Sm Concentrations Research Articles

Effect of dilute concentrations of Sm on the temperature‐dependent electrical and dielectric properties of ZnO

AbstractCompounds of undoped and samarium (Sm) doped ZnO have been prepared by standard solid‐state reaction method. X‐ray diffraction (XRD), Williamson‐Hall (W‐H) analysis, Transmission Electron Microscopy (TEM), temperature‐dependent electrical and dielectric studies have been done to characterize these materials. Inclusion of Sm as dopant in hexagonal wurtzite ZnO changes the lattice parameters to a small extent with some Sm aggregation at higher concentration. Also, the mean particle sizes of ZnO:Sm compounds showed an inter‐correlation with the Scherrer method, W‐H analysis as well as with TEM results. The electrical resistivity depicts an exponential decay and metal‐semiconductor transition (MST) at ~300 K for the pristine sample whereas there is large decrement in the resistivity with Sm doping. The analysis of σac of ZnO suggests that the power law is obeyed and indicated an increase in the ac conductivity with Sm content. The mechanism behind this type of conductivity is elucidated by small polaron tunneling (SPT) model of conductivity. The dependence of ln dc on the temperature inverse shows that the traps of electrons are thermally activated such that low and high temperature activation energies confirm the presence of vacancies and interstitials of both O and Zn ions. Thus, a high value of dielectric constant makes these materials suitable for high frequency and charge storage device applications.

Macroelement and microelement composition of mediastinal lymph nodes of patients with sarcoidosis

This study was aimed at measuring concentrations and investigation of relationships between macro- and microelements in mediastinal lymph nodes of patients with sarcoidosis. Methods. The study involved 28 patients (50% were males; median age, 42.5 (23; 53) years) with confirmed diagnosis of sarcoidosis. Autopsy samples from 13 individuals died from occasional causes (41.2% were males; median age, 43 (38.7; 61.3) years) were used for comparison. The groups did not differ in age and gender. Neutron activation analysis was used to investigate chemical elements in mediastinal lymph node tissue samples. Results. Concentrations of Ca, Cr, Fe, Co, Zn, Rb, Sb, Cs, Ba, Eu, Lu, Yb, Hf, Th, and U in the lymph node tissue of patients with sarcoidosis were increased, and concentration of zinc was decreased compared to control samples. Concentrations of Sm, Au, Sr, Nd, As, Br, Ag, Tb, Sc, Ta, Na, and La did not differ between the groups. Direct relationships were found in element groups Fe-Cr-Sb-Ca, Fe-U-Th, Co-U-Th, U-Cr, Th-Br, Sc-Zn, Eu-La, and Ce-Lu.

Biomineralization of Middle Rare Earth Element Samarium in Yeast and Bacteria Systems

ABSTRACTMicroorganisms play an important role in the mineralization of heavy metals in different environments. Previous studies have reported the phosphate mineralization of light (Ce) and heavy (Yb) rare earth elements with yeast. However, little is known about differences in the biomineralization process of middle rare earth elements (including Sm, Eu, Gd, Tb and Dy) by yeast and bacteria. We carried out a series of experiments to compare the sorption process of Sm by Saccharomyces cerevisiae (yeast), Pseudomonas fluorescens (gram-negative bacteria) and Bacillus subtilis (gram-positive bacteria) in initial pH 3, 4 and 5 solutions. The concentrations of Sm in exposure solutions decreased as a function of exposure time in all three systems, which revealed the accumulation of Sm by cells. In both yeast and bacteria systems, Sm(III) was mineralized to monazite(Sm) phase particles on cell surfaces at 5 days of exposure after a short-term adsorption process. In these three systems, nano-sized Sm phosphate formed more quickly on cell surfaces with higher pH exposure solutions. The formation of precipitation on bacterial cell surfaces was faster than in yeast. There were no significant differences in the sorption process of Sm between the two bacteria Pseudomonas fluorescens and Bacillus subtilis.

Structural, morphological, magnetic properties and cation distribution of Ce and Sm co-substituted nano crystalline cobalt ferrite

Rare earth Sm and Ce co-substituted nano crystalline cobalt ferrite, CoFe2-x-ySmxCeyO4 (x = y = 0.00, 0.5, 0.1, 0.12 and 0.25) have been synthesized by sol-gel combustion method to study structural, morphological and magnetic properties. X-ray diffraction (XRD) revealed the spinel structure with a secondary phase of RE2O3 for higher molar concentration of rare earth ions. Williamson-Hall equation used to determine crystallite size and strain produced. An increase in specific surface area and Strain, while a decrease in the crystallite size were observed with increasing Sm and Ce concentrations. Scanning electron microscopy (SEM) micrographs showed inhomogeneous grain distributions with some agglomerates, an average grain size was found to be 0.15 μm. Energy dispersive x-ray spectroscopy (EDAX) confirmed the stoichiometry of the samples. Surface morphology studies were carried out by Transmission electron microscopy (TEM) studies which corroborates the presence of agglomerations in the sample. Fourier transform infrared spectroscopy (FTIR) spectra confirmed the spinel phase by showing two frequency bands υ1 in frequency range 580-559 cm−1 and lower frequency band υ2 at 392-372 cm-1. The force constants calculated for tetrahedral position was found to be more than that of octahedral position. Based on structural properties a cation distribution was proposed. Vibrating sample magnetometer (VSM) technique at room temperature used to study the magnetic properties, saturation magnetization (Ms), coercivity (Hc), anisotropy constant and initial permeability. Ms and Hc were found decreasing with increasing concentration of rare earth ions which has been attributed to weakening of A-B interaction, due to decrease in particle size and surface effect. Yafet-Kittle (YK) angle was found increasing with rare earth concentrations. The Ms and Hc of cobalt ferrite particles can be tailored for various applications.

Dependence of samarium-soil interaction on samarium concentration: Implications for environmental risk assessment.

The sorption and desorption behaviour of samarium (Sm), an emerging contaminant, was examined in soil samples at varying Sm concentrations. The obtained sorption and desorption parameters revealed that soil possessed a high Sm retention capacity (sorption was higher than 99% and desorption lower than 2%) at low Sm concentrations, whereas at high Sm concentrations, the sorption-desorption behaviour varied among the soil samples tested. The fractionation of the Sm sorbed in soils, obtained by sequential extractions, allowed to suggest the soil properties (pH and organic matter solubility) and phases (organic matter, carbonates and clay minerals) governing the Sm-soil interaction. The sorption models constructed in the present work along with the sorption behaviour of Sm explained in terms of soil main characteristics will allow properly assessing the Sm-soil interaction depending on the contamination scenario under study. Moreover, the sorption and desorption Kd values of radiosamarium in soils were strongly correlated with those of stable Sm at low concentrations (r=0.98); indicating that the mobility of Sm radioisotopes and, thus, the risk of radioactive Sm contamination can be predicted using data from low concentrations of stable Sm.

Effect of Samarium (Sm) Addition on the Microstructure and Tensile Properties of Al–20%Si Casting Alloy

In the present work, the effect of Sm addition (0.2, 0.4, 0.6, and 0.8 wt%) on the microstructure evolution and tensile properties of as-cast hypereutectic Al–20%Si alloy were investigated. The scanning electron microscopy, X-ray diffraction (XRD), and electron probe microanalysis with wavelength dispersive spectroscopy (WDS) were used to quantitatively characterize the samples. The results indicated that the primary Si phases were significantly refined from coarse polygonal and star-like shape to fine block with smooth edges and corners when the addition of Sm increased from 0 to 0.6%. Furthermore, eutectic Si phases were fully modified from coarse platelet-like/needle-like structure to fine fibrous structure and discrete particles with the addition of 0.6%Sm. However, the primary and eutectic Si phases became coarser when the level of rare earth Sm reached 0.8%. The analysis of XRD and WDS shows that Sm mainly exists in the form of Al2Si2Sm compounds. In addition, the tensile properties of as-cast Al–20%Si alloy with different concentrations of Sm were investigated by tensile test. It was found that the ultimate tensile strength (UTS) and elongation (EL) gradually enhanced with the increasing concentration of Sm from 0 to 0.6% due to decrease of the size and the change of morphology on Si phases. Compared with unmodified Al–20%Si alloy, the UTS and EL values of Al–20%Si alloy with 0.6%Sm were increased by 48.5 and 68.8%, respectively.

Rare earth and precious elements in the urban sewage sludge and lake surface sediments under anthropogenic influence in the Republic of Benin

Nowadays, sewage sludge and water bodies are subjected to heavy pollution due to rapid population growth and urbanization. Heavy metal pollution represents one of the main challenges threatening our environment and the ecosystem. The present work aims to evaluate the contamination state of the sewage sludge and lake sediments in the Republic of Benin. Twenty metallic elements including 15 rare earth elements (Eu, Sb, Cs, Nd, Pr, Gd, La, Ce, Tb, Sm, Dy, Ho, Eu, Yb, and Lu) and five precious elements (Ag, Au, Pd, Pt, and Ru) were investigated using inductive plasma-mass spectrometry. Results showed broad range concentrations of the elements. Ce, La, and Nd were present in both sediments and sewage sludge at concentrations ranging 5.80-41.30mg/kg dry matter (DM), 3.23-15.60mg/kg DM, and 2.74-19.26mg/kg DM, respectively. Pr, Sm, Gd, Tb, Dy, Eu, Er, Yb, Cs, Ho, and Tm concentrations were lower (0.02-5.94mg/kg DM). Among precious elements, Ag was detected at the highest concentration in all sites (0.43-4.72mg/kg DM), followed by Pd (0.20-0.57mg/kg DM) and Au (0.01-0.57mg/kg DM). Ru and Pt concentrations were <0.20mg/kg DM in all samples. Pollution indices and enrichment factor indicated a strong to severe enrichment of the elements, mainly Ce and precious elements in both sediments and sewage sludge. This revealed a growing anthropogenic input which was also implied by principal component analysis. The evaluation of pollution loading index (PLI) indicated a moderate to strong contamination (0.12≤PLI≤0.58; 37≤PLI≤114, respectively, for rare earth elements and precious elements), while the degree of contamination indicated a moderate polymetallic contamination for rare earth elements and significant contamination for precious elements.

Effect of samarium doping on structural, optical and magnetic properties of vertically aligned ZnO nanorod arrays

Samarium doped vertically aligned one dimensional ZnO nanorod (NR) arrays were grown by vapor phase transport (VPT) method through vapor solid (VS) growth process. Influence of different concentrations (0% to 8%) of Sm (all Sm contents in the paper are in mass fraction) on the ZnO NR arrays were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), photoluminescence (PL), Raman spectroscopy and vibrating sample magnetometry (VSM) techniques, respectively. X-ray diffraction studies revealed that the ZnO NR arrays were perfectly oriented along (002) crystallographic orientation with wurtzite crystal structure. Photoluminescence results showed an increase in oxygen vacancies due to increase in Sm doping. M-H curves revealed enhanced ferromagnetic behavior, and the magnetic moment values were 0.45, 0.363, 1.694, 3.613 and 2.197 emu/cm3 for (0–8%) Sm doped ZnO NR arrays respectively. The curve revealed that paramagnetic behavior was observed for undoped ZnO NR arrays and on increasing the Sm dopant to 4%, paramagnetic switched to ferromagnetic behavior.

Nucleation kinetics in Al-Sm metallic glasses

The isothermal nucleation kinetics in Al-Sm metallic glasses with low Sm concentrations (xSm) was studied using molecular dynamics simulations in order to calculate time–temperature–transformation curves. The average delay time of Al nanocrystal nucleation was found to increase exponentially with xSm, whereas the estimated critical cooling rate necessary to avoid crystallization decreases exponentially with xSm. Sm solutes were found to suppress Al nucleation by increasing the attachment barrier and therefore by reducing the attachment frequency. The analysis shows that the attachment of Al to the evolving nucleus has the same characteristics as Al diffusion within the amorphous matrix and they both take place heterogeneously via collective movement of a group of Al atoms.

Structural, magnetic and magnetocaloric properties of (La1−xSmx)0.85K0.15MnO3 (x = 0.0, 0.1, 0.2 and 0.3) perovskite manganites

We have investigated effect of Sm ion substitution on structural, magnetic and magnetocaloric properties of sol-gel synthesized (La1−xSmx)0.85K0.15MnO3 (x = 0.0, 0.1, 0.2 and 0.3) perovskite manganites. X-ray diffraction analyses confirm that samples crystallize with rhombohedral symmetry in the R3̅c space group. The temperature dependence of magnetization measurements shows a clear ferromagnetic (FM)-paramagnetic (PM) phase transition with increasing temperature, and magnetic phase transition temperature (TC) decreases with increasing Sm concentration. For Sm concentrations (x = 0.0, 0.1, 0.2 and 0.3), magnetic field dependence of the maximum magnetic entropy change (−∆SMmax) are determined up to 5 T to be 7.32, 3.37, 3.28 and 2.70 J kg−1 K−1, respectively. These experimental values are also in good agreement with the calculation of the magnetic entropy change using Landau theory.

Protective effect of Salvia miltiorrhiza Bunge on 5-fluorouracil-induced oral mucositis.

Oral mucositis is a common side-effect caused by chemotherapy or radiotherapy occurring in the majority of cancer patients and is characterized by inflammation and ulcers in the oral mucosa. In the present study, we examined the protective effects of Salvia miltiorrhiza Bunge (SM) on oral mucositis induced by 5-fluorouracil (5-FU) in human pharyngeal cells and golden Syrian hamsters. We investigated the proliferation and antioxidant abilities of SM using MTT, 2-diphenyl-1-picrylhydrazyl (DPPH) and reactive oxygen species (ROS) assays in vitro. Additionally, TUNEL assay was performed, and the expression levels of nuclear factor-κB (NF-κB), caspase-3 and proinflammatory cytokines were assessed by immunoblotting. The results showed that SM increased the cell proliferation rate in human pharyngeal cells up to 128.97±9.7% compared with this rate in the untreated cells and exerted protective effects on mucosal injury caused by 5-FU treatment. In addition, all concentrations of SM increased DPPH scavenging ability and blocked ROS generation in the treated cells. Taken together, following SM treatment, expression of NF-κB and cleaved caspase-3 were significantly decreased followed by inhibition of cell death. These data suggest that SM could be used for the prevention and treatment of oral mucositis caused by cancer therapies.

Block Copolymer-Assisted Solvothermal Synthesis of Hollow Bi2MoO6 Spheres Substituted with Samarium.

Hollow spherical structures of ternary bismuth molybdenum oxide doped with samarium (Bi2-xSmxMoO6) were successfully synthesized via development of a Pluronic P123 (PEO20-PPO70-PEO20)-assisted solvothermal technique. Density functional theory calculations have been performed to improve our understanding of the effects of Sm doping on the electronic band structure, density of states, and band gap of the material. The calculations for 0 ≤ x ≤ 0.3 revealed a considerably flattened conduction band minimum near the Γ point, suggesting that the material can be considered to possess a quasi-direct band gap. In contrast, for x = 0.5, the conduction band minimum is deflected toward the U point, making it a distinctly indirect band gap material. The effects of a hollow structure as well as Sm substitution on the absorbance and fluorescence properties of the materials produced increased emission intensities at low Sm concentrations (x = 0.1 and 0.3), with x = 0.1 displaying a peak photoluminescence intensity 13.2 times higher than for the undoped bulk sample. Subsequent increases in the Sm concentration resulted in quenching of the emission intensity, indicative of the onset of a quasi-direct-to-indirect electronic band transition. These results indicate that both mesoscale structuring and Sm doping will be promising routes for tuning optoelectronic properties for future applications such as catalysis and photocatalysis.

Antimutagenic, Antigenotoxic, and Anticytotoxic Activities of Silybum Marianum [L.] Gaertn Assessed by the Salmonella Mutagenicity Assay (Ames Test) and the Micronucleus Test in Mice Bone Marrow

ABSTRACTSilymarin (SM), a standardized extract from Silybum marianum (L.) Gaertn., is composed mainly of flavonolignans, and silibinin (SB) is its major active constituent. The present study aimed to evaluate the antimutagenic activities of SM and SB using the Ames mutagenicity test in Salmonella Typhimurium, as well as their anticytotoxic and antigenotoxic activities using the mouse bone marrow micronucleus test. To assess antimutagenicity, Salmonella Typhimurium strains were treated with different concentrations of SM or SB and the appropriate positive control for each strain. To assess antigenotoxicity and anticytotoxicity, Swiss mice were treated with different concentrations of SM or SB and mitomycin C (MMC). The results showed that SM was not significantly effective in reducing the number of frameshift mutations in strain TA98, while SB demonstrated significant protection at higher doses (P < 0.05). Regarding strain TA 100, SM and SB significantly decreased mutagenicity (point mutations) (P < 0.05). The results of the antigenotoxic evaluation demonstrated that SM and SB significantly reduced the frequency of micronucleated polychromatic erythrocytes (MNPCE) (P < 0.05). The results also indicated that SM and SB significantly attenuated MMC-induced cytotoxicity (P < 0.05). Based on these results, both SM and SB presented antimutagenic, antigenotoxic, and anticytotoxic actions.

Structural and magnetic characterization of Sm-doped GaN grown by plasma-assisted molecular beam epitaxy

We have investigated structural, optical and magnetic properties of Sm-doped GaN thin films grown by plasma-assisted molecular beam epitaxy. Reflection high-energy electron diffraction and X-ray diffraction reveal that Ga1−xSmxN films with a SmN mole fraction of ∼8% or below are grown on GaN templates without segregation of any secondary phases. With increasing SmN mole fraction, the c-axis lattice parameter of the GaSmN films linearly increases. GaSmN films with low Sm concentrations exhibit inner-4f transitions of Sm3+ in photoluminescence spectra. The present findings show that Sm atoms are substituted for some Ga atoms as trivalent ions (Sm3+). The Ga1−xSmxN films display hysteresis loops in magnetization versus external magnetic field (M–H) curves even at 300 K. We will discuss the origin of these features together with the corresponding temperature dependences of magnetization.

Agricultural management, season and trace elements effects on volatile oil production from Melissa officinalis L. (Lemon balm)

The objective of this study was to provide information about organic and mineral fertilization, season and trace elements effects on volatile oil production by the species Melissa officinalis. Elemental concentration was determined by instrumental neutron activation analysis and atomic absorption spectrometry. The volatile oil was extracted by hydrodistillation and analyzed by gas chromatography coupled to a mass spectrometer. The elemental content and the main compounds vary according to agricultural management and season. The results indicate that the production of volatile oil main compounds from M. officinalis is correlated with the concentrations of Na, Co, Rb, Cd, Cs, La, Sm and Hf.

HDL-sphingomyelin reduction after weight loss by an energy-restricted diet is associated with the improvement of lipid profile, blood pressure, and decrease of insulin resistance in overweight/obese patients

BackgroundSphingomyelin (SM) diminishes the fluidity of the surface monolayer of high-density lipoproteins (HDL), affecting their intravascular metabolism and antiatherogenic properties. Since overweight is associated with an altered HDL structure, weight loss may result in changes in HDL subclasses, particularly in their SM content. Therefore, we determined the plasma SM concentrations associated to both total HDL and HDL subclasses after weight loss in obese patients. MethodsFifty overweight patients, 40 women and 10 men, aged 38.6±6.4 y, were given an energy-restricted diet according to their sex, age, and height. No physical activity was prescribed. Plasma SM concentrations of HDL subclasses were determined by a gel surface method developed for this study. Cholesterol of HDL subclasses was also determined by enzymatic methods performed on a gel surface. ResultsMean weight lost was 3.5±0.4kg after 6weeks of dietary intervention. As expected, insulin resistance and blood pressure decreased whereas lipid profile improved, except for HDL-cholesterol. SM in plasma and in all HDL subclasses significantly decreased after intervention. The magnitude of HDL-SM reduction was statistically associated with the amelioration of the components of the metabolic syndrome; the reduction of BMI explained the decrement of HDL-SM in a multivariate analysis. ConclusionHDL-SM decreased after weight loss by an energy-restricted diet. Further, the association of this decrement with the improvement of blood pressure, lipid profile and the decrease of insulin resistance, was statistically significant; all HDL subclasses were similarly affected. Whether a reduction in HDL-SM contributes to the cardiovascular benefits of weight loss remains to be elucidated.

Rare Earth Element Concentrations in Brazilian Benchmark Soils

ABSTRACT: Studies regarding background concentrations of rare earth elements (REEs) are scarce and have mainly focused on a limited number of soil types from the northern hemisphere. The aim of this study was to determine REE concentrations in thirty-five benchmark soils of Brazil. Composite soil samples were taken from areas under native vegetation or with minimal anthropogenic influence. Concentrations of La, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Lu, Dy, Er, Ho, Tb, Tm, Y, Sc, and Fe were determined [...]

Pressure-induced phase transition inLa1−xSmxO0.5F0.5BiS2

Electrical resistivity measurements on La$_{1-x}$Sm$_{x}$O$_{0.5}$F$_{0.5}$BiS$_{2}$ ($x$ = 0.1, 0.3, 0.6, 0.8) have been performed under applied pressures up to 2.6 GPa from 2 K to room temperature. The superconducting transition temperature $T$$_{c}$ of each sample significantly increases at a Sm-concentration dependent pressure $P$$_{\rm t}$, indicating a pressure-induced phase transition from a low-$T$$_{c}$ to a high-$T$$_{c}$ phase. The compounds that have higher Sm concentrations have higher $T$$_{c}$ values at ambient pressure; however, the $T$$_{c}$ values at $P$ $>$ $P$$_{\rm t}$ decrease with $x$ and $P$$_{\rm t}$ shifts to higher pressures with Sm substitution. In the normal state, semiconducting-like behavior is suppressed and metallic conduction is induced with increasing pressure in all of the samples. These results suggest that the pressure dependence of $T$$_{c}$ for the BiS$_{2}$-based superconductors is related to the lattice parameters at ambient pressure and enable us to estimate the evolution of $T$$_{c}$ for SmO$_{0.5}$F$_{0.5}$BiS$_{2}$ under pressure.

Tunable emission, energy transfer and charge compensation in SrMoO4:Sm(3+),Tb(3+),Na(+) phosphor.

A series of SrMoO4:Sm(3+),Tb(3+),Na(+) phosphors was synthesized using a high-temperature solid-state reaction method in air. On excitation at 290 nm, SrMoO4:Sm(3+),Tb(3+) phosphor emitted light that varied systematically from green to reddish-orange on changing the Sm(3+) and Tb(3+) ion concentrations. The emission intensities of SrMoO4:Sm(3+) and SrMoO4:Sm(3+),Tb(3+) phosphors were increased two to four times due to charge compensation when Na(+) was added as a charge compensator. The luminescence mechanism and energy transfer could be explained using energy-level diagrams of the MoO4(2-) group, Sm(3+) and Tb(3+) ions. SrMoO4:Sm(3+),Tb(3+),Na(+) could be used as reddish-orange phosphor in white light-emitting diodes (LEDs) based on an ~ 405 nm near-UV LED chip. This research is helpful in adjusting and improving the luminescence properties of other phosphors.

Sol-gel preparation and luminescent properties of red-emitting phosphor Sr-Ba-Mo-W-O-(Eu(3+),Sm(3+)).

Two series of red-emitting phosphors Sr-Ba-Mo-W-O:Eu,Sm and Sr-Ba-Mo-W-O:Eu have been synthesized by a sol-gel method. The effects of the chemical composition, concentrations of Sm(3+) and Eu(3+), the Sr(2+)/Ba(2+) ratio, and the W(6+)/Mo(6+) ratio on the luminescent properties were investigated. The as-prepared phosphors were characterized by X-ray diffraction and Raman spectra. Results showed that single phases of the two series were prepared. The compositions of Sr0.6 Ba0.13Mo0.8 W0.2O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10 had the strongest luminescent intensity. The excitation spectra of Sm(3+), Eu(3+) co-doped phosphors were broader and the strongest peak moved to 404 nm when compared with that of Eu(3+) single-doped phosphors. The luminescent intensity of the Sr0.6Ba0.13Mo0.8W0.2O4:Eu0.10 Sm0.08 at 618 nm were 2.8 times greater than that of Sr0.75Ba0.1Mo0.8 W0.2O4:Eu0.10. The luminescent intensity of Sr0.6Ba0.13Mo0.8 W0.2 O4:Eu0.10Sm0.08 and Sr0.75Ba0.1Mo0.8W0.2O4:Eu0.10 at 150 °C decreased to 56.8% and 50.3% of the initial value at room temperature, respectively.