Aquaeous Solution Research Articles

Magnetic Properties and Electrical Conductivity of NiFe2O4-MWNT/PVA Nanocomposite Films

Synthesis and characterization of NiFe2O4-MWNT/PVA nanocomposite films have been performed. NiFe2O4-MWNT as a filler of nanocomposite films was gained using a simple mixing method from an aquaeous solution containing Fe(NO3)3.9H2O, Ni(NO3)2.6H2O and MWNT. A wet paste-like filler was first characterized by Raman spectroscopy to confirm the presence of NiFe2O4 phase. Refering to the result of Raman spectra, it was known that nanocrystalline nickel ferrite (NiFe2O4) have been successfully synthesized.The morphological investigations using scanning electron microscopy (SEM) and energy dispersive spectroscopic (EDS) revealed that the filler has hair-like structure which correspond to the carbon nanotube with the results of atomic percentage ratio of Fe/Ni correspond to the phase formation of NiFe2O4. Nanocomposite films were made in 4 various concentrations (5, 10, 20, and 50 %vol filler) have been characterized in order to investigate their magnetic properties and electrical conductivity by using vibrating sample magnetometer (VSM) and Inductance-Capacitance-Resistance (LCR) meter. Based on magnetization hysteresis curves, the variation of filler addition has increased the magnetic properties of nanocomposite samples from diamagnetic into paramagnetic. It was also known that the electrical conductivity enhanced align with the increasing consentration of the filler in nanocomposite films.

Activated Carbons From KOH-activation Of Salacca Peels As Low Cost Potential Adsorbents For Dye Removal

Salacca peel was used to prepare activated carbon (AC) by chemical activation with potassium hydroxide (KOH). The activated carbon with the largest surface area and most developed porosity was then used in the batch adsorption experiments of methylene blue (MB). Activated carbons with a surface area of around 1939 m 2 /g were obtained. The adsorption equilibrium and kinetics of MB dyes from aquaeous solution on AC were also investigated. Adsorption isotherms of MB were correlated with the Langmuir, Freundich, Dubinin Radushkevich and Tempkin equations, and the heat of adsorption was determined. It was revealed that the Langmuir adsorption equation was more appropriate to represent the adsorption procedure of MB dyes compared to the other equations. Two simplified kinetic models including pseudo first- order and -second-order equations were used to evaluate the adsorption processes. The results indicated that the adsorption of MB dyes could be described properly by a pseudo-second-order equation. The kinetic parameters of this model were calculated and discussed.

Structural Preferences of Neuroprotective S14G-Humanin Peptide Analyzed by Molecular Modeling and Circular Dichroism

S14G-humanin (S14G-HN) is one of the latest of a new family of neuropeptides with protective action against Alzheimer's disease insults. The structure of S14G-HN was studied with both spectroscopic techniques and molecular dynamics simulation. Secondary structure predictions and modeling of backbone conformation were carried out. Side chain reconstruction, homology modeling and molecular dynamics (MD) simulations were performed on four different models. A beta strand tendency in residues 5 to 10 and a propensity to adopt turn or irregular conformation in residues 13 to 17 was found. Circular dichroism experimental studies of S14G-HN in aquaeous solution and in different 2,2,2-trifluoroethanol (TFE) concentrations were also performed. In the absence of TFE and at low TFE concentrations, CD spectra are indicative of a small degree of ordering in the peptide. On further increment of TFE concentration, changes occur that indicate the formation of a structured conformation. Both experimental and computational results indicate that S14G-HN has a reduced helical propensity, in contrast with wild type humanin, as well as a higher conformational flexibility.

Osteryoung Square Wave Voltammetric Determination of Phenazopyridine Hydrochloride in Human Urine and Tablet Dosage Forms Based on Electrochemical Reduction at Carbon Paste Electrode

An electroanalytical method was developed for the direct quantitative determination of phenazopyridine hydrochloride (PAP) or in other words, pyridium, in spiked human urine and tablet dosage forms. The electrochemical reduction and determination of PAP were carried out at carbon paste electrode (CPE) in various aquaeous solution in the pH range of 0.5-12.30 by (CV) and osteryoung square wave voltammetry (OSWV). The best results were obtained for the quantitative determination of PAP by OSWV method in 0.5 mol L-1 sulfuric acid at about pH 0.51. The peak current and peak potential depend on pH and scan rate were studied. The diffusion controlled nature of the peak was established. This electroanalytical procedure made it possible to determine PAP in the concentration range 2.5x10-8-2.5x10-6 mol L-1. Limit of detection (LOD) and limit of quantification (LOQ) were obtained as 7.5x10-9 and 2.5x10-8 mol L-1 respectively. Precision and accuracy of the developed method were checked by recovery studies in spiked urine and tablet dosage forms.

Heterogeneous phase equilibria as a basis for crevice corrosion modelling

The presented crevice corrosion model is intended to provide basic understanding of formation and dissolution of passivating layers during time dependent metal dissolution in an already deoxygenated crevice. It operates along a constant cathodic polarization curve in subsequent time steps with time dependent anodic polarization curves and corrosion currents. The anodic polarization curves are determined by dissoluted ionic chromium and respective Nernst potentials as well as by the mass of precipitated passivating chromiumhydroxide layers. All chemical reactions including diffusion of chloride into the model crevice configuration are assumed to be at equilibrium during the respective time steps. The amounts of passivating chromiumhydroxide masses are determined by lever‐rule application at increasing chromium and chloride contents in aquaeous solution of the quaternary water‐chromium‐hydrogen‐chloride phase diagram at various Nernst potentials. For this purpose, the established water–chromium Pourbaix diagram had to be redrawn in terms of ternary water‐chromium‐hydrogen phase diagrams for constant potentials. It was tentatively extended to the quaternary chloride including diagram based on literature results. This included solubility of chromiumchloride in hydrochloric acid and most probable effects of chloride ions on chromiumhydroxide solubility at saturation with chromium metal. The results of the interactive corrosion process are based on a crevice geometry drawn from previous publications and given initial solution concentrations as well as assumed polarization curves for time steps of one second. It is shown, how the process starts with concentration changes of chromium, chloride and hydrogen in the crevice, the subsequent formation of the passive layer and the corresponding decrease in the corrosion current and increase in the mixed potentials. In the presence of the chromiumhydroxide phase, however, chromium and hydrogen remain at low levels in the equilibrium aqaeous solution while chloride is increasing. The saturated solution reaches the four phase equilibrium concentration including saturation by chromium, chromiumhydroxide and chromiumchloride at corresponding Nernst potentials. The further increase in total chromium and chloride concentrations of the crevice then leads to initiation and propagation of crevice corrosion by formation of non‐passivating chromiumchloride at the expence and finally, the total dissolution of passivating chromiumhydroxide, at decreasing mixed potentials and increasing currents. Due to the low solubility of chromiumchloride in hydrochloric acid, the latter is finally formed with the result of the well‐known increase in crevice acidity. Thus, it is demonstrated that the acidification itself is not a requirement for crevice corrosion but rather a consequence of it.

The FLG motif in the N-terminal region of glucoprotein 41 of human immunodeficiency virus type 1 adopts a type-I beta turn in aqueous solution and serves as the initiation site for helix formation.

NMR and CD studies were carried out on a peptide representing the hydrophobic N-terminal domain of envelope glycoprotein of human immunodeficiency virus type-1 in solutions of varying polarity. It was found that in aquaeous solution the amide proton of glycine in the FLG motif resonated at a considerably high field and its chemical shift, within the limit of experimental precision, had a temperature coefficient of zero in the range studied. The upfield shift of NH of the glycine could be largely attributed to the ring-current effect of phenylalanine in the FLG motif that participated in a type-1 beta turn with a short Cbeta(i)-NH(i+2) distance. The slower proton-deuterion exchange for the glycine amide proton relative to that of other glycines was consistent with a folded structure for the motif in aquaeous solution. Results of the molecular simulation showed that this proton was shielded from the solvent by non-polar side chains of the amino acid residues surrounding the turn stabilized by hydrophobic interactions, thus explaining the zero temperature coefficient of the proton chemical shift. The structural stabilizing effect of the hydrophobic interaction was supported by the behavior of the proton in less polar Me2SO solution, in which the anomaly in the chemical shift and its temperature coefficient was less prominent. Detailed secondary-structure analysis suggested that the beta turn of the FLG motif may act as an initiation core for helix formation, probably because the turn readily transforms into helical form.

A combined density functional and molecular dynamics simulation of a quantum water molecule in aqueous solution

A combined ab initio density functional and classical molecular dynamics simulation is carried out for a quantum water molecule in aquaeous solution. The dipole moment and ground state energy are obtained for SPC and TIP3P water models. Both local spin density and Perdew nonlocal functionals are used in our calculation. The calculated dipole moment and potential energy agree well with experimental and other theoretical results.

Intercomparison of particle size spectrometers

METHODS The performance to assess the particle size distr ibut ion of a polydisperse aerosol of four low pressure impactors (LPI) and three optical particle counters (OPC) was studied. The ins t rumen t s used are listed in table 1. The polydisperse aerosol was produced by nebulizat ion of an aquaeous solution of sodiumbisulfite. A uniform mass concentrat ion of 0.5 m g m -3 was main ta ined in a 20 m 3 chamber vent i la ted wi th a flow rate of 320 m 3 h 1. The concentrat ion varied less t h a n 4 % as indicated by an automat ic mass sensor (TSI Microbalance Model 5000) and filter samples. The mass of the particles sampled with the impactors was evaluated by PIXE analysis of sulfur (Proton Induced X-ray Emission; Hietel and Tschiersch, 1988) and gravimetry as indicated in table 2 and figure 1. The four impactor samples were t aken wi thin a 3 hour period.

Addition compounds of bis(trifluoromethyl)mercury with tetraphenylphosphonium and tetraphenylarsonium halides and thiocyanates

Addition compounds of Hg(CF 3) 2 with [Ph 4P]X and [Ph 4As]X in the 1:1 ratio for X = Cl, Br, I as well as in the 1:2 ratio for X = SCN, were isolated from aquaeous solution and identified by elemental analysis and infrared spectroscopy. Molar conductance of the thiocyanate compounds in nitrobenzene solution points to its complex-salt nature defined as [Ph 4P] 2[Hg(CF 3) 2(SCN) 2] and [Ph 4As] 2[Hg(CF 3) 2-(SCN) 2], but not for the halide compounds. However, in the monoclinic crystals of the chloride ccompound, as shown by X-ray diffractometry, pairs of [Hg(CF 3) 2 molecules are bridged over by two chlorides in a centro-symmetrical dimer with the CHgC bond angle of 160.5(8)° and the Hg…Cl bond length of 2.823(3) and 2.837(4) Å. The structure was refined to the R factor of 0.053. When X = CN no addition compounds were obtained, the reaction products were HCF 3 and the complex salts [Ph 4P] 2- [Hg(CN)] 4 and [Ph 4As] 2[Hg(CN)] 4, not described so far.

Quantitative polarization microscopy demonstration of collagen type I and type III in histologic paraffin sections

The industrial dye Solophenyl Red 3 BL (Ciba-Geigy) dissolved in a saturated aquaeous solution of picric acid has proved suitable for differentiating between collagen types I and III in histological sections. When examined under polarization microscopy, type I fibers are radiant orange while type III fibers are green. Using 5 micron paraffin sections, an optimal staining procedure was determined: sections were first stained with Resorcin Fuchsin for elastic fibers and with Celestin Blue/Mayer's Hematoxylin for nuclear structures. The staining was then completed with 0.1 g Solophenyl Red/100 ml saturated aqueous solution of picric acid for 60 min at a pH value of 1.25. It was shown that the dye stained collagen selectively. With the aid of a photomultiplier, the spectral distribution of a series of lung sections adequately stained according to the optimized procedure was carried out using a monochromator and an interference filter, respectively. Both methods yielded identical peaks at 590 nm for the orange colored light of collagen type I and 490 nm for the green light of collagen type III. Application of appropriate filters permitted the intensity of the orange and green light at 590 nm and 490 nm to be measured. Long postmortem intervals did not affect the measured values. Quantitative inferences on the ratio of collagen I to collagen III could then be deduced from the ratio of the intensity of orange to green light. This index I/III is often applied in the diagnosis of discrete fibrotic changes in various organs.

ChemInform Abstract: Raman Spectra and Molecular Conformation of 2,4,4‐Trimethyl‐2‐pentanethiol as a Model Compound of a Hydrophobic Group of Triton X‐100 Surfactant.

Abstract Raman spectra of 2,4,4-trimethyl-2-pentanethiol were measured. The spectral analysis with the normal coordinate treatment indicated that this molecule takes the gauche conformation about the CCCS bond in the solid state and the trans and gauche conformations in the liquid state. The Raman bands due to the totally symmetric C&.zdbnd;C streching vibration of the t-butyl part of the 1,1,3,3-tetramethylbutyl group were found to be important to distinguish the two conformations. These key bands were applied to the interpretation of the Raman spectra of Triton X-100 surfactant which contains the p -(1,1,3,3-tetramethylbutyl)phenoxyl group as a hydrophobic moiety. The 1,1,3,3-tetramethylbutyl group of Triton X-100 molecules is shown to be predominantly in the gauche conformation in the liquid state and in aquaeous solution.

Raman spectra and molecular conformation of 2,4,4-trimethyl-2-pentanethiol as a model compound of a hydrophobic group of triton X-100 surfactant

Raman spectra of 2,4,4-trimethyl-2-pentanethiol were measured. The spectral analysis with the normal coordinate treatment indicated that this molecule takes the gauche conformation about the CCCS bond in the solid state and the trans and gauche conformations in the liquid state. The Raman bands due to the totally symmetric C&.zdbnd;C streching vibration of the t-butyl part of the 1,1,3,3-tetramethylbutyl group were found to be important to distinguish the two conformations. These key bands were applied to the interpretation of the Raman spectra of Triton X-100 surfactant which contains the p-(1,1,3,3-tetramethylbutyl)phenoxyl group as a hydrophobic moiety. The 1,1,3,3-tetramethylbutyl group of Triton X-100 molecules is shown to be predominantly in the gauche conformation in the liquid state and in aquaeous solution.

The complex formation of Cu(II) with triethanolamine in aqueous solution

The complex formation of Cu(II) ion with triethanolamine in aquaeous solution was studied by means of ESR spectroscopy. All detected species have a ligand-to-metal ratio one to one. Dimeric species have been found at neutral and basic pH. Values for the stability constants are given, log β 110 = 4.3, log β 11−1 = −1.9, log β 11−2 = −9.7, log β 22−2 = −1.1, log β 22−3 = −8.2, log β 22−4 = −16.2, and compared with those obtained in a potentiometric study. Deprotonation of hydroxyl groups of the ligand and formation of chelates is proposed from the results of 1H NMR spectroscopy.

Subsitution reactions of methylbis(dimethylglyoximato)rhodium(III) as a function of pH

The kinetics of axial ligation by pyridine of Ch 3Rh(DH) 2H 2O and the reverse hydrolysis reactions were studied in aquaeous solution as a function of pH. The kinetic data indicate that the lability of this complex is strongly influenced by the extent of protonation of the equatorial chelating ring, both the doubly protonated Ch 3Rh(DH 2)(DH)L + and the deprotonated Ch 3Rh(DH 2)(DH)L − species being more reactive than the species Ch 3Rh(DH) 2L, containing intact intramolecular hydrogen bonds. A comparison is made with the behaviour of the analogous Co(III) complexes.

A study of etching conditions and resolution power of plastic detector CR-39

Two Pershore Stacks (32 h cure cycle and 1% DOP and 96 h cure cycle and no additive) have been exposed to the Berkeley Bevalac Argon beam at 285 MeV/nuc and 425 MeV/nuc, respectively. Optimum etching conditions have been found to be 70°C temperature and 18 h etching time in 6.25 N OHNa aquaeous solution, corresponding to a mean bulk etch rate V B = (1.37±0.09) μm/h. The charge and mass resolution power of the detector has been evaluated as ΔZ ≈ 0.3 e and ΔA ≈ 2 a.m.u..

Correction - Analytical Study of the Phosphorescence of Purines in Aquaeous Solution at 77° K.

Correction - Analytical Study of the Phosphorescence of Purines in Aquaeous Solution at 77° K.