NOIRCAT – the Northern HIPASS Optical/IR Catalogue

We present the Northern HIPASS (H  i Parkes All-Sky Survey) Optical/Infrared Catalogue (NOIRCAT), an optical/near-infrared (NIR) counterpart to the Northern HIPASS Catalogue (NHICAT). Of the 1002 sources in NHICAT, 655 (66 per cent) have optical counterparts with matching optical velocities. A further 85 (8 per cent) sources have optical counterparts with matching velocities from previous radio emission-line surveys. We find a correlation between the gas and stellar content of the NOIRCAT sources. Our H  i -selected sample of isolated galaxies also presents a wider range in NIR colours than previous optically selected studies of regular, isolated galaxies. All H  i detections in optically unobscured fields could be matched with either a NASA/IPAC Extragalactic Database optical counterpart, or a galaxy visible in Second Palomar Observatory Sky Survey or Digitized Sky Survey images. However, as over 200 of these matched galaxies have no velocity information, further follow-up observations are needed to confirm the matches, and hence confirm or deny the existence of dark galaxies in this data set.     

How common is the Milky Way–satellite system alignment?

The highly flattened distribution of satellite galaxies in the Milky Way (MW) presents a number of puzzles. First, its polar alignment stands out from the planar alignments commonly found in other galaxies. Secondly, recent proper-motion measurements reveal that the orbital angular momentum of at least three, and possibly as many as eight, of the MW's satellites points (within  30°  ) along the axis of their flattened configuration, suggesting some form of coherent motion. In this paper, we use a high-resolution cosmological simulation to investigate whether this pattern conflicts with the expectations of the cold dark matter model of structure formation. We find that this seemingly unlikely setup occurs often: approximately 35 per cent of the time, we find systems in which the angular momentum of three individual satellites points along, or close to, the short axis of the satellite distribution. In addition, in 30 per cent of the systems we find that the net angular momentum of the six best-aligned satellites lies within  35°  of the short axis of the satellite distribution, as observed for the MW.     

Estimating palaeo-water depth from the physical rock record

Palaeo-water depth and its change with time is a key factor in environmental analysis and in sedimentology in general. The literature published on this topic and on related subjects, however, is substantial albeit scattered within and between different communities (geologists, oceanographers, engineers, physicists etc.). Here I focus on proxies for palaeo-bathymetry as obtained from the physical rock record. Floral, faunal and chemical evidence for palaeo-water depth, being equally important, must be dealt with elsewhere. An assessment of the main depth-related parameters in actualistic settings is presented and their applicability to the fossil sedimentary record discussed. The outcome reveals the full complexity of this topic. There is, for example, no such thing as an average wave-base depth applicable to a wide range of fossil case settings. This because wave and current climates in general, and particularly so in neritic and coastal settings, are intriguingly complex. Furthermore, observations from modern oceans are not a priori applicable to fossil ones. Acknowledging these problems and limitations, critically evaluated quantitative proposals for depth indicative facies and features in the sedimentary record are presented and error bars discussed.     

Partitioning behavior of chlorine and fluorine in the system apatite-melt-fluid. II: Felsic silicate systems at 200 MPa

Hydrothermal experiments were conducted to determine the partitioning of Cl between rhyolitic to rhyodacitic melts, apatite, and aqueous fluid(s) and the partitioning of F between apatite and these melts at ca. 200 MPa and 900-924 °C. The number of fluid phases in our experiments is unknown; they may have involved a single fluid or vapor plus saline liquid. The partitioning behavior of Cl between apatite and melt is non-Nernstian and is a complex function of melt composition and the Cl concentration of the system. Values of D_Cl^apat/melt (wt. fraction of: Cl in apatite/Cl in melt) vary from 1 to 4.5 and are largest when the Cl concentrations of the melt are at or near the Cl-saturation value of the melt. The Cl-saturation concentrations of silicate melts are lowest in evolved, silica-rich melts, so with elevated Cl concentrations in a system and with all else equal, the maximum values of D_Cl^apat/melt occur with the most felsic melt. In contrast, values of D_F^apat/melt range from 11 to 40 for these felsic melts, and many of these are an order of magnitude greater than those applying to basaltic melts at 200 MPa and 1066-1150 °C. The Cl concentration of apatite is a simple and linear function of the concentration of Cl in fluid. Values of D_Cl^fluid/apat for these experiments range from 9 to 43, and some values are an order of magnitude greater than those determined in 200-MPa experiments involving basaltic melts at 1066-1150 °C.In order to determine the concentrations and interpret the behavior of volatile components in magmas, the experimental data have been applied to the halogen concentrations of apatite grains from chemically evolved rocks of Augustine volcano, Alaska; Krakatau volcano, Indonesia; Mt. Pinatubo, Philippines; Mt. St. Helens, Washington; Mt. Mazama, Oregon; Lascar volcano, Chile; Santorini volcano, Greece, and the Bishop Tuff, California. The F concentrations of these magmas estimated from apatite-melt equilibria range from 0.06 to 0.12 wt% and are generally equivalent to the concentrations of F determined in the melt inclusions. In contrast, the Cl concentrations of the magmas estimated from apatite-melt equilibria (e.g., ca. 0.3-0.9 wt%) greatly exceed those determined in the melt inclusions from all of these volcanic systems except for the Bishop Tuff where the agreement is good. This discrepancy in estimated Cl concentrations of melt could result from several processes, including the hypothesis that the composition of apatite represents a comparatively Cl-enriched stage of magma evolution that precedes melt inclusion entrapment prior to the sequestration of Cl by coexisting magmatic aqueous and/or saline fluid(s).     

Structural characterization of terrestrial microbial Mn oxides from Pinal Creek, AZ

The microbial catalysis of Mn(II) oxidation is believed to be a dominant source of abundant sorption- and redox-active Mn oxides in marine, freshwater, and subsurface aquatic environments. In spite of their importance, environmental oxides of known biogenic origin have generally not been characterized in detail from a structural perspective. Hyporheic zone Mn oxide grain coatings at Pinal Creek, Arizona, a metals-contaminated stream, have been identified as being dominantly microbial in origin and are well studied from bulk chemistry and contaminant hydrology perspectives. This site thus presents an excellent opportunity to study the structures of terrestrial microbial Mn oxides in detail. XRD and EXAFS measurements performed in this study indicate that the hydrated Pinal Creek Mn oxide grain coatings are layer-type Mn oxides with dominantly hexagonal or pseudo-hexagonal layer symmetry. XRD and TEM measurements suggest the oxides to be nanoparticulate plates with average dimensions on the order of 11 nm thick × 35 nm diameter, but with individual particles exhibiting thickness as small as a single layer and sheets as wide as 500 nm. The hydrated oxides exhibit a 10-Å basal-plane spacing and turbostratic disorder. EXAFS analyses suggest the oxides contain layer Mn(IV) site vacancy defects, and layer Mn(III) is inferred to be present, as deduced from Jahn-Teller distortion of the local structure. The physical geometry and structural details of the coatings suggest formation within microbial biofilms. The biogenic Mn oxides are stable with respect to transformation into thermodynamically more stable phases over a time scale of at least 5 months. The nanoparticulate layered structural motif, also observed in pure culture laboratory studies, appears to be characteristic of biogenic Mn oxides and may explain the common occurrence of this mineral habit in soils and sediments.     

Nyerereite from carbonatite rocks at Vulture volcano: implications for mantle metasomatism and petrogenesis of alkali carbonate melts Research Article

Vulture volcano displays a wide range of mafic to alkaline, carbonate-, and/or CaO-rich volcanic rocks, with subvolcanic and plutonic rocks together with mantle xenoliths in pyroclastic ejecta. The roles of magmatic volatiles such as CO₂, S, and Cl have been determined from compositions and trapping temperatures of inclusions in phenocrysts, which include the Na-K-Ca-carbonate nyerereite within melilite. We surmise that this alkali carbonate crystallised from an appropriate carbonatitic melt at relatively high temperature. Carbonatitic metasomatic features are traceable throughout many of the mantle xenoliths, and various carbonatitic components are found in the late stage extrusive suite. There is no evidence that alkali carbonatite developed as a separate magma, but it may have been an important evolutionary stage. We compare the rare occurrence of nyerereite at Vulture with other carbonatites and with an unaltered kimberlite from the Udachnaya pipe. We review the evidence at Vulture for associated carbonatitic metasomatism in the mantle, and we suggest that low viscosity alkali carbonatitic melts may have a primary and much deeper origin than previously considered.     

Hydrogen isotope fractionation in freshwater and marine algae: II. Temperature and nitrogen limited growth rate effects

Zhang and Sachs [Hydrogen isotope fractionation in freshwater algae: I. Variations among lipids and species. Organic Geochemistry 38, 582–608, 2007] demonstrated that algal lipid δD values track water δD values with high fidelity (R² > 0.99), but that D/H fractionation varied among lipids and algal species. Here we report on the influence of temperature and nitrogen limitation on D/H fractionation in lipids from cultured microalgae. Two species of freshwater green algae, Eudorina unicocca and Volvox aureus, were grown in batch culture at 15 °C and 25 °C. Increased D/H fractionation of 2?4‰/°C occurred at the higher temperature in all lipids analyzed. The marine diatom Thalassiosira pseudonana was grown in continuous culture under nitrogen replete (NR) and nitrogen limited (NL) conditions, resulting in a growth rate that was 4.4 fold lower under the latter conditions. The fatty acid content of NL cells was approximately 4 fold higher than in NR cells, whereas the sterol content was similar in both. While sterols from the NL culture were enriched in deuterium by 37‰ relative to the NR culture, fatty acids from both cultures had similar δD values, implying that D/H fractionation during isoprenoid (branched) lipid synthesis is affected by nitrogen limitation, but D/H fractionation during acetogenic (linear) lipid synthesis is not. Cross-talk of the precursor isopentenyl diphosphate between the cytosolic MVA and plastidic DOXP/MEP synthetic pathways is a plausible mechanism for the observed D/H differences between isoprenoid and acetogenic lipids. This preliminary study highlights the need to consider both the type of lipid and potential changes in growth conditions in paleoenvironmental studies using lipid D/H ratios.     

Sectoral approaches to improve regional carbon budgets

Humans utilise about 40% of the earth’s net primary production (NPP) but the products of this NPP are often managed by different sectors, with timber and forest products managed by the forestry sector and food and fibre products from croplands and grasslands managed by the agricultural sector. Other significant anthropogenic impacts on the global carbon cycle include human utilization of fossil fuels and impacts on less intensively managed systems such as peatlands, wetlands and permafrost. A great deal of knowledge, expertise and data is available within each sector. We describe the contribution of sectoral carbon budgets to our understanding of the global carbon cycle. Whilst many sectors exhibit similarities for carbon budgeting, some key differences arise due to differences in goods and services provided, ecology, management practices used, land-management personnel responsible, policies affecting land management, data types and availability, and the drivers of change. We review the methods and data sources available for assessing sectoral carbon budgets, and describe some of key data limitations and uncertainties for each sector in different regions of the world. We identify the main gaps in our knowledge/data, show that coverage is better for the developed world for most sectors, and suggest how sectoral carbon budgets could be improved in the future. Research priorities include the development of shared protocols through site networks, a move to full carbon accounting within sectors, and the assessment of full greenhouse gas budgets.     

Spatiotemporal distribution of aridity indices based on temperature and precipitation in the extra-Carpathian regions of Romania

In the last decades, droughts are a recurrent phenomena in many regions of the world, especially in the subtropics and mid-latitudes, affecting more and more the society. Aridity indices are often used to identify regions prone to that phenomenon. In this paper, we used data recorded in 30 locations in the extra-Carpathian areas of Romania over the period 1961–2007. The De Martonne aridity index (I _DM) and the Pinna combinative index (I _P) were employed in order to identify critical areas in the most important agricultural regions of the country. Monthly, seasonal, annual, and winter wheat and maize growing season datasets of I _DM and annual values of I _P were calculated. The trends were identified using the Mann–Kendall test and Sen’s slope, while ordinary Kriging technique was employed for interpolation. The main findings are that the most vulnerable to semi-aridity are the southeastern regions, especially during the warm period of the year, and that for Romania, the use of I _DM is more appropriate compared to I _P.