Browsing by Author "Fischer, C."

The fluvial-aeolian Rotliegend succession exposed in a quarry near Magdeburg (Flechtinger Hohenzug, Northern Germany) is an analogue for deeply-buried gas-bearing Rotliegend sandstones in the Southern Permian Basin. The spatial configuration of bounding surfaces within this succession was reconstructed with reference to twelve profiles with 926 sample points. Generally sub-horizontal interdune migration surfaces were surveyed, and the areal extent of small-scale superimposition surfaces and the thicknesses of intervening strata were measured. Based on these observations and also on the extent of different lithofacies types and on corresponding porosity and permeability data, a 3D lithofacies model (including bounding surface configurations) incorporating porosity and radial permeability was created using PETRELT (TM) software. In the quarry, aeolian sandstones approximately 12 m thick (phi similar to 5-11 vol. %, kappa(radial) similar to 0.01-10mD) are separated into a number of tabular bed sets by sub-horizontal interdune migration surfaces. The surfaces are often associated with thin pelitic intervals with low permeabilities which originate from deflation and sheet flow events. Aeolian deposits consist mainly of two lithotypes: low-angle cross-bedded, and steeply cross-bedded medium-grained sandstones. Superimposition surfaces occur at the base of the low-angle cross-bedded sandstone bodies. The highest porosities and permeabilities occur within the steeply cross-bedded sandstones, reflecting intense eodiagenetic calcite and quartz cementation with subsequent calcite dissolution. The low-angle cross-bedded sandstones may act as flow baffles. This outcrop-derived, high resolution model may contribute to a better understanding of the subsurface architecture and reservoir properties of aeolian-fluvial successions. Taking into consideration the centimetre- to metre-scaled inhomogeneities observed at outcrop, lithotype modelling with reference to the occurrence of bounding surfaces may help to predict how similar reservoir rocks are partitioned.

The intravitreal administration of vascular endothelial growth factor (VEGF) inhibitors is the gold standard in the treatment of exudative age-related macular degeneration (AMD) but the possible risks of systemic, particularly cardiovascular side effects are still discussed. We prospectively followed 111 patients at the University Hospital in Gottingen with exudative AMD and intravitreal ocular treatment with bevacizumab and ranibizumab during the upload phase of 3 months using a questionnaire for documentation of possible cardiovascular events. In 5 out of 111 patients angina pectoris was observed and in 6 patients the antihypertensive medication had to be increased. No differences were found between bevacizumab and ranibizumab. A patient with pre-existing cardiovascular diseases suffered a stroke in the upload phase but no thromboembolic events were observed in the other patients. In this small but prospective clinical study no increased risk for cardiovascular events during the upload phase of the VEGF inhibitors ranibizumab and bevacizumab could be detected when taking the age and pre-existing cardiovascular diseases into consideration.

Black shale oxidative weathering plays a significant role in a variety of processes including acid mine drainage and atmospheric CO2 control. The modeling of weathering is highly dependent on reactive surface area. In this study it is shown that black shale oxidative weathering is regulated mainly by the external, geometrical surface area of rock polyhedrons and the organic matter's (OM) internal surface area. The internal rock surface area decreases dramatically during OM dissolution from similar to 15 m(2)/g to similar to 5 m(2)/g. A linear relationship was found between the decrease of internal rock surface area and quantity of OM dissolved. Optical roughness analyses of black and bleached shale surface area reveal the formation of macropores due to the dissolution of mesoporous and probably microporous OM. However, due to deconsolidation, the geometrical external rock polyhedron surface area increases during weathering. Black shale polyhedrons show a doubling of their external surface area as OM decreases. This provokes an increase of the shale volume which is easily accessible by fluids. The increase of the external rock surface area seems to be self-accelerating during weathering. The upscaling of external and internal rock surface area evolution during weathering presented in this study demonstrates the possible application of these results to the improved understanding of a chemical transport in a variety of natural systems. Copyright (c) 2005 Elsevier Ltd.

A high spectral resolution analysis of narrowband reflection filters based on resonant grating waveguide structures is presented. A tunable high-performance dye laser with similar to 0.15 cm(-1) line width and a beam analyzing system consisting of three simultaneously controlled CCD cameras were used to investigate grating waveguide resonances at wavelengths in the 694 nm and 633 nm ranges. A reflectivity of similar to 91% and a line width of similar to 0.55 nm were measured and theoretically modeled for a resonant reflection filter specifically designed for the ruby laser wavelength 694.2 nm. For a second grating waveguide structure, designed for the helium-neon laser emission wavelength 632.8 nm, we observed a thermal shift of its spectral resonance position of several nanometers, when increasing the sample temperature by some degrees. An inverse thermal shift was observed when the structure was subsequently cooled down to room temperature. Our results suggest implementation of grating waveguide devices combining a narrow line width with a tunability of the resonant response into innovative concepts for reflection filter and sensor applications.

The Watzke-Allen test (WAT) is a simple diagnostic tool designed for the diagnosis of full thickness macular holes (FTMH) but due to the rapid progress of imaging diagnostics it was replaced by spectral domain optical coherence tomography (SD-OCT) of macular pathologies. The aim of this study was to examine if the WAT is able to distinguish between the different FTMH stages. In 57 eyes of 57 patients with clinical evidance of FTMH, the WAT was first performed followed by SD-OCT examination and a distinction was made between a negative (slit beam normal) and a positive sign (slit beam modified as groove and hourglass configuration or completely broken). In 49 out of 57 patients the WAT was positive (hourglass 46 patients and broken 3 patients). Based on the SD-OCT results the following diagnoses were made: lamellar macular holes (LMH, 3 patients), vitreomacular traction (VMT, 4 patients), small macular hole (a parts per thousand currency signaEuro parts per thousand 250 A mu m, 5 patients), medium sized macular hole (250-400 A mu m, 11 patients) and large macular hole (a parts per thousand yenaEuro parts per thousand 400 A mu m, 34 patients). In 91 % of the patients with medium and large FTMH, the WAT was positive, whereas the WAT was positive in only 67 % of patients with small FTMH, VMT and LMH. The sensitivity for large and medium FTMH was 93 % but the specificity was only 33 %. The WAT was positive in a high percentage of patients with large and medium sized macular holes as well as patients with small macular holes and LMH. The sensitivity of certain indications for treatment was 93 % but the specificity was only 33 %; therefore, the WAT alone is not suitable for a certain preoperative differentiation of macular alterations.

An integration of methods to quantify the surface area of porous solid materials with a broad span of spatial resolution is presented. The application of it is to detect and quantify the rock surface area modifications caused by fluid-rock interactions on different scales from several nanometres to metres. The new approach is to study the fluid-accessible surface area of rock fragments during dissolution processes. In this paper, diverse methods for surface quantification at different levels of surface detail were adapted for the application of rock surface quantification and porosimetry measurements. The geometric external surface area of rock fragments can be determined by paraffin wax coating and, in special cases, by parallelepiped surface estimations. This geometrical surface area of rock polyhedrons is equal to the macroscopic bounding surface area of a rock volume. Representative surface details on the scale of micrometres to millimetres on geometrical surface area can be quantified by mechanical roughness analyses. The resultant roughness factors are compared to optical roughness quantifications by confocal laser scanning microscopy and white light interferometry and can indicate modifications of the pore space up to several hundred nanometres. The comparison of rock pore space data, measured by both mercury intrusion porosimetry and nitrogen adsorption, quantifies the surface area of pores with a diameter of approximately 2nm.

This article presents the spontaneous development of ocular complications in a case of dengue fever in a young tourist returning from Thailand. Despite severe inital clinical symptoms, a clear remission occurred after several months without any therapy; however, a partial atrophy of the optic nerve remained.

Oral miltefosine was administered to 39 human immunodeficiency virus (HIV)-infected patients with leishmaniasis for whom standard leishmaniasis treatment had failed. Initial response was achieved in 25 patients (64%), including 16 patients (43%) with initial parasitological cure. Repeated responses after relapse and tolerability of long courses of treatment indicate the potential for development of optimized dosage schemes.