The windows of SETI--frequency and time in the search for extraterrestrial intelligence     

Oliver BM 《The Planetary report》1987,7(6):23-25

On Earth intelligent life evolved as a natural consequence of the events set in motion when the planet formed over 4 billion years ago. Since chemical evolution and solar-system formation appear to be occurring throughout the universe, we theorize that our universe may be rich with planets populated by intelligent beings who, like us, can search for evidence of other technological civilizations. Terrestrial civilization now has this capability. But if we do not begin the search soon, we'll lose the opportunity to do it from Earth as interfering signals of Earthly origin rapidly close the microwave window.  相似文献   

A two-dimensional model for a solar prominence: Effect of an external magnetic field     

R. Oliver  J. L. Ballester  E. R. Priest 《Solar physics》1991,134(1):123-144

Using analytical approximations we study the effects of different external magnetic configurations on the half-width, mass, and internal magnetic structure of a quiescent solar prominence, modelled as a thin vertical sheet of cool plasma. Firstly, we build up a zeroth-order model and analyse the effects produced by a potential coronal field or a constant- force-free field. This model allows us to obtain the half-width and mass of the prominence for different values of the external field, pressure and shear angle. Secondly, the effects of these external magnetic configurations on a two-dimensional model proposed by Ballester and Priest (1987) are studied. The main effects are a change of the half-width with height, an increase of the mass, a decrease of the magnetic field strength with height and a change in the shape of the magnetic field lines.  相似文献   

Seasonal and daily variation of mercury evasion at coastal and off shore sites from the Mediterranean Sea   总被引：3，自引：0，他引：3  

Maria E. Andersson  Katarina Grdfeldt  Ingvar Wngberg  Francesca Sprovieri  Nicola Pirrone  Oliver Lindqvist 《Marine Chemistry》2007,104(3-4):214-226

Dissolved gaseous mercury (DGM) was measured continuously using two newly developed techniques and a manual technique. The continuous techniques were based on the equilibrium between the aqueous and gaseous phase (DGM = Hg_extr / H', Hg_extr is the measured mercury concentration in the gas phase, H' is the Henry's Law coefficient at the desired temperature). In order to calculate the annual mercury evasion from the Mediterranean Sea, diurnal and seasonal measurements of DGM, total gaseous mercury in air (TGM), water temperature and wind speed were performed. During August 2003, March–April 2004 and October–November 2004 measurements of these parameters were conducted on board the RV Urania. The continuous measurements of DGM showed a diurnal variation in concentration, at both coastal and off shore sites, with higher concentrations during daytime than nighttime. The concentration difference could be as large as 130 fM between day and night. The degree of saturation was calculated directly from the measurements, S = Hg_extr / TGM and was found to vary between the different seasons. The highest average degree of saturation (850%) and the largest variation in saturation (600–1150%) was observed during the summer. The spring showed the lowest variation (260–360%) and the lowest average degree of saturation (320%). The autumn also showed a large variation in saturation (500–1070%) but a lower average (740%) compared to the summer cruise. This might be explained by the temperature difference between the different seasons, since that parameter varied the most. The flux from the sea surface was calculated using the gas exchange model developed by Nightingale et al. [Nightingale, P.D., Malin, G., Law, C.S., Watson, A.J., Liss, P.S., Liddicoat, M.I., Boutin, J., Upstill-Goddard, R. C., 2000. In situ evaluation of air–sea gas exchange parameterization using novel conservative and volatile tracers. Global Biogeochemical Cycles, 14(1):373–387]. The evasion varied between the different seasons with the highest evasion during the autumn, 24.6 pmol m^− 2 h^− 1. The summer value was estimated to 22.3 pmol m^− 2 h^− 1 and the spring to 7.6 pmol m^− 2 h^− 1. Using this data the yearly evasion from the Mediterranean Sea surface was estimated to 77 tons.  相似文献   

Interconversion of iron(III) hydroxy complexes in seawater     

Oliver C. Zafiriou  Mary B. True 《Marine Chemistry》1980,8(4):281-288

Interconversion rates of the mononuclear ferric iron species Fe(OH)₃⁰ and Fe(OH)₂⁺ are derived and their implications for the behavior of these species in seawater are examined. The previously reported formation constant for Fe(OH)₃⁰ and its claimed extreme adsorptive reactivity in seawater are shown to be mutually inconsistent. Although Fe(OH)₃⁰ is probably a stoichiometrically minor dissolved iron species, its rapid formation from Fe(OH)₂⁺ could substantially enhance the rates of heterogeneous reaction rates of the [Fe(OH)₂⁺ + Fe(OH)₃⁰] pool if the latter species is very reactive.  相似文献   

The seasonal and diel distribution of lobster larvae (Homarus gammarus (Linnaeus)) in the neuston of Galway Bay     

Tully  Oliver; O Ceidigh  Padraig 《ICES Journal of Marine Science》1987,44(1):5-9

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Crustal structure between the Knipovich Ridge and the Van Mijenfjorden (Svalbard)     

Ritzmann  Oliver  Jokat  Wilfried  Mjelde  Rolf  Shimamura  Hideki 《Marine Geophysical Researches》2002,23(5-6):379-401

Marine Geophysical Research - The Alfred Wegener Institute of Polar and Marine Research, the University of Bergen and Hokkaido University acquired new seismic refraction data along a transect from...  相似文献   

Addressing the coral reef crisis in developing countries   总被引：2，自引：0，他引：2  

Johann D. Bell  Blake D. Ratner  Ilona Stobutzki  Jamie Oliver 《Ocean & Coastal Management》2006,49(12):976-985

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Reproductive health of brown trout inhabiting Swiss rivers with declining fish catch     

Oliver Körner  Etiënne L. M. Vermeirssen  Patricia Burkhardt-Holm 《Aquatic Sciences - Research Across Boundaries》2007,69(1):26-40

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Implications of Country-Level Decisions on the Specification of Crown Cover in the Definition of Forests for Land Area Eligible for Afforestation and Reforestation Activities in the CDM     

Louis V. Verchot  Robert Zomer  Oliver Van Straaten  Bart Muys 《Climatic change》2007,81(3-4):415-430

Within the Kyoto Protocol, countries have significant latitude to define a forest. The most important parameter affecting area designated as forest is the minimum crown density which can be set between 10 and 30 percent. The choice will have implications for the amount of land available in a country for afforestation and reforestation (A/R) activities within the Clean Development Mechanism (CDM). In this paper, we used GIS analysis to look at four case studies from countries involved in the EU-funded ENCOFOR project: Bolivia, Ecuador, Uganda and Kenya. We also looked at the effects of other factors that would exclude land from eligibility for A/R projects. A low threshold of 10 percent crown cover resulted in exclusion of 70 to 90 percent of the land area of all countries except Kenya, which differed from the other countries by its large dryland areas. Much less area was excluded when higher thresholds were used. The spatial analyses showed not only the effects of the choice of the crown cover criterion, but also where the land was available for CDM activities within each country at different thresholds. This is the first time that the effect of the crown cover element of the Kyoto forest definition on land availability and distribution for CDM A/R activities has been quantified. While there are a number of reasons to choose different thresholds, this analysis suggests that countries that are considering using CDM finance for rural development might want to select the higher minimum threshold for crown cover in order to maximize their participation and flexibility.  相似文献   

Persistence of vinyl chloride in ground water at the Woodlawn landfill Superfund site,northeastern Maryland,USA     

Alan M. Jacobs  Isam E. Amin  Oliver N. Fisher 《Environmental Geology》2007,52(7):1253-1260

Since landfill operations ceased in the early 1980s at the Woodlawn landfill Superfund site in northeastern Maryland, USA, the carcinogen vinyl chloride monomer (VCM) has persisted in the site ground water at concentrations in places greater than 100 ppb. Investigations of VCM concentrations from monitoring well data from 1981 through 1991, which were published in 2001, concluded that concentrations were cyclic and were not dissipating. Data from 1991 to 2000 confirm VCM persistence, showing concentration peaks as late as 1997 in the eastern part of the site. These values are significantly above both drinking water standards (>MCL of 2 ppb) and lifetime excess cancer risk (E-6 risk level) from exposure since birth (>0.024 ppb). Sources for VCM are landfill wastes (PVC-sludge) and effluent from an on-site transfer station. In addition to direct release of VCM from wastes, other chlorinated hydrocarbons, trichloroethene and perchloroethene (TCE and PCE) are also present in the ground water, and these compounds can degrade into VCM. Persistence of VCM concentrations is the result of leachate generation, mostly from multi-source wastes in the vadose zone, with subsequent infiltration into the regional aquifer. Increases in VCM concentrations (new leachate generation) alternated with decreases in VCM concentrations (infiltration without leachate) in a cyclic fashion, during this 20-year period.  相似文献