期刊文献+
共找到2,674篇文章
< 1 2 134 >
每页显示 20 50 100
Proteomic response of Phaeocystis globosa to nitrogen limitation
1
作者 Haisu LIU Ruiwang WEI +2 位作者 Qiangyong LEI Lei CUI Songhui LÜ 《Journal of Oceanology and Limnology》 SCIE CAS CSCD 2024年第1期141-149,共9页
Phaeocystis globosa is an important unicellular eukaryotic alga that can also form colonies.P.globosa can cause massive harmful algal blooms and plays an important role in the global carbon or sulfur cycling.Thus far,... Phaeocystis globosa is an important unicellular eukaryotic alga that can also form colonies.P.globosa can cause massive harmful algal blooms and plays an important role in the global carbon or sulfur cycling.Thus far,the ecophysiology of P.globosa has been investigated by numerous studies.However,the proteomic response of P.globosa to nitrogen depletion remains largely unknown.We compared four protein preparation methods of P.globosa for two-dimensional electrophoresis(2-DE)(Urea/Triton X-100 with trichloroacetic acid(TCA)/acetone precipitation;TCA/acetone precipitation;Radio Immuno Precipitation Assay(RIPA)with TCA/acetone precipitation;and Tris buffer).Results show that the combination of RIPA with TCA/acetone precipitation had a clear gel background and showed the best protein spot separation effect,based on which the proteomic response to nitrogen depletion was studied using 2-DE.In addition,we identified six differentially expressed proteins whose relative abundance increased or decreased more than 1.5-fold(P<0.05).Most proteins could not be identified,which might be attributed to the lack of genomic sequences of P.globosa.Under nitrogen limitation,replication protein-like,RNA ligase,and sn-glycerol-3-phosphate dehydrogenase were reduced,which may decrease the DNA replication level and ATP production in P.globosa cells.The increase of endonucleaseⅢand transcriptional regulator enzyme may affect the metabolic and antioxidant function of P.globosa cells and induce cell apoptosis.These findings provide a basis for further proteomic study of P.globosa and the optimization of protein preparation methods of marine microalgae. 展开更多
关键词 Phaeocystis globosa nitrogen limitation proteomic response two-dimensional electrophoresis
下载PDF
A Stroke-Limitation AMD Control System with Variable Gain and Limited Area for High-Rise Buildings
2
作者 Zuo-Hua Li Qing-Gui Wu +1 位作者 Jun Teng Chao-Jun Chen 《Computer Modeling in Engineering & Sciences》 SCIE EI 2024年第1期865-884,共20页
Collisions between a moving mass and an anti-collision device increase structural responses and threaten structural safety.An active mass damper(AMD)with stroke limitations is often used to avoid collisions.However,a ... Collisions between a moving mass and an anti-collision device increase structural responses and threaten structural safety.An active mass damper(AMD)with stroke limitations is often used to avoid collisions.However,a strokelimited AMD control system with a fixed limited area shortens the available AMD stroke and leads to significant control power.To solve this problem,the design approach with variable gain and limited area(VGLA)is proposed in this study.First,the boundary of variable-limited areas is calculated based on the real-time status of the moving mass.The variable gain(VG)expression at the variable limited area is deduced by considering the saturation of AMD stroke.Then,numerical simulations of a stroke-limited AMD control system with VGLA are conducted on a high-rise building structure.These numerical simulations show that the proposed approach has superior strokelimitation performance compared with a stroke-limited AMD control system with a fixed limited area.Finally,the proposed approach is validated through experiments on a four-story steel frame. 展开更多
关键词 High-rise buildings active control stroke limitations variable gain variable limited area
下载PDF
Fully Distributed Nash Equilibrium Seeking for High-Order Players With Actuator Limitations 被引量:4
3
作者 Maojiao Ye Qing-Long Han +1 位作者 Lei Ding Shengyuan Xu 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2023年第6期1434-1444,共11页
This paper explores the problem of distributed Nash equilibrium seeking in games, where players have limited knowledge on other players' actions. In particular, the involved players are considered to be high-order... This paper explores the problem of distributed Nash equilibrium seeking in games, where players have limited knowledge on other players' actions. In particular, the involved players are considered to be high-order integrators with their control inputs constrained within a pre-specified region. A linear transformation for players' dynamics is firstly utilized to facilitate the design of bounded control inputs incorporating multiple saturation functions. By introducing consensus protocols with adaptive and time-varying gains, the unknown actions for players are distributively estimated. Then, a fully distributed Nash equilibrium seeking strategy is exploited, showcasing its remarkable properties: (1) ensuring the boundedness of control inputs;(2) avoiding any global information/parameters;and (3) allowing the graph to be directed. Based on Lyapunov stability analysis, it is theoretically proved that the proposed distributed control strategy can lead all the players' actions to the Nash equilibrium. Finally, an illustrative example is given to validate effectiveness of the proposed method. 展开更多
关键词 Actuator limitation directed networks GAMES Nash equilibrium
下载PDF
Limitations of Lightning Rods in Preventing Direct Lightning Strikes 被引量:1
4
作者 Zhen CHEN Xiaofeng LUO +5 位作者 Jixi LIU Ziqin GAO Yixian QIU Xiaoning ZHANG Lingjin KONG Chunliang ZHANG 《Meteorological and Environmental Research》 CAS 2023年第4期59-62,共4页
Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invent... Since ancient times,lightning disasters have undoubtedly been an unstoppable threat to humanity.During thunderstorms,lightning often damages objects on the ground,such as buildings and structures.Since Franklin invented the lightning rod in 1752,lightning rods have been used worldwide to prevent direct lightning strikes in various fields such as high-voltage power transmission lines,outdoor chemical sites,highways,land and sea wind farms,and forest lightning fire protection.It has been proven that lightning accidents still occur frequently in places where lightning rods are installed and the protective angle method is used.In order to further study the protective effect of lightning rods and identify the shortcomings of lightning rod protection,negative lightning strikes are taken as the research object,to analyze the limitations of lightning rods in preventing direct lightning strikes from the working principle of lightning rods. 展开更多
关键词 Lightning rod Direct lightning strike Protective angle method limitation
下载PDF
A Multi-mode Electronic Load Sensing Control Scheme with Power Limitation and Pressure Cut-off for Mobile Machinery
5
作者 Min Cheng Bolin Sun +1 位作者 Ruqi Ding Bing Xu 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2023年第1期157-170,共14页
In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are ... In mobile machinery,hydro-mechanical pumps are increasingly replaced by electronically controlled pumps to improve the automation level,but diversified control functions(e.g.,power limitation and pressure cut-off)are integrated into the electronic controller only from the pump level,leading to the potential instability of the overall system.To solve this problem,a multi-mode electrohydraulic load sensing(MELS)control scheme is proposed especially considering the switching stability from the system level,which includes four working modes of flow control,load sensing,power limitation,and pressure control.Depending on the actual working requirements,the switching rules for the different modes and the switching direction(i.e.,the modes can be switched bilaterally or unilaterally)are defined.The priority of different modes is also defined,from high to low:pressure control,power limitation,load sensing,and flow control.When multiple switching rules are satisfied at the same time,the system switches to the control mode with the highest priority.In addition,the switching stability between flow control and pressure control modes is analyzed,and the controller parameters that guarantee the switching stability are obtained.A comparative study is carried out based on a test rig with a 2-ton hydraulic excavator.The results show that the MELS controller can achieve the control functions of proper flow supplement,power limitation,and pressure cut-off,which has good stability performance when switching between different control modes.This research proposes the MELS control method that realizes the stability of multi-mode switching of the hydraulic system of mobile machinery under different working conditions. 展开更多
关键词 Hydraulic control Load sensing MULTI-MODE Power limitation Mobile machinery
下载PDF
Potential and limitations of ChatGPT and generative artificial intelligence in medical safety education
6
作者 Xin Wang Xin-Qiao Liu 《World Journal of Clinical Cases》 SCIE 2023年第32期7935-7939,共5页
The primary objectives of medical safety education are to provide the public with essential knowledge about medications and to foster a scientific approach to drug usage.The era of using artificial intelligence to rev... The primary objectives of medical safety education are to provide the public with essential knowledge about medications and to foster a scientific approach to drug usage.The era of using artificial intelligence to revolutionize medical safety education has already dawned,and ChatGPT and other generative artificial intelligence models have immense potential in this domain.Notably,they offer a wealth of knowledge,anonymity,continuous availability,and personalized services.However,the practical implementation of generative artificial intelligence models such as ChatGPT in medical safety education still faces several challenges,including concerns about the accuracy of information,legal responsibilities,and ethical obligations.Moving forward,it is crucial to intelligently upgrade ChatGPT by leveraging the strengths of existing medical practices.This task involves further integrating the model with real-life scenarios and proactively addressing ethical and security issues with the ultimate goal of providing the public with comprehensive,convenient,efficient,and personalized medical services. 展开更多
关键词 Medical safety education ChatGPT Generative artificial intelligence POTENTIAL limitation
下载PDF
Assessment of the 2 Conventional Physiotherapy Sessions Alone versus One Session Associated to Kabat’s Method in the Rehabilitation of Buruli Ulcer Patients (PUB), with Functional Limitations in the District Hospital of Akonolinga, Cameroon
7
作者 Fred Dikongue Dikongue Faustin Tsatedem Atemkeng +4 位作者 Joseph Fondop Jean Hubert Donfack Alain Djam Nkomo Banga Mbida Mpoame 《Surgical Science》 2023年第6期428-435,共8页
Buruli ulcer (BU) is a chronic, indolent necrotizing disease of the skin and underlying tissues caused by Mycobacterium ulcerans, which may result in functional disability. This disease is the third most frequent infe... Buruli ulcer (BU) is a chronic, indolent necrotizing disease of the skin and underlying tissues caused by Mycobacterium ulcerans, which may result in functional disability. This disease is the third most frequent infection after leprosy and tuberculosis caused by a mycobacterium. The main objective of this study was to determine comparative effectiveness of conventional physiotherapy alone to its association with Kabat’s method in the management of post-Buruli ulcer functional limitations. This was an interventional randomized, comparative and prospective study. It took place at the district hospital of Akonolinga from the 12<sup>th</sup> June to 12<sup>th</sup> September 2016. The study was included, post-Buruli ulcer patients who matched the eligibility criteria, were under treatment in the physiotherapy unit, and who accepted to participate in our study. A questionnaire on the socio-demographic profile of participants, the ulcer localization, the limitation stage, previous medical history and functional mobility assessment scale was administered to the subjects before and after the intervention which lasted for twelve weeks. We had 2 groups: the case group received association of Kabat technique to conventional physiotherapy and the control group received conventional physiotherapy alone. We had 22 patients, 11 patients for the experimental group, 11 patients for the control group. The mean age was 26.18 years, 54.5% of female participation, 68.2% of leg localization, 59.1% patients with severe limitations of functional mobility, and preference for traditional medication 95.5%. After evaluation of efficiency, we concluded that there was no statistically significant difference between the two treatment protocols. Further studies with larger sample size are recommended. 展开更多
关键词 Buruli Ulcer Functional limitations PHYSIOTHERAPY Kabat Technique
下载PDF
Different Thought Patterns and the Limitation in Translation Between Chinese and English Language
8
作者 杨晖 《海外英语》 2013年第3X期7-9,共3页
Thought patterns and language are closely related,they are two aspect of the culture.Translation,a tool of intercultural communication,connects the different thought patterns.In this paper,a specific analysis of the l... Thought patterns and language are closely related,they are two aspect of the culture.Translation,a tool of intercultural communication,connects the different thought patterns.In this paper,a specific analysis of the limitation in translation caused by the difference is illustrated.Thus,translation is influenced deeply by the different thought patterns.The only way to get the reappearance to the culture in translation is to find out the principles of translation from the different thought patterns. 展开更多
关键词 THOUGHT PATTERNS TRANSLATION limitation
下载PDF
H_∞ Design for Sampled-Data Systems via Lifting Technique: Conditions and Limitation 被引量:5
9
作者 WANG Guang-Xiong LIU Yan-Wen HE Zhen 《自动化学报》 EI CSCD 北大核心 2006年第5期791-795,共5页
The initial motivation of the lifting technique is to solve the H∞control problems. However, the conventional weighted H∞design does not meet the conditions required by lifting, so the result often leads to a misjud... The initial motivation of the lifting technique is to solve the H∞control problems. However, the conventional weighted H∞design does not meet the conditions required by lifting, so the result often leads to a misjudgement of the design. Two conditions required by using the lifting technique are presented based on the basic formulae of the lifting. It is pointed out that only the H∞disturbance attenuation problem with no weighting functions can meet these conditions, hence, the application of the lifting technique is quite limited. 展开更多
关键词 Sampled-data control system lifting technique design limitation H∞synthesis
下载PDF
Limitation of fault-sealing and its control on hydrocarbon accumulation——An example from the Laoyemiao Oilfi eld of the Nanpu Sag 被引量:4
10
作者 Jiang Zhenxue Dong Yuexia +3 位作者 Li Hongyi Liu Luofu Liu Guangdi Li Xiaoying 《Petroleum Science》 SCIE CAS CSCD 2008年第4期295-301,共7页
Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a low... Based on previous studies on the internal structures of fault belts, the fault belts in the Laoyemiao Oilfield of the Nanpu Sag can be divided into three units, a crushed zone, an upper induced fracture zone and a lower induced fracture zone according to the log response characteristics. The upper induced fracture zone is characterized by the development of pervasive fractures and has a poor sealing or non-sealing capability. It therefore can act as pathways for hydrocarbon migration. The lower induced fracture zone consists of fewer fractures and has limited sealing capability. The crushed zone has a good sealing capability comparable to mudstone and can thus prevent lateral migration of fluid. Through physical modeling and comparing laboratory data with calculated data of oil column heights of traps sealed by faults, it is concluded that the fault-sealing capability for oil and gas is limited. When the oil column height reaches a threshold, oil will spill over from the top of reservoir along the lower induced fracture zone under the action of buoyancy, and the size of reservoir will remain unchanged. Analysis of the formation mechanisms of the fault-sealed reservoirs in the Nanpu Sag indicated that the charging sequence of oil and gas in the reservoir was from lower formation to upper formation, with the fault playing an important role in oil and gas accumulation. The hydrocarbon potential in reverse fault-sealed traps is much better than that in the consequent fault-sealed traps. The reverse fault-sealed traps are favorable and preferred exploration targets. 展开更多
关键词 limitation of fault-sealing fault belt oil column height hydrocarbon accumulation Nanpu Sag
下载PDF
Pancreatic neuroendocrine tumors: Therapeutic challenges and research limitations 被引量:4
11
作者 Gabriel Benyomo Mpilla Philip Agop Philip +1 位作者 Bassel El-Rayes Asfar Sohail Azmi 《World Journal of Gastroenterology》 SCIE CAS 2020年第28期4036-4054,共19页
Pancreatic neuroendocrine tumors(PNETs)are known to be the second most common epithelial malignancy of the pancreas.PNETs can be listed among the slowest growing as well as the fastest growing human cancers.The preval... Pancreatic neuroendocrine tumors(PNETs)are known to be the second most common epithelial malignancy of the pancreas.PNETs can be listed among the slowest growing as well as the fastest growing human cancers.The prevalence of PNETs is deceptively low;however,its incidence has significantly increased over the past decades.According to the American Cancer Society’s estimate,about 4032(>7%of all pancreatic malignancies)individuals will be diagnosed with PNETs in 2020.PNETs often cause severe morbidity due to excessive secretion of hormones(such as serotonin)and/or overall tumor mass.Patients can live for many years(except for those patients with poorly differentiated G3 neuroendocrine tumors);thus,the prevalence of the tumors that is the number of patients actually dealing with the disease at any given time is fairly high because the survival is much longer than pancreatic ductal adenocarcinoma.Due to significant heterogeneity,the management of PNETs is very complex and remains an unmet clinical challenge.In terms of research studies,modest improvements have been made over the past decades in the identification of potential oncogenic drivers in order to enhance the quality of life and increase survival for this growing population of patients.Unfortunately,the majority of systematic therapies approved for the management of advanced stage PNETs lack objective response or at most result in modest benefits in survival.In this review,we aim to discuss the broad challenges associated with the management and the study of PNETs. 展开更多
关键词 Pancreatic neuroendocrine tumors Gastroenteropancreatic neuroendocrine tumors Management limitation Novel Agents Emerging targets
下载PDF
Current Limitations and Challenges with Lactic Acid Bacteria: A Review 被引量:12
12
作者 Saeed A. Hayek Salam A. Ibrahim 《Food and Nutrition Sciences》 2013年第11期73-87,共15页
Lactic acid bacteria (LAB) play a critical role in food, agricultural, and clinical applications. The fast growing characteristics of LAB and their metabolic activity have been the key in most applications including f... Lactic acid bacteria (LAB) play a critical role in food, agricultural, and clinical applications. The fast growing characteristics of LAB and their metabolic activity have been the key in most applications including food production, agricultural industry, and probiotics. However, the biochemical and biophysical environments have significant effect on the growth and metabolic activity of LAB. While the biochemical conditions are most likely established, controlling and optimizing of biochemical conditions have many limitations and challenges. In addition to selecting the right strain, desirable metabolic processes required optimizing and controlling the available nutrients including sugars, peptides, free amino acids, minerals, and vitamins in addition to buffering agents. Thus, much of research was conducted to understand the impact of available nutrients on the growth and metabolic activities of LAB. However, only a few nutritional parameters could be controlled at a time while holding other parameters constant. The nutritional parameters may also interact with each other resulting in faulty results. Characteristics of LAB such as fastidiousness in their nutritional requirements, ability to produce acid and antimicrobial compounds, and variations in the nutritional requirements among strains have added additional limitations and challenges in this regard. Thus, chemically defined media (CDM) were suggested to deal with different limitations and challenges. However, due to differences in growth conditions, results obtained in CDM may face some obstacles when it comes to industrial applications. Thus, this paper aimed to review the recent data in regard to the role of the nutritional requirements of LAB in optimizing and controlling metabolic activities and to discuss the associated limitations and challenges. 展开更多
关键词 LACTIC Acid BACTERIA METABOLIC Activity NUTRITIONAL Requirements limitationS CHALLENGES
下载PDF
Limitations and potential design risks when applying empirically derived coal pillar strength equations to real-life mine stability problems 被引量:4
13
作者 Russell Frith Guy Reed 《International Journal of Mining Science and Technology》 EI CSCD 2019年第1期17-25,共9页
The method of determining coal pillar strength equations from databases of stable and failed case histories is more than 50 years old and has been applied in different countries by different researchers in a range of ... The method of determining coal pillar strength equations from databases of stable and failed case histories is more than 50 years old and has been applied in different countries by different researchers in a range of mining situations. While common wisdom sensibly limits the use of the resultant pillar strength equations and methods to design scenarios that are consistent with the founding database, there are a number of examples where failures have occurred as a direct result of applying empirical design methods to coal pillar design problems that are inconsistent with the founding database. This paper explores the reasons why empirically derived coal pillar strength equations tend to be problem-specific and should be considered as providing no more than a pillar strength ‘‘index." These include the non-consideration of overburden horizontal stress within the mine stability problem, an inadequate definition of supercritical overburden behavior as it applies to standing coal pillars, and the non-consideration of overburden displacement and coal pillar strain limits. All of which combine to potentially complicate and confuse the back-analysis of coal pillar strength from failed cases. A modified coal pillar design representation and model are presented based on coal pillars acting to reinforce a horizontally stressed overburden, rather than suspend an otherwise unstable self-loaded overburden or section, the latter having been at the core of historical empirical studies into coal pillar strength and stability. 展开更多
关键词 Coal PILLAR DESIGN PILLAR strength OVERBURDEN MECHANICS limitationS of PILLAR DESIGN
下载PDF
Towards hepatitis C virus elimination:Egyptian experience,achievements and limitations 被引量:2
14
作者 Dalia Omran Mohamed Alboraie +10 位作者 Rania A Zayed Mohamed-Naguib Wifi Mervat Naguib Mohamed Eltabbakh Mohamed Abdellah Ahmed Fouad Sherief Sahar Maklad Heba Hamdy Eldemellawy Omar Khalid Saad Doaa Mohamed Khamiss Mohamed El Kassas 《World Journal of Gastroenterology》 SCIE CAS 2018年第38期4330-4340,共11页
Worldwide, more than one million people die each year from hepatitis C virus(HCV) related diseases, and over 300 million people are chronically infected with hepatitis B or C. Egypt used to be on the top of the countr... Worldwide, more than one million people die each year from hepatitis C virus(HCV) related diseases, and over 300 million people are chronically infected with hepatitis B or C. Egypt used to be on the top of the countries with heavy HCV burden. Some countries are making advances in elimination of HCV, yet multiple factors preventing progress; remain for the majority. These factors include lack of global funding sources for treatment, late diagnosis, poor data, and inadequate screening. Treatment of HCV in Egypt has become one of the top national priorities since 2007. Egypt started a national treatment program intending to provide cure for Egyptian HCV-infected patients. Mass HCV treatment program had started using Pegylated interferon and ribavirin between 2007 and 2014. Yet, with the development of highly-effective direct acting antivirals(DAAs) for HCV, elimination of viral hepatitis has become a real possibility. The Egyptian National Committee for the Control of Viral Hepatitis did its best to provide Egyptian HCV patients with DAAs. Egypt adopted a strategy that represents a model of care that could help other countries with high HCV prevalence rate in their battle against HCV. This review covers the effects of HCV management in Egyptian real life settings and the outcome of different treatment protocols. Also, it deals with the current and future strategies for HCV prevention and screening as well as the challenges facing HCV elimination and the prospect of future eradication of HCV. 展开更多
关键词 Hepatitis C virus Egypt Direct ACTING ANTIVIRALS screening ELIMINATION limitationS
下载PDF
The Dosimetric Characteristics and Potential Limitation in Clinical Application of a Low Energy Photon Intra-Operative Radiotherapy System 被引量:2
15
作者 Zhenhua Xiao Ouyang Bin +2 位作者 Zhenyu Wang Botian Huang Bixiu Wen 《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 2015年第2期184-195,共12页
Purpose: To investigate the dosimetric characteristics of a low energy photon intra-operative radiotherapy (IORT) system and explore its potential limitation in clinical application. Methods: A special water phantom, ... Purpose: To investigate the dosimetric characteristics of a low energy photon intra-operative radiotherapy (IORT) system and explore its potential limitation in clinical application. Methods: A special water phantom, a parallel-plate ionization chamber and an electrometer were used to measure the depth dose rate, isotropy of dose distribution in X/Y plane, dosimetry reproducibility of bare probe and spherical applicators of different size which were used in comparison with the system data. Results: The difference in depth dose rate between the measurement and system data for bare probe is -2.16% ± 1.36%, the range of the relative deviation for isotropy in the X/Y plane is between -1.9% and 2.1%. The difference in depth dose rate, transfer coefficient, isotropy in X/Y plane between the measurement and system data for the whole set of spherical applicators is -10.0% - 2.3%, -8.9% - 4.2% and -1.6% - 2.6%, respectively. Higher surface dose rate and steeper gradient depth dose are observed in smaller spherical applicators. The depth dose rate and isotropy for bare probe and spherical applicators have been shown good reproducibility. The uncertainty of measurement is associated with the positioning accuracy, energy response, noise current and correction function f’(R). Conclusions: Thorough commissioning of the low energy photon IORT system helps us better understand the dosimetry characteristics, verify the system data, obtain adequate data for clinical application and routine quality assurance. The steep gradient depth dose and limited treatment range may restrain its potential in clinical application. 展开更多
关键词 INTRA-OPERATIVE RADIOTHERAPY Low Energy PHOTON Dosimetry ISOTROPY limitation
下载PDF
Effect of mass transfer limitations on catalyst performance during reduction and carburization of iron based Fischer-Tropsch synthesis catalysts 被引量:1
16
作者 Akbar Zamaniyan Yadollah Mortazavi +1 位作者 Abbas Ali Khodadadi Ali Nakhaei Pour 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2013年第5期795-803,共9页
Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously,but there is no suitable study on the existence of intraparticle diffusion limitations under pr... Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously,but there is no suitable study on the existence of intraparticle diffusion limitations under pretreatment steps (reduction and activation) and their effect on catalytic performance for iron based catalysts.In this study,Fe-Cu-La-SiO2 catalysts were prepared by co-precipitation method.To investigate the intraparticle mass transfer limitation under reduction,activation and reaction steps,and its effect on catalytic performance,catalyst pellets with different sizes of 6,3,1 and 0.5 mm have been prepared.All catalysts were calcined,pretreated and tested under similar conditions.The catalysts were activated in hydrogen (5%H2in N2) at 450℃ for 3 h and exposed to syngas (H2/CO=1) at 270℃ and atmospheric pressure for 40 h.Afterwards,FTS reaction tests were performed for approximately 120 h to reach steady state conditions at 290℃,17 bar and a feed flow (syngas H2/CO=1) rate of 3 L/h (STP).Using small pellets resulted in higher CO conversion,FT reaction rate and C5+ productivity as compared with larger pellets.The small pellets reached steady state conditions just 20 h after starting the reaction.Whereas for larger pellets,CO conversion,FT reaction rate and C5+ productivity increased gradually,and reached steady state and maximum values after 120 h of operation.The results illustrate that mass transfer limitations exist not only for FTS reaction but also for the reduction and carburization steps which lead to various phase formation through catalyst activation.Also the results indicate that some effects of mass transfer limitations in activation step,can be compensated in the reaction step.The results can be used for better design of iron based catalyst to improve the process economy. 展开更多
关键词 FISCHER-TROPSCH mass transfer limitation activation catalyst GTL
下载PDF
Phosphate limitation of phytoplankton growth in the Changjiang Estuary 被引量:5
17
作者 Hu Minghui, Yang Yiping, Xu Chunling and P. J. Harrison Oceanography Department of Xiamen University, Xiamen, ChinaSub-bureau of East China Sea, State Oceanic Administration, Shanghai, ChinaOceanography Department, U. B. C. , Canada 《Acta Oceanologica Sinica》 SCIE CAS CSCD 1990年第3期405-411,共7页
Laboratory experiments of bioassay with Pltaeodaetytum tricornutum, Chatoceros didymus, Chaetoreros calcitraus and Heterogtoea sp. sampled from the Changjiang Estuary in spring and summer, 1986, indicated that both N ... Laboratory experiments of bioassay with Pltaeodaetytum tricornutum, Chatoceros didymus, Chaetoreros calcitraus and Heterogtoea sp. sampled from the Changjiang Estuary in spring and summer, 1986, indicated that both N and P limit phytoplankton growth in the medium with N : P ranged between 8-30, and N limits phytoplankton production in the medium with N: P<8, while P is the limitary nutrient in the N : P>30. Generally, N : P in the Changjiang Estuary waters is 2 times higher than Redfield ratio. The bioassay experiments with high N : P water samples collected from Changjiang Estuary show that phytoplankton production is limited by P. Phytopiankton appears to give priority to the uptake of P at all periods of time. And the optimum N:P for phytoplankton growth is determined to be 18. 展开更多
关键词 Phosphate limitation of phytoplankton growth in the Changjiang Estuary
下载PDF
Responses of Lowland, Upland and Aerobic Rice Genotypes to Water Limitation During Different Phases 被引量:1
18
作者 Preethi VIJAYARAGHAVAREDDY YIN Xinyou +2 位作者 Paul CSTRUIK Udayakumar MAKARLA Sheshshayee SREEMAN 《Rice science》 SCIE CSCD 2020年第4期345-354,共10页
Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence.We exposed three contrasting rice genotypes,IR64,UPLRi7 and Apo(adapted to lowland,upla... Rice yield reduction due to water limitation depends on its severity and duration and on the phenological stage of its occurrence.We exposed three contrasting rice genotypes,IR64,UPLRi7 and Apo(adapted to lowland,upland and aerobic conditions,respectively),to three water regimes(puddle,100%and 60%field capacity)in pots during the vegetative(GSI),flowering(GSII)and grain filling(GSIII)stages.Stress at all the three stages significantly reduced yield especially in lowland genotype IR64.Effect of water limitation was more severe at GSII than at the other two stages.Stress at GSI stage reduced both source activity(leaf area and photosynthetic rate)and sink capacity(tiller number or panicle number per pot).When stress was imposed at GSII,spikelet fertility was most affected in all the three genotypes.In both GSII and GSIII,although leaf area was constant in all the three water regimes,estimated relative whole-plant photosynthesis was strongly associated with yield reduction.Reduced photosynthesis due to stress at any given stage was found to have direct impact on yield.Compared to the other genotypes,Apo had deeper roots and maintained a better water relation,thus,higher carbon gain and spikelet viability,and ultimately,higher biomass and productivity under water-limited conditions.Therefore,screening for these stage-dependent adaptive mechanisms is crucial in breeding for sustained rice production under water limitation. 展开更多
关键词 water limitation PHENOLOGY UPLAND aerobic Oryza sativa yield
下载PDF
The status,limitation and improvement of adoptive cellular immunotherapy in advanced urologic malignancies 被引量:1
19
作者 Haoqing Shi Xiangjie Qi +4 位作者 Bin Ma Yanwei Cao Lina Wang Lijiang Sun Haitao Niu 《Chinese Journal of Cancer Research》 SCIE CAS CSCD 2015年第2期128-137,共10页
In recent years, immunotherapy has been gradually established as the fourth frequently adopted antitumor therapy, following surgery, chemotherapy and radiotherapy, for advanced urologic malignancies with an improved u... In recent years, immunotherapy has been gradually established as the fourth frequently adopted antitumor therapy, following surgery, chemotherapy and radiotherapy, for advanced urologic malignancies with an improved understanding of theoretical basis, such as molecular biology and immunology. Thereinto, adoptive cellular immunotherapy (ACI) has become one of the hotspots, which comprises a variety of treatment approaches, such as TIL, CIK cell, ~'~ T cell, CAR-engineered T cell and Allogeneie stem cell transplantation (alloSCT). Although preclinical efficacy has been demonstrated remarkably, clinical trials could not consistently show the benefit due to multi-factors in complex immnnosuppressive microenvironment in vivo compared to that of in vitro. Here we review some timely aspects of ACI for advanced urologic malignancies, and describe the current status and limitation of immunotherapy from the cellular level. It's our expectation to provide prompting consideration of novel combinatorial ACI strategies and a resurgence of interest in ACI for advanced urologic malignancies. 展开更多
关键词 Adoptive cellular immunotherapy (ACI) limitation IMPROVEMENT urologic malignancies
下载PDF
Current self-limitation in a transverse nanosecond discharge with a slotted cathode 被引量:1
20
作者 N A ASHURBEKOV K O IMINOV +1 位作者 O A POPOV G S SHAKHSINOV 《Plasma Science and Technology》 SCIE EI CAS CSCD 2017年第3期69-74,共6页
A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy (few kV) ribbon electron beams. Conditions for the formation and extinction of electron bea... A high-voltage transverse pulsed nanosecond discharge with a slotted hollow cathode was found to be a source of high-energy (few kV) ribbon electron beams. Conditions for the formation and extinction of electron beams were experimentally studied in discharges in helium at pressures of 1-100 Torr. It was found that interaction of fast electrons with a non-uniform electric field near the slotted cathode led to limitation of the magnitude of the discharge current. A physical model was developed to describe the discharge current self-limitation that was in satisfactory agreement with the experimental results. Some technical solutions that are expected to increase the upper current limits in transverse nanosecond discharge are discussed. 展开更多
关键词 nanosecond discharge electron beams upper current limitation slotted cathode
下载PDF
上一页 1 2 134 下一页 到第
使用帮助 返回顶部