Pt-confinement catalyst with dendritic hierarchical pores on excellent sulfur-resistance for hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene

Metal confinement catalyst Mo S_(2)/Pt@TD-6%Ti(TD,TS-1/Dendritic mesoporous silica nanoparticles composite) in dendritic hierarchical pore structures was synthesized and showed excellent sulfur-resistance performance and stabilities in catalytic hydrodesulfurization reactions of probe sulfide molecules.The Mo S_(2)/Pt@TD-6%Ti catalyst combines the concepts of Pt-confinement effect and hydrogen spillover of Pt noble metal.The modified micropores of Mo/Pt@TD-6%Ti only allow the migration and dissociation of small H_(2) molecules(0.289 nm),and effectively keep the sulfur-containing compounds(e.g.H_(2)S,0.362 nm) outside.Thus,the Mo S_(2)/Pt@TD-6%Ti catalyst exhibits higher DBT and 4,6-DMDBT HDS activities because of the synergistic effect of the strong H_(2) dissociation ability of Pt and desulfurization ability of Mo S_(2) with a lower catalyst cost.This new concept combining H2dissociation performance of noble metal catalyst with the desulfurization ability of transition metal sulfide Mo S_(2) can protect the noble metal catalyst avoiding deactivation and poison,and finally guarantee the higher activities for DBT and 4,6-DMDBT HDS.

Multi-Panel Extra-Large Scale MIMO Based Joint Activity Detection and Channel Estimation for Near-Field Massive IoT Access

The extra-large scale multiple-input multiple-output(XL-MIMO)for the beyond fifth/sixth generation mobile communications is a promising technology to provide Tbps data transmission and stable access service.However,the extremely large antenna array aperture arouses the channel near-field effect,resulting in the deteriorated data rate and other challenges in the practice communication systems.Meanwhile,multi-panel MIMO technology has attracted extensive attention due to its flexible configuration,low hardware cost,and wider coverage.By combining the XL-MIMO and multi-panel array structure,we construct multi-panel XL-MIMO and apply it to massive Internet of Things(IoT)access.First,we model the multi-panel XL-MIMO-based near-field channels for massive IoT access scenarios,where the electromagnetic waves corresponding to different panels have different angles of arrival/departure(AoAs/AoDs).Then,by exploiting the sparsity of the near-field massive IoT access channels,we formulate a compressed sensing based joint active user detection(AUD)and channel estimation(CE)problem which is solved by AMP-EM-MMV algorithm.The simulation results exhibit the superiority of the AMP-EM-MMV based joint AUD and CE scheme over the baseline algorithms.

Quantitative heterogeneity and subgroup classification based on motility of breast cancer cells

Cancer cell motility and its heterogeneity play an important role in metastasis, which is responsible for death of 90% of cancer patients. Here, in combination with a microfluidic technique, single-cell tracking, and systematic motility analysis,we present a rapid and quantitative approach to judge the motility heterogeneity of breast cancer cells MDA-MB-231 and MCF-7 in a well-defined three-dimensional(3D) microenvironment with controllable conditions. Following this approach,identification of highly mobile active cells in a medium with epithelial growth factor will provide a practical tool for cell invasion and metastasis investigation of multiple cancer cell types, including primary cells. Further, this approach could potentially become a speedy(~ hours) and efficient tool for basic and clinical diagnosis.

Synthesis and Immobilization of Polystyrene-b-Polyvinyltriethoxysilane Micelles

Diblock copolymers polystyrene-block-polyvinyltriethoxysilane（PS-b-PVTES） were synthesized via atom transfer radical polymerization（ATRP）, which self-assembled into spherical micelles in solvent of THF-methanol mixtures. The self-assembled micelles were immobilized by cross-linking reaction of VTES in a shell layer of micelles. The chemical structures of block copolymers and morphology of micelles were characterized in detail. It was found that the size of immobilized micelles was strongly affected by the copolymer concentration, composition of mixture solvent, and block ratios.

An efficient multigrid-DEIM semi-reduced-order model for simulation of single-phase compressible flow in porous media

In this paper,an efcient multigrid-DEIM semi-reduced-order model is developed to accelerate the simulation of unsteady single-phase compressible fow in porous media.The cornerstone of the proposed model is that the full approximate storage multigrid method is used to accelerate the solution of fow equation in original full-order space,and the discrete empirical interpolation method(DEIM)is applied to speed up the solution of Peng-Robinson equation of state in reduced-order subspace.The multigrid-DEIM semi-reduced-order model combines the computation both in full-order space and in reducedorder subspace,which not only preserves good prediction accuracy of full-order model,but also gains dramatic computational acceleration by multigrid and DEIM.Numerical performances including accuracy and acceleration of the proposed model are carefully evaluated by comparing with that of the standard semi-implicit method.In addition,the selection of interpolation points for constructing the low-dimensional subspace for solving the Peng-Robinson equation of state is demonstrated and carried out in detail.Comparison results indicate that the multigrid-DEIM semi-reduced-order model can speed up the simulation substantially at the same time preserve good computational accuracy with negligible errors.The general acceleration is up to 50-60 times faster than that of standard semi-implicit method in two-dimensional simulations,but the average relative errors of numerical results between these two methods only have the order of magnitude 10^(−4)-10^(−6)%.

Calculation of cell face velocity of non-staggered grid system

In this paper, the cell face velocities in the discretization of the continu- ity equation, the momentum equation, and the scalar equation of a non-staggered grid system are calculated and discussed. Both the momentum interpolation and the linear interpolation are adopted to evaluate the coefficients in the discretized momentum and scalar equations. Their performances are compared. When the linear interpolation is used to calculate the coefficients, the mass residual term in the coefficients must be dropped to maintain the accuracy and convergence rate of the solution.

Selectively converting CO_(2) to HCOOH on Cu-alloys integrated in hematite-driven artificial photosynthetic cells

The integration of electrochemical CO_(2)reduction(CO_(2)RR) and photoelectrochemical water oxidation offers a sustainable access to valuable chemicals and fuels. Here, we develop a rapidly annealed hematite photoanode with a photocurrent density of 2.83 mA cm^(-2)at 1.7 VRHEto drive the full-reaction. We also present Cu-alloys electrocatalysis extended from CuInSnS4, which are superior in both activity and selectivity for CO_(2)RR. Specifically, the screened CuInSn achieves a CO_(2)to HCOOH Faradaic efficiency of 93% at a cell voltage of-2.0 V by assembling into artificial photosynthesis cell. The stability test of IT exhibits less than 3% degradation over 24 h. Furthermore, in-situ Raman spectroscopy reveals that both CO_(3)^(-2)and CO_(2)are involved in CO_(2)RR as reactants. The preferential affinity of C for H in the ^(*)HCO_(2)intermediate enables an improved HCOOH-selectivity, highlighting the role of multifunctional Cu in reducing the cell voltage and enhancing the photocurrent density.

Numerical simulation and analysis of confined turbulent buoyant jet with variable source

In this work, experimental and numerical investigations are undertaken for confined buoyant turbulent jet with varying inlet temperatures. Results of the experimental work and numerical simulations for the problem under consideration are presented. Four cases of different variable inlet temperatures and different flow rates are considered. The realizable k-ε turbulence model is used to model the turbulent flow. Comparisons show good agreements between simulated and measured results. The average devia- tion of the simulated temperature by realizable k-ε turbulent model and the measured temperature is within 2%. The results indicate that temperatures along the vertical axis vary, generally, in nonlinear fashion as opposed to the approximately linear varia- tion that was observed for the constant inlet temperature that was done in a previous work. Furthermore, thermal stratification exits, particularly closer to the entrance region. Further away from the entrance region the variation in temperatures becomes relatively smaller. The stratification is observed since the start of the experiment and continues during the whole course. Numerical experime- nts for constant, monotone increasing and monotone decreasing of inlet temperature are done to show its effect on the buoyancy force in terms of Richardson number.

Combined Effect of Magnetic Field and Thermal Dispersion on a Non-Darcy Mixed Convection

This paper is devoted to investigate the influences of thermal dispersion and magnetic field on a hot semi-infinite vertical porous plate embedded in a saturated Darcy-Forchheimer-Brinkman porous medium. The coefficient of thermal diffusivity has been assumed to be the sum of the molecular diffusivity and the dynamic diffusivity due to mechanical dispersion. The effects of transverse magnetic field parameter (Hartmann number Ha), Reynolds number Re (different velocities), Prandtl number Pr (different types of fluids) and dispersion parameter on the wall shear stress and the heat transfer rate are discussed.

Dissipative Particle Dynamics Simulation on Bonding Reaction Between Surface Modified Nanoparticles

A simulation study was carried out by using dissipative particle dynamics(DPD) method to explore the effects of properties of coating chains, such as length, density, rigidity of polymer chains, as well as the distance between nanoparticles on bonding reaction of coating chains grafted onto nanoparticles. The results show that bonding ratios of coated chains strongly depend on the length and density of coating chains. For nanoparticles with different coating densities, the optimum chain length for bonding reaction are varied. The rigidity of coating chains exhibits vigorous effects on bonding reaction that highly depends on chain lengths. DPD simulation can be used to study the bonding reaction between coated nanoparticles, which may help experimental synthesis of nanocomposites with excellent properties.

Conjugated microporous polymer membranes for chemical separations

Conjugated microporous polymers(CMPs) are a unique class of porous organic materials, which are constructed with π-conjugation structures leading to intrinsic micropores. The CMPs properties such as high surface area, intrinsic and rich micropores, interlocking and rigid structure, extensive π-conjugation and tunable band-gap, chemical and thermal stability, together with tailored functionalities, contribute to its abundant potential for application in fields such as photocatalysis, optoelectronics, energy storage, and chemical sensors. Recently, CMPs have gained importance in the field of membranes for chemical separation. In this review, we briefly discuss the historical development of CMPs, followed by a detailed description of the progress in state-of-the-art design, preparation, and application of CMPs in membranes. Additionally, we provide inference on the future prospects of CMPs as membranes.

STABILITY AND CONVERGENCE ANALYSIS OF SECOND-ORDER SCHEMES FOR A DIFFUSE INTERFACE MODEL WITH PENG-ROBINSON EQUATION OF STATE

In this paper, we present two second-order numerical schemes to solve the fourth order parabolic equation derived from a diffuse interface model with Peng-Robinson Equation of state （EOS） for pure substance. The mass conservation, energy decay property, unique solvability and L~ convergence of these two schemes are proved. Numerical results demon- strate the good approximation of the fourth order equation and confirm reliability of these two schemes.

Giant two-photon absorption of anatase TiO_(2) in Au/TiO_(2) core-shell nanoparticles

We report on deep-to-near-UV transient absorption spectra of core-shell Au∕SiO_(2) and Au∕TiO_(2) nanoparticles(NPs) excited at the surface plasmon resonance of the Au core, and of UV-excited bare anatase TiO_(2) NPs. The bleaching of the first excitonic transition of anatase TiO_(2) at ~3.8 e V is a signature of the presence of electrons/holes in the conduction band(CB)/valence band(VB) of the material. We find that while in bare anatase TiO_(2) NPs, two-photon excitation does not occur up to the highest used fluences(1.34 mJ∕cm^(2)), it takes place in the TiO_(2) shell at moderate fluences(0.18 mJ∕cm^(2)) in Au∕TiO_(2) core-shell NPs, as a result of an enhancement due to the plasmon resonance. We estimate the enhancement factor to be of the order of ~10~8–10~9. Remarkably, we observe that the bleach of the 3.8 eV band of TiO_(2) lives significantly longer than in bare TiO_(2), suggesting that the excess electrons/holes in the conduction/valence band are stored longer in this material.

Nitrogen Reduction to Ammonia by a Phosphorus-Nitrogen PN^(3) P-Mo(V)Nitride Complex:Significant Enhancement via Ligand Postmodification

Efforts to develop organometallic complexes for catalytic nitrogen reduction have seen significant progress in recent years.However,the strategies for improving the activity of the homogenous catalysts have mainly focused on alternating ligands and metals.Herein,we report that the activity and stability of a PN_(P-Mo pincer complex(2)toward dinitrogen(N_(2))reduction were greatly enhanced through postmodification of the PN^(3)P pincer framework of its parent complex(1).A high ratio of NH_(3)/Mo(3525)was achieved in the presence of SmI_(2)as a reductant.In sharp contrast,1 only afforded an NH_(3)/Mo ratio of 21.Moreover,when supported by an anionic pincer ligand,2 furnished a high oxidation state Mo(V)-nitride complex via N_(2)cleavage as a plausible key intermediate in the catalytic process,suggesting a catalytic cycle that may involve different oxidation states(Ⅱ/Ⅴ)from those with 10-πelectron configuration in the literature.

Simulation of buoyancy-induced turbulent flow from a hot horizontal jet

Experimental visualizations and numerical simulations of a horizontal hot water jet entering cold water into a rectangular storage tank are described. Three different temperature differences and their corresponding Reynolds numbers are considered. Both experimental visualization and numerical computations are carried out for the same flow and thermal conditions. The realizable k-e model is used for modeling the turbulent flow while the buoyancy is modeled using the Boussinesq approximation. Polynomial approximations of the water properties are used to compare with the Boussinesq approximation. Numerical solutions are obtained for unsteady flow while pressure, velocity, temperature and turbulence distributions inside the water tank as well as the Froude number are analyzed. The experimental visualizations are performed at intervals of five seconds for all different cases. The simulated results are compared with the visualized results, and both of them show the stratification phenomena and buoyancy force effects due to temperature difference and density variation. After certain times, depending on the case condition, the flow tends to reach a steady state.

Coupling effects of the A-site ions on high-performance potassium sodium niobate ceramics

Although vast efforts have been given to the phase boundary engineering(PBE) of potassium sodium niobate(KNN) ceramics by using chemical dopants,the inherent issues like the K/Na ratio were not paid enough attention,hindering the further understanding of physical mechanisms.Herein,we investigated the effect of the K/Na ratio on PBE-featured KNN-based ceramics.The K/Na ratio significantly influences the local A-site environment and thereby alters mesoscopic ferroelectric domains and macroscopic structure and performance.A much higher Na^(+)content results in the local stress heterogeneity,while a much higher K^(+)content brings in the local polar heterogeneity.Due to the appropriate coupling between the local stress and the polar heterogeneity,piezoelectric properties and the temperature stability of electrostrain are optimized on the Na-rich side.Therefore,beyond seeking appropriate chemical dopants,elaborately tailoring the K/Na ratio is also important for further improving the piezoelectric properties of PBE-featured KNN-based ceramics.

Impressive near-infrared brightness and singlet oxygen generation from strategic lanthanide-porphyrin double-decker complexes in aqueous solution

Although lanthanide double-decker complexes with hetero-macrocyclic ligands as functional luminescent and magnetic materials have promising properties,their inferior water solubility has negated their biomedical applications.Herein,four water-soluble homoleptic lanthanide(Ln=Gd,Er,Yb and La)sandwiches with diethylene-glycoldisubstituted porphyrins(DD)are reported,with their structures proven by both quantum chemical calculations and scanning tunneling microscopy.Our findings demonstrate that the near-infrared emission intensity and singlet oxygen(1O2)quantum yields of YbDD and GdDD in aqueous media are higher than those of the reported capped lanthanide monoporphyrinato analogues,YbN and GdN;the brightness and luminescence lifetime in water of YbDD are greater than those of YbN.This work provides a new dimension for the future design and development of molecular theranostics-based water-soluble double-decker lanthanide bisporphyrinates.

All-Perovskite Tandem Solar Cells:A Roadmap to Uniting High Efficiency with High Stability

CONSPECTUS:Organic−inorganic halide perovskite photovoltaics(PVs)only a decade-old fieldhave reached impressive power conversion efficiencies(PCEs)and passed industrial stability requirements(IEC 61215:2016 Damp Heat and Humidity Freeze tests),solidifying their status among candidates for next generation PVs.Among the various perovskite PV technologies,all-perovskite tandem solar cells(PTSCs)are frontrunners for commercialization.PTSCs unite a narrow-bandgap(NBG;Eg≈1.2 eV)perovskite back cell with a wide-bandgap(WBG;Eg≈1.7−1.9 eV)perovskite front cell.Despite their nascency,PTSCs have achieved certified PCEs of 24.8%and 24.2%for small-area(0.049 cm^2)and large-area devices(1.041 cm2),respectively.With further advances in materials development,PTSCs are capable of moving beyond the PCE limits of single-junction cells due to reduced thermalization losses and improved utilization of the solar spectrum.By contrast,the PCE of single-junction perovskite devices is already approaching its saturation level,which is already very close to the device’s Shockley−Queisser limit for a bandgap of around 1.55 eV.The tandem architecture,thus,provides the most viable path forward to further exploiting the potential of perovskite solar cells.However,PTSC technology faces a set of challenges distinct from those in perovskite single-junction devices because(i)NBG perovskitestypically achieved by Pb−Sn alloyingare prone to oxidation(Sn^2+to Sn^4+),which results in a high density of Sn vacancies that degrade the optoelectronic performance of NBG perovskite films,(ii)practically complete photon absorption and charge extraction require thick,NBG perovskite films having long carrier diffusion lengths,and(iii)WBG perovskites with high Br/(I+Br)ratio experience large voltage losses and inferior light stability due to surface trap states and phase segregation.In this Account,we discuss how to manage these considerations and maximize the power output in PTSCs via light management.We then review strategies,including composition-and additive-engineering,defect passivation,and matching charge transport layers,for enhancing the carrier diffusion length of NBG perovskite cells and mitigating voltage losses in WBG perovskite cells.We also summarize the advances made in the fabrication of PTSCs on the device level,especially the evolution of tunnel recombination junctions and tandem device architectures.Finally,we highlight further research efforts needed to overcome roadblocks to commercialization(e.g.,improving the environmental,thermal,and operating stability of these devices)and offer our perspective on the future development of this rapidly advancing field.

Recent advances in heterogeneous catalytic conversion of glucose to 5-hydroxymethylfurfural via green routes

With concerns of diminishing fossil fuel reserves and environmental deterioration, great efforts have been made to explore novel approaches of efficiently utilizing bio-renewable feedstocks to produce chemicals and fuels. 5-Hydroxymethylfurfural(HMF),generated from dehydration of six-carbon ketose, is regarded as a primary and versatile renewable building block to realize the goal of production of these high valued products from renewable biomass resources transformation. In this review, we summarize the recent advances via green routes in the heterogeneous reaction system for the catalytic production of HMF from glucose conversion, and emphasize reaction pathways of these reaction approaches based on the fundamental mechanistic chemistry as well as highlight the challenges(such as separation and purification of products, reusing and regeneration of catalyst, recycling solvent) in this field.

EFFICIENT LINEAR SCHEMES WITH UNCONDITIONAL ENERGY STABILITY FOR THE PHASE FIELD MODEL OF SOLID-STATE DEWETTING PROBLEMS

In this paper,we study linearly first and second order in time,uniquely solvable and unconditionally energy stable numerical schemes to approximate the phase field model of solid-state dewetting problems based on the novel"scalar auxiliary variable"(SAV)approach,a new developed efficient and accurate method for a large class of gradient flows.The schemes are based on the first order Euler method and the second order backward differential formulas(BDF2)for time discretization,and finite element methods for space discretization.The proposed schemes are proved to be unconditionally stable and the discrete equations are uniquely solvable for all time steps.Various numerical experiments are presented to validate the stability and accuracy of the proposed schemes.