Miracle-dz/UniFAR-FTUs huggingface dataset:
Elasticity of a majorite‐pyrope solid solution

The elastic properties of a solid solution consisting of 59 mole percent pyropic garnet and 41% Mg{sub 4}Si{sub 4}O{sub 12}-majorite (a high-pressure form of pyroxene), have been measured by Brillouin spectroscopy under ambient conditions. Values of the adiabatic bulk modulus, K{sub s} = 164 {plus minus} 15 GPa, and shear modulus, G = 89.4 {plus minus} 3.7 GPa, are similar to those for low-pressure aluminosilicate garnets. The enstatite-majorite reaction is characterized by a large (49%) increase in K{sub s} and a much smaller (13%) increase in G. The properties of low-pressure garnets suggest that the contrast in shear moduli for this reaction is probably larger in Ca-rich systems. Taken at face value, the STP properties of these phases imply that large quantities of Ca-rich clinopyroxene are needed in order to satisfy seismologically determined shear modulus gradients in the transition zone. This suggestion is, however, subject to considerable uncertainties in the pressure and temperature derivatives of elastic properties for mantle minerals, and the velocity structure of the transition zone.
Eddy shedding and energy conversions in the East Australian Current

[1] Mesoscale variability and eddy shedding in the Tasman Sea, particularly of the East Australian Current (EAC), is studied through the analysis of remotely sensed observations and outputs from a global ocean model. Previous observations of the western boundary current separation from the coast showed strong variability at periods ranging between 90 and 140 days. We show from satellite altimetric observations that rapid northward migration of the separation point of the EAC follows the formation of large eddies at periods of ∼100 days. After an eddy separation event the normally southward flowing current swiftly assumes a more zonal configuration near the separation latitude, with a cyclonic circulation developing inshore. The formation of large separation eddies is preceded by the southward propagation of sea level anomalies along the east Australian continental slope. From 25°S, sea level anomalies grow as they travel south, eventually being pinched off in the form of large anticyclones at ∼32°S, in the current retroflection area. Energy conversion terms in a global ocean model and in altimetric data suggest both barotropic and baroclinic instability may account for the growth of these anomalies as they propagate south. East of the main EAC jet there is evidence that eddies may be feeding potential energy back to the mean flow.
Agricultural Productivity, Drought, and Economic Growth in Sahel

A standardized precipitation index is used in a regression analysis to quantify the impact of climate change on agricultural productivity in Sahel. I first estimate a Malmquist productivity index and its efficiency and technical change components. I further assess the statistical significance of the indices by estimating some confidence intervals via a bootstrap method. In the second stage of the analysis, I use a Probit model to estimate the extent to which climate variables affect agricultural productivity. It appears that agricultural performance has been disastrous in many Sahelian countries from 1970 to 2000. Using a comparable cross-country measure of drought, I provide evidence that precipitation variability is constraining not only Sahel’s agricultural performance but also its economic growth. War also plays an equally detrimental role as drought in explaining the causes of Sahel’s economic downturn.
A global climate model study of CH4 emissions during the Holocene and glacial‐interglacial transitions constrained by ice core data

Ice core records show atmospheric methane mixing ratio and interpolar gradient varying with climate. Changes in wetland sources have been implicated as the basis for this observed variation in the record, but more recently, modeling studies suggest that changes in the CH4 sink resulting from changes in sea surface temperature (SST) and emissions of other volatile organic carbon (VOC) compounds by vegetation must also be considered. We use the Goddard Institute for Space Studies (GISS) General Circulation Model (GCM) with the GISS Tropospheric Chemistry Model to study the response of the methane mixing ratio to source changes during the Holocene and also to a changing chemical sink during glacial‐interglacial transitions. We combine model results with ice core data to demonstrate a method that provides constraints on changes in northern and tropical methane sources. Results show that within the Holocene, changes in the atmospheric methane mixing ratio and latitudinal gradient are not linear with respect to changing methane emissions. Tropical and northern emissions varied from preindustrial levels by as much as 38% and 15%, respectively, within the Holocene. At glacial‐interglacial transitions the methane mixing ratio is sensitive to changes in both VOC and tropical methane emissions and the sensitivity also depends strongly on the assumed SST shift. Our findings suggest that changes in the ice core methane record are likely the result of changes in both the source and the sink. Changes in the sink become especially important when changes in methane mixing ratio and/or climate are large.
Short Paper: Devonian and later movements on the Great Glen fault system, Scotland

On the Scottish mainland the Great Glen fault (GGF) displaces the Emsian to Frasnian Orcadian Old Red Sandstone (ORS) by only 25–29 km dextrally but net post–ORS dextral offsets in Shetland are much larger (120 km total). Most of the displacement (15–20 km) Permian initiation of the Inner Moray Firth Basin. It probably occurred between Frasnian cessation of Orcadian extension and accompanied transpressional inversion of the Orcadian Basin in the mid-late Carboniferous and/or possibly the late Devonian. Devono-Carboniferous transtension may also have occurred. The earlier history of the GGF includes late Caledonian sinistral motion which must have ceased by the late Emsian.
Importance et évolution des épidémies de la tordeuse des bourgeons de l’épinette dans l’est du Canada : l’apport de la dendrochronologie

The compilation of published spruce bud- worm outbreaks chronology established using host trees' ring width was used to study the spatial and temporal evolution of outbreaks that occurred during the 20th century in Eastern North America and particularly in nordic regions. The study includes 19 chronologies and 1257 sampled trees. Data are numerous for particular regions of Quebec but are scarce in other regions like eastern and central Ontario. A remarkable synchronism of the minimum radial growth associated to defoliation was observed between the different regions for the three outbreaks registered during the 20th century. The minimum radial growth was observed in the majority of the regions around 1914 for the first 20th century outbreak, between 1948 and 1952 for the second and between 1977 and 1979 for the third. The analysis of existing chronologies did not suggest an expansion of outbreaks from meridional region to nordic regions with less fir content. Chronologies from southern Quebec were synchronous with those of the Laurentide reserve and of the north of Saguenay - Lac Saint-Jean for the three 20th century outbreaks, up to the 50th parallel where fir populations are marginal. There was a small delay to the east for the first outbreak, in Bas-Saint-Lau- rent and Gaspesie. These results from dendrochronological analysis support the hypothesis following which the spruce bud- worm population dynamics in the nordic bo- real forest of the black spruce domain would not be based on an overflow of meridional populations during severe outbreaks but would rather results from a relatively synchronous increase of endemic populations.
Observed Dependence of Outgoing Longwave Radiation on Sea Surface Temperature and Moisture.

Abstract The authors have empirically examined the dependence of the outgoing longwave radiation (OLR) on sea surface temperature (Ts), precipitable water (W), and height-mean relative humidity (RH¯). The OLR is obtained from 4 yr of data from the Earth Radiation Budget Experiment (ERBE), while Ts, W, and RH¯ are obtained from objective analyses of rawinsonde and ship data. It is found that in the midlatitudes, the surface temperature explains over 80% of the variability in the clear-sky OLR (Fcs) and almost half of the variability in the total OLR (Ftot). It fails badly in the tropics and subtropics, however, where (Ts explains only about 20% of the variability in (Fcs, and is largely decoupled from Ftot. The two-dimensional contour plot of the OLR binned with respect to Ts and RH¯ is marked by distinct changes in the gradient that are consistent with inferences from earlier investigations. For low values of Ts (<10°C), the OLR depends mainly on Ts. For values of Ts above 10°C, the OLR depends increasing.
Contaminant Migration in Saturated Unconsolidated Geologic Deposits

This paper presents a brief review of the theory of solute migration through porous, nonindurated geologic deposits and examines the laboratory and field evidence upon which transport concepts are currently based. Existing predictive models are considered in relation to the recognized transport processes, including molecular diffusion, mechanical dispersion, and some types of chemical interactions.
Relationship between field‐aligned currents, diffuse auroral precipitation and the westward electrojet in the early morning sector

On the basis of Chatanika radar data and simultaneous Triad satellite data, the relationships between field-aligned currents, diffuse aurora, electric fields, and currents in the early morning sector are examined. The diffuse aurora is coincident with the upward region 2 field-aligned current. Within the upward region 2 field-aligned current, small-scale current structures are often present. These structures seem to coincide with small-scale electron density enhancements in the E region, which are probably produced by energetic electron precipitation. The westward electrojet extends across the region 2/region 1 boundary in the morning sector. The southward electric field is large at and poleward of this boundary. It is most probable that the region 2 field-aligned currents are closed by southward Pedersen currents within the ionosphere.
Rhythmic Linear Sand Bodies Caused by Tidal Currents

A study was made of bathymetric charts of those coast lines characterized by large vertical tidal ranges (greater than 10 feet). In these areas tidal currents are strong (1-5 knots) and may significantly affect sedimentation. Two characteristic types of sand accumulation were found which appear to be formed by these tidal currents. Both exhibit wave-like profiles, and are of a scale significant to oil exploration. The first type is here called "tidal current ridges. " These are rhythmic series of ridges oriented parallel with tidal currents. They are 25-100 feet high, 5-40 miles long, and spaced 1-6 miles apart. Most are composed of sand, but some may be mud or silt. Their spacing is proportional to the depth of water. Their origin appears to be related to the similar problem of the hydraulic geometry of stream channels. Although best developed in the Bay of Korea and the Gulf of Cambay, these ridges appear to be present wherever tidal current velocities range between 1 and 5 knots and a supply of sediment is available. The second type is sand waves. These are large ripple marks oriented perpendicular to the current direction. Recent evidence by European oceanographers has indicated that, whereas in rivers these waves are fairly small-scale features, in the open ocean they commonly have heights exceeding 25 feet. Cartwright and Stride have shown a wide distribution of sand waves of this size, particularly in the North Sea. Their relation to tidal current ridges is not known, although they appear to occur in the same environment. Since tidal currents are now significant in shallow ocean areas, their effect should be visible in a large percentage of the shallow-water deposits of the geologic past. In particular it is suggested that some of the lenticular sands of the Chester Series of Illinois, of the Cardium Formation of Canada, and of the Clinton sands of Ohio show tidal current effects. The rhythmic pattern of tidal current ridges and sand waves should be considered in the study of the distribution of these and other shoestring sands.
Comparison of volcanic features of Elysium /Mars/ and Tibesti /Earth/

The Elysium volcanic province on Mars and the Tibesti volcanic province in Chad, Africa, were studied using Mariner 9, Landsat and Apollo photography. Elysium Mons on Mars and Emi Koussi on Earth show remarkable similarities in summit caldera and flank morphologies. Each has a large central caldera —12 km in diameter and from 500 to 1,000 m deep; both calderas contain numerous craters and large, irregular pits. Channel-like features which head at the calderas and taper downslope show evidence of collapse and possible lava erosion. Elysium Mons rises some 14 ± 1.5 km above its base, and the summit is about 20 km above the 6.1-mbar mean martian pressure surface. Crater size/frequency analysis indicates most of the craters are of endogenic origin. The subdued, hummocky terrain on the flanks are distinctly different from the slopes of the younger Tharsis Ridge volcanoes, showing little if any sign of recent material flow. The lack of aqueous erosional forms on Elysium Mons argues strongly against recent (∼ 10 5 to 10 6 yr) pluvial episodes. The forms and associations of features throughout the Elysium region suggest that central volcanism started earlier in Elysium than in Tharsis and that the source of the Elysium volcanics has been chemically evolved, with evidence of silicic magma. Finally, the data are consistent with the view that the martian crust has been stable and essentially motionless for an extended period of martian geologic time.
Fire Behaviour Modelling in Tasmanian Buttongrass Moorlands I. Fuel Characteristics

As part of a program to develop fire management strategies for Tasmanian buttongrass moorlands fuel characteristics were sampled from a wide range of sites in western and southwestern Tasmania. Equations were developed to predict the total fuel loading and the dead fuel loading. These variables are shown in a subsequent paper to be correlated with fire behaviour. The best predictors of fuel loading were found to be geology, vegetation age (i.e. time since the last fire) and vegetation cover. Vegetation cover is difficult to assess consistently. It is shown that reasonable predictions can be made using age and geology alone. The dead fuel loading of a given age was found to be strongly related to the total fuel loading, independent of geology. Statistical techniques used to develop fuel models are discussed. Other fuel characteristics that could be used as inputs for the Rothermel fire behaviour model are also presented.
Spectral reflectance of sea foam in the visible and near-infrared: In situ measurements and remote sensing implications

The spectral reflectance of sea foam was measured at the Scripps Institution of Oceanography Pier, La Jolla, California, by viewing the sea surface radiometrically in a region of breaking waves. Foam reflectance was found to decrease substantially with wavelength in the near-infrared, contrary to the findings of previous studies, theoretical as well as experimental. Values in the visible (0.44 μm) were reduced by typically 40% at 0.85 μm, 50% at 1.02 μm, and 85% at 1.65 μm. The spectral effect was explained by the nature of the foam, which is composed of large bubbles of air separated by a thin layer of water (foam stricto sensu) and of bubbles of air injected in the underlayer. The presence of bubbles in the underlayer enhances water absorption and thus reduces reflectance in the near-infrared. For ocean color remote sensing, affected by the presence of foam and aerosols, the consequences of neglecting the spectral dependence of foam are dramatic. With only a small amount of foam, in the presence of aerosols or not and thus irrespective of aerosol type, the errors in the retrieved water reflectance at 0.44 μm are above 0.01, which does not meet the accuracy goal of 0.001 for biological applications. Since under normal conditions the effect of foam may have the same magnitude as the effect of aerosols, atmospheric corrections will be inaccurate (and useless) in many cases, even taking into account the spectral dependence of the foam reflectance. Space observations potentially contaminated by an effective foam reflectance (product of reflectance and fractional coverage) above 0.001, i.e., corresponding to wind speeds above 8 m s−1, should be eliminated systematically. Utilization of near-infrared wavelengths above 0.9 μm for atmospheric corrections of ocean color, possible with the moderate-resolution imaging spectrometer (MODIS), would aggravate the problem. The measurements also indicated that foam significantly affects the retrieval of aerosol turbidity at 0.85 and 1.02 μm for wind speeds above 10 m s−1 but impacts minimally turbidity estimates at 1.65 μm. Over the oceans the spectral range above 1 μm is definitely recommended for remote sensing of tropospheric aerosol load and type from space.
Thermal Structure of the Anadarko Basin

The Anadarko basin of Oklahoma is a two-stage Paleozoic cratonic basin with as much as 12 km (7.5 mi) or more of sedimentary fill. We present a present-day thermal model of the basin based on lithologic analysis at 3-m (10-ft) intervals in 63 wells, heat flow measurements at seven sites, and in-situ thermal conductivity calibration of the sediment section at two sites. We do not use BHT (bottom-hole temperature) information in the process, but we do, at the end of the process, compare the independently predicted temperatures to BHT information. The in-situ calibration of thermal conductivity was accomplished using detailed temperature logs and represents a new practical application for evaluating basin thermal characteristics. Shale exerts the most control on the temperature distribution because it is the most abundant lithology and has the lowest thermal conductivity. Shale comprises 47% by volume of rock in the basin and represents 75% of total thermal resistance, directly related to temperature gradient; therefore, shale dominates the thermal structure of the basin. Thus, the problems in sampling and in characterizing the in-situ thermal conductivity of shale from laboratory measurements represent a major limitation in basin thermal analysis; we use the in-situ calibration approach as a way to address the difficulty. The temperatures calculated do not mimic the structure of the sediments; i.e., the hottest area on a given age horizon in the lower Paleozoic is not in the most deeply buried part of the Anadarko basin. The combination of decreasing heat flow toward the Wichita Mountains and the facies changes in the Pennsylvanian units from marine shale (low thermal conductivity) in the basin to the granite wash (high thermal conductivity) toward the uplift results in the highest temperatures being displaced about 50 km (31 mi) northward into the basin. The pattern of vitrinite reflectance in the Woodford Shale is virtually identical to the present-day reconstructed temperature pattern; therefore, we conclude that the thermal pattern is and has been dominated by conductive heat transport.
Coordination of Sr and Mg in calcite and aragonite

Abstract Strontium and Mg in calcite and aragonite are widely used as proxies of temperature in palaeo-environmental reconstructions. We use X-ray absorption fine structure (XAFS) to examine Sr and Mg substitution in calcite and aragonite. We have measured the K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of Mg and Sr-bearing calcite and aragonite, plus the carbonates: strontianite, hydromagnesite, magnesite, dolomite and a suite of calcites with differing amounts of Mg. The Sr substitutes ideally for Ca in aragonite but causes a small (2%) dilation of the site. Strontium substitutes for octahedral Ca in calcite but with a 6.5% dilation and distortion. Magnesium in the calcites studied provides a variable XANES indicating that the Mg structural state in calcite is variable. Refinement of EXAFS gives Mg-O bond distances of ~2.12 Å, which are much smaller than the Ca-O bond distance of 2.35 Å but consistent with published amounts of relaxation of the calcite structure. The XANES and EXAFS are consistent with a model whereby some calcites contain nanodomains, e.g. of dolomite and/or huntite structures. The variability in the XANES can be explained by domains of different types and/or sizes. Substitution of Mg into aragonite has 9-fold coordination but relatively short bond distances (2.08 Å) demonstrating either: (1) substantial distortion of the site; or (2) that Mg is accommodated in nanodomains of an unknown phase. Variability in the Mg structural state in calcite may be linked to the variety of temperature dependences observed, e.g. in foraminiferal calcite.
Susceptibility of Eastern Oyster Early Life Stages to Road Surface Polycyclic Aromatic Hydrocarbons(PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are a class of chemical compounds that are mostly anthropogenic in nature, and they can become persistent organic contaminants in aquatic ecosystems. Runoff from impervious surfaces is one of the many ways contaminants enter the aquatic realm. Three different PAH concentrations were used to investigate the effects on oyster-egg fertilization, embryonic transformation to the D-shell veliger larva, and larvae settlement onto hard substrate. The three different concentrations of PAHs ranged from one that is environmentally relevant to the concentrations found in runoff from road surfaces, another that was tenfold more concentrated, and finally one that was one hundred times more concentrated. The extremely concentrated solution had negative effects on fertilization success after one hour of exposure, while the lesser concentrations showed significant deleterious effects after two hours of exposure. All of the three PAH solutions caused significant numbers of abnormalities in the embryonic transformation of embryos to D-stage larvae. Finally, the two more concentrated PAH solutions significantly inhibited the oyster larvae in successfully setting on the hard substrate. This study's results provide evidence that PAHs entering an aquatic ecosystem from runoff from road surfaces have the potential to inhibit oyster reproduction by negatively impacting three critical processes in the early life cycle of the Eastern oyster.
Replacement Processes in the Earth's Crust

A fundamental question in metamorphism is: What is the mechanism that converts one mineral assemblage into another in response to a change in the physical and/or chemical environment? The fact that aqueous fluids must be involved in such large-scale re-equilibration has been demonstrated by petrological, mineralogical, micro-structural and isotopic data. Fluid–mineral reactions take place by dissolution–precipitation processes, but converting one rock into another requires pervasive transport of reactive fluid through the entire rock. The generation of reaction-induced porosity and the spatial and temporal coupling of dissolution and precipitation can account for fluid and element transport through rocks and the replacement of one mineral assemblage by another.