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Osteoarthritis (OA) is a major health problem, characterized by progressive cartilage degeneration. Previous works have shown that mechanical loading can alleviate OA symptoms by suppressing catabolic activities. This study evaluated whether mechanical loading can enhance anabolic activities by facilitating the recruitment of stem cells for chondrogenesis. We evaluated cartilage degradation in a mouse model of OA through histology with H&E and safranin O staining. We also evaluated the migration and chondrogenic ability of stem cells using in vitro assays, including immunohistochemistry, immunofluorescence, and Western blot analysis. The result showed that the OA mice that received mechanical loading exhibited resilience to cartilage damage. Compared to the OA group, mechanical loading promoted the expression of Piezo1 and the migration of stem cells was promoted via the SDF-1/CXCR4 axis. Also, the chondrogenic differentiation was enhanced by the upregulation of SOX9, a transcription factor important for chondrogenesis. Collectively, the results revealed that mechanical loading facilitated cartilage repair by promoting the migration and chondrogenic differentiation of endogenous stem cells. This study provided new insights into the loading-driven engagement of endogenous stem cells and the enhancement of anabolic responses for the treatment of OA. [ABSTRACT FROM AUTHOR]

Gram-stain-positive, aerobic, non-spore-forming strains CCNWLXL 1-35T, CCNWLXL 12-2 and CCNWLXL 21-a, were isolated from wheat rhizosphere from Yangling, Shaanxi Province, China. Comparison of the 16S rRNA gene sequences showed that they belonged to the genus Arthrobacter and were closely related to Arthrobacter globiformis NBRC 12137T (97.95% similarity). Genomic relatedness analyses based on the average nucleotide identity and the genome-to-genome distance showed these strains constituted a single species. The major fatty acids was anteiso-C15:0. The polar lipids consist of diphosphatidylglycerol, phsophatidylethanolamine, phosphatidylglycerol, phosphatidylinositol and glycolipid. The predominant menaquinone was MK-9. The peptidoglycan type was A4α. Thus, these strains were classified as representing a novel species in the genus Arthrobacter, for which the name Arthrobacter rhizosphaerae sp. nov. is proposed. The type strain is CCNWLXL 1-35T (=JCM 34638T, =CCTCC AB 2021087T) and additional strains are CCNWLXL 12–2 (=JCM 35018, =CCTCC AB 2021546), CCNWLXL 21-a (=JCM 35019, =CCTCC AB 2021545). [ABSTRACT FROM AUTHOR]

Osteoarthritis (OA) is a whole joint disorder that is characterized by cartilage damage and abnormal remodeling of subchondral bone. Injecting adipose-derived stem cells (ASCs) into the knee joint cavity can assist in repairing osteoarthritic joints, but their ability to migrate to the damaged site is limited. Our previous studies have shown that knee loading can improve the symptoms of OA, but the effect and mechanism of knee loading on the migration of ASCs in OA remain unclear. We employed a mouse model of OA in the knee and applied knee loading (1 N at 5 Hz for 6 min/day for 2 weeks) after the intra-articular injection of ASCs. The cartilage and subchondral bone repair were assessed by histopathological analysis. Immunofluorescence assays were also used to analyze the migration of ASCs. Using cell cultures, we evaluated the migration of ASCs using the transwell migration and wound healing assays. In vivo experiments showed that knee loading promoted the migration of ASCs, increased the local SDF-1 level, and accelerated the repair of the OA-damaged sites. Mechanistically, the observed effects were blocked by the SDF-1/CXCR4 inhibitor. The in vitro results further revealed that knee loading promoted the migration of ASCs and the inhibition of SDF-1/CXCR4 significantly suppressed the beneficial loading effect. The results herein suggested that the migration of ASCs was enhanced by knee loading through the SDF-1/CXCR4 regulatory axis, and mechanical loading promoted the joint-protective effect of ASCs. [ABSTRACT FROM AUTHOR]

Ultralow-wear polyethylene (ULWPE), a type of polyethylene homocomposite with excellent wear resistance, has recently been reported; however, its underlying wear mechanism has yet to be clarified. In the current study, three different molecular weights of ULWPE from 205 to 748 kg/mol were experimentally evaluated on a multidirectional motion pin-on-disk wear tester under a contact pressure from 2 to 4 MPa, compared with conventional UHMWPE. The high wear resistance mechanism of ULWPE was investigated with respect to mechanical, microstructural, and surface properties. Compared with UHMWPE, ULWPE had excellent wear resistance. Structure and mechanical characterization showed that the crystallinity and lamellar thickness of ULWPE were significantly higher than those of UHMWPE, which endowed ULWPE with high hardness and strength. Despite its considerably smaller molecular weight than that of UHMWPE, ULWPE still had high interphase content, leading to its superior toughness. The crystallinity, lamellar thickness, Young’s modulus, yield stress, and elongation at break of ULWPE exhibited a downward trend with the increase of molecular weight. Conversely, the interphase content of ULWPE increased with the molecular weight increase. Among all the ULWPE samples, ULWPE with a molecular weight 748 kg/mol had the least wear, as a result of combined both excellent strength and adequate toughness. With an increase in contact pressure, the wear losses of different polymers tended to increase. The wear losses of the least wear ULWPE were 4.71 ± 0.04 mm3/Million Cycles (Mc), 5.11 ± 0.37 mm3/Mc, and 5.77 ± 0.62 mm3/Mc under 2, 3, and 4 MPa. Comprehensive strength and toughness reduced abrasive wear and adhesion wear, endowing ULWPE with excellent wear resistance. [ABSTRACT FROM AUTHOR]

The investigations of the branching chain have influence on the crystallization behaviors and structures in metallocene polyethylene (mPE) as compared to the Ziegler–Natta polyethylenes that have grown significantly since the introduction of metallocene catalytic polymerization in industrial applications. A zirconium dichloride complex, three intermediates, and methylaluminoxane were used as metallocene catalysts for the polymerization of ethylene to obtain the mPEs. The structures of the mPEs were characterized by 13C nuclear magnetic resonance (13C-NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and dynamic rheology method. The results on the crystallization of the mPEs showed master curve features and indicated fractal topology of the long-chain branch. The conflicting result obtained from the 13C NMR and rheology is due to the long-chain fractal structure. The successive self-nucleation and annealing (SSA) was used to characterize the length of crystallizable methylene sequence length (MSL) methylene sequence. It was found that the lamellar thickness calculated via Thomson-Gibbs equation exhibits two scaling relationships with MSL related to the molecular weight of the polyethylene chain entanglements M e . [ABSTRACT FROM AUTHOR]

Topochemical polymerization reactions hold the promise of producing ultra-high molecular weight crystalline polymers. However, the totality of topochemical polymerization reactions has failed to produce ultra-high molecular weight polymers that are both soluble and display variable functionality, which are restrained by the crystal-packing and reactivity requirements on their respective monomers in the solid state. Herein, we demonstrate the topochemical polymerization reaction of a family of para-azaquinodimethane compounds that undergo facile visible light and thermally initiated polymerization in the solid state, allowing for the first determination of a topochemical polymer crystal structure resolved via the cryoelectron microscopy technique of microcrystal electron diffraction. The topochemical polymerization reaction also displays excellent functional group tolerance, accommodating both solubilizing side chains and reactive groups that allow for post-polymerization functionalization. The thus-produced soluble ultra-high molecular weight polymers display superior capacitive energy storage properties. This study overcomes several synthetic and characterization challenges amongst topochemical polymerization reactions, representing a critical step toward their broader application. Topochemical polymerization reactions produce ultra-high molecular weight crystalline polymers. Here the authors show a family of para-azaquinodimethane compounds that undergo facile visible light and thermally initiated polymerization in the solid state and the crystal structure has been resolved via cryoelectron microscopy. [ABSTRACT FROM AUTHOR]

An accurate and convenient method is essential for measuring the terminal velocity of seeds dispersed by wind. Systematic and random errors produced by existing methods lower the accuracy and convenience in determining seed terminal velocity. In this study, a video camera was used to record the falling process of forty-one species of wind-borne seed with eight appendage structures and seven aerodynamic behaviors in a settling tower at a speed of 50 frames per second (fps). The videos were analyzed by Quick Time Player to determine seed acceleration height, acceleration time, and terminal velocity. The results showed that acceleration height and time, terminal velocity, and the difference between terminal velocity and descent velocity (DTD) increased with wing loading. Compared with dropping methods, the camera recording method eliminated the effect of acceleration and corrected seed terminal velocity. Based on wing loading, release heights were determined for accurate measurement of terminal velocity of different seeds. This method, due to its inexpensive equipment, high accuracy, easy observation and operation, can be applied to measure the terminal velocity of wind dispersed seeds, and provides a promising method in exploring the dispersal process of seeds. [ABSTRACT FROM AUTHOR]

Aims: How landscape configuration, dispersal agents and diaspore features interact to determine the input of seeds into the soil, which is the first part of the formation of a soil seed bank, is a major challenge. This study explored the role of diaspore traits and sand surface configuration in determining the number of seeds that become buried during wind dispersal. Methods: We investigated seed burial probability of 36 species with different diaspore traits under eight wind speeds and three sand surface configurations during wind dispersal by using a wind tunnel. Results: Wind speed rather than diaspore traits and sand surface configuration was the most important factor affecting the burial of seeds. Effects of slope direction and surface barrier on seed burial were regulated by wind speed. Effects of diaspore traits on seed burial were only significant at high wind speeds, and seed burial was more likely to be formed for small or flat elongated diaspores than for large or spherical ones. Conclusions: The effect of diaspore traits on seed burial is modified by the shifts in wind speed and sand surface configuration. [ABSTRACT FROM AUTHOR]

We report a facile strategy to synthesize intermetallic nanoparticle (iNP) electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles (NPs). ZIF-8 serves not only as precursor for N-doped carbon (NC), but also as Zn source for the formation of intermetallic or alloy NPs with the encapsulated metals. The resulting sub-4 nm PtZn iNPs embedded in NC exhibit high sintering resistance up to 1,000 °C. Importantly, the present methodology allows fine-tuning of both composition (e.g., PdZn and RhZn iNPs, as well as AuZn and RuZn alloy NPs) and size (2.4, 3.7, and 5.4 nm PtZn) of the as-formed bimetallic NPs. To the best of our knowledge, this is the first report of a metal-organic framework (MOF) with multiple functionalities, such as secondary metal source, carbon precursor, and size-regulating reagent, which promote the formation of iNPs. This work opens a new avenue for the synthesis of highly uniform and stable iNPs. [ABSTRACT FROM AUTHOR]

Abstract: The establishment of structure–property relationships in heterogeneous catalysis is of prime importance but remains a formidable challenge. Metal–organic frameworks (MOFs) featuring excellent chemical tunability are emerging as an auspicious platform for the atomic-level control of heterogeneous catalysis. Herein, we encapsulate palladium nanoparticles (Pd NPs) in a series of isoreticular mixed-linker MOFs, and the obtained MOF-Pd NPs catalysts were used to unveil the electronic and steric effects of linker substitution on the activity of these catalysts in the Suzuki–Miyaura cross-coupling reactions. Significantly, m-6,6′-Me2bpy-MOF-Pd exhibits a remarkable enhancement in the activity compared to non-functionalized m-bpy-MOF-Pd and m-4,4′-Me2bpy-MOF-Pd. This study unambiguously demonstrates that the stereoelectronic properties of linker units are crucial to the catalytic activity of nanoparticles encapsulated in MOFs. More interestingly, the trend of activity change is consistent with our previous work on catalytic sites generated in situ from Pd(II) coordinated in MOFs bearing the same functional groups, which suggests that both MOF-Pd NPs and MOF-Pd(II) catalysts generate similar active centers during Suzuki–Miyaura coupling reactions. This work paves a new avenue to the fabrication of advanced and tunable MOF-based catalysts through rational linker engineering.Graphical Abstract: We encapsulate palladium nanoparticles in a series of isoreticular mixed-linker MOFs, and the obtained Pd-doped MOFs catalysts were used to unveil the electronic and steric effects of linker substitution on the activity of these catalysts in the context of Suzuki–Miyaura cross-coupling reactions. Impressively, m-6,6′-Me2bpy-MOF-Pd exhibits a remarkable enhancement in the activity compared to non-functionalized m-bpy-MOF-Pd and m-4,4′-Me2bpy-MOF-Pd, thus implementing atomic-level controls of heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

A wide variety of near-fault strong ground motion records were collected from various tectonic environments worldwide and were used to study the peak value ratio and response spectrum ratio of the vertical to horizontal component of ground motion, focusing on the effect of earthquake magnitude, site conditions, pulse duration, and statistical component. The results show that both the peak value ratio and response spectrum ratio are larger than the 2/3 value prescribed in existing seismic codes, and the relationship between the vertical and horizontal ground motions is comparatively intricate. In addition, the effect of the near-fault ground motions on bridge performance is analyzed, considering both the material nonlinear characteristics and the P∼Δ effect. [ABSTRACT FROM AUTHOR]

The growing interest in two-dimensional imine-based covalent organic frameworks (COFs) is inspired by their crystalline porous structures and the potential for extensive π-electron delocalization. The intrinsic reversibility and strong polarization of imine linkages, however, leads to insufficient chemical stability and optoelectronic properties. Developing COFs with improved robustness and π-delocalization is highly desirable but remains an unsettled challenge. Here we report a facile strategy that transforms imine-linked COFs into ultrastable porous aromatic frameworks by kinetically fixing the reversible imine linkage via an aza-Diels-Alder cycloaddition reaction. The as-formed, quinoline-linked COFs not only retain crystallinity and porosity, but also display dramatically enhanced chemical stability over their imine-based COF precursors, rendering them among the most robust COFs up-to-date that can withstand strong acidic, basic and redox environment. Owing to the chemical diversity of the cycloaddition reaction and structural tunability of COFs, the pores of COFs can be readily engineered to realize pre-designed surface functionality. Despite recent success in developing new covalent organic frameworks (COFs) materials, synthesis of chemically stable COFs still remains challenging. Here the authors demonstrate a facile strategy that transforms imine-linked COFs into robust porous aromatic frameworks by kinetically fixing the reversible imine linkage via an aza-Diels-Alder cycloaddition reaction. [ABSTRACT FROM AUTHOR]