Inter-individual variation in sequestration (as measured by energy dispersive spectroscopy) predicts efficacy of defensive secretion in lubber grasshoppers

Summary. We tested whether inter-individual variation in concentration of sequestered compounds predicts defensive efficacy of the defensive secretion of onion-fed Eastern lubber grasshoppers. When fed onion, lubbers have the ability to sequester sulfur compounds into their defensive secretion, and the secretion from onion-fed lubbers is more deterrent of ants than the secretion from lubbers fed other diets (Jones et al. 1989). To test three hypotheses, we developed a method for measuring total sequestered sulfur in the secretion using energy dispersive spectroscopy (EDS). First, we found that lubbers fed an ad libitum, monophagous diet of onion produce more secretion and have higher concentrations of total sulfur in their secretions than lubbers fed other diets. These sulfur concentrations varied three-fold; we believe that this variation in the composition of defensive secretions stems from physiological variation. Second, our method was sensitive enough to detect sulfur in the secretion of some lubbers that had been fed onion only once. Third, the sulfur concentration of a secretion sample significantly predicted its ability to deter ants from foraging. Hence, our results suggest that inter-individual variation in defensive chemistry in insects offered the same diet may be ecologically important. Received 25 November 1997; accepted 5 February 1998.     

基于典型道路谱的模拟运输振动试验方法研究

针对深圳某一路段使用美国Lansmont公司开发的SAVER环境应力记录仪记录汽车运输过程中的环境应力,利用相关处理软件整理分析数据,最后在实验室中的通过电磁振动台的随机振动模式来进行模拟重现从而实现“Fieldtolab”。该方法用短时间的实验室内试验来代替长时间的实际运输过程,不仅绿色环保,而且省时省力,是一种值得推广的试验方法。     

基于知识图谱可视化视角的旅游灾害管理研究综述

如何进行旅游灾害管理是全球旅游目的地共同关注的问题.首先界定了旅游灾害管理的概念,然后在中国知网和Web of Science中分别筛选了168篇和180篇中英文文献,采用知识图谱文献可视化分析方法,绘制了发文量、作者和发文机构,以及关键词共现图谱.研究认为,国内外旅游灾害管理研究集中于旅游灾害风险、旅游风险评估、灾害...     

Influence of type of MVC test on electromyography measures of biceps brachii and triceps brachii

Objective. This study aimed to investigate the amplitude and frequency measures of the electromyography (EMG) signal in agonistic and antagonistic muscles (biceps brachii, triceps brachii). Methods. Fifteen males (22.9?±?2.1 years old) took three isometric maximum voluntary contraction (MVC) tests. Two tests were typical MVC tests for biceps brachii and triceps brachii. The third was a test often used to obtain MVC for forearm muscles (arm and forearm hanging down). The EMG signal was recorded during three isometric MVC muscle contractions and during a relaxation test. Results. There were no differences in amplitude between relaxation and MVC antagonist in static contraction, with higher values for frequency measures in relaxation. When biceps brachii and triceps brachii act as antagonists in an MVC test, frequency measures present lower values than when the muscles act as agonists. Biceps brachii shows much lower amplitude than during an agonist MVC contraction with similar spectral measures. Triceps brachii presents much higher values of spectral measures than during an agonist MVC test. Conclusion. The type of exerted force, i.e., if a muscle acted as an agonist, antagonist or stabilizer, affects the relationship between the time and frequency domain measures.     

餐饮业废油脂皂化工艺的探索

研究了废油脂的皂化方法和皂化机理。通过红外光谱分析废油脂皂化样品 ,对皂化度的影响因素进行了讨论。摸索出最佳皂化工艺条件 :皂化时间 4h ,皂化温度 10 0℃ ,碱液用量 (NaOH与废油脂的质量比 ) 1∶2 ,皂化用NaOH碱液浓度为 30 %。     

高层建筑结构在地震和风作用下的可靠度分析

作者基于等效风谱理论，给出了高层建筑结构在风荷载作用下可靠度分析的方法。在给定层间位移允许值时，对高层建筑结构在使用期限内在地震和风作用下的可靠度进行了比较研究。本文还探讨了高层建筑结构在地震和风联合作用下的可靠度问题。     

林火在空间上的波动性及其对全球变化的响应(Ⅰ)

研究表明,林火在时间方向具有一定的周期性,表现为一定频率的火周期。该文应用黑龙江省1980～1999年林火数据,分别计算出每年火灾发生的火点的质心经纬度坐标和火场面积质心的经纬度坐标,用波谱分析研究其质心随年份的波动现象。结果表明,1980-1999年的黑龙江省林火的火场质心分别是以东经126.97°,北纬49.63°为轴作东西、南北波动,波动具有明显的同期性,经度方向和纬度方向的周期均为3.3a,其东西南北波动的最大最小值分别为东经128.68°,北纬52.82°,东经123.08°,北纬46.86°。火点的质心分别以东经127.90°,北纬48.69°为轴作东西、南北方向的波动,波动不具有明显的周期性,其东西南北波动的最大最小值分别为东经129.22°,北纬50.37°,东经125.18°,北纬47.28°。     

用超声波无损检测技术检测混凝土的厚度

使用普通的超声换能器,用高频率换能器作发射端,低频率换能器作接收端,通过互相关谱分析,可以得到反射声波的到时,从而计算得到混凝土的厚度。实验表明,本方法对混凝土厚度的测量具有较高的精度和可靠性。     

室内多因素条件下香烟颗粒粒谱动态分布特征

烟颗粒粒径分布和浓度变化是探测香烟阴燃火灾初期的重要参数,研究香烟阴燃过程烟颗粒粒谱分布对火灾探测具有指导意义。实验通过在室内有风条件下展开,研究风速、位置、时间、烟源等因素对烟颗粒的粒径分布和形成规律的影响。结果表明:1随着时间的推移,GMD(Geometric Mean Diameter,几何平均直径)变大,烟颗粒数量浓度增加,但粒谱分布逐渐趋于稳定。2风速对颗粒粒谱形成的影响较为复杂,随着风速的增加,气流扰动加剧,烟颗粒浓度增加,GMD有减小的变化趋势。3在不同的位置,有风条件下烟颗粒随着气流迁移,最终在壁面处进行积累,离烟源越远位置,沿着风速方向浓度和GMD均变大。4烟颗粒的初始浓度也影响烟颗粒粒谱分布和运动特征,烟源数量越多,初始浓度越大,形成的烟颗粒浓度和GMD越大。     

冬季长江口渔场游泳动物群落种类组成和多样性的年代际变化

根据1991—2011年间3个代表年冬季长江口渔场的调查数据,对该海域游泳动物群落的年代际变化进行了研究。结果表明：1991—2011年,游泳动物种类数总体表现为升高的趋势,其中鱼类的增加幅度较小,甲壳类和头足类的增加幅度较大。以重量和尾数为代表的资源密度指数均表现出先下降后升高的趋势。平均体重先呈现急剧下降然后继续小幅下降的趋势。1991年优势种类数为7种,2001年为9种,2011年为7种,后2个年份和1991年相比,优势种发生了较大的更替。细点圆趾蟹（Ovalipes punctatus）和龙头鱼（Harpadon nehereus）为3个年份的共同优势种。游泳动物的站位平均种类数呈现持续升高趋势,而站位平均丰富度指数、多样度指数和均匀度指数则呈现出先升高再降低的趋势。1991和2001年、1991和2011年之间的平均相异性较高,均超过60%,而2001和2011年之间的平均相异性较低,为36.05%;引起群落差异的主要种类数呈增加的趋势,生态类群也逐渐扩大。游泳动物长度谱呈现逐渐变窄的趋势,主要是由于群落中的生物种类演替、小型鱼类数量增多和大型鱼类的群体年龄结构降低等原因造成的。