Dissecting the γ\gamma-ray emissions of the nearby galaxies NGC 1068 and NGC 253

Intrigued by recent high-energy study results for nearby galaxies with gamma-ray emission and in particular NGC~1068 that has been detected as a neutrino-emitting source by the IceCube Neutrino Observatory, we conduct detailed analysis of the $\gamma$-ray data for the galaxies NGC~1068 and NGC~253, obtained with the Large Area Telescope onboard {\it the Fermi Gamma-ray Space Telescope}. By checking for their possible spectral features and then constructing light curves in corresponding energy ranges, we identify flare-like activity from NGC ~1068 in $\geq$2\,GeV energy range and significant long-term variations of NGC~253 in $\geq$5\,GeV energy range. In the former, the emission appears harder in the two half-year flare-like events than that in the otherwise `quiescent' state. In the latter, there is a 2-times decrease in the flux before and after MJD~57023, which is clearly revealed by the test-statistic maps we obtain. Considering studies carried out and models proposed for the $\gamma$-ray emissions of the two sources, we discuss the implications of our findings. The jet in NGC~1068 may contribute to the \gr\ emission. The nature of the long-term variations in NGC~253 is not clear, but the variation part of the emission may be connected to the very-high-energy (VHE) emission of the galaxy and could be verified by VHE observations.Comment: 9 pages, 6 figures, 2 tables, submitted to Ap

Research progress of optoelectronic devices based on diamond materials

Diamond has a variety of unique characteristics, including integrates mechanics, electricity, heat, optics and other excellent properties, so that it is widely focus on the field of high and new technology, especially in the optoelectronic technology. Because diamond has the characteristics of high thermal conductivity, high breakdown field (10 mV/cm), high electron and hole mobility, it has a wide application prospect in high temperature, high power and high frequency photoelectric equipment. The wide bandgap (5.47 eV) makes diamond an ideal material in ultraviolet detectors (UV). Its high carrier mobility and breakdown field strength make it an ideal choice for field emission materials, which are expected to be used in high-power electronic devices in the next few years. At the same time, in addition to high hardness, it also has various of excellent physical properties, such as low coefficient of thermal expansion, low coefficient of friction, high acoustic propagation speed and high optical transmittance, so that it has broad application prospects in many fields such as machining, microelectronic devices, optical windows and surface coatings. In addition, diamond also has a high exciton binding energy (80 meV), which plays an important development in deep ultraviolet and high-energy particle detectors. In this article, the latest progress in the application of diamond-based optoelectronic devices is reviewed. A variety of advanced devices and physical phenomena are considered, for example, sensors, transistors, memory, Light-emitting diode (LEDs), ultraviolet detectors and field emission. This review will provide a new idea to promote the development of photoelectric applications based on diamond structure

Performance of Binderless Board Manufactured Using Camphor Tree Residue

Residue of the branch wood of camphor tree (Cinnamomum camphora) was used to manufacture binder-free biodegradable biomass fiberboard (bio-board) by the wet method. To investigate the mechanical properties of the bio-board, bending rupture stress and tensile rupture stress tests were measured and the effect of heating temperature and applied pressure on the performance of the bio-board was evaluated. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) were used to analyze the influencing factors on the microstructure and bond quality of the bio-boards. The overall density of the bio-boards exceeded 0.8 g/cm3 and the moisture content was below 10%, which conformed to the JIS A 5908 standard (2014) for the hardboard S20 type design specification. The bending rupture stress and tensile rupture stress continued to increase, and the dimensional stability continuously improved as the applied pressure and the heating temperature increased. However, when the heating temperature exceeded 170 °C, the increase in the rupture stress slowed down and the dimensional stability had been improved. Furthermore, increasing the heating temperature was more conducive for optimizing the bio-board’s performance than increasing the applied pressure

Dissecting the γ-Ray Emissions of the Nearby Galaxies NGC 1068 and NGC 253

Intrigued by recent high-energy study results for nearby galaxies with γ -ray emission and in particular NGC 1068 that has been detected as a neutrino-emitting source by the IceCube Neutrino Observatory, we conduct a detailed analysis of the γ -ray data of the galaxies NGC 1068 and NGC 253, obtained with the Large Area Telescope on board the Fermi γ -ray Space Telescope. By checking their possible spectral features and then constructing light curves in the corresponding energy ranges, we identify spectral-change activity from NGC 1068 in the ≥2 GeV energy range and long-term, statistically significant changes for NGC 253 in the ≥5 GeV energy range. In the former, the emission appears harder in two half-year periods than in the otherwise “quiescent” state. In the latter, an ∼two-fold decrease in the detection significance after MJD = 57023 is clearly revealed by the test-statistic maps we obtain. Considering the previous studies carried out and the various models proposed for the γ -ray emissions of the two sources, we discuss the implications of our findings. We suspect that a jet (or outflow) in NGC 1068 might contribute to the γ -ray emission. The nature of the long-term statistically significant changes for NGC 253 is not clear, but since the part of the GeV emission may be connected to the very-high-energy (VHE) emission from the center of the galaxy, it could be further probed with VHE observations

Recent applications of nanodiamond quantum biosensors: A review

The ultrafine biosensing technology reveals the mechanisms of various biochemical reactions in cells and the causes of complex diseases through the detection of cellular and subcellular structures. It has an irreplaceable role in the early diagnosis of diseases and in the evaluation of the effectiveness of drug therapy. Due to the complex media composition and ultrafine size of biological cells, traditional sensing technologies can hardly shoulder this difficult task. Nanodiamond (ND) is chemically inert, biocompatible, and nanoscale in size; therefore, it is a safe, non-invasive tool for intracellular sensing. In this Review, we will present the properties of nitrogen vacancy centers, silicon vacancy centers in ND, functionalization of ND, and brief principles of sensing, as well as the latest applications, opportunities, and challenges of ND biosensing

A Review on Optoelectronical Properties of Non-Metal Oxide/Diamond-Based p-n Heterojunction

Diamond holds promise for optoelectronic devices working in high-frequency, high-power and high-temperature environments, for example in some aspect of nuclear energetics industry processing and aerospace due to its wide bandgap (5.5 eV), ultimate thermal conductivity, high-pressure resistance, high radio frequency and high chemical stability. In the last several years, p-type B-doped diamond (BDD) has been fabricated to heterojunctions with all kinds of non-metal oxide (AlN, GaN, Si and carbon-based semiconductors) to form heterojunctions, which may be widely utilized in various optoelectronic device technology. This article discusses the application of diamond-based heterostructures and mainly writes about optoelectronic device fabrication, optoelectronic performance research, LEDs, photodetectors, and high-electron mobility transistor (HEMT) device applications based on diamond non-metal oxide (AlN, GaN, Si and carbon-based semiconductor) heterojunction. The discussion in this paper will provide a new scheme for the improvement of high-temperature diamond-based optoelectronics

Schottky Barrier-Based Built-In Electric Field for Enhanced Tumor Photodynamic Therapy

Photodynamic therapy’s antitumor efficacy is hindered by the inefficient generation of reactive oxygen species (ROS) due to the photogenerated electron–hole pairs recombination of photosensitizers (PS). Therefore, there is an urgent need to develop efficient PSs with enhanced carrier dynamics. Herein, we designed Schottky junctions composed of cobalt tetroxide and palladium nanocubes (Co3O4@Pd) with a built-in electric field as effective PS. The built-in electric field enhanced photogenerated charge separation and migration, resulting in the generation of abundant electron–hole pairs and allowing effective production of ROS. Thanks to the built-in electric field, the photocurrent intensity and carrier lifetime of Co3O4@Pd were approximately 2 and 3 times those of Co3O4, respectively. Besides, the signal intensity of hydroxyl radical and singlet oxygen increased to 253.4% and 135.9%, respectively. Moreover, the localized surface plasmon resonance effect of Pd also enhanced the photothermal conversion efficiency of Co3O4@Pd to 40.50%. In vitro cellular level and in vivo xenograft model evaluations demonstrated that Co3O4@Pd could generate large amounts of ROS, trigger apoptosis, and inhibit tumor growth under near-infrared laser irradiation. Generally, this study reveals the contribution of the built-in electric field to improving photodynamic performance and provides new ideas for designing efficient inorganic PSs

Photoluminescence and Electrical Properties of n-Ce-Doped ZnO Nanoleaf/p-Diamond Heterojunction

The n-type Ce:ZnO (NL) grown using a hydrothermal method was deposited on a p-type boron-doped nanoleaf diamond (BDD) film to fabricate an n-Ce:ZnO NL/p-BDD heterojunction. It shows a significant enhancement in photoluminescence (PL) intensity and a more pronounced blue shift of the UV emission peak (from 385 nm to 365 nm) compared with the undoped heterojunction (n-ZnO/p-BDD). The prepared heterojunction devices demonstrate good thermal stability and excellent rectification characteristics at different temperatures. As the temperature increases, the turn-on voltage and ideal factor (n) of the device gradually decrease. The electronic transport behaviors depending on temperature of the heterojunction at different bias voltages are discussed using an equilibrium band diagram and semiconductor theoretical model

Multihierarchically Profiling the Biological Effects of Various Metal-Based Nanoparticles in Macrophages under Low Exposure Doses

Thus far, tremendous efforts have been made to understand the biosafety of metal-based nanoparticles (MNPs). Nevertheless, most previous studies focused on specific adverse outcomes of MNPs at unrealistically high concentrations with little relevance to the National Institute for Occupational Safety and Health (NIOSH) exposure thresholds, and failed to comprehensively evaluate their toxicity profiles. To address these challenges, we here endeavored to multihierarchically profile the hazard effects of various popularly used MNPs in macrophages under low exposure doses. At these doses, no remarkable cell viability drop and cell death were induced. However, a cellular antioxidant defense system was seen to be initiated in cells by all MNPs even at these low concentrations, albeit to a differential extent and through different pathways, as reflected by differential induction of the antioxidant enzymes and Nrf2 signaling. Regarding inflammation, rare earth oxide nanomaterials (REOs) except nCeO₂ greatly increased IL-1β secretion in a NLRP3 inflammasome-dependent manner. By contrast, six REOs, AgNP-5nm, nFe₂O₃, nFe₃O₄, and nZnO were found to elevate TNF-α concentration through post-transcriptional regulation. Moreover, all MNPs except nCeO₂ drastically altered cellular membrane/cytoskeleton meshwork, but leading to different outcomes, with condensed cellular size and reduced numbers of protrusions by REOs and elongated protrusions by other MNPs. Consequently, REOs (e.g., nDy₂O₃ and nSm₂O₃) impaired phagocytosis of macrophages, and other MNPs (such as AgNP-25nm and nZnO) reversely enhanced macrophagic phagocytosis. Alterations of membrane and cytoskeleton meshwork induced by these MNPs also caused disordered membrane potential and calcium ion flux. Collectively, our data profiled the biological effects of different MNPs in macrophages under low exposure doses, and deciphered a complex network that links multiparallel pathways and processes to differential adverse outcomes