Material State Changes Research Articles

Detecting material state changes in the nucleolus by label-free digital holographic microscopy

Ribosome biogenesis is initiated in the nucleolus, a multiphase biomolecular condensate formed by liquid-liquid phase separation. The nucleolus is a powerful disease biomarker and stress biosensor whose morphology reflects function. Here we have used digital holographic microscopy (DHM), a label-free quantitative phase contrast microscopy technique, to detect nucleoli in adherent and suspension human cells. We trained convolutional neural networks to detect and quantify nucleoli automatically on DHM images. Holograms containing cell optical thickness information allowed us to define a novel index which we used to distinguish nucleoli whose material state had been modulated optogenetically by blue-light-induced protein aggregation. Nucleoli whose function had been impacted by drug treatment or depletion of ribosomal proteins could also be distinguished. We explored the potential of the technology to detect other natural and pathological condensates, such as those formed upon overexpression of a mutant form of huntingtin, ataxin-3, or TDP-43, and also other cell assemblies (lipid droplets). We conclude that DHM is a powerful tool for quantitatively characterizing nucleoli and other cell assemblies, including their material state, without any staining.

Pollinators and plants as ecosystem engineers: post‐dispersal fruits provide new habitats for other organisms

Ecosystem engineering consists of a ubiquitous and fundamental class of interactions where some organisms promote state changes in biotic and abiotic materials which indirectly affect others. Since the concept was created as a counterpoint to traditional flux‐based models, pollinators have never been considered to promote ecosystem engineering because they modulate the supply of resources used by seed/fruit consumers. However, dry fruits may persist in the environment for long periods after seed dispersion as empty structures that are an additional alternative for occupancy. These increase the realized niche of some organisms, being a clear example of biogenic habitats. Here, we demonstrate how pollination may boost ecosystem engineering using an illustrative case study based on a specialized interaction between a bee and an orchid with characteristic capsular fruits. We demonstrate that the orchid is fully dependent on the pollinator to set fruits. Post‐dispersal fruits are voluminous and remain attached to the plant for several years. By investigating the occupation patterns of arthropods, we show that post‐dispersal fruits are highly suitable for occupants when compared to pre‐dispersal and dispersing fruits. Only 13.3% of post‐dispersal fruits were never occupied, 33.3% had organisms inside and 53.3% showed signs of previous occupation. We propose that pollinators are allogenic engineers and plants autogenic, since they promote state changes through their actions and their own physical structure, respectively. Thus, pollination is a case of cooperative ecosystem engineering whereby the effects of the interaction between two or more species expand habitat suitability. Since most plants rely on pollination to set fruits, we suggest that pollination‐mediated engineering constitutes a widespread phenomenon. This offers a new perspective about the effects of pollination in nature, highlighting the importance of pollinators and opening new avenues of investigation of ecosystem dynamics and biodiversity maintenance.

Signs of Life – Hearts, Blood and our Breath

In their piece ‘Signs of Life - Hearts, Blood and our Breath: An artistic dialogue on embodiment and boundaries’, the authors and interdisciplinary artists Jane Prophet and Tobias Klein discuss three recent collaborative artworks made with Victor Leung and contextualise those works by referencing their individual art practices. Sensemaking with the heart and blood is central to these kinetic installation artworks: ‘Blood work 1.0’, ‘Blood work 2.0: Unruh’, and ‘Common Datum’. The trio made them by interweaving methods and approaches from arts-based inquiry and computer science within a feminist technoscience framework. Blood has historically been a powerful and often contested symbol in art, described by Anne Pollock, Professor of Global Health and Social Medicine, as ‘an object itself and an object within a network of objects’. This article considers the characteristics of blood and what it means to be human by triangulating between the chemical, physical and mechanical characteristics of blood. We focus on blood drawn from both human and nonhuman sources and the passage of air into the blood via the semi-permeable lung-heart connection. The artworks are inspired by the transfusion of blood and the use of organs donated by humans and extracted from nonhumans like horseshoe crabs. These biologically inspired, transparent kinetic sculptures depend on and transform the properties and qualities of blood in different species. The fluidity, coagulation and metal content of blood form the structures and movement of the sculptures. In addition, the artists incorporate shifting energies generated through visible mechanical and invisible magnetic forces to question-through-making the material properties and state change in blood flows.

Numerical simulation of the line of least resistanceduring the explosion of charges

Purpose. To establish the analytical regularity of the calculation of the maximum value of the line of least resistance (LLR) of the explosive (E), taking into account the physical and mechanical properties of the rock mass and the detonation characteristics of the explosive. The methodology of research. Numerical modeling by the finite element method (FEM) to change the stress-strain state of the model established the value of the LLR at different diameters of the charge cavity, the pressure of explosion products and the tensile strength of rocks. Regression analysis obtained an empirical pattern of changes in the LLR depending on the physical and mechanical properties of the rock mass and the detonation characteristics of explosives. Mathematical modeling establishes analytical regularities of LLR calculation for zones of crack formation and intensive fragmentation. Findings. According to the change in the stress state of the model material around the charging cavity, the empirical regularity of changing the maximum value of the LLR depending on the diameter of the charging cavity and the diameter of the explosive charge, the density and rate of detonation of explosives, the compressive and shear strength. According to the developed calculation scheme, analytical regularities of LLR calculation for zones of crack formation and intensive fragmentation are obtained. By comparing the results of LLR calculation according to the obtained regularities, the most correct formula for LLR calculation was chosen, which turned out to be the analytical regularity of LLR calculation for the zone of intensive fragmentation. The originality. The power law is established for determining the LLR of an E, which comprehensively takes into account the radius of the crush zone, the diameter of the charging cavity and charge, the density and detonation velocity of E, the compressive strength of rocks, their fracturing and compaction under the action of rock pressure, which makes it possible to calculate the parameters of drilling and blasting (D&B) for breaking massif along the zone of intensive fragmentation. Practical implications. According to the results of the research, an analytical regularity of the calculation of the LLR of the explosive charge in the zone of intensive fragmentation was obtained, the use of which will allow to rationalize the D&B parameters in ore mining with the help of industrial explosives.

Physical methods of processing melts of metal matrix composites: Сurrent state and prospects

This review focuses on the known theoretical and experimental results in the field of obtaining metal matrix composite materials by processing the melts using physical methods in the conditions of casting and metallurgical processes. The possibilities, advantages and disadvantages of various physical impact methods are considered from the standpoint of their effect on the structural and morphological characteristics, physicomechanical and operational properties of cast composite materials based on aluminum and its alloys. The paper provides a classification and a detailed description of physical methods used for melt processing when obtaining metal matrix composites depending on the melt state during processing (melting, pouring and crystallization) and according to the physical principle of the effects applied (thermal, electromagnetic, cavitation, mechanical, etc). The paper describes a contemporary view of the laws and mechanisms of the effect exerted by melt processing using physical methods on the structure and phase formation processes of as-cast metal matrix composites. The currently known effects of the impact on their structure are described from a qualitative and quantitative point of view, in particular, effects associated with a change in the wettability of particles, their distribution, dispersion and morphology, as well as with a change in the structural state of the matrix material. The paper systematizes the data on the properties of metal matrix composites obtained using physical impacts on the melt during melting and crystallization. The research shows the prospects for the development and practical application of physical impact methods for melts in the production of metal matrix composites based on various matrix materials and reinforcement systems including endogenously, exogenously and integrally reinforced composite materials. Priority areas of theoretical research and experimental development are discussed highlighting discussion areas and issues in the field of obtaining metal matrix composites using physical impacts on melts during melting and crystallization. Areas for future research in this field are proposed based on the systematic analysis of key problems limiting the widespread industrial use of physical methods for melt processing.

Implementation of Abaqus user subroutines and plugin for thermal analysis of powder-bed electron-beam-melting additive manufacturing process

Electron beam melting (EBM) is a metal powder bed fusion additive manufacturing (AM) technology that is widely used for making three-dimensional (3D) objects by adding materials layer by layer. EBM is a very complex thermal process which involves several physical phenomena such as moving heat source, material state change, and material deposition. Conventionally, these phenomena are implemented using in-house codes or embedding some user subroutines in commonly used commercial software packages, like Abaqus, which generally requires considerable expertise. Fortunately, recent versions of Abaqus offer a new plugin tool, AM Modeler, which provides a rather new and user-friendly method for performing additive manufacturing process simulation. In this work, taking Ti-6Al-4V as the particular example, we present all the details of the finite element (FE) implementation of both Abaqus user subroutines and AM Modeler plugin for thermal analysis of EBM additive manufacturing process. The melting pool shape and temperature profiles were predicted and verified against existing literature data. A 3D FE model was also developed to capture the heat transfer features in a real manufacturing process for printing a particular 3D object, “AM” characters, validating the capability of the proposed methods. To facilitate future design and thermal analysis of EBM process and to promote the use of AM Modeler plugin, the source codes including Abaqus user subroutines DFLUX and UMATHT as well as Python scripts for implementing AM Modeler are made available and could be downloaded from https://github.com/Dr-Ning-An/ebm-abaqus.

Low-Velocity Impact Characteristics of Hybrid Aluminum/CFRP Single Hat Sectioned Beam Adhesively Bonded Using Adhesive Tape

Single hat sectioned hybrid beams composed of aluminum and Carbon Fiber Reinforced Polymeric materials (CFRP), intended for structural applications in the automotive and aviation sectors, have been studied from the point of their energy absorption capabilities when submitted to transverse low-velocity impact loading. Carbon fiber-epoxy composite prepregs were placed on the inside of the single hat sectioned aluminum sheet and completely cured in the autoclave under the recommended curing cycle. The bonding process between the aluminum sheet and composite layers was achieved by using 3M VHB™ 4930 double-sided acrylic foam tape. Bonding the aluminum and composite layers through adhesive tape eliminates the requirement of surface preparation of the aluminum layer through chemical etching or mechanical abrasion and thereby the strength of the metallic layer is not reduced due to the formation micropores during the chemical etching process. Results are shown in terms of load-displacement and damage morphologies diagrams; characteristic trends are compared and discussed. It was observed that the presence of viscoelastic adhesive tape material restricts the rupture (visual cracks) failure of the outer aluminum layer, resulting in the only impact-induced indentation for all impact energies. Numerical simulations were also performed to characterize and predict the failure mechanism of such hybrid beams when subjected to impact loading. Numerical predictions showed good correlation with experimental results for all impact histories at low and medium impact energies but a showed slight discrepancy for highest impact energy and were not able to successfully capture the system response in the unloading region. Current modeling does not consider damage healing or recovery with unloading and it is difficult to account for such change in material state. This study provides the low-velocity impact characteristics and collapse behavior of the hybrid hat sectioned beams under tensile and shear forces developed by impact loading by providing insight to their primary damage mechanisms relative to the impact energies. It was found that the primary damage of the specimen’s changes from impact-induced indentation, minimal fiber breakage to partial perforation accompanied by larger indentation depth as the impact energy is increased from 6 to 12 J.

Direct measurement of force configurational entropy in jamming.

Thermal fluctuations are not large enough to lead to state changes in granular materials. However, in many cases, such materials do achieve reproducible bulk properties, suggesting that they are controlled by an underlying statistical mechanics analogous to thermodynamics. While themodynamic descriptions of granular materials have been explored, they have not yet been concretely connected to their underlying statistical mechanics. We make this connection concrete by providing a first-principles derivation of the multiplicity and thus the entropy of the force networks in granular packings. We directly measure the multiplicity of force networks using a protocol based on the phase space volume of allowed force configurations. Analogous to Planck's constant, we find a scale factor, h_{f}, that discretizes this phase space volume into a multiplicity. To determine this scale factor, we measure angoricity over a wide range of pressures using the method of overlapping histograms and find that in the absence of a fundamental quantum scale it is set solely by the system size and dimensionality. This concretely links thermodynamic approaches of angoricity with the microscopic multiplicity of the force network ensemble.

Comparison of residual stress on different three-dimensional multi-layer welding methods of welded hollow sphere joint in large-span structure by considering latent heat

This article quantitatively evaluated the influence of three-dimensional multi-layer welding on the welding residual stress of super-big diameter welded hollow sphere joint in the large-span spatial steel structure considering the influence of material state change using finite element method. First, this article proposed a conception of equivalent state change time—the virtual time of state change in the analysis of welding and cooling—which represents the heat absorbed or released during the change of solid and fluid states in welding material. The equivalent state change time increases the accuracy of the thermal analysis considering the latent heat of fusion in welding and cooling process. Second, this article simulated the numerical experiments of three welding methods including multi-layer symmetric welding, multi-layer sequential welding, and single-layer symmetric welding, which show that multi-layer symmetric welding not only increases the balance of supporting ability of structure but also decreases the value of maximum tensile residual stress, and it is better than the other two welding methods.

Identification of current material state in composites using a dielectric state variable

Damage development in composites is a complicated process, unlike metals where the failure is triggered by unstable growth of a single crack; failure in composites is triggered by interaction of multiple local damage events. The ‘beginning of the end’ in composites is well described in terms of ‘criticality’ and, identification of material state is an important step for predicting this criticality. Current non-destructive evaluation techniques can accurately map the damage zone but are incapable of identifying the material state. In the current research, the main intention is to observe and model the variation in dielectric response as a function of defect development and coupling to characterize the current material state (Characteristic Damage State (CDS), damage interaction) in unidirectional, woven glass fiber reinforced polymer composites loaded in quasi-static axial tension. The changes in dielectric response are correlated with change in material state validated by damage patterns obtained using edge replication techniques.

Microstructure and electrochemical properties of rapidly solidified Si–Ni alloys as anode for lithium-ion batteries

This paper reports an electrochemically highly reversible Si–Ni alloy based electrode through the microstructure and composition analysis using XRD and HR-TEM combined with EDS. Nano-Si (∼200nm) embedded in the inactive NiSi2/NiSi matrix synthesized using industrial-scale rapid solidification process (RSP). In addition, comprehensive analysis of HR-TEM images, dQ/dV and OCV plots provides powerful insights into the cycle life degradation of Si-alloys caused by the material state change upon cycling.

Finite Element Analysis of Interaction of Laser Beam with Material in Laser Metal Powder Bed Fusion Process.

A deep understanding of the laser-material interaction mechanism, characterized by laser absorption, is very important in simulating the laser metal powder bed fusion (PBF) process. This is because the laser absorption of material affects the temperature distribution, which influences the thermal stress development and the final quality of parts. In this paper, a three-dimensional finite element analysis model of heat transfer taking into account the effect of material state and phase changes on laser absorption is presented to gain insight into the absorption mechanism, and the evolution of instantaneous absorptance in the laser metal PBF process. The results showed that the instantaneous absorptance was significantly affected by the time of laser radiation, as well as process parameters, such as hatch space, scanning velocity, and laser power, which were consistent with the experiment-based findings. The applicability of this model to temperature simulation was demonstrated by a comparative study, wherein the peak temperature in fusion process was simulated in two scenarios, with and without considering the effect of material state and phase changes on laser absorption, and the simulated results in the two scenarios were then compared with experimental data respectively.

Исследование изменения микротвердости материала по глубине призматического образца при виброволновом нагружении

The investigation results of vibro-wave loading impact upon material state measurements of the prismatic sample at different distances are presented. The results obtained confirm a vibro-wave loading impact upon material state changes of a solid sample.

The Difference of Gestures between Scientists and Middle School Students in Scientific Discourse: Focus on Molecular Movement and the Change in State of Material

The Difference of Gestures between Scientists and Middle School Students in Scientific Discourse: Focus on Molecular Movement and the Change in State of Material

Nonlinear anisotropic electrical response of carbon fiber-reinforced polymer composites

Composites materials are often subjected to multi-physics conditions in different applications where, in addition to mechanical loads, they also need to sustain other types of loads such as electrical currents. Composite materials have heterogeneous electrical properties at the local level that can be different at the global level. In this study, electrical response was measured to explore how different lamina orientation and electrical current density affect anisotropic electrical properties of composite. For in-plane study, current was applied up to 80 kA/m2 for both unidirectional and quasi-isotropic composite. In thickness direction, maximum current density was 6 kA/m2. As expected, electrical properties are indeed dependent on fiber architecture which acts as conduction path in the laminate, and also depends on progressive increase in current density. Anisotropic electrical behavior was measured experimentally and the threshold of nonlinear behavior due to high current was identified. Threshold current density for unidirectional composite in fiber direction and for quasi isotropic are, respectively, 48.14 ± 4.3% kA/m2, 56.06 ± 4.4% kA/m2. For off-axis fiber laminates, this threshold limit shifts from 34.36 ± 5.9% kA/m2 to a lower value of 17.95 ± 7.9% kA/m2 as the fibers are oriented away from the x axis. In thickness direction, this threshold limit is in between 2.56 and 3.80 kA/m2. The electrical-thermal responses were also studied experimentally with thermography tests and the results were compared to indicate damage. A 3D X-ray microscope has been used to visualize and quantify (down to 1 micron) such local material state changes due to electrical current.

Modelling energy source and powder properties for the development of a thermal FE model of the EBM additive manufacturing process

The combination of additive manufacturing principles and electron beam (EB) technology allows complex metal parts, featuring excellent quality material, to be produced, whenever traditional methods are expensive or difficult to apply. Today, the optimization of process parameters, for a given metal powder, is generally attained through an empirical trial and error approach. Process simulation can be used as a tool for decision-making and process optimization, since a virtual analysis can help to facilitate the possibility of exploring “what if” scenarios. In this work, a new type of modelling has been introduced for energy source and powder material properties and it has been included in a thermal numerical model in order to improve the effectiveness and reliability of Electon Beam Melting (EBM) FE simulation. Several specific subroutines have been developed to automatically calculate the powder properties as temperature functions, and to consider the position of the beam during scanning as well as the material state changes from powder to liquid in the melting phase and from liquid to solid during cooling. A comparison of the numerical results and experimental data taken from literature has shown a good forecasting capability. The average deviations of the simulation from an experimental scan line width have been found to be below about 15%.

Multiphysics Based Simulation of Damage Progression in Composites

The long-term properties of continuous fiber reinforced composite materials are increasingly important as applications in airplanes, cars, and other safety critical structures are growing rapidly. Although a clear understanding has been established for initiation, growth and accumulation of damage, it is still unclear when and how the interactions of these local events lead to the development of a “critical” fracture path resulting in a sudden change of global properties and possible rupture. In the present paper, we simulate damage development in a neat polymeric resin using X-FEM analysis, and conduct concomitant dielectric response analysis with a COMSOLTM simulation model to study the collective defect structure as it develops in a model system. Our studies reveal inflection points in the predicted global dielectric response vs. strain that are related to changes in local damage growth rates and modes that clearly indicate impending fracture and capture the progressive change in material state.

Robust Room Temperature Hysteresis in an FeIII Spin Crossover Metallomesogen

AbstractThe high temperature magnetic and structural properties of an amphiphilic iron(III) spin crossover complex are reported. Thermal cycling reveals a scan rate‐dependent 20 K thermal hysteresis in the mT vs. T data close to room temperature. A fast scan rate is essential for the hysteresis but it is robust and reproducible after multiple thermal cycles. Differential scanning calorimetry and cross polarized microscopy are used to show that the magnetic switching aligns with a material state change from solid to ordered liquid phase on warming.

Do Small Canopy Gaps Created by Japanese Black Bears Facilitate Fruiting of Fleshy-Fruited Plants?

Japanese black bears often break branches when climbing trees and feeding on fruit in canopies, thereby creating small canopy gaps. However, the role of black bear-created canopy gaps has not been evaluated in the context of multiple forest dynamics. Our hypothesis was that small canopy gaps created by black bears improve light conditions, which facilitates fruiting of adult fleshy-fruited plants located beneath the gaps, and also that this chain interaction depends on interactions among the size of gaps, improved light conditions, forest layers, and life form of plants. The rPPFD, size of black bear-created canopy gaps, and fruiting/non-fruiting of fleshy-fruited plants were investigated in five forest layers beneath black-bear-created canopy gaps and closed canopies of Mongolian oak (Quercus crispula). We found that light conditions improved beneath black bear-disturbed trees with canopy gaps of large size, and the effect of improvement of light conditions was reduced with descending forest layers. Fruiting of fleshy-fruited plants, especially woody lianas and trees, was facilitated by the improvement of light conditions accompanied by an increase in the size of black-bear-created gaps. Data from this study revealed that canopy disturbance by black bears was key for improving light conditions and accelerating fruiting of fleshy-fruited trees and woody lianas in the canopy layers in particular. Therefore, our hypothesis was mostly supported. Our results provide evidence that Japanese black bears have high potential as ecosystem engineers that increase the availability of resources (light and fruit in this study) to other species by causing physical state changes in biotic materials (branches of Q. crispula in this study).

High-energy synchrotron x-ray techniques for studying irradiated materials

Abstract