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Spectral Characterization (spectral + characterization)
Selected AbstractsChemInform Abstract: Synthesis and Spectral Characterization of a Novel Series of Methylcinnamate Derivatives of 15-Crown-5.CHEMINFORM, Issue 41 2009Cihan Guenduez Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Two-Dye Core/Shell Zeolite Nanoparticles: A New Tool for Ratiometric pH MeasurementsADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Tristan Doussineau Abstract The preparation of core/shell nanoparticles that enable ratiometric pH measurement is described. The core of the nanoparticles consists of a zeolite- , matrix that exhibits a 3-hydroxyflavone reference dye within the porous network. Coating an amorphous silica shell containing a fluorosensor around the zeolite through the Stöber process provides pH sensitivity to the nanoparticles. Morphological characterization (dynamic light scattering, transmission electronic microscopy) demonstrates the control of the sensing silica shell around the zeolite cores, leading to highly monodisperse spherical nanoparticles, while structural characterization (wide-angle X-ray diffraction, nitrogen adsorption) shows the amorphous character of the shell. Spectral characterization via UV/Vis absorption and steady-state fluorescence shows good pH sensitivity of the resulting nanosensors with a pKa suitable for bioanalytical applications. [source] Spectral characterization of lysozyme adsorption on dye-affinity beadsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Nilgün Basar Abstract Cibacron Blue F3GA-attached magnetic poly(2-hydroxyethyl methacrylate) [mPHEMA] beads were prepared by suspension polymerization of HEMA in the presence of magnetite (Fe3O4) nanopowder. Average diameter size of the mPHEMA beads was 150,200 ,m. The characteristic functional groups of Cibacron Blue F3GA-attached mPHEMA beads were analyzed by Fourier transform infrared spectrometer (FTIR) and Raman scattering spectrometer. The lysozyme adsorption and desorption characteristics of Cibacron Blue F3GA-attached mPHEMA beads were also investigated using FTIR and Raman spectroscopic techniques. When the Raman spectrum of lysozyme adsorbed mPHEMA is evaluated characteristic Amide-I band appears at 1657 cm,1. The intensity of this band decreases in the spectrum of lysozyme desorbed mPHEMA sample. When the characteristic bands of lysozyme adsorbed and desorbed mPHEMA samples are compared, the band intensities of desorbed sample are lower than those of lysozyme adsorbed sample except for the band appearing at 656 cm,1 (Tyr vCS). © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Spectral characterization of static mixers.AICHE JOURNAL, Issue 2 2010The S-shaped micromixer as a case study Abstract We investigate the steady-state performance of a planar micromixer composed of several S-shaped units. Mixing efficiency is quantified by the decay of the scalar variance downstream the device for generic feeding conditions. We discuss how this decay is controlled by the spectral properties of the advection-diffusion Floquet operator, , that maps a generic scalar profile at the inlet of a single unit into the corresponding profile at the unit outlet section. Two advantages characterize the Floquet operator approach ,(i) it allows to analyze an arbitrarily long device and (ii) it provides a quantitative assessment of mixing efficiency that is independent of the feeding conditions and that depends solely on the interaction between advection and diffusion. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Biological hydroperoxides and singlet molecular oxygen generationIUBMB LIFE, Issue 4-5 2007Sayuri Miyamoto Abstract The decomposition of lipid hydroperoxides (LOOH) into peroxyl radicals is a potential source of singlet molecular oxygen (1O2) in biological systems. Recently, we have clearly demonstrated the generation of 1O2 in the reaction of lipid hydroperoxides with biologically important oxidants such as metal ions, peroxynitrite and hypochlorous acid. The approach used to unequivocally demonstrate the generation of 1O2 in these reactions was the use of an isotopic labeled hydroperoxide, the 18O-labeled linoleic acid hydroperoxide, the detection of labeled compounds by HPLC coupled to tandem mass spectrometry (HPLC-MS/MS) and the direct spectroscopic detection and characterization of 1O2 light emission. Using this approach we have observed the formation of 18O-labeled 1O2 by chemical trapping of 1O2 with anthracene derivatives and detection of the corresponding labeled endoperoxide by HPLC-MS/MS. The generation of 1O2 was also demonstrated by direct spectral characterization of 1O2 monomol light emission in the near-infrared region (, = 1270 nm). In summary, our studies demonstrated that LOOH can originate 1O2. The experimental evidences indicate that 1O2 is generated at a yield close to 10% by the Russell mechanism, where a linear tetraoxide intermediate is formed in the combination of two peroxyl radicals. In addition to LOOH, other biological hydroperoxides, including hydroperoxides formed in proteins and nucleic acids, may also participate in reactions leading to the generation 1O2. This hypothesis is currently being investigated in our laboratory. [source] Electrospray and matrix-assisted laser desorption/ionization mass spectral characterization of linear single nylon-6 oligomersJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2001Lu Shan Abstract Synthetic nylon-6 single molecular mass oligomers were studied by matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) mass spectrometry. These oligomers, considered as model compounds for the study of nylon-6 polymers, gave good mass spectrometric results using both MALDI and ESI. In spite of the gentle nature of both techniques, the MALDI and ESI spectra showed evidence of end-group cleavage from the oligomer chains. MALDI-MS was found to give similar fragmentation patterns for all of the oligomer samples. An increase in doubly charged ion signals with increasing oligomer mass was observed in the ESI mass spectra, as was end-group fragmentation. Signals from oligomer clusters were observed in ESI-MS for the dimer, tetramer and hexamer, most likely due to non-covalent bonding among the low-mass oligomer molecules. Copyright © 2001 John Wiley & Sons, Ltd. [source] Simulation of Real-Valued Discrete-Time Periodically Correlated Gaussian Processes with Prescribed Spectral Density MatricesJOURNAL OF TIME SERIES ANALYSIS, Issue 2 2007A. R. Soltani Abstract., In this article, we provide a spectral characterization for a real-valued discrete-time periodically correlated process, and then proceed on to establish a simulation procedure to simulate such a Gaussian process for a given spectral density. We also prove that the simulated process, at each time index, converges to the actual process in the mean square. [source] Mass spectral characterization of phloroglucinol derivatives hyperforin and adhyperforinRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2006Lekha Sleno Active phloroglucinol constituents of Hypericum perforatum (St. John's wort) extracts, hyperforin and adhyperforin, have been studied following ion activation using tandem mass spectrometry (MS/MS) and complemented by accurate mass measurements. These two compounds were readily analyzed as protonated and deprotonated molecules with electrospray ionization. MS/MS and MS3 data from a quadrupole-linear ion trap tandem mass spectrometer were employed to elucidate fragmentation pathways. Fourier transform ion cyclotron resonance measurements afforded excellent mass accuracies for the confirmation of elemental formulae of product ions formed via infrared multiphoton dissociation and sustained off-resonance irradiation collision-induced dissociation. Fragmentation schemes have been devised for the dissociation of hyperforin and adhyperforin in negative and positive ion modes. This information is expected to be especially valuable for the characterization of related compounds, such as degradation products, metabolites and novel synthetic analogs of hyperforin. Copyright © 2006 John Wiley & Sons, Ltd. [source] Modulation of Spectrokinetic Properties of o -Quinonoid Reactive Intermediates by Electronic Factors: Time-Resolved Laser Flash and Steady-State Photolysis Investigations of Photochromic 6- and 7-ArylchromenesCHEMISTRY - A EUROPEAN JOURNAL, Issue 17 2009Jarugu, Narasimha Moorthy Prof. Abstract A variety of differently substituted 6- and 7-arylchromenes such as that depicted undergo photoinduced CO bond cleavage to yield colored o -quinonoid intermediates. A combined analysis of ,s,ms (laser flash) and real-time kinetic data show that the o -quinonoid intermediates decay faster when the C2-aryl and C6-/C7-aryl rings contain electron-donating and electron-accepting groups, respectively. Similarly, the decay occurs slowly for the reversed scenario, while intermediate decay rates are observed when both substituents are electron donating. A ready synthetic accessibility of a series of 6- and 7-arylchromenes via Pd0 -catalyzed Suzuki coupling protocol has permitted a comprehensive investigation of the thermal decay behavior of a broad set of photogenerated o -quinonoid reactive intermediates. It is shown that substantial mesomeric effect between the benzopyran nucleus and the aryl ring at C6 or C7 position of the former renders significant absorption beyond 350,nm such that they are readily photoactivated to yield colored o -quinonoid intermediates. The absorption spectra of the latter are found to be strongly influenced by the substituents on C2-, C6- and C7-aryl rings; indeed the colored absorptions can be conveniently tuned by appropriate choice of substituents. The thermal decay (bleaching phenomenon), which is important from the point of view of their application in ophthalmic lenses, was investigated in each case by ,s,ms as well as real-time absorption spectroscopy. By careful experimentation, we have extracted the decay rate constants for Z,E and E,E o -quinonoid isomers of all 6- and 7-arylchromenes in an attempt to establish a correlation between the electronic attributes with their thermokinetic behavior. From a combined analysis of ,s,ms (laser flash) and real-time kinetic data, it is shown that the colored o -quinonoid intermediates decay faster when the C2-aryl and C6-/C7-aryl rings contain electron-donating and electron-accepting groups, respectively. In the same vein, the decay was found to occur slowly for the reversed scenario, while intermediate decay rates are observed when both substituents are electron-donating. Thus, any substituent on the C2-aryl ring that contributes mesomerically to the development of charge on the quinonoid oxygen, and any substituent on the C6-/C7-aryl ring that exerts ,I effect appear to expedite thermal decay. Furthermore, evidence is obtained for the first time from ,s time-resolved laser-flash spectroscopy for the formation and characterization of the trans,cis (E,Z) o -quinonoid isomer, which has heretofore eluded spectral characterization in the photochromic phenomena of pyrans. [source] | |||||||||||||