TY - JOUR A1 - Chewle, Surahit A1 - Emmerling, Franziska A1 - Weber, M. T1 - Effect of choice of solvent on crystallization pathway of paracetamol: An experimental and theoretical case study JF - Crystals N2 - The choice of solvents influences crystalline solid formed during the crystallization of active pharmaceutical ingredients (API). The underlying effects are not always well understood because of the complexity of the systems. Theoretical models are often insufficient to describe this phenomenon. In this study, the crystallization behavior of the model drug paracetamol in different solvents was studied based on experimental and molecular dynamics data. The crystallization process was followed in situ using time-resolved Raman spectroscopy. Molecular dynamics with simulated annealing algorithm was used for an atomistic understanding of the underlying processes. The experimental and theoretical data indicate that paracetamol molecules adopt a particular geometry in a given solvent predefining the crystallization of certain polymorphs KW - Crystallization KW - Nucleation KW - Polymorphism KW - Raman spectroscopy KW - Cassical nucleation theory PY - 2021 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-520052 DO - https://doi.org/10.3390/cryst10121107 SN - 2073-4352 VL - 10 IS - 12 SP - 1 EP - 10 PB - MDPI CY - Basel AN - OPUS4-52005 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sechi, R. A1 - Fackeldey, K. A1 - Chewle, Surahit A1 - Weber, M. T1 - SepFree NMF: A toolbox for analyzing the kinetics of sequential spectroscopic data JF - Algorithms N2 - This work addresses the problem of determining the number of components from sequential spectroscopic data analyzed by non-negative matrix factorization without separability assumption (SepFree NMF). These data are stored in a matrix M of dimension “measured times” versus “measured wavenumbers” and can be decomposed to obtain the spectral fingerprints of the states and their evolution over time. SepFree NMF assumes a memoryless (Markovian) process to underline the dynamics and decomposes M so that M = WH, with W representing the components’ fingerprints and H their kinetics. However, the rank of this decomposition (i.e., the number of physical states in the process) has to be guessed from pre-existing knowledge on the observed process. We propose a measure for determining the number of components with the computation of the minimal memory effect resulting from the decomposition; by quantifying how much the obtained factorization is deviating from the Markovian property, we are able to score factorizations of a different number of components. In this way, we estimate the number of different entities which contribute to the observed system, and we can extract kinetic information without knowing the characteristic spectra of the single components. This manuscript provides the mathematical background as well as an analysis of computer generated and experimental sequentially measured Raman spectra. KW - Kinetics from experiments KW - Separability assumption KW - Sequential spectroscopic data PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-559046 DO - https://doi.org/10.3390/a15090297 SN - 1999-4893 VL - 15 IS - 9 SP - 1 EP - 16 PB - MDPI CY - Basel AN - OPUS4-55904 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -