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1.
Siegfried Noack 《Accreditation and quality assurance》1998,3(11):436-443
An important part of quality assurance in any analytical laboratory is the production of comprehensive results integrating uncertainty measurements. Many testing laboratories face the problem that the expenditure required to evaluate small uncertainties (high precision and high accuracy) is often uneconomic. In most cases an uncertainty of high reliability has to be calculated from only a few data (one calibration, few replications, etc.). This problem can be solved by an expert system. To achieve this the analytical procedure has to be structured into a dialouge and divided into parts. The uncertainty has to be calculated for each part of the procedure. Addition of the individual uncertainties results in the combined and expanded uncertainty. During the dialouge the system should advise the analyst how to get an efficient and effective calculation of uncertainty. All calculations, mathematical and statistical procedures have to be surveyable but running the system should not be too time consuming for economic reasons. Within the scope of the EURECA-project initiated by the Eidgenössische Materialprüfungs- und Forschungsanstalt (EMPA), St. Gallen, Switzerland, expert system software is being developed in cooperation with other research institutes and manufacturers of analytical instruments. Using this software it will be possible to calculate the uncertainty for analytical procedures such as titration, atomic emission spectrometry (ICP-OES), atomic absorption spectrometry (AAS) and gas- and liquid chromatography (GC, HPLC). 相似文献
2.
Nearly transform limited femtosecond pulses tunable between 2.56 and 3.16 m have been generated by optical parametric amplification. The single stage parametric amplifier is pumped by a tunable high power femtosecond Ti:sapphire laser system at 1 kHz repetition rate and seeded by quasi-continuous wave (cw) radiation from the Q-switched Nd:YLF laser used to pump the regenerative amplifier. The 100 fs idler pulses are shorter than the pump pulses. The mechanism of the achieved pulse compression is discussed and experimental results are compared with numerical simulations. 相似文献
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New Ternary Phosphides and Arsenides of Cesium and Element of the 8th Transition Metal Group In the ternary systems Cesium/8th transition metal group/5th main group some new compounds were found and investigated. By single crystal measurements CsRh2P2 was found to crystallize in the space group 14/mmm with the lattice constants a = 390.11 pm and c = 1429.36 pm. The new compounds with the formula CsM2X2 (M = Fe, Co, Ru, Rh, Ir; X = P or As) crystallize in the ThCr2Si2-type structure, compounds of the formula Cs2MX2 (M = Ni, Pd, Pt; X = P or As) can be placed in a line with the K2PdP2-type structure. 相似文献
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Th. Freudenberg W. Radloff H. -H. Ritze V. Stert K. Weyers F. Noack I. V. Hertel 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1996,36(3-4):349-364
The formation of protonated and unprotonated ammonia cluster ions is studied by femtosecond two colour two photon pump-probe techniques applied to (NH3) n and (ND3) n clusters withn up to 8. The fourth harmonic (~ 200 nm, 6.2 eV, 160 fs) of a Ti: Sapphire laser pulse is used to excite the clusters in a state corresponding to theà state of NH3 while the third harmonic (267 nm, 4.65 eV) is used for the subsequent ionisation step. Employing a combination of the optical Bloch equations for the excitation process and rate equations for the cluster dynamics we calibrate the zero time delay and carefully analyse the time dependence of the pump-probe signal. Several distinct intermediate steps in the time evolution can be distinguished, having characteristic time constants ranging from 40 fs to over 100 ps. They are discussed in a consistent scheme for the excitation, ionisation and protonation dynamics, accounting also for characteristic differences observed between deuterated and undeuterated species. A particularly remarkable time dependence of the homogeneous (NH3) 2 + cluster ion signal is interpreted as a fingerprint of internally protonated neutral precursors of the type NH3NH2NH4. 相似文献
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Nano titanium dioxide (nTiO2), generally considered to be toxicologically inert, is manufactured in large quantities and extensively applied in consumer products. The small size and large surface area endow them with an active group or intrinsic toxicity. Advances in instrumentation are making Raman spectroscopy the tool of choice for an increasing number of (bio) chemical applications. One of the great advantages of this technique is its ability to provide information on the concentration, structure and interaction of biochemical molecules in their microenvironments within intact cells and tissues, non-destructively. Zebrafish (Danio rerio), one of the most important vertebrate model organisms used in developmental biology, are increasingly used in biomedical research, particularly as a model of human disease. In the present work, an attempt is made to study the effect of titanium dioxide, both nano and bulk, on the microenvironment of the liver tissues of Zebrafish using FT-Raman spectroscopy. The results of the present study suggest that TiO2 exposure demonstrate a marked influence on the microenvironments of the liver tissues of Zebrafish. A shift to a higher wavenumber and an increase in the intensity of the band at ∼1087 cm−1 in the TiO2 exposed tissues suggest that some of the conformational changes resulting from the alkali recovery process takes place due to TiO2 exposure. The decreased intensity ratio (I3220/I3400) observed in the titanium-exposed tissues suggests a decreased water domain size, which could be interpreted in terms of weaker hydrogen-bonded molecular species of water in the TiO2 exposed tissues. The observed shift of COO− bands to higher frequencies shows the disruption of salt bridges as a result of a change in the oppositely charged partners and due to the enhanced random coil conformation. The variation in the intensity ratio of the tyrosyl doublet (I858/I825) indicates variation in the hydrogen bonding of the phenolic hydroxyl group due to TiO2 exposure. The results further suggest that the microenvironments are greatly altered due to titanium nano exposure when compared to titanium bulk. In conclusion, the results indicate that FT-Raman spectroscopy might be a useful tool for rapid assessment of nano particle biological interactions. 相似文献
9.
Ivo Lakomy Daniel Sarbach Bruno Traber Christoph Arm Daniel Zuber Hanspeter Pfander Klaus Noack 《Helvetica chimica acta》1997,80(2):472-486
Starting from (R)-3-hydroxybutyric acid ((R)- 10 ) the C45- and C50-carotenoids (all-E,2S,2′S)-bacterioruberm ( 1 ), (all-E,2S,2′S)-monoanhydrobacterioruberin ( 2 ), (all-E,2S,2′S)-bisanhydrobacterioruberin ( 3 ), (all-E,2R,2′R)-3,4,3′,4′-tetrahydrobisanhydrobacterioruberin ( 5 ), and (all-E,S)-2-isopentenyl-3,4-dehydrorhodopin ( 6 ) were synthesized. By comparison of the chiroptical data of the natural and the synthetic compounds, the (2S)- and (2′S)-configuration of the natural products 1–3 and 6 was established. 相似文献
10.
Steinkellner O Noack F Ritze HH Radloff W Hertel IV 《The Journal of chemical physics》2004,121(4):1765-1770
Two-photon excitation with femtosecond laser pulses in the spectral range 240-250 nm was used to prepare vapor phase H(2)O and D(2)O in the C (1)B(1) and D (1)A(1) states. Both states are predissociated via the B (1)A(1) state, forming excited OH/OD(A (2)Sigma(+)) as well as ground state OH/OD(X (2)Pi). We used ultrashort infrared probe pulses (1.65-2.42 microm) to control the ratio between these excited and ground state fragments originating from the dissociation process. Time resolved detection of the OH/OD(A (2)Sigma(+)) --> OH/OD(X (2)Pi) fluorescence allows us to monitor the dynamics of the predissociation. For the heterogeneous predissociation out of the C(1)B(1) state life times of (0.5 +/- 0.1) ps and (1.2 +/- 0.1) ps were found for H(2)O and D(2)O, respectively. The purely homogeneous character of the predissociation out of the D (1)A(1) state was monitored. 相似文献