Search Results (5)

Argonauts or paper nautiluses are pelagic octopod cephalopods with a cosmopolitan distribution in tropical and subtropical waters around the world. Unlike other species of octopus, these are characterized by the fact that the female has a shell that serves as the breeding chamber for the eggs. Over time, this structure has been used as a taxonomic diagnostic character, causing problems in the systematics of this genus, with around 50 synonymies reported. Only two species, Argonauta argo and A. nouryi, have been reported in the Northern Humboldt Current System; however, there is taxonomic uncertainty regarding these species, which is reflected in the paralarvae (the first stage of life after hatching). In the paralarvae, the chromatophore patterns are considered to be conservative and reliable taxonomic characteristics. The objective of this study is to demonstrate the extensive variability in the chromatophore arrangement of Argonauta paralarvae in the Northern Humboldt Current using DNA barcoding and five species delimitation models. Our results include up to 11 different paralarvae morphotypes according to the pattern of chromatophores (number and arrangement) and 2 shell morphotypes. Species delimitation methods divided the 13 Argonauta morphotypes into two consensus molecular taxonomic units (MOTUs), A. argo and A. nouryi. Additionally, the results revealed an extensive morphological variability in the paralarvae and female shells of A. nouryi, demonstrating the importance of molecular data in studies involving species with different life stages, especially when this extensive morphological variability obscures conventional analyses. Full article

The double vertical-axis wind turbine (VAWT) system serves as a high-performance design solution. The Nautilus wind turbine investigated in this research imitated the structure of a Nautilus shell and is a vertical-axis drag-type wind turbine that exhibits relatively low efficiency. Therefore, the improvement of its wind energy efficiency is of paramount importance. This paper utilizes Computational Fluid Dynamics (CFD) software, based on the Reynolds-averaged Navier–Stokes equations and dynamic meshing techniques, to conduct numerical investigations on the aerodynamic performance of the Nautilus wind turbine array layout. The effects of wind direction, spacing ratio, and rotation direction are individually studied, and the interpretations and explanations are provided based on flow field characteristics. The results show that when the wind direction is 90°, i.e., a transverse layout, the closer the spacing between the transverse turbines, the higher the average power coefficient of the entire wind turbine system, with little effect from the three rotation directions. The maximum average power coefficient reached 28.9% and the power gain factor (TPGF) reached 11.1%. The enhancement effect primarily originates from the wake interaction among neighboring turbines. The experimental results showed a deviation of 8.1% compared to the CFD simulation results, thus validating the accuracy of the numerical CFD modeling. Ultimately, several array layouts are proposed, based on the prevalent wind direction and spacing ratio research. The enhancement of the wind turbine array’s situation could significantly increase the average efficiency of the entire wind turbine cluster. Consequently, this study provides a reference for the practical application of biomimetic vertical-axis drag-type wind turbine systems in actual engineering. Full article

In the past few years, advanced technologies such as floating offshore wind turbines (FOWT) and wave energy converters (WECs) have been developed. As demonstrated by the innovative hybrid platform Poseidon, the feasibility of combining floating wind turbines and wave energy converters has already been explored. Furthermore, diversification of offshore renewable energy technologies reduces power fluctuations and lowers investment costs. This paper focuses on the development of an integrated wind and wave platform and the creation of a numerical model to evaluate the system performance for the Belmullet site. The novel concept consists of the semi-submersible Nautilus platform, integrated with four-point absorbers. A hydro-servo-aero time-domain model, combining WEC-Sim with an in-house wind turbine model, simulated the device motion and estimated the power generated. The performance of the Wave Energy Converters (WECs) was optimised based on their Power Take Off (PTO) damping. Finally, the hybrid concept was compared with the simple FOWT concerning the energy produced, Levelized Cost of Energy (LCOE) and hydrodynamic stability. The hybrid configuration proved to be a promising solution with 10% lower LCOE and improved hydrodynamic stability evaluated in terms of nacelle acceleration and platform pitch motion. These results show that wind and wave could be one of the best solutions for the future of the marine energy sector and the energy transition. Full article

Molluscs are known for their ability to produce a calcified shell resulting from a genetically controlled and matrix-mediated process, performed extracellularly. The occluded organic matrix consists of a complex mixture of proteins, glycoproteins and polysaccharides that are in most cases secreted by the mantle epithelium. To our knowledge, the model studied here—the argonaut, also called paper nautilus—represents the single mollusc example where this general scheme is not valid: the shell of this cephalopod is indeed formed by its first dorsal arms pair and it functions as an eggcase, secreted by females only; furthermore, this coiled structure is fully calcitic and the organization of its layered microstructures is unique. Thus, the argonautid shell appears as an apomorphy of this restricted family, not homologous to other cephalopod shells. In the present study, we investigated the physical and biochemical properties of the shell of Argonauta hians, the winged argonaut. We show that the shell matrix contains unusual proportions of soluble and insoluble components, and that it is mostly proteinaceous, with a low proportion of sugars that appear to be mostly sulfated glycosaminoglycans. Proteomics performed on different shell fractions generated several peptide sequences and identified a number of protein hits, not shared with other molluscan shell matrices. This may suggest the recruitment of unique molecular tools for mineralizing the argonaut’s shell, a finding that has some implications on the evolution of cephalopod shell matrices. Full article

Background: This paper proposes a Nautilus isometric spiral vertical axis wind turbine, which is a new structure, and its aerodynamic performance and power generation performance need to be analyzed. Methods: A 3D model of the wind turbine was built and its aerodynamic performance was analyzed. Then the wind turbine power generation and grid-connected simulation platform was built by MATLAB/SIMULINK, and its power generation performance and subsequent grid connection were studied. Results: The basic parameters of the wind turbine were obtained. In order to improve efficiency, parameters such as pressure, torque, wind energy utilization rate and relative velocity of wind turbines with different blade numbers and different sizes were compared. In addition, by building a simulation platform for the power generation control system, the power generation characteristics and grid connection characteristic curves of the generator were obtained. Conclusions: When the number of blades is three and the ratio between the ellipse major axis and minor axis of the blade inlet is 0.76, the best efficiency of the wind turbine can be obtained. Application of the power generation control system used in this paper can achieve grid-connected operation of this wind turbine. It also confirmed that the Nautilus isometric spiral wind turbine has good performance and is worthy of in-depth research. Full article