Search Results (88)

A new desmid microalga species, Cosmarium yassinii A.A. Saber, El-Sheekh, Kouwets et Cantonati sp. nov., was isolated from two hyper-arid mountain valleys, so-called “wadis”, in the Eastern Desert of Egypt. The distinctive morphological features of this new species were established using light and scanning electron microscopy observations, and also by documenting its life-cycle stages. Taxonomically, C. yassinii is characterized by a cell wall sculpture consisting of isolated granules or small warts arranged circularly in the swollen mid-region of each semicell, never forming parallel vertical ridges or costae as in morphologically similar species, and the interesting shape of the marginal granules appears as small emarginate “combs” or crenae, including its knobby zygospores. Similarities and differences with the morphologically most closely related species are discussed in detail. Ecologically, C. yassinii seems to prefer alkaline freshwater environments with lower nutrient concentrations and a NaCl/HCO₃ water type. The detailed assessment and documentation of the biodiversity of these peculiar freshwater ecosystems are a fundamental prerequisite to adequately inform their protection strategies. Full article

This study systematically examines the influence of heat treatment on the microstructure and mechanical properties of the Mg-3.2Nd-2.5Gd-0.4Zn-0.5Zr (wt.%) alloy using optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and mechanical testing. The as-cast alloy consists mainly of an α-Mg matrix and Mg₃RE intermetallic phases. Solution treatment markedly improves microstructural homogeneity by dissolving most Mg-RE phases into the α-Mg matrix. Subsequent aging induces the formation of finely dispersed rare-earth precipitates, which contribute significantly to the improvement in hardness and strength. The optimal heat-treatment parameters are a solution treatment at 520 °C for 10 h followed by aging at 200 °C for 16 h (T6). After T6 treatment, the alloy exhibits an ultimate tensile strength (UTS) of 322 ± 2.0 MPa, a yield strength (YS) of 220 ± 23.0 MPa (increases of 53% and 88% relative to the as-cast alloy), and an elongation (EL) of 8.7 ± 0.2% at room temperature. At 150 °C, the UTS, YS, and EL reach 292 ± 2.6 MPa, 185 ± 1.1 MPa (41% and 62% improvements over the as-cast state), and 16 ± 1.0%, respectively, indicating excellent mechanical performance at elevated temperatures. Full article

Al-Zn-Mg-Cu alloys are widely used as heat-treatable ultra-high-strength materials in aerospace structural applications. While conventional single-stage aging enables high strength, advanced performance demands call for precise microstructural control via multi-stage aging. In this study, we employ a combination of scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) to investigate the microstructural evolution and its correlation with mechanical properties of AA7150 aluminum alloy subjected to two-step aging treatments, following a 6 h pre-aging at 120 °C. Through atomic-scale STEM imaging along the [110]_Al zone axis, we systematically characterize the precipitation behavior of GPII zones, η′ phases, and equilibrium η phases both within the grains and at grain boundaries under varying secondary aging (SA) conditions. Our results reveal that increasing the SA temperature from 140 °C to 180 °C leads to coarsening and reduced number density of intragranular precipitates, while promoting the continuous and coarse precipitation of η phases along grain boundaries, accompanied by a widening of the precipitation-free zone (PFZ). Notably, SA at 160 °C induces the formation of fine, uniformly dispersed nanoscale η′ precipitates in the alloy, as confirmed by XRD phase analysis. Aging at this temperature markedly enhances the mechanical properties, achieving an ultimate tensile strength (UTS) of 613 MPa and a yield strength (YS) of 598 MPa, while presenting an exceptionally broad peak-aging plateau. Owing to this feature, a moderate extension of the SA duration does not reduce strength and can further improve ductility, increasing the elongation (EL) to 14.26%. These results demonstrate a novel two-step heat-treatment strategy that simultaneously achieves ultra-high strength and excellent ductility, highlighting the critical role of advanced electron microscopy in elucidating phase-transformation pathways that inform microstructure-guided alloy design and processing. Full article

Dental caries, a prevalent biofilm-mediated chronic disease, causes enamel demineralization, pulp infection, and systemic complications. Dental plaque biofilm is the initiating factor for the occurrence and development of caries. Streptococcus mutans is an opportunistic pathogen linked to the structure and ecology of dental plaque biofilms. The molecular mechanism of S. mutans during biofilm ontogeny in driving cariogenesis has been extensively elucidated. Here, we observed that asiatic acid is a potent biofilm disruptor that selectively dismantles S. mutans biofilm architectures, prompting us to investigate its mechanism. The minimum biofilm inhibition concentration (MBIC) of asiatic acid on S. mutans was 62.5 μM, but the MBIC level did not substantially impede planktonic growth. Using the static active-attachment model, it was demonstrated that asiatic acid significantly reduced biofilm biomass (p < 0.001) and extracellular polysaccharides (EPS) content (p < 0.001), while concurrently diminishing acid production (p = 0.017) and metabolic activity (p = 0.014). Confocal and scanning electron microscopy further confirmed structural disintegration, including bacterial detachment and reduced biofilm thickness. Transcriptome analysis of S. mutans biofilm treated with asiatic acid revealed 454 differentially expressed genes (adjusted p < 0.05, |log₂FC| ≥ 1). Notably, genes related to the CiaRH two-component system (ciaR, ciaH), a central regulatory hub for biofilm maturation and acid tolerance. This disruption initiates a downstream cascade, causing a coordinated downregulation of critical gene clusters essential for virulence and pathogenesis, including stress response (htrA, clpP, groEL, dnaK), and the glucan-binding protein gene (gbpC) essential for biofilm structural integrity. These findings provide the first mechanistic evidence linking asiatic acid to transcriptional reprogramming in S. mutans biofilm, offering a novel ecological strategy for caries prevention by targeting key regulatory pathways. Full article

CoCrFeNiMn high entropy alloy (HEA) fabricated via laser-based powder bed fusion (PBF-LB/M) exhibits exceptional mechanical properties, including high strength, better ductility than titanium alloy, and superior corrosion resistance. This study simulates the intergranular fracture behavior of PBF-LB/M CoCrFeNiMn HEA under tensile loading by embedding cohesive elements with damage mechanisms into polycrystalline representative volume elements based on the crystal plasticity finite element method. The simulation results show good agreement with reported experimental stress–strain curves, demonstrating that the crystal plastic constitutive model combined with the cohesive constitutive model can accurately describe both the macroscopic response behavior and fracture failure behavior of the CoCrFeNiMn HEA. Furthermore, this work investigates the mechanical properties of the HEA in different tensile directions, the improvement of anisotropy through columnar-to-equiaxed grain transition, and the effect of texture strength on crack initiation and propagation. The results show that the polycrystalline CoCrFeNiMn HEA exhibits anisotropic mechanical properties: simulated yield strengths (YSs) are 436.9 MPa (in the scanning direction) and 484.7 MPa (in the building direction), tensile strengths (TSs) reach 639 MPa and 702.5 MPa, and elongations (ELs) are 10.6% and 21.8%, respectively. After equiaxed grain formation, the EL in the scanning direction increased from 10.6% to 17.2%, while the EL in the building direction decreased from 21.8% to 20.3%. Concurrently, the anisotropy coefficients of YS, TS, and EL decreased by 1.8%, 2.2%, and 36.1%, respectively. The cracks initiate at stress concentrations and subsequently propagate along grain boundaries until final fracture. Variations in texture strength significantly influence the crack initiation location and propagation path in the CoCrFeNiMn HEA. Full article

Background: Canine cranial cruciate ligament (CCL) rupture is a common orthopedic condition leading to stifle joint dysfunction, discomfort, and reduced mobility. Diagnosis typically involves radiography, computed tomography (CT), and magnetic resonance imaging (MRI). In this study, we conducted a retrospective analysis to evaluate the use of infrared thermography in assessing local temperature and thermal patterns in dogs with acute-onset lameness due to CCL rupture compared to those with intact ligaments. Methods: The study involved 12 dogs with cranial cruciate ligament rupture and nine dogs with intact ligaments. The stifle area of all dogs was clipped and scanned using a FLIR E50 thermographic camera. Two regions of interest (ROI), designated El1 and Bx1, were analyzed with FLIR Tools software 5.X by comparing the average of the maximum and of the mean temperature values between the two groups. Results: Thermal imaging revealed differences between the two groups of dogs, which were further supported by significantly higher temperatures in the El1 (lateral aspect of the stifle joint) and Bx1 (cranial aspect of the stifle joint) areas in the study group compared to the control group using a comparative analysis—two-sample t-test. In the El1 area, the study group showed a temperature increase of 1.8 °C compared to the control group, while in the Bx1 area, the difference was 1.76 °C. Conclusions: Infrared thermography shows potential to differentiate dogs with acute-onset lameness due to CCL rupture from dogs with intact ligaments, but further studies are needed to assess its accuracy in distinguishing it from other stifle pathologies. Full article

In the present study, an L-shaped multi-walled structure of NiTi shape memory alloy (SMA) was fabricated by using the wire arc additive manufacturing (WAAM) method on a titanium substrate. The present study aims to investigate the fabricated structure for microstructure, macrostructure, and mechanical properties. The 40 layers of L-shaped structure were successfully fabricated at optimized parameters of wire feed speed at 6 m/min, travel speed at 12 mm/s, and voltage at 20 V. The macrographs demonstrated the continuous bonding among the layers with complete fusion. The microstructure in the area between the two middle layers has exhibited a mixture of columnar grains (both coarse and fine), interspersed with dendritic colonies. The microstructure in the topmost layers has exhibited finer colonial structures in relatively greater numbers. The microhardness (MH) test has shown the average values of 283.2 ± 3.67 HV and 371.1 ± 5.81 HV at the bottom and topmost layers, respectively. A tensile test was conducted for specimens extracted from deposition and build directions, which showed consistent mechanical behavior. For the deposition direction, the average ultimate tensile strength (UTS) and elongation (EL) were obtained as 831 ± 22.91 MPa and 14.32 ± 0.55%, respectively, while the build direction has shown average UTS and EL values of 774 ± 6.56 MPa and 14.16 ± 0.21%, respectively. The elongation exceeding 10% in all samples suggests that the fabricated structure demonstrates properties comparable to those of wrought metal. Fractography of all tensile specimens has shown good ductility and toughness. Lastly, a differential scanning calorimetry test was carried out to assess the retention of shape memory effect for the fabricated structure. The authors believe that the findings of this work will be valuable for various industrial applications. Full article

Zn-Ag alloys are deemed extremely promising materials for manufacturing biodegradable medical implants. Nonetheless, their practical applications are still constrained by inferior mechanical properties. To tackle this issue, Zn-0.5Ag alloy was alloyed with Mg (0.2 wt.%) and processed by combined equal-channel angular pressing (ECAP) and rolling, with different rolling reductions (40%, 60%, and 75%). ECAP-processed Zn-0.5Ag-0.2Mg alloy exhibited superior mechanical properties to its as-cast counterpart. Subsequent rolling of 40% further enhances the mechanical performance of ECAP-processed Zn-0.5Ag-0.2Mg alloy, with yield strength (YS), ultimate tensile strength (UTS), and elongation (EL) reaching 255 MPa, 309 MPa, and 52%, respectively, surpassing the application requirements. As the rolling reduction increased to 60% and further to 75%, YS and UTS declined, whereas EL rose continuously. The underlying mechanisms for the variation in strength and ductility were elucidated based on microstructure evolution analysis through optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter diffraction (EBSD) characterizations. Full article

The wastewater treatment involves various techniques at different technological levels. Treatment takes place in several stages, of which coagulation and flocculation are the most important. Most suspended solids are indeed eliminated during this stage by the addition of a coagulant. In this research, bio-coagulant was extracted from pumpkin seed (PS) waste after extraction of the essential oils, and used with ferric chloride to treat wastewater from the plant of Chalghoum El Aid-Oued El Athmania Mila. In this study, the Box–Behnken design (BBD) with three factors was used to investigate the effect of pH, organic coagulant dosage Pumpkin seed extract (PSE), and chemical coagulant dosage (FeCl₃) on coagulation–flocculation performance in relation to turbidity, chemical oxygen demand (COD), aromatic organic matter (UV 254), and phosphate. The main characteristics of the raw water were turbidity (250 NTU), COD (640 mg/L), UV 254 (0.893 cm⁻¹), and phosphate (0.115 mg/L). The results obtained were very significant. All the statistical estimators (R² ≥ 97% and p ≤ 0.05) reveal that the models developed are statistically validated for simulating the coagulation–flocculation process. It should be noted that the residual values of turbidity, COD, UV 254, and phosphate after treatment by this process were 0.754 NTU; 190.88 mg/L; 0.0028 cm⁻¹; and 0.0149 mg/L, respectively. In this case, the pH, bio-coagulant dosage, and chemical coagulant dosage values were 4; 17.81 mL/L; and 10 mL/L, respectively. In this study, Fourier-transform infrared spectrometer (FTIR) and scanning electron microscope (SEM) characterization of the bio-coagulant proved the presence of the active functional groups responsible for coagulation, namely carboxyl group. Full article

The pursuit of effective climate change mitigation strategies is driving research into geological carbon dioxide (CO₂) storage. The present work explores the interaction of CO₂ with carbonate rocks from the El Abra formation in the Tampico-Misantla basin, focusing on the comparative influence of organic matter (OM) content on mineralization processes, hypothesizing that variations in OM content significantly modulate the mineralization process affecting both the rate and type of carbonate formation. Expanding on a previous study, CO₂ is studied and injected under high-pressure (1350-2350 PSI) and high-temperature (60–110 °C) conditions into two contrasting samples: one with high OM content and another with low OM content. Structural, morphological, and physical adsorption changes were evaluated through Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) analyses. The findings indicate that the mineralogy of El Abra promotes secondary carbonate precipitation, with rock–fluid interactions significantly enhanced by brine presence. Samples with high OM exhibited a dramatic reduction in average particle size from 13 μm to 2 μm, along with the formation of metastable phases, such as vaterite—evidenced by XRD peak shifting and modifications in the FT-IR spectrum of carbonate bands. Meanwhile, low-OM samples showed an increase in particle size from 1.6 μm to between 3.26 and 4.12 μm, indicating predominant recrystallization. BET analysis confirmed a significant porosity enhancement in high-OM samples (up to 2.918 m²/g). Therefore, OM content plays a critical role in modulating both the rate and type of mineralization, potentially enhancing physical storage capacity in low-OM samples. These integrated findings demonstrate that OM critically governs calcite dissolution, secondary carbonate formation, and microstructural evolution, providing key insights for optimizing CO₂ storage in complex carbonate reservoirs. Full article

The emergence of GaN-based micro-LEDs has revolutionized display technologies due to their superior brightness, energy efficiency, and thermal stability compared to traditional counterparts. However, the development of red-emitting micro-LEDs on silicon substrates (GaN-on-Si) faces significant challenges, among them including hydrogen-induced deactivation of p-GaN caused by hydrogen species generated from SiH₄ decomposition during SiO₂ passivation layer growth, which degrades device performance. This study systematically investigates the use of high-density metal-oxide dielectric passivation layers deposited by atomic layer deposition (ALD), specifically Al₂O₃ and HfO₂, to mitigate these effects and enhance device reliability. The passivation layers effectively suppress hydrogen diffusion and preserve p-GaN activation, ensuring improved ohmic contact formation and reduced forward voltage, which is measured by the probe station. The properties of the epitaxial layer and the cross-section morphology of the dielectric layer were characterized by photoluminescence (PL) and scanning electron microscopy (SEM), respectively. Experimental results reveal that Al₂O₃ exhibits superior thermal stability and lower current leakage under high-temperature annealing, while HfO₂ achieves higher light-output power (LOP) and efficiency under increased current densities. Electroluminescence (EL) measurements confirm that the passivation strategy maintains the intrinsic optical properties of the epitaxial wafer with minimal impact on Wp and FWHM across varying process conditions. The findings demonstrate the efficacy of metal-oxide dielectric passivation in addressing critical challenges in InGaN red micro-LED on silicon substrate fabrication, contributing to accelerating scalable and efficient next-generation display technologies. Full article

In a broad project designed to examine uranium transport by surface water from Sierra Peña Blanca to Laguna del Cuervo in the Chihuahuan Desert, sediments from intermittent streams and the lagoon have been extracted and studied. Two samples were sediments from the high area of the Sierra, close to the uranium deposit “El Nopal.” Moreover, 23 core segments extracted for dating sediments were analyzed to consider changes in the fine component concentrations. The techniques of scanning electron microscopy–energy dispersive X-ray spectroscopy, XRD in a conventional diffractometer, and high-resolution synchrotron XRD analysis were applied. The crystallographic objective of the present work was to evaluate the functionality of various methodologies when applied to cases of a detailed analysis of many polyphase samples with cryptocrystals. The methods for processing the experimental data were the Rietveld method in the current multi-pattern variant of the Fullprof program and the degree of crystallinity method for the rapid estimation of the proportion of cryptocrystals in a mixture. This last technique was developed with an ad hoc software package deposited in the GitLab public repository. Full article

During our research on the diversity of diatoms and green microalgae from Egypt, four new-to-science, newly recorded, and poorly known species were retrieved from different Egyptian habitats. The new benthic diatom species Halamphora shaabanii A.A. Saber, El-Sheekh, Levkov, H. Saber et Cantonati sp. nov., which could not be identified using the currently available literature, was described from the high-conductivity, oasis lake Abu Nuss in the El-Farafra Oasis, located in the Western Desert of Egypt, employing both light (LM) and scanning electron (SEM) microscopy observations. A detailed comparison of the biometrically distinctive traits, and ecological preferences, of this new diatom species revealed sufficient differentiations from its morphologically most closely related species: H. atacamana, H. caribaea, H. ectorii, H. gasseae, H. halophila, H. mosensis, H. poianensis, and H. vantushpaensis. Ecologically, Halamphora shaabanii can tolerate relatively high nutrients (N and P) and prefers saline inland environments with NaCl water types. The araphid diatom Pseudostaurosiropsis geocollegarum was observed in the epilithic diatom assemblages of the River Nile Damietta Branch and identified on the basis of LM and SEM. From an ecological standpoint, P. geocollegarum seems to prefer elevated nutrient concentrations (meso-eutraphentic species), reflecting different human influences on the freshwater River Nile Damietta Branch. Based on the available literature, this is the first documentation of this freshwater diatom species for Egypt, and the second record for the African continent. Two green motile microalgae, Chlamydomonas proboscigera and Gonium pectorale, were isolated and identified from the terrestrial biomes of the arid habitat “Wadi El-Atshan” in the Eastern Desert of Egypt. C. proboscigera is reported herein for the first time in the Egyptian algal flora, while G. pectorale is poorly documented in the available literature. In light of our findings, the Egyptian habitats, particularly the isolated desert ecosystems, are interesting biodiversity hotspots and have a richer algal microflora than earlier anticipated. Furthermore, more in-depth taxonomic studies, using a combined polyphasic approach, are needed not only to foster our knowledge of the Egyptian and African algal and cyanobacterial diversity and biogeography, but also to be further used in applied environmental sciences. Full article

Gold nanoparticles (Au NPs) are a promising target for research due to their small size and the resulting plasmonic properties, which depend, among other things, on the chosen reducer. This is important because removing excess substrate from the reaction mixture is problematic. However, Au NPs are an excellent component of various materials, enriching them with their unique features. One example is hydrogels, which provide a good, easily modifiable base for multiple applications such as cosmetics. For this purpose, various compounds, including hyaluronic acid (HA) and its derivatives, are distinguished by their high water-binding capacity and many characteristics resulting from their natural origin in organisms, including biocompatibility, biodegradability, and tissue regeneration. In this work Au NPs were synthesized using a green chemistry method, either by using onion extract as a reductant or chemically reducing them with sodium citrate. A complete characterization of the nanoparticles was carried out using the following methods: Fourier-Transform Infrared Spectroscopy (FT-IR), Electrophoretic (ELS), and Dynamic Light Scattering (DLS) as well as Transmission Electron Microscope (TEM) and Scanning Electron Microscope (SEM). Their antioxidant activity was also tested using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The results showed that the synthesized nanoparticles enrich the hydrogels with antioxidant properties and new surface properties (depending on the reducing agent, they can be more hydrophilic or hydrophobic). Preliminary observations indicated low cytotoxicity of the nanomaterials in both liquid form and as a hydrogel component, as well as their lack of penetration through pig skin. The cosmetic properties of hydrogel masks were also confirmed, such as increasing skin hydration. Full article

With the rapid development of hydrogen pipelines, their safety issues have become increasingly prominent. In order to evaluate the properties of pipeline materials under a high-pressure hydrogen environment, this study investigates the hydrogen embrittlement sensitivity of X70 welded pipe in a 10 MPa high-pressure hydrogen environment, using slow strain rate testing (SSRT) and low-cycle fatigue (LCF) analysis. The microstructure, slow tensile and fatigue fracture morphology of base metal (BM) and weld metal (WM) were characterized and analyzed by means of ultra-depth microscope, scanning electron microscope (SEM), electron backscattering diffraction (EBSD), and transmission electron microscope (TEM). Results indicate that while the high-pressure hydrogen environment has minimal impact on ultimate tensile strength (UTS) for both BM and WM, it significantly decreases reduction of area (RA) and elongation (EL), with RA reduction in WM exceeding that in BM. Under the nitrogen environment, the slow tensile fracture of X70 pipeline steel BM and WM is a typical ductile fracture, while under the high-pressure hydrogen environment, the unevenness of the slow tensile fracture increased, and a large number of microcracks appeared on the fracture surface and edges, with the fracture mode changing to ductile fracture + quasi-cleavage fracture. In addition, the high-pressure hydrogen environment reduces the fatigue life of the BM and WM of X70 pipeline steel, and the fatigue life of the WM decreases more than that of the BM as well. Compared to the nitrogen environment, the fatigue fracture specimens of BM and WM in the hydrogen environment showed quasi-cleavage fracture patterns, and the fracture area in the instantaneous fracture zone (IFZ) was significantly reduced. Compared with the BM of X70 pipeline steel, although the effective grain size of the WM is smaller, WM’s microstructure, with larger Martensite/austenite (M/A) constituents and MnS and Al-rich oxides, contributes to a heightened embrittlement sensitivity. In contrast, the second-phase precipitation of nanosized Nb, V, and Ti composite carbon-nitride in the BM acts as an effective irreversible hydrogen trap, which can significantly reduce the hydrogen embrittlement sensitivity. Full article