NaCl Solutions Of Different Concentrations Research Articles

Electrochemical properties and stability of emulsifier-free polystyrene latexes in 1: 1 electrolyte solutions

The electrokinetic and adsorption characteristics of monodisperse emulsifier-free latexes of polystyrene (particle sizes of 0.25–0.40 μm) with surface carboxyl and sulfo groups are comprehensively studied depending on pH and the concentration of background NaCl solutions. The constants of surface carboxyl group dissociation and surface complexation, as well as the adsorption potentials of OH− and Na+ ions, are calculated. The stability of latex suspensions is investigated and the coagulating concentrations of NaCl and HCl solutions are determined. An analysis of the curves plotted for the pair interaction between latex particles at different concentrations of NaCl solutions suggests that the system possesses an additional stability factor, which is probably associated with polymer chains that protrude over the particle surface into a solution.

Hydrate film growth at the interface between gaseous CO2 and sodium chloride solution

Greenhouse gas CO2 has become a serious problem for human beings. The hydrate technology has been considered as a possible approach to sequester CO2. In this work, the lateral growth rates of a CO2 hydrate film in aqueous NaCl solutions of different concentrations were measured by means of suspending a single gas bubble in liquid. The results show that the film growth rates depended on not only the driving force, but also the NaCl concentration, and the film growth rates decreased with the increasing NaCl concentration. The simple relationship vf∝ΔT 5/2 could be used to correlate the hydrate film growth rate of a CO2 + NaCl + water system by introducing a NaCl concentration-dependent coefficient. The film thickness was investigated experimentally and evaluated theoretically; the results show that it became thicker at a higher NaCl concentration when the temperature and pressure were specified. In addition, a series of interesting phenomena, such as the occurrence of double hydrate films, were displayed and discussed.

Diffusion mechanism of sodium ions in compacted montmorillonite under different NaCl concentration

Compacted bentonite, the major mineral being montmorillonite, is a candidate buffer material for geological disposal of high-level radioactive waste. The diffusion behavior of radionuclides in the compacted montmorillonite is an important issue to be clarified for the safety assessment of geological disposal. In this study, one-dimensional, non-steady diffusion experiments using 22Na at different diffusion temperatures and the measurement of the basal spacings by XRD were conducted for Na-montmorillonite saturated with NaCl solutions of different concentrations. Some basal spacings of the montmorillonite were found to decrease from 1.88 to 1.56 nm as the NaCl concentration increased from 0 to 0.1 M. The apparent self-diffusion coefficients at 298 K obtained in this study slightly increased as the NaCl concentration increased from 0 to 0.5 M, while the activation energies, calculated from the temperature dependences of the diffusion coefficients, were found to be 14, 22, and 17 kJ mol −1 at NaCl concentrations of 0, 0.1, and 0.5 M, respectively. These NaCl concentration dependences of the diffusion coefficients and their activation energies can be explained by assuming three independent diffusion processes (diffusion in pore water, on external surface of montmorillonite, and in interlayer of montmorillonite).

Application of a multi‐channel zero‐resistance current amplifier for screening processes

AbstractIn addition to being a very useful monitoring technique, electrochemical noise analysis is also particularly suitable for screening purposes. A multi‐channel zero‐resistance current amplifier was designed in order to be able to carry out multiple noise measurements simultaneously, thus allowing a greater number of tests to be performed in a given time. Electrochemical noise measurements were carried out on AA 2024 in NaCl solutions of different concentrations and in the presence of inhibitors to highlight the practical relevance of this analytical method. The results show that the noise data can be evaluated in a simple and clear way using the noise charge.

A surface plasmon resonance interferometer based on spatial phase modulation for protein array detection

Thousands of kinds of proteins exist in a single cell. Proteomics research aims to characterize these proteins and simultaneously analyse modifications and interactions on a large scale. Here we present a label-free surface plasmon resonance (SPR) imaging interferometer based on spatial phase modulation, which can be useful in this field. It consists of a light source, a SPR sensing unit, a special phase modulator, a photoelectric conversion unit and a computer. Collimated light is projected into a prism and reflected at the gold–glass interface. The p- and s-polarized components of the reflected light pass through a one-dimensional beam expander and a Wollaston prism, and form an interference pattern on a CCD. Interference images are acquired and transferred to the computer for data processing. Protein interaction on the gold surface leads to a local refractive index change and results in interference fringe phase shift. By calculating the phase shift, interaction information can be obtained. It is demonstrated that this technique can detect different concentrations of NaCl solutions, and the phase change generated by a 0.9% NaCl solution is about 10°. In protein–protein interaction experiments, a model system of rabbit IgG and goat–anti-rabbit IgG is tested. The maximum phase change is up to 12°. The phase resolution of the system is 0.2°, equivalent to the refractive index resolution of 3 × 10−5 RIU, and this value can be improved to 2 × 10−6 RIU just by increasing the gold thickness of the sensing chip. It is concluded that the sensitivity of the interferometer is enough to achieve larger capacity than that detected by the present protein micro-array products. These results suggest that the SPR interferometer based on spatial phase modulation provides a potential facility to meet the requirements in proteomics research.

Investigation of the Salting Out of Methane from Aqueous Electrolyte Solutions Using Computer Simulations

We calculate the excess chemical potential of methane in aqueous electrolyte solutions of NaCl using Monte Carlo computer simulations. In a recent work [Docherty et al. J. Chem. Phys. 2006, 125, 074510], we presented a new potential model for methane in water which is capable of describing accurately the excess chemical potential of methane in pure water over a range of temperatures, a quantity that can be related to the solubility and which is commonly used to study the hydrophobic effect. Here, we use the same potential model for the water-methane interactions and investigate the effect of added salt on the chemical potential of methane in the solution. The methane molecules are modeled as single Lennard-Jones (LJ) interaction sites, and the water molecules are modeled with the TIP4P/2005 model. A correcting factor of chi = 1.07 for the energetic Berthelot (geometric) combining rule of the methane-water interaction is also used, which mimics the polarization of methane in water. We consider NaCl as the salt and treat the ions with the Smith and Dang model (i.e., as charged LJ interaction sites). Ion-water, ion-ion, and ion-methane interactions are treated using Lorentz-Berthelot combining rules. In addition, the Coulombic potential is used to model charge-charge interactions which are calculated using the Ewald sum. We have carried out isobaric-isothermal (NpT) simulations to determine the equilibrium densities of the solutions. The simulation data is in excellent agreement with experimental densities of aqueous NaCl solutions of different concentration. Hydration numbers are also obtained and found to be in agreement with reported data. Canonical (NVT) simulations at the averaged densities are then performed using the Widom test-particle insertion method to obtain the excess chemical potential of methane in the saline solutions. An increase in the chemical potential of methane, corresponding to a salting out effect, is observed when salt is added to the solution. We investigate different concentrations and ion sizes. An overprediction of the salting out effect as compared with experimental data is observed, which we believe is due to the polarizing effect of the ions in the solution, which is not taken into account by the model. We also find a direct correlation between the increase in the chemical potential and the packing fraction of the solution and argue that the main cause of the observed salting out effect (as represented by an increase in the excess chemical potential) is the increase in the packing fraction of the solutions due to the added salt. Together, with this, we put forward an argument toward explaining the anomalous Hofmeister effect of Li(+).

Copper redeposition and surface enrichment during the dissolution of Al‐Cu alloys in different concentrations of NaCl solution. Part 2 – spectroscopic analysis measurements

PurposeThe paper aims to examine the enrichment of Cu, and the type of attack occurring during the dissolution of Al‐3.84%Cu alloy in 0.5 M NaCl.Design/methodology/approachThe approach is to use scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDX) and solution analyses using atomic absorption spectrophotometry.FindingsExamination of the surface after five days of immersion showed that Cu clusters had concentrated around the edges of the specimens and two types of localized corrosion were evident, pitting corrosion and the intergranular attack, which were concentrated mainly around the Cu clusters and in the regions where a higher concentration of Cu was evident. After 80 days of immersion, the higher concentration of Cu was distributed over nearly the entire surface and its concentration differed from one site to another.Originality/valueThe analysis results of the study confirmed the mechanism of simultaneous dissolution.

Copper redeposition and surface enrichment during the dissolution of Al‐Cu alloys in different concentrations of NaCl solution. Part 1 – electrochemical measurements

PurposeThe paper aims to study the dissolution of Al, Al‐3.84%Cu, Al‐5.22%Cu and Al‐11%Cu alloys in different concentrations of NaCl (10‐5‐10‐1 M).Design/methodology/approachThe approach is to use open circuit potential (OCP) and potentiostatic polarization measurements.FindingsResults obtained showed that, as the Cu content was increased in the Al‐Cu alloys, a steady state potential was rapidly reached. Addition of different concentrations of CuCl2 to 0.5 M NaCl demonstrated that by increasing the concentration of CuCl2 up to 2 ppm a greater increase in the OCP towards more anodic value occurred from the moment of immersion. Further increases in the concentration of CuCl2, up to 600 ppm, exhibited the same behavior.Originality/valueThe results of the study reveal that cathodic current was controlled by the oxygen in solution, while the anodic current increased with increased Cu content in the alloy.

A Network-based Analysis of Polyanion-binding Proteins Utilizing Yeast Protein Arrays

The high affinity of certain cellular polyanions for many proteins (polyanion-binding proteins (PABPs)) has been demonstrated previously. It has been hypothesized that such polyanions may be involved in protein structure stabilization, stimulation of folding through chaperone-like activity, and intra- and extracellular protein transport as well as intracellular organization. The purpose of the proteomics studies reported here was to seek evidence for the idea that the nonspecific but high affinity interactions of PABPs with polyanions have a functional role in intracellular processes. Utilizing yeast protein arrays and five biotinylated cellular polyanion probes (actin, tubulin, heparin, heparan sulfate, and DNA), we identified proteins that interact with these probes and analyzed their structural and amino acid sequence requirements as well as their predicted functions in the yeast proteome. We also provide evidence for the existence of a network-like system for PABPs and their potential roles as critical hubs in intracellular behavior. This investigation takes a first step toward achieving a better understanding of the nature of polyanion-protein interactions within cells and introduces an alternative way of thinking about intracellular organization.

Transfer of 226Ra, 85Sr and 137Cs from milk to milk products</p> </p>

Transfer of 226Ra, 85Sr and 137Cs from cow and sheep milk to various Syrian dairy products has been evaluated. Dairy products include Kashkivan cheese, braided cheese, Haloom cheese, Sircassian cheese, liquid cheese, native cheese, cottage, thick yogurt, butter and milk cream. The results showed that the percentage of 226Ra, 85Sr and 137Cs transferred from cow milk to milk cream (Pt=food processing retention factor´processing efficiency´100%) has reached 32%, 16% and 7%, respectively. Butter and liquid cheese were found to have the lowest percentage of transferred 226Ra, 85Sr and 137Cs. Most of the obtained Pt values of the studied radionuclides in thick yogurt were relatively low in spite of the high processing efficiencies of thick yogurt. Moreover, the transfer, Pt, of the studied radionuclides from cow milk to the prepared cheese was higher than those values determined for sheep milk. This is due to differences in chemical compositions of each type of milk. On the other hand, the treatment of Native cheese, most commonly consumed cheese in Syria, with different concentrations of NaCl solutions showed that 137Cs was completely removed from cheese soaking in 5% NaCl solution (soaking time of 48 hours), while 40% of 226Ra and 80% of 85Sr were also decontaminated using 0-2.5% NaCl solutions and soaking time of 48 hours. Based on the obtained results, industrialization processes of the dairy products that resulted the removal of radionuclides have been identified.

Effect of Salt Stress on the Regulation of Maize (Zea mays L.) Genes Involved in Polyamine Biosynthesis

A cDNA for spermidine synthase (SPDS), which converts putrescine to the higher polyamine spermidine using decarboxylated S-adenosylmethionine as a cofactor, was isolated from Zea mays leaves (Zmspds2A). Comparison of the deduced amino acid sequence revealed a high homology (81.9%) with Oryza sativa SPDS2. RT-PCR analyses showed that Zmspds2A was equally expressed in leaves, stem and roots. In contrast, transcripts of other genes related to polyamine biosynthesis (Zmodc, adc and samdc) showed tissue-specific regulation. The effect of salt stress on the expression of all these genes in maize leaves exposed to NaCl solutions of different concentrations was analysed. Our results showed that only Zmodc and Zmspds2A were up-regulated by salt stress; whereas the other two genes were barely affected by this treatment. In addition to Zmspds2A, a second transcript encoding a maize spermidine synthase (Zmspds2B) that also became up-regulated by salt stress, was identified. Comparison of partial cDNA sequences of transcripts Zmspds2A and Zmspds2B with the corresponding genomic DNA region revealed the existence of alternative splicing mechanism, opening a new aspect in plant polyamine biosynthesis modulation under abiotic stress.

Refractive index and concentration sensing of solutions using mechanically induced long period grating pair

We demonstrate the use of a pair of mechanically induced long period gratings (LPGs) for sensing the refractive index and concentration of liquids for which NaCl solutions of different concentrations and standard refractive index liquids are studied. The effect of varying the refractive index and/or concentration is reflected in changing output power loss values at resonance wavelengths. For a concentration change from 5 to 20 g per 100 ml, the maximum variation detected in optical output power is 20 pW, while for a refractive index variation from 1.446 to 1.458, it is 11 pW. These studies are quite useful for chemical, pharmaceutical, biological, and process control sensing applications.

Quantifying the effect of membrane potential in chemical osmosis across bentonite membranes by virtual short-circuiting

Clay liners are charged membranes and show semipermeable behavior regarding the flow of fluids, electrical charge, chemicals and heat. At zero gradients of temperature and hydrostatic pressure, a salt concentration gradient across a compacted clay sample induces not only an osmotic flux of water and diffusion of salt across the membrane but also an electrical potential gradient, defined as membrane potential. Laboratory experiments were performed on commercially available bentonite samples in a rigid-wall permeameter connected to two electrically insulated fluid reservoirs filled with NaCl solutions of different concentrations and equipped with Ag/AgCl electrodes to measure the electrical potential gradient. The effect of membrane potential could be cancelled out by short-circuiting the clay with the so-called virtual shortcut. The potential gradient across the sample is brought to zero with a negative feedback circuit. It was observed that the water flux and the diffusion of Cl − were hindered by the occurrence of a membrane potential, indicating that an electroosmotic counterflow is induced. Flow parameters were calculated with modified coupled flow equations of irreversible thermodynamics. They were in excellent agreement with values reported in the literature. Comparing the method of short-circuiting with a study elsewhere, where the electrodes were physically short-circuited, it was shown that the virtual shortcut is more appropriate because physically short-circuiting induces additional effects that are attributed to the fluxes.

Titration of poly(dA-dT) . poly(dA-dT) in solution at variable NaCl concentration.

CD and uv absorption data showed that high molecular weight poly(dA-dT) . poly(dA-dT), at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions of different concentrations, ranging from 0.005 to 0.600M. Similarly, titration of the polynucleotide with a strong base causes duplex-to-single strands transition. The base- and acid-induced transitions were both reversible by back-titration (with an acid or, respectively, with a base): the apparent pKa were the same in both directions. However, the number of protons per titratable site (adenine N1) required to reach half-denaturation was in great excess over the stoichiometric value; to a much larger extent, the same effect was observed also for the deprotonation of the N3H sites of thymine. Moreover, in the basic denaturation experiments, at low salt concentrations ([NaCl]< or =0.300M) less acid than calculated was needed to back-titrate the base excess to half-denaturation. Both effects could be qualitatively justified on the basis of the counterion condensation theory of polyelectrolytes and considering the energy barrier created by the negatively charged phosphodiester groups to the penetration of the OH- ions inside the double helix and the screening effect of the Na+ ions on such charges, in the deprotonation experiments.

Carbonate dissolution and precipitation in coastal environments: Laboratory analysis and theoretical consideration

We have conducted laboratory experiments to examine CaCO3 dissolution and precipitation in saltwater‐freshwater mixing zones, with a view to understanding and predicting porosity changes in coastal environments. Mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments. We used artificial seawater and NaCl solutions of different concentrations under different CO2 partial pressures and with different mixing ratios. Two‐dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used to measure calcium carbonate precipitation and dissolution, respectively. An important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation/dissolution that results from the nonlinear dependence of CaCO3 saturation upon electrolyte concentration. The theory demonstrates that the rate of dissolution or precipitation depends on the curvature (and sign) of the solubility as a function of salinity, the square of the salinity gradient, and the macroscopic dispersion coefficient. The theory is largely scale independent and depends upon field parameters that can be determined. Analysis of data from three field sites (Yucatan peninsula, Bermuda, and Mallorca) demonstrates excellent agreement between field observations and theory.

Characterization of PSII photochemistry and thermostability in salt-treated Rumex leaves

A study was conducted, using chlorophyll fluorescence, rapid fluorescence induction kinetics, and polyphasic fluorescence transients, to determine the effect of salt treatment and heat stress on PSII photochemistry in Rumex leaves. Salt treatment was accomplished by adding NaCl solutions of different concentrations ranging from 50 to 200 mmol/L. Heat stress was induced by exposing the plant leaves to temperatures ranging from 29 to 47 degrees C. The control plants were grown without NaCl treatment. The data acquired in this study showed that NaCl treatment alone had no effect on the maximal photochemistry of PSH or the polyphasic rise of chlorophyll fluorescence. However, the NaCl treatment modified heat stress on PSII photochemistry in Rumex leaves, which was manifested by a lesser heat-induced decrease in photochemical quenching (qP), efficiency of excitation energy capture by open PSII reaction centers (Fv'/Fm'), and quantum yield of PSII electron transport (phiPSII). The data also showed that NaCl treatment compromised the impact of heat stress on the capacity of transferring electrons from Q(A)- to Q(B). Furthermore, the NaCl treatment promoted heat resistance of O2-evolving complex (OEC). In summary, NaCl treatment enhanced the thermostability of PSII.

EFFECT OF WATER SALINITY ON SEEDS-GERMINATION OF OCIMUM BASILICUM L., ERUCA SATIVA L. AND PETROSELINUM HORTENSE HOFFM.

Seeds-germination is among all physiological processes one of the most sensitive to stresses. The use of brackish water can slow down the water absorption of seeds and consequently all processes linked with the use of reserves of nutrients and the development of embryos. Laboratory experiments have been carried out to study the effects of salinity on basil (Ocimum basilicum L.), rocket (Eruca sativa L.) and parsley (Petroselinum hortense Hoffm.) germination. Standard germination techniques have been employed using Petri dishes containing filter paper saturated with 11 different concentrations of NaCl solutions, varying from 0 to 10 mS cm-1. It appears that salinity has not significantly reduced germination percentages of basil and rocket. The parsley has turned out to be less tolerant thus showing a connection between germination percentages decreases and salinity increases. Mean germination time has proved to be more directly influenced by water salinity. Higher levels of water EC have significantly delayed the seeds-germination of basil, rucole and parsley.

Streaming potential through and on ultrafiltration membranes: Influence of salt retention

The pore size distribution of a polysulfone membrane has been obtained from computerised image analysis of scanning force microscopy pictures. The streaming potential on the active layer of this membrane has been measured when it is in contact with aqueous NaCl solutions of different concentrations. Finally, NaCl retention has been taken into account to allow the translation of measured electric potential to the actual streaming potentials through the membrane. It has been shown that it is possible if the diffusion potentials appearing through both the concentration polarisation and the membrane itself are taken into account. By a fitting procedure, the effective transport numbers are obtained, which prove to be adequate not only for high concentrations, when there is no significative electrical double layer overlapping, but also for all the concentrations range used leading to the same streaming potential than measured on the membrane. The so-obtained effective cation transport numbers are not equal to the free solution true transport numbers that are defined when no pressure is applied. They are very similar for the cation and the anion, what should be caused by the applied pressure that should make their mobilities almost equal. Only a little contribution from the diffusion potentials, caused by retention without a relevant separation of the ions, should remain.

Determination of the changes of the basic structures of silica species in dependence on the concentration of sodium chloride by FAB-MS

The chemical species of silica in NaCl solutions of different concentrations were identified by FAB-MS (fast atom bombardment mass spectrometry). The basic structures of silica species, such as cyclic pentamer (Si5 (OH)9O6-), linear pentamer (Sis(OH)11O5-), cyclic hexamer (Si6(OH)9O8-, Si6(OH)11O7-) and linear hexamer (Si6(OH)14 O6-), were identified, in addition to dimer (Si2(OH)5O2-), trimer (Si3(OH)7O3-) and cyclic tetramer (Si4(OH)7O5-). The patterns of changes of the peak intensities of the silicate complexes relative to the dimer with increasing NaCl concentration were classified into two types: that represented by linear silicate complexes and the other by cyclic silicate complexes. The differences in the type of chemical species and their changes according to the NaCl concentration reflect the number of bonds necessary for polymerization and hydrolysis of the silica complexes. The differences between the linear and the cyclic silicate type have some implications on the dissolution mechanism of silicate complexes, the hydration of the molecules and the equilibrium between solubility, hydrolysis, polymerization and the salting-out effect in NaCl solution.

Corrosion-Fatigue Behavior of an Annealed AISI 1045 Carbon Steel Coated with Electroless Nickel-Phosphorus

The influence of an industrial electroless nickel-phosphorus deposit on the corrosion-fatigue properties of an annealed AISI 1045 steel has been investigated. For this purpose, three corrosive media were selected: distilled water and two NaCl solutions of different concentration (3 and 5%) in distilled water. Corrosion-fatigue tests were conducted at alternating stress levels ranging between 219 and 329 MPa at a frequency of 50 Hz. The corrosion-fatigue properties of the coated and uncoated substrates are very similar when testing is conducted in salty water. However, for testing in distilled water the corrosion-fatigue properties of coated substrates were diminished in relation to the uncoated material. The fractographic analysis of the fracture surfaces revealed the presence of fatigue marks within the electroless nickel-phosphorus deposit, which indicate that the fracture mechanism of the coating is associated to the cyclic loading of the material.