Miracle-dz/UniFAR-FTUs huggingface dataset:
Carboniferous and Lower Permian sedimentological cycles and biotic events of South China

Abstract The sedimentary successions and four fossil groups, including rugose corals, brachiopods, fusulinaceans and conodonts, from the Carboniferous and Lower Permian of South China have been studied in order to reveal the sedimentary characteristics and evolutionary pattern of main biological groups in the East Tethyan region during the Late Palaeozoic Ice Age. The Lower Carboniferous lithology of South China is diverse, ranging from basinal and shelf carbonate rocks to coal measures and continental clastics, while the Upper Carboniferous and Lower Permian are composed mostly of shallow-marine carbonates. From uppermost Devonian to Lower Carboniferous, five major regression events are recognized at the topmost Devonian, middle and upper Tournaisian boundary, Tournasian–Viséan boundary, uppermost Viséan and the Mid-Carboniferous boundary in South China, separately. The Upper Carboniferous and Lower Permian shallow-water carbonate rocks consist of remarkable, high-frequency cyclothems. Moreover, another major sea-level fall is recognized and characterized by an extensive sedimentary hiatus at the Sakmarian–Artinskian boundary throughout South China. All of the sedimentary basins of South China were formed in extensional tectonic settings during this time; thus, multiple regressive events that occurred throughout South China should be primarily induced by glacio-eustatic drawdown. In addition, two biotic events characterized by a remarkable decline in the diversity of benthic biota and a turnover in the composition of fossil assemblages occurred, respectively, at the Mid-Carboniferous and Sakmarian–Artinskian boundaries, consistent with two major regressions, and were probably caused by the glaciations in Gondwana.
Mixing Linear Polymers with Rings and Catenanes: Bulk and Interfacial Behavior

We derive and parameterize effective interaction potentials between a multitude of different types of ring polymers and linear chains, varying the bending rigidity and solvent quality for the former species. We further develop and apply a density functional treatment for mixtures of both disconnected (chain–ring) and connected (chain-polycatenane) mixtures of the same, drawing coexistence binodals and exploring the ensuing response functions as well as the interface and wetting behavior of the mixtures. We show that worsening of the solvent quality for the rings brings about a stronger propensity for macroscopic phase separation in the linear-polycatenane mixtures, which is predominantly of the demixing type between phases of similar overall particle density. We formulate a simple criterion based on the effective interactions, allowing us to determine whether any specific linear-ring mixture will undergo a demixing phase separation.
A model‐based map of ground temperatures for the permafrost regions of Canada

A functional model of the permafrost‐climate system is applied at national scale, to produce a map of near‐surface ground temperatures in the permafrost regions of Canada. The TTOP model links the temperature at the top of permafrost (TTOP) to the climate through seasonal surface transfer functions and subsurface thermal properties. The parameters in the model were compiled at national scale for Canada, although the topographic effects of the Western Cordillera were not incorporated into the analysis. The objective of the study was accomplished by implementing the TTOP model within a Geographical Information System. The TTOP map is evaluated against the published Ground Temperature Map of Canada. The published map shows ground temperatures according to a scale of temperature classes, so TTOP values were categorized into the same classes. Across the permafrost regions of Canada, 72.1% of the area is in the same class in both maps, while 27.7% differs by one temperature class. Only 0.2% of the area differs by two temperature classes. The results suggest that the TTOP model can provide a rational and functional basis for relating near‐surface permafrost temperature and climate at national and regional scales. The model could be applied to the assessment of climate change impacts on the magnitude and distribution of permafrost temperatures. Copyright © 2001 John Wiley & Sons, Ltd.
Earth's punctuated tectonic evolution: cause and effect

Abstract Peaks in the Precambrian preserved crustal record are associated with major volcanic, tectonic and climatic events. These include addition of juvenile continental crust, voluminous high-temperature volcanism, massive mantle depletion, widespread orogeny and mineralization, large apparent polar wander velocity spikes, and subsequent palaeomagnetic intensity increases. These events impinge on the glaciation record, atmospheric and ocean chemistry, and on the rise of oxygen. Here we summarize and assess a number of geodynamic models that have been proposed to explain the observed episodicity in the Precambrian record. We find that episodic behaviour from nonlinear slab-driven models best explains the observed record. Examples of such slab-driven systems include mantle avalanches or episodic subduction. In these cases, rapid descent of slabs into the mantle drives fast plate motions and convergence at the surface. This is accompanied by large-scale upwellings of deep hot mantle, which contribute to voluminous volcanism. Further modelling will determine the relative importance of each mechanism, and reinforce the fundamental contribution of the mantle to the evolution of Earth's surface systems.
Floor assemblages from burned structures at Aguateca, Guatemala: A study of classic maya households

Abstract Investigations at the fortified Maya center of Aguateca, Guatemala, have revealed an unusual case of large-scale rapid abandonment. Structures in its epicenter were burned and abruptly abandoned during an attack by enemies at the end of the Late Classic period (A.C. 600–830). The excavation of burned structures has recovered rich floor assemblages, providing excellent data sets with which to examine household organization and activities. The residents engaged in a wide variety of activities, including food storage, preparation, and consumption, as well as the work of scribes/artists. The excavated structures were probably occupied by single nuclear families or smaller groups. These co-residential groups appear to have constituted important social and economic units, which may be called households.
Lithospheric heterogeneity in the Kyrgyz Tien Shan imaged by magnetotelluric studies

A 450 km long north‐south magnetotelluric profile spanning the Tien Shan from Kazakhstan to western China reveals lateral variations in the resistivity of the mantle lithosphere to depths of 140 km. Minimum changes of one order of magnitude in this depth range result from variations in temperature or composition, or both. Higher resistivities beneath a central portion of the range where the Moho is half as deep as elsewhere in the Tien Shan indicate a strong lithospheric block. We propose that this block protects this region of thin crust from appreciable deformation and instead transmits stresses due to India‐Asia plate convergence from the southern to the northern parts of the range.
Physics of a Thick Seasonal Snowpack with Possible Implications for Snow Algae

Abstract Instrumentation to study snowpack in situ was deployed in Lassen Volcanic National Park (LVNP), California, in an area of deep seasonal snow accumulation and known snow algal bloom recurrence. Included in the instrumentation were 11 temperature sensors, evenly spaced up to 2 m above the ground, which provided (1) temperature data within the snowpack when buried, and (2) estimates of snowpack height during accumulation and ablation periods. Beginning in April, moisture sensors measured a strong increase of snowpack liquid water content to greater than 15% by volume; this high melt content is usually coincident with the start of runoff from the snowpack. Snow depth profiles showed a rapid ablation of the final 2 m of the snowpack over about 23 days beginning in late June. SNTHERM numerical modeling confirmed that solar radiation was the dominant energy term throughout the melt season. By modeling a variety of snowpack parameters, such as albedo and initial snow density, we determined that the date of snow loss is the most sensitive observable that can be used to constrain the modeled parameters. These data sets from LVNP can also be applied to knowledge of snow algae lifecycles in deep snow to help understand whether the availability of light, water, or both controls the onset of snow algae germination at the base of a thick snowpack. Data and modeling indicate that meltwater was present throughout the snowpack beginning in March and runoff is initiated in April, when the snowpack was still several meters deep. However, significant levels of light did not penetrate to the soil until June, when the snow was less than 2 m deep.
Dominant-Node Theory and Monitoring-Rescue Method for Eliminating Undesired Operating Points in the Self-Biased Reference Generators

A self-biased voltage/current reference (VCR) generator provides bias for its embedded operational amplifier simply by itself. But during the power-up process, it is prone to be trapped into an undesired operating point called Trojan state (TS-UOP) that a conventional startup circuit (CSC) is unable to handle. This paper firstly simulates the power-up process of a self-biased VCR generator and discovers the dominant node that plays the leading role in the power-up convergence. Then, a dominant-node theory is proposed to find the dominant node based on the voltage-vertex directed dependency graph (DDG) and the Weight-Flow algorithm. In order to rescue the dominant node, a Monitoring-Rescue method is proposed as a general approach to enhanced startup circuits (ESCs) to eliminate TS-UOPs. An example of ESCs is designed in a 28-nm CMOS process. The measurement results verify that the ESC successfully helps the self-biased VCR generator converge to the desired operating point (DOP) regardless of the power-up ramping time range of <inline-formula> <tex-math notation="LaTeX">$\mathrm {100~ \mu \text { s} }$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$\mathrm {100~ \text {m} \text { s} }$ </tex-math></inline-formula> and the temperature range of <inline-formula> <tex-math notation="LaTeX">$\mathrm {-45~ ^{\circ}C}$ </tex-math></inline-formula> to <inline-formula> <tex-math notation="LaTeX">$\mathrm {115~ ^{\circ}C}$ </tex-math></inline-formula>.
New Perspectives on Soil Creep

Soil exhibit viscous creep behavior, and the creep strain rate is known to change greatly with time. Various possible reasons for the changing creep rate are considered. The writers propose a mechanism for interparticle sliding that is both viscous and frictional. The mechanism is based upon rate process theory and leads to an expression for the sliding velocity of two contacting particles in terms of the ratio between the tangential and normal contact force components. This interparticle sliding mechanism was incorporated into a numerical discrete element model of a large assembly of circular particles. Numerical simulations with the assembly displayed creep behavior that is very similar to soils. The creep rate increased with greater applied stress, decreased rapidly with time, and exhibited creep rupture at large stress levels. Changes in the creep rate are shown to result from the changes in contact forces that accompanied deformation of the entire assembly. Such deformation‐dependent changes are thou.
Effects of site conditions on regeneration of African mahogany (Khaya anthotheca) in a semi‐deciduous East African tropical rainforest

Restoration of high‐value timber trees in logged tropical forests is indispensable as a conservation strategy and for the enhancement of ecosystem services. Khaya anthotheca is a mahogany tree species of major restoration importance in Uganda. However, the factors affecting the natural regeneration success of this species are poorly understood. We determined the effect of selected site conditions on the abundance of K. anthotheca regeneration in the Budongo Forest Reserve. Two hundred and four 1,000 m2 inventory plots, each nested with four 4 m2 subplots, were systematically established in logged and unlogged sites within the study area. All trees greater than or equal to 10 cm DBH and natural regeneration (<10 cm DBH) were identified and recorded in the plots and subplots, respectively. We characterized plots by the density of conspecifics, light availability, ground cover of undergrowth, litter depth, soil pH, and basal area. Regression models were used to evaluate the variables that influenced regeneration abundance and occurrence. The density of adult conspecifics and soil pH were important. Regeneration abundance and occurrence increased with increasing density of adult conspecifics and decreased with increasing soil pH. Our results highlight that in addition to seed availability, soil pH was important for successful regeneration. This is one of the first K. anthotheca‐specific studies to evaluate more than a few environmental factors influencing the density of its naturally established seedlings in tropical African forests. The abundance and distribution of adult conspecifics in the canopy and soil pH should be considered in K. anthotheca restoration plans.
Analysis of rectangular and square anchors in cohesionless soil

Abstract Horizontal anchors are widely used in civil engineering projects to resist uplift loads. A few theories are available for predicting uplift capacity of rectangular/square anchors. The theoretical methods suggested by Meyerhof and Adams and Murray and Geddes estimated the uplift capacity of rectangular/square with significant errors. An analytical method based on Kötter's equation is proposed for estimating the net uplift capacity of a horizontal rectangular/square in cohesionless soil. Application of Kötter's equation gives distribution of soil reaction on the failure surface, which is assumed to be the frustum of a trapezoid with a characteristic angle of inclination with the horizontal. A closed form solution for the uplift capacity is obtained with no requirement of any charts or tables.
Provenance and Crustal Evolution of the Northern Yangtze Block Revealed by Detrital Zircons from Neoproterozoic–Early Paleozoic Sedimentary Rocks in the Yangtze Gorges Area, South China

Detrital zircon U-Pb ages of six sedimentary rocks in the northern Yangtze Block reveal three major age groups of 740–890 Ma, 1.9–2.1 Ga, and 2.4–2.55 Ga and two minor groups of 2.6–2.7 and 2.9–3.1 Ga. Although Lu-Hf isotope analysis suggest both juvenile crustal growth and reworking of old crust for all the age populations, juvenile input occurred mainly in the Archean and Neoproterozoic time, whereas Paleoproterozoic is a period dominated by recycling of preexisting crust. The predominant Neoproterozoic detritus is mainly derived from coeval igneous rocks distributed along the western and northwestern margin of the Yangtze Block. However, most of the pre-Neoproterozoic sediments cannot be matched with exposed basement rocks within the Yangtze Block. The similar age patterns of the sedimentary rocks in this study imply only a slight variation in the source regions from the Neoproterozoic to Silurian.
An early Hettangian coral reef in southern France: Implications for the end-Triassic reef crisis

Abstract The oldest known Jurassic coral reef is exposed in the Ardèche region of southern France. This reef site, consisting of at least three reefal bodies, is of early Hettangian age and thus immediately postdates the end-Triassic mass extinction, which is well known for its catastrophic effect on reef building. Bulk carbonate carbon isotopes of the limestones below the reef are likely to record environmental perturbations subsequent to the mass extinction. The main reef is surprisingly well developed (20 m in thickness, 200 m in lateral extent) and composed of at least four genera and six species of corals—not only holdover genera from the Triassic, but also one newly evolved genus (Phacelophyllia), contributed to reef construction. Just like their latest Triassic counterparts, the reef is dominated by phaceloid corals with a considerable contribution of microbialite. The reef predates similarly well developed structures by almost ten million years. The shelf setting of the reef renders it unlikely that refuges around oceanic islands are needed to explain survival of corals across the end-Triassic mass extinction.
The Perception of and Adaptation to Climate Change among Cocoa Farm Households in Ondo State, Nigeria

The study was conducted to examine the perception of and adaptation to climate change among cocoa farmers in Ondo State, Nigeria. Also, determinants of farmers’ level of perception and adaptation to change in climatic conditions were examined. Simple random sampling technique was used to select 200 farmers but after removing cases of incomplete or non-response, the final sample size came to 160 cocoa farmers. Descriptive statistics were used to analyse the farmers’ socio-economics characteristics while Heckman’s two-step procedure was used to identify the determinants of respondents’ perception and adaptation to climate change. The results revealed that the cocoa farmers’ population was ageing and cocoa production in the study area was dominated by men. The household size ranged between 1 and 20 persons while the mean was 8 persons. The majority of the farmers solely made use of hired labour. The average farm size was 7 hectares while 83.75 percent of cocoa farmers had no access to credit. Most of the respondents perceived climate change in the study area. In order to adapt to climate change, 10 different types of adaptation strategies were used by 83.75% of the farmers while 16.25% did nothing. 7 variables (age, education, farming experience, household size, farm size, access to extension services, and distance to farm input purchasing market) significantly determined whether or not cocoa farmers perceive climate change while again another 7 independent variables (age, education, farming experience, farm size, access to extension services, access to credit and training on climate change) significantly determined whether or not they would adapt to it. The study therefore, recommends that credit should be made available to the farmers and an effective extension service system should be put in place. DOI: 10.5901/ajis.2014. v3n1p147
Velocity and temperature fluctuations in a buoyancy‐driven current off Vancouver Island

An experiment to study buoyancy driving of the poleward flowing coastal current off the west coast of Vancouver Island was carried out from June to November 1984. The experiment consisted of two hydrographic surveys and a three-dimensional instrumented array that included 51 current/temperature sensors distributed on 18 moorings. Moorings were maintained across the mouth of the Strait of Juan de Fuca (to monitor the fluctuating buoyant source/sink) and along three cross-shelf transects roughly 40, 90, and 130 km north of the mouth of the strait. To detect possible incoming propagating coastal-trapped waves (CTWs), moorings were also located ∼10 and ∼30 km south of the mouth of the strait.The main thrust of the experiment was to attempt to identify signals specifically associated with buoyant outflow from the Strait of Juan de Fuca. Four such signals were identified. (1) A seasonally varying mean poleward flow over the mid and inner shelf. (2) Velocity and temperature fluctuations associated with buoyant plumes over the shelf. The plumes, which occur at roughly monthly and bimonthly intervals, are driven by anomalously strong freshwater pulses from the strait, and the associated fluctuations in the along-isobath component of velocity accounted for about 20% (10%) of the variance during summer (fall) in the region within about 50 km of the mouth of the strait. (3) Positive temperature anomalies (∼3°C) related to the cessation of strait outflow. These anomalies, which are strongest at and south of the mouth of the strait, occur during periods of regional southwesterly winds and have a south-to-north lag consistent with poleward advection of the pre-existing (usually cold) plume water at about 30 km d−1. (4) Phase modification of the wind-driven CTW and local wind-driven velocity signals across the mouth of the strait: a south to north phase difference of about 90° is observed across the mouth of the strait at low (<0.12 cpd) frequencies during both summer and fall. Statistical analysis as well as application of a first-mode wind-driven CTW model demonstrated that the dominant variance over the Vancouver Island shelf is related primarily to the first-mode wind-driven CTW (summer, ∼55%) or local wind forcing (fall, ∼80%). This being the case, and also because of the rugged shelf topography in the area, the analysis proved insufficient to identify definitively more subtle results of plume and strait processes such as the local generation of CTWs.
NanoSIMS analysis of organic carbon from the Tissint Martian meteorite: Evidence for the past existence of subsurface organic‐bearing fluids on Mars

Two petrographic settings of carbonaceous components, mainly filling open fractures and occasionally enclosed in shock‐melt veins, were found in the recently fallen Tissint Martian meteorite. The presence in shock‐melt veins and the deuterium enrichments (δD up to +1183‰) of these components clearly indicate a pristine Martian origin. The carbonaceous components are kerogen‐like, based on micro‐Raman spectra and multielemental ratios, and were probably deposited from fluids in shock‐induced fractures in the parent rock of Tissint. After precipitation of the organic matter, the rock experienced another severe shock event, producing the melt veins that encapsulated a part of the organic matter. The C isotopic compositions of the organic matter (δ13C = −12.8 to −33.1‰) are significantly lighter than Martian atmospheric CO2 and carbonate, providing a tantalizing hint for a possible biotic process. Alternatively, the organic matter could be derived from carbonaceous chondrites, as insoluble organic matter from the latter has similar chemical and isotopic compositions. The presence of organic‐rich fluids that infiltrated rocks near the surface of Mars has significant implications for the study of Martian paleoenvironment and perhaps to search for possible ancient biological activities on Mars.
Modeling the Hydrodynamics and Salinity of El-Burullus Lake (Nile Delta, Northern Egypt)

This study investigates issues related to hydrodynamics in Lake El-Burullus and flow patterns therein. Burullus Lake is the second largest lake in the northern Egyptian coast with a total area of 410 km. It was utilized Delft3D-flow module to develop a field validated hydrodynamic model. The shallow brackish Lake is mainly affected by uncontrolled creeping of development areas and growing inflow of untreated agricultural, municipal and industrial drainage water. The developed model was used to examine a potential mitigation alternative by decreasing the pollutant loads that enter the Lake i.e. diversion of existing drains. In this fashion the creation of a new development area near-by may be feasible. In addition, the effects of hydrodynamics on pollutant dispersion either from an individual drain or all drains together. The results of this study will be the base for the water quality modeling stage. Actually, this work is the first stage of an integrated Lake management. The study concluded that the developed model efficiently simulated the hydrodynamics of the Lake which can act as an effective decision support tool for improving the environmental conditions in the surroundings.