Molecular beam epitaxy growth of ferromagnetic Co sub(2)TiSi films on GasAs(001) substrates is presented and it is found that the optimum growth temperature is between 300-360 degreesC where the film ...is single phase and exhibits highly (0 0 1)-ordered crystal structure. The Co sub(2)TiSi films are ferromagnetic up to 300 K and the highest value of saturation magnetization obtained is 0.8 mu sub(B) Per formula unit. The Co sub(2)TiSi films also exhibit a very low degree of magnetic anisotropy along in-plane crystallographic directions. Expected values of Seebeck coefficient and resistivity measured at room temperature confirm good stoichiometry of the Co sub(2)TiSi films and indicate that this material is a promising candidate for both spincaloric and spintronic applications.
β-NaYF4 co-doped with Er3+ and Yb3+ ions were successfully synthesized at the reaction temperature as low as 180 °C by the two steps procedure using the rare-earth stearates as precursors. The XRD ...and TEM data show that the NaYF4 nanocrystals were relatively uniform with the approximate size of 50 nm and the dopants led to shrinking of NaYF4 crystals. Moreover, the EDX mapping analysis indicate that the Yb3+, Er3+ ions were distributed homogeneously in host matrix even the Yb3+ doping concentration as high as 25%. The PL spectroscopy was used to investigate the optical properties of these systems. The red/green emission ratio of Er3+ was controlled by changing the doping concentration in matrix. An increase of Yb3+ contents from 2 to 25 mol % induced a remarkably tunable emission from green to red. Addition, the highest red/green ratio was also achieved for the sample of 1% Er3+ and 20% Yb3+. Combining the results of the up-conversion emission intensity as a function of the pump power and luminescence data, the energy transfer mechanism between the Yb3+ sensitizers and Er3+ activators was demonstrated. The intense efficiency of red emission under 980 nm excitation provides the potential applications in bio-labeling and bio-imaging.
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•β-phase NaYF4 nanocrystals were achieved at low reaction temperature of 180 °C.•Nanocrystals size distributed uniformly in range of 40 ÷ 50 nm.•The doping ions dispersed homogeneously in host matrix even at high doping content.•Tunable green-to-red emission is controlled by changing the Yb3+ and Er3+ contents.•Energy transfer mechanism of Yb3+ sensitizer and Er3+ activator is demonstrated.
Three new bisindole alkaloids (1–3), possessing a rare carbon skeleton formed by two indole moieties fused via a dihydropyran unit, were isolated from the alkaloid extract of the stem bark of Gonioma ...malagasy. Their structure and absolute configuration were assigned thanks to a combination of one and two dimensional NMR spectroscopy and ECD calculations. These bisindole alkaloids are artifacts formed during alkaloid extraction.
reaction: see text Four C(11)N(5) diketopiperazine metabolites named verpacamides A (6), B (7), C (8), and D (9) consisting of a proline-arginine dipeptide skeleton have been isolated from the marine ...sponge Axinella vaceleti. Verpacamides A-D are a sequence of metabolites showing the transformation of proline and arginine into the oxidized guanidinyl-cyclo(Pro-Pro) 8 and 9. Compounds 6-9 are structurally and chemically related to C(11)N(5) pyrrole-2-aminoimidazole metabolites also isolated from the Axinellidae and Agelasidae families of sponges and exemplified by dispacamide A (4) and dibromophakellin (10).
Biological and chemical investigations of the methanolic crude extract of the Red Sea marine sponge Hyrtios erectus led to the isolation of a novel azepino-indole-type alkaloid named hyrtiazepine (2) ...and 5-hydroxy-1H-indole-3-carboxylic acid methyl ester (3), together with the known metabolites hyrtiosulawesine (1), 5-hydroxyindole-3-carbaldehyde (4), hyrtiosin A (5), and hyrtiosin B (6). Their structures were elucidated on the basis of mass spectrometry and detailed 2D NMR spectroscopic data. Hyrtiosulawesine (1) displayed a significant antiphospholipase A2 activity with an IC50 value of 14 μM in a fluorometric assay using Crotalus adamanteus venom phospholipase A2.
SETTING: Pham Ngoc Thach Hospital for Tuberculosis and Lung Diseases, the tertiary referral hospital for tuberculosis (TB) in Southern Vietnam.OBJECTIVE: To develop and evaluate a simple, rapid and ...accurate multiplex allele specific polymerase chain reaction (MAS-PCR) test to detect
rifampicin (RMP) resistance point mutations at codons 516, 526 or 531 in the rpoB gene of Mycobacterium tuberculosis.DESIGN: The novel MAS-PCR was compared with the commercial M. tuberculosis Drug Resistance (MTBDR) test in 104 RMP-resistant and 50 RMP-susceptible
routine isolates, defined by conventional 1% phenotypic susceptibility testing.RESULTS: The sensitivity of the MAS-PCR and MTBDR tests was respectively 83.7% (95%CI 75.1-90.2) and 93.3% (95%CI 86.6-97.3). Both tests were 100% specific. The negative predictive value was 74.6%
(95%CI 65.3-83.1) for the MAS-PCR and 87.7% (95%CI 80.0-93.6) for the MTBDR test.CONCLUSION: The MTBDR test, although more sensitive, is currently prohibitively expensive in resource-poor, high-burden settings. The MAS-PCR described here presents a less laborious economic alternative.
A susceptible result returned by either test cannot be used to exclude multidrug-resistant TB.
We investigate the chemical and morphological structure of the Au nanodots on Ge(111) which serve as catalysts for the formation of epitaxial Ge nanowires. The spatial localization of Au is ...investigated by X-ray spectromicroscopy and transmission electron microscopy. We show that dewetting of an Au film on Ge(111) gives rise to a thin Au-Ge wetting layer and Au-Ge dots. These dots are crystallized but not with a single crystallographic orientation. Thanks to the spatially resolved X-ray and transmission electron microscopy measurements, a chemical characterization of both binary Au-Ge catalysts and wetting layer is obtained at the nanoscale. We show that Ge vertical growth is achieved even without external Ge supply.
Topological insulators (TIs) like Bi$_2$Se$_3$ are a class of material with topologically protected surface states in which spin-momentum locking may enable spin-polarized and defect-tolerant ...transport. In this work, we achieved the epitaxial growth of Bi$_2$Se$_3$ thin films on germanium, which is a key material for microelectronics. Germanium also exhibits interesting properties with respect to the electron spin such as a spin diffusion length of several micrometers at room temperature. By growing Bi$_2$Se$_3$ on germanium, we aim at combining the long spin diffusion length of Ge with the spin-momentumlocking at the surface of Bi$_2$Se$_3$. We first performed a thorough structural analysis of Bi$_2$Se$_3$ films using electron and x-ray diffraction as well as atomic force microscopy. Then, magnetotransport measurements at low temperature showed the signature of weak antilocalization as a result of two-dimensional transport in the presence of spinorbit coupling. We interpret our results as the signature of magnetotransport in a single strongly coupled coherent channel in the presence of surface to bulk scattering. Interestingly, the magnetotransport measurements also point out that the conduction channel can be tuned between the Bi$_2$Se$_3$ film and the Ge layer underneath by means of the bias voltage or the applied magnetic field. This result suggests that the Bi$_2$Se$_3$/Ge junction is a promising candidate for tuning spin-related phenomena at interfacesbetween TIs and semiconductors.
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