Injectable and self-healing hydrogels with tissue adhesiveness and antibacterial activity as wound dressings for infected wound healing

The design of wound dressings with excellent self-healing ability, adequate adhesion, good biocompatibility, and potential antibacterial ability is of great significance for the healing of infected wounds arising from human activities. Herein, a series of multi-functional hydrogel dressings, poly(ionized isocyanoethyl methacrylate-glutamine)/poly(hexamethylene guanidine) (iG_x/PHMG_y) hydrogels, were obtained through homopolymerization of fully ionized isocyanoethyl methacrylate-glutamine (iIEM-Gln) in the presence of poly(hexamethylene guanidine) (PHMG), in which strong hydrogen bonds were formed among urea groups in the P (iIEM-Gln) chain to form a stable hydrogel network. The prepared iG_x/PHMG_y hydrogels exhibited adequate self-healing ability and tissue adhesion, which could be firmly adhered to the wound surface and remained intact during application. In addition, the presence of PHMG imparted good antibacterial activity to the hydrogels for the effective promotion of the wound healing in S. aureus infected skin wound on mice. Overall, this multi-functional hydrogel provides a facile and effective strategy for the design of infected wound dressings, and may show great potential in clinical applications.     

富里叶级数的收敛速度

对正弦和余弦富立叶级数,通过合并相邻同号项,使其重排成交错级数.讨论了重排形成的交错级数的敛散性.指出根据自变量x的不同取值,该交错级数可能是单调递减或周期递减的级数.按照莱布尼茨判定法提出了不同精度要求的级数项数的计算公式.选取一到三阶收敛的富立叶级数计算了不同比值精度及差值精度要求的级数项数.计算表明,在x的取值为2π的等分点时,富立叶级数的部分和随项数的增加单调地逼近其收敛值.在x的取值为其它点时,富立叶级数的部分和随项数的增加围绕收敛值上下变动,周期地逼近其收敛值.低收敛阶富立叶级数的收敛速度较慢.要达到0.01%的精度,一收敛阶富立叶级数需要数万项,二收敛阶富立叶级数也需要数百项.在不同计算点处,要达到相同的计算精度,需要的级数项数差别较大.     

甲基环己烷在9∽15.5 eV能量区的真空紫外光电离研究

利用具有同步辐射源的反射式飞行时间质谱仪，研究甲基环己烷的真空紫外光电离和光解离. 观测到母体离子C₇H₁₄⁺和碎片离子C₇H₁₃⁺，C₆H₁₁⁺，C₆H₁₀⁺，C₅H₁₀⁺，C₅H₉⁺，C₄H₈⁺，C₄H₇⁺和C₃H₅⁺的光电离效率曲线. 测定甲基环己烷的电离能为9.80±0.03 eV，通过光电离效率曲线确定其碎片离子的出现势. 在B3LYP/6-31G(d)水平上对过渡态、中间体和产物离子的优化结构进行表征，并使用G3B3方法计算其能量. 提出主要碎片离子的形成通道. 分子内氢迁移和碳开环是甲基环己烷裂解途径中最重要的过程.     

Visible-light-driven spirocyclization of epoxides via dual titanocene and photoredox catalysis

We describe the synergistic utilization of titanocene/photoredox dual catalysis driven by visible light for the radical opening/spirocyclization of easily accessible epoxyalkynes. This environmentally benign process uses the organic donor–acceptor fluorophore 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photocatalyst and Hantzsch ester (HE) as an electron donor instead of stoichiometric metallic reductants. The photocatalytic conditions showed exceptionally high reactivity for the synthesis of privileged and synthetically challenging spirocycles featuring a spiro all-carbon quaternary stereocenter. Cyclic voltammetry (CV) studies suggest that Cp₂Ti^IIICl is the catalytically active species.

We describe the synergistic utilization of titanocene/photoredox dual catalysis driven by visible light for radical opening/spirocyclization of easily accessible epoxyalkynes.

Over the last few decades, radical-based transformations have been increasingly used in organic synthesis due to their salient features, such as ease of generation, mild reaction conditions, and broad functional group compatibility.^1,2 As a mild single-electron-transfer (SET) reagent, titanocene monochloride (Cp₂Ti^IIICl) is considered a formidable tool in contemporary radical chemistry due to its ability to promote various fundamental radical-based transformations.^3–7 Cp₂Ti^IIICl was first introduced by Nugent and RajanBabu as a very mild stoichiometric reagent for the reductive opening of epoxides.^8–11 Later, the catalytic conditions developed by Gansäuer et al. (Scheme 1a)¹² employing stoichiometric amounts of active metals in combination with 2,4,6-collidine·HCl further expanded its applications and led to the discovery of a number of novel transformations.^13–16 The key to success was the formation of a stable complex A in reactions while decreasing the concentration of active Cp₂Ti^IIICl.^17,18 We were interested in the radical opening/cyclization reaction of epoxides which has attracted considerable attention from the synthetic community and has been used numerous times in the synthesis of natural products.^19,20 Nevertheless, this reaction required stoichiometric metallic reductants and proceeded slowly particularly with sterically hindered substrates even with high catalyst loading.²¹ Therefore, the development of an eco-friendly and efficient catalytic system with an expanded substrate scope is highly desirable.Open in a separate windowScheme 1Cp₂Ti^IIICl mediated radical opening/spirocyclization of epoxides; (a) generation of Ti^IIIvia a metal reduction approach; (b) dual titanocene/photoredox catalysis; (c) examples of drugs and natural products containing heterospirocycles.In recent years metallaphotoredox catalysis has been a new and rapidly growing research subject.^22–29 Photoredox processes can directly modulate the oxidation state of metals by electron transfer (ET).^30–33 Given that the generation of Ti^III is a SET process, we envisioned that the reduction could be facilitated by a photoredox-controlled process while overcoming the aforementioned limitations. On the other hand, spirocycles bearing a chiral spiro all-carbon quaternary carbon are particularly attractive synthetic targets in pharmaceutical development (Scheme 1c).^34–36 Such privileged rigid 3D structures offer the concomitant ability to project functionalities in all three-dimensional orientations and led to enhanced pharmacological activities of molecules. Thus significant attention has been paid to their synthesis.^37,38 Against this backdrop, here we describe our efforts on the synthesis of various heterospirocycles with the aid of photoredox catalysis.We chose epoxyalkyne 2a as a model substrate for optimization of reaction conditions. After a systematic variation of different reaction parameters, we were pleased to identify the optimal reaction conditions in which a mixture of Cp₂TiCl₂ (5.0 mol%), [Ir(dtbbpy)(ppy)₂]PF₆ (1a, 1.0 mol%, E^III/II_1/2 = −1.51 V vs. SCE in MeCN), HE (1.2 equiv.) and 2a (1.0 equiv.) in THF at room temperature under the irradiation of a 10 W 450 nm light emitting diode (LED) lamp for 12 hours afforded the desired product 3a in an excellent yield of 96% (13 : 1 d.r.) upon isolation (entry 1). Using a commercial 23 W compact fluorescent lamp (CFL) instead of the 10 W 450 nm LED did not compromise the overall yield of the reaction (entry 2). Notably, when the loading of Cp₂TiCl₂ was decreased to as low as only 2.0 mol%, the reaction still led to full conversion and produced 3a in 95% yield (entry 3). Further screening of other photosensitizers revealed that the cheap and readily obtained organic dye 4CzIPN 1b is a competent alternative, which led to full conversion with 94% isolated yield (entry 4). Importantly, the reaction did not proceed in the absence of Cp₂TiCl₂, HE, the photocatalyst, or visible light (entries 5–8). Various solvents, including DMF, MeOH, DMSO, and MeCN, were screened, and they all resulted in poor conversion. The use of other organic electron donors, such as triethylamine, triethanolamine, and ascorbic acid, afforded the product in poor yield.With satisfactory reaction conditions established, we then explored the scope of the cyclization reaction using 4CzIPN as the photosensitizer. Positively, the cyclization reaction worked well and afforded the desired variably heterospirocyclic products in good to excellent yield (Tables 2 and ​and3).3). The reaction allows the rapid construction of various 5/5, 5/6, 5/7 and 5/8 spiro-ring fused systems (3a–3k) bearing tetrahydrofuran or pyrrolidine motifs via the 5-exo cyclization pathway. Interesting, the diastereoselectivity of the cyclization reaction is highly correlated with the ring size in the substrates. Heterospirocycles containing a 5/5 spiro-ring fused system (3a–3f) were obtained with surprisingly high diastereoselectivity. In some cases (3b, 3c, and 3e) only a single isomer was obtained. The product 3d with a sterically hindered t-butyloxy carbonyl (Boc) protecting group on the N atom was obtained with reduced diastereoselectivity (5 : 1 d.r.). The diastereoselectivities dropped in 5/6, 5/7 and 5/8 spiro-ring fused systems. Given that enantioenriched epoxides could be easily obtained (e.g. via sharpless asymmetric epoxidation), this strategy provides access to optically active spirocycles featuring an all-carbon quaternary stereocenter with the transfer of stereochemical information from epoxides (3c, 3e and 3f). Bis-heterospirocyclic scaffolds were frequently employed in pharmaceutical chemistry. For example, bis-heterospirocyclic 3d is the core structure of DLK inhibitors³⁹ and XEN402 (ref. 40) (scheme 1c), which are used for treating neurodegeneration and congenital erythromelalgia respectively. Furthermore, 6-exo cyclization was also investigated under the standard conditions and smoothly produced a serious of drug-like 6-(trifluoromethyl)-3-pyridinesulfonyl piperidine derivatives including 6/5, 6/6 and 6/7 spiro-ring fused systems (5a–5k) in generally excellent yields. Moreover, cyclization reactions with epoxy-alkynes afforded products containing exocyclic-alkenes and free alcohols which were suitable for further functionalization. This approach provides access to a broad range of novel spirocyclic piperidine and pyrrolidine spirocycles which could be of interest to synthetic and medicinal chemists.Scope of 5-exo and 6-exo cyclization^a,b,c,d

Twist and sliding dynamics between interpenetrated frames in Ti-MOF revealing high proton conductivity

We report the design and synthesis of a titanium catecholate framework, MOF-217, comprised of 2,4,6-tri(3,4-dihydroxyphenyl)-1,3,5-triazine (TDHT) and isolated TiO₆ clusters, with 2-fold interpenetrated srs topology. The dynamics of the organic linker, breaking the C_3h symmetry, allowed for reversible twist and sliding between interpenetrated frames upon temperature change and the inclusion of small molecules. Introduction of 28 wt% imidazole into the pores of MOF-217, 28% Im-in-MOF-217, resulted in four orders of magnitude increase in proton conductivity, due to the appropriate accommodation of imidazole molecules and their proton transfer facilitated by the H-bond to the MOF structure across the pores. This MOF-based proton conductor can be operated at 100 °C with a proton conductivity of 1.1 × 10⁻³ S cm⁻¹, standing among the best performing anhydrous MOF proton conductors at elevated temperature. The interframe dynamics represents a unique feature of MOFs that can be accessed in the future design of proton conductors.

Twist and sliding dynamics observed in a titanium catecholate MOF induced by imidazole for efficient proton conduction.     

可溶性离子对煅烧烟气脱硫石膏水化的影响

本文主要研究了不同水溶性离子对煅烧烟气脱硫石膏水化过程，也就是对大块煅烧石膏向石膏转化的相变过程的影响. 研究表明，在煅烧石膏向石膏转化的相变过程中，所有的阳离子都能加速煅烧石膏的水化作用，其中Ca²⁺的加速效应最弱. 对于最终沉淀得到的晶体，除了钠离子外，晶体尺寸不受不同种类盐的影响. 而在钠离子中，可以观察到长度大于130 μm的巨型结晶. 本研究阐明了不同离子对煅烧石膏水化的影响，为原始的烟气脱硫石膏在实际应用前的预处理提供了充分的指导.     

50,52,53,54Cr光核反应数据评价

通过分析光子诱发52,50Cr核反应的各类实验数据，澄清52Cr光子吸收截面评价数据与中子、质子出射截面测量值间的分歧，给出了52Cr中子出射截面实验数据的修正；选取EGLO模型光子强度函数，结合准氘模型，给出光子吸收截面。在此基础上，采用最新研制的光子与中重核反应计算程序MEND-G，通过优化理论模型参数，包括剩余核的能级密度和对能修正参数，给出光子能量在200 MeV范围内的n、p、${{\rm{\alpha }}}$等粒子出射核反应的截面，52,50Cr的计算结果在30 MeV以下能区很好地符合了现有实验数据，并按国际标准ENDF/B-6库格式给出了50,52,53,54Cr的全套数据文档，便于核工程用户使用。