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148 results on '"Kaufmann Rolf"'

1. Biofilms in 3D porous media: Delineating the influence of the pore network geometry, flow and mass transfer on biofilm development

Author

Carrel, Maxence, Morales, Verónica L, Beltran, Mario A, Derlon, Nicolas, Kaufmann, Rolf, Morgenroth, Eberhard, and Holzner, Markus

Subjects
Fluid Mechanics and Thermal Engineering, Engineering, Biofilms, Hydrodynamics, Porosity, Rheology, Stress, Mechanical, X-Ray Microtomography, Biofilm, Three-dimensional porous medium, Three-dimensional particle tracking velocimetry, X-ray micro computed tomography, Wall shear stress, Concentration boundary layer thickness, Biofilm morphology, Environmental Engineering
Abstract

This study investigates the functional correspondence between porescale hydrodynamics, mass transfer, pore structure and biofilm morphology during progressive biofilm colonization of a porous medium. Hydrodynamics and the structure of both the porous medium and the biofilm are experimentally measured with 3D particle tracking velocimetry and micro X-ray Computed Tomography, respectively. The analysis focuses on data obtained in a clean porous medium after 36 h of biofilm growth. Registration of the particle tracking and X-ray data sets allows to delineate the interplay between porous medium geometry, hydrodynamic and mass transfer processes on the morphology of the developing biofilm. A local analysis revealed wide distributions of wall shear stresses and concentration boundary layer thicknesses. The spatial distribution of the biofilm patches uncovered that the wall shear stresses controlled the biofilm development. Neither external nor internal mass transfer limitations were noticeable in the considered system, consistent with the excess supply of nutrient and electron acceptors. The wall shear stress remained constant in the vicinity of the biofilm but increased substantially elsewhere.

Published
2018

5. Biofilm imaging in porous media by laboratory X-Ray tomography: Combining a non-destructive contrast agent with propagation-based phase-contrast imaging tools.

Author

Carrel, Maxence, Beltran, Mario A, Morales, Verónica L, Derlon, Nicolas, Morgenroth, Eberhard, Kaufmann, Rolf, and Holzner, Markus

Subjects
Biofilms, Barium Sulfate, Water, Ferrous Compounds, Fluorocarbon Polymers, Contrast Media, Imaging, Three-Dimensional, Tomography, X-Ray, Rheology, Porosity, General Science & Technology
Abstract

X-ray tomography is a powerful tool giving access to the morphology of biofilms, in 3D porous media, at the mesoscale. Due to the high water content of biofilms, the attenuation coefficient of biofilms and water are very close, hindering the distinction between biofilms and water without the use of contrast agents. Until now, the use of contrast agents such as barium sulfate, silver-coated micro-particles or 1-chloronaphtalene added to the liquid phase allowed imaging the biofilm 3D morphology. However, these contrast agents are not passive and potentially interact with the biofilm when injected into the sample. Here, we use a natural inorganic compound, namely iron sulfate, as a contrast agent progressively bounded in dilute or colloidal form into the EPS matrix during biofilm growth. By combining a very long source-to-detector distance on a X-ray laboratory source with a Lorentzian filter implemented prior to tomographic reconstruction, we substantially increase the contrast between the biofilm and the surrounding liquid, which allows revealing the 3D biofilm morphology. A comparison of this new method with the method proposed by Davit et al (Davit et al., 2011), which uses barium sulfate as a contrast agent to mark the liquid phase was performed. Quantitative evaluations between the methods revealed substantial differences for the volumetric fractions obtained from both methods. Namely, contrast agent-biofilm interactions (e.g. biofilm detachment) occurring during barium sulfate injection caused a reduction of the biofilm volumetric fraction of more than 50% and displacement of biofilm patches elsewhere in the column. Two key advantages of the newly proposed method are that passive addition of iron sulfate maintains the integrity of the biofilm prior to imaging, and that the biofilm itself is marked by the contrast agent, rather than the liquid phase as in other available methods. The iron sulfate method presented can be applied to understand biofilm development and bioclogging mechanisms in porous materials and the obtained biofilm morphology could be an ideal basis for 3D numerical calculations of hydrodynamic conditions to investigate biofilm-flow coupling.

Published
2017

19. Effect of aging on thermal conductivity of fiber-reinforced aerogel composites: An X-ray tomography study

Author

Iswara, Subramaniam, Griffa, Michele, Kaufmann, Rolf, Beltran, Mario, Huber, Lukas, Brunner, Samuel, Lattuada, Marco, M.Koebel, Matthias, and Malfait, Wim J.

Abstract

Silica aerogels display an ultra-low thermal conductivity (λ) and are used as thermal superinsulators. Here, we study the influence of aging and drying processes on the microstructure and thermal conductivity of fiber-reinforced silica aerogel composites. Glass wool-silica gel composites were aged for variable times, hydrophobized, and dried either at ambient pressure or from supercritical CO2 (scCO2). The X-ray micro- tomographic data display three distinct phases: silica aerogel, glass fibers, and macroscopic pores and cracks. The silica aerogel appears as a continuous medium in the tomograms because the spatial resolution (6–11 μm) is insufficient to resolve the aerogel mesopores (∼0.02–0.10 μm). For the composites prepared by ambient pressure drying, insufficient aging led to prominent drying shrinkage and cracking, and a high macro-porosity, as quantified by 3D image analysis. Insufficient aging also led to an increase in λ from 15.7 to 21.5 mW m−1 K−1. On the contrary, composites that were nearly free of cracks and displayed a constant λ of 16.3 ± 0.8 mW m−1 K−1 could be prepared by scCO2, independent of aging time. The thermal conductivity was reproduced from the macro-porosity to within 0.7 mW m−1 K−1 using simple thermal transport models consisting of thermal elements connected in series or parallel. Our results illustrate the usefulness of X-ray micro-tomography to quantify the 3D microstructure and its effects on the bulk composite properties and the data highlight the importance of aging for the production of low λ aerogel-fiber composites by ambient pressure drying.

Published
2019

21. A Novel Approach to Increase Robustness, Precision and High-Throughput Capacity of Single Cell Gel Electrophoresis.

Author

Cassano, Juan C., Roesslein, Matthias, Kaufmann, Rolf, Luethi, Thomas, Schicht, Oliver, Wick, Peter, and Hirsch, Cordula

Abstract

Routine use of the single cell gel electrophoresis assay in medical diagnostics and biomonitoring is prevented by its high variability. Several factors have been identified and can be grouped into four main categories: 1) the biological sample, 2) the assay protocol, 3) the physical parameters during electrophoresis and 4) the analysis. Even though scientific knowledge on the assay variability is available, not much has been done so far to tackle the issues from the technological side. Therefore, this study addresses the question in how far the precise and accurate control over the physical parameters of electrophoresis is able to reduce the variability of single cell gel electrophoresis assay results. All four above-mentioned categories make up the overall assay variability. To resolve the contribution from a single category, the remaining three have to be kept as constant as possible. To achieve this, we generated a set of x-ray treated control cells, worked according to a well-defined standard operating procedure, and one single operator performed the analysis. Thereby, variability resulting from the electrophoresis tank could be elucidated. We compared assay performance in two such tank systems: a newly developed electrophoresis tank that accurately controls voltage, temperature during the electrophoretic run and the homogeneity of the electric field, and a widely used commercially available standard platform tank. Our results demonstrate that, irrespective of the cellular sample and its intrinsic biological variability, accurate control over physical parameters considerably increases repeatability, reproducibility and precision of single cell gel electrophoresis. [ABSTRACT FROM AUTHOR]

Published
2020
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27. Dual energy phase contrast x-ray imaging with Talbot-Lau interferometer.

Author

Kottler, Christian, Revol, Vincent, Kaufmann, Rolf, and Urban, Claus

Subjects
X-rays, RADIOGRAPHY, IMAGING systems, RADIATION, DATA transmission systems, SPECTRUM analysis
Abstract

In weakly absorbing materials such as polymers and soft tissue, x-ray phase sensitive imaging methods can provide substantially enhanced contrast compared to classical, absorption based radiography. For specific applications, the latter can be applied in a dual energy scheme that helps to identify, discriminate and/or quantify materials. In this paper, we report on a new method that combines the idea of dual energy with x-ray phase contrast imaging and thus provides material sensitivity among poor absorbers. The dual energy modality cannot be applied in common phase contrast imaging schemes because of their demand for limited bandwidth or even monochromatic x-ray sources. Our new interferometric method based on diffraction gratings can overcome this shortcoming and thus simultaneously deliver x-ray phase contrast images for two distinct x-ray energy intervals. It has been shown that high quality images can be obtained with the dual energy phase setup. Energy spectra with 40 kV and 70 kV were applied to obtain low- and high-energy images, respectively. Furthermore, an estimation of the effective energy in the image formation process for absorption and phase contrast was experimentally determined. Examples are shown for which the dual energy phase contrast modality delivers complementary information on material composition when compared with the conventional dual energy scheme. [ABSTRACT FROM AUTHOR]

Published
2010
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34. LIST OF PARTICIPANTS

Author

Achtert, Günther, primary, Agosin., Moises, additional, Ahokas, Jorma T., additional, Altmann, Hans-Jürgen, additional, Alvares, Alvito P., additional, Arvela, Pentti I., additional, Baars, A.J., additional, Von Bahr, Christer, additional, Batt, Anne-Marie, additional, Belvedere, Giorgio, additional, Bend, John R., additional, Bentley, Philip, additional, Berg, Anders, additional, Berggren, Margareta, additional, Beyhl, Friedrich E., additional, Bock, Karl Walter, additional, Böttcher, Irmgard, additional, Boyd, G.S., additional, Breckenridge, Alasdair M., additional, Brunner, G., additional, Budczies, Babette, additional, Burchell, Brian, additional, Busch, U., additional, Capdevila, Jorge, additional, Carlström, Kjell, additional, Charuel, Claude, additional, Cho, Arthur K., additional, Conney, Allan H., additional, Coomes, Marguerite L., additional, Coon, M.J., additional, Cooper, David Y., additional, Cox, P.J., additional, Cremer-Schlede, Eva, additional, Davies, Donald S., additional, Debey, Marie-Pascale, additional, Denk, Helmut, additional, Dickins, Maurice, additional, Deutschmann, G., additional, Diehl, Horst, additional, Dietsch, Agnès, additional, Down, William H., additional, Duppel, Wilfried, additional, Dus, Karl M., additional, Dybing, Erik, additional, Ebel, D., additional, Eben, Anneliese, additional, Elcombe, C.R., additional, Ernster, Lars, additional, Estabrook, Ronald W., additional, Fann, William E., additional, Fauran, Francois, additional, Fellenius, Erik, additional, Franklin, Michael, additional, Garbe, Andreas, additional, Gelboin, Harry V., additional, Gielen, J., additional, Gillette, James R., additional, Glatt, Hans R., additional, Glazko, A.J., additional, Golan, Mario, additional, Gräfström, Roland, additional, Gram, Theodore E., additional, Gunsalus, I.C., additional, Gustafsson, Jan-Åke, additional, Hänninen, Osmo, additional, Haroz, Richard K., additional, Heinemeyer, Gerhard, additional, Herken, H., additional, Herzberg, Mala, additional, Herzberg, Wolfgang, additional, Hesse, Sigrun, additional, Hildebrandt, Alfred, additional, Hirata, Masaharo, additional, Hlavica, P., additional, Hoensch, Harald, additional, Hoffbauer, R.W., additional, Högberg, Johan, additional, Holtzman, J.L., additional, Ihlefeld, Heimbert, additional, Ingelman-Sundberg, Magnus, additional, Jakobsson, Sten, additional, Jauch, Rolf, additional, Jeffery, Elizabeth, additional, Jerina, D., additional, Jernström, Bengt, additional, Johannesen, Karin, additional, Joly, Jean-Gil, additional, Jonen, H.G., additional, Jonsson, John, additional, Kärki, Niilo, additional, Kahl, G.F., additional, Kahl, Regine, additional, Kaminsky, Laurence, additional, Kappas, A., additional, Kato, Ryuichi, additional, Kaufmann, Rolf, additional, Kewitz, Helmut, additional, Kexel, Hugo, additional, Kiese, Manfred, additional, Kim, Sangduk, additional, Koch-Weser, Jan, additional, Kremers, P., additional, Kupfer, David, additional, Larsen, John Chr., additional, Lang, Matti, additional, Lech, John J., additional, Lenk, Werner, additional, Levin, Wayne, additional, Lieber, Charles S., additional, Lind, Christina, additional, Lindeke, Björn, additional, Lissner, R., additional, Lübke, Klaus, additional, Maines, Mahin D., additional, Mannering, G.J., additional, Marlowe, Carolyn G., additional, Marniemi, Jukka, additional, Marselos, Marios, additional, Marsh, J., additional, Masters, Bettie Sue S., additional, Mattern, Ina E., additional, Meyer, Urs A., additional, Mercier, Michel, additional, Mieyal, John J., additional, Mitchell, Jerry R., additional, Mohn, Gertrud, additional, Moldéus, Peter, additional, Moron, Maria, additional, Mosser, Jacqueline, additional, Mull, Robert, additional, Muller-Eberhard, Ursula, additional, Narasimhulu, Skakunthola, additional, Nastainczyk, Wolfgang, additional, Neal, Robert, additional, Nebert, Daniel W., additional, Netter, K.J., additional, Noordhoek, J., additional, Novak, Raymond F., additional, Oesch, Franz, additional, Okuda, Kyuichio, additional, Omura, Tsuneo, additional, Orrenius, Sten, additional, Orton, Terence C., additional, Paigen, Beverly, additional, Paigen, Kenneth, additional, Parke, D.W., additional, Pawlak, Andrzey, additional, Pederson, Thomas C., additional, Pelkonen, Olavi, additional, Peterson, Julian A., additional, Philpot, Richard M., additional, DePierre, Joseph W., additional, Pitré, Davide, additional, Poensgen, Jutta, additional, Powis, G., additional, Prough, Russell A., additional, Pyykkö, Kaija, additional, Rafter, Joseph James, additional, Rahimtula, Anver, additional, Reed, Donald J., additional, Remmer, H., additional, Rendic, Slobodan, additional, Roots, Ivar, additional, Rosenthal, Otto, additional, Rubin, Alan, additional, Ruf, Hans-Heinrich, additional, Sato, Ryo, additional, Schenkman, John B., additional, Scheulen, M., additional, Schleyer, Heinz, additional, Schmassmann, H.U., additional, Schmelz, Eike, additional, Schmid, Jochen, additional, Schmidt, H.-L., additional, Schmoldt, Achim, additional, Schoene, Klaus, additional, Schoppler, J., additional, Schreiber, Eric, additional, Schulman, Martin, additional, Schulte-Hermann, Rolf, additional, Schüppel, R., additional, Schuster, Ingeborg, additional, Schwartzkopff, Thomas, additional, Seidegard, Janeric, additional, Sies, Helmut, additional, Siest, Gérard, additional, Sipal, Z., additional, Sligar, Stephen G., additional, Snyder, Robert, additional, Sotaniemi, Eero A., additional, Spitzauer, Peter, additional, Staudinger, Hansjürgen, additional, Stier, A., additional, Stitzel, Robert, additional, Tanaka, Minoru, additional, Temple, David J., additional, Temple, Cherrie, additional, Tennekes, H.A., additional, Terriere, Leon C., additional, Teschke, Rolf, additional, Thenot, Jean-Paul, additional, Thor, Hjördis, additional, Thorgeirsson, Snorri S., additional, Thurman, Ronald G., additional, Traylor, Teddy G., additional, Traylor, Patricia S., additional, Trifilieff, Elisabeth, additional, Tsibris, John C.M., additional, Tunek, Anders, additional, Cuong, Parcor Tuong Chi, additional, Uehleke, H., additional, Ullrich, Volker, additional, Vadi, Helena, additional, Vähäkangas, Kirsi, additional, Vainio, Harri, additional, Vatsis, Kostas P., additional, Vesell, Elliot S., additional, Viljakainen, Eila, additional, Visser, R., additional, Volz, Manfred, additional, Villeneuve, Jean-Pierre, additional, Waddell, William J., additional, Welch, Richard M., additional, Wende, Peter, additional, Wendt, Gemot, additional, Werringloer, Jürgen, additional, Weymann, Jürgen, additional, Wiebel, F.J., additional, Wolf, Roland C., additional, Wolff, Thomas, additional, Wollenberg, Peter, additional, Yang, C.S., additional, Yang, Shen K., additional, Yasukochi, Yukio, additional, Yesair, David W., additional, Zehnder, K., additional, Ziegler, Daniel M., additional, and Zimmer, Arno, additional

Published
1977
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35. (Invited) Three-Dimensional Epitaxial Si1-XGex, Ge and SiC Crystals on Deeply Patterned Si Substrates

Author

von Känel, Hans, primary, Isa, Fabio, additional, Falub, Claudiu V., additional, Barthazy, Eszter Judit, additional, Müller Gubler, Elisabeth, additional, Chrastina, Daniel, additional, Isella, Giovanni, additional, Kreiliger, Thomas, additional, Taboada, Alfonso Gonzalez, additional, Meduna, Mojmir, additional, Kaufmann, Rolf, additional, Neels, Antonia, additional, Dommann, Alex, additional, Niedermann, Philippe, additional, Mancarella, Fulvio, additional, Mauceri, Marco, additional, Puglisi, Marco, additional, Crippa, Danilo, additional, La Via, Francesco, additional, Anzalone, Ruggero, additional, Piluso, Nicolo, additional, Bergamaschini, Roberto, additional, Marzegalli, Anna, additional, and Miglio, Leo, additional

Published
2014
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37. Individual heterojunctions of 3D germanium crystals on silicon CMOS for monolithically integrated X‐ray detector (Phys. Status Solidi A 1∕2014)

Author

Kreiliger, Thomas, primary, Falub, Claudiu V., additional, Taboada, Alfonso G., additional, Isa, Fabio, additional, Cecchi, Stefano, additional, Kaufmann, Rolf, additional, Niedermann, Philippe, additional, Pezous, Aurélie, additional, Mouaziz, Schahrazède, additional, Dommann, Alex, additional, Isella, Giovanni, additional, and von Känel, Hans, additional

Published
2014
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38. Individual heterojunctions of 3D germanium crystals on silicon CMOS for monolithically integrated X‐ray detector

Author

Kreiliger, Thomas, primary, Falub, Claudiu V., additional, Taboada, Alfonso G., additional, Isa, Fabio, additional, Cecchi, Stefano, additional, Kaufmann, Rolf, additional, Niedermann, Philippe, additional, Pezous, Aurélie, additional, Mouaziz, Schahrazède, additional, Dommann, Alex, additional, Isella, Giovanni, additional, and von Känel, Hans, additional

Published
2013
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39. Business Engineering für KMU

Author

Winter, Robert, Bauer, Eric, Kaufmann, Rolf, Rusch, Josef, Brauchlin, Emil, and Pichler, J. Hanns

Subjects
information management
Published
2000

42. X-ray phase contrast imaging of soft tissue specimens

Author

Kottler, Christian, primary, Revol, Vincent, additional, Kaufmann, Rolf, additional, Maake, Caroline, additional, Stubinger, Stefan, additional, Von Rechenberg, Brigitte, additional, Kircher, Patrick R., additional, and Urban, Claus, additional

Published
2011
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44. 8 Gb/s 0.5 V integrated Ge-on-SOI photodetector

Author

Osmond, Johann, primary, Isella, Giovanni, additional, Chrastina, Daniel, additional, von Känel, Hans, additional, Kaufmann, Rolf, additional, Vivien, Laurent, additional, Rasigade, Gilles, additional, Marris-Morini, Delphine, additional, Crozat, Paul, additional, Cassan, Eric, additional, and Laval, Suzanne, additional

Published
2009
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50. Recent developments on X-ray phase contrast imaging technology at CSEM.

Author

Kottler, Christian, Revol, Vincent, Kaufmann, Rolf, Urban, Claus, Blanc, Nicolas, Niedermann, Philippe, Cardot, Francis, and Dommann, Alex

Subjects
ELECTRON microscopy, IMAGE analysis, DIFFRACTION gratings, INTERFEROMETERS, CONTRAST effect, X-ray tubes
Abstract

X-ray phase contrast imaging (XPCi) using the Talbot-Lau grating interferometer attracts increasing attention for its implementation in various fields of applications such as in the (bio-) medical domain, non-destructive testing or security. Since the method is compatible with laboratory X-ray tube sources as well as with large field of view digital X-ray image sensors, it has a large potential to provide XPCi for industrial and medical applications as widespread as conventional X-raying is. Here, we report on our recent results and measurements regarding the grating interferometer technology. [ABSTRACT FROM AUTHOR]

Published
2012
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