Advanced technology paths to global climate stability: energy for a greenhouse planet

Stabilizing the carbon dioxide-induced component of climate change is an energy problem. Establishment of a course toward such stabilization will require the development within the coming decades of primary energy sources that do not emit carbon dioxide to the atmosphere, in addition to efforts to reduce end-use energy demand. Mid-century primary power requirements that are free of carbon dioxide emissions could be several times what we now derive from fossil fuels (approximately 10(13) watts), even with improvements in energy efficiency. Here we survey possible future energy sources, evaluated for their capability to supply massive amounts of carbon emission-free energy and for their potential for large-scale commercialization. Possible candidates for primary energy sources include terrestrial solar and wind energy, solar power satellites, biomass, nuclear fission, nuclear fusion, fission-fusion hybrids, and fossil fuels from which carbon has been sequestered. Non-primary power technologies that could contribute to climate stabilization include efficiency improvements, hydrogen production, storage and transport, superconducting global electric grids, and geoengineering. All of these approaches currently have severe deficiencies that limit their ability to stabilize global climate. We conclude that a broad range of intensive research and development is urgently needed to produce technological options that can allow both climate stabilization and economic development.     

Molecular weight of human gamma interferon is similar to that of other human interferons

The molecular weight (as determined by molecular sieve chromatography) of human gamma interferon, formerly referred to as immune or type II interferon, is between 40,000 and 70,000. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, gamma interferon activity was recovered mainly from two regions of the gels corresponding to molecular weights of 20,000 and 25,000. The results suggest that in native form human gamma interferon may be aggregated.     

Assessment of soil structure repair due to wetting and drying cycles through 2D tomographic image analysis

Soil structure is very important in agriculture since it affects soil and plant root attributes, such as root system distribution, soil water and nutrient transport, and heat transfer. Degraded soil structures may be repaired by wetting and drying cycles due to changes in the soil pore system. Gamma-ray computed tomography (CT) was used as a tool to evaluate the effect of wetting/drying cycles on soil structure repair, using samples collected in aluminum cylinders. A first-generation tomograph with an ²⁴¹Am source and a 7.62 cm × 7.62 cm NaI(Tl) scintillation crystal detector coupled to a photomultiplier tube were employed. Image analysis and tomographic unit profiles showed that CT can provide an insight into sample structure in order to evaluate repairs and so improves the use of this tool in relation to the judgement of the quality of measured soil physical properties.     

Particle-size distribution of PAH in the air of a remote Norway spruce forest in northern Bavaria

The aim of the present study was to elucidate thedistribution of particulate polycyclic aromatichydrocarbons (PAH) in the air of a remote Norwayspruce (Picea abies (L.) karst.) stand.The study encompassed a total of twenty differentcongeners. Particles in ambient air were alternativelycollected by two different Berner cascade impactors atthe field site in Northern Bavaria over a 14-weeksperiod from the end of April through to the end ofJuly 1994 and subsequently analyzed for their PAHcontent. The concentrations of total suspendedparticulate matter (TSP) ranged from 9–31 μg m^-3,suggesting that the field site is an area with a lowlevel of airborne particles. There was a negativerelationship of total particle concentrations with theamount of canopy precipitation due to particle washout at precipitation events. The distribution of theparticle masses on the different size fractions witha maximum in the 1-μm range is typical for remoteareas and indicates a medium-range transport. Theaerosol-bound PAH load decreased from spring sampleswith 2–4 ng m^-3 to values <1 ng m^-3 in the summersamples. Concurrently, the proportion of low molecularweight congeners in the total PAH load declined.Frequently, the highest PAH concentrations (referringto the air) were found in the 0.1–3 μm sizeseparates (accumulation mode). The results suggestthat apart from PAH input to the soil with litter, dryand wet deposition of aerosol particles is animportant pathway of PAH contamination of acid forestsoils in the Fichtelgebirge mountain range.