Waltraud Kessler

Hochschule Reutlingen · Life Sciences

As the most abundant renewable aromatic polymer on the planet, lignin is gaining growing interest in replacing petroleum-based chemicals and products. However, only <5 % of industrial lignin waste is revalorized in its macromolecular form as additives, stabilizing agents or dispersant and surfactants. Herein, revalorization of this biomass was achi...

Process analytical technology (PAT) is a cross‐sectional technology and thus essential for future smart production. While in the past decades, the focus of process optimization strategies was on increasing efficiency, in the future, the focus will be on the sustainability of a production and its products. In addition, products will be increasingly...

Melamine-formaldehyde (MF) resins are widely used as surface finishes for engineered wood-based panels in decorative laminates. Since no additional glue is applied in lamination, the overall residual curing capacity of MF resins is of great technological importance. Residual curing capacity is measured by differential scanning calorimetry (DSC) as...

The isothermal curing of melamine resin is investigated by in-line infrared spectroscopy at different temperatures. The infrared spectra are decomposed into time courses of characteristic spectral patterns using Multivariate Curve Resolution (MCR). It was found that depending on the applied curing temperature, melamine films with different spectral...

During curing of thermosetting resins the technologically relevant properties of binders and coatings develop. However, curing is difficult to monitor due to the multitude of chemical and physical processes taking place. Precise prediction of specific technological properties based on molecular properties is very difficult. In this study, the poten...

The concept of process analytical technology (PAT) started around the 1970s with the advent of personal computers in combination with instrumental analytical chemistry. Over the years, increasingly sophisticated and holistic quality management concepts such as quality by design (QbD) were developed and strongly promoted, especially by the American...

Here, we study resin cure and network formation of solid melamine formaldehyde pre-polymer over a large temperature range via dynamic temperature curing profiles. Real-time infrared spectroscopy is used to analyze the chemical changes during network formation and network hardening. By applying chemometrics (multivariate curve resolution, MCR), the...

Quality by Design (QbD), Industrie 4.0 (i40) respectively the Industrial Internet of Things (IIoT) need context sensitive information for future smart manufacturing and processing. Data analytics together with intelligent process analytical technology sensors (PAT) are the enabling technologies to realize these concepts. This contribution tries to...

Intelligent manufacturing has attracted enormous interest in recent years. Since optical spectroscopy provides information on a molecular basis, it will play a major role in the future for the sensor technology. The paper demonstrates that the sensitivity and selectivity of different spectroscopic technologies has fundamental limitations due to the...

Hot melt extrusion (HME) is a well-known process within the plastic and food industries that has been utilized for the past several decades and is increasingly accepted by the pharmaceutical industry for continuous manufacturing. For tamper-resistant formulations of e.g. opioids, HME is the most efficient production technique. The focus of this stu...

Raman spectroscopy technique is widely used for the identification and characterisation of materials in the laboratory environment and, increasingly, for off-line, at-line, in-line and online Process Analytical Technologies (PAT) applications. The wide range of currently available Raman technologies had led to the requirement to update the existing...

Optical spectroscopy is able to detect not only the chemical composition of the species by their wavelength specific absorption k but also the morphological feature through their wavelength dependent scattering s. In standard multivariate data analysis in hyperspectral imaging, the focus of the chemometric treatment of the data cube is given on the...

Multiphoton-excited cellular autofluorescence is based on the emission of light by endogenous fluorescent biomolecules which are related to certain cellular functions such as structural arrangement and cellular metabolism. Because of their involvement in fundamental biological processes the analysis of endogenous fluorophores may provide informatio...

Autofluorescence and Raman measurements of U251-MG glioblastoma cells prior and subsequent to activation of tumor suppressor genes are compared. While phase contrast images and fluorescence intensity patterns of the tumor (control) cells and the less malignant cells are similar, differences can be deduced from fluorescence spectra and nanosecond d...

The objective of this paper is to provide a comprehensive review of best practice in hyperspectral imaging. The paper starts to review the taxonomy of the different spectral imaging techniques together with their advantages and disadvantages. The appropriate selection of cameras and spectrographs and their figures of merit are discussed and a detai...

The objective of this paper is to provide a comprehensive review of best practice in hyperspectral imaging. The paper starts to review the taxonomy of the different spectral imaging techniques together with their advantages and disadvantages. The appropriate selection of cameras and spectrographs and their figures of merit are discussed and a detai...

Autofluorescence and Raman spectra, images and decay kinetics of U251-MG glioblastoma cells prior and after activation of tumor suppressor genes are compared. While phase contrast images and fluorescence patterns of the tumor (control) cells and the less malignant cells are similar, differences can be deduced from autofluorescence spectra and decay...

In der Prozessdatenanalyse haben sich sowohl die Hauptkomponentenanalyse (PCA) als auch die Partial Least Square Regression (PLSR) als chemometrische Werkzeuge etabliert. Der wesentliche Nachteil von PCA und PLSR ist, dass die Hauptkomponenten abstrakte, sogenannte latente Variable darstellen und häufig den physikalisch chemischen Hintergrund nur u...

Mittels chemischer Bildgebung auf Basis spektralanalytischer Verfahren können biomolekulare Wechselwirkungen schneller, preiswerter, genauer und zuverlässiger als bisher nachgewiesen werden. Im folgenden Beitrag illustrieren wir dies mit Schwerpunkt auf der optischen Spektroskopie.

One of the most often used tools in process analytical technology (PAT) is NIR spectroscopy as a non-destructive fast and reliable method to identify and quantify active pharmaceutical ingredients (API) in tablets. Very little work has been devoted to analyse the effects of scatter on quantitative analysis of the chemical composition. A novel appro...

Control in biotechnology is still more related to univariate sensors, where only single component analysis is performed on the data. Very little work has yet been published on the use of spectroscopic methods in biotechnological systems. This is mainly due to the fact that in most cases water is the dominant component and the reacting species are a...

The laccase-catalysed transformation of indigo carmine (IC) with and without a redox active mediator was studied using online UV-visible spectroscopy. Deconvolution of the mixture spectra obtained during the reaction was performed on a model-free basis using multivariate curve resolution (MCR). Thereby, the time courses of educts, products, and rea...

The prelims comprise: * Vortitel * 200 Jahre Wiley -- Wissen für Generationen * Titelseite * Copyrightseite * Inhaltsverzeichnis * Vorwort

Was ist multivariate Datenanalyse?Datens?tze in der multivariaten DatenanalyseZiele der multivariaten Datenanalyse Einordnen, Klassifizierung der DatenMultivariate RegressionsverfahrenM?glichkeiten der multivariaten VerfahrenPr?fen auf Normalverteilung WahrscheinlichkeitsplotsBox-PlotsFinden von Zusammenh?ngen KorrelationsanalyseBivariate Datendars...

Durchf?hrung einer Hauptkomponentenanalyse (PCA) Beschreibung der DatenAufgabenstellungDatendatei einlesenDefinieren von Variablen- und ObjektbereichenSpeichern der DatentabellePlot der RohdatenVerwendung von qualitativen Variablen (kategoriale Variable)Berechnen eines PCA-ModellsInterpretation der PCA-Ergebnisse Erkl?rte Varianz (Explained Varianc...

Spektroskopische TransformationenSpektrennormierung Normierung auf den MittelwertVektornormierung auf die L?nge eins (Betrag-1-Norm)Gl?ttung Gl?ttung mit gleitendem MittelwertPolynomgl?ttung (Savitzky-Golay-Gl?ttung)BasislinienkorrekturAbleitungen Ableitung nach der Differenzenquotienten-Methode (Punkt-Punkt-Ableitung)Ableitung ?ber Polynomfit (Sav...

Zusammenfassung der Kalibrierschritte – KalibrierfehlerMöglichkeiten der Validierung Kreuzvalidierung (Cross Validation)Fehlerabschätzung aufgrund des Einflusses der Datenpunkte (Leverage Korrektur)Externe Validierung mit separatem TestsetBestimmen des Kalibrier- und Validierdatensets Kalibrierdatenset repräsentativ für Y-DatenraumKalibrierdatenset...

Klassische und inverse KalibrationUnivariate lineare RegressionMaßzahlen zur Überprüfung des Kalibriermodells (Fehlergrößen bei der Kalibrierung) Standardfehler der KalibrationMittlerer Fehler – RMSEStandardabweichung der Residuen – SEKorrelation und BestimmtheitsmaßSignifikanz und Interpretation der RegressionskoeffizientenGrafische Überprüfung de...

Geschichte der HauptkomponentenanalyseBestimmen der Hauptkomponenten Prinzip der HauptkomponentenanalyseWas macht die Hauptkomponentenanalyse?Grafische Erklärung der HauptkomponentenBedeutung der Faktorenwerte und Faktorenladungen (Scores und Loadings)Erklärte Varianz pro HauptkomponenteMathematisches Modell der Hauptkomponentenanalyse Mittenzentri...

VorversucheErstes KalibriermodellEinsatz des Kalibriermodells – ValidierphaseOffset in den Vorhersagewerten der zweiten TestphaseZusammenfassung der Schritte bei der Erstellung eines Online-Vorhersagemodells

Lignocellulosic fibres are high quality raw materials that have been used to produce a variety of technical fibre composites. The fibres assessed in this study were Picea abies and Fagus sylvatica high temperature thermomechanical pulps. In the case of effectively bonded composites their mechanical performance is mainly determined by the aspect rat...

An experimental design, in combination with oscillation-type densimetry is introduced as a novel procedure to optimise steam distillation for the determination of alcoholic strength in different types of alcoholic beverages. A central composite design was chosen to study the effects of variation in levels of receiver volume (25 and 50ml), steam pow...

In biotechnology, strong emphasis is placed on the development of wet chemical analysis and chromatography to separate target components from a complex matrix. In bioprocessing, the development of single compound biosensors is an important activity. The advantages of these techniques are their high sensitivity and specificity. Inline or online moni...

Both cDNA microarray and spectroscopic data provide indirect information about the chemical compounds present in the biological tissue under consideration. In this paper simple univariate and bivariate measures are used to investigate correlations between both types of high dimensional analyses. A large dataset of 42 hemp samples on which 3456 cDNA...

A VIS spectrometer was evaluated during 25 days of on-line operation. The spectrometer was installed above a conveyor belt carrying softwood chips to a continuous digester that was charged with 100 tonnes chips/h. We found that VIS spectroscopy can be used on-line both to predict chip properties and to monitor a continuous digester. Prediction mode...

Fibre formation in hemp (Cannabis sativa L.) is a dynamic process. In order to follow this process, the chemical composition of the hemp stem was studied during plant development using the acid and neutral detergent fibre and lignin methods. Additionally, near infra-red spectroscopy was carried out. To predict the chemical composition of the stem s...

A new method has been devised for measuring sound pulse amplitudes in helium, using as a thermometer the variation of sound velocity with temperature. The method has been applied to measure the transformation coefficients of second sound to vapour sound, and vice versa, at the free surface of liquid helium II. The results, interpreted in the light...

The corrosion of metals and the paint adhesion on metals is a result of the superposition of complex reactions on the surface, which depend on surface oxide thickness, its porosity and chemical composition. By means of diffuse reflectance spectroscopy and evaluation of the spectra by a Kohonen self-organizing map, it is possible to predict the futu...

In this paper we present a method for analyzing optical data with Kohonen's selforganizing feature map (SOM). Two applications are considered, the determination of presence and concentration of organic gases and solvants and the prediction of corrosion resistance of car body steels. Both applications use a similar method based on optical measuremen...

In a highly competitive market, an optimised processing plays a key role for the future of our industry. Intelligent processing is only feasible, when the materials and products are controlled directly during and after processing. Traditional methods for controlling corrosion are often very time consuming and destructive (e.g. corrosion under paint...

Chromate conversion layers of a thickness ranging from 20 to 250 nm on Al-alloys are characterized by EIS in 0.1 M Na2SO4 and optical measurements. A model is derived from these data which describes the corrosion mechanism of these samples. The main components of the equivalent circuit can be attributed to the diffusion barrier and to defect sites...

The corrosion of materials is a result of the superposition of complex reactions which depend on surface thickness, its porosity and chemical composition. By means of optical spectroscopy, especially diffuse reflectance spectroscopy, the surface of low carbon steel can be analysed within milliseconds. From these results it is possible to predict it...

Measurements of the velocity of sound in 4He gas have been made in the temperature range 2.129-1.282K. The results, and their interpretation in terms of the second virial coefficient, are presented. The variation of the second virial coefficient with temperature is found to be a continuation of that previously determined at higher temperatures.