Equivalent analytical model for liquid sloshing in a 2-D rectangular container with multiple vertical baffles by subdomain partition approach.

An equivalent analytical model of sloshing in a two-dimensional (2-D) rigid rectangular container equipped with multiple vertical baffles is presented. Firstly, according to the subdomain partition approach, the total liquid domain is partitioned into subdomains with the pure interface and boundary conditions. The separation of variables is utilized to achieve the velocity potential for subdomains. Then, sloshing characteristics are solved according to continuity and free surface conditions. According to the mode orthogonality of sloshing, the governing motion equation for sloshing under horizontal excitation is given by introducing generalized time coordinates. Besides, by producing the same hydrodynamic shear and overturning moment as those from the original container-liquid-baffle system, a mass-spring analytical model of the continuous liquid sloshing is established. The equivalent masses and corresponding locations are presented in the model. The feasibility of the present approach is verified by conducting comparative investigations. Finally, by utilizing normalized equivalent model parameters, the sloshing behaviors of the baffled container are investigated regarding baffle positions and heights as well as the liquid height, respectively.

Characterisation of transient electromagnetic signals during fixed interference sources in tunnel structure.

The detection effect of the transient electromagnetic method is ambiguous in engineering applications due to the existence of interference sources, so explaining the influence of these fixed interference sources on is crucial. In this paper, the response characterisation of transient electromagnetic signals of fixed interference sources are thoroughly investigated. First, the secondary field generated by these interference sources is analyzed, and a typical fixed interference source is calculated. Then, a sensitivity analysis of the transient electromagnetic response curve is carried out. Finally, the mathematical superposition method for multiple field sources is proposed and verified. The results illustrate that the transient electromagnetic response curve of uniform full-space surrounding rock with a single fixed interference source has an apparent lifting phenomenon in the middle stage and presents an approximate horizontal change rule at the late stage. The transient electromagnetic response curves of multiple field sources separately illustrate the response characterisation of different field sources at different time stages. These research results can provide a valuable reference for the on-site interpretation of detection signals.

Synthesis and labeling of α-(2,9)-trisialic acid with cyanine dyes for imaging of glycan-binding receptors on living cells.

A sugar epitope, α-(2,9)-trisialic acid, was synthesized and labeled by cyanine dyes through Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The cyanine tagged oligosialic acid can be utilized as an efficient fluorescent probe to image the glycan-binding receptors on PC-12 cells. The distribution of Sia-binding immunoglobulin-like lectins (Siglecs) for α-(2,9)-trisialic acid was visualized by Cy3/Cy5 or FRET channel fluorescence imaging.

Iron(II)-catalyzed asymmetric intramolecular olefin aminochlorination using chloride ion.

An iron-catalyzed enantioselective and diastereoselective intramolecular olefin aminochlorination reaction is reported (ee up to 92%, dr up to 15 : 1). In this reaction, a functionalized hydroxylamine and chloride ion are utilized as nitrogen and chlorine sources, respectively. This new method tolerates a range of synthetically valuable internal olefins that are all incompatible with existing asymmetric olefin aminochlorination methods.

Comparative studies on the O-sialylation with four different α/ß-oriented (N-acetyl)-5-N,4-O-carbonyl-protected p-toluenethiosialosides as donors.

Four types of 5-N,4-O-carbonyl-protected p-toluenethiosialosides were synthesized and their couplings with different acceptors were thoroughly investigated. The results indicate that the sialyl donor structure, the amount of glycosyl acceptor, and the detailed promotion conditions have great influence on the sialylation stereoselectivties and product yields. Under the (p-Tol)2SO/Tf2O activation conditions, the glycosylations with simple alcohols provided declined α-selectivities and higher yields with increasing the amounts of acceptors from 1.1 equiv to 2.0equiv. However, the outcome of same sialylation was independent of the relative amounts of sugar alcohol acceptors. With NIS/TfOH as promoter, the α-selectivities of the sialylations were significantly improved compared with the cases activated by (p-Tol)2SO/Tf2O. In general, the difference in configuration of N-acetylated sialyl donors (D2 and D4) has little effect on the sialylation yield and stereoselectivity. In contrast, the N-deacetylated α/ß sialyl donors (D1 and D3) show complex sialylation profiles with different acceptors.

Highly efficient α-C-sialylation promoted by (p-Tol)2SO/Tf2O with N-acetyl-5-N,4-O-oxazolidione protected thiosialoside as donor.

Based on a preactivation protocol with (p-Tol)2SO/Tf2O, a practical, straightforward, and high-yielding synthesis of α-sialyl C-glycosides was accomplished by coupling N-acetyl-5-N,4-O-oxazolidione protected thiosialoside with various trimethylsilyl enol ethers and allyltrimethylsilanes. High yields and excellent α-selectivities were obtained for the strong π-nucleophiles with large nucleophilicity values (N = 4.4-9.0), irrespective of whether silyl enol ethers, silyl ketene acetals or allyltrimethylsilanes were used for the electrophilic C-sialylation.

N-acetyl-5-N,4-O-oxazolidinone-protected sialyl sulfoxide: an α-selective sialyl donor with Tf2O/(Tol)2SO in dichloromethane.

Sweet as sugar: Sialyl sulfoxide protected by N-acetyl-5-N,4-O-oxazolidinone was readily prepared, and its coupling to various sugar acceptors was investigated. When the reaction was promoted by Tf(2)O/(Tol)(2)SO, efficient and highly α-selective sialylation yielded α(2,6), α(2,3), and α(2,4) glycosidic linkages between sialic acid and glucose/glacotose.

Tunable stereoselectivity during sialylation using an N-acetyl-5-N,4-O-oxazolidinone-protected p-toluene 2-thio-sialoside donor with Tf(2)O/Ph(2)SO/TTBPy.

An N-acetyl-5-N,4-O-oxazolidinone-protected p-toluene 2-thio-sialoside donor, promoted by Ph(2)SO/Tf(2)O/TTBPy, was thoroughly investigated in the coupling to various acceptors. The stereoselectivity of the sialylation was found to be dependent on the various reaction conditions, such as pre-activation time, reaction time, the amount of Ph(2)SO, and TTBPy. A detailed Ph(2)SO/Tf(2)O-promoted glycosylation mechanism was proposed, which contained three crucial reactive species: an oxacarbenium ion, C2-sialyloxosulfonium salts, and oxosulfonium supramers. Our research results indicate that it is possible to tune the stereoselectivity of the sialylation by carefully changing the reaction conditions. For instance, Ph(2)SO (2.0-3.0 equiv)/TTBPy (0-1.0 equiv) promotion gives higher α-selective sialylation in dichloromethane, while Ph(2)SO (4-5 equiv)/TTBPy (0 equiv) or Ph(2)SO (2.0 equiv)/TTBPy (2.0 equiv) affords lower stereoselectivity.