Evidence for a striped phase of high T c superconductor at the Fermi surface

A complete Fermi surface in the normal state of superconducting Bi₂Sr₂CaCu₂O_8+δ at the optimum doping (T _c = 91K) has been measured by angle scanning photoemission spectroscopy using synchrotron radiation. The Fermi surface reveals broken segments and hot spots of high photointensity along lines of k _y = n:0:23Å^?1 in the (π; π) direction. The pseudogap observed at (π,0) in underdoped materials is one of this missing segments. The results indicate the presence of characteristic subbands of a superlattice of quantum stripes. This is formed by an ordered array of ～ 14Å large stripes.     

Determination of pollutants in dwellings by neutron activation analysis and X-ray fluorescence

Metallic pollutants were measured in dwellings in Mexico City by instrumental neutron activation analysis (INAA) and X-ray fluorescence techniques. Monitoring was performed in the west side of the city and in the winter season. In general the average concentration of contaminants collected, when compared with the average concentrations reported in a previous paper, have increased with time and in the particular case of lead and mercury some samples are above the indicative WHO maximum levels.     

Phenoxy-benzothiadiazole dyes: Synthesis,photophysical properties and preliminary application in OLEDs

The synthesis of a phenoxy-benzothiadiazole (BTD) derivative is reported for the first time. This derivative was employed as an intermediate in the obtention of two novel highly fluorescent aryl-phenoxy-BTD dyes. Their photophysical properties were evaluated in solution and the results indicate a strong intramolecular charge transfer (ICT) character in the excited state. The luminophore 3a, possessing a donor-BTD-phenoxide architecture, exhibits superior fluorescence quantum yield (0.67) than the designed acceptor-BTD-phenoxide dye (0.06). After electrochemical and photoluminescence characterization of thin films of 3a, an OLED with the configuration ITO/PEDOT:PSS/3a/TPBi/LiF/Al was constructed. This device displayed a green emission centered at 547?nm, with CIE coordinates of (0.40, 0.55). For comparison, an OLED using a previously reported luminescent BTD-pyridyl derivative was also constructed. The OLED made with the phenoxy-BTD derivative operated using less current density and led to higher irradiance and electrical stability, indicating the high potential of ArO-BTD dyes for future application in electroluminescent devices.     

Molecular structure of 6-methyleneoxytetracycline hydrobromide

The structure of 4(dimethylamino)-1, 4, 4a, 5, 5a, 6, 11, 12a-octahydro-3, 5, 10, 12, 12a-pentahydroxy-6-methylene-1, 11-dioxo-2-naphthacenecarboxamide hydrobromide salt was determined by an X-ray analysis. One methacycline cation and one bromide anion were found in the asymmetric unit of an orthorhombic cell, space group P2₁2₁2₁,a 9.580(1),b 12.147(2),c 18.735(3) å,V2180.0(5) å³, Z4,D _c 1.59 g cm^–3, (MoK) 19.15 cm^–1. The structure was solved and refined toR(F) 0.062 andR _w(F) 0.064 by a full matrix least-squares procedure. The conformation of the methacycline cation is found to be similar to that reported for 6-demethyl-7-chlorotetracycline hydrochloride trihydrate.     

Ligand-controlled and nanoconfinement-boosted luminescence employing Pt(ii) and Pd(ii) complexes: from color-tunable aggregation-enhanced dual emitters towards self-referenced oxygen reporters

In this work, we describe the synthesis, structural and photophysical characterization of four novel Pd(ii) and Pt(ii) complexes bearing tetradentate luminophoric ligands with high photoluminescence quantum yields (Φ_L) and long excited state lifetimes (τ) at room temperature, where the results were interpreted by means of DFT calculations. Incorporation of fluorine atoms into the tetradentate ligand favors aggregation and thereby, a shortened average distance between the metal centers, which provides accessibility to metal–metal-to-ligand charge-transfer (³MMLCT) excimers acting as red-shifted energy traps if compared with the monomeric entities. This supramolecular approach provides an elegant way to enable room-temperature phosphorescence from Pd(ii) complexes, which are otherwise quenched by a thermal population of dissociative states due to a lower ligand field splitting. Encapsulation of these complexes in 100 nm-sized aminated polystyrene nanoparticles enables concentration-controlled aggregation-enhanced dual emission. This phenomenon facilitates the tunability of the absorption and emission colors while providing a rigidified environment supporting an enhanced Φ_L up to about 80% and extended τ exceeding 100 μs. Additionally, these nanoarrays constitute rare examples for self-referenced oxygen reporters, since the phosphorescence of the aggregates is insensitive to external influences, whereas the monomeric species drop in luminescence lifetime and intensity with increasing triplet molecular dioxygen concentrations (diffusion-controlled quenching).

Pt(ii) and Pd(ii) complexes with unprecedented photophysical properties were developed. Encapsulation in nanoparticles boosted their performance while rendering them as self-referenced oxygen sensors.     

Development and Validation of a Stability-Indicating LC Method for the Determination of Rupatadine in Pharmaceutical Formulations

A reversed-phase liquid chromatography (RP-LC) method was validated for the determination of rupatadine in pharmaceutical dosage forms. The LC method was carried out on a Gemini C₁₈ column (150 mm × 4.6 mm I.D.), maintained at 30 °C. The mobile phase consisted of ammonium acetate buffer (pH 3.0; 0.01 M) with 0.05% of 1-heptanesulfonic acid–acetonitrile (71.5:28.5, v/v), run at a flow rate of 1.0 mL min^?1 and using photodiode array (PDA) detection at 242 nm. The chromatographic separation was obtained with retention time of 5.15 min, and was linear in the range of 0.5–400 μg mL^?1 (r ² = 0.9999). The specificity and stability-indicating capability of the method was proven through the degradation studies and showing also, that there was no interference of the excipients. The accuracy was 100.39% with bias lower than 0.58%. The limits of detection and quantitation were 0.01 and 0.5 μg mL^?1, respectively. Moreover, method validation demonstrated acceptable results for precision, sensitivity and robustness. The proposed method was applied for the analysis of pharmaceutical dosage forms assuring the therapeutic efficacy.