Phase Sr Research Articles

Serum Cytokines and Histopathological Pattern of Idiopathic Nephrotic Syndrome in Saudi Children

Background: Nephrotic syndrome (NS) defined by massive continued losses of urinary proteins, resulting in hypoalbuminemia and edema. These are associated with complications such as increased susceptibility to infections, thromboembolism, altered lipid and carbohydrate metabolism and losses in binding proteins in the urine. Aim of the study: To evaluate the cytokines levels in different stages of idiopathic nephrotic syndrome (INS) and to determine the histopathological pattern of INS. Patients and Methods: Fifty two children with INS were divided into; steroid-sensitive group I (SS) (18/52) and steroid-resistant group II (SR)(34/52). Both groups subdivided into SS in relapse IA (8/18), SS in remission IB (10/18), and SR in relapse group IIA (25/34) and in remission group IIB (9/34). Twenty age-matched controls compared with data. The following parameters had assessed; serum levels of IFN-γ, IL-2, IL-4, IL-13 and IL-18 by using quantitative colorimetric ELISA test. Renal biopsy specimens were histopathologicaly studied. Results: Serum IFN-γ levels were significantly lower in the relapse phase of SS compared with the remission phase and controls. On the contrary, serum IL-4 and IL-13 levels were significantly higher in the relapse phase of SS and SR compared with the remission phases and controls. IL-18 levels were significantly higher in the relapse phase of SS and SR subgroups compared with the remission phases and the controls respectively. IL-4 and IL-13 significantly correlated with IL-18. All 34 SR nephrotic patients were submitted to renal biopsies, which showed focal segmental glomerulosclerosis (FSGS)(59%) the most common diagnosed entities of INS. Conclusions: Type-2 cytokines predominate in relapse phase of SS and SR patients and one could predict a good response to steroid therapy. IL-18 expression significantly correlated with this type-2 immune response. The primary glomerular diseases in Saudi children and FSGS are the most common diag-nosed entities.

Infrared spectra, Raman spectra, microwave dielectric properties and simulation for effective permittivity of temperature stable ceramics AMoO4–TiO2(A = Ca, Sr)

In this work, temperature stable microwave dielectric materials (1 - x)AMoO(4)-xTiO(2) (A = Ca, Sr) were prepared by a solid state reaction method. The phase composition, sintering behaviors, microstructures, microwave dielectric properties, effective permittivity and vibrational phonon modes were investigated. The X-ray diffraction pattern and scanning electron microscope analysis indicated that the AMoO(4) (A = Ca, Sr) phase could coexist with the TiO(2) phase. The effective dielectric constants of the AMoO(4)-TiO(2) composites were calculated by the finite element method (FEM), compared with the measured values and the numerical results obtained by the classical mixing rules. The correlation between the dielectric properties and the crystal structures were studied using IR and Raman spectroscopy. The infrared spectra were analyzed using the classical harmonic oscillator model, and revealed that the external vibration modes of AMoO(4) (A = Ca, Sr) had the most significant influence on the dielectric constant. The Raman spectra showed that there were strong interactions in the [MoO(4)] tetrahedron due to the sharp and intense Raman modes. Finally, the low-firing (900 °C) microwave dielectric ceramics were obtained with 3 wt% H(3)BO(3)-CuO addition (BCu), and they possess good microwave dielectric properties with ε(r) = 10.6-13, high Q×f values (40 700-72 050 GHz), and near-zero temperature coefficients of resonant frequency (TCF or τ(f) values). These results also show that (1 - x)AMoO(4)-xTiO(2)-BCu (A = Ca, Sr) ceramics are good candidates for microwave electronic device applications.

First-principles thermodynamic calculations and experimental investigation of Sr–Si–N–O system—synthesis of Sr2Si5N8:Eu phosphor

Thermodynamic stabilities of the phases of Sr–Si–N–O system were evaluated by simulating phase diagrams at various conditions based on first-principles density functional theory calculations. Synthesis conditions and stability of the compounds belonging to the system, in which oxidation and nitridation reactions are involved complicatedly, could be interpreted through this first systematic investigation on the two-gas system. Practical synthetic methods of nitrides, such as hydrogen-reduction and nitridation or carbothermal reduction and nitridation reactions, were studied with special attention. This study enabled us to calculate proper conditions for synthesis of the Sr2Si5N8 phase, which is drawing attention as a new phosphor material for light emitting diodes. The types of impurities appearing with deviation from the proper synthetic conditions were also investigated, which may provide information about optimizing synthesis conditions. Synthesis of Sr2Si5N8:Eu phosphor using SiO2, instead of conventionally used Si3N4, was predicted by first-principles calculations, and we succeeded in synthesizing Sr2Si5N8:Eu phosphor for the first time using all oxide raw materials under normal pressure on this basis. The results of this study are expected to provide useful guidelines for synthesis of nitrides and the established simulation method may effectively be applied to other multi-gas systems.

Stability Improvement of High-Pressure-Ratio Turbocharger Centrifugal Compressor by Asymmetrical Flow Control—Part II: Nonaxisymmetrical Self-Recirculation Casing Treatment

This is part II of a two-part paper involving the development of an asymmetrical flow control method to widen the operating range of a turbocharger centrifugal compressor with high-pressure ratio. A nonaxisymmetrical self-recirculation casing treatment (SRCT) as an instance of asymmetrical flow control method is presented. Experimental and numerical methods were used to investigate the impact of nonaxisymmetrical SRCT on the surge point of the centrifugal compressor. First, the influence of the geometry of a symmetric SRCT on the compressor performance was studied by means of numerical simulation. The key parameter of the SRCT was found to be the distance from the main blade leading edge to the rear groove (Sr). Next, several arrangements of a nonaxisymmetrical SRCT were designed, based on flow analysis presented in part I. Then, a series of experiments were carried out to analyze the influence of nonaxisymmetrical SRCT on the compressor performance. Results show that the nonaxisymmetrical SRCT has a certain influence on the performance and has a larger potential for stability improvement than the traditional symmetric SRCT. For the investigated SRCT, the surge flow rate of the compressor with the nonaxisymmetrical SRCTs is about 10% lower than that of the compressor with symmetric SRCT. The largest surge margin (smallest surge flow rate) can be obtained when the phase of the largest Sr is coincident with the phase of the minimum static pressure in the vicinity of the leading edge of the splitter blades.

Electronic structures and structural phase transition mechanism of from first-principles calculations

Abstract We investigate the electronic structures of the cubic and tetragonal phases of Sr 2 MgWO 6 . Calculated electronic structures show that the two phases are both wide indirect band gap semiconductors. Our phonon calculations indicate that the structural phase transition from cubic to tetragonal phase is because the phonon frequencies of Γ 4 + modes become imaginary. Our variable cell-shape relaxation results imply that a symmetry-allowed intermediate trigonal phase could be realized.

Unexpected Luminescence Properties of Sr0.25Ba0.75Si2O2N2:Eu2+—A Narrow Blue Emitting Oxonitridosilicate with Cation Ordering

Owing to a parity allowed 4f(6)((7)F)5d(1)→4f(7)((8)S(7/2)) transition, powders of the nominal composition Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) (2 mol% Eu(2+)) show surprising intense blue emission (λ(em)=472 nm) when excited by UV to blue radiation. Similarly to other phases in the system Sr(1-x)Ba(x)Si(2)O(2)N(2):Eu(2+), the described compound is a promising phosphor material for pc-LED applications as well. The FWHM of the emission band is 37 nm, representing the smallest value found for blue emitting (oxo)nitridosilicates so far. A combination of electron and X-ray diffraction methods was used to determine the crystal structure of Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+). HRTEM images reveal the intergrowth of nanodomains with SrSi(2)O(2)N(2) and BaSi(2)O(2)N(2)-type structures, which leads to pronounced diffuse scattering. Taking into account the intergrowth, the structure of the BaSi(2)O(2)N(2)-type domains was refined on single-crystal diffraction data. In contrast to coplanar metal atom layers which are located between layers of condensed SiON(3)-tetrahedra in pure BaSi(2)O(2)N(2), in Sr(0.25)Ba(0.75)Si(2)O(2)N(2):Eu(2+) corrugated metal atom layers occur. HRTEM image simulations indicate cation ordering in the final structure model, which, in combination with the corrugated metal atom layers, explains the unexpected and excellent luminescence properties.

스마트폰 사용 자세에 따른 운동역학적 변인 분석

The purpose of this study was to determine how smartphone use posture affects biomechanical variables and muscle activities. Eleven university students(age: <TEX>$22.2{\pm}2.6$</TEX> yrs, height: <TEX>$176.6{\pm}4.7$</TEX> cm, weight: <TEX>$69.5{\pm}7.5$</TEX> kg) who have no musculoskeletal disorder were recruited as the subject according to having experience in using the smartphone for more than one year. Angular velocity, muscle activity, and thumb finger pressure were determined for each trial. For each dependent variable, a one-way analysis of variance (ANOVA) with repeated measures was performed to test if significant difference existed among different three conditions (p<.05). The result showed that rotational angular velocity of the first metacarpal were increased in DESK posture compared with STAND posture during SU phase. The average nEMG values of FDI(First dorsal interosseous) were less in SIT and DESK posture compared with STAND posture during SR phase. These indicated that smartphone postures may effect the thumb ROM(Range of motion) and muscle activity. This has led to suggestions of the need for further kinetic and EMG analyses to evaluate best assess and characterize with smartphone use.

Morphologies of Al4Sr Intermetallic Phase and Its Modification Property upon A356 Alloys

In general, the modification performance of Al-Sr master alloys is primarily dependent upon the morphologies and sizes of the Al 4 Sr intermetallic phase. In this paper, the crystal structure, morphologies, sizes, hardness and elastic modulus of Al 4 Sr in Al-Sr master alloys prepared from variant processes were studied by means of optical metallurgical microscope, X-ray diffraction (XRD), scanning electron microscopy (SEM), and nanoindentation system. The results revealed that the microstructures and modification performance of the Al 4 Sr phase were related to the preparation processes. That is to say, when a “direct reaction-hot extrusion” process was used, the Al 4 Sr phase exhibited a homogeneous distribution in the Al matrix with small size and roundish shapes, which ensured the Al-Sr master alloy wire advantages involving high recovery, good reproducibility, no delitescence of modification, no corrosion on equipments, and good workability. However, in the case of the traditional “direct reaction” process, the Al 4 Sr phase was in large size with shapes of rectangular stripe and plates, which limited the Sr content increasing due to the brittleness of the Al-Sr alloy It was also found that the morphology and size of the Al 4 Sr phases changed during heat treatment at high temperature up to 600 °C.

High-temperature resistant glass-ceramics based on Sr-anorthite and tialite phases

We have identified a convenient strategy for the control of the thermal growth of monoclinic Sr-anorthite and tialite phases in Sr–Ti–Al–silicates. The proposed method gives rise to a novel glassceramic material with thermal, mechanical, and dielectric properties potentially interesting in applications which require high temperature resistant radiotransparent materials. Crucially, we have found that the selective growth of Al2TiO5 and monoclinic SrAl2Si2O8 is enabled by keeping the SrO/Al2O3 ratio lower than unity. This strategy permits to prevent the crystallisation of detrimental rutile and hexagonal Sr-anorthite. Interestingly, the stable properties of monoclinic Sr-anorthite, never used in conjunction with tialite, give rise to a glassceramic system with good mechanical resistance (micro-hardness 9.6GPa, modulus of rupture 100MPa) and with relatively stable values of thermal expansion (49×10−7°C−1 from 20 to 1250°C), thermal diffusivity (0.45×10−6m2s−1), thermal conductivity (1.0W°C−1m−1), and dielectric constant (8.2) up to 1200°C.

Deciphering the atomic structure of a complex Sr/Ge (100) phase via scanning tunneling microscopy and first-principles calculations

The details of a Sr-induced ($3\ifmmode\times\else\texttimes\fi{}4$) reconstruction on Ge(100) were examined using scanning tunneling microscopy (STM) and density functional theory. At 1/6 ML of Sr, this reconstruction is similar to the 1/6 ML ($3\ifmmode\times\else\texttimes\fi{}2$) Sr phase previously observed on Si. In contrast to Si, however, atomic-resolution images of the Sr-Ge phase exhibit more dramatic and unusual bias dependence in STM that could be explained with the help of first-principles calculations of minimum energy structures. Simulated STM images are in excellent agreement with the experimental data and allow the ($3\ifmmode\times\else\texttimes\fi{}2$) Sr-Si double dimer vacancy alloy model to be extended to the Ge surface through a more complex ($3\ifmmode\times\else\texttimes\fi{}4$) arrangement of its building blocks. The difference between Si and Ge is interpreted in terms of the lower Ge-Ge binding energy and differences in the interatomic bond lengths.

Méthodes d’exploration d’une myotonie

Magnesium based alloy is a biodegradable metal that has significant potential advantages as an implant material. Element alloying is one of the effective methods to modify the performance of the magnesium alloy. In the paper, Sr and Sn as alloy elements were simultaneously added into the Mg–Zr–Ca alloy to improve the corrosion resistance. The differences of Mg–Zr–Ca alloy and Mg–Zr–Ca–Sr–Sn alloy were compared. The X-ray diffractometer (XRD) and the scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to analysis the phases and the microstructure of the alloys. The results indicated that the addition of Sn could form Mg2Sn mainly within the grain interior; Sr phase was mainly detected along the grain boundary. Immersion tests and electrochemical measurements showed that the corrosion resistance was improved obviously with simultaneous addition of Sr and Sn in Mg–Zr–Ca alloy. It suggested that bio-magnesium based alloy can use Sr and Sn as effective alloy elements to modify its performance.

Effects of Sr and Sn on microstructure and corrosion resistance of Mg–Zr–Ca magnesium alloy for biomedical applications

Magnesium based alloy is a biodegradable metal that has significant potential advantages as an implant material. Element alloying is one of the effective methods to modify the performance of the magnesium alloy. In the paper, Sr and Sn as alloy elements were simultaneously added into the Mg–Zr–Ca alloy to improve the corrosion resistance. The differences of Mg–Zr–Ca alloy and Mg–Zr–Ca–Sr–Sn alloy were compared. The X-ray diffractometer (XRD) and the scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS) were used to analysis the phases and the microstructure of the alloys. The results indicated that the addition of Sn could form Mg2Sn mainly within the grain interior; Sr phase was mainly detected along the grain boundary. Immersion tests and electrochemical measurements showed that the corrosion resistance was improved obviously with simultaneous addition of Sr and Sn in Mg–Zr–Ca alloy. It suggested that bio-magnesium based alloy can use Sr and Sn as effective alloy elements to modify its performance.

Physicochemical Properties of Potential Cathode La1-xBaxMn1-yCryO3 and Anode Sr2NiMoO6 Materials for Solid-Oxide Fuel Cells

&lt;p&gt;The homogeneity area boundaries of La&lt;sub&gt;1-x&lt;/sub&gt;Ba&lt;sub&gt;x&lt;/sub&gt;Mn&lt;sub&gt;1-y&lt;/sub&gt;Cr&lt;sub&gt;y&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; solid solutions possessing orthorhombic and rhombohedral structures were established. A state diagram at 1373 K in air in the quaternary oxide system LaMnO&lt;sub&gt;3&lt;/sub&gt;-BaMnO&lt;sub&gt;3&lt;/sub&gt;-BaCrO&lt;sub&gt;4&lt;/sub&gt;-LaCrO&lt;sub&gt;3&lt;/sub&gt; was drawn for the first time. Partial substitution of Mn with Cr in La&lt;sub&gt;1-x&lt;/sub&gt;Ba&lt;sub&gt;x&lt;/sub&gt;MnO&lt;sub&gt;3&lt;/sub&gt; stored the thermal compatibility of the cathode with the any traditionally used electrolyte but reduced the electric conductivity of the potential cathode. Based on the linear lengthening measurements of La&lt;sub&gt;1-x&lt;/sub&gt;Ba&lt;sub&gt;x&lt;/sub&gt;Mn&lt;sub&gt;1-y&lt;/sub&gt;CryO&lt;sub&gt;3&lt;/sub&gt; and Sr&lt;sub&gt;2&lt;/sub&gt;NiMoO&lt;sub&gt;6&lt;/sub&gt; samples the values of the thermal expansion coefficients were calculated. It was established that the temperature of the structure transition from a tetragonal to a cubic phase in Sr&lt;sub&gt;2&lt;/sub&gt;NiMoO&lt;sub&gt;6&lt;/sub&gt; occurred at 508 K. It was stated that double perovskite Sr&lt;sub&gt;2&lt;/sub&gt;NiMoO&lt;sub&gt;6&lt;/sub&gt; in air did not react with (La&lt;sub&gt;0.9&lt;/sub&gt;Sr&lt;sub&gt;0.1&lt;/sub&gt;)&lt;sub&gt;0.98&lt;/sub&gt;Ga&lt;sub&gt;0.8&lt;/sub&gt;Mg&lt;sub&gt;0.2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; up to 1073 K.&lt;/p&gt;

Nanostructured crystals of Sr1−x R x F2+x fluorite phases and their ordering: 6. Microindentation analysis of crystals

Hardness, crack resistance, brittleness, and effective fracture energy have been studied for crystals of 24 fluorite phases Sr1 − x R x F2 + x (R are 14 rare earth elements (REEs); 0 < x ≤ 0.5) and SrF2 grown by the Bridgman method from a melt. These characteristics change nonlinearly with an increase in the REE content for Sr1 − x R x F2 + x (0 < x ≤ 0.5) with R = La, Nd, Sm, Gd, and Lu; it is maximum in the range x < 0.1 for all REEs. The changes in a number of REEs have been traced for an isoconcentration series of Sr0.90 R 0.10F2.10 crystals (R = La, Nd, Sm, Gd, Ho, Er-Lu, or Y) and crystals (similar in composition) with R = Tb and Dy. The hardness of Sr1 − x R x F2 + x crystals is higher by a factor of ∼2–3 than that of SrF2. The effect of decrease in microstresses in SrF2 crystals is confirmed by the isomorphic introduction of R 3+ ions into this crystalline matrix.

Nanostructured crystals of fluorite phases Sr1 − x R x F2 + x and their ordering: 7. A procedure for cluster modeling of Sr1 − x R x F2 + x Based on the Structure of an Ordered Phase (R = Lu)

Single crystals of the Sr1 − xLuxF2 + x nonstoichiometric phase (x = 0.095 and 0.189), which crystallizes in the CaF2 structure type (space group Fm\(\bar 3\)m), are studied by X-ray diffraction. A procedure for the cluster modeling of Sr1 − xLuxF2 + x based on the fine structural features of the Sr4Lu3F17 stoichiometric compound with a fluorite derivative structure (one of the ordered phases in the SrF2-LuF3 system) is proposed. The description of the structure of the Sr1−xLuxF2+x solid solutions is based on the octacubic configuration of the {M14 − nRnF64 + n} defect cluster. Structural data on the displacements of cations and anions in the ordered Sr4Lu3F17 phase (in relation to the undistorted fluorite phase) allow one to identify the distortions of the crystal lattice of the disordered (nonstoichiometric) Sr1− xLuxF2 + x phase.

Hall coefficient anomaly in the low-temperature high-field phase of Sr3Ru2O7

We report a study of the Hall effect of high-purity Sr${}_{3}$Ru${}_{2}$O${}_{7}$ single crystals. We establish an empirical correlation between the onset of its unusual low-temperature, high-field phase and a pronounced dip in the field-dependent Hall coefficient. Unlike the order parameter obtained from measurements of anisotropic resistivity, which is affected by the formation of domains, the Hall effect feature seems to reflect the nature of the ordering within a single domain. We checked for violations of the Onsager relations for the off-diagonal components of the resistivity tensor but do not detect any. We compare our observations to those on materials that have long-wavelength spin structures, and discuss them in relation to a growing body of theoretical work on the nature of the low-temperature phase in Sr${}_{3}$Ru${}_{2}$O${}_{7}$.

COMPARISON OF MAGNETIC BEHAVIOR OF Sr-HEXAFERRITE SYNTHESIZED BY CO-PRECIPITATION, SOL–GEL AND MICROWAVE COMBUSTION TECHNIQUES

Single phase Sr -hexaferrite nanoparticles have been synthesized by three different techniques, co-precipitation, sol–gel combustion and microwave combustion. The structure of the powders indicates that heat treatment at 900°C is sufficient to form SrO · 6Fe2O3 single phase in all the three cases. The nanoparticles with typical dimensions of 10 nm × 50 nm × 200 nm are plate shaped and do not show any preferential alignment. The nanoparticles in all the cases exhibit a hard magnetic behavior at room temperature. The coercivity of microwave combustion synthesized Sr -hexaferrite particles is the largest, 5112 Oe while that of co-precipitation synthesized particles is 2668 Oe. The microwave combustion synthesized particles exhibit highest magnetization of 70.5 emu g-1 at room temperature in a field of 2.0 T.

Symmetry-Breaking Lattice Distortion inSr3Ru2O7

The electronic nematic phase of Sr₃Ru₂O₇ is investigated by high-resolution in-plane thermal expansion measurements in magnetic fields close to 8 T applied at various angles Θ off the c axis. At Θ < 10° we observe a very small (10⁻⁷) lattice distortion which breaks the fourfold in-plane symmetry, resulting in nematic domains with interchanged a and b axis. At Θ ≳ 10° the domains are almost fully aligned and thermal expansion indicates an area-preserving lattice distortion of order 2 × 10⁻⁶ which is likely related to orbital ordering. Since the system is located in the immediate vicinity of a metamagnetic quantum critical end point, the results represent the first observation of a structural relaxation driven by quantum criticality.

Electrical properties of Sr–Bi–Mn–Fe–O thick-film NTC thermistors prepared by screen printing

The Sr–Bi–Mn–Fe–O (Sr:Bi:Mn:Fe = 0.2: x:0.5:0.3; x = 0.6, 0.8, 1.0, 1.2) thick films with good NTCR characteristics were produced by screen-printing, using a paste with organic binders alone. X-ray diffraction patterns of the thick films showed two main phases of Sr 0.3Bi 0.7MnO 3− y and SrFeO 3− m with perovskite structure besides some amount of the bismuth iron oxides. It was found by SEM that the films with the different Bi content have superior morphology and to be dense. The room-temperature resistivity ( ρ 25), thermistor constant ( B 25/85), and activation energy ( E a) of the Sr–Bi–Mn–Fe–O NTC thermistor films increased with the increase of Bi content. The values of ρ 25, B 25/85, and E a of the NTC thermistors were in the range of 406–1960 Ω cm, 3141–3693 K, and 0.275–0.324 eV, respectively. For composition x = 0.8, a maximum reliability of +3% resistivity drift and duration time over 800 h at aging temperature 300 °C were observed at sintering temperature 785 °C.

SR phase contrast imaging to address the evolution of defects during SiC growth

AbstractSliced SiC boule grown by physical vapor transport is investigated using synchrotron white beam phase contrast imaging combined with Bragg diffraction. The evolution of defects is revealed. In the early growth stage, foreign polytype inclusions not only induce massive generation of full‐core dislocations and dislocated micropipes but also attract them, forming slit‐type pores at the boundaries of inclusions.In the intermediate stage, when inclusions stop to grow and become overgrown by the matrix, the pore density significantly reduces, which is attributed to their transformation into new micropipes. In the later stage, the micropipe density decreases, providing evidence for their partial annihilation and healing. Mechanisms for the evolution from inclusions to pores and finally to micropipes during the crystal growth are further discussed.