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283 results on '"Köhler, J. Michael"'

5. Micro Continuous-Flow Synthesis of Metal Nanoparticles Using Micro Fluid Segment Technology

Author

Knauer, Andrea, Köhler, J. Michael, Aizawa, Masuo, Series editor, Greenbaum, Elias, Editor-in-chief, Andersen, Olaf S., Series editor, Austin, Robert H., Series editor, Barber, James, Series editor, Berg, Howard C., Series editor, Bloomfield, Victor, Series editor, Callender, Robert, Series editor, Chance, Britton, Series editor, Chu, Steven, Series editor, DeFelice, Louis J., Series editor, Deisenhofer, Johann, Series editor, Feher, George, Series editor, Frauenfelder, Hans, Series editor, Giaever, Ivar, Series editor, Gruner, Sol M., Series editor, Herzfeld, Judith, Series editor, Humayun, Mark S., Series editor, Joliot, Pierre, Series editor, Keszthelyi, Lajos, Series editor, Knox, Robert S., Series editor, Lewis, Aaron, Series editor, Lindsay, Stuart M., Series editor, Mauzerall, David, Series editor, Mielczarek, Eugenie V., Series editor, Niemz, Markolf, Series editor, Parsegian, V. Adrian, Series editor, Powers, Linda S., Series editor, Prohofsky, Earl W., Series editor, Rubin, Andrew, Series editor, Seibert, Michael, Series editor, Thomas, David, Series editor, Köhler, J. Michael, editor, and Cahill, Brian P., editor

Published
2014
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6. Electrical Switching of Droplets and Fluid Segments

Author

Budden, Matthias, Schneider, Steffen, Köhler, J. Michael, Cahill, Brian P., Aizawa, Masuo, Series editor, Greenbaum, Elias, Editor-in-chief, Andersen, Olaf S., Series editor, Austin, Robert H., Series editor, Barber, James, Series editor, Berg, Howard C., Series editor, Bloomfield, Victor, Series editor, Callender, Robert, Series editor, Chance, Britton, Series editor, Chu, Steven, Series editor, DeFelice, Louis J., Series editor, Deisenhofer, Johann, Series editor, Feher, George, Series editor, Frauenfelder, Hans, Series editor, Giaever, Ivar, Series editor, Gruner, Sol M., Series editor, Herzfeld, Judith, Series editor, Humayun, Mark S., Series editor, Joliot, Pierre, Series editor, Keszthelyi, Lajos, Series editor, Knox, Robert S., Series editor, Lewis, Aaron, Series editor, Lindsay, Stuart M., Series editor, Mauzerall, David, Series editor, Mielczarek, Eugenie V., Series editor, Niemz, Markolf, Series editor, Parsegian, V. Adrian, Series editor, Powers, Linda S., Series editor, Prohofsky, Earl W., Series editor, Rubin, Andrew, Series editor, Seibert, Michael, Series editor, Thomas, David, Series editor, Köhler, J. Michael, editor, and Cahill, Brian P., editor

Published
2014
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18. Investigation of mixture toxicity of widely used drugs caffeine and ampicillin in the presence of an ACE inhibitor on bacterial growth using droplet-based microfluidic technique

Author

Cao Jialan, Goldhan Juliane, Martin Karin, and Köhler J. Michael

Subjects
ace inhibitor captopril, antibiotic ampicillin, combinatorial effects, droplet-based microfluidic technique, mixture toxicity, Chemistry, QD1-999
Abstract

Droplet-based microfluidic technique is very suitable for a variety of screening processes. The cultivation within nanoliter segments and multidimensional microtoxicological screening of the Gram-negative bacterium Escherichia coli were studied under droplet-based microfluidic conditions. In order to evaluate the toxicity of the binary and ternary mixtures of antibiotic ampicillin and caffeine in the presence of the angiotensin-converting enzyme inhibitor captopril, a time-resolved optical double endpoint detection unit was applied. It included a microflow-through fluorimeter and photometer, which can simultaneously analyze changes in the endogenous autofluorescence signal and the cell density of E. coli cultivated inside 450-nl microfluid segments. As a result, strong nonlinear combination effects and a concentration-dependent antagonistic effect, as well as formation of activity summits on bolographic maps, were found. Our findings confirm the importance of multiparameter investigations for toxicological studies and could be taken into account in medical practice.

Published
2013
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22. Archaeal and Extremophilic Bacteria from Different Archaeological Excavation Sites.

Author

Köhler, J. Michael, Ehrhardt, Linda, and Günther, P. Mike

Subjects
*ARCHAEOLOGICAL excavations, *NUCLEOTIDE sequencing, *BACTERIAL communities, *PRINCIPAL components analysis, *DNA analysis
Abstract

Beside natural factors, human activities are important for the development of microbiomes. Thus, local soil bacterial communities are affected by recent activities such as agriculture, mining and industry. In addition, ancient human impacts dating back centuries or millennia have changed soils and can emboss the recent bacterial communities up to now, representing a certain long-term "memory of soil". Soil samples from five different archaeological excavation places were investigated for the presence of Archaea with a Next Generation Sequencing (NGS) analysis of the DNA coding for 16S r-RNA sequences. It was found that the abundance of Archaea differs strongly between less than one and more than 40 percent of bacteria. A Principal Component Analysis (PCA) of all samples shows that the archaeological excavation places can be distinguished from each other by the archaeal component of soil bacterial communities, which presents a typical pattern for each place. Most samples are marked by the dominance of Crenarchaeota, which are presented mainly by ammonia-related types. High contents of Nanoarchaeaota have been observed in one ash deposit of a historical saline and all samples of a historical tannery area. These samples are also marked by a significant presence of Dadabacteria. The specific abundancies of special Archaea—among them ammonia-oxidizing and sulphur-related types—are due obviously to former human activities and support the concept of the "ecological memory of soil". [ABSTRACT FROM AUTHOR]

Published
2023
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30. Induction of embryogenic development in haploid microspore stem cells in droplet-based microfluidics

Author

Richter, Felix, primary, Chen, Minqian, additional, Schaub, Patrick, additional, Wüst, Florian, additional, Zhang, Di, additional, Schneider, Steffen, additional, Groß, G. Alexander, additional, Mäder, Patrick, additional, Dovzhenko, Oleksandr, additional, Palme, Klaus, additional, Köhler, J. Michael, additional, and Cao, Jialan, additional

Published
2022
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44. Microfluidic Chamber Design for Controlled Droplet Expansion and Coalescence

Author

Kielpinski, Mark, Walther, Oliver, Cao, Jialan, Henkel, Thomas, Köhler, J. Michael, and Groß, G. Alexander

Subjects
droplet microfluidics, electrocoalescence, lcsh:Mechanical engineering and machinery, self-controlled, microfluidics, Article, segmented flow, compact disk CD-production, bypassed chamber, channel confined, labdisc, volume bridging, droplet, lcsh:TJ1-1570, network interface
Abstract

The defined formation and expansion of droplets are essential operations for droplet-based screening assays. The volumetric expansion of droplets causes a dilution of the ingredients. Dilution is required for the generation of concentration graduation which is mandatory for many different assay protocols. Here, we describe the design of a microfluidic operation unit based on a bypassed chamber and its operation modes. The different operation modes enable the defined formation of sub-µL droplets on the one hand and the expansion of low nL to sub-µL droplets by controlled coalescence on the other. In this way the chamber acts as fluidic interface between two fluidic network parts dimensioned for different droplet volumes. Hence, channel confined droplets of about 30-40 nL from the first network part were expanded to cannel confined droplets of about 500 to about 2500 nL in the second network part. Four different operation modes were realized: (a) flow rate independent droplet formation in a self-controlled way caused by the bypassed chamber design, (b) single droplet expansion mode, (c) multiple droplet expansion mode, and (d) multiple droplet coalescence mode. The last mode was used for the automated coalescence of 12 droplets of about 40 nL volume to produce a highly ordered output sequence with individual droplet volumes of about 500 nL volume. The experimental investigation confirmed a high tolerance of the developed chamber against the variation of key parameters of the dispersed-phase like salt content, pH value and fluid viscosity. The presented fluidic chamber provides a solution for the problem of bridging different droplet volumes in a fluidic network.

Published
2020

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