Back-Projected Signal-Based Self-Interferometric Phase Analysis Technique for Sea Surface Observation Using a Single Scatterometer System.

This manuscript presents a self-interferometric phase analysis technique for sea surface observation using a single scatterometer system. The self-interferometric phase is proposed to complement the imprecise analysis results due to the very meager signal strength measured at a high incident angle of more than 30°, which is a vulnerability of the existing analysis method using the Doppler frequency based on the backscattered signal strength. Moreover, compared to conventional interferometry, it is characterized by the phase-based analysis using consecutive signals from a single scatterometer system without any auxiliary system or channel. To apply the interferometric signal process on the moving sea surface observation, it is necessary to secure a reference target; however, this is hard to solve in practice. Hence, we adopted the back-projection algorithm to project the radar signals onto a fixed reference position above the sea surface, where the theoretical model for extracting the self-interferometric phase was derived from the radar-received signal model applying the back-projection algorithm. The observation performance of the proposed method was verified using the raw data collected at the Ieodo Ocean Research Station in Republic of Korea. In the observation result for wind velocity at the high incident angles of 40° and 50°, the self-interferometric phase analysis technique shows a better performance of a correlation coefficient of more than about 0.779 and an RMSE (root-mean-square error) of about 1.69 m/s compared to the existing method of a correlation coefficient of less than 0.62 and RMSE of more than 2.46 m/s.

Ancient marine sediment DNA reveals diatom transition in Antarctica.

Antarctica is one of the most vulnerable regions to climate change on Earth and studying the past and present responses of this polar marine ecosystem to environmental change is a matter of urgency. Sedimentary ancient DNA (sedaDNA) analysis can provide such insights into past ecosystem-wide changes. Here we present authenticated (through extensive contamination control and sedaDNA damage analysis) metagenomic marine eukaryote sedaDNA from the Scotia Sea region acquired during IODP Expedition 382. We also provide a marine eukaryote sedaDNA record of ~1 Mio. years and diatom and chlorophyte sedaDNA dating back to ~540 ka (using taxonomic marker genes SSU, LSU, psbO). We find evidence of warm phases being associated with high relative diatom abundance, and a marked transition from diatoms comprising <10% of all eukaryotes prior to ~14.5 ka, to ~50% after this time, i.e., following Meltwater Pulse 1A, alongside a composition change from sea-ice to open-ocean species. Our study demonstrates that sedaDNA tools can be expanded to hundreds of thousands of years, opening the pathway to the study of ecosystem-wide marine shifts and paleo-productivity phases throughout multiple glacial-interglacial cycles.

Episodes of Early Pleistocene West Antarctic Ice Sheet Retreat Recorded by Iceberg Alley Sediments.

Ice loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited ∼1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic 40Ar/39Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to "dirty" icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a ∼366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the ∼41-kyr (inter)glacial world.

Multifunctional Scatterometer System for Measuring Physical Oceanographic Parameters Using Range-Doppler FMCW Radar.

A multifunctional scatterometer system and optimized radar signal processing for simultaneous observation of various physical oceanographic parameters are described in this paper. Existing observation methods with microwave remote sensing techniques generally use several separate systems such as scatterometer, altimeter, and Doppler radar for sea surface monitoring, which are inefficient in system operation and cross-analysis of each observation data. To improve this point, we integrated separate measurement functions into a single observation system by adding a measurement function of Doppler frequency to the existing system. So it enables to simultaneously measure the range and polarimetric responses of backscattering as well as movements of the sea surface. Here, the simultaneous measurement function of Doppler frequency was implemented by sampling an FMCW (frequency modulated continuous wave) radar signal as 2D raw data consisting of fast- and slow-time samples, i.e., the range and backscattering of radar target signals are analyzed from the fast-time samples while the Doppler frequency by the radar target's movement extracts from the slow-time samples. Through the Fourier transformed-based range-Doppler signal process, distance (R), backscattering (σ°), and Doppler frequency (fD) are sequentially extracted from the 2D raw data, and a correlation to the physical oceanographic parameters is analyzed. Operability of the proposed system was examed through total 3 times of field campaigns from June 2017 to August 2020 and the observation data retrieved by the radar measurement data (R, σ°, fD) was also cross-analyzed with in-situ data: e.g., tide, significant wave height, and wind speed and direction. Differences in the comparative results as an observational accuracy are as follows. Tidal level (Root Mean Square Error 0.169 m (R)), significant wave height (RMSE 0.127 m (R), 0.362 m (σ°)), wind speed (RMSE 1.880 m/s (fD), 2.094 m/s (σ°)) and direction (18.84° (fD)).

Antiphased dust deposition and productivity in the Antarctic Zone over 1.5 million years.

The Southern Ocean paleoceanography provides key insights into how iron fertilization and oceanic productivity developed through Pleistocene ice-ages and their role in influencing the carbon cycle. We report a high-resolution record of dust deposition and ocean productivity for the Antarctic Zone, close to the main dust source, Patagonia. Our deep-ocean records cover the last 1.5 Ma, thus doubling that from Antarctic ice-cores. We find a 5 to 15-fold increase in dust deposition during glacials and a 2 to 5-fold increase in biogenic silica deposition, reflecting higher ocean productivity during interglacials. This antiphasing persisted throughout the last 25 glacial cycles. Dust deposition became more pronounced across the Mid-Pleistocene Transition (MPT) in the Southern Hemisphere, with an abrupt shift suggesting more severe glaciations since ~0.9 Ma. Productivity was intermediate pre-MPT, lowest during the MPT and highest since 0.4 Ma. Generally, glacials experienced extended sea-ice cover, reduced bottom-water export and Weddell Gyre dynamics, which helped lower atmospheric CO2 levels.

Sea Surface Imaging with a Shortened Delayed-Dechirp Process of Airborne FMCW SAR for Ocean Monitoring on Emergency.

A sea surface imaging technique for an emergency response using a ready-made frequency modulated continuous wave-synthetic aperture radar (FMCW SAR) system and its experimental results are described in this paper. The optimal range of radiowave incidence angle for sea surface imaging was analyzed by a theoretical scattering model and measurement data, and it was properly applied to the FMCW SAR system by readjusting the delayed-dechirp process. Raw data acquired through flight experiments were reconstructed to SAR image by the range-doppler algorithm. To verify the performance of the reconstructed sea surface image, dual-channel images collected by the configuration of the along-track interferometry were used, and then performance indicators such as signal attenuation, coherence, and phase difference were analyzed. Through this experimental study, it was confirmed that the ready-made FMCW SAR system without a function of the incident angle control can also conduct limited missions for maritime observation. It is possible to be an alternative resource for emergency response, in which the cases are requiring urgent maritime disaster detection and analysis.

Seasonal contrast of particulate organic carbon (POC) characteristics in the Geum and Seomjin estuary systems (South Korea) revealed by carbon isotope (δ13C and Δ14C) analyses.

In this study, we newly investigated surface water samples collected in two contrasting Korean estuary systems (i.e., closed Geum and open Seomjin estuaries) along a salinity gradient in winter (December) in 2016. The main objectives were to determine the source of particulate organic carbon (POC) in winter and to assess the environmental factors inducing seasonal differences in POC characteristics. Concentrations and dual carbon isotopes (δ13C and Δ14C) of POC were analyzed together with concentrations and stable carbon isotopes (δ13C) of dissolved inorganic carbon (DIC) and compared with those obtained in summer (August) in 2016. Our study provided a new insight that for both estuarine systems, the seasonal contrast in POC characteristics was associated with stronger wind-induced estuarine sediment resuspensions in winter than in summer providing a greater contribution of aged POC to the total POC pool in winter.

Advanced Interval Type-2 Fuzzy Sliding Mode Control for Robot Manipulator.

In this paper, advanced interval type-2 fuzzy sliding mode control (AIT2FSMC) for robot manipulator is proposed. The proposed AIT2FSMC is a combination of interval type-2 fuzzy system and sliding mode control. For resembling a feedback linearization (FL) control law, interval type-2 fuzzy system is designed. For compensating the approximation error between the FL control law and interval type-2 fuzzy system, sliding mode controller is designed, respectively. The tuning algorithms are derived in the sense of Lyapunov stability theorem. Two-link rigid robot manipulator with nonlinearity is used to test and the simulation results are presented to show the effectiveness of the proposed method that can control unknown system well.

JBIR-107, a new metabolite from the marine-sponge-derived actinomycete, Streptomyces tateyamensis NBRC 105047.

As part of our chemical screening program for new microbial secondary metabolites, we discovered a new compound, JBIR-107 (1), from the culture of Streptomyces tateyamensis NBRC 105047 isolated from a marine sponge sample. Extensive NMR and MS spectroscopic data enabled the structure of 1 to be determined as 5-acetamido-6-(4-(methyl(2-oxo-3-phenylpropyl)amino)phenyl)-4-oxohexanoic acid.

JBIR-129 and -139, cytotoxic 34-membered polyol macrolides of microbial origin.

New 34-membered polyol macrolides JBIR-129 (1) and JBIR-139 (2) were isolated from the culture of the terrestrial Streptomyces RK74. The planar structures of 1 and 2 were established on the basis of 1D and 2D NMR, ESI-TOF-MS, IR, and UV spectra. The relative configurations of the sugar units were determined by analyzing vicinal ¹H-¹H coupling constants and steric information. Both 1 and 2 showed cytotoxic activity against human ovarian adenocarcinoma SKOV-3 cells with IC50 values of 0.3 and 0.4 µM, respectively.

Tyrosyl-DNA phosphodiesterase 1 inhibitor from an anamorphic fungus.

Tyrosyl-DNA phosphodiesterase 1 (Tdp1) is an enzyme that catalyzes hydrolysis of 3'-phosphotyrosyl bonds and is involved in repair of irreversible topoisomerase I (Top1)-DNA covalent complexes. Tdp1 inhibitors are regarded as potential cancer therapeutics in combination with Top1 inhibitors, which are currently used to treat human cancers. While screening for Tdp1 inhibitors, we discovered a novel compound, JBIR-21 (1), from the culture of an anamorphic fungus, RF-13305. The structure of 1 was established by extensive NMR and MS analyses. Compound 1 showed inhibitory activity against Tdp1 (IC(50) value, 18 µM) and cytotoxic activity against cancer cell lines (IC(50) values, 3.5-13 µM). Compound 1 also exhibited antitumor activity in a mouse xenograft model without adverse effects.

New angucycline C-glycosides from Streptomyces sp. RI33.

In the course of our screening program for anticancer agents from natural sources, five new angucyclines, JBIR-90 (1), -116 (2), -91 (3), -92 (4) and -93 (5), were isolated from the fermentation broth of Streptomyces sp. RI33. The structures of 1-5 were elucidated on the basis of 1D and 2D NMR spectroscopy and MS analyses. Compounds 2-4 showed cytotoxic activities against malignant pleural mesothelioma cells at IC(50) values of 20-50 µM.

Induction of tubulin polymerization and apoptosis in malignant mesothelioma cells by a new compound JBIR-23.

Malignant pleural mesothelioma (MPM) is a highly aggressive tumor with a poor prognosis. Thus, novel therapeutic agents need to be developed for treating it. We recently reported the isolation of the novel anti-MPM compound designated as JBIR-23 from Streptomyces sp. AK-AB27. In this study, JBIR-23 exerted its cytotoxic effect on MPM cells by promotion of tubulin polymerization and G2/M arrest, which was followed by apoptosis induction via the caspase pathway through phosphorylation of p38 mitogen-activated protein kinase and c-jun N-terminal kinase. Furthermore, in vivo analysis demonstrated that JBIR-23 prevented tumor growth in tumor-bearing nude mice without evident side effects.

Neuroprotective effects of SG-168 against oxidative stress-induced apoptosis in PC12 cells.

Postmortem examinations of tissues of humans and rodents with a host of neurodegenerative conditions, including Alzheimer's and Parkinson's diseases, have identified oxidative damage in proteins, lipids, and DNA. The aim of this study was to better understand the cellular mechanisms of neuronal cell degeneration induced via oxidative stress and the protective roles of bioactive substance. In order to achieve this aim, we established a screening program to discover therapeutic agents that exhibit preferential neuroprotective activity in H(2)O(2)-treated PC12 cells. During the course of our screening program, we isolated an active compound, SG-168, from Dendrobium nobile Lindley and identified it as a neuroprotective agent. SG-168 was identified as a compound with an acetal skeleton, a prototypical compound, by electrospray ionization-mass spectrometry analysis and various nuclear magnetic resonance spectroscopic methods. The protective effect of SG-168 in PC12 cells with H(2)O(2)-induced oxidative damage was investigated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide reduction assay. As expected, incubation with H(2)O(2) for 2 hours resulted in cell viability of 31.8% compared to the control, while pretreatment of SG-168 increased cell viability by 15-50% compared to the H(2)O(2)-stressed control cells. These results showed that SG-168 inhibits H(2)O(2)-induced apoptotic cell death. Interestingly, flow cytometric analysis showed that H(2)O(2)-treated PC12 cells incubated with SG-168 exhibited greatly suppressed apoptosis. In summation, the results of this study suggest that SG-168 has potential as a new antioxidant agent against neuronal diseases.

JBIR-66, a new metabolite isolated from tunicate-derived Saccharopolyspora sp. SS081219JE-28.

In the course of our chemical screening program for new secondary metabolites, we isolated a new compound JBIR-66 (1) from the culture broth of the tunicate-derived actinomycete, Saccharopolyspora sp. SS081219JE-28. The structure of 1 was determined to be (3Z,6E,8E)-N-(4-acetamido-3-hydroxybutyl)-2-hydroxy-4,8-dimethylundeca-3,6,8-trienamide on the basis of extensive NMR and MS spectroscopic data.

Arctigenin blocks the unfolded protein response and shows therapeutic antitumor activity.

Cancer cells in poorly vascularized solid tumors are constantly or intermittently exposed to stressful microenvironments, including glucose deprivation, hypoxia, and other forms of nutrient starvation. These tumor-specific conditions, especially glucose deprivation, activate a signaling pathway called the unfolded protein response (UPR), which enhances cell survival by induction of the stress proteins. We have established a screening method to discover anticancer agents that could preferentially inhibit tumor cell viability under glucose-deprived conditions. Here we identify arctigenin (ARC-G) as an active compound that shows selective cytotoxicity and inhibits the UPR during glucose deprivation. Indeed, ARC-G blocked expression of UPR target genes such as phosphorylated-PERK, ATF4, CHOP, and GRP78, which was accompanied by enhanced phosphorylation of eIF2 alpha during glucose deprivation. The UPR inhibition led to apoptosis involving a mitochondrial pathway by activation of caspase-9 and -3. Furthermore, ARC-G suppressed tumor growth of colon cancer HT-29 xenografts. Our results demonstrate that ARC-G can be served as a novel type of antitumor agent targeting the UPR in glucose-deprived solid tumors.

Glycerol affects the acyl moieties of teicoplanin components produced by Actinoplanes teichomyceticus MSl2210.

Teicoplanin, a glycopeptide antibiotic, is composed of five main components, denoted T-A2-1 to T-A2-5. We investigated the use of glycerol as a carbon source affecting the teicoplanin components and its acyl moieties. As a result, we show the change of teicoplanin components, as well as an increase of total teicoplanin yields, caused by the addition of glycerol to the production medium. Analysis of the total cell lipids upon the addition of glycerol also showed a corresponding change in the proportion of teicoplanin, suggesting that glycerol strongly affects a change of teicoplanin branched acyl moieties.