Signature of topological states in antiferromagnetic Sm-substituted Bi2Te3.

An antiferromagnetic topological insulator has been predicted to be preserved by breaking both time-reversal symmetry and primitive lattice translational symmetry. However, the topological surface state has often been observed to disappear in an antiferromagnetic phase because the doped magnetic impurity acts as an extrinsic defect. In this study, we report the experimental signature of topological surface states coexisting with antiferromagnetic order in Sm-doped Bi2Te3. We fabricate single crystals of SmxBi2-xTe3 with x = 0.004, 0.010, and 0.025, where the Curie-Weiss law is satisfied at low temperatures but is violated at high temperatures due to the influence of the high energy states of J multiplets of Sm. For x = 0.025, e xotic physical properties are observed, such as the antiferromagnetic phase with the Néel temperature TN = 3.3 K, multi-band Hall effect with two conduction channel, and anisotropic Shubnikov-de Haas oscillations. In the antiferromagnetic phase, we detect the signature of nontrivial topological surface states with surface electron density ns = 7.9 × 1011 cm-2 and its high mobility µs = 2,200 cm2/Vs, compared to nb = 2.0 × 1019 cm-3 and µb = 2.3 cm2/Vs for bulk electrons. These observations suggest that SmxBi2-xTe3 is a candidate creating the new stage for the potential application of topological antiferromagnetic spintronics.

Comparison of pharmacokinetic characteristics of sildenafil citrate chewable tablets and film-coated tablets in healthy male subjects.

UI14SDF100CW is a chewable tablet of sildenafil citrate, which was developed to improve compliance through convenience of administration. The purpose of this study was to compare the pharmacokinetic (PK) properties of sildenafil citrate chewable tablets (UI14SDF100CW) and conventional sildenafil citrate film-coated tablets (Viagra®, Pfizer). A randomized, open-label, single dose, two-treatment, two-period, two-way crossover study was conducted in 60 healthy male volunteers. In each period, the subjects received a single oral dose of UI14SDF100CW or Viagra® (both tablets contain 140.45 mg of sildenafil citrate, which is equivalent to 100 mg of sildenafil). Serial blood samples were collected up to 24 h post-dose for PK analysis. The plasma concentration of sildenafil was determined using a validated HPLC-MS/MS assay. PK parameters of sildenafil were calculated using non-compartmental methods. The plasma concentration-time profiles of sildenafil in both formulations were similar. For UI14SDF100CW, the Cmax and AUClast of sildenafil were 1068.69 ± 458.25 (mean ± standard deviation) mg/L and 3580.59 ± 1680.29 h·mg/L, and the corresponding values for Viagra® were 1146.84 ± 501.70 mg/L and 3406.35 ± 1452.31 h·/L, respectively. The geometric mean ratios (90% confidence intervals) of UI14SDF100CW to Viagra® for Cmax and AUClast were 0.933 (0.853-1.021) and 1.034 (0.969-1.108), respectively, which met the bioequivalence criteria of Korean regulatory agency. In conclusion, UI14SDF100CW and Viagra® showed similar PK properties. Therefore, UI14SDF100CW can be an alternative to sildenafil for the treatment of erectile dysfunction, providing better compliance.

Nasal pH in patients with chronic rhinosinusitis before and after endoscopic sinus surgery.

PURPOSE: Physiologically acidic nasal pH depends on intact nasal mucosal function. The aim of this study was to determine nasal pH in patients with chronic rhinosinusitis and to investigate the changes in pH related to mucosal healing after endoscopic sinus surgery. MATERIALS AND METHODS: Normal subjects and the patients with chronic rhinosinusitis who showed no recurrence after endoscopic sinus surgery were enrolled. Using a portable pH meter and a glass-tipped probe, nasal pH was measured in the inferior meatus in normal subjects and patients before and after surgery at 3 months. RESULTS: The mean (±SD) nasal pH was 6.5 ± 0.5 (5.9 to 7.3) in 19 normal subjects, and 6.7 ± 0.6 (5.3 to 7.6) in 19 CRS patients before surgery, which showed no significant difference between the groups. The nasal pH values were in the range of 3.8-7.7 (mean ± SD 5.7 ± 0.9) at 3 months after surgery, and significantly lower than the preoperative values in patients (P=.004). The patients showing pH lower than 6.0 accounted for 10.5% before surgery, but 68.4% after surgery. CONCLUSIONS: Normal nasal pH was in the slightly acidic range, and the mean nasal pH of patients with chronic rhinosinusitis fell within normal limits as well, which indicates that chronic rhinosinusitis may not disturb the electrolyte milieu of the nasal mucosa. The average nasal pH measured at 3 months after endoscopic sinus surgery exhibited acidity of pH5.7. The factors causing a fall in nasal pH during the healing period after the sinus surgery remain to be elucidated.

Superparamagnetism of Cu2Se nanoparticles.

Cu2Se nanoparticles were synthesized using the standard Schlenk line and glove box techniques, with the hot-injection method. The X-ray diffraction (XRD) analysis showed that the initial nanoparticles were formed in a stoichiometric Cu2Se phase with a cubic structure. When the nanoparticles are exposed to air, the diffraction peaks shift to higher angles. This suggests that the nanoparticles are changed to a nonstoichiometric Cu2-deltaSe phase with copper vacancies. The mean size of the nanoparticles was about 7 nm. The magnetic results show that the initial nanoparticles were diamagnetic, and after 1-week air exposure, they became paramagnetic. This dramatic change from diamagnetic to paramagnetic can be explained by the oxidation of Cu+ into Cu2+ at the nanoparticle surface. In addition, the superparamagnetic properties were observed to have a blocking temperature of 150 K. The coercive field decreased as the temperature approached the blocking temperature, and eventually vanished above the blocking temperature.

Investigation of local environments in Nafion-SiO(2) composite membranes used in vanadium redox flow batteries.

Proton conducting polymer composite membranes are of technological interest in many energy devices such as fuel cells and redox flow batteries. In particular, polymer composite membranes, such as SiO(2) incorporated Nafion membranes, are recently reported as highly promising for the use in redox flow batteries. However, there is conflicting reports regarding the performance of this type of Nafion-SiO(2) composite membrane in the redox flow cell. This paper presents results of the analysis of the Nafion-SiO(2) composite membrane used in a vanadium redox flow battery by nuclear magnetic resonance (NMR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Fourier Transform Infra Red (FTIR) spectroscopy, and ultraviolet-visible spectroscopy. The XPS study reveals the chemical identity and environment of vanadium cations accumulated at the surface. On the other hand, the (19)F and (29)Si NMR measurement explores the nature of the interaction between the silica particles, Nafion side chains and diffused vanadium cations. The (29)Si NMR shows that the silica particles interact via hydrogen bonds with the sulfonic groups of Nafion and the diffused vanadium cations. Based on these spectroscopic studies, the chemical environment of the silica particles inside the Nafion membrane and their interaction with diffusing vanadium cations during flow cell operations are discussed. This study discusses the origin of performance degradation of the Nafion-SiO(2) composite membrane materials in vanadium redox flow batteries.

Membrane development for vanadium redox flow batteries.

Large-scale energy storage has become the main bottleneck for increasing the percentage of renewable energy in our electricity grids. Redox flow batteries are considered to be among the best options for electricity storage in the megawatt range and large demonstration systems have already been installed. Although the full technological potential of these systems has not been reached yet, currently the main problem hindering more widespread commercialization is the high cost of redox flow batteries. Nafion, as the preferred membrane material, is responsible for about 11% of the overall cost of a 1 MW/8 MWh system. Therefore, in recent years two main membrane related research threads have emerged: 1) chemical and physical modification of Nafion membranes to optimize their properties with regard to vanadium redox flow battery (VRFB) application; and 2) replacement of the Nafion membranes with different, less expensive materials. This review summarizes the underlying basic scientific issues associated with membrane use in VRFBs and presents an overview of membrane-related research approaches aimed at improving the efficiency of VRFBs and making the technology cost-competitive. Promising research strategies and materials are identified and suggestions are provided on how materials issues could be overcome.

Chloride supporting electrolytes for all-vanadium redox flow batteries.

This paper examines vanadium chloride solutions as electrolytes for an all-vanadium redox flow battery. The chloride solutions were capable of dissolving more than 2.3 M vanadium at varied valence states and remained stable at 0-50 °C. The improved stability appeared due to the formation of a vanadium dinuclear [V(2)O(3)·4H(2)O](4+) or a dinuclear-chloro complex [V(2)O(3)Cl·3H(2)O](3+) in the solutions over a wide temperature range. The all-vanadium redox flow batteries with the chloride electrolytes demonstrated excellent reversibility and fairly high efficiencies. Only negligible, if any, gas evolution was observed. The improved energy capacity and good performance, along with the ease in heat management, would lead to substantial reduction in capital cost and life-cycle cost, making the vanadium chloride redox flow battery a promising candidate for stationary applications.

Inhibition of the bacterial surface protein anchoring transpeptidase sortase by medicinal plants.

Inhibition by medicinal plant extracts of a recombinant sortase was evaluated for antibacterial drug discovery. The coding region of sortase, a transpeptidase that cleaves surface proteins of gram-positive bacteria, was amplified by PCR from the chromosome of Staphylococcus aureus ATCC 6538p with the exception of an N-terminal membrane anchor sequence, expressed in Escherichia coli, and purified by metal chelate affinity chromatography. The purified sortase had maximum activity at pH 7.5 and was stable at 20-45 degrees C for the cleavage of a synthetic fluorophore substrate. The enzyme inhibitory activity in medicinal plants was also evaluated for antibacterial drug discovery. Among 80 medicinal plants tested, Cocculus trilobus, Fritillaria verticillata, Liriope platyphylla, and Rhus verniciflua had strong inhibitory activity. The extract with the greatest activity was the ethyl acetate fraction derived from the rhizome of Cocculus trilobus (IC50 = 1.52 microg/ml).