Anti-inflammatory activity of nanocrystalline silver-derived solutions in porcine contact dermatitis

PubMed Central

2010-01-01

Background Nanocrystalline silver dressings have anti-inflammatory activity, unlike solutions containing Ag+ only, which may be due to dissolution of multiple silver species. These dressings can only be used to treat surfaces. Thus, silver-containing solutions with nanocrystalline silver properties could be valuable for treating hard-to-dress surfaces and inflammatory conditions of the lungs and bowels. This study tested nanocrystalline silver-derived solutions for anti-inflammatory activity. Methods Inflammation was induced on porcine backs using dinitrochlorobenzene. Negative and positive controls were treated with distilled water. Experimental groups were treated with solutions generated by dissolving nanocrystalline silver in distilled water adjusted to starting pHs of 4 (using CO2), 5.6 (as is), 7, and 9 (using Ca(OH)2). Solution samples were analyzed for total silver. Daily imaging, biopsying, erythema and oedema scoring, and treatments were performed for three days. Biopsies were processed for histology, immunohistochemistry (for IL-4, IL-8, IL-10, TNF-α, EGF, KGF, KGF-2, and apoptotic cells), and zymography (MMP-2 and -9). One-way ANOVAs with Tukey-Kramer post tests were used for statistical analyses. Results Animals treated with pH 7 and 9 solutions showed clear visual improvements. pH 9 solutions resulted in the most significant reductions in erythema and oedema scores. pH 4 and 7 solutions also reduced oedema scores. Histologically, all treatment groups demonstrated enhanced re-epithelialisation, with decreased inflammation. At 24 h, pMMP-2 expression was significantly lowered with pH 5.6 and 9 treatments, as was aMMP-2 expression with pH 9 treatments. In general, treatment with silver-containing solutions resulted in decreased TNF-α and IL-8 expression, with increased IL-4, EGF, KGF, and KGF-2 expression. At 24 h, apoptotic cells were detected mostly in the dermis with pH 4 and 9 treatments, nowhere with pH 5.6, and in both the epidermis and dermis with pH 7. Solution anti-inflammatory activity did not correlate with total silver content, as pH 4 solutions contained significantly more silver than all others. Conclusions Nanocrystalline silver-derived solutions appear to have anti-inflammatory/pro-healing activity, particularly with a starting pH of 9. Solutions generated differently may have varying concentrations of different silver species, only some of which are anti-inflammatory. Nanocrystalline silver-derived solutions show promise for a variety of anti-inflammatory treatment applications. PMID:20170497

Precipitation of CaCO3 due to the Uptake of CO2 in Aqueous Solutions - Mechanisms and Rates

NASA Astrophysics Data System (ADS)

Dietzel, M.; Purgstaller, B.; Rinder, T.; Niedermayr, A.

2012-12-01

In natural and man-made environments the exchange of CO2 between aqueous solutions and the atmosphere frequently induces precipitation of CaCO3 polymorphs. Liberation of gaseous CO2 is well known to induce carbonate formation and extensively studied. In contrast significant gaps of knowledge exist with respect to the combined CO2 uptake and CaCO3 formation, although it is known to be highly valid for many natural and man-made surroundings causing e.g. travertine and scaling in analogy to CO2 liberation. Recently CO2 uptake is also discussed for biomineralization issues and debated for CO2 sequestration by using alkaline residue materials. In the present study CO2 uptake and CaCO3 precipitation mechanisms and rates were experimentally studied by diffusion of CO2 through a polyethylene membrane from an inner to an outer solution containing carbonic acid and CaCl2 (10 mM), respectively. The pH of the outer solution was kept constant between 8.3 and 11.5 by pH stat. technique (25°C). At a critical Ion Activity Product (IAP) CaCO3 is formed in the outer solution. The NaOH titration curve and Ca2+ concentrations reflect CO2 uptake and CaCO3 precipitation rates. To discover the impact of a drift in pH due to CO2 uptake on CaCO3 precipitation hydrogeochemical modeling was applied. XRD, (micro)Raman pattern and SEM imaging reveal the formation of calcite and vaterite at pH 8.3 and 9, whereas at pH > 10 vaterite is additionally formed. However at a given pH the formation of individual CaCO3 polymorphs strongly depends on the CO2 uptake rate (adjusted by membrane thickness), which controls carbonate accumulation in the solution. At elevated pH of the outer solution the uptake rate of CO2 is significantly higher and less time for nucleation of CaCO3 is required compared to lower pH. Surprisingly at the total experimental time of ≈ 20 h the amount of precipitated CaCO3 is similar for all experiments. This can be explained by significant higher CaCO3 precipitation rates at low versus high pH if once a critical IAP is reached. If a drift in pH is permitted the internal Pco2 value can be used as a reliable proxy to evaluate whether uptake of CO2 results in an increase or decrease of IAP with a threshold value of 10-6.15 atm at 25°C (pH ≈ 11). The obtained relationships for CaCO3 formation through CO2 uptake are discussed for selected alkaline environments.

Cr(VI) removal by FeS-coated alumina, silica, and natural sand

NASA Astrophysics Data System (ADS)

Park, M.; Lee, S.; Jeong, H. Y.

2014-12-01

Removal of Cr(VI) was investigated using mackinawite (FeS)-coated mineral sorbents under anoxic conditions. The sorbents included alumina (Al), silica (WS), and natural sand (NS). By analysis of both solution and solid phases, all FeS-coated sorbents were found to reduce Cr(VI) into Cr(III). The sorption extent and mechanism of Cr(VI) strongly depended on the pH conditions. Only at pH 4.5, significant amounts of the dissolved Cr remained in the solution. Titration of dissolved Cr(III) and Fe(III) by NaOH solutions indicated that no bulk-phase precipitation occurred at pH 4.5. Also, the removal of Cr(VI) at pH 4.5 was the greatest by FeS-coated NS. Consistent with these, Cr-K edge EXAFS revealed that Cr was removed by FeS-coated NS via surface precipitation, and that it was immobilized by FeS-coated WS and Al by forming surface clusters. Regardless of FeS-coated sorbents, at pH 7.0 and pH 9.5, the initially added Cr(VI) was quantitatively removed from the solution phase. By EXAFS analysis, the Cr sorption by FeS-coated Al was mainly due to the bulk-phase precipitation of Cr(OH)3(s) or [Cr, Fe](OH)3(s). In case of FeS-coated WS and NS, the short Cr-Cr distance (~2.6 Å) at pH 7.0 and pH 9.5 was not simply accounted for by the bulk precipitation as either hydroxide (rCr-Cr ~ 3.0 Å), and it would rather result from the surface precipitation. Such a difference in the coordination structure among FeS-coated sorbents was likely due to in the lower surface area of the former available for the surface precipitation.

Soil solution Zn and pH dynamics in non-rhizosphere soil and in the rhizosphere of Thlaspi caerulescens grown in a Zn/Cd-contaminated soil.

PubMed

Luo, Y M; Christie, P; Baker, A J

2000-07-01

Temporal changes in soil solution properties and metal speciation were studied in non-rhizosphere soil and in the rhizosphere of the hyperaccumulator Thlaspi caerulescens J. & C. Presl (population from Prayon, Belgium) grown in a Zn- and Cd-contaminated soil. This paper focuses on soil solution Zn and pH dynamics during phytoextraction. The concentration of Zn in both non-rhizosphere and rhizosphere soil solutions decreased from 23 mg/l at the beginning to 2 mg/l at the end of the experiment (84 days after transplanting of seedlings), mainly due to chemical sorption. There was no significant difference in overall Zn concentration between the planted and the unplanted soil solutions (P > 0.05). Soil solution pH decreased initially and then increased slightly in both planted and unplanted soil zones. From 60 to 84 days after transplanting, the pH of the rhizosphere soil solution was higher than that of non-rhizosphere soil solution (P<0.05). Zn uptake by the hyperaccumulator plants was 8.8 mg per pot (each containing 1 kg oven-dry soil) on average. The data indicate that the potential of T. caerulescens to remove Zn from contaminated soil may not be related to acidification of the rhizosphere.

Effects of phytoextraction on heavy metal concentrations and pH of pore-water of biosolids determined using an in situ sampling technique.

PubMed

Huynh, T T; Laidlaw, W S; Singh, B; Gregory, D; Baker, A J M

2008-12-01

Heavy metal concentrations and pH of pore-water in contaminated substrates are important factors in controlling metal uptake by plants. We investigated the effects of phytoextraction on these properties in the solution phase of biosolids and diluted biosolids in a 12-month phytoextraction column experiment. Phytoextraction using Salix and Populus spp. temporarily decreased pore-water pH of the substrates over the experimental period followed by a return to initial pH conditions. Salixxreichardtii and Populus balsamifera effectively extracted Ni, Zn and Cd and actively mobilized these metals from the solid to the solution phase. S.xreichardtii had the stronger effect on mobilization of metals due to its larger root system. Phytoextraction did not affect Cu in the solution phase of the biosolids. Heavy metals were leached down to lower depths of the columns during the phytoextraction process.

Biophysical characterization and conformational stability of Ebola and Marburg virus-like particles.

PubMed

Hu, Lei; Trefethen, Jared M; Zeng, Yuhong; Yee, Luisa; Ohtake, Satoshi; Lechuga-Ballesteros, David; Warfield, Kelly L; Aman, M Javad; Shulenin, Sergey; Unfer, Robert; Enterlein, Sven G; Truong-Le, Vu; Volkin, David B; Joshi, Sangeeta B; Middaugh, C Russell

2011-12-01

The filoviruses, Ebola virus and Marburg virus, cause severe hemorrhagic fever with up to 90% human mortality. Virus-like particles of EBOV (eVLPs) and MARV (mVLPs) are attractive vaccine candidates. For the development of stable vaccines, the conformational stability of these two enveloped VLPs produced in insect cells was characterized by various spectroscopic techniques over a wide pH and temperature range. Temperature-induced aggregation of the VLPs at various pH values was monitored by light scattering. Temperature/pH empirical phase diagrams (EPDs) of the two VLPs were constructed to summarize the large volume of data generated. The EPDs show that both VLPs lose their conformational integrity above about 50°C-60°C, depending on solution pH. The VLPs were maximally thermal stable in solution at pH 7-8, with a significant reduction in stability at pH 5 and 6. They were much less stable in solution at pH 3-4 due to increased susceptibility of the VLPs to aggregation. The characterization data and conformational stability profiles from these studies provide a basis for selection of optimized solution conditions for further vaccine formulation and long-term stability studies of eVLPs and mVLPs. Copyright © 2011 Wiley-Liss, Inc.

pH Sensing Properties of Flexible, Bias-Free Graphene Microelectrodes in Complex Fluids: From Phosphate Buffer Solution to Human Serum.

PubMed

Ping, Jinglei; Blum, Jacquelyn E; Vishnubhotla, Ramya; Vrudhula, Amey; Naylor, Carl H; Gao, Zhaoli; Saven, Jeffery G; Johnson, Alan T Charlie

2017-08-01

Advances in techniques for monitoring pH in complex fluids can have a significant impact on analytical and biomedical applications. This study develops flexible graphene microelectrodes (GEs) for rapid (<5 s), very-low-power (femtowatt) detection of the pH of complex biofluids by measuring real-time Faradaic charge transfer between the GE and a solution at zero electrical bias. For an idealized sample of phosphate buffer solution (PBS), the Faradaic current is varied monotonically and systematically with the pH, with a resolution of ≈0.2 pH unit. The current-pH dependence is well described by a hybrid analytical-computational model, where the electric double layer derives from an intrinsic, pH-independent (positive) charge associated with the graphene-water interface and ionizable (negative) charged groups. For ferritin solution, the relative Faradaic current, defined as the difference between the measured current response and a baseline response due to PBS, shows a strong signal associated with ferritin disassembly and the release of ferric ions at pH ≈2.0. For samples of human serum, the Faradaic current shows a reproducible rapid (<20 s) response to pH. By combining the Faradaic current and real-time current variation, the methodology is potentially suitable for use to detect tumor-induced changes in extracellular pH. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Impact of pH and Calcium on the Uptake of Fluoride by Tea Plants (Camellia sinensis L.)

PubMed Central

RUAN, JIANYUN; MA, LIFENG; SHI, YUANZHI; HAN, WENYAN

2004-01-01

• Background and Aims Tea plants (Camellia sinensis L.) accumulate large amounts of fluoride (F) from soils containing normal F concentrations. The present experiments examined the effects of pH and Ca on F uptake by this accumulating plant species. • Methods The effect of pH was assessed in two experiments, one using uptake solutions with different pHs, and the other using lime, as CaO, applied to the soil. The effect of Ca was examined by analysing F concentrations in plants supplied with varying amounts of Ca, as Ca(NO3)2, either in uptake solutions or through the soil. • Key results F uptake was highest at solution pH 5·5, and significantly lower at pH 4·0. In the soil experiment, leaf F decreased linearly with the amounts of lime, which raised the soil pH progressively from 4·32 to 4·91, 5·43, 5·89 and, finally, 6·55. Liming increased the water‐soluble F content of the soil. Including Ca in the uptake solution or adding Ca to soil significantly decreased leaf F concentrations. The distribution pattern of F in tea plants was not altered by Ca treatment, with most F being allocated to leaves. The activity of F– in the uptake solution was unaffected and water‐soluble F in the soil was sometimes increased by added Ca. • Conclusions F uptake by tea plants, which are inherently able to accumulate large quantities of F, was affected both by pH and by Ca levels in the medium. The reduced F uptake following Ca application appeared not to be due simply to the precipitation of CaF2 in solution and soil or to the complexing of Ca and F in roots, although these factors cannot be dismissed. It was more likely due to the effect of Ca on the properties of cell wall or membrane permeability in the solution experiments, and to alteration of F speciations and their quantities in soil solutions following Ca application. PMID:14644914

Inorganic Carbon Source for Photosynthesis in the Seagrass Thalassia hemprichii (Ehrenb.) Aschers.

PubMed

Abel, K M

1984-11-01

Photosynthetic carbon uptake of the tropical seagrass Thalassia hemprichii (Ehrenb.) Aschers was studied by several methods. Photosynthesis in buffered seawater in media in the range of pH 6 to pH 9 showed an exponentially increasing rate with decreasing pH, thus indicating that free CO(2) was a photosynthetic substrate. However, these experiments were unable to determine whether photosynthesis at alkaline pH also contained some component due to HCO(3) (-) uptake. This aspect was further investigated by studying photosynthetic rates in a number of media of varying pH (7.8-8.61) and total inorganic carbon (0.75-13.17 millimolar). In these media, photosynthetic rate was correlated with free CO(2) concentration and was independent of the HCO(3) (-) concentration in the medium. Short time-course experiments were conducted during equilibration of free CO(2) and HCO(3) (-) after injection of (14)C labeled solution at acid or alkaline pH. High initial photosynthetic rates were observed when acidic solutions (largely free CO(2)) were used but not with alkaline solutions. The concentration of free CO(2) was found to be a limiting factor for photosynthesis in this plant.

In vitro hemolysis and buffer capacity studies with the novel marine anticancer agent kahalalide F and its reconstitution vehicle cremophor EL/ethanol.

PubMed

Nuijen, B; Bouma, M; Manada, C; Jimeno, J M; Bult, A; Beijnen, J H

2001-01-01

An in vitro biocompatibility study was performed with the pharmaceutical formulation of the investigational, marine-derived anticancer agent kahalalide F developed for early clinical studies. The pharmaceutical formulation consists of a lyophilized product containing 150 micrograms kahalalide F, 3 mg citric acid, 3 mg polysorbate 80, and 150 mg of sucrose per dosage unit, to be reconstituted with 3 mL of a mixture composed of Cremophor EL, ethanol, and water (5/5/90% v/v/v), resulting in a solution of pH 3 and to be further diluted in normal saline for infusion. The reconstituted product, infusion solutions, and Cremophor/ethanol (CE) vehicle were tested for hemolytic potential and buffer capacity. No significant hemolysis due to the kahalalide F formulation as well as the CE vehicle was found using both a static and dynamic test model. FB-ratio's (ratio of formulation solution (F) and volume of blood simulant (B) necessary to maintain physiological pH) as a measure of the buffer capacity of the kahalalide F infusion solutions examined indicated that no vascular irritation due to pH effects is expected in the intended administration schedule in the forthcoming Phase I study.

[Analyze nanofiltration separation rule of chlorogenic acid from low concentration ethanol by Donnan effect and solution-diffusion effect].

PubMed

Li, Cun-Yu; Liu, Li-Cheng; Jin, Li-Yang; Li, Hong-Yang; Peng, Guo-Ping

2017-07-01

To separate chlorogenic acid from low concentration ethanol and explore the influence of Donnan effect and solution-diffusion effect on the nanofiltration separation rule. The experiment showed that solution pH and ethanol volume percent had influences on the separation of chlorogenic acid. Within the pH values from 3 to 7 for chlorogenic acid in 30% ethanol, the rejection rate of chlorogenic acid was changed by 70.27%. Through the response surface method for quadratic regression model, an interaction had been found in molecule weight cut-off, pH and ethanol volume percent. In fixed nanofiltration apparatus, the existence states of chlorogenic acid determinedits separation rules. With the increase of ethanol concentration, the free form chlorogenic acid was easily adsorbed, dissolved on membrane surface and then caused high transmittance due to the solution-diffusion effect. However, at the same time, due to the double effects of Donnan effect and solution-diffusion effect, the ionic state of chlorogenic acid was hard to be adsorbed in membrane surface and thus caused high rejection rate. The combination of Box-Behnken design and response surface analysis can well optimize the concentrate process by nanofiltration, and the results showed that nanofiltration had several big advantages over the traditional vacuum concentrate technology, meanwhile, and solved the problems of low efficiency and serious component lossesin the Chinese medicines separation process for low concentration organic solvent-water solution. Copyright© by the Chinese Pharmaceutical Association.

The effect of pH and heat treatments on the foaming properties of purified α-lactalbumin from camel milk.

PubMed

Lajnaf, Roua; Picart-Palmade, Laetitia; Attia, Hamadi; Marchesseau, Sylvie; Ayadi, M A

2017-08-01

The effect of pH (4.3 or 6.5) and heat treatment (70°C or 90°C for 30min) on the foaming and interfacial properties of α-lactalbumin extracted from camel milk were studied. The increased temperature treatment changed the foaming properties of camel α-lactalbumin solution and its ability to unfold at the air-water interface. At neutral pH, heat treatment was found to improve foamability, whereas at acid pH (4.3) this property decreased. Foams were more stable after a heat treatment at pH 4.3 than at 6.5, due to higher levels of protein aggregation at low pH. Heat treatment at 90°C for 30min affected the physicochemical properties of the camel α-lactalbumin by increasing free thiol group concentration at pH 6.5. Heat treatment also caused changes in α-lactalbumin's surface charge. These results also confirm the pronounced aggregation of heated camel α-lactalbumin solution at acid pH. Copyright © 2017. Published by Elsevier B.V.

The Rainbow Connection.

ERIC Educational Resources Information Center

Hutton, Bill; Smith, Wayne L.

1984-01-01

Provides materials needed and procedures to illustrate the reversible color changes in certain organic acids on bases due to changes in pH. The technique employs three indicators which are colorless in acidic solution but form primary colors in basic solutions. Also discusses the free energy curve presented in many textbooks. (JM)

Arsenic removal from acidic solutions with biogenic ferric precipitates.

PubMed

Ahoranta, Sarita H; Kokko, Marika E; Papirio, Stefano; Özkaya, Bestamin; Puhakka, Jaakko A

2016-04-05

Treatment of acidic solution containing 5g/L of Fe(II) and 10mg/L of As(III) was studied in a system consisting of a biological fluidized-bed reactor (FBR) for iron oxidation, and a gravity settler for iron precipitation and separation of the ferric precipitates. At pH 3.0 and FBR retention time of 5.7h, 96-98% of the added Fe(II) precipitated (99.1% of which was jarosite). The highest iron oxidation and precipitation rates were 1070 and 28mg/L/h, respectively, and were achieved at pH 3.0. Subsequently, the effect of pH on arsenic removal through sorption and/or co-precipitation was examined by gradually decreasing solution pH from 3.0 to 1.6 (feed pH). At pH 3.0, 2.4 and 1.6, the highest arsenic removal efficiencies obtained were 99.5%, 80.1% and 7.1%, respectively. As the system had ferric precipitates in excess, decreased arsenic removal was likely due to reduced co-precipitation at pH<2.4. As(III) was partially oxidized to As(V) in the system. In shake flask experiments, As(V) sorbed onto jarosite better than As(III). Moreover, the sorption capacity of biogenic jarosite was significantly higher than that of synthetic jarosite. The developed bioprocess simultaneously and efficiently removes iron and arsenic from acidic solutions, indicating potential for mining wastewater treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Chromium(VI) Removal from Aqueous Solution by Magnetite Coated by a Polymeric Ionic Liquid-Based Adsorbent

PubMed Central

Ferreira, Thania Alexandra; Rodriguez, Jose Antonio; Paez-Hernandez, María Elena; Guevara-Lara, Alfredo; Barrado, Enrique; Hernandez, Prisciliano

2017-01-01

An evaluation of the chromium(VI) adsorption capacity of four magnetite sorbents coated with a polymer phase containing polymethacrylic acid or polyallyl-3-methylimidazolium is presented. Factors that influence the chromium(VI) removal such as solution pH and contact time were investigated in batch experiments and in stirred tank reactor mode. Affinity and rate constants increased with the molar ratio of the imidazolium. The highest adsorption was obtained at pH 2.0 due to the contribution of electrostatic interactions. PMID:28772865

Photochemistry of monodentate and bidentate carbonato complexes of rhodium (3). [applications to spacecraft fuel cells

NASA Technical Reports Server (NTRS)

Sheridan, P. S.

1980-01-01

A scheme for the photochemical fixation of water is proposed which involves a five-step reaction sequence; the first step involves the 2 electron reduction of a metal by a coordinated carbonate ligand, with corresponding oxidation of the carbonate to CO2 and O2. Ligand field photolysis of trans- (RH(en)2 H2O CO3) ClO4, and (Rh(en)2 CO3) CLO4 have been studied in the solid state and in aqueous solution at various pH values. Both salts are photoinert in the solid phase, but are quite photoreactive in aqueous solution. In solution, the monodentate ion undergoes efficient isomerization to a mixture of cis and trans - (Rh(en)2 H2O CO3)+, presumably with water exchange. A minor pH increase upon photolysis is evidence of inefficient carbonate (CO3 =) release, with formation of (Rh(en)2 (H2O)2)3+. In contrast, aqueous solutions of the bidentate carbonato complex undergo efficient pH decrease upon ligand field photolysis. Changes in the electronic spectrum (200-500 nm) and pH changes indicate that the desired redox is occurring. The pH increase is due to the aqueous behavior of CO2.

Stability and tribological performances of fluid phospholipid bilayers: effect of buffer and ions.

PubMed

Dekkiche, F; Corneci, M C; Trunfio-Sfarghiu, A-M; Munteanu, B; Berthier, Y; Kaabar, W; Rieu, J-P

2010-10-15

We have investigated the mechanical and tribological properties of supported Dioleoyl phosphatidylcholine (DOPC) bilayers in different solutions: ultrapure water (pH 5.5), saline solution (150 mM NaCl, pH 5.8), Tris buffer (pH 7.2) and Tris saline buffer (150 mM NaCl, pH 7.2). Friction forces are measured using a homemade biotribometer. Lipid bilayer degradation is controlled in situ during friction tests using fluorescence microscopy. Mechanical resistance to indentation is measured by force spectroscopy with an atomic force microscope. This study confirms that mechanical stability under shear or normal load is essential to obtain low and constant friction coefficients. In ultrapure water, bilayers are not resistant and have poor lubricant properties. On the other hand, in Tris saline buffer, they fully resist to indentation and exhibit low (micro=0.035) and stable friction coefficient with no visible wear during the 50 min of the friction test. The unbuffered saline solution improves the mechanical resistance to indentation but not the lubrication. These results suggest that the adsorption of ions to the zwiterrionic bilayers has different effects on the mechanical and tribological properties of bilayers: higher resistance to normal indentation due to an increase in bilayer cohesion, higher lubrication due to an increase in bilayer-bilayer repulsion. Copyright (c) 2010 Elsevier B.V. All rights reserved.

In-vitro investigations of a pH- and ionic-strength-responsive polyelectrolytic hydrogel using a piezoresistive microsensor

PubMed Central

Schulz, Volker; Guenther, Margarita; Gerlach, Gerald; Magda, Jules J.; Tathireddy, Prashant; Rieth, Loren; Solzbacher, Florian

2010-01-01

Environmental responsive or smart hydrogels show a volume phase transition due to changes of external stimuli such as pH or ionic strength of an ambient solution. Thus, they are able to convert reversibly chemical energy into mechanical energy and therefore they are suitable as sensitive material for integration in biochemical microsensors and MEMS devices. In this work, micro-fabricated silicon pressure sensor chips with integrated piezoresistors were used as transducers for the conversion of mechanical work into an appropriate electrical output signal due to the deflection of a thin silicon bending plate. Within this work two different sensor designs have been studied. The biocompatible poly(hydroxypropyl methacrylate-N,N-dimethylaminoethyl methacrylate-tetra-ethyleneglycol dimethacrylate) (HPMA-DMA-TEGDMA) was used as an environmental sensitive element in piezoresistive biochemical sensors. This polyelectrolytic hydrogel shows a very sharp volume phase transition at pH values below about 7.4 which is in the range of the physiological pH. The sensor's characteristic response was measured in-vitro for changes in pH of PBS buffer solution at fixed ionic strength. The experimental data was applied to the Hill equation and the sensor sensitivity as a function of pH was calculated out of it. The time-dependent sensor response was measured for small changes in pH, whereas different time constants have been observed. The same sensor principal was used for sensing of ionic strength. The time-dependent electrical sensor signal of both sensors was measured for variations in ionic strength at fixed pH value using PBS buffer solution. Both sensor types showed an asymmetric swelling behavior between the swelling and the deswelling cycle as well as different time constants, which was attributed to the different nature of mechanical hydrogel-confinement inside the sensor. PMID:21152365

Pitting Corrosion of alloy 690 in thiosulfate-containing chloride solutions

NASA Astrophysics Data System (ADS)

Tsai, Wen-Ta; Wu, Tsung-Feng

2000-01-01

The effects of thiosulfate ion and solution pH on pitting corrosion of Alloy 690 in chloride solution were explored. Potentiodynamic polarization measurements were conducted to evaluate pitting corrosion susceptibility of Alloy 690 in these environments. The results showed that pitting corrosion occurred in the mill-annealed (1050°C/5min) Alloy 690 in 1 wt% NaCl solution but not in 0.1 M Na 2S 2O 3 solution. The value of pitting nucleation potential ( Enp) determined in 1 wt% NaCl solution (without Na 2S 2O 3 ) increased with increasing solution pH value in the range of 2-10. The addition of Na 2S 2O 3 to 1 wt% NaCl solution greatly affected the pitting corrosion behavior, which was dependent on concentration. The preformed nickel sulfide surface film due to the presence of Na 2S 2O 3 caused Alloy 690 to become more susceptible to pitting corrosion in 1 wt% NaCl solution.

Effects of the pH and Concentration on the Stability of Standard Solutions of Proteinogenic Amino Acid Mixtures.

PubMed

Kato, Megumi; Yamazaki, Taichi; Kato, Hisashi; Yamanaka, Noriko; Takatsu, Akiko; Ihara, Toshihide

2017-01-01

To prepare metrologically traceable amino acid mixed standard solutions, it is necessary to determine the stability of each amino acid present in the mixed solutions. In the present study, we prepared amino acid mixed solutions using certified reference standards of 17 proteinogenic amino acids, and examined the stability of each of these amino acids in 0.1 N HCl. We found that the concentration of glutamic acid decreased significantly during storage. LC/MS analysis indicated that the instability of glutamic acid was due to the partial degradation of glutamic acid to pyroglutamic acid in 0.1 N HCl. Using accelerated degradation tests, we investigated several solvent compositions to improve the stability of glutamic acid in amino acid mixed solution, and determined that the change of the pH by diluting the mixed solution improved the stability of glutamic acid.

Biosorption of clofibric acid and carbamazepine in aqueous solution by agricultural waste rice straw.

PubMed

Liu, Zhanguang; Zhou, Xuefei; Chen, Xiaohua; Dai, Chaomeng; Zhang, Juan; Zhang, Yalei

2013-12-01

Due to their widespread use, clofibric acid (CA) and carbamazepine (CBZ) have been frequently detected simultaneously at relatively high concentrations in aquatic environments. In this study, agricultural waste rice straw was employed as a potentially low-cost, effective and easy-to-operate biosorbent (RSB) to remove CA and CBZ. The adsorption of both pharmaceuticals followed pseudo second-order kinetics, and intraparticle diffusion was an important rate-limiting step. The adsorption isotherms of both drugs were fit well with Freundlich model. The adsorption of CA onto RSB was exothermic and was more likely to be dominated by physical processes, while the adsorption of CBZ was endothermic. Solution pH was determined to be the most important factor for CA adsorption, such that the adsorption capacity of CA onto RSB increased with the decline of solution pH. In the lower range of solution pH below 3.1, the CA removal efficiency was enhanced with the increase of biosorbent dosage. The CBZ removal efficiency was enhanced with the increase of RSB dosage without pH control. The maximum adsorption capacities were 126.3 mg/g for CA and 40.0 mg/g for CBZ.

Analysis of the difference in color development in the dye-binding method due to the kind of buffer solution.

PubMed

Suzuki, Yuji

2006-06-01

In a dye-binding method using a pH indicator, color development has reportedly been affected by the kind of buffer solution used in the color reagent. This phenomenon was analyzed by using a calculation based on the assumption that the anion of the buffer solution also reacts with protein. Color development decreases with increases in the anion concentration of the buffer solution and in the equilibrium constant of the reaction between the anion and protein. The differences in color development due to the kind of buffer solution can be attributed to differences in the equilibrium constant of the reaction forming the anion-protein complex and to the concentration of the anion between the buffer solutions.

Pyrroloquinoline quinone (PQQ) is reduced to pyrroloquinoline quinol (PQQH2) by vitamin C, and PQQH2 produced is recycled to PQQ by air oxidation in buffer solution at pH 7.4.

PubMed

Mukai, Kazuo; Ouchi, Aya; Nagaoka, Shin-ichi; Nakano, Masahiko; Ikemoto, Kazuto

2016-01-01

Measurements of the reaction of sodium salt of pyrroloquinoline quinone (PQQNa2) with vitamin C (Vit C) were performed in phosphate-buffered solution (pH 7.4) at 25 °C under nitrogen atmosphere, using UV-vis spectrophotometry. The absorption spectrum of PQQNa2 decreased in intensity due to the reaction with Vit C and was changed to that of pyrroloquinoline quinol (PQQH2, a reduced form of PQQ). One molecule of PQQ was reduced by two molecules of Vit C producing a molecule of PQQH2 in the buffer solution. PQQH2, thus produced, was recycled to PQQ due to air oxidation. PQQ and Vit C coexist in many biological systems, such as vegetables, fruits, as well as in human tissues. The results obtained suggest that PQQ is reduced by Vit C and functions as an antioxidant in biological systems, because it has been reported that PQQH2 shows very high free-radical scavenging and singlet-oxygen quenching activities in buffer solutions.

Solution-mediated phase transformation of haloperidol mesylate in the presence of sodium lauryl sulfate.

PubMed

Greco, Kristyn; Bogner, Robin

2011-09-01

Forming a salt is a common way to increase the solubility of a poorly soluble compound. However, the solubility enhancement gained by salt formation may be lost due to solution-mediated phase transformation (SMPT) during dissolution. The SMPT of a salt can occur due to a supersaturated solution near the dissolving surface caused by pH or other solution conditions. In addition to changes in pH, surfactants are also known to affect SMPT. In this study, SMPT of a highly soluble salt, haloperidol mesylate, at pH 7 in the presence of a commonly used surfactant, sodium lauryl sulfate (SLS), was investigated. Dissolution experiments were performed using a flow-through dissolution apparatus with solutions containing various concentrations of SLS. Compacts of haloperidol mesylate were observed during dissolution in the flow-through apparatus using a stereomicroscope. Raman microscopy was used to characterize solids. The dissolution of haloperidol mesylate was significantly influenced by the addition of sodium lauryl sulfate. In conditions where SMPT was expected, the addition of SLS at low concentrations (0.1-0.2 mM) reduced the dissolution of haloperidol mesylate. In solutions containing concentrations of SLS above the critical micelle concentration (CMC) (10-15 mM), the dissolution of haloperidol mesylate increased compared to below the CMC. The solids recovered from solubility experiments of haloperidol mesylate indicated that haloperidol free base precipitated at all concentrations of SLS. Above 5 mM of SLS, Raman microscopy suggested a new form, perhaps the estolate salt. The addition of surfactant in solids that undergo solution-mediated phase transformation can add complexity to the dissolution profiles and conversion.

Cadmium triggers Elodea canadensis to change the surrounding water pH and thereby Cd uptake.

PubMed

Javed, M Tariq; Greger, Maria

2011-01-01

This study was aimed to investigate the influence of Elodea canadensis shoots on surrounding water pH in the presence of cadmium and the effect of plant-induced pH on cadmium uptake. The pH change in the surrounding nutrient solution and Cd uptake by Elodea shoots were investigated after cultivation of various plant densities (1, 3, 6 plants per 500 ml) in hydroponics at a starting pH of 4.0 and in the presence of different concentrations of cadmium (0, 0.1, 0.5 microM). Cadmium uptake was also investigated at different constant pH (4.0, 4.5, 5.5 and 6.5). To investigate if the pH change arose from photosynthetic activities, plants were grown under light, darkness or in the presence of a photosynthetic inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU), and 0.5 microM cadmium in the solution. Elodea had an ability to increase the surrounding water pH, when the initial pH was low, which resulted in increased accumulation of Cd. The higher the plant density, the more pronounced was the pH change. The pH increase was not due to the photosynthetic activity since the pH rise was more pronounced under darkness and in the presence of DCMU. The pH increase by Elodea was triggered by cadmium.

Catalytic degradation of picric acid by heterogeneous Fenton-based processes.

PubMed

Dulova, Niina; Trapido, Marina; Dulov, Aleksandr

2011-01-01

The efficiency of goethite, magnetite and iron powder (Fe0) in catalysing the Fenton-based oxidation of picric acid (PA) in aqueous solution was studied. The effect of pH, hydrogen peroxide concentration, and catalyst type and dosage on treatment efficacy was investigated. The adsorption of PA from aqueous solution by heterogeneous catalysts was also examined. The results demonstrated negligible PA removal in H2O2/alpha-FeOOH and H2O2/Fe3O4 systems independent of process pH, and hydrogen peroxide and catalyst dosage. The PA adsorption effects of both iron oxides turned out to be insignificant for all studied pH values and catalyst dosages. The H2O2/Fe0 system proved efficient at degrading PA, but only under acidic conditions (pH 3). The results indicated that, due to rather fast leaching of ferrous ions from the iron powder surface, PA degradation was carried out mainly by the classic Fenton oxidation mechanism in the bulk solution. The adsorption of PA onto the iron powder surface may also contribute to the overall efficiency of PA degradation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warner, Thomas; Jalilehvand, Farideh

Mercury(II) ions precipitate from aqueous cysteine (H 2Cys) solutions containing H 2Cys/Hg(II) mole ratio ≥ 2.0 as Hg( S-HCys) 2. In absence of additional cysteine, the precipitate dissolves at pH ~12 with the [Hg( S, N-Cys) 2] 2- complex dominating. With excess cysteine (H 2Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg( S-Cys) 4] 6- complexes form at pH = 11.0; in this work we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)-cysteine solutions in which C Hg(II) variedmore » between 8 – 9 mM and 80 – 100 mM, respectively, with H 2Cys/Hg(II) mole ratios from 4 to ~20. The solutions were prepared in the pH range 7.1 – 8.8, at the pH at which the initial Hg( S-HCys) 2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199Hg NMR, X-ray absorption and Raman spectroscopic techniques. Our results show that in the dilute solutions (C Hg(II) = 8 – 9 mM), mixtures of di-, tri- (major) and tetrathiolate complexes exist at moderate cysteine excess (C H2Cys ~ 0.16 M) at pH 7.1. In the more concentrated solutions (C Hg(II) = 80 – 100 mM) with high cysteine excess (C H2Cys > 0.9 M), tetrathiolate [Hg( S-cysteinate) 4] m-6 ( m = 0 – 4) complexes dominate in the pH range 7.3 – 7.8, with lower charge than for the [Hg( S-Cys) 4] 6- complex due to protonation of some ( m) of the amino groups of the coordinated cysteine ligands. In conclusion, the results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological / environmental systems.« less

Root-zone acidity affects relative uptake of nitrate and ammonium from mixed nitrogen sources

NASA Technical Reports Server (NTRS)

Vessey, J. K.; Henry, L. T.; Chaillou, S.; Raper, C. D. Jr; Raper CD, J. r. (Principal Investigator)

1990-01-01

Soybean plants (Glycine max [L.] Merr. cv Ransom) were grown for 21 days on 4 sources of N (1.0 mM NO3-, 0.67 mM NO3- plus 0.33 mM NH4+, 0.33 mM NO3- plus 0.67 mM NH4+, and 1.0 mM NH4+) in hydroponic culture with the acidity of the nutrient solution controlled at pH 6.0, 5.5, 5.0, and 4.5. Dry matter and total N accumulation of the plants was not significantly affected by N-source at any of the pH levels except for decreases in these parameters in plants supplied solely with NH4+ at pH 4.5. Shoot-to-root ratios increased in plants which had an increased proportion [correction of proporiton] of NH4(+)-N in their nutrient solutions at all levels of root-zone pH. Uptake of NO3- and NH4+ was monitored daily by ion chromatography as depletion of these ions from the replenished hydroponic solutions. At all pH levels the proportion of either ion that was absorbed increased as the ratio of that ion increased in the nutrient solution. In plants which were supplied with sources of NO3- plus NH4+, NH4+ was absorbed at a ratio of 2:1 over NO3- at pH 6.0. As the pH of the root-zone declined, however, NH4+ uptake decreased and NO3- uptake increased. Thus, the NH4+ to NO3- uptake ratio declined with decreases in root-zone pH. The data indicate a negative effect of declining root-zone pH on NH4+ uptake and supports a hypothesis that the inhibition of growth of plants dependent on NH4(+)-N at low pH is due to a decline in NH4+ uptake and a consequential limitation of growth by N stress.

pCO2 and pH regulation of cerebral blood flow

PubMed Central

Yoon, SeongHun; Zuccarello, Mario; Rapoport, Robert M.

2012-01-01

CO2 serves as one of the fundamental regulators of cerebral blood flow (CBF). It is widely considered that this regulation occurs through pCO2-driven changes in pH of the cerebral spinal fluid (CSF), with elevated and lowered pH causing direct relaxation and contraction of the smooth muscle, respectively. However, some findings also suggest that pCO2 acts independently of and/or in conjunction with altered pH. This action may be due to a direct effect of CSF pCO2 on the smooth muscle as well as on the endothelium, nerves, and astrocytes. Findings may also point to an action of arterial pCO2 on the endothelium to regulate smooth muscle contractility. Thus, the effects of pH and pCO2 may be influenced by the absence/presence of different cell types in the various experimental preparations. Results may also be influenced by experimental parameters including myogenic tone as well as solutions containing significantly altered HCO3− concentrations, i.e., solutions routinely employed to differentiate the effects of pH from pCO2. In sum, it appears that pCO2, independently and in conjunction with pH, may regulate CBF. PMID:23049512

A Surfactant-Free Synthesis Technique of Coral-Like Zno Hierarchical Structures for Photocatalytic Degradation of Resorcinol under UV Irradiation

NASA Astrophysics Data System (ADS)

Sin, Jin-Chung; Lam, Sze-Mun; Chin, Ying-Hui

2018-01-01

Hierarchical coral-like ZnO structures were successfully prepared by a surfactant-free wet chemical method. Various characterization tests were carried out to analyze the as-prepared ZnO samples. The coral-like ZnO was used to degrade resorcinol at three different solution pH values (pH 5.0, pH 8.0 and pH 11.0). It was observed that the resorcinol adsorption onto the ZnO was strongly dependent on the electrical charge properties of both photocatalyst and resorcinol. Photocatalytic degradation of resorcinol reached the highest at pH 11.0 due to high concentration of hydroxyl ions for hydroxyl radicals generation.

Layer by layer assembled films between hemoglobin and multiwall carbon nanotubes for pH-switchable biosensing.

PubMed

Pan, Zhongqin; Liu, Xiaojun; Xie, Jing; Bao, Ning; He, Hong; Li, Xiaodong; Zeng, Jiang; Gu, Haiying

2015-05-01

Although pH-switchable behaviors have been reported based on multilayer films modified electrodes, their pH-switchable biosensing is still difficult due to the existence of the electroactive mediator. In this study, we report the pH-dependable determination of hydrogen peroxide (H2O2) based on a four-bilayer film fabricated through layer by layer assembly between hemoglobin (Hb) and multiwall carbon nanotubes (MWCNTs). We observed that response of electroactive probe Fe(CN)6(3-) at the multilayer films was very sensitive and reversible to pH values of phosphate buffer solutions phosphate buffer solution with cyclic voltammetry. The reduction peak height of Fe(CN)6(3-) at the multilayer film could reach ∼221μA at pH 3.0 while 0μA at pH 9.0. The linear range for the detection of H2O2 at pH 3.0 was from 12.5μM to 10.4mM, which was much wider than that at pH 9.0. Our results demonstrated that the detection of H2O2 with the proposed modified electrode is dependent on pH values of phosphate buffer solution. Moreover, the component of multilayer films has impacts on the performance of biosensors with pH-switchable behaviors. Copyright © 2015 Elsevier B.V. All rights reserved.

pH-dependent optical properties of N-acetyl-L-cysteine-capped ZnSe(S) nanocrystals with intense/stable emissions

NASA Astrophysics Data System (ADS)

Soheyli, Ehsan; Sahraei, Reza; Nabiyouni, Gholamreza

2017-03-01

In the present study, a series of aqueous-based ZnSe(S) nanocrystals (NCs) was prepared at different solution pH ranging from 8 to 11.9, and using N-acetyl-L-cysteine (NAC) as capping agent. In addition to zinc blende structure, the X-ray diffraction studies demonstrated the quantum size regime of the ZnSe(S) NCs. To gain further insight toward the influence of the quantum confinement and pH values on optical properties of the as-prepared NCs, their UV-visible absorption and photoluminescence spectra were systematically analyzed. The absorption spectra experienced a red shift from 340 to 382 nm as the pH increased from 8.0 to 11.9, indicating the growth of the as-prepared ZnSe(S) NCs. The emission spectra also show the obvious red shift and the relative area of excitonic to trap emission, firstly increases from pH = 8.0 to 10.7, and then decreases by further increasing of the solution pH. The initial behavior might be due to the improved surface passivation of the trap dangling states by better deprotonation of thiol groups in NAC, whereas at pH >10.7, the faster growth rate of the ZnSe(s) NCs may lead to the formation of many defect sites. All of these phenomena were combined in the scheme which displays the effect of quantum confinement and solution pH on variation of the excitonic and trap-related emissions.

In situ chemical oxidation of BTEX and MTBE by ferrate: pH dependence and stability.

PubMed

Pepino Minetti, Roberto C; Macaño, Héctor R; Britch, Javier; Allende, M Carla

2017-02-15

Gasoline spills from underground storage tanks are a worldwide environmental problem. BTEX and MtBE are the compounds of gasoline that present the highest degree of migration due to their chemical properties, and are therefore able to impact groundwater reservoirs. In situ chemical oxidation (ISCO) is an emerging technology for groundwater remediation. Several compounds such as permanganate and hydrogen peroxide among others have been used as oxidants, a strong impact of pH on the relative stabilities and reduction potentials having been in each case determined. This paper presents a study of stability and degradation of BTEX and MtBE at different pH ranges of a novel oxidant for ISCO, potassium ferrate (K 2 FeO 4 ). To carry out this study, BTEX and MtBE solutions were prepared in different phosphate buffers (pH 5,8; 7; 9; 10 and 11) in concentration ratio of (FeO 4 -2 )/(BTEX+MtBE)=100:1. Each solution was analyzed at different times by gas chromatography with photoionization and tandem mass spectrometer detector. The results show a higher degree of degradation at pH 7 for Benzene and Toluene, and at pH 9 for Ethyl benzene and Xylenes, while MtBE proved recalcitrant to degradation by ferrate. The most favorable pH for stability of FeO 4 -2 solution was confirmed in 9-10. Copyright © 2016 Elsevier B.V. All rights reserved.

Formation of Hg(II) tetrathiolate complexes with cysteine at neutral pH

DOE PAGES

Warner, Thomas; Jalilehvand, Farideh

2016-01-04

Mercury(II) ions precipitate from aqueous cysteine (H 2Cys) solutions containing H 2Cys/Hg(II) mole ratio ≥ 2.0 as Hg( S-HCys) 2. In absence of additional cysteine, the precipitate dissolves at pH ~12 with the [Hg( S, N-Cys) 2] 2- complex dominating. With excess cysteine (H 2Cys/Hg(II) mole ratio ≥ 4.0), higher complexes form and the precipitate dissolves at lower pH values. Previously, we found that tetrathiolate [Hg( S-Cys) 4] 6- complexes form at pH = 11.0; in this work we extend the investigation to pH values of physiological interest. We examined two series of Hg(II)-cysteine solutions in which C Hg(II) variedmore » between 8 – 9 mM and 80 – 100 mM, respectively, with H 2Cys/Hg(II) mole ratios from 4 to ~20. The solutions were prepared in the pH range 7.1 – 8.8, at the pH at which the initial Hg( S-HCys) 2 precipitate dissolved. The variations in the Hg(II) speciation were followed by 199Hg NMR, X-ray absorption and Raman spectroscopic techniques. Our results show that in the dilute solutions (C Hg(II) = 8 – 9 mM), mixtures of di-, tri- (major) and tetrathiolate complexes exist at moderate cysteine excess (C H2Cys ~ 0.16 M) at pH 7.1. In the more concentrated solutions (C Hg(II) = 80 – 100 mM) with high cysteine excess (C H2Cys > 0.9 M), tetrathiolate [Hg( S-cysteinate) 4] m-6 ( m = 0 – 4) complexes dominate in the pH range 7.3 – 7.8, with lower charge than for the [Hg( S-Cys) 4] 6- complex due to protonation of some ( m) of the amino groups of the coordinated cysteine ligands. In conclusion, the results of this investigation could provide a key to the mechanism of biosorption and accumulation of Hg(II) ions in biological / environmental systems.« less

Removal of trivalent chromium from aqueous solution by zeolite synthesized from coal fly ash.

PubMed

Wu, Deyi; Sui, Yanming; He, Shengbing; Wang, Xinze; Li, Chunjie; Kong, Hainan

2008-07-15

The capability of 14 zeolites synthesized from different fly ashes (ZFAs) to sequestrate Cr(III) from aqueous solutions was investigated in a batch mode. The influence of pH on the sorption of Cr(III) was examined. ZFAs had a much greater ability than fly ash to remove Cr(III), due to the high cation exchange capacity (CEC) and the high acid neutralizing capacity (ANC) of ZFAs. The mechanism of Cr(III) removal by ZFAs involved ion exchange and precipitation. A high-calcium content in both the fly ashes and ZFAs resulted in a high ANC value and, as a result, a high immobilization capacity for Cr(III). The pH strongly influenced Cr(III) removal by ZFAs. Inside the solubility range, removal of chromium increased with increasing pH. Hydroxysodalite made from a high-calcium fly ash had a higher sorptive capacity for Cr(III) than the NaP1 zeolite from medium- and low-calcium fly ashes. On the other hand, at pH values above the solubility range, the efficiency of chromium removal by the ZFAs approached 100% due to the precipitation of Cr(OH)3 on the sorbent surfaces. It is concluded that ZFAs and high-calcium fly ashes may be promising materials for the purification of Cr(III) from water/wastewater.

Effect of pH on polyethylene glycol (PEG)-induced silk microsphere formation for drug delivery.

PubMed

Wu, Jianbing; Xie, Xusheng; Zheng, Zhaozhu; Li, Gang; Wang, Xiaoqin; Wang, Yansong

2017-11-01

The effects of changing solution pH in the range of 3.6-10.0 during a one-step silk microsphere preparation process, by mixing silk and polyethylene glycol (PEG), was assessed. The microspheres prepared at low pH (3.6) showed a more homogeneous size (1-3μm) and less porous texture than those prepared at neutral pH. High pH (10.0) inhibited microsphere formation, yielding small and inhomogeneous microspheres. Compared to neutral pH, low pH also increased the content of silk crystalline β-sheet structure from approx. 30% to above 40%. As a result, the microspheres produced at low pH were more thermally stable as well as resistant to chemical (8M urea) and enzymatic (protease XIV) degradation when compared to microspheres prepared at neutral pH. Doxorubicin hydrochloride (DOX) and curcumin (CUR) were successfully loaded in silk microspheres via control of solution pH. The loading efficiency of DOX was approx. 95% at pH7.0 and approx. 60% for CUR at pH3.6, attributed to charge-charge interactions and hydrophobic interactions between the silk and drug molecules, respectively. When PBS, pH7.4, was used as a medium for release studies, the pH3.6 microspheres released both drugs more slowly than the pH7.0 microspheres, likely due to the high content of crystalline β-sheet structure that enhanced drug-silk interactions as well as restricted drug molecule diffusion. Copyright © 2017. Published by Elsevier B.V.

An electrochemical quartz crystal microbalance study of magnesium dissolution

NASA Astrophysics Data System (ADS)

Ralston, K. D.; Thomas, S.; Williams, G.; Birbilis, N.

2016-01-01

A quartz crystal microbalance (QCM) was used in conjunction with electrochemical measurements to study dissolution of pure magnesium (Mg) sensors in dilute NaCl electrolytes. Open circuit potential and potentiodynamic polarisation experiments were conducted in 0.01 M NaCl, having pH values 3 (buffered) and 6 (unbuffered). In the pH 3 solution, the Mg sensor showed a net mass-loss during the electrochemical tests, whereas, in the unbuffered pH 6 solution Mg showed a net mass-gain, corresponding to the growth of an Mg(OH)2 film on its surface. The loss in the electrochemical efficiency of Mg dissolution due to such direct parasitic Mg(OH)2 growth has been estimated to be around 17-34%. This loss relates to the low capacities and voltage fluctuations reported during discharge of primary Mg batteries.

Lysozyme pattern formation in evaporating droplets

NASA Astrophysics Data System (ADS)

Gorr, Heather Meloy

Liquid droplets containing suspended particles deposited on a solid, flat surface generally form ring-like structures due to the redistribution of solute during evaporation (the "coffee ring effect"). The forms of the deposited patterns depend on complex interactions between solute(s), solvent, and substrate in a rapidly changing, far from equilibrium system. Solute self-organization during evaporation of colloidal sessile droplets has attracted the attention of researchers over the past few decades due to a variety of technological applications. Recently, pattern formation during evaporation of various biofluids has been studied due to potential applications in medical screening and diagnosis. Due to the complexity of 'real' biological fluids and other multicomponent systems, a comprehensive understanding of pattern formation during droplet evaporation of these fluids is lacking. In this PhD dissertation, the morphology of the patterns remaining after evaporation of droplets of a simplified model biological fluid (aqueous lysozyme solutions + NaCl) are examined by atomic force microscopy (AFM) and optical microscopy. Lysozyme is a globular protein found in high concentration, for example, in human tears and saliva. The drop diameters, D, studied range from the micro- to the macro- scale (1 microm -- 2 mm). In this work, the effect of evaporation conditions, solution chemistry, and heat transfer within the droplet on pattern formation is examined. In micro-scale deposits of aqueous lysozyme solutions (1 microm < D < 50 microm), the protein motion and the resulting dried residue morphology are highly influenced by the decreased evaporation time of the drop. The effect of electrolytes on pattern formation is also investigated by adding varying concentrations NaCl to the lysozyme solutions. Finally, a novel pattern recognition program is described and implemented which classifies deposit images by their solution chemistries. The results presented in this PhD dissertation provide insight into the evaporative behavior and pattern formation in droplets of simplified model biological fluids (aqueous lysozyme + NaCl). The patterns that form depend sensitively on the evaporation conditions, characteristic time and length scales, and the physiochemical properties of the solutions. The patterns are unique, dependent on solution chemistry, and may therefore act as a "fingerprint" in identifying fluid properties.

Corrosion Behavior of Titanium Grade 7 in Fluoride-Containing NaCl Brines

DOE Office of Scientific and Technical Information (OSTI.GOV)

NA

2004-05-18

Titanium Grade 7 (UNS R52400) is a titanium-based alloy with 0.12-0.25% Pd. The addition of the small amount of palladium is to ennoble the corrosion potential of Ti, thus improving the corrosion resistance of titanium in reducing environments. In most aqueous environments, Ti and Ti alloys demonstrate excellent corrosion resistance due to the protective oxide film that forms spontaneously and remains stable on the surface. However, Ti and Ti alloys are susceptible to corrosion in fluoride-containing environments due to the formation of complexes such as TiF{sub 6}{sup 2-} and TiF{sub 6}{sup 3-}, which are stable and soluble in electrolyte solutions.more » Without the presence of fluoride, only slight effects from [Cl{sup -}], pH and temperature have been reported [1]. It has been reported that the kinetics of passive corrosion of titanium in neutral solutions and controlled by the migration of the defects in the oxide across the surface film [2]. Thus, the increase in thickness and improvement in film properties, by thermal oxidation, would lead to a significant decrease in the susceptibility to film breakdown and in the passive corrosion rate. This report summarizes recent experiment results in studies of the environmental influence on the corrosion behavior of Titanium Grade 7 (Ti-7) in NaCl brines containing fluoride. The environmental factors to be studied include temperature, pH, chloride and fluoride concentration. This report also includes the effects of oxide film, formed during an anneal treatment, on the corrosion behavior of Ti-7. Polarization measurement techniques including potentiodynamic and potentiostatic scans were use3d to characterize corrosion kinetics and susceptibility. Due to the unique alloying in Titanium Grade 7, the long-term corrosion behavior is heavily influenced by the surface enrichment of Pd. Use of electrochemical impedance spectroscopy in conjunction with a potentiostatic scan will reveal the transformation in the corrosion behavior as a function of Pd enrichment on the metal surface. Surface characterization was done using various analytical techniques including X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and scanning electron microscopy (SEM). The effect of fluoride ion on the corrosion behavior of Ti-7 is strongly dependent on the solution pH. In neutral (pH 8) and alkaline (pH 11) solutions, fluoride did not affect the corrosion rate significantly even though it altered the anodic polarization curve drastically. With pH decreased to 4, the corrosion rate of Ti-7 was increased significantly by the presence of fluoride.« less

pH dependent antioxidant activity of lettuce (L. sativa) and synergism with added phenolic antioxidants.

PubMed

Altunkaya, Arzu; Gökmen, Vural; Skibsted, Leif H

2016-01-01

Influence of pH on the antioxidant activities of combinations of lettuce extract (LE) with quercetin (QC), green tea extract (GTE) or grape seed extract (GSE) was investigated for both reduction of Fremy's salt in aqueous solution using direct electron spin resonance (ESR) spectroscopy and in L-α-phosphatidylcholine liposome peroxidation assay measured following formation of conjugated dienes. All examined phenolic antioxidants showed increasing radical scavenging effect with increasing pH values by using both methods. QC, GTE and GSE acted synergistically in combination with LE against oxidation of peroxidating liposomes and with QC showing the largest effect. The pH dependent increase of the antioxidant activity of the phenols is due to an increase of their electron-donating ability upon deprotonation and to their stabilization in alkaline solutions leading to polymerization reaction. Such polymerization reactions of polyphenolic antioxidants can form new oxidizable -OH moieties in their polymeric products resulting in a higher radical scavenging activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Controlling adsorption of albumin with hyaluronan on silica surfaces and sulfonated latex particles.

PubMed

Berts, Ida; Fragneto, Giovanna; Porcar, Lionel; Hellsing, Maja S; Rennie, Adrian R

2017-10-15

Polysaccharides are known to modify binding of proteins at interfaces and this paper describes studies of these interactions and how they are modified by pH. Specifically, the adsorption of human serum albumin on to polystyrene latex and to silica is described, focusing on how this is affected by hyaluronan. Experiments were designed to test how such binding might be modified under relevant physiological conditions. Changes in adsorption of albumin alone and the co-adsorption of albumin and hyaluronan are driven by electrostatic interactions. Multilayer binding is found to be regulated by the pH of the solution and the molecular mass and concentration of hyaluronan. Highest adsorption was observed at pH below 4.8 and for low molecular mass hyaluronan (≤150kDa) at concentrations above 2mgml -1 . On silica with grafted hyaluronan, albumin absorption is reversed by changes in solvent pH due to their strong electrostatic attraction. Albumin physisorbed on silica surfaces is also rinsed away with dilute hyaluronan solution at pH 4.8. The results demonstrate that the protein adsorption can be controlled both by changes of pH and by interaction with other biological macromolecules. Copyright © 2017 Elsevier Inc. All rights reserved.

Characterization of polyphenol oxidase from the Manzanilla cultivar (Olea europaea pomiformis) and prevention of browning reactions in bruised olive fruits.

PubMed

Segovia-Bravo, Kharla A; Jarén-Galan, Manuel; García-García, Pedro; Garrido-Fernandez, Antonio

2007-08-08

The crude extract of the polyphenol oxidase (PPO) enzyme from the Manzanilla cultivar (Olea europaea pomiformis) was obtained, and its properties were characterized. The browning reaction followed a zero-order kinetic model. Its maximum activity was at pH 6.0. This activity was completely inhibited at a pH below 3.0 regardless of temperature; however, in alkaline conditions, pH inhibition depended on temperature and was observed at values above 9.0 and 11.0 at 8 and 25 degrees C, respectively. The thermodynamic parameters of substrate oxidation depended on pH within the range in which activity was observed. The reaction occurred according to an isokinetic system because pH affected the enzymatic reaction rate but not the energy required to carry out the reaction. In the alkaline pH region, browning was due to a combination of enzymatic and nonenzymatic reactions that occurred in parallel. These results correlated well with the browning behavior observed in intentionally bruised fruits at different temperatures and in different storage solutions. The use of a low temperature ( approximately 8 degrees C) was very effective for preventing browning regardless of the cover solution used.

Coupling the Alkaline-Surfactant-Polymer Technology and The Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding from swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetatexanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan gum gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar. Performance and produced polymer evaluation of four alkaline-surfactant-polymer projects concluded that only one of the projects could have benefited from combining the alkaline-surfactant-polymer and gelation technologies. Cambridge, the 1993 Daqing, Mellott Ranch, and the Wardlaw alkaline-surfacant-polymer floods were studied. An initial gel treatment followed by an alkaline-surfactant-polymer flood in the Wardlaw field would have been a benefit due to reduction of fracture flow.« less

Hydrolysis mechanism of methyl parathion evidenced by Q-Exactive mass spectrometry.

PubMed

Liu, Yuan; Zhang, Caixiang; Liao, Xiaoping; Luo, Yinwen; Wu, Sisi; Wang, Jianwei

2015-12-01

Organophosphorus pesticides (OPPs), a kind of widely used pesticides, are currently attracting great attention due to their adverse effects on human central nervous systems, particularly in children. Although the hydrolysis behavior of OPPs has been studied well, its hydrolysis mechanism remained controversial, especially at various pH conditions, partly due to their relatively complex structures and abundant moieties that were prone to be attacked by nucleophiles. The Q-Exactive mass spectrometer, part of those hybrid high-resolution mass spectrometers (HRMS), was used to determine hydrolysis products of methyl parathion (MP), a kind of OPPs in situ buffer aqueous solution with pH ranging from 1 to 13 in this study. Most of the complex hydrolysis products of MP were identified due to the high sensitivity and accuracy of HRMS. The results demonstrated that the hydrolysis rate and pathway of MP were strong pH dependent. With the increase of pH, the hydrolysis rate of MP increased, and two different reaction mechanisms were identified: SN (2)@P pathway dominated the hydrolysis process at high pH (e.g., pH ≥ 11) while SN (2)@C was the main behavior at low pH (e.g., pH ≤ 9). This study helps understand the hydrolysis mechanism of OPPs at various pH and extends the use of Q-Exactive mass spectrometry in identifying organic pollutants and their degradation products in environmental matrices.

Biosorption and Biomineralization of U(VI) by the Marine Bacterium Idiomarina loihiensis MAH1: Effect of Background Electrolyte and pH

PubMed Central

Morcillo, Fernando; González-Muñoz, María T.; Reitz, Thomas; Romero-González, María E.; Arias, José M.; Merroun, Mohamed L.

2014-01-01

The main goal of this study is to compare the effects of pH, uranium concentration, and background electrolyte (seawater and NaClO4 solution) on the speciation of uranium(VI) associated with the marine bacterium Idiomarina loihiensis MAH1. This was done at the molecular level using a multidisciplinary approach combining X-ray Absorption Spectroscopy (XAS), Time-Resolved Laser-Induced Fluorescence Spectroscopy (TRLFS), and High Resolution Transmission Electron Microscopy (HRTEM). We showed that the U(VI)/bacterium interaction mechanism is highly dependent upon pH but also the nature of the used background electrolyte played a role. At neutral conditions and a U concentration ranging from 5·10−4 to 10−5 M (environmentally relevant concentrations), XAS analysis revealed that uranyl phosphate mineral phases, structurally resembling meta-autunite [Ca(UO2)2(PO4)2 2–6H2O] are precipitated at the cell surfaces of the strain MAH1. The formation of this mineral phase is independent of the background solution but U(VI) luminescence lifetime analyses demonstrated that the U(VI) speciation in seawater samples is more intricate, i.e., different complexes were formed under natural conditions. At acidic conditions, pH 2, 3 and 4.3 ([U] = 5·10−4 M, background electrolyte  = 0.1 M NaClO4), the removal of U from solution was due to biosorption to Extracellular Polysaccharides (EPS) and cell wall components as evident from TEM analysis. The L III-edge XAS and TRLFS studies showed that the biosorption process observed is dependent of pH. The bacterial cell forms a complex with U through organic phosphate groups at pH 2 and via phosphate and carboxyl groups at pH 3 and 4.3, respectively. The differences in the complexes formed between uranium and bacteria on seawater compared to NaClO4 solution demonstrates that the actinide/microbe interactions are influenced by the three studied factors, i.e., the pH, the uranium concentration and the chemical composition of the solution. PMID:24618567

Toxicity of Pb and of Pb/Cd combination on the springtail Folsomia candida in natural soils: reproduction, growth and bioaccumulation as indicators.

PubMed

Bur, T; Crouau, Y; Bianco, A; Gandois, L; Probst, A

2012-01-01

The toxicity of Pb and Cd+Pb was assessed on the Collembola F. candida in two cultivated soils (SV and AU) with low organic matter (OM) content and circumneutral to basic pH, and an acid forested soil (EPC) with high OM content. Collembola reproduction and growth as well as metal content in Collembola body, in soil, exchangeable fraction and soil solutions, pH and DOC were investigated. Pb and Cd+Pb were the highest in exchangeable fraction and soil solution of the acidic soils. Soil solution pH decreased after metal spiking in every soil due to metal adsorption, which was similar for Cd and the highest in AU for Pb. With increasing Pb and Cd+Pb, the most important reproduction decrease was in EPC soil. The LOEC for reproduction after metal addition was 2400 (Pb) and 200/2400 (Cd/Pb), 1200 and 100/1200, 300 and 100/1200 μg g(-1) for AU, SV and EPC, respectively. The highest and the lowest Pb toxicity was observed for EPC and AU bulk soil, respectively. The metal in Collembola increased with increasing soil concentration, except in AU, but the decreasing BF(solution) with increasing concentrations indicates a limited metal transfer to Collembola or an increased metal removal. Loading high Pb concentrations decreases Cd absorption by the Collembola, but the reverse was not true. The highest Pb toxicity in EPC can be explained by pH and OM content. Because of metal complexation, OM might have a protective role but its ingestion by Collembola lead to higher toxicity. Metal bioavailability in Collembola differs from soil solution indicating that soil solution is not sufficient to evaluate toxicity in soil organisms. The toxicity as a whole decreased when metals were combined, except for Pb in AU, due to adsorption competition between Cd and Pb on clay particles and OM sites in AU and EPC soils, respectively. Copyright © 2011 Elsevier B.V. All rights reserved.

The Limitations of an Exclusively Colloidal View of Protein Solution Hydrodynamics and Rheology

PubMed Central

Sarangapani, Prasad S.; Hudson, Steven D.; Migler, Kalman B.; Pathak, Jai A.

2013-01-01

Proteins are complex macromolecules with dynamic conformations. They are charged like colloids, but unlike colloids, charge is heterogeneously distributed on their surfaces. Here we overturn entrenched doctrine that uncritically treats bovine serum albumin (BSA) as a colloidal hard sphere by elucidating the complex pH and surface hydration-dependence of solution viscosity. We measure the infinite shear viscosity of buffered BSA solutions in a parameter space chosen to tune competing long-range repulsions and short-range attractions (2 mg/mL ≤ [BSA] ≤ 500 mg/mL and 3.0 ≤ pH ≤ 7.4). We account for surface hydration through partial specific volume to define volume fraction and determine that the pH-dependent BSA intrinsic viscosity never equals the classical hard sphere result (2.5). We attempt to fit our data to the colloidal rheology models of Russel, Saville, and Schowalter (RSS) and Krieger-Dougherty (KD), which are each routinely and successfully applied to uniformly charged suspensions and to hard-sphere suspensions, respectively. We discover that the RSS model accurately describes our data at pH 3.0, 4.0, and 5.0, but fails at pH 6.0 and 7.4, due to steeply rising solution viscosity at high concentration. When we implement the KD model with the maximum packing volume fraction as the sole floating parameter while holding the intrinsic viscosity constant, we conclude that the model only succeeds at pH 6.0 and 7.4. These findings lead us to define a minimal framework for models of crowded protein solution viscosity wherein critical protein-specific attributes (namely, conformation, surface hydration, and surface charge distribution) are addressed. PMID:24268154

Microfluidic Fabrication of Cell Adhesive Chitosan Microtubes

PubMed Central

Oh, Jonghyun; Kim, Keekyoung; Won, Sung Wook; Cha, Chaenyung; Gaharwar, Akhilesh; Selimović, Šeila; Bae, Hojae; Lee, Kwang Ho; Lee, Dong Hwan; Lee, Sang-Hoon; Khademhosseini, Ali

2013-01-01

Chitosan has been used as a scaffolding material in tissue engineering due to its mechanical properties and biocompatibility. With increased appreciation of the effect of micro- and nanoscale environments on cellular behavior, there is increased emphasis on generating microfabricated chitosan structures. Here we employed a microfluidic coaxial flow-focusing system to generate cell adhesive chitosan microtubes of controlled sizes by modifying the flow rates of a chitosan pre-polymer solution and phosphate buffered saline (PBS). The microtubes were extruded from a glass capillary with a 300 μm inner diameter. After ionic crosslinking with sodium tripolyphosphate (TPP), fabricated microtubes had inner and outer diameter ranges of 70-150 μm and 120-185 μm. Computational simulation validated the controlled size of microtubes and cell attachment. To enhance cell adhesiveness on the microtubes, we mixed gelatin with the chitosan pre-polymer solution and adjusted the pH values of the chitosan pre-polymer solution with gelatin and TPP. During the fabrication of microtubes, fibroblasts suspended in core PBS flow adhered to the inner surface of chitosan-gelatin microtubes. To achieve physiological pH values, we adjusted pH values of chiotsan pre-polymer solution and TPP. In particular, we were able to improve cell viability to 92% with pH values of 5.8 and 7.4 for chitosan and TPP solution respectively. Cell culturing for three days showed that the addition of the gelatin enhanced cell spreading and proliferation inside the chitosan-gelatin microtubes. The microfluidic fabrication method for ionically crosslinked chitosan microtubes at physiological pH can be compatible with a variety of cells and used as a versatile platform for microengineered tissue engineering. PMID:23355068

Sorption of Lincomycin by Manure-Derived Biochars from Water

PubMed Central

Liu, Cheng-Hua; Chuang, Ya-Hui; Li, Hui; Teppen, Brian J.; Boyd, Stephen A.; Gonzalez, Javier M.; Johnston, Cliff T.; Lehmann, Johannes; Zhang, Wei

2018-01-01

The presence of antibiotics in agroecosystems raises concerns about the proliferation of antibiotic-resistant bacteria and adverse effects to human health. Soil amendment with biochars pyrolized from manures may be a win-win strategy for novel manure management and antibiotics abatement. In this study, lincomycin sorption by manure-derived biochars was examined using batch sorption experiments. Lincomycin sorption was characterized by two-stage kinetics with fast sorption reaching quasi-equilibrium in the first 2 d, followed by slow sorption over 180 d. The fast sorption was primarily attributed to surface adsorption, whereas the long-term slow sorption was controlled by slow diffusion of lincomycin into biochar pore structures. Two-day sorption experiments were performed to explore effects of biochar particle size, solid/water ratio, solution pH, and ionic strength. Lincomycin sorption to biochars was greater at solution pH 6.0 to 7.5 below the dissociation constant of lincomycin (7.6) than at pH 9.9 to 10.4 above its dissociation constant. The enhanced lincomycin sorption at lower pH likely resulted from electrostatic attraction between the positively charged lincomycin and the negatively charged biochar surfaces. This was corroborated by the observation that lincomycin sorption decreased with increasing ionic strength at lower pH (6.7) but remained constant at higher pH (10). The long-term lincomycin sequestration by biochars was largely due to pore diffusion plausibly independent of solution pH and ionic composition. Therefore, manure-derived biochars had lasting lincomycin sequestration capacity, implying that biochar soil amendment could significantly affect the distribution, transport, and bioavailability of lincomycin in agroecosystems. PMID:27065399

Use of UO 2 films for electrochemical studies

NASA Astrophysics Data System (ADS)

Miserque, F.; Gouder, T.; Wegen, D. H.; Bottomley, P. D. W.

2001-10-01

UO 2 films have been prepared by dc reactive sputtering of a uranium metal target in an Ar/O 2 atmosphere. We have used the films deposited on gold substrates as working electrodes for electrochemical investigations as simulating the surfaces of fuel pellets. Film composition was determined by photoelectron spectroscopy (XPS and UPS) and X-ray diffraction (XRD). The oxide stoichiometry as a function of deposition conditions was determined and the appropriate conditions for UO 2.0 formation established. AC impedance and cyclic voltammetry measurements were performed. A double RC electrical equivalent circuit was used to fit the data from impedance measurements, similar to those used in unirradiated UO 2 or spent fuel pellets. However due to the porosity or adhesion defects on the thin films that permitted a direct contact between the solution and the gold substrate, we were obliged to add a contribution simulating the water-gold system. Cyclic voltammetry measurements show the influence of pH on the dissolution mechanism. Alkaline solutions permit the formation of an oxidised layer (UO 2.33) which is not present in the acidic solutions. In both pH=2 and pH=6 solutions, a U VI species layer is formed.

IN VITRO INTERACTIONS BETWEEN LACTIC ACID SOLUTION AND ART GLASS-IONOMER CEMENTS

PubMed Central

Wang, Linda; Cefaly, Daniela Francisca Gigo; dos Santos, Janaína Lima; dos Santos, Jean Rodrigo; Lauris, José Roberto Pereira; Mondelli, Rafael Francisco Lia; Atta, Maria Teresa

2009-01-01

Objectives: Production of acids such as lactic acid contributes to establish a cariogenic environment that leads to dental substrate demineralization. Fluoride plays an important role in this case and, as fluoride-releasing materials, glass-ionomer cements are expected to contribute to minimize deleterious reactions. This study evaluated interactions of glass-ionomer cements used in atraumatic restorative treatment (ART-GICs) with an aqueous lactic acid solution, testing the null hypotheses that no changes occur in the pH of the solution or on the surface roughness and mass of the ART-GICs when exposed to lactic acid solution over a 6-week period. Material and Methods: Ketac Molar, Fuji IX, Vitro Molar and Magic Glass were tested, and compared to Filtek Z250 and Ketac Fil Plus as control groups. Six specimens of each material were made according to manufacturers' instructions. The pH of the solution and roughness and mass changes of each specimen were determined over 6 weeks. Each specimen was individually stored in 2 mL of 0.02 M lactic acid solution for 1 week, renewing the solution every week. pH of solution and mass of the specimens were monitored weekly, and surface roughness of the specimens was assessed before and at the end of the 6-week acid challenge. pH and mass data were analyzed statistically by repeated measures using one-way ANOVA and Tukey's post-hoc tests for each material. Paired t-tests were used for roughness analysis. Tukey's post-hoc tests were applied to verify differences of final roughness among the materials. Significance level was set at 5%. Results: The null hypotheses were partially rejected. All materials were able to increase the pH of the lactic acid solution and presented rougher surfaces after immersion, while mass change was minimal and generally not statistically significant. Conclusions: These findings can be helpful to predict the performance of these materials under clinical conditions. A protective action against the carious process with significant surface damage due to erosion may be expected. PMID:19668984

Linear adsorption of nonionic organic compounds from water onto hydrophilic minerals: Silica and alumina

USGS Publications Warehouse

Su, Y.-H.; Zhu, Y.-G.; Sheng, G.; Chiou, C.T.

2006-01-01

To characterize the linear adsorption phenomena in aqueous nonionic organic solute-mineral systems, the adsorption isotherms of some low-molecular- weightnonpolar nonionic solutes (1,2,3-trichlorobenzene, lindane, phenanthrene, and pyrene) and polar nonionic solutes (1,3-dinitrobenzene and 2,4-dinitrotoluene) from single-and binary-solute solutions on hydrophilic silica and alumina were established. Toward this objective, the influences of temperature, ionic strength, and pH on adsorption were also determined. It is found that linear adsorption exhibits low exothermic heats and practically no adsorptive competition. The solute-solid configuration and the adsorptive force consistent with these effects were hypothesized. For nonpolar solutes, the adsorption occurs presumably by London (dispersion) forces onto a water film above the mineral surface. For polar solutes, the adsorption is also assisted by polar-group interactions. The reduced adsorptive forces of solutes with hydrophilic minerals due to physical separation by the water film and the low fractions of the water-film surface covered by solutes offer a theoretical basis for linear solute adsorption, low exothermic heats, and no adsorptive competition. The postulated adsorptive forces are supported by observations that ionic strength or pH poses no effect on the adsorption of nonpolar solutes while it exhibits a significant effect on the uptake of polar solutes. ?? 2006 American Chemical Society.

Rigidity and pH dependent Morphology of Beta-Lactoglobulin Spherulites

NASA Astrophysics Data System (ADS)

Gayetsky, Lisa; Armstead, Douglas

2008-03-01

Beta-Lactoglobulin is a milk protein that will denature in acidic solution (less than 2.0 pH) and if heated for extended periods (greater than 18 hours) it will form radial structures called Spherulites. Spherulites, along with the amyloid fibrils that compose them, are of practical importance because they form in the human body and cause the amyloidosis diseases. Different amyloidosis are caused by different types of denatured proteins occurring in different parts of the body. Since it is believed that Spherulite formation is a generic protein characteristic, Beta-Lactoglobulin is a legitimate and easy to use protein to study these structures. In this study we are quantifying the shape of Beta-Lactoglobulin Spherulites to determine if the pH of the protein solution has an impact on the morphology due to side chain interactions or other causes. We are also testing the rigidity of these structures to determine the relevance of small shape changes.

Small angle neutron scattering (SANS) study of gastric mucin solutions

NASA Astrophysics Data System (ADS)

Hong, Z.; Bansil, R.; Waigh, T.; Turner, B.; Bhaskar, K. R.; Afdhal, N.; Lal, J.

2002-03-01

We report the first results from a SANS study of purified porcine gastric mucin solutions in D2O. The ability of this glycoprotein to protect the stomach epithelium from acid damage, may be due to a pH dependent conformational transition which leads to gelation at low pH Cao et. al. (Biophysical. J. 76, 1250, 1999). SANS measurements were made over the concentration range of 1 -15 mg/ml at pH 7, 4 and 2. The data indicate that at pH 7 the excluded volume exponent is 1.7, characteristic of swollen chains whereas at pH 2 this exponent increases to 2, indicating theta or poor solvent conditions, consistent with the hydrophobic interactions increasing at lower pH. From a Guinier analysis of the 1mg/ml data at low q's (0.003- 0.007 Å-1) we estimate the cross section radius of the effective cylinder to be 23nm and its length as 96nm in an unbuffered sample, i.e. close to pH 7. In the intermediate q-range (0.01 -0.1Å-1) at pH 7 a fit to the Debye chain gives radius of gyration Rg of 16nm. Mucin is best modelled as an elongated micelle with a cylindrical or worm-like chain to represent the protein core and the sugar chains forming the corona. Results of such calculations will be presented.

Characterizing the correlation between dephosphorization and solution pH in a calcined water treatment plant sludge.

PubMed

Zhou, Zhenming; Liu, Qidi; Li, Shuwen; Li, Fei; Zou, Jing; Liao, Xiaobin; Yuan, Baoling; Sun, Wenjie

2018-04-26

This study focused on characterizing the correlation between the dephosphorization process of calcined water treatment plant sludge (C-WTPS) and the solution initial pH in batch experiments. The specific aim was to illustrate the effect of different initial pH on the adsorption and desorption of phosphorous in C-WTPS. In addition, the effects of solution initial pH on the release of ammonia nitrogen and total organic carbon (TOC) from C-WTPS and the change of pH after adsorption were also investigated. The results demonstrated that the initial pH significantly influenced the adsorption of phosphorus on C-WTPS. When initial pH was increased from 3 to 10, the phosphorous absorption capacity reduced by 76.5%. Especially, when the initial pH reached to 11, the phosphorus adsorption capacity became a negative value, indicating that C-WTPS released phosphorus into the solution. The addition of C-WTPS to the solution had little impact on the initial pH of the solution. The absorbed phosphorous on C-WTPS was relatively stable in the pH range of 3 to 10. Nevertheless, when the solution pH was higher than 11, it can be easily released into the solution. Furthermore, by comparison with WTPS, C-WTPS released less ammonia nitrogen and TOC into the solution and adsorbed more phosphorus from the solution in the experimental pH range. Therefore, C-WTPS is more suitable to serve as a cost-effective sorbent for phosphorus removal.

Kinetics and equilibrium of solute diffusion into human hair.

PubMed

Wang, Liming; Chen, Longjian; Han, Lujia; Lian, Guoping

2012-12-01

The uptake kinetics of five molecules by hair has been measured and the effects of pH and physical chemical properties of molecules were investigated. A theoretical model is proposed to analyze the experimental data. The results indicate that the binding affinity of solute to hair, as characterized by hair-water partition coefficient, scales to the hydrophobicity of the solute and decreases dramatically as the pH increases to the dissociation constant. The effective diffusion coefficient of solute depended not only on the molecular size as most previous studies suggested, but also on the binding affinity as well as solute dissociation. It appears that the uptake of molecules by hair is due to both hydrophobic interaction and ionic charge interaction. Based on theoretical considerations of the cellular structure, composition and physical chemical properties of hair, quantitative-structure-property-relationships (QSPR) have been proposed to predict the hair-water partition coefficient (PC) and the effective diffusion coefficient (D (e)) of solute. The proposed QSPR models fit well with the experimental data. This paper could be taken as a reference for investigating the adsorption properties for polymeric materials, fibres, and biomaterials.

X-ray photoelectron spectroscopy and electrochemical studies of mild steel FeE500 passivation in concrete simulated water

NASA Astrophysics Data System (ADS)

Miserque, F.; Huet, B.; Azou, G.; Bendjaballah, D.; L'Hostis, V.

2006-11-01

In the context of the prediction of the long-term behaviour of reinforced concrete structures involved in the nuclear waste storage, the corrosion mechanisms of steels have to be assessed. When mild steel rebars are embedded in concrete, the chemical environment of the reinforcement is progressively modified, due to the carbonation of the concrete matrix. This modification leads to the variation of iron oxides properties formed at the steel/concrete interface, and the active corrosion can be initiated. The aim of this study is to evaluate the passivation behaviour and to provide insights into the depassivation of mild steel in concrete pore solution. In a young concrete, due to the alkalinity of the interstitial solution, steel reinforcement remains passive. Immersion tests of mild steel substrate in various alkaline solutions (from pH 13 to 10) have been performed. Due to the low thickness of the corrosion layers formed, X-ray photoelectron spectroscopy has been used to characterize them. In the passive domain, the corrosion products are similar for the various solutions. The corrosion layer is composed of a mixture of Fe3+ and Fe2+. A similar approach is used to determine the depassivation mechanism. The effect of various components such as carbonates, sulfates and silicates resulting from the dissolution of minerals of cement during the carbonation process is investigated. In addition to the surface analysis, the evolution of the electrochemical behaviour as function of the solution nature (pH) is evaluated with the help of electrochemical measurements (free corrosion potential, cyclic voltamperometry).

Electrosorption of As(III) in aqueous solutions with activated carbon as the electrode

NASA Astrophysics Data System (ADS)

Dai, Min; Xia, Ling; Song, Shaoxian; Peng, Changsheng; Rangel-Mendez, Jose Rene; Cruz-Gaona, Roel

2018-03-01

The electrosorption of As(III) in aqueous solutions by using activated carbon (AC) as the electrode was studied in this work. This study was performed through the measurements of adsorption and desorption, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS) and X-ray photoelectron spectra (XPS). Three parameters, applied voltage, solution pH and initial As(III) concentration, on the electrosoprtion of As(III) were investigated. The experimental results have demonstrated that the electrosorption followed three steps: migration of As(III) to the anode, oxidation of As(III) to As(V) and accumulation of As(V) in the electric double layers of the anode. The electrodorption capacity increased with increasing applied voltage and initial As(III) concentration, whereas the effect of pH was complicated for the variation of arsenite species and the competition of OH-. The oxidation of As(III) increased with the increasing voltage and pH due to the increasing redox potential acted on As(III). The electrosorption served to reduce the toxicity of arsenic and was a promising technology for As(III) removal from water.

Prediction of equilibrium parameters of adsorption of lead (II) ions onto diatomite

NASA Astrophysics Data System (ADS)

Salman, Taylan; Ardalı, Yüksel; Gamze Turan, N.

2013-04-01

Heavy metals from industrial wastewaters are one of the most important environmental issues to be solved today. Due to their toxicity and nonbiodegradable nature, heavy metals cause environmental and public health problems. Various techniques have been developed to remove heavy metals from aqueous solutions. These include chemical precipitation, reverse osmosis, ion Exchange and adsorption. Among them, adsorption is considered to be a particularly competitive and effective process for the removal of heavy metals from aqueous solutions. There is growing interest in using low cost, commercially available materials for the adsorption of heavy metals. Diatomite is a siliceous sedimentary rock having an amorphous form of silica (SiO2. nH2O) containing a small amount of microcrystalline material. It has unique combination of physical and chemical properties such as high porosity, high permeability, small particle size, large surface area, and low thermal conductivity. In addition, it is available in Turkey and in various locations around the world. Therefore, diatomite has been successfully used as adsorbent for the removal of heavy metals. The aim of the study is to investigate the adsorption properties of diatomite. The equilibrium adsorption data were applied to the Langmuir, Freundlich and Dubinin-Radushkevic (D-R) isotherm models. Adsorption experiments were performed under batch process, using Pb (II) initial concentration, pH of solution and contact time as variables. The results demonstrated that the adsorption of Pb (II) was strongly dependent on pH of solution. The effect of pH on adsorption of Pb(II) on diatomite was conducted by varying pH from 2 to 12 at 20 oC. In the pH range of 2.0-4.0, the adsorption percentage increases slightly as the pH increasing. At pH>4, the adsorption percentage decreases with increasing pH because hydrolysis product and the precipitation begin to play an important role in the sorption of Pb (II). At pH4, the maximum adsorption capacity of diatomite was found as 26.158 mg/g. The adsorption isotherms of Pb (II) on diatomite can be described well by the Freundlich model. The high adsorption capacity of diatomite makes it suitable low-cost material in the removal of Pb (II) from aqueous solutions.

Electrochemically induced disintegration of layer-by-layer-assembled thin films composed of 2-iminobiotin-labeled poly(ethyleneimine) and avidin.

PubMed

Sato, Katsuhiko; Kodama, Daisuke; Naka, Yukihisa; Anzai, Jun-ichi

2006-12-01

A layer-by-layer assembly composed of avidin and 2-iminobiotin-labeled poly(ethyleneimine) (ib-PEI) was prepared on the surface of a platinum (Pt) film-coated quartz resonator, and an electrochemically induced disintegration of the avidin-ib-PEI assembly was studied using a quartz crystal microbalance. The resonance frequency of a five-bilayer (avidin-ib-PEI)5 film-coated quartz resonator was increased upon application of an electric potential to the Pt layer of the quartz resonator, suggesting that the mass on the quartz resonator was decreased as a result of disintegration of the (avidin-ib-PEI)5 film, due to a pH change in the vicinity of the surface of the Pt-coated quartz resonator. It may be that the (avidin-ib-PEI)5 film assembly was decomposed by acidification of the local pH on the surface of the Pt layer, which in turn was induced through electrolysis of water on Pt, because ib-PEI forms complexes with avidin only in basic media. In pH 9 solution, the (avidin-ib-PEI)5 film was decomposed under the influence of an applied potential of 0.6-1.0 V versus Ag/AgCl. The (avidin-ib-PEI)5 film was decomposed almost completely within a minute in a low concentration buffer (1 mM, pH 9), while the decomposition was slower in 10 and 100 mM buffer solutions at the same pH. The decomposition of the assembly was rapid when the electrode potential was applied in pH 9 solutions, while the response was relatively slow in pH 10 and 11 solutions. All the results are rationalized on the basis of an electrochemically induced acidification of the local environment around the (avidin-ib-PEI)5 film on the Pt layer.

Humic acid protein complexation

NASA Astrophysics Data System (ADS)

Tan, W. F.; Koopal, L. K.; Weng, L. P.; van Riemsdijk, W. H.; Norde, W.

2008-04-01

Interactions of purified Aldrich humic acid (PAHA) with lysozyme (LSZ) are investigated. In solution LSZ is moderately positively and PAHA negatively charged at the investigated pH values. The proton binding of PAHA and of LSZ is determined by potentiometric proton titrations at various KCl concentrations. It is also measured for two mixtures of PAHA-LSZ and compared with theoretically calculated proton binding assuming no mutual interaction. The charge adaptation due to PAHA-LSZ interaction is relatively small and only significant at low and high pH. Next to the proton binding, the mass ratio PAHA/LSZ at the iso-electric point (IEP) of the complex at given solution conditions is measured together with the pH using the Mütek particle charge detector. From the pH changes the charge adaptation due to the interaction can be found. Also these measurements show that the net charge adaptation is weak for PAHA-LSZ complexes at their IEP. PAHA/LSZ mass ratios in the complexes at the IEP are measured at pH 5 and 7. At pH 5 and 50 mmol/L KCl the charge of the complex is compensated for 30-40% by K +; at pH 7, where LSZ has a rather low positive charge, this is 45-55%. At pH 5 and 5 mmol/L KCl the PAHA/LSZ mass ratio at the IEP of the complex depends on the order of addition. When LSZ is added to PAHA about 25% K + is included in the complex, but no K + is incorporated when PAHA is added to LSZ. The flocculation behavior of the complexes is also different. After LSZ addition to PAHA slow precipitation occurs (6-24 h) in the IEP, but after addition of PAHA to LSZ no precipitation can be seen after 12 h. Clearly, PAHA/LSZ complexation and the colloidal stability of PAHA-LSZ aggregates depend on the order of addition. Some implications of the observed behavior are discussed.

Protection of Reinforced Concrete Structures of Waste Water Treatment Reservoirs with Stainless Steel Coating Using Arc Thermal Spraying Technique in Acidified Water

PubMed Central

Lee, Han-Seung; Park, Jin-Ho; Singh, Jitendra Kumar; Ismail, Mohamed A.

2016-01-01

Waste water treatment reservoirs are contaminated with many hazardous chemicals and acids. Reservoirs typically comprise concrete and reinforcement steel bars, and the main elements responsible for their deterioration are hazardous chemicals, acids, and ozone. Currently, a variety of techniques are being used to protect reservoirs from exposure to these elements. The most widely used techniques are stainless steel plating and polymeric coating. In this study, a technique known as arc thermal spraying was used. It is a more convenient and economical method for protecting both concrete and reinforcement steel bar from deterioration in waste water treatment reservoirs. In this study, 316L stainless steel coating was applied to a concrete surface, and different electrochemical experiments were performed to evaluate the performance of coatings in different acidic pH solutions. The coating generated from the arc thermal spraying process significantly protected the concrete surface from corrosion in acidic pH solutions, owing to the formation of a double layer capacitance—a mixture of Cr3+ enriched with Cr2O3 and Cr-hydroxide in inner and Fe3+ oxide on the outer layer of the coating. The formation of this passive film is defective owing to the non-homogeneous 316L stainless steel coating surface. In the pH 5 solution, the growth of a passive film is adequate due to the presence of un-dissociated water molecules in the aqueous sulfuric acid solution. The coated surface is sealed with alkyl epoxide, which acts as a barrier against the penetration of acidic solutions. This coating exhibits higher impedance values among the three studied acidic pH solutions. PMID:28773875

Protection of Reinforced Concrete Structures of Waste Water Treatment Reservoirs with Stainless Steel Coating Using Arc Thermal Spraying Technique in Acidified Water.

PubMed

Lee, Han-Seung; Park, Jin-Ho; Singh, Jitendra Kumar; Ismail, Mohamed A

2016-09-03

Waste water treatment reservoirs are contaminated with many hazardous chemicals and acids. Reservoirs typically comprise concrete and reinforcement steel bars, and the main elements responsible for their deterioration are hazardous chemicals, acids, and ozone. Currently, a variety of techniques are being used to protect reservoirs from exposure to these elements. The most widely used techniques are stainless steel plating and polymeric coating. In this study, a technique known as arc thermal spraying was used. It is a more convenient and economical method for protecting both concrete and reinforcement steel bar from deterioration in waste water treatment reservoirs. In this study, 316L stainless steel coating was applied to a concrete surface, and different electrochemical experiments were performed to evaluate the performance of coatings in different acidic pH solutions. The coating generated from the arc thermal spraying process significantly protected the concrete surface from corrosion in acidic pH solutions, owing to the formation of a double layer capacitance-a mixture of Cr 3+ enriched with Cr₂O₃ and Cr-hydroxide in inner and Fe 3+ oxide on the outer layer of the coating. The formation of this passive film is defective owing to the non-homogeneous 316L stainless steel coating surface. In the pH 5 solution, the growth of a passive film is adequate due to the presence of un-dissociated water molecules in the aqueous sulfuric acid solution. The coated surface is sealed with alkyl epoxide, which acts as a barrier against the penetration of acidic solutions. This coating exhibits higher impedance values among the three studied acidic pH solutions.

Modeling hyporheic zone processes

USGS Publications Warehouse

Runkel, Robert L.; McKnight, Diane M.; Rajaram, Harihar

2003-01-01

Stream biogeochemistry is influenced by the physical and chemical processes that occur in the surrounding watershed. These processes include the mass loading of solutes from terrestrial and atmospheric sources, the physical transport of solutes within the watershed, and the transformation of solutes due to biogeochemical reactions. Research over the last two decades has identified the hyporheic zone as an important part of the stream system in which these processes occur. The hyporheic zone may be loosely defined as the porous areas of the stream bed and stream bank in which stream water mixes with shallow groundwater. Exchange of water and solutes between the stream proper and the hyporheic zone has many biogeochemical implications, due to differences in the chemical composition of surface and groundwater. For example, surface waters are typically oxidized environments with relatively high dissolved oxygen concentrations. In contrast, reducing conditions are often present in groundwater systems leading to low dissolved oxygen concentrations. Further, microbial oxidation of organic materials in groundwater leads to supersaturated concentrations of dissolved carbon dioxide relative to the atmosphere. Differences in surface and groundwater pH and temperature are also common. The hyporheic zone is therefore a mixing zone in which there are gradients in the concentrations of dissolved gasses, the concentrations of oxidized and reduced species, pH, and temperature. These gradients lead to biogeochemical reactions that ultimately affect stream water quality. Due to the complexity of these natural systems, modeling techniques are frequently employed to quantify process dynamics.

Facilitated strontium transport by remobilization of strontium-containing secondary precipitates in Hanford Site subsurface.

PubMed

Wang, Guohui; Um, Wooyong

2013-03-15

Significantly enhanced immobilization of radionuclides (such as (90)Sr and (137)Cs) due to adsorption and coprecipitation with neo-formed colloid-sized secondary precipitates has been reported at the U.S. Department of Energy's Hanford Site. However, the stability of these secondary precipitates containing radionuclides in the subsurface under changeable field conditions is not clear. Here, the authors tested the remobilization possibility of Sr-containing secondary precipitates (nitrate-cancrinite) in the subsurface using saturated column experiments under different geochemical and flow conditions. The columns were packed with quartz sand that contained secondary precipitates (nitrate-cancrinite containing Sr), and leached using colloid-free solutions under different flow rates, varying pH, and ionic strength conditions. The results indicate remobilization of the neo-formed secondary precipitates could be possible given a change of pH of ionic strength and flow rate conditions. The remobility of the neo-formed precipitates increased with the rise in the leaching solution flow rate and pH (in a range of pH 4-11), as well as with decreasing solution ionic strength. The increased mobility of Sr-containing secondary precipitates with changing background conditions can be a potential source for additional radionuclide transport in Hanford Site subsurface environments. Published by Elsevier B.V.

Heat and pH stability of alkali-extractable corn arabinoxylan and its xylanase-hydrolyzate and their viscosity behavior.

PubMed

Rumpagaporn, Pinthip; Kaur, Amandeep; Campanella, Osvaldo H; Patterson, John A; Hamaker, Bruce R

2012-01-01

In in vitro batch fermentations, both alkali-extractable corn arabinoxylan (CAX) and its xylanase-hydrolyzate (CH) were utilized by human fecal microbiota and produced similar short chain fatty acid (SCFA) contents and desirable long fermentation profiles with low initial gas production. Fortification of these arabinoxylans into processed foods would contribute desirable dietary fiber benefits to humans. Heat and pH stability, as well as viscosity behavior of CAX and CH were investigated. Size exclusion chromatography was used to analyze the molecular size distribution after treatment at different pH's and heating temperatures for different time periods. Treated under boiling and pressure cooking conditions at pH 3, CAX was degraded to a smaller molecular size, whereas the molecular size of the CH showed only a minor decrease. CAX and CH were mostly stable at neutral pH, except when CAX was treated under pressure for 60 min that slightly lowered molecular size. At 37 °C, neither CAX nor CH was adversely affected by treatment at low or neutral pH. The viscosities of solutions containing 5% and 10% of CAX were 48.7 and 637.0 mPa.s, respectively that were higher than those of solutions containing 5% and 10% of its hydrolyzate at shear rate 1 s⁻¹. The CAX solutions showed Newtonian flow behavior, whereas shear-thinning behavior was observed in CH solutions. In conclusion, the hydrolyzate of CAX has potential to be used in high fiber drinks due to its favorable fermentation properties, higher pH and heat stability, lower and shear-thinning viscosity, and lighter color than the native CAX. Arabinoxylan extracted by an alkali from corn bran is a soluble fiber with a desirable low initial and extended fermentation property. Corn arabinoxylan hydrolyzate using an endoxylanase was much more stable at different levels of acidity and heat than the native arabinoxylan, and showed lower solution viscosity and shear-thinning property that indicates its potential as an alternative functional dietary fiber for the beverage industry. © 2011 Institute of Food Technologists®

High-throughput hydrolysis of starch during permeation across α-amylase-immobilized porous hollow-fiber membranes

NASA Astrophysics Data System (ADS)

Miura, Suguru; Kubota, Noboru; Kawakita, Hidetaka; Saito, Kyoichi; Sugita, Kazuyuki; Watanabe, Kohei; Sugo, Takanobu

2002-02-01

Two kinds of supporting porous membranes, ethanolamine (EA) and phenol (Ph) fibers, for immobilization of α-amylase were prepared by radiation-induced graft polymerization of an epoxy-group-containing monomer, glycidyl methacrylate, onto a porous hollow-fiber membrane, and subsequent ring-opening with EA and Ph, respectively. An α-amylase solution was forced to permeate radially outward through the pores of the EA and Ph fibers. α-Amylase was captured at a density of 0.15 and 6.6 g/L of the membrane by the graft chain containing 2-hydroxyethylamino and phenyl groups, respectively. A permeation pressure of 0.10 MPa provided a space velocity of 780 and 1500 h -1 for the α-amylase-immobilized EA and Ph fibers, respectively. Quantitative hydrolysis of starch during permeation of a 20 g/L starch solution in the buffer across the α-amylase-immobilized Ph fiber was attained up to a space velocity of about 2000 h -1; this was achieved because of negligible diffusional mass-transfer resistance of the starch to the α-amylase due to convective flow, whereas an enzyme reaction-controlled system was observed for the α-amylase-immobilized EA fiber.

Nanoparticle titanium dioxide aqueous interfacial energy can be modified to control phase stability, coarsening, and morphology

NASA Astrophysics Data System (ADS)

Finnegan, Michael Patrick

The effect of solution chemistry on the phase stability, coarsening kinetics and morphology of titanium dioxide (TiO2) nanoparticles is investigated in order to attain efficient production pathways to desired nano-structures with optimal properties. To obtain sample, TiO2 was synthesized via hydrolysis of titanium isopropoxide producing an 85% anatase/15% brookite mixture. The titania was hydrothermally heated in an array of temperatures and pH values for various times. There are distinct phase stability fields for nanoscale titania based on pH alone due to slight interface charging behavior differences among the polymorphs. The mixture transforms to rutile below the pH of zero point of charge (ZPC) and remains anatase above the ZPC. This phenomenon is partially reversible. The solution chemistry also dictates the hydrothermal coarsening mechanism of the anatase polymorph. Ostwald ripening (OR) takes place in basic pH where titania solubility is elevated relative to neutral pH where lower solubility prevents rapid OR but allows for coarsening via oriented attachment (OA) of nanoparticles. This OA event can alter the symmetry of anatase causing unexpected and perhaps technically useful morphologies such as straight and curved nanorods during coarsening.

A Flexible Optical pH Sensor Based on Polysulfone Membranes Coated with pH-Responsive Polyaniline Nanofibers.

PubMed

Abu-Thabit, Nedal; Umar, Yunusa; Ratemi, Elaref; Ahmad, Ayman; Ahmad Abuilaiwi, Faraj

2016-06-27

A new optical pH sensor based on polysulfone (PSU) and polyaniline (PANI) was developed. A transparent and flexible PSU membrane was employed as a support. The electrically conductive and pH-responsive PANI was deposited onto the membrane surface by in situ chemical oxidative polymerization (COP). The absorption spectra of the PANI-coated PSU membranes exhibited sensitivity to pH changes in the range of 4-12, which allowed for designing a dual wavelength pH optical sensor. The performance of the membranes was assessed by measuring their response starting from high pH and going down to low pH, and vice versa. It was found that it is necessary to precondition the sensor layers before each measurement due to the slight hysteresis observed during forward and backward pH titrations. PSU membranes with polyaniline coating thicknesses in the range of ≈100-200 nm exhibited fast response times of <4 s, which are attributed to the porous, rough and nanofibrillar morphology of the polyaniline coating. The fabricated pH sensor was characterized by a sigmoidal response (R² = 0.997) which allows for pH determination over a wide dynamic range. All membranes were stable for a period of more than six months when stored in 1 M HCl solution. The reproducibility of the fabricated optical pH sensors was found to be <0.02 absorption units after one month storage in 1 M HCl solution. The performance of the optical pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device.

A Flexible Optical pH Sensor Based on Polysulfone Membranes Coated with pH-Responsive Polyaniline Nanofibers

PubMed Central

Abu-Thabit, Nedal; Umar, Yunusa; Ratemi, Elaref; Ahmad, Ayman; Ahmad Abuilaiwi, Faraj

2016-01-01

A new optical pH sensor based on polysulfone (PSU) and polyaniline (PANI) was developed. A transparent and flexible PSU membrane was employed as a support. The electrically conductive and pH-responsive PANI was deposited onto the membrane surface by in situ chemical oxidative polymerization (COP). The absorption spectra of the PANI-coated PSU membranes exhibited sensitivity to pH changes in the range of 4–12, which allowed for designing a dual wavelength pH optical sensor. The performance of the membranes was assessed by measuring their response starting from high pH and going down to low pH, and vice versa. It was found that it is necessary to precondition the sensor layers before each measurement due to the slight hysteresis observed during forward and backward pH titrations. PSU membranes with polyaniline coating thicknesses in the range of ≈100–200 nm exhibited fast response times of <4 s, which are attributed to the porous, rough and nanofibrillar morphology of the polyaniline coating. The fabricated pH sensor was characterized by a sigmoidal response (R2 = 0.997) which allows for pH determination over a wide dynamic range. All membranes were stable for a period of more than six months when stored in 1 M HCl solution. The reproducibility of the fabricated optical pH sensors was found to be <0.02 absorption units after one month storage in 1 M HCl solution. The performance of the optical pH sensor was tested and the obtained pH values were compared with the results obtained using a pH meter device. PMID:27355953

Influence of pH on Cr(VI) ions removal from aqueous solutions using carboxymethyl cellulose-based hydrogel as adsorbent

NASA Astrophysics Data System (ADS)

Anah, L.; Astrini, N.

2017-03-01

The major problem in heavy metal pollution is that these metals are not biodegradable and accordingly accumulate in the bodies of living organisms, causing dangerous diseases and serious cell disorder. According to World Health Organization (WHO), the long term exposure of Cr(VI) levels of over 0.1 ppm causes respiratory problems, liver and kidney damage, and carcinogenicity.Due to its easy operation and of various cheap adsorbents development, adsorption has been proved to be efficient and most economically attractive technique and feasible to the removal of toxic heavy metal from wastewater. The study aimed to report the removal of Cr(VI) ions from aqueous solutions through adsorption process using carboxymethyl cellulose-graft-poly(acrylic acid) (CMC-g-PAA) hydrogel as adsorbent.Effect of pH was studied to remove hexavalent chromium.Graft copolymerization of poly(acrylic acid) onto carboxymethyl cellulose was carried out in the presence of benzoyl peroxide redox initiator and methylenbisacrylamide as crosslinker agent. Batch experiments were carried out to investigate the effects ofinitial pH.The adsorption of Cr(VI) ions as a function of pH was conducted in the initial pH range of 1 to 8. The results indicated that acidic pH strongly favored the adsorption. The optimum pH for adsorption of Cr(VI) ranged from 1 to 3, and the maximum uptake of Cr(VI) from the solution was 6.53 mg/g at pH 1 and 30°C. FTIR spectroscopy, SEM analyses were performed on the adsorbent before and after Cr(VI) binding. All analyses confirmed the complexation of Cr(VI) ions on the adsorbent.

Hemolysis and cytotoxicity mechanisms of biodegradable magnesium and its alloys.

PubMed

Zhen, Zhen; Liu, Xiaoli; Huang, Tao; Xi, TingFei; Zheng, Yufeng

2015-01-01

Good hemocompatibility and cell compatibility are essential requirements for coronary stents, especially for biodegradable magnesium alloy stents, which could change the in situ environment after implanted. In this work, the effects of magnesium ion concentration and pH value on the hemolysis and cytotoxicity have been evaluated. Solution with different Mg(2+) concentration gradients and pH values of normal saline and cell culture media DMEM adjusted by MgCl2 and NaOH respectively were tested for the hemolysis and cell viability. Results show that even when the concentration of Mg(2+) reaches 1000 μg/mL, it has little destructive effect on erythrocyte, and the high pH value over 11 caused by the degradation is the real reason for the high hemolysis ratio. Low concentrations of Mg(2+) (<100 μg/mL) cause no cytotoxicity to L929 cells, of which the cell viability is above 80%, while high concentrations of Mg(2+) (>300 μg/mL) could induce obvious death of the L929 cells. The pH of the extract plays a synergetic effect on cytotoxicity, due to the buffer action of the cell culture medium. To validate this conclusion, commercial pure Mg using normal saline and PBS as extract was tested with the measurement of pH and Mg(2+) concentration. Pure Mg leads to a higher hemolysis ratio in normal saline (47.76%) than in buffered solution (4.38%) with different pH values and low concentration of Mg(2+). The Mg extract culture media caused no cytotoxicity, with pH=8.44 and 47.80 μg/mL Mg(2+). It is suggested that buffered solution and dynamic condition should be adopted in the hemolysis evaluation. Copyright © 2014. Published by Elsevier B.V.

[Massive transfusion of washed red blood cells: acid-base and electrolyth changes for different wash solutions].

PubMed

Sümpelmann, R; Schürholz, T; Marx, G; Ahrenshop, O; Zander, R

2003-09-01

The composition of normal saline (NaCl), the standard wash solution for cell saver autotransfusion, is considerably different from physiologic plasma values in small infants. Therefore, we investigated acid-base and electrolyte changes during massive cell saver autotransfusion with different wash solutions in young pigs. After approval by the animal protection authorities 15 young pigs (weight 10.6 +/- 1.1 kg, blood volume 848 +/- 88 ml, mean+/-SD) underwent 15 cycles of cell saver autotransfusion (Haemolite 2plus, Haemonetics). For each cycle, 100 ml arterial blood was withdrawn, washed with NaCl, physiologic multielectrolyte solution (PME, V Infusionslösung 296 mval Elektrolyte, Baxter) or physiologic erythrocyte protection solution (PEP, 3.2 % gelatine, pH 7.40, cHCO3 24 mmol/l), and then retransfused. Analyses of acid-base, electrolyte, and hematologic parameters were performed for systemic and washed blood samples. For NaCl there was a progressive decrease in systemic pH, HCO3 and base excess (BE) and an increase in chloride values (Cl) (p < 0.05). Use of PME slightly decreased pH (n. s.), whereas HCO3, BE and Cl remained stable. PEP slightly increased pH, HCO3 and BE, and decreased Cl (n. s.). Free hemoglobin increased in NaCl and PME (p < 0.05) and was below baseline in PEP (n. s.). Lactic acid course was comparable in all groups. The use of NaCl as wash solution for massive autotransfusion resulted in metabolic acidosis caused by dilution of HCO3 and increased Cl values. Fewer systemic acid-base and electrolyte changes were observed, when blood was washed with PME or PEP. The decreased hemoglobin release with PEP is possibly due to a gelatine specific electrostatic surface coating of erythrocyte membranes. For massive transfusion of washed red blood cells, physiologic multielectrolyte solution and physiologic erythrocyte protection solution should be preferred to NaCl, especially for small infants.

Controls on accumulation and soil solution partitioning of heavy metals across upland sites in United Kingdom (UK).

PubMed

Zia, Afia; van den Berg, Leon; Ahmad, Muhammad Nauman; Riaz, Muhammad; Zia, Dania; Ashmore, Mike

2018-05-31

A significant body of knowledge suggests that soil solution pH and dissolved organic carbon (DOC) strongly influence metal concentrations and speciation in porewater, however, these effects vary between different metals. This study investigated the factors influencing soil and soil solution concentrations of copper (Cu), lead (Pb), nickel (Ni) and zinc (Zn) under field conditions in upland soils from UK having a wide range of pH, DOC and organic matter contents. The study primarily focussed on predicting soil and soil solution metal concentrations from the data on total soil metal concentrations (HNO 3 extracts) and soil and soil solution properties (pH, DOC and organic matter content). We tested the multiple regression models proposed by Tipping et al. (2003) to predict heavy metal concentrations in soil solutions and the results indicated a better fit (higher R 2 values) in both studies for Pb compared to the Zn and Cu concentrations. Both studies observed consistent negative relationships of metals with pH and loss on ignition (LOI) suggesting an increase in soil solution metal concentrations with increasing acidity. The positive relationship between Pb concentrations in porewater and HNO 3 extracts was similar for both studies, however, similar relationships were not found for the Zn and Cu concentrations because of the negative coefficients for these metals in our study. The results of this study conclude that the predictive equations of Tipping et al. (2003) may not be applicable to the field sites where the range of DOC and metal concentrations is much lower than their study. Our study also suggests that the extent to which metals are partitioned into soil solution is lower in soils with a higher organic matter contents due to binding of these metals to soil organic matter. Copyright © 2018 Elsevier Ltd. All rights reserved.

Adsorption of superplasticizer admixtures on alkali-activated slag pastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Palacios, M.; Houst, Y.F.; Bowen, P.

2009-08-15

Alkali-activated slag (AAS) binders are obtained by a manufacturing process less energy-intensive than ordinary Portland cement (OPC) and involves lower greenhouse gasses emission. These alkaline cements allow the production of high mechanical strength and durable concretes. In the present work, the adsorption of different superplasticizer admixtures (naphthalene-based, melamine-based and a vinyl copolymer) on the slag particles in AAS pastes using alkaline solutions with different pH values have been studied in detail. The effect of the superplasticizers on the yield stress and plastic viscosity of the AAS and OPC pastes have been also evaluated. The results obtained allowed us to concludemore » that the adsorption of the superplasticizers on AAS pastes is independent of the pH of the alkaline solutions used and lower than on OPC pastes. However, the effect of the admixtures on the rheological parameters depends directly on the type and dosage of the superplasticizer as well as of the binder used and, in the case of the AAS, on the pH of the alkaline activator solution. In 11.7-pH NaOH-AAS pastes the dosages of the superplasticizers required to attain similar reduction in the yield stress are ten-fold lower than for Portland cement. In this case the superplasticizers studied show a fluidizing effect considerably higher in 11.7-pH NaOH-AAS pastes than in OPC pastes. In 13.6-pH NaOH-AAS pastes, the only admixture observed to affect the rheological parameters is the naphthalene-based admixture due to its higher chemical stability in such extremely alkaline media.« less

Improvement of physicomechanical properties of carbamazepine by recrystallization at different pH values.

PubMed

Javadzadeh, Yousef; Mohammadi, Ameneh; Khoei, Nazaninossadat Seyed; Nokhodchi, Ali

2009-06-01

The morphology of crystals has an appreciable impact role on the physicochemical properties of drugs. Drug properties such as flowability, dissolution, hardness and bioavailability may be affected by crystallinity behaviours of drugs. The objective of this study was to achieve an improved physicomechanical property of carbamazepine powder through recrystallization from aqueous solutions at different pH values. For this purpose, carbamazapine was recrystallized from aqueous solutions at different pH values (1, 7, 11). The morphology of crystals was investigated using scanning electron microscopy; X-ray powder diffraction (XRPD) was used to identify polymorphism; thermodynamic properties were analyzed using differential scanning calorimetery (DSC). Dissolution rate was determined using USP dissolution apparatus. Mechanical behavior of recrystallized carbamazepine powders was investigated by making tablets under different compaction pressure and measuring their hardness. SEM studies showed that the carbamazepine crystallization in different media affected the morphology and size of carbamazepine crystals. The shape of carbamazepine crystals changed from flaky or thin plate-like to needle shape. XRPD and DSC results ruled out any crystallinity changes occurring due to the temperature during recrystallization procedure or pH of crystallization media. The crushing strength of tablets indicated that all of the recrystallized carbamazepine samples had better compactiblity than the original carbamazepine powder. In vitro dissolution studies of carbamazepine samples showed a higher dissolution rate for carbamazepine crystals obtained from media with pH 11 and 1. Carbamazepine particles recrystallized from aqueous solutions of different pH values (all media) appeared to have superior mechanical properties to those of the original carbamazepine sample.

In situ optimization of pH for parts-per-billion electrochemical detection of dissolved hydrogen sulfide using boron doped diamond flow electrodes.

PubMed

Bitziou, Eleni; Joseph, Maxim B; Read, Tania L; Palmer, Nicola; Mollart, Tim; Newton, Mark E; Macpherson, Julie V

2014-11-04

A novel electrochemical approach to the direct detection of hydrogen sulfide (H2S), in aqueous solutions, covering a wide pH range (acid to alkali), is described. In brief, a dual band electrode device is employed, in a hydrodynamic flow cell, where the upstream electrode is used to controllably generate hydroxide ions (OH(-)), which flood the downstream detector electrode and provide the correct pH environment for complete conversion of H2S to the electrochemically detectable, sulfide (HS(-)) ion. All-diamond, coplanar conducting diamond band electrodes, insulated in diamond, were used due to their exceptional stability and robustness when applying extreme potentials, essential attributes for both local OH(-) generation via the reduction of water, and for in situ cleaning of the electrode, post oxidation of sulfide. Using a galvanostatic approach, it was demonstrated the pH locally could be modified by over five pH units, depending on the initial pH of the mobile phase and the applied current. Electrochemical detection limits of 13.6 ppb sulfide were achieved using flow injection amperometry. This approach which offers local control of the pH of the detector electrode in a solution, which is far from ideal for optimized detection of the analyte of interest, enhances the capabilities of online electrochemical detection systems.

The influence of carbon nanotubes on the properties of water solutions and fresh cement pastes

NASA Astrophysics Data System (ADS)

Leonavičius, D.; Pundienė, I.; Girskas, G.; Pranckevičienė, J.; Kligys, M.; Sinica, M.

2017-10-01

It is known, that the properties of cement-based materials can be significantly improved by addition of carbon nanotubes (CNTs). The dispersion of CNTs is an important process due to an extremely high specific surface area. This aspect is very relevant and is one of the main factors for the successful use of CNTs in cement-based materials. The influence of CNTs in different amounts (from 0 to 0.5 percent) on the pH values of water solutions and fresh cement pastes, and also on rheological properties, flow characteristics, setting time and EXO reaction of the fresh cement pastes was analyzed in this work. It was found that the increment of the amount of CNTs leads to decreased pH values of water solutions and fresh cement pastes, and also increases viscosity, setting times and EXO peak times of fresh cement pastes.

Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

NASA Astrophysics Data System (ADS)

Shimada, Hiroyuki; Minami, Hirotake; Okuizumi, Naoto; Sakuma, Ichiro; Ukai, Masatoshi; Fujii, Kentaro; Yokoya, Akinari; Fukuda, Yoshihiro; Saitoh, Yuji

2015-05-01

X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5'-monophosphate (CMP), 2'-deoxythymidine 5'-monophosphate (dTMP), and uridine 5'-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations. This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.

Nitrogen K-edge x-ray absorption near edge structure of pyrimidine-containing nucleotides in aqueous solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimada, Hiroyuki, E-mail: hshimada@cc.tuat.ac.jp; Minami, Hirotake; Okuizumi, Naoto

2015-05-07

X-ray absorption near edge structure (XANES) was measured at energies around the N K-edge of the pyrimidine-containing nucleotides, cytidine 5′-monophosphate (CMP), 2′-deoxythymidine 5′-monophosphate (dTMP), and uridine 5′-monophosphate (UMP), in aqueous solutions and in dried films under various pH conditions. The features of resonant excitations below the N K-edge in the XANES spectra for CMP, dTMP, and UMP changed depending on the pH of the solutions. The spectral change thus observed is systematically explained by the chemical shift of the core-levels of N atoms in the nucleobase moieties caused by structural changes due to protonation or deprotonation at different proton concentrations.more » This interpretation is supported by the results of theoretical calculations using density functional theory for the corresponding nucleobases in the neutral and protonated or deprotonated forms.« less

Passivation and electrochemical behavior of 316L stainless steel in chlorinated simulated concrete pore solution

NASA Astrophysics Data System (ADS)

Luo, Hong; Su, Huaizhi; Dong, Chaofang; Li, Xiaogang

2017-04-01

In this paper, the passivation and electrochemical behavior of 316L stainless steel in chlorinated simulated concrete pore solutions at different pH was evaluated by potentiodynamic measurements, electrochemical impedance spectroscopy. The composition of the passive film and surface morphology were investigated by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), and scanning electron microscopy, respectively. The results reveal that metastable pitting susceptibility, stable pitting corrosion, and composition of the passive film are influenced by pH value. After long time immersion, a bilayer structure passive film can be formed in this environment. The appearance of molybdates on the outermost surface layer, further enhancing the stability of the passive film. Moreover, the good pitting corrosion resistance of 316L stainless steel in simulated concrete pore solution without carbonated is mainly due to the presence of high Cr/Fe ratio and molybdates ions within the passive film.

Growth and shrinkage of pluronic micelles by uptake and release of flurbiprofen: variation of pH.

PubMed

Alexander, Shirin; de Vos, Wiebe M; Castle, Thomas C; Cosgrove, Terence; Prescott, Stuart W

2012-04-24

The micellization of Pluronic triblock copolymers (P103, P123, and L43) in the presence of flurbiprofen at different pH was studied by small-angle neutron scattering (SANS), pulsed-field gradient stimulated-echo nuclear magnetic resonance (PFGSE-NMR), and surface tension measurements. Addition of flurbiprofen to the Pluronic at low pH leads to an increase in the fraction of micellization, aggregation number, and the core radius of the micelles. However, changing the pH to above the pKa of flurbiprofen in an ethanol/water mixture (∼6.5) reduces the fraction of micellization and results in a weaker interaction between the drug and micelles due to the increased drug solubility in aqueous solution.

Reaction kinetics and oxidation products formation in the degradation of ciprofloxacin and ibuprofen by ferrate(VI).

PubMed

Zhou, Zhengwei; Jiang, Jia-Qian

2015-01-01

The treatment of ciprofloxacin (CIP) and ibuprofen (IBU) in test solutions by ferrate(VI) was investigated in this study. A series of jar test was performed in bench-scale at pH 6-9 and ferrate(VI) dose of 1-5 mg L(-1). Results demonstrated that ferrate(VI) removed CIP from test solutions efficiently, with above 70% of reduction under study conditions. In contrary, the removal rates of IBU were very low, less than 25% in all conditions. Raising ferrate(VI) dose improved the treatment performance, while the influence of solution pH was not significant at pH 6-9 compared with that of ferrate(VI) dose. In addition, kinetic studies of ferrate(VI) with both compounds were carried out at pH 8 and pH 9 (20 °C). Ferrate(VI) had a much higher reactivity with CIP than IBU at pH 8 and pH 9, with CIP's apparent second-order rate constants of 113.7±6.3 M(-1) s(-1) and 64.1±1.0 M(-1) s(-1), respectively. The rate constants of ferrate(VI) with IBU were less than 0.2 M(-1) s(-1) at pH 8 and pH 9. Furthermore, seven oxidation products (OPs) were formed during CIP degradation by ferrate(VI). The attack on the piperazinyl ring of the CIP by ferrate(VI) appeared to lead to the cleavage or hydroxylation of the rings, and the attack on the quinolone moiety by ferrate(VI) might lead to the cleavage of the double bond at the six-member heterocyclic ring. No OPs of IBU were detected during ferrate(VI) oxidation due to very small part of IBU was degraded by ferrate(VI). Copyright © 2014 Elsevier Ltd. All rights reserved.

Biobased, Internally pH-Sensitive Materials: Immobilized Yellow Fluorescent Protein as an Optical Sensor for Spatiotemporal Mapping of pH Inside Porous Matrices.

PubMed

Consolati, Tanja; Bolivar, Juan M; Petrasek, Zdenek; Berenguer, Jose; Hidalgo, Aurelio; Guisán, Jose M; Nidetzky, Bernd

2018-02-28

The pH is fundamental to biological function and its measurement therefore crucial across all biosciences. Unlike homogenous bulk solution, solids often feature internal pH gradients due to partition effects and confined biochemical reactions. Thus, a full spatiotemporal mapping for pH characterization in solid materials with biological systems embedded in them is essential. In here, therefore, a fully biocompatible methodology for real-time optical sensing of pH within porous materials is presented. A genetically encoded ratiometric pH sensor, the enhanced superfolder yellow fluorescent protein (sYFP), is used to functionalize the internal surface of different materials, including natural and synthetic organic polymers as well as silica frameworks. By using controlled, tailor-made immobilization, sYFP is homogenously distributed within these materials and so enables, via self-referenced imaging analysis, pH measurements in high accuracy and with useful spatiotemporal resolution. Evolution of internal pH is monitored in consequence of a proton-releasing enzymatic reaction, the hydrolysis of penicillin by a penicillin acylase, taking place in solution or confined to the solid surface of the porous matrix. Unlike optochemical pH sensors, which often interfere with biological function, labeling with sYFP enables pH sensing without altering the immobilized enzyme's properties in any of the materials used. Fast response of sYFP to pH change permits evaluation of biochemical kinetics within the solid materials. Thus, pH sensing based on immobilized sYFP represents a broadly applicable technique to the study of biology confined to the internally heterogeneous environment of solid matrices.

Stress corrosion cracking properties of 15-5PH steel

NASA Technical Reports Server (NTRS)

Rosa, Ferdinand

1993-01-01

Unexpected occurrence of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15-5PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a highly acidified sodium chloride (NaCl) aqueous solution. The selected alloy for the study was a 15-5PH steel in the H900 condition. The slow strain rate technique was selected to test the metals specimens.

Release rate of diazinon from microcapsule based on melamine formaldehyde

NASA Astrophysics Data System (ADS)

Noviana Utami C., S.; Rochmadi

2018-04-01

The microcapsule containing diazinon as the core material and melamine formaldehyde as the membrane material have been synthesized by in situ polymerization method. The microcapsule membrane in this research is melamine formaldehyde (MF). This research aims to study the effect of pH and temperature on the release rate of diazinon from microcapsule based on melamine formaldehyde in aqueous medium. The results showed that pH and temperature has little effect on the release rate of diazinon from microcapsule based on melamine formaldehyde. This is due to the diffusion through the microcapsule membrane is not influenced by the pH and temperature of the solution outside of microcapsule.

Transport of soil-aged silver nanoparticles in unsaturated sand.

PubMed

Kumahor, Samuel K; Hron, Pavel; Metreveli, George; Schaumann, Gabriele E; Klitzke, Sondra; Lang, Friederike; Vogel, Hans-Jörg

2016-12-01

Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting "soil-aged" Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nanoparticles for different unsaturated flow conditions and for pH=5 and pH=9. The soil-aged Ag NP were less mobile at pH=5 than at pH=9 due to lower electrostatic repulsion at pH=5 for both types of interfaces. Moreover, the physical flow field at different water contents modified the impact of chemical forces at the solid-water interface. An extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) model did not provide satisfactory explanation of the observed transport phenomena unlike for the citrate-coated case. For instance, the eDLVO model assuming sphere-plate geometry predicts a high energy barrier (>90 kT) for the solid-water interface, indicating that nanoparticle attachment is less likely. Furthermore, retardation through reversible sorption at the air-water interface was probably less relevant for soil-aged nanoparticles than for citrate-coated nanoparticles. An additional cation bridging mechanism and straining within the flow field may have enhanced nanoparticle retention at the solid-water interface. The results indicate that the mobility of engineered Ag nanoparticles is sensitive to solution chemistry, especially pH and the concentration of multivalent cations, and to the unsaturated flow conditions influencing particle interaction at biogeochemical interfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

Transport of soil-aged silver nanoparticles in unsaturated sand

NASA Astrophysics Data System (ADS)

Kumahor, Samuel K.; Hron, Pavel; Metreveli, George; Schaumann, Gabriele E.; Klitzke, Sondra; Lang, Friederike; Vogel, Hans-Jörg

2016-12-01

Engineered nanoparticles released into soils may be coated with humic substances, potentially modifying their surface properties. Due to their amphiphilic nature, humic coating is expected to affect interaction of nanoparticle at the air-water interface. In this study, we explored the roles of the air-water interface and solid-water interface as potential sites for nanoparticle attachment and the importance of hydrophobic interactions for nanoparticle attachment at the air-water interface. By exposing Ag nanoparticles to soil solution extracted from the upper soil horizon of a floodplain soil, the mobility of the resulting ;soil-aged; Ag nanoparticles was investigated and compared with the mobility of citrate-coated Ag nanoparticles as investigated in an earlier study. The mobility was determined as a function of hydrologic conditions and solution chemistry using column breakthrough curves and numerical modeling. Specifically, we compared the mobility of both types of nanoparticles for different unsaturated flow conditions and for pH = 5 and pH = 9. The soil-aged Ag NP were less mobile at pH = 5 than at pH = 9 due to lower electrostatic repulsion at pH = 5 for both types of interfaces. Moreover, the physical flow field at different water contents modified the impact of chemical forces at the solid-water interface. An extended Derjaguin-Landau-Verwey-Overbeek (eDLVO) model did not provide satisfactory explanation of the observed transport phenomena unlike for the citrate-coated case. For instance, the eDLVO model assuming sphere-plate geometry predicts a high energy barrier (> 90 kT) for the solid-water interface, indicating that nanoparticle attachment is less likely. Furthermore, retardation through reversible sorption at the air-water interface was probably less relevant for soil-aged nanoparticles than for citrate-coated nanoparticles. An additional cation bridging mechanism and straining within the flow field may have enhanced nanoparticle retention at the solid-water interface. The results indicate that the mobility of engineered Ag nanoparticles is sensitive to solution chemistry, especially pH and the concentration of multivalent cations, and to the unsaturated flow conditions influencing particle interaction at biogeochemical interfaces.

Degradation of bare and silanized silicon wafer surfaces by constituents of biological fluids.

PubMed

Dekeyser, C M; Buron, C C; Derclaye, S R; Jonas, A M; Marchand-Brynaert, J; Rouxhet, P G

2012-07-15

The 24 h stability of bare silicon wafers as such or silanized with CH(3)O-(CH(2)-CH(2)-O)(n)-C(3)H(6)-trichlorosilane (n=6-9) was investigated in water, NaCl, phosphate and carbonate solutions, and in phosphate buffered saline (PBS) at 37 °C (close to biological conditions regarding temperature, high ionic strength, and pH). The resulting surfaces were analyzed using ellipsometry, X-ray Reflectometry (XRR), X-ray Photoelectron Spectroscopy (XPS), and Atomic Force Microscopy (AFM). Incubation of the silanized wafers in phosphate solution and PBS provokes a detachment of the silane layer. This is due to a hydrolysis of Si-O bonds which is favored by the action of phosphate, also responsible for a corrosion of non-silanized wafers. The surface alteration (detachment of silane layer and corrosion of the non-silanized wafer) is also important with carbonate solution, due to a higher pH (8.3). The protection of the silicon oxide layer brought by silane against the action of the salts is noticeable for phosphate but not for carbonate. Copyright © 2012 Elsevier Inc. All rights reserved.

Effect of mineral surface properties (alumina, kaolinite) on the sorptive fractionation mechanisms of soil fulvic acids: Molecular-scale ESI-MS studies

NASA Astrophysics Data System (ADS)

Fleury, Guillaume; Del Nero, Mirella; Barillon, Rémi

2017-01-01

We addressed the effects of mineral surface properties (kaolinite versus Al-oxide) on the sorption-driven fractionation of a soil fulvic acid (FA) at acidic pH, mainly by means of ESI(-)-FTMS analysis of initial and supernatant solutions of FA sorption batch experiments. The MS data provided clear molecular-scale evidence of distinct mechanisms and molecular parameters controlling the FA fractionation upon its sorption on clay and oxide surfaces, respectively. Identification of sorbing and not-sorbing FA compounds in kaolinite-solution systems revealed a weak fractionation among members of sbnd CO2 series of aliphatics or not-condensed aromatics (NCAs) at pH 3.8, and almost no sorption of poorly-oxygenated polycyclic aromatic compounds (PACs) and NCAs. This first molecular-scale description of a FA fractionation in a clay-solution system suggests that H-bonding with low affinity sites (aluminol/silanol) on the basal planes of the clay particles is the main mechanism of sorption. Due to the predominance of such weak and poorly-selective mechanism, the sorption of aliphatic and NCA molecules bearing oxygenated functionalities was prevented at pH 5, due to dissolved Al competing successfully for their coordination. In contrast, a strong FA fractionation was observed onto alumina, with a preferential retention of PACs and highly-oxygenated aliphatics and NCAs. The major part of the poorly oxygenated aliphatics was left in solution. The sorption degree of NCAs and aliphatics was strongly correlated with molecular acidity. For PACs and poorly-oxygenated NCAs, the sorption was driven by reactions of surface ligand exchange (for the most oxygenated compounds) or by hydrophobic interactions (for the least oxygenated compounds).

The effects of surface chemistry of mesoporous silica materials and solution pH on kinetics of molsidomine adsorption

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dolinina, E.S.; Parfenyuk, E.V., E-mail: terrakott37@mail.ru

2014-01-15

Adsorption kinetics of molsidomine on mesoporous silica material (UMS), the phenyl- (PhMS) and mercaptopropyl-functionalized (MMS) derivatives from solution with different pH and 298 K was studied. The adsorption kinetics was found to follow the pseudo-second-order kinetic model for all studied silica materials and pH. Effects of surface functional groups and pH on adsorption efficiency and kinetic adsorption parameters were investigated. At all studied pH, the highest molsidomine amount is adsorbed on PhMS due to π–π interactions and hydrogen bonding between surface groups of PhMS and molsidomine molecules. An increase of pH results in a decrease of the amounts of adsorbedmore » molsidomine onto the silica materials. Furthermore, the highest adsorption rate kinetically evaluated using a pseudo-second-order model, is observed onto UMS and it strongly depends on pH. The mechanism of the adsorption process was determined from the intraparticle diffusion and Boyd kinetic film–diffusion models. The results showed that the molsidomine adsorption on the silica materials is controlled by film diffusion. Effect of pH on the diffusion parameters is discussed. - Graphical abstract: The kinetic study showed that the k{sub 2} value, the rate constant of pseudo-second order kinetic model, is the highest for molsidomine adsorption on UMS and strongly depends on pH because it is determined by availability and accessibility of the reaction sites of the adsorbents molsidomine binding. Display Omitted - Highlights: • The adsorption capacities of UMS, PhMS and MMS were dependent on the pH. • At all studied pH, the highest molsidomine amount is adsorbed on PhMS. • The highest adsorption rate, k{sub 2}, is observed onto UMS and strongly depends on pH. • Film diffusion was the likely rate-limiting step in the adsorption process.« less

40 CFR Appendix A to Subpart Ddd... - Free Formaldehyde Analysis of Insulation Resins by the Hydroxylamine Hydrochloride Method

Code of Federal Regulations, 2011 CFR

2011-07-01

..., readable to 0.01 g or better. 3.2pH meter, standardized to pH 4.0 with pH 4.0 buffer and pH 7 with pH 7.0... N sodium hydroxide solution. 4.2Hydroxylamine hydrochloride solution, 100 grams per liter, pH... stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0, using the...

BIO-REMEDIATED SOIL TECHNIQUES: SUSTAINABLE SOLUTIONS TO ENVIRONMENTAL PROBLEMS

EPA Science Inventory

The effect of ureolysis increases the surrounding pH of the environment due to the production of ammonia and bicarbonate. The result of this alkaline environment may change the relative abundance of members in the population, for example, by favoring the growth of alkalinop...

Dynamic aggregation of the mid-sized gadolinium complex {Ph4[Gd(DTTA)(H2O)2](-)3}.

PubMed

Jaccard, Hugues; Miéville, Pascal; Cannizzo, Caroline; Mayer, Cédric R; Helm, Lothar

2014-02-01

A compound binding three Gd(3+) ions, {Ph4[Gd(DTTA)(H2O)2](-) 3} (where H5DTTA is diethylenetriaminetetraacetic acid), has been synthesized around a hydrophobic center made up of four phenyl rings. In aqueous solution the molecules start to self-aggregate at concentrations well below 1 mM as shown by the increase of rotational correlation times and by the decrease of the translational self-diffusion constant. NMR spectra recorded in aqueous solution of the diamagnetic analogue {Ph4[Y(DTTA)(H2O)2](-)3} show that the aggregation is dynamic and due to intermolecular π-stacking interactions between the hydrophobic aromatic centers. From estimations of effective radii, it can be concluded that the aggregates are composed of two to three monomers. The paramagnetic {Ph4[Gd(DTTA)(H2O)2](-)3} exhibits concentration-dependent (1)H NMR relaxivities with high values of approximately 50 mM(-1) s(-1) (30 MHz, 25 °C) at gadolinium concentrations above 20 mM. A combined analysis of (1)H NMR dispersion profiles measured at different concentrations of the compound and (17)O NMR data measured at various temperatures was performed using different theoretical approaches. The fitted parameters showed that the increase in relaxivity with increasing concentration of the compound is due to slower global rotational motion and an increase of the Lipari-Szabo order parameter S(2).

VALIDATION FOR THE PERMANGANATE DIGESTION OF REILLEX HPQ ANION RESIN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kyser, E.

2009-09-23

The flowsheet for the digestion of Reillex{trademark} HPQ was validated both under the traditional alkaline conditions and under strongly acidic conditions. Due to difficulty in performing a pH adjustment in the large tank where this flowsheet must be performed, the recommended digestion conditions were changed from pH 8-10 to 8 M HNO{sub 3}. Thus, no pH adjustment of the solution is required prior to performing the permanganate addition and digestion and the need to sample the digestion tank to confirm appropriate pH range for digestion may be avoided. Neutralization of the acidic digestion solution will be performed after completion ofmore » the resin digestion cycle. The amount of permanganate required for this type of resin (Reillex{trademark} HPQ) was increased from 1 kg/L resin to 4 kg/L resin to reduce the amount of residual resin solids to a minimal amount (<5%). The length of digestion time at 70 C remains unchanged at 15 hours. These parameters are not optimized but are expected to be adequate for the conditions. The flowsheet generates a significant amount of fine manganese dioxide (MnO{sub 2}) solids (1.71 kg/L resin) and involves the generation of a significant liquid volume due to the low solubility of permanganate. However, since only two batches of resin (40 L each) are expected to be digested, the total waste generated is limited.« less

Evaluation of Sorption Mechanism of Pb (II) and Ni (II) onto Pea (Pisum sativum) Peels.

PubMed

Haq, Atta Ul; Saeed, Muhammad; Anjum, Salma; Bokhari, Tanveer Hussain; Usman, Muhammad; Tubbsum, Saiqa

2017-07-01

The present study was carried out to know the sorption mechanism of Pb (II) and Ni (II) in aqueous solution using pea peels under the influence of sorbent dose, pH, temperature, initial metal ion concentration and contact time. SEM and FTIR were used for characterization of pea peels. The study showed that solution pH affects sorption process and the optimum pH for Pb (II) was 6.0 while for that of Ni (II) was 7.0. Pseudo-second order kinetic model was found to be the most suitable one to explain the kinetic data not only due to high value of R 2 (>0.99) but also due to the closeness of the experimental sorption capacity values to that of calculated sorption capacity values of pseudo second order kinetic model. It can be seen from the results that Freundlich isotherm explains well the equilibrium data (R 2 >0.99). Sorption capacity of pea peels was 140.84 and 32.36 for Pb (II) and Ni (II) mg g -1 respectively. The positive value of ΔH° and negative values of ΔG° suggest that sorption of Pb (II) and Ni (II) onto pea peels is an endothermic and spontaneous process respectively.

Active Control of pH in the Bioculture System Through Carbon Dioxide Control

NASA Technical Reports Server (NTRS)

Monhollon, Luke; Pletcher, David; Hauss, Jessica

2016-01-01

For successful cell research, the growth culture environment must be tightly controlled. Deviance from the optimal conditions will mask the desired variable being analyzed or lead to inconstancies in the results. In standard laboratories, technology and procedures are readily available for the reliable control of variables such as temperature, pH, nutrient loading, and dissolved gases. Due to the nature of spaceflight, and the inherent constraints to engineering designs, these same elements become a challenge to maintain at stable values by both automated and manual approaches. Launch mass, volume, and power usage create significant constraints to cell culture systems; nonetheless, innovative solutions for active environmental controls are available. The acidity of the growth media cannot be measured through standard probes due to the degradation of electrodes and reliance on indicators for chromatography. Alternatively, carbon dioxide sensors are capable of monitoring the pH by leveraging the relationship between the partial pressure of carbon dioxide and carbonic acid in solution across a membrane. In microgravity cell growth systems, the gas delivery system can be used to actively maintain the media at the proper acidity by maintaining a suitable gas mixture around permeable tubing. Through this method, launch mass and volume are significantly reduced through the efficient use of the limited gas supply in orbit.

Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

PubMed

Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

2016-01-01

Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

Postrigor citric acid enhancement can alter cooked color but not fresh color of dark-cutting beef.

PubMed

Stackhouse, R J; Apple, J K; Yancey, J W S; Keys, C A; Johnson, T M; Mehall, L N

2016-04-01

In 2 experiments, dark-cutting (DC) beef strip loins were used to test the effects of citric acid-enhancement pH on visual and instrumental color of fresh and cooked steaks. In Exp. 1 and 2, each DC (mean pH = 6.57 and 6.65, respectively) and normal-pH, low USDA Choice (CH; mean pH = 5.48 and 5.51, respectively) strip loin was cut into 2 equal-length sections, and DC sections were injected to 111% of raw section weight with pH 3.5 to 5.0 (Exp. 1) or pH 2.0 to 3.5 (Exp. 2) solutions made by mixing citric acid in either 0.05% orthophosphate (PO) solution or tap water (HO) base solutions (Exp. 1) and 0.5% PO or 0.5% tripolyphosphate solution base solutions (Exp. 2). After enhancement, sections were cut into steaks, which were assigned to either 5 d of simulated retail display or cooked to 71°C for cooked color measurement. Postenhancement pH of DC steaks enhanced with pH 3.5 to 5.0 solutions did not ( ≥ 0.180) differ from that of nonenhanced DC steaks (Exp. 1) but linearly decreased ( < 0.001) as solution pH decreased from 3.5 to 2.0 (Exp. 2). Even though fresh color scores were increased ( < 0.001) by citric acid enhancement over untreated DC steaks during the first 3 d of display, fresh steak color never ( < 0.001) approached that of nonenhanced CH steaks. When compared with nonenhanced DC steaks, enhancement with pH 3.5 to 5.0 solutions received lower cooked color scores, whereas enhancing DC sections with pH 2.5 solutions produced cooked color and degree-of-doneness scores similar ( ≥ 0.113) to those of nonenhanced CH steaks (Exp. 2). Results indicated that the pH of citric acid enhancement solutions, regardless of base solution, were insufficient to improve the fresh color of DC beef; however, enhancement with pH 2.5 citric acid solutions effectively eliminated the persistent red cooked color typically associated with DC beef comparable with that of normal-pH beef.

Coupling the Alkaline-Surfactant-Polymer Technology and the Gelation Technology to Maximize Oil Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malcolm Pitts; Jie Qi; Dan Wilson

2005-12-01

Gelation technologies have been developed to provide more efficient vertical sweep efficiencies for flooding naturally fractured oil reservoirs or reservoirs with different sand lenses with high permeability contrast. The field proven alkaline-surfactant-polymer technology economically recovers 15% to 25% OOIP more crude oil than waterflooding froin swept pore space of an oil reservoir. However, alkaline-surfactant-polymer technology is not amenable to naturally fractured reservoirs or reservoirs with high permeability contrast zones because much of injected solution bypasses target pore space containing oil. This work investigates whether combining these two technologies could broaden applicability of alkaline-surfactant-polymer flooding into these reservoirs. Fluid-fluid interaction withmore » different gel chemical compositions and alkaline-surfactant-polymer solution with pH values ranging from 9.2 to 12.9 have been tested. Aluminum-polyacrylamide gels are not stable to alkaline-surfactant-polymer solutions at any pH. Chromium-polyacrylamide gels with polymer to chromium ion ratios of 25 or greater were stable to alkaline-surfactant-polymer solutions if solution pH was 10.6 or less. When the polymer to chromium ion was 15 or less, chromium-polyacrylamide gels were stable to alkaline-surfactant-polymer solutions with pH values up to 12.9. Chromium-xanthan gum gels were stable to alkaline-surfactant-polymer solutions with pH values of 12.9 at the polymer to chromium ion ratios tested. Silicate-polyacrylamide, resorcinol-formaldehyde, and sulfomethylated resorcinol-formaldehyde gels were also stable to alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Iron-polyacrylamide gels were immediately destroyed when contacted with any of the alkaline-surfactant-polymer solutions with pH values ranging from 9.2 to 12.9. Gel solutions under dynamic conditions of linear corefloods showed similar stability to alkaline-surfactant-polymer solutions as in the fluid-fluid analyses with the exception of the xanthan gum-chromium acetate gels. Aluminum-polyacrylamide flowing gels are not stable to alkaline-surfactant-polymer solutions of either pH 10.5 or 12.9, either in linear corefloods or in dual separate radial core, common manifold corefloods. Chromium acetate-polyacrylamide flowing and rigid tonguing gels are stable to subsequent alkaline-surfactant-polymer solution injection. Rigid tonguing chromium acetate-polyacrylamide gels maintained permeability reduction better than flowing chromium acetate-polyacrylamide gels. Chromium acetate gels were stable to injection of alkaline-surfactant-polymer solutions at 72 F, 125 F and 175 F in linear corefloods. Chromium acetate-polyacrylamide gels maintained diversion capability after injection of an alkaline-surfactant-polymer solution in stacked; radial coreflood with a common well bore. Chromium acetate-polyacrylamide gel used to seal fractured core maintain fracture closure if followed by an alkaline-surfactant-polymer solution. Chromium acetate-xanthan gum rigid gels are not stable to subsequent alkaline-surfactant-polymer solution injection at 72, 125, and 175 F. Silicate-polyacrylamide gels are not stable with subsequent injection of either a pH 10.5 or a 12.9 alkaline-surfactant-polymer solution. Resorcinol-formaldehyde gels were stable to subsequent alkaline-surfactant-polymer solution injection. When evaluated in a dual core configuration, injected fluid flows into the core with the greatest effective permeability to the injected fluid. The same gel stability trends to subsequent alkaline-surfactant-polymer injected solution were observed. Aluminum citrate-polyacrylamide, resorcinol-formaldehyde, and the silicate-polyacrylamide gel systems did not produce significant incremental oil in linear corefloods. Both flowing and rigid tonguing chromium acetate-polyacrylamide gels and the xanthan gum-chromium acetate gel system produced incremental oil with the rigid tonguing gel producing the greatest amount. Higher oil recovery could have been due to higher differential pressures across cores. Aluminum citrate-polyacrylamide gels, chromium acetate-polyacrylamide gels, silicate-polymer, and chromium-xanthan guin gels did not alter an alkaline-surfactant-polymer solution's ability to produce incremental oil. Incremental oil was reduced with the resorcinol-formaldehyde gel system. Total waterflood plus chemical flood oil recovery sequence recoveries were generally similar.« less

Geochemical evidence of present-day serpentinization

USGS Publications Warehouse

Barnes, I.; LaMarche, Valmore C.; Himmelberg, G.

1967-01-01

Ultrabasic (pH > 11) water issues from some fresh ultramafic bodies. The properties of the ultrabasic solutions are believed to be due to current reactions yielding serpentine from primary olivines and pyroxenes. The low concentrations of divalent iron, divalent magnesium, and dissolved silica from the serpentinization require an increase in rock volume.

Geochemical evidence of present-day serpentinization.

PubMed

Barnes, I; Lamarche, V C; Himmelberg, G

1967-05-12

Ultrabasic (pH > 11) water issues from some fresh ultramafic bodies. The properties of the ultrabasic solutions are believed to be due to current reactions yielding serpentine from primary olivines and pyroxenes. The low concentrations of divalent airon. divalent magnesium, and dissolved silica from the serpentinization require an increase in rock volume.

Evaluation of effects of pH and ionic strength on colloidal stability of IgG solutions by PEG-induced liquid-liquid phase separation.

PubMed

Thompson, Ronald W; Latypov, Ramil F; Wang, Ying; Lomakin, Aleksey; Meyer, Julie A; Vunnum, Suresh; Benedek, George B

2016-11-14

Colloidal stability of IgG antibody solutions is important for pharmaceutical and medicinal applications. Solution pH and ionic strength are two key factors that affect the colloidal stability of protein solutions. In this work, we use a method based on the PEG-induced liquid-liquid phase separation to examine the effects of pH and ionic strength on the colloidal stability of IgG solutions. We found that at high ionic strength (≥0.25M), the colloidal stability of most of our IgGs is insensitive to pH, and at low ionic strength (≤0.15M), all IgG solutions are much more stable at pH 5 than at pH 7. In addition, the PEG-induced depletion force is less efficient in causing phase separation at pH 5 than at pH 7. In contrast to the native inter-protein interaction of IgGs, the effect of depletion force on phase separation of the antibody solutions is insensitive to ionic strength. Our results suggest that the long-range electrostatic inter-protein repulsion at low ionic strength stabilizes the IgG solutions at low pH. At high ionic strength, the short-range electrostatic interactions do not make a significant contribution to the colloidal stability for most IgGs with a few exceptions. The weaker effect of depletion force at lower pH indicates a reduction of protein concentration in the condensed phase. This work advances our basic understanding of the colloidal stability of IgG solutions and also introduces a practical approach to measuring protein colloidal stability under various solution conditions.

Switchable nanoassembly from an azobenzene-containing dye.

PubMed

Wang, Jing; Ha, Chang-Sik

2011-07-01

In this work, we investigated optical properties and the morphology of the amphiphilic azobenzene dye 1 containing hydroxyl azobenzene and C10 alkyl chains. Since the hydroxyl group on 1 has a pKa of 9.38, the deprotonation of the hydroxyl group occurs at pH > pKa (9.38) and thus the 1 nanoparticles are negatively charged. The deprotonated hydroxyl group is hydrophilic relative to the long alkyl chain that is hydrophobic, while the hydrophobic and hydrophilic parts are connected by covalent bonds. When such an azobenzene molecule 1 with both hydrophobic and hydrophilic groups exists in solution, "self-aggregation" may occur due to the hydrophobic interaction between the long alkyl chains. The scattered morphology at pH 7.0 (neutral state) and the aggregated morphology at pH 10.5 (anionic state) of 1 were demostrated by transmission electron microscopy (TEM) and atomic force microscopy (AFM) images. Formation of supramolecular aggregation-induced vesicular-like structures are highly interesting due to the ability to respond to external triggers, pH. The pH value can be reversed by adding acid or base to the system, that is, switching the aggregation "on" and "off" can be repeated.

Determining the chemical exchange saturation transfer (CEST) behavior of citrate and spermine under in vivo conditions

PubMed Central

Basharat, Meer; deSouza, Nandita M.; Parkes, Harold G.

2015-01-01

Purpose To estimate the exchange rates of labile 1H in citrate and spermine, metabolites present in prostatic secretions, to predict the size of the citrate and spermine CEST effects in vivo. Methods CEST z‐spectra were acquired at high‐field [11.7 Tesla (T)] from citrate and spermine solutions at physiological pH (6.5) using saturation power 6 μT. CEST was performed at different temperatures to determine exchange regimes (slow, intermediate or fast). For low pH solutions of spermine, exchange rates were estimated from resonance line width, fitting z‐spectra using the Bloch equations incorporating exchange, and using quantifying exchange using saturation time experiments (QUEST). These rates were extrapolated to physiological pH. Results Citrate showed little CEST effect at pH 6.5 and temperature (T) = 310 K (maximum 0.001% mM‐1), indicating fast exchange, whereas spermine showed greater CEST effects (maximum 0.2% mM‐1) indicating intermediate‐to‐fast exchange. Extrapolating data acquired from low pH spermine solutions predicts exchange rates at pH 6.5 and T of 310 K of at least 2 × 104s‐1. Conclusion Citrate and spermine show minimal CEST effects at 11.7T even using high saturation power. These effects would be much less than 2% at clinical field‐strengths due to relatively faster exchange and would be masked by CEST from proteins. Magn Reson Med 76:742–746, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:26467055

Effects of system net charge and electrostatic truncation on all-atom constant pH molecular dynamics.

PubMed

Chen, Wei; Shen, Jana K

2014-10-15

Constant pH molecular dynamics offers a means to rigorously study the effects of solution pH on dynamical processes. Here, we address two critical questions arising from the most recent developments of the all-atom continuous constant pH molecular dynamics (CpHMD) method: (1) What is the effect of spatial electrostatic truncation on the sampling of protonation states? (2) Is the enforcement of electrical neutrality necessary for constant pH simulations? We first examined how the generalized reaction field and force-shifting schemes modify the electrostatic forces on the titration coordinates. Free energy simulations of model compounds were then carried out to delineate the errors in the deprotonation free energy and salt-bridge stability due to electrostatic truncation and system net charge. Finally, CpHMD titration of a mini-protein HP36 was used to understand the manifestation of the two types of errors in the calculated pK(a) values. The major finding is that enforcing charge neutrality under all pH conditions and at all time via cotitrating ions significantly improves the accuracy of protonation-state sampling. We suggest that such finding is also relevant for simulations with particle mesh Ewald, considering the known artifacts due to charge-compensating background plasma. Copyright © 2014 Wiley Periodicals, Inc.

Effects of system net charge and electrostatic truncation on all-atom constant pH molecular dynamics †

PubMed Central

Chen, Wei; Shen, Jana K.

2014-01-01

Constant pH molecular dynamics offers a means to rigorously study the effects of solution pH on dynamical processes. Here we address two critical questions arising from the most recent developments of the all-atom continuous constant pH molecular dynamics (CpHMD) method: 1) What is the effect of spatial electrostatic truncation on the sampling of protonation states? 2) Is the enforcement of electrical neutrality necessary for constant pH simulations? We first examined how the generalized reaction field and force shifting schemes modify the electrostatic forces on the titration coordinates. Free energy simulations of model compounds were then carried out to delineate the errors in the deprotonation free energy and salt-bridge stability due to electrostatic truncation and system net charge. Finally, CpHMD titration of a mini-protein HP36 was used to understand the manifestation of the two types of errors in the calculated pK a values. The major finding is that enforcing charge neutrality under all pH conditions and at all time via co-titrating ions significantly improves the accuracy of protonation-state sampling. We suggest that such finding is also relevant for simulations with particle-mesh Ewald, considering the known artifacts due to charge-compensating background plasma. PMID:25142416

Influence of pH on the transport of silver nanoparticles in saturated porous media: laboratory experiments and modeling

NASA Astrophysics Data System (ADS)

Flory, Jason; Kanel, Sushil R.; Racz, LeeAnn; Impellitteri, Christopher A.; Silva, Rendahandi G.; Goltz, Mark N.

2013-03-01

Given the ubiquity of silver nanoparticles (AgNPs) and their potential for toxic effects on both humans and the environment, it is important to understand their environmental fate and transport. The purpose of this study is to gain information on the transport properties of commercial AgNP suspensions in a glass bead-packed column under saturated flow conditions at different solution pH levels. Commercial AgNPs were characterized using high-resolution transmission electron microscopy, dynamic light scattering, X-ray photoelectron spectroscopy, ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. Transport data were collected at different pH levels (4, 6.5, 9, and 11) at fixed ionic strength. Capture of AgNPs increased as the pH of the solution increased from 4 to 6.5. Further increase in pH to 9 and 11 decreased the attachment of AgNPs to the glass beads. AgNP concentration versus time breakthrough data were simulated using an advection-dispersion model incorporating both irreversible and reversible attachment. In particular, a reversible attachment model is required to simulate breakthrough curve tailing at near neutral pH, when attachment is most significant. The laboratory and modeling study reveals that for natural groundwaters, AgNP transport in porous media may be retarded due to capture; but ultimately, most of the mass may be slowly released over time.

Thermodynamic characteristics of the interaction between nicotinic acid and phenylalanine in an aqueous buffer solution at 298 K

NASA Astrophysics Data System (ADS)

Badelin, V. G.; Tyunina, E. Yu.; Mezhevoi, I. N.; Tarasova, G. N.

2013-08-01

The interaction between L-phenylalanine and nicotinic acid is studied by solution calorimetry in an aqueous buffer solution (pH 7.35) at different ratios of the reagents. Experimental data on the enthalpy of dissolution of amino acid in the buffer solution of nicotinic acid at 298.15 K are calculated. The values of thermodynamic parameters for the complexation of L-phenylalanine with nicotinic acid are calculated. It is shown that the formation of a 1: 2 molecular complex is stabilized by the entropy factor due to the dominant role of the dehydration effect of initial reagents.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sundaramurthi, Prakash; Suryanarayanan, Raj

To effectively inhibit succinate buffer crystallization and the consequent pH changes in frozen solutions. Using differential scanning calorimetry (DSC) and X-ray diffractometry (XRD), the crystallization behavior of succinate buffer in the presence of either (i) a crystallizing (glycine, mannitol, trehalose) or (ii) a non-crystallizing cosolute (sucrose) was evaluated. Aqueous succinate buffer solutions, 50 or 200 mM, at pH values 4.0 or 6.0 were cooled from room temperature to -25 C at 0.5 C/min. The pH of the solution was measured as a function of temperature using a probe designed to function at low temperatures. The final lyophiles prepared from thesemore » solutions were characterized using synchrotron radiation. When the succinic acid solution buffered to pH 4.0, in the absence of a cosolute, was cooled, there was a pronounced shift in the freeze-concentrate pH. Glycine and mannitol, which have a tendency to crystallize in frozen solutions, remained amorphous when the initial pH was 6.0. Under this condition, they also inhibited buffer crystallization and prevented pH change. At pH 4.0 (50 mM initial concentration), glycine and mannitol crystallized and did not prevent pH change in frozen solutions. While sucrose, a non-crystallizing cosolute, did not completely prevent buffer crystallization, the extent of crystallization was reduced. Sucrose decomposition, based on XRD peaks attributable to {beta}-D-glucose, was observed in frozen buffer solutions with an initial pH of 4.0. Trehalose completely inhibited crystallization of the buffer components when the initial pH was 6.0 but not at pH 4.0. At the lower pH, the crystallization of both trehalose dihydrate and buffer components was evident. When retained amorphous, sucrose and trehalose effectively inhibited succinate buffer component crystallization and the consequent pH shift. However, when trehalose crystallized or sucrose degraded to yield a crystalline decomposition product, crystallization of buffer was observed. Similarly, glycine and mannitol, two widely used bulking agents, inhibited buffer component crystallization only when retained amorphous. In addition to stabilizing the active pharmaceutical ingredient, lyoprotectants may prevent solution pH shift by inhibiting buffer crystallization.« less

Fouling of nanofiltration, reverse osmosis, and ultrafiltration membranes by protein mixtures: the role of inter-foulant-species interaction.

PubMed

Wang, Yi-Ning; Tang, Chuyang Y

2011-08-01

Protein fouling of nanofiltration (NF), reverse osmosis (RO), and ultrafiltration (UF) membranes by bovine serum albumin (BSA), lysozyme (LYS), and their mixture was investigated under cross-flow conditions. The effect of solution chemistry, membrane properties, and permeate flux level was systematically studied. When the solution pH was within the isoelectric points (IEPs) of the two proteins (i.e., pH 4.7-10.4), the mixed protein system experienced more severe flux decline compared to the respective single protein systems, which may be attributed to the electrostatic attraction between the negatively charged BSA and positively charged LYS molecules. Unlike a typical single protein system, membrane fouling by BSA-LYS mixture was only weakly dependent on solution pH within this pH range, and increased ionic strength was found to enhance the membrane flux as a result of the suppressed BSA-LYS electrostatic attraction. Membrane fouling was likely controlled by foulant-fouled-membrane interaction under severe fouling conditions (elevated flux level and unfavorable solution chemistry that promotes fouling), whereas it was likely dominated by foulant-clean-membrane interaction under mild fouling conditions. Compared to nonporous NF and RO membranes, the porous UF membrane was more susceptible to dramatic flux decline due to the increased risk of membrane pore plugging. This study reveals that membrane fouling by mixed macromolecules may behave very differently from that by typical single foulant system, especially when the inter-foulant-species interaction dominates over the intra-species interaction in the mixed foulant system.

Dynamics of pH modification of an acidic protein bait used for tropical fruit flies (Diptera: Tephritidae).

PubMed

Heath, Robert R; Vazquez, Aime; Schnell, Elena Q; Villareal, Janett; Kendra, Paul E; Epsky, Nancy D

2009-12-01

Several species of Anastrepha and Bactrocera fruit flies (Diptera: Tephritidae) are captured in traps baited with the protein bait NuLure combined with borax (sodium tetraborate decahydrate) in an aqueous solution, typically 9% NuLure (vol:vol) with 3% borax (wt:vol). NuLure is an acid hydrolysate of corn and has an acidic pH. Addition of borax makes the solution more alkaline, and increase in alkalinity results in increase of ammonia release from the bait solution. This is a very dynamic system, with resultant pH affected by factors such as the amount of borax added, the pH of the water used for preparation, the age of the bait solution, and the development of microbial growth. Problems with borax include amount needed to increase alkalinity of NuLure solutions, which creates difficulties in disposing of spent bait in fruit fly trapping programs. Therefore, research was conducted to evaluate NaOH as an alternative method to increase alkalinity of NuLure solutions. Laboratory experiments compared effect of NaOH versus borax for pH modification on changes in pH and ammonia content of NuLure solutions over time. Although NuLure/NaOH solutions could be adjusted to a more alkaline pH than NuLure/borax solutions, borax plays a critical role in pH stability over time. However, the pH of NuLure/NaOH is stabilized when propylene glycol (10% vol:vol) was used to prepare the bait solution. The use of NaOH can provide an alternative to the use of borax to increase bait solution alkalinity.

DNase 1 Retains Endodeoxyribonuclease Activity Following Gold Nanocluster Synthesis

DTIC Science & Technology

2014-07-04

mM) was added to 2 mL of protein solution under vigorous stirring at 37 °C (Table 1). After 5 min, 200 μL of NaOH (1 M) was added to raise the pH to...12 for the 1, 5, and 10 mM HAuCl4 samples whereas 400 μL of NaOH (1M) was required to obtain a pH of 12 for the 20 mM HAuCl4 sample due to the... magnesium sulfate pH 5.0), containing 2 μg of dsDNA. The reaction was incubated at room temperature for 20 min followed by the addition of 2 units of

Soluble organic carbon and pH of organic amendments affect metal mobility and chemical speciation in mine soils.

PubMed

Pérez-Esteban, Javier; Escolástico, Consuelo; Masaguer, Alberto; Vargas, Carmen; Moliner, Ana

2014-05-01

We evaluated the effects of pH and soluble organic carbon affected by organic amendments on metal mobility to find out the optimal conditions for their application in the stabilization of metals in mine soils. Soil samples (pH 5.5-6.2) were mixed with 0, 30 and 60 th a(-1) of sheep-horse manure (pH 9.4) and pine bark compost (pH 5.7). A single-step extraction procedure was performed using 0.005 M CaCl2 adjusted to pH 4.0-7.0 and metal speciation in soil solution was simulated using NICA-Donnan model. Sheep-horse manure reduced exchangeable metal concentrations (up to 71% Cu, 75% Zn) due to its high pH and degree of maturity, whereas pine bark increased them (32% Cu, 33% Zn). However, at increasing dose and hence pH, sheep-horse manure increased soluble Cu because of higher soluble organic carbon, whereas soluble Cu and organic carbon increased at increasing dose and correspondingly decreasing pH in pine bark and non-amended treatments. Near the native pH of these soils (at pH 5.8-6.3), with small doses of amendments, there was minimum soluble Cu and organic carbon. Pine bark also increased Zn solubility, whereas sheep-horse manure reduced it as soluble Zn always decreased with increasing pH. Sheep-horse manure also reduced the proportion of free metals in soil solution (from 41% to 4% Cu, from 97% to 94% Zn), which are considered to be more bioavailable than organic species. Sheep-horse manure amendment could be efficiently used for the stabilization of metals with low risk of leaching to groundwater at low doses and at relatively low pH, such as the native pH of mine soils. Copyright © 2013 Elsevier Ltd. All rights reserved.

A High Frequency Analysis of Electromagnetic Plane Wave Scattering by a Fully Illuminated Perfectly Conducting Semi-Infinite Cone.

DTIC Science & Technology

1986-01-01

mn, 5] sin OdOd (B.39) 98 V Due to the orthogonality of the Legendre polynomials (shown in Appendix D), there is only a value when v = v’. This yields... some of his unpublished results. These results were for the special case of axial incidence on the semi- infinite cone, and were useful in verifying my... general solution. I express gratitude to Mr.(Ph.D. Candidate) Ming Cheng Liang for our many hours of discussion, and to my office mate Mr.(Ph.D

Considerations on prevention of phlebitis and venous pain from intravenous prostaglandin E(1) administration by adjusting solution pH: in vitro manipulations affecting pH.

PubMed

Kohno, Emiko; Nishikata, Mayumi; Okamura, Noboru; Matsuyama, Kenji

2008-01-01

Prostaglandin E(1) (PGE(1); Alprostadil Alfadex) is a potent vasodilator and inhibitor of platelet aggregation used to treat patients with peripheral vascular disease. The main adverse effects of intravenous PGE(1) administration, phlebitis and venous pain, arise from the unphysiologically low pH of infusion solutions. When PGE(1) infusion solutions with a pH value greater then 6 are used, phlebitis and venous pain are considered to be avoidable. Beginning with a PGE(1) infusion solution with pH greater than 6, we add the amount of 7% sodium bicarbonate needed to bring the solution to pH 7.4 if phlebitis or venous pain develops. In the present study we established a convenient nomogram showing the relationship between the titratable acidity of various infusion solutions and the volume of 7% sodium bicarbonate required to attain pH 7.4 for preventing the phlebitis and venous pain associated with PGE(1) infusion.

THE CONTRIBUTIONS OF NORMAL AND ANOMALOUS OSMOSIS TO THE OSMOTIC EFFECTS ARISING ACROSS CHARGED MEMBRANES WITH SOLUTIONS OF ELECTROLYTES

PubMed Central

Grim, Eugene; Sollner, Karl

1957-01-01

The osmotic effect arising across a porous membrane separating the solution of an electrolyte from water (or a more dilute solution) is ordinarily due to both normal osmosis, as it occurs also with non-electrolytes, and to "anomalous" osmosis. It is shown that the normal osmotic component cannot be measured quantitatively by the conventional comparison with a non-electrolytic reference solute. Anomalous osmosis does not occur with electroneutral membranes. Accordingly, with membranes which can be charged and discharged reversibly (without changes in geometrical structure), such as many proteinized membranes, the osmotic effects caused by an electrolyte can be measured both when only normal osmosis arises (with the membrane in the electroneutral state) and when normal as well as anomalous osmosis occurs (with the membrane in a charged state). The difference between these two effects is the true anomalous osmosis. Data are presented on the osmotic effects across an oxyhemoglobin membrane in the uncharged state at pH 6.75 and in two charged states, positive at pH 4.0 and negative at pH 10.0, with solutions of a variety of electrolytes using a concentration ratio of 2:1 over a wide range of concentrations. The rates of the movement of liquid across the membrane against an inconsequentially small hydrostatic head are recorded instead of, as conventional, the physiologically less significant pressure rises after a standard time. PMID:13439166

Removal of Pb(II), Cd(II), Cu(II), and Zn(II) by hematite nanoparticles: effect of sorbent concentration, pH, temperature, and exhaustion.

PubMed

Shipley, Heather J; Engates, Karen E; Grover, Valerie A

2013-03-01

Nanoparticles offer the potential to improve environmental treatment technologies due to their unique properties. Adsorption of metal ions (Pb(II), Cd(II), Cu(II), Zn(II)) to nanohematite was examined as a function of sorbent concentration, pH, temperature, and exhaustion. Adsorption experiments were conducted with 0.05, 0.1, and 0.5 g/L nanoparticles in a pH 8 solution and in spiked San Antonio tap water. The adsorption data showed the ability of nanohematite to remove Pb, Cd, Cu, and Zn species from solution with adsorption increasing as the nanoparticle concentration increased. At 0.5 g/L nanohematite, 100 % Pb species adsorbed, 94 % Cd species adsorbed, 89 % Cu species adsorbed and 100 % Zn species adsorbed. Adsorption kinetics for all metals tested was described by a pseudo second-order rate equation with lead having the fastest rate of adsorption. The effect of temperature on adsorption showed that Pb(II), Cu(II), and Cd(II) underwent an endothermic reaction, while Zn(II) underwent an exothermic reaction. The nanoparticles were able to simultaneously remove multiple metals species (Zn, Cd, Pb, and Cu) from both a pH 8 solution and spiked San Antonio tap water. Exhaustion experiments showed that at pH 8, exhaustion did not occur for the nanoparticles but adsorption does decrease for Cd, Cu, and Zn species but not Pb species. The strong adsorption coupled with the ability to simultaneously remove multiple metal ions offers a potential remediation method for the removal of metals from water.

Effects of solutions treated with oxygen radicals in neutral pH region on inactivation of microorganism

NASA Astrophysics Data System (ADS)

Kobayashi, Tsuyoshi; Hashizume, Hiroshi; Ohta, Takayuki; Ishikawa, Kenji; Hori, Masaru; Ito, Masafumi

2015-09-01

The inactivation of microorganisms using nonequilbrium atmospheric pressure plasmas has been attracted much attention due to the low temperature processing and high speed treatment. In this study, we have inactivated E. coli suspended in solutions with neutral pH using an atmospheric-pressure oxygen radical source which can selectively supply electrically neutral oxygen radicals. E. coli cells were suspended with deionized distilled water (DDW) (pH = 6.8) or phosphate buffered saline (PBS) (pH = 7.4) or Citrate-Na buffer (pH = 6.5). The treated samples were diluted and spread on nutrient agar (Nutrient Broth). They were cultured at 37° C. The inactivation effects of oxygen radicals on those cells in solutions were evaluated by colony-counting method. O2 diluted by Ar gas were employed as a working gas for the radical source. The total gas flow rate and the gas mixture ratio of O2/(Ar + O2) were set at 5 slm and 0.6%, respectively. The distance between the radical exit and the suspension surface were set at 10 mm. As a result, the D values for DDW(pH = 6.8), PBS(pH = 7.4) and Citrate-Na buffer(pH = 6.5) were estimated to be 1.4 min, 0.9 min and 16.8 min respectively. The inactivation rates in DDW, PBS were significantly different from that in Citrate-Na buffer. This work was partly supported by JSPS KAKENHI Grant Number 26286072 and project for promoting Research Center in Meijo University.

Acidic and basic solutions dissolve protein plugs made of lithostathine complicating choledochal cyst/pancreaticobiliary maljunction.

PubMed

Kaneko, Kenitiro; Ono, Yasuyuki; Tainaka, Takahisa; Sumida, Wataru; Ando, Hisami

2009-07-01

Symptoms of choledochal cysts are caused by protein plugs made of lithostathine, which block the long common channel and increase pancreaticobiliary ductal pressure. Agents that dissolve protein plugs can provide relief from or prevent symptoms. In the present study, drugs reportedly effective for pancreatic and biliary stones were used in dissolution tests. Protein plugs were obtained from choledochal cysts during surgery in two children (5- and 6-year-old girls). Plugs approximately 2 mm in diameter were immersed in citric acid, tartaric acid, dimethadione, bromhexine, dehydrocholic acid, sodium citrate, hydrochloric acid, and sodium hydroxide solutions under observation with a digital microscope. The pH of each solution was measured using a pH meter. Plugs dissolved in citric acid (5.2 mM; pH 2.64), tartaric acid (6.7 mM; pH 2.51), dimethadione (75 mM; pH 3.70), hydrochloric acid (0.5 mM; pH 3.13), and sodium hydroxide (75 mM; pH 12.75) solutions. Plugs did not dissolve in dimethadione (7.5 mM; pH 4.31), bromhexine (0.1%; pH 4.68), dehydrocholic acid (5%; pH 7.45), and sodium citrate (75 mM; pH 7.23) solutions. Protein plugs in choledochal cysts are dissolved in acidic and basic solutions, which may eliminate longitudinal electrostatic interactions of the lithostathine protofibrils.

Charge reversible gold nanoparticles for high efficient absorption and desorption of DNA

NASA Astrophysics Data System (ADS)

Wang, Can; Zhuang, Jiaqi; Jiang, Shan; Li, Jun; Yang, Wensheng

2012-10-01

Mercaptoundecylamine and mercaptoundecanoic acid co-modified Au nanoparticles were prepared by two-step ligand exchange of 6-mercaptohexanoic acid modified gold nanoparticles. Such particles terminated by appropriate ratios of the amine and carboxyl groups ( R N/C) were identified to show reversible charge on their surface, which were switchable by pH of the solution. The isoelectric point (IEP) of the particles is tunable by changing the ratios of the amine and carboxyl groups on the particle surfaces. The particles can absorb DNA effectively at pH lower than the IEP driven by the direct electrostatic interactions between DNA and the particle surface. When pH of the solutions was elevated to be higher than the IEP, the absorbed DNA can be released almost completely due to the electrostatic repulsion between the particle surface and DNA. With appropriate R N/C ratios of 0.8, the absorption and desorption efficiencies of DNA were 97 and 98 %, respectively, corresponding an extraction efficiency of 95 %. Such particles with reversible surface charges allow the high efficient extraction of DNA by simply changing pH instead of by changing salt concentration in the conventional salt bridge method.

Computer model of hydroponics nutrient solution pH control using ammonium.

PubMed

Pitts, M; Stutte, G

1999-01-01

A computer simulation of a hydroponics-based plant growth chamber using ammonium to control pH was constructed to determine the feasibility of such a system. In nitrate-based recirculating hydroponics systems, the pH will increase as plants release hydroxide ions into the nutrient solution to maintain plant charge balance. Ammonium is an attractive alternative to traditional pH controls in an ALSS, but requires careful monitoring and control to avoid overdosing the plants with ammonium. The primary advantage of using NH4+ for pH control is that it exploits the existing plant nutrient uptake charge balance mechanisms to maintain solution pH. The simulation models growth, nitrogen uptake, and pH of a l-m2 stand of wheat. Simulation results indicated that ammonium-based control of nutrient solution pH is feasible using a proportional integral controller. Use of a 1 mmol/L buffer (Ka = 1.6 x 10(-6)) in the nutrient solution is required.

Origin and evolution of osmoregulatory mechanisms in blue-green algae (cyanobacteria) as a function of metabolic and structural complexity: Reflections of Precambrian paleobiology

NASA Technical Reports Server (NTRS)

Yopp, John H.; Tindall, Donald R.; Pavlicek, Kenneth

1987-01-01

Major accomplishments underlying the basic understanding of cyanobacterial resistance to salt tolerance and osmotic stress were made. The methodology proposed included: the tracing of the pathways of formation of osmoregulatory solutes by traditional methods involving C-14 labelled substrates; gas chromatography; amino acid analysis; X-ray analysis using scanning transmission electron microscopy; and most importantly, C-13 labelled substrates, followed by Nuclear Magnetic Resonance (NMR) spectroscopy. It was found that the cyanobacteria employ a diversity of organic, osmoregulatory solutes. Osmoregulatory solutes were found to serve four functions: adjustment of water activity, noninhibition of enzymes; lowering of K sub m of enzymes to allow functioning at normal levels when the intracellular salt accumulates, and extending the pH optimum of enzymes as intracellular pH rises due to proton-potassium ion pump action during osmoregulation. Differences in osmoregulatory solutes may, but are not always, be attributed to differences in nutritional capabilities. The mechanism of osmoregulation and concomitant salt tolerance in halophilic cyanobacteria was elucidated. The activities of betaine and S-Adenosylhomocysteine hydrolase are discussed.

Method for producing rapid pH changes

DOEpatents

Clark, John H.; Campillo, Anthony J.; Shapiro, Stanley L.; Winn, Kenneth R.

1981-01-01

A method of initiating a rapid pH change in a solution by irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Method for producing rapid pH changes

DOEpatents

Clark, J.H.; Campillo, A.J.; Shapiro, S.L.; Winn, K.R.

A method of initiating a rapid pH change in a solution comprises irradiating the solution with an intense flux of electromagnetic radiation of a frequency which produces a substantial pK change to a compound in solution. To optimize the resulting pH change, the compound being irradiated in solution should have an excited state lifetime substantially longer than the time required to establish an excited state acid-base equilibrium in the solution. Desired pH changes can be accomplished in nanoseconds or less by means of picosecond pulses of laser radiation.

Calcium leaching behavior of cementitious materials in hydrochloric acid solution.

PubMed

Yang, Huashan; Che, Yujun; Leng, Faguang

2018-06-11

The calcium leaching behavior of cement paste and silica fume modified calcium hydroxide paste, exposed to hydrochloric acid solution, is reported in this paper. The kinetic of degradation was assessed by the changes of pH of hydrochloric acid solution with time. The changes of compressive strength of specimens in hydrochloric acid with time were tested. Hydration products of leached specimens were also analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric (TG), and atomic force microscope (AFM). Tests results show that there is a dynamic equilibrium in the supply and consumption of calcium hydroxide in hydrochloric acid solution, which govern the stability of hydration products such as calcium silicate hydrate (C-S-H). The decrease of compressive strength indicates that C-S-H are decomposed due to the lower concentration of calcium hydroxide in the pore solution than the equilibrium concentration of the hydration products. Furthermore, the hydration of unhydrated clinker delayed the decomposition of C-S-H in hydrochloric acid solution due to the increase of calcium hydroxide in pore solution of cementitious materials.

Properties of edible films based on pullulan-chitosan blended film-forming solutions at different pH

USDA-ARS?s Scientific Manuscript database

Influences of solution pH on the properties of pullulan-chitosan blended (Pul-Chi) films and the rheological properties of film-forming solutions were investigated. The extended conformation of chitosan in pH 4.0 solution increased intermolecular interactions with pullulan compared to the more compa...

Tetragonal Chicken Egg White Lysozyme Solubility in Sodium Chloride Solutions

NASA Technical Reports Server (NTRS)

Forsythe, Elizabeth L.; Judge, Russell A.; Pusey, Marc L.

1998-01-01

The solubility of chicken egg white lysozyme, crystallized in the tetragonal form was measured in sodium chloride solutions from 1.6 to 30.7 C, using a miniature column solubility apparatus. Sodium chloride solution concentrations ranged from 1 to 7% (w/v). The solutions were buffered with 0.1 M sodium acetate buffer with the solubility being measured at pH values in 0.2 pH unit increments in the range pH 4.0 to 5.4, with data also included at pH 4.5. Lysozyme solubility was found to increase with increases in temperature and decreasing salt concentration. Solution pH has a varied and unpredictable effect on solubility.

A Study of Novel Hexavalent Phosphazene Salts as Draw Solutes in Forward Osmosis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mark L. Stone; Aaron D. Wilson; Mason K. Harrup

2013-03-01

Two novel multi-valent salts based on phosphazene chemistry have been synthesized and characterized as forward osmosis (FO) draw solutes. Commercially obtained hexachlorocyclotriphosphazene was reacted with the sodium salt of 4-ethylhydroxybenzoate to yield hexa(4-ethylcarboxylatophenoxy)phosphazene. Hydrolysis, followed by and neutralization with NaOH or LiOH, of the resulting acidic moieties yielded water soluble sodium and lithium phosphazene salts, respectively. Degrees of dissociation were determined through osmometry over the range of 0.05-0.5 m, giving degrees of 3.08-4.95 per mole, suggesting a high osmotic potential. The Li salt was found to be more ionized in solution than the sodium salt, and this was reflected inmore » FO experiments where the Li salt gave higher initial fluxes (~ 7 L/m2h) as compared to the sodium salt (~6 L/m2h) at identical 0.07 m draw solution concentrations at 30 °C. Longer term experiments revealed no detectable degradation of the salts; however some hydrolysis of the cellulose acetate membrane was observed, presumably due to the pH of the phosphazene salt draw solution (pH = ~8).« less

Influence of the dentinal wall on the pH of sodium hypochlorite during root canal irrigation.

PubMed

Macedo, Ricardo Gomes; Herrero, Noemi Pascual; Wesselink, Paul; Versluis, Michel; van der Sluis, Luc

2014-07-01

The purpose of this study was to evaluate the influence of dentin on the pH levels of different concentrations of sodium hypochlorite (NaOCl) solutions over time and to evaluate if preconditioning of dentin with 17% EDTA or agitation of the NaOCl solution influences these pH levels. A novel clinically representative model that scales with the ratio of the irrigant volume to the dentin surface area of a human root canal was used. Three standardized bovine dentin bars (2 × 2 × 10 mm) were placed in a plastic test tube. A total of 150 tubes were distributed in 29 groups. In the first experiment, the pH of various NaOCl solutions, with different concentrations (3%, 6%, and 9%) and starting pH levels (5 and 12), was monitored during exposure to dentin between 10 and 300 seconds. In a second experiment, the effect of agitation (45 Hz) and pretreatment of dentin with 17% EDTA on the pH levels of various NaOCl solutions was studied after 30 seconds of exposure to dentin. The short-term chemical stability of the tested solutions was assessed for both the concentration and the pH. The exposure time (P < .001) and concentration of the NaOCl solution (P < .011) significantly influence the pH level after exposure to dentin. However, the change in pH is too small to induce a change in the irrigant antimicrobial/tissue dissolution capacity. Agitation of the irrigant and preconditioning of the dentin did not alter the pH (P > .05). Both the pH 5 and pH 12 solutions were chemically stable for 1 hour. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

PH Sensitive Polymers for Improving Reservoir Sweep and Conformance Control in Chemical Flooring

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mukul Sharma; Steven Bryant; Chun Huh

There is an increasing opportunity to recover bypassed oil from depleted, mature oilfields in the US. The recovery factor in many reservoirs is low due to inefficient displacement of the oil by injected fluids (typically water). The use of chemical flooding methods to increase recovery efficiencies is severely constrained by the inability of the injected chemicals to contact the bypassed oil. Low sweep efficiencies are the primary cause of low oil recoveries observed in the field in chemical flooding operations even when lab studies indicate high oil recovery efficiency. Any technology that increases the ability of chemical flooding agents tomore » better contact the remaining oil and reduce the amount of water produced in conjunction with the produced oil will have a significant impact on the cost of producing oil domestically in the US. This translates directly into additional economically recoverable reserves, which extends the economic lives of marginal and mature wells. The objective of this research project was to develop a low-cost, pH-triggered polymer for use in IOR processes to improve reservoir sweep efficiency and reservoir conformance in chemical flooding. Rheological measurements made on the polymer solution, clearly show that it has a low viscosity at low pH and exhibits a sudden increase in viscosity (by 2 orders of magnitude or more) at a pH of 3.5 to 4. This implies that the polymer would preferentially flow into zones containing water since the effective permeability to water is highest in these zones. As the pH of the zone increases due to the buffering capacity of the reservoir rock, the polymer solution undergoes a liquid to gel transition causing a sharp increase in the viscosity of the polymer solution in these zones. This allows operationally robust, in-depth conformance treatment of such water bearing zones and better mobility control. The rheological properties of HPAM solutions were measured. These include: steady-shear viscosity and viscoelastic behavior as functions of pH; shear rate; polymer concentration; salinity, including divalent ion effects; polymer molecular weight; and degree of hydrolysis. A comprehensive rheological model was developed for HPAM solution rheology in terms of: shear rate; pH; polymer concentration; and salinity, so that the spatial and temporal changes in viscosity during the polymer flow in the reservoir can be accurately modeled. A series of acid coreflood experiments were conducted to understand the geochemical reactions relevant for both the near-wellbore injection profile control and for conformance control applications. These experiments showed that the use hydrochloric acid as a pre-flush is not viable because of the high reaction rate with the rock. The use of citric acid as a pre-flush was found to be quite effective. This weak acid has a slow rate of reaction with the rock and can buffer the pH to below 3.5 for extended periods of time. With the citric acid pre-flush the polymer could be efficiently propagated through the core in a low pH environment i.e. at a low viscosity. The transport of various HPAM solutions was studied in sandstones, in terms of permeability reduction, mobility reduction, adsorption and inaccessible pore volume with different process variables: injection pH, polymer concentration, polymer molecular weight, salinity, degree of hydrolysis, and flow rate. Measurements of polymer effluent profiles and tracer tests show that the polymer retention increases at the lower pH. A new simulation capability to model the deep-penetrating mobility control or conformance control using pH-sensitive polymer was developed. The core flood acid injection experiments were history matched to estimate geochemical reaction rates. Preliminary scale-up simulations employing linear and radial geometry floods in 2-layer reservoir models were conducted. It is clearly shown that the injection rate of pH-sensitive polymer solutions can be significantly increased by injecting it at a pH below 3.5 (at a fixed bottom-hole pressure). This improvement in injectivity by a factor of 2 to 10 can have a significant impact on the economics of chemical flooding and conformance control applications. Simulation tools and experimental data presented in this report help to design and implement such polymer injection projects.« less

Fabrication of hydroxyapatite block from gypsum block based on (NH4)2HPO4 treatment.

PubMed

Suzuki, Yumiko; Matsuya, Shigeki; Udoh, Koh-ichi; Nakagawa, Masaharu; Tsukiyama, Yoshihiro; Koyano, Kiyoshi; Ishikawa, Kunio

2005-12-01

The aim of this study was to evaluate the feasibility of fabricating low-crystalline, porous apatite block using set gypsum as a precursor based on the fact that apatite is thermodynamically more stable than gypsum. When the set gypsum was immersed in 1 mol/L diammonium hydrogen phosphate aqueous solution at 100 degrees C, it transformed to low-crystalline porous apatite retaining its original shape. The transformation reaction caused a release of sulfate ions due to an ion exchange with phosphate ions, thus leading to a decrease in the pH of the solution. Then, due to decreased pH, dicalcium phosphate anhydrous--which has similar thermodynamic stability at lower pH--was also produced as a by-product. Apatite formed in the present method was low-crystalline, porous B-type carbonate apatite that contained approximately 0.5 wt% CO3, even though no carbonate sources--except carbon dioxide from air--were added to the reaction system. We concluded therefore that this is a useful bone filler fabrication method since B-type carbonate apatite is the biological apatite contained in bone.

The effect of gamma irradiation on rice protein aqueous solution

NASA Astrophysics Data System (ADS)

Baccaro, Stefania; Bal, Oya; Cemmi, Alessia; Di Sarcina, Ilaria

2018-05-01

The use of proteins as natural biopolymers are sensibly increasing in several application fields such as food industry, packaging and environment protection. In particular, rice proteins (RP) present good nutritional, hypoallergenic and healthful properties very interesting for human consumption. Since ionizing radiation can be successfully applied on protein containing systems involved in different industrial processes, this work aims to determine the effect of gamma radiation on 5 wt%-7.5 wt% RP aqueous solutions in a wide range of absorbed doses up to around 40 kGy. The changes of RP secondary and tertiary structures and their chemical composition were followed by UV-VIS absorbance spectroscopy, luminescence analysis and pH measurements. The experimental data showed the occurrence of the unfolding of RP chains with the increase of the absorbed dose and the formation of new molecules, due to the reaction among tryptophane and tyrosine amino acids and the radical species induced by gamma radiation. The results are also confirmed by the modification of the pH values measured for the irradiated solutions.

A coupled hydrodynamic-hydrochemical modeling for predicting mineral transport in a natural acid drainage system.

NASA Astrophysics Data System (ADS)

Zegers Risopatron, G., Sr.; Navarro, L.; Montserrat, S., Sr.; McPhee, J. P.; Niño, Y.

2017-12-01

The geochemistry of water and sediments, coupled with hydrodynamic transport in mountainous channels, is of particular interest in central Chilean Andes due to natural occurrence of acid waters. In this paper, we present a coupled transport and geochemical model to estimate and understand transport processes and fate of minerals at the Yerba Loca Basin, located near Santiago, Chile. In the upper zone, water presentes low pH ( 3) and high concentrations of iron, aluminum, copper, manganese and zinc. Acidity and minerals are the consequence of water-rock interactions in hydrothermal alteration zones, rich in sulphides and sulphates, covered by seasonal snow and glaciers. Downstream, as a consequence of neutral to alkaline lateral water contributions (pH >7) along the river, pH increases and concentration of solutes decreases. The mineral transport model has three components: (i) a hydrodynamic model, where we use HEC-RAS to solve 1D Saint-Venant equations, (ii) a sediment transport model to estimate erosion and sedimentation rates, which quantify minerals transference between water and riverbed and (iii) a solute transport model, based on the 1D OTIS model which takes into account the temporal delay in solutes transport that typically is observed in natural channels (transient storage). Hydrochemistry is solved using PHREEQC, a software for speciation and batch reaction. Our results show that correlation between mineral precipitation and dissolution according to pH values changes along the river. Based on pH measurements (and according to literature) we inferred that main minerals in the water system are brochantite, ferrihydrite, hydrobasaluminite and schwertmannite. Results show that our model can predict the transport and fate of minerals and metals in the Yerba Loca Basin. Mineral dissolution and precipitation process occur for limited ranges of pH values. When pH values are increased, iron minerals (schwertmannite) are the first to precipitate ( 2.5

Sludge-Derived Biochar for Arsenic(III) Immobilization: Effects of Solution Chemistry on Sorption Behavior.

PubMed

Zhang, Weihua; Zheng, Juan; Zheng, Pingping; Tsang, Daniel C W; Qiu, Rongliang

2015-07-01

Recycling sewage sludge by pyrolysis has attracted increasing attention for pollutant removal from wastewater and soils. This study scrutinized As(III) sorption behavior on sludge-derived biochar (SDBC) under different pyrolysis conditions and solution chemistry. The SDBC pyrolyzed at a higher temperature showed a lower As(III) sorption capacity and increasingly nonlinear isotherm due to loss of surface sites and deoxygenation-dehydrogenation. The Langmuir sorption capacity on SDBC (3.08-6.04 mg g) was comparable to other waste-derived sorbents, with the highest As(III) sorption on SDBC pyrolyzed at 400°C for 2 h. The As(III) sorption kinetics best fit with the pseudo-second-order equation, thus suggesting the significance of the availability of surface sites and initial concentration. Sorption of As(III) was faster than that of Cr(VI) but slower than that of Pb(II), which was attributed to their differences in molar volume (correlated to diffusion coefficients) and sorption mechanisms. The X-ray photoelectron spectra revealed an increase of oxide oxygen (O) with a decrease of sorbed water, indicative of ligand exchange with hydroxyl groups on SDBC surfaces. The As(III) sorption was not pH dependent in acidic-neutral range (pH < 8) due to the buffering capacity and surface characteristics of the SDBC; however, sorption was promoted by increasing pH in the alkaline range (pH > 8) because of As(III) speciation in solution. An increasing ionic strength (0.001-0.1 mol L) facilitated As(III) sorption, indicating the predominance of ligand exchange over electrostatic interactions, while high concentrations (0.1 mol L) of competing anions (fluoride, sulfate, carbonate, and phosphate) inhibited As(III) sorption. These results suggest that SDBC is applicable for As(III) immobilization in most environmentally relevant conditions. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Decreasing DOC trends in soil solution along the hillslopes at two IM sites in southern Sweden--geochemical modeling of organic matter solubility during acidification recovery.

PubMed

Löfgren, Stefan; Gustafsson, Jon Petter; Bringmark, Lage

2010-12-01

Numerous studies report increased concentrations of dissolved organic carbon (DOC) during the last two decades in boreal lakes and streams in Europe and North America. Recently, a hypothesis was presented on how various spatial and temporal factors affect the DOC dynamics. It was concluded that declining sulphur deposition and thereby increased DOC solubility, is the most important driver for the long-term DOC concentration trends in surface waters. If this recovery hypothesis is correct, the DOC levels should increase both in the soil solution as well as in the surrounding surface waters as soil pH rises and the ionic strength declines due to the reduced input of SO(4)(2-) ions. In this project a geochemical model was set up to calculate the net humic charge and DOC solubility trends in soils during the period 1996-2007 at two integrated monitoring sites in southern Sweden, showing clear signs of acidification recovery. The Stockholm Humic Model was used to investigate whether the observed DOC solubility is related to the humic charge and to examine how pH and ionic strength influence it. Soil water data from recharge and discharge areas, covering both podzols and riparian soils, were used. The model exercise showed that the increased net charge following the pH increase was in many cases counteracted by a decreased ionic strength, which acted to decrease the net charge and hence the DOC solubility. Thus, the recovery from acidification does not necessarily have to generate increasing DOC trends in soil solution. Depending on changes in pH, ionic strength and soil Al pools, the trends might be positive, negative or indifferent. Due to the high hydraulic connectivity with the streams, the explanations to the DOC trends in surface waters should be searched for in discharge areas and peat lands. Copyright © 2010 Elsevier B.V. All rights reserved.

Effect of pH and calcium on short-term NO3- fluxes in roots of barley seedlings

NASA Technical Reports Server (NTRS)

Aslam, M.; Travis, R. L.; Huffaker, R. C.

1995-01-01

The effect of pH and Ca2+ on net NO3- uptake, influx, and efflux by intact roots of barley (Hordeum vulgare L.) seedlings was studied. Seedlings were induced with NO3- or NO2-. Net NO3- uptake and efflux, respectively, were determined by following its depletion from, and accumulation in, the external solution. Since roots of both uninduced and NO2(-)-induced seedlings contain little internal NO3- initial net uptake rates are equivalent to influx (M. Aslam, R.L. Travis, R.C. Huffaker [1994] Plant Physiol 106: 1293-1301). NO3-, uptake (influx) by these roots was little affected at acidic pH. In contrast, in NO3(-)-induced roots, which accumulate NO3-, net uptake rates decreased in response to acidic pH. Under these conditions, NO3- efflux was stimulated and was a function of root NO3- concentration. Conversely, at basic pH, NO3- uptake by NO3- and NO2(-)-induced and uninduced roots decreased, apparently because of the inhibition of influx. Calcium had little effect on NO3- uptake (influx) by NO2(-)-induced roots at either pH 3 or 6. However, in NO3(-)-induced roots, lack of Ca2+ at pH 3 significantly decreased net NO3- uptake and stimulated efflux. The results indicate that at acidic pH the decrease in net NO3- uptake is due to the stimulation of efflux, whereas at basic pH, it is due to the inhibition of influx.

Particulate contamination of local anesthetic solutions.

PubMed

Cooley, R L; Lubow, R M

1981-05-01

Particulate contamination was found in one particular lot number of local anesthetic, lidocaine with 1:100,000 epinephrine. The contaminants were noticed in several cartridges of each container and varied in size from minute to several millimeters. Analysis of the foreign matter revealed the particles to be of a way or puttylike consistency; however, the sterility of the solution was not altered and the pH was still within acceptable limits. The contaminant was most likely wax or a combination of wax, silicone, and glycerin, which are constituents of the rubber stopper and its associated lubricants. This problem was most likely due to temperature changes during storage and shipment, but it was also possibly due to manufacturing discrepancies.

Effects of Chlorine Promoted Oxidation on Arsenic Release from Sulfide Minerals

NASA Astrophysics Data System (ADS)

West, N.; Schreiber, M.; Gotkowitz, M.

2007-12-01

High arsenic concentrations (>100 ppb) have been measured in wells completed in the Ordovician St. Peter sandstone aquifer of eastern Wisconsin. The primary source of arsenic is As-bearing sulfide minerals within the aquifer. Periodic disinfection of wells by chlorination may facilitate arsenic release to groundwater by increasing the rate of sulfide mineral oxidation. During typical well disinfection procedures, aquifer solids exposed along uncased portions of wells remain in direct contact with chlorine disinfection solutions for up to twenty-four hours. Due to the redox sensitivity of arsenic mobility in groundwater, it is important to evaluate the effect of repeatedly adding oxidizers to an arsenic impacted aquifer system. This study focuses on abiotic processes that mobilize arsenic from the solid phase during controlled exposure to chlorinated solutions. Two St. Peter samples with As concentrations of 21 and 674 ppm were selected for the experiments. Before reaction, the aquifer mineralogy is characterized using scanning electron microscopy (SEM) and electron microprobe analysis (EMPA). The samples are then reacted with solutions of 60 mg/L free chlorine, 1200 mg/L free chlorine, or nanopure water (control) at pH 7.0 and pH 8.5. These parameters represent typical solution chemistries present within the wells after disinfection. Solutions are sampled periodically during the experiments and analyzed for As, Fe, other trace metals such as Co, Mo, Cr, and Ni, and sulfate. Analysis of the post-reaction solids using SEM, EMPA, laser ablation ICP-MS and Raman techniques are used to document the changes in mineralogy due to chlorination and to document which solid phases contain As.

Effect of wood ash application on soil solution chemistry of tropical acid soils: incubation study.

PubMed

Nkana, J C Voundi; Demeyer, A; Verloo, M G

2002-12-01

The objective of this study was to determine the effect of wood ash application on soil solution composition of three tropical acid soils. Calcium carbonate was used as a reference amendment. Amended soils and control were incubated for 60 days. To assess soluble nutrients, saturation extracts were analysed at 15 days intervals. Wood ash application affects the soil solution chemistry in two ways, as a liming agent and as a supplier of nutrients. As a liming agent, wood ash application induced increases in soil solution pH, Ca, Mg, inorganic C, SO4 and DOC. As a supplier of elements, the increase in the soil solution pH was partly due to ligand exchange between wood ash SO4 and OH- ions. Large increases in concentrations of inorganic C, SO4, Ca and Mg with wood ash relative to lime and especially increases in K reflected the supply of these elements by wood ash. Wood ash application could represent increased availability of nutrients for the plant. However, large concentrations of basic cations, SO4 and NO3 obtained with higher application rates could be a concern because of potential solute transport to surface waters and groundwater. Wood ash must be applied at reasonable rates to avoid any risk for the environment.

Structure and Properties of Polymer Interphases

DTIC Science & Technology

1988-09-30

substrate primed with a dilute aqueous solution of y -aminopropyltriethoxy- silane (’APS), there was little reaction between the primer and adhesive and...of y -aminopropyltriethoxysilane (- Y -APS) at pH 10.4 for one minute, withdrawn, and blown dry with a stream of nitrogen gas. The resulting primer...cm-1 is due to the C= N stretching mode of imine groups formed by oxidation of the amino groups in the primer. The negative peak near 1740 cm𔃻 is due

Dual fluorescence of syringaldazine

NASA Astrophysics Data System (ADS)

Rajendiran, N.; Balasubramanian, T.

2007-11-01

The absorption and fluorescence spectra of syringaldazine (SYAZ) has been recorded in solvents of different polarity, pH and β-cyclodextrin (β-CD) and compared with syringaldehyde (SYAL). The inclusion complex of SYAZ with β-CD is investigated by UV-vis, fluorimetry, AM 1, FT-IR, 1H NMR and scanning electron microscope (SEM). Δ G value suggests the inclusion process is an exothermic and spontaneous. In all solvents a dual fluorescence is observed for SYAZ, whereas, SYAL shows a dual luminescence only in polar solvents. The excitation spectra for the 410 nm is different from 340 nm indicate two different species present in this molecule. In pH solutions: (i) a large red shifted maxima is observed in the dianion and is due to large interactions between the aromatic ring and (ii) the large blue shift at pH ˜4.5, is due to dissociation of azine group and formation of aldehyde. β-CD studies reveal that, SYAZ forms a 1:2 complex from 1:1 complex with β-CD.

Investigation of pH Influence on Skin Permeation Behavior of Weak Acids Using Nonsteroidal Anti-Inflammatory Drugs.

PubMed

Chantasart, Doungdaw; Chootanasoontorn, Siriwan; Suksiriworapong, Jiraphong; Li, S Kevin

2015-10-01

As a continuing effort to understand the skin permeation behavior of weak acids and bases, the objectives of the present study were to evaluate skin permeation of nonsteroidal anti-inflammatory drugs (NSAIDs) under the influence of pH, investigate the mechanism of pH effect, and examine a previous hypothesis that the effective skin pH for drug permeation is different from donor solution pH. In vitro permeability experiments were performed in side-by-side diffusion cells with diclofenac, ibuprofen, flurbiprofen, ketoprofen, and naproxen and human skin. The donor solution pH significantly affected skin permeation of NSAIDs, whereas no effect of the receiver pH was observed. Similar to previous observations, the apparent permeability coefficient versus donor solution pH relationships deviated from the predictions (fractions of unionized NSAIDs) according to the acid/base theory. The influences of the viable epidermis barrier, polar pathway transport, ion permeation across skin, and effective skin pH were investigated. The effective pH values for skin permeation determined using the NSAIDs (weak acids) in this study were different from those obtained previously with a weak base at the same donor solution pH conditions, suggesting that the observed permeability-pH relationships could not be explained solely by possible pH differences between skin and donor solution. © 2015 Wiley Periodicals, Inc. and the American Pharmacists Association.

Mussel-inspired polydopamine biopolymer decorated with magnetic nanoparticles for multiple pollutants removal.

PubMed

Zhang, Shengxiao; Zhang, Yuanyuan; Bi, Guoming; Liu, Junshen; Wang, Zhigang; Xu, Qiang; Xu, Hui; Li, Xiaoyan

2014-04-15

The polydopamine polymer decorated with magnetic nanoparticles (Fe3O4/PDA) was synthesized and applied for removal of multiple pollutants. The resulted Fe3O4/PDA was characterized with elemental analysis, thermo-gravimetric analyses, vibrating sample magnetometer, high resolution transmission electron microscope, Fourier transform infrared spectra, and X-ray photoelectron spectroscopy. The self-polymerization of dopamine could be completed within 8h, and Fe3O4 nanoparticles were embedded into PDA polymer. Superparamagnetism and large saturation magnetization facilitated collection of sorbents with a magnet. Based on the catechol and amine groups, the PDA polymer provided multiple interactions to combine with pollutants. To investigate the adsorption ability of Fe3O4/PDA, heavy metal ions and dyes were selected as target pollutants. The adsorption of pollutants was pH dependent due to the variation of surface charges at different solution pH. The removal efficiencies of cation pollutants enhanced with solution pH increasing, and that of anion pollutant was just the opposite. Under the optimal solution pH, the maximum adsorption capacity calculated from Langmuir adsorption isotherm for methylene blue, tartrazine, Cu(2+), Ag(+), and Hg(2+) were 204.1, 100.0, 112.9, 259.1, and 467.3 mg g(-1), respectively. The Fe3O4/PDA shows great potential for multiple pollutants removal, and this study is the first application of PDA polymer in environmental remediation. Copyright © 2014 Elsevier B.V. All rights reserved.

Experimental study of the bending elasticity of charged lipid bilayers in aqueous solutions with pH5

NASA Astrophysics Data System (ADS)

Mitkova, D.; Stoyanova-Ivanova, A.; Ermakov, Yu A.; Vitkova, V.

2012-12-01

Exposure to high concentrations of contaminations due to air polluting gases, vapours and aerosols and possibly altering the normal pH in the body could lead to undesirable changes in the properties of biological cells. Here, we study experimentally the mechanical properties of synthetic phospholipid bilayers containing increasing molar fractions (up to 0.15) of charged lipid (synthetic phosphatidylserine) in aqueous solutions with controlled ionic strength and at pH 5, which is slightly lower than the physiological values of pH. Our observations in phase contrast and fluorescence testified to the coexistence of two phases in membranes for temperatures below 29°C. Micro-sized inhomogeneities in vesicle membranes were systematically observed at temperatures lower than 29°C and for molar fractions of phosphatidylserine in the bilayer higher than 0.1. For the quantitative determination of the membrane bending rigidity, we applied thermal fluctuation analysis of the shape of quasispherical lipid vesicles. As far as the liquid-crystalline state of the bilayer is a necessary condition for the application of the experimental method, only vesicles satisfying this requirement were processed for determination of their membrane bending rigidity. The value obtained for the bending modulus of bilayers with 0.15 molar content of charged lipid is about two times higher than the bending modulus of uncharged membranes in the same bathing solution. These findings are in qualitative agreement with our previous results for the bending rigidity of charged bilayers, measured by vesicle micromanipulation.

Colloidal diatomite, radionickel, and humic substance interaction: a combined batch, XPS, and EXAFS investigation.

PubMed

Sheng, Guodong; Shen, Runpu; Dong, Huaping; Li, Yimin

2013-06-01

This work determined the influence of humic acid (HA) and fulvic acid (FA) on the interaction mechanism and microstructure of Ni(II) onto diatomite by using batch experiments, X-ray photoelectron spectroscopy (XPS), and extended X-ray absorption fine structure (EXAFS) methods. Macroscopic and spectroscopic experiments have been combined to see the evolution of the interaction mechanism and microstructure of Ni(II) in the presence of HA/FA as compared with that in the absence of HA/FA. The results indicated that the interaction of Ni(II) with diatomite presents the expected solution pH edge at 7.0, which is modified by addition of HA/FA. In the presence of HA/FA, the interaction of Ni(II) with diatomite increased below solution pH 7.0, while Ni(II) interaction decreased above solution pH 7.0. XPS analysis suggested that the enrichment of Ni(II) onto diatomite may be due to the formation of (≡SO)2Ni. EXAFS results showed that binary surface complexes and ternary surface complexes of Ni(II) can be simultaneously formed in the presence of HA/FA, whereas only binary surface complexes of Ni(II) are formed in the absence of HA/FA, which contribute to the enhanced Ni(II) uptake at low pH values. The results observed in this work are important for the evaluation of Ni(II) and related radionuclide physicochemical behavior in the natural soil and water environment.

The effect of pH on phosphorus availability and speciation in an aquaponics nutrient solution.

PubMed

Cerozi, Brunno da Silva; Fitzsimmons, Kevin

2016-11-01

The interaction between the main ions in aquaponics nutrient solutions affects chemical composition and availability of nutrients, and nutrient uptake by plant roots. This study determined the effect of pH on phosphorus (P) speciation and availability in an aquaponics nutrient solution and used Visual MINTEQ to simulate P species and P activity. In both experimental and simulated results, P availability decreased with increase in pH of aquaponics nutrient solutions. According to simulations, P binds to several cations leaving less free phosphate ions available in solution. High pH values resulted in the formation of insoluble calcium phosphate species. The study also demonstrated the importance of organic matter and alkalinity in keeping free phosphate ions in solution at high pH ranges. It is recommended though that pH in aquaponics systems is maintained at a 5.5-7.2 range for optimal availability and uptake by plants. Copyright © 2016 Elsevier Ltd. All rights reserved.

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2011 CFR

2011-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

40 CFR Appendix B to Subpart Nnn... - Free Formaldehyde Analysis of Insulation Resins by Hydroxylamine Hydrochloride

Code of Federal Regulations, 2010 CFR

2010-07-01

... 4.0 with pH 4.0 buffer and pH 7 with pH 7.0 buffer. 3.350-mL burette for 1.0 N sodium hydroxide. 3... hydrochloride solution, 100 grams per liter, pH adjusted to 4.00. 4.3Hydrochloric acid solution, 1.0 N and 0.1 N... magnetic stirrer. Confirm that the resin has dissolved. 5.4Adjust the resin/solvent solution to pH 4.0...

Surface sulfonamide modification of poly(N-isopropylacrylamide)-based block copolymer micelles to alter pH and temperature responsive properties for controlled intracellular uptake.

PubMed

Cyphert, Erika L; von Recum, Horst A; Yamato, Masayuki; Nakayama, Masamichi

2018-06-01

Two different surface sulfonamide-functionalized poly(N-isopropylacrylamide)-based polymeric micelles were designed as pH-/temperature-responsive vehicles. Both sulfadimethoxine- and sulfamethazine-surface functionalized micelles were characterized to determine physicochemical properties, hydrodynamic diameters, zeta potentials, temperature-dependent size changes, and lower critical solution temperatures (LCST) in both pH 7.4 and 6.8 solutions (simulating both physiological and mild low pH conditions), and tested in the incorporation of a proof-of-concept hydrophobic antiproliferative drug, paclitaxel. Cellular uptake studies were conducted using bovine carotid endothelial cells and fluorescently labeled micelles to evaluate if there was enhanced cellular uptake of the micelles in a low pH environment. Both variations of micelles showed enhanced intracellular uptake under mildly acidic (pH 6.8) conditions at temperatures slightly above their LCST and minimal uptake at physiological (pH 7.4) conditions. Due to the less negative zeta potential of the sulfamethazine-surface micelles compared to sulfadimethoxine-surface micelles, and the proximity of their LCST to physiological temperature (37°C), the sulfamethazine variation was deemed more amenable for clinically relevant temperature and pH-stimulated applications. Nevertheless, we believe both polymeric micelle variations have the capacity to be implemented as an intracellular drug or gene delivery system in response to mildly acidic conditions. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1552-1560, 2018. © 2018 Wiley Periodicals, Inc.

pH Neutralization of Aqueous Bio-Oil from Switchgrass Intermediate Pyrolysis Using Process Intensification Devices

DOE PAGES

Park, Lydia Kyoung-Eun; Ren, Shoujie; Yiacoumi, Sotira; ...

2017-07-20

Despite the potential carbon-neutrality of switchgrass bio-oil, its high acidity and diverse chemical composition limit its utilization. The objectives of this research are to investigate pH neutralization of bio-oil by adding various alkali solutions in a batch system and then perform neutralization using process intensification devices, including a static mixer and a centrifugal contactor. The results indicate that sodium hydroxide and potassium hydroxide are more appropriate bases for pH neutralization of bio-oil than calcium hydroxide due to the limited solubility of calcium hydroxide in aqueous bio-oil. Mass and total acid number (TAN) balances were performed for both batch and continuous-flowmore » systems. Upon pH neutralization of bio-oil, the TAN values of the system increased after accounting the addition of alkali solution. A bio-oil heating experiment showed that the heat generated during pH neutralization did not cause a significant increase in the acidity of bio-oil. The formation of phenolic compounds during neutralization was initially suspected of increasing the system’s overall TAN value because some of these compounds (e.g., vanillic acid) act as polyprotic acids and have a stronger influence on the TAN value than monoprotic acids (e.g., acetic acid). The amount of phenolics in separated bio-oil phases, however, did not change significantly after pH neutralization. In conclusion, process intensification devices provided sufficient mixing and separation of the organic and aqueous phases, suggesting a scale-up route for the bio-oil pH neutralization process.« less

pH Neutralization of Aqueous Bio-Oil from Switchgrass Intermediate Pyrolysis Using Process Intensification Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Lydia Kyoung-Eun; Ren, Shoujie; Yiacoumi, Sotira

Despite the potential carbon-neutrality of switchgrass bio-oil, its high acidity and diverse chemical composition limit its utilization. The objectives of this research are to investigate pH neutralization of bio-oil by adding various alkali solutions in a batch system and then perform neutralization using process intensification devices, including a static mixer and a centrifugal contactor. The results indicate that sodium hydroxide and potassium hydroxide are more appropriate bases for pH neutralization of bio-oil than calcium hydroxide due to the limited solubility of calcium hydroxide in aqueous bio-oil. Mass and total acid number (TAN) balances were performed for both batch and continuous-flowmore » systems. Upon pH neutralization of bio-oil, the TAN values of the system increased after accounting the addition of alkali solution. A bio-oil heating experiment showed that the heat generated during pH neutralization did not cause a significant increase in the acidity of bio-oil. The formation of phenolic compounds during neutralization was initially suspected of increasing the system’s overall TAN value because some of these compounds (e.g., vanillic acid) act as polyprotic acids and have a stronger influence on the TAN value than monoprotic acids (e.g., acetic acid). The amount of phenolics in separated bio-oil phases, however, did not change significantly after pH neutralization. In conclusion, process intensification devices provided sufficient mixing and separation of the organic and aqueous phases, suggesting a scale-up route for the bio-oil pH neutralization process.« less

Effects of acidic pH on voltage-gated ion channels in rat trigeminal mesencephalic nucleus neurons.

PubMed

Han, Jin-Eon; Cho, Jin-Hwa; Choi, In-Sun; Kim, Do-Yeon; Jang, Il-Sung

2017-03-01

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent K + and Ca 2+ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent K + currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent K + currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker Cs + (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent Ca 2+ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.

Analytical nanosphere sensors using quantum dot-enzyme conjugates for urea and creatinine.

PubMed

Ruedas-Rama, Maria J; Hall, Elizabeth A H

2010-11-01

An enzyme-linked analytical nanosphere sensor (ANSor) is described, responding to enzyme-substrate turnover in the vicinity of a quantum dot (QD) due to coimmobilized enzyme and pH sensitive ligand. QD capping by mercapto-alkanoic acids were rejected as a pH sensitive ligand, but with the use of a layer-by-layer assembly on mercaptopropionic capped QDs and an intermediate poly(allylamine hydrochloride) layer, anthraquinone sulfonate (calcium red, CaR) was introduced to modify the pKa in the immobilized system > 8. QD-CaR absorption shows spectral overlap with QD530 emission at all pHs and gives a complex pH dependent fluorescence resonance energy transfer (FRET) efficiency, due to excited state proton transfer (λ(ex) = 540 nm; λ(em) = 585 nm). In contrast QD615-CaR with spectral overlap between the QD and CaR gave a strong and reproducible pH response. QD-urease and QD-creatinine deiminase conjugates could be linked with pH changes produced by enzyme degradation of urea and creatinine, respectively. Close coupling between the pH sensitive QD and enzyme conjugate maximized signal compared with solution based assays: QD-urease and QD-CD bioconjugates were tested in model biological media (Dulbecco's modified Eagle's Medium and fetal calf serum) and in urine, showing a response in 3-4 min.

Measurements of spectral responses for developing fiber-optic pH sensor

NASA Astrophysics Data System (ADS)

Yoo, Wook Jae; Heo, Ji Yeon; Jang, Kyoung Won; Seo, Jeong Ki; Moon, Jin Soo; Park, Jang-Yeon; Park, Byung Gi; Cho, Seunghyun; Lee, Bongsoo

2011-01-01

In this study, we have fabricated a fiber-optic pH sensor, which is composed of a light source, a pH-sensing probe, plastic optical fibers and a spectrometer, for determining the degree of infection by Helicobacter pylori in the stomach. As pH indicators, phenol red and m-cresol purple are used, and pH liquid solutions are prepared by mixing phenol red or m-cresol purple solutions and various kinds of pH buffer solutions. The light emitted by a light source is guided by plastic optical fibers to the pH liquid solution, and the optical characteristic of a reflected light is changed according to the color variations of the pH indicator in the pH-sensing probe. Therefore, we have measured the intensities and wavelength shifts of the reflected lights, which change according to the color variations of indicators at different pH values, by using a spectrometer for spectral analysis. Also, the relationships between the pH values of liquid solutions and the optical properties of the modulated lights are obtained on the basis of the changes of the colors of indicators.

Use of gold nanoparticles as crosslink agent to form chitosan nanocapsules: study of the direct interaction in aqueous solutions.

PubMed

Prado-Gotor, R; López-Pérez, G; Martín, M J; Cabrera-Escribano, F; Franconetti, A

2014-06-01

A systematic study of the interaction between free anionic gold nanoparticles and chitosan in a solution is presented. A spectroscopic study of the interaction between 10nm gold nanoparticles and low molecular weight chitosan is reported as a function of the concentration and pH of the polymer in a solution. Zeta potential measurements and TEM images indicate the effective aggregation of the nanoparticles in the presence of chitosan. At the same time, anionic gold nanoparticles act as crosslink agents to form chitosan nanocapsules with an average molecular size of 260nm. The changes of the surface plasmon band due to the adsorption of the polymer on the nanoparticle surface allow using of the citrate gold nanoparticles as sensors of the polymer for analytical purposes. The limit of detection for chitosan biopolymer is 69nM. The optimum pH for the interaction between the biopolymer and the nanoparticles is found at a value of 6.4, obtained from spectrophotometric measurements and applying a deconvolution analysis of the experimental data. A simple model based on molecular surface electrostatic interactions is proposed to understand the pH dependence of the investigated system. Copyright © 2014 Elsevier Inc. All rights reserved.

Removal of inorganic mercury from aquatic environments by multi-walled carbon nanotubes.

PubMed

Yaghmaeian, Kamyar; Khosravi Mashizi, Reza; Nasseri, Simin; Mahvi, Amir Hossein; Alimohammadi, Mahmood; Nazmara, Shahrokh

2015-01-01

Mercury is considered as a toxic heavy metal in aquatic environments due to accumulation in bodies of living organisms. Exposure to mercury may lead to different toxic effects in humans including damages to kidneys and nervous system. Multi-walled carbon nanotubes (MWCNTs) were selected as sorbent to remove mercury from aqueous solution using batch technique. ICP instrument was used to determine the amount of mercury in solution. Moreover, pH, contact time and initial concentration of mercury were studied to determine the influence of these parameters on the adsorption conditions. Results indicate that the adsorption strongly depended on pH and the best pH for adsorption is about 7. The rate of adsorption process initially was rapid but it was gradually reduced with increasing of contact time and reached the equilibrium after 120 min. In addition, more than 85 % of initial concentration of 0.1 mg/l was removed at 0.5 g/l concentration of sorbent and contact time of 120 min. Meanwhile, the adsorption process followed the pseudo second-order model and the adsorption isotherms could be described by both the Freundlich and the Langmuir models. This study showed that MWCNTs can effectively remove inorganic mercury from aqueous solutions as adsorbent.

Retention and release of oil-in-water emulsions from filled hydrogel beads composed of calcium alginate: impact of emulsifier type and pH.

PubMed

Zeeb, Benjamin; Saberi, Amir Hossein; Weiss, Jochen; McClements, David Julian

2015-03-21

Delivery systems based on filled hydrogel particles (microgels) can be fabricated from natural food-grade lipids and biopolymers. The potential for controlling release characteristics by modulating the electrostatic interactions between emulsifier-coated lipid droplets and the biopolymer matrix within hydrogel particles was investigated. A multistage procedure was used to fabricate calcium alginate beads filled with lipid droplets stabilized by non-ionic, cationic, anionic, or zwitterionic emulsifiers. Oil-in-water emulsions stabilized by Tween 60, DTAB, SDS, or whey protein were prepared by microfluidization, mixed with various alginate solutions, and then microgels were formed by simple extrusion into calcium solutions. The microgels were placed into a series of buffer solutions with different pH values (2 to 11). Lipid droplets remained encapsulated under acidic and neutral conditions, but were released under highly basic conditions (pH 11) due to hydrogel swelling when the alginate concentration was sufficiently high. Lipid droplet release increased with decreasing alginate concentration, which could be attributed to an increase in the pore size of the hydrogel matrix. These results have important implications for the design of delivery systems to entrap and control the release of lipophilic bioactive components within filled hydrogel particles.

Adsorption removal of tannic acid from aqueous solution by polyaniline: Analysis of operating parameters and mechanism.

PubMed

Sun, Chencheng; Xiong, Bowen; Pan, Yang; Cui, Hao

2017-02-01

Polyaniline (PANI) prepared by chemical oxidation was studied for adsorption removal of tannic acid (TA) from aqueous solution. Batch adsorption studies were carried out under different adsorbent dosages, pH, ionic strength, initial TA concentration and coexisting anions. Solution pH had an important impact on TA adsorption onto PANI with optimal removal in the pH range of 8-11. TA adsorption on PANI at three ionic strength levels (0.02, 0.2 and 2molL -1 NaCl) could be well described by Langmuir model (monolayer adsorption process) and the maximum adsorption capacity was 230, 223 and 1023mgg -1 , respectively. Kinetic data showed that TA adsorption on PANI fitted well with pseudo-second-order model (controlled by chemical process). Among the coexisting anions tested, PO 4 3- significantly inhibited TA adsorption due to the enhancement of repulsive interaction. Continuous flow adsorption studies indicated good flexibility and adaptability of the PANI adsorbent under different flow rates and influent TA concentrations. The mechanism controlling TA adsorption onto PANI under different operating conditions was analyzed with the combination of electrostatic interactions, hydrogen bonding, π-π interactions and Van der Waals interactions. Copyright © 2016 Elsevier Inc. All rights reserved.

Complexing agents and pH influence on chemical durability of type I moulded glass containers.

PubMed

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-06-16

Among the factors that affect the glass surface chemical durability, pH and complexing agents presence in aqueous solution have the main role (1). Glass surface attack can be also related to the delamination issue with glass particles appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed (2,3). The present study emphasizes the possible synergy between a few complexing agents with pH on the borosilicate glass chemical durability. Hydrolytic attack was performed in small volume 23 ml type I glass containers autoclaved according to EP or USP for 1 hour at 121°C, in order to enhance the chemical attack due to time, temperature and the unfavourable surface/volume ratio. 0,048 M or 0.024 M (moles/liter) solutions of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid) and sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ± 0,05 units at fixed values 5,5-6,6-7-7,4-8-9 by LiOH diluted solution. Since silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by ICPAES. The work was completed by the analysis of the silicon release in the worst attack conditions, of moulded glass, soda lime type II and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by SEM was finally performed to check for the surface status after the worst chemical attack condition by citric acid. Copyright © 2017, Parenteral Drug Association.

Degradation of 4-aminoantipyrine by electro-oxidation with a boron-doped diamond anode: Optimization by central composite design, oxidation products and toxicity.

PubMed

de Melo da Silva, Lucas; Gozzi, Fábio; Sirés, Ignasi; Brillas, Enric; de Oliveira, Silvio Cesar; Machulek, Amilcar

2018-08-01

Electro-oxidation with electrogenerated H 2 O 2 (EO-H 2 O 2 ) was applied to treat acidic aqueous solutions of 4-aminoantipyrine (4-AA), a persistent drug metabolite of dipyrone, in sulfate medium. Trials were made using a boron-doped diamond anode in the presence of H 2 O 2 electrogenerated on site. A 2 4 central composite design (CCD) was employed to evaluate the effect of four independent variables, namely current density (j), pH, 4-AA concentration and electrolysis time, on the percentages of degradation and mineralization, as well as on mineralization current efficiency (MCE). Predicted responses agreed with observed values, showing linear trendlines with good R 2 and R 2 adj values. The degradation was optimum at j=77.5mAcm -2 , pH3.5 and 62.5mgL -1 4-AA, leading to 63% and 99% removal after 3 and 7min, respectively. For those solutions, the largest mineralization was found at j=77.5mAcm -2 , attaining 45% abatement at 175min. Low MCE values were obtained in all electrolyses. An initial route for 4-AA degradation is proposed based on one dimer and eleven aromatic and aliphatic intermediates detected in the treated solutions at pH3.5 by LC-MS. The initial 62.5mgL -1 solution at pH3.5 presented acute toxicity on Artemia salina larvae, with LC 50 =13.6mgL -1 , being substantially reduced after 3 and 7min of EO-H 2 O 2 at j=77.5mAcm -2 due to the formation of less toxic derivatives. Copyright © 2018 Elsevier B.V. All rights reserved.

Hydroquinone-Mediated Redox Cycling of Iron and Concomitant Oxidation of Hydroquinone in Oxic Waters under Acidic Conditions: Comparison with Iron-Natural Organic Matter Interactions.

PubMed

Jiang, Chao; Garg, Shikha; Waite, T David

2015-12-15

Interactions of 1,4-hydroquinone with soluble iron species over a pH range of 3-5 in the air-saturated and partially deoxygenated solution are examined here. Our results show that 1,4-hydroquinone reduces Fe(III) in acidic conditions, generating semiquinone radicals (Q(•-)) that can oxidize Fe(II) back to Fe(III). The oxidation rate of Fe(II) by Q(•-)increases with increase in pH due to the speciation change of Q(•-) with its deprotonated form (Q(•-)) oxidizing Fe(II) more rapidly than the protonated form (HQ(•)). Although the oxygenation of Fe(II) is negligible at pH < 5, O2 still plays an important role in iron redox transformation by rapidly oxidizing Q(•-) to form benzoquinone (Q). A kinetic model is developed to describe the transformation of quinone and iron under all experimental conditions. The results obtained here are compared with those obtained in our previous studies of iron-Suwannee River fulvic acid (SRFA) interactions in acidic solutions and support the hypothesis that hydroquinone moieties can reduce Fe(III) in natural waters. However, the semiquinone radicals generated in pure hydroquinone solution are rapidly oxidized by dioxygen, while the semiquinone radicals generated in SRFA solution are resistant to oxidation by dioxygen, with the result that steady-state semiquinone concentrations in SRFA solutions are 2-3 orders of magnitude greater than in solutions of 1,4-hydroquinone. As a result, semiquinone moieties in SRFA play a much more important role in iron redox transformations than is the case in solutions of simple quinones such as 1,4-hydroquinone. This difference in the steady-state concentration of semiquinone species has a dramatic effect on the cycling of iron between the +II and +III oxidation states, with iron turnover frequencies in solutions containing SRFA being 10-20 times higher than those observed in solutions of 1,4-hydroquinone.

Electrochemical study of the interaction between dsDNA and copper(I) using carbon paste and hanging mercury drop electrode.

PubMed

Stanić, Z; Girousi, S

2008-06-30

The interaction of copper(I) with double-stranded (ds) calf thymus DNA was studied in solution and at the electrode surface by means of transfer voltammetry using a carbon paste electrode (CPE) as working electrode in 0.2 M acetate buffer solution (pH 5.0). As a result of the interaction of Cu(I) between the base pairs of the dsDNA, the characteristic peaks of dsDNA, due to the oxidation of guanine and adenine, increased and after a certain concentration of Cu(I) a new peak at +1.37 V appeared, probably due to the formation of a purine-Cu(I) complex (dsDNA-Cu(I) complex). Accordingly, the interaction of copper(I) with calf thymus dsDNA was studied in solution as well as at the electrode surface using hanging mercury drop electrode (HMDE) by means of alternating current voltammetry (AC voltammetry) in 0.3 M NaCl and 50 mM sodium phosphate buffer (pH 8.5) as supporting electrolyte. Its interaction with DNA is shown to be time dependent. Significant changes in the characteristic peaks of dsDNA were observed after addition of higher concentration of Cu(I) to a solution containing dsDNA, as a result of the interaction between Cu(I) and dsDNA. All the experimental results indicate that Cu(I) can bind to DNA by electrostatic binding and form an association complex.

A method for calibrating pH meters using standard solutions with low electrical conductivity

NASA Astrophysics Data System (ADS)

Rodionov, A. K.

2011-07-01

A procedure for obtaining standard solutions with low electrical conductivity that reproduce pH values both in acid and alkali regions is proposed. Estimates of the maximal possible error of reproducing the pH values of these solutions are obtained.

Photo-catalytic Degradation and Sorption of Radio-cobalt from EDTA-Co Complexes Using Manganese Oxide Materials - 12220

DOE Office of Scientific and Technical Information (OSTI.GOV)

Koivula, Risto; Harjula, Risto; Tusa, Esko

2012-07-01

The synthesised cryptomelane-type α-MnO{sub 2} was tested for its Co-57 uptake properties in UV-photo-reactor filled with 10 μM Co-EDTA solution with a background of 10 mM NaNO{sub 3}. High cobalt uptake of 96% was observed after 1 hour of UV irradiation. As for comparison, a well-known TiO{sub 2} (Degussa P25) was tested as reference material that showed about 92% cobalt uptake after six hours of irradiation in identical experiment conditions. It was also noted that the cobalt uptake on cryptomelane with out UV irradiation was modest, only about 10%. Decreasing the pH of the Co-EDTA solution had severe effects onmore » the cobalt uptake mainly due to the rather high point of zero charge of the MnO{sub 2} surface (pzc at pH ∼4.5). Modifying the synthesis procedure we were able to produce a material that functioned well even in solution of pH 3 giving cobalt uptake of almost 99%. The known properties, catalytic and ion exchange, of manganese oxides were simultaneously used for the separation of EDTA complexed Co-57. Tunnel structured cryptomelane -type showed very fast and efficient Co uptake properties outperforming the well known and widely used Degussa P25 TiO{sub 2} in both counts. The layered structured manganese oxide, birnessite, reached also as high Co removal level as the reference material Degussa did but the reaction rate was considerably faster. Since the decontamination solutions are typically slightly acidic and the point of zero charge of the manganese oxides are rather high > pH 4.5 the material had to be modified. This modified material had tolerance to acidic solutions and it's Co uptake performance remained high in the solutions of lower pH (pH 3). Increasing the ion concentration of test solutions, background concentration, didn't affect the final Co uptake level; however, some changes in the uptake kinetics could be seen. The increase in EDTA/MoMO ratio was clearly reflected in the Co uptake curves. The obtained results of manganese oxide were very promising for the treatment of EDTA complexed Co solutions. The better performance values and cheaper production cost of manganese oxide, compared to titanium dioxide, is so big driving force that further studies on the material are evident. The possibilities for continuous treatment, instead of the fluidized bed -type batch experiment are investigated and the effects of other compounds affecting the de-complexation of Co-EDTA are further studied. (authors)« less

Combining hydrogen evolution and corrosion data - A case study on the economic viability of selected metal cathodes in microbial electrolysis cells

NASA Astrophysics Data System (ADS)

Brown, Robert Keith; Schmidt, Ulrike Christiane; Harnisch, Falk; Schröder, Uwe

2017-07-01

In this study, hydrogen evolution reaction (HER) catalytic and corrosion data is determined for selected metal cathode materials. The HER data was gathered using cyclic voltammetry (CV) in electrolytes with several pH values and varying current densities. Of the tested materials, the stainless steel alloy EN 1.4401/AISI 316 generally had the lowest HER overpotentials at the pH values 0.25, 7 and 9. At the higher pH values of 11 and 14 a custom NiMoFe alloy with a m/m% composition of 60-30-10 showed the lowest overpotentials. After each CV experiment, the electrolyte solution was analyzed to determine the corrosion of the metal cathodes. Results of corrosion measurements showed that the stainless steels EN 1.4401 had the lowest corrosion losses on average across all tested pH values. Combining HER and corrosion data revealed that: In the pH 9 electrolyte solution, EN 1.4401 was not always the best catalyst in terms of its overpotential, but it incurs the least material costs due to its lack of corrosion, this balance thereby making it the "best choice" under the given conditions. The combination of HER and corrosion data provides a more effective framework for discussing economic viability than either data set alone.

Forsterite surface composition in aqueous solutions: a combined potentiometric, electrokinetic, and spectroscopic approach

NASA Astrophysics Data System (ADS)

Pokrovsky, Oleg S.; Schott, Jacques

2000-10-01

Surfaces of natural and synthetic forsterite (Fo 91 and Fo 100) in aqueous solutions at 25°C were investigated using surface titrations in batch and limited residence time reactors, column filtration experiments, electrokinetic measurements (streaming potential and electrophoresis techniques), Diffuse Reflectance Infrared Spectroscopy (DRIFT), and X-ray Photoelectron Spectroscopy (XPS). At pH < 9, a Mg-depleted, Si-rich layer (<20 Å thick) is formed on the forsterite surface due to a Mg 2+ ↔ H + exchange reaction. Electrokinetic measurements yield a pH IEP value of 4.5 corresponding to the dominance of SiO 2 in the surface layer at pH < 9. In contrast, surface titrations of fresh powders give an apparent pH PZC of about 10 with the development of a large positive charge (up to 10 -4 mol/m 2 or 10 C/m 2) in the acid pH region. This may be explained by penetration of H + into the first unit cells of forsterite surface. The surface charge of acid-reacted forsterite is one or two orders of magnitude lower than that of unreacted forsterite with an apparent pH PZC at around 6.5 and a pH IEP value of 2.1 which is close to that for amorphous silica and reflects the formation of a silica-rich layer on the surface. XPS analyses indicate the penetration of hydrogen into the surface and the polymerization of silica tetrahedra in this leached layer. At pH > 10, a Si-deficient, Mg-rich surface layer is formed as shown by XPS analyses and the preferential Si release from the surface during column filtration experiments.

Preparation of Essential Oil-Based Microemulsions for Improving the Solubility, pH Stability, Photostability, and Skin Permeation of Quercetin.

PubMed

Lv, Xia; Liu, Tiantian; Ma, Huipeng; Tian, Yan; Li, Lei; Li, Zhen; Gao, Meng; Zhang, Jianbin; Tang, Zeyao

2017-11-01

Quercetin can bring many benefits to skin based on its various bioactivities. However, the therapeutic effect of quercetin is limited due to the poor water solubility, pH instability, light instability, and skin permeation. The aim of the present work was applying essential oil-based microemulsions to improve the solubility, pH stability, photostability, and skin permeation of quercetin for topical application. Peppermint oil (PO-ME), clove oil (CO-ME), and rosemary oil (RMO-ME) were selected as model essential oils. Microemulsions composed of Cremophor EL/1,2-propanediol/essential oils (47:23:30, w/w) were selected as model formulations, based on the pseudo-ternary phase diagram and the characterizations. In the solubility study, the solubility of quercetin was improved dozens of times by microemulsions. Quercetin was found instable under alkaline condition, with 50% degraded in the solution of pH 13. However, PO-ME, CO-ME, and RMO-ME could protect quercetin from the hydroxide ions, with 47, 9, and 12% of quercetin degraded. In the photostability study, the essential oil-based microemulsions showed the capability of protecting quercetin from degradation under UV radiation. Where more than 67% of quercetin was degraded in aqueous solution, while less than 7% of quercetin degraded in microemulsions. At last, the in vitro skin permeation study showed that the essential oil-based microemulsions could enhance the permeation capacity of quercetin by 2.5-3 times compared to the aqueous solution. Hence, the prepared essential oil microemulsions could improve the solubility, pH stability, photostability, and skin permeation of quercetin, which will be beneficial for its topical application.

Open-Gated pH Sensor Fabricated on an Undoped-AlGaN/GaN HEMT Structure

PubMed Central

Abidin, Mastura Shafinaz Zainal; Hashim, Abdul Manaf; Sharifabad, Maneea Eizadi; Rahman, Shaharin Fadzli Abd; Sadoh, Taizoh

2011-01-01

The sensing responses in aqueous solution of an open-gated pH sensor fabricated on an AlGaN/GaN high-electron-mobility-transistor (HEMT) structure are investigated. Under air-exposed ambient conditions, the open-gated undoped AlGaN/GaN HEMT only shows the presence of a linear current region. This seems to show that very low Fermi level pinning by surface states exists in the undoped AlGaN/GaN sample. In aqueous solution, typical current-voltage (I-V) characteristics with reasonably good gate controllability are observed, showing that the potential of the AlGaN surface at the open-gated area is effectively controlled via aqueous solution by the Ag/AgCl gate electrode. The open-gated undoped AlGaN/GaN HEMT structure is capable of distinguishing pH level in aqueous electrolytes and exhibits linear sensitivity, where high sensitivity of 1.9 mA/pH or 3.88 mA/mm/pH at drain-source voltage, VDS = 5 V is obtained. Due to the large leakage current where it increases with the negative gate voltage, Nernstian like sensitivity cannot be determined as commonly reported in the literature. This large leakage current may be caused by the technical factors rather than any characteristics of the devices. Surprisingly, although there are some imperfections in the device preparation and measurement, the fabricated devices work very well in distinguishing the pH levels. Suppression of current leakage by improving the device preparation is likely needed to improve the device performance. The fabricated device is expected to be suitable for pH sensing applications. PMID:22163786

Structural and surface functionality changes in reticulated vitreous carbon produced from poly(furfuryl alcohol) with sodium hydroxide additions

NASA Astrophysics Data System (ADS)

Oishi, Silvia Sizuka; Botelho, Edson Cocchieri; Rezende, Mirabel Cerqueira; Ferreira, Neidenêi Gomes

2017-02-01

The use of sodium hydroxide to neutralize the acid catalyst increases the storage life of poly(furfuryl alcohol) (PFA) resin avoiding its continuous polymerization. In this work, a concentrated sodium hydroxide solution (NaOH) was added directly to the PFA resin in order to minimize the production of wastes generated when PFA is washed with diluted basic solution. Thus, different amounts of this concentrated basic solution were added to the resin up to reaching pH values of around 3, 5, 7, and 9. From these four types of modified PFA two sample sets of reticulated vitreous carbon (RVC) were processed and heat treated at two different temperatures (1000 and 1700 °C). A correlation among cross-link density of PFA and RVC morphology, structural ordering and surface functionalities was systematically studied using Fourier transform infrared spectroscopy, scanning electron microscopy, Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy techniques. The PFA neutralization (pH 7) led to its higher polymerization degree, promoting a crystallinity decrease on RVC treated at 1000 °C as well as its highest percentages of carboxylic groups on surface. A NaOH excess (pH 9) substantially increased the RVC oxygen content, but its crystallinity remained similar to those for samples from pH 3 and 5 treated at 1000 °C, probably due to the reduced presence of carboxylic group and the lower polymerization degree of its cured resin. Samples with pH 3 and 5 heat treated at 1000 and 1700 °C can be considered the most ordered which indicated that small quantities of NaOH may be advantageous to minimize continuous polymerization of PFA resin increasing its storage life and improving RVC microstructure.

Separation of tricyclic antidepressants by capillary zone electrophoresis with N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) as an effective electrolyte additive.

PubMed

Dell'Aquila, Caterina

2002-09-05

Five tricyclic antidepressants (TADs), desipramyne, nortriptyline, imipramine, doxepin and amitriptyline, were separated by using the N,N,N',N'-tetramethyl-1,3-butanediamine (TMBD) as additive in the background electrolyte solution. Because the tricyclic antidepressants are similar in structure, mass and pka values, their separation, by capillary zone electrophoresis, requires the careful manipulation of parameters, such as the pH and the composition of the electrolyte solution. As basic drugs, the TADs interact with the silanol groups on the capillary wall giving rise to peak broadening and asymmetry, non reproducible migration times and failing in selectivity. Different concentrations of TMBD (40, 60, 100 and 150 mM) were used at pH 9.5, but only a 100 mM TMBD allowed a good separation and a high efficiency for all the TADs. At this pH the separation was not possible without additive. This result is due to the reduced electroosmotic flow whose mobility is at a value of 10(-9) m(2) V(-1) s(-1).

Weathering of primary minerals and mobility of major elements in soils affected by an accidental spill of pyrite tailing.

PubMed

Martín, Francisco; Diez, María; García, Inés; Simón, Mariano; Dorronsoro, Carlos; Iriarte, Angel; Aguilar, José

2007-05-25

In the present work, soil profiles were sampled 40 days and three years after an accidental pyrite tailing spill from the Aznalcóllar mine (S Spain) in order to figure out the effects of the acidic solution draining from the tailing. The composition of the acidic solution, the mineralogy, and the total and soluble content of the major elements were analysed at varying depths. The results show a weathering process of carbonates and of primary silicates. Calcium released is leached or reacts with the sulphate ions to form gypsum. Magnesium, aluminium and potassium tend to leach from the uppermost millimetres of the soil, accumulating where the pH>/=5.0; also the iron, probably forming more or less complex hydroxysulphates, precipitate in the upper 5 cm. The strong releasing of soluble salts increases the electrical conductivity, while the soluble potassium tends to decrease in the uppermost part of the soil due to the neoformation of jarosite. Iron is soluble only where the pH

Corrosion resistance of a laser spot-welded joint of NiTi wire in simulated human body fluids.

PubMed

Yan, Xiao-Jun; Yang, Da-Zhi

2006-04-01

The purpose of this study was to investigate corrosion resistance of a laser spot-welded joint of NiTi alloy wires using potentiodynamic tests in Hank's solution at different PH values and the PH 7.4 NaCl solution for different Cl- concentrations. Scanning electron microscope observations were carried out before and after potentiodynamic tests. The composition of a laser spot-welded joint and base metal were characterized by using an electron probe microanalyzer. The results of potentiodynamic tests showed that corrosion resistance of a laser spot-welded joint of NiTi alloy wire was better than that of base metal, which exhibited a little higher breakdown potential and passive range, and a little lower passive current density. Corrosion resistances of a laser spot-welded joint and base metal decreased with increasing of the Cl- concentration and PH value. The improvement of corrosion resistance of the laser spot-welded joint was due to the decrease of the surface defects and the increase of the Ti/Ni ratio. (c) 2005 Wiley Periodicals, Inc.

Electrochemical control of pH in a hydroponic nutrient solution

NASA Technical Reports Server (NTRS)

Schwartzkopf, S. H.

1986-01-01

The electrochemical pH control system described was found to provide a feasible alternative method of controlling nutrient solution pH for CELSS applications. The plants grown in nutrient solution in which the pH was controlled electrochemically showed no adverse effects. Further research into the design of a larger capacity electrode bridge for better control is indicated by the results of this experiment, and is currently under way.

Modeling the chemical kinetics of atmospheric plasma for cell treatment in a liquid solution

NASA Astrophysics Data System (ADS)

Kim, H. Y.; Lee, H. W.; Kang, S. K.; Wk. Lee, H.; Kim, G. C.; Lee, J. K.

2012-07-01

Low temperature atmospheric pressure plasmas have been known to be effective for living cell inactivation in a liquid solution but it is not clear yet which species are key factors for the cell treatment. Using a global model, we elucidate the processes through which pH level in the solution is changed from neutral to acidic after plasma exposure and key components with pH and air variation. First, pH level in a liquid solution is changed by He+ and He(21S) radicals. Second, O3 density decreases as pH level in the solution decreases and air concentration decreases. It can be a method of removing O3 that causes chest pain and damages lung tissue when the density is very high. H2O2, HO2, and NO radicals are found to be key factors for cell inactivation in the solution with pH and air variation.

In vitro degradation of ZM21 magnesium alloy in simulated body fluids.

PubMed

Witecka, Agnieszka; Bogucka, Aleksandra; Yamamoto, Akiko; Máthis, Kristián; Krajňák, Tomáš; Jaroszewicz, Jakub; Święszkowski, Wojciech

2016-08-01

In vitro degradation behavior of squeeze cast (CAST) and equal channel angular pressed (ECAP) ZM21 magnesium alloy (2.0wt% Zn-0.98wt% Mn) was studied using immersion tests up to 4w in three different biological environments. Hanks' Balanced Salt Solution (Hanks), Earle's Balanced Salt Solution (Earle) and Eagle minimum essential medium supplemented with 10% (v/v) fetal bovine serum (E-MEM+10% FBS) were used to investigate the effect of carbonate buffer system, organic compounds and material processing on the degradation behavior of the ZM21 alloy samples. Corrosion rate of the samples was evaluated by their Mg(2+) ion release, weight loss and volume loss. In the first 24h, the corrosion rate sequence of the CAST samples was as following: Hanks>E-MEM+10% FBS>Earle. However, in longer immersion periods, the corrosion rate sequence was Earle>E-MEM+10% FBS≥Hanks. Strong buffering effect provided by carbonate buffer system helped to maintain the pH avoiding drastic increase of the corrosion rate of ZM21 in the initial stage of immersion. Organic compounds also contributed to maintain the pH of the fluid. Moreover, they adsorbed on the sample surface and formed an additional barrier on the insoluble salt layer, which was effective to retard the corrosion of CAST samples. In case of ECAP, however, this effect was overcome by the occurrence of strong localized corrosion due to the lower pH of the medium. Corrosion of ECAP samples was much greater than that of CAST, especially in Hanks, due to higher sensitivity of ECAP to localized corrosion and the presence of Cl(-). The present work demonstrates the importance of using an appropriate solution for a reliable estimation of the degradation rate of Mg-base degradable implants in biological environments, and concludes that the most appropriate solution for this purpose is E-MEM+10% FBS, which has the closest chemical composition to human blood plasma. Copyright © 2016 Elsevier B.V. All rights reserved.

The reduction of chromium (VI) by iron (II) in aqueous solutions

NASA Astrophysics Data System (ADS)

Pettine, Maurizio; D'Ottone, Luca; Campanella, Luigi; Millero, Frank J.; Passino, Roberto

1998-05-01

The rates of the reduction of Cr(VI) with Fe(II) were measured in NaCl, NaClO 4, and natural seawater as a function of pH (1.5-8.7), temperature (5-40°C) and ionic strength (I = 0.01-2 M). The pseudo first-order rate constant (log k 1) showed a parabolic dependence on pH decreasing from 1.5 to 4.5 and increasing from 5.5 to 8.7. The kinetics of the reaction in these two regions of pH also showed different influences of temperature, ionic strength, and reductant concentration. The rate of Cr(VI) reduction is described by the general expression -d[Cr(VI)]/dt = k [Cr(VI)] [Fe(II)] where k (M -1 min -1) can be determined from the log k=6.74-1.01 pH-188.5/T for the pH range 1.5-4.5 (σ = 0.2) and log k=11.93+0.95 pH-4260.1/T-1.06 I 0.5 for the pH range 5-8.7 (σ = 0.2) from 5 to 40°C and 0.01 to 2 M ionic strength. The effect of pH, temperature, and ionic strength on the reaction indicates that the reactions at low pH are due to H2CrO4+ Fe2+limit→k H2 A-Feproducts While the reactions at high pH are due to HCrO4-+ FeOH+limit→k HA-FeOHproductsHCrO4-+ Fe(OH)2limit→k HA-Fe(OH)2 products The overall rate expression over the entire pH range can be determined from (H 2A = H 2CrO 4) k=k H2 A-Feα( H2A)α( Fe2+)+k HA-FeOHα( HA-)α( FeOH+)+k HA-Fe(OH)2 α( HA-)α( Fe(OH)2) where k H2A-Fe = 5 x 10 6, k HA-FeOH = 1 x 10 6, k HA-Fe (OH)2= 5 x 10 11. In oxic aqueous systems Cr(VI) competes with O 2 in the oxidation of Fe(II) and an extension of the rate law for Cr(VI) reduction with Fe(II) in oxygenated solutions is proposed. The application of this extended rate law to environmental conditions suggests that this reaction influences the distribution of oxidized and reduced species of chromium in oxic and anoxic waters.

Biosorption of copper, nickel and manganese using non-living biomass of marine alga, Ulva lactuca.

PubMed

Omar, Hanan Hafez

2008-04-01

The adsorption of Cu2+, Ni2+ and Mn2+ onto the marine algal biomass of Ulva lactuca was investigated in single and multimetal solutions. This study was intended to determine the role of different pH values (2-8) on the biosorption of metals at different concentrations (10, 20 and 30 mg L(-1)). The biosorption capacity of Cu2+, Ni2+ and Mn2+ for 10 mg L(-1) was the same as 20 and 30 mg L(-1), increase with increasing pH up to pH 5.0 and then decreased, in single and multimetal solutions. The optimum pH value was observed in the pH range 4-5 for Cu2+ and pH 5-6 for Ni2+ and Mn2+. The maximum biosorption capacities of tested alga for Cu2+, Ni2+ and Mn2+ were 92, 80 and 75%, respectively in single metal solution at 10 mg L(-1) and pH 5.0. At a further increase of pH (8.0) the biosorption process for Cu2+, Ni2+ and Mn2+ (75, 69 and 63%, respectively at 10 mg L(-1)) was decreased. The minimum biosorptions were 60, 49 and 44% for Cu2+, Ni2+ and Mn2+, respectively in single metal solution at 10 mg L(-1) and pH 2.0. In the multimetal solution, algal biomass exhibited the maximum and the minimum biosorption capacity at different pH values the same as in single metal solution. The inhibitory role of other ions on sorption process can be well observed in multimetal mixture, where biosorption capacity of Cu2+, Ni2+ and Mn2+ were significantly decreased in the multimetal solutions. The maximum biosorption was recorded for Cu2+ (83%) in solution of Cu2+ + Mn2+, Mn2+ (67%) in solution of Ni2 + Mn2+ and for Ni2+ (74%) in solution of Ni2+ + Mn2+ at the concentration 10 mg L(-1) and pH 5.0. The observed reduction in the biosorption of Cu2+, Ni2+ and Mn2+ (65, 57 and 52%, respectively at 10 mg L(-1) and pH 5.0) was more pronounced in the multimetal solution of Cu2 + Ni2+ + Mn2+ as compared with single metal solution. The results demonstrated that the affinity of the tested alga for sorption of the investigated metal ions in single and multimetal solutions runs in the order Cu2+ > Ni2+ > Mn2+. Biosorption equilibrium was established by the Langmuir and Freundlich isotherm models. According to the analyses conducted, the biosorption of Cu2+, Ni2+ and Mn2+ to Ulva lactuca was more consistent with Freundlich isotherm.

The influence of pH on biotite dissolution and alteration kinetics at low temperature

USGS Publications Warehouse

Acker, James G.; Bricker, O.P.

1992-01-01

Biotite dissolution rates in acidic solutions were determined in fluidized-bed reactors and flowthrough columns. Biotite dissolution rates increased inversely as a linear function of pH in the pH range 3-7, where the rate order n = -0.34. Biotite dissolved incongruently over this pH range, with preferential release of magnesium and iron from the octahedral layer. Release of tetrahedral silicon was much greater at pH 3 than at higher pH. Iron release was significantly enhanced by low pH conditions. Solution compositions from a continuous exposure flow-through column of biotite indicated biotite dissolves incongruently at pH 4, consistent with alteration to a vermiculite-type product. Solution compositions from a second intermittent-flow column exhibited elevated cation release rates upon the initiation of each exposure to solution. The presence of strong oxidizing agents, the mineral surface area, and sample preparation methodology also influenced the dissolution or alteration kinetics of biotite. ?? 1992.

Cold-set hydrogels made of whey protein nanofibrils with different divalent cations.

PubMed

Mohammadian, Mehdi; Madadlou, Ashkan

2016-08-01

Whey protein nanofibrils are gaining interest to fabricate cold-set hydrogels due to their ability to gel at lower concentrations than parent proteins. In the present research, fibrillated protein solution was gelled with three different divalent cation salts including CaCl2, MnCl2 and ZnCl2 and the textural and functional characteristics of the resulting hydrogel samples were studied. Atomic force microscopy indicated that the flexible micron-scaled fibrils with nanometric thickness (up to 8.0nm) that formed at pH 2.0 underwent breaking in length upon post-formation pH rise to 7.5. Whilst heat-denatured protein solution failed to form self-supporting gel at pH 7.5, fibrillated protein solution gelled by all three types of cations. Fibrillation increased the protein solution consistency coefficient (K) much more than heat denaturation. It was suggested based on Fourier-transform infra-red (FT-IR) spectra that some hydrogen bonds were disrupted by fibrillation. Zn(2+)-induced gel was firmer, had a higher water holding capacity and a more compact microstructure, as well, required a higher compressive stress to fracture than its counterparts. Nonetheless, the Mn(2+)- and Ca(2+)-induced gels disintegrated to a much lesser extent in both pepsin-free and pepsin-present simulated gastric juice than Zn(2+)-induced sample. Chitosan coating approximately halved the simulated degradability of all gel samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Characterization of cadmium biosorption by Exiguobacterium sp. isolated from farmland soil near Cu-Pb-Zn mine.

PubMed

Park, Jin Hee; Chon, Hyo-Taek

2016-06-01

Bacteria have the ability to bind heavy metals on their cell wall. Biosorption is a passive and energy-independent mechanism to adsorb heavy metals. The efficiency of heavy metal biosorption can vary depending on several factors such as the growth phase of bacteria, solution pH, and existence of competitive heavy metals. In this study, Exiguobacterium sp. isolated from farmland soil near a mine site were used, and optimal conditions for Cd biosorption in solution were investigated. As bacterial growth progressed, Cd biosorption increased, which is attributed to changes in the structure and composition of the cell wall during bacterial growth. The biosorption process was rapid and was completed within 30 min. Cadmium biosorption was highest at pH 7 due to the dissociation of hydrogen ions and the increase of negative charges with increasing pH. In the mixed metal solution of Cd, Pb, and Zn, the amount of biosorption was in the order of Pb>Cd>Zn while in a single metal solution, the order was Cd≥Pb>Zn. The maximum adsorption capacity for Cd by the isolated bacteria was 15.6 mg/g biomass, which was calculated from the Langmuir isotherm model. Different adsorption efficiencies under various environmental conditions indicate that, to control metal mobility, the conditions for biosorption should be optimized before applying bacteria. The results showed that the isolated bacteria can be used to immobilize metals in metal-contaminated wastewater.

Influence of soil solution cation composition on boron adsorption by soils

USDA-ARS?s Scientific Manuscript database

Boron (B) adsorption on five arid-zone soil samples from California was investigated as a function of solution pH (4-10) and cation composition (Na, Ca, or Mg). Boron adsorption increased with increasing solution pH, reached an adsorption maximum near pH 9, and decreased with further increases with...

Photodissolution of ferrihydrite in the presence of oxalic acid: an in situ ATR-FTIR/DFT study.

PubMed

Bhandari, Narayan; Hausner, Douglas B; Kubicki, James D; Strongin, Daniel R

2010-11-02

The photodissolution of the iron oxyhydroxide, ferrihydrite, in the presence of oxalic acid was investigated with vibrational spectroscopy, density functional theory (DFT) calculations, and batch geochemical techniques that determined the composition of the solution phase during the dissolution process. Specifically, in situ attenuated total reflection Fourier transform infrared spectroscopy (ATR- FTIR) was used to determine the structure of the adsorbed layer during the dissolution process at a solution pH of 4.5. DFT based computations were used to interpret the vibrational data associated with the surface monolayer in order to help determine the structure of the adsorbed complexes. Results showed that at pH 4.5, oxalate adsorbed on ferrihydrite adopted a mononuclear bidentate (MNBD) binding geometry. Photodissolution at pH 4.5 exhibited an induction period where the rate of Fe(II) release was limited by a low concentration of adsorbed oxalate due to the site-blocking of carbonate that was intrinsic to the surface of the ferrihydrite starting material. Oxalate displaced this initial carbonate over time, and the dissolution rate showed a corresponding increase. Irradiation of oxalate/ferrihydrite at pH 4.5 also ultimately led to the appearance of carbonate reaction product (distinct from carbonate intrinsic to the starting material) on the surface.

Effect of pH and the role of organic matter in the adsorption of isoproturon on soils.

PubMed

Ertli, Tímea; Marton, Aurél; Földényi, Rita

2004-11-01

Equilibrium measurements were carried out with the herbicide isoproturon on natural adsorbents (brown forest-, chernozem-, sandy soils and quartz) in different buffered media (pH 5, 7, 8 phosphate buffer). Adsorption isotherms were fitted by a multi-step adsorption equation providing numerical information used in the environmental propagation models and risk assessment works. In the adsorption of the slightly polar isoproturon the dissolved organic matter of the soil and the pH play an important role. At molecular level, results are interpreted by taking into consideration the hydrophobic interaction and the formation of hydrogen bonds between the surface and the solute. The observed adsorption behavior indicates that the organic matter content of the soils and its soluble fulvic acid, alkaline soluble humic acid and insoluble humin fractions were considerable different. The chernozem soil containing the highest amount of insoluble organic fraction proved to be a very efficient adsorbent. The brown forest and the sandy soils exhibit rather similar adsorbent properties but at pH 7 the latter containing more fulvic acid adsorbs less isoproturon due to the enhanced solubility of the soil organic matter. In alkaline conditions the negatively charged solute and the surface repel each other and the hydrophobic interactions are also weaker than in neutral media.

Immobilization of chromate in hyperalkaline waste streams by green rusts and zero-valent iron.

PubMed

Rogers, Christine M; Burke, Ian T; Ahmed, Imad A M; Shaw, Samuel

2014-01-01

Zero-valent iron (ZVI) and green rusts can be used as reductants to convert chromium from soluble, highly toxic Cr(VI) to insoluble Cr(III). This study compared the reduction rates of Cr(VI) by ZVI and two carbonate green rust phases in alkaline/hyperalkaline solutions. Batch experiments were carried out with synthetic chromate solutions at pH 7.7-12.3 and a chromite ore processing residue (COPR) leachate (pH approximately 12.2). Green rust removes chromate from high pH solutions (pH 10-12.5) very rapidly (<400 s). Chromate reduction rates for both green rust phases were consistently higher than for ZVI throughout the pH range studied; the surface area normalized rate constants were two orders of magnitude higher in the COPR leachate solution at pH 12.2. The performances of both green rusts were unaffected by changes in pH. In contrast, ZVI exhibited a marked decline in reduction rate with increasing pH to become almost ineffective above pH12.

Shelf-Life of Chlorine Solutions Recommended in Ebola Virus Disease Response.

PubMed

Iqbal, Qais; Lubeck-Schricker, Maya; Wells, Emma; Wolfe, Marlene K; Lantagne, Daniele

2016-01-01

In Ebola Virus Disease (EVD) outbreaks, it is widely recommended to wash living things (handwashing) with 0.05% (500 mg/L) chlorine solution and non-living things (surfaces, personal protective equipment, dead bodies) with 0.5% (5,000 mg/L) chlorine solution. Chlorine solutions used in EVD response are primarily made from powdered calcium hypochlorite (HTH), granular sodium dichloroisocyanurate (NaDCC), and liquid sodium hypochlorite (NaOCl), and have a pH range of 5-11. Chlorine solutions degrade following a reaction highly dependent on, and unusually sensitive to, pH, temperature, and concentration. We determined the shelf-life of 0.05% and 0.5% chlorine solutions used in EVD response, including HTH, NaDCC, stabilized NaOCl, generated NaOCl, and neutralized NaOCl solutions. Solutions were stored for 30 days at 25, 30, and 35°C, and tested daily for chlorine concentration and pH. Maximum shelf-life was defined as days until initial concentration fell to <90% of initial concentration in ideal laboratory conditions. At 25-35°C, neutralized-NaOCl solutions (pH = 7) had a maximum shelf-life of a few hours, NaDCC solutions (pH = 6) 2 days, generated NaOCl solutions (pH = 9) 6 days, and HTH and stabilized NaOCl solutions (pH 9-11) >30 days. Models were developed for solutions with maximum shelf-lives between 1-30 days. Extrapolating to 40°C, the maximum predicted shelf-life for 0.05% and 0.5% NaDCC solutions were 0.38 and 0.82 hours, respectively; predicted shelf-life for 0.05% and 0.5% generated NaOCl solutions were >30 and 5.4 days, respectively. Each chlorine solution type offers advantages and disadvantages to responders, as: NaDCC is an easy-to-import high-concentration effervescent powder; HTH is similar, but forms a precipitate that may clog pipes; and, NaOCl solutions can be made locally, but are difficult to transport. We recommend responders chose the most appropriate source chlorine compound for their use, and ensure solutions are stored at appropriate temperatures and used or replaced before expiring.

Antimicrobial effects of electrolytic products of sodium chloride--comparative evaluation with sodium hypochlorite solution and efficacy in handwashing.

PubMed

Hitomi, S; Baba, S; Yano, H; Morisawa, Y; Kimura, S

1998-11-01

We examined the in vitro bactericidal effects and efficacy on handwashing of water containing electrolytic products of sodium chloride (electrolytic water). The electrolytic water, whose pH and concentration of free residual chlorine were 6.7-6.9 and 20-22 ppm, respectively, showed equal reduction of both Staphylococcus aureus and Escherichia coli to dilution of commercially available sodium hypochlorite containing 60 ppm of free residual chlorine. This bactericidal effect was calculated to be due to hypochlorous acid, based on the pH and the amount of chlorine in solution. Handwashing with the electrolytic water reduced the numbers of S. aureus on hands by 1/10(2), while running water and 0.2% benzalkonium chloride with 80% ethanol gave a 1/10 and 1/10(5) reduction, respectively. We conclude that electrolytic water might be applicable for handwashing in place of running water.

Blending crystalline/liquid crystalline small molecule semiconductors: A strategy towards high performance organic thin film transistors

NASA Astrophysics Data System (ADS)

He, Chao; He, Yaowu; Li, Aiyuan; Zhang, Dongwei; Meng, Hong

2016-10-01

Solution processed small molecule polycrystalline thin films often suffer from the problems of inhomogeneity and discontinuity. Here, we describe a strategy to solve these problems through deposition of the active layer from a blended solution of crystalline (2-phenyl[1]benzothieno[3,2-b][1]benzothiophene, Ph-BTBT) and liquid crystalline (2-(4-dodecylphenyl) [1]benzothieno[3,2-b]benzothiophene, C12-Ph-BTBT) small molecule semiconductors with the hot spin-coating method. Organic thin film transistors with average hole mobility approaching 1 cm2/V s, much higher than that of single component devices, have been demonstrated, mainly due to the improved uniformity, continuity, crystallinity, and stronger intermolecular π-π stacking in blend thin films. Our results indicate that the crystalline/liquid crystalline semiconductor blend method is an effective way to enhance the performance of organic transistors.

Determining the chemical exchange saturation transfer (CEST) behavior of citrate and spermine under in vivo conditions.

PubMed

Basharat, Meer; deSouza, Nandita M; Parkes, Harold G; Payne, Geoffrey S

2016-09-01

To estimate the exchange rates of labile (1) H in citrate and spermine, metabolites present in prostatic secretions, to predict the size of the citrate and spermine CEST effects in vivo. CEST z-spectra were acquired at high-field [11.7 Tesla (T)] from citrate and spermine solutions at physiological pH (6.5) using saturation power 6 μT. CEST was performed at different temperatures to determine exchange regimes (slow, intermediate or fast). For low pH solutions of spermine, exchange rates were estimated from resonance line width, fitting z-spectra using the Bloch equations incorporating exchange, and using quantifying exchange using saturation time experiments (QUEST). These rates were extrapolated to physiological pH. Citrate showed little CEST effect at pH 6.5 and temperature (T) = 310 K (maximum 0.001% mM(-1) ), indicating fast exchange, whereas spermine showed greater CEST effects (maximum 0.2% mM(-1) ) indicating intermediate-to-fast exchange. Extrapolating data acquired from low pH spermine solutions predicts exchange rates at pH 6.5 and T of 310 K of at least 2 × 10(4) s(-1) . Citrate and spermine show minimal CEST effects at 11.7T even using high saturation power. These effects would be much less than 2% at clinical field-strengths due to relatively faster exchange and would be masked by CEST from proteins. Magn Reson Med 76:742-746, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.

Dissolution and solubility behavior of fenofibrate in sodium lauryl sulfate solutions.

PubMed

Granero, Gladys E; Ramachandran, Chandrasekharan; Amidon, Gordon L

2005-10-01

The solubility of fenofibrate in pH 6.8 McIlvaine buffers containing varying concentrations of sodium lauryl sulfate was determined. The dissolution behavior of fenofibrate was also examined in the same solutions with rotating disk experiments. It was observed that the enhancement in intrinsic dissolution rate was approximately 500-fold and the enhancement in solubility was approximately 2000-fold in a pH 6.8 buffer containing 2% (w/v) sodium lauryl sulfate compared to that in buffer alone. The micellar solubilization equilibrium coefficient (k*) was estimated from the solubility data and found to be 30884+/-213 L/mol. The diffusivity for the free solute, 7.15x10(-6) cm2/s, was calculated using Schroeder's additive molal volume estimates and Hayduk-Laurie correlation. The diffusivity of the drug-loaded micelle, estimated from the experimental solubility and dissolution data and the calculated value for free solute diffusivity, was 0.86x10(-6) cm2/s. Thus, the much lower enhancement in dissolution of fenofibrate compared to its enhancement in solubility in surfactant solutions appears to be consistent with the contribution to the total transport due to enhanced micellar solubilization as well as a large decrease (approximately 8-fold) in the diffusivity of the drug-loaded micelle.

Steady-state protein focusing in carrier ampholyte based isoelectric focusing: Part I-Analytical solution.

PubMed

Shim, Jaesool; Yoo, Kisoo; Dutta, Prashanta

2017-03-01

The determination of an analytical solution to find the steady-state protein concentration distribution in IEF is very challenging due to the nonlinear coupling between mass and charge conservation equations. In this study, approximate analytical solutions are obtained for steady-state protein distribution in carrier ampholyte based IEF. Similar to the work of Svensson, the final concentration profile for proteins is assumed to be Gaussian, but appropriate expressions are presented in order to obtain the effective electric field and pH gradient in the focused protein band region. Analytical results are found from iterative solutions of a system of coupled algebraic equations using only several iterations for IEF separation of three plasma proteins: albumin, cardiac troponin I, and hemoglobin. The analytical results are compared with numerically predicted results for IEF, showing excellent agreement. Analytically obtained electric field and ionic conductivity distributions show significant deviation from their nominal values, which is essential in finding the protein focusing behavior at isoelectric points. These analytical solutions can be used to determine steady-state protein concentration distribution for experiment design of IEF considering any number of proteins and ampholytes. Moreover, the model presented herein can be used to find the conductivity, electric field, and pH field. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stabilizing sodium hypochlorite at high pH: effects on soft tissue and dentin.

PubMed

Jungbluth, Holger; Marending, Monika; De-Deus, Gustavo; Sener, Beatrice; Zehnder, Matthias

2011-05-01

When sodium hypochlorite solutions react with tissue, their pH drops and tissue sorption decreases. We studied whether stabilizing a NaOCl solution at a high pH would increase its soft-tissue dissolution capacity and effects on the dentin matrix compared with a standard NaOCl solution of the same concentration and similar initial pH. NaOCl solutions were prepared by mixing (1:1) a 10% stock solution with water (standard) or 2 mol/L NaOH (stabilized). Physiological saline and 1 mol/L NaOH served as the controls. Chlorine content and alkaline capacity of NaOCl solutions were determined. Standardized porcine palatal soft-tissue specimens and human root dentin bars were exposed to test and control solutions. Weight loss percentage was assessed in the soft-tissue dissolution assay. Three-point bending tests were performed on the root dentin bars to determine the modulus of elasticity and flexural strength. Values between groups were compared using one-way analysis of variance with the Bonferroni correction for multiple testing (α < .05). Both solutions contained 5% NaOCl. One milliliter of the standard and the stabilized solution consumed 4.0 mL and 13.7 mL of a 0.1-mol/L HCl solution before they reached a pH level of 7.5, respectively. The stabilized NaOCl dissolved significantly more soft tissue than the standard solution, and the pH remained high. It also caused a higher loss in elastic modulus and flexure strength (P < .05) than the control solutions, whereas the standard solution did not. NaOH-stabilized NaOCl solutions have a higher alkaline capacity and are thus more proteolytic than standard counterparts. Copyright © 2011 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Effects of pH and elevated glucose levels on the electrochemical behavior of dental implants.

PubMed

Tamam, Evsen; Turkyilmaz, Ilser

2014-04-01

Implant failure is more likely to occur in persons with medically compromising systemic conditions, such as diabetes related to high blood glucose levels and inflammatory diseases related to pH levels lower than those in healthy people. The aim of this study was to investigate the effects of lower pH level and simulated- hyperglycemia on implant corrosion as these effects are critical to biocompatibility and osseointegration. The electrochemical corrosion properties of titanium implants were studied in four different solutions: Ringer's physiological solution at pH = 7.0 and pH = 5.5 and Ringer's physiological solution containing 15 mM dextrose at pH = 7 and pH = 5.5. Corrosion behaviors of dental implants were determined by cyclic polarization test and electrochemical impedance spectroscopy. Surface alterations were studied using a scanning electron microscope. All test electrolytes led to apparent differences in corrosion behavior of the implants. The implants under conditions of test exhibited statistically significant increases in I(corr) from 0.2372 to 1.007 μAcm(-2), corrosion rates from 1.904 to 8.085 mpy, and a decrease in polarization resistances from 304 to 74 Ω. Implants in dextrose-containing solutions were more prone to corrosion than those in Ringer's solutions alone. Increasing the acidity also yielded greater corrosion rates for the dextrose-containing solutions and the solutions without dextrose.

Influence of pH for the determination of serum albumin by a dye-binding method in the presence of a detergent.

PubMed

Suzuki, Yuji

2008-08-01

In the dye-binding method, the absorbance increase caused by a protein error of a pH indicator is observed only in a restricted pH range. However, this pH range in the presence of a detergent has not yet been examined. Thus, the author investigated the pH (pH(UL)) where the absorbance increase becomes zero by a calculation based on the chemical equilibrium of a protein error of a pH indicator, and by experiments using four sulfonephthalein dyes. The pH(UL) value changed only with the detergent concentration, but did not change at all due to the dye, buffer solution or protein concentrations. Although the pH(UL) value was different according to the kind of dye used, it correlated well with the pK(D) values (dissociation constant) of BPB, BCG, BCP and BTB. The characteristics of pH(UL) in the reactions of the four dyes indicated good agreement with that obtained by a calculation.

Regularities in Low-Temperature Phosphatization of Silicates

NASA Astrophysics Data System (ADS)

Savenko, A. V.

2018-01-01

The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.

An experimental study of Au removal from solution by non-metabolizing bacterial cells and their exudates

NASA Astrophysics Data System (ADS)

Kenney, Janice P. L.; Song, Zhen; Bunker, Bruce A.; Fein, Jeremy B.

2012-06-01

In this study, we examine the initial interactions between aqueous Au(III)-hydroxide-chloride aqueous complexes and bacteria by measuring the effects of non-metabolizing cells on the speciation and distribution of Au. We conducted batch Au(III) removal experiments, measuring the kinetics and pH dependence of Au removal, and tracking valence state transformations and binding environments using XANES spectroscopy. These experiments were conducted using non-metabolizing cells of Bacillus subtilis or Pseudomonas putida suspended in a 5 ppm Au(III)-(hydroxide)-chloride starting solution of 0.1 M NaClO4 to buffer ionic strength. Both bacterial species removed greater than 85% of the Au from solution after 2 h of exposure time below approximately pH 5. Above pH 5, the extent of Au removed from solution decreased with increasing pH, with less than approximately 10% removal of Au from solution above pH 7.5. Kinetics experiments indicated that the Au removal with both bacterial species was rapid at pH 3, and slowed with increasing pH. Reversibility experiments demonstrated that (1) once the Au was removed from solution, adjusting 35 the pH alone did not remobilize the Au into solution and (2) the presence of cysteine in solution in the reversibility experiments caused Au to desorb, suggesting that the Au was not internalized within the bacterial cells. Our results suggest that Au removal occurs as a two-step pH-dependent adsorption reduction process. The speciation of the aqueous Au and the bacterial surface appears to control the rate of Au removal from solution. Under low pH conditions, the cell walls are only weakly negatively charged and aqueous Au complexes adsorb readily and rapidly. With increasing pH, the cell wall becomes more negatively charged, slowing adsorption significantly. The XANES data demonstrate that the reduction of Au(III) by bacterial exudates is slower and less extensive than the reduction observed in the bacteria-bearing systems, and we conclude that Au reduction occurs most rapidly and extensively upon interaction with cell wall functional groups.

Searching for Clues to the Processes and Conditions of Past Martian Environments: The Roles of Episodic Solutions, Analog Sites and Fe-O(-H) Phases

NASA Astrophysics Data System (ADS)

King, P. L.; De Deckker, P.

2012-12-01

On Mars, limited solutions (water/brine) were likely present episodically. Gradients in solution abundance may have caused salt precipitation and re-solution, brine reflux, pH gradients, and cycling of anions and cations; we provide an example of such processes in a playa lake. We propose that on Mars, the limited, episodic solutions, pH and abundant Fe-O(-H) phases are significant factors in salt precipitation and in promoting adsorption/desorption of anions and cations. FACTORS LEADING TO EPISODIC SOLUTIONS: Episodic movement of solutions may be driven by punctuated processes that 1) remove surface materials (e.g., impact and sedimentary mass wasting and deflation); 2) add surface materials (e.g., impact, volcanic and sedimentary processes); and 3) increase temperature and/or decrease atmospheric pressure (e.g., seasons, diurnal cycles, variation in obliquity). Removal and addition of surface materials results in topographic gradients that change pressure gradients of any potential groundwater, films, or buried ground ice. For example, episodic fluid flow and salt precipitation/re-solution may occur at topographic discontinuities like craters/basins, channel walls, mounds and dunes. Such areas provide the opportunity to sample multiple fluid sources (with different pH, Eh and total dissolved solids, TDS) and they may be the foci of subsurface solution flow and surface transport. EARTH ANALOG: Interplay of the three processes above is seen in Lake Tyrrell (playa), western Victoria, Australia (McCumber, P, 1991 http://vro.dpi.vic.gov.au). During wetter periods, springs from the regional groundwater (low pH, oxidized, mod-high TDS) mix with lake waters and saline 'reflux' brines (mod. pH, reduced, high TDS) at the lake edge at the base of higher ground. The Br/Cl of the reflux brines indicates mineral re-solution. Gypsum and Fe-O(-H) phases precipitate near the lake edge. During hot, dry climate episodes the lake precipitates gypsum and carbonate, efflorescent salts are common, and these salts may form eolian dunes with fine particles. We may expect similar processes and mineral and chemical gradients in craters/basins on Mars like Gale Crater, the site of the Mars Science Laboratory mission. ROLE OF Fe-O(-H) PHASES: Nanophase Fe-O(-H)-phases are abundant on Mars and their precipitation results in an Fe-poor solution and salts (like Lake Tyrrell). Fe-O(-H) phases precipitate most readily at near-neutral pH; however, the high Fe of Mars' surface allows for pH>1. Nanophase Fe-O(-H)-phases have surface species that promote adsorption; which may be important in dry conditions like Mars. If we take goethite (FeO(OH)), the surface species and aqueous ions in solution are Fe3+ (pH<~2); Fe(OH)2+ (pH~2-3.5); Fe(OH)2+ (pH~3.5-~8); and FeOH4- (pH>~8). Other Fe-O(-H) phases have slightly different pH limits. Thus, at pH<~8, Fe-O(-H) surfaces sequester anions in surface complexes or in Fe-bearing salts (e.g. Fe3+-phosphate and sulfates, especially at pH<4). PO43- species have high adsorption affinity, followed by SO42-, Cl-(O) and Br-(O) species. At pH>~8, adsorption and exchange of cations are likely. These chemical variations may provide us with clues of the past pH on Mars.

The fate of silicon during glass corrosion under alkaline conditions: A mechanistic and kinetic study with the International Simple Glass

NASA Astrophysics Data System (ADS)

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Berthon, Claude; Wang, Zhaoying; Mitroshkov, Alexandre; Zhu, Zihua; Ryan, Joseph V.

2015-02-01

International Simple Glass - a six oxide borosilicate glass selected by the international nuclear glass community to improve the understanding of glass corrosion mechanisms and kinetics - was altered at 90 °C in a solution initially saturated with respect to amorphous 29SiO2. The pH90°C, was fixed at 9 at the start of the experiment and raised to 11.5 after 209 d by the addition of KOH. Isotope sensitive analytical techniques were used to analyze the solution and altered glass samples, helping to understand the driving forces and rate limiting processes controlling long-term glass alteration. At pH 9, the corrosion rate continuously drops and the glass slowly transforms into a uniform, homogeneous amorphous alteration layer. The mechanisms responsible for this transformation are water penetration through the growing alteration layer and ion exchange. We demonstrate that this amorphous alteration layer is not a precipitate resulting from the hydrolysis of the silicate network; it is mostly inherited from the glass structure from which the most weakly bonded cations (Na, Ca and B) have been released. At pH 11.5, the alteration process is very different: the high solubility of glass network formers (Si, Al, Zr) triggers the rapid and complete dissolution of the glass (dissolution becomes congruent) and precipitation of amorphous and crystalline phases. Unlike at pH 9 where glass corrosion rate decreased by 3 orders of magnitude likely due to the retroaction of the alteration layer on water dynamics/reactivity at the reaction front, the rate at pH 11.5 is maintained at a value close to the forward rate due to both the hydrolysis of the silicate network promoted by OH- and the precipitation of CSH and zeolites. This study provides key information for a unified model for glass dissolution.

Microfabricated Collector-Generator Electrode Sensor for Measuring Absolute pH and Oxygen Concentrations.

PubMed

Dengler, Adam K; Wightman, R Mark; McCarty, Gregory S

2015-10-20

Fast-scan cyclic voltammetry (FSCV) has attracted attention for studying in vivo neurotransmission due to its subsecond temporal resolution, selectivity, and sensitivity. Traditional FSCV measurements use background subtraction to isolate changes in the local electrochemical environment, providing detailed information on fluctuations in the concentration of electroactive species. This background subtraction removes information about constant or slowly changing concentrations. However, determination of background concentrations is still important for understanding functioning brain tissue. For example, neural activity is known to consume oxygen and produce carbon dioxide which affects local levels of oxygen and pH. Here, we present a microfabricated microelectrode array which uses FSCV to detect the absolute levels of oxygen and pH in vitro. The sensor is a collector-generator electrode array with carbon microelectrodes spaced 5 μm apart. In this work, a periodic potential step is applied at the generator producing transient local changes in the electrochemical environment. The collector electrode continuously performs FSCV enabling these induced changes in concentration to be recorded with the sensitivity and selectivity of FSCV. A negative potential step applied at the generator produces a transient local pH shift at the collector. The generator-induced pH signal is detected using FSCV at the collector and correlated to absolute solution pH by postcalibration of the anodic peak position. In addition, in oxygenated solutions a negative potential step at the generator produces hydrogen peroxide by reducing oxygen. Hydrogen peroxide is detected with FSCV at the collector electrode, and the magnitude of the oxidative peak is proportional to absolute oxygen concentrations. Oxygen interference on the pH signal is minimal and can be accounted for with a postcalibration.

Buffer capacity of biologics--from buffer salts to buffering by antibodies.

PubMed

Karow, Anne R; Bahrenburg, Sven; Garidel, Patrick

2013-01-01

Controlling pH is essential for a variety of biopharmaceutical process steps. The chemical stability of biologics such as monoclonal antibodies is pH-dependent and slightly acidic conditions are favorable for stability in a number of cases. Since control of pH is widely provided by added buffer salts, the current study summarizes the buffer characteristics of acetate, citrate, histidine, succinate, and phosphate buffers. Experimentally derived values largely coincide with values calculated from a model that had been proposed in 1922 by van Slyke. As high concentrated protein formulations become more and more prevalent for biologics, the self-buffering potential of proteins becomes of relevance. The current study provides information on buffer characteristics for pH ranges down to 4.0 and up to 8.0 and shows that a monoclonal antibody at 50 mg/mL exhibits similar buffer capacity as 6 mM citrate or 14 mM histidine (pH 5.0-6.0). Buffer capacity of antibody solutions scales linearly with protein concentration up to more than 200 mg/mL. At a protein concentration of 220 mg/mL, the buffer capacity resembles the buffer capacity of 30 mM citrate or 50 mM histidine (pH 5.0-6.0). The buffer capacity of monoclonal antibodies is practically identical at the process relevant temperatures 5, 25, and 40°C. Changes in ionic strength of ΔI=0.15, in contrast, can alter the buffer capacity up to 35%. In conclusion, due to efficient self-buffering by antibodies in the pH range of favored chemical stability, conventional buffer excipients could be dispensable for pH stabilization of high concentrated protein solutions. Copyright © 2013 American Institute of Chemical Engineers.

Engineering polyelectrolyte multilayer structure at the nanometer length scale by tuning polymer solution conformation.

NASA Astrophysics Data System (ADS)

Boddohi, Soheil; Killingsworth, Christopher; Kipper, Matt

2008-03-01

Chitosan (a weak polycation) and heparin (a strong polyanion) are used to make polyelectrolyte multilayers (PEM). PEM thickness and composition are determined as a function of solution pH (4.6 to 5.8) and ionic strength (0.1 to 0.5 M). Over this range, increasing pH increases the PEM thickness; however, the sensitivity to changes in pH is a strong function of ionic strength. The PEM thickness data are correlated to the polymer conformation in solution. Polyelectrolyte conformation in solution is characterized by gel permeation chromatography (GPC). The highest sensitivity of PEM structure to pH is obtained at intermediate ionic strength. Different interactions govern the conformation and adsorption phenomena at low and high ionic strength, leading to reduced sensitivity to solution pH at extreme ionic strengths. The correspondence between PEM thickness and polymer solution conformation offers opportunities to tune polymer thin film structure at the nanometer length scale by controlling simple, reproducible processing conditions.

The effect of pH on the corrosion behavior of intermetallic compounds Ni{sub 3}(Si,Ti) and Ni{sub 3}(Si,Ti) + 2Mo in sodium chloride solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Priyotomo, Gadang, E-mail: gada001@lipi.go.id; Nuraini, Lutviasari, E-mail: Lutviasari@gmail.com; Kaneno, Yasuyuki, E-mail: kaneno@mtr.osakafu-u.ac.id

The corrosion behavior of the intermetallic compounds, Ni{sub 3}(Si,Ti) (L1{sub 2}: single phase) and Ni{sub 3}(Si,Ti) + 2Mo (L1{sub 2} and (L12 + Ni{sub ss}) mixture region), has been investigated using an immersion test, electrochemical method and surface analytical method (SEM; scanning electron microscope and EDAX: Energy Dispersive X-ray) in 0.5 kmol/m{sup 3} NaCl solutions at various pH. The corrosion behavior of nickel alloy C-276 was studied under the same experimental conditions as a reference. It was found that the uniform attack was observed on Ni{sub 3}(Si,Ti) for the immersion test at lower pH, while the pitting attack was observedmore » on this compound for this test at neutral solution. Furthermore, Ni{sub 3}(Si,Ti)+2Mo had the preferential dissolution of L1{sub 2} compared to (L1{sub 2} + Ni{sub ss}) mixture region at lower pH, while pitting attack occurred in (L1{sub 2} + Ni{sub ss}) mixture region at neutral solution. For both intermetallic compounds, the magnitude of pitting and uniform attack decrease with increasing pH of solutions. From the immersion test and polarization curves, the corrosion resistance of Ni{sub 3}(Si,Ti)+2Mo is lower than that of Ni{sub 3}(Si,Ti), while the nickel alloy C-276 is the highest one at various pH of solutions. On the other hand, in the lower pH of solutions, the corrosion resistance of tested materials decreased significantly compared to those in neutral and higher pH of solutions.« less

Pore-water chemistry explains zinc phytotoxicity in soil.

PubMed

Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

2015-12-01

Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. Copyright © 2015 Elsevier Inc. All rights reserved.

Noncontact tomography and a pH-sensitive nanocomposite for monitoring osseointegrated prosthesis interfaces

NASA Astrophysics Data System (ADS)

Gupta, Sumit; Loh, Kenneth J.

2017-04-01

The main objective of this research is to develop a noncontact and noninvasive method for monitoring infections at the interface of human tissue and osseointegrated prostheses. The technique used here is centered on the theory of a noncontact permittivity imaging technique known as electrical capacitance tomography (ECT). This work is divided into two main parts. First, an ECT electrical permittivity reconstruction software and hardware system was developed. Second, a carbon nanotube-polyaniline nanocomposite thin film was designed and fabricated such that its electrical permittivity is sensitive to pH stimuli. The dielectric properties of this thin film were characterized as it was exposed to different pH buffer solutions. It is envisioned that osseointegrated implants can be pre-coated with the pH-sensitive nanocomposite prior to implant. When infection occurs and alters the local pH of tissue at the human-prosthesis interface, the dielectric property of the film would change accordingly. Then, ECT can interrogate the cross-section of the human limb and reconstruct its permittivity distribution, revealing localized changes in permittivity due to infection. To validate this concept, a prosthesis phantom was coated with the nanocomposite pH sensor and then immersed in different pH buffer solutions. ECT was conducted, and the results showed that the magnitude and location of subsurface, localized, pH changes could be detected. In general, noncontact tomography coupled with stimuliresponsive thin films could pave way for new modalities of noninvasive human body imaging, in particular, for patients with osseointegrated implants and prostheses.

Defining appropriate methods for studying toxicities of trace metals in nutrient solutions.

PubMed

Li, Zhigen; Wang, Peng; Menzies, Neal W; Kopittke, Peter M

2018-01-01

The use of inappropriate experimental conditions for examining trace metal phytotoxicity results in data of questionable value. The present study aimed to identify suitable parameters for study of phytotoxic metals in nutrient solutions. First, the literature was reviewed to determine the concentration of six metals (Cd, Cu, Hg, Ni, Pb, and Zn) from solution of contaminated soils. Next, the effects of pH, P, Cl, NO 3 , and four Fe-chelators were investigated by using thermodynamic modelling and by examining changes in root elongation rate of soybean (Glycine max cv. Bunya). The literature review identified that the solution concentrations of metals in soils were low, ranging from (µM) 0.069-11Cd, 0.19-15.8 Cu, 0.000027-0.000079 Hg, 1.0-8.7 Ni, 0.004-0.55 Pb, and 0.4-36.3 Zn. For studies in nutrient solution, pH should generally be low given its effects on solubility and speciation, as should the P concentration due to the formation of insoluble phosphate salts. The concentrations of Cl, NO 3 , and various chelators also influence metal toxicity through alteration of metal speciation. The nutrient solutions used to study metal toxicity should consider environmentally-relevant conditions especially for metal concentrations, with concentrations of other components added at levels that do not substantially alter metal toxicity. Copyright © 2017 Elsevier Inc. All rights reserved.

Influence of the marinating type on the morphological and sensory properties of horse meat.

PubMed

Vlahova-Vangelova, Dessislava B; Abjanova, Sholpan; Dragoev, Stefan G

2014-01-01

The aim of this study was to explore the influence of acid, alkaline and water-oil marinating on morphological changes and sensory properties of horse meat (m. Longissimus dorsi). Nine samples (C - control stored in air, AL - alkaline marinated in 2% polyphosphates and 2% sodium chloride brine solution, AC - acid marinated in 2% sodium lactate and 2% sodium chloride brine solution, WO - marinated in water-oil emulsion (50/50) contained and 2% sodium chloride and SC - marinated in 2% sodium chloride brine solution) were examined. After 24 h and 48 h of marinating changes in morphology of marinated meat, pH and sensory properties of raw and roasted samples were established. It was determined that sensory properties (aroma, flavor and tenderness) after roasting were classified as follows: AL48 > AL24 > AC24 > AC48 > SC48 > SC24 > WO24 > WO48 > С. Meat tenderness in AL48, AL24, AC24 and AC48 showed better results due to stronger morphological changes in connective and muscle tissues. Alkaline solutions were more suitable for horse meat marinating compared to acid solutions and the possible reason for strong action of alkaline solutions was lower internal meat pH. Alkaline marinating should be conducted for 24 h because after 48 h the meat acquires a soft and unusually tender texture. Water-oil marinating was not appropriate for horse meat.

Enhancing the stability of lithium ion Li1+x+yAlxTi2-xSiyP3-yO12 glass - ceramic conductors in aqueous electrolytes

NASA Astrophysics Data System (ADS)

Ioanniti, Marina Maria; Tenhaeff, Wyatt E.

2017-12-01

The stability of NASICON-type conducting glass-ceramic electrolyte, Li1+x+yAlxTi2-xSiyP3-yO12 (Ohara LICGC) has been characterized after prolonged exposure to deionized water and HCl(aq) solutions supported with LiCl. X-ray diffraction shows that the bulk crystallographic structure of the LICGC membranes remains unchanged when exposed to these solutions. Electrochemical impedance spectroscopy (EIS) shows that the conductivity of LICGC membranes immersed in deionized water remains stable over a one month period, while there is a significant increase in resistance when exposed to the acidic solutions. When exposed to pH 4 and 2 solutions for just 24 h, the resistances of the LICGC membrane increase by a factor of 8.5 and 23.5, respectively. EIS coupled with morphological characterization by scanning electron microscopy, shows that this resistance growth is due to the development of a surface layer on the LICGC membrane. However, this substantial increase in resistance can be mitigated by adding LiCl to the HCl solutions. For a pH 4 solution supported with 6.75 M LiCl, the impedance spectrum and surface morphology are qualitatively comparable to pristine, dry LICGC material, suggesting that surface layer formation was suppressed. This was also confirmed via cyclic voltammetry measurements in four-electrode electrochemical cells.

Evaluation of pH of Bathing Soaps and Shampoos for Skin and Hair Care.

PubMed

Tarun, Jose; Susan, Jose; Suria, Jacob; Susan, Veronica John; Criton, Sebastian

2014-09-01

Normal healthy skin has potential of hydrogen (pH) range of 5.4-5.9 and a normal bacterial flora. Use of soap with high pH causes an increase in skin pH, which in turn causes an increase in dehydrative effect, irritability and alteration in bacterial flora. The majority of soaps and shampoos available in the market do not disclose their pH. The aim of this study was to assess the pH of different brands of bathing soaps and shampoos available in the market. The samples of soaps and shampoos were collected from shops in the locality. The samples of different brands are coded before the analysis of the pH. Solution of each sample was made and pH was measured using pH meter. Majority of the soaps have a pH within the range of 9-10. Majority of the shampoos have a pH within the range of 6-7. The soaps and shampoos commonly used by the population at large have a pH outside the range of normal skin and hair pH values. Therefore, it is hoped that before recommending soap to patient especially those who have sensitive and acne prone skin, due consideration is given to the pH factor and also that manufacturers will give a thought to pH of soaps and shampoos manufactured by them, so that their products will be more skin and hair friendly.

First-Principles pH Theory

NASA Astrophysics Data System (ADS)

Kim, Yong-Hyun; Zhang, S. B.

2006-03-01

Despite being one of the most important macroscopic measures and a long history even before the quantum mechanics, the concept of pH has rarely been mentioned in microscopic theories, nor being incorporated computationally into first-principles theory of aqueous solutions. Here, we formulate a theory for the pH dependence of solution formation energy by introducing the proton chemical potential as the microscopic counterpart of pH in atomistic solution models. Within the theory, the general acid-base chemistry can be cast in a simple pictorial representation. We adopt density-functional molecular dynamics to demonstrate the usefulness of the method by studying a number of solution systems including water, small solute molecules such as NH3 and HCOOH, and more complex amino acids with several functional groups. For pure water, we calculated the auto- ionization constant to be 13.2 with a 95 % accuracy. For other solutes, the calculated dissociation constants, i.e., the so- called pKa, are also in reasonable agreement with experiments. Our first-principles pH theory can be readily applied to broad solution chemistry problems such as redox reactions.

Calcium Hypochlorite Solutions: Evaluation of Surface Tension and Effect of Different Storage Conditions and Time Periods over pH and Available Chlorine Content.

PubMed

Leonardo, Natália Gomes e Silva; Carlotto, Israel Bangel; Luisi, Simone Bonato; Kopper, Patrícia Maria Poli; Grecca, Fabiana Soares; Montagner, Francisco

2016-04-01

The aim of this study was to evaluate the pH and the available chlorine content from sodium hypochlorite (NaOCl) and calcium hypochlorite (Ca[OCl]2) solutions stored in different conditions and time periods and the surface tension of Ca(OCl)2 solutions in comparison with NaOCl. Solutions at 0.5%, 1%, 2.5%, and 5.25% concentrations were prepared. The pH level and the available chlorine content of freshly prepared solutions and solutions stored for 30, 60, and 90 days at 25°C, 4°C, or 37°C were evaluated in a digital pH meter and by titration, respectively. Surface tension was tested using a Du Nouy tensiometer (Sigma 702, Force Tensiometer; Attension, Espoo, Finland). Descriptive and inferential statistical analyses were performed. A precipitate formed by 2.5% and 5.25% Ca(OCl)2 solutions was observed. Ca(OCl)2 showed a higher concentration of available chlorine than NaOCl. Both 2.5% and 5.25% NaOCl and Ca(OCl)2 had a decrease in the available chlorine content when compared with freshly prepared solutions; 0.5% and 1% NaOCl tend to have a lower pH compared with 0.5% and 1% Ca(OCl)2. NaOCl, 5.25%, showed higher pH compared with 5.25% Ca(OCl)2. NaOCl and Ca(OCl)2 in 0.5% and 1% concentrations tend to show a reduced pH level, whereas 2.5% and 5.25% solutions showed an increase in pH. The heat contributed to the instability of the solutions. NaOCl showed lower surface tension values than Ca(OCl)2. Ca(OCl)2 solutions are extremely alkaline and tend to have more available chlorine content than NaOCl but have a higher surface tension than NaOCl. Regarding the available chlorine content, these solutions tend to be stable to 30 days of storage when kept at 4°C or at 25°C. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Department of Transportation Inhalation Test of Neutralized GB Hydrolysate in Sprague-Dawley Rats

DTIC Science & Technology

2009-05-01

a product solution resulting from chemically neutralizing GB with aqueous sodium hydroxide ( pH 12.8) as an acceptably treated waste that can be...transported offsite for secondary treatment. An acute inhalation toxicity test was conducted on a ph adjusted hydrolysate solution ( pH 7.8) to assess...day post-exposure period, an endpoint of the DOT study. The product solution from the neutralized ( pH 7.8) hydrolysate does not appear to pose an

Influence of non-adherent yeast cells on electrical characteristics of diamond-based field-effect transistors

NASA Astrophysics Data System (ADS)

Procházka, Václav; Cifra, Michal; Kulha, Pavel; Ižák, Tibor; Rezek, Bohuslav; Kromka, Alexander

2017-02-01

Diamond thin films provide unique features as substrates for cell cultures and as bio-electronic sensors. Here we employ solution-gated field effect transistors (SGFET) based on nanocrystalline diamond thin films with H-terminated surface which exhibits the sub-surface p-type conductive channel. We study an influence of yeast cells (Saccharomyces cerevisiae) on electrical characteristics of the diamond SGFETs. Two different cell culture solutions (sucrose and yeast peptone dextrose-YPD) are used, with and without the cells. We have found that transfer characteristics of the SGFETs exhibit a negative shift of the gate voltage by -26 mV and -42 mV for sucrose and YPD with cells in comparison to blank solutions without the cells. This effect is attributed to a local pH change in close vicinity of the H-terminated diamond surface due to metabolic processes of the yeast cells. The pH sensitivity of the diamond-based SGFETs, the role of cell and protein adhesion on the gate surface and the role of negative surface charge of yeast cells on the SGFETs electrical characteristics are discussed as well.

Study of the Microstructure Evolution of Low-pH Cements Based on Ordinary Portland Cement (OPC) by Mid- and Near-Infrared Spectroscopy, and Their Influence on Corrosion of Steel Reinforcement.

PubMed

García Calvo, José Luis; Sánchez Moreno, Mercedes; Alonso Alonso, María Cruz; Hidalgo López, Ana; García Olmo, Juan

2013-06-18

Low-pH cements are designed to be used in underground repositories for high level waste. When they are based on Ordinary Portland Cements (OPC), high mineral admixture contents must be used which significantly modify their microstructure properties and performance. This paper evaluates the microstructure evolution of low-pH cement pastes based on OPC plus silica fume and/or fly ashes, using Mid-Infrared and Near-Infrared spectroscopy to detect cement pastes mainly composed of high polymerized C-A-S-H gels with low C/S ratios. In addition, the lower pore solution pH of these special cementitious materials have been monitored with embedded metallic sensors. Besides, as the use of reinforced concrete can be required in underground repositories, the influence of low-pH cementitious materials on steel reinforcement corrosion was analysed. Due to their lower pore solution pH and their different pore solution chemical composition a clear influence on steel reinforcement corrosion was detected.

Black-to-Transmissive Electrochromism with Visible-to-Near-Infrared Switching of a Co(II)-Based Metallo-Supramolecular Polymer for Smart Window and Digital Signage Applications.

PubMed

Hsu, Chih-Yu; Zhang, Jian; Sato, Takashi; Moriyama, Satoshi; Higuchi, Masayoshi

2015-08-26

Black-to-transmissive electrochromism has been obtained with a Co(II)-based metallo-supramolecular polymer (polyCo). Thin films of polyCo, based on bisterpyridine ligand assembled with Co(II) metal ion, were constructed by spray casting the polymer onto ITO glass. With such simple fabricating means to form good-quality films, polyCo films show stable switching at the central metal ion of the Co(II)/Co(I) redox reaction when immersed in aqueous solution. With an increase in the pH of the aqueous electrolyte solution from neutral, the film exhibits a color response due to the interaction between the d-orbital electron and hydroxide ions affecting the d-d* transition. As a result, a nearly transparent-to-black electrochromic performance can be achieved with a transmittance difference at 550 nm of 74.3% (81.9-7.6%) in pH 13 solution. The light absorption of the film can be tuned over light regions from visible to near-infrared with a large attenuation.

Corrosion inhibition by inorganic cationic inhibitors on the high strength alumunium alloy, 2024-T3

NASA Astrophysics Data System (ADS)

Chilukuri, Anusha

The toxicity and carcinogenic nature of chromates has led to the investigation of environmentally friendly compounds that offer good corrosion resistance to AA 2024-T3. Among the candidate inhibitors are rare earth metal cationic (REM) and zinc compounds, which have received much of attention over the past two decades. A comparative study on the corrosion inhibition caused by rare earth metal cations, Ce3+, Pr3+, La3+ and Zn2+ cations on the alloy was done. Cathodic polarization showed that these inhibitor ions suppress the oxygen reduction reaction (ORR) to varying extents with Zn2+ providing the best inhibition. Pr3+ exhibited windows of concentration (100-300 ppm) in which the corrosion rate is minimum; similar to the Ce3+ cation. Scanning Electron Microscopy (SEM) studies showed that the mechanism of inhibition of the Pr3+ ion is also similar to that of the Ce3+ ion. Potentiodynamic polarization experiments after 30 min immersion time showed greatest suppression of oxygen reduction reaction in neutral chloride solutions (pH 7), which reached a maximum at a Zn2+ ion concentration of 5 mM. Anodic polarization experiments after 30 min immersion time, showed no anodic inhibition by the inhibitor in any concentration (0.1 mM - 10 mM) and at any pH. However, anodic polarization of samples immersed after longer immersion times (upto 4 days) in mildly acidic Zn2+ (pH 4) solutions showed significant reduction in anodic kinetics indicating that zinc also acts as a “slow anodic inhibitor”. In contrast to the polarization experiments, coupons exposed to inhibited acidic solutions at pH 4 showed complete suppression of dissolution of Al2CuMg particles compared to zinc-free solutions in the SEM studies. Samples exposed in pH 4 Zn2+-bearing solution exhibited highest polarization resistance which was also observed to increase with time. In deaerated solutions, the inhibition by Zn2+ at pH 4 is not observed as strongly. The ability to make the interfacial electrolyte alkaline is retarded in the absence of oxygen. As a result precipitation of Zn oxides and hydroxides was suppressed. Impedance in decarbonated chloride solutions showed that the absence of CO 2 reduces inhibition by Zn2+ at pH 4. The carbonate protective layer formed in aerated solutions is essential for providing better protection of the substrate at pH 4. Inhibitor cations were exchanged into insoluble ion-exchanging sodium bentonites and incorporated as pigments in organic coatings applied to AA 2024-T3 substrates. XRD of the pigments ensured ion exchange and UV-visible spectroscopy was used to characterize inhibitor ion release from the bentonites. Salt spray exposure tests on scribed panels were preformed and results were compared to those from SrCrO4 pigmented coatings. Zn-exchanged bentonite pigmented coatings showed better performance compared to the other exchanged bentonites when incorporated into epoxy coatings with total impedance magnitude in the same order as SrCrO4. PVB (Polyvinyl Butyral) coatings containing Zn bentonite, however, did not show superior behaviour in the impedance response due to less or no water uptake. Salt spray exposures for a period of 336 h, showed that Zn bentonite incorporated into PVB suppressed blistering compared to the neat PVB and other pigmented bentonites.

Alteration of chemical behavior of L-ascorbic acid in combination with nickel sulfate at different pH solutions in vitro

PubMed Central

Maniyar, Shaheen A; Jargar, Jameel G; Das, Swastika N; Dhundasi, Salim A; Das, Kusal K

2012-01-01

Objective To evaluate the alteration of chemical behavior of L-ascorbic acid (vitamin C) with metal ion (nickel) at different pH solutions in vitro. Methods Spectra of pure aqueous solution of L-ascorbic acid (E mark) compound and NiSO4 (H2O) (sigma USA) were evaluated by UV visible spectrophotometer. Spectral analysis of L-ascorbic acid and nickel at various pH (2.0, 7.0, 7.4 and 8.6) at room temperature of 29 °C was recorded. In this special analysis, combined solution of L-ascorbic acid and nickel sulfate at different pH was also recorded. Results The result revealed that λmax (peak wavelength of spectra) of L-ascorbic acid at pH 2.0 was 289.0 nm whereas at neutral pH 7.0, λmax was 295.4 nm. In alkaline pH 8.6, λmax was 295.4 nm and at pH 7.4 the λmax of L-ascorbic acid remained the same as 295.4 nm. Nickel solution at acidic pH 2.0 was 394.5 nm, whereas at neutral pH 7.0 and pH 7.4 were the same as 394.5 nm. But at alkaline pH 8.6, λmax value of nickel sulfate became 392.0 nm. The combined solution of L-ascorbic acid and nickel sulfate (6 mg/mL each) at pH 2.0 showed 292.5 nm and 392.5 nm, respectively whereas at pH 7.0, L-ascorbic acid showed 296.5 nm and nickel sulfate showed 391.5 nm. At pH 7.4, L-ascorbic acid showed 297.0 nm and nickel sulfate showed 394.0 nm in the combined solution whereas at pH 8.6 (alkaline) L-ascorbic acid and nickel sulfate were showing 297.0 and 393.5 nm, respectively. Conclusions Results clearly indicate an altered chemical behavior of L-ascorbic acid either alone or in combination with nickel sulfate in vitro at different pH. Perhaps oxidation of L-ascorbic acid to L-dehydro ascorbic acid via the free radical (HSc*) generation from the reaction of H2ASc + Ni (II) is the cause of such alteration of λmax value of L-ascorbic acid in the presence of metal nickel. PMID:23569901

Acid-Activatable Michael-Type Fluorescent Probes for Thiols and for Labeling Lysosomes in Live Cells.

PubMed

Dai, Chun-Guang; Du, Xiao-Jiao; Song, Qin-Hua

2015-12-18

A Michael addition is usually taken as a base-catalyzed reaction. Most fluorescent probes have been designed to detect thiols in slightly alkaline solutions (pH 7-9). The sensing reactions of almost all Michael-type fluorescent probes for thiols are faster in a high pH solution than in a low pH solution. In this work, we synthesized a series of 7-substituted 2-(quinolin-2-ylmethylene)malonic acids (QMAs, substituents: NEt2, OH, H, Cl, or NO2) and their ethyl esters (QMEs) as Michael-type fluorescent probes for thiols. The sensing reactions of QMAs and QMEs occur in distinct pH ranges, pH < 7 for QMAs and pH > 7 for QMEs. On the basis of experimental and theoretic studies, we have clarified the distinct pH effects on the sensing reactivity between QMAs and QMEs and demonstrated that two QMAs (NEt2, OH) are highly sensitive and selective fluorescent probes for thiols in acidic solutions (pH < 7) and promising dyes that can label lysosomes in live cells.

Characterization of zinc oxide thin film for pH detector

NASA Astrophysics Data System (ADS)

Hashim, Uda; Fathil, M. F. M.; Arshad, M. K. Md; Gopinath, Subash C. B.; Uda, M. N. A.

2017-03-01

This paper presents the fabrication process of the zinc oxide thin films for using to act as pH detection by using different PH solution. Sol-gel solution technique is used for preparing zinc oxide seed solution, followed by metal oxide deposition process by using spin coater on the silicon dioxide. Silicon dioxide layer is grown on the silicon wafer, then, ZnO seed solution is deposited on the silicon layer, baked, and annealing process carried on to undergo the characterization of its surface morphology, structural and crystalline phase. Electrical characterization is showed by using PH 4, 7, and 10 is dropped on the surface of the die, in addition, APTES solution is used as linker and also as a references of the electrical characterization.

The pH sensitive properties of carboxymethyl chitosan nanoparticles cross-linked with calcium ions.

PubMed

Kalliola, Simo; Repo, Eveliina; Srivastava, Varsha; Heiskanen, Juha P; Sirviö, Juho Antti; Liimatainen, Henrikki; Sillanpää, Mika

2017-05-01

In environmental applications the applied materials are required to be non-toxic and biodegradable. Carboxymethyl chitosan nanoparticles cross-linked with Ca 2+ ions (CMC-Ca) fulfill these requirements, and they are also renewable. These nanoparticles were applied to oil-spill treatment in our previous study and here we focused on enhancing their properties. It was found that while the divalent Ca 2+ ions are crucial for the formation of the CMC-Ca, the attractive interaction between NH 3 + and COO - groups contributed significantly to the formation and stability of the CMC-Ca. The stability decreased as a function of pH due to the deprotonation of the amino groups. Therefore, the nanoparticles were found to be fundamentally pH sensitive in solution, if the pH deviated from the pH (7-9) that was used in the synthesis of the nanoparticles. The pH sensitive CMC-Ca synthesized in pH 7 and 8 were most stable in the studied conditions and could find applications in oil-spill treatment or controlled-release of substances. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Avazbaeva, Zaure; Sung, Woongmo; Lee, Jonggwan

In this paper, it has been reported that an octadecylamine (ODA) Langmuir monolayer becomes unstable at low pH values with no measurable surface pressure at around pH 3.5, suggesting significant dissolution of the ODA molecule into the subphase solution (Albrecht, Colloids Surf. A 2006, 284–285, 166–174). However, by lowering the pH further, ODA molecules reoccupy the surface, and a full monolayer is recovered at pH 2.5. Using surface sum-frequency spectroscopy and pressure–area isotherms, it is found that the recovered monolayer at very low pH has a larger area per molecule with many gauche defects in the ODA molecules as comparedmore » to that at high pH values. This structural change suggests that the reappearance of the monolayer is due to the adsorbed Cl– counterions to the protonated amine groups, leading to partial charge neutralization. This proposition is confirmed by intentionally adding monovalent salts (i.e., NaCl, NaBr, or NaI) to the subphase to recover the monolayer at pH 3.5, in which the detailed structure of the monolayer is confirmed by sum frequency spectra and the adsorbed anions by X-ray reflectivity.« less

Chemical and physical properties affecting strontium distribution coefficients of surficial-sediment samples at the Idaho National Engineering and Environmental Laboratory, Idaho

USGS Publications Warehouse

Liszewski, M.J.; Rosentreter, J.J.; Miller, Karl E.; Bartholomay, R.C.

2000-01-01

The U.S. Geological Survey and Idaho State University, in cooperation with the U.S. Department of Energy, conducted a study to determine strontium distribution coefficients (K(d)s) of surficial sediments at the Idaho National Engineering and Environmental Laboratory (INEEL). Batch experiments using synthesized aqueous solutions were used to determine K(d)s, which describe the distribution of a solute between the solution and solid phase, of 20 surficial-sediment samples from the INEEL. The K(d)s for the 20 surficial-sediment samples ranged from 36 to 275 ml/g. Many properties of both the synthesized aqueous solutions and sediments used in the experiments also were determined. Solution properties determined were initial and equilibrium concentrations of calcium, magnesium, and strontium, pH and specific conductance, and initial concentrations of potassium and sodium. Sediment properties determined were grain-size distribution, bulk mineralogy, whole-rock major-oxide and strontium and barium concentrations, and Brunauer-Emmett-Teller (BET) surface area. Solution and sediment properties were correlated with strontium K(d)s of the 20 surficial sediments using Pearson correlation coefficients. Solution properties with the strongest correlations with strontium K(d)s were equilibrium pH and equilibrium calcium concentration correlation coefficients, 0.6598 and -0.6518, respectively. Sediment properties with the strongest correlations with strontium K(d)s were manganese oxide (MnO), BET surface area, and the >4.75-mm-grain-size fraction correlation coefficients, 0.7054, 0.7022, and -0.6660, respectively. Effects of solution properties on strontium K(d)s were interpreted as being due to competition among similarly charged and sized cations in solution for strontium-sorption sites; effects of sediment properties on strontium K(d)s were interpreted as being surface-area related. Multivariate analyses of these solution and sediment properties resulted in r2 values of 0.8071 when all five properties were used and 0.8043 when three properties, equilibrium pH, MnO, and BET surface area, were used.

Controlling silk fibroin particle features for drug delivery

PubMed Central

Lammel, Andreas; Hu, Xiao; Park, Sang-Hyug; Kaplan, David L.; Scheibel, Thomas

2010-01-01

Silk proteins are a promising material for drug delivery due to their aqueous processability, biocompatibility, and biodegradability. A simple aqueous preparation method for silk fibroin particles with controllable size, secondary structure and zeta potential is reported. The particles were produced by salting out a silk fibroin solution with potassium phosphate. The effect of ionic strength and pH of potassium phosphate solution on the yield and morphology of the particles was determined. Secondary structure and zeta potential of the silk particles could be controlled by pH. Particles produced by salting out with 1.25 M potassium phosphate pH 6 showed a dominating silk II (crystalline) structure whereas particles produced at pH 9 were mainly composed of silk I (less crystalline). The results show that silk I rich particles possess chemical and physical stability and secondary structure which remained unchanged during post treatments even upon exposure to 100% ethanol or methanol. A model is presented to explain the process of particle formation based on intra- and intermolecular interactions of the silk domains, influenced by pH and kosmotrope salts. The reported silk fibroin particles can be loaded with small molecule model drugs, such as alcian blue, rhodamine B, and crystal violet, by simple absorption based on electrostatic interactions. In vitro release of these compounds from the silk particles depends on charge – charge interactions between the compounds and the silk. With crystal violet we demonstrated that the release kinetics are dependent on the secondary structure of the particles. PMID:20219241

Saliva and tongue coating pH before and after use of mouthwashes and relationship with parameters of halitosis

PubMed Central

TOLENTINO, Elen de Souza; CHINELLATO, Luiz Eduardo Montenegro; TARZIA, Olinda

2011-01-01

Objectives The aim of this work was to evaluate saliva and tongue coating pH in oral healthy patients with morning bad breath before and after use of different oral mouthrinses. Material and Methods aliva and tongue coating pH of 50 patients allocated in 5 groups were measured respectively by a digital pHmeter and color pH indicators, before, immediately after and 30 min after rinsing 5 different mouthrinses: cetilpiridine chloride associated with sodium chloride, triclosan, enzymatic solution, essential oil and distilled water. Results Only triclosan and essential oil increased salivary pH immediately after rising. The enzymatic solution decreased salivary and tongue coating pH immediately after rinsing. Conclusion Salivary pH tended to be acidic while tongue coating pH tended to be alkaline, even after rising. Triclosan and essential oil mouthrinses increased salivary pH immediately after rinsing. Enzymatic solution decreased saliva and tongue coating pH immediately after rising. PMID:21552707

Manipulating energy transfer in copolymer-based nanocomposites by their controlled nanocaging and release of an ionic styryl dye: a case of an ultrasensitive pH sensor.

PubMed

Manna, Anamika; Sahoo, Dibakar; Chakravorti, Sankar

2012-03-01

We report an interesting pH-tunable energy transfer between an acceptor ionic styryl dye 2-(4-(dimethylamino)styryl)-1-methylpyridinium iodide and a donor charge-transfer dye 1,8-naphthalimide in a vesicular medium. The polyethylene-b-polyethylene glycol block copolymer intercalates with the sodium dodecyl sulfate anionic surfactant to form self-aggregated nanocomposites. These nanocomposites interact with the donor molecules in aqueous solution to form "vesicles", and the donor molecules become attached on the outer wall by hydrogen bonding. The acceptor molecules are observed to be loaded in the vesicular interior. By controlling the spectral overlap of the donor and acceptor molecules by changing the pH of the medium, the energy-transfer efficiency in vesicles has been studied. The efficiency of energy transfer in vesicular media (55%) is found to be less compared to that in aqueous media (80%) at pH 7. The fall in efficiency has been attributed to the perturbation imparted by the vesicular wall due to the good matching of the donor-acceptor distance with the wall thickness. At low pH, the efficiency shows an abrupt increase (95%) due to the release of the acceptor molecules from the vesicular medium causing subsequent reduction of donor-acceptor separation and an increase of the spectral overlap at that pH.

Phosphate Adsorption from Membrane Bioreactor Effluent Using Dowex 21K XLT and Recovery as Struvite and Hydroxyapatite

PubMed Central

Nur, Tanjina; Loganathan, Paripurnanda; Kandasamy, Jaya; Vigneswaran, Saravanamuthu

2016-01-01

Discharging phosphate through wastewaters into waterways poses a danger to the natural environment due to the serious risks of eutrophication and health of aquatic organisms. However, this phosphate, if economically recovered, can partly overcome the anticipated future scarcity of phosphorus (P) resulting from exhaustion of natural phosphate rock reserves. An experiment was conducted to determine the efficiency of removing phosphate from a membrane bioreactor effluent (pH 7.0–7.5, 20, 35 mg phosphate/L) produced in a water reclamation plant by adsorption onto Dowex 21K XLT ion exchange resin and recover the phosphate as fertilisers. The data satisfactorily fitted to Langmuir adsorption isotherm with a maximum adsorption capacity of 38.6 mg·P/g. The adsorbed phosphate was quantitatively desorbed by leaching the column with 0.1 M NaCl solution. The desorbed phosphate was recovered as struvite when ammonium and magnesium were added at the molar ratio of phosphate, ammonium and magnesium of 1:1:1 at pH 9.5. Phosphate was also recovered from the desorbed solution as hydroxyapatite precipitate by adding calcium hydroxide to the solution at a phosphate to calcium molar ratio of 1:2 at pH 7.0. The P contents of struvite and hydroxyapatite produced were close to those of the respective commercial phosphate fertilisers. PMID:26950136

Synthesis of walnut shell modified with titanium dioxide and zinc oxide nanoparticles for efficient removal of humic acid from aqueous solutions.

PubMed

Naghizadeh, Ali; Shahabi, Habibeh; Ghasemi, Fatemeh; Zarei, Ahmad

2016-12-01

The main aim of this research was to study the efficiency of modified walnut shell with titanium dioxide (TiO 2 ) and zinc oxide (ZnO) in the adsorption of humic acid from aqueous solutions. This experimental study was carried out in a batch condition to determine the effects of factors such as contact time, pH, humic acid concentration, dose of adsorbents (raw walnut shell, modified walnut shell with TiO 2 and ZnO) on the removal efficiency of humic acid. pH zpc of raw walnut shell, walnut shell modified with TiO 2 and walnut shell modified with ZnO were 7.6, 7.5, and 8, respectively. The maximum adsorption capacity of humic acid at concentration of 30 mg/L, contact time of 30 min at pH = 3 in an adsorbent dose of 0.02 g of walnut shell and ZnO and TiO 2 modified walnut shell were found to be 35.2, 37.9, and 40.2 mg/g, respectively. The results showed that the studied adsorbents tended to fit with the Langmuir model. Walnut shell, due to its availability, cost-effectiveness, and also its high adsorption efficiency, can be proposed as a promising natural adsorbent in the removal of humic acid from aqueous solutions.

Comparison of turbulence models and CFD solution options for a plain pipe

NASA Astrophysics Data System (ADS)

Canli, Eyub; Ates, Ali; Bilir, Sefik

2018-06-01

Present paper is partly a declaration of state of a currently ongoing PhD work about turbulent flow in a thick walled pipe in order to analyze conjugate heat transfer. An ongoing effort on CFD investigation of this problem using cylindrical coordinates and dimensionless governing equations is identified alongside a literature review. The mentioned PhD work will be conducted using an in-house developed code. However it needs preliminary evaluation by means of commercial codes available in the field. Accordingly ANSYS CFD was utilized in order to evaluate mesh structure needs and asses the turbulence models and solution options in terms of computational power versus difference signification. Present work contains a literature survey, an arrangement of governing equations of the PhD work, CFD essentials of the preliminary analysis and findings about the mesh structure and solution options. Mesh element number was changed between 5,000 and 320,000. k-ɛ, k-ω, Spalart-Allmaras and Viscous-Laminar models were compared. Reynolds number was changed between 1,000 and 50,000. As it may be expected due to the literature, k-ɛ yields more favorable results near the pipe axis and k-ωyields more convenient results near the wall. However k-ɛ is found sufficient to give turbulent structures for a conjugate heat transfer problem in a thick walled plain pipe.

Interactive effects of sulfadiazine and Cu(II) on their sorption and desorption on two soils with different characteristics.

PubMed

Xu, Yonggang; Yu, Wantai; Ma, Qiang; Zhou, Hua

2015-11-01

Antibiotics and heavy metals often coexist in soils due to land application of animal wastes and other sources of inputs. The aim of this study is to evaluate the interaction of Cu(II) and sulfadiazine (SDZ) regarding to their sorption and desorption on Brown soil (BS, luvisols) and Red soil (RS, Udic Ferrosols) using batch experiments. The presence of Cu(II) significantly enhanced sorption of SDZ on BS at pH>5.0, and this trend increased with increasing pH, which was mainly ascribed to the formation of ternary complexes of Cu-SDZ-soil and/or SDZ-Cu-soil. In contrast, Cu(II) only slightly increased SDZ sorption on RS at pH<5.0 due to the decrease of equilibrium solution pH, whereas it hardly affected SDZ sorption at pH>5.0 because RS had high oxides contents and low affinity for Cu(II). In addition, Cu(II) inhibited SDZ desorption from BS but promoted SDZ desorption from RS, which was related to their different sorption mechanisms. The presence of SDZ exerted no significant effect on the sorption of Cu(II) on the two soils at pH<6.5 because of its low sorption coefficients (Kd), while slightly decreased Cu(II) sorption at pH>6.5 by forming water-soluble complexes. Furthermore, SDZ had little effect on Cu(II) desorption from the two soils at natural pH. These results indicate that soil characteristics strongly influence the interactions of Cu(II) and SDZ on their sorption and desorption on soils. Copyright © 2015 Elsevier Ltd. All rights reserved.

Mechanical behavior of precipitation hardenable steels exposed to highly corrosive environment

NASA Technical Reports Server (NTRS)

Rosa, Ferdinand

1994-01-01

Unexpected occurrences of failures, due to stress corrosion cracking (SCC) of structural components, indicate a need for improved characterization of materials and more advanced analytical procedures for reliably predicting structures performance. Accordingly, the purpose of this study was to determine the stress corrosion susceptibility of 15 - 5 PH steel over a wide range of applied strain rates in a highly corrosive environment. The selected environment for this investigation was a 3.5 percent NaCl aqueous solution. The material selected for the study was 15 - 5 PH steel in the H 900 condition. The Slow Strain Rate technique was used to test the metallic specimens.

Technetium recovery from high alkaline solution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nash, Charles A.

2016-07-12

Disclosed are methods for recovering technetium from a highly alkaline solution. The highly alkaline solution can be a liquid waste solution from a nuclear waste processing system. Methods can include combining the solution with a reductant capable of reducing technetium at the high pH of the solution and adding to or forming in the solution an adsorbent capable of adsorbing the precipitated technetium at the high pH of the solution.

ANTICARIOGENIC POTENCIAL OF ACIDULATE SOLUTIONS WITH LOW FLUORIDE CONCENTRATION

PubMed Central

Delbem, Alberto Carlos Botazzo; Tiano, Gilberto Carlos; Alves, Karina Mirela Ribeiro Pinto; Cunha, Robson Frederico

2006-01-01

Objectives: The aim of this study was to verify the anticariogenic effect of acidulate solutions with low NaF concentration, using pH-cycling model and bovine enamel. Material and methods: Enamel blocks were submitted to the surface microhardness (SMH) test and randomly divided in 12 experimental and one placebo groups. The blocks were submitted to pH cycling for 7 days, with daily applications once/day of 0.05% NaF and 0.1% NaF and twice/day of 0.02% NaF solutions. Four different pH: 4.0, 5.0, 6.0 and 7.0 were used. Next, SMH test was again used to determine the surface microhardness percentage change (%SMH). Data obtained for %SMH were homogeneous and passed through variance analyses and Tukey's test (5%) as far as fluoride concentrations and pH. Results: The results showed that pH influenced %SMH in 0.02% NaF and 0.05% NaF solutions with pH 4.0, which had less mineral loss compared to pH 7.0 (p<0.05). The 0.02% NaF - pH 4.0, and 0.05% NaF – pH 7.0 groups showed similar results (p>0.05). A dose-response relationship was observed among the tested solutions, with better anticariogenic effect for the 0.1% NaF solution. Conclusion: The results suggest that the addition of citric acid to acidulate mouth rinses reduce mineral loss. PMID:19089268

The Semen pH Affects Sperm Motility and Capacitation.

PubMed

Zhou, Ji; Chen, Li; Li, Jie; Li, Hongjun; Hong, Zhiwei; Xie, Min; Chen, Shengrong; Yao, Bing

2015-01-01

As the chemical environment of semen can have a profound effect on sperm quality, we examined the effect of pH on the motility, viability and capacitation of human sperm. The sperm in this study was collected from healthy males to avoid interference from other factors. The spermatozoa cultured in sperm nutrition solution at pH 5.2, 6.2, 7.2 and 8.2 were analyzed for sperm total motility, progressive motility (PR), hypo-osmotic swelling (HOS) rate, and sperm penetration. Our results showed that these parameters were similar in pH 7.2 and 8.2 sperm nutrition solutions, but decreased in pH 5.2 and 6.2 solutions. The HOS rate exhibited positive correlation with the sperm total motility and PR. In addition, the sperm Na(+)/K(+)-ATPase activity at different pHs was measured, and the enzyme activity was significantly lower in pH 5.2 and 6.2 media, comparing with that in pH 8.2 and pH 7.2 solutions. Using flow cytometry (FCM) and laser confocal scanning microscopy (LCSM) analysis, the intracellular Ca2(+ )concentrations of sperm cultured in sperm capacitation solution at pH 5.2, 6.2, 7.2 and 8.2 were determined. Compared with that at pH 7.2, the mean fluorescence intensity of sperm in pH 5.2 and 6.2 media decreased significantly, while that of pH 8.2 group showed no difference. Our results suggested that the declined Na(+)/K(+)-ATPase activity at acidic pHs result in decreased sperm movement and capacitation, which could be one of the mechanisms of male infertility.

Treatment of As(V) and As(III) by electrocoagulation using Al and Fe electrode.

PubMed

Kuan, W H; Hu, C Y; Chiang, M C

2009-01-01

A batch electrocoagulation (EC) process with bipolar electrode and potentiodynamic polarization tests with monopolar systems were investigated as methods to explore the effects of electrode materials and initial solution pH on the As(V) and As(III) removal. The results displayed that the system with Al electrode has higher reaction rate during the initial period from 0 to 25 minutes than that of Fe electrode for alkaline condition. The pH increased with the EC time because the As(V) and As(III) removal by either co-precipitation or adsorption resulted in that the OH positions in Al-hydroxide or Fe-hydroxide were substituted by As(V) and As(III). The pH in Fe electrode system elevate higher than that in Al electrode because the As(V) removal substitutes more OH position in Fe-hydroxide than that in Al-hydroxide. EC system with Fe electrode can successfully remove the As(III) but system with Al electrode cannot because As(III) can strongly bind to the surface of Fe-hydroxide with forming inner-sphere species but weakly adsorb to the Al-hydroxide surface with forming outer-sphere species. The acidic solution can destroy the deposited hydroxide passive film then allow the metallic ions liberate into the solution, therefore, the acidic initial solution can enhance the As(V) and As(III) removal. The over potential calculation and potentiodynamic polarization tests reveal that the Fe electrode systems possess higher over potential and pitting potential than that of Al electrode system due to the fast hydrolysis of and the occurrence of Fe-hydroxide passive film.

NMR studies of proton exchange kinetics in aqueous formaldehyde solutions.

PubMed

Rivlin, Michal; Eliav, Uzi; Navon, Gil

2014-05-01

Aqueous solutions of formaldehyde, formalin, are commonly used for tissue fixation and preservation. Treatment with formalin is known to shorten the tissue transverse relaxation time T2. Part of this shortening is due to the effect of formalin on the water T2. In the present work we show that the shortening of water T2 is a result of proton exchange between water and the major constituent of aqueous solutions of formaldehyde, methylene glycol. We report the observation of the signal of the hydroxyl protons of methylene glycol at 2ppm to high frequency of the water signal that can be seen at low temperatures and at pH range of 6.0±1.5 and, at conditions where it cannot be observed by the single pulse experiment, it can be detected indirectly through the water signal by the chemical exchange saturation transfer (CEST) experiment. The above finding made it possible to obtain the exchange rate between the hydroxyl protons of the methylene glycol and water in aqueous formaldehyde solutions, either using the dispersion of the spin-lattice relaxation rate in the rotating frame (1/T1ρ) or, at the slow exchange regime, from the line width hydroxyl protons of methylene glycol. The exchange rate was ∼10(4)s(-1) at pH 7.4 and 37°C, the activation energy, 50.2kJ/mol and its pH dependence at 1.1°C was fitted to: k (s(-1))=520+6.5×10(7)[H(+)]+3.0×10(9)[OH(-)]. Copyright © 2014. Published by Elsevier Inc.

Interactions of Hydrazine and of Hydrazine Derivatives with Soil Constituents and with Soils.

DTIC Science & Technology

1982-01-31

exchangeable metal cations held by the clay and humic colloids, or the metal of the hydrous oxide colloids. The pH values of the natural soil solution of most...hydrazine into a soil system will tend to increase the pH of the soil solution . Hydrous oxides of iron and aluminium are insoluble at high pH, and these...aeration, and by the soil solution pH. Treatment of contaminated soils can alter these properties in order to promote the degradation or immobilization of

The colour degradation of anthocyanin-rich extract from butterfly pea (Clitoria ternatea L.) petal in various solvents at pH 7.

PubMed

Marpaung, Abdullah Muzi; Andarwulan, Nuri; Hariyadi, Purwiyatno; Nur Faridah, Didah

2017-10-01

A spectroscopic study was conducted to evaluate the colour degradation mechanism of anthocyanin-rich extract from butterfly pea petal. The extract was diluted in four different solvent systems, which were buffer solution pH 7 (AQ7) and the mixture of organic solvent with buffer solution pH 7 (4:1 v/v). The organic cosolvent involved were methanol (ME7), ethanol (ET7) and acetone (AC7). The samples were stored in containers with 0% and 50% headspace, and their colour intensity, total anthocyanin and hypsochromic shift were evaluated periodically. The rank of colour and anthocyanin degradation from the biggest was AQ7 > ME7 > ET7 > AC7. The longest hypsochromic shift was AQ7 > ME7 > ET7, while in AC7 the shift was absent. There was evidence that the volume of package headspace provoked colour stability. The colour degradation in AC7 was proposed to occur through hydrophobic interaction unfolding, and in AQ7 was through the deacylation, while in ME7 and ET7 was due to both mechanisms.

Hyaluronan–cisplatin conjugate nanoparticles embedded in Eudragit S100-coated pectin/alginate microbeads for colon drug delivery

PubMed Central

Tsai, Shiao-Wen; Yu, Ding-Syuan; Tsao, Shu-Wei; Hsu, Fu-Yin

2013-01-01

Hyaluronan–cisplatin conjugate nanoparticles (HCNPs) were chosen as colon-targeting drug-delivery carriers due to the observation that a variety of malignant tumors overexpress hyaluronan receptors. HCNPs were prepared by mixing cisplatin with a hyaluronan solution, followed by dialysis to remove trace elements. The cells treated with HCNPs showed significantly lower viability than those treated with cisplatin alone. HCNPs were entrapped in Eudragit S100-coated pectinate/alginate microbeads (PAMs) by using an electrospray method and a polyelectrolyte multilayer-coating technique in aqueous solution. The release profile of HCNPs from Eudragit S100-coated HCNP-PAMs was pH-dependent. The percentage of 24-hour drug release was approximately 25.1% and 39.7% in pH 1.2 and pH 4.5 media, respectively. However, the percentage of drug released quickly rose to 75.6% at pH 7.4. Moreover, the result of an in vivo nephrotoxicity study demonstrated that Eudragit S100-coated HCNP-PAMs treatment could mitigate the nephrotoxicity that resulted from cisplatin. From these results, it can be concluded that Eudragit S100-coated HCNP-PAMs are promising carriers for colonspecific drug delivery. PMID:23861585

Synthesis and characterization of a thermo-sensitive poly( N-methyl acryloylglycine methyl ester) used as a drug release carrier

NASA Astrophysics Data System (ADS)

Deng, Kui-Lin; Zhong, Hai-Bin; Jiao, Yi-Suo; Fan, Ting; Qiao, Xiao; Zhang, Peng-Fei; Ren, Xiao-Bo

2010-06-01

In this article, poly( N-methyl acryloylglycine methyl ester) (PNMAME) was prepared as a novel thermosensitive material with a lower critical solution temperature (LCST) at around 49.5°C. The chemical structures of the monomer NMAME and PNMAME were characterized by 1H NMR and IR measurements. The LCST was investigated systematically as a function of PNMAME concentration, inorganic salt solution and pH value. The results indicated that LCST of PNMAME was obviously dependent on PNMAME concentration and pH. The LCST was increased with a decrease in pH value and PNMAME concentration. To obtain a thermo-sensitive hydrogel with the phase transition temperature close to human body temperature, the copolymerization was conducted between NMAME and N-acryloylglycine ethyl ester (NAGEE). The release behavior of caffeine was evaluated at different temperatures and contents of cross-linkers ( N, N-methylenebis(acrylamide) (NMBA)). The increase of cross-linker content led to a decrease in the release rate of caffeine due to higher crossing density in the hydrogel network. In addition, a faster release of caffeine from the hydrogel with 3% NMBA at 37°C was found in contrast to that at 18°C.

A New Neutral-pH Low-GDP Peritoneal Dialysis Fluid

PubMed Central

Himmele, Rainer; Jensen, Lynn; Fenn, Dominik; Ho, Chih-Hu; Sawin, Dixie-Ann; Diaz-Buxo, Jose A.

2012-01-01

♦ Background: Conventional peritoneal dialysis fluids (PDFs) consist of ready-to-use solutions with an acidic pH. Sterilization of these fluids is known to generate high levels of glucose degradation products (GDPs). Although several neutral-pH, low-GDP PD solutions have been developed, none are commercially available in the United States. We analyzed pH and GDPs in Delflex Neutral pH (Fresenius Medical Care North America, Waltham, MA, USA), the first neutral-pH PDF to be approved by the US Food and Drug Administration. ♦ Methods: We evaluated whether patients (n = 26; age range: 18 - 78 years) could properly mix the Delflex Neutral pH PDF after standardized initial training. We further analyzed the concentrations of 10 different glucose degradation products in Delflex Neutral pH PDF and compared the results with similar analyses in other commercially available biocompatible PDFs. ♦ Results: All pH measurements (n = 288) in the delivered Delflex Neutral pH solution consistently fell within the labeled range of 7.0 ± 0.4. Analysis of mixing errors showed no significant impact on the pH results. Delflex Neutral pH, Balance (Fresenius Medical Care, Bad Homburg, Germany), BicaVera (Fresenius Medical Care), and Gambrosol Trio (Gambro Lundia AB, Lund, Sweden) exhibited similar low total GDP concentrations, with maximums in the 4.25% solutions of 88 μmol/L, 74 μmol/L, 74 μmol/L, and 79 μmol/L respectively; the concentration in Physioneal (Baxter Healthcare Corporation, Deerfield, IL, USA) was considerably higher at 263.26 μmol/L. The total GDP concentration in Extraneal (Baxter Healthcare Corporation) was 63 μmol/L, being thus slightly lower than the concentrations in the 4.25% glucose solutions, but higher than the concentrations in the 1.5% and 2.5% glucose solutions. ♦ Conclusions: The new Delflex Neutral pH PDF consistently delivers neutral pH with minimal GDPs. PMID:22383632

Adsorption of 4-n-Nonylphenol and Bisphenol-A on Magnetic Reduced Graphene Oxides: A Combined Experimental and Theoretical Studies.

PubMed

Jin, Zhongxiu; Wang, Xiangxue; Sun, Yubing; Ai, Yuejie; Wang, Xiangke

2015-08-04

Adsorption of 4-n-nonylphenol (4-n-NP) and bisphenol A (BPA) on magnetic reduced graphene oxides (rGOs) as a function of contact time, pH, ionic strength and humic acid were investigated by batch techniques. Adsorption of 4-n-NP and BPA were independent of pH at 3.0- 8.0, whereas the slightly decreased adsorption was observed at pH 8.0-11.0. Adsorption kinetics and isotherms of 4-n-NP and BPA on magnetic rGOs can be satisfactorily fitted by pseudo-second-order kinetic and Freundlich model, respectively. The maximum adsorption capacities of magnetic rGOs at pH 6.5 and 293 K were 63.96 and 48.74 mg/g for 4-n-NP and BPA, respectively, which were significantly higher than that of activated carbon. Based on theoretical calculations, the higher adsorption energy of rGOs + 4-n-NP was mainly due to π-π stacking and flexible long alkyl chain of 4-n-NP, whereas adsorption of BPA on rGOs was energetically favored by a lying-down configuration due to π-π stacking and dispersion forces, which was further demonstrated by FTIR analysis. These findings indicate that magnetic rGOs is a promising adsorbent for the efficient elimination of 4-n-NP/BPA from aqueous solutions due to its excellent adsorption performance and simple magnetic separation, which are of great significance for the remediation of endocrine-disrupting chemicals in environmental cleanup.

Origin of the instability of octadecylamine Langmuir monolayer at low pH

DOE PAGES

Avazbaeva, Zaure; Sung, Woongmo; Lee, Jonggwan; ...

2015-11-30

In this paper, it has been reported that an octadecylamine (ODA) Langmuir monolayer becomes unstable at low pH values with no measurable surface pressure at around pH 3.5, suggesting significant dissolution of the ODA molecule into the subphase solution (Albrecht, Colloids Surf. A 2006, 284–285, 166–174). However, by lowering the pH further, ODA molecules reoccupy the surface, and a full monolayer is recovered at pH 2.5. Using surface sum-frequency spectroscopy and pressure–area isotherms, it is found that the recovered monolayer at very low pH has a larger area per molecule with many gauche defects in the ODA molecules as comparedmore » to that at high pH values. This structural change suggests that the reappearance of the monolayer is due to the adsorbed Cl– counterions to the protonated amine groups, leading to partial charge neutralization. This proposition is confirmed by intentionally adding monovalent salts (i.e., NaCl, NaBr, or NaI) to the subphase to recover the monolayer at pH 3.5, in which the detailed structure of the monolayer is confirmed by sum frequency spectra and the adsorbed anions by X-ray reflectivity.« less

Alterations of thorium oxalate morphology by changing elementary precipitation conditions

NASA Astrophysics Data System (ADS)

Tyrpekl, V.; Beliš, M.; Wangle, T.; Vleugels, J.; Verwerft, M.

2017-09-01

Oxalates of actinide elements are widely used in research and industry mainly due to their low solubility in aqueous solution and easy conversion to oxide. Although thorium oxide is worldwide mostly produced by the oxalate precipitation and conversion route, the powder morphology obtained through this process is known to inhibit the packing and sintering step of the pellet production. The presented work investigates the effects of oxalate precipitation conditions on the final powder morphology. Among the precipitation conditions considered are: pH of the thorium feed solution, concentration, temperature and the order of addition (thorium solution in oxalic acid solution and vice versa) known as reverse/direct strike. Herein, we show that the morphology of the final oxalate depends significantly on the above mentioned precipitation parameters.

Optimizing acidified bleach solutions to improve sporicidal efficacy on building materials.

PubMed

Wood, J P; Calfee, M W; Clayton, M; Griffin-Gatchalian, N; Touati, A

2011-12-01

We evaluated whether lowering pH (with acetic acid) and raising free available chlorine (FAC) levels in bleach solutions would improve efficacy in inactivating Bacillus spores on different materials. We also determined how varying pH and FAC levels affected bleach stability. Acidified bleach solutions with pH levels of 4.5, 6 and 7.5 and FAC levels between 5000 and 10,000 ppm were evaluated for decontamination efficacy against Bacillus subtilis spores inoculated onto test coupons made from wood, ceramic and galvanized steel. Lowering the pH or increasing the FAC level improved efficacy in some of the tests, but depended on the material, which significantly affected decontamination efficacy. The acidified bleach at pH of 7.5 was significantly less effective than bleach at a pH of 4.5 or 6. The FAC levels in the bleach were the most stable at pH 4.5, and stability at pH 4.5 was not significantly affected by the initial FAC level. It may be advisable to use bleach solutions with lower pH (rather than high FAC levels) in light of both the decontamination efficacy and bleach stability results. For wood materials, use of sporicides other than acidified bleach may be warranted. These results may be useful in preparing acidified bleach solutions for decontamination of materials contaminated with spores such as Bacillus anthracis. © 2011 The Authors. Letters in Applied Microbiology © 2011 The Society for Applied Microbiology.

The Effects of Lime, Fertilizer, and Herbicide on Forest Soil Solution Chemistry and Northern Red Oak Radial Growth Following Shelterwood Harvest

Treesearch

Angela M Happel; William E. Sharpe

2004-01-01

Soil acidity, nutrient deficient soils, lack of light penetration, herbivory, and understory competition are the major obstacles encountered in regenerating and sustaining northern red oak. Changes in soils that may occur during soil acidifi- cation include: reduced soil pH, increased availability of aluminum (Al) and manganese (Mn), loss of base cations due to...

The origin of facet selectivity and alignment in anatase TiO 2 nanoparticles in electrolyte solutions: implications for oriented attachment in metal oxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sushko, M. L.; Rosso, K. M.

Atomic-to-mesoscale simulations were used to reveal the origin of oriented attachment between anatase TiO2 nanoparticles in aqueous HCl solutions. Analysis of the distance and pH dependence of interparticle interactions demonstrates that ion correlation forces are responsible for facet-specific attraction and rotation into lattice co-alignment at long-range. These forces give rise to a metastable solvent separated capture minimum on the disjoining pressure-distance curve, with the barrier to attachment largely due to steric hydration forces from structured intervening solvent.

Effects of pH values of hydrogen peroxide bleaching agents on enamel surface properties.

PubMed

Xu, B; Li, Q; Wang, Y

2011-01-01

This study investigated the influence of pH values of bleaching agents on the properties of the enamel surface. Sixty freshly extracted premolars were embedded in epoxy resin and mesiodistally sectioned through the buccal aspect into two parts. The sectioned slabs were distributed among six groups (n=10) and treated using different solutions. Group HCl was treated with HCl solution (pH=3.0) and served as a positive control. Group DW, stored in distilled water (pH=7.0), served as a negative control. Four treatment groups were treated using 30% hydrogen peroxide solutions with different pH values: group HP3 (pH=3.0), group HP5 (pH=5.0), group HP7 (pH=7.0), and group HP8 (pH=8.0). The buccal slabs were subjected to spectrophotometric evaluations. Scanning electron microscopy investigation and Micro-Raman spectroscopy were used to evaluate enamel surface morphological and chemical composition alterations. pH value has a significant influence on the color changes after bleaching (p<0.001). Tukey's multiple comparisons revealed that the order of color changes was HP8, HP7>HP5, HP3>HCl>DW. No obvious morphological alterations were detected on the enamel surface in groups DW, HP7, and HP8. The enamel surface of groups HCl and HP3 showed significant alterations with an erosion appearance. No obvious chemical composition changes were detected with respect to Micro-Raman analysis. Within the limitations of this study, it was concluded that no obvious morphological or chemical composition alterations of enamel surface were detected in the neutral or alkaline bleaching solutions. Bleaching solutions with lower pH values could result in more significant erosion of enamel, which represented a slight whitening effect.

Surface Complexation Modeling of Fluoride Adsorption by Soil and the Role of Dissolved Aluminum on Adsorption

NASA Astrophysics Data System (ADS)

Padhi, S.; Tokunaga, T.

2017-12-01

Adsorption of fluoride (F) on soil can control the mobility of F and subsequent contamination of groundwater. Hence, accurate evaluation of adsorption equilibrium is a prerequisite for understanding transport and fate of F in the subsurface. While there have been studies for the adsorption behavior of F with respect to single mineral constituents based on surface complexation models (SCM), F adsorption to natural soil in the presence of complexing agents needs much investigation. We evaluated the adsorption processes of F on a natural granitic soil from Tsukuba, Japan, as a function of initial F concentration, ionic strength, and initial pH. A SCM was developed to model F adsorption behavior. Four possible surface complexation reactions were postulated with and without including dissolved aluminum (Al) and Al-F complex sorption. Decrease in F adsorption with the increase in initial pH was observed in between the initial pH range of 4 to 9, and a decrease in the rate of the reduction of adsorbed F with respect to the increase in the initial pH was observed in the initial pH range of 5 to 7. Ionic strength variation in the range of 0 to 100mM had insignificant effect on F removal. Changes in solution pH were observed by comparing the solution before and after F adsorption experiments. At acidic pH, the solution pH increased, whereas at alkaline pH, the solution pH decreased after equilibrium. The SCM including dissolved Al and the adsorption of Al-F complex can simulate the experimental results quite successfully. Also, including dissolved Al and the adsorption of Al-F complex to the model explained the change in solution pH after F adsorption.

On the asymmetric adsorption of phenylalanine enantiomers by kaolin.

NASA Technical Reports Server (NTRS)

Bonner, W. A.; Flores, J.

1973-01-01

The attempt is described to verify a recent report that kaolin adsorbs D- and L-phenylalanine enantiomers to different extents from aqueous solutions at both pH 5.8 and pH 2. No evidence whatsoever could be found for the differential adsorption of D- versus L-phenylalanine by kaolin from either pH 6 or pH 2 solutions.

New recommendations for measuring collagen solubility.

PubMed

Latorre, María E; Lifschitz, Adrian L; Purslow, Peter P

2016-08-01

The heat-solubility of intramuscular collagen is usually conducted in 1/4 Ringer's solution at pH7.4, despite this ionic strength and pH being inappropriate for post-rigor meat. The current work studied the percentage of soluble collagen and hydrothermal isometric tension characteristics of perimysial strips on bovine semitendinosus muscles in either 1/4 Ringer's solution, distilled water, PBS, or a solution of the same salt concentration as 1/4 Ringer's but at pH5.6. Values of % soluble collagen were lower at pH7.4 than 5.6. Increasing ionic strength reduced % soluble collagen. The maximum perimysial isometric tension was independent of the bathing medium, but the percent relaxation was higher at pH7.4 than at pH5.6, and increased with ionic strength of the media. It is recommended that future measurements of collagen solubility and tests on connective tissue components of post-rigor meat should be carried out in a solution of concentrations NaCl and KCl equivalent to those in 1/4 Ringer's, but at pH5.6, a pH relevant to post-rigor meat. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physical stability comparisons of IgG1-Fc variants: effects of N-glycosylation site occupancy and Asp/Gln residues at site Asn 297

PubMed Central

KIM, JAE HYUN; JOSHI, SANGEETA B.; MIDDAUGH, C. RUSSELL; TOLBERT, THOMAS J.; VOLKIN, DAVID B.

2014-01-01

The structural integrity and conformational stability of various IgG1-Fc proteins produced from the yeast Pichia pastoris with different glycosylation site occupancy (di-, mono-, and non- glycosylated) was determined. In addition, the physical stability profiles of three different forms of non-glycosylated Fc molecules (varying amino acid residues at site 297 in the CH2 domain due to point mutations and enzymatic digestion of the Fc glycoforms) were also examined. The physical stability of these IgG1-Fc glycoproteins was examined as a function of pH and temperature by high throughput biophysical analysis using multiple techniques combined with data visualization tools (three index empirical phase diagrams and radar charts). Across the pH range of 4.0 to 6.0, the di- and mono- glycosylated forms of the IgG1-Fc showed the highest and lowest levels of physical stability respectively, with the non-glycosylated forms showing intermediate stability depending on solution pH. In the aglycosylated Fc proteins, the introduction of Asp (D) residues at site 297 (QQ vs. DN vs. DD forms) resulted in more subtle changes in structural integrity and physical stability depending on solution pH. The utility of evaluating the conformational stability profile differences between the various IgG1-Fc glycoproteins is discussed in the context of analytical comparability studies. PMID:24740840

A New Chemical Pathway Yielding A-Type Vitisins in Red Wines

PubMed Central

Araújo, Paula; Fernandes, Ana; de Freitas, Victor; Oliveira, Joana

2017-01-01

A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3-O-glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process. PMID:28375190

A New Chemical Pathway Yielding A-Type Vitisins in Red Wines.

PubMed

Araújo, Paula; Fernandes, Ana; de Freitas, Victor; Oliveira, Joana

2017-04-04

A new chemical pathway yielding A-type vitisins in red wines is proposed herein from the reaction between anthocyanins and oxaloacetic acid (OAA). This new chemical path is thought to occur in the first stages of the wine production even during the fermentation process. This is due to the revealed high reactivity of OAA with anthocyanins compared with the already known precursor (pyruvic acid, PA). In model solutions at wine pH (3.5), when malvidin-3- O -glucoside (mv-3-glc) is in contact with OAA and PA a decrease in the OAA concentration is observed along with the formation of A-type vitisin. Moreover, part of the OAA is also chemically converted into PA in model solutions. The reaction yields were also determined for OAA and PA using different mv-3-glc:organic acid molar ratios (1:0.5, 1:1, 1:5, 1:10; 1:50, and 1:100) and these values were always higher for OAA when compared to PA, even at the lowest molar ratio (1:0.5). The reaction yields were higher at pH 2.6 in comparison to pH 1.5 and 3.5, being less affected at pH 3.5 for OAA. These results support the idea that OAA can be at the origin of A-type vitisins in the first stages of wine production and PA in the subsequent ageing process.

Biocorrosion properties of antibacterial Ti-10Cu sintered alloy in several simulated biological solutions.

PubMed

Liu, Cong; Zhang, Erlin

2015-03-01

Ti-10Cu sintered alloy has shown strong antibacterial properties against S. aureus and E. coli and good cell biocompatibility, which displays potential application in dental application. The corrosion behaviors of the alloy in five different simulated biological solutions have been investigated by electrochemical technology, surface observation, roughness measurement and immersion test. Five different simulated solutions were chosen to simulate oral condition, oral condition with F(-) ion, human body fluids with different pH values and blood system. It has been shown that Ti-10Cu alloy exhibits high corrosion rate in Saliva pH 3.5 solution and Saliva pH 6.8 + 0.2F solution but low corrosion rate in Hank's, Tyrode's and Saliva pH 6.8 solutions. The corrosion rate of Ti-10Cu alloy was in a order of Hank's, Tyrode's, Saliva pH 6.8, Saliva-pH 3.5 and Saliva pH 6.8 + 0.2F from slow to fast. All results indicated acid and F(-) containing conditions prompt the corrosion reaction of Ti-Cu alloy. It was suggested that the Cu ion release in the biological environments, especially in the acid and F(-) containing condition would lead to high antibacterial properties without any cell toxicity, displaying wide potential application of this alloy.

Sodium-hydrogen exchange in guinea-pig ventricular muscle during exposure to hyperosmolar solutions.

PubMed Central

Whalley, D W; Hemsworth, P D; Rasmussen, H H

1991-01-01

1. The effect on intracellular pH (pHi) and intracellular Na+ activity (aNai) of exposure to hyperosmolar solutions was investigated in guinea-pig ventricular muscle using ion-sensitive microelectrodes. 2. Exposure of tissue to solution made hyperosmolar by the addition of 100 mM-sucrose produced an intracellular alkalinization of 0.10 pH units and hyperpolarization of the membrane potential. 3. When extracellular Na+ was reduced to 15 mM by substitution of NaCl with choline chloride, exposure to hyperosmolar solutions caused a decrease in pHi. Identical experiments using LiCl as the sodium substitute resulted in an increase in pHi of a magnitude similar to that seen at physiological Na+ levels. 4. In the presence of 50 microM-5-(N,N-dimethyl)amiloride (DMA), an inhibitor of Na(+)-H+ exchange, pHi decreased upon exposure to hyperosmolar solution. 5. The recovery of pHi from an intracellular acidosis (induced by brief exposure to NH4Cl) was enhanced in hyperosmolar solution when compared to recovery in isosmolar solution. This enhancement was observed even when aNai was markedly elevated (greater than 25 mM) by inhibition of the Na(+)-K+ pump. 6. There was an increase in aNai during exposure to hyperosmolar solutions. When the Na(+)-K+ pump was inhibited with dihydro-ouabain a component of this increase in aNai was sensitive to DMA. 7. We conclude that exposure of cardiac tissue to hyperosmolar solutions results in an intracellular alkalosis due to activation of the sarcolemmal Na(+)-H+ exchanger. Such changes should be considered when exposure to hyperosmolar solutions is used in the study of excitation-contraction coupling and cardiac muscle mechanics. PMID:1668347

Dissolution kinetics and biodurability of tremolite particles in mimicked lung fluids: Effect of citrate and oxalate

NASA Astrophysics Data System (ADS)

Rozalen, Marisa; Ramos, M. Elena; Huertas, F. Javier; Fiore, Saverio; Gervilla, Fernando

2013-11-01

The effect of citrate and oxalate on tremolite dissolution rate was measured at 37 °C in non-stirred flow-through reactors, using modified Gamble's solutions at pH 4 (macrophages), 7.4 (interstitial fluids) and 5.5 (intermediate check point) containing 0, 0.15, 1.5 and 15 mmol L-1 of citrate or oxalate. The dissolution rates calculated from Si concentration in the output solutions without organic ligands depend on pH, decreasing when the pH increases from -13.00 (pH 4) to -13.35 (pH 7.4) mol g-1 s-1 and following a proton-promoted mechanism. The presence of both ligands enhances dissolution rates at every pH, increasing this effect when the ligand concentration increases. Citrate produces a stronger effect as a catalyst than oxalate, mainly at more acidic pHs and enhances dissolution rates until 20 times for solutions with 15 mmol L-1 citrate. However, at pH 7.4 the effect is lighter and oxalate solutions (15 mmol L-1) only enhances dissolution rates eight times respect to free organic ligand solutions. Dissolution is promoted by the attack to protons and organic ligands to the tremolite surface. Magnesium speciation in oxalate and citrate solutions shows that Mg citrate complexes are more effective than oxalate ones during the alteration of tremolite in magrophages, but this tendency is the opposite for interstitial fluids, being oxalate magnesium complexes stronger. The biodurability estimations show that the destruction of the fibers is faster in acidic conditions (macrophages) than in the neutral solutions (interstitial fluid). At pH 4, both ligands oxalate and citrate reduce the residence time of the fibers with respect to that calculated in absence of ligands. Nevertheless, at pH 7.4 the presence of ligands does not reduce significantly the lifetime of the fibers.

Changes in soil solution Zn and pH and uptake of Zn by arbuscular mycorrhizal red clover in Zn-contaminated soil.

PubMed

Li, X; Christie, P

2001-01-01

Red clover plants inoculated with Glomus mosseae were grown in a sterile pasture soil containing 50 mg Zn kg(-1) in 'Plexiglas' (acrylic) containers with nylon net partitions (30 microm mesh) designed to separate the soil into a central root zone and two outer zones for hyphal growth with no root penetration. Two porous plastic soil moisture samplers were installed in each pot, one in the root compartment and the other in one of the hyphal compartments. The soil in the outer compartments was amended with one of the four application rates of Zn (as ZnSO4) ranging from 0 to 1000 mg kg(-1). Non-mycorrhizal controls were included, and there were five replicates of each treatment in a randomised block in a glasshouse. Uninoculated plants received supplementary P to avoid yield limitation due to low soil P status. Plants grew in the central compartment for nine weeks. Soil moisture samples were collected 4, 24 and 62 days after sowing to monitor changes in the Zn concentration and pH of the soil solution. At harvest, the mean mycorrhizal infection rate of inoculated plants ranged from 29% to 34% of total root length and was little affected by Zn application. Root and shoot yields were not affected by mycorrhizal infection. Plant Zn concentration and uptake were lower in mycorrhizal plants than non-mycorrhizal controls, and this effect was more pronounced with increasing Zn application rate to the soil. Soil solution Zn concentrations were lower and pH values were higher in mycorrhizal treatments than non-mycorrhizal controls and the mycorrhiza effect was more pronounced at higher Zn application rates. The protective effect of mycorrhiza against plant Zn uptake may have been associated with changes in Zn solubility mediated by changes in the soil solution pH, or by immobilisation of Zn in the extraradical mycelium.

Protective effect of TiF(4) solutions with different concentrations and pH on development of erosion-like lesions.

PubMed

Hove, L H; Holme, B; Stenhagen, K R; Tveit, A B

2011-01-01

To evaluate how concentration and pH of TiF(4) influence the erosion-protective effect. Specimens were treated with a TiF(4) solution: (1) 0.5 M F, pH 1.2, (2) 0.05 M F, pH 2.1, (3) 0.5 M F, pH 2.1, or (4) 0.05 M F, pH 1.2; then, they were exposed to HCl. After 2 min, the proportions of the area covered with the coating were 93, 71, 17 and 0% in groups 1-4. When present, the coating seemed to protect the surface. After 6 min, a coating could only be seen in group 1 (43%). Reducing the concentration of TiF(4) and increasing the pH of the solution decreased the protective effect. 2011 S. Karger AG, Basel.

Enhanced water-solubility and antibacterial activity of novel chitosan derivatives modified with quaternary phosphonium salt.

PubMed

Zhu, Dan; Cheng, Honghao; Li, Jianna; Zhang, Wenwen; Shen, Yuanyuan; Chen, Shaojun; Ge, Zaochuan; Chen, Shiguo

2016-04-01

Chitosan (CS) has been widely recognized as an important biomaterial due to its good antimicrobial activity, biocompatibility and biodegradability. However, CS is insoluble in water in neutral and alkaline aqueous solution due to the linear aggregation of chain molecules and the formation of crystallinity. This is one of the key factors that limit its practical applications. Therefore, improving the solubility of CS in neutral and alkaline aqueous solution is a primary research direction for biomedical applications. In this paper, a reactive antibacterial compound (4-(2,5-Dioxo-pyrrolidin-1-yloxycarbonyl)-benzyl)-triphenyl-phosphonium bromide (NHS-QPS) was synthesized for chemical modification of CS, and a series of novel polymeric antimicrobial agents, N-quaternary phosphonium chitosan derivatives (N-QPCSxy, x=1-2,y=1-4) were obtained. The water solubilities and antibacterial activities of N-QPCSxy against Escherichia coli and Staphylococcus aureus were evaluated compare to CS. The water solubility of N-QPCSxy was all better than that of CS at neutral pH aqueous solution, particularly, N-QPCS14 can be soluble in water over the pH range of 3 to 12. The antibacterial activities of CS derivatives were improved by introducing quaternary phosphonium salt, and antibacterial activity of N-QPCSxy increases with degree of substitution. Overall, N-QPCS14 represents a novel antibacterial polymer material with good antibacterial activity, waters solubility and low cytotoxicity. Copyright © 2015 Elsevier B.V. All rights reserved.

A fuel-cell-assisted iron redox process for simultaneous sulfur recovery and electricity production from synthetic sulfide wastewater.

PubMed

Zhai, Lin-Feng; Song, Wei; Tong, Zhong-Hua; Sun, Min

2012-12-01

Sulfide present in wastewaters and waste gases should be removed due to its toxicity, corrosivity, and malodorous property. Development of effective, stable, and feasible methods for sulfur recovery from sulfide attains a double objective of waste minimization and resource recovery. Here we report a novel fuel-cell-assisted iron redox (FC-IR) process for simultaneously recovering sulfur and electricity from synthetic sulfide wastewater. The FC-IR system consists of an oxidizing reactor where sulfide is oxidized to elemental sulfur by Fe(III), and a fuel cell where Fe(III) is regenerated from Fe(II) concomitantly with electricity producing. The oxidation of sulfide by Fe(III) is significantly dependent on solution pH. Increasing the pH from 0.88 to 1.96 accelerates the oxidation of sulfide, however, lowers the purity of the produced elemental sulfur. The performance of fuel cell is also a strong function of solution pH. Fe(II) is completely oxidized to Fe(III) when the fuel cell is operated at a pH above 6.0, whereas only partially oxidized below pH 6.0. At pH 6.0, the highest columbic efficiency of 75.7% is achieved and electricity production maintains for the longest time of 106 h. Coupling operation of the FC-IR system obtains sulfide removal efficiency of 99.90%, sulfur recovery efficiency of 78.6 ± 8.3%, and columbic efficiency of 58.6 ± 1.6%, respectively. These results suggest that the FC-IR process is a promising tool to recover sulfur and energy from sulfide. Copyright © 2012 Elsevier B.V. All rights reserved.

Controlling the Mesostructure Formation within the Shell of Novel Cubic/Hexagonal Phase Cetyltrimethylammonium Bromide-Poly(acrylamide-acrylic acid) Capsules for pH Stimulated Release.

PubMed

Tangso, Kristian J; Patel, Hetika; Lindberg, Seth; Hartley, Patrick G; Knott, Robert; Spicer, Patrick T; Boyd, Ben J

2015-11-11

The self-assembly of ordered structures in mixtures of oppositely charged surfactant and polymer systems has been exploited in various cleaning and pharmaceutical applications and continue to attract much interest since their discovery in the late twentieth century. The ability to control the electrostatic and hydrophobic interactions that dictate the formation of liquid crystalline phases in these systems is advantageous in manipulation of structure and rendering them responsive to external stimuli. Nanostructured capsules comprised of the cationic surfactant, cetyltrimethylammonium bromide (CTAB), and the diblock copolymer poly(acrylamide-acrylic acid) (PAAm-AA) were prepared to assess their potential as pH responsive nanomaterials. Crossed-polarizing light microscopy (CPLM) and small-angle X-ray scattering (SAXS) identified coexisting Pm3n cubic and hexagonal phases at the surfactant-polymer interface. The hydrophobic and electrostatic interactions between the oppositely charged components were studied by varying temperature and solution pH, respectively, and were found to influence the liquid crystalline nanostructure formed. The lattice parameter of the mesophases and the fraction of cubic phase in the system decreased upon heating. Acidic conditions resulted in the loss of the highly ordered structures due to protonation of the carboxylic acid group, and subsequent reduction of attractive forces previously present between the oppositely charged molecules. The rate of release of the model hydrophilic drug, Rhodamine B (RhB), from nanostructured macro-sized capsules significantly increased when the pH of the solution was adjusted from pH 7 to pH 2. This allowed for immediate release of the compound of interest "on demand", opening new options for structured materials with increased functionality over typical layer-by-layer capsules.

Improving alachlor biodegradability by ferrate oxidation.

PubMed

Zhu, Jian-Hang; Yan, Xi-Luan; Liu, Ye; Zhang, Bao

2006-07-31

Alachlor can be recalcitrant when present at high concentrations in wastewater. Ferrate oxidation was used as a pretreatment to improve its biodegradability and was evaluated by monitoring alachlor elimination and removal of COD(Cr) (chemical oxygen demand determined by potassium dichromate) during the oxidation process up to a value compatible with biological treatment. Ferrate oxidation resulted in elimination of alachlor followed by degradation of its intermediates. High pH suppressed alachlor removal and COD(Cr) removal due to the low redox potential of ferrate ions. Although alachlor can be totally eliminated within 10 min under optimized conditions (alachlor, 40 mg l(-1); ferrate:alachlor molar ratio, 2; and pH 7.0), its complete mineralization cannot be achieved by ferrate oxidation alone. Alachlor solution treated by ferrate for 10 min inhibited an up-flow biotreatment with activated sludge. The biodegradability of ferrate-pretreated solution improved when the treatment was increased to 20 min, at the point of which BOD(5)/COD(Cr) ratio of the treated solution was increased to 0.87 from 0.35 after 10 min treatment. Under optimized conditions, ferrate oxidation for 20 min resulted in total elimination of alachlor, partial removal of COD(Cr) and the ferrate-treated solution could be effectively treated by the up-flow activated sludge process.

High-sensitivity pH sensor using separative extended-gate field-effect transistors with single-walled carbon-nanotube networks

NASA Astrophysics Data System (ADS)

Pyo, Ju-Young; Cho, Won-Ju

2018-04-01

We fabricate high-sensitivity pH sensors using single-walled carbon-nanotube (SWCNT) network thin-film transistors (TFTs). The sensing and transducer parts of the pH sensor are composed of separative extended-sensing gates (ESGs) with SnO2 ion-sensitive membranes and double-gate structure TFTs with thin SWCNT network channels of ∼1 nm and AlO x top-gate insulators formed by the solution-deposition method. To prevent thermal process-induced damages on the SWCNT channel layer due to the post-deposition annealing process and improve the electrical characteristics of the SWCNT-TFTs, microwave irradiation is applied at low temperatures. As a result, a pH sensitivity of 7.6 V/pH, far beyond the Nernst limit, is obtained owing to the capacitive coupling effect between the top- and bottom-gate insulators of the SWCNT-TFTs. Therefore, double-gate structure SWCNT-TFTs with separated ESGs are expected to be highly beneficial for high-sensitivity disposable biosensor applications.

Predicting nitrogen and acidity effects on long-term dynamics of dissolved organic matter.

PubMed

Rowe, E C; Tipping, E; Posch, M; Oulehle, F; Cooper, D M; Jones, T G; Burden, A; Hall, J; Evans, C D

2014-01-01

Increases in dissolved organic carbon (DOC) fluxes may relate to changes in sulphur and nitrogen pollution. We integrated existing models of vegetation growth and soil organic matter turnover, acid-base dynamics, and organic matter mobility, to form the 'MADOC' model. After calibrating parameters governing interactions between pH and DOC dissolution using control treatments on two field experiments, MADOC reproduced responses of pH and DOC to additions of acidifying and alkalising solutions. Long-term trends in a range of acid waters were also reproduced. The model suggests that the sustained nature of observed DOC increases can best be explained by a continuously replenishing potentially-dissolved carbon pool, rather than dissolution of a large accumulated store. The simulations informed the development of hypotheses that: DOC increase is related to plant productivity increase as well as to pH change; DOC increases due to nitrogen pollution will become evident, and be sustained, after soil pH has stabilised. Copyright © 2013 Elsevier Ltd. All rights reserved.

Ion leaching and soil solution acidification in a vadose zone under soil treated with sewage sludge for agriculture.

PubMed

Borba, Ricardo Perobelli; Ribeirinho, Victor Sanches; de Camargo, Otávio Antonio; de Andrade, Cristiano Alberto; Kira, Carmen Silvia; Coscione, Aline Reneé

2018-02-01

In this study, we performed monitoring of the soil solution (SS) over 10 years on a loamy/clayey-textured Dark Red Dystroferric Oxisol that received sewage sludge for agricultural purposes. The SS was obtained by lysimeters installed along the walls of a well at 1 m, 2 m, 3 m, 4 m and 5 m in depth. The major ions found in the SS were NO 3 - , SO 4 2- , Cl - , Ca 2+ , Mg 2+ , Al 3+ , Pb 2+ , Cd 2+ and Zn 2+ , and the pH level ranged from 4 to 6.5 along the profile. Throughout the first three years of monitoring, the pH to a 3-m depth became more acidic, and in the last year, this trend reached 5 m. At the 5-m depth, the pH decreased from 6.5 to 4.5 from the first to the last monitoring. The SS acidification was provoked by both nitrite oxidation and ion leaching. The leaching of H + or the possible ion exchange/desorption of H + due to the leached cations (Ca 2+ and Mg 2+ ) at the 4-m and 5-m depth caused the pH decrease. The ionic strength (IS) of the solution controlled the ion leaching. The sludge application increased the IS to 3 m, increasing the density of the soil charges and its ability to absorb ions. After the sludge application was completed, there was a decrease in IS of the SS as well as a decrease in ion absorption and retention abilities, which promoted leaching to greater depths. During the entire monitoring process, NO 3 - , Cd and Pb remained above the potability limit. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sorption of vanadium (V) onto natural soil colloids under various solution pH and ionic strength conditions.

PubMed

Luo, Xiuhua; Yu, Lin; Wang, Changzhao; Yin, Xianqiang; Mosa, Ahmed; Lv, Jialong; Sun, Huimin

2017-02-01

Batch sorption kinetics and isothermal characteristics of V(V) were investigated on three natural soil colloids (manual loessial soil colloid (MSC), aeolian sandy soil colloid (ASC), and cultivated loessial soil colloid (CSC)) under various solution pH and ionic strength (IS) conditions. Colloids were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), and fourier transform infrared spectroscopy (FTIR). AFM micrographs showed CSC with an aggregated shape with larger particle diameter as compared with ASC and MSC. XRD spectra revealed the presence of different minerals in natural soil colloids including biotite, kaolinite, calcite and quartz, which might contribute to sorption process. The sorption ability decreased with increase of colloidal particle size. The sorption was mainly attributed to complexation by active carboxylate and alcohol groups of colloidal components. Sorption kinetics and isotherms of V(V) onto natural soil colloids were best fitted with Pseudo-second-order and Freundlich models. Langmuir model indicated that sorption capacity of MSC and ASC was comparable (285.7 and 238.1 mg g -1 ); however, CSC exhibited the lowest sorption capacity (41.5 mg g -1 ) due to its larger particle diameter and aggregated shape. The maximum V(V) sorption capacity reached plateau values at a solution pH ranged between 5.0 and 9.0 for MSC and ASC, and 6.0-8.0 for CSC. Sorption capacity of V(V) onto natural soil colloids decreased with increasing IS. Based on result of this study we can conclude that sorption of V(V) onto natural soil colloids is pH- and IS-dependent. These findings provide insights on the remediation of vanadium-contaminated soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

Method for removing metals from a cleaning solution

DOEpatents

Deacon, Lewis E.

2002-01-01

A method for removing accumulated metals from a cleaning solution is provided. After removal of the metals, the cleaning solution can be discharged or recycled. The process manipulates the pH levels of the solution as a means of precipitating solids. Preferably a dual phase separation at two different pH levels is utilized.

The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles.

PubMed

Vitali, Victoria; Sutka, Moira; Amodeo, Gabriela; Chara, Osvaldo; Ozu, Marcelo

2016-01-01

Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient ( P f ) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, P f determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast P f . We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites ( P f / P s ), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements, which very likely involve considerable cell volume changes within seconds to hours.

The Water to Solute Permeability Ratio Governs the Osmotic Volume Dynamics in Beetroot Vacuoles

PubMed Central

Vitali, Victoria; Sutka, Moira; Amodeo, Gabriela; Chara, Osvaldo; Ozu, Marcelo

2016-01-01

Plant cell vacuoles occupy up to 90% of the cell volume and, beyond their physiological function, are constantly subjected to water and solute exchange. The osmotic flow and vacuole volume dynamics relies on the vacuole membrane -the tonoplast- and its capacity to regulate its permeability to both water and solutes. The osmotic permeability coefficient (Pf) is the parameter that better characterizes the water transport when submitted to an osmotic gradient. Usually, Pf determinations are made in vitro from the initial rate of volume change, when a fast (almost instantaneous) osmolality change occurs. When aquaporins are present, it is accepted that initial volume changes are only due to water movements. However, in living cells osmotic changes are not necessarily abrupt but gradually imposed. Under these conditions, water flux might not be the only relevant driving force shaping the vacuole volume response. In this study, we quantitatively investigated volume dynamics of isolated Beta vulgaris root vacuoles under progressively applied osmotic gradients at different pH, a condition that modifies the tonoplast Pf. We followed the vacuole volume changes while simultaneously determining the external osmolality time-courses and analyzing these data with mathematical modeling. Our findings indicate that vacuole volume changes, under progressively applied osmotic gradients, would not depend on the membrane elastic properties, nor on the non-osmotic volume of the vacuole, but on water and solute fluxes across the tonoplast. We found that the volume of the vacuole at the steady state is determined by the ratio of water to solute permeabilites (Pf/Ps), which in turn is ruled by pH. The dependence of the permeability ratio on pH can be interpreted in terms of the degree of aquaporin inhibition and the consequently solute transport modulation. This is relevant in many plant organs such as root, leaves, cotyledons, or stems that perform extensive rhythmic growth movements, which very likely involve considerable cell volume changes within seconds to hours. PMID:27695468

Atmospheric Pressure Plasma Jet Treatment of Poly-ε-caprolactone Polymer Solutions To Improve Electrospinning.

PubMed

Grande, Silvia; Van Guyse, Joachim; Nikiforov, Anton Y; Onyshchenko, Iuliia; Asadian, Mahtab; Morent, Rino; Hoogenboom, Richard; De Geyter, Nathalie

2017-09-27

An atmospheric pressure plasma jet (APPJ) specifically designed for liquid treatment has been used in this work to improve the electrospinnability of a 5 w/v % solution of poly-ε-caprolactone (PCL) in a mixture of chloroform and N,N-dimethylformamide. Untreated PCL solutions were found to result in nonuniform fibers containing a large number of beads, whereas plasma-treated solutions (exposure time of 2-5 min) enabled the generation of beadless, uniform nanofibers with an average diameter of 450 nm. This enhanced electrospinnability was found to be mainly due to the highly increased conductivity of the plasma-modified PCL solutions. Consequently, more stretching of the polymer jet occurred during electrospinning, leading to the generation of bead-free fibers. Plasma treatment also results in an increased viscosity and decreased pH values. To explain these observed changes, optical emission spectroscopy (OES) has been used to examine the excited species present in the APPJ in contact with the PCL solution. This study revealed that the peaks attributed to H, CH, CH 2 , and C 2 species could be responsible for the degradation of solvent molecules and/or PCL structures during the plasma treatment. Size exclusion chromatography and X-ray photoelectron spectroscopy results showed that the molecular weight and the chemical composition of PCL were not significantly affected by the APPJ treatment. Plasma exposure mainly results in the degradation of the solvent molecules instead of modifying the PCL macromolecules, preserving the original polymer as much as possible. A hypothesis for the observed macroscopic changes in viscosity and pH values could be the generation of new chemical species such as HCl and/or HNO 3 . These species are characterized by their high conductivity, low pH values, and strong polarity and could enhance the solvent quality for PCL, leading to the expansion of the polymer coil, which could in turn explain the observed enhanced viscosity after plasma modification.

Aggregation and metal-complexation behaviour of THPP porphyrin in ethanol/water solutions as function of pH

NASA Astrophysics Data System (ADS)

Zannotti, Marco; Giovannetti, Rita; Minofar, Babak; Řeha, David; Plačková, Lydie; D'Amato, Chiara A.; Rommozzi, Elena; Dudko, Hanna V.; Kari, Nuerguli; Minicucci, Marco

2018-03-01

The effect of pH change on 5,10,15,20-Tetrakis(4-hydroxyphenyl)-21H,23H-porphine (THPP) with its aggregation as function of water-ethanol mixture was studied with UV-vis, fluorescence, Raman and computational analysis. In neutral pH, THPP was present as free-base and, increasing the water amount, aggregation occurred with the formation of H- and J-aggregates. The aggregation constant and the concentration of dimers were calculated, other information about the dimer aggregation were evaluated by computational study. In acidic pH, by the insertions of two hydrogens in the porphyrin rings, the porphyrin changed its geometry with a ring deformation confirmed by red-shifted spectrum and quenching in fluorescence; at this low pH, increasing the water amount, the acidic form (THPPH2)2 + resulted more stable due to a polar environment with stronger interaction by hydrogen bonding. In basic pH, reached by NH4OH, THPP porphyrin was able to react with alkali metals in order to form sitting-atop complex (M2THPP) confirmed by the typical absorption spectrum of metallo-porphyrin, Raman spectroscopy and by computational analysis.

Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids.

PubMed

Czarniak, Petra; Boddy, Michael; Sunderland, Bruce; Hughes, Jeff D

2016-01-01

The purpose of this study was to evaluate the chemical stability of Lincocin(®) (lincomycin hydrochloride) in commonly used intravenous fluids at room temperature (25°C), at accelerated-degradation temperatures and in selected buffer solutions. The stability of Lincocin(®) injection (containing lincomycin 600 mg/2 mL as the hydrochloride) stored at 25°C±0.1°C in sodium lactate (Hartmann's), 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin(®) in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined. Lincomycin hydrochloride w as found to maintain its shelf life at 25°C in sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days), and was least stable at pH 2 (calculated shelf life of 0.38 days). Lincocin(®) injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability.

pH- and thermo-responsive microcontainers as potential drug delivery systems: Morphological characteristic, release and cytotoxicity studies.

PubMed

Efthimiadou, Eleni K; Tapeinos, Christos; Tziveleka, Leto-Aikaterini; Boukos, Nikos; Kordas, George

2014-04-01

Polymeric pH- and thermo-sensitive microcontainers (MCs) were developed as a potential drug delivery system for cancer therapy. It is well known that cancer cells exhibit notable characteristics such as acidic pH due to glycolytic cycle and higher temperature due to their higher proliferation rate. Based on these characteristics, we constructed a dual pH- and thermo-sensitive material for specific drug release on the pathological tissue. The MC's fabrication is based on a two-step procedure, in which, the first step involves the core synthesis and the second one is related to the shell formation. The core consists of poly(methyl methacrylate (PMMA), while the shell consists of PMMA, poly(isopropylacrylamide), poly(acrylic acid) and poly(divinylbenzene). Three different types of MCs were synthesized based on the seed polymerization method. The synthesized MCs were characterized structurally by Fourier transform infrared and morphologically by scanning electron microscopy. Dynamic light scattering was also used to study their behavior in aqueous solution under different pH and temperature conditions. For the loading and release study, the anthracycline drug daunorubicin (DNR) was used as a model drug, and its release properties were evaluated under different pH and thermo-conditions. Cytotoxicity studies were also carried out against MCF-7 breast cancer and 3T3 mouse embryonic fibroblast cells. According to our results, the synthesized microcontainers present desired pH and thermo behavior and can be applied in drug delivery systems. It is worth mentioning that the synthesized microcontainers which incorporated the drug DNR exhibit higher toxicity than the free drug. Copyright © 2014 Elsevier B.V. All rights reserved.

Electrodeionization method

DOEpatents

Lin, YuPo J.; Hestekin, Jamie; Arora, Michelle; St. Martin, Edward J.

2004-09-28

An electrodeionization method for continuously producing and or separating and/or concentrating ionizable organics present in dilute concentrations in an ionic solution while controlling the pH to within one to one-half pH unit method for continuously producing and or separating and/or concentrating ionizable organics present in dilute concentrations in an ionic solution while controlling the pH to within one to one-half pH unit.

In vitro effects of bicarbonate and bicarbonate-lactate buffered peritoneal dialysis solutions on mesothelial and neutrophil function.

PubMed

Topley, N; Kaur, D; Petersen, M M; Jörres, A; Williams, J D; Faict, D; Holmes, C J

1996-02-01

The inclusion of bicarbonate in the formulation of peritoneal dialysis solutions may avoid the in vitro impairment of certain cell functions seen with acidic lactate-based fluids. The supranormal physiological levels of HCO3- and PCO2 inherent in such formulations may, however, not be biocompatible. This study compared the in vitro biocompatibility of a pH 5.2 lactate-based formulation with formulations containing either 40 mM lactate at pH 7.4, 38 mM HCO3- at pH 6.8 (PCO2 at approximately 240 mm Hg) or 7.4 (PCO2 at approximately 60 mm Hg), and 25 mM HCO3- plus 15 mM lactate at pH 6.8 (PCO2 at approximately 160 mm Hg) or 7.4 (PCO2 at approximately 40 mm Hg). Significant release of lactate dehydrogenase or decreases in ATP content by human peritoneal mesothelial cells (HPMC) and human peripheral polymorphonuclear leukocytes (PMN) after a 30-min exposure to each test solution was only seen with the pH 5.2 lactate-based fluid. The ATP content of HPMC exposed to this fluid returned to control levels after 30 min of recovery in M199 control medium but showed a trend toward decreasing ATP content at 240 min. Similarly, interleukin (IL)-1 beta-induced IL-6 synthesis by HPMC was also only significantly reduced by the pH 5.2 lactate solution. PMN chemiluminescence was unaffected by 30-min exposure to all test solutions except for the pH 5.2 lactate formulation. Staphylococcus epidermidis phagocytosis was reduced to between 46 to 57% of control with all test solutions except the pH 5.2 lactate solution, which further suppressed the chemiluminescence response to 17% of control. These data suggest that short exposure to supranormal physiological levels of HCO3- and PCO2 does not impair HPMC or PMN viability and function. Furthermore, neutral pH lactate-containing solutions show equivalent biocompatibility to bicarbonate-based ones.

Control of continuous phase PH using visible light to activate PH-dependent fibers and gels in a controlled and reversible manner

NASA Astrophysics Data System (ADS)

Zirino, Albert

1994-08-01

A transparent polyelectrolyte fiber or gel, such as crosslinked polyacrylic acid, which contracts and expands upon the addition of an acid or base to an aqueous medium solution, is placed in the same solution with a pH dependent dye, a colored photochromatic indicator dye. The dye preferably has a pAa value that is the same as the pH at a null contraction point of the fiber. By irradiating the solution with light of a wavelength of the absorption band of either the acid or base form of the dye, the solution pH is made to change, and the fiber is made to expand or contract, depending upon the wavelength. Thus, light energy is readily converted to work energy and may be used to power a pump, for example or an artificial muscle can be powered via an optical fiber.

High-Pressure-High-Temperature Processing Reduces Maillard Reaction and Viscosity in Whey Protein-Sugar Solutions.

PubMed

Avila Ruiz, Geraldine; Xi, Bingyan; Minor, Marcel; Sala, Guido; van Boekel, Martinus; Fogliano, Vincenzo; Stieger, Markus

2016-09-28

The aim of the study was to determine the influence of pressure in high-pressure-high-temperature (HPHT) processing on Maillard reactions and protein aggregation of whey protein-sugar solutions. Solutions of whey protein isolate containing either glucose or trehalose at pH 6, 7, and 9 were treated by HPHT processing or conventional high-temperature (HT) treatments. Browning was reduced, and early and advanced Maillard reactions were retarded under HPHT processing at all pH values compared to HT treatment. HPHT induced a larger pH drop than HT treatments, especially at pH 9, which was not associated with Maillard reactions. After HPHT processing at pH 7, protein aggregation and viscosity of whey protein isolate-glucose/trehalose solutions remained unchanged. It was concluded that HPHT processing can potentially improve the quality of protein-sugar-containing foods, for which browning and high viscosities are undesired, such as high-protein beverages.

Effect of pH of spray solution on the electrical properties of cadmium oxide thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hodlur, R. M.; Gunnagol, Raghu M.; Rabinal, M. K., E-mail: mkrabinal@yahoo.com

2015-06-24

Highly conducting transparent cadmium oxide thin films were prepared by conventional spray pyrolysis technique on glass at 375 °C substrate temperature. The pH of the spray solution was varied by adding ammonia/hydrochloric acid in the spray solution. The XRD pattern showed cubic phase. A lowest resistivity of 9.9 × 10{sup −4} Ω cm (with carrier concentration (n) = 5.1 × 10{sup 20} cm{sup −3}, mobility (µ)=12.4 cm{sup 2}/Vs) is observed for pH ∼12. The resistivity is tuned almost by three orders of magnitude by controlling the bath pH with optical transmittance more than 70 %. Thus, without any doping, the electricalmore » conductivity of CdO films could be easily tuned by simply varying the pH of spray solution without compromising the transparency and keeping the other deposition parameters fixed.« less

Carbonic anhydrase inhibitors modify intracellular pH transients and contractions of rat middle cerebral arteries during CO2/HCO3- fluctuations.

PubMed

Rasmussen, Jacob K; Boedtkjer, Ebbe

2018-03-01

The CO 2 /HCO 3 - buffer minimizes pH changes in response to acid-base loads, HCO 3 - provides substrate for Na + ,HCO 3 - -cotransporters and Cl - /HCO 3 - -exchangers, and H + and HCO 3 - modify vasomotor responses during acid-base disturbances. We show here that rat middle cerebral arteries express cytosolic, mitochondrial, extracellular, and secreted carbonic anhydrase isoforms that catalyze equilibration of the CO 2 /HCO 3 - buffer. Switching from CO 2 /HCO 3 - -free to CO 2 /HCO 3 - -containing extracellular solution results in initial intracellular acidification due to hydration of CO 2 followed by gradual alkalinization due to cellular HCO 3 - uptake. Carbonic anhydrase inhibition decelerates the initial acidification and attenuates the associated transient vasoconstriction without affecting intracellular pH or artery tone at steady-state. Na + ,HCO 3 - -cotransport and Na + /H + -exchange activity after NH 4 + -prepulse-induced intracellular acidification are unaffected by carbonic anhydrase inhibition. Extracellular surface pH transients induced by transmembrane NH 3 flux are evident under CO 2 /HCO 3 - -free conditions but absent when the buffer capacity and apparent H + mobility increase in the presence of CO 2 /HCO 3 - even after the inhibition of carbonic anhydrases. We conclude that (a) intracellular carbonic anhydrase activity accentuates pH transients and vasoconstriction in response to acute elevations of pCO 2 , (b) CO 2 /HCO 3 - minimizes extracellular surface pH transients without requiring carbonic anhydrase activity, and (c) carbonic anhydrases are not rate limiting for acid-base transport across cell membranes during recovery from intracellular acidification.

Solving general gauge theories on inner product spaces

NASA Astrophysics Data System (ADS)

Batalin, Igor; Marnelius, Robert

1995-02-01

By means of a generalized quartet mechanism we show in a model independent way that a BRST quantization on an inner product space leads to physical states of the form ph> = exp [ Q, ψ]ph> 0 where Q is the nilpotent BRST operator, ψ a hermitian fermionic gauge-fixing operator, and ph> o BRST invariant states determined by a hermitian set of BRST doublets in involution. ph> 0 does not belong to an inner product space although ph> does. Since the BRST quartets are split into two sets of hermitian BRST doublets there are two choices for ph> 0 and the corresponding ψ. When applied to general, both irreducible and reducible, gauge theories of arbitrary rank within the BFV formulation we find that ph> 0 are trivial BRST invariant states which only depend on the matter variables for one set of solutions, and for the other set ph> 0 are solutions of a Dirac quantization. This generalizes previous Lie group solutions obtained by means of a bigrading.

Hydrogen production by sodium borohydride in NaOH aqueous solution

NASA Astrophysics Data System (ADS)

Wang, Q.; Zhang, L. F.; Zhao, Z. G.

2018-01-01

The kinetics of hydrolysis reaction of NaBH4 in NaOH aqueous solution is studied. The influence of pH of the NaOH aqueous solution on the rate of hydrogen production and the hydrogen production efficiency are studied for the hydrolysis reaction of NaBH4. The results show that the activation energy of hydrolysis reaction of NaBH4 increased with the increase of the initial pH of NaOH aqueous solution.With the increasing of the initial pH of NaOH aqueous solution, the rate of hydrogen production and hydrogen production efficiency of NaBH4 hydrolysis decrease.

Investigation of the adsorption mechanism of a peptide in reversed phase liquid chromatography, from pH controlled and uncontrolled solutions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gritti, Fabrice; Guiochon, Georges A

2009-01-01

The single-component equilibrium adsorption of the tripeptide Leucyl-Leucyl-Leucine (LLL) on a high-efficiency Jupiter Proteo column (C{sub 12}) was investigated experimentally and modeled theoretically. The experimental equilibrium isotherms of LLL for adsorption on a C{sub 12} packing material from an aqueous solution of methanol (48%) and trifluoroacetic acid (0.1%) were measured by frontal analysis (FA). The FA measurements were done with two solutions, one in which the pH was controlled, the other in which it was not. Two solutions of LLL in the mobile phase were prepared (4.3 and 5.4 g/L) and their pH measured (2.94 and 2.88), respectively. The firstmore » solution was titrated with TFA to match the pH of the mobile phase (2.03), so its pH was controlled. The pH of the other solution was left uncontrolled. In both cases the isotherms could be modeled by a bi-Langmuir equation, a choice consistent with the bimodal affinity energy distribution (AED) obtained for LLL. The isotherm parameters derived from the inverse method (IM) of isotherm determination under controlled pH conditions (by fitting calculated profiles to experimental breakthrough profiles) are in a good agreement with those derived from the FA data. Under uncontrolled pH conditions, the application of IM suggests the coexistence of two different adsorption mechanisms. According to the isotherm parameters found by these three methods (FA, AED and IM), the C{sub 12}-bonded silica can adsorb around 500 and 70 g/L of LLL under controlled and uncontrolled pH conditions, respectively. The adsorption of LLL on the C{sub 12} material strongly depends on the pH of the mobile phase and on the quantity of TFA added, which plays the role of an ion-pairing agent.« less

Isolation of an oxomanganese(V) porphyrin intermediate in the reaction of a manganese(III) porphyrin complex and H2O2 in aqueous solution.

PubMed

Nam, Wonwoo; Kim, Inwoo; Lim, Mi Hee; Choi, Hye Jin; Lee, Je Seung; Jang, Ho G

2002-05-03

The reaction of [Mn(TF(4)TMAP)](CF(3)SO(3))(5) (TF(4)TMAP=meso-tetrakis(2,3,5,6-tetrafluoro-N,N,N-trimethyl-4-aniliniumyl)porphinato dianion) with H(2)O(2) (2 equiv) at pH 10.5 and 0 degrees C yielded an oxomanganese(V) porphyrin complex 1 in aqueous solution, whereas an oxomanganese(IV) porphyrin complex 2 was generated in the reactions of tert-alkyl hydroperoxides such as tert-butyl hydroperoxide and 2-methyl-1-phenyl-2-propyl hydroperoxide. Complex 1 was capable of epoxidizing olefins and exchanging its oxygen with H(2) (18)O, whereas 2 did not epoxidize olefins. From the reactions of [Mn(TF(4)TMAP)](5+) with various oxidants in the pH range 3-11, the O-O bond cleavage of hydroperoxides was found to be sensitive to the hydroperoxide substituent and the pH of the reaction solution. Whereas the O-O bond of hydroperoxides containing an electron-donating tert-alkyl group is cleaved homolytically, an electron-withdrawing substituent such as an acyl group in m-chloroperoxybenzoic acid (m-CPBA) facilitates O-O bond heterolysis. The mechanism of the O-O bond cleavage of H(2)O(2) depends on the pH of the reaction solution: O-O bond homolysis prevails at low pH and O-O bond heterolysis becomes a predominant pathway at high pH. The effect of pH on (18)O incorporation from H(2) (18)O into oxygenated products was examined over a wide pH range, by carrying out the epoxidation of carbamazepine (CBZ) with [Mn(TF(4)TMAP)](5+) and KHSO(5) in buffered H(2) (18)O solutions. A high proportion of (18)O was incorporated into the CBZ-10,11-oxide product at all pH values but this proportion was not affected significantly by the pH of the reaction solution.

Effects of pH and cation adsorption on colloidal stability of graphene oxide in aquatic environments

NASA Astrophysics Data System (ADS)

Terracciano, Amalia

The presented doctoral research aims to improve the current understanding of the chemistry of Graphene Oxide Nanoparticles (GONPs) in common water systems. The widespread demand and future use of this nanomaterial in a broad range of different applications (i.e. biomedical, electronic, environmental) will certainly lead to its release in the environment with consequent exposure of ecosystems to graphene oxide (GO) toxicity. The described scenario demand a careful investigation and deep understanding of the environmental behavior and fate of GONPs, especially in water systems. Therefore this study focused on the investigation the effects of pH some of the most common water electrolytes (monovalent and divalent) and on GO colloidal stability. The interactions between the selected ions and the GO functional groups was also studied. The mobility of GO in porous media was first studied through filtrations tests that determine influence of ionic strength (IS) and solution composition on GO mobility. The GONPs showed to be completely retained in the porous media in presence of 3.5 mM of CaCl2 and in tap water while no retention was found for 10 mM of NaCl solution. The results indicated significant impact of divalent cations on the mobility of GO. Serial experiments were performed to quantify the adsorption of several cations (Na+, Ca2+ and Ba2+) on GO. The divalent cations showed to be strongly adsorbed on the GO surface with increasing pH and cation concentrations, while no significant sodium adsorption was detected. Raman spectroscopy and XPS analysis also showed strong differences in the typical spectra of GO, before and after adsorption of Ca2+ and Ba2+ which suggest chemical bond formation with the GO functional groups. The aggregation regime and the colloidal stability of the GO suspension in presence of selected electrolytes (Na+, Mg2+, Ca2+ and Ba2+) as function of pH was also extensively studied. The zeta potential, which is index of the stability of a colloidal suspension, was found to became more negative for GO in NaCl solutions for solution pH from 4 to 10 which is due to increased deprotonation of carboxyl (-COOH) and hydroxyl (-COH) groups on GO. Values of the zeta potential higher than +/-30 indicated increase stability of the colloidal suspension; however in presence of Ca2+ in solution, the zeta potential of GONPs become less negative (>-10 mV) with formation of aggregates which can be attributed to increased Ca2+ adsorption, especially at high pH. The increase adsorption will neutralize the negative surface charge to reduce electrostatic repulsion and promote aggregation. The same trend was found in presence of Ba2+ in solution. The critical coagulation concentration (CCC) of GO also showed to be strongly affected by Ca2+ and pH. The CCC value of GO remained at about 48 mM NaCl with increasing pH from 4.4 to 7 while it dramatically decreased from about 1.7 to 0.3 mM in CaCl2 solution with increasing pH. The results of this study suggest that pH and divalent cations, especially Ca2+ could significantly affect the colloidal stability of GONPs and therefore influence their mobility in the environment. Moreover the interactions between Ca2+ and Ba2+ and the GO nanosheets showed to be particularly strong which suggest inner-sphere complexation formation. The findings obtained from this doctoral research will contribute in improving the understanding of the fate and transport of the GONPs in aquatic environments and to develop more suitable models to predict its behavior.

Geochemical behavior and dissolved species control in acid sand pit lakes, Sepetiba sedimentary basin, Rio de Janeiro, SE - Brazil

NASA Astrophysics Data System (ADS)

Marques, Eduardo D.; Sella, Sílvia M.; Bidone, Edison D.; Silva-Filho, Emmanoel V.

2010-12-01

This work shows the influence of pluvial waters on dissolved components and mineral equilibrium of four sand pit lakes, located in the Sepetiba sedimentary basin, SE Brazil. The sand mining activities promote sediment oxidation, lowering pH and increasing SO 4 contents. The relatively high acidity of these waters, similar to ore pit lakes environment and associated acid mine drainage, increases weathering rate, especially of silicate minerals, which produces high Al concentrations, the limiting factor for fish aquaculture. During the dry season, basic cations (Ca, Mg, K and Na), SiO 2 and Al show their higher values due to evapoconcentration and pH are buffered. In the beginning of the wet season, the dilution factor by rainwater increases SO 4 and decreases pH values. The aluminum monomeric forms (Al(OH) 2+ and Al(OH) 2+), the most toxic species for aquatic organisms, occur during the dry season, while AlSO 4+ species predominate during the wet season. Gibbsite, allophane, alunite and jurbanite are the reactive mineral phases indicated by PHREEQC modeling. During the dry season, hydroxialuminosilicate allophane is the main phase in equilibrium with the solution, while the sulphate salts alunite and jurbanite predominate in the rainy season due to the increasing of SO 4 values. Gibbsite is also in equilibrium with sand pit lakes waters, pointing out that hydrolysis reaction is a constant process in the system. Comparing to SiO 2, sulphate is the main Al retriever in the pit waters because the most samples (alunite and jurbanite) are in equilibrium with the solution in both seasons. This Al hydrochemical control allied to some precaution, like pH correction and fertilization of these waters, allows the conditions for fishpond culture. Equilibrium of the majority samples with kaolinite (Ca, Mg, Na diagrams) and primary minerals (K diagram) points to moderate weathering rate in sand pit sediments, which cannot be considered for the whole basin due to the anomalous acidification of the studied waters.

Adsorption and desorption of ammonium by maple wood biochar as a function of oxidation and pH.

PubMed

Wang, Bing; Lehmann, Johannes; Hanley, Kelly; Hestrin, Rachel; Enders, Akio

2015-11-01

The objective of this work was to investigate the retention mechanisms of ammonium in aqueous solution by using progressively oxidized maple wood biochar at different pH values. Hydrogen peroxide was used to oxidize the biochar to pH values ranging from 8.1 to 3.7, with one set being adjusted to a pH of 7 afterwards. Oxidizing the biochars at their lowered pH did not increase their ability to adsorb ammonium. However, neutralizing the oxygen-containing surface functional groups on oxidized biochar to pH 7 increased ammonia adsorption two to three-fold for biochars originally at pH 3.7-6, but did not change adsorption of biochars oxidized to pH 7 and above. The adsorption characteristics of ammonium are well described by the Freundlich equation. Adsorption was not fully reversible in water, and less than 27% ammonium was desorbed in water in two consecutive steps than previously adsorbed, for biochars with a pH below 7, irrespective of oxidation. Recovery using an extraction with 2M KCl increased from 34% to 99% of ammonium undesorbed by both preceding water extractions with increasing oxidation, largely irrespective of pH adjustment. Unrecovered ammonium in all extractions and residual biochar was negligible at high oxidation, but increased to 39% of initially adsorbed amounts at high pH, likely due to low amounts adsorbed and possible ammonia volatilization losses. Copyright © 2015 Elsevier Ltd. All rights reserved.

Complexing Agents and pH Influence on Chemical Durability of Type I Molded Glass Containers.

PubMed

Biavati, Alberto; Poncini, Michele; Ferrarini, Arianna; Favaro, Nicola; Scarpa, Martina; Vallotto, Marta

2017-01-01

Among the factors that affect the glass surface chemical durability, pH and complexing agents present in aqueous solution have the main role. Glass surface attack can be also related to the delamination issue causing glass particles' appearance in the pharmaceutical preparation. A few methods to check for glass containers delamination propensity and some control guidelines have been proposed. The present study emphasizes the possible synergy between a few complexing agents with pH on borosilicate glass chemical durability.Hydrolytic attack was performed in small-volume 23 mL type I glass containers autoclaved according to the European Pharmacopoeia or United States Pharmacopeia for 1 h at 121 °C, in order to enhance the chemical attack due to time, temperature, and the unfavorable surface/volume ratio. Solutions of 0.048 M or 0.024 M (M/L) of the acids citric, glutaric, acetic, EDTA (ethylenediaminetetraacetic acid), together with sodium phosphate with water for comparison, were used for the trials. The pH was adjusted ±0.05 units at fixed values 5.5, 6.6, 7, 7.4, 8, and 9 by LiOH diluted solution.Because silicon is the main glass network former, silicon release into the attack solutions was chosen as the main index of the glass surface attack and analysed by inductively coupled plasma atomic emission spectrophotometry. The work was completed by the analysis of the silicon release in the worst attack conditions of molded glass, soda lime type II glass, and tubing borosilicate glass vials to compare different glass compositions and forming technologies. Surface analysis by scanning electron microscopy was finally performed to check for the surface status after the worst chemical attack condition by citric acid. LAY ABSTRACT: Glass, like every packaging material, can have some usage limits, mainly in basic pH solutions. The issue of glass surface degradation particles that appear in vials (delamination) has forced a number of drug product recalls in recent years. To prevent such situations, pharmaceutical and biopharmaceutical manufacturers need to understand the reasons for accelerate surface glass corrosion mainly in the case of injectables.Some drugs can contain active components with known ability to corrode glass silica networks. Sometimes these ingredients are dissolved in an alkaline medium that dramatically increases the glass corrosion and potentially causes the issue. As this action is strongly affected by time and temperature, flaking may become visible only after a long storage time. The purpose of this investigation is to verify the borosilicate glass chemical durability during controlled conditions of time and temperature when in contact with testing solutions containing different complexing agents by varying the pH. Si concentration in the extract solution is taken as an index of glass dissolution during constant autoclaving conditions for 1 h at 121 °C, which simulates approximately five years of contact at room temperature.Acetate, citrate, ethylenediaminetetraacetic acid (EDTA), phosphate, and glutarate 0.048 M or 0.024 M solutions were used at increasing pH from 5.5 to 9.0. The chemical durability of two borosilicate tubing glass vials of different glass compositions were compared with the molded one in the worst attack conditions by citric acid. Even if no delamination issue has been experienced by this study in type I molded and tubing containers, the conclusions developed can provide pharmaceutical manufacturers with useful information to prevent glass delamination risk in their processes. © PDA, Inc. 2017.

Thermophysical properties of carboxylic and amino acid buffers at subzero temperatures: relevance to frozen state stabilization.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-06-02

Macromolecules and other thermolabile biologicals are often buffered and stored in frozen or dried (freeze-dried) state. Crystallization of buffer components in frozen aqueous solutions and the consequent pH shifts were studied in carboxylic (succinic, malic, citric, tartaric acid) and amino acid (glycine, histidine) buffers. Aqueous buffer solutions were cooled from room temperature (RT) to -25 °C and the pH of the solution was measured as a function of temperature. The thermal behavior of frozen solutions was investigated by differential scanning calorimetry (DSC), and the crystallized phases were identified by X-ray diffractometry (XRD). Based on the solubility of the neutral species of each buffer system over a range of temperatures, it was possible to estimate its degree of supersaturation at the subambient temperature of interest. This enabled us to predict its crystallization propensity in frozen systems. The experimental and the predicted rank orderings were in excellent agreement. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartrate systems, at initial pH < pK(a)(2), only the most acidic buffer component (neutral form) crystallized on cooling, causing an increase in the freeze-concentrate pH. In glycine buffer solutions, when the initial pH was ∼3 units < isoelectric pH (pI = 5.9), β-glycine crystallization caused a small decrease in pH, while a similar effect but in the opposite direction was observed when the initial pH was ∼3 units > pI. In the histidine buffer system, depending on the initial pH, either histidine or histidine HCl crystallized.

Solution and surface effects on plasma fibronectin structure

PubMed Central

1983-01-01

As assessed by electron microscopy, the reported shape of the plasma fibronectin molecule ranges from that of a compact particle to an elongated, rod-like structure. In this study, we evaluated the effects of solution and surface conditions on fibronectin shape. Freeze-dried, unstained human plasma fibronectin molecules deposited at pH 7.0-7.4 onto carbon films and examined by scanning transmission electron microscopy appeared relatively compact and pleiomorphic, with approximate average dimensions of 24 nm X 16 nm. Negatively stained molecules also had a similar shape but revealed greater detail in that we observed irregular, yarn-like structures. Glutaraldehyde-induced intramolecular cross-linking did not alter the appearance of plasma fibronectin. Molecules deposited at pH 2.8, pH 9.3, or after succinylation were less compact than those deposited at neutral pH. In contrast, fibronectin molecules sprayed onto mica surfaces at pH 7, rotary shadowed, and examined by transmission electron microscopy were elongated and nodular with a contour length of 120-130 nm. Sedimentation velocity experiments and electron microscopic observations indicate that fibronectin unfolds when it is succinylated, when the ionic strength is raised at pH 7, or when the pH is adjusted to 9.3 or 2.8. Greater unfolding is observed at pH 2.8 at low ionic strength (less than 0.01) compared with material at that pH in 0.15 M NaCl solution. We conclude that (a) the shape assumed by the fibronectin molecule can be strongly affected by solution conditions and by deposition onto certain surfaces; and that (b) the images of fibronectin seen by scanning transmission electron microscopy at neutral pH on carbon film are representative of molecules in physiologic solution. PMID:6417145

Individual and Co Transport Study of Titanium Dioxide NPs and Zinc Oxide NPs in Porous Media

PubMed Central

Kumari, Jyoti; Mathur, Ankita; Rajeshwari, A.; Venkatesan, Arthi; S, Satyavati; Pulimi, Mrudula; Chandrasekaran, Natarajan; Nagarajan, R.; Mukherjee, Amitava

2015-01-01

The impact of pH and ionic strength on the mobility (individual and co-transport) and deposition kinetics of TiO2 and ZnO NPs in porous media was systematically investigated in this study. Packed column experiments were performed over a series of environmentally relevant ionic strengths with both NaCl (0.1−10 mM) and CaCl2 (0.01–0.1mM) solutions and at pH 5, 7, and 9. The transport of TiO2 NPs at pH 5 was not significantly affected by ZnO NPs in solution. At pH 7, a decrease in TiO2 NP transport was noted with co-existence of ZnO NPs, while at pH 9 an increase in the transport was observed. At pH 5 and 7, the transport of ZnO NPs was decreased when TiO2 NPs was present in the solution, and at pH 9, an increase was noted. The breakthrough curves (BTC) were noted to be sensitive to the solution chemistries; the decrease in the breakthrough plateau with increasing ionic strength was observed under all examined pH (5, 7, and 9). The retention profiles were the inverse of the plateaus of BTCs, as expected from mass balance considerations. Overall, the results from this study suggest that solution chemistries (ionic strength and pH) are likely the key factors that govern the individual and co-transport behavior of TiO2 and ZnO NPs in sand. PMID:26252479

Minimizing back exchange in the hydrogen exchange-mass spectrometry experiment.

PubMed

Walters, Benjamin T; Ricciuti, Alec; Mayne, Leland; Englander, S Walter

2012-12-01

The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by 3-fold only reduced back exchange by ~2%, while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (<20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90% ± 5%.

Minimizing Back Exchange in the Hydrogen Exchange-Mass Spectrometry Experiment

NASA Astrophysics Data System (ADS)

Walters, Benjamin T.; Ricciuti, Alec; Mayne, Leland; Englander, S. Walter

2012-12-01

The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by 3-fold only reduced back exchange by ~2 %, while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (<20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90 % ± 5 %.

Influence of pH on the physical and electromagnetic properties of Mg–Mn ferrite synthesized by a solution combustion method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lwin, Nilar, E-mail: nilarlwin111@gmail.com; School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, 14300 Nibong Tebal, Penang; Othman, Radzali, E-mail: radzali@utem.edu.my

The synthesis of nano-crystalline Mg–Mn ferrites by a solution combustion method using citric acid and ammonia was investigated by varying the pH of the precursor solution, which played an important role in controlling the morphology of the synthesized powders. The phase formation, microstructure and electromagnetic properties were studied using X-ray diffraction, scanning electron microscopy, impedance analyzer and vibrating sample magnetometer. Single phase pure spinel Mg–Mn ferrite powders were obtained for all the samples at different pH (< 1, 3, 5, 7, 9). The results showed that an increase of pH improves the crystallinity of the Mg–Mn ferrite nanoparticles. The averagemore » grain size of sintered samples was found to decrease from 2 μm to 0.5 μm with increasing pH values from pH < 1 to pH 9, respectively. The dielectric constant of the samples with different pH is in the range of 7–12 from frequencies of 1 MHz to 1 GHz. The highest saturation magnetization (30.04 emu/g) was obtained for the sample with pH < 1. - Highlights: • Mg–Mn ferrites were synthesized by a solution combustion method with different pH. • Auto-combustion process resulted in the formation of single phase spinel ferrite. • An increase of pH improves the crystallinity of the Mg–Mn ferrite nanoparticles. • pH variation has influence on phase formation and morphology of the ferrite.« less

A new method for recovery of cellulose from lignocellulosic bio-waste: Pile processing.

PubMed

Tezcan, Erdem; Atıcı, Oya Galioğlu

2017-12-01

This paper presents a new delignification method (pile processing) for the recovery of cellulose from lignocellulosic bio-wastes, adapted from heap leaching technology in metallurgy. The method is based on the stacking of cellulosic materials in a pile, irrigation of the pile with aqueous reactive solution from the top, lignin and hemicellulose removal and enrichment of cellulose by the reactive solution while percolation occurs through the bottom of the pile, recirculating the reactive solution after adjusting several values such as chemical concentrations, and allow the system run until the desired time or cellulose purity. Laboratory scale systems were designed using fall leaves (FL) as lignocellulosic waste materials. The ideal condition for FL was noted as: 0.1g solid NaOH addition per gram of FL into the irrigating solution resulting in instant increase in pH to about 13.8, later allowing self-decrease in pH due to delignification over time down to 13.0, at which point another solid NaOH addition was performed. The new method achieved enrichment of cellulose from 30% to 81% and removal of 84% of the lignin that prevents industrial application of lignocellulosic bio-waste using total of 0.3g NaOH and 4ml of water per gram of FL at environmental temperature and pressure. While the stirring reactions used instead of pile processing required the same amount of NaOH, they needed at least 12ml of water and delignification was only 56.1%. Due to its high delignification performance using common and odorless chemicals and simple equipment in mild conditions, the pile processing method has great promise for the industrial evaluation of lignocellulosic bio-waste. Copyright © 2017 Elsevier Ltd. All rights reserved.

Structural characterization of nickel oxide/hydroxide nanosheets produced by CBD technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taşköprü, T., E-mail: ttaskopru@anadolu.edu.tr; Department of Physics, Çankırı Karatekin University, Çankırı 18100; Zor, M.

2015-10-15

Graphical abstract: SEM images of (a) as deposited β-Ni(OH)2 and (b) NiO samples deposited with pH 10 solution. The inset figures shows the absorbance spectra of (a) β-Ni(OH)2 and (b) NiO samples. - Highlights: • The formation of β-Ni(OH){sub 2} and NiO were confirmed with XRD, SEM, FT-IR and Raman. • Porous nickel oxide was synthesized after heat treatment of nickel hydroxide. • The increase in pH value changes the nanoflake structure to hexagonal nanosheet. • On increasing the pH from 8 to 11, the band gap decreases from 3.52 to 3.37 eV. - Abstract: Nickel hydroxide samples were depositedmore » onto glass substrates using Ni(NO{sub 3}){sub 2}·6H{sub 2}O and aqueous ammonia by chemical bath deposition technique. The influence of pH of solution was investigated by means of X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Raman spectroscopy, optical absorption and BET analysis. The as-deposited samples were identified as β-Ni(OH){sub 2}, were transformed into NiO after heat treatment in air at 500 °C for 2 h. Porous nickel oxide nanosheets are obtained by heating nickel hydroxide nanosheets. The optical transitions observed in the absorbance spectra below optical band gap is due to defects or Ni{sup 2+} vacancies in NiO samples. The band gap energy of NiO samples changes between 3.37 and 3.52 eV depending on the pH values.« less

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation.

PubMed

Liu, Xianli; Xu, Dong; Wu, Feng; Liao, Zhenhuan; Liu, Jiantong; Deng, Nansheng

2004-03-01

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals (*OH) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that *OH photoproduction increased from 1.80 to 2.74 microM by increasing the HA concentration from 10 to 40 mg L(-1) at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of *OH in the HA solution with Fe(III) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of *OH in HA solution with algae with or without Fe(III) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of *OH in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest *OH photoproduction at pH 4.0.

The removal of chloramphenicol from water through adsorption on activated carbon

NASA Astrophysics Data System (ADS)

Lach, Joanna; Ociepa-Kubicka, Agnieszka

2017-10-01

The presented research investigated the removal of chloramphenicol from water solutions on selected activated carbon available in three grades with different porous structure and surface chemical composition. Two models of adsorption kinetics were examined, i.e. the pseudo-first order and the pseudo-second order models. For all examined cases, the results of tests with higher value of coefficient R2 were described by the equation for pseudo-second order kinetics. The adsorption kinetics was also investigated on the activated carbons modified with ozone. The measurements were taken from the solutions with pH values of 2 and 7. Chloramphenicol was the most efficiently adsorbed on the activated carbon F-300 from the solutions with pH=7, and on the activated carbon ROW 08 Supra from the solutions with pH=2. The adsorption of this antibiotic was in the majority of cases higher from the solutions with pH=2 than pH=7. The modification of the activated carbons with ozone enhanced their adsorption capacities for chloramphenicol. The adsorption is influenced by the modification method of activated carbon (i.e. the duration of ozonation of the activated carbon solution and the solution temperature). The results were described with the Freundlich and Langmuir adsorption isotherm equations. Both models well described the obtained results (high R2 values).

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate.

PubMed

Sato, A C K; Perrechil, F A; Costa, A A S; Santana, R C; Cunha, R L

2015-09-01

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5mg/mL) and ferulic acid (5 and 10mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH3. At pH3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH5), larger droplet size (pH3, 5 and 7) and higher pseudoplasticity (pH5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase. Copyright © 2015 Elsevier Ltd. All rights reserved.

Probing pH difference between micellar solution and nanoscale water within common black film by fluorescent dye

NASA Astrophysics Data System (ADS)

Fu, Jingni; Zhang, Luning

2018-03-01

The protonation/deprotonation equilibrium of a fluorescent pH probe (carboxy-seminaphthorhodafluor-1, SNARF-1) within the nanoscale water layer confined in common black films (CBFs) has been studied. We find that SNARF-1 molecules feel a more acidic environment in CBFs than when they are in the bulk micellar solution, using the base/acid peak area ratio of the dye to indicate its microenvironment pH. Three surfactants are used to study the dependence of the pH drop versus charge: cationic (cetyltrimethylammonium bromide, CTAB), anionic (sodium dodecylsulphate, SDS) and nonionic (Triton X-100) species. The decrease of CBFs pH versus the pH of the micellar solution is the following: ΔpH ≈ 1.5 for CTAB (pH: 7.0-9.0), ΔpH ≈ 0.8 for SDS, and ΔpH ≈ 0.4 for Triton X-100. With the addition of electrolyte in CBFs, we observe large decrease the amplitude of the pH anomaly, thus suggesting an electrostatic origin of the pH change at nanoscale environment.

Effect of C(60) fullerene on the duplex formation of i-motif DNA with complementary DNA in solution.

PubMed

Jin, Kyeong Sik; Shin, Su Ryon; Ahn, Byungcheol; Jin, Sangwoo; Rho, Yecheol; Kim, Heesoo; Kim, Seon Jeong; Ree, Moonhor

2010-04-15

The structural effects of fullerene on i-motif DNA were investigated by characterizing the structures of fullerene-free and fullerene-bound i-motif DNA, in the presence of cDNA and in solutions of varying pH, using circular dichroism and synchrotron small-angle X-ray scattering. To facilitate a direct structural comparison between the i-motif and duplex structures in response to pH stimulus, we developed atomic scale structural models for the duplex and i-motif DNA structures, and for the C(60)/i-motif DNA hybrid associated with the cDNA strand, assuming that the DNA strands are present in an ideal right-handed helical conformation. We found that fullerene shifted the pH-induced conformational transition between the i-motif and the duplex structure, possibly due to the hydrophobic interactions between the terminal fullerenes and between the terminal fullerenes and an internal TAA loop in the DNA strand. The hybrid structure showed a dramatic reduction in cyclic hysteresis.

Biomimetic synthesis of silver nanoparticles and evaluation of their catalytic activity towards degradation of methyl orange

NASA Astrophysics Data System (ADS)

Manjari Mishra, Pravat; Bihari Pani, Khirod

2017-11-01

This paper described the significant effect of process variables like reductant concentrations, substrate concentration, reaction pH and reaction temperature on the size, morphology and yield of the silver nanoparticles (AgNPs) synthesized using aqueous leaf extract of a medicinal plant Momordica charantia (Bitter guard). By means of UV-vis spectroscopy, XRD analysis, TEM analysis and Fluorescence analysis, it is observed that the reaction solution containing 10-3 M of AgNO3 of pH 5.3  +  10 ml of aqueous leaf extract at normal room temperature, was optimum for synthesis of stable, polydisperse, predominantly spherical AgNPs with average size of 12.15 nm. FT-IR and TEM studies confirmed the stability of AgNPs was due to the capping of phytoconstituents present in the leaf extract. The aqueous solution of leaf extract containing AgNPs showed remarkable catalytic activity towards degradation of methyl orange (MO) in aqueous medium.

Transient bleaching of small PbS colloids. Influence of surface properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nenadovic, M.T.; Comor, M.I.; Vasic, V.

1990-08-09

Small PbS colloids with a particle diameter of 40 {angstrom} were prepared in aqueous solution, and their absorption spectra exhibit several maxima. Injection of electrons into these particles was achieved by using the pulse radiolysis technique. Excess electrons trapped on the surface lead to a blue shift in the absorption edge of colloids. The appearance of this shift depends critically on the method of colloid preparation. PbS and CdS colloids prepared at pH < 6 have long-lived bleaching, which disappears after several seconds. On the other hand, absorption bleaching does not appear after the addition of hydroxide ions to colloidalmore » solutions (pH > 8). The existence of a hydroxide ion on the particle surface most likely removes surface defects on which electrons are trapped. PbS colloids prepared in the presence of 3-mercapto-1,2-propanediol have an unstructured absorption spectrum, which is due to a wide particle size distribution (10-50 {angstrom}).« less

The coordination chemistry of the neutral tris-2-pyridyl silicon ligand [PhSi(6-Me-2-py)3].

PubMed

Plajer, Alex J; Colebatch, Annie L; Enders, Markus; García-Romero, Álvaro; Bond, Andrew D; García-Rodríguez, Raúl; Wright, Dominic S

2018-05-22

Difficulties in the preparation of neutral ligands of the type [RSi(2-py)3] (where 2-py is an unfunctionalised 2-pyridyl ring unit) have thwarted efforts to expand the coordination chemistry of ligands of this type. However, simply switching the pyridyl substituents to 6-methyl-pyridyl groups (6-Me-2-py) in the current paper has allowed smooth, high-yielding access to the [PhSi(6-Me-2-py)3] ligand (1), and the first exploration of its coordination chemistry with transition metals. The synthesis, single-crystal X-ray structures and solution dynamics of the new complexes [{PhSi(6-Me-2-py)3}CuCH3CN][PF6], [{PhSi(6-Me-2-py)3}CuCH3CN][CuCl2], [{PhSi(6-Me-2-py)3}FeCl2], [{PhSi(6-Me-2-py)3}Mo(CO)3] and [{PhSi(6-Me-2-py)3}CoCl2] are reported. The paramagnetic Fe2+ and Co2+ complexes show strongly shifted NMR resonances for the coordinated pyridyl units due to large Fermi-contact shifts. However, magnetic anisotropy also leads to considerable pseudo-contact shifts so that both contributions have to be included in the paramagnetic NMR analysis.

Biochemical enhancement of transdermal delivery with magainin peptide: modification of electrostatic interactions by changing pH.

PubMed

Kim, Yeu-Chun; Late, Sameer; Banga, Ajay K; Ludovice, Peter J; Prausnitz, Mark R

2008-10-01

Magainin is a naturally occurring, pore-forming peptide that has recently been shown to increase skin permeability. This study tested the hypothesis that electrostatic forces between magainin peptides and drugs mediate drug transport across the skin. Electrostatic interaction between positively charged magainin and a negatively charged model drug, fluorescein, was attractive at pH 7.4 and resulted in a 35-fold increase in delivery across human epidermis in vitro when formulated with 2% N-lauroylsarcosine in 50% ethanol. Increasing to pH 10 or 11 largely neutralized magainin's charge, which eliminated enhancement due to magainin. Shielding electrostatic interactions with 1-2M NaCl solution similarly eliminated enhancement. Showing the opposite dependence on pH, electrostatic interaction between magainin and a positively charged anti-nausea drug, granisetron, was largely neutralized at pH 10 and resulted in a 92-fold increase in transdermal delivery. Decreasing to pH 5 increased magainin's positive charge, which repelled granisetron and progressively decreased transdermal flux. Circular dichroism analysis, multi-photon microscopy, and FTIR spectroscopy showed no significant pH effect on magainin secondary structure, magainin deposition in stratum corneum, or stratum corneum lipid order, respectively. We conclude that magainin increases transdermal delivery by a mechanism involving electrostatic interaction between magainin peptides and drugs.

Biochemical enhancement of transdermal delivery with magainin peptide: Modification of electrostatic interactions by changing pH

PubMed Central

Kim, Yeu-Chun; Late, Sameer; Banga, Ajay K.; Ludovice, Peter J.; Prausnitz, Mark R.

2008-01-01

Magainin is a naturally occurring, pore-forming peptide that has recently been shown to increase skin permeability. This study tested the hypothesis that electrostatic forces between magainin peptides and drugs mediate drug transport across the skin. Electrostatic interaction between positively charged magainin and a negatively charged model drug, fluorescein, was attractive at pH 7.4 and resulted in a 35 fold increase in delivery across human epidermis in vitro when formulated with 2% N-lauroylsarcosine in 50% ethanol. Increasing to pH 10 or 11 largely neutralized magainin’s charge, which eliminated enhancement due to magainin. Shielding electrostatic interactions with 1–2 M NaCl solution similarly eliminated enhancement. Showing the opposite dependence on pH, electrostatic interaction between magainin and a positively charged anti-nausea drug, granisetron, was largely neutralized at pH 10 and resulted in a 59 fold increase in transdermal delivery. Decreasing to pH 5 increased magainin’s positive charge, which repelled granisetron and progressively decreased transdermal flux. Circular dichroism analysis, multi-photon microscopy, and FTIR spectroscopy showed no significant pH effect on magainin secondary structure, magainin deposition in stratum corneum, or stratum corneum lipid order, respectively. We conclude that magainin increases transdermal delivery by a mechanism involving electrostatic interaction between magainin peptides and drugs. PMID:18601987

Specific decrease in solution viscosity of antibodies by arginine for therapeutic formulations.

PubMed

Inoue, Naoto; Takai, Eisuke; Arakawa, Tsutomu; Shiraki, Kentaro

2014-06-02

Unacceptably high viscosity is observed in high protein concentration formulations due to extremely large therapeutic dose of antibodies and volume restriction of subcutaneous route of administration. Here, we show that a protein aggregation suppressor, arginine hydrochloride (ArgHCl), specifically decreases viscosity of antibody formulations. The viscosities of bovine gamma globulin (BGG) solution at 250 mg/mL and human gamma globulin (HGG) solution at 292 mg/mL at a physiological pH were too high for subcutaneous injections, but decreased to an acceptable level (below 50 cP) in the presence of 1,000 mM ArgHCl. ArgHCl also decreased the viscosity of BGG solution at acidic and alkaline pHs. Interestingly, ArgHCl decreased the viscosity of antibody solutions (BGG, HGG, and human immunoglobulin G) but not globular protein solutions (α-amylase and α-chymotrypsin). These results indicate not only high potency of ArgHCl as an excipient to decrease the solution viscosity of high concentration antibodies formulations but also specific interactions between ArgHCl and antibodies.

Brooker's merocyanine: Comparison of single crystal structures

NASA Astrophysics Data System (ADS)

Hayes, Kathleen L.; Lasher, Emily M.; Choczynski, Jack M.; Crisci, Ralph R.; Wong, Calvin Y.; Dragonette, Joseph; Deschner, Joshua; Cardenas, Allan Jay P.

2018-06-01

Brooker's merocyanine and its derivatives are well-studied molecules due to their very interesting optical properties. Merocyanine dyes exhibit different colors in solution depending on the solvent's polarity, pH, aggregation and intermolecular interactions. The synthesis of 1-methyl-4-[(oxocyclohexadienylidene)ethylidene]-1,4-dihydropyridine (MOED) dye yielded a particularly interesting solid state structure where in one crystal lattice, MOED and its protonated form are bound by hydrogen bonding interactions.

An electron transporting unit linked multifunctional Ir(III) complex: a promising strategy to improve the performance of solution-processed phosphorescent organic light-emitting diodes.

PubMed

Giridhar, Thota; Saravanan, Chinnusamy; Cho, Woosum; Park, Young Geun; Lee, Jin Yong; Jin, Sung-Ho

2014-04-18

An oxadiazole based electron transporting (ET) unit was glued to the heteroleptic Ir(III) complex (TPQIr-ET) and used as a dopant for phosphorescent organic light-emitting diodes (PhOLEDs). It shows superior device performance than the dopant without the ET unit (TPQIr) due to the balanced charge carrier injection by the ET unit.

Studies on the development of functional powder from citrus peel.

PubMed

Kang, H J; Chawla, S P; Jo, C; Kwon, J H; Byun, M W

2006-03-01

The suitability of citrus peels, generated as a by-product of the juice industry, as a source of antioxidants was investigated. Citrus peel powder was prepared by lyophilizing 70% ethanol extract from citrus peels. Extraction was carried out at room temperature (20 degrees C) for 72 h. The extract was subjected to gamma-irradiation treatment (20 kGy). The aqueous solutions of citrus peel powder were examined for color characteristics and antioxidant potential in terms of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, beta-carotene bleaching and nitrite scavenging activities. There were significant changes in Hunter color values due to irradiation. The a*- and b*-values decreased due to radiation treatment. DPPH radical scavenging, beta-carotene bleaching and nitrite scavenging activities were not affected by irradiation treatment. Nitrite scavenging activity was the highest in the extract at pH 1.2 followed by pH 4.2 and 6.0. These functional properties of the aqueous solution were found to be stable in heat treatment. It could significantly improve oxidative stability of lipids in fish meat system. Based on these results there may be opportunities to use citrus peel powder as a functional component in the food processing industry with gamma irradiation treatment improving its color characteristics without adversely influencing the functional properties.

Simultaneous recovery of Zn and Mn from used batteries in acidic and alkaline mediums: A comparative study.

PubMed

Abid Charef, S; Affoune, A M; Caballero, A; Cruz-Yusta, M; Morales, J

2017-10-01

A parallel study of acidic and alkaline leaching for the recovery of Mn and Zn from spent alkaline batteries is outlined. Using H 2 SO 4 as solvent and selecting appropriate conditions of temperature and concentration, all residues were dissolved except carbon. The separation and recovery of the two components were performed by electrodeposition with satisfactory results at pH values above 4 (current efficiency above 70% for Zn and Mn) but rather lower efficiencies as the pH decreased. Most of the Zn was selectively dissolved by alkaline leaching using a 6.5M NaOH solution, and its recovery was examined by means of both electrochemical and chemical processes. The expected formation of pure Zn by electrowinning failed due to the formation of ZnO, the content of which was highly dependent on the electrodeposition time. For short periods, Zn was the main component. For longer periods the electrodeposit consisted of agglomerated microparticles of ZnO with a minor fraction of Zn metal (barely 3% as measured by X-ray diffraction). A chemical reaction of the element with oxygen released at the anode surface might be responsible for its conversion to ZnO. A simple chemical route is described for the first time for the direct conversion of Zn(OH) 4 2- solution to nanostructured ZnO by lowering the pH to values around 12 using 2M HCl solution. Copyright © 2017 Elsevier Ltd. All rights reserved.

SEPARATION OF BARIUM VALUES FROM URANYL NITRATE SOLUTIONS

DOEpatents

Tompkins, E.R.

1959-02-24

The separation of radioactive barium values from a uranyl nitrate solution of neutron-irradiated uranium is described. The 10 to 20% uranyl nitrate solution is passed through a flrst column of a cation exchange resin under conditions favoring the adsorption of barium and certain other cations. The loaded resin is first washed with dilute sulfuric acid to remove a portion of the other cations, and then wash with a citric acid solution at pH of 5 to 7 to recover the barium along with a lesser amount of the other cations. The PH of the resulting eluate is adjusted to about 2.3 to 3.5 and diluted prior to passing through a smaller second column of exchange resin. The loaded resin is first washed with a citric acid solution at a pH of 3 to elute undesired cations and then with citric acid solution at a pH of 6 to eluts the barium, which is substantially free of undesired cations.

Incontinence Briefs Containing Spiral-Shaped Fiber Acidify Skin pH of Older Nursing Home Residents at Risk for Incontinence-Associated Dermatitis.

PubMed

Bliss, Donna Z; Bland, Peggy; Wiltzen, Kjerstie; Gannon, Alexandra; Wilhems, Anna; Mathiason, Michelle A; Turnbaugh, Robert

The study's purpose was to assess the pH of the skin of older (aged ≥75 years) incontinent nursing home residents after exposure to an incontinence brief containing spiral-shaped fiber wet with an alkaline solution mimicking urine or fecal pH and compared to skin pH after exposure to an industry standard brief wet with the same solution and various controls. The design was experimental, as conditions were applied to skin and skin pH was measured in random order, and subjects served as their own controls. The setting was a Midwestern nonprofit nursing home. The sample was 26 nursing home residents; their mean age was 87 years (SD = 6 years); 77% were female. Most (69%) had urinary incontinence alone, and 31% had dual urinary and fecal incontinence. Skin pH was measured in duplicate on 6 areas of the inner thighs and 6 areas of the volar surface of the forearms. Each area was exposed to 1 of 6 conditions applied in random order: an incontinence brief containing spiral-shaped fiber wet with an alkaline solution and one that was dry; a standard incontinence brief (without spiral-shaped fiber) wet with the same alkaline solution and one that was dry; the alkaline solution alone; and normal skin. On both the thighs and the forearms, skin pH was significantly lower (more acidic) after exposure to the incontinence brief containing spiral-shaped fiber wet with an alkaline solution compared to the wet standard brief and all other control conditions (P < .001). On thighs, the mean skin pH was 5.7 (SD = 0.5) after exposure to the wet brief with spiral-shaped fiber versus 6.4 (SD = 0.5) after exposure to the wet standard brief. On forearms, the mean skin pH was 5.3 (SD = 0.4) after exposure to the wet brief with spiral-shaped fiber versus 6.0 (SD = 0.4) after exposure to the wet standard brief. Incontinence briefs containing a spiral-shaped fiber significantly acidify the pH of the skin exposed to an alkaline solution, while industry standard briefs do not. Since alkaline skin pH is a risk factor for incontinence-associated dermatitis (IAD), results suggest that briefs with spiral-shaped fiber may help prevent IAD. Findings encourage further research.

Oligonucleoside assisted one pot synthesis and self-assembly of gold nanoparticles

NASA Astrophysics Data System (ADS)

Nimrodh Ananth, A.; Ghosh, Goutam; Umapathy, S.; Jothi Rajan, M. A.

2013-12-01

Gold nanoparticles (AuNPs) were synthesized using two different mono-deoxynucleosides, namely, deoxycytidine (dC) and deoxyadenosine (dA) and the size of the nanoparticles in aqueous dispersions was measured to be approximately 10 and 23 nm, respectively. It was also observed that the AuNPs, synthesized using deoxycytidine (dC), self-assembled to a stable cauliflower-type structure of size approximately 230 nm over a long period of ageing, during which the solution colour was seen continuously changing from pale yellow to deep green. The self-assembly of dC-Au nanoparticles (dC-AuNPs) with time was investigated using UV-visible spectroscopy and dynamic light scattering (DLS) techniques. We have also observed that the self-assembly of dC-AuNPs was dependent on the solution pH; i.e. the aggregates could be dissociated and re-associated upon varying the solution pH which we assumed to be due to breaking and forming of hydrogen bonds between --OH and ==O groups of dC among the neighbouring dC-AuNPs. In contrast, AuNPs synthesized using deoxyadenosine (dA-AuNPs) were quite stable in aqueous medium.

Characteristics of BPA removal from water by PACl-Al13 in coagulation process.

PubMed

Xiaoying, Ma; Guangming, Zeng; Chang, Zhang; Zisong, Wang; Jian, Yu; Jianbing, Li; Guohe, Huang; Hongliang, Liu

2009-09-15

This paper discussed the coagulation characteristics of BPA with polyaluminum chloride (PACl-Al(13)) as coagulant, examined the impact of coagulation pH, PACl-Al(13) dosage, TOC (total organic carbon) and turbidity on BPA removal, and analyzed the possible dominant mechanisms in water coagulation process. Formation and performance of flocs during coagulation processes were monitored using photometric dispersion analyzer (PDA). When the concentration of humic acid matters and turbidity was low in the solution, the experimental results showed that the removal of BPA experienced increase and subsequently decrease with the PACl-Al(13) dosage increasing. The optimal PACl-Al(13) dosage was found at BPA/PACl-Al(13)=1:2.6(M/M) under our experiment conditions. Results show that the maximum BPA removal efficiency occurred at pH 9.0 due to the adsorption by Al(13) aggregates onto BPA rather than charge neutralization mechanism by polynuclear aluminous salts in the solution. The humic acid matters and kaolin in the solution have significant effect on BPA removal with PACl-Al(13) in the coagulation. The BPA removal will be weakened at high humic matters. The removal rate of BPA increased and subsequently decreased with the turbidity increasing.

The effects of electrolysis on operational solutions in electromembrane extraction: The role of acceptor solution.

PubMed

Kubáň, Pavel; Boček, Petr

2015-06-12

Fundamental operational principle and instrumental set-up of electromembrane extraction (EME) suggest that electrolysis may play an important role in this recently developed micro-extraction technique. In the present study, the effect of electrolysis in EME is described comprehensively for the first time and it is demonstrated that electrolysis considerably influences EME performance. Micro-electromembrane extraction (μ-EME) across free liquid membrane formed by 1-pentanol was utilized for real-time monitoring of the electrolytically induced changes in composition of μ-EME solutions. These changes were visualized with a set of acid-base indicators. Changes in colours of their aqueous solutions revealed serious variations in their pH values, which occurred within seconds to minutes of the μ-EME process. Variations of up to eight pH units were observed for indicator solutions initially prepared in 1, 5 and 10mM hydrochloric acid. No or only negligible pH changes (less than 0.15 pH unit) were observed for indicator solutions prepared in 50 and 100mM acetic acid demonstrating that initial composition of the aqueous solutions was the crucial parameter. These results were also confirmed by theoretical calculations of maximum pH variations in the solutions, which were based on total electric charge transfers measured in the μ-EME systems, and by exact measurements of their pH values after μ-EMEs. Acceptor solutions that, in the current practice, consist predominantly of low concentrations of strong mineral acids or alkali hydroxides may thus not always ensure adequate EME performance, which was manifested by decrease in extraction recoveries of a basic drug papaverine. A suitable remedy to the observed effects is the application of acceptor solutions containing high concentrations of weak acids or bases. These solutions not only eliminate the decrease in recoveries but also serve well as matrices of extracted samples for subsequent analysis by capillary electrophoresis. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of Aging Temperature on Corrosion Behavior of Sintered 17-4 PH Stainless Steel in Dilute Sulfuric Acid Solution

NASA Astrophysics Data System (ADS)

Szewczyk-Nykiel, Aneta; Kazior, Jan

2017-07-01

The general corrosion behavior of sintered 17-4 PH stainless steel processed under different processing conditions in dilute sulfuric acid solution at 25 °C was studied by open-circuit potential measurement and potentiodynamic polarization technique. The corrosion resistance was evaluated based on electrochemical parameters, such as polarization resistance, corrosion potential, corrosion current density as well as corrosion rate. The results showed that the precipitation-hardening treatment could significantly improve the corrosion resistance of the sintered 17-4 PH stainless steel in studied environment. As far as the influence of aging temperature on corrosion behavior of the sintered 17-4 PH stainless steel is concerned, polarization resistance and corrosion rate are reduced with increasing aging temperature from 480 up to 500 °C regardless of the temperature of solution treatment. It can be concluded that the highest corrosion resistance in 0.5 M H2SO4 solution exhibits 17-4 PH after solution treatment at 1040 °C followed by aging at 480 °C.

The use of synthesized aqueous solutions for determining strontium sorption isotherms

USGS Publications Warehouse

Liszewski, M.J.; Bunde, R.L.; Hemming, C.; Rosentreter, J.; Welhan, J.

1998-01-01

The use of synthesized aqueous solutions for determining experimentally derived strontium sorption isotherms of sediment was investigated as part of a study accessing strontium chemical transport properties. Batch experimental techniques were used to determine strontium sorption isotherms using synthesized aqueous solutions designed to chemically represent water from a natural aquifer with respect to major ionic character and pH. A strontium sorption isotherm for a sediment derived using a synthesized aqueous solution was found to be most comparable to an isotherm derived using natural water when the synthesized aqueous solution contained similar concentrations of calcium and magnesium. However, it is difficult to match compositions exactly due to the effects of disequilibrium between the solution and the sediment. Strong linear relations between sorbed strontium and solution concentrations of calcium and magnesium confirm that these cations are important co-constituents in these synthesized aqueous solutions. Conversely, weak linear relations between sorbed strontium and solution concentrations of sodium and potassium indicate that these constituents do not affect sorption of strontium. The addition of silica to the synthesized aqueous solution does not appreciably affect the resulting strontium sorption isotherm.

Removal efficiency of methylene blue using activated carbon from waste banana stem: Study on pH influence

NASA Astrophysics Data System (ADS)

Misran, E.; Bani, O.; Situmeang, E. M.; Purba, A. S.

2018-02-01

The effort to remove methylene blue in artificial solution had been conducted using adsorption process. The abundant banana stem waste was utilized as activated carbon precursor. This study aimed to analyse the influence of solution pH to removal efficiency of methylene blue using activated carbon from banana stem as adsorbent. Activated carbon from banana stem was obtained by chemical activation using H3PO4 solution. Proximate analysis result showed that the activated carbon has 47.22% of fixed carbon. This value exhibited that banana stem was a potential adsorbent precursor. Methylene blue solutions were prepared at initial concentration of 50 ppm. The influence of solution pH was investigated with the use of 0.2 g adsorbent for 100 mL dye solution. The adsorption was conducted using shaker with at a constant rate of 100 rpm at room temperature for 90 minutes. The results showed that solution pH influenced the adsorption. The activated carbon from banana stem demonstrated satisfying performance since removal efficiencies of methylene blue were higher than 99%.

Edible bioactive fatty acid-cellulosic derivative composites used in food-packaging applications.

PubMed

Sebti, Issam; Ham-Pichavant, Frédérique; Coma, Véronique

2002-07-17

To develop biodegradable packaging that both acts as a moisture barrier and as antimicrobial activity, nisin and stearic acid were incorporated into a hydroxy propyl methyl cellulose (HPMC) based film. Fifteen percent (w/w HPMC) of stearic acid improved film moisture barrier. However, film mechanical resistance and film antimicrobial activity on Listeria monocytogenes and Staphylococcus aureus pathogenic strains were both reduced. This lower film inhibitory activity was due to interactions between nisin and stearic acid. The molecular interaction was modeled, and an equation was developed to calculate the nisin concentration needed to be incorporated into the film matrix to obtain a desired residual antimicrobial activity. Because the molecular interactions were pH dependent, the impact of the pH of the film-forming solution on film inhibitory activity was investigated. Adjusting the pH to 3 totally avoided stearic acid and nisin interaction, inducing a high film inhibitory activity.

A technique for collection of exudate from pea seedlings

NASA Technical Reports Server (NTRS)

Hanson, S. D.; Cohen, J. D.; Bandurski, R. S. (Principal Investigator)

1985-01-01

Ethylenediaminetetraacetic acid (EDTA), at concentrations higher than 1.0 millimolar, is phytotoxic to etiolated seedlings of Pisum sativum. Substantial vascular exudation from pea epicotyls could be obtained without tissue damage at 0.5 millimolar EDTA if the solution was buffered at pH 7.5 with sodium N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid. Treated seedlings exuded 950 micrograms (leucine equivalents) of ninhydrin-positive material per day and 870 micrograms (glucose equivalents) of anthrone-positive material per day. Amino acid analysis showed the exudate to have glutamine as the major amido nitrogen containing compound and sucrose was shown to be the major sugar. Radiolabeled tryptophan and sucrose applied to cotyledons were transferred through the epicotyl and into the collection medium. The pH profile for exudation shows half maximal exudation at pH 7.2, indicating the promotion of exudation by EDTA is probably not due simply to Ca2+ chelation.

Electrochemical characterization of AISI 316L stainless steel in contact with simulated body fluid under infection conditions.

PubMed

López, Danián Alejandro; Durán, Alicia; Ceré, Silvia Marcela

2008-05-01

Titanium and cobalt alloys, as well as some stainless steels, are among the most frequently used materials in orthopaedic surgery. In industrialized countries, stainless steel devices are used only for temporary implants due to their lower corrosion resistance in physiologic media when compared to other alloys. However, due to economical reasons, the use of stainless steel alloys for permanent implants is very common in developing countries. The implantation of foreign bodies is sometimes necessary in the modern medical practice. However, the complex interactions between the host and the can implant weaken the local immune system, increasing the risk of infections. Therefore, it is necessary to further study these materials as well as the characteristics of the superficial film formed in physiologic media in infection conditions in order to control their potential toxicity due to the release of metallic ions in the human body. This work presents a study of the superficial composition and the corrosion resistance of AISI 316L stainless steel and the influence of its main alloying elements when they are exposed to an acidic solution that simulates the change of pH that occurs when an infection develops. Aerated simulated body fluid (SBF) was employed as working solution at 37 degrees C. The pH was adjusted to 7.25 and 4 in order to reproduce normal body and disease state respectively. Corrosion resistance was measured by means of electrochemical impedance spectroscopy (EIS) and anodic polarization curves.

Electrochemical mineralization of cephalexin using a conductive diamond anode: A mechanistic and toxicity investigation.

PubMed

Coledam, Douglas A C; Pupo, Marília M S; Silva, Bianca F; Silva, Adilson J; Eguiluz, Katlin I B; Salazar-Banda, Giancarlo R; Aquino, José M

2017-02-01

The contamination of surface and ground water by antibiotics is of significant importance due to their potential chronic toxic effects to the aquatic and human lives. Thus, in this work, the electrochemical oxidation of cephalexin (CEX) was carried out in a one compartment filter-press flow cell using a boron-doped diamond (BDD) electrode as anode. During the electrolysis, the investigated variables were: supporting electrolyte (Na 2 SO 4 , NaCl, NaNO 3 , and Na 2 CO 3 ) at constant ionic strength (0.1 M), pH (3, 7, 10, and without control), and current density (5, 10 and 20 mA cm -2 ). The oxidation and mineralization of CEX were assessed by high performance liquid chromatography, coupled to mass spectrometry and total organic carbon. The oxidation process of CEX was dependent on the type of electrolyte and on pH of the solution due to the distinct oxidant species electrogenerated; however, the conversion of CEX and its hydroxylated intermediates to CO 2 depends only on their diffusion to the surface of the BDD. In the final stages of electrolysis, an accumulation of recalcitrant oxamic and oxalic carboxylic acids, was detected. Finally, the growth inhibition assay with Escherichia coli cells showed that the toxicity of CEX solution decreased along the electrochemical treatment due to the rupture of the β-lactam ring of the antibiotic. Copyright © 2016 Elsevier Ltd. All rights reserved.

Impaired drug absorption due to high stomach pH: a review of strategies for mitigation of such effect to enable pharmaceutical product development.

PubMed

Mitra, Amitava; Kesisoglou, Filippos

2013-11-04

Published reports have clearly shown that weakly basic drugs which have low solubility at high pH could have impaired absorption in patients with high gastric pH thus leading to reduced and variable bioavailability. Since such reduction in exposure can lead to significant loss of efficacy, it is imperative to (1) understand the behavior of the compound as a function of stomach pH to inform of any risk of bioavailability loss in clinical studies and (2) develop a robust formulation which can provide adequate exposure in achlorhydric patients. In this review paper, we provide an overview of the factors that can cause high gastric pH in human, discuss clinical and preclinical pharmacokinetic data for weak bases under conditions of normal and high gastric pH, and give examples of formulation strategies to minimize or mitigate the reduced absorption of weakly basic drugs under high gastric pH conditions. It should be noted that the ability to overcome pH sensitivity issues is highly compound dependent and there are no obvious and general solutions to overcome such effect. Further, we discuss, along with several examples, the use of biopharmaceutical tools such as in vitro dissolution, absorption modeling, and gastric pH modified animal models to assess absorption risk of weak bases in high gastric pH and also the use of these tools to enable development of formulations to mitigate such effects.

pH-Manipulated Underwater-Oil Adhesion Wettability Behavior on the Micro/Nanoscale Semicircular Structure and Related Thermodynamic Analysis.

PubMed

Tie, Lu; Guo, Zhiguang; Liu, Weimin

2015-05-20

Controlling oil of wettability behavior in response to the underwater out stimulation has shown promising applications in understanding and designing novel micro- or nanofluidic devices. In this article, the pH-manipulated underwater-oil adhesion wetting phenomenon and superoleophobicity on the micro- and nanotexture copper mesh films (CMF) were investigated. It should be noted that the surface exhibits underwater superoleophobicity under different pH values of the solution; however, the underwater-oil adhesion behavior on the surface is dramatically influenced by the pH value of the solution. On the basis of the thermodynamic analysis, a plausible mechanism to explain the pH-controllable underwater-oil adhesion and superoleophobic wetting behavior observed on a micro- and nanoscale semicircular structure has been revealed. Furthermore, variation of chemistry (intrinsic oil contact angle (OCA)) of the responsive surface that due to the carboxylic acid groups is protonated or deprotonated by the acidic or basic solution on free energy (FE) with its barrier (FEB) and equilibrium oil contact angle (EOCA) with it hysteresis (OCAH) are discussed. The result shows that a critical intrinsic OCA on the micro- and nano- semicircular texture is necessary for conversion from the oil Cassie impregnating to oil Cassie wetting state. In a water/oil/solid system, the mechanism reveals that the differences between the underwater OCA and oil adhesive force of the responsive copper mesh film under different pH values of solution are ascribed to the different oil wetting state that results from combining the changing intrinsic OCA and micro-/nanosemicircular structures. These results are well in agreement with the experiment.

The corrosion of titanium in alkaline peroxide bleach liquors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wyllie, W.E. II; Brown, B.E.; Duquette, D.J.

1994-12-31

An experimental program to determine the effects of hydrogen peroxide (H{sub 2}O{sub 2}) and of potential corrosion inhibitors on the corrosion behavior of titanium has been developed. Corrosion rates less than 0.25 mm/y were observed in laboratory bleach liquor at pH 12 to which 5 g/l of H{sub 2}O{sub 2} were added. At pH 13, with 10 g/l H{sub 2}O{sub 2}, the corrosion rates were unacceptably high in both sodium hydroxide (NaOH) and laboratory bleach liquor solutions (>8.38 mm/y). The preliminary results of inhibitor studies indicated that the addition of 3.7 g/l sodium silicate or 0.01 g/l calcium nitrate (Ca(NO{submore » 3}){sub 2}) effectively inhibited the corrosion of titanium exposed to 5 g/l of H{sub 2}O{sub 2} in NaOH solutions of pH 12. It was also found that in simulated paper mill chemistries, i.e., basic solutions containing 3.7 g/l sodium silicate and 0.6 g/l EDTA (ethylenediaminetetraacetic acid), corrosion rates increased markedly with the addition of 5 g/l H{sub 2}O{sub 2}. However, subsequent additions of peroxide resulted in corrosion rates which were even lower than those found in NaOH. This is believed to be due to the formation of a black scale on the surface of the sample. The addition of magnesium sulfate (MgSO{sub 4}) in the 0.1--0.5 g/l range also was shown to inhibit corrosion in the NaOH solution, but only after prior exposure to H{sub 2}O{sub 2}.« less

Precipitation characteristics of uranyl ions at different pHs depending on the presence of carbonate ions and hydrogen peroxide.

PubMed

Kim, Kwang-Wook; Kim, Yeon-Hwa; Lee, Se-yoon; Lee, Jae-Won; Joe, Kih-Soo; Lee, Eil-Hee; Kim, Jong-Seung; Song, Kyuseok; Song, Kee-Chan

2009-04-01

This work studied the dissolution of uranium dioxide and precipitation characteristics of uranyl ions in alkaline and acidic solutions depending on the presence of carbonate ions and H2O2 in the solutions at different pHs controlled by adding HNO3 or NaOH in the solution. The chemical structures of the precipitates generated in different conditions were evaluated and compared by using XRD, SEM, TG-DT, and IR analyses together. The sizes and forms of the precipitates in the solutions were evaluated, as well. The uranyl ions were precipitated in the various forms, depending on the solution pH and the presences of hydrogen peroxide and carbonate ions in the solution. In a 0.5 M Na2CO3 solution with H2O2, where the uranyl ions formed mixed uranyl peroxy-carbonato complexes, the uranyl ions were precipitated as a uranium peroxide of UO4(H20)4 at pH 3-4, and precipitated as a clarkeite of Na2U2Ox(OH)y(H2O)z above pH 13. In the same carbonate solution without H2O2, where the uranyl ions formed uranyl tris-carbonato complex, the uranyl ions were observed to be precipitated as a different form of clarkeite above pH 13. The precipitate of uranyl ions in a nitrate solution without carbonate ions and H2O2 at a high pH were studied together to compare the precipitate forms in the carbonate solutions.

Dissolution of glass wool, rock wool and alkaline earth silicate wool: morphological and chemical changes in fibers.

PubMed

Campopiano, Antonella; Cannizzaro, Annapaola; Angelosanto, Federica; Astolfi, Maria Luisa; Ramires, Deborah; Olori, Angelo; Canepari, Silvia; Iavicoli, Sergio

2014-10-01

The behavior of alkaline earth silicate (AES) wool and of other biosoluble wools in saline solution simulating physiological fluids was compared with that of a traditional wool belonging to synthetic vitreous fibers. Morphological and size changes of fibers were studied by scanning electron microscopy (SEM). The elements extracted from fibers were analyzed by inductively coupled plasma atomic emission spectrometry. SEM analysis showed a larger reduction of length-weighted geometric mean fiber diameter at 4.5 pH than at 7.4 pH. At the 7.4 pH, AES wool showed a higher dissolution rate and a dissolution time less than a few days. Their dissolution was highly non-congruent with rapid leaching of calcium. Unlike rock wool, glass wool dissolved more rapidly at physiological pH than at acid pH. Dissolution of AES and biosoluble rock wool is accompanied by a noticeable change in morphology while by no change for glass wool. Biosoluble rock wool developed a leached surface with porous honeycomb structure. SEM analysis showed the dissolution for glass wool is mainly due to breakage transverse of fiber at pH 7.4. AES dissolution constant (Kdis) was the highest at pH 7.4, while at pH 4.5 only biosoluble rockwool 1 showed a higher Kdis. Copyright © 2014 Elsevier Inc. All rights reserved.

Relation between the adsorbed quantity and the immersion enthalpy in catechol aqueous solutions on activated carbons.

PubMed

Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

2012-01-01

An activated carbon, Carbochem(TM)-PS230, was modified by chemical and thermal treatment in flow of H(2), in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pK(a). The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g(-1) for catechol aqueous solutions in a range of 20 at 1500 mg·L(-1).

Relation Between the Adsorbed Quantity and the Immersion Enthalpy in Catechol Aqueous Solutions on Activated Carbons

PubMed Central

Moreno-Piraján, Juan Carlos; Blanco, Diego; Giraldo, Liliana

2012-01-01

An activated carbon, CarbochemTM—PS230, was modified by chemical and thermal treatment in flow of H2, in order to evaluate the influence of the activated carbon chemical characteristics in the adsorption of the catechol. The catechol adsorption in aqueous solution was studied along with the effect of the pH solution in the adsorption process of modified activated carbons and the variation of immersion enthalpy of activated carbons in the aqueous solutions of catechol. The interaction solid-solution is characterized by adsorption isotherms analysis, at 298 K and pH 7, 9 and 11 in order to evaluate the adsorption value above and below that of the catechol pKa. The adsorption capacity of carbons increases when the solution pH decreases. The retained amount increases slightly in the reduced carbon to maximum adsorption pH and diminishes in the oxidized carbon. Similar conclusions are obtained from the immersion enthalpies, whose values increase with the solute quantity retained. In granular activated carbon (CAG), the immersion enthalpies obtained are between 21.5 and 45.7 J·g−1 for catechol aqueous solutions in a range of 20 at 1500 mg·L−1. PMID:22312237

The dissolution of quartz in dilute aqueous solutions of organic acids at 25°C

USGS Publications Warehouse

Bennett, P.C.; Melcer, M.E.; Siegel, D.I.; Hassett, J.P.

1988-01-01

The dissolution of quartz in dilute aqueous solutions of organic acids at 25° and standard pressure was investigated by the batch dissolution method. The bulk dissolution rate of quartz in 20 mmole/Kg citrate solutions at pH 7 was 8 to 10 times faster than that in pure water. After 1750 hours the concentration of dissolved silica in the citrate solution was 167 μmole/Kg compared to 50 μmole/Kg in water and a 20 mmole/Kg solution of acetate at pH 7. Solutions of salicylic, oxalic, and humic acids also accelerated the dissolution of quartz in aqueous solution at pH 7. The rate of dissolution in organic acids decreased sharply with decreasing pH.The possibility of a silica-organic acid complex was investigated using UV-difference spectroscopy. Results suggest that dissolved silica is complexed by citrate, oxalate and pyruvate at pH 7 by an electron-donor acceptor complex, whereas no complexation occurs between silica and acetate, lactate, malonate, or succinate. Three models are proposed for the solution and surface complexation of silica by organic acid anions which result in the accelerated dissolution and increased solubility of quartz in organic rich water.

Leaching of lead from new unplasticized polyvinyl chloride (uPVC) pipes into drinking water.

PubMed

Zhang, Yuanyuan; Lin, Yi-Pin

2015-06-01

Unplasticized polyvinyl chloride (uPVC) pipes have been used in the premise plumbing system due to their high strength, long-term durability, and low cost. uPVC pipes, however, may contain lead due to the use of lead compounds as the stabilizer during the manufacturing process. The release of lead from three locally purchased uPVC pipes was investigated in this study. The effects of various water quality parameters including pH value, temperature, and type of disinfectant on the rate of lead release were examined. The elemental mapping obtained using scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX) confirmed the presence of lead on the inner surfaces of the uPVC pipes and their surface lead weight percentages were determined. The leachable lead concentration for each pipe was determined using high strength acidic EDTA solutions (pH 4, EDTA = 100 mg/L). Lead leaching experiments using tap water and reconstituted tape water under static conditions showed that the rate of lead release increased with the decreasing pH value and increasing temperature. In the presence of monochloramine, lead release was faster than that in the presence of free chlorine.

Proton triggered emission and selective sensing of picric acid by the fluorescent aggregates of 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline.

PubMed

Mazumdar, Prativa; Maity, Samir; Shyamal, Milan; Das, Debasish; Sahoo, Gobinda Prasad; Misra, Ajay

2016-03-14

A heteroatom containing organic fluorophore 6,7-dimethyl-2,3-bis-(2-pyridyl)-quinoxaline (BPQ) is weakly emissive in solution but its emission properties are highly enhanced in the aggregated state due to the restriction of intramolecular rotation (RIR) and large amplitude vibrational modes, demonstrating the phenomenon, aggregation induced emission enhancement (AIEE). It has strong proton capture capability, allowing reversible fluorescence switching in basic and acidic medium and the emission color changes from blue to green in the aggregated state through protonation. It has been explained as a competition between intramolecular charge transfers (ICTs) and the AIEE phenomena at a lower pH range (pH ∼1-4). Such behavior enables it as a fluorescent pH sensor for detection in acidic and basic medium. Morphologies of the particles are characterized using optical and field emission scanning electron microscopic (FESEM) studies. The turn off fluorescence properties of aggregated BPQ have been utilized for the selective detection of picric acid and the fluorescence quenching is explained due to ground state complexation with a strong quenching constant, 7.81 × 10(4) M(-1).

Predicting the crystallization propensity of carboxylic acid buffers in frozen systems--relevance to freeze-drying.

PubMed

Sundaramurthi, Prakash; Suryanarayanan, Raj

2011-04-01

Selective crystallization of buffer components in frozen solutions is known to cause pronounced pH shifts. Our objective was to study the crystallization behavior and the consequent pH shift in frozen aqueous carboxylic acid buffers. Aqueous carboxylic acid buffers were cooled to -25°C and the pH of the solution was measured as a function of temperature. The thermal behavior of solutions during freezing and thawing was investigated by differential scanning calorimetry. The crystallized phases in frozen solution were identified by X-ray diffractometry. The malate buffer system was robust with no evidence of buffer component crystallization and hence negligible pH shift. In the citrate and tartarate systems, at initial pH

A validated UPLC-MS/MS method for the analysis of linezolid and a novel oxazolidinone derivative (PH027) in plasma and its application to tissue distribution study in rabbits.

PubMed

Hedaya, Mohsen A; Thomas, Vidhya; Abdel-Hamid, Mohamed E; Kehinde, Elijah O; Phillips, Oludotun A

2017-01-01

Linezolid is the first approved oxazolidinone antibacterial agent, whereas PH027 is a novel compound of the same class that exhibits good in vitro antibacterial activity. The objective of this study was to develop an UPLC-MS/MS assay for the analysis of linezolid and PH027 in plasma and to apply the method for comparative pharmacokinetic and tissue distribution studies of both compounds. Plasma samples and calibrators were extracted with diethyl ether after addition of the internal standard solution. After evaporation of the ether layer, the residue was reconstituted in mobile phase and injected into UPLC-MS/MS. The mobile phase consisted of 2mM ammonium acetate buffer solution and acetonitrile (70:30) at a flow rate of 0.2ml/min. Separation was achieved using UPLC BEH C 18 column, and quantitative determination of the analytes was performed using multiple-reaction monitoring (MRM) scanning mode. The method was validated by analyzing quality control tissue homogenate samples, and was applied to analyze tissue homogenate samples obtained following IV injections of linezolid and PH027 in rabbits. The developed UPLC-MS/MS method was linear in the concentration range of 50-5000ng/ml. Validation of the method proved that the method's precision, selectivity and stability were all within the acceptable limits. Linezolid and PH027 concentrations were accurately determined in the quality control tissue homogenate samples, and analysis of samples obtained following IV administration of the two compounds showed that the tissue to plasma concentration ratio of PH027 was higher than that of linezolid probably due to its higher lipophilicity. The developed UPLC-MS/MS method for the analysis of linezolid and PH027 in rabbit's plasma can accurately determine the concentrations of these compounds in different tissues. Copyright © 2016 Elsevier B.V. All rights reserved.

PHOTOMETRIC ORBITS OF EXTRASOLAR PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Robert A.

We define and analyze the photometric orbit (PhO) of an extrasolar planet observed in reflected light. In our definition, the PhO is a Keplerian entity with six parameters: semimajor axis, eccentricity, mean anomaly at some particular time, argument of periastron, inclination angle, and effective radius, which is the square root of the geometric albedo times the planetary radius. Preliminarily, we assume a Lambertian phase function. We study in detail the case of short-period giant planets (SPGPs) and observational parameters relevant to the Kepler mission: 20 ppm photometry with normal errors, 6.5 hr cadence, and three-year duration. We define a relevantmore » 'planetary population of interest' in terms of probability distributions of the PhO parameters. We perform Monte Carlo experiments to estimate the ability to detect planets and to recover PhO parameters from light curves. We calibrate the completeness of a periodogram search technique, and find structure caused by degeneracy. We recover full orbital solutions from synthetic Kepler data sets and estimate the median errors in recovered PhO parameters. We treat in depth a case of a Jupiter body-double. For the stated assumptions, we find that Kepler should obtain orbital solutions for many of the 100-760 SPGP that Jenkins and Doyle estimate Kepler will discover. Because most or all of these discoveries will be followed up by ground-based radial velocity observations, the estimates of inclination angle from the PhO may enable the calculation of true companion masses: Kepler photometry may break the 'msin i' degeneracy. PhO observations may be difficult. There is uncertainty about how low the albedos of SPGPs actually are, about their phase functions, and about a possible noise floor due to systematic errors from instrumental and stellar sources. Nevertheless, simple detection of SPGPs in reflected light should be robust in the regime of Kepler photometry, and estimates of all six orbital parameters may be feasible in at least a subset of cases.« less

Organic Carbon Release from Groundwater Sediments under Changing Geochemical Conditions

NASA Astrophysics Data System (ADS)

Tinnacher, R. M.; Bhattacharyya, A.; Fox, P. M.; Nico, P. S.

2016-12-01

Due to climate change, local weather patterns are expected to change, especially with respect to precipitation, the frequency of extreme storm water events, and `drought-like' conditions. This in turn, may affect groundwater recharge, the geochemical conditions in natural groundwater systems, and the chemical and microbiological processes involved in organic matter degradation. Besides the complexity of organic matter structures and local limitations in nutrients, the association of organic carbon with sediment minerals can strongly limit organic matter bioaccessability and degradability. In this study, we investigate how variations in groundwater chemistry, e.g. with respect to dissolved CO2 concentrations, may potentially affect the release of natural organic carbon from groundwater sediments, and render organic matter more bioaccessible. In lab-scale experiments under anaerobic conditions, aquifer sediments from the floodplain of the Colorado River (Rifle, USA) were brought into contact with fresh, organic-carbon free groundwater solutions, at natural or reduced CO2 concentration levels. During the repeated exchange of solutions at two temperature settings (room-temperature and 4 °C), supernatant solutions were characterized in terms of pH, dissolved metal and organic carbon (OC) concentrations, and potential changes in released OC characteristics. Sediment samples were evaluated for possible differences in Fe-speciation before and after the experiment based on EXAFS (bulk Fe K-edge). Preliminary results for 20 exchanges of groundwater solutions show a repeated release of low OC concentrations ( 0.5-2 mg OC/g sediment; 0.05-0.2% of sediment-associated OC) without any apparent depletion in the overall source term over 50 days. After 14 days, room-temperature samples released slightly higher OC concentrations than samples kept at 4 °C. An increase in solution pH, after switching to a `CO2-free' groundwater solution, did not trigger a higher OC release. Last, specific UV absorbance measurements for room-temperature samples suggest changes in released OC characteristics due to repeated solution exchanges. Additional sample characterization is ongoing, with the goal to elucidate potential changes in released OC characteristics over the course of the experiment.

On the Preparation of Buffer Solutions.

ERIC Educational Resources Information Center

Thomson, Bruce M.; Kessick, Michael A.

1981-01-01

Presents a method, suitable for use on programmable calculators, which allows calculation of the pH and ionic strength (I) of a mixed solution of salts of an acid or amounts necessary to produce a solution of a particular pH and I. Includes limitations when using the calculations described. (SK)

Macroscopic experimental and modeling evaluation of selenite and selenate adsorption mechanisms on gibbsite

USDA-ARS?s Scientific Manuscript database

Selenite Se(IV) and selenate Se(VI) selenium adsorption behavior was investigated on gibbsite as a function of solution pH and solution ionic strength. Adsorption of both Se redox states decreased with increasing solution pH. Electrophoretic mobility measurements showed downward shifts in point of...

Electrochemistry and dissolution kinetics of magnetite and ilmenite

USGS Publications Warehouse

White, A.F.; Peterson, M.L.; Hochella, M.F.

1994-01-01

Natural samples of magnetite and ilmenite were experimentally weathered in pH 1-7 anoxic solutions at temperatures of 2-65 ??C. Reaction of magnetite is described as [Fe2+Fe23+]O4(magnetite) + 2H+ ??? ??[Fe23+]O3(maghemite) + Fe2+ + H2O. Dynamic polarization experiments using magnetite electrodes confirmed that this reaction is controlled by two electrochemical half cells, 3[Fe2+Fe23+]O4(magnetite) ??? 4??[Fe23+]O3(maghemite) + Fe2+ + 2e- and [Fe2+Fe23+]O4(magnetite) + 8 H+ + 2e- ??? 3Fe2+ + 4H2O, which result in solid state Fe3+ reduction, formation of an oxidized layer and release of Fe(II) to solution. XPS data revealed that iron is present in the ferric state in the surfaces of reacted magnetite and ilmenite and that the Ti Fe ratio increased with reaction pH for ilmenite. Short-term (<36 h) release rates of Fe(II) were linear with time. Between pH 1 and 7, rates varied between 0.3 and 13 ?? 10-14 mol ?? cm-2 ?? s-1 for magnetite and 0.05 and 12.3 ?? 10-14 mol ?? cm-2 ?? s-1 for ilmenite. These rates are two orders of magnitude slower than electrochemical rates determined by Tafel and polarization resistance measurements. Discrepancies are due to both differences in geometric and BET surface area estimates and in the oxidation state of the mineral surface. In long-term closed-system experiments (<120 days), Fe(II) release slowed with time due to the passivation of the surfaces by increasing thicknesses of oxide surface layers. A shrinking core model, coupling surface reaction and diffusion transport, predicted that at neutral pH, the mean residence time for sand-size grains of magnetite and ilmenite will exceed 107 years. This agrees with long-term stability of these oxides in the geologic record. ?? 1994.

Functional Biomaterials: Solution Electrospinning and Gelation of Whey Protein and Pullulan

NASA Astrophysics Data System (ADS)

Sullivan, Stephanie Tolstedt

Utilizing biomaterials that are biodegradable, biocompatible and edible serve well for food products as well as biomedical applications. Biomaterials whey protein and pullulan both have these characteristics. Whey proteins (WP) have been used in food products for many years and more recently in pharmaceutical products. They have the ability to form both gels and stable foams. Pullulan (PULL) has also been used in both food and pharmaceutical products, and is a highly water soluble, non-gelling polysaccharide and has been used primarily as a film former. Herein, we investigate the ability of whey protein and pullulan to form nanofibers and gels. Combining their distinct properties allows the ability to uniquely manipulate nanofiber and gel characteristics and behavior for a variety of applications, from food to even tissue scaffolding. First, we determined the electrospinnability of aqueous whey protein solutions. Both whey protein isolate (WPI) and one of its major components beta--lactoglobulin (BLG), either in native or denatured form, yielded interesting micro and nanostructures when electrosprayed; while nanofiber production required blending with a spinnable polymer, poly(ethylene oxide) (PEO). WP:PEO solutions were also successfully electrospun at acidic pH (2≤pH≤3), which could improve shelf life. Fourier Transform Infrared Reflectance (FTIR) analysis of WP:PEO fiber mat indicated some variation in WP secondary structure with varying WPI concentration (as WPI increased, % alpha-helix increased and beta-turn decreased) and pH (as pH decreased from neutral (7.5) to acidic (2), % beta-sheet decreased and alpha-helix increased). X-ray Photoelectron Spectroscopy (XPS) also confirmed the presence of WP on the surface of the blend fibers, augmenting the FTIR analysis. Interestingly, WP:PEO composite nanofibers maintained its fibrous morphology at temperatures as high as 100 °C, above the 60 °C PEO melting point. Further, we show that the blend mats retained a fibrous structure after the heat treatment. Our second goal was to evaluate the ability of aqueous blends of whey protein and pullulan to form gels. We first looked at WP-PULL blend solutions at room temperature, finding an increasing linear trend in low shear viscosity as the relative concentration of pullulan increased. Blend solution samples were then heated to determine the ability of the blend solutions to form a gelled network. Starting with a homogeneous WP gel, adding PULL, at native mix or alkaline pH, maintained a transparent homogeneous microstructure, but resulted in weaker gels based on its response to stress. At WP isoelectric point (IEP) pH, both protein and blend gels became opaque due to protein aggregation, forming a particulate gel. All gels at the IEP were weaker, yielding at much lower stress and corresponding strain, due to the protein aggregation. The addition of transglutaminase enzyme yielded a stronger network than the native samples, while the addition of sodium trimetaphosphate salt yielded weaker gels and also induced relevant particle and/or course stranded microstructure in both pH 8 and IEP cases. The third part of this study demonstrated the ability of pullulan to form nanofibers in the solution electrospinning process. Aqueous pullulan solutions were able to form defect-free nanofibers with a minimum concentration of 15 w/w%. Pullulan and PULL:hydroxypropyl-beta- cyclodextrin (HPBCD) blend fibers were chemically crosslinked to form insoluble fibers using ethylene glycol diglycidyl ether (EGDGE), a chemical used in food contact coating applications. Next, solution blends of pullulan with whey protein were prepared and also electrospun at varying pH and relative biomaterial concentrations at 17 total w/w%. PULL-WP blend nanofiber mats were crosslinked via heat treatment and found to be both swellable and insoluble. When dried, the mats did not return to their original fiber state and instead appear to be gelatinous fibers in nature after soaking, and thereby making them potentially useful for tissue scaffolding applications. A fourth accomplishment was to utilize Near Infrared Reflectance (NIR) Spectroscopy and Chemometrics techniques to analyze commercial whey protein powder characteristics such as protein, fat and moisture content as well as pH. NIR has been utilized in the food and pharmaceutical industries for quality control as a valuable compliment to or replacement for more expensive testing such as High Performance Liquid Chromatography. Analysis resulted in the development of quantitative, linear regression models to correlate whey protein powder characteristics to NIR data. Whey protein's ability to form gels and pullulan's electrospinnability to form nanofibers is combined herein to form blends of both that can be changed with varying concentration, pH, temperature and supplementation with food-safe additives. The study correlates mechanical properties and microstructure of blend gels and nanofibers and provides a foundation for further study of swellable network for tissue application specifically in the use of pullulan-whey protein heat treated nanofiber mats.

Study of pH Stability of R-Salbutamol Sulfate Aerosol Solution and Its Antiasthmatic Effects in Guinea Pigs.

PubMed

Liu, Qing; Li, Qingrui; Han, Ting; Hu, Tingting; Zhang, Xuemei; Hu, Junhua; Hu, Hui; Tan, Wen

2017-09-01

Currently, all commercial available nebulized salbutamol in China is in its racemic form. It is known that only R-salbutamol (eutomer) has therapeutic effects, while S-salbutamol (distomer) may exacerbate asthma after chronic use. Therefore, it is an unmet clinical need to develop R-salbutamol as a nebulized product that is more convenient for young and old patients. In our study, a stable aerosol solution of R-salbutamol sulfate was established, and its antiasthmatic effects were confirmed. The decomposition rate and racemization effect of the R-salbutamol sulfate solution were evaluated over a pH range from 1 to 10 (except pH=7, 8) at 60°C. The aerodynamic particle size of the R-salbutamol sulfate solution and commercial RS-salbutamol sulfate solution were both tested in vitro by Next-Generation Impactor (NGI) in 5°C. Laser diffractometer was used to characterize the droplet-size distribution (DSD) of both solutions. We next conducted an in vivo animal study to document the antiasthmatic effect of R-salbutamol aerosol sulfate solution and determine the relationship to RS-salbutamol. The results showed that the R-salbutamol sulfate solution was more stable at pH 6. In vitro comparison studies indicated that there was no distribution difference between R-salbutamol sulfate solution and the commercial RS-salbutamol solution. The animal results showed that R-salbutamol was more potent than RS-salbutamol against the same dose of histamine challenge. Unlike commercial RS-salbutamol, which was acidified to a pH of 3.5 to extend bench life but may cause bronchoconstriction in asthmatic patients, the neutralized R-salbutamol solution was more suitable for clinic use.

Adsorption properties of the nanozirconia/anionic polyacrylamide system-Effects of surfactant presence, solution pH and polymer carboxyl groups content

NASA Astrophysics Data System (ADS)

Wiśniewska, Małgorzata; Chibowski, Stanisław; Urban, Teresa

2016-05-01

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate-SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level.

Characteristics and metal leachability of incinerated sewage sludge ash and air pollution control residues from Hong Kong evaluated by different methods.

PubMed

Li, Jiang-Shan; Xue, Qiang; Fang, Le; Poon, Chi Sun

2017-06-01

The improper disposal of incinerated sewage sludge ash (ISSA) and air pollution control residues (APCR) from sewage sludge incinerators has become an environmental concern. The physicochemical, morphological and mineralogical characteristics of ISSA and APCR from Hong Kong, and the leachability and risk of heavy metals, are presented in this paper. The results showed that a low hydraulic and pozzolanic potential was associated with the ISSA and APCR due to the presence of low contents of SiO 2 , Al 2 O 3 and CaO and high contents of P, S and Cl (especially for APCR). Although high concentrations of Zn and Cu (especially for ISSA) followed by Ni, Pb and As, Se were detected, a low leaching rate of these metals (especially at neutral and alkaline pH) rendered them classifiable as non-hazardous according to the U.S. EPA and Chinese national regulatory limits. The leached metals concentrations from ISSA and APCR were mainly pH dependent, and metals solubilization occurred mainly at low pH. Different leaching tests should be adopted based on the simulated different environmental conditions and exposure scenarios for assessing the leachability as contrasting results could be obtained due to the differences in complexing abilities and final pH of the leaching solutions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Improvement of drug loading onto ion exchange resin by cyclodextrin inclusion complex.

PubMed

Samprasit, Wipada; Rojanarata, Theerasak; Akkaramongkolporn, Prasert; Ngawhirunpat, Tanasait; Sila-on, Warisada; Opanasopit, Praneet

2013-11-01

Ion exchange resins have ability to exchange their counter ions for ionized drug in the surrounding medium, yielding "drug resin complex." Cyclodextrin can be applied for enhancement of drug solubility and stability. Cyclodextrin inclusion complex of poorly water-soluble NSAIDs, i.e. meloxicam and piroxicam, was characterized and its novel application for improving drug loading onto an anionic exchange resin, i.e. Dowex® 1×2, was investigated. β-Cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) were used for the preparation of inclusion complex with drugs in solution state at various pH. The inclusion complex was characterized by phase solubility, continuous variation, spectroscopic and electrochemistry methods. Then, the drug with and without cyclodextrin were equilibrated with resin at 1:1 and 1:2 weight ratio of drug and resin. Solubility of the drugs was found to increase with increasing cyclodextrin concentration and pH. The increased solubility was explained predominantly due to the formation of inclusion complex at low pH and the increased ionization of drug at high pH. According to characterization studies, the inclusion complex was successfully formed with a 1:1 stoichiometry. The presence of cyclodextrin in the loading solution resulted in the improvement of drug loading onto resin. Enhancing drug loading onto ion-exchange resin via the formation of cyclodextrin inclusion complex is usable in the development of ion-exchange based drug delivery systems, which will beneficially reduce the use of harmful acidic or basic and organic chemicals.

Effect of ozonation on minocycline degradation and N-Nitrosodimethylamine formation.

PubMed

Lv, Juan; Li, Yong M

2018-06-07

The objective of this study was to assess reactivity of Minocycline (MNC) towards ozone and determine the effects of ozone dose, pH value, and water matrix on MNC degradation as well as to characterize N-Nitrosodimethylamine (NDMA) formation from MNC ozonation. The MNC initial concentration of the solution was set in the range of 2-20 mg/L to investigate NDMA formation during MNC ozonation. Four ozone doses (22.5, 37.2, 58.0, and 74.4 mg/min) were tested to study the effect of ozone dose. For the evaluation of effects of pH value, pH was adjusted from 5 to 9 in the presence of phosphate buffer. MNC ozonation experiments were also conducted in natural water to assess the influence of water matirx. The influence of the typical component of natural water was also investigated with the addition of HA and NaHCO 3 solution. Results indicated that ozone was effective in MNC removal. Consequently, NDMA and dimethylamine (DMA) were generated from MNC oxidation. Increasing pH value enhanced MNC removal but led to greater NDMA generation. Water matrices, such as HCO 3 - and humic acid, affected MNC degradation. Conversely, more NDMA accumulated due to the inhibition of NDMA oxidation by oxidant consumption. Though ⋅OH can enhance MNC degradation, ozone molecules were heavily involved in NDMA production. Seven transformation products were identified. However, only DMA and the unidentified tertiary amine containing DMA group contributed to NDMA formation.

Physical stability comparisons of IgG1-Fc variants: effects of N-glycosylation site occupancy and Asp/Gln residues at site Asn 297.

PubMed

Alsenaidy, Mohammad A; Okbazghi, Solomon Z; Kim, Jae Hyun; Joshi, Sangeeta B; Middaugh, C Russell; Tolbert, Thomas J; Volkin, David B

2014-06-01

The structural integrity and conformational stability of various IgG1-Fc proteins produced from the yeast Pichia pastoris with different glycosylation site occupancy (di-, mono-, and nonglycosylated) were determined. In addition, the physical stability profiles of three different forms of nonglycosylated Fc molecules (varying amino-acid residues at site 297 in the CH 2 domain due to the point mutations and enzymatic digestion of the Fc glycoforms) were also examined. The physical stability of these IgG1-Fc glycoproteins was examined as a function of pH and temperature by high-throughput biophysical analysis using multiple techniques combined with data visualization tools (three index empirical phase diagrams and radar charts). Across the pH range of 4.0-6.0, the di- and monoglycosylated forms of the IgG1-Fc showed the highest and lowest levels of physical stability, respectively, with the nonglycosylated forms showing intermediate stability depending on solution pH. In the aglycosylated Fc proteins, the introduction of Asp (D) residues at site 297 (QQ vs. DN vs. DD forms) resulted in more subtle changes in structural integrity and physical stability depending on solution pH. The utility of evaluating the conformational stability profile differences between the various IgG1-Fc glycoproteins is discussed in the context of analytical comparability studies. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

The effect of surfactant-free TiO2 surface hydroxyl groups on physicochemical, optical and self-cleaning properties of developed coatings on polycarbonate

NASA Astrophysics Data System (ADS)

Yaghoubi, H.; Dayerizadeh, A.; Han, S.; Mulaj, M.; Gao, W.; Li, X.; Muschol, M.; Ma, S.; Takshi, A.

2013-12-01

TiO2 is a prototypical transition metal oxide with physicochemical properties that can be modified more readily through sol-gel synthesis than through other techniques. Herein, we report on the change in the density of the hydroxyl groups on the surface of synthesized surfactant-free TiO2 nanoparticles in water due to varying the pH (7.3, 8.3, 9.3 and 10.3) of the peroxotitanium complex, i.e. the amorphous sol, prior to refluxing. This resulted in colloidal solutions with differing crystallinity, nanoparticle size, optical indirect bandgaps and photocatalytic activity. It was shown that increasing the density of hydroxyl groups on TiO2 particles coupled with low-temperature annealing (90 °C) induced an anatase to rutile transformation. Increasing the pH of the peroxotitanium complex interrupted the formation of anatase phase in crystalline sol, as evidenced by intensity increases of the Raman bands at ˜822 (Ti-O-H) and 906 cm-1 (vibrational Ti-O-H) and an intensity decrease of the band at 150 cm-1 (anatase photonic Eg). Films prepared from higher pH suspensions showed lower roughness. The reaction rate constants for photo-induced self-cleaning activity of TiO2 films prepared from colloidal solutions at pH 7.3, 8.3, 9.3 and 10.3 were estimated at 0.017 s-1, 0.014 s-1, 0.007 s-1 and 0.006 s-1, respectively.

Treatability study of the effluent containing reactive blue 21 dye by ozonation and the mass transfer study of ozone

NASA Astrophysics Data System (ADS)

Velpula, Priyadarshini; Ghuge, Santosh; Saroha, Anil K.

2018-04-01

Ozonation is a chemical treatment process in which ozone reacts with the pollutants present in the effluent by infusion of ozone into the effluent. This study includes the effect of various parameters such as inlet ozone dose, pH of solution and initial concentration of dye on decolorization of dye in terms CRE. The maximum CRE of 98.62% with the reaction rate constant of 0.26 min-1 is achieved in 18 minutes of reaction time at inlet ozone dose of 11.5 g/m3, solution pH of 11 and 30 mg/L of initial concentration of dye. The presence of radical scavenger (Tertiary Butyl Alcohol) suppressed the CRE from 98.62% to 95.4% at high pH values indicates that the indirect mechanism dominates due to the presence of hydroxyl radicals which are formed by the decomposition of ozone. The diffusive and convective mass transfer coefficients of ozone are calculated as 1.78 × 10-5 cm2/sec and 0.075 min-1. It is observed that the fraction of resistance offered by liquid is very much high compared to gas phase indicates that the ozonation is a liquid phase mass transfer controlled operation.

Nitroimidazoles adsorption on activated carbon cloth from aqueous solution.

PubMed

Ocampo-Pérez, R; Orellana-Garcia, F; Sánchez-Polo, M; Rivera-Utrilla, J; Velo-Gala, I; López-Ramón, M V; Alvarez-Merino, M A

2013-07-01

The objective of this study was to analyze the equilibrium and adsorption kinetics of nitroimidazoles on activated carbon cloth (ACC), determining the main interactions responsible for the adsorption process and the diffusion mechanism of these compounds on this material. The influence of the different operational variables, such as ionic strength, pH, temperature, and type of water (ultrapure, surface, and waste), was also studied. The results obtained show that the ACC has a high capacity to adsorb nitroimidazoles in aqueous solution. Electrostatic interactions play an important role at pH<3, which favors the repulsive forces between dimetridazole or metronidazole and the ACC surface. The formation of hydrogen bonds and dispersive interactions play the predominant role at higher pH values. Modifications of the ACC with NH3, K2S2O8, and O3 demonstrated that its surface chemistry plays a predominant role in nitroimidazole adsorption on this material. The adsorption capacity of ACC is considerably high in surface waters and reduced in urban wastewater, due to the levels of alkalinity and dissolved organic matter present in the different types of water. Finally, the results of applying kinetic models revealed that the global adsorption rate of dimetridazole and metronidazole is controlled by intraparticle diffusion. Copyright © 2013 Elsevier Inc. All rights reserved.

Adsorption of sulfamethoxazole by magnetic biochar: Effects of pH, ionic strength, natural organic matter and 17α-ethinylestradiol.

PubMed

Reguyal, Febelyn; Sarmah, Ajit K

2018-07-01

Recent studies have shown the widespread occurrence of pharmaceuticals in the aquatic environment leading to increasing global concern on their potential adverse effects in the environment and public health. In this study, we evaluated the use of magnetic biochar derived from pine sawdust, one of New Zealand's major wood wastes, to remove an emerging contaminant, sulfamethoxazole (SMX), at different pH, ionic strength, natural organic matter (NOM) and a competing compound, 17α-ethinylestradiol (EE2). In single-solute system, the sorption of SMX onto magnetic biochar was found to be highly pH-dependent and slightly increased with increase in ionic strength. However, the effects of pH, ionic strength and NOM were relatively insignificant compared to the sorption inhibition caused by EE2 in binary-solute system. Both SMX and EE2 sorption onto the highly carbonised biochar in magnetic biochar were postulated to be due to the π-π electron donor acceptor and hydrophobic interaction. EE2 is more hydrophobic than SMX. Hence, strong competition between these compounds was identified where EE2 markedly inhibited the sorption of SMX onto magnetic biochar in all artificial environmental conditions studied. Copyright © 2018 Elsevier B.V. All rights reserved.

The erosion of carbonate stone by acid rain: Laboratory and field investigations

USGS Publications Warehouse

Baedecker, P.A.; Reddy, M.M.

1993-01-01

One of the goals of research on the effects of acidic deposition on carbonate stone surfaces is to define the incremental impact of acidic deposition relative to natural weathering processes on the rate of carbonate stone erosion. If rain that impacts carbonate stone surfaces is resident on the surface long enough to approach chemical equilibrium, the incremental effect of hydrogen ion is expected to be small (i.e., 6% for a rain of pH 4.0). Under nonequilibrium (i.e., high flow rate) conditions, kinetic considerations suggest that the incremental effect of hydrogen ion deposition could be quite significant. Field run-off experiments involving the chemical analysis of rain collected from inclined stone slabs have been used to evaluate stone dissolution processes under ambient conditions of wet and dry deposition of acidic species. The stoichiometry of the reaction of stone with hydrogen ion is difficult to define from the field data due to scatter in the data attributed to hydrodynamic effects. Laboratory run-off experiments show that the stoichiometry is best defined by a reaction with H+ in which CO2 is released from the system. The baseline effect caused by water in equilibrium with atmospheric CO2 is identical in the field and in laboratory simulation. The experiments show that the solutions are close enough to equilibrium for the incremental effect of hydrogen ion to be minor (i.e., 24% for marble for a rain of pH 4.0) relative to dissolution due to water and carbonic acid reactions. Stone erosion rates based on physical measurement are approximately double the recession rates that are due to dissolution (estimated from the observed calcium content of the run-off solutions). The difference may reflect the loss of granular material not included in recession estimates based on the run-off data. Neither the field nor the laboratory run-off experiments indicate a pH dependence for the grain-removal process.

Fluid Mechanical Properties of Silkworm Fibroin Solutions

NASA Astrophysics Data System (ADS)

Matsumoto, Akira

2005-11-01

The aqueous solution behavior of silk fibroin is of interest due to the assembly and processing of this protein related to the spinning of protein fibers that exhibit remarkable mechanical properties. To gain insight into the origins of this functional feature, it is desired to determine how the protein behaves under a range of solution conditions. Pure fibroin at different concentrations in water was studied for surface tension, as a measure of surfactancy. In addition, shear induced changes on these solutions in terms of structure and morphology was also determined. Fibroin solutions exhibited shear rate-sensitive viscosity changes and precipitated at a critical shear rate where a dramatic increase of 75-150% of the initial value was observed along with a decrease in viscosity. In surface tension measurements, critical micelle concentrations were in the range of 3-4% w/v. The influence of additional factors, such as sericin protein, divalent and monovalent cations, and pH on the solution behavior in relation to structural and morphological features will also be described.

A study on the swelling behavior of poly(acrylic acid) hydrogels obtained by electron beam crosslinking

NASA Astrophysics Data System (ADS)

Sheikh, N.; Jalili, L.; Anvari, F.

2010-06-01

Poly(acrylic acid) (PAA) hydrogels were prepared by using electron beam (EB) crosslinking of PAA homopolymer from its aqueous solutions. The swelling behavior of the hydrogels was studied as a function of the concentration of PAA solution, radiation dose, pH of the swelling medium and swelling time. Also the environmental pH effect on the water diffusion mode into hydrogels was investigated. These hydrogels clearly showed pH-sensitive swelling behavior with Fickian type of diffusion in the stomach-like pH medium (pH 1.3) and non-Fickian type in the intestine-like pH medium (pH 6.8).

Relationship Between pH and Electrochemical Corrosion Behavior of Thermal-Sprayed Ni-Al-Coated Q235 Steel in Simulated Soil Solutions

NASA Astrophysics Data System (ADS)

Wei, Wei; Wu, Xin-qiang; Ke, Wei; Xu, Song; Feng, Bing; Hu, Bo-tao

2017-09-01

Electrochemical corrosion behavior of a thermal-sprayed Ni-Al-coated Q235 steel was investigated in the simulated soil solutions at different pH values using measurements of potentiodynamic polarization curves and electrochemical impedance spectroscopy as well as surface analyses including x-ray diffraction analysis, scanning electron microscope equipped with an energy-dispersive x-ray spectroscopy and x-ray photoelectron spectroscopy. The results showed that the corrosion resistance of the Ni-Al-coated Q235 steel was dependent on the pH of the test solution. From pH = 3.53 to pH = 4.79, the corrosion resistance of the coated steel increased rapidly. In the pH range from 4.79 to 12.26, the corrosion resistance exhibited no significant change. At pH 13.25, the corrosion resistance of the sample was found to decrease. The calculated corrosion rate of Ni-Al-coated Q235 steel was lower than that of the uncoated Q235 steel and galvanized steel in all the test solutions. Over a wide range of pH values, the Ni-Al-coated Q235 steel exhibited extremely good corrosion resistance. The experimental data together with the potential-pH diagrams provided a basis for a detailed discussion of the related corrosion mechanisms of the coated steel.

Characterization of pH-fractionated humic acids derived from Chinese weathered coal.

PubMed

Zhang, Shuiqin; Yuan, Liang; Li, Wei; Lin, Zhian; Li, Yanting; Hu, Shuwen; Zhao, Bingqiang

2017-01-01

To reduce the compositional and structural heterogeneity of humic acids (HAs) and achieve better use of HA resources, in this study, we report a new sequential dissolution method for HAs derived from Chinese weathered coal. This method was used to separate HAs into seven fractions by adjusting the pH (3-10) of the extraction solution. The results showed that the HA fractions derived from Chinese weathered coal were concentrated up to 90.31% in the lower pH solutions (3-7). The compositional and structural characteristics of the HA fractions were determined by elemental analysis; ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and solid-state 13 C-nuclear magnetic resonance (NMR) spectroscopies; and other techniques. The results showed significant differences among the HA fractions. The concentrations of the total acidic groups and the carboxyl groups decreased with the increasing pH of the extraction solution. However, the HA fractions derived from extraction solutions with pH 3-4 had relatively lower aromaticity but a higher protonated carbon content. The HA fractions derived from extraction solutions with pH 6-7 had the highest aromaticity and the greatest abundance of COO/N-C=O. This study demonstrated that adjusting the pH of the extraction solution is one way to fractionate HAs from Chinese weathered coal and to obtain HA fractions with compositions and structures that could serve as useful material for study and utilization. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of pH, temperature and pulsed electric fields on the turbidity and protein aggregation of ovomucin-depleted egg white.

PubMed

Liu, Ya-Fei; Oey, Indrawati; Bremer, Phil; Carne, Alan; Silcock, Pat

2017-01-01

The effect of either pulsed electric fields (PEF) or thermal processing on protein aggregation of ovomucin-depleted egg white (OdEW) solutions at different pH was assessed by solution turbidity and SDS-PAGE. Heating to 60°C for 10min caused marked protein aggregation of OdEW at pH5, 7, and 9. At constant electric field strength (E=1.4-1.8kV/cm), PEF processing under high specific energy input (W spec =260-700kJ/kg) induced some protein aggregation at pH5 and 7, but not at either pH4 or 9. Similar effects of pH on protein aggregation were observed upon PEF processing at varied E (from 0.7 to 1.7kV/cm) but with constant W spec (713kJ/kg). Analysis by SDS-PAGE revealed that proteins in the OdEW solution at pH5 were most susceptible to both PEF- and heat-induced protein aggregation and lysozyme was only involved in the formation of insoluble aggregates under PEF. The present study shows that PEF treatment has considerable potential for minimizing protein aggregation in the processing of heat-labile egg white proteins. Retaining the OdEW proteins in solution during processing has potential industry application, for example, protein fortification of drinks with OdEW, where minimizing solution turbidity would be advantageous. Copyright © 2016 Elsevier Ltd. All rights reserved.

Hydrophobic interactions between polymethacrylic acid and sodium laureth sulfate in aqueous solutions

NASA Astrophysics Data System (ADS)

Yaremko, Z. M.; Fedushinskaya, L. B.; Burka, O. A.; Soltys, M. N.

2014-09-01

The role of hydrophobic interaction in the development of associative processes is demonstrated, based on the concentration dependences of the viscosity and pH of binary solutions of polymethacrylic acid as an anionic polyelectrolyte and sodium laureth sulfate as an anionic surfactant. It is found that the inflection point on the dependence of the difference between the pH values of binary solutions of polymethacrylic acid and sodium laureth sulfate on the polyelectrolyte concentration is a criterion for determining the predominant contribution from hydrophobic interaction, as is the inflection point on the dependence of pH of individual solutions of polymethacrylic acid on the polyelectrolyte concentration.

Conformations of gelatin in trivalent chromium salt solutions: Viscosity and dynamic light scattering study

NASA Astrophysics Data System (ADS)

Qiao, Congde; Zhang, Jianlong; Kong, Aiqun

2017-02-01

An investigation of the influences of pH, salt type, and salt concentration on the conformations of gelatin molecules in trivalent chromium salt solutions was performed by viscosity and dynamic light scattering (DLS) techniques. It was found that the viscosity behaviors as polyelectrolytes or polyampholytes depended on the charge distribution on the gelatin chains, which can be tuned by the value of pH of the gelatin solution. The intrinsic viscosity of gelatin in basic chromium sulfate aqueous solution at pH = 2.0 first decreased and then increased with increasing Cr(OH)SO4 concentration, while a monotonic decrease of the intrinsic viscosity of gelatin was observed in CrCl3 solution. However, the intrinsic viscosity of gelatin at pH = 5.0 was found to be increased first and then decreased with an increase in salt concentration in Cr(OH)SO4 solution, as well as in CrCl3 solution. We suggested that the observed viscosity behavior of gelatin in trivalent chromium salt solutions was attributed to the comprehensive effects of shielding, overcharging, and crosslinking (complexation) caused by the introduction of the different counterions. In addition, the average hydrodynamic radius ( R h ) of gelatin molecules in various salt solutions was determined by DLS. It was found that the change trend of R h with salt concentration was the same as the change of intrinsic viscosity. Based on the results of the viscosity and DLS, a possible mechanism for the conformational transition of gelatin chains with external conditions including pH, salt concentration, and salt type is proposed.

An Efficient Method for Co-purification of Eggshell Matrix Proteins OC-17, OC-116, and OCX-36

PubMed Central

2016-01-01

In this study, we improved the eggshell-membrane separation process by separating the shell and membrane with EDTA solution, evaluating effects of three different extraction solutions (acetic acid, EDTA, and phosphate solution), and co-purifying multiple eggshell proteins with two successive ion-exchange chromatography procedures (CM Sepharose Fast Flow and DEAE Sepharose Fast Flow). The recovery and residual rates of eggshell and membrane separated by the modified method with added EDTA solution were 93.88%, 91.15% and 1.01%, 2.87%, respectively. Ovocleidin-116 (OC-116) and ovocalyxin-36 (OCX-36) were obtained by loading 50 mM Na-Hepes, pH 7.5, 2 mM DTT and 350 mM NaCl buffer onto the DEAE-FF column at a flow rate of 1 mL/min, ovocleidin-17 (OC-17) was obtained by loading 100 mM NaCl, 50 mM Tris, pH 8.0 on the CM-FF column at a flow rate of 0.5 mL/min. The purities of OCX-36, OC-17 and OC-116 were 96.82%, 80.15% and 73.22%, and the recovery rates were 55.27%, 53.38% and 36.34%, respectively. Antibacterial activity test suggested that phosphate solution extract exhibited significantly higher activity against the tested bacterial strains than the acetic acid or EDTA extract, probably due to more types of proteins in the extract. These results demonstrate that this separation method is feasible and efficient. PMID:28115888

Surface reactions kinetics between nanocrystalline magnetite and uranyl.

PubMed

Missana, Tiziana; Maffiotte, César; García-Gutiérrez, Miguel

2003-05-01

Magnetite is the most important end member of iron corrosion products under reducing environment, which is the condition expected in a deep geological high level radioactive waste disposal. Nanocrystalline magnetite was synthesized in the laboratory and its physicochemical properties were analyzed in detail. The kinetics of the adsorption of U(VI) and the kinetics of the actinide reduction to a lower oxidation state, in presence of the oxide, were studied by means of batch sorption techniques and X-ray photoelectron spectroscopy (XPS) analysis. The results showed that the uranium sorption and reduction processes on the magnetite surface have very fast kinetics (hours), the reduction process being triggered by sorption. XPS measurements showed that the speciation of uranium at the surface does not show significant changes with time (from 1 day to 3 months), as well as the quantity of uranium detected at the surface. The surface speciation depended on the initial pH of the contact solution. Considering that the Eh of equilibrium between magnetite and the solution, under our experimental conditions, is slightly positive (50-100 mV), the uranium reduction would also be thermodynamically possible within the liquid phase. However, the kinetics of reduction in the liquid occur at a much slower rate which, in turn, has to depend on the attainment of the magnetite/solution equilibrium. The decrease of uranium in solution, observed after the uranyl adsorption stage, and particularly at acidic pH, is most probably due to the precipitation of U(IV) formed in the solution.

Polymerized PolyHEMA photonic crystals: pH and ethanol sensor materials.

PubMed

Xu, Xiangling; Goponenko, Alexander V; Asher, Sanford A

2008-03-12

The surface of monodisperse silica particles synthesized using the Stober process were coated with a thin layer of polystyrene. Surface charge groups were attached by a grafting polymerization of styrene sulfonate. The resulting highly charged monodisperse silica particles self-assemble into crystalline colloidal arrays (CCA) in deionized water. We polymerized hydroxyethyl methacrylate (HEMA) around the CCA to form a HEMA-polymerized crystalline colloidal array (PCCA). Hydrofluoric acid was utilized to etch out the silica particles to produce a three-dimensional periodic array of voids in the HEMA PCCA. The diffraction from the embedded CCA sensitively monitors the concentration of ethanol in water because the HEMA PCCA shows a large volume dependence on ethanol due to a decreased Flory-Huggins mixing parameter. Between pure water and 40% ethanol the diffraction shifts across the entire visible spectral region. We accurately modeled the dependence of the diffraction wavelength on ethanol concentration using Flory theory. We also fabricated a PCCA (which responds to pH changes in both low and high ionic strength solutions) by utilizing a second polymerization to incorporate carboxyl groups into the HEMA PCCA. We were also able to model the pH dependence of diffraction of the HEMA PCCA by using Flory theory. An unusual feature of the pH response is a hysteresis in response to titration to higher and lower pH. This hysteresis results from the formation of a Donnan potential at high pH which shifts the ionic equilibrium. The kinetics of equilibration is very slow due to the ultralow diffusion constant of protons in the carboxylated PCCA as predicted earlier by the Tanaka group.

Inner-Helmholtz potential development at the hematite (α-Fe 2O 3) (0 0 1) surface

NASA Astrophysics Data System (ADS)

Boily, Jean-François; Chatman, Shawn; Rosso, Kevin M.

2011-08-01

Electric potentials of the (0 0 1) surface of hematite were measured as a function of pH and ionic strength in solutions of sodium nitrate and oxalic acid using the single-crystal electrode approach. The surface is predominantly charge-neutral in the pH 4-14 range, and develops a positive surface potential below pH 4 due to protonation of μ-OH 0 sites (p K1,1,0,int = -1.32). This site is resilient to deprotonation up to at least pH 14 (-p K-1,1,0,int ≫ 19). The associated Stern layer capacitance of 0.31-0.73 F/m 2 is smaller than typical values of powders, and possibly arises from a lower degree of surface solvation. Acid-promoted dissolution under elevated concentrations of HNO 3 etches the (0 0 1) surface, yielding a convoluted surface populated by -OH20.5+ sites. The resulting surface potential was therefore larger under these conditions than in the absence of dissolution. Oxalate ions also promoted (0 0 1) dissolution. Associated electric potentials were strongly negative, with values as large as -0.5 V, possibly from metal-bonded interactions with oxalate. The hematite surface can also acquire negative potentials in the pH 7-11 range due to surface complexation and/or precipitation of iron species (0.0038 Fe/nm 2) produced from acidic conditions. Oxalate-bearing systems also result in negative potentials in the same pH range, and may include ferric-oxalate surface complexes and/or surface precipitates. All measurements can be modeled by a thermodynamic model that can be used to predict inner-Helmholtz potentials of hematite surfaces.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casella, Amanda J.; Hylden, Laura R.; Campbell, Emily L.

Knowledge of real-time solution properties and composition is a necessity for any spent nuclear fuel reprocessing method. Metal-ligand speciation in aqueous solutions derived from the dissolved commercial spent fuel is highly dependent upon the acid concentration/pH, which influences extraction efficiency and the resulting speciation in the organic phase. Spectroscopic process monitoring capabilities, incorporated in a counter current centrifugal contactor bank, provide a pathway for on-line real-time measurement of solution pH. The spectroscopic techniques are process-friendly and can be easily configured for on-line applications, while classic potentiometric pH measurements require frequent calibration/maintenance and have poor long-term stability in aggressive chemical andmore » radiation environments. Our research is focused on developing a general method for on-line determination of pH of aqueous solutions through chemometric analysis of Raman spectra. Interpretive quantitative models have been developed and validated under the range of chemical composition and pH using a lactic acid/lactate buffer system. The developed model was applied to spectra obtained on-line during solvent extractions performed in a centrifugal contactor bank. The model predicted the pH within 11% for pH > 2, thus demonstrating that this technique could provide the capability of monitoring pH on-line in applications such as nuclear fuel reprocessing.« less

Effects of solution chemistry on adsorption of selected pharmaceuticals and personal care products (PPCPs) by graphenes and carbon nanotubes.

PubMed

Liu, Fei-fei; Zhao, Jian; Wang, Shuguang; Du, Peng; Xing, Baoshan

2014-11-18

Adsorption of three selected pharmaceuticals and personal care products (PPCPs) (ketoprofen (KEP), carbamazepine (CBZ), and bisphenol A (BPA)) by two reduced graphene oxides (rGO1 and rGO2) and one commercial graphene was examined under different solution conditions. Single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs), and powdered graphite were also investigated for comparison. All adsorption isotherms followed the order of SWCNTs > rGO1 > rGO2 > MWCNTs > graphene > graphite, consistent with the orders of their surface areas and micropore volumes. After surface area normalization, adsorption affinities of the three PPCPs onto graphenes were lower than onto graphite, suggesting incomplete occupation for adsorption sites because of the aggregation of graphene sheets and the presence of oxygen-containing functional groups. The observed pH effects on adsorption correlated well with the pH-regulated distribution of the protonated neutral species of the three PPCPs. Increasing ionic strength from 0 to 20 mM increased KEP adsorption due to the electrostatic screening by Na(+) and Ca(2+). Both humic acid (HA) and sodium dodecylbenzenesulfonate (SDBS) suppressed PPCPs adsorption to all adsorbents, but their impacts onto graphenes were lower than those onto CNTs because of their lower adsorption by graphenes. More severe HA (or SDBS) effect was found on negatively charged KEP at the tested solution pH 6.50 due to the electrostatic repulsion between the same charged KEP and HA (or SDBS). The findings of the present study may have significant implications for the environmental fate assessment of PPCPs and graphene.

Structural and photodynamic properties of the anti-cancer drug irinotecan in aqueous solutions of different pHs.

PubMed

di Nunzio, Maria Rosaria; Douhal, Yasmin; Organero, Juan Angel; Douhal, Abderrazzak

2018-05-23

This work reports on photophysical studies of the irinotecan (IRT) anti-cancer drug in water solutions of different acidities (pH = 1.11-9.46). We found that IRT co-exists as mono-cationic (C1), di-cationic (C2), or neutral (N) forms. The population of each prototropic species depends on the pH of the solution. At pH = 1.11-3.01, the C1 and C2 structures are stabilized. At pH = 7.00, the most populated species is C1, while at pH values larger than 9.46 the N form is the most stable species. In the 1.11-2.61 pH range, the C1* emission is efficiently quenched by protons to give rise to the emission from C2*. The dynamic quenching constant, KD, is ∼32 M-1. While the diffusion governs the rate of excited-state proton-transfer (ESPT) under these conditions, the reaction rate increases with the proton concentration. A two-step diffusive Debye-Smoluchowski model was applied at pH = 1.11-2.61 to describe the protonation of C1*. The ESPT time constants derived for C1* are 382 and 1720 ps at pH = 1.11 and 1.95, respectively. We found that one proton species is involved in the protonation of C1* to give C2*, in the analyzed acidic pH range. Under alkaline conditions (pH = 9.46), the N form is the most stable structure of IRT. These results indicate the influence of the pH of the medium on the structural and dynamical properties of IRT in water solution. They may help to provide a better understanding on the relationship between the structure and biological activity of IRT.

Macroscopic experimental and modeling evaluation of selenite and selenate adsorption mechanisms on gibbsite

USDA-ARS?s Scientific Manuscript database

Selenite Se(IV) and selenate Se(VI) adsorption behavior was investigated on gibbsite as a function of solution pH and solution ionic strength. Adsorption of both Se redox states decreased with increasing solution pH. Electrophoretic mobility measurements showed downward shifts in point of zero cha...

Influence of Soil Solution Salinity on Molybdenum Adsorption by Soils

USDA-ARS?s Scientific Manuscript database

Molybdenum (Mo) adsorption on five arid-zone soils from California was investigated as a function of equilibrium solution Mo concentration (0-30 mg L-1), solution pH (4-8), and electrical conductivity (EC = 0.3 or 8 dS m-1). Molybdenum adsorption decreased with increasing pH. An adsorption maximum...

Evaluation of environmental compatibility of EAFD using different leaching standards.

PubMed

Sebag, M G; Korzenowski, C; Bernardes, A M; Vilela, A C

2009-07-30

A study on laboratory scale to evaluate the environmental compatibility of electric arc furnace dust (EAFD) is reported in this article. EAFD, a waste by-product of the steel-making process, was generated on a steel plant located in Brazil. Different leaching tests, NBR10005 (Brazilian), AFNORX31-210 (French), JST-13 (Japanese), DIN38414-S4 (German), TCLP (American), and NEN 7343 (Netherland) were conducted. These leaching procedures are batch tests and are columns conducted in a way that an equilibrium condition should be achieved. The pH of the medium showed a crucial parameter governing the release of metals from the solid phase into solution. As the pH of the medium varies with the leachant used, this determines the dissolution of the elements. Zn, Pb, Mn, Cd, and Cu presented high leachability at NBR10005 procedures (acid pH). Except Pb and Cr, the leachability of all others metals in leaching tests with alkaline pH decreases with the increase of the pH. NBR10005 classifies the EAFD as a hazardous waste due to high concentration of Pb and Cd in leachate. The column tests are presented in the following order of leaching: Pb>Cr>Zn>Mn>Cu>Cd.

Electrochemical Induced Calcium Phosphate Precipitation: Importance of Local pH

PubMed Central

2017-01-01

Phosphorus (P) is an essential nutrient for living organisms and cannot be replaced or substituted. In this paper, we present a simple yet efficient membrane free electrochemical system for P removal and recovery as calcium phosphate (CaP). This method relies on in situ formation of hydroxide ions by electro mediated water reduction at a titanium cathode surface. The in situ raised pH at the cathode provides a local environment where CaP will become highly supersaturated. Therefore, homogeneous and heterogeneous nucleation of CaP occurs near and at the cathode surface. Because of the local high pH, the P removal behavior is not sensitive to bulk solution pH and therefore, efficient P removal was observed in three studied bulk solutions with pH of 4.0 (56.1%), 8.2 (57.4%), and 10.0 (48.4%) after 24 h of reaction time. While P removal efficiencies are not generally affected by bulk solution pH, the chemical-physical properties of CaP solids collected on the cathode are still related to bulk solution pH, as confirmed by structure characterizations. High initial solution pH promotes the formation of more crystalline products with relatively high Ca/P molar ratio. The Ca/P molar ratio increases from 1.30 (pH 4.0) to 1.38 (pH 8.2) and further increases to 1.55 (pH 10.0). The formation of CaP precipitates was a typical crystallization process, with an amorphous phase formed at the initial stage which then transforms to the most stable crystal phase, hydroxyapatite, which is inferred from the increased Ca/P molar ratio from 1.38 (day 1) to the theoretical 1.76 (day 11) and by the formation of needle-like crystals. Finally, we demonstrated the efficiency of this system for real wastewater. This, together with the fact that the electrochemical method can work at low bulk pH, without dosing chemicals and a need for a separation process, highlights the potential application of the electrochemical method for P removal and recovery. PMID:28872838

Comparative study of buffered 50% glycolic acid (pH 3.0) + 0.5% salicylic acid solution vs Jessner's solution in patients with acne vulgaris.

PubMed

In Jae, Jeong; Dong Ju, Hyun; Dong Hyun, Kim; Yoon, Moon Soo; Lee, Hee Jung

2017-11-21

Superficial chemical peels are frequently used in acne vulgaris treatment. Although glycolic acid (GA) has been widely used in clinical practice, its pH ranges from 0.08-2.75 and thus should be neutralized after application to avoid burns. To evaluate treatment efficacy and safety of chemical peeling using buffered 50% GA (pH 3.0) + 0.5% salicylic acid (SA) solution that does not need to be neutralized in the treatment of acne vulgaris compared to the conventional peeling using Jessner's solution. We performed a prospective, randomized, evaluator-blind, split-face clinical trial. Twenty patients were randomized by assigning one side of each patient's face to receive a 50% GA (pH 3.0) + 0.5% SA peel (GA side) and the other side to receive the Jessner's solution (Jessner's solution side). All patients underwent 2 sessions of treatment spaced 2 weeks apart. Lesion count, acne severity, subjective efficacy assessment, and side effects were evaluated. The total lesion count was significantly reduced for the GA and Jessner's solution sides (P < .001). However, there was no significant difference in the total lesion count, acne severity, or subjective efficacy assessment between the 2 sides (P > .05). The GA side had fewer side effects than the Jessner's solution side. The results of this study suggest that chemical peeling using the 50% GA (pH 3.0) + 0.5% SA solution can be as effective and convenient as the conventional peeling using Jessner's solution in the treatment of acne vulgaris and may show fewer adverse events than the conventional peeling. © 2017 Wiley Periodicals, Inc.

pH : a key control of the nature and distribution of dissolved organic matter and associated trace metals in soil

NASA Astrophysics Data System (ADS)

Pédrot, M.; Dia, A.; Davranche, M.

2009-04-01

Dissolved organic matter is ubiquitous at the Earth's surface and plays a prominent role in controlling metal speciation and mobility from soils to hydrosystems. Humic substances (HS) are usually considered to be the most reactive fraction of organic matter. Humic substances are relatively small and formed by chemically diverse organic molecules, bearing different functional groups that act as binding sites for cations and mineral surfaces. Among the different environmental physicochemical parameters controlling the metal speciation, pH is likely to be the most important one. Indeed, pH affect the dissociation of functional groups, and thus can influence the HS structure, their ability to complex metals, their solubility degree allowing the formation of aggregates at the mineral surface. In this context, soil/water interactions conducted through batch system experiments, were carried out with a wetland organic-rich soil to investigate the effect of pH on the release of dissolved organic carbon (DOC) and associated trace elements. The pH was regulated between 4 and 7.5 using an automatic pH stat titrator. Ultrafiltration experiments were performed to separate the dissolved organic pool following decreasing pore sizes (30 kDa, 5 kDa and 2 kDa with 1 Da = 1 g.mol-1). The pH increase induced a significant DOC release, especially in heavy organic molecules (size >5 kDa) with a high aromaticity (>30 %). These were probably humic acids (HA). This HA release influenced (i) directly the trace element concentrations in soil solution since HA were enriched in several trace elements such as Th, REE, Y, U, Cr and Cu; and (ii) indirectly by the breaking of clay-humic complexes releasing Fe- and Al-rich nanoparticles associated with V, Pb and Ti. By contrast, at acid pH, most HS were complexed onto mineral surfaces. They also sequestered iron nanoparticles. Therefore, at low pH, most part of DOC molecules had a size < 5 kDa and lower aromaticity. Thus, the DOC was mostly composed of simple organic compounds little complexing. Consequently, the soil solution was depleted in trace elements such as Th, REE, Y, U, Cr, Cu, Al, Fe, V, Pb and Ti, but also enriched in Ca, Sr, Ba, Mn, Mg, Co, Zn and in a lesser proportion in Rb, Li and Ni. The aromaticity in the fractions <5 kDa was higher than in the fractions <30 kDa or <0.2 µm. Complementary experiments were performed to understand the HS size distribution and aromaticity according to pH and ionic strength .The molecular size and shape of HS is usually explained by two concepts: (i) the macropolymeric structure with heavy organic molecules considered to be flexible linear polyelectrolytes and (ii) the supramolecular structure with an association of a complex mixture of different molecules held together by dispersive weak forces. Ours results supported the HA supramolecular structure at neutral or basic pH conditions. But, at acid pH, a disruption of the humic supramolecular associations involved the release of small organic molecules with a high aromaticity. Moreover, this aromaticity variation can be due also to the presence of fulvic acids in the fractions <5 kDa and a mixture of heavy organic molecules little complexing in the fractions >5 kDa. These latter molecules displayed a low aromaticity decreasing the global aromaticity of the fractions <30 kDa and <0.2 µm. To summarize, these new data demonstrated that the DOC and trace element concentrations of the soil solutions were strongly controlled by pH. This parameter influenced the nature and the size of the DOC as well as, the trace element concentrations in the soil solutions, with a decreasing contribution of HA when pH decreased. This pH dependence is a key issue of concern since local (human pressure) and/or global (climatic) warning result in pH water changes.

The Effect of Temperature and Solution pH on the Nucleation of Tetragonal Lysozyme Crystals

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Jacobs, Randolph S.; Frazier, Tyralynn; Snell, Edward H.; Pusey, Marc L.

1999-01-01

Part of the challenge of macromolecular crystal growth for structure determination is obtaining crystals with a volume suitable for x-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of supersaturation, temperature, and pH on the nucleation rate of tetragonal lysozyme crystals. Batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over 1 week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Crystal numbers were found to increase with increasing supersaturation and temperature. The most significant variable, however, was pH; crystal numbers changed by two orders of magnitude over the pH range 4.0-5.2. Crystal size also varied with solution conditions, with the largest crystals obtained at pH 5.2. Having optimized the crystallization conditions, we prepared a batch of crystals under the same initial conditions, and 50 of these crystals were analyzed by x-ray diffraction techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

The molecular basis of the solution properties of hyaluronan investigated by confocal fluorescence recovery after photobleaching.

PubMed Central

Gribbon, P; Heng, B C; Hardingham, T E

1999-01-01

Hyaluronan (HA) is a highly hydrated polyanion, which is a network-forming and space-filling component in the extracellular matrix of animal tissues. Confocal fluorescence recovery after photobleaching (confocal-FRAP) was used to investigate intramolecular hydrogen bonding and electrostatic interactions in hyaluronan solutions. Self and tracer lateral diffusion coefficients within hyaluronan solutions were measured over a wide range of concentrations (c), with varying electrolyte and at neutral and alkaline pH. The free diffusion coefficient of fluoresceinamine-labeled HA of 500 kDa in PBS was 7.9 x 10(-8) cm(2) s(-1) and of 830 kDa HA was 5.6 x 10(-8) cm(2) s(-1). Reductions in self- and tracer-diffusion with c followed a stretched exponential model. Electrolyte-induced polyanion coil contraction and destiffening resulted in a 2.8-fold increase in self-diffusion between 0 and 100 mM NaCl. Disruption of hydrogen bonds by strong alkali (0.5 M NaOH) resulted in further larger increases in self- and tracer-diffusion coefficients, consistent with a more dynamic and permeable network. Concentrated hyaluronan solution properties were attributed to hydrodynamic and entanglement interactions between domains. There was no evidence of chain-chain associations. At physiological electrolyte concentration and pH, the greatest contribution to the intrinsic stiffness of hyaluronan appeared to be due to hydrogen bonds between adjacent saccharides. PMID:10512840

Trimerization Dictates Solution Opalescence of a Monoclonal Antibody.

PubMed

Yang, Teng-Chieh; Langford, Alex Jacob; Kumar, Sandeep; Ruesch, John Carl; Wang, Wei

2016-08-01

Opalescence, sometimes observed in antibody solutions, is thought to be mediated by light scattering of soluble oligomers or insoluble particulates. However, mechanistic features, such as stoichiometry and self-association affinity of oligomeric species related to opalescence, are poorly understood. Here, opalescence behavior of a monoclonal antibody (mAb-1) solution was studied over a wide range of solution conditions including different protein concentrations, pH, and in the presence or absence of salt. Hydrodynamic and thermodynamic properties of mAb-1 solutions were studied by analytical ultracentrifugation and dynamic light scattering. Opalescence in mAb-1 solutions is pH and concentration dependent. The degree of opalescence correlates with reversible monomer-trimer equilibrium detected by analytical ultracentrifugation. Increased trimer formation corresponds to increased opalescence in mAb-1 solutions at higher pH and protein concentrations. Addition of NaCl shifts this equilibrium toward monomer and reduces solution opalescence. This study demonstrates that opalescence in mAb-1 solutions does not arise from the light scattering of monomer or random molecular self-associations but is strongly correlated with a specific self-association stoichiometry and affinity. Importantly, at pH 5.5 (far below isoelectric point of mAb-1), the solution is not opalescent and with nonideal behavior. This study also dissects several parameters to describe the hydrodynamic and thermodynamic nonideality. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

An induced current method for measuring zeta potential of electrolyte solution-air interface.

PubMed

Song, Yongxin; Zhao, Kai; Wang, Junsheng; Wu, Xudong; Pan, Xinxiang; Sun, Yeqing; Li, Dongqing

2014-02-15

This paper reports a novel and very simple method for measuring the zeta potential of electrolyte solution-air interface. When a measuring electrode contacts the electrolyte solution-air interface, an electrical current will be generated due to the potential difference between the electrode-air surface and the electrolyte solution-air interface. The amplitude of the measured electric signal is linearly proportional to this potential difference; and depends only on the zeta potential at the electrolyte solution-air interface, regardless of the types and concentrations of the electrolyte. A correlation between the zeta potential and the measured voltage signal is obtained based on the experimental data. Using this equation, the zeta potential of any electrolyte solution-air interface can be evaluated quickly and easily by inserting an electrode through the electrolyte solution-air interface and measuring the electrical signal amplitude. This method was verified by comparing the obtained results of NaCl, MgCl2 and CaCl2 solutions of different pH values and concentrations with the zeta potential data reported in the published journal papers. Copyright © 2013 Elsevier Inc. All rights reserved.

pH Memory Effects of Tunable Block Copolymer Photonic Gels and Their Applications

NASA Astrophysics Data System (ADS)

Kang, Youngjong; Thomas, Edwin L.

2007-03-01

Materials with hysteresis, showing a bistable state to the external stimuli, have been widely investigated due to their potential applications. For example, they could be used as memory devices or optical switches when they have magnetic or optical hysteresis response to the external stimuli. Here we report pH tunable photonic gels which are spontaneously assembled from block copolymers. The general idea of this research is based on the selective swelling of block copolymer lamellar mesogels, where the solubility of one block is responsive to the change of pH. In this system, the domain spacing of the lamellar is varied with the extent of swelling. As a model system, we used protonated polystyrene-b-poly(2-vinly pyridine) (PS-b-P2VP) block copolymers forming lamellar structures. The photonic gel films prepared from protonated PS-b-P2VP show a strong reflectance in aqueous solution and the band position was varied with pH. Interestingly, a very strong optical hysteresis was observed while the reflection band of photonic gels was tuned by changing pH. We anticipate that pH tunable photonic gels with hysteresis can be applicable to novel applications such as a component of memory devices, photonic switches or drug delivery vehicles.

Prevention and management of silica scaling in membrane distillation using pH adjustment

DOE PAGES

Bush, John A.; Vanneste, Johan; Gustafson, Emily M.; ...

2018-02-27

Membrane scaling by silica is a major challenge in desalination, particularly for inland desalination of brackish groundwater or geothermal resources, which often contain high concentrations of silica and dissolved solids. Adjustment of feed pH may reduce silica scaling risk, which is important for inland facilities that operate at high water recoveries to reduce brine disposal costs. However, water recovery of reverse osmosis is also limited due to increased osmotic pressure with feed water concentration. Membrane distillation (MD) is a thermally driven membrane desalination technique that is not limited by increased osmotic pressure of the feed. In this investigation, pH adjustmentmore » was tested as a strategy to reduce silica scaling risk in the MD process. With feed water pH less than 5 or higher than 10, scaling impacts were negligible at silica concentrations up to 600 mg/L. Scaling rates were highest at neutral pH between 6 and 8. Cleaning strategies were also explored to remove silica scale from membranes. Cleaning using NaOH solutions at pH higher than 11 to induce dissolution of silica scale was effective at temporarily restoring performance; however, some silica remained on membrane surfaces and scaling upon re-exposure to supersaturated silica concentrations occurred faster than with new membranes.« less

Determining the Effect of pH on the Partitioning of Neutral, Cationic and Anionic Chemicals to Artificial Sebum: New Physicochemical Insight and QSPR Model.

PubMed

Yang, Senpei; Li, Lingyi; Chen, Tao; Han, Lujia; Lian, Guoping

2018-05-14

Sebum is an important shunt pathway for transdermal permeation and targeted delivery, but there have been limited studies on its permeation properties. Here we report a measurement and modelling study of solute partition to artificial sebum. Equilibrium experiments were carried out for the sebum-water partition coefficients of 23 neutral, cationic and anionic compounds at different pH. Sebum-water partition coefficients not only depend on the hydrophobicity of the chemical but also on pH. As pH increases from 4.2 to 7.4, the partition of cationic chemicals to sebum increased rapidly. This appears to be due to increased electrostatic attraction between the cationic chemical and the fatty acids in sebum. Whereas for anionic chemicals, their sebum partition coefficients are negligibly small, which might result from their electrostatic repulsion to fatty acids. Increase in pH also resulted in a slight decrease of sebum partition of neutral chemicals. Based on the observed pH impact on the sebum-water partition of neutral, cationic and anionic compounds, a new quantitative structure-property relationship (QSPR) model has been proposed. This mathematical model considers the hydrophobic interaction and electrostatic interaction as the main mechanisms for the partition of neutral, cationic and anionic chemicals to sebum.

Prevention and management of silica scaling in membrane distillation using pH adjustment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bush, John A.; Vanneste, Johan; Gustafson, Emily M.

Membrane scaling by silica is a major challenge in desalination, particularly for inland desalination of brackish groundwater or geothermal resources, which often contain high concentrations of silica and dissolved solids. Adjustment of feed pH may reduce silica scaling risk, which is important for inland facilities that operate at high water recoveries to reduce brine disposal costs. However, water recovery of reverse osmosis is also limited due to increased osmotic pressure with feed water concentration. Membrane distillation (MD) is a thermally driven membrane desalination technique that is not limited by increased osmotic pressure of the feed. In this investigation, pH adjustmentmore » was tested as a strategy to reduce silica scaling risk in the MD process. With feed water pH less than 5 or higher than 10, scaling impacts were negligible at silica concentrations up to 600 mg/L. Scaling rates were highest at neutral pH between 6 and 8. Cleaning strategies were also explored to remove silica scale from membranes. Cleaning using NaOH solutions at pH higher than 11 to induce dissolution of silica scale was effective at temporarily restoring performance; however, some silica remained on membrane surfaces and scaling upon re-exposure to supersaturated silica concentrations occurred faster than with new membranes.« less

Influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater

NASA Astrophysics Data System (ADS)

Uchikawa, Joji; Harper, Dustin T.; Penman, Donald E.; Zachos, James C.; Zeebe, Richard E.

2017-12-01

The ratio of boron to calcium (B/Ca) in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry. Applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric CO2 concentrations. However, precise controls on B/Ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties. To help establish a firm inorganic basis for interpreting the B/Ca records, we examined the effect of a suite of chemical parameters ([Ca2+], pH, [DIC], salinity and [PO43-]) on B/Ca in inorganic calcite precipitated in artificial seawater. These parameters were primarily varied individually while keeping all others constant, but we also tested the influence of pH and [DIC] at a constant calcite precipitation rate (R) by concurrent [Ca2+] adjustments. In the simple [Ca2+], pH and [DIC] experiments, both R and B/Ca increased with these parameters. In the pH-[Ca2+] and [DIC]-[Ca2+] experiments at constant R, on the other hand, B/Ca was invariant at different pH and decreased with [DIC], respectively. These patterns agree with the behavior of solution [BTotal/DIC] ratio such that, at a fixed [BTotal], it is independent of pH but decreases with [DIC]. Based on these results, R and [BTotal/DIC] ratio appear to be the primary controls on B/Ca in inorganic calcite, suggesting that both B(OH)4- and B(OH)3 are possibly involved in B incorporation. Moreover, B/Ca modestly increased with salinity and [PO43-]. Inorganic calcite precipitated at higher R and in the presence of oxyanions such as SO42- and PO43- in growth solutions often undergoes surface roughening due to formation of crystallographic defects, vacancies and, occasionally, amorphous/hydrous CaCO3. These non-lattice sites may provide additional space for B, particularly B(OH)3. Consequently, besides the macroscopic influence of R and bulk solution chemistry, molecular-scale processes associated with calcite nucleation can be an important consideration for B incorporation, especially in complex ionic solutions. Lastly, the covariance of B/Ca with [DIC] and salinity observed here qualitatively agrees with those in planktic foraminifers. It follows that their impact on foraminiferal B/Ca is partly inorganically driven, which may explain why the effect is evident across different species.

A renaissance of soaps? - How to make clear and stable solutions at neutral pH and room temperature.

PubMed

Wolfrum, Stefan; Marcus, Julien; Touraud, Didier; Kunz, Werner

2016-10-01

Soaps are the oldest and perhaps most natural surfactants. However, they lost much of their importance since "technical surfactants", usually based on sulfates or sulfonates, have been developed over the last fifty years. Indeed, soaps are pH- and salt-sensitive and they are irritant, especially to the eyes. In food emulsions, although authorized, they have a bad taste, and long-chain saturated soaps have a high Krafft temperature. We believe that most or perhaps all of these problems can be solved with modern formulation approaches. We start this paper with a short overview of our present knowledge of soaps and soap formulations. Then we focus on the problem of the lacking soap solubility at neutral pH values. For example, it is well known that with the food emulsifier sodium oleate (NaOl), clear and stable aqueous solutions can only be obtained at pH values higher than 10. A decrease in the pH value leads to turbid and unstable solutions. This effect is not compatible with the formulation of aqueous stable and drinkable formulations with neutral or even acidic pH values. However, the pH value/phase behavior of aqueous soap solutions can be altered by the addition of other surfactants. Such a surfactant can be Rebaudioside A (RebA), a steviol glycoside from the plant Stevia rebaudiana which is used as a natural food sweetener. In a recent paper, we showed the influence of RebA on the apKa value of sodium oleate in a beverage microemulsion and on its clearing temperature. In the present paper, we report on the effect of the edible bio-surfactant RebA, on the macroscopic and microscopic phase behavior of simple aqueous sodium oleate solutions at varying pH values. The macroscopic phase behavior is investigated by visual observation and turbidity measurements. The microscopic phase behavior is analyzed by acid-base titration curves, phase-contrast and electron microscopy. It turned out that even at neutral pH, aqueous NaOl/RebA solutions can be completely clear and stable for more than 50days at room temperature. This is for the first time that a long chain soap could be really solubilized in water at neutral pH at room temperature. At last, these findings were applied to prepare stable, highly translucent and drinkable aqueous solutions of omega-3-fatty acids at a pH value of 7.5. Copyright © 2016 Elsevier B.V. All rights reserved.

Endowing hexaphenylsilole with chemical sensory and biological probing properties by attaching amino pendants to the silolyl core

NASA Astrophysics Data System (ADS)

Dong, Yongqiang; Lam, Jacky W. Y.; Qin, Anjun; Li, Zhen; Liu, Jianzhao; Sun, Jingzhi; Dong, Yuping; Tang, Ben Zhong

2007-09-01

Hexaphenylsilole (HPS) was functionalized by two amino (A 2) groups, giving a new silole derivative of 1,1-bis[4-(diethylaminomethyl)phenyl]-2,3,4,5-tetraphenylsilole (A 2HPS) that is capable of detecting explosives, biomacromolecules and pH changes. A 2HPS is nonemissive when molecularly dissolved but becomes highly luminescent when aggregated. The emission of its nanoaggregates is quenched by picric acid with a high Ksv value (˜1.7 × 10 5 M -1). A 2HPS can dissolve in acidic aqueous media, due to the transformation of its amino groups to ammonium-salts. The resultant nonemissive aqueous solution is turned on by increasing its pH value or adding protein or DNA.

Effects of gastric pH on oral drug absorption: In vitro assessment using a dissolution/permeation system reflecting the gastric dissolution process.

PubMed

Kataoka, Makoto; Fukahori, Miho; Ikemura, Atsumi; Kubota, Ayaka; Higashino, Haruki; Sakuma, Shinji; Yamashita, Shinji

2016-04-01

The aim of the present study was to evaluate the effects of gastric pH on the oral absorption of poorly water-soluble drugs using an in vitro system. A dissolution/permeation system (D/P system) equipped with a Caco-2 cell monolayer was used as the in vitro system to evaluate oral drug absorption, while a small vessel filled with simulated gastric fluid (SGF) was used to reflect the gastric dissolution phase. After applying drugs in their solid forms to SGF, SGF solution containing a 1/100 clinical dose of each drug was mixed with the apical solution of the D/P system, which was changed to fasted state-simulated intestinal fluid. Dissolved and permeated amounts on applied amount of drugs were then monitored for 2h. Similar experiments were performed using the same drugs, but without the gastric phase. Oral absorption with or without the gastric phase was predicted in humans based on the amount of the drug that permeated in the D/P system, assuming that the system without the gastric phase reflected human absorption with an elevated gastric pH. The dissolved amounts of basic drugs with poor water solubility, namely albendazole, dipyridamole, and ketoconazole, in the apical solution and their permeation across a Caco-2 cell monolayer were significantly enhanced when the gastric dissolution process was reflected due to the physicochemical properties of basic drugs. These amounts resulted in the prediction of higher oral absorption with normal gastric pH than with high gastric pH. On the other hand, when diclofenac sodium, the salt form of an acidic drug, was applied to the D/P system with the gastric phase, its dissolved and permeated amounts were significantly lower than those without the gastric phase. However, the oral absorption of diclofenac was predicted to be complete (96-98%) irrespective of gastric pH because the permeated amounts of diclofenac under both conditions were sufficiently high to achieve complete absorption. These estimations of the effects of gastric pH on the oral absorption of poorly water-soluble drugs were consistent with observations in humans. In conclusion, the D/P system with the gastric phase may be a useful tool for better predicting the oral absorption of poorly water-soluble basic drugs. In addition, the effects of gastric pH on the oral absorption of poorly water-soluble drugs may be evaluated by the D/P system with and without the gastric phase. Copyright © 2016 Elsevier B.V. All rights reserved.

Gallium(III) complexes of DOTA and DOTA-monoamide: kinetic and thermodynamic studies.

PubMed

Kubícek, Vojtech; Havlícková, Jana; Kotek, Jan; Tircsó, Gyula; Hermann, Petr; Tóth, Eva; Lukes, Ivan

2010-12-06

Given the practical advantages of the (68)Ga isotope in positron emission tomography applications, gallium complexes are gaining increasing importance in biomedical imaging. However, the strong tendency of Ga(3+) to hydrolyze and the slow formation and very high stability of macrocyclic complexes altogether render Ga(3+) coordination chemistry difficult and explain why stability and kinetic data on Ga(3+) complexes are rather scarce. Here we report solution and solid-state studies of Ga(3+) complexes formed with the macrocyclic ligand 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, (DOTA)(4-), and its mono(n-butylamide) derivative, (DO3AM(Bu))(3-). Thermodynamic stability constants, log K(GaDOTA) = 26.05 and log K(GaDO3AM(Bu)) = 24.64, were determined by out-of-cell pH-potentiometric titrations. Due to the very slow formation and dissociation of the complexes, equilibration times of up to ∼4 weeks were necessary. The kinetics of complex dissociation were followed by (71)Ga NMR under both acidic and alkaline conditions. The GaDOTA complex is significantly more inert (τ(1/2) ∼12.2 d at pH = 0 and τ(1/2) ∼6.2 h at pH = 10) than the GaDO3AM(Bu) analogue (τ(1/2) ∼2.7 d at pH = 0 and τ(1/2) ∼0.7 h at pH = 10). Nevertheless, the kinetic inertness of both chelates is extremely high and approves the application of Ga(3+) complexes of such DOTA-like ligands in molecular imaging. The solid-state structure of the GaDOTA complex, crystallized from a strongly acidic solution (pH < 1), evidenced a diprotonated form with protons localized on the free carboxylate pendants.

Buffer capacity of 4% succinylated gelatin does not provide any advantages over acidic 6% hydroxyethyl starch 130/0.4 for acid-base balance during experimental mixed acidaemia in a porcine model.

PubMed

Esche, V; Russ, M; Melzer, S; Grossmann, B; Boemke, W; Unger, J K

2008-11-01

Four percent gelatine is an alkaline compound due to NH2 groups, whereas 6% hydroxyethyl starch 130/0.4 (HES130) has acidic features. We investigated whether these solutions lead to differences in acid-base balance in pigs during acidaemia and correction of pH. Anaesthetized pigs were randomized to HES130 or gelatine infusion (n = 5 per group). Animals received acid infusion (0.4 M solution of lactic acid and HCl diluted in normal saline) and low tidal volume ventilation (6-7 mL kg(-1), PaCO2 of 80-85 mmHg, pH 7.19-7.24). Measurements were made before and after induction of acidaemia, before and after correction of pH with haemofiltration (continuous venovenous haemofiltration) and tris-hydroxymethylaminomethane infusion. We measured parameters describing acid-base balance according to Stewart's approach, ketone body formation, oxygen delivery, haemodynamics, diuresis and urinary pH. Acid-base balance did not differ significantly between the groups. In HES130-treated pigs, the haemodilution-based drop of haemoglobin (1.4 +/- 1.0 g dL(-1), median +/- SD) was paralleled by an increase in the cardiac output (0.5 +/- 0.4 L min(-1). Lacking increases in cardiac output, gelatine-treated pigs demonstrated a reduction in oxygen delivery (149.4 +/- 106.0 mL min(-1)). Tris-hydroxymethylaminomethane volumes required for pH titration to desired values were significantly higher in the gelatine group (0.7 +/- 0.1 mL kg(-1) h(-1) vs. HES130: 0.5 +/- 0.2 mL kg(-1) h(-1)). The buffer capacity of gelatine did not lead to favourable differences in acid-base balance in comparison to HES130.

Gravity-driven pH adjustment for site-specific protein pKa measurement by solution-state NMR

NASA Astrophysics Data System (ADS)

Li, Wei

2017-12-01

To automate pH adjustment in site-specific protein pKa measurement by solution-state NMR, I present a funnel with two caps for the standard 5 mm NMR tube. The novelty of this simple-to-build and inexpensive apparatus is that it allows automatic gravity-driven pH adjustment within the magnet, and consequently results in a fully automated NMR-monitored pH titration without any hardware modification on the NMR spectrometer.

Parallel changes in intracellular water volume and pH induced by NH(3)/NH(4)(+) exposure in single neuroblastoma cells.

PubMed

Blanco, Víctor M; Márquez, Martín S; Alvarez-Leefmans, Francisco J

2013-01-01

Increased blood levels of ammonia (NH3) and ammonium (NH4(+)), i.e. hyperammonemia, leads to cellular brain edema in humans with acute liver failure. The pathophysiology of this edema is poorly understood. This is partly due to incomplete understanding of the osmotic effects of the pair NH3/NH4(+) at the cellular and molecular levels. Cell exposure to solutions containing NH3/NH4(+) elicits changes in intracellular pH (pHi), which can in turn affect cell water volume (CWV) by activating transport mechanisms that produce net gain or loss of solutes and water. The occurrence of CWV changes caused by NH3/NH4(+) has long been suspected, but the mechanisms, magnitude and kinetics of these changes remain unknown. Using fluorescence imaging microscopy we measured, in real time, parallel changes in pHi and CWV caused by brief exposure to NH3/NH4(+) of single cells (N1E-115 neuroblastoma or NG-108 neuroblastoma X glioma ) loaded with the fluorescent indicator BCECF. Changes in CWV were measured by exciting BCECF at its intracellular isosbestic wavelength (∼438 nm), and pHi was measured ratiometrically. Brief exposure to isosmotic solutions (i.e. having the same osmolality as that of control solutions) containing NH4Cl (0.5- 30 mM) resulted in a rapid, dose-dependent swelling, followed by isosmotic regulatory volume decrease (iRVD). NH4Cl solutions in which either extracellular [NH3] or [NH4(+)] was kept constant while the other was changed by varying the pH of the solution, demonstrated that [NH3]o rather than [NH4(+)]o is the main determinant of the NH4Cl-induced swelling. The iRVD response was sensitive to the anion channel blocker NPPB, and partly dependent on external Ca(2+). Upon removal of NH4Cl, cells shrank and displayed isosmotic regulatory volume increase (iRVI). Regulatory volume responses could not be activated by comparable CWV changes produced by anisosmotic solutions, suggesting that membrane stretch or contraction by themselves are not sufficient to trigger these responses. Inhibition of glutamine synthetase partially blocked the NH4Cl-induced swelling. A quantitative description of the osmotic changes produced by exposure to NH3/NH4(+) in single neurons and glial cells shows that ∼35 to 45% of the initial cell swelling can be explained by intracellular accumulation of NH4(+) due to rapid permeation and protonation of NH3. Another∼23% of the swelling can be accounted for by rapid glutamine accumulation. The results are discussed in terms of basic cell physiology and their potential relevance to the pathophysiology of hyperammonemic cellular brain edema. © 2014 S. Karger AG, Basel.

The Importance of pH, Oxygen, and Bitumen on the Oxidation and Precipitation of Fe(III)-(oxy)hydroxides during Hydraulic Fracturing of Oil/Gas Shales

NASA Astrophysics Data System (ADS)

Jew, A. D.; Dustin, M. K.; Harrison, A. L.; Joe-Wong, C. M.; Thomas, D.; Maher, K.; Brown, G. E.; Bargar, J.

2016-12-01

Due to the rapid growth of hydraulic fracturing in the United States, understanding the cause for the rapid production drop off of new wells over the initial months of production is paramount. One possibility for the production decrease is pore occlusion caused by the oxidation of Fe(II)-bearing phases resulting in Fe(III) precipitates. To understand the release and fate of Fe in the shale systems, we reacted synthesized fracture fluid at 80oC with shale from four different geological localities (Marcellus Fm., Barnett Fm., Eagle Ford Fm., and Green River Fm.). A variety of wet chemical and synchrotron-based techniques (XRF mapping and x-ray absorption spectroscopy) were used to understand Fe release and solid phase Fe speciation. Solution pH was found to be the greatest factor for Fe release. Carbonate-poor Barnett and Marcellus shale showed rapid Fe release into solution followed by a plateau or significant drop in Fe concentrations indicating mineral precipitation. Conversely, in high carbonate shales, Eagle Ford and Green River, no Fe was detected in solution indicating fast Fe oxidation and precipitation. For all shale samples, bulk Fe EXAFS data show that a significant amount of Fe in the shales is bound directly to organic carbon. Throughout the course of the experiments inorganic Fe(II) phases (primarily pyrite) reacted while Fe(II) bound to C showed no indication of reaction. On the micron scale, XRF mapping coupled with μ-XANES spectroscopy showed that at pH < 4.0, Fe(III) bearing phases precipitated as diffuse surface precipitates of ferrihydrite, goethite, and magnetite away from Fe(II) point sources. In near circum-neutral pH systems, Fe(III)-bearing phases (goethite and hematite) form large particles 10's of μm's in diameter near Fe(II) point sources. Idealized systems containing synthesized fracturing fluid, dissolved ferrous chloride, and bitumen showed that bitumen released during reaction with fracturing fluids is capable of oxidizing Fe(II) to Fe(III) at pH's 2.0 and 7.0. This indicates that bitumen can play a large role in Fe oxidation and speciation in the subsurface. This work shows that shale mineralogy has a significant impact on the morphology and phases of Fe(III) precipitates in the subsurface which in turn can significantly impact subsurface solution flow.

Dual modal endoscopic cancer detection based on optical pH sensing and Raman spectroscopy

NASA Astrophysics Data System (ADS)

Kim, Soogeun; Kim, ByungHyun; Sohn, Won Bum; Byun, Kyung Min; Lee, Soo Yeol

2017-02-01

To discriminate between normal and cancerous tissue, a dual modal approach using Raman spectroscopy and pH sensor was designed and applied. Raman spectroscopy has demonstrated the possibility of using as diagnostic method for the early detection of precancerous and cancerous lesions in vivo. It also can be used in identifying markers associated with malignant change. However, Raman spectroscopy lacks sufficient sensitivity due to very weak Raman scattering signal or less distinctive spectral pattern. A dual modal approach could be one of the solutions to solve this issue. The level of extracellular pH in cancer tissue is lower than that in normal tissue due to increased lactic acid production, decreased interstitial fluid buffering and decreased perfusion. High sensitivity and specificity required for accurate cancer diagnosis could be achieved by combining the chemical information from Raman spectrum with metabolic information from pH level. Raman spectra were acquired by using a fiber optic Raman probe, a cooled CCD camera connected to a spectrograph and 785 nm laser source. Different transmission spectra depending on tissue pH were measured by a lossy-mode resonance sensor based on fiber optic. The discriminative capability of pH-Raman dual modal method was evaluated using principal component analysis (PCA). The obtained results showed that the pH-Raman dual modal approach can improve discriminative capability between normal and cancerous tissue, which can lead to very high sensitivity and specificity. The proposed method for cancer detection is expected to be used in endoscopic diagnosis later.

Enzyme-polyelectrolyte multilayer assemblies on reduced graphene oxide field-effect transistors for biosensing applications.

PubMed

Piccinini, Esteban; Bliem, Christina; Reiner-Rozman, Ciril; Battaglini, Fernando; Azzaroni, Omar; Knoll, Wolfgang

2017-06-15

We present the construction of layer-by-layer (LbL) assemblies of polyethylenimine and urease onto reduced-graphene-oxide based field-effect transistors (rGO FETs) for the detection of urea. This versatile biosensor platform simultaneously exploits the pH dependency of liquid-gated graphene-based transistors and the change in the local pH produced by the catalyzed hydrolysis of urea. The use of an interdigitated microchannel resulted in transistors displaying low noise, high pH sensitivity (20.3µA/pH) and transconductance values up to 800 µS. The modification of rGO FETs with a weak polyelectrolyte improved the pH response because of its transducing properties by electrostatic gating effects. In the presence of urea, the urease-modified rGO FETs showed a shift in the Dirac point due to the change in the local pH close to the graphene surface. Markedly, these devices operated at very low voltages (less than 500mV) and were able to monitor urea in the range of 1-1000µm, with a limit of detection (LOD) down to 1µm, fast response and good long-term stability. The urea-response of the transistors was enhanced by increasing the number of bilayers due to the increment of the enzyme surface coverage onto the channel. Moreover, quantification of the heavy metal Cu 2+ (with a LOD down to 10nM) was performed in aqueous solution by taking advantage of the urease specific inhibition. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Adsorption of antimony onto iron oxyhydroxides: adsorption behavior and surface structure.

PubMed

Guo, Xuejun; Wu, Zhijun; He, Mengchang; Meng, Xiaoguang; Jin, Xin; Qiu, Nan; Zhang, Jing

2014-07-15

Antimony is detected in soil and water with elevated concentration due to a variety of industrial applications and mining activities. Though antimony is classified as a pollutant of priority interest by the United States Environmental Protection Agency (USEPA) and Europe Union (EU), very little is known about its environmental behavior and adsorption mechanism. In this study, the adsorption behaviors and surface structure of antimony (III/V) on iron oxides were investigated using batch adsorption techniques, surface complexation modeling (SCM), X-ray photon spectroscopy (XPS) and extended X-ray absorption fine structure spectroscopy (EXAFS). The adsorption isotherms and edges indicated that the affinity of Sb(V) and Sb(III) toward the iron oxides depended on the Sb species, solution pH, and the characteristics of iron oxides. Sb(V) adsorption was favored at acidic pH and decreased dramatically with increasing pH, while Sb(III) adsorption was constant over a broad pH range. When pH is higher than 7, Sb(III) adsorption by goethite and hydrous ferric oxide (HFO) was greater than Sb(V). EXAFS analysis indicated that the majority of Sb(III), either adsorbed onto HFO or co-precipitated by FeCl3, was oxidized into Sb(V) probably due to the involvement of O2 in the long duration of sample preservation. Only one Sb-Fe subshell was filtered in the EXAFS spectra of antimony adsorption onto HFO, with the coordination number of 1.0-1.9 attributed to bidentate mononuclear edge-sharing ((2)E) between Sb and HFO. Copyright © 2014 Elsevier B.V. All rights reserved.

Development of a novel probe sonication assisted enhanced loading of 5-FU in SPION encapsulated pectin nanocarriers for magnetic targeted drug delivery system.

PubMed

Dutta, Raj Kumar; Sahu, Saurabh

2012-09-01

A novel probe sonication method is developed to enhance loading of 5-fluorouracil (5-FU) in SPION encalsulated pectin nanocarriers of 100-150 nm size (referred here as MP-5FU nanocarriers). Probe sonication at 20 kHz for 60 min resulted in 5-FU loading efficiency of 33.2 ± 2.5%w/w and corresponding drug loading content of 18.2 ± 1.1 wt%. These are two folds higher than literature report of 5-FU loading in pectin. The enhanced loading is attributed to increase in the rate of dissolution of 5-FU in pectin due to transmission of kHz order sonic waves which increases temperature and pressure in the medium due to formation and collapsing of cavitation bubbles. The fabricated MP-5FU nanocarriers with saturation magnetization (43.13 emu/g) exhibited pH responsive, swelling controlled in vitro release of 5-FU in simulated gastric fluid at pH 1.2, in simulated intestinal fluid at pH 6.8, in simulated colonic fluid at pH 5.5, and in phosphate buffer solution at pH 7.4. The cytotoxicity of MP-5FU was measured by sulforhodamine B (SRB) assay and its GI(50) was more than 5mg/mL for cancer cells of HT-29 (colon) and Hep G2 (liver), while it was 3.7 mg/mL for cancer cells of MIA-PaCa-2 (Pancreas). Copyright © 2012 Elsevier B.V. All rights reserved.

Local environment around gold (III) in aqueous chloride solutions: An EXAFS spectroscopy study

NASA Astrophysics Data System (ADS)

Farges, Franã§Ois; Sharps, Julia A.; Brown, Gordon E., Jr.

1993-03-01

The local environment around Au (III) in aqueous solutions containing 1 M NaCl was determined as a function of pH and Au concentration using X-ray absorption spectroscopy (XAS) at ambient temperature and pressure. The solution Au concentrations studied were 10 - to 10 -3 M and the pH ranged between 2 and 9.2. No significant changes of Au speciation were detected with increasing Au concentration; however, major speciation changes were caused by variations in pH. At pH = 2, Au is coordinated by four Cl atoms ( mean d [AuCl] = 2.28 -2.29 ± 0.01 Å), whereas at pH 7.5 and 9.2, Au is coordinated by three Cl and one O (or OH) and by two Cl and two O (or OH), respectively ( mean d[AuCl] = 2.28 ± 0.02 Å; mean d[AuO or AuOH] = 1.97 ± 0.02 Å), indicating replacement of Cl by O (or OH) with increasing pH. In all solutions studied, the number of first-neighbors around Au(III) is close to four. XANES analysis suggests the presence of a square-planar geometry for AuX 4 ( X = Cl, O) at all pH values studied. These results are in excellent agreement with those from our previous Raman, resonance Raman, and UV/visible spectroscopy study of gold(III)-chloride solutions (PECK et al., 1991), which found that AuCl 4-, AuCl 3(OH) -, and AuCl 2(OH) 2- are the majority species in the pH ranges 2-6, 6-8.5, and 8.5-11, respectively. We did not find evidence for Au(I)Cl 2- or Au(I)Cl(OH) - complexes in our pH 7.5 and 9.2 solutions, as was recently suggested by PAN and WOOD (1991) for acidic gold chloride solutions at temperatures > 100°C, although we can't rule these complexes out as minority species (<10% of the total Au in solution). Our EXAFS results also provide the first direct evidence for Cl second neighbors around AuCl 4- complexes in the most acidic solutions studied ( pH = 2 and 4.5). These second-neighbor Cl atoms were also detected at low Au concentrations (10 -3 M) and are similar in number and arrangement to those observed in crystalline KAuCL 4·2H 2O (two Cl at a mean d[Au-Cl(2)] = 4.42 ± 0.03 Å). No evidence was found for second-neighbor Au atoms, which indicates little or no Au polymers or colloidal particles in any of the solutions studied. Our EXAFS results are in broad agreement with earlier predictions of Au speciation based on a variety of chemical measurements. Moreover, they directly confirm that mixed chloro-hydroxo Au (III) complexes are more stable than predicted on the basis of thermodynamically estimated stability constants.

CTAB-assisted hydrothermal synthesis of YVO 4:Eu 3+ powders in a wide pH range

NASA Astrophysics Data System (ADS)

Wang, Juan; Hojamberdiev, Mirabbos; Xu, Yunhua

2012-01-01

Rhombus-, rod-, soya bean- and aggregated soya bean-like YVO 4:Eu 3+ micro- and nanostructures were synthesized by a cetyltrimethylammonium bromide (CTAB)-assisted hydrothermal method at 180 °C for 24 h in a wide pH range. The as-synthesized powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence spectroscopy (PL). The XRD results confirmed the formation of phase-pure YVO 4:Eu 3+ powders with tetragonal structure under hydrothermal process in a wide pH range. Electron microscopic observations evidenced the morphological transformation of YVO 4:Eu 3+ powders from rhombus-like microstructure to rod-, soya bean, and aggregated soya bean-like nanostructures with an increase in the pH of the synthesis solution. The results from the PL measurements revealed that the intensities of PL emission peaks were significantly affected by the morphologies and crystallinity of samples due to the absence of an inversion symmetry at the Eu 3+ lattice site, and the highest luminescence intensity was observed for rod-like YVO 4:Eu 3+ powders.

Self-Propelled Oil Droplets and Their Morphological Change to Giant Vesicles Induced by a Surfactant Solution at Low pH.

PubMed

Banno, Taisuke; Tanaka, Yuki; Asakura, Kouichi; Toyota, Taro

2016-09-20

Unique dynamics using inanimate molecular assemblies based on soft matter have drawn much attention for demonstrating far-from-equilibrium chemical systems. However, there are no soft matter systems that exhibit a possible pathway linking the self-propelled oil droplets to formation of giant vesicles stimulated by low pH. In this study, we conceived an experimental oil-in-water emulsion system in which flocculated particles composed of a imine-containing oil transformed to spherical oil droplets that self-propelled and, after coming to rest, formed membranous figures. Finally, these figures became giant vesicles. From NMR, pH curves, and surface tension measurements, we determined that this far-from-equilibrium phenomenon was due to the acidic hydrolysis of the oil, which produced a benzaldehyde derivative as an oil component and a primary amine as a surfactant precursor, and the dynamic behavior of the hydrolytic products in the emulsion system. These findings afforded us a potential linkage between mobile droplet-based protocells and vesicle-based protocells stimulated by low pH.

A luminescent silver-saccharinato complex with S, S-diphenylsulfimide: Synthesis, spectroscopic, thermal, structural and DFT computational studies

NASA Astrophysics Data System (ADS)

Gumus, Sedat; Hamamci, Sevim; Yilmaz, V. T.; Kazak, Canan

2007-02-01

A new silver(I)-saccharinato (sac) complex with S, S-diphenylsulfimide, [Ag(sac)(Ph 2SNH)], has been prepared and characterized by elemental analysis, IR spectroscopy, thermal analysis and single crystal X-ray diffraction. X-ray diffraction analyses show that the title complex has a monomeric structure containing linearly coordinated silver(I) ion with an N-Ag-N angle of 173.80(10)°. The individual molecules are linked by strong N-H⋯O hydrogen bonds and aromatic stacking π⋯π interactions and packing of the molecules is further reinforced by C-H⋯π interactions. Ph 2SNH and [Ag(sac)(Ph 2SNH)] in solution at room temperature display intense blue luminescence with emission maxima at 380 and 408 nm, respectively. The photoluminescence properties have been investigated by DFT calculations, showing that the luminescence properties of the Ph 2SNH are due to intraligand transitions, while for the silver(I) complex, the luminescence was originated from several transitions including intraligand transitions and metal-to-ligand charge transfer (MLCT).

Microstructures, mechanical properties, and fracture behaviors of metal-injection molded 17-4PH stainless steel

NASA Astrophysics Data System (ADS)

Wu, Ming-Wei; Huang, Zeng-Kai; Tseng, Chun-Feng; Hwang, Kuen-Shyang

2015-05-01

Metal injection molding (MIM) is a versatile technique for economically manufacturing various metal parts with complicated shapes and excellent properties. The objective of this study was to clarify the effects of powder type (water-atomized and gas-atomized powders) and various heat treatments (sintering, solutioning, H900, and H1100) on the microstructures, mechanical properties, and fracture behaviors of MIM 17-4PH stainless steels. The results showed that better mechanical properties of MIM 17-4PH can be achieved with gas-atomized powder than with water-atomized powder due mainly to the lower silicon and oxygen contents and fewer SiO2 inclusions in the steels. The presence of 10 vol% δ ferrite does not impair the UTS or elongation of MIM 17-4PH stainless steels. The δ ferrite did not fracture, even though the neighboring martensitic matrix was severely cracked. Moreover, H900 treatment produces the highest hardness and UTS, along with moderate elongation. H1100 treatment produces the best elongation, along with moderate hardness and UTS.

Effect of different soil washing solutions on bioavailability of residual arsenic in soils and soil properties.

PubMed

Im, Jinwoo; Yang, Kyung; Jho, Eun Hea; Nam, Kyoungphile

2015-11-01

The effect of soil washing used for arsenic (As)-contaminated soil remediation on soil properties and bioavailability of residual As in soil is receiving increasing attention due to increasing interest in conserving soil qualities after remediation. This study investigates the effect of different washing solutions on bioavailability of residual As in soils and soil properties after soil washing. Regardless of washing solutions, the sequential extraction revealed that the residual As concentrations and the amount of readily labile As in soils were reduced after soil washing. However, the bioassay tests showed that the washed soils exhibited ecotoxicological effects - lower seed germination, shoot growth, and enzyme activities - and this could largely be attributed to the acidic pH and/or excessive nutrient contents of the washed soils depending on washing solutions. Overall, this study showed that treated soils having lower levels of contaminants could still exhibit toxic effects due to changes in soil properties, which highly depended on washing solutions. This study also emphasizes that data on the As concentrations, the soil properties, and the ecotoxicological effects are necessary to properly manage the washed soils for reuses. The results of this study can, thus, be utilized to select proper post-treatment techniques for the washed soils. Copyright © 2015 Elsevier Ltd. All rights reserved.

Conformal self-assembled thin films for optical pH sensors

NASA Astrophysics Data System (ADS)

Topasna, Daniela M.; Topasna, Gregory A.; Liu, Minghanbo; Tseng, Ching-Hung

2016-04-01

Simple, reliable, lightweight, and inexpensive thin films based sensors are still in intense development and high demand in many applications such as biomedical, industrial, environmental, military, and consumer products. One important class of sensors is the optical pH sensor. In addition, conformal thin film based sensors extend the range of application for pH optical sensors. We present the results on the fabrication and characterization of optical pH sensing coatings made through ionic self-assembled technique. These thin films are based on the combination of a polyelectrolyte and water-soluble organic dye molecule Direct Yellow 4. A series of films was fabricated and characterized in order to determine the optimized parameters of the polymer and of the organic dye solutions. The optical pH responses of these films were also studied. The transparent films were immersed in solutions at various temperature and pH values. The films are stable when immersed in solutions with pH below 9.0 and temperatures below 90 °C and they maintain their performance after longer immersion times. We also demonstrate the functionality of these coatings as conformal films.

Relationship of Cell Sap pH to Organic Acid Change During Ion Uptake 1

PubMed Central

Hiatt, A. J.

1967-01-01

Excised roots of barley (Hordeum vulgare, var. Campana) were incubated in KCl, K2SO4, CaCl2, and NaCl solutions at concentrations of 10−5 to 10−2 n. Changes in substrate solution pH, cell sap pH, and organic acid content of the roots were related to differences in cation and anion absorption. The pH of expressed sap of roots increased when cations were absorbed in excess of anions and decreased when anions were absorbed in excess of cations. The pH of the cell sap shifted in response to imbalances in cation and anion uptake in salt solutions as dilute as 10−5 n. Changes in cell sap pH were detectable within 15 minutes after the roots were placed in 10−3 n K2SO4. Organic acid changes in the roots were proportional to expressed sap pH changes induced by unbalanced ion uptake. Changes in organic acid content in response to differential cation and anion uptake appear to be associated with the low-salt component of ion uptake. PMID:16656506

Photoproduction of hydroxyl radicals in aqueous solution with algae under high-pressure mercury lamp.

PubMed

Liu, Xianli; Wu, Feng; Deng, Nansheng

2004-01-01

Photoproduction of hydroxyl radicals (*OH) could be induced in aqueous solution with algae (Nitzschia hantzschiana, etc.) and (or not) Fe3+ under high-pressure mercury lamp with an exposure time of 4 h. *OH was determined by HPLC using benzene as a probe. The photoproduction of *OH increased with increasing algae concentration. Fe3+ could enhance the photoproduction of *OH in aqueous solution with algae. The results showed that the photoproduction of *OH in algal solution with Fe3+ was greater than that in algal solution without Fe3+. The light intensity and pH affected the photoproduction of *OH in aqueous solution with algae with/without Fe3+. The photoproduction of *OH in aqueous solution with algae and Fe3+ under 250 W was greater than that under 125 W HPML. The photoproduction of *OH in algal solution (pH ranged from 4.0 to 7.0) with (or not) Fe3+ at pH 4 was the greatest.

Fate of cadmium at the soil-solution interface: a thermodynamic study as influenced by varying pH at South 24 Parganas, West Bengal, India.

PubMed

Karak, Tanmoy; Paul, Ranjit Kumar; Das, Sampa; Das, Dilip K; Dutta, Amrit Kumar; Boruah, Romesh K

2015-11-01

A study on the sorption kinetics of Cd from soil solution to soils was conducted to assess the persistence of Cd in soil solution as it is related to the leaching, bioavailability, and potential toxicity of Cd. The kinetics of Cd sorption on two non-contaminated alkaline soils from Canning (22° 18' 48.02″ N and 88° 39' 29.0″ E) and Lakshmikantapur (22° 06' 16.61″ N and 88° 19' 08.66″ E) of South 24 Parganas, West Bengal, India, were studied using conventional batch experiment. The variable soil suspension parameters were pH (4.00, 6.00, 8.18, and 9.00), temperatures (308, 318, and 328 K) and Cd concentrations (5-100 mg L(-1)). The average rate coefficient (kavg) and half-life (t1/2) values indicate that the persistence of Cd in soil solution is influenced by both temperature and soil suspension pH. The concentration of Cd in soil solution decreases with increase of temperature; therefore, Cd sorption on the soil-solution interface is an endothermic one. Higher pH decreases the t 1/2 of Cd in soil solution, indicating that higher pH (alkaline) is not a serious concern in Cd toxicity than lower pH (acidic). Based on the energy of activation (Ea) values, Cd sorption in acidic pH (14.76±0.29 to 64.45±4.50 kJ mol(-1)) is a surface control phenomenon and in alkaline pH (9.33±0.09 to 44.60±2.01 kJ mol(-1)) is a diffusion control phenomenon The enthalpy of activation (ΔH∓) values were found to be between 7.28 and 61.73 kJ mol(-1). Additionally, higher positive energy of activation (ΔG∓) values (46.82±2.01 to 94.47±2.36 kJ mol(-1)) suggested that there is an energy barrier for product formation.

Optimization of Photooxidative Removal of Phenazopyridine from Water

NASA Astrophysics Data System (ADS)

Saeid, Soudabeh; Behnajady, Mohammad A.; Tolvanen, Pasi; Salmi, Tapio

2018-05-01

The photooxidative removal of analgesic pharmaceutical compound phenazopyridine (PhP) from aqueous solutions by UV/H2O2 system with a re-circulated photoreactor was investigated. Response surface methodology (RSM) was employed to optimize the effect of operational parameters on the photooxidative removal efficiency. The investigated variables were: the initial PhP and H2O2 concentrations, irradiation time, volume of solution and pH. The analysis of variance (ANOVA) of quadratic model demonstrated that the described model was highly significant. The predicted values of the photooxidative removal efficiency were found to be in a fair agreement with experimental values ( R 2 = 0.9832, adjusted R 2 = 0.9716). The model predicted that the optimal reaction conditions for a maximum removal of PhP (>98%) were: initial PhP concentration less than 23 mg L-1, initial concentration of H2O2 higher than 470 mg L-1, solution volume less than 500 mL, pH close to 2 and irradiation time longer than 6 min.

Enhanced water-solubility, antibacterial activity and biocompatibility upon introducing sulfobetaine and quaternary ammonium to chitosan.

PubMed

Chen, Yuxiang; Li, Jianna; Li, Qingqing; Shen, Yuanyuan; Ge, Zaochuan; Zhang, Wenwen; Chen, Shiguo

2016-06-05

Chitosan (CS) has attracted much attention due to its good antibacterial activity and biocompatibility. However, CS is insoluble in neutral and alkaline aqueous solution, limiting its biomedical application to some extent. To circumvent this drawback, we have synthesized a novel N-quaternary ammonium-O-sulfobetaine-chitosan (Q3BCS) by introducing quaternary ammonium compound (QAC) and sulfobetaine, and its water-solubility, antibacterial activity and biocompatibility were evaluated compare to N-quaternary ammonium chitosan and native CS. The results showed that by introducing QAC, antibacterial activities and water-solubilities increase with degrees of substitution. The largest diameter zone of inhibition (DIZ) was improved from 0 (CS) to 15mm (N-Q3CS). And the water solution became completely transparent from pH 6.5 to pH 11; the maximal waters-solubility was improved from almost 0% (CS) to 113% at pH 7 (N-Q3CS). More importantly, by further introducing sulfobetaine, cell survival rate of Q3BCS increased from 30% (N-Q3CS) to 85% at 2000μg/ml, which is even greater than that of native CS. Furthermore, hemolysis of Q3BCS was dropped sharply from 4.07% (N-Q3CS) to 0.06%, while the water-solution and antibacterial activity were further improved significantly. This work proposes an efficient strategy to prepare CS derivatives with enhanced antibacterial activity, biocompatibility and water-solubility. Additionally, these properties can be finely tailored by changing the feed ratio of CS, glycidyl trimethylammonium chloride and NCO-sulfobetaine. Copyright © 2016 Elsevier Ltd. All rights reserved.

Preparation and evaluation of thermosensitive liposomal hydrogel for enhanced transcorneal permeation of ofloxacin.

PubMed

Hosny, Khaled Mohamed

2009-01-01

Ofloxacin, available as ophthalmic solution, has two major problems: first, it needs frequent administration every 4 hours or even every 1 hour to treat severe eye infection; second, there is formation of white crystalline deposit on cornea due to its pH-dependent solubility, which is very low at pH of corneal fluid. In order to provide a solution to previous problems, ofloxacin in this study is prepared as topically effective in situ thermosensitive prolonged release liposomal hydrogel. Two preparation procedures were carried out, leading to the formation of multilamellar vesicles (MLVs) and reverse-phase evaporation vesicles (REVs) at pH 7.4. Effects of method of preparation, lipid content, and charge inducers on encapsulation efficiency were studied. For the preparation of in situ thermosensitive hydrogel, chitosan/beta-glycerophosphate system was synthesized and used as carrier for ofloxacin liposomes. The effect of addition of liposomes on gelation temperature, gelation time, and rheological behaviors of the hydrogel were evaluated. In vitro transcorneal permeation was also determined. MLVs entrapped greater amount of ofloxacin than REVs liposomes at pH 7.4; drug loading was increased by including charge-inducing agent and by increasing cholesterol content until a certain limit. The gelation time was decreased by the addition of liposomes into the hydrogel. The prepared liposomal hydrogel enhances the transcorneal permeation sevenfold more than the aqueous solution. These results suggested that the in situ thermosensitive ofloxacin liposomal hydrogel ensures steady and prolonged transcorneal permeation, which improves the ocular bioavailability, minimizes the need for frequent administration, and decreases the ocular side effect of ofloxacin.

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion.

PubMed

Pimenta, A F R; Ascenso, J; Fernandes, J C S; Colaço, R; Serro, A P; Saramago, B

2016-12-30

Optimization of drug delivery from drug loaded contact lenses assumes understanding the drug transport mechanisms through hydrogels which relies on the knowledge of drug partition and diffusion coefficients. We chose, as model systems, two materials used in contact lens, a poly-hydroxyethylmethacrylate (pHEMA) based hydrogel and a silicone based hydrogel, and three drugs with different sizes and charges: chlorhexidine, levofloxacin and diclofenac. Equilibrium partition coefficients were determined at different ionic strength and pH, using water (pH 5.6) and PBS (pH 7.4). The measured partition coefficients were related with the polymer volume fraction in the hydrogel, through the introduction of an enhancement factor following the approach developed by the group of C. J. Radke (Kotsmar et al., 2012; Liu et al., 2013). This factor may be decomposed in the product of three other factors E HS , E el and E ad which account for, respectively, hard-sphere size exclusion, electrostatic interactions, and specific solute adsorption. While E HS and E el are close to 1, E ad >1 in all cases suggesting strong specific interactions between the drugs and the hydrogels. Adsorption was maximal for chlorhexidine on the silicone based hydrogel, in water, due to strong hydrogen bonding. The effective diffusion coefficients, D e , were determined from the drug release profiles. Estimations of diffusion coefficients of the non-adsorbed solutes D=D e ×E ad allowed comparison with theories for solute diffusion in the absence of specific interaction with the polymeric membrane. Copyright © 2016 Elsevier B.V. All rights reserved.

High performance flexible pH sensor based on carboxyl-functionalized and DEP aligned SWNTs

NASA Astrophysics Data System (ADS)

Liu, Lu; Shao, Jinyou; Li, Xiangming; Zhao, Qiang; Nie, Bangbang; Xu, Chuan; Ding, Haitao

2016-11-01

The detection and control of the pH is very important in many biomedical and chemical reaction processes. A miniaturized flexible pH sensor that is light weight, robust, and conformable is very important in many applications, such as multifunctional lab-on-a-chip systems or wearable biomedical devices. In this work, we demonstrate a flexible chemiresistive pH sensor based on dielectrophoresis (DEP) aligned carboxyl-functionalized single-walled carbon nanotubes (SWNTs). Decorated carboxyl groups can react with hydrogen (H+) and hydroxide (OH-) ions, enabling the sensor to be capable of sensing the pH. DEP is used to deposit well-organized and highly aligned SWNTs in desired locations, which improves the metal-nanotube interface and highly rapid detection of the pH, resulting in better overall device performance. When pH buffer solutions are dropped onto such SWNTs, the H+ and OH- ions caninteract with the carboxyl groups and affect the generation of holes and electrons in the SWNTs, leading to resistance variations in the SWNTs. The results shows that the relative resistance variations of the sensor increases linearly with increasing the pH values in the range from 5 to 9 and the response time ranges from 0.2 s to 22.6 s. The pH sensor also shows high performance in mechanical bendability, which benefited from the combination of flexible PET substrates and SWNTs. The SWNT-based flexible pH sensor demonstrates great potential in a wide range of areas due to its simple structure, excellent performance, low power consumption, and compatibility with integrated circuits.

Rare earth elements mobility processes in an AMD-affected estuary: Huelva Estuary (SW Spain).

PubMed

Lecomte, K L; Sarmiento, A M; Borrego, J; Nieto, J M

2017-08-15

Huelva Estuary is a transition zone where REE-rich acidic waters interact with saline-alkaline seawater. This mixing process influences the geochemical and mineralogical characteristics of particulate and dissolved fractions. The Tinto River has >11,000μgL -1 dissolved REE (pH=1.66), whereas seawater only reaches 8.75·10 -2 μgL -1 dissolved REE (pH=7.87). REE-normalized patterns in "pH<6 solutions" are parallel and show similarities, diminishing their concentration as pH increases. Sequential extraction performed on the generated precipitates of mixed solutions indicates that most REE are associated to the residual phase. In a second order, REE are associated with soluble salts at pH3 and 3.5 whereas in sediments generated at pH4 and 5, they are distributed in salts (1° extraction), poorly crystallized Fe-bearing minerals (schwertmannite, 3° extraction) and well crystallized Fe-bearing minerals (goethite - hematite, 4° extraction). Finally, precipitated REE are highest at pH6 newly formed minerals with a release to solution in higher pH. Copyright © 2017 Elsevier Ltd. All rights reserved.

Discrimination of fluorescence light-up effects induced by pH and metal ion chelation on a spirocyclic derivative of rhodamine B.

PubMed

Leite, Andreia; Silva, Ana M G; Cunha-Silva, Luís; de Castro, Baltazar; Gameiro, Paula; Rangel, Maria

2013-05-07

In the present work we describe the structure and the spectroscopic characterization of a spirocyclic derivative of a rhodamine B ligand whose properties allow discrimination of light-up effects induced by metal ion chelation and variation of pH. Distinction of the two effects is important for the use of this type of ligand to detect and monitor metal ions in aqueous solutions. The synthesis of the ligand was performed in two steps, which involve the reaction of rhodamine B with hydrazine hydrate to form rhodamine B hydrazide followed by condensation with 2-pyridinecarboxaldehyde and was successfully optimized using a solvent free approach under microwave irradiation. The ligand was obtained in the expected spirolactam form and was characterized in the solid state by EA, MS and single-crystal X-ray diffraction. The ligand was characterized in solution by NMR and absorption and fluorescence spectroscopies and its properties were found to be sensitive to pH and concentration of iron(III). The study of the fluorescence properties at variable pH shows that the compound is fluorescent in the range 2 < pH < 4 with maximum intensity at pH 3 and allowed the determination of two pK(a) values (pK(a1) = 2.98, pK(a2) = 2.89) and establishment of the corresponding distribution diagram. The very low pK(a) values guarantee that above pH equal to 4 the ligand is mostly present in the fully non-protonated and non-fluorescent form L. The study of the interaction of the ligand with iron(iii) was performed in DMSO and DMSO-H(2)O to exclude the influence of pH and due to the low solubility of the compound. The results indicate that the presence of iron(III) triggers the opening of the spirolactam form of the ligand and the maximum intensity obtained at a metal : ligand ratio of 1 : 2 is consistent with the formation of an iron(III) complex with the tridentate ligand.

Measurement of pH micro-heterogeneity in natural cheese matrices by fluorescence lifetime imaging

PubMed Central

Burdikova, Zuzana; Svindrych, Zdenek; Pala, Jan; Hickey, Cian D.; Wilkinson, Martin G.; Panek, Jiri; Auty, Mark A. E.; Periasamy, Ammasi; Sheehan, Jeremiah J.

2015-01-01

Cheese, a product of microbial fermentation may be defined as a protein matrix entrapping fat, moisture, minerals and solutes as well as dispersed bacterial colonies. The growth and physiology of bacterial cells in these colonies may be influenced by the microenvironment around the colony, or alternatively the cells within the colony may modify the microenvironment (e.g., pH, redox potential) due to their metabolic activity. While cheese pH may be measured at macro level there remains a significant knowledge gap relating to the degree of micro-heterogeneity of pH within the cheese matrix and its relationship with microbial, enzymatic and physiochemical parameters and ultimately with cheese quality, consistency and ripening patterns. The pH of cheese samples was monitored both at macroscopic scale and at microscopic scale, using a non-destructive microscopic technique employing C-SNARF-4 and Oregon Green 488 fluorescent probes. The objectives of this work were to evaluate the suitability of these dyes for microscale pH measurements in natural cheese matrices and to enhance the sensitivity and extend the useful pH range of these probes using fluorescence lifetime imaging (FLIM). In particular, fluorescence lifetime of Oregon Green 488 proved to be sensitive probe to map pH micro heterogeneity within cheese matrices. Good agreement was observed between macroscopic scale pH measurement by FLIM and by traditional pH methods, but in addition considerable localized microheterogeneity in pH was evident within the curd matrix with pH range between 4.0 and 5.5. This technique provides significant potential to further investigate the relationship between cheese matrix physico-chemistry and bacterial metabolism during cheese manufacture and ripening. PMID:25798136

Measurement of pH micro-heterogeneity in natural cheese matrices by fluorescence lifetime imaging.

PubMed

Burdikova, Zuzana; Svindrych, Zdenek; Pala, Jan; Hickey, Cian D; Wilkinson, Martin G; Panek, Jiri; Auty, Mark A E; Periasamy, Ammasi; Sheehan, Jeremiah J

2015-01-01

Cheese, a product of microbial fermentation may be defined as a protein matrix entrapping fat, moisture, minerals and solutes as well as dispersed bacterial colonies. The growth and physiology of bacterial cells in these colonies may be influenced by the microenvironment around the colony, or alternatively the cells within the colony may modify the microenvironment (e.g., pH, redox potential) due to their metabolic activity. While cheese pH may be measured at macro level there remains a significant knowledge gap relating to the degree of micro-heterogeneity of pH within the cheese matrix and its relationship with microbial, enzymatic and physiochemical parameters and ultimately with cheese quality, consistency and ripening patterns. The pH of cheese samples was monitored both at macroscopic scale and at microscopic scale, using a non-destructive microscopic technique employing C-SNARF-4 and Oregon Green 488 fluorescent probes. The objectives of this work were to evaluate the suitability of these dyes for microscale pH measurements in natural cheese matrices and to enhance the sensitivity and extend the useful pH range of these probes using fluorescence lifetime imaging (FLIM). In particular, fluorescence lifetime of Oregon Green 488 proved to be sensitive probe to map pH micro heterogeneity within cheese matrices. Good agreement was observed between macroscopic scale pH measurement by FLIM and by traditional pH methods, but in addition considerable localized microheterogeneity in pH was evident within the curd matrix with pH range between 4.0 and 5.5. This technique provides significant potential to further investigate the relationship between cheese matrix physico-chemistry and bacterial metabolism during cheese manufacture and ripening.

Dynamic light-scattering study of gelatin and aggregation of gastric mucin

NASA Astrophysics Data System (ADS)

Bansil, Rama; Cao, Xingxiang; Bhaskar, K. Ramakrishnan; LaMont, Jeffrey T.

1997-05-01

Dynamic light scattering studies show that concentration and pH play important roles in determining pig gastric mucin's (PGM) ability to aggregate and gel. At low concentrations, PGM macromolecules exist in solution predominantly in the form of monomers. At high concentrations, PGM macromolecules aggregate to form supra-macromolecular clusters. When the pH of the high concentration PGM solution is changed from 7.0 to 2.0, the system undergoes a sol-gel transition: from a solution of polydisperse aggregates to a gel. This pH and concentration dependent sol-gel transition of PGM solution may provide a mechanism for the mammalian stomach to protect itself against being digested by the gastric juice.

A pH-responsive wormlike micellar system of a noncovalent interaction-based surfactant with a tunable molecular structure.

PubMed

Kang, Wanli; Wang, Pengxiang; Fan, Haiming; Yang, Hongbin; Dai, Caili; Yin, Xia; Zhao, Yilu; Guo, Shujun

2017-02-08

Responsive wormlike micelles are very useful in a number of applications, whereas it is still challenging to create dramatic viscosity changes in wormlike micellar systems. Here we developed a pH-responsive wormlike micellar system based on a noncovalent constructed surfactant, which is formed by the complexation of N-erucamidopropyl-N,N-dimethylamine (UC 22 AMPM) and citric acid at the molar ratio of 3 : 1 (EACA). The phase behavior, aggregate microstructure and viscoelasticity of EACA solutions were investigated by macroscopic appearance observation, rheological and cryo-TEM measurements. It was found that the phase behavior of EACA solutions undergoes transition from transparent viscoelastic fluids to opalescent solutions and then phase separation with white floaters upon increasing the pH. Upon increasing the pH from 2.03 to 6.17, the viscosity of wormlike micelles in the transparent solutions continuously increased and reached ∼683 000 mPa s at pH 6.17. As the pH was adjusted to 7.31, the opalescent solution shows a water-like flowing behaviour and the η 0 rapidly declines to ∼1 mPa s. Thus, dramatic viscosity changes of about 6 magnitudes can be triggered by varying the pH values without any deterioration of the EACA system. This drastic variation in rheological behavior is attributed to the pH dependent interaction between UC 22 AMPM and citric acid. Furthermore, the dependence on concentration and temperature of the rheological behavior of EACA solutions was also studied to assist in obtaining the desired pH-responsive viscosity changes.

Determination of Odor Release in Hydrocolloid Model Systems Containing Original or Carboxylated Cellulose at Different pH Values Using Static Headspace Gas Chromatographic (SHS-GC) Analysis

PubMed Central

Lee, Sang Mi; Shin, Gil-Ok; Park, Kyung Min; Chang, Pahn-Shick; Kim, Young-Suk

2013-01-01

Static headspace gas chromatographic (SHS-GC) analysis was performed to determine the release of 13 odorants in hydrocolloid model systems containing original or regio-selectively carboxylated cellulose at different pH values. The release of most odor compounds was decreased in the hydrocolloid solutions compared to control, with the amounts of 2-propanol, 3-methyl-1-butanol, and 2,3-butanedione released into the headspace being less than those of any other odor compound in the hydrocolloid model systems. However, there was no considerable difference between original cellulose-containing and carboxylated-cellulose containing systems in the release of most compounds, except for relatively long-chain esters such as ethyl caprylate and ethyl nonanoate. The release from the original and carboxylated cellulose solutions controlled to pH 10 was significantly higher than that from solutions adjusted to pH 4 and 7 in the case of some esters (ethyl acetate, methyl propionate, ethyl propionate, ethyl butyrate, butyl propionate, ethyl caproate) and alcohols (2-propanol, 3-methyl-1-butanol), in particular, ethyl butyrate and 3-methyl-1-butanol. In contrast, the release of 2,3-butanedione from both the original and carboxylated cellulose solutions was increased at pH 4 and 7 compared to that at pH 10 by about 70% and 130%, respectively. Our study demonstrated that the release of some odorants could be changed significantly by addition of both original and carboxylated cellulose in hydrocolloid model systems, but only minor effect was observed in pH of the solution. PMID:23447013

Effect of pH on thermal stability of collagen in the dispersed and aggregated states (Short Communication)

PubMed Central

Russell, Allan E.

1974-01-01

Thermal stabilities of mature insoluble collagen, salt-precipitated fibrils of acid-soluble collagen and acid-soluble collagen in solution were compared as a function of acid pH. Both insoluble and precipitated collagens showed large parallel destabilization with decrease in pH, whereas the intrinsic stability of individual collagen molecules in dilute solution was comparatively unaffected. PMID:4478066

Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity.

PubMed

Gunasekera, Bhagya; Abou Diwan, Charbel; Altawallbeh, Ghaith; Kalil, Haitham; Maher, Shaimaa; Xu, Song; Bayachou, Mekki

2018-03-07

Nitric oxide (NO) release counteracts platelet aggregation and prevents the thrombosis cascade in the inner walls of blood vessels. NO-release coatings also prevent thrombus formation on the surface of blood-contacting medical devices. Our previous work has shown that inducible nitric oxide synthase (iNOS) films release NO fluxes upon enzymatic conversion of the substrate l-arginine. In this work, we report on the modulation of enzyme loading in layer-by-layer (LbL) thin films of inducible nitric oxide synthase oxygenase (iNOSoxy) on polyethylenimine (PEI). The layer of iNOSoxy is electrostatically adsorbed onto the PEI layer. The pH of the iNOSoxy solution affects the amount of enzyme adsorbed. The overall negative surface charge of iNOSoxy in solution depends on the pH and hence determines the density of adsorbed protein on the positively charged PEI layer. We used buffered iNOSoxy solutions adjusted to pHs 8.6 and 7.0, while saline PEI solution was used at pH 7.0. Atomic force microscopy imaging of the outermost layer shows higher protein adsorption with iNOSoxy at pH 8.6 than with a solution of iNOSoxy at pH 7.0. Graphite electrodes with PEI/iNOSoxy films show higher catalytic currents for nitric oxide reduction mediated by iNOSoxy. The higher enzyme loading translates into higher NO flux when the enzyme-modified surface is exposed to a solution containing the substrate and a source of electrons. Spectrophotometric assays showed higher NO fluxes with iNOSoxy/PEI films built at pH 8.6 than with films built at pH 7.0. Fourier transform infrared analysis of iNOSoxy adsorbed on PEI at pH 8.6 and 7.0 shows structural differences of iNOSoxy in films, which explains the observed changes in enzymatic activity. Our findings show that pH provides a strategy to optimize the NOS loading and enzyme activity in NOS-based LbL thin films, which enables improved NO release with minimum layers of PEI/NOS.

Formation of hydrotalcite in aqueous solutions and intercalation of ATP by anion exchange.

PubMed

Tamura, Hiroki; Chiba, Jun; Ito, Masahiro; Takeda, Takashi; Kikkawa, Shinichi; Mawatari, Yasuteru; Tabata, Masayoshi

2006-08-15

The formation reaction and the intercalation of adenosine triphosphate (ATP) were studied for hydrotalcite (HT), a layered double hydroxide (LDH) of magnesium and aluminum. Hydrotalcite with nitrate ions in the interlayer (HT-NO(3)) was formed (A) by dropwise addition of a solution of magnesium and aluminum nitrates (pH ca. 3) to a sodium hydroxide solution (pH ca. 14) until the pH decreased from 14 to 10 and (B) by dropwise addition of the NaOH solution to the solution of magnesium and aluminum nitrates with pH increasing from 3 to 10. The precipitate obtained with method B was contaminated with aluminum hydroxide and the crystallinity of the product was low, possibly because aluminum hydroxide precipitates at pH 4 or 5 and remains even after HT-NO(3) forms at pH above 8. With method A, however, the precipitate was pure HT-NO(3) with increased crystallinity, since the solubility of aluminum hydroxide at pH above and around 10 is high as dissolved aluminate anions are stable in this high pH region, and there was no aluminum hydroxide contamination. The formed HT-NO(3) had a composition of [Mg(0.71)Al(0.29)(OH)(2)](NO(3))(0.29).0.58H(2)O. To intercalate ATP anions into the HT-NO(3), HT-NO(3) was dispersed in an ATP solution at pH 7. It was found that the interlayer nitrate ions were completely exchanged with ATP anions by ion exchange, and the interlayer distance expanded almost twice with a free space distance of 1.2 nm. The composition of HT-ATP was established as [Mg(0.68)Al(0.32)(OH)(2)](ATP)(0.080)0.88H(2)O. The increased distance could be explained with a calculated molecular configuration of the ATP as follows: An ATP molecule is bound to an interlayer surface with the triphosphate group, the adenosine group bends owing to its bond angles and projects into the interlayer to a height of 1 nm, and the adenosine groups aligned in the interlayer support the interlayer distance.

An efficient and sensitive fluorescent pH sensor based on amino functional metal-organic frameworks in aqueous environment.

PubMed

Xu, Xiao-Yu; Yan, Bing

2016-04-28

A pH sensor is fabricated via a reaction between an Al(III) salt and 2-aminoterephthalic acid in DMF which leads to a MOF (Al-MIL-101-NH2) with free amino groups. The Al-MIL-101-NH2 samples show good luminescence and an intact structure in aqueous solutions with pH ranging from 4.0 to 7.7. Given its exceptional stability and pH-dependent fluorescence intensity, Al-MIL-101-NH2 has been applied to fluorescent pH sensing. Significantly, in the whole experimental pH range (4.0-7.7), the fluorescence intensity almost increases with increasing pH (R(2) = 0.99688) which can be rationalized using a linear equation: I = 2.33 pH + 26.04. In addition, error analysis and cycling experiments have demonstrated the accuracy and utilizability of the sensor. In practical applications (PBS and lake water), Al-MIL-101-NH2 also manifests its analytical efficiency in pH sensing. And the samples can be easily isolated from an aqueous solution by incorporating Fe3O4 nanoparticles. Moreover, the possible sensing mechanism based on amino protonation is discussed in detail. This work is on of the few cases for integrated pH sensing systems in aqueous solution based on luminescent MOFs.

An ultrasensitive method of real time pH monitoring with complementary metal oxide semiconductor image sensor.

PubMed

Devadhasan, Jasmine Pramila; Kim, Sanghyo

2015-02-09

CMOS sensors are becoming a powerful tool in the biological and chemical field. In this work, we introduce a new approach on quantifying various pH solutions with a CMOS image sensor. The CMOS image sensor based pH measurement produces high-accuracy analysis, making it a truly portable and user friendly system. pH indicator blended hydrogel matrix was fabricated as a thin film to the accurate color development. A distinct color change of red, green and blue (RGB) develops in the hydrogel film by applying various pH solutions (pH 1-14). The semi-quantitative pH evolution was acquired by visual read out. Further, CMOS image sensor absorbs the RGB color intensity of the film and hue value converted into digital numbers with the aid of an analog-to-digital converter (ADC) to determine the pH ranges of solutions. Chromaticity diagram and Euclidean distance represent the RGB color space and differentiation of pH ranges, respectively. This technique is applicable to sense the various toxic chemicals and chemical vapors by situ sensing. Ultimately, the entire approach can be integrated into smartphone and operable with the user friendly manner. Copyright © 2014 Elsevier B.V. All rights reserved.

Caustic Precipitation of Plutonium and Uranium with Gadolinium as a Neutron Poison

DOE Office of Scientific and Technical Information (OSTI.GOV)

VISSER, ANN E.; BRONIKOWSKI, MICHAEL G.; RUDISILL, TRACY S.

2005-10-18

The caustic precipitation of plutonium (Pu) and uranium (U) from Pu and U-containing waste solutions has been investigated to determine whether gadolinium (Gd) could be used as a neutron poison for precipitation with greater than a fissile mass containing both Pu and enriched U. Precipitation experiments were performed using both process solution samples and simulant solutions with a range of 2.6-5.16 g/L U and 0-4.3:1 U:Pu. Analyses were performed on solutions at intermediate pH to determine the partitioning of elements for accident scenarios. When both Pu and U were present in the solution, precipitation began at pH 4.5 and bymore » pH 7, 99% of Pu and U had precipitated. When complete neutralization was achieved at pH > 14 with 1.2 M excess OH{sup -}, greater than 99% of Pu, U, and Gd had precipitated. At pH > 14, the particles sizes were larger and the distribution was a single mode. The ratio of hydrogen:fissile atoms in the precipitate was determined after both settling and centrifuging and indicates that sufficient water was associated with the precipitates to provide the needed neutron moderation for Gd to prevent a criticality in solutions containing up to 4.3:1 U:Pu and up to 5.16 g/L U.« less

Reduction of Hexavalent Chromium by Green Tea Polyphenols and Green Tea Nano Zero-Valent Iron (GT-nZVI).

PubMed

Chrysochoou, M; Reeves, K

2017-03-01

This study reports on the direct reduction of hexavalent chromium [Cr(VI)] by green tea polyphenols, including a green tea solution and pure epigallocatechin gallate (EGCG) solution. A linear trend was observed between the amount of reduced Cr(VI) and the amount of added polyphenols. The green tea solution showed a continued decrease in the observed stoichiometry with increasing pH, from a maximum of 1.4 mol per gallic acid equivalent (GAE) of green tea at pH 2.5, to 0.2 mol/GAE at pH 8.8. The EGCG solution exhibited different behavior, with a maximum stoichiometry of 2 at pH 7 and minimum of 1.6 at pH 4.4 and 8.9. When green tea was used to first react with Fe 3+ and form GT-nZVI, the amount of Cr(VI) reduced by a certain volume of GT-nZVI was double compared to green tea, and 6 times as high considering that GT-nZVI only contains 33 % green tea.

Biosorption characteristics of Uranium (VI) from aqueous solution by pollen pini.

PubMed

Wang, Feihong; Tan, Lichao; Liu, Qi; Li, Rumin; Li, Zhanshuang; Zhang, Hongsen; Hu, Songxia; Liu, Lianhe; Wang, Jun

2015-12-01

Uranium biosorption from aqueous solutions by pollen pini (Pinus massoniana pollen) was studied in a bath system. The biosorbent was characterized by Fourier-transform infrared spectroscopy and scanning electron microscope. The influences of pH, contact time and initial uranium concentration at room temperature were investigated and the experimental curves were obtained. The pollen pini exhibited the highest uranium sorption capacity at pH 5.0 after 2 h contact. At pH 2.5 pollen pini also exhibited a good uranium loading capacity (>15%). Therefore biosorption characteristics of uranium from aqueous solution onto pollen pini were examined at pH 2.5 as well. The kinetics followed a pseudo-second-order rate equation and adsorption process was well fitted with the Freundlich isotherm at both pH. The adsorption of uranium by the biosorbent was confirmed by energy dispersive spectroscopy. The present study suggested that pollen pini could be a suitable biosorbent for biosorption uranium (VI) from aqueous solution in a fast, low cost and convenient approach. Copyright © 2015 Elsevier Ltd. All rights reserved.

ISFET pH Sensitivity: Counter-Ions Play a Key Role.

PubMed

Parizi, Kokab B; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H S Philip

2017-02-02

The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor.

ISFET pH Sensitivity: Counter-Ions Play a Key Role

PubMed Central

Parizi, Kokab B.; Xu, Xiaoqing; Pal, Ashish; Hu, Xiaolin; Wong, H. S. Philip

2017-01-01

The Field Effect sensors are broadly used for detecting various target analytes in chemical and biological solutions. We report the conditions under which the pH sensitivity of an Ion Sensitive Field Effect transistor (ISFET) sensor can be significantly enhanced. Our theory and simulations show that by using pH buffer solutions containing counter-ions that are beyond a specific size, the sensor shows significantly higher sensitivity which can exceed the Nernst limit. We validate the theory by measuring the pH response of an extended gate ISFET pH sensor. The consistency and reproducibility of the measurement results have been recorded in hysteresis free and stable operations. Different conditions have been tested to confirm the accuracy and validity of our experiment results such as using different solutions, various oxide dielectrics as the sensing layer and off-the-shelf versus IC fabricated transistors as the basis of the ISFET sensor. PMID:28150700

[Efficiency of photodecomposition of trace NDMA in water by UV irradiation].

PubMed

Xu, Bing-Bing; Chen, Zhong-Lin; Qi, Fei; Ma, Jun

2008-07-01

Efficiency of photodecomposition of trace NDMA by UV irradiation was investigated with analyzing the initial concentration of NDMA, solution pH, irradiation area, irradiation intensity and water quality effect on NDMA photolysis. NDMA could be effectively photodegraded by UV irradiation. The removal efficiency of NDMA was 97.5% after 5 min of UV irradiation. Effect of initial NDMA concentration on photodecomposition of NDMA was not remarkable. With pH value ascending, the removal rate of NDMA photodecomposition decreased. The yields of photoquantum were more under lower solution pH than that under higher pH. NDMA had fastest reaction rate at solution pH = 2.2. Removal efficiency of NDMA increased with the available irradiation area ascending. Increscent ultraviolet irradiation intensity was good for NDMA degradation. Water quality affected the removal of NDMA slightly. The removal efficiency of NDMA in tap water and Songhua River raw water were 96.7% and 94.8%, respectively.

An evaluation of MES (2(N-Morpholino)ethanesulfonic acid) and Amberlite IRC-50 as pH buffers for nutrient solution studies

NASA Technical Reports Server (NTRS)

Bugbee, B. G.; Salisbury, F. B.

1985-01-01

All buffering agents used to stabilize pH in hydroponic research have disadvantages. Inorganic buffers are absorbed and may become phytotoxic. Solid carbonate salts temporarily mitigate decreasing pH but provide almost no protection against increasing pH, and they alter nutrient absorption. Exchange resins are more effective, but we find that they remove magnesium and manganese from solution. We have tested 2(N-Morpholino)ethanesulfonic acid (MES) as a buffering agent at concentrations of 1 and 10 mol m-3 (1 and 10 mM) with beans, corn, lettuce, tomatoes, and wheat. MES appears to be biologically inert and does not interact significantly with other solution ions. Relative growth rates among controls and MES treatments were nearly identical for each species during the trial period. The pH was stabilized by 1 mol m-3 MES. This buffer warrants further consideration in nutrient research.

Markedly lowering the viscosity of aqueous solutions of DNA by additives.

PubMed

Elkin, Igor; Weight, Alisha K; Klibanov, Alexander M

2015-10-15

Aqueous solutions of DNAs, while relevant in drug delivery and as a target of therapies, are often very viscous making them difficult to use. Since less viscous solutions could enable targeted drug delivery and/or therapies, the purpose of the present work was to explore compounds capable of "thinning" such DNA solutions under pharmaceutically relevant conditions. To this end, viscosities of aqueous solutions of DNAs and model polyanions were examined at 25 °C in the absence and presence of a number of bulky organic salts (and related compounds) previously found to substantially lower the viscosities of concentrated protein solutions. Out of two dozen compounds tested, only three were found to be effective; the FDA-approved local anesthetics lidocaine, mepivacaine, and prilocaine at near-isotonic concentrations and pH 6.4 lowered solution viscosity of three different DNAs up to about 20 fold. The observed multi-fold viscosity reductions appear to be due to these bulky organic salts' structure-specific non-covalent binding to nucleotide bases resulting in denaturation (unwinding) to, and stabilization of, single-stranded DNA. Copyright © 2015 Elsevier B.V. All rights reserved.

Formulation and in vitro evaluation of cysteamine hydrochloride viscous solutions for the treatment of corneal cystinosis.

PubMed

Bozdağ, Sibel; Gümüş, Koray; Gümüş, Ozlem; Unlü, Nurşen

2008-09-01

In the present study, viscous solutions of cysteamine hydrochloride (CH) were prepared by using 0.5%, 1.0%, 1.5% or 3.0% of hydroxypropylmethylcellulose (HPMC) and were evaluated for their in-vitro characteristics and stability. Osmolalities, pH and viscosity of the formulations were determined. The influence of benzalkonium chloride and autoclave sterilization on solution characteristics was also investigated. For stability assessment, the viscous solutions were stored at +4 and +25 degrees C over 12 months. In-vitro characteristics and CH contents of the stored solutions were monitored. Irritation tests for the formulations were evaluated on rabbit eyes. Dialysis sac technique was used to perform in vitro release study of the solutions containing 1.0% and 1.5% HPMC. All of the viscous solutions tested showed non-newtonian (dilatant) flow behavior. Osmolality values were ranked between 351.2+/-6.2 and 355.1+/-7.9 mOsm kg(-1), and pH values were between 3.97+/-0.1 and 3.98+/-0.2 for all the solutions. Furthermore, no significant changes in dilatant behavior, osmolality or pH values of the pure HPMC solutions were observed. After addition of the excipients or CH-excipients, increased viscosity values were noted in these formulations. Neither benzalkonium chloride nor autoclave sterilization had any influence on viscosity, pH or osmolality values of the solution containing 1.5% HPMC. Stability studies showed that a faster decrease in the concentration of CH was observed in the formulations stored at 25 degrees C compared to those kept at 4 degrees C; no changes were determined in osmolality values of the solutions at all storage conditions. Increased pH and decreased viscosity values were noted in HPMC solutions containing CH and excipients, while no changes in these values were observed for pure HPMC solutions kept at 4 and 25 degrees C. In vitro release tests revealed that 81.2% and 85.3% of CH were released from the viscous solutions containing 1.5% and 1% HPMC, respectively, in 8h. No irritation was observed when the viscous solutions were tested on rabbit and human eyes.

Enamel demineralization and remineralization under plaque fluid-like conditions: a quantitative light-induced fluorescence study.

PubMed

Lippert, F; Butler, A; Lynch, R J M

2011-01-01

The present study investigated de- and remineralization in enamel lesions under plaque fluid (PF)-like conditions using quantitative light-induced fluorescence (QLF). Preformed lesions were exposed to partially saturated lactic acid solutions, varying in pH and fluoride concentration ([F]) based on a 5 × 3 factorial study design (0/0.1/0.5/1.5/4 ppm F; pH 4.9/5.2/5.5). Average fluorescence loss (ΔF) was monitored for 11 days. Subsequently, lesions were demineralized in a partially saturated acetic acid solution for two 24-hour periods. Data were analyzed using repeated measures analysis of covariance. Lesions exposed to PF at 4 ppm F and pH 5.5 showed not only the most remineralization (ΔΔF = 28.2 ± 14.0%) for all groups after 11 days, but also the most demineralization (ΔΔF = -19.3 ± 13.5%) after subsequent acetic acid exposure. Increased [F] resulted in more remineralization, regardless of pH. Higher pH values resulted in more remineralization. No remineralization was observed in lesions exposed to F-free solutions, regardless of pH. Remineralization was noticeable under the following conditions: pH 4.9 - [F] = 4 ppm, pH 5.2 - [F] ≥ 1.5 ppm, and pH 5.5 - [F] ≥ 0.5 ppm. Overall, [F] had a stronger effect on remineralization than pH. Subsequent demineralization showed that little protection was offered by PF-like solutions, and further demineralization compared with baseline was observed on lesions not remineralized initially. [F] had a stronger effect on net mineral change than pH. The present study has shown that QLF is a valuable tool in studying lesion de- and remineralization under PF-like conditions, where [F] was shown to be more important than pH. Copyright © 2011 S. Karger AG, Basel.

Nanofiltration of Mine Water: Impact of Feed pH and Membrane Charge on Resource Recovery and Water Discharge

PubMed Central

Mullett, Mark; Fornarelli, Roberta; Ralph, David

2014-01-01

Two nanofiltration membranes, a Dow NF 270 polyamide thin film and a TriSep TS 80 polyamide thin film, were investigated for their retention of ionic species when filtering mine influenced water streams at a range of acidic pH values. The functional iso-electric point of the membranes, characterized by changes in retention over a small pH range, were examined by filtering solutions of sodium sulphate. Both membranes showed changes in retention at pH 3, suggesting a zero net charge on the membranes at this pH. Copper mine drainage and synthetic solutions of mine influenced water were filtered using the same membranes. These solutions were characterized by pH values within 2 and 5, thus crossing the iso-electric point of both membranes. Retention of cations was maximized when the feed solution pH was less than the iso-electric point of the membrane. In these conditions, the membrane has a net positive charge, reducing the transmission rate of cations. From the recoveries of a range of cations, the suitability of nanofiltration was discussed relative to the compliance with mine water discharge criteria and the recovery of valuable commodity metals. The nanofiltration process was demonstrated to offer advantages in metal recovery from mine waste streams, concomitantly enabling discharge criteria for the filtrate disposal to be met. PMID:24957170

Use of metallurgical dust for removal chromium ions from aqueous solutions

NASA Astrophysics Data System (ADS)

Pająk, Magdalena; Dzieniszewska, Agnieszka; Kyzioł-Komosińska, Joanna; Chrobok, Michał

2018-01-01

The aim of the study was to determine the potential for the application of dust from steel plant as an effective sorbent for removing Cr(III) and Cr(VI) in the form of simple and complex ions - Acid Blue 193 dye from aqueous solutions. Three isotherms models were used to interpret the experimental results namely: Langmuir, Freundlich, and Dubinin-Radushkevich. Estimated equations parameters allowed to determine the binding mechanism. Based on laboratory studies it was found that the dust was characterized by high sorption capacities for Cr ions and dye from the aqueous solution. The sorption capacity of the dust for Cr(III) and Cr(VI) ions depended on the degree of oxidation, pH of solution and kind of anion and changed in series: Cr(III)-Cl pH=5.0> Cr(III)-SO4 pH=5.0> Cr(III)-Cl pH=3.0> Cr(III)-SO4 pH=3.0> Cr(VI) pH=5.0> Cr(VI) pH=3.0. Dust was also characterized by a high maximum sorption capacity of dye at a range of 38.2 - 91.7 mg/g, depending on the dose of dust. Based on the study it was found that dust from a steel plant, containing iron oxides, can be used as low-cost and effective sorbent to remove pollutions containing chromium ions, especially from acidic wastewater.

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements.

PubMed

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-13

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter ( n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA ( p < 0.05) while maximum calcium ion release was dependent on Vol of TSC ( p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution ( p < 0.05).

Effect of Exposed Surface Area, Volume and Environmental pH on the Calcium Ion Release of Three Commercially Available Tricalcium Silicate Based Dental Cements

PubMed Central

Rajasekharan, Sivaprakash; Vercruysse, Chris; Martens, Luc; Verbeeck, Ronald

2018-01-01

Tricalcium silicate cements (TSC) are used in dental traumatology and endodontics for their bioactivity which is mostly attributed to formation of calcium hydroxide during TSC hydration and its subsequent release of calcium and hydroxide ions. The aim of this study was to determine the effect of volume (Vol), exposed surface area (ESA) and pH of surrounding medium on calcium ion release. Three commercially available hydraulic alkaline dental cements were mixed and condensed into cylindrical tubes of varying length and diameter (n = 6/group). For the effect of ESA and Vol, tubes were immersed in 10 mL of deionized water. To analyze the effect of environmental pH, the tubes were randomly immersed in 10 mL of buffer solutions with varying pH (10.4, 7.4 or 4.4). The solutions were collected and renewed at various time intervals. pH and/or calcium ion release was measured using a pH glass electrode and atomic absorption spectrophotometer respectively. The change of pH, short-term calcium ion release and rate at which calcium ion release reaches maximum were dependent on ESA (p < 0.05) while maximum calcium ion release was dependent on Vol of TSC (p < 0.05). Maximum calcium ion release was significantly higher in acidic solution followed by neutral and alkaline solution (p < 0.05). PMID:29342837

Silicate release from glass for pharmaceutical preparations.

PubMed

Bohrer, Denise; Bortoluzzi, Fabiana; Nascimento, Paulo Cícero; Carvalho, Leandro Machado; Ramirez, Adrian Gustavo

2008-05-01

Glass is made of polymeric silica and other minor components, which are necessary for turning the silica into a material more easily moldable and resistant to temperature changes. Glass containers for pharmaceutical usage are classified according to their resistance to a chemical attack, a test carried out in the presence of water and heat. The test is designed to show the released alkalinity, a variable dependent on the amount of sodium oxide, one of the minor components added to the glass mass. In this work, the release of silica from glass by action of constituents from pharmaceutical formulations was investigated. The study included products used in large volumes and usually stored in glass containers. Solutions of amino acids, electrolytes, glucose, oligoelements and others such as heparin and sodium bicarbonate were individually stored in glass containers and heated at 121 degrees C for 30min, as in the water attack test. The test was also carried out only with water, where the pH varied from 2 to 12. The released silicate was measured either by photometry or atomic absorption spectrometry, depending on the nature of the sample. The results showed that silicate is released during the heating cycle even if the contact is with pure water only. The pH exerts a considerable influence on the release, being that the higher the pH, the higher the silica dissolved. An elevated pH, however, is not the only factor responsible for silica dissolution. While in the solutions of NaCl, KCl, Mg Cl2 and ZnSO4 and in most of the amino acids, the concentration of silicate was as high as in pure water (0.1-1.0mg Si/L). In the solutions of sodium acetate, bicarbonate and gluconate, its concentration was much higher, over 30mg Si/L. These results were confirmed by the analysis of commercial products, where in solutions of amino acids the level of silicate ranged from 0.14 to 0.19mg Si/L. On the other hand, calcium gluconate, sodium bicarbonate and potassium phosphate presented silicate levels from 1 to 4mg/L. Although silica is not considered a toxic substance for humans, it is necessary to be aware of its presence in solutions for parenteral nutrition due to the direct introduction into the bloodstream and the large volume usually administrated, even to pre-term infants.

Removal of phenol by activated alumina bed in pulsed high-voltage electric field.

PubMed

Zhu, Li-nan; Ma, Jun; Yang, Shi-dong

2007-01-01

A new process for removing the pollutants in aqueous solution-activated alumina bed in pulsed high-voltage electric field was investigated for the removal of phenol under different conditions. The experimental results indicated the increase in removal rate with increasing applied voltage, increasing pH value of the solution, aeration, and adding Fe2+. The removal rate of phenol could reach 72.1% when air aeration flow rate was 1200 ml/min, and 88.2% when 0.05 mmol/L Fe2+ was added into the solution under the conditions of applied voltage 25 kV, initial phenol concentration of 5 mg/L, and initial pH value 5.5. The addition of sodium carbonate reduced the phenol removal rate. In the pulsed high-voltage electric field, local discharge occurred at the surface of activated alumina, which promoted phenol degradation in the thin water film. At the same time, the space-time distribution of gas-liquid phases was more uniform and the contact areas of the activated species generated from the discharge and the pollutant molecules were much wider due to the effect of the activated alumina bed. The synthetical effects of the pulsed high-voltage electric field and the activated alumina particles accelerated phenol degradation.

Conditions and mechanisms for the formation of nano-sized Delafossite (CuFeO2) at temperatures ≤90 °C in aqueous solution

NASA Astrophysics Data System (ADS)

John, Melanie; Heuss-Aßbichler, Soraya; Ullrich, Aladin

2016-02-01

In this study, we present the mechanism of CuFeO2 formation in aqueous solution at low temperatures ≤90 °C, using sulfate salts as reactants. Furthermore, we demonstrate the influence of experimental conditions (alkalization, reaction and ageing temperature and time) on the synthesized nanoparticles. In all cases, GR-SO4, a Fe(II-III) layered double hydroxysulphate (Fe2+4Fe3+2(OH)12·SO4) and Cu2O precipitate first. During further OH- supply GR-SO4 oxidizes and forms Fe10O14(OH)2, Cu2O and CuFeO2 crystals. Due to the high pH further CuFeO2 crystals grow at the cost of the unstable intermediate products. The reaction rate increases with increasing ageing temperature, reaction pH and, in particular, NaOH concentrations in the solution. As a result, highly crystalline CuFeO2 (3R and 2H polytypes) nanoparticles showing hexagonal morphology can be synthesized at 70 °C within 10 h or at 50 °C within 1 week. The formation of 2H polytype is favored by additional OH- supply during the pH-stat time and rather low temperatures.

High field hyperpolarization-EXSY experiment for fast determination of dissociation rates in SABRE complexes

NASA Astrophysics Data System (ADS)

Hermkens, Niels K. J.; Feiters, Martin C.; Rutjes, Floris P. J. T.; Wijmenga, Sybren S.; Tessari, Marco

2017-03-01

SABRE (Signal Amplification By Reversible Exchange) is a nuclear spin hyperpolarization technique based on the reversible concurrent binding of small molecules and para-hydrogen (p-H2) to an iridium metal complex in solution. At low magnetic field, spontaneous conversion of p-H2 spin order to enhanced longitudinal magnetization of the nuclear spins of the other ligands occurs. Subsequent complex dissociation results in hyperpolarized substrate molecules in solution. The lifetime of this complex plays a crucial role in attained SABRE NMR signal enhancements. Depending on the ligands, vastly different dissociation rates have been previously measured using EXSY or selective inversion experiments. However, both these approaches are generally time-consuming due to the long recycle delays (up to 2 min) necessary to reach thermal equilibrium for the nuclear spins of interest. In the cases of dilute solutions, signal averaging aggravates the problem, further extending the experimental time. Here, a new approach is proposed based on coherent hyperpolarization transfer to substrate protons in asymmetric complexes at high magnetic field. We have previously shown that such asymmetric complexes are important for application of SABRE to dilute substrates. Our results demonstrate that a series of high sensitivity EXSY spectra can be collected in a short experimental time thanks to the NMR signal enhancement and much shorter recycle delay.

Photocatalytic degradation of H2S aqueous media using sulfide nanostructured solid-solution solar-energy-materials to produce hydrogen fuel.

PubMed

Lashgari, Mohsen; Ghanimati, Majid

2018-03-05

H 2 S is a corrosive, flammable and noxious gas, which can be neutralized by dissolving in alkaline media and employed as H 2 -source by utilizing inside semiconductor-assisted/photochemical reactors. Herein, through a facile hydrothermal route, a ternary nanostructured solid-solution of iron, zinc and sulfur was synthesized in the absence and presence of Ag-dopant, and applied as efficient photocatalyst of hydrogen fuel production from H 2 S media. The effect of pH on the photocatalyst performance was scrutinized and the maximum activity was attained at pH=11, where HS - concentration is high. BET, diffuse reflectance and photoluminescence studies indicated that the ternary solid-solution photocatalyst, in comparison to its solid-solvent (ZnS), has a greater surface area, stronger photon absorption and less charge recombination, which justify its superiority. Moreover, the effect of silver-dopant on the photocatalyst performance was examined. The investigations revealed that although silver could boost the absorption of photons and increase the surface area, it could not appreciably enhance the photocatalyst performance due to its weak influence on retarding the charge-recombination process. Finally, the phenomenon was discussed in detail from mechanistic viewpoint. Copyright © 2017 Elsevier B.V. All rights reserved.

Correlation of Surface Adsorption and Oxidation with a Floatability Difference of Galena and Pyrite in High-Alkaline Lime Systems.

PubMed

Niu, Xiaopeng; Ruan, Renman; Xia, Liuyin; Li, Li; Sun, Heyun; Jia, Yan; Tan, Qiaoyi

2018-02-27

When it comes to Pb-Zn ores with high amounts of pyrite, the major problem encountered is the low separation efficiency between galena and pyrite. By virtue of high dosage of lime and collector sodium diethyl dithiocarbamate (DDTC), pyrite and zinc minerals are depressed, allowing the galena to be floated. However, there have been significant conflicting reports on the flotation behavior of galena at high pH. In this context, correlation of the surface adsorption and oxidation with the floatability difference of galena and pyrite in high-alkaline lime systems would be a key issue for process optimization. Captive bubble contact angle measurements were performed on freshly polished mineral surfaces in situ exposed to lime solutions of varying pH as a function of immersion time. Furthermore, single mineral microflotation tests were conducted. Both tests indicated that the degree of hydrophobicity on the surfaces of galena and pyrite increased in the presence of DDTC at natural or mild pulp pH. While in a saturated lime solution, at pH 12.5, DDTC only worked for galena, but not for pyrite. Surface chemistry analysis by time-of-flight secondary ion mass spectrometry (Tof-SIMS) confirmed the preference of DDTC on the galena surface at pH 12.5, which contributed to a merit recovery. Further important evidence through measurements of Tof-SIMS, ion chromatography, and high-performance liquid chromatography indicated that in high-alkaline lime systems, the merit floatability of galena could exclude the insignificant contribution of elemental sulfur (S 8 ) and was dominantly attributed by the strong adsorption of DDTC. In contrast, the poor flotation response of pyrite at high pH was due to the prevailing adsorption of CaOH + species. This study provides an important surface chemistry evidence for a better understanding of the mechanism on the better selectivity in the galena-pyrite separation adopting high-alkaline lime systems.

Stabilizing effect of citrate buffer on the photolysis of riboflavin in aqueous solution

PubMed Central

Ahmad, Iqbal; Sheraz, Muhammad Ali; Ahmed, Sofia; Kazi, Sadia Hafeez; Mirza, Tania; Aminuddin, Mohammad

2011-01-01

In the present investigation the photolysis of riboflavin (RF) in the presence of citrate species at pH 4.0–7.0 has been studied. A specific multicomponent spectrophotometric method has been used to assay RF in the presence of photoproducts during the reactions. The overall first-order rate constants (kobs) for the photolysis of RF range from 0.42 to 1.08×10–2 min−1 in the region. The values of kobs have been found to decrease with an increase in citrate concentration indicating an inhibitory effect of these species on the rate of reaction. The second-order rate constants for the interaction of RF with total citrate species causing inhibition range from 1.79 to 5.65×10–3 M−1 min−1 at pH 4.0–7.0. The log k–pH profiles for the reactions at 0.2–1.0 M citrate concentration show a gradual decrease in kobs and the value at 1.0 M is more than half compared to that of k0, i.e., in the absence of buffer, at pH 5.0. Divalent citrate ions cause a decrease in RF fluorescence due to the quenching of the excited singlet state resulting in a decrease in the rate of reaction and consequently leading to the stabilization of RF solutions. The greater quenching of fluorescence at pH 4.0 compared to that of 7.0 is in accordance with the greater concentration of divalent citrate ions (99.6%) at that pH. The trivalent citrate ions exert a greater inhibitory effect on the rate of RF photolysis compared to that of the divalent citrate ions probably as a result of excited triplet state quenching. The values of second-order rate constants for the interaction of divalent and trivalent citrate ions are 0.44×10–2 and 1.06×10–3 M–1 min–1, respectively, indicating that the trivalent ions exert a greater stabilizing effect, compared to the divalent ions, on RF solutions. PMID:25755977

Non-monotonic swelling of surface grafted hydrogels induced by pH and/or salt concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Longo, Gabriel S.; Department of Biomedical Engineering, Northwestern University, Evanston, Illinois 60208; Chemistry of Life Processes Institute, Northwestern University, Evanston, Illinois 60208

2014-09-28

We use a molecular theory to study the thermodynamics of a weak-polyacid hydrogel film that is chemically grafted to a solid surface. We investigate the response of the material to changes in the pH and salt concentration of the buffer solution. Our results show that the pH-triggered swelling of the hydrogel film has a non-monotonic dependence on the acidity of the bath solution. At most salt concentrations, the thickness of the hydrogel film presents a maximum when the pH of the solution is increased from acidic values. The quantitative details of such swelling behavior, which is not observed when themore » film is physically deposited on the surface, depend on the molecular architecture of the polymer network. This swelling-deswelling transition is the consequence of the complex interplay between the chemical free energy (acid-base equilibrium), the electrostatic repulsions between charged monomers, which are both modulated by the absorption of ions, and the ability of the polymer network to regulate charge and control its volume (molecular organization). In the absence of such competition, for example, for high salt concentrations, the film swells monotonically with increasing pH. A deswelling-swelling transition is similarly predicted as a function of the salt concentration at intermediate pH values. This reentrant behavior, which is due to the coupling between charge regulation and the two opposing effects triggered by salt concentration (screening electrostatic interactions and charging/discharging the acid groups), is similar to that found in end-grafted weak polyelectrolyte layers. Understanding how to control the response of the material to different stimuli, in terms of its molecular structure and local chemical composition, can help the targeted design of applications with extended functionality. We describe the response of the material to an applied pressure and an electric potential. We present profiles that outline the local chemical composition of the hydrogel, which can be useful information when designing applications that pursue or require the absorption of biomolecules or pH-sensitive molecules within different regions of the film.« less

Colorimetric Detection of Thiophenol Based on a Phenolphthalein Derivative and Its Application as a Molecular Logic Gate.

PubMed

Kim, Hyunsu; Swamy, K M K; Kwon, Nahyun; Kim, Yonghee; Park, Sungsu; Yoon, Juyoung

2017-07-05

A phenolphthalein-based colorimetric probe bearing a dinitrobenzene group is reported as a thiophenol (PhSH)-selective chemodosimeter. PhSH can react with chemodosimeter 1 to afford phenolphthalein. The addition of PhSH to the aqueous solution of 1 followed by a change in pH of the resulting solution to basic induces a selective color change from colorless to pink. Furthermore, using PhSH and base as inputs and color change of 1 by naked eye as an output, leads to the construction of an AND logic gate. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Highly Efficient Solution-Processed Deep-Red Organic Light-Emitting Diodes Based on an Exciplex Host Composed of a Hole Transporter and a Bipolar Host.

PubMed

Huang, Manli; Jiang, Bei; Xie, Guohua; Yang, Chuluo

2017-10-19

With the aim to achieve highly efficient deep-red emission, we introduced an exciplex forming cohost, 4,4',4″-tris(3-methylphenylphenylamino)triphenylamine (m-MTDATA): 2,5-bis(2-(9H-carbazol-9-yl)phenyl)-1,3,4-oxadiazole (o-CzOXD) (1:1). Due to the efficient triplet up-conversion processes upon the exciplex forming cohost, excellent performances of the devices were achieved with deep-red emission. Using the heteroleptic iridium complexes as the guest dopants, the solution-processed deep-red phosphorescent organic light-emitting diodes (PhOLEDs) with the iridium(III) bis(6-(4-(tert-butyl)phenyl)phenanthridine)acetylacetonate [(TP-BQ) 2 Ir(acac)]-based phosphorescent emitter exhibited an electroluminescent peak at 656 nm and a maximum external quantum efficiency (EQE) of 11.9%, which is 6.6 times that of the device based on the guest emitter doped in the polymer-based cohost. The unique exciplex with a typical hole transporter and a bipolar material is ideal and universal for hosting the red PhOLEDs and tremendously improves the device performances.

PROTOPLASMIC POTENTIALS IN HALICYSTIS

PubMed Central

Blinks, L. R.

1935-01-01

Perfusion of the vacuole of living cells of Halicystis is described, the method employing two longitudinally fused capillaries as entrance and exit tubes. Natural sap, artificial sap, and sea water have been successfully perfused, with various additions and deficiencies, within the limits of physiological balance. In H. ovalis the P.D. remains positive and scarcely reduced in value when normal sea water, at pH 8.1, is perfused in the vacuole. In H. Osterhoutii the P.D. reverses in sign when the perfused solution has a higher pH than 6.5. In both cases a large P.D. persists when the solutions are the same on both sides of the protoplasm. In the absence of external gradients, there must be some internal gradient or asymmetry of the protoplasm itself to account for the P.D. Since appreciable currents are produced, there must be some metabolic activity as a source of energy. The higher normal P.D. in H. ovalis is not due to the higher KCl content of its sap (as earlier suggested by the author) since it persists nearly unchanged when sea water is substituted for sap. PMID:19872853

Functionalized dithiocarbamate chelating resin for the removal of Co2+ from simulated wastewater

NASA Astrophysics Data System (ADS)

Shi, Xuewei; Fu, Linwei; Wu, Yanyang; Zhao, Huiling; Zhao, Shuangliang; Xu, Shouhong

2017-12-01

Industrial wastewater that contains trace amounts of heavy metal ions is often seen in petrochemical industry. While this wastewater can not be directly discharged, it is difficult to treat due to the low concentration of metal ions. Introducing chelating reagents into this wastewater for selective ion adsorption, followed by a mechanical separation process, provides an appealing solution. Toward the success of this technology, the development of effective chelating resins is of key importance. In the present work, a chelating resin containing amino and dithiocarbamate groups was reported for the removal of Co(II) metal ions in trace concentrations from simulated wastewater. By investigating the adsorption performance of the chelating resin at different solution pH values, adsorbent dosages, contact time, initial ion concentrations, and adsorption temperatures, the maximum adsorption capacity of the resin for Co(II) was identified to be 24.89 mg g-1 for a 2 g L-1 adsorbent dosage and a pH value of 5. After four adsorption-desorption cycles, 97% of the adsorption capacity of the resin was maintained. The adsorption kinetics and thermodynamics were analyzed and discussed as well.

Acid base activity of live bacteria: Implications for quantifying cell wall charge

NASA Astrophysics Data System (ADS)

Claessens, Jacqueline; van Lith, Yvonne; Laverman, Anniet M.; Van Cappellen, Philippe

2006-01-01

To distinguish the buffering capacity associated with functional groups in the cell wall from that resulting from metabolic processes, base or acid consumption by live and dead cells of the Gram-negative bacterium Shewanella putrefaciens was measured in a pH stat system. Live cells exhibited fast consumption of acid (pH 4) or base (pH 7, 8, 9, and 10) during the first few minutes of the experiments. At pH 5.5, no acid or base was required to maintain the initial pH constant. The initial amounts of acid or base consumed by the live cells at pH 4, 8, and 10 were of comparable magnitudes as those neutralized at the same pHs by intact cells killed by exposure to gamma radiation or ethanol. Cells disrupted in a French press required higher amounts of acid or base, due to additional buffering by intracellular constituents. At pH 4, acid neutralization by suspensions of live cells stopped after 50 min, because of loss of viability. In contrast, under neutral and alkaline conditions, base consumption continued for the entire duration of the experiments (5 h). This long-term base neutralization was, at least partly, due to active respiration by the cells, as indicated by the build-up of succinate in solution. Qualitatively, the acid-base activity of live cells of the Gram-positive bacterium Bacillus subtilis resembled that of S. putrefaciens. The pH-dependent charging of ionizable functional groups in the cell walls of the live bacteria was estimated from the initial amounts of acid or base consumed in the pH stat experiments. From pH 4 to 10, the cell wall charge increased from near-zero values to about -4 × 10 -16 mol cell -1 and -6.5 × 10 -16 mol cell -1 for S. putrefaciens and B. subtilis, respectively. The similar cell wall charging of the two bacterial strains is consistent with the inferred low contribution of lipopolysaccharides to the buffering capacity of the Gram-negative cell wall (of the order of 10%).

Metal/Metal Oxide Differential Electrode pH Sensors

NASA Technical Reports Server (NTRS)

West, William; Buehler, Martin; Keymeulen, Didier

2007-01-01

Solid-state electrochemical sensors for measuring the degrees of acidity or alkalinity (in terms of pH values) of liquid solutions are being developed. These sensors are intended to supplant older electrochemical pH sensors that include glass electrode structures and reference solutions. The older sensors are fragile and subject to drift. The present developmental solid-state sensors are more rugged and are expected to be usable in harsh environments. The present sensors are based on a differential-electrode measurement principle. Each sensor includes two electrodes, made of different materials, in equilibrium with the solution of interest.

Molecular mechanism of plasma sterilization in solution with the reduced pH method: importance of permeation of HOO radicals into the cell membrane

NASA Astrophysics Data System (ADS)

Takai, Eisuke; Ikawa, Satoshi; Kitano, Katsuhisa; Kuwabara, Junpei; Shiraki, Kentaro

2013-07-01

Sterilization of certain infected areas of the human body surface is necessary for dental and surgical therapies. Because the blood is filled with body fluid, sterilization in solution is essential. In vitro solution sterilization has been successively carried out using a combination of low-temperature atmospheric-pressure plasma and the reduced pH method, where the solution is sufficiently acidic. Here, we show the molecular mechanism of such plasma sterilization in solution based on microbiology. Three kinds of bacteria were inactivated by plasma treatment under various pH conditions. The theoretical and experimental models revealed that the sterilization was characterized by the concentration of hydroperoxy radicals (HOO·), which were dependent on the pH value. Bacterial inactivation rates were proportional to the HOO· concentrations calculated by the theoretical model. To evaluate the penetration of radicals into the cell membrane, a bacterial model using dye-included micelles was used. Decolouration rates of the model were also in proportion with the calculated HOO· concentrations. These results indicate that the key species for plasma sterilization were hydroperoxy radicals. More importantly, the high permeation of hydroperoxy radicals into the cell membrane plays a key role for efficient bactericidal inactivation using the reduced pH method.

The Effect of Temperature and Solution pH on Tetragonal Lysozyme Nucleation Kinetics

NASA Technical Reports Server (NTRS)

Judge, Russell A.; Jacobs, Randolph S.; Frazier, Tyralynn; Snell, Edward H.; Pusey, Marc L.

1998-01-01

Part of the challenge of macromolecular crystal growth for structure determination is obtaining an appropriate number of crystals with a crystal volume suitable for x-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of supersaturation, temperature and pH on the nucleation rate of tetragonal lysozyme crystals. Batch crystallization plates were prepared at given solution concentrations and incubated at set temperatures over one week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions, Duplicate experiments indicate the reproducibility of the technique, Crystal numbers were found to increase with increasing supersaturation and temperature. The most significant variable however, was pH, where crystal numbers changed by two orders of magnitude over the pH range 4.0 to 5.2. Crystal size varied also with solution conditions, with the largest crystals being obtained at pH 5.2. Having optimized the crystallization conditions, a batch of crystals were prepared under exactly the same conditions and fifty of these crystals were analyzed by x-ray techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

Acid-base equilibrium in aqueous solutions of 1,3-dimethylbarbituric acid as studied by 13C NMR spectroscopy

NASA Astrophysics Data System (ADS)

Gryff-Keller, A.; Kraska-Dziadecka, A.

2011-12-01

13C NMR spectra of 1,3-dimethylbarbituric acid in aqueous solutions of various acidities and for various solute concentrations have been recorded and interpreted. The spectra recorded at pH = 2 and below contain the signals of the neutral solute molecule exclusively, while the ones recorded at pH = 7 and above only the signals of the appropriate anion, which has been confirmed by theoretical GIAO-DFT calculations. The signals in the spectra recorded for solutions of pH < 7 show dynamic broadenings. The lineshape analysis of these signals has provided information on the kinetics of the processes running in the dynamic acid-base equilibrium. The kinetic data determined this way have been used to clarify the mechanisms of these processes. The numerical analysis has shown that under the investigated conditions deprotonation of the neutral solute molecules undergoes not only via a simple transfer of the C-H proton to water molecules but also through a process with participation of the barbiturate anions. Moreover, the importance of tautomerism, or association, or both these phenomena for the kinetics of the acid-base transformations in the investigated system has been shown. Qualitatively similar changes of 13C NMR spectra with the solution pH variation have been observed for the parent barbituric acid.

Measurements and theoretical interpretation of points of zero charge/potential of BSA protein.

PubMed

Salis, Andrea; Boström, Mathias; Medda, Luca; Cugia, Francesca; Barse, Brajesh; Parsons, Drew F; Ninham, Barry W; Monduzzi, Maura

2011-09-20

The points of zero charge/potential of proteins depend not only on pH but also on how they are measured. They depend also on background salt solution type and concentration. The protein isoelectric point (IEP) is determined by electrokinetical measurements, whereas the isoionic point (IIP) is determined by potentiometric titrations. Here we use potentiometric titration and zeta potential (ζ) measurements at different NaCl concentrations to study systematically the effect of ionic strength on the IEP and IIP of bovine serum albumin (BSA) aqueous solutions. It is found that high ionic strengths produce a shift of both points toward lower (IEP) and higher (IIP) pH values. This result was already reported more than 60 years ago. At that time, the only available theory was the purely electrostatic Debye-Hückel theory. It was not able to predict the opposite trends of IIP and IEP with ionic strength increase. Here, we extend that theory to admit both electrostatic and nonelectrostatic (NES) dispersion interactions. The use of a modified Poisson-Boltzmann equation for a simple model system (a charge regulated spherical colloidal particle in NaCl salt solutions), that includes these ion specific interactions, allows us to explain the opposite trends observed for isoelectric point (zero zeta potential) and isoionic point (zero protein charge) of BSA. At higher concentrations, an excess of the anion (with stronger NES interactions than the cation) is adsorbed at the surface due to an attractive ionic NES potential. This makes the potential relatively more negative. Consequently, the IEP is pushed toward lower pH. But the charge regulation condition means that the surface charge becomes relatively more positive as the surface potential becomes more negative. Consequently, the IIP (measuring charge) shifts toward higher pH as concentration increases, in the opposite direction from the IEP (measuring potential). © 2011 American Chemical Society

Determination of the parameters controlling swelling of chemically cross-linked pH-sensitive poly(N-vinylimidazole) hydrogels.

PubMed

Molina, M Jesús; Gómez-Antón, M Rosa; Piérola, Inés F

2007-10-25

The number of variables controlling the behavior of ionic gels is large and very often some of them are unknown. The aim of this work is to interpret quantitatively the swelling behavior of pH sensitive gels, with the minimum number of simplifying assumptions. With this purpose, the equilibrium degree of swelling (S) and protonation (alpha) of chemically cross-linked poly(N-vinylimidazole) (PVI) immersed in aqueous salt solutions were measured as a function of the ionic strength (mu), in the whole range of pH. In acid solutions with pH in the range 0 to 4, imidazole moieties become protonated, and PVI behaves as a polyelectrolyte gel: S decreases upon increasing mu both for NaCl and for CaCl(2), with HCl as protonating acid. In aqueous solutions with larger pH, between 4 and 12, the hydrogel is practically neutral, and S increases as mu rises, showing a salting-in effect. From the quantitative analysis of these results, the following facts emerged. Protonation induces chain stiffness (as measured by the non-Gaussian factor) and worsening of the solvent quality of the aqueous media (as measured by the polymer-solvent interaction parameter). For alpha below 33%, swelling seems to be governed by the excess of mobile counterions inside the gel with respect to the bath, with a minor but still significantly negative contribution of the osmotic swelling pressure due to polymer-solvent mixing. Above 33% protonation, it is necessary to consider Manning counterion condensation to get parameters with physical meaning. The crossover between polyelectrolyte and salting-in effects corresponds to alpha and mu values with the same ionic and mixing contributions to the osmotic swelling pressure. The formation of ionic nonpermanent cross-links, with H(2)SO(4) as the protonating acid, was discarded.

Boric Acid Corrosion of Concrete Rebar

NASA Astrophysics Data System (ADS)

Pabalan, R. T.; Yang, L.; Chiang, K.–T.

2013-07-01

Borated water leakage through spent fuel pools (SFPs) at pressurized water reactors is a concern because it could cause corrosion of reinforcement steel in the concrete structure and compromise the integrity of the structure. Because corrosion rate of carbon steel in concrete in the presence of boric acid is lacking in published literature and available data are equivocal on the effect of boric acid on rebar corrosion, corrosion rate measurements were conducted in this study using several test methods. Rebar corrosion rates were measured in (i) borated water flowing in a simulated concrete crack, (ii) borated water flowing over a concrete surface, (iii) borated water that has reacted with concrete, and (iv) 2,400 ppm boric acid solutions with pH adjusted to a range of 6.0 to 7.7. The corrosion rates were measured using coupled multielectrode array sensor (CMAS) and linear polarization resistance (LPR) probes, both made using carbon steel. The results indicate that rebar corrosion rates are low (~1 μm/yr or less)when the solution pH is ~7.1 or higher. Below pH ~7.1, the corrosion rate increases with decreasing pH and can reach ~100 μm/yr in solutions with pH less than ~6.7. The threshold pH for carbon steel corrosion in borated solution is between 6.8 and 7.3.

Role of Self-Association and Supersaturation in Oral Absorption of a Poorly Soluble Weakly Basic Drug.

PubMed

Narang, Ajit S; Badawy, Sherif; Ye, Qingmei; Patel, Dhaval; Vincent, Maria; Raghavan, Krishnaswamy; Huang, Yande; Yamniuk, Aaron; Vig, Balvinder; Crison, John; Derbin, George; Xu, Yan; Ramirez, Antonio; Galella, Michael; Rinaldi, Frank A

2015-08-01

Precipitation of weakly basic drugs in intestinal fluids can affect oral drug absorption. In this study, the implications of self-association of brivanib alaninate in acidic aqueous solution, leading to supersaturation at basic pH condition, on its solubility and oral absorption were investigated. Self-association of brivanib alaninate was investigated by proton NMR spectroscopy, surface tension measurement, dynamic light scattering, isothermal titration calorimetry, and molecular modeling. Drug solubility was determined in various pH media, and its tendency to supersaturate upon pH shift was investigated in buffered and biorelevant aqueous solutions. Pharmacokinetic modeling of human oral drug absorption was utilized for parameter sensitivity analyses of input variables. Brivanib alaninate exhibited continuous, and pH- and concentration-dependent self-association. This phenomenon resulted in positive deviation of drug solubility at acidic pH and the formation of a stable supersaturated drug solution in pH-shift assays. Consistent with the supersaturation phenomenon observed in vitro, oral absorption simulations necessitated invoking long precipitation time in the intestine to successfully predict in vivo data. Self-association of a weakly basic drug in acidic aqueous solution can increase its oral absorption by supersaturation and precipitation resistance at the intestinal pH. This consideration is important to the selection of parameters for oral absorption simulation.

The effect of pH and chloride concentration on the stability and antimicrobial activity of chlorine-based sanitizers.

PubMed

Waters, Brian W; Hung, Yen-Con

2014-04-01

Chlorinated water and electrolyzed oxidizing (EO) water solutions were made to compare the free chlorine stability and microbicidal efficacy of chlorine-containing solutions with different properties. Reduction of Escherichia coli O157:H7 was greatest in fresh samples (approximately 9.0 log CFU/mL reduction). Chlorine loss in "aged" samples (samples left in open bottles) was greatest (approximately 40 mg/L free chlorine loss in 24 h) in low pH (approximately 2.5) and high chloride (Cl(-) ) concentrations (greater than 150 mg/L). Reduction of E. coli O157:H7 was also negatively impacted (<1.0 log CFU/mL reduction) in aged samples with a low pH and high Cl(-) . Higher pH values (approximately 6.0) did not appear to have a significant effect on free chlorine loss or numbers of surviving microbial cells when fresh and aged samples were compared. This study found chloride levels in the chlorinated and EO water solutions had a reduced effect on both free chlorine stability and its microbicidal efficacy in the low pH solutions. Greater concentrations of chloride in pH 2.5 samples resulted in decreased free chlorine stability and lower microbicidal efficacy. © 2014 Institute of Food Technologists®

Optimization of protein solution by a novel experimental design method using thermodynamic properties.

PubMed

Kim, Nam Ah; An, In Bok; Lee, Sang Yeol; Park, Eun-Seok; Jeong, Seong Hoon

2012-09-01

In this study, the structural stability of hen egg white lysozyme in solution at various pH levels and in different types of buffers, including acetate, phosphate, histidine, and Tris, was investigated by means of differential scanning calorimetry (DSC). Reasonable pH values were selected from the buffer ranges and were analyzed statistically through design of experiment (DoE). Four factors were used to characterize the thermograms: calorimetric enthalpy (ΔH), temperature at maximum heat flux (T( m )), van't Hoff enthalpy (ΔH( V )), and apparent activation energy of protein solution (E(app)). It was possible to calculate E(app) through mathematical elaboration from the Lumry-Eyring model by changing the scan rate. The transition temperature of protein solution, T( m ), increased when the scan rate was faster. When comparing the T( m ), ΔH( V ), ΔH, and E(app) of lysozyme in various pH ranges and buffers with different priorities, lysozyme in acetate buffer at pH 4.767 (scenario 9) to pH 4.969 (scenario 11) exhibited the highest thermodynamic stability. Through this experiment, we found a significant difference in the thermal stability of lysozyme in various pH ranges and buffers and also a new approach to investigate the physical stability of protein by DoE.

Stability of urea in solution and pharmaceutical preparations.

PubMed

Panyachariwat, Nattakan; Steckel, Hartwig

2014-01-01

The stability of urea in solution and pharmaceutical preparations was analyzed as a function of temperature (25°-60°C), pH (3.11-9.67), and initial urea concentration (2.5%-20%). This study was undertaken to (i) obtain more extensive, quantitative information relative to the degradation of urea in both aqueous and non-aqueous solutions and in pharmaceutical preparations, and (ii) test the effects of initial urea concentration, pH, buffer, and temperature values on urea degradation. The stability analysis shows that urea is more stable at the pH range of 4-8 and the stability of urea decreases by increase in temperature for all pH values. Within the experimental range of temperature and initial urea concentration values, the lowest urea degradation was found with lactate buffer pH 6.0. The urea decomposition rate in solution and pharmaceutical preparations shows the dependence of the initial urea concentrations. At higher initial urea concentrations, the rate of degradation is a decreasing function with time. This suggests that the reverse reaction is a factor in the degradation of concentrated urea solution. For non-aqueous solvents, isopropanol showed the best effort in retarding the decomposition of urea. Since the losses in urea is directly influenced by its stability at a given temperature and pH, the stability analysis of urea by the proposed model can be used to prevent the loss and optimize the operating condition for urea-containing pharmaceutical preparations.

Polyelectrolyte multilayer assembly as a function of pH and ionic strength using the polysaccharides chitosan and heparin.

PubMed

Boddohi, Soheil; Killingsworth, Christopher E; Kipper, Matt J

2008-07-01

The goal of this work is to explore the effects of solution ionic strength and pH on polyelectrolyte multilayer (PEM) assembly, using biologically derived polysaccharides as the polyelectrolytes. We used the layer-by-layer (LBL) technique to assemble PEM of the polysaccharides heparin (a strong polyanion) and chitosan (a weak polycation) and characterized the sensitivity of the PEM composition and layer thickness to changes in processing parameters. Fourier-transform surface plasmon resonance (FT-SPR) and spectroscopic ellipsometry provided in situ and ex situ measurements of the PEM thickness, respectively. Vibrational spectroscopy and X-ray photoelectron spectroscopy (XPS) provided details of the chemistry (i.e., composition, electrostatic interactions) of the PEM. We found that when PEM were assembled from 0.2 M buffer, the PEM thickness could be increased from less than 2 nm per bilayer to greater than 4 nm per bilayer by changing the solution pH; higher and lower ionic strength buffer solutions resulted in narrower ranges of accessible thickness. Molar composition of the PEM was not very sensitive to solution pH or ionic strength, but pH did affect the interactions between the sulfonates in heparin and amines in chitosan when PEM were assembled from 0.2 M buffer. Changes in the PEM thickness with pH and ionic strength can be interpreted through descriptions of the charge density and conformation of the polyelectrolyte chains in solution.

Can we predict uranium bioavailability based on soil parameters? Part 1: effect of soil parameters on soil solution uranium concentration.

PubMed

Vandenhove, H; Van Hees, M; Wouters, K; Wannijn, J

2007-01-01

Present study aims to quantify the influence of soil parameters on soil solution uranium concentration for (238)U spiked soils. Eighteen soils collected under pasture were selected such that they covered a wide range for those parameters hypothesised as being potentially important in determining U sorption. Maximum soil solution uranium concentrations were observed at alkaline pH, high inorganic carbon content and low cation exchange capacity, organic matter content, clay content, amorphous Fe and phosphate levels. Except for the significant correlation between the solid-liquid distribution coefficients (K(d), L kg(-1)) and the organic matter content (R(2)=0.70) and amorphous Fe content (R(2)=0.63), there was no single soil parameter significantly explaining the soil solution uranium concentration (which varied 100-fold). Above pH=6, log(K(d)) was linearly related with pH [log(K(d))=-1.18 pH+10.8, R(2)=0.65]. Multiple linear regression analysis did result in improved predictions of the soil solution uranium concentration but the model was complex.

Adsorption of dyes by ACs prepared from waste tyre reinforcing fibre. Effect of texture, surface chemistry and pH.

PubMed

Acevedo, Beatriz; Rocha, Raquel P; Pereira, Manuel F R; Figueiredo, José L; Barriocanal, Carmen

2015-12-01

This paper compares the importance of the texture and surface chemistry of waste tyre activated carbons in the adsorption of commercial dyes. The adsorption of two commercial dyes, Basic Astrazon Yellow 7GLL and Reactive Rifafix Red 3BN on activated carbons made up of reinforcing fibres from tyre waste and low-rank bituminous coal was studied. The surface chemistry of activated carbons was modified by means of HCl-HNO3 treatment in order to increase the number of functional groups. Moreover, the influence of the pH on the process was also studied, this factor being of great importance due to the amphoteric characteristics of activated carbons. The activated carbons made with reinforcing fibre and coal had the highest SBET, but the reinforcing fibre activated carbon samples had the highest mesopore volume. The texture of the activated carbons was not modified upon acid oxidation treatment, unlike their surface chemistry which underwent considerable modification. The activated carbons made with a mixture of reinforcing fibre and coal experienced the largest degree of oxidation, and so had more acid surface groups. The adsorption of reactive dye was governed by the mesoporous volume, whilst surface chemistry played only a secondary role. However, the surface chemistry of the activated carbons and dispersive interactions played a key role in the adsorption of the basic dye. The adsorption of the reactive dye was more favored in a solution of pH 2, whereas the basic dye was adsorbed more easily in a solution of pH 12. Copyright © 2015 Elsevier Inc. All rights reserved.

PROCESS OF SEPARATING PLUTONIUM FROM URANIUM

DOEpatents

Brown, H.S.; Hill, O.F.

1958-09-01

A process is presented for recovering plutonium values from aqueous solutions. It comprises forming a uranous hydroxide precipitate in such a plutonium bearing solution, at a pH of at least 5. The plutonium values are precipitated with and carried by the uranium hydroxide. The carrier precipitate is then redissolved in acid solution and the pH is adjusted to about 2.5, causing precipitation of the uranous hydroxide but leaving the still soluble plutonium values in solution.

Decrease of U(VI) Immobilization Capability of the Facultative Anaerobic Strain Paenibacillus sp. JG-TB8 under Anoxic Conditions Due to Strongly Reduced Phosphatase Activity

PubMed Central

Reitz, Thomas; Rossberg, Andre; Barkleit, Astrid; Selenska-Pobell, Sonja; Merroun, Mohamed L.

2014-01-01

Interactions of a facultative anaerobic bacterial isolate named Paenibacillus sp. JG-TB8 with U(VI) were studied under oxic and anoxic conditions in order to assess the influence of the oxygen-dependent cell metabolism on microbial uranium mobilization and immobilization. We demonstrated that aerobically and anaerobically grown cells of Paenibacillus sp. JG-TB8 accumulate uranium from aqueous solutions under acidic conditions (pH 2 to 6), under oxic and anoxic conditions. A combination of spectroscopic and microscopic methods revealed that the speciation of U(VI) associated with the cells of the strain depend on the pH as well as on the aeration conditions. At pH 2 and pH 3, uranium was exclusively bound by organic phosphate groups provided by cellular components, independently on the aeration conditions. At higher pH values, a part (pH 4.5) or the total amount (pH 6) of the dissolved uranium was precipitated under oxic conditions in a meta-autunite-like uranyl phosphate mineral phase without supplying an additional organic phosphate substrate. In contrast to that, under anoxic conditions no mineral formation was observed at pH 4.5 and pH 6, which was clearly assigned to decreased orthophosphate release by the cells. This in turn was caused by a suppression of the indigenous phosphatase activity of the strain. The results demonstrate that changes in the metabolism of facultative anaerobic microorganisms caused by the presence or absence of oxygen can decisively influence U(VI) biomineralization. PMID:25157416

Transient kinetic studies of pH-dependent hydrolyses by exo-type carboxypeptidase P on a 27-MHz quartz crystal microbalance.

PubMed

Furusawa, Hiroyuki; Takano, Hiroki; Okahata, Yoshio

2008-02-15

pH-Dependent kinetic parameters (k(on), k(off), and k(cat)) of protein (myoglobin) hydrolyses catalyzed by exo-enzyme (carboxypeptidase P, CPP) were obtained by using a protein-immobilized quartz crystal microbalance (QCM) in acidic aqueous solutions. The formation of the enzyme-substrate (ES) complex (k(on)), the decay of the ES complex (k(off)), and the formation of the product (k(cat)) could be analyzed by transient kinetics as mass changes on the QCM plate. The Kd (k(off)/k(on)) value was different from the Michaelis constant Km calculated from (k(off) + k(cat))/k(on) due to k(cat) > k(off). The rate-determining step was the binding step (k(on), and the catalytic rate k(cat) was faster than other k(on) and k(off) values. In the range of pH 2.5-5.0, values of k(on) gradually increased with decreasing pH showing a maximum at pH 3.7, values of k(off) were independent of pH, and k(cat) increased gradually with decreasing pH. As a result, the apparent rate constant (k(cat)/Km) showed a maximum at pH 3.7 and gradually increased with decreasing pH. The optimum pH at 3.7 of k(on) is explained by the optimum binding ability of CPP to the COOH terminus of the substrate with hydrogen bonds. The increase of k(cat) at the lower pH correlated with the decrease of alpha-helix contents of the myoglobin substrate on the QCM.

Electrochemical behavior of triflusal, aspirin and their metabolites at glassy carbon and boron doped diamond electrodes.

PubMed

Enache, Teodor Adrian; Fatibello-Filho, Orlando; Oliveira-Brett, Ana Maria

2010-08-01

The electrochemical behavior of triflusal (TRF) and aspirin (ASA), before and after hydrolysis in water and in alkaline medium using two different electrode surfaces, glassy carbon and boron doped diamond, was study by differential pulse voltammetry over a wide pH range. The hydrolysis products are 2-(hydroxyl)-4-(trifluoromethyl)-benzoic acid (HTB) for triflusal and salicylic acid (SA) for aspirin, which in vivo represent their main metabolites. The hydrolysis processes were also followed by spectrophotometry. The UV results showed complete hydrolysis after one hour for TRF and after two hours for ASA in alkaline solution. The glassy carbon electrode enables only indirect determination of TRF and ASA through the electrochemical detection of their hydrolysis products HTB and SA, respectively. The oxidation processes of HTB and SA are pH dependent and involve different numbers of electrons and protons. Moreover, the difference between the oxidation peak potential of SA and HTB was equal to 100 mV in the studied pH range from 1 to 8 due to the CF3 of the aromatic ring of HTB molecule. Due to its wider oxidation potential range, the boron doped diamond electrode was used to study the direct oxidation of TRF and ASA, as well as of their respective metabolites HTB and SA.

Multimodal Sensing Strategy Using pH Dependent Fluorescence Switchable System

NASA Astrophysics Data System (ADS)

Muthurasu, A.; Ganesh, V.

2016-12-01

Biomolecules assisted preparation of fluorescent gold nanoparticles (FL-Au NPs) has been reported in this work using glucose oxidase enzyme as both reducing and stabilizing agent and demonstrated their application through multimodal sensing strategy for selective detection of cysteine (Cys). Three different methods namely fluorescence turn OFF-ON strategy, naked eye detection and electrochemical methods are used for Cys detection by employing FL-Au NPs as a common probe. In case of fluorescence turn-OFF method a strong interaction between Au NPs and thiol results in quenching of fluorescence due to replacement of glucose oxidase by Cys at neutral pH. Second mode is based on fluorescence switch-ON strategy where initial fluorescence is significantly quenched by either excess acid or base and further addition of Cys results in appearance of rosy-red and green fluorescence respectively. Visual colour change and fluorescence emission arises due to etching of Au atoms on the surface by thiol leading to formation of Au nanoclusters. Finally, electrochemical sensing of Cys is also carried out using cyclic voltammetry in 0.1 M PBS solution. These findings provide a suitable platform for Cys detection over a wide range of pH and concentration levels and hence the sensitivity can also be tuned accordingly.

Solution and interfacial behavior of modified silicone polymers and their interactions with solid substrates

NASA Astrophysics Data System (ADS)

Purohit, Parag

Surface treatment is very important step in many applications such as fabric finishing, coatings, cosmetics and personal care. Silicone polymers are a class of organic/inorganic materials that show unique properties such as weak intermolecular forces and high flexibility enabling even a very high molecular weight chain to achieve optimal orientation on surfaces. Material properties such as softness, repellency, bounciness and friction can therefore be tailored by using appropriately modified silicone polymers. Despite wide applications, the underlying mechanisms of material modification are unknown and tailoring silicones for applications remains mostly empirical. Thus the objective of this research is to understand the solution and interfacial behavior of functionalized silicone polymers, which govern their performance in material modification. Modified silicones are simultaneously hydrophobic and oleophobic in nature and due to this nearly universal non-compatibility, the studies of these polymers present unusual challenges. Due to this incompatible nature, the functionalized silicone polymers were emulsified into O/W emulsions to study their solution and interfacial properties. The colloidal properties such as electrokinetic and droplet distribution of these emulsions are assumed to play an important role in the observed surface and physical properties of solid substrates (in present study, cellulosic substrates) as well the stability of emulsions itself. To understand the effects of modified silicones on cellulosic substrates a variety of techniques such as frictional analysis, scanning electron microscopy and atomic force microscopy that can probe from macro to nano level were used. It is hypothesized that the size distribution and charge of silicone emulsions as well as the physiochemical conditions such as pH, control silicone conformation which in turn affect the modification of the substrate properties. With bimodal droplet distribution of silicone emulsions, the nano-sized droplets can penetrate deeper into the substrate to provide bounciness, whereas macro-sized droplets can coat the top layer leading to friction reduction. It was observed that at pH 5.5 the silicone treatment resulted in charge reversal of fibers as opposed to treatment at pH 9.5. On a macroscopic scale 20% reduction in frictional coefficient of the fabric was observed after treatment with quaternized (cationically modified) silicones as compared to untreated fibers. It was also observed using AFM that the fibrils treated with quaternized silicones are uniform, well stacked and smoother than the untreated fibers. Spectroscopic analysis of treated fibers using Raman spectroscopy indicated a decrease in fiber stress as a function of modification of silicone polymer and the interaction pH. It is concluded that the protonated amine functional silicone (below pH 7) as well as the quaternized silicone interacts with the negatively charged cellulose fibers primarily through electrostatic interactions. It is proposed that this initial surface coating is a uniform thin film which allows further deposition of polymer from the emulsion. It was observed that at high pH the zetapotential of silicone emulsions decreases drastically and the nano emulsions turn turbid. It is proposed that the observed electrophoretic and nephelometric behavior at high pH is due to flocculation of nanosized droplets to micron size, which eventually leads to droplets coalescing and emulsion destabilization. It is also postulated that the nano emulsion possess a critical dilution concentration (CDC), above which dilution leads to rapid coalescence. This critical dilution phase was further confirmed through polarity parameter and excimer formation studies which show significantly different polymer and surfactant microstructures near the CDC. Hence it is concluded that the observed surface properties of the substrate obtained above the CDC are significantly different than those below the CDC. The results reveal the vital role of physiochemical parameters such as pH, droplet size, and concentration on the emulsion stability as well as the observed physical/chemical properties of the substrates.

[In vitro study of vitamins B1, B2 and B6 adsorption on zeolite].

PubMed

Basić, Zorica; Kilibarda, Vesna; Dobrić, Silva; Resanović, Radmila

2011-01-01

Zeolites are the hydratised alumosilicates of alcali and earthalcali cations, which have a long three-dimensional crystal structure. Preparations on the basis of zeolites are used for adsorption of organic and nonorganic toxic substances and they, also, find more and more use in veterinary and human medicine and pharmacy. The aim of this study was to evaluate the possibilities of zeolite to adsorb vitamins B1, B2 and B6 in acid and neutral solutions, as well as the characteristics of the process (saturability, reversibility and competitiveness). The specific and sensitive HPLC method with fluorescent detector was used for determination of vitamins B1, B2 and B6. Analyte separation and detection were carried out by applying the reverse-phase method on column C18. An in vitro experiment was done by testing the influence of pH value (2 and 7), concentration of vitamin solution (1, 2 and 5 mg/L), the length of contact with zeolite (10-180 min) and cation competitiveness on the exchange capacity, which is achieved by media and zeolite contact, as well as a possible vitamins desorption through changing pH value of the solution at 37 degrees C. Jon competitiveness was examined by adding commercial feed mixture (grower) with a defined content of the examined vitamins in zeolite solutions the pH = 2 and pH = 7. Vitamins B1, B2 and B6 were stable in both pH=2 and pH = 7 solutions at 37 degrees C, in the defined time intervals. In acid solution concentrations of vitamins significantly declined in the first 10 min, with no significant decline in further 30 min for all the three concentrations tests. In neutral solution, after the addition of 1% zeolite, decrease in vitamins concentrations was slightly lower than in acid solution, but also significant in the first 10 min of the contact with zeolite. It was found that zeolite, which adsorbed vitamins in acid solution, transferred in the neutral one released a significant quantity of adsorbed vitamins after 30 min of extraction on 37 degrees C. Vitamins B1, B2 and B6, from a commercial feed mixture in pH = 2 solution, at 37 degrees C, were significantly adsorbed on zeolite after 30 min of the contact (21.87%, 20.15% and 4.53%, respectively), while in neutral solution there was no statistically significant adsorption. Conclusion. Zeolite significantly adsorbs vitamins B1, B2 and B6 in acid and neutral solutions at 37 degrees C, already in the first 10 min of the contact. Adsorption was irreversible, but partly reversible after changing pH from acid to neutral. This is a significant ions competition for adsorption on zeolite in neutral solution, so no statistically significant vitamins B1, B2 and B6 adsorption occurs, while in acid solution competition is less, thus zeolite significantly adsorbs these vitamins, although in less degree than in conditions with no concurrent ions.

Making pH Tangible.

ERIC Educational Resources Information Center

McIntosh, Elizabeth; Moss, Robert

1995-01-01

Presents a laboratory exercise in which students test the pH of different substances, study the effect of a buffer on acidic solutions by comparing the behavior of buffered and unbuffered solutions upon the addition of acid, and compare common over-the-counter antacid remedies. (MKR)

Highly pH-responsive sensor based on amplified spontaneous emission coupled to colorimetry.

PubMed

Zhang, Qi; Castro Smirnov, Jose R; Xia, Ruidong; Pedrosa, Jose M; Rodriguez, Isabel; Cabanillas-Gonzalez, Juan; Huang, Wei

2017-04-07

We demonstrated a simple, directly-readable approach for high resolution pH sensing. The method was based on sharp changes in Amplified Spontaneous Emission (ASE) of a Stilbene 420 (ST) laser dye triggered by the pH-dependent absorption of Bromocresol Green (BG). The ASE threshold of BG:ST solution mixtures exhibited a strong dependence on BG absorption, which was drastically changed by the variations of the pH of BG solution. As a result, ASE on-off or off-on was observed with different pH levels achieved by ammonia doping. By changing the concentration of the BG solution and the BG:ST blend ratio, this approach allowed to detect pH changes with a sensitivity down to 0.05 in the 10-11 pH range.

Comparing the acidities of aqueous, frozen, and freeze-dried phosphate buffers: Is there a "pH memory" effect?

PubMed

Vetráková, Ľubica; Vykoukal, Vít; Heger, Dominik

2017-09-15

The concept of "pH memory" has been established in the literature for the correlation between the pH of a pre-lyophilization solution and the ionization state of freeze-dried powder (lyophile). In this paper, the concept of "pH memory" is explored for the system of an aqueous solution, a frozen solution, and a lyophile. Sodium and potassium phosphate buffers in the pH range of 5-9 were frozen and lyophilized with sulfonephthalein indicators as acidity probes, and their Hammett acidity functions were compared to the initial pH of the aqueous solution. The results show that the acidities of the lyophiles are somewhat changed compared to the initial pHs, but the acidities in the frozen state differ more substantially. The Hammett acidity functions of the frozen buffers were found to be markedly dissimilar from the initial pH, especially in the sodium phosphate frozen at 233K, where an increase in the initial pH led to a decrease in the Hammett acidity function of the frozen state at a certain pH range. The large acidification observed after freezing the sodium phosphate buffer was not detected in the lyophiles after the sample had been dried; the phenomenon is explained considering the formed crystals analyzed by X-ray powder diffraction. The results suggest that monitoring the final acidity of a lyophile is not sufficient to predict all the acidity changes throughout the whole lyophilization process. The importance of well-controlled freezing and lyophilization conditions follows from the results of the research. Copyright © 2017 Elsevier B.V. All rights reserved.

Human Apolipoprotein A1 at Solid/Liquid and Liquid/Gas Interfaces.

PubMed

Dogan, Susanne; Paulus, Michael; Forov, Yury; Weis, Christopher; Kampmann, Matthias; Cewe, Christopher; Kiesel, Irena; Degen, Patrick; Salmen, Paul; Rehage, Heinz; Tolan, Metin

2018-04-12

An X-ray reflectivity study on the adsorption behavior of human apolipoprotein A1 (apoA1) at hydrophilic and hydrophobic interfaces is presented. It is shown that the protein interacts via electrostatic and hydrophobic interactions with the interfaces, resulting in the absorption of the protein. pH dependent measurements at the solid/liquid interface between silicon dioxide and aqueous protein solution show that in a small pH range between pH 4 and 6, adsorption is increased due to electrostatic attraction. Here, the native shape of the protein seems to be conserved. In contrast, the adsorption at the liquid/gas interface is mainly driven by hydrophobic effects, presumably by extending the hydrophobic regions of the amphipathic helices, and results in a conformational change of the protein during adsorption. However, the addition of differently charged membrane-forming lipids at the liquid/gas interface illustrates the ability of apoA1 to include lipids, resulting in a depletion of the lipids from the interface.

Quasi-simultaneous Measurements of Ionic Currents by Vibrating Probe and pH Distribution by Ion-selective Microelectrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isaacs, H.S.; Lamaka, S.V.; Taryba, M.

2011-01-01

This work reports a new methodology to measure quasi-simultaneously the local electric fields and the distribution of specific ions in a solution via selective microelectrodes. The field produced by the net electric current was detected using the scanning vibrating electrode technique (SVET) with quasi-simultaneous measurements of pH with an ion-selective microelectrode (pH-SME). The measurements were performed in a validation cell providing a 48 ?m diameter Pt wire cross section as a source of electric current. A time lag between acquiring each current density and pH data-point was 1.5 s due to the response time of pH-SME. The quasi-simultaneous SVET-pH measurementsmore » that correlate electrochemical oxidation-reduction processes with acid-base chemical equilibria are reported for the first time. No cross-talk between the vibrating microelectrode and the ion-selective microelectrode could be detected under given experimental conditions.« less

Biotherapeutic formulation factors affecting metal leachables from stainless steel studied by design of experiments.

PubMed

Zhou, Shuxia; Evans, Brad; Schöneich, Christian; Singh, Satish K

2012-03-01

Trace amounts of metals are inevitably present in biotherapeutic products. They can arise from various sources. The impact of common formulation factors such as protein concentration, antioxidant, metal chelator concentration and type, surfactant, pH, and contact time with stainless steel on metal leachables was investigated by a design of experiments approach. Three major metal leachables, iron, chromium, and nickel were monitored by inductively coupled plasma-mass spectrometry. It was observed that among all the tested factors, contact time, metal chelator concentration, and protein concentration were statistically significant factors with higher temperature resulting in higher levels of leached metals. Within a pH range of 5.5-6.5, solution pH played a minor role for chromium leaching at 25°C. No statistically significant difference was observed due to type of chelator, presence of antioxidant, or surfactant. In order to optimize a biotherapeutic formulation to achieve a target drug product shelf life with acceptable quality, each formulation component must be evaluated for its impact.

Photodegradation of the antimicrobial triclocarban in aqueous systems under ultraviolet radiation.

PubMed

Ding, Shi-Ling; Wang, Xi-Kui; Jiang, Wen-Qiang; Meng, Xia; Zhao, Ru-Song; Wang, Chen; Wang, Xia

2013-05-01

This work aimed to investigate the effectiveness of ultraviolet (UV) radiation on the degradation of the antimicrobial triclocarban (TCC). We investigated the effects of several operational parameters, including solution pH, initial TCC concentration, photocatalyst TiO₂ loading, presence of natural organic matter, and most common anions in surface waters (e.g., bicarbonate, nitrate, and sulfate). The results showed that UV radiation was very effective for TCC photodegradation and that the photolysis followed pseudo-first-order kinetics. The TCC photolysis rate was pH dependent and favored at high pH. A higher TCC photolysis rate was observed by direct photolysis than TiO₂ photocatalysis. The presence of the inorganic ions bicarbonate, nitrate, and sulfate hindered TCC photolysis. Negative effects on TCC photolysis were also observed by the addition of humic acid due to competitive UV absorbance. The main degradation products of TCC were tentatively identified by gas chromatograph with mass spectrometer, and a possible degradation pathway of TCC was also proposed.

Formation of polyelectrolyte complexes with diethylaminoethyl dextran: charge ratio and molar mass effect.

PubMed

Le Cerf, Didier; Pepin, Anne Sophie; Niang, Pape Momar; Cristea, Mariana; Karakasyan-Dia, Carole; Picton, Luc

2014-11-26

The formation of polyelectrolyte complexes (PECs) between carboxymethyl pullulan and DEAE Dextran, was investigated, in dilute solution, with emphasis on the effect of charge density (molar ratio or pH) and molar masses. Electrophoretic mobility measurements have evidenced that insoluble PECs (neutral electrophoretic mobility) occurs for charge ratio between 0.6 (excess of polycation) and 1 (stoichiometry usual value) according to the pH. This atypical result is explained by the inaccessibility of some permanent cationic charge when screened by pH dependant cationic ones (due to the Hoffman alkylation). Isothermal titration calorimetry (ITC) indicates an endothermic formation of PEC with a binding constant around 10(5) L mol(-1). Finally asymmetrical flow field flow fractionation coupled on line with static multi angle light scattering (AF4/MALS) evidences soluble PECs with very large average molar masses and size around 100 nm, in agreement with scrambled eggs multi-association between various polyelectrolyte chains. Copyright © 2014 Elsevier Ltd. All rights reserved.

Development of device producing electrolyzed water for home care

NASA Astrophysics Data System (ADS)

Umimoto, K.; Nagata, S.; Yanagida, J.

2013-06-01

When water containing ionic substances is electrolyzed, electrolyzed water with strong bactericidal ability due to the available chlorine(AC) is generated on the anode side. Slightly acidic to neutral electrolyzed water (pH 6.5 to 7.5) is physiological pH and is suitable for biological applications. For producing slightly acidic to neutral electrolyzed water simply, a vertical-type electrolytic tank with an asymmetric structure was made. As a result, a small amount of strongly alkaline water was generated in the upper cathodic small chamber, and a large amount of weakly acidic water generated in the lower anodic large chamber. The pH and AC concentration in solutin mixed with both electrolyzed water were 6.3 and 39.5 ppm, respectively, This solution was slightly acidic to neutral electrolyzed water and had strong bactericidal activity. This device is useful for producing slightly acidic to neutral electrolyzed water as a disinfectant to employ at home care, when considering economic and environmental factors, since it returns to ordinary water after use.

Exploring the Effect of Surface Functionality on the Self-Assembly of Polyoxopalladate Macroions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haso, Fadi; Yang, Peng; Gao, Yunyi

2015-05-12

The solution behavior of the two polyoxo-13-palladates(II) ([Pd(II) 13 As(V) 8 O34 (OH)6 ](8-) and [Pd(II) 13 (As(V) Ph)8 O32 ](6-) ) was studied in detail. We discovered that the countercation-mediated attraction is the driving force for their self-assembly into larger architectures. However, the presence of phenyl groups in the periphery of [Pd(II) 13 (As(V) Ph)8 O32 ](6-) results in an enhanced attraction among these polyanions through hydrophobic interactions, which leads to completely different trends of assembly size for these two very similar clusters when decreasing solvent polarity. An increase of assembly size with increasing solvent polarity was observed formore » [Pd(II) 13 (As(V) Ph)8 O32 ](6-) , whereas for [Pd(II) 13 As (V) 8 O34 (OH)6 ](8-) it was the opposite, due to the absence of hydrophobic interactions.« less

Electrospray Ionization-Induced Protein Unfolding

NASA Astrophysics Data System (ADS)

Lin, Hong; Kitova, Elena N.; Johnson, Margaret A.; Eugenio, Luiz; Ng, Kenneth K. S.; Klassen, John S.

2012-12-01

Electrospray ionization mass spectrometry (ESI-MS) measurements were performed under a variety of solution conditions on a highly acidic sub-fragment (B3C) of the C-terminal carbohydrate-binding repeat region of Clostridium difficile toxin B, and two mutants (B4A and B4B) containing fewer acidic residues. ESI-MS measurements performed in negative ion mode on aqueous ammonium acetate solutions of B3C at low ionic strength ( I < 80 mM) revealed evidence, based on the measured charge state distribution, of protein unfolding. In contrast, no evidence of unfolding was detected from ESI-MS measurements made in positive ion mode at low I or in either mode at higher I. The results of proton nuclear magnetic resonance and circular dichroism spectroscopy measurements and gel filtration chromatography performed on solutions of B3C under low and high I conditions suggest that the protein exists predominantly in a folded state in neutral aqueous solutions with I > 10 mM. The results of ESI-MS measurements performed on B3C in a series of solutions with high I at pH 5 to 9 rule out the possibility that the structural changes are related to ESI-induced changes in pH. It is proposed that unfolding of B3C, observed in negative mode for solutions with low I, occurs during the ESI process and arises due to Coulombic repulsion between the negatively charged residues and liquid/droplet surface charge. ESI-MS measurements performed in negative ion mode on B4A and B4B also reveal a shift to higher charge states at low I but the magnitude of the changes are smaller than observed for B3C.

The impact of primary packaging on the quality of parenteral products.

PubMed

Solomun, Ljiljana; Ibric, Svetlana; Boltic, Zorana; Djuric, Zorica; Stupar, Biljana

2008-11-04

The unique approach in manufacturing of pharmaceutical dosage forms of active substances known to be unstable in aqueous solution is the introduction of lyophilization process. Nevertheless, these products must be reconstituted using the diluent from a separate container before application. The possible solution for this problem is the application of dual chamber vials comprising the freeze-dried product in a lower compartment of the vial and the solution for reconstitution in the upper chamber. The main issue in development of such product is the choice of contact packaging (rubber closures, glass vials and the container closure system as a whole). The most important parameter used for evaluation of the influence of contact material on product quality was the pH value. The results have shown that the type of vials (moulded or tubular glass) has no impact on pH shift of the solution for reconstitution (tested solution-TS), while significant differences in pH value of the TS were observed depending on the rubber closures formulation used (with some formulations, the pH shift during the test was 6.5-9.14). Benzyl alcohol assay during the tests remained unchanged. Integrity tests of the container closure system (CCS) have demonstrated the adequacy of the selected packaging system. The quality of the CCS of choice was confirmed in the course of stability studies, only parameters directly influenced by CCS being presented in this work: loss on drying and pH value. On the basis of these results, no changes in loss on drying were connected to CCS, and the pH value of the reconstituted solution remains unchanged in samples tested both ex-tempore and after in-use period of 48 h.

Quantification of Kinetic Rate Law Parameters of Uranium Release from Sodium Autunite as a Function of Aqueous Bicarbonate Concentrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gudavalli, Ravi; Katsenovich, Yelena; Wellman, Dawn M.

2013-09-05

ABSTRACT: Hydrogen carbonate is one of the most significant components within the uranium geochemical cycle. In aqueous solutions, hydrogen carbonate forms strong complexes with uranium. As such, aqueous bicarbonate may significantly increase the rate of uranium release from uranium minerals. Quantifying the relationship of aqueous hydrogen carbonate solutions to the rate of uranium release during dissolution is critical to understanding the long-term fate of uranium within the environment. Single-pass flow-through (SPTF) experiments were conducted to estimate the rate of uranium release from Na meta-autunite as a function of bicarbonate solutions (0.0005-0.003 M) under the pH range of 6-11 and temperaturesmore » of 5-60oC. Consistent with the results of previous investigation, the rate of uranium release from sodium autunite exhibited minimal dependency on temperature; but were strongly dependent on pH and increasing concentrations of bicarbonate solutions. Most notably at pH 7, the rate of uranium release exhibited 370 fold increases relative to the rate of uranium release in the absence of bicarbonate. However, the effect of increasing concentrations of bicarbonate solutions on the release of uranium was significantly less under higher pH conditions. It is postulated that at high pH values, surface sites are saturated with carbonate, thus the addition of more bicarbonate would have less effect on uranium release. Results indicate the activation energies were unaffected by temperature and bicarbonate concentration variations, but were strongly dependent on pH conditions. As pH increased from 6 to 11, activation energy values were observed to decrease from 29.94 kJ mol-1 to 13.07 kJ mol-1. The calculated activation energies suggest a surface controlled dissolution mechanism.« less

Adsorptive Removal of Nitrate from Aqueous Solution Using Nitrogen Doped Activated Carbon.

PubMed

Machida, Motoi; Goto, Tatsuru; Amano, Yoshimasa; Iida, Tatsuya

2016-01-01

Activated carbon (AC) has been widely applied for adsorptive removal of organic contaminants from aqueous phase, but not for ionic pollutants. In this study, nitrogen doped AC was prepared to increase the adsorption capacity of nitrate from water. AC was oxidized with (NH 4 ) 2 S 2 O 8 solution to maximize oxygen content for the first step, and then NH 3 gas treatment was carried out at 950°C to aim at forming quaternary nitrogen (N-Q) species on AC surface (Ox-9.5AG). Influence of solution pH was examined so as to elucidate the relationship between surface charge and adsorption amounts of nitrate. The results showed that Ox-9.5AG exhibited about twice higher adsorption capacity than non-treatment AC at any initial nitrate concentration and any equilibrium solution pH (pH e ) investigated. The more decrease in pH e value, the more adsorption amount of negatively charged nitrate ion, because the surface charge of AC and Ox-9.5AG could become more positive in acidic solution. The oxidation and consecutive ammonia treatments lead to increase in nitrogen content from 0.35 to 6.4% and decrease in the pH of the point of zero charge (pH pzc ) from 7.1 to 4.0 implying that positively charged N-Q of a Lewis acid was created on the surface of Ox-9.5AG. Based on a Langmuir data analysis, maximum adsorption capacity attained 0.5-0.6 mmol/g of nitrate and adsorption affinity was 3.5-4.0 L/mmol at pH e 2.5 for Ox-9.5AG.