Gábor Papp

Homogeneous hydrogenation of carbon dioxide and bicarbonate in aqueous solution catalyzed by water-soluble ruthenium(II) phosphine complexes

The water-soluble Ru(II)-phosphine complex, [{RuCl2(mTPPMS)(2)}(2)] was found a suitable catalyst for the hydrogenation of NaHCO3 to NaHCO2 in aqueous solution under mild conditions with catalyst turnover frequencies (TOFs) in the range of 35-50 h(-1) at 50degreesC and 10 bar total pressure. The suggested reaction mechanism involves the formation of Ru(II)-hydrides of the general formula [RuHX(mTPPMS)(4)] where X = H-, HCO3- or HCO2-. At 80degreesC and 95 bar total pressure, the reduction of NaHCO3 proceeded with high reaction rate (9600 h(-1)) hitherto unobserved in purely aqueous solutions. The reactions do not require the presence of organic amine additives, however, the addition of quinoline increased the rate considerably. Aqueous suspensions of calcium carbonate could also be hydrogenated with CO2/H-2 gas mixtures

A Charge/Discharge Device for Chemical Hydrogen Storage and Generation

Keywords: fuel cells · homogeneous catalysis · hydrogen · hydrogenation · ruthenium Reference EPFL-ARTICLE-169668doi:10.1002/anie.201104951View record in Web of Science Record created on 2011-10-21, modified on 2017-05-12

The role of heme oxygenase-related carbon monoxide and ventricular fibrillation in ischemic/reperfused hearts

Reperfusion-induced ventricular fibrillation (VF) and heme oxygenase (HO)-related carbon monoxide (CO) production in isolated ischemic/reperfused rat hearts were studied by gas chromatography. Hearts were subjected to 30 min ischemia followed by 2 h reperfusion, and the expression of HO-1 mRNA (about 4-fold) was observed in ischemic/reperfused-nonfibrillated hearts. In fibrillated hearts, the reduction (about 75%) in HO-1 mRNA expression was detected. These changes in HO-1 mRNA expression were reflected in tissue CO production. Thus, in the absence of VF, CO production was increased about 3.5-fold, while in the presence of VF, CO production was under the detectable level in comparison with the control group. Our results suggest that the stimulation of HO-1 mRNA expression may lead to the prevention of reperfusion VF via an increase in endogenous CO production. To prove this, hearts were treated with 1 microM of N-tert-butyl-alpha-phenylnitrone (PBN) as an inducer of HO-1. PBN treatment resulted in about 20 times increase in HO-1 mRNA expression, and even a higher production rate in endogenous CO. HO protein level and enzyme activity followed the same pattern, as it was observed in HO-1 mRNA expression, in fibrillated and nonfibrillated myocardium. Five mM/l of zinc-protoporphyrin IX (ZnPPIX) significantly blocked HO enzyme activity and increased the incidence of VF, therefore the application of ZnPPIX led to a significant reduction in HO-1 mRNA and protein expression. Our data provide direct evidence of an inverse relationship between the development of reperfusion-induced VF and endogenous CO production. Thus, interventions that are able to increase tissue CO content may prevent the development of reperfusion-induced VF.

DTM-based surface and volume approximation: geophysical applications

Based on earlier investigations, two new methods for local surface interpolation developed by us were applied to derive regular grids, that is Digital Terrain Models (DTM) from the digitized contour lines of two surfaces. These surfaces represent two main structural boundaries of the Earths crust, the pre-Tertiary basement and the Mohorovicic discontinuity in the Pannonian Basin, Hungary. The grids were used to model the volume of sediments and mantle material above the basement and below the Moho respectively in order to build up an initial version of a 3-D model of the crust in Hungary for regional gravity field modeling. n nThe grid representation provides an evident and elementary way for modeling a body by right rectangular prisms of Δx × Δy × z, where Δx and Δy are distances between grid knots in the X and Y directions respectively, and z represents a grid value at a grid knot. However, because of the nature of forward gravity modeling, the elementary prisms might be drawn together in a simple volume density distribution (e.g. homogeneous layer) and in such a way that the computation time can be reduced significantly. Therefore, a recursive algorithm for volume approximation by right rectangular prisms of a body determined by its DTM also was developed and applied in the determination of the 3-D crustal model in the Pannonian Basin.

Classical and non-classical phosphine-Ru(ii)-hydrides in aqueous solutions: Many, various, and useful

Hydrogenation of the water-soluble [{RuCl(2)(mtppms)(2)}(2)] (mtppms = monosulfonated triphenylphosphine) was studied in aqueous solutions in the presence of excess mtppms both with H(2) and with aqueous HCOONa. Depending on the reductant, the pH and H(2) pressure altogether nine hydride species were identified. In acidic solutions at 1 bar H(2) pressure the known [RuHCl(mtppms)(3)] (1) and [{RuHCl(mtppms)(2)}(2)] (3) were formed, however, elevated pressure led to the formation of trans-[RuH(2)(mtppms)(4)] (11). In basic solutions at atmospheric pressure cis-fac-[RuH(2)(H(2)O)(mtppms)(3)] (12) was observed which was readily replaced by [RuH(2)(η(2)-H(2))(mtppms)(3)] (13) at higher H(2) pressures. 13 is the first water-soluble and stable η(2)-H(2) Ru(II)-complex stabilized only by monodentate phosphine ligands. [RuHBr(mtppms)(3)] (9) and [RuHI(mtppms)(3)] (10) were obtained analogously to 1. In concentrated aqueous HCOONa solutions (often used in H-transfer hydrogenations) the major species was trans-[RuH(2)(HCOO)(mtppms)](-) (14) while in dilute solutions trans-[RuH(2)(H(2)O)(mtppms)(3)] (15) could be observed. Formation of these various hydride species offers an explanation for the earlier observed pH and pressure dependence of the rates and selectivities in hydrogenation of unsaturated aldehydes catalyzed by [{RuCl(2)(mtppms)(2)}(2)] + mtppms.

Investigation of sediment compaction in the Pannonian basin using 3D gravity modelling

Abstract The great number of geophysical and geological data available in Hungary has made possible the direct modelling of the density distribution of the upper crust. Without considering lateral inhomogeneities, a simple 1D theoretical model was introduced for the relationship between Bouguer gravity anomalies and basement depths to derive a general formula describing the vertical change of density in the sediments. The validity of the correlation model was investigated by direct 3D gravity modelling. The 1D model proved a satisfactory approximation, so it was applied to the observed gravity field over a selected area of the Pannonian basin, and an extensive analysis of the sediment compaction was carried out based on a high-resolution digital depth model (DDM) and volume model of the sediments covering the Pannonian basin with an average thickness of 2 km. The derived density-depth function of the selected area differs from the generally accepted vertical change of density estimated by geological-geophysical exploration, although the effect of the sediment compaction is clearly visible. The obtained density contrast function resulted in apparent density values for the sediments higher than given by the reference model used in 3D gravity field model computations. This systematic deviation may be a consequence of the crustal thinning which is supposed to be a consequence of basin evolution. A crust-mantle model of the investigated area extending below the Moho discontinuity was used to support this assumption.

Recurring mass movements on the Danube's bank at Dunaszekcső (Hungary) observed by geodetic methods

Abstract. In September 2007 a geodetic network based on GPS measurements, precise levelling and continuous borehole tilt measurements was established for surface displacement monitoring on the high bank of the River Danube at Dunaszekcső where a serious landslide began to develop at that time. The landslide took place on February 12, 2008. After rapid, enormous movements, which resulted in significant subsidence (8–10 m) and lateral displacements (4–5 m) on the high bank at Dunaszekcső and the emergence of a peninsula consisting of clastic material in the Danubes bed, the deformation rates significantly dropped. This observation was explained by the secondary metastable equilibrium of the moving blocks at that time. However, our subsequent geodetic data clearly showed that slow post-event movements (mainly subsidence, 0.5–1.0 cm/month) on both the northern and southern sliding blocks have been occurring for the last two years, which means that the sliding blocks did not reach an equilibrium in the mentioned period. At the same time, measurements on our extended geodetic network in the second half of 2010 referred to a possible southward spread of sliding (southern part of the Vár Hill) in the near future. Later on (spring 2011), field observations were also indicative of the initiation of movements on the southern part of the Vár Hill as predicted by the geodetic measurements. The areal extent of the block becoming unstable closely corresponds with the danger zone assigned by GPS observations.

Generalization techniques to reduce the number of volume elements for terrain effect calculations in fully analytical gravitational modelling

Beyond rectangular prism polyhedron, as a discrete volume element, can also be used to model the density distribution inside 3D geological structures. The calculation of the closed formulae given for the gravitational potential and its higher-order derivatives, however, needs twice more runtime than that of the rectangular prism computations. Although the more detailed the better principle is generally accepted it is basically true only for errorless data. As soon as errors are present any forward gravitational calculation from the model is only a possible realization of the true force field on the significance level determined by the errors. So if one really considers the reliability of input data used in the calculations then sometimes the “less” can be equivalent to the “more” in statistical sense. As a consequence the processing time of the related complex formulae can be significantly reduced by the optimization of the number of volume elements based on the accuracy estimates of the input data. New algorithms are proposed to minimize the number of model elements defined both in local and in global coordinate systems. Common gravity field modelling programs generate optimized models for every computation points (dynamic approach), whereas the static approach provides only one optimized model for all. Based on the static approach two different algorithms were developed. The grid-based algorithm starts with the maximum resolution polyhedral model defined by 3–3 points of each grid cell and generates a new polyhedral surface defined by points selected from the grid. The other algorithm is more general; it works also for irregularly distributed data (scattered points) connected by triangulation. Beyond the description of the optimization schemes some applications of these algorithms in regional and local gravity field modelling are presented too. The efficiency of the static approaches may provide even more than 90% reduction in computation time in favourable situation without the loss of reliability of the calculated gravity field parameters.

Expected accuracy of tilt measurements on a novel hexapod-based digital zenith camera system: A Monte-Carlo simulation study

Digital zenith camera systems (DZCS) are dedicated astronomical-geodetic measurement systems for the observation of the direction of the plumb line. A DZCS key component is a pair of tilt meters for the determination of the instrumental tilt with respect to the plumb line. Highest accuracy (i.e., 0.1 arc-seconds or better) is achieved in practice through observation with precision tilt meters in opposite faces (180° instrumental rotation), and application of rigorous tilt reduction models. A novel concept proposes the development of a hexapod (Stewart platform)-based DZCS. However, hexapod-based total rotations are limited to about 30°–60° in azimuth (equivalent to ±15° to ±30° yaw rotation), which raises the question of the impact of the rotation angle between the two faces on the accuracy of the tilt measurement. The goal of the present study is the investigation of the expected accuracy of tilt measurements to be carried out on future hexapod-based DZCS, with special focus placed on the role of the limited rotation angle. A Monte-Carlo simulation study is carried out in order to derive accuracy estimates for the tilt determination as a function of several input parameters, and the results are validated against analytical error propagation. As the main result of the study, limitation of the instrumental rotation to 60° (30°) deteriorates the tilt accuracy by a factor of about 2 (4) compared to a 180° rotation between the faces. Nonetheless, a tilt accuracy at the 0.1 arc-second level is expected when the rotation is at least 45°, and 0.05 arc-second (about 0.25 microradian) accurate tilt meters are deployed. As such, a hexapod-based DZCS can be expected to allow sufficiently accurate determination of the instrumental tilt. This provides supporting evidence for the feasibility of such a novel instrumentation. The outcomes of our study are not only relevant to the field of DZCS, but also to all other types of instruments where the instrumental tilt must be corrected. Examples include electronic theodolites or total stations, gravity meters, and other hexapod-based telescopes.

A study of different wavelength spectral components of the gravity field derived from various terrestrial data sets

In the general scheme of gravity field modelling long-, medium- and short-wavelength constituents of the gravity field derived from e.g. geopotential model, terrestrial data and digital terrain model respectively, are routinely combined. In this study, spectral characteristics of terrestrial data sets are investigated. The estimation of spectral sensitivity of gravity related quantities such as gravity anomaly, vertical deflections and gravity gradients was accomplished through Fourier PSD and covariance analysis depending on the spatial distribution of data points. The information content of the estimated spectra were validated on global and local levels to access their further utilization. The spectra were compared to the 1D spectrum of the gravitational field derived from spherical harmonic coefficients using a high resolution global gravitational model as well as to an analytical approximation. Besides the frequency domain investigations the information content regarding the different wavelength structure comprised in terrestrial and EGM2008 model is investigated in the space domain based on covariance analysis. As a combined validation process the gravity degree variances were transformed to the necessary auto- and cross covariance functions to predict geoid height from gravity anomaly, which ensures an independent validation process of the computed spectrum. Based on the spectral characteristics of terrestrial measurement spectral weights for spectral combination were derived involving global gravity field model, gravity and gravity gradient data in gravity field modelling. To determine the geoid in the whole spectral band the specific integral kernels in the spectral domain should be modified using the suggested spectral weights.