104,328 results on '"STABILITY"'
Search Results
2. An Integrated Deposition and Passivation Strategy for Controlled Crystallization of 2D/3D Halide Perovskite Films
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Kodalle, Tim, Byranvand, Malekshahi, Goudreau, Meredith, Das, Chittaranjan, Roy, Rajarshi, Kot, Małgorzata, Briesenick, Simon, Zohdi, Mohammadreza, Rai, Monika, Tamura, Nobumichi, Flege, Jan Ingo, Hempel, Wolfram, Sutter‐Fella, Carolin M, and Saliba, Michael
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Macromolecular and Materials Chemistry ,Chemical Sciences ,Physical Chemistry ,Engineering ,Materials Engineering ,2D/3D perovskites ,crystallization ,in situ characterization ,stability ,Physical Sciences ,Nanoscience & Nanotechnology ,Chemical sciences ,Physical sciences - Abstract
This work introduces a simplified deposition procedure for multidimensional (2D/3D) perovskite thin films, integrating a phenethylammonium chloride (PEACl)-treatment into the antisolvent step when forming the 3D perovskite. This simultaneous deposition and passivation strategy reduces the number of synthesis steps while simultaneously stabilizing the halide perovskite film and improving the photovoltaic performance of resulting solar cell devices to 20.8%. Using a combination of multimodal in situ and additional ex situ characterizations, it is demonstrated that the introduction of PEACl during the perovskite film formation slows down the crystal growth process, which leads to a larger average grain size and narrower grain size distribution, thus reducing carrier recombination at grain boundaries and improving the device's performance and stability. The data suggests that during annealing of the wet film, the PEACl diffuses to the surface of the film, forming hydrophobic (quasi-)2D structures that protect the bulk of the perovskite film from humidity-induced degradation.
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- 2024
3. Iceberg Hashing: Optimizing Many Hash-Table Criteria at Once.
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BENDER, MICHAEL A., CONWAY, ALEX, FARACH-COLTON, MARTÍN, KUSZMAUL, WILLIAM, and TAGLIAVINI, GUIDO
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ICEBERGS ,COMPUTER science - Abstract
Despite being one of the oldest data structures in computer science, hash tables continue to be the focus of a great deal of both theoretical and empirical research. A central reason for this is that many of the fundamental properties that one desires from a hash table are difficult to achieve simultaneously; thus many variants offering different trade-offs have been proposed. This article introduces Iceberg hashing, a hash table that simultaneously offers the strongest known guarantees on a large number of core properties. Iceberg hashing supports constant-time operationswhile improving on the state of the art for space efficiency, cache efficiency, and low failure probability. Iceberg hashing is also the first hash table to support a load factor of up to 1-o(1) while being stable, meaning that the positionwhere an element is stored only ever changes when resizes occur. In fact, in the setting where keys are T(logn) bits, the space guarantees that Iceberg hashing offers, namely that it uses at most log x |U | n x +O(n log logn) bits to store n items froma universeU, matches a lower bound by Demaine et al. that applies to any stable hash table. Iceberg hashing introduces new general-purpose techniques for some of the most basic aspects of hashtable design. Notably, our indirection-free technique for dynamic resizing, which we call waterfall addressing, and our techniques for achieving stability and very-high probability guarantees, can be applied to any hash table that makes use of the front-yard/backyard paradigm for hash table design. [ABSTRACT FROM AUTHOR]
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- 2023
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4. Atmospheric Humidity Underlies Irreproducibility of Formamidinium Lead Iodide Perovskites
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Park, Keonwoo, Tan, Shaun, Kodalle, Tim, Lee, Do‐Kyoung, Abdelsamie, Maged, Park, Ji‐Sang, Lee, Joo‐Hong, Jung, Sung‐Kwang, Ko, Jeong Hoon, Park, Nam‐Gyu, Sutter‐Fella, Carolin M, Yang, Yang, and Lee, Jin‐Wook
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Macromolecular and Materials Chemistry ,Chemical Sciences ,Physical Chemistry ,crystallizations ,halide perovskites ,humidity ,in situ studies ,reproducibility ,scalability ,solar cells ,stability ,Physical Sciences ,Engineering ,Nanoscience & Nanotechnology ,Chemical sciences ,Physical sciences - Abstract
Metal halide perovskite solar cells (PSCs) are infamous for their batch-to-batch and lab-to-lab irreproducibility in terms of stability and performance. Reproducible fabrication of PSCs is a critical requirement for market viability and practical commercialization. PSC irreproducibility plagues all levels of the community; from institutional research laboratories, start-up companies, to large established corporations. In this work, the critical function of atmospheric humidity to regulate the crystallization and stabilization of formamidinium lead triiodide (FAPbI3) perovskites is unraveled. It is demonstrated that the humidity content during processing induces profound variations in perovskite stoichiometry, thermodynamic stability, and optoelectronic quality. Almost counterintuitively, it is shown that the presence of humidity is perhaps indispensable to reproduce phase-stable and efficient FAPbI3-based PSCs.
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- 2024
5. Examining Pareto Law across department store shoppers.
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Tanusondjaja, Arry, Romaniuk, Jenni, Nenycz-Thiel, Magda, Sakashita, Mototaka, and Viswanathan, Vijay
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CUSTOMER retention ,CONSUMERS ,CUSTOMER loyalty programs ,DEPARTMENT stores ,CHAIN stores ,CUSTOMER loyalty ,REVENUE accounting - Abstract
Department stores invest in loyalty strategies that largely focus on retaining current high value customers in response to increasing competition in retail shopping. In this study, we examine the contribution of the top 20% customers for transaction frequency and value ("heavy buyers") to the total sales, and the consistency of this contribution across departments within a store. We also investigate the heavy buyer stability over time across 3 years, from over 550 million transactions from a department store chain in East Asia. The results show that the Pareto ratio of the top 20% spenders account for 71% of revenue (and 52% of the total transactions), and the top 20% transactors represent 58% of revenue (and 62% of total transactions), which may signal the role of such heavy buyers to overall stores sales. At each department level, the heavy buyers (by value) contribute from 65% to 86% of the department revenue. Despite this, the stability of the top 20% segment over time varies greatly by department from 11% to 74%. Finally, whether high value customers in one department store also translate across departments, depends mainly on the department size in terms of its shopper penetration. The research furthers our knowledge on Pareto Law, with important implications for customer retention strategies and loyalty programs especially for retailers. [ABSTRACT FROM AUTHOR]
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- 2023
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6. Identification of guar [Cyamopsis tetragonoloba (L.) Taub.] genotypes with wider adaptability to rainfed environments through stability analysis
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Sharma, Manish, Patel, P. J., Patel, P. R., and Patel, M. P.
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- 2024
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7. Stability analysis on elite genotypes of Indian Mustard (Brassica Juncea L.) in Terai Agro-Climatic region
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Sadhu, Supratim, Chakraborty, Moumita, Roy, Suvendu Kumar, Mondal, Amitava, and Dey, Susmita
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- 2024
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8. Temporal Variability of the Dominant Fecal Microbiota in Healthy Adult Cats.
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Sung, Chi-Hsuan, Marsilio, Sina, Pilla, Rachel, Wu, Yu-An, Cavasin, Joao, Hong, Min-Pyo, and Suchodolski, Jan
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Clostridium hiranonis ,Peptacetobacter hiranonis ,bile acid ,dysbiosis index ,feline ,microbiota ,stability ,variability - Abstract
While shifts in gut microbiota have been studied in diseased states, the temporal variability of the microbiome in cats has not been widely studied. This study investigated the temporal variability of the feline dysbiosis index (DI) and the abundance of core bacterial groups in healthy adult cats. The secondary aim was to evaluate the relationship between the fecal abundance of Clostridium hiranonis and the fecal concentrations of unconjugated bile acids. A total of 142 fecal samples collected from 17 healthy cats were prospectively included: nine cats with weekly collection over 3 weeks (at least four time points), five cats with monthly collection over 2 months (three time points), and three cats with additional collections for up to 10 months. The DI remained stable within the reference intervals over two months for all cats (Friedman test, p > 0.2), and 100% of the DI values (n = 142) collected throughout the study period remained within the RI. While some temporal individual variation was observed for individual taxa, the magnitude was minimal compared to cats with chronic enteropathy and antibiotic exposure. Additionally, the abundance of Clostridium hiranonis was significantly correlated with the percentage of fecal primary bile acids, supporting its role as a bile acid converter in cats.
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- 2024
9. Preferential cannibalism as a key stabilizing mechanism of intraguild predation systems with trophic polymorphic predators
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Woodie, Clara A and Anderson, Kurt E
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Biological Sciences ,Ecology ,Biotechnology ,Genetics ,Inducible trophic polymorphism ,Cannibalism ,Intraguild predation ,Preference ,Stability - Abstract
Abstract: Theory predicts intraguild predation (IGP) to be unstable despite its ubiquity in nature, prompting exploration of stabilizing mechanisms of IGP. One of the many ways IGP manifests is through inducible trophic polymorphisms in the intraguild (IG) predator, where a resource-eating predator morph competes with the intraguild (IG) prey for the shared resource while a top predator morph consumes the IG prey. Cannibalism is common in this type of system due to the top predator morph’s specialization on the trophic level below it, which includes the resource-eating predator morph. Here, we explore the consequences of inducible trophic polymorphisms in cannibal predators for IGP stability using an IGP model with and without cannibalism. We employ linear stability analysis and identify regions of coexistence based on the top predator morph’s preference for conspecifics vs. heterospecifics and the IG prey’s competitive ability relative to the resource-eating morph. Our findings reveal that preferential cannibalism (i.e., the preferential consumption of conspecifics) stabilizes the system when the IG prey and resource-eating morph have similar competitive abilities for the shared resource. Though original IGP theory finds that the IG prey must be a superior resource competitor as a general criterion for coexistence, this is not typically the case when the predator has an inducible trophic polymorphism and the resource-eating morph is specialized in resource acquisition. Preferential cannibalism may therefore be a key stabilizing mechanism in IGP systems with a cannibalistic, trophic polymorphic IG predators, providing further insight into what general mechanisms stabilize the pervasive IGP interaction.
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- 2024
10. Effects of copper doping on microstructural evolution and oxygen permeability of Ce0.8Sm0.2O2-δ-Sm0.6Sr0.4Fe1-xCuxO3-δ dual-phase oxygen permeable membranes.
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Yu, Qian, Liang, Bilin, Jia, Siqi, Li, Fang, and Li, Qiming
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ATMOSPHERIC carbon dioxide , *DOPING agents (Chemistry) , *SCANNING electron microscopy , *X-ray spectroscopy , *X-ray diffraction - Abstract
Ce 0.8 Sm 0.2 O 2-δ (wt.70 %)-Sm 0.6 Sr 0.4 Fe 1- x Cu x O 3-δ (wt.30 %) (SDC-SSFC) dual-phase oxygen permeable membranes were prepared by one-pot EDTA-citric acid combined complexing method. Effects of copper doping content on crystallographic phase, microstructure and oxygen permeability were deeply investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDXS). Systematic studies reveal that SDC as oxygen ion conductors and SSFC as electron conductor display an excellent synergistic effect only if a suitable doping content of copper was adopted. It can be found that Ce 0.8 Sm 0.2 O 2-δ -Sm 0.6 Sr 0.4 Fe 0.9 Cu 0.1 O 3-δ exhibits the highest oxygen permeation flux of up to about 0.61 ml cm−2 at 950 °C and lower oxygen permeation activation energy, which displays nearly a two-fold increase in oxygen permeability compared with the sample without any copper doping. If the copper doping content in B-site of SSFC perovskite exceeds about 30 %, a third phase, i.e., CuO, would appear in the bulk of SDC-SSFC dual-phase membrane and the grain size of CuO tend to gradually increase which would degrade the oxygen permeability of SDC-SSFC dual-phase membrane. Kinetical analysis showed that the critical membrane thickness (L c) of Ce 0.8 Sm 0.2 O 2-δ -Sm 0.6 Sr 0.4 Fe 0.9 Cu 0.1 O 3-δ membrane is close to approximately 0.6 mm, i.e., if the membrane thickness is larger than 0.6 mm, its rate-determining step would transform into the bulk-diffusion exchange from surface exchange. Meanwhile, Ce 0.8 Sm 0.2 O 2-δ -Sm 0.6 Sr 0.4 Fe 0.9 Cu 0.1 O 3-δ membrane exhibits a stable oxygen permeation flux of up to 0.32 ml cm−2·min−1 in pure CO 2 atmosphere for more than 120 h without any degradation. [ABSTRACT FROM AUTHOR]
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- 2024
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11. Structure stability and CO2 absorption mechanism on surfaces of B-site doped SrFeO3-δ perovskite ceramic membrane.
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Liu, Yanbo, Shen, Guocan, Li, Jiamin, Ma, Jiajie, Duan, Tong, Sun, Qiangchao, Chen, Sha, Lu, Xionggang, and Cheng, Hongwei
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CARBON sequestration , *SOLID oxide fuel cells , *CARBON dioxide , *THERMAL expansion , *LATTICE constants - Abstract
Perovskite oxides have huge potential applications in carbon capture and utilization as oxygen transport membranes (OTM) and solid oxide fuel cell (SOFC) electrodes. SrFeO 3- δ -based perovskite material, as the promising candidate, possesses high mixed ionic-electronic conductivity, but its partial application is impeded by poor stability under CO 2 conditions. In this work, SrFe 0.9 M 0.1 O 3- δ (SFM, M = Fe, Al, Zr, Nb, W) ceramic membranes were synthesized to study the effects of different valence B-site ions doping on the stability and CO 2 adsorption process of perovskite oxides. The phase structure, thermal expansion property, CO 2 tolerance, and CO 2 absorption mechanism on surfaces of SFM were investigated systematically. B-site doping stables the pure cubic structure, improves the high-temperature structural stability, and reduces the thermal expansion coefficient (TEC) by increasing the lattice parameters and metal-oxygen average binging energy (ABE) of SFM. Moreover, density functional theory (DFT) calculations indicate that although B-site ions doping promotes the adsorption of CO 2 on the FeO 2 -terminated, it inhibits CO 2 adsorption on the Sr-O-Sr site after Zr4+, Nb5+, and W6+ doping, causing the reduction of the CO 2 desorption. The results offer new insights for designing perovskite oxides in the carbon neutralization field. • Different valence ions B-site dope SrFeO 3- δ perovskite oxide used in the CCUS. • SrFe 0.9 M 0.1 O 3- δ (SFM, M = Fe, Al, Zr, Nb, W) ceramic membranes are synthesized. • The increase of lattice parameters stabilizes the cubic structure of SFM. • The structure stability at high temperatures is improved by B-site ion doping. • The CO 2 adsorption mechanism on the SFM surfaces is revealed by DFT calculations. [ABSTRACT FROM AUTHOR]
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- 2024
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12. Stabilization of nonlinear safety-critical systems by relaxed converse Lyapunov-barrier approach and its applications in robotic systems.
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Li, Haoqi, Hu, Jiangping, Hu, Xiaoming, and Ghosh, Bijoy K.
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Combining safety objectives with stability objectives is crucial for safety-critical systems. Existing studies generally unified these two objectives by constructing Lyapunov-type barrier functions. However, insufficient analysis of key set relationships within the system may render the proposed safety and stability conditions conservative, and these studies also did not provide how to use such conditions to design safety-stability control strategies. This paper proposed a feasible and constructive design to achieve stabilization of safety-critical systems by a relaxed converse Lyapunov-barrier approach. By analyzing the relationships between a series of sets associated with the safety-critical system, the stability and safety conditions can be appropriately relaxed. Then, with the help of relaxed converse control Lyapunov-barrier functions (RCCLBFs), a theoretical result was obtained for the stability of affine nonlinear systems with safety constraints. Subsequently, a constructive method was developed for a second-order strict-feedback system to transform the process of solving RCCLBFs into a Lyapunov-like stabilization problem. Finally, the proposed safety-stability control method is exerted on a robotic system and demonstrated by simulations. [ABSTRACT FROM AUTHOR]
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- 2024
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13. High-performance electrochromic devices composed of niobium tungsten oxide films.
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Kang, Kwang-Mo and Nah, Yoon-Chae
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TUNGSTEN oxides , *NIOBIUM oxide , *ELECTROCHROMIC substances , *OPTICAL modulation , *OXIDE coating , *ELECTROCHROMIC devices - Abstract
Electrochromic technology plays a pivotal role in various industries, offering significant benefits in energy efficiency and sustainability. By efficiently modulating sunlight, it reduces dependence on traditional climate control systems, thus decreasing overall energy consumption. Among electrochromic materials, tungsten oxide (WO 3) is highly favored for its outstanding stability and superior optical modulation amplitude. However, the escalating demands of commercial applications necessitate enhancements in electrochromic performance, achievable through doping or composite designs. This study investigates the electrochromic characteristics of novel niobium tungsten oxide (Nb 18 W 16 O 93) thin films, employing a gel electrolyte and examining their structural, optical, and electrochemical attributes. Compared to pure WO 3 , the Nb 18 W 16 O 93 -based electrochromic device exhibited a significant optical modulation of 55.1% in the visible spectrum and 31.3% in the near-infrared region. The gel-based device not only provides safety benefits over liquid electrolytes by mitigating leakage risks but also features rapid switching response times, with a coloration duration of 3.9 s and a bleaching interval of 3.6 s. Moreover, the device showcases exceptional long-term stability, retaining a ΔT of nearly 72% after 10,000 cycles. [ABSTRACT FROM AUTHOR]
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- 2024
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14. A mathematical model to study the role of dystrophin protein in tumor micro-environment.
- Author
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Padder, Ausif, Rahman Shah, Tafaz Ul, Afroz, Afroz, Mushtaq, Aadil, and Tomar, Anita
- Abstract
In this research work, the authors have developed a mathematical model to examine the interaction between dystrophin protein and tumor. The authors formulated a system of ordinary differential equations to describe the dynamics of the dystrophin-tumor interaction system. Jacobian matrix and Routh–Hurwitz stability techniques were used to determine equilibrium points, perform stability and bifurcation analysis, and establish the conditions required for the stability of the proposed model. Numerical simulations are performed using Euler's method to investigate the temporal evolution of the proposed model under different parameter values, such as tumor growth rate and feedback strength of dystrophin protein. The numerical results are presented in tables, and corresponding to each table, a graphical analysis is done. The graphical analysis includes creating phase portraits to visually represent stability regions around the equilibrium points, bifurcation diagrams to identify critical points, and time series analysis to highlight the behavior of the proposed model. The authors explore how variations in dystrophin expression impact tumor progression, identifying potential therapeutic implications of maintaining higher dystrophin levels. This comprehensive analysis enhances our understanding of the dystrophin-tumor interaction, providing a basis for further experimental validation and potential therapeutic strategies. [ABSTRACT FROM AUTHOR]
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- 2024
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15. Stability in Parametric Resonance of a Controlled Stay Cable with Time Delay.
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Peng, Jian, Xia, Hui, Sun, Hongxin, and Lenci, Stefano
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TIME delay systems , *MULTIPLE scale method , *EQUATIONS of motion , *NONLINEAR equations , *RESONANCE - Abstract
The stability of the parametric resonance of a controlled stay cable with time delay is investigated. The in-plane nonlinear equations of motion are initially determined via the Hamilton principle. Then, utilizing the method of multiple scales, the modulation equations that govern the nonlinear dynamics are obtained. These equations are then utilized to investigate the effect of time delays on the amplitude and frequency-response behavior and, subsequently, on the stability of the parametric resonance of the controlled cable, that it is shown to depend on the excitation amplitude and the commensurability of the delayed-response frequency to the excitation frequency. The stability region of the parametric resonance is shifted, and the effects of control on the cable become worse by increasing time delay. The work plays a guiding role in the parametric design of the control system for stay cables. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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16. The stabilizing effect of temperature and magnetic field on a 2D magnetic Bénard fluids.
- Author
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Lai, Suhua, Shen, Linxuan, Ye, Xia, and Zhao, Xiaokui
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MAGNETIC field effects , *MAGNETIC fluids , *MAGNETIC fields , *EULER equations , *HYDRAULIC couplings - Abstract
In this paper we study the stability of a special magnetic Bénard system near equilibrium, where there exists Laplacian magnetic diffusion and temperature damping but the velocity equation involves no dissipation. Without any velocity dissipation, the fluid velocity is governed by the two-dimensional incompressible Euler equation, whose solution can grow rapidly in time. However, when the fluid is coupled with the magnetic field and temperature through the magnetic Bénard system, we show that the solution is stable. Our results mathematically illustrate that the magnetic field and temperature have the effect of enhancing dissipation and contribute to stabilize the fluid. [ABSTRACT FROM AUTHOR]
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- 2024
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17. Crucial aspects for maintaining rAAV stability.
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Lengler, Johannes, Gavrila, Mia, Brandis, Janina, Palavra, Kristina, Dieringer, Felix, Unterthurner, Sabine, Fuchsberger, Felix, Kraus, Barbara, and Bort, Juan A. Hernandez
- Abstract
The storage of rAAV vectors for gene therapy applications is critical for ensuring a constant product quality and defined amount of medication at the time of administration. Therefore, we determined the influence of different storage conditions on the physicochemical and biological properties of rAAV8 and rAAV9 preparations. Particular attention was paid to short-term storage, which plays a crucial role in both the manufacturing process and in clinical applications. Additionally, we addressed the question, of viability of rAAV8 and rAAV9 when subjected to very low-temperature storage conditions (below −65 °C) or lyophilization. To determine the impact on rAAV vectors, various analyses were used, including the quantification of capsid and genome titers, as well as biopotency assessments, which are pivotal determinants in characterizing vector behavior and efficacy. Our data showed that freeze/thaw cycles hardly affected the functionality of rAAV9-aGAL vectors. In contrast, prolonged storage at room temperature for several days, resulted in a discernible decrease in biopotency despite consistent capsid and genome titers. When the storage temperature was further increased, the rAAV8-aGAL decay accelerated. For example, a short-term exposure of + 40 °C and more, led to a reduction in the physical viral titer and to an even faster decline in efficacy determined by biopotency. However, the addition of sucrose and sorbitol to the rAAV9-aGAL and rAAV9-GAA preparations reduced the temperature sensitivity of rAAV and improved its stability. Furthermore, exposure of rAAV9-aGAL to highly acidic conditions (pH 2.5) dramatically reduced its biopotency by 70% or more. Most interestingly, a long-term storage of rAAV9-aGAL and rAAV8-FVIII vectors over 12 and 36 months, respectively, demonstrated exceptional stability at storage temperatures below −65 °C. Also, lyophilization conserved functionality for at least 10 months. Our data showed how to maintain rAAV biopotency levels over the time without substantial loss. Storage at very low temperatures (below −65 °C) preserved its effectiveness over years. Overall, pH and temperature conditions during the manufacturing process, storage and clinical application are worth considering. Consistency in the rAAV capsid titer determination did not necessarily indicate the preservation of biopotency. In conclusion, our approach determined several options for maximizing rAAV stability. [ABSTRACT FROM AUTHOR]
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- 2024
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18. Genotype × environment interactions analysis for chickpea grain yield and related traits by a mixed model approach.
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Khan, Abdul Manan, Ali, Zulfiqar, Mohsin, Ata ul, Soomro, Aijaz Ahmed, Hussain, Khalid, Rafiq, Muhammad, Hussain, Niaz, Ahmad, Qadeer, Ahmed, Ishfaq, Khan, Muhammad Ijaz, Shaikh, Muhammad Naeem, Matloob, Amar, Akram, Zahid, Shabbir, Ghulam, Hassan, Mahmood ul, Waqas, Muhammad Umair, Hussain, Israr, Rani, Saima, Malik, Shahid Riaz, and Rehman, Ata ur
- Abstract
The study of genotype × environment interaction is crucial for plant breeders to introduce new cultivar(s) with improved and stable yield performance. The productivity of chickpea crops is very low in Pakistan. It requires the selection of genotypes with optimal productivity for diverse environmental conditions. Fourteen different chickpea genotypes were assessed using the linear mixed model to evaluate genotypes across four diverse chickpea growing regions, including Attock (Punjab), Bhakkar (Punjab), Karak (Khyber Pakhtunkhwa), and Larkana during the year 2017–19. The environmental effect was pronounced and contributed significantly to variation (25.8%) in grain yield. Analysing genotype × environmental interactions at multiple locations facilitates ranking superior genotypes that excel in specific or diverse environments. Notably, the genotypes, viz., Fakhr-e-Thal and Bhakkar-2011, demonstrated superior performance in terms of overall grain yield. Utilising a multitrait stability index, Bittal-2016 and Thal-2006 exhibited the most stable genotypes across various environments and were observed suitable for diverse growing regions. While, for specific environmental conditions, genotypes, i.e., KK-1, Noor-2013 and Fakhr-e-thal, exhibited higher yields and stability. This showed their adaptability to the particular environment. The present study revealed that Larkana as the mega environment was conducive to higher yield, while Attock, Bhakkar, and Karak sites were less favorable for KK-3, DG-89, and Dasht. The BLUP outperformed the AMMI in our analysis of evaluating multi-location trials. The integration of WAASBY and MTSI indices proved useful in differentiating between high yielding genotypes and those with stable performance. These tools are essential for breeders aiming to select genotypes that will perform consistently across diverse environmental conditions. [ABSTRACT FROM AUTHOR]
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- 2024
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19. Advancing precision in medical image segmentation: A performance analysis of loss functions for COVID‐19 lung infection segmentation in computed tomography images.
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Delgado, Emilio, Rodriguez‐Echeverria, Roberto, Fernández‐García, Antonio Jesús, Gutiérrez, Juan D., and Suero‐Rodrigo, Miguel Ángel
- Abstract
This study evaluates the effectiveness of three loss functions Asymmetric Unified Focal Loss (AUFL), Dice Similarity Coefficient Loss (DSCL), and Cross‐Entropy (CE) for segmenting COVID‐19 lung infections in computed tomography images. Detailed analyses using the intersection over union metric assessed each function's accuracy. AUFL achieved an average Dice Similarity Coefficient (DSC) of 85.18% ± 8.86%, outperforming DSCL 85.18% ± 8.86%, which had the same average DSC but less precise segmentation, and CE, which had an average DSC of 78.31% ± 11.93%. Segmentations using AUFL demonstrated more defined contours and better alignment with actual anatomical structures than those obtained with DSCL and CE. Observations revealed that AUFL‐generated segmentations had more precise boundaries and were more consistent with the expected anatomical regions of lung infections. This study is the first to quantitatively and qualitatively compare the effectiveness of AUFL, DSCL, and CE in segmenting COVID‐19 lung infections, providing concrete evidence of AUFL's superiority in segmentation performance and reliability for clinical applications. The findings underscore the importance of selecting appropriate loss functions to enhance segmentation in medical imaging, highlighting their crucial role in improving image‐based diagnostics and treatment. The study emphasizes the need for ongoing research to optimize these segmentation techniques further. [ABSTRACT FROM AUTHOR]
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- 2024
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20. Enhanced Performance of CsPbBr3 Nanocrystals via Dual Passivation.
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Sun, Yujiao, Cheng, Yongchao, Yang, Zijiang, Bian, Ce, Huang, Sheng, and Gu, Xiuquan
- Abstract
Perovskite CsPbBr3 nanocrystals show excellent optical properties. However, the nanocrystals encounter a major challenge of poor stability. In this study, an effective approach is proposed for enhancing the stability of CsPbBr3 nanocrystals via a dual passivation strategy, where the dual passivation layer is composed of alumina (Al2O3) and polymer ethylene‐vinyl acetate (EVA). The Al2O3 coating on the CsPbBr3 surface is realized by in situ oxidation of trimethyl aluminum (TMA), which passivated the surface defects while blocking the intrusion of water and oxygen. The EVA film is formed by a solution method, which can further block the water and oxygen, and form the flexible composite with perovskite CsPbBr3 nanocrystals with enhanced stability toward water and heat. After soaking for 360 h and heating for 5 h, the photoluminescence (PL) intensity is higher than that without passivation. The polymer EVA packaging strategy provided CsPbBr3 with excellent extensibility and flexibility at 100% and 200% tensile rates, the PL intensity remains 91% and 88% of the initial intensity, which returns to the initial value after stretching. The unique dual‐protection structure significantly improves the water and thermal stability of the nanocrystals. The strategy might point out the direction for the future application of perovskites. [ABSTRACT FROM AUTHOR]
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- 2024
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21. Quantifying the stability of refugee populations: a case study in Austria.
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Ali, Ola, Dervic, Elma, Stütz, Rainer, Nedelkoska, Ljubica, and Prieto-Curiel, Rafael
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ACCULTURATION ,RESIDENTIAL mobility ,HOUSING discrimination ,POLITICAL stability ,EMIGRATION & immigration ,REFUGEE children - Abstract
The global surge in displacement, with nearly 110 million people uprooted due to violence, underscores the pressing need to comprehend the challenges faced by refugees. Population growth, environmental crises, and political instability contribute to this crisis, projecting an escalating trend in the decades ahead. While hosting countries strive to address concerns related to labour markets, state provisions, and cultural integration, understanding the well-being of refugees upon entry needs to be more adequately explored. This study focuses on refugee stability and integration, employing Austria as a case study. Stability is assessed through residential movement, where more frequent moves indicate instability. Utilising comprehensive administrative data spanning November 2022 to November 2023, we examine residence movements as a proxy for stability. Our findings reveal a stark contrast in the stability of refugees compared to other migrant groups. Analysing movement profiles, we establish that refugees exhibit significantly higher rates of residential mobility than their counterparts, especially among male refugees. This imbalance persists even when comparing refugees to migrants from top refugee-sending countries without official refugee status. This study contributes valuable insights into the intricate dynamics of refugee stability, shedding light on the enduring challenges faced by this population. By examining movement patterns as a key indicator, we provide a nuanced understanding of the residential experiences of refugees, that can inform targeted policies and interventions for enhanced refugee well-being and integration. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
22. Evaluation of yield and stability of sugar beet (beta vulgaris L.) genotypes using GGE biplot and AMMI analysis.
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Yousefabadi, Vali-allah, Mehdikhani, Parviz, Nadali, Fathollah, Sharifi, Mastaneh, Azizi, Heydar, Ahmadi, Masoud, and Fasahat, Parviz
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GENOTYPE-environment interaction , *BEETS , *NATURAL immunity , *BLOCK designs , *GENOTYPES , *SUGAR beets - Abstract
Rhizomania is the most destructive sugar beet disease in the world, and in recent years, it has widespread in most of the sugar beet growing areas in Iran. Since the control of this soil-borne disease is a difficult task, the use of resistant genotypes is known as the best measure against the disease. The ultimate goal of sugar beet breeders is to produce genotypes that can be used in both infected and non-infected fields without any reduction in terms of yield and quality. Twenty-one sugar beet genotypes along with four controls were evaluated in randomized complete block design with four replications in fields with natural infection to rhizomania in five research stations. Important sugar beet traits including root yield, sugar yield, sugar content, and white sugar yield were evaluated for two years (2021 and 2022). For all traits, location was the main source of variation that spanned 33 to 55% of the total sum of the square followed by the location×year×genotype accounted for 3–40% of the variation. Based on the results of analysis of variance, multivariate stability parameters were computed to evaluate the genotypes' stability. The first two principal components (IPCA1 and IPCA2) generated by GGE biplot contributed for 31.3 and 17.5% difference in genotype×environment interaction for root yield, respectively. According to the GGE biplot, genotypes RM-11 and RM-12 were identified as the winning genotypes across environments for both root yield and white sugar yield traits whereas AMMI model identified RM-14 and RM-9 (for root yield) and RM-1 (for white sugar yield) as best genotypes. Based on the ideal genotype ranking, RM-11 and RM-10 were the best performer with a high mean yield as well as stability in the studied environments. The biplot rendered using the weighted average of absolute scores (WAASB) and root yield and white sugar yield identified RM-11 and RM-9 as superior genotypes in terms of yield and stability. The selected genotypes can be used in breeding programs to transfer the disease resistance and cultivar development. [ABSTRACT FROM AUTHOR]
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- 2024
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23. Limited stability of Hepatitis B virus RNA in plasma and serum.
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Ohlendorf, Valerie, Bremer, Birgit, Sandmann, Lisa, Mix, Carola, Tergast, Tammo, Cornberg, Markus, Wedemeyer, Heiner, Deterding, Katja, and Maasoumy, Benjamin
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RNA viruses , *THAWING , *BIOMARKERS - Abstract
Pregenomic hepatitis B virus RNA (HBV pgRNA) is a potential biomarker in the management of HBV infected patients. However, prior to the use in routine clinical practice potential confounders of test results need to be identified. This study investigates the stability of HBV pgRNA under various storage conditions. HBV-RNA level of 26 HBV patients were determined using the Roche cobas® 6800/8800 investigational HBV-RNA assay. Plasma and serum were stored for 6,48,169 h at 4,25 and 42 °C, respectively. Additionally, 10 serum and plasma samples underwent 4 or 11 cycles of freezing (−80 °C) and thawing (25 °C). A significant decline in mean pgRNA concentration compared to baseline was observed after storage for 48 h at 25 °C as well as after 6 h of storage at 42 °C. Accordingly, sub-analyses of predefined pgRNA baseline concentrations (≤ 10 cp/mL, > 10–100 cp/ml, > 100 cp/mL) revealed significant changes in pgRNA level after storage at 25 and 42 °C. No effect of freezing and thawing on pgRNA level was observed. A qualitative detection of HBV pgRNA is feasible in samples with > 100 cp/mL up to 48 h under storage temperatures of 4–42 °C. For most stable quantitative HBV pgRNA values storage at 4 °C should be preferred. [ABSTRACT FROM AUTHOR]
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- 2024
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24. Stability of equilibria and bifurcations for a fluid-solid interaction problem.
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Bonheure, Denis, Galdi, Giovanni P., and Gazzola, Filippo
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NAVIER-Stokes equations , *EQUILIBRIUM , *VELOCITY , *FLUIDS , *LIQUIDS - Abstract
We study certain significant properties of the equilibrium configurations of a rigid body subject to an undamped elastic restoring force, in the stream of a viscous liquid in an unbounded 3D domain. The motion of the coupled system is driven by a uniform flow at spatial infinity, with constant dimensionless velocity λ. We show that if λ is below a critical value, λ c (say), there is a unique and stable time-independent configuration, where the body is in equilibrium and the flow is steady. We also prove that, if λ < λ c , no oscillatory flow may occur. Successively, we investigate possible loss of uniqueness by providing necessary and sufficient conditions for the occurrence of a steady bifurcation at some λ s ≥ λ c. [ABSTRACT FROM AUTHOR]
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- 2024
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25. Paclitaxel loaded Capmul MCM and tristearin based nanostructured lipid carriers (NLCs) for glioblastoma treatment: screening of formulation components by quality by design (QbD) approach.
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Mittal, Pooja, Singla, Madhav, Smriti, kapoor, Ramit, Kumar, Dileep, Gupta, Saurabh, Gupta, Gaurav, and Bhattacharya, Tanima
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ZETA potential ,MATHEMATICAL optimization ,STEARIN ,CELL lines ,ORGANIC solvents ,PACLITAXEL - Abstract
Paclitaxel (PTX), a naturally occurring diterpenoid isolated from Taxus brevifolia, is a first-line drug for the treatment of glioblastoma; however, it suffers from the disadvantages of poor water solubility and nonspecific biodistribution, which cause serious side effects in the human body. The marketed formulation suffers from serious side effects, such as allergic reactions, neutropenia, and neuropathy, which require safe and effective formulations of PTX. In the present study, PTX was entrapped in a solid–liquid lipid mixture with the aid of a surfactant using a modified solvent evaporation technique. Higher entrapment of the impressive stability of the formulation was achieved by employing quality design-based strategies. Optimized levels by employing a numerical optimization technique for each factor, that is, surfactant concentration (X1), lipid concentration (X2), and amount of organic solvent (X3) were 0.3%, 0.76% & 8.3 ml respectively. The resultant formulation exhibited a particle size of 121.44 nm, entrapment efficiency of 94.27%, and zeta potential of −20.21 mV with unimodal size distribution. A reduction in the % crystalline index from 48 to 3.4% ensured the amorphous form of the entrapped drug inside the formulation, which precludes the fear of leakage and instability of the formulation. Cell line studies conducted on U87MG Cell lines also suggested that the NLC of paclitaxel are more effective than those of pure PTX. In summary, PTXNLC seem to be a superior alternative carrier system for the formulation industry to obtain higher entrapment with excellent stability. [ABSTRACT FROM AUTHOR]
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- 2024
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26. Prescribed‐time resilient current‐sensorless DC power converter control.
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Homayounzadeh, Maryam, Homayounzade, Mohamadreza, and Khooban, Mohammad‐Hassan
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ELECTRIC potential measurement ,ADAPTIVE control systems ,POWER resources ,INFORMATION storage & retrieval systems ,ALGORITHMS - Abstract
While conventional control techniques for stabilizing power electronic converters with constant‐power load (CPL) often rely on complete system state information, the associated challenges, including the cost and increased size due to the installation of multiple sensors, necessitate exploration of alternative methodologies. To address these concerns, a novel observer‐based sliding‐mode control approach is proposed. This approach aims to enhance cost‐effectiveness and reliability in the context of a DC‐DC buck converter supplying power to an unknown CPL. The core concept involves designing a state observer to estimate the system's current based on voltage measurements. A non‐certainty equivalent adaptive update law is then introduced to estimate the unknown CPL, incorporating feedback from voltage measurements and current estimation. To guarantee stability in the face of uncertainties in system parameters, a thorough analysis utilizing the Lyapunov theorem is conducted on the closed‐loop system. The efficacy and feasibility of the proposed control algorithm are substantiated through experimental results on the OPAL‐RT platform, showcasing its promising performance. [ABSTRACT FROM AUTHOR]
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- 2024
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27. Low‐frequency oscillations in MMC‐MVDC systems with high PV penetration: Modelling, mechanism, and assessment.
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Wu, Xiangyang, He, Lili, Li, Yang, Shuai, Zhikang, and Zhou, Ke
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HYBRID power systems ,MIMO systems ,STABILITY criterion ,SENSITIVITY analysis ,PHOTOVOLTAIC power systems - Abstract
This study investigates the low‐frequency oscillations (LFOs) in MMC‐MVDC systems with high photovoltaic (PV) penetration, considering the whole operating conditions of the grid‐connected MMC, including both the inverter and rectifier modes. First, the multi‐port impedance models of converters and networks are developed, upon which a stability criterion is defined. The mechanism of LFOs is then identified using bus participation analysis and parameter sensitivity analysis. In addition, the stable zones of the dominant parameters are identified, taking into account the whole operating conditions of the grid‐connected MMC. Interestingly, a phase‐locked loop may induce LFOs in two low‐frequency ranges. Finally, the experimental results confirm the correctness of the theoretical analysis. [ABSTRACT FROM AUTHOR]
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- 2024
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28. Lycopene-Loaded Emulsions: Chitosan Versus Non-Ionic Surfactants as Stabilizers.
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Álvarez-García, Sonia, Couarraze, Lucie, Matos, María, and Gutiérrez, Gemma
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NONIONIC surfactants , *HAZARDOUS substances , *CORONARY disease , *SOY oil , *BIOMEDICAL materials , *LYCOPENE , *BIODEGRADABLE materials - Abstract
Lycopene is a natural carotenoid with well-known benefits due to its antioxidant properties, including an anti-inflammatory effect in colorectal cancer and anti-angiogenic effects along with a reduction in the risk of prostate cancer and coronary heart disease. Due to their poor water solubility, photosensitivity and heat sensitivity, their incorporation in cosmetic and food matrices should be through encapsulation systems. In the present work, lycopene-loaded emulsions were prepared using two different types of stabilizers: non-ionic surfactants, testing several ratios of Tween 80 and Span 80, and chitosan, using chitosans of different viscosities and molecular weights. Soybean oil was found to be a suitable candidate for O/W emulsion preparation. Lycopene encapsulation efficiency (EE) of 70–75% and loading capacities of 0.14 mg/g were registered in stable emulsions stabilized either by non-ionic surfactants or acidified chitosans. Therefore, chitosan is a good alternative as a sustainable stabilizer to partially replace traditional synthetic ingredients with a new biodegradable, renewable and biocompatible material which could contribute to reduce the environmental impact as well as the ingestion of synthetic toxic materials by humans, decreasing their risk of suffering from chronic and complex pathologies, among which several types of cancer stand out. [ABSTRACT FROM AUTHOR]
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- 2024
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29. Hydrophobically Modified Polyacrylamide Incorporating Both Hydrophilic and Hydrophobic Units: Enhanced Printability and Stability in Aqueous Ink.
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Liu, Zhi-Rui, Tan, Li-Lin, Gao, Juan, Qin, Zi-Ye, Huo, Xin-Xin, and Liang, Zhi-Min
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INTRINSIC viscosity , *NUCLEAR magnetic resonance , *SCANNING electron microscopes , *ELECTRONIC paper , *INK-jet printing - Abstract
For this research, three hydrophobically modified polyacrylamides, HPAAB, HPAAF, and HPAAS, with multiple hydrophobic monomers were designed, synthesized, and used as thickeners in aqueous ink for digital ink-jet printing. The structures were characterized by Fourier transform infrared (FTIR) analysis and nuclear magnetic resonance (NMR) spectroscopy. The viscosity–average molecular weight was determined by intrinsic viscosity determination and was adjusted according to hydrophobic content. The critical association concentration (CAC) of polymers was measured simultaneously using the apparent viscosity method and the fluorescence spectrum. The formation of a network structure and the mechanism of hydrophobic association are visualized dynamically with a scanning electron microscope (SEM) at different concentrations. Under the same conditions, HPAAB exhibited excellent thickening ability across different pH levels, temperatures, and shear rates, which is caused by the longer hydrophobic side chain and the stronger hydrophobic effect of the behenyl polyoxyethylene ether methacrylate (BEM) group. Furthermore, an aqueous ink using HPAAB as a thickener displays significant printability and stability, functioning much better than a corresponding aqueous ink that uses a commercial thickener. This is the first example of a hydrophobic associating polyacrylamide, incorporating both hydrophilic and hydrophobic units within a single hydrophobic chain, thereby serving as an efficient thickener for aqueous ink. [ABSTRACT FROM AUTHOR]
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- 2024
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30. Molybdenum-Oxide-Modified PEDOT:PSS as Efficient Hole Transport Layer in Perovskite Solar Cells.
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Fan, Pu, Zhou, Zhipeng, Tian, Jianghao, and Yu, Junsheng
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SOLAR cells , *MOLYBDENUM oxides , *ELECTRIC conductivity , *PRODUCTION sharing contracts (Oil & gas) , *PEROVSKITE - Abstract
Over the last ten years, there has been a remarkable enhancement in the power conversion efficiency (PCE) of perovskite solar cells (PSCs), with poly (3,4-ethylenedioxythiohene):poly (styrenesulfonate) (PEDOT:PSS) emerging as a prevalent choice for the hole transport layer (HTL). Nevertheless, the evolution of the widely utilized PEDOT:PSS HTL has not kept pace with the swift advancements in PSC technology, attributed to its suboptimal electrical conductivity, acidic nature, and inadequate electron-blocking performance. This study presents a novel approach to enhance the HTL by introducing molybdenum oxide (MoO3) into the PEDOT:PSS, leveraging the conductivity and solution processing compatibility of MoO3. Two methods for MoO3 integration were explored: an ammonium molybdate tetrahydrate (AMT) precursor and the direct addition of MoO3 nanoparticles. The carrier dynamics of PSCs modified by MoO3 are significantly optimized. Therefore, the PCE of the device modified by AMT and molybdenum oxide is increased to 18.23 and 19.64%, respectively, and the stability of the device is also improved. This study emphasizes the potential of MoO3 in contributing to the development of more efficient and stable PSCs. [ABSTRACT FROM AUTHOR]
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- 2024
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31. Development of an Angular Stiffness Sensor to Measure Dental Implant Stability In Vitro.
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Xu, Weiwei, Chen, Yen-Wei, Nagatomo, Kanako, Liu, Yifeng, Zhou, Jihai, Dard, Michel, and Shen, I. Y.
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DENTAL implants , *CANCELLOUS bone , *FINITE element method , *STABILITY constants , *COMPACT bone - Abstract
This investigation aims to develop an angular stiffness sensor intended for measuring dental implant stability in bone. The sensor hardware included a tiny eccentric motor and an accelerometer to measure a flex constant of an implant with its abutment. The sensor software included a mechanics-based model to convert the flex constant to angular stiffness at the implant/abutment junction to indicate the stability. The sensor's accuracy and effectiveness are demonstrated through use of Sawbones slab models that mimic a mandibular premolar section. The models include a Branemark Mk III implant inserted into Sawbones slabs of 5 different densities with a locator abutment. An incremental insertion torque was first recorded while the implant was placed in the Sawbones models. Then benchtop experiments were conducted to measure resonance frequencies and angular stiffness. Results indicated that angular stiffness increased with Sawbones density, showing high correlation with the measured resonance frequency ( R = 0.977 ) and the incremental insertion torque ( R = 0.959 ). Finally, accuracy of the angular stiffness sensor is calibrated in light of the resonance frequency. Angular stiffness scores 99% and 95% accuracy for Sawbones models mimicking medium cancellous bones with and without a cortical layer, respectively. [ABSTRACT FROM AUTHOR]
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- 2024
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32. Grid Integration of Offshore Wind Energy: A Review on Fault Ride Through Techniques for MMC-HVDC Systems.
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Kumar, Dileep, Shireen, Wajiha, and Ram, Nanik
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RENEWABLE energy sources , *WIND power , *OFFSHORE wind power plants , *MECHANICAL energy , *FAULT location (Engineering) - Abstract
Over the past few decades, wind energy has expanded to become a widespread, clean, and sustainable energy source. However, integrating offshore wind energy with the onshore AC grids presents many stability and control challenges that hinder the reliability and resilience of AC grids, particularly during faults. To address this issue, current grid codes require offshore wind farms (OWFs) to remain connected during and after faults. This requirement is challenging because, depending on the fault location and power flow direction, DC link over- or under-voltage can occur, potentially leading to the shutdown of converter stations. Therefore, this necessitates the proper understanding of key technical concepts associated with the integration of OWFs. To help fill the gap, this article performs an in-depth investigation of existing alternating current fault ride through (ACFRT) techniques of modular multilevel converter-based high-voltage direct current (MMC-HVDC) for OWFs. These techniques include the use of AC/DC choppers, flywheel energy storage devices (FESDs), power reduction strategies for OWFs, and energy optimization of the MMC. This article covers both scenarios of onshore and offshore AC faults. Given the importance of wind turbines (WTs) in transforming wind energy into mechanical energy, this article also presents an overview of four WT topologies. In addition, this article explores the advanced converter topologies employed in HVDC systems to transform three-phase AC voltages to DC voltages and vice versa at each terminal of the DC link. Finally, this article explores the key stability and control concepts, such as small signal stability and large disturbance stability, followed by future research trends in the development of converter topologies for HVDC transmission such as hybrid HVDC systems, which combine current source converters (CSCs) and voltage source converters (VSCs) and diode rectifier-based HVDC (DR-HVDC) systems. [ABSTRACT FROM AUTHOR]
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- 2024
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33. Machine Vision to Provide Quantitative Analysis of Meltpool Stability for a Coaxial Wire Directed Energy Deposition Process.
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McLain, Braden, Mathenia, Remy, Sparks, Todd, and Liou, Frank
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SURFACE tension , *METAL fabrication , *REAL-time control , *SUBSTRATES (Materials science) , *MACHINE learning - Abstract
Wire-based additive manufacturing (AM) is at the forefront of complex metal fabrication because of its scalability for large components, potential for high deposition rates, and ease of use. A common goal of wire directed energy deposition (DED) is preserving a stable process throughout deposition. If too little energy is put into the deposition, the wire will stub into the substrate and begin oscillating, creating turbulence within the meltpool. If too much energy exists, the wire will overheat, causing surface tension to take over and create liquid drips as opposed to a solid bead. This paper proposes a computer vision technique to work as both a state detection and event detection system for wire stability. The model utilizes intensity variations along with frame-to-frame difference calculations to determine process stability. Because the proposed model does not rely on machine learning techniques, it is possible for an individual to interpret and adjust as they see fit. The first part of this paper describes creation and implementation of the model. The model's capability was then evaluated using a 1D laser power experiment, which generated a wide range of stability states across varying powers. The model's accuracy was evaluated through 3D geometry data gathered from the experimentally deposited beads. The model proved to be both capable and accurate and has potential to be used as a real-time control system with future work. [ABSTRACT FROM AUTHOR]
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- 2024
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34. Ion‐Dependent Stability of DNA Origami Nanostructures in the Presence of Photo‐Generated Reactive Oxygen Species.
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Rabbe, Lukas, Garcia‐Diosa, Jaime Andres, Grundmeier, Guido, and Keller, Adrian
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DNA folding , *DNA nanotechnology , *RED light , *REACTIVE oxygen species , *METHYLENE blue - Abstract
DNA origami nanostructures are promising carries for drug delivery applications. However, their limited stability under relevant conditions often presents a challenge. Herein, the structural stability of DNA origami nanostructures is investigated in a setting compatible with their application in photodynamic therapy (PDT). To this end, DNA origami triangles and six‐helix bundles (6HBs) are loaded with the clinically tested photosensitizer methylene blue, which upon irradiation with red light generates reactive oxygen species (ROS) that attack the DNA origami nanostructures. ROS‐induced structural damage is observed to depend on the ionic composition of the surrounding medium and becomes more severe at low ionic strength. Mg2+ ions can efficiently protect the DNA origami nanostructures from ROS‐induced damage and may even heal some of the damage obtained under Mg2+‐free conditions when added after irradiation. Finally, the employed DNA origami 6HBs are more resistant toward ROS‐induced structural damage than the triangles, which is attributed to their markedly different mechanical properties. These results thus provide some fundamental insights into the stabilizing role of DNA origami superstructure that may guide the selection or design of DNA origami nanocarriers with optimized stability for their application in PDT. [ABSTRACT FROM AUTHOR]
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- 2024
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35. The longitudinal patterns of depression subtypes and stressors in depression severity in the Canadian longitudinal study on aging (CLSA).
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Su, Yingying, Li, Muzi, Schmitz, Norbert, and Meng, Xiangfei
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MENTAL health services , *MENTAL depression , *LONGITUDINAL method , *AGING , *ADULTS - Abstract
Aim: The current study aims to characterize the longitudinal patterns of depression subtypes and investigate the associations among the stability of depression subtypes, COVID‐19‐related stressors, and depression severity. Methods: The study utilized data from the Canadian Longitudinal Study on Aging, which is a national, long‐term study of Canadian adults aged 45 and older (n = 12,957). Latent profile analysis was used to identify latent depression subtypes. Latent transition analysis was then applied to assess the stability of these subtypes over time. Hierarchical multivariate linear regression was used to explore the relationships among these identified depression subtypes, COVID‐19‐related stressors, and depression severity among males and females, respectively. Results: Distinct depression subtypes were identified. Except for atypical depression, other depression subtypes showed greater stability over time. We also found that melancholic depression (B = 9.432) and typical depression (B = 6.677) were strongly associated with depression severity during the pandemic. Health‐related stressors (B = 0.840), conflict (B = 3.639), difficulties accessing resources (B = 0.927), separation from family (B = 0.840), and caregiving experience (B = 0.764), were significantly associated with increased depression severity. Sex‐specific analyses also revealed differences in the associations between stressors and depression severity between males and females. Conclusions: This study contributes valuable insights into the latent clustering of depression subtypes and their stability. Stressors were associated with increased depression severity, with distinct associations observed among males and females. These findings have implications for targeted early interventions and integrated clinical management strategies by providing the evidence base for tailored mental health care during and after the pandemic. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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36. Stability and bifurcation analysis of a 2DOF dynamical system with piezoelectric device and feedback control.
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Bahnasy, Taher A., Amer, T. S., Abohamer, M. K., Abosheiaha, H. F., Elameer, A. S., and Almahalawy, A.
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POINCARE maps (Mathematics) , *EQUATIONS of motion , *DYNAMICAL systems , *PIEZOELECTRIC devices , *ELECTRIC power , *NONLINEAR dynamical systems - Abstract
This study aims to demonstrate the behaviors of a two degree-of-freedom (DOF) dynamical system consisting of attached mass to a nonlinear damped harmonic spring pendulum with a piezoelectric device. Such a system is influenced by a parametric excitation force on the direction of the spring's elongation and an operating moment at the supported point. A negative-velocity-feedback (NVF) controller is inserted into the main system to reduce the undesired vibrations that affect the system's efficiency, especially at the resonance state. The equations of motion (EOM) are derived by using Lagrangian equations. Through the use of the multiple-scales-strategy (MSS), approximate solutions (AS) are investigated up to the third order. The accuracy of the AS is verified by comparing them to the obtained numerical solutions (NS) through the fourth-order Runge-Kutta Method (RK-4). The study delves into resonance cases and solvability conditions to provide the modulation equations (ME). Graphical representations showing the time histories of the obtained solutions and frequency responses are presented utilizing Wolfram Mathematica 13.2 in addition to MATLAB software. Additionally, discusses the bifurcation diagrams, Poincaré maps, and Lyapunov exponent spectrums to show the various behavior patterns of the system. To convert vibrating motion into electrical power, a piezoelectric sensor is connected to the dynamical model, which is just one of the energy harvesting (EH) technologies with extensive applications in the commercial, industrial, aerospace, automotive, and medical industries. Moreover, the time histories of the obtained solutions with and without control are analyzed graphically. Finally, resonance curves are used to discuss stability analysis and steady-state solutions. [ABSTRACT FROM AUTHOR]
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- 2024
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37. Order Reduction of z-Domain Interval Systems by Advanced Routh Approximation Method.
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Kumar, Praveen, Rai, Pankaj, and Choudhary, Amit Kumar
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AUTOMATIC control systems , *DISCRETE-time systems , *TRANSFER functions , *PHYSICAL mobility , *MATHEMATICIANS - Abstract
Since decades mathematicians have been designing the transfer function for the available physical models followed by the involvement of control engineers to work on it. Through the study of the offered representations, many systems were found to be of higher order which are nevertheless not easy to study and analyze in their core form. Furthermore, again uncertainties within the system was found that cannot be ignored. All these increases the complexities for analysis of the physical systems. This demands a technique for order reduction to derive an approximate lower order representation of the higher order systems. In continuation, this paper is an attempt to propose a computationally efficient approach for obtaining the reduced interval model based on Routh Approximation technique. The proposed approach is a novel method for discrete-time interval system and is discussed in detail in the article content ahead. The provided examples offer the desired explanation for the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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38. Transformative impact of molybdenum on nickel phosphate hydrate electrodes towards superior energy storage application.
- Author
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Teli, Aviraj M., Beknalkar, Sonali A., Satale, Vinayak V., Lee, Jae Hyeop, Kim, Min Su, Shin, Jae Cheol, and Kim, Hong Hyuk
- Subjects
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NICKEL electrodes , *NICKEL phosphates , *ELECTRODE performance , *CARBON electrodes , *ENERGY storage , *SUPERCAPACITOR electrodes , *MOLYBDENUM - Abstract
Development of high capacity and long cycle life electrode materials is essential to improving energy storage capacity in electrochemical rechargeable devices. In order to be commercially viable, the synthesis of these materials must be straightforward, cost-effective, and ideally a single-step process. We present a binder-free synthesis method for nickel phosphate hydrate (NiPH) and nickel molybdenum phosphate hydrate (NiMoPH) on nickel foam via a simple hydrothermal process. X-ray diffraction (XRD) patterns confirmed the formation of NiPH and NiMoPH phases, while X-ray photoelectron spectroscopy (XPS) verified the presence of nickel (Ni), molybdenum (Mo), phosphorus (P), and oxygen (O) in the composite. Scanning electron microscopy (FE-SEM) revealed the formation of micro-flowers with plate-like structures in NiPH, which transformed into hexagonal rod-like structures upon the introduction of molybdenum in NiPH. This morphological and phase modification increased the charge storage capacity from 1441 mF/cm2 (NiPH) to 2945 mF/cm2 (NiMoPH) at 20 mA/cm2. The NiMoPH electrode demonstrated excellent capacitance retention of 91.8 % over 10,000 cycles. Additionally, asymmetric supercapacitor (ASS) devices were fabricated using NiPH and NiMoPH as positive electrodes and activated carbon (AC) as the negative electrode. The NiPH//AC and NiMoPH//AC configurations exhibited energy densities of 0.086 and 0.201 mWh/cm2, respectively, with the NiMoPH//AC device maintaining about 90 % capacitance retention over 15,000 cycles. This study demonstrates the potential of incorporating conductive transition metals to enhance electrode material performance in energy storage applications. Hydrothermally synthesized nickel phosphate hydrate (NiPH) and nickel molybdenum phosphate hydrate (NiMoPH) electrode materials for energy storage devices have been reported. The transformation of NiPH microplates into hexagonal rods upon the addition of molybdenum was observed. This structural modification and improved conductivity, induced by the inclusion of molybdenum, enhances the electrochemical energy storage performance of the electrodes. [Display omitted] [ABSTRACT FROM AUTHOR]
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- 2024
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39. Ilmenite-type NiTiO3 nanoparticles for oxygen evolution reaction.
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Gaddimath, Shivalingayya, Chandrakala, K. B., Lagashetty, Arunkumar, Dani, Santhoshkumar, Prabhu, C. P. Keshavananda, Giddaerappa, and Sannegowda, Lokesh Koodlur
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CATALYST supports , *SCANNING electron microscopy , *NICKEL catalysts , *CLEAN energy , *GREEN business , *FOAM , *HYDROGEN evolution reactions - Abstract
Perovskite materials are being studied extensively because of their unique and versatile properties and applications. The conductivity and electronic structure has attributed for their application in photo and electrocatalysis. Here, a smooth, facile, and self-propagating combustion method is used for the synthesis of NiTiO3 nanoparticles and evaluated as an efficient and economic catalyst for the oxygen evolution reaction (OER) for clean energy production. The designed catalyst was characterized by various spectro-analytical techniques as well as microscopic techniques. The X-ray diffraction profile of NiTiO3 nanoparticles portrayed the crystalline behavior of nanoparticles with an average crystallite size of 27.65 nm. The Transmission electron microscopic images exhibited the uniform distribution of NiTiO3 nanoparticles on the Ni-foam electrode surface. The catalyst supported on nickel foam exhibited better efficacy for catalyzing OER in 1.0 M KOH with a lower overpotential of 390 mV at a current density of 10 mA cm−2. The designed catalyst exhibited a lower Tafel slope value as well as better stability for OER. This study opens up the application of perovskite materials for water-splitting reactions. Schematics for the OER at NiTiO3 [ABSTRACT FROM AUTHOR]
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- 2024
- Full Text
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40. The use of an imperfect vaccination and awareness campaign in the control of antibiotic resistant gonorrhoea infection: A mathematical modelling perspective.
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Terefe, Y.A., Kassa, S.M., Asfaw, M.D., and Venter, C.
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BASIC reproduction number , *NEISSERIA gonorrhoeae , *VACCINE effectiveness , *INFECTIOUS disease transmission , *GONORRHEA - Abstract
The multi drug-resistant Neisseria gonorrhoeae has been classified by the World Health Organisation (WHO) as a high-priority global public health problem. This underlines the need for better understanding of the transmission dynamics and proposing an optimal intervention strategy to control the disease. In this article, a deterministic mathematical model for the transmission dynamics of gonorrhoea as an antibiotic resistant disease in a population with an imperfect vaccination is proposed and analysed. The model incorporates the classes of vaccinated individuals and individuals equipped with self protection interventions to reduce antibiotic resistant cases. The threshold parameter R 0 , the basic reproduction number, for the analysis of the model is calculated. In the given setting, the model exhibits a backward bifurcation for R 0 < 1. However, if the efficacy of the vaccine is 100% without a waning effect, the model is shown to be without a backward bifurcation and the disease-free equilibrium is globally asymptotically stable whenever R 0 < 1. The global sensitivity analysis of the model to variations in parameter values is also performed to determine the most influential parameters on the disease transmission. Moreover, the optimal control analysis of the full model is presented and the optimal intervention strategies are proposed. The proposed intervention strategies are shown to be able to control the disease within a relatively shorter period of time. Finally, numerical experiments are presented to support the theoretical analysis of the model. • Imperfect vaccination is not helpful to eradicate the disease from the population. • Awareness campaign about the antibiotic resistant strain can reduce the transmission of the disease. • Sensitive parameters for the transmission dynamics of the disease are identified. • With the use of the optimal control analysis, cost effective intervention measures are proposed. [ABSTRACT FROM AUTHOR]
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- 2024
- Full Text
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41. Understanding the Molecular Interactions Between Pandan Pigment and Food Components for Enhanced Thermal Stability.
- Author
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Chen, Junxia, Gu, Chunhe, Wang, Mengrui, Chang, Ziqing, Zhou, Junping, Yue, Mingzhe, Liu, Fei, and Feng, Zhen
- Subjects
RICE starch ,SOY proteins ,WHEY proteins ,PROTEIN stability ,FOOD color ,LACTOSE - Abstract
Pandan pigment (Pandanus amaryllifolius) is widely used as a natural food coloring and flavoring agent. However, its application in food is limited because of its susceptibility to thermal degradation during food processing, which affects both pigment stability and color. Despite its growing use, there is limited research on how common food ingredients can mitigate this degradation. This study addresses this gap by exploring the effects of sucrose, lactose, rice starch, whey protein, and soy protein isolate on the thermal and color stability of pandan pigment under various heating conditions (65 °C, 95 °C, 115 °C, and 121 °C for 15 min). Spectroscopic techniques (UV–visible, infrared, and fluorescence) and laser confocal microscopy were used to elucidate the molecular interactions. The results revealed that rice starch provided the strongest protection, followed by whey protein, soy protein isolate, lactose, and sucrose, although the protective effects decreased at higher temperatures. These findings offer new insights into the use of sugars and proteins to increase the thermal stability of natural pigments in food applications. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. Experimental Study on Characteristics of Filter Cake Formation in Slurry Shield Tunnelling Based on "Cutter-Soil" Interaction.
- Author
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Bai, Yang, Li, Yapeng, and Li, Lei
- Abstract
In recent years, more and more river-crossing and sea-crossing underwater tunnels have become the first choice for the construction of large channels in regions with developed river system. Relying on its superior pressure control mode and high security, Slurry Pressure Balance shield (SPB) is widely used in the construction of underwater tunnels with large cross-sections. The filter cake is an important medium to guarantee the stability of the excavation in SPB tunnelling. However, the mechanism of cutter on soil and filter cake (the interaction of "cutter-soil") are still unclear. In this study, a self-made test apparatus based on the interaction of "cutter-soil" is presented. The experiment results revealed that "cutter-soil" interaction, compared to cases without the interaction, reduced the impermeability and effective stress conversion rate of filter cake, which is unfavorable to guarantee the stability of the tunnel face. To overcome this problem, two methods were proposed: continuous injection of slurry with different densities and increasing the coarse particles of slurry. It is shown that the methods have improved filter the impermeability of cake formation, which contributes to the stability of the shield excavation face. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
43. R &d and market sharing agreements.
- Author
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Dollinger, Jérôme, Mauleon, Ana, and Vannetelbosch, Vincent
- Subjects
MARKETING agreements ,MARKET share ,CONSUMERS ,OLIGOPOLIES ,COALITIONS - Abstract
We analyze the formation of R &D alliances and market sharing (MS) agreements by which firms commit not to enter in each other's territory in oligopolistic markets. We show that R &D alliance structures are stable only in the presence of MS agreements. Thus, long lasting R &D alliances could signal the existence of some MS agreement in the industry. We characterize the set of stable symmetric pairs of coalition structures with identical R &D and MS structure. In addition, we show the stability of a class of asymmetric pairs of coalition structures where the most efficient firms form both an R &D and a MS agreement while the other firms do not form any MS agreement but form two smaller R &D alliances. Even though MS agreements are detrimental for consumers, we show that the stable pairs of coalition structures are a better outcome for consumers than no cooperation at all. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
44. A novel robust active damping control strategy based on H∞ loop shaping for the grid-tied LCL inverter.
- Author
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Sang, Wenju, Guo, Wenyong, Xu, Gang, Wei, Tongzhen, Shi, Changli, Liu, Zongjie, Xue, Han, He, Zhenning, Li, Junzhi, Shen, Jiazhen, Min, Ruiqi, Song, Shaobo, Li, Xiaoxu, and Hong, Yun
- Subjects
RESONANCE ,ELECTRIC inductance ,FACTORIZATION ,CAPACITORS - Abstract
LCL-type grid-connected inverters have been widely used in renewable power generation due to their size and cost advantages. However, the LCL filter has a problem of insufficient damping, which may lead to power system instability. Two common methods are used to address this problem: passive damping (PD) and active damping (AD). PD methods suppress resonance by adding resistors to the LCL filter, but this approach increases system losses. AD methods enhance damping through control to suppress resonance. Existing AD methods are often significantly affected by grid-side inductance perturbation, resulting in insufficient robustness. To address this issue, this article proposes a novel robust active damping (RAD) control strategy based on H∞ loop shaping. Simulation analysis and experimental research show that the RAD control method exhibits superior robustness compared with the traditional capacitor current active damping control. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
45. Hopf Bifurcation of Three-Dimensional Quadratic Jerk System.
- Author
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Rasul, Tahsin I. and Salih, Rizgar H.
- Subjects
HOPF bifurcations ,LIMIT cycles - Abstract
Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2024
- Full Text
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46. Monomer unfolding of a bacterial ESCRT‐III superfamily member is coupled to oligomer disassembly.
- Author
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Quarta, Ndjali, Bhandari, Tika Ram, Girard, Martin, Hellmann, Nadja, and Schneider, Dirk
- Abstract
The inner membrane associated protein of 30 kDa (IM30), a member of the endosomal sorting complex required for transport (ESCRT‐III) superfamily, is crucially involved in the biogenesis and maintenance of thylakoid membranes in cyanobacteria and chloroplasts. In solution, IM30 assembles into various large oligomeric barrel‐ or tube‐like structures, whereas upon membrane binding it forms large, flat carpet structures. Dynamic localization of the protein in solution, to membranes and changes of the oligomeric states are crucial for its in vivo function. ESCRT‐III proteins are known to form oligomeric structures that are dynamically assembled from monomeric/smaller oligomeric proteins, and thus these smaller building blocks must be assembled sequentially in a highly orchestrated manner, a still poorly understood process. The impact of IM30 oligomerization on function remains difficult to study due to its high intrinsic tendency to homo‐oligomerize. Here, we used molecular dynamics simulations to investigate the stability of individual helices in IM30 and identified unstable regions that may provide structural flexibility. Urea‐mediated disassembly of the IM30 barrel structures was spectroscopically monitored, as well as changes in the protein's tertiary and secondary structure. The experimental data were finally compared to a three‐state model that describes oligomer disassembly and monomer unfolding. In this study, we identified a highly stable conserved structural core of ESCRT‐III proteins and discuss the advantages of having flexible intermediate structures and their putative relevance for ESCRT‐III proteins. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
47. Stochastic optimization problems with nonlinear dependence on a probability measure via the Wasserstein metric.
- Author
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Kaňková, Vlasta
- Subjects
PROBABILITY measures ,DEPENDENCE (Statistics) ,NONLINEAR equations ,STOCHASTIC dominance - Abstract
Nonlinear dependence on a probability measure has recently been encountered with increasing intensity in stochastic optimization. This type of dependence corresponds to many situations in applications; it can appear in problems static (one-stage), dynamic with finite (multi-stage) or infinite horizon, and single- and multi-objective ones. Moreover, the nonlinear dependence can appear not only in the objective functions but also in the constraint sets. In this paper, we will consider static one-objective problems in which the nonlinear dependence appears in the objective function and may also appear in the constraint sets. In detail, we consider "deterministic" constraint sets, whose dependence on the probability measure is nonlinear, constraint sets determined by second-order stochastic dominance, and sets given by mean-risk problems. The last mentioned instance means that the constraint set corresponds to solutions which guarantee acceptable values of both criteria. To obtain relevant assertions, we employ the stability results given by the Wasserstein metric, based on the L 1 norm. We mainly focus on the case in which a solution has to be obtained on the basis of the data and of investigating a relationship between the original problem and its empirical version. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
48. Comparative analysis of newly graduated nurse support through periods of turmoil: lessons learnt for building a future workforce for uncertain times.
- Author
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Riches, Casey, Pitt, Rachael, Tyler, Scott, Wise, Megan, Watman, Philip, and Henderson, Amanda
- Subjects
- *
EMPLOYEE retention , *WORK , *GRADUATES , *INTERNSHIP programs , *EVALUATION of human services programs , *QUESTIONNAIRES , *LABOR turnover , *TERTIARY care , *DESCRIPTIVE statistics , *TRANSITIONAL programs (Education) , *NURSES' attitudes , *EMPLOYEE recruitment , *SOCIAL support , *EXPERIENTIAL learning , *LABOR supply - Abstract
Aim: To compare newly graduated nurse retention and employment experiences across two distinct graduate nurse programs through periods of health care delivery stability and instability. Background: A global nursing workforce shortage, coupled with increasing demands on health services, requires a specific focus on building capability and improved retention of nurses. The graduate nurse cohort is a critical supply source that potentially can be harnessed if their needs are better understood. Design: A longitudinal (2015–2023) cross-sectional design was used to examine retention and experiences of newly graduated nurses from two ('traditional, unit-based' versus 'mobile') supported programs. Methods: Retention rates were obtained through analysis of employment databases. Descriptive data on impressions and experiences was collected at two time points via a short series of questions contained in a survey, from graduate nurses who remained in employment. Results: Retention rates for graduate nurses were high (85%) during periods of stability, but even higher for the 'mobile' graduate nurse program. Both programs were adversely affected by instability however, the impact was substantial (around 50%) for the peak period of instability (2020) in the 'mobile' program. Survey data indicated that during the period of instability graduate nurses in traditional, unit-based programs had a more positive experience when compared with graduate nurses participating in the 'mobile' program; This contrasts with the period of stability, where graduate nurses in the 'mobile' program indicated more positive responses. Discussion: Findings re-emphasise the importance of supportive structures for newly graduated nurses as effective in retaining these staff. However, for the first time, evidence is provided that 'mobility', diversity, and difference can be viewed positively by graduate nurses. Furthermore, it provides improved understanding about mechanisms, support and boundaries, all interrelating factors, in 'stretching' capacity of graduate nurses. Conclusion: Longitudinal analysis of graduate nurses, participating in two diverse programs, through periods of stability and instability offers insights into their challenges and outcomes. These insights can directly inform targeted strategies for inclusion in supported programs that lead to improved graduate nurse retention and contribute to building an agile nursing workforce. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
49. Self-assembly antimicrobial peptide for treatment of multidrug-resistant bacterial infection.
- Author
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Ma, Xuanxuan, Yang, Na, Mao, Ruoyu, Hao, Ya, Li, Yuanyuan, Guo, Ying, Teng, Da, Huang, Yinhua, and Wang, Jianhua
- Subjects
- *
ANTIMICROBIAL peptides , *PEPTIDES , *ESCHERICHIA coli , *PATHOGENIC bacteria , *BOVINE mastitis , *GRAM-positive bacteria - Abstract
The wide-spreading of multidrug resistance poses a significant threat to human and animal health. Although antimicrobial peptides (AMPs) show great potential application, their instability has severely limited their clinical application. Here, self-assembled AMPs composed of multiple modules based on the principle of associating natural marine peptide N6 with ß-sheet-forming peptide were designed. It is noteworthy that one of the designed peptides, FFN could self-assemble into nanoparticles at 35.46 µM and achieve a dynamic transformation from nanoparticles to nanofibers in the presence of bacteria, resulting in a significant increase in stability in trypsin and tissues by 1.72–57.5 times compared to that of N6. Additionally, FFN exhibits a broad spectrum of antibacterial activity against multidrug-resistant (MDR) gram-positive (G+) and gram-negative (G−) bacteria with Minimum inhibitory concentrations (MICs) as low as 2 µM by membrane destruction and complemented by nanofiber capture. In vivo mouse mastitis infection model further confirmed the therapeutic potential and promising biosafety of the self-assembled peptide FFN, which can effectively alleviate mastitis caused by MDR Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and eliminate pathogenic bacteria. In conclusion, the design of peptide-based nanomaterials presents a novel approach for the delivery and clinical translation of AMPs, promoting their application in medicine and animal husbandry. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
50. An Energy Transfer-Based Bifurcation Detection Method for Nonlinear Rotating Systems: Enables Accurate Capture of Period-Doubling Bifurcation and Instability.
- Author
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Zhao, Runchao, Xu, Yeyin, Li, Zhitong, Chen, Zengtao, Xu, Zili, Chen, Zhaobo, and Jiao, Yinghou
- Subjects
- *
ROTATIONAL motion , *ENERGY transfer , *LYAPUNOV exponents , *ROTOR dynamics , *STABILITY criterion - Abstract
Rotor systems are widely used in industrial power generation and propulsion. Once the nonlinear contact stiffness and oil film force are taken into account, the dynamics and stability of rotor systems become quite complex, often accompanied by super-harmonic and chaotic motions. Furthermore, conventional methods face limitations in real-time detection of the bifurcations and complex nonlinear motions. This research investigates the bifurcations and stability induced by nonlinear factors in a rotor-bearing system from an energy perspective. Dynamic equations of a rotor-bearing system considering cubic term stiffness are established, the steady responses are obtained by the fourth-order Runge–Kutta method. The relationship between the bifurcations and energy transfers is analyzed numerically, the proposed stability criterion is validated by comparing the Lyapunov exponents. The bistable phenomenon of period-3 m (m = 0 , 1) motion is discussed in terms of numerical results and experiments which corresponds to the asymmetric jumps of the generalized energy. It is found that bifurcations and unstable motions of the nonlinear system can be captured accurately by detecting the energy transfers, the proposed generalized energy curve exhibits more detailed information than the conventional speed-up curve. These findings provide a new perspective on studying bifurcations and stability of rotating systems, which can be further applied in the condition monitoring, stability prediction as well as the design of nonlinear energy sink, representing significant progress in converting theory into engineering applications for rotor systems. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
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