Search

In this paper, we study a fully discrete finite element scheme of thermally coupled incompressible magnetohydrodynamic with temperature-dependent coefficients in Lipschitz domain. The variable coefficients in the MHD system and possible nonconvex domain may cause nonsmooth solutions. We propose a fully discrete Euler semi-implicit scheme with the magnetic equation approximated by Nédélec edge elements to capture the physical solutions. The fully discrete scheme only needs to solve one linear system at each time step and is unconditionally stable. Utilizing the stability of the numerical scheme and the compactness method, the existence of weak solution to the thermally coupled MHD model in three dimensions is established. Furthermore, the uniqueness of weak solution and the convergence of the proposed numerical method are also rigorously derived. Under the hypothesis of a low regularity for the exact solution, we rigorously establish the error estimates for the velocity, temperature and magnetic induction unconditionally in the sense that the time step is independent of the spacial mesh size.

This article investigates the fully discrete finite element approximation and error analysis for a diffuse interface model of the two-phase incompressible inductionless magnetohydrodynamics problem. This model consists of Cahn–Hilliard equations, Navier–Stokes equations and Poisson equations, which are nonlinearly coupled through convection, stresses, and Lorentz forces. To address this highly nonlinear and multi-physics system, we propose a fully discrete energy stable scheme with the finite element projection method for spatial discretization, in which the velocity and pressure are decoupled. The temporal discretization is a combination of the first-order Euler semi-implicit scheme and a convex splitting energy strategy. We show that the proposed scheme is mass-conservative, charge-conservative and unconditional energy stable. The error estimates for the phase variable, chemical potential, velocity, pressure, current density and electric potential are rigorously established. Finally, several three-dimensional numerical experiments are performed to illustrate the features of the proposed numerical method and verify the theoretical conclusions. • Propose a finite element fully discrete projection scheme to solve two-phase IMHD • The scheme is charge conservative, mass conservative, unconditionally energy stable • Establish the error estimates for all variables (φ , ω , u , p , J , ϕ) • Perform 3D numerical experiments to illustrate the features of the proposed scheme [ABSTRACT FROM AUTHOR]

To better understand postprandial glucose metabolic mechanisms in crustaceans, the pathways involved in glucose transport, breakdown, synthesis, and regulation were investigated in the giant freshwater prawn Macrobrachium rosenbergiiafter feeding. Prawns were fasted for 48 hours and then refed to satiation. Glucose and glycogen contents, along with the transcriptional levels of glucose metabolism-related genes, were measured at 0, 1, 3, 6, and 10 hours after feeding (HAF). Plasma glucose levels peaked at 3 HAF and returned to basal levels by 6–10 HAF. Hepatopancreas glucose followed a similar trend, except for a notable increase at 10 HAF, suggesting gluconeogenesis at this time point. Expression analysis of glucose transporter genes in hepatopancreas revealed a significant upregulation of GLUT1 at 3, 6, and 10 HAF, while GLUT2 showed significant decreases only at 6 HAF. Glycolysis-related genes (GKand PK) exhibited transient increases post-feeding, whereas the gluconeogenesis-related gene FBPwas initially suppressed, with expression recovering from 6 HAF onward. The glycogenesis-related gene GSwas significantly upregulated at 3, 6, and 10 HAF, correlating with increased glycogen levels in the hepatopancreas. Conversely, the expression of the glycogenolysis-related gene GDEwas inhibited after feeding, along with a decrease in the glycogenesis inhibitory gene GSK3. Genes in the insulin signaling pathway (ILP, PI3KCa, and AKT) were upregulated post-feeding, peaking at 3 HAF and subsequently declining. These results suggest that feeding stimulates the insulin signaling pathway and GLUT1 to transport excess glucose, inducing glycolysis and hepatopancreatic glycogenesis, while inhibiting gluconeogenesis and glycogenolysis.

The Fe3O4@Au nanostars, whose anisotropic shape couples the plasmons focused on the magnetic core with the branches of the gold shell, hold promise for surface enhanced Raman spectroscopy (SERS) applications. Assembly of monodisperse Fe3O4@Au nanostars induced by a magnetic field could lead to highly ordered superstructures, providing distinctive SERS activity. In this study, a simplified fabrication technique was developed to assemble Fe3O4@Au nanostars on the inner walls of a glass capillary into a highly sensitive, reproducible and recyclable SERS active glass capillary under controlled magnetic alignment. The strong dipole–dipole interactions between the neighboring nanoparticles lead to a close-packed pattern as an energetically favorable configuration. The magnetic dipolar interaction between the particles can be further tuned by the controlled anisotropic shape of the gold shell. The interparticle plasmon couplings and lightning rod effects of the Fe3O4@Au nanostars contributed to Raman enhancement. Based on the capillary action, capillaries can act as a microreactor for the sampling tools. We further demonstrate SERS-based colorant detection in the capillary which the target molecule can easily detect by simple adsorption of the colorants by capillary action. The Fe3O4@Au nanostars in the capillary with a long shelf life, high sensitivity and low cost promote the application of SERS technology in widespread fields.

Surface-enhanced Raman scattering (SERS) technique with naturally born analyte identification capability can achieve ultrahigh sensitivity. However, the sensitivity and quantification capability of SERS are assumed to be mutually exclusive. Here, we prohibit the formation of the ultrasensitive SERS sites to achieve a high quantification capability through separating the gold (Au) nanorods from approaching each other with thick metal organic framework (MOF) shells. The sensitivity decrease caused by the absence of the ultrasensitive SERS sites is compensated by the analyte enrichment function of a slippery surface. The porous MOF shell around the Au nanorod only allows analytes smaller than the pore size to approach the Au nanorods and contribute to the SERS spectrum within the complex sample, greatly enhancing the analyte identification capability. Overall, we have demonstrated an integrated SERS platform with analyte enrichment and analyte filtration function, realizing sensitive, quantitative, and size selective analyte identification in complex environments.

It is well-known that such non-conventional digital control schemes, such as generalized sampled-data hold functions, have clear advantages over the conventional single-rate digital control systems. However, they have theoretical negative aspects that deviation of the input can lead to intersample oscillations or intersample ripples. This paper investigates the zero dynamics of sampled-data models, as the sampling period tends to zero, composed of a new generalized hold polynomial function, a nonlinear continuous-time plant and a sampler in cascade. For a new design of generalized hold circuit, the authors give the approximate expression of the resulting sampled-data systems as power series with respect to a sampling period up to the some order term on the basis of the normal form representation for the nonlinear continuous-time systems, and remarkable improvements in the stability properties of discrete system zero dynamics may be achieved by using proper adjustment. Of particular interest are the stability conditions of sampling zero dynamics in the case of a new hold proposed. Also, an insightful interpretation of the obtained sampled-data models can be made in terms of minimal intersample ripple by design, where the ordinary multirate sampled systems have a poor intersample behavior. It has shown that the intersample behavior arising from the multirate input polynomial function can be localised by appropriately selecting the design parameters based on the stability condition of the sampling zero dynamics. The results presented here generalize the well-known notion of sampling zero dynamics from the linear case to nonlinear systems.

With cheap and easily available 1,2,3-thiadiazol-5-amine and amines as raw materials, cheap and reusable selenium as the catalyst, CO as the carbonylation reagent and O2as the oxidizing agent, the selenium-catalyzed oxidative carbonylation reaction of 1,2,3-thiadiazol-5-amine can proceed smoothly with a series of amines in one-pot manner in the presence of triethylamine, affording 1,2,3-thiadiazol-5-ylureas mostly in moderate to good yields.

The optical properties of monolayer molybdenum disulfide (MoS2)/Ag nanoparticle (NP) hybrids and their application to surface catalytic reactions were studied by transmission, photoluminescence (PL) and Raman spectroscopies. The local surface plasmon resonance (LSPR) of Ag nanoparticles was tuned to better match the exciton energy of monolayer MoS2. The PL of the hybrids was enhanced by more than 50 times when the local surface plasmon resonance (LSPR) peak was tuned systematically from 438 nm to 532 nm, indicating a stronger coupling and higher energy transfer rate between the plasmon of the Ag NPs and the excitons of the MoS2. Additionally, photocatalytic reactions of 4-nitrobenzenethiol (4NBT) were performed on the MoS2, the Ag nanoparticles, and the hybrid MoS2with Ag nanoparticles. On the MoS2substrate alone, there is no photocatalytic reaction. With a low laser intensity, the probability of a chemical reaction occurring for molecules directly adsorbed onto the Ag NPs is much lower than the probability of a reaction involving those molecules adsorbed onto the MoS2/Ag substrate. At a higher power, although the electric field was reduced by approximately 30% by the MoS2layer, there is better efficiency for the plasmon-exciton co-driven surface catalytic reactions on the MoS2/Ag substrate compared to the Ag substrate alone. Our findings illustrate the potential to control hot carriers for better surface catalytic reactions by tuning the exciton-plasmon coupling between the 2D transition metal dichalcogenides (TMDCs) and Ag NPs.

Plasmon-driven diazo coupling reaction of p-nitroaniline (PNA), containing both an amine group (−NH2) and a nitro group (−NO2), in ambient atmosphere environments remains unknown in experiments, on both metal nanoparticles and graphene-mediated metal nanostructures. Using the surface-enhanced Raman scattering (SERS) technique, we presented the surface coupling reactions of PNA under atmospheric environment, adsorbed on the Ag nanoparticle (AgNP) arrays, graphene-coated Ag nanoparticle (G/AgNPs) hybrids, and graphene-covered Ag nanowire (G/AgNW) composites, respectively. It was found that PNAs were converted into 4,4′-diaminoazobenzene (DAAB) through a selective reduction reaction, rather than oxidized into 4,4′-dinitroazobenzene (DNAB). These results may be useful for understanding the reaction mechanism for plasmon-driven chemical reactions of the molecules containing both amine groups and nitro groups under ambient conditions.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.