Morphological Transition Research Articles

High-Throughput Assembly of Compositionally Controlled 3D Cell Communities for Developmental Engineering.

Cell patterning for 3D culture has increased our understanding of how cells interact among themselves and with their environment during tissue morphogenesis. Building cell communities from the bottom up with size and compositional control is invaluable for studies of morphological transitions. Here, we detail Photolithographic DNA-programmed Assembly of Cells (pDPAC). pDPAC uses a photoactive polyacrylamide gel substrate to capture single-stranded DNA on a 2D surface in large-scale, highly resolved patterns using the photomask technology. Cells are then functionalized with a complementary DNA strand, enabling cells to be temporarily adhered to distinct locations only where their complementary strand is patterned. These temporary 2D patterns can be transferred to extracellular matrix hydrogels for 3D culture of cells in biomimetic microenvironments. Use of a polyacrylamide substrate has advantages, including a simpler photolithography workflow, lower non-specific cell adhesion, and lower stiction to ECM hydrogels during release of patterned hydrogels. The protocol is equally applicable to large (cm)-scale patterns and repetitive arrays of smaller-scale cell interaction or migration experiments.

Insight into continuous growth mechanisms of ZrO2-Al2O3 composite PEO coatings with superior cavitation erosion resistance

The ZrO2-Al2O3 composite coatings were fabricated on TiB2/2024Al composite by the plasma electrolytic oxidation (PEO) treatment with either monoclinic (m-ZrO2) or tetragonal zirconia (t-ZrO2) nanoparticles (NPs) addition. Such PEO coatings showed a double layer morphology due to the limited physical motion ability of ZrO2 colloidal particles into coatings. t-ZrO2 remained as the main phase in ZrO2-Al2O3 PEO composite coatings whether t-ZrO2 or m-ZrO2 NPs were added. Based on the microstructure analyses by focus ion beam plus scanning electron microscopy and transmission electron microscopy, ZrO2 showed netlike morphology in the outer layer with NPs partially melted at the mesh boundary and lines-like morphology fully melted at the inner mesh in the coating. A prominent morphological transition of ZrO2 was clearly observed at the interface between outer layer and inner layer. Therefore, the continuous growth mechanisms of ZrO2-Al2O3 composite PEO coatings were proposed in terms of morphological evolution process. Furthermore, electrochemical measurements and cavitation erosion tests were conducted to study the comprehensive surface properties (corrosion and impact resistance) of ZrO2-Al2O3 composite coatings. As a result, the ZrO2-Al2O3 composite PEO coatings with m-ZrO2 addition exhibited the greatly reduced corrosion rate, and superior cavitation erosion resistance. Accordingly, the underlying mechanisms for these improved properties were intensively discussed.

Coexistence and Coevolution of Wrinkle and Ridge Patterns in the Film-Substrate System by Uniaxial Compression.

Homogeneous wrinkles and localized patterns are ubiquitous in nature and are useful for a wide range of practical applications. Although various strain-driven surface instability modes have been extensively investigated in the past decades, understanding the coexistence, coevolution, and interaction of wrinkles and localized patterns is still a great challenge. Here, we report on the formation and evolution of coexisting wrinkle and ridge patterns in metal films deposited on poly(dimethylsiloxane) (PDMS) substrates by uniaxial compression. It is found that the evolving surface patterns show unique features of morphological transition from stages I to III: namely, transition from localized ridges to coexisting wrinkles and ridges, and finally to sinusoidal-like structures, as the compression increases. Based on the compressive strain-driven surface instability theory and finite element numerical simulation, the morphological features, transition behaviors, and underlying mechanisms of such complex patterns are investigated in detail, and the changes of amplitude and wavelength versus the strain are consistent with our experiments. This work could promote a better understanding of the effect of strain localization and the interaction of multiple surface patterns in hard film-soft substrate systems.

Unraveling Dynamic Helicity Inversion and Chirality Transfer through the Synthesis of Discrete Azobenzene Oligomers by an Iterative Exponential Growth Strategy.

Unraveling the chirality transfer mechanism of polymer assemblies and controlling their handedness is beneficial for exploring the origin of hierarchical chirality and developing smart materials with desired chiroptical activities. However, polydisperse polymers often lead to an ambiguous or statistical evaluation of the structure-property relationship, and it remains unclear how the iterative number of repeating units function in the helicity inversion of polymer assemblies. Herein, we report the macroscopic helicity and dynamic manipulation of the chiroptical activity of supramolecular assemblies from discrete azobenzene-containing oligomers (azooligomers), together with the helicity inversion and morphological transition achieved solely by changing the iterative chain lengths. The corresponding assemblies also differ from their polydisperse counterparts in terms of thermodynamic properties, chiroptical activities, and morphological control.

Unraveling Dynamic Helicity Inversion and Chirality Transfer through the Synthesis of Discrete Azobenzene Oligomers by an Iterative Exponential Growth Strategy

AbstractUnraveling the chirality transfer mechanism of polymer assemblies and controlling their handedness is beneficial for exploring the origin of hierarchical chirality and developing smart materials with desired chiroptical activities. However, polydisperse polymers often lead to an ambiguous or statistical evaluation of the structure–property relationship, and it remains unclear how the iterative number of repeating units function in the helicity inversion of polymer assemblies. Herein, we report the macroscopic helicity and dynamic manipulation of the chiroptical activity of supramolecular assemblies from discrete azobenzene‐containing oligomers (azooligomers), together with the helicity inversion and morphological transition achieved solely by changing the iterative chain lengths. The corresponding assemblies also differ from their polydisperse counterparts in terms of thermodynamic properties, chiroptical activities, and morphological control.

Diagnostic diagrams for ram pressure stripped candidates

ABSTRACT This paper presents a method for finding ram pressure stripped (RPS) galaxy candidates by performing a morphological analysis of galaxy images obtained from the Legacy survey. We consider a sample of about 600 galaxies located in different environments such as groups and clusters, tidally interacting pairs and the field. The sample includes 160 RPS previously classified in the literature into classes from J1 to J5, based on the increasing level of disturbances. Our morphological analysis was done using the astromorphlib software followed by the inspection of diagnostic diagrams involving combinations of different parameters like the asymmetry (A), concentration (C), Sérsic index (n), and bulge strength parameters $F(G,\, M_{20})$. We found that some of those diagrams display a distinct region in which galaxies classified as J3, J4, and J5 decouples from isolated galaxies. We call this region as the morphological transition zone and we also found that tidally interacting galaxies in pairs are predominant within this zone. Nevertheless, after visually inspecting the objects in the morphological transition zone to discard obvious contaminants, we ended up with 33 bona fide new RPS candidates in the studied nearby groups and clusters (Hydra, Fornax, and CLoGS sample), of which one-third show clear evidence of unwinding arms. Future works may potentially further increase significantly the samples of known RPS using such method.

Investigating the influence of thermal behavior on microstructure during solidification in laser powder bed fusion of AlSi10Mg alloys: A phase-field analysis

The utilization of the laser powder bed fusion (L-PBF) method in additive manufacturing experiments has revealed the intriguing potential to induce morphological evolutions within the solidification microstructure by manipulating the thermal conditions. Transitions of this nature can have a substantial impact on the ultimate texture and material properties of the product. This study utilizes numerical investigations to examine the microstructure evolution of the AlSi10Mg alloy, which is fabricated using the L-PBF process, under different thermal conditions. In order to investigate the changes in the microstructure, we employ a parameter phase-field (PF) model. This model effectively replicates the natural development of nuclei from inoculant particles and accurately simulates the transitions in the morphology. The PF model’s validity is determined through the numerical investigation of morphological transitions during directional solidification of the AlSi10Mg alloy. The model’s predictions are then compared to the analytical Hunt model. The formation of a columnar microstructure with a significantly reduced secondary dendrite arm spacing is observed when the ratio of the temperature gradient (G) to the solidification rate (R) is increased.

Different contributions of PROG1 and TAC1 to the angular kinematics of the main culm and tillers of wild rice (Oryza rufipogon).

PROG1is necessary but insufficient for the main culm inclination while TAC1partially takes part in it, and both genes promote tiller inclination in Asian wild rice. Asian wild rice (Oryza rufipogon), the ancestor of cultivated rice (O. sativa), has a prostrate architecture, with tillers branching from near the ground. The main culm of each plant grows upward and then tilts during the vegetative stage. Genes controlling tiller angle have been reported; however, their genetic contributions to the culm movement have not been quantified. Here, we quantified their genetic contributions to angular kinematics in the main culm and tillers. For the main culm inclination, one major QTL surrounding the PROG1 region was found. In cultivated rice, tillers firstly inclined and lately rose, while it kept inclining in wild rice. It was suggested that PROG1 affected the tiller elevation angle in the later kinematics, whereas TAC1 was weakly associated with the tiller angle in the whole vegetative stage. Micro-computed tomography (micro-CT) suggested that these angular changes are produced by the bending of culm bases. Because near-isogenic lines (NILs) of wild rice-type Prog1 and Tac1 alleles in the genetic background of cultivated rice did not show the prostrate architecture, the involvement of another gene(s) for inclination of the main culm was suggested. Our findings will not only contribute to the understanding of the morphological transition during domestication but also be used in plant breeding to precisely reproduce the ideal plant architecture by combining the effects of multiple genes.

In situ surface evolution dynamics of external-electric-field-triggered structural oscillation on Au(111)

Surface nanostructures serve as an essential role in determining intrinsic physical features and device performance in solid materials. Here, this work systematically investigates the surface dynamical evolution at the nanoscale on Au(111) induced by a “tip-to-surface” external electric field through a scanning tunneling microscope (STM). The Au(111) steps exhibit a “compact to fractal” reconstruction under a relatively high electric field, in which the transition is strengthened with increasing the applied electric field. Inversely, a “fractal to compact” morphological transition enables to be self-triggered at Au(111) surface steps upon a normal STM imaging electric field (very low). These two reversible structural changes are attributed to the diffusion-limited aggregation mechanism where the diffusion barriers were quantified as 0.64–0.75 eV varied with the regularity in step edges. In addition, we further simulate a “terrace-edge-kink” model to trace the effect of atomic coordination on structural transition, determining the surface step edge stability. This study presents insight into morphological and structural transformation at surface steps induced by variant external electric fields, establishing a deep understanding in the nature of surface evolution dynamics.

Construction of cobalt hexacyanoferrate multivoid nanoframes as efficient aqueous aluminum ion batteries

In the search for innovative materials for aqueous Al-ion batteries, Prussian blue analogs (PBAs) have drawn significant attention due to their open-framework structures. Yet, PBAs face challenges like restricted capacity and rapid capacity deterioration, primarily stemming from the scarcity of redox sites and their inherent structural instability. In the current research, a synthesis of Fe–Co PBA multivoid nanoframe structures was achieved through straightforward co-precipitation techniques, aimed at optimizing Al-ion storage. Key to enhancing their performance was the modulation of the hydrothermal self-assembly reaction duration. As a result of this modulation, a morphological transition from nanocubes to multivoid nanoframes became evident, leading to the exposure of a higher number of active sites. This morphological transition also minimized the effects of volumetric shifts during the electrochemical charge/discharge cycles. Performance analysis indicated that the Fe–Co PBA multivoid nanoframes demonstrated a stable specific capacity, reaching 43 mAh g⁻¹ over 2000 cycles at 0.5 A g⁻¹ . Impressively, even under the more demanding current density of 1 A g⁻¹ , the specific capacity remained a substantial 36 mAh g⁻¹ after the same number of cycles. Comprehensive ex situ evaluations further underscored the predominant charge storage mechanisms, highlighting the reversible redox activities of the involved transition metals, coupled with the insertion/extraction dynamics of Al³ ⁺ ions.

Solute trapping and non-equilibrium microstructure during rapid solidification of additive manufacturing

Solute transport during rapid and repeated thermal cycle in additive manufacturing (AM) leading to non-equilibrium, non-uniform microstructure remains to be studied. Here, a fully-coupled fluid dynamics and microstructure modelling is developed to rationalise the dynamic solute transport process and elemental segregation in AM, and to gain better understanding of non-equilibrium nature of intercellular solute segregation and cellular structures at sub-grain scale during the melting-solidification of the laser powder bed fusion process. It reveals the solute transport induced by melt convection dilutes the partitioned solute at the solidification front and promotes solute trapping, and elucidates the mechanisms of the subsequent microstructural morphology transitions to ultra-fine cells and then to coarse cells. These suggest solute trapping effect could be made used for reducing crack susceptibility by accelerating the solidification process. The rapid solidification characteristics exhibit promising potential of additive manufacturing for hard-to-print superalloys and aid in alloy design for better printability.

Effect of laser welding and laser wire filling on forming and properties of dissimilar steel welded joints

In order to study the effects of different welding methods and different butt gaps on the microstructure and properties of welded joints of steel with unequal thickness, the medium carbon steel of 2 mm 50CrV and low carbon steel of 6 mm SPHE were used as test materials, and the welding was carried out by single laser and laser wire filling welding. The results show that the laser wire filling welding can reduce the welding cracks, and with the increase of the butt gap, the melt height gradually decreases, and the weld morphology transitions from Y shape to H shape. With the increase of the butt gap, the weld defects form. The hardness of weld center decreases with the increase of butt gap. The average hardness of weld formed by laser welding alone is the highest, and the highest hardness of welded joint is located in the heat affected zone of 50CrV medium carbon steel. The tensile strength of welded joints first increases and then decreases with the increase of butt gaps. When the butt gap is 0.6 mm, the surface morphology is good and the tensile strength is the highest. The fracture position of the welding test is on the side of the 2 mm 50CrV medium carbon steel.

Respiration supports intraphagosomal filamentation and escape of Candida albicans from macrophages.

Candida albicans is a leading human fungal pathogen that often causes life-threatening infections in immunocompromised individuals. The ability of C. albicans to transition between yeast and filamentous forms is key to its virulence, and this occurs in response to many host-relevant cues, including engulfment by host macrophages. While previous efforts identified C. albicans genes required for filamentation in other conditions, the genes important for this morphological transition upon internalization by macrophages remained largely enigmatic. Here, we employed a functional genomic approach to identify genes that enable C. albicans filamentation within macrophages and uncovered a role for the mitochondrial ribosome, respiration, and the SNF1 AMP-activated kinase complex. Additionally, we showed that glucose uptake and glycolysis by macrophages support C. albicans filamentation. This work provides insights into the metabolic dueling that occurs during the interaction of C. albicans with macrophages and identifies vulnerabilities in C. albicans that could serve as promising therapeutic targets.

Chemical composition, antifungal, and anti-virulence action of the stem bark of Hancornia speciosa Gomes (Apocynaceae) against Candida spp.

Ethnopharmacological relevanceHancornia speciosa Gomes is a fruit and medicinal species used for treating infectious diseases of the genitourinary system. However, its mechanism of action against microbes is still not fully understood. Infections in the genitourinary system caused by Candida spp. are associated with its fungal resistance and pathogenicity. New plant-derived compounds are an alternative to fight these Candida infections. Aim of the studyThe objective of this study was to evaluate the anti-Candida effects of extracts of the stem bark of H. speciosa. This research investigated the chemical composition of sulfuric ether (EEHS) and methanolic (MEHS) extracts, their drug-modifying action on fluconazole, and their anti-virulence action on the morphological transition of Candida species. Materials and methodsThe extracts (EEHS and MEHS) of the stem bark of H. speciosa were chemically characterized via qualitative phytochemical screening and by liquid chromatography coupled with mass spectrometry (UPLC-MS-ESI-QTOF). The extracts were evaluated regarding their antifungal effects and fluconazole-modifying activity against Candida albicans, Candida krusei, and Candida tropicalis using the broth microdilution method. Additionally, the study evaluated the inhibition of fungal virulence in Candida species through morphological transition assays. ResultsThe phytochemical screening revealed the presence of anthocyanidins, anthocyanins, aurones, catechins, chalcones, flavones, flavonols, flavanones, leucoanthocyanidins, tannins (condensed and pyrogallic), and xanthones in both extracts of the stem bark of H. speciosa. The UPLC-MS-ESI-QTOF analysis identified the same compounds in both extracts, predominating phenolic compounds. Some compounds were first time recorded in this species: gluconic acid, cinchonain IIb, cinchonain Ib isomer, and lariciresinol hexoside isomers. Most of the intrinsic antifungal activity was observed for the MEHS against C. krusei (IC50: 58.41 μg/mL). At subinhibitory concentrations (MC/8), the EEHS enhanced the action of fluconazole against all Candida strains. The MEHS exhibited greater efficacy than fluconazole inhibiting C. krusei growth. The EEHS completely inhibited hyphae appearance and reduced pseudohyphae formation in C. albicans. ConclusionThe stem bark of H. speciosa is a rich source of bioactive compounds, especially phenolic. Phenolic compounds can have important roles in fighting infectious diseases of the genitourinary system, such as candidiasis. The extracts of H. speciosa improved the action of the drug fluconazole against Candida species, inhibited hyphae appearance, and reduced pseudohyphae formation. The results of this study can support the development of new therapeutics against resistant strains of Candida.

Effects of solutes and freezing front velocity on ice morphology in frozen ovine milk

Ovine milk is sometimes stored frozen until processing, and deterioration has been observed during frozen storage. Mechanisms for degradation have been proposed involving morphology of the frozen product. Freezing is also integral to freeze-drying, sometimes applied to ovine milk. Knowledge of factors influencing the frozen morphology in ovine milk may help avoid degradation or aid freeze-drying.Fractions were prepared from ovine milk and used to build milks of decreasing complexity from whole milk, skim milk, skim milk less casein (removed centrifugally), ovine milk ultrafiltration permeate and finally water. Cryo-Scanning-Electron Microscopy, and optical microscopy with a custom-built Bridgman furnace format freezing stage, were used to investigate the static morphology of frozen milk and then the morphology of advancing freezing fronts in ovine milk. Milk frozen slowly showed a significantly different morphology in the frozen state to milk that was frozen rapidly. The morphology of the freezing front was observed to change as the velocity increased, and as the composition of the sample being frozen changed. Increased freezing front velocities lead to the formation of columnar and then dendritic ice morphologies, and the freezing front velocities that lead to transitions in morphology increased with decreasing fluid complexity. A phase diagram was generated showing ice morphology on axes representing solution complexity and ice front velocity.Knowledge gained from the observations was used to design rapid freezing processes that preserve fresh milk properties, which have since been patented.

Biological effects of trans, trans-farnesol in Leishmania amazonensis.

Farnesol, derived from farnesyl pyrophosphate in the sterols biosynthetic pathway, is a molecule with three unsaturations and four possible isomers. Candida albicans predominantly secretes the trans, trans-farnesol (t, t-FOH) isomer, known for its role in regulating the virulence of various fungi species and modulating morphological transition processes. Notably, the evolutionary divergence in sterol biosynthesis between fungi, including Candida albicans, and trypanosomatids resulted in the synthesis of sterols with the ergostane skeleton, distinct from cholesterol. This study aims to assess the impact of exogenously added trans, trans-farnesol on the proliferative ability of Leishmania amazonensis and to identify its presence in the lipid secretome of the parasite. The study involved the addition of exogenous trans, trans-farnesol to evaluate its interference with the proliferation of L. amazonensis promastigotes. Proliferation, cell cycle, DNA fragmentation, and mitochondrial functionality were assessed as indicators of the effects of trans, trans-farnesol. Additionally, lipid secretome analysis was conducted, focusing on the detection of trans, trans-farnesol and related products derived from the precursor, farnesyl pyrophosphate. In silico analysis was employed to identify the sequence for the farnesene synthase gene responsible for producing these isoprenoids in the Leishmania genome. Exogenously added trans, trans-farnesol was found to interfere with the proliferation of L. amazonensis promastigotes, inhibiting the cell cycle without causing DNA fragmentation or loss of mitochondrial functionality. Despite the absence of trans, trans-farnesol in the culture supernatant, other products derived from farnesyl pyrophosphate, specifically α-farnesene and β-farnesene, were detected starting on the fourth day of culture, continuing to increase until the tenth day. Furthermore, the identification of the farnesene synthase gene in the Leishmania genome through in silico analysis provided insights into the enzymatic basis of isoprenoid production. The findings collectively offer the first insights into the mechanism of action of farnesol on L. amazonensis. While trans, trans-farnesol was not detected in the lipid secretome, the presence of α-farnesene and β-farnesene suggests alternative pathways or modifications in the isoprenoid metabolism of the parasite. The inhibitory effects on proliferation and cell cycle without inducing DNA fragmentation or mitochondrial dysfunction raise questions about the specific targets and pathways affected by exogenous trans, trans-farnesol. The identification of the farnesene synthase gene provides a molecular basis for understanding the synthesis of related isoprenoids in Leishmania. Further exploration of these mechanisms may contribute to the development of novel therapeutic strategies against Leishmania infections.

Dysregulation of the endoplasmic reticulum blocks recruitment of centrosome-associated proteins resulting in mitotic failure.

The endoplasmic reticulum (ER) undergoes a remarkable transition in morphology during cell division to aid in the proper portioning of the ER. However, whether changes in ER behaviors modulate mitotic events is less clear. Like many animal embryos, the early Drosophila embryo undergoes rapid cleavage cycles in a lipid-rich environment. Here, we show that mitotic spindle formation, centrosomal maturation, and ER condensation occur with similar time frames in the early syncytium. In a screen for Rab family GTPases that display dynamic function at these stages, we identified Rab1. Rab1 disruption led to an enhanced buildup of ER at the spindle poles and produced an intriguing 'mini-spindle' phenotype. ER accumulation around the mitotic space negatively correlates with spindle length/intensity. Importantly, centrosomal maturation is defective in these embryos, as mitotic recruitment of key centrosomal proteins is weakened after Rab1 disruption. Finally, division failures and ER overaccumulation is rescued by Dynein inhibition, demonstrating that Dynein is essential for ER spindle recruitment. These results reveal that ER levels must be carefully tuned during mitotic processes to ensure proper assembly of the division machinery.

Morphogenetic transitions in the adaptation of Candida albicans to the mammalian gut

Candida albicans is a pathobiont in humans that forms part of the mycobiota in healthy individuals and can cause different pathologies upon alterations of the host defenses. The mammalian gut is clinically relevant as this niche is the most common pool for bloodstream-derived infections. The ability of C. albicans to switch from yeast to hypha has been related to the commensal-to-pathogen transition and is, therefore, considered relevant in virulence. Recently, filaments have been implicated in the humoral response in the gut. C. albicans exhibits other morphologies that play different roles in pathogenicity and commensalism. This review focuses on the role of these morphological transitions in C. albicans proliferation and its establishment as a commensal in the mammalian gut, paying special attention to the transcription factors involved in their regulation.

Controlling carbon nanostructure synthesis in thermal plasma jet: Correlation of process parameters, plasma characteristics, and product morphology

Thermal plasma has emerged as an effective approach for producing carbon nanostructures without the need for specific catalysts nor substrates. While efforts have focused on the effect of process parameters such as reaction pressure, input power or carbon source, the intricate role and relationship with plasma characteristics like density and temperature are often overlooked due to the complexity of the environment. This study addresses this gap by establishing a correlation between process parameters, plasma characteristics, and product morphology, essential for controlling the growth of carbon nanostructures. We explored the impact of carbon precursor type (CH4 and C2H2), hydrogen, pressure, and flow rate on nanostructure formation. Using in situ optical emission spectroscopy (OES), we mapped the distribution of both temperature and dicarbon molecule (C2) density within the plasma jet. We demonstrate that the growth of low-density nanostructures, such as carbon nanohorns (CNHs), is favoured at dilute C2 local densities and high temperatures, while denser nanostructures, such as onion-like polyhedral graphitic nanocapsules (GNCs), are favoured at higher C2 densities and lower temperatures. The carbon density can be controlled by the flow rate and the pressure, which in turn significantly influence the nanostructure morphology, evolving from graphene nanoflakes (GNFs) to GNCs as either parameter increases. Increasing the H/C ratio from 1 to 8 resulted in a morphological transition from CNHs to GNFs. During the synthesis, the plasma jet temperature surpassed 3000 K, with crystalline growth occurring 50–100 mm below the nozzle.

In situ experiments in microgravity and phase-field simulations of the lamellar-to-rod transition during eutectic growth

In recent experiments on the solidification of the binary eutectic alloy succinonitrile-(D)camphor carried out on board of the International Space Station (ISS), a transition from rod to lamellar patterns was observed for low growth velocities. The transition was interpreted in terms of a competition between a propagative instability of lamellae and a drift induced by a transverse temperature gradient. Phase-field simulations of a symmetric model alloy support this scenario: for a fixed transverse temperature gradient, the transition from rods to lamellae occurs for a critical composition at fixed velocity, and for a critical velocity at fixed composition. Since the alloy and control parameters used in experiments and simulations are different, our results strongly suggest that this morphological transition is generic for eutectic alloys.