Basic Structural Units Research Articles

Structural investigation of lithium borate glasses by Raman spectroscopy: Quantitative evaluation of structural units and its correlation with density

Lithium borate glass is a widely studied system, mainly due to its good ionic conductivity, thermal conductivity and thermoluminescence properties. The properties of lithium borate glass are determined by its structure, and the change of microstructure unit has great influence on its properties. In this work, the xLi2O⋅(1-x) B2O3 (0.1 ≤ x ≤ 0.48) glass was studied by Raman spectroscopy combined with peaks fitting and density analysis. Through quantitative analysis of Raman spectrum, the change in trend of each structural unit as well as the change of the tetracoordinated boron content (N4) were obtained with the increase of Li2O content. Especially, a more detailed assignment and general transformation mechanism of structural units were presented, and the common inflection points of properties (mass density, molar volume, etc.) and structural units content changes were found. The correlation between the properties (mass density, atomic density and molar volume) and the basic structural units (BØ3, BØ2O− and BØ4−) of the lithium borate glass was established by the genetic function approximation algorithm (GFA). The study on the structural units in xLi2O⋅(1-x) B2O3 (0 ≤ x ≤ 0.48) glass network and the mutual transformation mechanism between each structural unit is helpful to explore the effects on macroscopic properties as the structural units change.

CATAD: exploring topologically associating domains from an insight of core-attachment structure.

Identifying topologically associating domains (TADs), which are considered as the basic units of chromosome structure and function, can facilitate the exploration of the 3D-structure of chromosomes. Methods have been proposed to identify TADs by detecting the boundaries of TADs or identifying the closely interacted regions as TADs, while the possible inner structure of TADs is seldom investigated. In this study, we assume that a TAD is composed of a core and its surrounding attachments, and propose a method, named CATAD, to identify TADs based on the core-attachment structure model. In CATAD, the cores of TADs are identified based on the local density and cosine similarity, and the surrounding attachments are determined based on boundary insulation. CATAD was applied to the Hi-C data of two human cell lines and two mouse cell lines, and the results show that the boundaries of TADs identified by CATAD are significantly enriched by structural proteins, histone modifications, transcription start sites and enzymes. Furthermore, CATAD outperforms other methods in many cases, in terms of the average peak, boundary tagged ratio and fold change. In addition, CATAD is robust and rarely affected by the different resolutions of Hi-C matrices. Conclusively, identifying TADs based on the core-attachment structure is useful, which may inspire researchers to explore TADs from the angles of possible spatial structures and formation process.

On-line monitoring of carbon nanostructure and soot reactivity in engine exhaust by dual-pulse laser-induced incandescence

In previous work, we introduced the dual-pulse two-color time-resolved laser-induced incandescence (DP-2C-TiRe-LII), which is possibly suitable for on-line monitoring of the nanostructural topology of inhomogeneous soot particle ensembles in transient flows. The method relies on the quantitative relationship between the size of the basic structural units (BSUs) embedded within primary particles and the ratio of the refractive-index function for absorption at two wavelengths E(m,λUV)/E(m,λNIR). As the size of BSUs increases, the band gap energy for an electronic π→π* transition becomes narrower increasing the wavelength for absorption and, hence, forcing E(m,λUV)/E(m,λNIR) to decrease. Once quantitative correlations between the carbon nanostructure, i.e., size of the BSUs, and a structure-associated particle property are available, its on-line monitoring becomes accessible through monitoring of E(m,λUV)/E(m,λNIR). The objective of this paper is to provide the proof-of-concept for on-line monitoring of an exemplary structure-associated particle property, viz. soot reactivity against oxidation, in an application from practice. For this, DP-2C-TiRe-LII is employed downstream of a gasoline direct injection (GDI) engine running under steady-state and transient operating conditions. Intrusive particle sampling in combination with an analytical toolbox comprising high-resolution transmission electron microscopy (HRTEM), pattern recognition methods, elemental analysis (EA), and thermogravimetric analysis (TGA) was applied to validate the results from DP-2C-TiRe-LII. Excellent agreement is found between particle properties derived via ex situ and in situ diagnostics. Moreover, the transformation of the time series of E(m,λUV)/E(m,λNIR) into probability density distributions seems to represent the BSU size distributions of the investigated soot particle ensembles. Likewise, soot reactivity is reflected in the distributions of E(m,λUV)/E(m,λNIR).

Functionalization of biomimetic mineralized collagen for bone tissue engineering.

Mineralized collagen (MC) is the basic unit of bone structure and function and is the main component of the extracellular matrix (ECM) in bone tissue. In the biomimetic method, MC with different nanostructures of neo-bone have been constructed. Among these, extra-fibrous MC has been approved by regulatory agencies and applied in clinical practice to play an active role in bone defect repair. However, in the complex microenvironment of bone defects, such as in blood supply disorders and infections, MC is unable to effectively perform its pro-osteogenic activities and needs to be functionalized to include osteogenesis and the enhancement of angiogenesis, anti-infection, and immunomodulation. This article aimed to discuss the preparation and biological performance of MC with different nanostructures in detail, and summarize its functionalization strategy. Then we describe the recent advances in the osteo-inductive properties and multifunctional coordination of MC. Finally, the latest research progress of functionalized biomimetic MC, along with the development challenges and future trends, are discussed. This paper provides a theoretical basis and advanced design philosophy for bone tissue engineering in different bone microenvironments.

Calcium-doped magnetic humic acid nano particles for the efficient removal of heavy metals from wastewater: the role of Ca

ABSTRACT Ca doping is an effective method for improving the adsorption capacity of HA–Fe aggregates and regulating their structures. Understanding the structural characteristics of Ca–HA–Fe aggregates can help explore their microscopic adsorption effect on heavy metals. However, the heterogeneity of HA results in an incomplete understanding of the structural characteristics of the ternary system of Ca–HA–Fe aggregates and adsorption of the quaternary system of Ca–HA–Fe–Pb/Cu/Cd. In this study, interactions between Ca–HA–Fe ternary and Ca–HA–Fe–Pb/Cu/Cd quaternary systems were discussed from a molecular perspective. The structures of the basic structural units of HA were identified. Density functional theory (DFT) was employed to calculate the stable states of basic structural units of HA and Ca2+. The results showed that hydroxyl and carboxyl groups exhibited the highest capacity to bind with Ca2+. The interactions among Ca, HA, and Fe led to the formation of network aggregates. The binding energies of functional groups for heavy metals and the feasibility of ion exchange were calculated by the method of experiment and DFT. According to the contribution of functional group complexation and ion exchange, the ion exchange values for Pb2+, Cu2+, and Cd2+ were 66.71%, 62.87%, and 60.79%, respectively, which indicated that Ca2+ ion exchange showed considerable potential in enhancing the adsorption capacity of heavy metals.

CONVERSION OF PROPANE TO FORMALDEHYDE ON IRON PHOSPHATE

Phosphates represent diverse complex systems, whose basic structural unit is tetrahedron. They are widely applied as catalysts, carriers of catalytic active substances, adsorbents and ion exchangers. Phosphoric acid and phosphates act as catalyst for reactions of alkylation, cracking, izomerization, polymerization, hydrogenation and dehydrogenation. Phosphates of some metals promote oxidation of normal alkanes with derivation of aldehydes, acids, spirits and maleic anhydride.
 The process of propane and propylene oxidation on iron phosphate is investigated, as well as the influence of such factors as temperature, contact time of the reacting mixture with the catalyst t, the ratio of oxygen and hydrocarbon concentration in a mixture, and the influence of hydrogen concentration on the given process is shown.
 It is demonstrated that the optimum conditions for the realization of propane oxidation process is the temperature of 973 K and t = 0.17 s. It is established that with excess propane in the reaction mixture propylene is the predecessor of formaldehyde. On the contrary, at small concentration of propane in the mixture formaldehyde will be derived immediately from propane. The schemes of propane and propylene oxidation in formaldehyde are offered.
 Keywords: catalyst; oxidatio; рhosphates; propane; propylene; formaldehyde.

Allyl halide induced electrochemical degradation of lignin into double-bonded phenolic monomers

Lignin is one of the major macromolecule in nature that contains an aromatic ring structure, and also a potential source of high-value products such as biofuels and chemicals. However, Lignin is a kind of complex heterogeneous polymer which can produce many degradation products during processing or treatment. These degradation products are difficult to separate, making it challenging to use lignin directly for high-value applications. This study proposes an electrocatalytic method to degrade lignin by using allyl halides to induce double-bonded phenolic monomers, while avoiding separation. In an alkaline solution, the three basic structural units (G, S, and H) of lignin were transformed into phenolic monomers by introducing allyl halide, which could effectively expand lignin application space. This reaction was achieved using a Pb/PbO2 electrode as the anode and copper as the cathode. It was further confirmed that double-bonded phenolic monomers were obtained by degradation. 3-allylbromide has more active allyl radicals and significantly higher product yields than 3-allylchloride. The yields of 4-allyl-2-methoxyphenol, 4-allyl-2,6-dimethoxyphenol and 2-allylphenol could reach 17.21 g/kg-lignin, 7.75 g/kg-lignin, and 0.67 g/kg-lignin respectively. These mixed double-bond monomers can be used as monomer materials for in-situ polymerization without further separation, which lays the foundation for high value-added applications of lignin.

A Neoteric View of sp2 Amorphous Carbon.

Presented is a concentrated synopsis of facilities of empirical and virtual analytics that, once applied, have provided a fully new vision of sp2 amorphous carbons. This study proved that the solids are multilevel structures, started with the first-level basic structural units (BSUs) and accomplished as macroscopic agglomerates of globular structures, consisting, in its turn, of stacked BSUs. BSUs present necklaced graphene molecules, size, and shape of which are governed by the relevant graphene domains while chemical composition in addition to basic carbon is controlled with heteroatoms of the necklaces. This study shows that BSUs and stacks of BSUs determine the short-range order of the solids and are the main subject of the applied analytics. The synopsis consists of two parts related to empirical and virtual analytics. The former is composed of sections related to structural determination, total and atomic chemical content evaluation and elicitation of the covalent bond composition. The second presents new analytic approaches based on the Digital Twins concept and virtual vibrational spectrometry. The synopsis is configured as an atlas composed of generalized pictures accompanied with necessary explanations to be discussed in detail in the extended references.

Molecular design and theoretical study of oxadiazole-bifurazan derivatives.

The design and synthesis of new high energy density materials is an important part of the research in the field of high energy materials. However, the synthesis of high-energy materials is very difficult and dangerous. Therefore, it is necessary to design the compounds in advance and evaluate the performance of the designed compounds, so as to screen the high-energy candidate compounds with excellent performance and provide reference for future synthesis and application. 1,2,5-oxadiazole (furazan) and 1,2,4-oxadiazole are five-membered nitrogen-oxygen heterocycles. Because their structures contain high-energy N-O, C=N bonds, they can effectively improve the energy density and oxygen balance of compounds, which has attracted widespread attention. In this paper, 42 kinds of oxadiazole-bifurazan energetic derivatives were designed by inserting different functional groups and changing the parent bridging groups with 1,2,4-oxadiazole and furazan as the basic structural units. Their electronic structures, aromaticity, heats of formation (HOFs), detonation properties, thermodynamic properties and electrostatic potential were systematically studied by density functional than theory (DFT). The results show that -C (NO2)3 has the greatest improvement effect on HOFs among all the substituent groups. The detonation performance of -N=N- bridged oxadiazole-bifurazan derivatives is better than that of -NH-NH- bridged derivatives. And -C(NO2)3 is the most effective group to improve the detonation performance and density of compounds. Compared with the parent compounds, when a -C(NO2)3 was introduced, the density increased by about 5.5%. A6 (D = 10.30 km·s-1, P = 48.86 GPa) and D6 (D = 9.57 km·s-1, P = 42.31 GPa) are the compounds with the best D and P among the designed compounds, which are higher than RDX and HMX, and are potential candidates for new high-energy materials. With the help of Gaussian16 software and Multiwfn 3.8 package, the B3LYP method in density functional theory was selected. The 6-311G (d, p) basis set was used to optimize the structure of the 42 derivatives, and the high-precision def2-TZVPP basis set was used to calculate the energy.

A review of advances in aptamer-based cell detection technology.

Since cells are the basic structural and functional units of organisms, the detection or quantitation of cells is one of the most common basic problems in life science research. The established cell detection techniques mainly include fluorescent dye labeling, colorimetric assay, and lateral flow assay, all of which employ antibodies as cell recognition elements. However, the widespread application of the established methods generally dependent on antibodies is limited, because the preparation of antibodies is complicated and time-consuming, and unrecoverable denaturation is prone to occur with antibodies. By contrast, aptamers that are generally selected through the systematic evolution of ligands by exponential enrichment can avoid the disadvantages of antibodies due to their controllable synthesis, thermostability, and long shelf life, etc. Accordingly, aptamers may serve as novel molecular recognition elements like antibodies in combination with various techniques for cell detection. This paper reviews the developed aptamer-based cell detection methods, mainly including aptamer-fluorescent labeling, aptamer-isothermal amplification assay, electrochemical aptamer sensor, aptamer-based lateral flow analysis, and aptamer-colorimetric assay. The principles, advantages, progress of application in cell detection and future development trend of these methods were specially discussed. Overall, different assays are suitable for different detection purposes, and the development of more accurate, economical, efficient, and rapid aptamer-based cell detection methods is always on the road in the future. This review is expected to provide a reference for achieving efficient and accurate detection of cells as well as improving the usefulness of aptamers in the field of analytical applications.

Droplets microfluidics platform-A tool for single cell research.

Cells are the most basic structural and functional units of living organisms. Studies of cell growth, differentiation, apoptosis, and cell-cell interactions can help scientists understand the mysteries of living systems. However, there is considerable heterogeneity among cells. Great differences between individuals can be found even within the same cell cluster. Cell heterogeneity can only be clearly expressed and distinguished at the level of single cells. The development of droplet microfluidics technology opens up a new chapter for single-cell analysis. Microfluidic chips can produce many nanoscale monodisperse droplets, which can be used as small isolated micro-laboratories for various high-throughput, precise single-cell analyses. Moreover, gel droplets with good biocompatibility can be used in single-cell cultures and coupled with biomolecules for various downstream analyses of cellular metabolites. The droplets are also maneuverable; through physical and chemical forces, droplets can be divided, fused, and sorted to realize single-cell screening and other related studies. This review describes the channel design, droplet generation, and control technology of droplet microfluidics and gives a detailed overview of the application of droplet microfluidics in single-cell culture, single-cell screening, single-cell detection, and other aspects. Moreover, we provide a recent review of the application of droplet microfluidics in tumor single-cell immunoassays, describe in detail the advantages of microfluidics in tumor research, and predict the development of droplet microfluidics at the single-cell level.

Binding by the Polycomb complex component BMI1 and H2A monoubiquitination shape local and long-range interactions in the Arabidopsis genome.

Three-dimensional (3D) chromatin organization is highly dynamic during development and seems to play a crucial role in regulating gene expression. Self-interacting domains, commonly called topologically associating domains (TADs) or compartment domains (CDs), have been proposed as the basic structural units of chromatin organization. Surprisingly, although these units have been found in several plant species, they escaped detection in Arabidopsis (Arabidopsis thaliana). Here, we show that the Arabidopsis genome is partitioned into contiguous CDs with different epigenetic features, which are required to maintain appropriate intra-CD and long-range interactions. Consistent with this notion, the histone-modifying Polycomb group machinery is involved in 3D chromatin organization. Yet, while it is clear that Polycomb repressive complex 2 (PRC2)-mediated trimethylation of histone H3 on lysine 27 (H3K27me3) helps establish local and long-range chromatin interactions in plants, the implications of PRC1-mediated histone H2A monoubiquitination on lysine 121 (H2AK121ub) are unclear. We found that PRC1, together with PRC2, maintains intra-CD interactions, but it also hinders the formation of H3K4me3-enriched local chromatin loops when acting independently of PRC2. Moreover, the loss of PRC1 or PRC2 activity differentially affects long-range chromatin interactions, and these 3D changes differentially affect gene expression. Our results suggest that H2AK121ub helps prevent the formation of transposable element/H3K27me1-rich long loops and serves as a docking point for H3K27me3 incorporation.

Well‐Designed Highly Conjugated Covalent Organic Frameworks as Light Responsive Oxidase Mimic for Effective Detection of Uric Acid

Covalent organic frameworks (COFs) are widely used in photocatalysis due to their periodic π–π arrays, high crystallinity, and adjustable bandgap. Herein, a new strategy for integrating polyphenyl building blocks in COFs is presented to improve the photocatalytic efficiency. To implement this strategy, a series of COFs with different numbers of phenyl groups are successfully designed and synthesized. By varying the number of phenyl units in the precursor, the COFs exhibit different bandgaps, band‐edge positions, carrier mobilities, and interfacial transfer resistances. The corresponding characterization reveals that the photocatalytic capacity of COFs increases with the number of phenyls in the basic structural unit. Further, under visible light irradiation, the COFs prepared from 1,3,5‐tris [4‐amino(1,1‐biphenyl‐4‐yl)] benzene (TABB) and 1,4‐benzenedicarboxaldehyde (BDB) (named TABB‐BDB COF) exhibit superior light‐responsive oxidase‐mimicking characteristic, which can catalyze the oxidation of 2,2′‐azino‐bis (3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS). Based on the aforementioned characteristics, TABB‐BDB COF is designed as a robust colorimetric probe for the inexpensive, highly sensitive, and rapid detection of uric acid (UA) with a linear range of 5–160 mg L−1. This study not only demonstrates COFs‐based light‐response oxidase mimicking for efficient UA detection but also provides an intelligent tactic for boosting the photocatalytic competence of COFs.

Micropores manipulation of medium-rank coal through aggregate structure evolution during coalification: A study based on HRTEM analysis

Micropores in coal, which can be manipulated by aggregate structure, have been widely considered to be a key factor affecting the gas adsorption of coal. In this study, to explore the aggregate structure evolution and its influence on micropores during coalification, a well characterized sample set of medium-rank coals from Shanxi province, covering a vitrinite reflectance (Ro) interval from 0.68% to 1.98%, was selected. High resolution transmission electron microscopy (HRTEM) and low-pressure CO2 adsorption experiments (LPCO2) were employed to quantify the evolution of aggregate structure and micropores in coal during coalification. The results show that the two methods give similar results for the micropore distribution. With the increase of coalification, four obvious stages are found for fringe length and distribution of micropores, with turning points appear near Ro = 1.20% and 1.50%, respectively, indicating that the coalification process are combination of continuity and jumping and related to the coalification jumps. The dominant fringes are short fringes (0.3 ∼ 0.54 nm) and intermediate fringes (0.55 ∼ 1.14 nm) in all coals, which contribute most to the curvature of c = 1.0 ∼ 1.04 and c greater than 1.04, separately, suggesting the existence of non-six-membered rings. The curvature of c = 1.0 ∼ 1.04 decreases while the curvature of c = 1.04 ∼ 1.15 increases with increasing Ro, indicating that the fringes mainly tend to bend in medium-rank coals. For micropores, most pores in coal were found to be in the range of 0.5 ∼ 0.8 nm based on the result of HRTEM images, which mostly appeared in the disorder regions featured with intermediate fringes. However, the pores of 0.8 ∼ 1.2 nm and 0.4 ∼ 0.5 nm are always found in the regions without the basic structural units (BSUs) in lower-rank coals and the edge regions stacked with long fringes in the higher-rank coals, respectively. This work provides a strategy to manipulate micropores of medium-rank coal through aggregate structure evolution during coalification, which is expected to provide theoretical basis for further research on gas adsorption of coal.

Studies of the Mechanism of Nucleosome Dynamics: A Review on Multifactorial Regulation from Computational and Experimental Cases

The nucleosome, which organizes the long coil of genomic DNA in a highly condensed, polymeric way, is thought to be the basic unit of chromosomal structure. As the most important protein-DNA complex, its structural and dynamic features have been successively revealed in recent years. However, its regulatory mechanism, which is modulated by multiple factors, still requires systemic discussion. This study summarizes the regulatory factors of the nucleosome's dynamic features from the perspective of histone modification, DNA methylation, and the nucleosome-interacting factors (transcription factors and nucleosome-remodeling proteins and cations) and focuses on the research exploring the molecular mechanism through both computational and experimental approaches. The regulatory factors that affect the dynamic features of nucleosomes are also discussed in detail, such as unwrapping, wrapping, sliding, and stacking. Due to the complexity of the high-order topological structures of nucleosomes and the comprehensive effects of regulatory factors, the research on the functional modulation mechanism of nucleosomes has encountered great challenges. The integration of computational and experimental approaches, the construction of physical modes for nucleosomes, and the application of deep learning techniques will provide promising opportunities for further exploration.

From molecular to sub-μm scale: The interplay of precursor concentrations, primary particle size, and carbon nanostructure during soot formation in counter-flow diffusion flames

The focus of this work is on counter-flow diffusion flames of C2H4/air near the sooting limit (fV < 500 ppb) to shed light on the transition of precursor molecules to primary soot particles and their nanostructure. The applied experimental techniques cover non-intrusive methods based on laser-induced incandescence (LII) for determination of soot volume fractions, primary particle sizes, and ratios of refractive indices for absorption at different wavelengths. The methods are complemented by intrusive methods such as sampling with microprobes and analysis of gas composition by gas chromatography and mass spectrometry, particle sizing by differential mobility analysis, and determining carbon nanostructures of particles by high-resolution transmission electron microscopy (HRTEM). For numerical simulation, the well-known ABF-model is applied.The experimentally determined structures of the counter-flow flames could be well reproduced within the experimental uncertainties by the ABF-model for varying fuel mass fractions and strain rates. The numerical simulations identify the different processes during particle formation and the main variation can be attributed to variation of surface growth rates when applying strain rates and fuel mass fractions leading to higher soot volume fractions. Particle size distributions detected in the fuel flow near and below the stagnation plane appear bimodal with distinct maxima at particles sizes about 5 nm and 20 nm. The nanostructure of the primary particles exhibits basic structural units (BSUs), that increase up to the size of 7 Å to 10 Å at increasing soot volume fractions from about 100 ppb to 300 ppb. This coincides with the increase of the mole fractions of the detectable soot precursors with increasing soot volume fraction. The ratios of refractive index functions for absorption E(m,λ532)/E(m,λ1064) and E(m,λ266)/E(m,λ1064) decrease approximately linearly with increasing soot volume fractions. This is corroborated by the analyses of HRTEM-images that clearly bring about increasing sized BSUs with increasing soot volume fractions causing a shift of the absorption to larger wavelengths.

Material characteristics of WO3/Bi2O3 substitution on the thermal, structural, and electrical properties of lithium calcium borate glasses

Glasses belonging to the xWO3-(30-x) Bi2O3–15Li2O–15CaO–40B2O3 (0 ≤ x ≤ 10) have been obtained by melt-quenching technique. With increasing the concentration of WO3, an increase in the measured glass transition temperature {T}_{mathrm{g}} and crystallization temperature {T}_{mathrm{c}} are observed, while the values of the thermal expansion coefficient decrease. Due to the unpaired pentavalent ions, the electron spin resonance spectra of glasses doped with {mathrm{WO}}_{3} them show unique signals. The results of Raman spectra show that the glass network is mainly constituted by [{mathrm{BiO}}_{6}], [{mathrm{BO}}_{3}], [{mathrm{BO}}_{4}], and [{mathrm{WO}}_{4}] basic structural units. The activation energies for all studied samples were observed to range from 0.02 to 0.08 eV, and the dielectric constant and the conductivities of the investigated glasses increased with increasing temperature. The electrical behavior of the prepared samples revealed their semiconducting character. The prepared samples are being investigated as potential semiconductor material candidates for use in electronic devices.

Dynamic morphology imaging of cardiomyocytes based on AFM

A cardiomyocyte is the basic structural and functional unit of the heart, which is the actual executor of the systolic function. The study of the contraction and relaxation characteristics of cardiomyocyte is of great significance to the physiological behavior and pathology of the heart. How to dynamically express its contraction and relaxation behaviors in 3D has become a challenging issue. Although the video analysis method under the optical microscope can observe the changes in the horizontal direction, it is difficult to describe the changes in the vertical direction. The atomic force microscope (AFM) can accurately express the mechanical and morphological characteristics of the changes in the vertical direction, but it cannot be fully expressed in real time because it is acquired by scanning with a single probe. In order to express the contraction and relaxation characteristics of cardiomyocyte accurately and three dimensionally, a dynamic imaging method in this study is proposed using the periodicity of AFM acquisition and the periodicity of cardiomyocyte contraction. Compared with the optical experiment, it is proven that this method can dynamically represent the contraction and relaxation processes of cardiomyocyte and solve the problem of how to express it in 3D. It brings a new way for the study of physiological characteristics of cardiomyocytes and dynamic imaging by AFM.

Structural transformation and anomalous diffusion in network forming liquid GeO2

In this study, we simulated the structural transformation and self-diffusion mechanism in liquid GeO2 oxide system. Under compression, structure of liquid GeO2 model tends to transform gradually from low-density phase to high-density phase. Concentration of basic structural units can be determined via density of material model. The average Ge–O bond distance in GeO4 tetrahedra is smaller than the ones in GeO5 pentahedra and GeO6 octahedra. Each GeOx polyhedron always exists a Ge–O bond with the longest length (the weakest bond). The diffusion mechanism in liquid GeO2 oxide system is via breaking the weakest bonds that accompany the change local coordination environment of Ge cations. The longest Ge–O bond in a GeO5 pentahedron is very weak in comparison to the one in other polyhedra. The diffusivity is significantly dependent on the number of GeO5 pentahedra. The increase of GeO5 under compression is the origin of anomalous diffusion in liquid GeO2 oxide. The increase of average Ge–O bond distance under compression is also clarified in this work.

Biodegradable silk fibroin scaffold doped with mineralized collagen induces bone regeneration in rat cranial defects

Compared with most nondegradable or slowly degradable bone repair materials, bioactive biodegradable porous scaffolds with certain mechanical strengths can promote the regeneration of both new bone and vasculature while the cavity created by their degradation can be replaced by the infiltration of new bone tissue. Mineralized collagen (MC) is the basic structural unit of bone tissue, and silk fibroin (SF) is a natural polymer with adjustable degradation rates and superior mechanical properties. In this study, a three-dimensional porous biomimetic composite scaffold with a two-component SF-MC system was constructed based on the advantages of both materials. The spherical mineral agglomerates of the MC were uniformly distributed on the surface and inside the SF skeleton, which ensured good mechanical properties while regulating the degradation rate of the scaffold. Second, the SF-MC scaffold had good osteogenic induction of bone marrow mesenchymal stem cells (BMSCs) and preosteoblasts (MC3T3-E1) and also promoted the proliferation of MC3T3-E1 cells. Finally, in vivo 5 mm cranial defect repair experiments confirmed that the SF-MC scaffold stimulated vascular regeneration and promoted new bone regeneration in vivo by means of in situ regeneration. Overall, we believe that this low-cost biomimetic biodegradable SF-MC scaffold with many advantages has some clinical translation prospects.