Miracle-dz/UniFAR-FTUs huggingface dataset:
Glacial‐interglacial differences in circulation and carbon cycling within the upper western North Atlantic

We investigated glacial-interglacial changes in the circulation and carbon cycling in the western North Atlantic subtropical gyre using hydrographic data and downcore records of the stable isotopic compositions of individual shells of Bahamian benthic foraminifera. Potential temperature-salinity-depth relations show that modern thermocline (∼200–1000 m) and deep (∼1000–2000 m) waters in the Providence Channels, Bahamas, originate in the Sargasso Sea and are typical of the subtropical gyre. Gradients in the stable isotopic compositions of late Holocene Planulina and Cibicidoides species from the bank margins (∼400 to 1500 m depth) reflect temperature, nutrient, and isotopic gradients of modern subtropical gyre waters. The difference between the δ18O of glacial maximum and late Holocene foraminifera is ∼2.1‰ for the upper 900 m of the water column and ∼1.6‰ for deeper waters, indicating that these waters were ∼4°C and ∼2°C cooler, respectively, during glacial time. The glacial temperature gradient (dT/dz) was similar to today, while the base of the thermocline was ∼100 m shallower. These results differ significantly from our earlier results from multiple shell δ18O analyses, which implied upper thermocline waters were only ∼1°C cooler and dT/dz was greater during the glacial maximum. The difference occurs because bioturbation adversely affects multiple shell analyses of glacial-aged samples from shallow water depths. At all depths above 1500 m, foraminiferal δ13C are greater during the glacial maximum than the late Holocene by at least 0.1 to 0.2‰ (as much as 0.6‰ in the lower thermocline), indicating that nutrient concentrations throughout the thermocline were reduced and there was no oxygen minimum zone during the glacial maximum. This suggests greater, more uniform ventilation of the thermocline. Results of single and multiple shell δ13C analyses of glacial age foraminifera compare favorably because samples most affected by mixing correspond to water depths where the glacial-interglacial change of δ13C was small. Cooler upper ocean waters during the glacial maximum reflect cooler temperatures at the ocean surface where isopycnal surfaces outcrop, including large areas of the subtropical ocean. A shallower thermocline base is consistent with southward migration of the northern edge of the subtropical gyre or increased mode water production. Enhanced thermocline ventilation is consistent with more vigorous winds and all isopycnal surfaces outcropping in the area of Ekman downwelling.
Pohlsepia Mazonensis, An Early ‘Octopus’ From The Carboniferous Of Illinois, USA

Pohlsepia mazonensis gen. et sp. nov. from the Mazon Creek Konservat Lagersta¨tte (Carboniferous) of Illinois is an exceptionally preserved soft‐bodied fossil coleoid, with well‐defined body and arms. Lacking an internal shell and possessing eight subequal and two modified arms, Pohlsepia can be compared with both the living cirrate octopods and the decabrachian sepiardarids, both of which lack a well‐developed internal skeleton. Given its sac‐like body, lack of a well‐defined head and presence of fins, Pohlsepia can be safely compared with modern cirrate octopods. It is the oldest known completely soft‐bodied coleoid and as such has great significance with respect to the phylogeny of the group, given that both the octobrachian and decabrachian clades have previously been thought to have evolved in the Jurassic. Key words: Coleoidea, Octobrachia, Konservat Lagersta¨tte, Mazon Creek, Carboniferous.
Numerical simulation of the light field in the hydrologic system using in situ inherent optical properties and matrix-operator method

A radiative transfer code to calculate the light field in the stratified hydrologic system is described and validated. The matrix-operator method is used. Chlorophyll-a and CDOM fluorescence and Raman scattering has also been incorporated into the code. Special emphasis is put on the treatment of phase function characterized by a sharp peak using δ-fit method. The code is validated by a model intercomparison for selected radiative transfer problems in the hydrologic system. Several profile data sets of inherent optical properties is obtained by using instruments of AC-s, Hydroscat-6 and others. These data sets were made in different hydrologic systems as Yangtze Estuary, and the East China sea. We use the IOPs measured in situ as input of radiative transfer code to simulate the light field in the hydrologic system. The preliminary result is presented in this paper.
Thermal conductivity measurements of particulate materials 2. Results

A line-heat source apparatus was assembled for the purpose of measuring thermal conductivities of particulate samples under low pressures of a carbon dioxide atmosphere. The primary result of this project is the compilation of the first comprehensive suite of measurements of the dependence of thermal conductivity on particle size. The thermal conductivity increases with increasing particle size and atmospheric pressure. In particular, over the range of Martian atmospheric pressures, from 1 to 7 torr, the thermal conductivity was found to be empirically related to approximately the square root of the particle diameter and the square of the cubed root of the atmospheric pressure. At the average pressure of the Martian surface (6 torr) the thermal conductivity varies from 0.011 W/m K, for particles less than 11 μm in diameter, to 0.11 W/m K, for particles 900 μm in diameter. These results differ significantly from the particle size dependence estimated for Mars from previous measurements, except for 200-μm particles, whose thermal conductivity is 0.053 W/m K. The thermal conductivities of larger particles are lower than the previous estimate, by 40% at 900 μm, and the thermal conductivities of smaller particles are higher than the previous estimate, by 60% at 11 μm. These newer estimates agree with other lines of evidence from Martian atmospheric and surficial processes and lead to improved particle size estimates for most of the planet's surface.
Modelling glacier response to measured mass-balance forcing

Abstract Measurements of summer and winter mass balances have been carried out over the past 53 years on Storglaciären, northern Sweden. Repeated surveys of the glacier have resulted in several maps of surface topography as well as a map of the bed topography A new time-dependent ice flow model allows us to compare the observed surface evolution of the glacier with that computed by the model using measured mass-balance maps as input. The computed volume change compares well with the measured change: the model replicates the distribution of surface elevation to within ±10 m over 30 years of integration. On the model side, these deviations can be attributed to the low-resolution discretization of the model domain as well as to the limited accuracy of the ice rheology and omitted basal sliding. On the other hand, the uncertainties of the topography and mass-balance maps match the model uncertainties. In this sense, the experiments are a validation of both model and observations.
High‐resolution interpretative geomorphological mapping of river valley environments using airborne LiDAR data

The availability of airborne LiDAR data provides a new opportunity to overcome some of the problems associated with traditional, field‐based, geomorphological mapping such as restrictions on access and constraints of time or cost. The combination of airborne LiDAR data and GIS technology facilitates the rapid production of geomorphological maps of floodplain environments; however, unfiltered LiDAR data, which include vegetation and buildings, are currently more suitable for geomorphological mapping than data that have been filtered to remove these features. Classification of LiDAR data according to elevation in a GIS enables the user to identify and delineate geomorphological features in a manner similar to field mapping, but it is necessary to use a range of classification intervals in order to map the various types of feature that occur within a single reach. Comparison of a LiDAR‐derived geomorphological map with an independently produced field geomorphological map showed a high degree of similarity between the results of the two methods, although ground‐truthing is essential in cases where a high degree of accuracy is required. Ground‐truthing of a LiDAR‐derived geomorphological map showed that around 80% of features mapped using both methods were identified from the LiDAR data, suggesting that the method is suitable for applications such as production of base maps for use in field mapping and selection of sites for detailed investigation. Copyright © 2007 John Wiley & Sons, Ltd.
Classification of bursting patterns: A tale of two ducks

Bursting is one of the fundamental rhythms that excitable cells can generate either in response to incoming stimuli or intrinsically. It has been a topic of intense research in computational biology for several decades. The classification of bursting oscillations in excitable systems has been the subject of active research since the early 1980s and is still ongoing. As a by-product, it establishes analytical and numerical foundations for studying complex temporal behaviors in multiple timescale models of cellular activity. In this review, we first present the seminal works of Rinzel and Izhikevich in classifying bursting patterns of excitable systems. We recall a complementary mathematical classification approach by Bertram and colleagues, and then by Golubitsky and colleagues, which, together with the Rinzel-Izhikevich proposals, provide the state-of-the-art foundations to these classifications. Beyond classical approaches, we review a recent bursting example that falls outside the previous classification systems. Generalizing this example leads us to propose an extended classification, which requires the analysis of both fast and slow subsystems of an underlying slow-fast model and allows the dissection of a larger class of bursters. Namely, we provide a general framework for bursting systems with both subthreshold and superthreshold oscillations. A new class of bursters with at least 2 slow variables is then added, which we denote folded-node bursters, to convey the idea that the bursts are initiated or annihilated via a folded-node singularity. Key to this mechanism are so-called canard or duck orbits, organizing the underpinning excitability structure. We describe the 2 main families of folded-node bursters, depending upon the phase (active/spiking or silent/nonspiking) of the bursting cycle during which folded-node dynamics occurs. We classify both families and give examples of minimal systems displaying these novel bursting patterns. Finally, we provide a biophysical example by reinterpreting a generic conductance-based episodic burster as a folded-node burster, showing that the associated framework can explain its subthreshold oscillations over a larger parameter region than the fast subsystem approach.
Elastic wave stimulation of oil reservoirs: Promising EOR technology?

Roughly 60% of oil resources in the world remains unproduced, partially due to limitations in existing enhanced recovery methods. This translates to approximately half a billion tons of oil left behind annually. Anecdotal production data, as well as historic field and laboratory experiments, have shown that low-amplitude seismic waves in the frequency range of roughly 1–500 Hz can enhance oil mobility and total recovery in mature reservoirs. It is estimated that, to date, various types of seismic and acoustic oilfield stimulation activities have produced an additional 11 million tons of oil in the Former Soviet Union alone. Unfortunately, field tests with different seismic sources have often yielded mixed or inconclusive results. In some cases seismic stimulation increased production rates by 50% or more, but in other cases production was unchanged or actually declined. So far, laboratory and field experiments have not been sufficiently comprehensive to define the physical conditions under which stress-wave stimulation is most effective. An exhaustive review of observations and research on this subject from the 1950s up through 1992 was published by Beresnev and Johnson (1994). The paper summarizes the important early research, including a large body of work published only in Russian. The major conclusion of the Beresnev and Johnson review was that the seismic stimulation method “has produced promising results; however, further testing and understanding of the mechanisms are necessary. ” This statement has motivated numerous sponsored research projects and industry evaluation programs over the last 10 years, particularly in the United States. Efforts in Russia have also been greatly expanded. Field tests are yielding more promising results as experimental controls and measurements are improved, but questions remain about how to predict optimum stimulation parameters for a particular reservoir, and what the statistical significance is of production changes observed during stimulation treatments. Laboratory experiments continue to …
Infrasound associated with the 2002 Denali fault earthquake, Alaska

Infrasonic waves associated with the November 3, 2002, magnitude 7.9 earthquake in Alaska were detected by the microphone array (I53US) in Fairbanks, Alaska. The epicenter of the earthquake lay some 150 km south of the Fairbanks array. Both seismic and acoustic signals were recorded successively by the microphone array. The fault rupture of the earthquake moved east‐southeast along the Denali‐Totschunda system fault for approximately 294 km. The northern side of the fault moved to the east and vertically upward relative to the southern side. Displacements up to 8.8 meters were measured at various points along the fault [ Eberhart‐Phillps et al., 2003 ]. The seismic P‐wave signal arrived at the array approximately 27 seconds after initiation of the rupture with a trace velocity of 5 km/sec. This was followed, some 12 minutes later, by an infrasonic wavetrain that had an average trace velocity of 0.34 km/sec and lasted about ten minutes. The azimuth of arrival of the infrasonic waves steadily moved eastward throughout the wave train apparently following the rupture's leading edge along the fault. The largest infrasonic signals, reaching over 12 Pa, came from the azimuth of the regions of largest ground motion along the fault. The source of the infrasound is taken to be the sudden local motion of the mountains in the Alaska Range along the Denali fault as they responded to the eastward‐propagating fault rupture.
Q structure of the Basin and Range from surface waves

Regionalized Rayleigh and Love wave attenuation coefficients have been measured across the Basin and Range province of western United States in the frequency range 0.02-0.2 Hz. The measurements were made by using the methods of Tsai and Aki (1969) and Yacoub and Mitchell (1977) adapted to work on any number of events simultaneously. Rayleigh wave Q values at low frequency approach values near 40, which are significantly lower than previous measurements in the western United States. Love wave Q values, on the other hand, are quite high at low frequencies. The authors suggest that interference between fundamental and higher modes may explain the Love wave observations. The Rayleigh and Love wave attenuation measurements have been inverted simultaneously for shear-wave attenuation as a function of depth. A frequency-independent Q model is consistent with both Rayleigh wave and short-period Love wave attenuation data. The shear-wave Q (Q/sub .beta./) model is characterized by low Q/sub . beta. / in the lower crust (Q/sub .beta. approx. 100) and Q/sub . beta. / decreasing in the upper mantle with lowest values (Q.beta. approx. 30) beneath 60 km depth. Forward modeling shows that a high-Q lower crust or upper mantle lid is inconsistent with the data. Our interpretation of thesemore » results is that the lithosphere is poorly developed beneath the Basin and Range and that the partially molten asthenosphere may reach very shallow depths, possibly to the base of the crust. This interpretation of the Q model in conjunction with a number of geological and geophysical evidence suggests that attenuation mechanisms involving partial melt predominate in the lower crust and upper mantle of the Basin and Range. « less
Diagenetic alteration of smectite in argillaceous sediments of the Rhinegraben (SW Germany)

Clay minerals of about 600 samples from drill cores in the Tertiary shales of the Rhinegraben, were analysed by X-ray diffraction methods. It was found that the abundance of smectite decreases with increasing amounts of mixed layer clays and illites, suggesting a diagenetic alteration of smectite with increasing temperatures of the sediments as was also observed in other sedimentary basins. As for the relation between smectite alteration and temperatures as measured in sample depths, in the marine Graue Schichtenfolge (Middle Oligocene) when temperatures reach 70°C and over, smectite no longer is to be found. In the limnic Bunte Niederroderner Schichten (Upper Oligocene) the maximum temperature of smectite occurrence is about 80°C. These temperatures also fit the results of former field studies of the thermal stability of smectite. In the brackish to limnic Obere and Untere Hydrobienschichten (Lower Miocene) however, smectite seems to have disappeared already at a temperature of over 30°C. Although the smectite distribution in the latter formations may depend partly on its inhomogenous deposition there is also evidence for the diagenetic alteration of smectite in these formations. The rapid disappearance of smectite in these formations was possibly caused by a greater availability of potassium ions since high permeability of these strata provide extraordinarily good mobility of the pore solutions. In the older Lymnaenmergel formation (Upper Eocene) a more advanced stage of smectite alteration is found as compared to the other formations at corresponding temperatures. This is considered to be the consequence of the longer duration of diagenesis and the rock salt inclusions of this saline formation which might have enriched the pore solutions with potassium ions.
Paleoecology of Suspension-Feeding Echinoderm Assemblages from the Upper Ordovician (Katian, Shermanian) Walcott-Rust Quarry of New York

Abstract The Walcott-Rust Quarry echinoderm fauna lived at the base of a carbonate ramp in moderately deep water (Benthic Assemblage 5 of Boucot and others) below wave base for all or most storms but within the photic zone. The inhabitants of the soft substrate were buried rapidly by distal carbonate turbidity currents or mudflows. Because of the episodic sedimentation, the organisms were opportunistic. The suspension-feeding echinoderms include nine crinoids, a rhombiferan, and a paracrinoid. They occur with a variety of filter-feeding bryozoan colonies, a few brachiopods, and numerous trilobites. Most suspension-feeding echinoderms were attached by small holdfasts to hard shelly substrates. Some of these substrates lay on the seafloor, whereas others may have been elevated when the larvae settled. Other types of holdfasts are distal stems that are tightly and permanently coiled around crinoid stems, open distal stem coils that lay on the substrate or were wrapped around soft objects, and recumbent stems running along the seafloor. The echinoderms occupied levels from the seafloor to almost a meter above it, whereas the bryozoans and brachiopods ranged from the seabed to a maximum height of about 10 cm. The sizes of the echinoderm food grooves and comparisons with their modern analogues along with filtration theory indicate that they ate food particles that were mostly larger than those taken by bryozoans. In general, the different taxa of suspension-feeding echinoderms living at the same elevation above the seafloor collected food particles of different maximum sizes and different mean sizes; however, they overlapped greatly with respect to smaller food items. The various crinoid species were able to feed at different ranges of ambient current velocities, which also tended to separate them ecologically. Crinoids having narrow food grooves were restricted to feeding on small food particles but they caught food items over a wide range of current velocities; the converse is also true, which suggests an evolutionary or behavioral tradeoff. As in most Ordovician crinoid communities, predation was comparatively low. Regenerated arms in crinoids reflect predation on about 1.8% of the individuals in the fauna and the most likely fossilized culprits are trilobites and straight nautiloids. Competition for space and attachment sites within and between species of the Walcott-Rust Quarry crinoid and rhombiferan assemblages does not seem to have been significant in regulating their ecological structure. Comparison with shallow-water crinoid assemblages of roughly the same age demonstrates that the Walcott-Rust Quarry faunas were less diverse and less complex. This could be caused by one or more of the following conditions that affected the Walcott-Rust fauna: lower average current velocities, the episodic sedimentological disturbances, higher suspended sediment content in the water, and softer substrates.
Inertial Oscillations due to a Moving Front

Abstract A solution for a concentrated line front translating at speed U is given. It is shown that the frequency is near-inertial if U≫c1, where c1 is the long internal wave speed of the first baroclinic mode. Each more has a charactristic frequency ωn associated with it. The spectra contain a near-inertial primary peak, composed of the higher modes, whose blue shift increases with depth. They also contain secondary peaks at higher internal wave frequencies if U is only slightly larger than c1. The flow field is intermittent, and involves a continuous interchange of energy between the surface layer and the stratified interior. The dominant period of this intermittency is the beating period of the first mode with a purely inertial oscillation. Short periods of apparent subinertial motion are also generated. Several features of the solution are in agreement with observations.
Evidence for a peculiar style of ground deformation inferred at Vesuvius volcano

We present results obtained via an innovative spaceborne SAR interferometry algorithm showing that the Somma‐Vesuvius volcanic complex, despite of its quiescent stage, is subject to a particular deformation process. This is characterized by a rather continuous subsidence, revealed by ERS satellite data and levelling surveys, between 1992 and 2000. These deformations are mainly localized in two zones involving the Vesuvius cone and a narrow annular area that, although not fully continuously, extends around the base of the Somma edifice. We propose an interpretation of subsidence at both sites involving joint effects of gravitational sliding and extensional tectonic stress occurring at the contact between different lithological units. Some simple elastic models show how such localized subsidence can be generated. These results shed new light on the Vesuvius dynamics and, more generally, on the link between gravitational effects of volcano loading and seismic‐deformative processes, which is a subject of intense scientific debate.