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- Author or Editor: J. Jansen x
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Abstract
The mathematical evaluation of the activation energy, E, of non-isothermal degradation reactions is usually made using the Ozawa/Flynn–Wall isoconversion principle and involves the numerical resolution of a set of integrals without closed form solution, which are solved by polynomial approximation or by numeric integration. In the present work, the isoconversion principle, originally described and maintained until now as an algebraic problem, was written as a set of ordinary differential equations (ODEs). The individual ODEs obtained are integrated by numeric methods and are used to estimate the activation energy of simulated examples. A least square error (LSE) objective function using the introduced ODEs was written to deal with multiple heating rate CaCO3 thermal decomposition TG experiments.
Abstract
Differential scanning calorimetry has been used to study the thermal effects during adsorption and desorption of water on different zeolite NaA samples. An attempt has been made to compare the thermal behaviour of a layer of zeoliete attached on metal ("by chemical bond") with zeolite powder pressed on metal. The dependence of the water uptake on temperature has been studied with a powdered sample. Isothermal measurements of the water uptake of the zeolite after activation, appeared the best way to determine the heat of adsorption. Calibration of the DSC was needed. The adsorbed amounts of water corresponding to the released heats were determined thermogravimetrically. Once the heat of adsorption is known, it is possible to determine the mass of active zeolite of thin synthesized zeolite layers on metal with DSC.
Abstract
Gas and oil companies frequently encounter build up of Naturally Occurring Radioactive Material (NORM) in their production and processing facilities. In the Netherlands NORM is subject to strict national regulations and, consequently, installations have to be screened on a regular basis. The availability of accurate and reliable NORM sampling and analysis techniques is therefore essential. A number of years ago, the 
Nederlandse Aardolie Maatschappij B.V.
(NAM) actively initiated an investigation on analysis techniques for NORM samples from gas and oil companies. Within this framework, Shell Research Amsterdam organized a four-stage interlaboratory test programme in which representative samples of increasing complexity were analyzed by a number of Dutch institutes. Whereas a large spread in results was observed in the first stage, results in the last stage deviated less than ±10% from the values certified by an independent referee institute, even for comple, sludge samples. It was found that in particular the use of different values for the 
-yields and branching ratios amongst the institutes was responsible for the initial spread.
Purpose
We previously found that homocysteine (Hcy)-induced apoptosis in endothelial cells coincided with increased NADPH oxidase (NOX) activity. In addition, in ischemic endothelial cells present in the heart, we showed that loss of serine protease dipeptidyl peptidase IV (DPP4) expression was correlated with induction of tissue factor (TF) expression. Since Hcy can initiate thrombosis through the induction of TF expression, in this study, we evaluated whether the inverse relation of TF and DPP4 is also Hcy-dependent and whether NOX-mediated reactive oxygen species (ROS) is playing a role herein.
Methods
Human umbilical vein endothelial cells (HUVECs) were incubated with 2.5 mM Hcy for 3 and 6 h. The effects of Hcy on DPP4 and TF expression and NOX2/p47phox-mediated nitrotyrosine (ROS) production were studied using digital-imaging microscopy.
Results
In HUVECs, high levels of Hcy showed a significant increase of TF expression and a concomitant loss of DPP4 expression after 6 h. In addition, NOX subunits NOX2 and p47phox were also significantly increased after 6 h of Hcy incubation and coincided with nitrotyrosine (ROS) expression. Interestingly, inhibition of NOX-mediated nitrotyrosine (ROS) with the use of apocynin not only reduced these effects, but also counteracted the effects of Hcy on TF and DPP4 expression.
Conclusion
These results indicate that the inverse relation of TF and DPP4 in endothelial cells is also Hcy-dependent and related to NOX activity.
Abstract
This paper describes the preparation of samples for an experiment to measure the cross-section for 235U(n,n′)235mU in a fast fission spectrum of neutrons provided by a fast pulsed reactor/critical assembly. Samples of 235mU have been prepared for the calibration of the internal conversion electron detector that is used for the 235mU measurement. Two methods are described for the preparation of 235mU. The first method used a U-Pu chemical separation based on anion-exchange chromatography and the second method used an alpha recoil collection method. Thin, uniform samples of 235mU+235U were prepared for the experiment using electrodeposition.
