Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PE...Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.展开更多
Composites containing nanoparticles of amorphous calcium phosphate （NACP） remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates （QAMs） with chain lengths （CLs...Composites containing nanoparticles of amorphous calcium phosphate （NACP） remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates （QAMs） with chain lengths （CLs） of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized： DMAPM （CL3）, DMAHM （CL6）, DMADDM （CL12）, DMAHDM （CL16）, and DMAODM （CL18）. Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite （n = 6; P 〉 0.1）. Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite （P 〈 0.05）; further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units （CFU） of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the C/reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.展开更多
Anionic surfantant sodium dodecyl sulfate （SDS）, cationic surfactant cetyl trimethyl ammonium bromide （CTAB） and acrylic acid （AA） were introduced as molecular models to study the interaction between montmorillo...Anionic surfantant sodium dodecyl sulfate （SDS）, cationic surfactant cetyl trimethyl ammonium bromide （CTAB） and acrylic acid （AA） were introduced as molecular models to study the interaction between montmorillonite and organic molecules with different charge or chain length. The compounds were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR） and 13C nuclear magnetic resonance （13C NMR）. The results show organic anion could interact strongly with montmorillonite, even the molecules could intercalate into the layers of MMT.展开更多
Pure organic room-temperature phosphorescence(RTP)materials have attracted wide attention owing to their excellent luminescent properties and great potential in various applications.In this work,iminostilbene and its ...Pure organic room-temperature phosphorescence(RTP)materials have attracted wide attention owing to their excellent luminescent properties and great potential in various applications.In this work,iminostilbene and its analogues are applied to realize RTP emission by copolymerizing with acrylamide.It can be concluded that the growth of alkane chain in monomers can enhance the lifetime and photoluminescence quantum yield of RTP emission,and polymers with the larger conjugated structure of the monomer show a longer RTP emission wavelength.This work provides a series of new pure organic RTP materials and might provide new thoughts for designing more advanced and superior RTP materials.展开更多
The intrinsic relationship between molecular chain length and the probability of chain reaction during poly（lactic acid） （PLA） hydrolysis was investigated by Monte Carlo simulation. The chain reaction rate was cal...The intrinsic relationship between molecular chain length and the probability of chain reaction during poly（lactic acid） （PLA） hydrolysis was investigated by Monte Carlo simulation. The chain reaction rate was calculated by introducing a power function of different molecular chain lengths. The hydrolysis of both amorphous and extended-chain crystal PLA was selected as the model system. It is found that, the chain reaction probability was proportional to the chain length with a power of 0.4 for amorphous PLA and 0.7-1 for extended-chain crystal PLA, respectively. These results indicate that PLA with longer chain length usually exhibits larger reaction rate than that with shorter length. Comparing the hydrolysis of the two kinds of PLA, the competition between longer and shorter chains in the different condensed structures is different.展开更多
In the polymerization process of methyl methacrylate (MMA), the Arrhenius parameters (activation energy and frequency factor) of propagating reaction monotonically decrease with increasing monomer conversion. At the b...In the polymerization process of methyl methacrylate (MMA), the Arrhenius parameters (activation energy and frequency factor) of propagating reaction monotonically decrease with increasing monomer conversion. At the beginning and middle stage of the propagating reaction, the increase of radical chain length is the main reason of above mentioned change. And at the end stage, the sharp decrease of k(p) indicates that the activation energy is approximately incline to zero and the propagating reaction is controlled by molecular diffusion motion.展开更多
Effects of temperature during grain-filling on chain length distribution and structure characteristics of 4 early-seasonindica rice cultivars were investigated under the environment-controlled conditions. The plants a...Effects of temperature during grain-filling on chain length distribution and structure characteristics of 4 early-seasonindica rice cultivars were investigated under the environment-controlled conditions. The plants at flowering stage weresubjected to two temperature treatments until maturity (the mean dairy air temperature, 22 and 32C for optimum temperaturetreatment and high temperature treatment, respectively). The result showed that high temperature during grain-fillingsignificantly decreased the long B-chain content and increased the intermediate B-chain content. But the effect of hightemperature on other starch chains appeared to be cultivar-dependant. The crystalline characteristics of rice starch werealso affected by temperature during grain-filling. The intensity at 18 2q of X-ray diffraction pattern of rice samples underhigh temperature was higher than those under optimum temperature, though all rice starches performed A-crystallinetype. Moreover, the intensity at 18 2q was positive correlation with intermediate B-chain content and negative correlationwith long B-chain content.展开更多
Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs)production,which mainly focused on single strain microorganism or activated sludge rather than artif...Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs)production,which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia.Here,a medium chain length PHAs(mcl-PHAs)producing Pseudomonas-Saccharomyces consortium with xylose as the main substrate was studied.Mcl-PHAs accumulation increased from 12.69 mg·L^-1 to 152.3 mg·L^-1 without any optimization method.The presence of Saccharomyces cerevisiae,though in a relatively low concentration,improved the sedimentation of cell mass of the mixed culture by 60%.Reasons for better sedimentation of the consortium were complex:first,the length of Pseudomonas putida increased two to three times in the consortium;second,the positive surface charge of P.putida was neutralized by S.cerevisiae;third,the adhesion proteins on the surface of S.cerevisiae interacted with the P.putida.展开更多
Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by mico-flotation tests. The two kinds of quaternary ammonium salts [RN(CH3)3] with diffe...Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by mico-flotation tests. The two kinds of quaternary ammonium salts [RN(CH3)3] with different chain lengths, dodecyltrimethylammonium chloride (DTAC) and cetyltrimethylammonium chloride (CTAC) were used as collectors for kaolinite in different particle size fractions (0.075–0.01 mm, 0.045–0.075 mm, 0–0.045 mm). The anomalous flotation behavior of kaolinite have been further explained based on crystal structure considerations by adsorption tests and molecular dynamics (MD) simulation. The results show that the flotation recovery of kaolinite in all different particle size fractions decreases with an increase in pH when DTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. The longer the carbon chain of QAS is, the higher the recoveries of coarse kaolinite (0.075–0.01 mm and 0.045–0.075 mm) are. But the flotation recovery of the finest kaolinite (0–0.045 mm) decreases with chain lengths of QAS collectors increasing, which is consistent with the flotation results of unsifted kaolinite (0–0.075 mm). It is explained by the froth stability related to the residual concentration of QAS collector. In lower residual concentration, the froth stability becomes worse. Within the range of flotation collector concentration, it's easy of CTAC to be completely adsorbed by kaolinite in the particle size fraction (0–0.045 mm), which led to lower flotation recovery. Moreover, it is interesting that the particle size of kaolinite is coarser, the flotation recovery is higher. The anomalous flotation behavior of kaolinite is rationalized based on crystal structure considerations. The results of MD simulations show that the (001) kaolinite surface has the strongest interaction with DTAC, compared with the (001), (010) and (110) surfaces. On the other hand, when particle size of kaolinite is altered, the number of basal planes and edge planes is changed. It is observed that the finer kaolinite particles size become, the greater relative surface area of edges is, and the more the number of edges is. It means that fine kaolinite particles have more edges to adsorb less cationic colletors than that of coarse kaolinite particles, which is responsible for the poorer floatability of fine kaolinite.展开更多
Productivity and international energy price shocks are reflected in PPI and CPI via industrial chains.China’s in-depth participation into the global value chains has increasingly lengthened its industrial production ...Productivity and international energy price shocks are reflected in PPI and CPI via industrial chains.China’s in-depth participation into the global value chains has increasingly lengthened its industrial production chains.The question is how the changing length of production chains will affect CPI and PPI,as well as CPI-PPI correlation?By constructing a global input-output price model,this paper offers a theoretical discussion on the impact of production chain length on the CPI-PPI divergence.Our findings suggest that the price shock of international bulk commodities has a greater impact on China’s PPI than that on CPI.The effects on both China’s PPI and CPI estimated by using the single-country input-output model are higher than the results estimated with the global input-output model.However,the difference between CPI and PPI variations estimated with the global input-output model is greater than the result estimated with the single-country input-output model,which supports the view that the lengthening of production chains,especially international production chains,leads to a divergence between CPI and PPI.Empirical results based on cross-national panel data also suggest that the lengthening of production chains has reduced the CPI-PPI correlation for countries,i.e.the lengthening of production chains has increased the PPI-CPI divergence.That is to say,policymakers should target not just CPI in maintaining price stability,but instead focus on the stability of both PPI and CPI.Efforts can be made to proactively adjust the price index system,and formulate the industrial chain price index.展开更多
Surface ligands of colloidal quantum dots(QDs)have a profound influence on their surface states,which has been verified in the studies of the effect of ligand head groups on the photoluminescence(PL)properties of QDs....Surface ligands of colloidal quantum dots(QDs)have a profound influence on their surface states,which has been verified in the studies of the effect of ligand head groups on the photoluminescence(PL)properties of QDs.However,the investigation of the ligand chain length is limited.Here,we systematically explored the effect of chain length on the Ag_(2)Se QDs by selecting three ligands,1-octanethiol(OTT),1-dodecanethiol(DDT),and 1-hexadecanethiol(HDT),with diverse chain lengths.We found that the PL intensity of Ag_(2)Se QDs increased with the decrease of the ligand chain length due to the enhanced passivation of surface defects emerging from the robust QD-ligand interface binding affinity and the weaker hydrophobic chain–chain interaction.Subsequently,AgAuSe QDs terminated with OTT were obtained by alloying parent OTT-Ag_(2)Se QDs with Au precursor with a record absolute PL quantum yield(PLQY)of 87.2%at 970 nm,facilitating ultrasensitive in vivo angiography imaging in a nude mouse model.We expect that our finding of the important role of the ligand chain length on the optical properties of QDs will be suggestive to the design and synthesis of high-quality QDs,and also look forward to the clinical applications of the ultra-bright AgAuSe QDs.展开更多
Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the stru...Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the structure of the admixture.Hence,the evaluation and generalization of the reports on the cement-admixture compatibility are challenging.In this study,three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content,anionic/nonionic molar ratio,and main chain length and different side chain lengths were produced.The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated.In addition,an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type,admixture/cement ratio,and elapsing time to the Marsh funnel flow time,mini-slump,slump flow,and compressive strength.The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems.However,the admixture having the shortest side chain was better with regard to flow retention.The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures.Regarding the behaviors of the admixtures in the cementitious systems,an optimal admixture side chain molecular weight is proposed.展开更多
The interfacial structure and adsorption mechanism of imidazolium-based ionic liquids(ILs)on Au(111)surface were investigated via first-principles calculation.Electron density analysis and Bader charge analysis were u...The interfacial structure and adsorption mechanism of imidazolium-based ionic liquids(ILs)on Au(111)surface were investigated via first-principles calculation.Electron density analysis and Bader charge analysis were used to explore the electronic structure of Au(111)-ILs interface.Computations show that the alkyl chain length and anions play a significant role in designing Au(111)-ILs interfacial structure.On the one hand,the stability of interface and adsorption energy tend to be enhanced as the alkyl chain length increases.It attributes to the methylene group of alkyl chain which could easily anchor on the gold interface.On the other hand,the difference in anions makes the adsorption behavior quite different.The adsorption energy follows the order:[C_(n)mim][Br]>[C_(n)mim][Cl]>[Cnmim][TFSA]>[C_(n)mim][OAc]>[C_(n)mim][PF6]>[C_(n)mim][BF_(4)].The nonfluorinated ILs(containing Br,Cl,and O atoms of anions)always have a drastic charge transfer among gold-ILs interface.However,the larger van der Waals(vdWs)volumes of the fluorinated anions have a more diffused electron density which lead to the relatively weak interaction.To sum up,a detailed and systematic investigation of the variation of anions and alkyl chain length of ILs which will affect the interfacial structure is fully studied.The above study could be helpful to understand electrode-electrolyte microscopic interface and design of functional materials for energy storage.展开更多
Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can pr...Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes.Nevertheless,previous studies have shown that the interpretation of n-alkane proxies,such as the average chain length(ACL),is often ambiguous since this proxy depends on more than one variable.Both vegetation and climate could exert controls on the n-alkane ACL,and hence its interpretation requires careful consideration,especially in regions like the Qinghai-Tibet Plateau(QTP)where topography,biome type and moisture source are highly variable.To further evaluate the influences of vegetation and climate on the ACL in high-elevation lakes,we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP.Our results show that the ACL across a climatic gradient is significantly affected by precipitation,rather than by temperature.The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition.Finally,we suggest that more caution is needed in the interpretation of ACL data in different regions.展开更多
Changes in ozone(O_(3))can be evaluated to inform policy effectiveness and develop reasonable emissions reduction measures.This study investigated the causes of summertime maximum daily 8-h average(MDA8)O_(3) variatio...Changes in ozone(O_(3))can be evaluated to inform policy effectiveness and develop reasonable emissions reduction measures.This study investigated the causes of summertime maximum daily 8-h average(MDA8)O_(3) variation between 2015 and 2020 in Nanjing,China,a megacity in the Yangtze River Delta(YRD)region,from the perspective of meteorological conditions and anthropogenic emissions of O_(3) precursors(VOCs and NO_(x)).Compared with 2015,the observed MDA8 O_(3) decreased by 19.1μg/m^(3) in August 2020.The indirect and indirect impacts of meteorological conditions contributed 44%of the decline,with temperature,relative humidity,and wind playing important roles in the O_(3) variation.The O_(3) drop by 10.7μg/m^(3)(56%of the total decrease)may have been due to the decreases in anthropogenic emissions of VOCs and NO_(x) by 7.8%and 11.7%,respectively.The longer hydroxyl(OH)radical chain length and higher ozone production efficiency(OPE)indicated that the reduction of anthropogenic emissions accelerated the RO_(x)(RO_(x)=OH+HO_(2)+RO_(2))and NO_(x) cycles in O_(3) production,making O_(3) more sensitive to NO_(x).This corresponded to the O_(3) formation shifting from a VOC-limited regime in 2015 to a transition regime in 2020 and O_(3) decrease with anthropogenic emission reduction.Hence,the joint control of O_(3) precursor emissions can effectively mitigate O_(3) pollution in Nanjing.展开更多
Four double-stranded DNA films with different chain lengths were prepared on 3-aminopropyltriethoxysilane(APS)-modified mica surfaces in the NaCl solution with concentration ranging from 0.001 to 0.1 M.By using an ato...Four double-stranded DNA films with different chain lengths were prepared on 3-aminopropyltriethoxysilane(APS)-modified mica surfaces in the NaCl solution with concentration ranging from 0.001 to 0.1 M.By using an atomic force microscope,the force-distance curves and friction behaviour of each DNA film were studied in the NaCl solution that was used in the sample preparation.When adsorbed on mica as films in salt solution,the conformation of DNA molecules would be a combination of loops and"train-like".As the chain length increased from 50 to 20000 bp,the extension rate of DNA film increased from 7.1to 11.5 in 0.001 mol/L NaCl solution,which suggested that the DNA molecule with long chain likely resulted in more extended conformation.In addition,under low normal load,low NaCl concentration could increase the friction of DNA film and the chain length revealed insignificant effect on the friction force of DNA film.Therefore,long chain DNA with low salt concentration is more conducive to the nanopore sequencing process,since extended conformation can make DNA molecules easier to reach into nanopore and the high friction can reduce the translocation speed.These results may benefit the development of the third-generation sequencing technique based on nanopore.展开更多
The limitations of native collagen,such as thermal stability and solubility in physiological environments,can be improved by applying bioconjugation and synthetic chemistry techniques.However,the exquisite control of ...The limitations of native collagen,such as thermal stability and solubility in physiological environments,can be improved by applying bioconjugation and synthetic chemistry techniques.However,the exquisite control of the modification site of collagen remains a challenge.In this work,pH-responsive poly(acrylic acid)(PAA)with dif-ferent chain lengths was attached to the N-terminal α-amino groups of succinylated collagen using a site-specific modification strategy.Additionally,the structure,thermal stability,and pH sensitivity of succinylated collagen were explored.The modification rate of amino groups in the succinylated collagen-PAA bioconjugate(SPSC-PAA)was eval-uated by the 2,4,6-trinitrobenzene sulfonic acid assay.The impact of N-terminal modification of PAA and its chain length on the thermal stability of collagen was explored by CD and DSC.These techniques revealed that the ther-mal stability of SPSC-Col is pH-responsive and closely related to the chain length of grafted PAA.The pH sensitivity of SPSC-PAA was further explored by rheology and turbidity.Subsquently,the critical pH and isoelectric point of SPSC-PAAs were also examined by turbidity and isoelectric point titration,respectively.This work provides a new insight into the N-terminal modification of collagen on its properties.展开更多
The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polym...The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polymer materials and the typically slow cooling rates.Recent advancements in fast cooling techniques have rendered the investigation of polymer crystallization at varying cooling rates an attractive area of research;however,a systematic quantitative framework for this process is still lacking.We employ a coarse-grained model for polyvinyl alcohol(CGPVA)in molecular dynamics simulations to study the crystallization of linear polymers with varying chain lengths under variable cooling rates.Monodisperse,bidisperse and polydisperse samples are simulated.We propose two formulae based on a two-phase assumption to fit the exothermal curves obtained during cooling.Based on these formulae,better estimations of crystallization temperatures are obtained and the effects of chain lengths and cooling rates are studied.It is found that the crystallization temperature increases with chain length,similar to the Gibbs-Thomson relation formelting temperature,indicating a strong relation between fast crystallization and glass formation in linear polymers.Extrapolation to the infinitely slow cooling rate provides an easy way in simulations to estimate the equilibrium crystallization temperature.The effective chain lengths of polydisperse and bidisperse samples are found to be the number-averaged chain lengths compared to the weight-averaged ones.The chain length-dependent crystallization exhibits crossover behavior near the entanglement length,indicating the effects of entanglements under fast cooling conditions.The effect of chain length dispersity on crystallization becomes more obvious under fast cooling conditions.展开更多
We chose a series of isoindigo-based conjugated polymer（ⅡDDT,ⅡDDT-C3 and ⅡDDT-C4） with different length of side chains and bifurcation positions to investigate the relationship between the degree of alignment and...We chose a series of isoindigo-based conjugated polymer（ⅡDDT,ⅡDDT-C3 and ⅡDDT-C4） with different length of side chains and bifurcation positions to investigate the relationship between the degree of alignment and the length of side chains and bifurcation positions.We found that the dichroic ratio was increased from 2.37 to 5.23 when the side chain was longer and the bifurcation position was away from the backbone.The π-π stacking distance was decreased from 3.67 A to 3.61 A when the bifurcation position was away from the backbone because of its smaller hindrance and the d-spacing of the（100）was increased from 20.06 A to 25.21 A when the side chain was longer.All the polymers were adopted an edge-on orientation with the backbone paralleled with the long axis of fibers.The weak interaction of side-chain in ⅡDDT-C4 was beneficial for the molecules being rearranged in parallel during the contact line receding and the strong n-n interaction could accelerate the interchain assembly of the parallel molecules through π-π interaction to form aligned fibers.展开更多
文摘Shear thickening fluids （STFs） based on additives with different concentrations and molecular chain lengths were investigated. STF samples were prepared with silica and additive dispersed in polyethylene glycol （PEG） 400, where three types of additives with different molecular chain lengths of PEG4000, PEG6000, and PEG10000 were used. For PEG10000, different concentrations, including 0, 1%, 3%, and 5%, were selected to study the influences of additive concentrations. Rheological properties of the samples were measured with a rheometer. The results show that the shear thickening effect was significantly enhanced with the increase of the concentration and the molecular chain length of additives. The mechanism of enhancement was quantitatively explained with the formation of large particles clusters.
基金supported by National Institutes of Health (NIH) R01DE17974 (Hockin HK Xu)National Natural Science Foundation of China grant 81400540 (Ke Zhang)a seed fund (Hockin HK Xu) from the University of Maryland School of Dentistry
文摘Composites containing nanoparticles of amorphous calcium phosphate （NACP） remineralize tooth lesions and inhibit caries. A recent study synthesized quaternary ammonium methacrylates （QAMs） with chain lengths （CLs） of 3-18 and determined their effects on a bonding agent. This study aimed to incorporate these QAMs into NACP nanocomposites for the first time to simultaneously endow the material with antibacterial and remineralizing capabilities and to investigate the effects of the CL on the mechanical and biofilm properties. Five QAMs were synthesized： DMAPM （CL3）, DMAHM （CL6）, DMADDM （CL12）, DMAHDM （CL16）, and DMAODM （CL18）. Each QAM was incorporated into a composite containing 20% NACP and 50% glass fillers. A dental plaque microcosm biofilm model was used to evaluate the antibacterial activity. The flexural strength and elastic modulus of nanocomposites with QAMs matched those of a commercial control composite （n = 6; P 〉 0.1）. Increasing the CL from 3 to 16 greatly enhanced the antibacterial activity of the NACP nanocomposite （P 〈 0.05）; further increasing the CL to 18 decreased the antibacterial potency. The NACP nanocomposite with a CL of 16 exhibited biofilm metabolic activity and acid production that were 10-fold lesser than those of the control composite. The NACP nanocomposite with a CL of 16 produced 2-log decreases in the colony-forming units （CFU） of total microorganisms, total streptococci, and mutans streptococci. In conclusion, QAMs with CLs of 3-18 were synthesized and incorporated into an NACP nanocomposite for the first time to simultaneously endow the material with antibacterial and remineralization capabilities. Increasing the C/reduced the metabolic activity and acid production of biofilms and caused a 2-log decrease in CFU without compromising the mechanical properties. Nanocomposites exhibiting strong anti-biofilm activity, remineralization effects, and mechanical properties are promising materials for tooth restorations that inhibit caries.
文摘Anionic surfantant sodium dodecyl sulfate （SDS）, cationic surfactant cetyl trimethyl ammonium bromide （CTAB） and acrylic acid （AA） were introduced as molecular models to study the interaction between montmorillonite and organic molecules with different charge or chain length. The compounds were characterized by X-ray diffraction （XRD）, Fourier transform infrared spectroscopy （FT-IR） and 13C nuclear magnetic resonance （13C NMR）. The results show organic anion could interact strongly with montmorillonite, even the molecules could intercalate into the layers of MMT.
基金the financial support from the National Natural Science Foundation of China (Nos. 21788102, 22125803, 22020102006 and 21871083)Program of Shanghai Academic/Technology Research Leader (No. 20XD1421300)+2 种基金‘Shu Guang’ Project supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation (No. 19SG26)the Innovation Program of Shanghai Municipal Education Commission (No. 2017–01–07–00–02-E00010)the Fundamental Research Funds for the Central Universities.
文摘Pure organic room-temperature phosphorescence(RTP)materials have attracted wide attention owing to their excellent luminescent properties and great potential in various applications.In this work,iminostilbene and its analogues are applied to realize RTP emission by copolymerizing with acrylamide.It can be concluded that the growth of alkane chain in monomers can enhance the lifetime and photoluminescence quantum yield of RTP emission,and polymers with the larger conjugated structure of the monomer show a longer RTP emission wavelength.This work provides a series of new pure organic RTP materials and might provide new thoughts for designing more advanced and superior RTP materials.
基金financially supported by the National Natural Science Foundation of China(No.21074112)
文摘The intrinsic relationship between molecular chain length and the probability of chain reaction during poly（lactic acid） （PLA） hydrolysis was investigated by Monte Carlo simulation. The chain reaction rate was calculated by introducing a power function of different molecular chain lengths. The hydrolysis of both amorphous and extended-chain crystal PLA was selected as the model system. It is found that, the chain reaction probability was proportional to the chain length with a power of 0.4 for amorphous PLA and 0.7-1 for extended-chain crystal PLA, respectively. These results indicate that PLA with longer chain length usually exhibits larger reaction rate than that with shorter length. Comparing the hydrolysis of the two kinds of PLA, the competition between longer and shorter chains in the different condensed structures is different.
文摘In the polymerization process of methyl methacrylate (MMA), the Arrhenius parameters (activation energy and frequency factor) of propagating reaction monotonically decrease with increasing monomer conversion. At the beginning and middle stage of the propagating reaction, the increase of radical chain length is the main reason of above mentioned change. And at the end stage, the sharp decrease of k(p) indicates that the activation energy is approximately incline to zero and the propagating reaction is controlled by molecular diffusion motion.
基金the National Natural Science Foundation of China(NSFC)(39803250 and 30070435).
文摘Effects of temperature during grain-filling on chain length distribution and structure characteristics of 4 early-seasonindica rice cultivars were investigated under the environment-controlled conditions. The plants at flowering stage weresubjected to two temperature treatments until maturity (the mean dairy air temperature, 22 and 32C for optimum temperaturetreatment and high temperature treatment, respectively). The result showed that high temperature during grain-fillingsignificantly decreased the long B-chain content and increased the intermediate B-chain content. But the effect of hightemperature on other starch chains appeared to be cultivar-dependant. The crystalline characteristics of rice starch werealso affected by temperature during grain-filling. The intensity at 18 2q of X-ray diffraction pattern of rice samples underhigh temperature was higher than those under optimum temperature, though all rice starches performed A-crystallinetype. Moreover, the intensity at 18 2q was positive correlation with intermediate B-chain content and negative correlationwith long B-chain content.
基金Supported by the National Basic Research Program of China(2014CB745100)the National Natural Science Foundation of China(21576197)+1 种基金Tianjin Research Program of Application Foundation and Advanced Technology(18JCYBJC23500)Tianjin Key Research&Development Program(16YFXTSF00460)
文摘Concerns about feasibility,separability,settleability,efficiency once hampered studies on polyhydroxyalkanoates(PHAs)production,which mainly focused on single strain microorganism or activated sludge rather than artificial microbial consortia.Here,a medium chain length PHAs(mcl-PHAs)producing Pseudomonas-Saccharomyces consortium with xylose as the main substrate was studied.Mcl-PHAs accumulation increased from 12.69 mg·L^-1 to 152.3 mg·L^-1 without any optimization method.The presence of Saccharomyces cerevisiae,though in a relatively low concentration,improved the sedimentation of cell mass of the mixed culture by 60%.Reasons for better sedimentation of the consortium were complex:first,the length of Pseudomonas putida increased two to three times in the consortium;second,the positive surface charge of P.putida was neutralized by S.cerevisiae;third,the adhesion proteins on the surface of S.cerevisiae interacted with the P.putida.
文摘Effects of particle size and chain length on flotation of quaternary ammonium salts (QAS) onto kaolinite have been investigated by mico-flotation tests. The two kinds of quaternary ammonium salts [RN(CH3)3] with different chain lengths, dodecyltrimethylammonium chloride (DTAC) and cetyltrimethylammonium chloride (CTAC) were used as collectors for kaolinite in different particle size fractions (0.075–0.01 mm, 0.045–0.075 mm, 0–0.045 mm). The anomalous flotation behavior of kaolinite have been further explained based on crystal structure considerations by adsorption tests and molecular dynamics (MD) simulation. The results show that the flotation recovery of kaolinite in all different particle size fractions decreases with an increase in pH when DTAC and CTAC are used as collectors. As the concentration of collectors increases, the flotation recovery increases. The longer the carbon chain of QAS is, the higher the recoveries of coarse kaolinite (0.075–0.01 mm and 0.045–0.075 mm) are. But the flotation recovery of the finest kaolinite (0–0.045 mm) decreases with chain lengths of QAS collectors increasing, which is consistent with the flotation results of unsifted kaolinite (0–0.075 mm). It is explained by the froth stability related to the residual concentration of QAS collector. In lower residual concentration, the froth stability becomes worse. Within the range of flotation collector concentration, it's easy of CTAC to be completely adsorbed by kaolinite in the particle size fraction (0–0.045 mm), which led to lower flotation recovery. Moreover, it is interesting that the particle size of kaolinite is coarser, the flotation recovery is higher. The anomalous flotation behavior of kaolinite is rationalized based on crystal structure considerations. The results of MD simulations show that the (001) kaolinite surface has the strongest interaction with DTAC, compared with the (001), (010) and (110) surfaces. On the other hand, when particle size of kaolinite is altered, the number of basal planes and edge planes is changed. It is observed that the finer kaolinite particles size become, the greater relative surface area of edges is, and the more the number of edges is. It means that fine kaolinite particles have more edges to adsorb less cationic colletors than that of coarse kaolinite particles, which is responsible for the poorer floatability of fine kaolinite.
基金the Special Project of the National Science Foundation of China(NSFC)“Open Development of China’s Trade and Investment:Basic Patterns,Overall Effects,and the Dual Circulations Paradigm”(Grant No.72141309)NSFC General Project“GVC Restructuring Effect of Emergent Public Health Incidents:Based on the General Equilibrium Model Approach of the Production Networks Structure”(Grant No.72073142)+1 种基金NSFC General Project“China’s Industrialization Towards Mid-and High-End Value Chains:Theoretical Implications,Measurement and Analysis”(Grant No.71873142)the Youth project of The National Social Science Fund of China“Research on the green and low-carbon development path and policy optimization of China’s foreign trade under the goal of‘dual carbon’”(Grant No.22CJY019).
文摘Productivity and international energy price shocks are reflected in PPI and CPI via industrial chains.China’s in-depth participation into the global value chains has increasingly lengthened its industrial production chains.The question is how the changing length of production chains will affect CPI and PPI,as well as CPI-PPI correlation?By constructing a global input-output price model,this paper offers a theoretical discussion on the impact of production chain length on the CPI-PPI divergence.Our findings suggest that the price shock of international bulk commodities has a greater impact on China’s PPI than that on CPI.The effects on both China’s PPI and CPI estimated by using the single-country input-output model are higher than the results estimated with the global input-output model.However,the difference between CPI and PPI variations estimated with the global input-output model is greater than the result estimated with the single-country input-output model,which supports the view that the lengthening of production chains,especially international production chains,leads to a divergence between CPI and PPI.Empirical results based on cross-national panel data also suggest that the lengthening of production chains has reduced the CPI-PPI correlation for countries,i.e.the lengthening of production chains has increased the PPI-CPI divergence.That is to say,policymakers should target not just CPI in maintaining price stability,but instead focus on the stability of both PPI and CPI.Efforts can be made to proactively adjust the price index system,and formulate the industrial chain price index.
基金the National Natural Science Foundation of China(Nos.21934007 and 22001262)the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20200254)China Postdoctoral Science Foundation(No.2019M661966).
文摘Surface ligands of colloidal quantum dots(QDs)have a profound influence on their surface states,which has been verified in the studies of the effect of ligand head groups on the photoluminescence(PL)properties of QDs.However,the investigation of the ligand chain length is limited.Here,we systematically explored the effect of chain length on the Ag_(2)Se QDs by selecting three ligands,1-octanethiol(OTT),1-dodecanethiol(DDT),and 1-hexadecanethiol(HDT),with diverse chain lengths.We found that the PL intensity of Ag_(2)Se QDs increased with the decrease of the ligand chain length due to the enhanced passivation of surface defects emerging from the robust QD-ligand interface binding affinity and the weaker hydrophobic chain–chain interaction.Subsequently,AgAuSe QDs terminated with OTT were obtained by alloying parent OTT-Ag_(2)Se QDs with Au precursor with a record absolute PL quantum yield(PLQY)of 87.2%at 970 nm,facilitating ultrasensitive in vivo angiography imaging in a nude mouse model.We expect that our finding of the important role of the ligand chain length on the optical properties of QDs will be suggestive to the design and synthesis of high-quality QDs,and also look forward to the clinical applications of the ultra-bright AgAuSe QDs.
基金The authors express their sincere gratitude to the Scientific and Technological Research Council of Turkey(Grant No.219M425)Bursa Uludag University Science and Technology Center(Grant Nos.AYP(MH)-2016/16,DDP(MH)-2018/9,and DDP(MH)-2019/15).The first author thanks TUBITAK for the scholarship provided by Grant No.217M408 during his PhD study.The authors would like to acknowledge Polisan Construction Chemicals Company and Bursa Ready Mixed Concrete for the provision of the materials and information on their properties.
文摘Despite the large variations in the behaviors of water-reducing admixtures upon changes in their structures,most previous reports on the cement-admixture compatibility did not provide suficient information on the structure of the admixture.Hence,the evaluation and generalization of the reports on the cement-admixture compatibility are challenging.In this study,three different polycarboxylate-ether-based water-reducing admixtures with the same free nonionic content,anionic/nonionic molar ratio,and main chain length and different side chain lengths were produced.The compatibility of these admixtures with a CEM I 42.5R-type cement was investigated.In addition,an analysis of variance was performed on the experiment results to evaluate the contributions of the admixture type,admixture/cement ratio,and elapsing time to the Marsh funnel flow time,mini-slump,slump flow,and compressive strength.The water-reducing admixtures having long or short side chains reduced the initial flow characteristics of the cementitious systems.However,the admixture having the shortest side chain was better with regard to flow retention.The side chain length of the admixture did not have significant effects on the compressive strength and water absorption capacity of the mortar mixtures and mini-slump performances of the cement paste mixtures.Regarding the behaviors of the admixtures in the cementitious systems,an optimal admixture side chain molecular weight is proposed.
基金supported by Taishan Scholars Program of Shandong Province(tsqn201909091)National Natural Science Foundation of China(U1704251,21722610)the High-Grade Talents Plan of Qingdao University.
文摘The interfacial structure and adsorption mechanism of imidazolium-based ionic liquids(ILs)on Au(111)surface were investigated via first-principles calculation.Electron density analysis and Bader charge analysis were used to explore the electronic structure of Au(111)-ILs interface.Computations show that the alkyl chain length and anions play a significant role in designing Au(111)-ILs interfacial structure.On the one hand,the stability of interface and adsorption energy tend to be enhanced as the alkyl chain length increases.It attributes to the methylene group of alkyl chain which could easily anchor on the gold interface.On the other hand,the difference in anions makes the adsorption behavior quite different.The adsorption energy follows the order:[C_(n)mim][Br]>[C_(n)mim][Cl]>[Cnmim][TFSA]>[C_(n)mim][OAc]>[C_(n)mim][PF6]>[C_(n)mim][BF_(4)].The nonfluorinated ILs(containing Br,Cl,and O atoms of anions)always have a drastic charge transfer among gold-ILs interface.However,the larger van der Waals(vdWs)volumes of the fluorinated anions have a more diffused electron density which lead to the relatively weak interaction.To sum up,a detailed and systematic investigation of the variation of anions and alkyl chain length of ILs which will affect the interfacial structure is fully studied.The above study could be helpful to understand electrode-electrolyte microscopic interface and design of functional materials for energy storage.
基金financially supported by the National Natural Science Foundation of China(Grant No.42171159)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0601).
文摘Long-chain n-alkanes are one of the most common organic compounds in terrestrial plants and they are well-preserved in various geological archives.n-alkanes are relatively resistant to degradation and thus they can provide high-fidelity records of past vegetation and climate changes.Nevertheless,previous studies have shown that the interpretation of n-alkane proxies,such as the average chain length(ACL),is often ambiguous since this proxy depends on more than one variable.Both vegetation and climate could exert controls on the n-alkane ACL,and hence its interpretation requires careful consideration,especially in regions like the Qinghai-Tibet Plateau(QTP)where topography,biome type and moisture source are highly variable.To further evaluate the influences of vegetation and climate on the ACL in high-elevation lakes,we examined the n-alkane distributions of the surface sediments of 55 lakes across the QTP.Our results show that the ACL across a climatic gradient is significantly affected by precipitation,rather than by temperature.The positive correlation between ACL and precipitation may be because of the effect of microbial degradation during deposition.Finally,we suggest that more caution is needed in the interpretation of ACL data in different regions.
基金supported by the National Natural Science Foundation of China(Grant Nos.42277095,42021004).
文摘Changes in ozone(O_(3))can be evaluated to inform policy effectiveness and develop reasonable emissions reduction measures.This study investigated the causes of summertime maximum daily 8-h average(MDA8)O_(3) variation between 2015 and 2020 in Nanjing,China,a megacity in the Yangtze River Delta(YRD)region,from the perspective of meteorological conditions and anthropogenic emissions of O_(3) precursors(VOCs and NO_(x)).Compared with 2015,the observed MDA8 O_(3) decreased by 19.1μg/m^(3) in August 2020.The indirect and indirect impacts of meteorological conditions contributed 44%of the decline,with temperature,relative humidity,and wind playing important roles in the O_(3) variation.The O_(3) drop by 10.7μg/m^(3)(56%of the total decrease)may have been due to the decreases in anthropogenic emissions of VOCs and NO_(x) by 7.8%and 11.7%,respectively.The longer hydroxyl(OH)radical chain length and higher ozone production efficiency(OPE)indicated that the reduction of anthropogenic emissions accelerated the RO_(x)(RO_(x)=OH+HO_(2)+RO_(2))and NO_(x) cycles in O_(3) production,making O_(3) more sensitive to NO_(x).This corresponded to the O_(3) formation shifting from a VOC-limited regime in 2015 to a transition regime in 2020 and O_(3) decrease with anthropogenic emission reduction.Hence,the joint control of O_(3) precursor emissions can effectively mitigate O_(3) pollution in Nanjing.
基金supported by the National Basic Research Program("973" Project)(Grant No.2011CB707604)the Natural Science Foundation of China(Grant Nos.91323103,51375409,21222401)
文摘Four double-stranded DNA films with different chain lengths were prepared on 3-aminopropyltriethoxysilane(APS)-modified mica surfaces in the NaCl solution with concentration ranging from 0.001 to 0.1 M.By using an atomic force microscope,the force-distance curves and friction behaviour of each DNA film were studied in the NaCl solution that was used in the sample preparation.When adsorbed on mica as films in salt solution,the conformation of DNA molecules would be a combination of loops and"train-like".As the chain length increased from 50 to 20000 bp,the extension rate of DNA film increased from 7.1to 11.5 in 0.001 mol/L NaCl solution,which suggested that the DNA molecule with long chain likely resulted in more extended conformation.In addition,under low normal load,low NaCl concentration could increase the friction of DNA film and the chain length revealed insignificant effect on the friction force of DNA film.Therefore,long chain DNA with low salt concentration is more conducive to the nanopore sequencing process,since extended conformation can make DNA molecules easier to reach into nanopore and the high friction can reduce the translocation speed.These results may benefit the development of the third-generation sequencing technique based on nanopore.
基金supported by the National Natural Science Foundation of China(Nos.22378320,22178277,21706201)Knowledge Innovation Program of Wuhan-Basi Research,China(No.2023020201010148)Appli cation Foundation Frontier Project of Wuhan Science and Technology Bureau,China(No.2019020701011478).
文摘The limitations of native collagen,such as thermal stability and solubility in physiological environments,can be improved by applying bioconjugation and synthetic chemistry techniques.However,the exquisite control of the modification site of collagen remains a challenge.In this work,pH-responsive poly(acrylic acid)(PAA)with dif-ferent chain lengths was attached to the N-terminal α-amino groups of succinylated collagen using a site-specific modification strategy.Additionally,the structure,thermal stability,and pH sensitivity of succinylated collagen were explored.The modification rate of amino groups in the succinylated collagen-PAA bioconjugate(SPSC-PAA)was eval-uated by the 2,4,6-trinitrobenzene sulfonic acid assay.The impact of N-terminal modification of PAA and its chain length on the thermal stability of collagen was explored by CD and DSC.These techniques revealed that the ther-mal stability of SPSC-Col is pH-responsive and closely related to the chain length of grafted PAA.The pH sensitivity of SPSC-PAA was further explored by rheology and turbidity.Subsquently,the critical pH and isoelectric point of SPSC-PAAs were also examined by turbidity and isoelectric point titration,respectively.This work provides a new insight into the N-terminal modification of collagen on its properties.
基金National Natural Science Foundation of China No.22341302.
文摘The crystallization behavior of polymers is significantly influenced by molecular chain length and the dispersion of varying chain lengths.The complexity of studying crystallization arises from the dispersity of polymer materials and the typically slow cooling rates.Recent advancements in fast cooling techniques have rendered the investigation of polymer crystallization at varying cooling rates an attractive area of research;however,a systematic quantitative framework for this process is still lacking.We employ a coarse-grained model for polyvinyl alcohol(CGPVA)in molecular dynamics simulations to study the crystallization of linear polymers with varying chain lengths under variable cooling rates.Monodisperse,bidisperse and polydisperse samples are simulated.We propose two formulae based on a two-phase assumption to fit the exothermal curves obtained during cooling.Based on these formulae,better estimations of crystallization temperatures are obtained and the effects of chain lengths and cooling rates are studied.It is found that the crystallization temperature increases with chain length,similar to the Gibbs-Thomson relation formelting temperature,indicating a strong relation between fast crystallization and glass formation in linear polymers.Extrapolation to the infinitely slow cooling rate provides an easy way in simulations to estimate the equilibrium crystallization temperature.The effective chain lengths of polydisperse and bidisperse samples are found to be the number-averaged chain lengths compared to the weight-averaged ones.The chain length-dependent crystallization exhibits crossover behavior near the entanglement length,indicating the effects of entanglements under fast cooling conditions.The effect of chain length dispersity on crystallization becomes more obvious under fast cooling conditions.
基金supported by the National Natural Science Foundation of China (Nos. 21334006, 51577138, 21474113)the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB12020300)
文摘We chose a series of isoindigo-based conjugated polymer（ⅡDDT,ⅡDDT-C3 and ⅡDDT-C4） with different length of side chains and bifurcation positions to investigate the relationship between the degree of alignment and the length of side chains and bifurcation positions.We found that the dichroic ratio was increased from 2.37 to 5.23 when the side chain was longer and the bifurcation position was away from the backbone.The π-π stacking distance was decreased from 3.67 A to 3.61 A when the bifurcation position was away from the backbone because of its smaller hindrance and the d-spacing of the（100）was increased from 20.06 A to 25.21 A when the side chain was longer.All the polymers were adopted an edge-on orientation with the backbone paralleled with the long axis of fibers.The weak interaction of side-chain in ⅡDDT-C4 was beneficial for the molecules being rearranged in parallel during the contact line receding and the strong n-n interaction could accelerate the interchain assembly of the parallel molecules through π-π interaction to form aligned fibers.
