Biomedical subjects
M Kühner
Publications and source records attributed to M Kühner.
[Detection of airborne cultivatable microorganisms from compost sites--emissions and imissions].
The statement presented here gives an overview and assessment of the procedures and concepts currently used for the collection and determination of airborne, culturable microorganisms at sources of emission within composting plants and in their near vicinity. The paper focuses on "classical" methods, which involve cultivation as an intermediate step for the determination of viable, airborne microorganisms. The theoretical and practical requirements on such methods are discussed. Results and experiences from recent investigations are described.
['Microbial air pollutants'. Emission sources and preventive measures].
Already in the planning or monitoring phase, measures have to be realized for the reduction in emissions of bio-aerosols in biological waste treatment plants. For this purpose, operation-related measures (in open and partially closed plants) and technology-related measures (in closed plants with automatic ventilation) can be taken. A survey on the currently feasible measures for reduction is submitted. The realization has to be adapted to the individual site and type of plant. An enormous demand for examinations is envisaged in order to enable a qualified assessment of the emission behaviour of diverse waste air systems or process steps.
[Composting with semipermeable covers, a possibility for reducing emissions of microbial aerosols].
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Functionalisation of Si/SiO2 and glass surfaces with ultrathin dextran films and deposition of lipid bilayers.
Dextran with molecular weight of 500 kDalton was covalently coupled to glass and Si/SiO2-surfaces by epoxy functionalisation or by photo reactive functionalisation of the solid surface. With the described methods we can control the deposited mass density between 0.3 and 4.8 ng/m2 corresponding to mean film thicknesses of a dry dextran film between 2 A and 30 A. We studied the structural properties (thickness, density) of ultrathin dextran layers coupled to silicon wafers of glass surfaces in humid atmosphere and under water by ellipsometry and reflection interference contrast microscopy (RICM) and developed a new method to measure the interfacial forces in ultrathin films. We demonstrate, that these hydrophilic polymer films from soft cushions which can be reversibly swollen both under water and in humidified air. In water the films swell up to thicknesses of about 600 to 800 A as measured by reflection interference contrast microscopy (RICM) and ellipsometry. The interaction of the polymer films with Si/SiO2-surfaces in contact with humidified air was studied by ellipsometry. We measured the thickness of the polymer layers as a function of the relative humidity of the atmosphere surrounding the sample in a hydration chamber. Depending on the humidity of the surrounding air and induced by the hydration the film thickness changes by about a factor of 10. Coupling of N-hydroxysuccinimide to dextran enables the functionalisation of the dextran cushions with a broad range of different specific binding molecules for various detection tasks. The possibility of soft hydrated dextran films as a cushion for the deposition of self healing lipid bilayers is shown.
Lipid mono- and bilayer supported on polymer films: composite polymer-lipid films on solid substrates.
We report the deposition of lipid monolayers and bilayers on polyacrylamide films deposited by radical chain reaction onto solid substrates in aqueous solutions. Polymer films of various degrees of monomer density and cross-linking are prepared. Lateral diffusion and fluorescent probe permeation measurements yield insight into the continuity of the lipid layers and show that monolayers exposed to air are much less sensitive towards polymer heterogeneities than bilayers below water, which is explained in terms of the wetting laws. The diffusion studies of lipid and lipopeptide probes yield absolute values of the frictional coefficients between the lipid layer and the polymer films and allow one to estimate the surface viscosity of the polymer film. The potential applications of supported membranes on soft thin polymer films for the preparation of biofunctionalized surfaces or biocompatible receptive surfaces for biosensors are discussed.
Relative effectiveness of various alternating frequencies of a power toothbrush.
The influence on plaque-removing efficiency of the alternating frequency of a powered brush has never been established. In the present study, a mechanical brush was tested at various alternations per minute (F1 = 2100, F2 = 2500, F3 = 3500). A double-blind, randomized, triple crossover design was applied. After a plaque growth phase, the test brushes were used under supervision for 90 s and the remaining plaque scored. A ridit analysis yielded significant differences between F2 and F1/F3. Odds ratios and frequency distributions demonstrated a clinically meaningful advantage for F2. Subjective evaluation by the participants confirmed the positive performance of F2. The results can be generalized in 3 ways: (1) the alternating frequency of a power brush influences its effectiveness, (2) high frequencies are not generally superior, (3) the test brush has its optimal cleaning efficiency at F2, which does not necessarily need to be true for other brands. It seems imperative to determine the optimal frequency for any new brush in a controlled study.
[Sensitivity of pocket diagnosis as a function of numbers of probings].
Probing depth (PD) is measured at 2, 4 or 6 sites per tooth. We sought to ascertain whether or not more measurements increase the sensitivity of assessing the severity of periodontitis. 2 probings compared with 4 probings per tooth resulted in 68% sensitivity for PD greater than 2 mm and 77% for PD greater than 4 mm. The mesio-buccal PD explains only 16% of the variance of the buccal/oral PD. Comprehensive examination of pockets should consist of a minimum of 4 probings per tooth.
[Studies on transferrin and iron metabolism in infants (author's transl)].
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