Microfluidically-assisted isolation and characterization of Achromobacter spanius from soils for microbial degradation of synthetic polymers and organic solvents. - In: Environments, ISSN 2076-3298, Bd. 9 (2022), 12, 147, S. 1-17
A micro segmented-flow approach was utilized for the isolation soil bacteria that can degrade synthetic polymers as polyethylene glycols (PEG) and polyacrylamide (PAM). We had been able to obtain many strains; among them, five Achromobacter spanius strains from soil samples of specific sampling sites that were connected with ancient human impacts. In addition to the characterization of community responses and isolating single strains, this microfluidic approach allowed for investigation of the susceptibility of Achromobacter spanius strains against three synthetic polymers, including PEG, PAM, and Polyvinylpyrrolidone (PVP) and two organic solvents known as 1,4-dioxane and diglyme. The small stepwise variation of effector concentrations in 500 nL droplets provides a detailed reflection of the concentration-dependent response of bacterial growth and endogenous autofluorescence activity. As a result, all five strains can use PEG600 as carbon source. Furthermore, all strains showed similar dose-response characteristics in 1,4-dioxane and diglyme. However, significantly different PAM- and PVP-tolerances were found for these strains. Samples from the surface soil of prehistorical rampart areas supplied a strain capable of degradation of PEG, PVP, and PAM. This study demonstrates on the one hand, the potential of microsegment flow for miniaturized dose-response screening studies and its ability to detect novel strains, and on the other hand, two of five isolated Achromobacter spanius strains may be useful in providing optimal growth conditions in bioremediation and biodegradation processes.
https://doi.org/10.3390/environments9120147
On the theory of the spin I = 1/2 double quantum NMR: effects of spins spatial displacements between RF pulses. - In: The journal of chemical physics, ISSN 1089-7690, Bd. 157 (2022), 22, S. 224108-1-224108-7
Spatial displacements of spins between radio frequency pulses in a Double-Quantum (DQ) nuclear magnetic resonance pulse sequence generate additional terms in the effective DQ Hamiltonian. We derive a simple expression that allows the estimation and control of these contributions to the initial rise of the DQ build up function by variation of experimental parameters in systems performing anomalous diffusion. The application of polymers is discussed.
https://doi.org/10.1063/5.0124510
Molybdenum disulfide transistors with enlarged van der Waals gaps at their dielectric interface via oxygen accumulation. - In: Nature electronics, ISSN 2520-1131, Bd. 5 (2022), 12, S. 849-858
Two-dimensional molybdenum disulfide (MoS2) is a potential alternative channel material to silicon for future scaled transistors. Scaling down the gate dielectric and maintaining a high-quality interface is challenging with such materials, because the atomic thickness of MoS2 makes it sensitive to defects common in amorphous gate oxides such as hafnium oxide (HfOx). Here we show that a van der Waals gap of 5.3 Å can be formed between HfOx and MoS2 via the ozone treatment of a hafnium disulfide (HfS2)/MoS2 stack. The ozone treatment converts the HfS2 flake into a HfOx dielectric, and excess oxygen accumulation at the interface widens the van der Waals gap. Experimental results and density functional theory calculations show that the increased gap decouples the interaction between the HfOx dielectric and MoS2 channel, allowing the intrinsic properties of the MoS2 semiconductor to be preserved. The resulting MoS2 van der Waals-gap-gated transistors exhibit a negligible hysteresis of 10 mV and average subthreshold slope of 63.1 mV dec−1, which is close to the physical Boltzmann limit of 60.0 mV dec−1. We also show that the transistors can be used to construct NOT, OR and AND logic gates.
https://doi.org/10.1038/s41928-022-00877-w
Charge and spin state of dilute Fe in NaCl and LiF. - In: Physical review, ISSN 2469-9969, Bd. 106 (2022), 17, 174108, S. 174108-1-174108-10
There is an apparent mismatch between electron paramagnetic resonance and Mössbauer spectroscopy results on the charge and spin states of dilute Fe impurities in NaCl; Mössbauer spectroscopy data have been interpreted in terms of high-spin Fe2+, while electron paramagnetic resonance studies suggest low-spin Fe1+. In the present study, the charge and spin states of dilute substitutional Fe impurities in NaCl and LiF have been investigated with 57Mn&flech;57Fe emission Mössbauer spectroscopy. A scheme is proposed which takes into account the effects of nearest-neighbor distances and electronegativity difference of the host atoms on the Mössbauer isomer shift and allows for the unequivocal differentiation between high-spin Fe2+ and high/low-spin Fe1+ in Mössbauer spectroscopy. From these considerations, the Mössbauer results are found to be consistent with dilute Fe impurities in NaCl and LiF in a low-spin Fe1+ state. These conclusions are supported by theoretical calculations of isomer shifts and formation energies based on the density-functional theory. The experimental results furthermore suggest that charge compensation of dilute Mn2+ dopants in NaCl and LiF is achieved by Na vacancies and F− interstitials, respectively.
https://doi.org/10.1103/PhysRevB.106.174108
Preface to the special issue “Scientific and Clinical Applications of Magnetic Carriers 2022”. - In: Journal of magnetism and magnetic materials, ISSN 1873-4766, Bd. 564 (2022), 2, 170205
https://doi.org/10.1016/j.jmmm.2022.170205
Optimizing the cavity-arm ratio of V-shaped semiconductor disk lasers. - In: Physical review applied, ISSN 2331-7019, Bd. 18 (2022), 6, S. 064070
Passively mode-locked semiconductor disk lasers have received tremendous attention from both science and industry. Their relatively inexpensive production combined with excellent pulse performance and great emission-wavelength flexibility make them suitable laser candidates for applications ranging from frequency-comb tomography to spectroscopy. However, due to the interaction of the active medium dynamics and the device geometry, emission instabilities occur at high pump powers and thereby limit their performance potential. Hence, understanding those instabilities becomes critical for an optimal laser design. Using a delay-differential equation model, we are able to detect, understand, and classify three distinct instabilities that limit the maximum achievable pump power for the fundamental mode-locking state and link them to characteristic positive-net-gain windows. We furthermore derive a simple analytic approximation in order to quantitatively describe the stability boundary. Our results enable us to predict the optimal laser-cavity configuration with respect to positive-net-gain instabilities and therefore may be of great relevance for the future development of passively mode-locking semiconductor disk lasers.
https://doi.org/10.1103/PhysRevApplied.18.064070
Hardware-in-the-loop testing of a hybrid brake-by-wire system for electric vehicles. - In: SAE International journal of vehicle dynamics, stability, and NVH, ISSN 2380-2170, Bd. 6 (2022), 4, S. 477-487
Richtiger Name des Verfassers: Florian Büchner
Recent trends in automotive engineering, such as electrification and automatization, are opening chances as well as challenges due to the increased demand on new chassis components (e.g., drivetrain, brakes, steering, suspension, etc.) and control methods. This fast-growing market requires new methods to frontload as much efforts as possible to early design stages. The present article deals with a relevant case study on anti-lock braking system (ABS) design and tuning via hardware-in-the-loop (HIL) tests and rapid control prototyping (RCP) techniques on a hybrid brake-by-wire (BBW) system. Three types of wheel slip control algorithms are tested and benchmarked against each other. It was demonstrated that HIL simulations are suitable to develop vehicle subsystems and control strategies in a quite realistic manner even if the target vehicle or prototype is not available yet. Moreover, the benefits of continuous control approaches against classical rule-based wheel slip control were shown. In the article, aspects such as brake system architecture, control design, HIL testing environment, validation studies, and their analysis are further being discussed.
https://doi.org/10.4271/10-06-04-0031
Physikalische Chemie : Trendbericht. - In: Nachrichten aus der Chemie, ISSN 1868-0054, Bd. 70 (2022), 5, S. 64-67
Die Aufklärung von Reaktionsmechanismen ist in der Katalyse wichtig, um die geschwindigkeitsbegrenzende Schritte zu verstehen und zu beschleunigen. Mit maschinellem Lernen lassen dann sich auf Basis der Mechanismen neue Katalysatoren entwickeln. Photochemische Umsetzungen in weichen Membranen folgen einer anderen Kinetik als Reaktionen in Lösung. Mikroschwimmer, Mikromotoren oder Phototaxis zählen zu aktiver Materie. Sie wandeln kontinuierlich Energie aus ihrer Umgebung um und bewegen sich autonom.
https://doi.org/10.1002/nadc.20224122539
EVOLVE&hahog;INFOMAX: an unsupervised learning principle of invariances for nonlinear dynamic systems. - In: Industrial & engineering chemistry research, ISSN 1520-5045, Bd. 61 (2022), 49, S. 18004-18016
Invariant features characterize the essential nature of things behind the apparently rapid and noisy changes. Thus, learning invariances become one of the key problems of machine learning. Slow-feature analysis (SFA) is one such method. However, slowness in the original SFA, which is used as the learning criterion, is defined based on the linear temporal dependency assumption. To overcome this limitation, a new learning principle is introduced in this paper to define slowness that is suitable for nonlinear dynamic systems from an information perspective. This new principle is called EVOLVE&hahog;INFOMAX as it seeks to maximize the information preservation of system states during dynamic evolution, while aligning each feature to having the same uncertainty and constraining the features to be quasi-independent. The theoretical properties of this new principle are rigorously justified, which shows the characteristics of the model behavior, the optimality of the induced estimator, and the relationship with maximum likelihood estimation. The equivalence to the original definition of SFA is also analyzed, and the existence of a solution is shown. Two case studies show the potential capabilities and flexibility of the proposed method in both slow-feature extraction and downstream tasks, such as process monitoring.
https://doi.org/10.1021/acs.iecr.2c03330
Activated carbon prepared from waste tire pyrolysis carbon black via CO2/KOH activation used as supercapacitor electrode. - In: Science China, ISSN 1869-1900, Bd. 65 (2022), 10, S. 2337-2347
As the quantity of waste tires increases, more pyrolysis carbon black (CBp), a type of low value-added carbon black, is being produced. However, the application of CBp has been limited. Therefore, it is necessary to identify and expand applications of CBp. This work focuses on the preparation of activated carbon (AC) from CBp using the physicochemical activation of carbon dioxide (CO2) and potassium hydroxide (KOH). Thereafter, AC is applied to the electrode of the electrical double-layer capacitor (EDLC). The AC prepared by CO2/KOH activation exhibited a hierarchical pore structure. The specific surface area increased from 415 to 733 m^2 g^-1, and in combination with low ash content of 1.51%, ensured abundant ion diffusion channels and active sites to store charge. The EDLC comprising the AC (AC-2) electrode prepared by excitation of CO2 (300 sccm) and KOH had a reasonable gravimetric specific capacitance of 192 F g^-1 at 0.5 A g^-1, and exhibited a good rate capability of 73% at 50 A g^-1 in a three-electrode system. Moreover, the EDLC device comprising the AC-2 electrode delivered excellent cycling stability (capacitance retention of 106% after 10000 cycles at 2 A g^-1 in a two-electrode system). Furthermore, a symmetric supercapacitor based on an AC electrode that exhibits a supreme energy density of 4.7 Wh kg^-1 and a maximum power density of 6362.6 W kg^-1 is demonstrated.
https://doi.org/10.1007/s11431-021-2032-3