Stochastic model for hepatitis B virus infection through maternal (vertical) and environmental (horizontal) transmission with applications to basic reproductive number estimation and economic appraisal of preventive strategies     

Hui-Fang Hung  Ya-Chuan Wang  Amy Ming-Fang Yen  Hsiu-Hsi Chen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(3):611-625

Elucidating the temporal natural history of Hepatitis B virus (HBV) infection provides not only useful information for assessing the spread of HBV infection but also a bedrock for economic appraisal of population-based preventive strategies (such as universal vaccination). HBV transmissions are transmitted through the maternal (vertical) route and environmental (horizontal) route. As the infection process from susceptible to active virus replication and finally to recovery state or to carrier state through both routes is not directly observable, mathematical models were therefore proposed to quantitatively elucidate the dynamic process of HBV infection with time. We began with a simple two-state model (from susceptible to infection) and further developed a five-state (including susceptible, latent phase, active viral replication, carrier, and recovery states) stochastic process to quantify the dynamics of HBV infection, making allowances for a mixed proportion of vertical and horizontal transmissions. The data used in the estimation, which were collected before implementation of a policy for universal HBV vaccination, were derived from several previous serum prevalence studies, including both low (northern) and high (southern) HBV prevalence areas, in Taiwan. The parameters obtained from stochastic models were converted to compute the basic reproductive number (R₀) in each study to indicate the extent of the spread of HBV infection. By linking the temporal natural history of HBV infection with the previously established Markov process for the sequelae of HBV infection (chronic hepatitis infection, liver cirrhosis, and hepatocelluar carcinoma), we developed a Markov cycle decision tree to evaluate the two population-based preventive strategies related to vaccination and maternal lamivudine use with a cost-effectiveness analysis. In the five-state model, horizontal transmission was found to contribute more to HBV infection than vertical transmission in the northern area (59 vs. 41 %), whereas vertical transmission was more likely than horizontal transmission in the southern area (80 vs. 20 %). After considering the parameters of the two transmission routes, annual infection rate (person-years) for susceptible subjects was higher in the northern area (0.35) than the southern area (0.011). A similar finding was noted for annual rate of the transition from the latent period to active viral replications (1.12 in the northern area and 0.072 in the southern area). Annual rate of the conversion from active viral replication to the carrier state was higher in the southern area (0.184) than the northern area (0.119). Annual recovery rates were 0.014 in the northern area and 0.024 in the southern area for the carrier and 0.048 and 0.088 for transient viremia. The R₀ at age 30 using the parameters obtained from the five-state stochastic model was estimated as 4.88 in the northern and 7.03 in the southern area. Regarding the findings of economic appraisal, both preventive strategies were cost-saving, yielding the negative value of incremental cost-effectiveness ratio, compared with the baseline group (no intervention), regardless of areas. The preventive strategies in the southern area were more cost-saving than those in the northern area. The consolidation of elucidating the temporal natural history of HBV infection, estimating basic reproductive number, and conducting an economic appraisal of population-based preventive strategy can aid health policy-makers in designing effective preventive strategies in other countries worldwide where HBV is still prevalent. However, the empirical findings on transmission routes and the temporal evolution of HBV infection varying with areas should be considered with great caution as only two studies were modeled.  相似文献   

Shear wave velocity measurements and soil–pile system identifications in dynamic centrifuge tests     

Chung-Jung Lee  Wen-Yi Hung  Chen-Hui Tsai  Ting Chen  Yichun Tu  Chin-Cheng Huang 《Bulletin of Earthquake Engineering》2014,12(2):717-734

This paper presents a pre-shaking technique for measuring the $V_{s}$ profile of sand deposits and determining the natural frequencies of the sand bed and soil-structure system in a centrifuge model at an acceleration of 80 g. The pre-shaking technique is a non-destructive test. It uses a shaker as a wave generation source and a vertical array of accelerometers embedded in the sand bed and the accelerometers attached to the pile head as receivers. The pre-shaking method can be easily used for in-flight subsurface exploration ( $V_{s}$ profile measurements) and in-flight system identification of soil-structure systems (natural frequency measurements). A soil–pile centrifuge model is used to demonstrate the versatility of pre-shaking during a routine centrifuge shaking table test. This paper discusses the testing setup, testing procedures, related SI techniques, and signal processing for the soil–pile system. The natural frequencies measured by the pre-shaking tests are consistent with theory-based results. This technique can be conducted at any time before and after major earthquake events occur in a test.  相似文献   

Features of the Distribution of Abnormal Gasgeochemical Fields in the Red River Rift (Gulf of Tonkin,South China Sea)     

Shakirov  R. B.  Hung  Duong Quoc  Syrbu  N. S.  Anh  Le Duc  Obzhirov  A. I.  Borzova  O. V.  Okulov  A. K.  Van Nam  Bui  Van Diep  Nguyen  Dong  Mai Duc  Legkodimov  A. A.  Shakirova  M. V.  Ponomareva  A. L.  Bakunina  M. S. 《Doklady Earth Sciences》2019,484(2):181-184

Doklady Earth Sciences - This paper reports the results of the third Russian–Vietnamese expedition (V.I. Il'ichev Pacific Oceanological Institute, Far East Branch, Russian Academy of...  相似文献   

东南亚断裂构造的演化     

高庭朝  阮友宣  黎文勇  范南雄  Mai Xuan Bach  Thai Anh Tuan 《大地测量与地球动力学》2005,25(1):51-60

本研究项目是采用诸如地质学解释、影像判读和地球物理探测等多种方法相结合进行的。在所得结果的基础上参考了越南国内外同行的一些资料编制了东南亚、越南及邻区的断裂构造图．其比例尺分别为1：4百万和1：1百万。分析所得结果显示出东南亚断裂构造演化的下列情况：1)在现今地质结构方面东南亚是欧亚岩石圈板块的东南部分．由一条消减带围绕．这条消减带的伸展从Myanmer开始,通过Nicobar,Java Timor直到东菲律宾。东南亚被Song Hong(即红河)断裂,Three Pagodas断裂和Hainam-Natuna断裂等2级断裂系统分成3个微板块。2)在早新生代．东南亚是分为5个微板块的。它们的分界断裂中有2个一级断裂(中央东海扩张带和Lupar-Kuching消减带)和3个二级断裂(即上述3个)。3)上述绝大多数二和三级断裂从晚新生代起活化且继承了从早新生代即已发生和发展了的二、三级断裂,但在某些条件下．运动方向却完全变成了相反,尤其是走滑运动的方向。我们的研究结果表明：在这一地区内,盆地、隆起、岩浆侵入、褶皱和局部断裂等构造的形成都取决于这些沿着一、二级走滑断裂的微板块运动。  相似文献   

浅地表地球物理技术在岩土工程中的应用与挑战          下载免费PDF全文

林志平  林俊宏  吴柏林  刘兴昌  洪瑛钧 《地球物理学报》2015,58(8):2664-2680

地球物理勘探方法在岩土工程的应用已有很长一段时间,但其成效与工程师的期待往往有不小的落差,以致于在一般的工程应用上仍不普遍.近年来浅地表地球物理技术有显着的进展,特别是在走时速度层析成像(Traveltime Tomography)、电阻率层析成像法(Electrical Resistivity Tomography)及多道瞬态面波法(Multichannel Analysis of Surface Wave).本文首先介绍这些方法在台湾岩土工程的应用,主要包括地层土壤液化潜能评估、坝体的安全检测、土壤与地下水污染调查及地基改良的质量管控等,应用案例以台湾常使用的地球物理勘探方法逐一介绍.虽然许多成功案例与新的应用方向对于浅地表地球物理技术在岩土工程应用的推广起了鼓舞作用,本文从工程师的角度提出地球物理勘探工程大量应用的挑战与瓶颈,包括如何提升探测数据的客观性、数据反演非唯一性问题、探测深度与分辨率的限制、实际条件违背反演基本假设的情况、以及地物性质与工程性质链接的不确定性问题,并进一步针对这些问题说明相关研究的进展与实务对策.希冀透过上述探讨,降低物探师与工程师认知上的差距,提升地球物理勘探在工程的应用的合理性与普及性.  相似文献   

The Nui Chua layered peridotite-gabbro complex as manifestation of Permo-Triassic mantle plume in northern Vietnam     

G.V. Polyakov  R.A. Shelepaev  Tran Trong Hoa  A.E. Izokh  P.A. Balykin  Ngo Thi Phuong  Tran Quoc Hung  Bui An Nien 《Russian Geology and Geophysics》2009,50(6):501-516

New data on the age, composition, formation conditions, and ore-geochemical specialization of the Nui Chua layered peridotite-gabbro complex are reported. They evidence that the complex resulted from the Permo-Triassic mantle plume activity in northern Vietnam (southern framing of the Yangtze Platform). Two series of mafic and ultramafic rocks differing in ore productivity—layered (PGE-Cu-Ni) and pegmatoid (Fe-Ti-V)—have been recognized within the complex. The first estimates of the composition of their parental melts have been obtained.  相似文献   

Trophic structure and functioning in a eutrophic and poorly flushed lagoon in southwestern Taiwan     

Lin HJ  Dai XX  Shao KT  Su HM  Lo WT  Hsieh HL  Fang LS  Hung JJ 《Marine environmental research》2006,62(1):61-82

Tapong Bay, a eutrophic and poorly flushed tropical lagoon, supports intensive oyster culture. Using the Ecopath approach and network analysis, a mass-balanced trophic model was constructed to analyze the structure and matter flows within the food web. The lagoon model is comprised of 18 compartments with the highest trophic level of 3.2 for piscivorous fish. The high pedigree index (0.82) reveals the model to be of high quality. The most-prominent living compartment in terms of matter flow and biomass in the lagoon is cultured oysters and bivalves, respectively. The mixed trophic impacts indicate that phytoplankton and periphyton are the most-influential living compartments in the lagoon. Comparative analyses with the eutrophic and well-flushed Chiku Lagoon and non-eutrophic tropical lagoons show that high nutrient loadings might stimulate the growth and accumulation of phytoplankton and periphyton and therefore support high fishery yields. However, net primary production, total biomass, fishery yields per unit area, and mean transfer efficiency of Tapong Bay were remarkably lower than those of Chiku Lagoon. The lower transfer efficiency likely results from the low mortality of cultured oysters and invasive bivalves from predation or the lower density of benthic feeders constrained by the hypoxic bottom water as a result of poor flushing. This might therefore result in a great proportion of flows to detritus. However, the hypoxic bottom water might further reduce the recycling of the entering detritus back into the food web. In contrast to many estuaries and tropical lagoons, poor flushing of this eutrophic tropical lagoon might induce a shift from detritivory to herbivory in the food web.  相似文献   

Evaluating practical macrophyte control tools on small agricultural waterways in Canterbury,New Zealand     

Kathryn E. Collins  Catherine M. Febria  Helen J. Warburton  Hayley S. Devlin  Kristy L. Hogsden  Brandon C. Goeller 《新西兰海洋与淡水研究杂志》2019,53(2):182-200

Excessive macrophytes can cause significant problems in agricultural waterways requiring active management. Conventional control techniques can have a range of adverse effects. We investigated several control tools in two experiments: firstly, we tested eight treatments at a small-scale (2?m?×?2?m). We found intensive hand weeding, weed mat and herbicide spraying to be effective treatments, reducing macrophyte cover to <5%. Hand weeding and weed mat immediately reduced cover, while dieback from herbicide took two months. Weed mat was a novel and effective control mechanism along stream banks. Secondly, we tested the impact of shading on macrophyte growth. Macrophyte growth was enhanced under partially shaded conditions, but with 80% effective shading over the entire channel, cover was reduced to 17%. Once treatments ceased, macrophytes grew back within 3–5 months. Long-term, control methods will require combinations of tools but will need to include optimal shading for the target species.  相似文献   

Waterfall notch-filtering for restoration of acoustic backscatter records from Admiralty Bay,Antarctica     

Luciano Fonseca  Edson Mintsu Hung  Arthur Ayres Neto  Fábio José Guedes Magrani 《Marine Geophysical Researches》2018,39(1-2):139-149

A series of multibeam sonar surveys were conducted from 2009 to 2013 around Admiralty Bay, Shetland Islands, Antarctica. These surveys provided a detailed bathymetric model that helped understand and characterize the bottom geology of this remote area. Unfortunately, the acoustic backscatter records registered during these bathymetric surveys were heavily contaminated with noise and motion artifacts. These artifacts persisted in the backscatter records despite the fact that the proper acquisition geometry and the necessary offsets and delays were applied during the survey and in post-processing. These noisy backscatter records were very difficult to interpret and to correlate with gravity-core samples acquired in the same area. In order to address this issue, a directional notch-filter was applied to the backscatter waterfall in the along-track direction. The proposed filter provided better estimates for the backscatter strength of each sample by considerably reducing residual motion artifacts. The restoration of individual samples was possible since the waterfall frame of reference preserves the acquisition geometry. Then, a remote seafloor characterization procedure based on an acoustic model inversion was applied to the restored backscatter samples, generating remote estimates of acoustic impedance. These remote estimates were compared to Multi Sensor Core Logger measurements of acoustic impedance obtained from gravity core samples. The remote estimates and the Core Logger measurements of acoustic impedance were comparable when the shallow seafloor was homogeneous. The proposed waterfall notch-filtering approach can be applied to any sonar record, provided that we know the system ping-rate and sampling frequency.  相似文献   

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Cao Dinh Trieu  Pham Nam Hung 《大地测量与地球动力学》2009,29(5):11-17

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