Nitrogen-15 and oxygen-18 characteristics of nitrous oxide: a global perspective

The global budget of N(2)O shows a significant imbalance between the known rate of destruction in the stratosphere and the estimated rates of natural and anthropogenic production in soils and the ocean. Measurements of the (15)N/(14)N and (18)O/(16)O ratios in two major tropospheric sources of N(2)O, tropical rain forest soils and fertilized soils, show that soil N(2)O from a tropical rain forest in Costa Rica and from sugar-cane fields in Maui is strongly depleted in both (15)N and (18)O relative to mean tropospheric N(2)O. A major source of heavy N(2)O, enriched in both (15)N and (18)O, must therefore be present to balance the light N(2)O from soils. One such source is the back-mixing flux of N(2)O from the stratosphere, which is enriched in (15)N and (18)O by photolysis and chemistry. However these return fluxes of (15)N and (18)O are so great that a large oceanic flux of N(2)O is required to balance the heavy isotope-enriched stratospheric flux. All these effects will be reflected in climatically related isotopic variations in trapped N(2)O in polar ice cores.     

Paleocirculation of the deep north atlantic: 150,000-year record of benthic foraminifera and oxygen-18

Benthic foraminiferal faunas in a piston core from 3331 meters at 44 degrees N on the Mid-Atlantic Ridge show striking variations in the relative abundance of species. Uvigerina peregrina, which is broadly distributed today in the South Atlantic and in the Pacific in water that has been long isolated from the surface, is absent in the North and Equatorial Atlantic at depths occupied by highly oxygenated North Atlantic deep water. This species dominated the fauna at this site for much of the past 150,000 years. It is suggested that North Atlantic deepwater production was much reduced or eliminated at times of Uvigerina peregrina abundance, as a result of cooling and stratification of the Norwegian Sea surface, coincident with the times of the southward migration of the polar front in the North Atlantic.     

Relation between long-term trends of oxygen-18 isotope composition of precipitation and climate

Stable isotope ratios of oxygen ((18)O/(16)O) and hydrogen (D/H) in water have long been considered powerful indicators of paleoclimate. However, quantitative interpretation of isotope variations in terms of climate changes is hampered by a limited understanding of physical processes controlling the global isotope behavior. Analysis was conducted of time series of (18)O content (delta (18)O) of monthly precipitation and surface air temperature available through the International Atomic Energy Agency-World Meteorological Organization global network, "Isotopes in Precipitation." This study indicates that long-term changes of isotopic composition of precipitation over mid-and high-latitude regions during the past three decades closely followed long-term changes of surface air temperature with the average 8180-temperature coefficient around 0.6 per mil per degree Celsius.     

Carbon-13 and oxygen-18 in dinosaur, crocodile, and bird eggshells indicate environmental conditions

We have gathered, from the nests of dinosaurs, and living and fossil birds, some evidence of the environment in which these creatures lived. However, our isotope determinations suggest it will be impossible to resolve the problem as to whether the dinosaurs were warm-or cold-blooded from the oxygen and carbon isotopes content of their shells.     

Migrations of california gray whales tracked by oxygen-18 variations in their epizoic barnacles

Barnacles attached to the California gray whale have oxygen isotope compositions that serve as a record of changing ocean temperatures as the whale migrates between arctic and subtropical waters. The isotopic values for the barnacles can be used to track whale migrations and to reconstruct the recent movements of beached whales. The method may be useful for tracing the movements of other animals, living or fossil, and for reconstructing the voyages of ancient ships.     

Water, hydrogen, deuterium, carbon, carbon-13, and oxygen-18 content of selected lunar material

The water content of the breccia is 150 to 455 ppm, with a deltaD from-580 to -870 per mil. Hydrogen gas content is 40 to 53 ppm with a deltaD of -830 to -970 per mil. The CO(2) is 290 to 418 ppm with delta (13)C = + 2.3 to + 5.1 per mil and delta(18)O = 14.2 to 19.1 per mil. Non-CO(2) carbon is 22 to 100 ppm, delta(13)C = -6.4 to -23.2 per mil. Lunar dust is 810 ppm H(2)O (D = 80 ppm) and 188 ppm total carbon(delta(13)C = -17.6 per mil). The (18)O analyses of whole rocks range from 5.8 to 6.2 per mil. The temperature of crystallization of type B rocks is 1100 degrees to 1300 degrees C, based on the oxygen isotope fractionation between coexisting plagioclase and ilmenite.     

The 18O/16O and 17O/16O ratios in atmospheric nitrous oxide: A mass-independent anomaly

Measurements of the oxygen isotope ratios (18O/16O and 17O/16O) in atmospheric nitrous oxide (N2O) from La Jolla, Pasadena, and the White Mountain Research Station (elevation, 3801 meters) in California and the White Sands Missile Range in New Mexico show that N2O has a mass-independent composition. These data suggest the presence of a previously undefined atmospheric process. The La Jolla samples can be explained by a mixing between an atmospherically derived source of mass-independent N2O and biologically derived mass-dependent N2O. Possible origins of the mass-independent anomaly in N2O are discussed.     

Oxygen isotopes: experimental vapor fractionation and variations in tektites

High-temperature (about 2800 degrees C) vapor fractionation of a silicate glass that originally contained 82 percent by weight of SiO(2) resulted in a decrease of the silica content to 45 percent. Oxygen isotope analyses show that the O(18)/O(16) ratio increased from 13.80 per mil in the starting material to 14.47 and 15.03 per mil in the residuum. This suggests that bediasites, which also exhibit an increase in this ratio with decreasing content of silica, have been subjected to a process of vapor fractionation.     

Atmospheric oxygen: isotopic composition and solubility fractionation

Atmospheric oxygen has been found to be enriched in oxygen-18 by 23.5 +/- 0.3 per mil relative to average ocean water (SMOW). Oxygen dissolved in seawater is further enriched in oxygen-18 by 0.85 per mil at 0 degrees C. The temperature dependence of the solubility enrichment is given by epsilon (per mil) = 0.85- 0.010 t ( degrees C). This result is in good agreement with earlier measurements of the solubility effect in distilled water.     

Early proterozoic microfossils and penecontemporaneous quartz cementation in the sokoman iron formation, Canada

Early Proterozoic microfossils from the Sokoman Iron Formation, northeastern Canada, are indistinguishable from those of the Gunflint Formation in both morphology and inferred community structure. The contemporaneity of the Sokoman assemblage with the Bitter Springs-like cyanobacteria of the Belcher Supergroup indicates that differences between the two major types of early Proterozoic microbiotas are primarily ecological and not temporal (evolutionary) in nature. In arenaceous iron formations, microfossils are restricted to peloids and are absent from pore-filling silica interpreted as cement. Cemented arenaceous intraclasts indicate that some of the silica was penecontemporaneous, and the abundance of minus-cement porosity in arenaceous iron formations demonstrates that early (pre-compaction) cementation was common.     

The Pex16p homolog SSE1 and storage organelle formation in Arabidopsis seeds

Mature Arabidopsis seeds are enriched in storage proteins and lipids, but lack starch. In the shrunken seed 1 (sse1) mutant, however, starch is favored over proteins and lipids as the major storage compound. SSE1 has 26 percent identity with Pex16p in Yarrowia lipolytica and complements pex16 mutants defective in the formation of peroxisomes and the transportation of plasma membrane- and cell wall-associated proteins. In Arabidopsis maturing seeds, SSE1 is required for protein and oil body biogenesis, both of which are endoplasmic reticulum-dependent. Starch accumulation in sse1 suggests that starch formation is a default storage deposition pathway.     

Quartz: preferred orientation in rocks produced by dauphine twinning

X-ray analyses of quartz aggregates deformed in the laboratory andin nature show a striking difference in the preferred orientation of the positive and negative trigonal forms. These observations may be accounted for by mechanically induced Dauphiné twinning. This orienting mechanism is unusual in that it requires no permanent strain.     

Association of human papillomavirus types 16 and 18 E6 proteins with p53

Human papillomavirus type 16 (HPV-16) is a DNA tumor virus that is associated with human anogenital cancers and encodes two transforming proteins, E6 and E7. The E7 protein has been shown to bind to the retinoblastoma tumor suppressor gene product, pRB. This study shows that the E6 protein of HPV-16 is capable of binding to the cellular p53 protein. The ability of the E6 proteins from different human papillomaviruses to form complexes with p53 was assayed and found to correlate with the in vivo clinical behavior and the in vitro transforming activity of these different papillomaviruses. The wild-type p53 protein has tumor suppressor properties and has also been found in association with large T antigen and the E1B 55-kilodalton protein in cells transformed by SV40 and by adenovirus type 5, respectively, providing further evidence that the human papillomaviruses, the adenoviruses, and SV40 may effect similar cellular pathways in transformation.     

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.     

Citrus flavonoid complex: chemical fractionation and biological activity

A study was made of the anti-inflammatory activity of the fractionated components of a citrus flavonoid complex. Several highly active components, distinct from hesperidin and naringin, were isolated and tested for anti-inflammatory activity. A method for evaluation of this biological activity is recommended.     

Water isotope ratios D/H, 18O/16O, 17O/16O in and out of clouds map dehydration pathways

Water isotope ratios have been measured by laser absorption spectroscopy in and out of cirrus clouds formed in situ and convectively generated in anvils over subtropical regions. Water vapor in the tropical and subtropical upper troposphere shows a wide range of isotopic depletion not observed previously. The range suggests that dehydration of upper tropospheric air occurs both by convective dehydration and by gradual dehydration mechanisms. Twenty-five percent of upper tropospheric water sampled is in ice particles whose isotopic signatures are used to identify those grown in situ from those lofted from below.     

氧化亚铁硫杆菌的磁性及铁源种类对磁小体合成的影响

氧化亚铁硫杆菌,通过氧化二价铁或还原态无机硫化物获得能量,在细胞内能合成磁性纳米颗粒。通过扫描电镜和透射电镜对氧化亚铁硫杆菌菌体进行分析。探讨了该菌的趋磁性以及不同铁源对菌体生长和磁小体合成的影响。结果表明:生长于9K培养基的细菌能够合成磁小体,单个细胞的磁小体数目大概为2个;干燥菌体和湿菌体都能被磁铁吸附;当有外加磁场时,细菌在半固体平板和光学显微镜下均可见趋磁性;氧化亚铁硫杆菌生长和磁小体合成的最佳铁源均为硫酸亚铁。     

异种材料罐体焊接工艺的研究

在异种材料焊接性能分析和MAG焊接试验的基础上,探讨了奥氏体不锈钢(0Cr18Ni9)和低温压力容器用钢(16MnDR)角接接头的焊接工艺。通过电网变电站高压开关设备(GIS)的焊接实践,获得较好的焊接接头,满足了压力容器规程对罐体的焊接要求。     

扬麦16、宁麦18超高产群体特征及株型指标研究

为给本地区超高产小麦品种的选育提供指导依据,对目前江苏淮南地区推广面积最大的小麦品种扬麦16和高产小麦新品种宁麦18（产量达8500 kg/hm2以上）的群体特征及株型指标进行研究。结果表明：高产群体花后干物质积累量与籽粒产量呈极显著正相关;叶面积系数（LAI）于孕穗期最大;叶片长表现为倒二叶＞倒三叶＞旗叶,宽表现为旗叶＞倒二叶＞倒三叶,倒二叶叶面积最大,倒二叶、倒三叶宽与产量呈显著负相关;节间配置为1∶2.5∶3.5∶（5～5.5）∶（8～9）。