As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a n...As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a noticeable lack of research on automatic hydraulic tensioners. This study presents a comprehensive calculation approach for the principal parameters of a hydraulic automatic tensioner. An efective method, grounded in hydraulics and multibody dynamics, was introduced for estimating the dynamic response of such a tensioner. The simulation model developed for the hydraulic tensioner is characterized by its rapid dynamic response, consistent operation, and high accuracy. The dynamic behavior of the tensioner was analyzed under varying boundary conditions, using sinusoidal signal excitation. It was observed that the maximum damping force increases with a decreasing leakage gap. Conversely, an increase in oil temperature or air content leads to a decrease in the maximum damping force. The reaction forces derived from these calculations align well with experimental results. This calculation and simulation approach ofers considerable value for the design of innovative hydraulic tensioners. It not only streamlines the design phase, minimizes the number of trials, and reduces product costs, but also provides robust insights for evaluating the performance of hydraulic tensioners.展开更多
Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only syste...Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only system parameters, such as configuration, hazard rate, coverage, repair rate, etc. along with periodic proof-tests （or inspection）. Not considering demand rate will give a pessimistic safety estimate for an application with low demand rate such as nuclear power plants, chemical plants, etc. In this paper, a basic model of IEC 61508 is used. The basic model is extended to incorporate process demand and behavior of electronic- and/or computer-based system following diagnosis or proof-test. A new safety index, probability of failure on actual demand （PFAD） based on extended model and demand rate is proposed. Periodic proof-test makes the model semi-Markovian, so a piece-wise continuous time Markov chain （CTMC） based method is used to derive mean state probabilities of elementary or aggregated state. Method to determine probability of failure on demand （PFD） （IEC 61508） and PFAD based on these state probabilities are described. In example, safety indices of PFD and PFAD are compared.展开更多
A quantitative real time reverse-transcription polymerase chain reaction （qRT-PCR） assay with specific primers recommended by the World Health Organization （WHO） has been widely used successfully for detection and...A quantitative real time reverse-transcription polymerase chain reaction （qRT-PCR） assay with specific primers recommended by the World Health Organization （WHO） has been widely used successfully for detection and monitoring of the pandemic H1N1/2009 influenza A virus. In this study, we report the design and characterization of a novel set of primers to be used in a qRT-PCR assay for detecting the pandemic H1N1/2009 virus. The newly designed primers target three regions that are highly conserved among the hemagglutinin （HA） genes of the pandemic HlN1/2009 viruses and are different from those targeted by the WHO-recommended primers. The qRT-PCR assays with the newly designed primers are highly specific, and as specific as the WHO-recommended primers for detecting pandemic H1N1/2009 viruses and other influenza viruses including influenza B viruses and influenza A viruses of human, swine, and raccoon dog origin. Furthermore, the qRT-PCR assays with the newly designed primers appeared to be at least 10-fold more sensitive than those with the WHO-recommended primers as the detection limits of the assays with our primers and the WHO-recommended primers were 2.5 and 25 copies of target RNA per reaction, respectively. When tested with 83 clinical samples, 32 were detected to be positive using the qRT-PCR assays with our designed primers, while only 25 were positive by the assays with the WHO-recommended primers. These results suggest that the qRT-PCR system with the newly designed primers represent a highly sensitive assay for diagnosis of the pandemic HIN1/2009 virus infection.展开更多
This paper presents a simplified Markov model to evaluate the reliability of phased-mission system(PMS). The time cost and storage requirement are very huge for traditional Markov model to analyze the PMS reliability ...This paper presents a simplified Markov model to evaluate the reliability of phased-mission system(PMS). The time cost and storage requirement are very huge for traditional Markov model to analyze the PMS reliability as the number of components increases to a large scale. The states merging method proposed in this paper can account for the PMS with subsystems consisting of identical components, and similar PMSs are common in real-world systems. The simplified Markov model by states merging has smaller number of system states, compared with the traditional one. Furthermore, for the above subsystems, the size of our model increases only linearly as the number of components increases, while the size of the traditional model exponentially increases.Finally, the effectiveness and correctness of our approach are analyzed by comparing with the traditional Markov method.展开更多
As a payload support system deployed on satellites,the turntable system is often switched among different working modes during the on-orbit operation,which can experience great state changes.In each mode,the missions ...As a payload support system deployed on satellites,the turntable system is often switched among different working modes during the on-orbit operation,which can experience great state changes.In each mode,the missions to be completed are different,consecutive and non-over-lapping,from which the turntable system can be considered to be a phased-mission system(PMS).Reliability analysis for PMS has been widely studied.However,the system mode cycle characteristic has not been taken into account before.In this paper,reliability analysis method of the satellite turntable system is proposed considering its multiple operation modes and mode cycle characteristic.Firstly,the multi-valued decision diagrams(MDD)manipulation rules between two adjacent mission cycles are proposed.On this basis,MDD models for the turntable system in different states are established and the reliability is calculated using the continuous time Markov chains(CTMC)method.Finally,the comparative study is carried out to show the effectiveness of our proposed method.展开更多
This paper discusses the mathematical description of hybrid event systems, consisting of continuous, discrete, even logic-judgment and inference-decision event systems. The description takes events as its core, and in...This paper discusses the mathematical description of hybrid event systems, consisting of continuous, discrete, even logic-judgment and inference-decision event systems. The description takes events as its core, and information interconnection as its tie. In this paper, an event, instead of a process, is regarded as an analyzed element. The hybrid event systems are described in mathematical models with the following tools: chains of time, generalized space and interconnecting information.展开更多
Dynamically reconfigurable Field Programmable Gate Array(dr-FPGA) based electronic systems on board mission-critical systems are highly susceptible to radiation induced hazards that may lead to faults in the logic or ...Dynamically reconfigurable Field Programmable Gate Array(dr-FPGA) based electronic systems on board mission-critical systems are highly susceptible to radiation induced hazards that may lead to faults in the logic or in the configuration memory. The aim of our research is to characterize self-test and repair processes in Fault Tolerant(FT) dr-FPGA systems in the presence of environmental faults and explore their interrelationships. We develop a Continuous Time Markov Chain(CTMC) model that captures the high level fail-repair processes on a dr-FPGA with periodic online Built-In Self-Test(BIST) and scrubbing to detect and repair faults with minimum latency. Simulation results reveal that given an average fault interval of 36 s, an optimum self-test interval of 48.3 s drives the system to spend 13% of its time in self-tests, remain in safe working states for 76% of its time and face risky fault-prone states for only 7% of its time. Further, we demonstrate that a well-tuned repair strategy boosts overall system availability, minimizes the occurrence of unsafe states, and accommodates a larger range of fault rates within which the system availability remains stable within 10% of its maximum level.展开更多
To solve the inventory coordination model in a multi-stage, multi-customer supply chain, this paper first analyzes the third model （integer powers of two multipliers at each firm） studied by Moutaz Khouja （2003）, ...To solve the inventory coordination model in a multi-stage, multi-customer supply chain, this paper first analyzes the third model （integer powers of two multipliers at each firm） studied by Moutaz Khouja （2003）, and the authors take a numerical example to prove that the third model is irrational to miss feasible solution. Then this paper puts up a new improved model （integer multiplier at each firm）, and takes the example to prove it gives better results than the integer powers of two multipliers at each firm.展开更多
AIM:To detect the expression of tumor necrosis factor-a(TNF-a)in colorectal cancer(CRC)cells among Saudi patients,and correlate its expression with clinical stages of cancer.METHODS:Archival tissue specimens were coll...AIM:To detect the expression of tumor necrosis factor-a(TNF-a)in colorectal cancer(CRC)cells among Saudi patients,and correlate its expression with clinical stages of cancer.METHODS:Archival tissue specimens were collected from 30 patients with CRC who had undergone surgical intervention at King Khalid University Hospital.Patient demographic information,including age and gender,tumor sites,and histological type of CRC,was recorded.To measure TNF-a m RNA expression in CRC,total RNA was extracted from tumor formalin-fixed,paraffinembedded,and adjacent normal tissues.Reverse transcription and reverse transcription polymerase chain reaction were performed.Colorectal tissue microarrays were constructed to investigate the protein expression of TNF-a by immunohistochemistry.RESULTS:The relative expression of TNF-a m RNA in colorectal cancer was significantly higher than that seen in adjacent normal colorectal tissue.High TNF-a gene expression was associated with StageⅢandⅣneoplasms when compared with earlier tumor stages(P=0.004).Eighty-three percent of patients(25/30)showed strong TNF-a positive staining,while only 10%(n=3/30)of patients showed weak staining,and 7%(n=2/30)were negative.We showed the presence of elevated TNF-a gene expression in cancer cells,which strongly correlated with advanced stages of tumor.CONCLUSION:High levels of TNF-a expression could be an independent diagnostic indicator of colorectal cancer,and targeting TNF-a might be a promising prognostic tool by assessment of the clinical stages of CRC.展开更多
Hepatitis B virus(HBV)is one of the important global health problems today.Infection with HBV can lead to a variety of clinical manifestations including severe hepatic complications like liver cirrhosis and hepatocell...Hepatitis B virus(HBV)is one of the important global health problems today.Infection with HBV can lead to a variety of clinical manifestations including severe hepatic complications like liver cirrhosis and hepatocellular carcinoma.Presently,routine HBV screening and diagnosis is primarily based on the immuno-detection of HBV surface antigen(HBsAg).However,identification of HBV DNA positive cases,who do not have detectable HBsAg has greatly encouraged the use of nucleic acid amplification based assays,that are highly sensitive,specific and are to some extent tolerant to sequence variation.In the last few years,the field of HBV molecular diagnostics has evolved rapidly with advancements in the molecular biology tools,such as polymerase chain reaction(PCR)and real-time PCR.Recently,apart of PCR based amplification methods,a number of isothermal amplification assays,such as loop mediated isothermal amplification,transcription mediated amplification,ligase chain reaction,and rolling circle amplification have been utilized for HBV diag-nosis.These assays also offer options for real time detection and integration into biosensing devices.In this manuscript,we review the molecular technologies that are presently available for HBV diagnostics,with special emphasis on isothermal amplification based technologies.We have also included the recent trends in the development of biosensors and use of next generation sequencing technologies for HBV.展开更多
AIM:To investigate three isoforms of survivin in colorectal adenocarcinomas.METHODS:We used the LightCycler Technology(Roche),along with a common forward primer and reverse primers specific for the splice variants and...AIM:To investigate three isoforms of survivin in colorectal adenocarcinomas.METHODS:We used the LightCycler Technology(Roche),along with a common forward primer and reverse primers specific for the splice variants and two common hybridization probes labeled with fluorescein and LightCycler-Red fluorophore(LC-Red 640).Real time quantitative polymerase chain reaction(PCR) was performed on cDNAs from 52 tumor specimens from colorectal cancer patients and 10 unrelated normal colorectal tissues.In the patients group,carcinoembryonic antigen(CEA) and CA19-9 tumor markers were also measured immunochemically.RESULTS:Wild type survivin mRNA isoform was expressed in 48%of the 52 tumor samples,survivin-2b in 38%and survivin-ΔΕx3 in 29%,while no expression was found in normal tissues.The mRNA expression of wild type survivin presented a significant correlation with the expression of the ratio of survivin-2b,survivin-ΔΕx3,survivin-2b/wild type survivin and survivin-ΔΕx3/wild type survivin(P<0.001).The mRNA expression of wildsurvivin and survivin-ΔΕx3 was related with tumor size and invasion(P=0.006 and P<0.005,respectively).A significant difference was found between survivin-2b and morphologic cancer type.Also,the ratio of survivin-ΔEx3/ wild-survivin was significantly associated with prognosis.No association was observed between the three isoforms and grade,metastasis,Dukes stage and gender.The three isoforms were not correlated with CEA and CA19-9.CONCLUSION:Survivin isoforms may play a role in cell apoptosis and their quantification could provide information about clinical management of patients suffering from colorectal cancer.展开更多
Helicobacter pylori are ubiquitous Gram-negative bacteria with a high estimated level of infection in the world populations, but a majority of the infected persons are asymptomatic. This pathogen has been classified b...Helicobacter pylori are ubiquitous Gram-negative bacteria with a high estimated level of infection in the world populations, but a majority of the infected persons are asymptomatic. This pathogen has been classified by the World Health Organization as a class I carcinogen and recognized as the causal agent of most peptic ulcers and chronic gastritis that might lead to stomach cancer. Although not all the transmission pathways of these bacteria into humans have been propedy identified, enough data have suggested that the oral-oral or fecal-oral ones are the main infection routes. Helicobacterpylori have been detected in non-treated water and in drinking water, which suggested that water might be an important infection source. As childhood is the critical period of infection, the aim of the present work was to examine the presence of Helicobacterpylori in soil samples from public playing areas of Spanish parks.展开更多
BACKGROUND Connective tissue growth factor(CTGF)is a mediator of transforming growth factor-beta signaling and plays a key role in connective tissue remodeling,inflammatory processes and fibrosis in various illnesses ...BACKGROUND Connective tissue growth factor(CTGF)is a mediator of transforming growth factor-beta signaling and plays a key role in connective tissue remodeling,inflammatory processes and fibrosis in various illnesses including cancer.AIM To investigate the role of CTGF in colorectal cancer(CRC)progression and to compare the CTGF expression with different clinicopathological parameters.METHODS Real-time polymerase chain reaction,immunohistochemistry and Western blotting was performed to evaluate the CTGF expression and the results were statistically analyzed against the clinicopathological variables of patient data using STATA software version 16.RESULTS CTGF expression levels in tumor specimens were significantly higher than their paired normal specimens.The higher protein expression levels showed a significant association with smoking,staging,tumor grade,invasion depth,necrosis of tumor tissue,and both lymphovascular and perineural invasion.As per the cox regression model and classification tree analysis,tumor-nodemetastasis stage and perineural invasion were important predictors for CTGF expression and prognosis of CRC patients.Survival analysis indicated that CTGF overexpression was associated with poorer overall and disease-free survival.CONCLUSION Expression of CTGF was increased in CRC and was linked with poor overall and disease-free survival of CRC patients.These findings support prior observations and thus CTGF may be a possible prognostic marker in CRC.展开更多
In the field of model-based system assessment,mathematical models are used to interpret the system behaviors.However,the industrial systems in this intelligent era will be more manageable.Various management operations...In the field of model-based system assessment,mathematical models are used to interpret the system behaviors.However,the industrial systems in this intelligent era will be more manageable.Various management operations will be dynamically set,and the system will be no longer static as it is initially designed.Thus,the static model generated by the traditional model-based safety assessment(MBSA)approach cannot be used to accurately assess the dependability.There mainly exists three problems.Complex:huge and complex behaviors make the modeling to be trivial manual;Dynamic:though there are thousands of states and transitions,the previous model must be resubmitted to assess whenever new management arrives;Unreusable:as for different systems,the model must be resubmitted by reconsidering both the management and the system itself at the same time though the management is the same.Motivated by solving the above problems,this research studies a formal management specifying approach with the advantages of agility modeling,dynamic modeling,and specification design that can be re-suable.Finally,three typical managements are specified in a series-parallel system as a demonstration to show the potential.展开更多
Cellular Automaton （CA） based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain （DTMC） analytical framewo...Cellular Automaton （CA） based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain （DTMC） analytical framework for a Nagel-Schreckenberg and Fukui Ishibashi combined CA model （W^2H traffic flow model） from microscopic point of view to capture the macroscopic steady state speed distributions. The inter-vehicle spacing Maxkov chain and the steady state speed Markov chain are proved to be irreducible and ergodic. The theoretical speed probability distributions depending on the traffic density and stochastic delay probability are in good accordance with numerical simulations. The derived fundamental diagram of the average speed from theoretical speed distributions is equivalent to the results in the previous work.展开更多
One of the main characteristics of Ad hoc networks is node mobility, which results in constantly changing in network topologies. Consequently, the ability to forecast the future status of mobility nodes plays a key ro...One of the main characteristics of Ad hoc networks is node mobility, which results in constantly changing in network topologies. Consequently, the ability to forecast the future status of mobility nodes plays a key role in QOS routing. We propose a random mobility model based on discretetime Markov chain, called ODM. ODM provides a mathematical framework for calculating some parameters to show the future status of mobility nodes, for instance, the state transition probability matrix of nodes, the probability that an edge is valid, the average number of valid-edges and the probability of a request packet found a valid route. Furthermore, ODM can account for obstacle environment. The state transition probability matrix of nodes can quantify the impact of obstacles. Several theorems are given and proved by using the ODM. Simulation results show that the calculated value can forecast the future status of mobility nodes.展开更多
We propose a probabilistic approach to modelling the propagation of the coronavirus disease 2019 (COVID-19) in Madagascar, with all its specificities. With the strategy of the Malagasy state, which consists of isolati...We propose a probabilistic approach to modelling the propagation of the coronavirus disease 2019 (COVID-19) in Madagascar, with all its specificities. With the strategy of the Malagasy state, which consists of isolating all suspected cases and hospitalized confirmed case, we get an epidemic model with seven compartments: susceptible (S), Exposed (E), Infected (I), Asymptomatic (A), Hospitalized (H), Cured (C) and Death (D). In addition to the classical deterministic models used in epidemiology, the stochastic model offers a natural representation of the evolution of the COVID-19 epidemic. We inferred <span><span style="font-family:Verdana;">the models with the official data provided by the COVID-19 Command Center (CCO) of Madagascar, between March and August 2020. The basic reproduction number <i></i></span><i><i><span style="font-family:Verdana;">R<sub></sub></span></i></i></span><i><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;"><sub>0</sub></span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;"></span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"></span></span></span></i> and the other parameters were estimated with a Bayesian approach. We developed an algorithm that allows having a temporal estimate of this number with confidence intervals. The estimated values are slightly lower than the international references. Generally, we were able to obtain a simple but effective model to describe the spread of the disease.展开更多
A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the...A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the birth and death process. Through the Kolmogorov forward equation and the theory of moment generating function, the corresponding population expectations are studied. The theoretical result of the stochastic model and deterministic version is also given. Finally, numerical simulations are carried out to substantiate the theoretical results of random walk.展开更多
Demand forecasting and big data analytics in supply chain management are gaining interest.This is attributed to the wide range of big data analytics in supply chain management,in addition to demand forecasting,and beh...Demand forecasting and big data analytics in supply chain management are gaining interest.This is attributed to the wide range of big data analytics in supply chain management,in addition to demand forecasting,and behavioral analysis.In this article,we studied the application of big data analytics forecasting in supply chain demand forecasting in the automotive parts industry to propose classifications of these applications,identify gaps,and provide ideas for future research.Algorithms will then be classified and then applied in supply chain management such as neural networks,k-nearest neighbors,time series forecasting,clustering,regression analysis,support vector regression and support vector machines.An extensive hierarchical model for short-term auto parts demand assess-ment was employed to avoid the shortcomings of the earlier models and to close the gap that regarded mainly a single time series.The concept of extensive relevance assessment was proposed,and subsequently methods to reflect the relevance of automotive demand factors were discussed.Using a wide range of skills,the factors and co-factors are expressed in the form of a correlation characteristic matrix to ensure the degree of influence of each factor on the demand for automotive components.Then,it is compared with the existing data and predicted the short-term historical data.The result proved the predictive error is less than 6%,which supports the validity of the prediction method.This research offers the basis for the macroeconomic regulation of the government and the production of auto parts manufacturers.展开更多
Given the overlapping endemic regions and clinical similarities between severe fever with thrombocytopenia syndrome(SFTS)and hemorrhagic fever with renal syndrome(HFRS),we developed a dual real-time fluorescence-based...Given the overlapping endemic regions and clinical similarities between severe fever with thrombocytopenia syndrome(SFTS)and hemorrhagic fever with renal syndrome(HFRS),we developed a dual real-time fluorescence-based reverse transcription quantitative polymerase chain reaction(RT-qPCR)method.Recombinant plasmids and synthetic ribonucleic acid(RNA)were constructed to evaluate the specificity,sensitivity and reproducibility of the assay.Additionally,we assessed the specificity of the assay using samples from three distinct groups:individuals with confirmed severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection(n=10),influenza A-positive individuals(n=10),and healthy controls.Receiver operating characteristic(ROC)curves were used to assess diagnostic accuracy,while the Kappa coefficient and linear regression analysis were employed to evaluate clinical applicability.Our method exhibited specificity for both SFTSV and Hantaan virus detection,with detection limits of 333 and 1,022 copies/mL using plasmids,and 1,247 and 898 copies/mL using synthetic RNA,respectively.We evaluated 100 clinical samples from each of SFTS and HFRS.The Kappa coefficients for both diseases were 0.96.The areas under the ROC curves were 0.991(P<0.001)and 0.989(P<0.001),respectively.The linear regression equations were as follows:log(y)=0.19+0.99 log(x)(R^(2)=0.95)for SFTS virus,and log(y)=0.01+0.65 log(x)(R^(2)=0.92)for Hantaan virus.We established an in-house RT-qPCR method for the rapid quantification of both pathogens,making it an ideal tool for early clinical differentiation.展开更多
文摘As a fundamental component of an automobile engine’s timing chain drive system, the hydraulic automatic tensioner signifcantly enhances fuel economy while minimizing system vibrations and noise. However, there is a noticeable lack of research on automatic hydraulic tensioners. This study presents a comprehensive calculation approach for the principal parameters of a hydraulic automatic tensioner. An efective method, grounded in hydraulics and multibody dynamics, was introduced for estimating the dynamic response of such a tensioner. The simulation model developed for the hydraulic tensioner is characterized by its rapid dynamic response, consistent operation, and high accuracy. The dynamic behavior of the tensioner was analyzed under varying boundary conditions, using sinusoidal signal excitation. It was observed that the maximum damping force increases with a decreasing leakage gap. Conversely, an increase in oil temperature or air content leads to a decrease in the maximum damping force. The reaction forces derived from these calculations align well with experimental results. This calculation and simulation approach ofers considerable value for the design of innovative hydraulic tensioners. It not only streamlines the design phase, minimizes the number of trials, and reduces product costs, but also provides robust insights for evaluating the performance of hydraulic tensioners.
文摘Quantitative safety assessment of safety systems plays an important role in decision making at all stages of system lifecycle, i.e., design, deployment and phase out. Most safety assessment methods consider only system parameters, such as configuration, hazard rate, coverage, repair rate, etc. along with periodic proof-tests （or inspection）. Not considering demand rate will give a pessimistic safety estimate for an application with low demand rate such as nuclear power plants, chemical plants, etc. In this paper, a basic model of IEC 61508 is used. The basic model is extended to incorporate process demand and behavior of electronic- and/or computer-based system following diagnosis or proof-test. A new safety index, probability of failure on actual demand （PFAD） based on extended model and demand rate is proposed. Periodic proof-test makes the model semi-Markovian, so a piece-wise continuous time Markov chain （CTMC） based method is used to derive mean state probabilities of elementary or aggregated state. Method to determine probability of failure on demand （PFD） （IEC 61508） and PFAD based on these state probabilities are described. In example, safety indices of PFD and PFAD are compared.
基金supported by grants from National Basic Research Program of China (No.2011CB504800)National Natural Science Foundation of China (No. 31100128 and 81030031)+3 种基金National Mega Project on Major Drug Development (2009ZX09103-678)National Small Business Innovation and Research (SBIR) Program of Chinathe Technology R & D Program of Jiangsu Province, China (BG20077035 and BG2008662)NIH (RO1-AI041927,RO1-AI050468, RO1-DE014145, and RO1-DE014842)
文摘A quantitative real time reverse-transcription polymerase chain reaction （qRT-PCR） assay with specific primers recommended by the World Health Organization （WHO） has been widely used successfully for detection and monitoring of the pandemic H1N1/2009 influenza A virus. In this study, we report the design and characterization of a novel set of primers to be used in a qRT-PCR assay for detecting the pandemic H1N1/2009 virus. The newly designed primers target three regions that are highly conserved among the hemagglutinin （HA） genes of the pandemic HlN1/2009 viruses and are different from those targeted by the WHO-recommended primers. The qRT-PCR assays with the newly designed primers are highly specific, and as specific as the WHO-recommended primers for detecting pandemic H1N1/2009 viruses and other influenza viruses including influenza B viruses and influenza A viruses of human, swine, and raccoon dog origin. Furthermore, the qRT-PCR assays with the newly designed primers appeared to be at least 10-fold more sensitive than those with the WHO-recommended primers as the detection limits of the assays with our primers and the WHO-recommended primers were 2.5 and 25 copies of target RNA per reaction, respectively. When tested with 83 clinical samples, 32 were detected to be positive using the qRT-PCR assays with our designed primers, while only 25 were positive by the assays with the WHO-recommended primers. These results suggest that the qRT-PCR system with the newly designed primers represent a highly sensitive assay for diagnosis of the pandemic HIN1/2009 virus infection.
基金the National Natural Science Foundation of China(No.71401172)
文摘This paper presents a simplified Markov model to evaluate the reliability of phased-mission system(PMS). The time cost and storage requirement are very huge for traditional Markov model to analyze the PMS reliability as the number of components increases to a large scale. The states merging method proposed in this paper can account for the PMS with subsystems consisting of identical components, and similar PMSs are common in real-world systems. The simplified Markov model by states merging has smaller number of system states, compared with the traditional one. Furthermore, for the above subsystems, the size of our model increases only linearly as the number of components increases, while the size of the traditional model exponentially increases.Finally, the effectiveness and correctness of our approach are analyzed by comparing with the traditional Markov method.
基金co-supported by the Natural Science Foundation of China(No.61833016)the Shaanxi Out-standing Youth Science Foundation(No.2020JC-34)+1 种基金the Shaanxi Science and Technology Innovation Team(No.2022TD-24)the Natural Science Foundation of Heilongjiang Province of China(No.LH2021F038).
文摘As a payload support system deployed on satellites,the turntable system is often switched among different working modes during the on-orbit operation,which can experience great state changes.In each mode,the missions to be completed are different,consecutive and non-over-lapping,from which the turntable system can be considered to be a phased-mission system(PMS).Reliability analysis for PMS has been widely studied.However,the system mode cycle characteristic has not been taken into account before.In this paper,reliability analysis method of the satellite turntable system is proposed considering its multiple operation modes and mode cycle characteristic.Firstly,the multi-valued decision diagrams(MDD)manipulation rules between two adjacent mission cycles are proposed.On this basis,MDD models for the turntable system in different states are established and the reliability is calculated using the continuous time Markov chains(CTMC)method.Finally,the comparative study is carried out to show the effectiveness of our proposed method.
文摘This paper discusses the mathematical description of hybrid event systems, consisting of continuous, discrete, even logic-judgment and inference-decision event systems. The description takes events as its core, and information interconnection as its tie. In this paper, an event, instead of a process, is regarded as an analyzed element. The hybrid event systems are described in mathematical models with the following tools: chains of time, generalized space and interconnecting information.
文摘Dynamically reconfigurable Field Programmable Gate Array(dr-FPGA) based electronic systems on board mission-critical systems are highly susceptible to radiation induced hazards that may lead to faults in the logic or in the configuration memory. The aim of our research is to characterize self-test and repair processes in Fault Tolerant(FT) dr-FPGA systems in the presence of environmental faults and explore their interrelationships. We develop a Continuous Time Markov Chain(CTMC) model that captures the high level fail-repair processes on a dr-FPGA with periodic online Built-In Self-Test(BIST) and scrubbing to detect and repair faults with minimum latency. Simulation results reveal that given an average fault interval of 36 s, an optimum self-test interval of 48.3 s drives the system to spend 13% of its time in self-tests, remain in safe working states for 76% of its time and face risky fault-prone states for only 7% of its time. Further, we demonstrate that a well-tuned repair strategy boosts overall system availability, minimizes the occurrence of unsafe states, and accommodates a larger range of fault rates within which the system availability remains stable within 10% of its maximum level.
文摘To solve the inventory coordination model in a multi-stage, multi-customer supply chain, this paper first analyzes the third model （integer powers of two multipliers at each firm） studied by Moutaz Khouja （2003）, and the authors take a numerical example to prove that the third model is irrational to miss feasible solution. Then this paper puts up a new improved model （integer multiplier at each firm）, and takes the example to prove it gives better results than the integer powers of two multipliers at each firm.
文摘AIM:To detect the expression of tumor necrosis factor-a(TNF-a)in colorectal cancer(CRC)cells among Saudi patients,and correlate its expression with clinical stages of cancer.METHODS:Archival tissue specimens were collected from 30 patients with CRC who had undergone surgical intervention at King Khalid University Hospital.Patient demographic information,including age and gender,tumor sites,and histological type of CRC,was recorded.To measure TNF-a m RNA expression in CRC,total RNA was extracted from tumor formalin-fixed,paraffinembedded,and adjacent normal tissues.Reverse transcription and reverse transcription polymerase chain reaction were performed.Colorectal tissue microarrays were constructed to investigate the protein expression of TNF-a by immunohistochemistry.RESULTS:The relative expression of TNF-a m RNA in colorectal cancer was significantly higher than that seen in adjacent normal colorectal tissue.High TNF-a gene expression was associated with StageⅢandⅣneoplasms when compared with earlier tumor stages(P=0.004).Eighty-three percent of patients(25/30)showed strong TNF-a positive staining,while only 10%(n=3/30)of patients showed weak staining,and 7%(n=2/30)were negative.We showed the presence of elevated TNF-a gene expression in cancer cells,which strongly correlated with advanced stages of tumor.CONCLUSION:High levels of TNF-a expression could be an independent diagnostic indicator of colorectal cancer,and targeting TNF-a might be a promising prognostic tool by assessment of the clinical stages of CRC.
基金Supported by Defence Research and Development Organization,Ministry of Defence,Government of India
文摘Hepatitis B virus(HBV)is one of the important global health problems today.Infection with HBV can lead to a variety of clinical manifestations including severe hepatic complications like liver cirrhosis and hepatocellular carcinoma.Presently,routine HBV screening and diagnosis is primarily based on the immuno-detection of HBV surface antigen(HBsAg).However,identification of HBV DNA positive cases,who do not have detectable HBsAg has greatly encouraged the use of nucleic acid amplification based assays,that are highly sensitive,specific and are to some extent tolerant to sequence variation.In the last few years,the field of HBV molecular diagnostics has evolved rapidly with advancements in the molecular biology tools,such as polymerase chain reaction(PCR)and real-time PCR.Recently,apart of PCR based amplification methods,a number of isothermal amplification assays,such as loop mediated isothermal amplification,transcription mediated amplification,ligase chain reaction,and rolling circle amplification have been utilized for HBV diag-nosis.These assays also offer options for real time detection and integration into biosensing devices.In this manuscript,we review the molecular technologies that are presently available for HBV diagnostics,with special emphasis on isothermal amplification based technologies.We have also included the recent trends in the development of biosensors and use of next generation sequencing technologies for HBV.
文摘AIM:To investigate three isoforms of survivin in colorectal adenocarcinomas.METHODS:We used the LightCycler Technology(Roche),along with a common forward primer and reverse primers specific for the splice variants and two common hybridization probes labeled with fluorescein and LightCycler-Red fluorophore(LC-Red 640).Real time quantitative polymerase chain reaction(PCR) was performed on cDNAs from 52 tumor specimens from colorectal cancer patients and 10 unrelated normal colorectal tissues.In the patients group,carcinoembryonic antigen(CEA) and CA19-9 tumor markers were also measured immunochemically.RESULTS:Wild type survivin mRNA isoform was expressed in 48%of the 52 tumor samples,survivin-2b in 38%and survivin-ΔΕx3 in 29%,while no expression was found in normal tissues.The mRNA expression of wild type survivin presented a significant correlation with the expression of the ratio of survivin-2b,survivin-ΔΕx3,survivin-2b/wild type survivin and survivin-ΔΕx3/wild type survivin(P<0.001).The mRNA expression of wildsurvivin and survivin-ΔΕx3 was related with tumor size and invasion(P=0.006 and P<0.005,respectively).A significant difference was found between survivin-2b and morphologic cancer type.Also,the ratio of survivin-ΔEx3/ wild-survivin was significantly associated with prognosis.No association was observed between the three isoforms and grade,metastasis,Dukes stage and gender.The three isoforms were not correlated with CEA and CA19-9.CONCLUSION:Survivin isoforms may play a role in cell apoptosis and their quantification could provide information about clinical management of patients suffering from colorectal cancer.
基金supported by the Ministry of Education and Science of Spain(No.CTM2005-106457-C05-05/TECNO),FPI grant from Ministry of Education and Science of Spain,and FI grant from the Comissionat per a Universitats i Recerca del Departament d'Innovació,Universitats i Empresa de la Generalitat de Catalunya i del Fons Social Europeu
文摘Helicobacter pylori are ubiquitous Gram-negative bacteria with a high estimated level of infection in the world populations, but a majority of the infected persons are asymptomatic. This pathogen has been classified by the World Health Organization as a class I carcinogen and recognized as the causal agent of most peptic ulcers and chronic gastritis that might lead to stomach cancer. Although not all the transmission pathways of these bacteria into humans have been propedy identified, enough data have suggested that the oral-oral or fecal-oral ones are the main infection routes. Helicobacterpylori have been detected in non-treated water and in drinking water, which suggested that water might be an important infection source. As childhood is the critical period of infection, the aim of the present work was to examine the presence of Helicobacterpylori in soil samples from public playing areas of Spanish parks.
基金Supported by Sher-I-Kashmir Institute of Medical Sciences,Srinagar Kashmir,India,No.SIMS/DF/17-467-73.
文摘BACKGROUND Connective tissue growth factor(CTGF)is a mediator of transforming growth factor-beta signaling and plays a key role in connective tissue remodeling,inflammatory processes and fibrosis in various illnesses including cancer.AIM To investigate the role of CTGF in colorectal cancer(CRC)progression and to compare the CTGF expression with different clinicopathological parameters.METHODS Real-time polymerase chain reaction,immunohistochemistry and Western blotting was performed to evaluate the CTGF expression and the results were statistically analyzed against the clinicopathological variables of patient data using STATA software version 16.RESULTS CTGF expression levels in tumor specimens were significantly higher than their paired normal specimens.The higher protein expression levels showed a significant association with smoking,staging,tumor grade,invasion depth,necrosis of tumor tissue,and both lymphovascular and perineural invasion.As per the cox regression model and classification tree analysis,tumor-nodemetastasis stage and perineural invasion were important predictors for CTGF expression and prognosis of CRC patients.Survival analysis indicated that CTGF overexpression was associated with poorer overall and disease-free survival.CONCLUSION Expression of CTGF was increased in CRC and was linked with poor overall and disease-free survival of CRC patients.These findings support prior observations and thus CTGF may be a possible prognostic marker in CRC.
基金the National Natural Science Foundation of China(52105070,U21B2074)Department of Science and Technology of Liaoning Province China(2033JH1/10400007).
文摘In the field of model-based system assessment,mathematical models are used to interpret the system behaviors.However,the industrial systems in this intelligent era will be more manageable.Various management operations will be dynamically set,and the system will be no longer static as it is initially designed.Thus,the static model generated by the traditional model-based safety assessment(MBSA)approach cannot be used to accurately assess the dependability.There mainly exists three problems.Complex:huge and complex behaviors make the modeling to be trivial manual;Dynamic:though there are thousands of states and transitions,the previous model must be resubmitted to assess whenever new management arrives;Unreusable:as for different systems,the model must be resubmitted by reconsidering both the management and the system itself at the same time though the management is the same.Motivated by solving the above problems,this research studies a formal management specifying approach with the advantages of agility modeling,dynamic modeling,and specification design that can be re-suable.Finally,three typical managements are specified in a series-parallel system as a demonstration to show the potential.
基金supported by the National Basic Research Program of China (Grant No 2007CB310800)the National Natural Science Foundation of China (Grant Nos 60772150 and 60703018)the National High Technology Research and Development Program of China (Grant No 2008AA01Z208)
文摘Cellular Automaton （CA） based traffic flow models have been extensively studied due to their effectiveness and simplicity in recent years. This paper develops a discrete time Markov chain （DTMC） analytical framework for a Nagel-Schreckenberg and Fukui Ishibashi combined CA model （W^2H traffic flow model） from microscopic point of view to capture the macroscopic steady state speed distributions. The inter-vehicle spacing Maxkov chain and the steady state speed Markov chain are proved to be irreducible and ergodic. The theoretical speed probability distributions depending on the traffic density and stochastic delay probability are in good accordance with numerical simulations. The derived fundamental diagram of the average speed from theoretical speed distributions is equivalent to the results in the previous work.
基金Acknowledgements This work is supported by the Postdoctoral Science Foundation of China under Grant No.20080431142.
文摘One of the main characteristics of Ad hoc networks is node mobility, which results in constantly changing in network topologies. Consequently, the ability to forecast the future status of mobility nodes plays a key role in QOS routing. We propose a random mobility model based on discretetime Markov chain, called ODM. ODM provides a mathematical framework for calculating some parameters to show the future status of mobility nodes, for instance, the state transition probability matrix of nodes, the probability that an edge is valid, the average number of valid-edges and the probability of a request packet found a valid route. Furthermore, ODM can account for obstacle environment. The state transition probability matrix of nodes can quantify the impact of obstacles. Several theorems are given and proved by using the ODM. Simulation results show that the calculated value can forecast the future status of mobility nodes.
文摘We propose a probabilistic approach to modelling the propagation of the coronavirus disease 2019 (COVID-19) in Madagascar, with all its specificities. With the strategy of the Malagasy state, which consists of isolating all suspected cases and hospitalized confirmed case, we get an epidemic model with seven compartments: susceptible (S), Exposed (E), Infected (I), Asymptomatic (A), Hospitalized (H), Cured (C) and Death (D). In addition to the classical deterministic models used in epidemiology, the stochastic model offers a natural representation of the evolution of the COVID-19 epidemic. We inferred <span><span style="font-family:Verdana;">the models with the official data provided by the COVID-19 Command Center (CCO) of Madagascar, between March and August 2020. The basic reproduction number <i></i></span><i><i><span style="font-family:Verdana;">R<sub></sub></span></i></i></span><i><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;"><sub>0</sub></span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><i><span style="font-family:Verdana;"></span></i></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;"></span></span></span></i> and the other parameters were estimated with a Bayesian approach. We developed an algorithm that allows having a temporal estimate of this number with confidence intervals. The estimated values are slightly lower than the international references. Generally, we were able to obtain a simple but effective model to describe the spread of the disease.
文摘A new stochastic epidemic model, that is, a general continuous time birth and death chain model, is formulated based on a deterministic model including vaccination. We use continuous time Markov chain to construct the birth and death process. Through the Kolmogorov forward equation and the theory of moment generating function, the corresponding population expectations are studied. The theoretical result of the stochastic model and deterministic version is also given. Finally, numerical simulations are carried out to substantiate the theoretical results of random walk.
文摘Demand forecasting and big data analytics in supply chain management are gaining interest.This is attributed to the wide range of big data analytics in supply chain management,in addition to demand forecasting,and behavioral analysis.In this article,we studied the application of big data analytics forecasting in supply chain demand forecasting in the automotive parts industry to propose classifications of these applications,identify gaps,and provide ideas for future research.Algorithms will then be classified and then applied in supply chain management such as neural networks,k-nearest neighbors,time series forecasting,clustering,regression analysis,support vector regression and support vector machines.An extensive hierarchical model for short-term auto parts demand assess-ment was employed to avoid the shortcomings of the earlier models and to close the gap that regarded mainly a single time series.The concept of extensive relevance assessment was proposed,and subsequently methods to reflect the relevance of automotive demand factors were discussed.Using a wide range of skills,the factors and co-factors are expressed in the form of a correlation characteristic matrix to ensure the degree of influence of each factor on the demand for automotive components.Then,it is compared with the existing data and predicted the short-term historical data.The result proved the predictive error is less than 6%,which supports the validity of the prediction method.This research offers the basis for the macroeconomic regulation of the government and the production of auto parts manufacturers.
基金supported by the National Key R&D Program of China(2022YFF1203201)National Natural Science Foundation of China(82072295)Beijing Research Center for Respiratory Infectious Diseases Project(BJRID2024-009).
文摘Given the overlapping endemic regions and clinical similarities between severe fever with thrombocytopenia syndrome(SFTS)and hemorrhagic fever with renal syndrome(HFRS),we developed a dual real-time fluorescence-based reverse transcription quantitative polymerase chain reaction(RT-qPCR)method.Recombinant plasmids and synthetic ribonucleic acid(RNA)were constructed to evaluate the specificity,sensitivity and reproducibility of the assay.Additionally,we assessed the specificity of the assay using samples from three distinct groups:individuals with confirmed severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection(n=10),influenza A-positive individuals(n=10),and healthy controls.Receiver operating characteristic(ROC)curves were used to assess diagnostic accuracy,while the Kappa coefficient and linear regression analysis were employed to evaluate clinical applicability.Our method exhibited specificity for both SFTSV and Hantaan virus detection,with detection limits of 333 and 1,022 copies/mL using plasmids,and 1,247 and 898 copies/mL using synthetic RNA,respectively.We evaluated 100 clinical samples from each of SFTS and HFRS.The Kappa coefficients for both diseases were 0.96.The areas under the ROC curves were 0.991(P<0.001)and 0.989(P<0.001),respectively.The linear regression equations were as follows:log(y)=0.19+0.99 log(x)(R^(2)=0.95)for SFTS virus,and log(y)=0.01+0.65 log(x)(R^(2)=0.92)for Hantaan virus.We established an in-house RT-qPCR method for the rapid quantification of both pathogens,making it an ideal tool for early clinical differentiation.
