Material Dispersion Research Articles

Mechanism of pin thread and flat features affecting material thermal flow behaviors and mixing in Al-Cu dissimilar friction stir welding

Three different features of pin models in Al-Cu dissimilar friction stir welding processes are established to analyse the effects of threads and flats on the two-phase material thermal flow behaviors. Based on computational fluid dynamics (CFD), a simulation methodology that calculates pins with complex morphologies through an adaptive force boundary is proposed. The pin characteristics are gradually optimized from “conical contour” to “conical-thread” and then to “thread-flats”. For dissimilar Al-Cu materials, the physical properties are weighted by the volume fractions of two-phase materials in the mixing zone. To build a dynamic adaptive contact model that varies with the material flow state, the interfacial friction shear stress is calculated by using the relative slip between the tool and material. The linkage effects between the “thread + flats” on the dissimilar Al/Cu welding mechanisms are systematically analysed. The enhancing mechanisms of the thread and flats on the material flow are different. The thread mainly reinforces the longitudinal migration of the Al/Cu materials, which is perpendicular to the horizontal plane. The flats effectively expand the plastic flow range and material mixing zone on the horizontal plane. These flow expanding effects are observed on the Z = 1 mm plane since the radial range of material flow enlarges from 2 mm to 3 mm under the action of the flats, while the horizontal flow range undergoes little change with the thread. The coupled mechanism of the “thread + flats” shows 0.06 s periodic strengthening, and the fluctuation threshold of the material flow velocity is wider, significantly improving the upwards stirring of the bottom material. The enhanced horizontal flow and vertical migration are beneficial to the uniform dispersion of the second-phase material (Cu) and local material softening for the formation of Al-Cu heterogeneous joints. Moreover, the accuracy of the model is verified by comparing the simulated and experimental TMAZ boundaries.

A novel coating strategy for graphene-modified Li1.2Mn0.54Ni0.13Co0.13O2 as cathode material for LIBs

In this study, reduced graphene oxide (RGO) coated Li1.2Mn0.54Co0.13Ni0.13O2 (RGO@LMNCO) materials with different amounts of RGO were synthesized using a facile hydrothermal method. The double electron layer on the graphene surface was opened by adding a certain amount of electrolyte（NaCl）to the solution to increase the activity of the graphene, thus contributing to the uniform dispersion of the nano-cathode material on the RGO and reducing the secondary agglomeration. The physical characterization and electrochemical test results confirmed that LMNCO material with 2 wt% RGO (2 wt%RGO@LMNCO) was most uniformly dispersed on RGO and exhibited the optimal overall electrochemical performance. The above result suggested that this strategy can be more conductive to exerting the superiority of RGO coating. RGO coating enhanced electronic and ionic conductivity while modifying the potential energy surface of LMNCO effectively and suppressing surface oxygen loss. Subsequently, it can be beneficial to avoid side reactions between the cathode material surface and the electrolyte. As a result, the surface stability of cathode materials was increased. The 2 wt%RGO@LMNCO electrode exhibited a maximum capacity of 308.7mAh g−1 at 0.2 C. With the increase of the charge/discharge current rate from 0.2 C to 10 C, it still reached 112.3mAh g−1. After 50 cycles at 0.2 C rate, the discharge capacity was decreased from 287.5 to 284.8 mAh·g−1, thus maintaining a capacity retention of 99.06%. Furthermore, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed to analyze the synthesized sample. The main reason for enhanced electrochemical performance is that the RGO-LMNCO synthesized by the novel coating strategy, which can more effectively exert the modulation effect of graphene on the cathode material surface, exhibits better dispersion and uniform coating.

Transporting Dispersed Cylindrical Granules: An Intelligent Strategy Inspired by an Elephant Trunk

Manipulating granular materials is a crucial function of robotic grippers. However, the existing approaches always suffer from low efficiency when dealing with large quantities of dispersed granules. To overcome this challenge, inspiration is drawn from an African elephant (Loxodonta Africana), which can employ both fingertip extensions on the trunk tip to efficiently grasp dispersed granular food all at once by mediating state transition of granules. Herein, this bio‐inspired intelligent strategy is integrated into a soft pneumatic gripper for transporting dispersed granules. To evaluate the critical actuation pressures while grasping granules, a library is constructed experimentally, and the effects of the initial relative height and relative lifting speed on the grasping success rate are examined. It is indicated in the experimental results that this trunk‐inspired robotic strategy leads to a success rate of over 90% and saves ≈50% duration of manipulation compared to the individual gripping fashion. Herein, new insights may be offered in this study into a novel manipulation strategy for efficiently transporting dispersed granular materials.

Physical compensation method for dispersion of multiple materials in swept source optical coherence tomography.

An ophthalmic swept source-optical coherence tomography (SS-OCT) system based on a high-speed scanning laser at 1060 nm with a scanning rate of 100 KHz is constructed. Since the sample arm of the interferometer is comprised of multiple glass materials, the ensuing dispersion severely degrades imaging quality. In this article, second-order dispersion simulation analysis for various materials was performed first, and dispersion equilibrium was implemented utilizing physical compensation methods. After dispersion compensation, an imaging depth in air of 4.013 mm was achieved in model eye experiments, and signal-to-noise ratio was enhanced by 11.6%, with a value of 53.8 dB. In vivo imaging of the human retina was performed to demonstrate structurally distinguishable retinal images, characterized by an axial resolution improvement of 19.8%, with a value of 7.7 μm close to the theoretical value of 7.5 μm. The proposed physical dispersion compensation method enhances imaging performance in SS-OCT systems, enabling visualization of several low scattering mediums.

Green Synthesis, Characterization, Antioxidant and Photocatalytic Dye Degradation Effects of Copper (Cu) Nanoparticles from the Aqueous Extract of Persea americana

Nanoparticles have played a very important role in modern research. This technology involves the synthesis of nanoparticles with controllable size, shape, and material dispersion at nanometer-scale lengths. In the current work, copper nanoparticles have been synthesized by simple green technology using Persea americana leaf extract. The formation of Cu NPs was monitored by recording UV-Vis absorption spectra showing surface plasmon resonance at 320 nm. The green synthetic copper nanoparticles will be further characterized by FT-IR, FESEM, EDS and XRD. FT-IR identified the presence of active groups and phenolic groups. The crystal morphology and size of the nanoparticles will be determined by FESEM and X-ray diffraction studies. It was found that the average particle size of the copper nanoparticles was in the range of 71 nm. These biosynthetic copper nanoparticles were tested for the photocatalytic dye degradation of commercially important textile dyes such as methylene blue The antioxidant activity of green synthesized nanoparticles from the fruit extract was analysed by DPPH-free radical scavenging assay method. The results show that green synthetic nanoparticles have strong dye degradation potential.

Temperature Dependence of the Thermo-Optic Coefficient of SiO2 Glass.

This paper presents a thorough analysis on the temperature dependence of the thermo-optic coefficient, dn/dT, of four bulk annealed pure-silica glass samples (type I-natural quartz: Infrasil 301; type II-quartz crystal powder: Heraeus Homosil; type III-synthetic vitreous silica: Corning 7980 and Suprasil 3001) from room temperature down to 0 K. The three/four term temperature dependent Sellmeier equations and respective coefficients were considered, which results from fitting to the raw data obtained by Leviton et al. The thermo-optic coefficient was extrapolated down to zero Kelvin. We have obtained dn/dT values ranging from 8.16 × 10-6 up to 8.53 × 10-6 for the four samples at 293 K and for a wavelength of 1.55 μm. For the Corning 7980 SiO2 glass, the thermo-optic coefficient decreases monotonically, from 8.74 × 10-6 down to 8.16 × 10-6, from the visible range up to the third telecommunication window, being almost constant above 1.3 μm. The Ghosh's model was revisited, and it was concluded that the thermal expansion coefficient only accounts for about 2% of the thermo-optic coefficient, and we have obtained an expression for the temperature behavior of the silica excitonic bandgap. Wemple's model was also analyzed where we have also considered the material dispersion in order to determine the coefficients and respective temperature dependences. The limitations of this model were also discussed.

Design of dispersion-flattened photonic crystal fiber with 800 nm wide low-dispersion band

We propose a new design for a dispersion-flattened photonic crystal fiber with 800 nm wide low-dispersion band by employing the imaginary-distance beam propagation method and the transparent boundary condition using BeamPROP simulation software. The chromatic dispersion of the fiber is −1.4 to 4.8 ps/nm·km in an 800 nm wavelength range of 1.1–1.9 μm. The effective mode area at a wavelength of 1.55 μm is 12.2 μm2 and the fiber can be easily joined to conventional nonlinear optical fiber with a small core. The calculated effective index is extremely linear via the wavelength, and the decision coefficient with an approximately straight function is 0.999996, this means the waveguide dispersion of the proposed PCF completely compensates for the material dispersion curves.

Study on the Properties and Morphology of Nano-ZnO Modified Asphalt Based on Molecular Dynamics and Experiments

Plenty of research has verified that nano-ZnO particles could improve the properties of asphalt, but studies on nano-ZnO-modified asphalt haven’t been conducted at the molecular level. Therefore, to investigate the effect of ZnO particles on the properties, structure and morphology of asphalt, the molecular dynamics (MD) methods were carried out. In this study, the models of asphalt, ZnO cluster and ZnO/asphalt blending systems with different particle sizes were built using Materials Studio software. Then, the interaction energies of ZnO/asphalt blending systems under different temperatures were calculated, and the effect of ZnO particles on the modulus and glass transition temperature of matrix asphalt was simulated. The results indicated that the bulk modulus of asphalt increased by ZnO with particle size at 4 Å, 6 Å, 8 Å and 10 Å increased by 15.09%, 12.46%, 10.06% and 8.51%, respectively, which can illustrate that the shear resistance ability and low-temperature properties of asphalt were enhanced. Compared with matrix asphalt, the glass transition temperature of the ZnO/asphalt system decreased by less than 0.1 K, indicating that ZnO’s effect on the low temperature of asphalt was not apparent. With the increase of ZnO particle size, the diffusion coefficient decreased sharply. Compared to matrix asphalt, when the particle size increased to 8 Å and 10 Å, the diffusion coefficient decreased by 13% and 22%, respectively. So, in practice projects, to achieve better dispersion of particle materials in base bitumen, a smaller particle size would be recommended. The results of the radial distribution function (RDF) and AFM simulation indicated that ZnO particles changed the micro-structure of asphalt and increased the roughness of the asphalt surface. As a result, ZnO particles bring matrix asphalt better physical properties.

Dispersion and Radiation Modelling in ESTE System Using Urban LPM

In cases of accidental or deliberate incidents involving a harmful agent in urban areas, a detailed modelling approach is required to include the building shapes and spatial locations. Simultaneously, when applied to crisis management, a simulation tool must meet strict time constraints. This work presents a Lagrangian particle model (LPM) for computing atmospheric dispersion. The model is implemented in the nuclear decision support system ESTE CBRN, a software tool developed to calculate the atmospheric dispersion of airborne hazardous materials and radiological impacts in the built-up area. The implemented LPM is based on Thomson’s solution for the nonstationary, three-dimensional Langevin equation model for turbulent diffusion. The simulation results are successfully analyzed by testing compatibility with Briggs sigma functions in the case of continuous release. The implemented LPM is compared with the Joint Urban 2003 Street Canyon Experiment for instantaneous puff releases. We compare the maximum concentrations and peak times measured during two intensive operational periods. The modeled peak times are mostly 10–20% smaller than the measured. Except for a few detector locations, the maximum concentrations are reproduced consistently. In the end, we demonstrate via calculation on single computers utilizing general-purpose computing on graphics processing units (GPGPU) that the implementation is well suited for an actual emergency response since the computational times (including dispersion and dose calculation) for an acceptable level of result accuracy are similar to the modeled event duration itself.

The Structural Changes and Its Impact on Optical Dispersion of PVA/PVP Embedded with Zinc Sulphate Nanoparticles and Irradiated with Electron-Beam

PVA/PVP films doped with zinc sulphate heptahydrate (ZnSO4·7H2O) nanoparticles (NPs) are prepared using an in situ chemical method. Furthermore, as-prepared samples are irradiated with an electron beam at doses of 20, 25, 30, 35, and 40 kGy. Elemental analyses using energy dispersive X-ray spectroscopy (EDXS) of the fresh films showed the existence of both zinc oxide and zinc sulphide as main and minor phases in sequence. Moreover, scanning electron microscope measurements (SEM) revealed that embedded Zn NPs have regular and evenly distributed pores inside PVA/PVP network. On the other hand, the structural variations due to e-beam irradiation are monitored by a high-resolution-transmission electron microscope (HR-TEM), which displayed that encapsulated Zn NPs are well dispersed and capped inside PVA/PVP structural network. The measured optical absorption coefficient (α) of PVA/PVP/zinc sulphate nanocomposite films showed an increase against e-beam dose. Moreover, the calculated optical energy gap, Eg, exhibited a reduction from 3.31 to 2.82 eV against the increase in irradiation dose. Evaluated values of wavelength at zero material dispersion (WZMD) indicated that e-beam irradiation can tune the structure of the studied samples to be used as a data transmitter in optical fiber telecommunication in the IR spectral range of 1.6842–1.0351 μm.

Evolution of the surface energy of BaTiO3 nanoparticles in the course of dispersant coating: An inverse gas chromatography study

Understanding the surface energy characteristics of nanoparticles is crucial for controlling their stability, dispersion, and subsequent material properties. In this study, we employed inverse gas chromatography (IGC) to investigate the changes in surface energy and its homogeneity of BaTiO3 nanoparticles during coating with a model dispersant, stearic acid (SA), at various coverage levels. The IGC results revealed that the SA coating led to a more stable and homogeneous dispersive surface energy, enhancing the overall stability of the nanoparticles. However, it also introduced heterogeneity in the specific surface energy, with a notable shift towards higher levels. The observed evolution of surface energy characteristics was consistent with trends of the adlayer formation as determined through conventional surface characterization techniques, including thermogravimetric analysis-gas chromatography mass spectrometry and diffuse reflectance infrared Fourier transform spectroscopy. The combined approach of IGC and conventional techniques suggested that the changes in surface energy characteristics were associated with the formation of a disordered organic adlayer through SA chemisorption at various surface sites on crystalline facets with diverse coordination configurations. This highlights the potential of IGC as a powerful monitoring tool for investigating molecular coatings on ceramic nanopowders. It enables not only the quantification of average surface states but also provides insights into their distribution, which is not practically achievable through other surface characterization techniques.

Methodology for the investigation of undeclared atmospheric releases of radionuclides: Application to recent radionuclide detections in Northern Europe from 2019 to 2022

Traces of radionuclides have been frequently detected in the European atmosphere for several years. The measured concentrations are usually very low, ranging from 0.1 to 10 μBq m−3, and do not pose any health or environmental problems.This study aims to diagnose the origin of small undeclared radionuclide releases into the atmosphere. An inverse modelling approach that combines environmental measurements and atmospheric transport modelling is first used to assess the source location of the release. In addition, the type and process of the nuclear facility from which the release could originate are investigated by identifying the isotope production pathways and comparing them with known typical inventories. These two parts of the proposed method are complementary and allow us to extract as much information as possible from a set of radionuclide measurement data.In a previous study, the origins of detections of various radionuclides (60Co, 134Cs, 137Cs, 103Ru, 106Ru, 141Ce, 95Nb, 95Zr) in Finland, Sweden and Estonia in June 2020 have been investigated.In this paper, the previous investigation is extended by analysing two additional events that occurred in northern Europe in July 2019 and May 2022, as well an overview of other unknown releases detected in Finland over the last decade. A more detailed analysis of the 2020 event is also provided by analysing new available environmental measurements.The calculations indicate that the source location of the three events appears to be in the same region, in Russian Federation. The most probable origin of the June 2020 release seems to be a primary ion exchange resin, after 2 to 5 months of decay, of a pressurized water reactor with fuel cladding failure, and dispersion of fissile material in the primary.The July 2019 and May 2022 events are of particularly noteworthy due to the simultaneous presence of 46Sc, which is neither produced nor in the fuel, nor in the primary loop of PWR or RBMK nuclear power plants, and typical corrosion-activated products from power plants (60Co). Two hypotheses are proposed to explain this source term: a mixture of various solid wastes or recently irradiated graphite from a RBMK reactor.The reliability of the methodology is demonstrated, in particular in the section dedicated to atmospheric transport modelling, and the successful association with source term analysis provides a valuable tool for future studies and assessments of both minor and major radionuclide releases.

Experimental investigation of powder mixed electrical discharge machining of LM-25/SiC composites: A response surface methodology coupled with desirability approach

ABSTRACT In the last few years, many experiments have been done on lightweight Al and SiCp MMCs for aerospace and automotive applications. The results have been consistent in the development of structural and super alloys. Present work explores the performance characteristics of powder mix EDM by machining Al, LM-25 alloy with various weight fractions of reinforcement (0%, 5%, and 10% SiC) and variable electrode material. The impact of heat treatment on the microstructure of Al LM-25/10%SiC MMC has also been examined. Experimental investigation has been conducted to examine the machine response by adjusting the process parameters by employing the statistical design of RSM. The machining characteristics have been estimated to assess the machine response, namely metal removal rate (MRR) and tool wear rate (TWR), which are closely related to process variables, discharge current (I p), pulse on time (Ton), servo voltage (V), different tool materials, varying work materials, and differing concentrations of abrasive particles. The ANOVA results show that tool material is the most crucial parameter for MRR, accounting for 11.90% of the total, followed by other process variables, and the pulse on time for TWR, accounting for 5.94% of the total. Scanning Electron Microscope (SEM) was used to examine the macrostructure of machined MMCs. A chemical microanalysis technique such as Energy Dispersive Spectroscopy (EDS) and X-ray diffraction (XRD) was used to determine the phase composition of the materials and material dispersion. Additionally, the desirability technique was used to identify the optimum machining conditions.

Wigner–Smith Time Delay Matrix for Electromagnetics: Systems With Material Dispersion and Losses

The Wigner-Smith (WS) time delay matrix relates a system’s scattering matrix to its frequency derivative and gives rise to so-called WS modes that experience well-defined group delays when interacting with the system. For systems composed of nondispersive and lossless materials, the WS time delay matrix previously was shown to consist of volume integrals of energy-like densities plus correction terms that account for the guiding, scattering, or radiating characteristics of the system. This study extends the use of the WS time delay matrix to systems composed of dispersive and lossy materials. Specifically, it shows that such systems’ WS time delay matrix can be expressed by augmenting the previously derived expressions with terms that account for the dispersive and lossy nature of the system, followed by a transformation that disentangles effects of losses from time delays. Analytical and numerical examples demonstrate the new formulation once again allows for the construction of frequency stable WS modes that experience well-defined group delays upon interacting with a system.

Evaluating Hyperbolic Dispersion Materials for Cancer Detection.

Current biosensors have limited application in clinical diagnostics as they lack the high order of specificity needed to detect low molecular analytes, especially in complex fluids (such as blood, urine, and saliva). In contrast, they are resistant to the suppression of non-specific binding. Hyperbolic metamaterials (HMMs) offer highly sought- after label-free detection and quantification techniques to circumvent sensitivity issues as low as 105 M concentration in angular sensitivity. This review discusses design strategies in detail and compares nuances in conventional plasmonic techniques to create susceptible miniaturized point-of-care devices. A substantial portion of the review is devoted to developing low optical loss reconfigurable HMM devices for active cancer bioassay platforms. A future perspective of HMM-based biosensors for cancer biomarker detection is provided.

Chromatic dispersion of soft contact lens materials

PurposeTo investigate and evaluate the chromatic dispersion of various hydrogel and silicon hydrogel contact lens materials. MethodsEighteen different soft contact lens materials with high and low water content in lens power of −1.00 DS were measured by one operator at temperature of 20 °C ± 0.5° soaked in ISO standard phosphate-buffered saline (PBS) and in their respective packaging solutions (PS). An analogue Abbe refractometer (Model Zuzi 320, AUXILAB, S.L., Navarra, Spain) was used for refractive index (RI) measurements at 5 different wavelengths. All contact lenses were presented in a random and masked order to the operator. The Bland-Altman method with 95 % limits of agreement (LoA) and coefficient of repeatability (CoR) was used to characterise the repeatability of refractive index measurements. The Abbe numbers for each material were calculated by entering the measured and interpolated refractive indices into the Abbe number equation. One-way ANOVA analysis was used to test if there were significant differences between the 5 different wavelengths (470 nm–680 nm) within each material. An unpaired t-test was used to determine if there were differences in refractive index or dispersion between packaging solution and PBS results. ResultsNelfilcon A (Dailies Aqua Comfort Plus) soaked in PS showed the best repeatability of all 18 examined soft contact lenses across all wavelengths with an average refractive index of 1.3848 for all 6 contact lenses with a standard deviation of 0.00064. The 95 % limits of agreement were between 1.3835 and 1.3860. The mean coefficient of repeatability for nelfilcon A was 0.00125. For contact lenses soaked in ISO Standard PBS comfilcon A (Biofinity) had the best repeatability. The average refractive index of all 6 contact lenses was 1.4041 with a standard deviation of 0.00031 and a coefficient of repeatability of 0.00060. The 95 % limits of agreement were between 1.4035 and 1.4047. The analysis with One-way ANOVA with multiple comparisons involving Holm-Sidak post-hoc, showed that there are significant differences (p < 0.001, Fratio = 376.2 between wavelengths and Fratio = 1559 between different refractive indices) in the refractive index of most common lens materials across the visible wavelength range. Based on unpaired t-test, there is no significant difference (p > 0.05) in the Abbe numbers of the tested lens materials whether they have been placed in the packaging solution or in standard PBS (p > 0.05, 95 % CI = −4.8070 to 5.8680, t = 0.2054). The Abbe numbers for the calculated contact lenses soaked in PS ranged between 43.7 and 89.9. For contact lenses stored in PBS the range was between 46.3 and 81.6. ConclusionThere is a good repeatability between repeated RI measurements taken from the same lens and from the same material. The significant differences between the refractive indices across the 5 different wavelengths showed the presence of chromatic dispersion in the 18 evaluated soft contact lens materials. Furthermore, it could be shown that there is no significant difference in dispersion whether the contact lenses are soaked in standard PBS or in their respective packaging solutions. With no other published data available as a reference, absolute accuracy of the calculated Abbe numbers remains to be confirmed, however, this study did confirm that significant chromatic dispersion exists in soft contact lens materials.

Magnetic gold catalysts obtained by sequential preparation for highly efficient catalytic reduction of nitroaromatics

Noble metal catalysts have received considerable interests owing to their glamorous properties and applications in heterogeneous catalysis. In this work, the magnetic Au nanoparticles catalysts were successful fabricated via sequential preparation strategy at room temperature. 4-nitrophenol was chosen as the model molecule to evaluate the catalytic reduction activity for the preparation of amines from their corresponding nitroaromatics. The results showed that the catalytic reaction related with 4-nitrophenol could be achieved in 3 min, and the catalyst could be easily reused at least 15 cycles without significant reduction in activity when the as-prepared Fe3O4@CB6@Au0.4% nanoparticles acted as the catalyst. It revealed that the as-prepared catalyst exhibited outstanding catalytic performance and cycling stability. The SEM and TEM images demonstrated that the Au species presented in composite system in the form of highly dispersed Au0 nanoparticles, playing a crucial role in the catalytic process. Therefore, the Au nanoparticles combined with Fe3O4@CB6 prepared by the sequential preparation strategy had excellent catalytic reduction properties for nitroaromatics, and the method could open a new way for the design of other highly dispersed nanometallic materials.

Investigation on Physico Chemical and X-ray Shielding Performance of Zinc Doped Nano-WO3 Epoxy Composite for Light Weight Lead Free Aprons.

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO3) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO3 nanoparticles of 20 to 400 nm were synthesized by an inexpensive and scalable chemical acid-precipitation method. The prepared nanoparticles were subjected to X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, photoluminescence, high-resolution-transmission electron microscope, scanning electron microscope, and the results showed that doping plays a critical role in influencing the physico-chemical properties. The prepared nanoparticles were used as shielding material in this study, which were dispersed in a non-water soluble durable epoxy resin polymer matrix and the dispersed materials were coated over a rexine cloth using the drop-casting method. The X-ray shielding performance was evaluated by estimating the linear attenuation coefficient (μ), mass attenuation coefficient (μm), half value layer (HVL), and X-ray percentage of attenuation. Overall, an improvement in X-ray attenuation in the range of 40-100 kVp was observed for the undoped WO3 nanoparticles and Zn-doped WO3 nanoparticles, which was nearly equal to lead oxide-based aprons (reference material). At 40 kVp, the percentage of attenuation of 2% Zn doped WO3 was 97% which was better than that of other prepared aprons. This study proves that 2% Zn doped WO3 epoxy composite yields a better particle size distribution, μm, and lower HVL value and hence it can be a convenient lead free X-ray shielding apron.

Solving partial differential equation for atmospheric dispersion of radioactive material using physics-informed neural network

The governing equations of atmospheric dispersion most often taking the form of a second-order partial differential equation (PDE). Currently, typical computational codes for predicting atmospheric dispersion use the Gaussian plume model that is an analytic solution. A Gaussian model is simple and enables rapid simulations, but it can be difficult to apply to situations with complex model parameters. Recently, a method of solving PDEs using artificial neural networks called physics-informed neural network (PINN) has been proposed. The PINN assumes the latent (hidden) solution of a PDE as an arbitrary neural network model and approximates the solution by optimizing the model. Unlike a Gaussian model, the PINN is intuitive in that it does not require special assumptions and uses the original equation without modifications. In this paper, we describe an approach to atmospheric dispersion modeling using the PINN and show its applicability through simple case studies. The results are compared with analytic and fundamental numerical methods to assess the accuracy and other features. The proposed PINN approximates the solution with reasonable accuracy. Considering that its procedure is divided into training and prediction steps, the PINN also offers the advantage of rapid simulations once the training is over.

Net cleaning impacts Atlantic salmon gill health through microbiome dysbiosis

IntroductionNet biofouling has a significant impact for the global salmon industry in the seawater grow-out stage in terms of its management. Current mitigation strategies occur primarily through the regular removal of biofouling using in situ cleaning. While in situ net cleaning is effective there is uncertainty as to whether the equipment or dispersed material has an impact upon the fish in the cages. Through direct contact with the environment, the significant surface area of the gill including its microbiome is directly exposed to the acute environmental changes generated by net cleaning. This study aimed to provide a detailed understanding of the impact of in situ net cleaning on Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) gill health.MethodsThree field trials were conducted on commercial fish farms in western Norway. Fouling organisms on net pens and flushed particles during in situ cleaning were identified and screened for major fish pathogens. Hydrographic profile measurements were performed to measure the impact on water quality. Gill samples were examined for histopathological changes, immune gene expression, and the prevalence of major pathogens. 16S rRNA amplicon sequencing was employed to explore the impact of net cleaning on gill microbiome.Results and discussionData obtained from these trials identified a diversity of fouling species including hydroids, algae, skeleton shrimps, and filter feeders on net pens, a direct impact on measured water quality indicators, a moderate change in gill inflammatory and antigen presentation activity at the level of mRNA, and a large significant change in gill microbiome. Observed changes in gill microbial community involved a decrease in bacterial richness coupled to an increase in identified bacterial genera related to negative health consequences. Parallel analyses for pathogens load in biofouling organisms and flushed particles highlighted the presence of several fish bacteria and parasites. However, minor changes were detected in salmon gill pathogen diversity and loading. Our results suggest that biofouling organisms may act as transient reservoirs for some fish pathogens but not viruses and that gill microbial dysbiosis could be related to the host stress response during and post net cleaning.