Constant Water Concentration Research Articles

With No Lysine (K) Kinases and Sodium Transporter Function in Solute Exchange with Implications for BP Regulation as Elucidated through Drosophila.

Like other multicellular organisms, the fruit fly Drosophila melanogaster must maintain homeostasis of the internal milieu, including the maintenance of constant ion and water concentrations. In mammals, the with no lysine (K) (WNK)-Ste20-proline/alanine rich kinase/oxidative stress response 1 kinase cascade is an important regulator of epithelial ion transport in the kidney. This pathway regulates SLC12 family cotransporters, including sodium-potassium-2-chloride, sodium chloride, and potassium chloride cotransporters. The WNK-Ste20-proline/alanine rich kinase/oxidative stress response 1 kinase cascade also regulates epithelial ion transport via regulation of the Drosophila sodium-potassium-2-chloride cotransporter in the Malpighian tubule, the renal epithelium of the fly. Studies in Drosophila have contributed to the understanding of multiple regulators of WNK pathway signaling, including intracellular chloride and potassium, the scaffold protein Mo25, hypertonic stress, hydrostatic pressure, and macromolecular crowding. These will be discussed together, with implications for mammalian kidney function and BP control.

Determining buffering capacity of polydimethylsiloxane-based passive dosing for hydrophobic organic compounds in large-volume bioassays

Polydimethylsiloxane (PDMS) is the most widely used material for passive dosing. However, the ability of PDMS to maintain constant water concentrations of chemicals in large-volume bioassays was insufficiently investigated. In this study, we proposed a kinetic-based method to determine the buffering capacity of PDMS for maintaining constant water concentrations of hydrophobic organic contaminants (HOCs) in large-volume bioassays. A good correlation between log Kow and PDMS-water partitioning coefficients (log KPW) was observed for HOCs with log Kow values ranging from 3.30 to 7.42. For low-molecular-weight HOCs, volatile loss was identified as the primary cause of unstable water concentrations in passive dosing systems. Slow desorption from PDMS resulted in a reduction of water concentrations for high-molecular-weight HOCs. The volume ratio of PDMS to water (RV) was the key factor controlling buffering capacity. As such, buffering capacity was defined as the minimum RV required to maintain 90% of the initial water concentration and was determined to be 0.0076–0.032 for six representative HOCs. Finally, passive dosing with an RV of 0.014 was validated to effectively maintain water concentrations of phenanthrene in 2-L and 96-h toxicity tests with adult mosquitofish. By determining buffering capacity of PDMS, this study recommended specific RV values for cost-efficient implementation of passive dosing approaches in aquatic toxicology, particularly in large-volume bioassays.

Analytical and numerical investigation of water diffusion through Raffia vinifera pith

ABSTRACT This work aims to develop analytical and numerical approaches for predicting the water diffusion through raffia vinifera pith using Fick’s law. A representative elementary volume consisting of a fiber surrounded by a layer of natural matrix is considered. Assuming that the physical properties of fiber and matrix are constant, the resulting equations are solved analytically by the separation of variables method and numerically by finite difference method. A constant water concentration is imposed at the external surface of material while the continuity of the moisture and flux is applied at the fiber/matrix interface. To test the computational results, physical properties of the two layers are set equal. The experimental solutions in this case are used as the reference results, and the present computational method results are compared. Results demonstrate that the maximum value of the relative error is less than 6.5% for numerical and 11% for analytical methods. The case of two layers with different physical properties is examined. Results indicate that the heterogeneity of raffia vinifera pith reduces considerably the water absorption in the fiber. This study can be applied to composite materials where the polymers are combined to natural fibers to achieve high mechanical properties of materials.

A new application with characterized oil-in-water-in-oil double emulsions: Gelatin-xanthan gum complexes for the edible oil industry

A novel oil-in-water-in-oil (O1/W/O2) double emulsion (DE) system was successfully created to decrease the saturated fat content. DEs stabilized with gelatin (GL), xanthan gum (XG), and solid fat crystals were generated using a two-stage emulsification process. Primary emulsions (PEs) containing 60 g/100 g and 20 g/100 g sunflower oil (SFO) were prepared with constant GL (at 1 g/100 g) and XG (at 0.6 g/100 g and 1.4 g/100 g) of the total emulsion, respectively. DEs at constant water concentrations containing SFO at 30, 38.3, 46.7, and 55 g/100 g and different water concentrations at 30, 40, 45, and 60 g/100 g were examined. The DE microstructure showed that SFO was encapsulated in internal water droplets, which were stabilized by interfacial accumulation of fat crystals. The hardness value of the DEs decreased from 13.40 to 3.42 N with increasing SFO. Amplitude and frequency sweep tests revealed a weak gel structure and elastic behavior of DEs. In addition, a decrease in gel stiffness was observed with an increase in SFO and water content. The results of the present study effectively demonstrated a new approach applicable for the edible oil industry, formulating O1/W/O2 DEs using a natural emulsifier (GL) and a stabilizer (XG).

Microwave and conventional treatment of low-cement high-alumina castables with different water-to-cement ratio; Part II. Dehydration

Modern refractory castables contain between 3.5 and 5 wt.-% water that is necessary for sufficient flow during emplacement and for the formation of hydrate phases, necessary for the green strength of the material. Prior to the high temperature use of this material, it must be dried very carefully to avoid explosive spalling.This paper will demonstrate that beside conventional drying of pre-shaped materials in resistance furnaces microwave radiation is an energy saving and rapid method to remove pore water as well as hydrate bond water from the castable. In comparison to resistance furnaces, the use of microwave radiation does not affect the castable properties as there are mechanical strength (MOR, CCS), open porosity and pore size distribution. This study proved microwave radiation as valuable alternative with a series of tabular alumina based low cement castables (LLC) in which the water-to-cement-ratio (wcr = 0.64, 0.75, 0.82 and 1.13) was systematically altered by changing the cement concentration at constant mixing water concentration of 4.5%.

Modeling of bubble‐size distribution in water and freon co‐blown free rise polyurethane foams

ABSTRACTA model has been developed to simulate the foam characteristics obtained, when chemical (water) and physical (Freon) blowing agents are used together for the formation of polyurethane foams. The model considers the rate of reaction, the consequent rise in temperature of the reaction mixture, nucleation of bubbles, and mass transfer of CO2 and Freon to them till the time of gelation. The model is able to explain the experimental results available in literature. It further predicts that the nucleation period gets reduced with increase in water (at constant Freon content), whereas with increase in Freon (at constant water) concentration nucleation period decreases marginally leading to narrower bubble‐size distribution. By the use of uniform sized nuclei added initially, the model predicts that the bubble‐size distribution can be made independent of the rate of homogeneous nucleation and can, thus, offer an extra parameter for its control. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40745.

Assessment of relative potential for Legionella species or surrogates inhalation exposure from common water uses

The Legionella species have been identified as important waterborne pathogens in terms of disease morbidity and mortality. Microbial exposure assessment is a tool that can be utilized to assess the potential of Legionella species inhalation exposure from common water uses. The screening-level exposure assessment presented in this paper developed emission factors to model aerosolization, quantitatively assessed inhalation exposures of aerosolized Legionella species or Legionella species surrogates while evaluating two generalized levels of assumed water concentrations, and developed a relative ranking of six common in-home uses of water for potential Legionella species inhalation exposure. Considerable variability in the calculated exposure dose was identified between the six identified exposure pathways, with the doses differing by over five orders of magnitude in each of the evaluated exposure scenarios. The assessment of exposure pathways that have been epidemiologically associated with legionellosis transmission (ultrasonic and cool mist humidifiers) produced higher estimated inhalation exposure doses than pathways where epidemiological evidence of transmission has been less strong (faucet and shower) or absent (toilets and therapy pool). With consideration of the large uncertainties inherent in the exposure assessment process used, a relative ranking of exposure pathways from highest to lowest exposure doses was produced using culture-based measurement data and the assumption of constant water concentration across exposure pathways. In this ranking, the ultrasonic and cool mist humidifier exposure pathways were estimated to produce the highest exposure doses, followed by the shower and faucet exposure pathways, and then the toilet and therapy pool exposure pathways.

Light Scattering and SAXS Study of AOT Microemulsion at Low Size Droplet

We study collective diffusion coefficient (Dc) of Water-in-oil nanoemulsions (L2 phase) stabilized by AOT and dispersed in n-Decane oils by dynamic light scattering (DLS). At constant water concentration we vary the oil concentration and there is clear evidence for a changing collective diffusion coefficient of the droplets in AOT nanoemuslion. The collective diffusion coefficient in AOT nanoemulsions is studied from relaxation investigations with dynamic light scattering. Also, we study the collective diffusion coefficient (Dc) of droplets with add the TBAC to the droplets of AOT nanoemulsion. We discuss the results with study structural investigations with small-angle x-ray scattering. The results of this study suggest that the formation of non-spherical aggregates at low concentration of droplets can describe the behavior of the collective diffusion coefficient at AOT nanoemulsion.

Long chain phenols-part 30: A rate study of the mannich reaction of phenols (with particular reference to 3-pentadecylphenol)

The rate of the Mannich reaction between 3-pentadecylphenol, di-n-propylamine and 40% aqueous formaldehyde in aqueous ethanol under basic conditions has been studied by an HPLC analytical technique following preliminary experiments with dimethylamine, diethylamine and morpholine. The effect of excess amine and excess formaldehyde, different temperatures and the influence of pH were investigated. Kinetic expressions involving the concentrations of the phenol, amine and formaldehyde have been obtained on the assumption of the participation of either (a) the aminal (methylene-bis-amine) or (b) the aminol (methylolamine) for five cases covering the various molar proportions of reactant used experimentally. Initially, to test the equations for reactions effected at constant water concentration, theoretical values of t (time) were obtained as the initial concentration (a) of the phenol was varied by increments by a/20 using trial values for the composite rate constant. In this manner the best visual fit between the experimental points and the theoretical curves was obtained. The rate constant corresponding to such a curve was subsequently refined using a least squares procedure to yield the value which minimised the sum of the residuals between the experimental and theoretical values. In all cases the sum of the residuals was smaller when the kinetic expression derived assuming participation of the aminal was employed. The latter assumption also led to a smaller dispersion in the values obtained for the composite reaction constant from the different experiments.

Phase behavior of supercritical CO2 microemulsion with food-grade surfactant AOT

Phase behavior of scCO2 microemulsion formed with food grade surfactant sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) was studied. Critical microemulsion concentration (cμc) was deduced from the dependence of pressure of cloud points on the concentration of surfactant AOT at constant temperature and water concentration. The results show that there are transition points on the cloud point curve in a very narrow range of concentration of surfactant AOT. The transition points were changed with the temperature and water concentration. These phenomena show that lower temperature is suitable to forming microemulsion droplet and the microemulsion with high water concentration is likely to absorb more surfactants to structure the interface.

Effect of boron on the water speciation in (alumino)silicate melts and glasses

Abstract The investigation of hydrous boro(alumino)silicate melts and glasses with near infrared (NIR) spectroscopy revealed an important effect of boron on the water speciation. In the NIR spectra of B-bearing glasses new hydroxyl-related bands develop at the high frequency side of the 4500 cm−1 peak. In NaAlSi3O8 + B2O3 glasses this new peak is present as a shoulder at 4650 cm−1, and in NaAlSi3O8-NaBSi3O8 (Ab-Rd) glasses it appears as a resolved peak at 4710 cm−1. These bands increase with increasing boron concentration, suggesting that they are due to B-OH complexes. Furthermore, the variations in the NIR spectra indicate that with increasing B-content, but constant total water concentration, the amount of structurally bonded hydroxyl groups increases at the expense of molecular H2O. For example, at a total water concentration of 4 wt.%, pure Rd-glass contains ∼50% more water as hydroxyl groups than pure Ab-glass. In-situ NIR spectroscopy at high P and T using a hydrothermal diamond-anvil cell was used to gain information about the temperature dependence of the water speciation in NaBSi3O8 melts. The data demonstrate the conversion of molecular H2O to hydroxyl groups with increasing temperature. However, a fully quantitative evaluation of the high T spectra was hampered by problems with defining the correct baseline in the spectra. As an alternative approach annealing experiments on a Rd-glass containing 2.8 wt.% water were performed. The results confirm the conversion of H2O to OH groups with increasing T, but also suggest that the OH groups represented by the 4710 cm−1 peak (B-OH) participate much less in the conversion reaction compared to X-OH, represented by the 4500 cm−1 peak.

Stir bar contamination: a method to establish and maintain constant water concentrations of poorly water-soluble chemicals in bioconcentration experiments

A novel experimental system to establish and maintain constant dissolved concentrations of poorly water-soluble compounds for bioconcentration experiments with algae was developed. Although still recommended in the literature as a “non-adsorptive” material, a commercially available Teflon stir bar that was preloaded with polychlorinated biphenyls (PCBs) proved to be an effective donor for partitioning controlled delivery. When placed in a bioconcentration test chamber, the PCB concentrations in water and in the headspace remained constant for up to 8 days. Henry's law constants determined in experiments using water only were in good accordance with values found in the literature, indicating that the chemical was truly dissolved. When algae ( Emiliana huxleyi, class prymnesiophyceae) were added to the chamber, the water and air concentrations varied initially but stabilised within several hours, and smooth uptake curves were obtained for the algae. This indicates that the contamination system compensates for chemical loss from the water column. In addition, the Henry's law constants and the headspace measurements were used to estimate what fraction of the PCB in filtered water was associated with dissolved organic carbon, opening the opportunity to constrain one of the major artefacts in bioconcentration experiments.

Dynamic air-water exchange of polychlorinated biphenyls in the New York-New Jersey Harbor Estuary.

Simultaneous measurements of polychlorinated biphenyls (PCBs) in the air and water over Raritan Bay and New York Harbor were taken in July 1998, allowing the first determinations of air-water exchange fluxes for this heavily impacted system. Average gas-phase concentrations of sigmaPCBs were 1.0 ng m(-3) above Raritan Bay and 3.1 ng m(-3) above New York Harbor. A similar gradient was observed for dissolved water concentrations (1.6 and 3.8 ng L(-1), respectively). Shallow slopes of log K(oc) vs log K(ow) plots indicated a colloidal contribution to the dissolved concentrations, and a three-phase partitioning model was therefore applied. PCBs associated with colloids ranged from 6% to 93% for trichloro- to nonachlorobiphenyls, respectively. Air-water gas exchange fluxes of sigmaPCBs exhibited net volatilization for both Raritan Bay at +400 ng m(-2) day(-1) and New York Harbor at +2100 ng m(-2) day(-1). The correction for the colloidal interactions decreased the volatilization flux of sigmaPCBs by about 15%. Net air-water exchange fluxes of PCBs are expected to remain positive throughout the year due to the large water-air fugacity gradient and relatively constant seasonal water concentrations. The volatilization fluxes are approximately 40 times greater than atmospheric deposition of PCBs via both wet and dry particle deposition, suggesting that the estuary acts as a net source of PCBs to the atmosphere year-round.

Particle size analysis of concentrated phospholipid microemulsions II. Photon correlation spectroscopy.

The solvated droplet size of concentrated water-in-oil (w/o) microemulsions prepared from egg and soy lecithin/water/isopropyl myristate and containing short-chain alcohol cosurfactants has been determined using photon correlation spectroscopy (PCS). The effect of increasing the water volume fraction (from 0.04 to 0.26) on the solvated size of the w/o droplets at 298 K has been investigated at 4 different surfactant/cosurfactant weight ratios (Km of 1:1, 1.5:1, 1.77:1, and 1.94:1); in all cases the total surfactant/cosurfactant concentration was kept constant at 25% w/w. In the case of the microemulsions prepared from egg lecthin, the diffusion coefficients obtained from PCS measurements were corrected for interparticulate interactions using a hard-sphere model that necessitated estimation of the droplet volume fractions, which in the present study were obtained from earlier total intensity light-scattering (TILS) studies performed on the same systems. Once corrected for hard-sphere interactions, the diffusion coefficients were converted to solvated radii using the Stokes-Einstein equation assuming spherical microemulsion droplets. For both egg and soy lecithin systems, no microemulsion droplets were detected at water concentrations less than 9 wt% regardless of the alcohol and Km used, suggesting that at low concentrations of added water, cosolvent systems were formed. At higher water concentrations, however, microemulsion droplets were observed. The changes in droplet size followed the expected trend in that for a fixed Km the size of the microemulsion droplets increased with increasing volume fraction of water. At constant water concentration, droplet size decreased slightly upon increasing Km. Interestingly, only small differences in size were seen upon changing the type of alcohol used. The application of the hard-sphere model to account for interparticulate interactions for the egg lecithin systems indicated that the uncorrected diffusion coefficients underestimated particle size by a factor of slightly less than 2. Reassuringly, the corrected droplet sizes agreed very well with those obtained from our earlier TILS study.

A vibrational spectroscopic study of water confined in benzene from ambient conditions up to high temperature and pressure

Mid-infrared and Raman spectroscopies have been used to characterise the evolution of the structure and the nature of the molecular interactions in benzene–water mixtures in the temperature range 25–305°C and at constant pressure P=160 bar. At ambient conditions, the fundamental transitions, namely, ν 1, ν 2, and ν 3, of water diluted in benzene, have been recorded. It is found from the analysis of the peak position and intensity that solitary water forms a weak π-hydrogen bond with benzene. At constant pressure (160 bar) and constant water concentration ( C H 2O =0.2 mol l −1), it is shown from the evolution of the Raman profile associated with the ν 1 mode that the hydrogen bond between water and benzene is weakened upon an increase of the temperature. Furthermore, in the same temperature range and as the concentration of water increases in the mixture, the analysis of the v 1 mode band shape shows that hydrogen-bonded dimers appear in the solution at the expense of the water–benzene complex.

Effects of urea, Na+ and Li+ ions on the kinetics and mechanism of intramolecular general base-catalyzed glycolysm of ionized phenyl salicylate in ethane-1,2-diol-acetonitrile solvents at a constant water concentration

Pseudo-first-order rate constants (k1) for the reaction of ethane-1,2-diol (DOL) with ionized phenyl salicylate (PS−), obtained in mixed DOL–CH3CN solvent at constant [H2O] and [NaOH], obey the relationship k1 = α[DOL]T/(1 + 2KA[DOL]T), where α is the apparent second-order rate constant, KA is the association constant for the dimerization of DOL and [DOL]T is the total concentration of DOL. The values of KA, in the presence of Na+ ions, decrease with increase in [H2O]. Lithium ions cause almost complete depolymerization of polymeric DOL (i.e. KA ≈ 0) under the experimental conditions imposed. The effect of 0.5 M urea on the structural behavior of the mixed solvent is kinetically insignificant. © 1998 John Wiley & Sons, Ltd.

A Small-Angle Neutron Scattering Study of Water in Carbon Dioxide Microemulsions

Phase behavior and small angle neutron scattering (SANS) experiments were performed on mixtures of D2O/CO2/ammonium carboxylate perfluoropolyether (PFPE) surfactant as a function of pressure (192−287 bar) and D2O composition (0.8−2.0 wt %) at 35 °C. SANS measurements provided direct evidence of water-swollen inverted micelles in CO2. At a constant PFPE concentration of 2.1 wt % in CO2, the microemulsion core radius increased from 20 to 36 Å as the D2O concentration increased from 0.8 to 2.0 wt %. For a constant water concentration, parameters extracted from model fits of the SANS spectra indicated that as the phase boundary was approached on reducing pressure, micellar structure remained essentially unchanged, while critical fluctuations increased.

Self-Assembly in a Mixture of Two Poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) Copolymers in Water

The self-assembly behavior in water of a mixture of two poly (ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) copolymers, (EO)13(PO)30(EO)13(L64) and (EO)37(PO)58(EO)37(P105), was explored at 25°C. The phase boundaries were established using2H-NMR and inspection under polarized light; the structure of the various lyotropic liquid crystalline (LLC) phases was determined with small-angle X-ray scattering, while viscosity and differential scanning calorimetry measurements were used to probe the isotropic water-rich solution region. Isotropic regions, similar to the neat polymers, are stable at high polymer content. The addition of water induces structure in the amphiphilic block copolymer system. An extended lamellar (D) LLC phase is formed at 20–25% water content; a hexagonal (E) and a cubic (I) LLC phases supersede D at higher water contents. In addition to the above, a narrow isotropic region (L′) is observed on the L64–water binary axis, in equilibrium with the E and the D phases. The hexagonal and lamellar LLC phases extended all the way from the L64-rich to the P105-rich side of the ternary L64–P105–water phase diagram; the characteristic hexagonal and lamellar structural dimensions varied linearly with P105 content in the L64–P105 mixture at a constant water concentration. An isotropic (micellar) solution phase (L1) dominates the high-water content corner of the ternary phase diagram. Viscosity measurements in this region provided evidence for increased interactions between the micelles as the boundary to the LLC phases was approached.

29Si NMR Kinetic Study of Tetraethoxysilane and Ethyl-Substituted Ethoxysilane Polymerization in Acidic Conditions

29Si NMR is used to quantify the polymerization kinetics of silicon alkoxide intermediates in acidic sol−gel processes well before gelation. Reaction conditions are chosen (a) to minimize interference by hydrolysis kinetics and differing degrees of hydrolysis and (b) to investigate the possibility of single-step copolymerization. At the composition chosen hydrolysis reactions rapidly reach pseudoequilibrium, so condensation rate coefficients can be easily determined. We compare condensation rate coefficients of hydrolyzed intermediates from tetraethoxysilane {Si(OEt)4}, ethyltriethoxysilane {EtSi(OEt)3}, and diethyldiethoxysilane {Et2Si(OEt)2} at a constant initial water and catalyst concentration. A surprisingly strong negative first-shell substitution effect is caused by connectivity for each system and is discussed. This substitution effect depends on the degree of condensation of both reacting groups but more so on the less connected one. We also comment on a decrease in condensation reactivity and an...

Dry matter accumulation into zygotic seed; a model and its application to artificial seeds

AbstractPea seed development on the mother plant consists of three phases, all limited by water concentration (WC). The first (P1) or embryogenesis sensu stricto takes place at constant WC (stable at 80%). During the phase P2, cotyledon filling or maturation, WC decreases linearly from 80 to 55% (physiological desiccation) but the water content stays constant while the dry weight increases until it stops abruptly (at 55% WC), at this time, the seed has almost reached its final dry weight, its maturity mass or physiological maturity. The third phase, P3, consists of a fast desiccation which leads to a WC of 18–14%, where the seed is mature and ready to harvest. Similar events occur in other grain legumes, in cereals where mass maturity is attained at a lower WC (close to 40%) and in other species including crop or weed species. An elementary model of pea seed dry-matter accumulation, based on the constancy of water content (P1) and the linear decrease of WC from 80 to 55% (P2), allows us to define a coefficient α linked to WC and to calculate dry matter changes versus α. This model, taking account of WC in other species, can be generalized easily. Maturation of the somatic embryo, occurring under conditions very close to those present in vivo around the zygotic embryo, follows a pattern of decrease of WC similar to that of the zygotic embryo. We expect that if cell number is similar in the somatic and the zygotic embryo, synseeds will be ready for trade in the near future since control of all the processes that lead to zygotic-like embryoids is now available.