Ray Structure Research Articles

Pyridine-2-olato bridged dirhodium(III) acyl organometallics: Synthesis, spectroscopic, structural and theoretical studies

The heterogeneous phase reaction of [Rh(MeLsb)(PPh3)2Cl2] (1) with the sodium salt of three different pyridine-2-olato ligands [Na(R‒Opy), R = H, Me, NO2] in dichloromethane–acetone–water medium afforded the complexes of type [Rh(Lal)(PPh3)(R-Opy)]2 (2(R)) in excellent yield. These are the first examples of dirhodium(III) acyl complexes with the bridging pyridine-2-olato ligand. The penta coordinated dirhodium(III) acyl complexes are formed by the cleavage of the RhCl and RhPPh3 bonds of the precursor complex 1. The two R-Opy ligands bridge the two rhodium centers through their OOpy donor centers. The conversion of 1→2(R) is attended with the concomitant hydrolysis of the aldiminium function in 1. The spectral (UV–vis, IR, NMR) data of the complexes are reported. The identity of 2(Me) has been established by single crystal X–ray structure determination which revealed distorted trigonal bipyramidal RhCNO2P coordination sphere. The Rh, C, N and Ophenolato atoms define the equatorial plane whereas Rh, OOpy and P atoms define the axial plane. The electronic structures and absorption spectra of the complexes are also scrutinized by the density functional theory (DFT) and time–dependent DFT calculations.

Terrestrial locomotion stability of undulating fin amphibious robots: Separated elastic fin rays and asynchronous control

To address the problem of poor postural stability in an undulating fin robot during terrestrial locomotion, this study proposes a novel design featuring separate elastic fin rays with an asynchronous control scheme for bilateral fin surfaces. In this scheme, the robotic fin ray structure and surface driving mode are innovatively designed to mitigate the pitch-angle instability caused by adverse factors, such as integral rigid fin rays and synchronized fin surfaces. Expanding on the ground dynamics model of the robot, this study examined the variation in the pitch angle of the robot body. In this study, an innovative design with separated elastic fin rays was proposed and their feasibility was validated through finite element simulations. In addition, a virtual simulation prototype of the robot was developed to verify the robot body stability under asynchronous fin surface control. The simulation results show that separate elastic fin rays and asynchronous control can effectively improve the postural stability of robots in terrestrial locomotion. In this study, a robot prototype was tested experimentally in various terrestrial environments. The experimental results indicate that equipping the robot with separated elastic fin rays and employing asynchronous motion control significantly enhances the motion postural stability across typical terrain conditions. The maximum pitch angle range can be reduced by 42.7–52.4%, providing new insights for the design of amphibious robots with undulating fins.

Devils in distress: Insights into the composition and genetic population structure of devil rays landed in the Southwestern Indian Ocean

Devil ray populations in the Southwestern Indian Ocean (SWIO) are facing alarming declines due to overexploitation driven by high demand for their products in international markets. Despite local and international conservation efforts, insufficient information on their genetic population structure and uncertainties in their taxonomy complicates effective conservation strategies. This study analysed sequences of the cytochrome oxidase subunit I gene (620 base pairs) from 120 devil rays landed in Tanzania to test two hypotheses: (i) whether devil ray populations in the SWIO have lower genetic diversity compared to those in other regions, and (ii) whether Mobula mobular and M. japanica are indeed synonyms of the same species. Our findings identified four devil ray species: Mobula mobular, M. kuhlii, M. tarapacana, and M. thurstoni, all classified as endangered on the IUCN Red List but lacking national protection. The study also confirmed the taxonomic alignment of M. mobular and M. japanica as the same species, validating previous findings. Additionally, M. thurstoni dominated the landed devil rays, accounting for over 70 % of the specimens, and exhibited higher haplotype and nucleotide diversities compared to populations in the Eastern Indian Ocean (EIO). Furthermore, populations of M. thurstoni in Tanzania showed limited historical genetic connectivity (FST = 0.176, p < 0.05) with those in the EIO and Brazil. The study calls for urgent action to revisit existing fishing regulations in Tanzania to ensure the protection of the identified endangered rays. It also advocates for unified conservation measures for the species formerly considered separate, M. mobular and M. japanica. While these findings should be validated with hypervariable nuclear markers, the observed patterns in genetic connectivity highlight the need for regional-specific conservation strategies aimed at addressing local threats such as overfishing and destructive fishing practices to ensure the sustainability of M. thurstoni populations across their range.

Skin-inspired ultra-tough, self-healing anisotropic wood-based electronic skin for multidimensional sensing

Skin is a flexible and stretchable sensor composed of anisotropic dermis (DM) and repairable epidermis (EM). It repairs itself when damaged and has a multi-dimensional sensing system that can assist the body in performing some complex multi-dimensional movements. Inspired by skin, we utilized natural wood as the skeleton and for the first time designed a low-cost, double-layer structure wood-based electronic skin (wood-eskin). Simple chemical treatments were employed to directionally regulate the ray structure of natural wood and to enhance its porosity. Subsequently, physical freeze-thawing was employed to facilitate the formation of an entangled network structure between the PVA solution and the wood nanofibers. Wood-eskin with multi-dimensional sensing was obtained by further introducing ions by immersing in salt solution. In comparison to the majority of contemporary bionic e-skins, wood-eskin exhibits superior mechanical properties. Additionally, it is capable of performing complex deformations, such as bending and knotting. After fracture, wood-eskin can also repair itself and recover ∼94 % of its mechanical properties. The oriented arrangement of cellulose nanofiber channels gives wood-eskin a multidimensional sensing capability that can be used to monitor more complex body movements. The low-cost, biodegradable wood-eskin exhibits similar functionality to human skin, and its potential for biomedical and bionic robotics applications is considerable.

New 1D Cd(II) coordination polymer based on L‒arginine ligand; Synthesis, X−ray structure, Hirshfeld analysis, DFT studies, and biological activity

The structural aspects of the newly synthesized 1D coordination polymer, [Cd(μ–L–Arg)(OSO3)(H2O)2]n with L−arginine (L−Arg) are presented. The Cd(II) is hepta−coordinated with one L‒Arg as a bridged bidentate ligand in addition to two water molecules and one sulphate group where both are monodentate ligands. The expansion of the coordination polymer along a–direction is occurred via two extra Cd–O bonds with the carboxylate group from another L−Arg in a neighboring complex unit. The significant interactions that controlled the molecular packing are O···H (52.8%) and H···H (32.2%) based on Hirshfeld topology analysis. The 1D polymeric structure of the Cd(II) is confirmed by the presence of obvious red spots in dnorm map related to the Cd−O coordinate bonds with the neighbouring molecule. The AIM investigation revealed that the Cd–O and Cd–N bonds have low covalent characters. The charge of Cd(II) is changed to 1.374 e as a consequence of complexation with the ligand groups. The orbital-orbital interactions included in the Cd–N and Cd–O bonds are analyzed using NBO calculations. The anticancer activity of the studied complex and L−Arg were screened versus human colorectal cell line (HCT−116). The results show that, the Cd(II) complex has better activity towards the tested cell line (IC50 = 166.15 ± 6.95 µg/mL) than its free ligand (IC50 = 224.42 ± 8.34 µg/mL). Also, the complex exhibits somewhat higher antibacterial activity compared with L‒Arg.

A Bioinspired Robotic Finger for Multimodal Tactile Sensing Powered by Fiber Optic Sensors

The rapid advancement of soft robotic technology emphasizes the growing importance of tactile perception. Soft grippers, equipped with tactile sensing, can gather interactive information crucial for safe human–robot interaction, wearable devices, and dexterous manipulation. However, most soft grippers with tactile sensing abilities have limited modes of tactile perception, restricting their dexterity and safety. In addition, existing tactile systems are often complicated, leading to unstable perception signals. Inspired by various organisms, a novel multimodal tactile‐sensing soft robotic finger is proposed. This finger, based on a modified fin ray structure, integrates a distributed fiber optic sensing system as part of its tactile sensory neural system. It replicates human finger capabilities, discerning contact forces as low as 0.01 N with exceptional sensitivity (106.96 mN nm−1). Through training neural networks models, the finger achieves an accuracy exceeding 96% in recognizing roughness, material stiffness, and finger pad position. Assembled into two‐finger parallel gripper, it demonstrates precise manipulation capabilities for fragile items like strawberries and potato chips. Moreover, through synergistic interplay of multimodal tactile sensing, this finger can successfully grasp an underwater transparent sphere, mitigating limitations of visual perception. The developed soft finger holds promise in various scenarios including hazardous environment detection and specialized grasping tasks.

Structure and Function of Gill Cover and Branchiostegal Rays in Teleostei

Structure and Function of Gill Cover and Branchiostegal Rays in Teleostei

Ray and caustic structure of Ince-Gauss beams

The Ince-Gauss beams, separable in elliptic coordinates, are studied through a ray-optical approach. Their ray structure can be represented over a Poincaré sphere by generalized Viviani curves (intersections of a cylinder and a sphere). This representation shows two topologically different regimes, in which the curve is composed of one or two loops. The overall beam shape is described by the ray caustics that delimit the beams’ bright regions. These caustics are inferred from the generalized Viviani curve through a geometric procedure that reveals connections with other physical systems and geometrical constructions. Depending on the regime, the caustics are composed either of two confocal ellipses or of segments of an ellipse and a hyperbola that are confocal. The weighting of the rays is shown to follow the two-mode meanfield Gross–Pitaevskii equations, which can be mapped to the equation of a simple pendulum. Finally, it is shown that the wave field can be accurately estimated from the ray description.

Analysis of Contact Force and Shape Change on Grasping a Square Object Using an Actual Fin Ray Soft Gripper.

The Fin Ray-type soft gripper (FRSG) is a typical soft gripper structure and applies the deformation characteristics of the Fin Ray structure. This structure functions to stabilize the grasping of an object by passive deformation due to external forces. To analyze the performance of detailed force without compromising the actual FRSG characteristics, it is effective to incorporate multiple force sensors into the grasping object without installing them inside the Fin Ray structure. Since the grasping characteristics of the FRSG are greatly affected by the arrangement of the crossbeams, it is also important to understand the correspondence between the forces and the geometry. In addition, the grasping characteristics of an angular object have not been verified in actual equipment. Therefore, in this study, a contact force measurement device with 16 force sensors built into the grasping object and a structural deformation measurement device using camera images were used to analyze the correspondence between force and structural deformation on an actual FRSG. In the experiment, we analyzed the influence of the crossbeam arrangement on the grasping force and the grasping conditions of the square (0°) and rectangular (45°) shapes, and state that an ideal grasp in a square-shaped (45°) grasp is possible if each crossbeam in the FRSG is arranged at a different angle.

The Early Allometric Growth and Osteological Ontogeny of Pot-Bellied Seahorse (Hippocampus abdominalis, L. 1827) under Mass-Scale Captive Breeding Conditions in North China

Seahorses are valuable species for their use in traditional Chinese medicine, as well as for the aquarium trade as ornamentals and curiosities. To balance market demand and reduce pressure on wild populations, many countries have undertaken commercial seahorse cultivation. Skeletal development plays a crucial role in fish fry culture, affecting external morphology, feeding, and movement. This study investigated the ontogeny allometry, timing, and progression of skeletal development in H. abdominalis from DAB (day after birth) 1 to DAB 100 under mass-scale captive breeding conditions in north China. The results of this study revealed the growth rate was significantly increased between DAB 30 and DAB 54. Allometry analysis revealed that in the early stage, the head, trunk, and tail demonstrated almost isometric growth. However, in the later stage, the head and trunk exhibited negative isometric growth, whereas the tail displayed positive isometric growth. Skeletal staining results showed that newborn seahorses do not have ossified bones until DAB 11 (SL 28.14 ± 2.94 mm). Ossification was primarily observed in the jaw region and the tubular nasal structure of the cranium, which indicated the importance of the early development of feeding organs. The initial formation of ossified vertebral columns was observed at DAB 13 (SL 26.48 ± 0.63 mm), with the complete ossification of all vertebrae occurring by DAB 45 (SL 54.87 ± 4.70 mm). Furthermore, the cranium, rings, and plates were all fully ossified by DAB 30. Ossification of the fins began at DAB 23 (SL 31.27 ± 4.05 mm). However, neither of them were fully ossified by DAB 100. The pelvic fin and the complete structure of the caudal fin were not observed, possibly because of caudal fin ray structure degeneration within the pouch. In addition, no skeletal deformities were observed in all the tested samples. The results of this study provide valuable information on the developmental biology of H. abdominalis, enriching our understanding of their growth and offering insights for optimizing fish fry breeding technologies.

I Like This New Me: Unravelling Population Structure of Mediterranean Electric Rays and Taxonomic Uncertainties within Torpediniformes.

The present study focused on the three species of electric rays known to occur in the Mediterranean Sea: Torpedo torpedo, Torpedo marmorata and Tetronarce nobiliana. Correct identification of specimens is needed to properly assess the impact of fisheries on populations and species. Unfortunately, torpedoes share high morphological similarities, boosting episodes of field misidentification. In this context, genetic data was used (1) to identify specimens caught during fishing operations, (2) to measure the diversity among and within these species, and (3) to shed light on the possible occurrence of additional hidden species in the investigated area. New and already published sequences of COI and NADH2 mitochondrial genes were analyzed, both at a small scale along the Sardinian coasts (Western Mediterranean) and at a large scale in the whole Mediterranean Sea. High levels of genetic diversity were found in Sardinian populations, being significantly different from other areas of the Eastern Mediterranean Sea due to the biotic and abiotic factors here discussed. Sardinian torpedoes can hence be indicated as priority populations/areas to be protected within the Mediterranean Sea. Moreover, sequence data confirmed that only the three species occur in the investigated area. The application of several 'species-delimitation' methods found evidence of cryptic species in the three species outside the Mediterranean Sea, as well as in other genera/families, suggesting the urgent need for future studies and a comprehensive revision of the order Torpediniformes for its effective conservation.

Ray phase verification at the Cassegrain antenna aperture

Large sections in textbooks and monographs on antenna technology, as well as publications in numerous periodicals are devoted to Cassegrain two-mirror antennas. In them it is possible to find various ratios for calculating the dimensions of the structural elements of the antenna system, which, at the same time, need preliminary verification of their accuracy by checking of the ray phase at the exit of the paraboloid aperture. In addition, it is necessary to develop a procedure for assessing the sensitivity of the system to the phase mismatch of the output rays at the antenna aperture caused by the deviation of the actual dimensions of the structural elements from the calculated ones. The purpose of the article is to develop a methodology for estimating the in-phase output rays at the aperture of the Cassegrain antenna parabolic mirror at the calculated values of the design parameters, as well as when they deviate from the nominal values. A simple method of computer-aided configuration construction of the ray structure in a two-mirror Cassegrain antenna has been developed. The influence of the deviation of the emitter position from a given starting point, as well as the shift of the focus of the counter-reflector from the focus of the parabola on the phasing of the rays has been investigated. The presented methodology makes it possible to verify the applicability of the calculated ratios borrowed from the literature. The presented method of estimating the common phase of the rays at the aperture of the Cassegrain antenna may be useful for the rapid verification of the ratios used in the design of its geometric structure. Also it can be used to estimate the permissible deviations of the geometric dimensions of the elements from the nominal values. Finally, the visibility of the focus graphic illustration facilitates the rejection of obviously unacceptable antenna implementation options.

Conjunction Ground Triangulation of Auroras and Magnetospheric Processes Observed by the Van Allen Probe Satellite near 6 Re

Conjunction observations of auroras with electron distributions and broadband electrostatic fluctuations on Van Allen Probe A satellite in the equatorial region are considered. Using triangulation measurements, the energy spectra of the precipitating electrons in the rayed auroral structures were determined for the 17 March 2015 event. A comparison of the spectra of precipitating electrons in the auroral rays with satellite measurements of electrons in the equatorial region related to the aurora showed their agreement. The concomitance between Van Allen Probe A broadband electric waves and auroral variations measured by the ground-based auroral camera was observed on 17 March 2015. This suggests that broadband electrostatic waves may be responsible for electron precipitation, leading to the formation of rayed structures in the aurora.

Oxovanadium and copper complexes of new unsymmetrically tetradentate ligands: X- ray structure, theoretical and NLO properties, catalytic oxidation and bromoperoxidase activities

A series of mononuclear oxovanadium VOLBz, VOLT and copper CuLBz, CuLT complexes containing unsymmetrical tetradentate Schiff base ligands were synthesized and fully characterized by conventional spectroscopic techniques such as FT-IR, UV–vis, 1HNMR and mass spectrometry (MS). Crystal structure data of CuLT, solved by X-ray diffraction, shows a monoclinic system with Cc space group and Z = 4 molecules per unit cell. The central copper ion adopts a nearly ideal square planar coordination geometry. Cyclic voltammetry of oxovanadium and copper complexes revealed quasi reversible redox couples corresponding to VOIV/VOV and CuI/CuII redox processes, respectively. The quantum calculations, performed by DFT and TD-DFT theory at the M062X/6-311**G/SDD level, agree well with the experimental data. The results show that the copper and the oxovanadium compounds have larger static and dynamic hyperpolarizability values than the urea. For instance, the β0 value of H2LT is about 68 times larger than that of the urea. The results predict that the studied compounds have the ability to be excellent second and third-order NLO materials. The prepared complexes catalyzed effectively homogeneous oxidation reaction of cyclohexene in the presence of H2O2 as oxidant. Higher conversion of 98% is attained using CuLBz as catalyst. The bromoperoxidase activity is explored in the oxidative bromination of phenol red as a trap employing the studied complexes which can be considered as potential functional models of bromoperoxidase, CuLBz catalyst exhibits the better catalytic activity, the reaction rate constant k is equal to 2.203×105 (mol L-1)-2s-1.

Phylogeography of sharks and rays: a global review based on life history traits and biogeographic partitions.

Considerable research exists on the life history traits, evolutionary history, and environmental factors that shape the population genetic structure of marine organisms, including sharks and rays. Conservation concerns are particularly strong for this group as they are highly susceptible to anthropogenic stressors due to a combination of life history traits including late maturity and low fecundity. Here, we provide a review and synthesis of the global phylogeography of sharks and rays. We examined existing data for 40 species of sharks belonging to 17 genera and 19 species of rays belonging to 11 genera. Median joining haplotype networks were constructed for each species for the mtDNA cytochrome C oxidase subunit I (COI), and an Analysis of Molecular Variance (AMOVA) was conducted to understand patterns of genetic diversity and structure across the three major ocean basins-the Indian, Atlantic and Pacific Oceans. Haplotype networks showed very shallow coalescence in most species, a finding previously reported for marine teleosts. Star topologies were predominant among sharks while complex mutational topologies predominated among rays, a finding we attribute to extremely limited dispersal in the early life history of rays. Population structuring varied amongst species groups, apparently due to differences in life history traits including reproductive philopatry, site fidelity, pelagic habitat, migratory habits, and dispersal ability. In comparison to reef-associated and demersal species, pelagic and semi pelagic species showed lower levels of structure between and within ocean basins. As expected, there is variation between taxa and groups, but there are also some broad patterns that can guide management and conservation strategies.

Ternary Unitary Quantum Lattice Models and Circuits in 2+1 Dimensions.

We extend the concept of dual unitary quantum gates introduced in Phys. Rev. Lett. 123, 210601 (2019)PRLTAO0031-900710.1103/PhysRevLett.123.210601 to quantum lattice models in 2+1 dimensions, by introducing and studying ternary unitary four-particle gates, which are unitary in time and both spatial dimensions. When used as building blocks of lattice models with periodic boundary conditions in time and space (corresponding to infinite temperature states), dynamical correlation functions exhibit a light ray structure. We also generalize solvable matrix product states introduced in Phys. Rev. B 101, 094304 (2020)PRBMDO2469-995010.1103/PhysRevB.101.094304 to two spatial dimensions with cylindrical boundary conditions, by showing that the analogous solvable projected entangled pair states can be identified with matrix product unitaries. In the resulting tensor network for evaluating equal-time correlation functions, the bulk ternary unitary gates cancel out. We delineate and implement a numerical algorithm for computing such correlations by contracting the remaining tensors.

Research on effects of different internal structures on the grasping performance of Fin Ray soft grippers

AbstractFin Ray soft grippers, as a notable passive compliant structures, can be easily actuated by external devices to adapt their shape to conform to a grasped object. Their unique ability is aided by their V-shaped structure and morphable material utilized by the Fin Ray finger. Thus, when the internal structure changes, the adaptability and grasping abilities also change. However, related works focus on the effects of changing key parameters on the grasping performance based on the Festo structure, and few works have explored the effects of changing the internal structure. To close the research gap, four different Fin Ray structures are presented in this article, and a parameter determination process was carried out by maximizing their adaptability by investigating the key parameters of each structure through finite element analysis. Then, the force responses of four selected Fin Ray structures are analyzed and experimentally validated. The results show that the No Internal Filling structure obtained by omitting the crossbeams is ideal for grasping delicate targets with the best adaptability and the minimum resultant force. The cross structure attained by adding vertical beams connected to crossbeams decreases the adaptability of the Fin Ray finger but significantly increases the contact force. The unsymmetric design of the branched structure significantly enhances the final contact force while improving the passive adaptation to objects. Thus, the application of the Fin Ray finger ranges from adaptive delicate grasping tasks to high-force manipulation tasks.

Comparative Wood Anatomy of Nepalese Ulmaceae

Wood structure of three Nepalese genus Ulmus, Celtis and Trema belonging to the family Ulmaceae are described. Altogether 12 wood samples of these three genus are collected from different localities and studied. The study showed ring porous, semi-ring porous or diffuse porous wood. Transition from early wood to late wood was abrupt in ring porous wood. Early wood pores one to three layered. Late wood pores arrangement in dendritic or ulmiform pattern. Perforation plate is simple and inter-vessel pit alternate. Fiber tracheids, tracheids and libriform fibers were non-perforated tracheal elements while wood parenchymatous cell was apotracheal, marginal and paratracheal. Rays were homo-or heterogeneous. Ulmus differs from Celtis in having ray structure and crystal location. A tentative key is prepared to identify the species based on wood character.

Distribution of the reef manta ray Mobula alfredi and the oceanic manta ray Mobula birostris in the Philippines: a collaborative effort for conservation.

Little is known about manta ray population size, structure and connectivity in the Philippines. In collaboration with dive operators, non-governmental organizations and authorities, sightings of manta rays were collated into a single national database. Using in-water photographs and videos gathered through citizen science and dedicated research efforts, this study compiled sightings between 2004 and 2020, showing 22 separate sites throughout the archipelago with manta rays present. A total of 392 individual reef manta rays (Mobula alfredi) and 107 oceanic manta rays (Mobula birostris) were identified from the collected footage. Four specific sites in the provinces of Masbate and Palawan together hosted 89% of all identified individuals and accounted for 95% of sightings, highlighting these areas are key aggregation sites. This study also reports the movements of M. birostris within the Philippines, based on photo-identification of three individuals moving 150 km between Cebu and Masbate. Despite the growing number of recreational divers in Daanbantayan and San Jacinto, an 80% decline in M. birostris sightings was observed at these sites. To ensure effective future conservation, it is recommended that efforts focus on the identification and protection of manta ray hotspots and migratory corridors, the creation of a sustainable tourism framework and, most important, the implementation of mitigation strategies to reduce fisheries interactions.

Evaluation of SLS 3D-Printed Filter Structures Based on Bionic Manta Structures.

We report on additively manufactured filter systems based on bionic manta ray structures and evaluate their filter performance. The filters are periodic lamella structures produced by selective laser sintering using PA12 polyamide powder. Two different lamella types are investigated, which are derived from two manta ray genera, namely, Mobula tarapacana and Manta birostris. The precipitator efficiency of sand particles in water is determined for both flow directions, which are referred to as the "wing" and "spoiler" arrangements. With a flat filter design, more than 90% of sand particles can be removed from the water. The variation of the lamella distance reveals that the filter effect is based on the different dynamic flow of particles and water rather than filtering by the hole size. The successful transformation of the primary flat filter design into a round filter structure is demonstrated with precipitator efficiencies above 95% and a ratio of filtered to unfiltered water of 1:1 being achieved, depending of the gap between the filter and the surrounding pipe. A shortening of the filter structure results in an unaltered precipitator efficiency but a lower ratio of filtered water. These results reveal the peculiar possibility to produce 3D round-shaped filters based on manta ray structures with additive manufacturing, achieving good precipitator efficiencies.