Fluid–structure interaction between a two-dimensional mat-type VLFS and solitary waves by the Green–Naghdi theory

The two-dimensional, nonlinear hydroelasticity of a mat-type very large floating structure (VLFS) is studied within the scope of linear beam theory for the structure and the nonlinear, Level I Green–Naghdi (GN) theory for the fluid. The beam equation and the GN equations are coupled through the kinematic and dynamic boundary conditions to obtain a new set of modified GN equations. These equations represent long-wave motion beneath an elastic plate. A set of jump conditions that are necessary for the continuity (or the matching) of the solutions in the open water region and that under the structure is derived through the use of the postulated conservation laws of mass, momentum, and mechanical energy. The resulting governing equations, subjected to the boundary and jump conditions, are solved by the finite-difference method in the time domain. The present model is applicable, for example, to the study of the hydroelastic response of a mat-type VLFS under the action of a solitary wave, or a frontal tsunami wave. Good agreement is observed between the model results and other published theoretical and numerical predictions, as well as experimental data. The results show that consideration of nonlinearity is important for accurate predictions of the bending moment of the floating elastic plate. It is found that the rigidity of the structure greatly affects the bending moment and displacement of the structure in this nonlinear theory.     

First-principles analysis of phonon thermal transport properties of two-dimensional WS_2/WSe_2 heterostructures

The van der Waals(vdW)heterostructures of bilayer transition metal dichalcogenide obtained by vertically stacking have drawn increasing attention for their enormous potential applications in semiconductors and insulators.Here,by using the first-principles calculations and the phonon Boltzmann transport equation(BTE),we studied the phonon transport properties of WS2/WSe2 bilayer heterostructures(WS2/WSe2-BHs).The lattice thermal conductivity of the ideal WS2/WSe2-BHs crystals at room temperature(RT)was 62.98 W/mK,which was clearly lower than the average lattice thermal conductivity of WS2 and WSe2 single layers.Another interesting finding is that the optical branches below 4.73 THz and acoustic branches have powerful coupling,mainly dominating the lattice thermal conductivity.Further,we also noticed that the phonon mean free path(MFP)of the WS2/WSe2-BHs(233 nm)was remarkably attenuated by the free-standing monolayer WS2(526 nm)and WSe2(1720 nm),leading to a small significant size effect of the WS2/WSe2-BHs.Our results systematically demonstrate the low optical and acoustic phonon modes-dominated phonon thermal transport in heterostructures and give a few important guidelines for the synthesis of van der Waals heterostructures with excellent phonon transport properties.     

The detection of tetrahydrofuran hydrate formation and saturation using magnetic resonance imaging technique

Tetrahydrofuran (THF) hydrate was formed in bulk as well as in glass beads pack with a mean diameter of 3.0 mm by controlling the temperature under ambient pressure. Images of THF hydrate formation procedure were obtained using the magnetic resonance imaging (MRI) technique. The experiment results showed that MRI is an effective method for the detection of hydrate formation. Saturation of hydrate formed both in bulk and glass beads can be confirmed by intensity integration of MRI images.     

Preparative separation of major xanthones from mangosteen pericarp using high‐performance centrifugal partition chromatography

Mangosteen fruit pericarp (MFP) is a rich source of xanthones, which has shown remarkable pharmacological activities. To isolate xanthones, previous methods included labor intensive and time‐consuming solid‐phase extractions (Sephadex LH20, silica gel) and sequential solvent extraction. In this study, major xanthones (α‐ and γ‐mangostins) in MFP were isolated at high purity in one step utilizing high‐performance centrifugal partition chromatography with solvent system composed of petroleum ether, ethyl acetate, methanol and water (10:5:5:1). In one run, 200 mg crude extract of MFP was injected and 55.4 mg α‐mangostin and 12.4 mg γ‐mangostin were obtained with the purity of 93.6 and 98.4%, respectively. The yields of them were 86.3 and 76.3%, respectively. As α‐ and γ‐mangostins are reported to show potent antioxidant, anti‐inflammatory and anticancer activities, this method can be used for the large‐scale production of them for future in vitro and in vivo biological studies.     

Mapping of phosphorylation sites in human MSK1 activated by a novel interaction with MRK‐β

The desire to map reliable phosphorylation signaling network has motivated the development of high‐performance techniques. Targeted biochemical studies and updated methods employing MS techniques are most used in mapping the phosphorylation sites and verifying novel interactions of kinases. Previously, we have established a novel method to efficiently facilitate more comprehensive, accurate phosphorylation site mapping of individual phosphoproteins by using combination of multiple stage MS analysis with target‐decoy database search against the much smaller targeted database. In this study, by applying this method, we have identified the phosphorylation sites in human MSK1 mitogen‐ and stress‐activated protein kinase 1), which has been proved to be a multi‐phosphorylated kinase that plays key roles in various cell functions, activated by a novel interaction with MRK‐β. The results show that this method can find out not only those previously identified active sites in MSK1, but also some novel phosphorylated sites, which correlates with biochemical evidence that, besides p38 and extracellular signal‐regulated kinase, MRK‐β could also activate MSK1 through direct interaction. Hence, we conclude this method is sensitive and reliable as expected and it can be further combined with automated screening and biochemical study in efficiently building up a more comprehensive phosphoprotein network.     

The synthesis of chloropropyl-functionalized silica hybrid monolithic column with modification of N,N-dimethyl-N-dodecylamine for capillary electrochromatography separation

A chloropropyl-functionalized silica (CP-silica) hybrid monolithic column was synthesized within the confines of a capillary via the sol–gel process using tetramethoxysilane (TMOS) and (3-chloropropyl)-trimethoxysilane (CPTMS) as the precursors. The resulting CP-silica hybrid monolith inside the capillary showed homogeneous macroporous morphology and was well attached to the inner wall of the capillary. The obtained CP-silica hybrid monolithic capillary column demonstrated the inherent hydrophobic property and could be applied as a reversed-phase stationary phase in CEC directly. Due to the great chemical reactivity of the incorporated chloro groups on the hybrid silica monolithic matrix, the chloropropyl moieties on the surface of the hybrid silica monolith matrix could be conveniently further modified by a tertiary amine of N,N-dimethyl-N-dodecylamine (DMDA) via the nucleophilic substitution reaction at 70 °C to introduce a dodecyl groups (C12) onto the CP-silica hybrid monolithic matrix. The resulting C12-silica hybrid monolithic column not only demonstrated the significantly enhanced hydrophobic property in the separation of alkylbenzenes in reversed-phase capillary electrochromatography (RP-CEC), but also the strong electroosmotic flow (EOF) in a wide pH range. Five alkylbenzenes could be baseline separated in 3 min with column efficiency ranging from 189 700 to 221 000 N/m with a 70% ACN running buffer in CEC.     

离子液体中微波辅助的 Lewis 酸催化纤维素制备 5-羟甲基糠醛

 以离子液体 1-丁基-3-甲基咪唑氯为溶剂, 以 CrCl3•6H2O 为催化剂, 直接转化纤维素生成 5-羟甲基糠醛 (HMF). 考察了微波辐射条件、反应温度、反应时间及催化剂用量对 HMF 产率的影响. 结果表明, 在最佳条件下, HMF 产率可达 55%.     

HPLC-MS-MS法测定水体中残留的氨基甲酸酯类农药

应用高效液相色谱-串联质谱(HPLC-MS-MS)联用技术,建立了检测水体中氨基甲酸酯类农药残留的方法。水样经氨基柱固相萃取,二氯甲烷洗脱,梯度流动相洗脱,电喷雾正离子(ESI+)模式采集、选择反应性监测模式(SRM)对定性、定量离子进行MS/MS测定。5种氨基甲酸酯类农药在5～200ng/L范围内线性关系良好,回收率为80%～92%,相对标准偏差均小于10%,方法检出限分别为:异丙威和仲丁威为1.4ng/L,克百威和甲萘威为1.5ng/L,恶虫威为1.6ng/L。该方法适用于水体中氨基甲酸酯类农药残留的检测。     

Towards efficient upconversion and downconversion of NaYF4:Ho3+,Yb3+ phosphors

NaYF₄ microcrystals co-doped with Ho³⁺ and Yb³⁺ were prepared by a facile hydrothermal synthesis. The products were characterized by X-ray diffractometer, scanning electron microscopy, and photoluminescence spectroscopy. Upon excitation with a 980 nm laser diode, the sample shows an intense green upconversion emission centered at 540 nm corresponding to the ⁵S₂→⁵I₈ transition of Ho³⁺. The quadratic dependence of the green emission intensity on the excitation power reveals a two-phonon upconversion process. On the contrary, upon excitation with 448 nm, both visible and near-infrared emissions peaked at 483, 540, 644, 749, and 978 nm are simultaneously observed, which could be assigned to the electronic transitions of Ho³⁺: ⁵F₃→⁵I₈, ⁵S₂→⁵I₈, ⁵F₅→⁵I₈, ⁵S₂→⁵I₇, and Yb³⁺: ²F_5/2→²F_7/2, respectively. The energy transfer processes between Ho³⁺ and Yb³⁺ ions and the involved mechanisms have been investigated and discussed.     

Solving semi-infinite programs by smoothing projected gradient method

In this paper, we study a semi-infinite programming (SIP) problem with a convex set constraint. Using the value function of the lower level problem, we reformulate SIP problem as a nonsmooth optimization problem. Using the theory of nonsmooth Lagrange multiplier rules and Danskin’s theorem, we present constraint qualifications and necessary optimality conditions. We propose a new numerical method for solving the problem. The novelty of our numerical method is to use the integral entropy function to approximate the value function and then solve SIP by the smoothing projected gradient method. Moreover we study the relationships between the approximating problems and the original SIP problem. We derive error bounds between the integral entropy function and the value function, and between locally optimal solutions of the smoothing problem and those for the original problem. Using certain second order sufficient conditions, we derive some estimates for locally optimal solutions of problem. Numerical experiments show that the algorithm is efficient for solving SIP.