Molecular signature of star formation at high redshifts

In recent years there has been much debate, both observational and theoretical, about the nature of star formation at high redshift. In particular, there seems to be strong evidence of a greatly enhanced star formation rate early in the Universe’s evolution. Simulations investigating the nature of the first stars indicate that these were large, with masses in excess of 100 solar masses. By the use of a chemical model, we have simulated the molecular signature of massive star formation for a range of redshifts, using different input models of metallicity in the early Universe. We find that, as long as the number of massive stars exceeds that in the Milky Way by factor of at least 1000, then several ‘hot-core’ like molecules should have detectable emission. Although we predict that such signatures should already be partly detectable with current instruments (e.g. with the VLA), facilities such as ALMA will make this kind of observation possible at the highest redshifts.     

Stakeholder analysis of the governance framework of a national SDI dataset – whose needs are met in the buildings and address register of the Netherlands?

ABSTRACT

National spatial data infrastructures are key to achieving the Digital Earth vision. In many cases, national datasets are integrated from local datasets created and maintained by municipalities. Examples are address, building and topographic information. Integration of local datasets may result in a dataset satisfying the needs of users of national datasets, but is it productive for those who create and maintain the data? This article presents a stakeholder analysis of the Basisregistratie Adressen en Gebouwen (BAG), a collection of base information about addresses and buildings in the Netherlands. The information is captured and maintained by municipalities and integrated into a national base register by Kadaster, the Cadastre, Land Registry and Mapping Agency of the Netherlands. The stakeholder analysis identifies organisations involved in the BAG governance framework, describes their interests, rights, ownerships and responsibilities in the BAG, and maps the relationships between them. Analysis results indicate that Kadaster and the municipalities have the highest relative importance in the governance framework of the BAG. The study reveals challenges of setting up a governance framework that maintains the delicate balance between the interests of all stakeholders. The results provide guidance for SDI role players setting up governance frameworks for national or global datasets.     

Spatial and temporal differences of Atlantic menhaden (Brevoortia tyrannus) recruitment across major drainages (1966–2004) of the Chesapeake Bay watershed

Atlantic menhaden (Brevoortia tyrannus) is well known for its commercial and ecological importance and has been historically declining in the Chesapeake Bay (Maryland), one of its principal nursery habitats along the eastern coast. Using data from the Striped Bass Seine Survey of the Maryland Department of Natural Resources (2003), we evaluated how the distribution of Atlantic menhaden has changed from 1966 to 2004 for 12 river drainages. We observed significant or marginally significant declines in 42% of the drainages, with drainages of the northern Bay showing the majority of those declines. Continued recruitment to several drainages of the Bay may partly explain why the adult spawning population is not declining. We determined if temporal changes in abundance were related to changes in salinity or water quality for five major drainages of the watershed. For one of these drainages, the Patuxent River, differences in productivity across sites largely explained differences in abundance. For the four remaining drainages, differences in recruitment could not be explained by productivity or salinity gradients. While reducing nitrogen loading and enhancing water clarity may improve Atlantic menhaden production, we suggest that the role of offshore processes on large-scale declines has been largely neglected and studies on larval ingression are necessary for further elucidation of spatial and temporal patterns of juvenile distribution in the Chesapeake Bay.     

Chlorine stable isotope studies of old groundwater,southwestern Great Artesian Basin,Australia

Stable Cl isotope ratios (³⁷Cl/³⁵Cl) were measured in groundwater samples from the southwestern flow system of the Great Artesian Basin, Australia to gain a better understanding of the Cl⁻ sources and transport mechanisms. δ³⁷Cl values range from 0‰ to −2.5‰ (SMOC), and are inversely correlated with Cl⁻ concentration along the inferred flow direction. The Cl isotopic compositions, in conjunction with other geochemical parameters, suggest that Cl⁻ in groundwaters is not derived from salt dissolution. Mixing of the recharge water with saline groundwater cannot explain the relationship between δ³⁷Cl and Cl⁻ concentration measured. Marine aerosols deposited via rainfall and subsequent evapotranspiration appear to be responsible for the Cl⁻ concentrations observed in wells that are close to the recharge area, and in groundwaters sampled along the southern transect. δ³⁷Cl values measured in the leachate of the Bulldog shale suggest that the aquitard is the subsurface source of Cl⁻ for the majority of groundwater samples studied. Diffusion is likely the mechanism through which Cl⁻ is transported from the pore water of the Bulldog shale to the aquifer. However, a more detailed study of the aquitard rocks is required to verify this hypothesis.     

Release of organic nitrogen compounds from Kerogen via catalytic hydropyrolysis

High hydrogen pressure pyrolysis (hydropyrolysis) was performed on samples of solvent extracted Kimmeridge Clay Formation source rock with a maturity equivalent to ca. 0.35% vitrinite reflectance. We describe the types and distributions of organic nitrogen compounds in the pyrolysis products (hydropyrolysates) using GC-MS. Compounds identified included alkyl-substituted indoles, carbazoles, benzocarbazoles, quinolines and benzoquinolines. The distributions of the isomers of methylcarbazoles, C₂-alkylcarbazoles and benzocarbazoles in the hydropyrolysates were compared to a typical North Sea oil. The hydropyrolysates compared to the North Sea oil, showed increased contributions from alkylcarbazole isomers where the nitrogen group is "exposed" (no alkyl substituents adjacent to the nitrogen functionality) and appreciable levels of benzo[b]carbazole relative to benzo[a]- and benzo[c]carbazoles. Hydropyrolysis is found to be an ideal technique for liberating appreciable quantities of heterocyclic organic nitrogen compounds from geomacromolecules. The products released from the immature Kimmeridge Clay are thought to represent a potential source of nitrogen compounds in the bound phase (kerogen) able to contribute to the free bitumen phase during catagenesis.     

Discussion to: ‘Guidelines on the use of inverse velocity method as a tool for setting alarm thresholds and forecasting landslides and structure collapses’ by T. Carlà, E. Intrieri,F. Di Traglia,T. Nolesini,G. Gigli and N. Casagli

The paper ‘Guidelines on the use of inverse velocity method as a tool for setting alarm thresholds and forecasting landslides and structure collapses’ by T. Carlà, E. Intrieri, F. Di Traglia, T. Nolesini, G. Gigli and N. Casagli deals with a sensitive topic for landslide risk management. Exploring the pre-failure behaviour of four different case histories, the authors proposed standard procedures for the application of the inverse velocity method (INV, Fukuzono 1985). Specifically, they suggested guidelines for the filtering of velocity data and an original and simple approach to automatically set the first and the second alarm thresholds using the inverse velocity method. The present discussion addresses three different topics: (1) data filter selection according to the features of monitoring instrument; (2) the importance of data sampling frequency for the forecasting analysis and (3) the influence of the starting point (SP in this discussion) for the application of INV analysis. Moreover, based on this matter, a new method is proposed to update the INV analysis on an ongoing basis.     

Identifying connections in a fractured rock aquifer using ADFTs

Fractured rock aquifers are difficult to characterize because of their extremely heterogeneous nature. Developing an understanding of fracture network hydraulic properties in these aquifers is difficult and time consuming, and field testing techniques for determining the location and connectivity of fractures in these aquifers are limited. In the Clare Valley, South Australia, well interference is an important issue for a major viticultural area that uses a fractured aquifer. Five fracture sets exist in the aquifer, all dipping > 25 degrees . In this setting, we evaluate the ability of steady-state asymmetric dipole-flow tests (ADFTs) to determine the connections between a test well and a set of piezometers. The procedure involves dividing a test well into two chambers using a single packer and pumping fluid from the upper chamber to the lower chamber. By conducting a series of tests at different packer elevations, an "input" signal is generated in fracture zones connected to the test well. By monitoring the "output" response of the hydraulic dipole field at piezometers, the connectivity of the fractures between the test well and piezometers can be determined. Results indicate the test well used in this study is connected in a complex three-dimensional geometry, with drawdown occurring above and below areas of potentiometric buildup. The ADFT method demonstrates that the aquifer evaluated in this study cannot be modeled effectively on the well scale using continuum flow models.     

Analyses of the Relationship Between Mucous Aggregates and Phytoplankton Communities in the Gulf of Trieste (Northern Adriatic Sea) by Multivariate Techniques

Abstract. Multivariate techniques (cluster analysis and Principal Component Analysis) applied on phytoplankton data collected in June, July, August, and September 1990, 1991, 1992, and 1993 in the Gulf of Trieste (Northern Adriatic Sea) highlighted a clear temporal pattern from 1990 to 1993. In the summer of 1991, phytoplankton communities showed a dramatic increase in the dinoflagellatddiatom ratio. In particular, during June and July 1991 only few specimens of diatoms ( Cylindrorhecu closreriurn. Probosciu alata, Nirzschio longissimu , and Nitzschiu spp.) were collected; this confirmed the diatom scarcity in the phytoplankton communities before and during the appearance of large mucous aggregates (mucilage) in July 1991 in the Gulf of Trieste. The differences observed between the structure of the phytoplankton communities inside the aggregates and in the ambient waters suggested two hypotheses: 1) the aggregates were not produced in the gulf, but were carried ints the gulf by the eastern bordering current; 2) the aggregates were produced by a few, scarce species with a high exudate production that are capable of quickly reaching a high reproductive rate within the aggregates.