The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration...The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca（HzPO4）2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient （Kn） increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg（OH）z＇MgCIz＇8H20 in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.展开更多
Aiming at measurement of granularity size of nonmetal grain, an algorithm of image segmentation and parameter calculation for microscopic overlapping grain image was studied. This algorithm presents some new attribute...Aiming at measurement of granularity size of nonmetal grain, an algorithm of image segmentation and parameter calculation for microscopic overlapping grain image was studied. This algorithm presents some new attributes of graph sequence from discrete attribute of graph,and consequently achieves the geometrical characteristics from input graph, and the new graph sequence in favor of image segmentation is recombined. The conception that image edge denoted with “twin-point” is put forward, base on geometrical characters of point, image edge is transformed into serial edge, and on recombined serial image edge, based on direction vector definition of line and some additional restricted conditions, the segmentation twin-points are searched with, thus image segmentation is accomplished. Serial image edge is transformed into twin-point pattern, to realize calculation of area and granularity size of nonmetal grain. The inkling and uncertainty on selection of structure element which base on mathematical morphology are avoided in this algorithm, and image segmentation and parameter calculation are realized without changing grain’s self statistical characters.展开更多
Income inequality among farmers living in different regions was an important form of territorial inequalities. Studying the territorial inequality of the net income per peasant was an emphasis of this paper, and Shand...Income inequality among farmers living in different regions was an important form of territorial inequalities. Studying the territorial inequality of the net income per peasant was an emphasis of this paper, and Shandong Province was pointed as the case study region. By the help of logistic regression, it could be found that the special distribution of the net income per peasant in Shandong Province was affected by three factors： distance to No.308 National Highway, distance to the coastline in the east of Shandong Province, and urbanization rates. Based on the decomposition of Gini index, the net income per peasant was divided into four parts, and it was found that the income from family business and salary were the two major sources of income. As to the mechanism for income inequality, it was proved that urbanization was still the key factor. In order to reduce income inequality, the local governments should promote urbanization through improving road networks, such as building highways, which could connect rural areas with the major nodes such as big cities and the port cities in the east.展开更多
Mobile ad hoc networking （MANET） has become an exciting and important technology in recent years, because of the rapid proliferation of wireless devices. Mobile ad hoc networks is highly vulnerable to attacks due to...Mobile ad hoc networking （MANET） has become an exciting and important technology in recent years, because of the rapid proliferation of wireless devices. Mobile ad hoc networks is highly vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, and lack of centralized monitoring and management point. The traditional way of protecting networks with firewalls and encryption software is no longer sufficient and effective for those features. A distributed intrusion detection approach based on timed automata is given. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then the timed automata is constructed by the way of manually abstracting the correct behaviours of the node according to the routing protocol of dynamic source routing （DSR）. The monitor nodes can verify the behaviour of every nodes by timed automata, and validly detect real-time attacks without signatures of intrusion or trained data. Compared with the architecture where each node is its own IDS agent, the approach is much more efficient while maintaining the same level of effectiveness. Finally, the intrusion detection method is evaluated through simulation experiments.展开更多
The nature of adhoc networks makes them vulnerable to security attacks. Many security technologies such as intrusion prevention and intrusion detection are passive in response to intrusions in that their countermea- s...The nature of adhoc networks makes them vulnerable to security attacks. Many security technologies such as intrusion prevention and intrusion detection are passive in response to intrusions in that their countermea- sures are only to protect the networks, and there is no automated network-wide counteraction against detected intrusions, the architecture of cooperation intrusion response based multi-agent is propose. The architecture is composed of mobile agents. Monitor agent resides on every node and monitors its neighbor nodes. Decision agent collects information from monitor nodes and detects an intrusion by security policies. When an intruder is found in the architecture, the block agents will get to the neighbor nodes of the intruder and form the mobile firewall to isolate the intruder. In the end, we evaluate it by simulation.展开更多
Time synchronization is a critical middleware service of wireless sensor networks. Researchers have already proposed some time synchronization algorithms. However, due to the demands for various synchronization precis...Time synchronization is a critical middleware service of wireless sensor networks. Researchers have already proposed some time synchronization algorithms. However, due to the demands for various synchronization precision, existing time synchronization algorithms often need to be adapted. So it is necessary to evaluate these adapted algorithms before use. Software simulation is a valid and quick way to do it. In this paper, we present a time synchronization simulator, Simsync, for wireless sensor networks. We decompose the packet delay into 6 delay components and model them separately. The frequency of crystal oscillator is modeled as Gaussian. To testify its effectiveness, we simulate the reference broadcast synchronization algorithm (RBS) and the timing-sync synchronization algorithm (TPSN) on Simsync. Simulated results are also presented and analyzed.展开更多
Based on the structural characteristics of the double-differenced normal equation, a new method was proposed to resolve the ambiguity float solution through a selection of parameter weights to construct an appropriate...Based on the structural characteristics of the double-differenced normal equation, a new method was proposed to resolve the ambiguity float solution through a selection of parameter weights to construct an appropriate regularized matrix, and a singular decomposition method was used to generate regularization parameters. Numerical test results suggest that the regularized ambiguity float solution is more stable and reliable than the least-squares float solution. The mean square error matrix of the new method possesses a lower correlation than the variancecovariance matrix of the least-squares estimation. The size of the ambiguity search space is reduced and the search efficiency is improved. The success rate of the integer ambiguity searching process is improved significantly when the ambiguity resolution by using constraint equation method is used to determine the correct ambiguity integervector. The ambiguity resolution by using constraint equation method requires an initial input of the ambiguity float solution candidates which are obtained from the LAMBDA method in the new method. In addition, the observation time required to fix reliable integer ambiguities can he significantly reduced.展开更多
This paper introduces a parking management system based on a wireless sensor network developed by our group. The system consists of a large amount of parking space monitoring nodes, a few parking guiding nodes, a sink...This paper introduces a parking management system based on a wireless sensor network developed by our group. The system consists of a large amount of parking space monitoring nodes, a few parking guiding nodes, a sink node and a management station. All the nodes exchange information with each other through wireless communication. The prototype of the parking management system has been implemented and the preliminary test results show that the performance of the system can satisfy the requirements of the application.展开更多
This paper focuses on fast algorithm for computing the assignment reduct in inconsistent incomplete decision systems. It is quite inconvenient to judge the assignment reduct directly ac-cording to its definition. We p...This paper focuses on fast algorithm for computing the assignment reduct in inconsistent incomplete decision systems. It is quite inconvenient to judge the assignment reduct directly ac-cording to its definition. We propose the judgment theorem for the assignment reduct in the inconsistent incomplete decision system, which greatly simplifies judging this type reduct. On such basis, we derive a novel attribute significance measure and construct the fast assignment reduction algorithm （F-ARA）, intended for com-puting the assignment reduct in inconsistent incomplete decision systems. Final y, we make a comparison between F-ARA and the discernibility matrix-based method by experiments on 13 Univer-sity of California at Irvine （UCI） datasets, and the experimental results prove that F-ARA is efficient and feasible.展开更多
Wireless sensor networks have already enabled numerous embedded wireless applications such as military, environmental monitoring, intelligent building, etc. Because micro-sensor nodes are supposed to operate for month...Wireless sensor networks have already enabled numerous embedded wireless applications such as military, environmental monitoring, intelligent building, etc. Because micro-sensor nodes are supposed to operate for months or even years with very limited battery power source, it is a challenge for researchers to obtain long operating hour without scarifying original system performances. In this paper, the energy consumption sources of the wireless sensor networks are firstly analyzed, with the digital processing and radio transceiver units being emphasized. Then, we introduce the design scheme of our energy-aware wireless sensor network (GAINS). In GAINS, techniques to conserve the energy are exploited including the energy optimization node, software and energy-efficient communication protocol. The design architecture of our ultra low power wireless sensor network (WO-LPP) is specially presented.展开更多
The detection of outliers and change points from time series has become research focus in the area of time series data mining since it can be used for fraud detection, rare event discovery, event/trend change detectio...The detection of outliers and change points from time series has become research focus in the area of time series data mining since it can be used for fraud detection, rare event discovery, event/trend change detection, etc. In most previous works, outlier detection and change point detection have not been related explicitly and the change point detections did not consider the influence of outliers, in this work, a unified detection framework was presented to deal with both of them. The framework is based on ALARCON-AQUINO and BARRIA's change points detection method and adopts two-stage detection to divide the outliers and change points. The advantages of it lie in that: firstly, unified structure for change detection and outlier detection further reduces the computational complexity and make the detective procedure simple; Secondly, the detection strategy of outlier detection before change point detection avoids the influence of outliers to the change point detection, and thus improves the accuracy of the change point detection. The simulation experiments of the proposed method for both model data and actual application data have been made and gotten 100% detection accuracy. The comparisons between traditional detection method and the proposed method further demonstrate that the unified detection structure is more accurate when the time series are contaminated by outliers.展开更多
The data gathering manner of wireless sensor networks, in which data is forwarded towards the sink node, would cause the nodes near the sink node to transmit more data than those far from it. Most data gathering mecha...The data gathering manner of wireless sensor networks, in which data is forwarded towards the sink node, would cause the nodes near the sink node to transmit more data than those far from it. Most data gathering mechanisms nowdo not do well in balancing the energy consumption among nodes with different distances to the sink, thus they can hardly avoid the problem that nodes near the sink consume energy more quickly, which may cause the network rupture from the sink node. This paper presents a data gathering mechanism called PODA, which grades the output power of nodes according to their distances from the sink node. PODA balances energy consumption by setting the nodes near the sink with lower output power and the nodes far from the sink with higher output power. Simulation results show that the PODA mechanism can achieve even energy consumption in the entire network, improve energy efficiency and prolong the network lifetime.展开更多
AIM: To develop an artificial neural network (ANN) model for predicting the resistance index (RI) of taxoids. METHODS: A dataset of 63 experimental data points were compiled from literatures and subdivided into traini...AIM: To develop an artificial neural network (ANN) model for predicting the resistance index (RI) of taxoids. METHODS: A dataset of 63 experimental data points were compiled from literatures and subdivided into training and external test sets randomly. Electrotopological state (E-state) indices were calculated to characterize molecular structure, together with a principle component analysis to reduce the variable space and analyze the relative importance of E-state indices. Back propagation neural network (BPNN) technique was used to build the models. Five-fold cross validation was performed and five models with different compounds composition in training and validation sets were built. The independent external test set was used to evaluate the predictive ability of models. RESULTS: The final model was proved to be good with the cross validation Qcv2 0.62, external testing R2 0.84 and the slope of the regression line through the origin for testing set is 0.9933. CONCLUSION: The QSAR model can predict the RI to a relative nicety, which will aid in the development of new anti-MDR taxoids.展开更多
The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in th...The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in the heliosphere. On day 72 of 1975, an ICME was observed by Helios 1 at 0.3 AU, while a similar solar wind structure was observed by IMP 8 at Earth on day 70 of 1975. On the basis of comparison of the plasma signatures and the transit time from Helios 1 to IMP 8, we hypothesize the observed ICMEs by both spacecraft are resulted from the same active region on the solar surface. A one-dimensional MHD model was used to track the ICME from Helios 1 (0.3 AU) to Earth. The observed plasma profiles and timing are close to those predicted by our MHD model and thus, give the supports to the model.展开更多
AIM: Previous studies identify that C7-OH epimers of taxoids are the thermodynamically more stable isomers due to the strong hydrogen bonding of the C7α-OH to the C4α-acetate acyl oxygen. In order to understand the ...AIM: Previous studies identify that C7-OH epimers of taxoids are the thermodynamically more stable isomers due to the strong hydrogen bonding of the C7α-OH to the C4α-acetate acyl oxygen. In order to understand the effects of certain structure modification on taxoids’ interactions with human hepatic cytochromes P450 better, the present study attempts to clarify the identity of the CYPs involved in 7-epi-Taxol, 7-epi-10-Deacetyl-Taxol, and their corresponding C7β-OH isomers metabolism and the underlying mechanisms are also to investigate. METHODS: LC/MS/MS was used to identify the structures of various taxoids metabolites by human liver microsomes. Incubations were conducted with CYP isoform specific inhibitors and recombinant human CYP isoforms to ascribe individual reaction to a single CYP isoform. RESULTS: Two monohydroxylated metabolites (M-1 and M-2) of 7-epi-Taxol were detected by LC/MS, and C3’ (M-1), C6 (M-2) were proposed as the possible hydroxylation sites. 7-epi-10-Deacetyl-Taxol was hydroxylated at C6 by human liver microsomes thus making M-3 as the unique primary metabolite. Chemical inhibition studies and assays with recombinant human CYPs indicated that C3’ (M-1) was generated predominantly by CYP3A4 and C6 (M-2, M-3) by CYP2C8. Compared with the formation of C6-OH-majorepi-Taxol decreased significantlympounds among all chemotherapeutic drugs, Paclitaxel, the Km for C6-hydroxylation of 7-epi-Taxol decreased significantly (13 versus 3 μmol/L, 8.5 versus 1.7 μmol/L) by human liver microsomes and recombinant human CYP2C8. Moreover, the overall metabolism of 7-epi-10-Deacetyl-Taxol increased to 20% in contrast with the low biotransformation rate of 10-deacetyl-Taxol (less than 0.8%). CONCLUSION: These findings suggest the distinct 3D conformation change of taxoids caused by the intromolecular hydrogen bonding may attribute a major role in the substrate recognition by CYP2C8 and lead C-6 of taxoids more accessible to the active site.展开更多
基金Project(B0210)supported by One Hundred Talent Project of Chinese Academy of SciencesProject(2008-G-158)supported by Science and Technology Tackling Key Program of Qinghai Province,China
文摘The effects of H3PO4 and Ca（H2PO4）2 on compressive strength, water resistance, hydration process of thermally decomposed magnesium oxychloride cement （TDMOC） pastes were studied. The mineral composition, hydration products and hydration heat release were analyzed by XRD, FT-IR, SEM and TAM air isothermal calorimeter, etc. After being modified by H3PO4 and Ca（HzPO4）2, the properties of the TDMOC are improved obviously. The compressive strength increases from 14.8 MPa to 48.1 MPa and 37.1 MPa, respectively. The strength retention coefficient （Kn） increases from 0.38 to 0.99 and 0.94, respectively. The 24 h hydration heat release decreases by 10% and 4% and the time of hydration peak appearing is delayed from 1 h to about 10 h. The XRD, FT-IR and SEM results show that the main composition is 5Mg（OH）z＇MgCIz＇8H20 in the modified TDMOC pastes. The possible mechanism for the strength enhancement was discussed. The purposes are to extend the potential applications of the salt lake magnesium resources and to improve the mechanical properties of TDMOC.
文摘Aiming at measurement of granularity size of nonmetal grain, an algorithm of image segmentation and parameter calculation for microscopic overlapping grain image was studied. This algorithm presents some new attributes of graph sequence from discrete attribute of graph,and consequently achieves the geometrical characteristics from input graph, and the new graph sequence in favor of image segmentation is recombined. The conception that image edge denoted with “twin-point” is put forward, base on geometrical characters of point, image edge is transformed into serial edge, and on recombined serial image edge, based on direction vector definition of line and some additional restricted conditions, the segmentation twin-points are searched with, thus image segmentation is accomplished. Serial image edge is transformed into twin-point pattern, to realize calculation of area and granularity size of nonmetal grain. The inkling and uncertainty on selection of structure element which base on mathematical morphology are avoided in this algorithm, and image segmentation and parameter calculation are realized without changing grain’s self statistical characters.
基金Supported by the Knowledge Innovation Program of Chinese Academy of Sciences (KZCX2-EW-304)National Natural Science Foundation of China(40635029,40871257)
文摘Income inequality among farmers living in different regions was an important form of territorial inequalities. Studying the territorial inequality of the net income per peasant was an emphasis of this paper, and Shandong Province was pointed as the case study region. By the help of logistic regression, it could be found that the special distribution of the net income per peasant in Shandong Province was affected by three factors： distance to No.308 National Highway, distance to the coastline in the east of Shandong Province, and urbanization rates. Based on the decomposition of Gini index, the net income per peasant was divided into four parts, and it was found that the income from family business and salary were the two major sources of income. As to the mechanism for income inequality, it was proved that urbanization was still the key factor. In order to reduce income inequality, the local governments should promote urbanization through improving road networks, such as building highways, which could connect rural areas with the major nodes such as big cities and the port cities in the east.
基金the National High Technology Development "863" Program of China (2006AA01Z436, 2007AA01Z452)the National Natural Science Foundation of China(60702042).
文摘Mobile ad hoc networking （MANET） has become an exciting and important technology in recent years, because of the rapid proliferation of wireless devices. Mobile ad hoc networks is highly vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, and lack of centralized monitoring and management point. The traditional way of protecting networks with firewalls and encryption software is no longer sufficient and effective for those features. A distributed intrusion detection approach based on timed automata is given. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then the timed automata is constructed by the way of manually abstracting the correct behaviours of the node according to the routing protocol of dynamic source routing （DSR）. The monitor nodes can verify the behaviour of every nodes by timed automata, and validly detect real-time attacks without signatures of intrusion or trained data. Compared with the architecture where each node is its own IDS agent, the approach is much more efficient while maintaining the same level of effectiveness. Finally, the intrusion detection method is evaluated through simulation experiments.
基金This project was supported by the National Natural Science Foundation of China (60672068)the National High Technology Development 863 Program of China (2006AA01Z436, 2007AA01Z452.)
文摘The nature of adhoc networks makes them vulnerable to security attacks. Many security technologies such as intrusion prevention and intrusion detection are passive in response to intrusions in that their countermea- sures are only to protect the networks, and there is no automated network-wide counteraction against detected intrusions, the architecture of cooperation intrusion response based multi-agent is propose. The architecture is composed of mobile agents. Monitor agent resides on every node and monitors its neighbor nodes. Decision agent collects information from monitor nodes and detects an intrusion by security policies. When an intruder is found in the architecture, the block agents will get to the neighbor nodes of the intruder and form the mobile firewall to isolate the intruder. In the end, we evaluate it by simulation.
基金Supported in part by National Basic Research Program of P. R. China(2005CB321604) in part by National Natural Science Foundation of P. R. China (90207002)
文摘Time synchronization is a critical middleware service of wireless sensor networks. Researchers have already proposed some time synchronization algorithms. However, due to the demands for various synchronization precision, existing time synchronization algorithms often need to be adapted. So it is necessary to evaluate these adapted algorithms before use. Software simulation is a valid and quick way to do it. In this paper, we present a time synchronization simulator, Simsync, for wireless sensor networks. We decompose the packet delay into 6 delay components and model them separately. The frequency of crystal oscillator is modeled as Gaussian. To testify its effectiveness, we simulate the reference broadcast synchronization algorithm (RBS) and the timing-sync synchronization algorithm (TPSN) on Simsync. Simulated results are also presented and analyzed.
文摘Based on the structural characteristics of the double-differenced normal equation, a new method was proposed to resolve the ambiguity float solution through a selection of parameter weights to construct an appropriate regularized matrix, and a singular decomposition method was used to generate regularization parameters. Numerical test results suggest that the regularized ambiguity float solution is more stable and reliable than the least-squares float solution. The mean square error matrix of the new method possesses a lower correlation than the variancecovariance matrix of the least-squares estimation. The size of the ambiguity search space is reduced and the search efficiency is improved. The success rate of the integer ambiguity searching process is improved significantly when the ambiguity resolution by using constraint equation method is used to determine the correct ambiguity integervector. The ambiguity resolution by using constraint equation method requires an initial input of the ambiguity float solution candidates which are obtained from the LAMBDA method in the new method. In addition, the observation time required to fix reliable integer ambiguities can he significantly reduced.
基金Supported by National Natural Science Foundation of P. R. China (60373049) National Basic Research Program of P.R.China (2006CB 3030000)
文摘This paper introduces a parking management system based on a wireless sensor network developed by our group. The system consists of a large amount of parking space monitoring nodes, a few parking guiding nodes, a sink node and a management station. All the nodes exchange information with each other through wireless communication. The prototype of the parking management system has been implemented and the preliminary test results show that the performance of the system can satisfy the requirements of the application.
基金supported by the National Natural Science Foundation of China(61363047)the Jiangxi Education Department(GJJ13760)the Science and Technology Support Foundation of Jiangxi Province(20111BBE50008)
文摘This paper focuses on fast algorithm for computing the assignment reduct in inconsistent incomplete decision systems. It is quite inconvenient to judge the assignment reduct directly ac-cording to its definition. We propose the judgment theorem for the assignment reduct in the inconsistent incomplete decision system, which greatly simplifies judging this type reduct. On such basis, we derive a novel attribute significance measure and construct the fast assignment reduction algorithm （F-ARA）, intended for com-puting the assignment reduct in inconsistent incomplete decision systems. Final y, we make a comparison between F-ARA and the discernibility matrix-based method by experiments on 13 Univer-sity of California at Irvine （UCI） datasets, and the experimental results prove that F-ARA is efficient and feasible.
基金Supported in part by National Basic Research Program of P. R. China (2005CB321604) in part by National Natural Science Foundation of P. R. China (90207002)
文摘Wireless sensor networks have already enabled numerous embedded wireless applications such as military, environmental monitoring, intelligent building, etc. Because micro-sensor nodes are supposed to operate for months or even years with very limited battery power source, it is a challenge for researchers to obtain long operating hour without scarifying original system performances. In this paper, the energy consumption sources of the wireless sensor networks are firstly analyzed, with the digital processing and radio transceiver units being emphasized. Then, we introduce the design scheme of our energy-aware wireless sensor network (GAINS). In GAINS, techniques to conserve the energy are exploited including the energy optimization node, software and energy-efficient communication protocol. The design architecture of our ultra low power wireless sensor network (WO-LPP) is specially presented.
基金Project(2011AA040603) supported by the National High Technology Ressarch & Development Program of ChinaProject(201202226) supported by the Natural Science Foundation of Liaoning Province, China
文摘The detection of outliers and change points from time series has become research focus in the area of time series data mining since it can be used for fraud detection, rare event discovery, event/trend change detection, etc. In most previous works, outlier detection and change point detection have not been related explicitly and the change point detections did not consider the influence of outliers, in this work, a unified detection framework was presented to deal with both of them. The framework is based on ALARCON-AQUINO and BARRIA's change points detection method and adopts two-stage detection to divide the outliers and change points. The advantages of it lie in that: firstly, unified structure for change detection and outlier detection further reduces the computational complexity and make the detective procedure simple; Secondly, the detection strategy of outlier detection before change point detection avoids the influence of outliers to the change point detection, and thus improves the accuracy of the change point detection. The simulation experiments of the proposed method for both model data and actual application data have been made and gotten 100% detection accuracy. The comparisons between traditional detection method and the proposed method further demonstrate that the unified detection structure is more accurate when the time series are contaminated by outliers.
基金Supported by National Natural Science Foundation of P. R. China (60434030, 60673178)
文摘The data gathering manner of wireless sensor networks, in which data is forwarded towards the sink node, would cause the nodes near the sink node to transmit more data than those far from it. Most data gathering mechanisms nowdo not do well in balancing the energy consumption among nodes with different distances to the sink, thus they can hardly avoid the problem that nodes near the sink consume energy more quickly, which may cause the network rupture from the sink node. This paper presents a data gathering mechanism called PODA, which grades the output power of nodes according to their distances from the sink node. PODA balances energy consumption by setting the nodes near the sink with lower output power and the nodes far from the sink with higher output power. Simulation results show that the PODA mechanism can achieve even energy consumption in the entire network, improve energy efficiency and prolong the network lifetime.
文摘AIM: To develop an artificial neural network (ANN) model for predicting the resistance index (RI) of taxoids. METHODS: A dataset of 63 experimental data points were compiled from literatures and subdivided into training and external test sets randomly. Electrotopological state (E-state) indices were calculated to characterize molecular structure, together with a principle component analysis to reduce the variable space and analyze the relative importance of E-state indices. Back propagation neural network (BPNN) technique was used to build the models. Five-fold cross validation was performed and five models with different compounds composition in training and validation sets were built. The independent external test set was used to evaluate the predictive ability of models. RESULTS: The final model was proved to be good with the cross validation Qcv2 0.62, external testing R2 0.84 and the slope of the regression line through the origin for testing set is 0.9933. CONCLUSION: The QSAR model can predict the RI to a relative nicety, which will aid in the development of new anti-MDR taxoids.
基金Supported by the National Natural Science Foundation of China(40325010)
文摘The chance of an Interplanetary Coronal Mass Ejection (ICME) observed by widely-separated spacecraft is rare. However, such an event provides us a good opportunity to study the propagation and evolution of ICMEs in the heliosphere. On day 72 of 1975, an ICME was observed by Helios 1 at 0.3 AU, while a similar solar wind structure was observed by IMP 8 at Earth on day 70 of 1975. On the basis of comparison of the plasma signatures and the transit time from Helios 1 to IMP 8, we hypothesize the observed ICMEs by both spacecraft are resulted from the same active region on the solar surface. A one-dimensional MHD model was used to track the ICME from Helios 1 (0.3 AU) to Earth. The observed plasma profiles and timing are close to those predicted by our MHD model and thus, give the supports to the model.
文摘AIM: Previous studies identify that C7-OH epimers of taxoids are the thermodynamically more stable isomers due to the strong hydrogen bonding of the C7α-OH to the C4α-acetate acyl oxygen. In order to understand the effects of certain structure modification on taxoids’ interactions with human hepatic cytochromes P450 better, the present study attempts to clarify the identity of the CYPs involved in 7-epi-Taxol, 7-epi-10-Deacetyl-Taxol, and their corresponding C7β-OH isomers metabolism and the underlying mechanisms are also to investigate. METHODS: LC/MS/MS was used to identify the structures of various taxoids metabolites by human liver microsomes. Incubations were conducted with CYP isoform specific inhibitors and recombinant human CYP isoforms to ascribe individual reaction to a single CYP isoform. RESULTS: Two monohydroxylated metabolites (M-1 and M-2) of 7-epi-Taxol were detected by LC/MS, and C3’ (M-1), C6 (M-2) were proposed as the possible hydroxylation sites. 7-epi-10-Deacetyl-Taxol was hydroxylated at C6 by human liver microsomes thus making M-3 as the unique primary metabolite. Chemical inhibition studies and assays with recombinant human CYPs indicated that C3’ (M-1) was generated predominantly by CYP3A4 and C6 (M-2, M-3) by CYP2C8. Compared with the formation of C6-OH-majorepi-Taxol decreased significantlympounds among all chemotherapeutic drugs, Paclitaxel, the Km for C6-hydroxylation of 7-epi-Taxol decreased significantly (13 versus 3 μmol/L, 8.5 versus 1.7 μmol/L) by human liver microsomes and recombinant human CYP2C8. Moreover, the overall metabolism of 7-epi-10-Deacetyl-Taxol increased to 20% in contrast with the low biotransformation rate of 10-deacetyl-Taxol (less than 0.8%). CONCLUSION: These findings suggest the distinct 3D conformation change of taxoids caused by the intromolecular hydrogen bonding may attribute a major role in the substrate recognition by CYP2C8 and lead C-6 of taxoids more accessible to the active site.
