Boosting photocatalytic hydrogen evolution enabled by SiO_(2)-supporting chiral covalent organic frameworks with parallel stacking sequence

Two-dimensional covalent organic frameworks(2D COFs)feature extendedπ-conjugation and ordered stacking sequence,showing great promise for high-performance photocatalysis.Periodic atomic frameworks of 2D COFs facilitate the in-plane photogenerated charge transfer,but the precise ordered alignment is limited due to the non-covalentπ-stacking of COF layers,accordingly hindering out-of-plane transfer kinetics.Herein,we address a chiral induction method to construct a parallelly superimposed stacking chiral COF ultrathin shell on the support of SiO_(2) microsphere.Compared to the achiral COF analogues,the chiral COF shell with the parallel AA-stacking structure is more conducive to enhance the built-in electric field and accumulates photogenerated electrons for the rapid migration,thereby affording superior photocatalytic performance in hydrogen evolution from water splitting.Taking the simplest ketoenamine-linked chiral COF as a shell of SiO_(2) particle,the resulting composite exhibits an impressive hydrogen evolution rate of 107.1 mmol g^(-1)h^(-1)along with the apparent quantum efficiency of 14.31% at 475 nm.Furthermore,the composite photocatalysts could be fabricated into a film device,displaying a remarkable photocatalytic performance of 178.0 mmol m^(-2)h^(-1)for hydrogen evolution.Our work underpins the surface engineering of organic photocatalysts and illustrates the significance of COF stacking structures in regulating electronic properties.

Study on Spatial Distribution of OM, N, P in Surface Soil around Lake Chaohu

The concentration of total nitrogen (TN), total phosphorus (TP) and organic material (OM) at sixty grid division in Lake Chaohu basin around the lake was studied, in order to investigate their spatial distribution characteristics. The results showed that the average concentrations of TN, TP and OM were 1027 mg/kg, 483 mg/kg, 1.95%, and their concentrations ranged from 253 mg/kg to 2273 mg/kg, 223 mg/kg to 1173 mg/kg and 0.291% to 5.48%, respectively. The high concentration areas were located at the basins of Tuogao river and Zhao river while the low concentration areas were located at basins of Pai river, Nanfei river and Dianpu river. The concentrations of TN and OM were higher in East part than in West part. The spatial distribution of TN, TP and OM concentrations of the surface soil showed inconsistent with those of the water quality of the inflow rivers and the lake and the TN and TP of lake sediment studied.

Distributed cooperative task planning algorithm for multiple satellites in delayed communication environment

Multiple earth observing satellites need to communicate with each other to observe plenty of targets on the Earth together. The factors, such as external interference, result in satellite information interaction delays, which is unable to ensure the integrity and timeliness of the information on decision making for satellites. And the optimization of the planning result is affected. Therefore, the effect of communication delay is considered during the multi-satel ite coordinating process. For this problem, firstly, a distributed cooperative optimization problem for multiple satellites in the delayed communication environment is formulized. Secondly, based on both the analysis of the temporal sequence of tasks in a single satellite and the dynamically decoupled characteristics of the multi-satellite system, the environment information of multi-satellite distributed cooperative optimization is constructed on the basis of the directed acyclic graph（DAG）. Then, both a cooperative optimization decision making framework and a model are built according to the decentralized partial observable Markov decision process（DEC-POMDP）. After that, a satellite coordinating strategy aimed at different conditions of communication delay is mainly analyzed, and a unified processing strategy on communication delay is designed. An approximate cooperative optimization algorithm based on simulated annealing is proposed. Finally, the effectiveness and robustness of the method presented in this paper are verified via the simulation.

水稻抗氧化性状遗传位点挖掘及候选基因分析

水稻(Oryza sativa)是世界上最重要的粮食作物之一。提高水稻抗氧化性,进而提高抗逆性是保障其高产稳产的重要途径。选用籼稻华占(HZ)和粳稻热研2号(Nekken2)及以其为亲本构建的120个重组自交系(RILs),分别在分蘖期、灌浆期和成熟期测定亲本及其后代剑叶、颖壳及籽粒中羟基自由基清除率、总酚含量、黄酮含量和花青苷含量,同时基于已构建的高密度遗传连锁图谱进行数量性状基因座(QTL)定位。结果共挖掘到62个与水稻抗氧化损伤有关的QTLs,其中LOD值最高达4.36。对这些QTL区间内相关候选基因的表达进行定量分析,结果表明LOC_Os06g01850、LOC_Os12g07820、LOC_Os12g07830和LOC_Os03g60509等13个基因的表达在不同时期的双亲间差异显著。研究挖掘到众多与水稻抗氧化性相关的QTLs,为进一步定位并克隆相关基因,选育抗性强且营养价值高的水稻新品种奠定基础。

Exosomes in malignant pleural effusions:Sources and applications

To the Editor:Malignant pleural effusion(MPE)is a collection of a large amount of exudativeuid in the pleural cavity that mainly originates from pleural metastases in patients with malignant tumors.The formation of MPE is related to angiogenesis,increased vascular permeability,lymphatic obstruction,immune reactions,and the tumor metastasis microenvironment,but molecular-based diagnostic and next-generation therapeutic strategies for MPE are still lacking.Exosomes are vesicles with a double-layered lipid membrane structure that are widely distributed in bodyuids and can be produced by almost all cells.Increased evidence has shown that exosomes are related to the development of MPE and are correlated with the efcacy of and response to targeted therapy or immunotherapy.Although exosomes are one of the main components of MPE,the source and functional role of exosomes in MPE are still unclear.

Highly stable, active and recyclable solid acid catalyst based on polymer-coated magnetic composite particles

A facile approach has been adopted for coating cross-linked polystyrene(PS) shells on the surface of Fe304 magnetic clusters using reflux-precipitation polymerization(RPP).Treating the PS shell with chlorosulfonic acid yields magnetic composite particles with acid functionality.By adjusting the amount and proportion of monomers(styrene and divinylbenzene),the obtained magnetic composite particle solid acid(MPM-5 S) exhibits a saturation magnetization value of 18 emu/g,a specific surface area of 243 m^2/g and an acid density of 2.113 mmol/g.The MPM-5 S magnetic solid acid catalyst was evaluated for esterification of oleic acid with methanol to prepare biodiesel.Under mild conditions,the conversion of oleic acid reached 91%,which was much higher than the catalytic activity of Amberlyst-15 and close to the catalytic activity of concentrated H2 SO4.The solid acid catalyst can be recovered by magnetic separation and reused three times maintaining over 95% of its initial catalytic activity.Additionally,the solid acid can be used to catalyze the dehydration of fructose to 5-hydroxymethylfurfural.

Dual-sided symmetric crystalline orientation of covalent organic framework membranes for unidirectional anhydrous proton conduction

Two-dimensional covalent organic frameworks(2D COFs)have sparkled wide-ranging research to explore proton-conducting materials.However,the powder-pressed pellets or continuous membranes of 2D COFs are composed of randomly arranged crystallites,which are undesirable for proton transport via a shortcut pathway.We report a controlled strategy for preparing a conformably oriented free-standing COF membrane to address the critical challenge.A monofunctional aldehyde precursor is used as a modulator to enhance reversible association and optimize growth orientation in an interfacial polymerization system.The preferred face-on alignment is achieved throughout the membrane from its flat side to the nanoflake-standing side and,in turn,generates the unidirectional pore channels for accommodating 1,2,4-triazole as proton carriers.The composite merges distinctive features including orientation,crystallinity,porosity,and mechanical strength into one system,exhibiting ultrafast and stable anhydrous proton conduction at high operating temperatures with low activation energy.Our findings offer an innovative strategy for the oriented crystallization of free-standing COF membranes for energy conversion applications.

Influence of conformational change of chain unit on the intrinsic negative thermal expansion of polymers

Negative thermal expansion(NTE) behavior has roused wide interest for the control of thermomechanical properties of functional materials.Although NTE behaviors have been found in kinds of compounds,it remains challenging for polymers to achieve intrinsic NTE property.In this work,we systematically studied the conformational change of dibenzocyclooctadiene(DBCOD) derivatives between chair(C) and twist-boat(TB) forms based on density-functional theo ry(DFT) calculations,and found clear evidence of the relationship between the structure of DBCOD units and the thermal contraction behavior of the related polymers.In order to obtain the polymer with NTE property,two conditions should be met for the thermal contracting DBCOD related units as follows:(i) the TB conformation can turn into C conformation as the temperature increases,and(ii) the volume of C conformation is smaller than that of TB conformation.This rule should offer a guidance to exploration of the new intrinsic NTE polymers in the future.

A roadway of exploring polymer science, a lifetime of nurturing polymer scientists

This special column is dedicated to Professor Shou-Kuan Fu on the occasion of his 80thbirthday.Prof. Shou-Kuan Fu, born in July, 1940 in Jiangsu Province. He obtained his B.S. in Chemistry from Department of Chemistry,Fudan University in 1962, then, he graduated from graduate school of Fudan University in 1966, under the supervision of Prof. TongYin Yu, a distinguished pioneer of polymer science in China and the founder of Department of Macromolecular Science at Fudan University.

Preparation and in vitro cytotoxicity study of poly (aspartic acid) stabilized magnetic nanoparticles

Biocompatible magnetic nanoparticles were prepared by co-precipitation method in the presence of poly(aspartic acid)(PAsp)as stabilizer,which was one of the most extensively studied and used poly(amino acids).As a biocompatible dispersant,PAsp was successfully attached to the Fe_(3)O_(4) nanoparticles,which was approved by Fourier transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM)and thermogravimetric analysis(TGA).From X-ray diffraction(XRD)and vibrating sample magnetometry(VSM)measurement results,it was found that PAsp stabilized iron oxide nanoparticles possess excellent Fe_(3)O_(4) crystal structure and superparamagnetic property.Compared with trisodium citrate stabilized magnetic nanoparticles,PAsp stabilized magnetic nanoparticles were biocompatible and with lower cytotoxicity,which makes it more applicable in medicine,biology and biomaterial science.