Skeletal Structures Research Articles

Geometric and Mechanical Properties of Ti6Al4V Skeletal Gyroid Structures Produced by Laser Powder Bed Fusion for Biomedical Implants

Skeletal gyroid structures possess promising applications in biomedical implants, owing to their smooth and continuously curved surfaces, open porosity, and customisable mechanical properties. This study simulated the geometric properties of Ti6Al4V skeletal gyroid structures, with relative densities ranging from 1.83% to 98.17%. The deformation behaviour of these structures was investigated through a combination of uniaxial compression tests and simulations, within a relative density range of 13.33% to 50% (simulation) and 15.19% to 41.69% (experimental tests). The results established explicit analytical correlations of pore size and strut diameter with the definition parameters of the structures, enabling precise control of these dimensions. Moreover, normalised Young’s modulus (ranging from 1.05% to 20.77% in simulations and 1.65% to 15.53% in tests) and normalised yield stress (ranging from 1.75% to 17.39% in simulations and 2.09% to 13.95% in tests) were found to be power correlated with relative density. These correlations facilitate the design of gyroid structures with low stiffness to mitigate the stress-shielding effect. The presence of macroscopic 45° fractures in the gyroid structures confirmed that the primary failure mechanism is induced by shear loads. The observed progressive failure and plateau region proved the bending-dominant behaviour and highlighted their excellent deformability. Additionally, the anisotropy of gyroid structures was confirmed through variations in stress and strain concentrations, deformation behaviour, and Young’s modulus under different loading directions.

A novel binomial-based fuzzy type-2 approach for topology and size optimization of skeletal structures

The current work introduces a new probability-based fuzzy type-2 decision mechanism to adjust the optimization process during the simultaneous size and topology optimization of the Skeletal structural systems. For the probabilistic part a binomial module is developed that feeds the fuzzy mechanism by forecasting success probability for future topological actions. The proposed fuzzy decision mechanism permanently monitors the optimization process and attends to dynamically tune the balance between size and topology actions. The presented strategy, by reducing the number of ineffective iterations, significantly enhances the efficiency of the optimization process. Since the proposed decision mechanism is designed as an auxiliary separate module it can be integrated with different optimization methods. Accordingly, in this study, it is integrated with four different optimization algorithms and applied to solve distinct size and topology problems. To comprehensively evaluate the effect of the proposed strategy a new performance index is defined and employed. The acquired results demonstrate that the proposed decision mechanism considerably enhances the search performance of the algorithms on handling the structural size and topology optimization problems.

Spongillidae (Porifera, Spongillidae) in the Subarctic of Western Siberia

When studying the zooperiphyton of reservoirs and watercourses in the Subarctic of Western Siberia, freshwater sponges were identified. The research was carried out in areas of the southern tundra and forested tundra belts, which in turn were conditionally divided into three zones: western, central and eastern. In total, the research covered 40 reservoirs and watercourses. Three species of sponges have been found: Spongilla lacustris, Ephydatia muelleri and Ephydatia fluviatilis. The most common species is S. lacustris, E. muelleri being less common, vs E. fluviatilis which occurs only occasionally. The maximum numbers of species and their occurrence were noted in forested tundra water bodies. Linear measurements and a dimensional analysis both of gemmules and elements of the skeleton of the sponges were carried out. A tendency was revealed to a decrease in size of the skeletal structures of the studied biological material in comparison with literature data.

Tuned African Vultures Optimization Algorithm for Optimal Design of Skeletal Structures Employing Multi-Stage Parameter Adjustment

Tuned African Vultures Optimization Algorithm for Optimal Design of Skeletal Structures Employing Multi-Stage Parameter Adjustment

Integrated formic acid and deep eutectic solvent mediated sustainable synthesis of cellulose nanocrystals from Sterculia foetida shells

The present study reports the green synthesis of cellulose nanocrystals from the shells of Sterculia foetida (SFS) cellulose. Three different methods, alkali, acid and organic acid, were screened for the maximum cellulose extraction. A maximum cellulose yield, 30.6 ± 0.84 w/w, was obtained using 90% formic acid at 110 °C in 120 min. The extracted cellulose was characterized and identified by instrumental analyses. SEM analysis showed skeletal rod-like microfibril structures and similar intra-fibrillar widths. CP/MAS 13C NMR and FTIR spectrum revealed the purity of cellulose and the absence of other components like hemicellulose and lignin. XRD study revealed a cellulose crystallinity index of 88.07%. BET analysis showed a good surface area (3.3213 m2/g) and a micro-pore area of 1.871 m2/g. The cellulose nanocrystals were synthesized from the extracted cellulose using deep eutectic solvents (DES), choline chloride and lactic acid (1:2 ratio). The cellulose nanocrystals (CNC) synthesized from DES-based exhibited zeta potential and particle size of −16.7 mV and 576.3 d.nm. DES-synthesized cellulose nanocrystals were spherical-like shapes, as observed from TEM images. The present results exposed that formic acid is an effective and green catalyst for the extraction of cellulose and DES for the sustainable synthesis of CNC.

Standardization of bone morphometry and mineral density assessments in zebrafish and other small laboratory fishes using x-ray radiography and micro-computed tomography.

Zebrafish and other small laboratory fishes are emerging as important animal models for investigating human skeletal development and diseases. In recent years, there has been a notable increase in research publications employing x-ray radiography and micro-computed tomography to analyze the skeletal structures of these animals. However, evaluating bone morphology and mineral density in small laboratory fish poses unique challenges compared to well-established small rodent models. The varied approaches to image acquisition, analysis, and reporting across studies have led to substantial obstacles in interpreting and comparing research findings. This article addresses the urgent need for standardized reporting of parameters and methodologies related to image acquisition and analysis, as well as the adoption of harmonized nomenclature. Furthermore, it offers guidance on anatomical terminology, units of measurement, and the establishment of minimal parameters for reporting, along with comprehensive documentation of methods and algorithms used for acquisition and analysis. We anticipate that adherence to these guidelines will enhance the consistency, reproducibility, and interpretability of reported measurements of bone density and morphometry in small fish models. These advancements are vital for accurately interpreting phenotypes and gene functions, particularly in the context of multi-center studies.

Assessment of variations in upper and lower gonial angle in children with mouth breathing habit

Background: Mouth breathing is one of the most common deleterious oral habits in children. The habitual position of muscles inside and outside the mouth will affect dental development. Mouth breathing influences skeletal growth and thereby affects the cephalometric parameters. The present study aimed to assess if there is any variation in upper and lower gonial angles in children with mouth breathing habit. Methods: The 33 patients in the age group of 8 to 12 years reporting to the Department of Pediatric and Preventive Dentistry with chief complaint of mouth breathing was selected for the study based on inclusion and exclusion criteria. Lateral cephalograms of these children were taken with a digital panoramic system under standard exposure factors, as recommended by the manufacturer. Upper and lower gonial angles were determined on the lateral cephalograms. The values obtained were tabulated and subjected to statistical evaluation. Results: The mean upper and lower gonial angles were seen to increase from the normal in children with mouth breathing habit. However, independent sample t test showed no statistically significant difference in upper and lower gonial angles with a p value of 0.598 in upper gonial angle and 0.714 in lower gonial angle. Contusions: Early detection of the changes in the upper and lower gonial angles can help a pediatric dentist in effectively framing a treatment plan in children with mouth breathing habit, to prevent further deterioration in the dental and skeletal structures and be able to correct the already occurred unfavourable changes in them.

Multifunctionalization of Alkenyl Alcohols via a Sequential Relay Process.

Aryl-substituted aliphatic amines are widely recognized as immensely valuable molecules. Consequently, the development of practical strategies for the construction of these molecules becomes increasingly urgent and critical. Here, we have successfully achieved multifunctionalization reactions of alkenyl alcohols in a sequential relay process, which enables transformation patterns of arylamination, deuterated arylamination, and methylenated arylamination to the easy access of multifarious arylalkylamines. Notably, a novel functionalization mode for carbonyl groups has been developed to facilitate the processes of deuterium incorporation and methylene introduction, thereby providing new means for the diverse transformations of carbonyl groups. This methodology displays a wide tolerance toward functional groups, while also exhibiting good applicability across various skeletal structures of alkenols and amines.

The Success of Miniscrew-Assisted Rapid Palatal Expansion (MARPE) in Adult Orthodontics: A Literature Review

This literature review examines the success and effectiveness of Miniscrew-Assisted Rapid Palatal Expansion (MARPE) in adult orthodontics. Traditional methods like Surgically Assisted Rapid Palatal Expansion (SARPE) have been commonly used for treating transverse maxillary deficiencies in adults, but they come with significant drawbacks, including higher biological and financial costs. MARPE, which utilizes mini screws to apply controlled forces for palatal expansion, offers a less invasive and more precise alternative. The review analyzes several studies and reports on MARPE's success in expanding skeletal and dental structures, improving respiratory function in obstructive sleep apnea (OSA) patients, and minimizing complications like unwanted tooth movement. Despite some challenges, such as asymmetrical expansion, MARPE has demonstrated a high success rate in adult orthodontics and presents a promising treatment option. Further high-quality, long-term studies are recommended to optimize treatment protocols and evaluate potential risks.

Characteristics of surface microlayer film under different freshwater environments: Physical, chemical, and biological properties

The surface microlayer film (SMF) has been observed worldwide in water environments and its environmental behavior plays a vital role in the migration and transformation of water pollutants. However, there has been little description and explanation of their characteristics in freshwater environments. Here, we investigate the characteristics of SMF under different freshwater trophic status. The results demonstrated that under sufficient nutrition, the interior characteristics of the SMF are densely arranged Fe3O4 skeletal structures, and the enrichment concentration of Fe3+ on the SMF reached 4.66 μg/mL, the dominant bacteria is Zoogloea. Under the constraint of nitrogen, the interior characteristics of the SMF is a tightly spherical encapsulated organic matter, the maximum enrichment concentration of Fe3+ on the SMF was only 0.75 μg/mL, Limnobacter and Acidocella are the dominant bacteria in the carbon and nitrogen constraint. Under iron constraint, the interior of the SMF is an entangled organic organism, and the coverage rate of the SMF was only 31.41 %, which decreased by 20.55 % and 8.58 %, compared with carbon and nitrogen constraint respectively, and the main microbial species is Cloacibacterium. These results reveal a strong correlation between water nutrient types and the formation of SMF, and established a connection between water pollution and SMF characteristics, provided a new approach for predicting water types using water surface microlayers, and have important implications for managing freshwater ecosystems.

A Review of Applications, Forms, Extraction, and Dissolution of Chitin

Background: Polymeric organic particles made by organisms or natural biopolymers, are considered as greener materials, more environmentally friendly and durable. Because of its exceptional structural properties, wide abundant, lack of toxicity, biocompatibility, simplicity of alteration and promised potentials, chitin is a sustainable material. It is composed of β(1,4)-linked N-acetyl-glucosamine units and represents the most abundant structural polysaccharide of invertebrates, including such marine phyla as sponges, corals, annelid worms, mollusks, and arthropods. This biopolymer is mostly found in the skeletal structures of invertebrates, and plays a crucial role in their rigidity, stiffness, and other mechanical properties. Chitin is recognized as one of the universal templates in biomineralization, with respect to both biocalcification and biosilicification. Conclusion: This review is concerned with chitin. For a set of uses, chitin with its derivatives are receiving more and more attention. The popularity of this plentiful biopolymer has skyrocketed in recent years. Studies on the use of chitin show that these biopolymers have a lot of potential for managing wounds, getting rid of toxic metals, farming, bone regenerative engineering, etc.

Skeletal magnesium content in Antarctic echinoderms along a latitudinal gradient

Ocean warming and acidification driven by anthropogenic CO2 emissions may impact the mineral composition of marine calcifiers. Species with high skeletal Mg content could be more susceptible in polar regions due to the increased solubility of CO2 at lower temperatures. We aimed to assess the environmental influence on skeletal Mg content of Antarctic echinoderms belonging to Asteroidea, Ophiuroidea, Echinoidea and Holothuroidea classes, along a latitudinal gradient from the South Shetland Islands to Rothera (Adelaide Island). We found that all skeletal structures, except for echinoid spines, exhibited high Mg content, with asteroids showing the highest levels. Our results suggest that asteroids and holothuroids exert a higher biological capacity to regulate Mg incorporation into their skeletons. In contrast, the variability observed in the skeletal Mg content of ophiuroids and echinoids appears to be more influenced by local environmental conditions. Species-specific differences in how environmental factors affect the skeletal Mg content can be thus expected as a response to global climate change.

Tubular Aggregates as a Marker of Aging in Skeletal Muscle.

Tubular aggregates (TA) are skeletal muscle structures that arise from the progressive accumulation of sarcoplasmic reticulum proteins, mainly with aging. Muscle regeneration plays a role in TA formation. TA quantification may aid in the evaluation of muscle aging and genetic muscle degeneration. TA form over time, appears in aging in normal murine muscles. TA reduction in injured conditions may be due to the degeneration-regeneration process in muscles, with loss of damaged muscle fibers and formation of new fibers that do not present protein aggregation. These new regenerated fibers do not improve the function capacity of the aged muscle. Here, we present a methodology for labeling and identifying tubular aggregates in muscle fibers and also the standardization of its quantification.

Quantifying attributes of boring bivalve populations in corals using micro-computed tomography

Bioerosion plays a crucial factor in shaping the structure and function of coral reef ecosystems, with bioeroders actively altering both the physical and ecological dynamics of coral substrates. Despite their importance, studying internal bioeroders in corals presents significant challenges owing to their cryptic nature within the skeletal structures. Additionally, invasive methods are often required to reveal the subtle and microscopic bioerosive alterations they induce in calcium carbonate substrates. Here, we demonstrate the effectiveness of high-resolution micro-computed tomography (μCT) in quantifying the abundance, size, distribution, and growth directions of coral bioeroders such as cryptic calcareous bivalves in the northern Red Sea. We scanned three coral species inhabited by bioeroders, followed by the utilization of three-dimensional image analysis software to identify, count, and measure each bivalve within the coral skeleton, along with quantifying boring cavity volumes. We revealed that μCT captures small boring cavities (< 1mm), providing more accurate abundance estimates of live and dead boring bivalves than the skeleton decalcification technique, with the added benefits of being rapid and non-destructive in contrast to traditional methods. Furthermore, measurements of empty cavity volumes enabled the estimations of the contribution of bioeroders to the overall coral skeletal porosity. Overall, our study highlights μCT as a practical and effective tool for studying cryptic coral bioeroders, providing novel ecological insights into bioeroder population ecology and coral-bioeroder interactions.

Anatomical description of a pygmy sperm whale, Kogia breviceps (Cetacea: Kogiidae), pre-term calf using CT scan and 3D reconstructions.

Little is known about the biology of pygmy sperm whales, Kogia breviceps (De Blainville, 1838), being that most anatomical descriptions for the species derive from necropsy after stranding or from osteological material preserved in museums. This species is rarely seen despite its wide distribution, and its reproductive behaviour is still being investigated. The eventual occurrence of pregnant female strandings and the collection and description of foetuses can give clues about the organisms' mostly unknown early development. However, this type of biological material is extremely rare, limiting anatomical analysis due to the risk of damage or loss. Here, we describe the external and internal anatomy of an 84 cm long K. breviceps foetus. The methods utilised were non-intrusive, meaning that no incisions were made on the specimen. The foetus was analysed using computed tomography images and a three-dimensional reconstruction of the skeleton. A great number of features were observed, such as axial and appendicular skeletal structures, internal organs, echolocation apparatus and umbilical cord, as well as diagnostic characters of the species, such as the asymmetrical skull, spermaceti chamber and false gill pigmentation. We suggest that more specimens on different stages of development should be analysed by the same technique, as well as further comparison with specimens from other taxa, in order to facilitate more comparative studies on embryonic and foetal development of cetaceans.

Atomic-scale bonding strength and failure mechanisms of HfC/Ni/Ni3Al interfaces on low-index crystal planes: A combined HRTEM and first-principles study

The carbide/matrix interface in superalloys is susceptible to cracking under mechanical stress, yet the failure mechanisms require further investigation. The cohesive strength and stability of 32 interface models, including HfC(001)/Ni(001), HfC(011)/Ni(001), HfC(111)/Ni(001), HfC(001)/Ni3Al(011), and HfC(111)/Ni3Al(111) within the DZ125 superalloys, were investigated using first-principles calculations and experimental methods. The results indicate that the majority of interfaces demonstrate negative adhesion work (Wad), indicating instability. However, Bridge4 model in HfC(001)/Ni3Al(011) show higher Wad and lower interface energy, suggesting improved stability. The interfacial cohesion is attributable to strong Ni-C covalent bonds. But interfacial fracture toughness results reveal that the majority of models are more susceptible to fracture at the interface. Fracture morphology analysis from tensile tests at room temperature and endurance tests at 760 °C/725 MPa confirms that cracks primarily initiate at the carbide/matrix interface. This study suggests that introducing Ta atoms could improve interface strength, as Ta-rich carbides reduce interfacial energy while increasing elastic energy, resulting in the formation of skeletal structures. The relationship between Hf-rich and Ta-rich carbides and their respective morphology was investigated. The findings provide insights into the failure mechanisms of carbide/matrix interface and offer theoretical guidance for enhancing interface strength in superalloy applications.

Accelerating segmentation of fossil CT scans through Deep Learning

Recent developments in Deep Learning have opened the possibility for automated segmentation of large and highly detailed CT scan datasets of fossil material. However, previous methodologies have required large amounts of training data to reliably extract complex skeletal structures. Here we present a method for automated Deep Learning segmentation to obtain high-fidelity 3D models of fossils digitally extracted from the surrounding rock, training the model with less than 1%-2% of the total CT dataset. This workflow has the capacity to revolutionise the use of Deep Learning to significantly reduce the processing time of such data and boost the availability of segmented CT-scanned fossil material for future research outputs. Our final Unet segmentation model achieved a validation Dice similarity of 0.96.

Exploring the Influence of Neomorphic Gekkotan Paraphalanges on Limb Modularity and Integration.

Digital specializations of geckos are widely associated with their climbing abilities. A recurring feature that has independently emerged within the sister families Gekkonidae and Phyllodactylidae is the presence of neomorphic paraphalanges (PPEs), usually paired, paraxial skeletal structures lying adjacent to interphalangeal and metapodial-phalangeal joints. The incorporation of PPEs into gekkotan autopodia has the potential to modify the modularity and integration of the ancestral limb pattern by affecting information flow among skeletal limb parts. Here we explore the influence of PPEs on limb organization using anatomical networks. We modeled the fore- and hindlimbs in species ancestrally devoid of PPEs (Iguana iguana and Gekko gecko) and paraphalanx-bearing species (Hemidactylus mabouia and Uroplatus fimbriatus). To further clarify the impact of PPEs we also expunged PPEs from paraphalanx-bearing network models. We found that PPEs significantly increase modularity, giving rise to tightly integrated sub-modules along the digits, suggesting functional specialization. Species-specific singularities also emerged, such as the trade-off between the presence of PPEs favoring modularity (along the proximodistal axis) and the interdigital webbing favoring integration (across the lateromedial axis) in the limbs of U. fimbriatus. The PPEs are characterized by low connectivity compared with other skeletal elements; nevertheless, this varies based on their specific location and seemingly reflects developmental constraints. Our results also highlight the importance of the fifth metatarsal in generating a shift in lepidosaurian hindlimb polarity that contrasts with the more symmetrical bauplan of tetrapods. Our findings support extensive modification of the autopodial system in association with the addition of the neomorphic and intriguing PPEs.

Improved semantic-guided network for skeleton-based action recognition

A fundamental issue in skeleton-based action recognition is the extraction of useful features from skeleton joints. Unfortunately, the current state-of-the-art models for this task have a tendency to be overly complex and parameterized, which results in low model training and inference time efficiency for large-scale datasets. In this work, we develop a simple but yet an efficient baseline for skeleton-based Human Action Recognition (HAR). The architecture is based on adaptive GCNs (Graph Convolutional Networks) to capture the complex interconnections within skeletal structures automatically without the need of a predefined topology. The GCNs are followed and empowered with an attention mechanism to learn more informative representations. This paper reports interesting accuracy on a large-scale dataset NTU-RGB+D 60, 89.7% and 95.0% on respectively Cross-Subject, and Cross-View benchmarks. On NTU-RGB+D 120, 84.6% and 85.8% over Cross-Subject and Cross-Setup settings, respectively. This work provides an improvement of the existing model SGN (Semantic-Guided Neural Networks) when extracting more discriminant spatial and temporal features.

The metalloproteinase PAPP-A is required for IGF-dependent chondrocyte differentiation and organization

Insulin-like growth factor (IGF) signaling is required for proper growth and skeletal development in vertebrates. Consequently, its dysregulation may lead to abnormalities of growth or skeletal structures. IGF is involved in the regulation of cell proliferation and differentiation of chondrocytes. However, the availability of bioactive IGF may be controlled by antagonizing IGF binding proteins (IGFBPs) in the circulation and tissues. As the metalloproteinase PAPP-A specifically cleaves members of the IGFBP family, we hypothesized that PAPP-A activity liberates bioactive IGF in cartilage. In PAPP-A knockout mice, the femur length was reduced and the mice showed a disorganized columnar organization of growth plate chondrocytes. Similarly, zebrafish lacking pappaa showed reduced length of Meckel’s cartilage and disorganized chondrocytes, reminiscent of the mouse knockout phenotype. Expression of chondrocyte differentiation markers (sox9a, ihha, and col10a1) was markedly affected in Meckel’s cartilage of pappaa knockout zebrafish, indicating that differentiation of chondrocytes was compromised. Additionally, the zebrafish pappaa knockout phenotype was mimicked by pharmacological inhibition of IGF signaling, and it could be rescued by treatment with exogenous recombinant IGF-I. In conclusion, our data suggests that IGF activity in the growing cartilage, and hence IGF signaling in chondrocytes, requires the presence of PAPP-A. The absence of PAPP-A causes aberrant chondrocyte organization and compromised growth in both mice and zebrafish.