Ongoing global warming accelerates release of relict terrigenous organic carbon from permafrost onto the Arctic shelf waters. When transported in the land-sea system, it can further be accumulated in ...bottom sediments in the shelf or deep-sea zone and undergo degradation and remineralization, which leads to critical environmental consequences. This study aims at assessing the sources and degradation degree of terrigenous organic matter in the surface sediments of the Eastern Arctic seas. Within this study, marine bottom sediments taken from the surface horizon (0–10 cm) were investigated. Sampling was carried out during the 2011–2019 marine research expeditions. Lateral consistency of hydrogen index values in modern marine sediments on the Eastern Arctic shelf (mainly in the Laptev Sea) is associated with the great contribution of heterogeneous biolabile terrestrial organic matter, in contrast to other Arctic waters, where growing hydrogen index values are associated with the consistently growing contribution of autochthonous organic matter with increasing distance from the coast. While considering the δ13C and HI/OI correlation, there are also significant deviations from the linear dependence which usually indicates a conservative marine geochemical regime. Sediments of the Buor-Khaya Bay are characterized by an increased HI/OI values in contrast to the deep-water sediments of the continental slope which shows lower hydrogen content and a higher proportion of oxygen-containing compounds, indicating a strong transformation of organic matter. These findings confirm a key role of terrigenous supply in specific biogeochemical conditions in the studied area and reveal that geochemical indicators of immature organic matter sources in the Eastern Arctic seas should be interpreted differently from other Arctic continental margins.
Rich brachiopod assemblages are known from the Lower and Middle Jurassic deposits of the Danubian and Getic tectonic units (eastern Serbia). A quantitative assessment of the relevant palaeontological ...data can shed light on the relationship of these units in the palaeospace. In the present study, the brachiopod assemblages from the Danubian and Getic tectonic units are compared with similarity indices (the Jaccard similarity of species, genera, families, and superfamilies, and the Czekanowski and Gower similarity of the genus–species, family–species, and superfamily-species diversity structures). This analysis is applied to five geological time slices when brachiopods flourished regionally, namely the Early Pliensbachian, the Late Bajocian, the Early Bathonian, the Middle Bathonian, and the Late Bathonian. Generally, the values of the indices imply moderate similarity. The similarity was significantly lower in the Middle Jurassic relatively to the Early Jurassic. The similarity of the Early Pliensbachian brachiopods of the Danubian and Getic tectonic units was significant relatively to the similarity between some European regions. The documented decrease in the similarity through the geological time can be explained by the increase in the global palaeobiogeographical differentiation in the Middle Jurassic.
Display omitted
•E Pliensbachian, L Bajocian, E, M, L Bathonian brachiopods from eastern Serbia•Moderate similarity of brachiopods between Danubian and Getic tectonic units•Similarity decreased significantly in M Jurassic relatively to E Jurassic.•Global palaeobiogeographical differentiation as trigger of similarity decrease
Using the first-principles calculations based on the coherent potential approximation, we study the electronic structure, magnetic moments and the bulk modulus of FeX alloys with IVB group elements ...(X = Si,Ge,Sn) in the Fe-rich concentration range (x = 0.0-0.25), which form a stability region of bcc-related phases. In agreement with experiment, our calculations reproduce well a peculiar non-monotonous behaviour of the bulk modulus in Fe-Si alloys with increasing Si concentration. Such a dependence is found for all bcc-related disordered and partially ordered Fe-Si phases A2, B2 and D03, which is in contrast with an earlier suggestion that the non-monotonous bulk modulus behaviour is related to partial ordering in Fe-Si. In addition, our results predict a similar behaviour in Fe-Ge and Fe-Sn alloys. It is shown that the observed behaviour of the bulk modulus is entirely related to the changes of the magnetic properties with chemical composition.
Biomimetics is an emerging field of science that adapts the working principles from nature to fine-tune the engineering design aspects to mimic biological structure and functions. The application ...mainly focuses on the development of medical implants for hard and soft tissue replacements. Additive manufacturing or 3D printing is an established processing norm with a superior resolution and control over process parameters than conventional methods and has allowed the incessant amalgamation of biomimetics into material manufacturing, thereby improving the adaptation of biomaterials and implants into the human body. The conventional manufacturing practices had design restrictions that prevented mimicking the natural architecture of human tissues into material manufacturing. However, with additive manufacturing, the material construction happens layer-by-layer over multiple axes simultaneously, thus enabling finer control over material placement, thereby overcoming the design challenge that prevented developing complex human architectures. This review substantiates the dexterity of additive manufacturing in utilizing biomimetics to 3D print ceramic, polymer, and metal implants with excellent resemblance to natural tissue. It also cites some clinical references of experimental and commercial approaches employing biomimetic 3D printing of implants.
The repair enzyme O
6
-methylguanine-DNA methyltransferase (MGMT) eliminates alkyl lesions that play the main anticancer role in alkylating chemotherapy. The inhibition of MGMT leads to increasing ...effectiveness of alkylating chemotherapy. In this study, new potential MGMT inhibitors were tested. It was found that some compounds demonstrate low cytotoxicity and high effectiveness in human cells in vitro
.
Chemical and strain-induced effective pair interactions of interstitial oxygen atoms in bcc Nb have been determined in supercell first-principles calculations using Vienna
ab initio simulation ...package (VASP). The strain-induced interactions are in reasonable agreement with those obtained earlier within a phenomenological microscopic Krivoglaz–Kanzaki–Khachaturyan model (KKKM). At the same time, the chemical interactions, which have been considered to be small in earlier theoretical considerations, turned out to be dominating at the first several coordination shells. The obtained interactions have been used in calculations of the concentration- and temperature-dependence of the internal friction Snoek peak. The theoretical results are found to be in good agreement with the existing experimental data.
▶
Ab initio calculations of chemical and strain-induced O–O pair interactions in bcc Nb. ▶ The Vienna
ab initio simulation package (VASP) was used. ▶ The chemical interactions dominate at the first several coordination shells. ▶ The obtained interactions used in calculations of the internal friction Snoek peak. ▶ The theoretical results are in good agreement with the existing experimental data.
Thermal expansion of materials is of fundamental practical relevance and arises from an interplay of several material properties. For nanocrystalline materials, accurate measurements of thermal ...expansion based on highprecision reference dilatometry allow inferring phenomena taking place at internal interfaces such as vacancy annihilation at grain boundaries. Here we report on measurements obtained for a severely deformed 316L austenitic steel, showing an anomaly in difference dilatometry curves which we attribute to the exceptionally high density of stacking faults. On the basis of ab intio simulations we report evidence that the peculiar magnetic state of the 316L austenitic steel causes stacking faults to expand more than the matrix. So far, the effect has only been observed for this particular austenitic steel but we expect that other magnetic materials could exhibit an even more pronounced anomaly.
Atomic ordering in Au-Pd alloys was studied by diffuse x-ray scattering and first-principles methods. Diffuse scattering was done of a single crystal of Au-48 at.% Pd that was aged at 703 K for 24 ...days. The weakly modulated short-range-order scattering exhibits diffuse maxima with an incommensurate wave vector, which can be related to a Fermi-surface nesting mechanism. From effective pair interaction parameters determined by the inverse Monte Carlo method, a one-dimensional long-period superstructure of the CH structure, LPS1, was found for AuPd. Concurrent electronic-structure calculations of the effective cluster interaction (ECI) parameters indicated the presence of another closely related superstructure, LPS2, at 0 K. At the same time, direct first-principles calculations of the total energies of the CH structure and further one-dimensional long-period superstructures predicted the stabilization of LPS4. Although the energy differences between these structures are small and a complex behavior of the effective interactions is expected due to the Fermi-surface nesting, experimental data and theoretical results both support the stabilization of a long-period superstructure of the CH structure for AuPd at 0 K. The ECI parameters determined by the screened generalized perturbation method also predicted a ground-state structure different from Au sub(7)Pd sub(5), previously obtained from cluster expansion calculations. Its energetic preference was confirmed by direct total-energy calculations.
The effect of composition on the antiphase boundary (APB) energy of Ni-based L1(2)-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The ...calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric gamma' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3d row. The elements from the left side of the 3d row increase the APB energy of the Ni-based L1(2)-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed.
The processes of hydrogen production from various types of fossil and renewable fuels are energy-intensive multi-route chemical reactions, and for their efficient implementation it is necessary to ...use selective and high-performance catalysts that combine high activity, thermal conductivity, and corrosion and thermal resistance. A general strategy for the design of catalytic systems for hydrogen production is outlined; it consists in the use of composite catalysts of the “metal nanoparticles/active oxide nanoparticles/structural oxide component/structured metal support” type; an approach for their directed synthesis is described. The structured metal support provides efficient heat removal or supply for exo- or endothermic reactions, possesses good hydrodynamic characteristics, and facilitates scale transition. The structural oxide component (aluminum oxide) provides thermal and corrosion resistance and a high specific surface area of the catalytic coating, as well as performing a protective function for the metal support. The active oxide component (mainly cerium–zirconium oxides) increases resistance to carbonization due to oxygen mobility and maintains a high dispersion of the active component due to its strong metal–support interaction. Metal nanoparticles 1–2 nm in size are involved in the activation of substrate molecules. FeCrAl alloy wire meshes, formed into cylindrical blocks of specified sizes, to be used as a heat-conducting substrate. By controlled annealing with the formation of a micron α-Al
2
O
3
layer and subsequent deposition of a η-Al
2
O
3
layer according to the Bayer method (through aluminum hydroxide), a structural layer of η-Al
2
O
3
with a “breathing” needle morphology was deposited onto the FeCrAl alloy surface; then the catalytic active component was deposited onto this layer by impregnation and/or deposition. The efficiency of the proposed strategy is shown for Rh/Ce
0.75
Zr
0.25
O
2 – δ
–η-Al
2
O
3
/FeCrAl catalysts for methane tri-reforming and Cu–CeO
2 – δ
/η-Al
2
O
3
/FeCrAl catalysts for dimethoxymethane steam reforming.
PDF
