Effect of Electrolyte Concentration on the Stern Layer Thickness at a Charged Interface

The chemistry and physics of charged interfaces is regulated by the structure of the electrical double layer (EDL). Herein we quantify the average thickness of the Stern layer at the silica (SiO₂) nanoparticle/aqueous electrolyte interface as a function of NaCl concentration following direct measurement of the nanoparticles’ surface potential by X‐ray photoelectron spectroscopy (XPS). We find the Stern layer compresses (becomes thinner) as the electrolyte concentration is increased. This finding provides a simple and intuitive picture of the EDL that explains the concurrent increase in surface charge density, but decrease in surface and zeta potentials, as the electrolyte concentration is increased.     

Cycloaddition of CS2 to N‐benzylaziridine to synthesize N‐benzylthiazolidine‐2‐thione: a novel reaction route proposed by DFT Study

N‐Benzylthiazolidine‐2‐thione is the key intermediate for the synthesis of pharmaceutically important compounds. A novel route for the synthesis of N‐benzylthiazolidine‐2‐thione through cycloaddition of CS₂ with N‐benzylaziridine in the presence of 1,3‐di‐tert‐butylimidazolium‐2‐dithocarboxylate ( catalyst I ) has been proposed by reliable computations performed within the formalism of density functional theory. The mechanism of the proposed reaction is similar to the cycloaddition of tertiary aziridines and carbon dioxide using a recyclable catalyst that is reported to provide access to 3‐substituted 2‐oxazolidones with excellent yield. Because the rate determining step needs to surmount a high energy barrier, the reaction route has been deciphered in high boiling solvent (1, 2‐ethanediol). The highlight of the mechanistic route detailed here is that the proposed pathway is a cyclic process that is exothermic in nature with the regeneration of the catalyst and involves simple reagents. Copyright © 2016 John Wiley & Sons, Ltd.     

Vapor-phase processable novel nonplanar donor-acceptor quateraryls for blue OLEDs(#)

A novel series of thermally stable blue light emitting quateraryls with a piperidine donor and a nitrile acceptor was prepared from a ketene- S, S-acetal under mild conditions without using an organometal catalyst. The performance of a blue quateraryl 6e was investigated by fabricating a multilayer OLED with a configuration of ITO/PEDOT:PSS (40 nm)/quateraryl (60 nm)/BCP (6 nm)/Alq(3) (20 nm)/LiF (0.5 nm)/Al (200 nm), which exhibited blue emission with a low turn on voltage of 4 V at a brightness of 0.22 cd/m(2).     

Emerging trends in miniaturized and microfluidic electrochemical sensing platforms

Electrochemical sensing has established a strong presence in diverse areas. The conventional electrochemical sensing approach consumes large sample volumes and reagents and requires bulky potentiostat, macro-electrodes, and other equipment. The synergistic integration of electrochemical sensing systems with miniaturized or microfluidic electrochemical devices and microelectrodes in a single platform provides rapid analysis with a disposable, reusable, and cost-effective platform for multiplexed point-of-care detections. Such microdevices have created scope for using several materials as electrodes and sensing platforms by using appropriate fabrication techniques. One of the most recent advancements in miniaturized devices includes the integration of automation and Internet of Things to realize fully automated and robust electrochemical microdevices. The review summarizes the emerging trends in fabrication methods of miniaturized and microfluidic devices, their multiple applications in real-time, integration of Internet of Things, automation, identifying research gaps with strategies for bridging these gaps, future outlook, and recent approaches to intelligent electrochemical sensing.     

Urea derivatives of piperazine doped with pyrazole-4-carboxylic acids: Synthesis and antimicrobial evaluation

A series of novel N-cycloalkyl/aryl-4-(1,3-diphenyl-1H-pyrazole-4-carbonyl)piperazine-1-carboxamides 9a-g has been synthesized for biological interest by simple base catalyzed reaction of various N-cycloalkyl/aryl isocyanates with (1,3-diphenyl-1H-pyrazol-4-yl)(piperazin-1-yl)methanone hydrochloride 8 . The compound 8 was synthesized in excellent yield by the reaction of 1,3-diphenyl-1H-pyrazole-4-carbonyl chloride with boc-piperazine followed by deprotection of boc group with dioxane-HCl. All the novel intermediates and urea derivatives have been screened for antimicrobial activity. The compound 9a was found an excellent compound to be active against all Gram (−ve) and Gram (+ve) bacterial strains E. coli, Y. enterocolitica, B. cereus, and S. aureus. It also showed comparable antifungal activity against C. albicans with MIC 78.1 μg/ml as compared to reference standard miconazole.     

Significance of Satellite DNA Revealed by Conservation of a Widespread Repeat DNA Sequence Among Angiosperms

The analysis of plant genome structure and evolution requires comprehensive characterization of repetitive sequences that make up the majority of plant nuclear DNA. In the present study, we analyzed the nature of pCtKpnI-I and pCtKpnI-II tandem repeated sequences, reported earlier in Carthamus tinctorius. Interestingly, homolog of pCtKpnI-I repeat sequence was also found to be present in widely divergent families of angiosperms. pCtKpnI-I showed high sequence similarity but low copy number among various taxa of different families of angiosperms analyzed. In comparison, pCtKpnI-II was specific to the genus Carthamus and was not present in any other taxa analyzed. The molecular structure of pCtKpnI-I was analyzed in various unrelated taxa of angiosperms to decipher the evolutionary conserved nature of the sequence and its possible functional role.     

Experimentally Evaluating Equilibrium Stress in Uniaxial Tests

Many models use the equilibrium stress, also sometimes known as the back stress, in characterizing the response of both polymeric and non-polymeric materials. We study the characteristics of the equilibrium and show that the tangent modulus and local Poisson’s ratio at equilibrium both are rate independent for common modeling assumptions. This fact is used to propose a method based on uniaxial tension or compression to measure the equilibrium stress, and the associated point’s tangent modulus and local Poisson’s ratio. The method is based on cyclic loading and identification of similar states with vastly different loading rates. The method is used to characterize the equilibrium stress in glassy polycarbonate, and the results are studied in regard to the possible error for such a measurement. The method is faster than most other proposed methods for calculating the equilibrium stress, and provides additional measurements of parameters at equilibrium that are normally not obtained.     

Grafting Vinyl Monomers onto Nylon 6 Fiber. IV. Graft Copolymerization of Ethyl Methacrylate onto Nylon 6 Fiber by Photoirradiation

Grafting of nylon 6 fiber was carried out using ethyl methacrylate (EMA) as the monomer in various water-alcohol systems (i.e., water-methanol, water-ethanol and water-n-propanol; water-alcohol ratio 1:1) at 70°C using a carbon arc lamp as the source of photochemical initiation. Percent graft add-on (% GAO) increases continuously and linearly with an increase in monomer concentration irrespective of the media used. The % GAO, however, decreases with an increase in the alkyl chain length of the alcohol used in the following order: water-methanol > water-ethanol > water-n-propanol. With an increase in the time period of grafting, % GAO and total polymer yield (% TPY) increase continuously in all three media whereas the grafting efficiency (GE) first increases and then falls after reaching a maximum level. Although a similar trend is maintained in the three systems, there is a decrease in overall % TPY and % GAO from the water-methanol system to the water-n-propanol system through the water-ethanol system.     

Risk-Sensitive Portfolio Optimization Problems with Fixed Income Securities

We discuss a class of risk-sensitive portfolio optimization problems. We consider the portfolio optimization model investigated by Nagai (SIAM J. Control Optim. 41:1779–1800, 2003). The model by its nature can include fixed income securities as well in the portfolio. Under fairly general conditions, we prove the existence of an optimal portfolio in both finite-horizon and infinite-horizon problems.