This study focused on Chinese doctoral recipients in social science disciplines in the U.S. and their decision making about returning to China upon graduation. In interviews of Chinese faculty who ...studied in the U.S. and Chinese PhD students currently in the U.S., we found that plans to return were associated with a blend of cultural, family, and academic ties. Political and economic factors interact with the influence of family ties. They were also apparent in the perceived prestige of studying in the U.S., which was believed to lead to a certain job offer from a Chinese university.
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•Potential LST driving factors are explored in a multidirectional perspective.•Polycentrism is introduced from the perspective of spatial configuration.•Three types of city centers ...pose varied UHI characteristics.•LST driving laws in different city centers of polycentric city is identified.•Multiple driving factors have bilinear or nonlinear interactions among them.
Revealing the dominant driving factors of land surface temperature (LST) plays an important role in mitigating the urban heat island (UHI) effect. Numerous international metropolises are developing polycentric forms under the process of suburbanization in conjunction with rapid urbanization, generating new UHI spatial patterns in internal urban areas. To comprehensively understand the effects of multi-factors on the thermal environment, our study examined a typical polycentric city, Tianjin. According to the concept of polycentrism, this study focused on three types of city “centers”: major city core, new district core and industrial park. Eleven potential driving factors of LST were explored from four layers, and the geo-detector model was applied to rank the explanatory degree of these factors on LST. Three different city centers of the polycentric city showed varied UHI spatial pattern characteristics, and their response to the effect of natural factors and social factors on LST were quite diverse. Heat island areas were distributed homogeneously in the major city core; the UHI pattern on the east-west axis was unbalanced in the new district core due to the unsaturated urban space and dynamic planning policies; in industrial park, production areas were segregated by green belts with clear boundaries. For the whole city and the major city core, the imperviousness factor had the highest explanatory rate for LST, followed by the greenness factor. In contrast to the results of previous studies, the wetness factors had a greater impact on LST in the new district core and industrial park, second only to the greenness factor. Furthermore, selected factors exhibited bilinear or nonlinear enhanced relationships in their interactions. The driving laws of LST in different city centers were summarized with an explorative case study, aimed at providing theoretical basis and practical guidance for optimizing urban thermal environment planning, especially for highly urbanized polycentric cities.
Depression is a common mental disease that mainly manifests as bad mood, decreased interest, pessimism, slow thinking, lack of initiative, poor diet and sleep. Patients with severe depression have ...suicidal tendencies. Exosomes are small vesicles released by the fusion of a multivesicular body and membranes, and they contain specific proteins, nucleic acids, and lipids related to the cells from which they originate. MicroRNAs (miRNAs) are 20-24 nt RNAs that can be packaged into exosomes and can play important regulatory roles. Astrocytes are the most abundant cell population in the central nervous system and have a close link to depression. Astrocyte activation could result in the release of inflammatory cytokines, including IL-1β, IL-6, and TNF-α, which could promote the symptoms of depression. In previous research, our team confirmed that NK cells regulate depression in mice. Here, we propose that miRNA in the exosomes from NK cells performs this antidepressant function.
Exosomes from NK cells were shown by in vivo and in vitro experiments to alleviate symptoms of chronic mild stress in mice and decrease pro-inflammatory cytokines release from astrocytes. The production of pro-inflammatory cytokines was assessed by ELISA. Microarray analysis was used to identify critical miRNAs. Luciferase reporter assays, qPCR, and other experiments were used to prove that exosomal miR-207 has an important role in alleviating the symptoms of stress in mice.
MiRNA-containing exosomes from NK cells could alleviate symptoms of chronic mild stress in mice. In vivo experiments showed that these exosomes decreased the levels of pro-inflammatory cytokines (IL-1β, IL-6, and TNF-α) released by astrocytes. By microarray analysis of exosome miRNA profiles, miR-207 was found to be overexpressed in exosomes derived from unstressed mice. Experiments confirmed that miR-207 directly targets TLR4 interactor with leucine-rich repeats (Tril) and inhibits NF-κB signaling in astrocytes. MiR-207 could decrease the release of pro-inflammatory cytokines and inhibit expression of Tril in vitro. In vivo experiments revealed that exosomes with low miR-207 levels showed decreased antidepressant activity.
Collectively, our findings revealed that exosomal miR-207 alleviated symptoms of depression in stressed mice by targeting Tril to inhibit NF-κB signaling in astrocytes.
Mesoporous Zn4O(−COO)6-based metal–organic frameworks (MOFs), including UMCM-1, MOF-205, MUF-7a, and the newly synthesized MOFs, termed ST-1, ST-2, ST-3, and ST-4 (ST = ShanghaiTech University), ...have been systematically investigated for ultrahigh capacity methane storage. Exceptionally, ST-2 was found to have the highest deliverable capacity of 289 cm3 STP/cm3 (567 mg/g) at 298 K and 5–200 bar, which surpasses all previously reported records held by porous materials. We illustrate that the fine-tuned mesoporosity is critical in further improving the deliverable capacities at ultrahigh pressure.
The role of microglia in spinal cord injury (SCI) remains ambiguous, partially due to the paucity of efficient methods to discriminate these resident microglia with blood-derived ...monocytes/macrophages. Here, we used pharmacological treatments to specifically eliminate microglia and subsequently to investigate the response of microglia after SCI in mice. We showed that treatment with colony stimulating factor 1 receptor (CSF1R) inhibitor PLX3397 eliminated ~90% microglia and did not affect other cell types in mouse spinal cord. PLX3397 treatment also induced a strong decrease in microglial proliferation induced by SCI. Depletion of microglia after SCI disrupted glial scar formation, enhanced immune cell infiltrates, reduced neuronal survival, delayed astrocyte repopulation, exacerbated axonal dieback, and impaired locomotor recovery. Therefore, our findings suggest microglia may play a protective role after SCI in mice.
Cell-free massive multiple-input multiple-output (MIMO) is a promising technology for the Internet of Things (IoT) because it can increase connectivity and provide considerable energy efficiency (EE) ...and spectral efficiency (SE). However, pilot contamination caused by pilot reuse severely limits the performance of the system. In this paper, we propose a left-null-space-based massive access method that can significantly reduce interference among users. The proposed method includes three stages: initial orthogonal access, left-null-space-based opportunistic access and data detection of all accessed users. The simulation results show that the proposed method can achieve much higher spectral efficiency than the existing massive access methods.
In multicell multiuser massive multi-input multi-output (MIMO) systems, pilot contamination degrades the uplink (UL) channel estimation performance. To mitigate the effect of pilot contamination, we ...propose a semiblind channel estimation method that does not require cell cooperation or statistical information of the channels. In the proposed method, we first sequentially estimate the UL data from different users in the target cell. To do that, for each user, we solve a constrained minimization problem to obtain an extracting vector and then use it to extract the desired data source from the observed mixture signal. An efficient algorithm is presented to solve the optimization problem. After the ambiguities in the extracted source are corrected with the aid of the pilot sequence, the estimates of the user UL data can be obtained. Based on the demodulated UL data of all users in the target cell, we finally obtain the least squares (LS) estimate of the channel. The pilot contamination effect is shown to be reduced as the UL data length grows. Simulation results demonstrate that the proposed method significantly outperforms some existing channel estimation methods that do not require cell cooperation or channel statistics.
•The Geographical detector tool is efficient for studying the relationship between UGS and LST.•The impact of UGS on LST varies significantly with different vegetation types and landscape ...patterns.•Landscape factors have bivariate or nonlinear enhanced interactions with each other.•This study provides an efficient evaluation framework for UGS based on an actual urban environment.
Urban green space (UGS) plays an indispensable role in urban spaces, providing important ecological services to compensate for natural environment functions damaged by rapid urbanization. Understanding the impact of the UGS landscape pattern on its environmental benefits in order to evaluate UGS quality is critical for increasing its use efficiency. Previous studies have frequently constructed evaluation indexes based on subjective assessment of UGS landscape patterns using principal component analysis, factor analysis, and other methods without combining the actual environmental benefits in a complex urban environment. We investigated the changes in land surface temperature (LST) under different UGS landscape patterns, which can help clarify the urban thermal environment effect of UGS, and constructed a comprehensive index, the Green Environmental Benefit Index (GEBI), for UGS evaluation. Our results show that: (1) spatial allocation and configuration of UGS impact LST at both landscape and class levels, and the impact varies significantly with different vegetation types and landscape patterns. (2) The influence of each pair of driving factors on UGS thermal environmental benefits is mutually enhanced, indicating that urban greening can be improved across multiple dimensions. (3) UGS evaluation based on GEBI is objective and compelling, where alleyways of the inner-city were identified as areas in need of greening optimization in the study area. Revealing more details of the UGS landscape pattern, this study can help to construct a scientific and objective evaluation model and provide a reference for urban greening optimization and planning.
Conventional corpus retrieval tools are susceptible to malicious attacks, leading to the tampering of corpus resources. To solve this problem, in order to improve the security of corpus retrieval, a ...tamper resistance retrieval method of corpus based on perceptual Hash computer algorithm is proposed. First, the four dimensional chaotic map is used to encrypt the corpus resources to achieve Tamper resistance processing of the original corpus resources. Then, the robust features of the corpus resources are extracted, and after decomposition and dimensionality reduction, the feature sequence is transformed into a perceptual hash sequence, which facilitates matching the retrieval keywords with the hash sequence in the corpus during retrieval, further avoiding unauthorized modifications. Finally, the perceptual hash sequence is input into the lightweight neural network for training, and a combination of coarse and fine granularity is used to match the perceptual hash corpus in the corpus with the retrieval hash sequence input by the user, obtaining the retrieval results. The experimental results show that the retrieval accuracy of this method is higher than 98%, the tampering rate of the corpus is 0, and the retrieval performance and practical application value are greatly improved.
Chitosan is a natural, biodegradable cationic polysaccharide, which has a similar chemical structure and similar biological behaviors to the components of the extracellular matrix in the ...biomineralization process of teeth or bone. Its excellent biocompatibility, biodegradability, and polyelectrolyte action make it a suitable organic template, which, combined with biomimetic mineralization technology, can be used to develop organic-inorganic composite materials for hard tissue repair. In recent years, various chitosan-based biomimetic organic-inorganic composite materials have been applied in the field of bone tissue engineering and enamel or dentin biomimetic repair in different forms (hydrogels, fibers, porous scaffolds, microspheres, etc.), and the inorganic components of the composites are usually biogenic minerals, such as hydroxyapatite, other calcium phosphate phases, or silica. These composites have good mechanical properties, biocompatibility, bioactivity, osteogenic potential, and other biological properties and are thus considered as promising novel materials for repairing the defects of hard tissue. This review is mainly focused on the properties and preparations of biomimetically mineralized composite materials using chitosan as an organic template, and the current application of various chitosan-based biomimetically mineralized composite materials in bone tissue engineering and dental hard tissue repair is summarized.
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