Search Results (9)

The Golgi of goblet cells represents a specialized machine for mucin glycosylation. This process occurs in a specialized form of the secretory pathway, which remains poorly examined. Here, using high-resolution three-dimensional electron microscopy (EM), EM tomography, serial block face scanning EM (SBF-SEM) and immune EM we analyzed the secretory pathway in goblet cells and revealed that COPII-coated buds on the endoplasmic reticulum (ER) are extremely rare. The ERES vesicles with dimensions typical for the COPII-dependent vesicles were not found. The Golgi is formed by a single cisterna organized in a spiral with characteristics of the cycloid surface. This ribbon has a shape of a cup with irregular perforations. The Golgi cup is filled with secretory granules (SGs) containing glycosylated mucins. Their diameter is close to 1 µm. The cup is connected with ER exit sites (ERESs) with temporal bead-like connections, which are observed mostly near the craters observed at the externally located cis surface of the cup. The craters represent conus-like cavities formed by aligned holes of gradually decreasing diameters through the first three Golgi cisternae. These craters are localized directly opposite the ERES. Clusters of the 52 nm vesicles are visible between Golgi cisternae and between SGs. The accumulation of mucin, started in the fourth cisternal layer, induces distensions of the cisternal lumen. The thickness of these distensions gradually increases in size through the next cisternal layers. The spherical distensions are observed at the edges of the Golgi cup, where they fuse with SGs and detach from the cisternae. After the fusion of SGs located just below the apical plasma membrane (APM) with APM, mucus is secreted. The content of this SG becomes less osmiophilic and the excessive surface area of the APM is formed. This membrane is eliminated through the detachment of bubbles filled with another SG and surrounded with a double membrane or by collapse of the empty SG and transformation of the double membrane lacking a visible lumen into multilayered organelles, which move to the cell basis and are secreted into the intercellular space where the processes of dendritic cells are localized. These data are evaluated from the point of view of existing models of intracellular transport. Full article

Laser-induced breakdown spectroscopy (LIBS) is widely used for online quantitative analysis in industries due to its rapid analysis and minimal damage. However, challenges like signal instability, matrix effects, and self-absorption hinder the measurement accuracy. Recent approaches, including the internal standard method and crater limitation method, aim to improve the stability but suffer from high computational demands or complexity. This study proposes a method to enhance LIBS stability by utilizing craters formed from laser ablation without external cavity assistance. It first improves the plasma temperature calculation reliability using multiple elemental spectral lines, after which electron density calculations are performed. By fitting plasma parameter curves based on laser pulse counts and using a laser confocal microscope for crater analysis, stable plasma conditions were found within crater areas of 0.400 mm² to 0.443 mm² and depths of 0.357 mm to 0.412 mm. Testing with elemental spectral lines of Ti II, K II, Ca I, and Fe I showed a significant reduction in the relative standard deviation (RSD) of the LIBS spectral line intensity, demonstrating an improved signal stability within specified crater dimensions. Full article

Regenerative medicine is an interdisciplinary field aiming at restoring pathologically damaged tissues and whole organs by cell transplantation in combination with proper supporting scaffolds. Gelatine-based ones are very attractive due to their biocompatibility, rapid biodegradability, and lack of immunogenicity. Gelatine-based composite hydrogels, containing strengthening agents to improve their modest mechanical properties, have been demonstrated to act as extracellular matrices (ECMs), thus playing a critical role in “organ manufacturing”. Inspired by the lysyl oxidase (LO)-mediated process of crosslinking, which occurs in nature to reinforce collagen, we have recently developed a versatile protocol to crosslink gelatine B (Gel B) in the presence or absence of LO, using properly synthesized polystyrene- and polyacrylic-based copolymers containing the amine or aldehyde groups needed for crosslinking reactions. Here, following the developed protocol with slight modifications, we have successfully crosslinked Gel B in different conditions, obtaining eight out of nine compounds in high yield (57–99%). The determined crosslinking degree percentage (CP%) evidenced a high CP% for compounds obtained in presence of LO and using the styrenic amine-containing (CP5/DMAA) and acrylic aldehyde-containing (CPMA/DMAA) copolymers as crosslinking agents. ATR-FTIR analyses confirmed the chemical structure of all compounds, while optical microscopy demonstrated cavernous, crater-like, and labyrinth-like morphologies and cavities with a size in the range 15–261 µm. An apparent density in the range 0.10–0.45 g/cm³ confirmed the aerogel-like structure of most samples. Although the best biodegradation profile was observed for the sample obtained using 10% CP5/DMAA (M3), high swelling and absorption properties, high porosity, and good biodegradation profiles were also observed for samples obtained using the 5–10% CP5/DMAA (M4, 5, 6) and 20% CPMA/DMAA (M9) copolymers. Collectively, in this work of synthesis and physicochemical characterization, new aerogel-like composites have been developed and, based on their characteristics, which fit well within the requirements for TE, five candidates (M3, M4, M5, M6, and M9) suitable for future biological experiments on cell adhesion, infiltration and proliferation, to confirm their effective functioning, have been identified. Full article

Impact basins are the dominant landforms on the lunar surface, and their geological evolution varies. This research studied the diversity in the geological evolution of three impact basins: the Dirichlet–Jackson Basin, the Nectaris Basin, and the Orientale Basin. First, the regional topography and geomorphology of the three basins were studied using the SLDEM2015 digital elevation model (DEM). Clementine ultraviolet–visible (UVVIS) data and Moon Mineralogy Mapper (M3) data were used to study the chemical composition and mineralogical composition of the three basins. Additionally, the lunar crust thickness data have been used to study the subsurface structure of the three basins. The topographical analogies of the three basins indicate that the shapes of the basins are cavity-like. However, the shape of the Dirichlet–Jackson basin is not an obvious cavity compared with the other basins. The positions with minimum and maximum crustal thickness of the three basins are located at the center and the rim. The uplift of the crust-mantle interface of the Nectaris Basin and Orientale Basin is relatively larger than in the Dirichlet–Jackson Basin. Below the center of the maria of the Nectaris Basin and Orientale Basin, collapses occurred at the crust–mantle interface. The concentrations of FeO and TiO₂ in the non-mare formation of the basin and maria show expected bimodal distributions. Moreover, we found exposures of olivine-rich materials in the Nectaris Basin and Orientale Basin which are located in the Rosse and Maunder craters, respectively. These exposures of olivine may be explained by the fact that the formation of the large impact basin, which might penetrate and blast away the upper lunar crust, excavating deep-seated material. Full article

Liquid-assisted laser ablation (LALA) has gained substantial attention as a method that can achieve desired chemical and physical properties. The fabrication of carbides (CdCO₃), oxides (CdO), and hydro-oxides (Cd(OH)₂) on Cd surfaces make them more useful in industrial and biomedical applications due to the enhancement of their physical properties. For this purpose, LALA of Cadmium (Cd) is performed using a KrF Excimer laser (248 nm, 20 ns) at varying numbers of pulses from 500 to 2000 at constant fluence (3.6 Jcm⁻²) in deionized water (DI) and ethanol. A comparison of the ablation behavior of Cd in DI water and alcohol (ethanol) environments is discussed in the present work. The surface structuring and enhancement of mechanical properties are also discussed in correlation with the changes produced in its crystallinity due to the increase in the chemical reactivity of Cd in both ambient environments. The surface features, chemical composition, structural and compositional analysis, and mechanical properties of irradiated targets are evaluated using a Scanning Electron Microscope (SEM), X-ray Diffraction (XRD), Fast Fourier Transform Infrared spectroscopic (FTIR), Energy Dispersive X-ray Spectroscopy (EDS), and a Nano-hardness tester. Pores, cavities, hillocks, wave-like ridges, nanoparticles, flake-like structures, and periodic surface structures are distinguished features on the Cd surface after irradiation. However, the density and size of pores and cavities are higher in water, whereas ethanol is favorable for the growth of craters and ripples. These features are attributable to various thermal and chemical phenomena induced by laser heating at the solid–liquid interface. Ethanol-assisted ablation is more favorable for enhancing the hardness of Cd as compared to DI water-assisted ablation due to the presence of maximum compressive stresses and minimum crystallite size (C.S.) caused by the diffusion of carbon into the target surface. Full article

A new element is proposed for producing an azimuthally polarized beam with a vortex phase dependence. The element is formed by two conical surfaces in such a way that the optical element resembles a mountain with a crater on top, like a volcano (volcanic cone is volcone). The element in the form of a refractive bi-conic axicon is fabricated by diamond turning, in which an internal conical cavity is made. Polarization conversion in this optical element occurs on the inner surface due to the refraction of beams at the Brewster angle. The outer surface is used to collimate the converted beam, which significantly distinguishes the proposed element from previously proposed approaches. The paper describes a method for calculating the path of beams through a refractive bi-conic axicon, taking into account phase and polarization conversions. In the case of incident circularly polarized radiation, azimuthally polarized ring-shape beam radiation is generated at the output. The proposed element is experimentally made of polymethyl methacrylate on a CNC milling machine. The experiment demonstrates the effectiveness of the proposed element. Full article

Dense yttrium oxyfluoride (YOF) coating was successfully deposited by suspension plasma spraying (SPS) with coaxial feeding. After deposition for 6 min at a plasma power of 105 kW, the thickness of the YOF coating was 55 ± 3.2 µm with a porosity of 0.15% ± 0.01% and the coating rate was ~9.2 µm/min. The crystalline structure of trigonal YOF was confirmed by X-ray diffractometry (XRD). The etching behavior of the YOF coating was studied using inductively coupled CHF₃/Ar plasma in comparison with those of the Al₂O₃ bulk and Y₂O₃ coating. Crater-like erosion sites and cavities were formed on the whole surface of the Al₂O₃ bulk and Y₂O₃ coating. In contrast, the surface of the YOF coating showed no noticeable difference before and after exposure to the CHF₃/Ar plasma. Such high resistance of the YOF coating to fluorocarbon plasma comes from the strongly fluorinated layer on the surface. The fluorination on the surface of materials was confirmed by X-ray photoelectron spectrum analysis (XPS). Depth profiles of the compositions of Al₂O₃, Y₂O₃, and YOF samples by XPS revealed that the fluorination layer of the YOF coating was much thicker than those of Al₂O₃ and Y₂O₃. These results indicate that if the inner wall of the semiconductor process chamber is coated by YOF using SPS, the generation of contamination particles would be minimized during the fluorocarbon plasma etching process. Full article

High-current pulsed electron beam (HCPEB) irradiation commonly induces crater-like cavities on irradiated surfaces, making them tribologically resemble textured ones. However, the effect of crater-like cavities on the lubricated tribological properties of HCPEB-treated surfaces has not been reported in the literature. This work was aimed at exploring the potential texturing effect of the crater-like cavities. Surfaces with continuous and uniform crater-like cavities were prepared through HCPEB irradiating a 400-nm thick Ta coating that was pre-deposited on polished M50 steel. Their boundary tribological behaviors were studied while sliding in chemically inert, low-viscosity hydrocarbon fuel JP-10 against a Si₃N₄ ball under 2.0–4.0 GPa. At 2.0 GPa, the coefficient of friction (COF) and wear rate of the polished M50 steel were above 0.16 on average, with large fluctuation, and 1.49 × 10⁻⁵ mm³/N·m (a rectangle-like profile of 167.9 μm × 8.1 μm), respectively. In comparison, the HCPEB-treated Ta coating had a stable, marginally fluctuant COF of 0.11 and a near-zero wear rate. Under other higher loads, the HCPEB-treated Ta coating still exhibited a stable COF of 0.11 on average with small fluctuation, and its wear track width was only half that of the M50 steel. The analysis of the wear topographies indicates that the substantial reduction in both the COF and wear rate was mainly due to the texturing effect originating from the crater-like cavities. Full article

This paper describes the use of a plasma electrolysis technique to apply a nanosilver coating to the surface of stainless steel to achieve hydrophobic properties. We propose an experimental reaction system, which includes stainless steel 316 as the two electrodes and an aqueous solution of potassium nitrate (KNO₃), silver nitrate (AgNO₃), and ammonium hydroxide (NH₄OH) as the electrolyte. Better results with a stainless steel surface coated by nanocrystalline Ag film are obtained using optimal parameters chosen through one-factor-at-a-time experiments. The main parameters consist of electrode distance, KNO₃ concentration, and AgNO₃ concentration. The experiment focuses on analyzing the impact of the plasma electrolysis technique on processing time. Variations in KNO₃ concentration show that 3 wt.% yields the worst result because it causes an uneven surface, whereas 5 wt.% gives excellent results because it creates an even, porous surface and the highest contact angle. An AgNO₃ concentration of 0.03 wt.% yields the best contact angle. With the same processing time, silver sediment increases as the KNO₃ concentration increases. With respect to variation in electrode distance, we find that when the distance is set at 20 mm, the contact angle exceeds 100° and results in hydrophobic properties on the specimen surface, while other distances yield a contact angle below 80°, resulting in hydrophilic surfaces. The SEM (scanning electron microscope) results show that the surface of the specimen is full of crater-like cavities that directly affect the contact angle. In this experiment, the contact angle yielding optimum hydrophobic properties is 134° ± 10°. Finally, using distribution patterns obtained by elemental analysis, the experimental results lead to an evenly distributed silver coating on the surface of specimens subjected to plasma electrolysis treatment. The study confirms that plasma electrolysis can be used to coat nanosilver onto stainless steel 316. Full article