Morphological Transition Research Articles

SEM and TEM Image Analysis for Morphology and Phase Transition of CZTS, Sb2Se3 and Perovskite Thin Films under Thermal Stress

SEM and TEM Image Analysis for Morphology and Phase Transition of CZTS, Sb2Se3 and Perovskite Thin Films under Thermal Stress

Role of Stretching-induced Crystallization on Mesoscale Morphology Transition of UHMWPE during Hot Stretching

Role of Stretching-induced Crystallization on Mesoscale Morphology Transition of UHMWPE during Hot Stretching

Spontaneous Formation of Polymeric Nanoribbons in Water Driven by π–π Interactions

AbstractA simple method was developed to produce polymeric nanoribbons and other nanostructures in water. This approach incorporates a perylene diimide (PDI) functionalized by triethylene glycol (TEG) as a hydrophobic supramolecular structure directing unit (SSDU) into the core of hydrophilic poly(N,N‐dimethylacrylamide) (PDMAc) chains using RAFT polymerization. All PDI‐functional polymers dissolved spontaneously in water, forming different nanostructures depending on the degree of polymerization (DPn): nanoribbons and nanocylinders for DPn=14 and 22, and spheres for DPn>50 as determined by cryo‐TEM and SAXS analyses. UV/Vis absorption spectroscopy was used to monitor the evolution of the PDI absorption signal upon dissolution. In solid form, all polymers show a H‐aggregate absorption signature, but upon dissolution in water, the shortest DPn forming nanoribbons evolved to show HJ‐aggregate absorption signals. Over time, the J‐aggregate band increased in intensity, while cryo‐TEM monitoring evidenced an increase in the nanoribbon's width. Heating the nanoribbons above 60 °C, triggered a morphological transition from nanoribbons to nanocylinders, due to the disappearance of J‐aggregates, while H‐aggregates were maintained. The study shows that the TEG‐PDI is a powerful SSDU to promote 2D or 1D self‐assembly of polymers depending on DPn through simple dissolution in water.

Spontaneous Formation of Polymeric Nanoribbons in Water Driven by π-π Interactions.

A simple method was developed to produce polymeric nanoribbons and other nanostructures in water. This approach incorporates a perylene diimide (PDI) functionalized by triethylene glycol (TEG) as a hydrophobic supramolecular structure directing unit (SSDU) into the core of hydrophilic poly(N,N-dimethylacrylamide) (PDMAc) chains using RAFT polymerization. All PDI-functional polymers dissolved spontaneously in water, forming different nanostructures depending on the degree of polymerization (DPn): nanoribbons and nanocylinders for DPn=14 and 22, and spheres for DPn>50 as determined by cryo-TEM and SAXS analyses. UV/Vis absorption spectroscopy was used to monitor the evolution of the PDI absorption signal upon dissolution. In solid form, all polymers show a H-aggregate absorption signature, but upon dissolution in water, the shortest DPn forming nanoribbons evolved to show HJ-aggregate absorption signals. Over time, the J-aggregate band increased in intensity, while cryo-TEM monitoring evidenced an increase in the nanoribbon's width. Heating the nanoribbons above 60 °C, triggered a morphological transition from nanoribbons to nanocylinders, due to the disappearance of J-aggregates, while H-aggregates were maintained. The study shows that the TEG-PDI is a powerful SSDU to promote 2D or 1D self-assembly of polymers depending on DPn through simple dissolution in water.

Nanoscale wettability characterization—Interpreting droplet morphological evolution in nanopores

AbstractNanoscale wettability, crucial for various disciplines in science and engineering, challenges traditional theory, particularly the Young's equation. This study proposes and validates a modified format of the Young's equation under nano‐confinement and, for the first time, the nano‐confined droplet morphological evolution and transition are investigated from thermodynamic theories and molecular dynamics simulation. The morphologies of droplets in nano‐silts, identified as double‐cap, single‐cap, and bridge‐shaped, underscore the critical roles of line tension and nano‐confinement in characterizing wetting behavior. In hydrophobic nano‐slits, droplets transition from the double‐cap to the single‐cap shape at the critical point of = 0.31 and to bridge shape at the critical point of = 0.40. Moreover, the relative width of the neck region in the bridge‐shaped droplets is found to stabilize at ratio of 1.8. Particularly, linear relationships have been established between the droplet contact angle and the parameter , which identify condensation and breakage of droplets within hydrophobic nano‐slits. This model effectively characterizes nanoscale wettability, with precise droplet behavior predictions, which could be beneficial to enhance nano‐fluid dynamics understanding and its applications in science and engineering.

Amyloid-like Aggregation Propensities of Metabolites- Homogentisic Acid, N-Acetyl Aspartic Acid and Isovaleric Acid.

The transformation of metabolites into amyloidogenic aggregates represent an intriguing dimension in the pathophysiology of metabolic disorders, including alkaptonuria, canavan disease, and isovaleric acidemia. Central to this phenomenon are the metabolites homogentisic acid (HA), N-acetyl aspartic acid (NAA), and isovaleric acid (IVA), which we found, weave an intricate network of self-assembled structures. Leveraging an array of microscopy techniques, we traced the morphological behavior of these assemblies that exhibit concentration and time-dependent morphological transitions from isolated globules to clustered aggregates. MD simulation studies suggest significant role of hydrogen bonding interactions in the aggregation process. While displaying strong amyloidogenic propensity in solution, these aged aggregates were significantly cytotoxic to mouse neural N2a cell lines. In vivo effect in Caenorhabditis elegans (C. elegans) nematode further validated cytotoxicity of aggregates. Our findings provide fresh insights to amyloidogenic nature of HA, NAA, and IVA aggregates and their possible role in associated metabolic disorders such as alkaptonuria, canavan disease and isovaleric acidemia.

Deciphering the molecular mechanism underlying morphology transition in two-component DNA-protein cophase separation.

Nucleic acid and protein co-condensates exhibit diverse morphologies crucial for fundamental cellular processes. Despite many previous studies that advanced our understanding of this topic, several interesting biophysical questions regarding the underlying molecular mechanisms remain. We investigated DNA and human transcription factor p53 co-condensates-a scenario where neither dsDNA nor the protein demonstrates phase-separation behavior individually. Through a combination of experimental assays and theoretical approaches, we elucidated: (1) the phase diagram of DNA-protein co-condensates at a certain observation time, identifying a phase transition between viscoelastic fluid and viscoelastic solid states, and a morphology transition from droplet-like to "pearl chain"-like co-condensates; (2) the growth dynamics of co-condensates. Droplet-like and "pearl chain"-like co-condensates share a common initial critical microscopic cluster size at the nanometer scale during the early stage of phase separation. These findings provide important insights into the biophysical mechanisms underlying multi-component phase separation within cellular environments.

Effects of hydrogen blending ratios and CO2 on hydrogen embrittlement of X65 steel in high-pressure offshore hydrogen-blended natural gas pipelines

In this study, the effects of hydrogen blending ratios and high CO2 content on hydrogen embrittlement (HE) of offshore natural gas X65 pipeline steel were investigated. In high-pressure hydrogen gas, the impact of hydrogen content on yield strength and tensile strength was minimal. However, the effect on elongation was more significant, with the area decreasing and the HE index increasing until the hydrogen-blended ratio approached 30%, at which point the HE index reached 8.94%. Introducing CO2 into high-pressure hydrogen-rich gas further increased the HE index with high CO2 content. At 40% CO2, the HE index was 2.42 times higher than in high-pressure hydrogen-blended mixtures (30% H2). Additionally, the local fracture morphology transitions from ductile to quasi-cleavage fracture with the addition of CO2 and H2.

Electrophysiological characteristics of lead-position-dependent electrogram uninterrupted transition during left bundle branch pacing

BackgroundThe interrupted technique of left bundle branch pacing (LBBP) limits the continuous monitoring of paced electrocardiogram (ECG) and intracardiac electrogram (EGM) transitions, which may result in overlooked or misinterpreted subtle transitions. ObjectivesThis study aimed to explore the electrophysiological characteristics of lead position-dependent EGM continuous transition to evaluate lead depth and investigate the clinical significance of transseptal pacing modalities. MethodsA continuous pacing and recording technique enabled by a rotatable connector was employed to allow the real-time monitoring of progressive changes in paced EGM and ECG morphology. Careful observations were conducted to evaluate whether there were significant changes in the amplitude and morphology of the ventricular current of injury (COI), R-wave peak times of V1 and V6, QRS duration, and impedance at different interventricular septal depths. ResultsThe study included 105 patients. Nonselective LBBP was achieved in 94 (89.5 %) patients, of whom 88 (83.8%) achieved selective LBBP (SLBBP). Left ventricular septal pacing was confirmed in 11 (11.5 %) patients. The amplitude of ventricular EGM predictably changed with radial septum depth and peaked in the interventricular septum (26.3±11.3 mV). As the lead was inserted into the left ventricular subendocardium, the ventricular COI declined to a level approximating that of the right septum (11.7 ± 6.3 mV for SLBBP versus 10.4 ± 5.8 mV for right ventricular septal pacing). When selective LBB capture occurred, significant morphological transitions in the ventricular COI were observed in the unfiltered EGM. ConclusionsThe continuous recording technique provides a more detailed understanding of pacing lead radial depth throughout implantation. COI amplitude and morphology variations can identify different pacing modalities, particularly in recognizing SLBBP.

Biochar as a UV Stabilizer: Its Impact on the Photostability of Poly(butylene succinate) Biocomposites.

In the present study, biocomposite materials were created by incorporating biochar (BC) at rates of 1, 2.5, and 5 wt.% into a poly(butylene succinate) (PBSu) matrix using a two-stage melt polycondensation procedure in order to provide understanding of the aging process. The biocomposites in film form were exposed to UV irradiation for 7, 14, and 21 days. Photostability was examined by several methods, such as Fourier transform infrared spectroscopy (FTIR), which proved that new carbonyl and hydroxyl groups were formed during UV exposure. Moreover, Differential Scanning Calorimetry (DSC) measurements were employed to record the apparent UV effect in their crystalline morphology and thermal transitions. According to the molecular weight measurements of composites, it was apparent that by increasing the biochar content, the molecular weight decreased at a slower rate. Tensile strength tests were performed to evaluate the deterioration of their mechanical properties during UV exposure, while Scanning Electron Microscopy (SEM) images illustrated the notable surface alternations. Cracks were formed at higher UV exposure times, to a lesser extent in PBSu/BC composites than in neat PBSu. Furthermore, the mechanism of the thermal degradation of neat PBSu and its biocomposites prior to and upon UV exposure was studied by Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). From all the obtained results it was proved that biochar can be considered as an efficient UV-protective additive to PBSu, capable of mitigating photodegradation.

Investigating Charge-Induced Transformations of Metal Nanoparticles in a Radically-Inert Liquid: A Liquid-Cell TEM Study.

We present a novel in situ liquid-cell transmission electron microscopy (TEM) approach to study the behavior of metal nanoparticles under high-energy electron irradiation. By utilizing a radically-inert liquid environment, we aim to minimize radiolysis effects and explore the influence of charge-induced transformations. We observed complex dynamics in nanoparticle behavior, including morphological changes and transitions between amorphous and crystalline states. These transformations are attributed to the delicate interplay between charge accumulation on the nanoparticles and enhanced radiolysis, suggesting a significant role for charge-assisted processes in nanoparticle evolution. Our findings provide valuable insights into the fundamental mechanisms driving nanoparticle behavior at the nanoscale and demonstrate the potential of liquid-cell TEM for studying complex physicochemical processes in controlled environments.

Influence of Si Content on the Microstructure, Wear Resistance, and Corrosion Resistance of FeCoNiCrAl0.7Cu0.3Six High Entropy Alloy

This study explores microstructure, wear, and corrosion resistance properties of FeCoNiCrAl0.7Cu0.3Six (x = 0, 0.2, 0.3, 0.5) high-entropy alloys. The FeCoNiCrAl0.7Cu0.3Six alloy contains FCC and BCC structures; as the x increases, the FeCoNiCrAl0.7Cu0.3Si0.2, FeCoNiCrAl0.7Cu0.3Si0.4, and FeCoNiCrAl0.7Cu0.3Si0.5 high-entropy alloys transition to BCC structures. The morphological transition in FeCoNiCrAl0.7Cu0.3Six evolves from bamboo leaf-like intergranular features to a discontinuous intergranular structure as Si content increases. The hardness of these alloys gradually increases with higher Si content. The addition of Si promotes a uniform distribution of Cr within and between grains, reducing the intergranular segregation of Cu. Al and Ni show a consistent pattern of elemental distribution throughout the alloy. Wear measurements of FeCoNiCrAl0.7Cu0.3Six alloys demonstrate that adding Si enhances wear resistance, resulting in smoother wear surfaces with reduced deformation. The wear mechanism for all alloys is primarily abrasive, with no brittle fractures observed. Corrosion resistance is optimized when Si content is 0.2, with pitting corrosion being the primary corrosion form.

Predicting rapid adaptation in time from adaptation in space: A 30-year field experiment in marine snails

Predicting the outcomes of adaptation is a major goal of evolutionary biology. When temporal changes in the environment mirror spatial gradients, it opens up the potential for predicting the course of adaptive evolution over time based on patterns of spatial genetic and phenotypic variation. We assessed this approach in a 30-year transplant experiment in the intertidal snail Littorina saxatilis . In 1992, snails were transplanted from a predation-dominated environment to one dominated by wave action. On the basis of spatial patterns, we predicted transitions in shell size and morphology, allele frequencies at positions throughout the genome, and chromosomal rearrangement frequencies. Observed changes closely agreed with predictions and transformation was both dramatic and rapid. Hence, adaptation can be predicted from knowledge of the phenotypic and genetic variation among populations.

Effect of quenching protocols on microstructure and corrosion morphology in a recycled Al–Mg–Si alloy: Tracing Cu impurities

In the present work, three different quenching protocols - water quenching (WQ), forced air quenching (FAQ) and air quenching (AQ) - were utilized to tailor the intragranular and intergranular preference of Cu impurities in a recycled AA6082 alloy. It is found that Cu tends to be incorporate in the precipitates at grain boundaries in the WQ-treated alloys. However, both AQ and FAQ protocols interestingly eliminate such intergranular Cu enrichment, consequently sequestering Cu solutes in (Mg, Si)-rich precipitates in grain interiors. As the quenching rates decrease, the FAQ- and AQ-treated alloys resultantly exhibit a positive shift in pitting potential, which is accompanied by a transition in corrosion morphology from boundary attack to pitting, with a notable reduction in corrosion depth.

Fluctuation-driven morphological patterning: An unconventional approach to morphogenesis

Recent experimental investigations into regeneration revealed a remarkable phenomenon: the morphological transformation of a tissue fragment from the incipient spherical configuration to a tubelike structure—the hallmark of a mature —has the dynamical characteristics of a first-order phase transition, with calcium field fluctuations within the tissue playing an essential role. This morphological transition was shown to be generated by activation over a barrier within an effective morphological potential that underlies morphogenesis. Inspired by this intriguing insight, we propose an unconventional mechanism where stochastic fluctuations drive the emergence of morphological patterns. Thus, the inherent fluctuations determine the nature of the dynamics and are not incidental noise in the background of the otherwise deterministic dynamics. Instead, they play an important role as a driving force that defines the attributes of the pattern formation dynamics and the nature of the transition itself. Here, we present a simple model that captures the essence of this mechanism for morphological pattern formation. Specifically, we consider a one-dimensional tissue arranged as a closed contour embedded in a two-dimensional space, where the local curvature of the contour is coupled to a non-negative scalar field. An effective temperature parameter regulates the strength of the fluctuations in the system. The tissue exhibits fluctuations near a circular shape at sufficiently low coupling strengths, but as the coupling strength exceeds some critical value, the circular state becomes unstable. The nature of the transition to the new state, namely whether it is a first-order-like or second-order-like transition, depends on the effective temperature and the effective cutoff on the wavelength of the spatial variations in the system. The former sets the level of noise, while the latter determines the height of the potential barrier between the initial circular state and the final deformed state of the tissue. It is also found that entropic barriers separate various metastable states of the system. Published by the American Physical Society 2024

Impact of human-induced alterations in bathymetry and geometry on tidal and salt dynamics: Thresholds for morphological dimensions in a convergent estuary

Estuary morphology changes significantly with intensive human intervention, resulting in dynamic structural variations in the estuary. However, little is known about the threshold sizes of estuary morphology that ensure water security. A two-dimensional width-averaged semi-analytical model is applied to explore the impacts of human-induced alterations in bathymetry and geometry on tidal and salt dynamics in Lingdingyang Bay (LDYB). Salt flux (Fs) is positively correlated with tidal flux (Ft) and negatively correlated with tidal energy flux (Fte). Greater geometric convergence reduces Ft and increase Fte. Increased water depth increases Ft and Fte. Thus, both greater geometric convergence and increased bathymetry enhance tidal hydrodynamics. Saltwater transport is weakened by greater geometric convergence and enhanced by increasing water depth. Sensitivity experiments are conducted using maximum water level and salt intrusion length as the criterion. Thresholds for morphological sizes in the LDYB are found to be a convergence ratio (convergence length over mouth width,LcB0) of 0.83–0.88 and a combined depth factor (α) of 1.04–1.07. Moreover, transition of the estuarine morphology from an exponential convergent shape to a prismatic shape had a limited effect on tidal hydrodynamics when the convergent length rate (e-folding convergence length over total convergence length,LeLc) is >0.61. These results notice that human activities, such as reclamation and tidal channel dredging, exacerbate the risk of salt intrusion and should be applied with caution.

Histone-like transcription factor Hfl1p in Candida albicans harmonizes nuclear and mitochondrial genomic network in regulation of energy metabolism and filamentation development

ABSTRACT Candida albicans is an opportunistic fungal pathogen known for surviving in various nutrient-limited conditions within the host and causing infections. Our prior research revealed that Hfl1p, an archaeal histone-like or Hap5-like protein, is linked to mitochondrial ATP generation and yeast-hyphae morphogenesis. However, the specific roles of Hfl1p in these virulence behaviours, through its function in the CBF/NF-Y complex or as a DNA polymerase II subunit, remain unclear. This study explores Hfl1p’s diverse functions in energy metabolism and morphogenesis. By combining proteomic analysis and phenotypic evaluations of the hfl1Δ/hfl1Δ mutant with ChIP data, we found that Hfl1p significantly impacts mitochondrial DNA-encoded CI subunits, the tricarboxylic acid (TCA) cycle, and morphogenetic pathways. This influence occurs either independently or alongside other transcription factors recognizing a conserved DNA motif (TAXXTAATTA). These findings emphasize Hfl1p’s critical role in linking carbon metabolism and mitochondrial respiration to the yeast-to-filamentous form transition, enhancing our understanding of C. albicans’ metabolic adaptability during morphological transition, an important pathogenic trait of this fungus. This could help identify therapeutic targets by disrupting the relationship between energy metabolism and cell morphology in C. albicans.

Fabrication of Hierarchical Nanostructures featuring Amplified Asymmetry through Co‐assembly of Liquid Crystalline Block Copolymer and Chiral Amphiphiles

The widespread presence of hierarchical asymmetric structures in nature has sparked considerable interest because of their unique functionalities. These ingenious structures across multiple scales often emerge from the transfer and amplification of asymmetry from chiral molecules under various synergistic effects. However, constructing artificial chiral asymmetric structures, particularly in developing hierarchical multicomponent structures analogous to those formed in nature through synergistic non‐covalent interactions, still presents tremendous challenges. Herein, we propose a co‐assembly strategy to fabricate hierarchical chiral mesostructures by combining a liquid crystalline block copolymer (LC‐BCP) with a small molecular amphiphile containing chiral alanine or phenylalanine as a linker. Through a classic solvent‐exchange process, chiral amphiphiles embedded within LC‐BCP finely regulate the LC ordering effect and facilitate transfer and amplification of asymmetry. Consequently, various co‐assembled structures with significant hierarchical chirality features are obtained through synergetic effects. Remarkably, subtle alterations to the side groups of amino acids in the amphiphiles effectively adjust the hierarchical morphology transition. Moreover, the covalent bonding sequence of amino acids in the amphiphiles emerges as a critical factor governing the formation of hierarchical nanofibers and multilayered vesicles exhibiting a superhelical sense.

Fabrication of Hierarchical Nanostructures Featuring Amplified Asymmetry Through Co-Assembly of Liquid Crystalline Block Copolymer and Chiral Amphiphiles.

The widespread presence of hierarchical asymmetric structures in nature has sparked considerable interest because of their unique functionalities. These ingenious structures across multiple scales often emerge from the transfer and amplification of asymmetry from chiral molecules under various synergistic effects. However, constructing artificial chiral asymmetric structures, particularly in developing hierarchical multicomponent structures analogous to those formed in nature through synergistic non-covalent interactions, still presents tremendous challenges. Herein, we propose a co-assembly strategy to fabricate hierarchical chiral mesostructures by combining a liquid crystalline block copolymer (LC-BCP) with a small molecular amphiphile containing chiral alanine or phenylalanine as a linker. Through a classic solvent-exchange process, chiral amphiphiles embedded within LC-BCP finely regulate the LC ordering effect and facilitate transfer and amplification of asymmetry. Consequently, various co-assembled structures with significant hierarchical chirality features are obtained through synergetic effects. Remarkably, subtle alterations to the side groups of amino acids in the amphiphiles effectively adjust the hierarchical morphology transition. Moreover, the covalent bonding sequence of amino acids in the amphiphiles emerges as a critical factor governing the formation of hierarchical nanofibers and multilayered vesicles exhibiting a superhelical sense.

PH-induced morphological reversible transition from microparticles to vesicles for effective bacteria entrapment

Polymer particles with stimuli-responsive properties offer promising applications in healthcare, chemical reactors, development of artificial cells and organelles, as well as in the entrapment of bacteria. In this study, a novel biocompatible, biodegradable, and pH-responsive diblock copolymer based on polylactide (PLA) and poly(2-(diisopropylamino)ethyl methacrylate) (PDPA) was synthesized via a metal-free one-pot/simultaneous ring-opening polymerization (ROP) and reversible addition-fragmentation chain transfer (RAFT) approach (ROP/RAFT). This copolymer was then employed to produce highly monodisperse microparticles using microfluidics droplet generation technique. Utilizing confocal microscopy imaging, a reversible pH-induced morphological transition from microparticles to vesicle-like structures was observed at pH 5.1. The reversible shift in morphology from microparticles to giant vesicles (Vs) in acidic environments is triggered by the protonation of amino groups of the PDPA block, rendering vesicle surfaces positively charged − an advantageous feature for attracting and engulfing negatively charged bacteria. Initial validation involved electrostatic interactions with negatively charged latex resin beads followed by assessing interaction capabilities with gram-negative bacteria, Escherichia coli (E. coli). Additionally, the reversible morphological transition of microparticles-to-vesicles was employed to study drug release at different pHs. This approach proven to be a promising strategy for targeted drug delivery and bacteria entrapment using smart pH-responsive microparticles.