Rational design of new in situ reduction of Ni(II)catalytic system for low-cost and large-scale preparation of porous aromatic frameworks

Porous aromatic framework 1(PAF-1)is an extremely representative nanoporous organic framework owing to its high stability and exceptionally high surface area.Currently,the synthesis of PAF-1 is catalyzed by the Ni(COD)2/COD/bpy system,suffering from great instability and high cost.Herein,we developed an in situ reduction of the Ni(II)catalytic system to synthesize PAF-1 in low cost and high yield.The active Ni(0)species produced from the NiCl_(2)/bpy/NaI/Mg catalyst system can effectively catalyze homocoupling of tetrakis(4-bromophenyl)methane at the room temperature to form PAF-1 with high Brunauer-Emmett-Teller(BET)-specific surface area up to 4948 m^(2) g^(−1)(Langmuir surface area,6785 m2 g−1).The possible halogen exchange and dehalogenation coupling mechanisms for this new catalytic process in PAF's synthesis are discussed in detail.The efficiency and universality of this innovative catalyst system have also been demonstrated in other PAFs'synthesis.This work provides a cheap,facile,and efficient method for scalable synthesis of PAFs and explores their application for high-pressure storage of Xe and Kr.

Error Estimate of the Fourier Collocation Method for the Benjamin-Ono Equation

In this paper,the Fourier collocation method for solving the generalized Benjamin-Ono equation with periodic boundary conditions is analyzed.Stability of the semi-discrete scheme is proved and error estimate in H^(1/2)-norm is obtained.

Effects of Different Land Cover Types on Soil Microbial Biomass Carbon and Nitrogen in the Lower Reaches of Niyang River

[Objectives]To comprehensively and deeply explore the effects of different land cover types in the lower reaches of Niyang River on soil microbial biomass carbon and nitrogen,and to provide a scientific basis for the rational use and sustainable management of land resources in this area.[Methods]Taking the 3 types of land cover(cultivated land,grass land and forest land)in the lower reaches of Niyang River in Tibet as the research object,the contents,distribution characteristics and relationships of soil organic carbon,organic nitrogen,microbial biomass carbon,microbial biomass nitrogen and readily oxidizable organic carbon,and their relationships were studied in 0-10,10-20,20-40,40-60,and 60-100 cm soil depth.[Results]The soil organic carbon content of forest land was higher than that of grass land and cultivated land;the vertical change trend of soil organic carbon content decreased with the increase of depth(P<0.05),and it was mainly concentrated in the soil with a depth of 0-20 cm.The soil organic carbon content was significantly different among forest land,grass land and cultivated land(P<0.05),but there was no significant difference between cultivated land and grass land(P>0.05).The soil organic nitrogen content was significantly different among cultivated land,grass land,and forest land(P<0.05),but there was no significant difference between grass land and forest land(P>0.05).The readily oxidizable organic carbon,microbial biomass carbon and nitrogen in forest land were higher than that in cultivated land and grass land.The change trend of soil readily oxidizable organic carbon,microbial biomass carbon and microbial biomass nitrogen was similar to the change of soil organic carbon content,showing a significant positive correlation.In addition to being subject to land cover,soil microbial biomass carbon and nitrogen content were also subject to the interaction of factors such as soil temperature,humidity,pH and vegetation types.[Conclusions]Changes in land cover significantly affect soil organic carbon and nitrogen,readily oxidizable organic carbon,microbial biomass carbon and nitrogen content.

Study on Bryophytes in Sygara Mountain

In order to identify the species of bryophytes in Sygara Mountain in Tibet,2390 samples in the area were collected,identified and analyzed. The results show that bryophytes of Sygara Mountain have 26 families,70 genera and 134 species; among them,25 families,69 genera and 133 species are mosses,and only one is liverwort,namely Conocephalum conicum( L.) Dum. 4 dominant families are in the descending order of Bryaceae,Dicranaceae,Pottiaceae,Polytrichaceae respectively,and the dominant genera are Hypnum,Brachythecium,Plagiomnium,Racomitrium and Dicranodontium.

Literature Analysis of Bryophytes in China during 2005-2015

In order to study China's bryophyte,this paper uses bibliometrics for statistical analysis of literature about China's bryophyte during 2005-2015.The results show that in terms of published article distribution of different journals,there are 13 kinds of journals with more than 5 papers about bryophyte,accounting for 32.5%; in terms of the number of papers published in different years,it was smallest in 2005,only 16,while it reached the largest number of 33 in 2008; in terms of the number of papers published for different first authors,there are most authors publishing less than 9 papers,accounting for 87.5%,there is only one author publishing 9 papers,and there are 5 people publishing more than 9 papers; in terms of author unit distribution,in the 278 articles collected,there are 12 units publishing papers of less than 6,accounting for 30%,the unit publishing the most papers(36) is Guizhou Normal University,5 units publish 6 papers,accounting for 12.5%,and the units publishing papers of less than 6 account for 57.5%; in terms of literature research level,there are most papers about basic and applied basic research(natural science),accounting for 91.2%,the papers about engineering and technology(natural science) account for 5.5%,and other papers account for 3.3%.

Differences of Soil Nutrient Contents under Different Land Use Patterns in Niyang River Basin

[Objectives]This study was conducted to investigate the variation characteristics of soil nutrient contents under different land use patterns in the middle and upper reaches of the Niyang River in Tibet.[Methods]With the cultivated land,grass land and forest land in the middle and upper reaches of the Niyang River as the research objects,216 soil samples were collected in layers(0-10,10-20,20-30 cm)by the standard sampling method,and the soil total nitrogen,alkali-hydrolyzable nitrogen,total potassium,available potassium,total phosphorus,available phosphorus and organic matter were determined.[Results]The contents of soil organic matter,total nitrogen and alkali-hydrolyzable nitrogen in the middle and upper reaches of Niyang River in Tibet ranked as forest land>grass land>cultivated land,and there were significant differences between the three(P<0.05).The total potassium contents of grass land and forest land were not much different,and the contents of available potassium exhibited an order of forest land>grass land>cultivated land.The distribution of soil total nutrients and available nutrients under different land use patterns showed a certain degree of surface aggregation.The contents of total nutrients and available nutrients in the soil at the 0-10 cm depth were significantly higher than those at 10-20 and 20-30 cm,and there were significant differences between the three(P<0.05).The average content of alkali-hydrolyzable nitrogen was the largest in forest soil and the smallest in cultivated land under the three land use patterns in the study area.The average content of soil available phosphorus in cultivated land(19.47 mg/kg)was significantly higher than those in grass land(5.73 mg/kg)and forest land(5.19 mg/kg).The above results indicate that long-term vegetation restoration can improve the soil quality of the middle and upper reaches of the Niyang River.[Conclusions]The results of this study research provide basic support for improving the soil effect in the area.

Effects of Different Land Use Patterns on Soil Properties in the Lower Reaches of Niyang River of Tibet

[Objectives]This study was conducted to provide scientific basis for rational utilization and sustainable management of agricultural and forestry land resources in southeast Tibet.[Methods]Soil samples were stratified by standard sampling method(0-10,10-20,20-40,40-60 and 60-100 cm)in the lower reaches of Niyang River Basin under three different types of land cover of forest,grassland and farmland.The effects of different land use on soil properties were studied.[Results]Soil temperature and humidity affected soil properties together.The pH value and bulk density increased with the increase of soil depth for farmland,grassland and forest soil.Natural forest had the highest soil nutrient contents,followed by farmland,and grassland had the lowest soil nutrient contents.Soil organic carbon and organic nitrogen contents decreased with the increase of soil depth in the three land use patterns,and the surface aggregation of soil organic carbon and organic nitrogen was more obvious.Compared with natural vegetation,the organic carbon content of farmland was significantly reduced by 8.5%-15.3%and the organic nitrogen content by 11.1%-11.7%.[Conclusions]The change of land use is a proper way to benefit the development of soil properties and improve soil properties and quality in Niyang River Basin.

Preface

This is a focused issue dedicated to the memory of the late Professor Ben-yu Guo(1942-2016),a prominent numerical analyst at Shanghai University and Shanghai Normal University,and a prolific researcher with more than 300 peer-reviewed publications,many of which are in prestigious journals.His work has been well recognized in the world and extensively cited.He received numerous prestigious awards,including a degree of Doctor of Science honoris causa from Sanford University in England.

Diversity Characteristics of Bryophytes on the Eastern and Western Slopes of Sejila Mountain

[Objectives]To study the characteristics of bryophytes in subalpine cold zone and related transition zone.[Methods]The study was divided into scale A and scale B.On the scale of A,specimens were collected from Tongmai-Pailong-Dongjiu-Lulang-Sejila Pass-Nyingchi Town-Bagi Village along the national Highway 318.A sample plot was set for each 100 m altitude increase,and samples were collected between each two sample plots as well.On the scale of B,bryophyte specimens were collected and studied in the fixed sample plot of the Tibetan Nyingchi Alpine forest Ecosystem Research Observatory.[Results]Through the sampling and collection of bryophytes in Sejila Mountain,more than 3000 specimens were identified with the classical classification method.There were 216 species of bryophytes belonging to 82 genera and 24 families.The bryophytes in the study area differed obviously in different vegetation types and slopes.The species richness of Sabina saltuaria-Abiesgeorgei var.smithii forest was the highest.Theαdiversity of Abiesgeorgei var.smithii forest was the highest,followed by Sabina saltuaria-Rhododendron forest,and that of alpine shrub was the lowest.Diversity studies showed that theβdiversity of Sabina saltuaria-Rhododendron forest and Rhododendron forest on the eastern slope was the largest,and those of alpine shrub and Sabina saltuaria-Abiesgeorgei var.smithii forest were the lowest.However,theβdiversity of Abiesgeorgei var.smithii forest on the western slope was the highest,and those of alpine shrub and Abiesgeorgei var.smithii forest were the lowest.[Conclusions]There are obvious differences in the distribution of bryophytes on the eastern and western slopes of Sejila Mountain of Tibet.

Triazine-based multicomponent metallacages with tunable structures for SO_(2) selective capture and conversion

The design of novel materials for sulfur dioxide(SO_(2))capture and conversion with considerable efficiency under mild conditions is of great significance for human health and environmental protection yet highly challenging.Herein,we report a series of triazine-based multicomponent metallacages via coordination-driven self-assembly of 2,4,6-tri(4-pyridyl)-1,3,5-triazine,cis-Pt(PEt3)2(OTf)2 and different tetracarboxylic ligands.As the increase of the length of the tetracarboxylates,the structures of the metallacages change from pyramids to extended octahedrons.Owing to their N-rich structure,these metallacages are further used for selective SO_(2)capture,showing good adsorption capacity and remarkable SO_(2)/CO_(2)selectivity in ambient conditions,suggesting their potential applications toward real flue gas desulfurization.The metallacages are further employed for the conversion of SO_(2)into value-added compounds,showing exceptional efficiency even dilute SO_(2)is used as the reactant.This study represents a type of structure-tunable triazinebased metallacages for SO_(2)capture and conversion,which will pave the way on the applications of metal-organic complexes for gas adsorption.

A LINEAR IM PLICIT Ll-LEGENDRE GALERKIN CHEBYSHEV COLLOCATION M ETHOD FOR GENERALIZED TIME- AND SPACE-FRACTIONAL BURGERS EQUATION

In this paper, a linear implicit Ll-Legendre Galerkin Chebyshev collocation method for the generalized time-and space-fractional Burgers equation is developed. A linear implicit finite difference scheme based on the L 1-algorithm for the Caputo fractional derivative is proposed for temporal discretization. And the Legendre Galerkin Chebyshev collocation method, based on the Legendre-Galerkin variational form, but the nonlinear term and the right-hand term are treated by Chebyshev-Gauss interpolation, is proposed for spatial discretization. Rigorous stability and convergence analysis are developed. Numerical examples are shown to demonstrate the accuracy, stability and effectiveness of the method.

A sample and hold circuit for pipelined ADC

A high performance sample-and-hold(S/H) circuit used in a pipelined analog-to-digital converter(ADC) is presented in this paper. Fully-differential capacitor flip-around architecture was used in this S/H circuit.A gain-boosted folded cascode operational transconductance amplifier(OTA) with a DC gain of 90 dB and a GBW of 738 MHz was designed. A low supply voltage bootstrapped switch was used to improve the linearity of the S/H circuit. With these techniques, the designed S/H circuit can reach 94 dB SFDR for a 48.9 MHz input frequency with 100 MS/s sampling rate. Measurement results of a 14-bit 100-MS/s pipeline ADC with designed S/H circuit are presented.

The Dissipative Spectral Methods for the First Order Linear Hyperbolic Equations

In this paper,we introduce the dissipative spectral methods(DSM)for the first order linear hyperbolic equations in one dimension.Specifically,we consider the Fourier DSM for periodic problems and the Legendre DSM for equations with the Dirichlet boundary condition.The error estimates of the methods are shown to be quasioptimal for variable-coefficients equations.Numerical results are given to verify high accuracy of the DSM and to compare the proposed schemes with some high performance methods,showing some superiority in long-term integration for the periodic case and in dealing with limited smoothness near or at the boundary for the Dirichlet case.