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Cyclic GMP-AMP synthase (cGAS) is a double-stranded DNA (dsDNA) sensor that functions in the innate immune system. Upon binding dsDNA in the cytoplasm, cGAS and dsDNA form phase-separated aggregates in which cGAS catalyzes synthesis of 2’3’-cyclic GMP-AMP that subsequently triggers a STING-dependent, type I IFN response. Here, we showed that cytoplasmic RNAs, especially tRNAs, regulate cGAS activity. We discovered that RNAs did not activate cGAS but rather promoted phase separation in vitro. In cells, cGAS colocalized with RNAs and formed phase-separated granules even in the absence of cytoplasmic dsDNA. An Opti-prep gradient analysis of cell lysates showed that the endogenous cGAS was associated with cytoplasmic RNAs in an aggregative form. Further in vitro assays showed that RNAs compete for binding of cGAS with dsDNA and inhibit cGAS activity when the dsDNA concentration is high and promote the formation of phase separations and enhance cGAS activity when the dsDNA concentration is low. Thus, cytoplasmic RNAs regulate cGAS activity by interfering with formation of cGAS-containing aggregates.

The outbreak of COVID-19 caused by SARS-CoV-2 in Wuhan and other cities of China is a growing global concern. Delay in diagnosis and limited hospital resources lead to a rapid spread of COVID-19. In this study, we investigate the effect of delay in diagnosis on the disease transmission with a new formulated dynamic model. Sensitivity analyses and numerical simulations reveal that, improving the proportion of timely diagnosis and shortening the waiting time for diagnosis can not eliminate COVID-19 but can effectively decrease the basic reproduction number, significantly reduce the transmission risk, and effectively prevent the endemic of COVID-19, e.g., shorten the peak time and reduce the peak value of new confirmed cases and new infection, decrease the cumulative number of confirmed cases and total infection. More rigorous prevention measures and better treatment of patients are needed to control its further spread, e.g., increasing available hospital beds, shortening the period from symptom onset to isolation of patients, quarantining and isolating the suspected cases as well as all confirmed patients.

Porous gallium nitride (GaN) luminescent materials were fabricated by photoelectrochemical etching using three different 1-ethyl-3-methylimidazolium ([EMIM])-based ionic liquids as the etchants. The as-etched porous GaN presents honeycomb shape, deep gully with some holes in the surroundings, and overlapping hole structure, which are significantly different from the planar GaN. Moreover, photoluminescence (PL) spectra indicates that the porous GaN has more excellent PL performance than the planar GaN. In general, reducing the etching time to 1 min, the PL intensity of porous GaN etched by [EMIM][OTF] is 9.27 times than that of the planar one. These results suggest that porous GaN etched by ionic liquid can be an outstanding substrate in the field of the luminescent material.

Bismuth-modified gallium nitride (Bi/GaN) electrode was fabricated using an in situ plating technique and simultaneously investigated for the detection of Cd2 + by square wave anodic stripping voltammetry (SWASV). Under the optimized conditions, the Bi/GaN electrode showed good linear amperometric responses for Cd2 + in the concentration range from 1 to 150 μg/L. The sensitivity was 0.54418 μA L μg− 1 (i.e., 59.8598 A M− 1) and the limit of detection (LOD) was 0.3 μg/L (i.e., 2.72 nM). Furthermore, the as-prepared Bi/GaN sensor has high repeatability, and retains 95% of its initial stripping peak current after 50 cycles. More importantly, the applicability of the sensor in real samples such as tap water, milk, and fetal bovine serum was researched. The recovery ranges from 92.3 to 106.7%, indicating that the as-fabricated Bi/GaN sensor has potential to monitor Cd2 + in practical environments.

Three-dimensional (3D) metal-semiconductor nanostructures as surface-enhanced Raman scattering (SERS) substrates were designed by in situ electrodeposition of gold nanoparticles (AuNPs) or in situ photodeposition of silver nanoparticles (AgNPs) on gallium nitride (GaN) nanoflowers (NFs) supports fabricated by metal-assisted photochemical etching of single crystalline GaN. 3D AuNPs/GaN NFs and AgNPs/GaN NFs substrates exhibit excellent enhancement effect for Rhodamine 6G (R6G) due to more “hot spots” in the same probing volume compared to 2D GaN based substrates. The enhancement factors of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates are up to 2.1 × 10 7 and 5.9 × 10 7 , respectively, and the corresponding detection limits of R6G are 10 −8 and 10 −10 M, respectively. Moreover, further study reveals both substrates have good reproducibility and long-term stability. The performance of the prepared substrates for biological application was demonstrated by the detection of bovine serum albumin (BSA). A series of characteristic bands of amides suggest BSA can be well adsorbed on the surface of the AuNPs/GaN NFs and AgNPs/GaN NFs substrates, which demonstrates our substrates have good biocompatibility and are promising candidates for SERS biosensors.

In this study, we report for the preparation of nickel phthalocyanine (NiPc) free-standing films on ionic liquid (IL) surface by a physical vapor deposition method. Different from on the solid substrate, the as-obtained film is α phase and with a 2D network structure. In addition, the good transferability of the film make it can be easily transferred onto any substrate for further device applications. The device based on these films shows good photoelectrical property, high stability and high photosensitivity.

Gallium nitride (GaN) nanowires (NWs) were fabricated by metal-assisted photochemical etching (MaPEtch). Gold nanoparticles (AuNPs) as metal catalyst were electrodeposited on the GaN substrate. SEM and HRTEM images show the surface of GaN NWs is smooth and clean without any impurity. SAED and FFT patterns demonstrate GaN NWs have single crystal structure, and the crystallographic orientation of GaN NWs is (0002) face. On the basis of the assumption of localized galvanic cells, combined with the energy levels and electrochemical potentials of reactants in this etching system, the generation, transfer and consumption of electron-hole pairs reveal the whole MaPEtch reaction process. Such easily fabricated GaN NWs have great potential for the assembly of GaN-based single-nanowire nanodevices.

The structural relaxation times of metallic glasses (MGs) are generally believed to decrease with increasing flow rate, also known as shear thinning. In this work, an extraordinary loading rate-independent creep relaxation time, in contrast to the decreasing Maxwell relaxation time with increasing loading rate, is observed for a La-based MG with pronounced Johari–Goldstein relaxation under nanoindentation. The Johari–Goldstein relaxation in the flow of MGs is suggested to be a form of local Newtonian flow and may be not crucial in shear thinning, whereas the main α relaxation is proposed to predominate in the shear thinning of MGs, based on the disparity between the creep relaxation time and the Maxwell relaxation time. These results improve the current understandings on the structural relaxation and its role in the shear thinning and plastic deformation of MGs.

Bismuth nanodendrites (BiNDs) were electrodeposited on planar gallium nitride (GaN) electrode via a differential pulse voltammetric technique to fabricate the non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed that the as-obtained BiNDs had numerous dendrite sub-branches, whose diameters ranged from 136 to 152 nm. The BiNDs/GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 µM to 1 mM with the sensitivity of 60.0 μA mM−1 cm−2. Another linear range was from 1 to 10 mM with the sensitivity of 23.3 μA mM−1 cm−2. The limit of detection (LOD) was 5 µM with the signal-to-noise ratio of 3. The applicability of the sensor was investigated to the H2O2 detection in real samples such as fetal bovine serum and milk, and the sensor exhibited excellent anti-interference capacity. The achieved results indicate that the as-prepared BiNDs/GaN sensor with good reproducibility and long-term stability was promising for detecting H2O2 in practical environments.

Gallium nitride (GaN) surface was etched by 0.3 M ethylenediamine tetraacetic acid disodium (EDTA-2Na) via photoelectrochemical etching technique. SEM images reveal the etched GaN surface becomes rough and irregular. The pore density is up to 1.9 × 10 9 per square centimeter after simple acid post-treatment. The difference of XPS spectra of Ga 3d, N 1s and O 1s between the non-etched and freshly etched GaN surfaces can be attributed to the formation of Ga–EDTA complex at the etching interface between GaN and EDTA-2Na. The proposed complexation dissolution mechanism can be broadly applicable to almost all neutral etchants under the prerequisite of strong light and electric field. From the point of view of environment, safety and energy, EDTA-2Na has obvious advantages over conventionally corrosive etchants. Moreover, as the further and deeper study of such nearly neutral etchants, GaN etching technology has better application prospect in photoelectric micro-device fabrication.

Porous gallium nitride (PGaN) layers were fabricated by metal-assisted photochemical etching (MaPCE) using electrodeposited platinum nanoparticles (PtNPs) or gold nanoparticles (AuNPs) as catalysts. After identification of a suitable negative potential and appropriate cyclic voltammetry (CV) conditions, high-density PtNPs or AuNPs were deposited onto a planar GaN substrate. Based on the concrete numerical values of energy levels, the generation, transfer and consumption of electrons and holes, and the assumption that localized galvanic cells are formed, an etching mechanism was proposed which may provide theoretical guidance for future work on etching of GaN and other semiconductor materials. Keywords: Gallium nitride, Metal-assisted photochemical etching, Electrodeposition, Noble metal nanoparticles

Here we report the electrodeposition of gold nanoparticles (AuNPs) onto porous GaN electrode obtained by photoelectrochemical etching planar GaN to fabricate a non-enzymatic hydrogen peroxide (H2O2) sensor. SEM images revealed porous GaN has uniformly high-porosity structure and the diameter of AuNPs is 5–16 nm. The AuNPs/porous GaN electrode exhibited good electrocatalytic activity toward the reduction of H2O2 and performed as amperometric sensor for the detection of H2O2. The AuNPs/porous GaN electrode showed linear amperometric responses for H2O2 in the concentration range from 10 to 100 μM with the sensitivity of 281.5 μA mM−1. The limit of detection (LOD) is 2 μM with a signal-to-noise ratio of 3. In addition, the AuNPs/porous GaN electrode exhibited good repeatability, reproducibility, selectivity and long-term stability for H2O2 detection, in the meanwhile, AuNPs showed excellent adhesive capacity to the porous GaN electrode, which was tested by continually sonicating the AuNPs/porous GaN electrode for 3 h. Above results demonstrated this simply prepared H2O2 sensor has good practicability and is promising to measure the analyte in practical applications.

Here we report an environment-friendly approach to fabricate porous GaN photoelectrode using ionic liquid as the etchant. SEM images revealed photo-assisted electrochemical etching (PECE) has better etching effect than electrochemical etching (ECE). Furthermore, Raman spectra demonstrated porous GaN obtained by PECE has better lattice integrity than that obtained by ECE. The photocurrent of porous GaN prepared by PECE is six times and two times of planar and porous GaN fabricated by ECE, respectively. Above results indicated porous GaN obtained by PECE can be a promising photoelectrode for optoelectronic applications.

This paper is devoted to exploring a diffusive predator-prey system with prey refuge and predator cannibalism. We investigate dynamics of this system, including dissipation and persistence, local and global stability of constant steady states, Turing instability, and nonexistence and existence of nonconstant steady state solutions. The influence of prey refuge and predator cannibalism on predator and prey biomass density is also considered by using a systematic sensitivity analysis. Our studies suggest that appropriate predator cannibalism has a positive effect on predator biomass density, and then high predator cannibalism may stabilize the predator-prey ecosystem and prevent the paradox of enrichment.

Acute pulmonary embolism (APE) with cardiac arrest (CA) is associated with a high mortality rate. Even upon return of the spontaneous circulation (ROSC), APE-CA survivors are prone to myocardial cell apoptosis, a key cellular mechanism that induces heart failure. A recent study by our group discovered a post-resuscitation imbalance in the serum angiotensin-converting enzyme (ACE)2/ACE axis of the renin-angiotensin system (RAS), as well as regressive cardiac function in a porcine model of APE-CA. However, it has remained elusive how this imbalance in the ACE2/ACE axis affects myocardial cell apoptosis. In the present study, western blot and immunohistochemical analyses demonstrated that the RAS was only activated in the left myocardium, as evidenced by a decreased ACE2/ACE ratio following APE-CA and ROSC, but not the right myocardium. Ultrastructural analysis confirmed myocardial apoptosis in the left and right myocardium. Furthermore, B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax) and caspase-3 levels were elevated and Bcl-2 levels were decreased in the left myocardium following APE-CA and ROSC. Treatment with the ACE inhibitor captopril for 30 min after initiation of ROSC prevented the increase in Bax and the decrease in Bcl-2 in the left myocardium compared with that in saline-treated pigs. Captopril also inhibited the activation of extracellular signal-regulated kinase (ERK)1/2 in the left myocardium. The results of the present study suggest that an imbalance in the ACE2/ACE axis has an important role in myocardial apoptosis following APE-CA, which may be attributed to decreased ERK1/2 activation. In addition, it was indicated that captopril prevents apoptosis in the left myocardium after ROSC.