Structural Position Research Articles

Structural Responsibility

I argue that current normative discussions of the responsibility for structural injustice are marred by an inadequate socio-theoretical view of structures and their functioning. This view reduces the relation between structures and actions to one of constraint: structures mainly inhibit transformative action; transformative action can only come from outside structures. I offer an alternative view of structures and their functioning that, drawing on and extending Sewell’s and Haslanger’s conceptions of structures and Arendt’s view of action, shows that actions are structurally and publicly constituted—they acquire social meaning in relation to structures, in a process of public interpretation—which is why they can transform the structures where they originate. Responsibility to dismantle unjust structures should then be understood as “structural responsibility”: responsibility to act from one’s structural position in ways that can disrupt the mechanisms of structural maintenance.

Source–Sink Structural Coupling Within Forest-Clustered Landscapes Drives Headstream Quality Dynamics in Mountainous Sub-Watersheds: A Case Study in Chongqing, China

Water environment quality is profoundly driven by a series of landscape characteristics. However, current knowledge is limited to the independent response of water quality to single landscape elements; this has led to poor knowledge of the potential role of structural coupling within landscapes in driving water quality changes, especially in those agroforestry-mixed mountainous watersheds with highly embedded forest-clustered landscapes and abundant headstreams. Given this fact, this study aims to evaluate whether and how the source–sink coupling structure of forest-clustered landscapes systematically drives headstream quality dynamics. We first systematically assessed the association pattern of source and sink structures within forest-clustered landscapes, and then innovatively proposed and constructed a functional framework of source–sink coupling structure of landscapes across 112 agroforestry-mixed mountainous sub-watersheds in Chongqing, China. On this basis, we further evaluated the driving pattern and predictive performance of the source–sink coupling structure of landscapes behind headstream quality dynamics. We report three findings: (1) headstream quality varied across agroforestry-mixed sub-watersheds, mapping out the source–sink structures and functions of landscapes; (2) there was significant functional coordination between source–sink structures of the forest-clustered landscapes, which significantly drove headstream quality dynamics; (3) the structural positioning and differences of the forest-clustered landscapes along the multivariate functional axes directly corresponded to and predicted headstream quality status. These findings together highlight a key logic that the response of water quality dynamics to landscapes is essentially that to the functional coupling between the source–sink structures of landscapes, rather than the simple combination of a single landscape contribution. This is the first study on the landscape–runoff association from the perspective of source–sink structural coupling, which helps to deepen understanding of the correlation mechanism between water dynamics and landscape systems, and provides a new functional dimension to the development of future landscape ecological management strategies from a local to a global scale.

Defect Passivation of Mn2+-Doped CsPbX3(X=Cl,Br) Perovskite Nanocrystals as Electrocatalyst for Overall Water Splitting.

Mn doping has been used to improve the physical chemistry of lead halide perovskite nanocrystals such as CsPbX3, where X is a halogen ion. In this paper, a two-phase method for Mn-doped CsPbX3 nanosheets (where X=Br, Cl), namely water-hexane system, is reported. Compared to conventional catalyst arrays, the band gap of CsPbBr3 nanocrystalline is easily tuned, the carrier diffusion distance is remote, the band edge position of the band structure is favorable for a wide range of electrocatalytic redox reactions, and the catalytic active site is maximally exposed, providing a larger electrolyte contact area. The porous hierarchical structure also accelerates the release of hydrogen bubbles. The results showed that the optimized Mn : CsPbBr3 catalyst exhibited excellent electrolytic performance of aquatic hydrogen in alkaline electrolyte (1 mol/L KOH). The overpotentials of the oxygen evolution reaction (OER) at the current densities of 10 and 100 mA cm-2 are only 114.4 and 505.4 mV, respectively, with a Tafel slope of 43 mV dec-1. At a current density of 10 mA cm-2, the excess potential required for the hydrogen evolution reaction (HER) is 158.6 mV and it exhibits excellent electrochemical stability. The Mn : CsPbBr3 nanocrystalline consists of two electrodes for hydrolysis of water, requiring only a voltage of 1.45 V. This provides implications for the optimization of electrocatalysts in alkaline electrolytes with the aim of developing next generation 2D electrocatalysts for overall water splitting.

The Sacred of Today?

Abstract Even if the sacred is a classical concept in religious studies and sociology, relatively little is known of its current empirical subjective varieties. This article explores what people today consider sacred at the intersection of religion and nonreligion. Our data (N=6938) was collected with face-to-face interviews (N=1965) and from an internet panel (N=4313) in Finland. We present both an overall picture on what people consider sacred and the results of exploring the effect of religiousness, political stance, and social structural positions. Respondents of both moderately religious and nonreligious groups tend to hold health, love, and close ones sacred. Our findings challenge a linear, dualistic view of religious versus nonreligious and show that sacred exceeds religious boundaries and is experienced by religious and nonreligious people alike, but in various ways. The concept of sacred can be used to detect the inner diversity of both religious and nonreligious identities.

25 years field test history and fatigue damage analysis for a scrapped ladle crane

Fatigue performances of ladle cranes will gradually decrease with the increase of service years. The service history and the fatigue damage of a scrapped ladle crane were investigated and analyzed in this paper. The test history of the ladle crane was collected and concluded, and the statistical parameters of lifting capacity and the crack condition during service were determined. The last comprehensive field test before scrapping the ladle crane was introduced in detail and the damage evolution was analyzed. The geometry measurement showed that the main girders’ stiffness had changed obviously. The stress test of the crack-prone positions of the metal structure revealed their remaining bearing capacity and the damage evolution characteristics. Further analysis proved that the static stiffness of the main girder has a closer relationship with damage deterioration. Some material property inspections were carried out for samples cut from the scrapped crane’s main girder, which were of the load-carrying part and the non-load-carrying part respectively. Results showed that the elastic modulus and hardness of the materials decreased evidently after service, while other mechanical properties did not change significantly. This study will provide useful references for further understanding of the fatigue characteristics and evolution behaviors of ladle cranes.

Research on Digital Construction Technology for Special-Shaped Shell Pipe Structures

The aesthetic appeal of special-shaped shell pipe structures makes them highly favored by architects and holds promising prospects for various applications. In the detailed design stage, NURBS curves should be divided into multiple continuous arcs due to the limitations of current steel structure fabrication equipment, which can only accommodate pipes with equal-curvature bends. However, the traditional manual fitting methods suffer from several issues including low efficiency, undercutting at the interface, poor smoothness of curves, and lack of control over tolerances. Furthermore, the weaker out-of-plane stiffness and utilization of bending arc pipe sections pose significant challenges in terms of spatial positioning and installation accuracy that need to be addressed. The study focuses on addressing these challenges by investigating digital construction technology for special-shaped shell pipe structures and developing a parametric algorithm that enables automatic fitting of spatial NURBS curves into multiple arcs, thereby achieving seamless curve fitting. A post-processing program was developed to enable the parametric generation of fabrication and installation information for structural members, which can be seamlessly integrated into the BIM database. Finally, structural position control technology is proposed to improve assembly efficiency and ensure consistency between the completed construction state and the design shape. The above digital construction technology has been applied in projects such as the Haihua Island International Conference Center. It can provide complete technical solutions for modeling of special-shaped shell pipe structures, including establishment of a member information database, fabrication at the workshop and installation on site, construction organization management, as well as installation accuracy control.

Shock petrographic and numerical modeling constraints on the morphology and size of the Morokweng impact structure, South Africa

AbstractThe 369 m deep M4 drill hole, located ~18 km NNW of the center of the 146 Ma Morokweng impact structure (MIS), intersects shocked Archean granitoid gneisses and subsidiary dolerite intrusions that are cut by faults, cataclasites and mm‐ to m‐wide suevitic and pseudotachylitic breccia dikes. The shock features in quartz in the gneisses and breccia dikes include decorated planar deformation features (PDFs), planar fractures, feather features, and toasting. Other minerals show features that may be shock‐related, such as multiple sets of planar features and alternate twin ladder structures in feldspars, kink bands in biotite, and planar features in titanite, apatite, and zircon; however, these are variably annealed and/or overprinted by hydrothermal alteration effects, and confirmation of their origin awaits further study. Universal Stage measurements of PDF sets in quartz from 12 gneissic target rocks and from lithic and mineral clasts in three suevitic and three pseudotachylitic breccia dikes reveal four dominant sets: (0001), {}, {} and {}. Based on these observations, the average peak shock pressure in these rocks is estimated at ≤16 GPa, which supports the original proximity (within one transient cavity radius) of these rocks to the point of impact. No discernible depth‐dependent shock attenuation was noted in the core. These shock levels and the elevated structural position of the rocks in the M4 core relative to the impact melt sheet intersected in drill holes closer to the center of the MIS suggest that the M4 lithologies represent part of the parautochthonous peak ring volume that subsequently experienced 1.5–2 km of post‐impact erosion before it was buried beneath younger sediments. Numerical modeling using the iSALE‐2D code suggests that the original Morokweng crater had a rim‐to‐rim diameter of between 70 and 80 km, and that the rocks in the M4 core were originally located at a depth of 7–8 km and a radial distance of 8–9 km from the point of impact.

Research on design method of inertial interference self-compensating balance

This paper proposes a design method for a wind tunnel balance that can compensate for inertial interference, aiming to address the issue of short effective time in pulse wind tunnels. This method also tackles the problem of the force measuring system’s inability to dampen quickly and the coupling of inertia vibration signals with the output signal of the balance, which affects aerodynamic measurement accuracy. The method calculates vibration displacement at specific positions of the balance structure using its acceleration, constructs compensation signals based on the relationship between these displacements and balance outputs, and then superimposes them onto the balance signal for compensation. The effectiveness of this compensation method is evaluated through finite element simulations and wind tunnel tests. The results demonstrate that by compensating for the balance signal, there is a significant reduction in the amplitude of the inertia vibration signal, leading to an enhancement in the repeatability accuracy of the measurement. This compensation method effectively solves under-compensation or over-compensation issues when accelerometers are placed on complex models with various modes, where obtaining accurate compensation signals becomes challenging. It provides a new technical approach to improve aerodynamic measurement accuracy by mitigating inertial interference during pulse wind tunnel testing.

Maximising the potential of National Cancer Mission Hub-like structures: A SWOT analysis approach

Abstract Cancer is a significant and urgent concern in public health, particularly in the context of an aging population like in Europe. It is estimated that new cancer cases will increase by 21% by 2040 in Europe. With the ambition of improving the lives of 3 million people by 2030, the European Commission launched 2 major initiatives: Europe’s Beating Cancer Plan (EBCP) and the Mission on Cancer (MoC). The EBCP is a policy-driven initiative aimed at supporting Member States in addressing the whole cancer continuum. It is supported by the MoC, a research driven initiative. Member States are implementing the EBCP and MoC in a way that fits their national contexts. This can take different forms, such as ‘cancer hub,’ ‘mirror group,’ or other similar structures. The role of these entities can vary, ranging from purely coordinating activities to involving more technical work. We performed a SWOT (Strengths, Weaknesses, Opportunities, and Threats) analysis with different national mission-hub-like (NCMH-like) structures to explore their strategic positioning. We collected results from 6 countries (Belgium, Italy, the Netherlands, Portugal, Poland, and Sweden) as part of the EU project ECHoS on setting NCMHs. Participants perceived that formal government endorsement, existing stakeholder mapping, and good stakeholder engagement as strengths for the structure. Whilst, they identified overlap with other ongoing initiatives and low stakeholder engagement as weaknesses that need to be addressed, the future of existing structures could be threatened by financial and human resources as well changing political landscape. National, regional alignment and the leverage of EU funding were recurrent opportunities to build on. Ultimately, NCMH-like structures can be leveraged to achieve national and European alignment on cancer initiatives, if they succeed in building a sustainable financial and governance structure. Key messages • National Cancer Mission Hub-like structures can build on existing initiatives to support the implementation of EU cancer initiatives if they achieve sustainable financial and governance structures. • SWOT framework is a good tool for a comprehensive overview of the strategic positioning of National Cancer Mission Hub-like structures in different European countries.

Adversarial robustness improvement for X-ray bone segmentation using synthetic data created from computed tomography scans

Deep learning-based image analysis offers great potential in clinical practice. However, it faces mainly two challenges: scarcity of large-scale annotated clinical data for training and susceptibility to adversarial data in inference. As an example, an artificial intelligence (AI) system could check patient positioning, by segmenting and evaluating relative positions of anatomical structures in medical images. Nevertheless, data to train such AI system might be highly imbalanced with mostly well-positioned images being available. Thus, we propose the use of synthetic X-ray images and annotation masks forward projected from 3D photon-counting CT volumes to create realistic non-optimally positioned X-ray images for training. An open-source model (TotalSegmentator) was used to annotate the clavicles in 3D CT volumes. We evaluated model robustness with respect to the internal (simulated) patient rotation α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document} on real-data-trained models and real&synthetic-data-trained models. Our results showed that real&synthetic- data-trained models have Dice score percentage improvements of 3% to 15% across different α\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\alpha$$\\end{document} groups compared to the real-data-trained model. Therefore, we demonstrated that synthetic data could be supplementary used to train and enrich heavily underrepresented conditions to increase model robustness.

Crystal structure of [Ni(OH2)6]Cl2·(18-crown-6)2·2H2O

The crystal structure of the title compound, hexaaquanickel(II) dichloride–1,4,7,10,13,16-hexaoxacyclooctadecane–water (1/2/2), [Ni(H2O)6]Cl2·2C12H24O6·2H2O, is reported. The asymmetric unit contains half of the Ni(OH2)6 moiety with a formula of C12H32ClNi0.50O10 at 105 K and triclinic (P 1) symmetry. The [Ni(OH2)6]2+ cation has close to ideal octahedral geometry with O—Ni—O bond angles that are within 3° of idealized values. The supramolecular structure includes hydrogen bonding between the water ligands, 18-crown-6 molecules, Cl− anions, and co-crystallized water solvent. Two crown ether molecules flank the [Ni(OH2)6]2+ molecule at the axial positions in a sandwich-like structure. The relatively symmetric hydrogen-bonding network is enabled by small Cl− counter-ions and likely influences the more idealized octahedral geometry of [Ni(OH2)6]2+.

Highly Efficient Sunlight‐Driven Photocatalytic Activity of Cu‐Doped BiOBr/g‐C3N4 Nanocomposite via Z‐Scheme Design

AbstractPharmaceutical pollutants introduce highly intricate compounds into the environment due to extensive structural and functional alterations resulting in adverse health effects on organisms. Herein, a novel nanocomposite is designed comprising Cu‐doped BiOBr nanoflakes and g‐C3N4 to form a dual absorber based on the organic‐inorganic electronic interface for photocatalytic degradation of tetracycline (TC). With incorporating Cu in BiOBr and compositing with g‐C3N4, the band gap decreased from 2.74 eV to 2.36 eV for BiOBr:Cu/g‐C3N4, and also light harvesting ability increased. The investigation into the degradation rate considered factors such as pH, TC concentration, photocatalyst dosage, and irradiation time, resulting in a TC degradation efficiency of 98 % within 60 min. In the prepared nanocomposite, photo‐generated electrons of BiOBr can recombine via Cu atoms as a mediator with holes in the valence band of g‐C3N4 due to their band structure position which leads to improved electron/hole separation and enhanced photocatalytic activity. The predominant active species involved in the degradation process were found to be superoxide radicals. Additionally, the photocatalyst exhibited excellent stability, retaining 88 % of its photocatalytic activity after four cycles.

Submicron Embedded Air/GaN Diffraction Gratings for Photonic Applications

AbstractThe integration of photonic elements with nitride optoelectronic structures allows control of emitted light properties, which is advantageous for achieving, e.g., a single wavelength lasing. Positioning of the photonic structures on the top surface of GaN‐based devices is problematic, in particular, for deposition of a metal contact to p‐type top layer. In this work, custom‐shaped submicron air channels arranged periodically 150 nm below the sample surface, forming an air/GaN diffraction grating embedded within a volume of the structure is proposed and fabricated. The fabrication process includes selective area Si ion implantation, GaN regrowth using plasma‐assisted molecular beam epitaxy, ultra‐high‐pressure annealing for efficient electrical activation of implanted Si without diffusion, and electrochemical etching for the removal of selectively doped material. Embedded air/GaN diffraction gratings with periodicity of 460 and 631 nm are shown. Width of air channels ranges from 46 to 320 nm. Angle and polarization resolved reflectivity measurements combined with theoretical modeling confirm the designed optical performance of the embedded diffraction gratings in the GaN volume. The presented design and fabrication of custom‐shaped, fully integrated photonic structures buried below the surface paves the way for novel type constructions of optoelectronic devices, such as compact distributed feedback laser diodes

Urbanism, discourse and class in Amdo Tibet: analysis of five Tibetan fictions as ethnography

ABSTRACT This article examines how Tibetans in the cultural region of Amdo experienced urbanization as a social process when it began intensifying in the region in the early 2000s. By using five pieces of Tibetan fiction as ethnographic data, this article looks at the process of urbanization from the angle of class, analyzing the formation of the urban Tibetan class in relation to social spaces in cities, and its structural position in society. This article further explores the subjectivity of urban Tibetans through the discourse and quoted speech of characters in fiction. In doing so, the article demonstrates that urbanization is occurring as a social process, and Lishaypa, or government workers, react to urbanization intensively as a class. This results in a new social demarcation being established among Tibetans, one based on urban residence and in which urban residents place themselves above rural villagers.

‘Rhythmite’, Ca29(SiO4)8Cl26, an Anthropogenic Phase from the Chelyabinsk Coal Basin (Ural, Russia) with a Complex Modular Structure Related to α-Ca3SiO4Cl2 (‘Albovite’): Crystal Structure, Raman Spectra, and Thermal Expansion

‘Rhythmite’, Ca29(SiO4)8Cl26, an anthropogenic calcium chloride silicate from the Chelyabinsk coal basin (South Ural, Russia), was investigated using chemical microprobe analysis, in situ single-crystal X-ray diffraction analysis (27–727 °C), and Raman spectroscopy. ‘Rhythmite’ is orthorhombic, Pnma: a = 17.0749(6), b = 15.1029(5), c = 13.2907(4) Å, and V = 3427.42(18) Å3 (R1 = 0.045). The crystal structure of ‘rhythmite’ consists of a porous framework formed by Ca-O bonds and SiO4 tetrahedra with additional Ca2+ cations and Cl− anions in the structure interstices. The framework is built up from multinuclear [Ca15(SiO4)4]14+ fundamental building blocks (FBBs) cut from the crystal structure of α-Ca3SiO4Cl2 (‘albovite’). The FBBs are linked by sharing common Ca atoms to form a network with an overall pcu topology. The empirical chemical formula was calculated as Ca29.02(Si7.89Al0.05P0.05)Ʃ7.99O32Cl26 (on the basis of Cl + O = 58). ‘Rhythmite’ is stable up to 627 °C and expands slightly anisotropically (αmax/αmin = 1.40) in the ab and bc planes and almost isotropically in the ac plane (α33/α11 = 1.02) with the following thermal expansion coefficients (×106 °C−1): α11 = 14.6(1), α22 = 20.5(4), α33 = 15.0(3), and αV = 50.1(6) (room temperature). During expansion, the silicate tetrahedra remain relatively rigid with average bond length changes of less than 0.5%. A structural complexity analysis indicates that ‘rhythmite’ is complex, with IG,total = 920.313 (bits/u.c.), which significantly exceeds the average value of structural complexity for silicates and is caused by the modular framework construction and the presence of a large number of independent positions in the crystal structure.

On the humanization of VHHs: Prospective case studies, experimental and computational characterization of structural determinants for functionality.

The humanization of camelid-derived variable domain heavy chain antibodies (VHHs) poses challenges including immunogenicity, stability, and potential reduction of affinity. Critical to this process are complementarity-determining regions (CDRs), Vernier and Hallmark residues, shaping the three-dimensional fold and influencing VHH structure and function. Additionally, the presence of non-canonical disulfide bonds further contributes to conformational stability and antigen binding. In this study, we systematically humanized two camelid-derived VHHs targeting the natural cytotoxicity receptor NKp30. Key structural positions in Vernier and Hallmark regions were exchanged with residues from the most similar human germline sequences. The resulting variants were characterized for binding affinities, yield, and purity. Structural binding modes were elucidated through crystal structure determination and AlphaFold2 predictions, providing insights into differences in binding affinity. Comparative structural and molecular dynamics characterizations of selected variants were performed to rationalize their functional properties and elucidate the role of specific sequence motifs in antigen binding. Furthermore, systematic analyses of next-generation sequencing (NGS) and Protein Data Bank (PDB) data was conducted, shedding light on the functional significance of Hallmark motifs and non-canonical disulfide bonds in VHHs in general. Overall, this study provides valuable insights into the structural determinants governing the functional properties of VHHs, offering a roadmap for their rational design, humanization, and optimization for therapeutic applications.

Two conserved arginine residues facilitate C-S bond cleavage and persulfide transfer in Suf family cysteine desulfurases.

Under conditions of oxidative stress or iron starvation, iron-sulfur cluster biogenesis in E. coli is initiated by the cysteine desulfurase, SufS, via the SUF pathway. SufS is a type II cysteine desulfurase that catalyzes the PLP-dependent breakage of an L-cysteine C-S bond to generate L-alanine and a covalent active site persulfide as products. The persulfide is transferred from SufS to SufE and then to the SufBC 2 D complex, which utilizes it in iron-sulfur cluster biogenesis. Several lines of evidence suggest two conserved arginine residues that line the solvent side of the SufS active site could be important for function. To investigate the mechanistic roles of R56 and R359, the residues were substituted using site-directed mutagenesis to obtain R56A/K and R359A/K SufS variants. Steady state kinetics indicated R56 and R359 have moderate defects in the desulfurase half reaction but major defects in the transpersulfurase step. Fluorescence polarization binding assays showed that the loss of activity was not due to a defect in forming the SufS/SufE complex. Structural characterization of R56A SufS shows loss of electron density for the α3-α4 loop at the R56/G57 positions, consistent with a requirement of R56 for proper loop conformation. The structure of R359A SufS exhibits a conformational change in the α3-α4 loop allowing R56 to enter the active site and mimics the residue's position in the PLP-cysteine aldimine structure. Taken together, the kinetic, binding, and structural data support a mechanism where R359 plays a role in linking SufS catalysis with modulation of the α3-α4 loop to promote a close-approach interaction of SufS and SufE conducive to persulfide transfer.

In Vitro Evaluation of New 5-Nitroindazolin-3-one Derivatives as Promising Agents against Trypanosoma cruzi

Chagas disease is a prevalent health problem in Latin America which has received insufficient attention worldwide. Current treatments for this disease, benznidazole and nifurtimox, have limited efficacy and may cause side effects. A recent study proposed investigating a wide range of nitroindazole and indazolone derivatives as feasible treatments. Therefore, it is proposed that adding a nitro group at the 5-position of the indazole and indazolone structure could enhance trypanocidal activity by inducing oxidative stress through activation of the nitro group by NTRs (nitroreductases). The study results indicate that the nitro group advances free radical production, as confirmed by several analyses. Compound 5a (5-nitro-2-picolyl-indazolin-3-one) shows the most favorable trypanocidal activity (1.1 ± 0.3 µM in epimastigotes and 5.4 ± 1.0 µM in trypomastigotes), with a selectivity index superior to nifurtimox. Analysis of the mechanism of action indicated that the nitro group at the 5-position of the indazole ring induces the generation of reactive oxygen species (ROS), which causes apoptosis in the parasites. Computational docking studies reveal how the compounds interact with critical residues of the NTR and FMNH2 (flavin mononucleotide reduced) in the binding site, which is also present in active ligands. The lipophilicity of the studied series was shown to influence their activity, and the nitro group was found to play a crucial role in generating free radicals. Further investigations are needed of derivatives with comparable lipophilic characteristics and the location of the nitro group in different positions of the base structure.

New Polymorphic Varieties of Boron Nitride with Diamond-Like TA-Type Phases

In this work, a theoretical study of new polymorphic varieties of boron nitride, which have diamond-like structures with boron and nitrogen atoms in equivalent structural positions, was carried out. The model construction of new phases of boron nitride was performed in the process of crosslinking precursor nanostructures. Single-walled boron nitride nanotubes with chirality indices (3;0), (4;0), and (6;0) were chosen as precursors for the model construction of diamond-like phases. Using the density functional theory method in the generalized gradient approximation, the possibility of stable existence of three new structural varieties of boron nitride with a diamond-like structure was established: BN-TA4, BN-TA5, BN-TA6. The structure of the BN-TA7 diamond-like phase turned out to be unstable and, in the process of geometric optimization, was transformed into the initial structure, a boron nitride nanotube (6;0). As a structural characteristic, the bulk density of the new polymorphs was determined, which is in the range from 2.613 to 3.0836 g/cm3. The sublimation energy of new polymorphic varieties ranges from 17.16 to 17.63 eV/(BN). The value of the band gap near the Fermi energy varies from 5.37 to 5.74 eV.

Arc-shaped faults of the Golden Valley gold field of the Midlands greenstone belt in Zimbabwe and their role in localization of the ore mineralization

A detailed analysis of the geological and structural position of gold and tungsten deposits in the Golden Valley ore field of the Midlands greenstone belt has demonstrated that most of the gold deposits are controlled by arc-shaped faults that taken together form a semicircular structure with dimensions of 9×11 km. In addition, these arc-shaped faults apparently control the distribution of dikes of porphyry granites, that are associated with gold ore veins. Quartz-scheelite and gold-quartz-scheelite veins together form a second, less distinct, semicircular structure comparable in size to the first one. The highlighted structures were formed around isometric Late Archean granodiorite massifs, Lion Hill and Whitewaters, respectively, and are partially overlapped in space. The magnetic fi ld, also, reveals one additional arc-shaped fault and a series of linear faults. This arc-shaped fault, in conjunction with its associated branching veins of the Golden Valley and Patchway deposits, represents the so-called “horsetail” structure that is characteristic for gold deposits. This fault that is the most favorable structure for localization of gold ore veins, as well as the proposed junctions of arc-shaped and linear faults of radial and northwestern orientations, are considered as the most promising areas where geological prospecting is recommended.