Miracle-dz/UniFAR-FTUs huggingface dataset:
A Multiphase Approach to the Modeling of Porous Media Contamination by Organic Compounds: 1. Equation Development

A multiphase approach to the modeling of aquifer contamination by organic compounds is developed. This approach makes it possible to describe the simultaneous transport of a chemical contaminant in three physical forms: as a nonaqueous phase, as a soluble component of an aqueous phase, and as a mobile fraction of a gas phase. The contaminant may be composed of, at most, two distinct components, one of which may be volatile and slightly water soluble and the other of which is both nonvolatile and insoluble in water. Equations which describe this complex system are derived from basic conservation of mass principles by the application of volume averaging techniques and the incorporation of various constitutive relations and approximations. Effects of matrix and fluid compressibilities, gravity, phase composition, interphase mass exchange, capillarity, diffusion, and dispersion are all considered. The resulting mathematical model consists of a system of three nonlinear partial differential equations subject to two equilibrium constraints. These equations relate five unknowns: two capillary pressures and three mass fractions.
Atmospheric responses to the redistribution of anthropogenic aerosols

The geographical shift of global anthropogenic aerosols from the developed countries to the Asian continent since the 1980s could potentially perturb the regional and global climate due to aerosol‐cloud‐radiation interactions. We use an atmospheric general circulation model with different aerosol scenarios to investigate the radiative and microphysical effects of anthropogenic aerosols from different regions on the radiation budget, precipitation, and large‐scale circulations. An experiment contrasting anthropogenic aerosol scenarios in 1970 and 2010 shows that the altered cloud reflectivity and solar extinction by aerosols results in regional surface temperature cooling in East and South Asia, and warming in the US and Europe, respectively. These aerosol‐induced temperature changes are consistent with the relative temperature trends from 1980 to 2010 over different regions in the reanalysis data. A reduced meridional streamfunction and zonal winds over the tropics as well as a poleward shift of the jet stream suggest weakened and expanded tropical circulations, which are induced by the redistributed aerosols through a relaxing of the meridional temperature gradient. Consequently, precipitation is suppressed in the deep tropics and enhanced in the subtropics. Our assessments of the aerosol effects over the different regions suggest that the increasing Asian pollution accounts for the weakening of the tropics circulation, while the decreasing pollution in Europe and US tends to shift the circulation systems southward. Moreover, the aerosol indirect forcing is predominant over the total aerosol forcing in magnitude, while aerosol radiative and microphysical effects jointly shape the meridional energy distributions and modulate the circulation systems.
A reply to the article ‘Permafrost in the Gruve-7 mine, Adventdalen, Svalbard’ by H. Christiansen, H. French & O. Humlum

The article titled ‘Permafrost in the Gruve-7 mine, Adventdalen, Svalbard’ (hereafter referred to as ‘the article’) in Norsk Geografisk Tidsskrift Norwegian Journal of Geography 59:2 (Christiansen et al. 2005, 109 115) addresses the important issues of permafrost-glacier interaction and the 3-dimensional structure of permafrost bodies. Based on temperature measurements from a mining corridor, conclusions are drawn about: a) active layer thickness; b) permafrost-glacier relationships; and c) the 3-dimensional structure of permafrost. These conclusions are questionable because the thermal effect of ventilation air appears to dominate the measured temperatures and cannot be (or at least has not been) separated from the desired undisturbed temperature field. This can be understood by theoretical analyses and by comparison with the data from the nearby Janssonhaugen borehole (Isaksen et al. 2000, also quoted in the article). Given a harmonic temperature boundary condition of amplitude A0 and a semi-infinite homogenous medium with a certain thermal diffusivity (k), the temperature amplitude (Az) at depth (z) below this boundary can be described as:
A new ice sheet model validated by remote sensing of the Greenland ice sheet

Accurate prediction of future sea level rise requires models that accurately reproduce and explain the recent observed dramatic ice sheet behaviours. This study presents a new multi-phase, multiple-rheology, scalable and extensible geofluid model of the Greenland ice sheet that shows the credential of successfully reproducing the mass loss rate derived from the Gravity Recovery and Climate Experiment (GRACE), and the microwave remote sensed surface melt area over the past decade. Model simulated early 21st century surface ice flow compares satisfactorily with InSAR measurements. Accurate simulation of the three metrics simultaneously cannot be explained by fortunate model tuning and give us confidence in using this modelling system for projection of the future fate of Greenland Ice Sheet (GrIS). Based on this fully adaptable three dimensional, thermo-mechanically coupled prognostic ice model, we examined the flow sensitivity to granular basal sliding, and further identified that this leads to a positive feedback contributing to enhanced mass loss in a future warming climate. The rheological properties of ice depend sensitively on its temperature, thus we further verified modelâŹs temperature solver against in situ observations. Driven by the NCEP/NCAR reanalysis atmospheric parameters, the ice model simulated GrIS mass loss rate compares favourably with that derived from the GRACE measurements, or about −147 km3/yr over the 2002–2008 period. Increase of the summer maximum melt area extent (SME) is indicative of expansion of the ablation zone. The modeled SME from year 1979 to 2006 compares well with the cross-polarized gradient ratio method (XPGR) observed melt area in terms of annual variabilities. A high correlation of 0.88 is found between the two time series. In the 30-year model simulation series, the surface melt exhibited large inter-annual and decadal variability, years 2002, 2005 and 2007 being three significant recent melt episodes.
Retrieval characteristics of non‐linear sea surface temperature from the Advanced Very High Resolution Radiometer

Criteria are proposed for evaluating sea surface temperature (SST) retrieved from satellite infra‐red imagery: bias should be small on regional scales; sensitivity to atmospheric humidity should be small; and sensitivity of retrieved SST to surface temperature should be close to 1 K K−1. Their application is illustrated for non‐linear sea surface temperature (NLSST) estimates. 233929 observations from the Advanced Very High Resolution Radiometer (AVHRR) on Metop‐A are matched with in situ data and numerical weather prediction (NWP) fields. NLSST coefficients derived from these matches have regional biases from −0.5 to +0.3 K. Using radiative transfer modelling we find that a 10% increase in humidity alone can change the retrieved NLSST by between −0.5 K and +0.1 K. A 1 K increase in SST changes NLSST by <0.5 K in extreme cases. The validity of estimates of sensitivity by radiative transfer modelling is confirmed empirically.
Block-tilting, transfer faults, and structural control of magmatic and hydrothermal processesin the TAG area, Mid-Atlantic Ridge 26°N

Seven Alvin dives (14 km total) and numerous deep-towed camera traverses using ANGUS and NOAA camera systems provide dense coverage of a 12-km2 portion of the eastern wall of the Mid-Atlantic Ridge in the TAG area (26°N lat.). These data, in conjunction with recent Soviet Mir submersible data, provide important constraints on the tectonic, magmatic, and hydrothermal history of this spreading center segment. Active hydrothermal venting occurs near the junction of the median valley floor and eastern median valley wall and appears to be tectonically controlled by the intersection of major fault zones. An east-west fault-line scarp interpreted as an accommodation zone intersects escarpments associated with 020°-trending (ridge-parallel) normal faults that bound the median valley floor. The accommodation zone permits differential extension and rotation between major crustal blocks to the north and south. On the basis of the distribution of tilted chalk beds and geochemical anomalies in sediments, this fault zone has been intermittently active for at least 5x104 yr. The accommodation zone has apparently provided a conduit of high permeability oriented at a high angle to the ridge axis. Observations and samples from areas surrounding active and inactive vent sites provide evidence for three distinct episodes for hydrothermal outflow driven by separate magmatic events. The geometry of this active system may have implications for the location of hydrothermal systems in active spreading regimes and for massive sulfide exploration in ophiolite terranes.
Measurements of dense snow avalanche basal shear to normal stress ratios (S/N)

We investigate frictional processes at the basal shear layer of snow flows. A chute is instrumented with basal force plates, velocity and flow height sensors to perform experiments with dry and wet snow. We find that a Mohr‐Coulomb relation of the form S = c + bN accurately describes the relation between normal (N) and shear stress (S). The Coulomb friction coefficient b ranges between 0.22 and 0.55. Several wet snow avalanches exhibited significant cohesion c ≈ 500 Pa. These quantitative measurements of stress, velocity and flow height allow us to probe the relation between basal work, internal dissipation and gravitational potential energy. We find that basal shearing is the primary frictional mechanism retarding snow flows. This mechanism shows no velocity dependence, contrary to many postulated constitutive relations for basal shearing in snow avalanches.
Le Châtelperronien de la grotte du Renne à Arcy-sur-Cure (Yonne). Données sédimentologiques et chronostratigraphiques

La grotte du Renne a Arcy-sur-Cure est l'un des gisements les plus importants pour la transition Paleolithique moyen/superieur mais sa position chronologique n 'est pas encore bien etablie. Une coupe a donc ete rouverte en 1998 pour reprendre des echantillons pour datation. Dans la perspective de la publication des donnees châtelperroniennes des fouilles Leroi- Gourhan, elle a permis de completer les informations stratigraphiques et sedimentologiques de la couche X et de montrer la coherence du depot. Un apercu du materiel mis au jour a cette occasion est egalement donne.
On the detectability of ocean surface waves by real and synthetic aperture radar

Real and synthetic aperture radars have been used in recent years to image ocean surface waves. Though wavelike patterns are often discernible on radar images, it is still not fully understood how they relate to the actual wave field. The present paper reviews and extends current models on the imaging mechanism. Linear transfer functions that relate the two-dimensional wave field to the real aperture radar (SLAR) image are calculated by using the two-scale wave model. It is noted that a description of the imaging process by these transfer functions can only be adequate for low to moderate sea states. Possible other mechanisms that contribute to the visibility of waves by real aperture radar at higher sea states, such as Bragg scattering from spontaneously generated short waves at peaked crests or in wave breaking regions, and Rayleigh scattering from air bubbles entrained in the water and from water droplets thrown into the air by breaking waves, are discussed in a qualitative way. The imaging mechanism for synthetic aperture radars (SAR's) is strongly influenced by wave motions (i.e., by the orbital velocity and acceleration associated with the long waves). The phase velocity of the long waves does not enter into the imaging process. Focusing of ocean wave imagery is attributed to orbital acceleration effects. The orbital motions lead to a degradation in resolution which causes image smear as well as a SAR inherent imaging mechanism called velocity bunching. The parameter range for which velocity bunching is a linear mapping process is calculated. It is shown that linearity holds only for a relative small range of ocean wave parameters: The likelihood that the transfer function is linear increases as the direction of wave propagation approaches the range direction, as the wavelength increases, and as the wave height decreases. Linearity is required for applying simple linear system theory for calculating the ocean wave spectrum from the gray level intensity spectrum of the image. Although, in general, the full ocean wave spectrum cannot be recovered from the SAR image by applying simple linear inversion techniques, it is concluded that for many cases in which the ocean wave spectrum is relatively narrow the dominant wavelength and direction can still be retrieved from the image even when the mapping transfer function is nonlinear. Finally, we compare our theoretical models for the imaging mechanisms with existing SLAR and SAR imagery of ocean waves and conclude that our theoretical models are in agreement with experimental data. In particular, our theory predicts that swell traveling in flight (azimuthal) direction is not detectable by SLAR but is detectable by SAR.
Evaluation of a Technique to Trap Lemmings Under the Snow

We attempted to live trap lemmings under the snow in their preferred winter habitat at two sites in the Canadian Arctic using chimney-like boxes. Lemmings used the boxes during winter, but we had very low trapping success in April and May. During spring trapping, in contrast to most of the winter, subnivean temperatures became colder than ambient air temperatures. We hypothesize that our low success in spring resulted from lemmings’ leaving the deeper snow areas where our boxes were located and moving to shallower snow or exposed tundra. We suggest that the trapping boxes could be successful if trapping occurred earlier during winter.
Continental-Scale Basin Water Storage Variation from Global and Dynamically Downscaled Atmospheric Water Budgets in Comparison with GRACE-Derived Observations

AbstractSince 2002, the Gravity Recovery and Climate Experiment (GRACE) has provided gravity-derived observations of variations in the terrestrial water storage. Because of the lack of suitable direct observations of large-scale water storage changes, a validation of the GRACE observations remains difficult. An approach that allows the evaluation of terrestrial water storage variations from GRACE by a comparison with those derived from aerologic water budgets using the atmospheric moisture flux divergence is presented. In addition to reanalysis products from the European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction, high-resolution regional atmospheric simulations were produced with the Weather Research and Forecast modeling system (WRF) and validated against globally gridded observational data of precipitation and 2-m temperature. The study encompasses six different climatic and hydrographic regions: the Amazon basin, the catchments of Lena and Yenisei, .
Pc5 field line resonance frequencies and structure observed by SuperDARN and CANOPUS

We have analyzed a number of low-m Pc5 field line resonance events observed simultaneously by one or more of the Super Dual Auroral Radar Network (SuperDARN) radars and the Canadian Auroral Network for the OPEN Unified Study (CANOPUS) magnetometer array. At times there was excellent agreement in the Pc5 signal frequencies observed by radar and magnetometers. For events with good agreement in the measured signal frequencies, there was also reasonable agreement in the observed resonance positions and m numbers. Sometimes, however, the ordering of frequencies by their spectral power did not coincide between the radar and magnetometer data and even the frequencies of the spectral peaks did not always coincide. In these cases, there was also some apparent discrepancy in the observed resonance positions and m numbers. The resonance half power widths observed by the magnetometers were found to be a factor of 2 - 6 wider than those measured with the radar, owing to the spatial integration by ground-based magnetometers of ionospheric current structures having scale size less than ionospheric height. Although there was general agreement in the direction of the longitudinal propagation, the m numbers obtained from the magnetometer data were found to be somewhat smaller that those calculated from the radar data. We consider and discuss possible reasons for the observed discrepancies.
Smallholder adoption of soil conservation technologies: evidence from upland projects in the Philippines

Soil erosion due to smallholder agriculture in upland areas of the Philippines is widely regarded as the country's most serious environmental problem. There have been many upland development projects involving the promotion of soil conservation and agroforestry measures. Yet adoption of such practices has been minimal. A research project was commissioned to investigate the technical and socio-economic factors limiting adoption of recommended soil conservation technologies. The project involved case studies of seven locations where conservation farming had been intensively promoted and adopted by a significant number of farmers. The research methods involved a combination of reconnaissance or rapid rural appraisal methods followed by a questionnaire survey of a sample of farmers from each site. This paper summarizes the project's findings regarding the farm-level factors associated with the adoption of recommended soil conservation technologies in the case-study sites. Its focus is on the attributes of the farm-household influencing the adoption-decision process, and the consequences of adoption at the level of the farm-household system. It was found that conservation farming technologies, particularly hedgerows, were widely seen by farmers who were aware of them as useful and even necessary, but it had required resource-intensive project intervention to get the adoption process going, and adoption was often constrained by farmers' specific circumstances, rather than their personal attributes and perceptions. A wider range of more profitable and less demanding conservation technologies was needed, promoted more flexibly and with greater, on-going support for farmers in their efforts to experiment with improved farming systems. Copyright (C) 1999 John Wiley gi Sons, Ltd.
Detrital zircon geochronology and regional correlation of metasedimentary rocks in the Coast Mountains, southeastern Alaska

U-Pb ages have been determined for 55 detrital zircon grains from a metasedimentary sequence along the west flank of the Coast Mountains in southeastern Alaska. These rocks belong to the Port Houghton assemblage, which consists of upper Paleozoic pelitic and psammitic schist, metaconglomerate, metabasalt, and marble. The Port Houghton assemblage rests unconformably(? ) on metamorphosed and deformed mid-Paleozoic arc-type volcanics (Endicott Arm assemblage), which gradationally overlie upper Proterozoic(? ) - lower Paleozoic continental margin strata (Tracy Arm assemblage). Three main clusters of ages are present: 330-365 Ma (19 grains), 1710-2000 Ma (27 grains), and 2450-2680 Ma (6 grains). Additional grains are approximately 2334, 2364, and 3324 Ma. Comparison of these ages with detrital zircon ages in other Cordilleran assemblages supports previous interpretations that metasedimentary rocks in the Coast Mountains (i) form a southwestern continuation of the Yukon-Tanana terrane of eastern Alaska and Yukon,.
Bioavailability of Engineered Nanoparticles in Soil Systems

AbstractNanotechnologies form a field of research that is still emerging with major gaps in knowledge regarding the behavior and potential toxicological risks of engineered nanoparticles (ENPs) in soils. While most of the studies are conducted in porous media (quartz and glass beads) and culture media, less frequently are the studies carried out in natural soils. However, the complex interactions occurring in soils, mediated by both soil components and soil organisms, are essential in bioavailability processes. Therefore, this paper is intended to highlight particularly the bioavailability of ENPs in soils. The potential release pathways of ENPs to soils are described and are faced with a lack of specific regulation and definitive nomenclature. This paper reviews a number of studies regarding ENP toxicological bioavailability on microorganisms and microfauna, mesofauna, and macrofauna inhabiting the soil, as well as on soil-plant systems. The paper especially discusses ENP behavior in soils that affect EN.
Concentration and foreign ownership of land in Brazil in the context of global land grabbing

This article analyses land concentration in Brazil and the changing patterns of land acquisitions predominantly through foreign investments. First we compare census data from 1996 and 2006 and identify an acceleration of land concentration. We then show the limitations of the official registry data for capturing the phenomenon of “foreignisation”, and complement this with an analysis of data from the Central Bank, which provide for some general conclusions. Our research into journalistic and business literature confirms and complements these findings. We discuss the historical context of land concentration in Brazil, highlighting its progressive institutionalisation through juridical and regulatory control of foreign access to land. The transformations underway are driven by changes in the market dynamics of key agricultural and forestry commodities, for the analysis of which we develop a typology of capital. Cet article analyse la concentration foncière au Brésil et les changements dans les modes d'acquisition de la terre résultant principalement des investissements étrangers. Notre comparaison des données des recensements de 1996 et 2006 indique d'abord une accélération de la concentration foncière. Puis, nous montrons les limites des données du registre foncier officiel pour cerner le phénomène de la main mise étrangère alors que les données de la Banque centrale permettent de tirer des conclusions sur les grandes tendances. Un examen des écrits journalistiques et d'affaires confirme et complète ces résultats. Nous traitons enfin du contexte historique de la concentration foncière brésilienne pour faire ressortir son institutionnalisation progressive à travers l'adoption de mesures juridiques et règlementaires de contrôle de l'accès à la terre. Les transformations en cours sont stimulées par les changements dans la dynamique des marchés des principaux produits agricoles et forestiers. Pour conclure, nous proposons une typologie des formes d'investissement à l'oeuvre.