Tail Structure Research Articles

A comparative study of the blue comets C/1908 R1 (Morehouse) and C/2016 R2 (Pan-STARRS)

The long-period comet C/1908 R1 (Morehouse) is distinguished by its early spectroscopic tail photography, which uncovered notably intense emission bands of N2+ and CO+ similar to the unusual characteristics of the atypical blue comet C/2016 R2 (Pan-STARRS). To probe potential parallels with C/2016 R2 further, we revisited the historical spectroscopic plates of C/1908 R1 while leveraging the New Astrometric Reduction of Old Observations (NAROO) project's advanced sub-micrometric scanner. We first reviewed the intensity ratio method, followed by a comprehensive spectroscopic analysis of the original historical plates to determine the comet's composition. Our analysis also encompassed an evaluation of C/1908 R1's dynamic trajectory using an N-body integrator and a detailed examination of tail morphology records. Our findings suggest that C/1908 R1 experienced no significant close encounters as it crossed the inner Solar System, anchoring its origins directly in the Oort Cloud and allowing us to ascertain that this was its inaugural voyage near the Sun. We determined a N2+ CO+ ratio of $ along with a dust-poor composition, particularities it shares with C/2016 R2. Moreover, by synthesizing observations of the tail's structure over the three-month period of visibility, we uncovered a link between tail dislocation events and aurora borealis sightings on Earth. This association underscores the comet tail’s heightened sensitivity to solar wind fluctuations due to its volatile makeup. The comet C/1908 R1 (Morehouse) emerges as one of the most unaltered relics of our Solar System's formation, offering another instance of a C/2016 R2-analogous comet. This underscores the importance of preserving and reexamining historical astronomical datasets, not only for historical significance but as a critical resource for contemporary scientific advancement.

Entropy production of active Brownian particles going from liquid to hexatic and solid phases

Abstract Due to its inherent intertwinement with irreversibility, entropy production is a prime observable to monitor in systems of active particles. In this numerical study, entropy production in the liquid, hexatic and solid phases of a two-dimensional system of active Brownian particles is examined at both average and fluctuation level. The trends of averages as functions of density show no singularity and marked changes in their derivatives at the hexatic-solid transition. Distributions show instead peculiar tail structures interpreted by looking at microscopic configurations. Particles in regions of low local order generate tail values according to different dynamical mechanisms: they move towards empty regions or bounce back and forth into close neighbours. The tail structures are reproduced by a simple single-particle model including an intermittent harmonic potential.

Experimental study on flow boiling heat transfer in rigid-tail rib-channel under rolling motion conditions

This study proposes a novel addition of rigid filamentous tail structure at the trailing edge of the ribs to enhance the heat transfer performance of flow boiling in mini-channel under rolling conditions. The flow boiling heat transfer characteristics of Novec649 in both rib-channel and rigid-tail rib-channel are experimentally investigated. Heat flux, inlet flow velocity, rolling angle and rolling period are considered as the variable parameters, which are 50 – 300 kW·m−2, 0.3 – 0.9 m·s−1, 0 – 15°, 10 – 20 s, respectively. The experimental results show that the rigid-tail structure improves the heat transfer performance of the channels within the entire range of thermal parameters, while increasing the pressure drop at high heat flux and/or high velocity. Compared with rib-channel, the rigid-tail structure exhibits the strongest enhancement in flow boiling heat transfer performance under high heat flux of qeff = 300 kW·m−2 and high flow velocity of vin = 0.9 m·s−1, and the heat transfer coefficient can be increased by 6.93 % at most. And increasing the rolling angle or decreasing the rolling period will decrease the average wall temperature by a maximum of 1.94 °C and increase the heat transfer performance factor j by a maximum of 8 % at vin = 0.3 m·s−1, qeff = 200 – 300 kW·m−2 for the rigid-tail rib-channel. Furthermore, the addition of a rigid-tail structure helps maintain smaller bubble sizes and a more uniform distribution in the mainstream region of the two-phase flow.

The dynamic regulatory network of phosphatidic acid metabolism: a spotlight on substrate cycling between phosphatidic acid and diacylglycerol.

Mammalian cells utilize over 1000 different lipid species to maintain cell and organelle membrane properties, control cell signaling and processes, and store energy. Lipid synthesis and metabolism are mediated by highly interconnected and spatiotemporally regulated networks of lipid-metabolizing enzymes and supported by vesicle trafficking and lipid-transfer at membrane contact sites. However, the regulatory mechanisms that achieve lipid homeostasis are largely unknown. Phosphatidic acid (PA) serves as the central hub for phospholipid biosynthesis, acting as a key intermediate in both the Kennedy pathway and the CDP-DAG pathway. Additionally, PA is a potent signaling molecule involved in various cellular processes. This dual role of PA, both as a critical intermediate in lipid biosynthesis and as a significant signaling molecule, suggests that it is tightly regulated within cells. This minireview will summarize the functional diversity of PA molecules based on their acyl tail structures and subcellular localization, highlighting recent tools and findings that shed light on how the physical, chemical, and spatial properties of PA species contribute to their differential metabolic fates and functions. Dysfunctional effects of altered PA metabolism as well as the strategies cells employ to maintain PA regulation and homeostasis will also be discussed. Furthermore, this review will explore the differential regulation of PA metabolism across distinct subcellular membranes. Our recent proximity labeling studies highlight the possibility that substrate cycling between PA and DAG may be location-dependent and have functional significance in cell signaling and lipid homeostasis.

Synthesis and characterization of chloroquine-modified albumin-binding siRNA-lipid conjugates for improved intracellular delivery and gene silencing in cancer cells.

siRNA therapeutics have considerable potential as molecularly-targeted therapeutics in malignant disease, but identification of effective delivery strategies that mediate rapid intracellular delivery while minimizing toxicity has been challenging. Our group recently developed and optimized an siRNA conjugate platform termed "siRNA-L 2 ," which harnesses non-covalent association with endogenous circulating albumin to extend circulation half-life and achieve tumor-selective delivery without the use of traditional cationic lipids or polymers for transfection. To improve intracellular delivery and particularly the endosomal escape properties of siRNA-L 2 towards more efficient gene silencing, we report synthesis of siRNA-CQ-L 2 conjugates, in which chloroquine (CQ), an endosomolytic quinoline alkaloid, is covalently incorporated into the branching lipid tail structure. We accomplished this via synthesis of a novel CQ phosphoramidite, which can be incorporated into a modular siRNA-L 2 backbone using on-column solid-phase synthesis through use of asymmetric branchers with levulinyl-protected hydroxide groups that allow covalent addition of pendant CQ repeats. We demonstrate that siRNA-CQ-L 2 maintains the ability to non-covalently bind albumin, and with multiple copies of CQ, siRNA-CQ-L 2 mediates higher endosomal disruption, cellular uptake/retention, and reporter gene knockdown in cancer cells. Further, in mice, the addition of CQ did not significantly affect circulation kinetics nor organ biodistribution and did not produce hematologic or organ-level toxicity. Thus, controlled, multivalent conjugation of albumin-binding siRNA-L 2 to endosomolytic small molecule compounds holds promise in improving siRNA-L 2 knockdown potency while maintaining albumin-binding properties and overall safety.

The influence of serrated trailing edge on pulsating pressure and noise performance of pump-jet propulsor under submarine self-propulsion condition

Owls make almost no noise when gliding, thanks to the unique feather structure at the tail of their wings. Drawing on the tail structure of the owl wings, the trailing edge of the duct in the pump-jet propulsor (PJP) system is improved. Based on the detached eddy simulation method, the influence of serrated trailing edge on the pulsating pressure and noise performance of a PJP under submarine self-propulsion conditions is numerically analyzed. The results show that the influence of the serrated trailing edge on the self-propulsion performance is negligible. The serrated trailing edge destroys the large-scale duct-induced vortices in the spanwise direction, and additional secondary vortices are formed in the wakefield, increasing the pulsating pressure of the downstream flow field. The pulsation amplitude of each order at the downstream monitoring point of the serrated duct PJP (SD-PJP) model is significantly greater than that of the benchmark PJP (BM-PJP) model. The serrated trailing edge can effectively reduce the noise of PJP. The maximum noise reduction in the axial and radial planes is 1.23 and 0.91 dB.

CryoEM Investigation of Three-Dimentional Structure of the Stx-Converting Bacteriophage ϕ24B

A modified method for culturing, concentrating, and purifying phage ϕ24B preparations was developed. In particular, a new lysogenic phage-producing strain lacking flagella was used, induction conditions were optimized, and purification in a sucrose gradient and concentration by deposition on a Freon 113 cushion were used. Using this method, a preparation of the Stx-converting bacteriophage ϕ24B was obtained, which was suitable for direct analysis by the cryoEM method. Based on cryoEM data for this phage, the first primary three-dimensional reconstruction of its virions was performed. The structure of the phage ϕ24B tail is described. It was shown that the adsorption apparatus of this virus is represented by six thin lateral fibrils and an axial fibril located at the end of the tail. This arrangement of the tail structure is consistent with the previously proposed hypothesis based on analysis of the receptor binding proteins (RBPs) of this bacteriophage.

A New Perspective on Türkiye's Sheep Population: Classification with Decision Trees

Decision trees are data mining algorithms that make interpreting the cause-effect relationship or classification between features with visual diagrams easy and do not require parametric assumptions. The aim of this study is to classify different sheep breeds raised in Turkey according to their origin and tail structure characteristics using a decision tree algorithm. It has been seen that the CART (Classification and Regression Trees) algorithm is sufficient for the classification of sheep breeds by obtaining low-risk values. According to the results of the study, it is seen that domestic sheep breeds are distributed to Eastern Anatolia, Mediterranean, Black Sea, and Central Anatolia Regions and imported breeds are distributed to all regions of Türkiye. The total population of these breeds was determined as 43.889.918 heads. As it can be understood, the Akkaraman breed ranks first with a rate of 40.88% of the total sheep stock. Next comes the Morkaraman breed with a rate of 11.68%. Thirdly, the most cultivated breed is Kıvırcık, whose rate is 8.82%. Merino sheep comes in fourth place with 8.43%. Awassi sheep are among the most common breeds in the fifth place. Hereby the distribution of sheep breeds in Türkiye has also been revealed and the distribution of breeds according to environmental conditions has been determined. The decision tree model generated using the CART algorithm for the distribution of sheep breeds in Turkey based on tail structures has been found to have a value (0.47). The proportion of sheep with a thin tail structure is 52.2%, while those with a semi-fatty tail structure are 17.5%, and those with a fatty tail structure are 30.2%. It has been determined that sheep breeds with thin tails are more commonly raised in Turkey. In the study, a decision tree model was also created using the CART algorithm to analyze the distribution of sheep populations in regions based on their origin, and it was found to have a value (0.26) with an accuracy rate of 74%. According to the research, 73.9% of sheep are domestic, while 26.1% are imported. When examining the distribution of origin by region, the region with the least number of imported sheep is Eastern Anatolia, while the highest proportions are found in the Mediterranean and Black Sea regions. The region with the lowest proportion of domestic sheep is the Mediterranean and Black Sea (70.4%), whereas the highest proportion is in the Eastern Anatolia region (82.6%).

A Hinge Moment Alleviation Control Strategy for Morphing Tail Aircraft Based on a Data-Driven Method

Morphing airplane technology is currently a focal point of research. For morphing airplanes, besides effective morphing strategies and control schemes, the hinge moment at the root of the vertical tail during morphing is a critical factor influencing flight safety. To prevent failure in tail morphing due to excessive hinge moments, this paper analyzes the hinge moment characteristics of the variable vertical tail structure in high-speed flight, based on a flying wing model from the China Aerodynamics Research and Development Center. The proposed adaptive morphing tail hinge moment reduction (AMTHR) method is model-free, utilizing real-time data to dynamically adjust the rudder and reduce hinge moments without requiring prior knowledge of system dynamics. This method utilizes the concept of extremum-seeking control by introducing periodic perturbations to the system and adjusting the control input based on their impact on the output. This approach drives the output toward an extremum point, enabling real-time reduction of the vertical tail hinge moment. Finally, the simulation analysis is carried out under the conditions of no wind and gust disturbance, and the effect of this method on the load reduction of the tail hinge moment is verified.

Constructing stress-release layer on Si nanoparticles for high-performance lithium storage

Tailing structures of silicon anode to alleviate the mechanical stress has an important significance in the development of lithium-ion batteries (LIBs). Herein, the stress-released layer of N-doped cubic carbon on the surface of Si nanoparticles (Si@NCC) is explored to stabilize the electrode. Endowed with the unique superiority, the Si@NCC electrode delivers an impressive lithium storage performance with high specific capacity of 630 mAh/g at 0.1 A/g, excellent cycling stability (72.0 % capacity retention after 100 cycles at 0.1 A/g) and good rate capability (375 mAh/g at 2 A/g). It has been demonstrated that the N-doped cubic carbon shell with high conductivity can effectively limit the expansion and agglomeration of Si nanoparticles. Besides, the COMSOL simulations of the stress distributions in materials confirm that the N-doped cubic carbon layer could remarkably decrease the stress originated from the volume expansion of Si nanoparticles during the lithiation. Therefore, this work provides ideas for the mechanical effect of Si-based anodes for lithium storage and sheds lights on the designing advanced materials toward high-performance energy storage devices.

The Sperm-Associated Antigen 11A (Spag11a) Knockout Mice Display Sub-Fertility and Perturbations in the Sperm Proteome.

Spermatogenesis and sperm maturation that occur in the testis and epididymis respectively are crucial for fertility. Factors secreted by the testicular and epididymal epithelial cells govern the processes of gametogenesis and maturation. Proteins encoded by the sperm-associated antigen 11a (Spag11a) gene are implicated as having a possible role in sperm maturation. However, studies that demonstrate their definite role in fertility and sperm function using knockout models have not yet reported. In this study, Spag11a knockout mice were generated, genotyped and the reproductive parameters (fecundity, sperm count, capacitation, and acrosome reaction) and sperm proteome were determined. Litter size and sperm count were decreased in the Spag11a knockout mice when compared to the wild-type controls. Spermatozoa from the knockout mice were able to undergo capacitation. However, acrosome reaction did not occur in sperm obtained from knockout mice. Structural abnormalities in the head and tail structures were evident in the spermatozoa of knockout mice. Perturbations in the expression of sperm proteins that are involved in gametogenesis were evident. The subfertility observed in Spag11a knockout mice could be a manifestation of lower sperm count, impaired acrosome reactions, and disturbances in the sperm proteome. The results of this study lend further support to the role of Spag11a gene in male gamete function.

Coarse-Grained Molecular Dynamics Simulation of Heterogeneous Polysorbate 80 Surfactants and their Interactions with Small Molecules and Proteins.

Polysorbate 80 (PS80) is widely used in pharmaceutical formulations, and its commercial grades exhibit certain levels of structural heterogeneity. The objective of this study was to apply coarse-grained molecular dynamics simulations to better understand the effect of PS80 heterogeneity on micelle self-assembly, the loading of hydrophobic small molecules into the micelle core, and the interactions between PS80 and a protein, bovine serum albumin (BSA). Four representative PS80 variants with different head and tail structures were studied. Our simulations found that PS80 structural heterogeneity could affect blank micelle properties such as solvent-accessible surface area, aggregation number, and micelle aspect ratio. It was also found that hydrophobic small molecules such as ethinyl estradiol preferentially partitioned into the PS80 micelle core and PS80 dioleates formed a more hydrophobic core compared to PS80 monooleates. Furthermore, multiple PS80 molecules could bind to BSA, and PS80 heterogeneity profoundly changed the binding ratio as well as the surfactant-protein contact area.

METTL3 -mediated m6A modification of circ_0000620 regulates cisplatin sensitivity and apoptosis in lung adenocarcinoma via the MiR-216b-5p/KRAS axis

Circular RNAs (circRNAs) are stable non-coding RNAs characterized by the absence of the conventional 5' cap and 3' polyadenylated tail structure. Its involvement in various aspects of cancers underscores its significance in oncology. Elevated expression of circ_0000620 was observed in both lung adenocarcinoma (LUAD) tissues and cell lines. In vitro, experiments demonstrated that the downregulation of circ_0000620 increased cisplatin sensitivity and promoted cell apoptosis while suppressing malignant characteristics such as cell migration and proliferation. Further investigation into the mechanism underlying the increased expression of circ_0000620 revealed that Methyltransferase 3, N6-Adenosine-Methyltransferase Complex Catalytic Subunit (METTL3) mediates the m6A methylation modification of circ_0000620, thereby promoting its stability and expression. Furthermore, circ_0000620 modulates the miR-216b-5p/KRAS axis to influence apoptosis and cisplatin sensitivity in both A549 and H1299 cell lines. These findings were corroborated by in vivo nude mouse experiments, which showed that knockdown of circ_0000620 inhibited tumor growth and proliferation. In summary, METTL3 plays a role in regulating the stability of circ_0000620 expression, and circ_0000620 exerts its effects on LUAD apoptosis and cisplatin sensitivity through the miR-216b-5p/KRAS signaling pathway.

Effects of dilution and age on perfume release from two mixed‐surfactant systems containing hydrotropes

AbstractThis study investigates the encapsulation and controlled release of perfume within micellar systems. We explored how perfume‐surfactant interactions and micelle structure influence fragrance delivery. Two mixed‐micelle systems, one with branched‐tail and the other with linear‐tail surfactants, were subjected to varying perfume concentrations, dilution, and time. Using small‐angle neutron scattering (SANS), gas chromatography‐mass spectrometry (GC‐MS), and statistical analysis, we determined that micelle size and shape are significantly affected by perfume content and dilution. While both systems exhibited similar trends, the branched‐tail system uniquely formed a lamellar phase at higher perfume levels. Our findings reveal a strong correlation between micelle geometry and headspace perfume concentration, highlighting the role of surfactant tail structure. This research provides fundamental insights into perfume‐micelle interactions, with potential applications in materials science and active ingredient delivery.

Injectable Nanorobot-Hydrogel Superstructure for Hemostasis and Anticancer Therapy of Spinal Metastasis

HighlightsSite-selective superassembly was used to synthesize a nanorobot with bionic rod-shaped head/hollow tail structure, exhibiting strong photothermal effect, high drug loading capacity, precise and controlled drug release, and excellent motility.Injectable regenerated silk fibroin (RSF) nanofibril hydrogels were developed via simple sonication, offering significant production, structural, and performance advantages.Nanorobot/thrombin (Thr)/RSF nanofibril hydrogels reduced intraoperative bleeding of hepatocellular carcinoma (HCC) spinal metastasis, provided starvation embolization, and prevented post-surgery recurrence.Nanorobot/Thr/RSF nanofibril hydrogels inhibited blood supply to residual tumors and reduced neovascularization, inhibiting post-surgery HCC spinal metastasis recurrence.

ASKAP reveals the radio tail structure of the Corkscrew Galaxy shaped by its passage through the Abell 3627 cluster

ABSTRACT Among the bent-tail radio galaxies common in galaxy clusters are some with long, collimated tails (so-called head-tail galaxies) shaped by their interactions with the intracluster medium (ICM). Here, we report the discovery of intricate filamentary structure in and beyond the ∼28 arcmin (570 kpc) long, helical radio tail of the Corkscrew Galaxy (1610–60.5, ESO 137-G007), which resides in the X-ray bright cluster Abell 3627 (D = 70 Mpc). Deep radio continuum data were obtained with wide-field phased array feeds on the Australian Square Kilometer Array Pathfinder (ASKAP) at 944 MHz and 1.4 GHz. While the bright (young) part of the Corkscrew Galaxy tail is highly collimated, the faint (old) part shows increasing oscillation amplitudes, break-ups, and filaments. We find a stunning set of arc-shaped radio filaments beyond and mostly orthogonal to the collimated Corkscrew tail end, forming a partial bubble. This may be the first detection of a ‘proto-lobe’ previously seen in 3D MHD simulations, formed by the face-on impact of the Corkscrew Galaxy with a shock front in the cluster outskirts. Interactions of the radio galaxy tail with the ICM are likely responsible for the tail collimation and shear forces within the ICM for its increasingly filamentary structure. We also report the discovery of small (∼20–30 kpc) ram-pressure stripped radio tails in four Abell 3627 cluster galaxies, located between the Corkscrew Galaxy and its prominent neighbour, the wide-angle tail (WAT) radio galaxy 1610–60.8 (ESO 137-G006).

Molecular Mechanisms and Enhancement of Piezoelectricity in the M13 Virus

AbstractUnderstanding the structure and function of bioelectric materials is challenging due to the complex nature of biomaterials and a lack of appropriate tools. The precisely defined structures and genetic tunability of viruses provide an excellent model system to investigate bioelectrical behavior in biomaterials. This study presents the molecular mechanisms of piezoelectricity in the M13 bacteriophage (phage) under various mechanical stresses for bio‐piezoelectric generation. A computational approach is used to calculate the piezoelectric tensors of the M13 phage and quantify its direction‐dependent dipole moments. By computationally designing negatively charged residues on the phage surface, the surface charge density is enhanced to 16.7 µC cm−2. Using genetic engineering, phages are experimentally designed with different charges and tail structures to create model phage nanostructures, including individual phages, vertically standing phage films, and horizontally aligned phage films. Their vertical, horizontal, and shear‐mode piezoelectric properties are then measured using scanning probe microscopy techniques. The resulting phage‐based piezoelectric energy generators exhibit an effective piezoelectric coefficient of 15.4 pm V−1 and a power density of 4.2 µW cm−2. This phage‐based bioengineering approach provides a versatile platform for investigating fundamental mechanisms of bioelectricity and designing bioelectric materials for applications in energy harvesting, biomemory, and biosensors.

P-154 Structural changes of the human sperm tail during the early post-fertilization

Abstract Study question What happens to the sperm tails that are no longer needed after the goal of fertilization has been achieved? Summary answer The sperm tail lost its fibrous sheath and changed to a coiled morphology with a whisker root-like structure at the tip during the early post-fertilization. What is known already The sperm tail has been thought to play only a role in allowing the head and neck to reach the oocyte. The flagellum is found in the mammalian sperm tail and consists of a middle, main, and terminal part. It also contains an axon composed of two central microtubules surrounded by nine peripheral microtubule doublets (9d + 2s microtubule pattern) surrounded by an accessory structure called the fibrous sheath (FS), but few studies have been conducted on the post-fertilization fate of the mammalian sperm tail. Study design, size, duration To investigate sperm tail structure from the pronuclear stage to the second cleavage, we used abnormally fertilized oocytes derived from either conventional in vitro fertilization (cIVF, n = 41) or intracytoplasmic sperm injection (ICSI, n = 11). In this study, abnormally fertilized oocytes were collected between March 2022 and November 2023 and subjected to immunofluorescence analysis and field emission scanning electron microscopy (FE-SEM) analysis. Participants/materials, setting, methods Under ethical approval, abnormally fertilized oocytes were donated by infertile couples undergoing cIVF or ICSI cycles at the Yamashita Shonan Yume Clinic in Japan. Informed consent was obtained from all participants. Immunofluorescence assay was performed to analyze sperm tail morphology using antibodies against H3K27me3, α-tubulin, and AKAP4. FE-SEM analysis was performed to detect the 9d + 2s structure characteristic of the sperm tail axon. Main results and the role of chance Tri-pronuclear zygotes derived from conventional in vitro fertilization (cIVF-derived 3PN) had two male pronuclei, whereas those derived from intracytoplasmic sperm injection (ICSI-derived 3PN) had one. Each zygote had the same number of coiled microtubule structures as the male pronucleus, and the 9d + 2s structure characteristic of the axon was identified, suggesting a sperm tail. No difference in sperm tail shape was observed between ICSI-derived 3PN and cIVF-derived 3PN. AKAP4, which is specifically localized in the FS associated with the principal piece of the flagellum, was observed in sperm tails attached to the zona pellucida but not in those in the oocyte, suggesting that the FS of the flagellum is lost before the pronuclear stage, leaving the microtubules of the axonemes exposed. The sperm tail was attached to one of the spindle poles during the first cleavage of abnormally fertilized oocytes, but no differences in the structure of the spindle pole with or without the sperm tail were observed. The tip of the sperm tail was branched like a “whisker root”, suggesting that the sperm tail was degraded from the end, but the degree of tip branching did not differ from the pronuclear stage to the second cleavage. Limitations, reasons for caution Normal fertilized oocytes were not used in this study because they are used for clinical treatment. The cell biological significance of sperm tail branching is currently unknown and requires further experimentation. Wider implications of the findings These findings shed light on the processes that occur during human fertilization, suggest new roles for the sperm tail, and may have implications for assisted fertilization approaches in the future. Trial registration number not applicable

Design and movement mechanism analysis of a multiple degree of freedom bionic crocodile robot based on the characteristic of “death roll”

AbstractThis paper introduces a multi‐degree of freedom bionic crocodile robot designed to tackle the challenge of cleaning pollutants and debris from the surfaces of narrow, shallow rivers. The robot mimics the “death roll” motion of crocodiles which is a technique used for object disintegration. First, the design incorporated a swinging tail mechanism using a multi‐section oscillating guide‐bar mechanism. By analyzing three‐, four‐, and five‐section tail structures, the four‐section tail was identified as the most effective structure, offering optimal strength and swing amplitude. Each section of the tail can reach maximum swing angles of 8.05°, 20.95°, 35.09°, and 43.84°, respectively, under a single motor's drive. Next, the robotic legs were designed with a double parallelogram mechanism, facilitating both crawling and retracting movements. In addition, the mouth employed a double‐rocker mechanism for efficient closure and locking, achieving an average torque of 5.69 N m with a motor torque of 3.92 N m. Moreover, the robotic body was designed with upper and lower segment structures and waterproofing function was also considered. Besides, the kinematic mechanism and mechanical properties of the bionic crocodile structure were analyzed from the perspectives of modeling and field tests. The results demonstrated an exceptional kinematic performance of the bionic crocodile robot, effectively replicating the authentic movement characteristics of a crocodile.

Signal of phase transition hidden in quasinormal modes of regular AdS black holes

We discuss the intrinsic relations between thermodynamic phase transitions and quasinormal modes in regular AdS black holes, specifically in the Bardeen and Hayward AdS classes. To this end, we calculate the quasinormal modes of massless scalar field perturbations around small and large black holes via the Horowitz-Hubeny method. By investigating the isobaric and isothermal phase transitions for Bardeen and Hayward AdS black holes in detail, we observe that a dramatic change of quasinormal modes appears near the phase transition point of small and large black holes, and that it corresponds to the swallow tail structure in the plane of Gibbs free energy with respect to pressure. Moreover, by analyzing the evolution of black holes along the coexistence curve of small and large black hole phases, we also observe the dramatic change in quasinormal modes. Such a phenomenon confirms the signal of the phase transition in the quasinormal mode spectrum, which can be understood as a thermodynamic signal hidden in the dynamical spectrum.