Single-carrier frequency-domain equalization (SC-FDE) is a promising technique for coherent underwater acoustic communications. The method has a lower peak-to-average power ratio than orthogonal frequency-division multiplexing (OFDM) and is more resistant to frequency offset. In this work, SC-FDE performance is evaluated using data collected during the 2009 Cooperative Array Performance Experiment (CAPEx09) that took place near Seattle, WA, USA. CAPEx09 had two densely populated vertical receiving arrays and a highly refractive environment, features that make it suitable for examining issues related to sensor positioning in range and depth. Two-channel equalization results show only a weak dependence on the spacing between the two sensors. Communications performance is interpreted in terms of relevant propagation physics, including acoustic ducting and rough surface scattering. The implications for undersea acoustic networks are discussed.Index Terms-Refraction, rough surface scattering, single-carrier frequency-domain equalization (SC-FDE), underwater acoustic communications.

Sargassum horneri, a sargassaceae brown alga, is one of the main species in the subtidal seaweeds flora extensively distributed in the Yellow and East China Sea. It has been proven that the phytosterols are an important class of bioactive substances in S. horneri. In this work, a counter-current chromatography approach is proposed for preparative separation of phytol and two analogue sterols from a crude extract of S. horneri. A two-phase solvent system composed of n-hexane-acetonitrile-methanol (5:5:6, v/v) was selected and optimized. The effects of rotary speed and flow rate on the retention of the stationary phase were carefully studied. Under the optimum conditions, phytol and two analogue sterols, fucosterol and saringosterol, were baseline separated, producing 19.8 mg phytol, 23.7 mg fucosterol, and 3.1 mg saringosterol from 300 mg of crude S. horneri extract in one-step separation. The purities of three target compounds were all above 85%. The structures of phytol and two sterols were identified by nuclear magnetic resonance spectroscopy.

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Unlike in radio communications, there is no standard statistical model for the channel impulse response in underwater acoustic communications. To compare the performance of different communications strategies requires data collected under common environmental conditions. In the present paper, a data-driven simulator is developed for comparing single- and multicarrier communications algorithms. Models for the time-varying channel impulse response over a particular bandwidth are first constructed using archival experimental data. The models are then driven with novel communications sequences of lesser bandwidth. The output is synthetic received data that can then be demodulated to evaluate communications performance. By applying reciprocity to the single-input, multiple-output archival data, both multiple receive arrays and multiple transmit arrays can be simulated. Communications performance for the synthetic data is compared to actual experimental results. [Work partially supported by the ONR.]

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Background: Lentil (Lens culinaris M.) is a legume widely consumed worldwide. It is rich in bioactive compounds, including polyphenolic compounds that contribute to positive health benefits. Methods: This study aimed to determine the phenolic content and antioxidant activity of black, red, green, and brown whole lentils. Towards this end, the lentils' phenolic compounds were evaluated regarding their total phenolic content (TPC), total flavonoid content (TFC), total tannin content (TTC), total condensed tannin (TCT), total proanthocyanin content (TPAC), total anthocyanin content (TAC). For the antioxidant activity 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP), 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), hydroxyl radical scavenging activity (•OH-RSA), ferrous ion chelating activity (FICA), reducing power assay (RPA) and phosphomolybdate (PMA) assay were accessed. To identify individual phenolic compounds, liquid chromatography-electrospray ionization quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF-MS 2 ) was used. Results: The results showed that green lentils exhibited the highest TPC (0.96 mg gallic acid equivalents (GAE)/g) whereas red lentils presented the highest TFC (0.06 mg quercetin equivalents (QE)/g). Black lentils were noted with the highest TCT (0.03 mg catechin equivalents (CE)/g), TPAC (0.009 mg cyanidin chloride equivalents (CCE)/g), and TAC (3.32 mg/100 g) contents. While the greatest TTC (2.05 mg tannic acid equivalents (TAE)/g) was observed in the brown lentil. Regarding the total antioxidant capacity, red lentils (4.01 mg ascorbic acid equivalents (AAE)/g) presented the greatest activity, whereas the lowest was found in the brown samples (2.31 mg AAE/g). The LC-ESI-QTOF-MS 2 tentatively identified a total of 22 phenolic compounds, containing 6 phenolic acids, 13 flavonoids, 2 lignans, and 1 other polyphenol. The relationships among phenolic compounds by Venn Diagram showed a high number of overlapping compounds in brown and red lentils (6.7%), and a low number of overlapping compounds between the green, brown, and black lentils (2.6%). Flavonoids were the most abundant phenolic compound within the studied whole lentils, with the brown lentils being the richest in phenolic compounds, especially flavonoids. Conclusions: This study emphasized a comprehensive understanding of the antioxidant potential of lentils and disclosed the phenolic distribution across various lentil samples. This may increase interest in the development of functional food products, nutraceutical ingredients, and pharmaceutical applications with lentils.