Photoelectrochemical (PEC) small-molecule oxidation can selectively transform substrates into high-value-added fine chemicals and increase the rate of cathode hydrogen evolution. Nevertheless, achieving high-selectivi...Photoelectrochemical (PEC) small-molecule oxidation can selectively transform substrates into high-value-added fine chemicals and increase the rate of cathode hydrogen evolution. Nevertheless, achieving high-selectivity PEC oxidation of small molecules to produce specific products is a very challenging task. In general, selectivity can be improved by changing the surface catalyticsites of the photoanode and modulating the interfacial environments of the reactions. Herein, recent advances in approaches to improving selective PEC oxidation of small molecules are introduced. We first briefly discuss the basic concept and fundamentals of small-molecule PEC oxidation. The reported approaches to improving the performance of selective PEC oxidation of small molecules are highlighted from two aspects: (1) changing the surface properties of photoanodes by selecting suitable materials or modifying the photoanodes and (2) mediating the oxidation reactions using redox mediators. The PEC oxidation mechanism of these studies is emphasized. We also discuss the challenges in this research direction and offer a perspective on the further development of selective PEC-based small-molecule transformation.展开更多
A novel dual-band ISGW cavity filter with enhanced frequency selectivity is proposed in this paper by utilizing a multi-mode coupling topology.Its cavity is designed to control the number of modes,and then the ports a...A novel dual-band ISGW cavity filter with enhanced frequency selectivity is proposed in this paper by utilizing a multi-mode coupling topology.Its cavity is designed to control the number of modes,and then the ports are determined by analyzing the coupling relationship between these selected modes.By synthesizing the coupling matrix of the filter,a nonresonating node(NRN)structure is introduced to flexibly tune the frequency of modes,which gets a dualband and quad-band filtering response from a tri-band filter no the NRN.Furthermore,a frequency selective surface(FSS)has been newly designed as the upper surface of the cavity,which significantly improves the bad out-of-band suppression and frequency selectivity that often exists in most traditional cavity filter designs and measurements.The results show that its two center frequencies are f01=27.50 GHz and f02=32.92GHz,respectively.Compared with the dual-band filter that there is no the FSS metasurface,the out-of-band suppression level is improved from measured 5 dB to18 dB,and its finite transmission zero(FTZ)numbers is increased from measured 1 to 4 between the two designed bands.Compared with the tri-band and quadband filter,its passband bandwidth is expanded from measured 1.17%,1.14%,and 1.13% or 1.31%,1.50%,0.56%,and 0.57% to 1.71% and 1.87%.In addition,the filter has compact,small,and lightweight characteristics.展开更多
Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In...Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.展开更多
The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-range...The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-ranged hydrocarbons,bio-jet fuels,or fatty alcohols with controllable selectivity is especially attractive in natural oil feedstock biorefineries.This review presents recent progress in catalytic deoxygenation of natural oils or related model compounds(e.g.,fatty acids)to renewable liquid fuels(green diesel and bio-jet fuels)and valuable fatty alcohols(unsaturated and saturated fatty alcohols).Besides,it discusses and compares the existing and potential strategies to control the product selectivity over heterogeneous catalysts.Most research conducted and reviewed has only addressed the production of one category;therefore,a new integrative vision exploring how to direct the process toward fuel and/or chemicals is urgently needed.Thus,work conducted to date addressing the development of new catalysts and studying the influence of the reaction parameters(e.g.,temperature,time and hydrogen pressure)is summarized and critically discussed from a green and sustainable perspective using efficiency indicators(e.g.,yields,selectivity,turnover frequencies and catalysts lifetime).Special attention has been given to the chemical transformations occurring to identify key descriptors to tune the selectivity toward target products by manipulating the reaction conditions and the structures of the catalysts.Finally,the challenges and future research goals to develop novel and holistic natural oil biorefineries are proposed.As a result,this critical review provides the readership with appropriate information to selectively control the transformation of natural oils into either biofuels and/or value-added chemicals.This new flexible vision can help pave the wave to suit the present and future market needs.展开更多
Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important r...Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.展开更多
This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3.A series of Sm_(x)Mn_(0.3-x)-xTi catalysts (x=0,0.1,0.15,0.2,and 0.3) were prepared by ...This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3.A series of Sm_(x)Mn_(0.3-x)-xTi catalysts (x=0,0.1,0.15,0.2,and 0.3) were prepared by co-precipitation.Activity tests indicated that the Sm_(0.15)Mn_(0.15)Ti catalyst showed superior performances,with a NO conversion of 100%and N_(2)selectivity above 87%at 180–300℃.The characterizations showed that Sm doping suppressed the crystallization of TiO_(2)and Mn2O3phases and increased the specific surface area and acidity.In particular,the surface area increased from 152.2 m^(2)·g^(-1)for Mn0.3Ti to 241.7 m^(2)·g^(-1)for Sm_(0.15)Mn_(0.15)Ti.These effects contributed to the high catalytic activity.The X-ray photoelectron spectroscopy (XPS) results indicated that the relative atomic ratios of Sm^(3+)/Sm and Oβ/O of Sm_(0.15)Mn_(0.15)Ti were 76.77at%and 44.11at%,respectively.The presence of Sm contributed to an increase in surface-absorbed oxygen (Oβ) and a decrease in Mn^(4+)surface concentration,which improved the catalytic activity.In the results of hydrogen temperature-programmed reduction(H_(2)-TPR),the presence of Sm induced a higher reduction temperature and lower H_(2)consumption (0.3 mmol·g^(-1)) for the Sm_(0.15)Mn_(0.15)Ti catalyst compared to the Mn0.3Ti catalyst.The decrease in Mn^(4+)weakened the redox property of the catalysts and increased the N_(2)selectivity by suppressing N_(2)O formation from NH3oxidation and the nonselective catalytic reduction reaction.The in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) revealed that NH3-SCR of NO over the Sm_(0.15)Mn_(0.15)Ti catalyst mainly followed the Eley–Rideal mechanism.Sm doping increased surface-absorbed oxygen and weakened the redox property to improve the NO conversion and N_(2)selectivity of the Sm_(0.15)Mn_(0.15)Ti catalyst.展开更多
Cladocera are filter feeders abundant in freshwaters,which consume phytoplankton particles in wide size and taxonomic ranges.The ability of cladocerans to control phytoplankton abundance by grazing is determined by va...Cladocera are filter feeders abundant in freshwaters,which consume phytoplankton particles in wide size and taxonomic ranges.The ability of cladocerans to control phytoplankton abundance by grazing is determined by various factors including the characteristics of phytoplankton.Freshwater salinization may reduce the strength of top-down grazing control of phytoplankton because of the detrimental effects of salinity on the grazing intensity of zooplankters.We performed grazing experiments with two species of Cladocera of different body lengths to test their ability to graze on phytoplankton in natural waters differing in salinity and size and taxonomic composition of food particles.Grazing experiments demonstrated that the grazing rate was mostly controlled by the abundance of phytoplankton in the medium.The grazing rate was reduced at salinity ca.above 3 g/L of NaCl in the medium.The lower grazing rate was observed in the medium with larger phytoplankton particles.Both species predominantly consumed phytoplankton particles with a diameter of 6-12μm,which may shift the size distribution of phytoplankton towards a larger average diameter of particles.The taxon-specific feeding was also observed,as both species predominantly consumed diatom algae.Thus,we found that because of grazing,the size and taxonomic characteristics of phytoplankton are shifted towards a less edible community.The detrimental effect of elevated salinity on grazing rate supports growing concern about freshwater salinization negatively affecting water quality,particularly reducing top-down grazing control of phytoplankton.展开更多
Andrographolide is the main active ingredient of Andrographis paniculata(Burm.f.)Nees,known as“natural antibiotic”.Here,for the purpose of discovering a more efficient,low-cost extraction and separation method,the r...Andrographolide is the main active ingredient of Andrographis paniculata(Burm.f.)Nees,known as“natural antibiotic”.Here,for the purpose of discovering a more efficient,low-cost extraction and separation method,the research status of andrographolide was reviewed.At present,researches only take extraction rate as the only index to optimize extraction parameters,but ignores the importance of extraction selectivity.It is usually meaningless to blindly pursue the extraction rate without considering the difficulty and cost of subsequent separation.So,factors affecting extraction selectivity such as solvent choice,temperature and physicochemical effects caused by extraction technique itself,are first discussed.Different extraction techniques for andrographolide were discussed by comparing the selectivity,efficiency and cost of extraction.The separation procedures of andrographolide such as decolorization,impurity removal,crystallization,membrane separation,solid-phase extraction and partition chromatography and their challenges and possible strategies are also discussed.It is hoped that this review can provide guidance for researchers who are committed to advancing the field of andrographolide extraction and purification.展开更多
Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is s...Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.展开更多
A problem in chemical analysis in connection with measurements of a substance normally occurring in a sample, or identification of a substance which should not exist in a sample, is insufficient selectivity. In this a...A problem in chemical analysis in connection with measurements of a substance normally occurring in a sample, or identification of a substance which should not exist in a sample, is insufficient selectivity. In this article, we analyze this problem and propose remedies. We use a real doping case to illustrate how chemical noise causes a serious selectivity problem, probably causing a false positive outcome.展开更多
Electroreduction of nitrate has been gaining wide attention in recent years owing to it's beneficial for converting nitrate into benign N_(2) from the perspective of electrocatalytic denitrification or into value-...Electroreduction of nitrate has been gaining wide attention in recent years owing to it's beneficial for converting nitrate into benign N_(2) from the perspective of electrocatalytic denitrification or into value-added ammonia from the perspective of electrocatalytic NH_(3) synthesis.By reason of the undesired formation of ammonia is dominant during electroreduction of nitrate-containing wastewater,chloride has been widely used to improve N_(2) selectivity.Nevertheless,selective electroreduction of nitrate to N2 gas in chloride-containing system poses several drawbacks.In this review,we focus on the key strategies for efficiently enhancing N_(2) selectivity of electroreduction of nitrate in chloride-free system,including optimal selection of elements,combining an active metal catalyst with another metal,manipulating the crystalline morphology and facet orientation,constructing core–shell structure catalysts,etc.Before summarizing the strategies,four possible reaction pathways of electro-reduction of nitrate to N_(2) are discussed.Overall,this review attempts to provide practical strategies for enhancing N2 selectivity without the aid of electrochlorination and highlight directions for future research for designing appropriate electrocatalyst for final electrocatalytic denitrifi-cation.展开更多
A common feature among neurodegenerative conditions is that ce rtain neuronal populations are selectively vulnerable to loss(Fu et al.,2018).By corollary,other neurons are selectively resilient,suggesting they may pos...A common feature among neurodegenerative conditions is that ce rtain neuronal populations are selectively vulnerable to loss(Fu et al.,2018).By corollary,other neurons are selectively resilient,suggesting they may possess unique features that support their survival.U nderstanding the basis of neuronal resilience or vulnerability would provide a logical strategy to identify factors that could be targeted therapeutically.展开更多
The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural...The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural using Hβ zeolite modified by organic acids for dealuminization to regulate its textural and acidic properties. It was found that citric acid-dealuminized Hβ zeolite possessed high specific surface areas, wide channels and high Brønsted acid amount, which facilitated the selective conversion of fructose to furfural with a maximum yield of 76.2% at433 K for 1 h in the γ-butyrolactone(GBL)-H_(2)O system, as well as the concomitant formation of 83.0% formic acid. The^(13)C-isotope labelling experiments and the mechanism revealed that the selective cleavage of C1–C2 or C5–C6 bond on fructose was firstly occurred to form pentose or C5 intermediate by weak Brønsted acid, which was then dehydrated to furfural by strong Brønsted acid. Also this dealuminized Hβ catalyst showed the great recycling performance and was active for the conversion of glucose and mannose.展开更多
Pattern matching method is one of the classic classifications of existing online portfolio selection strategies. This article aims to study the key aspects of this method—measurement of similarity and selection of si...Pattern matching method is one of the classic classifications of existing online portfolio selection strategies. This article aims to study the key aspects of this method—measurement of similarity and selection of similarity sets, and proposes a Portfolio Selection Method based on Pattern Matching with Dual Information of Direction and Distance (PMDI). By studying different combination methods of indicators such as Euclidean distance, Chebyshev distance, and correlation coefficient, important information such as direction and distance in stock historical price information is extracted, thereby filtering out the similarity set required for pattern matching based investment portfolio selection algorithms. A large number of experiments conducted on two datasets of real stock markets have shown that PMDI outperforms other algorithms in balancing income and risk. Therefore, it is suitable for the financial environment in the real world.展开更多
Radiomics is a non-invasive method for extracting quantitative and higher-dimensional features from medical images for diagnosis.It has received great attention due to its huge application prospects in recent years.We...Radiomics is a non-invasive method for extracting quantitative and higher-dimensional features from medical images for diagnosis.It has received great attention due to its huge application prospects in recent years.We can know that the number of features selected by the existing radiomics feature selectionmethods is basically about ten.In this paper,a heuristic feature selection method based on frequency iteration and multiple supervised training mode is proposed.Based on the combination between features,it decomposes all features layer by layer to select the optimal features for each layer,then fuses the optimal features to form a local optimal group layer by layer and iterates to the global optimal combination finally.Compared with the currentmethod with the best prediction performance in the three data sets,thismethod proposed in this paper can reduce the number of features fromabout ten to about three without losing classification accuracy and even significantly improving classification accuracy.The proposed method has better interpretability and generalization ability,which gives it great potential in the feature selection of radiomics.展开更多
Manganese superoxide dismutase(MnSOD)is an antioxidant that exists in mitochondria and can effectively remove superoxide anions in mitochondria.In a dark,high-pressure,and low-temperature deep-sea environment,MnSOD is...Manganese superoxide dismutase(MnSOD)is an antioxidant that exists in mitochondria and can effectively remove superoxide anions in mitochondria.In a dark,high-pressure,and low-temperature deep-sea environment,MnSOD is essential for the survival of sea cucumbers.Six MnSODs were identified from the transcriptomes of deep and shallow-sea sea cucumbers.To explore their environmental adaptation mechanism,we conducted environmental selection pressure analysis through the branching site model of PAML software.We obtained night positive selection sites,and two of them were significant(97F→H,134K→V):97F→H located in a highly conservative characteristic sequence,and its polarity c hange might have a great impact on the function of MnSOD;134K→V had a change in piezophilic a bility,which might help MnSOD adapt to the environment of high hydrostatic pressure in the deepsea.To further study the effect of these two positive selection sites on MnSOD,we predicted the point mutations of F97H and K134V on shallow-sea sea cucumber by using MAESTROweb and PyMOL.Results show that 97F→H,134K→V might improve MnSOD’s efficiency of scavenging superoxide a nion and its ability to resist high hydrostatic pressure by moderately reducing its stability.The above results indicated that MnSODs of deep-sea sea cucumber adapted to deep-sea environments through their amino acid changes in polarity,piezophilic behavior,and local stability.This study revealed the correlation between MnSOD and extreme environment,and will help improve our understanding of the organism’s adaptation mechanisms in deep sea.展开更多
Selective cleavage of Csp^(2)-OCH_(3)bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass.Here,a Co/Ni-based dual-atom catalyst...Selective cleavage of Csp^(2)-OCH_(3)bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass.Here,a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal–organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols(88.5%–99.9%yields),which had ca.4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts.The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps,and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp^(2)-OCH_(3)cleavage,as elaborated by theoretical calculations.Notably,the CoNi_(DA)@NC catalyst was highly recyclable,and exhibited excellent demethoxylation performance(77.1%yield)in real lignin monomer mixtures.Via in-situ cascade conversion processes assisted by dual-atom catalysis,various high-value N-containing chemicals,including caprolactams and cyclohexylamines,could be produced from lignin.展开更多
基金the National Natural Science Foundation of China (No. 22136005)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB36000000).
文摘Photoelectrochemical (PEC) small-molecule oxidation can selectively transform substrates into high-value-added fine chemicals and increase the rate of cathode hydrogen evolution. Nevertheless, achieving high-selectivity PEC oxidation of small molecules to produce specific products is a very challenging task. In general, selectivity can be improved by changing the surface catalyticsites of the photoanode and modulating the interfacial environments of the reactions. Herein, recent advances in approaches to improving selective PEC oxidation of small molecules are introduced. We first briefly discuss the basic concept and fundamentals of small-molecule PEC oxidation. The reported approaches to improving the performance of selective PEC oxidation of small molecules are highlighted from two aspects: (1) changing the surface properties of photoanodes by selecting suitable materials or modifying the photoanodes and (2) mediating the oxidation reactions using redox mediators. The PEC oxidation mechanism of these studies is emphasized. We also discuss the challenges in this research direction and offer a perspective on the further development of selective PEC-based small-molecule transformation.
基金supported by the National key research and development program of China(No.2021YFB2900401)by the National Natural Science Foundation of China(No.61861046)+1 种基金the key Natural Science Foundation of shenzhen(No.JCYJ20220818102209020)the key research and development program of shenzhen(No.ZDSYS20210623091807023)。
文摘A novel dual-band ISGW cavity filter with enhanced frequency selectivity is proposed in this paper by utilizing a multi-mode coupling topology.Its cavity is designed to control the number of modes,and then the ports are determined by analyzing the coupling relationship between these selected modes.By synthesizing the coupling matrix of the filter,a nonresonating node(NRN)structure is introduced to flexibly tune the frequency of modes,which gets a dualband and quad-band filtering response from a tri-band filter no the NRN.Furthermore,a frequency selective surface(FSS)has been newly designed as the upper surface of the cavity,which significantly improves the bad out-of-band suppression and frequency selectivity that often exists in most traditional cavity filter designs and measurements.The results show that its two center frequencies are f01=27.50 GHz and f02=32.92GHz,respectively.Compared with the dual-band filter that there is no the FSS metasurface,the out-of-band suppression level is improved from measured 5 dB to18 dB,and its finite transmission zero(FTZ)numbers is increased from measured 1 to 4 between the two designed bands.Compared with the tri-band and quadband filter,its passband bandwidth is expanded from measured 1.17%,1.14%,and 1.13% or 1.31%,1.50%,0.56%,and 0.57% to 1.71% and 1.87%.In addition,the filter has compact,small,and lightweight characteristics.
基金supported by the renewable energy and hydrogen projects in National Key Research and Development Plan of China(2019YFB1505000).
文摘Flue gas and coal bed methane are two important sources of greenhouse gases.Pressure swing adsorption process has a wide range of application in the field of gas separation,and the selection of adsorbent is crucial.In this regard,in order to assess the better adsorbent for separating CO_(2) from flue gas and CH_(4) from coal bed methane,adsorption isotherms of CO_(2),CH_(4) and N_(2) on activated carbon and carbon molecular sieve are measured at 303.15,318.15 and 333.15 K,and up to 250 kPa.The experimental data fit better with Langmuir 2 compared to Langmuir 3 and Langmuir-Freundlich models,and Clausius-Clapeyron equation was used to calculate the isosteric heat.Both the order of the adsorbed amount and the adsorption heat on the two adsorbents are CO_(2)>CH_(4)>N_(2).The adsorption kinetics are calculated by the pseudo-first kinetic model,and the order of adsorption rates on activated carbon is N_(2)-CH_(4)>CO_(2),while on carbon molecular sieve,it is CO_(2)-N_(2)>CH_(4).It is shown that relative molecular mass and adsorption heat are the primary effect on kinetics for activated carbon,while kinetic diameter is the main resistance factor for carbon molecular sieve.Moreover,the adsorption selectivity of CH_(4)/N_(2) and CO_(2)/N_(2) were estimated with the ideal adsorption solution theory,and carbon molecular sieve performed best at 318.15 K for both CO_(2) and CH_(4) separation.The study suggested that activated carbon is a better choice for separating flue gas and carbon molecular sieve can be a strong candidate for separating coal bed methane.
基金financially supported by the National Natural Science Foundation of China (No.21536007)the 111 Project (B17030)+1 种基金support from China Scholarship Council (CSC No.202006240156)the Spanish Ministry of Science,Innovation and Universities for the Juan de la Cierva (JdC)fellowships (Grant Numbers FJCI-2016-30847 and IJC2018-037110-I)awarded.
文摘The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-ranged hydrocarbons,bio-jet fuels,or fatty alcohols with controllable selectivity is especially attractive in natural oil feedstock biorefineries.This review presents recent progress in catalytic deoxygenation of natural oils or related model compounds(e.g.,fatty acids)to renewable liquid fuels(green diesel and bio-jet fuels)and valuable fatty alcohols(unsaturated and saturated fatty alcohols).Besides,it discusses and compares the existing and potential strategies to control the product selectivity over heterogeneous catalysts.Most research conducted and reviewed has only addressed the production of one category;therefore,a new integrative vision exploring how to direct the process toward fuel and/or chemicals is urgently needed.Thus,work conducted to date addressing the development of new catalysts and studying the influence of the reaction parameters(e.g.,temperature,time and hydrogen pressure)is summarized and critically discussed from a green and sustainable perspective using efficiency indicators(e.g.,yields,selectivity,turnover frequencies and catalysts lifetime).Special attention has been given to the chemical transformations occurring to identify key descriptors to tune the selectivity toward target products by manipulating the reaction conditions and the structures of the catalysts.Finally,the challenges and future research goals to develop novel and holistic natural oil biorefineries are proposed.As a result,this critical review provides the readership with appropriate information to selectively control the transformation of natural oils into either biofuels and/or value-added chemicals.This new flexible vision can help pave the wave to suit the present and future market needs.
基金partially financially supported by NSF CBET-2033343.J.Z.thanks the support from National Natural Science Foundation of China(52172293,51772072,and 51672065)the Fundamental Research Funds for the Central Universities(JZ2021HGQB0282 and PA2021GDSK0088)+3 种基金financial support from the Key R&D Projects of Anhui Province(202104b11020016)the 111 Project(B18018)the National Synchrotron Light Source II,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No.DE-SC0012704the use of facilities within the Eyring Materials Center at Arizona State University supported in part by NNCI-ECCS-1542160.
文摘Regulating the selectivity toward a target hydrocarbon product is still the focus of CO_(2)electroreduction.Here,we discover that the original surface Cu species in Cu gas-diffusion electrodes plays a more important role than the surface roughness,local pH,and facet in governing the selectivity toward C_(1)or C_(2)hydrocarbons.The selectivity toward C_(2)H_(4) progressively increases,while CH_(4) decreases steadily upon lowering the Cu oxidation species fraction.At a relatively low electrodeposition voltage of 1.5 V,the Cu gas-diffusion electrode with the highest Cu^(δ+)/Cu^(0)ratio favors the pathways of∗CO hydrogenation to form CH_(4) with maximum Faradaic efficiency of 65.4%and partial current density of 228 mA cm^(−2)at−0.83 V vs RHE.At 2.0 V,the Cu gas-diffusion electrode with the lowest Cu^(δ+)/Cu^(0)ratio prefers C-C coupling to form C_(2)+products with Faradaic efficiency topping 80.1%at−0.75 V vs RHE,where the Faradaic efficiency of C_(2)H_(4) accounts for 46.4%and the partial current density of C_(2)H_(4) achieves 279 mA cm^(−2).This work demonstrates that the selectivity from CH_(4) to C_(2)H_(4) is switchable by tuning surface Cu species composition of Cu gas-diffusion electrodes.
基金sponsored by the National Key R&D Program of China(Nos.2021YFC1910504,2019YFC 1907101,and 2019YFC1907103)the Key R&D Program of Ningxia Hui Autonomous Region,China(Nos.2020BCE01001 and 2021BEG01003)+3 种基金the National Natural Science Foundation of China(Nos.U2002212,51672024,52102058,and 52204414)the Xijiang Innovation and Entrepreneurship Team(No.2017A0109004)the Fundamental Research Funds for the Central Universities(Nos.FRF-TP20-097A1Z and FRF-TP-20-031A1)the Foshan Science and Technology Innovation Special Foundation(No.BK22BE001)。
文摘This work aims to study the improvement effect of Sm on Mn-based catalysts for selective catalytic reduction (SCR) of NO with NH3.A series of Sm_(x)Mn_(0.3-x)-xTi catalysts (x=0,0.1,0.15,0.2,and 0.3) were prepared by co-precipitation.Activity tests indicated that the Sm_(0.15)Mn_(0.15)Ti catalyst showed superior performances,with a NO conversion of 100%and N_(2)selectivity above 87%at 180–300℃.The characterizations showed that Sm doping suppressed the crystallization of TiO_(2)and Mn2O3phases and increased the specific surface area and acidity.In particular,the surface area increased from 152.2 m^(2)·g^(-1)for Mn0.3Ti to 241.7 m^(2)·g^(-1)for Sm_(0.15)Mn_(0.15)Ti.These effects contributed to the high catalytic activity.The X-ray photoelectron spectroscopy (XPS) results indicated that the relative atomic ratios of Sm^(3+)/Sm and Oβ/O of Sm_(0.15)Mn_(0.15)Ti were 76.77at%and 44.11at%,respectively.The presence of Sm contributed to an increase in surface-absorbed oxygen (Oβ) and a decrease in Mn^(4+)surface concentration,which improved the catalytic activity.In the results of hydrogen temperature-programmed reduction(H_(2)-TPR),the presence of Sm induced a higher reduction temperature and lower H_(2)consumption (0.3 mmol·g^(-1)) for the Sm_(0.15)Mn_(0.15)Ti catalyst compared to the Mn0.3Ti catalyst.The decrease in Mn^(4+)weakened the redox property of the catalysts and increased the N_(2)selectivity by suppressing N_(2)O formation from NH3oxidation and the nonselective catalytic reduction reaction.The in situ diffuse reflectance infrared Fourier transform spectra (DRIFTs) revealed that NH3-SCR of NO over the Sm_(0.15)Mn_(0.15)Ti catalyst mainly followed the Eley–Rideal mechanism.Sm doping increased surface-absorbed oxygen and weakened the redox property to improve the NO conversion and N_(2)selectivity of the Sm_(0.15)Mn_(0.15)Ti catalyst.
基金supported by the State Assignment of the Ministry of Science and Higher Education of the RF(No.0287-2021-0019).
文摘Cladocera are filter feeders abundant in freshwaters,which consume phytoplankton particles in wide size and taxonomic ranges.The ability of cladocerans to control phytoplankton abundance by grazing is determined by various factors including the characteristics of phytoplankton.Freshwater salinization may reduce the strength of top-down grazing control of phytoplankton because of the detrimental effects of salinity on the grazing intensity of zooplankters.We performed grazing experiments with two species of Cladocera of different body lengths to test their ability to graze on phytoplankton in natural waters differing in salinity and size and taxonomic composition of food particles.Grazing experiments demonstrated that the grazing rate was mostly controlled by the abundance of phytoplankton in the medium.The grazing rate was reduced at salinity ca.above 3 g/L of NaCl in the medium.The lower grazing rate was observed in the medium with larger phytoplankton particles.Both species predominantly consumed phytoplankton particles with a diameter of 6-12μm,which may shift the size distribution of phytoplankton towards a larger average diameter of particles.The taxon-specific feeding was also observed,as both species predominantly consumed diatom algae.Thus,we found that because of grazing,the size and taxonomic characteristics of phytoplankton are shifted towards a less edible community.The detrimental effect of elevated salinity on grazing rate supports growing concern about freshwater salinization negatively affecting water quality,particularly reducing top-down grazing control of phytoplankton.
基金the National Natural Science Foundation of China(No.81872956)。
文摘Andrographolide is the main active ingredient of Andrographis paniculata(Burm.f.)Nees,known as“natural antibiotic”.Here,for the purpose of discovering a more efficient,low-cost extraction and separation method,the research status of andrographolide was reviewed.At present,researches only take extraction rate as the only index to optimize extraction parameters,but ignores the importance of extraction selectivity.It is usually meaningless to blindly pursue the extraction rate without considering the difficulty and cost of subsequent separation.So,factors affecting extraction selectivity such as solvent choice,temperature and physicochemical effects caused by extraction technique itself,are first discussed.Different extraction techniques for andrographolide were discussed by comparing the selectivity,efficiency and cost of extraction.The separation procedures of andrographolide such as decolorization,impurity removal,crystallization,membrane separation,solid-phase extraction and partition chromatography and their challenges and possible strategies are also discussed.It is hoped that this review can provide guidance for researchers who are committed to advancing the field of andrographolide extraction and purification.
基金This work was supported by Financial support from the National Natural Science Foundation of China(21908189,21872121)the National Key R&D Program of China(2016YFA0202900)+1 种基金the Key Program supportedby theNaturalScience Foundationof ZhejiangProvince,China(LZ18B060002)the Key R&D Project of Zhejiang Province(2020C01133).
文摘Selective hydrogenation of phenol to cyclohexanone is intriguing in chemical industry.Though a few catalysts with promising performances have been developed in recent years,the basic principle for catalyst design is still missing owing to the unclear catalytic mechanism.This work tries to unravel the mechanism of phenol hydro-genation and the reasons causing the selectivity discrepancy on noble metal catalysts under mild conditions.Results show that different reaction pathways always firstly converge to the formation of cyclohexanone under mild conditions.The selectivity discrepancy mainly depends on the activity for cyclohexanone sequential hy-drogenation,in which two factors are found to be responsible,i.e.the hydrogenation energy barrier and the competitive chemisorption between phenol and cyclohexanone,if the specific co-catalyzing effect of H 2 O on Ru is not considered.Based on the above results,a quantitative descriptor,E b(one/pl)/E a,in which E a can be further correlated to the d band center of the noble metal catalyst,is proposed by the first time to roughly evaluate and predict the selectivity to cyclohexanone for catalyst screening.
文摘A problem in chemical analysis in connection with measurements of a substance normally occurring in a sample, or identification of a substance which should not exist in a sample, is insufficient selectivity. In this article, we analyze this problem and propose remedies. We use a real doping case to illustrate how chemical noise causes a serious selectivity problem, probably causing a false positive outcome.
基金supported by State Key Laboratory of Water Resource Protection and Utilization in Coal Mining(No.GJNY-18-73.17).
文摘Electroreduction of nitrate has been gaining wide attention in recent years owing to it's beneficial for converting nitrate into benign N_(2) from the perspective of electrocatalytic denitrification or into value-added ammonia from the perspective of electrocatalytic NH_(3) synthesis.By reason of the undesired formation of ammonia is dominant during electroreduction of nitrate-containing wastewater,chloride has been widely used to improve N_(2) selectivity.Nevertheless,selective electroreduction of nitrate to N2 gas in chloride-containing system poses several drawbacks.In this review,we focus on the key strategies for efficiently enhancing N_(2) selectivity of electroreduction of nitrate in chloride-free system,including optimal selection of elements,combining an active metal catalyst with another metal,manipulating the crystalline morphology and facet orientation,constructing core–shell structure catalysts,etc.Before summarizing the strategies,four possible reaction pathways of electro-reduction of nitrate to N_(2) are discussed.Overall,this review attempts to provide practical strategies for enhancing N2 selectivity without the aid of electrochlorination and highlight directions for future research for designing appropriate electrocatalyst for final electrocatalytic denitrifi-cation.
基金funded by the National Eye Institute(NIH) EY029360the Whitehall Foundation+1 种基金the TIRR Foundationthe Levy-Longenbaugh Research Award to NMT National Institute on Aging (NIH) F31AG067676 to CAW。
文摘A common feature among neurodegenerative conditions is that ce rtain neuronal populations are selectively vulnerable to loss(Fu et al.,2018).By corollary,other neurons are selectively resilient,suggesting they may possess unique features that support their survival.U nderstanding the basis of neuronal resilience or vulnerability would provide a logical strategy to identify factors that could be targeted therapeutically.
基金supported by Program for National Natural Science Foundation of China(Nos.22178135,21978104 and 22278419)the National Key Research and Development Program of China(No.2021YFC2101601)。
文摘The fructose-to-furfural transformation is facing major challenges in the selectivity and high efficiency. Herein, we have developed a simple and effective approach for the selective conversion of fructose to furfural using Hβ zeolite modified by organic acids for dealuminization to regulate its textural and acidic properties. It was found that citric acid-dealuminized Hβ zeolite possessed high specific surface areas, wide channels and high Brønsted acid amount, which facilitated the selective conversion of fructose to furfural with a maximum yield of 76.2% at433 K for 1 h in the γ-butyrolactone(GBL)-H_(2)O system, as well as the concomitant formation of 83.0% formic acid. The^(13)C-isotope labelling experiments and the mechanism revealed that the selective cleavage of C1–C2 or C5–C6 bond on fructose was firstly occurred to form pentose or C5 intermediate by weak Brønsted acid, which was then dehydrated to furfural by strong Brønsted acid. Also this dealuminized Hβ catalyst showed the great recycling performance and was active for the conversion of glucose and mannose.
文摘Pattern matching method is one of the classic classifications of existing online portfolio selection strategies. This article aims to study the key aspects of this method—measurement of similarity and selection of similarity sets, and proposes a Portfolio Selection Method based on Pattern Matching with Dual Information of Direction and Distance (PMDI). By studying different combination methods of indicators such as Euclidean distance, Chebyshev distance, and correlation coefficient, important information such as direction and distance in stock historical price information is extracted, thereby filtering out the similarity set required for pattern matching based investment portfolio selection algorithms. A large number of experiments conducted on two datasets of real stock markets have shown that PMDI outperforms other algorithms in balancing income and risk. Therefore, it is suitable for the financial environment in the real world.
基金Major Project for New Generation of AI Grant No.2018AAA0100400)the Scientific Research Fund of Hunan Provincial Education Department,China(Grant Nos.21A0350,21C0439,22A0408,22A0414,2022JJ30231,22B0559)the National Natural Science Foundation of Hunan Province,China(Grant No.2022JJ50051).
文摘Radiomics is a non-invasive method for extracting quantitative and higher-dimensional features from medical images for diagnosis.It has received great attention due to its huge application prospects in recent years.We can know that the number of features selected by the existing radiomics feature selectionmethods is basically about ten.In this paper,a heuristic feature selection method based on frequency iteration and multiple supervised training mode is proposed.Based on the combination between features,it decomposes all features layer by layer to select the optimal features for each layer,then fuses the optimal features to form a local optimal group layer by layer and iterates to the global optimal combination finally.Compared with the currentmethod with the best prediction performance in the three data sets,thismethod proposed in this paper can reduce the number of features fromabout ten to about three without losing classification accuracy and even significantly improving classification accuracy.The proposed method has better interpretability and generalization ability,which gives it great potential in the feature selection of radiomics.
基金Supported by the Guangdong Province Basic and Applied Basic Research Fund Project(No.2020A1515110826)the National Natural Science Foundation of China(No.42006115)the Major Scientific and Technological Projects of Hainan Province(No.ZDKJ2021036)。
文摘Manganese superoxide dismutase(MnSOD)is an antioxidant that exists in mitochondria and can effectively remove superoxide anions in mitochondria.In a dark,high-pressure,and low-temperature deep-sea environment,MnSOD is essential for the survival of sea cucumbers.Six MnSODs were identified from the transcriptomes of deep and shallow-sea sea cucumbers.To explore their environmental adaptation mechanism,we conducted environmental selection pressure analysis through the branching site model of PAML software.We obtained night positive selection sites,and two of them were significant(97F→H,134K→V):97F→H located in a highly conservative characteristic sequence,and its polarity c hange might have a great impact on the function of MnSOD;134K→V had a change in piezophilic a bility,which might help MnSOD adapt to the environment of high hydrostatic pressure in the deepsea.To further study the effect of these two positive selection sites on MnSOD,we predicted the point mutations of F97H and K134V on shallow-sea sea cucumber by using MAESTROweb and PyMOL.Results show that 97F→H,134K→V might improve MnSOD’s efficiency of scavenging superoxide a nion and its ability to resist high hydrostatic pressure by moderately reducing its stability.The above results indicated that MnSODs of deep-sea sea cucumber adapted to deep-sea environments through their amino acid changes in polarity,piezophilic behavior,and local stability.This study revealed the correlation between MnSOD and extreme environment,and will help improve our understanding of the organism’s adaptation mechanisms in deep sea.
基金the National Natural Science Foundation of China(22368014)the Guizhou Provincial S&T Project(ZK[2022]011,GCC[2023]011)+2 种基金the Natural Science Foundation of Guangxi Zhuang Autonomous Region(2023JJA120098)the Guangxi Key Laboratory of Green Chemical Materials and Safety Technology,the Beibu Gulf University(2022SYSZZ02,2022ZZKT04)the Guizhou Provincial Higher Education Institution Program(Qianjiaoji[2023]082)。
文摘Selective cleavage of Csp^(2)-OCH_(3)bond in lignin without breaking other types of C-O bonds followed by N-functionalization is fascinating for on-purpose valorization of biomass.Here,a Co/Ni-based dual-atom catalyst CoNiDA@NC prepared by in-situ evaporation and acid-etching of metal species from tailor-made metal–organic frameworks was efficient for reductive upgrading of various lignin-derived phenols to cyclohexanols(88.5%–99.9%yields),which had ca.4 times higher reaction rate than the single-atom catalyst and was superior to state-of-the-art heterogeneous catalysts.The synergistic catalysis of Co/Ni dual atoms facilitated both hydrogen dissociation and hydrogenolysis steps,and could optimize adsorption configuration of lignin-derived methoxylated phenols to further favor the Csp^(2)-OCH_(3)cleavage,as elaborated by theoretical calculations.Notably,the CoNi_(DA)@NC catalyst was highly recyclable,and exhibited excellent demethoxylation performance(77.1%yield)in real lignin monomer mixtures.Via in-situ cascade conversion processes assisted by dual-atom catalysis,various high-value N-containing chemicals,including caprolactams and cyclohexylamines,could be produced from lignin.