Complex Hierarchical Structure Research Articles

CRITERIA-BASED MODELING OF SHIPBOARD AVIATION SYSTEMS OPTIMIZATION PROCESS AT THE CREATION OF AIRCRAFT CARRIER

Criteria-based modeling is one of the new directions in the development of methods problems solving at optimization, evaluation and control of large systems with complex hierarchical structures, with a large number of distributed tasks, functions and processes, without using of iterative methods of sequential search for extremum. A criterion (probabilistic) model is constructed for each borderline shipboard aviation system, the adequacy of which is determined not so much by the degree of its correspondence to the real system, as by the goals of the operational functioning of an Aircraft Carrier. The construction of criteria models is carried out by the decomposition and structuring of the criteria space for the operational functioning of an Aircraft Carrier, up to the level of qualities and properties of shipboard aviation systems. The depth of structuring, that is, the number of hierarchical levels in the “cross-cutting” structural model, is determined for each priority of the objective function (functional optimality criterion), which make up the criteria space for optimization and evaluation of shipboard aviation systems during the operational functioning of an Aircraft Carrier at the sea crossing, during combat deployment, in defensive and offensive naval operations. “Cross-cutting” criterion process of optimization is established the conditions for observing the identity of the results of research and testing on the evaluation of parameters and characteristics of shipboard aviation systems, is established the requirements to the shipboard aviation systems and is formatted the Decision-Making Support System for the creation of the effective aircraft carrier with sequent evaluation of the requirements fulfillment on the all stages of the Aircraft Carriers Life Cycle.

Influence of experimental constraints on micromechanical assessment of micromachined hard-tissue samples

Continuing technological advancement of mechanical characterization at the microscale has enabled the isolation of micron-sized specimens and their direct mechanical characterization. Such techniques, initially developed for engineering materials and MEMS, can also be applied on hard biological materials. Bone is a material with a complex hierarchical structure ranging from the macro- all the way down to the nanoscale. To fully understand bone tissue mechanics, knowledge of the mechanics of all structural elements i.e. at every length scale is necessary. Particularly, the mechanical properties of microstructural elements, such as bone lamellae are still largely unknown. In the last decade, testing protocols have been devised to close this gap including bending and compression of micrometer-sized bone specimens. However, the precision and accuracy of results obtained have not been discussed. In this study, we aim to do exactly this: we validate microbeam bending by testing silicon microbeams with known mechanical constants, and evaluate the precision and sources of errors in both microbeam bending and micropillar compression by means of finite element (FE) modeling. Bending of Si-microbeams reproduced the expected value for the bending modulus within 17% accuracy, although the effect of geometrical uncertainties was estimated to result in relative errors of up to 50%. The deformation of constraining bulk material had a smaller influence, with relative errors of 11%, for microbeam bending and 25% for micropillar compression. For the latter this error could be sufficiently eliminated by the Sneddon correction. The tapering of micropillars had a negligible effect on overall apparent stiffness, but induced inhomogeneous stress state within micropillars may lead to superposed structural deformation mechanisms and be responsible for failure patterns observed in past studies.

Of forming loads on the mounting of shaft shafts in the hierarchic block environment under the influence of modern geodynamic movements

The subject of the research is the lining of mine shafts and surrounding rock mass. The subject matter is the features of the stress-strain behavior of lining and adjacent rock mass in shafts and near-shaft underground openings in the Tenth Anniversary of Independence of Kazakhstan mine located in the tectonically high-stress and low-strength rock mass. The loading of the lining in the shafts and near-shaft openings in the Tenth Anniversary of Independence of Kazakhstan mine during construction is investigated, and the damages of the lining in the course of drivage in the nonuniform stress field are analyzed. The long-term periodic in-situ instrumental monitoring of stress variation in the lining of the mine shafts and near-shaft openings revealed the main influences on the process of load formation on the lining in the conditions of post-limiting deformation of surrounding rock mass. It is validated that the surrounding rock mass of the mine has a complex hierarchical block structure and is subjected to modern geodynamic movements. As the depth of mining is increased, surrounding rock mass of the mine shafts transfers to the condition of postlimiting stresses and strains. As a consequence, the lining of the shafts and near-shaft openings at different stages of construction experiences nonuniform concentrated loads, which violates integrity of the lining.

The landscape of coadaptation in Vibrio parahaemolyticus.

Investigating fitness interactions in natural populations remains a considerable challenge. We take advantage of the unique population structure of Vibrio parahaemolyticus, a bacterial pathogen of humans and shrimp, to perform a genome-wide screen for coadapted genetic elements. We identified 90 interaction groups (IGs) involving 1,560 coding genes. 82 IGs are between accessory genes, many of which have functions related to carbohydrate transport and metabolism. Only 8 involve both core and accessory genomes. The largest includes 1,540 SNPs in 82 genes and 338 accessory genome elements, many involved in lateral flagella and cell wall biogenesis. The interactions have a complex hierarchical structure encoding at least four distinct ecological strategies. One strategy involves a divergent profile in multiple genome regions, while the others involve fewer genes and are more plastic. Our results imply that most genetic alliances are ephemeral but that increasingly complex strategies can evolve and eventually cause speciation.

Regulation of differentiation of annulus fibrosus-derived stem cells using heterogeneous electrospun fibrous scaffolds.

BackgroundTissue engineering of the annulus fibrosus (AF) shows promise as a treatment for patients with degenerative disc disease (DDD). However, it remains challenging due to the intrinsic heterogeneity of AF tissue. Fabrication of scaffolds recapitulating the specific cellular, componential, and microstructural features of AF, therefore, is critical to successful AF tissue regeneration.MethodsPoly-L-lactic acid (PLLA) fibrous scaffolds with various fiber diameters and orientation were prepared to mimic the microstructural characteristics of AF tissue using electrospinning technique. AF-derived stem cells (AFSCs) were cultured on the PLLA fibrous scaffolds for 7 days.ResultsThe morphology of AFSCs significantly varied when cultured on the scaffolds with various fiber diameters and orientation. AFSCs were nearly round on scaffolds with small fibers. However, they became spindle-shaped on scaffolds with large fibers. Meanwhile, upregulated expression of collagen-I gene happened in cells cultured on scaffolds with large fibers, while enhanced expression of collagen-II and aggrecan genes was seen on scaffolds with small fibers. The production of related proteins also showed similar trends. Further, culturing AFSCs on a heterogeneous scaffold by overlaying membranes with different fiber sizes led to the formation of a hierarchical structure approximating native AF tissue.ConclusionFindings from this study demonstrate that fibrous scaffolds with different fiber sizes effectively promoted the differentiation of AFSCs into specific cells similar to the types of cells at various AF zones. It also provides a valuable reference for regulation of cell differentiation and fabrication of engineered tissues with complex hierarchical structures using the physical cues of scaffolds.The translational potential of this articleEffective AF repair is an essential need for treating degenerative disc disease. Tissue engineering is a promising approach to achieving tissue regeneration and restoring normal functions of tissues. By mimicking the key structural features of native AF tissue, including fiber size and alignment, this study deciphered the effect of scaffold materials on the cell differentiation and extracellular matrix deposition, which provides a solid basis for designing new strategies toward more effective AF repair and regeneration.

Graphostructural modeling of discrete-argument systems

Graphostructural modeling is an effective tool for the analysis and control of social and economics systems. Graphs, hypergraphs and metagraphs are used to simulate complex hierarchical structures. In this paper we consider metagraphs and their matrices associated with 2D and 3D systems and cellular automatons; and their relationship with the transition from basic to associated models of cellular automatons. The transition to an associated model is a key step in developing the theory of discrete argument systems. In this paper with the simple examples of discrete-argument systems we demonstrate that matrix characteristics of the models, associated with such systems, are closely related to the matrix characteristics of associated metagraphs.

Underwater persistent bubble-assisted femtosecond laser ablation for hierarchical micro/nanostructuring

In this study, we demonstrate a technique termed underwater persistent bubble assisted femtosecond laser ablation in liquids (UPB-fs-LAL) that can greatly expand the boundaries of surface micro/nanostructuring through laser ablation because of its capability to create concentric circular macrostructures with millimeter-scale tails on silicon substrates. Long-tailed macrostructures are composed of layered fan-shaped (central angles of 45°–141°) hierarchical micro/nanostructures, which are produced by fan-shaped beams refracted at the mobile bubble interface (≥50° light tilt, referred to as the vertical incident direction) during UPB-fs-LAL line-by-line scanning. Marangoni flow generated during UPB-fs-LAL induces bubble movements. Fast scanning (e.g. 1 mm s−1) allows a long bubble movement (as long as 2 mm), while slow scanning (e.g. 0.1 mm s−1) prevents bubble movements. When persistent bubbles grow considerably (e.g. hundreds of microns in diameter) due to incubation effects, they become sticky and can cause both gas-phase and liquid-phase laser ablation in the central and peripheral regions of the persistent bubbles. This generates low/high/ultrahigh spatial frequency laser-induced periodic surface structures (LSFLs/HSFLs/UHSFLs) with periods of 550–900, 100–200, 40–100 nm, which produce complex hierarchical surface structures. A period of 40 nm, less than 1/25th of the laser wavelength (1030 nm), is the finest laser-induced periodic surface structures (LIPSS) ever created on silicon. The NIR-MIR reflectance/transmittance of fan-shaped hierarchical structures obtained by UPB-fs-LAL at a small line interval (5 μm versus 10 μm) is extremely low, due to both their extremely high light trapping capacity and absorbance characteristics, which are results of the structures’ additional layers and much finer HSFLs. In the absence of persistent bubbles, only grooves covered with HSFLs with periods larger than 100 nm are produced, illustrating the unique attenuation abilities of laser properties (e.g. repetition rate, energy, incident angle, etc) by persistent bubbles with different curvatures. This research represents a straightforward and cost-effective approach to diversifying the achievable hierarchical micro/nanostructures for a multitude of applications.

Hierarchically-structured metalloprotein composite coatings biofabricated from co-existing condensed liquid phases

Complex hierarchical structure governs emergent properties in biopolymeric materials; yet, the material processing involved remains poorly understood. Here, we investigated the multi-scale structure and composition of the mussel byssus cuticle before, during and after formation to gain insight into the processing of this hard, yet extensible metal cross-linked protein composite. Our findings reveal that the granular substructure crucial to the cuticle’s function as a wear-resistant coating of an extensible polymer fiber is pre-organized in condensed liquid phase secretory vesicles. These are phase-separated into DOPA-rich proto-granules enveloped in a sulfur-rich proto-matrix which fuses during secretion, forming the sub-structure of the cuticle. Metal ions are added subsequently in a site-specific way, with iron contained in the sulfur-rich matrix and vanadium coordinated by DOPA-catechol in the granule. We posit that this hierarchical structure self-organizes via phase separation of specific amphiphilic proteins within secretory vesicles, resulting in a meso-scale structuring that governs cuticle function.

Structural and mechanical evolution of Tridacna gigas during permineralization

Mollusk shells have highly complex hierarchical structures and unique mechanical properties, which have been widely studied, especially in fresh shells. However, few studies have revealed differences in the structure-property correlations of shells during the permineralization process, which occurs after organism death. To better understand the effect of permineralization on the microstructure and mechanical properties of shells, this study investigated and compared the compositions, microstructures, and mechanical properties of Tridacna gigas and permineralized J-Tridacna gigas. The results showed that permineralized J-Tridacna gigas possessed coarsened aragonite minerals, less anisotropy and organic matter, and higher hardness and strength than Tridacna gigas. The toughening mechanisms of Tridacna gigas, including crack deflection, aragonite platelet pull-out, and mineral bridges, were discovered during Vickers hardness tests. Moreover, the permineralization mechanism comprised three main steps: organic matter dissolution, aragonite plate compaction, and recrystallization. This work further elaborates the permineralization mechanism, which can help increase the crystal size and improve the strength and hardness of materials. Moreover, this study provides valuable insights into the design of bioinspired advanced materials with outstanding hardness and strength.

A Material Perspective of Wood, Smoke, and BBQ

For those of us who have attempted to barbecue (BBQ), wood matters. Smoking delicious meats is effectively a chemical process that involves control over combustion of organic materials. Here, we get joint insight from a local pitmaster and a materials scientist.

Polyoxometalate-Based Metal-Organic Framework Fractal Crystals

Summary Assembling complex hierarchical structures facilely to improve the accessibility of catalytic sites inside bulk catalysts has long been desired but remains challenging. Herein, we fabricate the hierarchical polyoxometalate-based metal-organic framework (POM@MOF) cuboctahedrons by solvent-assisted assembly, and propose a fractal growth mechanism. The great disparity in polarity of the dual solvents used endows them a different strength interaction with the POM. As a result, the polar enriched areas induced by the hydrophilic POM cause diffusion-limited aggregation along with the fractal growth. The obtained POM@MOF fractal crystallites possess an ordered layered surface and mesopores developed from the fractal growth and microscopic separation of the system. The cuboctahedron morphology is directed by the anisotropy of the Keggin units. This is of great significance in constructing hierarchical structures via fractal growth caused by diffusion limit by choosing some solvents with proper polarity disparity, which can be extended to other systems.

Biofabrication of neural microphysiological systems using magnetic spheroid bioprinting

The high attrition rate of neuro-pharmaceuticals as they proceed to market necessitates the development of clinically-relevant in vitro neural microphysiological systems that can be utilized during the preclinical screening phase to assess the safety and efficacy of potential compounds. Historically, proposed models have adhered to two distinct approaches; those that are biologically relevant (e.g.—organoids, spheroids) or those that provide engineering control (e.g.—bioprinting, microfluidics). Separately, these approaches fail to fully recapitulate the complex hierarchical structure of the nervous system, limiting their clinical applications. Furthermore, the reliance on manual implementation present in many models fails to effectively scale up or satisfy the consistency standards required for widespread industry adoption. This work serves as a proof-of-concept for merging the two approaches to create a neural microphysiological system that overcomes their individual limitations. Spinal cord spheroids, fabricated using magnetic nanoparticles, are positioned in a three-dimensional hydrogel construct using magnetic bioprinting. Resulting constructs demonstrate both localized cell–cell interactions and long-distance projections that mimic in vivo structure. The use of magnetic nanoparticles for spheroid formation provides batch-to-batch consistency in size and shape and reduces the reliance on trained experimenters for accurate placing for culture. Taken together, this combination approach provides the first steps towards developing a simple approach for integrating spheroid, hydrogel culture, and bioprinting as an alternative to more specialized and expensive processes.

Assessment of Elastic-Plastic Fracture Behavior of Cortical Bone Using a Small Punch Testing Technique.

The fracture properties of cortical bone are directly coupled to its complex hierarchical structure. The limited availability of bone material from many anatomic locations creates challenges for assessing the effect of bone heterogeneity and anisotropy on fracture properties. The small punch technique was employed to examine the fracture behavior of cortical bone in terms of area under the curve values obtained from load-load point displacement behavior. Fracture toughness of cortical bone was also determined in terms of J-toughness values obtained using a compact tension (CT) test. Area under the curve values obtained from the small punch test were correlated with the J-toughness values of cortical bone. The effects of bone density and compositional parameters on area under the curve and Jtoughness values were also analyzed using linear and multiple regression analysis. Area under the curve and J-toughness values are strongly and positively correlated. Bone density and %mineral content are positively correlated with both area under the curve and J-toughness values. The multiple regression analysis outcomes support these results. Overall, the findings support the hypothesis that area under the curve values obtained from small punch tests can be used to assess the fracture behavior of cortical bone.

Emergent Self-Assembly Pathways to Multidimensional Hierarchical Assemblies using a Hetero-Seeding Approach.

The controlled formation of complex and functional 1-, 2-, and 3D hierarchical assemblies from molecular building blocks represents a key current challenge. Herein, we report the use of a seeded growth approach for a series of perylenediimide-based molecules (PDIs 1-4) to access otherwise inaccessible self-assembly pathways that yield complex hierarchical structures. The key to the new approach is to use hetero-seeds which possess a different composition and morphology from that of the molecular building block. For example, a nanotube seed (from PDI 3) and a microribbon seed (from PDI 4) were found to initiate different self-assembly pathways for PDI 1, which normally assembles to yield nanocoils. This led to the formation of unprecedented 3D scroll-like and scarf-like hierarchical nanostructures, respectively. Also, the hetero-seeds from PDI 3 initiate hidden self-assembly pathways of PDI 2 to generate 1D tubular heterojunctions. Significantly, this new strategy offers new opportunities to create emergent and functional hierarchical and complex structures from small molecule precursors.

Deep Learning on Point Clouds and Its Application: A Survey.

Point cloud is a widely used 3D data form, which can be produced by depth sensors, such as Light Detection and Ranging (LIDAR) and RGB-D cameras. Being unordered and irregular, many researchers focused on the feature engineering of the point cloud. Being able to learn complex hierarchical structures, deep learning has achieved great success with images from cameras. Recently, many researchers have adapted it into the applications of the point cloud. In this paper, the recent existing point cloud feature learning methods are classified as point-based and tree-based. The former directly takes the raw point cloud as the input for deep learning. The latter first employs a k-dimensional tree (Kd-tree) structure to represent the point cloud with a regular representation and then feeds these representations into deep learning models. Their advantages and disadvantages are analyzed. The applications related to point cloud feature learning, including 3D object classification, semantic segmentation, and 3D object detection, are introduced, and the datasets and evaluation metrics are also collected. Finally, the future research trend is predicted.

Multiple-Membership Survival Analysis and Its Applications in Organizational Behavior and Management Research

Multilevel paradigms have permeated organizational research in recent years, greatly advancing our understanding of organizational behavior and management decisions. Despite the advancements made in multilevel modeling, taking into account complex hierarchical structures in data remains challenging. This is particularly the case for models used for predicting the occurrence and timing of events and decisions—often referred to as survival models. In this study, the authors construct a multilevel survival model that takes into account subjects being nested in multiple environments—known as a multiple-membership structure. Through this article, the authors provide a step-by-step guide to building a multiple-membership survival model, illustrating each step with an application on a real-life, large-scale, archival data set. Easy-to-use R code is provided for each model-building step. The article concludes with an illustration of potential applications of the model to answer alternative research questions in the organizational behavior and management fields.

Regulation of proteoglycan production by varying glucose concentrations controls fiber formation in tissue engineered menisci

Fibrillar collagens are highly prevalent in the extracellular matrix of all connective tissues and therefore commonly used as a biomaterial in tissue engineering applications. In the native environment, collagen fibers are arranged in a complex hierarchical structure that is often difficult to recreate in a tissue engineered construct. Small leucine rich proteoglycans as well as hyaluronan binding proteoglycans, aggrecan and versican, have been implicated in regulating fiber formation. In this study, we modified proteoglycan production in vitro by altering culture medium glucose concentrations (4500, 1000, 500, 250, and 125 mg/L), and evaluated its effect on the formation of collagen fibers inside tissue engineered meniscal constructs. Reduction of extracellular glucose resulted in a dose dependent decrease in total sulfated glycosaminoglycan (GAG) production, but minimal decreases of decorin and biglycan. However, fibromodulin doubled in production between 125 and 4500 mg/L glucose concentration. A peak in fiber formation was observed at 500 mg/L glucose concentration and corresponded with reductions in total GAG production. Fiber formation reduction at 125 and 250 mg/L glucose concentrations are likely due to changes in metabolic activity associated with a limited supply of glucose. These results point to proteoglycan production as a means to manipulate fiber architecture in tissue engineered constructs. Statement of significanceFibrillar collagens are highly prevalent in the extracellular matrix of all connective tissues; however achieving appropriate assembly and organization of collagen fibers in engineered connective tissues is a persistent challenge. Proteoglycans have been implicated in regulating collagen fiber organization both in vivo and in vitro, however little is known about methods to control proteoglycan production and the subsequent fiber organization in tissue engineered menisci. Here, we show that media glucose content can be optimized to control proteoglycan production and collagen fiber assembly, with optimal collagen fiber assembly occurring at sub-physiologic levels of glucose.

Reviewing recently developed technologies to direct cell activity through the control of pore size: From the macro- to the nanoscale.

Scaffold pore size plays a fundamental role in the regeneration of new tissue since it has been shown to direct cell activity in situ. It is well known that cellular response changes in relation with pores diameter. Consequently, researchers developed efficient approaches to realize scaffolds with controllable macro-, micro-, and nanoporous architecture. In this context, new strategies aiming at the manufacturing of scaffolds with multiscale pore networks have emerged, in the attempt to mimic the complex hierarchical structures found in living systems. In this review, we aim at providing an overview of the fabrication methods currently adopted to realize scaffolds with controlled, multisized pores highlighting their specific influence on cellular activity.

Conical micro-structures as a route for achieving super-repellency in surfaces with intrinsic hydrophobic properties

Hydrophobic surfaces like Lotus leaves show amazing self-cleaning properties with the apparent water contact angle above 150° and contact angle hysteresis below 10°. Thus, at low inclination angles, millimeter drops can roll-off easily. This effect can be a consequence of the air trapped below the drop, which allows the droplet to reach a superhydrophobic Cassie-Baxter state. However, the superhydrophobic state can be accompanied by very different adhesive properties due to the pinning of the droplet to the microstructures, implying that even in a hydrophobic or superhydrophobic state, the droplet might not roll-off easily. A superhydrophobic state with minimum adhesion to the surface has been the pursuit in many applications where a super-repellent state is highly desired. Many microstructures have been shown to be able to reach a superhydrophobic state, but only a few have been shown to be capable of achieving a super-repellent state without the help of more complex hierarchical structures. Here, we show that conical structures provide a template for designing super-repellent surfaces where the wetting characteristics look to be invariant in the microscale range. The conical structures can maintain a super-repellent state for all intrinsic contact angles larger than 90°, and the transition from the Cassie-Baxter to the Wenzel state is controlled by the apex angle of the conical structures. This finding advances the understanding of why conical structures can show a superhydrophobic state, which will be beneficial for the design of super-repellent surfaces with a wider intrinsic contact angle range.

3D analysis of the osteonal and interstitial tissue in human radii cortical bone.

Human cortical bone has a complex hierarchical structure that is periodically remodelled throughout a lifetime. This microstructure dictates the mechanical response of the tissue under a critical load. If only some structural features, such as the different porosities observed in bone, are primarily studied, then investigations may not fully consider the osteonal systems in three-dimensions (3D). Currently, it is difficult to differentiate osteons from interstitial tissue using standard 3D characterization methods. Synchrotron radiation micro-computed tomography (SR-μCT) in the phase contrast mode is a promising method for the investigation of osteons. In the current study, SR-μCT imaging was performed on cortical bone samples harvested from eight human radii (female, 50-91 y.o.). The images were segmented to identify Haversian canals, osteocyte lacunae, micro-cracks, as well as osteons. The significant correlation between osteonal and Haversian canal volume fraction highlights the role of the canals as sites where bone remodelling is initiated. The results showed that osteocyte lacunae morphometric parameters depend on their distance to cement lines, strongly suggesting the evolution of biological activity from the beginning to the end of the remodelling process. Thus, the current study provides new data on 3D osteonal morphometric parameters and their relationships with other structural features in humans.