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.

[Indirect azygos vein continuation syndrome with segmental agenesis and saccular aneurysm of the inferior vena cava]. / Indirektes Vena-azgos-Kontinuationssyndrom mit Segmentagenesie und sackulärem Aneurysma der Vena cava inferior.

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]. / Dopplersonographische Untersuchungen im Langzeitverlauf von Kindern mit hämolytisch-urämischem Syndrom.

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.

[Case report of ultrasound diagnosis of lissencephaly syndrome]. / Kasuistischer Beitrag zur sonografischen Diagnose des Lissenzephalie-Syndroms.

By means of casuistics a malformation of the central nervous system is represented. The clinical treatment, variations of the syndrome and theories of the aetiology are briefly described. Typical sonographic findings and the computer-tomographic picture are demonstrated. The essential morphologically facts striking facts of the lissencephaly consist of the internal hydrocephalus, epicortical fluid increase and agyria.

[The significance of HbA1 determination in children]. / Die Bedeutung der HbA1-Bestimmung im Kindesalter.

The determination of glycated haemoglobin permits a good evaluation of metabolic regulation of diabetics. The development of vascular complications depends on duration and degree of hyperglycemia. It is presented the different chemical reactions of glucose with proteins in diabetes. The consequences are structural and functional changes of a variety of human proteins. This is a part of long-term complications of diabetics. Collagen is used as an example for a protein with a relatively slow turnover rate that could allow for an accumulation of altered protein.

[Sonography in the diagnosis of Hodgkin's disease in childhood and adolescence]. / Die Sonografie bei der Diagnostik des Morbus Hodgkin im Kindes- und Jugendalter.

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.

[Treatment of post-hemorrhagic hydrocephalus in premature infants]. / Zur Problematik der Behandlung des posthämorrhagischen Hydrozephalus Frühgeborener.

Our experiences in the course of illness of very low birth weight infants suffered from posthemorrhagic hydrocephalus are described. Clinical proceedings for performing of the hydrocephalus are explained, advantages and disadvantages of treatment by serial lumbal punctures, influences of drugs on the dilatation of the ventricles and the insertion of ventriculo-peritoneal shunts are discussed. The outcome was unfavourable in hydrocephalus following Grad III ore IV hemorrhage. Therefore the prevention of severe hydrocephalus must be the common sense of obstetricians and neonatologists.