Is it a hindrance for an invasive aquatic species to spread across scattered habitat patches?

1. Despite their importance for aquatic biodiversity, ponds are among the most vulnerable freshwater habitats. Owing to their isolation in terrestrial environments, ponds are expected to be relatively well protected from biological invasions, but this depends on many factors. 2. The purpose of this study was to examine the influence of a range of variables (water quality, habitat, and landscape attributes) on the colonization of discrete ponds by a widespread aquatic invader, the red swamp crayfish Procambarus clarkii, which can disperse overland. 3. Investigations were conducted in two networks of ponds, each located in close proximity to a large invaded marsh. The two marshes under study differed in the length of time since the crayfish were introduced. 4. The proportions of colonized ponds and crayfish abundances were moderate in both networks, but higher in the network that had been invaded first. In both networks the distance to the marsh was the main predictor of pond colonization, considering similar energy costs to cross aquatic and terrestrial habitats for the recently invaded network, but assuming that dispersal was 25 times costlier across the terrestrial matrix than via streams for the earlier invaded network. Pond characteristics had no influence on crayfish occurrence in either network. Furthermore, predictions of pond invasion were lower for the recently invaded network. 5. The importance of the distance to the marsh indicates that natural dispersal was the main process of pond colonization by crayfish. Findings also suggested that overland dispersal was rare and costly. By contrast, streams were probably significant in facilitating crayfish dispersal. Differences between the two networks might arise from an invasion process still in progress in the recently invaded network. 6. From a management viewpoint, local actions are encouraged to prevent the spread of crayfish via streams. In addition, broader‐scale actions to mitigate other human disturbances would improve the outlook for pond biodiversity.     

基于GA–BP神经网络的番茄应力松弛参数的估计

为了实现机械手在抓取过程中对番茄应力松弛参数的快速准确估计,提出以BP神经网络为核心,遗传算法(GA)对BP神经网络初始权值和阈值进行优化的番茄应力松弛参数的估计方法:以番茄为样本,利用质构仪进行番茄应力松弛试验,并利用三元件广义Maxwell模型来表征番茄的应力松弛特性,通过拟合获取样本数据集;再以抓取力F、变形量D、作用时间t为输入,松弛特性参数E、Ee、η为输出构建BP神经网络模型,使用遗传算法对初始连接权值和阈值进行优化,获取最优参数的GA–BP神经网络估计模型;将该估计模型应用到机械手抓取过程中对番茄应力松弛参数的估计验证。结果表明:番茄应力松弛特性参数E、Ee和η的估计相对误差都在15%以内,且趋于稳定,该估计模型可对番茄应力松弛参数进行在线估计。     

基于改进VGG卷积神经网络的棉花病害识别模型

为实现自然条件下棉花病害图像准确分类,提出基于改进VGG-16卷积神经网络的病害识别模型。该模型在VGG-16网络模型基础上,优化全连接层层数,并用6标签SoftMax分类器替换原有VGG-16网络中的SoftMax分类器,优化了模型结构和参数,通过微型迁移学习共享预训练模型中卷积层与池化层的权值参数。从构建的棉花病害图像库中随机抽取病害图像样本作为训练集和测试集,用以测试该方法的性能。试验结果表明:该模型能有效提取出棉花病害叶片图像的多层特征图像,并通过Relu激活函数的处理更能凸显棉花病害的边缘信息与纹理信息,分辨率为512像素×512像素图像在样本训练与验证试验效果最好。在平均识别准确率方面,本研究模型较BP神经网络、支持向量机、AlexNET、GoogleNET、VGG-16NET效果最好,达到89.51%,实现对棉花的褐斑病、炭疽病、黄萎病、枯萎病、轮纹病、正常叶片的准确区分。该模型在棉花病害识别领域具备良好的分类性能,可实现自然条件下棉花病害的准确识别。     

Fucoxanthin,a Marine Carotenoid,Reverses Scopolamine-Induced Cognitive Impairments in Mice and Inhibits Acetylcholinesterase in Vitro

Fucoxanthin, a natural carotenoid abundant in edible brown seaweeds, has been shown to possess anti-cancer, anti-oxidant, anti-obesity and anti-diabetic effects. In this study, we report for the first time that fucoxanthin effectively protects against scopolamine-induced cognitive impairments in mice. In addition, fucoxanthin significantly reversed the scopolamine-induced increase of acetylcholinesterase (AChE) activity and decreased both choline acetyltransferase activity and brain-derived neurotrophic factor (BDNF) expression. Using an in vitro AChE activity assay, we discovered that fucoxanthin directly inhibits AChE with an IC₅₀ value of 81.2 μM. Molecular docking analysis suggests that fucoxanthin likely interacts with the peripheral anionic site within AChE, which is in accordance with enzymatic activity results showing that fucoxanthin inhibits AChE in a non-competitive manner. Based on our current findings, we anticipate that fucoxanthin might exhibit great therapeutic efficacy for the treatment of Alzheimer’s disease by acting on multiple targets, including inhibiting AChE and increasing BDNF expression.     

不同类型农户对耕地保护的认知差异及影响因素分析——基于山东省227户农户的问卷调查

以山东省227户农户调查数据为依据,通过分组对比,分析不同类型农户耕地保护政策认知差异及其影响因素.结果表明:(1)不同类型农户对耕地数量变化的认知存在差异,但农户总体认为近年来耕地数量有所减少,减少的耕地主要作为建设用地使用;(2)农户对耕地价值及相关耕地保护政策的认知水平普遍较低,且不同类型农户对同一政策以及同一类型农户对不同政策的认知情况存在显著差异;(3)不同类型农户对于耕地保护的意愿均较高;(4)农户对耕地保护的认知差异受到农户的年龄、受教育程度及年限、家庭收入、信息获取途径以及宣传等多重因素的影响.研究认为当农户明确自身的主体地位,且其自身对耕地保护政策的认知程度与耕地保护政策目标相一致时,农户对于耕地保护的自觉性与积极性便会得到充分激发,从而实现耕地资源持续高效利用.     

国家气象业务内网设计与实现

为改变气象系统内部服务平台分散的现状,国家气象信息中心对各国家级气象业务中心原先自建的气象、气候、观测、服务等若干小系统进行整合,构建国家气象业务内网,形成气象系统内部统一的国家级气象服务平台,提供一个能浏览、检索与综合显示实况监测、预报预测、预警信息、历史气候资料以及信息网络等业务信息的共享平台。国家气象业务内网使用MVC模式设计,为适应气象应用的特点,在J2EE应用架构(Struts+Spring+Hibernate)的基础上,对底层数据交互模块进行了封装,有效提高了系统的灵活性和开发效率。2015年3月国家气象业务内网2.0版业务运行,目前涵盖了探测、天气、气候等6大核心服务栏目、近100个子模块、近2 000余种业务产品,对各类气象业务起到了有效的支撑作用。     

基于无线传感器网络的温室大棚环境监测系统设计

针对目前温室大棚环境监测系统存在布线困难、灵活性低和成本高等问题,构建了基于无线传感器网络(WSN)的温室大棚环境监测系统,并重点对传感节点和网关节点进行了设计。该系统的传感器节点负责对环境参数进行采集,并通过无线传感器网络将数据发送到网关节点,网关节点再向远程监测平台传输数据。节点硬件的微处理器模块采用MSP430F149单片机进行数据处理和控制;无线通信模块由nRF905射频芯片及其外围电路组成,负责对数据进行传输和接收;传感器模块采用AM2301传感器进行数据测量;电源模块以LT1129-3.3、LT1129-5和Max660组成的电路提供3.3和±5.0 V电源。节点的无线路由协议和时间同步算法均采用C语言开发,实现节点数据采集与处理、规则转发和远程传输等功能。远程监测软件采用NET.ASP、HTML和C#开发,为用户提供形象直观的Web模式远程数据管理平台。该系统在青海省西宁市温室大棚进行了组网测试,结果表明系统运行稳定可靠,网络平均丢包率为2.4%,有效解决了温室环境监测系统中存在的问题,满足温室大棚栽培环境监测的应用要求。     

疾病费用预测的建模分析

果肉自溶是影响龙眼采后果实贮运、货架寿命和贮藏品质的重要因素。本文综述了龙眼果肉自溶过程的组织结构变化、生理生化变化及微生物侵染与自溶的关系、果肉自溶相关的分子生物学等的研究进展,探讨龙眼果肉自溶的机理和常用的保鲜技术,并提出未来研究的方向,以期对龙眼果实采后贮运保鲜提供参考。     

热力管道小漏温度场特征标定研究

泄漏特别是小漏预警对热力管道的安全维护具有重要意义。受空间分辨率的影响,分布式光纤传感器对小漏引起的局部温度变化测试精度较低,测量温度与实际温度差异较大。以布里渊光时域反射仪(BOTDR)作为测量手段,提出了一种建立分布式光纤测量温度与实际温度之间对应关系的方法。设计完成了小漏温度场模拟测量实验,通过高斯拟合对测量数据进行特征提取,再用人工神经网络建立测量温度与实际温度的映射模型。结果表明:设计的实验方案可获得代表管道小漏温度分布的先验数据,基于此训练的人工神经网络可确立实际温度场与BOTDR测量温度场的对应关系,提高了光纤测试精度并为泄漏预警策略的制定提供了依据。     

基于多信道路由控制的精量播种机优化设计

为了提高花生播种机播种的质量及作业效率,在花生引播机的路径和排种器的控制系统中,引入了多信道独立通信原理,降低了播种过程的漏种率;利用模糊神经网络控制原理,结合模糊域对花生播种机的结构进行了非线性优化设计。为了验证设计的花生精量播种机结构和控制系统的可靠性,对花生播种机进行了田间试验,结果表明:多信道路由花生播种机的合格率要明显高于传统的播种机,重播率要明显低于传统的播种机,破碎率和空穴率都比较低。这说明播种机的路径选择和排种器的控制都达到了最优,为花生播种机的研究和设计提供了理论依据。