Alkyl Chain Length- and Polymorph-Dependent Photomechanochromic Fluorescence of Anthracene Photodimerization in Molecular Crystals: Role of the Lattice Stiffness

Anthracene–pentiptycene hybrid systems 1-Cn , where n refers to the number of carbon atoms in the linear alkyl chain, crystallize in three different polymorphs, denoted Y (yellow), G (green), and B (blue) forms in terms of the fluorescence color. While all Y-form crystals show the same yellow-to-blue fluorescence color response to the photomechanical stress generated by the anthracene [4+4] photodimerization reaction, the four G forms exhibit distinct photomechanofluorochromism (PMFC): from green to blue for G-1-C4 , to orange for G-1-C7 , to red for G-1-C8 , and to red then blue for G-1-C9 , and the B forms show no photochromic activity. The intriguing RGB three-color PMFC and abnormal topochemical reactivity of G-1-C9 are attributed to inherent softness of the crystal lattice.     

Minimization of Entropy Generation Rate in Hydrogen Iodide Decomposition Reactor Heated by High-Temperature Helium

The thermochemical sulfur-iodine cycle is a potential method for hydrogen production, and the hydrogen iodide (HI) decomposition is the key step to determine the efficiency of hydrogen production in the cycle. To further reduce the irreversibility of various transmission processes in the HI decomposition reaction, a one-dimensional plug flow model of HI decomposition tubular reactor is established, and performance optimization with entropy generate rate minimization (EGRM) in the decomposition reaction system as an optimization goal based on finite-time thermodynamics is carried out. The reference reactor is heated counter-currently by high-temperature helium gas, the optimal reactor and the modified reactor are designed based on the reference reactor design parameters. With the EGRM as the optimization goal, the optimal control method is used to solve the optimal configuration of the reactor under the condition that both the reactant inlet state and hydrogen production rate are fixed, and the optimal value of total EGR in the reactor is reduced by 13.3% compared with the reference value. The reference reactor is improved on the basis of the total EGR in the optimal reactor, two modified reactors with increased length are designed under the condition of changing the helium inlet state. The total EGR of the two modified reactors are the same as that of the optimal reactor, which are realized by decreasing the helium inlet temperature and helium inlet flow rate, respectively. The results show that the EGR of heat transfer accounts for a large proportion, and the decrease of total EGR is mainly caused by reducing heat transfer irreversibility. The local total EGR of the optimal reactor distribution is more uniform, which approximately confirms the principle of equipartition of entropy production. The EGR distributions of the modified reactors are similar to that of the reference reactor, but the reactor length increases significantly, bringing a relatively large pressure drop. The research results have certain guiding significance to the optimum design of HI decomposition reactors.     

Interfacially Super-Assembled Benzimidazole Derivative-Based Mesoporous Silica Nanoprobe for Sensitive Copper (II) Detection and Biosensing in Living Cells

Mesoporous silica nanoparticles (MSNs) functionalized with benzimidazole-derived fluorescent molecules (DHBM) are fabricated via a feasible interfacial superassembly strategy for the highly sensitive and selective detection of Cu²⁺. DHBM-MSN exhibits an obvious quenching effect on Cu²⁺ in aqueous solutions, and the detection limit can be as low as 7.69×10⁻⁸ M. The DHBM-MSN solid-state sensor has good recyclability, and the silica framework can simultaneously improve the photostability of DHBM. Two mesoporous silica nanoparticles with different morphologies were specially designed to verify that nanocarriers with different morphologies do not affect the specific detectionability. The detection mechanism of the fluorescent probe was systematically elucidated by combining experimental results and density function theory calculations. Moreover, the detection system was successfully applied to detect Cu²⁺ in bovine serum, juice, and live cells. These results indicate that the DHBM-MSN fluorescent sensor holds great potential in practical and biomedical applications.     

Accelerated inexact composite gradient methods for nonconvex spectral optimization problems

Computational Optimization and Applications - This paper presents two inexact composite gradient methods, one inner accelerated and another doubly accelerated, for solving a class of nonconvex...     

Analysis of the dissipation kinetics of thiophanate‐methyl and its metabolite carbendazim in apple leaves using a modified QuEChERS–UPLC–MS/MS method

As one of the main fungicides for the apple leaf disease control, thiophanate‐methyl (TM) mainly exerts its fungicidal activity in the form of its metabolite carbendazim (MBC), whose dissipation kinetics is very distinct from that of its parent but has been paid little attention. The aim of this work was to investigate the dissipation kinetics of TM and its active metabolite MBC in apple leaves using a modified QuEChERS–UPLC–MS/MS method. The results showed that TM and MBC could be quickly extracted by this modified QuEChERS procedure with recoveries of 81.7–96.5%. The method linearity was in the range of 0.01–50.0 mg kg^?1 with the quantification limit of 0.01 mg kg^?1. Then this method was applied to the analysis of fungicide dissipation kinetics in apple leaves. The results showed that the dissipation kinetics of TM for the test in 3 months can be described by a first‐order kinetics model with a DT₅₀ (dissipation half‐life) range of 5.23–6.03 days and the kinetics for MBC can be described by a first‐order absorption–dissipation model with the T_max (time needed to reach peak concentration) range of 4.78–7.09 days. These models can scientifically describe the behavior of TM and MBC in apple leaves, which provides necessary data for scientific application.     

Cardy algebras and sewing constraints,II

This is the part II of a two-part work started in [18]. In part I, Cardy algebras were studied, a notion which arises from the classification of genus-0, 1 open–closed rational conformal field theories. In this part, we prove that a Cardy algebra also satisfies the higher genus factorisation and modular-invariance properties formulated in [7] in terms of the notion of a solution to the sewing constraints. We present the proof by showing that the latter notion, which is defined as a monoidal natural transformation, can be expressed in terms of generators and relations, which correspond exactly to the defining data and axioms of a Cardy algebra.     

Positive Solutions to a Fourth Order Boundary Value Problem

The authors consider a fourth order two-point boundary value problem. Some a priori estimates to positive solutions for the problem are obtained. Explicit sufficient conditions for existence and nonexistence of positive solutions to the problem are established. An example to illustrate the results is included.     

Preparation of 4′-Spirocyclobutyl Nucleoside Analogues as Novel and Versatile Adenosine Scaffolds

Despite the large variety of modified nucleosides that have been reported, the preparation of constrained 4′-spirocyclic adenosine analogues has received very little attention. We discovered that the [2+2]-cycloaddition of dichloroketene on readily available 4′-exo-methylene furanose sugars efficiently results in the diastereoselective formation of novel 4′-spirocyclobutanones. The reaction mechanism was investigated via density functional theory (DFT) and found to proceed either via a non-synchronous or stepwise reaction sequence, controlled by the stereochemistry at the 3′-position of the sugar substrate. The obtained dichlorocyclobutanones were converted into nucleoside analogues, providing access to a novel class of chiral 4′-spirocyclobutyl adenosine mimetics in eight steps from commercially available sugars. Assessment of the biological activity of designed 4′-spirocyclic adenosine analogues identified potent inhibitors for protein methyltransferase target PRMT5.