution state. In the solid state, the ionic and covalent forms for dichlorotriphenylphosphorane were observed along with hydrolyzed products, however, the degree of hydrolysis was dependent upon the rotor packing conditions. Calculation of the relative percent composition of dichlorotriphenylphosphorane with hydrolyzed product was made for samples prepared in air versus under nitrogen atmosphere. This information was critical in adjusting the amount of reagent used in chemical development syntheses and scale up laboratories. All hydrolyzed products were identified, based upon chemical comparisons with spectra of pure materials. Copyright © 2009 John Wiley & Sons, Ltd. [source] Review: Biological effects of organic arsenic compounds in seafood,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2002Teruaki Sakurai Abstract This review describes the results of our recent experiments concerning the in vitro biological effects of water-soluble organic arsenic compounds contained in seafood in murine immune effector cells using synthetic pure materials. A dimethyl organic arsenic compound in seaweed, viz. an arsenosugar, was weakly cytotoxic in murine alveolar macrophages during a 72,h incubation (50% lethal concentration in vitro, LC50,=,8,mmol,dm,3); conversely, it increased the cell viability of peritoneal macrophages at an optimal dose of 5,mmol,dm,3. Trimethyl arsenic compounds in marine animals, arsenocholine and arsenobetaine, were less toxic in murine splenocytes, thymocytes, Peyer's patch lymphocytes, peritoneal macrophages and alveolar macrophages in vitro, even over 10,mmol,dm,3. Interestingly, they significantly increased the cell viability of immature bone marrow cells at doses over 100,µmol dm,3, and induced the maturation of bone marrow cells especially into granulocytes. The tetramethyl arsenic compound, tetramethylarsonium hydroxide, isolated from some lower marine animals had no in vitro cytolethality on murine immune effector cells. Taken together, organic arsenic compounds in seafood are not very toxic in living systems. Copyright © 2002 John Wiley & Sons, Ltd. [source] High-performance liquid chromatography separation of enantiomers of mandelic acid and its analogs on a chiral stationary phaseCHIRALITY, Issue 5 2010Ritu Aneja Abstract The enantiomers of mandelic acid and its analogs have been chromatographically separated on a chiral stationary phase (CSP) derived from 4-(3,5-dinitrobenzamido) tetrahydrophenanthrene. The rationale of separations of these compounds is discussed with respect to the method development for determining enantiomeric purity and possibility of obtaining enantiomerically pure materials by high-pressure liquid chromatography. The relationship of analyte structure to the extent of enantiomeric separation has been examined and separation factors (,) are presented for various groups of structurally related compounds. Chiral recognition models have been suggested to account for the observed separations. These models provide mechanistic insights into the chiral recognition process. Chirality 2010. © 2009 Wiley-Liss, Inc. [source] | |||||||||||||