Hydrogen sensors and switches from electrodeposited palladium mesowire arrays

Hydrogen sensors and hydrogen-activated switches were fabricated from arrays of mesoscopic palladium wires. These palladium "mesowire" arrays were prepared by electrodeposition onto graphite surfaces and were transferred onto a cyanoacrylate film. Exposure to hydrogen gas caused a rapid (less than 75 milliseconds) reversible decrease in the resistance of the array that correlated with the hydrogen concentration over a range from 2 to 10%. The sensor response appears to involve the closing of nanoscopic gaps or "break junctions" in wires caused by the dilation of palladium grains undergoing hydrogen absorption. Wire arrays in which all wires possessed nanoscopic gaps reverted to open circuits in the absence of hydrogen gas.     

Artificial neural network implementation in single low-cost chip for the detection of insecticides by modeling of screen-printed enzymatic sensors response

This work presents a hardware implementation of artificial neural networks (ANNs) using a dsPIC^® microcontroller to resolve mixtures of pesticides measured by amperometric acetylcholinesterase (AChE) biosensors. The response of three biosensors with different concentrations of Chlorpyrifos Oxon (CPO) and Chlorfenvinfos (CFV) was modeled by two ANNs, which were implemented on the dsPIC^®. The performance of the ANNs was good, the prediction ability was better than 0.986 when the obtained values were compared with those expected for a set of eight external test samples, which were not used for training. This implementation is proposed to develop low-cost analytical chemical specialized tools.     

基于时间序列和神经网络的温室传感器节点故障诊断

温室无线传感器网络中故障节点会产生并传输错误数据,不仅消耗节点的能量和带宽,而且导致错误决策。针对此问题研究一种准确判断节点故障状态的方法。采用时序分析和遗传BP神经网络,建立基于时间序列和神经网络的传感器节点故障诊断系统,通过对传感器样本数据进行时序分析,提取模型参数作为特征向量,并以此对遗传BP神经网络进行网络训练,实现传感器节点故障的诊断。试验结果表明：该方法能够有效地识别传感器节点故障类型,15组测试样本的输出矢量与同类故障基准矢量的欧式距离和为0.007,识别正确率为100%。     

The Hedgehog pathway promotes blood-brain barrier integrity and CNS immune quiescence

The blood-brain barrier (BBB) is composed of tightly bound endothelial cells (ECs) and perivascular astrocytes that regulate central nervous system (CNS) homeostasis. We showed that astrocytes secrete Sonic hedgehog and that BBB ECs express Hedgehog (Hh) receptors, which together promote BBB formation and integrity during embryonic development and adulthood. Using pharmacological inhibition and genetic inactivation of the Hh signaling pathway in ECs, we also demonstrated a critical role of the Hh pathway in promoting the immune quiescence of BBB ECs by decreasing the expression of proinflammatory mediators and the adhesion and migration of leukocytes, in vivo and in vitro. Overall, the Hh pathway provides a barrier-promoting effect and an endogenous anti-inflammatory balance to CNS-directed immune attacks, as occurs in multiple sclerosis.     

土壤水分传感器实用性能对比研究

该文针对时域反射法（TDR）、频率分解法（FD）型土壤水分传感器和中国农业大学研制的基于驻波率原理（SWR）的新型土壤水分传感器,在德国北部典型的沙壤土、黄土、含煤沙土及含铅壤土土样上做了试验.根据采集的数据进行方差分析,结果表明:SWR型土壤水分传感器是一种高精度、高可靠性、受土壤质地影响不明显的快速土壤水分测量传感器,其性能可与世界先进TDR型和FD型土壤水分测量传感器相媲美.      

基于声学响应和BP神经网络检测鸡蛋裂纹

为了提高鸡蛋裂纹检测的准确性,建立了声学敲击检测鸡蛋裂纹的装置,采集和分析鸡蛋被敲击后的声音信号。提取了4个特征频率、偏斜度平均值和峰度平均值共6个特征参数,并作为神经网络的输入量,创建了基于MATLAB的结构为6-15-2的3层BP神经网络模型判别鸡蛋裂纹。检测结果显示:对蛋壳受各种程度破坏后的鸡蛋判别精度可达92%以上,对蛋壳完整的鸡蛋判别精度达到96%,对鸡蛋总体的判别精度可达94%。     

基于802.1x协议的访问控制与网络安全

基于计算机网络中安全问题日益严重,802.1x协议的网络接入控制协议开始被广泛应用,文章阐述了802.1x协议的组成部分以及工作机制,总结了802.1x协议的特点与在实际应用中的不足之处,分析了"完整"的网络接入控制具备的条件。     

植物缺磷及菌根信号转导网络

磷是植物生长发育的主要限制因子之一,主要以无机正磷酸盐的形态被植物吸收,而其在土壤中的移动性和生物有效性很低。为了适应磷缺乏的环境,植物进化出了包括与丛枝菌根真菌形成互惠共生体系在内的一系列适应性机制以增强对磷的吸收、转运和再利用等。所有的这些机制均是由复杂而精巧的分子调控网络控制的。近年来众多基因被鉴定并进行功能研究后与该调控网络联系起来,这些基因包括各种蛋白质基因和非编码RNA基因。本文旨在对当前该领域的研究进展作一总结,同时探讨植物缺磷与菌根信号转导途径间可能存在的相互关系。     

Mars north polar deposits: stratigraphy, age, and geodynamical response

The Shallow Radar (SHARAD) on the Mars Reconnaissance Orbiter has imaged the internal stratigraphy of the north polar layered deposits of Mars. Radar reflections within the deposits reveal a laterally continuous deposition of layers, which typically consist of four packets of finely spaced reflectors separated by homogeneous interpacket regions of nearly pure ice. The packet/interpacket structure can be explained by approximately million-year periodicities in Mars' obliquity or orbital eccentricity. The observed approximately 100-meter maximum deflection of the underlying substrate in response to the ice load implies that the present-day thickness of an equilibrium elastic lithosphere is greater than 300 kilometers. Alternatively, the response to the load may be in a transient state controlled by mantle viscosity. Both scenarios probably require that Mars has a subchondritic abundance of heat-producing elements.     

A network model of catecholamine effects: gain, signal-to-noise ratio, and behavior

At the level of individual neurons, catecholamine release increases the responsivity of cells to excitatory and inhibitory inputs. A model of catecholamine effects in a network of neural-like elements is presented, which shows that (i) changes in the responsivity of individual elements do not affect their ability to detect a signal and ignore noise but (ii) the same changes in cell responsivity in a network of such elements do improve the signal detection performance of the network as a whole. The second result is used in a computer simulation based on principles of parallel distributed processing to account for the effect of central nervous system stimulants on the signal detection performance of human subjects.     

加强网络心理调适,创新网络思想政治工作机制

积极推进思想政治教育进网络是高校思想政治工作的重要内容之一,也是教育部部署到各高校思想政治工作的一个重点.文中对加强大学生网络心理的调适,构建高校网络思想政治工作的新机制,以增强网络思想政治工作的针对性和实效性提出若干工作机制:加强网络文化建设,优化网络思想政治工作环境;建立网络心理辅导站,实现网络心理辅导与网络思想政治工作的有机结合;建立一支高素质的网络思想政治工作队伍.     

刺猬肉的营养成分及其品质评价

对野生动物刺猬（Erinaceuseuropaeus）肉的营养成分及其品质进行了理化及感官检验。结果表明：刺猬肌肉含蛋白质20．2％;脂肪8％;矿物质1％;熟肉率61．2％;肌纤维直径18．95±3．45μm;脂肪熔点20～38℃;碘价94～99。肌肉的感官指标良好,其营养成分及品质可与常用动物肉（猪、牛、羊、鸡、兔肉）相媲美;油脂与常用动物油脂相比,脂肪酸不和程度明显高于动物油脂,与花生油等多种植物油的不饱和程度相当。     

The most common errors of capacitance grain moisture sensors: effect of volume change during harvest

The objective of this study was to investigate the inaccuracy of a capacitance moisture sensor mounted on a combine harvester based on the datasets of six consecutive years. Variation of sensed volume is a major cause of measurement error for a capacitive sensor. The percentage of the sensed volume occupied by grain changes continuously by filling and emptying of the grain bin, which causes a large fluctuation in sensor output during on-the-go moisture sensing. At the beginning of the bin filling process when the grain bin is empty, under-measures were recorded and when it is approximately 60 % full, large over-measures are observed compared to the actual moisture values. This effect mainly influences the precision of the recorded site-specific moisture values and causes inaccurate yield maps. To assess the effect of varying sensed volume content during harvest operation, a bin level transmitter sensor was mounted on the top of the grain bin to continuously measure the height of the grain. A clear correlation between the actual amount of material (available space) in the grain bin to the bias from the standard moisture was demonstrated. The coefficient of determination was R² = 0.86 for corn (Zea mays L.) and R² = 0.87 for winter wheat (Triticum aestivum L.). By using equations generated from the datasets of consecutive years (2008, 2009 and 2010), an effective post-correction method for the recorded data is proposed.     

Synergies in alternative food network research: embodiment,diverse economies,and more-than-human food geographies

As ecologically and socially oriented food initiatives proliferate, the significance of these initiatives with respect to conventional food systems remains unclear. This paper addresses the transformative potential of alternative food networks (AFNs) by drawing on insights from recent research on food and embodiment, diverse food economies, and more-than-human food geographies. I identify several synergies between these literatures, including an emphasis on the pedagogic capacities of AFNs; the role of the researcher; and the analytical and political value of using assemblage and actor-network thinking to understand the far-reaching forces and power disparities confronting proponents of more ethical and sustainable food futures.