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Search Results: 1 - 10 of 34470 matches for " Guofa Zhou "
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CHARACTERIZING POPULATION SPATIAL PATTERNS AND SPATIOTEMPORAL CORRELATION USING ONE DIMENSIONAL SERIES MODELS
应用一维空间序列方法研究空间分布型与时空相关

Zhou Guofa,
周国法

生态学报 , 1997,
Abstract: 研究种九空间分布、种间人相关及种群与环境因子间空间相关的一维序列方法,包括一维序列抽样调查,单种群分布分析的方关菌和相关图方法及及时空相关分析的交叉相关图方法,提出了方向性和最大相关距离(平均聚集半径)两个描述空间分布和空间相关的特征量;第一次用数量方法建立了研究空间分布与建立空间预测模型的统一的分析模型,例1说明了传统判断分布型存在的缺陷和用一邓列方法解决的途径;例2包括分布的时序分布,不同虫态
Fast Economic Development Accelerates Biological Invasions in China
Wen Lin, Guofa Zhou, Xinyue Cheng, Rumei Xu
PLOS ONE , 2007, DOI: 10.1371/journal.pone.0001208
Abstract: Increasing levels of global trade and intercontinental travel have been cited as the major causes of biological invasion. However, indirect factors such as economic development that affect the intensity of invasion have not been quantitatively explored. Herein, using principal factor analysis, we investigated the relationship between biological invasion and economic development together with climatic information for China from the 1970s to present. We demonstrate that the increase in biological invasion is coincident with the rapid economic development that has occurred in China over the past three decades. The results indicate that the geographic prevalence of invasive species varies substantially on the provincial scale, but can be surprisingly well predicted using the combination of economic development (R2 = 0.378) and climatic factors (R2 = 0.347). Economic factors are proven to be at least equal to if not more determinant of the occurrence of invasive species than climatic factors. International travel and trade are shown to have played a less significant role in accounting for the intensity of biological invasion in China. Our results demonstrate that more attention should be paid to economic factors to improve the understanding, prediction and management of biological invasions.
Malaria mosquito control using edible fish in western Kenya: preliminary findings of a controlled study
Annabel FV Howard, Guofa Zhou, Francois X Omlin
BMC Public Health , 2007, DOI: 10.1186/1471-2458-7-199
Abstract: This fish was introduced into abandoned fishponds at an altitude of 1,880 m and the effect measured over six months on the numbers of mosquito immatures. For comparison an untreated control pond was used. During this time, all ponds were regularly cleared of emergent vegetation and fish re-stocking was not needed. Significant autocorrelation was removed from the time series data, and t-tests were used to investigate within a pond and within a mosquito type any differences before and after the introduction of O. niloticus. Mulla's formula was also used on the raw data to calculate the percentage reduction of the mosquito larvae.After O. niloticus introduction, mosquito densities immediately dropped in the treated ponds but increased in the control pond. This increase was apparently due to climatic factors. Mulla's formula was applied which corrects for that natural tendency to increase. The results showed that after 15 weeks the fish caused a more than 94% reduction in both Anopheles gambiae s.l. and Anopheles funestus (Diptera: Culicidae) in the treated ponds, and more than 75% reduction in culicine mosquitoes. There was a highly significantly reduction in A. gambiae s.l. numbers when compared to pre-treatment levels.This study reports the first field trial data on O. niloticus for malaria mosquito control and shows that this species, already a popular food fish in western Kenya, is an apparently sustainable mosquito control tool which also offers a source of protein and income to people in rural areas. There should be no problem with acceptance of this malaria control method since the local communities already farm this fish species.Mosquito control relies heavily on synthetic pyrethroids. Concern about the threat of strong forms of resistance [1] has stimulated renewed interest in alternative control methods including biological control and biopesticides. At present these methods are only operational against mosquito immatures [2-5], the best known being the use o
Temporal and spatial stability of Anopheles gambiae larval habitat distribution in Western Kenya highlands
Li Li, Ling Bian, Laith Yakob, Guofa Zhou, Guiyun Yan
International Journal of Health Geographics , 2009, DOI: 10.1186/1476-072x-8-70
Abstract: Using larval habitat data collected in western Kenya highlands during both dry and rainy seasons of 2003-2005, this study analyzed the seasonal and inter-annual changes in the spatial patterns in mosquito larval habitat distributions. We found that the spatial patterns of larval habitats had significant temporal variability both seasonally and inter-annually.The pattern of larval habitats is extremely important to the epidemiology of malaria because it results in spatial heterogeneity in the adult mosquito population and, subsequently, the spatial distribution of clinical malaria cases. Results from this study suggest that larval habitat management activities need to consider the dynamic nature of malaria vector habitats.A series of malaria outbreaks with high case-fatality rates has occurred in the African highlands in the past two decades [1-3]. The severe malaria situation in these highlands coupled with the spread of drug resistant parasites calls for the rapid implementation of effective malaria control programs. Currently, the use of bednets treated with pyrethroids is the major malaria control approach in Africa [4,5]. However, there are many limitations with this approach. First, bednets require a continuous retreatment with pyrethroids and regular replacement, which may be economically prohibitive for some Africans [6]. Second, bednets only protect users while they are under it, thereby resulting in reduced, but not eliminated, human-vector contact rates [7]. Third, bednet use imposes strong selection pressures for mosquito vectors to develop resistance to the insecticides [8]. It would therefore be prudent to develop alternative and more sustainable vector control measures, such as environmental management of larval habitat resources. Environmentally-friendly biological larvicides have shown some success in reducing malaria transmission [9,10]. Before this tool can become a widespread practice, however, it needs to be made more cost-effective. A key compon
Community-wide benefits of targeted indoor residual spray for malaria control in the Western Kenya Highland
Guofa Zhou, Andrew K Githeko, Noboru Minakawa, Guiyun Yan
Malaria Journal , 2010, DOI: 10.1186/1475-2875-9-67
Abstract: Indoor residual spray using lambda-cyhalothrin insecticide was carried out during the last week of April 2005 in 1,100 targeted houses, located in the valley bottom areas of Iguhu village, Kakamega district of western Kenya. Although the uphill areas are more densely populated, valleys are believed to be malaria transmission hotspots. The aim of the study was to measurably reduce the vector density and malaria transmission in uphill areas by focusing control on these hotspots. A cohort of 1,058 children from 1-5 yrs of age was randomly selected from a 4 km by 6 km study area for the baseline malaria prevalence survey after pre-clearing malaria infections during the third week of April 2005, and the prevalence of Plasmodium infections was tested bi-weekly. Seasonal changes in mosquito densities 12 months before the IRS and 12 months after the IRS was monitored quarterly based on 300 randomly selected houses. Monthly parasitological surveys were also carried out in the same area with 129-661 randomly selected school children of age 6-13 yrs.The result of monthly parasitological surveys indicated that malaria prevalence in school children was reduced by 64.4% in the intervention valley area and by 46.3% in the intervention uphill area after 12 months of follow-ups in contrast to nonintervention areas (valley or uphill). The cohort study showed an average of 4.5% fewer new infections biweekly in the intervention valley compare to nonintervention valley and the relative reduction in incidence rate by week 14 was 65.4%. The relative reduction in incidence rate in intervention uphill by week 14 was 46.4%. Anopheles gambiae densities were reduced by 96.8% and 51.6% in the intervention valley and intervention uphill, respectively, and Anopheles funestus densities were reduced by 85.3% and 69.2% in the intervention valley and intervention uphill, respectively.Vector control had significant indirect impact on the densely populated uphill areas when IRS was targeted to the high
Identification of malaria transmission and epidemic hotspots in the western Kenya highlands: its application to malaria epidemic prediction
Christine L Wanjala, John Waitumbi, Guofa Zhou, Andrew K Githeko
Parasites & Vectors , 2011, DOI: 10.1186/1756-3305-4-81
Abstract: The study was conducted in five sites in the western Kenya highlands, two U-shaped valleys (Iguhu, Emutete), two V-shaped valleys (Marani, Fort-Ternan) and one plateau (Shikondi) for 16 months among 6-15 years old children. Exposure to malaria was tested using circum-sporozoite protein (CSP) and merozoite surface protein (MSP) immunochromatographic antibody tests; malaria infections were tested by microscopic examination of thick and thin smears, the children's homes were georeferenced using a global positioning system. Paired t-test was used to compare the mean prevalence rates of the sites, K-function was use to determine if the clustering of malaria infections was significant.The mean antibody prevalence was 22.6% in Iguhu, 24% in Emutete, 11.5% in Shikondi, 8.3% in Fort-Ternan and 9.3% in Marani. The mean malaria infection prevalence was 23.3% in Iguhu, 21.9% in Emutete, 4.7% in Shikondi, 2.9% in Fort-Ternan and 2.4% in Marani. There was a significant difference in the antibodies and malaria infection prevalence between the two valley systems, and between the two valley systems and the plateau (P < 0.05). There was no significant difference in the antibodies and malaria infection prevalence in the two U-shaped valleys (Iguhu and Emutete) and in the V-shaped valleys (Marani and Fort Ternan) (P > 0.05). There was 8.5- fold and a 2-fold greater parasite and antibody prevalence respectively, in the U-shaped compared to the V-shaped valleys. The plateau antibody and parasite prevalence was similar to that of the V-shaped valleys. There was clustering of malaria antibodies and infections around flat areas in the U-shaped valleys, the infections were randomly distributed in the V-shaped valleys and less clustered at the plateau.This study showed that the V-shaped ecosystems have very low malaria prevalence and few individuals with an immune response to two major malaria antigens and they can be considered as epidemic hotspots. These populations are at higher risk of se
STUDY ON THE SPATIAL DISTRIBUTION PATTERN FORMATION
空间分布型的形成过程研究

ZHOU Guofa,XU Rumei,
周国法
,徐汝梅

生态学报 , 1998,
Abstract: Three types of spatial pattern formation processes,distribution transformation,generalized distribution and compounded distribution,are studied.The result of 11 kinds of generalized distribution and 9 kinds of compounded distribution is listed.Three types of spatial pattern determination methods,index of dispersion method,spatial autocorrelation method,and parameter changing method,are proposed,these methods are also used to determine how the spatial distribution was formed.The spatial pattern formation of pine caterpillar is used as a simulation example,the result indicates that the spatial distribution of pine caterpillar is compounded negative binomial distribution the individual group distributed randomly,individuals aggregate in individual group,and the distribution of individuals in group is Gramma distribution.
Three-Dimensional Reconstruction from Time-Domain Electromagnetic Waves
Hui Zhou;Dongling Qiu;Jinsong Shen;Guofa Li
PIER M , 2008, DOI: 10.2528/PIERM08110904
Abstract: An iterative time-domain algorithm for reconstructing three-dimensional (3-D) objects is presented, using normalized microwave data. The incident waveform information is excluded from the cost functional by normalizing the observed and calculated fields in the frequency domain. The exciting pulse used in the reconstruction can be freely selected by considering the bandwidth of the received data. Two numerical examples are shown to demonstrate that the proposed method can rebuild an inhomogeneous object from noisy data where different waveforms in the observation and reconstruction are used. Two normalized data sets from synthetic observed data and calculated data for a known model are illustrated too.
Utility of Health Facility-based Malaria Data for Malaria Surveillance
Yaw A. Afrane, Guofa Zhou, Andrew K. Githeko, Guiyun Yan
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0054305
Abstract: Background Currently, intensive malaria control programs are being implemented in Africa to reduce the malaria burden. Clinical malaria data from hospitals are valuable for monitoring trends in malaria morbidity and for evaluating the impacts of these interventions. However, the reliability of hospital-based data for true malaria incidence is often questioned because of diagnosis accuracy issues and variation in access to healthcare facilities among sub-groups of the population. This study investigated how diagnosis and treatment practices of malaria cases in hospitals affect reliability of hospital malaria data. Methodology/Principal Findings The study was undertaken in health facilities in western Kenya. A total of 3,569 blood smears were analyzed after being collected from patients who were requested by clinicians to go to the hospital’s laboratory for malaria testing. We applied several quality control measures for clinical malaria diagnosis. We compared our slide reading results with those from the hospital technicians. Among the 3,390 patients whose diagnoses were analyzed, only 36% had clinical malaria defined as presence of any level of parasitaemia and fever. Sensitivity and specificity of clinicians’ diagnoses were 60.1% (95% CI: 61.1?67.5) and 75.0% (95% CI: 30.8?35.7), respectively. Among the 980 patients presumptively treated with an anti-malarial by the clinicians without laboratory diagnosis, only 47% had clinical malaria. Conclusions/Significance These findings revealed substantial over-prescription of anti-malarials and misdiagnosis of clinical malaria. More than half of the febrile cases were not truly clinical malaria, but were wrongly diagnosed and treated as such. Deficiency in malaria diagnosis makes health facility data unreliable for monitoring trends in malaria morbidity and for evaluating impacts of malaria interventions. Improving malaria diagnosis should be a top priority in rural African health centers.
Recent Results and Current Status of BES
XU Guofa
Physics , 2001,
Abstract: The current status of BESII is reported. Some published results based on the data collected by BESI and some new preliminary results based on the BESII data are reviewed in this paper.
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