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

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