The purpose of this study was to identify factors that enhance and hinder interdisciplinary collaborative practice (ICP) among doctors and nurses at the Nnamdi Azikiwe teaching hospital, Nnewi, southeast Nigeria. The ...The purpose of this study was to identify factors that enhance and hinder interdisciplinary collaborative practice (ICP) among doctors and nurses at the Nnamdi Azikiwe teaching hospital, Nnewi, southeast Nigeria. The study was a cross-sectional descriptive survey and the quantitative method of data collection was employed. The population was all doctors irrespective of area of specialty and all nurses employed and working in the hospital as at the time of study. Proportionate stratified and convenience sampling methods were used to select study participants according to their categories. Using validated structured questionnaire, data were collected from 110 doctors and 95 nurses in the teaching hospital on their perception on ICP and factors that enhance/hinder ICP. Data were analyzed using both descriptive and inferential statistics. Specifically, frequencies, percentages, standard deviation and graphic presentation were used for descriptive analysis of scores while the unpaired t test of mean score using Graph Pad Prism, Version 5.30 was used to determine the influence of profession, gender, and years of experience on perception of ICP at 0.05 level of significance. The study found that both doctors and nurses have positive perception on ICP. Their years of experience have significant influence on their perception. Clear individual roles and good working relationships enhance ICP while giving priority to professional status rather than expertise was seen as a prominent hindrance to ICP. The study recommends collaborative continuing education for doctors and nurses to enhance ICP in patient care. In addition, the inclusion of interdisciplinary collaborative practice programmme into the curriculum of medical and nursing students (where it does not exist) would go a long way to strengthen ICP and decrease hindrances when they graduate.展开更多
O3-NaNi1/3Fe1/3Mn1/3O2is a promising layered cathode material with high specific capacity,low cost,and simple synthesis.However,sluggish kinetic hindrance is attributed to the size discrepancy between the large Na-ion...O3-NaNi1/3Fe1/3Mn1/3O2is a promising layered cathode material with high specific capacity,low cost,and simple synthesis.However,sluggish kinetic hindrance is attributed to the size discrepancy between the large Na-ion and narrow tetrahedral interstitial positions,leading to inferior rate capacity and low reversible capacity.Herein,F with light-weight and strong electronegativity is introduced to substitute O atoms in the bulk structure,which intensifies the bond strength of transition metal and oxygen and enlarges the Na+diffusion channel.In addition,density-functional theory(DFT) calculations demonstrate that the electrostatic interaction is weakened between Na+in the tetrahedral site and the transitionmetal cation directly below it,dramatically reducing the migration barriers of Na+diffusion.Consequently,the as-obtained NaNi1/3Fe1/3Mn1/3O1.95F0.05sample displays outstanding rate performance of 86.7 mA h g^(-1)at 10 C and excellent capacity retention of 84.1% after 100 cycles at 2 C.Moreover,a full cell configuration using a hard carbon anode reaches the energy density of 307.7 Wh kg^(-1).This strategy paves the way for novel means of modulating the Na-ion migration path for high-rate O3-type layered cathode materials.展开更多
Electrocatalytic CO_(2)reduction reaction to low-carbon alcohol is a challenging task,especially high selectivity for ethanol,which is mainly limited by the regulation of reaction intermediates and subsequent C–C cou...Electrocatalytic CO_(2)reduction reaction to low-carbon alcohol is a challenging task,especially high selectivity for ethanol,which is mainly limited by the regulation of reaction intermediates and subsequent C–C coupling.A Cu-Co bimetallic catalyst with CN vacancies is successfully developed by H_(2)cold plasma toward a high-efficiency CO_(2)RR into low-carbon alcohol.The Cu-Co PBA-V_(CN)(Prussian blue analogues with CN vacancies)electrocatalyst yields methanol and ethanol as major products with a total low-carbon alcohol FE of 83.8%(methanol:39.2%,ethanol:44.6%)at-0.9 V vs.RHE,excellent durability(100 h)and a small onset potential of-0.21 V.ATR-SEIRAS(attenuated total internal reflection surface enhanced infrared absorption spectroscopy)and DFT(density functional theory)reveal that the steric hindrance of V_(CN)can enhance the CO generation from*COOH,and the C–C coupling can also be increased by CO spillover on uniformly dispersed Cu atoms.This work provides a strategy for the design and preparation of electrocatalysts for CO_(2)RR into low-carbon alcohol products and highlights the impact of catalyst steric hindrance to catalytic performance.展开更多
Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal a...Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal an abnormal buried interface anion defect passivation mechanism depending on cationinduced steric hindrance.The IL molecules containing the same anion([BF4]^(-))and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface.It was revealed what passivated interfacial defects is mainly anions instead of cations.Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations,and facilitate the interaction between anions and SnO2as well as perovskites,which is conducive to interfacial defect passivation and ameliorating interfacial contact.It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations.The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite.Compared with the control device(21.54%),the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate(BAIMBF4)with maximum size cations achieves a significantly enhanced efficiency of 23.61%along with much increased moisture,thermal and light stabilities.展开更多
By analyzing the details of Araby,this paper is to prove that in Araby James Joyce puts the boy's personal yearning for idealized romance vis-à-vis several irresistible hindrances so as to reveal the doomed p...By analyzing the details of Araby,this paper is to prove that in Araby James Joyce puts the boy's personal yearning for idealized romance vis-à-vis several irresistible hindrances so as to reveal the doomed pointlessness of an individual's holding his ideal and passion in a reality with prevailing spiritual paralysis.展开更多
The exchange action of six types of organic phenols on clay surfaces in seawater is systematically studied in this work. The following significant conclusions are drawn from the experiments. (1) The interaction of org...The exchange action of six types of organic phenols on clay surfaces in seawater is systematically studied in this work. The following significant conclusions are drawn from the experiments. (1) The interaction of organic phenols with montmorillonite, illite and kaolinite in seawater is monovalent anion exchage.(2) Their isotherms of stepwise exchage on clay surfaces belong to the Langmuir type or stepwise type.(3) The discovery of the"steric hindrance effects of stepwise exchange of organic phenols on clays surfaces", and revelation of an exchange mechanisrn diffeient from that in references are the greatest achieverments in this work.展开更多
From rapid growth of cement industry in China there is serious pollution of powdered dust. After general analysis on factors influencing adoption of environmentally sound technology(EST) as well as economic benefit ...From rapid growth of cement industry in China there is serious pollution of powdered dust. After general analysis on factors influencing adoption of environmentally sound technology(EST) as well as economic benefit from adoption of dust removing technology and capital ability of cement firms to invest, the conclusion that the obstacles to EST in China cement sector are different from ones in other sectors was drawn. And then, hindrances to diffusion and adoption of EST in China cement were discussion by empirical study.展开更多
This paper investigates the bioseparation of binary protein mixtures using polystyrene based anion exchange resin. Adsorption experiments were conducted in batch mode using draft-tube internally recirculate dair lift ...This paper investigates the bioseparation of binary protein mixtures using polystyrene based anion exchange resin. Adsorption experiments were conducted in batch mode using draft-tube internally recirculate dair lift biocontactor in comparison with the conventional shake flask batch adsorption equilibrium experiments. Binary protein mixtures contained bovine serum albumin (BSA) and bovine haemoglobin (BHb) at different initial fractions. Results from single solute adsorption experiments in biocontactor showed that both proteins were equally adsorbed onto the resin with equilibrium reached in an equal time period. This represents similar affinities towards the negatively charged resin surface, although BSA was expected to adsorb through specific forces. Adsorption results showed that BSA has hindered the BHb adsorption in the biocontactor, although adsorption of both proteins was equally hindered in the shake flasks adsorption experiments. Moreover, adsorption of BHb was inhibited up to 29% in the presence of BSA compared to the adsorption of BHb from a solution containing single solute of BHb at the same initial concentration. Similarly, the presence of BHb has hindered the adsorption of BSA by 59%. Adsorptions of both BSA and BHb from binary solution when each formed 75% initial fraction while the other protein formed the remaining 25% were relatively low with equilibrium reached in shorter time. Moreover, considerable amount of proteins remained in the solution, which demonstrates that multilayer adsorption most likely didn’t occur at the relatively small protein concentrations used in the present study. In general, the higher adsorption of BHb can also be related to the compressibility of its molecules which allowed for higher adsorption capacity. The homogeneous and lower shear environment in the airlift biocontactor compared to the other conventional batch adsorption in shake flask reduced the compressibility of BHb that caused higher BSA adsorption from binary solutions of BSA and BHb, which allowed for better bioseparation of both proteins.展开更多
Effects of carboxyl functionalized MWCNTs on the cure behavior of epoxy resin (EPIKOTETM resin 862 and EPICURETM curing agent W) were investigated by using differential scanning calorimeter in dynamic scan mode. Resul...Effects of carboxyl functionalized MWCNTs on the cure behavior of epoxy resin (EPIKOTETM resin 862 and EPICURETM curing agent W) were investigated by using differential scanning calorimeter in dynamic scan mode. Results indicated that nanotubes could initiate cure reaction at lower temperature while only 0.1 wt% samples were able to suppress the peak temperature (Tp) consistently regardless of different heating rate due to their higher reaction rate, other two batches (0.2 wt% and 0.3 wt% CNT) showed hardly any change in Tp compared to neat samples. Furthermore, addition of small amount (0.1 wt%) of CNTs significantly reduced the activation energy of the system but further addition elevated that due to their retarding effect. Also, a correlation was established between the dispersion state of CNTs in epoxy and total heat of reaction (ΔH) where lower ΔH was considered as an indication of better interfacial interaction of CNTs with matrix and hence, better dispersion. The difference in curing behavior of three different CNT percentages was discussed in terms of their steric hindrance and state of dispersion in the matrix.展开更多
A diamine monomer 4,4′-methylenedianiline(MDA) was introduced to modify the polyimide of pyromellitic dianhydride(PMDA) and 4,4′-oxydianiline(ODA) by polycondensation. A series of polyamic acids was synthesize...A diamine monomer 4,4′-methylenedianiline(MDA) was introduced to modify the polyimide of pyromellitic dianhydride(PMDA) and 4,4′-oxydianiline(ODA) by polycondensation. A series of polyamic acids was synthesized from MDA and ODA of different molar ratios with PMDA of sum mole of moles of MDA and ODA, and polyimide films were obtained by thermal imidization. Polyimide(PI) films were characterized by tensile testing, dynamic mechanical analysis(DMA), thermal gravimetry analysis(TGA), Fourier transform infrared spectroscopy (FTIR), wide X-ray diffraction(WAXD) and molecular simulation. With the increase of MDA content, the tensile strength and thermal decomposition temperature remained generally stable compared with those of PMDA/ODA polyimide. Unexpectedly, the glass transition temperature(Tg) and Young's modulus increased from 388.7 °C and 2.37 GPa to 408.3 °C and 5.74 GPa, respectively. The results of WAXD and molecular simulation indicate the steric hindrance among hydrogen atoms of the linkage groups and adjacent phenyls enhanced the properties of the polyimide modified with MDA.展开更多
Gum arabic, an inexpensive dispersant widely used in the food industry, has great potential for application in building materials. In order to find out the dispersion effect of gum arabic and the factors influencing t...Gum arabic, an inexpensive dispersant widely used in the food industry, has great potential for application in building materials. In order to find out the dispersion effect of gum arabic and the factors influencing the holding capacity of gum arabic in cement during hydration, rheological properties of cement paste with added gum arabic were assessed in this paper. The results show that 0.10wt%-0.60wt% of gum arabic positively affects dispersion, lower dosages have negligible effect. High speed mixing is required to maintain the dispersion stability of gum arabic in cement paste. The optimum dosage of gum arabic to achieve best disperse-holding capacity of cement paste was 0.3wt%, and the minimum water-cement ratio needed to obtain a dispersion effect was 0.28.展开更多
A new four-coordinated manganese compound Mn2(BPTC) (BPTC =- biphenyl- 2,4,4',6-tetracarboxylate) with flu topology net was synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis con...A new four-coordinated manganese compound Mn2(BPTC) (BPTC =- biphenyl- 2,4,4',6-tetracarboxylate) with flu topology net was synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis confirms its crystal belongs to the monoclinic system, space group C2/c with a = 12.2092(11), b = 14.6932(9), c = 8.9998(10) A, t= 108.256(12)°, Z= 4, V= 1533.2(2) A3, Dc = 1.889 mg/m3,μ = 1.69, F(O00) = 864, the final R = 0.063 and wR = 0.201 for 1407 observed reflections (I 〉 20(/)). UV-Vis absorption spectrum shows the title compound has a strong absorption at 326 and 238 nm and the optical diffuse reflectance determination shows the band gap of the title compound is 3.15 eV. The theory calculation elucidated that the UV absorptions of the title compound mainly arise from the electron transition from bonding orbitals of BPTC4- ligand to the empty orbitals of BPTC4- and Mn(II) ions.展开更多
The hindrance in heavy-ion fusion reactions a deep sub-barrier energies is investigated using the double folding model with a hybrid method between the frozen and adiabatic density approximations.In this method,the de...The hindrance in heavy-ion fusion reactions a deep sub-barrier energies is investigated using the double folding model with a hybrid method between the frozen and adiabatic density approximations.In this method,the density distributions of the projectile and the target depend closely on the distance between them.As the distance decreased,the half-density radii of the colliding nucle gradually increased to the half-density radius of the compound nucleus.The total potential based on this non-frozen approximation generates a slightly shallower pocket and becomes more attractive inside the pocket compared to that obtained from the frozen approximation.A damping factor was used to simulate the decline of the coupled channel effects owing to the density rearrangement of the two colliding nuclei.The calculated fusion cross-sections and astrophysical S factors at the deep sub-barrier energies are both in good agreement with the experimental data for the medium-heavyNi+Ni and medium-lightMg+Si mass systems.In addition,it was concluded that the apparent maximum of the S factors most likely appears in fusion systems with strong coupling effects.展开更多
This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by ...This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by IR, 'H and ^(13)C NMR spectra. The substituent on 9-position of 7-methylene-trioxaspiro (4, 4) nonane affects the structure of polymer and polymerization activity. The polymerization mechanism is discussed.展开更多
In this paper,we have developed a decarboxylative amination of carboxylic acids with nitroarenes for the synthesis of secondary amines.The protocol is performed at mild conditions without the use of noble metals as ca...In this paper,we have developed a decarboxylative amination of carboxylic acids with nitroarenes for the synthesis of secondary amines.The protocol is performed at mild conditions without the use of noble metals as catalysts.A wide range of structurally diverse secondary amines could be obtained in good yields(up to 94%)with good functional group tolerance.This transformation shows good to excellent selectivity,avoiding the generation of over alkylated byproducts.展开更多
Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT)...Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT),leading to low coulombic efficiency and limited cycle stability.Thus,it is essential to opti-mize the solvation structure thereby achieving a rapid desolvation process in LMBs at LT.Herein,we introduce branch chain-rich diisopropyl ether(DIPE)into a 2.5 M Li bis(fluorosulfonyl)imide dipropyl ether(DPE)elec-trolyte as a co-solvent for high-performance LMBs at-20°C.The incorporation of DIPE not only enhances the disorder within the electrolyte,but also induces a steric hindrance effect form DIPE’s branch chain,excluding other solvent molecules from Li+solvation sheath.Both of these factors contribute to the weak interactions between Li^(+)and solvent molecules,effectively reducing the desolvation energy of the electrolyte.Consequently,Li(50μm)||LFP(mass loading~10 mg cm^(-2))cells in DPE/DIPE based electrolyte demonstrate stable performance over 650 cycles at-20°C,delivering 87.2 mAh g^(-1),and over 255 cycles at 25°C with 124.8 mAh g^(-1).DIPE broadens the electrolyte design from molecular structure considera-tions,offering a promising avenue for highly stable LMBs at LT.展开更多
The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) p...The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) perovskites were synthesized by trial-and-error testing spacing molecules. Here, we developed a steric hindrance regulation strategy to predictably synthesize BWLE perovskites. The molecules containing C–C(–NH_(2))–C groups were introduced into low-dimensional perovskites, which brings a large steric hindrance in-plane orientation. The bigger C–C(–NH_(2))–C bond angle would induce larger structural distortion in perovskites, which leads to the higher rate of self-trapping of excitons and the deeper self-trapping depth. The photoluminescence spectra of the synthesized perovskites can cover the cool-to-warm white light region. Overall, we fabricated a material library consisting of 40 kinds of BWLE compounds according to this strategy. Our findings develop a general strategy to synthesize BWLE perovskites and offer a material platform for optoelectronic applications.展开更多
A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functi...A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functionalized with trimethylammonium(QA),N-methylimidazole(Im),N-methylpyrrolidinium(Pyr)or N-methylpiperidinium(Pip)to construct the entire anion exchange membranes(AEMs).Benefited from prominent phase-separated morphology,PBO-x%-y(x=66,68,70;y=QA,Im,Pyr,Pip)AEMs with ion exchange capacity(IEC)approaching 2.0 meq·g^(−1)exhibited super high hydroxide conductivities.Thereinto,PBO-70%-Pip possessed the highest hydroxide conductivity of 137.3 mS·cm^(−1)at 80℃Moreover,all membranes exhibit low swelling ratio(SR)(the SR of PBO-66%-QA was just 8.6%at 80℃).That is,bulky steric hydrophobic groups play a crucial role in balancing the high hydroxide conductivity and low SR in AEMs.Furthermore,three AEMs(PBO-66%-QA,PBO-68%-Pyr,PBO-70%-Pip)showed good alkaline stability after immersion into 1.0 mol/L NaOH aqueous solution at 80℃for 480 h without any degradation.展开更多
The self-assembly reactions between mixed-ligand and tetrahydrate dysprosium acetate in the presence of mixed organic solvents lead to two structural similar dinuclear dysprosium complexes with composition formulas of...The self-assembly reactions between mixed-ligand and tetrahydrate dysprosium acetate in the presence of mixed organic solvents lead to two structural similar dinuclear dysprosium complexes with composition formulas of Dy_(2)(L_1)_(2)(L_(2))_(2)(CH_(3)OH)_(2)·CH_(2)Cl_(2)·CH_(3)OH(1) and Dy_(2)(L_1)_(2)(L_(3))_(2)(CH_(3)OH)_(2)·CH_(3)CN(2),where L_1,L_(2) and L_(3) represent the deprotonated form of 4-tert-butyl-2-(7-methoxybenzo[d]oxazol-2-yl)phenol,(E)-1-(((3,5-di-tert-butyI-2-hydroxyphenyI)imino)methyl)naphthalen-2-ol and(E)-2,4-di-tertbutyl-6-((2-hydroxybenzylidene)amino)phenol.The tiny difference of the core structure of 1 and 2 is derived from the steric hindrance of Schiff base ligands L_(2) and L_(3).Dynamic magnetic measurements reveal that 1 and 2 show frequency-dependent out-of-phase alternating-current susceptibility signal peaks at different temperatures under zero dc field,diagnostic of single-molecule magnet behavior.The experimental derived energy barrier to magnetization reversal for 1 and 2 is 108(1),47(2) and 33(3) K.Ab initio CASSCF calculations performed on 1 and 2 suggest that the origin of the difference in magnetic properties originates from the variation in the single-ion anisotropy that arises due to minor structural variation.Further,the equation to calculate the effective energy barrier for Dy_(2) proposed earlier is found to yield an excellent agreement with the experimental results.Solid state fluorescence measurements performed on 1 and 2 demonstrate that both exhibit two ligands centered components of fluorescent emissive,in addition,with different emitting colors and chromaticity coordinates.The discrepancy of fluorescence and single molecule magnet behavior showed by 1 and 2 can be attributed to the steric hindrance effect of Schiff base ligands.展开更多
文摘The purpose of this study was to identify factors that enhance and hinder interdisciplinary collaborative practice (ICP) among doctors and nurses at the Nnamdi Azikiwe teaching hospital, Nnewi, southeast Nigeria. The study was a cross-sectional descriptive survey and the quantitative method of data collection was employed. The population was all doctors irrespective of area of specialty and all nurses employed and working in the hospital as at the time of study. Proportionate stratified and convenience sampling methods were used to select study participants according to their categories. Using validated structured questionnaire, data were collected from 110 doctors and 95 nurses in the teaching hospital on their perception on ICP and factors that enhance/hinder ICP. Data were analyzed using both descriptive and inferential statistics. Specifically, frequencies, percentages, standard deviation and graphic presentation were used for descriptive analysis of scores while the unpaired t test of mean score using Graph Pad Prism, Version 5.30 was used to determine the influence of profession, gender, and years of experience on perception of ICP at 0.05 level of significance. The study found that both doctors and nurses have positive perception on ICP. Their years of experience have significant influence on their perception. Clear individual roles and good working relationships enhance ICP while giving priority to professional status rather than expertise was seen as a prominent hindrance to ICP. The study recommends collaborative continuing education for doctors and nurses to enhance ICP in patient care. In addition, the inclusion of interdisciplinary collaborative practice programmme into the curriculum of medical and nursing students (where it does not exist) would go a long way to strengthen ICP and decrease hindrances when they graduate.
基金supported by Shaanxi Province (2023-ZDLGY-24,2023-JC-QN-0588)Xi’an Key Laboratory of Clean Energy(2019219914SYS014CG036)the Open Foundation of State Key Laboratory for Advanced Metals and Materials (2022-Z01)。
文摘O3-NaNi1/3Fe1/3Mn1/3O2is a promising layered cathode material with high specific capacity,low cost,and simple synthesis.However,sluggish kinetic hindrance is attributed to the size discrepancy between the large Na-ion and narrow tetrahedral interstitial positions,leading to inferior rate capacity and low reversible capacity.Herein,F with light-weight and strong electronegativity is introduced to substitute O atoms in the bulk structure,which intensifies the bond strength of transition metal and oxygen and enlarges the Na+diffusion channel.In addition,density-functional theory(DFT) calculations demonstrate that the electrostatic interaction is weakened between Na+in the tetrahedral site and the transitionmetal cation directly below it,dramatically reducing the migration barriers of Na+diffusion.Consequently,the as-obtained NaNi1/3Fe1/3Mn1/3O1.95F0.05sample displays outstanding rate performance of 86.7 mA h g^(-1)at 10 C and excellent capacity retention of 84.1% after 100 cycles at 2 C.Moreover,a full cell configuration using a hard carbon anode reaches the energy density of 307.7 Wh kg^(-1).This strategy paves the way for novel means of modulating the Na-ion migration path for high-rate O3-type layered cathode materials.
基金the National Natural Science Foundation of China(21902017)the Project of Fundamental Research and Frontier Exploration of Chongqing(cstc2019jcyj-msxmX0052)+5 种基金the Foundation of Technological Innovation and Application Development of Chongqing(cstc2021jscx-msxmX0308)the Key Projects of Technology Innovation and Application Development of Chongqing(cstc2019jscx-gksbX0022)the Banan Science and Technology Foundation of Chongqing(2018TJ03,2020QC374)the Major Project of Science and Technology Research Program of Chongqing Education Commission of China(KJZD-M202101101)the Youth Project of Science and Technology Research Program of Chongqing Education Commission of China(KJQN20211107)the Scientific Research Foundation of Chongqing University of Technology(2020ZDZ022)。
文摘Electrocatalytic CO_(2)reduction reaction to low-carbon alcohol is a challenging task,especially high selectivity for ethanol,which is mainly limited by the regulation of reaction intermediates and subsequent C–C coupling.A Cu-Co bimetallic catalyst with CN vacancies is successfully developed by H_(2)cold plasma toward a high-efficiency CO_(2)RR into low-carbon alcohol.The Cu-Co PBA-V_(CN)(Prussian blue analogues with CN vacancies)electrocatalyst yields methanol and ethanol as major products with a total low-carbon alcohol FE of 83.8%(methanol:39.2%,ethanol:44.6%)at-0.9 V vs.RHE,excellent durability(100 h)and a small onset potential of-0.21 V.ATR-SEIRAS(attenuated total internal reflection surface enhanced infrared absorption spectroscopy)and DFT(density functional theory)reveal that the steric hindrance of V_(CN)can enhance the CO generation from*COOH,and the C–C coupling can also be increased by CO spillover on uniformly dispersed Cu atoms.This work provides a strategy for the design and preparation of electrocatalysts for CO_(2)RR into low-carbon alcohol products and highlights the impact of catalyst steric hindrance to catalytic performance.
基金financially supported by the Support Plan for Overseas Students to Return to China for Entrepreneurship and Innovation(cx2020003)the Fundamental Research Funds for the Central Universities(2020CDJ-LHZZ-074 and 2021CDJQY-022)Natural Science Foundation of Chongqing(cstc2020jcyjmsxmX0629)。
文摘Although ionic liquids(ILs)have been widely employed to heal the defects in perovskite solar cells(PSCs),the corresponding defect passivation mechanisms are not thoroughly understood up to now.Herein,we first reveal an abnormal buried interface anion defect passivation mechanism depending on cationinduced steric hindrance.The IL molecules containing the same anion([BF4]^(-))and different sizes of imidazolium cations induced by substituent size are used to manipulate buried interface.It was revealed what passivated interfacial defects is mainly anions instead of cations.Theoretical and experimental results demonstrate that the large-sized cations can weaken the ionic bond strength between anions and cations,and facilitate the interaction between anions and SnO2as well as perovskites,which is conducive to interfacial defect passivation and ameliorating interfacial contact.It can be concluded that interfacial chemical interaction strength and defect passivation effect are positively correlated with the size of cations.The discovery breaks conventional thinking that large-sized modification molecules would weaken their chemical interaction with perovskite.Compared with the control device(21.54%),the device based on 1,3-Bis(1-adamantyl)-imidazolium tetrafluoroborate(BAIMBF4)with maximum size cations achieves a significantly enhanced efficiency of 23.61%along with much increased moisture,thermal and light stabilities.
文摘By analyzing the details of Araby,this paper is to prove that in Araby James Joyce puts the boy's personal yearning for idealized romance vis-à-vis several irresistible hindrances so as to reveal the doomed pointlessness of an individual's holding his ideal and passion in a reality with prevailing spiritual paralysis.
基金Project supported by the National Natural Science Fund. (Nos. E 85111 and 4890275)
文摘The exchange action of six types of organic phenols on clay surfaces in seawater is systematically studied in this work. The following significant conclusions are drawn from the experiments. (1) The interaction of organic phenols with montmorillonite, illite and kaolinite in seawater is monovalent anion exchage.(2) Their isotherms of stepwise exchage on clay surfaces belong to the Langmuir type or stepwise type.(3) The discovery of the"steric hindrance effects of stepwise exchange of organic phenols on clays surfaces", and revelation of an exchange mechanisrn diffeient from that in references are the greatest achieverments in this work.
文摘From rapid growth of cement industry in China there is serious pollution of powdered dust. After general analysis on factors influencing adoption of environmentally sound technology(EST) as well as economic benefit from adoption of dust removing technology and capital ability of cement firms to invest, the conclusion that the obstacles to EST in China cement sector are different from ones in other sectors was drawn. And then, hindrances to diffusion and adoption of EST in China cement were discussion by empirical study.
文摘This paper investigates the bioseparation of binary protein mixtures using polystyrene based anion exchange resin. Adsorption experiments were conducted in batch mode using draft-tube internally recirculate dair lift biocontactor in comparison with the conventional shake flask batch adsorption equilibrium experiments. Binary protein mixtures contained bovine serum albumin (BSA) and bovine haemoglobin (BHb) at different initial fractions. Results from single solute adsorption experiments in biocontactor showed that both proteins were equally adsorbed onto the resin with equilibrium reached in an equal time period. This represents similar affinities towards the negatively charged resin surface, although BSA was expected to adsorb through specific forces. Adsorption results showed that BSA has hindered the BHb adsorption in the biocontactor, although adsorption of both proteins was equally hindered in the shake flasks adsorption experiments. Moreover, adsorption of BHb was inhibited up to 29% in the presence of BSA compared to the adsorption of BHb from a solution containing single solute of BHb at the same initial concentration. Similarly, the presence of BHb has hindered the adsorption of BSA by 59%. Adsorptions of both BSA and BHb from binary solution when each formed 75% initial fraction while the other protein formed the remaining 25% were relatively low with equilibrium reached in shorter time. Moreover, considerable amount of proteins remained in the solution, which demonstrates that multilayer adsorption most likely didn’t occur at the relatively small protein concentrations used in the present study. In general, the higher adsorption of BHb can also be related to the compressibility of its molecules which allowed for higher adsorption capacity. The homogeneous and lower shear environment in the airlift biocontactor compared to the other conventional batch adsorption in shake flask reduced the compressibility of BHb that caused higher BSA adsorption from binary solutions of BSA and BHb, which allowed for better bioseparation of both proteins.
文摘Effects of carboxyl functionalized MWCNTs on the cure behavior of epoxy resin (EPIKOTETM resin 862 and EPICURETM curing agent W) were investigated by using differential scanning calorimeter in dynamic scan mode. Results indicated that nanotubes could initiate cure reaction at lower temperature while only 0.1 wt% samples were able to suppress the peak temperature (Tp) consistently regardless of different heating rate due to their higher reaction rate, other two batches (0.2 wt% and 0.3 wt% CNT) showed hardly any change in Tp compared to neat samples. Furthermore, addition of small amount (0.1 wt%) of CNTs significantly reduced the activation energy of the system but further addition elevated that due to their retarding effect. Also, a correlation was established between the dispersion state of CNTs in epoxy and total heat of reaction (ΔH) where lower ΔH was considered as an indication of better interfacial interaction of CNTs with matrix and hence, better dispersion. The difference in curing behavior of three different CNT percentages was discussed in terms of their steric hindrance and state of dispersion in the matrix.
基金Supported by the National Natural Science Foundation of China(No.50973073)the Science and Technology Projects of Chengdu City, China(No.10GGYB114GX-182)
文摘A diamine monomer 4,4′-methylenedianiline(MDA) was introduced to modify the polyimide of pyromellitic dianhydride(PMDA) and 4,4′-oxydianiline(ODA) by polycondensation. A series of polyamic acids was synthesized from MDA and ODA of different molar ratios with PMDA of sum mole of moles of MDA and ODA, and polyimide films were obtained by thermal imidization. Polyimide(PI) films were characterized by tensile testing, dynamic mechanical analysis(DMA), thermal gravimetry analysis(TGA), Fourier transform infrared spectroscopy (FTIR), wide X-ray diffraction(WAXD) and molecular simulation. With the increase of MDA content, the tensile strength and thermal decomposition temperature remained generally stable compared with those of PMDA/ODA polyimide. Unexpectedly, the glass transition temperature(Tg) and Young's modulus increased from 388.7 °C and 2.37 GPa to 408.3 °C and 5.74 GPa, respectively. The results of WAXD and molecular simulation indicate the steric hindrance among hydrogen atoms of the linkage groups and adjacent phenyls enhanced the properties of the polyimide modified with MDA.
文摘Gum arabic, an inexpensive dispersant widely used in the food industry, has great potential for application in building materials. In order to find out the dispersion effect of gum arabic and the factors influencing the holding capacity of gum arabic in cement during hydration, rheological properties of cement paste with added gum arabic were assessed in this paper. The results show that 0.10wt%-0.60wt% of gum arabic positively affects dispersion, lower dosages have negligible effect. High speed mixing is required to maintain the dispersion stability of gum arabic in cement paste. The optimum dosage of gum arabic to achieve best disperse-holding capacity of cement paste was 0.3wt%, and the minimum water-cement ratio needed to obtain a dispersion effect was 0.28.
基金supported by the Natural Science Foundation of Fujian Province(No.2014J01029)the National Natural Science Foundation of China(No.91122028)
文摘A new four-coordinated manganese compound Mn2(BPTC) (BPTC =- biphenyl- 2,4,4',6-tetracarboxylate) with flu topology net was synthesized under hydrothermal conditions. Single-crystal X-ray diffraction analysis confirms its crystal belongs to the monoclinic system, space group C2/c with a = 12.2092(11), b = 14.6932(9), c = 8.9998(10) A, t= 108.256(12)°, Z= 4, V= 1533.2(2) A3, Dc = 1.889 mg/m3,μ = 1.69, F(O00) = 864, the final R = 0.063 and wR = 0.201 for 1407 observed reflections (I 〉 20(/)). UV-Vis absorption spectrum shows the title compound has a strong absorption at 326 and 238 nm and the optical diffuse reflectance determination shows the band gap of the title compound is 3.15 eV. The theory calculation elucidated that the UV absorptions of the title compound mainly arise from the electron transition from bonding orbitals of BPTC4- ligand to the empty orbitals of BPTC4- and Mn(II) ions.
基金supported by the National Natural Science Foundation of China(Nos.12105080,12105079,and 11975091)the Program for Innovative Research Team(in Science and Technology)in University of Henan Province,China(No.21IRTSTHN011)。
文摘The hindrance in heavy-ion fusion reactions a deep sub-barrier energies is investigated using the double folding model with a hybrid method between the frozen and adiabatic density approximations.In this method,the density distributions of the projectile and the target depend closely on the distance between them.As the distance decreased,the half-density radii of the colliding nucle gradually increased to the half-density radius of the compound nucleus.The total potential based on this non-frozen approximation generates a slightly shallower pocket and becomes more attractive inside the pocket compared to that obtained from the frozen approximation.A damping factor was used to simulate the decline of the coupled channel effects owing to the density rearrangement of the two colliding nuclei.The calculated fusion cross-sections and astrophysical S factors at the deep sub-barrier energies are both in good agreement with the experimental data for the medium-heavyNi+Ni and medium-lightMg+Si mass systems.In addition,it was concluded that the apparent maximum of the S factors most likely appears in fusion systems with strong coupling effects.
基金Supported by National Natural Science Foundation of China
文摘This paper describes the synthesis and free radical ring-opening polymerization of 2-methyl-and 2-methyl-9-n-butyl (-7-methylene-1, 4, 6-trioxaspiro (4, 4) nonane). The structures of the two polymers were verified by IR, 'H and ^(13)C NMR spectra. The substituent on 9-position of 7-methylene-trioxaspiro (4, 4) nonane affects the structure of polymer and polymerization activity. The polymerization mechanism is discussed.
基金National Key Research and Development Program of China(2022YFA1503200,2021YFC2101901)the National Natural Science Foundation of China(22122103,22101130,22001117,21971108,22271144)Fundamental Research Funds for the Central Universities(020514380304,020514380252,020514380272)for financial support.
文摘In this paper,we have developed a decarboxylative amination of carboxylic acids with nitroarenes for the synthesis of secondary amines.The protocol is performed at mild conditions without the use of noble metals as catalysts.A wide range of structurally diverse secondary amines could be obtained in good yields(up to 94%)with good functional group tolerance.This transformation shows good to excellent selectivity,avoiding the generation of over alkylated byproducts.
基金supported by the National Natural Science Foundation of China(Grant nos.92372118,52072224)the Youth Innovation Team Project of Shandong Provincial Education Department(2021KJ093)+3 种基金the Natural Science Foundation of Shandong Province(ZR2020YQ35)the Qilu Young Scholar Funding of Shandong Universitythe Young Elite Scientists Sponsorship Program by CAST(YESS,2019QNRC001)the Natural Science Foundation of Shandong Provincial(ZR2023ZD52)。
文摘Li metal batteries(LMBs)offer signifi-cant potential as high energy density alternatives;nev-ertheless,their performance is hindered by the slow desolvation process of electrolytes,particularly at low temperatures(LT),leading to low coulombic efficiency and limited cycle stability.Thus,it is essential to opti-mize the solvation structure thereby achieving a rapid desolvation process in LMBs at LT.Herein,we introduce branch chain-rich diisopropyl ether(DIPE)into a 2.5 M Li bis(fluorosulfonyl)imide dipropyl ether(DPE)elec-trolyte as a co-solvent for high-performance LMBs at-20°C.The incorporation of DIPE not only enhances the disorder within the electrolyte,but also induces a steric hindrance effect form DIPE’s branch chain,excluding other solvent molecules from Li+solvation sheath.Both of these factors contribute to the weak interactions between Li^(+)and solvent molecules,effectively reducing the desolvation energy of the electrolyte.Consequently,Li(50μm)||LFP(mass loading~10 mg cm^(-2))cells in DPE/DIPE based electrolyte demonstrate stable performance over 650 cycles at-20°C,delivering 87.2 mAh g^(-1),and over 255 cycles at 25°C with 124.8 mAh g^(-1).DIPE broadens the electrolyte design from molecular structure considera-tions,offering a promising avenue for highly stable LMBs at LT.
基金financial support from National Natural Science Foundation of China(21905154)and the Taishan Scholars Program.the Fundamental Research Funds for the Central Universities in China(020514380231021014380177)+3 种基金the National Natural Science Foundation of China(2217304421873048)the National Key R&D Program of China No.2020YFA0406104“Innovation&Entrepreneurship Talents Plan”of Jiangsu Province.
文摘The low-dimensional organic-inorganic halide perovskites with self-trapped exciton emission have promising prospects for single-phase white-light emitters. However, so far, these broadband white-light-emitting(BWLE) perovskites were synthesized by trial-and-error testing spacing molecules. Here, we developed a steric hindrance regulation strategy to predictably synthesize BWLE perovskites. The molecules containing C–C(–NH_(2))–C groups were introduced into low-dimensional perovskites, which brings a large steric hindrance in-plane orientation. The bigger C–C(–NH_(2))–C bond angle would induce larger structural distortion in perovskites, which leads to the higher rate of self-trapping of excitons and the deeper self-trapping depth. The photoluminescence spectra of the synthesized perovskites can cover the cool-to-warm white light region. Overall, we fabricated a material library consisting of 40 kinds of BWLE compounds according to this strategy. Our findings develop a general strategy to synthesize BWLE perovskites and offer a material platform for optoelectronic applications.
基金the National Natural Science Foundation of China(No.52130307)Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(No.2018-K05).
文摘A series of brominated polynorbornene derivatives,including bulky steric hydrophobic groups and highly physical and chemical stable backbones,were synthesized via ring-opening metathesis polymerization and post-functionalized with trimethylammonium(QA),N-methylimidazole(Im),N-methylpyrrolidinium(Pyr)or N-methylpiperidinium(Pip)to construct the entire anion exchange membranes(AEMs).Benefited from prominent phase-separated morphology,PBO-x%-y(x=66,68,70;y=QA,Im,Pyr,Pip)AEMs with ion exchange capacity(IEC)approaching 2.0 meq·g^(−1)exhibited super high hydroxide conductivities.Thereinto,PBO-70%-Pip possessed the highest hydroxide conductivity of 137.3 mS·cm^(−1)at 80℃Moreover,all membranes exhibit low swelling ratio(SR)(the SR of PBO-66%-QA was just 8.6%at 80℃).That is,bulky steric hydrophobic groups play a crucial role in balancing the high hydroxide conductivity and low SR in AEMs.Furthermore,three AEMs(PBO-66%-QA,PBO-68%-Pyr,PBO-70%-Pip)showed good alkaline stability after immersion into 1.0 mol/L NaOH aqueous solution at 80℃for 480 h without any degradation.
基金Project supported by National Natural Science Foundation of China (21601143)Natural Science Foundation of Shaanxi Province (2021JM309)+2 种基金Open Funds of the State Key Laboratory of Rare Earth Resource of Changchun Institute of Applied Chemistry (RERU2021012)Science and Technology Innovation Team Program of Shaanxi Province (2022TD-32) and DST/SERB (CRG/2018/000430,DST/SJF/CSA03/2018-10SB/SJF/2019-20/12)。
文摘The self-assembly reactions between mixed-ligand and tetrahydrate dysprosium acetate in the presence of mixed organic solvents lead to two structural similar dinuclear dysprosium complexes with composition formulas of Dy_(2)(L_1)_(2)(L_(2))_(2)(CH_(3)OH)_(2)·CH_(2)Cl_(2)·CH_(3)OH(1) and Dy_(2)(L_1)_(2)(L_(3))_(2)(CH_(3)OH)_(2)·CH_(3)CN(2),where L_1,L_(2) and L_(3) represent the deprotonated form of 4-tert-butyl-2-(7-methoxybenzo[d]oxazol-2-yl)phenol,(E)-1-(((3,5-di-tert-butyI-2-hydroxyphenyI)imino)methyl)naphthalen-2-ol and(E)-2,4-di-tertbutyl-6-((2-hydroxybenzylidene)amino)phenol.The tiny difference of the core structure of 1 and 2 is derived from the steric hindrance of Schiff base ligands L_(2) and L_(3).Dynamic magnetic measurements reveal that 1 and 2 show frequency-dependent out-of-phase alternating-current susceptibility signal peaks at different temperatures under zero dc field,diagnostic of single-molecule magnet behavior.The experimental derived energy barrier to magnetization reversal for 1 and 2 is 108(1),47(2) and 33(3) K.Ab initio CASSCF calculations performed on 1 and 2 suggest that the origin of the difference in magnetic properties originates from the variation in the single-ion anisotropy that arises due to minor structural variation.Further,the equation to calculate the effective energy barrier for Dy_(2) proposed earlier is found to yield an excellent agreement with the experimental results.Solid state fluorescence measurements performed on 1 and 2 demonstrate that both exhibit two ligands centered components of fluorescent emissive,in addition,with different emitting colors and chromaticity coordinates.The discrepancy of fluorescence and single molecule magnet behavior showed by 1 and 2 can be attributed to the steric hindrance effect of Schiff base ligands.