43 research outputs found

    Correlation between Grafting Density and Confined Crystallization Behavior of Poly(ethylene glycol) Grafted to Silica

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    The interfacial interactions of polymer-nanoparticles have dramatical effects on the crystallization behavior of grafted polymers. In this study, methoxy polyethylene glycol (MPEG) (molecular weights 750, 2000 and 4000 g mol−1) was grafted onto amino-modified nanosized silica (SiO2-NH2) by the “grafting to” method. The effects of the grafting density and molecular weight on the confined crystallization of grafted MPEG (MPEG-g-SiO2) were systematically investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and wide-angle X-ray scattering (WAXS). It was found that confinement effects are stronger when lower molecular weights of grafted MPEG are employed. These grafted MPEG chains are more difficult to stretch out on SiO2-NH2 surfaces than when they are free in the bulk polymer. Both crystallization temperature (Tc) and crystallinity of grafted MPEG chains decrease with reductions of grafting density. Additionally, covalent bonding effects and interfacial interaction confinement effects are strengthened by the decrease in grafting density, leading to an increase in decomposition temperature and to the disappearance of the self-nucleation Domain (i.e., Domain II), when self-nucleation experiments are performed by DSC. Overall isothermal crystallization kinetics was studied by DSC and the results were analyzed with the Avrami equation. An Avrami index of n≈3 was obtained for neat MPEG (indicating that instantaneous spherulites are formed). However, in the case of MPEG-g-SiO2 with the lowest grafting density, the Avrami index of (n) was less than 1 (first order kinetics or lower), indicating that nucleation is the determining factor of the overall crystallization kinetics, a signature for confined crystallization. At the same time, the crystallization from the melt for this MPEG-g-SiO2 with the lowest grafting density occurs at Tc ≈-30 ÂșC, a temperature close to the glass transition temperature (Tg) of MPEG, indicating that this confined MPEG crystallizes from homogeneous nuclei.This project was supported by the National Natural Science Foundation of China (21574141) and the Ministry of Science and Technology of China (2017YFE0117800). The authors gratefully acknowledge the funding of project BIODEST, Research and Innovation Staff Exchange (RISE) H2020-MSCA-RISE-2017-778092. The authors thank beamline BL16B1 (Shanghai Synchrotron Radiation Facility) for providing the beam time and helps during experiments

    A Cooperative High-Speed Positioning Control System for Dual-Axis Permanent-Magnet Linear Motor

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    The Smart Cross Platform guarantees content compatibility of various smart devices and supports numerous programming languages, which is a solution to increasing development productivity. The SVM (Smart Virtual Machine) is the core virtual machine of the smart cross platform. This paper presents a technology which allows the SVM previously operating on smart devices to operate in the web environment. In the whole design and implementation of the SVM operating in the web based environment, this paper focuses on the interpreter, which is used as a method to execute the contents

    Probing Interface of Perovskite Oxide Using Surface-specific Terahertz Spectroscopy

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    The surface/interface species in perovskite oxides play an essential role in many novel emergent physical phenomena and chemical processes. With low eigen-energy in the terahertz region, such species at buried interfaces remain poorly understood due to the lack of feasible experimental techniques. Here, we show that vibrational resonances and two-dimensional electron gas at the interface can be characterized using surface-specific nonlinear spectroscopy in the terahertz range. This technique uses intra-pulse difference frequency mixing (DFM) process, which is allowed only at surface/interface of a medium with inversion symmetry. Sub-monolayer sensitivity can be achieved using the state-of-the-art detection scheme for the terahertz emission from surface/interface. As a demonstration, Drude-like nonlinear response from the two-dimensional electron gas emerging at LaAlO3/SrTiO3 or Al2O3/ SrTiO3 interface was successfully observed. Meanwhile, the interfacial vibrational spectrum of the ferroelectric soft mode of SrTiO3 at 2.8 THz was also obtained that was polarized by the surface field in the interfacial region. The corresponding surface/interface potential, which is a key parameter for SrTiO3-based interface superconductivity and photocatalysis, can now be determined optically via quantitative analysis on the polarized phonon spectrum. The interfacial species with resonant frequencies in the THz region revealed by our method provide more insights into the understanding of physical properties of complex oxides.Comment: arXiv admin note: substantial text overlap with arXiv:2207.1461

    Enhanced Global-Brain Functional Connectivity in the Left Superior Frontal Gyrus as a Possible Endophenotype for Schizophrenia

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    The notion of dysconnectivity in schizophrenia has been put forward for many years and results in substantial attempts to explore altered functional connectivity (FC) within different networks with inconsistent results. Clinical, demographical, and methodological heterogeneity may contribute to the inconsistency. Forty-four patients with first-episode, drug-naive schizophrenia, 42 unaffected siblings of schizophrenia patients and 44 healthy controls took part in this study. Global-brain FC (GFC) was employed to analyze the imaging data. Compared with healthy controls, patients with schizophrenia and unaffected siblings shared enhanced GFC in the left superior frontal gyrus (SFG). In addition, patients had increased GFC mainly in the thalamo-cortical network, including the bilateral thalamus, bilateral posterior cingulate cortex (PCC)/precuneus, left superior medial prefrontal cortex (MPFC), right angular gyrus, and right SFG/middle frontal gyrus and decreased GFC in the left ITG/cerebellum Crus I. No other altered GFC values were observed in the siblings group relative to the control group. Further ROC analysis showed that increased GFC in the left SFG could separate the patients or the siblings from the controls with acceptable sensitivities. Our findings suggest that increased GFC in the left SFG may serve as a potential endophenotype for schizophrenia

    Phytic acid modified NH2-MIL-101 via Mannich reaction for highly efficient uranium (â…„) extraction from seawater

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    An essential part of achieving sustainable uranium resource development was the search for a suitable adsorbent capable of efficiently capturing uranium (â…„) from seawater. Here, a modified metal-organic framework (PA-MIL-101) was prepared by phosphorylation of NH2-MIL-101 with phytic acid (PA). PA-MIL-101 exhibited a specific surface area of 252 m2∙g−1 and proved exceptionally adept at extracting uranium (â…„) from seawater. Batch experiments were conducted to examine how environmental conditions such as pH and natural seawater affect the uranium adsorption performance of the materials. The adsorption capacity of PA-MIL-101 exhibited a remarkable performance, showcasing a substantial 41.8% increase compared to NH2-MIL-101 (the adsorption capacity increased to 416.7 mg∙g−1 at pH = 7 in 100 mg∙L−1 U(â…„) solution). Due to the fast adsorption kinetics, PA-MIL-101 achieves a saturation level of 72.1% within the first 5 min. The removal rate was further elevated to 88.48% in the more intricate natural seawater. The reusability of PA-MIL-101 was demonstrated through five recycling cycles. The porous material PA-MIL-101 has abundant P=O and P–OH active sites, which can strongly complex with uranium (â…„). This feature makes PA-MIL-101 perform effective in natural seawater. Therefore, PA-MIL-101 is considered as a promising supersorbent for efficient removal of uranium (â…„)

    The Synergistic Effect of Microwave Radiation and Hypergravity on Rats and the Intervention Effect of Rana Sylvatica Le Conte Oil

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    Aim: The phenomena of hypergravity and microwave radiation are widespread, which cause more and more concern for the hazards to human health. The aim of this study was to investigate the synergistic effect of microwave radiation and hypergravity on rats and observe the protective effect of Rana sylvatica Le conte oil. Methods: Rats were exposed to microwave radiation and hypergravity, and the rat weight, the climbing pole height, serum enzyme activities, blood urea nitrogen concentration, and total antioxidant capacity were detected. Results: The climbing pole height, the activities of choline acetyl transferase and cholinesterase, and the total antioxidant capacity decreased, whereas the activities of alanine aminotransferase, aspartate aminotransferase, areatine kinase, isocitric dehydrogenase, hydroxybutyrate dehydrogenase, and the blood urea nitrogen concentration increased in the hypergravity irradiation group as compared with the others. Conclusion: These results imply that the motion and nervous system of rats might be affected critically by the synergistic effect of microwave radiation and hypergravity, and it causes damage to most rat organs, such as the bone, skeletal muscle, liver, heart, and kidney, and the antioxidant effect is also damaged, while the injury resulted from it could be protected by Rana sylvatica Le conte oil
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