Androgens alter the tuning of electroreceptors

Weakly electric fish possess electroreceptors that are tuned to their individual electric organ discharge frequencies. One genus, Sternopygus, displays both ontogenetic and seasonal shifts in these frequencies, possibly because of endocrine influences. Systemic treatment with androgens lowers the discharge frequencies in these animals. Concomitant with these changes in electric organ discharge frequencies are decreases in electroreceptor best frequencies; hence the close match between discharge frequency and receptor tuning is maintained. These findings indicate that the tuning of electroreceptors is dynamic and that it parallels natural shifts in electric organ discharge frequency.     

Classical conditioning of electric organ discharge rate in mormyrids

Weakly electric fish of the African family Mormyridae emit pulses at variable intervals with a distribution skewed toward longer intervals. Fourteen specimens of the genera Mormyrops, Gnathonemus, and Marcusenius were classically conditioned to increase briefly their discharge frequency. The unconditioned stimulus was electric shock and the conditioned stimulus was light. These results are novel in that the overt conditioned response involves neither secretion nor movement.     

Neuronal analysis of wave form in the time domain: midbrain units in electric fish during social behavior

A fish of the genus Eigenmannia responds differently to a neighboring conspecific fish with a slightly higher frequency of the electric organ discharge than its own than to one with a slightly lower such frequency than its own. When the two frequencies are beating against each other the special wave shape of the electric organ discharge leads to asymmetries of the beat pattern which are distinct for the two cases. Midbrain neurons, called "deltaF recoders," sign and magnitude of the frequency difference on the basis of these patterns. that is, in the time rather than the frequency domain.     

Amazonian ecology: tributaries enhance the diversity of electric fishes

Neotropical rivers support a diverse array of endemic taxa, including electric fishes of the order Gymnotiformes. A comprehensive survey of the main channels of the Amazon River and its major tributaries (>2000-kilometer transect) yielded 43 electric fish species. Biogeographical analyses suggest that local mainstem electric fish diversity is enhanced by tributaries. Mainstem species richness tends to increase downstream of tributary confluences, and species composition is most similar between tributaries and adjacent downstream mainstem locations. These findings support a "nodal" or heterogeneous model of riverine community organization across a particularly extensive and diverse geographical region.     

Night-Shocker: Predatory Behavior of the Pacific Electric Ray (Torpedo californica)

Diving observations off Santa Barbara, California, indicate that Pacific electric rays (Torpedo californica) enter inshore reefs at night and actively prey on fish with the aid of powerful electric discharges.     

Primitive earth synthesis of nicotinic acid derivatives

Nicotinonitrile, 2-cyanopyridine, and 4-cyanopyridine can be synthesized under primitive earth conditions by the action of electric discharges on ethylene and ammonia. The electric discharge first synthesizes pyridine and hydrogen cyanide, which react in the discharge to form the cyanopyridines. Nicotinonitrile would have hydrolyzed in the primitive ocean to nicotinamide and nicotinic acid.     

兴山县香溪河流域农业源氮磷排放估算及时空特征分析

基于典型调查与统计分析,应用排污系数法估算了兴山县香溪河流域2007-2013年种植业源、畜禽养殖业源和农村生活源TN、TP污染物的排放量,并对排放量、排放强度及其时空格局进行了分析。结果表明,香溪河流域农业面源污染TN、TP年均排放量分别为 1 145.2、56.5 t·a^-1,排放强度分别为44.5、2.14 kg·hm^-2·a^-1.农业源TN和TP的年排放量逐年增加,2013年较2007年增幅分别为38.0%和85.1%,TN:TP为21:1,TN排放占主导,为香溪河流域兴山县段重点防控指标。从各类污染源贡献来看,畜禽养殖业源是TN的主要贡献源,占农业源污染总量的77.9%;种植业源是TP的主要贡献源,占55.4%.从不同源氮磷排放量空间格局来看,各乡镇中水月寺镇、黄粮镇和峡口镇的TN、TP排放量均最高。从氮磷排放强度空间格局来看,峡口镇、高桥乡和黄粮镇对TN排放强度最高;峡口镇、昭君镇和黄粮镇对TP排放强度最高。     

尼日利亚稻田养鱼加灯光诱虫应用效果分析

在尼日利亚科基州进行不同沟凼的稻田养鱼加灯光诱虫应用研究，其沟凼模式分围沟和十字沟，灯光以煤油灯代替电灯，鱼稻品种均为当地常见品种。结果表明，开挖占稻田面积10％～15％不同类型的鱼沟或鱼坑，其投入成本相同，鱼稻产量相近，均比单纯稻田收入增加3．5～4．5倍。示范成果还进一步验证了以往在尼日利亚进行的灯光诱虫试验结论，即在稻田养鱼中增加灯光诱虫，能够将有害昆虫变为鱼的全价饲料，减少稻田的病虫害，鱼、稻分别增产14％和9．5％，达到经济效益和生态效益双丰收。     

直流电场中鲤的行为特性及体长与电刺激阈值的关系

用行为学的方法测量了鲤Cyprinus carpio在直流电场中的电刺激阈值,并分析了电刺激阈值与体长的关系。结果表明,鲤的感电能力与鱼体所处的位置相关,即感电反应中鲤有游向阴极的现象,头部朝向阳极是鲤趋电反应的主要特征。鲤在各反应阶段的电场强度阈值和电流密度阈值与体长相关,鱼体的状态电压与体长无关。     

电激励信号对果品电参数的影响

研究了电激励信号的频率和电压对苹果、猕猴桃和梨电参数的影响。结果表明,随着电激励信号频率的增大,果品的电容、电阻以及损耗角正切值均减小;当信号电压小于电压临界值时,果品的各项电参数值基本保持不变,但当信号电压大于该临界值时,随着电压的增大,果品的电容和电阻值减小,损耗角正切急剧增大。不同果品的电压临界值不同,10kHz信号频率下,苹果、猕猴桃和梨的电压临界值分别为0.8,1.8和1.4V。     

金属表面电火花镀盖强化机的改进与扩大应用

金属表面电火花镀盖强化工艺是利用多种合金材料作为电极,依靠脉冲放电产生的局部高温,将电极材料移镀和熔渗到工件表层或刀模具的刀口部位,形成一层新的合金涂层。从而使工件表层得到强化、合金化和增厚的目的。电火花强化工艺虽引进较早,由于长期受镀敷层厚度小、表面光洁度和生产率低的原因,限制了该工艺进一步发展和扩大应用。作者针对上述缺点进行一些改进和试验研究,初步解决了表面光洁度和生产率低与镀敷层厚度小的问題,从而提高了镀敷层质量和扩大了应用范围。     

半干旱区滴头流量对土壤水分变化影响的研究

缺水问题严重制约了我国北方干旱半干旱地区作物的产量,交替滴灌是一种有效的节水灌水方式,而不同的土壤质地与气候条件应选择不同的滴头流量。本文研究了干旱区不同的滴头流量下土壤水分再分布及土壤蒸发的变化规律,结果表明,地表湿润圈的大小直接影响到蒸发量的大小。滴头流量越大,地表的湿润半径越大,蒸发损失也越大。滴头流量的大小直接影响土壤水分在水平和垂直方向的动态。滴头流量不同,其蒸发损失也不同。     

Scavenger Probe Sampling: A Method for Studying Gaseous Free Radicals

Scavenger probe sampling for determining the concentration of certain gaseous free radicals and atoms has been used to study flames and electric discharges. Combining microprobe sampling and chemical scavenging with mass spectral analysis, this technique offers high spatial resolution, absolute concentration determination, and high temperature applicability. The reactions of hydrogen atoms with chlorinated hydrocarbons and oxygen atoms with nitrogen dioxide were used for scavenging. The results were reproducible and proportional to concentration. In an electric discharge oxygen atom concentrations agreed with gas phase titration determinations. The gas phase titration measures atom flux rather than concentration, and differences as high as 20 percent were observed. A method for deriving concentration from flux measurements is discussed.     

Television image of a large upward electrical discharge above a thunderstorm system

An image of an unusual luminous electrical discharge over a thunderstorm 250 kilometers from the observing site has been obtained with a low-light-level television camera. The discharge began at the cloud tops at 14 kilometers and extended into the clear air 20 kilometers higher. The image, which had a duration of less than 30 milliseconds,resembled two jets or fountains and was probably caused by two localizd electric charge concentrations at the cloud tops. Large upward discharges may create a hazard for aircraft and rocket launches and, by penetrating into the ionosphere, may initiate whistler waves and other effects on a magnetospheric scale. Such upward electrical discharges may account for unexplained photometric observations of distant lightning events that showed a low rise rate of the luminous pulse and no electromagnetic sferic pulse of the type that accompanies cloud-to-earth lightning strokes. An unusually high rate of such photometric events was recorded during the night of 22 to 23 September 1989 during a storm associated with hurricane Hugo.     

A dielectric polymer with high electric energy density and fast discharge speed

Dielectric polymers with high dipole density have the potential to achieve very high energy density, which is required in many modern electronics and electric systems. We demonstrate that a very high energy density with fast discharge speed and low loss can be obtained in defect-modified poly(vinylidene fluoride) polymers. This is achieved by combining nonpolar and polar molecular structural changes of the polymer with the proper dielectric constants, to avoid the electric displacement saturation at electric fields well below the breakdown field. The results indicate that a very high dielectric constant may not be desirable to reach a very high energy density.     

海南山地森林溪流鱼类群落的初步研究

2008年7月至2009年9月对海南岛自然保护区的鱼类组成和生境进行了调查,共采集鱼类39种,隶属5目15科34属.鱼类群落中以山区溪流性小型鱼类为主.鲤科鱼类是其中最大的类群,构成鱼类区系成分的主体.万泉河水系有27种,多于昌化江水系的25种和南渡江水系的21种,植物食性占12.82％,动物食性占23.08％,杂食性...     

2006-2016年间我国畜禽养殖业氮元素入水通量估算

近年来,我国畜禽养殖业发展迅速,同时规模化养殖水平不断提高,大量畜禽养殖产生的不经有效处理的排泄物也给陆地水环境带来了严重负担,为了评估近十年来我国畜禽养殖氮元素排放通量的变化以及养殖模式转变带来的影响,本研究采用污染物排放因子法,估算了在2006-2016年期间,我国规模化和散养的畜禽养殖向陆地水环境中排放的氮元素通量,重点分析了不同地区（华北、华东、中南、西南和西北）和不同畜禽养殖类型（包括羊、猪、肉牛、奶牛、蛋鸡和肉鸡）氮元素入水通量分布特征。计算结果表明,在2006-2016年期间,全国由畜禽养殖排入水体中的氮元素平均通量为4384 Gg,最大和最小值分别为4832 Gg（2006年）和4010 Gg（2008年）,中南和华北地区是我国的畜禽养殖氮元素排放的主要地区,华东和西南次之,西北地区最少,2016年华北、中南、华东、西南和西北地区的畜禽养殖氮元素水体流失通量比例分别为27%、26%、20%、17%、10%。2016年由规模化养殖所带来的氮元素入水通量占该年畜禽养殖业氮元素入水总通量的53%。在所有畜禽中,猪和肉牛是我国畜禽养殖氮元素进入水体的主要排放单元,2016年猪和肉牛养殖的氮元素入水通量占总量的68%。同时,不同畜禽养殖类型之间氮元素排放通量差异显著,在所有畜禽中,羊、肉牛和蛋鸡经散养排放的氮元素通量较大,而猪和肉鸡的氮元素排放则主要来源于规模化养殖。     

Surface discharges on natural dielectrics in the solar system

When Earth-orbiting spacecraft are exposed to large fluxes of energetic charged particles, electric discharges occur on circuit boards, solar panels, and other dielectric surfaces. Large fluxes of energetic partides can produce such discharges on natural materials in the solar system. Surface discharges will occur under a variety of conditions, but particularly favorable environments are expected to occur within the magnetospheres of the giant planets; an example is the surface of Io.     

电除尘器中粉尘预荷电的试验研究

采用线管式预荷电器对粉尘颗粒在不同条件下的荷电量进行研究,并在不同条件下对其预荷电性能进行了对比试验.结果表明,采用直流和脉冲电压供电方式时,在电压达到临界值之前,颗粒的荷电量均随电压升高而增加,脉冲电压供电方式荷电量升高较快,荷质比高出直流电压荷电1个数量级;负电晕放电的颗粒荷电量明显高于正电晕放电;电晕放电的荷电量随颗粒粒径的增大而增大;预荷电器中的荷电理论计算必须考虑粒子密度及其输运项.     

2016—2020年太湖鱼类群落结构变化及对太湖水环境的响应

基于2016—2020年太湖10个鱼类采样站位和33个水环境站点监测数据,分析研究了近年来太湖鱼类群落结构变化及其对水环境的响应。调查结果表明,2020年共在太湖调查发现鱼类56种,主要优势种为刀鲚、鲫、鲤,相对重要性指数分别为9 219.28、1 698.78和1 075.27。太湖87.9%的鱼类全长在200 mm以下,88.2%的鱼类体质量在50 g以下。2016年以来,共在太湖发现鱼类68种,太湖水环境总体保持稳定,但鱼类群落结构发生了较大变化,优势种发生明显改变。统计结果表明,2016年以来太湖鱼类群落结构多样性指数与主要水环境指标之间无显著相关性,太湖外排水量、人工增殖放流对太湖鱼类群落结构具有重要影响。研究表明,需结合太湖水环境状况建立太湖鱼类精细化捕捞方案及鲢鳙鱼增殖放流方案,引导太湖鱼类群落结构恢复并最大程度发挥太湖鲢鳙鱼控藻潜力。