Clusters Of Structures Research Articles

A New Insight on the Pulverization Mechanisms of FeSi75 Alloy by Understanding Its Solidification Process

Easy pulverization of FeSi75 alloy during its crushing, storage, and transportation, inducing huge loss of such alloy annually, has been a critical problem. In this research, the pulverization mechanisms of FeSi75 alloy have been understood by introducing a range of characterization techniques to find out correlations between the alloy microstructure, mechanical properties, formation of PH3, and the pulverization during its solidification process. The experiments are carried out under different isothermal quenching temperatures and casting cooling rates. The results show that during the cooling process, the eutectic reaction occurs and produces the low‐ductility ζ phase, which leads to cracks in the microstructure and higher pulverization possibility. Moreover, sulfides and phosphides precipitate on the Fe‐Si microstructure and form clustered structures, and the release of PH3 increases with decreasing temperature. The internal stresses generate by phase transformations, the low‐ductility ζ phase, and the precipitation of sulfides and phosphides at crack sites collectively lead to the pulverization of FeSi75 alloy. It is also found that the grain size becomes smaller and more uniform at higher casting cooling rates, which effectively prevents the precipitation and enrichment of sulfides and phosphides, reduces PH3 release, and hence could prevent the pulverization of FeSi75 alloy.

A force-density framework for flexible multi-body dynamic analysis of clustered tensegrity structures

This paper develops a versatile and effective force-density framework for the flexible multi-body dynamic analysis of clustered tensegrity structures. In this framework, the force density is selected as the basic variable instead of force, and the clustered tensegrity structure is mathematically described in a vector and matrix form, encompassing topology, geometry, material, and force properties. A non-negative variable is defined as an indicator of the member stress state, and a complementary function is constructed to address the discontinuity issues that arise from the unidirectional axial stiffness of cables. Dynamic formulas are established within this force-density framework, with nodal coordinates selected as generalized parameters and formulations constructed in a matrix form. A complementary framework is established as an alternative for solving the dynamic equations, transforming the isolated steps of Newton’s iteration and cable state judgment (slack or tension) into a unified one, bringing more potential for improving solving efficiency. Numerical simulations are carried out to validate the approach, demonstrating that it effectively reveals the dynamic oscillation, tension changes, and cable slack behavior of clustered tensegrity structures during shape control. Comparative studies highlight the advantage of computational efficiency. The method proposed in this paper provides a robust mathematical model for studying clustered tensegrity structures, particularly regarding the shape control of deployable, active, and intelligent structures, aiding in understanding dynamic oscillation, tension changes, and cable slack behavior during their deformation. The methods can also be applied to cable net structures and other prestressed pin-jointed systems.

Effect of Mn element on shock response in CoCrFeNiMnx high entropy alloys

Abstract The effect of Mn element on shock response of CoCrFeNiMn x high entropy alloys (HEAs) are investigated using molecular dynamics simulations. Structural analysis shows that Mn-rich CoCrFeNiMn x HEA has a larger average atomic volume. The elastic properties of CoCrFeNiMn x HEAs under various hydrostatic pressures are studied, revealing that the elastic modulus decreases with increasing of Mn content. The shock thermodynamic parameters are quantitatively analyzed. The Mn-dependent shock Hugoniot relationship of CoCrFeNiMn x HEAs is obtained: U s = 1.25 + (5.21–0.011x)U p. At relatively high shock pressure, the increase in Mn content promotes the formation of clustered BCC structures and hinders the development of dislocations. In addition, more FCC structures in Mn-rich CoCrFeNiMn x HEAs transform into disordered structures during spallation. Spall strength decreases with increasing Mn content. This study can provide a reference for the design and application of CoCrFeNiMn HEAs under shock loading.

Neutrino halo profiles: HR-DEMNUni simulation analysis

Using the high-resolution HR-DEMNUni simulations, we computed neutrino profiles within virialized dark matter haloes. These new high-resolution simulations allowed us to revisit fitting formulas proposed in the literature and provided updated fitting parameters that extend to less massive haloes and lower neutrino masses than previously in the literature, in accordance with new cosmological limits. The trend we observe for low neutrino masses is that, for dark matter halo masses below ∼ 4 × 1014 h -1 M ⊙, the presence of the core becomes weaker and the profile over the whole radius is closer to a simple power law. We also characterised the neutrino density profile dependence on the solid angle within clustered structures: a forward-backward asymmetry larger than 10% was found when comparing the density profiles from neutrinos along the direction of motion of cold dark matter particles within the same halo. In addition, we looked for neutrino wakes around halo centres produced by the peculiar motion of the halo itself. Our results suggest that the wakes effect is present in haloes with masses greater than 3 × 1014 h -1 M ⊙ where a mean displacement of 0.06h -1Mpc was found.

Extraction and characterization of valuable compounds from chicken sternal cartilage: Type II collagen and chondroitin sulfate

Type II collagen (Col II) and chondroitin sulfate (CS) are the main macromolecules in the extracellular matrix. This study investigated the characteristics of Col II and CS obtained from chicken sternal cartilage (CSC) via enzymatic hydrolysis for various treatment times. For Col II and CS, the highest efficiency of enzymatic hydrolysis was achieved after 24 and 6 h of treatment, respectively. The average molecular weights were α1 chain-130 kDa, β chain-270 kDa for Col II, and 80.27 kDa for CS. Fourier transform infrared spectroscopy revealed that the Col II samples maintained their triple-helical structure and that the predominant type of CS was chondroitin-4-sulfate. Scanning electron microscopy revealed that the Col II and CS samples possessed fibrillar and clustered structures, respectively. This study suggests that collagen and CS obtained from CSC can be used as promising molecules for application in food and pharmaceutical industries.

Melanopsin in the human and chicken choroid

The choroid embedded in between retina and sclera is essential for retinal photoreceptor nourishment, but is also a source of growth factors in the process of emmetropization that converts retinal visual signals into scleral growth signals. Still, the exact control mechanisms behind those functions are enigmatic while circadian rhythms are involved. These rhythms are attributed to daylight influences that are melanopsin (OPN4) driven. Recently, OPN4-mRNA has been detected in the choroid, and while its origin is unknown we here seek to identify the underlying structures using morphological methods.Human and chicken choroids were prepared for single- and double-immunohistochemistry of OPN4, vasoactive intestinal peptide (VIP), substance P (SP), CD68, and α-smooth muscle actin (ASMA). For documentation, light-, fluorescence-, and confocal laser scanning microscopy was applied. Retinal controls proved the reliability of the OPN4 antibody in both species.In humans, OPN4 immunoreactivity (OPN4-IR) was detected in nerve fibers of the choroid and adjacent ciliary nerve fibers. OPN4+ choroidal nerve fibers lacked VIP, but were co-localized with SP. OPN4-immunoreactivity was further detected in VIP+/SP + intrinsic choroidal neurons, in a hitherto unclassified CD68-negative choroidal cell population thus not representing macrophages, as well as in a subset of choroidal melanocytes. In chicken, choroidal nerve fibers were OPN4+, and further OPN4-IR was detected in clustered suprachoroidal structures that were not co-localized with ASMA and therefore do not represent non-vascular smooth-muscle cells. In the choroidal stroma, numerous cells displayed OPN4-IR, the majority of which was VIP-, while a few of those co-localized with VIP and were therefore classified as avian intrinsic choroidal neurons. OPN4-immunoreactivity was absent in choroidal blood vessels of both species.In summary, OPN4-IR was detected in both species in nerve fibers and cells, some of which could be identified (ICN, melanocytes in human), while others could not be classified yet. Nevertheless, the OPN4+ structures described here might be involved in developmental, light-, thermally-driven or nociceptive mechanisms, as known from other systems, but with respect to choroidal control this needs to be proven in upcoming studies.

Aqueous Ionic Liquid Mixtures as Minimal Models of Lipid Bilayer Membranes.

We introduce aqueous ionic liquid (IL) mixtures, specifically mixtures of 1-butyl-3-imidazoliumtetrafluoroborate (BMImBF4), with water as a minimal model of lipid bilayer membranes. Imidazolium-based ILs are known to form clustered nanoscale structures in which local inhomogeneities, micellar or lamellar structures, are formed to shield hydrophobic parts of the cation from the polar cosolvent (water). To investigate these nanostructures, dynamic light scattering (DLS) on samples with different mixing ratios of water and BMImBF4 was performed. At mixing ratios of 50% and 45% (v/v), small and homogeneous nanostructures can indeed be detected. To test whether, in particular, these stable nanostructures in aqueous mixtures may mimic the effects of phospholipid bilayer membranes, we further investigated their interaction with myelin basic protein (MBP), a peripheral, intrinsically disordered membrane protein of the myelin sheath. Using dynamic light scattering (DLS), continuous wave (CW) and pulse electron paramagnetic resonance (EPR), and small-angle X-ray scattering (SAXS) on recombinantly produced, "healthy" charge variants rmC1WT and double cysteine variant C1S17CH85C, we find that the size and the shape of the determined nanostructures in an optimum mixture offer model membranes in which the protein exhibits native behavior. SAXS measurements illuminate the size and shape of the nanostructures and indicate IL-rich "beads" clipped together by functional MBP, one of the in vivo roles of the protein in the myelin sheath. All the gathered data combined indicate that the 50% and 45% aqueous IL mixtures can be described as offering minimal models of a lipid mono- or bilayer that allow native processing and potential study of at least peripheral membrane proteins like MBP.

Modeling and optimization of costs associated with the development of clustered organizational management structures in construction companies

The article aims to examine models and methods of cost optimization associated with the development of clustered organizational structures in construction companies. The research methodology involved an analysis of existing approaches, simulation modeling, and econometric equation analysis. As a result, different approaches to cost estimation and optimization applied in the construction sphere are presented. Particular attention is paid to the development of complex models and their optimization under the conditions of uncertainty through simulation modeling of various scenarios of cluster organizational structures in construction companies. The analysis also includes an assessment of the advantages and disadvantages of econometric semi-linear dynamic equations and the feasibility of their application. The discussion section emphasizes the importance of integrating different optimization methods to achieve the most optimal outcome in the management of construction companies. Further research directions are outlined. The results can be relevant when formulating development strategies and making investment decisions in the construction sphere. The research conclusions confirm the significance of applying modern cost optimization methods to improve the management efficiency of construction companies and their competitiveness in the market of construction services.

T-cell receptor determinants of response to chemoradiation in locally-advanced HPV16-driven malignancies.

The effect of chemoradiation on the anti-cancer immune response is being increasingly acknowledged; however, its clinical implications in treatment responses are yet to be fully understood. Human papillomavirus (HPV)-driven malignancies express viral oncogenic proteins which may serve as tumor-specific antigens and represent ideal candidates for monitoring the peripheral T-cell receptor (TCR) changes secondary to chemoradiotherapy (CRT). We performed intra-tumoral and pre- and post-treatment peripheral TCR sequencing in a cohort of patients with locally-advanced HPV16-positive cancers treated with CRT. An in silico computational pipeline was used to cluster TCR repertoire based on epitope-specificity and to predict affinity between these clusters and HPV16-derived epitopes. Intra-tumoral repertoire diversity, intra-tumoral and post-treatment peripheral CDR3β similarity clustering were predictive of response. In responders, CRT triggered an increase peripheral TCR clonality and clonal relatedness. Post-treatment expansion of baseline peripheral dominant TCRs was associated with response. Responders showed more baseline clustered structures of TCRs maintained post-treatment and displayed significantly more maintained clustered structures. When applying clustering by TCR-specificity methods, responders displayed a higher proportion of intra-tumoral TCRs predicted to recognise HPV16 peptides. Baseline TCR characteristics and changes in the peripheral T-cell clones triggered by CRT are associated with treatment outcome. Maintenance and boosting of pre-existing clonotypes are key elements of an effective anti-cancer immune response driven by CRT, supporting a paradigm in which the immune system plays a central role in the success of CRT in current standard-of-care protocols.

Formation of three-dimensional (3D) Self-Assembled Clusters of Anisotropic Janus Particles in Microgravity

Abstract The self-assembly of colloidal particles enables the creation of complex materials with tailored properties. This process, particularly involving anisotropic particles, can lead to the formation of structurally unique and complex assemblies that are not achievable with isotropic particles. On Earth, gravitational forces limit the investigation of these particles’ intrinsic motion and interactions, posing significant challenges to comprehensively understanding the fundamental forces governing their interactions. To overcome these limitations, this study, in collaboration with NASA’s Glenn Research Center (GRC), employs the Light Microscopy Module (LMM) aboard the International Space Station (ISS) to observe the self-assembly phenomena of anisotropic particles under microgravity conditions. Our investigation shows that anisotropic Janus particles with their distinctive properties can spontaneously organize into ordered structures under microgravity. This directional interaction among anisotropic particles is expected to enable control over assembly processes, forming three-dimensional (3D) clustered structures that are unattainable on Earth. Thus, this study not only advances our understanding of particle self-assembly in microgravity but also opens new avenues for synthesizing materials with novel functionalities through the unique assembly of anisotropic colloids.

Investigating nuclei produced in 9Li +11B reaction

In this contribution, a preliminary analysis of the first part of the experiment S2012 conducted at the ISAC-II facility of Canada’s particle accelerator center TRIUMF in Vancouver will be presented. The experiment aims to study highly clustered structures of nuclei created in multi-nucleon transfer reactions of 9Li radioactive beam on natural boron target (11B and 10B). The main objective of the experiment is to study exotic structures created in neutron-rich 16C nucleus in the range of higher excitation energies. The analysis presented here probes the existence of exotic cluster configurations and the quality of detected results using the invariant mass techniques.

Late pre-Hispanic fog oasis settlements and long-term human occupation on the Peruvian central coast from satellite imagery

Fog oases (lomas) present pockets of verdant vegetation within the arid coastal desert of Andean South America and archaeological excavation within some of the oases has revealed a long history of human exploitation of these landscapes. Yet lomas settlements are under-represented in archaeological datasets due to their tendency to be located in remote inter-valley areas. Here, the authors employ satellite imagery survey to map the locations of anthropogenic surface features along the central Peruvian coast. They observe two categories of archaeological features, large corrals and clustered structures, and document a concentration of settlement features within lomas landscapes that suggests a pre-Hispanic preference for both short- and long-term occupation of these verdant oases.

Clustered networks as informal elements of access and power: a study in a honey producers association

Networks observed from the perspective of the structural dimension present their complexity at the level of positions existing in a social arrangement. These positions have the power to define roles among the actors immersed in social relationships, providing advantages and differentiated access to the network actors. In this context, the present study aims to understand how the relational structure among the producers linked with an association of honey producers in the interior of Paraná state influences the social dynamics. The methodology used is quantitative and qualitative of exploratory nature and conducted as a case study. The data were collected through the sociometric evaluation questionnaire and interviews with actors selected from their position in the network enabled the understanding of the influence of social structures on network governance, establishing powers parallel to formal powers and building clustered structures that allow access and power different from those formally constituted. It evidenced that access to knowledge and resources are results of the social structures composed by the arrangement of relationships established within the producers' association, creating conditions of advantages and disadvantages for the actors immersed in the network. It was also possible to note that the routines established by governance have an influence on the formation of the network structure.

Shared ancestry of algal symbiosis and chloroplast sequestration in foraminifera.

Foraminifera are unicellular organisms that established the most diverse algal symbioses in the marine realm. Endosymbiosis repeatedly evolved in several lineages, while some engaged in the sequestration of chloroplasts, known as kleptoplasty. So far, kleptoplasty has been documented exclusively in the rotaliid clade. Here, we report the discovery of kleptoplasty in the species Hauerina diversa that belongs to the miliolid clade. The existence of kleptoplasty in the two main clades suggests that it is more widespread than previously documented. We observed chloroplasts in clustered structures within the foraminiferal cytoplasm and confirmed their functionality. Phylogenetic analysis of 18S ribosomal RNA gene sequences showed that H. diversa branches next to symbiont-bearing Alveolinidae. This finding represents evidence of of a relationship between kleptoplastic and symbiotic foraminifera.. Analysis of ribosomal genes and metagenomics revealed that alveolinid symbionts and kleptoplasts belong to the same clade, which suggests a common ancestry.

Analysis of clustered cable-actuation strategies of V-Expander tensegrity structures

This study presents an analysis method to design cable-actuated clustered V-Expander tensegrity elementary cells based on the nonlinear tensegrity statics. Clustered actuation takes advantage of the presence of cable elements in a tensegrity structure by allowing cables to run over frictionless joints. The study first provides the nonlinear static equations of clustered tensegrity structures. Then, it introduces the topology of V-Expander tensegrity elementary cells, which vary in complexity and aspect ratio. To achieve cable actuation, specific sets of cables are chosen from the complete pool of cables to serve as the active elements of V-Expander cells. During actuation, the length of these active cables decreases. The actuation efficiency of each specific choice of active cable is computed to find the optimal actuation strategy. The proposed approach can be utilized to analyze and design other types of cable-driven tensegrity structures, with applications to morphing structures and soft robots.

Bias reduction and robustness for Gaussian longitudinal data analysis

In the analysis of clustered or longitudinal data structures, such as those coming from surveys or trials, it is desirable to accurately estimate the dependence parameters within repeated measurements. Marginal models together with the generalized estimating equation allow to consistently estimate regression coefficients. Inference may be problematic for small and moderate sample sizes, or with models involving many covariates. Moreover, the correlation structure may be misspecified leading to a substantial bias in the sandwich covariance matrix estimator. The paper focuses on Gaussian with exchangeable correlation matrix model and proposes to use adjustments of the score function aiming at mean and median bias reduction of maximum likelihood estimates. Extensive simulation studies show a remarkable performance of the proposed methods. In addition, we show that the bias reduction methods maintain an appreciable robustness with respect to the maximum likelihood under misspecification of the correlation matrix.

Role of Charge Ordering in the Dynamics of Cluster Formation in Associated Liquids.

Liquids are archetypes of disordered systems, yet liquids of polar molecules are locally more ordered than nonpolar molecules, due to the Coulomb interaction based charge ordering phenomenon. Hydrogen bonded liquids, such as water or alcohols, for example, represent a special type of polar liquids, in that they form labile clustered local structures. For water, in particular, hydrogen bonding and the related local tetrahedrality, play an important role in the various attempts to understand this liquid. However, labile structures imply dynamics, and it is not clear how it affects the understanding of this type of liquids from purely static point of view. Herein, we propose to reconsider hydrogen bonding as a charge ordering process. This concept allows us to demonstrate the insufficiency of the analysis of the microscopic structure based solely on static pair correlation functions, and the need for dynamical correlation functions, both in real and reciprocal space. The subsequent analysis allows to recover several aspects of our understanding of hydrogen bonded liquids, but from the charge order perspective. For water, it confirms the jump rotation picture found recently, and it allows to rationalize the contradicting pictures that arise when following the interpretations based on hydrogen bonding. For alcohols, it allows to understand the dynamical origin of the scattering prepeak, which does not exist for water, despite the fact that both these liquids have very similar hydroxyl group chain clusters. The concept of charge ordering complemented by the analysis of dynamical correlation functions appear as a promising way to understand microheterogeneity in complex liquids and mixtures from kinetics point of view.

Spatio-temporal variation in avian taxonomic, functional, and phylogenetic diversity and its relevance for conservation in a wetland ecosystem in Myanmar

Wetland ecosystems host an extensive number of avian species and play therefore a key role in biodiversity conservation. However, avifauna in wetlands is severely impacted by the anthropogenic transformation of natural habitats into other land uses. Understanding how habitat changes influence avian community dynamics is crucial for effective management and conservation of bird habitats. Here, we assessed spatio-temporal variation in taxonomic, functional, and phylogenetic diversity, and assembly structures of the bird community in the Indawgyi Wetland Ecosystem in Myanmar. Bird surveys were seasonally conducted at 120 sample plots, which were equally distributed among four habitat types subject to different level of human influences (natural lake habitat, seasonally flooded grasslands, riparian forest, and agricultural land). Across habitat types, functional and phylogenetic diversity were the highest in the lake habitat, especially during the migration season, and the lowest in the cultivated habitat. Our results indicated over-dispersed functional and phylogenetic structures in the lake habitat, with clustered structures in the remaining habitats. Diversity of species important for conservation was also higher in the lake habitat and in areas far away from human disturbances. Spatial variation of bird community diversity suggests that conservation efforts in this ecosystem should concentrate more on the lake habitat and associated grassland habitats. Moreover, our results suggest the need for habitat restoration in riparian forests and increased sustainable agricultural practices in order to improve the contribution of these habitats to the diversity in the avifauna community. Our study highlighted the importance of integrating functional and phylogenetic dimensions into biodiversity analyses providing broader ecological insights for conservation.

A machine learning-based probabilistic computational framework for uncertainty quantification of actuation of clustered tensegrity structures.

Clustered tensegrity structures integrated with continuous cables are lightweight, foldable, and deployable. Thus, they can be used as flexible manipulators or soft robots. The actuation process of such soft structure has high probabilistic sensitivity. It is essential to quantify the uncertainty of actuated responses of the tensegrity structures and to modulate their deformation accurately. In this work, we propose a comprehensive data-driven computational approach to study the uncertainty quantification (UQ) and probability propagation in clustered tensegrity structures, and we have developed a surrogate optimization model to control the flexible structure deformation. An example of clustered tensegrity beam subjected to a clustered actuation is presented to demonstrate the validity of the approach and its potential application. The three main novelties of the data-driven framework are: (1) The proposed model can avoid the difficulty of convergence in nonlinear Finite Element Analysis (FEA), by two machine learning methods, the Gauss Process Regression (GPR) and Neutral Network (NN). (2) A fast real-time prediction on uncertainty propagation can be achieved by the surrogate model, and (3) Optimization of the actuated deformation comes true by using both Sequence Quadratic Programming (SQP) and Bayesian optimization methods. The results have shown that the proposed data-driven computational approach is powerful and can be extended to other UQ models or alternative optimization objectives.

Equilibrium and stiffness study of clustered tensegrity structures with the consideration of pulley sizes

This paper presents the equilibrium and stiffness study of planar clustered tensegrity structures (CTS) considering pulley sizes. We first derive the geometric relationship between clustered strings and pulleys, where the nodal vector is chosen as the generalized coordinate. Then, the equilibrium equations of the planar clustered tensegrity structure with pulleys based on the Lagrangian method are given. Since the stiffness of a structure is usually weakened when using clustering strings, we formulate the tangent stiffness matrix equations for analysis. It is also shown that as pulley sizes go to zero, the governing equations of the planar clustered tensegrity system with pulleys yield to the classical clustered tensegrity structure without pulleys, which is consistent with the existing literature. Three examples are demonstrated to validate the given theory. The proposed method allows one to conduct equilibrium, stiffness, and robustness studies of planar clustered tensegrity structures with pulleys. Nevertheless, the approach developed in this paper is not limited to tensegrity structures. It can also be applied to a wide range of applications with pulley-rope systems, such as drilling rigs, ocean platform anchors, and cargo cranes.