TY - JOUR A1 - Hass, Roland A1 - Reich, Oliver T1 - Photon density wave spectroscopy for dilution-free sizing of highly concentrated nanoparticles during starved-feed polymerization JF - ChemPhysChem : a European journal of chemical physics and physical chemistry KW - analytical methods KW - fiber-optical spectroscopy KW - nanoparticles KW - photon density wave spectroscopy KW - polymerization Y1 - 2011 U6 - https://doi.org/10.1002/cphc.201100323 SN - 1439-4235 VL - 12 IS - 14 SP - 2572 EP - 2575 PB - Wiley-Blackwell CY - Malden ER - TY - GEN A1 - Hass, Roland A1 - Sandmann, Michael A1 - Reich, Oliver T1 - Photonic sensing in highly concentrated biotechnical processes by photon density wave spectroscopy T2 - Proceedings SPIE 10323, 25th International Conference on Optical Fiber Sensors N2 - Photon Density Wave (PDW) spectroscopy is introduced as a new approach for photonic sensing in highly concentrated biotechnical processes. It independently quantifies the absorption and reduced scattering coefficient calibration-free and as a function of time, thus describing the optical properties in the vis/NIR range of the biomaterial during their processing. As examples of industrial relevance, enzymatic milk coagulation, beer mashing, and algae cultivation in photo bioreactors are discussed. KW - Photon Density Wave Spectroscopy KW - multiple light scattering KW - fermentation KW - algae cultivation KW - process analytical technology KW - fiber spectroscopy Y1 - 2017 SN - 978-1-5090-4850-2 U6 - https://doi.org/10.1117/12.2263617 SN - 0277-786X SN - 1996-756X VL - 10323 PB - IEEE CY - New York ER - TY - GEN A1 - Werner, Peter A1 - Münzberg, Marvin A1 - Hass, Roland A1 - Reich, Oliver T1 - Process analytical approaches for the coil-to-globule transition of poly(N-isopropylacrylamide) in a concentrated aqueous suspension T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - The coil-to-globule transition of poly(N-isopropylacrylamide) (PNIPAM) microgel particles suspended in water has been investigated in situ as a function of heating and cooling rate with four optical process analytical technologies (PAT), sensitive to structural changes of the polymer. Photon Density Wave (PDW) spectroscopy, Focused Beam Reflectance Measurements (FBRM), turbidity measurements, and Particle Vision Microscope (PVM) measurements are found to be powerful tools for the monitoring of the temperature-dependent transition of such thermo-responsive polymers. These in-line technologies allow for monitoring of either the reduced scattering coefficient and the absorption coefficient, the chord length distribution, the reflected intensities, or the relative backscatter index via in-process imaging, respectively. Varying heating and cooling rates result in rate-dependent lower critical solution temperatures (LCST), with different impact of cooling and heating. Particularly, the data obtained by PDW spectroscopy can be used to estimate the thermodynamic transition temperature of PNIPAM for infinitesimal heating or cooling rates. In addition, an inverse hysteresis and a reversible building of micrometer-sized agglomerates are observed for the PNIPAM transition process. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 944 KW - poly(N-isopropylacrylamide) KW - Photon Density Wave spectroscopy KW - Focused Beam Reflectance Measurement KW - turbidity measurement KW - Particle Vision Microscope measurement KW - rate-dependent lower critical solution temperature Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-431162 SN - 1866-8372 IS - 944 SP - 807 EP - 819 ER - TY - JOUR A1 - Bressel, Lena A1 - Reich, Oliver T1 - Theoretical and experimental study of the diffuse transmission of light through highly concentrated absorbing and scattering materials Part I: Monte-Carlo simulations JF - Journal of quantitative spectroscopy & radiative transfer N2 - 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. KW - Monte-Carlo simulations KW - Multiple light scattering KW - Dependent light scattering KW - Hard sphere model in the Percus-Yevick Approximation KW - Yukawa model in the Mean Spherical Approximation KW - Polymer dispersions Y1 - 2014 U6 - https://doi.org/10.1016/j.jqsrt.2014.01.007 SN - 0022-4073 SN - 1879-1352 VL - 146 SP - 190 EP - 198 PB - Elsevier CY - Oxford ER - TY - CHAP A1 - Asche, Hartmut A1 - Böckmann, Christine A1 - Laue, Steffen A1 - Löhmannsröben, Hans-Gerd A1 - Lemke, Matthias A1 - Schober, Lars A1 - Reich, Oliver A1 - Lück, Erika A1 - Schütte, Marc A1 - Domsch, Horst A1 - Makower, Alexander A1 - Scheller, Frieder W. A1 - Stöcklein, Wolfgang A1 - Wollenberger, Ursula A1 - Schultze, Rainer A1 - Hengstermann, Theo A1 - Schael, Frank T1 - Umweltforschung für das Land Brandenburg : Projekt Umweltanalytik / Umweltmeßtechnik / Informationssysteme Y1 - 2000 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-3862 SP - 176 EP - 227 ER - TY - JOUR A1 - Löhmannsröben, Hans-Gerd A1 - Schael, Frank A1 - Reich, Oliver A1 - Lemke, Matthias A1 - Schober, Lars T1 - Untersuchung von organischer Bodensubstanz und Bodengasen mit laser-spektroskopischer in-situ Meßtechnik Y1 - 2000 ER - TY - JOUR A1 - Adebayo, Segun Emmanuel A1 - Hashim, Norhashila A1 - Hass, Roland A1 - Reich, Oliver A1 - Regen, Christian A1 - Münzberg, Marvin A1 - Abdan, Khalina A1 - Hanafi, Marsyita A1 - Zude-Sasse, Manuela T1 - Using absorption and reduced scattering coefficients for non-destructive analyses of fruit flesh firmness and soluble solids content in pear JF - Postharvest Biology and Technology N2 - Quality attributes of fruit determine its acceptability by the retailer and consumer. The objective of this work was to investigate the potential of absorption (μa) and reduced scattering (μs’) coefficients of European pear to analyze its fruit flesh firmness and soluble solids content (SSC). The absolute reference values, μa* (cm−1) and μs’* (cm−1), of pear were invasively measured, employing multi-spectral photon density wave (PDW) spectroscopy at preselected wavelengths of 515, 690, and 940 nm considering two batches of unripe and overripe fruit. On eight measuring dates during fruit development, μa and μs’ were analyzed non-destructively by means of laser light backscattering imaging (LLBI) at similar wavelengths of 532, 660, and 830 nm by means of fitting according to Farrell’s diffusion theory, using fix reference values of either μa* or μs’*. Both, the μa* and the μa as well as μs’* and μs’ showed similar trends. Considering the non-destructively measured data during fruit development, μa at 660 nm decreased 91 till 141 days after full bloom (dafb) from 1.49 cm−1 to 0.74 cm−1 due to chlorophyll degradation. At 830 nm, μa only slightly decreased from 0.41 cm−1 to 0.35 cm−1. The μs’ at all wavelengths revealed a decreasing trend as the fruit developed. The difference measured at 532 nm was most pronounced decreasing from 24 cm−1 to 10 cm−1, while at 660 nm and 830 nm values decreased from 15 cm−1 to 13 cm−1 and from 10 cm−1 to 8 cm−1, respectively. When building calibration models with partial least-squares regression analysis on the optical properties for non-destructive analysis of the fruit SSC, μa at 532 nm and 830 nm resulted in a correlation coefficient of R = 0.66, however, showing high measuring uncertainty. The combination of all three wavelengths gave an enhanced, encouraging R = 0.89 for firmness analysis using μs’ in the freshly picked fruit. KW - Absorption KW - Non-destructive KW - Pear KW - Quality KW - Scattering Y1 - 2017 U6 - https://doi.org/10.1016/j.postharvbio.2017.04.004 SN - 0925-5214 SN - 1873-2356 VL - 130 SP - 56 EP - 63 PB - Elsevier CY - Amsterdam ER -