Effect of phenol derivatives on molecular dimensions of poly(N-vinyl-2-pyrrolidone) in aqueous solution

The unperturbed dimensions and thermodynamic parameters of poly(N-vinyl-2-pyrrolidone) (PVP) were studied in aqueous solutions in the presence of certain phenolic cosolutes (phenol, catechol, hydroquinone, resorcinol, and phloroglucinol). The intrinsic viscosities at 25degreesC and the theta temperature, linear and thermodynamic expansions, and root mean square end to end distances were evaluated for the system that was employed. The sequence was obtained due to the effectiveness of the cosolutes in the order of phloroglucinol > resorcinol > hydroquinone > catechol > phenol. The effects of these cosolutes on the main thermodynamic parameters were reported to be due to the number and position of hydroxyl groups present. The thermodynamic interaction parameter was also evaluated and the enthalpic and entropic contributions were verified. The condition required for the theta temperature to correspond to a Flory interaction parameter of 0.5 was well provided, yielding a theta temperature of almost 0.5 for the system under study. (C) 2002 John Wiley Sons, Inc

Removal of some textile dyes from aqueous solutions by poly(N-vinyl-2-pyrrolidone) and poly(N-vinyl-2-pyrrolidone)/K2S2O8 hydrogels

Poly(N-vinyl-2-pyrrolidone)/water and poly(N-vinyl-2-pyrrolidone)/K2S2O8/water systems are hydrogels prepared by irradiation with gamma-rays at ambient temperature. Both hydrogel systems were employed for diffusion and swelling experiments in various textile dyes aqueous solutions (textile dyes such as Cibacron Blue (CB) F3GA, Methyl Orange (MO), Congo Red (CR)). For these hydrogel systems, swelling studies indicated that swelling percentages increased in the following order: MO > CB F3GA > CR at fixed dose 96 kGy. Because of this reason MO dye solution has been chosen and all swelling properties are investigated for 26, 64, 96 and 124 kGy. The swelling capabilities of PVP and PVP/K2S2O8 hydrogels in MO dye solution vary in the range of 400-1500%. The diffusion of dye solutions PVP and PVP/K2S2O8 hydrogels was assumed to be Fickian character. The swelling behavior of PVP and PVP/K2S2O8 hydrogels exhibits second-order kinetic in all dye solutions. Diffusion coefficient, initial swelling rate, swelling rate constant, maximum swelling and equilibrium water/dye content were found for all gel systems in dye solutions. (C) 2003 Elsevier Ltd. All rights reserved

Swelling behavior of poly(N-vinyl-2-pyrrolidone) and poly(N-vinyl-2-pyrrolidone)/K2S2O8 hydrogels in alpha-lactose solutions

Hydrogels with varying cross-linking densities, and average molecular weights between two consecutive cross-links, were prepared from the binary poly(N-vinyl-2-pyrrohdone)/water and ternary poly(N-vinyl-2-pyrrolidone)/water/K2S2O8 systems by irradiation withy gamma-rays at ambient temperature. Both hydrogel systems were employed for diffusion and swelling experiments in 0.00278 M alpha-lactose solution at room temperature. Diffusion of alpha-lactose solution into hydrogels was found to be of the Fickian type. The percent swelling, equilibrium swelling, initial rate of swelling, swelling rate of constant, equilibrium water/alpha-lactose content, and diffusion constant values were determined for PVP and PVP/K2S2O8 hydrogel systems in 0.00278 M alpha-lactose solution. (C) 2003 Wiley Periodicals, Inc

Essential oil composition of roots, aerial parts and fruits of Ferulago pauciradiata Boiss. & Heldr

67th International Congress and Annual Meeting of the Society-for-Medicinal-Plant-and-Natural-Product-Research (GA) -- SEP 01-05, 2019 -- Innsbruck, AUSTRIAWOS: 000503772900251…Soc Med Plant & Nat Prod Res, French Soc Pharmacognos

Sea-level changes during the late Pleistocene-Holocene on the southern shelves of the Black Sea

Seismic profiles and gravity cores collected from shelf areas off the Sakarya Delta and Thrace Peninsula, together with available previous studies, were evaluated in this research. A masjhoerl f-crossing erosional unconformity was observed, lying as deep as-120 m along the southern margin of the Black Sea. This erosional surface indicates a lowstand of the Black Sea's lake. The present shelf edge was therefore a former paleoshore environment of the preexisting Neoeuxinian basin. Unit 1 overlies the erosional surface and includes a widespread, thin mud drape, the Sakarya Delta, and various irregular depositional features off the Thrace Peninsula. Unit 2 was deposited at the shelf edge and consists of a lowstand sedimentary wedge (off the Sakarya Delta) and seaward prograding clinoforms (off the Thrace Peninsula), all indicative of deposition during the lowstand. Radiometric dates from sedimentary cores collected above the erosional unconformity vary between 11.8 and 8.6 ky BP. Further studies will be required to obtain a better understanding of the timing and intensity of these sea-level changes. © 2007 Springer