Cyano‐Functionalized Triarylamines on Coinage Metal Surfaces: Interplay of Intermolecular and Molecule–Substrate Interactions

The self‐assembly of cyano‐functionalized triarylamine derivatives on Cu(111), Ag(111) and Au(111) was studied by means of scanning tunnelling microscopy, low‐energy electron diffraction, X‐ray photoelectron spectroscopy and density functional theory calculations. Different bonding motifs, such as antiparallel dipolar coupling, hydrogen bonding and metal coordination, were observed. Whereas on Ag(111) only one hexagonally close‐packed pattern stabilized by hydrogen bonding is observed, on Au(111) two different partially porous phases are present at submonolayer coverage, stabilized by dipolar coupling, hydrogen bonding and metal coordination. In contrast to the self‐assembly on Ag(111) and Au(111), for which large islands are formed, on Cu(111), only small patches of hexagonally close‐packed networks stabilized by metal coordination and areas of disordered molecules are found. The significant variety in the molecular self‐assembly of the cyano‐functionalized triarylamine derivatives on these coinage metal surfaces is explained by differences in molecular mobility and the subtle interplay between intermolecular and molecule–substrate interactions.     

Synthesis of dual‐functional poly(6‐azidohexylmethacrylate) brushes by a RAFT agent carrying carboxylic acid end groups

Novel types of dual‐functional surface‐attached polymer brushes were developed by interface‐mediated reversible addition‐fragmentation chain transfer (RAFT) polymerization of 6‐azidohexylmethacrylate using the surface‐immobilized RAFT agent and the free initiator. The interface‐mediated RAFT polymerization produced silicon substrate coated with dual‐functional (azido groups from monomer and carboxylic acid groups from RAFT agent) poly(6‐azidohexylmethacrylate) [poly (AHMA)] with a grafting density as high as 0.59 chains/nm². Dual‐functional polymer brushes can represent an attractive chemical platform to deliberately introduce other molecular units at specific sites. The azido groups of the poly(AHMA) brushes can be modified with alkyl groups via click reaction, known for their DNA hybridization, while the carboxylic acid end groups can be reacted with amine groups via amide reaction, known for their antifouling properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1696–1706     

Metabolic control analysis of trio enzymes system

For practical purposes the calculation of rate constants is not particularly valuable, since their physical significance is not clear. Of greater practical use are metabolic control coefficients and elasticities. Given the definition of the flux control coefficients , concentration control coefficient and elasticity . We can calculate symbolic formulae for these using computer algebra techniques. These are then functions of V_max, K_m, K_i enzyme and concentrations. Having derived estimates of V_max, K_m, K_i using the fitting method we can then calculate values of the control coefficients and elasticities. Furthermore we can calculate the metabolic control parameters using symbolic values for the conventional kinetic parameters. Using these we have verified the summation and connectivity theorems. This is a useful cross check on the reliability of the calculations.     

Application of ultrasonic-assisted cloud point extraction/flame atomic absorption spectrometry (UA-CPE/FAAS) for preconcentration and determination of low levels of antimony in some beverage samples

Due to be able to migrate or leach from food packaging materials into the foods and/or beverages, development of a new, sensitive and selective analytical methods for low levels of antimony as a food contaminant is of great importance in terms of food safety. In this context, an ultrasonic-assisted cloud point extraction method was developed for the preconcentration and determination of antimony as Sb(III) using 4-(2-thiazolylazo)resorcinol (TAR) and 2-(2-thiazolylazo)-p-cresol (TAC) as chelating agents and sodium dodecyl sulfate as signal enhancing agent at pH 6.0 and mediated by nonionic surfactant, t-octylphenoxypolyethoxyethanol by flame atomic absorption spectrometry. Using the optimized conditions, the calibration curves obtained from Sb(III) with TAR and TAC were linear in the concentration ranges of 0.5–180 and 1–180 μg L^?1 with detection limits of 0.13 and 0.28 μg L^?1, respectively. The precision (as relative standard deviations, RSDs) was lower than 3.9 % (25 and 100 μg L^?1, n: 6). The method accuracy was validated by the analysis of two standard reference materials. The results obtained were statistically in a good agreement with the certified values at 95 % confidence limit. The method has successfully been applied to the determination of Sb(III) and total Sb in selected beverages, milk and fruit-flavored milk products before and after pre-reduction of Sb(V) to Sb(III) with a mixture of KI/ascorbic acid in acidic media. The Sb(V) contents of samples were quantitatively calculated from analytical difference between total Sb and Sb(III) levels.     

Electrochemical Analysis of Liposome-encapsulated Colistimethate Sodium

In this study, the neutral and cationic liposomal formulations of Colistimethate sodium (CMS), an antibiotic for multi-drug resistant gram-negative bacteria, were prepared and electrochemical quantification of CMS from these liposomes were achieved. This is the first study of the electrochemical detection of CMS released from liposomes. First, the electrochemical properties of CMS were analysed, then the encapsulation efficiency, and the release kinetic of CMS from liposomes were determined with Differential Pulse Voltammetry (DPV) measurements. In addition, Cyclic Voltammetry were applied to determine oxidation signal of CMS. A higher encapsulation efficiency was found in the cationic liposome compared to the neutral liposome. Moreover, CMS was controlled released from liposomes with zero-order drug release kinetics.     

Two-phase flow instabilities in a horizontal single boiling channel

A study of the stability of an electrically heated single channel, forced convection horizontal system was conducted by using Freon-11 as the test fluid. Two major modes of oscillations, namely, density-wave type (high frequency) and pressure-drop type (low frequency) oscillations have been observed. The steady-state operating characteristics and stable and unstable regions are determined as a function of heat flux, exit orifice diameter and mass flow rate. Different modes of oscillations and their characteristics have been investigated. The effect of the exit restriction on the system stability has also been studied.A mathematical model has been developed to predict the transient behavior of boiling two-phase systems. The model is based on homogenous flow assumption and thermodynamic equilibrium between the liquid and vapor phases. The transient characteristics of boiling two-phase flow horizontal system are obtained for various heat inputs, flow rates and exit orifice diameters by perturbing the governing equations around a steady state. Theoretical and experimental results have been compared.     

A range-free method to determine antoine vapor-pressure heat transfer-related equation coefficients using the Boubaker polynomial expansion scheme

In this study, a range-free method is proposed in order to determine the Antoine constants for a given material (salicylic acid). The advantage of this method is mainly yielding analytical expressions which fit different temperature ranges.     

Structure and electrochemical behaviour of Bis[N‐(4‐methylphenyl)salicylaldimine]copper(II) N,N′dimethylformamide solvate

The molecular model of mononuclear complex formed, through a reaction between N‐(4‐methylphenyl)salicylaldimine and Cu^II ion was determined using x‐ray diffraction method. The Cu^II coordination was found to have a distorted square‐planar structure and a cis coordination geometry was observed within the surrounding of the copper. The electro chemical behaviour of the mononuclear copper complex was studied with cyclic voltammetry.