@article{ZakrevskyyCywinskiCywinskaetal.2014,
  author    = {Zakrevskyy, Yuriy and Cywinski, Piotr and Cywinska, Magdalena and Paasche, Jens and Lomadze, Nino and Reich, Oliver and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Santer, Svetlana},
  title     = {Interaction of photosensitive surfactant with DNA and poly acrylic acid},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4862679},
  pages     = {8},
  year      = {2014},
  language  = {en}
}
@article{SchlappaBresselReichetal.2023,
  author    = {Schlappa, Stephanie and Bressel, Lena and Reich, Oliver and M{\"u}nzberg, Marvin},
  title     = {Advanced particle size analysis in high-solid-content polymer dispersions using photon density wave spectroscopy},
  series = {Polymers},
  volume    = {15},
  journal   = {Polymers},
  number    = {15},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2073-4360},
  doi       = {10.3390/polym15153181},
  pages     = {17},
  year      = {2023},
  abstract  = {High-solid-content polystyrene and polyvinyl acetate dispersions of polymer particles with a 50 nm to 500 nm mean particle diameter and 12-55\% (w/w) solid content have been produced via emulsion polymerization and characterized regarding their optical and physical properties. Both systems have been analyzed with common particle-size-measuring techniques like dynamic light scattering (DLS) and static light scattering (SLS) and compared to inline particle size distribution (PSD) measurements via photon density wave (PDW) spectroscopy in undiluted samples. It is shown that particle size measurements of undiluted polystyrene dispersions are in good agreement between analysis methods. However, for polyvinyl acetate particles, size determination is challenging due to bound water in the produced polymer. For the first time, water-swelling factors were determined via an iterative approach of PDW spectroscopy error (X-2) minimization. It is shown that water-swollen particles can be analyzed in high-solid-content solutions and their physical properties can be assumed to determine the refractive index, density, and volume fraction in dispersion. It was found that assumed water swelling improved the reduced scattering coefficient fit by PDW spectroscopy by up to ten times and particle size determination was refined and enabled. Particle size analysis of the water-swollen particles agreed well with offline-based state-of-the-art techniques.},
  language  = {en}
}
@article{SchaelReichLoehmannsroeben2000,
  author    = {Schael, Frank and Reich, Oliver and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {Near infrared diode laser spectroscopy of organic compounds in turbid aqueous solutions},
  isbn      = {0-9528666-1-7},
  year      = {2000},
  abstract  = {Diffuse reflectance measurements and photon migration studies with near infrared (NIR) diode lasers were employed to elucidate experimental methods for determining absorption and scattering coefficients and species concentrations in highly scattering solutions. Applicability of theoretical approaches were established by investigating model systems with absorbing (e.g. ink, malachite green) and scattering (e.g. milk powder, caolinit) species in aqueous solution. While diffuse reflectance measurements practically requires calibration procedures, photon migration studies allow quantitative determination of absorption and scattering coefficients of turbid solutions consistent with absorptions coefficients obtained from Lambert-Beer's law. Furthermore, NIR absorption spectra of water, chlorinated hydrocarbons (chloroform, 1,2-dichloroethane, trichloroethene) and of various sugars (\$alpha\$-D-glucose, sucrose, maltose) are discussed. Spectral variations of NIR water absorption with temperature and solvents are exammined. Exemplary, NIR diode laser detection of water in acetone/water mixtures is performed.},
  language  = {en}
}
@article{SchaelReich2001,
  author    = {Schael, Frank and Reich, Oliver},
  title     = {In-situ-Analytik heterogener Medien mit frequenz- und leistungsmodulierten Diodenlasern},
  year      = {2001},
  abstract  = {Electronic intensity and frequency modulation of diode lasers enables new perspectives for highly sensitive analytical in-situ techniques. For analyis of "heterogeneous" media, which may consist of coexisting gaseous, liquid, and solid phases and often show multiple light scattering, non-invasive techniques with outstanding performance characteristics can be developed. Analysis of photon density waves launched by intensity-modulated lasers provide an elegant way for the determination of absorption and scattering coefficients of multiple scattering media. The absorption coefficient can be used for qualitative and quantitative analysis of chemical constituents (which absorb in the range of the laser wavelengths). The scattering coefficient allows characterization of physical and morphological properties of the sample. In the current work, applicability of appropriate radiation transport models was investigated with simple light scattering solutions and compared with results obtained from the treatment according to the theory of Kubelka and Munk. Measurements of human blood samples are discussed. A new method for determination of water vapor partial pressure in a polyurethane foam with a frequency-modulated external cavity diode laser is discussed.},
  language  = {de}
}
@article{SchaelEngelhardReich2001,
  author    = {Schael, Frank and Engelhard, Sonja and Reich, Oliver},
  title     = {Optische Sensorik f{\"u}r die in-situ-Analytik von Brauprozessen},
  year      = {2001},
  language  = {de}
}
@article{SandmannMuenzbergBresseletal.2022,
  author    = {Sandmann, Michael and M{\"u}nzberg, Marvin and Bressel, Lena and Reich, Oliver and Hass, Roland},
  title     = {Inline monitoring of high cell density cultivation of Scenedesmus rubescens in a mesh ultra-thin layer photobioreactor by photon density wave spectroscopy},
  series = {BMC Research Notes / Biomed Central},
  volume    = {15},
  journal   = {BMC Research Notes / Biomed Central},
  number    = {1},
  publisher = {Biomed Central (London)},
  address   = {London},
  issn      = {1756-0500},
  doi       = {10.1186/s13104-022-05943-2},
  pages     = {7},
  year      = {2022},
  abstract  = {Objective Due to multiple light scattering that occurs inside and between cells, quantitative optical spectroscopy in turbid biological suspensions is still a major challenge. This includes also optical inline determination of biomass in bioprocessing. Photon Density Wave (PDW) spectroscopy, a technique based on multiple light scattering, enables the independent and absolute determination of optical key parameters of concentrated cell suspensions, which allow to determine biomass during cultivation. Results A unique reactor type, called "mesh ultra-thin layer photobioreactor" was used to create a highly concentrated algal suspension. PDW spectroscopy measurements were carried out continuously in the reactor without any need of sampling or sample preparation, over 3 weeks, and with 10-min time resolution. Conventional dry matter content and coulter counter measurements have been employed as established offline reference analysis. The PBR allowed peak cell dry weight (CDW) of 33.4 g L-1. It is shown that the reduced scattering coefficient determined by PDW spectroscopy is strongly correlated with the biomass concentration in suspension and is thus suitable for process understanding. The reactor in combination with the fiber-optical measurement approach will lead to a better process management.},
  language  = {en}
}
@article{SalffnerBoehmReichetal.2014,
  author    = {Salffner, Katharina and Boehm, Michael and Reich, Oliver and L{\"o}hmannsr{\"o}ben, Hans-Gerd},
  title     = {A broadband cavity ring-down spectrometer based on an incoherent near infrared light source},
  series = {Applied physics : B, Lasers and optics},
  volume    = {116},
  journal   = {Applied physics : B, Lasers and optics},
  number    = {4},
  publisher = {Springer},
  address   = {New York},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-014-5762-9},
  pages     = {785 -- 792},
  year      = {2014},
  language  = {en}
}
@article{RuizHassReich2012,
  author    = {Ruiz, Salome Vargas and Hass, Roland and Reich, Oliver},
  title     = {Optical monitoring of milk fat phase transition within homogenized fresh milk by Photon Density Wave spectroscopy},
  series = {International dairy journal},
  volume    = {26},
  journal   = {International dairy journal},
  number    = {2},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0958-6946},
  doi       = {10.1016/j.idairyj.2012.03.012},
  pages     = {120 -- 126},
  year      = {2012},
  abstract  = {Photon Density Wave (PDW) spectroscopy was applied for temperature dependent monitoring of melting and crystallization of milk fat within homogenized fresh milk. As an in-line process analytical technique, PDW spectroscopy quantifies continuously the optical properties of turbid material, providing an insight into its structural processes. Here, the measured absorption coefficients reflect temperature as well as fat content of milk and the reduced scattering coefficients probe physical changes of the light scattering fat droplets and casein micelles. Thermal processing reveals breakpoints within the temperature trend of the reduced scattering coefficient of fat containing milk. Found at 16 degrees C and 24 degrees C while cooling and heating, respectively, they are associated to the phase transitions of milk fat. Continuous isothermal measurement of the optical coefficients showed that the crystallization process requires several hours. The strongly changing reduced scattering coefficient implies that the thermal history of milk will have a major impact on any method based on light scattering as quantitative analytical technique.},
  language  = {en}
}
@article{MunzkeSaundersOmranietal.2012,
  author    = {Munzke, Dorit and Saunders, John and Omrani, Hengameh and Reich, Oliver and Loock, Hans-Peter},
  title     = {Modeling of fiber-optic fluorescence probes for strongly absorbing samples},
  series = {Applied optics},
  volume    = {51},
  journal   = {Applied optics},
  number    = {26},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1559-128X},
  doi       = {10.1364/AO.51.006343},
  pages     = {6343 -- 6351},
  year      = {2012},
  abstract  = {The dynamic range of fiber-optic fluorescent probes such as single fibers and fiber bundles is calculated for strongly absorbing samples, such as process liquids, foodstuffs, and lubricants. The model assumes an excitation beam profile based on a Lambertian light source and uses analytical forms of the collection efficiency, followed by an Abel transformation and numerical integration. It is found that the effect of primary absorption of the excitation light and secondary absorption of the fluorescence is profound. For fiber bundles and bifurcated fiber probes, the upper accessible concentration limit is roughly given by the absorption length of the primary and secondary absorption. Fluorescence detectors that are placed at right angles to the excitation beam axis or collinear to the beam axis are equally strongly affected by secondary absorption. A probe in which the same fiber is used for excitation and for collection of the fluorescence emerges as the fiber probe with the largest accessible concentration range.},
  language  = {en}
}
@article{MunzkeBoehmReich2015,
  author    = {Munzke, Dorit and B{\"o}hm, Michael and Reich, Oliver},
  title     = {Gaseous Oxygen Detection Using Hollow-Core Fiber-Based Linear Cavity Ring-Down Spectroscopy},
  series = {Journal of lightwave technology},
  volume    = {33},
  journal   = {Journal of lightwave technology},
  number    = {12},
  publisher = {Inst. of Electr. and Electronics Engineers},
  address   = {Piscataway},
  issn      = {0733-8724},
  doi       = {10.1109/JLT.2015.2397177},
  pages     = {2524 -- 2529},
  year      = {2015},
  abstract  = {We demonstrate a method for the calibration-free and quantitative analysis of small volumes of gaseous samples. A 10 m hollow-core photonic bandgap fiber is used as the sample cell (volume = 0.44 mu L) and is placed inside a linear resonator setup. The application of cavity ring-down spectroscopy and in consideration of rather small coupling losses, this leads to an increased effective optical path length of up to 70 m. This implies a volume per optical interaction path length of 6.3 nL.m(-1). We used tunable diode laser spectroscopy at 760 nm and scanned the absorption for oxygen sensing. The optical loss due to sample absorption is obtained by measuring the ring-down time of light propagating inside the cavity. The resultant absorption coefficient shows a discrepancy of only 5.1\% comparing to the HITRAN database. This approach is applicable for sensitive measurements if only submicroliter sample volumes are available.},
  language  = {en}
}