Advances in Physical Chemistry http://www.hindawi.com The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Dielectric Relaxation Studies of 2-Butoxyethanol with Aniline and Substituted Anilines Using Time Domain Reflectometry Tue, 18 Feb 2014 11:27:01 +0000 http://www.hindawi.com/journals/apc/2014/659531/ The complex dielectric spectra of 2-butoxyethanol with aniline and substituted anilines like aniline, o-chloroaniline, m-chloroaniline, o-anisidine and m-anisidine binary mixtures in the composition of different volumes of percent (0%, 25%, 50%, 75%, and 100%) have been measured as a function of frequency between 10 MHz and 30 GHz at 298.15 K. The dielectric parameters like static dielectric constant and relaxation time have been obtained by using least square fit method. By using these parameters , effective Kirkwood correlation factor , corrective Kirkwood correlation factor , Bruggeman factor , excess dielectric constant , and excess inverse relaxation time values are calculated and discussed to yield information on the dipolar alignment and molecular rotation of the binary liquid mixtures. From all the derived dielectric parameters, molecular interactions are interpreted through hydrogen bonding. P. Jeevanandham, S. Kumar, P. Periyasamy, and A. C. Kumbharkhane Copyright © 2014 P. Jeevanandham et al. All rights reserved. Oxidation of Tetracaine Hydrochloride by Chloramine-B in Acid Medium: Kinetic Modeling Mon, 10 Feb 2014 10:04:44 +0000 http://www.hindawi.com/journals/apc/2014/238984/ Tetracaine hydrochloride (TCH) is one of the potent local anaesthetics. A kinetic study of oxidation of tetracaine hydrochloride by sodium N-chlorobenzenesulfonamide (chloramine-B or CAB) has been carried in HClO4 medium at 303 K. The rate shows first-order dependence on , shows fractional–order dependence on , and is self-governing on acid concentration. Decrease of dielectric constant of the medium, by adding methanol, increased the rate. Variation of ionic strength and addition of benzenesulfonamide or NaCl have no significant effect on the rate. The reaction was studied at different temperatures and the activation parameters have been evaluated. The stoichiometry of the reaction was found to be 1 : 5 and the oxidation products were identified by spectral analysis. The conjugate free acid C6H5SO2NHCl of CAB is postulated as the reactive oxidizing species. The observed results have been explained by plausible mechanism and the related rate law has been deduced. Jayachamarajapura Pranesh Shubha and Puttaswamy Copyright © 2014 Jayachamarajapura Pranesh Shubha and Puttaswamy. All rights reserved. Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure Wed, 15 Jan 2014 17:06:56 +0000 http://www.hindawi.com/journals/apc/2014/710487/ Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs) and hydroxy double salts (HDSs) can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers. Stephen Majoni and Jeanne M. Hossenlopp Copyright © 2014 Stephen Majoni and Jeanne M. Hossenlopp. All rights reserved. Synthesis and Study of Electrical Properties of SbTeI Thu, 09 Jan 2014 08:54:26 +0000 http://www.hindawi.com/journals/apc/2014/965350/ Needle shaped SbTeI crystals were obtained by solid state reaction. Electrical resistance was measured in the temperature range of 4 K to 550 K. SbTeI shows a metallic behavior from 4 K to 300 K, and at higher temperature (>300 K), it shows semiconducting behavior. Unlike SbSI, this material shows almost zero resistance around 550 K. It shows a piezoelectric behavior with a capacitance of 717 pF and its carrier density and nobilities are found to be 2.12 × 1016 cm−3 and 1.01 cm2/(V·s), respectively. Crystals of SbTeI are characterized by XRD, SEM, and Raman analysis. Electrical activation energy is found to be 0.52 eV. It is suggested that this material may be studied for its application as a superconductor with Tc higher than room temperature. Harish K. Dubey, L. P. Deshmukh, D. E. Kshirsagar, Madhuri Sharon, and Maheshwar Sharon Copyright © 2014 Harish K. Dubey et al. All rights reserved. Solvent Effect on Photoinitiator Reactivity in the Polymerization of 2-Hydroxyethyl Methacrylate Wed, 18 Dec 2013 12:51:01 +0000 http://www.hindawi.com/journals/apc/2013/838402/ Efficacy of photoinitiators such as riboflavin (RF), camphorquinone (CQ), and safranin T (ST) and triethanolamine as a coinitiator has been compared in carrying out the polymerization of 2-hydroxyethyl methacrylate (HEMA) in aqueous and organic solvents. HEMA solutions were polymerized in the presence of RF, CQ, and ST using a low intensity visible radiation source. HEMA was assayed by a UV spectrophotometric method during the initial stages of the reactions (i.e., ~5% change). A comparison of the efficacy of photoinitiators in causing HEMA polymerization showed that RF is more efficient than CQ and ST. The rate of polymerization is directly related to solvent dielectric constant and inversely related to the solvent viscosity. RF is the most efficient photoinitiator in the polymerization of HEMA and the highest rate of reaction occurs in aqueous solutions. A general scheme for the polymerization of HEMA in the presence of photoinitiators is presented. Iqbal Ahmad, Kefi Iqbal, Muhammad Ali Sheraz, Sofia Ahmed, Syed Abid Ali, Sadia Hafeez Kazi, Tania Mirza, Raheela Bano, and Mohammad Aminuddin Copyright © 2013 Iqbal Ahmad et al. All rights reserved. Second Harmonic Generation, Electrooptical Pockels Effect, and Static First-Order Hyperpolarizabilities of 2,2′-Bithiophene Conformers: An HF, MP2, and DFT Theoretical Investigation Mon, 16 Dec 2013 08:44:47 +0000 http://www.hindawi.com/journals/apc/2013/394697/ The static and dynamic electronic (hyper)polarizabilities of the equilibrium conformations of 2,2′-bithiophene (anti-gauche and syn-gauche) were computed in the gas phase. The calculations were carried out using Hartree-Fock (HF), Møller-Plesset second-order perturbation theory (MP2), and density functional theory methods. The properties were evaluated for the second harmonic generation (SHG), and electrooptical Pockels effect (EOPE) nonlinear optical processes at the typical nm of the Nd:YAG laser. The anti-gauche form characterized by the dihedral angle of 137° (MP2/6-311G**) is the global minimum on the potential energy surface, whereas the syn-gauche rotamer ( = 48°, MP2/6-311G**) lies ca. 0.5 kcal/mol above the anti-gauche form. The structural properties of the gauche structures are rather similar to each other. The MP2 electron correlation effects are dramatic for the first-order hyperpolarizabilities of the 2,2′-bithiophenes, decreasing the HF values by ca. a factor of three. When passing from the anti-gauche to the syn-gauche conformer, the static and frequency-dependent first-order hyperpolarizabilities increase by ca. a factor of two. Differently, the electronic polarizabilities and second-order hyperpolarizabilities of these rotamers are rather close to each other. The syn-gauche structure could be discriminated from the anti-gauche one through its much more intense SHG and EOPE signals. Andrea Alparone Copyright © 2013 Andrea Alparone. All rights reserved. Demicellization of Polyethylene Oxide in Water Solution under Static Magnetic Field Exposure Studied by FTIR Spectroscopy Tue, 08 Oct 2013 12:05:17 +0000 http://www.hindawi.com/journals/apc/2013/485865/ FTIR spectroscopy was used to investigate the alterations of the vibration bands in the mid-infrared region of Polyethylene oxide in aqueous solution at 25 mg/mL concentration under exposure up to 4 h to a static magnetic field at 200 mT. FTIR spectroscopic analysis of PEO solution in the range 3500–1000 cm−1 evidenced the stretching vibrations of ether band, C–H symmetric-antisymmetric and bending vibrations of methylene groups, and the C–O–C stretching band. A significant decrease in intensity of symmetric and asymmetric stretching CH2 vibration bands occurred after 2 h and 4 h of exposure, followed by a significant decrease in intensity of scissoring bending in plane CH2 vibration around 1465 cm−1. Finally, the C–O–C stretching band around 1080 cm−1 increased in intensity after 4 h of exposure. This result can be attributed to the increase of formation of the intermolecular hydrogen bonding that occurred in PEO aqueous solution after SMF exposure, due to the reorientation of PEO chain after exposure to SMF. In this scenario, the observed decrease in intensity of CH2 vibration bands can be understood as well considering that the reorientation of PEO chain under the applied SMF induces PEO demicellization. Emanuele Calabrò and Salvatore Magazù Copyright © 2013 Emanuele Calabrò and Salvatore Magazù. All rights reserved. Volumetric, Viscometric and Excess Properties of Binary Mixtures of 1-Iodobutane with Benzene, Toluene, o-Xylene, m-Xylene, p-Xylene, and Mesitylene at Temperatures from 303.15 to 313.15 K Tue, 20 Aug 2013 09:19:21 +0000 http://www.hindawi.com/journals/apc/2013/932103/ Densities and viscosities have been determined for binary mixtures of 1-iodobutane with benzene, toluene, o-xylene, m-xylene, p-xylene, and mesitylene at 303.15, 308.15, and 313.15 K for the entire composition range at atmospheric pressure. The excess molar volumes, , deviations in viscosity, Δη, and excess Gibbs’ free energy of activation flow, Δ have been calculated from the experimental values. The experimental data were fitted to Redlich-Kister polynomial equation. The variations of these parameters with composition of the mixtures and temperature have been discussed in terms of molecular interactions occurring in these mixtures. Further, the viscosities of these binary mixtures were calculated theoretically from their corresponding pure component data by using empirical relations like Bingham, Arrhenius and Eyring, Kendall and Munroe, Hind, Katti and Chaudhari, Grunberg and Nissan, and Tamura and Kurata. Comparison of various interaction parameters has been expressed to explain the intermolecular interactions between iodobutane and selected hydrocarbons. Sangita Sharma, Khushbu Thakkar, Paras Patel, and Madhuresh Makavana Copyright © 2013 Sangita Sharma et al. All rights reserved. The Lattice Compatibility Theory LCT: Physical and Chemical Arguments from the Growth Behavior of Doped Compounds in terms of Bandgap Distortion and Magnetic Effects Tue, 09 Jul 2013 10:01:43 +0000 http://www.hindawi.com/journals/apc/2013/578686/ Physical and chemical arguments for the recently discussed materials-related Lattice Compatibility Theory are presented. The discussed arguments are based on some differences of Mn ions incorporation kinetics inside some compounds. These differences have been evaluated and quantified in terms of alteration of bandgap edges, magnetic patterns, and Faraday effect. K. Boubaker Copyright © 2013 K. Boubaker. All rights reserved. Comparative Biosorption Studies of Hexavalent Chromium Ion onto Raw and Modified Palm Branches Sun, 07 Jul 2013 15:03:14 +0000 http://www.hindawi.com/journals/apc/2013/159712/ The waste of palm branches (PB) was tested for its ability to remove chromium (VI) from aqueous solution by batch and column experiments. Palm branches chemically modified with an oxidizing agent (sulphuric acid) then coated with chitosan and surfactant (hexadecyl trimethyl ammonium bromide surfactant, HDTMA), respectively, were carried out to improve the removal performance of PB. The results of their Cr (VI) removal performances are pH dependent. The adsorption data could be well interpreted by the Langmuir, Freundlich, and Flory-Huggins isotherm models. The maximum adsorption capacity obtained from the Langmuir model for the chitosan coated oxidized palm branches is 55 mg/mg. The adsorption process could be described by pseudo-second-order kinetic model. The intraparticle diffusion study revealed that film diffusion might be involved. The biosorbents were successfully regenerated using 1 M HCL solution. Mona A. Shouman, Nady A. Fathy, Soheir A. Khedr, and Amina A. Attia Copyright © 2013 Mona A. Shouman et al. All rights reserved. Calculated Entropies for n-Heptane, 2-Methylhexane, 2,3-Dimethylpentane, and Radicals from the Loss of H Atoms Tue, 18 Jun 2013 13:40:21 +0000 http://www.hindawi.com/journals/apc/2013/673065/ Entropy data are reported using different calculation methods for internal rotors on n-heptane, 2-methylhexane, and 2,3-dimethylpentane and on the different radical sites of each species corresponding to the loss of a hydrogen atom for temperatures between 298 and 1500 K. Structures, moments of inertia, vibration frequencies, and internal rotor potentials are calculated at the B3LYP/6-31G(d,p) level of theory. Comparisons with experimental literature data suggest limitations inuse of the rigid-rotor harmonic-oscillator (HO) approximation and advantages to the use of internal rotation contributions for entropy relative to torsion frequencies. The comparisons suggest the need to include contributions from all internal rotors where the barriers are at or below those of the above molecules. Calculation of entropy from the use of internal rotor contributions provides acceptable approximations to available literature values. Entropy values for radicals corresponding to carbon sites on these hydrocarbons are presented. Jason M. Hudzik and Joseph W. Bozzelli Copyright © 2013 Jason M. Hudzik and Joseph W. Bozzelli. All rights reserved. Polyethylene Glycols as Efficient Catalysts for the Oxidation of Xanthine Alkaloids by Ceric Ammonium Nitrate in Acetonitrile: A Kinetic and Mechanistic Approach Mon, 10 Jun 2013 17:47:20 +0000 http://www.hindawi.com/journals/apc/2013/835610/ Kinetics of oxidation of xanthine alkaloids, such as Xanthine (XAN), hypoxanthine (HXAN), caffeine (CAF), theophylline (TPL), and theobromine (TBR), have been studied with ceric ammonium nitrate (CAN) using poly ethylene glycols (PEG) as catalysts. Reaction obeyed first order kinetics in both [CAN] and [Xanthine alkaloid]. Highly sluggish CAN-xanthine alkaloid reactions (in acetonitrile media even at elevated temperatures) are enhanced in presence PEGs (PEG-200, -300, -400, -600). An increase in [PEG] increased the rate of oxidation linearly. This observation coupled with a change in absorption of CAN in presence of PEG, [H–(OCH2–CH2)n–O–NH4Ce(NO3)4(CH3CN)] (PEG bound CAN species), is considered to be more reactive than CAN. The mechanism of oxidation in PEG media has been explained by Menger-Portnoy’s enzymatic model. S. Shylaja, K. C. Rajanna, K. Ramesh, K. Rajendar Reddy, and P. Giridhar Reddy Copyright © 2013 S. Shylaja et al. All rights reserved. Study of Bovine Serum Albumin Solubility in Aqueous Solutions by Intrinsic Viscosity Measurements Wed, 29 May 2013 16:40:22 +0000 http://www.hindawi.com/journals/apc/2013/360239/ The behavior of bovine serum albumin (BSA) in water is scarcely studied, and the thermodynamic properties arising from the experimental measurements have not been reported. Intrinsic viscosity measurements are very useful in assessing the interaction between the solute and solvent. This work discussed in a simple determination of the enthalpy of BSA in aqueous solution when the concentration ranges from 0.2 to 36.71% wt. and the temperature from 35 to C. The relationship between the concentration and intrinsic viscosity is determined according to the method of Huggins. The temperature increase reduces the ratio between inherent viscosity and concentration (). This is reflected in the Van't Hoff curve. Furthermore, this work proposes hydrodynamic cohesion value as an indicator of the degree of affinity of protein with water and thermodynamic implications in conformational changes. Martin Alberto Masuelli Copyright © 2013 Martin Alberto Masuelli. All rights reserved. Calculation of Thermal Pressure Coefficient of R11, R13, R14, R22, R23, R32, R41, and R113 Refrigerants by Data Tue, 28 May 2013 16:37:09 +0000 http://www.hindawi.com/journals/apc/2013/327419/ For thermodynamic performance to be optimized particular attention must be paid to the fluid’s thermal pressure coefficients and thermodynamic properties. A new analytical expression based on the statistical mechanics is derived for R11, R13, R14, R22, R23, R32, R41, and R113 refrigerants, using the intermolecular forces theory. In this paper, temperature dependency of the parameters of R11, R13, R14, R22, R23, R32, R41, and R113 refrigerants to calculate thermal pressure coefficients in the form of first order has been developed to second and third orders and their temperature derivatives of new parameters are used to calculate thermal pressure coefficients. These problems have led us to try to establish a function for the accurate calculation of the thermal pressure coefficients of R11, R13, R14, R22, R23, R32, R41, and R113 refrigerants based on statistical-mechanics theory for different refrigerants. Vahid Moeini and Mahin Farzad Copyright © 2013 Vahid Moeini and Mahin Farzad. All rights reserved. Self-Organization Schemes towards Thermodynamic Stable Bulk Heterojunction Morphologies: A Perspective on Future Fabrication Strategies of Polymer Photovoltaic Architectures Tue, 16 Apr 2013 11:29:03 +0000 http://www.hindawi.com/journals/apc/2013/948189/ Research efforts to improve our understanding of electronic polymers are developing fast because of their promising advantages over silicon in photovoltaic solar cells. A major challenge in the development of polymer photovoltaic devices is the viable fabrication strategies of stable bulk heterojunction architecture that will retain functionality during the expected lifetime of the device. Block copolymer self-assembly strategies have attracted particular attention as a scalable means toward thermodynamically stable microstructures that combine the ideal geometrical characteristics of a bulk heterojunction with the fortuitous combination of properties of the constituent blocks. Two primary routes that have been proposed in the literature involve the coassembly of block copolymers in which one domain is a hole conductor with the electron-conducting filler (such as fullerene derivatives) or the self-assembly of block copolymers in which the respective blocks function as hole and electron conductor. Either way has proven difficult because of the combination of synthetic challenges as well as the missing understanding of the complex governing parameters that control structure formation in semiconducting block copolymer blends. This paper summarizes important findings relating to structure formation of block copolymer and block copolymer/nanoparticle blend assembly that should provide a foundation for the future design of block copolymer-based photovoltaic systems. A. Benmouna, R. Benmouna, M. R. Bockstaller, and I. F. Hakem Copyright © 2013 A. Benmouna et al. All rights reserved. Theoretical Study on the Static (Hyper)Polarizabilities of α-t-Bu-ω-CN-Poly(methylphenyl)silane Sun, 31 Mar 2013 16:11:30 +0000 http://www.hindawi.com/journals/apc/2013/905910/ The static linear and nonlinear optical properties of the σ-conjugated polymer α-t-Bu-ω-CN-poly(methylphenyl)silane (PMS) are studied at the Coupled-Perturbed Hartree-Fock (CPHF) level with 6-31+G(d) basis set. The calculated results reveal that the static first hyperpolarizabilities of this system increase with the main chain length and have a good agreement with experiments. The (hyper)polarizabilities per unit cell have been extrapolated to infinite chain limit and a comparison is made to those of polysilane and polyacetylene (PA). Besides, other structural properties depending on the σ-conjugated Si–Si skeleton length are investigated as well. Electron correlation effect is estimated and it turns out that the MP2 static first hyperpolarizability is about times larger than the corresponding CPHF value for the polymer with . Jing Li, Liang Peng, and Feng Long Gu Copyright © 2013 Jing Li et al. All rights reserved. Quantum-Dynamical Theory of Electron Exchange Correlation Wed, 20 Mar 2013 09:45:23 +0000 http://www.hindawi.com/journals/apc/2013/497267/ The relationship between the spin of an individual electron and Fermi-Dirac statistics (FDS), which is obeyed by electrons in the aggregate, is elucidated. The relationship depends on the use of spin-dependent quantum trajectories (SDQT) to evaluate Coulomb’s law between any two electrons as an instantaneous interaction in space and time rather than as a quantum-mean interaction in the form of screening and exchange potentials. Hence FDS depends in an ab initio sense on the inference of SDQT from Dirac’s equation, which provides for relativistic Lorentz invariance and a permanent magnetic moment (or spin) in the electron’s equation of motion. Schroedinger’s time-dependent equation can be used to evaluate the SDQT in the nonrelativistic regime of electron velocity. Remarkably FDS is a relativistic property of an ensemble of electron, even though it is of order in the nonrelativistic limit, in agreement with experimental observation. Finally it is shown that covalent versus separated-atoms limits can be characterized by the SDQT. As an example of the use of SDQT in a canonical structure problem, the energies of the 1Σg and 3Σu states of H2 are calculated and compared with the accurate variational energies of Kolos and Wolniewitz. Burke Ritchie and Charles A. Weatherford Copyright © 2013 Burke Ritchie and Charles A. Weatherford. All rights reserved. Sorption of from Aqueous Solution unto Modified Rice Husk: Isotherms Studies Mon, 18 Mar 2013 13:31:36 +0000 http://www.hindawi.com/journals/apc/2013/842425/ Investigation of the sorption potential of rice husk, an agricultural waste, as an adsorbent was carried out. The rice husk was modified with orthophosphoric acid and was used for adsorption of lead (II) ions (Pb2+) from aqueous solution. Physicochemical properties of the modified rice husk were determined. Equilibrium sorption data were confirmed with Langmuir, Freundlich and Temkin adsorption isotherms. On the basis of adsorption isotherm graphs, values were determined to be 0.995, 0.916, and 0.797 for Langmuir, Temkin, and Freundlich isotherms, respectively, indicating that the data fitted well into the adsorption isotherms, but Langmuir isotherm is a better model. The maximum monolayer coverage from Langmuir studies,  mg/g, Langmuir isotherm constant,  L/mg, and the separation factor, at 100 mg/L of lead(II) ions indicating that the sorption process, was favourable. The suitability of modified rice husk as an adsorbent for the removal of lead ions from aqueous solution and its potential for pollution control is established. A. O. Dada, J. O. Ojediran, and Abiodun Paul Olalekan Copyright © 2013 A. O. Dada et al. All rights reserved. Polyethylene Glycols as Efficient Media for Decarboxylative Nitration of α,β-Unsaturated Aromatic Carboxylic Acids by Ceric Ammonium Nitrate in Acetonitrile Medium: A Kinetic and Mechanistic Study Mon, 04 Mar 2013 17:00:12 +0000 http://www.hindawi.com/journals/apc/2013/146585/ Polyethylene glycols (PEGs) were found to be efficient media for decarboxylative nitration of α,β-unsaturated aromatic carboxylic acids by ceric ammonium nitrate (CAN) in acetonitrile to give β-nitrostyrene derivatives. Kinetics of the reaction exhibited second order kinetics with a first order dependence on [CAN] and [substrate]. Reactions were too sluggish to be studied in the absence of PEG; therefore detailed kinetics were not taken up. Reaction times were reduced from 24 hrs to few hours. The catalytic activity was found to be in the increasing order PEG-300 > PEG-400 > PEG-600 > PEG-200. Mechanism of PEG-mediated reactions was explained by Menger-Portnoy's scheme as applied in micellar kinetics. K. Ramesh, S. Shylaja, K. C. Rajanna, P. Giridhar Reddy, and P. K. Saiprakash Copyright © 2013 K. Ramesh et al. All rights reserved. Synergistic Effect of [Ru(III) + Ir(III)] in N-Bromosuccinimide Reaction with Certain Aliphatic Ketones: A Kinetic Study Tue, 25 Dec 2012 15:38:16 +0000 http://www.hindawi.com/journals/apc/2012/292908/ Dramatic rate enhancements have been observed in the oxidation of acetone (MMK), ethyl methyl ketone (EMK), and isobutyl methyl ketone (IBMK) by N-bromosuccinimide (NBS) in the presence of a mixture of metal ions [Ru(III) + Ir(III)]. The rate of oxidation in the the [Ru(III) + Ir(III)] system is much faster than either in the Ru(III) or in Ir(III) catalyzed system. The order in [NBS] was found to be zero both in catalyzed as well as uncatalyzed reactions. However, the order in [ketone] changed from unity to a fractional one in metal ion catalyzed systems. On the basis of kinetic features, the most plausible mechanism involving the oxidation of [Ir(III)-ketone] by Ru(III) to give [Ir(V)-ketone] and Ru(I) in the rate limiting step is proposed. Ru(I) thus formed is oxidized by NBS to Ru(III) in a fast step is discussed and individual rate parameters were evaluated. P. Giridhar Reddy, K. Ramesh, S. Shylaja, K. C. Rajanna, and S. Kandlikar Copyright © 2012 P. Giridhar Reddy et al. All rights reserved. Structural Studies on Nonequilibrium Microstructures of Dioctyl Sodium Dodecyl Sulfosuccinate (Aerosol-OT) in p-Toluenesulfonic Acid and Phosphatidylcholine Sat, 08 Dec 2012 10:41:14 +0000 http://www.hindawi.com/journals/apc/2012/798492/ Several microstructures are evolved at the interface when sparingly soluble solid surfactants come in contact with water. One class of these microstructures is termed as “myelin figures”; these were observed when phosphatidylcholine came in contact with water. Although the myelins are initially simple rod-like, complex forms like helices, coils and so forth. appear in the later stage. Finally, the myelins fuse together to form a complex mosaic-like structure. When studied by taking a cross-section using cryoscanning electron microscopy, it revealed concentric circular pattern inside the myelin figures. The cross-sections of (dioctyl sodium dodecyl sulfosiccinate) AOT/water system myelin internal structures were lost. When p-toluenesulfonic acid (PTS) 2 wt% was present in the water phase, AOT myelins revealed the internal microstructures. It has annular concentric ring-like structure with a core axon at the centre. Further investigation revealed new microstructures for the first time having multiple axons in the single-myelin strand. M. K. Temgire, C. Manohar, Jayesh Bellare, and S. S. Joshi Copyright © 2012 M. K. Temgire et al. All rights reserved. Kinetics and Mechanism of Oxidation of L-Ascorbic Acid by Pt(IV)(aq) in Aqueous Hydrochloric Acid Medium Tue, 20 Nov 2012 09:03:46 +0000 http://www.hindawi.com/journals/apc/2012/143734/ Reduction of [PtCl6]2− by L-ascorbic acid (H2ASc) in 0.1 M aqueous acid medium has been investigated spectrophotometrically under pseudo-first order condition at [PtCl6]2− = 0.005–0.007 mol dm−3, 0.05 ≤ [H2ASc]/mol dm−3 ≤ 0.3, 298 K ≤ ≤ 308 K, [H+] = 0.14 mol dm−3,  mol dm−3. The redox reaction follows the rate law: d[Pt(IV)]/dt = [H2ASc][Pt(IV)], where is the second-order rate constant and [H2ASc] is the total concentration of ascorbic acid. Electron transfer from [H2ASc] to Pt(IV) center leading to the release of two halide ions and formation of the reaction products, square planner Pt(II) halide complex, and dehydrated ascorbic acid is suggested. This redox reaction follows an outersphere mechanism as Pt(IV) complex is substituted inert. Activation parameters were calculated corresponding to rate of electron transfer reaction . Activation parameters favor the electron transfer reaction. Sadhana Senapati, S. P. Das, and A. K. Patnaik Copyright © 2012 Sadhana Senapati et al. All rights reserved. Characterization of the Chemical Kinetics in an O2/HMDSO RF Plasma for Material Processing Mon, 19 Nov 2012 13:58:07 +0000 http://www.hindawi.com/journals/apc/2012/205380/ Experimental study of the plasma gas phase in low-pressure radiofrequency discharges of oxygen and hexamethyldisiloxane is presented. The plasma phase has been studied by means of optical emission spectroscopy. Mass spectroscopy of the neutral and of the charged species has been performed too, directly sampling the plasma gas phase, by a dedicated spectrometer. We also measured the ion energy distribution. We have studied the influence of the operating conditions on the plasma gas-phase composition which plays a primary role in the formation process of SiO2 films, which are known for their important applicative uses. Ruggero Barni, Stefano Zanini, and Claudia Riccardi Copyright © 2012 Ruggero Barni et al. All rights reserved. A Theoretical Investigation of the Ring Strain Energy, Destabilization Energy, and Heat of Formation of CL-20 Wed, 24 Oct 2012 09:25:49 +0000 http://www.hindawi.com/journals/apc/2012/175146/ The cage compound CL-20 (a.k.a., 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, HNIW, or 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane) is a well-studied high-energy-density material (HEDM). The high positive gas- ) and solid- () phase heat of formation values for CL-20 conformers have often been attributed to the strain energy of this cage compound and, by implication, to the conventional ring strain energy (CRSE) inherent in isowurtzitane which may be viewed as a “parent compound” (although not the synthetic precursor) of CL-20. values and destabilization energies (DSEs), which include the contribution from CRSE, were determined by computation using a relatively new multilevel ab intio model chemistry. Compared to cubane, isowurtzitane does not have an exceptionally high CRSE. It is about the same as that of cyclopropane and cyclobutane. These investigations demonstrate that instead of the CRSE inherent in the isowurtzitane parent compound, the relatively high and DSE values of CL-20 conformers must be due, primarily, to torsional strain (Pitzer strain), transannular strain (Prelog strain), and van der Waals interactions that occur due to the presence of the six >N–NO2 substituents that replace the six methylene (–CH2–) groups in the isowurtzitane parent compound. These conclusions are even more pronounced when 2,4,6,8,10,12-hexaazaisowurtzitane is viewed as the “parent compound.” John A. Bumpus Copyright © 2012 John A. Bumpus. All rights reserved. Excess Transport Properties of Binary Mixtures of Quinoline with Xylenes at Different Temperatures Thu, 11 Oct 2012 08:25:33 +0000 http://www.hindawi.com/journals/apc/2012/324098/ The ultrasonic velocity and density of binary liquid mixtures of quinoline with o-xylene, m-xylene, and p-xylene have been measured over the entire range of composition at = 303.15, 308.15, 313.15, and 318.15 K. Using these data, various parameters like adiabatic compressibility (β), intermolecular free length (), and acoustic impedance () and some excess parameters like excess adiabatic compressibility (), excess intermolecular free length (), excess acoustic impedance (), and excess ultrasonic velocity () have been calculated for all the three mixtures. The calculated deviations and excess functions have been fitted to Redlich-Kister polynomial equation. The observed deviations have been explained on the basis of the intermolecular interactions present in these mixtures. Sk. Fakruddin, Ch. Srinivasu, B. R. Venkateswara Rao, and K. Narendra Copyright © 2012 Sk. Fakruddin et al. All rights reserved. Microscopic Rate Constants of Crystal Growth from Molecular Dynamic Simulations Combined with Metadynamics Thu, 30 Aug 2012 17:42:46 +0000 http://www.hindawi.com/journals/apc/2012/135172/ Atomistic simulation of crystal growth can be decomposed into two steps: the determination of the microscopic rate constants and a mesoscopic kinetic Monte Carlo simulation. We proposed a method to determine kinetic rate constants of crystal growth. We performed classical molecular dynamics on the equilibrium liquid/crystal interface of argon. Metadynamics was used to explore the free energy surface of crystal growth. A crystalline atom was selected at the interface, and it was displaced to the liquid phase by adding repulsive Gaussian potentials. The activation free energy of this process was calculated as the maximal potential energy density of the Gaussian potentials. We calculated the rate constants at different interfacial structures using the transition state theory. In order to mimic real crystallization, we applied a temperature difference in the calculations of the two opposite rate constants, and they were applied in kinetic Monte Carlo simulation. The novelty of our technique is that it can be used for slow crystallization processes, while the simple following of trajectories can be applied only for fast reactions. Our method is a possibility for determination of elementary rate constants of crystal growth that seems to be necessary for the long-time goal of computer-aided crystal design. Dániel Kozma and Gergely Tóth Copyright © 2012 Dániel Kozma and Gergely Tóth. All rights reserved. Predicting Heats of Explosion of Nitroaromatic Compounds through NBO Charges and 15N NMR Chemical Shifts of Nitro Groups Thu, 30 Aug 2012 15:39:52 +0000 http://www.hindawi.com/journals/apc/2012/304686/ This work presents a new quantitative model to predict the heat of explosion of nitroaromatic compounds using the natural bond orbital (NBO) charge and 15N NMR chemical shifts of the nitro groups (15NNitro) as structural parameters. The values of the heat of explosion predicted for 21 nitroaromatic compounds using the model described here were compared with experimental data. The prediction ability of the model was assessed by the leave-one-out cross-validation method. The cross-validation results show that the model is significant and stable and that the predicted accuracy is within 0.146 MJ kg−1, with an overall root mean squared error of prediction (RMSEP) below 0.183 MJ kg−1. Strong correlations were observed between the heat of explosion and the charges (R2 = 0.9533) and 15N NMR chemical shifts (R2 = 0.9531) of the studied compounds. In addition, the dependence of the heat of explosion on the presence of activating or deactivating groups of nitroaromatic explosives was analyzed. All calculations, including optimizations, NBO charges, and 15NNitro NMR chemical shifts analyses, were performed using density functional theory (DFT) and a 6-311+G(2d,p) basis set. Based on these results, this practical quantitative model can be used as a tool in the design and development of highly energetic materials (HEM) based on nitroaromatic compounds. Ricardo Infante-Castillo and Samuel P. Hernández-Rivera Copyright © 2012 Ricardo Infante-Castillo and Samuel P. Hernández-Rivera. All rights reserved. Conformational Analysis of Quaternary Ammonium-Type Ionic Liquid Cation, N,N-Diethyl-N-methyl-N-(2-methoxyethyl) Ammonium Cation Thu, 23 Aug 2012 07:56:24 +0000 http://www.hindawi.com/journals/apc/2012/829523/ Conformational preference of N,N-diethyl-N-methyl-N-(2-methoxyethyl) ammonium cation ([DEME]+), which is one of the quaternary ammonium-based ionic liquid cation, in the gas phase has been investigated using a density functional theory (DFT) calculation. Eight candidates for the stable conformers of [DEME]+ exist in the gas phase, and can it energetically classify into two groups. One is a five conformers group, which has the N+⋯O− intramolecular attractive interaction form (the folded form). The other is a three conformers group, which is the noninteraction form (the extended form). The transformation from the folded form to the extended form induces large changes in the dipole moment and partial charges of N and O atoms. Here we show that the difference in the dipole moment and partial charges of N and O atoms associated with the conformational change of [DEME]+ are closely related to the molecular orientation of [DEME]-based ionic liquids in the liquid state. Takahiro Takekiyo, Yusuke Imai, Hiroshi Abe, and Yukihiro Yoshimura Copyright © 2012 Takahiro Takekiyo et al. All rights reserved. Positronium in a Liquid Phase: Formation, Bubble State and Chemical Reactions Tue, 21 Aug 2012 11:18:50 +0000 http://www.hindawi.com/journals/apc/2012/431962/ The present approach describes the 𝑒+ fate since its injection into a liquid until its annihilation. Several stages of the 𝑒+ evolution are discussed: (1) energy deposition and track structure of fast positrons: ionization slowing down, number of ion-electron pairs, typical sizes, thermalization, electrostatic interaction between 𝑒+ and the constituents of its blob, and effect of local heating; (2) positronium formation in condensed media: the Ore model, quasifree Ps state, intratrack mechanism of Ps formation; (3) fast intratrack diffusion-controlled reactions: Ps oxidation and ortho-paraconversion by radiolytic products, reaction rate constants, and interpretation of the PAL spectra in water at different temperatures; (4) Ps bubble models. Inner structure of positronium (wave function, energy contributions, relationship between the pick-off annihilation rate and the bubble radius). Sergey V. Stepanov, Vsevolod M. Byakov, Dmitrii S. Zvezhinskiy, Gilles Duplâtre, Roman R. Nurmukhametov, and Petr S. Stepanov Copyright © 2012 Sergey V. Stepanov et al. All rights reserved. Electromagnetic Fields Effects on the Secondary Structure of Lysozyme and Bioprotective Effectiveness of Trehalose Thu, 09 Aug 2012 11:28:35 +0000 http://www.hindawi.com/journals/apc/2012/970369/ FTIR spectroscopy was used to investigate the effects of extremely low frequency (50 Hz) electromagnetic field and of microwaves at 900 MHz on the secondary structure of a typical protein, the lysozyme, evaluating the bioprotective effectiveness of trehalose. Lysozyme in D2O solution (60 mg/ml) was exposed to 50 Hz frequency electromagnetic field at 180 μT. The FTIR spectra indicated an increase of CH2 group at 1921 and 1853 cm−1 after 3 h of exposure. Such effect was not observed after the addition of trehalose (150 mg/mL) at the same exposure conditions. Lysozyme dissolved in D2O at the concentration of 100 mg/mL was exposed up to 4 h to 900 MHz mobile phone microwaves at 25 mA/m. A significant increase in intensity of the amide I vibration band in the secondary structure of the protein was observed after 4 h exposure to microwaves. This effect was inhibited by the presence of trehalose at the concentration of 150 mg/mL. Fourier self-deconvolution spectral analysis of lysozyme in D2O solution after exposure to microwaves revealed an increase in intensity of the conformational components of amide I mode, particularly of β-sheet and turn that can be attributed to disorder and unfolding processes of the protein. Emanuele Calabrò and Salvatore Magazù Copyright © 2012 Emanuele Calabrò and Salvatore Magazù. All rights reserved.