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91.
H. A. Michelsen M. A. Linne B. F. Kock M. Hofmann B. Tribalet C. Schulz 《Applied physics. B, Lasers and optics》2008,93(2-3):645-656
This paper presents an analysis of several equations used to model laser-induced incandescence (LII) of soot. The analysis focuses on sub-models of the change in particle enthalpy during sublimation, conduction, and oxidation. Assuming that pressure is constant, expressing the conductive cooling rate in terms of enthalpy instead of energy, thereby accounting for expansion work, increases the signal decay rate and has an effect comparable to increasing the thermal accommodation coefficient from 0.30 to 0.38. Accounting for oxidative heating decreases the signal decay rate and has an effect comparable to decreasing the accommodation coefficient from 0.30 to 0.25. As an estimate of magnitude of these effects, primary particle sizes inferred from signal decay rates measured at low fluences may be over-predicted by as much as 17% if oxidation is neglected in the model at O2 partial pressures of ~0.2 bar, under-predicted by 24% if expansion work is neglected, and under-predicted by only 9% if both are neglected. This paper also provides updated parameterizations for average enthalpies of formation, molecular weights, and total pressures of sublimed carbon clusters for use in LII models. 相似文献
92.
The copper content of some geological samples has been determined by thermal neutron activation and subsequent coincidence gamma-spectrometry, taking advantage of the 180 degrees annihilation quanta of (64)Cu. By this means the interference of (24)Na, which is often the major gamma-activity induced in geological materials, is greatly reduced. The method is precise to about +/- 5 %, and the error is of the same order. The method should be especially attractive for application to samples with a copper content of 100-1000 ppm. 相似文献
93.
Kimmo A Michelsen Daniël LA van den Hove Christoph Schmitz Olivier Segers Jos Prickaerts Harry WM Steinbusch 《BMC neuroscience》2007,8(1):107
Background
Both prenatal stress (PS) and postnatal chronic mild stress (CMS) are associated with behavioral and mood disturbances in humans and rodents. The aim of this study was to reveal putative PS- and/or CMS-related changes in basal spine morphology and density of pyramidal neurons in the rat medial prefrontal cortex (mPFC). 相似文献94.
Georgios M. Kontogeorgis Ioannis TsivintzelisMichael L. Michelsen Erling H. Stenby 《Fluid Phase Equilibria》2011,301(2):244-256
Association equations of state like SAFT, CPA and NRHB have been previously applied to many complex mixtures. In this work we focus on two of these models, the CPA and the NRHB equations of state and the emphasis is on the analysis of their predictive capabilities for a wide range of applications. We use the term predictive in two situations: (i) with no use of binary interaction parameters, and (ii) multicomponent calculations using binary interaction parameters based solely on binary data. It is shown that the CPA equation of state can satisfactorily predict CO2-water-glycols-alkanes VLE and water-MEG-aliphatic hydrocarbons LLE using interaction parameters obtained from the binary data alone. Moreover, it is demonstrated that the NRHB equation of state is a versatile tool which can be employed equally well to mixtures with pharmaceuticals and solvents, including mixed solvents, as well as phase equilibria in mixtures containing glycols. The importance of considering the solvation of CO2-water (in CPA) when the model is applied to multicomponent mixtures as well as of the multiple associations in heavy glycol-water mixtures (in NRHB) is investigated. 相似文献
95.
Andresen LC Konestabo HS Maraldo K Holmstrup M Ambus P Beier C Michelsen A 《Rapid communications in mass spectrometry : RCM》2011,25(11):1485-1496
The rising atmospheric CO(2) concentration, increasing temperature and changed patterns of precipitation currently expose terrestrial ecosystems to altered environmental conditions. This may affect belowground nutrient cycling through its intimate relationship with the belowground decomposers. Three climate change factors (elevated CO(2), increased temperature and drought) were investigated in a full factorial field experiment at a temperate heathland location. The combined effect of biotic and abiotic factors on nitrogen and carbon flows was traced in plant root → litter → microbe → detritivore/omnivore → predator food-web for one year after amendment with (15)N(13)C(2)-glycine. Isotope ratio mass spectrometry (IRMS) measurement of (15)N/(14)N and (13)C/(12)C in soil extracts and functional ecosystem compartments revealed that the recovery of (15)N sometimes decreased through the chain of consumption, with the largest amount of bioactive (15)N label pool accumulated in the microbial biomass. The elevated CO(2) concentration at the site for 2 years increased the biomass, the (15)N enrichment and the (15)N recovery in detritivores. This suggests that detritivore consumption was controlled by both the availability of the microbial biomass, a likely major food source, and the climatic factors. Furthermore, the natural abundance δ(13)C of enchytraeids was significantly altered in CO(2)-fumigated plots, showing that even small changes in δ(13)C-CO(2) can be used to detect transfer of carbon from primary producers to detritivores. We conclude that, in the short term, the climate change treatments affected soil organism activity, possibly with labile carbohydrate production controlling the microbial and detritivore biomass, with potential consequences for the decomposition of detritus and nutrient cycling. Hence, there appears to be a strong coupling of responses in carbon and nitrogen cycling at this temperate heath. 相似文献
96.
97.
Bindslev H Nielsen SK Porte L Hoekzema JA Korsholm SB Meo F Michelsen PK Michelsen S Oosterbeek JW Tsakadze EL Westerhof E Woskov P;TEXTOR team 《Physical review letters》2006,97(20):205005
Here we present the first measurements by collective Thomson scattering of the evolution of fast-ion populations in a magnetically confined fusion plasma. 150 kW and 110 Ghz radiation from a gyrotron were scattered in the TEXTOR tokamak plasma with energetic ions generated by neutral beam injection and ion cyclotron resonance heating. The temporal behavior of the spatially resolved fast-ion velocity distribution is inferred from the received scattered radiation. The fast-ion dynamics at sawteeth and the slowdown after switch off of auxiliary heating is resolved in time. The latter is shown to be in close agreement with modeling results. 相似文献
98.
Dieter Wöhrle Maria Shopova Jörg G. Moser Holger Kliesch Ulrike Michelsen Silke Müller Andrea Weitemeyer 《Macromolecular Symposia》1996,105(1):127-138
Different possibilities of macromolecular metal complexes as photosensitizers (PS) for their potential use in the photodynamic therapy of cancer are described. The prepared metal porphyrazin derivatives (metals: Zn(II), Si(IV)(X)2) exhibit long wavelength absorption and high singlet oxygen quantum yields under irradiation. One possibility is the incorporation of the PSs in liposomal vesicles giving hydrophobic conjugates with low densitiy proteins in the serum after injection. Good tumor accumulation and photodynamic activities are observed. Increased tumor uptake is also known for Pcs covalently connected via the ligand to poly(ethylene glycol monomethyl ether). New compounds contain the hydrophilic polymer at axial substituents of Si(X)2Pc and Si(X)2Nc. Some newly synthesized compounds with only one functional group exhibit the possibility of coupling to macromolecules like e.g. monoclonal antibodies. 相似文献