Optimal modification of poly(Vinylidene fluoride) membrane surface by using surfacemodifying macromolecules for application in membrane distillation

The optimal engineering of the surface properties was performed for poly(vinylidene fluoride) (PVDF) membrane with hydrophobic surface-modifying macromolecules (SMMs). For this aim, new hydrophobic SMM additives were synthesized using polyurethane chemistry and characterized for water contact angle, fluorine content and average molecular weight. Both modified PVDF/SMM and neat PVDF membranes were prepared through phase inversion method in a single casting step and characterized by means of scanning electron microscope, energy-dispersive X-ray spectroscopy and contact angle goniometry. The optimum preparation conditions were determined using response surface methodology. The effects of the main casting variables, such as PVDF concentration, SMM concentration and solvent evaporation time, on the surface properties of the synthesized membrane were identified and used to prepare optimal PVDF/SMM membrane. The prepared membranes were tested for permeation flux and salt rejection efficiency by membrane distillation process. The results indicate that the optimally modified membrane yields high permeate flux of around 17.5 kg/m2 h and total salt rejection efficiency of 99.9 % compared with pristine membranes. In particular, the hydrophobicity of the modified membrane significantly increases up to 108° at water contact angle, through presented surface modification procedure

Kinetics investigation of direct natural gas conversion by oxidative coupling of methane

Since 1982 there has been much research on the Oxidativecoupling of methane (OCM) process. The main obstacle for converting methane directly to more valuable products by heterogeneous catalysis is the low selectivity at high conversions; the products are more reactive than methane. The main goal of this work is to study the kinetics of OCM reaction and classifies them. We find that with considering almost all reaction steps of the other models, reaction network of Stanch et al. has the best accuracy in comparison with the other models

First report on the isolation of melittin from Iranian honey bee venom and evaluation of its toxicity on gastric cancer AGS cells

Background: It has been previously reported that melittin, the main ingredient of honey bee venom, has anticancer properties. However, there appears to be no earlier study focusing on the isolation of melittin from Iranian honey bee venom (Apis mellifera meda), and evaluation of its effect on cancerous cells. Methods: We isolated melittin using reversed-phase high performance liquid chromatography, and its potential toxicity on gastric cancer AGS cells was determined with an MTT [3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide] assay. Furthermore, to ascertain whether melittin induces apoptosis or necrosis in these cells, morphological evaluation, DNA fragmentation assay, propidium podide and annexin-V-FITC dual staining, and flow cytometric analysis were also conducted. Results: The results of our study suggested that melittin inhibited the proliferation of AGS cells in a dose and time-dependent trend. All of the above four distinct assays indicated that melittin induces necrosis in AGS cells at concentrations of ≥ 1 μg/mL. Conclusion: The present study indicated that melittin has an anticancer effect on gastric cancer AGS cells and stimulates necrotic cell death in these cells