Coarse sediment transport in mountain streams in Colorado and Wyoming,USA

Since the early 1990s, US Forest Service researchers have made thousands of bedload measurements in steep, coarse‐grained channels in Colorado and Wyoming, USA. In this paper we use data from 19 of those sites to characterize patterns and rates of coarse sediment transport for a range of channel types and sizes, including step–pool, plane‐bed, pool–riffle, and near‐braided channels. This effort builds upon previous work where we applied a piecewise regression model to (1) relate flow to rates of bedload transport and (2) define phases of transport in coarse‐grained channels. Earlier, the model was tested using bedload data from eight sites on the Fraser Experimental Forest near Fraser, Colorado. The analysis showed good application to those data and to data from four supplementary channels to which the procedure was applied. The earlier results were, however, derived from data collected at sites that, for the most part, have quite similar geology and runoff regimes. In this paper we evaluate further the application of piecewise regression to data from channels with a wider range of geomorphic conditions. The results corroborate with those from the earlier work in that there is a relatively narrow range of discharges at which a substantial change in the nature of bedload transport occurs. The transition from primarily low rates of sand transport (phase I) to higher rates of sand and coarse gravel transport (phase II) occurs, on average, at about 80 per cent of the bankfull (1·5‐year return interval) discharge. A comparison of grain sizes moved during the two phases showed that coarse gravel is rarely trapped in the samplers during phase I transport. Moreover, the movement and capture of the D₁₆ to D₂₅ grain size of the bed surface seems to correspond with the onset of phase II transport, particularly in systems with largely static channel surfaces. However, while there were many similarities in observed patterns of bedload transport at the 19 studied sites, each had its own ‘bedload signal’ in that the rate and size of materials transported largely reflected the nature of flow and sediment particular to that system. Published in 2005 by John Wiley & Sons, Ltd.     

The deuterium enrichment of individual amino acids in carbonaceous meteorites: A case for the presolar distribution of biomolecule precursors

The δD values of over 40 amino acids and two pyridine carboxylic acids of the Murchison and Murray meteorites have been obtained by compound-specific isotopic analyses. For compounds with no known terrestrial distribution, these values range from approximately +330‰ (for cyclic leucine) to +3600‰ (for 2-amino-2,3-dimethylbutyric acid). The latter value is the highest ever recorded for a soluble organic compound in meteorites and nears deuterium to hydrogen ratios observed remotely in interstellar molecules. Deuterium content varies significantly between molecular species and is markedly higher for amino acids having a branched alkyl chain. The δD value of Murray l-isovaline, with an enantiomeric excess of ∼ 6% in the meteorite, was within experimental error of that determined for the combined dl-isovaline enantiomers. Overall, the hydrogen isotope composition of meteoritic amino acids is relatively simple and their δD values appear to vary more with the structure of their carbon chains than with the number and relative distribution of their functionalities or ¹³C content. The magnitude and extent of deuterium enrichment shared by many and varied amino acids in meteorites indicate that cosmic regimes such as those found in the interstellar medium were capable of producing, if not all the amino acids directly, at least a suite of their direct precursors that was abundant, varied, and considerably saturated.     

Greenhouse Gas Dynamics of an Increased Use of Wood in Buildings in Switzerland

Long-living wood products contribute to the mitigation of climate change in many ways. They act as a carbon pool during their service life, as they withdraw CO₂ from its natural cycle. After their service life, they can stitute for fossil fuels if they are incinerated in adequate furnaces. Furthermore, wood products can stitute for more energy-intense products made of ‘conventional’ materials. This paper quantifies the stitution and pool effects of an increased use of wood in the building sector in Switzerland for the years 2000–2130. Life cycle data on greenhouse gas (GHG) emissions of 12 wood products and their stitutes are used as proxies for relevant building products; this data is linked to the forecasted wood flows for each group of building products in a cohort-model. For the political assessment, GHG effects occurring abroad and in Switzerland are distinguished. The results show that the pool effect of an increased use of long-living wood products is of minor importance, whereas the energetic and material stitution effects are much more relevant, especially on a long-term. For construction products, the Swiss share of the GHG effect related to the material stitution is relatively high, as mainly nationally produced materials are stituted for. For interior products, the Swiss share of the GHG effect related to the material stitution is rather small because mainly imports are stituted for. The results must be considered as rough estimates. Nonetheless, these calculations show that an increased use of wood in the building sector is a valid and valuable option for the mitigation of greenhouse gas emissions and for reaching GHG emission targets in a mid- to long-term. Still, the pool and stitution capacity of an increased use of wood is relatively small compared to the overall GHG emissions of Switzerland.     

Collapse of primordial clouds — II. The role of dark matter

In this article we extend the study performed in our previous article of the collapse of primordial objects. We here analyse the behaviour of the physical parameters for clouds ranging from 10⁷ to 10¹⁵ M_⊙. We study the dynamical evolution of these clouds in two ways: as purely baryonic clouds and as clouds with non-baryonic dark matter included. We start the calculations at the beginning of the recombination era, following the evolution of the structure until the collapse (which we defined as the time when the density contrast of the baryonic matter is greater than 10⁴). We analyse the behaviour of several physical parameters of the clouds (e.g. the density contrast and the velocities of the baryonic matter and the dark matter) as a function of time and radial position in the cloud. In this study all physical processes that are relevant to the dynamical evolution of the primordial clouds, such as for example photon drag (due to the cosmic background radiation) and hydrogen molecular production, besides the expansion of the Universe, are included in the calculations. In particular we find that the clouds with dark matter collapse at higher redshift when we compare the results with the purely baryonic models. As a general result we find that the distribution of the non-baryonic dark matter is more concentrated than the baryonic one. It is important to stress that we do not take into account the putative virialization of the non-baryonic dark matter; we just follow the time and spatial evolution of the cloud, solving its hydrodynamical equations. We also studied the role of cooling–heating processes in the purely baryonic clouds.     

A Fully Depleted pn-Junction CCD for Infrared-, UV- and X- ray detection

This paper describes the performance of the Fully Depleted pn-junction CCD (pn-CCD) system, developed for ESA's XMM-satellite mission for soft x-ray imaging and spectroscopy in the single photon counting mode in the 100 eV to 10 keV photon range. The 58 mm x 60 mm large pn-CCD array, designed and fabricated at the Semiconductor Lab (Halbleiterlabor) of the Max-Planck-Institut, uses pn-junctions for registers and as backside structure. This concept naturally enables full depletion of the detector volume independent of the silicon wafer's resistivity and thickness, and as such make it an efficient detector for the x-ray region and the infrared. For high detection efficiency in the soft x-ray region and UV, an ultrathin pn-CCD backside deadlayer has been realized. Each pn-CCD-channel is equipped with its own on-chip JFET amplifier which, in combination with the CAMEX-amplifier and multiplexing chip, facilitates parallel readout and fast data rate: the cooled pn-CCD system can be read out at a data rate up to 3 MHz with an electronic noise floor of ENC < 5 e-.     

Non-tropical carbonate deposits on the modern New Zealand shelf

Extensive (ca. 50,000 km²) shallow-marine platforms (< 250 m) off northern (34°S) and southern (48°S) New Zealand, and more local areas of shelf between, are blanketed by skeletal carbonate sediments > 70% CaCO₃), despite proximity to a tectonically active plate margin. In these regions the terrigenous sediment supply is presently low, and growth of epibenthos is fostered by firm substrates (rock, gravels, shells, seaweeds) and the generally energetic nature and high nutrient levels of open-shelf waters. Rapid transition into adjacent terrigenous-dominated facies is characteristic. Irrespective of water depth, the carbonates are coarse-grained and fragmental; carbonate mud is rare. Calcite dominates over aragonite. High-Mg calcite, widespread off northern New Zealand, is rare in the south. Skeletal material is dominated by bryozoans and bivalve molluscs, with significant local contributions from foraminifers, barnacles, calcareous red algae and echinoderms. The name bryomol is suggested for this distinctive temperate-region skeletal carbonate facies, which can be usefully subdivided based on dominant zoarial growth forms of the bryozoan component, known to be habitat-related. Bioerosion is an important mechanism of skeletal fragmentation and degradation. Many grains, especially aragontic bivalves, are infested by endolithic borers and have low preservation potential. Ages of skeletal material in the surficial deposits range from more than 20,000 years B.P. to modern, which is consistent with both low rates of carbonate production and sediment accumulation, and the wide range in preservation state of grains. Some data suggest that the skeletal carbonates are dispersed and mixed mainly during infrequent movement of sand ribbons, sand waves and sand sheets driven by storm-assisted tidal flows. Tracts of modern, palimpsest and relict carbonates can occur in juxtaposition.

The facies characteristics of the New Zealand shelf carbonate deposits contrast significantly with those of the classical Bahaman-type carbonate model. However, they are similar to those reported from many other mid- to high-latitude carbonate shelves, and afford good analogues for most onland occurrences of New Zealand Cenozoic limestones.     

Orthogneisses of the Spessart crystalline complex,Northwest Bavaria: Indicators of the geotectonic environment?

The orthogneisses of the Spessart crystalline complex are derived from a granitic to granodioritic magma of S-type character which must have formed by anatexis of continental crust. It intruded into a relatively shallow crustal level, 410–420 Ma ago, at the Silurian. Trace element characteristics are consistent with a post-collision geotectonic environment testifying to extensional tectonics at the end of the Caledonian era.

---

Zusammenfassung Die Orthogneise des Spessartkristallins lassen sich von einem granitischen bis granodioritischen Magma von S-Typ-Charakter ableiten, das durch Anatexis kontinentaler Kruste entstanden sein mu\ und in ein relativ oberflächennahes Krustenniveau intrudierte. Die Platznahme erfolgte vor 410–420 Ma, d. h. im Silur. Die Spurenelement-Muster der Orthogneise entsprechen denen von Post-Kollisions-Granitoiden, was als Hinweis auf eine Phase der Dehnungstektonik am Ende der kaledonischen ära bewertet werden kann.

---

Résumé Les orthogneiss du Spessart sont dérivés d'un magma granitique à granodioritique de type S qui doit s'Être formé par anatexie de la croûte continentale. Ce magma a été intrudé dans un niveau peu profond de la croûte il y a 410–420 Ma c'est-à-dire au Silurien. La distribution des éléments en traces est en accord avec celle des granitoÏdes formés dans un contexte géodynamique de post-collision. Cette observation est en faveur d'une phase d'extension tectonique à la fin du cycle calédonien.

---

, — Wojcieszów-Kalke. , — . . , , , , .

     

Proterozoic deformation of the East Saharan Craton in Southeast Libya, South Egypt and North Sudan

The basement areas in Southeast Libya, South Egypt and North Sudan, west of the Nile, between Gebel Uweinat and the Bayuda Desert, are part of an approximately 1000-km-wide, complexly folded, polymetamorphic zone with a regional N-NNE-NE-ENE trend of foliation and fold axis. Since this belt extends southwestward into the area of Zalingei in the southern Darfur block (West Sudan), it is named the Northern Zalingei fold zone. Sr and Nd isotopic studies suggest that this zone is older than Pan-African and further indicate that, apart from Archean rocks in the Gebel Uweinat area, this belt is of Early-Middle Proterozoic age. An Early-Middle Proterozoic three-stage deformational and anatectic event established the present-day fold and fault geometry in the western parts of this zone in the Gebel Uweinat—Gebel Kamil area. The Pan-African tectono-thermal episode was most effective in the eastern part of the belt, near the boundary with the Nubian Shield volcano-sedimentary-ophiolite-granitoid assemblages. It caused migmatization, granite emplacement, mylonitization and large-scale wrench faulting which was related to Late Proterozoic accretionary and collisional events of the Arabian-Nubian Shield with the margin of the East Saharan Craton.