Waning magmatic activity along the Southern Explorer Ridge revealed through fault restoration of rift topography

International audienceWe combine high-resolution bathymetry acquired using the Autonomous Underwater Vehicle ABE with digital seafloor imagery collected using the remotely operated vehicle ROPOS across the axial valley of the Southern Explorer Ridge (SER) to infer the recent volcanic and tectonic processes. The SER is an intermediate spreading ridge located in the northeast Pacific. It hosts the Magic Mountain hydrothermal vent. We reconstruct the unfaulted seafloor terrain at SER based on calculations of the vertical displacement field and fault parameters. The vertical changes between the initial and the restored topographies reflect the integrated effects of volcanism and tectonism on relief-forming processes over the last 11,000-14,000 years. The restored topography indicates that the axial morphology evolved from a smooth constructional dome >500 m in diameter, to a fault-bounded graben, ~500 m wide and 30-70 m deep. This evolution has been accompanied by changes in eruptive rate, with deposition of voluminous lobate and sheet flows when the SER had a domed morphology, and limited-extent low-effusion rate pillow eruptions during graben development. Most of the faults shaping the present axial valley postdate the construction of the dome. Our study supports a model of cyclic volcanism at the SER with periods of effusive eruptions flooding the axial rift, centered on the broad plateau at the summit of the ridge, followed by a decrease in eruptive activity and a subsequent dominance of tectonic processes, with minor low-effusion rate eruptions confined to the axial graben. The asymmetric shape of the axial graben supports an increasing role of extensional processes, with a component of simple shear in the spreading processes

The Ecology and Management of Urban Pondscapes

<p>Small water bodies provide valuable ‘blue space’ in urban environments, creating a network of semi-natural habitat patches for wildlife as well as providing a wide range of ecosystem services.  However, the diverse and interacting anthropogenic stressors imposed by the urban environment pose considerable challenges for the effective management of these habitats. We outline some of the key factors that appear to influence urban pond biodiversity: land use with the local (and often small-scale) catchment, the connectivity of ponds through the landscape, and the nature of emergent and riparian vegetation. We argue that all three factors can be incorporated into a landscape-scale planning framework that can target particular areas for creation and amelioration of pond habitats.  Such a joined-up approach is currently lacking from most urban planning frameworks, but could provide an opportunity to maximise services provided by urban wetlands at the landscape scale.  We emphasise the application of recent ecological advances in our understanding of urban ponds to management guidelines, which have largely come in the form of gardening guides. This management will be required not only to enhance the biodiversity value of urban ponds, but also to control the less desirable elements of aquatic biodiversity such as invasive species and disease vectors that may pose a particular risk in urban environments.  Finally, we note the lack of a comprehensive conservation strategy for ponds and highlight key legislation and guidance that can help to fill the gap. The fact that pond value lies in the aggregation of multiple habitats distributed through the landscape challenges our existing approach to habitat protection.  However, contemporary approaches to pond creation for mitigation through planning processes and programmes of pond creation provide an opportunity to implement truly large-scale strategic habitat management. It is imperative that ecologists and conservationists are involved in the future planning process and its implementation.</p

Flavourful hadronic physics

We review theoretical approaches to form factors that arise in heavy-meson decays and are hadronic expressions of non-perturbative QCD. After motivating their origin in QCD factorisation, we retrace their evolution from quark-model calculations to non-perturbative QCD techniques with an emphasis on formulations of truncated heavy-light amplitudes based upon Dyson-Schwinger equations. We compare model predictions exemplarily for the B\to\pi transition form factor and discuss new results for the g_{D*D\pi} coupling in the hadronic D* decay.Comment: Based on a talk given at Light Cone 2009: Relativistic Hadronic And Particle Physics, 8-13 July 2009, Sao Jose dos Campos, Sao Paulo, Brazi

Carpooling with ecologists, geographers and taxonomists: perceptions from conducting environmental research in tropical regions

Greater than 80% of species on Earth are awaiting formal description, and simultaneously, many of these species unknown to science are becoming extinct. Here we highlight the importance and benefits of collaborating and working in interdisciplinary research groups, to improve quality and efficiency of both ecological and taxonomic research. The aim of this paper is to share and critique two methods used when conducting environmental field research in taxonomically data-poor parts of the world, such as Borneo. Through discussions with geographers, ecologists and taxonomists these two methods are evaluated. We conclude with a suggested solution to push taxonomic knowledge barriers by creating inter-disciplinary communities of researchers who work together to improve taxonomic identifications

Vegetation control on soil organic matter dynamics

Soil organic matter (SOM) formation is one of the least understood steps of the global carbon cycle. An example is uncertainty around the role of plant communities in regulating SOM formation and turnover. Here we took advantage of the highly controlled conditions at the San Dimas lysimeter installation to quantify the influence of oak and pine vegetation on SOM dynamics. SOM turnover rates, estimated using total C and C-14 content of litter and physically separable soil fractions, were faster under oak than under pine. In contrast to the rapid turnover for the oak litter (<2 years), the delay in litter incorporation into the mineral soil under pine was a controlling factor of SOM fluxes. (C) 2001 Published by Elsevier Science Ltd

A High Statistics Search for Ultra-High Energy Gamma-Ray Emission from Cygnus X-3 and Hercules X-1

We have carried out a high statistics (2 Billion events) search for ultra-high energy gamma-ray emission from the X-ray binary sources Cygnus X-3 and Hercules X-1. Using data taken with the CASA-MIA detector over a five year period (1990-1995), we find no evidence for steady emission from either source at energies above 115 TeV. The derived upper limits on such emission are more than two orders of magnitude lower than earlier claimed detections. We also find no evidence for neutral particle or gamma-ray emission from either source on time scales of one day and 0.5 hr. For Cygnus X-3, there is no evidence for emission correlated with the 4.8 hr X-ray periodicity or with the occurrence of large radio flares. Unless one postulates that these sources were very active earlier and are now dormant, the limits presented here put into question the earlier results, and highlight the difficulties that possible future experiments will have in detecting gamma-ray signals at ultra-high energies.Comment: 26 LaTeX pages, 16 PostScript figures, uses psfig.sty to be published in Physical Review

Soil-landscape and climatic relationships in the middle Miocene of the Madrid Basin

The Miocene alluvial-lacustrine sequences of the Madrid Basin, Spain, formed in highly varied landscapes. The presence of various types of palaeosols allows assessment of the effects of local and external factors onsedimentation, pedogenesis and geomorphological development. In the northern, more arid, tectonicallyactive arca, soils were weakly developed in aggrading alluvial fans, dominated by mass flows. reflecting high sedimentation rates. In more distal parts of the fans and in playa lakes calcretes and dolocretes developed: the former were associated with Mg-poor fan sediments whitc: the latter formed on Mg-rich lake clays exposed during minar lake lowstands. The nonh-east part of the basin had a less arid climate. Alluvial fans in this area were dominated by stream Aood deposits, sourced by carbonate terrains. Floodplain and freshwater lakc deposits formed in distal areas. The high local supply of calcium carbonate may have contributed to the preferential developmenl on calcretes on the fans. Both the fan and floodplain palaeosols exhibit pedofacies relationships and more mature soils developed in settings more distant from the sediment sources. Palaeosols also developed on pond and lake margin carbonates, and led to the formation of palustrine limestones. The spatial distributions and stratigraphies of palaeosols in the Madrid Basin alluvial fans suggest that soil formation was controlled by local factors. These palaeosols differ from those seen in Quatemary fans. Which are characterized by climatically induced periods of stability and instability

Measurement of the 240Pu(n,f) cross-section at the CERN n-TOF facility : First results from experimental area II (EAR-2)

The accurate knowledge of the neutron-induced fission cross-sections of actinides and other isotopes involved in the nuclear fuel cycle is essential for the design of advanced nuclear systems, such as Generation-IV nuclear reactors. Such experimental data can also provide the necessary feedback for the adjustment of nuclear model parameters used in the evaluation process, resulting in the further development of nuclear fission models. In the present work, the 240Pu(n,f) cross-section was measured at CERN's n-TOF facility relative to the well-known 235U(n,f) cross section, over a wide range of neutron energies, from meV to almost MeV, using the time-of-flight technique and a set-up based on Micromegas detectors. This measurement was the first experiment to be performed at n-TOF's new experimental area (EAR-2), which offers a significantly higher neutron flux compared to the already existing experimental area (EAR-1). Preliminary results as well as the experimental procedure, including a description of the facility and the data handling and analysis, are presented

New measurement of the 242Pu(n,γ) cross section at n-TOF-EAR1 for MOX fuels : Preliminary results in the RRR

The spent fuel of current nuclear reactors contains fissile plutonium isotopes that can be combined with 238U to make mixed oxide (MOX) fuel. In this way the Pu from spent fuel is used in a new reactor cycle, contributing to the long-term sustainability of nuclear energy. The use of MOX fuels in thermal and fast reactors requires accurate capture and fission cross sections. For the particular case of 242Pu, the previous neutron capture cross section measurements were made in the 70's, providing an uncertainty of about 35% in the keV region. In this context, the Nuclear Energy Agency recommends in its "High Priority Request List" and its report WPEC-26 that the capture cross section of 242Pu should be measured with an accuracy of at least 7-12% in the neutron energy range between 500 eV and 500 keV. This work presents a brief description of the measurement performed at n-TOF-EAR1, the data reduction process and the first ToF capture measurement on this isotope in the last 40 years, providing preliminary individual resonance parameters beyond the current energy limits in the evaluations, as well as a preliminary set of average resonance parameters

The measurement programme at the neutron time-of-flight facility n-TOF at CERN

Neutron-induced reaction cross sections are important for a wide variety of research fields ranging from the study of nuclear level densities, nucleosynthesis to applications of nuclear technology like design, and criticality and safety assessment of existing and future nuclear reactors, radiation dosimetry, medical applications, nuclear waste transmutation, accelerator-driven systems and fuel cycle investigations. Simulations and calculations of nuclear technology applications largely rely on evaluated nuclear data libraries. The evaluations in these libraries are based both on experimental data and theoretical models. CERN's neutron time-of-flight facility n-TOF has produced a considerable amount of experimental data since it has become fully operational with the start of its scientific measurement programme in 2001. While for a long period a single measurement station (EAR1) located at 185 m from the neutron production target was available, the construction of a second beam line at 20 m (EAR2) in 2014 has substantially increased the measurement capabilities of the facility. An outline of the experimental nuclear data activities at n-TOF will be presented