Design and Development of an Autonomous Underwater Helicopter for Ecological Observation of Coral Reefs.

Real-time status monitoring is an important prerequisite for coral reef ecological protection. Existing equipment does not provide an ocean observation platform with adequate mobility and efficiency. This paper describes the design considerations of a proposed autonomous underwater helicopter (AUH) dedicated for ecological observation of coral reefs, including the system architecture, electronic devices, sensors and actuators, and explains the path control algorithm and controller to follow a specific path for ocean exploration. The structure and dynamic model of the AUH are first introduced, and then the corresponding simplification is made for motion analysis. Furthermore, computational fluid dynamics (CFD) simulation is carried out to evaluate the dynamic performance of the AUH. Fuzzy-PID control algorithm is utilized to achieve a good antidisturbance effect. In order to validate the performance of the proposed underwater vehicle, a field test was performed, and results confirmed the feasibility of the proposed prototype.

Layer-Averaged Water Temperature Sensing in a Lake by Acoustic Tomography with a Focus on the Inversion Stratification Mechanism.

Continuous sensing of water parameters is of great importance to fluid dynamic progress study in oceans, coastal areas and inland waters. The acoustic tomography technique can perform water temperature field measurements horizontally and vertically using sound wave travel information. The layer-averaged water temperature can also be measured with the acoustic tomography method. However, investigations focusing on the stratified mechanism, which consists of stratification form and its influence on inversion error, are seldom performed. In this study, an acoustic tomography experiment was carried out in a reservoir along two vertical slices to observe the layer-averaged water temperature. Specifically, multi-path sound travel information is identified through ray tracing using high-precision topography data obtained via a ship-mounted ADCP during the experiment. Vertical slices between sound stations are divided into different layers to study layer division inversion methods in different preset types. The inversion method is used to calculate the average water temperature and inversion temperature error of every layer. Different layer methods are studied with a comparison of results. The layer division principle studied in this paper can be used for layer-averaged water temperature sensing with multi-path sound transmission information.

Mapping Small-Scale Horizontal Velocity Field in Panzhinan Waterway by Coastal Acoustic Tomography.

Mapping small-scale high-precision velocity fields is of great significance to oceanic environment research. Coastal acoustic tomography (CAT) is a frontier technology used to observe large-scale velocity field in the horizontal slice. Nonetheless, it is difficult to observe the velocity field using the CAT in small-scale areas, specifically where the flow field is complex such as ocean ranch and artificial upwelling areas. This paper conducted a sound transmission experiment using four 50 kHz CAT systems in the Panzhinan waterway. Notably, sound transmission based on the round-robin method was recommended for small-scale CAT observation. The travel time between stations, obtained by correlation of raw data, was applied to reconstruct the horizontal velocity fields using Tapered Least Square inversion. The minimum net volume transport was 8.7 m3/s at 12:32, 1.63% of the total inflow volume transport indicating that the observational errors were acceptable. The relative errors of the range-average velocity calculated by differential travel time were 1.54% (path 2) and 0.92% (path 6), respectively. Moreover, the inversion velocity root-mean-square errors (RMSEs) were 0.5163, 0.1494, 0.2103, 0.2804 and 0.2817 m/s for paths 1, 2, 3, 4 and 6, respectively. The feasibility and acceptable accuracy of the CAT method in the small-scale velocity profiling measurement were validated. Furthermore, a three-dimensional (3-D) velocity field mapping should be performed with combined analysis in horizontal and vertical slices.

Short-Range Water Temperature Profiling in a Lake with Coastal Acoustic Tomography.

Coastal acoustic tomography (CAT), as an innovative technology, can perform water temperature measurements both in horizontal and vertical slices. Investigations on vertical slice observations are significantly fewer in number than horizontal observations due to difficulties in multi-path arrival peak identification. In this study, a two-station sound transmission experiment is carried out in Thousand-Island Lake, Hangzhou, China, to acquire acoustic data for water temperature profiling. Time windows, determined by range-independent ray simulation, are used to identify multi-path arrival peaks and obtain corresponding sound wave travel times. Special attention is paid to travel time correction, whose errors are caused by position drifting by more than 2 m of moored stations. The sound speed and temperature profiling are divided into four layers and are calculated by regularized inversion. Results show a good consistency with conductivity-temperature-depth (CTD) measurements. The root mean square error (RMSE) of water temperature is 0.3494, 0.6838, 1.0236 and 1.0985 °C for layer 1, 2, 3 and 4, respectively. The fluctuations of measurement are further smoothed by the moving average, which decreases the RMSE of water temperature to 0.2858, 0.4742, 0.7719 and 0.9945 °C, respectively. This study illustrates the feasibility and high accuracy of the coastal acoustic tomography method in short-range water temperature measurement. Furthermore, 3D water temperature field profiling can be performed with combined analyzing in horizontal and vertical slices.

Prediction of pH Value by Multi-Classification in the Weizhou Island Area.

Ocean acidification is changing the chemical environment on which marine life depends. It causes a decrease in seawater pH and changes the water quality parameters of seawater. Changes in water quality parameters may affect pH, a key indicator for assessing ocean acidification. Therefore, it is particularly important to study the correlation between pH and various water quality parameters. In this paper, several water quality parameters with potential correlation with pH are investigated, and multiple linear regression, softmax regression, and support vector machine are used to perform multi-classification. Most importantly, experimental data were collected from Weizhou Island, China. The classification results show that the pH has a strong correlation with salinity, temperature, and dissolved oxygen. The prediction accuracy of the classification is good, and the correlation with dissolved oxygen is the most significant. The prediction accuracies of the three methods for multi-classifiers based on the above three factors reach 87.01%, 87.77%, and 89.04%, respectively.

Water Temperature Observation by Coastal Acoustic Tomography in Artificial Upwelling Area.

Artificial upwelling is a geoengineering method to repair and improve marine ecosystems, and its operation requires long-term and continuous temperature field observation. However, existing methods are rarely seen to accomplish such observation. In this study, we investigate the coastal acoustic tomography (CAT) to obtain the long-term horizontal temperature field of an artificial upwelling area in an anechoic tank. We conduct four sets of experiments with different CAT station numbers and compare their data with those collected from temperature sensors. By analyzing the travel time from the CAT experiments, the horizontal temperature field of the upwelling area could be mapped. The CAT results and the comparison results show that the surface temperature of the observed area decreases by approximately 3 °C after upwelling, while the temperature of where the CAT is deployed decreases by about 1 °C; the temperature is lowest at the center of the upwelling area. Increasing the number of stations and station spacing would improve the temperature mapping accuracy. Therefore, the feasibility of using the CAT system to observe artificial upwelling is proved valid. This study indicates the potential application of CAT in temperature field observation in artificial upwelling area in the sea.

On-site visualized classification of transparent hazards and noxious substances on a water surface by multispectral techniques.

This paper investigated the use of spectra and multispectral images for on-site visualized classification of transparent hazards and noxious substances (HNS), such as benzene, xylene, and palm oil, floating on a water surface with the potential use for rapid classification of multiple HNS during a leak accident. Partial least-squares discrimination analysis (PLS-DA) and least-squares support vector machine (LS-SVM) models achieved a classification accuracy of 100% for spectral reflectance (325-900 nm) and multispectral image at nine wavelengths. Wavelength division and selection were applied for spectra and spectral images, respectively, to reduce the difficulty in data collection and to simplify the redundant bands. This was followed by PLS-DA and LS-SVM modeling. The LS-SVM model based on the least wavelengths (365, 410, 450, and 850 nm) of multispectral images was suggested as the most effective method for on-site visualized classification of transparent HNS on a water surface.

A Combined Ray Tracing Method for Improving the Precision of the USBL Positioning System in Smart Ocean.

The ultra-short baseline positioning system (USBL) has the advantages of flexible application and easy installation, and it plays an extremely important role in the underwater positioning and communication. The error of the USBL in underwater positioning is mainly caused by a ranging error due to ray tracing, a phase difference error of the USBL, and acoustic noise in the underwater communication. Most of these errors are related to the changes in the sound speed during its propagation through the ocean. Therefore, when using the USBL for underwater detection, it is necessary to correct the sound speed profile in the detection area and optimize the ray tracing. Taking into account the actual conditions, this paper aims at correcting the model of underwater sound speed propagation and improving the tracking method of sound lines when the marine environment in the shallow sea area changes. This paper proposes a combined ray tracing method that can adaptively determine whether to use the constant sound speed ray tracing method or the equal gradient ray tracing method. The theoretical analysis and simulation results show that the proposed method can effectively reduce the error of slant distance in USBL compared with the traditional acoustic tracking method and the constant sound speed ray tracing method. The proposed sound ray correction algorithm solves the contradiction between the number of iterations and the reduction of positioning error and has engineering application value.

Anti-colorectal cancer effects of tripolinolate A from Tripolium vulgare.

Tripolinolate A (TLA) is recently identified as a new compound from a halophyte plant Tripolium vulgare and has been shown to have significant in vitro activity against the proliferation of colorectal cancer and glioma cells. This study was designed to further investigate the effects of TLA on the proliferation of human normal cells, and the apoptosis and cell cycle in colorectal cancer cells, and the growth of tumors in the colorectal cancer-bearing animals. The data obtained from this study demonstrated that: 1) TLA had much less cytotoxicity in the human normal cells than the colorectal cancer cells; 2) TLA remarkably induced apoptosis in the human colorectal cancer cells and blocked cell cycle at G2/M phase, and 3) TLA had significant anti-colorectal cancer activity in the tumor-bearing animals.

Antiproliferative cyclodepsipeptides from the marine actinomycete Streptomyces sp. P11-23B downregulating the tumor metabolic enzymes of glycolysis, glutaminolysis, and lipogenesis.

Two cyclodepsipeptides and a known cyclodepsipeptide valinomycin were isolated from a culture of the marine actinomycete Streptomyces sp. P11-23B. Their structures were established based on NMR, HRESIMS, and MS-MS spectroscopic interpretation as well as by chemical degradation. Both streptodepsipeptides P11A and P11B inhibited proliferation of different glioma cell lines, with IC50 values ranging from 0.1 µM to 1.4 µM. Streptodepsipeptide P11A was found to block the cell cycle at the G0/G1 phase and induce apoptosis in glioma cells. Further investigation demonstrated that streptodepsipeptide P11A downregulated expression of HK2, PFKFB3, PKM2, GLS, and FASN, important tumor metabolic enzymes. Data from this study suggested that targeting multiple tumor metabolic regulators might be one anti-glioma mechanism of streptodepsipeptide P11A. A possible mechanism for this class of streptodepsipeptides is reported herein.

Bioactive Polycyclic Quinones from Marine Streptomyces sp. 182SMLY.

Chemical investigation of the cultures of marine Streptomyces sp. 182SMLY led to the discovery of two new polycyclic anthraquinones, which were elucidated as N-acetyl-N-demethylmayamycin (1) and streptoanthraquinone A (2) based on the extensive spectroscopic analysis including 2D NMR, HRESIMS, and an electronic circular dichroism (ECD) calculation. Both anthraquinones remarkably suppressed the proliferation of four different glioma cell lines with IC50 values in a range from 0.5 to 7.3 µM and induced apoptosis in the glioma cells. The ratios of IC50 for normal human astrocytes to IC50 for glioma cells were 6.4-53 for 1 and >14-31 for 2. N-acetyl-N-demethylmayamycin (1) also inhibited the growth of methicillin-resistant Staphylococcus aureus with MIC 20.0 µM.

A new curvularin glycoside and its cytotoxic and antibacterial analogues from marine actinomycete Pseudonocardia sp. HS7.

Five curvularin macrolides (1-5) were isolated from the cultured broth of marine actinomycete Pseudonocardia sp. HS7 that was obtained from the cloacal aperture of sea cucumber Holothuria moebii. The structures of these isolates were characterized as (11S,15R)-11-hydroxycurvularin (1), (11R,15R)-11-hydroxycurvularin (2), curvularin-7-O-α-D-glucopyranoside (3), trans-dehydrocurvularin (4) and curvularin (5) based on their NMR and HRESIMS data as well as chemical degradation. Compound 3 is a new macrolide with a rare α-D-glucopyranose substituent. Compounds 1-4, 5a and 5c (the acyl products of 5), suppressed the proliferation of all six tested cancer cell lines and 4 is the most active compound with IC50 values ranging from 0.59 to 3.39 µM. The 11-hydroxycurvularins 1 and 2 also showed antibacterial activity inhibiting the growth of Escherichia coli.

Synthesis and bioactivity of tripolinolate A from Tripolium vulgare and its analogs.

A new coniferol derivative, named as tripolinolate A (1), and 11 known compounds (2-12) were isolated from whole plants of Tripolium vulgare Nees. The structure of this new compound was determined as 4-(2S-methylbutyryl)-9-acetyl-coniferol based on its NMR and HRESIMS spectral analyses. A simple and efficient method was designed to prepare tripolinolate A and its 19 analogs including nine new chemical entities for bioactive assay. Tripolinolate A and its analog 4,9-diacetyl-coniferol were found to be the two most active compounds that significantly inhibited the proliferation of different cancer cell lines with IC50 values ranging from 0.36 to 12.9µM and induced apoptosis in tumor cells. Structure-activity relationship analysis suggested that the molecular size of acyl moieties at C-4 and C-9 position might have an effect on the activity of this type of coniferol derivatives.

Bioactive sulfated saponins from sea cucumber Holothuria moebii.

The bioactive ingredients of sea cucumber Holothuria moebii were investigated, and four sulfated saponins (1-4) and one desulfated saponin (3B) with an unusual 3,4-epoxy xylose were obtained from this study. Compound 2 is a new triterpenoid saponin and 3B is a new artificial compound. On the basis of the extensive NMR and HRESIMS data, their structures were assigned as 3-O-[ß-D-quinovopyranosyl-(1 → 2)-4-sodium sulfato-ß-D-xylopyranosyl]-25-acetoxy-22-oxo-9(11)-holostene-3ß,12α,17α-triol (2) and 3-O-[ß-D-quinovopyranosyl-(1 → 2)-3,4-epoxy-ß-xylopyranosyl]-22,25-epoxy-9(11)-holostene-3ß,12α,17α-triol (3B). Compounds 1-4 showed activity suppressing the proliferation of four different glioma cells with IC50 values ranging from 0.99 to 8.64 µM. New saponin 2 significantly induced apoptosis in human glioblastoma U87-MG cells and reduced the expression levels of several glioma metabolic enzymes of glycolysis and glutaminolysis. This study reveals for the first time that selectively targeting multiple glioma metabolic regulators of glycolysis and glutaminolysis might be one of the anti-glioma mechanisms of saponin 2.

Bioactive triterpenoid saponins and phenolic compounds against glioma cells.

A total of 54 natural origin compounds were evaluated for their activity in inhibiting the proliferation of glioma cells. Results showed that four Aesculus polyhydroxylated triterpenoid saponins (3-6), six Gleditsia triterpenoid saponins (7-12), and five phenolic compounds (43-46, 51) had dose-dependent activity suppressing the proliferation of both C6 and U251 cells. Structure-activity relationship analysis suggested that the acetyl group at C-28 for the Aesculus saponins and the monoterpenic acid moiety for the Gleditsia saponins could be critical for the activity of these active compounds. Aesculioside H (4), gleditsioside A (7), and feuric acid 3,4-dihydroxyphenethyl ester (FADPE, 46) were the three most active compounds from the different types of the active compounds and induced apoptosis and necrosis in glioma cells.