New 1982 — 1990 photometry of λ Andromedae and its 11-year cycle

We present photoelectric photometry of λ And never before published, obtained between February 1982 and December 1990 at 29 different observatories. Then we combine it with all other photometry available to us (previously published, contained in the I.A.U. Commission 27 Archives, and obtained with the Vanderbilt 16-inch automatic telescope but not yet published), to yield a 14.8-year data base. Analysis reveals a long-term cycle in mean brightness, with a full range of 0^m.15 and a period of 11.4 ± 0.4 years. Because most of our new photometry was concentrated in the 1983-84 observing season, we analyze that one well-defined light curve with a two-spot model. Spot A keeps a 0^m.04 amplitude throughout four rotation cycles whereas the amplitude of spot B diminishes from 0^m.09 down almost to 0^m.03. The spot rotation periods were 55^d.9 ± 0^d.6 and 520^d.8 ± 1^d.0, respectively.     

Timing of deformation in the Norseman-Wiluna Belt, Yilgarn Craton, Western Australia

Establishing relative and absolute time frameworks for the sedimentary, magmatic, tectonic and gold mineralisation events in the Norseman-Wiluna Belt of the Archean Yilgarn Craton of Western Australia, has long been the main aim of research efforts. Recently published constraints on the timing of sedimentation and absolute granite ages have emphasized the shortcomings of the established rationale used for interpreting the timing of deformation events. In this paper the assumptions underlying this rationale are scrutinized, and it is shown that they are the source of significant misinterpretations. A revised time chart for the deformation events of the belt is established. The first shortening phase to affect the belt, D₁, was preceded by an extensional event D_1e and accompanied by a change from volcanic-dominated to plutonic-dominated magmatism at approximately 2685–2675 Ma. Later extension (D_2e) controlled deposition of the ca 2655 Ma Kurrawang Sequence and was followed by D₂, a major shortening event, which folded this sequence. D₂ must therefore have started after 2655 Ma—at least 20 Ma later than previously thought and after the voluminous 2670–2655 Ma high-Ca granite intrusion. Younger transcurrent deformation, D₃–D₄, waned at around 2630 Ma, suggesting that the crustal shortening deformation cycle D₂–D₄ lasted approximately 20–30 Ma, contemporaneous with low-volume 2650–2630 Ma low-Ca granites and alkaline intrusions. Time constraints on gold deposits suggest a late mineralisation event between 2640–2630 Ma. Thus, D₂–D₄ deformation cycle and late felsic magmatism define a 20–30 Ma long tectonothermal event, which culminated with gold mineralisation. The finding that D₂ folding took place after voluminous high-Ca granite intrusion led to research into the role of competent bodies during folding by means of numerical models. Results suggest that buoyancy-driven doming of pre-tectonic competent bodies trigger growth of antiforms, whereas non-buoyant, competent granite bodies trigger growth of synforms. The conspicuous presence of pre-folding granites in the cores of anticlines may be a result from active buoyancy doming during folding.     

Microphysical properties of stratocumulus clouds during ACE‐2

Microphysical measurements performed during 8 flights of the CLOUDYCOLUMN component of ACE‐2, with the Meteo‐France Merlin‐IV, are analyzed in terms of droplet number concentration and size. The droplet concentration is dependent upon the aerosol properties within the boundary layer. Its mean value over a flight varies from 55 cm⁻³, for the cleanest conditions, to 244 cm⁻³, for the most polluted one. For each flight, the variability of the concentration, in selected cloud regions that are not affected by mixing with dry air or drizzle scavenging, ranges from 0.5 to 1.5 of the mean value. The mean volume diameter increases with altitude above cloud base according to the adiabatic cloud model. The frequency distribution of mean droplet volume normalized by the adiabatic value, for the selected regions, shows the same dispersion as the distribution of normalized concentration. The values of droplet concentration versus mean volume diameter are then examined in sub‐adiabatic samples to characterize the effects of mixing and drizzle scavenging. Finally, the ratio of mean volume diameter to effective diameter is analyzed and a simple relationship between these 2 crucial parameters is proposed.     

NIGHTGLOW: an instrument to measure the Earth’s nighttime ultraviolet glow—results from the first engineering flight

We have designed and built an instrument to measure and monitor the “nightglow” of the Earth’s atmosphere in the near ultraviolet (NUV). In this paper we describe the design of this instrument, called NIGHTGLOW. NIGHTGLOW is designed to be flown from a high altitude research balloon, and circumnavigate the globe. NIGHTGLOW is a NASA, University of Utah, and New Mexico State University project. A test flight took place from Palestine, Texas on July 5, 2000, lasting about 8 h. The instrument performed well and landed safely in Stiles, Texas with little damage. The resulting measurements of the NUV nightglow are compared with previous measurements from sounding rockets and balloons.     

Recent warming in southeastern Zaire (Central Africa) inferred from disturbed geothermal gradients

Several temperature-depth profiles measured in Kasai and in Shaba provinces of Zaire using mining exploration boreholes exhibit a significant negative temperature gradient near the surface. This anomalous curvature which extends to 100–200 m depth could reflect the effect of variations in surface conditions. Applying the theory of heat conduction in a semi-infinite homogeneous medium, these profiles indicate a surface warming by 3–4°C. This warming is related to the effect of the environmental changes associated with the mining exploitation and the urbanization during the last 40–90 years.     

Laboratory simulation of infrared astrophysical features

Laboratory infrared emission and absorption spectra have been taken of terrestrial silicates, meteorites and lunar soils in the form of micrometer and sub-micrometer grains. The emission spectra were taken in a way that imitates telescopic observations. The purpose was to see which materials best simulate the 10 m astrophysical feature.The emission spectra of dunite, fayalite and Allende give a good fit to the 10 m broadband emission feature of comets Bennett and Kohoutek. A study of the effect of grain size on the presence of the 10 m emission feature of dunite shows that for particles larger than 37 m no feature is seen.The emission spectrum of the Murray meteorite, a Type 2 carbonaceous chondrite, is quite similar to the intermediate resolution spectrum of comet Kohoutek in the 10 m region. Hydrous silicates or amorphous magnesium silicates in combination with high-temperature condensates, such as olivine or anorthite, would yield spectra that match the intermediate resolution spectrum of comet Kohoutek in the 10 m region. Glassy olivine and glassy anorthite in approximately equal proportions would also give a spectrum that is a good fit to the cometary 10 m feature.Invited contribution to the Proceedings of a Workshop onThermodynamics and Kinetics of Dust Formation in the Space Medium held at the Lunar and Planetary Institute, Houston, 6 8 September, 1978.     

Cosmic ray ionization of the Jovian atmosphere

An approximate form of the Boltzmann equation has been used to obtain local ionization rates due to the absorption of galactic cosmic rays in the Jovian atmosphere. It is shown that the muon flux component of the cosmic ray-induced cascade may be especially importannt in ionizing the atmosphere at levels where the total number density exceeds 10¹⁹ cm^?3 (well below the ionospheric layers produced by solar euv). A model containing both positive and negative ion reactions has been employed to compute equilibrium electron and ion number densities. Peak electron number densities on the order of 10³ cm^?3 may be expected even at relatively low magnetic latitudes. The dominant positive ions are NH₄⁺ and C_nH_m⁺ cluster ions, with n ? 2; it is suggested that the absorption of galactic cosmic ray energy at such relatively high pressures in the Jovian atmosphere $\text{(M ? 10}{}^{18}\text{to}\text{10}{}^{20}\text{cm}{}^{\mathrm{?3}}\text{)}$ and the subsequent chemical reactions may be instrumental in the local formation of complex hydrocarbons.     

Improved approaches to ecotoxicity testing of petroleum products

Crude oils produced in the North West shelf of Western Australia are highly volatile, a characteristic not shared by most of the Northern Hemisphere crude oils on which internationally accepted toxicity test protocols were developed. Because of this volatility and some other factors, the LC50 and EC50 values obtained from acute toxicity tests will be significantly affected by the changes of toxicant concentration in test solutions during the period of exposure. To address these issues all steps of a standard protocol for crude oil toxicity testing have been revised. A systematic study has been performed on factors which affect petroleum hydrocarbon solubilisation in aqueous systems during test solution preparations. The influence of mixing time, agitation energy and volume/interface ratio on a hydrocarbon concentration in a water-soluble fraction (WSF) was studied for heavy, medium and light crude oils. A study of the sensitivity of marine unicellular algae to WSF of crude oils was conducted with Isochrysis sp., Nannochloropsis-like sp. and Nitzchia closterium. Total concentrations of hydrocarbons dissolved in test solutions were estimated by UV-spectrometry and GC/FID chemical analyses. When the toxicant concentration decreased during the exposure period, the EC50 values derived from initial or final concentrations either underestimate or overestimate toxicity, respectively. Therefore, weighted average concentrations (WAC) calculated for the whole test period were recommended for expressing hydrocarbon concentrations in test solutions of crude oils. Toxicity indices calculated from WAC of total hydrocarbons for different crude oils can be compared regardless of the rates of hydrocarbon loss.