Size fractionation methods: measuring plutonium in respirable dust

Methods used to evaluate the inhalation hazard of soil contaminated with plutonium were investigated. Four soil fractionation procedures were used to separate three size fractions of soil particles taken from two locations at the Department of Energy's Rocky Flats facility. The results show that increasing amounts of soil mass and plutonium activity (0.5 to 38 percent and 7 to 84 percent, respectively) remain in the fraction of soil smaller than 10 micrometers as the in situ particle associations are increasingly disrupted by physical and chemical forces. The introduction of forces of dispersion unrelated to ambient conditions yields results that are unrelated to the original particle associations.     

Size of the Chloroplast Genome in Codium fragile

Chloroplasts isolated from the siphonous green alga Codium fragile yield circular DNA molecules averaging 27.3 micrometers in length and 56 x 10(6) daltons in molecular size. This chloroplast genome is 25 to 30 percent smaller than any reported. The small size of the Codium chloroplast genome may represent a primitive evolutionary condition in green plants.     

Cristobalite in volcanic ash of the soufriere hills volcano, montserrat, british west indies

Crystalline silica (mostly cristobalite) was produced by vapor-phase crystallization and devitrification in the andesite lava dome of the Soufriere Hills volcano, Montserrat. The sub-10-micrometer fraction of ash generated by pyroclastic flows formed by lava dome collapse contains 10 to 24 weight percent crystalline silica, an enrichment of 2 to 5 relative to the magma caused by selective crushing of the groundmass. The sub-10-micrometer fraction of ash generated by explosive eruptions has much lower contents (3 to 6 percent) of crystalline silica. High levels of cristobalite in respirable ash raise concerns about adverse health effects of long-term human exposure to ash from lava dome eruptions.     

添加不同材料对肥料中氮磷在土壤中淋出特性的影响

采用6种不同类型的材料与化学肥料复合,通过间歇淋溶实验,研究了不同材料对肥料中N、P淋出特性的影响。结果表明,CK处理(施用化学肥料),经过6次淋溶,氮素淋容量占所施氮素的13%左右,硅酸钠对氮素后期淋溶有一定的促进作用,而沸石、胡敏酸、PAM、柠檬酸对氮素淋溶有一定抑制作用,其中以PAM和柠檬酸抑制作用较大,氮素淋溶量只占所施氮素的6.7%左右。氮素累积淋溶量与时间的关系可用指数方程y=aebt来描述。胡敏酸、PAM、柠檬酸对磷素淋溶有促进作用,以柠檬酸的促进作用最强,而其它材料表现出一定的抑制作用;磷素累积淋溶量与时间的关系可以用双常数方程lny=A Blnt来描述,其中柠檬酸处理使方程的B值最大,反映磷素淋溶量随时间变化增加最快。     

Airborne studies of the emissions from the volcanic eruptions of mount st. Helens

The concentrations of particles less than 10 micrometers in diameter in the ash emissions from Mount St. Helens have been more than 1000 times greater than those in the ambient air. Mass loadings of particles less than 2 micrometers in diameter were generally several hundred micrograms per cubic meter. In the ash clouds, produced by the large eruption on 18 May 1980, the concentrations of several trace gases generally were low. In other emissions, significant, but variable, concentrations of sulfur gases were measured. The 18 May eruption produced nuées ardentes, lightning flashes, and volcanic hail.     

Size distributions and mineralogy of ash particles in the stratosphere from eruptions of mount st. Helens

Samples from the stratosphere obtained by U-2 aircraft after the first three major eruptions of Mount St. Helens contained large globules of liquid acid and ash. Because of their large size, these globules had disappeared from the lower stratosphere by late June 1980, leaving behind only smaller acid droplets. Particle-size distributions and mineralogy of the stratospheric ash grains demonstrate in-homogeneity in the eruption clouds.     

Surface properties of lunar samples

Fine-grained samples disrupted after exposure to oxygen and oxygen with 3.5 percent water above 2 torr. Chemical etching revealed plastic deformation in some samples, adhesion due to impact melting in others, dislocations in crystalline phases and evidence that some glasses were partially devitrified. Specimens of rock that were fractured in ultrahigh vacuum exhibited a time-dependent adhesion and a network of localized electrostatically charged areas.     

Crystallization of NADP-specific isocitrate dehydrogenase

The first crystalline preparation of isocitrate dehydrogenase specific for nicotinamide adenine dinucleotide phosphate has been obtained with enzyme isolated from Escherichia coli. Scanning electron microscopy was employed to elucidate the structure of the crystals, which were found to exist as regular octahedrons ranging in size from 5 to 90 micrometers.     

Polycrystalline CVD Diamond Films with High Electrical Mobility

Advances in the deposition process have led to dramatic improvements in the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconductivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is comparable to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for the CVD diamond and 300 picoseconds for single-crystal diamond. The collection distance at a field of 10 kilovolts per centimeter is 15 micrometers for the CVD diamond as compared to 30 micrometers for natural diamonds. The electrical qualities appear to correlate with the width of the diamond Raman peak. Also, although the collection distance at the highest fields in the films nearly equals the average grain size, there is no evidence of deleterious grain boundary effects.     

Particle concentration in the asteroid belt from pioneer 10

The spatial concentration and size distribution for particles measured by the asteroid/meteoroid detector on Pioneer 10 between 2 and 3.5 astronomical units are presented. The size distribution is from about 35 micrometers to 10 centimeters. The exponent of the size dependence varies from approximately -1.7 for the smallest to approximately -3.0 for the largest size measured.     

Uricotelism and low evaporative water loss in a South American frog

A South American anuran (Phyllomedusa sauvagii) produced large amounts of semisolid urate when it was maintained on a diet of insects. Rates of evaporative water loss in Phyllomedusa sauvagii were only about 5 to 10 percent of those other anurans tested and were similar to those of lizards of comparable size.     

城市环境中毛白杨和油松叶片表面颗粒污染物的观察

本文旨在观察北京地区不同环境中毛白杨和油松叶片表面颗粒污染物状况。选择毛白杨和油松分别代表阔叶乔木和针叶常绿树种。在2014年6、10月分别采集样品,利用环境扫描电镜和X-射线能谱仪对2个采样点2种树种叶表滞留的颗粒物进行了粒径与数量统计及来源解析。结果表明:PM2.5是毛白杨和油松叶表总颗粒物的主要成分,颗粒物主要滞留在毛白杨叶片的上表面和油松针叶的平面;在单位叶面积上,油松叶表面的颗粒物较毛白杨多;西直门样地叶表的PM2.5数量多于奥林匹克森林公园,10月份叶表滞留的颗粒物数量多于6月份。西直门样品除硅铝酸盐颗粒外还包括烟尘集合体和飞灰颗粒,且含有较多的S元素;与奥林匹克森林公园相比,PM2.5污染较重的西直门地区样品气孔较小、密度较大。      

Composition of the mount st. Helens ashfall in the moscow-pullman area on 18 may 1980

Mineralogical and chemical analyses of the ashfall from Mount St. Helens on 18 May 1980 indicate that there were two distinct ashes. The early dark ash is composed principally of plagioclase and lithic fragments of plagioclase and glass with titanium-rich magnetite and some basaltic hornblende and orthopyroxene. The later pale ash, four-fifths by weight of the whole fallout, is 80 percent glass with plagioclase as the principal crystalline phase. Quartz and potassium feldspar are rare to absent in both ashes. Chemical analyses of nine ash fractions and of the glass in each type emphasize the differences between the two ash types and their chemical homogeneity.     

Selective herbivory in tassel-eared squirrels: role of monoterpenes in ponderosa pines chosen as feeding trees

Ponderosa pine twigs collected from trees used by tassel-eared squirrels as sources of cortical tissue for food contained smaller amounts of monoterpenes than twigs from similar trees not used by the squirrels as food sources. Of the 18 monoterpenes isolated from the twig samples, alpha-pinene was the best single predictor of food source trees. In experiments with captive tassel-eared squirrels, consumption of a preferred food was inversely correlated with the concentration of alpha-pinene added to the food.     

Electron diffraction and imaging of uncompressed monolayers of amphiphilic molecules on vitreous and hexagonal ice

A new approach is described for probing domains of ordered self-assemblies of amphiphilic monolayers at the aqueous solution interface. The method has potential importance for the study of membrane structure, Langmuir-Blodgett films, and nucleation processes of two-and three-dimensional crystals. Electron diffraction (ED) patterns indicative of two-dimensional crystalline self-assembly were obtained from samples, which were examined by cryo-electron microscopy, of monolayers of water-insoluble amphiphiles on vitrified aqueour substrates. The apparent hexagonal symmetry of an ED pattern from a C(16)H(33)OH monolayer was interpreted in terms of multiple twinning. Monolayers of the CL(31)H(63)OH and cadmium salt of C(19)H(39)CO(2)H that were studied by dark-field techniques displayed faceted two-dimensional crystallites with a maximal size of 1 to 2 micrometers. Epitaxial nucleation of hexagonal ice by the C(31)H(63)OH monolayer has also been demonstrated by ED.     

Aerosols from the soufriere eruption plume of 17 april 1979

Aerosol samples collected from the 17 April 1979 eruption plume of Soufriere, St. Vincent, at altitudes between 1.8 and 5.5 kilometers were physically and chemically very similar to the ash that fell on the island. Higher altitude samples (7.3 and 9.5 kilometers) had a much lower ash content but comparable concentrations of sulfate, which were above the background concentration found at these altitudes.     

Size distribution of fine particles from coal combustion

Measurements of the particle size distribution at the outlets of six coal-fired utility boilers showed a peak at a particle diameter near 0.1 micrometer. This submicrometer mode appears to be a general feature of coal combustion that results from a volatilization-condensation process in the boiler. At the boilers tested, the submicrometer mode contained 0.2 to 2.2 percent of the total fly ash mass. The importance of this mode is greater than its small quantity suggests because particles in the submicrometer size range are often much more difficult to collect with conventional particulate control devices than larger particles. Thus, the submicrometer mode may significantly influence the design and selection of future power plant emission controls. The particle mass in the submicrometer mode was correlated with the nitric oxide concentration in the flue gas. This correlation suggests that control of nitric oxide by modification of the combustion conditions may reduce the generation and emission of submicrometer particles.     

Magnesium isotopic composition of interplanetary dust particles

The magnesium isotopic composition of some extraterrestrial dust particles has been measured. The particles are believed to be samples of interplanetary dust, a significant fraction of which originated from the disaggregation of comets and may contain preserved isotopic anomalies. Improvements in mass spectrometric and sample preparation techniques have made it possible to measure the magnesium isotopic composition of the dust particles, which are typically 10 micrometers in size and contain on the order of 10(-10) gram of magnesium. Of the 13 samples analyzed, nine have the terrestrial magnesium isotopic composition within 2 parts per thousand, and one shows isotopic mass fractionation of 1.1 percent per mass unit. A subset of the particles, described as chondritic aggregates, are very close to normal isotopic composition, but their normalized isotopic ratios appear to show nonlinear effects of 3 to 4 parts per thousand, which is near the present limit of detection for samples of this size. The isotopic composition of calcium was also determined in one particle and found to be normal within 2 percent. It is clear that the isotopic composition of interplanetary dust particles can be determined with good precision. Collection of dust particles during the earth's passage through a comet tail or an intense meteor stream may permit laboratory analysis of material from a known comet.     

Alpha-decay--induced fracturing in zircon: the transition from the crystalline to the metamict state

A natural single crystal of zircon, ZrSiO(4,) from Sri Lanka exhibited zonation due to alpha-decay damage. The zones vary in thickness on a scale from one to hundreds of micrometers. The uranium and thorium concentrations vary from zone to zone such that the alpha-decay dose is between 0.2 x 10(16) and 0.8 x 10(16) alpha-events per milligram (0.15 to 0.60 displacement per atom). The transition from the crystalline to the aperiodic metamict state occurs over this dose range. Differential expansion of individual layers due to variations in their alpha-decay dose caused a systematic pattern of fractures that do not propagate across aperiodic layers. High-resolution transmission electron microscopy revealed a systematic change in the microstructure from a periodic atomic array to an aperiodic array with increasing alpha-decay dose. At doses greater than 0.8 x 10(16) alpha-events per milligram there is no evidence for long-range order. This type of damage will accumulate in actinide-bearing, ceramic nuclear waste forms. The systematic pattern of fractures would occur in crystalline phases that are zoned with respect to actinide radionuclides.     

Sintered diamond compacts with a cobalt binder

Diamond powder can be successfully cemented with cobalt. At 62 kilobars the sintering occurs over the temperature range from 1570 degrees to 1610 degrees C. The maximum microhardness of the compact ( 3000 kilograms per square millimeter on the Knoop scale) is obtained with a mixture of 20 percent cobalt (by volume) and a diamond particle size of 1 to 5 micrometers.