Multiscale Characterization and Biomimetic Design of Porcupine Quills for Enhanced Mechanical Performance.

The mechanical properties of porcupine quills have attracted the interest of researchers due to their unique structure and composition. However, there is still a knowledge gap in understanding how these properties can be utilized to design biomimetic structures with enhanced performance. This study delves into the nanomechanical and macro-mechanical properties of porcupine quills, unveiling varied elastic moduli across different regions and cross sections. The results indicated that the elastic moduli of the upper and lower epidermis were higher at 8.13 ± 0.05 GPa and 7.71 ± 0.14 GPa, respectively, compared to other regions. In contrast, the elastic modulus of the mid-dermis of the quill mid-section was measured to be 7.16 ± 0.10 GPa. Based on the micro- and macro-structural analysis of porcupine quills, which revealed distinct variations in elastic moduli across different regions and cross sections, various biomimetic porous structures (BPSs) were designed. These BPSs were inspired by the unique properties of the quills and aimed to replicate and enhance their mechanical characteristics in engineering applications. Compression, torsion, and impact tests illustrated the efficacy of structures with filled hexagons and circles in improving performance. This study showed enhancements in maximum torsional load and crashworthiness with an increase in filled structures. Particularly noteworthy was the biomimetic porous circular structure 3 (BPCS_3), which displayed exceptional achievements in average energy absorption (28.37 J) and specific energy absorption (919.82 J/kg). Finally, a response surface-based optimization method is proposed to enhance the design of the structure under combined compression-torsion loads, with the goal of reducing mass and deformation. This research contributes to the field of biomimetics by exploring the potential applications of porcupine quill-inspired structures in fields such as robotics, drive shafts, and aerospace engineering.

Aluminium tolerance and stomata operation: Towards optimising crop performance in acid soil.

Stomatal operation is crucial for optimising plant water and gas exchange and represents a major trait conferring abiotic stress tolerance in plants. About 56% of agricultural land around the globe is classified as acidic, and Al toxicity is a major limiting factor affecting plant performance in such soils. While most of the research work in the field discusses the impact of major abiotic stresses such as drought or salinity on stomatal operation, the impact of toxic metals and, specifically aluminium (Al) on stomatal operation receives much less attention. We aim to fill this knowledge gap by summarizing the current knowledge of the adverse effects of acid soils on plant stomatal development and operation. We summarised the knowledge of stomatal responses to both long-term and transient Al exposure, explored molecular mechanisms underlying plant adaptations to Al toxicity, and elucidated regulatory networks that alleviate Al toxicity. It is shown that Al-induced stomatal closure involves regulations of core stomatal signalling components, such as ROS, NO, and CO2 and key elements of ABA signalling. We also discuss possible targets and pathway to modify stomatal operation in plants grown in acid soils thus reducing the impact of Al toxicity on plant growth and yield.

Effect of Multistage Solution Aging Heat Treatment on Mechanical Properties and Precipitated Phase Characteristics of High-Strength Toughened 7055 Alloy.

In this paper, a one-step hot extrusion dual-stage solution treatment method is employed to fabricate high-strength and tough T-shaped complex cross-section 7055 (Al-Zn-Mg-Cu-Zr) alloy profiles, and a detailed investigation is conducted on the microstructure and mechanical properties. The results indicate that the comprehensive mechanical properties of the 7055 aluminum extruded alloy using the two-stage solution aging treatment are excellent. This is particularly evident in the balance between strength and ductility, where outstanding strength is accompanied by a plasticity that is maintained at 13.2%. During the extrusion process, the deformation textures are mainly composed of brass and copper, forming a 15.1% recrystallization texture Cube. In addition, the equilibrium phase η(MgZn2) precipitated in the grain is the main strengthening phase, and there are large discontinuous grain boundary precipitates at the grain boundary, which hinders the grain boundary dislocation movement and has great influence on the mechanical properties of alloy materials.

A new C19-diterpenoid alkaloid in Aconitum georgei Comber.

Nine diterpenoid alkaloids were isolated from Aconitum georgei Comber belonging to the genus Aconitum in Ranunculaceae family. Their structures were determinated by using HR-ESI-MS and 1 D/2D NMR spectra as geordine (1), yunaconitine (2), chasmanine (3), crassicauline A (4), forestine (5), pseudaconine (6), 14-acetylalatisamine (7), austroconitine B (8), and talatisamine (9). Among them, compound 1 is a previously undescribed aconitine-type C19-diterpenoid alkaloid, and compounds 3, and 5-9 have not previously been isolated from this species. The results of in vitro experiments indicated that new compound 1 possesses mild anti-inflammatory activity, which inhibited the production of NO in LPS-activated RAW 264.7 cells with an inhibition ratio of 29.75% at 50 µM.

Capillary efficiency study in leaf vein morphology inspired channels.

Inspired by the capillary transport function of plant leaf veins, this study proposes three typical leaf vein features by observing a large number of leaves, including wedge shape, branch asymmetry, as well as hierarchical arrangement, and investigates their capillary transport mechanism. Not only a preliminary theoretical analysis of capillary flow in the bio-inspired channels was carried out, but the COMSOL Multiphysics simulation software was also used to simulate gas-liquid two-phase flow in biomimetic channels. The results reveal the efficient transport mechanism of the leaf vein inspired structure and provide insight into the design of capillary transmission channels.

The Design of a Biomimetic Hierarchical Thin-Walled Structure Inspired by a Lotus Leaf and Its Mechanical Performance Analysis.

Inspired by the macro- and microstructures of the lotus leaf, a series of biomimetic hierarchical thin-walled structures (BHTSs) was proposed and fabricated, exhibiting improved mechanical properties. The comprehensive mechanical properties of the BHTSs were evaluated using finite element (FE) models constructed in ANSYS, which were validated by the experimental results. Light-weight numbers (LWNs) were used as an index to assess these properties. The simulation results were compared with the experimental data to validate the findings. The compression results indicated that the maximum load carried by each BHTS was very similar, with the highest bearing load being 32,571 N and the lowest being 30,183 N, resulting in only a 7.9% difference between them. In terms of the LWN-C values, the BHTS-1 exhibited the highest value at 318.51 N/g, while the BHTS-6 had the lowest value at 295.16 N/g. For the torsion and bending results, these findings suggested that increasing the bifurcation structure at the end side of the thin tube branch significantly improved the torsional resistance properties of the thin tube. For the impact characteristics of the proposed BHTSs, enhancing the bifurcation structure at the end of the thin tube branch significantly increased the energy absorption capacity and improved the energy absorption (EA) and the specific energy absorption (SEA) values of the thin tube. The BHTS-6 had the best structural design in terms of both the EA and SEA among all the BHTSs, but its CLE value was slightly lower than that of the BHTS-7, indicating slightly lower structural efficiency. This study provides a new idea and method for developing new lightweight and high-strength materials as well as designing more effective energy absorption structures. At the same time, this study has important scientific value in understanding how biological structures in nature exhibit their unique mechanical properties.

The Flexible Armor of Chinese Sturgeon: Potential Contribution of Fish Skin on Fracture Toughness and Flexural Response.

Fish skin is a biological material with high flexibility and compliance and can provide good mechanical protection against sharp punctures. This unusual structural function makes fish skin a potential biomimetic design model for flexible, protective, and locomotory systems. In this work, tensile fracture tests, bending tests, and calculation analyses were conducted to study the toughening mechanism of sturgeon fish skin, the bending response of the whole Chinese sturgeon, and the effect of bony plates on the flexural stiffness of the fish body. Morphological observations showed some placoid scales with drag-reduction functions on the skin surface of the Chinese sturgeon. The mechanical tests revealed that the sturgeon fish skin displayed good fracture toughness. Moreover, flexural stiffness decreased gradually from the anterior region to the posterior region of the fish body, which means that the posterior region (near the tail) had higher flexibility. Under large bending deformation, the bony plates had a specific inhibition effect on the bending deformation of the fish body, especially in the posterior region of the fish body. Furthermore, the test results of the dermis-cut samples showed that the sturgeon fish skin had a significant impact on flexural stiffness, and the fish skin could act as an external tendon to promote effective swimming motion.

The Armor of the Chinese Sturgeon: A Study of the Microstructure and Mechanical Properties of the Ventral Bony Plates.

Benefiting from their unique morphological characteristics and structural properties, the ventral bony plates of the Chinese sturgeon are excellent biological protective tissue. In this work, we studied the micro- and macro-morphology and mechanical properties of the ventral bony plates of the Chinese sturgeon to elucidate the special protective mechanisms of the bony plates. Experiments involving scanning electron microscopy and energy-dispersive X-ray spectroscopy revealed that the bony plates possess a hierarchical structure and a ridge-like shape. This structure comprises a surface layer containing mineralized nanocrystals and an internal layer containing mineralized collagen fibers. From the surface layer to the internal layer, the degree of mineralization decreases gradually. Nanoindentation, tension, and compression tests demonstrated that the bony plates feature excellent mechanical properties and a high specific tensile strength comparable to that of stainless steel. Moreover, water can significantly improve the fracture toughness and deformability of the bony plates and effectively enhance the damage tolerance of the structures. The obtained results concerning the microstructure-property-function relationships of the ventral bony plates of the Chinese sturgeon may provide novel insights for designing protective structures that are both lightweight and high strength.

Unique structures and material properties of the skin in different body regions of three species of fish.

Benefitting from its unique helically arranged fiber structures, fish skin is a superior biological protective tissue. Reported here is a study of the microscopic morphological characteristics and mechanical properties of the skin of three species of fish, that is, Taihu white fish (Erythroculter ilishaeformis), grouper (Cichlasoma managuense), and yellowfin seabream (Ditrema temminckii Bleeker), revealing the special protective mechanisms of fish skin. Experiments involving scanning electron microscopy show that the stratum compactum is the main part of fish skin and comprises helically stacked fibers, with the helical ply angles of the fibrous layers differing significantly for the different fish species and in different regions of their bodies. Tension and penetration experiments show that fish skin provides a fish's body with considerable mechanical protection from lacerations and bites inflicted by its natural enemies. Moreover, the mechanical tests show that fish skin has two different defensive mechanisms against tension and penetration loads, thereby offering a novel idea for designing body armor that is both flexible and tough.

Incidence and Risk Factors of Surgical Complications and Anastomotic Leakage After Transanal Total Mesorectal Excision for Middle and Low Rectal Cancer.

PURPOSE: Transanal total mesorectal excision (taTME) is a promising surgical procedure for middle and low rectal cancer; however, it is linked to significant morbidity. This study aimed to determine the incidence of postoperative surgical complications and anastomotic leakage following taTME and to identify their associated risk factors. METHODS: The prospective clinical data of 114 patients, who underwent taTME and primary anastomosis for mid-low rectal cancer between November 2016 and June 2022, were retrospectively analyzed. Univariate and multivariate analyses were performed to identify clinical characteristics and risk factors for predicting surgical complications and anastomotic leakage. RESULTS: Surgical complications occurred in 40 (35.1%) patients within the first 30 days following surgery. Based on the Clavien-Dindo classification, minor complications (Clavien-Dindo grades I + II) accounted for 30.7%, while major complications (Clavien-Dindo grades III + IV) accounted for only 4.4%. None of the patients died within 30 days. The incidence of anastomotic leakage was 15.8%: 4.4% as grade A (5 cases), 9.6% as grade B (11 cases), and 1.8% as grade C (2 cases). Preoperative T3-4 was identified as an independent risk factor for surgical complications (p = 0.031) by multivariate analysis. American Society of Anesthesiology score ≥ 3 (P = 0.021) and incomplete total mesorectal excision specimens (P = 0.030) were significantly associated with the risk of anastomotic leakage. CONCLUSIONS: In this study, the incidence of surgical complications and anastomotic leakage in taTME aligned with previously reported rates. Preoperative T3-4 was significantly associated with surgical complications. American Society of Anesthesiology score ≥ 3 and incomplete TME specimens independently increased the risk of anastomotic leakage.

Bending Study of Six Biological Models for Design of High Strength and Tough Structures.

High strength and tough structures are beneficial to increasing engineering components service span. Nonetheless, improving structure strength and, simultaneously, toughness is difficult, since these two properties are generally mutually exclusive. Biological organisms exhibit both excellent strength and toughness. Using bionic structures from these biological organisms can be solutions for improving these properties of engineering components. To effectively apply biological models to design biomimetic structures, this paper analyses strengthening and toughening mechanisms of six fundamentally biological models obtained from biological organisms. Numerical models of three-point bending test are established to predict crack propagation behaviors of the six biological models. Furthermore, the strength and toughness of six biomimetic composites are experimentally evaluated. It is identified that the helical model possesses the highest toughness and satisfying strength. This work provides more detailed evidence for engineers to designate bionic models to the design of biomimetic composites with high strength and toughness.

Analysis of the topological motifs of the cellular structure of the tri-spine horseshoe crab (Tachypleus tridentatus) and its associated mechanical properties.

Topological motifs in pore architecture can profoundly influence the structural properties of that architecture, such as its mass, porosity, modulus, strength, and surface permeability. Taking the irregular cellular structure of the tri-spine horseshoe crab as a research model, we present a new approach to the quantitative description and analysis of structure-property-function relationships. We employ a robust skeletonization method to construct a curve-skeleton that relies on high-resolution 3D tomographic data. The topological motifs and mechanical properties of the long-range cellular structure were investigated using the Grasshopper plugin and uniaxial compression test to identify the variation gradient. Finite element analysis was conducted for the sub-volumes to obtain the variation in effective modulus along the three principal directions. The results show that the branch length and node distribution density varied from the tip to the base of the sharp corner. These node types formed a low-connectivity network, in which the node types 3-N and 4-N tended to follow the motifs of ideal planar triangle and tetrahedral configurations, respectively, with the highest proportion of inter-branch angles in the angle ranges of 115-120° and 105-110°. In addition, mapping the mechanical gradients to topological properties indicated that narrower profiles with a given branch length gradient, preferred branch orientation, and network connectedness degree are the main factors that affect the mechanical properties. These factors suggest significant potential for designing a controllable, irregularly cellular structure in terms of both morphology and function.

Identification of QTL for Stem Traits in Wheat (Triticum aestivum L.).

Lodging in wheat (Triticum aestivum L.) is a complicated phenomenon that is influenced by physiological, genetics, and external factors. It causes a great yield loss and reduces grain quality and mechanical harvesting efficiency. Lodging resistance is contributed by various traits, including increased stem strength. The aim of this study was to map quantitative trait loci (QTL) controlling stem strength-related features (the number of big vascular bundles, stem diameter, stem wall thickness) using a doubled haploid (DH) population derived from a cross between Baiqimai and Neixiang 5. Field experiments were conducted during 2020-2022, and glasshouse experiments were conducted during 2021-2022. Significant genetic variations were observed for all measured traits, and they were all highly heritable. Fifteen QTL for stem strength-related traits were identified on chromosomes 2D, 3A, 3B, 3D, 4B, 5A, 6B, 7A, and 7D, respectively, and 7 QTL for grain yield-related traits were identified on chromosomes 2B, 2D, 3D, 4B, 7A, and 7B, respectively. The superior allele of the major QTL for the number of big vascular bundle (VB) was independent of plant height (PH), making it possible to improve stem strength without a trade-off of PH, thus improving lodging resistance. VB also showed positive correlations with some of the yield components. The result will be useful for molecular marker-assisted selection (MAS) for high stem strength and high yield potential.

Regional Entrepreneurship, Business Environment, and High-Quality Economic Development: An Empirical Analysis of Nine Urban Agglomerations in China.

The article selects socioeconomic data related to 146 prefecture-level cities included in nine city clusters from 2014 to 2018 to establish a city-level socioeconomic system in China. A sensitivity analysis of regional entrepreneurship and economic quality development based on system dynamics was conducted to explore the changes in regional entrepreneurship and economic quality development over time and their sensitivity factors. In this way, the dynamic evolution mechanism of the system can be portrayed, and the optimization of the system can be achieved through the coordination of the factors within the system. The article sets up three scenarios to explore the fluctuations in regional entrepreneurship and economic quality development when three sensitive factors, namely, business environment, financial services scale, and innovation environment, change. Findings: There are differences in the development of cities within city clusters. The business environment and high-quality economic development of the central cities within the city cluster are stronger than those of the non-central cities. Therefore, regions should focus on synergistic development within city clusters when formulating related policies. The variation of regional entrepreneurship development and economic quality development, after a factor in the system is changed, is asymmetric. Because the sensitivity of different urban clusters and the way they are affected by sensitive factors varies, the state should pay more attention to the adaptability of cities when formulating corresponding policy measures and adapt its policy measures to the sensitivity characteristics of each region according to local conditions.

Mathematical model and nanoindentation properties of the claws of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae).

Scanning electron microscopy (SEM) was used to observe the macroscopic, microscopic, and cross-sectional structures of the claws of Cyrtotrachelus buqueti Guer (Coleoptera: Curculionidae), and a mathematical model of a claw was used to investigate the structure-function relationships. To improve the quality of the SEM images, a non-local means (NLM) algorithm and an improved NLM algorithm were applied. After comparison and analysis of five classical edge-detection algorithms, the boundaries of the structural features of the claw were extracted based on a B-spline wavelet algorithm, and the results showed that the variable curvature of the beetle claw enhances its adhesion force and improves its strength. Adhesion models of the claw were established, and the mechanical properties of its biomaterials were measured using nanoindentation. Considering that the presence of water can affect the hardness and Young's modulus, both 'dry' and 'wet' samples were examined. For the dry samples, the hardness and Young's modulus were 0.197 ± 0.074 GPa and 1.105 ± 0.197 GPa, respectively, whereas the respective values for the wet samples were both lower at 0.071 ± 0.030 GPa and 0.693 ± 0.163 GPa. This study provides data that can inform the design of climbing robots.

Magnetic Resonance Imaging and Serum AFP-L3 and GP-73 in the Diagnosis of Primary Liver Cancer.

Objective: To investigate the combined application value of magnetic resonance imaging (MRI) combined with serum alpha-fetoprotein (AFP)-L3 and Golgi protein (GP)-73 in the diagnosis of primary liver cancer. Methods: The data of 200 patients with suspected liver cancer admitted to our hospital from February 2020 to February 2021 were retrospectively analyzed, and they were randomly divided into an experimental group and a control group, with 100 cases in each group. The experimental group received a combined detection of MRI with serum AFP-L3 and GP-73, and the control group adopted traditional diagnostic methods (spiral computed tomography and serum AFP). The diagnostic yields of the two groups were compared. Surgical resection was performed after the diagnosis of primary liver cancer, and the correlation between the efficacy and combined detection of MRI with serum AFP-L3 and GP-73 levels was analyzed. Results: The two groups presented comparable general information (P >0.05). The surgical results showed 160 cases of primary liver cancer, including 75 cases in the experimental group and 85 cases in the control group, and 40 cases of benign liver lesions. The diagnostic accuracy of the experimental group (73/75, 95%) was significantly higher than that of the control group (76/85, 86%) (P < 0.05). The serum levels of AFP-L3, GP-73, and AFP in patients with primary liver cancer were remarkably decreased after surgery (P < 0.001). The preoperative and postoperative AFP-L3, GP-73, and AFP levels of patients with primary liver cancer were significantly higher than those of patients with benign liver lesions. The AUC (95% CI) for the combined detection of MRI and serum AFP-L3 and GP-73 levels in patients with surgically confirmed primary liver cancer was 0.747 (0.619-0.874). Conclusion: MRI combined with serum AFP-L3 and GP-73 presents favorable diagnostic efficiency in the diagnosis of primary liver cancer, which is worthy of clinical application.

Effectiveness of Biofeedback Therapy in Patients with Bowel Dysfunction Following Rectal Cancer Surgery: A Systemic Review with Meta-Analysis.

OBJECTIVE: To identify, systematically review and synthesize the evidence on the effectiveness of biofeedback therapy in patients with bowel dysfunction following rectal cancer surgery. DATA SOURCES: Four electronic databases (PubMed 1974-2021; Embase1980-2021; Cochrane databases and the trial registers) were systematically searched by reviewers from inception through March 2021. STUDY SELECTION: Randomized controlled trials (RCTs), cohort studies, and case series studies were included for adults with bowel dysfunction following rectal cancer surgery. All participants received an intervention of biofeedback treatment. Any outcomes that can evaluate the patient's bowel function were the primary research endpoint, while the quality of life was the second endpoint. The disagreements between the two reviewers were resolved after discussion and the third independent reviewer's ruling. As a result, 12 of 185 studies met selection criteria and were included in the review. DATA EXTRACTION: We designed an electronic data extraction form and data were extracted independently. The methodological quality of included studies was assessed using the Cochrane Risk of Bias, the MINORS scale, and the Institute of Health Economics scale. DATA SYNTHESIS: Meta-analyses were conducted for case series only and narrative syntheses were completed. Key findings included significant improvements in bowel function as well as health-related quality of life after biofeedback therapy. (Wexner score: t=7, MD=3.33; 95% CI [2.48, 4.18]) and (Vaizey score: t=3, MD=2.46; 95% CI [1.98, 2.93]). Subgroup analysis of Wexner score: receiving electrical stimulation therapy (t=3, MD=2.36; 95% CI [1.51, 3.22]), not receiving electrical stimulation (t=4, MD=3.79;95% CI[2.66, 4.93]); not receiving adjuvant chemoradiotherapy (t=3, MD=2.42;95% CI[1.61, 3.24]), chemotherapy and radiotherapy (t=1, MD=4.10; 95% CI [2.90, 5.30]), radiotherapy and chemotherapy on parts of patients (t=2, MD=3.46;95% CI [1.41, 5.51]), chemotherapy (t=1, MD=4.81; 95% CI [3.38, 6.24]); performing ISR (t=2, MD=3.32;95% CI [0.37, 6.27]), performing AR (t=4, MD=3.08; 95% CI [2.12, 4.04]), performing PLRAS surgery (t=1, MD=4.10;95% CI[2.90, 5.30]). CONCLUSION: Although biofeedback therapy may improve intestinal function and quality of life as well as anal function reflected by ARM after surgery, patient satisfaction is still unclear. Due to the scarcity of data, good-quality research is required to delve deeper. CLINICAL TRIAL REGISTRATION NUMBER: CRD42020192658.

Cross-Modal Object Detection Based on a Knowledge Update.

As an important field of computer vision, object detection has been studied extensively in recent years. However, existing object detection methods merely utilize the visual information of the image and fail to mine the high-level semantic information of the object, which leads to great limitations. To take full advantage of multi-source information, a knowledge update-based multimodal object recognition model is proposed in this paper. Specifically, our method initially uses Faster R-CNN to regionalize the image, then applies a transformer-based multimodal encoder to encode visual region features (region-based image features) and textual features (semantic relationships between words) corresponding to pictures. After that, a graph convolutional network (GCN) inference module is introduced to establish a relational network in which the points denote visual and textual region features, and the edges represent their relationships. In addition, based on an external knowledge base, our method further enhances the region-based relationship expression capability through a knowledge update module. In summary, the proposed algorithm not only learns the accurate relationship between objects in different regions of the image, but also benefits from the knowledge update through an external relational database. Experimental results verify the effectiveness of the proposed knowledge update module and the independent reasoning ability of our model.

Influence of Pleistocene climate fluctuations on the demographic history and distribution of the critically endangered Chinese pangolin (Manis pentadactyla).

BACKGROUND: Pleistocene climate fluctuations have strongly modified species genetic diversity and distributions. The Chinese pangolin (Manis pentadactyla) has been recognized as a critically endangered animal due to heavy poaching and trafficking. However, the effect of Pleistocene climate fluctuations on the genetic diversity and spatial distribution of the Chinese pangolin remains largely unknown. Here, we combined whole genome sequencing data, analysis of complete mitochondrial genomes, and a large amount of occurrence data from field surveys to infer the ancestral demographic history and predict the past spatial dynamics of the Chinese pangolin in Guangdong Province, China. RESULTS: Our results indicated that there were two subpopulations, which showed similar trends of population size change in response to past climatic changes. We estimated a peak effective population size (Ne) during the last interglacial (LIG), followed by a marked decrease (~ 0.5 to fivefold change) until the last glacial maximum (LGM) and a rebound to a small peak population size during the Mid-Holocene (MH). The estimated time of the separation event between two subpopulations was approximately 3,000-2,500 years ago (ka). We estimated that the distribution of suitable areas shrank by 14.4% from the LIG to LGM, followed by an expansion of 31.4% from the LGM to MH and has been stable since then. In addition, we identified an elevational shift and suitable area decreased significantly during the LGM, but that the geographic extent of suitable areas in the western region increased from the LIG to present. The eastern region of Guangdong Province had the highest habitat suitability across all the climate scenarios. CONCLUSIONS: Our results suggested that Pleistocene climate fluctuations played an important role in shaping patterns of genetic diversity and spatial distribution, and that human stressors likely contributed to the recent divergence of two Chinese pangolin subpopulations sampled here. We argue that a key protected area should be established in the eastern region of Guangdong Province. As such, this study provides a more thorough understanding of the impacts of Pleistocene climate fluctuations impacts on a mammalian species in southern China and suggests more robust management and conservation plans for this Critically Endangered species of special interest.

Structural characterization and regulation of the mechanical properties of the carapace cuticle in tri-spine horseshoe crab (Tachypleus tridentatus).

Horseshoe crab (order Xiphosura) has a large and thick carapace that has evolved as a protective tool to defend against predators and resist impacts from surf-zone turbulence. The naturally occurring spatial variation in the mechanical properties of the carapace cuticle need to be investigated to understand their regulatory mechanism and the underlying design strategies. In this work, we used a combination of high-resolution optical microscopy, scanning electron microscopy, (SEM) and energy-dispersive X-ray spectroscopy (EDS) to evaluate the multiscale microstructure and elemental composition of the cuticle of tri-spine horseshoe crab (Tachypleus tridentatus). The moduli, ultimate strengths, and failure strains of the three individual layers and the entire cuticle were systematically characterized in both the dry and hydrated states. The failure behaviors and energy absorption of the cuticle involved stress stiffening, toughness mechanism and environmental adaptation were analyzed qualitatively and quantitatively and then correlated with the morphological features in different cuticle regions. The mechanical properties are primarily influenced by the endocuticle thickness ratio; a higher thickness ratio corresponds to more stacking of the vertical lamellae, leading to a lower modulus, weaker strength, and greater elongation of the endocuticle. Radial energy is absorbed primarily by the endocuticle, with the energy absorbed in the radial direction being nearly twice that absorbed in the circumferential direction. This is attributed to the larger failure strain and relatively small decrease in the stress plateau in the radial direction. The findings provide a deeper understanding of how nature modulates the cuticle's mechanical properties and inspiration for developing high-performance synthetic composites.