Search Results (1,025)

The surface recrystallization model of the fully amorphized C₃H₅-molecular-ion-implanted silicon (Si) substrate is investigated. Transmission electron microscopy is performed to observe the amorphous/crystalline interface near the C₃H₅-molecular-ion-implanted Si substrate surface after the subsequent recovery thermal annealing treatment. At a depth of high-concentration carbon of approximately 4.8 × 10²⁰ atoms/cm³, recrystallization from the crystalline template to the surface by solid-phase epitaxial growth is partially delayed, and the activation energy was estimated to be 2.79 ± 0.14 eV. The change in the crystalline fraction of the fully amorphized C₃H₅-molecular-ion-implanted Si substrate surface is quantitatively evaluated from the binding energy of Si 2p spectra by X-ray photoelectron spectroscopy. Using the Kolmogorov–Johnson–Mehl–Avrami equation, the surface recrystallization of the fully amorphized C₃H₅-molecular-ion-implanted Si substrate is assumed to proceed two-dimensionally, and its activation energy is obtained as 2.71 ± 0.28 eV without the effect of carbon. Technology computer-aided design (TCAD) process simulations calculate recrystallization under the effect of high-concentration carbon and demonstrate the reach of some crystalline regions to the surface first. In the fully amorphized C₃H₅-molecular-ion-implanted Si substrate, it is considered that recrystallization is partially delayed due to high-concentration carbon and surface recrystallization proceeds two-dimensionally from some crystalline regions reaching the surface first. Full article

Wireless power transfer (WPT) systems have ushered in a new era for wearable and implantable technologies, introducing opportunities for enhanced device functionality. A pivotal aspect in improving these devices is the optimization of electromagnetic transmission. This paper presents several solutions to improve electromagnetic transmission to an implantable/wearable device. Several scatterers are considered to mimic objects that can be easily worn by a patient, such as necklaces and bracelets, or easily integrated into textile fabric. An analytical method is employed to address the scattering by cylindrical objects above a biological tissue, modeled as a multilayer. Expansions into cylindrical waves, also represented through plane-wave spectra, are used to express the scattered fields in each medium. Numerical results for both the case of conducting and of dielectric cylindrical scatterers are presented at a frequency of the Industrial, Scientific and Medical band ($f=2.45$ GHz), showing possible configurations of worn objects for electromagnetic field intensification. Full article

The transmission spectrum of a twin-waveguide cavity is systematically analyzed based on coupled mode theory, using the transfer matrix method (TMM). The results show that the traveling-wave transmission spectra of the twin-waveguide cavity is entirely determined by the coherent coupling effect involving the parameters of the effective refractive indices of the upper and lower waveguides, the coupling length Lc, and the ratio of the cavity length L to the coupling length (L/Lc). Filters with single, double, or triple-notch filtering could be obtained by choosing an appropriate L/Lc value. When the facet reflection is taken into consideration, the traveling-wave transmission spectrum is modified by the Fabry––Perot (FP) resonance, making it a standing-wave transmission spectrum. As a result, resonance splitting has been observed in the transmission spectrum of twin-waveguide resonators with high facet reflectivity. Further analysis shows that such an abnormal resonance phenomenon can be attributed to the destructive interference between the two FP resonance modes of the upper and lower waveguide through coherent coupling. In addition, narrow bandwidth amplification has also been observed through asymmetric facet reflections. Undoubtedly, all these unique spectral characteristics should be beneficial to the twin-waveguide cavity, achieving many more functions and being widely used in photonic integration circuits (PICs). Full article

Pseudomonas fragi (P. fragi) is usually detected in low-temperature meat products, and seriously threatens food safety and human health. Therefore, the study investigated the antibacterial mechanism of linalool against P. fragi from membrane damage and metabolic disruption. Results from field-emission transmission electron microscopy (FETEM) and atomic force microscopy (AFM) showed that linalool damage membrane integrity increases surface shrinkage and roughness. According to Fourier transform infrared (FTIR) spectra results, the components in the membrane underwent significant changes, including nucleic acid leakage, carbohydrate production, protein denaturation and modification, and fatty acid content reduction. The data obtained from amino acid metabolomics indicated that linalool caused excessive synthesis and metabolism of specific amino acids, particularly tryptophan metabolism and arginine biosynthesis. The reduced activities of glucose 6-phosphate dehydrogenase (G6PDH), malate dehydrogenase (MDH), and phosphofructokinase (PFK) suggested that linalool impair the respiratory chain and energy metabolism. Meanwhile, genes encoding the above enzymes were differentially expressed, with pfkB overexpression and zwf and mqo downregulation. Furthermore, molecular docking revealed that linalool can interact with the amino acid residues of G6DPH, MDH and PFK through hydrogen bonds. Therefore, it is hypothesized that the mechanism of linalool against P. fragi may involve cell membrane damage (structure and morphology), disturbance of energy metabolism (TCA cycle, EMP and HMP pathway) and amino acid metabolism (cysteine, glutamic acid and citrulline). These findings contribute to the development of linalool as a promising antibacterial agent in response to the food security challenge. Full article

Phononic or acoustic bandgap materials have often been made using a polymer matrix with metal inclusions such as tin and steel, which have high densities compared to the matrix material. Acoustic bandgaps are observed when waves are not transmitted at certain frequencies. These have been applied in cavity resonators, acoustic waveguides, and more. This paper introduces a concept of using cement as the surrounding matrix and carbon nanotubes as the core inclusions to develop phononic materials. The exhibition of a bandgap makes it possible for the cementitious phononic material to be used as a sensor for cement cracking and defects in oil well bores. This paper discusses ways to optimize the characteristics of the carbon nanotube core to develop gaps in transmission spectra. It shows the behavior of the cementitious material with changing filling fraction, location of core cells, and surrounding defects, creating a pathway for paradigm-shifting non-destructive sensing technologies. Full article

Estimating line impedance is relevant in transmission and distribution networks, in particular for planning and control. The large number of deployed PMUs has fostered the use of passive indirect methods based on network model identification. Electrified railways are a particular example of a distribution network, with moving highly dynamic loads, that would benefit from line impedance information for energy efficiency and optimization purposes, but for which many of the methods used in industrial applications cannot be directly applied. The estimate is carried out onboard using a passive method in a single-point perspective, suitable for implementation with energy metering onboard equipment. A comparison of two methods is carried out based on the non-linear least mean squares (LMS) optimization of an over-determined system of equations and on the auto- and cross-spectra of the pantograph voltage and current. The methods are checked preliminarily with a simulated synthetic network, showing good accuracy, within 5%. They are then applied to measured data over a 20 min run over the Swiss $16.7$ Hz railway network. Both methods are suitable to track network impedance in real time during the train journey; but with suitable checks on the significance of the pantograph current and on the values of the coefficient of determination, the LMS method seems more reliable with predictable behavior. Full article

Nanoparticles have been widely applied to treat emulsion-containing wastewater in the form of chemical demulsifiers, such as SiO₂, Fe₃O₄, and graphene oxide (GO). Owing to their asymmetric structures and selective adsorption, Janus nanoparticles show greater application potential in many fields. In the present work, the novel magnetic Janus graphene oxide (MJGO) nanoparticle was successfully prepared by grafting magnetic Fe₃O₄ to the surface of the JGO, and its demulsifying ability to treat a crude oil-in-water emulsion was evaluated. The MJGO structure and its magnetic intensity were verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and magnetization saturation (MS) tests. Compared with GO and JGO, MJGO displayed the superior efficiency (>96%) to demulsify the crude oil-in-water emulsion, which can be attributed to the reduced electrostatic repulsion between MJGO and the emulsion droplets. Furthermore, the effects of pH and temperature on the demulsification performance of MJGO were also studied. Lastly, the recyclability of MJGO largely reduced the cost of demulsifiers in separating crude oil and water. The current research presents an efficient and recyclable demulsifier, which provides a new perspective for the structural design of nanomaterials and their application in the field of demulsification. Full article

This paper studies the synthesis, characterization, and application of ZnFe₂O₄ nanoparticles for the removal of rhodamine b dye from aqueous media. Utilizing the combustion procedure, ZnFe₂O₄ nanoparticles were synthesized using two different fuels: glutamine (SG) and L-arginine (SA). In addition, the synthesized ZnFe₂O₄ nanoparticles were characterized through various techniques, including Fourier transform infrared (FTIR), X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray (EDX), high resolution transmission electron microscope (HR-TEM), and Brunauer-Emmett-Teller (BET) surface area analysis. XRD analysis verified the creation of a ZnFe₂O₄ cubic spinel structure without any contaminants, revealing average crystallite sizes of 43.72 and 29.38 nm for the SG and SA samples, respectively. The FTIR spectra exhibited peaks indicative of metal-oxygen bond stretching, verifying the presence of a spinel formation. Elemental analysis via EDX confirmed the stoichiometric composition typical of zinc ferrite. In addition, FE-SEM imaging displayed that the SG and SA samples are composed of particles with irregular and spherical shapes, measuring average diameters of 135.11 and 59.89 nm, respectively. Furthermore, the BET surface area of the SG and SA samples is 60 and 85 m²/g, respectively. The maximum adsorption capacity of the SA sample (409.84 mg/g) towards rhodamine b dye was higher than that of the SG sample (279.33 mg/g), which was ascribed to its larger surface area and porosity. Kinetic and equilibrium studies revealed that the adsorption process of rhodamine b dye onto the SG and SA samples followed the Langmuir isotherm and pseudo-second-order model. Thermodynamic analysis indicated that the adsorption process was spontaneous, exothermic, and physical. The study concludes that ZnFe₂O₄ nanoparticles synthesized using L-arginine (SA) exhibit enhanced rhodamine b dye removal efficiency due to their smaller size, increased surface area, and higher porosity compared to those synthesized with glutamine (SG). The optimum conditions for the adsorption process of rhodamine b dye were found to be at pH 10, a contact time of 70 min, and a temperature of 298 K. These findings underscore the potential of L-arginine-synthesized ZnFe₂O₄ nanoparticles for effective and sustainable environmental cleanup applications. Full article

The gadolinium vanadate doped with samarium (GdVO₄:Sm³⁺) nanopowder was prepared by the solution combustion synthesis (SCS) method. After synthesis, in order to achieve full crystallinity, the material was annealed in air atmosphere at 900 °C. Phase identification in the post-annealed powder samples was performed by X-ray diffraction, and morphology was investigated by high-resolution scanning electron microscope (SEM) and transmission electron microscope (TEM). Photoluminescence characterization of emission spectrum and time resolved analysis was performed using tunable laser optical parametric oscillator excitation and streak camera. In addition to samarium emission bands, a weak broad luminescence emission band of host VO₄³⁻ was also observed by the detection system. In our earlier work, we analyzed the possibility of using the host luminescence for two-color temperature sensing, improving the method by introducing the temporal dependence in line intensity ratio measurements. Here, we showed that further improvements are possible by using the machine learning approach. To facilitate the initial data assessment, we incorporated Principal Component Analysis (PCA), t-Distributed Stochastic Neighbor Embedding (t-SNE) and Uniform Manifold Approximation and Projection (UMAP) clustering of GdVO4:Sm³⁺ spectra at various temperatures. Good predictions of temperature were obtained using deep neural networks. Performance of the deep learning network was enhanced by data augmentation technique. Full article

Surface longwave radiation (SLR) plays a pivotal role in the Earth’s energy balance, influencing a range of environmental processes and climate dynamics. As the demand for high spatial resolution remote sensing products grows, there is an increasing need for accurate SLR retrieval with enhanced spatial detail. This study focuses on the development and validation of models to estimate SLR using measurements from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) sensor. Given the limitations posed by fewer spectral bands and data products in ASTER compared to moderate-resolution sensors, the proposed approach combines an atmospheric radiative transfer model MODerate resolution atmospheric TRANsmission (MODTRAN) with the Light Gradient Boosting Machine algorithm to estimate SLR. The MODTRAN simulations were performed to construct a representative training dataset based on comprehensive global atmospheric profiles and surface emissivity spectra data. Global sensitivity analyses reveal that key inputs influencing the accuracy of SLR retrievals should reflect surface thermal radiative signals and near-surface atmospheric conditions. Validated against ground-based measurements, surface upward longwave radiation (SULR) and surface downward longwave radiation (SDLR) using ASTER thermal infrared bands and surface elevation estimations resulted in root mean square errors of 17.76 W/m² and 25.36 W/m², with biases of 3.42 W/m² and 3.92 W/m², respectively. Retrievals show systematic biases related to extreme temperature and moisture conditions, e.g., causing overestimation of SULR in hot humid conditions and underestimation of SDLR in arid conditions. While challenges persist, particularly in addressing atmospheric variables and cloud masking, this work lays a foundation for accurate SLR retrieval from high spatial resolution sensors like ASTER. The potential applications extend to upcoming satellite missions, such as the Landsat Next, and contribute to advancing high-resolution remote sensing capabilities for an improved understanding of Earth’s energy dynamics. Full article

Tunability of properties is one of the most important features of 2D materials, among which graphene is attracting the most attention due to wide variety of its possible applications. Here, we demonstrated that the carrier concentration in graphene can be efficiently tuned by the material of the dielectric substrate on which it resides. To this end, we fabricated samples of CVD-grown graphene transferred onto silicon wafers covered with alumina, titanium dioxide, and silicon dioxide. We measured the transmission spectra of these samples using a time-domain terahertz spectrometer and extracted the Drude frequency-dependent graphene conductivity. We found that the sheet resistance of graphene is strongly affected by the underlying dielectric material, while the carrier scattering time remains the same. The carrier concentration value was found to range from $7\times {10}^{11}/{\mathrm{c}\mathrm{m}}^2$ in the case of alumina and $4.5\times {10}^{12}/{\mathrm{c}\mathrm{m}}^2$ in the case of titanium dioxide. These estimations are consistent with what can be extracted from the position of the G-peak in the Raman spectra of graphene. Our results show a way to control the graphene doping level in applications where it does not have to be adjusted. Full article

Terahertz (THz) spectroscopy has demonstrated significant potential for substance detection due to its low destructiveness and due to the abundance of molecular fingerprint absorption signatures that it contains. However, there is limited research on the fingerprint detection of substances at different temperatures. Here, we propose a THz metamaterial slit array sensor that exploits localized surface plasmons to enhance the electric field within the slit. The transmission peak frequency can be modulated via temperature adjustments. This method enables the detection of molecular absorption characteristics at multiple spectral frequency points, thereby achieving a specific and highly sensitive detection of characteristic analyte fingerprint spectra. Additionally, the sensor supports the detection of substances at multiple temperatures and sensitively identifies changes in their absorption properties as a function of temperature. Our research has employed temperature variation to achieve a highly sensitive and specific detection of trace analytes, offering a new solution for THz molecular detection. Full article

Fe₇₈B₁₅Sn₇ and (Fe₃Co₁)₇₈B₁₅Sn₇ amorphous metallic alloys were prepared using the method of planar flow casting. The amorphous nature of ribbons containing 7 at. % Sn was verified by X-ray diffraction. The resulting chemical composition was checked by flame atomic absorption spectroscopy and by mass spectrometry with inductively coupled plasma. The microstructure of the as-quenched metallic glasses was investigated by 57-Fe and 119-Sn Mössbauer spectrometry. The experiments were performed with transmission geometry at 300 K, 100 K, and 4.2 K, and in an external magnetic field of 6 T. The replacement of a quarter of the Fe by Co did not cause significant modifications of the hyperfine interactions in the 57-Fe nuclei. The observed minor variations in the local magnetic microstructure were attributed to alterations in the topological short-range order. However, the in-field 57-Fe Mössbauer spectra indicated a misalignment of the partial magnetic moments. On the other hand, the presence of Co considerably affected the local magnetic microstructure of the 119-Sn nuclei. This was probably due to the higher magnetic moment of Co, which induces transfer fields and polarization effects on the diamagnetic Sn atoms. Full article

Carbon quantum dots (CQDs) have been investigated for biomedical applications in medical imaging due to their fluorescent properties, overall long-term stability, and excellent cytocompatibility and biocompatibility. Lignin is an organic polymer in the tissues of woody plants. It is also considered a byproduct of the wood and pulp industries. Hence, it presents as a renewable source of carbon nanoparticles. In this study, we report the synthesis and material and biological characterization of two colloidal suspensions of CQDs in water derived from lignin-based carbon. One was the native form of CQDs derived from lignin carbon, and the second was doped with nitrogen to evaluate material differences. Material characterization was carried out using various commonly used techniques, including Fourier transform infrared spectroscopy (FTIR), emission and absorbance spectra, zeta potential, transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Thin films of CQDs were formed on glass and silicon substrates to assess the in vitro cytocompatibility with human mesenchymal stem cells (hMSCs). Observations suggest that the two forms of CQDs promote cell attachment within 24 h and sustain it for at least 7 days. The overall structure and shape of cells suggest a lack of any adverse or toxic effects of CQDs. The data lay down the novel foundation to support the use of lignin-derived CQDs in tissue engineering applications. Full article

Scholars are looking for solutions to substitute hazardous substances in manufacturing nanocellulose from bio-sources to preserve the world’s growing environmental consciousness. During the past decade, there has been a notable increase in the use of cellulose nanocrystals (CNCs) in modern science and nanotechnology advancements because of their abundance, biocompatibility, biodegradability, renewability, and superior mechanical properties. Spherical cellulose nanocrystals (J–CNCs) were successfully synthesized from Jenfokie micro-cellulose (J–MC) via sulfuric acid hydrolysis in this study. The yield (up to 58.6%) and specific surface area (up to 99.64 m²/g) of J–CNCs were measured. A field emission gun–scanning electron microscope (FEG-SEM) was used to assess the morphology of the J–MC and J–CNC samples. The spherical shape nanoparticles with a mean nano-size of 34 nm for J–CNCs were characterized using a transmission electron microscope (TEM). X-ray diffraction (XRD) was used to determine the crystallinity index and crystallinity size of J–CNCs, up to 98.4% and 6.13 nm, respectively. The chemical composition was determined using a Fourier transform infrared (FT–IR) spectroscope. Thermal characterization of thermogravimetry analysis (TGA), derivative thermogravimetry (DTG), and differential thermal analysis (DTA) was conducted to identify the thermal stability and cellulose pyrolysis behavior of both J–MC and J–CNC samples. The thermal analysis of J–CNC indicated lower thermal stability than J–MC. It was noted that J–CNC showed higher levels of crystallinity and larger crystallite sizes than J–MC, indicating a successful digestion and an improvement of the main crystalline structure of cellulose. The X-ray diffraction spectra and TEM images were utilized to establish that the nanocrystals’ size was suitable. The novelty of this work is the synthesis of spherical nanocellulose with better properties, chosen with a rich source of cellulose from an affordable new plant (studied for the first time) by stepwise water-retted extraction, continuing from our previous study. Full article