Near-infrared properties of i-drop galaxies in the Hubble Ultra Deep Field

We analyse near-infrared Hubble Space Telescope ( HST )/Near-Infrared Camera and Multi-Object Spectrometer F 110 W ( J ) and F 160 W ( H ) band photometry of a sample of 27 i '-drop candidate   z ≃ 6  galaxies in the central region of the HST /Advanced Camera for Surveys Ultra Deep Field . The infrared colours of the 20 objects not affected by near neighbours are consistent with a high-redshift interpretation. This suggests that the low-redshift contamination of this i '-drop sample is smaller than that observed at brighter magnitudes, where values of 10–40 per cent have been reported. The J – H colours are consistent with a slope flat in   f_ν ( f_λ ∝λ⁻²)  , as would be expected for an unreddened starburst. However, there is evidence for a marginally bluer spectral slope  ( f_λ ∝λ^−2.2)  , which is perhaps indicative of an extremely young starburst (∼10 Myr old) or a top heavy initial mass function and little dust. The low levels of contamination, median photometric redshift of   z ∼ 6.0  and blue spectral slope, inferred using the near-infrared data, support the validity of the assumptions in our earlier work in estimating the star formation rates, and that the majority of the i -drop candidates galaxies lie at   z ∼ 6  .     

Magnetic properties as indicators of pedogenic and pyrogenic processes at the Upper Paleolithic site of Kostenki 14

In geoarchaeological studies, there is an issue with distinguishing between natural and anthropogenic signals in pedological paleoarchives. With the pedostratigraphy of the Upper Paleolithic site of Kostenki 14, this issue is reflected by problems with the determination of features of pedogenic and pyrogenic processes. This issue was addressed by means of a thorough analysis of the magnetic properties of paleosols accompanied by micromorphological observations. Most of the humic samples were shown to be a result of pedogenesis, but two samples (a Paleolithic hearth sample and a sample from paleosol IIc) had features of intensely burnt material. The difference in the typical intensity of large-scale (natural or human-induced) and local-scale anthropogenic fire allowed for suggesting that the magnetic properties of the burnt sample were the result of an anthropogenically controlled fire event, that is, a hearth. This study shows that the magnetic properties of paleosols can be used to differentiate anthropogenic activity, in particular—burning, from pedogenic processes. This indicator is especially helpful in finding disturbed combustion features when the hearth structure is lost. This methodology used to demonstrate the local human-induced pyrogenic effect at the Upper Paleolithic site can contribute to the discussion of the niche construction effect of human activities in the Pleistocene.     

Hydrogen fluence in Genesis collectors: Implications for acceleration of solar wind and for solar metallicity

NASA's Genesis mission was flown to capture samples of the solar wind and return them to the Earth for measurement. The purpose of the mission was to determine the chemical and isotopic composition of the Sun with significantly better precision than known before. Abundance data are now available for noble gases, magnesium, sodium, calcium, potassium, aluminum, chromium, iron, and other elements. Here, we report abundance data for hydrogen in four solar wind regimes collected by the Genesis mission (bulk solar wind, interstream low‐energy wind, coronal hole high‐energy wind, and coronal mass ejections). The mission was not designed to collect hydrogen, and in order to measure it, we had to overcome a variety of technical problems, as described herein. The relative hydrogen fluences among the four regimes should be accurate to better than ±5–6%, and the absolute fluences should be accurate to ±10%. We use the data to investigate elemental fractionations due to the first ionization potential during acceleration of the solar wind. We also use our data, combined with regime data for neon and argon, to estimate the solar neon and argon abundances, elements that cannot be measured spectroscopically in the solar photosphere.     

Assessment of δ13C and C/N ratios in bulk organic matter as palaeosalinity indicators in Holocene and Lateglacial isolation basin sediments,northwest Scotland

Carbon isotopes (δ¹³C) and C/N ratios from bulk organic matter have recently been used as alternative proxies for relative sea‐level (RSL) reconstruction where there are problems associated with conventional biological indictors. A previous study on a single isolation basin (Upper Loch nan Eala) in northwest Scotland has shown a clear relationship between δ¹³C, C/N ratios and palaeosalinity from Younger Dryas and Holocene aged sediments. In this paper we present results of δ¹³C and C/N ratio analyses from other isolation basins in northwest Scotland over the Holocene and the Lateglacial period in order to validate this technique. The results from the Holocene sequences support the earlier findings that this technique can be used to identify RSL change from isolation basins over the Holocene in this region. The relationship between δ¹³C, C/N ratios and RSL change is not apparent in sediments of Lateglacial age. Other environmental variables such as atmospheric CO₂ concentration, poor vegetation development and temperature influence δ¹³C values during this period. Copyright © 2007 John Wiley & Sons, Ltd.     

Volcanic ash clouds affecting Northern Europe: the long view

The volcanic ash or ‘tephra’ cloud resulting from the relatively small (volume and VEI) eruption of the Icelandic volcano Eyjafjallajökull in 2010 caused major air travel disruption, at substantial global economic cost. On several occasions in the past few centuries, Icelandic eruptions have created ash and/or sulphur dioxide clouds which were detected over Europe (e.g. Hekla in 1947, Askja in 1875, and Laki in 1783). However, these historical observations do not represent a complete record of events serious enough to disrupt aviation in Europe. The only feasible evidence for this is within the geological tephra record. Ash layers are preserved in bogs and lakes where tephra deposited from the atmosphere is incorporated in the peat/mud. In this article we: 1, introduce the analysis of the Northern European sedimentary tephra record; 2, discuss our findings and modelling results; 3, highlight how these were misinterpreted by the popular media; and 4, use this experience to outline several existing problems with current tephra studies and suggest agendas for future research.     

A rare reflection effect eclipsing sdB+dM binary: 2M 1533+3759

In this paper, we report a rare reflection effect eclipsing sdB+dM binary, 2M?1533+3759. It is the seventh eclipsing sdB+dM binary that has been discovered to date. This system has an orbital period of 0.16177042 day and a velocity semi-amplitude of 71.1 km?s^?1. Using a grid of zero-metallicity NLTE model atmospheres, we derived T _eff=29250 K, log?g=5.58 and [He/H]=?2.37 from spectra taken near the reflection effection minimum. Lightcurve modeling resulted in a system mass ratio of 0.301 and an orbital inclination angle of 86.6°. The derived primary mass for 2M?1533+3759, 0.376±0.055 M _⊙, is significantly lower than the canonical mass (0.48 M _⊙) found for most previously investigated sdB stars. This implies an initial progenitor mass >1.8 M _⊙, at least a main sequence A star and perhaps even one massive enough to undergo non-degenerate helium ignition.     

Interviewing landed elites in post-war Guatemala

This essay explores the methodological challenges of conducting ethnographic research among economic and managerial elites in Guatemala’s landed sector during the country’s post-war transition. Guatemala’s 34-year civil war ended with peace accords in 1996. From the mid 1990s through 2001, I conducted interviews with leading representatives of the private sector in Guatemala, including the owners and top managers of the country’s sugar plantations. The Guatemalan sugar elite describes itself as the new face of the private sector in Central America, implementing “corporate social responsibility” programs linked to the World Bank and other international agencies. Questions of access and interview dynamics are often discussed in relation to qualitative research on “elites.” Yet, I found the interview process to be less complicated than I anticipated. Of greater concern were the problems of research dissemination and praxis. The experience discussed here raises questions about whether research on particular elite groups can be sustained over long periods of time.     

Solar shield: forecasting and mitigating space weather effects on high-voltage power transmission systems

In this paper, central elements of the Solar Shield project, launched to design and establish an experimental system capable of forecasting the space weather effects on high-voltage power transmission system, are described. It will be shown how Sun–Earth system data and models hosted at the Community Coordinated Modeling Center (CCMC) are used to generate two-level magnetohydrodynamics-based forecasts providing 1–2 day and 30–60 min lead-times. The Electric Power Research Institute (EPRI) represents the end-user, the power transmission industry, in the project. EPRI integrates the forecast products to an online display tool providing information about space weather conditions to the member power utilities. EPRI also evaluates the economic impacts of severe storms on power transmission systems. The economic analysis will quantify the economic value of the generated forecasting system. The first version of the two-level forecasting system is currently running in real-time at CCMC. An initial analysis of the system’s capabilities has been completed, and further analysis is being carried out to optimize the performance of the system. Although the initial results are encouraging, definite conclusions about system’s performance can be given only after more extensive analysis, and implementation of an automatic evaluation process using forecasted and observed geomagnetically induced currents from different nodes of the North American power transmission system. The final output of the Solar Shield will be a recommendation for an optimal forecasting system that may be transitioned into space weather operations.     

Aspects on the origin of the precursory magnetic anomalies of the Mw 6.4 Aquila earthquake

An anomalous behaviour of the scaling exponent derived from the detrended fluctuation analysis (DFA) of the time series of low frequency variations of the horizontal and vertical magnetic field components has been recently reported as being observed 2 months prior to the Mw 6.3 earthquake on 6 April 2009, close to L’Aquila city, Italy. Here, we suggest a possible physical explanation of this effect based on the experience from similar measurements in Greece. In particular, for example, we compare these observations associated with Aquila earthquake with the ones of the Mw 6.6 earthquake on 13 May 1995 at Kozani-Grevena, Greece where both magnetic field variations and seismic electric signals (SES) were recorded. Almost 1 month before the latter earthquake, anomalous variations in both electric and magnetic field were detected, the time series of that were analysed by means of DFA and led to an exponent close to unity. Similarly, the calculated DFA exponent for the Aquila earthquake time series of the anomalous magnetic field variations 2 months before the main shock was also found close to unity. These results could imply that in the case of Aquila, according to the Maxwell’s laws, one should expect to observe simultaneously with the magnetic signal an associated SES activity, provided that an appropriate station to monitoring the earth’s electric field variations in the same area was available. Hence, it seems that similar underlying non-linear dynamic processes in mechanical and as well as electromagnetic sense, with features of criticality, dominated in both pre-focal areas.