Type II Intramolecular [5+2] Cycloaddition: Facile Synthesis of Highly Functionalized Bridged Ring Systems

A type II intramolecular oxidopyrylium‐mediated [5+2] cycloaddition reaction allows the efficient and diastereoselective formation of various highly functionalized and synthetically challenging bridged seven‐membered ring systems (such as bicyclo[4.4.1]undecane, bicyclo[4.3.1]decane, bicyclo[5.4.1]dodecane, and bicyclo[6.4.1]]tridecane). This simple, thermal, direct transformation has a broad substrate scope and is high yielding, with high functional‐group tolerance and unique endo selectivity. The highly strained tricyclic cores of ingenol mebutate (picato) and cyclocitrinol are synthesized efficiently and diastereoselectively using this methodology.     

Rapid Formation of a Supramolecular Polypeptide–DNA Hydrogel for In Situ Three‐Dimensional Multilayer Bioprinting

A rapidly formed supramolecular polypeptide–DNA hydrogel was prepared and used for in situ multilayer three‐dimensional bioprinting for the first time. By alternative deposition of two complementary bio‐inks, designed structures can be printed. Based on their healing properties and high mechanical strengths, the printed structures are geometrically uniform without boundaries and can keep their shapes up to the millimeter scale without collapse. 3D cell printing was demonstrated to fabricate live‐cell‐containing structures with normal cellular functions. Together with the unique properties of biocompatibility, permeability, and biodegradability, the hydrogel becomes an ideal biomaterial for 3D bioprinting to produce designable 3D constructs for applications in tissue engineering.     

Synthesis of 2-(phenoxymethyl)oxirane derivatives through unexpected rearrangement of oxiran-2-ylmethyl benzenesulfonates

The synthesis of 2-(phenoxymethyl)oxirane derivatives from oxiran-2-ylmethyl benzenesulfonates was developed through a base promoted rearrangement. A new C-O bond was formed along with the unexpected cleavage of C-S bond via this process. This unusual reaction was characterized with mild reaction conditions, high efficiency, and excellent functional group tolerance. A plausible reaction mechanism was proposed on the basis of experimental results and control experiments.     

Synthetic study of solanoeclepin A: Cyclobutane cyclization via SmI2-additive-mediated reaction and D ring functionalization

The construction of tricyclo[5.2.1.0^1,6]decene skeleton was achieved by cyclobutane ring formation via improved radical reaction using SmI₂-H₂O-HFIP and SmI₂-LiCl conditions in good yields. Those additives were studied to increase the reactivity of SmI₂. Two interesting reactions via neighboring group participations are described for introducing the C4 oxygen functionality by the assistance of C6 substituent in a regioselective manner.     

Cu/ZnO@H-β-P催化剂在合成气制备液化石油气反应中的性能研究

采用共沉淀法制备Cu/ZnO催化剂、水热合成法制备H-β分子筛、通过物理包膜法制备了具有核壳结构的Cu/ZnO@H-β-P催化剂,并用于合成气制备液化石油气(LPG)反应。通过XRD、NH3-TPD、BET和SEM-EDS等手段对催化剂进行了表征,利用固定床连续反应装置对催化剂进行了活性评价。结果表明,Cu/ZnO@H-β-P催化剂是具有中孔的核壳结构材料,其协同作用打破了原有的热力学平衡,促进了甲醇→DME→LPG串联反应的连续进行。与物理混合的Mix-Cu/ZnO-H-β催化剂相比,Cu/ZnO@H-β-P催化剂的CO转化率和LPG选择性更高,空速和反应温度对催化剂活性影响明显,最佳空速和反应温度分别为2 400 h~(-1)和350℃。使用Cu/ZnO@H-β-P催化剂在最佳条件下进行合成气制备LPG反应,CO转化率达到了57.22%,LPG选择性达到了60.52%。     

Threshold dynamics of a stochastic Keizer’s model with stochastic incidence

In this paper, we incorporate stochastic incidence of a chemical reaction into the standard Keizer’s open chemical reaction. We prove that a positive stationary distribution (PSD) for the associated chemical master equation exists and is globally asymptotically stable. We present threshold dynamics of the stochastic Keizer’s model in term of the profile of the PSD for both finite and infinite volume size V. This establishes a sharp link between deterministic Keizer’s model and the stochastic model. In this way, we resolve Keizer’s paradox from a new perspective. This simple model reveals that such stochastic incidence incorporated, though negligible when V goes to infinity, may play an indispensable role in the stochastic formulation for irreversible biochemical reactions.     

Well-posedness for parametric optimization problems with variational inclusion constraint

In this paper, we study the well-posedness for the parametric optimization problems with variational inclusion problems as constraint (or the perturbed problem of optimization problems with constraint). Furthermore, we consider the relation between the well-posedness for the parametric optimization problems with variational inclusion problems as constraint and the well-posedness in the generalized sense for variational inclusion problems.     

Algorithms with new parameter conditions for split variational inclusion problems in Hilbert spaces with application to split feasibility problem

Split variational inclusion problem is an important problem, and it is a generalization of the split feasibility problem. In this paper, we present feasible algorithms for the split variational inclusion problems in Hilbert spaces, and provide convergence theorems for these algorithms. As application, we study the split feasibility problem in real Hilbert spaces. Final, numerical results are given for our main results.     

Construction of a cryogen‐free thermal desorption gas chromatographic system with off‐the‐shelf components for monitoring ambient volatile organic compounds

An automated gas chromatographic system aimed at performing unattended measurements of ambient volatile organic compounds was configured and tested. By exploiting various off‐the‐shelf components, the thermal desorption unit was easily assembled and can be connected with any existing commercial gas chromatograph in the laboratory to minimize cost. The performance of the complete thermal desorption gas chromatographic system was assessed by analyzing a standard mixture containing 56 target nonmethane hydrocarbons from C₂–C₁₂ at sub‐ppb levels. Particular attention was given to the enrichment efficiency of the C₂ compounds, such as ethane (b.p. = –88.6°C) and ethylene (b.p. = –104.2°C), due to their extremely high volatilities. Quality assurance was performed in terms of the linearity, precision and limits of detection of the target compounds. To further validate the system, field measurements of target compounds in ambient air were compared with those of a commercial total hydrocarbon analyzer and a carbon monoxide analyzer. Highly coherent results from the three instruments were observed during a two‐month period of synchronized measurements. Moreover, the phenomenon of opposite diurnal variations between the biogenic isoprene and anthropogenic species was exploited to help support the field applicability of the thermal desorption gas chromatographic method.     

Simultaneous determination of Repaglinide and Irbesartan in biological plasmas using micellar enhanced excitation-emission matrix fluorescence coupled with ATLD method

A highly sensitive and selective 3D excitation-emission fluorescence method has been proposed to rapidly quantify the combined antidiabetics Repaglinide(Re) and Irbesartan(Ir) in rat and human plasmas with the aid of second-order calibration method based on alternating trilinear decomposition(ATLD) method. Re and Ir with weak fluorescence can be endowed with strong fluorescent property by changing the microenvironment in samples and improving the fluorescence quantum yield by using an appropriate micellar enhanced surfactant. The enhanced excitation-emission matrix fluorescence of Re and Ir can be accurately resolved and can simultaneously attain the optimal concentration even in the presence of a potentially strong intrinsic fluorescence from complex biological matrices, such as rat and human plasmas, by using the ATLD method, which completely exploits the "second-order advantage". The average recoveries of Re and Ir obtained from ATLD with the factor number of 3(N=3) were 101.0%±4.3% and 99.1%±4.1% for rat plasma and 100.5%±5.4% and 97.1%±3.6% for human plasma. Several statistical methods, including Student's t-test, figures of merit, and elliptical joint confidence region, have been utilized to evaluate the accuracy of the proposed method. Results show that the developed method can maintain second-order advantage in simultaneous determinations of the weak fluorescent analytes of interest in different biological plasma matrices.