Inhibition of cold rolled steel corrosion in sulphuric acid solution by 2-mercapto-1-methylimidazole: Time and temperature effects treatments

2-Mercapto-1-methylimidazole (MMI) has been evaluated as a corrosion inhibitor for cold rolled steel in aerated 2 M H₂SO₄ by gravimetric method. The effect of MMI on the corrosion rate was determined at various immersions time and concentrations. The effect of the temperature on the corrosion behaviour with addition of different concentrations of MMI was studied in the temperature range 30–60 °C. The MMI acts as an effective corrosion inhibitor for cold rolled in sulphuric acid medium. The inhibition process is attributed to the formation of an adsorbed film of MMI on the metal surface which protects the metal against corrosion. The protection efficiency increased with increase in inhibitor concentration at various immersions time and decreased with increase in temperature. Adsorption of MMI on the cold rolled steel surface is found to obey the Langmuir adsorption isotherm. Some thermodynamic functions of dissolution and adsorption processes were also determined.     

Hierarchically porous nanostructures through phosphonate-metal alkoxide condensation and growth using functionalized dendrimeric building blocks

Controlled titanium alkoxide mineralization in the presence of phosphonated, dendrimeric nano-building blocks provides a new family of hierarchically porous dendrimer-bridged titanium dioxide materials.     

A new design of pulsed laser diode driver system for multistate quantum key distribution

In this paper, we describe a new design of laser diode driver system based on MOSFET current mirror and digital signal controller (DSC). The system is designed to emit stream pairs of photons from three semiconductor laser diodes. The DSC is able to switch between the three laser diodes at constant rate. The duty cycle is maintained at 1% in order to reduce its thermal effect and thus prolong the laser diodes’ life cycles. The MOSFET current mirror circuits are capable of delivering constant modulation current with peak current up to 58 mA to each laser diode. This laser driver system will allow the generating biphotons automatically with qubit rate around 8-13% for μ less than or equal to 1, thus making it practical for six-states quantum key distribution implementation.     

Dramatic substituent effects on the mechanisms of nucleophilic attack on Se—S bridges

The reactions of XSeSX, XSeSY, and YSeSX (X, Y = CH₃, NH₂, OH, F) with F^? and CN^? nucleophiles have been investigated by means of B3PW91/6‐311+G(2df,p) and G4 calculations. In systems where the two substituents are not identical (XSeSY), the more stable of the two possible isomers corresponds to those in which the most electronegative substituent is attached to Se. Nucleophilic attack takes place at Se, independent of the nature of the nucleophile, with the only exception being XSeSF (X = CH₃, NH₂, OH), in which case the attack occurs at S. In agreement with recent results for disulfide and diselenide linkages, the mechanisms leading to Se—S bond cleavage are not always the more favorable ones because for highly electronegative substituents the most favorable process is fission of the chalcogen‐substituent bond. These dissimilarities in the observed reactivity pattern as a function of the electronegativity of the substituents are due to the fact that the σ‐type Se—S antibonding orbital, which for low‐electronegative substituents is the lowest unnoccupied molecular orbital (LUMO), becomes strongly destabilized when the electronegativity of the substituent increases, and is replaced by an antibonding π‐type Se‐X (or S‐X) orbital. In contrast, however, with what has been found for disulfide and diselenide derivatives, the observed reactivity does not change with the nature of the nucleophile. The activation strain model provides interesting insight into these processes, showing that in most cases the activation barriers are the consequence of subtle differences in the strain or in the interaction energies. © 2013 Wiley Periodicals, Inc.     

Reactivity and Characterization of the Radical Copolymerization of Itaconic Acid with Some Conventional Monomers

Abstract

Radical copolymerizations of itaconic acid (IA) with acrylamide (Am), N-vinyl pyrrolidone (NVP), ethyl methacrylate (EMA), and methyl methacrylate (MMA) were carried out in dioxane in the presence of azobisisobutyronitrile as the initiator at 65°C. The monomer reactivity ratios (r ₁, r ₂), Q, and e for IA with the four monomers were determined. The reactivity ratios show a tendency toward alternation, while the Q and e of IA indicate that it is an electron-accepting monomer. The polymers obtained were characterized by FT-IR, x-ray diffraction, intrinsic viscosity, and thermal stability measurements.     

Voltammetric detection of uridin diphosphate glucuronosyl transferase 1A9 (UGT1A9) gene corresponding oligonucleotide covering promoter region from −268 to −280 including (A/T) polymorphism at position −275 and optimization of the detection factors

In this study, we developed a new peptide nucleic acid (PNA) biosensor for detection of a single nucleotide polymorphism (SNP) in the UGT1A9 gene promoter region via electrochemical assay. The sensor relies on the immobilization of a 13-mer single stranded PNA probe related to the UGT1A9 gene on the Au electrode (AuE). The hybridization between the probe and its complementary sequence (DcUG275) as the target was studied by differential pulse voltammetry (DPV) of methylene blue (MB) signal. In this approach the extent of hybridization is evaluated on the basis of the difference between DPV signals of MB accumulated on the probe-AuE and MB accumulated on the probe-target-AuE. Some experimental variables affecting the performance of the biosensor including oxygen interference during the assay, probe immobilization time, probe concentration and MB accumulation time were investigated. The PNA probe modified AuE in its optimum condition was shown to be an effective sensor for the detection of hybridization and point mutations. The obtained detection limit of the utilized biosensor has been calculated as 22 nm.     

The influence of porosity of ammonium perchlorate (AP) on the thermomechanical and thermal properties of the AP/polyvinylchloride (PVC) composite propellants

The influence of porous ammonium perchlorate (P_OAP) on the thermomechanical and combustion behavior of solid rocket propellants based on polyvinylchloride binder has been investigated. Differential scanning calorimetry, differential thermogravimetry, dynamic mechanical thermal analysis, and scanning electronic microscopy measurements were used for thermomechanical and thermal decomposition properties assessment. The results obtained indicate that lower glass transitions of the propellants and catalytic effect of combustion are obtained with P_OAP.     

Electrospray tandem mass spectrometric analysis of novel synthetic quinoxalinone derivatives

Electrospray ionization tandem mass spectrometry (ESI-MS/MS) using a hybrid QqToF-MS/MS instrument has aided the structural characterization and differentiation of a novel series of medicinal synthetic 1-N-glycoside-quinoxalinone derivatives. These derivatives 7 and 8 are formed by an amino bond between the cyclic N-1 of the quinoxaline moiety and the C-6 position of a fully protected methyl or allyl alpha-D-mannofuranoside 3 and 4, and subsequent deprotection of the mannopyranoside moiety. In general the novel synthetic quinoxaline derivatives afforded the protonated molecules in ESI. The breakdown routes of the protonated molecules were rationalized by conducting low-energy CID-MS/MS analyses. In addition, re-confirmation of the various established fragmentation routes was achieved by conducting a series of ESI-CID-QqTof-MS/MS product ion scans on various selected precursor ions, which were initiated by CID in the atmospheric pressure/vacuum interface using a higher declustering potential. ESI-QqToF-MS/MS analysis has proven to be a specific and very sensitive method for the structural identification in the gas phase of these novel glycoquinoxalinamine derivatives.     

Spectrofluorimetric determination of drugs containing active methylene group using N1-methyl nicotinamide chloride as a fluorigenic agent

A spectrofluorimetric method was described for the determination of drugs containing active methylene groups adjacent to carbonyl groups. The method was applied successfully to the determination of three life saving cardiovascular drugs, with narrow therapeutic indices: pentoxifylline (I), propafenone hydrochloride (II) and acebutolol hydrochloride (III), in laboratory-prepared mixtures, in commercial tablets and in plasma samples. The method involved the reaction of each of the tested drugs with N1-methyl nicotinamide chloride (NMNCl) in the presence of alkali, followed by addition of formic acid, where highly fluorescent reaction products were produced. The produced fluorescence were measured quantitatively at 472 nm (lambdaex 352 nm), 409 nm (lambdaex 310 nm) and 451 nm (lambdaex 266 nm) for (I), (II), and (III) respectively. The method was linear over concentration ranges of 10-1000 microg/ml , 0.2-12 microg/ml and 0.08-10 microg/ml in standard solutions for (I), (II), and (III) respectively. In spiked human plasma samples, calibration graphs were linear over concentration ranges of 20-1000 microg/ml, 0.2-15 microg/ml and 0.08-10 microg/ml for (I), (II), and (III) respectively. The method showed good accuracy, specificity and precision in both laboratory-prepared mixtures and spiked human plasma samples. The proposed method is simple, with low instrumentation requirements, suitable for quality control application, bioavailability and bioequivalency studies.     

On the explicit solutions of forms of the Sylvester and the Yakubovich matrix equations

In this paper, we consider the explicit solutions of two matrix equations, namely, the Yakubovich matrix equation V−AVF=BW and Sylvester matrix equations AV−EVF=BW,AV+BW=EVF and AV−VF=BW. For this purpose, we make use of Kronecker map and Sylvester sum as well as the concept of coefficients of characteristic polynomial of the matrix A. Some lemmas and theorems are stated and proved where explicit and parametric solutions are obtained. The proposed methods are illustrated by numerical examples. The results obtained show that the methods are very neat and efficient.