Coal, containing all the elements that are present in nature and more than 200 minerals, has a complex chemical structure, making it one of the most complex geological materials. Inorganic matter in ...coal includes minerals (in which element concentration may vary from trace to major), non-crystalline mineraloids, and elements with non-mineral associations such as those occurring in pore waters, organically bound, or in an organic association. Understanding the modes of occurrence of elements in coal is important because, theoretically, they provide useful information on peat deposition, diagenesis and epigenesis of coal, coal-hosted basin formation, and the regional geological background or evolution. Practically, the modes of occurrence of elements play a significant role in affecting coal mining, coal preparation, coal combustion, and coal utilization, and in exerting adverse effects on both the environment and human health. The modes of occurrence of critical elements in coal and coal ash are key factors for designing the method and technology required for extracting critical metals from coal or coal ash. In this paper, the following aspects are reviewed, including the modes of occurrence of 73 elements and rare gases that occur in coal (with the exceptions of organically associated C, H, O, and N), the definition of modes of occurrence and their practical and academic significance, analytical methods for determining modes of occurrence of elements in coal and their advantages and limitations, and reported modes of occurrence of elements in coal and their likely associations.
Overall, the modes of occurrence of elements in coal are classified into inorganic, organic, and intimate organic associations. Although there are common modes of occurrence of many elements in coal, there are many exceptions and most, if not all, elements have multiple modes of occurrence. Each mode of occurrence of an element may also show different levels of confidence, namely, certain, probable, possible, doubtful, unlikely, and may occur in coal with different frequencies, namely abundant, common, uncommon, rare, and unlikely. For each element, the authors present concluding comments viewpoints on the modes of occurrence of almost each element in coal that is listed in the old literature.
The different modes of occurrence for each element in different coals depend on the geological conditions of coal formation, and do not necessarily indicate inconsistency in the reported results. However, due to limitations of the analytical methods used, some data relating the modes of occurrence of elements in coal are not convincing, and in some cases are invalid or even misleading. Overall, while precisely determining the concentrations of many elements in coal is not difficult, determination of the modes of occurrence of some elements, particularly those with low concentrations and high volatility, is still a challenge. Although analytical methods certainly play critical roles in determining the modes of occurrence of elements in coal, in-depth understanding of the nature of the coal and host-rocks and the geological background of coal formation is very useful in investigating when and how these modes of occurrence of elements were formed.
The composition of continental subduction-zone fluids varies dramatically from dilute aqueous solutions at subsolidus conditions to hydrous silicate melts at supersolidus conditions, with variable ...concentrations of fluid-mobile incompatible trace elements. At ultrahigh-pressure (UHP) metamorphic conditions, supercritical fluids may occur with variable compositions. The water component of these fluids primarily derives from structural hydroxyl and molecular water in hydrous and nominally anhydrous minerals at UHP conditions. While the breakdown of hydrous minerals is the predominant water source for fluid activity in the subduction factory, water released from nominally anhydrous minerals provides an additional water source. These different sources of water may accumulate to induce partial melting of UHP metamorphic rocks on and above their wet solidii. Silica is the dominant solute in the deep fluids, followed by aluminum and alkalis. Trace element abundances are low in metamorphic fluids at subsolidus conditions, but become significantly elevated in anatectic melts at supersolidus conditions. The compositions of dissolved and residual minerals are a function of pressure-temperature and whole-rock composition, which exert a strong control on the trace element signature of liberated fluids. The trace element patterns of migmatic leucosomes in UHP rocks and multiphase solid inclusions in UHP minerals exhibit strong enrichment of large ion lithophile elements (LILE) and moderate enrichment of light rare earth elements (LREE) but depletion of high field strength elements (HFSE) and heavy rare earth elements (HREE), demonstrating their crystallization from anatectic melts of crustal protoliths. Interaction of the anatectic melts with the mantle wedge peridotite leads to modal metasomatism with the generation of new mineral phases as well as cryptic metasomatism that is only manifested by the enrichment of fluid-mobile incompatible trace elements in orogenic peridotites. Partial melting of the metasomatic mantle domains gives rise to a variety of mafic igneous rocks in collisional orogens and their adjacent active continental margins. The study of such metasomatic processes and products is of great importance to understanding of the mass transfer at the slab-mantle interface in subduction channels. Therefore, the property and behavior of subduction-zone fluids are a key for understanding of the crust-mantle interaction at convergent plate margins.
Retrotransposons as regulators of gene expression Elbarbary, Reyad A.; Lucas, Bronwyn A.; Maquat, Lynne E.
Science (American Association for the Advancement of Science),
02/2016, Letnik:
351, Številka:
6274
Journal Article
Recenzirano
Odprti dostop
Transposable elements (TEs) are both a boon and a bane to eukaryotic organisms, depending on where they integrate into the genome and how their sequences function once integrated. We focus on two ...types of TEs: long interspersed elements (LINEs) and short interspersed elements (SINEs). LINEs and SINEs are retrotransposons; that is, they transpose via an RNA intermediate. We discuss how LINEs and SINEs have expanded in eukaryotic genomes and contribute to genome evolution. An emerging body of evidence indicates that LINEs and SINEs function to regulate gene expression by affecting chromatin structure, gene transcription, pre-mRNA processing, or aspects of mRNA metabolism. We also describe how adenosine-to-inosine editing influences SINE function and how ongoing retrotransposition is countered by the body's defense mechanisms.
Nektar++ is an open-source software framework designed to support the development of high-performance scalable solvers for partial differential equations using the spectral/hp element method. ...High-order methods are gaining prominence in several engineering and biomedical applications due to their improved accuracy over low-order techniques at reduced computational cost for a given number of degrees of freedom. However, their proliferation is often limited by their complexity, which makes these methods challenging to implement and use. Nektar++ is an initiative to overcome this limitation by encapsulating the mathematical complexities of the underlying method within an efficient C++ framework, making the techniques more accessible to the broader scientific and industrial communities. The software supports a variety of discretisation techniques and implementation strategies, supporting methods research as well as application-focused computation, and the multi-layered structure of the framework allows the user to embrace as much or as little of the complexity as they need. The libraries capture the mathematical constructs of spectral/hp element methods, while the associated collection of pre-written PDE solvers provides out-of-the-box application-level functionality and a template for users who wish to develop solutions for addressing questions in their own scientific domains.
Program title: Nektar++
Catalogue identifier: AEVV_v1_0
Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEVV_v1_0.html
Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland
Licensing provisions: MIT
No. of lines in distributed program, including test data, etc.: 1052456
No. of bytes in distributed program, including test data, etc.: 42851367
Distribution format: tar.gz
Programming language: C++.
Computer: Any PC workstation or cluster.
Operating system: Linux/UNIX, OS X, Microsoft Windows.
RAM: 512 MB
Classification: 12.
External routines: Boost, FFTW, MPI, BLAS, LAPACK and METIS (www.cs.umn.edu)
Nature of problem:
The Nektar++ framework is designed to enable the discretisation and solution of time-independent or time-dependent partial differential equations.
Solution method:
Spectral/hp element method
Running time:
The tests provided take a few minutes to run. Runtime in general depends on mesh size and total integration time.
The Moon is thought to have formed from material ejected by a giant impact that took place at the end of Earth's accretion. The material ejected to space generated a large hot structure where ...material beyond the Roche limit accreted to form the Moon. It has long been known that the Moon is characterized by abundances in moderately volatile elements (MVE) lower than that of the Earth, while more recent studies have established that the concentrations in refractory elements are similar to the bulk Silicate Earth. The thermodynamic conditions that prevailed after this impact are poorly known and understanding the origin of the Moon-Earth differences in MVE requires a knowledge of the volatility of elements under these conditions. In this study, we reexamine the volatility of a large set of geochemically relevant elements and attempt to determine the P-T conditions under which volatiles were putatively separated from the liquid material. Our model predicts very different condensation temperatures due to higher pressures, compared with the conditions of the Solar Nebula and we extend the values of these temperatures to a wide number of trace elements (Se, Ag, Pt, Mo, W, Zn, Sn, Sb, Rb, Cs, U, Th, Cr, Ni, Co, Ga, Ge, Cu, and P). Our modeling shows that the observed lunar compositions cannot be explained by a single set of P and T conditions. Rather, it is best explained by a mixture between high-temperature condensates (~4000 K) and low temperature condensates (2000-2500 K). An important constraint is that for the low temperature condensates, liquid metal must have been stable and this is crucial for matching the abundance of volatile siderophile elements in the bulk Moon.
•New condensation temperatures for trace elements during Moon formation were calculated.•Lunar condensates were formed by mixing high-T and low-T condensates.•Liquid metal must have been present to explain the volatile siderophile element pattern in the Moon.
The mean composition of ocean ridge basalts Gale, Allison; Dalton, Colleen A.; Langmuir, Charles H. ...
Geochemistry, geophysics, geosystems : G3,
03/2013, Letnik:
14, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The mean composition of mid‐ocean ridge basalts (MORB) is determined using a global data set of major elements, trace elements, and isotopes compiled from new and previously published data. A global ...catalog of 771 ridge segments, including their mean depth, length, and spreading rate enables calculation of average compositions for each segment. Segment averages allow weighting by segment length and spreading rate and reduce the bias introduced by uneven sampling. A bootstrapping statistical technique provides rigorous error estimates. Based on the characteristics of the data, we suggest a revised nomenclature for MORB. “ALL MORB” is the total composition of the crust apart from back‐arc basins, N‐MORB the most likely basalt composition encountered along the ridge >500 km from hot spots, and D‐MORB the depleted end‐member. ALL MORB and N‐MORB are substantially more enriched than early estimates of normal ridge basalts. The mean composition of back‐arc spreading centers requires higher extents of melting and greater concentrations of fluid‐mobile elements, reflecting the influence of water on back‐arc petrogenesis. The average data permit a re‐evaluation of several problems of global geochemistry. The K/U ratio reported here (12,340 ± 840) is in accord with previous estimates, much lower than the estimate of Arevalo et al. (2009). The low Sm/Nd and 143Nd/144Nd ratio of all morb and N‐MORB provide constraints on the hypothesis that Earth has a non‐chondritic primitive mantle. Either Earth is chondritic in Sm/Nd and the hypothesis is incorrect or MORB preferentially sample an enriched reservoir, requiring a large depleted reservoir in the deep mantle.
Key points
We present a carefully compiled MORB database, unparalleled in size and coverageWe rigorously establish the mean composition of MORB
Pigmented and non-pigmented rice varieties (grown in different areas) were collected in China, Yunnan, to investigate the content of macro-, trace elements and potentially toxic elements (PTEs), and ...to assess the health risk associated with dietary intake. The order of elemental concentrations in rice was Mn > Zn > Fe > Cu > Se for trace elements, P > K > Mg > Ca > Na for macro elements, and Cr > As > Cd for PTEs. Rice with a high concentration of essential elements also associated with a high content of PTEs. In addition, higher content of Cr, Mn and Na were found in pigmented rice. The health risk assessment showed that the daily intake of all elements was below the tolerable limit (UL). Moreover the intake of Fe, Zn and Se was far from sufficient for the nutrient requirement. The PTEs in rice dominated the health risk. Of concern is that this rice consumption is likely to contribute to carcinogenic risks in the long term and that adults are at higher health risk from pigmented rice compared to non-pigmented rice. This study confirms that the lack of essential micronutrients in rice and the health risk associated with rice diets should remain a concern.
Continental basalts generally display enrichment of fluid-mobile elements and depletion of high-field-strength elements, similar to those that evolved in the subduction environment, but different ...from oceanic basalts. Based on the continental flood basalt database for six large igneous provinces, together with rift-related basalt data from the Basin and Range Province, this study aimed to test the validity of geochemical tectonic discrimination diagrams in distinguishing arc-like intra-continental basalts from arc basalts and to further investigate the role of deep-Earth water cycling in producing arc-like signatures in large-scale intra-continental basalts. Our evaluation shows that arc-like intra-continental basalts can be distinguished from arc basalts by integrating the following factors: (1) the FeO, MgO, and Al2O3 concentrations of the primary melt; (2) TiV, ZrZr/Y, ZrTi, and Ti/VZr/SmSr/Nd discrimination diagrams; (3) the coexistence of arc-like and OIB-like subtype basalts within the same province; (4) primitive mantle-normalized trace element distribution patterns. The similarity of enrichment in fluid-mobile elements (Ba, Rb, Sr, U, and K) between arc-like and true arc basalts suggests the importance of water flux melting in producing arc-like signatures in continental basalts. Experimentally determined liquid lines of descent (LLD) imply high magma water concentrations for continental flood basalts (CFBs) and the Basin and Range basalts. Furthermore, estimates based on the Al2O3–LLD method indicates 4.0–5.0wt% pre-eruptive magma H2O concentration for CFBs and the Basin and Range basalts. The tight relationships between H2O/Ce and Ba/La, Ba/Nb and Rb/Nb based on global arc basalt data were further used to estimate the primary H2O concentrations. With the exception of the Emeishan CFBs (mainly containing 4.0–5.6wt% H2O), all other CFBs investigated have similar estimated primary H2O contents, with values ranging from 1.0 to 2.0wt%. The estimated primary H2O content of the Basin and Range basalts is extremely high and up to 10.0wt%. Thus, this study demonstrates that water flux melting played an important role in the generation of many intra-continental igneous provinces. This new finding was further employed to investigate the tectonic setting of 320–270Ma basalts in Inner Mongolia, North China. Most basalts from three key rock units (i.e. Amushan, Benbatu, and Dashizhai formations) from the Central Asian Orogenic belt are classified as non-arc types. The estimated magma H2O concentrations suggest a strong link between H2O content and arc-like geochemical signatures. Together with established geological evidence, we proposed that these 320–270Ma basaltic rocks were most likely produced in a post-orogenic extensional environment facilitated by subducted slab-driven deep-Earth fluid cycling. We propose a mantle transition zone water-filtering model that links deep-Earth fluid cycling, large-scale intra-continental basaltic magmatism, and supercontinent cycles into a self-organized system.
•Arc-like continental basalts have 4.0–5.0wt% magma H2O concentration.•Primary melts of CFBs have 1.0–2.0wt% H2O concentration.•Arc-like geochemical signatures related to deep-Earth water cycling.•Arc-like continental basalts can be distinguished from arc basalts using the proposed factors.
This study aimed to shed further light on the capacity of macrophytes to translocate, accumulate and bioindicate the levels of trace elements present in contaminated water and sediments. ...Specifically, this study aimed to find evidence whether translocation, accumulation and bioindication are dependent on the kind of trace element and plant species. To investigate the correlation between trace elements in plants and in the environment, the concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn were analyzed in twenty different wetland plants, and in water and sediments from a wetland area affected by urban and industrial pollutants. Results showed that wetland plants share some common characteristics such as high tolerance to toxic element levels, capacity of phytostabilization and different element concentrations in the various organs. Moreover, element translocation from sediments to roots seems more influenced by the kind of plant species and trace element, whereas translocation across the various organs seems mainly species-specific. No clear patterns of trace element translocation were identified according to plant life forms.
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•Capacity of trace element accumulation is independent of plant life forms.•Translocation from sediment to roots is mainly species- and element-specific.•Translocation across internal tissues is mainly species-specific.•Wetland plants are potentially suitable for the phytostabilization of trace elements.
The skeleton is a target organ for most metals. This leads to their bioaccumulation, either as storage of useful oligoelements or as a protection against damage by toxic elements. The different ...events leading to their accumulation in this organ, under constant remodeling, are not fully understood, nor the full subsequent impact on bone metabolism. This lack of knowledge is particularly true for lanthanides and actinides, whose use has been increasing over recent decades. These metals, known as f-elements, present chemical similarities and differences. After a comparison of the biologically relevant physicochemical properties of lanthanides and actinides, and a brief reminder of the main events of bone metabolism, this review considers the results published over the past decade regarding the interaction between bones and f-elements. Emphasis will be given to the molecular events, which constitute the basis of the most recent toxicological studies in this domain but still need further investigation. Ionic exchanges with the inorganic matrix, interactions with bone proteins, and cellular mechanism disturbances are mainly considered in this review.
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