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Underwater images often suffer from degradation caused by light attenuation and turbidity, resulting in poor image quality. Due to the domain gap between source domain and target domain and the lack of pair images in certain datasets, most learning-based methods exhibit limited performance in preserving image details and ensuring model stability, with poor generalization ability. To address these challenges, this paper proposes an effective adversarial transfer learning method for underwater image enhancement with specially designed hybrid loss. Our approach employs domain adaptation techniques based on adversarial transfer learning to automatically learn image features and patterns from both underwater and air images. Specifically, we design domain-adaptive generators to establish forward and backward processes between the source and target domains. Additionally, we introduce hybrid losses for domain adaptation, facilitating effective enhancement of underwater images. The forward generator demonstrates promising generalization. Experimental results demonstrate the high feasibility and effectiveness of our proposed method in enhancing underwater images, offering a powerful solution for both underwater and air images. [ABSTRACT FROM AUTHOR]

Many efforts have been taken in recent years to push atomic gravimeters toward practical applications. We demonstrate an atomic gravimeter named NIM-AGRb2 that is transportable and suitable for high-precision gravity measurements. Constraint-structured active vibration isolation (CS-AVI) is used to reduce the ground vibration noise. The constraint structure in CS-AVI ensures that the isolation platform only has vertical translation, with all other degrees of freedom (DoFs) being constrained. Therefore, the stability of active vibration isolation is enhanced. With the implementation of CS-AVI, the sensitivity of NIM-AGRb2 reached as low as 20.5 μGal/Hz1/2. The short-term sensitivity could be further reduced to 10.8 μGal/Hz1/2 in a seismologic observation station. Moreover, we evaluated the system noise of the gravimeter, and the results were consistent with our observations. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) layered transition metal dichalcogenides such as MoS2 have been viewed as the most favorable candidates for replacing noble metals in catalyzing the hydrogen evolution reaction in water splitting owing to their earth abundance, superb chemical stability, and appropriate Gibbs free energy. However, due to its low number of catalytic sites and basal catalytic inertia, the pristine MoS2 displayed intrinsically unsatisfactory HER catalytic activity. Here, the hydrogen evolution catalytic activities of nanostructured MoS2 powder before and after plasma modification with nitrogen doping were experimentally compared, and the influence of treatment parameters on the hydrogen evolution catalytic performance of MoS2 has been studied. The feasibility of regulating hydrogen evolution catalytic activity by nitrogen doping of MoS2 was verified based on density functional theory calculations. Our work demonstrates a more convenient and faster way to develop cheap and efficient MoS2-based catalysts for electrochemical hydrogen evolution reactions. Additionally, theoretical studies reveal that N-doped MoS2 exhibits strong hybridization between Mo-d and N-p states, causing magnetism to evolve, as confirmed by experiments. [ABSTRACT FROM AUTHOR]

Platinum-based drugs are widely used as first-line anti-tumor chemotherapy agents. However, they also have nonnegligible side effects due to the free drugs in circulation. Therefore, it is necessary to develop efficient and safe delivery systems for better tumor cell targeting. Hydrogel is a promising anti-tumor drug carrier that can form a platinum/hydrogel combination system for drug release, which has shown better anti-tumor effects in some studies. However, there is a lack of systematic summary in this field. This review aims to provide a comprehensive overview of the platinum/hydrogel combination system with the following sections: firstly, an introduction of platinum-based drugs; secondly, an analysis of the platinum/hydrogel combination system; and thirdly, a discussion of the advantages of the hydrogel-based delivery system. We hope this review can offer some insights for the development of the platinum/hydrogel combination system for better cancer therapy. The common raw materials used in the formation of hydrogels include polysaccharides, copolymers, and polypeptides, which can be cross-linked to create hydrogels. In the case of platinum-based anti-cancer drugs such as cisplatin, carboplatin, and oxaliplatin, they can be combined with hydrogels through physical or chemical forces, resulting in a platinum/hydrogel combination.Hydrogels play a crucial role in cancer treatment by enabling the controlled and gradual release of platinum-based drugs in response to stimuli, thereby enhancing the efficacy of cancer treatment through immune system enhancement, targeted administration, and promotion of cell apoptosis. Once the drug delivery is achieved, the hydrogel can degrade naturally in the body within a few days without exhibiting side effects. [ABSTRACT FROM AUTHOR]

Layered transition metal dichalcogenides (TMDs) provide a favorable research platform for the advancement of spintronics and valleytronics because of their unique spin-valley coupling effect, which is attributed to the absence of inversion symmetry coupled with the presence of time-reversal symmetry. To maneuver the valley pseudospin efficiently is of great importance for the fabrication of conceptual devices in microelectronics. Here, we propose a straightforward way to modulate valley pseudospin with interface engineering. An underlying negative correlation between the quantum yield of photoluminescence and the degree of valley polarization was discovered. Enhanced luminous intensities were observed in the MoS2/hBN heterostructure but with a low value of valley polarization, which was in stark contrast to those observed in the MoS2/SiO2 heterostructure. Based on the steady-state and time-resolved optical measurements, we reveal the correlation between exciton lifetime, luminous efficiency, and valley polarization. Our results emphasize the significance of interface engineering for tailoring valley pseudospin in two-dimensional systems and probably advance the progression of the conceptual devices based on TMDs in spintronics and valleytronics. [ABSTRACT FROM AUTHOR]

2D materials are regarded as ideal candidates for fabricating flexible devices in electronics, due to their intrinsic clean surface and malleability. However, due to the weak interaction between 2D materials and the substrates underneath, bending or stretching will inevitably cause severe slippage, which degrades the device's performance or even leads to failure. The realization of no slippage between 2D materials and substrates under ultrahigh strain has become a key topic in the field of flexible electronics. Here, a strategy to overcome this limitation, by which strain can be effectively transferred to 2D materials is demonstrated. By applying this improved method to few‐layer β‐InSe, it is found that the loaded strain reaches as high as 7.2% without any slippage, along with an apparent redshift of ≈4.18 cm−1 in Raman scattering signals. The evolution trend of bandgap observed in the luminous properties of β‐InSe is consistent with the author's density functional theory (DFT) calculations. This convenient method can be intensively expanded to other van der Waals (vdW) layered materials and sheds light on flexible electronic applications. [ABSTRACT FROM AUTHOR]

Satellite data is of high importance for ocean environment monitoring and protection. However, due to the missing values in satellite data, caused by various force majeure factors such as cloud cover, bad weather and sensor failure, the quality of satellite data is reduced greatly, which hinders the applications of satellite data in practice. Therefore, a variety of methods have been proposed to conduct missing data imputation for satellite data to improve its quality. However, these methods cannot well learn the short-term temporal dependence and dynamic spatial dependence in satellite data, resulting in bad imputation performance when the data missing rate is large. To address this issue, we propose the Spatio-Temporal Attention Generative Adversarial Network (STA-GAN) for missing value imputation in satellite data. First, we develop the Spatio-Temporal Attention (STA) mechanism based on Graph Attention Network (GAT) to learn features for capturing both short-term temporal dependence and dynamic spatial dependence in satellite data. Then, the learned features from STA are fused to enrich the spatio-temporal information for training the generator and discriminator of STA-GAN. Finally, we use the generated imputation data by the trained generator of STA-GAN to fill the missing values in satellite data. Experimental results on real datasets show that STA-GAN largely outperforms the baseline data imputation methods, especially for filling satellite data with large missing rates. [ABSTRACT FROM AUTHOR]

For absolute gravimeters, which play important roles in geophysics and geological exploration, an ultra-low-frequency vertical vibration isolator is necessary to achieve the required measurement precision. A novel active vibration isolator that uses a geometric anti-spring (GAS) structure has been proposed by our team at Tsinghua University previously, but its performance is mainly limited by the large-scale drift in the detection signal of the system. In this paper, after a brief theoretical introduction to the overall system, recent improvements in this novel vibration isolator are presented. The main improvements to the isolator are the use of new blades in the GAS structure and the addition of an extra compensation circuit to eliminate the drift. The improved prototype has a resonance period of 29.2 s and a continuous working time of several days, as compared with the resonance period of 19.2 s and a working time lasting only several minutes of the previous prototype. Experiments show that the improved prototype performs well in the homemade T-1 laser-interferometry absolute gravimeter. The standard error of the mean (SEM) of a 50-drop measurement performed in Tsinghua University is reduced significantly from 404 μGal (1 μGal = 1 × 10−8 m s−2) without the vibration isolator to 10.8 μGal with the improved prototype at its best level. Additionally, the SEM of a 50-set measurement (including 800 drops) lasting for 25 h achieves 5.9 μGal with the improved prototype. [ABSTRACT FROM AUTHOR]

The absolute gravimeter plays an important role in metrology, geophysics, and geological exploration. Seismic and environmental vibration has been one of the most serious factors limiting its performance. Consequently, an ultralow-frequency vertical vibration isolator is required to significantly improve its measurement precision. A novel active vertical vibration isolator employing geometric antispring (GAS) structure is proposed in this paper. The payload is supported by a GAS structure fixed on an inner frame, and the inner frame is hung by coil springs from the base. The relative movement of the payload with respect to the inner frame is detected, and the inner frame is driven by a voice coil actuator controlled by a feedback circuit to track the payload’s motion. The new isolator has a compact size, and it can be used for different load ranges by tuning the GAS structure. The practical closed-loop system has a resonant period of 19.2 s, compared with the period of 0.74 s in an open-loop system. Experiments showed that the new isolator has great performance in a homemade T-1 absolute gravimeter, reducing the measurement deviation by a factor of 32. It is expected to be used in both free-falling and atomic-interference absolute gravimeters. Future improvements may include optimizing the mechanical structure and integrating a temperature control subsystem. [ABSTRACT FROM AUTHOR]