Recent publications
Anionic microporous polymer networks were synthesised via Yamamoto polymerization of a fluorinated tetraarylborate monomer. The network charge density can be controlled by varying the incorporation ratio of a neutral tetraphenylmethane comonomer. The resulting polymer networks demonstrated exceptional stability under ambient conditions and achieved specific surface areas of up to 1500 m² g⁻¹. The anionic nature of the networks simplifies postsynthetic ion exchange, enabling the incorporation of catalytically active cationic species. As a proof of concept, the molecular cationic Crabtree's catalyst was immobilised within the network, yielding a solid‐state material that efficiently catalyzed the gas‐phase hydrogenation of ethylene to ethane under mild conditions.
- Christina Sanchez-Stockhammer
- Julie Winter
- Antonia Friebel
The LediZ project at University of Munich has been digitizing Holocaust survivors’ testimonies for public access via interactive digital testimonies (IDTs). Users of these IDTs engage with survivors’ pre-recorded answers by asking questions in natural German speech and writing through an interface. These questions are matched by a dialogue system with the video providing the best answer to each question, so that users watching the video have the impression of a real meaningful interaction. However, the IDTs were first only available in German and thus limited in scope. The LeDiT project at TU Chemnitz therefore aimed to create an English-language version of Holocaust survivor Abba Naor’s testimony with subtitles, to ensure broader international accessibility and impact. The present contribution outlines the most important steps in the development of Abba Naor’s English IDT and explains the general principles underlying the translation from English to German. The largest part of the contribution is devoted to the discussion of individual decisions that had to be made in order to arrive at the best possible translation. The paper closes with an outlook on how Abba Naor’s English-language IDT can be employed in educational contexts, and the appendix lists all English questions.
- Maria Saladina
- Carsten Deibel
The fill factor (FF) is a critical parameter for solar cell efficiency, but its analytical description is challenging due to the interplay between recombination and charge extraction processes. A significant factor contributing to FF losses, beyond recombination, that has not received much attention is the influence of charge transport. In most state-of-the-art organic solar cells, the primary limitations of the FF do not just arise from non-radiative recombination, but also from low conductivity of the organic semiconductors. A closer look reveals that even in the highest efficiency cells, performance losses due to transport resistance are significant. This finding highlights the need for refined models to predict the FF accurately.
Here, we extend the analytical model for transport resistance to a more general case by systematically incorporating energetic disorder. We introduce a straightforward set of equations to predict the FF of a solar cell, enabling the differentiation of losses attributed to recombination and transport resistance. Our analytical model is validated with a large set of experimental current–voltage and light intensity-dependent open-circuit voltage data for a wide range of temperatures. Based on our findings, we provide valuable insights into strategies for mitigating FF losses, guiding the development of more efficient solar cell designs and optimisation strategies.
Being alone is a basic and prevalent human experience, yet little is known about its effects on social identity. When alone, social identity may weaken because individuals feel their groups are less valuable or less salient. Conversely, it may strengthen because craving for bonding increases in-group perceived value. We tested these ideas with five experiments (N = 1312). Study 1, using existing groups, and Study 2, using minimal groups, showed that aloneness (vs. being with others) reduced in-group identity through its effect on in-group esteem. In Study 3, this effect was equivalent to the effect observed following social exclusion. Study 4 showed that individuals alone were indifferent in allocating money between in-group and out-group members. Last, Study 5 indicated that these effects do not stem from reduced salience of in-group members when alone. In conclusion, an alone mindset affects social identity by decreasing in-group esteem, signalling broad social implications for this basic social condition.
This study examines whether the growing disparity in labor productivity between firms in Canada is associated with the ability of these firms to grow in the Canadian economy. Using Canada’s Corporate Tax Statistics Universal File, we identify an inverted U-shaped relationship between labor productivity and fixed-asset growth rates, which subsequently results in a negative association between growing dispersion and lower growth rates. Econometric analyses reveal that a 1% increase in productivity dispersion leads to a 0.06 percentage point reduction in industry-level growth rates. We consider Schumpeterian and other evolutionary approaches for explaining this phenomenon and propose a simple population dynamics model.
Wearable technologies open up new avenues for the assessment of individual physical activity behaviour. Particularly, free-living heart rate (HR) data assessed by optical sensors are becoming widely available. However, while an abundancy of scientific information and guidance exists for the processing of raw acceleration data, no universal recommendations for the utilization of continuous HR recordings during free-living conditions are available. Towards Intelligent Health and Well-Being: Network of Physical Activity Assessment (INTERLIVE®) is a joint European initiative of six universities and one industrial partner. The consortium was founded in 2019 and strives towards developing best-practice recommendations in the context of consumer wearables and smartphones. The aim of this scoping review (following PRISMA-ScR procedures) and recommendations was to provide best-practice protocols for deriving individual physical activity profiles from continuous HR recordings by wearables. The recommendations were developed through an initial scoping review, grey literature searches of promotional material and user manuals of leading wearable manufacturers as well as evidence-informed discussions among the members of the INTERLIVE®-network. The scoping review was performed on the generic domains required for physical activity assessment, namely: (1) ‘assessment of maximal heart rate’, (2) ‘determination of basal and/or resting heart rate’ and (3) ‘heart rate-derived intensity zones’, for which we finally included a total of 72, 2 and 11 eligible papers, respectively. Gathering recent knowledge, we provide a decision tree and detailed recommendations for the analysis of free-living HR data to derive individual physical activity profiles. Moreover, we also provide examples of HR-metric calculations that help to illustrate data processing and reporting.
We consider Haar multiplier operators acting on Sobolev spaces, and more generally Triebel-Lizorkin spaces , for indices in which the Haar system is not unconditional. When m depends only on the Haar frequency, we give a sufficient condition for the boundedness of in , in terms of the variation norms , which is optimal in u (up to endpoints) when .
New axial piston pumps with fixed displacement volumes, such as the high efficient power package (HEPP) pumps operate at variable rotational speeds and thus variable flow rates in a wide range. Using intelligent pump control systems, small and light packages are possible. In contrast, the fluid pulsations vary due to the rotational speed and have to be controlled avoiding stress or wear in the hydraulic system components (e.g. seals of tubing) and potentially impacting cabin noise. Due to the excitation frequencies, a broadband silencer for high pressure applications is required. This is realised by a multi-Helmholtz-resonator (MHR) concept within one cylindrical volume. The design will be adapted for pump-specific frequency characteristics in aircraft hydraulic conditions and fine adjusted during test verification by means of an adjustable tube-inside a pressure shell. For cost, weight and complexity reason a common broadband attenuator is integrated in the hydraulic circuit connecting the two redundant HEPP motorpumps. The attenuator position is optimised to achieve maximal acoustic performance and minimize pulsation stress on the pump, especially at the main operating point. The proof of concept has been achieved experimentally comparing a HEPP piston pump with and without the MHR.
The ion-molecule reaction N⁺ + O2 has been investigated experimentally using crossed beam velocity map imaging in the collision energy range from 0.15 eV to 3.0 eV. From the differential scattering cross sections, information on the branching ratios, the electronic states and vibrational levels populated in the two product channels, O 2+ + N and NO⁺ + O, have been obtained. These data are compared with previous results obtained using a rotatable ion source setup developed many years ago at the University of Freiburg, Germany. Furthermore, a small fraction of NO⁺ products populate excited electronic states as observed in chemiluminescence measurements.
For over a century, cubic equations of state (EoS) have been used to calculate density and phase equilibria of pure fluids and mixtures. Despite a century’s development with hundreds of resulting cubic EoS, their accuracy in liquid phase density calculations is still unsatisfactory. In this work, a new cubic EoS was developed to improve the accuracy of liquid phase density calculation while keeping similar accuracy of other properties. The new cubic EoS, named YFR (Yang-Frotscher-Richter) EoS, was developed based on the functional form of the Patel–Teja (PT) EoS [p = RT/(v − b) − a/(v(v + b) + c(v − b)]. In the PT EoS, parameters b and c are linked to an empirical critical compressibility factor ξc, and all these three parameters are constants for a pure fluid. By contrast, in the YFR EoS, ξc, b, and c are functions of temperature, and the equations describing this dependency were developed with symbolic regression. This is the key to improving liquid phase density calculation, although it leads to thermodynamic inconsistencies at high pressures. The application range of the new cubic EoS is thus limited to pressures up to 100 MPa. The YFR EoS was developed using nearly all pure fluids available in NIST’s REFPROP 10.0 database, with reference values computed with REFPROP. The average of the absolute value of relative deviations (AARD) of liquid phase densities calculated with the YFR EoS from reference values is approximately 2 %, compared to 3 % when using the Patel–Teja–Valderrama (PTV) EoS and 6 % when using the Peng-Robinson (PR) EoS. The YFR EoS has been implemented in our self-developed OilMixProp 1.0 software package.
Fullerenes are statically pleasant species featuring symmetric cages, which can be modified upon reduction. Here, we theoretically account for the variation of 13C‐NMR patterns in C60 and C70 upon six‐fold reduction and the overall variation of the enabled shielding/deshielding regions induced by π and σ electrons according to different orientations of the external field and the related anisotropy. Our results show a significant modification of the chemical shift given by the main variation of the σ33 (or δ33) shielding component under the principal axis system (PAS) of the chemical shift anisotropy (CSA) at the representative carbon nucleus. For C606‐ a shielding cone property is enabled from any orientation, accounting for a significant spherical aromatic character. In contrast, in C706‑, a shielding cone is reserved only for an axial‐oriented field, with a deshielding cone behavior obtained from the complementary equatorial orientations. The overall anisotropy shows an inner isotropic region for C60 and C606‐, with a continuous anisotropic outer contour for the latter. In contrast, C70 and C706‐ both show larger anisotropies, given the lesser spherical shape in addition to the modified π‐surface. Such information is useful for further rationalizing the implementation of magnetic anisotropic molecular devices into fullerene‐based materials.
Professionalisation and digitalisation have become ubiquitous concepts for overcoming all kinds of social challenges. This article examines the relation between these two processes in the case of the Austrian police emergency service. Based on a practice form analysis of mass media discourse, the implementation of a computer-aided dispatch system and the practices in emergency control rooms, we trace conflicts of competence regarding the digital mediatisation. The article shows how media technology and professional competences are mutually reconfigured in this process. In this context, the concept of de/professionalisation refers to the simultaneity of heterogeneous professional demands and requirements. Based on the empirical findings, a grounded theoretical model is developed, which can be applied beyond the case to capture the interactions and contested nature of professionalisation and digital mediatisation.
We provide a computer-assisted approach to ensure that a given discrete-time polynomial system is (asymptotically) stable. Our framework relies on constructive analysis together with formally certified sums of squares Lyapunov functions. The crucial steps are formalized within the proof assistant . We illustrate our approach with an example issued from the control system literature.
The minimal widths of three bounded subsets of the unit sphere associated to a unit vector in a normed linear space are studied, and three related geometric constants are introduced. New characterizations of inner product spaces are also presented. From the perspective of minimal width, strong ε-symmetry of Birkhoff orthogonality is introduced, and its relation to ε-symmetry of Birkhoff orthogonality is shown. Unlike most of the existing parameters of the underlying space, these new constants are full dimensional in nature.
Near-infrared (NIR) controlled drug delivery systems have drawn a lot of attention throughout the past few decades due to the deep penetration depth and comparatively minor side effects of the stimulus. In this study, we introduce an innovative approach for gastric cancer treatment by combining photothermal infrared-sensitive gold nanorods (AuNRs) with a conjugated microporous polymer (CMP) to create a drug delivery system tailored for transporting the cytostatic drug 5-fluorouracil (5-FU). CMPs are fully conjugated networks with high internal surface areas that can be precisely tailored to the adsorption and transport of active compounds through the right choice of chemical functionalities. By incorporation of surfactant-stabilized AuNRs into the CMP synthesis in dimethylformamide (DMF) the surfactant shell is destabilized and subsequently replaced by the CMP. Particularly, low initial surfactant concentrations led to uniform distribution of the AuNRs in the polymer matrix. Importantly, the integrated AuNRs maintain their plasmonic properties, as was confirmed via electron energy loss spectroscopy. Therefore, the significant photothermal properties are translated to the hybrid material as shown in a proof-of-principle experiment. Further, in an approximated gastric environment, 5-FU release studies were conducted with and without NIR stimulus. Thereby it was observed that increased Brownian motion due to the NIR irradiation not only accelerates the release but also increases the total released amount by influencing the adsorption–desorption equilibrium. This remarkable level of control of the release process underlines the immense potential of this hybrid material for precise and targeted drug delivery.
Novel composite combinations are needed to meet the broad mechanical requirements for lightweight structures by integrating various properties within a single structure. This includes high structural rigidity and impact resistance with low overall density. Fiber metal laminates (FMLs) are advanced composite materials composed of an alternating stacking sequence of metal alloys layers and fiber-reinforced polymers. However, FMLs exhibit lower puncture deformation potential compared to fiber-reinforced thermoplastics (FRTPs). To address this limitation, polyurethane (PUR) foam with 3D continuous fiber-reinforcement, is investigated as padding. The FML, manufactured via thermoforming, is based on basalt fiber-reinforced polyamide 6 and two layers of aluminum alloy. The PUR foam is fabricated through structural reaction injection molding and reinforced with a spacer fabric. Subsequently, low velocity impact tests are conducted for this novel composite and its single components. The results unveil significant insights into the impact behavior of the materials. The highest perforation resistance of 81 J is achieved by the FML padded with 3D continues fiber-reinforced polyurethane foam while offering equal deformation capability as without reinforced PUR foam. These findings underscore the superior impact performance of the fiber metal laminate padded with 3D continues fiber-reinforced polyurethane foam, offering valuable insights for the advancement of impact-resistant materials in various engineering applications.
This paper deals with a method for strain determination around boreholes in plastic specimens in the context of residual stress analyses. In contrast to the frequently used hole drilling method with strain gauges, the strains are determined using digital image correlation (DIC). In the investigations presented, load stresses occur instead of residual stresses, which is caused by defined loading conditions. Furthermore, an adaption of the hole drilling method is developed, called staggered machining, which includes the successive drilling of a larger and a smaller borehole to obtain deformation data in larger depths compared to the conventional approach. For strain evaluation, a special method is used with parametrisation of an annulus around the borehole. In this region, B‐spline approximation of the DIC displacements is carried out using an optimisation procedure of the smoothing parameter. The tests of the entire method show very plausible and precise results. Furthermore, a comparison with simulation demonstrates good correlation of the strain distributions.
The intramolecular migration of three hydrogen atoms from one moiety of a gaseous radical cation to the other prior to fragmentation is an extremely rare type of redox reaction. Within the scope of this investigation, this scenario requires an ionized but electron‐rich arene acceptor bearing a para‐(3‐hydroxyalkyl) residue. The precise mechanism of such unidirectional 3H transfer processes, including the order of the individual H transfer steps, has remained unclear in spite of previous isotope labelling and recent infrared ion spectroscopy (IRIS) studies. Herein, the details of this peculiar process have been investigated for ionized 4‐(N,N‐dimethylaminophenyl)‐2‐butanol, 2, by state‐of‐the‐art density functional theory (DFT) calculations. The energetically most favorable pathway consists of a sequence of successive 1,4‐, 1,6‐ and 1,5‐H steps. During these steps the secondary alcohol functionality is oxidized to a carbonyl group and the radical‐cationic aniline ring is reduced to an ionized 2,3‐dihydroaniline unit. Several alternative sequences, such as three successive 1,5‐H shifts, could be excluded. A concomitant unidirectional 2H migration reaction of the ion 2 was also investigated and the intermediacy of ion‐neutral complexes (INCs) enabling sequential hydride and proton transfer was confirmed by the calculations.
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