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In a melt with the base mol% composition 25Na2O-15B2O3-60SiO2, doped with chromium and manganese, a redox reaction takes place during cooling the melt. This reaction was studied using high temperature UV-vis spectroscopy. Above 600 °C, the reaction is in equilibrium and shifted during cooling to the Cr3+ and Mn3+ species. At temperatures between 500 and 600 °C, the kinetics of the redox reaction is decisive and the cooling rate plays an important part. At temperatures < 500 °C, the reaction is frozen in. The smaller the cooling rate, the smaller is the Cr6+ concentration and the lower is the fictive redox temperature.The kinetics of the reaction was described by a differential equation assuming Arrhenian behaviour. The equation was numerically solved and fictive temperatures were calculated. These temperatures depended on cooling rate similar to Bartenev equation. Activation energies calculated hereof were around 38 kJ?mol−1 larger than those inserted into the kinetic equation. The experimentally determined activation energy is 565 kJ?mol−1, a value much larger than the activation energies of diffusion of the polyvalent elements. The rate determining step in the case of the Cr3+/Cr6+/Mn2+/Mn3+ system is the electron transfer reaction, because a notable structural rearrangement is necessary during the course of the electron transfer reaction (Cr3+ and Cr6+ occur in octahedral and tetrahedral coordination, respectively). The latter leads to a large inner reorganisation energy and to an activation energy similar to that of the viscous flow. In the case of the redox reaction between copper and arsenic, the activation energy is much smaller (210 kJ?mol−1), because here the coordination numbers do not change during the course of the redox reaction. 相似文献
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Low-voltage-operating organic electrochemical light-emitting cells (LECs) and transistors (OECTs) can be realized in robust device architectures, thus enabling easy manufacturing of light sources using printing tools. In an LEC, the p-n junction, located within the organic semiconductor channel, constitutes the active light-emitting element. It is established and fixated through electrochemical p- and n-doping, which are governed by charge injection from the anode and cathode, respectively. In an OECT, the electrochemical doping level along the organic semiconducting channel is controlled via the gate electrode. Here we report the merger of these two devices: the light-emitting electrochemical transistor, in which the location of the emitting p-n junction and the current level between the anode and cathode are modulated via a gate electrode. Light emission occurs at 4 V, and the emission zone can be repeatedly moved back and forth within an interelectrode gap of 500 μm by application of a 4 V gate bias. In transistor operation, the estimated on/off ratio ranges from 10 to 100 with a gate threshold voltage of -2.3 V and transconductance value between 1.4 and 3 μS. This device structure opens for new experiments tunable light sources and LECs with added electronic functionality. 相似文献
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R. Springer und H. Isak 《Fresenius' Journal of Analytical Chemistry》1964,199(5):363-366
Zusammenfassung Polyäthylenglykole vermögen die Existenz von Chromperoxid zu stabilisieren. Dabei wird die Oktettlücke des in freiem Zustande äußerst unbeständigen CrO5 durch das freie Elektronenpaar der Äthersauerstoffatome der Polyäthylenglykole besetzt. Auf dieser Stabilisierung des tiefblauen CrO5 basiert der hier beschriebene Nachweis der Polyäthylenglykole.
9. Mitteilung: Springer, R., u. H. Isak: Dtsch. Apotheker-Ztg. 103, 525 (1963). 相似文献
Summary Polyethylene glycols have the ability to stabilize chromium peroxide. The octet gap of CrO5 (which is extremely unstable in the free state) is filled up by the free electron pair of the ether oxygen atoms of the polyethylene glycols. The described detection of polyethylene glycols is based on this stabilisation of the dark blue CrO5.
9. Mitteilung: Springer, R., u. H. Isak: Dtsch. Apotheker-Ztg. 103, 525 (1963). 相似文献
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Madhushaw RJ Lo CY Hwang CW Su MD Shen HC Pal S Shaikh IR Liu RS 《Journal of the American Chemical Society》2004,126(47):15560-15565
Treatment of a series of 2',2'-disubstituted (o-ethynyl)styrenes with TpRu(PPh(3))(CH(3)CN)(2)PF(6) (10 mol %) in benzene (80 degrees C, 12-18 h) efficiently gave 2-alkenyl-1H-indene derivatives. This catalytic reaction represents an atypical enyne cycloisomerization with skeletal rearrangement of starting enyne, where the C=C bond is completely cleaved and inserted by the terminal alkynyl carbon. The reaction mechanism was elucidated by a series of deuterium and (13)C labeling experiments, as well as by changing the substituents at the phenyl moieties. The mechanism is proposed to involve the following key steps: 5-endo-dig cyclization of ruthenium-vinylidene intermediate, a nonclassical ion formation, and the "methylenecyclopropane-trimethylenemethane" rearrangement. 相似文献
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Calculations of effective diffusivities in three-dimensional, spatially periodic porous media are performed. For isotropic systems, it is found that, for a given porosity, the predicted value of the effective diffusivity matches experimental results for randomly-packed beds of spheres. Furthermore, the three-dimensional geometry yields approximately the same results as previous calculations employing two-dimensional representations, indicating a relative insensitivity of the effective diffusivity to local geometry. Regarding anisotropic systems, for which two-dimensional modes fail, it is found that there is a significant improvement in the prediction of the effective diffusivity perpendicular to the bedding plane when the three-dimensional model is employed using one adjustable parameter. However, the three-dimensional model overestimates the effective diffusivity parallel to the bedding plane.Notation
a, b
Geometric parameters (Figure 3)
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c
Solute concentration
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D
Diffusion coefficient
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D
eff
Effective diffusivity tensor
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E
Dimensionless effective diffusivity, defined by Equation (3.1)
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f
Vector function, defined in Equation (2.8)
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l
Characteristic length of the pore scale
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L
Characteristic length of the macroscopic scale
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L
a
, L
b
Geometric parameters (Figure 3)
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n
Unit vector perpendicular to the fluid-solid interface
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r
0
Size of the averaging volume
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t
Time
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t
*
Characteristic time
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U
Unit tensor
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V
Averaging volume
Greek Letters
Porosity
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Parameter defined by Equation (3.4)
Indices
Fluid phase
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Solid phase 相似文献
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Michelle Carey Eugene G. Gath Kevin Hayes 《Journal of computational and graphical statistics》2017,26(3):671-681
Ordinary differential equations (ODEs) are equalities involving a function and its derivatives that define the evolution of the function over a prespecified domain. The applications of ODEs range from simulation and prediction to control and diagnosis in diverse fields such as engineering, physics, medicine, and finance. Parameter estimation is often required to calibrate these theoretical models to data. While there are many methods for estimating ODE parameters from partially observed data, they are invariably subject to several problems including high computational cost, complex estimation procedures, biased estimates, and large sampling variance. We propose a method that overcomes these issues and produces estimates of the ODE parameters that have less bias, a smaller sampling variance, and a 10-fold improvement in computational efficiency. The package GenPen containing the Matlab code to perform the methods described in this article is available online. 相似文献
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An optical model or complex potential has been used in a relatively simple fashion to provide an interpretation of several molecular dynamics experiments. Rather than attempting a quantitative curve fit to the available data using a phenomenological optical potential (which is certainly possible) we have correlated certain physically reasonable features of the complex potential with general trends in the reaction dynamics. As an explicit example, the relationship between the range characteristics of the optical potential and the dependence of the reaction probability upon the kinetic energy of the reactants is derived. Other correlations are also presented, such as the dependence of the reaction probability upon impact parameter and degree of rotational excitation. The power of such a treatment obviously lies in its general applicability to complex systems as well as in its ability to often provide a simple physical understanding of some rather anomalous features of the reaction dynamics. 相似文献