The use of pure oxygen for aeration in aerobic wastewater treatment: A review of its potential and limitations.

In aerobic wastewater treatment, aeration is the most critical element of the treatment system. It supplies microorganisms with the required dissolved oxygen, maintains solids in suspension and, in membrane bioreactors, it controls fouling. However, conventional activated sludge is limited to the treatment of low strength wastewaters, as higher loadings require both higher biomass and higher dissolved oxygen concentrations. By replacing air with pure oxygen, oxygen transfer rates increase at lower flowrates. In this work, the potential and limitations of pure oxygen aeration are reviewed. The effect of the system's operational parameters and the mixed liquor characteristics on oxygen transfer, and vice versa, are determined. Pure oxygen treats higher loadings without compromising effluent quality. Fine bubbles are more efficient in oxygen transfer due to their increased contact area. However, pure oxygen is not always essential, so it is recommended to be restricted to applications where air is not adequate.

Plasma gelsolin promotes re-epithelialization.

Woundhealing disorders characterized by impaired or delayed re-epithelialization are a serious medical problem that is painful and difficult to treat. Gelsolin (GSN), a known actin modulator, supports epithelial cell regeneration and apoptosis. The aim of this study was to estimate the potential of recombinant gelsolin (rhu-pGSN) for ocular surface regeneration to establish a novel therapy for delayed or complicated wound healing. We analyzed the influence of gelsolin on cell proliferation and wound healing in vitro, in vivo/ex vivo and by gene knockdown. Gelsolin is expressed in all tested tissues of the ocular system as shown by molecular analysis. The concentration of GSN is significantly increased in tear fluid samples of patients with dry eye disease. rhu-pGSN induces cell proliferation and faster wound healing in vitro as well as in vivo/ex vivo. TGF-ß dependent transcription of SMA is significantly decreased after GSN gene knockdown. Gelsolin is an inherent protein of the ocular system and is secreted into the tear fluid. Our results show a positive effect on corneal cell proliferation and wound healing. Furthermore, GSN regulates the synthesis of SMA in myofibroblasts, which establishes GSN as a key protein of TGF-ß dependent cell differentiation.

Level-set reconstruction algorithm for ultrafast limited-angle X-ray computed tomography of two-phase flows.

Tomographic image reconstruction is based on recovering an object distribution from its projections, which have been acquired from all angular views around the object. If the angular range is limited to less than 180° of parallel projections, typical reconstruction artefacts arise when using standard algorithms. To compensate for this, specialized algorithms using a priori information about the object need to be applied. The application behind this work is ultrafast limited-angle X-ray computed tomography of two-phase flows. Here, only a binary distribution of the two phases needs to be reconstructed, which reduces the complexity of the inverse problem. To solve it, a new reconstruction algorithm (LSR) based on the level-set method is proposed. It includes one force function term accounting for matching the projection data and one incorporating a curvature-dependent smoothing of the phase boundary. The algorithm has been validated using simulated as well as measured projections of known structures, and its performance has been compared to the algebraic reconstruction technique and a binary derivative of it. The validation as well as the application of the level-set reconstruction on a dynamic two-phase flow demonstrated its applicability and its advantages over other reconstruction algorithms.

Compact high-resolution gamma-ray computed tomography system for multiphase flow studies.

In this paper, a compact high-resolution gamma-ray Computed Tomography (CompaCT) measurement system for multiphase flow studies and tomographic imaging of technical objects is presented. Its compact and robust design makes it particularly suitable for studies on industrial facilities and outdoor applications. Special care has been given to thermal ruggedness, shock resistance, and radiation protection. Main components of the system are a collimated (137)Cs isotopic source, a thermally stabilised modular high-resolution gamma-ray detector arc with 112 scintillation detector elements, and a transportable rotary unit. The CompaCT allows full CT scans of objects with a diameter of up to 130 mm and can be operated with any tilting angle from 0° (horizontal) to 90° (vertical).

Feasibility study for mega-electron-volt electron beam tomography.

Electron beam tomography is a promising imaging modality for the study of fast technical processes. But for many technical objects of interest x rays of several hundreds of keV energy are required to achieve sufficient material penetration. In this article we report on a feasibility study for fast electron beam computed tomography with a 1 MeV electron beam. The experimental setup comprises an electrostatic accelerator with beam optics, transmission target, and a single x-ray detector. We employed an inverse fan-beam tomography approach with radiographic projections being generated from the linearly moving x-ray source. Angular projections were obtained by rotating the object.

Experimental facility for two- and three-dimensional ultrafast electron beam x-ray computed tomography.

An experimental facility is described, which has been designed to perform ultrafast two-dimensional (2D) and three-dimensional (3D) electron beam computed tomographies. As a novelty, a specially designed transparent target enables tomography with no axial offset for 2D imaging and high axial resolution 3D imaging employing the cone-beam tomography principles. The imaging speed is 10 000 frames per second for planar scanning and more than 1000 frames per second for 3D imaging. The facility serves a broad spectrum of potential applications; primarily, the study of multiphase flows, but also in principle nondestructive testing or small animal imaging. In order to demonstrate the aptitude for these applications, static phantom experiments at a frame rate of 2000 frames per second were performed. Resulting spatial resolution was found to be 1.2 mm and better for a reduced temporal resolution.

High resolution gamma ray tomography scanner for flow measurement and non-destructive testing applications.

We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/ mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

[Bilateral nasal remission spectroscopy allows the side separated continuous measurement of changes in swelling of the nasal mucosa]. / Schwellungsänderungen in der Nase: Die bilaterale nasale Remissionsspektroskopie zum seitengetrennten Echtzeit-Monitoring.

INTRODUCTION: In earlier studies optical transmission spectroscopy showed that continuous monitoring of changes in the swelling of the nasal mucosa is possible. However, independent measurement in both sides of the nose cannot be achieved by this method. With the aim of achieving real-time monitoring of endonasal swelling separately for both nostrils we developed the new method of bilateral nasal remission spectroscopy for this pilot study. MATERIALS AND METHODS: In nasal remission spectroscopy, light at a wavelength of 790 nm (close to the isobestic point of hemoglobin) is beamed into each side of the nose, and the light that is backscattered by the internal nasal tissue is measured continuously on the same nasal side. To evaluate the principle of this new method a pilot study was conducted in five healthy probands subjected to a one-sided (unilateral) nasal histamine provocation test (0.14 ml, 2 mg/ml). RESULTS: In each proband single-sided nasal histamine provocation led to an increase in light extinction on the provoked side by an average of 0.18 optical densities (OD). In four of the five probands a slight increase (0.04 OD) in light extinction was observed on the other side of the nose. CONCLUSION: Nasal remission spectroscopy seems to allow single-side, continuous monitoring on both sides of the nose. Therefore, the method could also be suitable for use in studies of the nasal cycle, as well as for objectivisation of nasal allergen provocation tests.

Optical measurement of nasal swellings.

We introduce a new optical method to noninvasively and continuously measure the swelling process of the nasal mucosa whereby we use light of different wavelengths in the red and near-infrared range which is transilluminated through the nasal tissue and whose extinction is recorded as a function of time. From the temporal and spectral extinction data, we are able to extract characteristic parameters that describe the swelling process quantitatively by means of a regression-type parameter estimation algorithm. The method has been applied to the nasal allergen provocation test and verified on a limited number of volunteers.

[Optical Rhinometry. Continuous, direct measurement of swelling of the nasal mucosa with allergen provocation. Real-time monitoring of the nasal provocation test using optical rhinometry]. / Die optische Rhinometrie. Kontinuierliche, direkte Messung der Schwellung der Nasenschleimhaut bei Allergenprovokation.

BACKGROUND: Various methods exist for measuring swelling of the nasal mucosa. This is necessary in order to make the nasal provocation test objective. With the new method of optical rhinometry, it is possible to measure swelling of the mucosa directly from outside of the nose in real-time. The measurement is carried out with monochromatic near-infrared light of different wavelengths, the intensity change of which are recorded and displayed during the swelling. MATERIALS AND METHODS: With the help of a specially developed prototype of an optical rhinometer, we carried out measurements on 15 subjects having positive nasal provocation tests with histamine and allergens, negative provocation tests with allergens in non-allergics, negative provocation tests with control solution, and decongestion with xylometazoline. RESULTS: We found significant differences between positive and negative provocation tests ( P<0.01). Decongestion was different from all other groups ( P<0.01). Nasal congestion subjectively reported by the subject always correlated with the optical rhinometry findings. CONCLUSION: The objective assessment of nasal swelling using optical rhinometry seems reliable. The course of the endonasal swelling can thereby be monitored in real-time. The measurement is largely independent of the cooperation of the patient. The swelling is measured directly and not indirectly via air flow resistance.

[Determination of tissue optical parameters using HF modulation spectroscopy]. / Bestimmung gewebeoptischer Parameter mittels HF-Modulationsspektroskopie.

Radio frequency modulation spectroscopy is a capable method to determine tissue optical parameters in-vivo. For the eventual purpose of clinical measurements we have developed and tested an rf laser spectroscopy device which enables a measurement of the spatial amplitude and phase shift profiles of backscattered modulated laser light. Spectral absorption and scattering coefficients are computed by inverse formulas derived from analytical solutions of the diffusion model of light transport in a semi-infinite geometry.

[Modeling light distribution in nasal tissue structures]. / Modellierung der Lichtausbreitung in nasalen Gewebestrukturen.

There are different applications in the field of optical diagnostics in which the theories explaining the light transport in tissue do not lead to simple solutions for complicate geometric conditions. In these cases the Monte Carlo method provides a powerful tool to solve this problem statistically. In order to simulate the light transport in the nasal region a model was created which includes the structure depending on the swelling of the mucous membrane as well as the Monte Carlo model. Using this model it is possible to evaluate the measured values qualitatively. However, due to the long distance between light source and detector the statistical error becomes a major problem for reliable statements.

Fast image reconstruction for optical absorption tomography in media with radially symmetric boundaries.

In this paper we present a reconstruction algorithm to invert the linearized problem in optical absorption tomography for objects with radially symmetric boundaries. This is a relevant geometry for functional volume imaging of body regions that are sensitive to ionizing radiation, e.g., breast and testis. From the principles of diffuse light propagation in scattering media we derive the governing integral equations describing the effects of absorption variations on changes in the measurement data. Expansion of these equations into a Neumann series and truncation of higher-order terms yields the linearized forward imaging operator. For the proposed geometry we utilize an invariance property of this operator, which greatly reduces the problem dimensionality. This allows us to compute the inverse by singular value decomposition and consequently to apply regularization techniques based on the knowledge of the singular value spectrum. The inversion algorithm is highly efficient computing slice images as fast as convolution-backprojection algorithms in computed tomography (CT). To demonstrate the capacity of the inversion scheme we present reconstruction results for synthetic and phantom measurement data.