TY - JOUR A1 - Abouzar, Maryam H. A1 - Poghossian, Arshak A1 - Cherstvy, Andrey G. A1 - Pedraza, Angela M. A1 - Ingebrandt, Sven A1 - Schöning, Michael Josef T1 - Label-free electrical detection of DNA by means of field-effect nanoplate capacitors: Experiments and modeling JF - Physica Status Solidi (a) N2 - Label-free electrical detection of consecutive deoxyribonucleic acid (DNA) hybridization/denaturation by means of an array of individually addressable field-effect-based nanoplate silicon-on-insulator (SOI) capacitors modified with gold nanoparticles (Au-NP) is investigated. The proposed device detects charge changes on Au-NP/DNA hybrids induced by the hybridization or denaturation event. DNA hybridization was performed in a high ionic-strength solution to provide a high hybridization efficiency. On the other hand, to reduce the screening of the DNA charge by counter ions and to achieve a high sensitivity, the sensor signal induced by the hybridization and denaturation events was measured in a low ionic-strength solution. High sensor signals of about 120, 90, and 80 mV were registered after the DNA hybridization, denaturation, and re-hybridization events, respectively. Fluorescence microscopy has been applied as reference method to verify the DNA immobilization, hybridization, and denaturation processes. An electrostatic charge-plane model for potential changes at the gate surface of a nanoplate field-effect sensor induced by the DNA hybridization has been developed taking into account both the Debye length and the distance of the DNA charge from the gate surface. Y1 - 2012 U6 - http://dx.doi.org/10.1002/pssa.201100710 SN - 1862-6319 VL - 209 SP - 925 EP - 934 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Atlas, Glen A1 - Brealey, David A1 - Dhar, Sunil A1 - Dikta, Gerhard A1 - Singer, Meryvn T1 - Additional hemodynamic measurements with an esophageal Doppler monitor: a preliminary report of compliance, force, kinetic energy, and afterload in the clinical setting JF - Journal of clinical monitoring and computing N2 - The esophageal Doppler monitor (EDM) is a minimally-invasive hemodynamic device which evaluates both cardiac output (CO), and fluid status, by estimating stroke volume (SV) and calculating heart rate (HR). The measurement of these parameters is based upon a continuous and accurate approximation of distal thoracic aortic blood flow. Furthermore, the peak velocity (PV) and mean acceleration (MA), of aortic blood flow at this anatomic location, are also determined by the EDM. The purpose of this preliminary report is to examine additional clinical hemodynamic calculations of: compliance (C), kinetic energy (KE), force (F), and afterload (TSVRi). These data were derived using both velocity-based measurements, provided by the EDM, as well as other contemporaneous physiologic parameters. Data were obtained from anesthetized patients undergoing surgery or who were in a critical care unit. A graphical inspection of these measurements is presented and discussed with respect to each patient’s clinical situation. When normalized to each of their initial values, F and KE both consistently demonstrated more discriminative power than either PV or MA. The EDM offers additional applications for hemodynamic monitoring. Further research regarding the accuracy, utility, and limitations of these parameters is therefore indicated. KW - Acceleration KW - Velocity KW - Kinetic energy KW - Force KW - Compliance KW - Afterload KW - Contractility KW - Volume status KW - Esophageal Doppler monitor Y1 - 2012 SN - 1573-2614 U6 - http://dx.doi.org/10.1007/s10877-012-9386-5 IS - 26 SP - 473 EP - 482 PB - Springer Nature CY - London ER - TY - JOUR A1 - Bassam, Rasha A1 - Hescheler, Jürgen A1 - Temiz Artmann, Aysegül A1 - Artmann, Gerhard A1 - Digel, Ilya T1 - Effects of spermine NONOate and ATP on the thermal stability of hemoglobin JF - BMC Biophysics N2 - Background Minor changes in protein structure induced by small organic and inorganic molecules can result in significant metabolic effects. The effects can be even more profound if the molecular players are chemically active and present in the cell in considerable amounts. The aim of our study was to investigate effects of a nitric oxide donor (spermine NONOate), ATP and sodium/potassium environment on the dynamics of thermal unfolding of human hemoglobin (Hb). The effect of these molecules was examined by means of circular dichroism spectrometry (CD) in the temperature range between 25°C and 70°C. The alpha-helical content of buffered hemoglobin samples (0.1 mg/ml) was estimated via ellipticity change measurements at a heating rate of 1°C/min. Results Major results were: 1) spermine NONOate persistently decreased the hemoglobin unfolding temperature T u irrespectively of the Na + /K + environment, 2) ATP instead increased the unfolding temperature by 3°C in both sodium-based and potassium-based buffers and 3) mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions. Moreover, the presence of potassium facilitated a partial unfolding of alpha-helical structures even at room temperature. Conclusion The obtained data might shed more light on molecular mechanisms and biophysics involved in the regulation of protein activity by small solutes in the cell. KW - Nitric Oxide Donor KW - NONOate KW - Circular Dichroism KW - Nitric Oxide Y1 - 2012 U6 - http://dx.doi.org/10.1186/2046-1682-5-16 SN - 2046-1682 VL - 5 PB - BioMed Central CY - London ER - TY - JOUR A1 - Bohrn, U. A1 - Stütz, E. A1 - Fuchs, K. A1 - Fleischer, M. A1 - Schöning, Michael Josef A1 - Wagner, P. T1 - Monitoring of irritant gas using a whole-cell-based sensor system JF - Sensors and Actuators B: Chemical N2 - Cell-based sensors for the detection of gases have long been underrepresented, due to the cellular requirement of being cultured in a liquid environment. In this work we established a cell-based gas biosensor for the detection of toxic substances in air, by adapting a commercial sensor chip (Bionas®), previously used for the measurement of pollutants in liquids. Cells of the respiratory tract (A549, RPMI 2650, V79), which survive at a gas phase in a natural context, are used as biological receptors. The physiological cell parameters acidification, respiration and morphology are continuously monitored in parallel. Ammonia was used as a highly water-soluble model gas to test the feasibility of the sensor system. Infrared measurements confirmed the sufficiency of the medium draining method. This sensor system provides a basis for many sensor applications such as environmental monitoring, building technology and public security. Y1 - 2012 U6 - http://dx.doi.org/10.1016/j.snb.2012.05.088 SN - 0925-4005 VL - 175 SP - 208 EP - 217 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Bäcker, Matthias A1 - Raue, Markus A1 - Schusser, Sebastian A1 - Jeitner, C. A1 - Breuer, L. A1 - Wagner, P. A1 - Poghossian, Arshak A1 - Förster, Arnold A1 - Mang, Thomas A1 - Schöning, Michael Josef T1 - Microfluidic chip with integrated microvalves based on temperature- and pH-responsive hydrogel thin films JF - Physica Status Solidi (a) N2 - Two types of microvalves based on temperature-responsive poly(N-isopropylacrylamide) (PNIPAAm) and pH-responsive poly(sodium acrylate) (PSA) hydrogel films have been developed and tested. The PNIPAAm and PSA hydrogel films were prepared by means of in situ photopolymerization directly inside the fluidic channel of a microfluidic chip fabricated by combining Si and SU-8 technologies. The swelling/shrinking properties and height changes of the PNIPAAm and PSA films inside the fluidic channel were studied at temperatures of deionized water from 14 to 36 °C and different pH values (pH 3–12) of Titrisol buffer, respectively. Additionally, in separate experiments, the lower critical solution temperature (LCST) of the PNIPAAm hydrogel was investigated by means of a differential scanning calorimetry (DSC) and a surface plasmon resonance (SPR) method. Mass-flow measurements have shown the feasibility of the prepared hydrogel films to work as an on-chip integrated temperature- or pH-responsive microvalve capable to switch the flow channel on/off. Y1 - 2012 U6 - http://dx.doi.org/10.1002/pssa.201100763 SN - 1862-6319 VL - 209 IS - 5 SP - 839 EP - 845 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Grinsven, Bart van A1 - Bon, Natalie vanden A1 - Strauven, Hannelore A1 - Grieten, Lars A1 - Murib, Mohammed A1 - Jiménez Monroy, Kathia L. A1 - Janssens, Stoffel D. A1 - Haenen, Ken A1 - Schöning, Michael Josef A1 - Vermeeren, Veronique A1 - Ameloot, Marcel A1 - Michiels, Luc A1 - Thoelen, Ronald A1 - Ceuninck, Ward de A1 - Wagner, Patrick T1 - Heat-Transfer Resistance at Solid-Liquid Interfaces: A Tool for The Detection of Single Nucleotide Polymorphisms in DNA. JF - ACS Nano N2 - In this article, we report on the heat-transfer resistance at interfaces as a novel, denaturation-based method to detect single-nucleotide polymorphisms in DNA. We observed that a molecular brush of double-stranded DNA grafted onto synthetic diamond surfaces does not notably affect the heat-transfer resistance at the solid-to-liquid interface. In contrast to this, molecular brushes of single-stranded DNA cause, surprisingly, a substantially higher heat-transfer resistance and behave like a thermally insulating layer. This effect can be utilized to identify ds-DNA melting temperatures via the switching from low- to high heat-transfer resistance. The melting temperatures identified with this method for different DNA duplexes (29 base pairs without and with built-in mutations) correlate nicely with data calculated by modeling. The method is fast, label-free (without the need for fluorescent or radioactive markers), allows for repetitive measurements, and can also be extended toward array formats. Reference measurements by confocal fluorescence microscopy and impedance spectroscopy confirm that the switching of heat-transfer resistance upon denaturation is indeed related to the thermal on-chip denaturation of DNA. Y1 - 2012 U6 - http://dx.doi.org/10.1021/nn300147e SN - 1936-086X VL - 6 IS - 3 SP - 2712 EP - 2721 PB - ACS Publications CY - Washington, DC ER - TY - JOUR A1 - Grotendorst, Johannes T1 - IAS Winter School: Hierarchical Methods for Dynamics in Complex Molecular Systems JF - Innovatives Supercomputing in Deutschland : inSiDE. 10 (2012), H. 1 Y1 - 2012 SP - 104 PB - - ER - TY - JOUR A1 - Gutheil, Inge A1 - Berg, Tommy A1 - Grotendorst, Johannes T1 - Performance Analysis of Parallel Eigensolvers of two Libraries on BlueGene/P JF - Journal of Mathematics and Systems Science N2 - Many applications in computational science and engineering require the computation of eigenvalues and vectors of dense symmetric or Hermitian matrices. For example, in DFT (density functional theory) calculations on modern supercomputers 10% to 30% of the eigenvalues and eigenvectors of huge dense matrices have to be calculated. Therefore, performance and parallel scaling of the used eigensolvers is of upmost interest. In this article different routines of the linear algebra packages ScaLAPACK and Elemental for parallel solution of the symmetric eigenvalue problem are compared concerning their performance on the BlueGene/P supercomputer. Parameters for performance optimization are adjusted for the different data distribution methods used in the two libraries. It is found that for all test cases the new library Elemental which uses a two-dimensional element by element distribution of the matrices to the processors shows better performance than the old ScaLAPACK library which uses a block-cyclic distribution. KW - performance analysis KW - Elemental KW - ScaLAPACK KW - eigensolvers KW - Numerical linear algebra Y1 - 2012 U6 - http://dx.doi.org/10.17265/2159-5291/2012.04.003 SN - 2159-5291 VL - 2 IS - 4 SP - 231 EP - 236 PB - David Publishing CY - Libertyville ER - TY - JOUR A1 - Hasan, Istabrak A1 - Keil, Ludger A1 - Staat, Manfred A1 - Wahl, Gerhard A1 - Bourauel, Christoph T1 - Determination of the frictional coefficient of the implant-antler interface : experimental approach JF - Biomedical Engineering / Biomedizinische Technik N2 - The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5–0.7 and 0.3–0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens. Y1 - 2012 SN - 1862-278X VL - 57 IS - 5 SP - 359 EP - 363 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Huck, Christina A1 - Poghossian, Arshak A1 - Wagner, Patrick A1 - Schöning, Michael Josef T1 - Combined amperometric/field-effect sensor for the detection of dissolved hydrogen JF - Sensors and actuators B: Chemical N2 - Real-time and reliable monitoring of the biogas process is crucial for a stable and efficient operation of biogas production in order to avoid digester breakdowns. The concentration of dissolved hydrogen (H₂) represents one of the key parameters for biogas process control. In this work, a one-chip integrated combined amperometric/field-effect sensor for monitoring the dissolved H₂ concentration has been developed for biogas applications. The combination of two different transducer principles might allow a more accurate and reliable measurement of dissolved H₂ as an early warning indicator of digester failures. The feasibility of the approach has been demonstrated by simultaneous amperometric/field-effect measurements of dissolved H₂ concentrations in electrolyte solutions. Both, the amperometric and the field-effect transducer show a linear response behaviour in the H₂ concentration range from 0.1 to 3% (v/v) with a slope of 198.4 ± 13.7 nA/% (v/v) and 14.9 ± 0.5 mV/% (v/v), respectively. Y1 - 2012 U6 - http://dx.doi.org/10.1016/j.snb.2012.10.050 SN - 0925-4005 N1 - Part of special issue "Selected Papers from the 14th International Meeting on Chemical Sensors" VL - 187 SP - 168 EP - 173 PB - Elsevier CY - Amsterdam ER -