@article{HeuermannEmmrichBongartz2022,
  author    = {Heuermann, Holger and Emmrich, Thomas and Bongartz, Simon},
  title     = {Microwave spark plug to support ignitions with high compression ratios},
  series = {IEEE Transactions on Plasma Science},
  journal   = {IEEE Transactions on Plasma Science},
  number    = {Early Access},
  publisher = {IEEE},
  issn      = {1939-9375},
  doi       = {10.1109/TPS.2022.3183690},
  pages     = {1 -- 6},
  year      = {2022},
  abstract  = {Upcoming gasoline engines should run with a larger number of fuels beginning from petrol over methanol up to gas by a wide range of compression ratios and a homogeneous charge. In this article, the microwave (MW) spark plug, based on a high-speed frequency hopping system, is introduced as a solution, which can support a nitrogen compression ratio up to 1:39 in a chamber and more. First, an overview of the high-speed frequency hopping MW ignition and operation system as well as the large number of applications are presented. Both gives an understanding of this new base technology for MW plasma generation. Focus of the theoretical part is the explanation of the internal construction of the spark plug, on the achievable of the high voltage generation as well as the high efficiency to hold the plasma. In detail, the development process starting with circuit simulations and ending with the numerical multiphysics field simulations is described. The concept is evaluated with a reference prototype covering the frequency range between 2.40 and 2.48 GHz and working over a large power range from 20 to 200 W. A larger number of different measurements starting by vector hot-S11 measurements and ending by combined working scenarios out of hot temperature, high pressure and charge motion are winding up the article. The limits for the successful pressure tests were given by the pressure chamber. Pressures ranged from 1 to 39 bar and charge motion up to 25 m/s as well as temperatures from 30◦ to 125◦.},
  language  = {en}
}
@article{MonakhovaDiehl2022,
  author    = {Monakhova, Yulia and Diehl, Bernd W.K.},
  title     = {Multinuclear NMR screening of pharmaceuticals using standardization by 2H integral of a deuterated solvent},
  series = {Journal of Pharmaceutical and Biomedical Analysis},
  volume    = {209},
  journal   = {Journal of Pharmaceutical and Biomedical Analysis},
  number    = {Article number: 114530},
  publisher = {Elsevier},
  isbn      = {0731-7085},
  doi       = {10.1016/j.jpba.2021.114530},
  year      = {2022},
  abstract  = {NMR standardization approach that uses the 2H integral of deuterated solvent for quantitative multinuclear analysis of pharmaceuticals is described. As a proof of principle, the existing NMR procedure for the analysis of heparin products according to US Pharmacopeia monograph is extended to the determination of Na+ and Cl- content in this matrix. Quantification is performed based on the ratio of a 23Na (35Cl) NMR integral and 2H NMR signal of deuterated solvent, D2O, acquired using the specific spectrometer hardware. As an alternative, the possibility of 133Cs standardization using the addition of Cs2CO3 stock solution is shown. Validation characteristics (linearity, repeatability, sensitivity) are evaluated. A holistic NMR profiling of heparin products can now also be used for the quantitative determination of inorganic compounds in a single analytical run using a single sample. In general, the new standardization methodology provides an appealing alternative for the NMR screening of inorganic and organic components in pharmaceutical products.},
  language  = {en}
}
@article{MolinnusJanusFangetal.2022,
  author    = {Molinnus, Denise and Janus, Kevin Alexander and Fang, Anyelina C. and Drinic, Aleksander and Achtsnicht, Stefan and K{\"o}pf, Marius and Keusgen, Michael and Sch{\"o}ning, Michael Josef},
  title     = {Thick-film carbon electrode deposited onto a biodegradable fibroin substrate for biosensing applications},
  series = {Physica status solidi (a)},
  volume    = {219},
  journal   = {Physica status solidi (a)},
  number    = {23},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1862-6319},
  doi       = {10.1002/pssa.202200100},
  pages     = {1 -- 9},
  year      = {2022},
  abstract  = {This study addresses a proof-of-concept experiment with a biocompatible screen-printed carbon electrode deposited onto a biocompatible and biodegradable substrate, which is made of fibroin, a protein derived from silk of the Bombyx mori silkworm. To demonstrate the sensor performance, the carbon electrode is functionalized as a glucose biosensor with the enzyme glucose oxidase and encapsulated with a silicone rubber to ensure biocompatibility of the contact wires. The carbon electrode is fabricated by means of thick-film technology including a curing step to solidify the carbon paste. The influence of the curing temperature and curing time on the electrode morphology is analyzed via scanning electron microscopy. The electrochemical characterization of the glucose biosensor is performed by amperometric/voltammetric measurements of different glucose concentrations in phosphate buffer. Herein, systematic studies at applied potentials from 500 to 1200 mV to the carbon working electrode (vs the Ag/AgCl reference electrode) allow to determine the optimal working potential. Additionally, the influence of the curing parameters on the glucose sensitivity is examined over a time period of up to 361 days. The sensor shows a negligible cross-sensitivity toward ascorbic acid, noradrenaline, and adrenaline. The developed biocompatible biosensor is highly promising for future in vivo and epidermal applications.},
  language  = {en}
}
@article{EngelmannPourshahidiShalabyetal.2022,
  author    = {Engelmann, Ulrich M. and Pourshahidi, Mohammad Ali and Shalaby, Ahmed and Krause, Hans-Joachim},
  title     = {Probing particle size dependency of frequency mixing magnetic detection with dynamic relaxation simulation},
  series = {Journal of Magnetism and Magnetic Materials},
  volume    = {563},
  journal   = {Journal of Magnetism and Magnetic Materials},
  number    = {In progress, Art. No. 169965},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0304-8853},
  doi       = {10.1016/j.jmmm.2022.169965},
  year      = {2022},
  abstract  = {Biomedical applications of magnetic nanoparticles (MNP) fundamentally rely on the particles' magnetic relaxation as a response to an alternating magnetic field. The magnetic relaxation complexly depends on the interplay of MNP magnetic and physical properties with the applied field parameters. It is commonly accepted that particle core size is a major contributor to signal generation in all the above applications, however, most MNP samples comprise broad distribution spanning nm and more. Therefore, precise knowledge of the exact contribution of individual core sizes to signal generation is desired for optimal MNP design generally for each application. Specifically, we present a magnetic relaxation simulation-driven analysis of experimental frequency mixing magnetic detection (FMMD) for biosensing to quantify the contributions of individual core size fractions towards signal generation. Applying our method to two different experimental MNP systems, we found the most dominant contributions from approx. 20 nm sized particles in the two independent MNP systems. Additional comparison between freely suspended and immobilized MNP also reveals insight in the MNP microstructure, allowing to use FMMD for MNP characterization, as well as to further fine-tune its applicability in biosensing.},
  language  = {en}
}
@article{PourshahidiEngelmannOffenhaeusseretal.2022,
  author    = {Pourshahidi, Ali Mohammad and Engelmann, Ulrich M. and Offenh{\"a}usser, Andreas and Krause, Hans-Joachim},
  title     = {Resolving ambiguities in core size determination of magnetic nanoparticles from magnetic frequency mixing data},
  series = {Journal of Magnetism and Magnetic Materials},
  volume    = {563},
  journal   = {Journal of Magnetism and Magnetic Materials},
  number    = {In progress, Art. No. 169969},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0304-8853},
  doi       = {10.1016/j.jmmm.2022.169969},
  year      = {2022},
  abstract  = {Frequency mixing magnetic detection (FMMD) has been widely utilized as a measurement technique in magnetic immunoassays. It can also be used for the characterization and distinction (also known as "colourization") of different types of magnetic nanoparticles (MNPs) based on their core sizes. In a previous work, it was shown that the large particles contribute most of the FMMD signal. This leads to ambiguities in core size determination from fitting since the contribution of the small-sized particles is almost undetectable among the strong responses from the large ones. In this work, we report on how this ambiguity can be overcome by modelling the signal intensity using the Langevin model in thermodynamic equilibrium including a lognormal core size distribution fL(dc,d0,σ) fitted to experimentally measured FMMD data of immobilized MNPs. For each given median diameter d0, an ambiguous amount of best-fitting pairs of parameters distribution width σ and number of particles Np with R2 > 0.99 are extracted. By determining the samples' total iron mass, mFe, with inductively coupled plasma optical emission spectrometry (ICP-OES), we are then able to identify the one specific best-fitting pair (σ, Np) one uniquely. With this additional externally measured parameter, we resolved the ambiguity in core size distribution and determined the parameters (d0, σ, Np) directly from FMMD measurements, allowing precise MNPs sample characterization.},
  language  = {en}
}
@article{MonakhovaDiehl2022,
  author    = {Monakhova, Yulia and Diehl, Bernd W.K.},
  title     = {Nuclear magnetic resonance spectroscopy as an elegant tool for a complete quality control of crude heparin material},
  series = {Journal of Pharmaceutical and Biomedical Analysis},
  volume    = {219},
  journal   = {Journal of Pharmaceutical and Biomedical Analysis},
  number    = {Article number: 114915},
  publisher = {Elsevier},
  address   = {New York, NY},
  issn      = {0731-7085},
  doi       = {10.1016/j.jpba.2022.114915},
  year      = {2022},
  abstract  = {Nuclear magnetic resonance (NMR) spectrometric methods for the quantitative analysis of pure heparin in crude heparin is proposed. For quantification, a two-step routine was developed using a USP heparin reference sample for calibration and benzoic acid as an internal standard. The method was successfully validated for its accuracy, reproducibility, and precision. The methodology was used to analyze 20 authentic porcine heparinoid samples having heparin content between 4.25 w/w \% and 64.4 w/w \%. The characterization of crude heparin products was further extended to a simultaneous analysis of these common ions: sodium, calcium, acetate and chloride. A significant, linear dependence was found between anticoagulant activity and assayed heparin content for thirteen heparinoids samples, for which reference data were available. A Diffused-ordered NMR experiment (DOSY) can be used for qualitative analysis of specific glycosaminoglycans (GAGs) in heparinoid matrices and, potentially, for quantitative prediction of molecular weight of GAGs. NMR spectrometry therefore represents a unique analytical method suitable for the simultaneous quantitative control of organic and inorganic composition of crude heparin samples (especially heparin content) as well as an estimation of other physical and quality parameters (molecular weight, animal origin and activity).},
  language  = {en}
}
@article{BurgerLindnerRumpfetal.2022,
  author    = {Burger, Ren{\´e} and Lindner, Simon and Rumpf, Jessica and Do, Xuan Tung and Diehl, Bernd W.K. and Rehahn, Matthias and Monakhova, Yulia and Schulze, Margit},
  title     = {Benchtop versus high field NMR: Comparable performance found for the molecular weight determination of lignin},
  series = {Journal of Pharmaceutical and Biomedical Analysis},
  volume    = {212},
  journal   = {Journal of Pharmaceutical and Biomedical Analysis},
  number    = {Article number: 114649},
  publisher = {Elsevier},
  address   = {New York, NY},
  isbn      = {0731-7085},
  doi       = {10.1016/j.jpba.2022.114649},
  year      = {2022},
  abstract  = {Lignin is a promising renewable biopolymer being investigated worldwide as an environmentally benign substitute of fossil-based aromatic compounds, e.g. for the use as an excipient with antioxidant and antimicrobial properties in drug delivery or even as active compound. For its successful implementation into process streams, a quick, easy, and reliable method is needed for its molecular weight determination. Here we present a method using 1H spectra of benchtop as well as conventional NMR systems in combination with multivariate data analysis, to determine lignin's molecular weight (Mw and Mn) and polydispersity index (PDI). A set of 36 organosolv lignin samples (from Miscanthus x giganteus, Paulownia tomentosa and Silphium perfoliatum) was used for the calibration and cross validation, and 17 samples were used as external validation set. Validation errors between 5.6\% and 12.9\% were achieved for all parameters on all NMR devices (43, 60, 500 and 600 MHz). Surprisingly, no significant difference in the performance of the benchtop and high-field devices was found. This facilitates the application of this method for determining lignin's molecular weight in an industrial environment because of the low maintenance expenditure, small footprint, ruggedness, and low cost of permanent magnet benchtop NMR systems.},
  language  = {en}
}
@article{MonakhovaSobolevaFedotovaetal.2022,
  author    = {Monakhova, Yulia and Soboleva, Polina M. and Fedotova, Elena S. and Musina, Kristina T. and Burmistrova, Natalia A.},
  title     = {Quantum chemical calculations of IR spectra of heparin disaccharide subunits},
  series = {Computational and Theoretical Chemistry},
  volume    = {1217},
  journal   = {Computational and Theoretical Chemistry},
  number    = {Article number: 113891},
  publisher = {Elsevier},
  address   = {New York, NY},
  isbn      = {2210-271X},
  doi       = {10.1016/j.comptc.2022.113891},
  year      = {2022},
  abstract  = {Heparin is a natural polysaccharide, which plays essential role in many biological processes. Alterations in building blocks can modify biological roles of commercial heparin products, due to significant changes in the conformation of the polymer chain. The variability structure of heparin leads to difficulty in quality control using different analytical methods, including infrared (IR) spectroscopy. In this paper molecular modelling of heparin disaccharide subunits was performed using quantum chemistry. The structural and spectral parameters of these disaccharides have been calculated using RHF/6-311G. In addition, over-sulphated chondroitin sulphate disaccharide was studied as one of the most widespread contaminants of heparin. Calculated IR spectra were analyzed with respect to specific structure parameters. IR spectroscopic fingerprint was found to be sensitive to substitution pattern of disaccharide subunits. Vibrational assignments of calculated spectra were correlated with experimental IR spectral bands of native heparin. Chemometrics was used to perform multivariate analysis of simulated spectral data.},
  language  = {en}
}
@article{LindnerBurgerRutledgeetal.2022,
  author    = {Lindner, Simon and Burger, Ren{\´e} and Rutledge, Douglas N. and Do, Xuan Tung and Rumpf, Jessica and Diehl, Bernd W. K. and Schulze, Margit and Monakhova, Yulia},
  title     = {Is the calibration transfer of multivariate calibration models between high- and low-field NMR instruments possible? A case study of lignin molecular weight},
  series = {Analytical chemistry},
  volume    = {94},
  journal   = {Analytical chemistry},
  number    = {9},
  publisher = {ACS Publications},
  address   = {Washington, DC},
  isbn      = {1520-6882},
  doi       = {10.1021/acs.analchem.1c05125},
  pages     = {3997 -- 4004},
  year      = {2022},
  abstract  = {Although several successful applications of benchtop nuclear magnetic resonance (NMR) spectroscopy in quantitative mixture analysis exist, the possibility of calibration transfer remains mostly unexplored, especially between high- and low-field NMR. This study investigates for the first time the calibration transfer of partial least squares regressions [weight average molecular weight (Mw) of lignin] between high-field (600 MHz) NMR and benchtop NMR devices (43 and 60 MHz). For the transfer, piecewise direct standardization, calibration transfer based on canonical correlation analysis, and transfer via the extreme learning machine auto-encoder method are employed. Despite the immense resolution difference between high-field and low-field NMR instruments, the results demonstrate that the calibration transfer from high- to low-field is feasible in the case of a physical property, namely, the molecular weight, achieving validation errors close to the original calibration (down to only 1.2 times higher root mean square errors). These results introduce new perspectives for applications of benchtop NMR, in which existing calibrations from expensive high-field instruments can be transferred to cheaper benchtop instruments to economize.},
  language  = {en}
}
@article{MuellerSeginWeigandetal.2022,
  author    = {Mueller, Tobias and Segin, Alexander and Weigand, Christoph and Schmitt, Robert H.},
  title     = {Feature selection for measurement models},
  series = {International journal of quality \& reliability management},
  journal   = {International journal of quality \& reliability management},
  number    = {Vol. ahead-of-print, No. ahead-of-print.},
  publisher = {Emerald Group Publishing Limited},
  address   = {Bingley},
  issn      = {0265-671X},
  doi       = {10.1108/IJQRM-07-2021-0245},
  year      = {2022},
  abstract  = {Purpose In the determination of the measurement uncertainty, the GUM procedure requires the building of a measurement model that establishes a functional relationship between the measurand and all influencing quantities. Since the effort of modelling as well as quantifying the measurement uncertainties depend on the number of influencing quantities considered, the aim of this study is to determine relevant influencing quantities and to remove irrelevant ones from the dataset. Design/methodology/approach In this work, it was investigated whether the effort of modelling for the determination of measurement uncertainty can be reduced by the use of feature selection (FS) methods. For this purpose, 9 different FS methods were tested on 16 artificial test datasets, whose properties (number of data points, number of features, complexity, features with low influence and redundant features) were varied via a design of experiments. Findings Based on a success metric, the stability, universality and complexity of the method, two FS methods could be identified that reliably identify relevant and irrelevant influencing quantities for a measurement model. Originality/value For the first time, FS methods were applied to datasets with properties of classical measurement processes. The simulation-based results serve as a basis for further research in the field of FS for measurement models. The identified algorithms will be applied to real measurement processes in the future.},
  language  = {en}
}