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We report a facile design of an ultra-thin broadband metamaterial absorber (MA) for C-band applications by utilizing a single layer of a metal-dielectric-metal structure of FR-4 substrate. The absorption performances are characterized using a numerical method. The proposed MA exhibits the broadband absorption response over the entire C-band spectrum range from 4.0 GHz to 8.0 GHz with absorptivity above 90% and the high absorptivity is remained over 80% for a large incident angle up to 40° under both transverse electric (TE) and transverse magnetic (TM) polarizations over the band. The origin of absorption mechanism is explained by the electric and surface current distributions, which is also supported by the retrieved constitutive electromagnetic parameters, significantly affected by magnetic resonance. In addition, compared with the previous reports, the proposed MA presents a greater practical feasibility in term of low-profile and wide incident angle insensitivity, suggesting that the proposed absorber is a promising candidate for C-band applications.

This Article has been retracted. Please see the Retraction Note for more detail: https://doi.org/10.1038/s41598-021-81808-1 .

We report a facile design of an ultra-thin broadband metamaterial absorber (MA) for C-band applications by utilizing a single layer of a metal-dielectric-metal structure of FR-4 substrate. The absorption performances are characterized using a numerical method. The proposed MA exhibits the broadband absorption response over the entire C-band spectrum range from 4.0 GHz to 8.0 GHz with absorptivity above 90% and the high absorptivity is remained over 80% for a large incident angle up to 40° under both transverse electric (TE) and transverse magnetic (TM) polarizations over the band. The origin of absorption mechanism is explained by the electric and surface current distributions, which is also supported by the retrieved constitutive electromagnetic parameters, significantly affected by magnetic resonance. In addition, compared with the previous reports, the proposed MA presents a greater practical feasibility in term of low-profile and wide incident angle insensitivity, suggesting that the proposed absorber is a promising candidate for C-band applications.

Introduction: Cancer is a highly lethal disease with a significantly high mortality rate. One of the most commonly used methods for treatment is radiation therapy. However, cancer treatment using radiotherapy is a time-consuming process that requires significant manual work from planners and doctors. In radiation therapy treatment planning, determining the dose distribution for each of the regions of the patient’s body is one of the most difficult and important tasks. Nowadays, artificial intelligence has shown promising results in improving the quality of disease treatment, particularly in cancer radiation therapy. Objectives: The main objective of this study is to build a high-performance deep learning model for predicting radiation therapy doses for cancer and to develop software to easily manipulate and use this model. Materials and Methods: In this paper, we propose a custom 3D convolutional neural network model with a U-Net-based architecture to automatically predict radiation doses during cancer radiation therapy from CT images. To ensure that the predicted doses do not have negative values, which are not valid for radiation doses, a rectified linear unit (ReLU) function is applied to the output to convert negative values to zero. Additionally, a proposed loss function based on a dose–volume histogram is used to train the model, ensuring that the predicted dose concentrations are highly meaningful in terms of radiation therapy. The model is developed using the OpenKBP challenge dataset, which consists of 200, 100, and 40 head and neck cancer patients for training, testing, and validation, respectively. Before the training phase, preprocessing and augmentation techniques, such as standardization, translation, and flipping, are applied to the training set. During the training phase, a cosine annealing scheduler is applied to update the learning rate. Results and Conclusions: Our model achieved strong performance, with a good DVH score (1.444 Gy) on the test dataset, compared to previous studies and state-of-the-art models. In addition, we developed software to display the dose maps predicted by the proposed model for each 2D slice in order to facilitate usage and observation. These results may help doctors in treating cancer with radiation therapy in terms of both time and effectiveness.

Nitrogen-doped TiO2 nanotube arrays (N-TNAs) were successfully fabricated by a simple thermal annealing process in ambient N2 gas at 450 °C for 3 h. TNAs with modified morphologies were prepared by a two-step anodization using an aqueous NH4F/ethylene glycol solution. The N-doping concentration (0–9.47 at %) can be varied by controlling N2 gas flow rates between 0 and 500 cc/min during the annealing process. Photocatalytic performance of as-prepared TNAs and N-TNAs was studied by monitoring the methylene blue degradation under visible light (λ ≥ 400 nm) illumination at 120 mW·cm−2. N-TNAs exhibited appreciably enhanced photocatalytic activity as compared to TNAs. The reaction rate constant for N-TNAs (9.47 at % N) reached 0.26 h−1, which was a 125% improvement over that of TNAs (0.115 h−1). The significant enhanced photocatalytic activity of N-TNAs over TNAs is attributed to the synergistic effects of (1) a reduced band gap associated with the introduction of N-doping states to serve as carrier reservoir, and (2) a reduced electron‒hole recombination rate.

Each level of the coronary artery has different sizes and properties. The primary coronary arteries usually have high contrast to the background, while the secondary coronary arteries have low contrast to the background and thin structures. Furthermore, several small vessels are disconnected or broken up vascular segments. It is a challenging task to use a single model to segment all coronary artery sizes. To overcome this problem, we propose a novel segmenting method for coronary artery extraction from angiograms based on the primary and secondary coronary artery. Our method is a coarse-to-fine strategic approach for extracting coronary arteries in many different sizes. We construct the first U-net model to segment the main coronary artery extraction and build a new algorithm to determine the junctions of the main coronary artery with the secondary coronary artery. Using these junctions, we determine regions of the secondary coronary arteries (rectangular regions) for a secondary coronary artery-extracted segment with the second U-net model. The experiment result is 76.40% in terms of Dice coefficient on coronary X-ray datasets. The proposed approach presents its potential in coronary vessel segmentation.

Plectranthus amboinicus (Lour.) Spreng is a valuable medicinal plant that has been used for a long time in Vietnam. Previous studies have shown that Plectranthus amboinicus exhibited several useful pharmacological effects. This study evaluated total polyphenol, flavonoid contents and anti-oxidant potential of the leaf extract of Plectranthus amboinicus. The phenolic content and flavonoid content achieved 26,84 ±0.91 μg GAE/mg and 12,14 ± 0,42 μg QE/mg, respectively. Ethanol extract (IC50 = 48,23 μg/ml) showed potent antioxidant activity. According to the results of the present investigation, the plant showed significant antioxidant activity that is applicable for the treatment of various diseases.

The main content of the article refers to the consideration of factors and their influence on the implementation of occupational safety and hygiene (OSH) risk assessment at enterprises operating in fields with high risks of occupational safety and hygiene in Vietnam. Although the Law on Occupational Safety and Hygiene in Vietnam has been in effect for 5 years, both employees and employers have not yet fully and effectively applied contents related to workplace safety and hygiene. In addition, some guiding contents of this work gradually reveal certain limitations. Based on the guidance on OSH risk assessment currently being applied in Vietnam, combined with standards related to corporate social responsibility (CSR) according to ISO 26000, ISO 45001. The author has developed a questionnaire to survey employers at 230 enterprises operating in industries and occupations with high risks of labor accidents and occupational diseases according to regulations. The results show that there are four factors that affect the implementation of OSH risk assessment in the following order: (1) the ability of business managers, (2) the sense of responsibility of employees and their representatives, (3) labor safety training and (4) legal regulations and safety instructions. In addition, there are many opinions on further improving regulations and OSH risk assessment processes. Based on the results of this research, we would like to make some recommendations to improve the legal system related to the OSH risk assessment process and CSR, and help relevant parties better understand the benefits and raise their awareness of the issue.

Background Infectious keratitis remains a significant cause of vision impairment worldwide, particularly in developing countries like Vietnam, where socio-economic factors and environmental conditions contribute to its prevalence. Purposes This study aims to investigate the epidemiology, risk factors, and microbiological causes of infectious keratitis at Ho Chi Minh City Eye Hospital, Vietnam, from August 2019 to January 2020. Methods A descriptive study of 56 cases was analyzed using microbiological tests, including smear microscopy, culture, and RT-PCR. Results Bacterial and fungal pathogens were the most common causes of infection, each responsible for approximately 35.71% of cases, with 17.86% exhibiting polymicrobial infections. Risk factors for infectious keratitis included trauma, systemic conditions like diabetes, and ocular conditions such as previous herpetic keratitis. Furthermore, RT-PCR was found to be more sensitive than traditional culture methods in detecting bacterial pathogens. Conclusion These findings underscore the importance of timely intervention and improved diagnostic methods to mitigate the burden of infectious keratitis in Vietnam.

Highly porous metal oxide nanostructures are attractive candidates for many applications because of their rich pores. In this paper, some highly porous metal oxide nanosheets, including, but not limited to, Co3O4, and α-Fe2O3 have been successfully synthesized by a simple and scalable route with the aid of konjac glucomannan (KGM). The Co-KGM and Fe-KGM composite plates as precursors that were fabricated by the impregnation of KGM template in respective metal nitrate solution. After that, these composites were calcined in an air environment to form the highly porous metal oxide nanosheets because the KGM nanofibrils as sacrificial template that was combusted at high temperature. The route would offer an efficient solution to fabricate metal oxide nanosheets with highly porous textures. Furthermore, the highly porous hematite nanostructures showed excellent catalytic activity for benzylation benzene by benzyl chloride with fast conversion and high selectivity indicated promising aspects of these materials.