Decrease In Cell Volume Research Articles

Actin cytoskeletal reorganization is involved in hyperosmotic stress-induced autophagy in tubular epithelial cells

Tubular epithelial cells are routinely exposed to severe changes in osmolarity. Although the autophagic activity of cells is an indispensable process to maintain cellular homeostasis and respond to stressors, the effect of hyperosmotic stress on autophagic activity in tubular epithelial cells remains unknown. The aim of this study was to determine the effect of hyperosmotic stress on autophagy in rat kidney tubular epithelial cells focusing on the role of actin and microtubule cytoskeletons. Normal rat kidney (NRK)-52E cells exposed to mannitol-induced hyperosmotic stress. As a result, NRK-52E cells showed elevated protein levels of the autophagosome marker LC3-II, indicating enhancement of the autophagic flux. Hyperosmotic stress also transiently decreased cell volume and caused the reorganization of actin and microtubule cytoskeletal structures in NRK-52E cells. The inhibition of the actin cytoskeleton reorganization by cytochalasin D impaired the increase in the levels of LC3-II; however, disassembly of the microtubules following treatment with nocodazole did not affect the increase. These results indicate that hyperosmotic stress can induce autophagy mediated by the reorganization of the actin cytoskeleton in tubular epithelial cells.

Crystallographic structural variations in nano-crystalline Sc2O3 under pressure

The present manuscript reports high-pressure investigations on nano-crystalline Scandium Oxide (Sc2O3) through synchrotron angle dispersive x-ray diffraction technique (ADXRD) up to a pressure of ∼35.4 GPa using a diamond-anvil cell (DAC). The sample, having a cubic bixbyite structure at ambient conditions, underwent substantial changes in crystallographic parameters under the application of external pressure, while exhibiting phase stability i.e. does not undergo any structural phase transition up to 35.4 GPa. The lattice parameters and the unit cell volume decrease significantly with an increase in pressure, revealing the compressible nature of the crystal structure. The pressure-volume data is fitted using the third-order Birch-Murnaghan equation of state to calculate the bulk modulus and its first derivative, which yields zero pressure bulk modulus of 217(35) GPa, with = 12(4) and the corresponding ambient volume per unit molecule comes out to be 59.18(18) Å3.

Piceatannol induces regulatory T cells and modulates the inflammatory response and adipogenesis

The beneficial effects of the polyphenolic compound piceatannol (PC) has been reported for metabolic diseases, antiproliferative, antioxidant, and anti-cancer properties. Despite its beneficial effects on inflammatory diseases, little is known about how PC regulates inflammatory responses and adipogenesis. Therefore, this study was designed to determine the effects of PC on the inflammatory response and adipogenesis. The effect of PC on splenocytes, 3T3-L1 adipocytes, and RAW264.7 macrophages was analyzed by flow cytometry, qRT-PCR, morphometry, and western blot analysis. PC induced apoptosis in activated T cells in a dose-dependent manner using stimulated splenocytes and reduced the activation of T cells, altered T cell frequency, and interestingly induced the frequency of regulatory T (Treg) cells as compared to controls. PC suppressed the expression of TNF-α, iNOS, IL-6R, and NF-κB activation in RAW264.7 macrophages after lipopolysaccharides (LPS)-induction as compared to the control. Interestingly, PC altered the cell morphology of 3T3-L1 adipocytes with a concomitant decrease in cell volume, lipid deposition, and TNF-α expression, but upregulation of leptin and IL-1β. Our findings suggested that PC induced apoptosis in activated T cells, decreased immune cell activation and inflammatory response, and hindered adipogenesis. This new set of data provides promising hope as a new therapeutic to treat both inflammatory disease and obesity.

Microstructural insight into the thermal decomposition of MgCl2·6H2O examined by in-situ high-temperature X-ray powder diffraction

A sequential thermal conversion of MgCl2·6H2O, including dehydration, hydrolysis and decomposition, was studied in terms of microstructure using in-situ high-temperature X-ray diffraction. The dehydration is occurred serially from room temperature to 208 ​°C that resulted in ∼48% weight loss. A decrease in unit cell volume is more prominent during dehydration until the monohydrate formed. The volume of monohydrate is slightly increased upon monoclinic to orthorhombic conversion. A gradual decrease in crystallite size is observed during the entire period of dehydration, resulting from lattice distortions upon ongoing lattice vibrations. The dehydration is also accounted for increased lattice strain. The hydrolysis of monohydrate produced magnesium chloride hydroxide, which is partly crystalline in nature. The magnesium chloride hydroxide increased its crystallinity upon further heating and decomposed to stable MgO at 458 ​°C. The hydrolysis and decomposition, both are occurred by the elimination of HCl that resulted in ∼28% weight loss. The MgO is formed under increased crystallite size and decreased lattice strain. The unit cells of MgO are packed tightly, minimizing the influence of ongoing lattice vibrations. At elevated temperatures, major steps that are involved in lattice stabilization are the elimination of water and HCl followed by rearrangement to minimize unfavorable interactions.

Effects of pressure on structural, mechanical, and electronic properties of chalcopyrite compound CuAlS2

First-principles method is performed to investigate the structural, electronic, elastic and mechanical characteristics of the tetragonal CuAlS2 in the pressure range from 0 to 10 GPa. The results indicated that both the lattice constant and cell volume decrease with the increase of pressure, which are matched well with available previous values. The pressure has a more significant influence on the c direction than the a and b direction. The obtained elastic constants reveal the tetragonal CuAlS2 is mechanically stable between 0 and 10 GPa. The bulk, shear, and Young’s modulus are evaluated by Voigt-Reuss-Hill approximation. All these elastic moduli exhibit a monotonic feature as a function of pressure. The Poisson’s ratio, Pugh’s criterion, and Cauchy pressure indicate that ternary chalcopyrite semiconductor CuAlS2 is ductile against pressure. Meanwhile, the analysis of the electronic structures reveals that the states near the valence band top are derived from Cu 3d and S 3p orbitals, and the lowest conduction band is composed of Al 3p and S 3p orbitals. We expect that the findings predicted the physical properties of this compound will promote future experimental studies on CuAlS2.

Structural and Spectroscopic Effects of Li+ Substitution for Na+ in LixNa1−xCaLa0.5Er0.05Yb0.45(MoO4)3 Upconversion Scheelite-Type Phosphors

New triple molybdates LixNa1−xCaLa0.5(MoO4)3:Er3+0.05/Yb3+0.45 (x = 0, 0.05, 0.1, 0.2, 0.3) were manufactured successfully using the microwave-assisted sol-gel-based technique (MAS). Their room-temperature crystal structures were determined in space group I41/a by Rietveld analysis. The compounds were found to have a scheelite-type structure. In Li-substituted samples, the sites of big cations were occupied by a mixture of (Li, Na, La, Er, Yb) ions, which provided a linear cell volume decrease with the Li content increase. The increased upconversion (UC) efficiency and Raman spectroscopic properties of the phosphors were discussed in detail. The mechanism of optimization of upconversion luminescence upon Li content variation was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. The UC luminescence maximized at lithium content x = 0.05. The mechanism of UC optimization was shown to be due to the control of excitation/energy transfer channel, while the control of luminescence channels played a minor role. Over the whole spectral range, the Raman spectra of LixNa1−xCaLa0.5(MoO4)3 doped with Er3+ and Yb3+ ions were totally superimposed with the luminescence signal of Er3+ ions, and increasing the Li+ content resulted in the difference of Er3+ multiple intensity. The density functional theory calculations with the account for the structural disorder in the system of Li, Na, Ca, La, Er and Yb ions revealed the bandgap variation from 3.99 to 4.137 eV due to the changing of Li content. It was found that the direct electronic transition energy was close to the indirect one for all compounds. The determined chromaticity points (ICP) of the LiNaCaLa(MoO4)3:Er3+,Yb3+ phosphors were in good relation to the equal-energy point in the standard CIE (Commission Internationale de L’Eclairage) coordinates.

Effect of low-volume blood withdrawal on hematological biomarkers

Introduction
 The hematological module of the Athlete Biological Passport (ABP) consists of individual and longitudinal monitoring of hematological parameters biomarkers responsive to erythropoiesis alteration. Based on an adaptive Bayesian model, the ABP seeks to identify non-physiological variations that may correspond to different types of blood doping. In this context, the impact of a standard blood donation (500 ml) was evident on the ABP parameters, hence supporting the robustness of the model. However, there is only scarce evidence of single or multiple withdrawals of smaller volumes of blood, closer to a modern blood doping strategy. This study investigated the impact of low-volume blood withdrawal on hematological variables for anti-doping purposes.
 Methods
 Twelve healthy subjects (7 women and 5 men; 26 ±6 yrs, 170 ±7 cm; 65 ±7 kg) were recruited. After baseline measurement, 140 ml whole blood was withdrawn with subsequent measures of hematological parameters by flow cytometry (Sysmex XN-1000, Sysmex Corporation, Japan) for 3 weeks. Blood volumes (BV) and total hemoglobin mass (Hbmass) were determined by means of a validated CO-rebreathing method. Ferritin (FERR) concentration was additionally measured by chemifluminescence immunoassay technique. Individual profiles were generated using the official ABP adaptive model using the official software platform of the World Anti-Doping Agency (WADA). Mixed model repeated measures analyses were run for each parameter to determine whether changes in the dependent (hematological variables) variables differed over time (fixed factor).
 Results
 43.2 ±8 g of hemoglobin was removed during the 140 ml blood withdrawal. A significant decrease in Hbmass (726 ±185 vs. 709 ±189 g; p = 0.007) and Red Blood Cell Volume (RBCV; 2190 ±521 vs. 2129 ±552 L; p = 0.028) was observed at D + 7 with a return to basal value at D + 14. No significant variations were observed for the primary and secondary variables of the ABP. No Atypical Passport Finding (ATPF) were generated in the individual ABP profiles. Conversely, FERR was significantly downregulated at D + 7 (95.8 ±76 vs. 87.1 ±76 μg/l; p = 0.018).
 Discussion/Conclusion
 While the ABP has demonstrated substantial advantages for traditional doping scenarios, our results challenge the indirect detection of low-volume blood withdrawals in a contemporary blood doping scenario. The impact of low-volume autologous blood transfusion on time trial performance has recently been demonstrated, supporting the need for novel biomarkers with extended detection windows. Hbmass could hence represent an additional marker to screen blood doping while technical issues for the use of CO-rebreathing remain. FERR as a marker of altered iron metabolism was there against shown to be sensitive and possibly suitable for outlining low-volume blood transfusion. The large inter-subject variability underlines the importance of individual longitudinal monitoring to provide sufficient sensitivity in the interpretation of hematological variations. Our study finally confirms that even low-volume blood withdrawals are associated with significant hematological changes while frequent blood samples and additional biomarkers are certainly required to better tackle blood doping strategies using such low-volume transfusions.

Red shift of lead-free halide perovskite RbCaCl3 under pressure for enhancing optoelectronic performance

This study focuses on the exploration of pressure effects on the structural, electronic, optical, and mechanical properties of a cubic halide perovskite RbCaCl3 using density functional theory. The calculated values of lattice constant and unit cell volume at zero pressure are justified by the previous experimental and theoretical studies. As pressure is applied both the lattice constant and unit cell volume decrease steadily because of bond length reduction inside the material. The indirect band gap nature of the studied perovskite transforms into direct under applied pressure of 40 GPa and more. Moreover, the band gap value significantly reduces under pressure effect from ultraviolet to visible energy region. Though the bonding nature of both Rb−Cl and Ca−Cl is initially ionic, the induced pressure slightly reduces the ionicity of Rb−Cl and makes the Ca−Cl bond covalent. The optical absorption reveals a red shift in the visible energy region advantageous for using RbCaCl3 in solar cell applications. In addition, the overall optical analysis reveals that the pressure-induced compound is more suitable for optoelectronic device applications than that of zero pressure system. The external hydrostatic pressure significantly affects the mechanical properties of titled compound, making it more ductile and anisotropic.

High-temperature properties of the solid solution BaNi2(V1−xPxO4)2

The polycrystalline samples of BaNi2(V1−xPxO4)2 (x ​= ​0–1) were prepared via a solution combustion synthesis. The study of the crystal structure shows that the substitution of vanadium (5+) cations by smaller phosphorus (5+) cations leads to compression of the [Ni2(V1−xPxO4)2]∞ layers in the ab plane with a decrease in the unit cell volume of BaNi2(V1−xPxO4)2. As a result, the BaO12 polyhedra are elongated along the c axis. The melting point increases monotonically with increasing phosphorus concentration. The linear dependence of the relative elongation (ΔL/L0) of samples on temperature after 500 ​°C becomes S-shaped. The electrical conductivity (σ) of BaNi2(V1−xPxO4)2 was measured in the range of 300–900 ​°C. Electron transfer in BaNi2(V1−xPxO4)2 established to occur along the Ni–O–Ni chains and is explained by the formation of Ni3+.

A CLINICAL NOTE ON CANINE TRYPANOSOMIASIS

Trypanosomes are widely distributed extra erythrocytic protozoan of animals. Wereported a Trypanosomes infection from the blood of a bulldog. An 18 months old male was presentedin the Pet Hospital of RCVetS, Lahore, Pakistan with a history of anorexia, emaciation, and pyrexia.Clinical examination of the dog indicated pale mucosa due and increase capillary refill time.Microscopic examination of blood films confirmed the Trypanosomes infection. Hematologicalanalysis of the blood of the dog indicated a decrease in Total erythrocyte count, hemoglobinconcentration, and Pack cell volume except for erythrocyte sedimentation rate. Differential leukocytecount revealed all parameters were unremarkable except Neutropenia, Eosinophilia, Lymphocytosis,and Thrombocytopenia. Serum analysis showed hyperproteinemia, elevated bilirubin, Blood ureanitrogen (BUN), Hypoglycaemia, and a decreased level of Gamma-glutamyl transferase (GGT). Thisdirected us to work on heamo parasites in companion animals.

New Rare Earth-Doped Bilayered Perovskite Oxide Photocatalysts Sr2La0.5R0.5FeMnO7 (R = La, Nd, Sm, Gd, Dy) for the Degradation of Highly Toxic Methylene Blue Dye in Wastewater under Visible Light: Structural, Optical, and Magnetic Properties.

This paper presents the rare earth doping effect on the structural, optical, and magnetic properties of bilayered Ruddlesden-Popper oxides Sr2La0.5R0.5FeMnO7 (R = La, Nd, Sm, Gd, Dy). Moreover, we are reporting for the first time a new rare earth-doped bilayered perovskite oxide series for the highly toxic methylene blue dye degradation in wastewater under visible light. Structural analysis of the PXRD data using the Rietveld refinements confirms the formation of the phases in tetragonal symmetry with the I4/mmm space group. The unit cell lattice parameters (a & c) and the cell volume (V) decrease monotonically from La- to Dy-doped samples owing to the decrease in the lanthanide ionic radii. The X-ray photoelectron spectroscopy analysis indicates the existence of the Mn ions in the mixed valence state. The DRS study shows that the energy band gap value decreases on moving from La to Gd substitution; however, it further increases for the Dy-doped sample. The magnetic measurements reveal that all the phases exhibit dominant anti-ferromagnetic interactions with Neel temperature (T N) observed at 150, 147, 138, 113, and 117 K for La-, Nd-, Sm-, Gd-, and Dy-substituted phases, respectively. However, the presence of an unsaturated hysteresis loop observed in the isothermal magnetic field (H) vs magnetization (M) plot also indicates the existence of weak ferromagnetic interactions. The investigation of the photocatalytic activity of the synthesized samples was done by carrying out photo-oxidative degradation of methylene blue (MB) dye pollutants. The results show that the photodegradation enhances by doping with heavier rare earth ions with the exception of the Dy-doped sample. The Gd-doped catalyst shows the maximum degradation efficiency of 99.03% in 50 min under visible light irradiation. The scavenging experiments confirmed that the·OH was the main/dominant oxidizing agent involved in the degradation of the MB dye.

SYNTHESIS OF LiFe1-xNixPO4/C USING THE REFLUX WITH MICROWAVE IRRADIATION METHOD

The aim of this study was to synthesize LiFe1-xNixPO4/C with x = 0; 0.05; 0.07; 0.09 using the reflux method assisted by microwave irradiation. The goal was to increase the value of the electronic conductivity and reaction rate of Li+ compounds. The results showed that the method successfully synthesized LiFePO4/C and LiFe1-xNixPO4/C with an orthorhombic crystal structure in the Pnma space group. The optimum reflux-microwave irradiation time was 10 minutes, and increasing moles of Ni doping lead to a decrease in the lattice parameters cell volume. The crystalline size ranged from 21.42–22.62 nm, and the surface of the compound particles was irregular. The compound LiFe0.93Ni0.07PO4/C had the highest conductivity (5.45 × 10-7 S/cm).

A first principle study of structural and electrical properties of novel Li2FeO3/Li2FeO2F Li-ion battery cathode material

Li-ion battery cathode materials, namely Li2FeO3 and Li2FeO2F, are investigated using noble evaluation approaches for the electrical properties, assuming that the reacted-unreacted structure interface is acting as a semiconductor junction. The evaluations are done by calculating different methods of density functional theory, and consequently resulted in lattice parameters and their changes, structural properties, and also density of states (DOS) diagrams to assess electrical properties. The approach assigns a value for each evaluated cathode material and provides a semi-quantitative criterion in the matter of rate-capability for having a comparison between the materials. It also considers the configuration of the unreacted-reacted structures with respect to each other and also the electric field direction simultaneously. Results from structural data showed that evaluated cathode materials face a significant amount of cell volume decrease during the delithiation process, thus it is expected that it has a strong impact on their cyclability and lifetime. According to the rate-capability criterion values obtained from the DOS diagrams calculated via GGA+U and GGA, results show that the presence of the Fluorine element inside the structure can improve the rate-capability.

Subcellular Localization of Homomeric TASK3 Channels and Its Presumed Functional Significances in Trigeminal Motoneurons

Somatic expressions of either heteromeric TASK1/3 or homomeric TASK1/1 channels have been reported in various neurons, while expression of homomeric TASK3/3 channels has been re-ported only in dendrites. However, it is not known why homomeric TASK3/3 channels are hardly seen in somata of CNS neurons. Given the absence of somatic TASK3/3 channels, it should be clarified why dendritic expression of TASK3/3 channels is inevitable and necessary and how differentially distributed TASK1/1 and TASK3/3 channels play roles in soma-to-dendritic integration. Here, we addressed these questions. We found that TASK3-transfected HEK293 cells showed decreases in cell volume after being transferred from the cultured medium to HEPES Ringer, suggesting that expressions of TASK3 channels in cell bodies cause an osmolarity problem. Using TASK1- and TASK3-transfected oocytes, we also found that cGMP application slightly suppressed TASK3 currents while it largely enhanced TASK1 currents, alleviating the difference between TASK1 and TASK3 currents at physiological pH. As larger motoneurons have extensive dendritic trees while smaller motoneurons have poor ones, cGMP could integrate Ia-EPSPs to recruit small and large motoneurons synchronously by differentially modulating TASKI and TASK3 channels which were complementary distributed in soma and dendrites of motoneurons in the dorsolateral part of the trigeminal motor nucleus.

Ranolazine Attenuates Brain Inflammation in a Rat Model of Type 2 Diabetes.

Recent studies suggest a pathogenetic association between metabolic disturbances, including type 2 diabetes (T2DM), and cognitive decline and indicate that T2DM may represent a risk factor for Alzheimer's disease (AD). There are a number of experimental studies presenting evidence that ranolazine, an antianginal drug, acts as a neuroprotective drug. The aim of the present study was to evaluate the effects of ranolazine on hippocampal neurodegeneration and astrocytes activation in a T2DM rat model. Diabetes was induced by a high fat diet (HFD) and streptozotocin (STZ) injection. Animals were divided into the following groups: HFD/STZ + Ranolazine, HFD/STZ + Metformin, HFD/STZ + Vehicle, NCD + Vehicle, NCD + Ranolazine and NCD + Metformin. The presence of neurodegeneration was evaluated in the hippocampal cornus ammonis 1 (CA1) region by cresyl violet staining histological methods, while astrocyte activation was assessed by western blot analysis. Staining with cresyl violet highlighted a decrease in neuronal density and cell volume in the hippocampal CA1 area in diabetic HFD/STZ + Vehicle rats, while ranolazine and metformin both improved T2DM-induced neuronal loss and neuronal damage. Moreover, there was an increased expression of GFAP in the HFD/STZ + Vehicle group compared to the treated diabetic groups. In conclusion, in the present study, we obtained additional evidence supporting the potential use of ranolazine to counteract T2DM-associated cognitive decline.

QCM sensor provides insight into the role of pivotal ions in cellular regulatory volume decrease.

All vertebrate cells generally self-regulate for sustaining homeostasis and cell functions. As a major regulatory mechanism, regulatory volume decrease (RVD) occurs in hypotonicity-induced cell swelling, and then shrinking by the efflux of intracellular osmolytes and water, in which the ions K+, Cl-, and Ca2+ play a key role in the RVD process. We observed that these pivotal ions could result in novel RVD behaviors under repeatedly hypotonic stimulation. However, there is a lack of valid means for assessing the effect of pivotal ions on RVD. In this work, we proposed an effective measurement process based on a quartz crystal microbalance (QCM) combined with cell function of RVD for revealing acute variations in cell volume regulation induced by the pivotal ions. A QCM sensor was implemented by adhering MCF-7 cells to a poly-l-lysine-modified gold chip and cyclic stimulation with hypotonic NaCl medium, in which a frequency shift (Δf) showed the superior feasibility of the technique in exhibiting RVD behaviors. With the increase in the number of cycles, the RVD values decreased progressively under three stimulation cycles with hypotonic NaCl alone. Compared with the first cycle, the RVD level in the second and third cycles declined by 60.7±1.7% and 82.1±1.6% (n=3), respectively; conversely, it recovered in NaCl-KCl solution, but was significantly enhanced by 52.2±0.8% in NaCl-CaCl2 solution. Moreover, the inhibition of chloride channels to block Cl- efflux also decreased the RVD level by 56.2±3.0%. The results indicate that these ions (K+, Cl-, Ca2+) are all able to affect the function of RVD, among which intracellular Cl- depletion reduced RVD during measurement, but which recovered with K+ supplement, and Ca2+ enhanced RVD due to activation of ion channels. Therefore, this work provides a comprehensive assessment of cellular behavior and offers an innovative method for gaining insight into cellular functions and mechanisms. A novel strategy was conducted by integrating a quartz crystal microbalance (QCM) with the function of cell volume regulation for analyzing the role of the pivotal ions ( K+, Cl-, Ca2+) in NaCl media on the behaviors of regulatory cell volume decrease (RVD).

Magnesium‐Substituted Zinc Ferrite as a Promising Nanomaterial for the Development of Humidity Sensors

Herein, the synthesis of zinc ferrite (ZnFe2O4) nanomaterials, substituted with magnesium (Mg), using the sol–gel autocombustion method, is reported. Powder X‐ray diffraction (PXRD), Fourier‐transform infrared (FTIR), field‐emission scanning electron microscopy (FESEM), and energy‐dispersive X‐ray spectroscopy (EDX) are used to characterize the synthesized Mg‐substituted ZnFe2O4. PXRD results show that unit cell volume and crystallite size decrease when the concentration of Mg ions rises. PXRD confirms that the nanomaterial has a single phase with the Fd3m space group. EDX confirms that the material is composed of Mg, Zn, Fe, and O elements. The FTIR spectra show a clear indication of the spinel ferrite structure, and the bands in the high‐frequency region reveal the hygroscopic nature of the prepared materials. The synthesized nanomaterial is used as a sensing element for the development of a humidity sensor. The average sensitivity (2.93 MΩ/%RH) is found to be highest for the composition Mg0.1Zn0.9Fe2O4. The response and recovery times of the fabricated thin‐film humidity sensor are 31 and 53 s, respectively. The developed sensing material has good repeatability (≈98%) and excellent stability.

Enhancing the structural, optical and electrical conductivity properties of ZnO nanopowders through Dy doping

• Doping ZnO nanopowders with different Dy percentages was successfully achieved with the co-precipitation method. • XRD analysis reveals a decrease in the lattice parameters and cell volume of the ZnO lattice due to stress relaxation induced by the formation of Dy 2 O 3 secondary on the surface of the nanoparticles. • Crystalline quality was improved on Dy doping. • The optical band gap was decreased on Dy doping where the disorder increased. • Electrical conductivity of ZnO was enhanced by increasing Dy doping concentration up to an optimum doping concentration of 4% and then lowered significantly. In this work, pure ZnO and Dy-doped ZnO nanopowdres (NPs) with varying doping concentration of Dy from 1 to 5 % were successfully synthesized by the co-precipitation method. The effect of Dy doping on the structure, morphology, optical and electrical conductivity of ZnO has been studied. XRD analysis shows that Dy-doped ZnO nanostructures exhibit primary wurtzite structure and a cubic Dy 2 O 3 secondary phase. The average crystallite sizes were found to be 20.14 nm for pure ZnO and in the range of 24–33 nm for Dy-doped NPs. Crystallite size of Dy-doped ZnO NPs increases with increasing Dy concentration from 1 % to 3 % and then decreases as Dy increases. The decrease in crystallite size was explained by the formation of Dy - O - Z n bonds on the surface of ZnO. Lattice parameters ( a and c ) and unit cell volume ( V ) decrease as Dy content is initially increased up to 2 % then increase for further increase in Dy content. The initial decrease in a , c and V is due to strain relaxation stresses resulting from the formation of Dy 2 O 3 secondary phase. FTIR spectra indicate the formation of the secondary phase and confirm the successful incorporation of Dy 3 + ions into Zn 2 + sites in ZnO structure. Optical band gap of pure and Dy-doped ZnO nanoparticles was evaluated from diffuse reflectance spectroscopy (DRS) spectra and found to be reduced in Dy-doped samples. Optical band gap decreases from 3.269 eV to 3.226 eV for the 1 % Dy-doped sample then increases on further increasing Dy concentration up to 4 % (3.252 eV) and slightly decrease again at 5 % (3.247 eV). PL emission spectra of Dy-doped samples, show the enhancement of the orange-red emission and the appearance of emission band at around 580 nm which may be assigned to the electrical dipole transition of Dy 3 + ions. The electrical conductivity was enhanced by increasing Dy concentration up to an optimum doping concentration of 4 %, then decreases significantly due to scattering of charge carriers caused by the excess of the secondary phase on the surface of ZnO nanoparticles.

Thermal behavior of natural stellerite: high-temperature X-ray powder diffraction and IR spectroscopy study.

The thermal behavior of stellerite from the Savinskoye deposit (Transbaikalia, Russia), Ca7.69Na0.25K0.06(Si56.24Al15.76)O144·53.39H2O, was investigated by in situ high-temperature X-ray powder diffraction (HTXRPD) and ex situ HT infrared (IR) spectroscopic analysis. Four different HTXRPD experimental procedures were used to study the thermal behavior of the powder samples: (1) RT-750°C, (2) RT-220°C -RT, (3) 200-350-RT °C, and (4) 350-700°C. Electron probe microanalysis and single-crystal X-ray diffraction were preliminary used to determine the chemical composition and crystal structure of stellerite. The A → B phase transition (Fmmm → Amma) starts at ∼110°C and is completed at about 140°C (in situ HTXRPD) and 200°C (ex situ HTIR) depending on the experimental conditions. It involves a cell volume decrease of 5.8% (Experiment 1). The thermal expansion of stellerite is more pronounced along the b and c axes, with αa: αb: αc (× 10-5) = 2.50:-25.52:-6.84 at 100°C, 0.44:-21.75:-25.64 at 150°C after the completion of the phase transition, and 3.06:-1.86:-16.94 at 500°C. The reverse B → A transition occurs at temperatures below 100°C during slow cooling (Experiment 2), however, it does not occur upon rapid cooling (Experiment 3). The B → D phase transition above 300°C is not observed (Experiment 4). The temperature barrier of phase transition in the ex situ HTIR spectroscopy experiment is shifted towards high temperatures. The heating above 200°C leads to an increase of 3430cm-1 and a decrease of 3600 and 3260cm-1 bands, which correspond to the stretching vibration of H2O. The heating above 400°C causes complete dehydration of the stellerite.

Structural phase transition and variation of magnetoresistance in the stoichiometric double perovskite Sr2−yNdyFe1+xMo1−xO6 (0.05 ≤ y ≤ 0.45 and x = y/2)

The interplay between magnetic, megneto-transport and structural properties of Nd-doped double perovskite Sr2−yNdyFe1+xMo1−xO6, in the range 0.05 <y ​< ​0.45 for x ​= ​y/2 and synthesized by solid state reaction, has been investigated. Specifically, it has been shown that the observed tetragonal to monoclinic crystallographic phase transition at the Nd composition in the range y ​= ​0.10 to y ​= ​0.15 is in close relationship with its magnetic and magnetoresistive behavior. The observed crystallographic transition, confirmed by X-ray diffraction experiments, is consistent with the decrease of the unit cell volume when the Nd doping content increases. Besides, the Curie temperature determined by thermogravimetric experiments increases with the Nd content just after the structural transition. Furthermore, the increase of Nd doping up to y ​= ​0.45 in the double perovskite structure leads to a magnetization loss about 98% as a result of the increase of both, anti-site defects and the number of charge carriers. The progressive magnetization loss with Nd doping is also responsible for the observed monotonic decrease of the magnetoresistance ratio due to the predominance of the antiferromagnetic order. Particularly, the electrical behavior in the vicinity of the crystallographic transition is characterized by a very slight increase followed by a rapid drop of the magnetoresistance ratio, which is originated by the corresponding fluctuations of the saturation magnetization.