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排序方式: 共有189条查询结果,搜索用时 15 毫秒
41.
F. v. Fillinger J. Jolles K. Reicher E. H. Stein A. C. Andersen Ivar Bang Clarence E. May B. Oppler E. Herzfeld E. Salkowski Carl Neuberg Omer Schewket Alessandro Bernardi H. Schirokauer G. G. Wilenko A. W. Peters Lester Reed Harry Koenigsfeld O. Tunmann J. Amann 《Analytical and bioanalytical chemistry》1914,53(4-5):334-340
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J.?ChenEmail author A.?Hangauer R.?Strzoda M.-C.?Amann 《Applied physics. B, Lasers and optics》2011,103(2):381-386
A random porous fiber for transporting terahertz (THz) waves is proposed in this paper. The fiber, which to the best of our
knowledge has not been investigated previously, has its core composed by randomly distributed air holes. A numerical study
was carried out near 1 THz, showing that the new fiber possesses some improved fiber properties compared to the regular periodic
porous fiber: the power fraction confined in the core is higher, the dispersion becomes lower, and more importantly a flatter
dispersion curve appears within the frequency range of 0.8 THz to 1.4 THz. 相似文献
45.
Spectrofluorimetric determination of pharmaceutical compounds with the cerium(IV)—cerium(III) system
The compounds to be determined are oxidised by cerium(IV). The concentration of cerium(III) formed is measured spectrofluorimetrically. The method has been used both in solution and, by fluorodensitometry, on t.l.c. plates. Detection limits of some substances are 15 ng ml-1 for the solution method and 5 ng per spot for the t.l.c. method. 相似文献
46.
S. Schilt K. Zogal B. K?gel P. Meissner M. Maute R. Protasio M.-C. Amann 《Applied physics. B, Lasers and optics》2010,100(2):321-329
An extensive characterization of the spectral properties of a largely tunable laser in the 1.56-μm spectral range is reported.
This device combines a vertical-cavity surface-emitting laser (VCSEL) with a micro-machined (MEMS) Bragg mirror in a very
compact arrangement. The large tunability obtained by an electro-thermal actuation of the MEMS mirror makes this device very
attractive for high-resolution spectroscopy. Relevant laser parameters for the implementation of wavelength modulation spectroscopy
techniques in gas sensing, such as tuning and modulation properties, are presented. A preliminary gas spectroscopy experiment
performed with this laser is also shown. 相似文献
47.
J. Chen A. Hangauer R. Strzoda M.-C. Amann 《Applied physics. B, Lasers and optics》2010,100(2):331-339
In this paper, an improved signal processing method is given, aiming at a sensitivity improvement of the tunable diode laser spectroscopy based gas concentration measurement. The gas absorption spectrum is probed with an optimum wavelength scanning function which enables a more efficient curve fit than for traditional linear wavelength scanning. The wavelength scanning function is determined to be optimum, in the sense that the variance of the estimated concentration noise is minimized. This optimum scanning function depends on the signal model used in curve fitting. Several models including interfering gas spectra and etalon fringes are examined. Compared to the gas absorption spectrum recorded by ramping the wavelength linearly, the optimum spectrum waveforms have a cascade structure, which means that the optimum scanning preferably samples important points of the spectrum. The new method theoretically enables a factor of ~2 improvement on detection sensitivity of the estimated concentration. Furthermore, direct spectroscopy is superior to second harmonic detection, because the concentration noise can be an additional factor of ~2 lower. 相似文献
48.
Boguslaw Buszewski Jacek Nowaczyk Tomasz Ligor Pawel Olszowy Magdalena Ligor Bartlomiej Wasiniak Wolfram Miekisch Jochen K. Schubert Anton Amann 《Journal of separation science》2009,32(14):2448-2454
The aim of this study was the preparation of polypyrrole (PPy) fibers for solid phase microextraction (SPME). PPy coatings were obtained during the electrochemical polymerization process. The utility of various metal wires (Fe, Cu, Ag, Cu/Ag, kanthal and medical stainless steel) as a support for polymers was compared. Various experimental conditions of the synthesis process such as scan rate, voltage limits and number of scans and deposition time were applied. The average polymer thickness was in the range of 7–125 μm and its weight was in the scope of 0.65–5.6 mg. Different techniques, mainly elemental analysis, Fourier transform infrared spectroscopy, microscopy, and chromatography were performed for the characterization of obtained fibers with microporous structure. The extraction efficiency of cardiovascular drugs (metoprolol, propranolol, oxprenolol, propafenone and mexiletine) by means of fibers was tested. The concentration of mentioned compounds in standard solution was in the span of 10–150 ng/mL. LC‐MS was employed for determination of drugs in desorption solution. LODs varied from 0.013 to 1.51 ng/mL for metoprolol and mexiletine respectively. The repeatability of extraction was obtained with the RSD values lower than 10%. 相似文献
49.
A phenanthridinium-containing DNA building block was synthesized as an ethidium nucleoside analogue starting from 3,8-diamino-6-phenyl-phenanthridine. Using this building block, oligonucleotides bearing the phenanthridinium moiety as an artificial DNA base were prepared via automated solid-phase phosphoramidite chemistry. The modified phenanthridinium-containing DNA duplexes were characterized by UV/vis absorption spectroscopy (including the melting behavior), CD spectroscopy, and steady-state fluorescence spectroscopy. These experiments reveal the expected similarity of the synthetic phenanthridinium moiety with noncovalently bound ethidium. More importantly, the results show clearly that the artificial phenanthridinium base is intercalated within the DNA base stack. The counterbase as part of the complementary strand seems to have only a minor influence on the intercalation properties of the phenanthridinium moiety. 相似文献
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