Search

A series of novel perovskites LaM 0.25 Mn 0.75 O 3− δ (M = Fe, Co, Ni, Cu) are considered as promising cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Polycrystalline powders of LaM 0.25 Mn 0.75 O 3− δ are synthesized by a modified Pechini method. Powder X-ray Rietveld refinements reveal that LaM 0.25 Mn 0.75 O 3− δ series are in the orthorhombic perovskite structure within Pnma (no. 62) space group at room temperature. In situ high temperature X-ray diffractions indicate the existence of phase transformation from the orthorhombic Pnma phase to a higher symmetrical rhombohedral phase at elevated temperatures without any second phase formation for all these compounds. Multivalent states of M (Fe, Co, Ni and Cu) and Mn ions are testified by X-ray photoelectron spectroscopy measurement (XPS). The electrical conductivity are measured to be 39.6, 85.3 and 48.1, 99.4 S cm −1 for M = Fe, Co, Ni and Cu, respectively and the corresponding impedance are 0.131, 0.106, 0.107 and 0.0634 Ω cm 2 at 850 °C. Among these compounds, LaCu 0.25 Mn 0.75 O 3 −δ exhibits the highest electrical conductivity and the lowest electrode polarization resistances, which is consistent with its calculated smallest band gap and lowest oxygen vacancy formation energy. Moreover, they all exhibit excellent chemical compatibility with prototypical electrolyte Ce 0.8 Sm 0.2 O 2−δ (SDC). While the overall electrochemical properties of LaM 0.25 Mn 0.75 O 3 −δ (M = Fe, Co, Ni) are high enough to fulfill the practical applications. Thus, these LaM 0.25 Mn 0.75 O 3− δ (M = Fe, Co, Ni, Cu) compounds are potential cathode materials for IT-SOFCs. [ABSTRACT FROM AUTHOR]

The synthesis, crystal structure, and dielectric properties of the titled compounds were described. The structural symmetry was determined to be monoclinic P 2 1 / n (No. 14) space group. Based on the highly ordered array of alternating MgO 6 and SbO 6 octahedra, these double perovskites exhibited significant octahedral tilting distortion according to the Glazer's notation system a − a − c + . As the result of substituting different rare earth ions from La 3+ to Nd 3+ , both the tolerance factor ( t ) and coordination number (CN) were reduced simultaneously and the B-site lattice distorted more heavily with the increase in chemical pressure by adopting smaller Ln 3+ ion. For the investigation of dielectric properties, all the samples consistently presented weak frequency dependent characteristic with relatively low dielectric constant ( ε ') and low tangent loss (tan δ ). With the shrinkage of the Ln 3+ ion size, the corresponding ε ' decreased remarkably and the dispersive tan δ peaks around 300 K shifted to low temperature, indicating that the space-charge-hopping mechanism dominated permittivity property can be tuned by controlling the degree of lattice distortion via substituting different Ln 3+ ions. [ABSTRACT FROM AUTHOR]

As a mixed oxygen ionic and electronic conductor, SrFe0.8Mo0.2O3-δ is confirmed to be a good cathode material for intermediate-temperature solid-state fuel cells (IT-SOFCs). The sample of SrFe0.8Mo0.2O3-δ is synthesized by a solid-state reaction method. Pure cubic SrFe0.8Mo0.2O3-δ perovskite, with space group of Pm-3m (no. 221) and lattice parameter a =3.9120(1) Å, is determined via Powder X-ray Rietveld refinements. X-ray photoelectron spectroscopy testifies the existence of mixed oxidation states Fe2+/3+/4+ and Mo5+/6+ in the crystal. Thermogravimetry analysis consistently shows that the SrFe0.8Mo0.2O3-δ begins to the loss of lattice oxygen at about 450°C, which overlaps to the inflection temperature of the electrical conductivity profile. The maximum electrical conductivity obtained is about 50.20Scm−1 at 450°C, and the impedance 0.11 Ω cm2 at 850°C. The performance demonstrates that SrFe0.8Mo0.2O3-δ is a potential candidate as a cathode material for IT-SOFCs. [ABSTRACT FROM AUTHOR]

Abstract: To date great efforts have been devoted to the development of solid oxide fuel cell (SOFC) devices that is able to run at intermediate temperature (IT) and to retain good electrochemical performance as in the high temperature regime. To this end, Tantalum (Ta) is doped into Sr2Fe1.5Mo0.5−x Ta x O6−δ (0.0 ≤ x ≤ 0.15) to further improve the electrochemical performance as the cathode materials for IT-SOFC. Pure orthorhombic Sr2Fe1.5Mo0.5−x Ta x O6−δ (0.0 ≤ x ≤ 0.15) samples, with space group Pnma (no. 62), are synthesized by a two-step method and identified via the powder X-ray Rietveld refinements. X-ray photoelectron spectroscopy and thermogravimetry results consistently show that the number of oxygen vacancy increases with the increasing of Ta content. The thermal expansion compatibility of the samples is found to match the electrolyte of La0.9Sr0.4Ga0.1Mg0.2O3−δ (LSGM) better than that of cobalt-containing electrode compounds. Finally, the higher oxygen vacancy concentration leads to the enhanced ionic conductivity although electrical conductivity is slightly decreased due to the oxygen vacancy blocking. Therefore, Ta-doped Sr2Fe1.5Mo0.5O6−δ is proved to be a promising candidate for future cathode materials of IT-SOFC. [Copyright &y& Elsevier]

In order to optimize the electrical properties of co-doped ceria electrolytes, Ce 0.8 Ca 0.15 Sm 0.05 O 2− δ (CCS) sintered at different temperatures (1150 °C, 1200 °C, 1250 °C, 1300 °C and 1350 °C for 8 h) have been prepared and systematically investigated. It is found that among these samples sintered at different conditions, the electrical conductivity ( σ ) measured at 800 °C can be ranked as: CCS 1250 °C : σ CCS 1250 ° C 800 ° C = 2.38 × 10 −2 S cm −1 > CCS 1200 °C : σ CCS 1200 ° C 800 ° C = 1.81 × 10 −2 S cm −1 > CCS 1150 °C : σ CCS 1150 ° C 800 ° C = 1.50 × 10 −2 S cm −1 > CCS 1300 °C : σ CCS 1300 ° C 800 ° C = 1.26 × 10 −2 S cm −1 > CCS 1350 °C : σ CCS 1350 ° C 800 ° C = 0.68 × 10 −2 S cm −1 . The electrical conductivity of CCS increases with the increase of sintering temperatures, and the 1250 °C-sintered sample presents the highest conductivity because of the best microstructures. However, the electrical conductivity of CCS decreases when the sintering temperatures goes beyond 1250 °C. We attribute this to the phase instability. It reveals that microstructures and the phase stability have important effects on the optimization of electrical properties for the co-doped ceria electrolytes. [ABSTRACT FROM AUTHOR]

Abstract: Natural bioactive compounds have been studied for a long time for their chemopreventive and therapeutic potential in several chronic inflammatory diseases, including cancer. However, their physicochemical properties generally result in poor chemical stability and lack of in vivo bioavailability. Very few human clinical trials have addressed absorption, distribution, metabolism, and excretion of these compounds in relation to efficacy. This limits the use of these valuable natural compounds in the clinic. In this study, we examined caffeic acid (derivatives), carvacrol (derivatives), thymol, pterostilbene (derivatives), and N-(3-oxo-dodecanoyl)-l-homoserine lactone. These are natural compounds with strong anti-inflammatory properties derived from plants and bacteria. However, these compounds have poor water solubility or are chemically unstable. To overcome these limitations we have prepared liposomal formulations. Our results show that lipophilic 3-oxo-C12-homoserine lactone and stilbene derivatives can be loaded into liposomal lipid bilayer with efficiencies of 50–70%. Thereby, the liposomes solubilize these compounds, allowing intravenous administration without use of solvents. When compounds could not be loaded into the lipid bilayer (carvacrol and thymol) or are rapidly extracted from the liposomes in the presence of serum albumin (3-oxo-C12-homoserine lactone and pterostilbene derivatives), derivatization of the compound into a water-soluble prodrug was shown to improve loading efficiency and encapsulation stability. The phosphate forms of carvacrol and pterostilbene were loaded into the aqueous interior of the liposomes and encapsulation was unaffected by the presence of serum albumin. Chemical instability of resveratrol was improved by liposome-encapsulation, preventing inactivating cis–trans isomerization. For caffeic acid, liposomal encapsulation did not prevent oxidation into a variety of products. Still, by derivatization into a phenyl ester, the compound could be stably encapsulated without chemical degradation. Despite the instability of liposome-association of 3-oxo-C12-homoserine lactone and resveratrol, intravenous administration of these compounds inhibited tumor growth for approximately 70% in a murine tumor model, showing that simple solubilization can have important therapeutic benefits. [Copyright &y& Elsevier]

Abstract: Thin iron films have been grown on (001) GaAs substrates by low pressure metal organic chemical vapor deposition (LP-MOCVD) at different temperatures with the pressure of 150 Torr. X-ray diffraction (XRD) analysis showed that all films have only one strong diffraction peak (110). The surface of Fe film became smooth with increasing the growth temperature. Magnetization measurements showed that the Fe films grown at different temperatures were ferromagnetic with easy axis parallel to the film surface and hard axis perpendicular to the substrates. The field dependence of magnetization along two axes showed a remarkable difference, implying that the samples have strong magnetic anisotropy. Furthermore, when the applied magnetic field is perpendicular to the Fe surface, a sharp jump in the hysteresis loop could be observed, followed by a broad shoulder, which is related to the interface effect, the existence of carbon and the formation of 180∘/90∘ magnetic domains. [Copyright &y& Elsevier]

• A 1.7 μm CW and pulse Tm-doped fiber laser is proposed and demonstrated. • Variable pulse generated mechanisms can be achieved by a modulated pump. • The laser had a high SMSR of 59 dB and a 3 dB linewidth of 0.18 nm. • The range of repetition rate can be switched from kHz to dozens of MHz. A 1.7 μm Tm-doped continue-wave and pulse fiber laser based on variable pulse generated mechanisms is proposed and experimentally demonstrated. The modulated pump was used to generate pulses in the cavity by switching mechanisms easily (gain-switched, self-saturable absorber and active mode-locking via pump modulation (AMPM)). In the laser scheme, a 1.55 μm amplified optically modulated signal generator was used as a homemade pump, including a semiconductor laser, a pulse signal driver and an erbium-doped fiber amplifier (EDFA). A 3-m long thulium-doped fiber (TDF) was pumped to obtained gain which covered 1.7 µm band. A Fiber Bragg Grating (FBG) is employed as a spectrum filter. Using the proposed scheme, we achieved the laser with a central wavelength of 1727.92 nm. The laser had a high Side-Mode Suppression Ratio (SMSR) of 59 dB and a 3 dB linewidth of 0.18 nm. Additionally, we modulated the pump, and the pulse train with a repetition rate from 10 kHz to100 kHz based on gain-switched mechanism was obtained. Aim to increase the repetition rate, the generation of self-mode-locked pulses with a repetition rate of 11.39 MHz was observed associating with a self-saturable absorber using a CW pump. Moreover, We adjusted the modulated frequency of pump to match with the free spectral range of the cavity, the pulse train with repetition rate of 11.39 MHz was obtained with higher signal power based on AMPM, and the serval order harmonic mode-locking states with repetition rate from 22.78 MHz to 45.56 MHz were demonstrated with the appropriate pump frequency. [ABSTRACT FROM AUTHOR]

This study assessed the tolerability and pharmacokinetic (PK) properties of a new-generation oxazolidinone, contezolid (MRX-I), and its major inactive metabolite, M2, after single oral administrations of 800, 1200, and 1600 mg in the fed state, and compared the efficacy of 3 dosing regimens in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infection based on PK/pharmacodynamic (PD) analysis. A Phase I study at a single study center was conducted with 2 parts. In the first part, 20 healthy subjects received a single oral dose of 1200 or 1600 mg of contezolid or placebo in the fed state in a double-blind, placebo-controlled, dose-escalation tolerance study. In the second part of the study, 52 subjects received a single oral dose of 800 mg of contezolid in the fed state in a single-center, randomized, blinded, 4-period, crossover, thorough QT study. Noncompartmental analyses were used to evaluate the PK properties of contezolid and M2. Steady-state concentrations of contezolid following the 3 dosing regimens (800, 1200, and 1600 mg q12h) were simulated by employing a newly developed 2-compartmental PK model. The minimum inhibitory concentration (MIC) distributions of contezolid were analyzed in 178 Staphylococcus , Enterococcus, and Streptococcus clinical isolates. Monte Carlo simulations were conducted to predict the efficacy of the 3 dosing regimens to obtain probability of target attainment and cumulative fraction of response. Single-dose oral administrations of 800, 1200, and 1600 mg of contezolid were well tolerated in healthy subjects in the fed state, and nonlinear PK was observed. The mean plasma exposures to M2 exceeded 17.3% of contezolid exposure in the 3 groups. Both MIC 50 and MIC 90 (MICs that inhibit the growth of 50% and 90% of microorganisms, respectively) of contezolid against MRSA were 1 mg/L with clinical isolates from China. PK/PD analysis and Monte Carlo simulations predicted that 800 mg q12h of oral contezolid would be efficacious against MRSA infection, with a MIC of ≤4 mg/L (probability of target attainment, >90%; cumulative fraction of response, >90%). Contezolid is a well-tolerated treatment option for MRSA infection, including at supratherapeutic doses up to 1600 mg. The regimen of 800 mg q12h could achieve efficacy in treating bacterial infection with MRSA. To our knowledge, this is the first PK study to predict that a dosing regimen of 800 mg q12h of oral contezolid is sufficient for treating MRSA infection, with a MIC of ≤4 mg/L. A Phase III study of this suggested dosing regimen is being conducted. Chinadrugtrials.org.cn identifier: CTR20161074. [ABSTRACT FROM AUTHOR]