Matrix Solution Research Articles

Magnetic Circular Dichroism of Oxide Films: Study of Electronic, Magnetic and Charge States

Semiconductor materials based on ZnO and RE3+MnO3 oxides are considered as potential candidates for spintronics. This article presents the methodology and results of studying the effect of magnetic circular dichroism for Zn1-xCoxO, Zn1-x-yCoxAlyO and RE1-x 3+Ax 2+MnO3 film structures in the visible radiation range. It has been shown that the magnetic circular dichroism behavior of the manganite films reflects not only the magnetic, but also the charge component of the material. This indicates the possibility of studying the magnetic and transport characteristics of the films using the magnetic circular dichroism spectroscopy. Since the magnetic circular dichroism effect also directly probes the ground and excited electronic states of the film, it has been obtained data that update calculated parameters for describing the manganites band structure. In the case of the Zn1-xCoxO and Zn1-x-yCoxAlyO films, the magnetic circular dichroism spectroscopy acts as a tool for detecting Co nanoparticles in the solid solution matrix of ZnO:Co and ZnO:(Co+Al).

Low-resource dynamic loading identification of nonlinear system using pretraining

To address the challenge of load identification in nonlinear systems, an audio neural network-based method called WaveNet is proposed that leverages its capability to capture long-term dependencies in mechanical systems, enabling accurate load identification. Unlike traditional dynamic load identification methods that often encounter difficulties with matrix solutions, this approach takes advantage of WaveNet’s capabilities, enhancing both accuracy and efficiency. We integrate pre-training and transfer learning techniques to address the data scarcity challenges often encountered in real-world engineering applications. By transferring features across distributed datasets, this method reduces the dependency on single-task data, thereby improving model robustness. The performance of the WaveNet method is rigorously evaluated against traditional benchmarks such as Multilayer Perceptron (MLP) and Convolutional Neural Network (CNN) benchmarks under random load conditions applied to a complex structural framework. The proposed method achieves a root mean squared error (RMSE) of 1.521 and a determination coefficient (R²) of 0.996 in the random load case, demonstrating superior accuracy compared to other approaches. Moreover, its applicability is verified through simulations of both impact load and harmonic load scenarios, showcasing the effectiveness of transfer learning in overcoming domain discrepancies. Finally, the method is tested in random experiments to validate its engineering applicability. The results highlight the significant accuracy improvement in low-resource tasks achieved through pre-training, showcasing the potential and value of the proposed method.

Determination of 42 antimicrobials in disinfection products by dispersive solid phase extraction-high performance liquid chromatography-tandem mass spectrometry

Antimicrobials inhibit the growth and reproduction of microorganisms thereby alleviating skin and other problems caused by microorganisms. Antimicrobials are classified into different categories, including antibacterials, antifungals, and antivirals, among others, and include azoles, sulfonamides, tetracyclines, quinolones, and many other classes of synthetic and natural compound. The inappropriate or excessive use of antimicrobials can damage skin and other human organs and increase antimicrobial resistance. Relevant regulations and standards clearly state that antimicrobials are prohibited for use as ingredients in disinfection products. However, since antimicrobials enhance the disinfection or antibacterial effect of a product, with a significant short-term effect, antimicrobials are occasionally illegally added to disinfectant products, including those intended for human use. Therefore, establishing testing methods that provide technical support for enforcing regulations is an urgent objective. Herein, a method was established for the analysis of 42 antimicrobials in disinfection products, that is applicable to common types of disinfection-product matrix, including creams, gels, and aqueous solutions, using high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) combined with dispersive solid phase extraction. The 42 antimicrobials comprise antibacterials, antifungals, and antivirals, and include seven sulfonamides, ten quinolones, three lincosamides, five tetracyclines, three macrolides, eight azoles, three purine nucleoside analogs, one furan, one nonpolyene antifungal, and one steroid. Briefly, 0.2 g of a sample was first dispersed in 2 mL of water and then extracted with 10 mL of 0.5% formic acid in acetonitrile, with 3 g of anhydrous Na2SO4 added to remove water. After centrifugation, 5 mL of the supernatant was cleaned using dispersive solid phase extraction with EMR-Lipid as the adsorbent. Lipids, waxes, surfactants, and moisturizing lubricants are commonly used as cream and gel matrices. Matrix substances containing long carbon chains dissolved in acetonitrile were removed using the EMR-Lipid adsorbent. Target analytes were separated on a Poroshell 120 EC-C18 analytical chromatography column (150 mm×3.0 mm, 2.7 μm), with 0.1% formic acid in acetonitrile and 0.1% formic acid aqueous solution used as mobile phases under gradient-elution conditions. The target analytes in the test solution were detected in positive ionization (ESI+) and multi-reaction-monitoring (MRM) modes. Analytes were characterized in terms of their retention times and selected ions, and quantified using the external-standard method. The main factors affecting method response, recovery, and sensitivity, such as the extraction method and solvent, purification method and adsorbent, mobile phase, and MS conditions, were examined during sample pretreatment and instrumental analysis. The 42 antimicrobials were effectively separated under the optimized experimental conditions; the target compounds exhibited linear working curves in the 0.25-5.0 mg/kg concentration range, with correlation coefficients (r) greater than 0.99. Limits of detection (LODs) for the 42 antimicrobials were determined from the signal-to-noise ratios (S/N) of their chromatographic peaks. LODs of 0.03-0.10 mg/kg were determined for the three matrices using 0.2-g samples and 10-mL test solution. Recoveries of 80.3-109.8%, with relative standard deviations (RSDs) of less than 9.8%, were obtained by determining three levels of each target analyte added to the three blank matrices; this process was repeated for six parallel samples. The developed method was used to analyze antimicrobials in commercially available disinfection products, with two sample batches testing positive. The established method is simple, accurate, precise, and suitable for the rapid screening and quantification of antimicrobials in disinfection products. This study provides powerful technical support for regulating the illegal addition of related antimicrobials to disinfection products.

Effect of texture, grain boundary constitution, and molybdenum partitioning on corrosion and hydrogen permeation behavior of pulse electrodeposited Ni-Mo coatings

Microstructural evolution, electrochemical corrosion and hydrogen permeation in pulse electrodeposited Ni-Mo coatings (2, 4, 8, and 11wt% Mo) were investigated. Electrochemical impedance spectroscopy and potentiodynamic polarization measurements revealed improved corrosion resistance at an optimum Mo content. The corrosion current density icorr and polarization resistance Rp values obtained were 13.8 μA/cm2 and 1745 Ωcm2 respectively for pure Ni coating while the icorr and Rp values obtained were 1.7 μA/cm2 and 5406 Ωcm2 respectively for Ni-4wt% Mo coating. Further, increase in the Mo content beyond 4 wt% increased the corrosion rate. Nevertheless, corrosion resistance of Ni-Mo coatings was found to be higher than the pure Ni coating. Ni-Mo coatings contained relatively Mo-enriched clusters in a solid solution matrix. The highest corrosion resistance of Ni-4wt% Mo coating was due to lower energy (001) and (111) textures, lower energy grain boundary constitution, and low coating strain. In Ni-4wt% Mo coating, Mo-enriched Ni-Mo nanoclusters inhibited hydrogen passage by providing a torturous path. In contrast, a high fraction of high-angle grain boundaries (compared to pure Ni coating) facilitated hydrogen permeation leading to a similar extent of hydrogen permeation through pure Ni and Ni-4wt% Mo coatings.

Disturbance observer-based fuzzy adaptive switched tuning control of uncertain nonlinear systems with full state constraints

This article examines the issue of disturbance observer-based fuzzy adaptive switched tuning output feedback control for a family of uncertain nonlinear systems subjected to full state constraints. By introducing monotonically bounded positive time-varying gain functions (TVGFs), a set of improved intermediate-variable-based disturbance observers (IVBDOs) is devised. Applying the convex combination technique and the LMI toolbox, the solution of the observation gain matrix is realized. Combining the switched tuning control function and the composite integral barrier Lyapunov method, a new switching nature controller is constructed. Particularly, the developed framework overcomes the conservatism of conventional constraints. Through theoretical analysis, it is exhibited that for any given initial value of the system, all states of the system are enclosed within predetermined compact sets while all signals are bounded. Lastly, simulation and experimental results under unknown disturbances attest the validity and superiority of the suggested strategy.

Utilization of Schiff base ligands to chelate Ag+ for highly specific and sensitive Hg2+/Ag+ immunoassay

In this study, a planar benzothiazole Schiff base derivative ZX1 was designed and synthesized to selectively precipitate silver ions, in conjunction with the immunoassay detection of Hg2+ ions. The silver chelation process was highly effective in the pH range of 7–10, with a silver ion precipitation ratio of 99.9 %. The coordination behavior of ZX1 with Ag+ was studied using a series of spectroscopic measurements, topography analysis and DFT calculation. The shortest bond distances were 2.251 and 2.254 Å between nitrogen atom of thiazole and Ag+. Weak interactions were analyzed using the interaction region indicator (IRI) method and VMD. The immunoassay was developed through an anti-Hg2+/Ag+ monoclonal antibody, which showed similar sensitivities for Ag+ and Hg2+. The selectivity and anti-interference ability of the Schiff base ligands were tested for some hard metal ions and several anions. With co-existence of interference ion Ag+, Hg2+ was detected in rice matrix solution with 77 %∼123.5 % recovery by addition of ZX1 as the masking reagent and 90.3 %∼115 % for wheat matrix. This research provides a promising immunoassay strategy for simultaneous detection of silver ions and mercury ions in food matrix by utilization of Schiff base ligands. This novel Schiff base ligand was then used as the pre-treatment reagent to remove silver ions within 5 min for detection of Hg2+ or detection of both Ag+ and Hg2+ based on a novel bi-specific heavy metal antibody.

Liquid chromatography-mass spectrometric method for the simultaneous analysis of branched-chain amino acids and their ketoacids from dried blood spot as secondary analytes for the detection of maple syrup urine disease

BackgroundMaple syrup urine disease (MSUD) is an aminoacidopathy caused by a defective branched-chain alpha-ketoacid dehydrogenase complex, leading to the accumulation of branched-chain amino acids (BCAAs) and their respective keto acids (BCKAs). A comprehensive test was developed to measure BCAAs and BCKAs using LC-MS from dried blood spot (DBS) samples for the diagnosis and prevention of MSUD in newborns and infants. MethodsAnalytes were extracted from DBS using a methanol:0.1 % v/v formic acid solution (75:25) containing internal standards and analyzed on a Luna PFP column (150 mm × 4.6 mm, 3 µm) at a flow rate of 0.3 mL/min. The method was validated for linearity, accuracy, precision, recovery, carry-over, matrix effect, hematocrit, blood volume, and punch position effects. Biomarker stability in the matrix and stock solution was assessed. Correlation with the plasma method was determined using Pearson’s correlation coefficient and Bland-Altman analysis. The method established reference ranges for the Udupi district population in South India. ResultsThe method demonstrated linearity (r2 > 0.99), with a lower limit of detection at 2 µM (BCAA) and 1 µM (BCKA), and acceptable recovery of QC samples. Hematocrit, blood volume, punch position, and storage condition effects were within acceptable limits. Correlation and Bland-Altman analysis showed strong interconvertibility between plasma and DBS assays. Reference ranges for leucine, isoleucine, valine, KIC, KIV, and KMV were established. ConclusionThe developed DBS method, requiring no derivatization and involving simple sample preparation with short run times, is a cost-effective and reliable approach for the confirmatory diagnosis of MSUD.

Design solutions to optimise acoustic requirements for specific work activities in open-plan offices

A high level of concentration is required in open-plan offices, which entails an optimized acoustic environment. The aim is to create a fit-employee environment in which speech privacy is guaranteed without compromising the sense of cooperation among occupants. The purpose of this study is to investigate the design solutions which optimize the acoustic requirements of ISO 3382-3 for a specific work activity defined in ISO 22955, such as non-collaborative work, collaborative work between people and mixed between collaborative and non-collaborative. The case study is one open-plan office occupied by 12 workers, which was not compliant with the standard. Acoustic measurements were used to calibrate the acoustic model in the Odeon software. Two screen and cubicle heights, three types of ceilings and two wall absorption configurations have been tested in a matrix of solutions for the office in the simulation model. This allowed us to investigate the design solutions that guarantee optimal values for the acoustical parameters chosen for each specific activity.

Flanking transmission from structure-borne sound sources in heavyweight buildings over multiple junctions

In many buildings, rooms that contain vibrationally-active machinery are not always adjacent to habitable rooms; hence it is useful to be able to predict vibration transmission over multiple junctions to non-adjacent rooms. In the first version of the European Standard EN 12354 Part 5 (2009) the equivalent vibration reduction index was introduced to account for transmission across multiple junctions. This was removed in the 2023 version but there remains a need for these estimates at the design stage of a building. This paper compares predictions of vibration transmission from a wall to different receiving rooms in a large heavyweight building. The SEA matrix solution is compared with SEA path analysis using different numbers of paths to assess whether path analysis is feasible, and if so, what errors can be expected when using a limited number of paths. An alternative approach to path analysis is to use transmission functions for heavyweight buildings, and an initial assessment is made to see whether these are expected to vary significantly depending on the position in the building.

Excellent radiation resistance via enforced local non-directional He diffusion in a WTaCrV multicomponent alloy containing coherent ordered nanoprecipitates

We design and investigate a W15Ta15Cr35V35 (at.%) multicomponent alloy (MCA) with exceptional radiation resistance. The sintered WTaCrV alloy exhibits a body-centered cubic (BCC) matrix with dispersed coherent ordered nanoprecipitates. After ∼3-hour irradiation under 400 keV He+ at room temperature (RT) and 450°C with a fluence of 2 × 1017 ions/cm2, the irradiation hardening values of the MCA are about a quarter of those of pure tungsten counterparts irradiated at identical conditions. Besides, helium bubbles generated in the irradiated matrix of the MCA are much smaller, compared with those in the pure tungsten and other tungsten-rich alloys previously reported. The exceptional radiation resistance of the present WTaCrV alloy can be mainly attributed to two synergistic mechanisms. First, the high lattice distortion of the solid solution matrix promotes the local non-directional diffusion of irradiation defects, effectively suppressing the aggregation of irradiation defects and helium atoms along specific orientations. This facilitates more uniform nucleation of helium bubbles in the alloy matrix. Second, carbon was introduced during fast hot pressing sintering as interstitial solute to form carbon-rich coherent ordered nanoprecipitates. The carbon-vacancy complexes generated in the nanoprecipitates inhibit the nucleation and aggregation of helium atoms at the vacancies during He+ irradiation. The above two mechanisms synergistically enhance the resistance against He+ irradiation. This work thus demonstrates a design strategy for high radiation resistance alloys by introducing well-tuned ordered coherent nanoprecipitates in multicomponent alloy systems.

CALCULATION OF FLAT SHELLS BY THE BOUNDARY ELEMENT METHOD

This article describes the iterative process of solving the problem of the stress-strain state of a long flexible cylindrical panel. Stress-strain state and the study of the stability of flat shells taking into account the physical, mechanical properties of the material, the process of deformation change. It is based on sequential approximation methods and the boundary element method (MGE). The results of algorithmic weighting are presented in the form of a table showing what value each band represents. The equations are determined by solving twelve unknown values of functions at the ends of the segment. Linear problems of elasticity theory and plate theory fundamental solutions have a simple form, so the method is widely used here. For flat shells, the matrix of fundamental solutions is determined by complex volumetric expressions, and for flat shells - by special functions. Therefore, there is little research on solving problems in the theory of flat shells by the boundary element method. In this regard, an urgent topic of research is the development of methods of boundary integral equations for solving linear and nonlinear problems in the theory of flat shells based on the application of fundamental solutions defined by simple analytical expressions. The scientific novelty of the work consists in the development of a methodology for assessing the reliability of thin-walled spatial structures using the boundary element method.

New insight for designing high-strength medium-entropy alloy with resistance to intermediate-temperature embrittlement by nitrogen-induced Ti-rich precipitation mechanism

Intermediate-temperature embrittlement is a common problem faced by many multi-component alloys. In this study, we propose the introduction of nitrogen into a lightweight TiVNb medium-entropy alloy to enhance solution strengthening and induce titanium segregation. Titanium-rich precipitates in turbine blade-like structures near the grain boundaries of a body-centred cubic solution matrix yield alloys that exhibit tensile ductility at intermediate temperatures. The titanium-rich precipitates dominantly have a face-centred cubic structure coupled with a small amount of hexagonal close-packed structure. The size of the titanium-rich phase increases with increasing nitrogen content from 0.5 % to 1.5 %, as does the alloy strength. The tensile yield strength of TiVNb-N1.5 reaches 1247 MPa at room temperature and 623 MPa at 800 °C, with a strain of 10 %. These values indicate that the prepared alloy overcomes the ultra-low strain of the base alloy at intermediate temperatures. By combining the MRS-Swap algorithm with the density functional theory, the formation mechanism of Ti-rich phases is deduced. This study further elucidates the types and pathways of interstitial elements that can induce FCC-Ti formation.

Growth temperature-dependent properties of electrodeposited CdSe thin films for optoelectronic application

Cadmium selenide (CdSe) thin films were synthesized using a two-electrode electrodeposition technique in potentiostatic mode. The solution matrix contains 0.3 M Cd(NO3)2.4H2O and 0.03 M SeO2 on conductive glass substrates/fluorine-doped tin oxide (FTO). The electrodeposited CdSe thin films were examined at various growth temperatures of 55, 65, and 85 °C, both as-deposited (AD) and annealed (HT) samples. A polycrystalline cubic structure of the prepared CdSe thin films was identified using x-ray powder diffraction. The energy bandgap of films was found to vary with deposition temperature and was recorded as 1.85, 2.00, and 2.13 eV for AD and 1.86, 2.16 and 2.70 eV for HT samples deposited at 55, 65, and 85 °C, respectively. Surface morphology images show that the form and grain size varied with growth temperature. The average surface roughness varied with deposition temperature. The elemental analysis confirmed that the proportion of cadmium (Cd) increased while that of Se decreased as the deposition temperature increased for both AD and HT films. The film that was deposited at low temperature (55 °C) can be as a layer for absorption. Conversely, however the film deposited at a high growth temperature (85 °C) is capable of serving as a buffer layer in thin-film solar cell technology.

Removal of Pb2+ and Cu2+ from artificial geothermal brine by zeolite at various salinity and temperature conditions

Natural zeolite (predominantly clinoptilolite - Ca) was tested for application in geothermal facilities to remove copper (Cu2+) and lead (Pb2+) from formation fluids. Batch and dynamic flow-through (only for lead ions) experiments were performed at different salinities (I = 0.1 and 1 mol/L) in NaCl or CaCl2 solutions at up to 115 °C (batch experiments) and up to 130 °C (flow-through experiments), respectively. The batch experiments resulted in an uptake of up to 24 % at an initial concentration of 0.3 g/L and up to 93 % at 0.03 g/L of Pb2+ and 115 °C. For Cu2+, the uptake reached 100 % from initial 0.004 g/L. The presence of CaCl2 in the solution matrix reduced the uptake of the heavy metals as compared to the NaCl matrix. The Pb2+ uptake by zeolite granulates at dynamic flow-through conditions at 130 °C was 52 % of the initial value of 20.7 mg/L during the 180 min experimental time. Based on the results from batch experiments the data fitting indicated a site density of monovalent exchange sites of 3.0 ± 2.6 mmol/g solid and a cation exchange capacity (CEC) of 295 ± 26 meq/100 g zeolite. The Pb2+ uptake process by zeolite gave a KD value of log K = 1.53. These calculations were not possible for Cu2+ uptake indicating that the uptake mechanisms of Cu2+ at high salinities are too complex to be simulated.To explain the uptake processes at given conditions various structural analysis were performed. Infrared spectroscopy indicated a cation exchange of lighter ions in the crystal structure of zeolite by the heavier ions Cu2+ and Pb2+ at 650 to 750 cm−1. After the treatment with heavy metals, two new bands were detected at 2902 and 2982 cm−1, which were not observed in the natural zeolite. With X-ray diffraction (XRD) new crystalline phases were detected in the treated zeolite samples that could be attributed in case of Pb2+ uptake to cottunite (PbCl2) and laurionite (PbOHCl) and in the case of Cu2+ uptake to Cu2Cl(OH)3 and CuCl2. The simulated G(r)s supported these observations regarding Pb2+ uptake. Using electron microscopy methods, both mechanisms (ion exchange and mineral precipitation) were confirmed: the formation of new Pb2+ and Cu2+ containing mineral phases on the surface of the zeolite granules and the uniform distribution of chloro-coordinated complexes of Cu2+ and Pb2+ on the pore surfaces inside the zeolite.

Facile fabrication of the immuno-MALDI-MS chip for the enrichment of abused drug in human urine integrated with MALDI-MS analysis

BackgroundDrug abuse can result in both physical and mental health issues for individuals, and can also contribute to broader societal problems. The number of drug abuse cases rose to 296 million in 2021. The sample pretreatment methods commonly employed typically require longer processing times and occasionally necessitate derivatization. Furthermore, with the increase in sample sizes, traditional chromatography-mass spectrometry methods for analyzing abused drugs were no longer sufficient to handle such numerous samples. In this study, immuno-MALDI-MS chip were fabricated for specific enrichment of illicit drugs, integrating with the rapid and accurate capabilities of MALDI-MS for high-throughput analysis of drug abuse. ResultsThe immuno-MALDI-MS chip was successfully prepared by coating an aluminum chip with antibody-conjugated boronic acid-modified gold nanoparticles. Ketamine, a frequently abused illicit drug, served as the proof of concept for this study. The immuno-MALDI-MS chip was employed to selectively enrich ketamine in human urine samples, facilitating direct MALDI-MS analysis with the addition of α-CHCA matrix solution. The challenge of detecting abused drugs, exacerbated by interfering peaks in the low m/z region from salts and small molecules in human urine samples, was successfully overcome. The developed method exhibited a wide linear range of 10–5000 ng/mL with a limit of detection of 3.3 ng/mL for ketamine. Notably, the proposed method enabled high-throughput screening and accurate confirmation of ketamine concentrations in suspects' urine samples within few minutes, requiring a minimal sample volume of 1 μL. The obtained data were in complete agreement with the previous GC/MS analysis. SignificanceA straightforward, cost-effective and sensitive method for the selective enrichment and absolute quantification of abused drugs was developed using a homemade immuno-MALDI-MS chip integrated with MALDI-MS analysis. This method combines the advantages of immunoassay and mass spectrometry, offering both speed and accuracy. The reported method for the quantification of ketamine in human urine offers a practical approach and has the potential to analyze emerging new psychoactive substances in the future.

Deposition of CdSe Nanocrystals in Highly Porous SiO2 Matrices-In Situ Growth vs. Infiltration Methods.

Embedding quantum dots into porous matrices is a very beneficial approach for generating hybrid nanostructures with unique properties. In this contribution we explore strategies to dope nanoporous SiO2 thin films made by atomic layer deposition and selective wet chemical etching with precise control over pore size with CdSe quantum dots. Two distinct strategies were employed for quantum dot deposition: in situ growth of CdSe nanocrystals within the porous matrix via successive ionic layer adsorption reaction, and infiltration of pre-synthesized quantum dots. To address the impact of pore size, layers with 10 nm and 30 nm maximum pore diameter were used as the matrix. Our results show that though small pores are potentially accessible for the in situ approach, this strategy lacks controllability over the nanocrystal quality and size distribution. To dope layers with high-quality quantum dots with well-defined size distribution and optical properties, infiltration of preformed quantum dots is much more promising. It was observed that due to higher pore volume, 30 nm porous silica shows higher loading after treatment than the 10 nm porous silica matrix. This can be related to a better accessibility of the pores with higher pore size. The amount of infiltrated quantum dots can be influenced via drop-casting of additional solvents on a pre-drop-casted porous matrix as well as via varying the soaking time of a porous matrix in a quantum dot solution. Luminescent quantum dots deposited via this strategy keep their luminescent properties, and the resulting thin films with immobilized quantum dots are suited for integration into optoelectronic devices.

Crystal field optimization, luminescence enhancement and thermal stability of novel K2NaAl0.4Ga0.6F6:Mn4+ solid solution red phosphor for high-performance warm WLED

Mn4+-doped fluoride phosphors have important application value in the background light and WLED lighting fields. Therefore, the synthesis of efficient and stable Mn4+-doped red phosphor is of great application value. In this study, a series of red-emitting K2NaAl1-yGayF6:xMn4+ (y = 0, 0.2, 0.4, 0.6, 0.8 and 1) (x = 0.01, 0.03, 0.05, 0.07 and 0.09) solid solution phosphors are successfully synthesized by simple coprecipitation method. The synthesis strategy of simple crystal structure optimization is proposed to realize simultaneously the crystal field optimization, luminescence enhancement and thermal stability of red phosphor. The calculation and theoretical analysis of crystal field strength are used to prove that solid solution matrix K2NaAl0.4Ga0.6F6 is the most ideal matrix material. X-ray powder diffraction, energy-dispersive X-ray spectrometer and scanning electron microscope are employed to determine the crystal structure, composition and morphology of all samples. Optical properties are characterized using excitation spectra, emission spectra and fluorescence lifetime curves. Moreover, the CIE coordinates of red-light show that the phosphor has low correlated color temperature and excellent color purity. Intriguingly, the as-prepared K2NaAl0.4Ga0.6F6:Mn4+ phosphor possesses admirable thermal quenching behavior and color stability at high temperature. At a temperature of 423 K, the photoluminescence intensity can be maintained at 52 % of the original intensity (298 K). The activation energy, the chromaticity shift and chromaticity coordinate variation are also systematically calculated. More importantly, A high-performance warm WLED with low correlated color temperature (CCT = 3982 K) and high color rendering index (Ra = 93.7) is achieved by using K2NaAl0.4Ga0.6F6:Mn4+ as a red-emitting material. These results demonstrate that K2NaAl0.4Ga0.6F6:Mn4+ red phosphor provides a novel choice for the warm WLED required for indoor lighting.

Anomalous temperature-dependent strength of copper alloy manufactured by laser-beam powder bed fusion

This study reports an anomalous temperature-dependent tensile behavior of laser-beam powder bed fusion (PBF-LB) processed Cu–Cr–Zr alloy. The yield strength of the alloy initially decreases as the temperature increases to 200±5 MPa and then increases to 350±11 MPa at 500°C before reducing to 234±6 MPa at 600°C. The microstructure consists of elongated Cu grains with a high concentration of Cr solute (∼1 mass%), resulting from rapid solidification during the PBF-LB process. Transmission electron microscopy for the specimens deformed at 500°C revealed the presence of numerous nanoscale Cr-rich particles embedded inside the supersaturated solid solution of the Cu matrix. Nanoscale particles can act as barriers to dislocation motion, leading to an increase in internal stress during plastic deformation at elevated temperatures. This work provides the high potential of post heat treatments for achieving superior mechanical performance using high solute supersaturation formed by the PBF-LB process.

Evaluation of morphology, physical and mechanical properties of hyaluronic acid matrices of various molecular weights by atomic force microscopy

Using atomic force microscopy the morphology of 1 and 2 % sodium hyaluronate solutions matrix with low molecular weight (LM) and high molecular weight (HM) hyaluronic acid (HA) fabricated by bioenzymatic synthesis was evaluated. The presence of a proteoglycan aggregate with processes of the core protein in the absence of sulfated glycosaminoglycans was established. The effect of irradiation with a light flux on the ordering of the HA matrix was observed. Intermolecular consolidation of high molecular HA was established. The elastic modulus of the matrix with LM and HM HA has also been determined.

Manifold Gaussian Variational Bayes on the Precision Matrix.

We propose an optimization algorithm for variational inference (VI) in complex models. Our approach relies on natural gradient updates where the variational space is a Riemann manifold. We develop an efficient algorithm for gaussian variational inference whose updates satisfy the positive definite constraint on the variational covariance matrix. Our manifold gaussian variational Bayes on the precision matrix (MGVBP) solution provides simple update rules, is straightforward to implement, and the use of the precision matrix parameterization has a significant computational advantage. Due to its black-box nature, MGVBP stands as a ready-to-use solution for VI in complex models. Over five data sets, we empirically validate our feasible approach on different statistical and econometric models, discussing its performance with respect to baseline methods.