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Characterization and propagation of partially coherent fields radiated by sources with univariable cross-spectral density
No full textA new class of partially coherent light sources, the sources with uni-variable cross-spectral density, has been recently introduced. Their cross-spectral density is obtained starting from any function of a single complex argument having non-negative Taylor coefficients. This allows the conception of a virtually infinite number of physically realizable partially coherent sources. Here, the main characteristics of sources of this class are investigated through examples, with particular reference to the irradiance and coherence properties across the source plane and upon propagation, both in the near and in the far field. Furthermore, since the coherent modes of such sources present optical vortices, parameters quantifying the vortex structure of the field across the source plane are also evaluated for the presented cases
Valorization of agricultural waste: green synthesis of ZnO nanoparticles from artichoke stem (Cynara scolymus) and cardoon extract (Cynara cardunculus) for photocatalytic applications
No full textThis paper presents a simple, efficient, and a green, eco-friendly method to synthesize ZnO nanoparticles through Artichoke and Cardoon waste as biological reducing agents. This strategy minimizes the utilization of environmentally dangerous chemicals in the production process. The ZnO nanoparticles were characterized through UV-Vis spectroscopy, FTIR, XRD, and SEM-EDX, confirming their formation and properties. Furthermore, the photocatalytic efficiency of the synthesized ZnO nanoparticles using a green approach against dyes was successfully demonstrated
4U 1556-60 as a very faint neutron star X-ray binary at 700 pc with an undetected radio jet
No full textis a low-mass X-ray binary that was discovered more than 50 years ago as a persistent X-ray source; however, very little was known about it. Recently, obtained a parallax for the optical counterpart that places at a distance of only about 700 pc, making it one of the closest X-ray binaries known to date. This close distance drastically alters what was previously assumed about the source.
We revisit in light of the newly determined distance of 700 pc, reinterpreting its literature and presenting new X-ray and radio observations to better understand various characteristics of the system.
We investigated the optical spectra and luminosity and the X-ray spectral and timing properties, and we performed the first targeted radio observation for the source in 45 years. These can be used to infer binary and accretion properties from independent methods.
We conclude that a scenario in which is a candidate ultracompact neutron star X-ray binary at a distance of ∼700 pc is able to explain the observed properties of the source. It resides at a persistent X-ray luminosity of an unusual value for a typical X-ray binary, but similar to several ultracompact systems. The ratio of the X-ray to optical luminosity is very high, also suggesting a physically small accretion disk. The radio jet is undetected with a very deep upper limit of 3 which is about 10^3 times fainter than the expected black hole jet correlation, strongly indicating a neutron star accretor. The X-ray spectrum is dominated by a power law, and the X-ray timing properties are also consistent with observations of other very low accretion rate X-ray binaries. No spin or orbital periodicity are found in the X-ray data. Future observations, especially to determine its orbital period, will further aid in understandin
The origin of sinusoidal brightness variations in F- to O-type stars through radial velocities
No full textStellar variability may originate from various phenomena such as binarity, pulsations, or rotation. These mechanisms can induce flux variations of similar magnitudes, shapes, and periods.
We aim to determine mechanisms responsible for the sinusoidal variations in main-sequence stars hotter than 6500,K.
We conducted our analysis using TESS long-cadence data complemented with high-resolution spectra from three spectrographs. From the initial sample of almost 46,000 objects, we selected 35 targets for spectroscopic follow-up. The comparison of light curves and radial-velocity curves allowed for the robust classification of these targets.
Among the 35 selected objects, 18 displayed variability, suggesting the presence of a companion (including the discovery of seven new binary systems and one candidate for a triple-star system), one was identified as a new pulsator, nine as new candidates for spotted stars, and seven objects had uncertain classification. Our analysis shows that at least half of randomly selected stars with sinusoidal brightness variations are binaries.
The presented results illustrate the need for an individual approach to stellar classification, especially in cases where the photometric data alone is insufficient for determining the underlying phenomena behind the observed variations
Characterising injection signatures in Jupiter’s ultraviolet aurora using Juno observations
No full textDiscrete features in Jupiter's ultraviolet aurora have been interpreted as signatures of plasma injections in the middle magnetosphere. There exists some ambiguity as to whether magnetodisc scattering or high-latitude Alfvénic acceleration best describes the observed properties of these injection signatures, and also the extent to which extent arcs in the outer emission are related to injections. Many injection signatures are the result of the evolution of dawn storms; however, there is limited evidence that non-dawn-storm injection signatures are sometimes present in the aurora. We use automatic detection of these discrete features, alongside data from Juno-UVS and in situ measurements by other Juno instruments, to show that scattering likely accounts for most of the electron precipitation associated with injection signatures. Additionally, there is evidence that injection signatures can be classified into two types: dawn-storm and non-dawn-storm. Arc-like features in the outer emission show very similar properties to traditional blob-like injection signatures and may consist of sequences of injection signatures that have broadened into an arc via energy-dependent electron drift
Environmental history of filament galaxies. Stellar mass assembly and star formation of filament galaxies
No full textGalaxy properties, such as stellar mass and star formation rate, correlate with their position within the cosmic web. Although galaxy properties can be correlated with a specific environment at a certain cosmic epoch, they may have experienced different environments at previous times. This `environmental history', which is closely linked to pre-processing, is bound to leave an imprint on the observable and physical properties of galaxies. In this work, we use the Galaxy Evolution and Assembly (GAEA) semi-analytic model and the magneto-hydrodynamic IllustrisTNG simulation to reconstruct the environmental histories of galaxies that today reside in filaments between z=0 and z=4. Our goal is to understand how galaxy properties are related to their past environments and to uncover the role of the cosmic web in shaping their present-day properties. This approach enables us to determine whether and when filamentary structures influence galaxy evolution. We find that filament galaxies at z=0 are a heterogeneous mix of populations with distinct environmental histories, and a clear dependency on the infall times into filaments. The vast majority of filament galaxies at z=0 have experienced group processing at some stage of their evolution, with only ∼20% of galaxies remaining centrals throughout their life. For low-mass filament galaxies (̊m 9 10) are affected by the filament environment, regardless of being centrals or satellites. Massive galaxies that have never been satellites and that entered filaments more than 9 Gyr ago show accelerated stellar mass assembly and higher quenched fractions relative to the field, due to a higher frequency of merger events inside filaments. Moreover, the most massive ̊m łog ((M_ star / M_ sun ) > 11) galaxies typically accreted onto filaments over 9 Gyr ago and have never become satellites within a larger halo, highlighting the role of filaments in building up the high-mass end of the galaxy population
Synthesis and Characterization of Nickel Ferrite/Activated Carbon Nanocomposites as Radar Wave Absorbing Materials at X-Band Frequency
No full textIn this study, nickel ferrite/activated carbon nanocomposites have been fabricated using iron sand as radar wave absorbing materials at X-Band frequency. The formation of nanocomposites was confirmed by the appearance of Ni, Fe, O, and C elements obtained from the energy dispersive X-ray spectrum, which were the main constituent elements for nickel ferrite and activated carbon. In addition, X-ray diffraction characterization confirmed that the nickel ferrite/activated carbon nanocomposites had an inverse cubic spinel structure and a crystallite size of 11.10 nm. Scanning electron microscopy characterization showed that the nickel ferrite/activated carbon nanocomposites were irregularly spherical with an average particle size of about 46.12 nm. According to the vibrating sample magnetometer characterization, the saturation magnetization of the nanocomposites was 24.26 emu/g with superparamagnetic behavior of the nickel ferrite/activated carbon nanocomposites. Interestingly, the nickel ferrite/activated carbon exhibited a minimum reflection loss of −13.5 dB at a frequency of 7.24 GHz with an effective bandwidth of 1.11 GHz, along with an absorption efficiency higher than 90%. These results indicate that nickel ferrite/activated carbon nanocomposites exhibit promising potential as radar wave absorbing materials at X-band frequency
Validation and performance assessment of a WD-XRF fused bead method for accurate quantification of scandium in nickel laterite deposits
No full textThis study focuses on the validation and performance assessment of the Wavelength Dispersive X-ray Fluorescence (WD-XRF) fused bead method for scandium quantification in nickel laterite ores. The calibration of the instrument showed a high correlation (R2 = 0.9962), with a Limit of Detection (LoD) of 20 ppm and a precision of 1.28% RSD. Accuracy was confirmed with good recoveries ranging from 98.05% to 101.46%. The relative expanded uncertainty was calculated at 5.89%. Method and instrumental reproducibility were confirmed by quality control (QC) Chart monitoring using certified reference materials (CRMs) and by relative error (RE) values below 10% for duplicate pulverized samples. The mode of scandium concentration in the samples was found to be 140 ppm. Overall, these results demonstrate that the WD-XRF fused bead method shows good validation performance, with excellent linearity, precision, accuracy, reproducibility, low expanded uncertainty and a low LoD for scandium quantification in complex matrices such as nickel laterite ores
Green Synthesis of Nickel-rich Ni
No full textNickel-rich layered oxides such as LiNixCoyAl1−x−yO2 (NCA) are attractive cathode materials for lithium-ion batteries because they can deliver high energy density at reduced cobalt content. However, conventional co-precipitation routes typically require external acid/base dosing for pH control, which increases chemical consumption and generates salt-rich effluents. Here, we propose an electrochemical (acid-free) synthesis route using a bipolar-membrane electrolyzer to generate H+ and OH− in situ from water, thereby replacing reagent-based pH adjustment. A mixed Ni–Co–Al sulfate solution (Ni:Co:Al = 89:8:3) was processed at 60 °C and electrolyzed at 0.08 A cm−2 for 60 and 120 min. The resulting deposits were washed and dried, then lithiated with LiOH (Li:cathode precursor=1.05:1) and calcined (500 °C/6 h followed by 800 °C/20 h). SEM revealed hierarchical secondary aggregates with a flower-like morphology that became more consolidated at longer electrolysis time. EDS confirmed the presence of Ni, Co, and Al in the deposits. XRD showed reflections consistent with a layered NCA-type structure when compared with the reference card (JCPDS 87-1562), with the 120 min sample exhibiting sharper and better-resolved peaks; minor secondary phases were also detected, indicating incomplete phase purity under the present conditions. Overall, the bipolar membrane-assisted route demonstrates a feasible pathway to reduce external chemical inputs in Ni-rich cathode precursor synthesis, while highlighting the processing window required to strengthen phase formation toward layered NCA
Synthesis and characterization of HAp/Fe
No full textThis study aims to synthesize and characterize hydroxyapatite/magnetite (HAp/Fe₃O₄) nanocomposites derived from chicken bones as potential materials for bone implants and eco-friendly adsorbents. Synthesis was conducted using the sol-gel method with calcination temperatures varied of 500⁰C, 600⁰C, and 700⁰C. Characterization was performed using XRD, FTIR, SEM-EDX, UV-Vis, and AAS. XRD results showed that at 700⁰C, a pure hydroxyapatite phase was formed with the highest crystallinity reaching 96.25% and a crystallite size of 20.14 nm, indicating an increase in the regularity of the crystal structure. FTIR analysis confirmed the presence of typical HAp functional groups (O–H and PO 3-) as well as Fe–O groups from Fe3O4, indicating the successful formation of stable HAp/Fe3O4 magnetic composites at high temperatures. SEM-EDX results showed a porous morphology with particle sizes ranging from 4–20 nm, while AAS analysis shows a decrease in Ca ion content with increasing temperature, indicating an increase in the efficiency of HAp crystal structure formation. Furthermore, UV-Vis data showed an increase in absorbance at 200 nm with a value of 3.11 and a concentration of 0.816 ppm, indicating higher purity and structural regularity. Overall, the HAp/Fe3O4 nanocomposite at 700⁰C has high thermal stability, good crystal structure, and great potential for application as an environmentally friendly biomaterial