Visualization of water drying in porous materials by X-ray phase contrast imaging.

We present in this study results from X-ray tomographic microscopy with synchrotron radiation performed both in attenuation and phase contrast modes on a limestone sample during two stages of water drying. No contrast agent was used in order to increase the X-ray attenuation by water. We show that only by using the phase contrast mode it is possible to achieve enough water content change resolution to investigate the drying process at the pore-scale. We performed 3D image analysis of the time-differential phase contrast tomogram. We show by the results of such analysis that it is possible to obtain a reliable characterization of the spatial redistribution of water in the resolved pore system in agreement with what expected from the theory of drying in porous media and from measurements performed with other approaches. We thus show the potential of X-ray phase contrast imaging for pore-scale investigations of reactive water transport processes which cannot be imaged by adding a contrast agent for exploiting the standard attenuation contrast imaging mode.

Segmentation of elemental EDS maps by means of multiple clustering combined with phase identification.

An imaging concept is proposed for the phase identification and segmentation of elemental map images from energy dispersive spectroscopy. The procedure starts with presegmentation using common clustering algorithms, continues with automated identification of the chemical compositions, followed by their screening by professional expertise. The ultimate phases are finally clustered by applying a minimum Euclidean distance classifier. The potential, performance and limitations of the approach are presented on energy dispersive spectroscopy maps acquired by a scanning electron microscope and conducted on samples produced from cement clinker, natural rock and hydrated cement mortar. Nevertheless, the technique is suitable for arbitrary types of materials and general devices for energy dispersive spectroscopy acquisition. It is an approach for extending common energy dispersive spectroscopy analysis by means of visual examination and ratio plots towards quantitative rating.

Quantification of fly ash in hydrated, blended Portland cement pastes by backscattered electron imaging.

An automated image analysis procedure for the segmentation of anhydrous fly ash from backscattered electron images of hydrated, fly ash blended Portland cement paste is presented. A total of six hundred backscattered electron images per sample are acquired at a magnification of 2000. Characteristic features of fly ash particles concerning grey level, shape and texture were used to segment anhydrous fly ash by a combination of grey level filtering, grey level segmentation and morphological filtering techniques. The thresholds for the grey level segmentation are determined for each sample by semiautomatic histogram analysis of the full image stack of each sample. The analysis of the presented dataset reveals a standard deviation of the reaction degree of fly ash of up to 4.3%. The results agree with a selective dissolution method to quantify the reaction degree of fly ash showing the potential of the presented image analysis procedure.

Focussed ion beam nanotomography reveals the 3D morphology of different solid phases in hardened cement pastes.

Due to the development of integrated low-keV back-scattered electron detectors, it has become possible in focussed ion beam nanotomography to segment not only solid matter and porosity of hardened cement paste, but also to distinguish different phases within the solid matter. This paper illustrates a method that combines two different approaches for improving the contrast between different phases in the solid matrix of a cement paste. The first approach is based on the application of a specially developed 3D diffusion filter. The second approach is based on a modified data-acquisition procedure during focussed ion beam nanotomography. A pair of electron images is acquired for each slice in the focussed ion beam nanotomography dataset. The first image is captured immediately after ion beam milling; the second image is taken after a prolonged exposure to electron beam scanning. The acquisition of complementary focussed ion beam nanotomography datasets and processing the images with a 3D anisotropic diffusion filter allows distinguishing different phases within the hydration products.

Diagnostic evaluation of a real-time RT-PCR assay for routine diagnosis of classical swine fever in wild boar.

The aim of the study was to evaluate a real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for routine diagnosis of classical swine fever (CSF) in wild boar by using 1000 spleen homogenates that were tested previously negative by virus isolation and 26 homogenates from which CSF virus could be isolated. All 26 positive samples in the virus isolation assay also were found to be positive in real-time RT-PCR. Additionally further 10 samples were detected by real-time RT-PCR out of the 1000 negative samples in the virus isolation. With a commercial CSF antigen-ELISA only 14 out of the 36 real-time RT-PCR positive samples could be detected. The sequence analysis of all ten samples that tested positive by real-time RT-PCR and negative by virus isolation revealed CSF virus-specific sequences. Based on the assumption that all samples with a CSF virus-specific sequence or positive in the virus isolation test originated from truly CSF virus-infected wild boar, the following sensitivity values were calculated as antigen-ELISA, 39%; virus isolation, 72% and real-time RT-PCR, 100%. The use of real-time RT-PCR instead of antigen-ELISA and virus isolation as a routine tool for control and eradication of CSF in wild boar populations is recommended.

Three-dimensional analysis of porous BaTiO3 ceramics using FIB nanotomography.

Three-dimensional (3D) data represent the basis for reliable quantification of complex microstructures. Therefore, the development of high-resolution tomography techniques is of major importance for many materials science disciplines. In this paper, we present a novel serial sectioning procedure for 3D analysis using a dual-beam FIB (focused ion beam). A very narrow and reproducible spacing between the individual imaging planes is achieved by using drift correction algorithms in the automated slicing procedure. The spacing between the planes is nearly of the same magnitude as the pixel resolution on scanning electron microscopy images. Consequently, the acquired stack of images can be transformed directly into a 3D data volume with a voxel resolution of 6 x 7 x 17 nm. To demonstrate the capabilities of FIB nanotomography, a BaTiO3 ceramic with a high volume fraction of fine porosity was investigated using the method as a basis for computational microstructure analysis and the results compared with conventional physical measurements. Significant differences between the particle size distributions as measured by nanotomography and laser granulometry indicate that the latter analysis is skewed by particle agglomeration/aggregation in the raw powder and by uncertainties related to calculation assumptions. Significant differences are also observed between the results from mercury intrusion porosimetry (MIP) and 3D pore space analysis. There is strong evidence that the ink-bottle effect leads to an overestimation of the frequency of small pores in MIP. FIB nanotomography thus reveals quantitative information of structural features smaller than 100 nm in size which cannot be acquired easily by other methods.

Use of indicators for monitoring the reduction of pathogens in animal waste treated in biogas plants.

The possibility of including bacterial indicators in programmes for monitoring the disinfection of animal waste treated in biogas plants was examined. Five full-scale plants receiving waste from several farms were monitored. Of these, two used thermophilic and one mesophilic digestion exclusively whereas two employed a two stage process involving thermophilic pretreatment followed by mesophilic digestion. For each plant the reducing effect on bacterial pathogens present in the incoming waste and on E. coli and enterococci indigenous to the waste was followed over long periods of time (six to 16 months). It was found that both E. coli and enterococci could be used as indicators to monitor the reduction of vegetative bacterial pathogens, but the use of enterococci would give the broadest "safety margin" in this respect. It is concluded that thermophilic as well as mesophilic digestion with thermophilic pretreatment will result in a sufficient reduction of both vegetative pathogenic bacteria and intestinal parasites occurring in concentrations usually found in animal waste to allow for unrestricted use of the de-gassed material in agriculture. This cannot be said for mesophilic digestion used alone. To achieve a sufficient reduction in the number of pathogens during the digestion process, a decrease in the enterococcal concentration of at least 3-4 log10 units should be accomplished, which for normal waste would correspond to a maximum concentration of these bacteria in treated material in the order of 10(2) cfu/ml. It is suggested that enterococcal counts in newly digested material should be one of the parameters in a monitoring programme aimed at controlling the hygienic state of the end-product from large biogas plants.

Influence of sustained stretch on late muscular responses to magnetic brain stimulation in patients with upper motor neuron lesions.

Late muscular responses to transcranial magnetic stimulation occur in healthy subjects only in tonically active muscles with a proportional relationship between the amount of the EMG-response and the voluntary innervation strength. In hemiparetic stroke patients late potentials are elicited in chronically spastic hand flexors without voluntary background muscular activity probably reflecting enhanced excitability of spinal alpha-motoneurons in the spastic state. When spastic muscle hypertonus has been diminished by sustained muscle stretch late EMG-potentials are reduced or have disappeared completely. The relation between spastic muscle hypertonus and the late muscular response potentials as well as the possible mechanisms of sustained muscle stretch on the response characteristics to transcranial magnetic stimulation in spastic flexor muscles of the hand are discussed.

A comparison of the efficiency of Rappaport-Vassiliadis, tetrathionate and selenite broths with and without pre-enrichment for the isolation of Salmonella in animal waste biogas plants.

A total of 481 samples of biomass from biogas plants treating slurry and other types of animal waste were examined for the presence of salmonellae by means of five different isolation methods. In 131 samples, Salmonella was isolated by means of one or more methods. A statistical evaluation of the isolation frequencies showed that Rappaport-Vassiliadis broth was significantly better than selenite broth with and without pre-enrichment and tetrathionate broth with pre-enrichment, whereas tetrathionate broth without pre-enrichment was significantly poorer than the other four methods. For each of the thirty different Salmonella serotypes, the isolation frequencies for the five methods are presented. Remarkably, Rappaport-Vassiliadis broth had very high isolation frequencies and tetrathionate broth with and without pre-enrichment had very low isolation frequencies for Salmonella typhimurium as well as Salmonella dublin.

3-D repositioning and differential images of volumetric CT measurements.

In quantitative computed tomography (QCT), time serial measurements are performed to detect a global bone density loss or to identify localized bone density changes. A prerequisite for an unambiguous analysis is the comparison of identical bone volumes. Usually, manual repositioning is too coarse. A mathematical procedure that allows matching two three-dimensional image volumes is presented. The algorithm is based on correlation techniques. The procedure has been optimized and applied to computer-tomographic 3-D images of the human knee. It has been tested with both artificially created and in vivo measured image data. Typical differential images calculated from real bone measurements are presented.

Early detection of osteoarthritis by 3D computed tomography.

Osteoarthritis is a common disease that constitutes a considerable socioeconomic burden. So far no radiological procedure was available that allowed the disease to be detected in an early stage. Monitoring disease progression and efficacy of therapeutic procedures was also not possible.We present a measuring procedure and describe evaluation tools that are based on 3D computed tomography. The procedure provides quantitative data on pathological features known to be associated with osteoarthritis such as subchondral sclerosis, osteophytes, joint space narrowing, and bone lesions. It is fully three dimensional, the results are operator independent and describe global as well as local parameters. Changes in these parameters are evaluated from differential images. For that purpose a 3D matching procedure based on translation and rotation-specific correlation techniques is used that allows a repositioning of the bone objects with a mismatch of less than 0.3 mm with regard to translations and 0.250 with regard to rotations.The use of the new tools for measurement, repositioning and evaluation is illustrated with the results from a clinical study. Patients with mild osteoarthritis of the knee joint, healthy controls and osteoporotic patients, all in the same age range of 60 to 75 years, were examined during three years. The cortical to trabecular bone ratio describing subchondral sclerosis proved to be especially helpful to distinguish early osteoarthritic cases from age matched controls. Disease progression is best shown by the increase in the number of detected bone lesions, a reduction of the mean distance between femur and tibia and an increase in the cortical to trabecular bone ratio. Hence the presented procedure appears to have a great potential in diagnosis and treatment monitoring of osteoarthritis.

[Clinical aspects and surgery of complicated and uncomplicated Meckel's diverticulum]. / Klinik und Chirurgie des komplizierten und unkomplizierten Meckel'schen Divertikels.

Our series of 43 complicated and 35 uncomplicated cases of Meckel's diverticula is reviewed. The complicated courses displayed the typical symptoms, e.g. ileus, hemorrhage, inflammation, perforation with peritonitis. Indication and tactics and techniques of surgical intervention are based on the individual course. Incidental diagnosis of Meckel's diverticulum during coeliotomy indicates resection, because diverticula of normal gross appearance present with microscopic alterations in 29% which could evoke major complications.

Urinary caffeine metabolites in man. Age-dependent changes and pattern in various clinical situations.

In an exploratory study the 24-h urinary excretion pattern of caffeine and 14 of its major metabolites was studied in 32 volunteers (adults, adolescents and children), 14 patients either with end stage renal disease or liver cirrhosis, 7 heavy smokers and 27 patients on therapy with cimetidine, allopurinol, theophylline or phenytoin. Caffeine and its metabolites were quantified by UV-absorption after liquid/liquid-extraction and HPLC-separation, which ensured proper analysis of 1-methyluric acid. In adults the renal excretion of caffeine derivatives corresponded to an intake of 509 mg caffeine/day, with 1-methyluric acid as the predominant metabolite. About 69% of caffeine was degraded by the paraxanthine pathway, and theobromine- (19%) and the theophylline pathway (14%) were less important. The ratio of paraxanthine formation to urinary caffeine concentration (= clearance equivalent) was about 2.2 ml.min-1.kg-1 in adults, and the corresponding ratios for theophylline and theobromine were 0.43 ml.min-1.kg-1 and 0.59 ml.min-1.kg-1, respectively. As expected, caffeine degradation was impaired in patients with cirrhosis and was increased in persons who smoked heavily or who were on phenytoin therapy. The results document the possibility of noninvasively investigating gross differences in caffeine disposition by analysis of the urinary pattern of its metabolites.