Synthesis and luminescence properties of Sm3+ doped CaTiO3 nanophosphor for application in white LED under NUV excitation

CaTiO3:Sm3+ (1-11 mol%) nanophosphors were successfully synthesized by a low temperature solution combustion method LCS]. The structural and morphological properties of the phosphors were studied by using Powder X-ray diffractometer (PXRD), Fourier transform infrared (FTIR), X-ray photo electron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). TEM studies indicate that the size of the phosphor is similar to 20-35 nm. Photoluminescence (PL) properties of Sm3+ (1-11 mol%) doped CaTiO3 for NUV excitation (407 nm) was studied in order to investigate the possibility of its use in White light emitting diode (WLED) applications. The emission spectra consists of intra 4f transitions of Sm3+, such as (4)G(5/2) -> H-6(5/2) (561 nm), (4)G(5/2) -> H-6(7/2) (601-611 nm), (4)G(5/2) -> H-6(9/2) (648 nm) and (4)G(5/2) -> H-6(11/2) (703 nm) respectively. Further, the emission at 601-611 nm show strong orange-red emission and can be applied to the orange-red emission of phosphor for the application for near ultra violet (NUV) excitation. Thermoluminescence (TL) of the samples irradiated with gamma source in the dose range 100-500 Gy was recorded at a heating rate of 5 degrees C s(-1). Two well resolved glow peaks at 164 degrees C and 214 degrees C along with shouldered peak at 186 degrees C were recorded. TL intensity increases up to 300 Gy and thereafter, it decreases with further increase of dose. The kinetic parameters namely activation energy (E), frequency factor (s) and order of kinetics were estimated and results were discussed in detail. (C) 2014 Elsevier B.V. All rights reserved.

Digestive ripening facilitated atomic diffusion at nanosize regime: Case of AuIn2 and Ag3In intermetallic nanoparticles

Monodisperse colloidal gold-indium (AuIn2) intermetallic nanoparticles have been synthesized from Au and In colloids using the digestive ripening process. Formation of the intermetallic proceeds via digestive ripening facilitated atomic diffusion of Au and In atoms from the Au and In nanoparticles followed simultaneously by their growth in the solution. Optimization of the reaction temperature was found to be crucial for the formation of AuIn2 intermetallic from gold and indium nanoparticles. Transmission electron microscopy revealed the presence of nearly monodisperse nanoparticles of Au and AuIn2 with particle size distribution of 3.7 +/- 1.0 nm and 5.0 +/- 1.6 nm, respectively. UV-visible spectral studies brought out the absence of SPR band in pure AuIn2 intermetallic nanoparticles. Optical study and electron microscopy, in combination with powder X-ray diffraction established phase pure AuIn2 intermetallic nanoparticles unambiguously. The potential of such an unprecedented approach has been further exploited in the synthesis of Ag3In intermetallic nanoparticles with the dimension of less than 10 nm. (C) 2014 Elsevier B.V. All rights reserved.

Comparison of structural and luminescence properties of Dy2O3 nanopowders synthesized by co-precipitation and green combustion routes

Dysprosium oxide (Dy2O3) nanopowders were prepared by co-precipitation (CP) and eco-friendly green combustion (GC) routes. SEM micrographs prepared by CP route show smooth rods with various lengths and diameters while, GC route show porous, agglomerated particles. The results were further confirmed by TEM. Thermoluminescence (TL) responses of the nanopowder prepared by both the routes were studied using gamma-rays. A well resolved glow peak at 353 degrees C along with less intense peak at 183 degrees C was observed in GC route while, in CP a single glow peak at 364 degrees C was observed. The kinetic parameters were estimated using Chen's glow peak route. Photoluminescence (PL) of Dy2O3 shows peaks at 481, 577,666 and 756 nm which were attributed to Dy3+ transitions of F-4(9/2)-H-6(15/2), H-6(11/2), H-6(11/2) and H-6(9/2), respectively. Color co-ordinate values were located in the white region as a result the product may be useful for the fabrication of WLED'S. (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.

Luminescence studies and EPR investigation of derived Eu doped ZnO

ZnO:Eu (0.1 mol%) nanopowders have been synthesized by auto ignition based low temperature solution combustion method. Powder X-ray diffraction (PXRD) patterns confirm the nanosized particles which exhibit hexagonal wurtzite structure. The crystallite size estimated from Scherrer's formula was found to be in the range 35-39 nm. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) studies reveal particles are agglomerated with quasi-hexagonal morphology. A blue shift of absorption edge with increase in band gap is observed for Eu doped ZnO samples. Upon 254 nm excitation, ZnO:Eu nanopowders show peaks in regions blue (420-484 nm), green (528 nm) and red (600 nm) which corresponds to both Eu2+ and Eu3+ ions. The electron paramagnetic resonance (EPR) spectrum exhibits a broad resonance signal at g= 4.195 which is attributed to Eu2+ ions. Further, EPR and thermo-luminescence (TL) studies reveal presence of native defects in this phosphor. Using TL glow peaks the trap parameters have been evaluated and discussed. (C) 2014 Elsevier B.V. All rights reserved.

From Selective-ID to Full-ID IBS without Random Oracles

Since its induction, the selective-identity (sID) model for identity-based cryptosystems and its relationship with various other notions of security has been extensively studied. As a result, it is a general consensus that the sID model is much weaker than the full-identity (ID) model. In this paper, we study the sID model for the particular case of identity-based signatures (IBS). The main focus is on the problem of constructing an ID-secure IBS given an sID-secure IBS without using random oracles-the so-called standard model-and with reasonable security degradation. We accomplish this by devising a generic construction which uses as black-box: i) a chameleon hash function and ii) a weakly-secure public-key signature. We argue that the resulting IBS is ID-secure but with a tightness gap of O(q(s)), where q(s) is the upper bound on the number of signature queries that the adversary is allowed to make. To the best of our knowledge, this is the first attempt at such a generic construction.

Photoluminescence, thermoluminescence and EPR studies of solvothermally derived Ni2+ doped Y(OH)(3) and Y2O3 multi-particle-chain microrods

Rod like structures of hexagonal Y(OH)(3):Ni2+ and cubic Y2O3:Ni2+ phosphors have been successfully synthesized by solvothermal method. X-ray diffraction studies of as-formed product shows hexagonal phase, whereas the product heat treated at 700 degrees C shows pure cubic phase. Scanning electron micrographs (SEM) of Y(OH)(3):Ni2+ show hexagonal rods while Y2O3:Ni2+ rods were found to consist of many nanoparticles stacked together forming multi-particle-chains. EPR studies suggest that the site symmetry around Ni2+ ions is predominantly octahedral. PL spectra show emission in blue, green and red regions due to the T-3(1)(P-3)->(3)A(2)(F-3), T-1(2)(D-1)->(3)A(2)(F-3) and T-1(2)(D-1)-> T-3(2)(F-3) transitions of Ni2+ ions, respectively. TL studies were carried out for Y(OH)(3):Ni2+ and Y2O3:Ni2+ phosphor upon gamma-dose for 1-6 kGy. A single well resolved glow peaks at 195 and 230 degrees C were recorded for Y(OH)(3):Ni2+ and Y2O3:Ni2+, respectively. The glow peak intensity increases linearly up to 4 kGy and 5 kGy for Y(OH)(3):Ni2+ and Y2O3:Ni2+, respectively. The kinetic parameters such as activation energy (E), frequency factor (s) and order of kinetics (b) were estimated by different methods. The phosphor follows simple glow peak structure, linear response with gamma dose, low fading and simple trap distribution, suggesting that it is quite suitable for radiation dosimetry. (C) 2014 Elsevier B.V. All rights reserved.

Vertex Cover Gets Faster and Harder on Low Degree Graphs

The problem of finding an optimal vertex cover in a graph is a classic NP-complete problem, and is a special case of the hitting set question. On the other hand, the hitting set problem, when asked in the context of induced geometric objects, often turns out to be exactly the vertex cover problem on restricted classes of graphs. In this work we explore a particular instance of such a phenomenon. We consider the problem of hitting all axis-parallel slabs induced by a point set P, and show that it is equivalent to the problem of finding a vertex cover on a graph whose edge set is the union of two Hamiltonian Paths. We show the latter problem to be NP-complete, and also give an algorithm to find a vertex cover of size at most k, on graphs of maximum degree four, whose running time is 1.2637(k) n(O(1)).

Improved tuning of the extended concentric tube resonator for wide-band transmission loss

Transmission loss (TL) of a simple expansion chamber (SEC) consists of periodic domes with sharp troughs. This limits practical application of the SEC in the variable-speed automobile exhaust systems. Three-fourths of the troughs of the SEC can be lifted by appropriate tuning of the extended inlet/outlet lengths. However, such mufflers suffer from high back pressure and generation of aerodynamic noise due to free shear layers at the area discontinuities. Therefore, a perforate bridge is made between the extended inlet and outlet. It is shown that the TL curve of a concentric tube resonator (CTR) can also be lifted in a similar way by proper tuning of the extended unperforated lengths. Differential lengths have to be used to correct the inlet/outlet lengths in order to account for the perforate inertance. The resonance peak frequencies calculated by means of the 1-D analysis are compared with those of the 3-D FEM, and appropriate differential lengths are calculated. It is shown how different geometric characteristics of the muffler and mean flow affect the differential lengths. A general correlation is obtained for the differential lengths by considering seven relevant geometric and environmental parameters in a comprehensive parametric study. The resulting expressions would help in design of extended-tube CTR for wide-band TL. (C) 2014 Institute of Noise Control Engineering.

Synthesis, luminescence properties and EPR investigation of hydrothermally derived uniform ZnO hexagonal rods

One-dimensional (1D) zinc oxide (ZnO) hexagonal rods have been successfully synthesized by surfactant free hydrothermal process at different temperatures. It can be found that the reaction temperature play a crucial role in the formation of ZnO uniform hexagonal rods. The possible formation processes of 1-D ZnO hexagonal rods were investigated. The zinc hydroxide acts as the morphology-formative intermediate for the formation of ZnO nanorods. Upon excitation at 325 nm, the sample prepared at 180 degrees C show several emission bands at 400 nm (similar to 3.10 eV), 420 nm (similar to 2.95 eV), 482 nm (similar to 2.57 eV) and 524 nm (similar to 2.36 eV) corresponding to different kind of defects. TL studies were carried out by pre-irradiating samples with gamma-rays ranging from 1 to 7 kGy at room temperature. A well resolved glow peak at similar to 354 degrees C was recorded which can be ascribed to deep traps. Furthermore, the defects associated with surface states in ZnO nano-structures are characterized by electron paramagnetic resonance. (C) 2014 Elsevier B.V. All rights reserved.

BIOMASS GASIFICATION TO SUBSTITUTE FOSSIL FUEL IN FOOD INDUSTRY

Food industries like biscuit and confectionary use significant amount of fossil fuel for thermal energy. Biscuit manufacturing in India is carried out both by organized and unorganized sector. The ratio of organized to unorganized sector is 60 : 40 (1). The total biscuit manufacturing in the organized sector India in 2008 was about 1.7 million metric tons (1). Accounting for the unorganized sector in India, the total biscuit manufacturing would have been about 2.9 million metric tons/annum. A typical biscuit baking is carried in a long tunnel kiln with varying temperature in different zones. Generally diesel is used to provide the necessary heat energy for the baking purpose, with temperature ranging from 190 C in the drying zone to about 300 C in the baking area and has to maintain in the temperature range of +/- 5 C. Typical oil consumption is about 40 litres per ton of biscuit production. The paper discusses the experience in substituting about 120 lts per hour kiln for manufacturing about 70 tons of biscuit daily. The system configuration consists of a 500 kg/hr gasification system comprising of a reactor, multicyclone, water scrubbers, and two blowers for maintaining the constant gas pressure in the header before the burners. Cold producer gas is piped to the oven located about 200 meters away from the gasifier. Fuel used in the gasification system is coconut shells. All the control system existing on the diesel burner has been suitably adapted for producer gas operation to maintain the total flow, A/F control so as to maintain the temperature. A total of 7 burners are used in different zones. Over 17000 hour of operation has resulted in replacing over 1800 tons of diesel over the last 30 months. The system operates for over 6 days a week with average operational hours of 160. It has been found that on an average 3.5 kg of biomass has replaced one liter of diesel.

Autoinhibitory mechanism and activity-related structural changes in a mycobacterial adenylyl cyclase

An adenylyl cyclase from Mycobacterium avium, Mal 120, is a functional orthologue of a pseudogene Rv1120c from Mycobacterium tuberculosis. We report the crystal structure of Mal 120 in a monomeric form and its truncated construct as a dimer. Mal 120 exists as a monomer in solution and crystallized as a monomer in the absence of substrate or inhibitor. An additional alpha-helix present at the N-terminus of the monomeric structure blocks the active site by interacting with the substrate binding residues and occupying the dimer interface region. However, the enzyme has been found to be active in solution, indicating the movement of the helix away from the interface to facilitate the formation of active dimers in conditions favourable for catalysis. Thus, the N-terminal helix of Ma1120 keeps the enzyme in an autoinhibited state when it is not active. Deletion of this helix enabled us to crystallize the molecule as an active homodimer in the presence of a P-site inhibitor 2',5'-dideoxy-3'-ATP, or pyrophosphate along with metal ions. The substrate specifying lysine residue plays a dual role of interacting with the substrate and stabilizing the dimer. The dimerization loop region harbouring the second substrate specifying residue, an aspartate, shows significant differences in conformation and position between the monomeric and dimeric structures. Thus, this study has not only revealed that significant structural transitions are required for the interconversion of the inactive and the active forms of the enzyme, but also provided precise nature of these transitions. (C) 2015 Elsevier Inc. All rights reserved.

Identification of type and degree of railway ballast fouling using ground coupled GPR antennas

GPR is widely used for ballast fouling identification, however, there are no robust guidelines to find the degree and type of fouling quantitatively. In this study, GPR studies were carried out on model and actual railway tracks using three ground coupled antennas and considering three fouling materials. Three ground coupled antennas viz., 100 MHz, 500 MHz and 800 MHz antennas were used for the initial survey and it was found that the 800 MHz ground coupled antenna is an optimum one to get quality results. Three major fouling materials viz., screened/broken ballast, coal and iron ore were used to construct prototype model sections, which were 1/2 of the actual Indian broad-gauge railway track. A separate model section has been created for each degree and type of fouling and GPR surveys were carried out. GPR study shows that increasing the fouling content results in a decrease in the Electromagnetic Wave (EMW) velocity and an increase in the dielectric constant. EMW velocity of ballast fouled with screened ballast was found to be more than coal fouled ballast and iron ore fouled ballast at any degree of fouling and EMW velocity of iron ore fouled ballast was found to be less than coal and screen ballast fouled ballast. Dielectric constant of iron ore fouled ballast was found to be higher than coal and screen ballast fouled ballast for all degrees of fouling. Average slope of the trend line of screen ballast fouled section is low (25.6 degrees), coal fouled ballast is medium (27.8 degrees) and iron ore fouled ballast is high (47.6 degrees). (C) 2016 Elsevier B.V. All rights reserved.

MIXED NORM ESTIMATES FOR THE RIESZ TRANSFORMS ON SU (2)

In this paper we prove mixed norm estimates for Riesz transforms on the group SU(2). From these results vector valued inequalities for sequences of Riesz transforms associated to Jacobi differential operators of different types are deduced.

Efecto de tres presentaciones de pienso sobre la productividad en conejos de engorde

El presente trabajo experimental se realizó, con el objetivo de estudiar el efecto de presentación del alimento, sobre los rendimientos productivos en conejos de engorde. Se aplica con tres tratamientos. A los animales del grupo control (Tl) se les suministró un pienso comercial en forma de harina. En el segundo tratamiento (T2) se suministró el mismo pienso en forma de amasijo (76% harina y 24% agua) y en el tercer tratamiento (T3) los animales consumieron el mismo pienso comercial pero en forma de gránulos o pellet. Se utilizaron 45 gazapos (de ambos sexos), de 42 días de edad de la raza Neozelandés blanco (NZB), con un peso vivo inicial promedio de 0.877 Kg. y se llevaron a los 77 días de edad con un promedio final de 1.849 Kg. de peso vivo. Para la evaluación estadística se empleó un diseño completamente aleatorio (DCA) con tres tratamientos y cinco repeticiones por tratamiento. Cada unidad experimental (jaulas de 0.40 mt2) estaba constituida por tres gazapos distribuidos aleatoriamente a los que se les registraron diariamente el consumo de alimento y semanalmente el aumento de peso vivo. Los parámetros (ANDEVA) fueron la promedio de alimento cada tratamiento. analizados estadísticamente por medio de ganancia media diaria (Kg/día), el consumo (Kg. MS/día) y el índice de conversión por todas las variables estudiadas se vieron afectadas por la forma de presentación del pienso y se registraron diferencias significativas entre los tratamientos, resultando que la ganancia media diaria (kg./día), fue similar en los tratamientos T1 y T2, pienso en forma de harina y pienso en forma de amasijo; pero si hubo diferencias significativas (P < 0.01) en relación al tratamiento T3, pienso en forma de gránulo (I, 0.02525; II, 0.02406 y III, 0.03395) respectivamente. Nuestros resultados demuestran que el consumo de pienso (kg. MS/día) difiere significativamente (P < 0.01) con un mayor consumo de pienso granulado (I, 0.06333; II, 0.07478 y III, 0.08854) respectivamente. A través del procedimiento de separación de medias (D.M.S.) se encontró que los índices de conversión para los alimentos en forma de harina y gránulo o pellet fueron similares, pero fue mayor el valor presentado por el amasijo (I, 2,51; II, 3.10 y III, 2.60) respectivamente. Durante el ensayo los animales del tratamiento tres (pienso granulado) fueron los primeros en alcanzar el peso comercial (2,072 kg.) a los 35 días del engorde, en tanto en los tratamientos I y II los pesos finales registrados fueron 1,753 y 1.721 kg de peso vivo respectivamente. Luego de analizados los resultados obtenidos se pudo detectar diferencias significativas debido a un mayor consumo y crecimiento en los animales que consumieron pienso granulado.