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981.
Abstruct Quasi-set theory provides a mathematical background for dealing with coll ections of indistinguishable elementary particles.
In this paper, we show how to obtain the quantum statistics into the scope of quasi-set theory and we also discuss the Helium
atom, which represents the simplest example where indistinguishability plays an important role. One of the advantages of our
approach is that one of the most basic principles of quantum theory, namely, the Indistinguishability Postulate, does not
need to be assumed even implicitely in the axiomatic basis of quantum mechanics. 相似文献
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Andrew B. Moyes Andrew J. Schauer Rolf T. W. Siegwolf David R. Bowling 《Rapid communications in mass spectrometry : RCM》2010,24(7):894-900
We present a novel technique in which the carbon isotope ratio (δ13C) of soil CO2 is measured from small gas samples (<5 mL) injected into a stream of CO2‐free air flowing into a tunable diode laser absorption spectrometer (TDL). This new method extends the dynamic range of the TDL to measure CO2 mole fractions ranging from ambient to pure CO2, reduces the volume of sample required to a few mL, and does not require field deployment of the instrument. The measurement precision of samples stored for up to 60 days was 0.23‰. The new TDL method was applied with a simple gas well sampling technique to obtain and measure gas samples from shallow soil depth increments for CO2 mole fraction and δ13C analysis, and subsequent determination of the δ13C of soil‐respired CO2. The method was tested using an artificial soil system containing a controlled CO2 source and compared with an independent method using the TDL and an open soil chamber. The profile and chamber estimates of δ13C of an artificially produced CO2 flux were consistent and converged to the δ13C of the CO2 source at steady state, indicating the accuracy of both methods under controlled conditions. The new TDL method, in which a small pulse of sample is measured on a carrier gas stream, is analogous for the TDL technique to the development of continuous‐flow configurations for isotope ratio mass spectrometry. While the applications presented here are focused on soil CO2, this new TDL method could be applied in a number of situations requiring measurement of δ13C of CO2 in small gas samples with ambient to high CO2 mole fractions. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Leugers A Neithamer DR Sun LS Hetzner JE Hilty S Hong S Krause M Beyerlein K 《Journal of combinatorial chemistry》2003,5(3):238-244
This study has demonstrated that high-throughput FTIR transmission measurements using a newly designed array-based support formed using silicon wells and a silicon wafer is a very useful and robust tool for the characterization of polymer composition for combinatorial materials research. The comonomer content in copolymers can be measured accurately with a fully automated throughput of >300 samples/day (8 h). The transmission measurement is more robust, reliable, and easier to automate than other spectroscopic methods. The support itself provides excellent resistance to aggressive organic solvents at elevated temperatures and allows the unattended deposition and preparation of polymer films for infrared analysis. Because of the excellent durability of the support with respect to the solvent, the support can be rinsed and reused many times. This high-throughput approach to infrared transmission spectroscopy can be used for measuring a wide array of polymer characteristics: vinyl content, geometrical isomers, crystallinity, and tacticity. As well, this IR approach can be used to predict the oxidative stability of the antioxidant packages. Because the support provides a means of containing hot polymer solutions while the solvent evaporates, the support is also suitable for high-throughput nanoindentation methods for the determination of modulus and other physical properties of the polymer. 相似文献
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Franke D Lorbach V Esser S Dose C Sprenger GA Halfar M Thömmes J Müller R Takors R Müller M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(17):4188-4196
Cyclohexadiene-trans-5,6-diols such as (S,S)-2,3-dihydroxy-2,3-dihydrobenzoic acid (2,3-trans-CHD) have been shown to be of importance as chiral starting materials for the syntheses of bioactive substances, especially for the syntheses of carbasugars. By using methods of metabolic-pathway engineering, the Escherichia coli genes entB and entC, which encode isochorismatase and isochorismate synthase, were cloned and over-expressed in E. coli strains with a deficiency of entA, which encodes 2,3-dihydroxybenzoate synthase. A 30-fold increase in the corresponding EntB/EntC enzyme activities affects the accumulation of 2,3-trans-CHD in the cultivation medium. Although the strains did not contain deletions in chorismate-utilising pathways towards aromatic amino acids, neither chorismate nor any other metabolic intermediates were found as by-products. Fermentation of these strains in a 30 L pH-controlled stirred tank reactor showed that 2,3-trans-CHD could be obtained in concentrations of up to 4.6 g L(-1). This demonstrates that post-chorismate metabolites are accessible on a preparative scale by using techniques of metabolic-pathway engineering. Isolation and separation from fermentation salts could be performed economically in one step through anion-exchange chromatography or, alternatively, by reactive extraction. Starting from 2,3-trans-CHD as an example, we established short syntheses towards new carbasugar derivatives. 相似文献