基于长短时记忆神经网络（LSTM）的降雨径流模拟及预报

长短时记忆神经网络(LSTM)具有很强的时间序列关系拟合能力,非常适用于模拟及预报流域产汇流这一复杂的时间序列过程。基于LSTM针对不同预见期的径流预报分别建立了流域降雨径流模型,以探讨LSTM在水文预报当中的应用。模型采用流域降雨、气象及水文数据作为输入,不同预见期后的径流过程作为输出,率定期为14a,验证期为2a。结果显示,在预见期为0～2d时LSTM预报精度很高,在预见期为3d时预报精度较差,但仍优于新安江模型。隐藏层神经元数量作为神经网络复杂程度的代表既会影响模型预报精度,也会影响模型训练速度。而输入数据长度则仅会在预见期为0的条件下影响模型预报效果。     

一种基于粗集的目标识别信息提取算法

目标识别的原始信息往往很粗糙难以直接用于计算.粗集理论是一种对数据进行处理和挖掘的不确定性系统理论,基于此理论提出一种对原始数据进行信息提取的算法.采用关系表存储原始信息,通过简化关系表删去冗余信息,达到提取有用信息的目的.该方法运用粗集理论强大的属性约简和规则生成能力,生成的规则简单准确.与其它计算方法比较,粗集在处理粗糙信息方面有计算量小、抗扰性和传递性好的优点.     

采用扩散和阶跃模型分析微型气敏元件时间特性

利用粉末反溅方法研制了酒敏灵敏度>20的性能良好的Si基SnO2/CeO2旁热式气敏元件,给出了重要参数之一的传感特征响应和恢复时间的实验结果,典型的稳态特征响应时间值在2.5 s以上,恢复时间在7 s以上;提出使用扩散反应模型对特征时间的物理意义及过程分析,在给定的边界条件下进行了解释;同时,建立了一种简单系统阶跃响应数学模型,并结合Matlab软件进行特征响应和恢复时间曲线处理的数学方法;最后,设计了有源串联相位超前微分网络以降低优化特征时间、提高元件响应速度.仿真和结果表明,特征时间显著减小,可提前约40%.     

REHYDRATION KINETICS OF MICROWAVE-DRIED OKRAS AS AFFECTED BY DRYING CONDITIONS

The aim of the present work was to understand the effect of drying conditions (microwave output powers and sample amounts) and rehydration temperature on rehydration kinetics of microwave-dried okras. Four different models, Peleg's, Weibull, first order and exponential association, were applied to experimental data, and the corresponding parameters of the models were obtained. In addition, the kinetic parameters of the models were correlated with the ratio of microwave output power to sample amount and temperature. Although all the models applied provided a good agreement with the experimental data with high values of the coefficient of determination of R ², the first-order kinetic model was chosen as the appropriate model because of its simplicity. By using the kinetic parameters of this model, the activation energy for rehydration kinetics was estimated as 1.15 kJ/mol.

PRACTICAL APPLICATIONS

Drying, in general, is a means of removal of water from the material. The purpose of drying food products is to allow longer periods of storage with minimized packaging requirements, reduce shipping weights, and preserve seasonal plants and make them available to consumers during the whole year. Besides these advantages, some important changes take place, as structural and physicochemical modifications, which affect the final product quality during dehydration. Rehydration is a complex process aimed at the restoration of raw material properties when dried material contacted with water, and can be considered as a measure of the injury to the material caused by drying. The objective of rehydration study is to attain as many products in their original characteristics as fast as possible. An improved knowledge of rehydration kinetics would significantly enhance the feasibility of this process.     

Oleic acid binding and transport capacity of human red cell membrane

Resealed human red cell membranes, ghosts, bind oleate (OL) by a limited number of sites when equilibrated at 37 degrees C, pH 7.3 with OL bound to bovine serum albumin (BSA) in molar ratios below 1.5. The binding capacity is 34 +/- 2.2 nmol g-1 ghosts with a dissociation equilibrium constant (37 degrees C) Kdm 1.38 +/- 0.15 fold Kd of albumin binding Kdm is temperature independent and approximately 7-8 nM. Exchange efflux kinetics at 0 degrees C to buffers of various albumin concentrations ([BSAy]) is biexponential and is analysed in terms of a three-compartment model. Accordingly the ratio of inner to outer membrane leaflet binding sites is 0.450 +/- 0.018 and the rate constant of unidirectional flux from inside to outside is 0.067 +/- 0.01 s-1. The rate constant of flux from the extracellular side of the membrane to BSAy increases with the square root of [BSAy] as expected of an unstirred layer effect. This provides an estimate of the dissociation rate constant of OL-BSA complex at 0 degrees C of 0.0063 +/- 0.0003 s-1. Exchange efflux from ghosts containing four different [BSAi] obeys the expected kinetics of a three-compartment approximation of the theoretical model. Accounting for the effect of an unstirred fluid inside ghosts, the rate coefficients fit the values predicted by the parameters obtained by the studies of albumin-free ghosts. The results show that the OL transport across the membrane is mediated exclusively by the asymmetrically distributed binding sites. The differences between transport sites of three long-chain fatty acids suggest that they are protein determined microdomains of phospholipids.     

Phenotypic distribution of T cells in human nasal mucosa differs from that in the gut

Phenotypic and functional studies are required to understand the immunoregulatory role of mucosal T cells. Information about T cells in the human upper respiratory tract is limited and conflicting. Therefore, we phenotyped T cells in nasal mucosa by means of multicolor in situ immunofluorescence. In normal mucosa, most CD3+ intraepithelial lymphocytes (IELs) and lamina propria lymphocytes (LPLs) (> 90%) expressed T-cell receptor (TCR)alpha/beta, and only approximately 5% expressed TCRgamma/delta. Although most IELs in the surface epithelium were CD8+ (64%), many expressed CD4 (30%) and the CD4 phenotype dominated (55%) only slightly in the lamina propria. This result was strikingly different from that obtained for comparable compartments in histologically normal jejunal mucosa, where IELs consisted of 83% CD8+ and LPLs of 73% CD4(+) T cells. Nasal CD3+ IELs and LPLs were mainly CD45RO+CD45RA- and usually expressed CD7. The integrin alphaEbeta7 was, as expected, more common on IELs than on LPLs (78 versus 20%). In conclusion, nasal T cells show several similarities to those of the normal jejunum but some notable differences exist, especially a relative increase in CD4+ T cells in the epithelium and a decrease in the lamina propria. It should be explored whether this disparity, together with an increased expression of epithelial adhesion molecules, might contribute to local immunological overstimulation and partly explain the relatively high frequency of airway allergy.     

Species differences in the metabolic activation of tamoxifen into genotoxic derivatives: risk assessment in women

A prospective study was conducted comparing the sensitivity of the pp65 antigenemia assay (AGA) to that of the shell-vial culture (SVC) inoculated with increasing quantities of polymorphonuclear leukocytes (PMNLs) in the detection of cytomegalovirus (CMV) in peripheral blood. From the cellular suspension, three SVCs were inoculated with 200,000, 400,000, and 800,000 PMNLs, respectively. Of the 201 patients studied, 67 (31.9%) had positive results in one of the two analytic tests (AGA or SVC). In this group, 13 (19.4%) presented a negative AGA assay; 13 (19.4%) an AGA of 1; 13 (19.4%) an AGA of between 2 and 5; and 28 (41.8%) an AGA with a value > 6 PMNL-positive x 100,000 PMNLs. The SVC inoculated with 200,000 PMNLs detected the presence of CMV in 42 cases (62.6%); 55 (82%) with 400,000; and 64 (95.5%) with 800,000. Statistically significant differences were observed between the isolation capacities of the SVC inoculated with 200,000 and 400,000, and the SVC inoculated with 800,000 PMNLs (p = 0.0001). In the comparison of the overall sensitivity of the AGA with that of the SVC with 200,000, the AGA was found to be significantly more sensitive (p = 0.0052). When comparing with the SVC with 400,000 PMNLs, the two techniques were found to be equally sensitive; and in the comparison with the SVC with 800,000, the culture displayed a greater detection sensitivity (p = 0.0023). According to these results, it seems evident that the increase in the absolute number of PMNLs inoculated in the SVC leads to a significant increase in the sensitivity of the SVC in the detection of low-level viremia by CMV.     

Alumina composite membranes prepared by MOCVD

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Influence of the type of family predisposition on the age of ulcer disease onset

Anthrax toxin consists of three separate proteins, protective antigen (PA), lethal factor (LF), and edema factor (EF). PA binds to the receptor on mammalian cells and facilitates translocation of EF or LF into the cytosol. PA is the primary component of several anthrax vaccines. In this study we expressed and purified PA from Escherichia coli. The purification of PA from E. coli was possible after transporting the protein into the periplasmic space using the outer membrane protein A signal sequence. The purification involved sequential chromatography through hydroxyapatite, DEAE Sepharose CL-4B, followed by Sephadex G-100. The typical yield of purified PA from this procedure was 500 microg/liter. PA expressed and purified from E. coli was similar to the PA purified from Bacillus anthracis in its ability to lyse a macrophage cell line (J774A.1). The present results suggest that a signal sequence is required for the efficient translocation of PA into E. coli periplasmic space.