Geochemical and lithologic response of an upland watershed over the past 800 years to landscape changes in Southern Burgundy, France.

This study is an integrated analysis of the interaction between human and environmental systems within a small watershed in Southern Burgundy, France. The main objectives for this study were to understand the key environmental drivers for sediment erosion and nutrient availability in the watershed, and how those drivers were recorded in the pond sediment over the past 800 years. Future climate variability, interacting with land-use changes (e.g. intensification of agriculture) may have detrimental impacts on water quality, water availability, and crop yields in the Burgundy region. Thus, the examination of historical human landscape changes and interactions with climate in Burgundy can provide scientific data that policy makers and farmers can use to move toward sustainable land-management policies and practices, developing resilient systems, more robust in the face of future challenges. Records of high-resolution geochemical, biological, and lithological data were reconstructed from the sediments of two small, Medieval-aged reservoirs. Geochemical proxies including scanning X-ray Fluorescence, stable isotope (δ13C and δ15N), and elemental analyses (carbon, nitrogen, and phosphorus) were used to understand changes in erosion and productivity. Additionally, pollen analysis provided a record of changes in plant abundance and land cover through time. This reconstructed history was directly compared with historically documented changes in land-use within Burgundy using historical maps, parish/civil records, and agricultural reports. Results from this study suggest humans have driven most of the changes recorded in the pond sediment. In particular, changes in agricultural practices, such as increased livestock production, resulted in increased erosion to the ponds. Further, activities such as hemp processing and chemical fertilization both resulted in episodes of eutrophication. Ultimately, this work provides a framework for predicting future impacts of agricultural policies on the Burgundian landscape, and utilizes a multiproxy approach to landscape history that may be applied to other regions. Furthermore, this study documents landscape history within a paleoenvironmental context, and in a geographic area where studies on environmental archives (i.e. reservoir sediments, tree rings, etc.) are scarce. Therefore, these data are particularly important to formulating sustainable land-management practices and policies to create a more resilient Burgundy in the face of future climate change

Multi-frequency, Multi-temporal, Brush Fire Scar Analysis in a Semi-Arid Urban Environment

The number of forest fires has increased dramatically over the past five years in western areas of the United States, due to both human and natural causes. Urban areas, such as the city of Phoenix, continue to increase in size and population, with a majority of the development occurring in rural areas that have burned, or are threatened by brush fires. As people move into these environments there is an increased risk of damage to human property and lives due to fires. These areas have experienced a number of recent brush fires that have been expensive to fight, and caused a considerable amount of property damage. The ability to predict and control fires is thus increasingly important as urban centers encroach upon rural lands. Remote sensing can be utilized to characterize fire scarred areas, and predict areas that have an increased risk for burning again in the future. Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER), Landsat Thematic Mapper (TM), and Spaceborne Imaging Radar - C (SIR-C) remote sensing data have been combined with a geographic information system (GIS) to characterize fire scars in a semi-arid urban area outside of Phoenix, Arizona. This data was also used to quantify the relationship of fire scar age to vegetative recovery. In addition to the remote sensing aspect of this project, an initial geomorphological investigation was conducted to determine the effect of fire on sediment flux and landscape evolution. Detailed topographic surveys, combined with sediment trap data, were used to examine differences in erosion between burned and unburned catchments. These results have implications for potential flooding risks due to removal of vegetative cover by fires. By combining remote sensing data with a GIS database, and through comparison with geomorphic/sedimentological investigations, this work may permit city officials and urban planners to better calculate potential risks for both future fire and flood hazards within the region

Relativistic Mergers of Supermassive Black Holes and their Electromagnetic Signatures

Coincident detections of electromagnetic (EM) and gravitational wave (GW) signatures from coalescence events of supermassive black holes are the next observational grand challenge. Such detections will provide the means to study cosmological evolution and accretion processes associated with these gargantuan compact objects. More generally, the observations will enable testing general relativity in the strong, nonlinear regime and will provide independent cosmological measurements to high precision. Understanding the conditions under which coincidences of EM and GW signatures arise during supermassive black hole mergers is therefore of paramount importance. As an essential step towards this goal, we present results from the first fully general relativistic, hydrodynamical study of the late inspiral and merger of equal-mass, spinning supermassive black hole binaries in a gas cloud. We find that variable EM signatures correlated with GWs can arise in merging systems as a consequence of shocks and accretion combined with the effect of relativistic beaming. The most striking EM variability is observed for systems where spins are aligned with the orbital axis and where orbiting black holes form a stable set of density wakes, but all systems exhibit some characteristic signatures that can be utilized in searches for EM counterparts. In the case of the most massive binaries observable by the Laser Interferometer Space Antenna, calculated luminosities imply that they may be identified by EM searches to z = 1, while lower mass systems and binaries immersed in low density ambient gas can only be detected in the local universe.Comment: 19 pages, 15 figures, version accepted for publicatio

Anti-de Sitter curvature radius constrained by quasars in brane-world scenarios

This paper is intended to investigate the luminosity due to accretion of gas in supermassive black holes (SMBHs) in the center of quasars, using a brane-world scenario naturally endowed with extra dimensions, whereon theories formulated introduce corrections in the field equations at high energies. SMBHs possess the necessary highly energetic environment for the introduction of these corrections, which are shown to produce small deviations in all SMBH properties and, consequentely, corrections in the accretion theory that supports quasars radiative processes. The radiative flux observed from quasars indicates these deviations, from which the magnitude of the AdS$_5$ bulk curvature radius, and consequently the extra dimension compactification radius is estimated.Comment: 11 pages, RevTeX, Eq.(2) and (3) expanded, and comments thereon update