Transmission Electron Microscopy Research Articles

Scanning Transmission Electron Microscopy Analysis of the Si(111)–AlN–GaN Nanowire Interface Grown by Polarity‐ and Site‐Controlled Growth Method

In GaN‐on‐Si nanowire integration schemes, where the nanowires are contacted through the substrate, the interfaces between silicon substrate, AlN buffer layer, and GaN nanowire are of high interest. Herein, analysis by scanning transmission electron microscopy (STEM) of GaN nanowires grown on Si(111) by metal–organic vapor phase epitaxy using a polarity‐ and site‐controlled growth method is presented. This method is based on prestructuring the substrate, ex situ oxidation of the surface, and in situ oxide layer desorption. First, an AlN layer is grown to prevent melt‐back etching. Samples are prepared for STEM by focused ion beam cutting. STEM measurements in three different regions reveal that the AlN buffer material is polycrystalline. The degree of polycrystallinity is found to depend on the observed region: the highest degree exists at the field area between nanowires and the lowest at the sidewall of the Si‐pillars. On the sidewall, the ‐direction of the AlN grain is tilted by 30.1° with regard to the Si{111} sidewall plane, leading to reduced lattice mismatch at this location. The growth of GaN is competing with diffusion of Ga atoms through grain boundaries. The dominant mechanism is dependent on the region, leading to site‐controlled growth of nanowires.

Effect of the Pyrolysis Environment in a Complex Compound in the Synthesis of In0.6Ga0.4N Powders and their Characterization

In this work, the comparison between nitrogen and air synthesis environments in obtaining In0.6Ga0.4N powders is presented, and the effect of how the air environment can reduce the pyrolysis temperature of In0.6Ga0.4N powders to 271 °C using the thermal gravimetric analysis, and derivative thermogravimetry methods. X‐ray diffraction patterns demonstrate the presence of a cubic phase in nanocrystallites, in addition to less presence of the hexagonal phase. In contrast, scanning electron microscopy micrographs show a surface morphology of irregular agglomerates with a porous appearance and the presence of nonuniform plates. Energy‐dispersive spectroscopy and X‐ray photoelectron spectroscopy spectra demonstrate the presence of elemental contributions of gallium, indium, and nitrogen. At the same time, transmission electron microscopy shows the cubic structure and an interplanar distance of 2.7 Å for the (200) plane. Raman scattering shows the presence of E2(high) vibration mode for the hexagonal phase with a value of 560 cm−1. Finally, the photoluminescence spectrum shows an energy emission at 1.39 eV (886 nm), which is associated with the emission of the In0.6Ga0.4N powders.

From STEM-EDXS data to phase separation and quantification using physics-guided NMF

Abstract We present the development of a new algorithm which combines state-of-the-art energy-dispersive X-ray (EDX) spectroscopy theory and a suitable machine learning formulation for the hyperspectral unmixing of scanning transmission electron microscope EDX spectrum images. The algorithm is based on non-negative matrix factorization (NMF) incorporating a physics-guided factorization model. It optimizes a Poisson likelihood, under additional simplex constraint together with user-chosen sparsity-inducing and smoothing regularizations, and is based on iterative multiplicative updates. The fluorescence of X-rays is fully modeled thanks to state-of-the-art theoretical work. It is shown that the output of the algorithm can be used for a direct chemical quantification. With this approach, it is straightforward to include a priori knowledge on the specimen such as the presence or absence of certain chemical elements in some of its phases. This work is implemented within two open-source Python packages, espm and emtables, which are used here for data simulation, data analysis and quantification. Using simulated data, we demonstrate that incorporating physical modeling in the decomposition helps retrieve meaningful components from spatially and spectrally mixed phases, even when the data are very noisy. For synthetic data with a higher signal, the regularizations yield a tenfold increase in the quality of the reconstructed abundance maps compared to standard NMF. Our approach is further validated on experimental data with a known ground truth, where state-of-the art results are achieved by using prior knowledge about the sample. Our model can be generalized to any other scanning spectroscopy techniques where underlying physical modeling can be linearized.

Effects of CFTR-ENaC on spinal cord edema after spinal cord injury

Abstract Objective To explore the role of cystic fibrosis transmembrane conduction regulator (CFTR)-Epithelial sodium channel (ENaC) in spinal cord edema after spinal cord injury (SCI) and the related mechanism. Methods Lipopolysaccharide (LPS)-treated M1830 astrocytes were applied as the SCI in vitro model. Immunohistochemistry, real-time PCR, and Western blotting were utilized to detect CFTR and ENaC expression. Enzyme-linked immunosorbent assay was used to measure inflammatory cytokines including TNF-α, IL-1β, IL-6, and IL-18. Transmission electron microscope examined ultrastructure changes, while CFTR-172 or Capsazepine treatment assessed their effects on edema and inflammation. Western blot analysis was employed to evaluate the PI3K, p-PI3K, AKT, and p-AKT signaling pathways in treated cells. Results LPS-treated M1830 cells exhibited increased levels of CFTR and pro-inflammatory cytokines, including TNF-α, IL-1β, IL-6, and IL-18, alongside decreased ENaC expression and suppressed p-PI3K/PI3K and p-AKT/AKT levels. Degeneration of the myelin sheath and axons was observed in LPS-treated M1830, while changes in ultrastructural were recovered after adding CFTR-172 or Capsazepine. The level of CFTR, TNF-α, IL-1β, IL-6, and IL-18 was decreased, while the level of ENaC, p-PI3K/PI3K, and p-AKT/AKT was increased obviously in LPS-treated M1830 with CFTR-172, Capsazepine, or IGF-1. Conclusion Down-regulation of CFTR and up-regulation of ENaC can attenuate inflammation in SCI by activating the PI3K/AKT signaling pathway, highlighting a new therapeutic approach for SCI treatment. These findings address a critical gap in current SCI treatments and suggest a novel intervention strategy targeting ion channel regulation.

Leaf Anatomical Adaptation and Chloroplast Ultrastructure Changes Upon Magnesium Foliar Application of Faba Bean (Vicia faba L.) Grown Under Drought Stress

ABSTRACTBackgroundDrought stress (DS) impedes plant growth and development by impairing the uptake of nutrients, such as magnesium, which is central to many physiological processes, particularly photosynthesis. Leaf application was proposed to be an effective strategy to compensate for inadequate Mg2+ supply from the nutrient solution.AimThe present study is designed to investigate the role of Mg2+ leaf application in ameliorating leaf anatomy and chloroplast ultrastructure changes in faba beans grown under DS.MethodsHydroponically grown plants were subjected to DS under various levels of Mg2+, i.e. sufficient (0.5 mM), deficient (0 mM), and leaf‐application (250 mM). Light and transmission electron microscopy (TEM) were conducted to examine leaf anatomy and ultrastructural changes.ResultsMg2+ deficiency alone and under DS significantly affected plant biomass and photosynthesis. Additionally, sucrose concentration, oxidative stress, and lipid peroxidation were increased. Accordingly, the excessive deposition of photoassimilates in source organs due to the inhibition of phloem loading results in a disruption of the thylakoid structures leading to chloroplast damage. In the current study leaf application of Mg2+ partially ameliorated physiological functions, most notably chlorophyll concentration, photosynthesis and transpiration rate, plant biomass, and preservation of ultrastructure of the chloroplast.ConclusionAlthough the Mg application via roots enhanced drought tolerance, compared to Mg2+ leaf application. However, Mg2+ leaf application was proven to be an efficient strategy in mitigating DS in field trials. Therefore, Mg2+ foliar application should be prioritized for further investigation under relevant environmental stress conditions.

Metal Acetate-Enhanced Microwave Pyrolysis of Waste Textiles for Efficient Syngas Production

The production of waste textiles has increased rapidly in the past two decades along with the rapid development of the economy, the majority of which has been either landfilled or incinerated, resulting in energy loss and environmental pollution. Microwave pyrolysis, which can transform heterogeneous and complex waste feedstocks into value-added products, is considered one of the most competitive technologies for processing waste textiles. However, achieving selective product formation during the microwave pyrolysis of waste textiles remains a significant challenge. Herein, sodium acetate, potassium acetate, and nickel acetate were introduced into waste textiles through an impregnation method as raw materials to improve the pyrolysis efficiency. The optimized process parameters indicated that nickel acetate had the most favorable promotional effect of the three acetates. Notably, the waste textiles containing 1.0% Ni exhibited the highest gas production rate, with the hydrogen-containing combustible gas reaching 81.1% and 61.0%, respectively. Using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy to characterize the waste textiles before and after pyrolysis, it was found that nickel acetate was converted into metallic nickel (Ni0) during microwave pyrolysis. This active site significantly enhanced the pyrolysis process, and as the gas yield increased, the disorder of the resulting pyrolytic carbon also rose. The proposed Ni0-enhanced microwave pyrolysis mediated by nickel acetate offers a novel method for the efficient disposal and simultaneous resource recovery of waste textiles.

Cryopreservation of Noble Scallop Mimachlamys nobilis sperm: Optimization study of cooling rate and thawing temperature

In marine biology reproduction research, the cryopreservation of sperm is a crucial area, especially for economically valuable species. Effective freezing techniques help maintain genetic diversity and support sustainable development in aquaculture. This study examined the effects of freezing protocols and thawing methods on the cryopreservation of Mimachlamys nobilis sperm. Experimental results indicated that a cooling rate of 5 °C/min and an equilibration time of 5 minutes were the most suitable conditions for maintaining the structural and functional integrity of the sperm. Comparisons of different thawing temperatures showed that 38 °C provided the best results, minimizing ice recrystallization and cellular damage. Additionally, it was found that a 10 % concentration of DMSO effectively balanced protection and cytotoxicity, maintaining sperm viability and motility. Transmission electron microscopy further revealed the impact of freezing conditions on sperm, including damage to the plasma membrane, dissolution, blurring and swelling of the acrosome and mitochondria, and cristae fragmentation and loss. This study emphasizes the importance of optimizing freezing and thawing protocols and accurately controlling cryoprotectant concentration, providing key insights for the effective long-term preservation of M.nobilis sperm. This is significant for the conservation of marine organisms and aquaculture.

CNSC-07. OLIGODENDROGLIAL IMPAIRMENT IN WHITE MATTER TRACTS FOLLOWING NEUROFIBROMATOSIS TYPE 1 (NF1) GERMLINE MUTATION OR CARBOPLATIN TREATMENT

Abstract Neurofibromatosis type 1 (NF1) is a cancer predisposition syndrome due to mutations in the NF1 gene. The disease affects 1 in 2500-3000 people worldwide and patients are predisposed to neoplasms such as optic pathway glioma, plexiform neurofibroma. In addition, NF1 patients often experience neurological issues such as learning difficulties. Unfortunately, there is no cure for NF1 yet. Chemotherapy (e.g., carboplatin) remains the first-line treatment for NF1-associated low-grade glioma; while effective in reducing tumor burden, it does not reliably restore neuronal function. In this study, we sought to determine how chemotherapy and Nf1 germline mutations influence neurological function, using genetically engineered mice of NF1. Nf1-heterozygous mice received carboplatin (60 mg/kg/day) or vehicle every other day for one week. Their optic nerves were collected and processed for immunofluorescence and transmission electron microscopy (EM). We found that carboplatin treatment reduces the density of oligodendrocytes in Nf1-heterozygous mice and impairs myelination. Moreover, a similar effect of carboplatin was observed in wild-type mice, suggesting that carboplatin impairs oligodendroglia independent of the NF1 status and the effect of carboplatin should also be evaluated in the non-NF1 context. In another set of experiments, we sought to understand how germline Nf1 mutations influences oligodendroglia. Whereas we did not observe a difference in optic nerve oligodendrocyte density in mice with an engineered mutation targeting the GTPase-activating protein-related domain (GRD) domain of the Nf1 gene, a reduction of oligodendrocyte density was observed in mice harboring a patient-derived mutation (R1809C), which localizes outside of the GRD. A similar effect was observed in the corpus callosum of Nf1+/R1809C mice together with myelin impairment, suggesting a RAS-independent mechanism of Nf1 regulation of oligodendrocytes. Together, these findings indicate that both Nf1 germline mutations and chemotherapy could contribute to oligodendrocyte and myelin deficits in white matter tracts.

SIRT1-Dependent Neuroprotection by Resveratrol in TOCP-Induced Spinal Cord Injury: Modulation of ER Stress and Autophagic Flux

This study explores the neuroprotective effects of resveratrol (Resv) against tri-o-cresyl phosphate (TOCP)-induced neurotoxicity in the spinal cord of adult hens. It is well documented that TOCP exposure causes significant neurodegeneration via mechanisms that involve endoplasmic reticulum (ER) stress and impaired autophagy. In this experiment, adult hens were assigned to one of four groups: Control, Resv, TOCP, and TOCP + Resv. The spinal cord tissues were examined through transmission electron microscopy, hematoxylin and eosin (HE) staining, Nissl staining, and Western blotting to evaluate key proteins associated with ER stress and autophagy. Additionally, RT-qPCR and immunofluorescence were employed to measure sirtuin1 (SIRT1) expression. The findings revealed that TOCP induced severe ultrastructural damage, including disrupted myelin sheaths, dilated ER, and extensive neurodegeneration, as confirmed by histological evaluations. The expression levels of GRP78, p-PERK, p-eIF2α, ATF4, CHOP, Beclin-1, P62, and LC3-II were also significantly elevated by TOCP. However, Resv treatment markedly attenuated these pathological changes by reducing ER stress, restoring autophagic flux, and upregulating SIRT1 expression, preserving spinal cord integrity. These results indicate that Resv can effectively counteract TOCP-induced neurotoxicity by modulating ER stress and autophagy, underscoring its potential as a therapeutic agent for neuroprotection.

Evaluation of degradation phenomena in the electric potential distribution inside organic light-emitting diodes by electron holography

Understanding the intrinsic degradation processes of organic light-emitting diodes is necessary to improve their lifetimes. This intrinsic degradation is typically caused by carrier injection at the interface between the hole transport layer (HTL) and the emissive layer (EML). However, revealing the charge behavior in this local region with a high spatial resolution remains challenging. Thus, this study employed electron holography, a transmission electron microscopy (TEM) technique, to measure the nanometer scale potential distribution inside an OLED composed of N,N′-di-[(1-naphthyl)-N,N′-diphenyl]-(1,1′-biphenyl)-4,4′-diamine (α-NPD) and tris-(8-hydroxyquinoline)aluminum (Alq3) that was degraded via continuous voltage application. The α-NPD and Alq3 functioned as the HTL and EML, respectively. The degraded OLED was found to exhibit several potential distributions, depending on the local positions from which the TEM samples were lifted out of the same bulk sample. The distributions included (i) formation of a potential valley at the α-NPD/Alq3 interface, (ii) disappearance of electric fields within the organic layers, and (iii) similar distribution to original before degradation. We suggest that the degradation was caused by charge accumulation, cationization of Alq3, and local failures. Thus, this study revealed the influence of electric degradation at the nanometer scale because of charge injection to the α-NPD/Alq3 interface. Electron holographic degradation analysis near the HTL/EML interface is expected to aid in the development of design guidelines for preventing device degradation and thus extend device lifetime.

Effect of pinless friction stir processing on microstructure and properties of surface modification layer of 2024 aluminum alloy

Friction stir processing (FSP) is an advanced material surface modification technology that is both green and energy-efficient. This technology plays a crucial role in regulating the surface microstructure of alloys and improving alloys’ surface properties. It reaches this through the synergistic effect of non-equilibrium thermodynamic and surface mechanical deformation. In this work, the surface modification of an aluminum alloy was performed using pin-less FSP. Then, the modified surface was analyzed using stress–strain curves, optical microscopy (OM), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical tests to investigate the impact of spindle velocity on the properties of the modified layer. Results of the study show that after undergoing pinless FSP modification treatment, the surface of the alloy appears bright and flat. The modified layer displays refined grains and numerous dispersed second-phase particles. Furthermore, the grains in the modified layer exhibit a gradient distribution from the surface to the matrix. Regarding the properties, compared to the base material (BM), the yield strength (σ 0.2) and tensile strength (σ b ) of the alloy-modified layer were increased by 34.8% and 29.4%, respectively. The maximum elongation (δ) of the modified coating reached 22.3%. The modified layer exhibits a tough-brittle mixed fracture pattern. Additionally, the modified layer’s corrosion resistance significantly improves. The performance of the modified coating shows the most significant improvement when the spindle speed reaches 1000 rpm.

Diethyl butylmalonate attenuates cognitive deficits and depression in 5×FAD mice

BackgroundAlzheimer’s disease (AD), characterized by cognitive impairment and depression, is currently one of the intractable problems due to the insufficiency of intervention strategies. Diethyl butylmalonate (DBM) has recently attracted extensive interest due to its anti-inflammatory role in macrophages. However, it is still unknown whether DBM has a beneficial effect on cognitive deficits and depression.MethodsDBM was administrated to 5×FAD and C57BL/6J mice by intraperitoneal injection. Novel object recognition, Y-maze spatial memory, Morris water maze and nest building tests were used to evaluate cognitive function. Moreover, the tail suspension test, forced swimming test, open field test and the elevated plus maze test were used to assess depression. Transmission electron microscopy, Golgi-Cox staining, immunofluorescence, RT-qPCR and western blot were utilized to determine the neuropathological changes in the hippocampus and amygdala of mice.ResultsMultiple behavioral tests showed that DBM effectively mitigated cognitive deficit and depression in 5×FAD mice. Moreover, DBM significantly attenuated synaptic ultrastructure and neurite impairment in the hippocampus of 5×FAD mice, paralleled by the improvement of the deficits of PSD95 and BDNF proteins. In addition, DBM decreased the accumulation of microglia and downregulated neuroinflammation in the hippocampus and amygdala of 5×FAD mice.ConclusionThis study provides evidence that DBM ameliorates cognitive deficits and depression via improvement of the impairment of synaptic ultrastructure and neuroinflammation, suggesting that DBM is a potential drug candidate for treating AD-related neurodegeneration.

EXTH-38. EVALUATION OF STORAGE CONDITIONS ON SERUM-DERIVED EXTRACELLULAR VESICLES IN BRAIN TUMOR SAMPLES

Abstract Tumor-derived Extracellular Vesicles (EVs) are emerging as potential liquid biopsy tool in the field of cancer diagnosis and therapeutic targets. The functionality of EVs depends on its diverse cargo, which is known to alter host-receipient cells. Nevertheless, extracting EVs while preserving its integrity and functionality of its contents is challenging, specifically in Low-middle Income countries (LMIC) countries. Our study focussed on extraction of serum derived EVs analysis from brain-tumor samples encompassing Oligodendrogliomas, Astrocytomas and Glioblastomas. The stability of EVs were examined in serum stored for 2 years at -80°C to understand the effect of preservation and storage in different conditions, that were left exposed to room temperature for variable periods of time before freezing. To explore the optimal suitable conditions, EVs were isolated from serum samples using IZON column size-exclusion based-method, and evaluated for structural integrity and stability through nanoparticle tracking analysis (NTA) and transmission electron microscopy (TEM) technology. Interestingly, the majority of isolated vesicles exhibited round, intact structure with bilayer membrane of size varying between 30 - 250nm. Moreover, protein content of EVs positive markers (CD63, CD81 and CD9) was also detected with minimal contaminations evidenced by weak bands for negative marker (ApoB), as determined by Western blot analysis. Further, column-based EV-derived RNA demonstrated optimal yield and purity was confirmed by RNA integrity number (RIN) using Qubit. While cryopreservation had minimum detrimental effects on mRNA sample quality, leaving it exposed to room temperature before freezing had a significant effect on EV isolation, as samples were often haemolyzed. This will provide insights in optimizing pre-analytical and analytical procedures for more effective outcomes in the clinical setting

Enhancing stability and bioactivity of Chondrus ocellatus polyphenols through nanoparticle fabrication

This article aimed to fabricate Chondrus ocellatus polyphenols (COPs)-gelatin-chitosan nanoparticles to enhance their stability and bioactivity. Different preparation conditions were tested to investigate the effects of formulation on nanoparticle fabrication. Free radical scavenging activity of COPs and their nanoparticles were compared. The consequences revealed that optimal preparation was obtained with a chitosan (CS) concentration of 0.5 mg/mL, gelatin (Gel) concentration of 1.0 mg/mL, COPs concentration of 5.0 mg/mL, and Gel-CS-COPs mass ratio of 2:1:1. The resultant nanoparticles had the particle size of 39.79 ± 5.15 nm and encapsulation efficiency of 60.95 % ± 1.86 %. The COPs-Gel-CS nanoparticles were distributed uniformly, and no obvious aggregation was observed by transmission electron microscopy. Nanoencapsulation of the COPs significantly improved their antioxidative stability. This study provided a potential formulation for the application of Chondrus ocellatus polyphenols in antioxidant activities.

Bioleaching of Printed Circuit Board Waste to Obtain Metallic Nanoparticles

In this work, a biological recovery of metals (copper and gold) from computer printed circuit board (PCB) waste was carried out by bioleaching using Aspergillus niger. Three bioleaching methods comprising one or two steps or using spent medium were tested in an incubator shaker at 30 °C and 160 rpm with different PCB waste concentrations (2.5 to 10 g/L). Glucose was used as the carbon source. The best condition evaluated was carried out in a stirred tank reactor. The FTIR spectrum confirmed the presence of oxalic, citric, and gluconic acids. A. niger showed an efficiency of bioleaching of up to 100% and 42.5% for copper and gold, respectively, using the two-step method with 2.5 g/L PCB waste after 14 days of the process. The efficiency of bioleaching in a stirred tank reactor was 83% for copper and 24% for gold. The mean metallic particle size obtained after bioleaching varied according to the PCB waste concentration (2.5–10 g/L) added in the experiments. A transmission electron microscope analysis confirmed the synthesis of metallic nanoparticles with spherical morphology. The results indicated that the PCBs bioleaching process with A. niger can be an environmentally friendly alternative to current mechanical and metallurgical processes for metal leaching.

Characterization of HZO Films Fabricated by Co-Plasma Atomic Layer Deposition for Ferroelectric Memory Applications

Plasma-enhanced atomic layer deposition (ALD) is a common method for fabricating Hf0.5Zr0.5O2 (HZO) ferroelectric thin films that can be performed using direct-plasma (DP) and remote-plasma (RP) methods. This study proposed co-plasma ALD (CPALD), where DPALD and RPALD are applied simultaneously. HZO films fabricated using this method showed wake-up-free polarization properties, no anti-ferroelectricity, and high fatigue endurance when DPALD and RPALD started simultaneously. To minimize defects in the film that could negatively affect the low polarization properties and fatigue endurance, the direct plasma power was reduced to 75 W. Thus, excellent fatigue endurance for at least 109 cycles was obtained under a high total remanent polarization of 47.3 μC/cm2 and an applied voltage of 2.5 V. X-ray photoelectron spectroscopy and transmission electron microscopy were used to investigate the mechanisms responsible for these properties. The HZO films fabricated by CPALD contained few lattice defects (such as nonstoichiometric hafnium, nonlattice oxygen, and residual carbon) and no paraelectric phase (m-phase). This was attributed to the low-carbon residuals in the film, as high-energy activated radicals were supplied by the adsorbed precursors during film formation. This facilitated a smooth transition to the o-phase during heat treatment, which possessed ferroelectric properties.

Atomic‐Scale Order and Disorder Induced Diverse Topological Spin Textures in Self‐Intercalated Van der Waals Magnets Cr1+δTe2

AbstractThe intercalation of magnetic atoms into van der Waals (vdW) gaps offers a versatile approach for manipulating local magnetic ordering in vdW magnets. However, these intercalated magnetic atoms are often intricately positioned within the gaps, resulting in an ambiguous impact on local magnetic interactions and spin configurations. Herein, the atomic and magnetic structures of self‐intercalated prototype materials Cr1+δTe2 are comprehensively investigated using transmission electron microscopy, elucidating the correlation between the concentration and distribution of intercalated Cr atoms and the evolution of spin textures. The observed transitions from topological Néel‐type skyrmions to non‐topological type‐II bubbles, and ultimately to trivial ferromagnetic domains, underscore the complex nature of these magnetic spin textures. The complexity of the local structural arrangements is further revealed through integrating atomic‐resolution imaging, revealing the disorder‐order‐disorder transitions manifested by the distribution of intercalated atoms. The modulation of intercalated atomic structure shapes the observed spin textures by affecting the Dzyaloshinskii−Moriya interaction (DMI), inter/intra‐layer coupling, and magnetic anisotropy. These findings provide profound insights into the structure‐magnetism relationship, offering promising avenues for engineering the magnetic properties of vdW magnets at the atomic level.

Dynamics of ultrastructural changes in the yolk syncytial layer and its microenvironment during gastrulation and early postembryonic development of <i>Hemichromis Bimaculatus</i>

BACKGROUND: In fish embryogenesis, the yolk sac is the critical provisional organ, actively functioning during the embryonic and early postembryonic stages. Its primary role is trophic, facilitated in Teleostei by a specialized structure — the yolk syncytial layer (YSL). Ultrastructural transformations of this layer during gastrulation and early postembryonic development, as well as its interaction with migrating muscle fibers and melanophores, are probably necessary for the efficient use of nutrients by the developing embryo. The yolk sac’s role in the embryogenesis of Hemichromis bimaculatus may extend beyond current conceptions. AIM: To study the structural organization of the Jewel Cichlid (H. bimaculatus) yolk sac during the embryonic and early postembryonic development. MATERIALS AND METHODS: The research was involved 22 embryos and larvae of H. bimaculatus from 1 to 7 days after egg laying. The morphological features of the yolk sac were studied using light and transmission electron microscopy. RESULTS: By day 2, the yolk sac was separated from the embryo by the trunk fold. Its main structure was the YSL, containing numerous nuclei, microvilli, mitochondria and phagolysosomes. The morphological features of the YSL were similar to those of the placental symplastotrophoblast and indicated high functional activity. The yolk sac mesenchyme contained blood vessels, migrating melanophores, and muscle fibers. The periderm, covered with a special shell, fuunctioned as the primary skin of the embryo. The transition to exogenous nutrition in Jewel Cichlid larvae was accompanied by a significant decrease in yolk sac size with its subsequent involution. CONCLUSIONS: The trophic function of the yolk sac in H. bimaculatus is mediated by the YSL, which, during gastrulation and postembryonic development, interacts with a number of structures present in the yolk sac wall. Migrating muscle fibers promote activation of yolk granules; accumulation of toxic metabolic products is associated with melanophores. The special structure of the periderm protects both the yolk sac and the embryo from external influences.

Nano-aluminum double coated with copper and HTPB by one pot method and its catalysis on AP

ABSTRACT Organic-inorganic double-coated aluminum nanopowders (HTPB/Cu/nAl) were synthesized using a one-pot method. The morphology and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The analysis revealed that Cu particles were uniformly dispersed around the nAl core, while HTPB formed a coating on the Cu/nAl surface. The thermal oxidation kinetics and catalytic effects on ammonium perchlorate (AP) were investigated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The results indicated a 9% increase in the active aluminum content of the double-coated nanopowders compared to uncoated nAl, and a reduction in the average activation energy for thermal oxidation from 297.75 kJ·mol-1 to 218.85 kJ·mol-1. The HTPB coating enhanced the friction and impact sensitivity of the Cu/nAl particles. Adding 5% HTPB/Cu/nAl to AP advanced the low- and high-temperature decomposition peaks by 5°C and 40°C, respectively, while reducing the activation energy of AP from 85.61 kJ·mol-1 to 79.79 kJ·mol-1. This addition significantly influenced the thermal decomposition of AP, improving combustion efficiency and enhancing compatibility within composite propellant formulations.

Effect of aging temperature on the microstructural evolution and mechanical properties of 18Ni (200) maraging steel

Herein, we used transmission electron microscopy (TEM), electron backscattering diffraction (EBSD), and X-ray diffractometry (XRD) to investigate the effects of different aging temperatures on reversed austenite and precipitates in 18Ni (200) maraging steel, as well as their evolving patterns of cryogenic toughness and strength. Aging at 510 °C was found to enhance cryogenic toughness at −196 °C and deliver peak strength, which is attributable to the significant aging-strengthening effect and the reversed austenite. Furthermore, this study investigated the factors that contribute to the formation and high stability of reversed austenite and quantitatively assessed the contributions of aging strengthening, dislocation strengthening, and grain-boundary strengthening to yield strength at various aging temperatures.