Synthesis, characterization and spectroscopic investigation of Cr3+ doped wollastonite nanophosphor

This work explores the preparation of nanocrystalline Cr3+ (1-5 mol%) doped CaSiO3 phosphors by solution combustion process and study of its photoluminescence (PL) behavior. The nanopowders are well characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infra-red (FTIR) spectroscopy. PXRD results confirm monoclinic phase upon calcination at 950 degrees C for 3 h. SEM micrographs indicates that the powder is highly porous and agglomerated. The TEM images show the powder to consist of spherical shaped particles of size similar to 30-60 nm. Upon 323 nm excitation, the emission profile of CaSiO3:Cr3+ exhibits a narrow red emission peak at 641 nm due to E-2 -> (4)A(2) transition and broad band at 722 nm due to T-4(2g) -> (4)A(2g). It is observed that PL intensity increases with increase in Cr3+ concentration and highest PL intensity is observed for 3 mol% doped sample. The PL intensity decreases with further increase in Cr3+ doping. This decrease in PL intensity beyond 3 mol% is ascribed to concentration quenching. Racah parameters are calculated to describe the effects of electron-electron repulsion within the crystal lattice. The parameters show 21% reduction in the Racah parameter of free ion and the complex, indicating the moderate nephelauxetic effect in the lattice. (C) 2014 Elsevier B.V. All rights reserved.

Gd1.96-xYxEu0.04O3 (x=0.0, 0.49, 0.98, 1.47, 1.96 mol%) nanophosphors: Propellant combustion synthesis, structural and luminescence studies

Gd1.96-xYxEu0.04O3 (x = 0.0, 0.49, 0.98, 1.47, 1.96 mol%) nanophosphors were synthesized by propellant combustion method at low temperature (400 degrees C). The powder X-ray diffraction patterns of as formed Gd1.96Eu0.04O3 showed monoclinic phase, however with the addition of yttria it transforms from monoclinic to pure cubic phase. The porous nature increases with increase of yttria content. The particle size was estimated from Scherrer's and W-H plots which was found to be in the range 30-40 nm. These results were in well agreement with transmission electron microscopy studies. The optical band gap energies estimated were found to be in the range 5.32-5.49 eV. PL emission was recorded under 305 nm excitation show an intense emission peak at 611 nm along with other emission peaks at 582, 641 nm. These emission peaks were attributed to the transition of D-5(0) —> F-7(J) (J = 0, 1, 2, 3) of Eu3+ ions. It was observed that PL intensity increases with increase of Y content up to x = 0.98 and thereafter intensity decreases. CIE color co-ordinates indicates that at x = 1.47 an intense red bright color can be achieved, which could find a promising application in flat panel displays. The cubic and monoclinic phases show different thermoluminescence glow peak values measured under identical conditions. The response of the cubic phase to the applied dose showed good linearity, negligible fading, and simple glow curve structure than monoclinic phase indicating that suitability of this phosphor in dosimetric applications. (C) 2014 Elsevier B.V. All rights reserved.

In vitro exposure of tobacco specific nitrosamines decreases the rat lung phospholipids by enhanced phospholipase A(2) activity

Tobacco-specific nitrosamines (TSNA) have implications in the pathogenesis of various lung diseases and conditions are prevalent even in non-smokers. N-nitrosonornicotine (NNN) and 4-(methyl nitrosamino)-1-(3-pyridyl)-1-butanone (NNK) are potent pulmonary carcinogens present in tobacco product and are mainly responsible for lung cancer. TSNA reacts with pulmonary surfactants, and alters the surfactant phospholipid. The present study was undertaken to investigate the in vitro exposure of rat lung tissue slices to NNK or NNN and to monitor the phospholipid alteration by P-32]orthophosphate labeling. Phospholipid content decreased significantly in the presence of either NNK or NNN with concentration and time dependent manner. Phosphatidylcholine (PC) is the main phospholipid of lung and significant reduction was observed in PC similar to 61%, followed by phosphatidylglycerol (PG) with 100 mu M of NNK, whereas NNN treated tissues showed a reduction in phosphatidylserine (PS) similar to 60% and PC at 250 mu M concentration. The phospholipase A(2) assays and expression studies reveal that both compounds enhanced phospholipid hydrolysis, thereby reducing the phospholipid content. Collectively, our data demonstrated that both NNK and NNN significantly influenced the surfactant phospholipid level by enhanced phospholipase A(2) activity. (C) 2014 Elsevier Ltd. All rights reserved.

GdAlO3:Eu3+:Bi3+ nanophosphor: Synthesis and enhancement of red emission for WLEDs

GdAlO3, GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ nanophosphors were synthesised by solution combustion technique. Pure orthorhombic phase was obtained from powder X-ray diffraction (PXRD) studies. Scanning electron microscopy (SEM) micrographs showed the porous, agglomerated and irregular shaped particles. The particle size obtained by transmission electron microscopy (TEM) measurement was in good agreement with the values obtained by Debye Scherrer's and W-H plots. The selected area electron diffraction (SAED) pattern show single crystalline nature of the sample. Photoluminescence (PL) measurements were carried out for GdAlO3:Eu3+ and GdAlO3:Eu3+:Bi3+ phosphors excited at a wavelength of 274 nm. The characteristic emission peaks of Eu3+ ions were recorded at 590, 614, 655 and 695 nm corresponding to D-5(0) -> F-7(J) (J = 1, 2, 3, 4) transitions respectively. However, with addition of Bi3+ ions in GdAlO3:Eu3+, PL intensity drastically enhanced. Orange red color was tuned to deep red color with the addition of Bi3+ ions in GdAlO3:Eu3+ phosphor. Therefore, the phosphor was highly useful as red component in WLEDs. A single well resoled glow peak at 225 degrees C was recorded in GdAlO3 and GdAlO3:Eu3+. Further, with addition of Bi3+ ions, an additional peak at 300 degrees C was recorded. TL glow curves of different UV-exposed GdAlO3:Eu3+:Bi3+ show two TL peaks at 207 and 300 degrees C respectively. The 207 degrees C peak show simple glow peak structure and its intensity increases linearly up to 25 mm and after that it decrease. (C) 2014 Elsevier B.V. All rights reserved.

Combustion synthesized tetragonal ZrO2: Eu3+ nanophosphors: Structural and photoluminescence studies

Novel crystalline tetragonal ZrO2: Eu3+ phosphors were prepared by a facile and efficient low temperature solution combustion method at 400 +/- 10 degrees C using oxalyl dihydrazide (ODH) as fuel. The powder X-ray diffraction patterns and Rietveld confinement of as formed ZrO2: Eu3+ (1-11 mol%) confirmed the presence of body centered tetragonal phase. The crystallite size estimated from Scherrer's and W-H plots was found to be in the range of 7-17 nm. These results were in good agreement with transmission electron microscopy studies. The calculated microstrain in most of the planes indicated the presence of tensile stress along various planes of the particles. The observed space group (P4(2)/nmc) revealed the presence of cations in the 2b positions (0.75, 0.25, 0.25) and the anions in the 4d positions (0.25, 0.25, 0.45). The optical band gap energies estimated from Wood and Tauc's relation was found to be in the range 4.3-4.7 eV. Photoluminescence (PL) emission was recorded under 394 and 464 nm excitation shows an intense emission peak at 605 nm along with other emission peaks at 537, 592, 605 and 713 nm. These emission peaks were attributed to the transition of D-5(0) -> F-7(J) (J = 0, 1, 2, 3) of Eu3+ ions. The high ratio of Intensity of (D-5(0) -> F-7(2)) and (D-5(0) -> F-7(1)) infers that Eu3+ occupies sites with a low symmetry and without an inversion center. CIE color coordinates indicated the red regions which could meet the needs of illumination devices. (C) 2014 Elsevier B.V. All rights reserved.

Amorphous W-S-N thin films: The atomic structure behind ultra-low friction

Amorphous W-S-N in the form of thin films has been identified experimentally as an ultra-low friction material, enabling easy sliding by the formation of a WS2 tribofilm. However, the atomic-level structure and bonding arrangements in amorphous W-S-N, which give such optimum conditions for WS2 formation and ultra-low friction, are not known. In this study, amorphous thin films with up to 37 at.% N are deposited, and experimental as well as state-of-the-art ab initio techniques are employed to reveal the complex structure of W-S-N at the atomic level. Excellent agreement between experimental and calculated coordination numbers and bond distances is demonstrated. Furthermore, the simulated structures are found to contain N bonded in molecular form, i.e. N-2, which is experimentally confirmed by near edge X-ray absorption fine structure and X-ray photoelectron spectroscopy analysis. Such N-2 units are located in cages in the material, where they are coordinated mainly by S atoms. Thus this ultra-low friction material is shown to be a complex amorphous network of W, S and N atoms, with easy access to W and S for continuous formation of WS2 in the contact region, and with the possibility of swift removal of excess nitrogen present as N-2 molecules. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Spectral characterizations and photophysical properties of one-step synthesized blue fluorescent 4 `-aryl substituted 2,2 `:6 `,2 `'-terpyridine for OLEDs application

We have synthesized a series of 4'-aryl substituted 2,2':6',2 `'-terpyridine (terpy) derivatives, namely 4'-(4-methylphenyl)-2,2':6',2 `'-terpyridine (C-1), 4'-(2-furyl)-2,2':6'2 `'-terpyridine (C-2), and 4'-(3,4,5-trimethoxyphenyl)-2,2':6',2 `'-terpyridine (C-3). The synthesized terpy compounds were characterized by elemental analyses, FTIR, NMR (H-1 and C-13), and ESI-Mass spectrometry. Photophysical, electrochemical and thermal properties of terpy compounds were systematically studied. Maximum excitation band was observed between 240 and 330 nm using UV-visible spectra, and maximum emission peaks from PL spectra were observed at 385, 405 and 440 nm for C-1, C-2 and C-3 respectively. Fluorescence lifetime (tau) of the fluorophores was found to be 035 and 1.55 ns at the excitation wavelength of 406 nm for C-1 and C-2 respectively, and tau value for C-3 was found to be 0.29 ns at the excitation wavelength of 468 nm. We noticed that the calculated values of HOMO energy levels were increased from 5.96 (C-1) to 6.08 (C-3) eV, which confirms that C-3 derivative is more electrons donating in nature. The calculated electrochemical band gaps were 2.95, 2.82 and 3.02 eV for C-1, C-2 and C-3 respectively. These blue fluorescent emitter derivatives can be used as an electron transport and electroluminescent material to design the blue fluorescent organic light emitting diode (OLED) applications. (C) 2015 Elsevier B.V: All rights reserved.

Incorporation of Cr3+ ions in tuning the magnetic and transport properties of nano zinc ferrite

Cost effective and low temperature synthesis methods namely solution combustion and hydrothermal methods were used to prepare chromium incorporated nanocrystalline zinc ferrites. The effect of incorporation of low concentration Cr3+ ions on the structural, morphological, magnetic and transport properties of the zinc ferrite compounds were investigated. The crystalline nature and size variation with chromium content were valid from powder x-ray diffraction. Particles size and crystallite size variation were valid from scanning electron microscopy and transmission electron microscopy respectively. With the increase in chromium incorporation, the crystallite and particles sizes were decreased. Fourier transform infrared spectroscopy (FTIR) studies confirmed the presence of strong metal-oxygen bonds. The elastic properties of the materials in both the methods were estimated by FTIR studies. Magnetic properties namely saturation magentization, remanent magnetization and coercivity values were decreased with increase in Cr3+ ions concentration. The dielectric properties of the samples decreased with increase in the Cr3+ ions. The dielectric constant was observed to be of the order of 10(6) at low frequency and almost 1 at higher frequency range. The activation energy estimated using Arrhenius plots was of the order of 0.182 eV and 0.368 eV respectively for the compounds prepared by solution combustion and hydrothermal methods. The emission spectra of the samples excited at 344 nm were reported using photoluminescence (PL) spectroscopy. Further, the approximate energy band gap(E-g) was estimated from PL studies. The E-g of the materials were lie in the range of 2.11-1.98 eV. (C) 2015 Elsevier B.V. All rights reserved.

Influencia de diferentes periodos de destete en conejas primiparas en el municipio de Diriamba, Departamento de Carazo, Nicaragua

Este trabajo fue realizado en la Quinta "Myriam", ubicada en el municipio de Diriamba, departamento de Carazo, Nicaragua, propiedad del Dr. Jorge Ferreira. La ubicación geográfica del municipio está comprendida entre los 11° 50' y 12° 00' de Latitud Norte y entre los 86° 00' y 86° 15' de Longitud Oeste, cuenta con una elevación de 551 m.s.n.m., los datos meteorológicos de la zona en los últimos cuatro años (90-93) en cuanto a temperatura, humedad relativa y precipitación promedio fueron: 23.8 °C, 84% y 1184,5 mm respectivamente, (INETER, Departamento de Estadística, 1993). En el presente ensayo, se utilizó un diseño estadístico completamente aleatorizado (DCA), mediante el cual se evaluó el efecto de 3 tratamientos (15, 30 y 45 días de destete) sobre las variables Peso de la Camada al Destete (PCD), Peso de la Madre al Destete (PMD), Peso de la Madre al Segundo Parto (PSP), Ganancia Media Diaria del Parto 1 al Parto 2 (GMDp 1.P2) , con 4 repeticiones por tratamiento, éstas repeticiones estuvieron constituidas por conejas primíparas, las cuales tuvieron un peso que osciló entre 3 - 3.18 kg. y edad homogénea de 7 meses. Las variables fueron sometidas a la prueba de Duncan para determinar la superioridad en rango por tratamiento. Mediante el análisis de varianza se encontró que el efecto de los tratamientos resultó ser altamente significativo sobre la variable Peso de la Camada al Destete (PCD) (P0.01), significativo sobre las variables Peso de la Madre al Segundo Parto (PSP) y Ganancia Media Diaria del Parto 1 al Parto 2 (GMD p 1.P2) (P0.1) y no significativo sobre la variable Peso de la Madre al Destete (PMD) (NS). El efecto de la covariable Peso al Primer Parto (P1P) resultó ser altamente significativo sobre las variables Peso de la Madre al Destete (PMD) y Peso de la Madre al Segundo Parto (PSP) (P0.01). Después de someter las variables a la prueba de DUNCAN se encontraron los siguientes promedios por tratamiento: Peso de la Camada al Destete (PCD) ; T.15 días 1.538 kg P.V.(C), T.30 días 3.360 kg P.V. (B), T.45 días 4.523 kg P.V. (A), Peso de la Madre al Destete (PMD); T.15 días 3.649 kg P.V. (A) T.30 días 3.549 kg P.V. (A), T.45 dias 3.493 kg P.V.(A). Peso de la Madre al Segundo Parto (PSP); T.15 días 3. 449 kg P.V. (B), T.30 días 3.628 kg P.V. (AB), T.45 días 3.777 kg P.V.(A). Ganancia Media Diaria del Parto 1 al Parto 2 (GMD p 1.P2) T .15 días (2.071 g (B), T.30 días 2.718 g (AB), T.45 días 2. 975 g (A). Los promedios y desviaciones standard para las variables Ganancia Media Diaria del Parto 1 al Destete 1 (GMDp1-D1)y Ganancia Media Diaria del Destete l al Parto 2 (GMDD1.P2) por tratamiento fueron: GMD P1-D1; T.l5 días 3.84 g ± 0.50 g, T.30 días 2.54 g ± 0.64 g, T.45 días 2.37 g ± 0.72 g. GMD D1-P2; T.l5 días 2.26 g ± 0.54 g, T.30 días 3.17 g ± 0.74 g, T.45 días 3.93 g ± 0.28 g. Se encontró que el alimento tipo único suministrado a los animales bajo experimentación, cumplió con los requerimientos nutricionales de la especie estudiada. Los costos encontrados por hembra, por tratamiento, fueron C$ 197.21 destete de 15 días, C$ 220.28 destete de 30 días, C$ 243 .1.4 destete de 45 días. Los costos por gazapo destetado fueron de C$ 5.48 destete de 15 días, C$ 6.12 destete de 30 días, C$ 8.10 destete de 45 días.

Ancillary ligand effects : from zirconium(IV)-catalyzed homogeneous propylene polymerization to platinum(II)-mediated C-H bond activation

A series of C_s- and C₁-symmetric doubly-linked ansa-metallocenes of the general formula {1,1'-SiMe₂-2,2'-E-('ƞ⁵-C₅H₂-4-R¹)-(ƞ⁵-C₅H-3',5'-(CHMe₂)₂)}ZrC₂ (E = SiMe₂ (1), SiPh₂ (2), SiMe₂ -SiMe₂ (3); R¹ = H, CHMe₂, C₅H₉, C₆H₁₁, C₆H₅) has been prepared. When activated by methylaluminoxane, these are active propylene polymerization catalysts. 1 and 2 produce syndiotactic polypropylenes, and 3 produces isotactic polypropylenes. Site epimerization is the major pathway for stereoerror formation for 1 and 2. In addition, the polymer chain has slightly stronger steric interaction with the diphenylsilylene linker than with the dimethylsilylene linker. This results in more frequent site epimerization and reduced syndiospecificity for 2 compared to 1.

C₁-Symmetric ansa-zirconocenes [1,1 '-SiMe₂-(C₅H₄)-(3-R-C₅H₃)]ZrCl₂ (4), [1,1 '-SiMe₂-(C₅H₄)-(2,4-R₂-C₅H₂)]ZrCl₂ (5) and [1,1 '-SiMe₂-2,2 '-(SiMe₂-SiMe₂)-(C₅H₃)-( 4-R-C₅H₂)]ZrCl₂ (6) have been prepared to probe the origin of isospecificity in 3. While 4 and 3 produce polymers with similar isospecificity, 5 and 6 give mostly hemi-isotactic-like polymers. It is proposed that the facile site epimerization via an associative pathway allows rapid equilibration of the polymer chain between the isospecific and aspecific insertion sites. This results in more frequent insertion from the isospecific site, which has a lower kinetic barrier for chain propagation. On the other hand, site epimerization for 5 and 6 is slow. This leads to mostly alternating insertion from the isospecific and aspecific sites, and consequently, a hemi-isotactic-like polymers. In comparison, site epimerization is even slower for 3, but enchainment from the aspecific site has an extremely high kinetic barrier for monomer coordination. Therefore, enchainment occurs preferentially from the isospecific site to produce isotactic polymers.

A series of cationic complexes [(ArN=CR-CR=NAr)PtMe(L)]⁺[BF₄]⁺ (Ar = aryl; R = H, CH₃; L = water, trifluoroethanol) has been prepared. They react smoothly with benzene at approximately room temperature in trifluoroethanol solvent to yield methane and the corresponding phenyl Pt(II) cations, via Pt(IV)-methyl-phenyl-hydride intermediates. The reaction products of methyl-substituted benzenes suggest an inherent reactivity preference for aromatic over benzylic C-H bond activation, which can however be overridden by steric effects. For the reaction of benzene with cationic Pt(II) complexes, in which the diimine ligands bear 3,5-disubstituted aryl groups at the nitrogen atoms, the rate-determining step is C-H bond activation. For the more sterically crowded analogs with 2,6-dimethyl-substituted aryl groups, benzene coordination becomes rate-determining. The more electron-rich the ligand, as reflected by the CO stretching frequency in the IR spectrum of the corresponding cationic carbonyl complex, the faster the rate of C-H bond activation. This finding, however, does not reflect the actual C-H bond activation process, but rather reflects only the relative ease of solvent molecules displacing water molecules to initiate the reaction. That is, the change in rates is mostly due to a ground state effect. Several lines of evidence suggest that associative substitution pathways operate to get the hydrocarbon substrate into, and out of, the coordination sphere; i.e., that benzene substitution proceeds by a solvent- (TFE-) assisted associative pathway.

气相传输平衡法在Sr^2＋：α-BBO衬底上制备β-BBO薄膜的研究

采用气相传输平衡技术在掺Sr^2＋的α-BBO（001）衬底上制备了β-BBO薄膜，研究了粉料配比、VTE处理温度以及恒温时间对薄膜质量的影响。结果表明，在适当的粉料配比、VTE处理温度以及恒温时间下，在Sr^2＋：α-BBO晶片表层制备呈c轴高度择优取向的、没有第二相物质的β-BBO薄膜，其双晶摇摆曲线半峰宽值FWHM为1000＂，显示出β-BBO薄膜较好的结晶质量。并对气相传输平衡技术制备β-BBO薄膜的机理进行了初步的探讨。

Note sur les premiers essais de capture du crabe profond Geryon quinquedens en Côte d'Ivoire

First experiments to trap the deep sea red crab Geryon quinquedens off Côte d'Ivoire have had good success. The yields obtained are similar to those observed off the northeastern coast of the United States and off Angola, where commercial fisheries have been developed for some years.

Lipid breakdown in oil sardine (Sardinella longiceps) during frozen storage

The problem of hydrolysis of lipids and consequent accumulation of free fatty acids and development of rancidity due to oxidation of the lipids are major problems in frozen storage of oil sardine (Sardinella longiceps). The course of the phospholipid breakdown, production of free fatty acids and the changes taking place in the major unsaturated fatty acids during frozen storage are described in this paper. The rate of free fatty acid production is faster in the fish, with the higher fat content. Unlike in lean fish, the neutral lipids are found to contribute substantially to the free fatty acid production. The fatty acids most affected during storage are C sub(20:5) and C sub(22:6). The polyene indices were found to decrease during storage. These effects are more pronounced in the fish with the higher fat content.

Purification and cloning of a novel C-type lectin-like protein with platelet aggregation activity from Trimeresurus mucrosquamatus venom

TMVA, a novel C-type lectin-like protein that induces platelet aggregation in a dose-dependent manner, was purified from the venom of Trimeresurus mucrosquamatus. It consists of two subunits, alpha (15,536 Da) and beta (14,873 Da). The mature amino acid sequences of the a (135 amino acids) and beta subunits (123 amino acids) were deduced from cloned cDNAs. Both of the sequences show great similarity to C-type lectin-like venom proteins, including a carbohydrate recognition domain. The cysteine residues of TMVA are conserved at positions corresponding to those of flavocetin-A and convulxin, including the additional Cys135 in the alpha subunit and Cys3 in the beta subunit. SDS-PAGE, mass spectrometry analysis and amino acid sequence showed that native TMVA exists as two convertible multimers Of (alphabeta)(2) and (alphabeta)(4) with molecular weights of 63,680 and 128,518 Da, respectively. The (alphabeta)(2) complex is stabilized by an interchain disulfide bridge between the two alphabeta-heterodimers, whereas the stabilization of the (alphabeta)(4) complex seems to involve non-covalent interactions between the (alphabeta)(2) complexes. (C) 2002 Elsevier Science Ltd. All rights reserved.