Sections of convex bodies and splitting problem for selections

Let and be any convex-valued lower semicontinuous mappings and let be any linear surjection. The splitting problem is the problem of representation of any continuous selection f of the composite mapping L(F₁;F₂) in the form f=L(f₁;f₂), where f₁ and f₂ are some continuous selections of F₁ and F₂, respectively. We prove that the splitting problem always admits an approximate solution with fi being an ε-selection (Theorem 2.1). We also propose a special case of finding exact splittings, whose occurrence is stable with respect to continuous variations of the data (Theorem 3.1) and we show that, in general, exact splittings do not exist even for the finite-dimensional range.     

Monolayers at solid–solid interfaces probed with infrared spectroscopy

The sensitivities of infrared spectra of thin adsorbate layers measured in either transmission, internal reflection or external reflection can be greatly increased if a light incidence medium with a high refractive index such as an IR-transparent solid material is used. This increase in sensitivity is due to the strong enhancement of the perpendicular electric field in a thin layer of low refractive index sandwiched between two high refractive index materials. Based on model calculations of a hypothetical sample layer, the influence and optimization of experimental parameters such as incidence angle, sample layer thickness and optical contact between layers are investigated. Under optimized conditions, this enhancement can exceed a factor of 100 when compared to conventional surface IR techniques. In addition, the spectra of sandwiched sample layers are governed by a uniform surface selection rule, such that only the perpendicular vibrational components are enhanced, and they permit a straightforward, substrate-independent analysis of surface orientations. Experimental examples of monolayer spectra of long-chain hydrocarbon compounds adsorbed onto gold and silicon substrates and contacted with a germanium crystal used as the incidence medium demonstrate the simple experimental realization and unprecedented sensitivity of this sandwich technique, and they offer novel insights into the chemistry and structure of monolayers confined and compressed between two solid surfaces. Figure IR reflection spectrum of a monolayer of a fatty acid methyl ester sandwiched between silicon and germanium.     

Improved resolution in (13)C solid-state spectra through spin-state-selection

The application of a spin-state-selective coherence transfer experiment (INADEQUATE-SSS) to solid-state NMR spectroscopy is described. Two-dimensional (13)C double-quantum/single-quantum spectra without J splittings in both dimensions lead to enhanced spectral resolution. The method is demonstrated to significantly improve the spectral resolution of the crowded C'-C(alpha) region of two proteins.     

Reversible Inhibitors Arrest ClpP in a Defined Conformational State that Can Be Revoked by ClpX Association

Caseinolytic protease P (ClpP) is an important regulator of Staphylococcus aureus pathogenesis. A high‐throughput screening for inhibitors of ClpP peptidase activity led to the identification of the first non‐covalent binder for this enzyme class. Co‐crystallization of the small molecule with S. aureus ClpP revealed a novel binding mode: Because of the rotation of the conserved residue proline 125, ClpP is locked in a defined conformational state, which results in distortion of the catalytic triad and inhibition of the peptidase activity. Based on these structural insights, the molecule was optimized by rational design and virtual screening, resulting in derivatives exceeding the potency of previous ClpP inhibitors. Strikingly, the conformational lock is overturned by binding of ClpX, an associated chaperone that enables proteolysis by substrate unfolding in the ClpXP complex. Thus, regulation of inhibitor binding by associated chaperones is an unexpected mechanism important for ClpP drug development.     

Time-Dependent Photodynamic Therapy for Multiple Targets: A Highly Efficient AIE-Active Photosensitizer for Selective Bacterial Elimination and Cancer Cell Ablation

Pathogen infections and cancer are two major human health problems. Herein, we report the synthesis of an organic salt photosensitizer (PS), called 4TPA-BQ, by a one-step reaction. 4TPA-BQ presents aggregation-induced emission features. Owing to the aggregation-induced reactive oxygen species generated and a sufficiently small ΔE_ST, 4TPA-BQ shows a satisfactorily high ¹O₂ generation efficiency of 97.8 %. In vitro and in vivo experiments confirmed that 4TPA-BQ exhibited potent photodynamic antibacterial performance against ampicillin-resistant Escherichia coli with good biocompatibility in a short time (15 minutes). When the incubation duration persisted long enough (12 hours), cancer cells were ablated efficiently, leaving normal cells essentially unaffected. This is the first reported time-dependent fluorescence-guided photodynamic therapy in one individual PS, which achieves ordered and multiple targeting simply by varying the external conditions. 4TPA-BQ reveals new design principles for the implementation of efficient PSs in clinical applications.     

Nickel(II) Bisporphyrin-Fused Pentacenes Exhibiting Abnormal High Stability

A series of largely π-extended multichromophoric molecules including cross-conjugated, half cross-conjugated, conjugation-interrupted and linearly conjugated systems were synthesized and characterized. These multichromophoric molecular systems revealed interesting structural-property relationships. Bisporphyrin-fused pentacenes Pen-1 b and Pen-2 a showed rich redox chemistry with 7 and 8 observable redox states, respectively. The linearly-conjugated bisporphyrin-fused pentacenes ( Pen-1 b and Pen-2 a ) possess much narrower HOMO–LUMO gaps (1.65 and 1.42 eV redox, respectively) and higher HOMO energy levels than those of their pentacene analogues (2.23 and 2.01 eV redox, respectively), similar to those of much less stable hexacenes and heptacenes. An estimated half-life of >945 h was obtained for bisporphyrin-fused pentacene Pen-2 a , which is much longer than that of its pentacene analogue ( BPE-P , half-life, 33 h).     

“化学教育技术”核心词汇及其研究进展*——基于对2006-2017年国内核心期刊文献的分析

信息技术和化学课程的整合给教育行业带来崭新的变化,涌现出“化学教育技术”等新领域,为该领域确定作为研究热点的15个核心词汇,简述其研究方法和选词原则,并对核心词汇的发展进行分类和统计分析,从侧面反映我国化学教育技术的研究现状和进展,并为该领域的发展提出相关建议。     

Comparison of Heuristic Criteria for Fuzzy Rule Selection in Classification Problems

This paper compares heuristic criteria used for extracting a pre-specified number of fuzzy classification rules from numerical data. We examine the performance of each heuristic criterion through computational experiments on well-known test problems. Experimental results show that better results are obtained from composite criteria of confidence and support measures than their individual use. It is also shown that genetic algorithm-based rule selection can improve the classification ability of extracted fuzzy rules by searching for good rule combinations. This observation suggests the importance of taking into account the combinatorial effect of fuzzy rules (i.e., the interaction among them).     

A sweep-based algorithm for the fleet size and mix vehicle routing problem

This paper presents a new sweep-based heuristic for the fleet size and mix vehicle routing problem. This problem involves two kinds of decisions: the selection of a mix of vehicles among the available vehicle types and the routing of the selected fleet. The proposed algorithm first generates a large number of routes that are serviced by one or two vehicles. The selection of routes and vehicles to be used is then made by solving to optimality, in polynomial time, a set-partitioning problem having a special structure. Results on a set of benchmark test problems show that the proposed heuristic produces excellent solutions in short computing times. Having a fast but good solution method is needed for transportation companies that rent a significant part of their fleet and consequently can take advantage of frequent changes in fleet composition. Finally, the proposed heuristic produced new best-known solutions for three of the test problems; these solutions are reported.     

Absorption spectra of unequal width bilayer graphene nanoribbons in a spatially modulated electric field

The optical absorption spectra of unequal width bilayer graphene nanoribbons can be effectively tuned by a spatially modulated electric field. The absorption spectra exhibit many prominent peaks’ structure owing to the one-dimensional subbands. The number, spectral intensity, and frequency of the absorption peaks depend sensitively on the magnitude, period and phase of the modulated electric potential. The relative displacement between the top and bottom nanoribbons also has strong influence on the spectra. For unequal width bilayer graphene nanoribbons without the interlayer hoppings, there exists an optical selection rule originating from the spatial symmetry of the electron wave functions. Most importantly, such a selection rule can be disrupted by the presence of the interlayer atomic interactions or a spatially modulated electric field. These theoretical predictions can be validated by absorption spectroscopy experiments.