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Peristaltic transport of water-based silver nanoparticles in a symmetric channel with convective walls is explored. Analysis has been carried out in the presence of heat source-sink, viscous dissipation, and mixed convection. Lubrication approach has been utilized. Resulting coupled system is solved numerically using the shooting method. Graphical analysis for flow quantities and heat transfer has been made. Results show that the addition of silver nanoparticles considerably reduces the velocity and temperature of the fluid. Enhancement in heat transfer rate at the wall for large nanoparticle volume fraction is also reported. Interesting outcomes of this study are summarized. PACS Nos.: 47.85.Dh, 47.50.-d, 44.30.+v, 47.55.pb. Nous etudions le transport peristaltique de nanoparticules d'argent dans une base d'eau, circulant dans un canal a parois convectives. L'analyse se fait en presence de sources-puits thermiques, de dissipation visqueuse et de convection mixte. Nous utilisation l'approximation de lubrification. Les equations couplees decrivant le systeme sont solutionnees numeriquement avec la methode de tir. Nous presentons une analyse graphique des quantites pertinentes a l'ecoulement et au transfert de chaleur. Les resultats montrent que l'addition des nanoparticules d'argent reduit considerablement la vitesse et la temperature du fluide. Nous observons une augmentation du transfert de chaleur aux parois pour de grandes fractions en volume de nanoparticules et proposons des suites interessantes a cette etude. [Traduit par la Redaction], 1. Introduction Suspension of nanoparticles of metals in usual heat transfer fluids like water, engine oil, ethylene glycol mixture, etc., has proven a novel technique to enhance the thermal conductivity [...]

The effect of polyethylene glycols (PEGs) with molecular weights of 2000, 6000, 13000, and 20000 on the sensitivity of the thermal lens determination of cobalt(III) using nitroso-R-salt and 2-nitroso-1-naphthol is studied. At the polymer concentration as low as 10%, the sensitivity coefficient significantly increases and the detection limit decreases by a factor of 1.5-2 with respect to the determination in an aqueous medium without PEG. This effect is accompanied by an increase in sensitivity due to an increase in the absorbance of the cobalt complexes in PEG solutions at the operating wavelength. Under optimal conditions, the detection limits for cobalt(III) are 6 and 10 ng/mL with nitroso-R-salt and 2-nitroso-1-naphthol, respectively. Keywords: thermal lens spectrometry, polyethylene glycol, mixed media, cobalt, nitroso-R-salt, 2-nitroso-1naphthol DOI: 10.1134/S1061934813120095, A significant dependence of the signal on the medium properties is a feature of thermal lens spectrometry (TLS), that enable one to achieve a higher detection sensitivity by using additives [...]

Conformational changes in the electronic properties of the chemical group attached to the [C.sub.[gamma]]-methylene of methionine 35(Met35) are investigated by molecular dynamic simulation of amyloid [beta](A[beta](1-42)) monomer in aqueous solution. The oxidation of Met35 not only decreases the residue's hydrophobicity, but also its interaction with surrounding residues and water, resulting in changes in the structure of the C-terminus hydrophobic region.

The photoexcitation of guanine cation radical in frozen aqueous solution of one-electron-oxidized RNA compounds resulting in the formation of sugar radicals is investigated by electron spin resonance and density functional theory. The results confirm that photoexcitation of guanine cation radical and not its N1 deprotonated species results in the formation of neutral sugar radicals in RNA systems.

Monte Carlo structure simulations are used to study water-dioxane interactions in aqueous solutions with increasing dioxane concentrations. The structure analysis shows that in aqueous solution the dioxane molecules arrange at a distance of 4-8 [Angstrom] for the ring symmetry and each dioxane oxygen forms one hydrogen bond to a water molecule, indicating dioxanes unique hydrogen-bond acceptor character.

Detailed structural study of [Be.sup.2} ion is carried out using neutron diffraction of concentrated solutions of beryllium chloride at three different concentrations. The results from all three solutions suggest that the [Be.sup.2} ion has a well-defined 4-fold coordinated shell dominated by oxygen atoms.

The generation of singlet molecular oxygen by irradiation of meso-tetra(N-methyl-4-pyridyl)prophine adsorbed on porous Vycor glass is investigated. The excited state of the adsorbed complex is quenched by [O.sub.2] to give singlet oxygen, which is found in the surrounding aqueous solution.

The aqueous solution properties of polyglycidol-based analogues are examined by rhealogy in relation to pluronic block polymers. Shear thinning is observed at concentrations above the critical micellization concentration. Zero shear viscosities are maximum at polyglycidol content of 50% wt, and decreased with increase in temperature.

A novel chemosensor array is developed for saccharides and saccharide derivatives that have operated in aqueous media at physiological pH. This method can be used in real-life samples involving saccharides as well as for sensing other desired analytes.

The study report on the measurement of homogeneous nucleation temperature, [T.sub.H], in the presence of aqueous mixed salt systems of varying compositions and ionic strengths is presented.

A modified version of the acceleration model is developed for the reactions in ice, which has included the total molar change involved in reactions in ice. The results have shown that the acceleration of reactions in the unfrozen solution of ice is not an abnormal phenomenon.

The preparation of five triazene-arylene oligomers and investigations of their folding properties in aqueous solution are reported. The analysis has shown the folding behavior of five triazene-arylene oligomers whose folding properties can be controlled by the presence of cucurbit[n]uril molecular containers and also responds to the presence of competing chemical stimuli.

The photophysical properties of the thiopyrylium dye 1-S and the related thio (6-S0 and selenopyrylium (6-Se) analogues in aqueous solution were examined. It was shown that not only the fluorescence yield for the production of [1.sup.O.sub.2] increase upon binding to DAN in these systems but also the quantum yield.

The roles of intra- and intermolecular correlations in cavity formation in n-hexane, contrasting hardsphere solvation in aqueous and nonaqueous solution are addressed.

Vibrational broad bandwidth sum frequency generation spectroscopy was used to investigate the organization of 1-butanol and 1-hexanol at their air-liquid interface of aqueous, aqueous ammonium bisulfate and sulfuric acid solutions. It was found that at aqueous, ammonium bisulfate and at most sulfuric acid solution surfaces, butanol molecules organize in all-trans conformations indicating that butanol self-aggregates while hexanol chains were disordered at the surface of their respective solutions.

The effect of changing the fraction of charged monomer units of the polyion in aqueous polyion-oppositely charged surfactant complex salts is examined. It is shown that the average surfactant aggregation number in the surfactant aggregates has decreased when the fraction of charged monomers is decreased.

A microfluidic device denoted the Phase Chip is designed to measure and manipulate the phase diagram of multicomponent fluid mixtures. The phase diagram of a polymer/salt mixture is measured on-chip and validated off-chip and the protein crystallization rates are enhanced through the manipulation of the kinetics of nucleation and growth.

The synthesis and characterization of a series of water-soluble 2-(2'-arylsulfonamidophenyl)benzimidazole derivatives containing electron-donating and accepting groups attached to various positions of the fluorophore [pi]-system in aqueous solution are described. The analysis has described the substituent effects on the photophysical properties of this class of excited-state intramolecular proton transfer (ESIPT) fluorophores in an aqueous environment and has also given guidelines for designing emission ratiometric pH.

The synthesis and characterization of the pivalic acid ester N-pivaloxy-2-amino-1-methyl-6-1H-imidazo[4,5-b]pyridine and the characterization of its reactions in aqueous media are presented. The correlation of nitrenium ion selectivity with the mutagenicity and carcinogenicity of PhIP is examined.

A novel approach for controlling the size of Ir[O.sub.2] nanoparticles and stabilizing 2nm diameter particles by hydrolysis of aqueous Ir[Cl.sup.2-.sub.6] is discussed. It is suggested that chelation of surface Ir atoms is a significant parameter in stabilizing these nanoparticles against aggregation.

The study of the interactions between the hydrophobic and ionic solutes in aqueous guanidinium (Gdm) chloride and urea solutions provides a better understanding of the protein denaturation mechanism. The results show that the primary mechanism of denaturation involves a direct electrostatic interaction between the denaturant molecules and proteins.

Electrochemical, complexation, and electronic properties of uranyl(VI) and (V) carbonato complexes in an aqueous N[a.sub.2]C[O.sub.3] solution was investigated to define the appropriate conditions for preparing pure uranyl(V) samples. Cyclic voltammetry using three different working electrodes of platinum, gold, and glassy carbon suggests that the electrochemical reaction of uranyl(VI) carbonate species proceeds quasi-reversibly.

The development of in situ chemical sensors is critical for present-day expeditionary oceanography and the new mode of ocean observing systems that we are entering. New sensors take a significant amount of time to develop; therefore, validation of techniques in the laboratory for use in the ocean environment is necessary. Laser-induced breakdown spectroscopy (LIBS) is a promising in situ technique for oceanography. Laboratory investigations on the feasibility of using LIBS to detect analytes in bulk liquids at oceanic pressures were carried out. LIBS was successfully used to detect dissolved Na, Mn, Ca, K, and Li at pressures up to 2.76 x [10.sup.7] Pa. The effects of pressure, laser-pulse energy, interpulse delay, gate delay, temperature, and NaCl concentration on the LIBS signal were examined. An optimal range of laser-pulse energies was found to exist for analyte detection in bulk aqueous solutions at both low and high pressures. No pressure effect was seen on the emission intensity for Ca and Na, and an increase in emission intensity with increased pressure was seen for Mn. Using the dual-pulse technique for several analytes, a very short interpulse delay resulted in the greatest emission intensity. The presence of NaCl enhanced the emission intensity for Ca, but had no effect on peak intensity of Mn or K. Overall, increased pressure, the addition of NaCl to a solution, and temperature did not inhibit detection of analytes in solution and sometimes even enhanced the ability to detect the analytes. The results suggest that LIBS is a viable chemical sensing method for in situ analyte detection in high-pressure environments such as the deep ocean. OCIS codes: 010.4450, 140.3440, 300.6360.

The [Cm.sup.3} hydration sphere is quantified in solution, especially the distances and numbers of waters in the first and second coordination spheres. The increase in splitting of the Cm-water distances in the first coordination sphere can be explained in terms of its potential relevance to the decrease in coordinating waters with decreasing ionic radius about the f-ion in solution.

The local composition of a cosolvent in the vicinity of a protein surface and its dependence on various factors are analyzed using the Kirkwood-Bluff fluctuation theory for ternary mixture. The Schellman exchange model is used to study the association between the preferential binding parameter in water + lysozyme + urea mixtures and the urea concentration.

A study was conducted to explore the effects of oxygen in the photoreduction of 1,4-benzoquinone (BQ), 1,4-naphthoquinone (NQ), and a series of derivatives in aqueous solution in the presence of acetonitrile and formate, aliphatic amines. The overall reaction is observed to be oxidation of the donors and conversion of oxygen via the hydroperoxyl/superoxide radical into hydrogen peroxide.

A study was conducted to understand the complexation between [U.sup.VI] and 1-hydroxyethane-1,1-diphosphoric acid (HEDPA) in acidic to neutral and basic solutions. It was found that [U.sup.VI] forms a number of 1:1, 1:2 and 2:2 complexes with HEDPA in solution and the complexes formed are highly protonated in strongly acidic solutions and unprotonated and mixed hydroxyl HEDPA complexes in neutral and basic solutions.

The study makes use of the transient infrared (IR) absorption measurements to analyze the picosecond thermometry of the protein molecules, when placed in an aqueous environment. The small temperature changes, as well as the various measured transient absorption changes are found to be highly in accordance with the static temperature dependence of protein, as the thermally induced changes in the IR absorption reach the equilibrium within a few picoseconds.

The combination of a two-state model and the dielectric continuum model were used to theoretically investigate the Creutz-Taube complexes in aqueous solution. The electronic structures are found to be very sensitive to the metal, ligand, and solvent and the origins of the difference are the smaller overlap integral and larger energy difference between two diabatic states of which electronic structure is almost localized on each metal center.

The combination of a two-state model and the dielectric continuum model were used to theoretically investigate the Creutz-Taube complexes in aqueous solution. The electronic structures are found to be very sensitive to the metal, ligand, and solvent and the origins of the difference are the smaller overlap integral and larger energy difference between two diabatic states of which electronic structure is almost localized on each metal center.

Enzyme-based reagentless biosensors were developed using the model system of glucose dehydrogenase (GDH) and its nicotinamide adenine dinucleotide cofactor (NA[D.sup.+]). The biosensors were prepared following an approach similar to the concept of molecular imprinting. To this end, the [N.sup.1]-carboxymethyl--NA[D.sup.+] species were covalently attached to polyamino--saccharide chains of chitosan (CHIT) and allowed to interact with GDH in an aqueous solution. The bioaffinity interactions between the NA[D.sup.+] and GDH were secured by cross-linking the system with the glutaric dialdehyde (GDI)-modified CHIT. Electron conductive films of such CHIT--NA[D.sup.+]--GDH--GDI--CHIT macrocomplexes (MC) were prepared on glassy carbon (GC) electrodes by adding carbon nanotubes (CNT) and evaporating water. Electrochemical analysis of the GC/ CNT--MC electrodes revealed that, in contrast to the oxidase-based electrodes, they acted as oxygen-independent reagentless biosensors. The application of Nation to such biosensors predictably improved their selectivity and, unexpectedly, enhanced their sensitivity by an order of magnitude.

Various absorption and fluorescence measurements are carried out to study the aqueous solutions containing pentaoxyethylene nonyl phenyl ether (NPE) in the presence of beta-cyclodextrin, which is further used to analyze the effect of complexation on the aggregation of the surfactant. The results prove that encapsulating agents can be widely used for avoiding the clouding process of nonionic surfactants, hence making it useful for a wide range of applications.

The small-angle neutron scattering method is used to investigate the aqueous mixed micellar solutions of perflouropolyether carboxylic salts with ammonium counterions, as their shapes and dimensions are highly affected by the presence of the n3 surfactant. The analysis reveals that a close packing of the tails leads to a decrease in the micellar curvature and repulsions between the polar heads, which ultimately leads to a micellar growth in the ellipsoids with greater axial ratios.

A study employs the Fourier transform infrared and the NMR spectroscopy to analyze the effects of the ionic liquids on the aggregation behavior of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers in the aqueous solution. The research has proved to be extremely helpful in studying such effects and shows that at low concentration of the BmimBr, miscelles are formed in the aqueous solution.

Several experimental and theoretical predictions based on the modulated temperature differential scattering calorimetry are used to study the phase transformations in aqueous low molar mass poly(vinyl methyl ether) solutions. The process used is extremely sensitive towards the measuring board and confirms all the observed properties like the solvent melting line, bimodal lower critical solution temperature (LCST), as well as the upper critical solution temperature (UCST) miscibility gaps.

Ab initio quantum mechanical/molecular mechanical (QM/MM) molecular dynamics (MD) simulations are performed at the Hartree-Fock (HF) level for the zinc(II)-diamine complexes in aqueous solution. QM/MM MD simulations provide details about the stability of the zinc(II)-diamine complexes in acqueous solution while the only stable species of the zinc(II)-diamine complex in aqueous solution is the trigonal bipyramidal triaquodiamminezine(II) complex.

Self-assembly formation of sodium salts of three N-acyl peptide surfactants, sodium N-(4-n-dodecyloxybenzoyl)-L-alyl-L-valinate (SDBAV), L-valyl-L-alaninate (SDBVA), and l-valyl-L-valinate (SDBVV) are investigated. They are shown to spontaneously form large vesicles in dilute aqueous solution and the cac values of the amphiphiles are very low which implies that the free energy of formation of vesicles is lower.

By using a 27-MHz piezoelectric quartz oscillator connected with a vector network analyzer, we obtained resonance frequency decreases (-[DELTA][F.sub.water]) and energy dissipation increases ([DELTA][D.sub.water]) during binding of biotinylated bovine serum albumin, biotinylated ssDNA, biotinylated dsDNA, and biotinylated pullulan to a NeutrAvidin-immobilized 27-MHz quartz crystal microbalance (QCM) plate in aqueous solution, as well as in the wet air phase (98% humidity, -[DELTA][F.sub.wet] and [DELTA][D.sub.wet]) and in the dry air phase (-[DELTA][F.sub.air] and [DELTA][D.sub.air] * -[DELTA][F.sub.water] indicates the total mass of the molecule, bound water, and vibrated water in aqueous solutions. -[DELTA][F.sub.wet] indicates the total mass of the molecule and bound water. -[DELTA][F.sub.air] simply shows the real mass of the molecule on the QCM. In terms of results, (-[DELTA][F.sub.wet])/(-[DELTA][F.sub.air]) values indicated the bound water ratios per unit biomolecular mass were on the order of pullulan (2.1-2.2) > DNAs = proteins (1.4-1.6) > polystyrene (1.0). The (-[DELTA][F.sub.water])/(-[DELTA][F.sub.air]) values indicated the hydrodynamic water (bound and vibrated water) ratios per unit biomolecular mass were on the order of dsDNA (6.5) > ssDNA = pullulan (3.5-4.4) > proteins (2.4-2.5) > polystyrene (1.0). Energy dissipation parameters per unit mass in water ([DELTA][D.sub.water]/(-[DELTA][F.sub.air])) were on the order of pullulan > dsDNA > ssDNA > proteins > polystyrene. Energy dissipation in the wet and dry air phases ([DELTA][D.sub.wet] and [DELTA][D.sub.air]) were negligibly small, which indicates even these biomolecules act as elastic membranes in the air phase (without aqueous solution). We obtained a good linear relationship between [(-[DELTA][F.sub.water])/ (-[DELTA][F.sub.air]) - 1], which is indicative of hydration and [DELTA][D.sub.water]/(-[DELTA][F.sub.air]) of proteins. The aforementioned values suggest that the energy dissipation of proteins was mainly caused by hydration and that proteins themselves are elastic molecules without energy dissipation in aqueous solutions. On the contrary, plots in cases of denatured proteins, DNAs, and pullulans were relatively deviant toward the large hydration and energy dissipation from the theoretical line as perfect elastic materials, meaning that the large energy dissipation occurs because of viscoelastic properties of denatured proteins, linear DNAs, and pullulans in the water phase, in addition to energy dissipation due to the hydration of molecules. These two parameters could characterize various biomolecules with structural properties in aqueous solutions.

A new gold-nanoparticle (AuNP)-based sensor for detecting Hg(II) ions in aqueous solution has been developed. Rhodamine B (RB) molecules that are highly fluorescent in bulk solution fluoresce weakly when they are adsorbed onto AuNP surfaces as a result of fluorescence resonance energy transfer and collision with AuNPs. In the presence of metal ions such as Hg(II), RB molecules are released from the AuNP surface and thus restore the florescence of RB. The modulation of the photoluminescence quenching efficiency of RB-AuNPs in the presence of Hg(II) ions can achieve a large turn-on fluorescence enhancement (400-fold) in aqueous solution, and the entire detection takes less than 10 min. We have improved the selectivity of the probe further by modifying the AuNP surfaces with thiol ligands (mercaptopropionic acid, mercaptosuccinic acid, and homocystine) and adding a chelating ligand (2,6-pyridinedicarboxylic acid) to the sample solutions. Under the optimum conditions, the selectivity of this system for Hg(II) over other metal ions in aqueous solutions is remarkably high (50-fold or more), and its LOD for Hg(II) in the matrix pond water is 2.0 ppb. Our approach demonstrated the feasibility of using the developed nanosensor for rapid determination of Hg(II) in aqueous environmental samples and in batteries.

Monte Carlo simulations are used to establish the potential of mean force between two globular proteins in an aqueous electrolyte solution. After fitting this potential to an analytic function, first-order perturbation theory to predict the phase behavior of aqueous lysozyme solutions that contain a specific electrolyte and it shows that interactions between a pair of lysozyme particles become more attractive when the 0.2M electrolyte changes from NaCl to NaI to NaSCN.

The three-phase electrooxidation of the N-vinylcarbazole monomer that is present only in the supporting electrolyte free-organic phase is described. The method allows the determination of the depth of penetration of anions from the aqueous phase into the organic phase and also allows the deposition of polymers of different forms such as collars, cylinders, and semicrystals.

Absorption, steady-state fluorescence and time-resolved fluorescence measurements are used to investigate the interaction of acridinedione dyes with urea and its derivatives in water and methanol. The hydrophobic interaction of dye with urea in aqueous solution predominates due to the weakening of the hydrogen bonding of the solvent and urea derivatives and the photoinduced electron transfer (PET) process is used as a marker to identify the hydrophobic interaction.

Carbon nanotube electrochemical transistors integrated with microfluidic channels are used to examine the effects of aqueous electrolyte solutions on the electron-transport properties of single isolated carbon nanotubes and also the pH and concentration supporting inert electrolytes. The pH-dependent charging of Si[O.sub.2] substrate is ruled out as the origin is based on measurements with suspended nanotube transistors, whereas increasing the ionic strength has led to reduce pH response.

A combined quantum mechanics/molecular mechanics (QM/MM) molecular dynamics simulations is used to study the structural and dynamical properties of N[O.sub.3.sup.-] in dilute aqueous solution. The analysis of the dynamics properties has indicated a better suitability of the HF method when compared to the B3LYP-density functional theory (DFT) approach.

Evidence of catalytic [O.sub.2] evolution from water induced by adsorption of [(O[H.sub.2])(terpy)Mn[([mu]-O).sub.2]Mn(terpy)(O[H.sub.2]).sup.3+], where terpy = 2,2':6 ,2'-terpyridine, onto solid clay is illustrated. It shows that the concentration and localization of [(O[H.sub.2])(terpy)Mn[([mu]-O).sub.2]Mn(terpy)(O[H.sub.2]).sup.3+] adsorbed on clay as well as the distance between anionic sites on clay statistically related to its cation exchange capacity are the important factors for the cooperative catalysis.

The freeze/thaw procedure is used to prepare the surfactant-containing poly(vinyl alcohol) (PVA) cryogels by drying and reswelling hydrogel patches in decyltrimethylammonium ([C.sub.10]TAB) aqueous solutions. It is shown that ([C.sub.10]TAB) micellization is unperturbed by the confinement of the surfactant molecules within the polymeric network of a freeze/thaw PVA hydrogel, and there is no direct surfactant-polymer interaction taking place.

A demonstration that the Pt nanoparticle catalyzed formation of gold nanoparticles in aqueous solution involves the mediation of H species preadsorbed on a Pt nanocrystal surface (Pt-H) is presented. The favorable dissociative adsorption of H2 on the Pt nanocrystal surface produces Pt-H species, which has a higher reducing power than H2 or acrylate in the solution for the reduction of Au[Cl.sub.4.sup.-].