Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Spectra

  • ESI-M spectrum
  • EXAF spectrum
  • SER spectrum
  • UV-Vi spectrum
  • UV-vi spectrum
  • XA spectrum
  • XANE spectrum
  • absorbance spectrum
  • absorption spectrum
  • action spectrum
  • age spectrum
  • antibacterial spectrum
  • autism spectrum
  • bipolar spectrum
  • broad spectrum
  • broader spectrum
  • calculated spectrum
  • cathodoluminescence spectrum
  • cd spectrum
  • cell spectrum
  • cid spectrum
  • circular dichroism spectrum
  • cl spectrum
  • clinical spectrum
  • clinicopathological spectrum
  • compact steep spectrum
  • complex spectrum
  • component spectrum
  • continuous spectrum
  • core-level spectrum
  • correlation spectrum
  • corresponding spectrum
  • density spectrum
  • derivative spectrum
  • design spectrum
  • dichroism spectrum
  • dielectric spectrum
  • difference spectrum
  • different spectrum
  • diffraction spectrum
  • diffuse reflectance spectrum
  • discrete spectrum
  • disease spectrum
  • diverse spectrum
  • doppler spectrum
  • eeg power spectrum
  • el spectrum
  • elastic response spectrum
  • electroluminescence spectrum
  • electromagnetic spectrum
  • electron ionization mass spectrum
  • electron paramagnetic resonance spectrum
  • electron spectrum
  • electronic absorption spectrum
  • electronic spectrum
  • electrospray ionization mass spectrum
  • electrospray mass spectrum
  • emission spectrum
  • energy spectrum
  • entire spectrum
  • entire visible spectrum
  • epr spectrum
  • esi mass spectrum
  • esi spectrum
  • esr spectrum
  • essential spectrum
  • excitation spectrum
  • experimental spectrum
  • extinction spectrum
  • fluorescence emission spectrum
  • fluorescence spectrum
  • fourier transform infrared spectrum
  • fourier-transform infrared spectrum
  • frequency spectrum
  • ft-ir spectrum
  • ft-raman spectrum
  • ftir spectrum
  • full spectrum
  • galaxy spectrum
  • heterogeneous spectrum
  • high-resolution nmr spectrum
  • high-resolution spectrum
  • histological spectrum
  • hmbc spectrum
  • hsqc spectrum
  • impedance spectrum
  • infrared absorption spectrum
  • infrared spectrum
  • integrate spectrum
  • ion mass spectrum
  • ion spectrum
  • ionization mass spectrum
  • ir spectrum
  • laboratory spectrum
  • large spectrum
  • light spectrum
  • line spectrum
  • loading spectrum
  • loss spectrum
  • luminescence spectrum
  • magnetic resonance spectrum
  • maldi mass spectrum
  • mass spectrum
  • matter power spectrum
  • measured spectrum
  • mode spectrum
  • morphological spectrum
  • mr spectrum
  • ms2 spectrum
  • ms3 spectrum
  • msn spectrum
  • mutation spectrum
  • mutational spectrum
  • mössbauer spectrum
  • narrow spectrum
  • nir spectrum
  • nmr spectrum
  • noesy spectrum
  • nuclear magnetic resonance spectrum
  • observed spectrum
  • optical absorption spectrum
  • optical spectrum
  • paramagnetic resonance spectrum
  • phenotypic spectrum
  • phonon spectrum
  • photocurrent spectrum
  • photoelectron spectrum
  • photoluminescence spectrum
  • photoluminescent spectrum
  • pl spectrum
  • point spectrum
  • political spectrum
  • power density spectrum
  • power spectrum
  • pr spectrum
  • product ion mass spectrum
  • product ion spectrum
  • proton nmr spectrum
  • proton spectrum
  • quality spectrum
  • radio spectrum
  • raman scattering spectrum
  • raman spectrum
  • ray spectrum
  • reference spectrum
  • reflectance spectrum
  • reflection spectrum
  • reflectivity spectrum
  • resolution spectrum
  • resonance raman spectrum
  • resonance spectrum
  • response spectrum
  • rotational spectrum
  • rr spectrum
  • scattering spectrum
  • size spectrum
  • solar spectrum
  • solid-state nmr spectrum
  • solution spectrum
  • spin resonance spectrum
  • steep spectrum
  • substrate spectrum
  • synthetic spectrum
  • tandem mass spectrum
  • template spectrum
  • theoretical spectrum
  • time spectrum
  • time-resolved spectrum
  • transform infrared spectrum
  • transient absorption spectrum
  • transmission spectrum
  • transmittance spectrum
  • tumor spectrum
  • two-dimensional nmr spectrum
  • type spectrum
  • ultraviolet absorption spectrum
  • ultraviolet spectrum
  • uv absorption spectrum
  • uv spectrum
  • uv-visible absorption spectrum
  • uv-visible spectrum
  • vibrational spectrum
  • vis absorption spectrum
  • vis spectrum
  • visible absorption spectrum
  • visible spectrum
  • vivo spectrum
  • whole spectrum
  • wide spectrum
  • wider spectrum
  • x-ray absorption spectrum
  • x-ray diffraction spectrum
  • x-ray photoelectron spectrum
  • x-ray spectrum
  • xp spectrum

  • Terms modified by Spectra

  • spectrum analysis
  • spectrum condition
  • spectrum data
  • spectrum disease
  • spectrum disorder
  • spectrum disorders
  • spectrum feature
  • spectrum measurement
  • spectrum only
  • spectrum radio source
  • spectrum reveal
  • spectrum shows
  • spectrum similar
  • spectrum source

  • Selected Abstracts


    ABSTRACT On five separate occasions, eight volunteers were asked to consume five edible gels with known texture and flavour properties. The electrical activity of their temporal and masseter muscles was recorded using electromyography (EMG). The electrode voltages were sampled at a rate of 1 kHz, starting when each volunteer began to masticate, and terminating when the volunteer indicated that the gel's flavour could no longer be perceived. Data from the mastication phase (first 20 s) were Fourier transformed to give a power spectrum in the frequency domain. Upon visual examination, the low frequency (< 10 Hz) region was found to contain spectral features that differ between volunteers, and the differences were generally consistent between sessions. Principal component analysis (PCA) supported this finding, by showing some clustering of the scores from different volunteers. However, when PCA was applied to the whole of the frequency range, the clustering became much more pronounced, indicating that higher frequencies also contribute to the distinction between volunteers. Clusters of readings from each volunteer were almost entirely separated using internally cross-validated canonical variate analysis (CVA), showing that each individual demonstrated characteristic and consistent mastication behaviour. Finally, a statistically significant association was found between the integrated power spectrum and the concentration of flavour compound in the gels; however, a similar relationship was discovered to exist between the flavour and the texture, as determined by cutting and compression. Hence, it was not possible to determine conclusively whether flavour alone has an effect on mastication characteristics. [source]


    Justin Broackes
    To the familiar idea of an undetectable spectrum inversion some have added the idea of inverted earth. This new combination of ideas is even harder to make coherent, particularly as it applies to a supposed inversion of black and white counteracted by an environmental switch of these. Black and white exhibit asymmetries in their connections with illumination, shadow and visibility, which rule out their being reversed. And since the most saturated yellow is light and the most saturated blue dark, yellow and blue could not be reversed unless light and dark could be. The difficulties suggest some more general morals for how to think of the role of "qualia" in colour perception. [source]


    Eric Marcus
    Various thought-experiments have been offered as independent support for the possibility of intentionalism-defeating spectrum inversion, but they do not succeed. I refute what I take to be the four best arguments for holding that the thought-experiments do in fact provide such support: the implausible error argument, the symmetry argument, the no-inference argument and the best theory of representation argument. I thus offer a defence of intentionalism against a long-standing objection. [source]


    ANZ JOURNAL OF SURGERY, Issue 6 2005
    Laurence Gluch
    The discovery of the phenomenon of nuclear magnetic resonance occurred just 60 years ago. The profusion of subsequent discoveries in this domain has led to the development of magnetic resonance spectroscopy , refined as an analytical tool to discern molecular structure , and magnetic resonance imaging, a cornerstone of modern radiology. Observable alterations in cellular structure and metabolism can be discerned using the non-destructive chemical analysis of magnetic resonance spectroscopy in vitro or in vivo. Differences may thus be discerned between malignant and normal tissues. [source]

    Book review: Organic Structures from Spectra, 4th edition.

    Daniel D. Traficante Professor Emeritus
    No abstract is available for this article. [source]

    Spectroscopic Diagnostics of Pulsed arc Plasmas for Particle Generation

    K. Behringer
    Abstract Pulsed arc plasmas were diagnosed by means of emission spectroscopy. A capacitor was discharged through argon and hydrogen leading to a few cycles of damped current oscillation with ,120 ,s period and 5-12 kA maximum current. Spectroscopic measurements in the visible range were carried out in order to characterise the electron temperature and density in the arc channel as well as electron and gas temperatures in the afterglow plasmas. Spectra were integrated over 10 ,s time windows and shifted in time from pulse to pulse. The plasmas also contained substantial fractions of electrode material (brass), namely copper and zinc. The electron density was measured in the conventional way from the broadening of H, or from the Ar I Stark width. In the arc channel, it ranged from about 3 · 1022 to 2 · 1023 m,3. The broadening of Zn II lines could also be used. Ratios of Ar I to Ar II and of Zn I to Zn II line intensities were analysed for the electron temperature. Line pairs were found which lay conveniently close in one frame of the spectrometer allowing automatic on-line analysis without relying on reproducibility. Atomic physics models including opacity were developed for Ar II and Zn II in order to check the existence of a Boltzmann distribution of their excited states. These calculations showed that the observed levels were in fact close to thermodynamic equilibrium, in particular, if the resonance lines were optically thick. Electron temperature measurements yielded values between 14000 K and 21000 K. The gas temperature in the afterglow, where particles should have formed, was derived from the rotational and vibrational temperatures of C2 molecular bands. Ratios between Cu I line intensities yielded the electron temperatures. Both were found to be a few 1000 K. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    On the Time-Resolved Optogalvanic Spectra of Neon and Krypton

    N. K. Piracha
    Abstract In this work time resolved optogalvanic signals associated with transitions excited from the first metastable state of neon and krypton have been studied. These gases have similar energy state configurations and it is of significant interest to study their time resolved optogalvanic waveforms resulting from transitions belonging to the states of same quantum numbers. The experimentally observed optogalvanic signals recorded for different discharge currents have been fitted to a theoretical model to obtain parameters that determine amplitudes, instrumental time constants and decay rates of the 1s levels. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Relative increase in choline in the occipital cortex in chronic fatigue syndrome

    B. K. Puri
    Puri BK, Counsell SJ, Zaman R, Main J, Collins AG, Hajnal JV, Davey NJ. Relative increase in choline in the occipital cortex in chronic fatigue syndrome. Acta Psychiatr Scand 2002: 106: 224,226. © Blackwell Munksgaard 2002. Objective:,To test the hypothesis that chronic fatigue syndrome (CFS) is associated with altered cerebral metabolites in the frontal and occipital cortices. Method:,Cerebral proton magnetic resonance spectroscopy (1H MRS) was carried out in eight CFS patients and eight age- and sex-matched healthy control subjects. Spectra were obtained from 20 × 20 × 20 mm3 voxels in the dominant motor and occipital cortices using a point-resolved spectroscopy pulse sequence. Results:,The mean ratio of choline (Cho) to creatine (Cr) in the occipital cortex in CFS (0.97) was significantly higher than in the controls (0.76; P=0.008). No other metabolite ratios were significantly different between the two groups in either the frontal or occipital cortex. In addition, there was a loss of the normal spatial variation of Cho in CFS. Conclusion:,Our results suggest that there may be an abnormality of phospholipid metabolism in the brain in CFS. [source]

    Copper-Azide-Thioarylazoimidazoles , Structure, Spectra, Redox Properties, Magnetism and Theoretical Interpretation

    Prasenjit Bhunia
    Abstract Azido-copper(II) and -copper(I) complexes of 1-alkyl-2-[(o -thioalkyl)phenylazo]imidazole (SRaaiNR,) have been prepared and studied. Complex 2 [Cu(SRaaiNR,)(,1,1 -N3)(N3)]2 dimerises via end-to-end (,1,3)-N3 to form a tetrameric structure. Azido-copper(I) complexes of the ligands are obtained as MeOH-bridged dimers, [Cu(SRaaiNR,)(N3)(,-OHMe)]2 (3). The electronic spectra suggest that a small reorganisation energy (0.08 eV) is associated with the change in electronic configuration, structure and oxidation state from CuII to CuI. Redox interconversion, CuII , CuI, [Cu(SMeaaiNMe)(,-N3)(N3)]2 (2a) , [Cu(SMeaaiNMe)(N3)(,-OHCH3)]2 (3a), has been performed in one case. The tetranuclear complex shows ferromagnetic and antiferromagnetic interactions. The spectra, redox chemistry and magnetism are explained by DFT studies. [source]

    Minerals as Model Compounds for Cu/ZnO Catalyst Precursors: Structural and Thermal Properties and IR Spectra of Mineral and Synthetic (Zincian) Malachite, Rosasite and Aurichalcite and a Catalyst Precursor Mixture

    Malte Behrens
    Abstract The Cu/ZnO system is a model for Cu/ZnO/Al2O3 catalysts, which are employed industrially for the synthesis of methanol. These catalysts are usually prepared from mixed basic carbonate precursors. A complex phase mixture, with constituents structurally related to the minerals rosasite andaurichalcite, is present at the industrially applied composition (Cu/Zn , 70:30). Using minerals and phase-pure synthetic samples as references, a comprehensive characterisation of such a phase mixture, including the determination of the individual compositions of the different phases, has been attempted by complementary analytical laboratory techniques (XRD, TGA, IR). The results are critically discussed in light of the complexity of the system. A thermally very stable carbonate species , well-known for mixed synthetic systems , is also detected for the mineral reference samples. Significant amounts of amorphous phases are found to be present in the synthetic zincian malachite sample but not in synthetic aurichalcite or the catalyst precursor. A simplified explanation for the shift of the characteristic 20 reflection of the malachite structure as a function of Zn incorporation based on the varying average Jahn,Teller distortion of the MO6 octahedra is proposed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

    Binuclear Mixed Valence Oxovanadium(IV/V) Complexes Containing a [OVIV(,-Ooxo)(,-Ophen)VVO]2+ Core: Synthesis, EPR Spectra, Molecular and Electronic Structure

    Amrita Mondal
    Abstract Binuclear mixed valence oxovanadium(IV/v) complexes of general formula [V2O3L] containing a [OVIV(,-Ooxo)(,-Ophen)VVO]2+ core have been synthesised using conformationally labile N4O3 -coordinating heptadentate ligands (H3L). The X-ray structure of one complex has been examined. Solution EPR spectra revealed that the unpaired electron of the complexes is delocalised between the two vanadium centres. The simulated EPR spectrum of one complex confirms this experimental observation. DFT studies have been performed using crystallographic coordinates in order to obtain further insight into the electronic structure of this type of molecule. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

    Exchange Interactions at the Supramolecular Level , Synthesis, Crystal Structure, Magnetic Properties, and EPR Spectra of [Mn(MAC)(TCNQ)2] (MAC = Pentaaza Macrocyclic Ligand; TCNQ·, = Radical Anion of 7,7,8,8-Tetracyano- p -quinodimethane)

    Augustin M. Madalan
    Abstract The reaction between [Mn(MAC)(H2O)2]Cl2·4H2O and LiTCNQ (MAC = 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene) affords a complex with the formula [Mn(MAC)(TCNQ)2] (1), whose crystal structure has been determined. Its structure consists of neutral mononuclear entities. The manganese(II) ion is heptacoordinated, with a pentagonal bipyramidal geometry. The apical positions are occupied by the TCNQ·, radicals, while the macrocyclic ligand is coordinated at the equatorial positions. The seven Mn,N distances range from 2.273(3) to 2.301(6) Å. The strong intermolecular ,,, stacking interactions between the TCNQ radicals (3.2 Å) leads to weave-like infinite chains, which propagate along the crystallographic c axis. The cryomagnetic investigation of 1 revealed a weak intermolecular antiferromagnetic coupling of the Mn2+ ions (J = ,0.18 cm,1), which is mediated by the diamagnetic (TCNQ)22, pairs resulting from the stacking interactions in the crystal. The intermolecular exchange interaction between the Mn2+ ions was further confirmed by variable temperature EPR spectroscopic measurements [|J| = 0.15(5) cm,1], which have been carried out in both the X and Q bands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

    4- and 4,5-Substituted N -Methoxythiazole-2(3H)-thiones , Preparation,UV/Vis Spectra, and Assignment of Electronic Transitions in Comparison to N -Methoxypyridine-2(1H)-thione Using Time-Dependent Density Functional Theory Calculations

    Jens Hartung
    Abstract Experimentally observed absorptions in UV/Vis spectra of N -methoxy-4-methylthiazole-2(3H)-thione, N -methoxy-5-(p -methoxyphenyl)-4-methylthiazole-2(3H)-thione, N -methoxypyridine-2(1H)-thione, and selected N -hydroxy derivatives thereof have been assigned to ,,,*-type transitions as dominating character, using the results from ab initio calculations [time-dependent density functional theory (TD)RI-BLYP/TZVPP]. Theory further predicts that electronic excitations in N -methoxythiazole-2(3H)-thiones on one side and N -meth-oxypyridine-2(1H)-thione on the other side differ significantly with respect to character and statistical weight of contributing transitions. These effects originate predominantly from contributions of the endocyclic sulfur atom onto orbital energies and shapes in thiazole-2(3H)-thiones, and may be intensified by substituents such as a p -methoxyphenyl group located in position 5. Since the majority of the calculated spectral differences between thiazole- and pyridinethiones refers to excitations of low intensity, the findings from the present study correlate with two important experimental facts: (i) Apart from minor shifts in the exact spectral location of UV/Vis absorptions, electronic spectra of N -hydroxy- or N -methoxy-substituted pyridine-2(1H)-thiones and thiazole-2(3H)-thiones are surprisingly similar in shape. (ii) N -alkoxypyridine-2(1H)-thiones and N -alkoxythiazole-2(3H)-thiones liberate upon UV/Vis excitation oxygen-centered radicals with a comparable efficiency. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source]

    Identification of Chiral cis- and trans- 2-Stannyloxazolidines by Their NMR Spectra and Solid-State Structures

    Jean-Christophe Cintrat
    Abstract The assignment of cis and trans configurations in N -protected 4-substituted 2-tributylstannyl-1,3-oxazolidines by NMR has been achieved through the use of extrapolations of Karplus,Kitching-type relationships for 3J(119Sn,C,Z,13C) to establish the shape of the oxazolidine ring. Examination of 3J(H,H) allowed the determination of torsion angles for the substituents on C4 and C5, discrimination being completed by comparison of the H2 chemical shifts, together with the 2J(Sn,C,H2) values. The validity of the method was subsequently corroborated by comparison of the results obtained for the liquid phase with those obtained from radiocrystallographic structures of triphenylstannyl analogues or DFT calculations on trimethylstannyl analogues. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

    Quantitative solid-state 13C NMR spectroscopy of organic matter fractions in lowland rice soils

    R. J. Smernik
    Summary Spin counting on solid-state 13C cross-polarization (CP) nuclear magnetic resonance (NMR) spectra of two humic fractions isolated from tropical lowland soils showed that only 32,81% of potential 13C NMR signal was detected. The observability of 13C NMR signal (Cobs) was higher in the mobile humic acid (MHA) than in the calcium humate (CaHA) fraction, and increased with increasing intensity of irrigated rice cropping. NMR observability appeared to be related to the nature of the organic carbon, with phenol- and methoxyl-rich samples having the higher values of Cobs. The Bloch decay (BD) technique provided more quantitatively reliable 13C NMR spectra, as evidenced by values of Cobs in the range 91,100% for seven of the eight humic fractions studied. The BD spectra contained considerably more aryl and carbonyl signal, and less O,alkyl and alkyl signal, with the greatest differences between CP and BD spectra observed for the samples with low Cobs(CP). The causes of low CP observability were investigated using the spectral editing technique RESTORE ( REstoration of Spectra via TCH and T One Rho (T1,H) Editing). Rapid T1,H relaxation was found to be primarily responsible for the under-representation of carbonyl carbon, whereas inefficient cross-polarization was primarily responsible for the under-representation of aryl carbon in CP spectra. Proton NMR relaxation rates T1H and T1,H were found to correlate with other NMR properties and also with cropping management. Non-uniform rates of T1H relaxation in two of the CaHA fractions enabled the generation of proton spin relaxation editing subspectra. [source]

    Instant centre frequency at anaesthetic induction , a new way to analyse sympathovagal balance,

    Edmundo Pereira De Souza Neto
    Abstract The instant centre frequency (ICF) of RR interval has been proposed as a global index to analyse the sympathovagal interaction in the heart. The aim of this study was to assess the ICF during anaesthesia to test if it can reliably capture the neural control of the cardiovascular system. Twenty-four ASA II or III patients scheduled for cardiac surgery were included in the study. They were allocated in two groups: control, no treatment (group 1, n = 12), and beta-adrenergic blockade by atenolol (group 2, n = 12). Spectra of pulse interval series were computed with a time,frequency method and they were divided into: very low frequency (VLF, 0.000,0.040 Hz), low frequency (LF, 0.050,0.150 Hz) and high frequency (HF, 0.160,0.500 Hz). Normalized power was obtained by dividing the cumulative power within each frequency band (LF or HF) by the sum of LF and HF; the ratio of LF/HF was also calculated. Instant centre frequency is a time-varying parameter that the evolution along time of the gravity centrum of a local spectrum. All spectral indexes were recorded at the following time points: before induction, after induction and before intubation, during intubation, and after intubation. The atenolol group had lower normalized LF and the LF/HF ratio (P < 0.05) higher HF before induction; and lower LF/HF ratio after induction and before intubation (P < 0.05). The ICF was higher in atenolol group at all times. The ICF shifted towards HF frequency after induction and before intubation and shifted towards LF during intubation in both groups. The autonomic nervous system control on the heart through the interaction of sympathetic and parasympathetic reflex mechanisms could be studied by the ICF. The ICF may assess the autonomic cardiac modulation and may provide useful information for anaesthetic management. [source]

    Conformational Analysis and CD Calculations of Methyl-Substituted 13-Tridecano-13-lactones

    Elena Voloshina
    Conformational models covering an energy range of 3,kcal/mol were calculated for (13S)-tetradecano-13-lactone (3), (12S)-12-methyltridecano-13-lactone (4), and (12S,13R)-12-methyltetradecano-13-lactone (8), starting from a semiempirical Monte-Carlo search with AM1 parametrization, and subsequent optimization of the 100 best conformers at the 6-31G*/B3LYP and then the TZVP/B3LYP level of density-functional theory. CD Spectra for these models were calculated by the time-dependent DFT method with the same functional and basis sets as for the ground-state calculations and Boltzmann weighting of the individual conformers. The good correlation of the calculated and experimental spectra substantiates the interpretation of these conformational models for the structure,odor correlation of musks. Furthermore, the application of the quadrant rule in the estimation of the Cotton effect for macrolide conformers is critically discussed. [source]

    NMR Characterization of Complex p- Oligophenyl Scaffolds by Means of Aliasing Techniques to Obtain Resolution-Enhanced Two-Dimensional Spectra

    Damien Jeannerat
    The usefulness of computer-assisted aliasing to secure maximal resolution of signal clusters in 1H- and 13C-NMR spectra (which is essential for structure determination by HMBC 2D NMR spectroscopy) in minimal acquisition time is exemplified by the complete characterization of the two complementary p -octiphenyls 1 and 2 with complex substitution patterns. The need for digital resolution near 1,Hz/pt to dissect the extensive signal clusters in the NMR spectra of these refined oligomers excluded structure determination under routine conditions. High resolution was secured by exploiting the low signal density in the 13C dimension of HMBC spectra by using computer-assisted aliasing to maximize signal density. Based on the observed shifts in DEPT and 1H-decoupled 13C-NMR spectra of 1 and 2, computer-assisted aliasing allowed to reduce the number of required time increments by a factor of 20 to 30 compared to full-width spectra with identical resolution. Without signal-to-noise constraints, this computer-assisted aliasing reduced the acquisition time for high-resolution NMR spectra needed for complete characterization of refined oligomers 1 and 2 by the same factor (e.g., from over a day to about an hour). With resolved signal clusters in fully aliased HSQC and HMBC spectra, unproblematic structure determination of 1 and 2 is demonstrated by unambiguous assignment of all C- and H-atoms. These findings demonstrate that computer-assisted aliasing of the underexploited 13C dimension makes extensive molecular complexity accessible by conventional multidimensional heteronuclear NMR experiments without extraordinary efforts. [source]

    Synthesis, CD Spectra, and Enzymatic Stability of ,2 -Oligoazapeptides Prepared from (S)-2-Hydrazino Carboxylic Acids Carrying the Side Chains of Val, Ala, and Leu

    Gérald Lelais
    , -Peptides offer the unique possibility to incorporate additional heteroatoms into the peptidic backbone (Figs.,1 and 2). We report here the synthesis and spectroscopic investigations of ,2 -peptide analogs consisting of (S)-3-aza- , -amino acids carrying the side chains of Val, Ala, and Leu. The hydrazino carboxylic acids were prepared by a known method: Boc amidation of the corresponding N -benzyl- L - , -amino acids with an oxaziridine (Scheme,1). Couplings and fragment coupling of the 3-benzylaza- ,2 -amino acids and a corresponding tripeptide (N -Boc/C -OMe strategy) with common peptide-coupling reagents in solution led to ,2 -di, ,2 -tri-, and ,2 -hexaazapeptide derivatives, which could be N -debenzylated (4,9; Schemes,2,4). The new compounds were identified by optical rotation, and IR, 1H- and 13C-NMR, and CD spectroscopy (Figs.,4 and 5) and high-resolution mass spectrometry, and, in one case, by X-ray crystallography (Fig.,3). In spite of extensive measurements under various conditions (temperatures, solvents), it was not possible to determine the secondary structure of the ,2 -azapeptides by NMR spectroscopy (overlapping and broad signals, fast exchange between the two types of NH protons!). The CD spectra of the N -Boc and C -OMe terminally protected hexapeptide analog 9 in MeOH and in H2O (at different pH) might arise from a (P)- 314 -helical structure. The N -Boc- ,2 -tri and N -Boc- ,2 -hexaazapeptide esters, 7 and 9, were shown to be stable for 48,h against the following peptidases: pronase, proteinase,K, chymotrypsin, trypsin, carboxypeptidase,A, and 20S proteasome. [source]

    Nanocomposite Films Assembled from Genetically Engineered Filamentous Viruses and Gold Nanoparticles: Nanoarchitecture- and Humidity-Tunable Surface Plasmon Resonance Spectra

    ADVANCED MATERIALS, Issue 9 2009
    Aihua Liu
    Nanocomposite films are prepared by layer-by-layer (LBL) assembly of cationic genetically engineered rodlike nontoxic viruses and anionic spherical Au nanoparticles. The cationic viruses electrostatically interact with the anionic Au nanoparticles to drive the LBL assembly. The nanocomposite films exhibit humidity-dependent surface plasmon resonance spectra (see figure). [source]

    Fabrication of Hollow Metal "Nanocaps" and Their Red-Shifted Optical Absorption Spectra,

    ADVANCED MATERIALS, Issue 10 2005
    J. Liu
    Cap-shaped metal nanoparticles (see Figure) have optical spectra with significant absorption in the infrared. Such shapes, produced by physical vapor deposition onto a polymer-particle template, can be readily separated from one another provided that deposition is carried out at an inclination to the plane of the template. The effect of composition, angle of deposition, and thickness on the properties of the cap-shaped particles is discussed. [source]

    Use of electron spin resonance measurements on irradiated sperma lentil seeds to indicate accidental irradiation

    Mustafa Korkmaz
    Summary The results of electron spin resonance studies on ,-irradiated micro- and macrosperma lentil seeds are reported. Spectra of non-irradiated intact sperma were composed of an equally spaced sextet originating from the presence of Mn2+ ions and a single weak resonance line. Irradiation produced a linear increase in the radical signal intensity in the radiation dose range (0.5,5 kGy) studied, without affecting the Mn2+ signal. Signal intensities of both sperma followed compound exponential decay curves originating from the presence of three different radical species. Heating the sperma cause irreversible decreases in both radical and Mn2+ signal intensities. Two radical species, described in the present work, and a radical of unknown origin were used to explain the experimental results. [source]

    Deblurring Images: Matrices, Spectra and Filtering by Per Christian Hansen, James G. Nagy, Dianne P. O'Leary

    Paul Marriott
    No abstract is available for this article. [source]

    Discrimination of cyanobacterial strains isolated from saline soils in Nakhon Ratchasima, Thailand using attenuated total reflectance FTIR spectroscopy

    Somchanh Bounphanmy
    Abstract A method was developed whereby high quality FTIR spectra could be rapidly acquired from soil-borne filamentous cyanobacteria using ATR FTIR spectroscopy. Spectra of all strains displayed bands typical of those previously reported for microalgae and water-borne cyanobacteria, with each strain having a unique spectral profile. Most variation between strains occurred in the C,O stretching and the amide regions. Soft Independent Modelling by Class Analogy (SIMCA) was used to classify the strains with an accuracy of better than 93%, with best classification results using the spectral region from 1800,950 cm,1. Despite this spectral region undergoing substantial changes, particularly in amide and C,O stretching bands, as cultures progressed through the early-, mid- to late-exponential growth phases, classification accuracy was still good (,80%) with data from all growth phases combined. These results indicate that ATR/FTIR spectroscopy combined with chemometric classification methods constitute a rapid, reproducible, and potentially automated approach to classifying soil-borne filamentous cyanobacteria. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Spectra of wavelet scale coefficients from process acoustic measurements as input for PLS modelling of pulp quality,

    JOURNAL OF CHEMOMETRICS, Issue 8-10 2002
    Anders Björk
    Abstract Acoustic and vibration signals are captured by simple standard accelerometers. These can often be mounted directly on operative process equipment, creating a completely non-invasive measurement system. The signals from the accelerometer are then amplified, digitized by an analogue-to-digital converter and stored in some suitable format in a PC. The method most often used for signal processing of acoustic data has been to apply variants of fast Fourier transform (FFT) on sampled data to produce a frequency domain representation. An alternative way tried here is to use the fast wavelet transform (FWT) in combination with FFT. The FWT has the advantage that it produces time-resolved representations and, on each time scale, different features can be extracted. However, in this case, time resolution has no meaning, since the starting points for data acquisitions were not fixed. The wavelet step can be seen as a series of pre-filters and it is here followed by FFT on coefficients at each wavelet scale. The results are compared to those obtained after FFT on the complete time series. We have used spectra of wavelet scale coefficients in an attempt to model pulp quality with PLS. In this case the number of points in the resulting wavelet multiresolution spectrum (WT-MRS) can be limited to a low number, e.g. 255 compared to 1025 with direct FFT on the time series. In the PLS modelling step the advantage is that the first two components describe Y much better than when using the conventional approach, e.g. 72% explained Y variance compared to 40%. A second advantage is that the model requires fewer coefficients. Copyright © 2002 John Wiley & Sons, Ltd. [source]

    A randomized comparison of plateletpheresis with the same donors using four blood separators at a single blood center,

    Grace C. Tenorio
    Abstract At one blood center, each of 20 donors underwent plateletpheresis on four blood cell separators in random order. We compared the CS3000+, Amicus V 2.41, MCS Plus, and Spectra LRS V 7 Turbo regarding platelet (PLT) yield, pre- and post-procedure PLT counts, percent fall in donor PLT count, process time, efficiency, PLT product and donor PLT volume (MPV). Using , 150 × 109 PLTs/L pre-donation counts, a goal was set of 4.5 × 1011 PLTs unit in up to 100 minutes processing time. Results were (mean values) PLT yields of Amicus, Spectra, CS3000+, and MCS Plus: 4.3, 4.6, 4.3, 4.0 × 1011 PLTS, respectively; percent donor PLT fall: 24, 32, 30, 29%, respectively; processing times: 50, 74, 87, 101 minutes, respectively; relative efficiency (RE): 2.2, 1.6, 1.2,1.0, respectively (based on the MCS Plus performance with RE of 1 = 4 × 109 PLTS/min); PLT product MPV: 6.7, 7.4, 6.8,7.1 fL, respectively; pre-procedure donor MPV: 7.7, 7.3, 7.6 and 7.6 fL, respectively; and percent donor MPV change: ,5.2, 0, ,6.6, and ,10%, respectively. Significant changes in the donor MPV were noted (P < 0.05) but could not be related to product MPV. Spectra seemed to collect larger PLTs (higher MPV); the significance remains unknown for both donors and recipients. Importantly, all four separators gave acceptable and comparable PLT yields (P < 0.05) with Spectra trending higher. The short process time and high RE together indicate highly efficient collections particularly by Amicus and Spectra. J. Clin. Apheresis 17:170,176, 2002. © 2002 Wiley-Liss, Inc. [source]

    Comparison of CD34+ cell collection efficiency on the COBE Spectra and Fenwal CS-3000 plus

    C.D. Ford
    Abstract Optimal collections of mobilized CD34+ cells are important in terms of both patient toxicity and cost. The factors that determine CD34+ collection efficiency (CD34eff) of cell separators have not been well studied. In addition, because several cell separators are available, the type of collection device may also be a significant variable. Previous studies comparing the Baxter-Fenwal CS3000 and the COBE Spectra have not yielded consistent conclusions. Therefore, we retrospectively analyzed the collection outcomes of 163 consecutive donors with a peripheral CD34+ cell concentration (pCD34) of ,5 cells/,l on the first collection that had been harvested on one or the other device. The CS3000 was found to yield a significantly higher CD34eff (50% vs. 39%, P = 0.006). However, donors were not balanced for several prognostic factors, which may contribute to CD34eff including mobilization with G-CSF vs. chemotherapy+G-CSF, average flow rate, and total volume of peripheral blood processed. When appropriate variables were included in a stepwise multiple variable analysis, cell separator type emerged as a significant independent predictive factor for CD34eff (P = 0.018). Our data indicates that the CS3000 will, on average, show a higher absolute CDeff of 8%. Furthermore, since the two devices differ in mechanism, prognostic factors may also differ. Comparisons suggest that peripheral blood WBC and hematocrit may be more important predictors for the CS3000. J. Clin. Apheresis 17:17,20, 2002. © 2002 Wiley-Liss, Inc. [source]

    Therapeutic plasma exchange: A paired comparison of Fresenius AS104 vs.

    COBE Spectra
    Abstract For therapeutic plasma exchange (TPE), continuous flow separators are known to be efficient as exemplified by Fresenius AS104 and COBE Spectra. The AS104 uses an interface monitoring system in the centrifuge during TPE, whereas Spectra uses computer algorithms to establish the plasma-cell interface. To determine the plasma collection efficiency (PLCE), anticoagulant (AC) volumes used, and platelets (PLT) lost of the AS104 and the Spectra, we performed a prospective paired comparison of 20 TPE (each machine). The study included 17 patients, 1.3 plasma volume exchanges (without AC), equal inlet rates, and AC ratio of 13:1. Processing times did not include reinfuse mode. Platelet loss was determined by sampling the collection bags. Inlet rates were between 60,110 ml/min. Diagnosis included peripheral neuropathies, TTP and cryoglobulinemia. The AS104 had significantly (P<0.0001) lower average whole blood processed (F:6,601 vs. S:8,584 ml), AC volume (F:532 vs. S:719 ml), and processing time (F:80 vs. S:102 minutes) than Spectra. The AS104 had significantly (P<0.0001) higher average plasma flow rates (F:53 vs. S:44 ml/minute), plasma collection efficiency (F:90 vs. S:69%), and platelet loss (F:2.0 vs. S:0.14 × 1011 plt) than Spectra. Platelet loss correlated with inlet flow rate with the AS104 but not with the Spectra. The AS104 has a significantly higher collection efficiency than Spectra allowing it to remove the same amount of plasma in significantly less time, by processing significantly less blood, using significantly less AC, but removing significantly more platelets than Spectra. J. Clin. Apheresis. 16:61,66, 2001. © 2001 Wiley-Liss, Inc. [source]

    Effect of Components Extracted from Okara on the Physicochemical Properties of Soymilk and Tofu Texture

    Kyoko Toda
    ABSTRACT:, The physicochemical properties of soymilk and the texture of tofu were compared with regard to 2 kinds of soymilk, one of which was prepared by squeezing homogenates before heating and the other was prepared by squeezing after heating raw soymilk with okara, residue of soymilk production. Relative particulate protein content and viscosity were higher and pH was lower in the soymilk prepared by the latter method, in which liberated lipid bodies were decreased and more lipids were precipitated with protein after centrifugation, suggesting a change in the interaction between proteins and lipids. A difference in the distribution of proteins and lipids was also implied by analysis with a laser particle size analyzer. The breaking stress of tofu made with 0.30% glucono-delta-lactone increased in accordance with an increase in particulate protein. The calcium and magnesium contents increased in soymilk prepared by squeezing after heating with okara. Viscosity was slightly increased and pH decreased by adding calcium to the soymilk, but the particulate protein content and breaking stress of tofu did not increase significantly. To examine the effect of macromolecules, okara was extracted by boiling and dialyzed. Viscosity and particulate protein content in soymilk increased as the dialyzed extracts of the okara were added. The breaking stress of tofu was increased by adding the dialyzed extracts but excessive amounts of the extracts resulted in softer tofu. Spectra of Fourier-transform infrared spectroscopy and electrophoresis-separated patterns of proteins indicated that the dialyzed extracts contained mainly polysaccharides and the Basic 7S globulin protein. [source]

    Passport Examination by Polarized Infrared Spectra

    Shigeru Sugawara M.S.
    Abstract:, In this study, a new nondestructive technique for passport examination is proposed. In this technique, linearly polarized light is used to measure Fourier transform infrared (FT-IR) reflectance spectra of films on the biographical data page. Thirty genuine and thirty-five counterfeit Japanese passports and five marketed films pasted on name cards were examined. The measured spectra were analyzed as follows. The absorption spectra were obtained by the Kramers,Kronig transformations of reflectance spectra. The peak ratios were then calculated from the absorption spectra by adding the peak areas at 1126 and 1263 cm,1 and dividing the result by the peak area at 1727 cm,1. When nonpolarized light was used, the samples could not be distinguished by comparing the peak ratios. However, when polarized light was used, they were successfully distinguished by the comparison. Therefore, polarized light is useful for the forensic discrimination of passport films by the measurement of FT-IR spectra. [source]