Hyperbolic metamaterials (HMMs), an unusual class of electromagnetic metamaterials, have found important applications in various fields due to their distinctive properties. A surprising feature of ...HMMs is that even continuous HMMs can possess topological edge modes. However, previous studies based on equal-frequency surface (analogy of Fermi surface) may not correctly capture the topology of entire bands. Here we develop a topological band description for continuous HMMs that can be described by a non-Hermitian Hamiltonian formulated from Maxwell's equations. We find two types of three-dimensional non-Hermitian triply degenerate points with complex linear dispersions and topological charges ±2 and 0 induced by chiral and gyromagnetic effects. Because of the photonic nature, the vacuum band plays an important role for topological edge states and bulk-edge correspondence in HMMs. The topological band results are numerically confirmed by direct simulation of Maxwell's equations. Our work presents a general non-Hermitian topological band treatment of continuous HMMs, paving the way for exploring interesting topological phases in photonic continua and device implementations of topological HMMs.
A two-dimensional nanotrench cavity grating on a thick gold film was fabricated by using e-beam lithography. Optical reflection spectra from the fabricated device were measured at oblique angles of ...incidence for TE and TM polarizations. Near perfect light absorption was observed at different wavelengths for TE and TM polarizations at oblique angles of incidence. The peak absorption wavelength of TM polarization red-shifts significantly as angle of incidence increases. The peak absorption wavelength of TE polarization blue-shifts slightly as incident angle increases. Using finite-difference time-domain (FDTD) simulations, two orders of magnitude magnetic field enhancement was revealed inside nanotrenches, indicating strong light trapping inside the nanostructure. The fabricated device was investigated as a refractive index chemical sensor. It was found that sensitivity increases for TM polarization and decreases for TE polarization when angle of incidence increases from zero.
Hyperbolic metamaterial (HMM) is a unique type of anisotropic material that can exhibit metal and dielectric properties at the same time. This unique characteristic results in it having unbounded ...isofrequency surface contours, leading to exotic phenomena such as spontaneous emission enhancement and applications such as super-resolution imaging. However, at optical frequencies, HMM must be artificially engineered and always requires a metal constituent, whose intrinsic loss significantly limits the experimentally accessible wave vector values, thus negatively impacting the performance of these applications. The need to reduce loss in HMM stimulated the development of the second-generation HMM, termed active HMM, where gain materials are utilized to compensate for metal’s intrinsic loss. With the advent of topological photonics that allows robust light transportation immune to disorders and defects, research on HMM also entered the topological regime. Tremendous efforts have been dedicated to exploring the topological transition from elliptical to hyperbolic dispersion and topologically protected edge states in HMM, which also prompted the invention of lossless HMM formed by all-dielectric material. Furthermore, emerging twistronics can also provide a route to manipulate topological transitions in HMMs. In this review, we survey recent progress in topological effects in HMMs and provide prospects on possible future research directions.
Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity ...over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.
Benzotriazole ultraviolet stabilizers (BUVSs) are widely used additives in industrial materials and personal care products that protect products from ultraviolet damage. Due to their high production ...volume and potential to bioaccumulate, BUVSs are an environmental pollutant of concern. In this study, juvenile zebrafish (Danio rerio) were exposed to 4 BUVSs (UV-234, UV-326, UV-329, and UV-P) at 10 and 100 μg/L for 28 d. BUVSs induced hepatic vacuolization and nuclei pyknosis in the liver following 100 μg/L UV-234 and UV-329 exposure. Transcriptomic analysis in the liver uncovered pathways related to inflammation that were affected by BUVSs. Based upon these data, we measured the expression levels of 9 genes involved in AHR-IL17/IL22 pathway in zebrafish larvae exposed to each BUVSs at one dose of either 10 or 100 μg/L for 6 days in a second set experiment. Transcript levels of interleukins il17a and il22 were decreased, while il6 mRNA was increased with exposure to UV-234, UV-329, and UV-P. No change to targeted transcripts was observed with UV-326 treatments. Moreover, cyp1a1 and ahr2 levels were increased in larvae treated with 100 μg/L UV-329 or UV-P. Consistent with expression data, protein abundance of IL22 was decreased by 29% with exposure to 100 μg/L UV-P. Taken together, these results demonstrate that exposure to different benzotriazole congeners may be associated with immunotoxicity in zebrafish through the AHR-IL17/IL22 pathway, and this may be associated with hepatic damage with prolonged exposures. This study provides new insight into unique pathways perturbed by specific BUVSs congeners.
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•100 μg/L UV-234 and UV-329 caused hepatic damage in juvenile zebrafish.•Pathways related to inflammation were commonly perturbed by BUVSs.•The mRNA levels of il17a, il22, il6, cyp1a1and ahr2 were affected by BUVSs.•Protein levels of IL22 were decreased by 100 μg/L UV-P in larval zebrafish.
Butylated hydroxytoluene (BHT) is one of the most frequently used synthetic phenolic antioxidants added to food and consumer products such as plastics as a preservative. Due to its high production ...volume, BHT has been detected in aquatic environments, raising concerns about sub-lethal toxicity. However, there are limited toxicological data for BHT, especially in fish. In this study, zebrafish embryos were exposed to BHT at concentrations ranging 0.01–100 μM for up to 6 days post fertilization (dpf). Acute toxicity was assessed, and experiments revealed that BHT had a 96 h LC50 value of 57.61 μM. At sub-lethal doses (0.1–60 μM), BHT markedly decreased heart rates of zebrafish embryos at 48 h and 72 h by ∼25–30%. Basal and maximal respiration of zebrafish embryos at 24 hpf were decreased by 59.3% and 41.4% respectively following exposure to 100 μM BHT. Behavior in zebrafish was measured at 6 dpf following exposures to 0.01–10 μM BHT. Locomotor behaviors (e.g. total distance moved and velocity) were significantly increased in larvae at doses higher than 0.1 μM BHT. In addition, dark-avoidance behavior was decreased following exposure to 0.01 μM BHT, while conversely, it was increased in zebrafish exposed to 0.1 μM BHT. To investigate potential underlying mechanisms that could explain behavioral changes, transcripts involved in dopamine signaling were measured. Relative expression of dat mRNA was increased in larval fish from the 0.01 μM BHT treatment, while there were no effects on dat mRNA levels at higher concentrations. The mRNA levels of drd3 were decreased in zebrafish from the 1 μM BHT treatment. Taken together, BHT can affect the expression of the dopamine system, which is hypothesized to be related to the abnormal anxiety-associated behavior of larval zebrafish.
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•Butylated hydroxytoluene is an environmental pollutant.•Heart rates of zebrafish embryos at 48 h and 72 h were decreased by ∼25–30%.•BHT increased locomotor behaviors of zebrafish larvae.•Low dose BHT decreased larval dark-avoidance behavior.•Levels of dat was increased while drd3 was decreased in response to BHT.
Single‐image rain removal is an important problem in the field of computer vision aimed at recovering clean images from rainy images. In recent years, data‐driven convolutional neural network ...(CNN)‐based rain removal methods have achieved significant results, but most of them cannot fully focus on the contextual information in rain‐containing images, which leads to the failure of recovering some of the background details of the images that have been corrupted due to the aggregation of rain streaks. With the success of Transformer‐based models in the field of computer vision, global features can be easily acquired to better help recover details in the background of an image. However, Transformer‐based models often require a large number of parameters during the training process, which makes the training process very difficult and makes it difficult to apply them to specific devices for execution in reality. The authors propose a Recursive Attention Collaboration Network, which consists of a recursive Swin‐transformer block (STB) and a CNN‐based feature fusion block. The authors designed the Recursively Integrate Transformer Block (RITB), which consists of several STBs recursively connected, that can effectively reduce the number of parameters of the model. The final part of the module can integrate the local information from the STBs. The authors also design the Feature Enhancement Block, which can better recover the details of the background information corrupted by rain streaks of different density shapes through the features passed from the RITB. Experiments show that the proposed network has an effective rain removal effect on both synthetic and real datasets and has fewer model parameters than other mainstream methods.
Fish-like robot is a special autonomous underwater vehicle with broad application prospects. Some previous studies concentrated on the hydrodynamics of free-swimming fish-like robots. But the ...hydrodynamic performance of fish-like robot swimming with a tilt angle in constrained space has not been well studied, and the influence of environmental wave and current on its is also still unclear. In this paper, the experiment devices, including a physical fish-like robot, a hydrodynamics measurement platform, and a six-axis force sensor, are used to study the effect of attack angle and environmental condition on the hydrodynamics of near-surface swimming fish-like robot. Nine attack angles, five oscillating amplitudes, and three environmental conditions are analyzed in the experiments. It shows that thrust force decreases when caudal fin passes above water surface, but the increased difference between gravity force and buoyancy force will compensate the decreased force generated by caudal fin when fish-like robot swims with certain dive angle. The extra reaction force generated by solid bottom boundary will promote the thrust force and vertical force. The surface water wave condition or surface water current condition also has obvious effects on hydrodynamic performance. This paper provides a new perspective to the research on the hydrodynamic performance of fish-like robot and will do favor in the development of fish-like robot.
...the total effective rate (TER) of each type of operation was calculated according to an evaluation standard. According to the results of gastroscopy and X-ray barium meal examination, seven ...patients had cardiac stricture: two, two, and three in the NF, TF, and DF groups, respectively. The critical findings were as follows: (1) patients underwent HR successfully, which indicated that the procedure was safe; (2) the operative time, intra-operative blood loss, and post-operative hospital stay in the HR group were significantly lower than in the fundoplication groups; (3) patients who underwent HR had a lower rehospitalization rate caused by surgical complications; and (4) at 1.5-year follow-up, acid regurgitation and heartburn scores in all four groups were lower than the corresponding pre-operative scores, and there was no significant difference in the TER among the four surgical groups. ...laparoscopic HH repair and HR were safe and effective in the treatment of patients with GERD and HH.
Introduction
Anaerobic ammonium oxidation (anammox) plays a vital role in the global nitrogen cycle by oxidizing ammonium to nitrogen under anaerobic environments. However, the existence, abundance, ...and diversity of anammox bacteria between different temperatures are less studied, particularly in purple paddy soils.
Methods
13
C-DNA stable-isotope probe combined with Illumina MiSeq high-throughput sequencing was employed to explore soil abundance and diversity of anammox bacteria. In doing so, 40–60 cm depth soils from typical purple paddy soils in Chongqing, southwest China, were cultured under
12
CO
2
-labeled and
13
CO
2
-labeled at 35°C, 25°C, 15°C, and 5°C for 56 days.
Results and Discussion
Anammox bacteria were not labeled at all by
13
CO
2
at 5°C. The highest abundance of anammox bacteria was found at 25°C (3.52 × 10
6
~3.66 × 10
6
copies·g
−1
dry soil), followed by 35°C and 15°C (2.01 × 10
6
~2.37 × 10
6
copies·g
−1
dry soil) and almost no increase at 5°C. The relative abundance of
Candidatus Jettenia
sp. was higher at 25°C and 15°C, while
Candidatus Brocadia
sp. was higher at 35°C and 5°C. Our results revealed differences in anammox bacteria at different temperatures in purple paddy soils, which could provide a better understanding of soil N cycling regulated by anammox bacteria.
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