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A modified method for the quantitative determination of atmospheric perfluoroalkylcycloalkanes (PFCs) using thermal desorption coupled with gas chromatography and detection by negative ion chemical ionization–mass spectrometry was developed. Using an optimized analytical system, a commercially available Al2O3 porous layer open tubular (PLOT) capillary column (30 m × 0.25 mm) deactivated with Na2SO4 was used for separation of PFCs. Improvements in the separation of PFCs, the corresponding identification and the limit of detection of PFCs using this method and column are presented. The method was successfully applied to determine the atmospheric background concentrations of a range of PFCs from a number of samples collected at a rural site in Germany. The results of this study suggest that the method outlined using the Al2O3-PLOT-S capillary column has good sensitivity and selectivity, and that it can be deployed in a routine laboratory process for the analysis of PFCs in the future research work. In addition, the ability of this column to separate the isomers of one of the lower boiling PFCs (perfluorodimethylcyclobutane) and its ability to resolve perfluoroethylcyclohexane offer the opportunity for single-column analysis for multiple PFCs. 相似文献
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Ultralow jitter pulse trains are produced from a passively mode-locked, erbium/ytterbium co-doped, planar waveguide laser by use of high-bandwidth feedback control acting on the physical cavity length and optical pump power. Synchronization of a 750-MHz, fundamentally mode-locked laser to an external clock signal yields an ultralow, root-mean-square relative timing jitter of 14.4 fs integrated from 10 Hz to the Nyquist frequency of 375 MHz. 相似文献
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Zusammenfassung Für tierexperimentelle Untersuchungen wurde ein im Benzolkern durch14C markiertes p-Dimethylaminoazobenzol benötigt. Es wird ein Verfahren zur Herstellung dieser Verbindung in kleinen Mengen aus 1-14C-Anilin beschrieben.Herrn Prof. Dr.A. Franke zum 80. Geburtstag gewidmet. 相似文献
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Jacek Gasiorowski Sameh Boudiba Kurt Hingerl Christoph Ulbricht Valeria Fattori Francesca Tinti Nadia Camaioni Reghu Menon Stefanie Schlager Louiza Boudida Niyazi Serdar Sariciftci Daniel Ayuk Mbi Egbe 《Journal of Polymer Science.Polymer Physics》2014,52(4):338-346
An anthracene‐containing poly(arylene‐ethynylene)‐alt‐poly(arylene‐vinylene) (PAE‐PAV) of general constitutional unit (? Ph? C?C? Anthr? C?C? Ph? CH?CH? Anthr? CH?CH)n bearing two 2‐ethylhexyloxy solubilizing side chains on each phenylene (Ph) unit has been synthesized and characterized. The basic electrochemical characterization was done, showing the existence of two non‐reversible oxidation and one reversible reduction peaks. The optical properties, the real and imaginary part of the dielectric function, were probed using spectroscopic ellipsometry (SE). The vibrational structure of the undoped/doped polymer was investigated using Fourier transformed infrared spectroscopy. A strong change in the polaronic absorption was observed during the doping, which after modeling revealed the existence of two separated transitions. The optical changes upon doping were additionally recorded using the SE technique. Similar to the results from FT‐IR spectroscopy, two new in‐the‐gap absorptions were found. Moreover, the electrical conductivity as well as the mobility of positive carriers were measured. In the undoped state, the conductivity of the polymer was found to be below the detection limit (<μS cm?1), after doping the conductivity increased to 0.69 S cm?1. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014 , 52, 338–346 相似文献
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Schrand AM Huang H Carlson C Schlager JJ Omacr Sawa E Hussain SM Dai L 《The journal of physical chemistry. B》2007,111(1):2-7
Finely divided carbon particles, including charcoal, lampblack, and diamond particles, have been used for ornamental and official tattoos since ancient times. With the recent development in nanoscience and nanotechnology, carbon-based nanomaterials (e.g., fullerenes, nanotubes, nanodiamonds) attract a great deal of interest. Owing to their low chemical reactivity and unique physical properties, nanodiamonds could be useful in a variety of biological applications such as carriers for drugs, genes, or proteins; novel imaging techniques; coatings for implantable materials; and biosensors and biomedical nanorobots. Therefore, it is essential to ascertain the possible hazards of nanodiamonds to humans and other biological systems. We have, for the first time, assessed the cytotoxicity of nanodiamonds ranging in size from 2 to 10 nm. Assays of cell viability such as mitochondrial function (MTT) and luminescent ATP production showed that nanodiamonds were not toxic to a variety of cell types. Furthermore, nanodiamonds did not produce significant reactive oxygen species. Cells can grow on nanodiamond-coated substrates without morphological changes compared to controls. These results suggest that nanodiamonds could be ideal for many biological applications in a diverse range of cell types. 相似文献
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Laura K. Braydich-Stolle Nicole M. Schaeublin Richard C. Murdock Jingkun Jiang Pratim Biswas John J. Schlager Saber M. Hussain 《Journal of nanoparticle research》2009,11(6):1361-1374
Certain properties that nanoparticles possess differentiate them from their bulk counterparts, and these characteristics must
be evaluated prior to nanoparticle studies and include: size, shape, dispersion, physical and chemical properties, surface
area, and surface chemistry. Early nanotoxicity studies evaluating TiO2 have yielded conflicting data which identify either size or crystal structure as the mediating property for nano-TiO2 toxicity. However, it is important to note that none of these studies examined size with the crystal structure composition
controlled for or examined crystal structure while controlling the nanoparticle size. The goal of this study was to evaluate
the role of size and crystal structure in TiO2 nanotoxicity while controlling for as many other nanoproperties as possible using the HEL-30 mouse keratinocyte cell line
as a model for dermal exposure. In the size-dependent studies, all the nanoparticles are 100% anatase, and aggregate sizes
were determined in order to take into account the effect of agglomeration on size-dependent toxicity. In addition, varying
crystal structures were assessed while the size of the nanoparticles was controlled. We were able to identify that both size
and crystal structure contribute to cytotoxicity and that the mechanism of cell death varies based on crystal structure. The
100% anatase TiO2 nanoparticles, regardless of size, induced cell necrosis, while the rutile TiO2 nanoparticles initiated apoptosis through formation of reactive oxygen species (ROS). 相似文献
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Helmut Spreitzer Andrea Pichler Wolfgang Holzer Claudia Schlager 《Helvetica chimica acta》1998,81(1):40-45
Khusimone ( 1 ), one of the main odor-donating compounds of vetiver oil, is subject of the following study on structure/odor relationship. The omittance of the methano bridge of the tricyclic khusimone should lead to the bicyclic partial structure (−)- 2 . Unexpectedly, (−)- 2 could not be obtained since epimerization favored (−)- 16 . The stereochemical key step of the synthesis of the hydrazulene nucleus is based on a highly diastereoselective conjugate addition to a chiral oxocyclopent-1-ene-1-carboxylate. 相似文献
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Kyung O. Yu Christin M. Grabinski Amanda M. Schrand Richard C. Murdock Wei Wang Baohua Gu John J. Schlager Saber M. Hussain 《Journal of nanoparticle research》2009,11(1):15-24
The present study was designed to examine the uptake, localization, and the cytotoxic effects of well-dispersed amorphous
silica nanoparticles in mouse keratinocytes (HEL-30). Mouse keratinocytes were exposed for 24 h to various concentrations
of amorphous silica nanoparticles in homogeneous suspensions of average size distribution (30, 48, 118, and 535 nm SiO2) and then assessed for uptake and biochemical changes. Results of transmission electron microscopy revealed all sizes of
silica were taken up into the cells and localized into the cytoplasm. The lactate dehydrogenase (LDH) assay shows LDH leakage
was dose- and size-dependent with exposure to 30 and 48 nm nanoparticles. However, no LDH leakage was observed for either
118 or 535 nm nanoparticles. The mitochondrial viability assay (MTT) showed significant toxicity for 30 and 48 nm at high
concentrations (100 μg/mL) compared to the 118 and 535 nm particles. Further studies were carried out to investigate if cellular
reduced GSH and mitochondria membrane potential are involved in the mechanism of SiO2 toxicity. The redox potential of cells (GSH) was reduced significantly at concentrations of 50, 100, and 200 μg/mL at 30 nm
nanoparticle exposures. However, silica nanoparticles larger than 30 nm showed no changes in GSH levels. Reactive oxygen species
(ROS) formation did not show any significant change between controls and the exposed cells. In summary, amorphous silica nanoparticles
below 100 nm induced cytotoxicity suggest size of the particles is critical to produce biological effects. 相似文献