Non-LTE modeling of supernova-fallback disks

We present a first detailed spectrum synthesis calculation of a supernova-fallback disk composed of iron. We assume a geometrically thin disk with a radial structure described by the classical α-disk model. The disk is represented by concentric rings radiating as plane-parallel slabs. The vertical structure and emission spectrum of each ring is computed in a fully self-consistent manner by solving the structure equations simultaneously with the radiation transfer equations under non-LTE conditions. We describe the properties of a specific disk model and discuss various effects on the emergent UV/optical spectrum. We find that strong iron-line blanketing causes broad absorption features over the whole spectral range. Limb darkening changes the spectral distribution up to a factor of four depending on the inclination angle. Consequently, such differences also occur between a blackbody spectrum and our model. The overall spectral shape is independent of the exact chemical composition as long as iron is the dominant species. A pure iron composition cannot be distinguished from silicon-burning ash. Non-LTE effects are small and restricted to few spectral features.     

Numerical simulation of a managed aquifer recharge system designed to supply drinking water to the city of Amsterdam,The Netherlands

Managed aquifer recharge (MAR) is increasingly used to secure drinking water supply worldwide. The city of Amsterdam (The Netherlands) depends largely on the MAR in coastal dunes for water supply. A new MAR scheme is proposed for the production of 10 × 10⁶ m³/year, as required in the next decade. The designed MAR system consists of 10 infiltration ponds in an artificially created sandbank, and 25 recovery wells placed beneath the ponds in a productive aquifer. Several criteria were met for the design, such as a minimum residence time of 60 days and maximum drawdown of 5 cm. Steady-state and transient flow models were calibrated. The flow model computed the infiltration capacity of the ponds and drawdowns caused by the MAR. A hypothetical tracer transport model was used to compute the travel times from the ponds to the wells and recovery efficiency of the wells. The results demonstrated that 98% of the infiltrated water was captured by the recovery wells which accounted for 65.3% of the total abstraction. Other sources include recharge from precipitation (6.7%), leakages from surface water (13.1%), and natural groundwater reserve (14.9%). Sensitivity analysis indicated that the pond conductance and hydraulic conductivity of the sand aquifer in between the ponds and wells are important for the infiltration capacity. The temperature simulation showed that the recovered water in the wells has a stable temperature of 9.8–12.5 °C which is beneficial for post-treatment processes. The numerical modelling approach is useful and helps to gain insights for implementation of the MAR.

     

Travelling and hunting in a changing Arctic: assessing Inuit vulnerability to sea ice change in Igloolik, Nunavut

The observations of community members and instrumental records indicate changes in sea ice around the Inuit community of Igloolik, in the Canadian territory of Nunavut. This paper characterizes local vulnerability to these changes, identifying who is vulnerable, to what stresses, and why, focusing on local and regional use of sea ice for the harvesting of renewable resources and travel. This analysis is coupled with instrumental and sea ice data to evaluate changing temperature/wind/sea ice trends over time, to complement local observations. We demonstrate the relationships between changing sea ice conditions/dynamics and harvesting activities (i.e. dangers and accessibility), with specific emphasis on ringed seal and walrus seasonal hunting, to illustrate current sea ice exposures that hunters are facing. Community members are adapting to such changes, as they have done for generations. However, current adaptive capacity is both enabled, and constrained, by social, cultural, and economic factors that manifest within the modern northern Hamlet. Enabling factors include the ability of hunters to manage or share the risks associated with sea ice travel, as well as through their flexibility in resource use, as facilitated by sophisticated local knowledge and land/navigational skills. Constraining factors include the erosion of land-based knowledge and skills, altered sharing networks, as well as financial and temporal limitations on travel/harvesting. The differential ability of community members to balance enabling and constraining factors, in relation to current exposures, comprises their level of vulnerability to sea ice change.     

Major and trace elements in German bottled water,their regional distribution,and accordance with national and international standards

The market for mineral water has been growing steadily over the last few years. Germany is the country with the highest number of bottled mineral water brands (908 bottled water samples from 502 wells/brands were analyzed). The per capita consumption of mineral water in Germany in 2003 was 129 L. A wide range of values of one to seven orders of magnitude was determined for 71 elements in the bottled water samples analyzed by ICP-QMS, ICP-AES, IC, titration, photometric, conductometric and potentiometric methods. A comparison of the element concentrations and the legal limits for both bottled and tap water (EU, Germany, US EPA, WHO) shows that only 70% of the 908 mineral water samples fulfill the German and EU drinking water (i.e., tap water) regulations for all parameters (not including pH) for which action levels are defined. Nearly 5% of the bottled water samples not fulfill the German and EU regulations for mineral and table water. Comparison of our results with the current German and European action levels for mineral and table water shows that only 42 of the bottled water samples exceed the limits for one or more of the following elements: arsenic, nitrate, nitrite, manganese, nickel and barium concentrations. Ten of the bottled water samples contain uranium concentrations above the 10 μg/L recommended limit.     

X‐ray energy spectra of CAL87

We present X‐ray spectral analysis of the super‐soft source CAL87 using ASCA, Chandra, XMM‐Newton observations. Early ASCA CCD spectrum reported a strong oxygen absorption edge, which is considered to originate in the an optically thick white‐dwarf atmosphere. On the other hand, contemporaneous grating observations by Chandra and XMM‐Newton indicate emission line dominated spectra, which obviously indicate the optically thin origin. Fitting all the available CCD (ASCA and XMM‐Newton) and grating spectra (XMM‐Newton and Chandra) simultaneously, we show that the CAL87 X‐ray energy spectrum is in fact composed of both an optically thick component with deep absorption edges and an optically thin component with numerous emission lines. The current result supports the standard SSS model that the primary source of X‐ray emission is nuclear burning in the white dwarf atmosphere, surrounded by a highly photoionised, optically thin corona (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

West African monsoon: is the August break “breaking” in the eastern humid zone of Southern Nigeria?

In July, heating of the continents in the Northern Hemisphere results in strengthened monsoon systems which bring rains to West Africa. In Nigeria, the annual rainfall total decreases from over 3,800 mm at Forcados on the coast to under 650 mm at Maiduguri in the north-east of the country. June, July, August and September are the rainiest months throughout the country. In many parts of the south, however, there is “supposed to be” a slight break in the rains for some 2 to 3 weeks in late July and early August or the so called “August break”. In this study, we are underscoring the obvious that climate is changing. The daily series of rainfall data for 1983–2003 analyzed between the months of July–August for some sites in the Eastern humid zone of Southern Nigeria shows that the “August break” may indeed “be breaking”. We have discussed some practical approaches to climate change research in this monsoon region.     

OH absorption coefficients of rutile and cassiterite deduced from nuclear reaction analysis and FTIR spectroscopy

Summary The OH content of four rutile and two cassiterite single-crystals was studied by nuclear reaction analysis (NRA) and by polarised FTIR microspectroscopy. The OH absorption bands of both minerals are centered around 3300 cm⁻¹ with different absorption features. The analytical H₂O content determined by NRA ranges from 70 to 820 wt.ppm. The integrated molar absorption coefficients deduced from the total integrated OH absorbances are equal to 38000 lċmol⁻¹ _H2Oċcm⁻² for rutile and 65000 lċmol⁻¹ _H2Oċcm⁻² for cassiterite. For both minerals the absorption coefficients are significantly smaller than those expected from the linear calibration curves given by Paterson (1982) and by Libowitzky and Rossman (1997).

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Zusammenfassung OH-Absorptionskoeffizienten von Rutil und Cassiterit ermittelt durch Kernreaktions-Analyse und FTIR Spektroskopie Der OH-Gehalt von vier Rutil- und zwei Cassiterit-Einkristallen wurde mittels Kernreaktions-Analyse (NRA) und polarisierter FTIR Mikrospektroskopie untersucht. Die OH Absorptionsbanden beider Minerale sind um 3.300 cm⁻¹ zentriert, mit unterschiedlichen Absorptionserscheinungen. Der analytische H₂O-Gehalt, der mit NRA bestimmt wurde, schwankt von 70 bis 820 Gew.ppm. Die integrierten molaren Absorptionskoeffizienten, die auf den gesamten integrierten OH-Absorptionen basieren, betragen etwa 38.000 lċmol⁻¹ _H2Oċcm⁻² für Rutil and 65.000 lċmol⁻¹ _H2Oċcm⁻² für Cassiterit. Für beide Minerale sind die Absorptionskoeffizienten signifikant kleiner als die, die auf Grund der linearen Kalibrationskurven von Paterson (1982) und Libowitzky und Rossmann (1997) zu erwarten sind.

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Received January 4, 2000; revised version accepted April 10, 2000     

25 years of mineral exploration and discovery in Indonesia

This paper traces the history of mineral exploration in Indonesia between 1967 and 1992, and discusses various technical aspects, such as area selection, exploration and discovery methods, and significant geologic features of the more important new discoveries.Exploration activity over the past 25 years can be divided into four main phases. Phase 1 (1967–1976) mostly involved investigations of mineral prospects and districts previously identified by the Dutch. These investigations resulted in many discoveries, including: a major copper-gold district (skarn-porphyry copper) in Irian Jaya, where exploration is still in progress (resources identified to date: 28 Mt Cu and 2,700 t Au); large nickel resources in Eastern Indonesia (13 Mt Ni); significant onshore and offshore tin resources in the Sumateran tin belt (0.13 Mt Sn); and large but low grade bauxite deposits in West Kalimantan (300 Mt Al₂O₃). Of the eight Contracts of Work signed between 1967 and 1972, six reached the mining stage. Phase 2 (1970–1975) consisted of an extensive porphyry copper search in the Sunda arc, the western arc of Sulawesi and the central belt of Irian Jaya. Best results were obtained from northern Sulawesi, where follow-up between 1976 and 1982 identified three potentially economic copper-gold deposits (1.7 Mt Cu and 140 t Au) and one subeconomic molybdenum porphyry system (0.8 Mt Mo). During Phase 3 (1981–1988) extensive coal exploration in South and East Kalimantan delineated over 5,000 Mt of coal of varying rank and quality, including 1,500 Mt as measured reserves in 17 deposits, eight of which have been developed to date. Phase 4 (1984–1990) involved a major gold rush, focused primarily on the Cenozoic magmatic belts of Kalimantan, Sulawesi, Moluccas and the Sunda arc. Over 80 primary and alluvial gold prospects were drill tested. Five of these were brought into production (two alluvial deposits, two new hard rock discoveries and one Dutch mine), containing approximately 135 tonnes of mineable gold, and several other projects are under development or undergoing feasibility studies. Total geological resources identified to date are estimated to contain about 700 tonnes of gold. Exploration during phase 4 also resulted in several gold-rich porphyry copper discoveries, including a major deposit in Sumbawa (2.7 Mt Cu and 250 t Au). Intermittent exploration for uranium, diamonds and lead/zinc since 1969 has been largely unsuccessful.Exploration is now passing to the next phase, which is likely to be multi-commodity in nature with a strong focus on gold, copper and coal. A number of deposits outlined during earlier phases will be developed.The unprecedented high level of mineral exploration activity over the past 25 years can be attributed to Indonesia's mineral prospectivity and favourable investment climate. Given a continued competitive commercial environment and sustained commodity prices, the next 25 years should see further strong development of the country's mineral resources.     

Regional policy in Nigeria

The Nigerian growth-pattern, with its shift from more labour-intensive and resource-based to more capital-intensive and import-based industries, caused an increasing spatial concentration of productive forces, resulting in deteriorating living conditions for the majority of the population in rural and in urban areas. The Nigerian government never had a systematic regional policy. The impact of its general economic policy, however, fostered spatial polarisation by favouring import-based industries of the highest technological level while discriminating against other economic activities. As the scope for decentralisation within this pattern of accumulation is extremely limited, the problem cannot be solved by instruments of regional policy but only by altering the overall growth-pattern.     

Einfluss korrelativer Abhängigkeiten auf simulierte Zeitreihen: Empfindlichkeit des Fiering-Modells gegenüber Veränderungen der Korrelationsstruktur

The simulation of time series is based on estimated statistical parameters of the empirical time series. The Fiering Model generating monthly sums of streamflows is used as an example for the simulation in order to account for the error of the model, theoretically and practically, caused by statistically inprecise parameter estimation. The sensitivity of this model, especially to the correlation coefficients, is analyzed by means of systematic variations of the correlation coefficients, since these are most affected by the error of estimation. No significant dependency could be found comparing the empirical and simulated parameters mean, standard deviation, and skewness. From this follows, that the importance of the correlation coefficients in the Fiering Model is generally overestimated. The results are given for monthly sums of streamflows at four stations with different hydrological characteristics.