A short duration of the Cretaceous-Tertiary boundary event: evidence from extraterrestrial helium-3

Analyses of marine carbonates through the interval 63.9 to 65.4 million years ago indicate a near-constant flux of extraterrestrial helium-3, a tracer of the accretion rate of interplanetary dust to Earth. This observation indicates that the bolide associated with the Cretaceous-Tertiary (K-T) extinction event was not accompanied by enhanced solar system dustiness and so could not have been a member of a comet shower. The use of helium-3 as a constant-flux proxy of sedimentation rate implies deposition of the K-T boundary clay in (10 +/- 2) x 10(3) years, precluding the possibility of a long hiatus at the boundary and requiring extremely rapid faunal turnover.     

High-latitude dust over the North Atlantic: inputs from Icelandic proglacial dust storms

Mineral aerosols play an important role in the atmosphere-ocean climate system. Research has focused almost exclusively on sources in low-latitude arid regions, but here we show that there are substantial sources in cold, higher latitudes. A 6-year record of measurements made on Heimaey, an island south of Iceland, reveals frequent dust events with concentrations exceeding 20 micrograms per cubic meter. Much of this potentially iron-rich dust is transported southward and deposited in the North Atlantic. Emissions are highest in spring and spatially and temporally associated with active glacial outwash plains; large dust events appear to be associated with glacial outburst floods. In response to global warming, ice retreat on Iceland and in other glacierized areas is likely to increase dust emissions from these regions.     

A carbonate-rich, hydrated, interplanetary dust particle: possible residue from protostellar clouds

Transmission electron microscopy of a hydrated interplanetary dust particle (IDP) indicates that it contains abundant magnesium-iron carbonates, primarily breunnerite and magnesian siderite. This IDP displays a strong absorption band at 6.8 micrometers in its infrared spectrum, similar to that in certain protostellar spectra. The carbonates probably account for the 6.8-micrometer band in the IDP spectrum, suggesting that carbonate also may occur in interstellar dust and be the source of the controversial 6.8-micrometer feature from the protostellar spectra.     

东莞大岭山7种林分凋落物的养分动态

应用网格法设置样地调查东莞大岭山林分凋落物的伞N、全P和全K含量,利用地统计学并结合地理信息系统的空间分析功能,分析了凋落物养分空间分布特征,研究了凋落物养分的季节性变化.结果表明:全N、全P和全K的最佳拟合模型分别为球状模型、指数模型和高斯模型,其块金值与基台值之比分别为0.278、0.592和0.579,属于中等程度空间相关.     

Fluoride distribution and biological availability in the fallout from mount st. Helens, 18 to 21 may 1980

Concentrations of fluoride in the ash fallout in central Washington from the 18 May 1980 eruption of Mount St. Helens varied severalfold, but none are high enough to constitute any immediate hazard to animal life. The heaviest fallout (Moses Lake) contained 113 parts per million (ppm) of acid-labile fluoride, but of this only 11 ppm was water-soluble and 20 ppm was available to rats. The fluoride concentrations in the urine of cattle feeding for 4 days on hay contaminated with this ash were essentially normal. Samples of ash from other areas generally had higher concentrations of acid-labile fluoride but lower concentrations of water-soluble fluoride. The concentration of water-soluble fluoride was inversely correlated with the coarseness of the fallout.     

Mount st. Helens ash from the 18 may 1980 eruption: chemical, physical, mineralogical, and biological properties

Samples of ash from the 18 May 1980 eruption of Mount St. Helens were collected from several locations in eastern Washington and Montana. The ash was subjected to a variety of analyses to determine its chemical, physical, mineralogical, and biological characteristics. Chemically, the ash samples were of dacitic composition. Particle size data showed bimodal distributions and differed considerably with location. However, all samples contained comparable amounts of particles less than 3.5 micrometers in diameter (respirable fraction). Mineralogically, the samples ranged from almost totally glassy to almost totally crystalline. Crystalline samples were dominated by plagioclase feldspar (andesine) and orthopyroxene (hypersthene), with smaller amounts of titanomagnetite and hornblende. All but one of the samples contained from less than 1 percent to 3 percent free crystalline silica (quartz, trydimite, or cristobalite) in both the bulk samples and 1 to 2 percent in the fractions smaller than 3.5 micrometers. The long-lived natural radionuclide content of the ash was comparable to that of crustal material; however, relatively large concentrations of short-lived radon daughters were present and polonium-210 content was inversely correlated with particle size. In vitro biological tests showed the ash to be nontoxic to alveolar macrophages, which are an important part of the lungs' natural clearance mechanism. On the basis of a substantial body of data that has shown a correlation between macrophage cytotoxicity and fibrogenicity of minerals, the ash is not predicted to be highly fibrogenic.     

Biology,invasion and management of the agricultural invader: Fall armyworm,Spodoptera frugiperda(Lepidoptera: Noctuidae)

The fall armyworm(FAW), Spodoptera frugiperda(J. E. Smith), is native to the Americas. It has rapidly invaded 47 African countries and 18 Asian countries since the first detection of invasion into Nigeria and Ghana in 2016. It is regarded as a super pest based on its host range(at least 353 host plants), its inherent ability to survive in a wide range of habitats, its strong migration ability, high fecundity, rapid development of resistance to insecticides/viruses and its gluttonous characteristics. The inherently superior biological characteristics of FAW contribute to its invasiveness. Integrated pest management(IPM) of FAW has relied on multiple applications of monitoring and scouting, agricultural control, chemical pesticides, viral insecticides, sex attractants, bio-control agents(parasitoids, predators and entomopathogens) and botanicals. Knowledge gaps remain to be filled to:(1) understand the invasive mechanisms of S. frugiperda;(2) understand how to prevent its further spread and(3) provide better management strategies. This review summarizes the biological characters of FAW, their association with its invasiveness and IPM strategies, which may provide further insights for future management.     

Upper Pleistocene Radiocarbon-Dated Artefacts from the Northern Yukon: Man was in Beringia 27,000 years ago

The evidence presented here indicates that man lived in the eastern part of the Beringian refugium before the peak of the late Wisconsin glaciation (27). He had sharp, stone tools intended for working bone and means of breaking large mammoth bones. Probably he hunted mammoth and caribou, and prepared the skins of the caribou for use as clothing and perhaps shelter. It is possible that he migrated to southern North America, although evidence for the presence of man there prior to the peak of the Wisconsin glaciation is at present in dispute (28). We do not know whether his culture should be classified as Mousteroid or Aurignacoid in Müller-Beck's scheme (23), whose criteria are taken from stone implements of which we have none, although we infer their presence. Our data suggest that in Beringia, and therefore probably in Siberia and the Far East, the transition from Middle Paleolithic to Upper Paleolithic levels of technology occurred at a relatively early date. This raises the larger question: Did the transition from Middle to Upper Paleolithic occur simultaneously in many parts of the world, or did it begin in and spread from one area (23)?     

Long-range atmospheric transport of soil dust from Asia to the tropical north pacific: temporal variability

The concentration of airborne soil dust at Enewetak Atoll(11 degrees N, 162 degrees E) in April 1979 was 2.3 micrograms per cubic meter but decreased steadily to 0.02 microgram per cubic meter over the next 5 months. The spring dust is probably derived from China; its deposition rate ( approximately 0.3 millimeter per 1000 years) suggests that it may be a significant contributor to the deep-sea sediments of the North Pacific.     

Radon-222 in the North Atlantic trade winds: its relationship to dust transport from Africa

The concentration of radon-222 in air was measured during a flight from Miami to Barbados to Dakar and return; concentrations ranged from 1 to 55 picocuries per standard cubic meter of air and were highest in areas of dense haze, which were present along most of the flight path across the Atlantic Ocean. The haze is attributed to dust originating from the arid regions of western Africa. Radon-222 may be useful as a tracer for African air parcels over the equatorial Atlantic.     

Gender discrimination and its impact on income,productivity, and technical efficiency: evidence from Benin

This paper examines the occurrence and impact of gender discrimination in access to production resources on the income, productivity, and technical efficiency of farmers. Through an empirical investigation of farmers from Koussin-Lélé, a semi-collective irrigated rice scheme in central Benin, we find that female rice farmers are particularly discriminated against with regard to scheme membership and access to land and equipment, resulting in significant negative impacts on their productivity and income. Although women have lower productivity, they are as technically efficient as men. The findings suggest that there is considerable scope for improving the productivity of women through increasing their access to production resources.