Search Results (82)

Consensus protocols for a multi-agent networked system consist of strategies that align the states of all agents that share information according to a given network topology, despite challenges such as communication limitations, time-varying networks, and communication delays. The special orthogonal group $SO\left(n\right)$ plays a key role in applications from rigid body attitude synchronization to machine learning on Lie groups, particularly in fields like physics-informed learning and geometric deep learning. In this paper, N-agent consensus protocols are proposed on the Lie group $SO\left(4\right)$ and the corresponding tangent bundle $TSO\left(4\right)$, in which the state spaces are $SO{\left(4\right)}^N$ and $TSO{\left(4\right)}^N$, respectively. In particular, when using communication topologies such as a ring graph for which the local stability of non-consensus equilibria is retained in the closed loop, a consensus protocol that leverages a reshaping strategy is proposed to destabilize non-consensus equilibria and produce consensus with almost global stability on $SO{\left(4\right)}^N$ or $TSO{\left(4\right)}^N$. Lyapunov-based stability guarantees are obtained, and simulations are conducted to illustrate the advantages of these proposed consensus protocols. Full article

Background: This study aimed to evaluate the long-term stability of maxillary molar distalization in the treatment of Class II malocclusion. Methods: This study included 40 patients (31 males and 9 females) who received fixed orthodontic treatment after maxillary molar distalization. Orthodontic models and lateral cephalograms were evaluated at three time points: pre-treatment (T1), after orthodontic treatment (T2), and long-term follow-up (T3). The mean ages of the patients’ ages at T1, T2, and T3 were 13.02, 15.97, and 22.05 years, respectively. The statistical analysis included paired t-tests and Wilcoxon signed-rank tests. The statistical significance was set at p < 0.05. Results: The statistical analysis indicated no gender-related differences. A significant distalization of maxillary first molars was observed at T2 compared to T1 (p < 0.001). Despite a minor relapse, a statistically significant distalization was observed in T3-T1 (p < 0.001). The vertical skeletal angles, which increased during the treatment period, decreased at T3-T2. The molar relationship was almost maintained after long-term follow-up (p < 0.001). Conclusions: The maxillary molar distalization achieved in the Class II treatment was maintained in the long term. The vertical skeletal measurements decreased to their initial values in the long term. The Class I molar relationship did not change during the completion of the growth. This study hypothesized that the maxillary molar distalization achieved during fixed orthodontic treatment can be maintained in the long term without significant relapse. Full article

We consider a parabolic equation with a singular potential in a bounded domain $\Omega \subset {\mathbb{R}}^n.$ The main result is a Lipschitz stability estimate for an inverse source problem of determining a spatial varying factor $f\left(x\right)$ of the source term $R(x,t)f\left(x\right).$ We obtain a consistent stability result for any $\mu \le p_1{\mu }^{*},$ where $p_1>0$ is the lower bound of $p\left(x\right)$ and ${\mu }^{*}={(n-2)}^2/4,$ and this condition for $\mu$ is also almost a consistently optimal condition for the existence of solutions. The main method we used is the Carleman estimate, and the proof for the inverse source problem relies on the Bukhgeim–Klibanov method. Full article

Solar photovoltaic/thermal (PV/T) systems can simultaneously solve PV overheating and obtain high-quality thermal energy through nanofluid spectral splitting technology. However, the existing nanofluid splitting devices have insufficient short-wavelength extinction and stability defects. To achieve the precise matching of the nanofluid splitting performance with the optimal spectral window of the PV/T system, this paper carries out a relevant study on the optical properties of Al nanoparticles and proposes an Al@Ag nanoparticle. The optical behaviors of nanoparticles and nanofluids are numerically analyzed using the finite-difference time-domain (FDTD) method and the Beer–Lambert law. The results demonstrate that adjusting particle size enables modulation of nanoparticle extinction performance, including extinction intensity and resonance peak range. The Al@Ag core–shell structure effectively mitigates the oxidation susceptibility of pure Al nanoparticles. Furthermore, coating Al nanoparticles with an Ag shell significantly enhances their extinction efficiency in the short-wavelength range (350–640 nm). After dispersing Al nanoparticles into water to form a nanofluid, the transmittance in the short-wavelength range is significantly reduced compared to pure water. Compared to 50 nm pure Al particles, the Al@Ag nanofluid further reduces the transmittance by up to 13% in the wavelength range of 350–650 nm, while having almost no impact on the transmittance in the photovoltaic window (640–1080 nm). Full article

PIWI-interacting RNAs (piRNAs) are small noncoding RNAs that are almost exclusively expressed in germ cells to silence harmful transposons to maintain genome stability. PIWIL4 is guided by its associated piRNAs to transposable elements, where it recruits the DNA methylation apparatus and instructs de novo DNA methylation. Herein, we identified a missense variant of PIWIL4 (c.805 C>T p.R269W) in two infertile males. Homozygous male mice carrying the orthologous knock-in variant displayed elevated transposable element expression and aberrant gene expression during the first wave of spermatogenesis, despite exhibiting normal sperm counts and morphology. Mechanistically, the mutated site altered the piRNA-binding ability of PIWIL4 and led to the derepression of endogenous LINE-1 elements. In summary, we identified a piRNA binding mutation in PIWIL4 that may be involved in human nonobstructive azoospermia. Full article

Dehydration is known to affect the rate of electron transfer backreaction from the light-induced charge separation state P⁺Q_A⁻ to the neutral ground state PQ_A in photosynthetic bacterial Reaction Centers. On the other hand, a 20 s continuous illumination period has been demonstrated to induce (at 297 K) formation of one or more light-adapted states at different levels of dehydration; these light-adapted states are believed to be related to peculiar response(s) from the protein. In this work, we applied time-resolved rapid-scan FTIR difference spectroscopy to investigate the protein response under dehydrated conditions (RH = 11%) at 281 K both after a flash and under prolonged continuous illumination. Time-resolved FTIR difference spectra recorded after a laser flash show a protein recovery almost synchronous to the electron transfer backreaction P⁺Q_A⁻ → PQ_A. Time-resolved FTIR difference spectra recorded after 20.5 s of continuous illumination (RH = 11%, T = 281 K) surprisingly show almost the same kinetics of electron transfer back reaction compared to spectra recorded after a laser flash. This means that the mechanism of formation of a light-adapted stabilized state is less effective compared to the same hydration level at 297 K and to the RH = 76% hydration level (both at 281 K and 297 K). Time-resolved FTIR difference spectra after continuous illumination also suggest that the 1666 cm⁻¹ protein backbone band decays faster than marker bands for the electron transfer back reaction P⁺Q_A⁻ → PQ_A. Finally, FTIR double-difference spectra (FTIR difference spectrum recorded after 18.4 s illumination minus flash-induced FTIR difference spectrum) suggest that at RH = 11%, a light-adapted state different from the one observed at RH = 76% is formed. A possible interpretation is that at RH = 11%, the protein response is modified by the fact that only protons can move easily, differently from water molecules, as instead observed for RH = 76%. This probably makes the formation of a real light-adapted P⁺Q_A⁻ stabilized state at RH = 11% unfeasible. Full article

The application of nanocomposites based on polyacrylamide hydrogels as well as silica nanoparticles in various tasks related to the petroleum industry has been rapidly developing in the last 10–15 years. Analysis of the literature has shown that the introduction of nanoparticles into hydrogels significantly increases their structural and mechanical characteristics and improves their thermal stability. Nanocomposites based on hydrogels are used in different technological processes of oil production: for conformance control, water shutoff in production wells, and well killing with loss circulation control. In all these processes, hydrogels crosslinked with different crosslinkers are used, with the addition of different amounts of nanoparticles. The highest nanoparticle content, from 5 to 9 wt%, was observed in hydrogels for well killing. This is explained by the fact that the volumes of injection of block packs are counted only in tens of cubic meters, and for the sake of trouble-free workover, it is very important to preserve the structural and mechanical properties of block packs during the entire repair of the well. For water shutoff, the volumes of nanocomposite injection, depending on the well design, are from 50 to 150 m³. For conformance control, it is required to inject from one to several thousand cubic meters of hydrogel with nanoparticles. Naturally, for such operations, service companies try to select compositions with the minimum required nanoparticle content, which would ensure injection efficiency but at the same time would not lose economic attractiveness. The aim of the present work is to develop formulations of nanocomposites with increased structural and mechanical characteristics based on hydrogels made of partially hydrolyzed polyacrylamide crosslinked with resorcinol and paraform, with the addition of commercially available nanosilica, as well as to study their thermal degradation, which is necessary to predict the lifetime of gel shields in reservoir conditions. Hydrogels with additives of pyrogenic (HCSIL200, HCSIL300, RX380) and hydrated (white carbon black grades: ‘BS-50’, ‘BS-120 NU’, ‘BS-120 U’) nanosilica have been studied. The best samples in terms of their structural and mechanical properties have been established: nanocomposites with HCSIL200, HCSIL300, and BS-120 NU. The addition of hydrophilic nanosilica HCSIL200 in the amount of 0.4 wt% to a hydrogel consisting of partially hydrolyzed polyacrylamide (1%), resorcinol (0.04%), and paraform (0.09%) increased its elastic modulus by almost two times and its USS by almost three times. The thermal degradation of hydrogels was studied at 140 °C, and the experimental time was converted to the exposure time at 80 °C using Van’t Hoff’s rule. It was found that the nanocomposite with HCSIL200 retains its properties at a satisfactory level for 19 months. Filtration studies on water-saturated fractured reservoir models showed that the residual resistance factor and selectivity of the effect of nanocomposites with HCSIL200 on fractures are very high (226.4 and 91.6 for fracture with an opening of 0.05 cm and 11.0 for porous medium with a permeability of 332.3 mD). The selectivity of the isolating action on fractured intervals of the porous formation was noted. Full article

In order to evaluate the feasibility of vegetable residues compost used as the growth medium for Brassica chinensis L. seedings, the effects of membrane covering and superphosphate application on the performance of tomato and mushroom residues aerobic compost were investigated. In the composting process, four treatments (T1: non-cover with non-addition, T2: membrane-covered with non-addition, T3: non-cover with superphosphate addition, and T4: membrane-covered with superphosphate addition) were explored. The results showed that membrane covering could effectively promote the degradation of lignocellulose, it had about 70% higher degradation rate than non-covered compost. The effect of superphosphate application was not significant. The humification indexes in Fourier Transform Infrared Spectroscopy (FTIR) and the fluorescence parameters were the main factors affecting the GI and chemical properties. The results manifested the membrane covering possess a higher conversion rate of humic substances, indicating better maturity. All the compost could almost meet the requirements of seedling substrate performance standards, especially the membrane-covered sample T2 had higher germination index (GI) value more than 100% and higher nutrient concentrations. Then, the four compost products were mixed with vermicompost, perlite, and vermiculite for the Brassica chinensis L. seedling raising experiment (T1B, T2B, T3B, T4B). It has been found that the compost-based substrate T2B with the best stability and maturity showed better seedling growth, and even comparable to peat substrate. Full article

Background: The elbow joint is stabilized by complex interactions between bony structures and soft tissues, notably the lateral and medial collateral ligaments. Posterolateral rotatory instability (PLRI), a form of elbow instability, is challenging to diagnose due to overlapping symptoms with other conditions. The radiocapitellar line (RCL) is a radiographic tool for assessing humeroradial alignment and elbow stability, but its diagnostic accuracy remains debated. This study aims to provide normative data on RCL deviations in healthy individuals to improve diagnostic criteria for PLRI. Methods: A prospective study was conducted with 53 healthy individuals (27 males, 26 females) aged 18–45 years. MRI scans of the participants’ elbows were performed in maximum extension and supination to assess radiocapitellar deviations (RCDs). Two orthopedic surgeons independently analyzed the images to evaluate RCDs and assess interobserver reliability. Statistical analyses, including independent t-tests and Pearson correlations, were used to explore the relationship between RCDs, demographic factors, and elbow stability. Results: The average RCD in the cohort was 1.77 mm (SD 1.06 mm). Notably, 62.9% of participants had deviations greater than 1.2 mm, while 12.9% exceeded 3.4 mm, thresholds traditionally used to diagnose PLRI. Gender and age did not significantly influence RCD values. The interobserver reliability was almost good (ICC = 0.87), supporting the consistency of the RCL measurements. Conclusions: Significant RCDs occur even in asymptomatic individuals, challenging the current diagnostic thresholds for PLRI based solely on RCL measurements. A comprehensive assessment that includes clinical, anatomical, and functional evaluations is essential for accurate diagnosis. These findings highlight the need for refined diagnostic criteria and further research into elbow stability. Full article

The longitudinal and transverse nuclear magnetic resonance relaxivity dispersion (NMRD) of ¹H in water induced by the paramagnetic relaxation enhancement (PRE) of dissolved lanthanide ions (Ln³⁺) can become very strong. Longitudinal and transverse ¹H NMRD for Gd³⁺, Dy³⁺, Er³⁺ and Ho³⁺ were measured from 20 MHz/0.47 T to 1382 MHz/32.5 T, which extended previous studies by a factor of more than two in the frequency range. For the NMRD above 800 MHz, we used a resistive magnet, which exhibits reduced field homogeneity and stability in comparison to superconducting and permanent NMR magnets. These drawbacks were addressed by dedicated NMRD methods. In a comparison of NMRD measurements between 800 MHz and 950 MHz performed in both superconducting and resistive magnets, it was found that the longitudinal relaxivities were almost identical. However, the magnetic field fluctuations of the resistive magnet strongly perturbed the transverse relaxation. The longitudinal NMRDs are consistent with previous work up to 600 MHz. The transverse NMRD nearly scales with the longitudinal one with a factor close to one. The data can be interpreted within a PRE model that comprises the dipolar hyperfine interactions between the ¹H and the paramagnetic ions, as well as a Curie spin contribution that is dominant at high magnetic fields for Dy³⁺, Er³⁺ and Ho³⁺. Our findings provide a solid methodological basis and valuable quantitative insights for future high-frequency NMRD studies, enhancing the measurement accuracy and applicability of PRE models for paramagnetic ions in aqueous solutions. Full article

Serine β-lactamase TEM-1 is the first β-lactamase discovered and is still common in Gram-negative pathogens resistant to β-lactam antibiotics. It hydrolyzes penicillins and cephalosporins of early generations. Some of the emerging TEM-1 variants with one or several amino acid substitutions have even broader substrate specificity and resistance to known covalent inhibitors. Key amino acid substitutions affect catalytic properties of the enzyme, and secondary mutations accompany them. The occurrence of the secondary mutation M182T, called a “global suppressor”, has almost doubled over the last decade. Therefore, we performed saturating mutagenesis at position 182 of TEM-1 to determine the influence of this single amino acid substitution on the catalytic properties, thermal stability, and ability for thermoreactivation. Steady-state parameters for penicillin, cephalothin, and ceftazidime are similar for all TEM-1 M182X variants, whereas melting temperature and ability to reactivate after incubation at a higher temperature vary significantly. The effects are multidirectional and depend on the particular amino acid at position 182. The M182E variant of β-lactamase TEM-1 demonstrates the highest residual enzymatic activity, which is 1.5 times higher than for the wild-type enzyme. The 3D structure of the side chain of residue 182 is of particular importance as observed from the comparison of the M182I and M182L variants of TEM-1. Both of these amino acid residues have hydrophobic side chains of similar size, but their residual activity differs by three-fold. Molecular dynamic simulations add a mechanistic explanation for this phenomenon. The important structural element is the V159-R65-E177 triad that exists due to both electrostatic and hydrophobic interactions. Amino acid substitutions that disturb this triad lead to a decrease in the ability of the β-lactamase to be reactivated. Full article

This paper explores the stability and dynamics of a three-dimensional evaporating/condensing film while falling down a heated/cooled incline. Instead of using the Hertz–Knudsen–Langmuir relation, a more comprehensive phase-change boundary condition is employed. A nonlinear differential equation is derived based on the Benny-type equation, which takes into account gravity, energy transport, vapor recoil, effective pressure, and evaporation. The impact of effective pressure and vapor recoil on instability is studied using a linear stability analysis. The results show that spanwise perturbations can amplify the destabilizing effects of vapor recoil, leading to instability. Energy transport along the interface has almost no effect on the stability of the system, but it does influence the linear wave speed. Nonlinear evolution demonstrates that, in contrast to the vapor recoil effect, effective pressure can improve stability and delay film rupture. The self-similar solution demonstrates that the minimal film thickness decreases as ${(t_r-t)}^{1/2}$ and ${(t_r-t)}^{1/3}$ under the dominance of evaporation and vapor recoil, respectively. Full article

In this paper, we constructed a new and robust fixed point iterative scheme called the UO iterative scheme for the approximation of a contraction mapping. The scheme converges strongly to the fixed point of a contraction mapping. A rate of convergence result is shown with an example, and our scheme, when compared, converges faster than some existing iterative schemes in the literature. Furthermore, the stability and data dependence results are shown. Our new scheme is applied in the approximation of the solution to the oxygen diffusion model. Finally, our results are applied in the approximation of the solution to the boundary value problems using Green’s functions with an example. Full article

Both grape pomace and whey are waste products from the food industry that are rich in valuable ingredients. The utilization of these two by-products is becoming increasingly possible as consumer awareness of upcycling increases. The biological activities of grape pomace extract (GPE) are diverse and depend on its bioavailability, which is influenced by processes in the digestive system. In this work, goat whey protein (GW) was used as the primary coating to protect the phenolic compounds of GPE during the spray drying process. In addition, trehalose (T), sucrose (S), xylose (X), and maltodextrin (MD) were added to the goat whey proteins as co-coatings and protein stabilizers. All spray drying experiments resulted in microcapsules (MC) with a high encapsulation efficiency (77.6–95.5%) and yield (91.5–99.0%) and almost 100% recovery of phenolic compounds during the release test. For o-coumaric acid, the GW-coated microcapsules (MC) showed a bioavailability index of up to 731.23%. A semi-crystalline structure and hydrophilicity were characteristics of the MC coated with 10% T, S, X, or 5% MD. GW alone or in combination with T, S, MD, or X proved to be a promising carrier for polyphenols from grape pomace extract and ensured good bioavailability of these natural antioxidants. Full article

RPL—Routing Protocol for Low-Power and Lossy Networks (usually pronounced “ripple”)—is the de facto standard for IoT networks. However, it neglects to exploit IoT devices’ full capacity to optimize their transmission power, mainly because it is quite challenging to do so in parallel with the routing strategy, given the dynamic nature of wireless links and the typically constrained resources of IoT devices. Adapting the transmission power requires dynamically assessing many parameters, such as the probability of packet collisions, energy consumption, the number of hops, and interference. This paper introduces Adaptive Control of Transmission Power for RPL (ACTOR) for the dynamic optimization of transmission power. ACTOR aims to improve throughput in dense networks by passively exploring different transmission power levels. The classic solutions of bandit theory, including the Upper Confidence Bound (UCB) and Discounted UCB, accelerate the convergence of the exploration and guarantee its optimality. ACTOR is also enhanced via mechanisms to blacklist undesirable transmission power levels and stabilize the topology of parent–child negotiations. The results of the experiments conducted on our 40-node, 12-node testbed demonstrate that ACTOR achieves a higher packet delivery ratio by almost 20%, reduces the transmission power of nodes by up to 10 dBm, and maintains a stable topology with significantly fewer parent switches compared to the standard RPL and the selected benchmarks. These findings are consistent with simulations conducted across 7 different scenarios, where improvements in end-to-end delay, packet delivery, and energy consumption were observed by up to 50%. Full article