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51.
Schulz K Schlenz K Metasch R Malt S Römhild W Dressler J 《Journal of chromatography. A》2008,1200(2):235-241
A rapid headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) method has been developed for the determination of anethole in serum samples. Anethole is a characteristic marker for the consumption of aniseed spirits. This method enabled the detection of anethole with a limit of detection (LoD) of 3.6 ng/ml and a limit of quantification (LoQ) of 5.3 ng/ml in serum samples with a good degree of precision intraday (2.8%) and interday (4.5%). Experiments were conducted with one volunteer, in which the subject consumed the alcoholic drink ouzo on 3 different days under controlled conditions. At defined intervals, blood samples were taken from the subject. Using these blood samples, the concentration-time profiles for anethole were determined. In blood samples taken from 50 drivers who claimed to have consumed drinks containing anethole (ouzo, raki and the German aniseed liqueur "Küstennebel") before the taking of the blood sample, anethole was detected in the serum in concentrations of between 5.4 and 17.6 ng/ml in 10 cases. This is the first report describing the qualitative and quantitative determination of a beverage-characteristic aroma compound - in this case anethole - in serum samples after consumption of alcoholic beverages. 相似文献
52.
Juliana S.F. Pereira Paola A. Mello Diogo P. Moraes Fábio A. Duarte Valderi L. Dressler Guenter Knapp Érico M.M. Flores 《Spectrochimica Acta Part B: Atomic Spectroscopy》2009
In this study, microwave-induced combustion (MIC) of extra-heavy crude oil is proposed for further chlorine and sulfur determination by inductively coupled plasma optical emission spectrometry (ICP OES). Combustion was carried out under oxygen pressure (20 bar) in quartz vessels using ammonium nitrate (50 µl of 6 mol l− 1 solution) as ignition aid. Samples were wrapped with polyethylene film and placed on a quartz holder positioned inside the quartz vessels. The need for an additional reflux step after combustion and the type and concentration of absorbing solution (water, 0.02 to 0.9 mmol l− 1 H2O2, 10 to 100 mmol l− 1 (NH4)2CO3 or 0.1 to 14 mol l− 1 HNO3) were studied. The influence of sample mass, O2 pressure and maximum pressure attained during the combustion process were investigated. Recoveries from 92 to 102% were obtained for Cl and S for all absorbing solutions. For comparison, Cl and S determination was also performed by ion chromatography (IC) using 25 mmol l− 1 (NH4)2CO3 as absorbing solution. Using MIC with a reflux step the agreement was better than 95% for certified reference materials of similar composition (crude oil, petroleum coke, coal and residual fuel oil). Microwave-assisted digestion and water extraction in high pressure closed vessels were also evaluated. Using these procedures the maximum recoveries were 30 and 98% for Cl and S, respectively, using microwave-assisted digestion and 70% for Cl and less than 1% for S by water extraction procedure. Limits of detection by ICP OES were 12 and 5 µg g− 1 for Cl and S, respectively, and the corresponding values by IC were 1.2 and 8 µg g− 1. Using MIC it was possible to digest simultaneously up to eight samples resulting in a solution suitable for the determination of both analytes with a single combustion step. 相似文献
53.
Dvorak J Brüchle W Chelnokov M Dressler R Düllmann ChE Eberhardt K Gorshkov V Jäger E Krücken R Kuznetsov A Nagame Y Nebel F Novackova Z Qin Z Schädel M Schausten B Schimpf E Semchenkov A Thörle P Türler A Wegrzecki M Wierczinski B Yakushev A Yeremin A 《Physical review letters》2006,97(24):242501
Theoretical calculations predict 270Hs (Z=108, N=162) to be a doubly magic deformed nucleus, decaying mainly by alpha-particle emission. In this work, based on a rapid chemical isolation of Hs isotopes produced in the 26Mg+248Cm reaction, we observed 15 genetically linked nuclear decay chains. Four chains were attributed to the new nuclide 270Hs, which decays by alpha-particle emission with Qalpha=9.02+/-0.03 MeV to 266Sg which undergoes spontaneous fission with a half-life of 444(-148)(+444) ms. A production cross section of about 3 pb was measured for 270Hs. Thus, 270Hs is the first nucleus for which experimental nuclear decay properties have become available for comparison with theoretical predictions of the N=162 shell stability. 相似文献
54.
Three methods (Lang-topgraphy, one-crystal-rocking curves with scan-step-registration, two-crystal-diffractometry (TCD) with a large registered area) were tested. The reached parameters as well as advantages and disadvantages are discussed. The purpose of the examination is the application of CaF2-crystals with high diameters (⪆ 100 mm) in high-performance optics for the UV-lithography. Especially in this context the influence of defects of the crystal structure on the index of refraction has been examined. 相似文献
55.
56.
Grain structures of CaF2 crystals are examined by X-ray topography (Berg-Barrett-technique) and two-crystal-diffractometry. The possibilities of these techniques for the examination of samples with grain structures are discussed. 相似文献
57.
58.
L. Dressler 《Crystal Research and Technology》1986,21(8):1085-1089
Relationships between the residual stress fields in fluorite and the regime of temperature during the crystal growth have been examined. Beside heat conduction the internal heat transfer in the growing crystal by radiation is important, and therefore an effective anisotropy of heat transfer properties in axial and radial direction exists. 相似文献
59.
M. Buck Ch. Dressler M. Grunze T. Schaich W. Schrepp D. Segal F. Träger 《Fresenius' Journal of Analytical Chemistry》1994,349(1-3):58-62
In two different types of experiments, polymer films on gold substrates were investigated by optical second harmonic generation (SHG). Thickness dependent ex situ measurements on Langmuir-Blodgett films of the octadecylammonium salt of polyamic acid (PACS) show a preferential orientation of the polymer molecules. In situ SHG experiments were performed to monitor the growth of polyamic acid films deposited from the gas phase. Pyromellitic dianhydride (PMDA), 4,4-oxydianiline (ODA), and 4,4-diaminodiphenyl disulfide (DAPS) served as monomers. Similar to the Langmuir-Blodgett films, an oriented growth is observed. The thickness dependence of the SHG signal is strongly dependent on the interfacial chemistry which is very different for the two amines used as monomers. Based on a comprehensive three layer model, the relation between the structure of the films and the SHG signal is discussed. 相似文献
60.
M. Nofz J. Pauli M. Dressler Ch. Jügeg W. Altenburg 《Journal of Sol-Gel Science and Technology》2006,38(1):25-35
A new method of preparing concentrated alumo-sols, the hydrolysis of Al-tri-sec-butylate in acidic aqueous media at 85°C,
was studied in detail by varying the H2O/Al- and NO3
−/Al-ratios in wide ranges. The components of the sols were characterized by 27Al NMR spectroscopy. The pH-value depends on both the chosen H2O/Al- and NO3
−/Al-ratio and on the aging time of the sols and reflects the composition of the sols. Al13 polycations were detected in sols with a pH-value between 3.0 and 3.7. As a new result its presence was shown by NMR below
3.4. The Al13 content of the sols increased with pH and the maximum fraction of Al13 polycations was detected in the sol with the highest pH (3.7). Nearly 65% of the entire aluminium content of this solution
is bound in the Al13 polycations. Hence, a new synthetic method for the preparation of Al13 ions containing sols was developed.
Aging studies of the sols showed, that the Al13 polycations were more stable in solutions with higher pH-value. Al13 polycations were detected after an aging time of four months only in sols with a pH-value of 3.7. Tempering the aged sols
at 40° to 80°C caused formation of Al13 and also of Al30 polycations. 相似文献