Mr Values Research Articles

Predicting Resilient Modulus of Fine‐Grained Soils Using Support Vector Machine‐RBF and Random Forest

The resilient modulus (Mr) of subgrade soils is an important element in road pavement structural design procedures. However, because of regional differences in soil parameters and the nature of test procedures, determining Mr in the laboratory has become cumbersome. The purpose of this study is to develop a reliable soft computing approach for forecasting Mr of subgrade soils using support vector machine‐based linear kernel (SVM‐LR), polynomial kernel (SVM‐Poly), radial basic function (SVM‐RBF), and random forest (RF) techniques. For this purpose, a dataset of 138 soil samples from diverse geographical locations in Ethiopia was gathered, and the models were trained and tested using an 85% training and 15% test data split. All of the recommended models used confining pressure (CP), notional maximum axial stress (NmaxAS), specific gravity, P#200, silt%, clay%, liquid limit (LL), plasticity index (PI), maximum dry density, Wopt, and swell as input variables. The correctness of the proposed models was assessed by comparing predicted and observed Mr values with various statistical approaches such as root means square error (RMSE), mean squared error (MSE), mean absolute error (MAE), and determination coefficient (R2). The support vector machine RBF model outperformed all other models in validation, with R2 values of 0.99 and 0.91, MAE of 0.1 and 1.76, MSE of 0.01 and 29.54, and RMSE of 0.1 and 5.43. The Taylor diagrams of the test and training datasets show that the SVM‐RBF model outperforms the other models. Sensitivity analysis was performed to explore the impact of input variable quantity on the output of Mr for the MPL model, and it was determined that the top five essential parameters are, in decreasing order, LL, P#200, silt%, PI, and clay%. In contrast, the nominal maximum axial stress and Gs have the least impact.

Studies of Fe<sub>3</sub>O<sub>4</sub> Nanoparticles Prepared by Co-Precipitation Method of FeSO<sub>4</sub> and FeCl<sub>3</sub> Solution

The magnetic properties of magnetite nanoparticles (Fe3O4 NPs) are being investigated. Fe3O4 NPs were prepared using the co-precipitation method and oven dried. The magnetic properties are influenced by the electron environments of the Fe3+ ions within the iron oxide structure. XPS spectra of Fe3+ (2p3/2) and (2p1/2) show peaks around 706.45 eV and 720.76 eV, respectively. Furthermore, magnetite NPs dried at 60 °C exhibited the largest hysteresis loop at 50K and less at 300K. In addition, the values of Ms and Mr indicate ferromagnetic behavior in Fe3O4 NPs. The result of this material shows high Ms (~38.638 emu/g) at 50K with Hc of 3.094K (near ferromagnetism) and ~33.843 emu/g at 300K with Hc of 0.000K (superparamagnetic). However, these magnetic properties are utilized for biomaterial applications such as separating biomolecules or coating core shells for nanoparticles, which presents an option for future biomedical technology.

Size effects on the magnetic properties of a system of ε-Fe2O3 nanoparticles embedded in a SiO2 xerogel matrix

A representative series of samples consisting of fine ε-Fe2O3 nanoparticles uniformly distributed over the SiO2 xerogel matrix with an iron oxide content of 5–33 wt % has been synthesized and studied by mutually complementary physical methods. It has been shown by the X-ray diffractometry and high-resolution electron microscopy examination that, with increasing iron oxide concentration, the average particle size <d> increases from 4 to 11 nm. According to the X-ray diffractometry and Mӧssbauer spectroscopy data, the samples with an iron oxide content of 5–20 wt % are single-phase, while at the highest Fe2O3 concentration (33 wt %), the β-Fe2O3 and α-Fe2O3 phases arise. As the average particle size <d> increases, a monotonic increase in coercivity HC and remanent magnetization MR of the synthesized systems at room temperature is observed, which is indicative of their magnetic hysteresis. The magnetic transition known to occur in the ε–Fe2O3 oxide manifests itself in all the investigated samples as a drastic change in the HC and MR values at 150–75 K. At the same time, a thorough analysis of the temperature dependence of the real part of the ac magnetic susceptibility χ′ has shown that the particles with a size smaller than a critical value of dC ∼6.5 nm do not undergo the magnetic transition and have a much lower magnetic anisotropy constant as compared with coarser particles (d > dC). It has been found that, in the low-temperature region, the magnetic moments of these fine particles experience superparamagnetic blocking. It has been established that the size effects that arise in ultra-fine ε–Fe2O3 particles has a serious impact on the macroscopic magnetic properties of the highly dispersed systems based on them.

Comparison of Lab vs. Backcalculated Moduli of Virgin Aggregate and Recycled Aggregate Base Layers

The resilient modulus (MR) and the backcalculated modulus from the FWD testing (EFWD) of the unbound layers are critical inputs in the analysis/design of pavements. Several studies have tried to develop a conversion factor between these two parameters, while the nonlinear stress dependency of unbound materials and the pavement strain response are mostly missing from the literature. This study aims to compare the laboratory-measured MR of recycled aggregate base (RAB) materials and a virgin aggregate base using field-based EFWD and tries to establish pavement’s responses to loading using vertical strains from both the MR and EFWD values of the respective materials as comparability parameters between the two. For this purpose, a control virgin aggregate (VA, limestone) and three types of RAB materials were selected to construct four test sections. The test sections were modeled in layered elastic- and finite-element-based pavement response models to calculate the vertical strains at the mid-depth of the base and top of the subgrade layers. A comparison of the lab-calculated vertical strains using MR with actual vertical strains in the field from EFWD showed that there was no relationship between the two stiffness parameters in all tested RABs. The vertical strains, based on the lab MR, undermined the stiffness of the recycled aggregates in the field. In contrast, the values of EFWD based on the vertical strains remained close to the MR strains of limestone (VA) throughout the testing period, establishing an EFWD vs. MR relationship (MR = 0.87 EFWD). The results also show that fine RCA was a better-performing material over three years. This research not only explores how the hydration process in RABs limits the development of MR-EFWD correlations but also underscores the need to consider real-world conditions when assessing their performance.

Effect of Nb-doping and AC annealing on the microstructure, magnetism and magnetoimpedance of metallic fibers

This paper systematically studies the changes in the microstructure and magnetic properties of CoFeSiBNb series metallic fibers before and after AC annealing. The influence of current intensity on the magneto-impedance (MI) effect of the fibers is analyzed and the mechanism of current annealing to improve the MI characteristics is further revealed. The results show that the surface of the CoFeSiBNb metallic fibers before and after AC annealing is smooth and continuous, the tensile strength of CoFeSiBNb3 fiber is 5.15 GPa and it is the most stable and fracture-reliable. After AC annealing, metallic fibers' general magnetic properties and MI ratio increase at first with current intensity and then decrease at higher intensities. Specifically, the 140 mA AC annealed metallic fiber shows excellent magnetic properties with Ms, μm, Hc, and Mr values reaching 94.38 emu/g, 0.4326, 34.36 Oe, and 13.94 emu/g, respectively. With an excitation frequency of f = 1 MHz, the fiber's [ΔZ/Zmax]max, ξmax, Hk, and Hp reached 216.81%, 31.04 %/Oe, 1 Oe, and 2 Oe, respectively. During the current annealing process, Joule heat eliminates residual stresses in the fibers while forming atomically ordered micro-domains, which improves the degree of its organizational order. Meanwhile, a stable toroidal magnetic field is generated, which promotes the distribution of the magnetic domain structure of the fibers, thereby improving the MI effect.

Exploring the structural, optical, dielectric and magnetic properties of rare earth samarium doped Ca-Mg based Ca0.5Mg0.5Fe12−xSmxO19 ferrite nanoparticles

The emergence of M-type hexaferrite presents an encouraging alternative to rare earth magnets, due to its economic feasibility and outstanding magnetic properties. This makes it a viable option for applications in the electric automotive and magnetic industry applications. In this study, we utilized a sol–gel auto-combustion technique to synthesize a series of samarium (Sm) doped calcium-magnesium (Ca-Mg) hexaferrite samples having chemical formula Ca0.5Mg0.5Fe12−xSmxO19 (x = 0.00, 0.05, 0.10, 0.15, and 0.20). The XRD analysis confirmed the crystal structure of the synthesized materials, revealing a consistent magneto-plumbite phase across all samples. Scanning electron microscopy (SEM) investigations further confirmed the homogeneous distribution and agglomeration of nanostructures. FTIR analysis identified the presence of two primary absorption bands in Ca-Mg hexaferrites with both bands exhibiting a shift towards lower frequency ranges with increasing doping levels. The dielectric loss (ε″) and dielectric constant (ε′) were higher at lower frequencies but decreased as the frequency increased. Additionally, higher concentrations of samarium resulted in further reductions in both dielectric loss (ε″) and dielectric constant (ε′). Notably, saturation magnetization (Ms) and remanence (Mr) values demonstrated an increasing trend with higher degrees of Sm+3 substitution, while coercivity (Hc) values exhibited relative stability. Our findings indicate that these materials possess promising magnetic parameters falling within the ranges of 31.52–37.77 emu·g−1 for Ms, 18.16–21.53 emu·g−1 for Mr, and 2.088–2.243 kOe for Hc, suggesting their potential utility across diverse applications including permanent magnets used in electric vehicle motors, storage devices, microwave components, and electromagnetic radiation absorbers.

Novel CdFe2O4 nanoparticles facile synthesis and their applications towards practical ammonia detection: an effect of annealing

Cadmium ferrite (CdFe2O4) nanoparticles were synthesized via a simple co-precipitation method, and the effect of annealing temperature over the prepared samples’ structural, morphological, and optical properties was analyzed by varying the temperatures 700, 800, and 900 °C. The x-ray diffraction (XRD) studies revealed that the prepared samples are highly crystalline in nature and belong to a cubic spinel crystal structure, and the crystallite size increases from 32 to 59 nm with respect to the increasing temperature. The surface morphology of the ferrite samples showed the uniformly distributed highly agglomerated particles with larger voids for the ferrite nanoparticles annealed at 900 °C. Optical properties of the prepared CdFe2O4 samples were carried out by diffused reflectance spectroscopy (DRS) and the optical band gap of the samples were found to be 2.57, 2.55 and 2.53 eV. The Vibrating sample magnetometer (VSM) studies at room temperature showcased that the nanoparticle samples possess ferromagnetic behavior, and the magnetization (Ms), Coercivity (Hc), and Retentivity (Mr) values were found to be 27.5 × 10−3 emu g−1, 237.60 Oe, and 1976 × 10−6 emu/g for the CdFe2O4 sample annealed at 900 °C. The gas sensing studies were carried out with the presence of target gas ammonia, and its significant sensing parameters such as gas responsivity (S%), rise time, and recovery times were determined, and these values of CdFe2O4 samples annealed at 900 °C were observed to be 1610%, 7.1 s, and 2.2 s. Our findings strongly suggest that the CdFe2O4 samples annealed at 900 °C hold significant promise as a multifunctional material, particularly in gas-sensing applications. This potential opens an exciting avenue for further research and development.

Magnetic and structural enhanced characterization of Zr-Al substituted M-type barium hexaferrite

Co-precipitation method was used to fabricate Zr-Al substituted M-Type barium hexagonal ferrite with a unique composition Ba1-xZr0.5x Al0.3 Fe11.7 O19 (x = 0.0, 0.1, 0.2, 0.3, 0.4, and 0.5). The materials were characterized using Fourier Transform Infrared spectroscopy and a magnetic hysteresis loop. For each sample, the values of Ms, Hc, Mr, remanence ratios (Mr/Ms), and magneton number (nB) are determined using M-H loops. The Mr/Ms ratio of the synthesized hexaferrites particles is between 0.001017 and 0.143103, indicating a single magnetic domain. FTIR spectroscopy was used to study the inter-atomic forces and gives information about the absorption and emission spectrum for solids, liquids and gases. The results indicate that the synthesized compounds may have potential use as perpendicular magnetic recording media due to the growing trend in saturation magnetization, remanence, and coercivity.

Magnetic properties of hard-soft MnBi/FeNi@C exchange coupled nanostructures via cryo-milling

The extremely important permanent magnets encounter uncertainty and cost variations due to utilization of rare earths as prime components. Hence, the exchange coupled magnets comprised of hard and soft magnets in different proportions are explored to optimize the magnetic properties and cost. In this line, we prepared exchange coupled magnets of MnBi with FeNi@C nanoparticles (varying compositions = 10, 15 and 20 wt %) via cryogenic ball milling route. Out of these, the nanocomposite with MnBi and 15 wt% FeNi@C provided a coercivity value of 7.9 kOe with saturation magnetization and remanance values of 63 and 38 emu/g respectively. This exchange coupled magnet shown improvement in the MS, HC and Mr values by 53, 18 and 90 % respectively as compared to MnBi alone. The carbon layer over FeNi@C phase (MS = 147 emu/g) as well as cryomilling facilitated the formation of its exchange coupled magnet with MnBi.

Evolution of magnetization of Bi1-ySmyFe1-xTixO3 ceramics at the morphotropic phase boundary attested by multistep magnetization measurements, time aging and electric field

Bi1-ySmyFe1-xTixO3 ceramics with compositions at the rhombohedral- orthorhombic morphotropic phase boundary (y = 0.1, 0.12, 0 ≤ x ≤ 0.1) were prepared by solid state reaction method. Analysis of the crystal structure of the compounds based on the results of laboratory and synchrotron X-ray diffraction measurements as well as Raman spectroscopy experiments revealed a coexistence of the rhombohedral phase (SG R3c) and the anti-polar orthorhombic phase (SG Pbam) in the compounds Bi0.88Sm0.12Fe1-xTixO3 with 0 ≤ x ≤ 0.1; the compounds Bi0.9Sm0.10Fe1-xTixO3 are characterized by the mixed structural state for the concentration range 0 ≤ x ≤ 0.06 and by the single phase rhombohedral state within 0.06 < x ≤ 0.1. Room temperature magnetization measurements demonstrate a gradual increase of remanent magnetization with Ti content in the compounds of both systems up to the maximal value of MR ∼0.28 emu/g for compounds with x = 0.06 which is followed by a decrease in magnetization with further titanium doping. Temperature decrease leads to a reduction of remanent magnetization which is mainly caused by a partial recovery of spatially modulated spin structure occurred in the compounds of both systems. Time aging of the compounds for about ∼1 year leads to a drastic increase of MR, which is caused by a change in the structural phase ratio, homogeneity of the structural state and a contribution of unbounded spins demonstrated by low field measurements. Subjecting of the annealed compounds to external electric field of E ∼40 kV/cm leads to a decrease of magnetization associated with backward structural transformations and redistribution of the local structural defects in the compounds.

Tailoring the structural, magnetic and dielectric properties in holmium doped Ca-Ba hexaferrite nanoparticles by regulating the Ca-Ba (1:1) concentration for magnetic and electric applications

This work reports the synthesis and characterizations of holmium (Ho) doped Ba-Ca hexaferrites (Ba0.5Ca0.5Fe12-xHoxO19). Structural analysis confirms the pure hexagonal phase throughout, and morphology shows the uniformly distributed hexagonal-shaped particles. The incorporation of Ho3+ ions significantly enhanced magnetic properties, as evidenced by vibrating sample magnetometry (VSM), attributed to the reconfiguration of Fe3+ ions and the reinforcement of superexchange interactions. Across all samples, magnetic hysteresis (M−H) loops exhibited a consistent hard ferrimagnetic behavior, with saturation magnetization (Ms) values varying within the range of 28.64 to 36.33 emu/g, remanent magnetization (Mr) from 16.24 to 20.68 emu/g, and coercivity (Hc) from 1.771 to 2.059 kOe, respectively. The composition with x = 0.09 demonstrated the highest Ms, Mr, and Hc values. The dielectric properties underscore the potential applications of fabricated M−type hexaferrites in microwave technology due to their low dissipation factor and ε“, pivotal for minimizing signal attenuation in crucial components such as filters and resonators. Moreover, Ho doped Ba-Ca hexaferrites present promising alternatives to magnets in electric vehicle applications, suggesting avenues for further research and optimization in this domain.

Low-carbon metakaolin precursor for one-part and two-part geopolymer activation of demolition wastes

A critical part of civil engineering infrastructure works is to develop innovative construction materials for a low-carbon future development. This study delved into the feasibility of using metakaolin (MK) as a low-carbon precursor for one-part and two-part geopolymer stabilization of recycled demolition wastes. In this research, the effects of MK precursor were evaluated in combination with construction and demolition (C&D) waste aggregates such as crushed brick (CB), reclaimed asphalt (RAP) and recycled concrete (RCA) using one-part and two-part geopolymer activation. Various geotechnical tests were performed including compaction tests, repeated triaxial loading tests (RLT), unconfined compressive strength tests (UCS) and microstructural analysis. Results from this study indicated significant strength development of MK mixtures for both one-part and two-part geopolymer options. Furthermore, one-part geopolymer also showed better activation than two-part geopolymer under 7 days and 20℃ curing condition. Additionally, 30 % MK mixtures were optimal for road construction applications based on the obtained results. At 28 days or 40 ℃, MK mixtures performed best with RCA and CB as main aggregates, showing strength improvement of up to 250 % compared to 7 days and 20 ℃ curing condition. Resilient modulus (Mr) results indicated that the optimal mixtures experienced good resilient behavior with average Mr values ranging from 150 MPa to 200 MPa. Overall, MK precursor was found to be a suitable material for stabilizing demolition aggregates using geopolymer under various curing conditions.

Tuning of optoelectronic performance of SrTiO3 by surface termination and thickness

The outstanding optical and electrical properties make ternary oxides highly suitable for advanced optoelectronic applications comparing to the traditional silicon-based materials and heterostructures. SrTiO3 (STO), a pivotal perovskite oxide with a direct energy band gap of 3.2 eV, exhibits significant promise in ultraviolet (UV) photodetection. However, the photovoltaic performance of homoepitaxial STO has long been neglected. In this study, we investigated the optoelectronic characteristics of STO by manipulating the crucial factors of surface termination and thickness using oxide molecular beam epitaxy (oxide MBE). We achieved an exceptional charge carrier mobility of 56.5975 cm2 V-1s−1, along with an impressive ON/OFF ratio of 6000 % and a specific detectivity (D*) of 2.95 × 109 Jones (cm Hz1/2 W−1) under near-UV irradiation at room temperature. We observed a thickness-dependent semiconductor-to-metal transition with a critical thickness of 3.5 u.c. STO. The metallic STO displayed an extremely high mobility exceeding 105 cm2 V−1 s−1, accompanied by a substantial MR value exceeding 1000 % at 3 K. Furthermore, the thickness-dependent Hall effect and photoluminescence (PL) indicated that oxygen defects may govern the semiconducting/metallic behavior of STO. This study illustrates the optoelectrical capabilities of homoepitaxial STO, paving the way for advanced and high-performance photodetection in intricate optical materials and devices through homoepitaxy.

Cell PCI Assignment Method Based on Particle Swarm Optimization

In order to streamline PCI allocation within cells for diminished conflicts, interferences, and complexities, an innovative methodology is introduced. A novel approach employing Particle Swarm Optimization (PSO) is employed to gauge and enhance cellular performance in wireless communications. We developed a comprehensive database for 2067 active cells along with their collision, interference, and confusion matrices. Utilizing regression tree models to analyze the influence of PCI configurations on MR values, coupled with PSO's capacity to refine PCI configurations, significantly reduces MR values, consequently boosting network performance. This study exemplifies the effective integration of machine learning and optimization algorithms into enhancing wireless network efficiency, offering network operators a valuable decision-making tool in intricate scenarios.

Green synthesis, characterization, and photocatalytic activity of superparamagnetic MgFe2O4@ZnAl2O4 nanocomposites

MgFe2O4@ZnAl2O4 magnetic nanocomposites were synthesized with the easy and green sol–gel method, and their photocatalytic efficiency was followed toward degradation of reactive blue 222 (RB222) dye under visible light irradiation. Prepared nanocomposites were fully characterized. The SEM and TEM images revealed the spherical morphology of the produced nanocomposites, with average size of 20–25 nm. The XRD pattern of sample exhibited the successful synthesis of the MgFe2O4@ZnAl2O4 MNCs with crystallite size 13 nm. The saturation magnetization (Ms) of the nanocomposites was examined using VSM, indicating a value of 6.59 emu/g. The absence of Hc and Mr values confirms the superparamagnetic nature of the nanoparticles. In addition, the surface area was calculated to be 78.109 m2/g utilizing BET analysis, and the band gap was determined to be 1.88 eV by DRS analysis. The photocatalytic, photolysis, and adsorption performance were investigated and result shown photodegradation activity was higher than others. These results confirm the synergetic effect between the MgFe2O4@ZnAl2O4 MNCs and visible light irradiation to degradation of organic dye. The results indicate that rapid degradation of 96% of RB222 dye occurred in just 10 min, with a TOC removal rate of approximately 59%. Furthermore, radical scavenger agents also clarified photodegradation of RB222 dye.

Determination of the molecular weight of native molecules of γ-hydroxybutyrate dehydrogenase isoforms obtained from maize (Zea mays L.) seedlings by gel chromatography

It is known that under oxygen deficiency the functioning of the tricarboxylic acid cycle is impaired, resulting in the activation of an alternative pathway, the GABA shunt. It maintains the functioning of the citric acid cycle by providing succinic acid. The key phase of this bypass is a reaction catalysed by succinate semialdehyde dehydrogenase (SSADH, EC 1.1.1.16). Under oxygen deficiency, SSADH ceases to function efficiently. This leads to the accumulation of succinic acid semialdehyde in the mitochondrial matrix and its high level adversely affects the plant cell metabolism. γ–hydroxybutyrate dehydrogenase (HBDH, EC 1.1.1.61) is an enzyme belonging to the group of oxidoreductases. It transforms γ–hydroxybutyrate into succinic acid semialdehyde, participating in the process of its detoxification, which is important in the maintenance of plant metabolism under oxygen deficiency. To date, unfortunately, there are no data on the biochemical and kinetic features of γ–hydroxybutyrate dehydrogenase. In this regard, our laboratory developed a method for purification of HBDH from green maize leaves, which makes it possible to study the physicochemical properties of this enzyme. During the study, we obtained γ-hydroxybutyrate dehydrogenase from 7-day-old seedlings of Zea mays L. by a five-stage purification. Homogenised plant material with extracted proteins was subjected to two-stage ammonium sulphate fractionation. The catalytic activity was determined spectrophotometrically at λ=340 nm by the amount of reduced NAD+. To remove ammonium salts, we used gel filtration through Sephadex G-25. Proteins were separated according to their charge by DEAE-Sephacel ion exchange chromatography. The enzyme was desorbed using a linear sodium chloride gradient (100-300 mM). The use of gel chromatography through Sephadex G-200 made it possible to determine the molecular mass of the purified enzyme isoforms. The homogeneity of enzyme preparations was confirmed by electrophoresis in polyacrylamide gel with universal AgNO3 staining. We used the tetrazolium method to confirm that the obtained protein preparations were γ-hydroxybutyrate dehydrogenase. As a result, homogeneous preparations of two isoforms of the enzyme (HBDH1 and HBDH2) were obtained. The first isoform of γ-hydroxybutyrate dehydrogenase was 185.7 times purified with a yield of 10% and had a specific activity of 343.6 U/mg of protein. The purification rate of the second isoform was 209 times with a yield of 7.74%. The specific activity of the obtained preparation was 386.7 U/mg of protein. Using gel chromatography through Sephadex G-200, we determined the molecular mass of native molecules of hydroxybutyrate dehydrogenase. We found that in 7-day-old maize seedlings the investigated enzyme was presented in low-molecular and high-molecular forms: for HBDH1 the Mr value was ⁓60.3 kDa, while for HBDH2 the molecular mass of the enzyme was 286 kDa.

Influence of Bi3+ ions on structural, morphology, elemental, vibrational, optical, magnetic, NLO and optical limiting properties of lanthanum ferrites nanoparticles

Nanoparticles of LaFe1-xBixO3 were successfully synthesized through the microwave combustion process (MCP) employing l-alanine as the fuel source. XRD and FT-IR analyses conclusively confirmed the orthorhombic structure of lanthanum ferrite, with the mean crystallite size varying between 56.32 and 25.43 nm. The optical energy gap value, calculated from UV–vis spectra, fell within the range of 1.84 to 2.49 eV. EDX analyses verified the presence of Bi, La, Fe, and O elements. Furthermore, FE-SEM images exhibited the nanoparticles' distinctive aggregated spherical morphology. Notably, VSM analysis showcased the robust diamagnetic behavior of LaFe1-xBixO3 nanoparticles. In photoluminescence's spectra, the samples underwent excitation with a wavelength of 315 nm. The values of Hc (coercivity) and Mr (remanence) fell within the range of 121.98 to 332.39 Oe and 0.1592 to 0.0907 emu/g for LaFe1-xBixO3 respectively. Z-scan experiments yielded values for the nonlinear susceptibility, index of nonlinear refraction, and coefficient of nonlinear absorption. The findings from optical limiting studies serve as additional verification, underscoring the suitability of these materials as promising options for integration into devices, including optical switches and optical power limiters.

Diagnostic value of MR and CT enterography in post-operative recurrence of Crohn's disease: a systematic review and meta-analysis.

Post-operative recurrence is a critical issue in the surveillance of Crohn's disease after ileocecal resection. This meta-analysis aims to assess the diagnostic yield of enterography techniques in post-operative recurrence of Crohn's disease. A systematic electronic bibliographic databases search was conducted. The inclusion criteria of original articles were: Utilized MR enterography or CT enterography after ileocolonic resection; Documented recurrence by ileo-colonoscopy (Rutgeerts' score ≥ i2); Provided crude data of diagnostic performance. A random-effect method was used for analysis. Relative risk and diagnostic value of each imaging feature were calculated. Eleven studies (11 populations and 589 patients) were included (4 CTE and 7 MRE with 248 and 341 patients, respectively). The pooled sensitivity and specificity of the enterography were 91% (95% CI: 0.85-0.95) and 75% (95% CI: 0.56-0.87), respectively. The pooled sensitivity and specificity of CTE were 93% (95% CI: 0.87-0.96) and 67% (95% CI: 0.35-0.90), respectively. MRE revealed pooled sensitivity and specificity of 90% (95% CI: 0.78-0.96) and 78% (95% CI: 0.57-0.90), respectively. The inter-study heterogeneity was low for sensitivity (I2 = 29%, p-value = 0.17) and high for specificity (I2 = 85%, p-value < 0.01). Wall enhancement, anastomosis wall thickening, anastomosis stenosis, pre-anastomotic dilatation, penetrating lesion, comb sign, and perivisceral edema were significantly higher in POR patients. Wall thickening and penetrating lesion were the most sensitive (81%) and specific (97%) findings, respectively. MRE and CTE exhibit high sensitivity and acceptable specificity (especially MRE) for detection of recurrence in Crohn's disease which makes them an effective initial screening tool and reserves ileo-colonoscopy for those patients with inconclusive enterography results.

Production of High-Coercive nanostructured Nd-Fe-B alloy by chemical method

For the first time, a nanostructured alloy powder with high coercive force was obtained by a chemical method without the addition of Dy, which can compete with physical methods of production. The work carried out a study of the influence of stoichiometric composition on the magnetic properties of nanostructured Nd-Fe-B alloys. Alloys with different contents of Nd, Fe, and B were synthesized: Nd12Fe84B6, Nd14Fe80B6, Nd16Fe76B8, and Nd16Fe72B8. With a decrease in the iron content in the first two compositions, a decrease in the iron content in the soft magnetic phase α-Fe was observed, which led to an increase in the coercive force Hc and a decrease in the values of Ms and Mr. Experiments have shown that an increase in the content of Nd and B promotes the formation of the hard magnetic phase Nd2Fe14B and an increase in the coercive force. For example, the nanostructured Nd16Fe76B8 alloy demonstrated a maximum coercive force of Hc = 8439 Oe, while compensating for the values of Ms (109 emu*g−1) and Mr (78 emu*g−1). A comprehensive study of the nanostructured Nd16Fe76B8 alloy was carried out, including structural analysis. XRD using FullProff and Vesta software revealed the tetragonal crystal structure of the Nd2Fe14B phase, providing details of the atomic arrangement. The unit cell contains four layers with Nd and Fe atoms, and boron atoms are embedded in the center of the octahedron of Nd and Fe atoms, playing an important role in the magnetic exchange interaction. The results of Mössbauer spectroscopy confirmed the presence of the Nd2Fe14B phase and revealed details of the state of Fe atoms in the structure of six sextets.

Effect of grain size on the dielectric and magnetic properties of YFeO3 ceramics densified by microwave sintering and spark plasma sintering from powders synthesized via reverse chemical co-precipitation

YFeO3 (YFO) ceramics were synthesized by reverse co-precipitation at different pH values followed by microwave sintering (MS) and spark plasma sintering (SPS) techniques. Also, the effect of the grain size on the magnetic and dielectric properties of the sintered ceramics was examined using various characterization methods. Moreover, FESEM micrographs showed that the particle size of the calcined samples has declined by increasing the pH value. Furthermore, the magnetization curves exhibited weak ferromagnetic behavior in the pre-sintered powder samples. Besides, the Ms value was enhanced from 1.26emu/g to 2.3emu/g by an increase in pH from 8.5 to 10.5 owing to reducing the particle size and subsequently raising the amount of uncompensated surface spins. Furthermore, the powder samples showed an increase in the Hc and Mr values from 15Oe to 28Oe and 0.127emu/g to 0.296emu/g, respectively, with a reduction in particle size from 0.632 μm to 0.272 μm. Additionally, the specimens processed through the sintering techniques demonstrated a remarkable reduction in magnetic characteristics. Therefore, a decrease in magnetic saturation values from 2.3emu/g to 0.43emu/g for the MS sample and to 0.17emu/g for the SPS specimen was attributed to a marked reduction in the amount of free surfaces and subsequently uncompensated surface spins. At last, the observed dielectric characteristics of all the sintered pellets had a common dielectric behavior. This signifies that by increasing the frequency the ε′ and tanδ decline at lower frequencies and become frequency-independent at higher frequencies based upon the Maxwell-Wagner polarization theory. On the other hand, the ε′ value for the SPS sample produced at pH = 10.5 underwent a decline of 2.5 times at the low frequency of 200 Hz compared to the MS one due to the significant decrement of the grain boundaries on account of the coarsening of grains.