Biogenic potassium salt particles as seeds for secondary organic aerosol in the Amazon

The fine particles serving as cloud condensation nuclei in pristine Amazonian rainforest air consist mostly of secondary organic aerosol. Their origin is enigmatic, however, because new particle formation in the atmosphere is not observed. Here, we show that the growth of organic aerosol particles can be initiated by potassium-salt-rich particles emitted by biota in the rainforest. These particles act as seeds for the condensation of low- or semi-volatile organic compounds from the atmospheric gas phase or multiphase oxidation of isoprene and terpenes. Our findings suggest that the primary emission of biogenic salt particles directly influences the number concentration of cloud condensation nuclei and affects the microphysics of cloud formation and precipitation over the rainforest.     

Phytoplankton and cloudiness in the Southern Ocean

The effect of ocean biological productivity on marine clouds is explored over a large phytoplankton bloom in the Southern Ocean with the use of remotely sensed data. Cloud droplet number concentration over the bloom was twice what it was away from the bloom, and cloud effective radius was reduced by 30%. The resulting change in the short-wave radiative flux at the top of the atmosphere was -15 watts per square meter, comparable to the aerosol indirect effect over highly polluted regions. This observed impact of phytoplankton on clouds is attributed to changes in the size distribution and chemical composition of cloud condensation nuclei. We propose that secondary organic aerosol, formed from the oxidation of phytoplankton-produced isoprene, can affect chemical composition of marine cloud condensation nuclei and influence cloud droplet number. Model simulations support this hypothesis, indicating that 100% of the observed changes in cloud properties can be attributed to the isoprene secondary organic aerosol.     

Cloud condensation nuclei on the atlantic seaboard of the United States

Concentrations of cloud condensation nuclei measured along the East Coast from Virginia to Long Island ranged from 1000 to 3500 per cubic centimeter as compared to 100 per cubic centimeter in clean maritime air and 300 per cubic centimeter in continental air. The global anthropogenic production rate of cloud condensation nuclei may be comparable to the natural production rate; in some industrial areas cloud condensation nuclei are dominated by anthropogenic sources.     

First plasma wave observations at uranus

Radio emissions from Uranus were detected by the Voyager 2 plasma wave instrument about 5 days before closest approach at frequencies of 31.1 and 56.2 kilohertz. About 10 hours before closest approach the bow shock was identified by an abrupt broadband burst of electrostatic turbulence at a radial distance of 23.5 Uranus radii. Once Voyager was inside the magnetosphere, strong whistler-mode hiss and chorus emissions were observed at radial distances less than about 8 Uranus radii, in the same region where the energetic particle instruments detected intense fluxes of energetic electrons. Various other plasma waves were also observed in this same region. At the ring plane crossing, the plasma wave instrument detected a large number of impulsive events that are interpreted as impacts of micrometer-sized dust particles on the spacecraft. The maximum impact rate was about 30 to 50 impacts per second, and the north-south thickness of the impact region was about 4000 kilometers.     

Evidence for liquid-phase cirrus cloud formation from volcanic aerosols: climatic implications

Supercooled droplets in cirrus uncinus cell heads between -40 degrees and -50 degrees C are identified from Project FIRE [First ISCCP (International Satellite Cloud Climatology Project) Regional Experiment] polarization lidar measurements. Although short-lived, complexes of these small liquid cells seem to have contributed importantly to the formation of the cirrus. Freezing-point depression effects in solution droplets, apparently resulting from relatively large cloud condensation nuclei of volcanic origin, can be used to explain this rare phenomenon. An unrecognized volcano-cirrus cloud climate feedback mechanism is implied by these findings.     

Infrared Astronomy After IRAS

The 250,000 sources in the recently issued Infrared Astronomy Satellite (IRAS) all-sky infrared catalog are a challenge to astronomy. Many of these sources will be studied with existing and planned ground-based and airborne telescopes, but many others can no longer even be detected now that IRAS has ceased to operate. As anticipated by advisory panels of the National Academy of Sciences for a decade, study of the IRAS sources will require the Space Infrared Telescope Facility (SIRTF), a cooled, pointed telescope in space. This instrument may be the key to our understanding of cosmic birth-the formation of planets, stars, galaxies, active galactic nuclei, and quasars. Compared with IRAS and existing telescopes, SIRTF's power derives from a thousandfold gain in sensitivity over five octaves of the spectrum.     

Voyager 2 plasma wave observations at saturn

The first inbound Voyager 2 crossing of Saturn's bow shock [at 31.7 Saturn radii (RS), near local noon] and the last outbound crossing (at 87.4 RS, near local dawn) had similar plasma wave signatures. However, many other aspects of the plasma wave measurements differed considerably during the inbound and outbound passes, suggesting the presence of effects associated with significant north-south or noon-dawn asymmetries, or temporal variations. Within Saturn's magnetosphere, the plasma wave instrument detected electron plasma oscillations, upper hybrid resonance emissions, half-gyrofrequency harmonics, hiss and chorus, narrowband electromagnetic emissions and broadband Saturn radio noise, and noise bursts with characteristics of static. At the ring plane crossing, the plasma wave instrument also detected a large number of intense impulses that we interpret in terms of ring particle impacts on Voyager 2.     

The interaction of the atmosphere of Enceladus with Saturn's plasma

During the 14 July 2005 encounter of Cassini with Enceladus, the Cassini Plasma Spectrometer measured strong deflections in the corotating ion flow, commencing at least 27 Enceladus radii (27 x 252.1 kilometers) from Enceladus. The Cassini Radio and Plasma Wave Science instrument inferred little plasma density increase near Enceladus. These data are consistent with ion formation via charge exchange and pickup by Saturn's magnetic field. The charge exchange occurs between neutrals in the Enceladus atmosphere and corotating ions in Saturn's inner magnetosphere. Pickup ions are observed near Enceladus, and a total mass loading rate of about 100 kilograms per second (3 x 10(27) H(2)O molecules per second) is inferred.     

Cu^2＋胁迫诱导花鲢血细胞凋亡的研究

以花鲢Aristichthys nobilis（Rich）血细胞为研究对象,选用不同浓度的铜离子（Cu^2＋）进行不同时间的胁迫诱导,通过瑞士姬姆萨染色和AO／EB荧光染色,在光学和荧光显微镜下观察细胞形态变化,并统计凋亡率。结果表明：在Cu^2＋的胁迫作用下。花鲢血细胞呈现细胞变圆、核变圆、核边缘化、形成凋亡小体等凋亡形态特征,且凋亡细胞随着Cu^2＋浓度的增加和作用时间的延长而增加。表明Cu^2＋能诱导花鲢血细胞发生典型的凋亡,而且细胞凋亡率与Cd^2＋的浓度和处理时间成明显的剂量一效应关系。     

干扰素通过上调BAX蛋白表达诱导肝癌细胞凋亡的研究

[目的]探讨干扰素(IFN)体外诱导肝癌细胞凋亡及其相关基因表达的作用。[方法]不同浓度的干扰素(IFN)处理肝癌细胞系CBRH-7919细胞不同时间后,光学显微镜下观察其形态学改变,用琼脂糖凝胶电泳检测作用不同时间干扰素对其细胞凋亡的影响,利用细胞免疫组化技术检测不同作用时间下BAX蛋白表达量的变化。[结果]干扰素作用肝癌细胞后,可看到较为典型的细胞凋亡形态学变化:细胞体积缩小,变形,细胞膜完整;细胞核固缩,染色质凝集,核碎裂,染色质片段化,凋亡小体形成等。琼脂糖凝胶电泳测得随着干扰素浓度的增高,出现典型的DNA LADDER。随着时间的增加BAX蛋白表达量出现增加,尤以48 h较明显。[结论]IFN可以诱导肝癌细胞凋亡,可能是由于IFN上调了BAX蛋白的表达,从而增强了自身对肝癌细胞的凋亡作用。     

Natural Versus Anthropogenic Factors Affecting Low-Level Cloud Albedo over the North Atlantic

Cloud albedo plays a key role in regulating Earth's climate. Cloud albedo depends on column-integrated liquid water content and the density of cloud condensation nuclei, which consists primarily of submicrometer-sized aerosol sulfate particles. A comparison of two independent satellite data sets suggests that, although anthropogenic sulfate emissions may enhance cloud albedo immediately adjacent to the east coast of the United States, over the central North Atlantic Ocean the variability in albedo can be largely accounted for by natural marine and atmospheric processes that probably have remained relatively constant since the beginning of the industrial revolution.     

Dissipation of marine stratiform clouds and collapse of the marine boundary layer due to the depletion of cloud condensation nuclei by clouds

When the production of cloud condensation nuclei in the stratocumulus-topped marine boundary layer is low enough, droplet collisions can reduce concentrations of cloud droplet numbers to extremely low values. At low droplet concentrations a cloud layer can become so optically thin that cloud-top radiative cooling cannot drive vertical mixing. Under these conditions, model simulations indicate that the stratocumulus-topped marine boundary layer collapses to a shallow fog layer. Through this mechanism, marine stratiform clouds may limit their own lifetimes.     

Condensation nuclei: production of very large numbers in country air

When relatively clean country air is exposed to the saturated vapor of iodine or turpentine, very large numbers of condensation nuclei develop. It is believed that such air contains clusters of molecules that are polymerized by the vapor of turpentine or iodine to form nuclei.     

智能仪表量程自动切换

智能仪表能按所编程序将被测模拟量分成若干量程,并自动寻找合适的量程,使仪表工作在最佳状态。该仪表采用输入网络,相应输入、输出接口,自动从九种量程中选择合适的一种量程测量被测电压。文中,作者详细地介绍了测量流程和转换流程的工作原理。     

Size matters more than chemistry for cloud-nucleating ability of aerosol particles

Size-resolved cloud condensation nuclei (CCN) spectra measured for various aerosol types at a non-urban site in Germany showed that CCN concentrations are mainly determined by the aerosol number size distribution. Distinct variations of CCN activation with particle chemical composition were observed but played a secondary role. When the temporal variation of chemical effects on CCN activation is neglected, variation in the size distribution alone explains 84 to 96% of the variation in CCN concentrations. Understanding that particles' ability to act as CCN is largely controlled by aerosol size rather than composition greatly facilitates the treatment of aerosol effects on cloud physics in regional and global models.     

Measurements of cloud condensation nuclei in the stratosphere around the plume of mount st. Helens

Measurements of cloud condensation nuclei were made from small samples of stratospheric air taken from a U-2 aircraft at altitudes ranging from 13 to 19 kilometers. The measured concentrations of nuclei both in and outside the plume from the May and June 1980 eruptions of Mount St. Helens were higher than expected, ranging from about 100 to about 1000 per cubic centimeter active at 1 percent supersaturation.     

水稻淀粉胚乳细胞发育期间程序性死亡的研究

 应用透射电子显微镜观察水稻淀粉胚乳细胞核在发育期间的形态变化。结果表明,伴随淀粉胚乳发育进程,其细胞核呈现染色质凝聚这一程序性细胞死亡(PCD)的典型特征。水稻胚乳细胞还出现核变形、核膜破裂、核基质进入胞质乃至核降解形成核残体的现象,细胞核从变形到解体是以一种有序的方式进行,证实水稻淀粉胚乳的细胞死亡是程序性细胞死亡。EVANS BLUE染色结果表明,水稻淀粉胚乳细胞死亡顺序是由胚乳中部向四周扩展。随发育进程,水稻胚乳中的超氧物歧化酶(SOD)和过氧化氢酶(CAT)活性持续下降。对水稻淀粉胚乳中的DNA进行     

Studies on the Programmed Cell Death in Rice During Starchy Endosperm Development

Morphological variations of the nucleus in starchy endosperm cell were observed by the electron-transmisson microscope during endosperm development in rice. Along with the development of the starchy endosperm,the nuclei of the cells showed chromatin condensation,the typical feature of programmed cell death(PCD). The nuclei also showed nucleus deformation,disruption of nuclear envelope,nucleoplasm leaking into the cytoplasm and nucleus disintegration resulting in nuclear residue formation. From the nucleus deformation to the nucleus disintegration,the morphological changes of the nucleus were orderly progressive. This indicated that the cell death of starchy endosperm in rice was programmed cell death. Evans Blue staining observation showed that the cell death was initially detected in the central part of starchy endosperm in rice,then expanded outward. The activities of superoxide dismutase(SOD)and catalase(CAT)in rice starchy endosperm both descended continuously as development progressed. The analysis of DNA of rice starchy endosperm did not show the presence of DNA laddering. The above results showed that the cell death of starchy endosperm in rice was a special form of PCD.     

毛乌素沙地不同下垫面地表凝结水形成过程

水分是制约干旱半干旱地区植物生长的主要因子。土壤凝结水数量虽小,但作为一种持续稳定的水源,对于维持干旱半干旱地区的生态平衡至关重要。为了深入了解下垫面差异对地表凝结水形成过程的影响,于2014年7—8月采用称质量法,在毛乌素沙地使用微渗仪对裸沙地、油蒿林地、沙柳林地的地表凝结水形成进行观测,并对相关气象因子和土壤温度进行同步监测。结果表明:1)地表凝结水形成在日落后即刻开始,而在日出约1 h后停止,3种下垫面地表凝结水形成规律近似;油蒿和沙柳林地的地表凝结水结束时间晚于裸沙地,有助于延长林地隐花植物和微生物对凝结水的吸收时间。2)在观测期(17 d),裸沙地、油蒿林地、沙柳林地的地表凝结水总量依次为3.332、2.382、1.817 mm,裸沙地日均凝结水量显著大于油蒿和沙柳林地(P0.05),表明灌丛覆盖会改变近地面性质和林内小气候,导致地表凝结水量减少。3)地表凝结水量与空气相对湿度呈极显著正相关关系(P0.01),与气温呈极显著负相关关系(P0.01),与风速呈显著负相关关系(P0.05)。以上研究结果可为毛乌素沙地潜在水资源评估和生态系统管理提供依据。      

黄艾美耳球虫(Eimeria flavescens)小配子体发育及其超微结构的研究

利用透射电镜和扫描电镜对黄艾美耳球虫小配子体的发育过程及小配子的超微结构进行了研究。小配子的发育过程可分为小配子体生长阶段和小配子分化阶段。小配子体生长阶段发生与裂殖生殖相似的核分裂,内部产生裂痕,体积增大;小配子分化阶段,其核上方出现中心粒,同时限制膜连同核、线粒体向带虫空泡中突出,进而中心粒的中央微管消失转变成基粒,二根鞭毛从基粒长出,突入带虫泡;核的致密部进入小配子而成为小配子的核。小配子分化过程中鞭毛的形成先于体部。成熟的小配子香蕉形,外被一层单位膜.鞭毛两根,附加微管4+1+1。