The Experts below are selected from a list of 1044 Experts worldwide ranked by ideXlab platform

Bernhard Lendl - One of the best experts on this subject based on the ideXlab platform.

  • Sensitivity-Enhanced Fourier Transform Mid-Infrared Spectroscopy Using a Supercontinuum Laser Source.
    Applied Spectroscopy, 2020
    Co-Authors: Ivan Zorin, Bernhard Lendl, Jakob Kilgus, Kristina Duswald, Bettina Heise, Markus Brandstetter
    Abstract:

    Fourier transform infrared (FT-IR) spectrometers have been the dominant technology in the field of mid-infrared (Mid-IR) Spectroscopy for decades. Supercontinuum laser sources operating in the mid-...

  • Towards ultrasound enhanced Mid-IR Spectroscopy for sensing bacteria in aqueous solutions
    Microfluidics BioMEMS and Medical Microsystems XVI, 2018
    Co-Authors: Stephan Freitag, Andreas Schwaighofer, Stefan Radel, Bernhard Lendl
    Abstract:

    We employ attenuated total reflection (ATR) Mid-IR technology for sensing of bacteria present in aqueous solution. In ATR Spectroscopy, the penetration depth of the evanescent field extends to approx. 1-2 micrometers into the aqueous solution depending on the refractive index of the employed materials (Si, ZnS, Ge) used as attenuated total reflection (ATR) element and the geometry of the optical set-up. Due to the flow profile in the microfluidic cell, an additional force is required to bring particles into the evanescent field for measurement. For that purpose, we employ standing ultrasound waves produced between a sound source vibrating at approx. 2 MHz and the ATR crystal acting as a reflector. This ultrasonic trap is integrated into the microfluidic channel. As aqueous solution is passing through that acoustofluidic cell, particles are concentrated in the nodal plane of the standing ultrasound wave, forming particle conglomerates. By selecting appropriate experimental conditions, it is then possible to press bacteria against the crystal surface for interaction with the evanescent wave (as well as to keep them away from the ATR element). Our current work aims at establishing a custommade US-ATR-IR setup for signal enhancement of bacteria (e.g. E. coli, P. aeruginosa as well as Salmonella) in drinking water.

  • Quantum cascade lasers (QCLs) in biomedical Spectroscopy
    Chemical Society Reviews, 2017
    Co-Authors: Andreas Schwaighofer, Markus Brandstetter, Bernhard Lendl
    Abstract:

    Quantum cascade lasers (QCL) are the first room temperature semiconductor laser source for the Mid-IR spectral region, triggering substantial development for the advancement of Mid-IR Spectroscopy. Mid-IR Spectroscopy in general provides rapid, label-free and objective analysis, particularly important in the field of biomedical analysis. Due to their unique properties, QCLs offer new possibilities for development of analytical methods to enable quantification of clinically relevant concentration levels and to support medical diagnostics. Compared to FTIR Spectroscopy, novel and elaborated measurement techniques can be implemented that allow miniaturized and portable instrumentation. This review illustrates the characteristics of QCLs with a particular focus on their benefits for biomedical analysis. Recent applications of QCL-based Spectroscopy for analysis of a variety of clinically relevant samples including breath, urine, blood, interstitial fluid, and biopsy samples are summarized. Further potential for technical advancements is discussed in combination with future prospects for employment of QCL-based devices in routine and point-of-care diagnostics.

  • Fabrication and characterization of a vertical lamination micromixer for Mid-IR Spectroscopy
    Sensors and Actuators B-chemical, 2011
    Co-Authors: Wolfgang Buchegger, Christoph Wagner, Martin Kraft, Bernhard Lendl, P. Svasek, Michael J. Vellekoop
    Abstract:

    Abstract A multilamination micromixer for time resolved infrared Spectroscopy, optimized by fluid simulations is characterized by fluidic means for different flow rates. The mixer is fabricated with silicon micromachining techniques. Using four instead of two lamination layers yields a reduction of the diffusion length and decreases mixing time significantly. Measurement results show the ultrafast mixing performance of this micromixer (

  • Time-resolved Mid-IR Spectroscopy of (bio)chemical reactions in solution utilizing a new generation of continuous-flow micro-mixers
    Analytical and Bioanalytical Chemistry, 2011
    Co-Authors: Christoph Wagner, Wolfgang Buchegger, Michael J. Vellekoop, Martin Kraft, Bernhard Lendl
    Abstract:

    A specially designed micro-mixer made of silicon, calcium fluoride, and silicone with an optical transmission path of 8 μm has been used for Mid-IR Spectroscopy monitoring of mixing-induced chemical reactions in the low millisecond time regime. The basic principle of the proposed continuous-flow technique is to mix two liquids introduced in two times two alternatingly stacked layers through diffusion at the entrance of a 200 μm wide, 1 cm long micro-fluidic channel also serving as measurement area. By using this special, dedicated arrangement, diffusion lengths and hence the mixing times can be significantly shortened and the overall performance improved in comparison to previous systems and alternative methods. Measurements were carried out in transmission mode using an Fourier transform infrared (FTIR) microscope, recording spectra with spot sizes of 180 × 100 μm2 each at defined spots along this channel. Each of these spots corresponds to a specific reaction time: moving the measurement spot towards the entry yields shorter reaction times, moving it towards the channel’s end gives longer reaction times. This principle is generic in nature and provides a solution for accurate, chemically induced triggering of reactions requiring the mixing of two liquid reagents or reagent solutions. A typical experiment thus yields up to 85 time-coded data points, covering a time span from 1 to 80 ms at a total reagent consumption of only about 125 μL. Using the fast neutralization reaction of acetic acid with sodium hydroxide as a model, the time required for 90% mixing was determined to be around 4 ms. Additionally, first experiments on ubiquitin changing its secondary structure from native to “A-state” were carried out, illustrating the potential for time-resolved measurements of proteins in aqueous solutions.

Urs Von Stockar - One of the best experts on this subject based on the ideXlab platform.

  • A simple method to monitor and control methanol feeding of Pichia pastoris fermentations using Mid-IR Spectroscopy
    Journal of Biotechnology, 2006
    Co-Authors: Jonas Schenk, Ian Marison, Urs Von Stockar
    Abstract:

    Abstract Mid-infrared FTIR Spectroscopy is an efficient tool for the monitoring of bioprocesses, since it is fast and able to detect many compounds simultaneously. However, complex and time-consuming calibration procedures are still required, and have inhibited the spreading of these instruments. A simple and quick method to calibrate a FTIR instrument was developed for the control of fed-batch fermentations of the methylotrophic yeast Pichia pastoris. Based on the assumptions that (1) only substrate concentration may change significantly during a fed-batch process and (2) absorbance can be considered as proportional to concentration, a linear two-point calibration was implemented. Long-term instability of the instrument had to be addressed in order to get accurate results: two fixed points, on both sides of substrate absorbance peak, were used to perform on-line a linear correction of the signal drift. Fed-batch experiments at constant methanol (substrate) concentration ranging from 0.8 to 15 g l−1 were carried out. Off-line HPLC control analysis showed a good agreement with on-line FTIR data, with standard error of prediction values

  • Monitoring and control of Gluconacetobacter xylinus fed-batch cultures using in situ Mid-IR Spectroscopy.
    Journal of biotechnology, 2004
    Co-Authors: Henri Kornmann, Sergio Valentinotti, Philippe Duboc, Ian Marison, Urs Von Stockar
    Abstract:

    A partial least-squares calibration model, relating mid-infrared spectral features with fructose, ethanol, acetate, gluconacetan, phosphate and ammonium concentrations has been designed to monitor and control cultivations of Gluconacetobacter xylinus and production of gluconacetan, a food grade exopolysaccharide (EPS). Only synthetic solutions containing a mixture of the major components of culture media have been used to calibrate the spectrometer. A factorial design has been applied to determine the composition and concentration in the calibration matrix. This approach guarantees a complete and intelligent scan of the calibration space using only 55 standards. This calibration model allowed standard errors of validation (SEV) for fructose, ethanol, acetate, gluconacetan, ammonium and phosphate concentrations of 1.16 g/l, 0.36 g/l, 0.22 g/l, 1.54 g/l, 0.24 g/l and 0.18 g/l, respectively. With G. xylinus, ethanol is directly oxidized to acetate, which is subsequently metabolized to form biomass. However, residual ethanol in the culture medium prevents bacterial growth. On-line spectroscopic data were implemented in a closed-loop control strategy for fed-batch fermentation. Acetate concentration was controlled at a constant value by feeding ethanol into the bioreactor. The designed fed-batch process allowed biomass production on ethanol. This was not possible in a batch process due to ethanol inhibition of bacterial growth. In this way, the productivity of gluconacetan was increased from 1.8 x 10(-3) [C-mol/C-mol substrate/h] in the batch process to 2.9 x 10(-3) [C-mol/C-mol substrate/h] in the fed-batch process described in this study.

  • Monitoring and control of Gluconacetobacter xylinus fed-batch cultures using in situ Mid-IR Spectroscopy
    Journal of Biotechnology, 2004
    Co-Authors: Henri Kornmann, Sergio Valentinotti, Philippe Duboc, Ian Marison, Urs Von Stockar
    Abstract:

    A partial least-squares calibration model, relating Mid-IR spectral features with fructose, ethanol, acetate, gluconacetan, phosphate and ammonium concns. has been designed to monitor and control cultivations of Gluconacetobacter xylinus and prodn. of gluconacetan, a food grade exopolysaccharide (EPS). Only synthetic solns. contg. a mixt. of the major components of culture media have been used to calibrate the spectrometer. A factorial design has been applied to det. the compn. and concn. in the calibration matrix. This approach guarantees a complete and intelligent scan of the calibration space using only 55 stds. This calibration model allowed std. errors of validation (SEV) for fructose, ethanol, acetate, gluconacetan, ammonium and phosphate concns. of 1.16 g/l, 0.36 g/l, 0.22 g/l, 1.54 g/l, 0.24 g/l and 0.18 g/l, resp. With G. xylinus, ethanol is directly oxidized to acetate, which is subsequently metabolized to form biomass. However, residual ethanol in the culture medium prevents bacterial growth. Online spectroscopic data were implemented in a closed-loop control strategy for fed-batch fermn. Acetate concn. was controlled at a const. value by feeding ethanol into the bioreactor. The designed fed-batch process allowed biomass prodn. on ethanol. This was not possible in a batch process due to ethanol inhibition of bacterial growth. In this way, the productivity of gluconacetan was increased from 1.8 * 10-3 [C-mol/C-mol substrate/h] in the batch process to 2.9 * 10-3 [C-mol/C-mol substrate/h] in the fed-batch process described in this study. [on SciFinder (R)]

  • Adaptive control of a G. xylinus fed-batch fermentation using in situ Mid-IR Spectroscopy
    2003
    Co-Authors: Henri Kornmann, Sergio Valentinotti, Martin Rhiel, Urs Von Stockar
    Abstract:

    Bacterial exopolysaccharides (EPS) have unique rheol. properties due to their high purity and regular structure. Thus, the food industry frequently uses EPS as thickening, gelling or stabilizing agents. The strain Gluconacetobacter xylinus I 2281 is capable of producing with a very high yield a new sol. EPS named gluconacetan, which is composed of rhamnose, glucose, mannose and glucuronic acid. Growth of these bacteria presents many features that represent a real challenge for both monitoring and control. High EPS concns. in the culture broth cannot be filtered and thus, classical online monitoring tools, such as qFlow Injection Anal.q or chromatog. methods, are no longer suitable to follow the fermn. Another problem is related to the ethanol concn. in the reactor. This compd. is the main substrate for biomass prodn. Cells convert it to acetate and metabolize this last to form biomass. When ethanol concn. is above a certain threshold, the enzymic system that digests acetate is inhibited. As a result, biomass growth is stopped and acetate accumulates in the reactor. It is thus necessary to maintain the ethanol concn. in the reactor at a very low concn. In this work fed-batch fermn. of G. xylinus was performed. A concd. ethanol soln. was used as the feed soln. A very simple and novel adaptive control strategy was used to maintain the acetate concn. in the reactor const. Consequently ethanol concn. was forced to remain very low. In situ MIR Spectroscopy, a non-invasive optical sensor system that is insensitive to the viscosity changes in the broth was used to monitor simultaneously ethanol, acetate, ammonium, phosphates and fructose concns. Both the control strategy and the exptl. results will be presented. [on SciFinder (R)]

E. A. Romanova - One of the best experts on this subject based on the ideXlab platform.

  • Chalcogenide fiber loop probe for the Mid-IR Spectroscopy of oil products.
    Optics Express, 2020
    Co-Authors: E. A. Romanova, S. V. Korsakova, Andrey G. Rozhnev, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    A theoretical approach based on the electromagnetic theory of optical fibers has been applied in the analysis of the evanescent modes of a chalcogenide fiber bend used as a probe in a fiber-based spectroscopic sensor, by the example of the detection of small amounts of an antigel additive in a diesel fuel. The absorbance of the loop probe calculated for each mode was compared with the results of spectrometer-based measurements. The role of the higher-order evanescent modes of a fiber bend has been revealed. The efficiency of using a loop probe has been shown to depend on conditions of light launching into the probe.

  • Using Higher-Order Modes of Chalcogenide Optical Fibers for the Optimization of Evanescent Wave Mid-IR Spectroscopy
    Technical Physics Letters, 2019
    Co-Authors: S. V. Korsakova, E. A. Vinogradova, E. A. Romanova, V. S. Shiryaev
    Abstract:

    On the basis of a new theoretical approach that is proposed for solving tasks of the evanescent wave Mid-IR Spectroscopy, it is shown that the dispersion properties of higher-order modes of a multimode chalcogenide optical fiber partly immersed into an absorbing medium can be used for the creation of fiber-optic devices combining the functions of a supercontinuum generator and a sensing element for Mid-IR spectroscopic sensors. The propagation of radiation in higher-order modes makes it possible to control the position of zero dispersion of group velocity and to generate supercontinuum with near-IR pumping. Using higher-order evanescent modes in a sensing element, it will be possible to increase its sensitivity and expand the dynamic range.

  • Analysis of Characteristics of the Sensing Elements for the Fiber-Based Evanescent Wave Spectroscopy in the Mid-IR
    Optics and Spectroscopy, 2018
    Co-Authors: S. V. Korsakova, E. A. Romanova, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    Characteristics of the sensing element of a fiber sensor for evanescent wave Mid-IR Spectroscopy have been studied within the electromagnetic theory of fiber waveguides by using the problem of determining the concentration of aqueous acetone solutions as an example. A multimode chalcogenide fiber was used as a sensing element. It has been shown that the selective excitation of the fiber modes may provide the possibility to increase the sensitivity of the fiber sensing element, decrease the minimum detectable concentration of a substance in a solution, and enhance the range of measured solution concentrations.

  • Novel Approach for Design of Fiber-Based Evanescent Wave Sensors for the Mid-Infrared Spectroscopy
    2018 20th International Conference on Transparent Optical Networks (ICTON), 2018
    Co-Authors: E. A. Romanova, S. V. Korsakova, A.p. Velmuzhov, Andrei Rozhnev, Vladimir Shiryaev
    Abstract:

    In this paper, a theoretical approach based on electromagnetic theory of optical fibers is used for analysis and optimisation of sensing elements of the fiber-based evanescent wave sensors for the Mid-IR Spectroscopy. We have demonstrated that excitation of the higher-order modes of a single-index fiber, engineering of refractive index profile of a core-clad fiber and a fiber bending are efficient ways for the sensor optimisation.

  • Evanescent wave sensors for Mid-IR Spectroscopy
    Saratov Fall Meeting 2015: Third International Symposium on Optics and Biophotonics and Seventh Finnish-Russian Photonics and Laser Symposium (PALS), 2016
    Co-Authors: S. V. Korsakova, E. A. Romanova
    Abstract:

    An important problem of investigation of the air and water contamination by the Mid-IR Spectroscopy is discussed. A model of evanescent wave sensor made of a multimode waveguide transparent in the Mid-IR spectral range is developed. Transmittance and sensitivity of a sensing element consisting of an input chalcogenide waveguide and a sensing waveguide depend on distribution of the guided modes amplitudes in the sensing waveguide. We have demonstrated that excitation of higher-order modes is important for optimal performance of such a sensor.

Vladimir Shiryaev - One of the best experts on this subject based on the ideXlab platform.

  • Chalcogenide fiber loop probe for the Mid-IR Spectroscopy of oil products.
    Optics Express, 2020
    Co-Authors: E. A. Romanova, S. V. Korsakova, Andrey G. Rozhnev, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    A theoretical approach based on the electromagnetic theory of optical fibers has been applied in the analysis of the evanescent modes of a chalcogenide fiber bend used as a probe in a fiber-based spectroscopic sensor, by the example of the detection of small amounts of an antigel additive in a diesel fuel. The absorbance of the loop probe calculated for each mode was compared with the results of spectrometer-based measurements. The role of the higher-order evanescent modes of a fiber bend has been revealed. The efficiency of using a loop probe has been shown to depend on conditions of light launching into the probe.

  • Analysis of Characteristics of the Sensing Elements for the Fiber-Based Evanescent Wave Spectroscopy in the Mid-IR
    Optics and Spectroscopy, 2018
    Co-Authors: S. V. Korsakova, E. A. Romanova, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    Characteristics of the sensing element of a fiber sensor for evanescent wave Mid-IR Spectroscopy have been studied within the electromagnetic theory of fiber waveguides by using the problem of determining the concentration of aqueous acetone solutions as an example. A multimode chalcogenide fiber was used as a sensing element. It has been shown that the selective excitation of the fiber modes may provide the possibility to increase the sensitivity of the fiber sensing element, decrease the minimum detectable concentration of a substance in a solution, and enhance the range of measured solution concentrations.

  • Novel Approach for Design of Fiber-Based Evanescent Wave Sensors for the Mid-Infrared Spectroscopy
    2018 20th International Conference on Transparent Optical Networks (ICTON), 2018
    Co-Authors: E. A. Romanova, S. V. Korsakova, A.p. Velmuzhov, Andrei Rozhnev, Vladimir Shiryaev
    Abstract:

    In this paper, a theoretical approach based on electromagnetic theory of optical fibers is used for analysis and optimisation of sensing elements of the fiber-based evanescent wave sensors for the Mid-IR Spectroscopy. We have demonstrated that excitation of the higher-order modes of a single-index fiber, engineering of refractive index profile of a core-clad fiber and a fiber bending are efficient ways for the sensor optimisation.

S. V. Korsakova - One of the best experts on this subject based on the ideXlab platform.

  • Chalcogenide fiber loop probe for the Mid-IR Spectroscopy of oil products.
    Optics Express, 2020
    Co-Authors: E. A. Romanova, S. V. Korsakova, Andrey G. Rozhnev, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    A theoretical approach based on the electromagnetic theory of optical fibers has been applied in the analysis of the evanescent modes of a chalcogenide fiber bend used as a probe in a fiber-based spectroscopic sensor, by the example of the detection of small amounts of an antigel additive in a diesel fuel. The absorbance of the loop probe calculated for each mode was compared with the results of spectrometer-based measurements. The role of the higher-order evanescent modes of a fiber bend has been revealed. The efficiency of using a loop probe has been shown to depend on conditions of light launching into the probe.

  • Using Higher-Order Modes of Chalcogenide Optical Fibers for the Optimization of Evanescent Wave Mid-IR Spectroscopy
    Technical Physics Letters, 2019
    Co-Authors: S. V. Korsakova, E. A. Vinogradova, E. A. Romanova, V. S. Shiryaev
    Abstract:

    On the basis of a new theoretical approach that is proposed for solving tasks of the evanescent wave Mid-IR Spectroscopy, it is shown that the dispersion properties of higher-order modes of a multimode chalcogenide optical fiber partly immersed into an absorbing medium can be used for the creation of fiber-optic devices combining the functions of a supercontinuum generator and a sensing element for Mid-IR spectroscopic sensors. The propagation of radiation in higher-order modes makes it possible to control the position of zero dispersion of group velocity and to generate supercontinuum with near-IR pumping. Using higher-order evanescent modes in a sensing element, it will be possible to increase its sensitivity and expand the dynamic range.

  • Analysis of Characteristics of the Sensing Elements for the Fiber-Based Evanescent Wave Spectroscopy in the Mid-IR
    Optics and Spectroscopy, 2018
    Co-Authors: S. V. Korsakova, E. A. Romanova, A.p. Velmuzhov, T.v. Kotereva, M.v. Sukhanov, Vladimir Shiryaev
    Abstract:

    Characteristics of the sensing element of a fiber sensor for evanescent wave Mid-IR Spectroscopy have been studied within the electromagnetic theory of fiber waveguides by using the problem of determining the concentration of aqueous acetone solutions as an example. A multimode chalcogenide fiber was used as a sensing element. It has been shown that the selective excitation of the fiber modes may provide the possibility to increase the sensitivity of the fiber sensing element, decrease the minimum detectable concentration of a substance in a solution, and enhance the range of measured solution concentrations.

  • Novel Approach for Design of Fiber-Based Evanescent Wave Sensors for the Mid-Infrared Spectroscopy
    2018 20th International Conference on Transparent Optical Networks (ICTON), 2018
    Co-Authors: E. A. Romanova, S. V. Korsakova, A.p. Velmuzhov, Andrei Rozhnev, Vladimir Shiryaev
    Abstract:

    In this paper, a theoretical approach based on electromagnetic theory of optical fibers is used for analysis and optimisation of sensing elements of the fiber-based evanescent wave sensors for the Mid-IR Spectroscopy. We have demonstrated that excitation of the higher-order modes of a single-index fiber, engineering of refractive index profile of a core-clad fiber and a fiber bending are efficient ways for the sensor optimisation.

  • Evanescent wave sensors for Mid-IR Spectroscopy
    Saratov Fall Meeting 2015: Third International Symposium on Optics and Biophotonics and Seventh Finnish-Russian Photonics and Laser Symposium (PALS), 2016
    Co-Authors: S. V. Korsakova, E. A. Romanova
    Abstract:

    An important problem of investigation of the air and water contamination by the Mid-IR Spectroscopy is discussed. A model of evanescent wave sensor made of a multimode waveguide transparent in the Mid-IR spectral range is developed. Transmittance and sensitivity of a sensing element consisting of an input chalcogenide waveguide and a sensing waveguide depend on distribution of the guided modes amplitudes in the sensing waveguide. We have demonstrated that excitation of higher-order modes is important for optimal performance of such a sensor.