Data replication is a key way to design a disaster tolerance system. This paper presents a replication driver layer-based data replication system on FreeBSD （FRS）. The system is embedded into the replication device ...Data replication is a key way to design a disaster tolerance system. This paper presents a replication driver layer-based data replication system on FreeBSD （FRS）. The system is embedded into the replication device driver layer, does not depend on specific storage devices and logical volume manager, and can achieve replication on data block level. The design considerations and decisions in defining FRS are described in detail.展开更多
Objective To explore the effect of the interaction between microphage colony-stimulating factor(M-CSF)and minichromosome maintenance protein-7(Mcm7)on DNA replication in HeLa cells.Methods pCMV/nuc/myc,pCMV/nuc/GFP an...Objective To explore the effect of the interaction between microphage colony-stimulating factor(M-CSF)and minichromosome maintenance protein-7(Mcm7)on DNA replication in HeLa cells.Methods pCMV/nuc/myc,pCMV/nuc/GFP and pCMV/nuc/M-CSF vector were stably transfected into HeLa cells by Lipofectamine,respectively.After screening with G418,the expression and localization of M-CSF in HeLa cells were verified by RT-PCR,Western blot and immunofluorescence staining.The statue and interaction between intracellular M-CSF and Mcm7 in HeLa cells was analyzed by co-immunoprecipitation.The effect of the interaction between M-CSF and Mcm7 on DNA replication was analyzed by a mammalian cell or cell-free DNA replication system in vitro.Results The results indicated that the M-CSF-transfected HeLa cells stably express both M-CSF mRNA and protein,and that M-CSF protein is located to the nuclei of HeLa cells mentioned above.To further analyze the status and interaction between intracellular M-CSF and Mcm7,the Mcm7 from HeLa cells was precipitated with anti-Mcm7 antibody and followed by Protein A/G PLUS agarose.The precipitation was blotted with anti-M-CSF monoclonal antibody.The results show that M-CSF was coprecipitated with Mcm7,so intracellular M-CSF existed in Mcm7-bound state.The DNA replication experiments reveal that a higher percentage of the replicating nuclei is present either in unsynchronized or in both synchronized G1 and S phase M-CSF-transfected HeLa cells,compared with both pCMV/nuc-transfected and un-transfected HeLa cells,which suggests that interaction between M-CSF and Mcm7 promote both the initiation and elongation of DNA replication.Conclusions M-CSF directly interacts with Mcm7.The interaction between M-CSF and Mcm7 promotes both the initiation and elongation of DNA replication.展开更多
We propose a catalytically activated replication-decline model of three species, in which two aggregates of the same species can coagulate themselves, an A aggregate of any size can replicate itself with the help of B...We propose a catalytically activated replication-decline model of three species, in which two aggregates of the same species can coagulate themselves, an A aggregate of any size can replicate itself with the help of B aggregates, and the decline of A aggregate occurs under the catalysis of C aggregates. By means of mean-field rate equations, we derive the asymptotic solutions of the aggregate size distribution ak（t） of species A, which is found to depend strongly on the competition among three mechanisms： the self-coagulation of species A, the replication of species A catalyzed by species B, and the decline of species A catalyzed by species C. When the self-coagulation of species A dominates the system, the aggregate size distribution a^（t） satisfies the conventional scaling form. When the catalyzed replication process dominates the system, ak（t） takes the generalized scaling form. When the catalyzed decline process dominates the system, ak（t） approaches the modified scaling form.展开更多
In order to study the relationship between replicative status and human leucocyte antigens(HLA),HLA class Ⅱ antigen on hepatocyte membrane was analyzed in liver biopsies from 49 pa-tients with chronic hepatitis B vir...In order to study the relationship between replicative status and human leucocyte antigens(HLA),HLA class Ⅱ antigen on hepatocyte membrane was analyzed in liver biopsies from 49 pa-tients with chronic hepatitis B virus infection.The results revealed that expression of HLA classⅡ antigen on hepatocyte membrane was observed in 57% (13/23) of hepatitis B e antigen (HBeAg)positive,only in 15% (4/26) of anti-HBe positive carriers.The display of HLA class Ⅱ antigen onhepatocyte membrane yeas found in 65% (11/17) hepatitis B core antigen (HBcAg) positive and in19% (6/32) HBcAg negative patients with chronic hepatitis B virus infection.There was nosignificant difference in the expression of HLA class Ⅱ antigen on hepatocyte membrane between mi-nor hepatic diseases and active liver diseases.These findings suggested that display of HLA classⅡ antigen on hepatocyte membrane might be associated with viral replication in the chronic hepati-tis B virus carriers.展开更多
DNA polymerases are an essential class of enzymes or molecular motors that catalyze processive DNA syntheses during DNA replications. A critical issue for DNA polymerases is their molecular mechanism of processive DNA...DNA polymerases are an essential class of enzymes or molecular motors that catalyze processive DNA syntheses during DNA replications. A critical issue for DNA polymerases is their molecular mechanism of processive DNA replication. We have proposed a model for chemomechanical coupling of DNA polymerases before, based on which the predicted results have been provided about the dependence of DNA replication velocity upon the external force on Klenow fragment of DNA polymerase I. Here, we performed single molecule measurements of the replication velocity of Klenow fragment under the external force by using magnetic tweezers. The single molecule data verified quantitatively the previous theoretical predictions, which is critical to the chemomechanical coupling mechanism of DNA polymerases. A prominent characteristic for the Klenow fragment is that the replication velocity is independent of the assisting force whereas the velocity increases largely with the increase of the resisting force,attains the maximum velocity at about 3.8 pN and then decreases with the further increase of the resisting force.展开更多
As an important branch of federated learning,vertical federated learning(VFL)enables multiple institutions to train on the same user samples,bringing considerable industry benefits.However,VFL needs to exchange user f...As an important branch of federated learning,vertical federated learning(VFL)enables multiple institutions to train on the same user samples,bringing considerable industry benefits.However,VFL needs to exchange user features among multiple institutions,which raises concerns about privacy leakage.Moreover,existing multi-party VFL privacy-preserving schemes suffer from issues such as poor reli-ability and high communication overhead.To address these issues,we propose a privacy protection scheme for four institutional VFLs,named FVFL.A hierarchical framework is first introduced to support federated training among four institutions.We also design a verifiable repli-cated secret sharing(RSS)protocol(32)-sharing and combine it with homomorphic encryption to ensure the reliability of FVFL while ensuring the privacy of features and intermediate results of the four institutions.Our theoretical analysis proves the reliability and security of the pro-posed FVFL.Extended experiments verify that the proposed scheme achieves excellent performance with a low communication overhead.展开更多
This paper presents a solution for optimal business continuity, with storage architecture for enterprise applications, which will ensure zero data loss and quick recovery. The solution makes use of Internet protocol s...This paper presents a solution for optimal business continuity, with storage architecture for enterprise applications, which will ensure zero data loss and quick recovery. The solution makes use of Internet protocol storage area network （IPSAN）, which is used for data management without burdening the application server, as well as mix of synchronous and semi-synchronous replication techniques to replicate data to remote disaster recovery site. We have presented the detailed design of both synchronous and semi-synchronous with case study of using open source database postgres to prove our point for optimal business continuity. The theoretical presentation is also given for the same.展开更多
Understanding genetic variation is important for efficiently selecting excellent clones and utilizing genetic resources during tree breeding. We investigated 16 growth traits of 50 32-year-old Pinus koraiensis clones....Understanding genetic variation is important for efficiently selecting excellent clones and utilizing genetic resources during tree breeding. We investigated 16 growth traits of 50 32-year-old Pinus koraiensis clones. Analyses of variance showed that all the test traits differed significantly among clones. Average height, diameter at breast height(DBH), and volume of all clones were 10.41 m, 21.30 cm,and 0.148 m3, respectively. Phenotypic coefficients of variation and repeatabilities of traits ranged from 4.37 to48.03% and from 0.013 to 0.900, respectively. There exists significant positive correlations among heights, diameter at different heights(1.3, 3.0, 5.0 m), and volumes; genetic correlation was close to phenotype correlation. Using four growth traits(height, DBH, volume, average crown width)as indices for a comprehensive evaluation, five clones(PK11, PK 19, PK 04, PK 14, and PK 28), whose traits scored in the top 10%, were selected as elite clones. For these clones,genetic gains in height, DBH, volume and crown height were 8.58, 13.02, 32.72 and 3.83%, respectively. These results provide important information for improving P.koraiensis breeding programs.展开更多
To reduce the time required to complete the regeneration process of erasure codes, we propose a Tree-structured Parallel Regeneration (TPR) scheme for multiple data losses in distributed storage systems. Under the sch...To reduce the time required to complete the regeneration process of erasure codes, we propose a Tree-structured Parallel Regeneration (TPR) scheme for multiple data losses in distributed storage systems. Under the scheme, two algorithms are proposed for the construction of multiple regeneration trees, namely the edge-disjoint algorithm and edge-sharing algorithm. The edge-disjoint algorithm constructs multiple independent trees, and is simple and appropriate for environments where newcomers and their providers are distributed over a large area and have few intersections. The edge-sharing algorithm constructs multiple trees that compete to utilize the bandwidth, and make a better utilization of the bandwidth, although it needs to measure the available band-width and deal with the bandwidth changes; it is therefore difficult to implement in practical systems. The parallel regeneration for multiple data losses of TPR primarily includes two optimizations: firstly, transferring the data through the bandwidth optimized-paths in a pipe-line manner; secondly, executing data regeneration over multiple trees in parallel. To evaluate the proposal, we implement an event-based simulator and make a detailed comparison with some popular regeneration methods. The quantitative comparison results show that the use of TPR employing either the edge-disjoint algorithm or edge-sharing algorithm reduces the regeneration time significantly.展开更多
MapReduce is a popular program- ming model for processing large-scale datasets in a distributed environment and is a funda- mental component of current cloud comput- ing and big data applications. In this paper, a hea...MapReduce is a popular program- ming model for processing large-scale datasets in a distributed environment and is a funda- mental component of current cloud comput- ing and big data applications. In this paper, a heartbeat mechanism for MapReduce Task Scheduler using Dynamic Calibration （HMTS- DC） is proposed to address the unbalanced node computation capacity problem in a het- erogeneous MapReduce environment. HMTS- DC uses two mechanisms to dynamically adapt and balance tasks assigned to each com- pute node： 1） using heartbeat to dynamically estimate the capacity of the compute nodes, and 2） using data locality of replicated data blocks to reduce data transfer between nodes. With the first mechanism, based on the heart- beats received during the early state of the job, the task scheduler can dynamically estimate the computational capacity of each node. Us- ing the second mechanism, unprocessed Tasks local to each compute node are reassigned and reserved to allow nodes with greater capacities to reserve more local tasks than their weaker counterparts. Experimental results show that HMTS-DC performs better than Hadoop and Dynamic Data Placement Strategy （DDP） in a dynamic environment. Furthermore, an en- hanced HMTS-DC （EHMTS-DC） is proposed bv incorporatin historical data. In contrastto the ＂slow start＂ property of HMTS-DC, EHMTS-DC relies on the historical computation capacity of the slave machines. The experimental results show that EHMTS-DC outperforms HMTS-DC in a dynamic environment.展开更多
Background:Large area forest inventories often use regular grids(with a single random start)of sample locations to ensure a uniform sampling intensity across the space of the surveyed populations.A design-unbiased est...Background:Large area forest inventories often use regular grids(with a single random start)of sample locations to ensure a uniform sampling intensity across the space of the surveyed populations.A design-unbiased estimator of variance does not exist for this design.Oftentimes,a quasi-default estimator applicable to simple random sampling(SRS)is used,even if it carries with it the likely risk of overestimating the variance by a practically important margin.To better exploit the precision of systematic sampling we assess the performance of five estimators of variance,including the quasi default.In this study,simulated systematic sampling was applied to artificial populations with contrasting covariance structures and with or without linear trends.We compared the results obtained with the SRS,Matern’s,successive difference replication,Ripley’s,and D’Orazio’s variance estimators.Results:The variances obtained with the four alternatives to the SRS estimator of variance were strongly correlated,and in all study settings consistently closer to the target design variance than the estimator for SRS.The latter always produced the greatest overestimation.In populations with a near zero spatial autocorrelation,all estimators,performed equally,and delivered estimates close to the actual design variance.Conclusion:Without a linear trend,the SDR and DOR estimators were best with variance estimates more narrowly distributed around the benchmark;yet in terms of the least average absolute deviation,Matern’s estimator held a narrow lead.With a strong or moderate linear trend,Matern’s estimator is choice.In large populations,and a low sampling intensity,the performance of the investigated estimators becomes more similar.展开更多
An animal model of epidemic(Japanese)B encephalitis was estabilisged by injecting theJin Wei Yah 1 stain of B encephalitis virus into the peritoneal cavity of mice.The ultrastructuralchanges of the nerve cells in thei...An animal model of epidemic(Japanese)B encephalitis was estabilisged by injecting theJin Wei Yah 1 stain of B encephalitis virus into the peritoneal cavity of mice.The ultrastructuralchanges of the nerve cells in their brains were studied,special attention being paid to some types ofnerve cell in the cerebellar cortex.The infectet Purkinje cells and especially the granular cells showedspecial and inter,sting pathological features.These were compared with the changes found in the in-fected nerve cells in the cerebral cortex,diencephalon and mesencephalon.A radiating structure consisting of a microveside-microtubule aggregation body at the centerand endoplastic reticulum or virus replication multivesicular structures around it was often found in thein fected nerve cells.Its morphological features were described in detail,and its significance and the se-quenoe of events of its development discussed.In the late stage of infection,virus particles were found in the nuclei of part of the necroticcells.It is considered that they entered the nuclei from the cytoplasm during or after the death of theinfected cells.The observation smade in this study have comfimed in the granular cell of the cerebellum theidea of Chert et al.that the encephalitis B virus particle can he formed in the perinudear cistem ofthe infected nerve cell,and have brought forth further information in this respect.The way of releaseof the virus particles from the infected nerve cells observed in this study is fundamentally consistentwith that observed by Chen et al.but most of the virus particles left the nerve cell via the cell pro-展开更多
基金supported by 863 Program under Grant No. 2009AA01A404
文摘Data replication is a key way to design a disaster tolerance system. This paper presents a replication driver layer-based data replication system on FreeBSD （FRS）. The system is embedded into the replication device driver layer, does not depend on specific storage devices and logical volume manager, and can achieve replication on data block level. The design considerations and decisions in defining FRS are described in detail.
文摘Objective To explore the effect of the interaction between microphage colony-stimulating factor(M-CSF)and minichromosome maintenance protein-7(Mcm7)on DNA replication in HeLa cells.Methods pCMV/nuc/myc,pCMV/nuc/GFP and pCMV/nuc/M-CSF vector were stably transfected into HeLa cells by Lipofectamine,respectively.After screening with G418,the expression and localization of M-CSF in HeLa cells were verified by RT-PCR,Western blot and immunofluorescence staining.The statue and interaction between intracellular M-CSF and Mcm7 in HeLa cells was analyzed by co-immunoprecipitation.The effect of the interaction between M-CSF and Mcm7 on DNA replication was analyzed by a mammalian cell or cell-free DNA replication system in vitro.Results The results indicated that the M-CSF-transfected HeLa cells stably express both M-CSF mRNA and protein,and that M-CSF protein is located to the nuclei of HeLa cells mentioned above.To further analyze the status and interaction between intracellular M-CSF and Mcm7,the Mcm7 from HeLa cells was precipitated with anti-Mcm7 antibody and followed by Protein A/G PLUS agarose.The precipitation was blotted with anti-M-CSF monoclonal antibody.The results show that M-CSF was coprecipitated with Mcm7,so intracellular M-CSF existed in Mcm7-bound state.The DNA replication experiments reveal that a higher percentage of the replicating nuclei is present either in unsynchronized or in both synchronized G1 and S phase M-CSF-transfected HeLa cells,compared with both pCMV/nuc-transfected and un-transfected HeLa cells,which suggests that interaction between M-CSF and Mcm7 promote both the initiation and elongation of DNA replication.Conclusions M-CSF directly interacts with Mcm7.The interaction between M-CSF and Mcm7 promotes both the initiation and elongation of DNA replication.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10875086 and 11145004)
文摘We propose a catalytically activated replication-decline model of three species, in which two aggregates of the same species can coagulate themselves, an A aggregate of any size can replicate itself with the help of B aggregates, and the decline of A aggregate occurs under the catalysis of C aggregates. By means of mean-field rate equations, we derive the asymptotic solutions of the aggregate size distribution ak（t） of species A, which is found to depend strongly on the competition among three mechanisms： the self-coagulation of species A, the replication of species A catalyzed by species B, and the decline of species A catalyzed by species C. When the self-coagulation of species A dominates the system, the aggregate size distribution a^（t） satisfies the conventional scaling form. When the catalyzed replication process dominates the system, ak（t） takes the generalized scaling form. When the catalyzed decline process dominates the system, ak（t） approaches the modified scaling form.
文摘In order to study the relationship between replicative status and human leucocyte antigens(HLA),HLA class Ⅱ antigen on hepatocyte membrane was analyzed in liver biopsies from 49 pa-tients with chronic hepatitis B virus infection.The results revealed that expression of HLA classⅡ antigen on hepatocyte membrane was observed in 57% (13/23) of hepatitis B e antigen (HBeAg)positive,only in 15% (4/26) of anti-HBe positive carriers.The display of HLA class Ⅱ antigen onhepatocyte membrane yeas found in 65% (11/17) hepatitis B core antigen (HBcAg) positive and in19% (6/32) HBcAg negative patients with chronic hepatitis B virus infection.There was nosignificant difference in the expression of HLA class Ⅱ antigen on hepatocyte membrane between mi-nor hepatic diseases and active liver diseases.These findings suggested that display of HLA classⅡ antigen on hepatocyte membrane might be associated with viral replication in the chronic hepati-tis B virus carriers.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 11674381, 21991133, 11774407, 11874415, 1187441431770812)+3 种基金the Key Research Program on Frontier Science (Grant No. QYZDB-SSWSLH045)the National Key Research and Development Program of China (Grant No. 2016YFA0301500)the CAS Strategic Priority Research Program (Grant No. XDB37010100)the National Laboratory of Biomacromolecules (Grant No. 2020kf02)。
文摘DNA polymerases are an essential class of enzymes or molecular motors that catalyze processive DNA syntheses during DNA replications. A critical issue for DNA polymerases is their molecular mechanism of processive DNA replication. We have proposed a model for chemomechanical coupling of DNA polymerases before, based on which the predicted results have been provided about the dependence of DNA replication velocity upon the external force on Klenow fragment of DNA polymerase I. Here, we performed single molecule measurements of the replication velocity of Klenow fragment under the external force by using magnetic tweezers. The single molecule data verified quantitatively the previous theoretical predictions, which is critical to the chemomechanical coupling mechanism of DNA polymerases. A prominent characteristic for the Klenow fragment is that the replication velocity is independent of the assisting force whereas the velocity increases largely with the increase of the resisting force,attains the maximum velocity at about 3.8 pN and then decreases with the further increase of the resisting force.
基金supported in part by ZTE Industry-University-Institute Cooperation Funds under Grant No. 202211FKY00112Open Research Projects of Zhejiang Lab under Grant No. 2022QA0AB02Natural Science Foundation of Sichuan Province under Grant No. 2022NSFSC0913
文摘As an important branch of federated learning,vertical federated learning(VFL)enables multiple institutions to train on the same user samples,bringing considerable industry benefits.However,VFL needs to exchange user features among multiple institutions,which raises concerns about privacy leakage.Moreover,existing multi-party VFL privacy-preserving schemes suffer from issues such as poor reli-ability and high communication overhead.To address these issues,we propose a privacy protection scheme for four institutional VFLs,named FVFL.A hierarchical framework is first introduced to support federated training among four institutions.We also design a verifiable repli-cated secret sharing(RSS)protocol(32)-sharing and combine it with homomorphic encryption to ensure the reliability of FVFL while ensuring the privacy of features and intermediate results of the four institutions.Our theoretical analysis proves the reliability and security of the pro-posed FVFL.Extended experiments verify that the proposed scheme achieves excellent performance with a low communication overhead.
文摘This paper presents a solution for optimal business continuity, with storage architecture for enterprise applications, which will ensure zero data loss and quick recovery. The solution makes use of Internet protocol storage area network （IPSAN）, which is used for data management without burdening the application server, as well as mix of synchronous and semi-synchronous replication techniques to replicate data to remote disaster recovery site. We have presented the detailed design of both synchronous and semi-synchronous with case study of using open source database postgres to prove our point for optimal business continuity. The theoretical presentation is also given for the same.
基金financially supported by the Innovation Project of State Key Laboratory of Tree Genetics and Breeding(Northeast Forestry University)(No.C02)the Fundamental Research Funds for the Central Universities(2572015EA03)+1 种基金China Postdoctoral Science Foundation(2014M561315)the National Natural Science Fund(31500549)
文摘Understanding genetic variation is important for efficiently selecting excellent clones and utilizing genetic resources during tree breeding. We investigated 16 growth traits of 50 32-year-old Pinus koraiensis clones. Analyses of variance showed that all the test traits differed significantly among clones. Average height, diameter at breast height(DBH), and volume of all clones were 10.41 m, 21.30 cm,and 0.148 m3, respectively. Phenotypic coefficients of variation and repeatabilities of traits ranged from 4.37 to48.03% and from 0.013 to 0.900, respectively. There exists significant positive correlations among heights, diameter at different heights(1.3, 3.0, 5.0 m), and volumes; genetic correlation was close to phenotype correlation. Using four growth traits(height, DBH, volume, average crown width)as indices for a comprehensive evaluation, five clones(PK11, PK 19, PK 04, PK 14, and PK 28), whose traits scored in the top 10%, were selected as elite clones. For these clones,genetic gains in height, DBH, volume and crown height were 8.58, 13.02, 32.72 and 3.83%, respectively. These results provide important information for improving P.koraiensis breeding programs.
基金supported by the National Grand Fundamental Research of China (973 Program) under Grant No. 2011CB302601the National High Technology Research and Development of China (863 Program) under GrantNo. 2013AA01A213+2 种基金the National Natural Science Foundation of China under Grant No. 60873215the Natural Science Foundation for Distinguished Young Scholars of Hunan Province under Grant No. S2010J5050Specialized Research Fund for the Doctoral Program of Higher Education under Grant No. 20124307110015
文摘To reduce the time required to complete the regeneration process of erasure codes, we propose a Tree-structured Parallel Regeneration (TPR) scheme for multiple data losses in distributed storage systems. Under the scheme, two algorithms are proposed for the construction of multiple regeneration trees, namely the edge-disjoint algorithm and edge-sharing algorithm. The edge-disjoint algorithm constructs multiple independent trees, and is simple and appropriate for environments where newcomers and their providers are distributed over a large area and have few intersections. The edge-sharing algorithm constructs multiple trees that compete to utilize the bandwidth, and make a better utilization of the bandwidth, although it needs to measure the available band-width and deal with the bandwidth changes; it is therefore difficult to implement in practical systems. The parallel regeneration for multiple data losses of TPR primarily includes two optimizations: firstly, transferring the data through the bandwidth optimized-paths in a pipe-line manner; secondly, executing data regeneration over multiple trees in parallel. To evaluate the proposal, we implement an event-based simulator and make a detailed comparison with some popular regeneration methods. The quantitative comparison results show that the use of TPR employing either the edge-disjoint algorithm or edge-sharing algorithm reduces the regeneration time significantly.
文摘MapReduce is a popular program- ming model for processing large-scale datasets in a distributed environment and is a funda- mental component of current cloud comput- ing and big data applications. In this paper, a heartbeat mechanism for MapReduce Task Scheduler using Dynamic Calibration （HMTS- DC） is proposed to address the unbalanced node computation capacity problem in a het- erogeneous MapReduce environment. HMTS- DC uses two mechanisms to dynamically adapt and balance tasks assigned to each com- pute node： 1） using heartbeat to dynamically estimate the capacity of the compute nodes, and 2） using data locality of replicated data blocks to reduce data transfer between nodes. With the first mechanism, based on the heart- beats received during the early state of the job, the task scheduler can dynamically estimate the computational capacity of each node. Us- ing the second mechanism, unprocessed Tasks local to each compute node are reassigned and reserved to allow nodes with greater capacities to reserve more local tasks than their weaker counterparts. Experimental results show that HMTS-DC performs better than Hadoop and Dynamic Data Placement Strategy （DDP） in a dynamic environment. Furthermore, an en- hanced HMTS-DC （EHMTS-DC） is proposed bv incorporatin historical data. In contrastto the ＂slow start＂ property of HMTS-DC, EHMTS-DC relies on the historical computation capacity of the slave machines. The experimental results show that EHMTS-DC outperforms HMTS-DC in a dynamic environment.
文摘Background:Large area forest inventories often use regular grids(with a single random start)of sample locations to ensure a uniform sampling intensity across the space of the surveyed populations.A design-unbiased estimator of variance does not exist for this design.Oftentimes,a quasi-default estimator applicable to simple random sampling(SRS)is used,even if it carries with it the likely risk of overestimating the variance by a practically important margin.To better exploit the precision of systematic sampling we assess the performance of five estimators of variance,including the quasi default.In this study,simulated systematic sampling was applied to artificial populations with contrasting covariance structures and with or without linear trends.We compared the results obtained with the SRS,Matern’s,successive difference replication,Ripley’s,and D’Orazio’s variance estimators.Results:The variances obtained with the four alternatives to the SRS estimator of variance were strongly correlated,and in all study settings consistently closer to the target design variance than the estimator for SRS.The latter always produced the greatest overestimation.In populations with a near zero spatial autocorrelation,all estimators,performed equally,and delivered estimates close to the actual design variance.Conclusion:Without a linear trend,the SDR and DOR estimators were best with variance estimates more narrowly distributed around the benchmark;yet in terms of the least average absolute deviation,Matern’s estimator held a narrow lead.With a strong or moderate linear trend,Matern’s estimator is choice.In large populations,and a low sampling intensity,the performance of the investigated estimators becomes more similar.
文摘An animal model of epidemic(Japanese)B encephalitis was estabilisged by injecting theJin Wei Yah 1 stain of B encephalitis virus into the peritoneal cavity of mice.The ultrastructuralchanges of the nerve cells in their brains were studied,special attention being paid to some types ofnerve cell in the cerebellar cortex.The infectet Purkinje cells and especially the granular cells showedspecial and inter,sting pathological features.These were compared with the changes found in the in-fected nerve cells in the cerebral cortex,diencephalon and mesencephalon.A radiating structure consisting of a microveside-microtubule aggregation body at the centerand endoplastic reticulum or virus replication multivesicular structures around it was often found in thein fected nerve cells.Its morphological features were described in detail,and its significance and the se-quenoe of events of its development discussed.In the late stage of infection,virus particles were found in the nuclei of part of the necroticcells.It is considered that they entered the nuclei from the cytoplasm during or after the death of theinfected cells.The observation smade in this study have comfimed in the granular cell of the cerebellum theidea of Chert et al.that the encephalitis B virus particle can he formed in the perinudear cistem ofthe infected nerve cell,and have brought forth further information in this respect.The way of releaseof the virus particles from the infected nerve cells observed in this study is fundamentally consistentwith that observed by Chen et al.but most of the virus particles left the nerve cell via the cell pro-
