Vertex partition of hypergraphs and maximum degenerate subhypergraphs. - In: Electronic Journal of Graph Theory and Applications, ISSN 2338-2287, Bd. 9 (2021), 1, S. 1-9
https://doi.org/10.5614/ejgta.2021.9.1.1
Updated insights into 3D architecture electrodes for micropower sources. - In: Advanced materials, ISSN 1521-4095, Bd. 33 (2021), 45, 2103304, insges. 17 S.
Microbatteries (MBs) and microsupercapacitors (MSCs) are primary on-chip micropower sources that drive autonomous and stand-alone microelectronic devices for implementation of the Internet of Things (IoT). However, the performance of conventional MBs and MSCs is restricted by their 2D thin-film electrode design, and these devices struggle to satisfy the increasing IoT energy demands for high energy density, high power density, and long lifespan. The energy densities of MBs and MSCs can be improved significantly through adoption of a 2D thick-film electrode design; however, their power densities and lifespans deteriorate with increased electrode thickness. In contrast, 3D architecture electrodes offer remarkable opportunities to simultaneously improve MB and MSC energy density, power density, and lifespan. To date, various 3D architecture electrodes have been designed, fabricated, and investigated for MBs and MSCs. This review provides an update on the principal superiorities of 3D architecture electrodes over 2D thick-film electrodes in the context of improved MB and MSC energy density, power density, and lifespan. In addition, the most recent and representative progress in 3D architecture electrode development for MBs and MSCs is highlighted. Finally, present challenges are discussed and key perspectives for future research in this field are outlined.
https://doi.org/10.1002/adma.202103304
Recent development of electrocatalytic CO2 reduction application to energy conversion. - In: Small, ISSN 1613-6829, Bd. 17 (2021), 44, 2100323, insges. 29 S.
Im Titel ist "2" tiefgestellt
Carbon dioxide (CO2) emission has caused greenhouse gas pollution worldwide. Hence, strengthening CO2 recycling is necessary. CO2 electroreduction reaction (CRR) is recognized as a promising approach to utilize waste CO2. Electrocatalysts in the CRR process play a critical role in determining the selectivity and activity of CRR. Different types of electrocatalysts are introduced in this review: noble metals and their derived compounds, transition metals and their derived compounds, organic polymer, and carbon-based materials, as well as their major products, Faradaic efficiency, current density, and onset potential. Furthermore, this paper overviews the recent progress of the following two major applications of CRR according to the different energy conversion methods: electricity generation and formation of valuable carbonaceous products. Considering electricity generation devices, the electrochemical properties of metal-CO2 batteries, including Li-CO2, Na-CO2, Al-CO2, and Zn-CO2 batteries, are mainly summarized. Finally, different pathways of CO2 electroreduction to carbon-based fuels is presented, and their reaction mechanisms are illustrated. This review provides a clear and innovative insight into the entire reaction process of CRR, guiding the new electrocatalysts design, state-of-the-art analysis technique application, and reaction system innovation.
https://doi.org/10.1002/smll.202100323
Control of port-Hamiltonian systems with minimal energy supply. - In: European journal of control, ISSN 1435-5671, Bd. 62 (2021), S. 33-40
We investigate optimal control of linear port-Hamiltonian systems with control constraints, in which one aims to perform a state transition with minimal energy supply. Decomposing the state space into dissipative and non-dissipative (i.e. conservative) subspaces, we show that the set of reachable states is bounded w.r.t. the dissipative subspace. We prove that the optimal control problem exhibits the turnpike property with respect to the non-dissipative subspace, i.e., for varying initial conditions and time horizons optimal state trajectories evolve close to the conservative subspace most of the time. We analyze the corresponding steady-state optimization problem and prove that all optimal steady states lie in the non-dissipative subspace. We conclude this paper by illustrating these results by a numerical example from mechanics.
https://doi.org/10.1016/j.ejcon.2021.06.017
Molecular characterization of hematopoietic stem cells after in vitro amplification on biomimetic 3D PDMS cell culture scaffolds. - In: Scientific reports, ISSN 2045-2322, Bd. 11 (2021), 21163, S. 1-14
Hematopoietic stem cell (HSC) transplantation is successfully applied since the late 1950s. However, its efficacy can be impaired by insufficient numbers of donor HSCs. A promising strategy to overcome this hurdle is the use of an advanced ex vivo culture system that supports the proliferation and, at the same time, maintains the pluripotency of HSCs. Therefore, we have developed artificial 3D bone marrow-like scaffolds made of polydimethylsiloxane (PDMS) that model the natural HSC niche in vitro. These 3D PDMS scaffolds in combination with an optimized HSC culture medium allow the amplification of high numbers of undifferentiated HSCs. After 14 days in vitro cell culture, we performed transcriptome and proteome analysis. Ingenuity pathway analysis indicated that the 3D PDMS cell culture scaffolds altered PI3K/AKT/mTOR pathways and activated SREBP, HIF1α and FOXO signaling, leading to metabolic adaptations, as judged by ELISA, Western blot and metabolic flux analysis. These molecular signaling pathways can promote the expansion of HSCs and are involved in the maintenance of their pluripotency. Thus, we have shown that the 3D PDMS scaffolds activate key molecular signaling pathways to amplify the numbers of undifferentiated HSCs ex vivo effectively.
https://doi.org/10.1038/s41598-021-00619-6
Hamiltonicity of randomly perturbed graphs. - In: Extended abstracts EuroComb 2021, (2021), S. 38-44
The theory of randomly perturbed graphs deals with the properties of graphs obtained as the union of a deterministic graph H and a random graph G. We study Hamiltonicity in two distinct settings. In both of them, we assume H is some deterministic graph with minimum degree at least αn, for some α (possibly depending on n). We first consider the case when G is a random geometric graph, and obtain an asymptotically optimal result. We then consider the case when G is a random regular graph, and obtain different results depending on the regularity.
Path decompositions of random directed graphs. - In: Extended abstracts EuroComb 2021, (2021), S. 702-706
In this work we consider extensions of a conjecture due to Alspach, Mason, and Pullman from 1976. This conjecture concerns edge decompositions of tournaments into as few paths as possible. There is a natural lower bound for the number paths needed in an edge decomposition of a directed graph in terms of its degree sequence; the conjecture in question states that this bound is correct for tournaments of even order. The conjecture was recently resolved for large tournaments, and here we investigate to what extent the conjecture holds for directed graphs in general. In particular, we prove that the conjecture holds with high probability for the random directed graph Dn,pDn,pD_{n,p} for a large range of p.
Nanocomplex of Berberine with C60 fullerene is a potent suppressor of Lewis lung carcinoma cells invasion in vitro and metastatic activity in vivo. - In: Materials, ISSN 1996-1944, Bd. 14 (2021), 20, 6114, insges. 15 S.
Im Titel ist "60" tiefgestellt
Effective targeting of metastasis is considered the main problem in cancer therapy. The development of herbal alkaloid Berberine (Ber)-based anticancer drugs is limited due to Ber’ low effective concentration, poor membrane permeability, and short plasma half-life. To overcome these limitations, we used Ber noncovalently bound to C60 fullerene (C60). The complexation between C60 and Ber molecules was evidenced with computer simulation. The aim of the present study was to estimate the effect of the free Ber and C60-Ber nanocomplex in a low Ber equivalent concentration on Lewis lung carcinoma cells (LLC) invasion potential, expression of epithelial-to-mesenchymal transition (EMT) markers in vitro, and the ability of cancer cells to form distant lung metastases in vivo in a mice model of LLC. It was shown that in contrast to free Ber its nanocomplex with C60 demonstrated significantly higher efficiency to suppress invasion potential, to downregulate the level of EMT-inducing transcription factors SNAI1, ZEB1, and TWIST1, to unblock expression of epithelial marker E-cadherin, and to repress cancer stem cells-like markers. More importantly, a relatively low dose of C60-Ber nanocomplex was able to suppress lung metastasis in vivo. These findings indicated that сomplexation of natural alkaloid Ber with C60 can be used as an additional therapeutic strategy against aggressive lung cancer.
https://doi.org/10.3390/ma14206114
Design and analysis of a mechanical ventilation system based on cams. - In: Heliyon, ISSN 2405-8440, Bd. 7 (2021), 10, e08195, S. 1-16
Low-cost mechanical ventilators have been developed in order to deal with the shortage of traditional ventilators whose quantity is not sufficient in an emergency context in Perú. Protofy, a company from Spain, designed one of the first low-cost mechanical ventilation systems OxyGEN which was approved by a medicine agency in its country in special context of COVID 19. Therefore, as main of this article, a redesign of this system named OxygenIP.PE was carried out according to local requirements and available technology, but maintaining its working concept based on compression mechanism by cams. Sensors were added and a control algorithm of the respiratory rate was developed. Ventilation curves monitoring over time was implemented; in this sense, a mathematical model of the whole system was developed. OxygenIP.PE was redesigned, fabricated, and tested measuring its ventilation curves over time. Results indicate that this redesign provides a sturdy equipment able to work during a longer lifetime than the original. The replicability of the ventilation curves behavior is ensured, while the mechanism dimensions are adapted for a particular airbag resuscitator. The mathematical model of the whole system can satisfactorily determine the ventilation curves over time and is used to show the air pressure, volume, and flow as a function of the compression arm's angular position and differential pressure through the breathing circuit measurement, furthermore the algorithms designed as a consequence of the mathematical model were implemented for Raspberry and ARDUINO microcontrollers. There were obtained parameters of pressure 10-65 cmH2O, airflow 50-65 l/m, volume 0-0.5 l, at two values of beat per minute (BPM) 15 and 25.
https://doi.org/10.1016/j.heliyon.2021.e08195
A route to obtaining low-defect III-V epilayers on Si(100) utilizing MOCVD. - In: Crystal growth & design, ISSN 1528-7505, Bd. 21 (2021), 10, S. 5603-5613
Low-defect III-V multilayer structures grown on Si(100) open opportunities for a wide range of cost-effective high-performance photovoltaic and optoelectronic devices. For that, (Al)GaP epilayers prepared almost lattice-matched on Si(100) substrates can serve as high-quality virtual substrates for subsequent heteroepitaxial growth. The evolution of crystal defects, such as stacking fault pyramids or threading dislocations, needs to be impeded already during the first preparation step, the III-V-on-Si nucleation, as they tend to propagate into the subsequently grown layers and increase nonradiative electron-hole recombination rates, which finally degrade the device performance. We establish a ternary GaP/AlP pulsed nucleation process on Si(100) substrates fabricated by metalorganic chemical vapor deposition, and compare it to the defect evolution from pure GaP nucleation layers (NLs). The entire procedure was optically monitored in situ using reflection anisotropy spectroscopy. Crystal defects were investigated by electron channeling contrast imaging. GaP grown on GaP/AlP NLs exhibits drastically reduced densities of threading dislocations and stacking faults by 1 and 2 orders of magnitude, respectively, compared to buffer layers grown on binary GaP NLs. We observed that the surface morphology at the initial stage of growth of these buffer layers is significantly smoother compared to the buffer layers grown on pure GaP NLs using atomic force microscopy. The proposed nucleation procedure here is supposed to substantially improve the crystalline quality of III-V buffer layers integrated on Si(100) wafers.
https://doi.org/10.1021/acs.cgd.1c00410