Reversible Postsynthetic Modification in a Metal–Organic Framework

Postsynthetic modification (PSM) of metal–organic frameworks (MOFs) provides access to functional materials and advanced porous solid engineering. Herein, we report the reversible PSM of a multivariate isoreticular MOF by applying dynamic furan-maleimide Diels–Alder (DA) chemistry. The key step involves incorporating a furan group into the MOF via “click” PSM, which can then undergo repeated cycles of modification and de-modification with maleimides. The structural integrity, crystallinity, and porosity of the furan-appended MOF remained intact even after three consecutive PSM/de-modification cycles using three different functionalized maleimides.     

A novel image encryption algorithm using chaos and reversible cellular automata

In this paper, a novel image encryption scheme is proposed based on reversible cellular automata (RCA) combining chaos. In this algorithm, an intertwining logistic map with complex behavior and periodic boundary reversible cellular automata are used. We split each pixel of image into units of 4 bits, then adopt pseudorandom key stream generated by the intertwining logistic map to permute these units in confusion stage. And in diffusion stage, two-dimensional reversible cellular automata which are discrete dynamical systems are applied to iterate many rounds to achieve diffusion on bit-level, in which we only consider the higher 4 bits in a pixel because the higher 4 bits carry almost the information of an image. Theoretical analysis and experimental results demonstrate the proposed algorithm achieves a high security level and processes good performance against common attacks like differential attack and statistical attack. This algorithm belongs to the class of symmetric systems.     

Boundedness of solutions for reversible system via Moser's twist theorem

In this paper we consider the problem of the boundedness of all solutions for the reversible system

     

Electricity Storage With High Roundtrip Effciency in a Reversible Solid Oxide Cell Stack

We theoretically investigate the electricity storage/generation in a reversible solid oxide cell stack. The system heat is for the first time tentatively stored in a phase-change metal when the stack is operated to generate electricity in a fuel cell mode and then reused to store electricity in an electrolysis mode. The state of charge (H₂ frication in cathode) effectively enhances the open circuit voltages (OCVs) while the system gas pressure in electrodes also increases the OCVs. On the other hand, a higher system pressure facilitates the species diffusion in electrodes that therefore accordingly improve electrode polarizations. With the aid of recycled system heat, the roundtrip efficiency reaches as high as 92% for the repeated electricity storage and generation.     

四甲基对联苯二胺光敏化聚苯乙烯砜及其模型化合物二苄基砜分解机理的研究

N、N、 N’、N’-四平基对联苯二胺(NTMB)和 3、3’、5、5’-四甲基对联苯二胺(TMB)可以有效地光敏化二苄基砜(DBS)分解和聚苯乙烯砜(PSS)降解。敏化作用是按电子转移机理进行的,电子转移过程可以由NTMB的单重激发态,也可以由三重激发态发生。由三重态电子转移产生的三重态离子自由基对进一步反应生成产物的效率比单重态离子自由基对的效率高10倍。     

Study of a dynamical system with a strange attractor and invariant tori

A simple three-dimensional time-reversible system of ODEs with quadratic nonlinearities is considered in a recent paper by Sprott (2014). The author finds in this system, that has no equilibria, the coexistence of a strange attractor and invariant tori. The goal of this letter is to justify theoretically the existence of infinite invariant tori and chaotic attractors. For this purpose we embed the original system in a one-parameter family of reversible systems. This allows to demonstrate the presence of a Hopf-zero bifurcation that implies the birth of an elliptic periodic orbit. Thus, the application of the KAM theory guarantees the existence of an extremely complex dynamics with periodic, quasiperiodic and chaotic motions. Our theoretical study is complemented with some numerical results. Several bifurcation diagrams make clear the rich dynamics organized around a so-called noose bifurcation where, among other scenarios, cascades of period-doubling bifurcations also originate chaotic attractors. Moreover, a cross section and other numerical simulations are also presented to illustrate the KAM dynamics exhibited by this system.     

Controlled radical polymerization of cholesteryl acrylate and its block copolymer with styrene via the RAFT process

Reversible addition fragmentation chain transfer (RAFT) polymerization of cholesteryl acrylate (ChA) was conducted using S-1-dodecyl-S′-(α,α′-dimethyl-α′′-acetic acid)trithiocarbonate as CTA and AIBN as initiator in toluene at 80 °C. The polymerization was investigated at two different CTA concentrations (0.025 and 0.040 M). Polymerization of ChA with CTA concentration of 0.040 M proceeds in a controlled/living manner as evidenced by linear increase of the molecular weight with conversion and narrow polymer polydispersity (PDI < 1.2). With lower initial CTA concentration, namely 0.025 M, although poly(cholesteryl acrylate) (PChA) exhibiting narrow molecular weight distributions could be synthesized, the polymerization showed relatively low control with many termination products. Chain extension polymerizations were performed starting from either the PChA or the polystyrene (PS) block, and well-defined copolymers based on ChA and styrene were prepared. Thermal properties of PChA and PS-b-PChA copolymer were investigated by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), and the results showed that both PChA and PS-b-PChA are amorphous polymers. PChA begins to decompose at ca. 218 °C with maximum weight loss rate at 351 °C, while PS-b-PChA shows double weight loss rate peaks located at 345 and 415 °C, respectively.     

Efficient Purification of Camptothecin via Aqueous Two-phase System Composed of 1,1,3,3-Tetramethylguanidinium Benzoate Ionic Liquid and K2CO3

After being hydrolyzed into corresponding hydrosoluble carboxylate by 1,1,3,3,-tetramethylguanidine (TMG), camptothecin was extracted via the aqueous two-phase systems composed of ionic liquid 1,1,3,3- tetramethylguanidinium(TMGM) carboxylate and K₂CO₃, and was regenerated at the final by dilute aqueous hydrochloric acid. Among the ionic liquids, TMGM benzoate showed the best effect, TMGM formate the worst, this results were consistent with the liposolubilities of different carboxylic acid components in the ionic liquids. Through two-step extraction of TMGM benzoate ionic liquid/K₂CO₃ aqueous two-phase under a favorable condition, camptothecin was obtained in a purity of 98.3% and a total yield of 85.1%, from the crude camptothecin extract with a purity of 14.2%.     

氧化还原可逆荧光探针的研究及其在细胞成像中的应用进展

细胞氧化还原可逆状态的动态变化可以提供丰富的生理、病理信息,因此可以瞬时、动态检测细胞氧化还原状态变化的分析方法越来越受到人们的关注.基于荧光探针的荧光分析法因其直观、简便、可原位操作、信息丰富等特点,近年来在氧化还原分析等研究方面得到了较为广泛的应用.本文对近年来氧化还原可逆荧光探针研究及其在细胞成像中的应用进展进行了评述,并对其发展前景进行了展望.引用文献54篇.