Scientific publications of the Saarland University
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LumEDA: image luminance based contactless correlates of electrodermal responses
Get PDFObjective. Electrodermal activity (EDA) is a marker of psychophysiological arousal and is usually a
measure of the skin conductance which is associated with sweat gland activity. Recent studies have
shown that it is possible to estimate the EDA using contactless video based methods. Approach.
Sensor EDA signals (SenEDA) and videos of the the palm were recorded simultaneously from over
30 participants under various stimuli (audio, video, cognitive and physiological). The luminance
information from the video data was used to track sweat gland activity on the skin surface and
extract the contactless signal luminance based EDA (LumEDA). Main results. Comparison of the
SenEDA and LumEDA signals showed a high positive correlation between the two as expected.
Significance. Under suitable illumination, simple spatial filters can be used to track sweat gland
activity which can then be used to estimate signals analogous to the EDA. Such video based
methods also facilitate spatio-temporal analysis of EDA correlates over larger areas of the body
Adapting Energy Conservation Building Code-2023 for the Diverse Climates of Pakistan: A Path to Affordable Energy Efficiency and Sustainable Living
Get PDFIn Pakistan and most other developing nations, the residential building sector is one of
the highest energy-consuming domains. The residential sector has the highest share of
50% of final electricity use of the country. Though Energy Conservation Building Codes
(ECBC-2023) provide structured energy guidelines, no work has been performed to quantify
the actual energy-saving potential of code-compliant retrofits in residential buildings. This
study investigates the performance of ECBC-compliant retrofitting strategies for residential
buildings under Pakistan’s diverse climatic conditions. The Passive House Planning
Package (PHPP), a validated simulation tool, was used to assess energy performance
improvements through building envelope interventions such as thermal insulation, solar
shading, window glazing, and optimal orientation. Field data were collected from three
representative cities, Multan (hot desert), Taxila (humid subtropical), and Quetta (cold
semi-arid), to simulate both conventional and energy-efficient building scenarios. The
results showed substantial seasonal energy savings in all three climates. During the
heating period, energy savings were 48%, 50%, and 60% for Taxila, Multan, and Quetta,
respectively. Similarly, energy savings during the cooling season were 44%, 33%, and
16%. Life cycle economic analysis revealed that these retrofits yielded Net Present Values
(NPVs) of USD 752 (Taxila), USD 1226 (Multan), and USD 1670 (Quetta) over a 30-year
period, with discounted payback periods ranging from 6 to 10 years. Furthermore, a life
cycle assessment demonstrated that retrofitted buildings yielded up to 26% reduction
in overall carbon emissions, combining both embodied and operational sources. The
findings highlight that ECBC-2023 is not only a technically viable solution for energy
savings but also financially attractive in residential retrofitting. By incorporating localized
climate responsiveness into ECBC-compliant building design, the study provides a practical
roadmap for achieving Pakistan’s energy efficiency goals. Additionally, the outcomes serve
as a basis for informing policy initiatives, supporting building code adaptation, and raising
public awareness of sustainable housing practices
Beyond aversion – principles of appropriate algorithmic decision-making in human resource management
Get PDFAs algorithmic decision-making (ADM) becomes increasingly embedded in human resource management (HRM), concerns such as a lack of fairness and accountability raise urgent questions about its appropriateness. This study addresses the need for ADM evaluation by developing a coherent framework of principles grounded in the task-technology fit approach. It elaborates a balanced triad of nine indispensable ADM principles—methodical (veracity, accuracy, validity), managerial (relevancy, quality, efficiency), and ethical (fairness, accountability, transparency)—and validates them through a systematic literature review of 126 ADM artifacts in HRM. The analysis reveals a troubling lack of attention to ethical and managerial dimensions, while even methodical aspects are often neglected—with the notable exception of accuracy. Building on these findings, the study outlines a forward-looking agenda to operationalize, calibrate, implement, evaluate, and codify ADM principles, ultimately promoting responsible, appropriate ADM in HRM that reflects an evaluative stance beyond mere aversion
Revealing the impact of surface composition of electrodeposited Сu and Ni nanoparticles on the specific electrooxidation of uric acid
Get PDFThe electrodeposition of transition metal nanoparticles (NPs) enables the formation of structures with complex
surface chemistry and enhanced catalytic properties. However, their electrocatalytic behavior can differ signif icantly from that of NPs synthesized by other methods, due to the formation of defect oxides, hydroxides, and
distinct interactions with molecular oxygen. This study investigates the role of uric acid (UA) polarizability
during complexation with catalytic centers of electrodeposited copper (Cu-NPs) and nickel (Ni-NPs) nano particles both containing surface defect oxides and the influence of molecular oxygen on UA detection under
alkaline conditions. The results show that although Cu-NPs exhibit higher sensitivity toward UA, this is
accompanied by reduced specificity due to side interactions with oxygen. In contrast, Ni-NPs enhance UA
polarizability without engaging in oxygen interactions, leading to more specific UA electrooxidation. These
findings offer insight into the design of electrodeposited electrocatalysts with tailored specificity for UA
detection
Polyelectrolyte metallopolymer particles for efficient PFAS capture and release
Get PDFIn technologies for PFAS removal, one of the biggest challenges is combining high adsorption capacity with excellent regeneration capabilities. In recent years, metallopolymer-based materials have shown promising potential in both aspects. In this work, we present two convenient ways to functionalize organic microparticles with charged, functional moieties (cobaltocenium), either through a one-pot reaction via siloxane-condensation or by straightforward ring-opening reaction of epoxides. After characterization of the novel adsorbent materials by state-of-the-art analytics to verify the successful functionalization, their performance for PFAS adsorption and regeneration was investigated. To gain insight into the adsorption mechanism, experiments were first conducted at low concentrations (20 μg L−1) and in equilibrium, showing adsorption for both materials of up to 97 % for PFOA and PFOS. Furthermore, an increase in adsorption within an ionic matrix of commercial drinking water and an adsorbent preference at different pH values was demonstrated. Analysis of the influence of the concentration indicates multilayer adsorption beyond simple ion-paring, best described by a Brunauer-Emmett-Teller mechanism. Moreover, utilizing a straightforward column setup, the total PFOA capacity is analyzed, revealing a 4–5-fold increase upon functionalization, leading to 215 mg g−1 and 296 mg g−1 PFOA adsorption. Overall, column-based adsorption experiments showed promising results at low (20 μg L−1) and medium (2.25 mg L−1) PFAS concentrations. Finally, reusability and regeneration studies further revealed an excellent desorption performance upon multiple cycles and PFAS elution of up to 88 ± 4 %
Thermodynamic analysis and modeling of Pd-Ni-S bulk metallic glass-forming system
Get PDFThis study explores both experimental and computational aspects of the thermophysical properties of the novel ternary BMG-forming Pd-Ni-S system. Unlike more complex quinary BMG-formers, this ternary system's simplicity allows for applying the CALPHAD approach to model the underlying thermodynamics governing glass formation.
Experimental investigations include quantifying specific heat capacity and studying crystallization across various compositions critical for generating essential input data. Using a two-state approach, initial modeling of the undercooled liquid and glass is conducted for individual elements and extended to the ternary system. Model predictions are validated against experimental findings and iteratively optimized. Using the parallel tangent method, the Gibbs free energy of crystalline and liquid phases at different compositions are calculated, providing a more accurate estimation of the nucleation driving force of the first forming phase compared to the conventional thermodynamic approach. These calculated driving forces are then used to model the isothermal Time-Temperature-Transformation (TTT) diagrams, and finally for the estimation of the interfacial energy between liquid and crystal during primary crystallization, which plays an important role in the glass-forming ability of this system. The experimental and calculated results are found to be compatible for near-eutectic compositions
On the biphasic nature of the N400-P600 complex underlying language comprehension
Get PDFThe ERP literature on language comprehension reveals variability in observing monophasic N400 versus biphasic N400-P600 effects in response to incongruent input, with the reasons for this inconsistency remaining unclear. Two interrelated factors may contribute: spatiotemporal overlap between the N400 and P600, where a strong N400-effect can obscure the P600, and the P600’s sensitivity to depth of processing, as determined by the experimental setting. Building on previous findings reporting monophasic N400-effects with plausibility judgments, we investigated whether comprehension questions, encouraging more natural reading and deeper processing of the full content, would elicit a biphasic effect, suggesting reduced component overlap in such settings. Using a design fully crossing lexical association and plausibility, we found that the N400 is modulated by association and the P600 by plausibility. Crucially, a biphasic pattern emerged for implausible and unrelated words, suggesting a mitigation of component overlap compared to previous studies employing plausibility judgments. We interpret the results in light of current accounts of the N400 and P600, arguing that the empirical evidence strongly supports single-stream over multi-stream models. Importantly, our findings highlight the critical role of both component overlap and task demands in shaping the data that inform the development and evaluation of theoretical models
Ni-Nb-P-Based bulk metallic glasses: Alloy development, thermodynamics, kinetics, structure, and mechanical properties
No full textHigh-strength Ni-Nb-based bulk metallic glasses exhibit exceptional mechanical properties, including strengths up to 3 GPa, elasticity of 2%, and hardness around 900 HV5, while their limited glass-forming ability (GFA) restricts broader industrial applications. To address this limitation, various alloying strategies are explored, with the primary focus on the effect of P and Ta on GFA, thermophysical properties, mechanical behavior, and atomic structure. Micro-alloying with P increases the critical casting thickness dc from 2 mm in binary Ni-Nb to 5 mm in the optimized ternary composition Ni59.2Nb38.8P2. Further refinement results in Ni59.2Nb33.8Ta5P2, achieving a record-breaking dc of 6 mm. Thermodynamic functions, viscosity, and kinetic fragility are evaluated around the glass transition and equilibrium liquid, providing insights into the driving force for crystallization and kinetic slowdown during cooling. Synchrotron X-ray diffraction studies reveal delayed crystallization and structural ordering, demonstrating a stabilized supercooled liquid state. On the downside, the applied strategies lead to reduced ductility and fracture toughness, with Ni59.2Nb38.8P2 emerging as optimal choice, balancing high GFA, strength and decent toughness. In addition, the correlation between amorphous structure and mechanical properties is further elaborated in an excursion across different metallic glass families, providing deeper insights into the underlying structure-property relation.Hochfeste metallische Massivgläser auf Ni-Nb-Basis zeichnen sich durch außergewöhnliche mechanische Eigenschaften aus, darunter Festigkeiten bis zu 3 GPa, eine Elastizitätsgrenze von 2% und eine Härte von etwa 900 HV5. Ihre begrenzte Glasbildungsfähigkeit (GFA) schränkt jedoch eine industrielle Anwendung ein. Um diese Limitierung zu überwinden, wird der Einfluss verschiedener Legierungselemente, insbesondere von P und Ta, auf die GFA, die thermophysikalische Eigenschaften, das mechanische Verhalten und die atomare Struktur untersucht. Mikrolegieren mit P erhöht die kritische Gussdicke dc von 2 mm in binärem Ni-Nb auf 5 mm in Ni59.2Nb38.8P2. Eine gezielte Weiterentwicklung führt zur Zusammensetzung Ni59.2Nb33.8Ta5P2, die eine rekordverdächtige kritische Gussdicke von 6 mm erreicht. Die Untersuchung der thermodynamischen Funktionen, der Viskosität und der Fragilität liefert Einblicke in die treibenden Kräfte der Kristallisation und die kinetische Verlangsamung. Synchrotron-Röntgenbeugungsstudien zeigen eine verzögerte Kristallisation und erhöhte strukturelle Ordnung, was auf eine stabilisierte unterkühlte Schmelze hindeutet. Auf der Kehrseite führen die angewandten Strategien zu verminderter Duktilität und Bruchzähigkeit, wobei Ni59.2Nb38.8P2 sich als optimale Wahl erweist, die den besten Kompromiss zwischen hoher GFA, Festigkeit und angemessener Zähigkeit darstellt. Zudem wird die Korrelation zwischen amorpher Struktur und mechanischen Eigenschaften metallischer Gläser vertieft
Novel approaches in clinical toxicology using high-resolution MS/MS and dual LC for analyzing biological samples
Get PDFAnalytical methods utilizing high-resolution tandem mass spectrometry (HRMS/MS) coupled to liquid chromatography (LC) allow the reliable detection and quantification of harmful compounds and drugs across various biological samples. This dissertation aimed to explore the capabilities of a state-of-the-art Orbitrap-based mass spectrometer paired with a dual LC system. The focus was on developing LC-HRMS/MS methods that prioritize time-efficient sample preparation, flexible and sustainable analytical strategies, and sufficient sensitivity to enable detection of analytes with diverse physico-chemical properties. Four distinct methods were developed and validated, encompassing the analysis of both low and high molecular weight compounds in plasma, the implementation of antibody-based extraction techniques for detecting toxic peptides in plasma and urine, and a comparative study of microflow LC versus analytical flow LC for identifying selected abused drugs in oral fluid. While certain limitations were observed during method development and validation, the resulting methods proved effective in addressing critical toxicological questions. This work highlighted the flexibility and versatility of current LC-HRMS/MS instruments and analysis in the field of analytical toxicology.Analytische Methoden basierend auf hochauflösender Tandem-Massenspektrometrie (HRMS/MS) gekoppelt an Flüssigchromatographie (LC) ermöglichen die Detektion und Quantifizierung von schädlichen Verbindungen und Arzneistoffen in verschiedenen biologischen Proben. Diese Dissertation zielte darauf ab, die Möglichkeiten eines modernen Orbitrap-basierten Massenspektrometers in Verbindung mit einem dualen LC System zu untersuchen. Der Schwerpunkt lag auf der Entwicklung von LCHRMS/ MS Methoden, um eine zeitsparende Probenvorbereitung, flexible und nachhaltige Analysestrategien sowie eine ausreichende Empfindlichkeit für den Nachweis von Analyten mit unterschiedlichen physikalisch-chemischen Eigenschaften zu ermöglichen. Vier verschiedene Methoden wurden entwickelt und validiert, welche die Analyse von Verbindungen mit niedrigem und hohem Molekulargewicht in Plasma, die Anwendung von Extraktionstechniken auf Antikörperbasis zum Nachweis toxischer Peptide in Plasma und Urin sowie eine vergleichende Studie zur Mikrofluss LC und analytischen LC zur Identifizierung ausgewählter missbräuchlich verwendeter Drogen in Speichel umfassten. Methodenentwicklung und Validierung zeigten bestimmte Limitationen auf, die resultierenden Methoden erwiesen sich aber als wirksam bei der Beantwortung kritischer toxikologischer Fragestellungen. Diese Arbeit verdeutlicht die Flexibilität und Vielseitigkeit aktueller LC-HRMS/MS-Instrumente und Analysen im Bereich der analytischen Toxikologie
Synthesis and crystal structure analysis of substituted bi-cyclo-[3.3.1]nona-nones
Get PDFPolycyclic polyprenylated acylphloroglucinols (PPAPs) are a
class of structurally complex natural products predominantly
isolated from plants of the Hypericum and Garcinia genera.
Characterized by a highly oxygenated polycyclic core densely
decorated with various substituents, these compounds exhibit
remarkable chemical diversity and biological activity (Yang et
al., 2018). Notably, a single representative can already cover a
wide range of different activities. The most important of these
may include anti-inflammatory, antibacterial and antiviral
activity, as well as cytotoxicity, antitumour properties and use
as an antidepressant and neuroprotective agent. Hyperforin,
the most prominent and best-studied PPAP to date, may serve
as an example of the latter point in particular (Richard, 2014).
The pronounced bicyclic framework, common to most PPAPs
and many other natural compounds (Roy et al., 2023), makes
them particularly compelling for research in natural product
chemistry and medicinal applications