Optimization of the reflux ratio for methanol–water stage distillation column

In this paper, the enthalpy-concentration method was applied in order to model a steady-state continuous methanol–water mixture distillation column. This work includes three steps; first, to develop a code in MATLAB v.7.6 to apply to the mathematical model of the column. The second step is to simulate the column using HYSIS v.3.2. While the third is the calculation of the optimized reflux ratio to minimize the operating cost. For a distillation tower such as the methanol–water splitter in this study, there are relatively few degrees of freedom that can be manipulated in order to minimize operating costs; the reflux ratio can influence the steady-state operating point and therefore the daily costs. In this paper, we have discussed the trade-offs between reflux ratios and operating costs. A correlation is derived to define the optimum value of the reflux ratio as an exponential function of a certain economic parameter of energy prices and depreciation costs. We demonstrate that, at low energy prices or high equipment depreciation costs, the optimum reflux factor is high.     

Antibacterial and antibiofilm activity of nanochelating based silver nanoparticles against several nosocomial pathogens

The emergence of multi‐drug resistant (MDR) bacteria and dynamic pattern of infectious diseases demand to develop alternative and more effective therapeutic strategies. Silver nanoparticles (AgNPs) are among the most widely commercialized engineered nanomaterials, because of their unique properties and increasing use for various applications in nanomedicine. This study for the first time aimed to evaluate the antibacterial and antibiofilm activities of newly synthesized nanochelating based AgNPs against several Gram‐positive and ‐negative nosocomial pathogens. Nanochelating technology was used to design and synthesize the AgNPs. The cytotoxicity was tested in human cell line using the MTT assay. AgNPs minimal inhibitory concentration (MIC) was determined by standard broth microdilution. Antibiofilm activity was assayed by a microtiter‐plate screening method. The two synthesized AgNPs including AgNPs (A) with the size of about 20‐25 nm, and AgNPs (B) with 30‐35 nm were tested against Staphylococcus aureus, Staphylococcus epidermidis, Acinetobacter baumannii, and Pseudomonas aeruginosa. AgNPs exhibited higher antibacterial activity against Gram‐positive strains. AgNPs were found to significantly inhibit the biofilm formation of tested strains in concentration 0.01 to 10 mg/mL. AgNPs (A) showed significant effective antibiofilm activity compared to AgNPs (B). In summary, our results showed the promising antibacterial and antibiofilm activity of our new nanochelating based synthesized AgNPs against several nosocomial pathogens.     

A highly diastereoselective five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates

A novel one-pot, five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates is described. A mixture of phenacyl bromide, malononitrile, isocyanide, and two equivalents of a dialkyl acetylenedicarboxylate undergoes a novel 1:1:1:2 addition reaction at ambient temperature in absolute ethanol to produce diastereoselectively the title compounds in good yields.     

Electronic surface states of Cu(1 1 0) surface

Surface states are a unique and important class of quantum states that shave an important effect on the electronic properties of Cu(1 1 0) surface. The Cu(1 1 0) surface has been studied using ultraviolet photoemission spectroscopy (PES), inverse photoemission spectroscopy (IPES), and reflection anisotropy spectroscopy (RAS), and shows a resonance in the RAS spectra at 2.1 eV due to a transition between occupied and unoccupied surface states. The unoccupied surface state involved in the RAS transition at an energy of 1.7 eV at the point of the surface Brillouin zone has been investigated using IPES and the occupied surface state is seen in PES spectra at 0.45 eV below the Fermi level. The energy difference of the surface states, 2.15 eV, is a good match to the transition energy found in the RAS experiments.     

TBHP/R4N+X– promoted hydroaroylation of dialkyl azodicarboxylates with methyl arenes,aldehydes, aryl methanols and arylmethyl chlorides

Efficient TBHP/R₄N⁺X^– promoted hydroaroylations of dialkyl azo-1,2-dicarboxylates with methyl arenes, aldehydes, aryl methanols and arylmethyl chlorides are described. These oxidation/oxygenation and hydroaroylation processes were carried out by tert-butyl hydroperoxide as terminal oxidant/oxygen source, and were catalyzed by tetrabutylammonium bromide and tricaprylmethylammonium chloride as the driving force. During this investigation, all these hydroaroylating sources were found to be highly efficient reagents without the need of any transition-metal.     

The zeta potential of PMMA in contact with electrolytes of various conditions: Theoretical and experimental investigation

Many unit operations required in microfluidics can be realised by electrokinetic phenomena. Electrokinetic phenomena are related to the presence of electrical surface charges of microfluidic substrates in contact with a liquid. As surface charges cannot be directly measured, the zeta potential is considered as the relevant parameter instead. PMMA is an attractive microfluidic substrate since micron‐sized features can be manufactured at low costs. However, the existence of PMMA surface charges is not well understood and the zeta potential data found in the literature show significant disagreement. In this article, we present a thorough investigation on the zeta potential of PMMA. We use computations of the potential distribution in the electrical double layer to predict the influence of various electrolyte parameters. The generated knowledge is compared to extensive experiments where we investigate the influence of ionic strength, pH, temperature and the nature of the electrolyte. Our findings imply that two different mechanisms influence the zeta potential depending on the pH value. We propose pure shielding in the acidic and neutral milieus while adsorption of co‐ions occurs along with shielding in the alkaline milieu.     

An efficient one-pot,multi-component diastereoselective synthesis of functionalized cyclopenta[c]chromenes

A novel one-pot, multi-component diastereoselective synthesis of functionalized cyclopenta[c]chromenes is described. This transformation proceeds via a Michael addition-cyclization reaction sequence between trialkyl phosphites, dialkyl acetylenedicarboxylates and in situ generated 2-(1-(2-oxo-2H-chromen-3-yl)alkylidene)malononitriles from the condensation of 3-acyl-2H-chromen-2-ones and malononitrile.