Single hydrophone source localization

The method presented in this paper assumes that the received signal is a linear combination of delayed and attenuated uncorrelated replicas of the source emitted waveform. The set of delays and attenuations, together with the channel environmental conditions, provide sufficient information for determining the source location. If the transmission channel is assumed known, the source location can be estimated by matching the data with the acoustic field predicted by the model conditioned on the estimated delay set. This paper presents alternative techniques that do not directly attempt to estimate time delays from the data but, instead, estimate the subspace spanned by the delayed source signal paths. Source Localization is then done using a family of measures of the distance between that subspace and the subspace spanned by the replicas provided by the model. Results obtained on the INTIMATE'96 data set, in a shallow-water acoustic channel off the coast of Portugal, show that a sound source emitting a 300-800-Hz LFM sweep could effectively be localized in range or depth over an entire day     

Impacts of future climatic and land cover changes on the hydrological regime of the Madeira River basin

Brazilian strategic interest in the Madeira River basin, one of the most important of the southern Amazon tributaries, includes the development of hydropower to satisfy the country’s growing energy needs and new waterways to boost regional trade and economic development. Because of evidences that climate change impacts the hydrological regime of rivers, the aim of this study was to assess how global climate change and regional land cover change caused by deforestation could affect the river’s hydrological regime. To achieve this goal, we calibrated a large-scale hydrological model for the period from 1970–1990 and analyzed the ability of the model to simulate the present hydrological regime when climate model simulations were used as input. Climate change projections produced by climate models were used in the hydrological model to generate scenarios with and without regional land-use and land-cover changes induced by forest conversion to pasture for the period from 2011–2099. Although results show variability among models, consensus scenarios indicated a decrease in the low-flow regime. When the simulations included forest conversion to pasture, climate change impacts on low flows were reduced in the upper basin, while, in the lower basin, discharges were affected along the whole year due to the more vigorous land-use conversion in the Brazilian region of the basin.     

Solar Sources of Interplanetary Coronal Mass Ejections During the Solar Cycle 23/24 Minimum

We examine solar sources for 20 interplanetary coronal mass ejections (ICMEs) observed in 2009 in the near-Earth solar wind. We performed a detailed analysis of coronagraph and extreme ultraviolet (EUV) observations from the Solar Terrestrial Relations Observatory (STEREO) and Solar and Heliospheric Observatory (SOHO). Our study shows that the coronagraph observations from viewpoints away from the Sun–Earth line are paramount to locate the solar sources of Earth-bound ICMEs during solar minimum. SOHO/LASCO detected only six CMEs in our sample, and only one of these CMEs was wider than 120^°. This demonstrates that observing a full or partial halo CME is not necessary to observe the ICME arrival. Although the two STEREO spacecraft had the best possible configuration for observing Earth-bound CMEs in 2009, we failed to find the associated CME for four ICMEs, and identifying the correct CME was not straightforward even for some clear ICMEs. Ten out of 16 (63 %) of the associated CMEs in our study were “stealth” CMEs, i.e. no obvious EUV on-disk activity was associated with them. Most of our stealth CMEs also lacked on-limb EUV signatures. We found that stealth CMEs generally lack the leading bright front in coronagraph images. This is in accordance with previous studies that argued that stealth CMEs form more slowly and at higher coronal altitudes than non-stealth CMEs. We suggest that at solar minimum the slow-rising CMEs do not draw enough coronal plasma around them. These CMEs are hence difficult to discern in the coronagraphic data, even when viewed close to the plane of the sky. The weak ICMEs in our study were related to both intrinsically narrow CMEs and the non-central encounters of larger CMEs. We also demonstrate that narrow CMEs (angular widths ≤?20^°) can arrive at Earth and that an unstructured CME may result in a flux rope-type ICME.     

Annama H chondrite—Mineralogy,physical properties,cosmic ray exposure,and parent body history

The fall of the Annama meteorite occurred early morning (local time) on April 19, 2014 on the Kola Peninsula (Russia). Based on mineralogy and physical properties, Annama is a typical H chondrite. It has a high Ar‐Ar age of 4.4 Ga. Its cosmic ray exposure history is atypical as it is not part of the large group of H chondrites with a prominent 7–8 Ma peak in the exposure age histograms. Instead, its exposure age is within uncertainty of a smaller peak at 30 ± 4 Ma. The results from short‐lived radionuclides are compatible with an atmospheric pre‐entry radius of 30–40 cm. However, based on noble gas and cosmogenic radionuclide data, Annama must have been part of a larger body (radius >65 cm) for a large part of its cosmic ray exposure history. The ¹⁰Be concentration indicates a recent (3–5 Ma) breakup which may be responsible for the Annama parent body size reduction to 30–35 cm pre‐entry radius.     

The optical performance of the PILOT instrument from ground end-to-end tests

The Polarized Instrument for Long-wavelength Observation of the Tenuous interstellar medium (PILOT) is a balloon-borne astronomy experiment designed to study the linear polarization of thermal dust emission in two photometric bands centred at wavelengths 240 μm (1.2 THz) and 550 μm (545 GHz), with an angular resolution of a few arcminutes. Several end-to-end tests of the instrument were performed on the ground between 2012 and 2014, in order to prepare for the first scientific flight of the experiment that took place in September 2015 from Timmins, Ontario, Canada. This paper presents the results of those tests, focussing on an evaluation of the instrument’s optical performance. We quantify image quality across the extent of the focal plane, and describe the tests that we conducted to determine the focal plane geometry, the optimal focus position, and sources of internal straylight. We present estimates of the detector response, obtained using an internal calibration source, and estimates of the background intensity and background polarization.     

First evidence of complex dental practice about 1300 BP in Mesoamerica revealed by absolute geomagnetic intensity

Deliberated dental modifications and mutilations are known since prehistoric times. The Mayas and other ancient cultures in Mesoamerica were considered pioneers of such practice. The evidences of therapeutic intervention, however, are still poorly documented and credible examples are extremely scarce. One of the burials excavated at the locality of La Mina (Michoacan, Mexico) corresponds to a 30-35 year old male individual named Alvaro, who presented a well-marked dental deformation. Moreover, Alvaro had a quite deep and symmetrical perforation in the upper right canine–a treatment similar to the procedure of endodontics or root canal. The archaeological context of Alvaro’s habitat was dated using the archaeomagnetic method applied to pottery samples unambiguously correlated to the burial. The analysis supplied a time interval between 647 and 825 AD suggesting the first evidence of complex dental practice in the Americas.     

Spatial patterns and temporal stability of soil moisture across a range of scales in a semi‐arid environment

The antecedent soil moisture status of a catchment is an important factor in hydrological modelling. Traditional Hortonian infiltration models assume that the initial moisture content is constant across the whole catchment, despite the fact that even in small catchments antecedent soil moisture exhibits tremendous spatial heterogeneity. Spatial patterns of soil water distribution across three transects (two in a burnt area and one in an unburnt area) in a semi‐arid area were studied. At the transect scale, when the factors affecting soil moisture were limited to topographical position or local topography, spatial patterns showed time stability, but when other factors, such as vegetation, were taken into account, the spatial patterns became time unstable. At the point scale, and in the same areas, topographical position was the main factor controlling time stability. Scale dependence of time stability was studied and local topography and vegetation presence were observed to play an important role for the correlation between consecutive measures depending on the scale. Copyright © 2000 John Wiley & Sons, Ltd.     

Insights into Ceres's evolution from surface composition

Inspired by the recent results of the Dawn mission, thermodynamic models of rock alteration and brine evaporation have been used to help understand the conditions under which water–rock interaction took place within the dwarf planet Ceres. This analysis constrains Ceres's early history and offers a framework within which future observations may be interpreted. A broad range of alteration conditions have been simulated using the Geochemist's Workbench and PHREEQC software, associated with the FREZCHEM model that constrains the consequences of freezing the liquid phase in equilibrium with the observed mineralogical assemblage. Comparison of the modeling results with observed surface mineralogy at Ceres indicates advanced alteration under a relatively high fugacity of hydrogen, a conclusion that is consistent with predictions for, and observations of, large ice‐rich bodies. The simulations suggest production of methane that could help regulate the redox environment and possibly form clathrate hydrates upon freezing of the early ocean. The detection of localized occurrences of natrite (sodium carbonate) at the surface of Ceres provides key constraints on the composition of fluids that are necessarily alkaline. In addition, the combined hydrothermal and freezing simulations suggest that hydrohalite may be abundant in Ceres's subsurface, similar to Earth's polar regions. The global homogeneity of Ceres's surface, made of material formed at depth, suggests a large‐scale formation mechanism, while local heterogeneities associated with impact craters and landslides suggest that some form of sodium carbonate and other salts are accessible in the shallow subsurface.