Miracle-dz/UniFAR-FTUs huggingface dataset:
YIELDING AND FLOW OF SAND UNDER PRINCIPAL STRESS AXES ROTATION

ABSTRACT In order to investigate the influence of inherent anisotropy on the yielding and plastic flow of loose and dense sand, a series of experiments involving a wide range of principal stress axes directions were carried out on hollow cylindrical specimens of Toyoura sand using a torsional shear test apparatus. Stress paths involving cycles of stress reversal and stress axis rotation were performed in order to identify the states of stress at which plastic flow begins to take place. The test results revealed well-defined families of yield loci having identical shapes in the stress space independent of the density of sand. Experimental evidence presented here shows that the direction of the plastic strains for different stress increments is not uniquely established indicating the non-existence of a unique plastic potential. Consequently, within the framework of conventional theory of plasticity, the yielding and flow of sand can only be explained with the concept of multiple yield surfaces.
Cyclic geomagnetic changes in Mid-Cretaceous rhythmites, Italy

Magnetic secular variation is recorded as a quasi-rhythmical process of uncertain origin. Rhythmic changes recorded in the Scisti a Fucoidi in the central Apennines of Italy, pelagic sediments of Mid-Cretaceous (Late Albian) age, show strong correspondence to patterns of orbital variation. In the same strata cyclic magnetic variations are found with peaks in the same range (105, 40, 26,19 kyr). These results appear to support earlier suggestions that secular variations may be related to these astronomical patterns.
Strength of slightly serpentinized peridotites: Implications for the tectonics of oceanic lithosphere

We deformed cores of peridotite with ∼10%–15% lizardite and chrysotile serpentine to determine the influence of serpentine content on the strength and the style of deformation. The strength, the pressure dependence of strength, and the nominally nondilatant mode of brittle deformation of slightly serpentinized peridotites are comparable to those of pure serpentinites. These results indicate that deformation is accommodated primarily by serpentine, while olivine, despite being the more abundant component, remains nominally undeformed. On the basis of these data and previous work, we determine that the transition from a “strong,” dilatant dunite rheology to a “weak,” nondilatant serpentinite rheology is not a linear function of the degree of serpentinization. Instead, an abrupt transition in strength is observed at low degrees of serpentinization. The pressure of the transition from localized to distributed deformation also decreases abruptly, from >1000 MPa to 150–350 MPa. The change in rheological behavior occurs at a serpentine content of 10%–15% or less, which corresponds to published compressional seismic velocity of >7.8–7.5 km/s at a pressure of 200 MPa. The seismic velocity of the oceanic lithosphere, particularly of that formed at slow spreading ridges, can thus provide constraints on its mechanical properties at depth. Because slightly serpentinized peridotites have a rheology similar to that of pure serpentinite, significant lithospheric weakening may occur after the onset of alteration near or at the ridge axis.
Assembling the stratigraphic record: depositional patterns and time‐scales in an experimental alluvial basin

Our understanding of sedimentation in alluvial basins is best for very short and very long time‐scales (those of bedforms to bars and basinwide deposition, respectively). Between these end members, the intermediate time‐scales of stratigraphic assembly are especially hard to constrain with field data. We address these ‘mesoscale’ fluvial dynamics with data from an experimental alluvial system in a basin with a subsiding floor. Observations of experimental deposition over a range of time‐scales illustrate two important properties of alluvial systems. First, ephemeral flows are disproportionately important in basin filling. Lack of correlation between flow occupation and sedimentation indicates that channelized flows serve mainly as conduits for sediment, while most deposition occurs via short‐lived unchannelized flow events. Second, there is a characteristic time required for individual depositional events to average to basin‐scale stratal patterns. This time can be scaled in terms of the time required for a single channel‐depth of aggradation, and in this form is constant through a four‐fold variation of experimental subsidence rate.
Sources of Awareness and Perception of the Effects of Climate Change among Sesame Producers in the Southern Agricultural Zone of Nasarawa State, Nigeria

The study was conducted to determine the sources of awareness of climate change and ascertain the perception of the effects among sesame producers in the Southern Agricultural Zone of Nasarawa State, Nigeria. A multistage random sampling technique was used in selecting 180 sesame farmers that participated in the study. Descriptive statistics were used in analyzing data. Major results show that both males and females mostly (40%) between the ages of 31-40 years were involved in sesame production. The level of education was low. Increased rains, insect infestation and torrential downpours were perceived as effects of climate change. Sesame farmers’ had adapted to such changes through the use of chemicals, insect powders, early planting and early harvesting. Results also show that extension agents, radio and television were the major sources of awareness of the effects of climate change. The study concluded with the recommendation that farmers’ awareness of the devastating effects of climate change is very critical for helping them adapt to climate change and need to be urgently strengthened by extension service so as to sustain sesame production even in the event of climate change.
World-Wide Delivery of River Sediment to the Oceans

New data and new estimates from old data show that rivers with large sediment loads (annual discharges greater than about $$15 \times 10^{6}$$ tons) contribute about $$7 \times 10^{9}$$ tons of suspended sediment to the ocean yearly. Extrapolating available data for all drainage basins, the total suspended sediment delivered by all rivers to the oceans is about $$13.5 \times 10^{9}$$ tons annually; bedload and flood discharges may account for an additional $$1-2 \times 10^{9}$$ tons. About 70% of this total is derived from southern Asia and the larger islands in the Pacific and Indian Oceans, where sediment yields are much greater than for other drainage basins.
Incorporation of Soil Bulk Density in Simulating Root Distribution of Winter Wheat and Maize in Two Contrasting Soils

Root length density (RLD) in a soil profile is an important factor in determining the root uptake of water and nutrients from soil. Accurate descriptions of the RLD distribution are important in developing models to simulate the flux of water and nutrients in fields. However, the normal vertical root length distribution in a soil profile is usually disrupted because of soil heterogeneity. This study used field-measured RLD of winter wheat (Triticum aestivum L.) and maize (Zea mays L.) from two soils in the North China Plain from 2007 to 2010 to examine the effects of soil physical characteristics on the RLD distribution of the double-cropping system. The results showed that RLD distribution pattern was significantly affected by soil bulk density under sufficient water supply. The existence of a hard soil pan under the tillage layer greatly influenced the distribution curve of the RLD. Without bulk density modification, there was an apparent difference between measured and modeled RLD resulting in either overestimating or underestimating root length at certain soil depths. Introducing bulk density into an RLD simulation model significantly reduced the errors of simulated and measured RLD throughout the root zone profile.
Stress-induced redistribution of yttrium and heavy rare-earth elements (HREE) in garnet during high-grade polymetamorphism

Abstract Almandine garnet (Alm62.6Pyr11.4Sps8.4And6.5Grs4.0) exceptionally rich in Y2O3 (1.8.2.3 wt%), Sc2O3 (0.11-0.23 wt%), HREE2O3 (1.9.2.3 wt%), and Na2O (~0.3 wt%) occurs in Precambrian quartzofeldspatic granulites (T ~ 860°C) on Hisarøya, Western Gneiss Region, Norway. The granulites were partially reequilibrated to eclogite-facies (P = 14.9 ± 1.3 kbar, T = 649 ± 67°C) and amphibolite-facies assemblages during the Caledonian Orogeny. The granulite-facies garnet is reequilibrated in an outer zone, typically ~4 μm thick, where both Y2O3 and HREE2O3 concentrations decrease to 1.2 wt%, and overgrown by Caledonian garnet with Y2O3 and HREE2O3 both below 0.1 wt%. The granulitefacies cores are also reequilibrated to lower Y2O3 and HREE2O3 (both ~1.8 wt%) along deformation structures including microfaults with horsetails, en-echelon bands, and splaying features around the tip of fractures. Locally, these reequilibrated zones, typically 10.20 μm across, have shoulders with higher Y and HREE (~2.9 wt%) than in the original garnet, suggesting closed-system behavior for these elements. In addition, the garnet locally displays a complex mesh-like pattern with high and low HREE and Y bands, possibly related to strain. Two charge-balancing mechanisms account for Y and HREE incorporation: (1) the yttrium aluminum garnet (Y2Al2O6, YAG) substitution involving incorporation of Al into the tetrahedral site is dominant in the granulite-facies garnet, and (2) coupled substitution with Na into the dodecahedral site is increasingly important during high-P reequilibration. The internal closed-system reequilibration of the granulite-facies garnet may be related to stress concentrations build up in garnet during the eclogite-facies event. Local stress concentrations during propagation of fractures may be the driving force behind the redistribution of elements seen within cores of granulite-facies garnet
Global patterns of ocean transparency: Implications for the new production of the open ocean

Climatological mean fields of ocean transparency derived from Secchi depth measurements held by the National Oceanographic Data Center are presented. Clearly evident are the major coastal upwelling regions off Peru, northwest and south Africa as well as the coastally enriched areas globally. The central gyre regions in both North Atlantic and North Pacific waters are separated by a sharp discontinuity in water clarity from the more northern waters; the change in Secchi depth across this subtropical front is equivalent to a difference of ∼1 mg chlorophyll a m−3 over meridional distances of 1000 km. Sufficient data exist in the western Pacific to demonstrate that the front migrates approximately 1000 km seasonally from a northern extreme at ∼28° N in September–November, to a southern extreme at 18° N in March–May. A simple explanation for this feature, which is also clearly evident in recent satellite ocean color images of the the northern ocean basins, is offered in terms of the effective vertical ‘upwelling’ and resulting new production associated with seasonal variations in deep convective mixing.
Grain fracture in 3D numerical simulations of granular shear

We present a new method to implement realistic grain fracture in 3D numerical simulations of granular shear. We use a particle based model that includes breakable bonds between individual particles allowing the simulation of fracture of large aggregate grains during shear. Grain fracture simulations produce a comminuted granular material that is texturally comparable to natural and laboratory produced fault gouge. Our model is initially characterized by monodisperse large aggregate grains and gradually evolves toward a fractal distribution of grain sizes with accumulated strain. Comminution rate and survival of large grains is sensitive to applied normal stress. The fractal dimension of the resultant grain size distributions (2.3 ± 0.3 and 2.9 ± 0.5) agree well with observations of natural gouges and theoretical results that predict a fractal dimension of 2.58.
Direction mutation pressure of SARS-CoV-2 helps to understand the past and predict the future evolution: C>U and G>U biased mutagenesis forces the majority of amino-acid substitutions to be from CG-rich losers to U-rich gainers

Evolution is a function of mutagenesis and selection. To analyse the role of mutagenesis on the structure of the SARS-CoV-2 genome, we reconstructed the mutational spectrum, which was highly C>U and G>U biased. This bias forces the SARS-CoV-2 genome to become increasingly U-rich unless selection cancels it. We analysed the consequences of this bias on the composition of the most neutral (four-fold degenerate synonymous substitutions) and the least neutral positions (nonsynonymous substitutions). The neutral nucleotide composition is already highly saturated by U and, according to our model, it is at equilibrium, suggesting that in the future, we don’t expect any more increase in U. However, nonsynonymous changes continue slowly evolve towards equilibrium substituting CG-rich amino-acids (“losers”) with U-rich ones (“gainers”). This process is universal for all genes of SARS-CoV-2 as well as for other coronaviridae species. In line with the direction mutation pressure hypothesis, we show that viral-specific amino acid content is associated with the viral-specific mutational spectrum due to the accumulation of effectively neutral slightly deleterious variants (losers to gainers) during the molecular evolution. The tuning of a protein space by the mutational process is expected to be typical for species with relaxed purifying selection, suggesting that the purging of slightly-deleterious variants in the SARS-CoV-2 population is not very effective, probably due to the fast expansion of the viral population during the pandemic. Understanding the mutational process can help to design more robust vaccines, based on gainer-rich motifs, close to the mutation-selection equilibrium.
Climatological significance of δ18O in north Tibetan ice cores

Oxygen isotopic ratios (δ18O) of precipitation samples collected over several years at three meteorological stations on the northern Tibetan Plateau were used to conduct the first investigation of the relationship between δ18O and contemporaneous air temperatures (Ta). Inferring past temperatures from δ18O measured in recently acquired Tibetan ice cores necessitates establishing whether a δ18O-Ta relationship exists. For each station a strong temporal relationship is found between δ18O and Ta, particularly for monthly averages which remove synoptic-scale influences such as changes in condensation level, condensation temperature, and moisture sources. Moisture source is identified as a major factor in the spatial distribution of δ18O, but air temperature determines the temporal fluctuations of δ18O at individual sites on the northern Tibetan Plateau. The 30-year records of annually averaged δ18O from three different ice coring sites are not correlated significantly with contemporaneous air temperature records from their closest meteorological station (150 to 200 km). However, since 1960 the three air temperature records reveal a modest warming trend, while the three contemporaneous δ18O records show a modest 18O enrichment.
A quantitative study of ionospheric density gradients at midlatitudes

The subauroral ionosphere, at the magnetic latitudes which characterize the northeastern United States, is subject to severe F region ionospheric density structuring due to the space weather effects of magnetospheric disturbance electric fields. Communications and navigation systems relying on transionospheric propagation must be able to compensate for the effects of the sharp changes (>10X) in total electron content (TEC) associated with the ionospheric trough and storm time disturbance effects at midlatitudes. The Millstone Hill incoherent scatter radar database has been used to investigate the spatial extent and temporal evolution of TEC and density altitude/latitude structure at middle and subauroral latitudes as a function of solar cycle, local time, and level of geomagnetic activity. More than 11,000 radar elevation scans covering >20° of latitude and altitudes between 150 and 750 km have been used to identify the characteristics of the density gradient near the equatorward edge of the ionospheric trough in a variety of circumstances spanning 20 years and two solar cycles. Pronounced density gradients can be identified in ∼35% of the Millstone Hill scans, and we present a statistical characterization of average magnitude and location for these steepest TEC gradients. In some cases (especially near noon) the equatorward edge of the trough lies poleward of our observational field of view, and gradients associated with phenomena other than the trough contribute to our statistics. On most days the trough appears in the radar scans between 1600 and 2000 magnetic local time (MLT). Larger TEC gradients occur at solar maximum and when the background TEC is higher. The steepest gradients occur in an environment of high TEC (at solar maximum and adjacent to regions of storm-enhanced density (SED)), when the processes which generate the trough are strongest (high Kp). High gradient values occur in the sunlit sector, with maximum values of TEC gradient (∼10 TEC/deg latitude, with 1 TEC unit = 10 16 el m -2 ) found in the postnoon ionosphere. Mean solar maximum TEC gradient at 1600 MLT is 3-4 TEC/deg for Kp 100 over New England and TEC gradients of ∼50 TEC/deg.
Pliocene aridity and Neogene landscape evolution recorded by a fluvial sediment system (Campaspe Formation) in northeast Queensland

Campaspe Formation, a surficial, fluviatile, sand-dominated unit, is extensively developed in the Charters Towers region of north Queensland where it covers an area of 11 000 km2, overlying Paleozoic basement and erosional remnants of Paleogene Southern Cross Formation. In the northern part of its distribution, it is interlayered with, and overlain by, flows of Nulla Basalt. It is dated as mid-Pliocene, based on the 3.48 Ma age of the Myrrilumbing Flow interlayered with its upper part, an antiquity consistent with thin ferricrete locally developed at its surface. The formation defines the Campaspe Surface at an elevation of 200–440 m in the present landscape, falling gently from upland to the west towards the current channel of the Burdekin River. This surface is a relict alluvial plain little incised by easterly flowing tributaries of the Burdekin River and has survived, essentially intact, from the early Pliocene. Geometry of the formation is established from some 2000 mineral exploration drill holes and seismic profiling. It has an average thickness of some 60 m, reaching a maximum of over 200 m. It blankets a pre-existing, low relief landscape in which a basement ridge divides it into two sub-basins that mirror the present drainage. The formation consists of poorly sorted sandstone with minor conglomerate and siltstone, and contains paleosol horizons with associated calcrete. Matrix supported sandstone in the succession, indicates deposition in part from hyperconcentrated flows. Sandstones generally show poorly defined planar layering as typical of ephemeral overbank and terminal splay sediment bodies but beds with cross-lamination, indicating fluvial channel bed forms, are also present. They are characterised by pore-filling silt and mud, largely emplaced by post-depositional infiltration, such that the unit produces essentially no groundwater. Facies attributes are consistent with fluvial deposition in ephemeral, dry climate, distributary system, with inefficient cross-drainage discharge that induced aggradation, resulting in a substantial sediment body perched in the landscape. Framework grain compositions show the formation to be mineralogically mature, representing erosional debris derived from intense weathering in an earlier climatic regime recorded, at least in part, by duricrust developed in the fluviatile–lacustrine Southern Cross Formation of Paleogene age. Such duricrust intervals are now upstanding in the landscape, representing erosional remnants from inverted relief developed in a mid-Cenozoic, pluvial, landscape cycle. Paleoclimatic signature of the Campaspe Formation extends the record of Pliocene aridity, widely recognised elsewhere in Australia, to northeast Queensland. In large part the landscape of the Charters Towers district is relict from the early Pliocene and is in the process of readjusting to more pluvial climatic regimes. By implication, Pliocene aridity has, on a small scale, exerted a strong influence on the present physiography of Australian landscapes.
The response of ozone to solar proton events during solar cycle 21 - The observations

We have analyzed ozone profile data from the solar backscattered ultraviolet instrument on NIMBUS 7 from 1979 to the present and have found clear cases of ozone destruction associated with five solar proton events (SPE's) of this solar cycle: on June 7, 1979, August 21, 1979, October 13–14, 1981, July 13, 1982, and December 8, 1982. During the SPE on July 13, 1982, the largest of this solar cycle, we observed no depletion at all at 45 km but a 15% ozone depletion at 50 km increasing to 28% depletion at 55 km, all at a solar zenith angle of 85°. We find that there is a strong variation of the observed depletion with solar zenith angle, with maximum depletion occurring at the largest zenith angles (near 85°) decreasing with distance from the terminator. The observed depletion in every case was short lived, disappearing within hours of the end of the SPE, suggesting that HOx reactions were responsible for the observed ozone depletion.
Dynamic Analysis Pipeline in Real Time Monitoring Scenario

Social networks offer researchers a unique opportunity to study human communication and social phenomena on an unprecedented scale. However, the variability in the amount of data generated at different times poses a challenge to research in this area. This paper presents an analysis pipeline that uses Twitter data to efficiently process and analyze social media posts in real time. It does not require resources to be designed for maximum load. The approach is based on three key components: implementing analysis processes as independent microservices, using a publish-subscribe communication system, and implementing automatic scaling mechanisms. These factors enable a flexible, robust, and scalable analysis pipeline. It can dynamically adapt to changing workloads and ensure optimal resource utilization.
Seepage control in tailings dams

It is common for the rate of seepage through a tailings embankment to be estimated on the basis of a conventional flow net analysis assuming steady seepage conditions. Moreover an impervious seal is generally recommended against the upstream face of the dam to minimize seepage flow through the sand embankment. This study shows that, due to rapid rates of placing, slimes can exist in an under-consolidated state. Field measurements are cited in support of the theory and the implications of under-consolidated slimes in the pond are discussed in detail. Procedures to analyse the utility of an upstream seal are also discussed and design examples reflecting actual operating conditions are given.
Climate and Circulation of the Tropics

This is a very comprehensive effort in numerous important areas, such as interannual variability, regional circulation, climatology, tropical glaciers, and past climates. The emphasis, in most of these areas, would be called “climatological. ” It is quite detailed, full of adequate references and historical accounts. The approach is descriptive. However, in many sections the paragraphs are too full of authors' names with only very brief explanations of their findings.