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The compression-induced deformation mechanisms of boron carbide (B4C) have not been well understood due to its complex crystal structure. Here, we investigate the mechanical behaviors and deformation mechanisms of B4C under various compression conditions, using molecular dynamics simulations with a machine-learning force field. Two structural transitions in B4C under bulk compression are identified: the formation of new chains–icosahedra bonds, and icosahedral deconstruction. The former triggers the "pop-in" event observed in the nanoindentation experiments due to chain bending, while the latter facilitates icosahedral sliding and amorphization. Furthermore, the results reveal a mechanism involving an intermediate structure characterized by the development of new chains–icosahedra bonds across the entire model, followed by the amorphization process. This mechanism induced by increased stress in icosahedra due to the new chains–icosahedra bond formation plays an important role in significantly improving the strength and ductility of B4C. In contrast, B4C with free surfaces or nanopores exhibits a direct transformation from chain bending to icosahedral deconstruction without the intermediate structure formation, consequently reducing strength and ductility. However, this intermediate configuration is not stable and maintained only under stress, because structural recovery within non-amorphized regions occurs after amorphization under quasi-static compression with a relaxed stress state. This study provides a thorough understanding of the deformation behaviors and mechanisms of B4C. [ABSTRACT FROM AUTHOR]

Burning of high-energy condensed systems may include the formation of an intermediate structure (skeleton layer, which significantly affects the burning process). The influence of binder curing on the formation of such a structure is studied experimentally. It is demonstrated that the laws of the skeleton layer formation during binder curing depend to a large extent on the polymer structure. A specific role of the substance acting as a binder is determined. The basic features of modeling phenomena in the surface layer with and without the skeleton layer are presented. The possibility of predicting a number of characteristics of the burning process is demonstrated. [ABSTRACT FROM AUTHOR]

We define an order polarity to be a polarity |$(X,Y,{\operatorname{R}})$| where |$X$| and |$Y$| are partially ordered, and we define an extension polarity to be a triple |$(e_X,e_Y,{\operatorname{R}})$| such that |$e_X:P\to X$| and |$e_Y:P\to Y$| are poset extensions and |$(X,Y,{\operatorname{R}})$| is an order polarity. We define a hierarchy of increasingly strong coherence conditions for extension polarities, each equivalent to the existence of a preorder structure on |$X\cup Y$| such that the natural embeddings, |$\iota _X$| and |$\iota _Y$|⁠ , of |$X$| and |$Y$|⁠ , respectively, into |$X\cup Y$| preserve the order structures of |$X$| and |$Y$| in increasingly strict ways. We define a Galois polarity to be an extension polarity satisfying the strongest of these coherence conditions and where |$e_X$| and |$e_Y$| are meet- and join-extensions, respectively. We show that for such polarities the corresponding preorder on |$X\cup Y$| is unique. We define morphisms for polarities, providing the class of Galois polarities with the structure of a category, and we define an adjunction between this category and the category of |$\varDelta _1$| -completions and appropriate homomorphisms. [ABSTRACT FROM AUTHOR]

• A highly efficient quasi-periodic intermediate structure is introduced for Perovskite/Si tandem solar cells. • The proposed FC(3,3) intermediate structure provides 5% enhancement in conversion efficiency. • Optimized silver nanoparticles in the thin-film Si bottom cell provide effective light trapping. • Silver nanoparticles and the intermediate structure improved the conversion efficiency by 18.2%. In this study, an optimized quasi-periodic intermediate structure has been introduced to enhance the performance of perovskite/Si tandem solar cells. The proposed FC(3,3) intermediate structure consists of seven alternating layers of SiO 2 and TiO 2 with a total thickness of 1150 nm. The results obtained by the transfer matrix method and the finite difference time domain analysis are in good agreement and prove that the proposed intermediate structure enhances the conversion efficiency of the device by 5%. Also, the absorption efficiency of the bottom cell (thin-film Si layer) with reduced thickness to 5 μm has been improved by the implementation of Ag nanoparticles with optimized radius of 125 nm. Short current density enhancement of ~88% has been obtained for the thin-film Si cell after applying the proposed intermediate structure and Ag nanoparticles. [ABSTRACT FROM AUTHOR]

In this paper, the free join- and meet-completions of an L-ordered set are built and characterized. Then we give the definitions of Δ1-directed objects and intermediate structures, and show that the Δ1-directed object precisely is the Dedekind-MacNeille completion of the intermediate structure in the bounded L-lattice case. [ABSTRACT FROM AUTHOR]

High-performance but low-cost structural materials with nanoscale precipitations are vitally important for engineering applications in advanced industry systems. Thus far, the classical nucleation mechanism assumes a critical nucleus of a homogeneous composition up to a sharp boundary with a large energy barrier of nucleation. A fine dispersion of nanoscale precipitates often requires strong solute supersaturations with expensive alloying additions or otherwise deteriorated strength-ductility, weldability, and fabricability. The simultaneous satisfaction of all these mutually exclusive requirements is the longstanding issue for the design of advanced materials for structural applications. In this alloy design, we have adopted a revolutionary approach of ultra-strong iron-based alloys that have resolved all these key issues through non-classical nanoscale precipitations and multi-elemental partitioning. Such an alloy design strategy offers a unique approach to control nanoscale precipitates with low solute supersaturations. Fine precipitations so designed lead to the strong enhancement of both the precipitate-dislocation interactions and work-hardening capacity, resulting with a sharp increase of the yield strength (YS) to as high as 1500 MPa and tensile ductility up to 15%. Furthermore, our design assures outstanding fabricability together with superior post-weld properties through dense nanoscale reprecipitations (∼1024 m −3) in a well economical manner for production. The non-classical actions unfold brand new pathways for precipitation of various intermediate structures and chemistries with low energy barriers, especially useful for the design of sustainable and economical modern alloy systems. (a) The all-in-one ultra-strong iron-based alloy design through careful non-classical nanoscale multi-elemental partitioning and precipitate nucleation controls. Such a strategy turns the embrittling equilibrium precipitates at grain boundaries to fine dispersion of nanoscale multi-component precipitates, especially important in advanced alloy designs with low solute supersaturations. (b) The outstanding mechanical properties of our all-in-one ultra-strong iron-based alloys. (c) Our all-in-one ultra-strong alloys outperform other high-specific strength alloy systems such as Ti-6Al-4 V and Al 7075. A significant cost reduction of our alloys by more than 90% in comparison with the conventional ordered intermetallic strengthened steel alloys, Marage 200 for instance. (d) The superb post-weld mechanical performances with zero strength loss of our alloys due to nano-reprecipitations. [Display omitted] [ABSTRACT FROM AUTHOR]

Objective: By observing body surface temperature variation of the intermediate structures of the Lung (Fei) and Large Intestine (Dachang) exterior-interior relationship in asthmatic patients, to investigate the pathological response on the pathway of channels and to substantiate the objective existence of the intermediary structures. Methods: The study included 60 subjects meeting the bronchial asthma inclusion criteria (experimental group) and 60 healthy subjects (normal control group). ATIR-M301 infrared thermal imaging device was used for detecting body surface temperature of the subjects and collecting the infrared thermal images. The temperature values of the intermediate structures of Lung and Large Intestine exterior-interior relationship [throat, Quepen, elbow, nose, Lieque (LU 7), Pianli (LI 6)], control areas (0.2 cm lateral to the above structures) and Yintang (EX-HN 3) were measured on the infrared thermal image by infrared imaging system. Then, the above temperature values were compared and analyzed within and between two groups. Results: There were insignificant differences between the temperature on the left and right sides of the intermediate structures (Quepen, elbow, LU 7, LI 6) in normal control group ( P>0.05). Except for that of Quepen, there were insignifificant differences between the temperature of the intermediate structures and their corresponding control areas in normal control group ( P>0.05). In the experimental group, the temperature on the left and right sides of the intermediate structures (Quepen, elbow, LU 7, LI 6) showed statistically signifificant differences ( P<0.05 or P<0.01); the temperature difference between intermediate structure (throat, Quepen, elbow, nose, LI 6) and their respective control areas were also significant ( P<0.05 or P<0.01). The temperature of the intermediate structures (throat, Quepen, elbow, LU7, LI 6) between the experimental group and normal control group showed signifificant differences ( P<0.05 or P<0.01). Conclusions: This study is an initial step to validate the objective existence of Lung and Large Intestine exterior-interior relationship intermediate structures, as described in the Chinese classical medical literatures, through the functional imaging angle. The intermediate structures are the pathological reaction areas of the bronchial asthmatic patients. [ABSTRACT FROM AUTHOR]

Mycobacterium tuberculosis ( Mtb ) lacking functional homoserine transacetylase (HTA) is compromised in methionine biosynthesis, protein synthesis, and in the activity of multiple essential S -adenosyl-l-methionine-dependent enzymes. Additionally, deficient mutants are further disarmed by the toxic accumulation of lysine due to a redirection of the metabolic flux toward the lysine biosynthetic pathway. Studies with deletion mutants and crystallographic studies of the apoenzyme have, respectively, validated Mtb HTA as an essential enzyme and revealed a ligandable binding site. Seeking a mechanistic characterization of this enzyme, we report crucial structural details and comprehensive functional characterization of Mtb HTA. Crystallographic and mass spectral observation of the acetylated HTA intermediate and initial velocity studies were consistent with a ping-pong kinetic mechanism. Wild-type HTA and its site-directed mutants were kinetically characterized with a panel of natural and alternative substrates to understand substrate specificity and identify critical residues for catalysis. Titration experiments using fluorescence quenching showed that both substrates─acetyl-CoA and l-homoserine─engage in a strong and weak binding interaction with HTA. Additionally, substrate inhibition by acetyl-CoA and product inhibition by CoA and O -acetyl-l-homoserine were proposed to form the basis of a feedback regulation mechanism. By furnishing key mechanistic and structural information, these studies provide a foundation for structure-based design efforts around this attractive Mtb target.

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