Average Earth Research Articles

Estimation and Investigation of the Variability of Tropospheric Radio Refractivity and Radio Field Strength over Accra, Ghana

he average refractivity gradient and the average effective earth radius (k – factor) estimated for Accra during the period under investigation were found to be -44.1405 N-units/km and 1.39 respectively suggesting that the propagation in this geographical location is mostly super – refractive. The highest and lowest mean values of FSV were found during the dry and rainy seasons in the months of January and June with 3.0998 dB and 0.0158 dB respectively.

Stable W and Mo isotopic evidence for increasing redox-potentials from the Paleoarchean towards the Paleoproterozoic deep ocean

The scavenging of dissolved trace metals such as chromium (Cr), molybdenum (Mo) and tungsten (W) and their authigenic enrichment in sedimentary archives mainly occur by particle shuttling that cause resolvable isotope fractionation. Because their scavenging is also dependent on the local marine redox potential and the overall marine chemical environment, the stable isotope composition of these elements in Archean sediments is widely used as paleoredox proxy. Tungsten, a new element in this tool box, is dissolved as the oxyanion tungstate (WO42−) at extremely low marine redox potentials and can thus help to reconstruct the earliest changes in the marine redox state.We tested the applicability of stable W isotopes as a new paleoredox proxy of the atmosphere–ocean system. We analyzed the δ186/184W of Precambrian igneous rocks to investigate the detrital background δ186/184W signature. This Precambrian igneous inventory (PII) shows δ186/184W values between −0.007 and +0.097‰, identical to the range of modern igneous crustal rocks, which indicates that the average Earth’s crust δ186/184W remained constant over billions of years. Furthermore, we present δ186/184W values of euxinic sediments from the Black Sea as a modern sedimentary analog, which we then compare with δ186/184W data of Archean and Proterozoic black shales (3.47–2.3 Ga). Modern Black Sea sapropels reveal crustal-like δ186/184W values between +0.050 and +0.071‰ suggesting limited authigenic enrichment of W in euxinic environments. Similarly, post-Great Oxidation Event shales (2.3 Ga) show crustal- or PII-like δ186/184W values indicating the deposition in euxinic or oxic environment. However, the Archean shale sample suites show elevated W concentrations and fractionated δ186/184W values up to +0.246‰, which we attribute to authigenic enrichment of heavy seawater W in a ferruginous setting. Thus, black shales δ186/184W values can help to distinguish between anoxic-ferruginous and euxinic depositional environments.Furthermore, we combine previously published Cr and Mo isotope data with new Cr and W isotope data to quantify the evolution of the marine redox state during the Archean. By combining the Eh-pH stability fields of W and Mo with the δ186/184W and δ98/95Mo values of Precambrian sediments, we suggest a 3-step evolution of the Precambrian ocean. (1) From 3.47 to 3.0 Ga, the Eh of a dominantly ferruginous ocean was between −0.4 V and −0.25 V, enabling the persistence of soluble WO42− but not MoO42− and thus only the authigenic enrichment of isotopically fractionated W. (2) Starting from 3.0 Ga, the Eh of some shallow-marine environments increased above −0.25 V, as indicated by δ98/95Mo values above the detrital background in shallow-marine sediments, while the Eh of the deep ocean still remained below −0.25 V indicated by the lack of authigenic Mo enrichment and fractionated δ98/95Mo values in deep-sea shales. (3) After 2.7 Ga elevated δ98/95Mo and δ186/184W values in deep-marine sediments suggest that the Eh of the ferruginous open-ocean now also increased above −0.25 V. We therefore suggest that the combination of δ98/95Mo and δ186/184W values of shales is a very promising tool to investigate earliest changes in marine redox conditions during the Archean.

A Mg Isotopic Perspective on the Mobility of Magnesium During Serpentinization and Carbonation of the Oman Ophiolite

AbstractAlteration of mantle peridotite in the Samail ophiolite forms secondary minerals, mainly serpentine and Mg‐rich carbonates. Magnesium accounts for ∼25 – 30% of peridotite mass and its mobility can be used to trace this alteration. We report the first set of Mg isotope measurements from peridotites and their alteration products in Oman. Partially serpentinized peridotites have Mg isotope ratios that are indistinguishable from estimates for the average mantle and bulk silicate earth (δ26Mg = −0.25 ± 0.04‰). However, more extensively altered peridotite samples show large shifts in Mg isotopic composition. The range of δ26Mg values for our suite of alteration products from the mantle section is ∼4.5‰ (from −3.39‰ to 1.19‰), or >60% of the total range of terrestrial variability in δ26Mg values. Serpentine veins are typically enriched in 26Mg (max δ26Mg value = 0.96‰) whereas Mg‐carbonate veins are associated with low 26Mg/24Mg ratios (magnesite δ26Mg = −3.3‰, dolomite δ26Mg = −1.91‰). Our preferred explanation for the range in δ26Mg values involves coprecipitation of serpentine and carbonates at water‐to‐rock ratios >103. The coincidence of alteration products characterized by δ26Mg values that are both lower and higher than bulk silicate Earth and the finite 14C ages of the carbonates suggest that both serpentinization and carbonation are ongoing in Oman. Rates of calcite precipitation in travertines inferred from Δ26Mgcal‐fl suggest that travertine formation in Oman sequesters a total of 106–107 kg CO2/yr, consistent with previous estimates.

A Consistent Model of Terrestrial Planet Magnetospheres and Rotations in Our Solar System

The Sun comprises 99.9% of the solar system mass so it is expected that Sun terrestrial planet interactions can influence the motion as well as the rotation of the terrestrial planets. Gravity affects the planet orbital motions while the changing magnetic fields of the Sun can influence the planet rotations. Planets that manifest a magnetic field dominate any weaker magnetic fields from the Sun, but the rotation of terrestrial planets without a magnetic field interacts with the changing Sun’s field dependent on the electrical conductivity of the core region. It is determined that the average planet density becomes a useful quantity to describe the magnetic state of a terrestrial planet. An average density of 5350 ± 50 kg/m3 is hypothesized to separate planets that develop magnetospheres from those that do not. Planets with higher average densities, Mercury and Earth, developed magnetospheres. While those with lower average densities, Venus and Mars never developed magnetospheres. Terrestrial planets with magnetospheres are the ones to also exhibit plate tectonics. The small size of Mercury led to Mercury only exhibiting a frozen in magnetization of potentially magnetic regions. The lack of magnetospheres as well as lack of plate tectonics prevented the continual transfer of core heat to the surface that limited the surface vulcanism to an initial phase. For Venus, it meant that the surface regions would only sporadically convulse. In this picture, the apparent anomalous axial rotation of Venus is a natural consequence of the rotation of the Sun. For Mars with relatively low surface temperatures, it meant that there was little heat exchange through the crust that would allow the lower crust to retain large amounts of water. For Mars to have initially had flowing liquid water required that the atmosphere at that time contained high concentrations of infrared absorbing gases at least as compared to the present level of infrared absorbing gases on the Earth. The terrestrial planets have iron based cores because iron has the highest binding energy per nucleon that can be made in the steady state lives of massive stars no matter how massive. This suggests that many of the conclusions reached here may also be applicable to exoplanets.

Converted-wave model building and imaging based on common-focus-point methodology

Seismic images can be viewed as photographs for underground rocks. These images can be generated from different reflections of elastic waves with different rock properties. Although the dominant seismic data processing is still based on the acoustic wave assumption, elastic wave processing and imaging have become increasingly popular in recent years. A major challenge in elastic wave processing is shear-wave (S-wave) velocity model building. For this reason, we have developed a sequence of procedures for estimating seismic S-wave velocities and the subsequent generation of seismic images using converted waves. We have two main essential new supporting techniques. The first technique is the decoupling of the S-wave information by generating common-focus-point gathers via application of the compressional-wave (P-wave) velocity on the converted seismic data. The second technique is to assume one common VP/ VS ratio to approximate two types of ratios, namely, the ratio of the average earth layer velocity and the ratio of the stacking velocity. The benefit is that we reduce two unknown ratios into one, so it can be easily scanned and picked in practice. The PS-wave images produced by this technology could be aligned with the PP-wave images such that both can be produced in the same coordinate system. The registration between the PP and PS images provides cross-validation of the migrated structures and a better estimation of underground rock and fluid properties. The S-wave velocity, computed from the picked optimal ratio, can be used not only for generating the PS-wave images, but also to ensure well registration between the converted-wave and P-wave images.

High temperatures modify plant responses to abiotic stress conditions.

Climate change is altering environments in which plants and different crops grow and survive. We already experienced an increase in worldwide average earth surface temperatures, as well as frequency and extent of damaging heat waves. These conditions collide in the field with other abiotic stresses such as water deficit, high salinity, increased light irradiation, and so on, generating complex harmful conditions that destabilize agricultural systems. The conditions generated during these episodes of stress combination greatly differ from those occurring in the field when different stress factors occur individually; conditions that have been the focus of study for decades. Fortunately, knowledge of physiological and molecular responses to stress combinations and the cost they inflict on plant growth and yield has been exponentially increasing in the past several years. Understanding plant performance under multiple stress combinations will allow breeding crops capable of maintaining yield production under the new climatic conditions. Here, after reviewing recent data on physiological, hormonal and transcriptional responses to different stress combinations, we highlight the importance of photodamage avoidance, abscisic and jasmonic acid signaling, and the upregulation of genes involved in oxidation-reduction processes, photosynthesis and protein metabolism, for plant acclimation to conditions of high temperatures, in combination with other common abiotic stress factors such as drought or salinity. Finally, we propose new approaches to investigate the response of plants to stress combinations and discuss strategies for improving crop resilience to stress combination.

The 142Nd/144Nd variations in mantle-derived rocks provide constraints on the stirring rate of the mantle from the Hadean to the present

Early silicate differentiation events for the terrestrial planets can be traced with the short-lived 146Sm-142Nd system (∼100-My half-life). Resulting early Earth-produced 142Nd/144Nd variations are an excellent tracer of the rate of mantle mixing and thus a potential tracer of plate tectonics through time. Evidence for early silicate differentiation in the Hadean (4.6 to 4.0 Ga) has been provided by 142Nd/144Nd measurements of rocks that show both higher and lower (±20 ppm) values than the present-day mantle, demonstrating major silicate Earth differentiation within the first 100 My of solar system formation. We have obtained an external 2σ uncertainty at 1.7 ppm for 142Nd/144Nd measurements to constrain its homogeneity/heterogeneity in the mantle for the last 2 Ga. We report that most modern-day mid-ocean ridge basalt and ocean island basalt samples as well as continental crustal rocks going back to 2 Ga are within 1.7 ppm of the average Earth 142Nd/144Nd value. Considering mafic and ultramafic compositions, we use a mantle-mixing model to show that this trend is consistent with a mantle stirring time of about 400 My since the early Hadean. Such a fast mantle stirring rate supports the notion that Earth's thermal and chemical evolution is likely to have been largely regulated by plate tectonics for most of its history. Some young rocks have 142Nd/144Nd signatures marginally resolved (∼3 ppm), suggesting that the entire mantle is not equally well homogenized and that some silicate mantle signatures from an early differentiated mantle (>4.1 Ga ago) are preserved in the modern mantle.

Computational study of stack/terminal topologies for perovskite based bifacial tandem solar cells

With the rapid progress on perovskite (PVK) and bifacial solar cells, there is a huge interest in integrating PVK with established technologies such as crystalline silicon (c-Si) and CIGS for bifacial tandem structures. Here we use self-consistent optical/electrical simulations to compare various stack/terminal configurations for bifacial tandem solar cells having PVK as the top cell. In particular, we compare a non-conventional three-terminal four-junction (3T-4J) twin bifacial tandem configuration with standard two-junction bifacial tandem structures having a monolithic two-terminal (2T-2J) or mechanically stacked four-terminal (4T-2J) integration. We show that the optimal design of 2T-2J cell is strongly albedo dependent – the cell designed for a given albedo will perform sub-optimally for other albedo due to the current-matching constraint. A mechanically stacked 4T-2J cell, on the other hand, can perform optimally for a broad range of albedo, albeit at the cost of additional processing complications. The 3T-4J twin tandem cell could offer a relatively simpler process through back-to-back bonding of two identical monolithic 2J tandem cells with superior utilization of albedo in a broad range. The potential benefit of 3T-4J cell could however be limited due to a high front reflection, hence necessitating anti-reflection approaches. We further quantify the effect of bottom subcell material on the efficiency for PVK tandem cells. Using state-of-the-art bottom subcells, efficiency of 33% and 30% respectively could be achieved at the average Earth albedo of ∼30%. By integrating advanced anti-reflectance techniques, the absolute cell efficiency could further be improved by ∼4%.

Seasonal Variation of Heavy Metal Concentrations in Farm Soils of Sreepur Industrial Area of Gazipur, Bangladesh: Pollution Level Assessment

A study was conducted to measure the seasonal variation of different heavy metal contents in farm soils of Sreepur Upazila of Gazipur district and to assess their pollution level. Industrial affected and non-affected soil samples were collected from 5 locations in three seasons viz. pre-monsoon (April), monsoon (August), and dry season (January), thus a total of 30 soil samples were analyzed for this study. Concentrations of different heavy metals (Cd, Pb, Cr, Ni, Cu, and Zn) in soil samples were determined by an Atomic Absorption Spectrophotometer (AAS). The mean total concentration of Cd, Pb, Cr, Ni, Cu and Zn in industrial affected soils were trace, 12.05, 101.10, 51.32, 20.79 and 55.40 mg kg-1, respectively in the pre-monsoon, trace, 28.54, 40.96, 22.70, 2.46 and 7.72 mg kg-1, respectively in the monsoon and 0.27, 10.49, 39.45, 20.69, 1.85 and 4.11 mg kg-1, respectively in the dry season. All heavy metal concentrations in industrial affected soil samples were higher than the corresponding non-affected sites. The study results revealed that Cd contents in the dry season and Pb contents in the monsoon season for industrial affected soils were higher compared to the average earth’s crust abundance value. The geoaccumulation index (Igeo) values for Pb of industrial affected soils ranged from 0.30-0.85 in the monsoon that means Igeo class 1, indicating unpolluted/moderately polluted soil quality. Furthermore, the calculated Igeo value for one industrial affected location revealed moderate soil pollution by Cr in the pre-monsoon season and unpolluted/moderately polluted soil quality by Ni and Cd in the pre-monsoon and the dry season, respectively. The measured pollution load index (PLI) values were also higher in all industrially polluted sites than corresponding non-polluted sites in three seasons, which indicates pollution load due to anthropogenic sources.

Effects of Heat stress and molecular mitigation approaches in orphan legume, Chickpea.

Global warming has an adverse impact on agriculture and food security is in doldrums around the world. A sharp increase in the temperature of earth is expected and may lead to ~ 1.8-4°C rise in average earth temperature by the year 2100. Thus, heat stress isa critical factor for plant growth development and crop yield. Chickpea, which is an important leguminous crop and rich source of proteins is also a heat sensitive crop but high temperature exceeding 35°C inhibit its productivity. Climate-smart agriculture seems to be a plausible approach to minimize the drastic effect of climate change on plant's adaptation. This may help in better selection of tolerant cultivars of chickpea that can be used in breeding programmes for heat stress tolerance in chickpea. Also the biotechnological approaches using candidate genes expressed in transgenics plants may play pivotal role in the production of climate resilient chickpea plants. Some preliminary findings using CAP2, Galactinol synthase genes, proteomic approaches, RNA seq data, stay green traits and -OMICS in general, have proved to be promising. A close collaboration between agronomists, plant physiologists, geneticists, biotechnologists is the pressing need and must be envisioned in order to address heat stress tolerance in chickpea under the prevailing climatic conditions and continuously increasing temperature. In the context of global heat stress and climate change, adaptation and mitigation are the keywords for employing transdisciplinary methodologies with respect to plant growth, development and agronomy.

The average Phanerozoic CO2 degassing flux estimated from the O-isotopic composition of seawater

The degassing rate of CO2 from the solid Earth, and matching burial rate, is critical to understanding the long-term carbon and oxygen cycles and the maintenance of a habitable climate. However, estimates of modern CO2 degassing rates vary by more than a factor of four and uncertainties are even larger further back in Earth history. Both the crustal C-inventory and C-isotope mass balance suggests that over long timescales ∼70-90% of the CO2 degassed from the solid Earth is drawn-down through silicate weathering reactions (subaerial and submarine). These reactions involve dissolution of silicate minerals, that typically formed at relatively high temperatures, and formation of silicate and carbonate minerals in low temperature aqueous environments. These new low temperature minerals have much higher δ18O than their precursors; thus the rate of degassing of CO2 is tied to the rate of removal of materials with high δ18O from the hydrosphere into weathering products. Maintaining a near-constant O-isotopic composition of the ocean over the Phanerozoic means that this weathering sink of isotopically heavy O must have equaled the source of isotopically heavy O to the ocean. This isotopically heavy oxygen largely comes from high-temperature hydrothermal vent fluids at mid-ocean ridges. New O-isotope data for the previously under-sampled lower oceanic crust from fast-spreading ridges, along with a compilation of published O-isotopic compositions of other sections of oceanic crust altered at high-temperatures, allows the magnitude of this high δ18O flux to be quantified. Modelling the coupled O-isotope and CO2 mass balance constrains suggests that the average Phanerozoic solid Earth CO2 degassing rate was ∼3.4 Tmolyr−1 (10th to 90th percentile of 1.8-5.3 Tmolyr−1). This is substantially lower than has been suggested by some recent studies, and is at or below the lower end of the range of previous estimates, with wide ranging implications for our understanding of the long term C cycle.

Rare Earth Element Contents in Soil Samples Collected from the Zone between Burdur and Isparta and the Assessment of Their Origin and Geochemical Properties

This study was carried out in 5 locations between Burdur and Isparta in the inner southern part of Isparta Bend. The study aims to determine the rare earth element (REE) concentrations in the soil samples collected from the field and to interpret the origin of the high concentrations detected. In this context, a total of 104 samples were collected from Canakli Village (19 samples), Cobanisa Village (34 samples), Kuyubasi Village (17 samples), Kuzca Village (17 samples), and Yilanli Village (17 samples) in the study field. The average ∑REE (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) concentration values of the samples by their locations were determined to be Cobanisa (821.88 ppm) > Yilanli (723.39 ppm) > Kuzca (692.54 ppm) > Canakli (583.46 ppm) > Kuyubasi (484.04 ppm). The average light rare earth element (LREEs) concentration (such as La 229 ppm, Ce 378 ppm) of the samples collected from all locations is higher than the average rare earth element concentration in the Earth’s crust. According to the Chondrite-normalized Rare Earth Elements diagram, the distributions of the rare earth elements in these 5 locations were determined to be very similar and the high concentrations were considered to occur under similar conditions or originated from similar sources. In this context, based on the idea that Golcuk Volcanism may be the source of high concentrations, the rare earth element concentrations of Golcuk Volcanism in the northwest of the zone were compared to those taken from the study area and the values were found to be consistent with each other.

Financial impacts of climate change mitigation policies and their macroeconomic implications: a stock-flow consistent approach

ABSTRACTTo what extent can worldwide carbon pricing foster the transition towards a low-carbon economy and mitigate the effects of global warming? We address this question by assessing the financial impacts and macroeconomic implications of carbon pricing and public subsidies. More specifically, we evaluate the extent to which such policies are sustainable by computing the probability of remaining below two thresholds that we argue to be indicative of the stability of our current economy and climate: (1) a temperature anomaly above +2°C (a commonly acknowledged target, including in the 2015 Paris Agreement, to potentially avoid nonlinearities in the climate system) and (2) a large global debt-to-output ratio of 270%.Key policy insightsThe upper-bound of the carbon pricing corridor advocated in the High-Level Commission on Carbon Prices (2017. Report of the high-level commission on carbon prices. Washington, DC: World Bank), when implemented together with additional public subsidies on abatement costs in the private sector, is likely to successfully ensure sustainable economic growth by the end of the century.The probability that these climate policies will allow us to cap the average Earth temperature deviation at below +2.5°C by the end of this century is about 50%.Without a strong public commitment, the impact of climate change on gross output and capital, which captures nonlinear effects such as tipping points, appears to be powerful enough to pull the world economy towards a debt-deflationary field, potentially leading to forced degrowth in the second half of the twenty-first century.

Evaluation of induced trench twin culverts constructed in deep fill

When culverts are installed beneath high embankments, earth loads become excessive and the induced trench construction method is a viable design option to reduce the culvert loads to acceptable levels. However, limited field studies evaluating the performance of induced trench twin culverts are reported in the literature and the practicality and effectiveness of the induced trench construction method (in general) has been subject to recent criticism. This paper describes the performance of twin 3048 mm inside-diameter reinforced concrete culverts constructed with an induced trench beneath 15.3 m of fill. Research instruments and autonomous data acquisition systems were installed during construction to monitor (i) culvert earth pressures, (ii) embankment deformations, and (iii) groundwater elevations in the vicinity of the compressible fill. The experimental observations recorded throughout the construction phase are presented herein; the embankment deformations are indicative of effective positive arching within the induced trench region, and the average earth pressure at the culvert crown was reduced to approximately 48% of the overburden soil pressure. The experimental data are compared with those reported in the literature by others, and the conclusions attained from this study demonstrate the effectiveness of the induced trench construction method.

Computational modelling of monolithically stacked perovskite/silicon tandem solar cells using monofacial and bifacial designs

As the efficiency of conventional silicon (Si) solar cell is reaching closer to its thermodynamic limit, its tandem integration with emerging perovskite (PVK) solar cell is being widely explored. In this work, we use self-consistent optical and electrical simulations to computationally explore monolithically stacked 2-terminal (2-T), 2-junction (2-J) PVK/Si tandem solar cell. The optical model is based on Lambert-Beer Law while electrical model is based on drift-diffusion approach. The tandem solar cell is explored for both monofacial and bifacial configurations. The simulations show that the cell design for optimal operations is highly dependent on perovskite thickness and albedo. Under optimal design, the bifacial PVK/Si tandem cell exhibits ∼32.5% for average earth albedo of 30%. Moreover, the cell exhibits a remarkable temperature coefficient of ∼-0.27%. Moreover, our simulation results are in good agreement with both experimental and highly intensive optical model based simulation data. With our computationally inexpensive optical model, the optimal cell design for different tandem structures can be explored in a much easier way.

Geochemical Evaluation of Enrichment of Rare-Earth and Critical Elements in Coal Wastes from Jurassic and Permo-Carboniferous Coals in Ordos Basin, China

Coal waste is a potential source of rare-earth elements (REEs) and some economically critical elements recovery. The present study reports the abundance and enrichment of REEs and critical elements in the Hancheng Permo-Carboniferous (Weibei coalfield) and Binxian Jurassic coals (Huanglong coalfield) of Shaanxi, China. The Binxian coal is distinctly enriched in all REEs. The Hancheng coal is enriched in Y, Ce, Sc, La, Yb, Nd, Pr, Gd, Er, Sm and Dy and depleted in Lu, Eu, Ho, Tb and Tm, compared with that of the average earth’s crust abundance (ECA), world coal and the US coal. In the Binxian raw coal, the REEs contents, namely Sc 13.8, Y 13.1, La 27.8, Ce 48.49, Sm 4.1, Nd 22, Eu 0.8, Gd 3.8, Pr 5.43, Dy 2.5, Er 1.4 and Yb 1.3 in mg kg−1. The contents (mg kg−1) of REEs in the Hancheng raw coal were Sc 8.8, Y 18.6, La 34.8, Ce 60.2, Nd 26, Yb 1.8, Eu 01, Pr 6.71, Sm 5.3, Dy 3.4, Tb 0.66, Er 1.9 and Gd 5.16. The contents (mg kg−1) of critical elements in the Binxian raw coal were Cr 30.8, Pb 41.5, Ni 49.7, Cu 35.7, Ba 257.9, V 51.7, Zn 63.1, Li 135, Ga 20.6, U 2.9, Th 10.2 As 12.7, Al 98,887, Fe 23,916 and Ti 4289. The contents (mg kg−1) of critical elements in the Hancheng coal were Cr 384, Pb 56.1, Ni 93.9, Cu 49.5, Ba 371, V 90.7, Zn 7653, Li 183, Ga 35.9, U 4.9, Th 17.7, As 10.1, Al 108,344, Fe 20,433 and Ti 2873. The contents of REEs in the Binxian and Hancheng coals were not in a promising range, whereas some of the critical elements were highly abundant. The Al2O3/TiO2 ratio indicated that the Ordos Basin sediment was derived from intermediate-felsic rocks with a slight variation (r = 0.98). The Eu and Gd show positive anomalies with negative Ce anomalies almost in all the samples. The positive anomalies of Gd represent the intrusion of hydrothermal fluid with possibly Ba interference in the Binxian coal. The high volatile matter in the Binxian coal reflects bituminous to anthracite coal, whereas the low volatility of the Hancheng coal reflects peat to lignite coal. The recovery of the REEs and critical elements as a by-product from these coals may not only increase the revenue but will also lead to an improvement in the environmental quality.

An Adjoint Technique for Estimation of Interstation Phase and Group Dispersion from Ambient Noise Cross Correlations

AbstractA method of extracting group and phase velocity dispersions jointly for Love‐ and Rayleigh‐wave observations is presented. This method uses a spectral element representation of a path average Earth model parameterized with density, shear‐wave velocity, radial anisotropy, and VP/VS ratio. An initial dispersion curve is automatically estimated using a heuristic approach to prevent misidentification of the phase. A second step then more accurately fits the observed noise correlation function (NCF) between interstation pairs in the frequency domain. For good quality cross correlations with reasonable signal‐to‐noise ratio, we are able to very accurately fit the spectrum of NCFs and hence obtain reliable estimates of both phase and group velocity jointly for Love and Rayleigh surface waves. In addition, we also show how uncertainties can be estimated with linearized approximations from the Jacobians and subsequently used in tomographic inversions.

Effect of Water Temperature to Survival and Development of Larvae of Two Local Aedes Aegypti Strains

Global warming has been reported in last decades. Chang-es in average Earth’s temperature may affect the physiology of many insect species, especially the ones which act as a human disease vec-tor, like Aedes aegypti. In this study, the effect of increasing water temperature on physiological components related to development period, sex ratio, and body size of two distinctively strains, VCRU (Vector Control Research Unit) and Pangandaran. Thirty larvae of each strain kept inside distilled water with the temperature of 25°C, 27°C, 30°C, 33°C, 35°C, 40°C which replicated three times. Observa-tions were conducted until all larvae metamorphed into adults or all larvae dead. Development rate and time were analyzed by frequency dependent mean. The result showed that the optimum temperature for larvae development of VCRU strain was 27-30°C with a survival rate of 84% while it was 30°C for Pangandaran strain, with the surviv-al rate of 83%. Larvae of both strains showed 100% mortality rate when kept inside a container with water temperature exceed 33°C. Both strains showed the highest and the lowest male:female ratio at similar water temperature which were 33°C and 30°C, respec-tivelly. Highest and lowest ratio of VCRU was 1.25 and 0.6, respec-tively, while it was 1.4 and 0.6 for Pangandaran. In general, larvae lived in increasing water temperature showed reducing wing width.

Numerical and theoretical research on stress distribution in the loosening zone of the trapdoor problem

SummaryThe traditional theory of soil arching effect was developed on the assumption that stress distribution in the loosening zone is uniform. However, because of the deflection of principal stress' direction, the stress distribution in the loosening zone is actually ununiform. For the evaluation of principal stress axis deflection and stress redistribution, a discrete element method numerical model of trapdoor problem is established for the simulation of soil arching effect. Based on the numerical results, an arc shape of major principal stress trajectory and uniform horizontal stress distribution at the same depth of the loosening zone are adopted. An analytical model is raised to estimate the average loosening earth pressure acting on the trapdoor and stress distribution in the loosening zone at a limit state. In addition, comparison studies are carried out between the predictions of the proposed solutions and discrete element method numerical results as well as available model test results, thereby validating the accuracy of the proposed theoretical model. Both numerical and theoretical results indicate that the vertical stress distribution in the loosening zone is obviously ununiform. The load acting in the middle of loosening zone is transferred toward two sides so that the vertical stress distribution in loosening zone is concave.

The Importance of the Inelastic and Elastic Structures of the Crust in Constraining Glacial Density, Mass Change, and Isostatic Adjustment From Geodetic Observations in Southeast Alaska

AbstractElastic deformation of the solid Earth in response to ice mass loss offers a promising constraint on the density of glacial material lost. Further, the elastic response to modern deglaciation is important to constrain for studies of glacial isostatic adjustment to determine the mantle's structure and rheology. Models of this elastic uplift are commonly based on the 1‐D, seismically derived global average Preliminary Reference Earth Model and typically neglect uncertainties that can arise from regional differences in elastic structure from that of the global average, lateral heterogeneities within the region, and inelastic behavior of the crust. We quantify these uncertainties using an ensemble of 1‐D local elastic structure models and empirical relations for the effects of inelasticity in the upper ∼10 km of the crust. In Southeast Alaska, modeling elastic uplift rates with local elastic structures results in up to a 20–40% difference from those modeled with the Preliminary Reference Earth Model. Although these differences are limited to regions near to ice‐covered areas, they are comparable to the differences in uplift rates expected from the loss of firn versus loss of ice. Far from ice‐covered areas, where most of the region's GPS observations were made, these differences become insignificant and do not affect previous glacial isostatic adjustment studies in the region. The methods presented here are based on the globally available LITHO1.0 seismic model and open source software, and the approach of using an ensemble of 1‐D elastic structures can be easily adapted to other regions around the world.