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We have used resonant Raman scattering as a novel, noninvasive in vivo optical technique to measure the concentration of macular carotenoid pigments in the living human retina. Using a backscattering geometry and resonant molecular excitation in the visible, we measure the Raman peaks that originate from the single- and double-bond stretch vibrations of the p -conjugated molecule's carbon backbone. The Raman signals scale linearly with carotenoid content, whereas the required laser excitation is well under safety limits for macular exposure. The Raman technique is objective and quantitative and may lead to a new method for rapid screening of carotenoid pigment levels in large human populations that are at risk for vision loss from age-related macular degeneration, the leading cause of blindness of the elderly in the United States. 相似文献
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Dembski S Rupp S Gellermann C Batentschuk M Osvet A Winnacker A 《Journal of colloid and interface science》2011,358(1):32-38
SiO(2)/Zn(2)SiO(4):Mn(2+) core-shell nanoparticles with mean diameters in the range of 55-220 nm were prepared by a modified Pechini sol-gel method followed by lyophilization and annealing at temperatures of 800-1100°C. The as-synthesized nanoparticles were characterized by transmission electron microscopy, X-ray diffraction analysis, and photoluminescence spectroscopy. The results demonstrate that the crystal structure of the shell and the optical properties can be tuned by the annealing temperature and a variation of the concentration of doping ions. Under UV excitation, the samples emit green luminescence with its maximum at 525 nm, typical for the Mn(2+) ions in α-Zn(2)SiO(4). The resulting nanoparticles were successfully modified with amine and carboxyl functions with respect to a later attachment of biological moieties. 相似文献
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Synthesis and Characterization of the Organic Surface Modifications of Monodisperse Colloidal Silica
Monodisperse colloidal silica spheres were prepared from tetraethylorthosilicate in mixtures of water, ammonia and ethanol. The surfaces of the spheres were successfully modified by chemical reaction with silane coupling agents. Several qualitative and quantitative methods were employed to analyse the organic surface modifications. As a result, the surface coverage of silica spheres with silane coupling agents could be calculated using different characterization methods. 相似文献
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Eike Gellermann Uwe Klingebiel Thomas Pape Fabio Dall Antonia Thomas R. Schneider Stefan Schmatz 《无机化学与普通化学杂志》2001,627(12):2581-2588
Silylhydrazines and Dimeric N,N′‐Dilithium‐N,N′‐bis(silyl)hydrazides – Syntheses, Reactions, Isomerisations Di‐tert.‐butylchlorosilane reacts with dilithiated hydrazine in a molar ratio to give the N,N′‐bis(silyl)hydrazine, [(Me3C)2SiHNH]2, ( 5 ). Isomeric tris(silyl)hydrazines, N‐difluorophenylsilyl‐N′,N′‐bis(dimethylphenylsilyl)hydrazine ( 7 ) and N‐difluorophenylsilyl‐N,N′‐bis(dimethylphenylsilyl)hydrazine ( 8 ) are formed in the reaction of N‐lithium‐N′‐N′‐bis(dimethylphenylsilyl)hydrazide and F3SiPh. Isomeric bis(silyl)hydrazines, (Me3C)2SiFNHNHSiMe2Ph ( 9 ) and (Me3C)2‐ SiF(PhMe2Si)N–NH2 ( 10 ) are the result of the reaction of di‐tert.‐butylfluorosilylhydrazine and ClSiMe2Ph in the presence of Et3N. Quantum chemical calculations for model compounds demonstrate the dyotropic course of the rearrangement. The monolithium derivative of 5 forms a N‐lithium‐N′,N′‐bis(silyl)hydrazide ( 11 ). The dilithium salts of 5 ( 13 ) and of the bis(tert.‐butyldiphenylsilyl)hydrazine ( 12 ) crystallize as dimers with formation of a central Li4N4 unit. The formation of 12 from 11 occurs via a N′ → N‐silyl group migration. Results of crystal structure analyses are reported. 相似文献
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R. Gellermann H. Jordan D. Hebert K. Fröhlich P. Szymczak N. Meinert 《Isotopes in environmental and health studies》2013,49(12):561-565
Early assessment of groundwater vulnerability during groundwater exploration is an important precondition for effective protection. Any attempt to assess the “vulnerability” is confronted with the very different factors influencing this property. In this paper we present a new concept to combine different factors on an objective basis. A protection index γ is defined and it is shown that this index can be obtained by the additative combination of a self-cleaning index (γs), a retardation index (γR) and a dilution index (γv). For the estimation of the latter one, isotope techniques are suitable. With lumped-parameter models, easy formulae are derived for the calculation of γv from tritium data. The applicability of this approach was tested with data from two field studies. The results obtained show that a reasonable assessment of groundwater vulnerability can be achieved. However, a lot of problems and questions remains to be solved by further investigation. 相似文献
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K. Fröhlich D. Hebert R. Gellermann 《Isotopes in environmental and health studies》2013,49(4):163-164
Das radioaktive Urmveltnuklid Tritium (3H: T1/2 = 12,43 a) gelangt mit den einsickernden Niederschlägen aus der Atmosphäre in das Grundwasser. Durch seinen radioaktiven Zerfall vermindert sich seine Aktivitatskonzentration in Abhängigkeit von der Verweilzeit im Grundwasserbereich. Das in Quellen oder anderen Aufschlüssen zutage tretende Grundwasser ist in der Regel eine Mischung von Anteilen unterschiedlicher Verweilzeit. Tritiummessungen konnen somit zur Bestimmung der Verweilzeitverteilung, die hydrogeologische Informationen über Fließ- und Mischungsverhalten, Neubildung sowie Geschütztheit von Grundwasser einschließt, beitragen [1]. Für die Untersuchungen zur Genese, zum Fließverhalten und zum Schutz der Mineralwässer von Bad Brambach wurden deshalb auch Tritiummessungen einbezogen [2]. Zur Tritiumanalyse wurden die Wasserproben nach vorheriger elektrolytischer Tritiumanreicherung ontweder zu Ethan synthetisiert und im Proportionalzählrohr gemessen, oder einem Szintillationscocktail zugemischt und in einem Flüssigkeitsszintillationsspektrometer gemessen [1]. Die beprobten Quellen bzw. Bohrungen, die Tritiummeßwerte und deren erste modolltheoretische Auswertung sind in Tab. 1 zusammengestellt. Diesen Resultaten zufolgo besitzen die Bad Brambacher Minoralwässer relativ 相似文献
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Für fünf Stationen im südlichen Teil der DDR werden Monats- und Jahresmittel der Tritiumkonzentration im Niederschlag der Jahre 1975/76 mitgeteilt. Im Februar und September 1975 traten ungewöhnlich hohe mittlere monatliche Tritiumkonzentrationen mit Spitzenwerten oberhalb 1000 T. E. auf. Die zeitliche Zuordnung dieser Tritiumkonzentrationen zu einzelnen Niederschlagsereignissen sowie die möglichen Ursachen der hohen Tritiumkonzentrationen werden diskutiert. 相似文献
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Michael Schneider Thomas Ballweg Lennart Groß Carsten Gellermann Angela Sanchez‐Sanchez Vanessa Fierro Alain Celzard Karl Mandel 《Particle & Particle Systems Characterization》2019,36(6)
Herein, the development of a novel composite particle system prepared from superparamagnetic Fe3O4@SiO2 microparticles as core and coated with a carbon shell is presented. The coating with carbon is done by pyrolyzing furan resin, which was previously deposited on the particle surface by poly‐merization of furfuryl alcohol. The novel composite material thus combines magnetic and sorptive properties. Upon pyrolysis the magnetic material is converted from magnetite to α‐iron and fayalite, changing its behavior from superparamagnetic to ferromagnetic with nearly zero remanence. The magnetic properties can be utilized to magnetically collect the particles dispersed in fluids, whereas the sorptive properties of the carbon shell can be used to remove organic contaminants from these fluids. The adsorption behavior of the composite particles and a potential electrochemical regeneration route are investigated, using the model dye methylene blue. 相似文献
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We have imaged the spatial distribution of macular carotenoid pigments (MPs) in the human retina, employing Raman spectroscopy. Using excised human eyecups as initial test samples and resonant excitation of the pigment molecules with narrow-bandwidth blue light from a mercury arc lamp, we record Raman images originating from the carbon-carbon double-bond stretch vibrations of the molecules. Preliminary Raman images reveal significant differences in the MPs of different samples in regard to absolute levels as well as spatial variation. This technique holds promise as a method of rapid screening of MPs in large populations at risk for vision loss from age-related macular degeneration, a leading cause of blindness. 相似文献