Global telescope networks for astronomy education

Ever wanted to give school students or the public a closer look at the stars, without worrying about the vagaries of the UK weather? Paul Roche and Rachel Dodds from the Faulkes Telescope Project explain how you can do just that – without even leaving the classroom!     

Characterization of potential zones of dust generation at eleven stations in the southern Sahara

Summary Synoptic wind data for multi-decadal periods at eleven stations located in the southern Sahara region (Agadez, Atar, Bilma, Dori, Gao, Kayes, Nema, Niamey, Nouadhibou, Ouagadougou and Tessalit) are used to study the monthly dust deflation power over the region. We found that, regardless of the conditions of the soil, the deflation power (or wind efficiency) is not sufficient to generate significant amounts of aerosols south of 15°N. North of this latitude, the deflation power is much larger, with potential zones of either very strong deflation (Nouadhibou and Bilma) or severe deflation (Gao, Tessalit, Nema, Atar, Agadez). Stations in the Sahel region such as Gao, Agadez and Tessalit are characterized by a gradual reinforcement of the deflation power between 1970 and 1984 in correspondence of increasing desertification over the region. During this same period, Bilma, a well know region of dust source, experienced a major reduction in deflation power due to shifts in large scale wind patterns.     

The Galactic Thick Disk – Status

The status of the Galactic thick disk is reviewed. Consideration of the recent literature suggests that its vertical scale height and normalisation with respect to the thin disk remain uncertain to within a factor two, with values reported in the ranges 750–1500 pc, and 0.02–0.13, respectively. The bulk of the thick disk has kinematics (σ_U, σ_V, σ_W) = (65, 54, 38 km s^-1), and lags the thin disk by some 40 km s^-1; differences of opinion exists as to whether kinematics change with distance from the Galactic plane. The bulk of the thick disk has [Fe/H] ∼ −0.6, with little or no evidence for a vertical gradient. The question of gradients is critical for an understanding of thick disk cosmogony and needs closer attention. The reality of the so-called metal-weak thick disk (material having disklike kinematics and [Fe/H] ≤ −1.0) is also considered. The case for such material seems to be steadily growing: in the range −1.6 ≤ [Fe/H] ≤ −1.0, recent estimates suggest ρ_MWTD/ρ_Halo ∼ 0.1-0.3. While many workers regard the thick disk as a discrete entity, the caveat is made that this is a sufficient condition, but not one necessarily required by the observations. Best practice requires that both the discrete model and the alternative extended configuration be compared with observational data to examine the relative likelihood of their relevance. Recent theoretical advances are also discussed, together with the need for in situ measurements of the thick disk away from the Galactic plane. This revised version was published online in July 2006 with corrections to the Cover Date.     

Distribution and accumulation rate of ore elements in Holocene and Late Glacial Sediments of the Deryugin Basin,Sea of Okhotsk

Results of the study of contents and accumulation rates of Fe, Mn, and a number of trace elements in Upper Quaternary sediments of the Deryugin Basin are presented. Maps of the average contents and accumulation rates of excess Fe, Mn, Zn, Ba, Ni, Pb, Cu, and Mo in sediments of the first oxygen isotope stage (OIS) have been plotted. Anomalous contents and accumulation rates are confined to peripheral zones of the Deryugin sedimentary basin and large fracture zones. Different mechanisms of the influence of fluid-dynamic processes on the rate of hydrogenic and biogenic accumulation of ore elements are assumed.Translated from Litologiya i Poleznye Iskopaemye, No. 2, 2005, pp. 115–132.Original Russian Text Copyright © 2005 by Astakhov, Gorbarenko, Bakhareva, Gretskaya, Sattarova.     

A Simple Model for the Movement of Fire Smoke in a Confined Tunnel

Fires in tunnels are unfortunately frequent occurrences often with tragic outcomes. A recent example is the fire on the funicular train at the ski resort in Kaprun (Austria), which caused nearly 160 deaths. Design engineers and risk analysts require knowledge of the fluid dynamics of the fire and smoke movement to answer questions such as how much oxygen can access and feed the fire, and what concentration of smoke will the people be exposed to. As an example in the Austrian accident the geometry was a long tunnel with fire doors closed at one end, and with a fire initiated near the closed (lower) end. The hot smoke from the fire is a source of buoyancy; the smoke reaches the ceiling of the tunnel, and then develops along the ceiling as a wall-bounded plume. The motion of the smoke is driven by a buoyancy force, but at the same time, mechanisms of turbulent heat and mass transfer act as a brake to this motion. In this paper we present how a generic model describing a semi-enclosed buoyancy-driven flow can be interpreted and used in the modelling of fire smoke movement in a confined tunnel. A consideration of the net pollutant volume flux through the tunnel leads to predictions for the variation of concentrations along the tunnel. The smoke concentrations near the fire smoke source scale linearly with the length of the tunnel, with higher concentrations at the lower section of the tunnel, as could be expected. Similarly the concentration of oxygen making its way through to the fire source decreases linearly with the length of the tunnel. A lower bound estimate of the smoke residence time can be obtained based on smoke concentration predictions from the model.     

Interaction of Tectonic and Surface Geological Processes

1. Introduction to surface processesThe shape or morphology of Earth's surface is basically the result of the interplay between two competing forces - mountain building and erosion. Tectonic forces, driven by thermal energy from Earth's interior, cause the rocks of the crust to be folded, faulted and uplifted into high plateaus and mountain belts. As soon as uplift begins, the processes of erosion, driven by gravity, start to wear away the rocks. Masses of weathered rock move downhill under t…