Neutron Diffraction Studies on La2-xDyxCa2xBa2Cu4+2xOz Superconductors

Structural studies on Dy-substituted La-2125 type superconductors have been carried out by neutron diffraction experiments at room temperature using a monochromatic neutron beam of wavelength lambda = 1.249 Angstroms. A series of samples with La2-xDyxCa2xBa2Cu4+2xOz stoichiometric composition, for x = 0.1 - 0.5, have been studied for their structural properties. A tetragonal Y-123 unit cell was taken as the starting model for the Rietveld analysis. All the samples fit into the starting model, exhibiting no structural transition taking place with increasing dopant concentration. The results of Rietveld analysis and structural properties are discussed in detail

Novel synthesis and ring closure reactions of 3-hydrazino-1,2,4-triazolo[3,4-<i style="">b</i>]benzothiazole

625-6273-Hydrazino-1,2,4-triazolo[3,4-b]benzothiazole 2 is prepared by heating 3-chloro-1,2,4-triazino[3,4-b]benzothiazole-4(H)-one 1 with hydrazine hydrate. This transformation takes place with decarbonylation resulting in ring contraction and simultaneous replacement of chlorine by hydrazino group. Compound 2 on heating independently with urea and carbon disulphide in the presence of alkali gave 3'-hydroxy 3 and 3'-mercapto-1,2,4-triazolo[4',5':1,5]-1,2,4-triazolo[3,4-b] benzothiazole 4 respect­ively. Treatment of cold solution of 2 in phosphoric acid with sodium nitrite solution affords 1,2,3,4-tetra­zolo[1',5':1,5]-1,2, 4-triazolo[3,4-b]benzothiazole 5. 3'-Aryl-1, 2, 4-triazolo[4',5':1,5]-1, 2, 4-triazolo[3,4-b] benzothiazoles 7a-e have been also prepared by the reaction of 2 with aryl aldehydes in the presence of acetic acid

Novel synthesis and antibacterial activity of 15-iminobenzothiazolo[2,3-<i style="">b</i>] pyrimido[5,6-<i style="">e</i>]pyrimido[2,3-<i style="">b</i>]benzothiazol-14(<i>H</i>)-one and its 3,10-disubstituted derivatives

834-837Novel heterocyclic compound 15-iminobenzothiazolo[2,3-b]pyrimido[5,6-e]pyrimido[2,3-b] benzothiazol-14(H)-one and its 3,10-disubstituted derivatives 3a-l have been synthesized by the reaction of 2-thiomethyl-3-cyano-8-H/substituted-pyrimido[2,1-b]benzothiazol-4(H)-one 1a-c with 2-amino-6-H/ substituted benzothiazoles 2a-d

Transport studies on La0.8-xPr0.2SrxMnO3 manganite films

In this communication, we report the results of the studies on structural, microstructural, transport and magnetotransport behavior of L0.8-xPr0.2SrxMnO3 (LPSMO) (x=0.1, 0.2 and 0.3) manganite films grown on (100) single crystalline SrTiO3 (STO) substrate using low cost chemical solution deposition (CSD) method. Films with similar compositions were also grown using sophisticated pulsed laser deposition (PLD) technique and results of structural and transport studies obtained for CSD grown films were compared with PLD grown films. Structural studies show that all the CSD and PLD grown films possess single crystalline nature with compressive and tensile strain, respectively. Surface morphology, studied using atomic force microscope (AFM), reveals the island like grain morphology in CSD grown films while PLD grown films possess smooth film surfaces. Carrier density dependent transport properties of the films have been discussed in the context of zener double exchange (ZDE) mechanism. Lower resistivity and higher transition temperature (T-p) observed in CSD grown films as compared to PLD grown films have been discussed in the light of structural strain and surface morphology of the films. Various models and mechanisms have been employed to understand the charge transport in CSD and PLD grown films. Also, observation of low temperature resistivity minima behavior in all the CSD and PLD grown LPSMO films has been explained in the context of electron-electron scattering mechanism. (C) 2015 Elsevier B.V. All rights reserved

Effects of a dynamic membrane formed with polyethylene glycol on the ultrafiltration of natural organic matter

The formation of a dynamic membrane (DM) was investigated using polyethylene glycol (PEG) (molecular weight of 35000 g/mol, concentration of 1 g/L). Two natural organic matters (NOM), Dongbok Lake NOM (DLNOM) and Suwannee River NOM (SRNOM) were used in the ultrafiltration experiments along with PEG. To evaluate the effects of the DM with PEG on ultrafiltration, various transport experiments were conducted, and the analyses of the NOM in the membrane feed and permeate were performed using high performance size exclusion chromatography, and the effective pore size distribution (effective PSD) and effective molecular weight cut off (effective MWCO) were determined. The advantages of DM formed with PEG can be summarized as follows: (1) PEG interferes with NOM transmission through the ultrafiltration membrane pores by increasing the retention coefficient of NOM in UF membranes, and (2) low removal of NOM by the DM is affected by external factors, such as pressure increases during UF membrane filtration, which decreases the effective PSD and effective MWCO of UF membranes. However, a disadvantage of the DM with PEG was severe flux decline; thus, one must be mindful of both the positive and negative influences of the DM when optimizing the UF performance of the membraneclose0

Effects of crossflow velocity and transmembrane pressure on microfiltration of oil-in-water emulsions

This study addresses the issue of oil removal from water using hydrophilic porous membranes. The effective separation of oil-in-water dispersions involves high flux of water through the membrane and, at the same time, high rejection rate of the oil phase. The effects of transmembrane pressure and crossflow velocity on rejection of oil droplets and thin oil films by pores of different cross-section are investigated numerically by solving the Navier-Stokes equation. We found that in the absence of crossflow, the critical transmembrane pressure, which is required for the oil droplet entry into a circular pore of a given surface hydrophilicity, agrees well with analytical predictions based on the Young-Laplace equation. With increasing crossflow velocity, the shape of the oil droplet is strongly deformed near the pore entrance and the critical pressure of permeation increases. We determined numerically the phase diagram for the droplet rejection, permeation, and breakup depending of the transmembrane pressure and shear rate. Finally, an analytical expression for the critical pressure in terms of geometric parameters of the pore cross-section is validated via numerical simulations for a continuous oil film on elliptical and rectangular pores.Comment: 31 pages, 10 figure