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排序方式: 共有96条查询结果,搜索用时 46 毫秒
1.
A. Craig W. H. Jacobson A. Meyer N. Welwart A. Seuthe H. N. Marr B. S. Evans G. E. F. Lundell J. A. Scherrer E. Stelling F. J. Mück A. Kling A. Lassieur L. Bertiaux C. C. Bissett P. de Pauw J. Heslinga A. Bartsch R. E. Lee W. H. Fegeley F. H. Reichel und E. Saz 《Fresenius' Journal of Analytical Chemistry》1927,71(1-2):83-90
Ohne Zusammenfassung 相似文献
2.
Summary Gas chromatography has been employed in the separation of mixtures of air, carbon dioxide, nitrous oxide and a volatile anaesthetic (halothane, isoflurane or enflurane) on a single Chromosorb 101 column by temperature programming from room temperature. Calibration over the required range for the analysis of exhaled air, demonstrated good linearity with a repeatability for test mixtures of about 1%. 相似文献
3.
Iain L. Marr Petra Kluge Laura Main Vincent Margerin Cyrille Lescop 《Mikrochimica acta》1995,119(3-4):219-232
Three sets of samples have been investigated in some detail. One set is from a river polluted by mine workings, containing substantial levels of Fe, Mn,Cu, Zn and Ni with traces of many other metals. The second set consists of typical estuarine sediments contaminated from a wide range of industrial sources, and the third set consists of oily drilling cuttings from the sea bottom in the vicinity of a North Sea oil production platform.These samples have been subjected to treatment 1) with EDTA at two different pH's (extracts) 2) with HNO3/H2O2 3) with HNO3/HCl and 4) with HNO3/HCl/HF (digests). EDTA recoveries, compared toaqua regia digests, are often very reproducible, not dependent on pH, and usually significantly low. Nitric/peroxide andaqua regia digests often give very close results suggesting that these are meaningful values indicating the maximum levels of polluting metals in the sediments. However, the triple acid digest with HF does sometimes give higher values (and reasonable agreement for CRM's such as MESS-1) but with poorer reproducibility. 相似文献
4.
The enzyme catalysed oxidation of ferrocene and some substituted ferrocenes to the corresponding ferricinium ions by hydrogen peroxide in the presence of native or immobilized horseradish peroxidase has been studied. Initial and maximum rates of oxidation have been determined. It was found that the oxidation was independent of the hydrogen peroxide concentration. The oxidation of ferrocene was effected also by horseradish peroxidase in a coupled system with glucose oxidase in the absence of any added hydrogen peroxide. 相似文献
5.
Wang Q Barclay JE Blake AJ Davies ES Evans DJ Marr AC McInnes EJ McMaster J Wilson C Schröder M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(14):3384-3396
A novel [NiS4Fe2(CO)6]cluster (1: 'S(4)'=(CH(3)C(6)H(3)S(2))(2)(CH(2))(3)) has been synthesised, structurally characterised and has been shown to undergo a chemically reversible reduction process at -1.31 V versus Fc(+)/Fc to generate the EPR-active monoanion 1(-). Multifrequency Q-, X- and S-band EPR spectra of (61)Ni-enriched 1(-) show a well-resolved quartet hyperfine splitting in the low-field region due to the interaction with a single (61)Ni (I=3/2) nucleus. Simulations of the EPR spectra require the introduction of a single angle of non-coincidence between g(1) and A(1), and g(3) and A(3) to reproduce all of the features in the S- and X-band spectra. This behaviour provides a rare example of the detection and measurement of non-coincidence effects from frozen-solution EPR spectra without the need for single-crystal measurements, and in which the S-band experiment is sensitive to the non-coincidence. An analysis of the EPR spectra of 1(-) reveals a 24 % Ni contribution to the SOMO in 1(-), supporting a delocalisation of the spin-density across the NiFe(2) cluster. This observation is supported by IR spectroscopic results which show that the CO stretching frequencies, nu(CO), shift to lower frequency by about 70 cm(-1) when 1 is reduced to 1(-). Density functional calculations provide a framework for the interpretation of the spectroscopic properties of 1(-) and suggest that the SOMO is delocalised over the whole cluster, but with little S-centre participation. This electronic structure contrasts with that of the Ni-A, -B, -C and -L forms of [NiFe] hydrogenase in which there is considerable S participation in the SOMO. 相似文献
6.
Dr. Ádám Eördögh Annabell Martin Prof. Dr. Pablo Rivera-Fuentes 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(71):e202202832
Single-molecule localization microscopy (SMLM) can reveal nanometric details of biological samples, but its high phototoxicity hampers long-term imaging in live specimens. A significant part of this phototoxicity stems from repeated irradiations that are necessary for controlled switching of fluorophores to maintain the sparse labeling of the sample. Lower phototoxicity can be obtained using fluorophores that blink spontaneously, but controlling the density of single-molecule emitters is challenging. We recently developed photoregulated fluxional fluorophores (PFFs) that combine the benefits of spontaneously blinking dyes with photocontrol of emitter density. These dyes, however, were limited to imaging acidic organelles in live cells. Herein, we report a systematic study of PFFs that culminates in probes that are functional at physiological pH and operate at longer wavelengths than their predecessors. Moreover, these probes are compatible with HaloTag labeling, thus enabling timelapse, single-molecule imaging of specific protein targets for exceptionally long times. 相似文献
7.
Brian Spencer Robert A Marr Edward Rockenstein Leslie Crews Anthony Adame Rewati Potkar Christina Patrick Fred H Gage Inder M Verma Eliezer Masliah 《BMC neuroscience》2008,9(1):109
Background
Proteolytic degradation has emerged as a key pathway involved in controlling levels of the Alzheimer's disease (AD)-associated amyloid-β (Aβ) peptide in the brain. The endopeptidase, neprilysin, has been implicated as a major Aβ degrading enzyme in mice and humans. Previous short and intermediate term studies have shown the potential therapeutic application of neprilysin by delivering this enzyme into the brain of APP transgenic mice using gene transfer with viral vectors. However the effects of long-term neprilysin gene transfer on other aspects of Aβ associated pathology have not been explored yet in APP transgenic mice. 相似文献8.
R. Nowka I. L. Marr T. M. Ansari H. Müller 《Fresenius' Journal of Analytical Chemistry》1999,364(6):533-540
Solid sampling graphite furnace atomic absorption spectroscopy (SS-GFAAS) has been used for the determination of traces of
heavy metals (Cd, Pb, Cu, Cr, Ni, V and As) in barytes over a wide concentration range, e.g. Cd from 0.023 to 27.0 μg/g and
Pb from 1.54 to 3509 μg/g.The necessity of determining heavy metals in commercial barytes (naturally occurring barium sulfate),
a mineral important to the oil industry because of its use in drilling muds, is discussed. The problems presented by the analysis
of this difficult matrix are elegantly solved by using SS-GFAAS for the direct determination of heavy metals. A high-performance
graphite furnace AAS with D2-background correction system and a transversely heated graphite atomizer was used for the investigations. The spectrometer
was combined with a mechanical sampling module and an ultramicrobalance. The transfer of solid samples (sample weights 0.031–0.686
mg) into the atomizer was carried out by using an optimized graphite platform as the sample carrier. Calibration curve techniques
and standard addition methods were employed using external standards (CRMs). Problems associated with signal deformations
like multiple peaks, tailing or shoulders are also discussed and possibilities to solve the problems are given. The influence
of the homogeneity of solid samples on the precision and accuracy are shown in a real example. The results obtained by SS-GFAAS
were compared with results by other methods like X-ray fluorescence spectroscopy (XRF) and flame AAS after aqua regia microwave extraction. This study has demonstrated that SS-GFAAS is a very powerful and easy-to-use method for quick and accurate
analysis of barytes.
Received: 9 November 1998 / Revised: 29 January 1999 / Accepted: 2 February 1999 相似文献
9.
This paper describes anisotropy of various second moments along with detailed mean velocities in the human breathing zone.
High anisotropy levels have been anticipated due to the complexity of the flow and low Reynolds number in our cubicle sized
setting. The measurement system is a standard stereo PIV system acquiring data along a sinusoidal breathing waveform in the
breathing zone of a thermal manikin both with and without rotational motion. Results suggest that the airflow due to breathing
is anisotropic. Because of this, common isotropic assumptions made in this environment are not admissible. 相似文献
10.
Analysis of recorded acoustic gunshot signals to determine firearm waveform characteristics requires an understanding of the impulsive signal events, how the waveforms vary among different sources, and how the waveforms are affected by the environment and the recording system. This paper presents empirical results from waveforms produced by different small firearms and an analysis of their variations under different and controlled conditions. Acoustic signals were generated using multiple firearm makes and models firing different ammunition types. Simultaneous recordings from the microphones located at different distances from the source and at different azimuth angles (from the line-of-fire) were used to study source characteristics and sound propagation effects. The results indicate that recorded gunshot waveforms generally consist of multiple acoustic events, and these are observable depending on the received distance and azimuth angle. The source blast size, microphone distance, and microphone azimuth angle are the primary factors affecting the recorded muzzle blast characteristics. Ground or object reflections and ballistic shockwaves and their reflections can interfere with the muzzle blast waveform and its measurements. This experiment confirmed and quantified the wide range of correlation results between waveforms recorded from different source, microphone distance, and microphone angle configurations. 相似文献