The face stability problem is a major concern for tunnels excavated in rock masses governed by the Hoek-Brown strength criterion.To provide an accurate prediction for the theoretical solution of the critical face pres...The face stability problem is a major concern for tunnels excavated in rock masses governed by the Hoek-Brown strength criterion.To provide an accurate prediction for the theoretical solution of the critical face pressure,this study adopts the piecewise linear method(PLM)to account for the nonlinearity of the strength envelope and proposes a new multi-horn rotational mechanism based on the Hoek-Brown strength criterion and the associative flow rule.The analytical solution of critical support pressure is derived from the energy-work balance equation in the framework of the plastic limit theorem;it is formulated as a multivariable nonlinear optimization problem relying on 2m dependent variables(m is the number of segments).Meanwhile,two classic linearized measures,the generalized tangential technique(GTT)and equivalent Mohr-Coulomb parameters method(EMM),are incorporated into the analysis for comparison.Surprisingly,the parametric study indicates a significant improvement in support pressure by up to 13%compared with the GTT,and as expected,the stability of the tunnel face is greatly influenced by the rock strength parameters.The stress distribution on the rupture surface is calculated to gain an intuitive understanding of the failure at the limit state.Although the limit analysis is incapable of calculating the true stress distribution in rock masses,a rough approximation of the stress vector on the rupture surface is permitted.In the end,sets of normalized face pressure are provided in the form of charts for a quick assessment of face stability in rock masses.展开更多
Epilepsy is believed to be associated with the abnormal synchronous neuronal activity in the brain,which results from large groups or circuits of neurons.In this paper,we choose to focus on the temporal lobe epilepsy,...Epilepsy is believed to be associated with the abnormal synchronous neuronal activity in the brain,which results from large groups or circuits of neurons.In this paper,we choose to focus on the temporal lobe epilepsy,and establish a cortex network of multiple coupled neural populations to explore the epileptic activities under electromagnetic induction.We demonstrate that the epileptic activities can be controlled and modulated by electromagnetic induction and coupling among regions.In certain regions,these two types of control are observed to show exactly reverse effects.The results show that the strong electromagnetic induction is conducive to eliminating the epileptic seizures.The coupling among regions has a conduction effect that the previous normal background activity of the region gives way to the epileptic discharge,owing to coupling with spike wave discharge regions.Overall,these results highlight the role of electromagnetic induction and coupling among the regions in controlling and modulating epileptic activities,and might provide novel insights into the treatments of epilepsy.展开更多
目的:探讨血清胆固醇水平及其动态变化与卒中后认知障碍(PSCI)之间的关系。方法:招募首次急性缺血性脑卒中患者。在卒中发病3~6个月后使用蒙特利尔认知量表(MoCA)评估患者的认知功能,分为PSCI组和无PSCI组,比较两组血清胆固醇基线和3~6...目的:探讨血清胆固醇水平及其动态变化与卒中后认知障碍(PSCI)之间的关系。方法:招募首次急性缺血性脑卒中患者。在卒中发病3~6个月后使用蒙特利尔认知量表(MoCA)评估患者的认知功能,分为PSCI组和无PSCI组,比较两组血清胆固醇基线和3~6个月随访时水平及其变化值。采用了Pearson相关分析和logistic回归分析探索血清胆固醇水平与PSCI的关系。结果:本研究纳入107例患者,其中PSCI组46例,无PSCI组61例。PSCI患者随访时血清总胆固醇(TC)和低密度脂蛋白胆固醇(LDL-C)水平明显高于无PSCI组患者(3.74±1.04 vs 3.38±0.76,P=0.042;2.20±0.96 vs 1.87±0.67,P=0.039),且指标下降幅度小,但是无统计学意义(P>0.05)。PSCI组患者随访时血清TC水平(r=-0.332,P=0.024)及其变化值(r=-0.334,P=0.023)、LDL-C水平(r=-0.316,P=0.032)及其变化值(r=-0.332,P=0.024)均与延迟回忆呈负相关。单因素回归分析中显示卒中后3~6个月时的LDL-C水平(OR:1.687,95%CI:1.004-2.835,P=0.048)和TC水平(OR:1.609,95%CI:0.997-2.598,P=0.052)与PSCI有关,调整混杂因素后无统计学差异(P>0.05)。结论:在卒中发病3~6个月时,患者血清LDL-C及TC水平与PSCI之间存在着相关性,且与延迟回忆呈负相关,而血清胆固醇变化值与PSCI无相关性。展开更多
With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in o...With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in order to satisfy the requirement of different applications,various advanced 5 G technologies have been developed in full swing.However,before applying these 5 G related technologies in practical systems,effective testing methods are needed to evaluate these technologies in a real,comprehensive,rapid and flexible manner.However,the testing methods are faced with new challenges along with the continuous development of the new 5 G technologies.In this paper,we present a survey of 5 G testing,including solutions and opportunities.In particular,two cases are considered,i.e.,channel modelling and overthe-air(OTA) testing of antenna systems.Specifically,a non-stationary channel model is proposed to characterize and test massive multiple-input multiple-output(MIMO) channel.In addition,we propose two probe subset selection algorithms for three-dimensional(3 D) OTA testing,which minimizes the number of probe antennas while ensuring the accuracy of the target channel emulation.Finally,future research directions and challenges on 5 G testing are given.展开更多
Reverse water gas shift(RWGS) reaction can be served as a pivotal stage of transitioning the abundant CO_2 resource into chemicals or hydrocarbon fuels, which is attractive for the CO_2 utilization and of eventually s...Reverse water gas shift(RWGS) reaction can be served as a pivotal stage of transitioning the abundant CO_2 resource into chemicals or hydrocarbon fuels, which is attractive for the CO_2 utilization and of eventually significance in enabling a rebuilt ecological system for unconventional fuels. This concept is appealing when the process is considered as a solution for the storage of renewable energy, which may also find a variety of potential end uses for the outer space exploration. However, a big challenge to this issue is the rational design of high temperature endurable RWGS catalysts with desirable CO product selectivity. In this work, we present a comprehensive overview of recent publications on this research topic,mainly focusing on the catalytic performance of RWGS reaction over three major kinds of heterogeneous catalysts, including supported metal catalysts, mixed oxide catalysts and transition metal carbides. The reaction thermodynamic analysis, kinetics and mechanisms are also described in detail. The present review attempts to provide a general guideline about the construction of well-performed heterogeneous catalysts for the RWGS reaction, as well as discussing the challenges and further prospects of this process.展开更多
A reduction in gray matter volume is common in patients with chronic back pain,and different types of pain are associated with gray matter abnormalities in distinct brain regions.To examine differences in brain morpho...A reduction in gray matter volume is common in patients with chronic back pain,and different types of pain are associated with gray matter abnormalities in distinct brain regions.To examine differences in brain morphology in patients with low back pain or neck and upper back pain,we investigated changes in gray matter volume in chronic back pain patients having different sites of pain using voxel-based morphometry.A reduction in cortical gray matter volume was found primarily in the left postcentral gyrus and in the left precuneus and bilateral cuneal cortex of patients with low back pain.In these patients,there was an increase in subcortical gray matter volume in the bilateral putamen and accumbens,right pallidum,right caudate nucleus,and left amygdala.In upper back pain patients,reduced cortical gray matter volume was found in the left precentral and left postcentral cortices.Our findings suggest that regional gray matter volume abnormalities in low back pain patients are more extensive than in upper back pain patients.Subcortical gray matter volume increases are found only in patients with low back pain.展开更多
The oxide-zeolite process provides a promising way for one-step production of aromatics from syngas,whereas the reasons for the dramatic effect of intimacy between oxide and zeolite in the composite catalyst on the pr...The oxide-zeolite process provides a promising way for one-step production of aromatics from syngas,whereas the reasons for the dramatic effect of intimacy between oxide and zeolite in the composite catalyst on the product selectivity are still unclear. In order to explore the optimal intimacy and the essential influence factors, ZnCrOxcombined with ZSM-5 are employed to prepare the composite catalysts with different distances between the two components by changing the mixing methods. An aromatic selectivity of 74%(with CO conversion to be 16%) is achieved by the composite catalyst when the intimacy is in the range of nanometer. A so-called ‘iterative reactions’ mechanism of intermediates over oxides is then proposed and studied: the intermediate chemical can undergo a hydrogenation reaction on oxide.So the shorter the intermediates stay on oxide, the more of chance for C-C coupling takes place on zeolite to form aromatics. Moreover, the aero-environments of reaction is found to impact on the extent of iterative reaction as well. Therefore, when the intimacy between the two components changes, the extent of iterative reactions vary, resulting in alteration of product distribution. This work provides new insight in understanding the mechanisms during the complex process of OX-ZEO composite catalysis and sheds light to the design of a high-yield catalyst for synthetization of aromatics from syngas.展开更多
In recent years, the streamflow of the Laohahe Basin in China showed a dramatic decrease during the rainy season as a result of climate change and/or human activities. The objective of this work was to document signif...In recent years, the streamflow of the Laohahe Basin in China showed a dramatic decrease during the rainy season as a result of climate change and/or human activities. The objective of this work was to document significant streamflow changes caused by land use and land cover(LULC) changes and to quantify the impacts of the observed changes in Laohahe Basin. In the study area, the observed streamflow has been influenced by LULC changes, dams, and irrigation from rivers, industry, livestock and human consumption. Most importantly, the growth of population and gross domestic product(GDP) accompanied by the growth in industrial and agricultural activities, which led to LULC changes with increased residential land and cropland and decreased grassland since 2000s. Statistical methods and Variable Infiltration Capacity(VIC) hydrological model were used to estimate the effects of climate change and LULC changes on streamflow and evaportranspiration(ET). First, the streamflow data of the study area were divided into three sub-periods according to the Pettitt test. The hydrological process was then simulated by VIC model from 1964 to 2009. Furthermore, we compared the simulated results based on land use scenarios in 1989, 1999 and 2007, respectively for exploring the effect of LULC changes on the spatio-temporal distribution of streamflow and ET in the Laohahe Basin. The results suggest that, accompanied with climate change, the LULC changes and human water consumption appeared to be the most likely factors contributing to the significant reduction in streamflow in the Laohahe Basin by 64% from1999 to 2009.展开更多
Reverse water gas shift(RWGS) reaction can serve as a pivotal stage in the CO_2 conversion processes,which is vital for the utilization of CO_2.In this study,RWGS reaction was performed over Pt/CeO_2 catalysts at the ...Reverse water gas shift(RWGS) reaction can serve as a pivotal stage in the CO_2 conversion processes,which is vital for the utilization of CO_2.In this study,RWGS reaction was performed over Pt/CeO_2 catalysts at the temperature range of 200-500℃ under ambient pressure.Compared with pure CeO_2,Pt/CeO_2catalysts exhibited superior RWGS activity at lower reaction temperature.Meanwhile,the calculated TOF and E_a values are approximately the same over these Pt/CeO_2 catalysts pretreated under various calcination conditions,indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO_2.TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO_2 support and remarkably increased the content of Ce^(3+) sites on the catalyst surface.Furthermore,the CO TPSR-MS signal under the condition of pure CO_2 flow over Pt/CeO_2catalyst is far lower than that under the condition of adsorbed CO_2 with H_2-assisted flow,revealing that CO_2 molecules adsorbed on Ce^(3+) active sites have difficult in generating CO directly.Meanwhile,the adsorbed CO_2 with the assistance of H_2 can form formate species easily over Ce^(3+) active sites and then decompose into Ce^(3+)-CO species for CO production,which was identified by in-situ FTIR.展开更多
The emergence of multidrug-resistant bacteria creates an urgent need for alternative antibiotics with new mechanisms of action. In this study, we synthesized a novel type of antimicrobial agent, Ac r_3-NLS, by conjuga...The emergence of multidrug-resistant bacteria creates an urgent need for alternative antibiotics with new mechanisms of action. In this study, we synthesized a novel type of antimicrobial agent, Ac r_3-NLS, by conjugating hydrophobic acridines to the N-terminus of a nuclear localization sequence(NLS), a short cationic peptide. To further improve the antimicrobial activity of our agent, dimeric(Acr_3-NLS)_2 was simultaneously synthesized by joining two monomeric Acr_3-NLS together via a disulfide linker. Our results show that Acr_3-NLS and especially(Acr_3-NLS)_2 display signifi cant antimicrobial activity against gramnegative and gram-positive bacteria compared to that of the NLS. Subsequently, the results derived from the study on the mechanism of action demonstrate that Acr_3-NLS and(Acr_3-NLS)_2 can kill bacteria by membrane disruption and DNA binding. The double targets—cell membrane and intracellular DNA—will reduce the risk of bacteria developing resistance to Acr_3-NLS and(Acr_3-NLS)_2. Overall, this study provides a novel strategy to design highly eff ective antimicrobial agents with a dual mode of action for infection treatment.展开更多
Objective This study was designed to determine the methylation profile of four CpGs and the genotypes of two CpG-SNPs located in promoter region of DIO2 in patients with Kashin-Beck disease(KBD).We also analyzed the i...Objective This study was designed to determine the methylation profile of four CpGs and the genotypes of two CpG-SNPs located in promoter region of DIO2 in patients with Kashin-Beck disease(KBD).We also analyzed the interaction between the CpGs methylations and CpG-SNPs.Methods Whole blood specimens were collected from 16 KBD patients and 16 healthy subjects.Four CpGs and two CpG-SNPs in the promoter regions of DIO2 were detected using matrix-assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS).The CpGs methylation levels were compared between samples from KBD patients and healthy subjects.The methylation levels were also analyzed in KBD patients with different CpG-SNP genotypes.Results The mRNA expression of DIO2 in whole blood of KBD patients was significnatly lower than in healthy controls(P<0.05).The methylation levels of DIO2-1_CpG_3 in KBD patients were significantly higher than those in healthy controls(P<0.05).The methylation levels of four CpGs were not significantly different between KBD patients and healthy controls.The methylation level of DIO2-1_CpG_3 in the promoter region of DIO2 in KBD patients with GA/AA genotype was significantly higher than that of KBD patients with GG genotype(P<0.05).Conclusion The methylation level of DIO2 increases in KBD patients.Similar trends exist in KBD carriers of variant genotypes of CpG-SNPs DIO2 rs955849187.展开更多
The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biocha...The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biochar sam-ples were synthesized form kenaf to adsorb methylene blue(MB),which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aroma tic heterocyclic ring.By tuning the raw materials and pyrolysis temperature,a super adsorption capacity about 164.21 mg·g^(-1) was obtained over the biochar that pyrolyzed at 700℃ with the kenaf fiber as raw material Through the physical adsorption,elemental analysis,FTIR spectra and NH_(3)-TPD,it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB,and the acidic sites would also assist the adsorption process.Besides,the adsorption kinetic model was ftted and calculated,implying the MB physically adsorbed on the bio-char rapidly and then occurred chemical adsorption on the acidic sites.In addition,through KBC700 recycling experiments,it was found that kenaf biochar had a good binding force to MB,which effectively avoided secondary pollution.This work provides important insights for the adsorption mechanism of MB by biochar,also offers some guidance for the further synthesis of biochar from various biomass.展开更多
Amorphous materials are one of the important candidates for improving heterogeneous photocata-lysts because of their unique electronic structures and abundant catalytic sites originating from dis-order atomic arrangem...Amorphous materials are one of the important candidates for improving heterogeneous photocata-lysts because of their unique electronic structures and abundant catalytic sites originating from dis-order atomic arrangements.However,there is still much room for the development of new crys-talline/amorphous heterogeneous composites for photocatalytic application.Hence efficient synthetic strategies for preparing new crystalline/amorphous heterojunctions are highly desired.Herein,we have realized the deep optimization of photocatalytic activity by fabricating crystalline/amorphous Cu_(2)O/Ti-Fe layer double hydroxide(LDH)heterojunctions.Thanks to the typical Z-scheme mechanism originating from the crystalline/amorphous interfaces,the photocharge separation and catalytic active sites obviously enhance compared to single Cu_(2)O and LDH counterparts.As expected,the photocatalytic removal of tetra-cycline(TC)of the as-prepared Cu_(2)O/Ti-Fe LDH was over 5.2 and 2.2 times those of the pristine Cu_(2)O nanospheres and Ti-Fe LDH nanosheets.This work illustrates the origin of crystalline Cu_(2)O nanospheres encapsulated in amorphous Ti-Fe layer double hydroxide nanosheets for enhanced photocatalytic activity driven by visible light,and provide a general Cu_(2)O-templated solution-phase synthetic method for the synthesis of novel double-metal layer double hydroxide amorphous nanostructures.展开更多
Ruthenium(Ru)has been regarded as one of the most promising alternatives to substitute Pt for catalyzing alkaline hydrogen evolution reaction(HER),owing to its inherent high activity and being the cheapest platinum-gr...Ruthenium(Ru)has been regarded as one of the most promising alternatives to substitute Pt for catalyzing alkaline hydrogen evolution reaction(HER),owing to its inherent high activity and being the cheapest platinum-group metal.Herein,based on the idea of strong metal–support interaction(SMSI)regulation,Ru/TiN catalysts with different degrees of TiN overlayer over Ru nanoparticles were fabricated,which were applied to the alkaline electrolytic water.Characterizations reveal that the TiN overlayer would gradually encapsulate the Ru nanoparticles and induce more electron transfer from Ru nanoparticles to TiN support by the Ru–N–Ti bond as the SMSI degree increased.Further study shows that the exposed Ru–TiN interfaces greatly promote the H_(2) desorption capacity.Thus,the Ru/TiN-300 with a moderate SMSI degree exhibits excellent HER performance,with an overpotential of 38 mV at 10 mA cm^(−2).Also,due to the encapsulation role of TiN overlayer on Ru nanoparticles,it displays super long-term stability with a very slight potential change after 24 h.This study provides a deep insight into the influence of the SMSI effect between Ru and TiN on HER and offers a novel approach for preparing efficient and stable HER electrocatalysts through SMSI engineering.展开更多
Transition-metal oxyhydroxides are attractive catalysts for oxygen evolution reactions(OERs).Further studies for developing transition-metal oxyhydroxide catalysts and understanding their catalytic mechanisms will ben...Transition-metal oxyhydroxides are attractive catalysts for oxygen evolution reactions(OERs).Further studies for developing transition-metal oxyhydroxide catalysts and understanding their catalytic mechanisms will benefit their quick transition to the next catalysts.Herein,Mo-doped CoOOH was designed as a high-performance model electrocatalyst with durability for 20 h at 10 mAcm−2.Additionally,it had an overpotential of 260 mV(glassy carbon)or 215 mV(nickel foam),which was 78 mV lower than that of IrO_(2)(338 mV).In situ,Raman spectroscopy revealed the transformation process of CoOOH.Calculations using the density functional theory showed that during OER,doped Mo increased the spin-up density of states and shrank the spin-down bandgap of the 3d orbits in the reconstructed CoOOH under the electrochemical activation process,which simultaneously optimized the adsorption and electron conduction of oxygen-related intermediates on Co sites and lowered the OER overpotentials.Our research provides new insights into the methodical planning of the creation of transition-metal oxyhydroxide OER catalysts.展开更多
A ZnO–SnO_2 nanowires(NWs) array, as a metal oxide semiconductor, was successfully synthesized by a near-field electrospinning method for the applications as high performance ultraviolet photodetectors. Ultraviolet p...A ZnO–SnO_2 nanowires(NWs) array, as a metal oxide semiconductor, was successfully synthesized by a near-field electrospinning method for the applications as high performance ultraviolet photodetectors. Ultraviolet photodetectors based on a single nanowire exhibited excellent photoresponse properties to 300 nm ultraviolet light illumination including ultrahigh I_(on)/I_(off) ratios(up to 10~3), good stability and reproducibility because of the separation between photo-generated electron-hole pairs. Moreover, the NWs array shows an enhanced photosensing performance. Flexible photodetectors on the PI substrates with similar tendency properties were also fabricated. In addition, under various bending curvatures and cycles, the as-fabricated flexible photodetectors revealed mechanical flexibility and good stable electrical properties, showing that they have the potential for applications in future flexible photoelectron devices.展开更多
基金supported by Fundamental Research Funds for the central universities of Central South University(No.2022ZZTS0153).
文摘The face stability problem is a major concern for tunnels excavated in rock masses governed by the Hoek-Brown strength criterion.To provide an accurate prediction for the theoretical solution of the critical face pressure,this study adopts the piecewise linear method(PLM)to account for the nonlinearity of the strength envelope and proposes a new multi-horn rotational mechanism based on the Hoek-Brown strength criterion and the associative flow rule.The analytical solution of critical support pressure is derived from the energy-work balance equation in the framework of the plastic limit theorem;it is formulated as a multivariable nonlinear optimization problem relying on 2m dependent variables(m is the number of segments).Meanwhile,two classic linearized measures,the generalized tangential technique(GTT)and equivalent Mohr-Coulomb parameters method(EMM),are incorporated into the analysis for comparison.Surprisingly,the parametric study indicates a significant improvement in support pressure by up to 13%compared with the GTT,and as expected,the stability of the tunnel face is greatly influenced by the rock strength parameters.The stress distribution on the rupture surface is calculated to gain an intuitive understanding of the failure at the limit state.Although the limit analysis is incapable of calculating the true stress distribution in rock masses,a rough approximation of the stress vector on the rupture surface is permitted.In the end,sets of normalized face pressure are provided in the form of charts for a quick assessment of face stability in rock masses.
基金Project supported by the National Natural Science Foundation of China(Nos.11772254 and 11972288)the Innovation Foundation for Doctor Dissertation of Northwestern Polytechnical University of China(No.CX2021106)。
文摘Epilepsy is believed to be associated with the abnormal synchronous neuronal activity in the brain,which results from large groups or circuits of neurons.In this paper,we choose to focus on the temporal lobe epilepsy,and establish a cortex network of multiple coupled neural populations to explore the epileptic activities under electromagnetic induction.We demonstrate that the epileptic activities can be controlled and modulated by electromagnetic induction and coupling among regions.In certain regions,these two types of control are observed to show exactly reverse effects.The results show that the strong electromagnetic induction is conducive to eliminating the epileptic seizures.The coupling among regions has a conduction effect that the previous normal background activity of the region gives way to the epileptic discharge,owing to coupling with spike wave discharge regions.Overall,these results highlight the role of electromagnetic induction and coupling among the regions in controlling and modulating epileptic activities,and might provide novel insights into the treatments of epilepsy.
基金the National Key R&D Program of China(2016YFA0202804)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020400)+2 种基金the Youth Innovation Promotion Association CAS for financial supportthe National Natural Science Foundation of China(21506204,21476226)Dalian Science Foundation for Distinguished Young Scholars(2016RJ04)~~
文摘目的:探讨血清胆固醇水平及其动态变化与卒中后认知障碍(PSCI)之间的关系。方法:招募首次急性缺血性脑卒中患者。在卒中发病3~6个月后使用蒙特利尔认知量表(MoCA)评估患者的认知功能,分为PSCI组和无PSCI组,比较两组血清胆固醇基线和3~6个月随访时水平及其变化值。采用了Pearson相关分析和logistic回归分析探索血清胆固醇水平与PSCI的关系。结果:本研究纳入107例患者,其中PSCI组46例,无PSCI组61例。PSCI患者随访时血清总胆固醇(TC)和低密度脂蛋白胆固醇(LDL-C)水平明显高于无PSCI组患者(3.74±1.04 vs 3.38±0.76,P=0.042;2.20±0.96 vs 1.87±0.67,P=0.039),且指标下降幅度小,但是无统计学意义(P>0.05)。PSCI组患者随访时血清TC水平(r=-0.332,P=0.024)及其变化值(r=-0.334,P=0.023)、LDL-C水平(r=-0.316,P=0.032)及其变化值(r=-0.332,P=0.024)均与延迟回忆呈负相关。单因素回归分析中显示卒中后3~6个月时的LDL-C水平(OR:1.687,95%CI:1.004-2.835,P=0.048)和TC水平(OR:1.609,95%CI:0.997-2.598,P=0.052)与PSCI有关,调整混杂因素后无统计学差异(P>0.05)。结论:在卒中发病3~6个月时,患者血清LDL-C及TC水平与PSCI之间存在着相关性,且与延迟回忆呈负相关,而血清胆固醇变化值与PSCI无相关性。
基金supported by the National Natural Science of Foundation for Creative Research Groups of China(No.61421061)
文摘With the development of wireless communication technology,the fifth generation mobile communications system(5 G) emerges at a historic moment and devotes itself to open the curtain of the information age.Recently,in order to satisfy the requirement of different applications,various advanced 5 G technologies have been developed in full swing.However,before applying these 5 G related technologies in practical systems,effective testing methods are needed to evaluate these technologies in a real,comprehensive,rapid and flexible manner.However,the testing methods are faced with new challenges along with the continuous development of the new 5 G technologies.In this paper,we present a survey of 5 G testing,including solutions and opportunities.In particular,two cases are considered,i.e.,channel modelling and overthe-air(OTA) testing of antenna systems.Specifically,a non-stationary channel model is proposed to characterize and test massive multiple-input multiple-output(MIMO) channel.In addition,we propose two probe subset selection algorithms for three-dimensional(3 D) OTA testing,which minimizes the number of probe antennas while ensuring the accuracy of the target channel emulation.Finally,future research directions and challenges on 5 G testing are given.
基金supported by the National Natural Science Foundation of China(Nos.21506204 and 21476226)China Ministry of Science and Technology under contact of 2016YFB0600902+3 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020400)State Grid Cooperation of China(SGRI-DL-71-16-015)Dalian Science Foundation for Distinguished Young Scholars(2016RJ04)the Youth Innovation Promotion Association of CAS
文摘Reverse water gas shift(RWGS) reaction can be served as a pivotal stage of transitioning the abundant CO_2 resource into chemicals or hydrocarbon fuels, which is attractive for the CO_2 utilization and of eventually significance in enabling a rebuilt ecological system for unconventional fuels. This concept is appealing when the process is considered as a solution for the storage of renewable energy, which may also find a variety of potential end uses for the outer space exploration. However, a big challenge to this issue is the rational design of high temperature endurable RWGS catalysts with desirable CO product selectivity. In this work, we present a comprehensive overview of recent publications on this research topic,mainly focusing on the catalytic performance of RWGS reaction over three major kinds of heterogeneous catalysts, including supported metal catalysts, mixed oxide catalysts and transition metal carbides. The reaction thermodynamic analysis, kinetics and mechanisms are also described in detail. The present review attempts to provide a general guideline about the construction of well-performed heterogeneous catalysts for the RWGS reaction, as well as discussing the challenges and further prospects of this process.
基金supported partially by two grants from the National Natural Science Foundation of China,No.30870686 and 81371530
文摘A reduction in gray matter volume is common in patients with chronic back pain,and different types of pain are associated with gray matter abnormalities in distinct brain regions.To examine differences in brain morphology in patients with low back pain or neck and upper back pain,we investigated changes in gray matter volume in chronic back pain patients having different sites of pain using voxel-based morphometry.A reduction in cortical gray matter volume was found primarily in the left postcentral gyrus and in the left precuneus and bilateral cuneal cortex of patients with low back pain.In these patients,there was an increase in subcortical gray matter volume in the bilateral putamen and accumbens,right pallidum,right caudate nucleus,and left amygdala.In upper back pain patients,reduced cortical gray matter volume was found in the left precentral and left postcentral cortices.Our findings suggest that regional gray matter volume abnormalities in low back pain patients are more extensive than in upper back pain patients.Subcortical gray matter volume increases are found only in patients with low back pain.
基金the National Key R&D Program of China(2016YFA0202804)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB17020400)+2 种基金the National Natural Science Foundation of China(Nos.21506204,21476226)Dalian Science Foundation for Distinguished Young Scholars(2016RJ04)the Youth Innovation Promotion Association CAS for financial support
文摘The oxide-zeolite process provides a promising way for one-step production of aromatics from syngas,whereas the reasons for the dramatic effect of intimacy between oxide and zeolite in the composite catalyst on the product selectivity are still unclear. In order to explore the optimal intimacy and the essential influence factors, ZnCrOxcombined with ZSM-5 are employed to prepare the composite catalysts with different distances between the two components by changing the mixing methods. An aromatic selectivity of 74%(with CO conversion to be 16%) is achieved by the composite catalyst when the intimacy is in the range of nanometer. A so-called ‘iterative reactions’ mechanism of intermediates over oxides is then proposed and studied: the intermediate chemical can undergo a hydrogenation reaction on oxide.So the shorter the intermediates stay on oxide, the more of chance for C-C coupling takes place on zeolite to form aromatics. Moreover, the aero-environments of reaction is found to impact on the extent of iterative reaction as well. Therefore, when the intimacy between the two components changes, the extent of iterative reactions vary, resulting in alteration of product distribution. This work provides new insight in understanding the mechanisms during the complex process of OX-ZEO composite catalysis and sheds light to the design of a high-yield catalyst for synthetization of aromatics from syngas.
基金financed by the National Natural Science Foundation of China (41201031)the Special Basic Research Fund for Methodology in Hydrology of Ministry of Sciences and Technology, China (2011IM011000)+2 种基金the Innovative Research Team Project of Basic Research Funds for National University at State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering (2009585412)the 111 Project of Ministry of Education and State Administration of Foreign Experts Affairs, China (B08048)the National Key Technology R&D Program by Ministry of Sciences and Technology, China (2013BAC10B02)
文摘In recent years, the streamflow of the Laohahe Basin in China showed a dramatic decrease during the rainy season as a result of climate change and/or human activities. The objective of this work was to document significant streamflow changes caused by land use and land cover(LULC) changes and to quantify the impacts of the observed changes in Laohahe Basin. In the study area, the observed streamflow has been influenced by LULC changes, dams, and irrigation from rivers, industry, livestock and human consumption. Most importantly, the growth of population and gross domestic product(GDP) accompanied by the growth in industrial and agricultural activities, which led to LULC changes with increased residential land and cropland and decreased grassland since 2000s. Statistical methods and Variable Infiltration Capacity(VIC) hydrological model were used to estimate the effects of climate change and LULC changes on streamflow and evaportranspiration(ET). First, the streamflow data of the study area were divided into three sub-periods according to the Pettitt test. The hydrological process was then simulated by VIC model from 1964 to 2009. Furthermore, we compared the simulated results based on land use scenarios in 1989, 1999 and 2007, respectively for exploring the effect of LULC changes on the spatio-temporal distribution of streamflow and ET in the Laohahe Basin. The results suggest that, accompanied with climate change, the LULC changes and human water consumption appeared to be the most likely factors contributing to the significant reduction in streamflow in the Laohahe Basin by 64% from1999 to 2009.
基金National Natural Science Foundation of China (nos.21476226 and 21506204)National Key Projects for Fundamental Research and Development of China (2016YFB0600902)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17020400)the Youth Innovation Promotion Association CAS for financial support
文摘Reverse water gas shift(RWGS) reaction can serve as a pivotal stage in the CO_2 conversion processes,which is vital for the utilization of CO_2.In this study,RWGS reaction was performed over Pt/CeO_2 catalysts at the temperature range of 200-500℃ under ambient pressure.Compared with pure CeO_2,Pt/CeO_2catalysts exhibited superior RWGS activity at lower reaction temperature.Meanwhile,the calculated TOF and E_a values are approximately the same over these Pt/CeO_2 catalysts pretreated under various calcination conditions,indicating that the RWGS reaction is not affected by the morphologies of anchored Pt nanoparticles or the primary crystallinity of CeO_2.TPR and XPS results indicated that the incorporation of Pt promoted the reducibility of CeO_2 support and remarkably increased the content of Ce^(3+) sites on the catalyst surface.Furthermore,the CO TPSR-MS signal under the condition of pure CO_2 flow over Pt/CeO_2catalyst is far lower than that under the condition of adsorbed CO_2 with H_2-assisted flow,revealing that CO_2 molecules adsorbed on Ce^(3+) active sites have difficult in generating CO directly.Meanwhile,the adsorbed CO_2 with the assistance of H_2 can form formate species easily over Ce^(3+) active sites and then decompose into Ce^(3+)-CO species for CO production,which was identified by in-situ FTIR.
基金the grants from the National Natural Science Foundation of China (81402776 and 81202400)the Key National S&T Progra m "Major New Drug Development" of the Ministry of Science and Technology of China (2012ZX09504001-003)+2 种基金the Fundamental Research Funds for the Central Universities (lzujbky-2014-142 and lzujbky-2015-169)the Specialized Research Fund for the Doctoral Program of Higher Education of China (20130211130005)China Postdoctoral Science Foundation (2013T60896)
文摘The emergence of multidrug-resistant bacteria creates an urgent need for alternative antibiotics with new mechanisms of action. In this study, we synthesized a novel type of antimicrobial agent, Ac r_3-NLS, by conjugating hydrophobic acridines to the N-terminus of a nuclear localization sequence(NLS), a short cationic peptide. To further improve the antimicrobial activity of our agent, dimeric(Acr_3-NLS)_2 was simultaneously synthesized by joining two monomeric Acr_3-NLS together via a disulfide linker. Our results show that Acr_3-NLS and especially(Acr_3-NLS)_2 display signifi cant antimicrobial activity against gramnegative and gram-positive bacteria compared to that of the NLS. Subsequently, the results derived from the study on the mechanism of action demonstrate that Acr_3-NLS and(Acr_3-NLS)_2 can kill bacteria by membrane disruption and DNA binding. The double targets—cell membrane and intracellular DNA—will reduce the risk of bacteria developing resistance to Acr_3-NLS and(Acr_3-NLS)_2. Overall, this study provides a novel strategy to design highly eff ective antimicrobial agents with a dual mode of action for infection treatment.
基金supported by the National Natural Science Foundation of China(82073494)Key Re-search and Development Program of Shaanxi Prov-ince(2020SF-076)+1 种基金Special R&D Program Proj-ect of Chinese Academy of Se-enriched Industry(2020FXZX0501)the Subject Innovation Team of Shaanxi University of Chinese Medicine(132041933).
文摘Objective This study was designed to determine the methylation profile of four CpGs and the genotypes of two CpG-SNPs located in promoter region of DIO2 in patients with Kashin-Beck disease(KBD).We also analyzed the interaction between the CpGs methylations and CpG-SNPs.Methods Whole blood specimens were collected from 16 KBD patients and 16 healthy subjects.Four CpGs and two CpG-SNPs in the promoter regions of DIO2 were detected using matrix-assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF-MS).The CpGs methylation levels were compared between samples from KBD patients and healthy subjects.The methylation levels were also analyzed in KBD patients with different CpG-SNP genotypes.Results The mRNA expression of DIO2 in whole blood of KBD patients was significnatly lower than in healthy controls(P<0.05).The methylation levels of DIO2-1_CpG_3 in KBD patients were significantly higher than those in healthy controls(P<0.05).The methylation levels of four CpGs were not significantly different between KBD patients and healthy controls.The methylation level of DIO2-1_CpG_3 in the promoter region of DIO2 in KBD patients with GA/AA genotype was significantly higher than that of KBD patients with GG genotype(P<0.05).Conclusion The methylation level of DIO2 increases in KBD patients.Similar trends exist in KBD carriers of variant genotypes of CpG-SNPs DIO2 rs955849187.
基金This work was supported by National Natural Science Foundation of China(51903131)Natural Science Foundation of Shandong Province(ZR2019QEM007)+2 种基金Key Research and Development Program of Shandong Province(2020CXGC011101)State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(ZKT16 and ZKT21)Special Foundation of“Taishan Scholar”Construction Program(ts20190932).
文摘The toxic dyestuff's from printing and dyeing wastewater have caused serious damages to the ecological environ-ment,thus exploring effective methods to remove them having become a key topic.Here,a series of biochar sam-ples were synthesized form kenaf to adsorb methylene blue(MB),which was acted as the dye representative for the test of adsorption capacity due to the presence of abundant double bond and aroma tic heterocyclic ring.By tuning the raw materials and pyrolysis temperature,a super adsorption capacity about 164.21 mg·g^(-1) was obtained over the biochar that pyrolyzed at 700℃ with the kenaf fiber as raw material Through the physical adsorption,elemental analysis,FTIR spectra and NH_(3)-TPD,it was found the high surface area and pore volume of biochar played a key role in the adsorption of MB,and the acidic sites would also assist the adsorption process.Besides,the adsorption kinetic model was ftted and calculated,implying the MB physically adsorbed on the bio-char rapidly and then occurred chemical adsorption on the acidic sites.In addition,through KBC700 recycling experiments,it was found that kenaf biochar had a good binding force to MB,which effectively avoided secondary pollution.This work provides important insights for the adsorption mechanism of MB by biochar,also offers some guidance for the further synthesis of biochar from various biomass.
文摘Amorphous materials are one of the important candidates for improving heterogeneous photocata-lysts because of their unique electronic structures and abundant catalytic sites originating from dis-order atomic arrangements.However,there is still much room for the development of new crys-talline/amorphous heterogeneous composites for photocatalytic application.Hence efficient synthetic strategies for preparing new crystalline/amorphous heterojunctions are highly desired.Herein,we have realized the deep optimization of photocatalytic activity by fabricating crystalline/amorphous Cu_(2)O/Ti-Fe layer double hydroxide(LDH)heterojunctions.Thanks to the typical Z-scheme mechanism originating from the crystalline/amorphous interfaces,the photocharge separation and catalytic active sites obviously enhance compared to single Cu_(2)O and LDH counterparts.As expected,the photocatalytic removal of tetra-cycline(TC)of the as-prepared Cu_(2)O/Ti-Fe LDH was over 5.2 and 2.2 times those of the pristine Cu_(2)O nanospheres and Ti-Fe LDH nanosheets.This work illustrates the origin of crystalline Cu_(2)O nanospheres encapsulated in amorphous Ti-Fe layer double hydroxide nanosheets for enhanced photocatalytic activity driven by visible light,and provide a general Cu_(2)O-templated solution-phase synthetic method for the synthesis of novel double-metal layer double hydroxide amorphous nanostructures.
基金supported by the National Natural Science Foundation of China(Grant Nos.22075159,22002066)Shandong Taishan Scholars Project(Grant Nos.ts20190932,tsqn202103058)+1 种基金Open Fund of Hubei Key Laboratory of Processing and Application of Catalytic Materials(Grant No.202203404)Postdoctoral Applied Research Project in Qingdao,and the Youth Innovation Team Project of Shandong Provincial Education Department(Grant No.2019KJC023).
文摘Ruthenium(Ru)has been regarded as one of the most promising alternatives to substitute Pt for catalyzing alkaline hydrogen evolution reaction(HER),owing to its inherent high activity and being the cheapest platinum-group metal.Herein,based on the idea of strong metal–support interaction(SMSI)regulation,Ru/TiN catalysts with different degrees of TiN overlayer over Ru nanoparticles were fabricated,which were applied to the alkaline electrolytic water.Characterizations reveal that the TiN overlayer would gradually encapsulate the Ru nanoparticles and induce more electron transfer from Ru nanoparticles to TiN support by the Ru–N–Ti bond as the SMSI degree increased.Further study shows that the exposed Ru–TiN interfaces greatly promote the H_(2) desorption capacity.Thus,the Ru/TiN-300 with a moderate SMSI degree exhibits excellent HER performance,with an overpotential of 38 mV at 10 mA cm^(−2).Also,due to the encapsulation role of TiN overlayer on Ru nanoparticles,it displays super long-term stability with a very slight potential change after 24 h.This study provides a deep insight into the influence of the SMSI effect between Ru and TiN on HER and offers a novel approach for preparing efficient and stable HER electrocatalysts through SMSI engineering.
基金The National Natural Science Foundation of China(Grant Nos.52072114 and 51922008)the 111 Project(Grant No.D17007),the Henan Center for Outstanding Overseas Scientists(Grant No.GZS2018003)+2 种基金Xinxiang Major Science and Technology Projects(Grant No.21ZD001)Guangdong Innovative and Entrepreneurial Research Team Program(2016ZT06N500)Guangdong Provincial Key Laboratory of Energy Materials for Electric Power(2018B030322001)all provided financial support for this work.
文摘Transition-metal oxyhydroxides are attractive catalysts for oxygen evolution reactions(OERs).Further studies for developing transition-metal oxyhydroxide catalysts and understanding their catalytic mechanisms will benefit their quick transition to the next catalysts.Herein,Mo-doped CoOOH was designed as a high-performance model electrocatalyst with durability for 20 h at 10 mAcm−2.Additionally,it had an overpotential of 260 mV(glassy carbon)or 215 mV(nickel foam),which was 78 mV lower than that of IrO_(2)(338 mV).In situ,Raman spectroscopy revealed the transformation process of CoOOH.Calculations using the density functional theory showed that during OER,doped Mo increased the spin-up density of states and shrank the spin-down bandgap of the 3d orbits in the reconstructed CoOOH under the electrochemical activation process,which simultaneously optimized the adsorption and electron conduction of oxygen-related intermediates on Co sites and lowered the OER overpotentials.Our research provides new insights into the methodical planning of the creation of transition-metal oxyhydroxide OER catalysts.
基金supported by the National Science Foundation of China(No.61504136)the State Key Laboratory of Applied Optics,Changchun Institute of Optics,Fine and Physics,Chinese Academy of Sciences
文摘A ZnO–SnO_2 nanowires(NWs) array, as a metal oxide semiconductor, was successfully synthesized by a near-field electrospinning method for the applications as high performance ultraviolet photodetectors. Ultraviolet photodetectors based on a single nanowire exhibited excellent photoresponse properties to 300 nm ultraviolet light illumination including ultrahigh I_(on)/I_(off) ratios(up to 10~3), good stability and reproducibility because of the separation between photo-generated electron-hole pairs. Moreover, the NWs array shows an enhanced photosensing performance. Flexible photodetectors on the PI substrates with similar tendency properties were also fabricated. In addition, under various bending curvatures and cycles, the as-fabricated flexible photodetectors revealed mechanical flexibility and good stable electrical properties, showing that they have the potential for applications in future flexible photoelectron devices.
