Formation of intercalate-like structures by heat treatment of K2CO3-carbon in an inert atmosphere

Treatment of K₂CO₃-activated carbon and K₂CO₃-coal in a nitrogen flow at 1100 K results in the formation of metallic potassium. X-ray analysis revealed that the heat-treated samples have structures similar to those of potassium-graphite intercalation compounds. Potassium acts probably as a graphitizing agent. By heat treatment of K₂CO₃-graphite under the same conditions metallic potassium was not formed and neither could intercalation structures be detected by X-ray analysis.     

Grip to the Colon by Means of Macroscopic Adhesion-Controlled Friction

Manipulating friction without applying high normal forces is important for an intestine inspection and intervention device in order to eliminate the risk of tissue damage. One possible solution is to generate friction by means of adhesive forces. The adhesive forces should be high to offer sufficient grip without needing high normal forces. The generated friction is then called adhesion-controlled and depends on the size of the area in contact. Adhesion-controlled friction is well known to be dominant at microscopic and molecular levels. According to this paper, adhesion-controlled friction can be applicable on the macroscopic scale as well and, more specifically, within a range of forces in which friction is usually considered to be load-controlled. The intestine inspection and intervention device manipulates the friction with the colonic wall by means of mucoadhesive films. In this way, grip with high static friction is achieved without the need to apply high normal forces and friction is altered by changing the size of the area of the mucoadhesive film. Friction theories on different scales are revisited and considered in order to understand the dominant phenomena and the principles associated with this macroscopic adhesion-controlled friction.     

System calibration and statistical image reconstruction for ultra-high resolution stationary pinhole SPECT

For multipinhole single-photon emission computed tomography (SPECT), iterative reconstruction algorithms are preferred over analytical methods, because of the often complex multipinhole geometries and the ability of iterative algorithms to compensate for effects like spatially variant sensitivity and resolution. Ideally, such compensation methods are based on accurate knowledge of the position-dependent point spread functions (PSFs) specifying the response of the detectors to a point source at every position in the instrument. This paper describes a method for model-based generation of complete PSF lookup tables from a limited number of point-source measurements for stationary SPECT systems and its application to a submillimeter resolution stationary small-animal SPECT system containing 75 pinholes (U-SPECT-I). The method is based on the generalization over the entire object to be reconstructed, of a small number of properties of point-source responses which are obtained at a limited number of measurement positions. The full shape of measured point-source responses can almost be preserved in newly created PSF tables. We show that these PSFs can be used to obtain high-resolution SPECT reconstructions: the reconstructed resolutions judged by rod visibility in a micro-Derenzo phantom are 0.45 mm with 0.6-mm pinholes and below 0.35 mm with 0.3-mm pinholes. In addition, we show that different approximations, such as truncating the PSF kernel, with significant reduction of reconstruction time, can still lead to acceptable reconstructions.      

Salinity modelling by inverted Gaussian parameters of soil reflectance spectra

This paper presents an approach to estimate soil salinity through modelling of soil spectra using an inverted Gaussian (IG) function. The approach is tested on experimental datasets including measurements of soil physicochemical properties and their spectral reflectance which are obtained under controlled laboratory conditions. The near-infrared (NIR) and shortwave infrared (SWIR) region of the salt-affected soil spectra were fitted to an inverted Gaussian curve. Parameters of the fitted curve, such as functional depth, distance to the inflection point and area under curve, were then used as predictors in regression analysis to estimate soil salinity levels. The results suggest a successful estimation of salinity levels, especially, for soil samples treated with epsomite and bischofite solutions. Amongst the calculated IG parameters, the area under fitted curve resulted in the most accurate estimations. The results demonstrate the relative utility of high spectral resolution data for estimating soil salinity under laboratory controlled conditions.     

The challenge of computer mathematics

Progress in the foundations of mathematics has made it possible to formulate all thinkable mathematical concepts, algorithms and proofs in one language and in an impeccable way. This is not in spite of, but partially based on the famous results of G?del and Turing. In this way statements are about mathematical objects and algorithms, proofs show the correctness of statements and computations, and computations are dealing with objects and proofs. Interactive computer systems for a full integration of defining, computing and proving are based on this. The human defines concepts, constructs algorithms and provides proofs, while the machine checks that the definitions are well formed and the proofs and computations are correct. Results formalized so far demonstrate the feasibility of this 'computer mathematics'. Also there are very good applications. The challenge is to make the systems more mathematician-friendly, by building libraries and tools. The eventual goal is to help humans to learn, develop, communicate, referee and apply mathematics.     

Path selection in multi-layer networks

Multi-layer networks are computer networks where the configuration of the network can be changed dynamically at multiple layers. However, in practice, technologies at different layers may be incompatible to each other, which necessitates a careful choice of a multi-layer network model. Not much work has been done on path selection in multi-layer networks. In this paper, we describe how to represent a multi-layer network and we provide algorithms for selecting paths in them. Throughout the paper we will use examples drawn from practical experience with routing in hybrid optical networks.     

Changed isoflavone Levels in Red Clover (<Emphasis Type="Italic">Trifolium pratense</Emphasis> L.) Leaves with Disturbed Root Nodulation in Response to Waterlogging

The effect of disturbed root nodulation on the quantitative and qualitative composition of the main isoflavonoid glucoside–malonates, glucosides, and aglycones in the leaves of Trifolium pratense L. grown under waterlogging conditions was investigated. Isoflavonoids are involved in the regulation of root nodule activity and the establishment of the mycorrhizal association. Isoflavonoid determination was performed using reversed-phase liquid chromatography coupled to mass spectrometric and UV absorbance detection. In response to waterlogging, the concentrations of biochanin A and biochanin A–7-O-glucoside–malonate, biochanin A–7-O-glucoside, and genistein–7-O-glucoside in the leaves increased two- to threefold after a lag period of 3 wk because of disturbed root nodulation. The other isoflavones detected—formononetin, formononetin–7-O-glucoside–malonate, and formononetin–7-O-glucoside—did not show any significant changes related to waterlogging. After restoring normal soil water conditions, the concentrations of biochanin A and its glucoside and glucoside–malonate rapidly returned to the initial values, whereas the concentration of genistein–7-O-glucoside remained high.     

High performance monolithic catalysts for hydrogenation reactions

The performances of two different monolithic catalysts are compared in the selective hydrogenation of fatty acid methyl esters (FAMEs). The monolith samples were a classical square channel cordierite and one modified with -Al₂O₃ blocking the macroporosity of the cordierite and rounding the channel cross section. On both samples a carbon layer was applied by carbonization of a polyfurfuryl alcohol coating obtained by dipcoating. The carbon was oxidized to create anchoring sites for ion exchange with a tetraamminepalladium(II) nitrate solution resulting in a carbon supported Pd catalyst. The rounded channels yielded an even carbon layer, whereas in the square channels an uneven carbon distribution resulted and penetration in the wall. The rounded channel shows a superior performance compared to the square channel sample in the partial hydrogenation of FAMEs, evidenced by the much lower formation of trans double bonds at similar hydrogenation levels of the double bonds. This is ascribed to the much shorter diffusion distances of the reactants and products.     

Visualization of time-dependent data with feature tracking and event detection

This paper presents an innovative method to analyze and visualize time-dependent evolution of features. The analysis and visualization of time-dependent data are complicated because of the immense number of data involved. However, if the scientist's main interest is the evolution of certain features, it suffices to show the evolution of these features. The task of the visualization method is to extract the features from all frames, to determine the correspondences between features in successive frames, to detect significant events or stages in the evolution of the features, and, finally, to visualize the results. The method described here performs all these steps, and it is applied to a number of applications.