@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{SchlappaBrenkerBresseletal.2021,
  author    = {Schlappa, Stephanie and Brenker, Lee Josephine and Bressel, Lena and Hass, Roland and M{\"u}nzberg, Marvin},
  title     = {Process characterization of polyvinyl acetate emulsions applying inline photon density wave spectroscopy at high solid contents},
  series = {Polymers / Molecular Diversity Preservation International},
  volume    = {13},
  journal   = {Polymers / Molecular Diversity Preservation International},
  number    = {4},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2073-4360},
  doi       = {10.3390/polym13040669},
  pages     = {15},
  year      = {2021},
  abstract  = {The high solids semicontinuous emulsion polymerization of polyvinyl acetate using poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated by optical spectroscopy. The suitability of Photon Density Wave (PDW) spectroscopy as inline Process Analytical Technology (PAT) for emulsion polymerization processes at high solid contents (>40\% (w/w)) is studied and evaluated. Inline data on absorption and scattering in the dispersion is obtained in real-time. The radical polymerization of vinyl acetate to polyvinyl acetate using ascorbic acid and sodium persulfate as redox initiator system and poly (vinyl alcohol-co-vinyl acetate) as protective colloid is investigated. Starved-feed radical emulsion polymerization yielded particle sizes in the nanometer size regime. PDW spectroscopy is used to monitor the progress of polymerization by studying the absorption and scattering properties during the synthesis of dispersions with increasing monomer amount and correspondingly decreasing feed rate of protective colloid. Results are compared to particle sizes determined with offline dynamic light scattering (DLS) and static light scattering (SLS) during the synthesis.},
  language  = {en}
}
@misc{BresselHerzogReich2019,
  author    = {Bressel, Lena and Herzog, Bernd and Reich, Oliver},
  title     = {Monte-Carlo simulations of light transport in dense materials},
  series = {Diffuse Optical Spectroscopy and Imaging},
  volume    = {11074},
  journal   = {Diffuse Optical Spectroscopy and Imaging},
  publisher = {SPIE},
  address   = {Bellingham},
  isbn      = {978-1-5106-2841-0},
  issn      = {0277-786X},
  doi       = {10.1117/12.2527076},
  pages     = {3},
  year      = {2019},
  abstract  = {Monte-Carlo calculations are carried out to simulate the light transport in dense materials. Focus lies on the calculation of diffuse light transmission through films of scattering and absorbing media considering additionally the effect of dependent scattering. Different influences like interaction type between particles, particle size, composition etc. can be studied by this program. Simulations in this study show major influences on the diffuse transmission. Further simulations are carried out to model a sunscreen film and study best compositions of this film and will be presented.},
  language  = {en}
}
@article{MinkMcHardyBresseletal.2019,
  author    = {Mink, Albert and McHardy, Christopher and Bressel, Lena and Rauh, Cornelia and Krause, Mathias J.},
  title     = {Radiative transfer lattice Boltzmann methods},
  series = {Journal of quantitative spectroscopy \& radiative transfer},
  volume    = {243},
  journal   = {Journal of quantitative spectroscopy \& radiative transfer},
  publisher = {Pergamon Press},
  address   = {Oxford},
  issn      = {0022-4073},
  doi       = {10.1016/j.jqsrt.2019.106810},
  year      = {2019},
  abstract  = {The numerical prediction of radiative transport is a challenging task due to the complexity of the radiative transport equation. We apply the lattice Boltzmann method (LBM), originally developed for fluid flow problems, to solve the radiative transport in volume. One model (meso RTLBM) is derived directly from a discretization of the radiative transport equation, yielding in a precise but numerical costly scheme. The second model (macro RTLBM) solves the Helmholtz equation, which is a proper approximation for highly scattering volumes. Both numerical algorithms are validated against Monte-Carlo data for a set of 35 optical parameters, which correspond to radiative transport ranging from ballistic to diffuse regimes. Together with a set of four benchmark simulations, the comprehensive validation concludes the overall quality and detects asymptotic trends for radiative transport LBM. Furthermore, an accuracy map is presented, which summarizes the error for all parameters. This graph allows to determine the validity range for both radiative transport LBM at a glance. Finally, comprehensive guidelines are formulated to facilitate the choice of the radiative transport LBM model.},
  language  = {en}
}
@phdthesis{Bressel2016,
  author    = {Bressel, Lena},
  title     = {Bedeutung der abh{\"a}ngigen Streuung f{\"u}r die optischen Eigenschaften hochkonzentrierter Dispersionen},
  school      = {Universit{\"a}t Potsdam},
  pages     = {154, XL},
  year      = {2016},
  language  = {de}
}
@article{BresselReich2014,
  author    = {Bressel, Lena and Reich, Oliver},
  title     = {Theoretical and experimental study of the diffuse transmission of light through highly concentrated absorbing and scattering materials Part I: Monte-Carlo simulations},
  series = {Journal of quantitative spectroscopy \& radiative transfer},
  volume    = {146},
  journal   = {Journal of quantitative spectroscopy \& radiative transfer},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0022-4073},
  doi       = {10.1016/j.jqsrt.2014.01.007},
  pages     = {190 -- 198},
  year      = {2014},
  abstract  = {In many technical materials and commercial products like sunscreen or paint high particle and absorber concentrations are present. An important parameter for slabs of these materials is the diffuse transmission of light, which quantifies the total amount of directly and diffusely transmitted light. Due to the high content of scattering particles not only multiple scattering but also additional dependent scattering occurs. Hence, simple analytical models cannot be applied to calculate the diffuse transmission. In this work a Monte-Carlo program for the calculation of the diffuse transmission of light through dispersions in slab-like geometry containing high concentrations of scattering particles and absorbers is presented and discussed in detail. Mie theory is applied for the calculation of the scattering properties of the samples. Additionally, dependent scattering is considered in two different models, the well-known hard sphere model in the Percus-Yevick approximation (HSPYA) and the Yukawa model in the Mean Spherical Approximation (YMSA). Comparative experiments will show the accurateness of the program as well as its applicability to real samples [1]. (C) 2014 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{BresselHassReich2013,
  author    = {Bressel, Lena and Hass, Roland and Reich, O.},
  title     = {Particle sizing in highly turbid dispersions by Photon Density Wave spectroscopy},
  series = {JOURNAL OF QUANTITATIVE SPECTROSCOPY \& RADIATIVE TRANSFER},
  volume    = {126},
  journal   = {JOURNAL OF QUANTITATIVE SPECTROSCOPY \& RADIATIVE TRANSFER},
  number    = {1},
  publisher = {PERGAMON-ELSEVIER SCIENCE LTD},
  address   = {OXFORD},
  issn      = {0022-4073},
  doi       = {10.1016/j.jqsrt.2012.11.031},
  pages     = {122 -- 129},
  year      = {2013},
  abstract  = {Photon Density Wave (PDW) spectroscopy is presented as a fascinating technology for the independent determination of scattering (mu(s)\’ and absorption (ita) properties of highly turbid liquid dispersions. The theory is reviewed introducing new expressions for the PDW coefficients k(I) and k(Phi). Furthermore, two models for dependent scattering, namely the hard sphere model in the Percus-Yevick Approximation (HSPYA) and the Yukawa model in the Mean Spherical Approximation (YMSA), are experimentally examined. On the basis of the HSPYA particle sizing is feasible in dispersions of high ionic strength. It is furthermore shown that in dialyzed dispersions or in technical copolymers with high particle charge only the YMSA allows for correct dilution-free particle sizing. (C) 2013 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{HassMuenzbergBresseletal.2013,
  author    = {Hass, Roland and M{\"u}nzberg, Marvin and Bressel, Lena and Reich, Oliver},
  title     = {Industrial applications of photon density wave spectroscopy for in-line particle sizing [Invited]},
  series = {Applied optics},
  volume    = {52},
  journal   = {Applied optics},
  number    = {7},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1559-128X},
  doi       = {10.1364/AO.52.001423},
  pages     = {1423 -- 1431},
  year      = {2013},
  abstract  = {Optical spectroscopy in highly turbid liquid material is often restricted by simultaneous occurrence of absorption and scattering of light. Photon Density Wave (PDW) spectroscopy is one of the very few, yet widely unknown, technologies for the independent quantification of these two optical processes. Here, a concise overview about modern PDW spectroscopy is given, including all necessary equations concerning the optical description of the investigated material, dependent light scattering, particle sizing, and PDW spectroscopy itself. Additionally, it is shown how the ambiguity in particle sizing, arising from Mie theory, can be correctly solved. Due to its high temporal resolution, its applicability to highest particle concentrations, and its purely fiber-optical probe, PDW spectroscopy possesses all fundamental characteristics for optical in-line process analysis. Several application examples from the chemical industry are presented. (C) 2013 Optical Society of America},
  language  = {en}
}
@article{HilleBergBresseletal.2008,
  author    = {Hille, Carsten and Berg, Maik and Bressel, Lena and Munzke, Dorit and Primus, Philipp and L{\"o}hmannsr{\"o}ben, Hans-Gerd and Dosche, Carsten},
  title     = {Time-domain fluorescence lifetime imaging for intracellular pH sensing in living tissues},
  doi       = {10.1007/s00216-008-2147-0},
  year      = {2008},
  abstract  = {pH sensing in living cells represents one of the most prominent topics in biochemistry and physiology. In this study we performed one-photon and two-photon time-domain fluorescence lifetime imaging with a laser-scanning microscope using the time-correlated single-photon counting technique for imaging intracellular pH levels. The suitability of different commercial fluorescence dyes for lifetime-based pH sensing is discussed on the basis of in vitro as well of in situ measurements. Although the tested dyes are suitable for intensity-based ratiometric measurements, for lifetime- based techniques in the time-domain so far only BCECF seems to meet the requirements of reliable intracellular pH recordings in living cells.},
  language  = {en}
}