Miracle-dz/UniFAR-FTUs huggingface dataset:
Neutron-induced 37Ar recoil ejection in Ca-rich minerals and implications for 40Ar/39Ar dating

Abstract The 40Ar/39Ar dating technique requires the transformation of 39K into 39Ar by neutron activation. Neutron activation has undesirable secondary effects such as interfering isotope production, and recoil of 39Ar and 37Ar atoms from their (dominant) targets of K and Ca. In most cases, the grains analysed are large enough (>50 μm) such that the amount of target atoms ejected from the grains is small and has a negligible effect on the ages obtained. However, increasing needs to date fine-grained rocks requires constraining, and in some cases correcting for, the effect of nuclear recoil. Previous quantitative studies of recoil loss focus mostly on 39Ar. However, 37Ar loss can affect the ages of Ca-rich minerals via interference corrections on 36Ar (and, to a lesser extent, 39Ar), yielding lower 40Ar*/39ArK and, thus, an age spuriously too young. New results focused on 37Ar recoil by measuring the apparent age of multi-grain populations of Ca-rich minerals including Fish Canyon plagioclase (FCp) and Hb3gr hornblende, with discrete sizes ranging from 210 to <5 µm. We use previous result on sanidine grains to correct for the 39Ar recoil loss. For the finest fractions, FCp and Hb3gr apparent ages are younger than the 39Ar recoil-corrected ages expected for these minerals, with a maximum deviation of −40% (FCp) and −21% (Hb3gr) reached for grains below 5 μm. We calculate 37Ar-depletion values ranging from approximately 30 to 91% and from approximately 28 to 98% for plagioclase and hornblende, respectively. This results in x0 values (mean thickness of the partial depletion layer) of 3.3±0.4 μm (2σ; FCp) and 3.6±1.4 μm (Hb3gr), significantly higher than suggested by current models. The reason for the substantial 37Ar loss is not well understood, but might be related to the radiation damage caused to the mineral during irradiation. x0 (39Ar) and x0 (37Ar) values obtained in this study, along with crystal dimensions, can be used for correcting 40Ar/39Ar ages from 39Ar and 37Ar recoil loss. We also discuss the relevance of our results to vacuum-encapsulation studies and isotopic redistribution in fine-grained minerals. Supplementary material: Annex 1, 2 and 3 are available at www.geolsoc. org.uk/SUP18610. Annex 1 and 2: Raw argon data corrected for blank, mass discrimination and radioactive decay for Fish Canyon plagioclase (Annex 1) and Hb3gr hornblende (Annex 2). Annex 3: Step-heating 40Ar/39Ar age spectra for FCp (Fig. A3.1) and Hb3gr (Fig. A3.2).
Stress–strain–strain rate relation for the compressibility of sensitive natural clays

Four types of oedometer tests (constant rate of strain tests, controlled gradient tests, multiple-stage loading tests and creep tests) were carried out on a variety of Champlain sea clays. Results obtained on five sites are used to demonstrate that the rheological behaviour of these clays is controlled by a unique stress-strain-strain rate relationship. This relationship can be simply described by two curves (σ-p′-ɛv and (σ′/σp′)-ɛv). The significance, the practical implications and the limitations of the model are also discussed. Quatre types d'essais oedometriques (a vitesse constante de deformation, a gradient controle, a chargement en plusieurs etapes et avec fluage) ont ete effectues sur diverses argiles marines Champlain. Les resultats obtenus sur cinq sites sont utilises pour demontrer que le comportement rheologique de ces argiles est regi par une relation unique contrainte-deformation/vitesse de deformation. Cette relation peut etre decrite de facon tres simple par deux courbes (σp-ɛv et (σv′/σp′.
Fragmentation in the Val Pola rock avalanche, Italian Alps

[1] Grain size data from the deposit of the 1987 Val Pola rock avalanche (central Italian Alps) are compared with data concerning rock avalanching, rock fragmentation, and comminution. The Weibull distribution fits a small part of the entire particle-size distribution of debris samples, with a mean value of the curve shape factor of 0.54 ± 0.28. This is typical of multiple comminution, or fragmentation with much shearing. A fractal distribution fits over a greater size range. Computed fractal dimensions range between 1.3 and 3.2 within the deposit, with average values of about 2.6–2.7. These values cover the range between the theoretical values of the plane-of-weakness model (1.97) and the pillar-of-strength model (2.84) and are close to the theoretical value for the constrained comminution model (2.58). These suggest that both texturally mature and immature deposits are present and that more than a single comminution process acted during the rock avalanche motion. Variation of the grain size distribution within the deposit and grain size segregation show as trends in the fractal dimension and arise from variation in the fragmentation process. A variety of different physical and empirical laws suggest that 1–30% of the energy expended in the rock avalanche was consumed in fragmentation.
On the Chemical Climate and its Variation with the Atmospheric Circulation Pattern

A study of the chemical composition of monthly precipitation samples from a number of stations in Sweden brings out the existence of significant variations in the relative proportions of chlorides and sodium depending upon the general character of the prevailing circulation. In maritime westerly flows the weight ratio of chloride to sodium decreases eastward to values which lie far below the value characteristic of sea water. In precipitation falling from arctic or polar continental air masses the chloride component is almost completely absent. The highest amounts of chlorides relative to sodium are observed in precipitation from warm and most air masses reaching Sweden from the south or southeast. Significant variations are observed also in the yearly means of the sodium and sulphur deposits depending upon the dominance of maritime or continental air currents. A sketch map of the “average” chloride concentration in European precipitation prepared from miscellaneous older data lends support to the results of the analysis of the monthly data. The separation of the chemical components indicated by this study would seem to be of considerable geochemical interest since it would permit different maritime salts to be deposited in widely separated parts of the continents. It is not inconceivable that a detailed study of the association between different circulation patterns and the corresponding chemical climates might permit us to draw inferences concerning variations in the atmospheric circulation during post-glacial times, e.g. from the data on the chemical stratification in raised bogs now becoming available through the investigations by Mattson and Koutler-Andersson . DOI: 10.1111/j.2153-3490.1955. tb01145.x
Multilevel cloud retrieval using multispectral HIRS and AVHRR data: Nighttime oceanic analysis

A multispectral, multiresolution (MSMR) method is developed for analyzing scenes of overlapping cloud layers. The MSMR method is applied to data from the NOAA 11 advanced very high resolution radiometer (AVHRR) and the high-resolution infrared radiometer sounder (HIRS-2). The data are from a nighttime oceanic scene in which a semitransparent cirrus veil overlays a large-scale stratus cloud. Low-cloud and clear-sky radiances are determined using a spatial coherence technique. Middle to upper level cloud pressures and radiances are estimated from HIRS-2 15+m CO2 band radiometric data. The MSMR method improves the interpretation of a nighttime, oceanic scene containing thin cirrus over a large-scale stratiform cloud. If, for example, the same scene is analyzed using only the AVHRR 10%pm channel, the accompanying retrieved cloud heights are found to be between the cirrus and stratus cloud heights and are incorrectly identified as midlevel altostratus clouds. Theoretical radiative transfer model results for both water droplet spheres and randomly oriented hexagonal ice crystals are compared to observed AVHRR brightness temperature differences (BTD) between the 3.7- and 10.8-pm channels (BTD34) and between the 10.8- and 12- pm channels (BTD4') to distinguish among the effects of cloud optical depth, particle size, and phase for both single-layer clouds and overlapping two-layer clouds. Theoretical BTD calculations are used to estimate the range of effective particle sizes for each cloud layer. The data for the cirrus in the case study region near Bermuda are consistent with theoretical results for relatively small randomly oriented hexagonal ice crystals. The observed BTD34 and BTD45 values are lower for the cirrus above a lower-level cloud than for single-level cirrus with no underlying cloud. In certain cases the BTD analysis provides a way to distinguish between clouds composed of supercooled water droplets rather than ice particles. Analysis of nighttime data permits determination of stratus infrared optical depths smaller than 4.
A Turbulent and Suspended Sediment Transport Model for Plunging Breakers

Extensive studies have suggested a high concentration of suspended sediment near the free surface induced by strong plunging breakers. However, prediction by models have not been successful because of the localized interactions among the plunging jet, turbulent production, and sediment movement. This study proposes a new calculation model for turbulent flow and suspended sediment transport in the surf zone. A numerical model was developed to simulate the flow and sediment motion in connection with plunging breakers in the surf zone. The Reynolds-Averaged Navier-Stokes (RANS) equations in two spatial dimensions were employed to simulate the flow field together with a κ-ε model for the turbulence and the Volume of Fluid (VOF) method for multiple free-surface tracking. An advection-diffusion equation was used for the suspended sediment concentration with a bottom boundary condition following the reference concentration formulation. Performance of the suspended sediment transport model under plunging breaking waves were examined through the comparison with experimental data. Good agreement between the model and experimental data was obtained for the surface elevation and velocity, turbulent kinetic energy, eddy viscosity and suspended sediment concentration. The overturning waves, plunging jet and transport of high concentration of suspended sediment near the free surface are reproduced by the present model with selected fine mesh resolution. The study shows the applicability of the present model in the turbulent and suspended sediment dominated region induced by strong plunging breakers.
Pore shrinkage dependency of inorganic and organic soils on wetting and drying cycles

Cycles of wetting and drying (WD) occur naturally in soils and affect the pore structure through altered hydraulic stresses. Two organic-rich soils, a Eutric Histosol and a Histic Gleysol, and two inorganic soils, a Calcic Gleysol and a Dystric Gleysol, ranging in texture and microstructure, were investigated. Undisturbed soil samples were predried to either -100 kPa water potential by using a ceramic plate or to 30°C by using an oven and then resaturated for one or three WD cycles. In addition, different combinations defined by the intensity, frequency, and sequence of WD cycles were analyzed. Soil structure was altered significantly if the intensity of drying was severe at 30°C, while drying to -100 kPa had only a small effect. The frequency and sequence of WD cycles did not alter the structure and shrinkage behavior significantly. Compared with the initial pore volume, intense WD cycles decreased it by 23.6 to 60.1% in the two organic-rich soils, whereas it increased by 1.5 to 4.8% in the silty Calcic Gleysol and by 3.6 to 15.1% in the clayey Dystric Gleysol. Both organic-rich soils showed more shrinkage but less swelling than did the two inorganic soils. Intense WD cycles altered the water potential vs. void ratio curves of the two organic-rich soils more gradually, while steeper patterns were observed for the two inorganic soils. This study shows that the changes in soil structure and pore shrinkage depend mostly on the maximum intensity of previous WD cycles.
Introduction to Special Section: Stress Triggers, Stress Shadows, and Implications for Seismic Hazard

Many aspects of earthquake mechanics remain an enigma as we enter the closing years of the twentieth century. One potential bright spot is the realization that simple calculations of stress changes may explain some earthquake interactions, just as previous and on going studies of stress changes have begun to explain human-induced seismicity. This paper, which introduces the special section “Stress Triggers, Stress Shadows, and Implications for Seismic Hazard,” reviews many published works and presents a compilation of quantitative earthquake interaction studies from a stress change perspective. This synthesis supplies some clues about certain aspects of earthquake mechanics. It also demonstrates that much work remains before we can understand the complete story of how earthquakes work.
A review of the use of radio-echo sounding in glaciology

Radio-echo sounding (RES), or radar, is an established geophysical technique that has been, and continues to be, applied to investigate a variety of ice-mass properties. This review presents the physical theory and principles of radio-glaciology, and describes the various types of radar equipment commonly used, including modern, ground-penetrating radar (GPR) systems. The range of glaciological applications these systems have been used to investigate is summarized, along with promising avenues of current and future research.
Melting and refreezing beneath Roi Baudouin Ice Shelf (East Antarctica) inferred from radar, GPS, and ice core data

indicate that this reflector pattern is best fit by including basal melting of at least 15 cm a � 1 . This rate of melting is low compared with rates observed on larger ice shelves in both West and East Antarctica. Ice cores extracted from a rift system close to the ice-rise promontory show several meters of marine ice accreted beneath the shelf. These observations of low rates of basal melting, and limited distribution of accreted marine ice suggest that either Antarctic surface water may reach the ice shelf base or that circulation beneath the shelf is likely dominated by the production of high salinity shelf water rather than the incursion of circumpolar deep water, implying a weak sub-shelf circulation system here. Many of the ice shelves located along the coast of Dronning Maud Land are, like Roi Baudouin Ice Shelf, characterized by frequent ice rises and promontories. Therefore, it is highly likely that these are also of shallow bathymetry and are subject to similarly weak side-shelf basal melting and refreezing.
Unsupervised Multi-Person 3D Human Pose Estimation From 2D Poses Alone

Current unsupervised 2D-3D human pose estimation (HPE) methods do not work in multi-person scenarios due to perspective ambiguity in monocular images. Therefore, we present one of the first studies investigating the feasibility of unsupervised multi-person 2D-3D HPE from just 2D poses alone, focusing on reconstructing human interactions. To address the issue of perspective ambiguity, we expand upon prior work by predicting the cameras' elevation angle relative to the subjects' pelvis. This allows us to rotate the predicted poses to be level with the ground plane, while obtaining an estimate for the vertical offset in 3D between individuals. Our method involves independently lifting each subject's 2D pose to 3D, before combining them in a shared 3D coordinate system. The poses are then rotated and offset by the predicted elevation angle before being scaled. This by itself enables us to retrieve an accurate 3D reconstruction of their poses. We present our results on the CHI3D dataset, introducing its use for unsupervised 2D-3D pose estimation with three new quantitative metrics, and establishing a benchmark for future research.
Unusual trilobite biofacies from the Lower Ordovician of the Argentine Cordillera Oriental: new insights into olenid palaeoecology

Balseiro, D. , Waisfeld, B.G. & Buatois, L.A. 2010: Unusual trilobite biofacies from the Lower Ordovician of the Argentine Cordillera Oriental: new insights into olenid palaeoecology. Lethaia, Vol. 44, pp. 58–75. The study of biofacies has proven to be relevant in the understanding of trilobite palaeoecology, palaeobiogeography and macroevolution. The widespread Olenid biofacies is one of the best known, and is usually interpreted as occuring in dysoxic environments. Tremadocian successions of the Argentinian Cordillera Oriental bear a diverse and long-studied olenid-dominated fauna. Based on cluster analysis, five distinct biofacies are defined for the middle Tremadocian (Tr2 stage slice), distributed from shelf (below storm wave base) to lower-shoreface settings (above fair-weather wave base). Ordination shows biofacies along two gradients, a bathymetrical one and another related to oxygen content. All of them are dominated both taxonomically and ecologically by olenids. This detailed quantitative palaeoecological study challenges current views suggesting instead that the Olenidae dominated a broad range of environments, from oxygenated shallow-marine to dysoxic deep-marine. Comparisons with largely coeval trilobite records from geodynamically and palaeobiogeographically disparate sites suggest that siliciclastic sedimentation appears as the most influential controlling environmental factor upon olenid distribution and dominance. Further comparisons across different climatic belts show that siliciclastic input controlled trilobite diversity gradients, even more than latitude. From an autoecological viewpoint distribution of traditional olenid morphotypes shows no relation to depth or to oxygen content, and at least some members of the group appear to have had the possibility of coping with low oxygen content, rather than being restricted to oxygen-deficient environments. The analysis performed herein, together with recent research on the group, demonstrate that factors controlling olenid distribution are more complex than previously envisaged. □Biofacies, diversity, Olenidae, palaeoecology, Tremadocian, trilobite.
Long-memory flow models in reservoir analysis: What is their practical value?

The theoretical value of long-memory stochastic models lies in their ability to generate time series that resemble long historic records of some geophysical processes better than do short-memory models. Since the use of short-memory streamflow models has become standard practice in reservoir design, it is worth asking whether the suspected theoretical superiority of long-memory models justifies a change in this practice; in other words, whether their theoretical appeal can be translated into better design of storage reservoirs. This paper analyzes the problem from the point of view of the differences in reservoir performance reliability obtained on the basis of long- and short-memory models fitted to the same historic streamflow record of a length typically encountered in reservoir design. It appears that the differences in reliability resulting from the replacement of one model by the other (shorter memory yields higher reliability) are small compared both to (1) the accuracy of measurement of the socioeconomic impact of reliability changes and (2) the accuracy of estimating the reliability itself on the basis of available streamflow records and for economically relevant lengths of reservoir operation periods. Thus it is argued that given the socioeconomic and hydrologic data typically available for reservoir planning and design, the replacement of short-memory models with long-memory models in reservoir analyses cannot be objectively justified. It is suggested that for a long time to come the use of long-memory models will, in principle, remain equivalent to the use of a small safety factor in the intrinsically inaccurate estimate of reservoir performance reliability.
Experimental deformation of synthetic magnetite‐bearing calcite sandstones: Effects on remanence, bulk magnetic properties, and magnetic anisotropy

We have quantified effects of experimental deformation on the magnetic properties of a set of synthetic “calcite sandstone” samples containing magnetite. The deformation was carried out in a microcomputer-controlled apparatus that adjusted the applied differential stress as needed to maintain a constant strain rate of 10−5 s−1. Most samples were deformed under dry conditions, but a few were deformed with a pore fluid present; the samples deformed under dry conditions required substantially higher differential stresses. Macroscopically ductile shortening strains of up to 25% produced the following irreversible changes in magnetic properties: (1) increased bulk coercivity, remanence coercivity, and mean anhysteretic remanence susceptibility; (2) decreased mean low-field susceptibility; (3) decreases in the component of remanence parallel to shortening; (4) smaller decreases for most samples in the component normal to shortening, resulting in a net “rotation” of the remanence away from the shortening axis; (5) larger decreases in the normal component in a few samples, resulting in a net “rotation” of the remanence towards the shortening axis; (6) increased magnetic anisotropy; and (7) increased “deformation” of initial magnetic ellipsoids. A comparison of data for samples deformed under dry and wet conditions (higher and lower differential stresses, respectively) indicates that remanence reorientation and susceptibility anisotropy are controlled primarily by bulk strain (i.e., rotation and displacement of particles), whereas coercivity and anhysteretic anisotropy are controlled dominantly by microstrain or intragranular stress.
Simultaneous transport of solutes and water under transient unsaturated flow conditions

Theoretical and mathematical tools for analyzing transient one-dimensional (vertical) simultaneous transfer of noninteracting solute and water in unsaturated soils are developed. The transient diffusion convection equation is solved numerically by an approach that eliminates the effect of numerical dispersion. The numerical results are compared with some analytical solutions for steady water flow. For transient infiltration the results are compared with field data reported by Warrick et al. These comparisons indicate that the theory as well as the numerical method is reliable and can be used with confidence. Results are given for typical cases of infiltration, redistribution, and evaporation of water from the soil and their effect on dispersion coefficients and salt concentration profiles.
The Changing Rainfall Pattern and Its Implication for Flood Frequency in Makurdi, Northern Nigeria

The study deals with analysis of recent changes in the characteristics of extreme rainfall and their implication for flood frequency in Makurdi. Data on extreme daily rainfall, evapotranspiration and flood occurrences were collected for analysis. The annual rainfall was analysed for trends using spearman rank correlation coefficient, annual rainfall variability analysed using standardized rainfall anomaly index while recurrence intervals were analysed using Gumbell Extreme probability theory. The results of the analysis show among other things that there was a remarkable continuous downward trend in annual rainfall amounts; that the period between 1996 and 2001 witnessed the highest frequencies of extreme rainfall events and flood frequencies; that major floods were associated with high recurrence intervals, and that the seasonality of flooding in Makurdi occurs between May and October. @JASEM