We study strong deflection gravitational lensing by a Lee-Wick ultracompact object. Its unique feature is a series of relativistic images inside its photon sphere, which are absent in the case of a ...black hole. We obtain its observables and estimate them for the supermassive black holes Sgr A* and M87* respectively in the Galactic center and in the center of M87. We find that the innermost relativistic image is a very promising signature according to its angular separation from the photon sphere and its considerable brightness. A preliminary bound on the UV scale of such an object is estimated based on the shadow of M87*.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this paper, decentralized computing is used as an entry point to review the latest research results on network security issues through two methods, namely task assignment and hierarchical ...analysis, and construct a network security posture assessment model based on decentralized computing. A control framework is constructed by utilizing the functional complementarity of continuous authentication and security threat assessment in order to facilitate real-time observation of the security situation of the network and timely elimination of malicious nodes. A quantitative network security threat posture assessment model is constructed through hierarchical analysis to observe the extent of the breach of confidentiality and integrity of network information based on the security threat posture index. The effectiveness of the network security posture assessment model and method proposed in this paper was verified by empirical analysis in a simulated environment. The results show that after the simulated attack lasts for 12 minutes, the network security risk index measured by the assessment model in the test cascade case becomes larger with the intensification of the network attack, and the risk index value is up to 5.5. In summary, the network security posture assessment model based on decentralized computing designed in this paper can quickly reflect the changes in the security status of the underlying network and provide administrators with the current security status of the network in a macroscopic way.
Human body motion can generate a biological electric field and a current, creating a voltage gradient of −10 to −90 mV across cell membranes. In turn, this gradient triggers cells to transmit signals ...that alter cell proliferation and differentiation. Several cell types, counting osteoblasts, neurons and cardiomyocytes, are relatively sensitive to electrical signal stimulation. Employment of electrical signals in modulating cell proliferation and differentiation inspires us to use the electroactive polymers to achieve electrical stimulation for repairing impaired tissues. Electroactive polymers have found numerous applications in biomedicine due to their capability in effectively delivering electrical signals to the seeded cells, such as biosensing, tissue regeneration, drug delivery, and biomedical implants. Here we will summarize the electrical characteristics of electroactive polymers, which enables them to electrically influence cellular function and behavior, including conducting polymers, piezoelectric polymers, and polyelectrolyte gels. We will also discuss the biological response to these electroactive polymers under electrical stimulation. In particular, we focus this review on their applications in regenerating different tissues, including bone, nerve, heart muscle, cartilage and skin. Additionally, we discuss the challenges in tissue regeneration applications of electroactive polymers. We conclude that electroactive polymers have a great potential as regenerative biomaterials, due to their ability to stimulate desirable outcomes in various electrically responsive cells.
Curing cancer has been one of the greatest conundrums in the modern medical field. To reduce side-effects associated with the traditional cancer therapy such as radiotherapy and chemotherapy, ...photothermal therapy (PTT) has been recognized as one of the most promising treatments for cancer over recent years. PTT relies on ablation agents such as nanomaterials with a photothermal effect, for converting light into heat. In this way, elevated temperature could kill cancer cells while avoiding significant side effects on normal cells. This theory works because normal cells have a higher heat tolerance than cancer cells. Thus, nanomaterials with photothermal effects have attracted enormous attention due to their selectivity and non-invasive attributes. This review article summarizes the current status of employing nanomaterials with photothermal effects for anti-cancer treatment. Mechanisms of the photothermal effect and various factors affecting photothermal performance will be discussed. Efficient and selective PTT is believed to play an increasingly prominent role in cancer treatment. Moreover, merging PTT with other methods of cancer therapies is also discussed as a future trend.
Implantation of stem cells for tissue regeneration faces significant challenges such as immune rejection and teratoma formation. Cell‐free tissue regeneration thus has a potential to avoid these ...problems. Stem cell derived exosomes do not cause immune rejection or generate malignant tumors. Here, exosomes that can induce osteogenic differentiation of human mesenchymal stem cells (hMSCs) are identified and used to decorate 3D‐printed titanium alloy scaffolds to achieve cell‐free bone regeneration. Specifically, the exosomes secreted by hMSCs osteogenically pre‐differentiated for different times are used to induce the osteogenesis of hMSCs. It is discovered that pre‐differentiation for 10 and 15 days leads to the production of osteogenic exosomes. The purified exosomes are then loaded into the scaffolds. It is found that the cell‐free exosome‐coated scaffolds regenerate bone tissue as efficiently as hMSC‐seeded exosome‐free scaffolds within 12 weeks. RNA‐sequencing suggests that the osteogenic exosomes induce the osteogenic differentiation by using their cargos, including upregulated osteogenic miRNAs (Hsa‐miR‐146a‐5p, Hsa‐miR‐503‐5p, Hsa‐miR‐483‐3p, and Hsa‐miR‐129‐5p) or downregulated anti‐osteogenic miRNAs (Hsa‐miR‐32‐5p, Hsa‐miR‐133a‐3p, and Hsa‐miR‐204‐5p), to activate the PI3K/Akt and MAPK signaling pathways. Consequently, identification of osteogenic exosomes secreted by pre‐differentiated stem cells and the use of them to replace stem cells represent a novel cell‐free bone regeneration strategy.
Exosomes secreted from human mesenchymal stem cells (hMSCs) pre‐differentiated for a certain period of time can serve as inducers to induce osteogenic differentiation of hMSCs in vitro. They can decorate 3D printed titanium alloy scaffolds, which are further implanted into radial bone defect. They are found to enable the scaffolds to achieve efficient cell‐free bone regeneration in vivo.
Trifluoromethylation‐based difunctionalization of alkenes provides a step‐economical route to CF3‐containing polyfunctionalized organics. New and scalable processes are highly desired in this field. ...Here, we report a simple and environmentally benign method for olefinic thiocyanotrifluoromethylation. Using PhICF3Cl as unique CF3 agent and NaSCN as the SCN source, the difunctionalization of alkenes selectively occurs on water at ambient condition. Mechanism studies suggest a radical process in which SCN anion is proposed to act as not only reductive initiator but also S‐nucleophile. All tested reactions are compatible with mono‐, di‐, tri‐, and tetra‐substituted alkenes and with high functional group tolerance. This method is also suitable for the selenocyanotrifluoromethylation of alkenes. Therefore, a sustainable platform has been established to synthesize valuable β‐trifluoromethylated thio(seleno)cyanates in a green way.
A sustainable platform has been established to synthesize valuable β‐trifluoromethylated thio(seleno)cyanates in a green way. Using PhICF3Cl as unique CF3 agent and NaSCN as the SCN source, the difunctionalization of alkenes selectively occurs on water at ambient condition. Mechanism studies suggest a radical process in which SCN anion is proposed to act as not only reductive initiator but also S‐nucleophile. This method is also suitable for the selenocyanotrifluoromethylation of alkenes.
An ultrasensitive and highly selective electrochemical assay was first attempted by combining the rolling circle amplification (RCA) reaction with poly(thymine)-templated copper nanoparticles ...(CuNPs) for cascade signal amplification. As proof of concept, prostate specific antigen (PSA) was selected as a model target. Using a gold nanoparticle (AuNP) as a carrier, we synthesized the primer–AuNP–aptamer bioconjugate for signal amplification by increasing the primer/aptamer ratio. The specific construction of primer–AuNP–aptamer/PSA/anti-PSA sandwich structure triggered the effective RCA reaction, in which thousands of tandem poly(thymine) repeats were generated and directly served as the specific templates for the subsequent CuNP formation. The signal readout was easily achieved by dissolving the RCA product-templated CuNPs and detecting the released copper ions with differential pulse stripping voltammetry. Because of the designed cascade signal amplification strategy, the newly developed method achieved a linear range of 0.05–500 fg/mL, with a remarkable detection limit of 0.020 ± 0.001 fg/mL PSA. Finally, the feasibility of the developed method for practical application was investigated by analyzing PSA in the real clinical human serum samples. The ultrasensitivity, specificity, convenience, and capability for analyzing the clinical samples demonstrate that this method has great potential for practical disease diagnosis applications.
•The modification methods of vanadium redox flow battery electrode were discussed.•Modifying the electrode can improve the performance of vanadium redox flow battery.•Synthetic strategy, morphology, ...structure, and property have been researched.•The design and future development of vanadium redox flow battery were prospected.
Vanadium redox flow battery (VRFB) is considered to be one of the most promising renewable energy storage devices. Although the first generation of VRFB has been successfully implemented in many projects, its low energy efficiency limits its large-scale application. The redox reaction of vanadium ions has an important influence on the energy efficiency of VRFB. However, the pristine carbon-based materials have poor catalytic activity on vanadium ion and cannot meet the demand. Therefore, in order to improve the catalytic activity of carbon-based materials on vanadium ion, the modification of carbon-based materials has received extensive attention. In this review, the research progress on the modification of carbon-based materials was discussed from the aspects of intrinsic treatment and introduction of catalysts. Intrinsic treatment is mainly reviewed from thermal treatment, acid treatment, electrochemical treatment, chemical etching and heteroatom doping, etc. Introduction of catalysts is mainly reviewed from the introduction of metal, metal compounds, carbon-based, and other catalyst, etc. Finally, practical suggestions are put forward for the further development of VRFB.
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