Synthetic Aperture Radar (SAR) remote sensing data can be used as an effective alternative to detect surface water and provide useful information regarding operational flood monitoring, in particular for the improvement of rapid flood assessments. However, this application frequently requires standard and simple, yet robust, algorithms. Although thresholding approaches meet these requirements, limitations such as data inequality over large spatial regions and challenges in estimating optimal threshold values remain. Here, we propose a new method for SAR water extraction named Hammock Swing Thresholding (HST). We applied this HST approach to four SAR remote sensing datasets, namely, Sentinel-1, ALOS-2, TerraSAR-X, and RadarSAT-2 for flood inundation mapping for a case study focusing on the Tam Nong district in the Vietnam Mekong delta. A 2D calibrated Hydrologic Engineering Centers River Analysis System (HEC-RAS) model was coupled with the HST outputs in order to estimate the optimal thresholds (OTs) where the SAR-based water masks fitted best with HEC-RAS’s inundation patterns. Our results showed that water levels extracted from Sentinel-1 data best agreed with the HEC-RAS water extent (88.3%), following by ALOS-2 (85.9%), TerraSAR-X (77.2%). and RadarSAT-2 (72%) at OTs of −15, 68, 21, and 35 decibel (dB), respectively. Generated flood maps indicated changes in the flood extent of the flooding seasons from 2010 and 2014–2016 with variations in spatial extent appearing greater in the TerraSAR-X and RadarSAT-2 higher resolution maps. We recommend the use of OTs in applications of flood monitoring using SAR remote sensing data, such as for an open data cube (ODC).

Chlorophyll-a is one of the most important water quality parameters that can be observed by satellite imagery. It plays a significant function in the aquatic environments of rapidly developing coastal cities such as Ha Long City, Vietnam. Urban population growth, coal mining, and tourist activities have affected the water quality of Ha Long Bay. This work uses Sentinel-2/Multispectral Instrument (MSI) imagery data to a calibrated ocean chlorophyll 2-band (OC-2) model to retrieve chlorophyll-a (chl-a) concentration in the bay from 2019 to 2021. The variability of chlorophyll-a during seasons over the study area was inter-compared. The chlorophyll-a concentration was mapped by analyzing the time series of water cover on the Google Earth Engine platform. The results show that the OC-2 model was calibrated well to the conditions of the study areas. The calibrated model accuracy increased nearly double compared with the uncalibrated OC-2 model. The seasonal assessment of chl-a concentration showed that the phytoplankton (algae) developed well in cold weather during fall and winter. Spatially, algae grew densely inside and in the surroundings of aquaculture, urban, and tourist zones. In contrast, coal mining activities did not result in algae development. We recommend using the Sentinel-2 data for seawater quality monitoring and assessment. Future work might focus on model calibration with a longer time simulation and more in situ measured data. Moreover, manual atmospheric correction of optical remote sensing is crucial for coastal environmental studies.

Socio-economic development has promoted the modification of land cover patterns in the coastal area of Ha Long, Cam Pha cities since the 1990s. The urban growth, together with intensive coal mining activities, has improved the life quality of residents. However, it has also caused many environmental problems in this region. Change detection techniques based on post-classification comparison were applied for monitoring the spatial and temporal evolution of land covers. The confusion matrix for 2001 and 2019 showed high overall accuracy (97.99%, 94.95%) and Kappa coefficient (0.97, 0.92), respectively. Statistics from classified images have revealed that man-made features increased by about 15.32%, while natural features, mangrove jungles, and water bodies decreased 10.64%, 1.96%, 2.72%, respectively, and urban evolution presents various dynamics, soft in the first period (1991–2001), but stronger in the second period (2001–2019) with different characteristics. The study also expresses the constraint of topographic and geologic resources, which have prevented the urban development in this coastal area. Such obtained results are very important for understanding interactions and relations between natural and human phenomena and they may help authorities by providing indicators and maps able to highlight necessary actions for sustainable development.

Đặt vấn đề: Phẫu thuật mạch máu là loại phẫu thuật tương đối phức tạp và đa dạng, với nhiều biến chứng như nhiễm khuẩn vết mổ, nhiễm khuẩn mảnh ghép, viêm phổi, nhồi máu cơ tim, xuất huyết, thuyên tắc mạch/huyết khối… trong đó, thường gặp là nhiễm khuẩn vết mổ và nhiễm khuẩn mảnh ghép. Hiện nay, kháng sinh dự phòng là biện pháp hiệu quả nhất để kiểm soát tình trạng này. Phương pháp: Tổng hợp từ các nghiên cứu và hướng dẫn điều trị được tìm kiếm trên PubMed, GoogleScholar, Google. Kết quả: 112 trong số 1227 kết quả được lựa chọn và đưa vào bài tổng quan, trong đó bao gồm 90 nghiên cứu và 22 hướng dẫn điều trị. Kết luận: Trong phẫu thuật mạch máu, các hướng dẫn đa số khuyến cáo sử dụng kháng sinh dự phòng (KSDP) cho phẫu thuật động mạch chủ bụng và chi dưới, các phẫu thuật ghép vật liệu nhân tạo hoặc đặt stent. Phác đồ kháng sinh thường được lựa chọn là cephalosporin thế hệ 1 – C1G (cefazolin) hoặc cephalosporin thế hệ 2 – C2G (cefuroxim), dùng trong vòng 60 phút trước khi rạch da và ngừng sử dụng trong vòng 24 giờ sau phẫu thuật.

A zirconium catalyst system supported on MCM-41 (S-Z) with various weight components (4-20 wt.%) Was synthesized by the sol-gel method. Structure and Morphology Catalysts were characterized by X-RD, TEM, BET, FT-IR and TPD-NH3 methods. In this catalyst, ZrO2 is highly dispersed on the surface of MCM-41 capillaries. Catalytic activity and selectivity were evaluated by the effectiveness of mild hydrothermal decomposition of cellulose to 5-hydroxymethyl furfural (5-HMF). The results show that a catalyst with medium acidity exhibits a high selectivity of 5-HMF. Keywords: S-Zr/MCM-41 materials, sol-gel methods, cellulose, 5-HMF.