Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and...Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and it shows unprecedented catalytic performance in light alkane aromatization,considering activity,product selectivity and catalytic stability.The average aromatics yields in ethane aromatization at 600℃and WHSV of 0.8 h^(-1) within 28 h and in propane aromatization at 580℃and WHSV of 1.1 h^(-1) within 20 h reach~18.4%and~70.8%with benzene,toluene and xylenes(BTX)accounting for~96%and~88%of aromatics,respectively.Ga-MH-ZSM-5-0.41 gave a TON for formation of aromatics(TON_(aromatics))from propane as high as 57479,whereas the reported catalysts maximally show a TON_(aromatics) of 5514.This also holds true for ethane aromatization;the TON_(aromatics) obtained on Ga-MH-ZSM-5-0.41 was³3845 in contrast to£392 on reported non-noble metal catalysts.The catalytic activity of Ga-MH-ZSM-5 highly depends on Ga species structures.[Ga(OH)]^(2+)ions are predominant species at Ga loading≤0.3 wt%,while more[Ga(OH)_(2)]^(+)and GaO_(x) oligomers are formed with increasing Ga content.Upon reduction with H_(2),[Ga(OH)]^(2+)and[Ga(OH)_(2)]^(+)are transformed into[GaH]^(2+)and[GaH_(2)]^(+)species,which show a propane dehydrogenation rate of 300 and 15 times of that of Brønsted acid sites respectively.The light alkanes are mainly dehydrogenated into light olefins on[GaH]^(2+)species,and then,oligomerized and cyclized into(alkyl)cycloalkanes on H^(+)sites,which is followed by possible ring expansion on H^(+)and sequential dehydrogenations into aromatics primarily on[GaH]^(2+).展开更多
Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the as...Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.展开更多
Phytoplankton functional groups have gained increasing attention in recent years.To understand the composition of phytoplankton functional groups in Poyang Lake and their drivers,field investigations were conducted ov...Phytoplankton functional groups have gained increasing attention in recent years.To understand the composition of phytoplankton functional groups in Poyang Lake and their drivers,field investigations were conducted over three years:2013,2014,and 2016.Phytoplankton were dominated by diatoms,contributing from 20.19%to 57.57%of the total biomass,followed by cyanobacteria,9.81%-39.98%.Microcystis sp.and Anabaena sp.were the dominant species among cyanobacteria.Twenty-six functional groups were identified among 72 genera or species,and fiver groups(P,B,MP,H1,and G)were categorized dominant.All of dominant groups except H1 were tolerate highly fluctuating mixing intensities and showed a typical monthly succession variation.Water temperature,water level,and nutrients are key drivers for the variation of phytoplankton communities at taxonomic and functional levels.Both of redundancy and variation partitioning analyses showed that environmental variables might explain functional groups better than taxonomic communities,implying that the functional groups were more advantageous in showing the effects of environmental conditions than taxonomic compositions.Hydrological conditions have a crucial influence on phytoplankton assemblage dynamics in highly variable water regime lakes,but not in the largest ones.The functional groups method is suitable for identifying the spatial and seasonal characteristics of aquatic environments that significantly affected by water regimes.展开更多
AIM To investigate the incidence and risk factors of portosplenomesenteric vein thrombosis(PSMVT) in the early stage of severe acute pancreatitis(SAP).METHODS Patients with SAP in a tertiary care setting from January ...AIM To investigate the incidence and risk factors of portosplenomesenteric vein thrombosis(PSMVT) in the early stage of severe acute pancreatitis(SAP).METHODS Patients with SAP in a tertiary care setting from January 2014 to December 2016 were retrospectively reviewed. All contrast-enhanced computed tomography(CT) studies were reassessed and reviewed. Clinical outcome measures were compared between SAP patients with and without PSMVT in the early stage of the disease. Univariate and multivariate logistic regression analyses were sequentially performed to assess potential risk factors for the development of PSMVT in SAP patients. A receiver operating characteristic(ROC) curve was generated for the qualifying independent risk factors.RESULTS Twenty-five of the one hundred and forty(17.86%) SAP patients developed PSMVT 6.19 ± 2.43 d after acute pancreatitis(AP) onset. PSMVT was confirmed by contrast-enhanced CT. Multivariate stepwise logistic regression analyses showed that Balthazar's CT severity index(CTSI) scores [odds ratio(OR): 2.742; 95% confidence interval(CI): 1.664-4.519; P = 0.000], hypoalbuminemia(serum albumin level < 25 g/L)(OR: 32.573; 95%CI: 2.711-391.353; P = 0.006) and gastrointestinal wall thickening(OR: 4.367, 95%CI: 1.218-15.658; P = 0.024) were independent risk factors for PSMVT developed in patients with SAP. The area under the ROC curve for Balthazar's CTSI scores was 0.777(P = 0.000), the sensitivity was 52%, and the specificity was 93% at a cut-off value of 5.5.CONCLUSION High Balthazar's CTSI scores, hypoalbuminemia and gastrointestinal wall thickening are independent risk factors for PSMVT developed in the early stage of SAP.展开更多
BACKGROUND Recurrence of primary choledocholithiasis commonly occurs after complete removal of stones by therapeutic endoscopic retrograde cholangiopancreatography(ERCP). The potential causes of the recurrence of chol...BACKGROUND Recurrence of primary choledocholithiasis commonly occurs after complete removal of stones by therapeutic endoscopic retrograde cholangiopancreatography(ERCP). The potential causes of the recurrence of choledocholithiasis after ERCP are unclear.AIM To analyze the potential causes of the recurrence of choledocholithiasis after ERCP.METHODS The ERCP database of our medical center for the period between January 2007 and January 2016 was retrospectively reviewed, and information regarding eligible patients who had choledocholithiasis recurrence was collected. A 1:1 case-control study was performed for this investigation. Data including general characteristics of the patients, past medical history, ERCP-related factors,common bile duct(CBD)-related factors, laboratory indicators, and treatment was analyzed by univariate and multivariate logistic regression analysis and KaplanMeier analysisly.RESULTS First recurrence of choledocholithiasis occurred in 477 patients; among these patients, the second and several instance(≥ 3 times) recurrence rates were 19.5%and 44.07%, respectively. The average time to first choledocholithiasis recurrence was 21.65 mo. A total of 477 patients who did not have recurrence were selected as a control group. Multivariate logistic regression analysis showed that age > 65 years(odds ratio [OR] = 1.556; P = 0.018), combined history of choledocholithotomy(OR = 2.458; P < 0.01), endoscopic papillary balloon dilation(OR = 5.679; P = 0.000), endoscopic sphincterotomy(OR = 3.463; P = 0.000), CBD stent implantation(OR = 5.780; P = 0.000), multiple ERCP procedures(≥2; OR =2.75; P = 0.000), stones in the intrahepatic bile duct(OR = 2.308; P = 0.000),periampullary diverticula(OR = 1.627; P < 0.01), choledocholithiasis diameter ≥10 mm(OR = 1.599; P < 0.01), bile duct-duodenal fistula(OR = 2.69; P < 0.05),combined biliary tract infections(OR = 1.057; P < 0.01), and no preoperative antibiotic use(OR = 0.528; P < 0.01) were independent risk factors for the recurrence of choledocholithiasis after ERCP.CONCLUSION Patient age greater than 65 years is an independent risk factor for the development of recurrent choledocholithiasis following ERCP, as is history of biliary surgeries, measures during ERCP, and prevention of postoperative complications.展开更多
In the petroleum industry,detection of multi-phase fluid flow is very important in both surface and down-hole measurements.Accurate measurement of high rate of water or gas multi-phase flow has always been an academic...In the petroleum industry,detection of multi-phase fluid flow is very important in both surface and down-hole measurements.Accurate measurement of high rate of water or gas multi-phase flow has always been an academic and industrial focus.NMR is an efficient and accurate technique for the detection of fluids;it is widely used in the determination of fluid compositions and properties.This paper is aimed to quantitatively detect multi-phase flow in oil and gas wells and pipelines and to propose an innovative method for online nuclear magnetic resonance(NMR)detection.The online NMR data acquisition,processing and interpretation methods are proposed to fill the blank of traditional methods.A full-bore straight tube design without pressure drop,a Halbach magnet structure design with zero magnetic leakage outside the probe,a separate antenna structure design without flowing effects on NMR measurement and automatic control technology will achieve unattended operation.Through the innovation of this work,the application of NMR for the real-time and quantitative detection of multi-phase flow in oil and gas wells and pipelines can be implemented.展开更多
Tremendous progress of developing nuclear magnetic resonance(NMR)fluid analyzer has been witnessed in the oil industry for last two decades.This device allows extensive and accurate exploration of fluid properties,suc...Tremendous progress of developing nuclear magnetic resonance(NMR)fluid analyzer has been witnessed in the oil industry for last two decades.This device allows extensive and accurate exploration of fluid properties,such as its hydrogen content,composition,viscosity,hydrogen index(HI),mud filtrate invasion,gas to oil ratio,average velocity,velocity distribution etc.,in the situations of in situ downhole or surface Petro-pipelines.In this review article,we focus on the design principle,manufacturing,implementation,methodology and applications of NMR fluid analyzer to oil and gas industry.A detailed description of the state-of-art NMR fluid analyzers was firstly given to exhibit their respective characteristics.With these experiences on hand,we introduced a series of NMR fluid analyzers designed by us at China University of Petroleum-Beijing with continuous optimizations,in terms of magnet construction,antenna layout,circuit design and operating surroundings.These systems discussed in this article have been demonstrated to achieve multiple NMR parameter acquisition when the fluid is in stationary or flowing state.In the end,a prototype was fabricated and validated considering a vast of engineering influences,such as variable temperatures in a large range,high pressure,limited volume,detection efficiency,etc.A particular emphasis of this paper is to expedite the measurement efficiency of the NMR fluid analyzer to reduce the operation costs.This dilemma can be Figured out by upgrading both pulse sequence and observational mode.For different fluid states,two rapid pulse sequences were proposed to sufficiently obtain the multi-dimensional NMR correlation map.Meanwhile,two observational modes were developed to take full advantage of the polarization time,during which the individual antenna was systematically switched.Another domain of interest in this review concerns the applications of this new tool.For stationary fluids case,accurate identification of fluid properties is of great value for scheme building in oil and gas exploration process.Particularly,it can acquire the fluid content by different NMR responses of different components.In addition,with Bloembergen theory and Stokes-Einstein equation,not only molecular dynamics and composition,but also oil viscosity can be readily evaluated.Moreover,HI information of crude oils will be speculated through partial least square regression.As for flowing fluids case,velocity is a significant parameter to understand the in situ fluid exploitation and therefore evaluate the productivity of certain oil wells or pipelines.Regarding to the unique magnet and antenna designs in our NMR fluid analyzer;this review adopts two distinct methods to obtain flow velocity at a wide rating scale.The first one is a time-of-flight method adaptive in a homogeneous magnetic field,which is suitable in the case of fluid at high flow velocity.The other one relies on the adjacent echo phase difference at a magnetic field with constant gradient,which is preferred for relatively low flow velocity.In the near future,this tool will be tested underground to offer individual fluid velocities by combining both the stationary and flowing analysis methods.展开更多
Covalent modification of shortened multiwalled carbon nanombes （MWNTs） with a natural low molecular weight chitosan （LMCS） was accomplished by the nucleophilic substitution reaction. The LMCS modified MWNTs （MWNT...Covalent modification of shortened multiwalled carbon nanombes （MWNTs） with a natural low molecular weight chitosan （LMCS） was accomplished by the nucleophilic substitution reaction. The LMCS modified MWNTs （MWNT-LMCS） were characterized by FTIR, solid-state ^13C NMR, and XPS spectroscopies, thermogravimetric analysis, and transmission electron microscopy. The results revealed that amino and primary hydroxyl groups of the LMCS participated mainly in the formation of the MWNT-LMCS conjugates. The MWNT-LMCS consists of 58 wt.% LMCS, and about four molecular chains of the LMCS were attached to 1000 carbon atoms of the nanotube sidewalls. As a novel derivative of the MWNTs, the MWNT-LMCS not only solved in DMF, DMAc and DMSO, but also in aqueous acetic acid solution.展开更多
In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in te...In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in terms of energy.However,in practice,the efficiency of energy harvesting is often low due to the limited device capability.In this paper,we formulate three types of different EH architectures,i.e.,the harvest-use architecture,the harvest-store-use architecture,and the harvest-use-store architecture from the perspective of energy storage efficiency.We propose resource allocation schemes to jointly design the sensor power and duty-cycle via an alternating optimization algorithm under the above EH architectures,in both simultaneous and non-simultaneous harvesting and utilization models,aiming at achieving a higher throughput and energy efficiency.Non-ideal circuit power is also considered.Numerical results show that our proposed schemes under EH architectures outperform the existing classic continuous transmission schemes.展开更多
The recent emerging progress of quantum dot ink(QD-ink)has overcome the complexity of multiple-step colloidal QD(CQD)film preparation and pronouncedly promoted the device performance.However,the detrimental hydroxyl(O...The recent emerging progress of quantum dot ink(QD-ink)has overcome the complexity of multiple-step colloidal QD(CQD)film preparation and pronouncedly promoted the device performance.However,the detrimental hydroxyl(OH)ligands induced from synthesis procedure have not been completely removed.Here,a halide ligand additive strategy was devised to optimize QD-ink process.It simultaneously reduced sub-bandgap states and converted them into iodide-passivated surface,which increase carrier mobility of the QDs films and achieve thicker absorber with improved performances.The corresponding power conversion efficiency of this optimized device reached 10.78%.(The control device was 9.56%.)Therefore,this stratege can support as a candidate strategy to solve the QD original limitation caused by hydroxyl ligands,which is also compatible with other CQD-based optoelectronic devices.展开更多
The surface glycoproteins of coronaviruses play an important role in receptor binding and cell entry. Different coronaviruses interact with their specific receptors to enter host cells. Lentiviruses pseudotyped with t...The surface glycoproteins of coronaviruses play an important role in receptor binding and cell entry. Different coronaviruses interact with their specific receptors to enter host cells. Lentiviruses pseudotyped with their spike proteins(S) were compared to analyze the entry efficiency of various coronaviruses. Our results indicated that S proteins from different coronaviruses displayed varied abilities to mediate pseudotyped virus infection. Furthermore, the cell tropisms of porcine epidemic diarrhea virus(PEDV) and transmissible gastroenteritis virus(TGEV) have been characterized by live and pseudotyped viruses. Both live and pseudoviruses could infected VeroCCL-81(monkey kidney), Huh-7(human liver), and PK-15(pig kidney) cells efficiently. CCL94(cat kidney) cells could be infected efficiently by TGEV but not PEDV. Overall, our study provides new insights into the mechanisms of viral entry and forms a basis for antiviral drug screening.展开更多
文摘Aromatization of light alkanes is a value-added process in both petrochemical and coal chemical industries.Here,single[Ga(OH)]^(2+)ion-exchanged mesoporous hollow-structured ZSM-5(Ga-MH-ZSM-5)material was prepared,and it shows unprecedented catalytic performance in light alkane aromatization,considering activity,product selectivity and catalytic stability.The average aromatics yields in ethane aromatization at 600℃and WHSV of 0.8 h^(-1) within 28 h and in propane aromatization at 580℃and WHSV of 1.1 h^(-1) within 20 h reach~18.4%and~70.8%with benzene,toluene and xylenes(BTX)accounting for~96%and~88%of aromatics,respectively.Ga-MH-ZSM-5-0.41 gave a TON for formation of aromatics(TON_(aromatics))from propane as high as 57479,whereas the reported catalysts maximally show a TON_(aromatics) of 5514.This also holds true for ethane aromatization;the TON_(aromatics) obtained on Ga-MH-ZSM-5-0.41 was³3845 in contrast to£392 on reported non-noble metal catalysts.The catalytic activity of Ga-MH-ZSM-5 highly depends on Ga species structures.[Ga(OH)]^(2+)ions are predominant species at Ga loading≤0.3 wt%,while more[Ga(OH)_(2)]^(+)and GaO_(x) oligomers are formed with increasing Ga content.Upon reduction with H_(2),[Ga(OH)]^(2+)and[Ga(OH)_(2)]^(+)are transformed into[GaH]^(2+)and[GaH_(2)]^(+)species,which show a propane dehydrogenation rate of 300 and 15 times of that of Brønsted acid sites respectively.The light alkanes are mainly dehydrogenated into light olefins on[GaH]^(2+)species,and then,oligomerized and cyclized into(alkyl)cycloalkanes on H^(+)sites,which is followed by possible ring expansion on H^(+)and sequential dehydrogenations into aromatics primarily on[GaH]^(2+).
基金supported by the National Energy R&D Center of Petroleum Refining Technology(RIPP,SINOPEC),the National Natural Science Foundation of China(Grants 22161132028,22172177,22225205,22372191 and 22372178)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB0540000)+2 种基金the International Partnership Program of the Chinese Academy of Sciences(314GJH2022022FN)Natural Science Foundation of Hubei Province(2021CFA021)Hubei International Scientific and Technological Cooperation Program(2024EHA043)and Base(SH2303).
文摘Organic structure directingagents(OSDAs),suchas tetrapropylammonium(TPA)cations,serve as crucial templates for the formation of zeolite frameworks.These organic molecules interact with inorganic species,guiding the assembly of the zeolite structure.In this study,we inves-tigate the complex interplay between boron species and TPA cations during the crystallization of[B,Al]-ZSM-5 zeolites.Two-dimensional(2D)11B-{1H}cross-polarization heteronuclear correlation(CP-HECTOR)NMRexperiments elucidate distinct interactions between two boron species,B(IV)-1 and B(IV)-2,and the propyl chain of the TPAs.Amorphous B(IV)-1 species exhibit a strong preference for proximity to the nitrogen cation center of the OSDAs,while framework B(IV)-2 species engage with components situated at greater distances from the cation center.Moreover,13C-{11B}symmetry-based resonance-echo saturation-pulse double-resonance(S-RESPDOR)experiments revealed that framework boron species preferentially occupy the straight channels of the MFI structure,as evidenced by their interaction with specificmethyl groups on the TPAmolecules.This observation provides valuable insights into the crystallization mechanism of boron-based zeolites,suggesting that the conformation and orientation of the OSDA molecules play a critical role in determining the location of boron atoms within the zeolite framework.
基金Supported by the Science and Technology Project of Jiangxi Provincial Department of Education(Nos.GJJ211938,GJJ211933)the National Natural Science Foundation of China(No.52260026)+2 种基金the Science and Technology Research and Development Project of China Railway Group Limited(No.2021-Major-08)the Major Science and Technology Program of Jiangxi Provincial Department of Water Resources(No.202224ZDKT22)the Young Talents Training Project of Jiangxi Province(No.20204BCJL23040)。
文摘Phytoplankton functional groups have gained increasing attention in recent years.To understand the composition of phytoplankton functional groups in Poyang Lake and their drivers,field investigations were conducted over three years:2013,2014,and 2016.Phytoplankton were dominated by diatoms,contributing from 20.19%to 57.57%of the total biomass,followed by cyanobacteria,9.81%-39.98%.Microcystis sp.and Anabaena sp.were the dominant species among cyanobacteria.Twenty-six functional groups were identified among 72 genera or species,and fiver groups(P,B,MP,H1,and G)were categorized dominant.All of dominant groups except H1 were tolerate highly fluctuating mixing intensities and showed a typical monthly succession variation.Water temperature,water level,and nutrients are key drivers for the variation of phytoplankton communities at taxonomic and functional levels.Both of redundancy and variation partitioning analyses showed that environmental variables might explain functional groups better than taxonomic communities,implying that the functional groups were more advantageous in showing the effects of environmental conditions than taxonomic compositions.Hydrological conditions have a crucial influence on phytoplankton assemblage dynamics in highly variable water regime lakes,but not in the largest ones.The functional groups method is suitable for identifying the spatial and seasonal characteristics of aquatic environments that significantly affected by water regimes.
基金the National Natural Science Foundation of China,No.81760120
文摘AIM To investigate the incidence and risk factors of portosplenomesenteric vein thrombosis(PSMVT) in the early stage of severe acute pancreatitis(SAP).METHODS Patients with SAP in a tertiary care setting from January 2014 to December 2016 were retrospectively reviewed. All contrast-enhanced computed tomography(CT) studies were reassessed and reviewed. Clinical outcome measures were compared between SAP patients with and without PSMVT in the early stage of the disease. Univariate and multivariate logistic regression analyses were sequentially performed to assess potential risk factors for the development of PSMVT in SAP patients. A receiver operating characteristic(ROC) curve was generated for the qualifying independent risk factors.RESULTS Twenty-five of the one hundred and forty(17.86%) SAP patients developed PSMVT 6.19 ± 2.43 d after acute pancreatitis(AP) onset. PSMVT was confirmed by contrast-enhanced CT. Multivariate stepwise logistic regression analyses showed that Balthazar's CT severity index(CTSI) scores [odds ratio(OR): 2.742; 95% confidence interval(CI): 1.664-4.519; P = 0.000], hypoalbuminemia(serum albumin level < 25 g/L)(OR: 32.573; 95%CI: 2.711-391.353; P = 0.006) and gastrointestinal wall thickening(OR: 4.367, 95%CI: 1.218-15.658; P = 0.024) were independent risk factors for PSMVT developed in patients with SAP. The area under the ROC curve for Balthazar's CTSI scores was 0.777(P = 0.000), the sensitivity was 52%, and the specificity was 93% at a cut-off value of 5.5.CONCLUSION High Balthazar's CTSI scores, hypoalbuminemia and gastrointestinal wall thickening are independent risk factors for PSMVT developed in the early stage of SAP.
文摘BACKGROUND Recurrence of primary choledocholithiasis commonly occurs after complete removal of stones by therapeutic endoscopic retrograde cholangiopancreatography(ERCP). The potential causes of the recurrence of choledocholithiasis after ERCP are unclear.AIM To analyze the potential causes of the recurrence of choledocholithiasis after ERCP.METHODS The ERCP database of our medical center for the period between January 2007 and January 2016 was retrospectively reviewed, and information regarding eligible patients who had choledocholithiasis recurrence was collected. A 1:1 case-control study was performed for this investigation. Data including general characteristics of the patients, past medical history, ERCP-related factors,common bile duct(CBD)-related factors, laboratory indicators, and treatment was analyzed by univariate and multivariate logistic regression analysis and KaplanMeier analysisly.RESULTS First recurrence of choledocholithiasis occurred in 477 patients; among these patients, the second and several instance(≥ 3 times) recurrence rates were 19.5%and 44.07%, respectively. The average time to first choledocholithiasis recurrence was 21.65 mo. A total of 477 patients who did not have recurrence were selected as a control group. Multivariate logistic regression analysis showed that age > 65 years(odds ratio [OR] = 1.556; P = 0.018), combined history of choledocholithotomy(OR = 2.458; P < 0.01), endoscopic papillary balloon dilation(OR = 5.679; P = 0.000), endoscopic sphincterotomy(OR = 3.463; P = 0.000), CBD stent implantation(OR = 5.780; P = 0.000), multiple ERCP procedures(≥2; OR =2.75; P = 0.000), stones in the intrahepatic bile duct(OR = 2.308; P = 0.000),periampullary diverticula(OR = 1.627; P < 0.01), choledocholithiasis diameter ≥10 mm(OR = 1.599; P < 0.01), bile duct-duodenal fistula(OR = 2.69; P < 0.05),combined biliary tract infections(OR = 1.057; P < 0.01), and no preoperative antibiotic use(OR = 0.528; P < 0.01) were independent risk factors for the recurrence of choledocholithiasis after ERCP.CONCLUSION Patient age greater than 65 years is an independent risk factor for the development of recurrent choledocholithiasis following ERCP, as is history of biliary surgeries, measures during ERCP, and prevention of postoperative complications.
基金supported by the National Natural Science Foundation of China(Grant No.51704327)
文摘In the petroleum industry,detection of multi-phase fluid flow is very important in both surface and down-hole measurements.Accurate measurement of high rate of water or gas multi-phase flow has always been an academic and industrial focus.NMR is an efficient and accurate technique for the detection of fluids;it is widely used in the determination of fluid compositions and properties.This paper is aimed to quantitatively detect multi-phase flow in oil and gas wells and pipelines and to propose an innovative method for online nuclear magnetic resonance(NMR)detection.The online NMR data acquisition,processing and interpretation methods are proposed to fill the blank of traditional methods.A full-bore straight tube design without pressure drop,a Halbach magnet structure design with zero magnetic leakage outside the probe,a separate antenna structure design without flowing effects on NMR measurement and automatic control technology will achieve unattended operation.Through the innovation of this work,the application of NMR for the real-time and quantitative detection of multi-phase flow in oil and gas wells and pipelines can be implemented.
基金supported by National Natural Science Foundation of China(Grant Nos.21427812,41674137,51974337)National Science and Technology Major Project of China(2017ZX05019002-008)+1 种基金National"111 Project"(B13010)"863 Project"(2013AA064605)。
文摘Tremendous progress of developing nuclear magnetic resonance(NMR)fluid analyzer has been witnessed in the oil industry for last two decades.This device allows extensive and accurate exploration of fluid properties,such as its hydrogen content,composition,viscosity,hydrogen index(HI),mud filtrate invasion,gas to oil ratio,average velocity,velocity distribution etc.,in the situations of in situ downhole or surface Petro-pipelines.In this review article,we focus on the design principle,manufacturing,implementation,methodology and applications of NMR fluid analyzer to oil and gas industry.A detailed description of the state-of-art NMR fluid analyzers was firstly given to exhibit their respective characteristics.With these experiences on hand,we introduced a series of NMR fluid analyzers designed by us at China University of Petroleum-Beijing with continuous optimizations,in terms of magnet construction,antenna layout,circuit design and operating surroundings.These systems discussed in this article have been demonstrated to achieve multiple NMR parameter acquisition when the fluid is in stationary or flowing state.In the end,a prototype was fabricated and validated considering a vast of engineering influences,such as variable temperatures in a large range,high pressure,limited volume,detection efficiency,etc.A particular emphasis of this paper is to expedite the measurement efficiency of the NMR fluid analyzer to reduce the operation costs.This dilemma can be Figured out by upgrading both pulse sequence and observational mode.For different fluid states,two rapid pulse sequences were proposed to sufficiently obtain the multi-dimensional NMR correlation map.Meanwhile,two observational modes were developed to take full advantage of the polarization time,during which the individual antenna was systematically switched.Another domain of interest in this review concerns the applications of this new tool.For stationary fluids case,accurate identification of fluid properties is of great value for scheme building in oil and gas exploration process.Particularly,it can acquire the fluid content by different NMR responses of different components.In addition,with Bloembergen theory and Stokes-Einstein equation,not only molecular dynamics and composition,but also oil viscosity can be readily evaluated.Moreover,HI information of crude oils will be speculated through partial least square regression.As for flowing fluids case,velocity is a significant parameter to understand the in situ fluid exploitation and therefore evaluate the productivity of certain oil wells or pipelines.Regarding to the unique magnet and antenna designs in our NMR fluid analyzer;this review adopts two distinct methods to obtain flow velocity at a wide rating scale.The first one is a time-of-flight method adaptive in a homogeneous magnetic field,which is suitable in the case of fluid at high flow velocity.The other one relies on the adjacent echo phase difference at a magnetic field with constant gradient,which is preferred for relatively low flow velocity.In the near future,this tool will be tested underground to offer individual fluid velocities by combining both the stationary and flowing analysis methods.
文摘Covalent modification of shortened multiwalled carbon nanombes （MWNTs） with a natural low molecular weight chitosan （LMCS） was accomplished by the nucleophilic substitution reaction. The LMCS modified MWNTs （MWNT-LMCS） were characterized by FTIR, solid-state ^13C NMR, and XPS spectroscopies, thermogravimetric analysis, and transmission electron microscopy. The results revealed that amino and primary hydroxyl groups of the LMCS participated mainly in the formation of the MWNT-LMCS conjugates. The MWNT-LMCS consists of 58 wt.% LMCS, and about four molecular chains of the LMCS were attached to 1000 carbon atoms of the nanotube sidewalls. As a novel derivative of the MWNTs, the MWNT-LMCS not only solved in DMF, DMAc and DMSO, but also in aqueous acetic acid solution.
基金This work was supported in part by the National Natural Science Foundation of China under Grants 61801145,61972113,61901138,and 61871426in part by the Shenzhen Science and Technology Program under Grants JCYJ20180306171800589,JCYJ20190806112215116,and KQTD 20190929172545139+2 种基金in part by the Natural Science Foundation of Guangdong Province under Grant 2018A030313298in part by the Guangdong Science and Technology Planning Project under Grant 2018B030322004in part by the Natural Scientific Research Innovation Foundation in Harbin Institute of Technology under Grant HIT.NSRIF.2020076.
文摘In the emerging sixth generation(6G)communication network,energy harvesting(EH)is a promising technology to achieve the unlimited energy supply and hence makes the wireless communication systems self-sustainable in terms of energy.However,in practice,the efficiency of energy harvesting is often low due to the limited device capability.In this paper,we formulate three types of different EH architectures,i.e.,the harvest-use architecture,the harvest-store-use architecture,and the harvest-use-store architecture from the perspective of energy storage efficiency.We propose resource allocation schemes to jointly design the sensor power and duty-cycle via an alternating optimization algorithm under the above EH architectures,in both simultaneous and non-simultaneous harvesting and utilization models,aiming at achieving a higher throughput and energy efficiency.Non-ideal circuit power is also considered.Numerical results show that our proposed schemes under EH architectures outperform the existing classic continuous transmission schemes.
基金financially supported by National Natural Science Foundation of China (61874165,51761145048,and 21833009)the Foundation of Shenzhen Science and Technology Innovation Committee (JCYJ20170413113645633)+2 种基金Major State Basic Research Development Program of China (2016YFB0700702)the Guangdong-Hong Kong joint innovation project (2016A050503012)Guangdong Natural Science Funds for Distinguished Young Scholars (2015A030306044)
文摘The recent emerging progress of quantum dot ink(QD-ink)has overcome the complexity of multiple-step colloidal QD(CQD)film preparation and pronouncedly promoted the device performance.However,the detrimental hydroxyl(OH)ligands induced from synthesis procedure have not been completely removed.Here,a halide ligand additive strategy was devised to optimize QD-ink process.It simultaneously reduced sub-bandgap states and converted them into iodide-passivated surface,which increase carrier mobility of the QDs films and achieve thicker absorber with improved performances.The corresponding power conversion efficiency of this optimized device reached 10.78%.(The control device was 9.56%.)Therefore,this stratege can support as a candidate strategy to solve the QD original limitation caused by hydroxyl ligands,which is also compatible with other CQD-based optoelectronic devices.
基金supported by the National Natural Science Foundation of China (Grant No.31372440)
文摘The surface glycoproteins of coronaviruses play an important role in receptor binding and cell entry. Different coronaviruses interact with their specific receptors to enter host cells. Lentiviruses pseudotyped with their spike proteins(S) were compared to analyze the entry efficiency of various coronaviruses. Our results indicated that S proteins from different coronaviruses displayed varied abilities to mediate pseudotyped virus infection. Furthermore, the cell tropisms of porcine epidemic diarrhea virus(PEDV) and transmissible gastroenteritis virus(TGEV) have been characterized by live and pseudotyped viruses. Both live and pseudoviruses could infected VeroCCL-81(monkey kidney), Huh-7(human liver), and PK-15(pig kidney) cells efficiently. CCL94(cat kidney) cells could be infected efficiently by TGEV but not PEDV. Overall, our study provides new insights into the mechanisms of viral entry and forms a basis for antiviral drug screening.
