Assessment of Upstream Human Intervention Coupled with Climate Change Impact for a Transboundary River Flow Regime: Nile River Basin

Water Resources Management - The aim of this article is to determine how human interventions in upstream countries coupled with drought events are affecting the flow regime of downstream countries...     

Boosted hydrogen evolution activity from Sr doped ZnO/CNTs nanocomposite as visible light driven photocatalyst

CNTs were decorated onto Sr doped ZnO nanoparticles to construct an efficient photocatalyst via a facile sol-gel method. The as-fabricated Sr doped ZnO/CNTs with recyclability exhibits Sr and CNTs content dependent hydrogen evolution activit under visible light illumination. The Sr doped ZnO/CNTs photocatalyst shows the highest hydrogen evolution rate of 2732.2 μmolh^?1g^?1, which is 33.7 and 2.83 times higher than pure ZnO and Sr doped ZnO photocatalysts, respectively. The improved hydrogen evolution activity of Sr doped ZnO/CNTs is primarily assigned to high surface area, Sr doping and construction of heterojunction, which can extend the light absorption, decrease the optical band gap and improve the charge separation. Moreover, the underlying photocatalytic mechanism is proposed on the basis of Mott-Schottky study and explains the interfacial charge transfer process from ZnO to CNTs and Sr. This work open new strategies to synthesize CNTs based nanocomposite for hydrogen evolution.     

Synthesis and spectroscopic studies of some new azobenzenesulfonamide

Abstract

Diazotized sulfadiazine derivative (1) was coupled with some nitrogen heterocyclic namely (thiazolone derivatives 2a–c, thiazole derivatives 4a–c and barbituric acid derivatives 6a,b) to give the corresponding azo compounds 3a–c, 5a–c and 7a,b in good yields. The newly synthesized azo benzene sulfonamide dyes were recorded their UV visible spectra in the region 200–600?nm in four different solvents and discussed the effect of solvents, substituent and effect of acid and base on the absorption values of these dyes.     

Development and in vitro characterization of chitosan-coated polymeric nanoparticles for oral delivery and sustained release of the immunosuppressant drug mycophenolate mofetil

Objective: To develop an oral sustained release formulation of mycophenolate mofetil (MMF) for once-daily dosing, using chitosan-coated polylactic acid (PLA) or poly(lactic-co-glycolic) acid (PLGA) nanoparticles. The role of polymer molecular weight (MW) and drug to polymer ratio in encapsulation efficiency (EE) and release from the nanoparticles was explored in vitro.

Methods: Nanoparticles were prepared by a single emulsion solvent evaporation method where MMF was encapsulated with PLGA or PLA at various polymer MW and drug: polymer ratios. Subsequently, chitosan was added to create coated cationic particles, also at several chitosan MW grades and drug: polymer ratios. All the formulations were evaluated for mean diameter and polydispersity, EE as well as in vitro drug release. Differential scanning calorimetry (DSC), surface morphology, and in vitro mucin binding of the nanoparticles were performed for further characterization.

Results: Two lead formulations comprise MMF: high MW, PLA: medium MW chitosan 1:7:7 (w/w/w), and MMF: high MW, PLGA: high MW chitosan 1:7:7 (w/w/w), which had high EE (94.34% and 75.44%, respectively) and sustained drug release over 12?h with a minimal burst phase. DSC experiments revealed an amorphous form of MMF in the nanoparticle formulations. The surface morphology of the MMF NP showed spherical nanoparticles with minimal visible porosity. The potential for mucoadhesiveness was assessed by changes in zeta potential after incubation of the nanoparticles in mucin.

Conclusion: Two chitosan-coated nanoparticles formulations of MMF had high EE and a desirable sustained drug release profile in the effort to design a once-daily dosage form for MMF.