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  • 1
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A full assignment of the 13C signals of four pentacyclic triterpenes confirms the results obtained by 1H NMR analysis of steroidal methyls, resolving the stereochemistry of the oxidation product of 3-β-acetoxyolean-12-en-30-oic acid methyl ester.
    Additional Material: 1 Tab.
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A time-resolved reflectance and transmittance spectrophotometer was developed and used to evaluate noninvasively and simultaneously the absorption and transport scattering spectra of bulk turbid media. The experimental setup, based on mode-locked dye and titanium:sapphire lasers and on an electronic chain for time-correlated single photon counting, was fully automated to make in vivo measurements on biological tissues feasible. The optical characterization of breast, of interest for the development of optical mammography, was performed in vivo on a wide spectral range (610–1010 nm). In particular, the absorption spectral features of the main tissue components (hemoglobin, water, and lipids) were recognized with different relative weight, depending on the age and the measurement position. Best fit with the absorption spectra of the main constituents was performed to evaluate their relative concentration in tissues. © 1999 American Institute of Physics.
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 348-350 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoluminescence decay curves and nanosecond time-gated spectra were measured from silicon implanted SiO2 layers after thermal annealing. Different ion fluences and annealing times were tested. Three components emitting blue-green light with lifetimes of about 0.4, 2, and 10 ns were detected. The peak position of all components moves to longer wavelengths upon increasing the ion fluence. This short-wavelength emission seems to be related to the presence of extended defects acting as precursors of nanocrystals. A slower (microsecond) component, centered in the near infrared and attributed to nanocrystals, was also identified in the highest fluence implant considered (3×1017 cm−2). © 1997 American Institute of Physics.
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An effective projection imaging technique is proposed that allows not only detection of realistic optical inhomogeneities in highly diffusive media, but also the discrimination between scattering and absorption contributions. The method is based on information derived from time-resolved transmittance measurements. Scattering inhomogeneities are discriminated using maps of the transport scattering coefficient, as provided by best fitting of the diffusion theory to experimental data. Absorption variations are effectively classified by time gating on the tail of the transmittance pulse. © 1996 American Institute of Physics.
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  • 5
    ISSN: 1612-1112
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new solvent system has been found which, in comparison with the solvent system butanol — glacial acetic acid — water (BAW), permits a sharper paper chromatographic separation of the 3-monoglucosides and the 3,5-diglucosides of the six common anthocyanidins. Some solvent systems have also proved successful for thin-layer chromatography on silica gel of several mixtures from different sources, obtaining sharp resolution with precoated plates without any adsorbent activation.
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  • 6
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 3-Substituierte Azetidinone-(2) (1) lassen sich N-acylieren und N-hydroxymethylieren. 3.3-Dialkyl-Derivate vom Typ 1a können auch mit 2-Dialkylamino-äthylhalogeniden N-alkyliert werden. N-Benzoylmethyl-azetidinone-(2) (10) und N-Vinyl-azetidinon-(2) (12) entstehen beim Ringschluß substituierter β-Brompropionsäureamide vom Typ 9 und 11.
    Additional Material: 4 Tab.
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  • 7
    ISSN: 0935-6304
    Keywords: Gas chromatography, GC ; Fused silica capillary columns ; Eigenvector projection ; Pygeum africanum bark ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The components of Pygeum africanum bark extracts, used for the treatment of benign prostatic hypertrophy, were characterized by high resolution gas chromatography (HRGC) and mass spectrometry (MS). Among various compounds n-docosyl trans-ferulate was identified and quantitated by HRGC as a derivative of n-docosanol, which is considered to be one of the active components of the extract. The origin of different Pygeum a. extracts can be studied by eigenvector projection of HRGC profiles with computer assistance.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The use of 13X zeolite (0.1-0.4-mm granules), treated with 2N and 0.01N HCI, 0.01M citric acid, 0.1M citric-phosphate buffer (pH 3.6), and in untreated form to adsorb glucose oxidase of fungal origin and microbial catalase was examined. Physicochemical analysis of the support demonstrated that its crystalline structure, greatly altered by the HCl and buffer, could be partially maintained with citric acid. The specific adsorption of the enzymes increased with decreasing pH and proved to be considerable for all the supports. The stability with storage at 25°C is strictly correlated with the titrable acidity of the activated zeolite expressed as meq NaOH/g and with pH value of the activation solution. It proved to be lower than 55 h for both enzymes if adsorbed on zeolite treated with 2N HCl, and 15-fold and 30-fold higher for glucose oxidase and catalase adsorbed, respectively, on zeolite treated with the 0.1M citric-phosphate buffer and 0.01M citric acid. The specific adsorption of glucose oxidase and catalase was, respectively, 1840 U/g at pH 3.0 and 6910 U/g at pH 5.0. Their half-life at 25°C with storage at pH 3.5 for the former and at pH 5.0 for the latter was 800 and 1560 h vs. 40 and 110 h for the corresponding free enzymes.
    Additional Material: 3 Ill.
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  • 9
    ISSN: 1434-1948
    Keywords: Pyrrolizinato complexes ; Tetracyanoethylene ; Phthalocyanines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes of NiII, CuII, ZnII, and CoIII containing the 1,2,6,7-tetracyano-3,5-dihydro-3,5-diiminopyrrolizinide (L) and the 2,4-tert-butylacetylacetonide (DPM) ligands have been synthesized and characterized. The absorption optical spectra of these species and of the corresponding ML2 complexes in coordinating solvents are compared with those of metal-phthalocyanines (MPc) and hydrogen-phthalocyanine (H2Pc), respectively. The comparison shows a close similarity, especially for the nickel-containing species, in the low-energy spectral region where the first π→π* transitions occur (Q band). The Q band position of the pyrrolizinato complexes is much more dependant on the metal than is the case for MPc. For the same metal, the Q band position is also dependant on the M-N bond lengths in the molecular plane. For M = Ni, a reduction of this distance causes a red-shift of the Q band and a decrease of its maximum intensity. These conclusions are based on the X-ray molecular structure of the solvent-free NiL(DPM) complex and its pyridine solvate NiL(DPM)(Pyr)2 · 2 Pyr and on their solvatochromism. A symmetry-based correlation diagram between the frontier orbitals of the pyrrolizinato-complexes and the phthalocyanines is proposed.
    Additional Material: 7 Ill.
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  • 10
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Endo-polygalacturonase (endo-PG) was immobilized on a wide range of natural and synthetic macromolecular supports and their modified derivatives representing many chemical classes, including esters, amides, phenols, alkyl- and arylamines, and carboxyl derivatives. The immobilization entailed methods of adsorption alone as well as covalent bond formation using glutaraldehyde or carbodiimide or via the diazo-coupling reaction. The most promising system proved to be immobilization on trimalehylchitosan (TMC) via adsorption followed by treatment with glutaraldehyde (GA). The binding capacity of the support is on the order of 13,000 IU/g, half of which is active. Various properties of immobilized endo-PG were evaluated. The optimum pH of the enzyme shifted to the alkaline side. The relative catalytic activity was considerably high even at room temperature and remained so above 70°C. The thermal stability at pH 3-4 was notably improved by immobilization, the half-time doubling. Finally, the apparent Km was greater for immobilized endo-PG than for native enzyme, while the Vmax was smaller for the immobilized enzyme.
    Additional Material: 4 Ill.
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