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Effect of substituting molybdenum atoms with tungsten on photocatalyst activity of cesium salt of keggin type polyoxometalates decorated magnetic ceria
摘要： Herein the potential use of cesium salts of polyoxometalate incorporated ceria and magnetic ceria as a photocatalyst for the photodegradation of Congo red was studied. Polyoxometalates salts (cesium salts of tungestophosphoric acid (H3PW12O40), molybdophosphoric acid (H3PMo12O40), and 6-molybdo tungestophosphoric acid (H3PW6Mo6O40)), having Keggin structure with large cations like Cs+, are porous materials. The morphological and structural studies of synthesized nanocomposites were carried out using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR), N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM). Results indicated that the Fe3O4@CeO2/Cs-PMoyW12-yO40 and CeO2/Cs-PMoyW12-yO40 (y=0, 6, 12) nanocomposites are successfully synthesized. UV-vis diffuse reflectance spectroscopy determined the absorption edge and band gap energies of the prepared nanocomposites as a direct semiconductor. All the obtained structures were applied as photocatalys for degradation of Congo red dye in aqueous solutions under visible light. The Fe3O4@CeO2/Cs-PMo6W6O40 photocatalyst exhibited the highest photocatalytic activity under visible light.
关键词： Photocatalyst,Ceria,Polyoxometalate,Congo red,Nanocomposite,Magnetic
更新于2025-09-04 15:30:14
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A Study on the Weak Ferromagnetism of Nanocrystalline Stannous Oxide Induced by L-Shaped O-Sn-O Vacancies
摘要： Nanocrystalline stannous oxide (SnO) powder has been prepared by ball-milling of micron-SnO in a nitrogen atmosphere. A cation deficiency of 6.5% was found in the nano-SnO sample by X-ray photoelectron spectroscopy. After annealing at 350, 450, or 550℃ under dynamic vacuum conditions, oxygen vacancies were found in the nano-SnO samples, as verified by electron paramagnetic resonance experiments. The samples displayed weak ferromagnetism; that with both 6.5% Sn and at least 7.5% O vacancies showed the maximum saturation magnetization, reaching almost 1.7×10?3 emu/g at room temperature. The O vacancies tended to gather around Sn vacancies. An L-shaped defect model composed of one Sn and two O vacancies has been established, and its ferromagnetism has been calculated by a first-principles method. We found that the L-shaped defect induced a magnetic moment of 0.55 μB in the SnO lattice, the main contribution to which came from a spin-polarized electron in the p orbital of a corner Sn atom.
关键词： Magnetic,Nanocrystalline Stannous Oxide,Plasmonics,L-Shaped O-Sn-O Vacancies,Weak Ferromagnetism,Optical,Hybrid Materials
更新于2025-09-04 15:30:14
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All-Optical Poling and Two-Photon Absorption in Heterocyclic Azo Dyes with Different Side Groups
摘要： We investigated the optical properties of heterocyclic azo dyes with different side groups prepared: as powders, in PMMA matrix and side-chain polymers. We characterized the nonlinear optical effects of these compounds by Z-scan and all-optical poling techniques and supported these experiments with theoretical modeling. It was also found that these materials show strong two-photon absorption cross-sections exceeding 20 GM, which is one order of magnitude stronger than that of similar materials (azobenzene and p-aminoazobenzene). Our study reveals the dominant role of the side-chain system over the guest-host one and stress out the importance of the substituent in the efficiency of the poling process.
关键词： All-Optical Poling,Hybrid Materials,Heterocyclic Azo Dyes,Two-Photon Absorption,Plasmonics,Optical,Magnetic
更新于2025-09-04 15:30:14
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Segmentation of photospheric magnetic elements corresponding to coronal features to understand the EUV and UV irradiance variability
摘要： Context. The magnetic ?eld plays a dominant role in the solar irradiance variability. Determining the contribution of various magnetic features to this variability is important in the context of heliospheric studies and Sun-Earth connection. Aims. We studied the solar irradiance variability and its association with the underlying magnetic ?eld for a period of ?ve years (January 2011–January 2016). We used observations from the Large Yield Radiometer (LYRA), the Sun Watcher with Active Pixel System detector and Image Processing (SWAP) on board PROBA2, the Atmospheric Imaging Assembly (AIA), and the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Methods. The Spatial Possibilistic Clustering Algorithm (SPoCA) is applied to the extreme ultraviolet (EUV) observations obtained from the AIA to segregate coronal features by creating segmentation maps of active regions (ARs), coronal holes (CHs) and the quiet sun (QS). Further, these maps are applied to the full-disk SWAP intensity images and the full-disk (FD) HMI line-of-sight (LOS) magnetograms to isolate the SWAP coronal features and photospheric magnetic counterparts, respectively. We then computed full-disk and feature-wise averages of EUV intensity and line of sight (LOS) magnetic ?ux density over ARs/CHs/QS/FD. The variability in these quantities is compared with that of LYRA irradiance values. Results. Variations in the quantities resulting from the segmentation, namely the integrated intensity and the total magnetic ?ux density of ARs/CHs/QS/FD regions, are compared with the LYRA irradiance variations. We ?nd that the EUV intensity over ARs/CHs/QS/FD is well correlated with the underlying magnetic ?eld. In addition, variations in the full-disk integrated intensity and magnetic ?ux density values are correlated with the LYRA irradiance variations. Conclusions. Using the segmented coronal features observed in the EUV wavelengths as proxies to isolate the underlying magnetic structures is demonstrated in this study. Sophisticated feature identi?cation and segmentation tools are important in providing more insights into the role of various magnetic features in both the short- and long-term changes in the solar irradiance.
关键词： Sun: magnetic ?elds,Sun: corona,Sun: atmosphere
更新于2025-09-04 15:30:14
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Effect of Polyethylene Glycol Surface Charge Functionalization of SWCNT on the in vitro and in vivo Nanotoxicity and Biodistribution Monitored Noninvasively using MRI
摘要： The current study evaluated in vitro and in vivo toxicity of carboxyl or amine PEG surface functionalization of single walled carbon nanotubes (SWCNTs). Assessments of cytotoxicity, genotoxicity, immunotoxicity and oxidative stress were performed in vitro and in vivo (in a one-month follow-up study). The SWCNT biodistribution was investigated using noninvasive MRI. Results confirmed the enhanced biocompatibility of PEG-functionalized SWCNTs compared to non-functionalized materials with significant decreases (p<0.05) in the percentage of cell viability and increases in ROS generation, mitochondrial membrane potential, cell apoptosis, oxidative stress generation and oxidative DNA damage in vitro. PEG-functionalized SWCNTs with amine terminals were found to induce prominent increases in ROS generation, mitochondrial membrane potential, and oxidative stress compared to carboxy functionalized SWCNTs. No significant difference in the biodistribution of either PEG-COOH or PEG-NH2 functionalized SWCNTs was observed in MRI. In vivo assessments revealed a statistically significant increase (p<0.05) in oxidative stress as early as 24 h in serum and liver; however, all values normalized at 2 weeks’ investigation time point. DNA damage was minimal with either PEG-COOH or PEG-NH2 functionalized SWCNTs after two weeks’ exposure. The negatively charged SWCNTs caused lesser DNA damage compared to positively charged samples. Carboxy-functionalized SWCNTs did not caused substantial changes in inflammatory mediators and were found to be significantly safer than non-functionalized SWCNTs and may pave the way for novel biomedical applications in cancer diagnosis and therapy.
关键词： Nanotoxicity,Cytotoxicity,Carbon nanotubes,In vivo biodistribution,Magnetic Resonance Imaging
更新于2025-09-04 15:30:14
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Valley Subband Splitting in Bilayer Graphene Quantum Point Contacts
摘要： We report a study of one-dimensional subband splitting in a bilayer graphene quantum point contact in which quantized conductance in steps of 4e2=h is clearly defined down to the lowest subband. While our source-drain bias spectroscopy measurements reveal an unconventional confinement, we observe a full lifting of the valley degeneracy at high magnetic fields perpendicular to the bilayer graphene plane for the first two lowest subbands where confinement and Coulomb interactions are the strongest and a peculiar merging or mixing of K and K0 valleys from two nonadjacent subbands with indices eN; N t 2T, which are well described by our semiphenomenological model.
关键词： conductance quantization,magnetic field,quantum point contact,valley degeneracy,bilayer graphene
更新于2025-09-04 15:30:14
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[IEEE 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Paris (2018.7.8-2018.7.13)] 2018 Conference on Precision Electromagnetic Measurements (CPEM 2018) - Pyrolytic Carbon: Applications of Diamagnetic Levitation in Metrology
摘要： This paper presents some current or potential applications the diamagnetic property of pyrolytic carbon (PyC). The magnetic repulsion force acting between a piece of PyC placed in a magnetic flux density can be used as magnetic spring either to control the position of the sensitive sensor part or to detect change of a physical quantity to be measured. Several examples of PyC-based sensors are presented.
关键词： Magnetic levitation,Force meter,Pyrolytic carbon,Accelerometer,Tiltmeter,Inertia balance,Laser power
更新于2025-09-04 15:30:14
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Gold nanoparticles – an optical biosensor for RNA quantification for cancer and neurologic disorders diagnosis
摘要： The objective of this study is to develop a facile tool for the absolute detection and quantification of nucleic acid transcripts, using a gold nanoparticle-based optical biosensor. Topoisomerase 1 (TOP1) and tyrosyl DNA phosphodiesterase 2 (TDP2) were among the nucleic acid transcripts of choice due to their role as genomic instability biomarkers and their implication in various cancers and neurologic disorders. This opens the door to develop a simple tool that can be used for diagnosing and monitoring treatment response for such diseases, overcoming the requirements for high cost, time, and complexity of the existing technologies for the absolute quantification of transcripts of interest.
关键词： RNA extraction,genomic instability,tumor markers,gold aggregating gold,TDP2,TOP1,neurodegenerative diseases,magnetic nanoparticles
更新于2025-09-04 15:30:14
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Electromagnetic Wave Theory for Calculation of Exact Magnetic Field in Case of BWO
摘要： Overall efficiency of high power microwave generating device depends upon input current in the form of electron beam and currents required for electromagnets. In order to increase the efficiency of device, if electromagnets are replaced by permanent magnets, overall efficiency of device shall increase. So, calculation of exact magnetic field is required. In this paper, the exact relation of magnetic field required in high power microwave generation using Backward Wave Oscillator (BWO) is found. BWO interacts with slow waves and is the most promising device to produce high power microwaves. The interaction involves the beams from high current density and the waveguide mode. An exact relation that specifically relates the various parameters of the waveguide like slow wave structures (SWS) dimensions, input beam voltage and operational frequency with axial magnetic field is derived. The derived equation gives calculation of exact values of magnetic field for focusing of beams. Theoretical and simulated work show good agreement with the previously available experimental data. So, with the derived electromagnetic wave relation exact value of magnetic field is calculated for desired frequency and power regime.
关键词： High current electron,High power microwave,Wiggler,Magnetic field,Oscillator
更新于2025-09-04 15:30:14
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An ellipsoid convex enhancement filter for detection of asymptomatic intracranial aneurysm candidates in CAD frameworks
摘要： Various kinds of enhancement filters have been developed in computer-aided diagnostic (CAD) frameworks for asymptomatic intracranial aneurysms in magnetic resonance angiography (MRA). However, many bending or branching portions on vessels are also enhanced by the conventional filters as false positives in 3.0 T MRA, which can visualize smaller vessels compared with 1.5 T MRA. To overcome this problem, this study focused on developing an ellipsoid convex enhancement (ECE) filter, which can selectively enhance aneurysms while reducing false positive contrasts on bending or branching portions on vessels, for detection of asymptomatic intracranial aneurysm candidates in CAD frameworks. The ECE filter was mathematically designed to enhance various convex regions in the intensity space such as convex aneurysms, in which the ratio of the shortest and longest diameters for aneurysms corresponds to the ratio of reciprocals of the square roots of the first and third eigenvalues of a Hessian matrix. The proposed ECE filter was evaluated by measuring an average contrast for false positive models and free-response receiver operating characteristic curves between two simple CAD frameworks using the ECE and conventional filters based on a leave-one-out-by-patient test. MRA images for thirty patients (male: 10, female: 20; age: 48–86 yr, mean: 69.2) with 31 unruptured aneurysms (longest diameter: 2.0–5.5 mm, mean: 3.7 mm) were selected for this study. The average contrast for false positive models was reduced by 51.4% using the ECE filter, compared with the conventional filter for the convex regions with ratios of the shortest and longest diameters less than 0.4. The number of false positives per case was decreased from 41.1 to 22.8 on average at a sensitivity of 87% by using the ECE filter. The ECE filter would be useful for boosting the performance of the CAD framework of asymptomatic intracranial aneurysms by providing higher contrast aneurysms and lower contrast false positives such as bending or branching portions on vessels.
关键词： unruptured intracranial aneurysm,ellipsoid convex enhancement (ECE) filter,magnetic resonance angiography (MRA),computer-aided diagnosis (CAD)
更新于2025-09-04 15:30:14