Differential porosimetry and permeametry for random porous media

Accurate determination of geometrical and physical properties of natural porous materials is notoriously difficult. Continuum multiscale modeling has provided carefully calibrated realistic microstructure models of reservoir rocks with floating point accuracy. Previous measurements using synthetic microcomputed tomography (μ-CT) were based on extrapolation of resolution-dependent properties for discrete digitized approximations of the continuum microstructure. This paper reports continuum measurements of volume and specific surface with full floating point precision. It also corrects an incomplete description of rotations in earlier publications. More importantly, the methods of differential permeametry and differential porosimetry are introduced as precision tools. The continuum microstructure chosen to exemplify the methods is a homogeneous, carefully calibrated and characterized model for Fontainebleau sandstone. The sample has been publicly available since 2010 on the worldwide web as a benchmark for methodical studies of correlated random media. High-precision porosimetry gives the volume and internal surface area of the sample with floating point accuracy. Continuum results with floating point precision are compared to discrete approximations. Differential porosities and differential surface area densities allow geometrical fluctuations to be discriminated from discretization effects and numerical noise. Differential porosimetry and Fourier analysis reveal subtle periodic correlations. The findings uncover small oscillatory correlations with a period of roughly 850μm, thus implying that the sample is not strictly stationary. The correlations are attributed to the deposition algorithm that was used to ensure the grain overlap constraint. Differential permeabilities are introduced and studied. Differential porosities and permeabilities provide scale-dependent information on geometry fluctuations, thereby allowing quantitative error estimates.

Two-dimensional spectroscopy for the study of ion coulomb crystals

Ion Coulomb crystals are currently establishing themselves as a highly controllable test bed for mesoscopic systems of statistical mechanics. The detailed experimental interrogation of the dynamics of these crystals, however, remains an experimental challenge. In this work, we show how to extend the concepts of multidimensional nonlinear spectroscopy to the study of the dynamics of ion Coulomb crystals. The scheme we present can be realized with state-of-the-art technology and gives direct access to the dynamics, revealing nonlinear couplings even in the presence of thermal excitations. We illustrate the advantages of our proposal showing how two-dimensional spectroscopy can be used to detect signatures of a structural phase transition of the ion crystal, as well as resonant energy exchange between modes. Furthermore, we demonstrate in these examples how different decoherence mechanisms can be identified.

Influence of different substrates on the performance of a two-stage high pressure anaerobic digestion system

The two-stage autogenerative high-pressure digestion technique is a novel and promising approach for the production of gaseous fuels or upgraded biogas. This new technique is described in the patent DE 10 2011 015415 A1 and integrates biogas production, its upgrading and pressure boosting in one process. Anaerobic digestion under elevated pressure conditions leads to decreasing pH-values in the digestate due to the augmented formation of carboxylic acid. Model calculations carried out to evaluate the two-stage design showed that the pH-value in the pressurized anaerobic filter has a major influence on the methane content of the biogas produced. Within this study, the influence of the nitrogen content as one of the most important buffering substances on the performance of the system has been tested. The results show that higher NH4 contents lead to higher pH-values in the digester and as a consequence to higher methane contents.

Silicone implants--a possible confounder for urinary platinum background concentrations?

INTRODUCTION

Urinary platinum excretion from occupationally unexposed population is very low. Up to now, in Germany, dental noble metal alloys and a platinum based chemotherapy have been identified as reason for elevated urine concentrations. As fabrication of silicone involves platinum as catalyst, this study examines the potential release of platinum from silicone breast implants by quantifying urinary platinum concentration.

METHODS AND RESULTS

Platinum release from three different types of silicone implants into saline solution was measured in a laboratory experiment. It showed a strong increase of platinum concentration during the first 30 min and high platinum concentrations even after 60 h. In the following field study urinary platinum concentrations were determined from 30 women with dental gold alloy restorations and 28 women without such dental inlays. Median platinum concentrations were 5.2 ng/l urine (21.2 ng/g creatinine) for the women with dental gold inlays and 6.0 ng/l urine (5.4 ng/g creatinine) for those without. Compared with the urinary platinum concentrations provided by the German Environmental Survey (GerES) for the general female population the urinary platinum levels of women with silicone implants of the presented study were significantly higher, both for the study groups with and without dental gold alloy inlays.

CONCLUSIONS

Silicone breast implants must be considered as a new confounder and as a further contributor to elevated urinary platinum concentrations in human platinum background reference values of women.

[Indirect azygos vein continuation syndrome with segmental agenesis and saccular aneurysm of the inferior vena cava]

Indirect vena azygos continuation syndrome and aneurysm are rare variations of the inferior vena cava (IVC). In this article we describe the ultrasound, angiographic and CT appearance of a 14-year-old girl with this congenital anormaly of the IVC.

[Doppler ultrasound studies of long-term follow-up of children with hemolytic-uremic syndrome]

AIM

In the present study, we compared the diagnostic value of Doppler sonography with "B-Imaging" in the acute and chronical period of the HUS in children.

METHOD

For this, we analysed the Doppler sonographic measurement (Acuson-128) from 3 patients in the acute stage of the disease and 14 patients after approximately 5 years. All patients examined in the chronic stage of the disease had been treated by peritoneal dialysis in the acute stage. As a control, the Doppler sonographic analysis of the A. renalis was performed in 25 healthy children.

RESULTS

During the acute phase of the HUS, we found a significant increase in both the resistive index (RI) and the pulsatility index (PI). In addition, the diastolic current in the A. renalis was decreased or the blood flow was reversed. The kidney volume as well as the echo was increased in all cases. A recovery of the kidney observed as beginning diuresis coincided with a return to normal parameters in the Doppler sonographic measurement. In patients examined after 5 years, both the RI and the PI value was significantly (p < 0.01) different from the control group. These parameters correlate with the effective renal plasma flow, but not with the glomerular filtration rate.

CONCLUSION

We conclude that in the acute stage of the HUS either "B-Imaging" or duplex sonography yield pathological parameter values. For the observation of the renal symptoms during the chronic phase of the disease, duplex sonography is clearly superior.

[Sonography in the diagnosis of Hodgkin's disease in childhood and adolescence]

We are reporting about the results of the staging by ultrasound in 11 children with Hodgkin's disease. Sonography stands the test as a method that reliably predicts abdominal involvement in patients with Hodgkin lymphoma. Only in a few cases an indication for an additional computerized tomography is given. A demonstration of typical ultrasonic findings takes place.