1,3,4-Oxadiazole N-Mannich Bases: Synthesis,Antimicrobial, and Anti-Proliferative Activities

The reaction of 5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thione 3 with formaldehyde solution and primary aromatic amines or 1-substituted piperazines, in ethanol at room temperature yielded the corresponding N-Mannich bases 3-arylaminomethyl-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 4a–l or 3-[(4-substituted piperazin-1-yl)methyl]-5-(3,4-dimethoxyphenyl)-1,3,4-oxadiazole-2(3H)-thiones 5a–d, respectively. The in vitro inhibitory activity of compounds 4a–l and 5a–d was assessed against pathogenic Gram-positive, Gram-negative bacteria, and the yeast-like pathogenic fungus Candida albicans. The piperazinomethyl derivatives 5c and 5d displayed broad-spectrum antibacterial activities the minimal inhibitory concentration (MIC) 0.5–8 μg/mL) and compounds 4j, 4l, 5a, and 5b showed potent activity against the tested Gram-positive bacteria. In addition, the anti-proliferative activity of the compounds was evaluated against prostate cancer (PC3), human colorectal cancer (HCT-116), human hepatocellular carcinoma (HePG-2), human epithelioid carcinoma (HeLa), and human breast cancer (MCF7) cell lines. The optimum anti-proliferative activity was attained by compounds 4l, 5a, 5c, and 5d.     

New ion exchange membrane derived from sulfochlorated polyether sulfone for electrodialysis desalination of brackish water

The purpose of this work is to study the desalination of brackish water using a new ion exchange membrane, made from sulfochlorated polyethersulfone (Cl‐PES), and crosslinked using aminated polyethersulfone (NH2‐PES) as a crosslinking reagent. This membrane, named ClNH2 membrane, has been obtained by reaction between Cl‐PES with 1.3 SO₂Cl groups per monomer unit and 0.2 equivalent amount of NH2‐PES. ClNH2 membrane has been characterized in terms of contact angle, transport number, intrinsic conductivity, and water uptake (as a function of temperature). Electrodialysis performances of the newly synthetized membranes have been measured using an electrodialysis cell at a laboratory scale and compared to commercial membranes. All the experiments have been performed using synthetic brackish water solutions prepared from sodium chloride salts with different concentrations (varying from 0.5 to 5.0 g/L). The concentration of different water samples obtained has been found to be below the amount recommended by the World Health Organization (WHO) for drinking water.     

Photochemically Produced Superhydrophobic Silane@polystyrene-Coated Polypropylene Fibrous Network for Oil/Water Separation

Cost-effective separation of oil and immiscible organic contaminants from water has become an urgent challenge to protect aquatic and human life from devastating effects. Therefore, it has become imperative to develop super-selective materials for efficiently separating oil from water. In this work, a superhydrophobic surface has been formed that consists of a silane@polystyrene-coated polypropylene fibrous network (silane@PS-PPF) for efficient separation of accidentally spilled oil from water. The superhydrophobic PPFs were designed by a simple, cost-effective two-step process that includes photochemically controlled polymerization of styrene and subsequent dip coating in octadecyltrichlorosilane solution. The hydrophobic surface (CA=129°±4°) of the PS coated PPF after treating with silane was turned into a superhydrophobic body (CA=161°±2°). The achieved silane@PS-PPF fibrous network selectively allowed the fast permeation of the oils and non-polar organic liquids by altogether rejecting water during operation. The separation efficiency for various oils from the contaminated water was 96 to 99%, with a high flux in the range of 7606±312 L m⁻²h⁻¹ to 9870±151 L m⁻²h⁻¹. Apart from being used as a filter, the silane@PS-PPF was also used as an oil absorber and has shown an absorption capacity in the range of 1185 to 1535% for various oils. We anticipate that the developed silane@PS-PPF, due to its facile synthetic route, cost-effectiveness, and high performance, can be effectively used in oily wastewater treatment and clean-up of large oil spills from water.     

Polyacrylic acid/polyaniline composite as efficient adsorbent for uranium extraction from nuclear industrial effluent

Journal of Radioanalytical and Nuclear Chemistry - Polyacrylic acid/polyaniline composite (a three-dimensional cross-linked hydrophilic chelating polymeric sorbent) was improved for promoted...     

The influence of treatment temperature on the acidity of MWCNT oxidized by HNO3 or a mixture of HNO3/H2SO4

The nature of multi-walled carbon nanotubes (MWCNTs) varies with the change in oxidation conditions. In this work, the effect of treatment temperatures on the acidity of MWCNTs was studied. Oxidation was performed by refluxing the MWCNTs in nitric acid or mixtures of sulfuric acid and nitric acid at different temperatures. After oxidative treatment, a quantitative characterization of o-MWCNTs has been performed using acid-base titrations which show that the number of surface acidic functional groups increased by increasing the treatment temperatures. Energy dispersive X-ray (EDX) measurements show that the oxygen content increased with increasing treatment temperatures. Fourier transform infrared absorption spectroscopy (FTIR) was used for qualitative characterization. It has been demonstrated that the acidity is a function of the type of oxidizing agent used and the treatment temperatures. Due to the importance in attachment strategies and functionalization, this study adds to the global discussion of the possibility of controlling the MWCNTs’ surface chemistry which plays a crucial role in determining its reactivity.     

Forthcoming articles

Other Index

Forthcoming articles     

Adiabatic Theorems for Quantum Resonances

We study the adiabatic time evolution of quantum resonances over time scales which are small compared to the lifetime of the resonances. We consider three typical examples of resonances: The first one is that of shape resonances corresponding, for example, to the state of a quantum-mechanical particle in a potential well whose shape changes over time scales small compared to the escape time of the particle from the well. Our approach to studying the adiabatic evolution of shape resonances is based on a precise form of the time-energy uncertainty relation and the usual adiabatic theorem in quantum mechanics. The second example concerns resonances that appear as isolated complex eigenvalues of spectrally deformed Hamiltonians, such as those encountered in the N-body Stark effect. Our approach to study such resonances is based on the Balslev-Combes theory of dilatation-analytic Hamiltonians and an adiabatic theorem for nonnormal generators of time evolution. Our third example concerns resonances arising from eigenvalues embedded in the continuous spectrum when a perturbation is turned on, such as those encountered when a small system is coupled to an infinitely extended, dispersive medium. Our approach to this class of examples is based on an extension of adiabatic theorems without a spectral gap condition. We finally comment on resonance crossings, which can be studied using the last approach.     

In-medium modifications of hadron properties

The in-medium modifications of hadron properties are briefly discussed. We restrict the discussion to the lattice QCD calculations for the hadron masses, screening masses, decay constants and wave functions. We review the progress made so far and describe how to broaden its horizon.     

First principles calculation of field emission from carbon nanotubes with nitrogen and boron doping

We investigate the field emission properties of nitrogenated and boronated carbon nanotubes using time-dependent density functional theory, where the wave function propagation is performed using the Crank–Nicholson algorithm. We extract the current–voltage characteristics of the emitted electrons from nanotubes with different doping configurations. We found that boron doping alone either impedes, or slightly enhances, field emission. Nitrogen generally enhances the emission current, and the current is sensitive to the location of the nitrogen dopant in the nanotube. Doping with both nitrogen and boron will generally enhance emission, and the closer the nitrogen dopant is to the tip, the higher is the emitted current. The emitted charge cloud from nitrogen-doped carbon nanotubes, however, diffuse more than that from pristine ones, our simulations show the emergence of a branching structure from the charge cloud, which suggests that nitrogenated carbon nanotubes are less convenient for use in precision beam applications.