Preparation and characterization of glycidyl methacrylate organo bridges grafted mesoporous silica SBA-15 as ibuprofen and mesalamine carrier for controlled release.

PubMed

Rehman, Fozia; Rahim, Abdur; Airoldi, Claudio; Volpe, Pedro L O

2016-02-01

Mesoporous silica SBA-15 was synthesized and functionalized with bridged polysilsesquioxane monomers obtained by the reaction of 3-aminopropyltriethoxy silane with glycidyl methacrylate in 2:1 ratio. The synthesized mesoporous silica materials were characterized by elemental analysis, infrared spectroscopy, nuclear magnetic resonance spectroscopy, nitrogen adsorption, X-ray diffraction, thermogravimetry and scanning electron microscopy. The nuclear magnetic resonance in the solid state is in agreement with the sequence of carbon distributed in the attached organic chains, as expected for organically functionalized mesoporous silica. After functionalization with organic bridges the BET surface area was reduced from 1311.80 to 494.2m(2)g(-1) and pore volume was reduced from 1.98 to 0.89cm(3)g(-1), when compared to original precursor silica. Modification of the silica surface with organic bridges resulted in high loading capacity and controlled release of ibuprofen and mesalamine in biological fluids. The Korsmeyer-Peppas model better fits the release data indicating Fickian diffusion and zero order kinetics for synthesized mesoporous silica. The drug release rate from the modified silica was slow in simulated gastric fluid, (pH1.2) where less than 10% of mesalamine and ibuprofen were released in initial 8h, while comparatively high release rates were observed in simulated intestinal (pH6.8) and simulated body fluids (pH7.2). The preferential release of mesalamine at intestinal pH suggests that the modified silica could be a simple, efficient, inexpensive and convenient carrier for colon targeted drugs, such a mesalamine and also as a controlled drug release system. Copyright © 2015 Elsevier B.V. All rights reserved.

Biochemically enhanced oil recovery and oil treatment

DOEpatents

Premuzic, E.T.; Lin, M.

1994-03-29

This invention relates to the preparation of new, modified organisms, through challenge growth processes, that are viable in the extreme temperature, pressure and pH conditions and salt concentrations of an oil reservoir and that are suitable for use in microbial enhanced oil recovery. The modified microorganisms of the present invention are used to enhance oil recovery and remove sulfur compounds and metals from the crude oil. 62 figures.

Removal of microcystin-LR from drinking water using a bamboo-based charcoal adsorbent modified with chitosan.

PubMed

Zhang, Hangjun; Zhu, Guoying; Jia, Xiuying; Ding, Ying; Zhang, Mi; Gao, Qing; Hu, Ciming; Xu, Shuying

2011-01-01

A new kind of low-cost syntactic adsorbent from bamboo charcoal and chitosan was developed for the removal of microcystin-LR from drinking water. Removal efficiency was higher for the syntactic adsorbent when the amount of bamboo charcoal was increased. The optimum dose ratio of bamboo charcoal to chitosan was 6:4, and the optimum amount was 15 mg/L; equilibrium time was 6 hr. The adsorption isotherm was non-linear and could be simulated by the Freundlich model (R2 = 0.9337). Adsorption efficiency was strongly affected by pH and natural organic matter (NOM). Removal efficiency was 16% higher at pH 3 than at pH 9. Efficiency rate was reduced by 15% with 25 mg/L NOM (UV254 = 0.089 cm(-1)) in drinking water. This study demonstrated that the bamboo charcoal modified with chitosan can effectively remove microcystin-LR from drinking water.

Experimental investigation and modeling of dissolved organic carbon removal by coagulation from seawater.

PubMed

Jeong, Sanghyun; Sathasivan, Arumugam; Kastl, George; Shim, Wang Geun; Vigneswaran, Saravanamuthu

2014-01-01

Coagulation removes colloidal matters and dissolved organic carbon (DOC) which can cause irreversible membrane fouling. However, how DOC is removed by coagulant is not well-known. Jar test was used to study the removal of hydrophobic and hydrophilic DOC fractions at various doses (0.5-8.0 mg-Fe(+3) L(-1)) of ferric chloride (FeCl3) and pH (5.0-9.0). Natural organic matter (NOM) in seawater and treated seawater were fractionated by liquid chromatography-organic carbon detector (LC-OCD). Compared to surface water, the removal of DOC in seawater by coagulation was remarkably different. Majority of DOC could be easily removed with very low coagulant dose (<5.0 mg-Fe(+3) L(-1)) and the removal efficiency did not vary with pH, but the DOC composition in treated water had significantly changed. Hydrophobic fraction (HB) was better removed at high pH while hydrophilic fraction (HF) was better removed at low pH. A modified model of Kastl et al. (2004) which assumed that the removal occurred by adsorption of un-dissociated compounds onto ferric hydroxide was formulated and successfully validated against the jar test data. Copyright © 2013 Elsevier Ltd. All rights reserved.

A De Novo Floral Transcriptome Reveals Clues into Phalaenopsis Orchid Flower Development

PubMed Central

Huang, Jian-Zhi; Lin, Chih-Peng; Cheng, Ting-Chi; Chang, Bill Chia-Han; Cheng, Shu-Yu; Chen, Yi-Wen; Lee, Chen-Yu; Chin, Shih-Wen; Chen, Fure-Chyi

2015-01-01

Phalaenopsis has a zygomorphic floral structure, including three outer tepals, two lateral inner tepals and a highly modified inner median tepal called labellum or lip; however, the regulation of its organ development remains unelucidated. We generated RNA-seq reads with the Illumina platform for floral organs of the Phalaenopsis wild-type and peloric mutant with a lip-like petal. A total of 43,552 contigs were obtained after de novo assembly. We used differentially expressed gene profiling to compare the transcriptional changes in floral organs for both the wild-type and peloric mutant. Pair-wise comparison of sepals, petals and labellum between peloric mutant and its wild-type revealed 1,838, 758 and 1,147 contigs, respectively, with significant differential expression. PhAGL6a (CUFF.17763), PhAGL6b (CUFF.17763.1), PhMADS1 (CUFF.36625.1), PhMADS4 (CUFF.25909) and PhMADS5 (CUFF.39479.1) were significantly upregulated in the lip-like petal of the peloric mutant. We used real-time PCR analysis of lip-like petals, lip-like sepals and the big lip of peloric mutants to confirm the five genes’ expression patterns. PhAGL6a, PhAGL6b and PhMADS4 were strongly expressed in the labellum and significantly upregulated in lip-like petals and lip-like sepals of peloric-mutant flowers. In addition, PhAGL6b was significantly downregulated in the labellum of the big lip mutant, with no change in expression of PhAGL6a. We provide a comprehensive transcript profile and functional analysis of Phalaenopsis floral organs. PhAGL6a PhAGL6b, and PhMADS4 might play crucial roles in the development of the labellum in Phalaenopsis. Our study provides new insights into how the orchid labellum differs and why the petal or sepal converts to a labellum in Phalaenopsis floral mutants. PMID:25970572

Comparison study of phosphorus adsorption on different waste solids: Fly ash, red mud and ferric-alum water treatment residues.

PubMed

Wang, Ying; Yu, Yange; Li, Haiyan; Shen, Chanchan

2016-12-01

The adsorption of phosphorus (P) onto three industrial solid wastes (fly ash, red mud and ferric-alum water treatment residual (FAR)) and their modified materials was studied systematically via batch experiments. Compared with two natural adsorbents (zeolite and diatomite), three solid wastes possessed a higher adsorption capacity for P because of the higher Fe, Al and Ca contents. After modification (i.e., the fly ash and red mud modified by FeCl 3 and FARs modified by HCl), the adsorption capacity increased, especially for the modified red mud, where more Fe bonded P was observed. The P adsorption kinetics can be satisfactorily fitted using the pseudo-second-order model. The Langmuir model can describe well the P adsorption on all of the samples in our study. pH and dissolved organic matter (DOM) are two important factors for P adsorption. Under neutral conditions, the maximum adsorption amount on the modified materials was observed. With the deviation from pH7, the adsorption amount decreased, which resulted from the change of P species in water and surface charges of the adsorbents. The DOM in water can promote P adsorption, which may be due to the promotion effects of humic-Fe(Al) complexes and the pH buffer function exceeds the depression of competitive adsorption. Copyright © 2016. Published by Elsevier B.V.

Overexpression of PhEXPA1 increases cell size, modifies cell wall polymer composition and affects the timing of axillary meristem development in Petunia hybrida.

PubMed

Zenoni, Sara; Fasoli, Marianna; Tornielli, Giovanni Battista; Dal Santo, Silvia; Sanson, Andrea; de Groot, Peter; Sordo, Sara; Citterio, Sandra; Monti, Francesca; Pezzotti, Mario

2011-08-01

• Expansins are cell wall proteins required for cell enlargement and cell wall loosening during many developmental processes. The involvement of the Petunia hybrida expansin A1 (PhEXPA1) gene in cell expansion, the control of organ size and cell wall polysaccharide composition was investigated by overexpressing PhEXPA1 in petunia plants. • PhEXPA1 promoter activity was evaluated using a promoter-GUS assay and the protein's subcellular localization was established by expressing a PhEXPA1-GFP fusion protein. PhEXPA1 was overexpressed in transgenic plants using the cauliflower mosaic virus (CaMV) 35S promoter. Fourier transform infrared (FTIR) and chemical analysis were used for the quantitative analysis of cell wall polymers. • The GUS and GFP assays demonstrated that PhEXPA1 is present in the cell walls of expanding tissues. The constitutive overexpression of PhEXPA1 significantly affected expansin activity and organ size, leading to changes in the architecture of petunia plants by initiating premature axillary meristem outgrowth. Moreover, a significant change in cell wall polymer composition in the petal limbs of transgenic plants was observed. • These results support a role for expansins in the determination of organ shape, in lateral branching, and in the variation of cell wall polymer composition, probably reflecting a complex role in cell wall metabolism. © 2011 The Authors. New Phytologist © 2011 New Phytologist Trust.

Influence of variation in mobile phase pH and solute pK(a) with the change of organic modifier fraction on QSRRs of hydrophobicity and RP-HPLC retention of weakly acidic compounds.

PubMed

Han, Shu-ying; Liang, Chao; Zou, Kuan; Qiao, Jun-qin; Lian, Hong-zhen; Ge, Xin

2012-11-15

The variation in mobile phase pH and ionizable solute dissociation constant (pK(a)) with the change of organic modifier fraction in hydroorganic mobile phase has seemingly been a troublesome problem in studies and applications of reversed phase high performance liquid chromatography (RP-HPLC). Most of the early studies regarding the RP-HPLC of acid-base compounds have to measure the actual pH of the mixed mobile phase rigorously, sometimes bringing difficulties in the practices of liquid chromatographic separation. In this paper, the effect of this variation on the apparent n-octanol/water partition coefficient (K(ow)″) and the related quantitative structure-retention relationship (QSRR) of logK(ow)″ vs. logk(w), the logarithm of retention factor of analytes in neat aqueous mobile phases, was investigated for weakly acidic compounds. This QSRR is commonly used as a classical method for K(ow) measurement by RP-HPLC. The theoretical and experimental derivation revealed that the variation in mobile phase pH and solute pK(a) will not affect the QSRRs of acidic compounds. This conclusion is proved to be suitable for various types of ion-suppressors, i.e., strong acid (perchloric acid), weak acid (acetic acid) and buffer salt (potassium dihydrogen phosphate/phosphoric acid, PBS). The QSRRs of logK(ow)″ vs. logk(w) were modeled by 11 substituted benzoic acids using different types of ion-suppressors in a binary methanol-water mobile phase to confirm our deduction. Although different types of ion-suppressor all can be used as mobile phase pH modifiers, the QSRR model obtained by using perchloric acid as the ion-suppressor was found to have the best result, and the slightly inferior QSRRs were obtained by using acetic acid or PBS as the ion-suppressor. Copyright © 2012 Elsevier B.V. All rights reserved.

Displacement chromatography on cyclodextrin silicas. IV. Separation of the enantiomers of ibuprofen.

PubMed

Farkas, G; Irgens, L H; Quintero, G; Beeson, M D; al-Saeed, A; Vigh, G

1993-08-13

A displacement chromatographic method has been developed for the preparative separation of the enantiomers of ibuprofen using a beta-cyclodextrin silica stationary phase. The retention behavior of ibuprofen was studied in detail: the log k' vs. polar organic modifier concentration, the log k' vs. pH, the log k' vs. buffer concentration and the log k' vs. 1/T relationships; also, the alpha vs. polar organic modifier concentration, the alpha vs. pH, the alpha vs. buffer concentration and the log alpha vs. 1/T relationships have been determined in order to find the carrier solution composition which results in maximum chiral selectivity and sufficient, but not excessive solute retention (1 < k' < 30). 4-tert.-Butylcyclohexanol, a structurally similar but more retained compound than ibuprofen, was selected as displacer for the separation. Even with an alpha value as small as 1.08, good preparative chiral separations were observed both in the displacement mode and in the overloaded elution mode, up to a sample load of 0.5 mg.

Effects of water quality parameters on boron toxicity to Ceriodaphnia dubia.

PubMed

Dethloff, Gail M; Stubblefield, William A; Schlekat, Christian E

2009-07-01

The potential modifying effects of certain water quality parameters (e.g., hardness, alkalinity, pH) on the acute toxicity of boron were tested using a freshwater cladoceran, Ceriodaphnia dubia. By comparison, boron acute toxicity was less affected by water quality characteristics than some metals (e.g., copper and silver). Increases in alkalinity over the range tested did not alter toxicity. Increases in water hardness appeared to have an effect with very hard waters (>500 mg/L as CaCO(3)). Decreased pH had a limited influence on boron acute toxicity in laboratory waters. Increasing chloride concentration did not provide a protective effect. Boron acute toxicity was unaffected by sodium concentrations. Median acute lethal concentrations (LC(50)) in natural water samples collected from three field sites were all greater than in reconstituted laboratory waters that matched natural waters in all respects except for dissolved organic carbon. Water effect ratios in these waters ranged from 1.4 to 1.8. In subsequent studies using a commercially available source of natural organic matter, acute toxicity decreased with increased dissolved organic carbon, suggesting, along with the natural water studies, that dissolved organic carbon should be considered further as a modifier of boron toxicity in natural waters where it exceeds 2 mg/L.

Capillary gas chromatographic separation of organic bases using a pH-adjusted basic water stationary phase.

PubMed

Darko, Ernest; Thurbide, Kevin B

2016-09-23

The use of a pH-adjusted water stationary phase for analyzing organic bases in capillary gas chromatography (GC) is demonstrated. Through modifying the phase to typical values near pH 11.5, it is found that various organic bases are readily eluted and separated. Conversely, at the normal pH 7 operating level, they are not. Sodium hydroxide is found to be a much more stable base than ammonium hydroxide for altering the pH due to the higher volatility and evaporation of the latter. In the basic condition, such analytes are not ionized and are observed to produce good peak shapes even for injected masses down to about 20ng. By comparison, analyses on a conventional non-polar capillary GC column yield more peak tailing and only analyte masses of 1μg or higher are normally observed. Through carefully altering the pH, it is also found that the selectivity between analytes can be potentially further enhanced if their respective pKa values differ sufficiently. The analysis of different pharmaceutical and petroleum samples containing organic bases is demonstrated. Results indicate that this approach can potentially offer unique and beneficial selectivity in such analyses. Copyright © 2016 Elsevier B.V. All rights reserved.

Conformational changes of a chemically modified HRP: formation of a molten globule like structure at pH 5

PubMed Central

Bamdad, Kourosh; Ranjbar, Bijan; Naderi-Manesh, Hossein; Sadeghi, Mehdi

2014-01-01

Horseradish peroxidase is an all alpha-helical enzyme, which widely used in biochemistry applications mainly because of its ability to enhance the weak signals of target molecules. This monomeric heme-containing plant peroxidase is also used as a reagent for the organic synthesis, biotransformation, chemiluminescent assays, immunoassays, bioremediation, and treatment of wastewaters as well. Accordingly, enhancing stability and catalytic activity of this protein for biotechnological uses has been one of the important issues in the field of biological investigations in recent years. In this study, pH-induced structural alterations of native (HRP), and modified (MHRP) forms of Horseradish peroxidase have been investigated. Based on the results, dramatic loss of the tertiary structure and also the enzymatic activity for both forms of enzymes recorded at pH values lower than 6 and higher than 8. Ellipticiy measurements, however, indicated very slight variations in the secondary structure for MHRP at pH 5. Spectroscopic analysis also indicated that melting of the tertiary structure of MHRP at pH 5 starts at around 45 °C, which is associated to the pKa of His 42 that has a serious role in keeping of the heme prostethic group in its native position through natural hydrogen bond network in the enzyme structure. According to our data, a molten globule like structure of a chemically modified form of Horseradish peroxidase at pH 5 with initial steps of conformational transition in tertiary structure with almost no changes in the secondary structure has been detected. Despite of some conformational changes in the tertiary structure of MHRP at pH 5, this modified form still keeps its catalytic activity to some extent besides enhanced thermal stability. These findings also indicated that a molten globular state does not necessarily preclude efficient catalytic activity. PMID:26417287

Coupling of organic and inorganic aerosol systems and the effect on gas–particle partitioning in the southeastern US

PubMed Central

Pye, Havala O. T.; Zuend, Andreas; Fry, Juliane L.; Isaacman-VanWertz, Gabriel; Capps, Shannon L.; Appel, K. Wyat; Foroutan, Hosein; Xu, Lu; Ng, Nga L.; Goldstein, Allen H.

2018-01-01

Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2× sulfate, RN/2S ≈ 0.8 to 0.9) with approximately 70% of total ammonia and ammonium (NHx) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+]air (H+ in μgm−3 air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid–liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic–organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C≥0.6) compounds including several isoprene-derived tracers as well as levoglu-cosan but decrease particle-phase partitioning for low O: C, monoterpene-derived species.

Coupling of organic and inorganic aerosol systems and the effect on gas-particle partitioning in the southeastern US

NASA Astrophysics Data System (ADS)

Pye, Havala O. T.; Zuend, Andreas; Fry, Juliane L.; Isaacman-VanWertz, Gabriel; Capps, Shannon L.; Wyat Appel, K.; Foroutan, Hosein; Xu, Lu; Ng, Nga L.; Goldstein, Allen H.

2018-01-01

Several models were used to describe the partitioning of ammonia, water, and organic compounds between the gas and particle phases for conditions in the southeastern US during summer 2013. Existing equilibrium models and frameworks were found to be sufficient, although additional improvements in terms of estimating pure-species vapor pressures are needed. Thermodynamic model predictions were consistent, to first order, with a molar ratio of ammonium to sulfate of approximately 1.6 to 1.8 (ratio of ammonium to 2 × sulfate, RN/2S ≈ 0.8 to 0.9) with approximately 70 % of total ammonia and ammonium (NHx) in the particle. Southeastern Aerosol Research and Characterization Network (SEARCH) gas and aerosol and Southern Oxidant and Aerosol Study (SOAS) Monitor for AeRosols and Gases in Ambient air (MARGA) aerosol measurements were consistent with these conditions. CMAQv5.2 regional chemical transport model predictions did not reflect these conditions due to a factor of 3 overestimate of the nonvolatile cations. In addition, gas-phase ammonia was overestimated in the CMAQ model leading to an even lower fraction of total ammonia in the particle. Chemical Speciation Network (CSN) and aerosol mass spectrometer (AMS) measurements indicated less ammonium per sulfate than SEARCH and MARGA measurements and were inconsistent with thermodynamic model predictions. Organic compounds were predicted to be present to some extent in the same phase as inorganic constituents, modifying their activity and resulting in a decrease in [H+]air (H+ in µg m-3 air), increase in ammonia partitioning to the gas phase, and increase in pH compared to complete organic vs. inorganic liquid-liquid phase separation. In addition, accounting for nonideal mixing modified the pH such that a fully interactive inorganic-organic system had a pH roughly 0.7 units higher than predicted using traditional methods (pH = 1.5 vs. 0.7). Particle-phase interactions of organic and inorganic compounds were found to increase partitioning towards the particle phase (vs. gas phase) for highly oxygenated (O : C ≥ 0.6) compounds including several isoprene-derived tracers as well as levoglucosan but decrease particle-phase partitioning for low O : C, monoterpene-derived species.

Enzyme-modified electrolyte-gated organic field-effect transistors

NASA Astrophysics Data System (ADS)

Buth, Felix; Donner, Andreas; Stutzmann, Martin; Garrido, Jose A.

2012-10-01

Organic solution-gated field-effect transistors (SGFETs) can be operated at low voltages in aqueous environments, paving the way to the use of organic semiconductors in bio-sensing applications. However, it has been shown that these devices exhibit only a rather weak sensitivity to standard electrolyte parameters such as pH and ionic strength. In order to increase the sensitivity and to add specificity towards a given analyte, the covalent attachment of functional groups and enzymes to the device surface would be desirable. In this contribution we demonstrate that enzyme modified organic SGFETs can be used for the in-situ detection of penicillin in the low μM regime. In a first step, silane molecules with amine terminal groups are grafted to α-sexithiophene-based thin film transistors. Surface characterization techniques like X-ray photoemission confirm the modification of the surface with these functional groups, which are stable in standard aqueous electrolytes. We show that the presence of surface-bound amphoteric groups (e.g. amino or carboxylic moieties) increases the pH-sensitivity of the organic SGFETs. In addition, these groups serve as anchoring sites for the attachment of the enzyme penicillinase. The resulting enzyme-FETs are used for the detection of penicillin, enabling the study of the influence of the buffer strength and the pH of the electrolyte on the enzyme kinetics. The functionalization of the organic FETs shown here can be extended to a large variety of enzymes, allowing the specific detection of different chemical and biochemical analytes.

Prediction of the chromatographic retention of acid-base compounds in pH buffered methanol-water mobile phases in gradient mode by a simplified model.

PubMed

Andrés, Axel; Rosés, Martí; Bosch, Elisabeth

2015-03-13

Retention of ionizable analytes under gradient elution depends on the pH of the mobile phase, the pKa of the analyte and their evolution along the programmed gradient. In previous work, a model depending on two fitting parameters was recommended because of its very favorable relationship between accuracy and required experimental work. It was developed using acetonitrile as the organic modifier and involves pKa modeling by means of equations that take into account the acidic functional group of the compound (carboxylic acid, protonated amine, etc.). In this work, the two-parameter predicting model is tested and validated using methanol as the organic modifier of the mobile phase and several compounds of higher pharmaceutical relevance and structural complexity as testing analytes. The results have been quite good overall, showing that the predicting model is applicable to a wide variety of acid-base compounds using mobile phases prepared with acetonitrile or methanol. Copyright © 2015 Elsevier B.V. All rights reserved.

Modified kinetic-hydraulic UASB reactor model for treatment of wastewater containing biodegradable organic substrates.

PubMed

El-Seddik, Mostafa M; Galal, Mona M; Radwan, A G; Abdel-Halim, Hisham S

2016-01-01

This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt.

Interactions between organic amendments and phosphate fertilizers modify phosphate sorption processes in an acid soil

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

Sckefe, C.R.; Patti, A.F.; Clune, T.S.

2008-07-15

To determine how organic amendments and phosphate fertilizers interact to modify P sorption processes, three phosphate fertilizers were applied to lignite- and compost-amended acid soil and incubated for either 3 or 26 days. The fertilizers applied were potassium dihydrogen phosphate, triple superphosphate, and diammonium phosphate (DAP). After 3 days of incubation, sorption of all three P sources was decreased in the lignite-amended treatments, whereas P sorption was increased in the compost-amended treatments. Increased incubation time (26 days) resulted in significantly decreased P sorption when DAP was added to lignite-amended treatments. Addition of triple superphosphate increased P sorption in lignite- andmore » compost-amended treatments and decreased solution pH compared with DAP application. In addition to the effect of P source, differences in P sorption between the lignite- and compost-amended treatments were driven by differences in solution chemistry, predominantly solution pH and cation dynamics. Soil amendment and fertilizer addition also increased microbial activity in the incubation systems, as measured by carbon dioxide respiration. It is proposed that the combination of lignite and DAP may contribute to decreased P sorption in acid soils, with the positive effects likely caused by both chemical and biological processes, including the formation of soluble organic-metal complexes.« less

Sorption of nonpolar aromatic contaminants by chlorosilane surface modified natural minerals.

PubMed

Huttenloch, P; Roehl, K E; Czurda, K

2001-11-01

The efficacy of the surface modification of natural diatomite and zeolite material by chlorosilanes is demonstrated. Chlorosilanes used were trimethylchlorosilane (TMSCI), tert-butyldimethylchlorosilane (TBDMSCI), dimethyloctadecylchlorosilane (DMODSCI), and diphenyldichlorosilane (DPDSCI) possessing different headgroups and chemical properties. Silanol groups of the diatomite and zeolite were modified by chemical reaction with the chlorosilanes resulting in a stable covalent attachment of the organosilanes to the mineral surface. The alteration of surface properties of the modified material was proved by measurements of water adsorption capacity, total organic carbon (TOC) content, and thermoanalytical data. The surface modified material showed great stability even when exposed to extremes in ionic strength, pH, and to pure organic solvents. Sorption of toluene, o-xylene, and naphthalene from water was greatly enhanced by the surface modification compared to the untreated materials which showed no measurable sorption of these compounds. The enhanced sorption was dependent on the organic carbon content as well as on chemical characteristics of the chlorosilanes used. Batch sorption experiments showed that the phenyl headgroups of DPDSCI have the best affinity for aromatic compounds. Removal from an aqueous solution of 10 mg/L of naphthalene, o-xylene, and toluene was 71%, 60%, and 30% for surface modified diatomite and 51%, 30%, and 16% for modified clinoptilolite, respectively. Sorption data were well described by the Freundlich isotherm equation, which indicated physical adsorption onto the lipophilic surface rather than partitioning into the surface organic phase. The chlorosilane modified materials have an apparent potential for application in environmental technologies such as permeable reactive barriers (PRB) or wastewater treatment.

Enantiomeric separation of some demethylated analogues of clofibric acid by capillary zone electrophoresis and nano-liquid chromatography.

PubMed

Fantacuzzi, Marialuigia; Bettoni, Giancarlo; D'Orazio, Giovanni; Fanali, Salvatore

2006-03-01

The enantiomeric separation of some demethylated analogues of clofibric acid, namely 2-(6-chloro-benzothiazol-2-ylsulfanyl)-, 2-(6-methoxy-benzothiazol-2-ylsulfanyl)-, 2-(quinolin-2-yloxy)-, 2-(6-chloro-quinolin-2-yloxy)-, 2-(7-chloro-quinolin-4-yloxy)-propionic acid (compounds A-E, respectively), has been studied by CZE and nano-LC using for the first technique two beta-CD derivatives and vancomycin added to the BGE and vancomycin-modified silica particles for the second one, with the aim to find the optimum experimental conditions for the baseline resolution. The type and the concentration of the chiral selector added to the BGE, the buffer pH, the type of organic modifier and its concentration, the capillary temperature and the applied voltage played a very important role in the enantioresolution of the analysed compounds. The use of 6-monodeoxy-6-monoamino-beta-CD allowed to achieve baseline resolution of four of five clofibric acid derivatives in less than 10 min while heptakis-(2,3,6-tri-O-methyl)-beta-CD partially resolved the same compounds in their enantiomers. Employing vancomycin as the chiral selector in CZE, the counter-current partial filling method was chosen achieving baseline resolution of four analytes. All the studied compounds were enantioresolved employing a capillary column packed with vancomycin stationary phase by nano-LC, and the resolution was strongly influenced by the concentration of the organic modifier and by the pH of the mobile phase. The best results were achieved at pH 4.5 in presence of 60% of methanol (MeOH). However, longer analysis times were observed in the experiments carried out by nano-LC.

Adsorption of natural organic matter and disinfection byproduct precursors from surface water onto TiO2 nanoparticles: pH effects, isotherm modelling and implications for using TiO2 for drinking water treatment.

PubMed

Gora, Stephanie L; Andrews, Susan A

2017-05-01

Titanium dioxide is a photocatalyst that can remove organic contaminants of interest to the drinking water treatment industry, including natural organic matter (NOM) and disinfection byproduct (DBP) precursors. The photocatalytic reaction occurs in two steps: adsorption of the contaminant followed by degradation of the adsorbed contaminant upon irradiation with UV light. The second part of this process can lead to the formation of reactive intermediates and negative impacts on treated water quality, such as increased DBP formation potential (DBPfp). Adsorption alone does not result in the formation of reactive intermediates and thus may prove to be a safe way to incorporate TiO 2 into drinking water treatment processes. The goal of this study was to expand on the current understanding of NOM adsorption on TiO 2 and examine it in a drinking water context by observing NOM adsorption from real water sources and evaluating the effects of the resulting reductions on the DBPfp of the treated water. Bottle point isotherm tests were conducted with raw water from two Canadian water treatment plants adjusted to pH 4, pH 6 and pH 8 and dosed with TiO 2 nanoparticles. The DOC results were a good fit to a modified Freundlich isotherm. DBP precursors and liquid chromatography with organic carbon detection NOM fractions associated with DBP formation were removed to some extent at all pHs, but most effectively at pH 4. Copyright © 2017 Elsevier Ltd. All rights reserved.

Exploring Liquid Sequential Injection Chromatography to Teach Fundamentals of Separation Methods: A Very Fast Analytical Chemistry Experiment

ERIC Educational Resources Information Center

Penteado, Jose C.; Masini, Jorge Cesar

2011-01-01

Influence of the solvent strength determined by the addition of a mobile-phase organic modifier and pH on chromatographic separation of sorbic acid and vanillin has been investigated by the relatively new technique, liquid sequential injection chromatography (SIC). This technique uses reversed-phase monolithic stationary phase to execute fast…

The effect of different π-bridge configuration on bi-anchored triphenylamine and phenyl modified triphenylamine based dyes for dye sensitized solar cell (DSSC) application: A theoretical approach.

PubMed

Pounraj, P; Mohankumar, V; Pandian, M Senthil; Ramasamy, P

2018-01-01

Twenty eight bi-anchored triphenylamine (TH-1 to TH-14) and phenyl modified triphenylamine (PH-TH-1 to PH-TH-14) based metal free organic dyes are designed for DSSC application. The electronic effect of different π-bridge configurations in donor-π-bridge-acceptor (D-π-A) 2 structure was theoretically simulated and verified using density functional theory (DFT) and time dependent density functional theory (TD-DFT). The triphenylamine and phenyl modified triphenylamine groups are used as donor and cyanoacrylic acid group is used as acceptor. Thiophene and cyanovinyl groups are used as π-bridge. The ground state molecular structure was optimized by density functional theory and the electronic absorption spectra were calculated by time dependent density functional theory. The light harvesting efficiency (LHE), dye regeneration energy (ΔG reg ) and electron injection energy (ΔG inject ) are determined by computational examination. It is observed that, when the number of π-bridge increases, the band gap of the dye decreases. Also the absorption maximum and molar extinction coefficient of the dyes are increased. Theoretical result shows that the thiophene-cyanovinyl and thiophene-thiophene-cyanovinyl-cyanovinyl configurations give broader and red shifted absorption spectrum compared to other configurations. Also the results of phenyl modified triphenylamine (PH-TH) dyes clearly show better absorption and dye regeneration energy compared to TH dyes. Copyright © 2017 Elsevier Inc. All rights reserved.

Poly(propyleneimine) glycodendrimers non-covalently bind ATP in a pH- and salt-dependent manner - model studies for adenosine analogue drug delivery.

PubMed

Gorzkiewicz, Michał; Buczkowski, Adam; Appelhans, Dietmar; Voit, Brigitte; Pułaski, Łukasz; Pałecz, Bartłomiej; Klajnert-Maculewicz, Barbara

2018-06-10

Adenosine analogue drugs (such as fludarabine or cladribine) require transporter-mediated uptake into cells and subsequent phosphorylation for anticancer activity. Therefore, application of nanocarrier systems for direct delivery of active triphosphate forms has been proposed. Here, we applied isothermal titration calorimetry and zeta potential titration to determine the stoichiometry and thermodynamic parameters of interactions between 4th generation poly(propyleneimine) dendrimers (unmodified or sugar-modified for increased biocompatibility) and ATP as a model adenosine nucleotide. We showed that glycodendrimers have the ability to efficiently interact with nucleoside triphosphates and to form stable complexes via electrostatic interactions between the ionized phosphate and amino groups on the nucleotide and the dendrimer, respectively. The complexation process is spontaneous, enthalpy-driven and depends on buffer composition (strongest interactions in organic buffer) and pH (more binding sites in acidic pH). These properties allow us to consider maltose-modified dendrimers as especially promising carriers for adenosine analogues. Copyright © 2018 Elsevier B.V. All rights reserved.

Heterogeneous electro-Fenton using modified iron-carbon as catalyst for 2,4-dichlorophenol degradation: influence factors, mechanism and degradation pathway.

PubMed

Zhang, Chao; Zhou, Minghua; Ren, Gengbo; Yu, Xinmin; Ma, Liang; Yang, Jie; Yu, Fangke

2015-03-01

Modified iron-carbon with polytetrafluoroethylene (PTFE) was firstly investigated as heterogeneous electro-Fenton (EF) catalyst for 2,4-dichlorophenol (2,4-DCP) degradation in near neutral pH condition. The catalyst was characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), and the effects of some important operating parameters such as current intensity and pH on the 2,4-DCP degradation were investigated. After the catalyst modification with 20% PTFE, the degradation performance maintained well with much lower iron leaching, and at current intensity 100 mA, initial pH 6.7, catalyst loading 6 g/L, the degradation efficiency of 2,4-DCP could exceed 95% within 120 min treatment. Two-stage pseudo first-order kinetics of 2,4-DCP degradation was observed, including a slow anodic oxidation stage (first-stage) and much faster heterogeneous EF oxidation (second-stage), in which the automatic drop of pH in the first-stage initiated the Fe(2+) release from micro-electrolysis and thus benefited to the subsequent EF reaction. Aromatic intermediates such as 3,5-dichlorocatechol, 4,6-dichlororesorcinol and 2-chlorohydroquinone were detected by GC-MS. Oxalic acid, acetic acid, formic acid and Cl(-) were quantified by ion chromatograph. Based on these analysis as well as the detection of H₂O₂ and OH, a possible mechanism and degradation pathway for 2,4-DCP were proposed. This work demonstrated that such a heterogeneous EF using cheap modified Fe-C catalyst was promising for organic wastewater treatment in initial neutral pH condition. Copyright © 2014 Elsevier Ltd. All rights reserved.

Adsorption-regeneration by heterogeneous Fenton process using modified carbon and clay materials for removal of indigo blue.

PubMed

Almazán-Sánchez, Perla Tatiana; Solache-Ríos, Marcos J; Linares-Hernández, Ivonne; Martínez-Miranda, Verónica

2016-01-01

Indigo blue dye is mainly used in dyeing of denim clothes and its presence in water bodies could have adverse effects on the aquatic system; for this reason, the objective of this study was to promote the removal of indigo blue dye from aqueous solutions by iron and copper electrochemically modified clay and activated carbon and the saturated materials were regenerated by a Fenton-like process. Montmorillonite clay was modified at pH 2 and 7; activated carbon at pH 2 and pH of the system. The elemental X-ray dispersive spectroscopy analysis showed that the optimum pH for modification of montmorillonite with iron and copper was 7 and for activated carbon was 2. The dye used in this work was characterized by infrared. Unmodified and modified clay samples showed the highest removal efficiencies of the dye (90-100%) in the pH interval from 2 to 10 whereas the removal efficiencies decrease as pH increases for samples modified at pH 2. Unmodified clay and copper-modified activated carbon at pH 2 were the most efficient activated materials for the removal of the dye. The adsorption kinetics data of all materials were best adjusted to the pseudo-second-order model, indicating a chemisorption mechanism and the adsorption isotherms data showed that the materials have a heterogeneous surface. The iron-modified clay could be regenerated by a photo-Fenton-like process through four adsorption-regeneration cycles, with 90% removal efficiency.

Effects of organic silicon compounds as additives on charge-discharge cycling efficiencies of lithium in nonaqueous electrolytes for rechargeable lithium cells

NASA Astrophysics Data System (ADS)

Yanagisawa, Ryota; Endo, Hisayuki; Unno, Masafumi; Morimoto, Hideyuki; Tobishima, Shin-ichi

2014-11-01

Influence of mixing organic silicon compounds into 1 M (M: mol L-1) LiPF6-ethylene carbonate (EC)/ethylmethyl carbonate (EMC) (mixing volume ratio = 3:7) mixed solvent electrolytes on charge-discharge cycling efficiencies of lithium metal negative electrodes is examined. As organic silicon compounds, polyether-modified siloxanes with polyethylene oxide chains, chlorotrimethylsilane, tetraethoxysilane, cis-tetra [isobutyl (dimethylsiloxy)] cyclotetrasiloxane and cage-type silsesquioxane are investigated. Charge-discharge cycling tests of lithium are galvanostatically carried out using stainless steel working electrodes. Charge-discharge cycling efficiencies of lithium tend to improve by mixing organic silicon compounds. A cage-type silsesquioxane, octaphenyloctasilsesquioxane (Ph8T8) exhibits the highest cycling efficiency of approximately 80% with small mixing amount of 0.02 M Ph8T8. Mechanism of enhancement of lithium cycling efficiencies by mixing organic silicon compounds is considered to be due to the suppression of excess reduction of LiPF6-EC/EMC by lithium and the growth of surface film on lithium.

Dissolution-modulating mechanism of pH modifiers in solid dispersion containing weakly acidic or basic drugs with poor water solubility.

PubMed

Tran, Phuong Ha-Lien; Tran, Thao Truong-Dinh; Lee, Kyoung-Ho; Kim, Dong-Jin; Lee, Beom-Jin

2010-05-01

Although the solid dispersion method has been known to increase the dissolution rate of poorly water-soluble drugs by dispersing them in hydrophilic carriers, one obstacle of the solid dispersion method is its limited solubilization capacity, especially for pH-dependent soluble drugs. pH-modified solid dispersion, in which pH modifiers are incorporated, may be a useful method for increasing the dissolution rate of weakly acidic or basic drugs. Sufficient research, including the most recent reports, was undertaken in this review. How could the inclusion of the pH the pH modifiers in the solid dispersion system change drug structural behaviors, molecular interactions, microenvironmental pH, and/or release rate of pH modifiers, relating with the enhanced dissolution of weakly acidic or weakly basic drugs with poor water solubility? These questions have been investigated to determine the dissolution-modulating mechanism of pH modifiers in solid dispersion containing weakly acidic or basic drugs. It is believed that step-by-step mechanistic approaches could provide the ultimate solution for solubilizing several poorly water-soluble drugs with pH-dependent solubility from a solid dispersion system, as well as provide ideas for developing future dosage systems.

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.

Efficient recyclable organic solar cells on cellulose nanocrystal substrates with a conducting polymer top electrode deposited by film-transfer lamination

Treesearch

Yinhua Zhou; Talha M. Khan; Jen-Chieh Liu; Canek Fuentes-Hernandez; Jae Won Shim; Ehsan Najafabadi; Jeffrey P. Youngblood; Robert J. Moon; Bernard Kippelen

2014-01-01

We report on efficient solar cells on recyclable cellulose nanocrystal (CNC) substrates with a new device structure wherein polyethylenimine-modified Ag is used as the bottom electron-collecting electrode and high-conductivity poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS, PH1000) is used as the semitransparent top holecollecting electrode. The...

Heavy Metal Uptake by Herbs. IV. Influence of Soil pH on the Content of Heavy Metals in Valeriana officinalis L.

PubMed

Adamczyk-Szabela, Dorota; Markiewicz, Justyna; Wolf, Wojciech M

The aim of the study was to estimate the influence of soil pH on the uptake of copper, zinc, and manganese by Valeriana officinalis . Preliminary studies involved soil analyses to determine acidity, organic matter content, and copper, zinc, and manganese total and bioavailable forms. The study involved atomic absorption spectrometry to determine the concentration of the elements, and mineral soil of pH = 5.1 was used in the study, as being typical for central Poland. The copper, zinc, and manganese contents were determined in plants grown in soils which had been modified to cover a wide range of pH values 3÷13. The intensity of germination was strongly pH dependent with the highest yield obtained in original, unmodified soil. Surprisingly, high soil alkalinity stimulated copper and manganese uptake while at the same time resulting in a decrease in zinc content.

Selectivity in reversed-phase separations: general influence of solvent type and mobile phase pH.

PubMed

Neue, Uwe D; Méndez, Alberto

2007-05-01

The influence of the mobile phase on retention is studied in this paper for a group of over 70 compounds with a broad range of multiple functional groups. We varied the pH of the mobile phase (pH 3, 7, and 10) and the organic modifier (methanol, acetonitrile (ACN), and tetrahydrofuran (THF)), using 15 different stationary phases. In this paper, we describe the overall retention and selectivity changes observed with these variables. We focus on the primary effects of solvent choice and pH. For example, transfer rules for solvent composition resulting in equivalent retention depend on the packing as well as on the type of analyte. Based on the retention patterns, one can calculate selectivity difference values for different variables. The selectivity difference is a measure of the importance of the different variables involved in method development. Selectivity changes specific to the type of analyte are described. The largest selectivity differences are obtained with pH changes.

Review on the preparation and modified technologies of microencapsulated red phosphorus

NASA Astrophysics Data System (ADS)

Cheng, Chen; Du, Shiguo; Yan, Jun

2017-10-01

Coated by a compact shell structure, pristine red phosphorus transforms into microcapsule red phosphorus (MCRP) with lower PH3 emission and improved compatibility with polymer matrix. Diverse kinds of microcapsule red phosphorus are classified by shell material, i.e.organic shell material MCRP, inorganic shell material MCRP and composite shell material MCRP. Furthermore, the modified technology to make up deficiencies of MCRP is also introduced in the lecture. Aiming at the existing microencapsulation craft, a more harmless and high-efficiency process should be presented, and ultrafine MCRP is also urgent to be prepared.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing.

PubMed

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2015-02-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2', 7'-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12-7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field.

Reflection-mode micro-spherical fiber-optic probes for in vitro real-time and single-cell level pH sensing

PubMed Central

Yang, Qingbo; Wang, Hanzheng; Lan, Xinwei; Cheng, Baokai; Chen, Sisi; Shi, Honglan; Xiao, Hai; Ma, Yinfa

2014-01-01

pH sensing at the single-cell level without negatively affecting living cells is very important but still a remaining issue in the biomedical studies. A 70 μm reflection-mode fiber-optic micro-pH sensor was designed and fabricated by dip-coating thin layer of organically modified aerogel onto a tapered spherical probe head. A pH sensitive fluorescent dye 2′, 7′-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF) was employed and covalently bonded within the aerogel networks. By tuning the alkoxide mixing ratio and adjusting hexamethyldisilazane (HMDS) priming procedure, the sensor can be optimized to have high stability and pH sensing ability. The in vitro real-time sensing capability was then demonstrated in a simple spectroscopic way, and showed linear measurement responses with a pH resolution up to an average of 0.049 pH unit within a narrow, but biological meaningful pH range of 6.12–7.81. Its novel characterizations of high spatial resolution, reflection mode operation, fast response and high stability, great linear response within biological meaningful pH range and high pH resolutions, make this novel pH probe a very cost-effective tool for chemical/biological sensing, especially within the single cell level research field. PMID:25530670

Analysis of pharmaceutical biodegradation of WWTP sludge using composting and identification of certain microorganisms involved in the process.

PubMed

Iranzo, María; Gamón, Miguel; Boluda, Rafael; Mormeneo, Salvador

2018-06-04

Pharmaceuticals (PhCs) are organic contaminants that have been detected in wastewater, surface water, and soils throughout the world. The presence of 10 commonly used PhCs in Spain (azithromycin, benzylpenicillin, citalopram, fluconazole, fluoxetine, ibuprofen, irbesartan, olanzapine, telmisartan, and venlafaxine) was analysed at four wastewater treatment plants, and the changes in their concentrations during treatment were assessed. Although certain some PhCs were degraded in the treated water, their presence in sewage sludge increased in all cases. The sewage sludge was composted using rice straw to degrade the PhCs, and the composting efficiency was modified by changes in the relative C/N ratio of the composting blend. Using a simple microbiological culture process for enrichment, 11 different strains of microorganisms that degraded specific PhCs were identified. Ibuprofen and azithromycin were metabolized by one and four strains, respectively, and both PhCs were used as a carbon source; in addition, six strains used irbesartan as a nitrogen source. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of Mild Acid on Gene Expression in Staphylococcus aureus

PubMed Central

Weinrick, Brian; Dunman, Paul M.; McAleese, Fionnuala; Murphy, Ellen; Projan, Steven J.; Fang, Yuan; Novick, Richard P.

2004-01-01

During staphylococcal growth in glucose-supplemented medium, the pH of a culture starting near neutrality typically decreases by about 2 units due to the fermentation of glucose. Many species can comfortably tolerate the resulting mildly acidic conditions (pH, ∼5.5) by mounting a cellular response, which serves to defend the intracellular pH and, in principle, to modify gene expression for optimal performance in a mildly acidic infection site. In this report, we show that changes in staphylococcal gene expression formerly thought to represent a glucose effect are largely the result of declining pH. We examine the cellular response to mild acid by microarray analysis and define the affected gene set as the mild acid stimulon. Many of the genes encoding extracellular virulence factors are affected, as are genes involved in regulation of virulence factor gene expression, transport of sugars and peptides, intermediary metabolism, and pH homeostasis. Key results are verified by gene fusion and Northern blot hybridization analyses. The results point to, but do not define, possible regulatory pathways by which the organism senses and responds to a pH stimulus. PMID:15576791

Soil pH effects on the interactions between dissolved zinc, non-nano- and nano-ZnO with soil bacterial communities.

PubMed

Read, Daniel S; Matzke, Marianne; Gweon, Hyun S; Newbold, Lindsay K; Heggelund, Laura; Ortiz, Maria Diez; Lahive, Elma; Spurgeon, David; Svendsen, Claus

2016-03-01

Zinc oxide nanoparticles (ZnO NPs) are used in an array of products and processes, ranging from personal care products to antifouling paints, textiles, food additives, antibacterial agents and environmental remediation processes. Soils are an environment likely to be exposed to manmade nanoparticles due to the practice of applying sewage sludge as a fertiliser or as an organic soil improver. However, understanding on the interactions between soil properties, nanoparticles and the organisms that live within soil is lacking, especially with regards to soil bacterial communities. We studied the effects of nanoparticulate, non-nanoparticulate and ionic zinc (in the form of zinc chloride) on the composition of bacterial communities in soil with a modified pH range (from pH 4.5 to pH 7.2). We observed strong pH-dependent effects on the interaction between bacterial communities and all forms of zinc, with the largest changes in bacterial community composition occurring in soils with low and medium pH levels (pH 4.8 and 5.9). The high pH soil (pH 7.2) was less susceptible to the effects of zinc exposure. At the highest doses of zinc (2500 mg/kg dw soil), both nano and non-nano particulate zinc applications elicited a similar response in the soil bacterial community, and this differed significantly to the ionic zinc salt treatment. The results highlight the importance of considering soil pH in nanotoxicology studies, although further work is needed to determine the exact mechanisms controlling the toxicity and fate and interactions of nanoparticles with soil microbial communities.

Soil-modified carbon paste electrode: a useful tool in environmental assessment of heavy metal ion binding interactions.

PubMed

Svegl, I G; Ogorevc, B

2000-08-01

Carbon paste electrodes (CPEs) modified with different soils in their native form were prepared to create a soil-like solid phase suitable for application in studies of heavy metal ion uptake and binding interactions. The preparation of CPEs modified with five different soils was examined and their heavy metal ion uptake behavior investigated using a model Cu(II) aqueous solution. Metal ions were accumulated under open circuit conditions and were determined after a medium exchange using differential pulse anodic stripping voltammetry, applying preelectrolysis at -0.7 V. The soil-modified CPE accumulation behavior, including the linearity of the current response versus Cu(II) concentration, the influence of the pH on the solution, and the uptake kinetics, was thoroughly investigated. The correlation between the soil-modified CPE uptake capability and the standard soil parameters, such as ion exchange capacity, soil pH, organic matter and clay content, were evaluated for all five examined soils. The influence of selected endogenous cations (K(I), Ca(II), Fe(III)) on the transfer of Cu(II) ions from a solution to the simulated soil solid phase was examined and is discussed. Preliminary examinations of the soil-modified CPE uptake behavior with some exogenous heavy metal ions of strong environmental interest (Pb(II), Hg(II), Cd(II) and Ag(I)) are also presented. This work demonstrates some attractive possibilities for the application of a soil-modified CPE in studying soil-heavy metal ion binding interactions, with a further potential use as a new environmental sensor appropriate for fist on-site testing of polluted soils.

Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

NASA Astrophysics Data System (ADS)

Gonzalez, Julia; Peña, Jasquelin

2016-04-01

Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the labile fraction may lower solution pH into a regime that favours abiotic oxidation of recalcitrant C by MnO2. This project demonstrates that the co-occurrence of mineral particles with metabolically active cells provides a direct link between the C and Mn cycles.

Photobleaching of chromophoric dissolved organic matter (CDOM) in the Yangtze River estuary: kinetics and effects of temperature, pH, and salinity.

PubMed

Song, Guisheng; Li, Yijie; Hu, Suzheng; Li, Guiju; Zhao, Ruihua; Sun, Xin; Xie, Huixiang

2017-06-21

The kinetics and temperature-, pH- and salinity-dependences of photobleaching of chromophoric dissolved organic matter (CDOM) in the Yangtze River estuary (YRE) were evaluated using laboratory solar-simulated irradiation and compared to those of Suwannee River humic substances (SRHSs). Nearly all CDOM in water at the head of the estuary (headwater herein) was photobleachable in both summer and winter, while significant fractions of CDOM (13-29%) were resistant to photobleaching in saltier waters. The photobleaching rate constant in the headwater was 25% higher in summer than that in winter. The absorbed photon-based photobleaching efficiency (PE) increased with temperature following the linear Arrhenius equation. For a 20 °C increase in temperature, PE increased by ∼45% in the headwater and by 70-81% in the saltier waters. PE for YRE samples exhibited minima at pH from 6 to 7 and increased with both lower and higher pH values, contrasting the consistent increase in PE with pH shown by SRHSs. No consistent effect of salinity on PE was observed for both SRHSs and YRE samples. Photobleaching increased the spectral slope coefficient between 275 nm and 295 nm in summer, consistent with the behavior of SRHSs, but decreased it in winter, implying a difference in the molecular composition of chromophores between the two seasons. Temperature, salinity, and pH modified the photoalteration of the spectral shape but their effects varied spatially and seasonally. This study demonstrates that CDOM quality, temperature, and pH should be incorporated into models involving quantification of photobleaching.

Catalytic wet peroxide oxidation of aniline in wastewater using copper modified SBA-15 as catalyst.

PubMed

Kong, Liming; Zhou, Xiang; Yao, Yuan; Jian, Panming; Diao, Guowang

2016-01-01

SBA-15 mesoporous molecular sieves modified with copper (Cu-SBA-15) were prepared by pH-adjusting hydrothermal method and characterized by X-ray diffraction, BET, transmission electron microscopy, UV-Vis and (29)Si MAS NMR. The pH of the synthesis gel has a significant effect on the amount and the dispersion of copper on SBA-15. The Cu-SBA-15(4.5) (where 4.5 denotes the pH value of the synthesis gel) modified with highly dispersed copper was used as catalyst for the oxidation of aniline by H2O2. The Cu-SBA-15(4.5) shows a higher catalytic activity compared to CuO on the surface of SBA-15. The influences of reaction conditions, such as initial pH of the aqueous solutions, temperature, as well as the dosages of H2O2 and catalyst were investigated. Under weakly alkaline aqueous solution conditions, the aniline conversion, the H2O2 decomposition and the total organic carbon (TOC) removal could be increased significantly compared to the acid conditions. The percentage of leaching Cu(2+) could be decreased from 45.0% to 3.66% when the initial pH of solution was increased from 5 to 10. The TOC removal could be enhanced with the increases of temperature, H2O2 and catalyst dosage, but the aniline conversion and H2O2 decomposition change slightly with further increasing dosage of catalyst and H2O2. At 343 K and pH 8.0, 100% aniline conversion and 66.9% TOC removal can be achieved under the conditions of 1.0 g/L catalyst and 0.05 mol/L H2O2 after 180 min. Although copper might be slightly leached from catalyst, the homogeneous Cu(2+) contribution to the whole catalytic activity is unimportant, and the highly dispersed copper on SBA-15 plays a dominant role.

Effects of soil pH on the Vicia-micronucleus genotoxicity assay.

PubMed

Dhyèvre, Adrien; Foltête, Anne Sophie; Aran, Delphine; Muller, Serge; Cotelle, Sylvie

2014-11-01

In the field of contaminated sites and soil management, chemical analyses only bring typological data about pollution. As far as bioavailability and effects on organisms are concerned, we need ecotoxicology tools. In this domain, among many existing tests, we chose to study genotoxicity because it is a short-term endpoint with long-term consequences. The aim of this study is to assess the effects of soil pH on the results of the Vicia faba root tip micronucleus test for the two following reasons: (i) to define the pH range within which the test can be performed without modifying the soil to be tested, within the framework of the ISO standard of the test and (ii) to provides information about the effects of the pH on the genotoxic potential of soils. In this context, we modified the pH of a standard soil with HCl or NaOH and we spiked the matrix with copper (2, 4 and 8 mmol kg(-1) dry soil) or with maleic hydrazide, an antigerminative chemical (5, 10 and 20 μmol kg(-1) dry soil). We concluded that the pH had no effect on the mitotic index or micronucleus frequency in the root cells of the negative controls: extreme pH values did not induce micronucleus formation in root cells. Moreover, according to our results, the Vicia-micronucleus test can be performed with pH values ranging between 3.2 and 9.0, but in the ISO 29200 "Soil quality--assessment of genotoxic effects on higher plants--V. faba micronucleus test" we recommended to use a control soil with a pH value ranging between 5 and 8 for a more accurate assessment of chemical genotoxicity. We also found that acid pH could increase the genotoxic potential of pollutants, especially heavy metals. With hydrazide maleic spiked soil, plants were placed in a situation of double stress, i.e. toxicity caused by extreme pH values and toxicity induced by the pollutant. Copyright © 2014 Elsevier B.V. All rights reserved.

Effects of Two Traditional Chinese Cooking Oils, Canola and Pork, on pH and Cholic Acid Content of Faeces and Colon Tumorigenesis in Kunming Mice.

PubMed

He, Xiao-Qiong; Duan, Jia-Li; Zhou, Jin; Song, Zhong-Yu; Cichello, Simon Angelo

2015-01-01

Faecal pH and cholate are two important factors that can affect colon tumorigenesis, and can be modified by diet. In this study, the effects of two Chinese traditional cooking oils (pork oil and canola/rapeseed oil) on the pH and the cholic acid content in feces, in addition to colon tumorigenesis, were studied in mice. Kunming mice were randomized into various groups; negative control group (NCG), azoxymethane control group (ACG), pork oil group (POG), and canola oil Ggroup (COG). Mice in the ACG were fed a basic rodent chow; mice in POG and COG were given 10% cooking oil rodent chow with the respective oil type. All mice were given four weekly AOM (azoxymethane) i.p. injections (10 mg/kg). The pH and cholic acid of the feces were examined every two weeks. Colon tumors, aberrant crypt foci and organ weights were examined 32 weeks following the final AOM injection. The results showed that canola oil significantly decreased faecal pH in female mice (P<0.05), but had no influence on feces pH in male mice (P>0.05). Pork oil significantly increased the feces pH in both male and female mice (P<0.05). No significant change was found in feces cholic acid content when mice were fed 10% pork oil or canola oil compared with the ACG. Although Kunming mice were not susceptible to AOM-induced tumorigenesis in terms of colon tumor incidence, pork oil significantly increased the ACF number in male mice. Canola oil showed no influence on ACF in either male or female mice. Our results indicate that cooking oil effects faecal pH, but does not affect the faecal cholic acid content and thus AOM-induced colon neoplastic ACF is modified by dietary fat.

Fluoride removal in water by a hybrid adsorbent lanthanum-carbon.

PubMed

Vences-Alvarez, Esmeralda; Velazquez-Jimenez, Litza Halla; Chazaro-Ruiz, Luis Felipe; Diaz-Flores, Paola E; Rangel-Mendez, Jose Rene

2015-10-01

Various health problems associated with drinking water containing high fluoride levels, have motivated researchers to develop more efficient adsorbents to remove fluoride from water for beneficial concentrations to human health. The objective of this research was to anchor lanthanum oxyhydroxides on a commercial granular activated carbon (GAC) to remove fluoride from water considering the effect of the solution pH, and the presence of co-existing anions and organic matter. The activated carbon was modified with lanthanum oxyhydroxides by impregnation. SEM and XRD were performed in order to determine the crystal structure and morphology of the La(III) particles anchored on the GAC surface. FT-IR and pK(a)'s distribution were determined in order to elucidate both the possible mechanism of the lanthanum anchorage on the activated carbon surface and the fluoride adsorption mechanism on the modified material. The results showed that lanthanum ions prefer binding to carboxyl and phenolic groups on the activated carbon surface. Potentiometric titrations revealed that the modified carbon (GAC-La) possesses positive charge at a pH lower than 9. The adsorption capacity of the modified GAC increased five times in contrast to an unmodified GAC adsorption capacity at an initial F(-) concentration of 20 mg L(-1). Moreover, the presence of co-existing anions had no effect on the fluoride adsorption capacity at concentrations below 30 mg L(-1), that indicated high F(-) affinity by the modified adsorbent material (GAG-La). Copyright © 2015 Elsevier Inc. All rights reserved.

Stimuli-sensitive polymeric micelles as anticancer drug carriers.

PubMed

Na, Kun; Sethuraman, Vijay T; Bae, You Han

2006-11-01

Amphiphilic block copolymers often form core-shell type micelles by self-organization of the blocks in an aqueous medium or under specific experimental conditions. Polymeric micelles constructed from these polymers that contain a segment whose physical or chemical properties respond to small changes in environmental conditions are collectively called 'stimuli-sensitive' micelles. This class of nano-scaled constructs has been investigated as a promising anti-cancer drug carrier because the micelles are able to utilize small environmental changes and modify drug release kinetics, biodistribution and the interactions with tissues and cells. This review summarizes the recent progress in stimuli-sensitive micelles for tumor chemotherapy, particularly for those responding to hyperthermic conditions, tumor pH and endosomal/lysosomal pH.

Surface modification of poly(L-lactic acid) to improve its cytocompatibility via assembly of polyelectrolytes and gelatin.

PubMed

Lin, Yuan; Wang, Luling; Zhang, Peibiao; Wang, Xin; Chen, Xuesi; Jing, Xiabin; Su, Zhaohui

2006-03-01

Poly(L-lactide) (PLLA) surface was modified via aminolysis by poly(allylamine hydrochloride) (PAH) at high pH and subsequent electrostatic self-assembly of poly(sodium styrenesulfonate) (PSS) and PAH, and the process was monitored by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. These modified PLLAs were then used as charged substrates for further incorporation of gelatin to improve their cytocompatibility. The amphoteric nature of the gelatin was exploited and the gelatin was adsorbed to the negatively charged PLLA/PSS and positively charged PLLA/PAH at pH=3.4 and 7.4, respectively. XPS and water contact angle data indicated that the gelatin adsorption at pH=3.4 resulted in much higher surface coverage by gelatin than at pH=7.4. All the modified PLLA surfaces became more hydrophilic than the virgin PLLA. Chondrocyte culture was used to test the cell attachment, cell morphology and cell viability on the modified PLLA substrates. The results showed that the PAH and PSS modified PLLA exhibited better cytocompatibility than virgin PLLA, and the incorporation of the gelatin on these modified PLLA substrates further improved their cytocompatibility, with the PLLA/PSS substrate treated with the gelatin at pH=3.4 being the best, exceeding the chondrocyte compatibility of the tissue culture polystyrene.

Zn2+-dependent surface behavior of diacylglycerol pyrophosphate and its mixtures with phosphatidic acid at different pHs

PubMed Central

Villasuso, Ana L.; Wilke, Natalia; Maggio, Bruno; Machado, Estela

2014-01-01

Diacylglycerol pyrophosphate (DGPP) is a minor lipid that attenuates the phosphatidic acid (PA) signal, and also DGPP itself would be a signaling lipid. Diacylglycerol pyrophosphate is an anionic phospholipid with a pyrophosphate group attached to diacylglycerol that was shown to respond to changes of pH, thus affecting the surface organization of DGPP and their interaction with PA. In this work, we have investigated how the presence of Zn2+ modulates the surface organization of DGPP and its interaction with PA at acidic and basic pHs. Both lipids formed expanded monolayers at pHs 5 and 8. At pH 5, monolayers formed by DGPP became stiffer when Zn2+was added to the subphase, while the surface potential decreased. At this pH, Zn2+ induced a phase transition from an expanded to a condensed-phase state in monolayers formed by PA. Conversely, at pH 8 the effects induced by the presence of Zn2+ on the surface behaviors of the pure lipids were smaller. Thus, the interaction of the bivalent cation with both lipids was modulated by pH and by the ionization state of the polar head groups. Mixed monolayers of PA and DGPP showed a non-ideal behavior and were not affected by the presence of Zn2+ at pH 8. This could be explained considering that when mixed, the lipids formed a closely packed monolayer that could not be further modified by the cation. Our results indicate that DGPP and PA exhibit expanded- and condensed-phase states depending on pH, on the proportion of each lipid in the film and on the presence of Zn2+. This may have implications for a possible role of DGPP as a signaling lipid molecule. PMID:25120554

Tartrazine modified activated carbon for the removal of Pb(II), Cd(II) and Cr(III).

PubMed

Monser, Lotfi; Adhoum, Nafaâ

2009-01-15

A two in one attempt for the removal of tartrazine and metal ions on activated carbon has been developed. The method was based on the modification of activated carbon with tartrazine then its application for the removal of Pb(II), Cd(II) and Cr(III) ions at different pH values. Tartrazine adsorption data were modelled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacities qm were 121.3, 67 and 56.7mgg(-1) at initial pH values of 1.0, 6.0 and 10, respectively. The adsorption of tartrazine onto activated carbon followed second-order kinetic model. The equilibrium time was found to be 240min at pH 1.0 and 120min at pH 10 for 500mgL(-1) tartrazine concentration. A maximum removal of 85% was obtained after 1h of contact time. The presence of tartrazine as modifier enhances attractive electrostatic interactions between metal ions and carbon surface. The adsorption capacity for Pb(II), Cd(II) and Cr(III) ions has been improved with respect to non-modified carbon reaching a maximum of 140%. The adsorption capacity was found to be a pH dependent for both modified and non-modified carbon with a greater adsorption at higher pH values except for Cr(III). The enhancement percent of Pb(II), Cd(II) and Cr(III) at different pH values was varied from 28% to 140% with respect to non-modified carbon. The amount of metal ions adsorbed using static regime was 11-40% higher than that with dynamic mode. The difference between adsorption capacities could be attributed to the applied flow rate.

Preparation of dual-stimuli-responsive liposomes using methacrylate-based copolymers with pH and temperature sensitivities for precisely controlled release.

PubMed

Sugimoto, Takumi; Yamazaki, Naoko; Hayashi, Takaaki; Yuba, Eiji; Harada, Atsushi; Kotaka, Aki; Shinde, Chiharu; Kumei, Takayuki; Sumida, Yasushi; Fukushima, Mitsuhiro; Munekata, Yuki; Maruyama, Keiichi; Kono, Kenji

2017-07-01

Dual-signal-sensitive copolymers were synthesized by copolymerization of methoxy diethylene glycol methacrylate, methacrylic acid, and lauroxy tetraethylene glycol methacrylate, which respectively provide temperature sensitivity, pH sensitivity, and anchoring to liposome surfaces. These novel copolymers, with water solubility that differs depending on temperature and pH, are soluble in water under neutral pH and low-temperature conditions, but they become water-insoluble and form aggregates under acidic pH and high-temperature conditions. Liposomes modified with these copolymers exhibited enhanced content release at weakly acidic pH with increasing temperature, although no temperature-dependent content release was observed in neutral conditions. Interaction between the copolymers and the lipid monolayer at the air-water interface revealed that the copolymer chains penetrate more deeply into the monolayer with increasing temperature at acidic pH than at neutral pH, where the penetration of copolymer chains was moderate and temperature-independent at neutral pH. Interaction of the copolymer-modified liposomes with HeLa cells demonstrated that the copolymer-modified liposomes were adsorbed quickly and efficiently onto the cell surface and that they were internalized more gradually than the unmodified liposomes through endocytosis. Furthermore, the copolymer-modified liposomes enhanced the content release in endosomes with increasing temperature, but no such temperature-dependent enhancement of content release was observed for unmodified liposomes. Copyright © 2017 Elsevier B.V. All rights reserved.

Predictions of diagenetic reactions in the presence of organic acids

NASA Astrophysics Data System (ADS)

Harrison, Wendy J.; Thyne, Geoffrey D.

1992-02-01

Stability constants have been estimated for cation complexes with anions of monofunctional and difunctional acids (combinations of Ca, Mg, Fe, Al, Sr, Mn, U, Th, Pb, Cu, Zn with formate, acetate, propionate, oxalate, malonate, succinate, and salicylate) between 0 and 200°C. Difunctional acid anions form much more stable complexes than monofunctional acid anions with aluminum; the importance of the aluminum-acetate complex is relatively minor in comparison to aluminum oxalate and malonate complexes. Divalent metal cations such as Mg, Ca, and Fe form more stable complexes with acetate than with difunctional acid anions. Aluminum-oxalate can dominate the species distribution of aluminum under acidic pH conditions, whereas the divalent cation-acetate and oxalate complexes rarely account for more than 60% of the total dissolved cation, and then only in more alkaline waters. Mineral thermodynamic affinities were calculated using the reaction path model EQ3/6 for waters having variable organic acid anion (OAA) contents under conditions representative of those found during normal burial diagenesis. The following scenarios are possible: 1) K-feldspar and albite are stable, anorthite dissolves 2) All feldpars are stable 3) Carbonates can be very unstable to slightly unstable, but never increase in stability. Organic acid anions are ineffective at neutral to alkaline pH in modifying stabilities of aluminosilicate minerals whereas the anions are variably effective under a wide range of pH in modifying carbonate mineral stabilities. Reaction path calculations demonstrate that the sequence of mineral reactions occurring in an arkosic sandstone-fluid system is only slightly modified by the presence of OAA. A spectrum of possible sandstone alteration mineralogies can be obtained depending on the selected boundary conditions: EQ3/6 predictions include quartz overgrowth, calcite replacement of plagioclase, albitization of plagioclase, and the formation of porosity-occluding calcite cement, smectite, and illite, all of which are commonly documented in rocks. Under some circumstances, OAA-bearing waters are less effective at producing porosity in an arkosic sandstone than are OAA-free waters. In the scenarios modeled in this study the role of OAA in fluid-rock interactions is to contribute to the total alteration assemblage but not necessarily to dominate it, except under exceptional circumstances that might include, for example, hydrocarbon contaminant plumes in aquifers, wetland environments, and within hydrocarbon source-rocks.

Functionalized mesoporous silica materials for molsidomine adsorption: Thermodynamic study

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

Alyoshina, Nonna A.; Parfenyuk, Elena V., E-mail: evp@iscras.ru

2013-09-15

A series of unmodified and organically modified mesoporous silica materials was prepared. The unmodified mesoporous silica was synthesized via sol–gel synthesis in the presence of D-glucose as pore-forming agent. The functionalized by phenyl, aminopropyl and mercaptopropyl groups silica materials were prepared via grafting. The fabricated adsorbent materials were characterized by Fourier transform infrared spectroscopy (FTIR) analysis, N{sub 2} adsorption/desorption and elemental analysis methods. Then their adsorption properties for mesoionic dug molsidomine were investigated at 290–313 K and physiological pH value. Thermodynamic parameters of molsidomine adsorption on the synthesized materials have been calculated. The obtained results showed that the adsorption processmore » of molsidomine on the phenyl modified silica is the most quantitatively and energetically favorable. The unmodified and mercaptopropyl modified silica materials exhibit significantly higher adsorption capacities and energies for molsidomine than the aminopropyl modified sample. The effects are discussed from the viewpoint of nature of specific interactions responsible for the adsorption. - Graphical abstract: Comparative analysis of the thermodynamic characteristics of molsidomine adsorption showed that the adsorption process on mesoporous silica materials is controlled by chemical nature of surface functional groups. Molsidomine adsorption on the phenyl modified silica is the most quantitatively and energetically favorable. Taking into account ambiguous nature of mesoionic compounds, it was found that molsidomine is rather aromatic than dipolar. Display Omitted - Highlights: • Unmodified and organically modified mesoporous silica materials were prepared. • Molsidomine adsorption on the silica materials was studied. • Phenyl modified silica shows the highest adsorption capacity and favorable energy. • Molsidomine exhibits the lowest affinity to aminopropyl modified silica.« less

A comparison of two methods for quantifying soil organic carbon of alpine grasslands on the Tibetan Plateau.

PubMed

Chen, Litong; Flynn, Dan F B; Jing, Xin; Kühn, Peter; Scholten, Thomas; He, Jin-Sheng

2015-01-01

As CO2 concentrations continue to rise and drive global climate change, much effort has been put into estimating soil carbon (C) stocks and dynamics over time. However, the inconsistent methods employed by researchers hamper the comparability of such works, creating a pressing need to standardize the methods for soil organic C (SOC) quantification by the various methods. Here, we collected 712 soil samples from 36 sites of alpine grasslands on the Tibetan Plateau covering different soil depths and vegetation and soil types. We used an elemental analyzer for soil total C (STC) and an inorganic carbon analyzer for soil inorganic C (SIC), and then defined the difference between STC and SIC as SOCCNS. In addition, we employed the modified Walkley-Black (MWB) method, hereafter SOCMWB. Our results showed that there was a strong correlation between SOCCNS and SOCMWB across the data set, given the application of a correction factor of 1.103. Soil depth and soil type significantly influenced on the recovery, defined as the ratio of SOCMWB to SOCCNS, and the recovery was closely associated with soil carbonate content and pH value as well. The differences of recovery between alpine meadow and steppe were largely driven by soil pH. In addition, statistically, a relatively strong correlation between SOCCNS and STC was also found, suggesting that it is feasible to estimate SOCCNS stocks through the STC data across the Tibetan grasslands. Therefore, our results suggest that in order to accurately estimate the absolute SOC stocks and its change in the Tibetan alpine grasslands, adequate correction of the modified WB measurements is essential with correct consideration of the effects of soil types, vegetation, soil pH and soil depth.

A Comparison of Two Methods for Quantifying Soil Organic Carbon of Alpine Grasslands on the Tibetan Plateau

PubMed Central

Chen, Litong; Flynn, Dan F. B.; Jing, Xin; Kühn, Peter; Scholten, Thomas; He, Jin-Sheng

2015-01-01

As CO2 concentrations continue to rise and drive global climate change, much effort has been put into estimating soil carbon (C) stocks and dynamics over time. However, the inconsistent methods employed by researchers hamper the comparability of such works, creating a pressing need to standardize the methods for soil organic C (SOC) quantification by the various methods. Here, we collected 712 soil samples from 36 sites of alpine grasslands on the Tibetan Plateau covering different soil depths and vegetation and soil types. We used an elemental analyzer for soil total C (STC) and an inorganic carbon analyzer for soil inorganic C (SIC), and then defined the difference between STC and SIC as SOCCNS. In addition, we employed the modified Walkley-Black (MWB) method, hereafter SOCMWB. Our results showed that there was a strong correlation between SOCCNS and SOCMWB across the data set, given the application of a correction factor of 1.103. Soil depth and soil type significantly influenced on the recovery, defined as the ratio of SOCMWB to SOCCNS, and the recovery was closely associated with soil carbonate content and pH value as well. The differences of recovery between alpine meadow and steppe were largely driven by soil pH. In addition, statistically, a relatively strong correlation between SOCCNS and STC was also found, suggesting that it is feasible to estimate SOCCNS stocks through the STC data across the Tibetan grasslands. Therefore, our results suggest that in order to accurately estimate the absolute SOC stocks and its change in the Tibetan alpine grasslands, adequate correction of the modified WB measurements is essential with correct consideration of the effects of soil types, vegetation, soil pH and soil depth. PMID:25946085

Impacts of Near-Future Ocean Acidification and Warming on the Shell Mechanical and Geochemical Properties of Gastropods from Intertidal to Subtidal Zones.

PubMed

Leung, Jonathan Y S; Connell, Sean D; Nagelkerken, Ivan; Russell, Bayden D

2017-11-07

Many marine organisms produce calcareous shells as the key structure for defense, but the functionality of shells may be compromised by ocean acidification and warming. Nevertheless, calcifying organisms may adaptively modify their shell properties in response to these impacts. Here, we examined how reduced pH and elevated temperature affect shell mechanical and geochemical properties of common grazing gastropods from intertidal to subtidal zones. Given the greater environmental fluctuations in the intertidal zone, we hypothesized that intertidal gastropods would exhibit more plastic responses in shell properties than subtidal gastropods. Overall, three out of five subtidal gastropods produced softer shells at elevated temperature, while intertidal gastropods maintained their shell hardness at both elevated pCO 2 (i.e., reduced pH) and temperature. Regardless of pH and temperature, degree of crystallization was maintained (except one subtidal gastropod) and carbonate polymorph remained unchanged in all tested species. One intertidal gastropod produced less soluble shells (e.g., higher calcite/aragonite) in response to reduced pH. In contrast, subtidal gastropods produced only aragonite which has higher solubility than calcite. Overall, subtidal gastropods are expected to be more susceptible than intertidal gastropods to shell dissolution and physical damage under future seawater conditions. The increased vulnerability to shell dissolution and predation could have serious repercussions for their survival and ecological contributions in the future subtidal environment.

Synthesis and adsorption of silica gel modified 3-aminopropyltriethoxysilane (APTS) from corn cobs against Cu(II) in water

NASA Astrophysics Data System (ADS)

Purwanto, Agung; Yusmaniar, Ferdiani, Fatmawati; Damayanti, Rachma

2017-03-01

Silica gel modified APTS was synthesized from silica gel which was obtained from corn cobs via sol-gel process. Silica gel was synthesized from corn cobs and then chemically modified with silane coupling agent which has an amine group (NH2). This process resulting modified silica gel 3-aminopropyltriethoxysilane (APTS). Characterization of silica gel modified APTS by SEM-EDX showed that the size of the particles of silica gel modified APTS was 20µm with mass percentage of individual elements were nitrogen (N) 15.56%, silicon (Si) 50.69% and oxygen (O) 33.75%. In addition, silica gel modified APTS also showed absorption bands of functional groups silanol (Si-OH), siloxane (Si-O-Si), and an aliphatic chain (-CH2-), as well as amine (NH2) from FTIR spectra. Based on the characterization of XRD, silica gel 2θ of 21.094° and 21.32° respectively. It indicated that both material were amorphous. Determination of optimum pH and contact time on adsorption of silica gel 3-aminopropyltriethoxysilane (APTS) against Cu(II). The optimum pH and contact time was measured by using AAS. Optimum pH of adsorption silica gel modified APTS against metal Cu(II) could be obtained at pH 6 while optimum contact time was at 30 minutes, with the process of adsorption metal Cu(II) occured based on the model Freundlich isotherm.

Interactions between hydrated cement paste and organic acids: Thermodynamic data and speciation modeling

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

De Windt, Laurent, E-mail: laurent.dewindt@mines-paristech.fr; Bertron, Alexandra; Larreur-Cayol, Steeves

2015-03-15

Interactions of short-chain organic acids with hydrated cement phases affect structure durability in the agro-food and nuclear waste industries but can also be used to modify cement properties. Most previous studies have been experimental, performed at fixed concentrations and pH, without quantitatively discriminating among polyacidity effects, or complexation and salt precipitation processes. This paper addresses such issues by thermodynamic equilibrium calculations for acetic, citric, oxalic, succinic acids and a simplified hydrated CEM-I. The thermodynamic constants collected from the literature allow the speciation to be modeled over a wide range of pH and concentrations. Citric and oxalic had a stronger chelatingmore » effect than acetic acid, while succinic acid was intermediate. Similarly, Ca-citrate and Ca-oxalate salts were more insoluble than Ca-acetate and Ca-succinate salts. Regarding aluminium complexation, hydroxyls, sulfates, and acid competition was highlighted. The exploration of acid mixtures showed the preponderant effect of oxalate and citrate over acetate and succinate.« less

Photosynthetic activity buffers ocean acidification in seagrass meadows

NASA Astrophysics Data System (ADS)

Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

2014-01-01

Macrophytes growing in shallow coastal zones characterised by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH changes in shallow (5-12 m) seagrass (Posidonia oceanica) meadows spanning 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr)) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean, max and range pHNBS and max and range ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced max and min ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. Max and range ΩAr within the meadow showed a positive trend with the calcium carbonate load of the leaves, pointing to a possible link between structural parameters, ΩAr and carbonate deposition. Calcifying organisms, e.g. epiphytes with carbonate skeletons, may benefit from the modification of the carbonate system by the meadow. There is, however, concern for the ability of seagrasses to provide modifications of similar importance in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, on which LAI is based. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

Development of melamine modified urea formaldehyde resins based o nstrong acidic pH catalyzed urea formaldehyde polymer

Treesearch

Chung-Yun Hse

2009-01-01

To upgrade the performance of urea-formaldehyde (UF) resin bonded particleboards, melamine modified urea-formaldehyde (MUF) resins based on strong acidic pH catalyzed UF polymers were investigated. The study was conducted in a series of two experiments: 1) formulation of MUF resins based on a UF polymer catalyzed with strong acidic pH and 2) determination of the...

A spectroscopic study on stability of curcumin as a function of pH in silica nanoformulations, liposome and serum protein

NASA Astrophysics Data System (ADS)

Jain, Beena

2017-02-01

The effect of pH on the stability of curcumin formulated with different carriers has been studied spectroscopically. This was investigated by monitoring the absorption and emission kinetics and fluorescence decay time of four different curcumin formulations suspended in buffer with pH varying from 5 to 8.5. The carriers were organically modified silica NP (SiNP) having 3-amino propyl and/or vinyl groups, liposome and serum protein. The results reveal that stability of curcumin formulated with SiNP functionalized with 3-amino propyl group (SiNP-VA) is significantly higher as compared to SiNP with only vinyl group (SiNP-V) and buffer but lower as compared to serum protein and liposome. However, fluorescence quantum yield (QY) is highest in SiNP-VA among all the nano formulations at pH 7.4 and below, which is attributed to the excited state interaction of curcumin with the amino groups of SiNP-VA. Results suggest that SiNP-VA could be an effective carrier for curcumin, which may have applications for imaging and drug delivery.

Separation of pharmacologically active nitrogen-containing compounds on silica gels modified with 6,10-ionene, dextran sulfate, and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ioutsi, A. N.; Shapovalova, E. N.; Ioutsi, V. A.; Mazhuga, A. G.; Shpigun, O. A.

2017-12-01

New stationary phases for HPLC are obtained via layer-by-layer deposition of polyelectrolytes and studied: (1) silica gel modified layer-by-layer with 6,10-ionene and dextran sulfate (Sorbent 1); (2) silica gel twice subjected to the above modification (Sorbent 2); and (3) silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate (Sorbent 3). The effect the content of the organic solvent in the mobile phase and the concentration and pH of the buffer solution have on the chromatographic behavior of several pharmacologically active nitrogen-containing compounds is studied. The sorbents are stable during the process and allow the effective separation of beta-blockers, calcium channel blockers, alpha-agonists, and antihistamines. A mixture of caffeine, nadolol, tetrahydrozoline, pindolol, orphenadrine, doxylamine, carbinoxamine, and chlorphenamine is separated in 6.5 min on the silica gel modified with 6,10-ionene, gold nanoparticles, and dextran sulfate.

Acid and Base Stress and Transcriptomic Responses in Bacillus subtilis▿†

PubMed Central

Wilks, Jessica C.; Kitko, Ryan D.; Cleeton, Sarah H.; Lee, Grace E.; Ugwu, Chinagozi S.; Jones, Brian D.; BonDurant, Sandra S.; Slonczewski, Joan L.

2009-01-01

Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K+/H+ antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids. PMID:19114526

Acid and base stress and transcriptomic responses in Bacillus subtilis.

PubMed

Wilks, Jessica C; Kitko, Ryan D; Cleeton, Sarah H; Lee, Grace E; Ugwu, Chinagozi S; Jones, Brian D; BonDurant, Sandra S; Slonczewski, Joan L

2009-02-01

Acid and base environmental stress responses were investigated in Bacillus subtilis. B. subtilis AG174 cultures in buffered potassium-modified Luria broth were switched from pH 8.5 to pH 6.0 and recovered growth rapidly, whereas cultures switched from pH 6.0 to pH 8.5 showed a long lag time. Log-phase cultures at pH 6.0 survived 60 to 100% at pH 4.5, whereas cells grown at pH 7.0 survived <15%. Cells grown at pH 9.0 survived 40 to 100% at pH 10, whereas cells grown at pH 7.0 survived <5%. Thus, growth in a moderate acid or base induced adaptation to a more extreme acid or base, respectively. Expression indices from Affymetrix chip hybridization were obtained for 4,095 protein-encoding open reading frames of B. subtilis grown at external pH 6, pH 7, and pH 9. Growth at pH 6 upregulated acetoin production (alsDS), dehydrogenases (adhA, ald, fdhD, and gabD), and decarboxylases (psd and speA). Acid upregulated malate metabolism (maeN), metal export (czcDO and cadA), oxidative stress (catalase katA; OYE family namA), and the SigX extracytoplasmic stress regulon. Growth at pH 9 upregulated arginine catabolism (roc), which generates organic acids, glutamate synthase (gltAB), polyamine acetylation and transport (blt), the K(+)/H(+) antiporter (yhaTU), and cytochrome oxidoreductases (cyd, ctaACE, and qcrC). The SigH, SigL, and SigW regulons were upregulated at high pH. Overall, greater genetic adaptation was seen at pH 9 than at pH 6, which may explain the lag time required for growth shift to high pH. Low external pH favored dehydrogenases and decarboxylases that may consume acids and generate basic amines, whereas high external pH favored catabolism-generating acids.

A multifunctional metal-organic framework based tumor targeting drug delivery system for cancer therapy

NASA Astrophysics Data System (ADS)

Wang, Xiao-Gang; Dong, Zhi-Yue; Cheng, Hong; Wan, Shuang-Shuang; Chen, Wei-Hai; Zou, Mei-Zhen; Huo, Jia-Wei; Deng, He-Xiang; Zhang, Xian-Zheng

2015-09-01

Drug delivery systems (DDSs) with biocompatibility and precise drug delivery are eagerly needed to overcome the paradox in chemotherapy that high drug doses are required to compensate for the poor biodistribution of drugs with frequent dose-related side effects. In this work, we reported a metal-organic framework (MOF) based tumor targeting DDS developed by a one-pot, and organic solvent-free ``green'' post-synthetic surface modification procedure, starting from the nanoscale MOF MIL-101. Owing to the multifunctional surface coating, premature drug release from this DDS was prevented. Due to the pH responsive benzoic imine bond and the redox responsive disulfide bond at the modified surface, this DDS exhibited tumor acid environment enhanced cellular uptake and intracellular reducing environment triggered drug release. In vitro and in vivo results showed that DOX loaded into this DDS exhibited effective cancer cell inhibition with much reduced side effects.Drug delivery systems (DDSs) with biocompatibility and precise drug delivery are eagerly needed to overcome the paradox in chemotherapy that high drug doses are required to compensate for the poor biodistribution of drugs with frequent dose-related side effects. In this work, we reported a metal-organic framework (MOF) based tumor targeting DDS developed by a one-pot, and organic solvent-free ``green'' post-synthetic surface modification procedure, starting from the nanoscale MOF MIL-101. Owing to the multifunctional surface coating, premature drug release from this DDS was prevented. Due to the pH responsive benzoic imine bond and the redox responsive disulfide bond at the modified surface, this DDS exhibited tumor acid environment enhanced cellular uptake and intracellular reducing environment triggered drug release. In vitro and in vivo results showed that DOX loaded into this DDS exhibited effective cancer cell inhibition with much reduced side effects. Electronic supplementary information (ESI) available: Synthesis procedure, 1HNMR, ESI-MS and additional data. See DOI: 10.1039/c5nr04045k

The Evolution of Electrospray Generated Droplets is Not Affected by Ionization Mode

NASA Astrophysics Data System (ADS)

Liigand, Piia; Heering (Suu), Agnes; Kaupmees, Karl; Leito, Ivo; Girod, Marion; Antoine, Rodolphe; Kruve, Anneli

2017-10-01

Ionization efficiency and mechanism in ESI is strongly affected by the properties of mobile phase. The use of mobile-phase properties to accurately describe droplets in ESI source is convenient but may be inadequate as the composition of the droplets is changing in the plume due to electrochemical reactions occurring in the needle tip as well as continuous drying and fission of droplets. Presently, there is paucity of research on the effect of the polarity of the ESI mode on mobile phase composition in the droplets. In this paper, the change in the organic solvent content, pH, and droplet size are studied in the ESI plume in both ESI+ and ESI- ionization mode. We introduce a rigorous way - the absolute pH (pHabs H 2 O) - to describe pH change in the plume that takes into account organic solvent content in the mobile phase. pHabs H 2 O enables comparing acidities of ESI droplets with different organic solvent contents. The results are surprisingly similar for both ionization modes, indicating that the dynamics of the change of mobile-phase properties is independent from the ESI mode used. This allows us to conclude that the evolution of ESI droplets first of all proceeds via the evaporation of the organic modifier and to a lesser extent via fission of smaller droplets from parent droplets. Secondly, our study shows that qualitative findings related to the ESI process obtained on the ESI+ mode can almost directly be applied also in the ESI- mode. [Figure not available: see fulltext.

Retention of ionisable compounds on high-performance liquid chromatography XVII. Estimation of the pH variation of aqueous buffers with the change of the methanol fraction of the mobile phase.

PubMed

Subirats, Xavier; Bosch, Elisabeth; Rosés, Martí

2007-01-05

The use of methanol-aqueous buffer mobile phases in HPLC is a common election when performing chromatographic separations of ionisable analytes. The addition of methanol to the aqueous buffer to prepare such a mobile phase changes the buffer capacity and the pH of the solution. In the present work, the variation of these buffer properties is studied for acetic acid-acetate, phosphoric acid-dihydrogenphosphate-hydrogenphosphate, citric acid-dihydrogencitrate-hydrogencitrate-citrate, and ammonium-ammonia buffers. It is well established that the pH change of the buffers depends on the initial concentration and aqueous pH of the buffer, on the percentage of methanol added, and on the particular buffer used. The proposed equations allow the pH estimation of methanol-water buffered mobile phases up to 80% in volume of organic modifier from initial aqueous buffer pH and buffer concentration (before adding methanol) between 0.001 and 0.01 mol L(-1). From both the estimated pH values of the mobile phase and the estimated pKa of the ionisable analytes, it is possible to predict the degree of ionisation of the analytes and therefore, the interpretation of acid-base analytes behaviour in a particular methanol-water buffered mobile phase.

Colorimetric Detection and Identification of Natural and Artificial Sweeteners

PubMed Central

Musto, Christopher J.; Lim, Sung H.; Suslick, Kenneth S.

2009-01-01

A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments made from indicators immobilized in an organically modified silane (ormosil). The array has been used to detect and identify 14 different natural and artificial sweeteners at millimolar concentrations as well as commonly used individual serving sweetener packets. The array has shown excellent reproducibility and long shelf-life and has been optimized to work in the biological pH regime. PMID:20337402

Engineering Tough Materials: Biomimetic Eggshell

DTIC Science & Technology

2015-01-30

as for chicke , go se, turkey, duck, guinea fowl, pheasant[21], nd ostrich[41], rhea and emu[42]. There are differences in the amino acid sequences of...modified  to  incorporate  a  wide   range  of  organic  molecules  [ Meldrum  2003],  both  natural  and  synthetic,  to...by a 24-h soak in 5% by weight ethylene diamine tetraacetic acid (EDTA) solution, pH 7.4, made from powdered EDTA and NaOH pellets (Sigma- Aldrich

Colorimetric detection and identification of natural and artificial sweeteners.

PubMed

Musto, Christopher J; Lim, Sung H; Suslick, Kenneth S

2009-08-01

A disposable, low-cost colorimetric sensor array has been created by pin-printing onto a hydrophilic membrane 16 chemically responsive nanoporous pigments that are comprised of indicators immobilized in an organically modified silane (ormosil). The array has been used to detect and identify 14 different natural and artificial sweeteners at millimolar concentrations, as well as commonly used individual-serving sweetener packets. The array has shown excellent reproducibility and long shelf life and has been optimized to work in the biological pH regime.

Process for producing modified microorganisms for oil treatment at high temperatures, pressures and salinity

DOEpatents

Premuzic, Eugene T.; Lin, Mow

1996-02-20

This invention relates to the preparation of new, modified organisms, through challenge growth processes, that are viable in the extreme temperature, pressure and pH conditions and salt concentrations of an oil reservoir and that are suitable for use in microbial enhanced oil recovery. The modified microorganisms of the present invention are used to enhance oil recovery and remove sulfur compounds and metals from the crude oil. The processes are comprised of steps which successively limit the carbon sources and increase the temperature, pressure and salinity of the media. This is done until microbial strains are obtained that are capable of growing in essentially crude oil as a carbon source and at a temperature range from about 70.degree. C. to 90.degree. C., at a pressure range from about 2,000 to 2,500 psi and at a salinity range from about 1.3 to 35%.

Process for producing modified microorganisms for oil treatment at high temperatures, pressures and salinity

DOEpatents

Premuzic, E.T.; Lin, M.

1996-02-20

This invention relates to the preparation of new, modified organisms, through challenge growth processes, that are viable in the extreme temperature, pressure and pH conditions and salt concentrations of an oil reservoir and that are suitable for use in microbial enhanced oil recovery. The modified microorganisms of the present invention are used to enhance oil recovery and remove sulfur compounds and metals from the crude oil. The processes are comprised of steps which successively limit the carbon sources and increase the temperature, pressure and salinity of the media. This is done until microbial strains are obtained that are capable of growing in essentially crude oil as a carbon source and at a temperature range from about 70 C to 90 C, at a pressure range from about 2,000 to 2,500 psi and at a salinity range from about 1.3 to 35%. 68 figs.

Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium—Thermodynamic of adsorption process

NASA Astrophysics Data System (ADS)

Guerra, Denis Lima; Pinto, Alane Azevedo; Airoldi, Claudio; Viana, Rúbia Ribeiro

2008-12-01

Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298±1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic (Δ intH=-4.15-5.98 kJ mol -1) accompanied by increase in entropy (Δ intS=41.32-62.20 J k -1 mol -1) and Gibbs energy (Δ intG=-22.44-24.56 kJ mol -1). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid-liquid interface in the spontaneous process.

[Preparation of HDTMA-modified Zeolite and Its Performance in Nitro-phenol Adsorption from Wastewaters].

PubMed

Guo, Jun-yuan; Wang, Bin

2016-05-15

In this study, natural zeolite was modified by HDTMA. Effects of the modified conditions, HDTMA-modified zeolite doses, solution pH values, and reaction time on nitro-phenol removal were investigated, and the adsorption kinetics and isotherms were discussed. Compared with natural zeolite, HDTMA-modified zeolite showed better performance in nitro-phenol removal. An adsorption capacity of 2.53 mg · g⁻¹ was achieved when the concentration of HDTMA solution (pH = 10) was 1.2% in preparation of modified zeolite. This adsorption capacity was higher than that obtained by natural zeolite (0.54 mg · g⁻¹). In adsorption tests, when HDTMA- modified zeolite dose was adjusted to 8 g · L⁻¹, the removal efficiency of nitro-phenol reached 93.9% after 90 min reaction, with wastewater pH of 6. Furthermore, the nitro-phenol adsorption process could be well fitted to the pseudo-first-order kinetics model (R² > 0.90), whereas the adsorption isotherm results indicated that Langmuir model provided the best fitting for the equilibrium data at different temperatures, with R² of higher than 0.90.

Controllable synthesis of a novel magnetic core-shell nanoparticle for dual-modal imaging and pH-responsive drug delivery

NASA Astrophysics Data System (ADS)

Xu, Chen; Zhang, Cheng; Wang, Yingxi; Li, Liu; Li, Ling; Whittaker, Andrew K.

2017-12-01

In this study, novel magnetic core-shell nanoparticles Fe3O4@La-BTC/GO have been synthesized by the layer-by-layer self-assembly (LBL) method and further modified by attachment of amino-modified PEG chains. The nanoparticles were thoroughly characterized by x-ray diffraction, FTIR, scanning electron microscopy and transmission electron microscopy. The core-shell structure was shown to be controlled by the LBL method. The drug loading of doxorubicin (DOX) within the Fe3O4@La-BTC/GO-PEG nanoparticles with different numbers of deposited layers was investigated. It was found that DOX loading increased with increasing number of metal organic framework coating layers, indicating that the drug loading can be controlled through the controllable LBL method. Cytotoxicity assays indicated that the Fe3O4@La-BTC/GO-PEG nanoparticles were biocompatible. The DOX was released rapidly at pH 3.8 and pH 5.8, but at pH 7.4 the rate and extent of release was greatly attenuated. The nanoparticles therefore demonstrate an excellent pH-triggered drug release. In addition, the particles could be tracked by magnetic resonance imaging (MRI) and fluorescence optical imaging (FOI). A clear dose-dependent contrast enhancement in T 2-weighted MR images and fluorescence images indicate the potential of these nanoparticles as dual-mode MRI/FOI contrast agents.

Improving dissolution and oral bioavailability of pranlukast hemihydrate by particle surface modification with surfactants and homogenization

PubMed Central

Ha, Eun-Sol; Baek, In-hwan; Yoo, Jin-Wook; Jung, Yunjin; Kim, Min-Soo

2015-01-01

The present study was carried out to develop an oral formulation of pranlukast hemihydrate with improved dissolution and oral bioavailability using a surface-modified microparticle. Based on solubility measurements, surface-modified pranlukast hemihydrate microparticles were manufactured using the spray-drying method with hydroxypropylmethyl cellulose, sucrose laurate, and water and without the use of an organic solvent. The hydrophilicity of the surface-modified pranlukast hemihydrate microparticle increased, leading to enhanced dissolution and oral bioavailability of pranlukast hemihydrate without a change in crystallinity. The surface-modified microparticles with an hydroxypropylmethyl cellulose/sucrose laurate ratio of 1:2 showed rapid dissolution of up to 85% within 30 minutes in dissolution medium (pH 6.8) and oral bioavailability higher than that of the commercial product, with approximately 2.5-fold and 3.9-fold increases in area under the curve (AUC0→12 h) and peak plasma concentration, respectively. Therefore, the surface-modified microparticle is an effective oral drug delivery system for the poorly water-soluble therapeutic pranlukast hemihydrate. PMID:26150699

[Study on the kinetics of organo-clay removing red tide organisms].

PubMed

Wu, Ping; Yu, Zhi-ming

2007-07-01

The kinetics of red tide organisms (Heterosigma akashiwo and Scrippsiella trochoidea) coagulation with clays modified by dialkyl-polyoxyethenyl quaternary ammonium compound (DPQAC) was studied using spectrophotometer and fluorometry, and the effects of different kinds and concentrations of clays, the second component DPQAC added in clays and pH on the coagulation rate were examined. When using spectrophotometer, the coagulation kinetics of red tide organism coagulation with organo-clays is well fit for the bimolecular reaction model; while using fluorometry, it is fit for the hyperbola model much better. Moreover, the results also prove that using fluorometry can avoid the great change of permeance efficiency caused by clays' sedimentation when using spectrophotometer, which has availably avoided the influence of clays' sedimentation and reflected the essential of algal coagulation and sedimentation well and truly. The results of two studying methods show that the coagulation rate is more rapid in the system of kaolin than in that of bentonite; increasing the concentration of clays and DPQAC and increasing pH all can accelerate coagulation, and among those increasing the concentration of DPQAC is the most efficient way of increasing the removal efficiency and coagulation rate.

Adsorption of arsenic(III) into modified lamellar Na-magadiite in aqueous medium-Thermodynamic of adsorption process

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

Lima Guerra, Denis; Azevedo Pinto, Alane; Airoldi, Claudio

2008-12-15

Synthetic Na-magadiite sample was used for organofunctionalization process with N-propyldiethylenetrimethoxysilane and bis[3-(triethoxysilyl)propyl]tetrasulfide, after expanding the interlayer distance with polar organic solvents such as dimethylsulfoxide (DMSO). The resulted materials were submitted to process of adsorption with arsenic solution at pH 2.0 and 298{+-}1 K. The adsorption isotherms were adjusted using a modified Langmuir equation with regression nonlinear; the net thermal effects obtained from calorimetric titration measurements were adjusted to a modified Langmuir equation. The adsorption process was exothermic ({delta}{sub int}H=-4.15-5.98 kJ mol{sup -1}) accompanied by increase in entropy ({delta}{sub int}S=41.32-62.20 J k{sup -1} mol{sup -1}) and Gibbs energy ({delta}{sub int}G=-22.44-24.56 kJmore » mol{sup -1}). The favorable values corroborate with the arsenic (III)/basic reactive centers interaction at the solid-liquid interface in the spontaneous process. - Grapical Abstract: The results suggest that the adsorption capacities increased with an increase of reactive basic centers in the pendant organic chains of the intercalated agent.« less

Chiral analysis of UV nonabsorbing compounds by capillary electrophoresis using macrocyclic antibiotics: 1. Separation of aspartic and glutamic acid enantiomers.

PubMed

Bednar, P; Aturki, Z; Stransky, Z; Fanali, S

2001-07-01

Glycopeptide antibiotics, namely vancomycin or teicoplanin, were evaluated in capillary electrophoresis for the analysis of UV nonabsorbing compounds such as aspartic and glutamic acid enantiomers. Electrophoretic runs were performed in laboratory-made polyacrylamide-coated capillaries using the partial filling-counter current method in order to avoid the presence on the detector path of the absorbing chiral selector. The background electrolyte consisted of an aqueous or aqueous-organic buffer in the pH range of 4.5-6.5 of sorbic acid/histidine and the appropriate concentration of chiral selector. Several experimental parameters such as antibiotic concentration and type, buffer pH, organic modifier, type and concentration of absorbing co-ion (for the indirect UV detection) were studied in order to find the optimum conditions for the chiral resolution of the two underivatized amino acids in their enantiomers. Among the two investigated chiral selectors, vancomycin resulted to be the most useful chiral selector allowing relatively high chiral resolution of the studied compounds even at low concentration. The optimized method (10 mM sorbic acid/histidine, pH 5, and 10 mM of vancomycin) was used for the analysis of real samples such as teeth dentine and beer.

Photosynthetic activity buffers ocean acidification in seagrass meadows

NASA Astrophysics Data System (ADS)

Hendriks, I. E.; Olsen, Y. S.; Ramajo, L.; Basso, L.; Steckbauer, A.; Moore, T. S.; Howard, J.; Duarte, C. M.

2013-07-01

Macrophytes growing in shallow coastal zones characterized by intense metabolic activity have the capacity to modify pH within their canopy and beyond. We observed diel pH ranges is in shallow (5-12 m) seagrass (Posidonia oceanica) meadows from 0.06 pH units in September to 0.24 units in June. The carbonate system (pH, DIC, and aragonite saturation state (ΩAr) and O2 within the meadows displayed strong diel variability driven by primary productivity, and changes in chemistry were related to structural parameters of the meadow, in particular, the leaf surface area available for photosynthesis (LAI). LAI was positively correlated to mean and max pHNBS and max ΩAr. Oxygen production positively influenced the range and maximum pHNBS and the range of ΩAr. In June, vertical mixing (as Turbulent Kinetic Energy) influenced ΩAr, while in September there was no effect of hydrodynamics on the carbonate system within the canopy. ΩAr was positively correlated with the calcium carbonate load of the leaves, demonstrating a direct link between structural parameters, ΩAr and carbonate deposition. There was a direct relationship between ΩAr, influenced directly by meadow LAI, and CaCO3 content of the leaves. Therefore, calcifying organisms, e.g. epiphytes with carbonate skeletons, might benefit from the modification of the carbonate system by the meadow. The meadow might be capable of providing refugia for calcifiers by increasing pH and ΩAr through metabolic activity. There is, however, concern for the ability of seagrasses to provide this refugia function in the future. The predicted decline of seagrass meadows may alter the scope for alteration of pH within a seagrass meadow and in the water column above the meadow, particularly if shoot density and biomass decline, both strongly linked to LAI. Organisms associated with seagrass communities may therefore suffer from the loss of pH buffering capacity in degraded meadows.

Investigations on humic acid removal from water using surfactant-modified zeolite as adsorbent in a fixed-bed reactor

NASA Astrophysics Data System (ADS)

Elsheikh, Awad F.; Ahmad, Umi Kalthom; Ramli, Zainab

2017-10-01

Natural organic matter (NOM) is ubiquitous in aquatic environments and has recently become an issue of worldwide concern in drinking water treatment. The major component of NOM is humic acids (HA). In this study, a natural zeolite (mordenite) was modified employing hexadecyltrimethylammonium bromide (HDTMA) to enhance greater efficient sites for sorption of HA. The natural zeolite and surfactant-modified zeolite (SMZ) were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FT-IR), N2 Adsorption-desorption isotherms and BET-specific surface area, thermographic analysis, derivative thermographic analysis (TGA-DTA) and Field emission scanning electron microscopy (FESEM). A fixed-bed reactor was used for the removal of HA and the effects of different experimental parameters such as HDTMA loading levels, HA solution flow rate, solution pH and eluent concentration were investigated. The results indicated that the SMZ bed with HDTMA loading of 75% of external cation exchange capacity (ECEC) at a flow rate of 2 BV/h and pH of 10 showed the greatest enhanced removal efficiency of HA while ethanol solutions (25%v/v) with feed flow rate of 2 BV/h were sufficient for complete regeneration of SMZ and desorption of HA. Measurements of surface area of SMZ indicated that a monolayer formation of the surfactant at those conditions allowed the optimum removal of HA.

Mold Pectinase Modified with Dialdehyde Derivatives of Dextran and Cellulose.

PubMed

Kobayashi, M; Chiba, Y; Funane, K; Ohya, S; Kato, Y

1996-01-01

Chemical modification of mold pectinase with dextran- and cellulose-dialdehydes was examined to improve the enzyme characteristics. The modified pectinase with dextran-dialdehyde retained about 50% of the original activity, and more than 80% of the total amino groups were modified. HPLC gel filtration analysis showed an increase in molecular weight of the reaction product. Reaction with cellulose-dialdehyde provided an immobilized form of pectinase. The immobilized pectinase was resistant to both acidic and alkaline pHs, and also acquired heat stability at 60°C. The optimum pH of the modified enzyme shifted from pH 4.5 to 5.0-5.5, and this enzyme had higher activity at neutral pH regions than the native enzyme. A rather low recovery of immobilized enzyme (14.5%) should be improved by the combination with various methods hitherto established.

Aluminium uptake and translocation in Al hyperaccumulator Rumex obtusifolius is affected by low-molecular-weight organic acids content and soil pH.

PubMed

Vondráčková, Stanislava; Száková, Jiřina; Drábek, Ondřej; Tejnecký, Václav; Hejcman, Michal; Müllerová, Vladimíra; Tlustoš, Pavel

2015-01-01

High Al resistance of Rumex obtusifolius together with its ability to accumulate Al has never been studied in weakly acidic conditions (pH > 5.8) and is not sufficiently described in real soil conditions. The potential elucidation of the role of organic acids in plant can explain the Al tolerance mechanism. We established a pot experiment with R. obtusifolius planted in slightly acidic and alkaline soils. For the manipulation of Al availability, both soils were untreated and treated by lime and superphosphate. We determined mobile Al concentrations in soils and concentrations of Al and organic acids in organs. Al availability correlated positively to the extraction of organic acids (citric acid < oxalic acid) in soils. Monovalent Al cations were the most abundant mobile Al forms with positive charge in soils. Liming and superphosphate application were ambiguous measures for changing Al mobility in soils. Elevated transport of total Al from belowground organs into leaves was recorded in both lime-treated soils and in superphosphate-treated alkaline soil as a result of sufficient amount of Ca available from soil solution as well as from superphosphate that can probably modify distribution of total Al in R. obtusifolius as a representative of "oxalate plants." The highest concentrations of Al and organic acids were recorded in the leaves, followed by the stem and belowground organ infusions. In alkaline soil, R. obtusifolius is an Al-hyperaccumulator with the highest concentrations of oxalate in leaves, of malate in stems, and of citrate in belowground organs. These organic acids form strong complexes with Al that can play a key role in internal Al tolerance but the used methods did not allow us to distinguish the proportion of total Al-organic complexes to the free organic acids.

Radiolabeling of DOTA-like conjugated peptides with generator-produced 68Ga and using NaCl-based cationic elution method

PubMed Central

Mueller, Dirk; Breeman, Wouter A P; Klette, Ingo; Gottschaldt, Michael; Odparlik, Andreas; Baehre, Manfred; Tworowska, Izabela; Schultz, Michael K

2017-01-01

Gallium-68 (68Ga) is a generator-produced radionuclide with a short half-life (t½ = 68 min) that is particularly well suited for molecular imaging by positron emission tomography (PET). Methods have been developed to synthesize 68Ga-labeled imaging agents possessing certain drawbacks, such as longer synthesis time because of a required final purification step, the use of organic solvents or concentrated hydrochloric acid (HCl). In our manuscript, we provide a detailed protocol for the use of an advantageous sodium chloride (NaCl)-based method for radiolabeling of chelator-modified peptides for molecular imaging. By working in a lead-shielded hot-cell system, 68Ga3+ of the generator eluate is trapped on a cation exchanger cartridge (100 mg, ∼8 mm long and 5 mm diameter) and then eluted with acidified 5 M NaCl solution directly into a sodium acetate-buffered solution containing a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or DOTA-like chelator-modified peptide. The main advantages of this procedure are the high efficiency and the absence of organic solvents. It can be applied to a variety of peptides, which are stable in 1 M NaCl solution at a pH value of 3–4 during reaction. After labeling, neutralization, sterile filtration and quality control (instant thin-layer chromatography (iTLC), HPLC and pH), the radiopharmaceutical can be directly administered to patients, without determination of organic solvents, which reduces the overall synthesis-to-release time. This procedure has been adapted easily to automated synthesis modules, which leads to a rapid preparation of 68Ga radiopharmaceuticals (12–16 min). PMID:27172166

Radiolabeling of DOTA-like conjugated peptides with generator-produced (68)Ga and using NaCl-based cationic elution method.

PubMed

Mueller, Dirk; Breeman, Wouter A P; Klette, Ingo; Gottschaldt, Michael; Odparlik, Andreas; Baehre, Manfred; Tworowska, Izabela; Schultz, Michael K

2016-06-01

Gallium-68 ((68)Ga) is a generator-produced radionuclide with a short half-life (t½ = 68 min) that is particularly well suited for molecular imaging by positron emission tomography (PET). Methods have been developed to synthesize (68)Ga-labeled imaging agents possessing certain drawbacks, such as longer synthesis time because of a required final purification step, the use of organic solvents or concentrated hydrochloric acid (HCl). In our manuscript, we provide a detailed protocol for the use of an advantageous sodium chloride (NaCl)-based method for radiolabeling of chelator-modified peptides for molecular imaging. By working in a lead-shielded hot-cell system,(68)Ga(3+) of the generator eluate is trapped on a cation exchanger cartridge (100 mg, ∼8 mm long and 5 mm diameter) and then eluted with acidified 5 M NaCl solution directly into a sodium acetate-buffered solution containing a DOTA (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) or DOTA-like chelator-modified peptide. The main advantages of this procedure are the high efficiency and the absence of organic solvents. It can be applied to a variety of peptides, which are stable in 1 M NaCl solution at a pH value of 3-4 during reaction. After labeling, neutralization, sterile filtration and quality control (instant thin-layer chromatography (iTLC), HPLC and pH), the radiopharmaceutical can be directly administered to patients, without determination of organic solvents, which reduces the overall synthesis-to-release time. This procedure has been adapted easily to automated synthesis modules, which leads to a rapid preparation of (68)Ga radiopharmaceuticals (12-16 min).

Removal of antibiotics from water in the coexistence of suspended particles and natural organic matters using amino-acid-modified-chitosan flocculants: A combined experimental and theoretical study.

PubMed

Jia, Shuying; Yang, Zhen; Ren, Kexin; Tian, Ziqi; Dong, Chang; Ma, Ruixue; Yu, Ge; Yang, Weiben

2016-11-05

Contamination of trace antibiotics is widely found in surface water sources. This work delineates removal of trace antibiotics (norfloxacin (NOR), sulfadiazine (SDZ) or tylosin (TYL)) from synthetic surface water by flocculation, in the coexistence of inorganic suspended particles (kaolin) and natural organic matter (humic acid, HA). To avoid extra pollution caused by petrochemical products-based modification reagents, environmental-friendly amino-acid-modified-chitosan flocculants, Ctrp and Ctyr, with different functional aromatic-rings structures were employed. Jar tests at various pHs exhibited that, Ctyr, owning phenol groups as electron donors, was favored for elimination of cationic NOR (∼50% removal; optimal pH: 6; optimal dosage: 4mg/L) and TYL (∼60% removal; optimal pH: 7; optimal dosage: 7.5mg/L), due to π-π electron donator-acceptor (EDA) effect and unconventional H-bonds. Differently, Ctrp with indole groups as electron acceptor had better removal rate (∼50%) of SDZ anions (electron donator). According to correlation analysis, the coexisted kaolin and HA played positive roles in antibiotics' removal. Detailed pairwise interactions in molecular level among different components were clarified by spectral analysis and theoretical calculations (density functional theory), which are important for both the structural design of new flocculants aiming at targeted contaminants and understanding the environmental behaviors of antibiotics in water. Copyright © 2016 Elsevier B.V. All rights reserved.

Microenvironmental pH-modification to improve dissolution behavior and oral absorption for drugs with pH-dependent solubility.

PubMed

Taniguchi, Chika; Kawabata, Yohei; Wada, Koichi; Yamada, Shizuo; Onoue, Satomi

2014-04-01

Drug release and oral absorption of drugs with pH-dependent solubility are influenced by the conditions in the gastrointestinal tract. In some cases, poor oral absorption has been observed for these drugs, causing insufficient drug efficacy. The pH-modification of a formulation could be a promising approach to overcome the poor oral absorption of drugs with pH-dependent solubility. The present review aims to summarize the pH-modifier approach and strategic analyses of microenvironmental pH for formulation design and development. We also provide literature- and patent-based examples of the application of pH-modification technology to solid dosage forms. For the pH-modification approach, the microenvironmental pH at the diffusion area can be altered by dissolving pH-modifying excipients in the formulation. The modulation of the microenvironmental pH could improve dissolution behavior of drugs with pH-dependent solubility, possibly leading to better oral absorption. According to this concept, the modulated level of microenvironmental pH and its duration can be key factors for improvement in drug dissolution. The measurement of microenvironmental pH and release of pH-modifier would provide theoretical insight for the selection of an appropriate pH-modifier and optimization of the formulation.

Fungal extracellular phosphatases: their role in P cycling under different pH and P sources availability.

PubMed

Della Mónica, I F; Godoy, M S; Godeas, A M; Scervino, J M

2018-01-01

The aim of this work is to analyse the effect of pH, fungal identity and P chemical nature on microbial development and phosphatase release, discussing solubilization and mineralization processes in P cycling. P solubilizing fungi (Talaromyces flavus, T. helicus L, T. helicus N, T. diversus and Penicillium purpurogenum) were grown under three pH conditions (6, 6·5 and 8·5) and with different inorganic (calcium, iron, aluminium and rock) and organic (lecithin and phytate) P sources. P solubilization, mineralization, growth and phosphatase production were recorded. Acid and neutral environments maximized fungal development and P recycling. P chemical nature changed the phosphatases release pattern depending on the fungal identity. Acid phosphatase activity was higher than alkaline phosphatases, regardless of pH or sample times. Alkaline phosphatases were affected by a combination of those factors. P chemical nature and pH modify fungal growth, P mineralization and solubilization processes. The underlying fungal identity-dependent metabolism governs the capacity and efficiency of P solubilization and mineralization. P solubilization and mineralization processes are interrelated and simultaneously present in soil fungi. This study constitutes a reference work to improve the selection of fungal bioinoculants in different environmental conditions, highlighting their role in P cycling. © 2017 The Society for Applied Microbiology.

Manufacture and application of RuO2 solid-state metal-oxide pH sensor to common beverages.

PubMed

Lonsdale, W; Wajrak, M; Alameh, K

2018-04-01

A new reproducible solid-state metal-oxide pH sensor for beverage quality monitoring is developed and characterised. The working electrode of the developed pH sensor is based on the use of laser-etched sputter-deposited RuO 2 on Al 2 O 3 substrate, modified with thin layers of sputter-deposited Ta 2 O 5 and drop-cast Nafion for minimisation of redox interference. The reference electrode is manufactured by further modifying a working electrode with a porous polyvinyl butyral layer loaded with fumed SiO 2 . The developed pH sensor shows excellent performance when applied to a selection of beverage samples, with a measured accuracy within 0.08 pH of a commercial glass pH sensor. Copyright © 2017 Elsevier B.V. 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.

Disintegration of sublingual tablets: proposal for a validated test method and acceptance criterion.

PubMed

Weda, M; van Riet-Nales, D A; van Aalst, P; de Kaste, D; Lekkerkerker, J F F

2006-12-01

In the Netherlands the market share of isosorbide dinitrate 5 mg sublingual tablets is dominated by 2 products (A and B). In the last few years complaints have been received from health care professionals on product B. During patient use the disintegration of the tablet was reported to be slow and/or incomplete, and ineffectiveness was experienced. In the European Pharmacopoeia (Ph. Eur.) no requirement is present for the disintegration time of sublingual tablets. The purpose of this study was to compare the in vitro disintegration time of products A and B, and to establish a suitable test method and acceptance criterion. A and B were tested with the Ph. Eur. method described in the monograph on disintegration of tablets and capsules as well as with 3 modified tests using the same Ph. Eur. apparatus, but without movement of the basket-rack assembly. In modified test 1 and modified test 2 water was used as medium (900 ml and 50 ml respectively), whereas in modified test 3 artificial saliva was used (50 ml). In addition, disintegration was tested in Nessler tubes with 0.5 and 2 ml of water. Finally, the Ph. Eur. method was also applied to other sublingual tablets with other drug substances on the Dutch market. With modified test 3 no disintegration could be achieved within 20 min. With the Ph. Eur. method and modified tests 1 and 2 product A and B differed significantly (p < 0. 001), with product B having longer disintegration times. These 3 methods were capable of discriminating between products and between batches. The time measured with the Ph. Eur. method was significantly lower compared to modified tests 1 and 2 (p < 0.001) and correlated well with the Nessler tube results. It is concluded that the in vivo complaints on product B could be related to the in vitro data. Furthermore, it is proposed that for immediate release of sublingual tablets the disintegration time should be tested. The Ph. Eur. method is considered suitable for this test. In view of the products currently on the market and taking into consideration requirements in the United States Pharmacopeia and Japanese Pharmacopoeia, an acceptance criterion of not more than 2 min is proposed.

Fabrication of magnetite nano particles and modification with metal organic framework of Zn(2+) for sorption of doxycyline.

PubMed

Ghassemi Nooreini, Mahsa; Ahmad Panahi, Homayon

2016-10-15

This study presents a novel method for synthesis and characterization of a metal-organic framework and application in drug delivery. The first step was synthesis of amino functionalized magnetite that was then modified by a metal-organic framework of Zn(2+). This newly developed nano-sorbent was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive x-ray spectroscopy, thermogravimetric analysis, vibrating sample magnetometer and x-ray diffraction. Doxycycline was loaded to the nano-sorbent and effects of the variable parameters, kinetics of adsorption, release and capacity of adsorption were investigated. Test results specified maximum sorption of 21.5mgg(-1) for doxycycline in conditions of nano-sorbent at pH 7 and optimum time of 10min. Equilibrium adsorption data were analyzed by the Langmuir, Freundlich and Temkin models. Results showed that about 40% of doxycycline was released in simulated gastric fluid for the 30min and more than 70% was released in simulated intestinal fluid during 12h. These results were satisfactory and demonstrate that this new nano-sorbent modified with metal-organic framework had a good level of efficiency for drug delivery of doxycycline. Copyright © 2016 Elsevier B.V. All rights reserved.

Field guide for collecting and processing stream-water samples for the National Water-Quality Assessment Program

USGS Publications Warehouse

Shelton, Larry R.

1994-01-01

The U.S. Geological Survey's National Water-Quality Assessment program includes extensive data- collection efforts to assess the quality of the Nations's streams. These studies require analyses of stream samples for major ions, nutrients, sediments, and organic contaminants. For the information to be comparable among studies in different parts of the Nation, consistent procedures specifically designed to produce uncontaminated samples for trace analysis in the laboratory are critical. This field guide describes the standard procedures for collecting and processing samples for major ions, nutrients, organic contaminants, sediment, and field analyses of conductivity, pH, alkalinity, and dissolved oxygen. Samples are collected and processed using modified and newly designed equipment made of Teflon to avoid contamination, including nonmetallic samplers (D-77 and DH-81) and a Teflon sample splitter. Field solid-phase extraction procedures developed to process samples for organic constituent analyses produce an extracted sample with stabilized compounds for more accurate results. Improvements to standard operational procedures include the use of processing chambers and capsule filtering systems. A modified collecting and processing procedure for organic carbon is designed to avoid contamination from equipment cleaned with methanol. Quality assurance is maintained by strict collecting and processing procedures, replicate sampling, equipment blank samples, and a rigid cleaning procedure using detergent, hydrochloric acid, and methanol.

Fluorescent Nanocrystals Reveal Regulated Portals of Entry into and Between the Cells of Hydra

PubMed Central

Tortiglione, Claudia; Quarta, Alessandra; Malvindi, Maria Ada; Tino, Angela; Pellegrino, Teresa

2009-01-01

Initially viewed as innovative carriers for biomedical applications, with unique photophysical properties and great versatility to be decorated at their surface with suitable molecules, nanoparticles can also play active roles in mediating biological effects, suggesting the need to deeply investigate the mechanisms underlying cell-nanoparticle interaction and to identify the molecular players. Here we show that the cell uptake of fluorescent CdSe/CdS quantum rods (QRs) by Hydra vulgaris, a simple model organism at the base of metazoan evolution, can be tuned by modifying nanoparticle surface charge. At acidic pH, amino-PEG coated QRs, showing positive surface charge, are actively internalized by tentacle and body ectodermal cells, while negatively charged nanoparticles are not uptaken. In order to identify the molecular factors underlying QR uptake at acidic pH, we provide functional evidence of annexins involvement and explain the QR uptake as the combined result of QR positive charge and annexin membrane insertion. Moreover, tracking QR labelled cells during development and regeneration allowed us to uncover novel intercellular trafficking and cell dynamics underlying the remarkable plasticity of this ancient organism. PMID:19888325

Local pH Monitoring of Small Cluster of Cells using a Fiber-Optic Dual-Core Micro-Probe.

PubMed

Chen, Sisi; Yang, Qingbo; Xiao, Hai; Shi, Honglan; Ma, Yinfa

2017-03-31

Biological studies of tissues and cells have enabled numerous discoveries, but these studies still bear potential risks of invalidation because of cell heterogeneity. Through high-accuracy techniques, recent studies have demonstrated that discrepancies do exist between the results from low-number-cell studies and cell-population-based results. Thus the urgent need to re-evaluate key principles on limited number of cells has been provoked. In this study, a novel designed dual-core fiber-optic pH micro-probe was fabricated and demonstrated for niche environment pH sensing with high spatial resolution. An organic-modified silicate (OrMoSils) sol-gel thin layer was functionalized by entrapping a pH indicator, 2', 7'-Bis (2-carbonylethyl)-5(6)-carboxyfluorescein (BCECF), on a ~70 μm sized probe tip. Good linear correlation between fluorescence ratio of I 560 nm /I 640 nm and intercellular pH values was obtained within a biological-relevant pH range from 6.20 to 7.92 (R 2 = 0.9834), and with a pH resolution of 0.035 ± 0.005 pH units. The probe's horizontal spatial resolution was demonstrated to be less than 2mm. Moreover, the probe was evaluated by measuring the localized extracellular pH changes of cultured human lung cancer cells (A549) when exposed to titanium dioxide nanoparticles (TiO 2 NPs). Results showed that the probe has superior capability for fast, local, and continual monitoring of a small cluster of cells, which provides researchers a fast and accurate technique to conduct local pH measurements for cell heterogeneity-related studies.

The Coral Reef pH-stat: An Important Defense Against Ocean Acidification? (Invited)

NASA Astrophysics Data System (ADS)

Andersson, A. J.; Yeakel, K.; Bates, N.; de Putron, S.; Collins, A.

2013-12-01

Concerns have been raised on how coral reefs will be affected by ocean acidification (OA), but there are currently no direct predictions on how seawater CO2 chemistry and pH within coral reefs might change in response to OA. Projections of future changes in seawater pH and aragonite saturation state have only been applied to open ocean conditions surrounding coral reef environments rather than the reef systems themselves. The seawater CO2 chemistry within heterogenous coral reef systems can be significantly different from that of the open ocean depending on the residence time, community composition and the major biogeochemical processes occurring on the reef, i.e., net ecosystem organic carbon production and calcification, which combined act to modify the seawater chemistry. We argue that these processes and coral reefs in general could as a pH-stat, partly regulating seawater pH on the reef and offsetting changes in seawater chemistry imposed by ocean acidification. Based on observations from the Bermuda coral reef, we show that a range of anticipated biogeochemical responses of coral reef communities to OA by the end of this century could partially offset changes in seawater pH by an average of 12% to 24%.

A facile and efficient method to modify gold nanorods with thiolated DNA at a low pH value.

PubMed

Shi, Dangwei; Song, Chen; Jiang, Qiao; Wang, Zhen-Gang; Ding, Baoquan

2013-03-28

We report a simple, rapid and efficient strategy for modification of gold nanorods (AuNRs) with thiolated DNA at low solution pH and high salt concentration. DNA functionalized AuNRs were then used to assemble with DNA modified gold nanoparticles to form discrete satellite nanostructures.

Micellar versus hydro-organic mobile phases for retention-hydrophobicity relationship studies with ionizable diuretics and an anionic surfactant.

PubMed

Ruiz-Angel, M J; Carda-Broch, S; García-Alvarez-Coque, M C; Berthod, A

2004-03-19

Logarithm of retention factors (log k) of a group of 14 ionizable diuretics were correlated with the molecular (log P o/w) and apparent (log P(app)) octanol-water partition coefficients. The compounds were chromatographed using aqueous-organic (reversed-phase liquid chromatography, RPLC) and micellar-organic mobile phases (micellar liquid chromatography, MLC) with the anionic surfactant sodium dodecyl sulfate (SDS), in the pH range 3-7, and a conventional octadecylsilane column. Acetonitrile was used as the organic modifier in both modes. The quality of the correlations obtained for log P(app) at varying ionization degree confirms that this correction is required in the aqueous-organic mixtures. The correlation is less improved with SDS micellar media because the acid-base equilibriums are shifted towards higher pH values for acidic compounds. In micellar chromatography, an electrostatic interaction with charged solutes is added to hydrophobic forces; consequently, different correlations should be established for neutral and acidic compounds, and for basic compounds. Correlations between log k and the isocratic descriptors log k(w), log k(wm) (extrapolated retention to pure water in the aqueous-organic and micellar-organic systems, respectively), and psi0 (extrapolated mobile phase composition giving a k = 1 retention factor or twice the dead time), and between these descriptors and log P(app) were also satisfactory, although poorer than those between log k and log P(app) due to the extrapolation. The study shows that, in the particular case of the ionizable diuretics studied, classical RPLC gives better results than MLC with SDS in the retention hydrophobicity correlations.

Solution phase and membrane immobilized iron-based free radical reactions: Fundamentals and applications for water treatment

NASA Astrophysics Data System (ADS)

Lewis, Scott Romak

Membrane-based separation processes have been used extensively for drinking water purification, wastewater treatment, and numerous other applications. Reactive membranes synthesized through functionalization of the membrane pores offer enhanced reactivity due to increased surface area at the polymer-solution interface and low diffusion limitations. Oxidative techniques utilizing free radicals have proven effective for both the destruction of toxic organics and non-environmental applications. Most previous work focuses on reactions in the homogeneous phase; however, the immobilization of reactants in membrane pores offers several advantages. The use of polyanions immobilized in a membrane or chelates in solution prevents ferric hydroxide precipitation at near-neutral pH, a common limitation of iron(Fe(II/III))-catalyzed hydrogen peroxide (H 2O2) decomposition. The objectives of this research are to develop a membrane-based platform for the generation of free radicals, degrade toxic organic compounds using this and similar solution-based reactions, degrade toxic organic compounds in droplet form, quantify hydroxyl radical production in these reactions, and develop kinetic models for both processes. In this study, a functionalized membrane containing poly(acrylic acid) (PAA) was used to immobilize iron ions and conduct free radical reactions by permeating H2O2 through the membrane. The membrane's responsive behavior to pH and divalent cations was investigated and modeled. The conversion of Fe(II) to Fe(III) in the membrane and its effect on the decomposition of hydrogen peroxide were monitored and used to develop kinetic models for predicting H2O2 decomposition in these systems. The rate of hydroxyl radical production, and hence contaminant degradation can be varied by changing the residence time, H2O2 concentration, and/or iron loading. Using these membrane-immobilized systems, successful removal of toxic organic compounds, such as pentachlorophenol (PCP), from water was demonstrated. Another toxic organic compound of interest for water treatment applications is trichloroethylene (TCE). Due to its limited solubility in water, a majority of the TCE is often present in the form of droplets. In this study, effective TCE droplet degradation using chelate-modified, iron-catalyzed free radical reactions at near-neutral pH was demonstrated. In order to predict the degradation of aqueous and non-aqueous phase TCE for these reactions, a mathematical model was constructed through the use of droplet mass transfer correlations and free radical reaction kinetics. KEYWORDS: Functionalized membrane, free radical, hydrogen peroxide, chelate-modified, membrane reactor

Phosphorus sorption-desorption and effects of temperature, pH and salinity on phosphorus sorption in marsh soils from coastal wetlands with different flooding conditions.

PubMed

Bai, Junhong; Ye, Xiaofei; Jia, Jia; Zhang, Guangliang; Zhao, Qingqing; Cui, Baoshan; Liu, Xinhui

2017-12-01

Wetland soils act as a sink or source of phosphorus (P) to the overlaying water due to phosphorus sorption-desorption processes. Litter information is available on sorption and desorption behaviors of phosphorus in coastal wetlands with different flooding conditions. Laboratory experiments were conducted to investigate phosphorus sorption-desorption processes, fractions of adsorbed phosphorus, and the effects of salinity, pH and temperature on phosphorus sorption on soils in tidal-flooding wetlands (TW), freshwater-flooding wetlands (FW) and seasonal-flooding wetlands (SW) in the Yellow River Delta. Our results showed that the freshly adsorbed phosphorus dominantly exists in Occluded-P and Fe/AlP and their percentages increased with increasing phosphorus adsorbed. Phosphorus sorption isotherms could be better described by the modified Langmuir model than by the modified Freundlich model. A binomial equation could be properly used to describe the effects of salinity, pH, and temperature on phosphorus sorption. Phosphorus sorption generally increased with increasing salinity, pH, and temperature at lower ranges, while decreased in excess of some threshold values. The maximum phosphorus sorption capacity (Q max ) was larger for FW soils (256 mg/kg) compared with TW (218 mg/kg) and SW soils (235 mg/kg) (p < 0.05). The percentage of phosphorus desorption (P des ) in the FW soils (7.5-63.5%) was much lower than those in TW (27.7-124.9%) and SW soils (19.2-108.5%). The initial soil organic matter, pH and the exchangeable Al, Fe and Cd contents were important factors influencing P sorption and desorption. The findings of this study indicate that freshwater restoration can contribute to controlling the eutrophication status of water bodies through increasing P sorption. Copyright © 2017 Elsevier Ltd. All rights reserved.

Voltammetric behavior of dopamine at a glassy carbon electrode modified with NiFe(2)O(4) magnetic nanoparticles decorated with multiwall carbon nanotubes.

PubMed

Ensafi, Ali A; Arashpour, B; Rezaei, B; Allafchian, Ali R

2014-06-01

Voltammetric behavior of dopamine was studied on a glassy carbon electrode (GCE) modified-NiFe(2)O(4) magnetic nanoparticles decorated with multiwall carbon nanotubes. Impedance spectroscopy and cyclic voltammetry were used to characterize the behavior of dopamine at the surface of modified-GCE. The modified electrode showed a synergic effect toward the oxidation of dopamine. The oxidation peak current is increased linearly with the dopamine concentration (at pH7.0) in wide dynamic ranges of 0.05-6.0 and 6.0-100μmolL(-1) with a detection limit of 0.02μmolL(-1), using differential pulse voltammetry. The selectivity of the method was studied and the results showed that the modified electrode is free from interference of organic compounds especially ascorbic acid, uric acid, cysteine and urea. Its applicability in the determination of dopamine in pharmaceutical, urine samples and human blood serum was also evaluated. The proposed electrochemical sensor has appropriate properties such as high selectivity, low detection limit and wide linear dynamic range when compared with that of the previous reported papers for dopamine detection. Copyright © 2014 Elsevier B.V. All rights reserved.

Modified spectrophotometer for multi-dimensional circular dichroism/fluorescence data acquisition in titration experiments: application to the pH and guanidine-HCI induced unfolding of apomyoglobin.

PubMed

Ramsay, G; Ionescu, R; Eftink, M R

1995-08-01

In a previous paper (Ramsay and Eftink, Biophys. J. 66:516-523) we reported the development of a modified spectrophotometer that can make nearly simultaneous circular dichroism (CD) and fluorescence measurements. This arrangement allows multiple data sets to be collected during a single experiment, resulting in a saving of time and material, and improved correlation between the different types of measurements. The usefulness of the instrument was shown by thermal melting experiments on several different protein systems. This CD/fluorometer spectrophotometer has been further modified by interfacing with a syringe pump and a pH meter. This arrangement allows ligand, pH, and chemical denaturation titration experiments to be performed while monitoring changes in the sample's CD, absorbance, fluorescence, and light scattering properties. Our data acquisition program also has an ability to check whether the signals have approached equilibrium before the data is recorded. For performing pH titrations we have developed a procedure which uses the signal from a pH meter in a feedback circuit in order to collect data at evenly spaced pH intervals. We demonstrate the use of this instrument with studies of the unfolding of sperm whale apomyoglobin, as induced by acid pH and by the addition of guanidine-HCI.

Modified spectrophotometer for multi-dimensional circular dichroism/fluorescence data acquisition in titration experiments: application to the pH and guanidine-HCI induced unfolding of apomyoglobin.

PubMed Central

Ramsay, G; Ionescu, R; Eftink, M R

1995-01-01

In a previous paper (Ramsay and Eftink, Biophys. J. 66:516-523) we reported the development of a modified spectrophotometer that can make nearly simultaneous circular dichroism (CD) and fluorescence measurements. This arrangement allows multiple data sets to be collected during a single experiment, resulting in a saving of time and material, and improved correlation between the different types of measurements. The usefulness of the instrument was shown by thermal melting experiments on several different protein systems. This CD/fluorometer spectrophotometer has been further modified by interfacing with a syringe pump and a pH meter. This arrangement allows ligand, pH, and chemical denaturation titration experiments to be performed while monitoring changes in the sample's CD, absorbance, fluorescence, and light scattering properties. Our data acquisition program also has an ability to check whether the signals have approached equilibrium before the data is recorded. For performing pH titrations we have developed a procedure which uses the signal from a pH meter in a feedback circuit in order to collect data at evenly spaced pH intervals. We demonstrate the use of this instrument with studies of the unfolding of sperm whale apomyoglobin, as induced by acid pH and by the addition of guanidine-HCI. Images FIGURE 2 PMID:8527683

A simple scheme to determine potential aquatic metal toxicity from mining wastes

USGS Publications Warehouse

Wildeman, T.R.; Smith, K.S.; Ranville, J.F.

2007-01-01

A decision tree (mining waste decision tree) that uses simple physical and chemical tests has been developed to determine whether effluent from mine waste material poses a potential toxicity threat to the aquatic environment. For the chemical portion of the tree, leaching tests developed by the United States Geological Survey, the Colorado Division of Minerals and Geology (Denver, CO), and a modified 1311 toxicity characteristic leaching procedure (TCLP) test of the United States Environmental Protection Agency have been extensively used as a surrogate for readily available metals that can be released into the environment from mining wastes. To assist in the assessment, element concentration pattern graphs (ECPG) are produced that compare concentrations of selected groups of elements from the three leachates and any water associated with the mining waste. The MWDT makes a distinction between leachates or waters with pH less than or greater than 5. Generally, when the pH values are below 5, the ECPG of the solutions are quite similar, and potential aquatic toxicity from cationic metals, such as Pb, Cu, Zn, Cd, and Al, is assumed. Below pH 5, these metals are mostly dissolved, generally are not complexed with organic or inorganic ligands, and hence are more bioavailable. Furthermore, there is virtually no carbonate alkalinity at pH less than 5. All of these factors promote metal toxicity to aquatic organisms. On the other hand, when the pH value of the water or the leachates is above 5, the ECPG from the solutions are variable, and inferred aquatic toxicity depends on factors in addition to the metals released from the leaching tests. Hence, leachates and waters with pH above 5 warrant further examination of their chemical composition. Physical ranking criteria provide additional information, particularly in areas where waste piles exhibit similar chemical rankings. Rankings from physical and chemical criteria generally are not correlated. Examples of how this decision tree has been applied in assessing mine sites are discussed. Copyright ?? Taylor & Francis Group, LLC.

Characterization of nano-clay reinforced phytagel-modified soy protein concentrate resin.

PubMed

Huang, Xiaosong; Netravali, Anil N

2006-10-01

Phytagel and nano-clay particles were used to improve the mechanical and thermal properties and moisture resistance of soy protein concentrate (SPC) resin successfully. SPC and Phytagel were mixed together to form a cross-linked structure. The Phytagel-modified SPC resin (PH-SPC) showed improved tensile strength, modulus, moisture resistance, and thermal stability as compared to the unmodified SPC resin. The incorporation of 40% Phytagel and 20% glycerol led to an overall 340% increase in the tensile strength (over 50 MPa) and approximately 360% increase in the Young's modulus (over 710 MPa) of the SPC resin. Nano-clay was uniformly dispersed into PH-SPC resin to further improve the properties. The PH-SPC (40% Phytagel) resin modified with 7% clay nanoparticles (CPH-SPC) had a modulus of 2.1 GPa and a strength of 72.5 MPa. The dynamic mechanical properties such as storage modulus together with the glass transition temperature of the modified resins were also increased by the addition of clay nanoparticles. The moisture resistance of the CPH-SPC resin was higher as compared to both SPC and PH-SPC resins. The thermal stability of the CPH-SPC resin was seen to be higher as compared to the unmodified SPC.

Restoration of CpG Methylation in The Egf Promoter Region during Rat Liver Regeneration.

PubMed

Deming, Li; Ziwei, Li; Xueqiang, Guo; Cunshuan, Xu

2015-01-01

Epidermal growth factor (EGF) is an important factor for healing after tissue damage in diverse experimental models. It plays an important role in liver regeneration (LR). The objective of this experiment is to investigate the methylation variation of 10 CpG sites in the Egf promoter region and their relevance to Egf expression during rat liver regenera- tion. As a follow up of our previous study, rat liver tissue was collected after rat 2/3 partial hepatectomy (PH) during the re-organization phase (from days 14 to days 28). Liver DNA was extracted and modified by sodium bisulfate. The methylation status of 10 CpG sites in Egf promoter region was determined using bisulfite sequencing polymerase chain reaction (PCR), as BSP method. The results showed that 3 (sites 3, 4 and 9) out of 10 CpG sites have strikingly methylation changes during the re-organization phase compared to the regeneration phase (from 2 hours to 168 hours, P=0.002, 0.048 and 0.018, respectively). Our results showed that methylation modification of CpGs in the Egf promoter region could be restored to the status before PH operation and changes of methylation didn't affect Egf mRNA expression during the re-organization phase.

Restoration of CpG Methylation in The Egf Promoter Region during Rat Liver Regeneration

PubMed Central

Deming, Li; Ziwei, Li; Xueqiang, Guo; Cunshuan, Xu

2015-01-01

Epidermal growth factor (EGF) is an important factor for healing after tissue damage in diverse experimental models. It plays an important role in liver regeneration (LR). The objective of this experiment is to investigate the methylation variation of 10 CpG sites in the Egf promoter region and their relevance to Egf expression during rat liver regenera- tion. As a follow up of our previous study, rat liver tissue was collected after rat 2/3 partial hepatectomy (PH) during the re-organization phase (from days 14 to days 28). Liver DNA was extracted and modified by sodium bisulfate. The methylation status of 10 CpG sites in Egf promoter region was determined using bisulfite sequencing polymerase chain reaction (PCR), as BSP method. The results showed that 3 (sites 3, 4 and 9) out of 10 CpG sites have strikingly methylation changes during the re-organization phase compared to the regeneration phase (from 2 hours to 168 hours, P=0.002, 0.048 and 0.018, respectively). Our results showed that methylation modification of CpGs in the Egf promoter region could be restored to the status before PH operation and changes of methylation didn’t affect Egf mRNA expression during the re-organization phase. PMID:26464832

Magnetorheological finishing of chemical-vapor deposited zinc sulfide via chemically and mechanically modified fluids.

PubMed

Salzman, Sivan; Romanofsky, Henry J; Giannechini, Lucca J; Jacobs, Stephen D; Lambropoulos, John C

2016-02-20

We describe the anisotropy in the material removal rate (MRR) of the polycrystalline, chemical-vapor deposited zinc sulfide (ZnS). We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6 MR fluids, variations were found in the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.

Quantitative determination of Escherichia coli based on the electrochemical measurement of bacterial catalase activity using H2O2-selective organic/inorganic-hybrid sol-gel film-modified Pt electrode.

PubMed

Hasebe, Yasushi; Fukuzawa, Michiru; Matsuhisa, Hironori

2009-01-01

Quantitative determination of Escherichia coli (E. coli) concentration was achieved by measuring the intrinsic catalase activity of E. coli using novel H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode. This hybrid sol-gel film is composed of three kinds of organosilanes and two biopolymers (i.e., chitosan and bovine serum albumin), and exhibited an excellent permselectivity toward H2O2 based on a size-exclusive mechanism. The steady-state anodic current for 100 [xmol/L H2O2 at +0.6 V (vs. Ag/AgCl) in 0.1 mol/L phosphate buffer (pH 6.5) solution was apparently diminished by the addition of E. coli samples, due to the decomposition of H2O2 by intrinsic catalase activity of E. coli. The time-dependent decrease in current (-AI/At) was significantly dependent on the E. coli concentration. The -AI/At was enhanced by the permeabilization pretreatment of E. coli samples with the mixed solution of polymyxin B and lysozyme. This H2O2-selective organic/inorganic-hybrid sol-gel film-modified platinum (Pt) wire electrode allowed quantitative determination of E. coli concentration ranging from 10(6) to 10(9) CFU/mL within 30 min. This method required no label and complicated procedure, and allowed rapid, simple and cost-effective quantitative electrochemical determination of catalase-positive bacteria.

Novel PLA modification of organic microcontainers based on ring opening polymerization: synthesis, characterization, biocompatibility and drug loading/release properties.

PubMed

Efthimiadou, E K; Tziveleka, L-A; Bilalis, P; Kordas, G

2012-05-30

In the current study, poly lactic acid (PLA) modified hollow crosslinked poly(hydroxyethyl methacrylate) (PHEMA) microspheres have been prepared, in order to obtain a stimulus-responsive, biocompatible carrier with sustained drug release properties. The synthetical process consisted of the preparation of poly(methacrylic acid)@poly(hydroxyethyl methacrylate-co-N,N'-methylene bis(acrylamide)) microspheres by a two stage distillation-precipitation polymerization technique using 2,2'-azobisisobutyronitrile as initiator. Following core removal, a PLA coating of the microspheres was formed, after ring opening polymerization of DL-lactide, attributing the initiator's role to the active hydroxyl groups of PHEMA. The anticancer drug daunorubicin (DNR) was selected for the study of loading and release behavior of the coated microspheres. The loading capacity of the PLA modified microspheres was found to be four times higher than that of the parent ones (16% compared to 4%). This coated microspherical carrier exhibited a moderate pH responsive drug release behavior due to the pH dependent water uptake of PHEMA, and PLA hydrolysis. The in vitro cytotoxicity of both the parent and the DNR-loaded or empty modified hollow microspheres has been also examined on MCF-7 breast cancer cells. The results showed that although the empty microspheres were moderately cytotoxic, the DNR-loaded microspheres had more potent anti-tumor effect than the free drug. Therefore, the prepared coated microspheres are interesting drug delivery systems. Copyright © 2012 Elsevier B.V. All rights reserved.

Use of vancomycin silica stationary phase in packed capillary electrochromatography I. Enantiomer separation of basic compounds.

PubMed

Desiderio, C; Aturki, Z; Fanali, S

2001-02-01

Chiral separation of basic compounds was achieved by using 75 or 100 microm ID fused-silica capillaries packed with a vanoomycin-modified diol silica stationary phase. The capillary was firstly packed for about 12 cm with a slurry mixture composed of diolsilica (3:1) then with the vancomycin modified diol-silica (3:1) (23 cm), and finally with diol-silica (3:1) for about 2 cm. Frits were prepared by a heating wire at the two ends of the capillary; the detector window was prepared at 8.5 cm from the end of the capillary where vancomycin was not present. The influence of the mobile phase composition (pH and concentration, organic modifier type and concentration) on the velocity of the electroosmotic flow, chiral resolution and enantioselectivity was studied. Good enantiomeric resolution was achieved for atenolol, oxprenolol, propranolol, and venlafaxine using a mobile phase composition of 100 mM ammonium acetate solution (pH 6)/water/acetonitrile (5:5:90 v/v/v) while for terbutaline a mixture of 5:15:80 v/v/v provided the best separations. The use of methanol instead of acetonitrile caused a general increase of enantiomer resolution of the studied compounds together with a reduction of efficiency and detector response. However, the combination of acetonitrile and methanol in the mobile phase (as, e.g., 10% methanol and 80% acetonitrile) allowed to improve the enantiomer resolution with satisfactory detector response.

A Combined Model To Predict the Functionality of the Bacteriocin-Producing Lactobacillus sakei Strain CTC 494

PubMed Central

Leroy, Frédéric; De Vuyst, Luc

2003-01-01

The use of bacteriocin-producing lactic acid bacteria for improved food fermentation processes seems promising. However, lack of fundamental knowledge about the functionality of bacteriocin-producing strains under food fermentation conditions hampers their industrial use. Predictive microbiology or a mathematical estimation of microbial behavior in food ecosystems may help to overcome this problem. In this study, a combined model was developed that was able to estimate, from a given initial situation of temperature, pH, and nutrient availability, the growth and self-inhibition dynamics of a bacteriocin-producing Lactobacillus sakei CTC 494 culture in (modified) MRS broth. Moreover, the drop in pH induced by lactic acid production and the bacteriocin activity toward Listeria as an indicator organism were modeled. Self-inhibition was due to the depletion of nutrients as well as to the production of lactic acid. Lactic acid production resulted in a pH drop, an accumulation of toxic undissociated lactic acid molecules, and a shift in the dissociation degree of the growth-inhibiting buffer components. The model was validated experimentally. PMID:12571034

Effect of pH and complementary ion concentration on nitrate removal using puroliteA400 Resin impregnated Cu in batch system

NASA Astrophysics Data System (ADS)

Turmuzi, M.; Tarigan, Z. N.; Nadapdap, L.; Batubara, F.

2018-02-01

The total nitrogen content in water bodies should be below 50 mg NO3 -/L (11.3 mgN/l) World Health Organization (WHO) 2006. The content of nitrogen exceeding the quality standard threshold will cause damage to the aquatic ecosystem and be carcinogenic to humans. The Purolite A-400 resin will be modified with Cu metal by batch method to see the adsorption allowance of nitrate in synthetic liquid waste with nitrate concentration of 50 mg/l. This study will evaluate the effect of pH and complementary ions on the adsorption process. From the result of the research, the second order pseudo model is the most suitable adsorption kinetics model. For the adsorption isotherms the most suitable model is the Freundlich adsorption isotherm model. The optimum pH conditions were at the range of 8.5. The addition of complementary ions sulfate and phosphate did not show any significant change, but sulfate is the most effective complementary ion with a content of 20 mg/l.

Enantioseparation on cellulose dimethylphenylcarbamate-modified zirconia monolithic columns by reversed-phase capillary electrochromatography.

PubMed

Kumar, Avvaru Praveen; Park, Jung Hag

2010-06-25

This work reports the preparation of monolithic zirconia chiral columns for separation of enantiomeric compounds by capillary electrochromatography (CEC). Using sol-gel technology, a porous monolith having interconnected globular-like structure with through-pores is synthesized in the capillary column as a first step in the synthesis of monolithic zirconia chiral capillary columns. In the second step, the surface of the monolith is modified by coating with cellulose tris(3,5-dimethylphenylcarbamate) (CDMPC) as the chiral stationary phase to obtain a chiral column (CDMPCZM). The process of the preparation of the zirconia monolithic capillary column was investigated by varying the concentrations of the components of the sol solution including polyethylene glycol, water and acetic acid. CDMPCZM is mechanically stable and no bubble formation was detected with the applied current of up to 30 microA. The enantioseparation behavior of the CDMPCZM columns was investigated by separating a set of 10 representative chiral compounds by varying the applied voltage and pH and organic composition of the aqueous organic mobile phases. Copyright 2010 Elsevier B.V. All rights reserved.

Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: a systematic review.

PubMed

Ulrich, Silvia; Schneider, Simon R; Bloch, Konrad E

2017-12-01

Exercise performance is determined by oxygen supply to working muscles and vital organs. In healthy individuals, exercise performance is limited in the hypoxic environment at altitude, when oxygen delivery is diminished due to the reduced alveolar and arterial oxygen partial pressures. In patients with pulmonary hypertension (PH), exercise performance is already reduced near sea level due to impairments of the pulmonary circulation and gas exchange, and, presumably, these limitations are more pronounced at altitude. In studies performed near sea level in healthy subjects, as well as in patients with PH, maximal performance during progressive ramp exercise and endurance of submaximal constant-load exercise were substantially enhanced by breathing oxygen-enriched air. Both in healthy individuals and in PH patients, these improvements were mediated by a better arterial, muscular, and cerebral oxygenation, along with a reduced sympathetic excitation, as suggested by the reduced heart rate and alveolar ventilation at submaximal isoloads, and an improved pulmonary gas exchange efficiency, especially in patients with PH. In summary, in healthy individuals and in patients with PH, alterations in the inspiratory Po 2 by exposure to hypobaric hypoxia or normobaric hyperoxia reduce or enhance exercise performance, respectively, by modifying oxygen delivery to the muscles and the brain, by effects on cardiovascular and respiratory control, and by alterations in pulmonary gas exchange. The understanding of these physiological mechanisms helps in counselling individuals planning altitude or air travel and prescribing oxygen therapy to patients with PH.

Phosphorylation of psyllium seed polysaccharide and its characterization.

PubMed

Rao, Monica R P; Warrier, Deepa U; Gaikwad, Snehal R; Shevate, Prachi M

2016-04-01

Psyllium is widely used as a medicinally active natural polysaccharide for treating conditions like constipation, diarrhea, and irritable bowel syndrome, inflammatory bowel disease, ulcerative colitis and colon cancer. Studies have been performed to characterize and modify the polysaccharide obtained from psyllium seed husk and to evaluate its use as a pharmaceutical excipient, but no studies have been performed to evaluate the properties of the polysaccharide present in psyllium seeds. The present study focuses on phosphorylation of psyllium seed polysaccharide (PPS) using sodium tri-meta phosphate as the cross-linking agent. The modified phosphorylated psyllium seed polysaccharide was then evaluated for physicochemical properties, rheological properties, spectral analysis, thermal analysis, crosslinking density and acute oral toxicity studies. The modified polysaccharide (PhPPS) has a high swelling index due to which it can be categorized as a hydrogel. The percent increase in swelling of PhPPS as compared to PPS was found to be 90.26%. The PPS & PhPPS mucilages of all strengths were found to have shear thinning properties. These findings are suggestive of the potential use of PhPPS as gelling & suspending agent. PhPPS was found to have a mucoadhesive property which was comparable with carbopol. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of a composite chiral stationary phase from BSA and β-cyclodextrin-bonded silica.

PubMed

Yao, Bixia; Yang, Xinmei; Guo, Lizhen; Kang, Shanshan; Weng, Wen

2014-01-01

A composite chiral stationary phase (CSP) derived from bovine serum albumin (BSA) and β-cyclodextrin (CD)-bonded silica was prepared. 2,4,6-Trichloro-1,3,5-triazine was used as a cross-linker. The obtained CSP was applied to the enantioseparation of tryptophan, hydrobenzoin, phenylalanine and mandelic acid. The influences of eluent pH value, organic modifier and column temperature on the retention and enantioseparation were discussed. Tryptophan and hydrobenzoin achieved excellent resolution on the composite CSP. For tryptophan, the highest selectivity, 2.79, was achieved with 1% of methanol at pH 8.0. For hydrobenzoin, the selectivity could reach 1.42. The chromatographic results were compared with that on β-CD-bonded or BSA-immobilized CSP. © The Author [2014]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Evaluation of Removal Mechanisms in a Graphene Oxide-Coated Ceramic Ultrafiltration Membrane for Retention of Natural Organic Matter, Pharmaceuticals, and Inorganic Salts.

PubMed

Chu, Kyoung Hoon; Fathizadeh, Mahdi; Yu, Miao; Flora, Joseph R V; Jang, Am; Jang, Min; Park, Chang Min; Yoo, Sung Soo; Her, Namguk; Yoon, Yeomin

2017-11-22

Functionalized graphene oxide (GO), derived from pure graphite via the modified Hummer method, was used to modify commercially available ceramic ultrafiltration membranes using the vacuum method. The modified ceramic membrane functionalized with GO (ceramic GO ) was characterized using a variety of analysis techniques and exhibited higher hydrophilicity and increased negative charge compared with the pristine ceramic membrane. Although the pure water permeability of the ceramic GO membrane (14.4-58.6 L/m 2 h/bar) was slightly lower than that of the pristine membrane (25.1-62.7 L/m 2 h/bar), the removal efficiencies associated with hydrophobic attraction and charge effects were improved significantly after GO coating. Additionally, solute transport in the GO nanosheets of the ceramic GO membrane played a vital role in the retention of target compounds: natural organic matter (NOM; humic acid and tannic acid), pharmaceuticals (ibuprofen and sulfamethoxazole), and inorganic salts (NaCl, Na 2 SO 4 , CaCl 2 , and CaSO 4 ). While the retention efficiencies of NOM, pharmaceuticals, and inorganic salts in the pristine membrane were 74.6%, 15.3%, and 2.9%, respectively, these increased to 93.5%, 51.0%, and 31.4% for the ceramic GO membrane. Consequently, the improved removal mechanisms of the membrane modified with functionalized GO nanosheets can provide efficient retention for water treatment under suboptimal environmental conditions of pH and ionic strength.

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.

[The construction of cell-penetrating peptide R8 and pH sensitive cleavable polyethylene glycols co-modified liposomes].

PubMed

Zhang, Li; Wang, Yang; Gao, Hui-le; He, Qin

2015-06-01

The purpose of the study is to construct R8 peptide (RRRRRRRR) and pH sensitive polyethylene glycols (PEG) co-modified liposomes (Cl-Lip) and utilize them in breast cancer treatment. The co-modified liposomes were prepared with soybean phospholipid, cholesterol, DSPE-PEG2K-R8 and PEG5K-Hz-PE (pH sensitive PEG). The size and zeta potential of Cl-Lip were also characterized. The in vitro experiment demonstrated that the Cl-Lip had high serum stability in 50% fetal bovine serum. The cellular uptake of Cl-Lip under different pre-incubated conditions was evaluated on 4T1 cells. And the endocytosis pathway, lysosome escape ability and tumor spheroid penetration ability were also evaluated. The results showed the particle size of the Cl-Lip was (110.4 ± 5.2) nm, PDI of the Cl-Lip was 0.207 ± 0.039 and zeta potential of the Cl-Lip was (-3.46 ± 0.05) mV. The cellular uptake of Cl-Lip on 4T1 cells was pH sensitive, as the cellular uptake of Cl-Lip pre-incubated in pH 6.0 was higher than that of pH 7.4 under each time point. The main endocytosis pathways of Cl-Lip under pH 6.0 were micropinocytosis and energy-dependent pathway. At the same time, the Cl-Lip with pre-incubation in pH 6.0 had high lysosome escape ability and high tumor spheroid penetration ability. All the above results demonstrated that the Cl-Lip we constructed had high pH sensitivity and is a promising drug delivery system.

Assessment of possible solid-phase phosphate sorbents to mitigate eutrophication: Influence of pH and anoxia.

PubMed

Mucci, Maíra; Maliaka, Valentini; Noyma, Natalia Pessoa; Marinho, Marcelo Manzi; Lürling, Miquel

2018-04-01

Managing eutrophication remains a challenge to water managers. Currently, the manipulation of biogeochemical processes (i.e., geo-engineering) by using phosphorus-adsorptive techniques has been recognized as an appropriate tool to manage the problem. The first step in finding potential mitigating materials is conducting a sequence of upscaling studies that commence with controlled laboratory experiments. Here, the abilities of 10 possible solid-phase-sorbents (SPS) to adsorb P were examined. Four materials adsorbed P, and two of these materials were modified, i.e., a lanthanum-modified-bentonite (LMB) and an aluminum-modified-zeolite (AMZ), and had the highest adsorption capacities of 11.4 and 8.9mgPg -1 , respectively. Two natural materials, a red soil (RS) and a bauxite (BAU), were less efficient with adsorption capacities of 2.9 and 3.4mgPg -1 , respectively. Elemental composition was not related to P adsorption. Since SPS might be affected by pH and redox status, we also tested these materials at pH values of 6, 7, 8 and 9 and under anoxic condition. All tested materials experienced decreased adsorption capacities under anoxic condition, with maximum adsorptions of 5.3mgPg -1 for LMB, 5.9mgPg -1 for AMZ, 0.2mgPg -1 for RS and 0.2mgPg -1 for BAU. All materials were able to adsorb P across the range of pH values that were tested. The maximum adsorption capacities of LMB and RS were highest at pH6, AMZ was higher at a pH of 9 and BAU at a pH of 8. Thus, pH influenced P adsorption differently. Given the effects of pH and anoxia, other abiotic variables should also be considered. Considering the criteria that classify a useful SPS (i.e., effective, easy to produce, cheap and safe), only the two modified materials that were tested seem to be suitable for upscaling to enclosure studies with anoxic sediments. Copyright © 2017 Elsevier B.V. All rights reserved.

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.

Human sweet taste receptor mediates acid-induced sweetness of miraculin

PubMed Central

Koizumi, Ayako; Tsuchiya, Asami; Nakajima, Ken-ichiro; Ito, Keisuke; Terada, Tohru; Shimizu-Ibuka, Akiko; Briand, Loïc; Asakura, Tomiko; Misaka, Takumi; Abe, Keiko

2011-01-01

Miraculin (MCL) is a homodimeric protein isolated from the red berries of Richadella dulcifica. MCL, although flat in taste at neutral pH, has taste-modifying activity to convert sour stimuli to sweetness. Once MCL is held on the tongue, strong sweetness is sensed over 1 h each time we taste a sour solution. Nevertheless, no molecular mechanism underlying the taste-modifying activity has been clarified. In this study, we succeeded in quantitatively evaluating the acid-induced sweetness of MCL using a cell-based assay system and found that MCL activated hT1R2-hT1R3 pH-dependently as the pH decreased from 6.5 to 4.8, and that the receptor activation occurred every time an acid solution was applied. Although MCL per se is sensory-inactive at pH 6.7 or higher, it suppressed the response of hT1R2-hT1R3 to other sweeteners at neutral pH and enhanced the response at weakly acidic pH. Using human/mouse chimeric receptors and molecular modeling, we revealed that the amino-terminal domain of hT1R2 is required for the response to MCL. Our data suggest that MCL binds hT1R2-hT1R3 as an antagonist at neutral pH and functionally changes into an agonist at acidic pH, and we conclude this may cause its taste-modifying activity. PMID:21949380

Performance and stability of an expanded granular sludge bed reactor modified with zeolite addition subjected to step increases of organic loading rate (OLR) and to organic shock load (OSL).

PubMed

Pérez-Pérez, T; Pereda-Reyes, I; Pozzi, E; Oliva-Merencio, D; Zaiat, M

2018-01-01

This paper shows the effect of organic shock loads (OSLs) on the anaerobic digestion (AD) of synthetic swine wastewater using an expanded granular sludge bed (EGSB) reactor modified with zeolite. Two reactors (R1 and R2), each with an effective volume of 3.04 L, were operated for 180 days at a controlled temperature of 30 °C and hydraulic retention time of 12 h. In the case of R2, 120 g of zeolite was added. The reactors were operated with an up-flow velocity of 6 m/h. The evolution of pH, total Kjeldahl nitrogen, chemical oxygen demand (COD) and volatile fatty acids (VFAs) was monitored during the AD process with OSL and increases in the organic loading rate (OLR). In addition, the microbial composition and changes in the structure of the bacterial and archaeal communities were assessed. The principal results demonstrate that the presence of zeolite in an EGSB reactor provides a more stable process at higher OLRs and after applying OSL, based on both COD and VFA accumulation, which presented with significant differences compared to the control. Denaturing gradient gel electrophoresis band profiles indicated differences in the populations of Bacteria and Archaea between the R1 and R2 reactors, attributed to the presence of zeolite.

Equilibrium, Kinetic, and Thermodynamic Studies on the Adsorption of Cadmium from Aqueous Solution by Modified Biomass Ash

PubMed Central

Zheng, Xuebo; Cui, Hongbiao; Zhu, Zhenqiu; Liang, Jiani

2017-01-01

Natural biomass ash of agricultural residuals was collected from a power plant and modified with hexagonal mesoporous silica and functionalized with 3-aminopropyltriethoxysilane. The physicochemical and morphological properties of the biomass ash were analyzed by ICP-OES, SEM, TEM-EDS, FTIR, and BET analysis. The adsorption behavior of the modified product for Cd2+ in aqueous solution was studied as a function of pH, initial metal concentration, equilibrium time, and temperature. Results showed that the specific surface area of the modified product was 9 times that of the natural biomass ash. The modified biomass ash exhibited high affinity for Cd2+ and its adsorption capacity increased sharply with increasing pH from 4.0 to 6.0. The maximum adsorption capacity was 23.95 mg/g in a pH 5 solution with an initial metal concentration of 50 mg/L and a contact time of 90 min. The adsorption of Cd2+ onto the modified biomass ash was well fitted to the Langmuir model and it followed pseudo-second-order kinetics. Thermodynamic analysis results showed that the adsorption of Cd2+ was spontaneous and endothermic in nature. The results suggest that the modified biomass ash is promising for use as an inexpensive and effective adsorbent for Cd2+ removal from aqueous solution. PMID:28348509

Direct Estimation of Local pH Change at Infection Sites of Fungi in Potato Tubers.

PubMed

Tardi-Ovadia, R; Linker, R; Tsror Lahkim, L

2017-01-01

Fungi can modify the pH in or around the infected site via alkalization or acidification, and pH monitoring may provide valuable information on host-fungus interactions. The objective of the present study was to examine the ability of two fungi, Colletotrichum coccodes and Helminthosporium solani, to modify the pH of potato tubers during artificial inoculation in situ. Both fungi cause blemishes on potato tubers, which downgrades tuber quality and yield. Direct visualization and estimation of pH changes near the inoculation area were achieved using pH indicators and image analysis. The results showed that the pH of the area infected by either fungus increased from potato native pH of approximately 6.0 to 7.4 to 8.0. By performing simple analysis of the images, it was also possible to derive the growth curve of each fungus and estimate the lag phase of the radial growth: 10 days for C. coccodes and 17 days H. solani. In addition, a distinctive halo (an edge area with increased pH) was observed only during the lag phase of H. solani infection. pH modulation is a major factor in pathogen-host interaction and the proposed method offers a simple and rapid way to monitor these changes.

Photoautotrophic Production of Biomass, Laurate, and Soluble Organics by Synechocystis sp. PCC 6803

NASA Astrophysics Data System (ADS)

Nguyen, Binh Thanh

Photosynthesis converts sunlight to biomass at a global scale. Among the photosynthetic organisms, cyanobacteria provide an excellent model to study how photosynthesis can become a practical platform of large-scale biotechnology. One novel approach involves metabolically engineering the cyanobacterium Synechocystis sp. PCC 6803 to excrete laurate, which is harvested directly. This work begins by defining a working window of light intensity (LI). Wild-type and laurate-excreting Synechocystis required an LI of at least 5 muE/m2-s to sustain themselves, but are photo-inhibited by LI of 346 to 598 muE/m2-s. Fixing electrons into valuable organic products, e.g., biomass and excreted laurate, is critical to success. Wild-type Synechocystis channeled 75% to 84% of its fixed electrons to biomass; laurate-excreting Synechocystis fixed 64 to 69% as biomass and 6.6% to 10% as laurate. This means that 16 to 30% of the electrons were diverted to non-valuable soluble products, and the trend was accentuated with higher LI. How the Ci concentration depended on the pH and the nitrogen source was quantified by the proton condition and experimentally validated. Nitrate increased, ammonium decreased, but ammonium nitrate stabilized alkalinity and Ci. This finding provides a mechanistically sound tool to manage Ci and pH independently. Independent evaluation pH and Ci on the growth kinetics of Synechocystis showed that pH 8.5 supported the fastest maximum specific growth rate (mumax): 2.4/day and 1.7/day, respectively, for the wild type and modified strains with LI of 202 muE/m2-s. Half-maximum-rate concentrations (KCi) were less than 0.1 mM, meaning that Synechocystis should attain its mumax with a modest Ci concentration (≥1.0 mM). Biomass grown with day-night cycles had a night endogenous decay rate of 0.05-1.0/day, with decay being faster with higher LI and the beginning of dark periods. Supplying light at a fraction of daylight reduced dark decay rate and improved overall biomass productivity. This dissertation systematically evaluates and synthesizes fundamental growth factors of cyanobacteria: light, inorganic carbon (Ci), and pH. LI remains the most critical growth condition to promote biomass productivity and desired forms of biomass, while Ci and pH now can be managed to support optimal productivity.

Comparison of leaching characteristics of heavy metals in APC residue from an MSW incinerator using various extraction methods.

PubMed

Chiang, Kung-Yuh; Tsai, Chen-Chiu; Wang, Kuen-Sheng

2009-01-01

This study investigates four extraction methods (water extraction, toxicity characteristics leaching procedure (TCLP), modified TCLP with pH control, and sequential chemical extraction (SCE)), each representing different liquid-to-solid (L/S) ratios, pH controls, and types of leachant, and their effects on the leaching concentration of heavy metals in municipal solid waste (MSW) incinerator air pollution control (APC) residue. The results indicated that for extraction with distilled water, the heavy metal leaching concentration (mg/l) decreased with L/S ratio, but the amount of heavy metal released (AHMR), defined as the leached amount of heavy metals to the weight of the tested sample (mg/kg), increased with an increase in L/S ratio, in the range of 2-100. The results also showed that both the leaching concentration and the amount of released metals were strongly pH-dependent in the TCLP and modified TCLP tests. In the case of pHs lower than 6.5, the leaching concentrations of Cd, Pb, Cu, Zn, and Cr decreased with an increase in pH. As pH increased higher than 6.5, Cr and Zn were almost insoluble. Meanwhile, Cd and Cu also showed a similar trend but at pHs of 8.5 and 7.5, respectively. Due to the nature of amphoteric elements, in the case of pHs higher than 7, the Pb leaching concentration increased with increasing pH. In modified TCLP tests with the pH value controlled at the same level as in the SCE test, the heavy metal speciation approached the extractable carbonate bound fraction by the SCE. Both amounts of targeted metals leached from the SCE and modified TCLP tests were much higher than those for the regular TCLP and water extraction tests.

Aluminium Uptake and Translocation in Al Hyperaccumulator Rumex obtusifolius Is Affected by Low-Molecular-Weight Organic Acids Content and Soil pH

PubMed Central

Vondráčková, Stanislava; Száková, Jiřina; Drábek, Ondřej; Tejnecký, Václav; Hejcman, Michal; Müllerová, Vladimíra; Tlustoš, Pavel

2015-01-01

Background and Aims High Al resistance of Rumex obtusifolius together with its ability to accumulate Al has never been studied in weakly acidic conditions (pH > 5.8) and is not sufficiently described in real soil conditions. The potential elucidation of the role of organic acids in plant can explain the Al tolerance mechanism. Methods We established a pot experiment with R. obtusifolius planted in slightly acidic and alkaline soils. For the manipulation of Al availability, both soils were untreated and treated by lime and superphosphate. We determined mobile Al concentrations in soils and concentrations of Al and organic acids in organs. Results Al availability correlated positively to the extraction of organic acids (citric acid < oxalic acid) in soils. Monovalent Al cations were the most abundant mobile Al forms with positive charge in soils. Liming and superphosphate application were ambiguous measures for changing Al mobility in soils. Elevated transport of total Al from belowground organs into leaves was recorded in both lime-treated soils and in superphosphate-treated alkaline soil as a result of sufficient amount of Ca available from soil solution as well as from superphosphate that can probably modify distribution of total Al in R. obtusifolius as a representative of “oxalate plants.” The highest concentrations of Al and organic acids were recorded in the leaves, followed by the stem and belowground organ infusions. Conclusions In alkaline soil, R. obtusifolius is an Al-hyperaccumulator with the highest concentrations of oxalate in leaves, of malate in stems, and of citrate in belowground organs. These organic acids form strong complexes with Al that can play a key role in internal Al tolerance but the used methods did not allow us to distinguish the proportion of total Al-organic complexes to the free organic acids. PMID:25880431

Photo-Fenton and modified photo-Fenton at neutral pH for the treatment of emerging contaminants in wastewater treatment plant effluents: a comparison.

PubMed

Klamerth, N; Malato, S; Agüera, A; Fernández-Alba, A

2013-02-01

This study compares two different solar photo-Fenton processes, conventional photo-Fenton at pH3 and modified photo-Fenton at neutral pH with minimal Fe (5 mg L⁻¹) and minimal initial H₂O₂ (50 mg L⁻¹) concentrations for the degradation of emerging contaminants in Municipal Wastewater Treatment Plants effluents in solar pilot plant. As Fe precipitates at neutral pH, complexing agents which are able to form photoactive species, do not pollute the environment or increase toxicity have to be used to keep the iron in solution. This study was done using real effluents containing over 60 different contaminants, which were monitored during treatment by liquid chromatography coupled to a hybrid quadrupole/linear ion trap mass analyzer (LC-QTRAP-MS/MS) operating in selected reaction monitoring (SRM) mode. Concentrations of the selected contaminants ranged from a few ng L⁻¹ to tens of μg L⁻¹. It was demonstrated in all cases the removal of over 95% of the contaminants. Photo-Fenton at pH3 provided the best treatment time, but has the disadvantage that the water must be previously acidified. The most promising process was photo-Fenton modified with Ethylenediamine-N,N'-disuccinic acid (EDDS), as the pH remained in the neutral range. Copyright © 2012 Elsevier Ltd. All rights reserved.

Variation in pH of Model Secondary Organic Aerosol during Liquid-Liquid Phase Separation.

PubMed

Dallemagne, Magda A; Huang, Xiau Ya; Eddingsaas, Nathan C

2016-05-12

The majority of atmospheric aerosols consist of both organic and inorganic components. At intermediate relative humidity (RH), atmospheric aerosol can undergo liquid-liquid phase separation (LLPS) in which the organic and inorganic fractions segregate from each other. We have extended the study of LLPS to the effect that phase separation has on the pH of the overall aerosols and the pH of the individual phases. Using confocal microscopy and pH sensitive dyes, the pH of internally mixed model aerosols consisting of polyethylene glycol 400 and ammonium sulfate as well as the pH of the organic fraction during LLPS have been directly measured. During LLPS, the pH of the organic fraction was observed to increase to 4.2 ± 0.2 from 3.8 ± 0.1 under high RH when the aerosol was internally mixed. In addition, the high spatial resolution of the confocal microscope allowed us to characterize the composition of each of the phases, and we have observed that during LLPS the organic shell still contains large quantities of water and should be characterized as an aqueous organic-rich phase rather than simply an organic phase.

Potency determination of factor VIII and factor IX for new product labelling and postinfusion testing: challenges for caregivers and regulators.

PubMed

Dodt, J; Hubbard, A R; Wicks, S J; Gray, E; Neugebauer, B; Charton, E; Silvester, G

2015-07-01

A workshop organized by the European Medicines Agency and the European Directorate for the Quality of Medicines and HealthCare was held in London, UK on November 28-29, 2013, to provide an overview of the current knowledge of the characterization of new factor VIII (FVIII) and factor IX (FIX) concentrates with respect to potency assays and testing of postinfusion material. The objective was to set the basis for regulatory authorities' discussion on the most appropriate potency assay for the individual products, and European Pharmacopoeia (Ph. Eur.) discussion on whether to propose revision of the Ph. Eur. monographs with respect to potency assays in the light of information on new FVIII and FIX concentrates. The workshop showed that for all products valid assays vs. the international concentrate standards were obtained and potency could be expressed in International Units. The Ph. Eur. chromogenic potency assay gave valid assay results which correlate with in vivo functionality of rFVIII products. For some modified rFVIII products and all modified rFIX products, one-stage clotting assay methods result in different potencies depending on the activated partial thromboplastin time reagent. As a consequence, monitoring of patients' postinfusion levels is challenging but it was pointed out that manufacturers are responsible for providing the users with appropriate information for use and laboratory testing of their product. Strategies to avoid misleading determination of patents' plasma levels, e.g. information on suitable assays, laboratory standards or correction factors were discussed. © 2015 John Wiley & Sons Ltd.

Micellar liquid chromatography

NASA Astrophysics Data System (ADS)

Basova, Elena M.; Ivanov, Vadim M.; Shpigun, Oleg A.

1999-12-01

Background and possibilities of practical applications of micellar liquid chromatography (MLC) are considered. Various retention models in MLC, the effects of the nature and concentration of surfactants and organic modifiers, pH, temperature and ionic strength on the MLC efficiency and selectivity are discussed. The advantages and limitations of MLC are demonstrated. The performance of MLC is critically evaluated in relationship to the reversed-phase HPLC and ion-pair chromatography. The potential of application of MLC for the analysis of pharmaceuticals including that in biological fluids and separation of inorganic anions, transition metal cations, metal chelates and heteropoly compounds is described. The bibliography includes 146 references.

Lipophilicity of a series of 1,2-benzisothiazol-3(2H)-ones determined by reversed-phase thin-layer chromatography.

PubMed

Sławik, Tomasz; Kowalski, Cezary

2002-04-05

The lipophilicity (R(Mo)) and specific hydrophobic surface area of seven 1,2-benzisothiazol-3(2H)-ones have been determined by reversed-phase TLC and the effect of different mobile-phase modifiers (acetone, acetonitrile, methanol) on the retention has been studied. The linear correlations between the volume fraction of the organic solvent and the R(M) values over a limited range were established for each solute with high values of correlation coefficients (>0.99). The influence of solvent pH on R(M) values was investigated.

A liposome-based antigen delivery system using pH-sensitive fusogenic polymers for cancer immunotherapy.

PubMed

Yuba, Eiji; Harada, Atsushi; Sakanishi, Yuichi; Watarai, Shinobu; Kono, Kenji

2013-04-01

Highly pH-sensitive liposomes that deliver antigenic molecules into cytosol through fusion with or destabilization of endosome were prepared by surface modification of egg yolk phosphatidylcholine/dioleoylphosphatidylethanolamine (1/1, mol/mol) liposomes with 3-methylglutarylated poly(glycidol) of linear (MGlu-LPG) or hyperbranched structure (MGlu-HPG). These polymer-modified liposomes were stable at neutral pH, but they became strongly destabilized below pH 6, which corresponds to the pH of endosome. These polymer-modified liposomes were taken up by murine dendritic cells (DCs) more efficiently than the unmodified liposomes were through an endocytic pathway. They introduced entrapped ovalbumin (OVA) molecules into cytosol. Subcutaneous or nasal administration of the polymer-modified liposomes loaded with OVA induced generation of OVA-specific cytotoxic T cells (CTL) much more effectively than the unmodified liposomes loaded with OVA. Furthermore, administration of the polymer-modified OVA-loaded liposomes to mice bearing E.G7-OVA tumor significantly reduced the tumor burden, although the OVA-loaded unmodified liposomes only slightly affected tumor growth. Results suggest that the polymer-modified liposomes with highly pH-sensitive destabilizing property are promising as antigen carriers for efficient cancer immunotherapy. Copyright © 2012 Elsevier Ltd. All rights reserved.

Effect of lipase immobilization on resolution of (R, S)-2-octanol in nonaqueous media using modified ultrastable-Y molecular sieve as support.

PubMed

Dai, Dazhang; Xia, Liming

2006-07-01

The lipase from Penicillium expansum PED-03 (PEL) was immobilized onto modified ultrastable-Y (USY) molecular sieve and the resolution of (R, S)- 2-octanol was carried out in a bioreactor in nonaqueous media by the immobilized lipase. It was found that the conversion rate, enantiomeric excess (ee) value, and enantioselectivity (E) value of the resolution catalyzed by PEL immobilized on modified USY molecular sieve were much higher than those of the reaction catalyzed by free PEL and PEL immobilized on other supports. Immobilized on modified USY molecular sieve, the PEL exhibited obvious activity within a wider pH range and at a much higher temperature and showed a markedly enhanced stability against thermal inactivation, by which the suitable pH of the buffer used for immobilization could be "memorized." The conversion rate of the reaction catalyzed by PEL immobilized on modified USY molecular sieve reached 48.84%, with excellent enantioselectivity (average E value of eight batches >460) in nonaqueous media at "memorial" pH 9.5, 50 degrees C for 24 h, demonstrating a good application potential in the production of optically pure (R, S)-2-octanol.

Modeling CO2 degassing and pH in a stream-aquifer system

USGS Publications Warehouse

Choi, J.; Hulseapple, S.M.; Conklin, M.H.; Harvey, J.W.

1998-01-01

Pinal Creek, Arizona receives an inflow of ground water with high dissolved inorganic carbon (57-75 mg/l) and low pH (5.8-6.3). There is an observed increase of in-stream pH from approximately 6.0-7.8 over the 3 km downstream of the point of groundwater inflow. We hypothesized that CO2 gas-exchange was the most important factor causing the pH increase in this stream-aquifer system. An existing transport model, for coupled ground water-surface water systems (OTIS), was modified to include carbonate equilibria and CO2 degassing, used to simulate alkalinity, total dissolved inorganic carbon (C(T)), and pH in Pinal Creek. Because of the non-linear relation between pH and C(T), the modified transport model used the numerical iteration method to solve the non-linearity. The transport model parameters were determined by the injection of two tracers, bromide and propane. The resulting simulations of alkalinity, C(T) and pH reproduced, without fitting, the overall trends in downstream concentrations. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that C(T) and pH in stream water were controlled by the mixing of ground water with stream water and CO2 degassing. The relative importance of these two processes varied spatially depending on the hydrologic conditions, such as stream flow velocity and whether a reach gained or lost stream water caused by the interaction with the ground water. The coupled transport model with CO2 degassing and generalized sensitivity analysis presented in this study can be applied to evaluate carbon transport and pH in other coupled stream-ground water systems.An existing transport model for coupled groundwater-surface water systems was modified to include carbonate equilibria and CO2 degassing. The modified model was used to simulate alkalinity, total dissolved inorganic carbon (CT) and pH in Pinal Creek. The model used the numerical iteration method to solve the nonlinear relation between pH and CT. A multi-parametric sensitivity analysis (MPSA) was used to identify the relative sensitivities of the predictions to six of the physical and chemical parameters used in the transport model. MPSA results implied that CT and pH in the stream water were controlled by the mixing of groundwater with stream water and CO2 degassing.

Natural organic matter (NOM) adsorption to multi-walled carbon nanotubes: effect of NOM characteristics and water quality parameters.

PubMed

Hyung, Hoon; Kim, Jae-Hong

2008-06-15

The effect of natural organic matter (NOM) characteristics and water quality parameters on NOM adsorption to multiwalled carbon nanotubes (MWNT) was investigated. Isotherm experiment results were fitted well with a modified Freundlich isotherm model that took into account the heterogeneous nature of NOM. The preferential adsorption of the higher molecular weight fraction of NOM was observed by size exclusion chromatographic analysis. Experiments performed with various NOM samples suggested that the degree of NOM adsorption varied greatly depending on the type of NOM and was proportional to the aromatic carbon content of NOM. The NOM adsorption to MWNT was also dependent on water quality parameters: adsorption increased as pH decreased and ionic strength increased. As a result of NOM adsorption to MWNT, a fraction of MWNT formed a stable suspension in water and the concentration of MWNT suspension depended on the amount of NOM adsorbed per unit mass of MWNT. The amount of MWNT suspended in water was also affected by ionic strength and pH. The findings in this study suggested that the fate and transport of MWNT in natural systems would be largely influenced by NOM characteristics and water quality parameters.

Review on State-of-the-art in Polymer Based pH Sensors

PubMed Central

Korostynska, Olga; Arshak, Khalil; Gill, Edric; Arshak, Arousian

2007-01-01

This paper reviews current state-of-the-art methods of measuring pH levels that are based on polymer materials. These include polymer-coated fibre optic sensors, devices with electrodes modified with pH-sensitive polymers, fluorescent pH indicators, potentiometric pH sensors as well as sensors that use combinatory approach for ion concentration monitoring. PMID:28903277

Gold Binding by Native and Chemically Modified Hops Biomasses

PubMed Central

López, M. Laura; Peralta-Videa, J. R.; de la Rosa, G.; Armendáriz, V.; Herrera, I.; Troiani, H.; Henning, J.

2005-01-01

Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass (Humulus lupulus) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage binding at pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively. PMID:18365087

Hydrophilic interaction liquid chromatography in the speciation analysis of selenium.

PubMed

Sentkowska, Aleksandra; Pyrzynska, Krystyna

2018-02-01

The hydrophilic interaction liquid chromatography (HILIC) coupled to mass spectrometry was employed to study retention behavior of selected selenium compounds using two different HILIC stationary phases: silica and zwitterionic. Two organic solvents - acetonitrile and methanol - were compared as a component of mobile phase. Separation parameters such as a content of organic modifier, the eluent pH and inorganic buffer concentration were investigated. Based on all observations, methanol seems to be beneficial for the separation of studied compounds. The optimal HILIC separation method involved silica column and eluent composed of 85% MeOH and CH 3 COONH 4 (8 mM, pH 7) was compared to RP method in terms of time of the single run, the separation efficiency and limit of detection. Copyright © 2018 Elsevier B.V. All rights reserved.

Ordered cubic nanoporous silica support MCM-48 for delivery of poorly soluble drug indomethacin

NASA Astrophysics Data System (ADS)

Zeleňák, Vladimír; Halamová, Dáša; Almáši, Miroslav; Žid, Lukáš; Zeleňáková, Adriána; Kapusta, Ondrej

2018-06-01

Ordered MCM-48 nanoporous silica (SBET = 923(3) m2·g-1, VP = 0.63(2) cm3·g-1) with cubic Ia3d symmetry was used as a support for drug delivery of anti-inflammatory poorly soluble drug indomethacin. The delivery from parent, unmodified MCM-48, and 3-aminopropyl modified silica carrier was studied into the simulated body fluids with the pH = 2 and pH = 7.4. The studied samples were characterized by thermal analysis (TG/DTG-DTA), N2 adsorption/desorption, infrared spectroscopy (FT-IR), powder XRD, SEM, HRTEM methods, measurements of zeta potential (ζ) and dynamic light scattering (DLS). The determined content of indomethacin in pure MCM-48 was 21 wt.% and in the amine-modified silica MCM-48A-I the content was 45 wt.%. The release profile of the drug, in the time period up to 72 h, was monitored by TLC chromatographic method. It as shown, that by the modification of the surface, the drug release can be controlled. The slower release of indomethacin was observed from amino modified sample MCM-48A-I in the both types of studied simulated body fluids (slightly alkaline intravenous solution with pH = 7.4 and acidic gastric fluid with pH = 2), which was supported and explained by zeta potential and DLS measurements. The amount of the released indomethacin into the fluids with various pH was different. The maximum released amount of the drug was 97% for sample containing unmodified silica, MCM-48-I at pH = 7.4 and lowest released amount, 57%, for amine modified sample MCM-48A-I at pH = 2. To compare the indomethacin release profile four kinetic models were tested. Results showed, that that the drug release based on diffusion Higuchi model, mainly governs the release.

Magnetorheological finishing of chemical-vapor deposited zinc sulfide via chemically and mechanically modified fluids

DOE PAGES

Salzman, Sivan; Romanofsky, Henry J.; Giannechini, Lucca J.; ...

2016-02-19

In this study, we describe the anisotropy in the material removal rate (MRR) of the polycrystalline, chemical-vapor deposited zinc sulfide (ZnS).We define the polycrystalline anisotropy via microhardness and chemical erosion tests for four crystallographic orientations of ZnS: (100), (110), (111), and (311). Anisotropy in the MRR was studied under magnetorheological finishing (MRF) conditions. Three chemically and mechanically modified magnetorheological (MR) fluids at pH values of 4, 5, and 6 were used to test the MRR variations among the four single-crystal planes. When polishing the single-crystal planes and the polycrystalline with pH 5 and pH 6MR fluids, variations were found inmore » the MRR among the four single-crystal planes and surface artifacts were observed on the polycrystalline material. When polishing the single-crystal planes and the polycrystalline with the modified MR fluid at pH 4, however, minimal variation was observed in the MRR among the four orientations and a reduction in surface artifacts was achieved on the polycrystalline material.« less

Modifying and reacting to the environmental pH can drive bacterial interactions

PubMed Central

Ratzke, Christoph

2018-01-01

Microbes usually exist in communities consisting of myriad different but interacting species. These interactions are typically mediated through environmental modifications; microbes change the environment by taking up resources and excreting metabolites, which affects the growth of both themselves and also other microbes. We show here that the way microbes modify their environment and react to it sets the interactions within single-species populations and also between different species. A very common environmental modification is a change of the environmental pH. We find experimentally that these pH changes create feedback loops that can determine the fate of bacterial populations; they can either facilitate or inhibit growth, and in extreme cases will cause extinction of the bacterial population. Understanding how single species change the pH and react to these changes allowed us to estimate their pairwise interaction outcomes. Those interactions lead to a set of generic interaction motifs—bistability, successive growth, extended suicide, and stabilization—that may be independent of which environmental parameter is modified and thus may reoccur in different microbial systems. PMID:29538378

[Differential Effect and Mechanism of in situ Immobilization of Cadmium Contamination in Soil Using Diatomite Produced from Different Areas].

PubMed

Zhu, Jian; Wang, Ping; Lin, Yan; Lei, Ming-jing; Chen, Yang

2016-02-15

In order to understand the difference of in situ immobilization effect and mechanism of Cd contamination in soil using diatomite produced from different areas, the test was conducted using diatomite produced from Yunnan Tengchong, Jilin Linjiang, Zhejiang Shengzhou and Henan Xinyang of China as modifiers to immobilize cadmium contamination in simulated soil. The results indicated that the diatomite from all the four producing areas could effectively immobilize available Cd in soil, decreasing the available Cd content in soil by 27.7%, 28.5%, 30.1% and 57.2%, respectively when the adding concentration was 30 g x kg(-1). Their ability for immobilizing available Cd in soil followed the sequence of Henan Xinyang > Zhejiang Shengzhou > Jilin Linjiang > Yunnan Tengchong. It was also found that the physical and chemical properties of diatomite played a main role in soil cadmium immobilization, lower bulk density, larger specific surface area, more micro pores and wider distribution range of aperture were more favorable for available Cd immobilization. The results also showed that, the diatomite could control Cd contamination by changing soil physical and chemical properties, among these properties, pH and organic matter content were the key factors, increasing soil pH value and organic matter content was favorable for available cadmium immobilization, while the soil water content had little effect on available cadmium immobilization. The control of soil cadmium contamination by using diatomite to change cation exchange capacity was limited by time in some degree. The diatomite produced from Henan Xinyang, Zhejiang Shengzhou and Yunnan Tengchong increased the soil pH value and organic matter content, and was favorable for available Cd immobilization, while the diatomite from Jilin Linjiang showed converse effect.

Use of modified diatomaceous earth for removal and recovery of viruses in water.

PubMed Central

Farrah, S R; Preston, D R; Toranzos, G A; Girard, M; Erdos, G A; Vasuhdivan, V

1991-01-01

Diatomaceous earth was modified by in situ precipitation of metallic hydroxides. Modification decreased the negative charge on the diatomaceous earth and increased its ability to adsorb viruses in water. Electrostatic interactions were more important than hydrophobic interactions in virus adsorption to modified diatomaceous earth. Filters containing diatomaceous earth modified by in situ precipitation of a combination of ferric chloride and aluminum chloride adsorbed greater than 80% of enteroviruses (poliovirus 1, echovirus 5, and coxsackievirus B5) and coliphage MS2 present in tap water at ambient pH (7.8 to 8.3), even after filtration of 100 liters of tap water. Viruses adsorbed to the filters could be recovered by mixing the modified diatomaceous earth with 3% beef extract plus 1 M NaCl (pH 9). Images PMID:1768124

PH adjustment of power plant cooling water with flue gas/fly ash

DOEpatents

Brady, Patrick V.; Krumhansl, James L.

2015-09-22

A system including a vessel including a heat source and a flue; a turbine; a condenser; a fluid conduit circuit disposed between the vessel, the turbine and the condenser; and a diverter coupled to the flue to direct a portion of an exhaust from the flue to contact with a cooling medium for the condenser water. A method including diverting a portion of exhaust from a flue of a vessel; modifying the pH of a cooling medium for a condenser with the portion of exhaust; and condensing heated fluid from the vessel with the pH modified cooling medium.

Pilot scale test of a produced water-treatment system for initial removal of organic compounds

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

Sullivan, Enid J; Kwon, Soondong; Katz, Lynn

A pilot-scale test to remove polar and non-polar organics from produced water was performed at a disposal facility in Farmington NM. We used surfactant-modified zeolite (SMZ) adsorbent beds and a membrane bioreactor (MBR) in combination to reduce the organic carbon content of produced water prior to reverse osmosis (RO). Reduction of total influent organic carbon (TOC) to 5 mg/L or less is desirable for efficient RO system operation. Most water disposed at the facility is from coal-bed gas production, with oil production waters intermixed. Up to 20 gal/d of produced water was cycled through two SMZ adsorbent units to removemore » volatile organic compounds (BTEX, acetone) and semivolatile organic compounds (e.g., napthalene). Output water from the SMZ units was sent to the MBR for removal of the organic acid component of TOC. Removal of inorganic (Mn and Fe oxide) particulates by the SMZ system was observed. The SMZ columns removed up to 40% of the influent TOC (600 mg/L). BTEX concentrations were reduced from the initial input of 70 mg/L to 5 mg/L by the SMZ and to an average of 2 mg/L after the MBR. Removal rates of acetate (input 120-170 mg/L) and TOC (input up to 45 mg/L) were up to 100% and 92%, respectively. The water pH rose from 8.5 to 8.8 following organic acid removal in the MBR; this relatively high pH was likely responsible for observed scaling of the MBR internal membrane. Additional laboratory studies showed the scaling can be reduced by metered addition of acid to reduce the pH. Significantly, organic removal in the MBR was accomplished with a very low biomass concentration of 1 g/L throughout the field trial. An earlier engineering evaluation shows produced water treatment by the SMZ/MBR/RO system would cost from $0.13 to $0.20 per bbl at up to 40 gpm. Current estimated disposal costs for produced water are $1.75 to $4.91 per bbl when transportation costs are included, with even higher rates in some regions. Our results suggest that treatment by an SMZ/MBR/RO system may be a feasible alternative to current methods for produced water treatment and disposal.« less

Titania-Coated Silica Alone and Modified by Sodium Alginate as Sorbents for Heavy Metal Ions

NASA Astrophysics Data System (ADS)

Kołodyńska, D.; Gęca, M.; Skwarek, E.; Goncharuk, O.

2018-04-01

The novel organic-inorganic biohybrid composite adsorbent was synthesized based on nanosized silica-titania modified with alginate within the development of effective adsorbent for heavy metal ions. Effects of metal species Cu(II), Zn(II), Cd(II), and Pb(II); concentrations; pH; temperature; and adsorption onto titania-coated silica (ST20) initial or modified by sodium alginate (ST20-ALG) were studied. The equilibrium and kinetic data of metal ions adsorption were analyzed using Langmuir and Freundlich adsorption models and kinetic models: pseudo first order, pseudo second order, intraparticle kinetic model, and Elovich. The maximum sorption capacities observed were higher for the ST20-ALG composite compared to the initial ST20 oxide for all studied metal ions, namely their values for ST20-ALG were 22.44 mg g- 1 for Cu(II) adsorption, 19.95 mg g- 1 for Zn(II), 18.85 mg g- 1 for Cd(II), and 32.49 mg g- 1 for Pb(II). Structure and properties of initial silica-titania ST20 and modified by sodium alginate ST20-ALG adsorbents were analyzed using nitrogen adsorption/desorption isotherms, ATR-FTIR, SEM-EDS, and pHpzc techniques.

Emulsions Stabilized by Chitosan-Modified Silica Nanoparticles: pH Control of Structure-Property Relations.

PubMed

Alison, Lauriane; Demirörs, Ahmet F; Tervoort, Elena; Teleki, Alexandra; Vermant, Jan; Studart, Andre R

2018-05-29

In food-grade emulsions, particles with an appropriate surface modification can be used to replace surfactants and potentially enhance the stability of emulsions. During the life cycle of products based on such emulsions, they can be exposed to a broad range of pH conditions and hence it is crucial to understand how pH changes affect stability of emulsions stabilized by particles. Here, we report on a comprehensive study of the stability, microstructure, and macroscopic behavior of pH-controlled oil-in-water emulsions containing silica nanoparticles modified with chitosan, a food-grade polycation. We found that the modified colloidal particles used as stabilizers behave differently depending on the pH, resulting in unique emulsion structures at multiple length scales. Our findings are rationalized in terms of the different emulsion stabilization mechanisms involved, which are determined by the pH-dependent charges and interactions between the colloidal building blocks of the system. At pH 4, the silica particles are partially hydrophobized through chitosan modification, favoring their adsorption at the oil-water interface and the formation of Pickering emulsions. At pH 5.5, the particles become attractive and the emulsion is stabilized by a network of agglomerated particles formed between the droplets. Finally, chitosan aggregates form at pH 9 and these act as the emulsion stabilizers under alkaline conditions. These insights have important implications for the processing and use of particle-stabilized emulsions. On one hand, changes in pH can lead to undesired macroscopic phase separation or coalescence of oil droplets. On the other hand, the pH effect on emulsion behavior can be harnessed in industrial processing, either to tune their flow response by altering the pH between processing stages or to produce pH-responsive emulsions that enhance the functionality of the emulsified end products.

Modelling study of soil C, N and pH response to air pollution and climate change using European LTER site observations.

PubMed

Holmberg, Maria; Aherne, Julian; Austnes, Kari; Beloica, Jelena; De Marco, Alessandra; Dirnböck, Thomas; Fornasier, Maria Francesca; Goergen, Klaus; Futter, Martyn; Lindroos, Antti-Jussi; Krám, Pavel; Neirynck, Johan; Nieminen, Tiina Maileena; Pecka, Tomasz; Posch, Maximilian; Pröll, Gisela; Rowe, Ed C; Scheuschner, Thomas; Schlutow, Angela; Valinia, Salar; Forsius, Martin

2018-05-31

Current climate warming is expected to continue in coming decades, whereas high N deposition may stabilize, in contrast to the clear decrease in S deposition. These pressures have distinctive regional patterns and their resulting impact on soil conditions is modified by local site characteristics. We have applied the VSD+ soil dynamic model to study impacts of deposition and climate change on soil properties, using MetHyd and GrowUp as pre-processors to provide input to VSD+. The single-layer soil model VSD+ accounts for processes of organic C and N turnover, as well as charge and mass balances of elements, cation exchange and base cation weathering. We calibrated VSD+ at 26 ecosystem study sites throughout Europe using observed conditions, and simulated key soil properties: soil solution pH (pH), soil base saturation (BS) and soil organic carbon and nitrogen ratio (C:N) under projected deposition of N and S, and climate warming until 2100. The sites are forested, located in the Mediterranean, forested alpine, Atlantic, continental and boreal regions. They represent the long-term ecological research (LTER) Europe network, including sites of the ICP Forests and ICP Integrated Monitoring (IM) programmes under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP), providing high quality long-term data on ecosystem response. Simulated future soil conditions improved under projected decrease in deposition and current climate conditions: higher pH, BS and C:N at 21, 16 and 12 of the sites, respectively. When climate change was included in the scenario analysis, the variability of the results increased. Climate warming resulted in higher simulated pH in most cases, and higher BS and C:N in roughly half of the cases. Especially the increase in C:N was more marked with climate warming. The study illustrates the value of LTER sites for applying models to predict soil responses to multiple environmental changes. Copyright © 2017 Elsevier B.V. All rights reserved.

Reduction and removal of Cr(VI) from aqueous solutions using modified byproducts of beer production.

PubMed

Cui, Haojie; Fu, Minglai; Yu, Shen; Wang, Ming Kuang

2011-02-28

Biosorption, as an effective and low-cost technology treating industrial wastewaters containing Cr(VI), has become a significant concern worldwide. In this work, acid-modified byproducts of beer production (BBP) were used to remove Cr(VI) from aqueous solutions. Removal of Cr(VI) increases as the pH is decreased from 4.0 to 1.5, but the maximum of total Cr removal is obtained in a pH range from 2.0 to 2.5. Nearly 60% of the initial Cr(VI) (100 mg L(-1)) was adsorbed or reduced to Cr(III) within the first 10 min at pH 2.0. The Cr(VI) removal capability of acid-modified BBP materials was almost completely retained after regenerating with acid. FT-IR and XPS spectra revealed that carboxylate and carboxyl groups on the surface of modified BBP materials play a major role in Cr(VI) binding and reduction, whereas amide and other groups play a minor role in the Cr(VI) removal process. Copyright © 2010 Elsevier B.V. All rights reserved.

Global and local disturbances interact to modify seagrass palatability.

PubMed

Jiménez-Ramos, Rocío; Egea, Luis G; Ortega, María J; Hernández, Ignacio; Vergara, Juan J; Brun, Fernando G

2017-01-01

Global change, such as warming and ocean acidification, and local anthropogenic disturbances, such as eutrophication, can have profound impacts on marine organisms. However, we are far from being able to predict the outcome of multiple interacting disturbances on seagrass communities. Herbivores are key in determining plant community structure and the transfer of energy up the food web. Global and local disturbances may alter the ecological role of herbivory by modifying leaf palatability (i.e. leaf traits) and consequently, the feeding patterns of herbivores. This study evaluates the main and interactive effects of factors related to global change (i.e. elevated temperature, lower pH levels and associated ocean acidification) and local disturbance (i.e. eutrophication through ammonium enrichment) on a broad spectrum of leaf traits using the temperate seagrass Cymodocea nodosa, including structural, nutritional, biomechanical and chemical traits. The effect of these traits on the consumption rates of the generalist herbivore Paracentrotus lividus (purple sea urchin) is evaluated. The three disturbances of warming, low pH level and eutrophication, alone and in combination, increased the consumption rate of seagrass by modifying all leaf traits. Leaf nutritional quality, measured as nitrogen content, was positively correlated to consumption rate. In contrast, a negative correlation was found between feeding decisions by sea urchins and structural, biomechanical and chemical leaf traits. In addition, a notable accomplishment of this work is the identification of phenolic compounds not previously reported for C. nodosa. Our results suggest that global and local disturbances may trigger a major shift in the herbivory of seagrass communities, with important implications for the resilience of seagrass ecosystems.

Primary producers may ameliorate impacts of daytime CO2 addition in a coastal marine ecosystem

PubMed Central

Silbiger, Nyssa J.; Bernatchez, Genevieve; Sorte, Cascade J.B.

2018-01-01

Predicting the impacts of ocean acidification in coastal habitats is complicated by bio-physical feedbacks between organisms and carbonate chemistry. Daily changes in pH and other carbonate parameters in coastal ecosystems, associated with processes such as photosynthesis and respiration, often greatly exceed global mean predicted changes over the next century. We assessed the strength of these feedbacks under projected elevated CO2 levels by conducting a field experiment in 10 macrophyte-dominated tide pools on the coast of California, USA. We evaluated changes in carbonate parameters over time and found that under ambient conditions, daytime changes in pH, pCO2, net ecosystem calcification (NEC), and O2 concentrations were strongly related to rates of net community production (NCP). CO2 was added to pools during daytime low tides, which should have reduced pH and enhanced pCO2. However, photosynthesis rapidly reduced pCO2 and increased pH, so effects of CO2 addition were not apparent unless we accounted for seaweed and surfgrass abundances. In the absence of macrophytes, CO2 addition caused pH to decline by ∼0.6 units and pCO2 to increase by ∼487 µatm over 6 hr during the daytime low tide. As macrophyte abundances increased, the impacts of CO2 addition declined because more CO2 was absorbed due to photosynthesis. Effects of CO2addition were, therefore, modified by feedbacks between NCP, pH, pCO2, and NEC. Our results underscore the potential importance of coastal macrophytes in ameliorating impacts of ocean acidification. PMID:29761055

Strain improvement of Pichia kudriavzevii TY13 for raised phytase production and reduced phosphate repression.

PubMed

Qvirist, Linnea; Vorontsov, Egor; Veide Vilg, Jenny; Andlid, Thomas

2017-03-01

In this work, we present the development and characterization of a strain of Pichia kudriavzevii (TY1322), with highly improved phytate-degrading capacity. The mutant strain TY1322 shows a biomass-specific phytate degradation of 1.26 mmol g -1  h -1 after 8 h of cultivation in a high-phosphate medium, which is about 8 times higher compared with the wild-type strain. Strain TY1322 was able to grow at low pH (pH 2), at high temperature (46°C) and in the presence of ox bile (2% w/v), indicating this strain's ability to survive passage through the gastrointestinal tract. The purified phytase showed two pH optima, at pH 3.5 and 5.5, and one temperature optimum at 55°C. The lower pH optimum of 3.5 matches the reported pH of the pig stomach, meaning that TY1322 and/or its phytase is highly suitable for use in feed production. Furthermore, P. kudriavzevii TY1322 tolerates ethanol up to 6% (v/v) and shows high osmotic stress tolerance. Owing to the phenotypic characteristics and non-genetically modified organisms nature of TY1322, this strain show great potential for future uses in (i) cereal fermentations for increased mineral bioavailability, and (ii) feed production to increase the phosphate bioavailability for monogastric animals to reduce the need for artificial phosphate fortification. © 2016 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

Primary producers may ameliorate impacts of daytime CO2 addition in a coastal marine ecosystem.

PubMed

Bracken, Matthew E S; Silbiger, Nyssa J; Bernatchez, Genevieve; Sorte, Cascade J B

2018-01-01

Predicting the impacts of ocean acidification in coastal habitats is complicated by bio-physical feedbacks between organisms and carbonate chemistry. Daily changes in pH and other carbonate parameters in coastal ecosystems, associated with processes such as photosynthesis and respiration, often greatly exceed global mean predicted changes over the next century. We assessed the strength of these feedbacks under projected elevated CO 2 levels by conducting a field experiment in 10 macrophyte-dominated tide pools on the coast of California, USA. We evaluated changes in carbonate parameters over time and found that under ambient conditions, daytime changes in pH, p CO 2 , net ecosystem calcification ( NEC ), and O 2 concentrations were strongly related to rates of net community production ( NCP ). CO 2 was added to pools during daytime low tides, which should have reduced pH and enhanced p CO 2 . However, photosynthesis rapidly reduced p CO 2 and increased pH, so effects of CO 2 addition were not apparent unless we accounted for seaweed and surfgrass abundances. In the absence of macrophytes, CO 2 addition caused pH to decline by ∼0.6 units and p CO 2 to increase by ∼487 µatm over 6 hr during the daytime low tide. As macrophyte abundances increased, the impacts of CO 2 addition declined because more CO 2 was absorbed due to photosynthesis. Effects of CO 2 addition were, therefore, modified by feedbacks between NCP , pH, p CO 2 , and NEC . Our results underscore the potential importance of coastal macrophytes in ameliorating impacts of ocean acidification.

pH controls over methanogenesis and iron reduction along soil depth profile in Arctic tundra

NASA Astrophysics Data System (ADS)

Zheng, J.; Gu, B.; Wullschleger, S. D.; Graham, D. E.

2017-12-01

Increasing soil temperature in the Arctic is expected to accelerate rates of soil organic matter decomposition. However, the magnitude of this impact is uncertain due to the many physical, chemical, and biological processes that control the decomposition pathways. Varying soil redox conditions present a key control over pathways of organic matter decomposition by diverting the flow of reductants among different electron accepting processes and further driving acid-base reactions that alter soil pH. In this study we investigated the pH controls over anaerobic carbon mineralization, methanogenesis, Fe(III) reduction and the interplay between these processes across a range of pH and redox conditions. pH manipulation experiments were conducted by incubating soils representing organic, mineral, cryoturbated transitional layers and permafrost. In the experiments we sought to understand (1) if methanogenesis or Fe(III) reduction had similar pH optima; (2) if this pH response also occurs at `upstream' fermentation process; and (3) if pH alters organo-mineral association or organic matter sorption and desorption and its availability for microbial degradation. Our preliminary results suggest that the common bell-shaped pH response curve provides a good fit for both Fe(III) reduction and methanogenesis, with optimum pH at 6.0-7.0. Exceptions to this were found in transitional layer where methanogenesis rates positively correlated with increasing pH, with maximum rates measured at pH 8.5. It is likely that the transitional layer harbors distinct groups of methanogens that prefer a high pH. Variations in the optimum pH of Fe(III) reduction and methanogenesis may play a significant role in regulating organic matter decomposition pathways and thus greenhouse gas production in thawing soils. These results support biogeochemical modeling efforts to accurately simulate organic matter decomposition under changing redox and pH conditions.

Adsorption of pharmaceuticals onto isolated polyamide active layer of NF/RO membranes.

PubMed

Liu, Yan-Ling; Wang, Xiao-Mao; Yang, Hong-Wei; Xie, Yuefeng F

2018-06-01

Adsorption of trace organic compounds (TrOCs) onto the membrane materials has a great impact on their rejection by nanofiltration (NF) and reverse osmosis (RO) membranes. This study aimed to investigate the difference in adsorption of various pharmaceuticals (PhACs) onto different NF/RO membranes and to demonstrate the necessity of isolating the polyamide (PA) active layer from the polysulfone (PS) support layer for adsorption characterization and quantification. Both the isolated PA layers and the PA+PS layers of NF90 and ESPA1 membranes were used to conduct static adsorption tests. Results showed that apparent differences existed between the PA layer and the PA+PS layer in the adsorption capacity of PhACs as well as the time necessary to reach the adsorption equilibrium. PhACs with different physicochemical properties could be adsorbed to different extents by the isolated PA layer, which was mainly attributed to electrostatic attraction/repulsion and hydrophobic interactions. The PA layer of ESPA1 exhibited apparently higher adsorption capacities for the positively charged PhACs and similar adsorption capacities for the neutral PhACs although it had significantly less total interfacial area (per unit membrane surface area) for adsorption compared to the PA layer of NF90. The higher affinity of the PA layer of ESPA1 for the PhACs could be due to its higher capacity of forming hydrogen bonds with PhACs resulted from the modified chemistry with more -OH groups. This study provides a novel approach to determining the TrOC adsorption onto the active layer of membranes for the ease of investigating adsorption mechanisms. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sol-gel open tubular ODS columns with reversed electroosmotic flow for capillary electrochromatography.

PubMed

Hayes, J D; Malik, A

2001-03-01

Sol-gel chemistry was successfully used for the fabrication of open tubular columns with surface-bonded octadecylsilane (ODS) stationary-phase coating for capillary electrochromatography (OT-CEC). Following column preparations, a series of experiments were performed to investigate the performance of the sol-gel coated ODS columns in OT-CEC. The incorporation of N-octadecyldimethyl[3-(trimethoxysilyl)propyl]ammonium chloride as one of the sol-gel precursors played an important role in the electrochromatographic performance of the prepared columns. This chemical reagent possesses a chromatographically favorable, bonded ODS moiety, in conjunction with three methoxy groups allowing for sol-gel reactivity. In addition, a positively charged nitrogen atom is present in the molecular structure of this reagent and provides a positively charged capillary surface responsible for the reversed electroosmotic flow (EOF) in the columns during CEC operation. Comparative studies involving the EOF within such sol-gel ODS coated and uncoated capillaries were performed using acetonitrile and methanol as the organic modifiers in the mobile phase. The use of a deactivating reagent, phenyldimethylsilane, in the sol-gel solution was evaluated. Efficiency values of over 400,000 theoretical plates per meter were achieved in CEC on a 64 cm x 25 microm i.d. sol-gel ODS open tubular column. Test mixtures of polycyclic aromatic hydrocarbons, benzene derivatives, and aromatic aldehydes and ketones were used to evaluate the CEC performances of both nondeactivated and deactivated open tubular sol-gel columns. The effects of mobile-phase organic modifier contents and pH on EOF in such columns were evaluated. The prepared sol-gel ODS columns are characterized by switchable electroosmotic flow. A pH value of approximately 8.5 was found correspond to the isoelectric point for the prepared sol-gel ODS coatings.

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.

Optimization of monomethoxy polyethyleneglycol-modified oxalate decarboxylase by response surface methodology.

PubMed

Long, Han; Cai, XingHua; Yang, Hui; He, JunBin; Wu, Jia; Lin, RiHui

2017-09-01

In order to improve the stability of oxalate decarboxylase (Oxdc), response surface methodology (RSM), based on a four-factor three-level Box-Behnken central composite design was used to optimize the reaction conditions of oxalate decarboxylase (Oxdc) modified with monomethoxy polyethyleneglycol (mPEG5000). Four independent variables such as the ratio of mPEG-aldehyde to Oxdc, reaction time, temperature, and reaction pH were investigated in this work. The structure of modified Oxdc was identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Fourier transform infrared (FTIR) spectroscopy, the stability of the modified Oxdc was also investigated. The optimal conditions were as follows: the mole ratio of mPEG-aldehyde to Oxdc of 1:47.6, time of 13.1 h, temperature at 29.9 °C, and the reaction pH of 5.3. Under optimal conditions, experimental modified rate (MR = 73.69%) and recovery rate (RR = 67.58%) were matched well with the predicted value (MR = 75.11%) and (RR = 69.17%). SDS-PAGE and FTIR analysis showed that mPEG was covalently bound to the Oxdc. Compared with native Oxdc, the modified Oxdc (mPEG-Oxdc) showed higher thermal stability and better tolerance to trypsin or different pH treatment. This work will provide a further theoretical reference for enzyme modification and conditional optimization.

Study of properties of modified silicones at solid-liquid interface: fabric-silicone interactions.

PubMed

Purohit, P; Somasundaran, P; Kulkarni, R

2006-06-15

Silicones are special reagents that impart desired surface properties such as softness, bounciness and antiwrinkle properties to fabrics and related materials. Although these finishing processes have been practiced routinely, very little is known about the mechanisms involved in modification so that they could be improved. The current study was undertaken to develop basic understanding of the mechanisms responsible for surface modification of fibers using silicones. PDMS based amino silicone emulsions, quaternized to various degrees using dimethyl sulphate, were used in the present study. The electrokinetic properties of the modified silicones were studied as a function of pH. It was expected that the silicone emulsions would show a steady positive zeta potential throughout the pH range due to the quaternization by dimethyl sulphate. Surprisingly, a sudden drop in the zeta potential was observed around pH 8 with the samples turning hazy in the pH range of 8-10. Turbidimetric studies also showed a sudden increase in the turbidity in the pH range 8-10 where commercial processes also encounter problems. It was concluded that the emulsions were destabilized at pH 8-10 thus rendering them ineffective for surface treatment. In order to identify reason for the improvement in fabric properties, fiber structure was monitored using atomic force microscopy. It was observed that the treated fibers were far smoother, relaxed and uniform as compared to the untreated fibers. Thus the morphology of the fabric is modified in a specific way by treatment with specialty silicones.

Sulfate reduction in sulfuric material after re-flooding: Effectiveness of organic carbon addition and pH increase depends on soil properties.

PubMed

Yuan, Chaolei; Fitzpatrick, Rob; Mosley, Luke M; Marschner, Petra

2015-11-15

Sulfuric material is formed upon oxidation of sulfidic material; it is extremely acidic, and therefore, an environmental hazard. One option for increasing pH of sulfuric material may be stimulation of bacterial sulfate reduction. We investigated the effects of organic carbon addition and pH increase on sulfate reduction after re-flooding in ten sulfuric materials with four treatments: control, pH increase to 5.5 (+pH), organic carbon addition with 2% w/w finely ground wheat straw (+C), and organic carbon addition and pH increase (+C+pH). After 36 weeks, in five of the ten soils, only treatment +C+pH significantly increased the concentration of reduced inorganic sulfur (RIS) compared to the control and increased the soil pore water pH compared to treatment+pH. In four other soils, pH increase or/and organic carbon addition had no significant effect on RIS concentration compared to the control. The RIS concentration in treatment +C+pH as percentage of the control was negatively correlated with soil clay content and initial nitrate concentration. The results suggest that organic carbon addition and pH increase can stimulate sulfate reduction after re-flooding, but the effectiveness of this treatment depends on soil properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Mechanism of increased clearance of glycated albumin by proximal tubule cells

PubMed Central

Wagner, Mark C.; Myslinski, Jered; Pratap, Shiv; Flores, Brittany; Rhodes, George; Campos-Bilderback, Silvia B.; Sandoval, Ruben M.; Kumar, Sudhanshu; Patel, Monika; Ashish

2016-01-01

Serum albumin is the most abundant plasma protein and has a long half-life due to neonatal Fc receptor (FcRn)-mediated transcytosis by many cell types, including proximal tubule cells of the kidney. Albumin also interacts with, and is modified by, many small and large molecules. Therefore, the focus of the present study was to address the impact of specific known biological albumin modifications on albumin-FcRn binding and cellular handling. Binding at pH 6.0 and 7.4 was performed since FcRn binds albumin strongly at acidic pH and releases it after transcytosis at physiological pH. Equilibrium dissociation constants were measured using microscale thermophoresis. Since studies have shown that glycated albumin is excreted in the urine at a higher rate than unmodified albumin, we studied glucose and methylgloxal modified albumins (21 days). All had reduced affinity to FcRn at pH 6.0, suggesting these albumins would not be returned to the circulation via the transcytotic pathway. To address why modified albumin has reduced affinity, we analyzed the structure of the modified albumins using small-angle X-ray scattering. This analysis showed significant structural changes occurring to albumin with glycation, particularly in the FcRn-binding region, which could explain the reduced affinity to FcRn. These results offer an explanation for enhanced proximal tubule-mediated sorting and clearance of abnormal albumins. PMID:26887834

In vitro wear rates of materials under different loads and varying pH.

PubMed

Shabanian, Mitra; Richards, Lindsay C

2002-06-01

Despite the need for information about the wear characteristics of restorative materials, there have been few systemic studies of the factors that influence the rate of material wear. This study compared the wear rates of enamel and 3 tooth-colored restorative materials under different loads (0, 3.2, 6.7, and 9.95 kg) and pH levels (1.2, 3.3, and 7.0). An electromechanical tooth wear machine was used so that standard restorations representing 3 materials could be worn by opposing enamel under controlled conditions. The wear rates of enamel, composite (Z100), a conventional glass ionomer cement (Fuji IX), and a resin-modified glass ionomer cement (Fuji II LC) were compared at a range of loads (0 to 9.95 kg) and pH levels (1.2 to 7.0) and also at different sites across each restoration. Ten specimens were randomly assigned to each experimental group. Wear assessment was performed with a modified light microscope to quantify the height changes at defined points across wear facets. Four-way analysis of variance was used to compare wear rates among materials, pH levels, loads, and sites. Post-hoc t tests identified significant differences between specific pairs of experimental conditions (P<.05). The wear rates of enamel and the other test materials varied significantly with pH (P<.0001), load (P<.0001), and type of material (P<.0001). Enamel wear was influenced most by varied pH, whereas the composite was least affected by acid. The conventional glass ionomer cement was more susceptible than the composite to the effects of varied pH; the acid susceptibility of the resin-modified glass ionomer cement was generally between that of the composite and conventional glass ionomer cement. Enamel and the conventional glass ionomer cement were affected similarly by load. The composite was more resistant than the conventional glass ionomer cement to wear at higher loads; the resin-modified glass ionomer cement exhibited intermediate load resistance. Within the limitations of this study, the 3 test materials were more resistant than enamel to acid, with the composite demonstrating the lowest susceptibility to acid. The acid- and load-resistance of the resin-modified glass ionomer cement was consistently less than that of the composite and greater than that of the conventional glass ionomer cement.

Identification and Modulation of the Key Amino Acid Residue Responsible for the pH Sensitivity of Neoculin, a Taste-Modifying Protein

PubMed Central

Nakajima, Ken-ichiro; Yokoyama, Kanako; Koizumi, Taichi; Koizumi, Ayako; Asakura, Tomiko; Terada, Tohru; Masuda, Katsuyoshi; Ito, Keisuke; Shimizu-Ibuka, Akiko; Misaka, Takumi; Abe, Keiko

2011-01-01

Neoculin occurring in the tropical fruit of Curculigo latifolia is currently the only protein that possesses both a sweet taste and a taste-modifying activity of converting sourness into sweetness. Structurally, this protein is a heterodimer consisting of a neoculin acidic subunit (NAS) and a neoculin basic subunit (NBS). Recently, we found that a neoculin variant in which all five histidine residues are replaced with alanine elicits intense sweetness at both neutral and acidic pH but has no taste-modifying activity. To identify the critical histidine residue(s) responsible for this activity, we produced a series of His-to-Ala neoculin variants and evaluated their sweetness levels using cell-based calcium imaging and a human sensory test. Our results suggest that NBS His11 functions as a primary pH sensor for neoculin to elicit taste modification. Neoculin variants with substitutions other than His-to-Ala were further analyzed to clarify the role of the NBS position 11 in the taste-modifying activity. We found that the aromatic character of the amino acid side chain is necessary to elicit the pH-dependent sweetness. Interestingly, since the His-to-Tyr variant is a novel taste-modifying protein with alternative pH sensitivity, the position 11 in NBS can be critical to modulate the pH-dependent activity of neoculin. These findings are important for understanding the pH-sensitive functional changes in proteinaceous ligands in general and the interaction of taste receptor–taste substance in particular. PMID:21559382

pH-sensitive optrode

DOEpatents

Hirschfeld, Tomas B.; Wang, Francis T.

1989-01-01

An apparatus is provided for remotely monitoring pH. A support material is provided on which organic dye molecules are covalently attached at a surface density falling within a predetermined range. The pH dependent fluorescence response of the bound organic dye molecules depends critically on surface density of the organic dye molecules bound to the support material and the nature of the covalent linkage betwen the organic dye molecules and the support material. The invention is operated by contacting the support material on which the organic dye is attached with the fluid whose pH is to be determined. When in contact, the organic dye on the support material is illuminated so that it is caused to fluoresce. The intensity of organic dye fluorescence is then related to pH.

pH and Organic Carbon Dose Rates Control Microbially Driven Bioremediation Efficacy in Alkaline Bauxite Residue.

PubMed

Santini, Talitha C; Malcolm, Laura I; Tyson, Gene W; Warren, Lesley A

2016-10-18

Bioremediation of alkaline tailings, based on fermentative microbial metabolisms, is a novel strategy for achieving rapid pH neutralization and thus improving environmental outcomes associated with mining and refining activities. Laboratory-scale bioreactors containing bauxite residue (an alkaline, saline tailings material generated as a byproduct of alumina refining), to which a diverse microbial inoculum was added, were used in this study to identify key factors (pH, salinity, organic carbon supply) controlling the rates and extent of microbially driven pH neutralization (bioremediation) in alkaline tailings. Initial tailings pH and organic carbon dose rates both significantly affected bioremediation extent and efficiency with lower minimum pHs and higher extents of pH neutralization occurring under low initial pH or high organic carbon conditions. Rates of pH neutralization (up to 0.13 mM H + produced per day with pH decreasing from 9.5 to ≤6.5 in three days) were significantly higher in low initial pH treatments. Representatives of the Bacillaceae and Enterobacteriaceae, which contain many known facultative anaerobes and fermenters, were identified as key contributors to 2,3-butanediol and/or mixed acid fermentation as the major mechanism(s) of pH neutralization. Initial pH and salinity significantly influenced microbial community successional trajectories, and microbial community structure was significantly related to markers of fermentation activity. This study provides the first experimental demonstration of bioremediation in bauxite residue, identifying pH and organic carbon dose rates as key controls on bioremediation efficacy, and will enable future development of bioreactor technologies at full field scale.

A survey of water activity and pH values in fresh pasta packed under modified atmosphere manufactured in Argentina and Uruguay.

PubMed

Schebor, C; Chirife, J

2000-07-01

The water activity (a(w)) and pH values of commercially available filled fresh pasta and gnocchi packed under modified atmosphere and manufactured in Argentina and Uruguay were examined. The retail survey included 58 samples (several brands) of filled pasta and 11 samples of gnocchi. Fillings consisted of different combinations of cheese (various types), beef, ricotta, ham, chicken, and spinach. The survey revealed that the a(w) values of the 58 samples of filled pasta ranged from 0.916 to 0.973, and their pH values ranged from 5.2 to 7.0. The a(w) of gnocchi was consistently higher and ranged from 0.936 to 0.983, with pH values from 4.8 to 6.4. Some samples of filled pasta and most gnocchi samples were found to have a(w) and pH values that would support growth of spores of Clostridium botulinum, if present, under conditions of temperature abuse (i.e., 30 degrees C).

Controlling harmful algae blooms using aluminum-modified clay.

PubMed

Liu, Yang; Cao, Xihua; Yu, Zhiming; Song, Xiuxian; Qiu, Lixia

2016-02-15

The performances of aluminum chloride modified clay (AC-MC), aluminum sulfate modified clay (AS-MC) and polyaluminum chloride modified clay (PAC-MC) in the removal of Aureococcus anophagefferens were compared, and the potential mechanisms were analyzed according to the dispersion medium, suspension pH and clay surface charges. The results showed that AC-MC and AS-MC had better efficiencies in removing A.anophagefferens than PAC-MC. The removal mechanisms of the three modified clays varied. At optimal coagulation conditions, the hydrolysates of AC and AS were mainly monomers, and they transformed into Al(OH)3(am) upon their addition to algae culture, with the primary mechanism being sweep flocculation. The PAC mainly hydrolyzed to the polyaluminum compounds, which remained stable when added to the algae culture, and the flocculation mainly occurred through polyaluminum compounds. The suspension pH significantly influenced the aluminum hydrolysate and affected the flocculation between the modified clay and algae cells. Copyright © 2016 Elsevier Ltd. All rights reserved.

Gold Binding by Native and Chemically Modified Hops Biomasses

DOE PAGES

López, M. Laura; Gardea-Torresdey, J. L.; Peralta-Videa, J. R.; ...

2005-01-01

Heavy metals from mining, smelting operations and other industrial processing facilities pollute wastewaters worldwide. Extraction of metals from industrial effluents has been widely studied due to the economic advantages and the relative ease of technical implementation. Consequently, the search for new and improved methodologies for the recovery of gold has increased. In this particular research, the use of cone hops biomass ( Humulus lupulus ) was investigated as a new option for gold recovery. The results showed that the gold binding to native hops biomass was pH dependent from pH 2 to pH 6, with a maximum percentage binding atmore » pH 3. Time dependency studies demonstrated that Au(III) binding to native and modified cone hops biomasses was found to be time independent at pH 2 while at pH 5, it was time dependent. Capacity experiments demonstrated that at pH 2, esterified hops biomass bound 33.4 mg Au/g of biomass, while native and hydrolyzed hops biomasses bound 28.2 and 12.0 mg Au/g of biomass, respectively. However, at pH 5 the binding capacities were 38.9, 37.8 and 11.4 mg of Au per gram of native, esterified and hydrolyzed hops biomasses, respectively.« less

Antenna Effect on the Organic Spacer-Modified Eu-Doped Layered Gadolinium Hydroxide for the Detection of Vanadate Ions over a Wide pH Range.

PubMed

Jeong, Heejin; Lee, Byung-Il; Byeon, Song-Ho

2016-05-04

The excitation of the adsorbed vanadate group led to the red emission arising from the efficient energy transfer to Eu-doped layered gadolinium hydroxide (LGdH:Eu). This light-harvesting antenna effect allowed LGdH:Eu to detect selectively a vanadate in aqueous solution at different pHs. Because vanadate exists in various forms by extensive oligomerization and protonation reactions in aqueous solution depending on pH, it is important to detect a vanadate regardless of its form over a wide pH range. In particular, spacer molecules with long alkyl chains greatly facilitated access of a vanadate antenna into the interlayer surface of LGdH:Eu. The concomitant increase in adsorption capacity of LGdH:Eu achieved a strong antenna effect of vanadate on the red emission from Eu(3+). When a suspension containing LGdH:Eu nanosheets (1.0 g/L) was used, the vanadate concentration down to 1 × 10(-5) M could even be visually monitored, and the detection limit based on the (5)D0 → (7)F2 emission intensity could reach 4.5 × 10(-8) M.

Impacts of beaver ponds on dissolved organic matter cycling in small temperate streams.

NASA Astrophysics Data System (ADS)

Larsen, J.; Lambert, T.; Larsen, A.; Lane, S.

2017-12-01

Beavers are engineers that modify the structure of river reaches and their hydrological functioning. By building dams, they modify the travel time of running waters and can lead to the flooding of surrounding soils and terrestrial vegetation, with potentially significant impact on biogeochemical cycles. Contradictory effects of beaver ponds on dissolved organic matter (DOM) concentration and composition have however been reported, and the underlying reasons are still unclear. In this study, we aimed to investigate the role of the landscape morphology as an important driver determining how a beaver population can affect stream DOM cycling. Four streams localized in Switzerland and Germany were visited during different seasons (spring, summer, winter) and monitored at upstream and downstream locations of beaver ponds across a hydrological cycle. The sites differed in terms of river channel morphology, presence or absence of floodplain, and vegetation cover. DOM composition was investigated through absorbance and fluorescence measurements coupled with parallel factor analysis (PARAFAC) along with stream water quality (nutrients, pH, dissolved oxygen and water temperature). The results show that the effects of beaver dams were variable, and emphasizes the importance of the geomorphological context.

Hydrochemistry indicating groundwater contamination and the potential fate of chlorohydrocarbons in combined polluted groundwater: a case study at a contamination site in North China.

PubMed

Huang, Shuang-Bing; Han, Zhan-Tao; Zhao, Long; Kong, Xiang-Ke

2015-05-01

Groundwater contamination characteristics and the potential fate of chlorohydrocarbons were investigated at a combined polluted groundwater site in North China. Groundwater chemistry and (2)D and (18)O isotope compositions indicated that high salination of groundwater was related with chemical pollution. The elevated salinity plume was consistent with the domain where typical chlorohydrocarbon contaminants occurred. The concentrations of heavy metals, oxidation-reduction potential, and pH in organic polluted areas significantly differed from those in peripheral (background) areas, indicating modified hydrochemistry possibly resulting from organic pollution. Under the presented redox conditions of groundwater, monochlorobenzene oxidation may have occurred when the trichlorohydrocarbons underwent reductive dechlorination. These findings suggested that inorganic hydrochemistry effectively indicated the occurrence of chemical contamination in groundwater and the potential fate of chlorohydrocarbons.

Thermal stability and gel quality of myofibrillar protein as affected by soy protein isolates subjected to an acidic pH and mild heating.

PubMed

Niu, Haili; Xia, Xiufang; Wang, Chao; Kong, Baohua; Liu, Qian

2018-03-01

Thermal stability and gel quality of myofibrillar protein were evaluated with regard to the addition of native soy protein isolates (SPI) and SPI subjected to acidic pH and mild heating (modified SPI). Compared with the control, the addition of modified SPI increased the compression force of the protein gel and decreased water loss (P<0.05). Differential scanning calorimetry results showed that an addition of 0.75% native SPI decreased the first transition temperature (P<0.05), and addition of 0.5% and 0.75% modified SPI exhibited no appreciable changes on it (P>0.05), indicating that a higher concentration of modified SPI would not damage the protein thermal stability. Moreover, the addition of modified SPI enhanced hydrogen bonding and disulphide linkages. Atomic force microscopy analysis revealed that the addition of modified SPI decreased the roughness of the mixed myofibrillar protein gels. Overall, modified SPI has the potential to improve myofibrillar protein gel texture and water holding capacity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Safe and efficient pH sensitive tumor targeting modified liposomes with minimal cytotoxicity.

PubMed

Wang, Lilin; Geng, Di; Su, Haijia

2014-11-01

Incorporating the pH-sensitivity of octylamine grafted poly aspartic acid (PASP) with the biocompatibility of liposomes, a novel pH sensitive drug delivery system, octylamine-graft-PASP (PASP-g-C8) modified liposomes (OPLPs), was obtained. Since hydrophobic chains have been grafted into PASP backbones, the octylamine chain could act as the "anchor" to implant onto liposomes. The structure of PASP-g-C8, involving long-chain and hydrophobic anchors can significantly enhance the stability of the drug carrier. The shortcoming of single PASP chain modified liposomes (PLPs), that cannot sustain a slow and controlled release especially in a physiological pH solution (resembling normal tissues of pH 7.4) is thus overcome. Drug release experiments were carried out and the result showed that OPLPs sustained a slow and steady release in comparison with PLPs in the physiological pH 7.4 environment. However, OPLPs can provide a fast release in subacid environment (pH 5.0 of resembled tumor tissues). The results of diameter analysis and zeta potential demonstrated that OPLPs presented a larger diameter and higher electronegativity. Furthermore, in the "chain-anchor" structure of PASP-g-C8, the degree of substitution (DS) of the "anchor" is a remarkable factor to alter the pH-sensitivity of OPLPs. The in vitro tumor inhibition and cell toxicity studies revealed that tumor cells treated with OPLPs survived only 35.0% after 48 h whereas normal cells survived 100% in the same condition. The pH sensitive OPLPs are promising tumor targeting drug delivery with high tumor inhibition and insignificant cytotoxicity. Copyright © 2014. Published by Elsevier B.V.

Biological mechanisms supporting adaptation to ocean acidification in coastal ecosystems

NASA Astrophysics Data System (ADS)

Hendriks, Iris E.; Duarte, Carlos M.; Olsen, Ylva S.; Steckbauer, Alexandra; Ramajo, Laura; Moore, Tommy S.; Trotter, Julie A.; McCulloch, Malcolm

2015-01-01

The direct influence of anthropogenic CO2 might play a limited role in pH regulation in coastal ecosystems as pH regulation in these areas can be complex. They experience large variability across a broad range of spatial and temporal scales, with complex external and internal drivers. Organisms influence pH at a patch scale, where community metabolic effects and hydrodynamic processes interact to produce broad ranges in pH, (˜0.3-0.5 pH units) over daily cycles and spatial scales (mm to m) particularly in shallow vegetated habitats and coral reefs where both respiration and photosynthetic activity are intense. Biological interactions at the ecosystem scale, linked to patchiness in habitat landscapes and seasonal changes in metabolic processes and temperature lead to changes of about 0.3-0.5 pH units throughout a year. Furthermore, on the scale of individual organisms, small-scale processes including changes at the Diffusive Boundary Layer (DBL), interactions with symbionts, and changes to the specific calcification environment, induce additional changes in excess of 0.5 pH units. In these highly variable pH environments calcifying organisms have developed the capacity to alter the pH of their calcifying environment, or specifically within critical tissues where calcification occurs, thus achieving a homeostasis. This capacity to control the conditions for calcification at the organism scale may therefore buffer the full impacts of ocean acidification on an organism scale, although this might be at a cost to the individual. Furthermore, in some areas, calcifiers may potentially benefit from changes to ambient seawater pH, where photosynthetic organisms drawdown CO2.

High-performance liquid chromatographic enantioseparation of 2-aminomono- and dihydroxycyclopentanecarboxylic and 2-aminodihydroxycyclohexanecarboxylic acids on macrocyclic glycopeptide-based phases.

PubMed

Berkecz, Róbert; Ilisz, István; Benedek, Gabriella; Fülöp, Ferenc; Armstrong, Daniel W; Péter, Antal

2009-02-06

The direct separation of the enantiomers of four 2-aminomono- or dihydroxycyclopentanecarboxylic acids and four 2-aminodihydroxycyclohexanecarboxylic acids was performed on chiral stationary phases containing macrocyclic glycopeptide antibiotics such as teicoplanin (Astec Chirobiotic T and T2), teicoplanin aglycone (Chirobiotic TAG) or ristocetin A (Chirobiotic R) as chiral selectors. The effects of the nature of organic modifiers, the pH, the mobile phase composition and the structures of the analytes on the separation were investigated. Chirobiotic TAG, and in some cases Chirobiotic T, proved to be the most useful of these columns. The elution sequence was determined in most cases.

pH-sensitive optrode

DOEpatents

Hirschfeld, T.B.; Wang, F.T.

1989-02-07

An apparatus is provided for remotely monitoring pH. A support material is provided on which organic dye molecules are covalently attached at a surface density falling within a predetermined range. The pH dependent fluorescence response of the bound organic dye molecules depends critically on surface density of the organic dye molecules bound to the support material and the nature of the covalent linkage between the organic dye molecules and the support material. The invention is operated by contacting the support material on which the organic dye is attached with the fluid whose pH is to be determined. When in contact, the organic dye on the support material is illuminated so that it is caused to fluoresce. The intensity of organic dye fluorescence is then related to pH. 4 figs.

Anti-biofilm action of nitric oxide-releasing alkyl-modified poly(amidoamine) dendrimers against Streptococcus mutans.

PubMed

Backlund, Christopher J; Worley, Brittany V; Schoenfisch, Mark H

2016-01-01

The effect of nitric oxide (NO)-releasing dendrimer hydrophobicity on Streptococcus mutans killing and biofilm disruption was examined at pH 7.4 and 6.4, the latter relevant to dental caries. Generation 1 (G1) poly(amidoamine) (PAMAM) dendrimers were modified with alkyl epoxides to generate propyl-, butyl-, hexyl-, octyl-, and dodecyl-functionalized dendrimers. The resulting secondary amines were reacted with NO to form N-diazeniumdiolate NO donor-modified dendrimer scaffolds (total NO ∼1μmol/mg). The bactericidal action of the NO-releasing dendrimers against both planktonic and biofilm-based S. mutans proved greatest with increasing alkyl chain length and at lower pH. Improved bactericidal efficacy at pH 6.4 was attributed to increased scaffold surface charge that enhanced dendrimer-bacteria association and ensuing membrane damage. For shorter alkyl chain (i.e., propyl and butyl) dendrimer modifications, increased antibacterial action at pH 6.4 was due to faster NO-release kinetics from proton-labile N-diazeniumdiolate NO donors. Octyl- and dodecyl-modified PAMAM dendrimers proved most effective for eradicating S. mutans biofilms with NO release mitigating dendrimer scaffold cytotoxicity. We report the antibacterial and anti-biofilm efficacy of dual-action nitric oxide (NO)-releasing dendrimers against S. mutans, an etiological agent in dental caries. This work was undertaken to enhance the anti-biofilm action of these scaffolds by employing various alkyl chain modifications. Furthermore, we evaluated the ability of NO to eradicate cariogenic biofilms. We found that at the lower pH associated with dental caries (pH ∼6.4), NO has a more pronounced antibacterial effect for alkyl modifications less capable of biofilm penetration and membrane disruption. Of greatest significance, we introduce dendrimers as a new macromolecular antibacterial agent against the cariogenic bacteria S. mutans. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Potentiation of pH-sensitive polymer-modified liposomes with cationic lipid inclusion as antigen delivery carriers for cancer immunotherapy.

PubMed

Yoshizaki, Yuta; Yuba, Eiji; Sakaguchi, Naoki; Koiwai, Kazunori; Harada, Atsushi; Kono, Kenji

2014-09-01

Cationic lipid-incorporated liposomes modified with pH-sensitive polymers were prepared by introducing 3, 5-didodecyloxybenzamidine as a cationic lipid to egg yolk phosphatidylcholine liposomes modified with 3-methylglutarylated hyperbranched poly(glycidol) (MGlu-HPG) as a pH-sensitive polymer. These liposomes were stable at neutral pH, but were destabilized below pH 6.0 because MGlu-HPG changed its characteristics from hydrophilic to hydrophobic in response to the pH decrease. Cationic lipid inclusion improved their pH sensitivity at weakly acidic pH and association of liposomes with murine dendritic cell (DC) lines. Cationic lipid-incorporated liposomes delivered entrapped ovalbumin (OVA) molecules not only to cytosol but also to endosome/lysosome. Treatment with cationic lipid-incorporated liposomes induced up-regulation of antigen presentation-involved molecules on DCs, the promotion of cytokine production, and antigen presentation via both major histocompatibility complex (MHC) class I and II molecules. Especially, antigen presentation via MHC class II was promoted by cationic lipid inclusion, which might correspond to efficient endosome/lysosome delivery of OVA. Subcutaneous administration of OVA-loaded cationic lipid-incorporated liposomes induced antigen-specific antibody production in serum and Th1-dominant immune responses in the spleen. Furthermore, administration of the cationic lipid-incorporated liposomes to mice bearing E.G7-OVA tumor more significantly reduced the tumor volume than liposomes without cationic lipids. Therefore, cationic lipid inclusion into pH-sensitive polymer-modified liposomes, which can achieve both efficient antigen intracellular delivery and activation of antigen presenting cell, is an effective approach to develop antigen carriers for efficient cancer immunotherapy. Copyright © 2014 Elsevier Ltd. All rights reserved.

Investigation of the Dissolution Profile of Gliclazide Modified-Release Tablets Using Different Apparatuses and Dissolution Conditions.

PubMed

Skripnik, K K S; Riekes, M K; Pezzini, B R; Cardoso, S G; Stulzer, H K

2017-07-01

In the absence of an official dissolution method for modified-release tablets of gliclazide, dissolution parameters, such as apparatuses (1, 2, and 3), rotation speeds, pH, and composition of the dissolution medium were investigated. The results show that although the drug presents a pH-mediated solubility (pH 7.0 > 6.8 > 6.4 > 6.0 > 5.5 > 4.5), the in vitro release of the studied tablets was not dependent on this parameter, despite of the apparatus tested. On the other hand, the rotation speed demonstrated a greater influence (100 rpm >50 rpm). Using similar hydrodynamic conditions, the three different apparatuses were compared in pH 6.8 and provided the following trend: apparatus 1 at 100 rpm >2 at 50 rpm ≈3 at 10 dpm. As a complete, but slow release is expected from modified-release formulations, apparatus 2, in phosphate buffer pH 6.8 and 100 rpm, were selected as the optimized dissolution method. In comparison to apparatus 1 under the same conditions, the paddle avoids the stickiness of formulation excipients at the mesh of the basket, which could prejudice the release of gliclazide. Results obtained with biorelevant medium through the developed dissolution method were similar to the buffer solution pH 6.8. The application of the optimized method as a quality control test between two different brands of gliclazide modified-release tablets showed that both dissolution profiles were considered similar by the similarity factor (f2 = 51.8). The investigation of these dissolution profiles indicated a dissolution kinetic following first-order model.

AND logic-like pH- and light-dual controlled drug delivery by surface modified mesoporous silica nanoparticles.

PubMed

Zhao, Junwei; He, Zhaoshuai; Li, Biao; Cheng, Tanyu; Liu, Guohua

2017-04-01

Recently, the controlled drug delivery system has become a potential platform for biomedical application. Herein, we developed a pH and light-dual controlled cargo release system exhibiting AND logic based on MCM-41 mesoporous silica nanoparticles, which was surface modified using β-cyclodextrin (β-CD) with imine bond and azobenzene derivative. The complex of β-CD and azobenzene derivative effectively blocked the cargo delivery in pH=7.0 phosphate buffered saline (PBS) solution without 365nm UV light irradiation. The cargo was fully released when both factors of acidic environment (pH=5.0 PBS) and 365nm UV light irradiation were satisfied, meanwhile only very little cargo was delivered if one factor was satisfied. The result also demonstrates that the opening/closing of the gate and the release of the cargo in small portions can be controlled. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhancement of chromate reduction in soils by surface modified biochar.

PubMed

Mandal, Sanchita; Sarkar, Binoy; Bolan, Nanthi; Ok, Yong Sik; Naidu, Ravi

2017-01-15

Chromium (Cr) is one of the common metals present in the soils and may have an extremely deleterious environmental impact depending on its redox state. Among two common forms, trivalent Cr(III) is less toxic than hexavalent Cr(VI) in soils. Carbon (C) based materials including biochar could be used to alleviate Cr toxicity through converting Cr(VI) to Cr(III). Incubation experiments were conducted to examine Cr(VI) reduction in different soils (Soil 1: pH 7.5 and Soil 2: pH 5.5) with three manures from poultry (PM), cow (CM) and sheep (SM), three respective manure-derived biochars (PM biochar (PM-BC), CM biochar (CM-BC) and SM biochar (SM-BC)) and two modified biochars (modified PM-BC (PM-BC-M) and modified SM-BC (SM-BC-M)). Modified biochar was synthesized by incorporating chitosan and zerovalent iron (ZVI) during pyrolysis. Among biochars, highest Cr(VI) reduction was observed with PM-BC application (5%; w/w) (up to 88.12 mg kg -1 ; 45% reduction) in Soil 2 (pH 5.5). The modified biochars enhanced Cr(VI) reduction by 55% (SM-BC-M) compared to manure (29%, SM) and manure-derived biochars (40% reduction, SM-BC). Among the modified biochars, SM-BC-M showed a higher Cr(VI) reduction rate (55%) than PM-BC-M (48%) in Soil 2. Various oxygen-containing surface functional groups such as phenolic, carboxyl, carbonyl, etc. on biochar surface might act as a proton donor for Cr(VI) reduction and subsequent Cr(III) adsorption. This study underpins the immense potential of modified biochar in remediation of Cr(VI) contaminated soils. Copyright © 2016 Elsevier Ltd. All rights reserved.

Changes in soil parameters under continuous plastic mulching in strawberry cultivation

NASA Astrophysics Data System (ADS)

Muñoz, Katherine; Diehl, Dörte; Scopchanova, Sirma; Schaumann, Gabriele E.

2016-04-01

Plastic mulching (PM) is a widely used practice in modern agriculture because they generate conditions for optimal yield rates and quality. However, information about long-term effects of PC on soil quality parameters is scarce. The aim of this study is to compare the effect of three different mulching managements on soil quality parameters. Sampling and methodology: Three different managements were studied: Organic mulching (OM), 2-years PM and 4-years PM. Soil samples were collected from irrigated fields in 0-5, 5-10 and 10-30 cm depths and analyzed for water content (WC), pH, dissolved organic carbon (DOC), total soil carbon (Ctot) and cation exchange capacity (CECeff). Results and discussion: Mulching management has an influence on soil parameters. The magnitude of the effects is influenced by the type (organic agriculture practice vs. plastic mulching practice) and duration of the mulching. PM modified the water distribution through the soil column. WC values at the root zone were in average 10% higher compared to those measured at the topsoil. Under OM, the WC was lower than under PM. The pH was mainly influenced by the duration of the managements with slightly higher values after 4 than after 2-years PM. Under PM, aqueous extracts of the topsoil (0-5 cm depth) contained in average with 8.5±1.8 mg/L higher DOC than in 10-30 cm depth with 5.6±0.5 mg/L, which may indicate a mobilization of organic components in the upper layers. After 4-years PM, Ctot values were slightly higher than after 2-years PM and after OM. Surprisingly, after 4-years PM, CECeff values were with 138 - 157 mmolc/kg almost 2-fold higher than after 2-years PM and OM which had with 74 - 102 mmolc/kg comparable CECeff values. Long-term PM resulted in changes of soil pH and slightly increased Ctot which probably enhanced the CECeff of the soil. However, further investigations of the effect of PM on stability of soil organic matter and microbial community structure are needed.

The Role of the Novel Nuclear Tyrosine Kinase, RAK, in Breast Cancer Biology (TR950012)

DTIC Science & Technology

1999-07-01

INVESTIGATOR: Paul M. Armistead, Ph.D. Holden H. Thorp, Ph.D. CONTRACTING ORGANIZATION : University of North Carolina Chapel Hill, North Carolina 27599...Biology (TR950012) 6. AUTHOR(S) Paul M. Armistead, Ph.D.. Holden H. Thorp, Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) University of...Materiel Command Fort Detrick, Maryland 21702-5012 5. FUNDING NUMBERS DAMD17-96-1-6067 8. PERFORMING ORGANIZATION REPORT NUMBER 10. SPONSORING

Amazon kaolinite functionalized with diethylenetriamine moieties for U(VI) removal: thermodynamic of cation-basic interactions.

PubMed

Guerra, Denis L; Leidens, Victor L; Viana, Rúbia R; Airoldi, Claudio

2010-08-15

The compound N-[3-(trimethoxysilyl)propyl]diethylenetriamine (MPDET) was anchored onto Amazon kaolinite surface (KLT) by heterogeneous route. The modified and natural kaolinite clay samples were characterized by transmission electron microscopy (TEM), scanning electron microscopic (SEM), N(2) adsorption, powder X-ray diffraction, thermal analysis, ion exchange capacities, and nuclear magnetic nuclei of (29)Si and (13)C. The well-defined peaks obtained in the (13)C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The adsorption of uranyl on natural (KLT) and modified (KLT(MPDET)) kaolinite clays was investigated as a function of the solution pH, metal concentration, temperature, and ionic strength. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 8.37 x 10(-3) and 13.87 x 10(-3) mmol g(-1) for KLT and KLT(MPDET) at 298 K, respectively. The energetic effects (Delta(int)H, Delta(int)G, and Delta(int)S) caused by metal cations adsorption were determined through calorimetric titrations. Copyright 2010. Published by Elsevier B.V.

Buffer capacity of the coelomic fluid in echinoderms.

PubMed

Collard, Marie; Laitat, Kim; Moulin, Laure; Catarino, Ana I; Grosjean, Philippe; Dubois, Philippe

2013-09-01

The increase in atmospheric CO2 due to anthropogenic activity results in an acidification of the surface waters of the oceans. The impact of these chemical changes depends on the considered organisms. In particular, it depends on the ability of the organism to control the pH of its inner fluids. Among echinoderms, this ability seems to differ significantly according to species or taxa. In the present paper, we investigated the buffer capacity of the coelomic fluid in different echinoderm taxa as well as factors modifying this capacity. Euechinoidea (sea urchins except Cidaroidea) present a very high buffer capacity of the coelomic fluid (from 0.8 to 1.8mmolkg(-1) SW above that of seawater), while Cidaroidea (other sea urchins), starfish and holothurians have a significantly lower one (from -0.1 to 0.4mmolkg(-1) SW compared to seawater). We hypothesize that this is linked to the more efficient gas exchange structures present in the three last taxa, whereas Euechinoidea evolved specific buffer systems to compensate lower gas exchange abilities. The constituents of the buffer capacity and the factors influencing it were investigated in the sea urchin Paracentrotus lividus and the starfish Asterias rubens. Buffer capacity is primarily due to the bicarbonate buffer system of seawater (representing about 63% for sea urchins and 92% for starfish). It is also partly due to coelomocytes present in the coelomic fluid (around 8% for both) and, in P. lividus only, a compound of an apparent size larger than 3kDa is involved (about 15%). Feeding increased the buffer capacity in P. lividus (to a difference with seawater of about 2.3mmolkg(-1) SW compared to unfed ones who showed a difference of about 0.5mmolkg(-1) SW) but not in A. rubens (difference with seawater of about 0.2 for both conditions). In P. lividus, decreased seawater pH induced an increase of the buffer capacity of individuals maintained at pH7.7 to about twice that of the control individuals and, for those at pH7.4, about three times. This allowed a partial compensation of the coelomic fluid pH for individuals maintained at pH7.7 but not for those at pH7.4. Copyright © 2013 Elsevier Inc. All rights reserved.

Removal of aniline and phenol from water using raw and aluminum hydroxide-modified diatomite.

PubMed

Wu, C D; Zhang, J Y; Wang, L; He, M H

2013-01-01

The feasibility of using raw diatomite and aluminum hydroxide-modified diatomite (Al-diatomite) for removal of aniline and phenol from water was investigated. Their physicochemical characteristics such as pHsolution, point of zero charge (pHPZC), surface area, Fourier transform infrared (FT-IR) and scanning electron microscopy was determined. After the raw diatomite was modified, the surface area of Al-diatomite increases from 26.67 to 82.65 m(2) g(-1). The pHPZC and pHsolution (10%) occurred around pH 5.2 and pH 8.6, respectively. The removal rates of aniline and phenol on diatomite and Al-diatomite decreased with increasing solution pH, while surface charge density decreased. The adsorption of aniline and phenol on diatomite presented a good fit to the Langmuir and Freundlich models, but the models are not fit to forecast the adsorption of aniline and phenol on Al-diatomite. The study indicated that electrostatic interaction was a dominating mechanism of aniline and phenol sorption onto Al-diatomite.

A two-stage path planning approach for multiple car-like robots based on PH curves and a modified harmony search algorithm

NASA Astrophysics Data System (ADS)

Zeng, Wenhui; Yi, Jin; Rao, Xiao; Zheng, Yun

2017-11-01

In this article, collision-avoidance path planning for multiple car-like robots with variable motion is formulated as a two-stage objective optimization problem minimizing both the total length of all paths and the task's completion time. Accordingly, a new approach based on Pythagorean Hodograph (PH) curves and Modified Harmony Search algorithm is proposed to solve the two-stage path-planning problem subject to kinematic constraints such as velocity, acceleration, and minimum turning radius. First, a method of path planning based on PH curves for a single robot is proposed. Second, a mathematical model of the two-stage path-planning problem for multiple car-like robots with variable motion subject to kinematic constraints is constructed that the first-stage minimizes the total length of all paths and the second-stage minimizes the task's completion time. Finally, a modified harmony search algorithm is applied to solve the two-stage optimization problem. A set of experiments demonstrate the effectiveness of the proposed approach.

Dextran derivative-based pH-sensitive liposomes for cancer immunotherapy.

PubMed

Yuba, Eiji; Tajima, Naoki; Yoshizaki, Yuta; Harada, Atsushi; Hayashi, Hiroshi; Kono, Kenji

2014-03-01

pH-Sensitive dextran derivatives having 3-methylglutarylated residues (MGlu-Dex) were prepared by reacting dextran with 3-methyl-glutaric anhydride. MGlu-Dex changed the protonation state and their characteristics from hydrophilic to hydrophobic in neutral and acidic pH regions. Surface modification of egg yolk phosphatidylcholine liposomes with MGlu-Dex produced highly pH-sensitive liposomes that were stable at neutral pH but which were destabilized strongly in the weakly acidic pH region. MGlu-Dex-modified liposomes were taken up efficiently by dendritic cells and delivered entrapped ovalbumin (OVA) molecules into the cytosol. When MGlu-Dex-modified liposomes loaded with OVA were administered subcutaneously to mice, the antigen-specific humoral and cellular immunity was induced more effectively than the unmodified liposomes loaded with OVA. Furthermore, administration of MGlu-Dex-modified liposomes loaded with OVA to mice bearing E.G7-OVA tumor significantly suppressed tumor growth and extended the mice survival. Results suggest that MGlu-Dex-modified liposomes are promising for the production of safe and potent antigen delivery systems that contribute to the establishment of efficient cancer immunotherapy. Copyright © 2013 Elsevier Ltd. All rights reserved.

Voltammetric enzyme sensor for urea using mercaptohydroquinone-modified gold electrode as the base transducer.

PubMed

Mizutani, F; Yabuki, S; Sato, Y

1997-01-01

A voltammetric urea-sensing electrode was prepared by combining a lipid-attached urease layer with a 2,5-dihydroxythiophenol-modified gold electrode. A self-assembled monolayer of dihydroxythiophenol was prepared on the gold surface by soaking the electrode into an ethanolic solution containing the modifier. A layer of the lipid-attached enzyme and that of acetyl cellulose overcoat were successively made on the dihydroxythiophenol-modified electrode by applying a dip-coating procedure. The addition of urea in a test solution (10 mM phosphate buffer, pH 7.0) brought about an increase of pH near the urease layer. The pH shift accompanied a negative shift of the anodic peak, which corresponded to the electro-oxidation of dihydroxyphenol moiety to form quinone, on the linear sweep voltammograms for the urease/dihydroxythiophenol electrode. The concentration of urea (0.2-5 mM) could be determined by measuring the electrode current at -0.05 V versus Ag/AgCl from the voltammogram. The electrode was applied to the determination of urea in human urine; the measurement of electrode current at such a low potential provided the urea determination without any electrochemical interference from L-ascorbic acid and uric acid.

Engineering a pH-Regulated Switch in the Major Light-Harvesting Complex of Plants (LHCII): Proof of Principle.

PubMed

Liguori, Nicoletta; Natali, Alberto; Croce, Roberta

2016-12-15

Under excess light, photosynthetic organisms employ feedback mechanisms to avoid photodamage. Photoprotection is triggered by acidification of the lumen of the photosynthetic membrane following saturation of the metabolic activity. A low pH triggers thermal dissipation of excess absorbed energy by the light-harvesting complexes (LHCs). LHCs are not able to sense pH variations, and their switch to a dissipative mode depends on stress-related proteins and allosteric cofactors. In green algae the trigger is the pigment-protein complex LHCSR3. Its C-terminus is responsible for a pH-driven conformational change from a light-harvesting to a quenched state. Here, we show that by replacing the C-terminus of the main LHC of plants with that of LHCSR3, it is possible to regulate its excited-state lifetime solely via protonation, demonstrating that the protein template of LHCs can be modified to activate reversible quenching mechanisms independent of external cofactors and triggers.

Analytical Enantioseparation of β-Substituted-2-Phenylpropionic Acids by High-Performance Liquid Chromatography with Hydroxypropyl-β-Cyclodextrin as Chiral Mobile Phase Additive.

PubMed

Tong, Shengqiang; Zhang, Hu; Yan, Jizhong

2016-04-01

Analytical enantioseparation of five β-substituted-2-phenylpropionic acids by high-performance liquid chromatography with hydroxypropyl-β-cyclodextrin (HP-β-CD) as chiral mobile phase additive was established in this paper, and chromatographic retention mechanism was studied. The effects of various factors such as the organic modifier, different ODS C18 columns and concentration of HP-β-CD were investigated. The chiral mobile phase was composed of methanol or acetonitrile and 0.5% triethylamine acetate buffer at pH 3.0 added with 25 mmol L(-1) of HP-β-CD, and baseline separations could be reached for all racemates. As for chromatographic retention mechanism, it was found that there was a negative correlation between the concentration of HP-β-CD in mobile phase and the retention factor under constant pH value and column temperature. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Chromatographic determination of Fe chelated by ethylenediamine-N-(o-hydroxyphenylacetic)-N'-(p-hydroxyphenylacetic) acid in commercial EDDHA/Fe3+ fertilizers.

PubMed

García-Marco, Sonia; Torreblanca, Ana; Lucena, Juan J

2006-02-22

EDDHA/Fe3+ chelates are the most common fertilizers used to solve Fe chlorosis in established crops. Commercial products contain two regioisomers, ethylenediamine-N,N'-bis(o-hydroxyphenylacetic) acid (o,o-EDDHA)/Fe3+ and ethylenediamine-N-(o-hydroxyphenylacetic)-N'-(p-hydroxyphenylacetic) acid (o,p-EDDHA)/Fe3+. Although several chromatographic methods exist for the determination of Fe3+ chelated by the o,o-EDDHA isomer, no method has been described for the quantification of Fe3+ chelated by o,p-EDDHA. In this work, factors that affect the behavior of o,p-EDDHA/Fe3+ in ion pair chromatography are reviewed: pH, ion pair reagent, and organic modifier. The best chromatographic performance was obtained with an aqueous mobile phase at pH 6.0 containing 35% acetonitrile and 5 mM tetrabutylammonium hydroxide under isocratic elution conditions. This method was applied to the quantification of commercial samples.

Optimization of Nutrients and Culture Conditions for Alkaline Protease Production Using Two Endophytic Micrococci: Micrococcus aloeverae and Micrococcus yunnanensis.

PubMed

Prakash, Om; Nimonkar, Yogesh; Chavadar, Mahesh S; Bharti, Nidhi; Pawar, Shrikant; Sharma, Ashutosh; Shouche, Yogesh S

2017-06-01

An endophytic species of Micrococcus was isolated from Aloe vera leaf (syn. Aloe barbadensis ) and screened for protease production with five other species of Micrococcus . Data indicated that endophytic Micrococcus aloeverae AE-6 MCC 2184 T and Micrococcus yunnanensis DSM 21948 T showed efficient protease production potential and secreted active protease at high salt (10%), temperature (40 °C) and in wide range of pH 8-10. Unlike M . yunnanensis DSM 21948 T , protease production by M . aloeverae AE-6 MCC 2184 T was stringently controlled by pH. Protease induction study using different group of peptides, peptide carbohydrates and peptide macronutrient combinations showed variable response with both the organisms. Result indicated that the amount of protease was not directly related to cell biomass but it depends on nature of inducible peptides. In this study we also developed a modified agar-well assay for semi-quantitative data from large number of replicates.

Modified Protein Improves Vitiligo Symptoms in Mice

MedlinePlus

... Vitiligo Symptoms in Mice Spotlight on Research Modified Protein Improves Vitiligo Symptoms in Mice By Colleen Labbe, ... D., Ph.D., Rush University. Altering a key protein involved in the development of vitiligo may protect ...

Adsorption of Cu2+ to biomass ash and its modified product.

PubMed

Xu, Lei; Cui, Hongbiao; Zheng, Xuebo; Liang, Jiani; Xing, Xiangyu; Yao, Lunguang; Chen, Zhaojin; Zhou, Jing

2017-04-01

Ash produced by biomass power plants has great potential for the removal of heavy metal ions from aqueous solution. The pollution of toxic heavy metals to water is a worldwide environmental problem. Discharges containing copper, in particular, are strictly controlled because the excessive copper can cause serious harm to the environment and human health. This work aims to investigate the adsorption characteristics of copper ions in aqueous solution by biomass ash and the modified products, and to evaluate their potential application in water pollution control. The biomass ash was modified with a mesoporous siliceous material and functionalized with 3-aminopropyltriethoxysilane. The surface properties of the biomass ash and the new matrix were studied to evaluate their adsorption property for Cu 2+ ions at different pHs, initial metal concentrations and the thermodynamic and kinetic were studied. The chemical and morphological properties of this modified material are analyzed; the specific surface area of the modified biomass ash was nine times that of the initial ash. Both of the two materials showed a strong affinity for Cu 2+ , and the Langmuir model could best represent the adsorption characteristics of Cu 2+ on the two kinds of materials. The adsorption capacity of copper on the material increased with the increase of pH and pH 6 was the optimum pH. Thermodynamic analysis results showed that the adsorption of Cu 2+ was spontaneous and endothermic in nature. The adsorptions of Cu 2+ onto the modified biomass ash followed pseudo-second-order kinetics.

Effect of temperature on the protonation of N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid in aqueous solutions: Potentiometric and calorimetric studies

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

Li, Xingliang; Zhang, Zhicheng; Endrizzi, Francesco

2015-06-01

The TALSPEAK process (Trivalent Actinide Lanthanide Separations by Phosphorus-reagent Extraction from Aqueous Komplexes) has been demonstrated in several pilot-scale operations to be effective at separating trivalent actinides (An 3+) from trivalent lanthanides (Ln 3+). However, fundamental studies have revealed undesired aspects of TALSPEAK, such as the significant partitioning of Na +, lactic acid, and water into the organic phase, thermodynamically unpredictable pH dependence, and the slow extraction kinetics. In the modified TALSPEAK process, the combination of the aqueous holdback complexant HEDTA (N-(2-hydroxyethyl)ethylenediamine-N,N',N'-triacetic acid) with the extractant HEH[EHP] (2-ethyl(hexyl) phosphonic acid mono-2-ethylhexyl ester) in the organic phase has been found tomore » exhibit a nearly flat pH dependence between 2.5 and 4.5 and more rapid phase transfer kinetics for the heavier lanthanides. To help understand the speciation of Ln 3+ and An 3+ in the modified TALSPEAK, systematic studies are underway on the thermodynamics of major reactions in the HEDTA system under conditions relevant to the process (e.g., higher temperatures). Thermodynamics of the protonation and complexation of HEDTA with Ln 3+ were studied at variable temperatures. Equilibrium constants and enthalpies were determined by a combination of techniques including potentiometry and calorimetry. This paper presents the protonation constants of HEDTA at T = (25 to 70) °C. The potentiometric titrations have demonstrated that, stepwise, the first two protonation constants decrease and the third one slightly increases with the increase of temperature. This trend is in good agreement with the enthalpy of protonation directly determined by calorimetry. The results of NMR analysis further confirm that the first two protonation reactions occur on the diamine nitrogen atoms, while the third protonation reaction occurs on the oxygen of a carboxylate group. These data, in conjunction with the thermodynamic parameters of Ln 3+/An 3+ complexes with HEDTA at different temperatures, will help to predict the speciation and temperature-dependent behavior of Ln 3+/An 3+ in the modified TALSPEAK process.« less

Effects of tilmicosin treatment on Pasteurella haemolytica organisms in nasal secretion specimens of calves with respiratory tract disease.

PubMed

Frank, G H; Briggs, R E; Loan, R W; Purdy, C W; Zehr, E S

2000-05-01

To determine the effect of tilmicosin treatment on number of Pasteurella haemolytica (PH) organisms in nasal secretion specimens of calves with respiratory tract disease. 206 British mixed-breed beef calves, 2 to 5 months old. In 2 separate studies of outbreaks, calves (study 1, n = 101; study 2, n = 105) that developed respiratory tract disease after transport to a feedlot were treated with tilmicosin. Nasal secretion specimens were examined for PH organisms to determine the status of colonization. In both studies, PH serotypes A1 and A6 were isolated. In study 1, tilmicosin treatment eliminated or markedly reduced the number of PH organisms in calves on days 1, 4, and 5 after treatment. In study 2, tilmicosin treatment eliminated PH organisms in calves on days 1, 2, 5, and 6 after treatment. Overall, tilmicosin treatment increased the number of culture-positive calves that became culture-negative and decreased the number of culture-negative calves that became culture-positive for up to 6 days after treatment. Tilmicosin treatment decreased the number of PH organisms in nasal secretion specimens, which indicated that fewer PH organisms were available to infect the lungs or to infect other calves. By reducing colonization, prophylactic use of tilmicosin before transport or at the time of arrival at a feedlot is likely to reduce the incidence of acute respiratory tract disease in calves for the initial several days after arrival, which is the period when they are most susceptible to infectious organisms.

Protein Complexation and pH Dependent Release Using Boronic Acid Containing PEG-Polypeptide Copolymers.

PubMed

Negri, Graciela E; Deming, Timothy J

2017-01-01

New poly(L-lysine)-b-poly(ethylene glycol) copolypeptides have been prepared, where the side-chain amine groups of lysine residues are modified to contain ortho-amine substituted phenylboronic acid, i.e., Wulff-type phenylboronic acid (WBA), groups to improve their pH responsive, carbohydrate binding properties. These block copolymers form nanoscale complexes with glycosylated proteins that are stable at physiological pH, yet dissociate and release the glycoproteins under acidic conditions, similar to those found in endosomal and lysosomal compartments within cells. These results suggest that WBA modified polypeptide copolymers are promising for further development as degradable carriers for intracellular protein delivery. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of pH adjustment and sodium ions on sour taste intensity of organic acids

USDA-ARS?s Scientific Manuscript database

Protonated organic acid species have been shown to be the primary stimuli responsible for sour taste of organic acids. However, we have observed that sour taste may be modulated when the pH of acid solutions is raised using sodium hydroxide. Objectives were to evaluate the effect of pH adjustment on...

Ecological suicide in microbes.

PubMed

Ratzke, Christoph; Denk, Jonas; Gore, Jeff

2018-05-01

The growth and survival of organisms often depend on interactions between them. In many cases, these interactions are positive and caused by a cooperative modification of the environment. Examples are the cooperative breakdown of complex nutrients in microbes or the construction of elaborate architectures in social insects, in which the individual profits from the collective actions of her peers. However, organisms can similarly display negative interactions by changing the environment in ways that are detrimental for them, for example by resource depletion or the production of toxic byproducts. Here we find an extreme type of negative interactions, in which Paenibacillus sp. bacteria modify the environmental pH to such a degree that it leads to a rapid extinction of the whole population, a phenomenon that we call ecological suicide. Modification of the pH is more pronounced at higher population densities, and thus ecological suicide is more likely to occur with increasing bacterial density. Correspondingly, promoting bacterial growth can drive populations extinct whereas inhibiting bacterial growth by the addition of harmful substances-such as antibiotics-can rescue them. Moreover, ecological suicide can cause oscillatory dynamics, even in single-species populations. We found ecological suicide in a wide variety of microbes, suggesting that it could have an important role in microbial ecology and evolution.

Coordination polymer nanocapsules prepared using metal-organic framework templates for pH-responsive drug delivery

NASA Astrophysics Data System (ADS)

Tang, Lei; Shi, Jiafu; Wang, Xiaoli; Zhang, Shaohua; Wu, Hong; Sun, Hongfan; Jiang, Zhongyi

2017-07-01

A facile, efficient, and versatile approach is presented to synthesize pH-responsive nanocapsules (˜120 nm) by combining the advantages of metal-organic frameworks (MOFs) and metal-organic thin films. ZIF-8 nanoparticles are used as templates on which a thin film coating of iron(III)-catechol complexes is derived from the coordination between dopamine-modified alginate (AlgDA) and iron(III) ions. After the template removal, nanocapsules with a pH-responsive wall are obtained. Doxorubicin (Dox), a typical anticancer drug, is first immobilized in ZIF-8 frameworks through coprecipitation and then encapsulated in nanocapsules after the removal of ZIF-8. The structure of the iron(III)-catechol complex varies with pH value, thus conferring the Dox@Nanocapsules with tailored release behavior in vitro. Cytotoxicity tests illustrate the highly effective cytotoxicity of Dox@Nanocapsules towards cancer cells. This study provides a new method for preparing smart nanocapsules and offers more opportunities for the controlled delivery of drugs.

Effects of soil properties on the uptake of pharmaceuticals into earthworms.

PubMed

Carter, Laura J; Ryan, Jim J; Boxall, Alistair B A

2016-06-01

Pharmaceuticals can enter the soil environment when animal slurries and sewage sludge are applied to land as a fertiliser or during irrigation with contaminated water. These pharmaceuticals may then be taken up by soil organisms possibly resulting in toxic effects and/or exposure of organisms higher up the food chain. This study investigated the influence of soil properties on the uptake and depuration of pharmaceuticals (carbamazepine, diclofenac, fluoxetine and orlistat) in the earthworm Eisenia fetida. The uptake and accumulation of pharmaceuticals into E. fetida changed depending on soil type. Orlistat exhibited the highest pore water based bioconcentration factors (BCFs) and displayed the largest differences between soil types with BCFs ranging between 30.5 and 115.9. For carbamazepine, diclofenac and fluoxetine BCFs ranged between 1.1 and 1.6, 7.0 and 69.6 and 14.1 and 20.4 respectively. Additional analysis demonstrated that in certain treatments the presence of these chemicals in the soil matrices changed the soil pH over time, with a statistically significant pH difference to control samples. The internal pH of E. fetida also changed as a result of incubation in pharmaceutically spiked soil, in comparison to the control earthworms. These results demonstrate that a combination of soil properties and pharmaceutical physico-chemical properties are important in terms of predicting pharmaceutical uptake in terrestrial systems and that pharmaceuticals can modify soil and internal earthworm chemistry which may hold wider implications for risk assessment. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Size-Controlled Dissolution of Organic-Coated Silver Nanoparticles

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

Ma, Rui; Levard, Clément; Marinakos, Stella M.

2012-04-02

The solubility of Ag NPs can affect their toxicity and persistence in the environment. We measured the solubility of organic-coated silver nanoparticles (Ag NPs) having particle diameters ranging from 5 to 80 nm that were synthesized using various methods, and with different organic polymer coatings including poly(vinylpyrrolidone) and gum arabic. The size and morphology of Ag NPs were characterized by transmission electron microscopy (TEM). X-ray absorption fine structure (XAFS) spectroscopy and synchrotron-based total X-ray scattering and pair distribution function (PDF) analysis were used to determine the local structure around Ag and evaluate changes in crystal lattice parameters and structure asmore » a function of NP size. Ag NP solubility dispersed in 1 mM NaHCO{sub 3} at pH 8 was found to be well correlated with particle size based on the distribution of measured TEM sizes as predicted by the modified Kelvin equation. Solubility of Ag NPs was not affected by the synthesis method and coating as much as by their size. Based on the modified Kelvin equation, the surface tension of Ag NPs was found to be {approx}1 J/m{sup 2}, which is expected for bulk fcc (face centered cubic) silver. Analysis of XAFS, X-ray scattering, and PDFs confirm that the lattice parameter, {alpha}, of the fcc crystal structure of Ag NPs did not change with particle size for Ag NPs as small as 6 nm, indicating the absence of lattice strain. These results are consistent with the finding that Ag NP solubility can be estimated based on TEM-derived particle size using the modified Kelvin equation for particles in the size range of 5-40 nm in diameter.« less

The influence of addition of ion-pairing acid and organic modifier of the mobile phase on retention and migration of peptides in pressurized planar electrochromatography system with octadecyl silica-based adsorbent.

PubMed

Gwarda, Radosław Ł; Dzido, Tadeusz H

2018-07-13

In our previous papers we have investigated the influence of the mobile phase composition on mechanism of retention, selectivity and efficiency of peptide separation in various high-performance thin-layer chromatography (HPTLC) systems with commercially available silica-based adsorbents. We have also investigated the influence of pH of the mobile phase buffer on migration and separation of peptides in pressurized planar electrochromatography (PPEC). Here we investigate the influence of concentration of ion-pairing additive, and concentration and type of organic modifier of the mobile phase on migration of peptides in PPEC system with octadecyl silica-based adsorbent, and with the same set of the solutes as before. We compare our current results with the results obtained before for similar HPTLC and PPEC systems, and discuss the influence of particular variables on retention, electrophoretic mobility of solutes and electroosmotic flow of the mobile phase. We show, that the final selectivity of peptide separation results from co-influence of all the three factors mentioned. Concentration of organic modifier of the mobile phase, as well as concentration of ion-pairing additive, affect the retention, the electrophoretic mobility, and the electroosmotic flow simultaneously. This makes independent optimization of these factors rather difficult. Anyway PPEC offers much faster separation of peptides with quite different selectivity, in comparison to HPTLC, with similar adsorbents and similar mobile phase composition. However, we also present and discuss the issue of extensive tailing of peptide zones in the PPEC in comparison to similar HPTLC systems. Copyright © 2018 Elsevier B.V. All rights reserved.

Modeling and predicting the biofilm formation of Salmonella Virchow with respect to temperature and pH.

PubMed

Ariafar, M Nima; Buzrul, Sencer; Akçelik, Nefise

2016-03-01

Biofilm formation of Salmonella Virchow was monitored with respect to time at three different temperature (20, 25 and 27.5 °C) and pH (5.2, 5.9 and 6.6) values. As the temperature increased at a constant pH level, biofilm formation decreased while as the pH level increased at a constant temperature, biofilm formation increased. Modified Gompertz equation with high adjusted determination coefficient (Radj(2)) and low mean square error (MSE) values produced reasonable fits for the biofilm formation under all conditions. Parameters of the modified Gompertz equation could be described in terms of temperature and pH by use of a second order polynomial function. In general, as temperature increased maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation decreased; whereas, as pH increased; maximum biofilm quantity, maximum biofilm formation rate and time of acceleration of biofilm formation increased. Two temperature (23 and 26 °C) and pH (5.3 and 6.3) values were used up to 24 h to predict the biofilm formation of S. Virchow. Although the predictions did not perfectly match with the data, reasonable estimates were obtained. In principle, modeling and predicting the biofilm formation of different microorganisms on different surfaces under various conditions could be possible.

CO2 controlled flocculation of microalgae using pH responsive cellulose nanocrystals

NASA Astrophysics Data System (ADS)

Eyley, Samuel; Vandamme, Dries; Lama, Sanjaya; van den Mooter, Guy; Muylaert, Koenraad; Thielemans, Wim

2015-08-01

Cellulose nanocrystals were grafted with imidazole functionalities up to DS 0.06 using a one-pot functionalization strategy. The resulting nanocrystals were shown to have a pH responsive surface charge which was found to be positive below pH 6 and negative above pH 7. These imidazolyl cellulose nanocrystals were tested for flocculation of Chlorella vulgaris using CO2 to induce flocculation. Up to 90% flocculation efficiency was achieved with 200 mg L-1 dose. Furthermore, the modified cellulose nanocrystals showed good compatibility with the microalgae during cultivation, giving potential for the production of reversible flocculation systems.Cellulose nanocrystals were grafted with imidazole functionalities up to DS 0.06 using a one-pot functionalization strategy. The resulting nanocrystals were shown to have a pH responsive surface charge which was found to be positive below pH 6 and negative above pH 7. These imidazolyl cellulose nanocrystals were tested for flocculation of Chlorella vulgaris using CO2 to induce flocculation. Up to 90% flocculation efficiency was achieved with 200 mg L-1 dose. Furthermore, the modified cellulose nanocrystals showed good compatibility with the microalgae during cultivation, giving potential for the production of reversible flocculation systems. Electronic supplementary information (ESI) available: Spectra for all products. See DOI: 10.1039/C5NR03853G

Identification and characterization of yeasts causing chalk mould defects on par-baked bread.

PubMed

Deschuyffeleer, N; Audenaert, K; Samapundo, S; Ameye, S; Eeckhout, M; Devlieghere, F

2011-08-01

Pichia anomala, Hyphopichia burtonii and Saccharomycopsis fibuligera are spoilage yeasts causing chalk mould defects on par-baked breads packaged under modified atmosphere. The first objective of this study was to identify yeasts isolated from spoiled par-baked breads by means of a RAPD protocol and to determine the dominant spoilers amongst identified strains. The second objective was to determine the effects of water activity (a(w)) and pH value on the growth rates and lag phase durations of P. anomala, H. burtonii and S. fibuligera. 95% of the yeasts tested were identified as P. anomala and 5% as S. fibuligera, H. burtonii was not detected. In order to investigate the effect of a(w) and pH the growth of the three yeasts was tested within an a(w) range of 0.88-0.98 and a pH range of 2.8-8.0. P. anomala was able to grow from pH 2.8 to 8 without a clear optimum. S. fibuligera and H. burtonii showed a pH optimum for growth of 5. The optimum water activity for growth was different for the three strains and varied between 0.96 and 0.98. These growth data were further used to develop secondary models that describe the relationship between a(w) and the radial or colony growth rate (g, mm/d) or the lag phase duration (λ, d). The identification of the spoilage organisms and a good understanding of the effects of a(w) and pH on the growth behavior is essential for future development of adequate conservation strategies against chalk mould defects. Copyright © 2011 Elsevier Ltd. All rights reserved.

A comparative study for adsorption of lysozyme from aqueous samples onto Fe3O4 magnetic nanoparticles using different ionic liquids as modifier.

PubMed

Kamran, Sedigheh; Absalan, Ghodratollah; Asadi, Mozaffar

2015-12-01

In this paper, nanoparticles of Fe3O4 as well as their modified forms with different ionic liquids (IL-Fe3O4) were prepared and used for adsorption of lysozyme. The mean size and the surface morphology of the nanoparticles were characterized by TEM, XRD and FTIR techniques. Adsorption studies of lysozyme were performed under different experimental conditions in batch system on different modified magnetic nanoparticles such as, lysozyme concentration, pH of the solution, and contact time. Experimental results were obtained under the optimum operational conditions of pH 9.0 and a contact time of 10 min when initial protein concentrations of 0.05-2.0 mg mL(-1) were used. The isotherm evaluations revealed that the Langmuir model attained better fits to the equilibrium data than the Freundlich model. The maximum obtained adsorption capacities were 370.4, 400.0 500.0 and 526.3 mg of lysozyme for adsorption onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br] per gram of adsorbent, respectively. The Langmuir adsorption constants were 0.004, 0.019, 0.024 and 0.012 L mg(-1) for adsorptions of lysozyme onto Fe3O4 and modified magnetic nanoparticles by [C4MIM][Br], [C6MIM][Br] and [C8MIM][Br], respectively. The adsorption capacity of lysozyme was found to be dependent on its chemical structure, pH of the solution, temperature and type of ionic liquid as modifier. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated. Furthermore, the thermodynamic parameters were calculated. Protein could desorb from IL-Fe3O4 nanoparticles by using NaCl solution at pH 9.5 and was reused.

Acid-base equilibria inside amine-functionalized mesoporous silica.

PubMed

Yamaguchi, Akira; Namekawa, Manato; Kamijo, Toshio; Itoh, Tetsuji; Teramae, Norio

2011-04-15

Acid-base equilibria and effective proton concentration inside a silica mesopore modified with a trimethyl ammonium (TMAP) layer were studied by steady-state fluorescence experiments. The mesoporous silica with a dense TMAP layer (1.4 molecules/nm(2)) was prepared by a post grafting of N-trimethoxysilylpropyl-N,N,N-trimethylammonium at surfactant-templated mesoporous silica (diameter of silica framework =3.1 nm). The resulting TMAP-modified mesoporous silica strongly adsorbed of anionic fluorescence indicator dyes (8-hydroxypyrene-1,3,6-trisulfonate (pyranine), 8-aminopyrene-1,3,6-trisulfonate (APTS), 5,10,15,20-tetraphenyl-21H,23H-porphinetetrasulfonic acid disulfuric acid (TPPS), 2-naphthol-3,6-disulfonate (2NT)) and fluorescence excitation spectra of these dyes within TMAP-modified mesoporous silica were measured by varying the solution pH. The fluorescence experiments revealed that the acid-base equilibrium reactions of all pH indicator dyes within the TMAP-modified silica mesopore were quite different from those in bulk water. From the analysis of the acid-base equilibrium of pyranine, the following relationships between solution pH (pH(bulk)) and the effective proton concentration inside the pore (pH(pore)) were obtained: (1) shift of pH(pore) was 1.8 (ΔpH(pore)=1.8) for the pH(bulk) change from 2.1 to 9.1 (ΔpH(bulk)=7.0); (2) pH(pore) was not simply proportional to pH(bulk); (3) the inside of the TMAP-modified silica mesopore was suggested to be in a weak acidic or neutral condition when pH(bulk) was changed from 2.0 to 9.1. Since these relationships between pH(bulk) and pH(pore) could explain the acid-base equilibria of other pH indicator dyes (APTS, TPPS, 2NT), these relationships were inferred to describe the effective proton concentration inside the TMAP-modified silica mesopore. © 2011 American Chemical Society

Design and characterization of sulfide-modified nanoscale zerovalent iron for cadmium(II) removal from aqueous solutions

NASA Astrophysics Data System (ADS)

Lv, Dan; Zhou, Xiaoxin; Zhou, Jiasheng; Liu, Yuanli; Li, Yizhou; Yang, Kunlun; Lou, Zimo; Baig, Shams Ali; Wu, Donglei; Xu, Xinhua

2018-06-01

Nanoscale zero-valent iron (nZVI) has high removal efficiency and strong reductive ability to organic and inorganic contaminants, but concerns over its stability and dispersity limit its application. In this study, nZVI was modified with sulfide to enhance Cd(II) removal from aqueous solutions. TEM and SEM analyses showed that sulfide-modified nZVI (S-nZVI) had a core-shell structure of nano-sized spherical particles, and BET results proved that sulfide modification doubled the specific surface area from 26.04 to 50.34 m2 g-1 and inhibited the aggregation of nZVI. Mechanism analysis indicated that Cd(II) was immobilized through complexation and precipitation. Cd(II) removal rate on nZVI was only 32% in 2 h, while complete immobilization could be achieved in 15 min on S-nZVI, and S-nZVI with an optimal S/Fe molar ratio of 0.3 offered a cadmium removal capacity of about 150 mg g-1 at pH 7 and 303 K. The process of Cd(II) immobilization on S-nZVI was fitted well with pseudo-second-order kinetic model, and the increase of temperature favored Cd(II) immobilization, suggesting an endothermic process. The presence of Mg2+ and Ca2+ hindered Cd(II) removal while Cu2+ did the opposite, which led to the order as Cu2+ > control > Mg2+ > Ca2+. The removal rate of 20 mg L-1 Cd(II) maintained a high level with the fluctuation of environmental conditions such as pH, ion strength and presence of HA. This study demonstrated that S-nZVI could be a promising adsorbent for Cd(II) immobilization from cadmium-contaminated water.

Development of pH Sensitive Nanoparticles for Intestinal Drug Delivery Using Chemically Modified Guar Gum Co-Polymer.

PubMed

Varma, Vegesna Naga Sravan Kumar; Shivakumar, Hosakote Gurumalappa; Balamuralidhara, Veerna; Navya, Manne; Hani, Umme

2016-01-01

The aim of the research work was to chemically modify guargum (GG) as a pH sensitive co-polymer and formulating intestinal targeting ESO nanoparticles (NPs) using the synthesized co-polymer. Poly acrylamide-grafted-guar gum (PAAm-g-GG) co-polymer was synthesized by free radical polymerization. Chemical modification of PAAm-g-GG by alkaline hydrolysis results in formation of a pH-sensitive co-polymer. The effect of GG and acryl amide (AAm) on grafting was studied. Esomeprazole magnesium (ESO) loaded pH sensitive NPs were prepared by nano-emulsification polymer crosslinking method and characterized. Sixteen formulations were prepared and the concentration of process variables wasvaried to obtain nanoparticles of 200-600 nm. The NPs were found to be homogenous in size distribution. The encapsulation efficiency and drug loading ranged from 33.2% to 50.1% and 12.2% to 17.2% respectively. Particle size, encapsulation efficiency and drug loading increasedalong with co-polymer concentration. In-vitro release studies at pH 1.2 for 2 h, followed by pH 6.8 showed that environment pH significantly affected the drug release. SEM has shown that NPsare spherical with smooth surface. The pH sensitive PAAm-g-GGNPs resisted the initial release of the drug from the drug loaded NPs in acidic pH and delayed the release process to a longer period in alkaline environment.

Development of pH Sensitive Nanoparticles for Intestinal Drug Delivery Using Chemically Modified Guar Gum Co-Polymer

PubMed Central

Varma, Vegesna Naga Sravan Kumar; Shivakumar, Hosakote Gurumalappa; Balamuralidhara, Veerna; Navya, Manne; Hani, Umme

2016-01-01

The aim of the research work was to chemically modify guargum (GG) as a pH sensitive co-polymer and formulating intestinal targeting ESO nanoparticles (NPs) using the synthesized co-polymer. Poly acrylamide-grafted-guar gum (PAAm-g-GG) co-polymer was synthesized by free radical polymerization. Chemical modification of PAAm-g-GG by alkaline hydrolysis results in formation of a pH-sensitive co-polymer. The effect of GG and acryl amide (AAm) on grafting was studied. Esomeprazole magnesium (ESO) loaded pH sensitive NPs were prepared by nano-emulsification polymer crosslinking method and characterized. Sixteen formulations were prepared and the concentration of process variables wasvaried to obtain nanoparticles of 200-600 nm. The NPs were found to be homogenous in size distribution. The encapsulation efficiency and drug loading ranged from 33.2% to 50.1% and 12.2% to 17.2% respectively. Particle size, encapsulation efficiency and drug loading increasedalong with co-polymer concentration. In-vitro release studies at pH 1.2 for 2 h, followed by pH 6.8 showed that environment pH significantly affected the drug release. SEM has shown that NPsare spherical with smooth surface. The pH sensitive PAAm-g-GGNPs resisted the initial release of the drug from the drug loaded NPs in acidic pH and delayed the release process to a longer period in alkaline environment. PMID:27610149

Introducing a decomposition rate modifier in the Rothamsted Carbon Model to predict soil organic carbon stocks in saline soils.

PubMed

Setia, Raj; Smith, Pete; Marschner, Petra; Baldock, Jeff; Chittleborough, David; Smith, Jo

2011-08-01

Soil organic carbon (SOC) models such as the Rothamsted Carbon Model (RothC) have been used to estimate SOC dynamics in soils over different time scales but, until recently, their ability to accurately predict SOC stocks/carbon dioxide (CO(2)) emissions from salt-affected soils has not been assessed. Given the large extent of salt-affected soils (19% of the 20.8 billion ha of arable land on Earth), this may lead to miss-estimation of CO(2) release. Using soils from two salt-affected regions (one in Punjab, India and one in South Australia), an incubation study was carried out measuring CO(2) release over 120 days. The soils varied both in salinity (measured as electrical conductivity (EC) and calculated as osmotic potential using EC and water content) and sodicity (measured as sodium adsorption ratio, SAR). For soils from both regions, the osmotic potential had a significant positive relationship with CO(2)-C release, but no significant relationship was found between SAR and CO(2)-C release. The monthly cumulative CO(2)-C was simulated using RothC. RothC was modified to take into account reductions in plant inputs due to salinity. A subset of non-salt-affected soils was used to derive an equation for a "lab-effect" modifier to account for changes in decomposition under lab conditions and this modifier was significantly related with pH. Using a subset of salt-affected soils, a decomposition rate modifier (as a function of osmotic potential) was developed to match measured and modelled CO(2)-C release after correcting for the lab effect. Using this decomposition rate modifier, we found an agreement (R(2) = 0.92) between modelled and independently measured data for a set of soils from the incubation experiment. RothC, modified by including reduced plant inputs due to salinity and the salinity decomposition rate modifier, was used to predict SOC stocks of soils in a field in South Australia. The predictions clearly showed that SOC stocks are reduced in saline soils. Therefore both the decomposition rate modifier and plant input modifier should be taken into account when accounting for SOC turnover in saline soils. Since modeling has previously not accounted for the impact of salinity, our results suggest that previous predictions may have overestimated SOC stocks.

Modification of a single tryptophan residue in human Cu,Zn-superoxide dismutase by peroxynitrite in the presence of bicarbonate.

PubMed

Yamakura, F; Matsumoto, T; Fujimura, T; Taka, H; Murayama, K; Imai, T; Uchida, K

2001-07-09

Human recombinant Cu,Zn-SOD was reacted with peroxynitrite in a reaction mixture containing 150 mM potassium phosphate buffer (pH 7.4) 25 mM sodium bicarbonate, and 0.1 mM diethylenetriamine pentaacetic acid. Disappearance of fluorescence emission at 350 nm, which could be attributed to modification of a single tryptophan residue, was observed in the modified enzyme with a pH optimum of around 8.4. A fluorescence decrease with the same pH optimum was also observed without sodium bicarbonate, but with less efficiency. Amino acid contents of the modified enzyme showed no significant difference in all amino acids except the loss of a single tryptophan residue of the enzyme. The peroxynitrite-modified enzyme showed an increase in optical absorption around 350 nm and 30% reduced enzyme activity based on the copper contents. The modified enzyme showed the same electron paramagnetic resonance spectrum as that of the control enzyme. The modified Cu,Zn-SOD showed a single protein band in sodium dodecyl sulfate--polyacrylamide gel electrophoresis (SDS--PAGE) and five protein bands in non-denaturing PAGE. From this evidence, we conclude that nitration and/or oxidation of the single tryptophan 32 and partial inactivation of the enzyme activity of Cu,Zn-SOD is caused by a peroxynitrite-carbon dioxide adduct without perturbation of the active site copper integrity.

Nitrogen removal performance of anaerobic ammonia oxidation (ANAMMOX) in presence of organic matter.

PubMed

Zhu, Weiqiang; Zhang, Peiyu; Yu, Deshuang; Dong, Huiyu; Li, Jin

2017-06-01

A sequencing batch reactor (SBR) was used to test the nitrogen removal performance of anaerobic ammonium oxidation (ANAMMOX) in presence of organic matter. Mesophilic operation (30 ± 0.5 °C) was performed with influent pH 7.5. The results showed, independent of organic matter species, ANAMMOX reaction was promoted when COD was lower than 80 mg/L. However, specific ANAMMOX activity decreased with increasing organic matter content. Ammonium removal efficiency decreased to 80% when COD of sodium succinate, sodium potassium tartrate, peptone and lactose were 192.5, 210, 225 and 325 mg/L, respectively. The stoichiometry ratio resulting from different OM differed largely and R 1 could be as an indicator for OM inhibition. When COD concentration was 240 mg/L, the loss of SAA resulting from lactose, peptone, sodium potassium tartrate and sodium succinate were 28, 36, 50 and 55%, respectively. Sodium succinate had the highest inhibitory effect on SAA. When ANAMMOX process was used to treat wastewater containing OM, the modified Logistic model could be employed to predict the NRE max .

Alleviation of environmental risks associated with severely contaminated mine tailings using amendments: Modeling of trace element speciation, solubility, and plant accumulation.

PubMed

Pardo, Tania; Bes, Cleménce; Bernal, Maria Pilar; Clemente, Rafael

2016-11-01

Tailings are considered one of the most relevant sources of contamination associated with mining activities. Phytostabilization of mine spoils may need the application of the adequate combination of amendments to facilitate plant establishment and reduce their environmental impact. Two pot experiments were set up to assess the capability of 2 inorganic materials (calcium carbonate and a red mud derivate, ViroBind TM ), alone or in combination with organic amendments, for the stabilization of highly acidic trace element-contaminated mine tailings using Atriplex halimus. The effects of the treatments on tailings and porewater physico-chemical properties and trace-element accumulation by the plants, as well as the processes governing trace elements speciation and solubility in soil solution and their bioavailability were modeled. The application of the amendments increased tailings pH and decreased (>99%) trace elements solubility in porewater, but also changed the speciation of soluble Cd, Cu, and Pb. All the treatments made A. halimus growth in the tailings possible; organic amendments increased plant biomass and nutritional status, and reduced trace-element accumulation in the plants. Tailings amendments modified trace-element speciation in porewater (favoring the formation of chlorides and/or organo-metallic forms) and their solubility and plant uptake, which were found to be mainly governed by tailing/porewater pH, electrical conductivity, and organic carbon content, as well as soluble/available trace-element concentrations. Environ Toxicol Chem 2016;35:2874-2884. © 2016 SETAC. © 2016 SETAC.

Aminopyridine modified Spirulina platensis biomass for chromium(VI) adsorption in aqueous solution.

PubMed

Bayramoglu, Gulay; Akbulut, Aydin; Arica, M Yakup

Chemical modification of Spirulina platensis biomass was realized by sequential treatment of algal surface with epichlorohydrin and aminopyridine. Adsorptive properties of Cr(VI) ions on native and aminopyridine modified algal biomass were investigated by varying pH, contact time, ionic strength, initial Cr(VI) concentration, and temperature. FTIR and analytical analysis indicated that carboxyl and amino groups were the major functional groups for Cr(VI) ions adsorption. The optimum adsorption was observed at pH 3.0 for native and modified algal biomasses. The adsorption capacity was found to be 79.6 and 158.7 mg g(-1), for native and modified algal biomasses, respectively. For continuous system studies, the experiments were conducted to study the effect of important design parameters such as flow rate and initial concentration of metal ions, and the maximum sorption capacity was observed at a flow rate of 50 mL h(-1), and Cr(VI) ions concentration 200 mg L(-1) with modified biomass. Experimental data fitted a pseudo-second-order equation. The regeneration performance was observed to be 89.6% and 94.3% for native and modified algal biomass, respectively.

Inhibition of Photocatalytic Activity of Basic Blue-41 by ZnO Modified Surface with Amino Silane

NASA Astrophysics Data System (ADS)

Limsapapkasiphon, S.; Sirisaksoontorn, W.; Songsasen, A.

2018-03-01

The reduction of the photo catalytic efficiency of ZnO can be achieved by modifying its surface with amino silane, which synthesized through condensation reaction under basic condition. The pH of solution was varied from 8 to 14 during the synthesis and was found that pH 12 was the most suitable pH for the preparation. All of ZMAS were characterized by Elemental Analysis which showed the highest percentage of nitrogen at 3.1064% and IR technique which indicated the Si-O-Zn bond at about 1000 cm-1. The photodegradation property of ZMAS prepared at pH 8-12 toward basic blue 41 was retarded when compared with the unmodified ZnO. Effect of mole ratio of ZnO:APTES (1:0.1, 1:0.5, 1:1, and 1:2) in the preparation of ZMAS was investigated. The photodegration activity of ZMAS prepared at mole ratio of ZnO:APTES as 1:0.5 to 1:2 toward basic blue 41 was retarded when compared with the unmodified ZnO. The coating of amino silane on ZnO surface did not have much effect on the band gap energy of modified ZnO. The absorption edge of ZMAS was only slightly shifted from 392 to 397 nm.

An all-water-based system for robust superhydrophobic surfaces.

PubMed

Liu, Mingming; Hou, Yuanyuan; Li, Jing; Tie, Lu; Guo, Zhiguang

2018-06-01

Superhydrophobic surfaces with micro-/nanohierarchical structures are mechanically weak. Generally, organic solvents are used to dissolve or disperse organic adhesives and modifiers to enhance the mechanical strength of superhydrophobic surfaces. In this work, an all-water-based spraying solution is developed for the preparation of robust superhydrophobic surfaces, which contains ZnO nanoparticles, aluminum phosphate as an inorganic adhesive, and polytetrafluoroethylene with low surface energy. The all-water-based system is appreciated for low price and less pollution. Importantly, the prepared superhydrophobic surfaces are durable enough against various harsh conditions (such as UV irradiation for 12 h, pH values from 1 to 13, and temperatures from -10 to 300 °C for 12 h) and physical damages (including sandpaper abrasion and sand impact tests for 50 cycles). In addition, the obtained interfacial materials show promise for practical applications such as anti-icing and oil-water separation. Copyright © 2018 Elsevier Inc. All rights reserved.

Mobility of adsorbed Cry1Aa insecticidal toxin from Bacillus thuringiensis (Bt) on montmorillonite measured by fluorescence recovery after photobleaching (FRAP)

NASA Astrophysics Data System (ADS)

Helassa, Nordine; Daudin, Gabrielle; Noinville, Sylvie; Janot, Jean-Marc; Déjardin, Philippe; Staunton, Siobhán; Quiquampoix, Hervé

2010-06-01

The insecticidal toxins produced by genetically modified Bt crops are introduced into soil through root exudates and tissue decomposition and adsorb readily on soil components, especially on clays. This immobilisation and the consequent concentration of the toxins in "hot spots" could increase the exposure of soil organisms. Whereas the effects on non-target organisms are well documented, few studies consider the migration of the toxin in soil. In this study, the residual mobility of Bt Cry1Aa insecticidal toxin adsorbed on montmorillonite was assessed using fluorescence recovery after photobleaching (FRAP). This technique, which is usually used to study dynamics of cytoplasmic and membrane molecules in live cells, was applied for the first time to a protein adsorbed on a finely divided swelling clay mineral, montmorillonite. No mobility of adsorbed toxin was observed at any pH and at different degrees of surface saturation.

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

Preliminary study on optimization of pH, oxidant and catalyst dose for high COD content: solar parabolic trough collector

PubMed Central

2013-01-01

In the present study, solar photocatalytic oxidation has been investigated through laboratory experiments as an alternative to conventional secondary treatment for the organic content reduction of high COD wastewater. Experiments have been performed on synthetic high COD wastewater for solar photocatalytic oxidation using a parabolic trough reactor. Parameters affecting the oxidation of organics have been investigated. The experimental design followed the sequence of dark adsorption studies of organics, followed by photolytic studies (in absence of catalyst) and finally photocatalytic studies in presence and absence of additional oxidant (H2O2). All the experimental studies have been performed at pH values of 2, 4, 6,8,10 and the initial pH value of the wastewater (normal pH). For photocatalytic studies, TiO2 has been used as a photocatalyst. Optimization of catalyst dose, pH and H2O2 concentration has been done. Maximum reduction of organic content was observed at the normal pH value of the wastewater (pH = 6.8). The reaction rate was significantly enhanced in presence of hydrogen peroxide. The optimum pH other than the Normal was in the alkaline range. Acidic pH was not found to be favourable for organic content reduction. pH was found to be a dominant factor affecting reaction rate even in presence of H2O2 as an additional oxidant. Also, the solar detoxification process was effective in treating a waste with a COD level of more than 7500 mg/L, which is a otherwise a difficult waste to treat. It can therefore be used as a treatment step in the high organic wastewater treatment during the primary stage also as it effectively reduces the COD content by 86%. PMID:23369352

Acidogenic fermentation of iron-enhanced primary sedimentation sludge under different pH conditions for production of volatile fatty acids.

PubMed

Lin, Lin; Li, Xiao-Yan

2018-03-01

Iron-based chemically enhanced primary sedimentation (CEPS) is increasingly adopted for wastewater treatment in mega cities, producing a large amount of sludge (Fe-sludge) with a high content of organics for potential organic resource recovery. In this experimental study, acidogenic fermentation was applied treat FeCl 3 -based CEPS sludge for production of volatile fatty acids (VFAs) at different pHs. Batch fermentation tests on the Fe-sludge with an organic content of 10 g-COD/L showed that the maximum VFAs production reached 2782.2 mg-COD/L in the reactor without pH control, and it reached 688.4, 3095.3, and 2603.7 mg-COD/L in reactors with pHs kept at 5.0, 6.0 and 8.0, respectively. Analysis of the acidogenesis kinetics and enzymatic activity indicated that the alkaline pH could accelerate the rate of organic hydrolysis but inhibited the further organic conversion to VFAs. In semi-continuous sludge fermentation tests, the VFAs yield in the pH6 reactor was 20% higher than that in the control reactor without pH regulation, while the VFAs yield in the pH8 reactor was 10% lower than the control. Illumina MiSeq sequencing revealed that key functional microorganisms known for effective sludge fermentation, including Bacteroidia and Erysipelotrichi, were enriched in the pH6 reactor with an enhanced VFAs production, while Clostridia became more abundant in the pH8 reactor to stand the unfavorable pH condition. The research presented acidogenic fermentation as an effective process for CEPS sludge treatment and organic resource recovery and provided the first insight into the related microbial community dynamics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impact of a modified carbonated beverage on human dental plaque and salivary pH: an in vivo study.

PubMed

Sardana, V; Balappanavar, A Y; Patil, G B; Kulkarni, N; Sagari, S G; Gupta, K D

2012-01-01

To assess the plaque and salivary pH changes at different time intervals in vivo after consumption of a carbonated beverage modified with sodium fluoride and calcium phosphate. Twenty-four subjects aged 18-25 years were recruited and randomly assigned to three groups (group A, original drink Sprite; group B, Sprite with sodium fluoride; group C, Sprite with calcium phosphate). Collection of pooled plaque and unstimulated saliva was done before and after the drinks were consumed by the subjects at 5-, 10-, 20- and 30-minute intervals. The pH rise was higher with group C for plaque and group B for saliva. Modification of the test carbonated beverage with calcium phosphate and fluoride may exert some protective potential, especially in high caries risk candidates.

Chemical equilibrium modeling of organic acids, pH, aluminum, and iron in Swedish surface waters.

PubMed

Sjöstedt, Carin S; Gustafsson, Jon Petter; Köhler, Stephan J

2010-11-15

A consistent chemical equilibrium model that calculates pH from charge balance constraints and aluminum and iron speciation in the presence of natural organic matter is presented. The model requires input data for total aluminum, iron, organic carbon, fluoride, sulfate, and charge balance ANC. The model is calibrated to pH measurements (n = 322) by adjusting the fraction of active organic matter only, which results in an error of pH prediction on average below 0.2 pH units. The small systematic discrepancy between the analytical results for the monomeric aluminum fractionation and the model results is corrected for separately for two different fractionation techniques (n = 499) and validated on a large number (n = 3419) of geographically widely spread samples all over Sweden. The resulting average error for inorganic monomeric aluminum is around 1 µM. In its present form the model is the first internally consistent modeling approach for Sweden and may now be used as a tool for environmental quality management. Soil gibbsite with a log *Ks of 8.29 at 25°C together with a pH dependent loading function that uses molar Al/C ratios describes the amount of aluminum in solution in the presence of organic matter if the pH is roughly above 6.0.

Recovery of gold as a type of porous fiber by using biosorption followed by incineration.

PubMed

Park, Seong-In; Kwak, In Seob; Bae, Min A; Mao, Juan; Won, Sung Wook; Han, Do Hyeong; Chung, Yong Sik; Yun, Yeoung-Sang

2012-01-01

This study introduces a new process for the recovery of gold in porous fiber form by the incineration of Au-loaded biosorbent fiber from gold-cyanide solutions. For the recovery of gold from such aqueous solutions, polyethylenimine (PEI)-modified bacterial biosorbent fiber (PBBF) and PEI-modified chitosan fiber (PCSF) were developed and used. The maximum uptakes of Au(I) ions were estimated as 421.1 and 251.7 mg/g at pH 5.5 for PBBF and PCSF, respectively. Au-loaded biosorbents were freeze-dried and then incinerated to oxidize their organic constituents while simultaneously obtaining reduced gold. As a result, porous metallic gold fibers were obtained with 60 μm of diameter. Scanning electron microscopic (SEM) analysis and mercury porosimetry revealed the fibers to have 60 μm of diameter and to be highly porous and hollow. The proposed process therefore offers the potential for the efficient recovery of metallic porous gold fibers using combined biosorption and incineration. Copyright © 2011 Elsevier Ltd. All rights reserved.

Enantioseparation of dopa and related compounds by cyclodextrin-modified microemulsion electrokinetic chromatography.

PubMed

Borst, Claudia; Holzgrabe, Ulrike

2008-09-19

A chiral microemulsion electrokinetic chromatography method has been developed for the enantiomeric separation of 3,4-dihydroxyphenylalanine (dopa), its precursors phenylalanine and tyrosine, and the structurally related substance methyldopa. The separations were achieved using an oil-in-water microemulsion, which consisted of the oil-compound ethyl acetate, the surfactant sodium dodecylsulfate (SDS), the co-surfactant 1-butanol, the organic modifier propan-2-ol and 20mM phosphate buffer pH 2.5 or 2.0 as aqueous phase. For enantioseparation sulfated beta-cyclodextrin was added. The resolution of each racemate was optimized by varying the concentration of the buffer and all components of the microemulsion. Enantioseparation could be achieved for dl-dopa, dl-phenylalanine and dl-tyrosine within 13 min with a resolution of 4.3, 3.1 and 3.3, respectively, and for methyldopa in 17 min (Rs: 1.4). The established methods allowed the detection of dopa, phenylalanine, tyrosine and methyldopa with a limit at 0.5, 1.0, 0.2 and 2.0 microg/ml.

Effect of different gas stunning methods on Manchega suckling lamb meat packed under different modified atmospheres.

PubMed

Bórnez, R; Linares, M B; Vergara, H

2010-04-01

Forty-nine Manchega breed male suckling lambs were used in this experiment. The effect of CO(2) concentration and exposure time at stunning [80% CO(2) for 90 s (G1); 90% CO(2) for 90 s (G2); 90% CO(2) for 60 s (G3); 80% CO(2) for 60 s (G4)] plus an electrically stunned control group (G5) was assessed for pH, colour (L(*), a(*), b(*), C(*) and h(*)), water holding capacity (WHC), drip loss (DL), cooking loss (CL) and shear force (SF) in samples packed under two different types of modified atmospheres (MA: MA A: 70%O(2)+30%CO(2); MA B: 69.3%N(2)+30%CO(2)+0.7%CO) at 7, 14 and 21 d post-packaging. The lowest pH was found in G4 and in G5. The highest WHC and the lowest CL were found in G2 and G3 groups (P<0.05). Modified atmospheres did not affect on pH, WHC, CL and DL, although a significant effect (P<0.001) on colour was found at all the analysis times. Both the type of stunning and the modified atmosphere affected SF values. 2009 Elsevier Ltd. All rights reserved.

Optimization of calcium phosphate fine ceramic powders preparation

NASA Astrophysics Data System (ADS)

Sezanova, K.; Tepavitcharova, S.; Rabadjieva, D.; Gergulova, R.; Ilieva, R.

2013-12-01

The effect of biomimetic synthesis method, reaction medium and further precursor treatments on the chemical and phase composition, crystal size and morphology of calcium phosphates was examined. Nanosized calcium phosphate precursors were biomimetically precipitated by the method of continuous precipitation in three types of reaction media at pH 8: (i) SBF as an inorganic electrolyte system; (ii) organic (glycerine) modified SBF (volume ratio of 1:1); (iii) polymer (10 g/l xanthan gum or 10 g/l guar gum) modified SBF (volume ratio of 1:1). After maturation (24 h) the samples were lyophilized, calcinated at 300°C for 3 hours, and washed with water, followed by new gelation, lyophilization and step-wise (200, 400, 600, 800, and 1000°C, each for 3 hours) sintering. The reaction medium influenced the chemical composition and particle size but not the morphology of the calcium phosphate powders. In all studied cases bi-phase calcium phosphate fine powders with well-shaped spherical grains, consisting of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) with a Ca/P ratio of 1.3 - 1.6 were obtained. The SBF modifiers decreased the particle size of the product in the sequence guar gum ˜ xanthan gum < glycerin < SBF medium.

Fabrication and adsorption properties of hybrid fly ash composites

NASA Astrophysics Data System (ADS)

Gao, Mengfan; Ma, Qingliang; Lin, Qingwen; Chang, Jiali; Ma, Hongzhu

2017-02-01

In order to realize the utilization of fly ash (FA) as industrial solid waste better, high-efficient inorganic/organic hybrid composite adsorbents derived from (Ca(OH)2/Na2FeO4) modified FA (MF) was fabricated. The hydrophilic cationic polymer (P(DMDAAC-co-AAM) or hydrophobic modifier (KH-570) were used. The prepared composites were characterized by X-ray fluorescence spectroscopy, energy dispersive spectroscopy, scanning electron microscopy, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, thermogravimetry, and contact angle test. The adsorption of cationic composites MF/P(DMDAAC-co-AAM) towards Orange II in wastewater was investigated. The results show that: adsorption amount of 24.8 mg/g with 2000 mg/L of composites, 50 mg/L Orange II, original pH (6-8), at 40 min and room temperature, was obtained. Meanwhile, oil adsorption ratio Q(g/g) of hydrophobic composites MF/KH-570 was also evaluated. The maximum Q of 17.2 g/g to kerosene was obtained at 40 min. The isotherm and kinetics of these two adsorption processes were also studied. The results showed that the fabricated MF composites modified with hydrophilic or hydrophobic group can be used to adsorb dye in wastewater or oil effectively.

Modified sugar beet pectin induces apoptosis of colon cancer cells via interaction with the neutral sugar side-chains

USDA-ARS?s Scientific Manuscript database

Pectins extracted from a variety of sources and modified with heat and/or pH have previously been shown to exhibit activity towards several cancer cell lines. However, the structural basis for the anti-cancer activity of modified pectin requires clarification. Sugar beet and citrus pectin extracts h...

Extracellular Polymeric Substances (EPS) of Freshwater Biofilms Stabilize and Modify CeO2 and Ag Nanoparticles

PubMed Central

Kroll, Alexandra; Behra, Renata; Kaegi, Ralf; Sigg, Laura

2014-01-01

Streams are potential receiving compartments for engineered nanoparticles (NP). In streams, NP may remain dispersed or settle to the benthic compartment. Both dispersed and settling NP can accumulate in benthic biofilms called periphyton that are essential to stream ecosystems. Periphytic organisms excrete extracellular polymeric substances (EPS) that interact with any material reaching the biofilms. To understand the interaction of NP with periphyton it is therefore crucial to study the interaction of NP with EPS. We investigated the influence of EPS on the physicochemical properties of selected NP (CeO2, Ag) under controlled conditions at pH 6, 7.6, 8.6 and light or dark exposure. We extracted EPS from five different periphyton communities, characterized the extracts, and exposed CeO2 and carbonate-stabilized Ag NP (0.5 and 5 mg/L, both 25 nm primary particle size) and AgNO3 to EPS (10 mg/L) over two weeks. We measured NP size distribution, shape, primary particle size, surface plasmon resonance, and dissolution. All EPS extracts were composed of biopolymers, building blocks of humic substances, low molecular weight (Mr) acids, and small amphiphilic or neutral compounds in varying concentrations. CeO2 NP were stabilized by EPS independent of pH and light/dark while dissolution increased over time in the dark at pH 6. EPS induced a size increase in Ag NP in the light with decreasing pH and the formation of metallic Ag NP from AgNO3 at the same conditions via EPS-enhanced photoreduction. NP transformation and formation were slower in the extract with the lowest biopolymer and low Mr acid concentrations. Periphytic EPS in combination with naturally varying pH and light/dark conditions influence the properties of the Ag and CeO2 NP tested and thus the exposure conditions within biofilms. Our results indicate that periphytic organisms may be exposed to a constantly changing mixture of engineered and naturally formed Ag NP and Ag+. PMID:25333364

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.

DETERMINATION OF DITHIOCARBAMATE PESTICIDES IN WASTEWATERS

EPA Science Inventory

A method was modified and validated for the determination of dithiocarbamate pesticides in wastewaters. The developed method consists of sample pH adjustment to pH 12.2; removal of indigenous CS2 by purging in a vortex evaporator; acidification of the sample to hydrolyze dithioca...

Fluorescein transport properties across artificial lipid membranes, Caco-2 cell monolayers and rat jejunum.

PubMed

Berginc, Katja; Zakelj, Simon; Levstik, Lea; Ursic, Darko; Kristl, Albin

2007-05-01

Membrane transport characteristics of a paracellular permeability marker fluorescein were evaluated using artificial membrane, Caco-2 cell monolayers and rat jejunum, all mounted in side-by-side diffusion cells. Modified Ringer buffers with varied pH values were applied as incubation salines on both sides of artificial membrane, cell culture monolayers or rat jejunum. Passive transport according to pH partition theory was determined using all three permeability models. In addition to that, active transport of fluorescein in the M-S (mucosal-to-serosal) direction through rat jejunum was observed. The highest M-S P(app) values regarding the active transport through the rat jejunum were observed in incubation saline with pH 6.5. Fluorescein transport through the rat jejunum was inhibited by DIDS (4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid) and alpha-CHC (alpha-cyano-4-hydroxycinnamic acid). Thus, we assume that two pH-dependent influx transporters could be involved in the fluorescein membrane transport through the intestinal (jejunal) epithelium. One is very likely an MCT (monocarboxylic acid cotransporter) isoform, inhibited by specific MCT inhibitor alpha-CHC, while the involvement of the second one with overlapping substrate/inhibitor specificities (most probably a member of the organic anion-transporting polypeptide family, inhibited at least partially by DIDS) could not be excluded.

Reactivity of catecholamine-driven Fenton reaction and its relationships with iron(III) speciation.

PubMed

Melin, Victoria; Henríquez, Adolfo; Freer, Juanita; Contreras, David

2015-03-01

Fenton reaction is the main source of free radicals in biological systems. The reactivity of this reaction can be modified by several factors, among these iron ligands are important. Catecholamine (dopamine, epinephrine, and norepinephrine) are able to form Fe(III) complexes whose extension in the coordination number depends upon the pH. Fe(III)-catecholamine complexes have been related with the development of several pathologies. In this work, the ability of catecholamines to enhance the oxidative degradation of an organic substrate (veratryl alcohol, VA) through Fenton and Fenton-like reactions was studied. The initial VA degradation rate at different pH values and its relationship to the different iron species present in solution were determined. Furthermore, the oxidative degradation of VA after 24 hours of reaction and its main oxidation products were also determined. The catecholamine-driven Fenton and Fenton-like systems showed higher VA degradation compared to unmodified Fenton or Fenton-like systems, which also showed an increase in the oxidation state of the VA degradation product. All of this oxidative degradation takes place at pH values lower than 5.50, where the primarily responsible species would be the Fe(III) mono-complex. The presence of Fe(III) mono-complex is essential in the ability of catecholamines to increase the oxidative capacity of Fenton systems.

Factors regulating nitrification in aquatic sediments: Effects of organic carbon, nitrogen availability, and pH

USGS Publications Warehouse

Strauss, E.A.; Mitchell, N.L.; Lamberti, G.A.

2002-01-01

We investigated the response in nitrification to organic carbon (C) availability, the interactive effects of the C: nitrogen (N) ratio and organic N availability, and differing pH in sediments from several streams in the upper midwestern United States. In addition, we surveyed 36 streams to assess variability in sediment nitrification rates. Labile dissolved organic carbon (DOC) additions of 30 mg C??L-1 (as acetate) to stream sediments reduced nitrification rates (P < 0.003), but lower concentration additions or dilution of ambient DOC concentration had no effect on nitrification. C:N and organic N availability strongly interacted to affect nitrification (P < 0.0001), with N availability increasing nitrification most at lower C:N. Nitrification was also strongly influenced by pH (P < 0.002), with maximum rates occurring at pH 7.5. A multiple regression model developed from the stream survey consisted of five variables (stream temperature, pH, conductivity, DOC concentration, and total extractable NH4+) and explained 60% of the variation observed in nitrification. Our results suggest that nitrification is regulated by several variables, with NH4+ availability and pH being the most important. Organic C is likely important at regulating nitrification only under high environmental C:N conditions and if most available C is relatively labile.

Efficiency Improvement of Some Agricultural Residue Modified Materials for Textile Dyes Absorption

NASA Astrophysics Data System (ADS)

Boonsong, P.; Paksamut, J.

2018-03-01

In this work, the adsorption efficiency was investigated of some agricultural residue modified materials as natural bio-adsorbents which were rice straw (Oryza sativa L.) and pineapple leaves (Ananas comosus (L.) Merr.) for the removal of textile dyes. Reactive dyes were used in this research. The improvement procedure of agricultural residue materials properties were alkali-acid modification with sodium hydroxide solution and hydrochloric acid solution. Adsorption performance has been investigated using batch experiments. Investigated adsorption factors consisted of adsorbent dose, contact time, adsorbent materials and pH of solution. The results were found that rice straw had higher adsorption capacity than pineapple leaves. The increasing of adsorption capacity depends on adsorbent dose and contact time. Moreover, the optimum pH for dye adsorption was acidic range because lowering pH increased the positively charges on the adsorbent surface which could be attacked by negatively charge of acid dyes. The agricultural residue modified materials had significant dye removal efficiency which these adsorbents could be used for the treatment of textile effluent in industries.

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.

Syntheses, structures and properties of two new organic-inorganic hybrid materials based on ε-Zn Keggin units {ε-PMo(V)8Mo(VI)4O(40-x)(OH)(x)Zn4}.

PubMed

Miao, Hao; Hu, Gonghao; Guo, Jiuyu; Wan, Hongxiang; Mei, Hua; Zhang, Yu; Xu, Yan

2015-01-14

Two novel organic-inorganic hybrids, Na[PMo(V)8Mo(VI)4O38(OH)2Zn4][pyim]2·1.5H2O [ε(pyim)2] (pyim = 2-(2-pyridyl)-imidazole) and [PMo(V)8Mo(VI)4O37(OH)3Zn4]2[pyim]6·4H2O [ε2(pyim)6], based on ε-Zn Keggin units {ε-PMo(V)8Mo(VI)4O(40-x)(OH)(x)Zn4}, have been successfully synthesized under hydrothermal conditions by controlling the pH values. Structural analysis indicates that the framework of ε(pyim)2 is a 1D chain constructed by monomeric ε-Zn units modified by pyim ligands, while ε2(pyim)6 is an isolated structural compound with dimeric ε-Zn units modified by pyim ligands. This is the first isolated structure of the ε-Keggin POMs system. The luminescent and electrochemical properties of ε(pyim)2 and ε2(pyim)6 were investigated. ε2(pyim)6 also shows high catalytic activity for the esterification of phosphoric acid with equimolar lauryl alcohol to monoalkyl phosphate ester (MAP).

Medium pH, carbon and nitrogen concentrations modulate the phosphate solubilization efficiency of Penicillium purpurogenum through organic acid production.

PubMed

Scervino, J M; Papinutti, V L; Godoy, M S; Rodriguez, M A; Della Monica, I; Recchi, M; Pettinari, M J; Godeas, A M

2011-05-01

To study phosphate solubilization in Penicillium purpurogenum as function of medium pH, and carbon and nitrogen concentrations. Tricalcium phosphate (CP) solubilization efficiency of P. purpurogenum was evaluated at acid or alkaline pH using different C and N sources. Glucose- and (NH(4) )(2) SO(4) -based media showed the highest P solubilization values followed by fructose. P. purpurogenum solubilizing ability was higher in cultures grown at pH 6·5 than cultures at pH 8·5. Organic acids were detected in both alkaline and neutral media, but the relative percentages of each organic acid differed. Highest P release coincided with the highest organic acids production peak, especially gluconic acid. When P. purpurogenum grew in alkaline media, the nature and concentration of organic acids changed at different N and C concentrations. A factorial categorical experimental design showed that the highest P-solubilizing activity, coinciding with the highest organic acid production, corresponded to the highest C concentration and lowest N concentration. The results described in the present study show that medium pH and carbon and nitrogen concentrations modulate the P solubilization efficiency of P. purpurogenum through the production of organic acids and particularly that of gluconic acid. In the P solubilization optimization studies, glucose and (NH(4) )(2) SO(4) as C and N sources allowed a higher solubilization efficiency at high pH. This organism is a potentially proficient soil inoculant, especially in P-poor alkaline soils where other P solubilizers fail to release soluble P. Further work is necessary to elucidate whether these results can be extrapolated to natural soil ecosystems, where different pH values are present. Penicillium purpurogenum could be used to develop a bioprocess for the manufacture of phosphatic fertilizer with phosphate calcium minerals. © 2011 The Authors. Journal of Applied Microbiology © 2011 The Society for Applied Microbiology.

Nanostructural modification of a model homogalacturonan with a novel pectin methylesterase: Effects of pH on nanostructure, enzyme mode of action and substrate functionality

USDA-ARS?s Scientific Manuscript database

A pectin methylesterase (CpL-PME) present in a commercial papain preparation was used to modify the amount and distribution of charge in a model pectic homogalacturonan (HG) at pH 4.5 and pH 7.5. Introduced negatively charged demethylesterified blocks (DMB) were excised as oligomers with a limited e...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors.

PubMed

Yang, Jiang; Kwak, Tae-Joon; Zhang, Xiaodong; McClain, Robert; Chang, Woo-Jin; Gunasekaran, Sundaram

2016-11-22

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (µPAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

Surface interactions between nanoscale iron and organic material: Potential uses in water treatment process units

NASA Astrophysics Data System (ADS)

Storms, Max

Membrane systems are among the primary emergent technologies in water treatment process units due to their ease of use, small physical footprint, and high physical rejection. Membrane fouling, the phenomena by which membranes become clogged or generally soiled, is an inhibitor to optimal efficiency in membrane systems. Novel, composite, and modified surface materials must be investigated to determine their efficacy in improving fouling behavior. Ceramic membranes derived from iron oxide nanoparticles called ferroxanes were coated with a superhydrophillic, zwitterionic polymer called poly (sulfobetaine methacrylate) (polySBMA) to form a composite ceramic-polymeric membrane. Membrane samples with and without polySBMA coating were subjected to fouling with a bovine serum albumin solution and fouling was observed by measuring permeate flux at 10 mL intervals. Loss of polySBMA was measured using total organic carbon analysis, and membrane samples were characterized using x-ray diffraction, scanning electron microscopy, and optical profilometry. The coated membrane samples decreased initial fouling rate by 27% and secondary fouling rate by 24%. Similarly, they displayed a 30% decrease in irreversible fouling during the initial fouling stage, and a 27% decrease in irreversible fouling in the secondary fouling stage; however, retention of polySBMA sufficient for improved performance was not conclusive. The addition of chemical disinfectants into drinking water treatment processes results in the formation of compounds called disinfection by-products (DBPs). The formation of DBPs occurs when common chemical disinfectants (i.e. chlorine) react with organic material. The harmful effects of DBP exposure require that they be monitored and controlled for public safety. This work investigated the ability of nanostructured hematite derived from ferroxane nanoparticles to remove organic precursors to DBPs in the form of humic acid via adsorption processes. The results show that pH and ionic strength have an effect on adsorption capacity and mechanism. At lower ionic strengths, the adsorption isotherms are closely correlated with the Freundlich adsorption isotherm model, while at higher ionic strength, the isotherms are closely related to the Langmuir adsorption isotherm model. Lower pH systems facilitate better adsorption capacities than higher pH systems, and lower ionic strength systems facilitate better adsorption than higher ionic strength systems.

[Effects of simulated acid rain on decomposition of soil organic carbon and crop straw].

PubMed

Zhu, Xue-Zhu; Huang, Yao; Yang, Xin-Zhong

2009-02-01

To evaluate the effects of acid rain on the organic carbon decomposition in different acidity soils, a 40-day incubation test was conducted with the paddy soils of pH 5.48, 6.70 and 8.18. The soils were amended with 0 and 15 g x kg(-1) of rice straw, adjusted to the moisture content of 400 g x kg(-1) air-dried soil by using simulated rain of pH 6.0, 4.5, and 3.0, and incubated at 20 degrees C. The results showed that straw, acid rain, and soil co-affected the CO2 emission from soil system. The amendment of straw increased the soil CO2 emission rate significantly. Acid rain had no significant effects on soil organic carbon decomposition, but significantly affected the straw decomposition in soil. When treated with pH 3.0 acid rain, the amount of decomposed straw over 40-day incubation in acid (pH 5.48) and alkaline (pH 8.18) soils was 8% higher, while that in neutral soil (pH 6.70) was 15% lower, compared to the treatment of pH 6.0 rain. In the treatment of pH 3.0 acid rain, the decomposition rate of soil organic C in acid (pH 5.48) soil was 43% and 50% (P < 0.05) higher than that in neutral (pH 6.70) and alkaline (pH 8.18) soils, while the decomposition rate of straw in neutral soil was 17% and 16% (P < 0.05) lower than that in acid and alkaline soils, respectively.

High efficiency removal of triclosan by structure-directing agent modified mesoporous MIL-53(Al).

PubMed

Dou, Rongni; Zhang, Junya; Chen, Yuancai; Feng, Siyuan

2017-03-01

In order to expand the potential applications of metal-organic frameworks (MOFs), structure directing agents modified mesoporous MIL-53(Al) (MIL-53(Al)-1) was investigated to adsorb triclosan (TCS) with two different initial concentrations. MIL-53(Al)-1 with high mesoporosity and total pore volume exhibited higher adsorption capacity and 4.4 times faster adsorption of TCS at low concentration (1 mg L -1 ) than that of microporous MIL-53(Al). Also, mesoporous as well as microporous MIL-53(Al) showed significant higher adsorption capacity and two orders of magnitude greater fast uptake of TCS than two kinds of mesoporous-activated carbon. The adsorption of TCS onto MIL-53(Al)-1 released more energy and had higher disorderliness than TCS on MIL-53(Al). The superior adsorption characteristics of MIL-53(Al)-1 were preserved over a wide pH range (4-9), at high concentration of ionic strengths, and in the presence of coexisting compounds (anions, cations, phenol, aniline, and humic acid). The selectivity adsorption and Fourier transform infrared (FT-IR) spectra revealed that TCS adsorption on MIL-53(Al)s was mainly driven by hydrophobicity interaction assisted with hydrogen bonding on MIL-53(Al)s. MIL-53(Al)s can be effectively regenerated several times by washing with 90% methanol-water (pH 11). All of the above results demonstrated MIL-53(Al)s are promising adsorbents for water purification. Graphical abstract.

Thermal modification of activated carbon surface chemistry improves its capacity as redox mediator for azo dye reduction.

PubMed

Pereira, L; Pereira, R; Pereira, M F R; van der Zee, F P; Cervantes, F J; Alves, M M

2010-11-15

The surface chemistry of a commercial AC (AC(0)) was selectively modified, without changing significantly its textural properties, by chemical oxidation with HNO(3) (AC(HNO3)) and O(2) (AC(O2)), and thermal treatments under H(2) (AC(H2)) or N(2) (AC(N2)) flow. The effect of modified AC on anaerobic chemical dye reduction was assayed with sulphide at different pH values 5, 7 and 9. Four dyes were tested: Acid Orange 7, Reactive Red 2, Mordant Yellow 10 and Direct Blue 71. Batch experiments with low amounts of AC (0.1 g L(-1)) demonstrated an increase of the first-order reduction rate constants, up to 9-fold, as compared with assays without AC. Optimum rates were obtained at pH 5 except for MY10, higher at pH 7. In general, rates increased with increasing the pH of point zero charge (pH(pzc)), following the trend AC(HNO3) < AC(O2) < AC(0) < AC(N2) < AC(H2). The highest reduction rate was obtained for MY10 with AC(H2) at pH 7, which corresponded to the double, as compared with non-modified AC. In a biological system using granular biomass, AC(H2) also duplicated and increase 4.5-fold the decolourisation rates of MY10 and RR2, respectively. In this last experiment, reaction rate was independent of AC concentration in the tested range 0.1-0.6 g L(-1). Copyright © 2010 Elsevier B.V. All rights reserved.

pH-Switchable Interaction of a Carboxybetaine Ester-Based SAM with DNA and Gold Nanoparticles.

PubMed

Filip, Jaroslav; Popelka, Anton; Bertok, Tomas; Holazova, Alena; Osicka, Josef; Kollar, Jozef; Ilcikova, Marketa; Tkac, Jan; Kasak, Peter

2017-07-11

We describe a self-assembled monolayer (SAM) on a gold surface with a carboxybetaine ester functionality to control the interaction between DNA and gold nanoparticles via pH. The negatively charged phosphate backbone of DNA interacts with and adsorbs to the positively charged carboxybetaine esters on the SAM. DNA release can be achieved by the hydrolysis of carboxybetaine ester (CBE) to a zwitterionic carboxybetaine state. Furthermore, the adsorption of negatively charged citrate-capped gold nanoparticles to a SAM-modified plain gold surface can be controlled by the pH. The SAM based on carboxybetaine ester allows for the homogeneous adsorption of particles, whereas the SAM after hydrolysis at high pH repels AuNP adsorption. The antifouling surface properties of the surface modified with carboxybetaine were investigated with protein samples.

Modified Rice Straw as Adsorbent Material to Remove Aflatoxin B1 from Aqueous Media and as a Fiber Source in Fino Bread

PubMed Central

Mohamed, Sherif R.; El-Desouky, Tarek A.; Hussein, Ahmed M. S.; Mohamed, Sherif S.; Naguib, Khayria M.

2016-01-01

The aims of the current work are in large part the benefit of rice straw to be used as adsorbent material and natural source of fiber in Fino bread. The rice straw was subjected to high temperature for modification process and the chemical composition was carried out and the native rice straw contained about 41.15% cellulose, 20.46% hemicellulose, and 3.91% lignin while modified rice straw has 42.10, 8.65, and 5.81%, respectively. The alkali number was tested and showed an increase in the alkali consumption due to the modification process. The different concentrations of modified rice straw, aflatoxin B1, and pH were tested for removal of aflatoxin B1 from aqueous media and the maximum best removal was at 5% modified rice straw, 5 ng/mL aflatoxin B1, and pH 7. The modified rice straw was added to Fino bread at a level of 5, 10, and 15% and the chemical, rheological, baking quality, staling, and sensory properties were studied. Modified rice straw induced an increase of the shelf life and the produced Fino bread has a better consistency. PMID:26989411

[Adsorption of phenol chemicals by surfactant-modified zeolites].

PubMed

Xie, Jie; Wang, Zhe; Wu, De-Yi; Li, Chun-Jie

2012-12-01

Two kinds of zeolites were prepared from fly ash and modified by surfactant subsequently. Surfactant-modified zeolites were studied for adsorption of phenol chemicals (phenol, p-chlorphenol, bisphenol A). It showed that the adsorption affinity of zeolite to phenol chemicals was significantly improved after surfactant modification. The adsorption isotherms of phenol chemicals were well fitted by the Langmuir isotherm. For the two surfactant-surfactant modified zeolites, the maximum adsorption amounts of phenol, p-chlorphenol, and bisphenol A calculated from the Langmuir equation were 37.7, 52.36, 90.9 mg x g(-1) and 10.7, 22.83, 56.8 mg x g(-1), respectively. When pH values of solutions were higher than the pK(a) values of phenol chemicals, the removal efficiencies were getting higher with the increase of pH values. The octanol/water partition coefficient (K(ow)) was also found to be an important factor affecting adsorption of phenol chemicals by the modified zeolites. Higher K(ow) value, which means the greater hydrophobicity of the chemicals, resulted in a higher removal.

Composite wastewater treatment by aerated electrocoagulation and modified peroxi-coagulation processes.

PubMed

Kumar, Abhijeet; Nidheesh, P V; Suresh Kumar, M

2018-08-01

Treatment of composite wastewater generating from the industrial estates is a great challenge. The present study examines the applicability of aerated electrocoagulation and modified peroxi-coagulation processes for removing color and COD from composite wastewater. Iron plates were used as anodes and cathodes in both electrochemical processes and experiments were carried out in a working volume of 2 L. Aeration enhanced the efficiency of electrocoagulation process significantly. More than 50% of COD and 60% of color were removed after 1 h of electrocoagulation process operated at pH 3 and applied voltage of 1 V. Efficiency of the modified peroxi-coagulation process was significantly higher than that of aerated electrocoagulation. COD and color removal efficiencies of the modified peroxi-coagulation process were found as 77.7% and 97%, respectively after 1 h of electrolysis operated at 1 V, solution pH 3 and 50 mM hydrogen peroxide addition. This improved efficiency of modified peroxi-coagulation compared to aerated electrocoagulation is mainly due to the attack of in-situ generated hydroxyl radicals. Copyright © 2018 Elsevier Ltd. All rights reserved.

High pH ammonia toxicity, and the search for life on the Jovian planets.

PubMed

Deal, P H; Souza, K A; Mack, H M

1975-10-01

Jovian plants have enviroments apparently suitable for the evolution of life, but nevertheless, present severe challenges to organisms. One such challenge arises from the presence of ammonia. Ammonia is an efficient biocide, its effect being dependent on pH as well as on concentration. The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural enviornments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, survival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is, nevertheless, two to three orders of magnitude longer than for E. coli. Our data support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

PHOS-Select Iron Affinity beads enrich peptides for detection of organophosphorus adducts on albumin

PubMed Central

Jiang, Wei; Dubrovskii, Yaroslav A; Podolskaya, Ekaterina P; Murashko, Ekaterina A; Babakov, Vladimir; Nachon, Florian; Masson, Patrick; Schopfer, Lawrence M; Lockridge, Oksana

2013-01-01

Albumin is covalently modified by organophosphorus toxicants (OP) on tyrosine 411, but less than 1% of albumin is modified in humans by lethal OP doses that inhibit 95% of plasma butyrylcholinesterase. A method that enriches OP-modified albumin peptides could aid analysis of low dose exposures. Soman or chlorpyrifos oxon treated human plasma was digested with pepsin. Albumin peptides were enriched by binding to Fe3+ beads at pH 11 and eluted with pH 2.6 buffer. Similarly, mouse and guinea pig albumin modified by chlorpyrifos oxon were digested with pepsin and enriched by binding to Fe3+ beads. Peptides were identified by MALDI-TOF/TOF mass spectrometry. PHOS-select Iron Affinity beads specifically enriched albumin peptides VRY411TKKVPQVST and LVRY411TKKVPQVST in a pepsin digest of human plasma. The unmodified as well as OP-modified peptides bound to the beads. The binding capacity of 500 μl beads was the pepsin digest of 2.1 μL human plasma. The limit of detection was 0.2% of OP-modified albumin peptide in 0.43 μL plasma. Enrichment of OP-modified albumin peptides by binding to Fe3+ beads is a method with potential application to diagnosis of OP pesticide and nerve agent exposure in humans, mice, and guinea pigs. PMID:24187955

Degradation of Acid Orange 7 by peroxymonosulfate activated with the recyclable nanocomposites of g-C3N4 modified magnetic carbon.

PubMed

Guo, Furong; Lu, Jiahua; Liu, Qing; Zhang, Ping; Zhang, Aiqing; Cai, Yingjie; Wang, Qiang

2018-08-01

Carbon-based catalysts have attracted high attention since they are greener and cheaper, while magnetic nanomaterials are very useful in environmental application because of the easy recovery and operation given by the magnetic separability. Therefore, graphitic carbon nitride modified magnetic carbon nanocomposites Fe 3 O 4 @C/g-C 3 N 4 was prepared herein for the first time as a new carbon-based catalyst for the activation of peroxymonosulfate (PMS). The catalytic properties of Fe 3 O 4 @C/g-C 3 N 4 in activating PMS for the degradation of Acid Orange 7 (AO 7), a model organic pollutant, were investigated. AO 7 degradation efficiency was significantly enhanced after modification of Fe 3 O 4 @C with g-C 3 N 4 , and the composite Fe 3 O 4 @C/g-C 3 N 4 from loading of 5 wt% g-C 3 N 4 and calcined at 300 °C for 30 min exhibited the best performance. AO 7 could be efficiently decolorized using the "Fe 3 O 4 @C/C 3 N 4 (5%) + PSM" system within the pH range of 2-6, and 97% of AO 7 could be removed in 20 min without pH adjustment (pH = 4). Radical quenching and EPR studies confirmed that both sulfate and hydroxyl radicals produced from PMS activation were the active species responsible for the oxidation of AO 7. The degradation mechanism was suggested based on the experimental results and XPS analyses. It was proposed that the CO groups on the carbon surface of Fe 3 O 4 @C rather than the CO in g-C 3 N 4 played a key role as the active sites for PMS activation. The catalyst was magnetically separable and displayed good stability and reusability, thus providing a potentially green catalyst for sustainable remediation of organic pollutants. Copyright © 2018 Elsevier Ltd. All rights reserved.

High Ph, Ammonia Toxicity, and the Search for Life on the Jovian Planets

NASA Technical Reports Server (NTRS)

Deal, P. H.; Souza, K. A.; Mack, H. M.

1975-01-01

The effects of pH and ammonia concentration were studied separately, where possible, on a variety of organisms, including some isolated from natural environments of high pH and/or ammonia concentration. Escherichia coli and Bacillus subtilis are both extremely sensitive to ammonia. An aerobic organism (growth up to pH 11.4) from an alkaline spring is more resistant, but exhibits a toxic response to ammonia at a pH much lower than its maximum for growth. The greatest ammonia resistance has been found in an unidentified organism growing at near neutral pH. Even in this case, however, urvival at ammonia concentrations reasonably expected on the Jovian planets is measured in hours. This is two to three orders of magnitude longer than for E. coli. Results support the tentative conclusion that contamination of the Jovian planets with terrestrial organisms that can grow is unlikely. However, the range of toxic response noted, coupled with the observation that terrestrial life has not been exposed to high ammonia concentrations for millions of years, suggests that adaptation to greater ammonia tolerance may be possible.

Environmental Fate and Transport of a New Energetic Material, CL-20

DTIC Science & Technology

2006-03-01

Microbiology M.Sc. Biochemistry M.Sc. Chemistry Ph.D. Chemistry Ph.D. Ecotoxicology M.Sc.A. Environmental Engineering B.Sc. Chemistry B.Sc...Determine enzymes responsible for initiating the degradation of CL-20. 5. Conduct a battery of ecotoxicological tests to determine the toxic effects of...chrysosporium. The strain ATCC 24725 was maintained on Yeast Peptone Dextrose (YPD) plates and was cultivated in the modified Kirk’s nitrogen- limited medium (pH

Ocean acidification modulates the incorporation of radio-labeled heavy metals in the larvae of the Mediterranean sea urchin Paracentrotus lividus.

PubMed

Dorey, Narimane; Martin, Sophie; Oberhänsli, François; Teyssié, Jean-Louis; Jeffree, Ross; Lacoue-Labarthe, Thomas

2018-10-01

The marine organisms which inhabit the coastline are exposed to a number of anthropogenic pressures that may interact. For instance, the accumulation of toxic metals present in coastal waters is expected to be modified by ocean acidification through e.g. changes in physiological performance and/or elements availability. Changes in bioaccumulation due to lowering pH are likely to be differently affected depending on the nature (essential vs. non-essential) and speciation of each element. The Mediterranean is of high concern for possible cumulative effects due to strong human influences on the coastline. The aim of this study was to determine the effect of ocean acidification (from pH 8.1 down to -1.0 pH units) on the incorporation kinetics of six trace metals (Mn, Co, Zn, Se, Ag, Cd, Cs) and one radionuclide ( 241 Am) in the larvae of an economically- and ecologically-relevant sea urchin of the Mediterranean coastline: Paracentrotus lividus. The radiolabelled metals and radionuclides added in trace concentrations allowed precise tracing of their incorporation in larvae during the first 74 h of their development. Independently of the expected indirect effect of pH on larval size/developmental rates, Paracentrotus lividus larvae exposed to decreasing pHs incorporated significantly more Mn and Ag and slightly less Cd. The incorporation of Co, Cs and 241 Am was unchanged, and Zn and Se exhibited complex incorporation behaviors. Studies such as this are necessary prerequisites to the implementation of metal toxicity mitigation policies for the future ocean. We discuss possible reasons and mechanisms for the specific effect of pH on each metals. Copyright © 2018 Elsevier Ltd. All rights reserved.

Modified Fe3O4- hydroxyapatite nanocomposites as heterogeneous catalysts in three UV, Vis and Fenton like degradation systems

NASA Astrophysics Data System (ADS)

Valizadeh, S.; Rasoulifard, M. H.; Dorraji, M. S. Seyed

2014-11-01

The magnetite-hydroxyapatite (M-HAP) nanocomposites were prepared by a chemical co- precipitation procedure and characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and diffuse reflectance spectra (DRS). The ability of the synthesized catalyst for photocatalytic degradation of Acid Blue 25 (AB25), as an organic dye, under UV irradiation was studied. The catalyst was modified employing transition metals (Mn, Fe, Co, Ni, Cu and Zn) trying to improve the catalytic performance of HAP in absence of UV irradiation and in the presence of hydrogen peroxide i.e. a Fenton like reaction. The best results obtained for Cu and Co modified M-HAPs and the effect of operational parameters such pH, amount of catalyst and hydrogen peroxide concentration was studied. In order to investigate the performance of HAP based photocatalyst in visible light region, M-HAP was modified with silver ions. At the end, Langmuir-Hinshelwood kinetic expression used to evaluate and compare the catalytic systems. The strongest degradation activity was observed for Ag-M-HAP/Vis system because of Ag3PO4 formation. Apparent reaction rate constant (Kapp) by Ag-M-HAP/Vis was 63, 36 and 19 times faster than Cu-M-HAP(II)/H2O2, Co-M-HAP(II)/H2O2 and M-HAP (I)/UV systems, respectively.

Aqueous or solvent based surface modification: The influence of the combination solvent - organic functional group on the surface characteristics of titanium dioxide grafted with organophosphonic acids

NASA Astrophysics Data System (ADS)

Roevens, Annelore; Van Dijck, Jeroen G.; Geldof, Davy; Blockhuys, Frank; Prelot, Benedicte; Zajac, Jerzy; Meynen, Vera

2017-09-01

To alter the versatility of interactions at its surface, TiO2 is modified with organophosphonic acids (PA). A thorough understanding of the role of all synthesis conditions is necessary to achieve controlled functionalization. This study reports on the effect of using water, toluene and their mixtures when performing the modification of TiO2 with PA. Sorption and calorimetry measurements of surface interactions with various probing species clearly indicate that, by grafting PA in water, clear differences appear in the distribution of organic groups on the surface. Also the functional group of the PA determines the impact of using water as solvent. Modification in toluene results in a higher modification degree for propylphosphonic acid (3PA), as the solvent-solute interaction may hinder the grafting with phenylphosphonic acid (PhPA) in toluene. Water is preferred as solvent for PhPA modification as stabilizing π-OH interactions enhance surface grafting overcoming the competitive interaction of water at the surface as observed with 3PA. By using water in toluene mixtures for the functionalization of TiO2 with 3PA, the degree of functionalization is higher than when only water or toluene is used. Furthermore, adding small amounts of water leads to the formation of titanium propylphosphonates, next to surface grafting.

Enhanced heterogeneous photo-Fenton process modified by magnetite and EDDS: BPA degradation.

PubMed

Huang, Wenyu; Luo, Mengqi; Wei, Chaoshuai; Wang, Yinghui; Hanna, Khalil; Mailhot, Gilles

2017-04-01

In this research, magnetite and ethylenediamine-N,N'-disuccinic acid (EDDS) are used in a heterogeneous photo-Fenton system in order to find a new way to remove organic contaminants from water. Influence of different parameters including magnetite dosage, EDDS concentration, H 2 O 2 concentration, and pH value were evaluated. The effect of different radical species including HO · and HO 2 · /O 2 ·- was investigated by addition of different scavengers into the system. The addition of EDDS improved the heterogeneous photo-Fenton degradation of bisphenol A (BPA) through the formation of photochemically efficient Fe-EDDS complex. This effect is dependent on the H 2 O 2 and EDDS concentrations and pH value. The high performance observed at pH 6.2 could be explained by the ability of O 2 ·- to generate Fe(II) from Fe(III) species reduction. GC-MS analysis suggested that the cleavage of the two benzene rings is the first degradation step followed by oxidation leading to the formation of the benzene derivatives. Then, the benzene ring was opened due to the attack of HO · radicals producing short-chain organic compounds of low molecular weight like glycerol and ethylene glycol. These findings regarding the capability of EDDS/magnetite system to promote heterogeneous photo-Fenton oxidation have important practical implications for water treatment technologies.

Afforestation neutralizes soil pH.

PubMed

Hong, Songbai; Piao, Shilong; Chen, Anping; Liu, Yongwen; Liu, Lingli; Peng, Shushi; Sardans, Jordi; Sun, Yan; Peñuelas, Josep; Zeng, Hui

2018-02-06

Soil pH regulates soil biogeochemical processes and has cascading effects on terrestrial ecosystem structure and functions. Afforestation has been widely adopted to increase terrestrial carbon sequestration and enhance water and soil preservation. However, the effect of afforestation on soil pH is still poorly understood and inconclusive. Here we investigate the afforestation-caused soil pH changes with pairwise samplings from 549 afforested and 148 control plots in northern China. We find significant soil pH neutralization by afforestation-afforestation lowers pH in relatively alkaline soil but raises pH in relatively acid soil. The soil pH thresholds (T pH ), the point when afforestation changes from increasing to decreasing soil pH, are species-specific, ranging from 5.5 (Pinus koraiensis) to 7.3 (Populus spp.) with a mean of 6.3. These findings indicate that afforestation can modify soil pH if tree species and initial pH are properly matched, which may potentially improve soil fertility and promote ecosystem productivity.

Preferential adsorption of fluorescing fulvic and humic acid components on activated carbon using flow field-flow fractionation analysis.

PubMed

Schmit, Kathryn H; Wells, Martha J M

2002-02-01

Activated carbon treatment of drinking water is used to remove natural organic matter (NOM) precursors that lead to the formation of disinfection byproducts. The innate hydrophobic nature and macromolecular size of NOM render it amenable to sorption by activated carbon. Batch equilibrium and minicolumn breakthrough adsorption studies were performed using granular activated carbon to treat NOM-contaminated water. Ultraviolet (UV) absorption spectroscopy and flow field-flow fractionation analysis using tandem diode-array and fluorescence detectors were used to monitor the activated carbon sorption of NOM. Using these techniques, it was possible to study activated carbon adsorption properties of UV absorbing, fluorescing and nonfluorescing, polyelectrolytic macromolecules fractionated from the total macromolecular and nonmacromolecular composition of NOM. Adsorption isotherms were constructed at pH 6 and pH 9. Data were described by the traditional and modified Freundlich models. Activated carbon capacity and adsorbability were compared among fractionated molecular subsets of fulvic and humic acids. Preferential adsorption (or adsorptive fractionation) of polyelectrolytic, fluorescing fulvic and humic macromolecules on activated carbon was observed. The significance of observing preferential adsorption on activated carbon of fluorescing macromolecular components relative to nonfluorescing components is that this phenomenon changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the composition that existed in the aqueous phase prior to adsorption. Likewise, it changes the composition of dissolved organic matter remaining in equilibrium in the aqueous phase relative to the adsorbed phase. This research increases our understanding of NOM interactions with activated carbon which may lead to improved methods of potable water production.

Polyethylenimine-modified fungal biomass as a high-capacity biosorbent for Cr(VI) anions: sorption capacity and uptake mechanisms.

PubMed

Deng, Shubo; Ting, Yen Peng

2005-11-01

Heavy metal pollution in the aqueous environment is a problem of global concern. Biosorption has been considered as a promising technology for the removal of low levels of toxic metals from industrial effluents and natural waters. A modified fungal biomass of Penicillium chrysogenum with positive surface charges was prepared by grafting polyethylenimine (PEI) onto the biomass surface in a two-step reaction. The presence of PEI on the biomass surface was verified by FTIR and X-ray photoelectron spectroscopy (XPS) analyses. Due to the high density of amine groups in the long chains of PEI molecules on the surface, the modified biomass was found to possess positive zeta potential at pH below 10.4 as well as high sorption capacity for anionic Cr(VI). Using the Langmuir adsorption isotherm, the maximum sorption capacity for Cr(VI) at a pH range of 4.3-5.5 was 5.37 mmol/g of biomass dry weight, the highest sorption capacity for Cr(VI) compared to other sorbents reported in the literature. Scanning electronic microscopy (SEM) provided evidence of chromium aggregates formed on the biomass surface. XPS results verified the presence of Cr(III) on the biomass surface in the pH range 2.5-10.5, suggesting that some Cr(VI) anions were reduced to Cr(III) during the sorption. The sorption kinetics indicated that redox reaction occurred on the biomass surface, and whether the converted Cr(III) ions were released to solution or adsorbed on the biomass depended on the solution pH. Sorption mechanisms including electrostatic interaction, chelation, and precipitation were found to be involved in the complex sorption of chromium on the PEI-modified biomass.

Determination of nickel in water, food, and biological samples by electrothermal atomic absorption spectrometry after preconcentration on modified carbon nanotubes.

PubMed

Taher, Mohammad Ali; Mazaheri, Lida; Ashkenani, Hamid; Mohadesi, Alireza; Afzali, Daryoush

2014-01-01

A new and sensitive SPE method using modified carbon nanotubes for extraction and preconcentration, and electrothermal atomic absorption spectrometric determination of nickel (Ni) in real samples at ng/L levels was investigated. First, multiwalled carbon nanotubes were oxidized with concentrated HNO3, then modified with 2-(5-bormo-2-pyridylazo)-5-diethylaminophenol reagent. The adsorption was achieved quantitatively on a modified carbon nanotubes column in a pH range of 6.5 to 8.5; the adsorbed Ni(II) ions were then desorbed by passing 5.0 mL of 1 M HNO3. The effects of analytical parameters, including pH of the solution, eluent type and volume, sample volume, flow rate of the eluent, and matrix ions, were investigated for optimization of the presented procedure. The enrichment factor was 180, and the LOD for Ni was 4.9 ng/L. The method was applied to the determination of Ni in water, food, and biological samples, and reproducible results were obtained.

The effect of pH on chronic aquatic nickel toxicity is dependent on the pH itself: Extending the chronic nickel bioavailability models.

PubMed

Nys, Charlotte; Janssen, Colin R; Van Sprang, Patrick; De Schamphelaere, Karel A C

2016-05-01

The environmental quality standard for Ni in the European Commission's Water Framework Directive is bioavailability based. Although some of the available chronic Ni bioavailability models are validated only for pH ≤ 8.2, a considerable fraction of European surface waters has a pH > 8.2. Therefore, the authors investigated the effect of a change in pH from 8.2 to 8.7 on chronic Ni toxicity in 3 invertebrate (Daphnia magna, Lymnaea stagnalis, and Brachionus calyciflorus) and 2 plant species (Pseudokirchneriella subcapitata and Lemna minor). Nickel toxicity was almost always significantly higher at pH 8.7 than at pH 8.2. To test whether the existing chronic Ni bioavailability models developed for pH ≤ 8.2 can be used at higher pH levels, Ni toxicity at pH 8.7 was predicted based on Ni toxicity observed at pH 8.2. This resulted in a consistent underestimation of toxicity. The results suggest that the effect of pH on Ni(2+) toxicity is dependent on the pH itself: the slope of the pH effect is steeper above than below pH 8.2 for species for which a species-specific bioavailability model exists. Therefore, the existing chronic Ni bioavailability models were modified to allow predictions of chronic Ni toxicity to invertebrates and plants in the pH range of 8.2 to 8.7 by applying a pH slope (SpH ) dependent on the pH of the target water. These modified Ni bioavailability models resulted in more accurate predictions of Ni toxicity to all 5 species (within 2-fold error), without the bias observed using the bioavailability models developed for pH ≤ 8.2. The results of the present study can decrease the uncertainty in implementing the bioavailability-based environmental quality standard under the Water Framework Directive for high-pH regions in Europe. © 2015 SETAC.

Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment

DOE PAGES

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

2016-01-29

Applications of bio-oil are limited by its challenging properties including high moisture content, low pH, high viscosity, high oxygen content, and low heating value. Separation of switchgrass bio-oil components by adding water, organic solvents (hexadecane and octane), and sodium hydroxide may help to overcome these issues. Acetic acid and phenolic compounds were extracted in aqueous and organic phases, respectively. Polar chemicals, such as acetic acid, did not partition in the organic solvent phase. Acetic acid in the aqueous phase after extraction is beneficial for a microbial-electrolysis-cell application to produce hydrogen as an energy source for further hydrodeoxygenation of bio-oil. Organicmore » solvents extracted more chemicals from bio-oil in combined than in sequential extraction; however, organic solvents partitioned into the aqueous phase in combined extraction. When sodium hydroxide was added to adjust the pH of aqueous bio-oil, organic-phase precipitation occurred. As the pH was increased, a biphasic aqueous/organic dispersion was formed, and phase separation was optimized at approximately pH 6. The neutralized organic bio-oil had approximately 37% less oxygen and 100% increased heating value than the initial centrifuged bio-oil. In conclusion, the less oxygen content and increased heating value indicated a significant improvement of the bio-oil quality through neutralization.« less

Separation of switchgrass bio-oil by water/organic solvent addition and pH adjustment

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

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

Applications of bio-oil are limited by its challenging properties including high moisture content, low pH, high viscosity, high oxygen content, and low heating value. Separation of switchgrass bio-oil components by adding water, organic solvents (hexadecane and octane), and sodium hydroxide may help to overcome these issues. Acetic acid and phenolic compounds were extracted in aqueous and organic phases, respectively. Polar chemicals, such as acetic acid, did not partition in the organic solvent phase. Acetic acid in the aqueous phase after extraction is beneficial for a microbial-electrolysis-cell application to produce hydrogen as an energy source for further hydrodeoxygenation of bio-oil. Organicmore » solvents extracted more chemicals from bio-oil in combined than in sequential extraction; however, organic solvents partitioned into the aqueous phase in combined extraction. When sodium hydroxide was added to adjust the pH of aqueous bio-oil, organic-phase precipitation occurred. As the pH was increased, a biphasic aqueous/organic dispersion was formed, and phase separation was optimized at approximately pH 6. The neutralized organic bio-oil had approximately 37% less oxygen and 100% increased heating value than the initial centrifuged bio-oil. In conclusion, the less oxygen content and increased heating value indicated a significant improvement of the bio-oil quality through neutralization.« less

Effects of pH and Redox Gradients on Prebiotic Organic Synthesis and the Generation of Free Energy in Simulated Hydrothermal Systems

NASA Astrophysics Data System (ADS)

Barge, L. M.; Flores, E.; Abedian, Y.; Maltais, T.; Cameron, R.; Hermis, N.; Chin, K.; Russell, M. J.; Baum, M. M.

2017-07-01

Hydrothermal minerals in alkaline vents can promote phosphorus and organic concentration, redox reactions driven by catalytic metal sulfides, and the ambient pH and redox gradients can affect the synthesis of organics.

The Influence of pH on Prokaryotic Cell Size and Temperature

NASA Astrophysics Data System (ADS)

Sundararajan, D.; Gutierrez, F.; Heim, N. A.; Payne, J.

2015-12-01

The pH of a habitat is essential to an organism's growth and success in its environment. Although most organisms maintain a neutral internal pH, their environmental pH can vary greatly. However, little research has been done concerning an organism's environmental pH across a wide range of taxa. We studied pH tolerance in prokaryotes and its relationship with biovolume, taxonomic classification, and ideal temperature. We had three hypotheses: pH and temperature are not correlated; pH tolerance is similar within taxonomic groups; and extremophiles have small cell sizes. To test these hypotheses, we used pH, size, and taxonomic data from The Prokaryotes. We found that the mean optimum external pH was neutral for prokaryotes as a whole and when divided by domain, phylum, and class. Using ANOVA to test for pH within and among group variances, we found that variation of pH in domains, phyla, classes, and families was greater than between them. pH and size did not show much of a correlation, except that the largest and smallest sized prokaryotes had nearly neutral pH. This seems significant because extremophiles need to divert more of their energy from growth to maintain a neutral internal pH. Acidophiles showed a larger range of optimum pH values than alkaliphiles. A similar result was seen with the minimum and maximum pH values of acidophiles and alkaliphiles. While acidophiles were spread out and had some alkaline maximum values, alkaliphiles had smaller ranges, and unlike some acidophiles that had pH minimums close to zero, alkaliphile pH maximums did not go beyond a pH of 12. No statistically significant differences were found between sizes of acidophiles and alkaliphiles. However, optimum temperatures of acidophiles and alkaliphiles did have a statistically significant difference. pH and temperature had a negative correlation. Therefore, pH seems to have a correlation with cell size, temperature, and taxonomy to some extent.

Initial pH of medium affects organic acids production but do not affect phosphate solubilization.

PubMed

Marra, Leandro M; de Oliveira-Longatti, Silvia M; Soares, Cláudio R F S; de Lima, José M; Olivares, Fabio L; Moreira, Fatima M S

2015-06-01

The pH of the culture medium directly influences the growth of microorganisms and the chemical processes that they perform. The aim of this study was to assess the influence of the initial pH of the culture medium on the production of 11 low-molecular-weight organic acids and on the solubilization of calcium phosphate by bacteria in growth medium (NBRIP). The following strains isolated from cowpea nodules were studied: UFLA03-08 (Rhizobium tropici), UFLA03-09 (Acinetobacter sp.), UFLA03-10 (Paenibacillus kribbensis), UFLA03-106 (Paenibacillus kribbensis) and UFLA03-116 (Paenibacillus sp.). The strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 solubilized Ca3(PO4)2 in liquid medium regardless of the initial pH, although without a significant difference between the treatments. The production of organic acids by these strains was assessed for all of the initial pH values investigated, and differences between the treatments were observed. Strains UFLA03-09 and UFLA03-10 produced the same acids at different initial pH values in the culture medium. There was no correlation between phosphorus solubilized from Ca3(PO4)2 in NBRIP liquid medium and the concentration of total organic acids at the different initial pH values. Therefore, the initial pH of the culture medium influences the production of organic acids by the strains UFLA03-08, UFLA03-09, UFLA03-10 and UFLA03-106 but it does not affect calcium phosphate solubilization.

Phenotypic and functional analysis of human SLC26A6 variants in patients with familial hyperoxaluria and calcium oxalate nephrolithiasis.

PubMed

Monico, Carla G; Weinstein, Adam; Jiang, Zhirong; Rohlinger, Audrey L; Cogal, Andrea G; Bjornson, Beth B; Olson, Julie B; Bergstralh, Eric J; Milliner, Dawn S; Aronson, Peter S

2008-12-01

Urinary oxalate is a major risk factor for calcium oxalate stones. Marked hyperoxaluria arises from mutations in 2 separate loci, AGXT and GRHPR, the causes of primary hyperoxaluria (PH) types 1 (PH1) and 2 (PH2), respectively. Studies of null Slc26a6(-/-) mice have shown a phenotype of hyperoxaluria, hyperoxalemia, and calcium oxalate urolithiasis, leading to the hypothesis that SLC26A6 mutations may cause or modify hyperoxaluria in humans. Cross-sectional case-control. Cases were recruited from the International Primary Hyperoxaluria Registry. Control DNA samples were from a pool of adult subjects who identified themselves as being in good health. PH1, PH2, and non-PH1/PH2 genotypes in cases. Homozygosity or compound heterozygosity for SLC26A6 variants. Functional expression of oxalate transport in Xenopus laevis oocytes. 80 PH1, 6 PH2, 8 non-PH1/PH2, and 96 control samples were available for SLC26A6 screening. A rare variant, c.487C-->T (p.Pro163Ser), was detected solely in 1 non-PH1/PH2 pedigree, but this variant failed to segregate with hyperoxaluria, and functional studies of oxalate transport in Xenopus oocytes showed no transport defect. No other rare variant was identified specifically in non-PH1/PH2. Six additional missense variants were detected in controls and cases. Of these, c.616G-->A (p.Val206Met) was most common (11%) and showed a 30% reduction in oxalate transport. To test p.Val206Met as a potential modifier of hyperoxaluria, we extended screening to PH1 and PH2. Heterozygosity for this variant did not affect plasma or urine oxalate levels in this population. We did not have a sufficient number of cases to determine whether homozygosity for p.Val206Met might significantly affect urine oxalate. SLC26A6 was effectively ruled out as the disease gene in this non-PH1/PH2 cohort. Taken together, our studies are the first to identify and characterize SLC26A6 variants in patients with hyperoxaluria. Phenotypic and functional analysis excluded a significant effect of identified variants on oxalate excretion.

The synthesis and properties of linear A-π-D-π-A type organic small molecule containing diketopyrrolopyrrole terminal units.

PubMed

Zhang, Shanshan; Niu, Qingfen; Sun, Tao; Li, Yang; Li, Tianduo; Liu, Haixia

2017-08-05

A novel linear A-π-D-π-A-type organic small molecule Ph2(PDPP) 2 consisting diketopyrrolopyrrole (DPP) as acceptor unit, biphenylene as donor unit and acetylene unit as π-linkage has been successfully designed and synthesized. Its corresponding thermal, photophysical and electrochemical properties as well as the photoinduced charge-separation process were investigated. Ph2(PDPP) 2 exhibits high thermal stability and it can be soluble in common organic solvents such as chloroform and tetrahydrofuran. The photophysical properties show that DPP 2 Ph 2 harvests sunlight over the entire visible spectrum range in the thin-film state (300-800nm). DPP 2 Ph 2 has lower band gaps and appropriate energy levels to satisfy the requirement of solution-processable organic solar cells. The efficient photoinduced charge separation process was clearly observed between DPP 2 Ph 2 with PC 61 BM and the K sv value was found to be as high as 2.13×10 4 M -1 . Therefore, these excellent properties demonstrate that the designed A-π-D-π-A-type small molecule Ph2(PDPP) 2 is the prospective candidate as donor material for organic photovoltaic material. Copyright © 2017 Elsevier B.V. All rights reserved.

Efficient adsorption of Hg (II) ions in water by activated carbon modified with melamine

NASA Astrophysics Data System (ADS)

Qin, Hangdao; Meng, Jingling; Chen, Jing

2018-04-01

Removal of Hg (II) ions from industrial wastewater is important for the water treatment, and adsorption is an efficient treatment process. Activated carbon (AC) was modified with melamine, which introduced nitrogen-containing functional groups onto AC surface. Original AC and melamine modified activated carbon (ACM) were characterized by elemental analysis, N2 adsorption-desorption, determination of the pH of the point of zero charge (pHpzc) and X-ray photoelectron spectroscopy (XPS) and their performance in the adsorption of Hg(II) ions was investigated. Langmuir model fitted the experimental data of equilibrium isotherms well. ACM showed the higher Hg (II) ions adsorption capacity, increasing more than more than 1.8 times compared to the original one. Moreover, ACM showed a wider pH range for the maximum adsorption than the parent AC.

Adsorption of Acid Blue 25 dye by bentonite and surfactant modified bentonite

NASA Astrophysics Data System (ADS)

Jeeva, Mark; Wan Zuhairi, W. Y.

2018-04-01

Adsorption of Acid Blue (AB 25) from water via batch adsorption experiments onto Na-Bentonite (NB) and CTAB-modified bentonite (CTAB-Ben) was investigated. Studies concerning the factors influencing the adsorption capacities of NB and CTAB-Ben, such as initial dye concentration, adsorbent dosage, pH, contact time and temperature were investigated and discussed. The results revealed that CTAB-modified bentonite demonstrated high adsorption capacities toward acid dyes, while NB exhibited sorption capacities lower than CTAB-Ben. The maximum adsorption efficiency was found to be 50% at an AB 25 concentration of 50 mg/L, adsorbent dosage of 1.8 g/L, reaction time of 90 min and equilibrium pH of 11. The results of isotherm study fit the Langmuir and Freundlich models (R2 > 0.93) and (R2 > 0.9) respectively.

Development of soft extraction method for structural characterization of boreal forest soil proteins with MALDI-TOF/MS

NASA Astrophysics Data System (ADS)

Kanerva, Sanna; Ketola, Raimo A.; Kitunen, Veikko; Smolander, Aino; Kotiaho, Tapio

2010-05-01

Nitrogen (N) is usually the nutrient restricting productivity in boreal forests. Forest soils contain a great amount of nitrogen, but only a small part of it is in mineral form. Most part of soil N is bound in the structures of different organic compounds such as proteins, peptides, amino acids and more stabilized, refractory compounds. Due to the fact that soil organic N has a very important role in soil nutrient cycling and in plant nutrition, there is a need for more detailed knowledge of its chemistry in soil. Conventional methods to extract and analyze soil organic N are usually very destructive for structures of higher molecular weight organic compounds, such as proteins. The aim of this study was to characterize proteins extracted from boreal forest soil by "soft" extraction methods in order to maintain their molecular structure. The organic layer (F) from birch forest floor containing 78% of organic matter was sieved, freeze dried, pulverized, and extracted with a citrate or phosphate buffer (pH 6 or 8). Sequential extraction with the citrate or phosphate buffer and an SDS buffer (pH 6.8), slightly modified from the method of Chen et al. (2009, Proteomics 9: 4970-4973), was also done. Proteins were purified from the soil extract by extraction with buffered phenol and precipitated with methanol + 0.1M ammonium acetate at -20°C. Characterization of proteins was performed with matrix assisted laser desorption ionization - time-of-flight mass spectrometry (MALDI-TOF/MS) and the concentration of total proteins was measured using Bradford's method. Bovine serum albumin (BSA) was used as a positive control in the extractions and as a standard protein in Bradford's method. Our results showed that sequential extraction increased the amount of extracted proteins compared to the extractions without the SDS-buffer; however, it must be noted that the use of SDS-buffer very probably increased denaturization of proteins. Purification of proteins from crude soil extracts by phenol extraction was essential prior to measurement of total proteins; there seemed to be a lot of compounds in crude soil extracts that interfere with the analysis of total proteins, causing overestimation in protein concentration. pH of the buffer solution did not seem to be very crucial for the extractability of soil natural proteins, but at the higher pH, the amount of interfering compounds increased. However, the recovery of BSA added was clearly higher at the higher pH. When the protein precipitates were analyzed with MALDI-TOF/MS, a large curve, most likely formed from wide peaks of several compounds, indicate that most of the compounds in the precipitate were <15 kDa or ~20-50 kDa in molecular weight. It seems that in order to identify individual proteins from mass spectra, a separation of compounds with varying molecular weight is needed before the MALDI-TOF/MS analysis. Due to the fact that a relatively high amount of BSA added was not recovered by the extractions and that the intensity of the signals observed in mass spectra was low, it is questionable whether it is possible to extract soil natural proteins effectively from soils containing a high amount of organic matter without destructing the structures of proteins.

Modeling of pathogen survival during simulated gastric digestion.

PubMed

Koseki, Shige; Mizuno, Yasuko; Sotome, Itaru

2011-02-01

The objective of the present study was to develop a mathematical model of pathogenic bacterial inactivation kinetics in a gastric environment in order to further understand a part of the infectious dose-response mechanism. The major bacterial pathogens Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. were examined by using simulated gastric fluid adjusted to various pH values. To correspond to the various pHs in a stomach during digestion, a modified logistic differential equation model and the Weibull differential equation model were examined. The specific inactivation rate for each pathogen was successfully described by a square-root model as a function of pH. The square-root models were combined with the modified logistic differential equation to obtain a complete inactivation curve. Both the modified logistic and Weibull models provided a highly accurate fitting of the static pH conditions for every pathogen. However, while the residuals plots of the modified logistic model indicated no systematic bias and/or regional prediction problems, the residuals plots of the Weibull model showed a systematic bias. The modified logistic model appropriately predicted the pathogen behavior in the simulated gastric digestion process with actual food, including cut lettuce, minced tuna, hamburger, and scrambled egg. Although the developed model enabled us to predict pathogen inactivation during gastric digestion, its results also suggested that the ingested bacteria in the stomach would barely be inactivated in the real digestion process. The results of this study will provide important information on a part of the dose-response mechanism of bacterial pathogens.

Modeling of Pathogen Survival during Simulated Gastric Digestion ▿

PubMed Central

Koseki, Shige; Mizuno, Yasuko; Sotome, Itaru

2011-01-01

The objective of the present study was to develop a mathematical model of pathogenic bacterial inactivation kinetics in a gastric environment in order to further understand a part of the infectious dose-response mechanism. The major bacterial pathogens Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella spp. were examined by using simulated gastric fluid adjusted to various pH values. To correspond to the various pHs in a stomach during digestion, a modified logistic differential equation model and the Weibull differential equation model were examined. The specific inactivation rate for each pathogen was successfully described by a square-root model as a function of pH. The square-root models were combined with the modified logistic differential equation to obtain a complete inactivation curve. Both the modified logistic and Weibull models provided a highly accurate fitting of the static pH conditions for every pathogen. However, while the residuals plots of the modified logistic model indicated no systematic bias and/or regional prediction problems, the residuals plots of the Weibull model showed a systematic bias. The modified logistic model appropriately predicted the pathogen behavior in the simulated gastric digestion process with actual food, including cut lettuce, minced tuna, hamburger, and scrambled egg. Although the developed model enabled us to predict pathogen inactivation during gastric digestion, its results also suggested that the ingested bacteria in the stomach would barely be inactivated in the real digestion process. The results of this study will provide important information on a part of the dose-response mechanism of bacterial pathogens. PMID:21131530

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.

Characteristics of strain-sensitive photonic crystal cavities in a flexible substrate.

PubMed

No, You-Shin; Choi, Jae-Hyuck; Kim, Kyoung-Ho; Park, Hong-Gyu

2016-11-14

High-index semiconductor photonic crystal (PhC) cavities in a flexible substrate support strong and tunable optical resonances that can be used for highly sensitive and spatially localized detection of mechanical deformations in physical systems. Here, we report theoretical studies and fundamental understandings of resonant behavior of an optical mode excited in strain-sensitive rod-type PhC cavities consisting of high-index dielectric nanorods embedded in a low-index flexible polymer substrate. Using the three-dimensional finite-difference time-domain simulation method, we calculated two-dimensional transverse-electric-like photonic band diagrams and the three-dimensional dispersion surfaces near the first Γ-point band edge of unidirectionally strained PhCs. A broken rotational symmetry in the PhCs modifies the photonic band structures and results in the asymmetric distributions and different levels of changes in normalized frequencies near the first Γ-point band edge in the reciprocal space, which consequently reveals strain-dependent directional optical losses and selected emission patterns. The calculated electric fields, resonant wavelengths, and quality factors of the band-edge modes in the strained PhCs show an excellent agreement with the results of qualitative analysis of modified dispersion surfaces. Furthermore, polarization-resolved time-averaged Poynting vectors exhibit characteristic dipole-like emission patterns with preferentially selected linear polarizations, originating from the asymmetric band structures in the strained PhCs.

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.

The Possible Reduction Mechanism of Volatile Sulfur Compounds during Durian Wine Fermentation Verified in Modified Buffers.

PubMed

Lu, Yuyun; Fong, Alicia Sarah Yoke Ling; Chua, Jian-Yong; Huang, Dejian; Lee, Pin-Rou; Liu, Shao-Quan

2018-06-15

Durian fruit is rich in volatile sulfur compounds (VSCs), especially thiols and disulfides, which contribute to its onion-like odor. After fermentation, these VSCs were reduced to trace or undetectable levels in durian wine. The possible reduction mechanism of these VSCs (especially diethyl disulfide and ethanethiol) was investigated in a modified buffer in the presence of sulfite at different pH. An interconversion between diethyl disulfide and ethanethiol was found to be dependent on the pH: the higher the pH, the higher production of ethanethiol. It is suggested that, during durian wine fermentation, disulfides endogenous to durian pulp might be firstly converted into their corresponding thiols in the presence of reductant sulfite formed by yeast. The produced thiols as well as the thiols endogenous to the durian pulp were then removed by the mannoproteins of yeast lees.

Attitudes to genetically modified food over time: How trust in organizations and the media cycle predict support.

PubMed

Marques, Mathew D; Critchley, Christine R; Walshe, Jarrod

2015-07-01

This research examined public opinion toward genetically modified plants and animals for food, and how trust in organizations and media coverage explained attitudes toward these organisms. Nationally representative samples (N=8821) over 10 years showed Australians were less positive toward genetically modified animals compared to genetically modified plants for food, especially in years where media coverage was high. Structural equation modeling found that positive attitudes toward different genetically modified organisms for food were significantly associated with higher trust in scientists and regulators (e.g. governments), and with lower trust in watchdogs (e.g. environmental movement). Public trust in scientists and watchdogs was a stronger predictor of attitudes toward the use of genetically modified plants for food than animals, but only when media coverage was low. Results are discussed regarding the moral acceptability of genetically modified organisms for food, the media's role in shaping public opinion, and the role public trust in organizations has on attitudes toward genetically modified organisms. © The Author(s) 2014.

Polyaniline (PANI) modified bentonite by plasma technique for U(VI) removal from aqueous solution

NASA Astrophysics Data System (ADS)

Liu, Xinghao; Cheng, Cheng; Xiao, Chengjian; Shao, Dadong; Xu, Zimu; Wang, Jiaquan; Hu, Shuheng; Li, Xiaolong; Wang, Weijuan

2017-07-01

Polyaniline (PANI) modified bentonite (PANI/bentonie) was synthesized by plasma induced polymerization of aniline on bentonite surface, and applied to uptake of uranium(VI) ions from aqueous solution. The as-synthesized PANI/bentonie was characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). Batch adsorption technique was utilized to investigate the adsorption of U(VI) on bentonite and PANI/bentonite. The adsorption of U(VI) (10 mg/L) on PANI/bentonite surface is fairly depend on solution pH, ionic strength, and temperature in solution. The modified PANI on PANI/bentonite surface significantly enhances its adsorption capability for U(VI). The presence of humic acid (HA) can sound enhance U(VI) adsorption on PANI/bentonite at pH < 6.5 because of the strong complexation, and inhibits U(VI) adsorption at pH > 6.5. According to the thermodynamic parameters, the adsorption of U(VI) on PANI/bentonite surface is a spontaneous and endothermic process. The results highlight the application of PANI/bentonite composites as candidate material for the uptake of trace U(VI) from aqueous solution.

Heavy metals content in degraded agricultural soils of a mountain region related to soil properties

NASA Astrophysics Data System (ADS)

Navarro-Pedreño, José; Belén Almendro-Candel, María; Gómez, Ignacio; Jordán, Manuel M.; Bech, Jaume; Zorpas, Antonis

2017-04-01

Agriculture has been practiced for long time in Mediterranean regions. Intensive agriculture and irrigation have developed mainly in the valleys and coastal areas. In the mountainous areas, dry farming has been practiced for centuries. Soils have been fertilized using mainly organic amendments. Plants extracted nutrients and other elements like heavy metals presented in soils and agricultural practices modified soil properties that could favor the presence of heavy metals. In this work, it has been checked the content of heavy metals in 100 agricultural soils samples of the NorthWest area of the province of Alicante (Spain) which has been long cultivated with cereals and olive trees, and now soils are abandoned and degraded because of the low agricultural yields. European policy has the aim to improve the sustainable agriculture and recover landscapes of mountain regions. So that, it is important to check the state of the soils (Marques et al. 2007). Soils samples (arable layer) were analyzed determining: pH (1:5, w/v, water extract), equivalent calcium carbonate content, organic matter by Walkley-Black method (Nelson and Sommers 1996), micronutrients (Cu, Fe, Mn, Zn) extracted with DTPA (Lindsay and Norvell, 1978) and measured by atomic absorption spectrometry, and total content of metals (Cd, Cr, Ni, Pb) measured in soil samples after microwave acid digestion (Moral et al. 1996), quantifying the content of metals by ICP analysis. The correlation between soil properties and metals. The results indicated that pH and carbonates are the most important properties of these soils correlated with the metals (both micronutrients and heavy metals). The available micronutrients (all of them) are close correlated with the pH and carbonates in soils. Moreover, heavy metals like Pb and Ni are related to available Mn and Zn. Keywords: pH, carbonates, heavy metals, abandoned soils. References: Lindsay,W.L., andW.A. Norvell. 1978. "Development of a DTPA Soil Test for Zinc, Iron, Manganese and Copper." Soil Science Society of America Journal 42: 421-428. Marques,M.J., R. Jimenez-Ballesta, A. Á lvarez, and R. Bienes. 2007. "Spanish Research on Soil Damage." Science of the Total Environment 378: 1-4. Moral, R., J. Navarro-Pedreño, I. Gómez, and J. Mataix. 1996. "Quantitative Analysis of Organic Residues: Effects of Samples Preparation in the Determination of Metal." Communications in Soil Science and Plant Analysis 27: 753-761. Nelson, D.W., and L.E. Sommers. 1996. "Total Carbon, Organic Carbon, and Organic Matter." In Methods of Soil Analysis. Part 3. Chemical Methods, edited by D.L. Sparks, A.L. Page, P.A. Helmke, R.H. Loeppert, P.N. Soltanpour, M.A. Tabatabai, C.T. Johnston, M.E. Sumner. Madison, WI: American Society of Agronomy.

The variations of aluminium species in mountainous forest soils and its implications to soil acidification.

PubMed

Bradová, Monika; Tejnecký, Václav; Borůvka, Luboš; Němeček, Karel; Ash, Christopher; Šebek, Ondřej; Svoboda, Miroslav; Zenáhlíková, Jitka; Drábek, Ondřej

2015-11-01

Aluminium (Al) speciation is a characteristic that can be used as a tool for describing the soil acidification process. The question that was answered is how tree species (beech vs spruce) and type of soil horizon affect Al speciation. Our hypotesis is that spruce and beech forest vegetation are able to modify the chemical characteristics of organic horizon, hence the content of Al species. Moreover, these characteristics are seasonally dependent. To answer these questions, a detailed chromatographic speciation of Al in forest soils under contrasting tree species was performed. The Jizera Mountains area (Czech Republic) was chosen as a representative mountainous soil ecosystem. A basic forestry survey was performed on the investigated area. Soil and precipitation samples (throughfall, stemflow) were collected under both beech and spruce stands at monthly intervals from April to November during the years 2008-2011. Total aluminium content and Al speciation, pH, and dissolved organic carbon were determined in aqueous soil extracts and in precipitation samples. We found that the most important factors affecting the chemistry of soils, hence content of the Al species, are soil horizons and vegetation cover. pH strongly affects the amount of Al species under both forests. Fermentation (F) and humified (H) organic horizons contain a higher content of water extractable Al and Al(3+) compared to organo-mineral (A) and mineral horizons (B). With increasing soil profile depth, the amount of water extractable Al, Al(3+) and moisture decreases. The prevailing water-extractable species of Al in all studied soils and profiles under both spruce and beech forests were organically bound monovalent Al species. Distinct seasonal variations in organic and mineral soil horizons were found under both spruce and beech forests. Maximum concentrations of water-extractable Al and Al(3+) were determined in the summer, and the lowest in spring.

Derivatizing weak polyelectrolytes--solution properties, self-aggregation, and association with anionic surfaces of hydrophobically modified poly(ethylene imine).

PubMed

Griffiths, Peter C; Paul, Alison; Fallis, Ian A; Wellappili, Champa; Murphy, Damien M; Jenkins, Robert; Waters, Sarah J; Nilmini, Renuka; Heenan, Richard K; King, Stephen M

2007-10-15

The physical properties of weak polyelectrolytes may be tailored via hydrophobic modification to exhibit useful properties under appropriate pH and ionic strength conditions as a consequence of the often inherently competing effects of electrostatics and hydrophobicity. Pulsed-gradient spin-echo NMR (PGSE-NMR), electron paramagnetic resonance (EPR), small-angle neutron scattering (SANS) surface tension, fluorescence, and pH titration have been used to examine the solution conformation and aggregation behavior of a series of hydrophobically modified hyperbranched poly(ethylene imine) (PEI) polymers in aqueous solution, and their interaction with sodium dodecylsulfate (SDS). PGSE-NMR gave a particularly insightful picture of the apparent molecular weight distribution. The presence of the hydrophobes led to a lower effective charge on the polymer at any given pH, compared to the (parent) nonmodified samples. Analysis of the SANS data showed that the propensity to form highly elliptical or rod-like aggregates at higher pHs, reflecting both the changes in protonation behavior induced by the hydrophobic modification and an hydrophobic interaction, but that these structures were disrupted with decreasing pH (increasing charge). The parent samples were not surface active yet the hydrophobically modified samples show pronounced surface activity and the presence of small hydrophobic domains. The surface activity increased with an increase in the degree of modification. On addition of SDS, the onset of the formation of polymer/surfactant complexes was insensitive to the degree of modification with the resultant PEI/SDS complexes resembling the size and shape of simple SDS micelles. Indeed, the presence of the SDS effectively nullifies the effects of the hydrophobe. Hydrophobic modification is therefore a viable option to tailor pH dependent properties, whose effects may be removed by the presence of surfactant.

pH sensitive core-shell magnetic nanoparticles for targeted drug delivery in cancer therapy.

PubMed

Lungu, Iulia Ioana; Rădulescu, Marius; Mogoşanu, George Dan; Grumezescu, Alexandru Mihai

2016-01-01

In the last decade, nanobiotechnology has evolved rapidly with an extensive impact on biomedical area. In order to improve bioavailability and minimize adverse effects, drug delivery systems based on magnetic nanocomposites are under development mainly for cancer imaging and antitumor therapy. In this regard, pH sensitive core-shell magnetic nanoparticles (NPs) with accurate controlled size and shape are synthesized by various modern methods, such as homogeneous precipitation, coprecipitation, microemulsion or polyol approaches, high temperature and hydrothermal reactions, sol-gel reactions, aerosol÷vapor processes and sonolysis. Due to their unique combined physico-chemical and biological properties (such as higher dispensability, chemical and thermal stability, biocompatibility), pH responsive core-shell magnetic NPs are widely investigated for controlled release of cytostatic drugs into the tumor site by means of pH change: magnetite@silicon dioxide (Fe3O4@SiO2), Fe3O4@titanium dioxide (TiO2), β-thiopropionate-polyethylene glycol (PEG)-modified Fe3O4@mSiO2, Fe3O4 NPs core coated with SiO2 with an imidazole group modified PEG-polypeptide (mPEG-poly-L-Asparagine), polyacrylic acid (PAA) and folic acid (FA) coating of the iron oxide NP core, methoxy polyethylene glycol-block-polymethacrylic acid-block-polyglycerol monomethacrylate (MPEG-b-PMAA-b-PGMA) attached by a PGMA block to a Fe3O4 core, PEG-modified polyamidoamine (PAMAM) dendrimer shell with Fe3O4 core and mesoporous silica coated on Fe3O4, mostly coated with an anticancer drug. This review paper highlights the modern research directions currently employed to demonstrate the utility of the pH responsive core-shell magnetic NPs in diagnosis and treatment of oncological diseases.

Differential modification of seawater carbonate chemistry by major coral reef benthic communities

NASA Astrophysics Data System (ADS)

Page, Heather N.; Andersson, Andreas J.; Jokiel, Paul L.; Rodgers, Ku'ulei S.; Lebrato, Mario; Yeakel, Kiley; Davidson, Charlie; D'Angelo, Sydney; Bahr, Keisha D.

2016-12-01

Ocean acidification (OA) resulting from uptake of anthropogenic CO2 may negatively affect coral reefs by causing decreased rates of biogenic calcification and increased rates of CaCO3 dissolution and bioerosion. However, in addition to the gradual decrease in seawater pH and Ω a resulting from anthropogenic activities, seawater carbonate chemistry in these coastal ecosystems is also strongly influenced by the benthic metabolism which can either exacerbate or alleviate OA through net community calcification (NCC = calcification - CaCO3 dissolution) and net community organic carbon production (NCP = primary production - respiration). Therefore, to project OA on coral reefs, it is necessary to understand how different benthic communities modify the reef seawater carbonate chemistry. In this study, we used flow-through mesocosms to investigate the modification of seawater carbonate chemistry by benthic metabolism of five distinct reef communities [carbonate sand, crustose coralline algae (CCA), corals, fleshy algae, and a mixed community] under ambient and acidified conditions during summer and winter. The results showed that different communities had distinct influences on carbonate chemistry related to the relative importance of NCC and NCP. Sand, CCA, and corals exerted relatively small influences on seawater pH and Ω a over diel cycles due to closely balanced NCC and NCP rates, whereas fleshy algae and mixed communities strongly elevated daytime pH and Ω a due to high NCP rates. Interestingly, the influence on seawater pH at night was relatively small and quite similar across communities. NCC and NCP rates were not significantly affected by short-term acidification, but larger diel variability in pH was observed due to decreased seawater buffering capacity. Except for corals, increased net dissolution was observed at night for all communities under OA, partially buffering against nighttime acidification. Thus, algal-dominated areas of coral reefs and increased net CaCO3 dissolution may partially counteract reductions in seawater pH associated with anthropogenic OA at the local scale.

Stability and Transport of Cerium Oxide Nanoparticles in Aqueous Environment: Effect of pH, Ionic Strength, and Organic Matter.

EPA Science Inventory

This study investigated the stability and transport of CeO2 NPs under the influence of pH, natural/manmade organic matter, and electrolyte (NaCl) concentrations. In column test, effluent concentration of CeO2 NPs was close to the influent at pH 10, while most NPs deposited on san...

Phenotypic and Functional Analysis of Human SLC26A6 Variants in Patients With Familial Hyperoxaluria and Calcium Oxalate Nephrolithiasis

PubMed Central

Monico, Carla G.; Weinstein, Adam; Jiang, Zhirong; Rohlinger, Audrey L.; Cogal, Andrea G.; Bjornson, Beth B.; Olson, Julie B.; Bergstralh, Eric J.; Milliner, Dawn S.; Aronson, Peter S.

2008-01-01

Background Urinary oxalate is a major risk factor for calcium oxalate stones. Marked hyperoxaluria arises from mutations in two separate loci, AGXT and GRHPR, the causes of primary hyperoxaluria (PH) types 1 and 2, respectively. Studies of null Slc26a6 (−/−) mice have revealed a phenotype of hyperoxaluria, hyperoxalemia and calcium oxalate urolithiasis, leading to the hypothesis that SLC26A6 mutations may cause or modify hyperoxaluria in humans. Study Design Cross-sectional, case-control. Setting & Participants Cases were recruited from the International Primary Hyperoxaluria Registry. Control DNA samples were from a pool of adult subjects who identified themselves as being in good health. Predictor PH1, PH2, non-PH1/PH2 genotypes in cases. Outcomes & Measures Homozygosity or compound heterozygosity for SLC26A6 variants. Functional expression of oxalate transport in Xenopus oocytes. Results A total of 80 PH1, 6 PH2, 8 non-PH1/PH2 and 96 control samples were available for SLC26A6 screening. A rare variant, c.487C>T (p.Pro163Ser) was detected solely in one non-PH1/PH2 pedigree but this variant failed to segregate with hyperoxaluria, and functional studies of oxalate transport in Xenopus oocytes revealed no transport defect. No other rare variant was identified specifically in non-PH1/PH2. Six additional missense variants were detected in controls and in cases. Of these, c.616G>A (p.Val206Met) was most common (11%), and showed a 30% reduction in oxalate transport. To test p.Val206Met as a potential modifier of hyperoxaluria, we extended screening to PH1 and PH2. Heterozygosity for this variant did not affect plasma or urine oxalate in this population. Limitations We did not have a sufficient number of cases to determine whether homozygosity for p.Val206Met might significantly affect urine oxalate. Conclusions SLC26A6 was effectively ruled out as the disease gene in this non-PH1/PH2 cohort. Taken together, our studies are the first to identify and characterize SLC26A6 variants in hyperoxaluria. Phenotypic and functional analysis excluded a significant effect of identified variants on oxalate excretion. PMID:18951670

Rhamnogalacturonan I containing homogalacturonan inhibits colon cancer cell proliferation by decreasing ICAM1 expression

USDA-ARS?s Scientific Manuscript database

Pectin modified with pH, heat or enzymes, has previously been shown to exhibit anti-cancer activity. However, the structural requirements for bioactive modified pectins have rarely been addressed. In this study several pectin extracts representing different structural components of pectin were asses...

Biosorption properties of citrus peel derived oligogalacturonides, enzyme-modified pectin and peel hydrolysis residues

USDA-ARS?s Scientific Manuscript database

Data is presented on the biosorption properties of modified pectins and pectin fragments using lead as a model cation. Samples tested for their sorption capacity are Narrow-Range Size-Classes of galacturonic acid oligomers, well characterized homogalacturonan demethylations series produced at pH 7....

The effects of salinity, pH, and dissolved organic matter on acute copper toxicity to the rotifer, Brachionus plicatilis ("L" strain).

PubMed

Arnold, W R; Diamond, R L; Smith, D S

2010-08-01

This paper presents data from original research for use in the development of a marine biotic ligand model and, ultimately, copper criteria for the protection of estuarine and marine organisms and their uses. Ten 48-h static acute (unfed) copper toxicity tests using the euryhaline rotifer Brachionus plicatilis ("L" strain) were performed to assess the effects of salinity, pH, and dissolved organic matter (measured as dissolved organic carbon; DOC) on median lethal dissolved copper concentrations (LC50). Reconstituted and natural saltwater samples were tested at seven salinities (6, 11, 13, 15, 20, 24, and 29 g/L), over a pH range of 6.8-8.6 and a range of dissolved organic carbon of <0.5-4.1 mg C/L. Water chemistry analyses (alkalinity, calcium, chloride, DOC, hardness, magnesium, potassium, sodium, salinity, and temperature) are presented for input parameters to the biotic ligand model. In stepwise multiple regression analysis of experimental results where salinity, pH, and DOC concentrations varied, copper toxicity was significantly related only to the dissolved organic matter content (pH and salinity not statistically retained; alpha=0.05). The relationship of the 48-h dissolved copper LC50 values and dissolved organic carbon concentrations was LC50 (microg Cu/L)=27.1xDOC (mg C/L)1.25; r2=0.94.

Impact on the Fe redox cycling of organic ligands released by Synechococcus PCC 7002, under different iron fertilization scenarios. Modeling approach

NASA Astrophysics Data System (ADS)

Samperio-Ramos, Guillermo; González-Dávila, Melchor; Santana-Casiano, J. Magdalena

2018-06-01

The kinetics of Fe redox transformations are of crucial importance in determining the bioavailability of iron, due to inorganic Fe(II) and Fe weakly organic complexes being the most easily assimilated species by phytoplankton. The role played by the natural organic ligands excreted by the cyanobacteria Synecococcus PCC 7002 on the iron redox chemistry was studied at different stages of growth, considering changes in the organic exudation of the cyanobacteria, associated with growth under two different scenarios of iron availability. The oxidation/reduction processes of iron were studied at nanomolar levels and under different physicochemical conditions of pH (7.2- 8.2), temperature (5- 35 °C) and salinity (10- 37). The presence of natural organic exudates of Synechococcus affected the redox behavior of iron. A pH-dependent and photo-induced Fe(III) reduction process was detected in the presence of exudates produced under Fe-Low conditions. Photolytic reactions also modified the reactivity of those exudates with respect to Fe(II), increasing its lifetime in seawater. Without light mediated processes, organic ligands excreted under iron deficient conditions intensified the Fe(II) oxidation at pH < 7.5. The organic exudates released under High-Fe conditions retarded the Fe(II) oxidation rate, as a function of DOC produced. The changes in the apparent oxidation rate were fitted to polynomial functions for both of the Fe-scenarios considered. A kinetic modeling approach to describe the speciation and the contribution of individual Fe(II) species to the overall oxidation rate was applied, considering the experimental data and delimiting the equilibrium and redox constants between iron and the major ligands present in solution. Two organic type ligands for the exudates of Synechococcus PCC 7002, with different iron-chelation properties were included in the model. The Fe(II) speciation was radically affected when organic ligands were considered. The individual contributions to the overall Fe(II) oxidation rate demonstrated that these organic ligands played a key role in the oxidation process, although their contributions were dependent on the prescribed iron conditions. The study, therefore, suggests that the variability in the composition and nature of organic exudates released, due to iron availability conditions, might determine the redox behaviour of iron in seawater.

Development and characterization of ferrihydrite-modified diatomite as a phosphorus adsorbent.

PubMed

Xiong, Wenhui; Peng, Jian

2008-12-01

A novel phosphorus adsorbent, ferrihydrite-modified diatomite was developed and characterized in this study. The ferrihydrite-modified diatomite was made through surface modification treatments including NaOH treatment and ferrihydrite deposition on raw diatomite. In the NaOH treatment, surface SiO(2) of diatomite was partially dissolved in the NaOH solution. The dissolved Si contributed to form the stable 2-line ferrihydrite which deposited into the macropores and mesopores of diatomite. Blocking macropores and larger mesopores of diatomite with 0.24g Fe/g of 2-line ferrihydrite resulted in a specific surface area of 211.1m(2)/g for the ferrihydrite-modified diatomite, which is 8.5-fold increase than the raw diatomite (24.77m(2)/g). The surface modification also increased the point of zero charge (pH(PZC)) values to 10 for the ferrihydrite-modified diatomite from 5.8 for the raw diatomite. Because of the increased surface area and surface charge, the maximum adsorption capacity of ferrihydrite-modified diatomite at pH 4 and pH 8.5 was increased from 10.2mgP/g and 1.7mgP/g of raw diatomite to 37.3mgP/g and 13.6mgP/g, respectively.

Development and Validation of a Stability-Indicating HPLC Method for Imidapril and Its Degradation Products Using a Design of Experiment (DoE) Approach.

PubMed

Arumugam, Abiramasundari; Joshi, Amita; Vasu, Kamala K

2017-11-01

The present work focused on the application of design of experiment (DoE) principles to the development and optimization of a stability-indicating method (SIM) for the drug imidapril hydrochloride and its degradation products (DPs). The resolution of peaks for the DPs and their drug in a SIM can be influenced by many factors. The factors studied here were pH, gradient time, organic modifier, flow rate, molar concentration of the buffer, and wavelength, with the aid of a Plackett-Burman design. Results from the Plackett-Burman study conspicuously showed influence of two factors, pH and gradient time, on the analyzed response, particularly, the resolution of the closely eluting DPs (DP-5 and DP-6) and the retention time of the last peak. Optimization of the multiresponse processes was achieved through Derringer's desirability function with the assistance of a full factorial design. Separation was achieved using a C18 Phenomenex Luna column (250 × 4.6 mm id, 5 µm particle size) at a flow rate of 0.8 mL/min at 210 nm. The optimized mobile phase composition was ammonium-acetate buffer (pH 5) in pump A and acetonitrile-methanol (in equal ratio) in pump B with a run time of 40 min using a gradient method.

Spray drying of silica microparticles for sustained release application with a new sol-gel precursor.

PubMed

Wang, Bifeng; Friess, Wolfgang

2017-10-30

A new precursor, tetrakis(2-methoxyethyl) orthosilicate (TMEOS) was used to fabricate microparticles for sustained release application, specifically for biopharmaceuticals, by spray drying. The advantages of TMEOS over the currently applied precursors are its water solubility and hydrolysis at moderate pH without the need of organic solvents or catalyzers. Thus a detrimental effect on biomolecular drug is avoided. By generating spray-dried silica particles encapsulating the high molecular weight model compound FITC-dextran 150 via the nano spray dryer Büchi-90, we demonstrated how formulation parameters affect and enable control of drug release properties. The implemented strategies to regulate release included incorporating different quantities of dextrans with varying molecular weight as well as adjusting the pH of the precursor solution to modify the internal microstructures. The addition of dextran significantly altered the released amount, while the release became faster with increasing dextran molecular weight. A sustained release over 35days could be achieved with addition of 60 kD dextran. The rate of FITC-Dextran 150 release from the dextran 60 containing particles decreased with higher precursor solution pH. In conclusion, the new precursor TMEOS presents a promising alternative sol-gel technology based carrier material for sustained release application of high molecular weight biopharmaceutical drugs. Copyright © 2017 Elsevier B.V. All rights reserved.

Adsorption of arsenic ions on Brazilian sepiolite: effect of contact time, pH, concentration, and calorimetric investigation.

PubMed

Guerra, Denis L; Batista, Adriano C; da Costa, Paulo C Corrêa; Viana, Rúbia R; Airoldi, Claudio

2010-06-01

The original sepiolite clay mineral has been collected from Amazon region, Brazil. The compound 2-aminomethylpyridine (AMP) was anchored onto Amazon sepiolite surface by heterogeneous route. The natural (SPT) and modified (SPT(AMP)) sepiolite samples were characterized by elemental analysis, SEM, N(2) adsorption, and nuclear magnetic nuclei of (29)Si and (13)C. The well-defined peaks obtained in the (13)C NMR spectrum in the 0-160 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove As(V) from aqueous solution was followed by a series of adsorption isotherms at room temperature and pH 4.0. The maximum number of moles adsorbed was determined to be 7.26×10(-2) and 11.70×10(-2) mmol g(-1) for SPT and SPT(AMP), respectively. In order to evaluate the clay samples as adsorbents in dynamic system, a glass column was fulfilled with clay samples (1.0 g) and it was fed with 2.0×10(-2) mmol dm(-3) As(V) at pH 4.0. The energetic effects caused by metal cations adsorption were determined through calorimetric titrations. Thermodynamics indicated the existence of favorable conditions for such As(V)-nitrogen interactions. Copyright © 2010. Published by Elsevier Inc.

Powdered activated carbon adsorption of two fishy odorants in water: Trans,trans-2,4-heptadienal and trans,trans-2,4-decadienal.

PubMed

Li, Xin; Wang, Jun; Zhang, Xiaojian; Chen, Chao

2015-06-01

Powdered activated carbon (PAC) adsorption of two fishy odorants, trans,trans-2,4-heptadienal (HDE) and trans,trans-2,4-decadienal (DDE), was investigated. Both the pseudo first-order and the pseudo second-order kinetic models well described the kinetics curves, and DDE was more readily removed by PAC. In isotherm tests, both Freundlich and Modified Freundlich isotherms fitted the experimental data well. PAC exhibited a higher adsorption capacity for DDE than for HDE, which could be ascribed to the difference in their hydrophobicity. The calculated thermodynamic parameters (ΔG0, ΔH0, and ΔS0) indicated an exothermic and spontaneous adsorption process. PAC dosage, pH, and natural organic matter (NOM) presence were found to influence the adsorption process. With increasing PAC dosage, the pseudo first-order and pseudo second-order rate constants both increased. The value of pH had little influence on HDE or DDE molecules but altered the surface charge of PAC, and the maximum adsorption capacity occurred at pH9. The presence of NOM, especially the fraction with molecular weight less than 1k Dalton, hindered the adsorption. The study showed that preloaded NOM impaired the adsorption capacity of HDE or DDE more severely than simultaneously fed NOM did. Copyright © 2015. Published by Elsevier B.V.

Investigation of the retention/pH profile of zwitterionic fluoroquinolones in reversed-phase and ion-interaction high performance liquid chromatography.

PubMed

Pistos, C; Tsantili-Kakoulidou, A; Koupparis, M

2005-09-15

The retention/pH profiles of three fluoroquinolones, ofloxacin, norfloxacin and ciprofloxacin, was investigated by means of reversed-phase high performance liquid chromatography (RP-HPLC) and reversed-phase ion-interaction chromatography (RP-IIC), using an octadecylsilane stationary phase and acetonitrile as organic modifier. Sodium hexanesulphonate and tetrabutylammonium hydroxide were used as sources of counter ions in ion-interaction chromatography. The retention/pH profiles under in RP-HPLC were compared to the corresponding lipophilicity/pH profiles. Despite the rather hydrophilic nature of the three fluoroquinolones positive retention factors were obtained while there was a shift of the retention maximum towards more acidic pH values. This behavior was attributed mainly to non-hydrophobic silanophilic interactions with the silanized silica gel material of the stationary phase. In ion-interaction chromatography the effect of counter ions over a broad pH range was found to be ruled rather by the ion pair formation in the mobile phase which led to a drastic decrease in retention as a consequence of the disruption of the zwitterionic structure and thereupon the deliberation of a net charge in the molecules. At pH values at which zwitterionic structure was not favored both the ion-exchange and ion pair formation mechanisms were assumed to contribute to the retention.

Preparation and evaluation of molecularly imprinted polymers based on 9-ethyladenine for the recognition of nucleotide bases in capillary electrochromatography.

PubMed

Huang, Yi-Chen; Lin, Chun-Chi; Liu, Chuen-Ying

2004-02-01

A molecularly imprinted polymer (MIP) comprising 9-ethyladenine was polymerized in situ inside the capillary for the electrochromatographic separation of nucleotide bases. The capillary wall was first functionalized with 3-trimethoxysilylpropyl methacrylate (10% v/v) and 1,1-diphenyl-2-picrylhydrazyl (0.01% w/v) in toluene. Following this treatment, the capillary was filled with acetonitrile containing 9-ethyladenine, methacrylic acid, ethylene glycol dimethacrylate, and initiator. After polymerization, the MIP was shrunk into a film against the inner wall of the capillary with the syringe pump. The template was then removed with methanol under nitrogen flow. For evaluation the feasibility of the MIP column for the separation of nucleotide bases, some parameters including the pH, concentration of the background electrolyte, the applied voltage as well as the effect of organic modifier were studied. The migration behavior of nucleotide bases on the MIP column was also compared with that on the bare fused-silica column. The results indicated that the MIP columns demonstrated better recognition properties at a pH range of 6-8. The efficiency (plates/m) at pH 8 for the nonimprinted analyte was 75,300 for cytosine, 50,200 for thymine, and 14,800 for guanine. However, the efficiency for the imprinted analyte, adenine, was quite low. This was evidenced by the broad peak, yielding only 2600 plates/m.

BIOACCESSIBILITY TESTS ACCURATELY ESTIMATE ...

EPA Pesticide Factsheets

Hazards of soil-borne Pb to wild birds may be more accurately quantified if the bioavailability of that Pb is known. To better understand the bioavailability of Pb to birds, we measured blood Pb concentrations in Japanese quail (Coturnix japonica) fed diets containing Pb-contaminated soils. Relative bioavailabilities were expressed by comparison with blood Pb concentrations in quail fed a Pb acetate reference diet. Diets containing soil from five Pb-contaminated Superfund sites had relative bioavailabilities from 33%-63%, with a mean of about 50%. Treatment of two of the soils with P significantly reduced the bioavailability of Pb. The bioaccessibility of the Pb in the test soils was then measured in six in vitro tests and regressed on bioavailability. They were: the “Relative Bioavailability Leaching Procedure” (RBALP) at pH 1.5, the same test conducted at pH 2.5, the “Ohio State University In vitro Gastrointestinal” method (OSU IVG), the “Urban Soil Bioaccessible Lead Test”, the modified “Physiologically Based Extraction Test” and the “Waterfowl Physiologically Based Extraction Test.” All regressions had positive slopes. Based on criteria of slope and coefficient of determination, the RBALP pH 2.5 and OSU IVG tests performed very well. Speciation by X-ray absorption spectroscopy demonstrated that, on average, most of the Pb in the sampled soils was sorbed to minerals (30%), bound to organic matter 24%, or present as Pb sulfate 18%. Ad

Selective separation of uranium using alizarin red S (ARS)-modified anion-exchange resin or by flotation of U-ARS chelate

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

Khalifa, M.E.

An alizarin red S (ARS)-modified anion exchange resin was prepared by a simple reaction of ARS with the anion exchange Doulite A101 and used for the efficient sorption of uranium from aqueous media. The effect of various parameters on the sorption of U(VI) (pH effect, sorption kinetics, resin capacity and breakthrough curves) was investigated. The modified resin sorbs U(VI) over a wide range of pH (2.8--5) with a maximum sorption capacity of 0.68 mmol/g at pH 3.2 to 4.0. Iron(III), Zr(IV), Ti(IV), Cu(II), and Th(IV) ions are also sorbed to different extents, but Be(II), Bi(III), Ca(II), Mg(II), Pb(II), Hg(II), Zn(II),more » Cd(II), Al(III), Mn(II), Co(II) and Ni(II) are not sorbed; thus, conditions for separating U(VI) from these metal ions have been identified. For eluting U(VI) from the resin, 0.2 mol/L HCl was used and the recovery recorded was as high as 99.9%. The use of ARS is extended to float uranium quantitatively and selectively from aqueous media at pH {approx} 4 by using oleic acid as a surfactant. The different parameters affecting the flotation process have also been investigated. Uranium(VI) has been effectively separated from natural water samples and certified uranium ores using both procedures.« less

Effect of organic matter on cyanide removal by illuminated titanium dioxide or zinc oxide nanoparticles

PubMed Central

2013-01-01

Effect of different type of organic compounds (humic acid, oxalate, ethylenediaminetetraacetic acid, nitrilotriacetic acid, phenol) on the photocatalytic removal of cyanide with TiO2 or ZnO was studied in this work with variation of the solution pH, contact time, initial cyanide concentration and type of organic compounds. Photocatalytic oxidation efficiency of cyanide with TiO2 was greatly affected by the solution pH. It increased as the solution pH decreased. Also maximum removal of cyanide by ZnO was observed near at neutral pH because of the reduced photocatalytic activity of ZnO at exceedingly low and high pH values originated from either acidic/photochemical corrosion of the catalyst and/or surface passivation with Zn(OH)2. Removal efficiency of cyanide greatly decreased in the presence of humic acid, ethylenediaminetetraacetic acid, nitrilotriacetic acid compared to that without presence of organic compound because of the competitive oxidation as well as surface blocking by relatively large organic compounds. The oxidation pattern of cyanide was better described by first-order kinetic model. Finally photocatalytic reaction with TiO2 or ZnO can be effectively applied to treat synthetic wastewater contaminated with cyanide. PMID:24499704

Improved methane production from waste activated sludge with low organic content by alkaline pretreatment at pH 10.

PubMed

Feng, L Y; Yang, L Q; Zhang, L X; Chen, H L; Chen, J

2013-01-01

Sludge with low organic content always results in an unsatisfactory performance, even failure of anaerobic digestion. The alkaline pretreatment effect on anaerobic digestion of sludge with low organic content has seldom been studied although it gives many benefits for sludge with high organic content. In this study the influence of alkaline pretreatment (pH 10, an effective alkaline pH) on the solubilization and methane production from waste activated sludge (WAS) with low organic content was investigated. Results from biochemical methane potential (BMP) experiments showed that anaerobic biodegradability of WAS was greatly improved by alkaline pretreatment at pH 10. Methane production from the current WAS under conditions of pretreatment time 4 h and digestion time 15 d was 139.6 mL/g VS (volatile solids), much higher than that from the unpretreated WAS with digestion time of 20 d (75.2 mL/g VS). Also, the solubilization of WAS was significantly accelerated by alkaline pretreatment. Mechanism exploration indicated that the general activities of anaerobic microorganisms, specific activities of key enzymes and the amounts of methanogens were enhanced by alkaline pretreatment at pH 10, showing good agreement with methane production.

Acid-degradable lactobionic acid-modified soy protein nanogels crosslinked by ortho ester linkage for efficient antitumor in vivo.

PubMed

Cheng, Xu; Qin, Jiejie; Wang, Xin; Zha, Qian; Yao, Weijing; Fu, Shengxiang; Tang, Rupei

2018-05-03

It remains a crucial challenge to achieve efficient cellular uptake and intracellular drug release in tumor cells for the nanoscale drug delivery systems. Herein, acid-degradable nanogels were prepared by cross-linking methacrylated soy protein with an acid-labile ortho ester cross-linker (NG1), and then modified with lactobionic acid (LA) to give tumor-targeted nanogels (NG2). Both NG1 and NG2 displayed excellent stability in neutral environment, while showed pH-triggered degradation behaviors under mildly acidic conditions resulting from the breakage of ortho ester bonds. Doxorubicin (DOX) was successfully loaded into nanogels, which exhibited an accelerated release at low pH. In vitro cell studies demonstrated that LA-modified nanogels could effectively improve cellular internalization, show higher cytotoxicity and apoptosis toward asialoglycoprotein receptor (ASGPR) over-expressed HepG2 cells. In vivo antitumor experimentproved that LA modification could significantly enhance the tumor-targeting ability of nanogels and increase DOX concentration in tumor site, leading to better therapeutic efficacy. Histological analysis further demonstrated that soy protein-based nanogels did not cause any damage to normal organs. Overall, these pH-sensitive and tumor-targeting soy protein-based nanogels can be potential drug carriers for efficient tumor treatment. Copyright © 2018. Published by Elsevier B.V.

Effect of dry mycelium of Penicillium chrysogenum fertilizer on soil microbial community composition, enzyme activities and snap bean growth.

PubMed

Wang, Bing; Liu, Huiling; Cai, Chen; Thabit, Mohamed; Wang, Pu; Li, Guomin; Duan, Ziheng

2016-10-01

The dry mycelium fertilizer (DMF) was produced from penicillin fermentation fungi mycelium (PFFM) following an acid-heating pretreatment to degrade the residual penicillin. In this study, it was applied into soil as fertilizer to investigate its effects on soil properties, phytotoxicity, microbial community composition, enzyme activities, and growth of snap bean in greenhouse. As the results show, pH, total nitrogen, total phosphorus, total potassium, and organic matter of soil with DMF treatments were generally higher than CON treatment. In addition, the applied DMF did not cause heavy metal and residual drug pollution of the modified soil. The lowest GI values (<0.3) were recorded at DMF8 (36 kg DMF/plat) on the first days after applying the fertilizer, indicating that severe phytotoxicity appeared in the DMF8-modified soil. Results of microbial population and enzyme activities illustrated that DMF was rapidly decomposed and the decomposition process significantly affected microbial growth and enzyme activities. The DMF-modified soil phytotoxicity decreased at the late fertilization time. DMF1 was considered as the optimum amount of DMF dose based on principal component analysis scores. Plant height and plant yield of snap bean were remarkably enhanced with the optimum DMF dose.

Development of modified release diltiazem HCl tablets using composite index to identify optimal formulation.

PubMed

Gohel, M C; Patel, M M; Amin, A F

2003-05-01

This article reports the preparation of tartaric acid treated ispaghula husk powder for the development of modified release tablets of diltiazem HCl by adopting direct compression technique and a 32 full factorial design. The modified ispaghula husk powder showed superior swelling and gelling as compared to untreated powder. Addition of compaction augmenting agent such as dicalcium phosphate was found to be essential for obtaining tablets with adequate crushing strength. In order to improve the crushing strength of diltiazem HCl tablets, to modulate drug release pattern, and to obtain similarity of dissolution profiles in distilled water and simulated gastric fluid (pH 1.2), modified guar gum was used along with modified ispaghula husk powder and tartaric acid. A novel composite index, which considers a positive or a negative deviation from an ideal value, was calculated considering percentage drug release in 60, 300, and 540 min as dependent variables for the selection of a most appropriate batch. Polynomial equation and contour plots are presented. The concept of similarity factor (f2) was used to prove similarity of dissolution in water and simulated gastric fluid (pH 1.2).

Prolonged acid rain facilitates soil organic carbon accumulation in a mature forest in Southern China.

PubMed

Wu, Jianping; Liang, Guohua; Hui, Dafeng; Deng, Qi; Xiong, Xin; Qiu, Qingyan; Liu, Juxiu; Chu, Guowei; Zhou, Guoyi; Zhang, Deqiang

2016-02-15

With the continuing increase in anthropogenic activities, acid rain remains a serious environmental threat, especially in the fast developing areas such as southern China. To detect how prolonged deposition of acid rain would influence soil organic carbon accumulation in mature subtropical forests, we conducted a field experiment with simulated acid rain (SAR) treatments in a monsoon evergreen broadleaf forest at Dinghushan National Nature Reserve in southern China. Four levels of SAR treatments were set by irrigating plants with water of different pH values: CK (the control, local lake water, pH ≈ 4.5), T1 (water pH=4.0), T2 (water pH=3.5), and T3 (water pH=3.0). Results showed reduced pH measurements in the topsoil exposed to simulated acid rains due to soil acidification. Soil respiration, soil microbial biomass and litter decomposition rates were significantly decreased by the SAR treatments. As a result, T3 treatment significantly increased the total organic carbon by 24.5% in the topsoil compared to the control. Furthermore, surface soil became more stable as more recalcitrant organic matter was generated under the SAR treatments. Our results suggest that prolonged acid rain exposure may have the potential to facilitate soil organic carbon accumulation in the subtropical forest in southern China. Copyright © 2015 Elsevier B.V. All rights reserved.

Electrochemical sensor for hazardous food colourant quinoline yellow based on carbon nanotube-modified electrode.

PubMed

Zhao, Jun; Zhang, Yu; Wu, Kangbing; Chen, Jianwei; Zhou, Yikai

2011-09-15

A novel electrochemical method using multi-wall carbon nanotube (MWNT) film-modified electrode was developed for the detection of quinoline yellow. In pH 8 phosphate buffer, an irreversible oxidation peak at 0.71V was observed for quinoline yellow. Compared with the unmodified electrode, the MWNT film-modified electrode greatly increases the oxidation peak current of quinoline yellow, showing notable enhancement effect. The effects of pH value, amount of MWNT, accumulation potential and time were studied on the oxidation peak current of quinoline yellow. The linear range is from 0.75 to 20mgL(-1), and the limit of detection is 0.5mgL(-1). It was applied to the detection of quinoline yellow in commercial soft drinks, and the results consisted with the value that obtained by high-performance liquid chromatography. Copyright © 2011 Elsevier Ltd. All rights reserved.

Adsorption of aluminum and lead from wastewater by chitosan-tannic acid modified biopolymers: Isotherms, kinetics, thermodynamics and process mechanism.

PubMed

Badawi, M A; Negm, N A; Abou Kana, M T H; Hefni, H H; Abdel Moneem, M M

2017-06-01

Chitosan was reacted by tannic acid to obtain three modified chitosan biopolymer. Their chemical structures were characterized by FTIR and elemental analysis. The prepared biopolymers were used to adsorb Al(III) and Pb(II) metal ions from industrial wastewater. The factors affecting the adsorption process were biosorbent amount, initial concentration of metal ion and pH of the medium. The adsorption efficiency increased considerably with the increase of the biosorbent amount and pH of the medium. The adsorption process of biosorbent on different metal ions was fitted by Freundlich adsorption model. The adsorption kinetics was followed Pseudo-second-order kinetic model. The adsorption process occurred according to diffusion mechanism which was confirmed by the interparticle diffusion model. The modified biopolymers were efficient biosorbents for removal of Pb(II) and Al(III) metal ions from the medium. Copyright © 2017 Elsevier B.V. All rights reserved.

Strategies to overcome pH-dependent solubility of weakly basic drugs by using different types of alginates.

PubMed

Gutsche, S; Krause, M; Kranz, H

2008-12-01

Weakly basic drugs demonstrate higher solubility at lower pH, thus often leading to faster drug release at lower pH. The objective of this study was to achieve pH-independent release of weakly basic drugs from extended release formulations based on the naturally occurring polymer sodium alginate. Three approaches to overcome the pH-dependent solubility of the weakly basic model drug verapamil hydrochloride were investigated. First, matrix tablets were prepared by direct compression of drug substance with different types of sodium alginate only. Second, pH-modifiers were added to the drug/alginate matrix systems. Third, press-coated tablets consisting of an inner pH-modifier tablet core and an outer drug/sodium alginate coat were prepared. pH-Independent drug release was achieved from matrix tablets consisting of selected alginates and drug substance only. Alginates are better soluble at higher pH. Therefore, they are able to compensate the poor solubility of weakly basic drugs at higher pH as the matrix of the tablets dissolves faster. This approach was successful when using alginates that demonstrated fast hydration and erosion at higher pH. The approach failed for alginates with less-pronounced erosion at higher pH. The addition of fumaric acid to drug/alginate-based matrix systems decreased the microenvironmental pH within the tablets thus increasing the solubility of the weakly basic drug at higher pH. Therefore, pH-independent drug release was achieved irrespective of the type of alginate used. Drug release from press-coated tablets did not provide any further advantages as compound release remained pH-dependent.

Effect of Microenvironmental pH Modulation on the Dissolution Rate and Oral Absorption of the Salt of a Weak Acid - Case Study of GDC-0810.

PubMed

Hou, Hao Helen; Jia, Wei; Liu, Lichuan; Cheeti, Sravanthi; Li, Jane; Nauka, Ewa; Nagapudi, Karthik

2018-01-29

The purpose of this work is to investigate the effect of microenvironmental pH modulation on the in vitro dissolution rate and oral absorption of GDC-0810, an oral anti-cancer drug, in human. The pH-solubility profile of GDC-0810 free acid and pH max of its N-Methyl-D-glucamine (NMG) salt were determined. Precipitation studies were conducted for GDC-0810 NMG salt at different pH values. GDC-0810 200-mg dose NMG salt tablet formulations containing different levels of sodium bicarbonate as the pH modifier were tested for dissolution under the dual pH-dilution scheme. Three tablet formulations were evaluated in human as a part of a relative bioavailability study. A 200-mg dose of GDC-0810 was administered QD with low fat food. Intrinsic solubility of GDC-0810 free acid was found to be extremely low. The pH max of the NMG salt suggested a strong tendency for form conversion to the free acid under GI conditions. In vitro dissolution profiles showed that the dissolution rate and extent of GDC-0810 increased with increasing the level of sodium bicarbonate in the formulation. The human PK data showed a similar trend for the geometric mean of C max and AUC 0-t for formulations containing 5%, 10%, and 15% sodium bicarbonate, but the difference is not statistically significant. Incorporation of a basic pH modifier, sodium bicarbonate, in GDC-0810 NMG salt tablet formulations enhanced in vitro dissolution rate of GDC-0810 via microenvironmental pH modulation. The human PK data showed no statistically significant difference in drug exposure from tablets containing 5%, 10%, and 15% sodium bicarbonate.

DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING NATURAL ORGANIC MATTER IN SOILS AND WATER

EPA Science Inventory

Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

Detection of elevated right ventricular extracellular volume in pulmonary hypertension using Accelerated and Navigator-Gated Look-Locker Imaging for Cardiac T1 Estimation (ANGIE) cardiovascular magnetic resonance.

PubMed

Mehta, Bhairav B; Auger, Daniel A; Gonzalez, Jorge A; Workman, Virginia; Chen, Xiao; Chow, Kelvin; Stump, Claire J; Mazimba, Sula; Kennedy, Jamie L W; Gay, Elizabeth; Salerno, Michael; Kramer, Christopher M; Epstein, Frederick H; Bilchick, Kenneth C

2015-12-21

Assessment of diffuse right ventricular (RV) fibrosis is of particular interest in pulmonary hypertension (PH) and heart failure (HF). Current cardiovascular magnetic resonance (CMR) T1 mapping techniques such as Modified Look-Locker inversion recovery (MOLLI) imaging have limited resolution, but accelerated and navigator-gated Look-Locker imaging for cardiac T1 estimation (ANGIE) is a novel CMR sequence with spatial resolution suitable for T1 mapping of the RV. We tested the hypothesis that patients with PH would have significantly more RV fibrosis detected with MRI ANGIE compared with normal volunteers and patients having HF with reduced (LV) ejection fraction (HFrEF) without co-existing PH, independent of RV dilitation and dysfunction. Patients with World Health Organization group 1 or group 4 PH, patients with HFrEF without PH, and normal volunteers were recruited to undergo contrast-enhanced CMR. RV and LV extracellular volume fractions (RV-ECV and LV-ECV) were determined using pre-contrast and post-contrast T1 mapping using ANGIE (RV and LV) and MOLLI (LV only). Thirty-two participants (53.1% female, median age 52 years, IQR 26-65 years) were enrolled, including n = 12 with PH, n = 10 having HFrEF without co-existing PH, and n = 10 normal volunteers. ANGIE ECV imaging was of high quality, and ANGIE measurements of LV-ECV were highly correlated with those of MOLLI (r = 0.91; p < 0.001). The RV-ECV in PH patients was 27.2% greater than the RV-ECV in normal volunteers (0.341 v. 0.268; p < 0.0001) and 18.9% greater than the RV-ECV in HFrEF patients without PH (0.341 v. 0.287; p < 0.0001). RV-ECV was greater than LV-ECV in PH (RV-LV difference = 0.04), but RV-ECV was nearly equivalent to LV-ECV in normal volunteers (RV-LV difference = 0.002) (p < 0.0001 for RV-LV difference in PH versus normal volunteers). RV-ECV was linearly associated with both increasing RVEDVI (p = 0.049) and decreasing RVEF (p = 0.04) in a multivariable linear model, but PH was still associated with greater RV-ECV even after adjustment for RVEDVI and RVEF. Pre- and post-contrast ANGIE imaging provides high-resolution ECV determination for the RV. PH is independently associated with increased RV-ECV even after adjustment for RV dilatation and dysfunction, consistent with an independent effect of PH on fibrosis. ANGIE RV imaging merits further clinical evaluation in PH.

Organic light-emitting devices using spin-dependent processes

DOEpatents

Vardeny, Z. Valy; Wohlgenannt, Markus

2010-03-23

The maximum luminous efficiency of organic light-emitting materials is increased through spin-dependent processing. The technique is applicable to all electro-luminescent processes in which light is produced by singlet exciton decay, and all devices which use such effects, including LEDs, super-radiant devices, amplified stimulated emission devices, lasers, other optical microcavity devices, electrically pumped optical amplifiers, and phosphorescence (Ph) based light emitting devices. In preferred embodiments, the emissive material is doped with an impurity, or otherwise modified, to increase the spin-lattice relaxation rate (i.e., decrease the spin-lattice time), and hence raise the efficiency of the device. The material may be a polymer, oligomer, small molecule, single crystal, molecular crystal, or fullerene. The impurity is preferably a magnetic or paramagnetic substance. The invention is applicable to IR, UV, and other electromagnetic radiation generation and is thus not limited to the visible region of the spectrum. The methods of the invention may also be combined with other techniques used to improve device performance.

Practical method development for the separation of monoclonal antibodies and antibody-drug-conjugate species in hydrophobic interaction chromatography, part 1: optimization of the mobile phase.

PubMed

Rodriguez-Aller, Marta; Guillarme, Davy; Beck, Alain; Fekete, Szabolcs

2016-01-25

The goal of this work is to provide some recommendations for method development in HIC using monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) as model drug candidates. The effects of gradient steepness, mobile phase pH, salt concentration and type, as well as organic modifier were evaluated for tuning selectivity and retention in HIC. Except the nature of the stationary phase, which was not discussed in this study, the most important parameter for modifying selectivity was the gradient steepness. The addition of organic solvent (up to 15% isopropanol) in the mobile phase was also found to be useful for mAbs analysis, since it could provide some changes in elution order, in some cases. On the contrary, isopropanol was not beneficial with ADCs, since the most hydrophobic DAR species (DAR6 and DAR8) cannot be eluted from the stationary phase under these conditions. This study also illustrates the possibility to perform HIC method development using optimization software, such as Drylab. The optimum conditions suggested by the software were tested using therapeutic mAbs and commercial cysteine linked ADC (brentuximab-vedotin) and the average retention time errors between predicted and experimental retention times were ∼ 1%. Copyright © 2015 Elsevier B.V. All rights reserved.

RP-HPLC ANALYSIS OF ACIDIC AND BASIC DRUGS IN SYSTEMS WITH DIETHYLAMINE AS ELUENTS ADDITIVE.

PubMed

Petruczynik, Anna; Wroblewski, Karol; Strozek, Szymon; Waksmundzka-Hajnos, Monika

2016-11-01

The chromatographic behavior of some basic and acidic drugs was studied on Cl 8, Phenyl-Hexyl and Polar RP columns with methanol or acetonitrile as organic modifiers of aqueous mobile phases containing addition of diethylamine. Diethylamine plays a double function of silanol blocker reagent in analysis of basic drugs and ion-pair reagent in analysis of acidic drugs. Most symmetrical peaks and highest system efficiency were obtained on Phenyl-Hexyl and Polar RP columns in tested mobile phase systems compared to results obtained on C18 column. A new rapid, simple, specific and accurate reverse phase liquid chromatographic method was developed for the simultaneous determination of atorvastatin - antihyperlipidemic drug and amlodipine - calcium channel blocker in one pharmaceutical formulation. Atorvastatin is an acidic compounds while amlodipine is a basic substance. The chromatographic separation was carried out on Phenyl-Hexyl column by gradient elution mode with acetonitrile as organic modifier, acetate buffer at pH 3.5 and Q.025 M/L diethylamine. The proposed method was validated for specificity, precision, accuracy, linearity, and robustness. The linearity range of atorvastatin and amlodipine for 5 - 100 μg/mL was obtained with limits of-detection (LOD) 3.2750 gg/mL and 3.2102 μg/mL, respectively. The proposed method made use of DAD as a tool for peak identity and purity confirmation.

A rapid method for detection of genetically modified organisms based on magnetic separation and surface-enhanced Raman scattering.

PubMed

Guven, Burcu; Boyacı, İsmail Hakkı; Tamer, Ugur; Çalık, Pınar

2012-01-07

In this study, a new method combining magnetic separation (MS) and surface-enhanced Raman scattering (SERS) was developed to detect genetically modified organisms (GMOs). An oligonucleotide probe which is specific for 35 S DNA target was immobilized onto gold coated magnetic nanospheres to form oligonucleotide-coated nanoparticles. A self assembled monolayer was formed on gold nanorods using 5,5'-dithiobis (2-nitrobenzoic acid) (DTNB) and the second probe of the 35 S DNA target was immobilized on the activated nanorod surfaces. Probes on the nanoparticles were hybridized with the target oligonucleotide. Optimization parameters for hybridization were investigated by high performance liquid chromatography. Optimum hybridization parameters were determined as: 4 μM probe concentration, 20 min immobilization time, 30 min hybridization time, 55 °C hybridization temperature, 750 mM buffer salt concentration and pH: 7.4. Quantification of the target concentration was performed via SERS spectra of DTNB on the nanorods. The correlation between the target concentration and the SERS signal was found to be linear within the range of 25-100 nM. The analyses were performed with only one hybridization step in 40 min. Real sample analysis was conducted using Bt-176 maize sample. The results showed that the developed MS-SERS assay is capable of detecting GMOs in a rapid and selective manner. This journal is © The Royal Society of Chemistry 2012

Effect of soil organic matter content and pH on the toxicity of ZnO nanoparticles to Folsomia candida.

PubMed

Waalewijn-Kool, Pauline L; Rupp, Svenja; Lofts, Stephen; Svendsen, Claus; van Gestel, Cornelis A M

2014-10-01

Organic matter (OM) and pH may influence nanoparticle fate and effects in soil. This study investigated the influence of soil organic matter content and pH on the toxicity of ZnO-NP and ZnCl2 to Folsomia candida in four natural soils, having between 2.37% and 14.7% OM and [Formula: see text] levels between 5.0 and 6.8. Porewater Zn concentrations were much lower in ZnO-NP than in ZnCl2 spiked soils, resulting in higher Freundlich sorption constants for ZnO-NP. For ZnCl2 the porewater Zn concentrations were significantly higher in less organic soils, while for ZnO-NP the highest soluble Zn level (23mgZn/l) was measured in the most organic soil, which had the lowest pH. Free Zn(2+) ion concentrations were higher for ZnCl2 than for ZnO-NP and were greatly dependent on pH (pHpw) and dissolved organic carbon content of the pore water. The 28-d EC50 values for the effect of ZnCl2 on the reproduction of F. candida increased with increasing OM content from 356 to 1592mgZn/kg d.w. For ZnO-NP no correlation between EC50 values and OM content was found and EC50 values ranged from 1695 in the most organic soil to 4446mgZn/kg d.w. in the higher pH soil. When based on porewater and free Zn(2+) concentrations, EC50 values were higher for ZnCl2 than for ZnO-NP, and consistently decreased with increasing pHpw. This study shows that ZnO-NP toxicity is dependent on soil properties, but is mainly driven by soil pH. Copyright © 2014 Elsevier Inc. All rights reserved.

Highly selective and sensitive sensor based on an organic electrochemical transistor for the detection of ascorbic acid.

PubMed

Zhang, Lijun; Wang, Guiheng; Wu, Di; Xiong, Can; Zheng, Lei; Ding, Yunsheng; Lu, Hongbo; Zhang, Guobing; Qiu, Longzhen

2018-02-15

In this study, an organic electrochemical transistor sensor (OECT) with a molecularly imprinted polymer (MIP)-modified gate electrode was prepared for the detection of ascorbic acid (AA). The combination of the amplification function of an OECT and the selective specificity of MIPs afforded a highly sensitive, selective OECT sensor. Cyclic voltammetry and electrochemical impedance spectroscopy measurements were carried out to monitor the stepwise fabrication of the modified electrodes and the adsorption capacity of the MIP/Au electrodes. Atomic force microscopy was employed for examining the surface morphology of the electrodes. Important detection parameters, pH and detection temperature were optimized. With the change in the relative concentration of AA from 1μM to 100μM, the MIP-OECT sensor exhibited a low detection limit of 10nM (S/N > 3) and a sensitivity of 75.3μA channel current change per decade under optimal conditions. In addition, the MIP-OECT sensor exhibited excellent specific recognition ability to AA, which prevented the interference from other structurally similar compounds (e.g., aspartic acid, glucose, uric acid, glycine, glutathione, H 2 O 2 ), and common metal ions (K + , Na + , Ca 2+ , Mg 2+ , and Fe 2+ ). In addition, a series of vitamin C beverages were analyzed to demonstrate the feasibility of the MIP-OECT sensor. Using the proposed principle, several other sensors with improved performance can be constructed via the modification of organic electrochemical transistors with appropriate MIP films. Copyright © 2017 Elsevier B.V. All rights reserved.

Application of magnesium modified corn biochar for phosphorus removal and recovery from swine wastewater.

PubMed

Fang, Ci; Zhang, Tao; Li, Ping; Jiang, Rong-feng; Wang, Ying-cai

2014-09-05

The recycling of lost phosphorus (P) is important in sustainable development. In line with this objective, biochar adsorption is a promising method of P recovery. Therefore, our study investigates the efficiency and selectivity of magnesium modified corn biochar (Mg/biochar) in relation to P adsorption. It also examines the available P derived from postsorption Mg/biochar. Mg/biochar is rich in magnesium nanoparticles and organic functional groups, and it can adsorb 90% of the equilibrium amount of P within 30 min. The Mg/biochar P adsorption process is mainly controlled by chemical action. The maximum P adsorption amount of Mg/biochar is 239 mg/g. The Langmuir-Freundlich model fits the P adsorption isotherm best. Thermodynamics calculation shows ∆H > 0, ∆G < 0, ∆S > 0, and it demonstrates the P adsorption process is an endothermic, spontaneous, and increasingly disordered. The optimal pH is 9. The amounts of P adsorbed by Mg/B300, Mg/B450, and Mg/B600 from swine wastewater are lower than that adsorbed from synthetic P wastewater by 6.6%, 4.8%, and 4.2%, respectively. Mg/biochar is more resistant to pH and to the influence of coexisting ions than biochar. Finally, postsorption Mg/biochar can release P persistently. The P release equilibrium concentrations are ordered as follows: Mg/B600 > Mg/B450 > Mg/B300. The postsorption Mg/B300, Mg/B450, and Mg/B600 can release 3.3%, 3.9%, and 4.4% of the total adsorbed P, respectively, per interval time.

Coumarin-modified microporous-mesoporous Zn-MOF-74 showing ultra-high uptake capacity and photo-switched storage/release of U(VI) ions.

PubMed

Zhang, Le; Wang, Lin Lin; Gong, Le Le; Feng, Xue Feng; Luo, Ming Biao; Luo, Feng

2016-07-05

Driven by an energy crisis but consequently puzzled by various environmental problems, uranium, as the basic material of nuclear energy, is now receiving extensive attentions. In contrast to numerous sorbents applied in this field, metal-organic framework (MOFs), as a renovated material platform, has only recently been developed. How to improve the adsorption capacity of MOF materials towards U(VI) ions, as well as taking advantage of the nature of these MOFs to design photo-switched behaviour for photo-triggered storage/release of U(VI) ions are at present urgent problems and great challenges to be solved. Herein, we show a simple and facile method to target the goal. Through coordination-based post-synthetic strategy, microporous- mesoporous Zn-MOF-74 was easily functionalized by grafting coumarin on coordinatively unsaturated Zn(II) centers, yielding a series of coumarin-modified Zn-MOF-74 materials. The obtained samples displayed ultra-high adsorption capacity for U(VI) ions from water at pH value of 4 with maximum adsorption capacities as high as 360 mg/g (the record value in MOFs) and a remarkable photo-switched capability of 50 mg/g at pH value of 4. To the best of knowledge, and in contrast to the well-known photo-switched behaviour towards CO2, dye (propidium iodide), as well as fluorescence observed in MOFs, this is the first study that shows a photo-switched behaviour towards radioactive U(VI) ions in aqueous solution. Copyright © 2016 Elsevier B.V. All rights reserved.

Nanometer-sized ceria-coated silica-iron oxide for the reagentless microextraction/preconcentration of heavy metals in environmental and biological samples followed by slurry introduction to ICP-OES.

PubMed

Dados, A; Paparizou, E; Eleftheriou, P; Papastephanou, C; Stalikas, C D

2014-04-01

A slurry suspension sampling technique is developed and optimized for the rapid microextraction of heavy metals and analysis using nanometer-sized ceria-coated silica-iron oxide particles and inductively coupled plasma optical emission spectrometry (ICP-OES). Magnetic-silica material is synthesized by a co-precipitation and sol-gel method followed by ceria coating through a precipitation. The large particles are removed using a sedimentation-fractionation procedure and a magnetic homogeneous colloidal suspension of ceria-modified iron oxide-silica is produced for microextraction. The nanometer-sized particles are separated from the sample solution magnetically and analyzed with ICP-OES using a slurry suspension sampling approach. The ceria-modified iron oxide-silica does not contain any organic matter and this probably justifies the absence of matrix effect on plasma atomization capacity, when increased concentrations of slurries are aspirated. The As, Be, Mo, Cr, Cu, Pb, Hg, Sb, Se and V can be preconcentrated by the proposed method at pH 6.0 while Mn, Cd, Co and Ni require a pH ≥ 8.0. Satisfactory values are obtained for the relative standard deviations (2-6%), recoveries (88-102%), enrichment factors (14-19) and regression correlation coefficients as well as detectability, at sub-μg L(-1) levels. The applicability of magnetic ceria for the microextraction of metal ions in combination with the slurry introduction technique using ICP is substantiated by the analysis of environmental water and urine samples. Copyright © 2013 Elsevier B.V. All rights reserved.

Competitive adsorption of Cd2+, Pb2+ and Ni2+ onto Fe3+-modified argillaceous limestone: Influence of pH, ionic strength and natural organic matters.

PubMed

He, Shuran; Li, Yongtao; Weng, Liping; Wang, Jinjin; He, Jinxian; Liu, Yonglin; Zhang, Kun; Wu, Qihong; Zhang, Yulong; Zhang, Zhen

2018-10-01

In present study, the feasibility of applying a natural adsorbent with Fe 3+ modification (Fe 3+ -modified argillaceous limestone, FAL) on the competitive adsorption of heavy metals (i.e., Cd 2+ , Pb 2+ and Ni 2+ ) was evaluated. The current results revealed an efficient adsorption on Cd 2+ , Pb 2+ and Ni 2+ in mono-metal system. Further experiments demonstrated a high selectivity of Pb 2+ during the competitive adsorption of Cd 2+ , Pb 2+ and Ni 2+ . The adsorption selectivity of the metal ions followed the order of Pb ≫ Cd > Ni. In addition, both pH and ionic strength are important factors affecting the metal adsorptions. It is interestingly that various NOMs (i.e., humic acid (HA) and glycine (Gly)) exerted different effects on the adsorption behaviors, probably due to the different affinities for Pb 2+ , Cd 2+ and Ni 2+ and the redistribution of newly-formed metal-DOM complexes. X-ray photoelectron spectroscopy (XPS) analysis together with X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) analysis revealed that the metal adsorptions were mainly regulated via the synergistic mechanisms of ion exchange by Na + , Ca 2+ , and Al 3+ , precipitation to form CdCO 3 and Pb 2 (OH) 2 (CO 3 ) 2 , as well as complexes of FAL-OPb and FAL-ONi by hydroxyl groups on the surface of FAL. The application of FAL would be a promising option in leading to an efficient heavy metal removal. Copyright © 2018 Elsevier B.V. All rights reserved.

Two-way feedback between biology and deep Earth processes

NASA Astrophysics Data System (ADS)

Sleep, N. H.; Pope, E.; Bird, D.

2012-12-01

The presence of the metamorphic products of banded iron formation and black shale indicate that the Earth teemed with life by the time of the earliest preserved rocks, ca. 3.85 Ga. Iron and sulfur-based anoxygenic photosynthesis with full carbon cycles was present by this time. The pH of the ocean was ~8. The lack of older rock record cloaks pre-biotic evolution and the origin of life. Nascent and early life obtained energy from chemical disequilibria in rocks rather than sunlight. Appraising putative rock pre-biological environments is difficult in that life has modified the composition of the atmosphere, the hydrosphere, and sedimentary rocks. It has greatly affected the composition of crystalline crustal rocks and measurably modified the mantle. Conversely, hard crustal rocks and the mantle likely sequester a very ancient record of last resort. Theory provides additional insight. The Earth's surface and interior cooled following the moon-forming impact. The oceans passed through conditions favored by thermophile organisms before becoming clement. Ocean pH was ~6 and bars of CO2 existed in the atmosphere. Subduction removed the CO2 into the mantle before the time of rock record. Serpentinite likely existed in land, tidal, and marine environments as it does today. Seafloor spreading and arc volcanism likely drove hydrothermal circulation. The late heavy bombardment occurred after ca. 4.1 Ga; low heat flow environments and hence habitable subsurface refugia existed. It is conceivable that one or a few ocean-boiling impacts left thermophile survivors in their wake. Overall, the molecular biology of extant life likely conserves features that relate to its earliest abodes.

Application of Magnesium Modified Corn Biochar for Phosphorus Removal and Recovery from Swine Wastewater

PubMed Central

Fang, Ci; Zhang, Tao; Li, Ping; Jiang, Rong-feng; Wang, Ying-cai

2014-01-01

The recycling of lost phosphorus (P) is important in sustainable development. In line with this objective, biochar adsorption is a promising method of P recovery. Therefore, our study investigates the efficiency and selectivity of magnesium modified corn biochar (Mg/biochar) in relation to P adsorption. It also examines the available P derived from postsorption Mg/biochar. Mg/biochar is rich in magnesium nanoparticles and organic functional groups, and it can adsorb 90% of the equilibrium amount of P within 30 min. The Mg/biochar P adsorption process is mainly controlled by chemical action. The maximum P adsorption amount of Mg/biochar is 239 mg/g. The Langmuir-Freundlich model fits the P adsorption isotherm best. Thermodynamics calculation shows ∆H > 0, ∆G < 0, ∆S > 0, and it demonstrates the P adsorption process is an endothermic, spontaneous, and increasingly disordered. The optimal pH is 9. The amounts of P adsorbed by Mg/B300, Mg/B450, and Mg/B600 from swine wastewater are lower than that adsorbed from synthetic P wastewater by 6.6%, 4.8%, and 4.2%, respectively. Mg/biochar is more resistant to pH and to the influence of coexisting ions than biochar. Finally, postsorption Mg/biochar can release P persistently. The P release equilibrium concentrations are ordered as follows: Mg/B600 > Mg/B450 > Mg/B300. The postsorption Mg/B300, Mg/B450, and Mg/B600 can release 3.3%, 3.9%, and 4.4% of the total adsorbed P, respectively, per interval time. PMID:25198685

Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

NASA Astrophysics Data System (ADS)

Guerra, Denis L.; Leidens, Victor L.; Viana, Rúbia R.; Airoldi, Claudio

2010-05-01

The compound N 1-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of 29Si and 13C. The well-defined peaks obtained in the 13C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0. The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k2 values 16.0 and 25.1 mmol g -1 min -1 ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations.

Controlled and localized delivery of c-myc AS-ODN to cells by 3-aminopropyl-trimethoxylsilane modified SBA-15 mesoporous silica

NASA Astrophysics Data System (ADS)

Zhang, Juan; Chen, Minmin; Zhao, Xiqiu; Zhang, Min; Mao, Jinxiang; Cao, Xichuan; Zhang, Zhuoqi

2018-01-01

SBA-15 mesoporous silicate was synthesized and functionalized with 3-aminopropyl organic groups through a post-synthesis method. The materials were characterized consecutively by powder X-ray diffraction (XRD), N2 adsorption/desorption analysis and solid-state magic-angle spinning 29Si nuclear magnetic resonance (MAS NMR). Human c-myc anti-sense oligodeoxyneucleotide (AS-ODN) was selected as a model molecule to be loaded onto the surface of bare and functionalized SBA-15 via different loading conditions. It has been found that the amount of AS-ODN incorporated into the porous matrix is strongly dependent on the surface properties, pH of the loading solvent and AS-ODN concentration. The release behaviour of AS-ODN from modified SBA-15 materials was also investigated and depended on conditions chosen. Cellular uptake of the eluted AS-ODN into Hela cells was observed by fluorescent microscopy. The materials showed excellent cytocompatibility. The AS-ODN keeps full transfection and expression activities indicating its structural integrity. The functionalized SBA-15 is an excellent prospect as a biomedical material candidate for the future.

The influence of total organic carbon (TOC) on the relationship between acid neutralizing capacity (ANC) and fish status in Norwegian lakes.

PubMed

Lydersen, Espen; Larssen, Thorjørn; Fjeld, Eirik

2004-06-29

Acid neutralizing capacity (ANC) is the parameter most commonly used as chemical indicator for fish response to acidification. Empirical relationships between fish status of surface waters and ANC have been documented earlier. ANC is commonly calculated as the difference between base cations ([BC]=[Ca2+]+[Mg2+]+[N+]+[K+]) and strong acid anions ([SAA]=[SO4(2)-]+[NO3-]+[Cl-]). This is a very robust calculation of ANC, because none of the parameters incorporated are affected by the partial pressure of CO2, in contrast to the remaining major ions in waters, pH ([H+]), aluminum ([Aln+]), alkalinity ([HCO3-/CO3(2)-]) and organic anions ([An-]). Here we propose a modified ANC calculation where the permanent anionic charge of the organic acids is assumed as a part of the strong acid anions. In many humic lakes, the weak organic acids are the predominant pH-buffering system. Because a significant amount of the weak organic acids have pK-values<3.0-3.5, these relatively strong acids will permanently be deprotonated in almost all natural waters (i.e. pH>4.5). This means that they will be permanently present as anions, equal to the strong acid inorganic anions, SO4(2)-, NO3- and Cl-. In the literature, natural organic acids are often described as triprotic acids with a low pK1 value. Assuming a triprotic model, we suggest to add 1/3 of the organic acid charge density to the strong acid anions in the ANC calculation. The suggested organic acid adjusted ANC (ANC(OAA)), is then calculated as follows: ANC(OAA)=[BC]-([SAA]+1/3CD*TOC) where TOC is total organic carbon (mg C L(-1)), and CD=10.2 is charge density of the organic matter (microeq/mg C), based on literature data from Swedish lakes. ANC(OAA) gives significant lower values of ANC in order to achieve equal fish status compared with the traditional ANC calculation. Using ANC(OAA) the humic conditions in lakes are better taken into account. This may also help explain observations of higher ANC needed to have reproducing fish populations in lakes with higher TOC concentrations. Copryright 2003 Elsevier B.V.

Recent developments in water quality monitoring for Space Station reclaimed wastewaters

NASA Technical Reports Server (NTRS)

Small, John W.; Verostko, Charles E.; Linton, Arthur T.; Burchett, Ray

1987-01-01

This paper discusses the recent developments in water quality monitoring for Space Station reclaimed wastewaters. A preprototype unit that contains an ultraviolet absorbance organic carbon monitor integrated with pH and conductivity sensors is presented. The preprototype has provisions for automated operation and is a reagentless flow-through system without any gas/liquid interfaces. The organic carbon monitor detects by utraviolet absorbance the organic impurities in reclaimed wastewater which may be correlated to the organic carbon content of the water. A comparison of the preprototype organic carbon detection values with actual total organic carbon measurements is presented. The electrolyte double junction concept for the pH sensor and fixed electrodes for both the pH and conductivity sensors are discussed. In addition, the development of a reagentless organic carbon analyzer that incorporates ultraviolet oxidation and infrared detection is presented. Detection sensitivities, hardware development, and operation are included.

Surface modification of amine-functionalised graphite for preparation of cobalt hexacyanoferrate (CoHCF)-modified electrode: an amperometric sensor for determination of butylated hydroxyanisole (BHA).

PubMed

Prabakar, S J Richard; Narayanan, S Sriman

2006-12-01

A cobalt hexacyanoferrate (CoHCF)-modified graphite paraffin wax composite electrode was prepared by a new approach. An amine-functionalised graphite powder was used for the fabrication of the electrode. A functionalised graphite paraffin wax composite electrode was prepared and the surface of the electrode was modified with a thin film of CoHCF. Various parameters that influence the electrochemical behaviour of the modified electrode were studied by varying the background electrolytes, scan rates and pH. The modified electrode showed good electrocatalytic activity towards the oxidation of butylated hydroxyanisole (BHA) under optimal conditions and showed a linear response over the range from 7.9 x 10(-7) to 1.9 x 10(-4) M of BHA with a correlation coefficient of 0.9988. The limit of detection was 1.9 x 10(-7) M. Electrocatalytic oxidation of BHA was effective at the modified electrode at a significantly reduced potential and at a broader pH range. The utility of the modified electrode as an amperometric sensor for the determination of BHA in flow systems was evaluated by carrying out hydrodynamic and chronoamperometric experiments. The modified electrode showed very good stability and a longer shelf life. The modified electrode was applied for the determination of BHA in spiked samples of chewing gum and edible sunflower oil. The advantage of this method is the ease of electrode fabrication, good stability, longer shelf life, low cost and its diverse application for BHA determination.

Design and validation of a new ratiometric intracellular pH imaging probe using lanthanide-doped upconverting nanoparticles.

PubMed

Du, Shuoren; Hernández-Gil, Javier; Dong, Hao; Zheng, Xiaoyu; Lyu, Guangming; Bañobre-López, Manuel; Gallo, Juan; Sun, Ling-Dong; Yan, Chun-Hua; Long, Nicholas J

2017-10-17

pH homeostasis is strictly controlled at a subcellular level. A deregulation of the intra/extra/subcellular pH environment is associated with a number of diseases and as such, the monitoring of the pH state of cells and tissues is a valuable diagnostic tool. To date, only a few tools have been developed to measure the pH in living cells with the spatial resolution needed for intracellular imaging. Among the techniques available, only optical imaging offers enough resolution and biocompatibility to be proposed for subcellular pH monitoring. We present herein a ratiometric probe based on upconversion nanoparticles modified with a pH sensitive moiety for the quantitative imaging of pH at the subcellular level in living cells. This system provides the properties required for live cell quantitative imaging i.e. positive cellular uptake, biocompatibility, long wavelength excitation, sensitive response to pH within a biologically relevant range, and self-referenced signal.

Effects of tetraethyl orthosilicate (TEOS) on the light and temperature stability of a pigment from Beta vulgaris and its potential food industry applications.

PubMed

Molina, Gustavo A; Hernández-Martínez, Angel Ramon; Cortez-Valadez, Manuel; García-Hernández, Fernando; Estevez, Miriam

2014-11-05

A novel, simple and inexpensive modification method using TEOS to increase the UV light, pH and temperature stability of a red-beet-pigment extracted from Beta vulgaris has been proposed. The effects on the molecular structure of betalains were studied by FTIR spectroscopy. The presence of betacyanin was verified by UV-Vis spectroscopy and its degradation in modified red-beet-pigment was evaluated and compared to the unmodified red-beet-pigment; performance improvements of 88.33%, 16.84% and 20.90% for UV light, pH and temperature stability were obtained, respectively,. Measurements of reducing sugars, phenol, and antioxidant contents were performed on unmodified and modified red-beet-pigment and losses of close to 21%, 54% and 36%, respectively, were found to be caused by the addition of TEOS. Polar diagrams of color by unmodified and modified red-beet-pigment in models of a beverage and of a yogurt were obtained and the color is preserved, although here is a small loss in the chromaticity parameter of the modified red-beet-pigment.

Adsorption of Pb(II) using silica gel composite from rice husk ash modified 3-aminopropyltriethoxysilane (APTES)-activated carbon from coconut shell

NASA Astrophysics Data System (ADS)

Yusmaniar, Purwanto, Agung; Putri, Elfriyana Awalita; Rosyidah, Dzakiyyatur

2017-03-01

Silica gel modified by 3-aminopropyltriethoxysilane (APTES) was synthesized from rice husk ash combined with activated carbon from coconut shell yielded the composite adsorbent. The composite was characterized by Fourier Transform Infra Red spectroscopy (FT-IR), Electron Dispersive X-Ray (EDX), Surface Area Analyzer (SAA) and adsorption test by Atomic Absorption Spectrometry (AAS). This composite adsorbent has been used moderately for the removal of lead ions from metal solutions and compared with silica gel modified APTES and activated carbon. The adsorption experiments of Pb -ions by adsorbents were performed at different pH and contact time with the same metal solutions concentration, volume solution, and adsorbent dosage. The optimum pH for the adsorption was found to be 5.0 and the equilibrium was achieved for Pb with 20 min of contact time. Pb ions adsorption by composite silica gel modified APTES-activated carbon followed by Langmuir isotherm model with qmax value of 46.9483 mg/g that proved an adsorbent mechanism consistent to the mechanism of monolayer formation.

Phosphorus Amendment Efficacy for In Situ Remediation of ...

EPA Pesticide Factsheets

A validated method is needed to measure reductions of in vitro bioaccessible (IVBA) Pb in urban soil remediated with amendments. This study evaluated the effect of in vitro extraction solution pH and glycine buffer on bioaccesible Pb in P-treated soils. Two Pb-contaminated soils (790-1300 mg Pb kg-1), one from a garden and one from a city lot in Cleveland, OH, were incubated in a bench scale experiment for 1 yr. Six phosphate amendments, including bone meal, fish bone, poultry litter, monoammonium phosphate, diammonium phosphate, and triple superphosphate, were added to containers at two application rates. Lead IVBA was assessed using USEPA Method 1340 and three modified versions of this method. Modifications included using solutions with pH 1.5 and 2.5 as well as using solutions with and without 0.4 mol L-1 glycine. Soil amendments were effective in reducing IVBA Pb in these soils as measured by pH 1.5 with glycine buffer. The greatest reductions in IVBA Pb, from 5 to 26%, were found using pH 2.5 extractions. Lead mineral results showed several soil amendments promoted Pb phosphate formation, an indicator of remediation success. A significant negative linear relationship between reduction in IVBA Pb and Pb-phosphate formation was found only for pH 2.5 without glycine extraction solution. A modified USEPA Method 1340 without glycine and using pH 2.5 has the potential to predict P soil treatment efficacy and reductions in bioavailable Pb. Developing mana

Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells

PubMed Central

Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Riov, Joseph; Belausov, Eduard; Kochanek, Betina; Tucker, Mark L.; Meir, Shimon

2015-01-01

In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2’,7’-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H+-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression. PMID:25504336

Effects of simulated acid rain on pollen physiology and ultrastructure in the apple.

PubMed

Bellani, L M; Rinallo, C; Muccifora, S; Gori, P

1997-01-01

Viability, germination and tube length were investigated in pollen grains of field-grown 'Summerred' apple trees (Malus domestica Borkh) exposed to deionized water, rainfall or simulated acid rain at pH 5.6, 4.0 and 3.0. Pollen viability and germination significantly decreased with lower values of pH and with increasing number of treatments. The effects of pH 5.6 and natural rainfall were not significant. Electron microscope investigation of vegetative pollen cells of plants exposed to acid rain at pH 4.0 and 3.0 showed modified features in mitochondria, plastids and endoplasmic reticulum.

Molecular gated-AlGaN/GaN high electron mobility transistor for pH detection.

PubMed

Ding, Xiangzhen; Yang, Shuai; Miao, Bin; Gu, Le; Gu, Zhiqi; Zhang, Jian; Wu, Baojun; Wang, Hong; Wu, Dongmin; Li, Jiadong

2018-04-18

A molecular gated-AlGaN/GaN high electron mobility transistor has been developed for pH detection. The sensing surface of the sensor was modified with 3-aminopropyltriethoxysilane to provide amphoteric amine groups, which would play the role of receptors for pH detection. On modification with 3-aminopropyltriethoxysilane, the transistor exhibits good chemical stability in hydrochloric acid solution and is sensitive for pH detection. Thus, our molecular gated-AlGaN/GaN high electron mobility transistor acheived good electrical performances such as chemical stability (remained stable in hydrochloric acid solution), good sensitivity (37.17 μA/pH) and low hysteresis. The results indicate a promising future for high-quality sensors for pH detection.

Influence of Nutrient Impregnated into Zeolite Addition on Anaerobic Digestion of Palm Oil Mill Effluent (POME)

NASA Astrophysics Data System (ADS)

Mellyanawaty, M.; Chusna, F. M. A.; Sudibyo, H.; Nurjanah, N.; Budhijanto, W.

2018-03-01

Palm oil mill effluent (POME) was wastewater generated from palm oil milling activities which was brownish liquid, acidic with pH 3-4, and contained soluble materials which were hazardous to the environment. It was characterized by high organic loading (COD 40,000–60,000 mg/L). According to its characteristics, POME was identified as a potential source to generate renewable energy through anaerobic digestion. In other words, a combination of wastewater treatment and renewable energy production would be an additional advantage to the palm oil industries. Methanogenesis was the rate limiting step in anaerobic digestion. In the conventional anaerobic digester, it required large reactors and long retention time. The addition of microbial immobilization media was to improve anaerobic reactor performance in term of higher organic removal and methane production. Additionally, better performance could lead to reduction of reactor volume and shorter retention time in high rate anaerobic digester. The loading of essential microorganism nutrient into the media might increase the affinity of bacteria to attach and grow on the media surface. Activating or inhibition effects of natural and modified zeolite addition in anaerobic digestion of POME was studied in batch reactors using erlenmeyer of 1,000 mL at COD concentrations of about 8,000 mg/L. Zeolite was impregnated with nickel and magnesium at concentrations of 0.0561 mg Ni/g zeolite and 0.0108 mg Mg/g zeolite. The effect of the different zeolite addition was determined by the measurement of soluble COD (sCOD), Volatile Fatty Acids (VFAs) and biogas production. Greater effect of modified zeolite was observed in zeolite impregnated with nickel with a 54% increase of biogas production. Meanwhile, the modified zeolite impregnated with magnesium had no positive impact to the methanogenic bacteria activities.

Influence of soil pH on the sorption of ionizable chemicals: modeling advances.

PubMed

Franco, Antonio; Fu, Wenjing; Trapp, Stefan

2009-03-01

The soil-water distribution coefficient of ionizable chemicals (K(d)) depends on the soil acidity, mainly because the pH governs speciation. Using pH-specific K(d) values normalized to organic carbon (K(OC)) from the literature, a method was developed to estimate the K(OC) of monovalent organic acids and bases. The regression considers pH-dependent speciation and species-specific partition coefficients, calculated from the dissociation constant (pK(a)) and the octanol-water partition coefficient of the neutral molecule (log P(n)). Probably because of the lower pH near the organic colloid-water interface, the optimal pH to model dissociation was lower than the bulk soil pH. The knowledge of the soil pH allows calculation of the fractions of neutral and ionic molecules in the system, thus improving the existing regression for acids. The same approach was not successful with bases, for which the impact of pH on the total sorption is contrasting. In fact, the shortcomings of the model assumptions affect the predictive power for acids and for bases differently. We evaluated accuracy and limitations of the regressions for their use in the environmental fate assessment of ionizable chemicals.

Preparation of granular activated carbons from composite of powder activated carbon and modified β-zeolite and application to heavy metals removal.

PubMed

Seyedein Ghannad, S M R; Lotfollahi, M N

2018-03-01

Heavy metals are continuously contaminating the surface and subsurface water. The adsorption process is an attractive alternative for removing the heavy metals because of its low cost, simple operation, high efficiency, and flexible design. In this study, influences of β-zeolite and Cu-modified β-zeolite on preparation of granular activated carbons (GACs) from a composite of powder activated carbon (PAC), methylcellulose as organic binder, bentonite as inorganic binder, and water were investigated. A number of granular samples were prepared by controlling the weight percentage of binder materials, PAC and zeolites as a reinforcing adsorbent. Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction techniques were employed to characterize zeolite, modified zeolite and produced GAC. The produced GACs were used as the adsorbent for removal of Zn +2 , Cd 2+ and Pb 2+ ions from aqueous solutions. The results indicated that the adsorption of metals ions depended on the pH (5.5) and contact time (30 min). Maximum adsorption of 97.6% for Pb 2+ , 95.9% for Cd 2+ and 91.1% for Zn +2 occurred with a new kind of GAC made of Cu-modified β-zeolite. The Zn +2 , Cd 2+ and Pb 2+ ions sorption kinetics data were well described by a pseudo-second order model for all sorbents. The Langmuir and Freundlich isotherm models were applied to analyze the experimental equilibrium data.

PH DEPENDENT TOXICITY OF FIVE METALS TO THREE MARINE ORGANISMS

EPA Science Inventory

The pH of natural marine systems is relatively stable; this may explain why metal toxicity changes with pH have not been well documented. However, changes in metal toxicity with pH in marine waters are of concern in toxicity testing. During porewater toxicity testing pH can chang...

Nanofiber-structured hydrogel yarns with pH-response capacity and cardiomyocyte-drivability for bio-microactuator application.

PubMed

Wu, Shaohua; Duan, Bin; Qin, Xiaohong; Butcher, Jonathan T

2017-09-15

Polymeric hydrogels have great potential in soft biological micro-actuator applications. However, inappropriate micro-architecture, non-anisotropy, weak biomechanics, and inferior response behaviors limit their development. In this study, we designed and manufactured novel polyacrylonitrile (PAN)-based hydrogel yarns composed with uniaxially aligned nanofibers. The nanofibrous hydrogel yarns possessed anisotropic architecture and robust mechanical properties with flexibility, and could be assembled into defined scaffold structures by subsequent processes. The as-prepared hydrogel yarns showed excellent pH response behaviors, with around 100% maximum length and 900% maximum diameter changes, and the pH response was completed within several seconds. Moreover, the hydrogel yarns displayed unique cell-responsive abilities to promote the cell adhesion, proliferation, and smooth muscle differentiation of human adipose derived mesenchymal stem cells (HADMSC). Chicken cardiomyocytes were further seeded onto our nanofibrous hydrogel yarns to engineer living cell-based microactuators. Our results demonstrated that the uniaxially aligned nanofibrous networks within the hydrogel yarns were the key characteristics leading to the anisotropic organization of cardiac cells, and improved sarcomere organization, mimicking the cardiomyocyte bundles in the native myocardium. The construct is capable of sustaining spontaneous cardiomyocyte pumping behaviors for 7days. Our PAN-based nanofibrous hydrogel yarns are attractive for creating linear microactuators with pH-response capacity and biological microactuators with cardiomyocyte-drivability. A mechanically robust polyacrylonitrile-based nanofibrous hydrogel yarn is fabricated by using a modified electrospinning setup in combination with chemical modification processes. The as-prepared hydrogel yarn possesses a uniaxially aligned nanofiber microarchitecture and supports a rapid, pH-dependent expansion/contraction response within a few seconds. Embryonic cardiomyocytes-seeded hydrogel yarn improves the sarcomere organization and mimics the cardiomyocyte bundles in the native myocardium, which sustains spontaneous cardiomyocyte pumping behaviors. The nanofibrous hydrogel yarn has several advantages over traditional bulk hydrogel scaffolds in terms of robust biomechanics, anisotropic aligned architecture, and superior pH response behaviors. Our nanofibrous hydrogel yarn holds the potential to be developed into novel linear and biological microactuators for various biomedical applications. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Organically Modified Silicas on Metal Nanowires

PubMed Central

2010-01-01

Organically modified silica coatings were prepared on metal nanowires using a variety of silicon alkoxides with different functional groups (i.e., carboxyl groups, polyethylene oxide, cyano, dihydroimidazole, and hexyl linkers). Organically modified silicas were deposited onto the surface of 6-μm-long, ∼300-nm-wide, cylindrical metal nanowires in suspension by the hydrolysis and polycondensation of silicon alkoxides. Syntheses were performed at several ratios of tetraethoxysilane to an organically modified silicon alkoxide to incorporate desired functional groups into thin organosilica shells on the nanowires. These coatings were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy. All of the organically modified silicas prepared here were sufficiently porous to allow the removal of the metal nanowire cores by acid etching to form organically modified silica nanotubes. Additional functionality provided to the modified silicas as compared to unmodified silica prepared using only tetraethoxysilane precursors was demonstrated by chromate adsorption on imidazole-containing silicas and resistance to protein adsorption on polyethyleneoxide-containing silicas. Organically modified silica coatings on nanowires and other nano- and microparticles have potential application in fields such as biosensing or nanoscale therapeutics due to the enhanced properties of the silica coatings, for example, the prevention of biofouling. PMID:20715881

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.

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).

Ratiometric, visual, dual-signal fluorescent sensing and imaging of pH/copper ions in real samples based on carbon dots-fluorescein isothiocyanate composites.

PubMed

Zhu, Xinxin; Jin, Hui; Gao, Cuili; Gui, Rijun; Wang, Zonghua

2017-01-01

In this article, a facile aqueous synthesis of carbon dots (CDs) was developed by using natural kelp as a new carbon source. Through hydrothermal carbonization of kelp juice, fluorescent CDs were prepared and the CDs' surface was modified with polyethylenimine (PEI). The PEI-modified CDs were conjugated with fluorescein isothiocyanate (FITC) to fabricate CDs-FITC composites. To exploit broad applications, the CDs-FITC composites were developed as fluorescent sensing or imaging platforms of pH and Cu 2+ . Analytical performances of the composites-based fluorescence (FL) sensors were evaluated, including visual FL imaging of pH in glass bottle, ratiometric FL sensing of pH in yogurt samples, visual FL latent fingerprint and leaf imaging detection of [Cu 2+ ], dual-signal FL sensing of [Cu 2+ ] in yogurt and human serum samples. Experimental results from ratiometric, visual, dual-signal FL sensing and imaging applications confirmed the high feasibility, accuracy, stabilization and simplicity of CDs-FITC composites-based FL sensors for the detection of pH and Cu 2+ ions in real samples. Copyright © 2016 Elsevier B.V. All rights reserved.

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

Cobalt sorption onto anaerobic granular sludge: isotherm and spatial localization analysis.

PubMed

van Hullebusch, Eric D; Gieteling, Jarno; Zhang, Min; Zandvoort, Marcel H; Daele, Wim Van; Defrancq, Jacques; Lens, Piet N L

2006-01-24

This study investigated the effect of different feeding regimes on the cobalt sorption capacity of anaerobic granular sludge from a full-scale bioreactor treating paper mill wastewater. Adsorption experiments were done with non-fed granules in monometal (only Co) and competitive conditions (Co and Ni in equimolar concentrations). In order to modify the extracellular polymeric substances and sulfides content of the granules, the sludge was fed for 30 days with glucose (pH 7, 30 degrees C, organic loading rate=1.2 g glucose l(-1) day-1) in the presence (COD/SO4(2-)=1) or absence of sulfate. The partitioning of the sorbed cobalt between the exchangeable, carbonates, organic matter/sulfides and residual fractions was determined using a sequential extraction procedure (modified Tessier). Experimental equilibrium sorption data for cobalt were analysed by the Langmuir, Freundlich and Redlich-Peterson isotherm equations. The total Langmuir maximal sorption capacity of the sludge fed with glucose and sulfate loaded with cobalt alone displayed a significantly higher maximal cobalt sorption (Qmax =18.76 mg g-1 TSS) than the sludge fed with glucose alone (Qmax =13.21 mg g-1 TSS), essentially due to an increased sorption capacity of the exchangeable (30-107%) and organic/sulfides fractions (70-30%). Environmental scanning electron microscopy coupled with an energy dispersive X-ray analysis of granular cross-sections showed that mainly iron minerals (i.e. iron sulfides) were involved in the cobalt accumulation. Moreover, the sorbed cobalt was mainly located at the edge of the granules. The sorption characteristics of the exchangeable and carbonates fractions fitted well to the Redlich-Peterson model (intermediate multi-layer sorption behaviour), whereas the sorption characteristics of the organic matter/sulfides and residual fractions fitted well to the Langmuir model (monolayer sorption behaviour). The organic matter/sulfides fraction displayed the highest affinity for cobalt for the three sludge types investigated.

Adsorption of sulfamethoxazole and sulfapyridine antibiotics in high organic content soils.

PubMed

Chen, Kuen-Lin; Liu, Li-Chun; Chen, Wan-Ru

2017-12-01

Many antibiotics, including sulfonamides, are being frequently detected in soil and groundwater. Livestock waste is an important source of antibiotic pollution, and sulfonamides may be present along with organic-rich substances. This study aims to investigate the sorption reaction of two sulfonamides, sulfamethoxazole (SMZ) and sulfapyridine (SPY) in two organic-rich sorbents: a commercial peat soil (38.41% carbon content) and a composted manure (24.33% carbon content). Batch reactions were conducted to evaluate the impacts of pH (4.5-9.5) and background ions (0.001 M-0.1 M CaCl 2 ) on their sorption. Both linear partitioning and Freundlich sorption isotherms fit the reaction well. The n values of Freundlich isotherm were close to 1 in most conditions suggesting that the hydrophobic partition is the major adsorption mechanism. In terms of SMZ, K d declined with increases in the pH. SPY has a pyridine group that is responsible for adsorption at high pH values, and thus, no significant trend between K d and pH was observed. At high pH ranges, SPY sorption deviated significantly from linear partitioning. The results suggested the sorption mechanism of these two sulfonamide antibiotics tended to be hydrophobic partitioning under most of the experimental conditions, especially at pH values lower than their corresponding pK a2. The fluorescence excitation emission matrix and dissolved organic carbon leaching test suggested composted manure has higher fulvic acid organics and that peat soil has higher humus-like organics. Small organic molecules showed stronger affinity toward sulfonamide antibiotics and cause the composted manure to exhibit higher sorption capacity. Overall, this study suggests that the chemical structure and properties of sulfonamides antibiotics and the type of organic matter in soils will greatly influence the fate and transport of these contaminants into the environment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Acidification of apple and orange hosts by Penicillium digitatum and Penicillium expansum.

PubMed

Vilanova, L; Viñas, I; Torres, R; Usall, J; Buron-Moles, G; Teixidó, N

2014-05-16

New information about virulence mechanisms of Penicillium digitatum and Penicillium expansum could be an important avenue to control fungal diseases. In this study, the ability of P. digitatum and P. expansum to enhance their virulence by locally modulating the pH of oranges and apples was evaluated. For each host, pH changes with a compatible pathogen and a non-host pathogen were recorded, and the levels of different organic acids were evaluated to establish possible relationships with host pH modifications. Moreover, fruits were harvested at three maturity stages to determine whether fruit maturity could affect the pathogens' virulence. The pH of oranges and apples decreased when the compatible pathogens (P. digitatum and P. expansum, respectively) decayed the fruit. The main organic acid detected in P. digitatum-decayed oranges was galacturonic acid produced as a consequence of host maceration in the rot development process. However, the obtained results showed that this acid was not responsible for the pH decrease in decayed orange tissue. The mixture of malic and citric acids could at least contribute to the acidification of P. digitatum-decayed oranges. The pH decrease in P. expansum decayed apples is related to the accumulation of gluconic and fumaric acids. The pH of oranges and apples was not affected when the non-host pathogen was not able to macerate the tissues. However, different organic acid contents were detected in comparison to healthy tissues. The main organic acids detected in P. expansum-oranges were oxalic and gluconic and in P. digitatum-apples were citric, gluconic and galacturonic. Further research is needed to identify the pathogenicity factors of both fungi because the contribution of organic acids has profound implications. Copyright © 2014 Elsevier B.V. All rights reserved.

In vitro analysis of the physical properties of contact lens blister pack solutions.

PubMed

Menzies, Kara L; Jones, Lyndon

2011-04-01

Since the initial development of silicone hydrogels, many modifications to the bulk and surface properties of the lenses have been undertaken to improve the wettability and comfort of the lenses. Recently, manufacturers have incorporated various "wetting agents" or surface-active agents into the blister packaging solutions (BPSs) of the lenses to improve initial comfort of the lens on eye. The purpose of this study was to measure and compare the pH, surface tension (ST), viscosity, and osmolality of BPSs for a variety of silicone hydrogel and polyHEMA-based hydrogel lenses. In addition, two saline solutions were tested for comparison purposes. The pH, osmolality, ST, and viscosity were measured for the BPSs for lotrafilcon B and lotrafilcon A and lotrafilcon B with a "modified BPS" (m-lotrafilcon A, m-lotrafilcon B) (CIBA Vision, Duluth, GA); balafilcon A (Bausch & Lomb, Rochester, NY); galyfilcon A, senofilcon A, and narafilcon A (Johnson & Johnson, Jacksonville, FL); and comfilcon A and enfilcon A (CooperVision, Pleasanton, CA) and BPSs from two conventional polyHEMA-based materials-etafilcon A (Johnson & Johnson) and omafilcon A (CooperVision). The two saline solutions tested were Unisol (Alcon, Fort Worth, TX) and Softwear Saline (CIBA Vision). The pH results for the two saline solutions and all BPSs remained in the pH range of tears (6.6-7.8). The ST of the modified BPS was significantly lower (p < 0.01) than the original non-modified BPS. Viscosity measurements ranged between 0.90 and 1.00 cP for all BPSs and saline solutions, except for the modified BPS, which had significantly higher viscosities (p < 0.001). Osmolality measurements were not significantly different (p > 0.05) between BPSs made by the same manufacturer but were significantly different compared with BPSs made by different manufacturers (p < 0.05). The incorporation of wetting agents and surfactants into BPSs does alter the physical properties of the BPSs, which may have clinical implications regarding initial in-eye comfort.

Cytotoxicity of modified glass ionomer cement on odontoblast cells.

PubMed

Chen, Song; Mestres, Gemma; Lan, Weihua; Xia, Wei; Engqvist, Håkan

2016-07-01

Recently a modified glass ionomer cement (GIC) with enhanced bioactivity due to the incorporation of wollastonite or mineral trioxide aggregate (MTA) has been reported. The aim of this study was to evaluate the cytotoxic effect of the modified GIC on odontoblast-like cells. The cytotoxicity of a conventional GIC, wollastonite modified GIC (W-mGIC), MTA modified GIC (M-mGIC) and MTA cement has been evaluated using cement extracts, a culture media modified by the cement. Ion concentration and pH of each material in the culture media were measured and correlated to the results of the cytotoxicity study. Among the four groups, conventional GIC showed the most cytotoxicity effect, followed by W-mGIC and M-mGIC. MTA showed the least toxic effect. GIC showed the lowest pH (6.36) while MTA showed the highest (8.62). In terms of ion concentration, MTA showed the largest Ca(2+) concentration (467.3 mg/L) while GIC showed the highest concentration of Si(4+) (19.9 mg/L), Al(3+) (7.2 mg/L) and Sr(2+) (100.3 mg/L). Concentration of F(-) was under the detection limit (0.02 mg/L) for all samples. However the concentrations of these ions are considered too low to be toxic. Our study showed that the cytotoxicity of conventional GIC can be moderated by incorporating calcium silicate based ceramics. The modified GIC might be promising as novel dental restorative cements.

Solid State pH Sensor Based on Light Emitting Diodes (LED) As Detector Platform

PubMed Central

Lau, King Tong; Shepherd, R.; Diamond, Danny; Diamond, Dermot

2006-01-01

A low-power, high sensitivity, very low-cost light emitting diode (LED)-based device developed for low-cost sensor networks was modified with bromocresol green membrane to work as a solid-state pH sensor. In this approach, a reverse-biased LED functioning as a photodiode is coupled with a second LED configured in conventional emission mode. A simple timer circuit measures how long (in microsecond) it takes for the photocurrent generated on the detector LED to discharge its capacitance from logic 1 (+5 V) to logic 0 (+1.7 V). The entire instrument provides an inherently digital output of light intensity measurements for a few cents. A light dependent resistor (LDR) modified with similar sensor membrane was also used as a comparison method. Both the LED sensor and the LDR sensor responded to various pH buffer solutions in a similar way to obtain sigmoidal curves expected of the dye. The pKa value obtained for the sensors was found to agree with the literature value.

Study on kinetics of adsorption of humic acid modified by ferric chloride on U(VI)

NASA Astrophysics Data System (ADS)

Zhang, Y. Y.; Lv, J. W.; Song, Y.; Dong, X. J.; Fang, Q.

2017-11-01

In order to reveal the adsorption mechanism of the ferric chloride modified humic acid on uranium, the influence of pH value and contact time of adsorption on uranium was studied through a series of batch experiments. Meanwhile, the adsorption kinetics was analyzed with pseudo-first order kinetic model and pseudo-second order kinetic model. The results show that adsorption is affected by the pH value of the solution and by contract time, and the best condition for adsorption on uranium is at pH=5 and the adsorption equilibrium time is about 80 min. Kinetics of HA-Fe adsorption on uranium accords with pseudo-second order kinetic model. The adsorption is mainly chemical adsorption, and complexes were produced by the reaction between uranium ions and the functional groups on the surface of HA-Fe, which can provide reference for further study of humic acid effecting on the migration of U(VI) in soil.

Accomplishing Equilibrium in ALSEP: Demonstrations of Modified Process Chemistry on 3-D Printed Enhanced Annular Centrifugal Contactors

DOE PAGES

Brown, M. Alex; Wardle, Kent E.; Lumetta, Gregg; ...

2016-12-01

Here, the major components of the modified ALSEP process have been demonstrated on a modified 2-cm annular centrifugal contactor with an enhanced mixing zone using stable fission products and radiotracers. The results show that by decreasing the pH of the minor actinide stripping solution, using HEDTA instead of DTPA, and increasing contact time, the process is very effective in separating americium from the lanthanides and the fission products.

MCM-41 impregnated with A zeolite precursor: Synthesis, characterization and tetracycline antibiotics removal from aqueous solution

PubMed Central

Liu, Minmin; Hou, Li-an; Yu, Shuili; Xi, Beidou; Zhao, Ying; Xia, Xunfeng

2013-01-01

In this paper, the MCM-41 has been modified by impregnation with zeolite A to prepare a kind of new adsorbent. The adsorption of TC from aqueous solutions onto modified MCM-41 has been studied. It was discovered that the adsorption capability of zeolite A modified MCM-41 (A-MCM-41) increased dramatically after modification. The modified MCM-41 was characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption, Fourier Transform Infrared (FTIR) analysis, Transmission electron microscopy (TEM) images, and 29Si and 27Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectra. The modified MCM-41 structure was still retained after impregnated with zeolite A but the surface area and pore diameter decreased due to pore blockage. The adsorption of TC on modified MCM-41 was discussed regarding various parameters such as pH, initial TC concentration, and the reaction time. The pH effects on TC adsorption indicated that the adsorbents had better adsorption performances in acidic and neutral conditions. The adsorption isotherms were fitted well by the Langmuir model. The adsorption kinetics was well described by both pseudo-second order equation and the intra-particle diffusion model. The adsorption behavior in a fixed-bed column system followed Thomas model. The adsorption behavior of TC was the chemical adsorption with an ion exchange process and electrostatic adsorption. PMID:24976787

Ammonium pyrrolidine dithiocarbamate anchored Symphoricarpus albus biomass for lead(II) removal: batch and column biosorption study.

PubMed

Akar, Sibel Tunali; Arslan, Derya; Alp, Tugba

2012-08-15

The biosorption properties of APDC modified S. albus were tested in batch and column conditions. Effective experimental parameters such as pH, biosorbent dosage, contact time, temperature, initial lead(II) ion concentration, flow rate and bed height were investigated. The biosorption capacity of modified biosorbent was at maximum when lead(II) solution pH and biosorbent dosage were 5.5 and 2.0 g L(-1), respectively. The biosorption equilibrium was established in 20 min. Langmuir isotherm fitted well to the equilibrium data and kinetics is found to fit pseudo-second-order model. Increase in ionic strength of lead(II) solutions caused a slight decrease in the biosorption yield of APDC-modified biosorbent. Co-ions affected the biosorption performance of modified biomass up to maximum 20.81% reduction. Column biosorption of lead(II) showed higher biosorption yields at lower flow rates. Required time of breakthrough point was found to be 200 min. The recommended mechanism was found to depend mainly on electrostatic interaction, ion-exchange and complex formation. The ion-exchange mechanism for lead(II) biosorption onto the modified biosorbent is verified from the ionic strength effect and EDX analysis. Carbonyl, phosphate and CN groups on the modified surface of S. albus were found to responsible for complexation with lead(II). Copyright © 2012 Elsevier B.V. All rights reserved.

MCM-41 impregnated with A zeolite precursor: Synthesis, characterization and tetracycline antibiotics removal from aqueous solution.

PubMed

Liu, Minmin; Hou, Li-An; Yu, Shuili; Xi, Beidou; Zhao, Ying; Xia, Xunfeng

2013-05-01

In this paper, the MCM-41 has been modified by impregnation with zeolite A to prepare a kind of new adsorbent. The adsorption of TC from aqueous solutions onto modified MCM-41 has been studied. It was discovered that the adsorption capability of zeolite A modified MCM-41 (A-MCM-41) increased dramatically after modification. The modified MCM-41 was characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, Fourier Transform Infrared (FTIR) analysis, Transmission electron microscopy (TEM) images, and 29 Si and 27 Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR) spectra. The modified MCM-41 structure was still retained after impregnated with zeolite A but the surface area and pore diameter decreased due to pore blockage. The adsorption of TC on modified MCM-41 was discussed regarding various parameters such as pH, initial TC concentration, and the reaction time. The pH effects on TC adsorption indicated that the adsorbents had better adsorption performances in acidic and neutral conditions. The adsorption isotherms were fitted well by the Langmuir model. The adsorption kinetics was well described by both pseudo-second order equation and the intra-particle diffusion model. The adsorption behavior in a fixed-bed column system followed Thomas model. The adsorption behavior of TC was the chemical adsorption with an ion exchange process and electrostatic adsorption.

Analysis of sesquiterpenes in Valeriana officinalis by capillary electrophoresis.

PubMed

Mikell, J R; Ganzera, M; Khan, I A

2001-12-01

A capillary electrophoresis (CE) method permitting the determination of the main sesquiterpenes in Valeriana officinalis has been developed. A separation of valerenic acid and its hydroxy and acetoxy derivatives, three compounds characteristic for the species, was achieved using a 40 mM phosphate-borate buffer at pH 8.5, which contained 10% isopropanol as organic modifier. Applied temperature and voltage were 35 degrees C and 17.5 kV, respectively. This setup allowed a baseline separation of the three compounds within 8 min, with a detection limit of 5.8 micrograms/ml or less. Out of six market products analyzed, only one contained a detectable amount of the marker compounds, with 0.54% of hydroxyvalerenic acid and 0.13% valerenic acid, respectively. The quantitative results were comparable to those obtained by HPLC.

RuO2 pH Sensor with Super-Glue-Inspired Reference Electrode

PubMed Central

Wajrak, Magdalena; Alameh, Kamal

2017-01-01

A pH-sensitive RuO2 electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO2 working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO2 pH-sensitive working electrode and a SiO2-PVB junction-modified RuO2 reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices. PMID:28878182

RuO₂ pH Sensor with Super-Glue-Inspired Reference Electrode.

PubMed

Lonsdale, Wade; Wajrak, Magdalena; Alameh, Kamal

2017-09-06

A pH-sensitive RuO₂ electrode coated in a commercial cyanoacrylate adhesive typically exhibits very low pH sensitivity, and could be paired with a RuO₂ working electrode as a differential type pH sensor. However, such sensors display poor performance in real sample matrices. A pH sensor employing a RuO₂ pH-sensitive working electrode and a SiO₂-PVB junction-modified RuO₂ reference electrode is developed as an alternative high-performance solution. This sensor exhibits a performance similar to that of a commercial glass pH sensor in some common sample matrices, particularly, an excellent pH sensitivity of 55.7 mV/pH, a hysteresis as low as 2.7 mV, and a drift below 2.2 mV/h. The developed sensor structure opens the way towards the development of a simple, cost effective, and robust pH sensor for pH analysis in various sample matrices.

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.

NCCU/BBRI-Duke/Urology Partnership In Prostate Cancer Research

DTIC Science & Technology

2011-06-01

Joellen Schildkraut, Ph.D.; David Tulis , Ph.D.; Leon Sun, Ph 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES...Following Radical Prostatectomy among Men with Localized Prostate Cancer: A Community- Based Intervention Investigators: Dave Tulis Ph.D., NCCU/BBRI

Preparation of hemoglobin-modified boron-doped diamond for acrylamide biosensors

NASA Astrophysics Data System (ADS)

Umam, K.; Saepudin, E.; Ivandini, T. A.

2017-04-01

Boron-doped diamond (BDD) electrode was modified with haemoglobin to develop electrochemical biosensors of acrylamide. Prior to modify with haemoglobin, the BDD was modified by gold nanoparticles to increase the affinity of BDD against haemoglobin. The electrochemical behaviour of the electrode in the presence of acrylamide was studied in comparison to haemoglobin-modified gold electrodes. Cyclic voltammetry indicated the optimum responses in 0.1 M sodium acetate buffer at pH 5. The responses were linear to the acrylamide concentration range of 5-50 μM with an estimated detection limit of 5.14 μM, suggesting that the electrode was promising for acrylamide biosensors.

Effects of process variables on the yield stress of rheologically modified biomass

Treesearch

Joseph R. Samaniuk; C Tim Scott; Thatcher W. Root; Daniel J. Klingenberg

2015-01-01

Additives that alter the rheology of lignocellulosic biomass suspensions were tested under conditions of variable pH, temperature, and solid concentration. The effects of certain ions, biomass type, after the addition of rheological modifier were also examined. Torque and vane rheometry were used to measure the yield stress of samples. It was found that the...

A theoretical approach to excessive CO2 expiration due to lactate production in exercise.

PubMed

Yano, T

1987-01-01

Cerretelli et al. (1982) proposed a model to estimate pH changes due to lactate production in exercise. This model was modified in the present study so as to express the relationship between CO2 excess and lactate production. The modified model fitted to the data reported on endurance-trained men.

Melamine-modified urea formaldehyde resin for bonding particleboards

Treesearch

Chung-Yun Hse; Feng Fu; Hui Pan

2008-01-01

For the development of a cost-effective melamine-modified urea formaldehyde resin (MUF), the study evaluated the effects of reaction pH and melamine content on resin properties and bond performance of the MUF resin adhesive systems. Eight resins, each with three replicates, were prepared in a factorial experiment that included two formulation variables: two reaction...

The interplay between pH sensitivity and label-free protein detection in immunologically modified nano-scaled field-effect transistor.

PubMed

Shalev, Gil; Rosenwaks, Yossi; Levy, Ilan

2012-01-15

We present experimental results in order to establish a correlation between pH sensitivity of immunologically modified nano-scaled field-effect transistor (NS-ImmunoFET) with their sensing capacity for label-free detection. The NS-ImmunoFETs are fabricated from silicon-on-insulator (SOI) wafers and are fully-depleted with thickness of ~20 nm. The data shows that higher sensitivity to pH entails enhanced sensitivity to analyte detection. This suggests that the mechanism of analyte detection as pure electrostatic perturbation induced by antibody-analyte interaction is over simplified. The fundamental assumption, in existing models for field-effect sensing mechanism assumes that the analyte molecules do not directly interact with the surface but rather stand 'deep' in the solution and away from the dielectric surface. Recent studies clearly provide contradicting evidence demonstrating that antibodies lie down flat on the surface. These observations led us to propose that the proteins that cover the gate area intimately interact with active sites on the surface thus forming a network of interacting sites. Since sensitivity to pH is directly correlated with the amount of amphoteric sites, we witness a direct correlation between sensitivity to pH and analyte detection. The highest and lowest threshold voltage shift for a label-free and specific detection of 6.5 nM IgG were 40 mV and 2.3 mV for NS-ImmunoFETs with pH sensitivity of 35 mV/decade and 15 mV/decade, respectively. Finally, physical modeling of the NS-ImmunoFET is presented and charge of a single IgG protein at pH 6 is calculated. The obtained value is consistent with charge of IgG protein cited in literature. Copyright © 2011 Elsevier B.V. All rights reserved.

CZE separation of strawberry anthocyanins with acidic buffer and comparison with HPLC.

PubMed

Comandini, Patrizia; Blanda, Giampaolo; Cardinali, Andrea; Cerretani, Lorenzo; Bendini, Alessandra; Caboni, Maria Fiorenza

2008-10-01

Anthocyanins, the major colourants of strawberries, are polar pigments that are positively charged at low pH. Herein, we have assessed a new analytical method for the separation of anthocyanins using CZE. Acidic buffer solutions (pH <2) were employed in order to maintain pigments in the cation flavylium form and achieve high molar absorptivity at 510 nm. These spectral properties enabled us to identify strawberry anthocyanins in a preliminary stage by detection in the visible range, although the method was optimised at 280 nm to obtain the best S/N. The effects of buffer composition highlighted the necessity of adding an organic modifier to the running buffer to obtain a suitable separation. The electrophoretic method permitted the separation of the three main anthocyanins of strawberry extracts, namely pelargonidin 3-glucoside (Pg-glu), pelargonidin 3-rutinoside and cyanidin 3-glucoside. The electrophoretic results, expressed as retention time and separation efficiency of the major anthocyanin (Pg-glu), were compared to those achieved in HPLC, the analytical technique traditionally used for the investigation of anthocyanins in vegetable matrix. The content of Pg-glu in strawberries (cv. Camarosa), calculated with HPCE and HPLC methods, resulted respectively in 11.41 mg/L and 11.37 mg/L.

Simultaneous determination of ezetimibe and simvastatin in pharmaceutical preparations by MEKC.

PubMed

Yardimci, Ceren; Ozaltin, Nuran

2010-02-01

A micellar electrokinetic capillary chromatography method was developed and validated for the simultaneous determination of ezetimibe and simvastatin in pharmaceutical preparations. The influence of buffer concentration, buffer pH, sodium dodecyl sulphate (SDS) concentration, organic modifier, capillary temperature, applied voltage, and injection time was investigated, and the method validation studies were performed. The optimum separation for these analytes was achieved in less than 10 min at 30 degrees C with a fused-silica capillary column (56 cm x 50 microm i.d.) and a 25mM borate buffer at pH 9.0 containing 25mM SDS and 10% (v/v) acetonitrile. The samples were injected hydrodynamically for 3 s at 50 mbar, and the applied voltage was +30.0 kV. Detection wavelength was set at 238 nm. Diflunisal was used as internal standard. The method was suitably validated with respect to stability, specificity, linearity, limits of detection and quantification, accuracy, precision, and robustness. The limits of detection and quantification were 1.0 and 2.0 microg/mL for both ezetimibe and simvastatin, respectively. The method developed was successfully applied to the simultaneous determination of ezetimibe and simvastatin in pharmaceutical preparations.

Improved HPLC method with the aid of chemometric strategy: determination of loxoprofen in pharmaceutical formulation.

PubMed

Venkatesan, P; Janardhanan, V Sree; Muralidharan, C; Valliappan, K

2012-06-01

Loxoprofen belongs to a class of Nonsteroidal anti-inflammatory drug acts by inhibiting isoforms of cyclo-oxygenase 1 and 2. In this study an improved RP-HPLC method was developed for the quantification of loxoprofen in pharmaceutical dosage form. For that purpose an experimental design approach was employed. Factors-independent variables (organic modifier, pH of the mobile phase and flow rate) were extracted from the preliminary study and as dependent variables three responses (loxoprofen retention factor, resolution between loxoprofen probenecid and retention time of probenecid) were selected. For the improvement of method development and optimization step, Derringer's desirability function was applied to simultaneously optimize the chosen three responses. The procedure allowed deduction of optimal conditions and the predicted optimum was acetonitrile: water (53:47, v/v), pH of the mobile phase adjusted at to 2.9 with ortho phosphoric acid. The separation was achieved in less than 4minutes. The method was applied in the quality control of commercial tablets. The method showed good agreement between the experimental data and predictive value throughout the studied parameter space. The optimized assay condition was validated according to International conference on harmonisation guidelines to confirm specificity, linearity, accuracy and precision.

Separation of dietary omega-3 and omega-6 fatty acids in food by capillary electrophoresis.

PubMed

Soliman, Laiel C; Donkor, Kingsley K; Church, John S; Cinel, Bruno; Prema, Dipesh; Dugan, Michael E R

2013-10-01

A lower dietary omega-6/omega-3 (n-6/n-3) fatty acid ratio (<4) has been shown to be beneficial in preventing a number of chronic illnesses. Interest exists in developing more rapid and sensitive analytical methods for profiling fatty acid levels in foods. An aqueous CE method was developed for the simultaneous determination of 15 n-3 and n-6 relevant fatty acids. The effect of pH and concentration of buffer, type and concentration of organic modifier, and additive on the separation was investigated in order to determine the best conditions for the analysis. Baseline separations of the 15 fatty acids were achieved using 40 mM borate buffer at pH 9.50 containing 50 mM SDS, 10 mM β-cyclodextrin, and 10% acetonitrile. The developed CE method has LODs of <5 mg/L and good linearity (R(2) > 0.980) for all fatty acids studied. The proposed method was successfully applied to the determination of n-3 and n-6 fatty acids in flax seed, Udo® oils and a selection of grass-fed and grain-fed beef muscle samples. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Chromatographic behavior of zwitterionic enalapril-exploring the conditions for lipophilicity assessment.

PubMed

Gikas, Spyros; Tsopelas, Fotios; Giaginis, Costas; Dimitrakopoulos, John; Livadara, Theodora; Archontaki, Helen; Tsantili-Kakoulidou, Anna

2008-11-04

The chromatographic behavior of enalapril was investigated under different stationary and mobile phase conditions in an effort to unravel interferences in the underlying retention mechanism, which would affect its relation to octanol-water partitioning. Extrapolated retention factors, logk(w), were used as relevant chromatographic indices. The retention/pH profile was established and the peak split phenomenon, associated with cis/trans interconversion, was also monitored as a function of pH. The pH at maximum retention and minimum peak split occurrence was chosen for further investigation, so that the presence of zwitterionic structure was guaranteed and any effect of cis/trans interconversion could be ignored. Retention of zwitterionic enalapril was found to be very sensitive to mobile phase conditions in regard to organic modifier as well to the aqueous component. The use of morpholine-propanesulfonic acid (MOPS) as buffer and the presence of n-octanol as mobile phase additive proved critical factors for maximum suppression of secondary interactions. Nevertheless, the corresponding extrapolated retention factor was considerably larger than octanol-water logD value at the isoelectric point. However, logk(w) could be successfully converted to logD by means of a calibration equation established for ionized acidic compounds.

Chiral recognition ability of an (S)-naproxen- imprinted monolith by capillary electrochromatography.

PubMed

Xu, Yan-Li; Liu, Zhao-Sheng; Wang, He-Fang; Yan, Chao; Gao, Ru-Yu

2005-02-01

The racemic naproxen was selectively recognized by capillary electrochromatography (CEC) on an (S)-naproxen-imprinted monolith, which was prepared by an in situ thermal-initiated polymerization. The recognition selectivity of a selected monolith strictly relied on the CEC conditions involved. The factors that influence the imprinting selectivity as well as the electroosmotic flow (EOF), including the applied voltage, organic solvent, salt concentration and pH value of the buffer, column temperature, and surfactant modifiers were systematically studied. Once the column was prepared, the experiment results showed that the successful chiral recognition was dependent on CEC variables. For example: the recognition could be observed in acetonitrile and ethanol electrolytes, while methanol and dimethyl sulfoxide (DMSO) electrolytes had no chiral recognition ability. The buffer with pH values of 2.6 or 3.0 at a higher salt concentration had chiral recognition ability. Column temperatures of 25-35 degrees C were optimal. Three surfactants, sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB), and polyoxyethylene sorbitan monolaurate (Tween 20), can improve the recognition. Baseline resolution was obtained under optimized conditions and the column efficiency of the later eluent (S)-naproxen was 90 000 plates/m.

Molybdenum isotope fractionation during adsorption to organic matter

NASA Astrophysics Data System (ADS)

King, E. K.; Perakis, S. S.; Pett-Ridge, J. C.

2018-02-01

Organic matter is of emerging interest as a control on molybdenum (Mo) biogeochemistry, and information on isotope fractionation during adsorption to organic matter can improve interpretations of Mo isotope variations in natural settings. Molybdenum isotope fractionation was investigated during adsorption onto insolubilized humic acid (IHA), a surrogate for organic matter, as a function of time (2-170 h) and pH (2-7). For the time series experiment performed at pH 4.2, the average Mo isotope fractionation between the solution and the IHA (Δ98Mosolution-IHA) was 1.39‰ (±0.16‰, 2σ, based on 98Mo/95Mo relative to the NIST 3134 standard) at steady state. For the pH series experiment, Mo adsorption decreased as pH increased from 2.0 to 6.9, and the Δ98Mosolution-IHA increased from 0.82‰ to 1.79‰. We also evaluated natural Mo isotope patterns in precipitation, foliage, organic horizon, surface mineral soil, and bedrock from 12 forested sites in the Oregon Coast Range. The average Mo isotope offset observed between precipitation and organic (O) horizon soil was 2.1‰, with light Mo isotopes adsorbing preferentially to organic matter. Fractionation during adsorption to organic matter is similar in magnitude and direction to prior observations of Mo fractionation during adsorption to Fe- and Mn- (oxyhydr)oxides. Our finding that organic matter influences Mo isotope composition has important implications for the role of organic matter as a driver of trace metal retention and isotopic fractionation.

Effect of dietary selenium source (organic vs. mineral) and muscle pH on meat quality characteristics of pigs.

PubMed

Calvo, Luis; Toldrá, Fidel; Rodríguez, Ana I; López-Bote, Clemente; Rey, Ana I

2017-01-01

This study evaluates the effect of organic (Se-enriched yeast; SeY) versus inorganic selenium (sodium selenite; SeS) supplementation and the different response of selenium source according to muscle pH on pork meat quality characteristics. Pigs ( n  = 30) were fed the Se-supplemented diets (0.3 mg/kg) for 65 days. Neither electric conductivity (EC) nor drip loss were affected by the selenium source. The SeY group had lower TBARS in muscle samples after day 7 of refrigerated storage and higher a * values on days 1 and 7 than the SeS group. The effect of dietary selenium source on some meat quality characteristics was affected by muscle pH. Hence, as the muscle pH increases, the drip loss decreases but this effect is more marked with the dietary organic Se enrichment. Muscle pH seems to modulate the action of selenium in pork, especially some meat characteristics such as drip loss.

The natural diatomite from caldiran-van (Turkey): electroanalytical application to antimigraine compound naratriptan at modified carbon paste electrode.

PubMed

Calışkan, Necla; Sögüt, Eda; Saka, Cafer; Yardım, Yavuz; Sentürk, Zuhre

2010-09-01

This paper is the first report describing the characterization of local diatomite of Caldiran-Van region (Eastern Anatolia, Turkey). Special attention was paid to the ability of its electroanalytical performance at modified electrodes and to the potential application of diatomite-modified electrode. For this purpose, the determination of Naratriptan which is a novel oral triptan (5-hydroxytryptamine receptor agonist) in migraine treatment, by means of a carbon paste electrode modified with 10% (w/w) of diatomite was studied using cyclic and square-wave voltammetry. The experimental conditions that affect the electrode reaction process were studied in terms of pH of the supporting electrolyte, scan rate, accumulation variables, modifier composition and square-wave parameters. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 4.0 at 0.84 V (vs. Ag/AgCl) (a pre-concentration step being carried out with an open circuit at 120 s). The process could be used to determine Naratriptan concentrations in the range 5x10(-7)-9x10(-7) M, with a detection limit of 1.25x10(-7) M (46.5 mug L(-1)). The applicability of the method to spiked human urine samples was illustrated.

Magnetically modified sheaths of Leptothrix sp. as an adsorbent for Amido black 10B removal

NASA Astrophysics Data System (ADS)

Angelova, Ralitsa; Baldikova, Eva; Pospiskova, Kristyna; Safarikova, Mirka; Safarik, Ivo

2017-04-01

The goal of this study was to assess the biosorption of Amido black 10B dye from aqueous solutions on magnetically modified sheaths of Leptothrix sp. in a batch system. The magnetic modification of the sheaths was performed using both microwave synthesized iron oxide nano- and microparticles and perchloric acid stabilized ferrofluid. The native and both magnetically modified sheaths were characterized by SEM. Various parameters significantly affecting the adsorption process, such as pH, contact time, temperature and initial concentration, were studied in detail using the adsorbent magnetized by both methods. The highest adsorption efficiency was achieved at pH 2. The maximum adsorption capacities of both types of magnetized material at room temperature were found to be 339.2 and 286.1 mg of dye per 1 g of ferrofluid modified and microwave synthesized particles modified adsorbent, respectively. Thermodynamic study of dye adsorption revealed a spontaneous and endothermic process in the temperature range between 279.15 and 313.15 K. The data were fitted to various equilibrium and kinetic models. Experimental data matched well with the pseudo-second-order kinetics and Freundlich isotherm model. The Leptothrix sheaths have excellent efficacy for dye adsorption. This material can be used as an effective, low-cost adsorbent.

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

Ma, W.; Edelman, T.; van Beersum, I.

Soil samples were taken from 31 sites near Eindhoven, The Netherlands, mainly along transects of 1 to 15 km from the nearest zinc smelter. Earthworms (Lumbricus rubellus) were taken from the upper 20 cm soil layer and analyzed from accumulation of Cd, Zn, Pb and Cu by atomic absorption spectrophotometry. Cd, Zn, and Pb appeared to be more strongly accumulated by L. rubellus when present in soil with a low pH value. Cu was the only exception in this regard; its uptake by L. rubellus was not significantly influenced by soil pH. The organic matter content of the soil playedmore » a significant role only in the worm uptake of Pb. Soil Pb content, soil pH, and soil organic matter content together accounted for almost 70% of the variance in worm Pb content. The results indicate that L. rubellus accumulates Pb more strongly in soil with a low pH and low organic matter content than in soil with higher values of these parameters. The demonstrated influence of pH and organic matter content on element concentration in earthworms emphasizes the importance of soil factors in governing the entrance of toxic metal elements into the food web. (JMT)« less

Characterization of NF1 Protein Ubiquitination

DTIC Science & Technology

2008-06-01

Ubiquitination PRINCIPAL INVESTIGATOR: Koko Murakami, Ph.D. Victor A Fried, Ph.D. CONTRACTING ORGANIZATION: New York Medical College...NUMBER W81XWH-07-1-0432 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Koko Murakami, Ph.D.; Victor A Fried, Ph.D. 5d. PROJECT NUMBER 5e. TASK

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.

Unique spatial and cellular expression patterns of Hoxa5, Hoxb4 and Hoxb6 proteins in normal developing murine lung are modified in pulmonary hypoplasia

PubMed Central

Volpe, MaryAnn Vitoria; Wang, Karen Ting Wai; Nielsen, Heber Carl; Chinoy, Mala Romeshchandra

2009-01-01

Background Hox transcription factors modulate signaling pathways controlling organ morphogenesis and maintain cell fate and differentiation in adults. Retinoid signaling, key in regulating Hox expression, is altered in pulmonary hypoplasia. Information on pattern-specific expression of Hox proteins in normal lung development and in pulmonary hypoplasia is minimal. Our objective was to determine how pulmonary hypoplasia alters temporal, spatial and cellular expression of Hoxa5, Hoxb4 and Hoxb6 proteins compared to normal lung development. Methods Temporal, spatial and cellular Hoxa5, Hoxb4 and Hoxb6 expression was studied in normal (untreated) and nitrofen-induced hypoplastic (NT-PH) lungs from gestational day 13.5, 16, 19 fetuses and neonates using western blot and immunohistochemistry. Results Modification of protein levels and spatial and cellular Hox expression patterns in NT-PH lungs was consistent with delayed lung development. Distinct protein isoforms were detected for each Hox protein. Expression levels of the Hoxa5 and Hoxb6 isoforms changed with development and further in NT-PH lungs. Compared to normal lungs, Gd19 and neonatal NT-PH lungs had decreased Hoxb6 and increased Hoxa5 and Hoxb4. Hoxa5 cellular localization changed from mesenchyme to epithelia earlier in normal lungs. Hoxb4 was expressed in mesenchyme and epithelial cells throughout development. Hoxb6 remained mainly in mesenchymal cells around distal airways. Conclusions Unique spatial and cellular expression of Hoxa5, Hoxb4 and Hoxb6 participates in branching morphogenesis and terminal sac formation. Altered Hox protein temporal and cellular balance of expression either contributes to pulmonary hypoplasia or functions as a compensatory mechanism attempting to correct abnormal lung development and maturation in this condition. PMID:18553509

Micellar electrokinetic chromatography method for the determination of several natural red dyestuff and lake pigments used in art work.

PubMed

Maguregui, M I; Alonso, R M; Barandiaran, M; Jimenez, R M; García, N

2007-06-22

The identification of organic colorants used in artistic paintings is an important information source for reconstructing the working techniques found in a particular work and for defining a programme for the restoration and conservation of the painting. In this work, sodium dodecyl sulfate (SDS) was used as a surfactant in micellar electrokinetic chromatography (MEKC) for separating a broad range of red organic pigments, based on their colouring matters: madder (colouring matters: alizarin, quinizarin and purpurin), cochineal (colouring matter: carminic acid), red sandalwood (colouring matter: santalin), brazilwood (colouring matter: brazilin), lac dye (colouring matter: laccaic acid) and dragon's blood (colouring matter: dracorhodin). The running electrolyte used was 20 mM borax (pH 9), containing 20 mM SDS and 10% acetonitrile as organic modifier. Separation was carried out by applying a +20 kV voltage at the injection end, 25 degrees C and 214 nm/254 nm as detection wavelengths. All colorants were separated within less than 13 min with a good baseline resolution. The method was applied to the analysis of paint samples obtained from the Diocesan Museum of Holy Art of Bilbao.

Pedogenic formation of montmorillonite from a 2:1-2:2 intergrade clay mineral

USGS Publications Warehouse

Malcolm, R.L.; Nettleton, W.D.; McCracken, R.J.

1968-01-01

Montmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1-2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4⋅5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1-2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5-6).It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1-2:2 intergrade clay mineral. The combined effects of low pH (below 4⋅5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4⋅5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization.The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1-2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter.

Spatial distribution of pH and organic matter in urban soils and its implications on site-specific land uses in Xuzhou, China.

PubMed

Mao, Yingming; Sang, Shuxun; Liu, Shiqi; Jia, Jinlong

2014-05-01

The spatial variation of soil pH and soil organic matter (SOM) in the urban area of Xuzhou, China, was investigated in this study. Conventional statistics, geostatistics, and a geographical information system (GIS) were used to produce spatial distribution maps and to provide information about land use types. A total of 172 soil samples were collected based on grid method in the study area. Soil pH ranged from 6.47 to 8.48, with an average of 7.62. SOM content was very variable, ranging from 3.51 g/kg to 17.12 g/kg, with an average of 8.26 g/kg. Soil pH followed a normal distribution, while SOM followed a log-normal distribution. The results of semi-variograms indicated that soil pH and SOM had strong (21%) and moderate (44%) spatial dependence, respectively. The variogram model was spherical for soil pH and exponential for SOM. The spatial distribution maps were achieved using kriging interpolation. The high pH and high SOM tended to occur in the mixed forest land cover areas such as those in the southwestern part of the urban area, while the low values were found in the eastern and the northern parts, probably due to the effect of industrial and human activities. In the central urban area, the soil pH was low, but the SOM content was high, which is mainly attributed to the disturbance of regional resident activities and urban transportation. Furthermore, anthropogenic organic particles are possible sources of organic matter after entering the soil ecosystem in urban areas. These maps provide useful information for urban planning and environmental management. Copyright © 2014 Académie des sciences. Published by Elsevier SAS. All rights reserved.

Bromination of aromatic compounds by residual bromide in sodium chloride matrix modifier salt during heated headspace GC/MS analysis.

PubMed

Fine, Dennis D; Ko, Saebom; Huling, Scott

2013-12-15

Analytical artifacts attributed to the bromination of toluene, xylenes, and trimethylbenzenes were found during the heated headspace gas chromatography/mass spectrometry (GC/MS) analysis of aqueous samples. The aqueous samples were produced from Fenton-like chemical oxidation reactions and contained aromatic compounds, hydrogen peroxide (H2O2), and ferric sulfate. Prior to GC/MS headspace analysis, the samples were acidified (pH<2), and sodium chloride was amended to the headspace vial as a matrix modifier. The brominated artifacts were generated during heated headspace analysis. Further, when samples were spiked with a mixture of volatile chlorinated and aromatic compounds (50 µg/L), poor spike recoveries of toluene and xylenes occurred, and in some cases complete loss of trimethylbenzenes and naphthalene resulted. Where poor recovery of aromatic spike compounds occurred, brominated aromatic compounds were found. The only significant source of bromine in the reaction scheme is the bromide typically present (<0.01% w/w) in the sodium chloride amended to the samples. Conversely, brominated artifacts were absent when a buffered salt mixture composed of sodium chloride and potassium phosphate dibasic/monobasic was used as a matrix modifier and raised the sample pH (pH~6). This indicated that the brominated artifacts resulted from the reaction of the aromatic compounds with BrCl, which was formed by the reaction of H2O2, chloride, and bromide under acidic conditions. An alternative matrix modifier salt is recommended that prevents the bromination reaction and avoids these deleterious effects on sample integrity during headspace analysis. Published by Elsevier B.V.

pH-Responsive Mercaptoundecanoic Acid Functionalized Gold Nanoparticles and Applications in Catalysis

PubMed Central

Ansar, Siyam M.; Chakraborty, Saptarshi

2018-01-01

Mercaptoundecanoic acid (MUA) functionalized gold nanoparticles (AuNP-MUA) were synthesized and demonstrated to possess pH-triggered aggregation and re-dispersion, as well as the capability of phase transfer between aqueous and organic phases in response to changes in pH. The pH of aggregation for AuNP-MUA is consistent with the pKa of MUA (pH ~4) in solution, while AuNP-MUA phase transition between aqueous and organic phases occurs at pH ~9. The ion pair formation between the amine group in octadecylamine (ODA), the carboxylate group in MUA, and the hydrophobic alkyl chain of ODA facilitates the phase transfer of AuNP-MUA into an organic medium. The AuNP-MUA were investigated as a reusable catalyst in the catalytic reduction of 4-nitrophenol by borohydride—a model reaction for AuNPs. It was determined that 100% MUA surface coverage completely inhibits the catalytic activity of AuNPs. Decreasing the surface coverage was shown to increase catalytic activity, but this decrease also leads to decreased colloidal stability, recoverability, and reusability in subsequent reactions. At 60% MUA surface coverage, colloidal stability and catalytic activity were achieved, but the surface coverage was insufficient to enable redispersion following pH-induced recovery. A balance between AuNP colloidal stability, recoverability, and catalytic activity with reusability was achieved at 90% MUA surface coverage. The AuNP-MUA catalyst can also be recovered at different pH ranges depending on the recovery method employed. At pH ~4, protonation of the MUA results in reduced surface charge and aggregation. At pH ~9, ODA will form an ion-pair with the MUA and induce phase transfer into an immiscible organic phase. Both the pH-triggered aggregation/re-dispersion and aqueous/organic phase transfer methods were employed for catalyst recovery and reuse in subsequent reactions. The ability to recover and reuse the AuNP-MUA catalyst by two different methods and different pH regimes is significant, based on the fact that nanoparticle-catalyzed reactions may occur under different pH conditions. PMID:29772775

Multimodality Image-Guided HDR/IMRT in Prostate Cancer: Combined Molecular Targeting Using Nanoparticle MR, 3D MRSI, and 11C Acetate PET Imaging

DTIC Science & Technology

2005-08-01

Ph.D. Panos Fatouros, Ph.D. Jerry Hirsch, MSc, PharmD Rhonda Hoyle Kristin Schmidt Dorin Tudor, Ph.D. Jie Liu CONTRACTING ORGANIZATION: Virginia...McClish, Ph.D., Panos Fatouros, Ph.D., Jerry Hirsch, MSc, PharmD, 5e. TASK NUMBER Rhonda Hoyle, Kristin Schmidt, Dorin Tudor, Ph.D., Jie Liu 5f. WORK UNIT

Total cross sections of electron scattering by molecules NF3, PF3, N(CH3)3, P(CH3)3, NH(CH3)2, PH(CH3)2, NH2CH3 and PH2CH3 at 30-5000 eV

NASA Astrophysics Data System (ADS)

Shi, D. H.; Sun, J. F.; Zhu, Z. L.; Liu, Y. F.

2010-04-01

Total cross sections of electron scattering by eight molecules NF3, PF3, N(CH3)3, P(CH3)3, NH(CH3)2, PH(CH3)2, NH2CH3 and PH2CH3, which have some structural similarities, are calculated at the Hartree-Fork level by the modified additivity rule approach [D.H. Shi, J.F. Sun, Z.L. Zhu, H. Ma, Y.F. Liu, Eur. Phys. J. D 45, 253 (2007); D.H. Shi, J.F. Sun, Y.F. Liu, Z.L. Zhu, X.D. Yang, Chin. Opt. Lett. 4, 192 (2006)]. The modified additivity rule approach takes into considerations that the contributions of the geometric shielding effect vary as the energy of incident electrons, the dimension of target molecule, the number of electrons in the molecule and the number of atoms constituting the molecule. The present investigations cover the impact energy range from 30 to 5000 eV. The quantitative total cross sections are compared with those obtained by experiments and other theories. Excellent agreement is observed even at energies of several tens of eV. It shows that the modified additivity rule approach is applicable to carry out the total cross section calculations of electron scattering by these molecules at intermediate and high energies, in particular over the energy range above 80 eV or so. It proves that the microscopic molecular properties, such as the geometrical size of the target and the number of atoms constituting the molecule, are of crucial importance in the TCS calculations. The new results for PH(CH3)2 and PH2CH3 are also presented at energies from 30 to 5000 eV, although no experimental and theoretical data are available for comparison. In the present calculations, the atoms are still represented by the spherical complex optical potential, which is composed of static, exchange, polarization and absorption terms.

Estimation of the toxicity of sulfadiazine to Daphnia magna using negligible depletion hollow-fiber liquid-phase microextraction independent of ambient pH

NASA Astrophysics Data System (ADS)

Liu, Kailin; Xu, Shiji; Zhang, Minghuan; Kou, Yahong; Zhou, Xiaomao; Luo, Kun; Hu, Lifeng; Liu, Xiangying; Liu, Min; Bai, Lianyang

2016-12-01

The toxicity of ionizable organic compounds to organisms depends on the pH, which therefore affects risk assessments of these compounds. However, there is not a direct chemical method to predict the toxicity of ionizable organic compounds. To determine whether hollow-fiber liquid-phase microextraction (HF-LPME) is applicable for this purpose, a three-phase HF-LPME was used to measure sulfadiazine and estimate its toxicity to Daphnia magna in solutions of different pH. The result indicated that the sulfadiazine concentrations measured by HF-LPME decreased with increasing pH, which is consistent with the decreased toxicity. The concentration immobilize 50% of the daphnids (EC50) in 48 h calculated from nominal concentrations increased from 11.93 to 273.5 mg L-1 as the pH increased from 6.0 to 8.5, and the coefficient of variation (CV) of the EC50 values reached 104.6%. When calculated from the concentrations measured by HF-LPME (pH 12 acceptor phase), the EC50 ranged from 223.4 to 394.6 mg L-1, and the CV decreased to 27.60%, suggesting that the concentrations measured by HF-LPME can be used to estimate the toxicity of sulfadiazine irrespective of the solution pH.

Biochemical Composition and Assembly of Biosilica-associated Insoluble Organic Matrices from the Diatom Thalassiosira pseudonana*

PubMed Central

Kotzsch, Alexander; Pawolski, Damian; Milentyev, Alexander; Shevchenko, Anna; Scheffel, André; Poulsen, Nicole; Shevchenko, Andrej; Kröger, Nils

2016-01-01

The nano- and micropatterned biosilica cell walls of diatoms are remarkable examples of biological morphogenesis and possess highly interesting material properties. Only recently has it been demonstrated that biosilica-associated organic structures with specific nanopatterns (termed insoluble organic matrices) are general components of diatom biosilica. The model diatom Thalassiosira pseudonana contains three types of insoluble organic matrices: chitin meshworks, organic microrings, and organic microplates, the latter being described in the present study for the first time. To date, little is known about the molecular composition, intracellular assembly, and biological functions of organic matrices. Here we have performed structural and functional analyses of the organic microrings and organic microplates from T. pseudonana. Proteomics analysis yielded seven proteins of unknown function (termed SiMat proteins) together with five known silica biomineralization proteins (four cingulins and one silaffin). The location of SiMat1-GFP in the insoluble organic microrings and the similarity of tyrosine- and lysine-rich functional domains identifies this protein as a new member of the cingulin protein family. Mass spectrometric analysis indicates that most of the lysine residues of cingulins and the other insoluble organic matrix proteins are post-translationally modified by short polyamine groups, which are known to enhance the silica formation activity of proteins. Studies with recombinant cingulins (rCinY2 and rCinW2) demonstrate that acidic conditions (pH 5.5) trigger the assembly of mixed cingulin aggregates that have silica formation activity. Our results suggest an important role for cingulins in the biogenesis of organic microrings and support the hypothesis that this type of insoluble organic matrix functions in biosilica morphogenesis. PMID:26710847

Biochar contribution to soil pH buffer capacity

NASA Astrophysics Data System (ADS)

Tonutare, Tonu; Krebstein, Kadri; Utso, Maarius; Rodima, Ako; Kolli, Raimo; Shanskiy, Merrit

2014-05-01

Biochar as ecologically clean and stable form of carbon has complex of physical and chemical properties which make it a potentially powerful soil amendment (Mutezo, 2013). Therefore during the last decade the biochar application as soil amendment has been a matter for a great number of investigations. For the ecological viewpoint the trend of decreasing of soil organic matter in European agricultural land is a major problem. Society is faced with the task to find possibilities to stabilize or increase soil organic matter content in soil and quality. The availability of different functional groups (e.g. carboxylic, phenolic, acidic, alcoholic, amine, amide) allows soil organic matter to buffer over a wide range of soil pH values (Krull et al. 2004). Therefore the loss of soil organic matter also reduces cation exchange capacity resulting in lower nutrient retention (Kimetu et al. 2008). Biochar can retain elements in soil directly through the negative charge that develops on its surfaces, and this negative charge can buffer acidity in the soil. There are lack of investigations about the effect of biochar to soil pH buffering properties, The aim of our investigation was to investigate the changes in soil pH buffer capacity in a result of addition of carbonizated material to temperate region soils. In the experiment different kind of softwood biochars, activated carbon and different soil types with various organic matter and pH were used. The study soils were Albeluvisols, Leptosols, Cambisols, Regosols and Histosols . In the experiment the series of the soil: biochar mixtures with the biochar content 0 to 100% were used. The times of equiliberation between solid and liquid phase were from 1 to 168 hours. The suspension of soil: biochar mixtures was titrated with HCl solution. The titration curves were established and pH buffer capacities were calculated for the pH interval from 3.0 to 10.0. The results demonstrate the dependence of pH buffer capacity from soil type, organic matter and type of added carbonizated material. Our study showed that the biochar content has significant role in total pH buffer capacity in soil:biochar system . References. Kimetu, J.M., Lehmann, J., Ngoze, S.O., Mugendi, D.N., Kinyangi, J., Riha, S.J., Verchot, L., Recha, J.W., Pell, A.N. 2008. Reversibility of Soil Productivity Decline with Organic Matter of Differing Quality Along a Degradation Gradient. Ecosystems, 11, 726-739. Krull, E. S., Skjemstad, J.O., Baldock, J.A. 2004 'Functions of Soil Organic Matter and the Effect on Soil Properties'. GRDC report. Project CSO 00029. Mutezo, W.T., 2013. Early crop growth and yield responses of maize (Zea mays) to biochar applied on soil. International Working Paper Series, 13/03, 50 pp.

Surface complexation modeling of zinc sorption onto ferrihydrite.

PubMed

Dyer, James A; Trivedi, Paras; Scrivner, Noel C; Sparks, Donald L

2004-02-01

A previous study involving lead(II) [Pb(II)] sorption onto ferrihydrite over a wide range of conditions highlighted the advantages of combining molecular- and macroscopic-scale investigations with surface complexation modeling to predict Pb(II) speciation and partitioning in aqueous systems. In this work, an extensive collection of new macroscopic and spectroscopic data was used to assess the ability of the modified triple-layer model (TLM) to predict single-solute zinc(II) [Zn(II)] sorption onto 2-line ferrihydrite in NaNO(3) solutions as a function of pH, ionic strength, and concentration. Regression of constant-pH isotherm data, together with potentiometric titration and pH edge data, was a much more rigorous test of the modified TLM than fitting pH edge data alone. When coupled with valuable input from spectroscopic analyses, good fits of the isotherm data were obtained with a one-species, one-Zn-sorption-site model using the bidentate-mononuclear surface complex, (triple bond FeO)(2)Zn; however, surprisingly, both the density of Zn(II) sorption sites and the value of the best-fit equilibrium "constant" for the bidentate-mononuclear complex had to be adjusted with pH to adequately fit the isotherm data. Although spectroscopy provided some evidence for multinuclear surface complex formation at surface loadings approaching site saturation at pH >/=6.5, the assumption of a bidentate-mononuclear surface complex provided acceptable fits of the sorption data over the entire range of conditions studied. Regressing edge data in the absence of isotherm and spectroscopic data resulted in a fair number of surface-species/site-type combinations that provided acceptable fits of the edge data, but unacceptable fits of the isotherm data. A linear relationship between logK((triple bond FeO)2Zn) and pH was found, given by logK((triple bond FeO)2Znat1g/l)=2.058 (pH)-6.131. In addition, a surface activity coefficient term was introduced to the model to reduce the ionic strength dependence of sorption. The results of this research and previous work with Pb(II) indicate that the existing thermodynamic framework for the modified TLM is able to reproduce the metal sorption data only over a limited range of conditions. For this reason, much work still needs to be done in fine-tuning the thermodynamic framework and databases for the TLM.

Minimising alkalinity and pH spikes from Portland cement-bound Bauxsol (seawater-neutralized red mud) pellets for pH circum-neutral waters.

PubMed

Despland, Laure M; Clark, Malcolm W; Aragno, Michel; Vancov, Tony

2010-03-15

Bauxsol reagents (powder, slurry, or pellet forms) are powerful tools in environmental remediation and water and sewage treatment However, when used in circum-neutral water treatments, cement-bound Bauxsol pellets produce a sustained pH and alkalinity spike due to the presence of unreacted CaO in the cement binder. This study developed a pellet treatment system to minimize the alkalinity/pH spike. The recipe for pelletization consisted of Bauxsol powder, ordinary Portland cement (OPC), hydrophilic fumed silica, aluminum powder, a viscosity modifier, and water. Several batches (including different ratios and sizes) were run using modified makeup waters (H(2)0 + CO(2) or NaHCO(3)) or curing brines (CO(2), NaHCO(3), or Mg/CaCl(2)). Alkalinity, pH stability, and slake durability tests were performed on pellets before and/or after curing. The best result for reducing the alkalinity/pH spike was obtained from a MgCl(2), CaCl(2) bath treatment using a Bauxsol:cement ratio of 2.8:1 (pH 8.28; alkalinity 75.1 mg/L) for a 100 g batch or 245:1 (pH 8.05; alkalinity 35.4 mg/L) for a 1 kg batch. Although brine curing does provide a control on pH/alkalinity release, the pellets may still contain unreacted CaO. Therefore, a freshwater rinse of pellets before treating circum-neutral waters is recommended as is the continued investigation of alternative pellet binders.

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.

Ferric chloride modified zeolite in wastewater on Cr (VI) adsorption characteristics

NASA Astrophysics Data System (ADS)

Wu, Xiaoqing; Zhang, Kang; Chen, Wen; Zhang, Hua

2018-03-01

Zeolite was modified by ferric chloride(Fe-Z) removal Cr (VI) ion from wastewater. The results showed that the effect of Cr(VI) adsorption on modified zeolite depended significantly on pH. It is favorable for the adsorption of Cr(VI) in acid condition. The Langmuir isotherm model has high fitting accuracy with experimental data, demonstrated that is monolayer adsorption and chemical adsorption.The pseudo-second-order equation provided the best correlation to the data. The model can describe the adsorption reaction process well.

Development of an extended-range fiber optic pH sensor using evanescent wave absorption of sol-gel-entrapped pH indicators

NASA Astrophysics Data System (ADS)

Butler, Thomas M.; MacCraith, Brian D.; McDonagh, Colette M.

1995-09-01

The sol-gel process has been used to entrap pH indicators in porous glass coatings for sensor applications. This sensor is based on evanescent wave absorption using an unclad optical fiber dipcoated with the pH sensitive coating. The entrapped pH indicators show a broadening of the pH range with respect to the behavior in solution giving accurate measurement over three pH units when one indicator is used (bromophenol blue) and over six pH units (pH 3-9) when two indicators are used (bromophenol blue and bromocresol purple). The response of the pH sensor was monitored by measuring absorption at 590 nm referenced against a nonabsorbing region of the spectrum. This enabled the use of LED sources together with low cost photodiodes. The sensor displayed short response time and good repeatability. The thickness and stability of the pH sensitive coatings can be influenced by modifying the composition of the starting sol mixture. The evanescent absorption, and hence the sensitivity of the sensor, can be increased by selectively launching higher order modes in the fiber. These issues together with a full sensor characterization will be reported.

DISSOLVED ORGANIC MATTER AND METALS: EFFECTS OF PH ON PARTITIONING

EPA Science Inventory

Eighteen Dutch soils were extracted in aqueous solutions at varying pH. Extracts were analyzed for Cd, Cu, Ni, Pb, and Zn by ICP-AES. Extract dissolved organic carbon (DOC) was fractionated into three operationally defined fractions: hydrophilic acids (Hyd), fulvic acids (FA), an...

Remote-loading labeling of liposomes with (99m)Tc-BMEDA and its stability evaluation: effects of lipid formulation and pH/chemical gradient.

PubMed

Li, Shihong; Goins, Beth; Phillips, William T; Bao, Ande

2011-03-01

Efficient, convenient, and stable radiolabeling plays a critical role for the monitoring of liposome behavior via either blood sampling, organ distribution, or noninvasive nuclear imaging. The direct labeling of liposome-carrying drugs without any prior modification undoubtedly is convenient and optimal for liposomal drug testing. In this article, we investigated the effect of various lipid formulations and pH/chemical gradients on the radiolabeling efficiency and entrapment stability of technetium-99m ((99m)Tc) remotely loaded into liposomes, using (99m)Tc-N,N-bis(2-mercaptoethyl)-N',N'-diethyl-ethylenediamine ((99m)Tc-BMEDA) complex. The tested liposomes either contained unsaturated lipid or possessed various surface charges. (99m)Tc could be efficiently loaded into various premanufactured liposomes containing either an ammonium sulfate pH, citrate pH, or glutathione (GSH) chemical gradient. (99m)Tc-entrapment stabilities of these liposomes in phosphate-buffered saline (PBS; pH 7.4) buffer at 25°C were mainly dependent on the pH/chemical gradient, but not lipid formulation. Stability sequence was ammonium sulfate pH-gradient>citrate pH-gradient>GSH-gradient. Stabilities of (99m)Tc-liposomes in 50% fetal bovine serum (FBS)/PBS (pH 7.4) buffer at 37°C are dependent on both lipid formulation and pH/chemical gradient. Specifically, (99m)Tc labeling of the ammonium sulfate pH-gradient liposomes were less stable in 50% FBS/PBS than in PBS, whereas noncationic liposomes with citrate pH- or GSH-gradient displayed higher stability, except that anionic citrate pH-gradient liposomes showed no stability difference in these two media. Cationic liposomes aggregated in 50% FBS/PBS, forming a new discrete fraction with larger particle sizes. These in vitro characterization results have indicated the optimism of using (99m)Tc-BMEDA for labeling pH/GSH gradient liposomes without the requirement of modifying lipid formulation for liposomal therapeutic-agent development.

Dual stimuli polysaccharide nanovesicles for conjugated and physically loaded doxorubicin delivery in breast cancer cells.

PubMed

Pramod, P S; Shah, Ruchira; Jayakannan, Manickam

2015-04-21

The present work reports the development of pH and enzyme dual responsive polysaccharide vesicular nano-scaffolds for the administration of doxorubicin via physical loading and polymer-drug conjugation to breast cancer cells. Dextran was suitably modified with a renewable resource 3-pentadecyl phenol unit through imine and aliphatic ester chemical linkages that acted as pH and esterase enzyme stimuli, respectively. These dual responsive polysaccharide derivatives self-organized into 200 ± 10 nm diameter nano-vesicles in water. The water soluble anticancer drug doxorubicin (DOX·HCl) was encapsulated in the hydrophilic pocket to produce core-loaded polysaccharide vesicles whereas chemical conjugation produced DOX anchored at the hydrophobic layer of the dextran nano-vesicles. In vitro studies revealed that about 70-80% of the drug was retained under circulatory conditions at pH = 7.4 and 37 °C. At a low pH of 6.0 to 5.0 and in the presence of esterase; both imine and ester linkages were cleaved instantaneously to release 100% of the loaded drugs. Cytotoxicity assays on Wild Type Mouse Embryonic Fibroblasts (WTMEFs) confirmed the non-toxicity of the newly developed dextran derivatives at up to 500 μg mL(-1) in PBS. MTT assays on fibroblast cells revealed that DOX·HCl loaded nano-vesicles exhibited better killing abilities than DOX conjugated polymer nano-vesicles. Both DOX loaded and DOX conjugated nano-vesicles were found to show significant killing in breast cancer cells (MCF 7). Confocal microscopy images confirmed the uptake of DOX loaded (or conjugated) nano-vesicles by cells compared to free DOX. Thus, the newly developed pH and enzyme dual responsive polysaccharide vesicular assemblies are potential drug vectors for the administration of DOX in both loaded and chemically conjugated forms for the efficient killing of breast cancer cells.

Cytochrome c conjugated to ZnO-MAA nanoparticles: the study of interaction and influence on protein structure.

PubMed

Simšíková, Michaela; Antalík, Marián; Kaňuchová, Mária; Skvarla, Jiří

2013-08-01

Nanoparticle-protein conjugates have potential for numerous applications due to the combination of the properties of both components. In this paper we studied the conjugation of horse heart cytochrome c with ZnO nanoparticles modified by mercaptoacetic acid (MAA) which may be a material with great potential in anticancer therapy as a consequence of synergic effect of both components. Cyt c adsorption to the ZnO-MAA NPs surface was studied by UV-vis spectroscopy and by a dynamic light scattering in various pH. The results indicate that the optimal pH for the association of protein with modified nanoparticles is in range 5.8-8.5 where 90-96% of cytochrome c was assembled on ZnO-MAA nanoparticles. The interaction of proteins with nanoparticles often results in denaturation or loss of protein function. Our observations from UV-vis spectroscopy and circular dichroism performed preserved protein structure after the interaction with modified nanoparticles. Copyright © 2013 Elsevier B.V. All rights reserved.

Changes of pH and peroxide value in carp (Cyprinus carpio) cuts packaged in modified atmosphere

NASA Astrophysics Data System (ADS)

Milijašević, M.; Babić Milijašević, J.; Đinović-Stojanović, J.; Vesković Moračanin, S.; Lilić, S.

2017-09-01

The aim of our research was to examine the influence of packaging in modified atmosphere on the pH and peroxide value in muscle of common carp (Cyprinus carpio), as well as to determine the most suitable gas mixtures for packing of that freshwater species. Three sample groups of carp cuts were investigated. One group of carp cuts was placed on top of flaked ice placed in polystyrene boxes. Two other groups were packaged in modified atmosphere with different gas ratios: 80%O2+20%CO2 (MAP 1) and 90%CO2+10%N2 (MAP 2). All carp cuts were stored in the same conditions at 3±0.5°C, and on 1, 3, 5, 7, 9, 11, 13, 15. and 17 days of storage, chemical testing was performed. The results obtained indicate that the packaging of common carp under 90%CO2+10%N2 slowed proteolytic reaction as well as secondary lipid oxidation.

Formulation and characterization of ORMOSIL particles loaded with budesonide for local colonic delivery.

PubMed

Petrovska-Jovanovska, Vesna; Geskovski, Nikola; Crcarevska, Maja Simonoska; Memed, Oya; Petruševski, Gjorgji; Chachorovska, Marina; Petrusevska, Marija; Poceva-Panovska, Ana; Mladenovska, Kristina; Ugarkovic, Sonja; Glavas-Dodov, Marija

2015-04-30

In this study, hybrid silica xerogel particles were developed as carriers of budesonide (BDS) for efficient local treatment of inflammatory bowel diseases (IBD). Organically modified silica particles (ORMOSILs) were prepared by co-condensation of 3-aminopropyltriethoxysilane (APTES) and tetraethyl orthosilicate (TEOS) by an ambient temperature acid catalysed sol-gel process followed by spray-drying. Formulation for preparation of BDS-loaded particles was optimized and their physicochemical parameters and drug release profiles were evaluated in vitro. Optimal formulation had a small particle size (mean diameter of 1.45±0.02μm) with unimodal narrow size distribution and high encapsulation efficiency (98.0 ± 1.85%). Due to the positive surface charge originated from amino group of APTES, ORMOSILs showed excessive mucoadhesiveness in comparison to native TEOS particles. The drug release decreased with increasing pH from 2.0 to 7.4. In order to avoid undesirable erroneous performance in the upper GI tract, particles were additionally coated with Eudragit(®) FS 30D, as a barrier to the drug release at pH range from 2.0 to 7.0. After Eudragit(®) FS 30D coating, the release of BDS in acidic media was sustained, while no significant differences in drug release were observed at pH 7.4. In conclusion, pH-responsive ORMOSILs showed great potential for efficient BDS delivery to the colon region. Copyright © 2015 Elsevier B.V. All rights reserved.

Development of bone-like zirconium oxide nanoceramic modified chitosan based porous nanocomposites for biomedical application.

PubMed

Bhowmick, Arundhati; Pramanik, Nilkamal; Jana, Piyali; Mitra, Tapas; Gnanamani, Arumugam; Das, Manas; Kundu, Patit Paban

2017-02-01

Here, zirconium oxide nanoparticles (ZrO 2 NPs) were incorporated for the first time in organic-inorganic hybrid composites containing chitosan, poly(ethylene glycol) and nano-hydroxypatite (CS-PEG-HA) to develop bone-like nanocomposites for bone tissue engineering application. These nanocomposites were characterized by FT-IR, XRD, TEM combined with SAED. SEM images and porosity measurements revealed highly porous structure having pore size of less than 1μm to 10μm. Enhanced water absorption capacity and mechanical strengths were obtained compared to previously reported CS-PEG-HA composite after addition of 0.1-0.3wt% of ZrO 2 NPs into these nanocomposites. The mechanical strengths and porosities were similar to that of human spongy bone. Strong antimicrobial effects against gram-negative and gram-positive bacterial strains were also observed. Along with getting low alkalinity pH (7.4) values, similar to the pH of human plasma, hemocompatibility and cytocompatibility with osteoblastic MG-63 cells were also established for these nanocomposites. Addition of 15wt% HA-ZrO 2 (having 0.3wt% ZrO 2 NPs) into CS-PEG (55:30wt%) composite resulted in greatest mechanical strength, porosity, antimicrobial property and cytocompatibility along with suitable water absorption capacity and compatibility with human pH and blood. Thus, this nanocomposite could serve as a potential candidate to be used for bone tissue engineering. Copyright © 2016 Elsevier B.V. All rights reserved.

A novel coating concept for ileo-colonic drug targeting: proof of concept in humans using scintigraphy.

PubMed

Varum, F J O; Hatton, G B; Freire, A C; Basit, A W

2013-08-01

The in vivo proof of concept of a novel double-coating system, based on enteric polymers, which accelerated drug release in the ileo-colonic region, was investigated in humans. Prednisolone tablets were coated with a double-coating formulation by applying an inner layer composed of EUDRAGIT S neutralised to pH 8.0 and a buffer salt (10% KH₂PO₄), which was overcoated with layer of standard EUDRAGIT S organic solution. For comparison, a single coating system was produced by applying the same amount of EUDRAGIT S organic solution on the tablet cores. Dissolution tests on the tablets were carried out using USP II apparatus in 0.1N HCl for 2 h and subsequently in pH 7.4 Krebs bicarbonate buffer. For comparison, tablets were also tested under the USP method established for modified release mesalamine formulations. Ten fasted volunteers received the double-coated and single-coated tablets in a two-way crossover study. The formulations were radiolabelled and followed by gamma scintigraphy; the disintegration times and positions were recorded. There was no drug release from the single-coated or double-coated tablets in 0.1N HCl for 2h. The single-coated tablets showed slow release in subsequent Krebs bicarbonate buffer with a lag time of 120 min, while in contrast drug release from the double-coated tablets was initiated at 60 min. In contrast, using the USP dissolution method, normally employed for modified release mesalamine products, no discrimination was attained. The in vivo disintegration of the single-coated EUDRAGIT S tablets in the large intestine was erratic. Furthermore, in 2 volunteers, the single-coated tablet was voided intact. Double-coated tablets disintegrated in a more consistent way, mainly in the ileo-caecal junction or terminal ileum. The accelerated in vivo disintegration of the double-coating EUDRAGIT S system can overcome the limitations of conventional enteric coatings targeting the colon and avoid the pass-through of intact tablets. Moreover, Krebs bicarbonate buffer has the ability to discriminate between formulations designed to target the ileo-colonic region. Copyright © 2013 Elsevier B.V. All rights reserved.

Ocean acidification impact on copepod swimming and mating behavior: consequences for population dynamics

NASA Astrophysics Data System (ADS)

Seuront, L.

2010-12-01

There is now ample evidence that ocean acidification caused by the uptake of additional carbon dioxide from the atmosphere at the ocean surface will severely impact on marine ecosystem structure and function. To date, most research effort has focused on the impact of ocean acidification on calcifying marine organisms. These include the dissolution of calcifying plankton, reduced growth and shell thickness in gastropods and echinoderms and declining growth of reef-building corals. The effects of increasing the partial pressure in carbon dioxide and decreasing carbonate concentrations on various aspects of phytoplankton biology and ecology have received some attention. It has also recently been shown that the ability of fish larvae to discriminate between the olfactory cues of different habitat types at settlement and to detect predator olfactory cues are impaired at the level of ocean acidification predicted to occur around 2100 on a business-as-usual scenario of CO2 emissions. Average ocean pH has decreased by 0.1 units since the pre-industrial times, and it is predicted to decline another 0.3-0.4 units by 2100, which nearly corresponds to a doubling PCO2. In addition, some locations are expected to exhibit an even greater than predicted rate of decline. In this context, understanding the direct and indirect links between ocean acidification and the mortality of marine species is critical, especially for minute planktonic organisms such as copepods at the base of the ocean food chains. In this context, this work tested if ocean acidification could affect copepod swimming behavior, and subsequently affect, and ultimately disrupt, the ability of male copepods to detect and follow the pheromone plume produced by conspecific females. To ensure the generality and the ecological relevance of the present work, the species used for the experimentation are two of the most common zooplankton species found in estuarine and coastal waters of the Northern Hemisphere, the calanoid copepods Eurytemora affinis and Temora longicornis. Behavioral and mating experiments were conducted under conditions of control seawater (pH = 8.1) and conditions of ocean pH expected to occur circa 2100 (i.e. pH = 7.8 to 7.6) because of present and future CO2 emissions under the SRES A2 scenario. Our results indicate that ocean acidification modifies E. affinis and T. longicornis swimming and mating behaviors, and mating success. Specifically, ocean acidification significantly (i) modifies the stochastic properties of successive displacements, leading to decrease mate encounter rates when copepods cannot rely on female pheromone plumes (i.e. under turbulent conditions) and (ii) decreases the ability of males to detect females pheromone trails, to accurately follow trails and to successfully track a female. This led to a significant decrease in contact and capture rates from control to acidified seawater. These results indicate that ocean acification decreases the ability of male copepods to detect, track and capture a female, hence suggest an overall impact on population fitness and dynamics.

Application of Brazilian kaolinite clay as adsorbent to removal of U(VI) from aqueous solution: Kinetic and thermodynamic of cation-basic interactions

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

Guerra, Denis L., E-mail: denis@cpd.ufmt.b; Leidens, Victor L.; Viana, Rubia R.

2010-05-15

The compound N{sup 1}-[3-(trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route. The modified and natural kaolinite samples were characterized by transmission electron microscopy, scanning electron microscopic, X-ray diffraction, and nuclear magnetic nuclei of {sup 29}Si and {sup 13}C. The well-defined peaks obtained in the {sup 13}C NMR spectrum in the 5.0-62.1 ppm region confirmed the attachment of organic functional groups as pendant chains bonded into the porous clay. The ability of these materials to remove U(VI) from aqueous solution was followed by a series of adsorption isotherms adjusted to a Sips equation at room temperature and pH 4.0.more » The kinetic parameters analyzed by the Lagergren and Elovich models gave a good fit for a pseudo-second order reaction with k{sub 2} values 16.0 and 25.1 mmol g{sup -1} min{sup -1} ranges for natural and modified kaolinite clays, respectively. The energetic effects caused by metal ion adsorption were determined through calorimetric titrations. - Graphical abstract: This investigation reports the use of original and modified kaolinites as alternative absorbents. The compound N-[3-trimethoxysilyl)propyl]diethylenetriamine was anchored onto Amazon kaolinite surface by heterogeneous route.« less

Carbon Dioxide Adsorption Behavior of Modified HKUST-1

NASA Astrophysics Data System (ADS)

Ma, Lan; Tang, Huamin; Zhou, Chaohua; Zhang, Hongpeng; Yan, Chunxiao; Hu, Xiaochun; Yang, Yang; Yang, Weiwei; Li, Yuming; He, Dehua

2014-12-01

A kind of typical metal-organic frameworks (MOFs) material, HKUST-1 was prepared by hydrothermal method and characterized by XRD and SEM. The results of characterizations manifested that HKUST-1 showed a regular octahedral crystal structure. The as-prepared HKUST-1 was modified by several kinds of organic base materials and the CO2 adsorption behaviors of modified HKUST-1 materials were evaluated. The CO2 adsorption capacities of different base modified HKUST-1 varied with the base intensity of modified organic base materials.

EFFECTS OF PH, SOLID/SOLUTION RATIO, IONIC STRENGTH, AND ORGANIC ACIDS ON PB AND CD SOPRTION ON KAOLINITE

EPA Science Inventory

Potentiometric and ion-selective electrode titrations together with batch sorption/desorption experiments, were performed to explain the aqueous and surface complexation reactions between kaolinite, Pb, Cd and three organic acids. Variables included pH, ionic strength, metal conc...

Binding of leachable components of polymethyl methacrylate (PMMA) and peptide on modified SPR chip

NASA Astrophysics Data System (ADS)

Szaloki, M.; Vitalyos, G.; Harfalvi, J.; Hegedus, Cs

2013-12-01

Many types of polymers are often used in dentistry, which may cause allergic reaction, mainly methyl methacrylate allergy due to the leachable, degradable components of polymerized dental products. The aim of this study was to investigate the interaction between the leachable components of PMMA and peptides by Fourier-transform Surface Plasmon Resonance (FT SPR). In our previous work binding of oligopeptides (Ph.D.-7 and Ph.D.-12 Peptide Library Kit) was investigated to PMMA surface by phage display technique. It was found that oligopeptides bounded specifically to PMMA surface. The most common amino acids were leucine and proline inside the amino acids sequences of DNA of phages. The binding of haptens, as formaldehyde and methacrylic acid, to frequent amino acids was to investigate on the modified gold SPR chip. Self assembled monolayer (SAM) modified the surface of gold chip and ensured the specific binding between the haptens and amino acids. It was found that amino acids bounded to modified SPR gold and the haptens bounded to amino acids by creating multilayer on the chip surface. By the application of phage display and SPR modern bioanalytical methods the interaction between allergens and peptides can be investigated.

Shelf-life extension of cod fillets with an acetate buffer spray prior to packaging under modified atmospheres.

PubMed

Boskou, G; Debevere, J

2000-01-01

Fresh cod fillets (Gadus morhua) were sprayed with a 10% acetate buffer (pH 5.6), packed with an industrial gas-flushing packaging machine under modified atmospheres (50% CO2--45% O2--5% N2, 2 cm3/1 g gas/product ratio) and stored at 7 degrees C for 12 days. Control cod fillets were directly packed and stored under the same conditions. A reduction of the aerobic plate counts was observed immediately after the cod fillets had been sprayed. During storage under modified atmospheres, there was complete inhibition of H2S-producing bacteria and Enterobacteriaceae in the treated cod fillets. Production of total volatile bases and trimethylamine (TMA) was inhibited in treated fillets for 10 days' storage under modified atmospheres. Inhibition of TMA production can be attributed to growth inhibition of H2S-producing bacteria, inhibition of the trimethylamine oxide (TMAO)-dependent metabolism of TMAO-reducing bacteria and the stable pH during storage. The shelf-life, at 7 degrees C, of treated cod fillets, based on cooked flavour score, was almost 12 days, ca 8 days more than shelf-life of the control fillets.

Abscission of flowers and floral organs is closely associated with alkalization of the cytosol in abscission zone cells.

PubMed

Sundaresan, Srivignesh; Philosoph-Hadas, Sonia; Riov, Joseph; Belausov, Eduard; Kochanek, Betina; Tucker, Mark L; Meir, Shimon

2015-03-01

In vivo changes in the cytosolic pH of abscission zone (AZ) cells were visualized using confocal microscopic detection of the fluorescent pH-sensitive and intracellularly trapped dye, 2',7'-bis-(2-carboxyethyl)-5(and-6)-carboxyfluorescein (BCECF), driven by its acetoxymethyl ester. A specific and gradual increase in the cytosolic pH of AZ cells was observed during natural abscission of flower organs in Arabidopsis thaliana and wild rocket (Diplotaxis tenuifolia), and during flower pedicel abscission induced by flower removal in tomato (Solanum lycopersicum Mill). The alkalization pattern in the first two species paralleled the acceleration or inhibition of flower organ abscission induced by ethylene or its inhibitor 1-methylcyclopropene (1-MCP), respectively. Similarly, 1-MCP pre-treatment of tomato inflorescence explants abolished the pH increase in AZ cells and pedicel abscission induced by flower removal. Examination of the pH changes in the AZ cells of Arabidopsis mutants defective in both ethylene-induced (ctr1, ein2, eto4) and ethylene-independent (ida, nev7, dab5) abscission pathways confirmed these results. The data indicate that the pH changes in the AZ cells are part of both the ethylene-sensitive and -insensitive abscission pathways, and occur concomitantly with the execution of organ abscission. pH can affect enzymatic activities and/or act as a signal for gene expression. Changes in pH during abscission could occur via regulation of transporters in AZ cells, which might affect cytosolic pH. Indeed, four genes associated with pH regulation, vacuolar H(+)-ATPase, putative high-affinity nitrate transporter, and two GTP-binding proteins, were specifically up-regulated in tomato flower AZ following abscission induction, and 1-MCP reduced or abolished the increased expression. © The Author 2014. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Covalent Organic Framework Functionalized with 8-Hydroxyquinoline as a Dual-Mode Fluorescent and Colorimetric pH Sensor.

PubMed

Chen, Long; He, Linwei; Ma, Fuyin; Liu, Wei; Wang, Yaxing; Silver, Mark A; Chen, Lanhua; Zhu, Lin; Gui, Daxiang; Diwu, Juan; Chai, Zhifang; Wang, Shuao

2018-05-09

Real-time and accurate detection of pH in aqueous solution is of great significance in chemical, environmental, and engineering-related fields. We report here the use of 8-hydroxyquinoline-functionalized covalent organic framework (COF-HQ) for dual-mode pH sensing. In the fluorescent mode, the emission intensity of COF-HQ weakened as the pH decreased, and also displayed a good linear relationship against pH in the range from 1 to 5. In addition, COF-HQ showed discernible color changes from yellow to black as the acidity increased and can be therefore used as a colorimetric pH sensor. All these changes are reversible and COF-HQ can be recycled for multiple detection runs owing to its high hydrolytical stability. It can be further assembled into a mixed matrix membrane for practical applications.

Not all GMOs are crop plants: non-plant GMO applications in agriculture.

PubMed

Hokanson, K E; Dawson, W O; Handler, A M; Schetelig, M F; St Leger, R J

2014-12-01

Since tools of modern biotechnology have become available, the most commonly applied and often discussed genetically modified organisms are genetically modified crop plants, although genetic engineering is also being used successfully in organisms other than plants, including bacteria, fungi, insects, and viruses. Many of these organisms, as with crop plants, are being engineered for applications in agriculture, to control plant insect pests or diseases. This paper reviews the genetically modified non-plant organisms that have been the subject of permit approvals for environmental release by the United States Department of Agriculture/Animal and Plant Health Inspection Service since the US began regulating genetically modified organisms. This is an indication of the breadth and progress of research in the area of non-plant genetically modified organisms. This review includes three examples of promising research on non-plant genetically modified organisms for application in agriculture: (1) insects for insect pest control using improved vector systems; (2) fungal pathogens of insects to control insect pests; and (3) virus for use as transient-expression vectors for disease control in plants.

Inhibition of DNA-Dependent Protein Kinase Activity for Breast Cancer Therapy

DTIC Science & Technology

2002-06-01

Dependent Protein Kinase Activity for Breast Cancer Therapy PRINCIPAL INVESTIGATOR: Chin-Rang Yang, Ph.D. CONTRACTING ORGANIZATION: University of Rochester...Activity for Breast Cancer Therapy 6. AUTHOR(S) Chin-Rang Yang, Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT...The formation of DNA double strand breaks (DSBs) correlates well with lethality of cancer cells following ionizing radiation (IR). The DNA-dependent

Anti-Estrogen Regulation of Macrophage Products that Influence Breast Cancer Cell Proliferation and Susceptibility to Apoptosis

DTIC Science & Technology

2004-08-01

Susceptibility to Apoptosis PRINCIPAL INVESTIGATOR: Theodore Bremner, Ph.D. CONTRACTING ORGANIZATION: Howard University Washington, DC 20060 REPORT DATE...S) Theodore Bremner, Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION Howard University REPORT NUMBER Washington...Bremner, Howard University , Washington, DC Tamoxifen (TMX) is the most widely used anti-estrogen for breast cancer prevention and treatment, but its

Organically modified clay supported chitosan/hydroxyapatite-zinc oxide nanocomposites with enhanced mechanical and biological properties for the application in bone tissue engineering.

PubMed

Bhowmick, Arundhati; Banerjee, Sovan Lal; Pramanik, Nilkamal; Jana, Piyali; Mitra, Tapas; Gnanamani, Arumugam; Das, Manas; Kundu, Patit Paban

2018-01-01

The objective of this study is to design biomimetic organically modified montmorillonite clay (OMMT) supported chitosan/hydroxyapatite-zinc oxide (CTS/HAP-ZnO) nanocomposites (ZnCMH I-III) with improved mechanical and biological properties compared to previously reported CTS/OMMT/HAP composite. Fourier transform infrared spectroscopy, powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy were used to analyze the composition and surface morphology of the prepared nanocomposites. Strong antibacterial properties against both Gram-positive and Gram-negative bacterial strains were established for ZnCMH I-III. pH and blood compatibility study revealed that ZnCMH I-III should be nontoxic to the human body. Cytocompatibility of these nanocomposites with human osteoblastic MG-63 cells was also established. Experimental findings suggest that addition of 5wt% of OMMT into CTS/HAP-ZnO (ZnCMH I) gives the best mechanical strength and water absorption capacity. Addition of 0.1wt% of ZnO nanoparticles into CTS-OMMT-HAP significantly enhanced the tensile strengths of ZnCMH I-III compared to previously reported CTS-OMMT-HAP composite. In absence of OMMT, control sample (ZnCH) also showed reduced tensile strength, antibacterial effect and cytocompatibility with osteoblastic cell compared to ZnCMH I. Considering all of the above-mentioned studies, it can be proposed that ZnCMH I nanocomposite has a great potential to be applied in bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Molybdenum isotope fractionation during adsorption to organic matter

USGS Publications Warehouse

King, Elizabeth K.; Perakis, Steven; Pett-Ridge, Julie C.

2018-01-01

Organic matter is of emerging interest as a control on molybdenum (Mo) biogeochemistry, and information on isotope fractionation during adsorption to organic matter can improve interpretations of Mo isotope variations in natural settings. Molybdenum isotope fractionation was investigated during adsorption onto insolubilized humic acid (IHA), a surrogate for organic matter, as a function of time (2–170 h) and pH (2–7). For the time series experiment performed at pH 4.2, the average Mo isotope fractionation between the solution and the IHA (Δ98Mosolution-IHA) was 1.39‰ (± 0.16‰, 2σ, based on 98Mo/95Mo relative to the NIST 3134 standard) at steady state. For the pH series experiment, Mo adsorption decreased as pH increased from 2.0 to 6.9, and the Δ98Mosolution-IHA increased from 0.82‰ to 1.79‰. We also evaluated natural Mo isotope patterns in precipitation, foliage, organic horizon, surface mineral soil, and bedrock from 12 forested sites in the Oregon Coast Range. The average Mo isotope offset observed between precipitation and organic (O) horizon soil was 2.1‰, with light Mo isotopes adsorbing preferentially to organic matter. Fractionation during adsorption to organic matter is similar in magnitude and direction to prior observations of Mo fractionation during adsorption to Fe- and Mn- (oxyhydr)oxides. Our finding that organic matter influences Mo isotope composition has important implications for the role of organic matter as a driver of trace metal retention and isotopic fractionation.

Characterization of Bc1-2, Bc1-xL, and Bax Pore Formation and Their Role in Apoptosis Regulation

DTIC Science & Technology

2002-01-01

Bcl-2, Bcl-xL, and Bax Pore Formation and Their Role in Apoptosis Regulation PRINCIPAL INVESTIGATOR: Frank Stenner -Liewen, Ph.D. Sharon Schendel, Ph.D...AUTHOR(S) Frank Stenner -Liewen, Ph.D. Sharon Schendel, Ph.D. John C. Reed, M.D., Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING

Aqueous Cr(VI) reduction by electrodeposited zero-valent iron at neutral pH: acceleration by organic matters.

PubMed

Liu, Junxi; Wang, Chuan; Shi, Jianying; Liu, Hong; Tong, Yexiang

2009-04-15

This work investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe(0)) at neutral pH. The ED Fe(0) prepared in a solution containing mixture of saccharin, L-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe(0) was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe(0) activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe(0) corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.

Characterization and Performance of Melamine Enhanced Urea Formaldehyde Resin for Bonding Southern Pine Particleboard

Treesearch

Qi-Ning Sun; Chung-Yun Hse; Todd F. Shupe

2011-01-01

Urea-formaldehyde resins modified by melamine were synthesized by four catalysts (H2SO4, HCl, H3PO4, and NaOH/NH4OH) with a F/U/M molar ratio of 1.38/1/0.074. Resin structure and thermal behavior were studied by 13C-NMR and DSC techniques. For H2SO4, HCl, and H3PO4 catalysts, resins were prepared by two stage pH adjustment: the first pH stage was set at 1.25 (H3PO4 pH...

Spatial variability of isoproturon mineralizing activity within an agricultural field: geostatistical analysis of simple physicochemical and microbiological soil parameters.

PubMed

El Sebai, T; Lagacherie, B; Soulas, G; Martin-Laurent, F

2007-02-01

We assessed the spatial variability of isoproturon mineralization in relation to that of physicochemical and biological parameters in fifty soil samples regularly collected along a sampling grid delimited across a 0.36 ha field plot (40 x 90 m). Only faint relationships were observed between isoproturon mineralization and the soil pH, microbial C biomass, and organic nitrogen. Considerable spatial variability was observed for six of the nine parameters tested (isoproturon mineralization rates, organic nitrogen, genetic structure of the microbial communities, soil pH, microbial biomass and equivalent humidity). The map of isoproturon mineralization rates distribution was similar to that of soil pH, microbial biomass, and organic nitrogen but different from those of structure of the microbial communities and equivalent humidity. Geostatistics revealed that the spatial heterogeneity in the rate of degradation of isoproturon corresponded to that of soil pH and microbial biomass.

Influence of the isomerism on the sorption of imazamethabenz-methyl by soil.

PubMed

Pinna, Maria Vittoria; Pusino, Alba

2013-04-01

The sorption of meta and para isomers of the herbicide imazamethabenz-methyl, methyl 6-[(RS)-4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl]-m- or p-toluate, by three soils and soil organic matter, was studied. Sorption isotherms conformed to the Freundlich equation. It was found that pH was the main factor influencing the adsorption in all of the systems. The highest level of sorption was measured on soils with low pH and high organic carbon content. Moreover, at low pH value, the soil rich in smectite clays, favoured the sorption of meta rather than para isomer. The higher affinity of clay surfaces for the meta isomer of the herbicide is due to the stabilization of the meta protonated form by resonance. At all pH values, the sorption on soil organic matter did not differ between two isomers. Copyright © 2012 Elsevier Ltd. All rights reserved.

Enhanced removal of As (V) from aqueous solution using modified hydrous ferric oxide nanoparticles

PubMed Central

Huo, Lijuan; Zeng, Xibai; Su, Shiming; Bai, Lingyu; Wang, Yanan

2017-01-01

Hydrous ferric oxide (HFO) is most effective with high treatment capacity on arsenate [As(V)] sorption although its transformation and aggregation nature need further improvement. Here, HFO nanoparticles with carboxymethyl cellulose (CMC) or starch as modifier was synthesized for the purpose of stability improvement and As(V) removal from water. Comparatively, CMC might be the optimum stabilizer for HFO nanoparticles because of more effective physical and chemical stability. The large-pore structure, high surface specific area, and the non-aggregated nature of CMC-HFO lead to increased adsorption sites, and thus high adsorption capacities of As(V) without pre-treatment (355 mg·g−1), which is much greater than those reported in previous studies. Second-order equation and dual-mode isotherm model could be successfully used to interpret the sorption kinetics and isotherms of As(V), respectively. FTIR, XPS and XRD analyses suggested that precipitation and surface complexation were primary mechanisms for As(V) removal by CMC modified HFO nanoparticles. A surface complexation model (SCM) was used to simulate As adsorption over pH 2.5–10.4. The predominant adsorbed arsenate species were modeled as bidentate binuclear surface complexes at low pH and as monodentate complexes at high pH. The immobilized arsenic remained stable when aging for 270 d at room temperature. PMID:28098196

Enhanced removal of As (V) from aqueous solution using modified hydrous ferric oxide nanoparticles

NASA Astrophysics Data System (ADS)

Huo, Lijuan; Zeng, Xibai; Su, Shiming; Bai, Lingyu; Wang, Yanan

2017-01-01

Hydrous ferric oxide (HFO) is most effective with high treatment capacity on arsenate [As(V)] sorption although its transformation and aggregation nature need further improvement. Here, HFO nanoparticles with carboxymethyl cellulose (CMC) or starch as modifier was synthesized for the purpose of stability improvement and As(V) removal from water. Comparatively, CMC might be the optimum stabilizer for HFO nanoparticles because of more effective physical and chemical stability. The large-pore structure, high surface specific area, and the non-aggregated nature of CMC-HFO lead to increased adsorption sites, and thus high adsorption capacities of As(V) without pre-treatment (355 mg·g-1), which is much greater than those reported in previous studies. Second-order equation and dual-mode isotherm model could be successfully used to interpret the sorption kinetics and isotherms of As(V), respectively. FTIR, XPS and XRD analyses suggested that precipitation and surface complexation were primary mechanisms for As(V) removal by CMC modified HFO nanoparticles. A surface complexation model (SCM) was used to simulate As adsorption over pH 2.5-10.4. The predominant adsorbed arsenate species were modeled as bidentate binuclear surface complexes at low pH and as monodentate complexes at high pH. The immobilized arsenic remained stable when aging for 270 d at room temperature.

Smart Nanoparticles Undergo Phase Transition for Enhanced Cellular Uptake and Subsequent Intracellular Drug Release in a Tumor Microenvironment.

PubMed

Ye, Guihua; Jiang, Yajun; Yang, Xiaoying; Hu, Hongxiang; Wang, Beibei; Sun, Lu; Yang, Victor C; Sun, Duxin; Gao, Wei

2018-01-10

Inefficient cellular uptake and intracellular drug release at the tumor site are two major obstacles limiting the antitumor efficacy of nanoparticle delivery systems. To overcome both problems, we designed a smart nanoparticle that undergoes phase transition in a tumor microenvironment (TME). The smart nanoparticle is generated using a lipid-polypetide hybrid nanoparticle, which comprises a PEGylated lipid monolayer shell and a pH-sensitive hydrophobic poly-l-histidine core and is loaded with the antitumor drug doxorubicin (DOX). The smart nanoparticle undergoes a two-step phase transition at two different pH values in the TME: (i) At the TME (pH e : 7.0-6.5), the smart nanoparticle swells, and its surface potential turns from negative to neutral, facilitating the cellular uptake; (ii) After internalization, at the acid endolysosome (pH endo : 6.5-4.5), the smart nanoparticle dissociates and induces endolysosome escape to release DOX into the cytoplasm. In addition, a tumor-penetrating peptide iNRG was modified on the surface of the smart nanoparticle as a tumor target moiety. The in vitro studies demonstrated that the iNGR-modified smart nanoparticles promoted cellular uptake in the acidic environment (pH 6.8). The in vivo studies showed that the iNGR-modified smart nanoparticles exerted more potent antitumor efficacy against late-stage aggressive breast carcinoma than free DOX. These data suggest that the smart nanoparticles may serve as a promising delivery system for sequential uptake and intracellular drug release of antitumor agents. The easy preparation of these smart nanoparticles may also have advantages in the future manufacture for clinical trials and clinical use.

Synthesis of iron composites on nano-pore substrates: identification and its application to removal of cyanide.

PubMed

Do, Si-Hyun; Jo, Young-Hoon; Park, Ho-Dong; Kong, Sung-Ho

2012-11-01

Two types of nano-pore substrates, waste-reclaimed (WR) and soil mineral (SM) with the relatively low density, were modified by the reaction with irons (i.e. Fe(II):Fe(III)=1:2) and the applicability of the modified substrates (i.e. Fe-WR and Fe-SM) on cyanide removal was investigated. Modification (i.e. Fe immobilization on substrate) decreased the BET surface area and PZC of the original substrates while it increased the pore diameter and the cation exchange capacity (CEC) of them. XRD analysis identified that maghemite (γ-Fe(2)O(3)) and iron silicate composite ((Mg, Fe)SiO(3)) existed on Fe-WR, while clinoferrosilite (FeSiO(3)) was identified on Fe-SM. Cyanide adsorption showed that WR adsorbed cyanide more favorably than SM. The adsorption ability of both original substrates was enhanced by the modification, which increased the negative charges of the surfaces. Without the pH adjustment, cyanide was removed as much as 97% by the only application of Fe-WR, but the undesirable transfer to hydrogen cyanide was possible because the pH was dropped to around 7.5. With a constant pH of 12, only 54% of cyanide was adsorbed on Fe-WR. On the other hand, the pH was kept as 12 without adjustment in Fe-WR/H(2)O(2) system and cyanide was effectively removed by not only adsorption but also the catalytic oxidation. The observed first-order rate constant (k(obs)) for cyanide removal were 0.49 (± 0.081) h(-1). Moreover, the more cyanate production with the modified substrates indicated the iron composites, especially maghemite, on substrates had the catalytic property to increase the reactivity of H(2)O(2). Copyright © 2012 Elsevier Ltd. All rights reserved.

Magnetorheological finishing with chemically modified fluids for studying material removal of single-crystal ZnS

NASA Astrophysics Data System (ADS)

Salzman, S.; Romanofsky, H. J.; Clara, Y. I.; Giannechini, L. J.; West, Garrett J.; Lambropoulos, J. C.; Jacobs, S. D.

2013-09-01

Magnetorheological finishing (MRF) of polycrystalline, chemical-vapor-deposited (CVD) zinc sulfide (ZnS) and zinc selenide (ZnSe) can leave millimeter-size artifacts on the part surface. These pebble-like features come from the anisotropic mechanical and chemical properties of the ceramic material and from the CVD growth process itself. The resulting surface texture limits the use of MRF for polishing aspheric and other complex shapes using these important infrared (IR) ceramics. An investigation of the individual contributions of chemistry and mechanics to polishing of other polycrystalline ceramics has been employed in the past to overcome similar material anisotropy problems. The approach taken was to study the removal process for the different single-crystal orientations that comprise the ceramic, making adjustments to mechanics (polishing abrasive type and concentration) and polishing slurry chemistry (primarily pH) to equalize the removal rate for all crystal orientations. Polishing with the modified slurry was shown to prevent the development of surface texture. Here we present mechanical (microhardness testing) and chemical (acid etching) studies performed on the four single-crystal orientations of ZnS: 100, 110, 111, and 311. We found that the (111) plane is 35% to 55% harder and 30% to 40% more resistant to chemical etching than the other three planes. This relatively high degree of variation in these properties can help to explain the surface texture developed from MRF of the polycrystalline material. Theoretical calculations of microhardness, planar, and bond densities are presented and compared with the experimental data. Here surface characterization of these single-crystal orientations of ZnS for material removal and roughness with chemically modified MR fluids at various pH levels between pH 4 and pH 6 are presented for the first time.

pH-modulation of chloride channels from the sarcoplasmic reticulum of skeletal muscle.

PubMed

Kourie, J I

1999-01-01

The understanding of the role of cytoplasmic pH in modulating sarcoplasmic reticulum (SR) ion channels involved in Ca2+ regulation is important for the understanding of the function of normal and adversely affected muscles. The dependency of the SR small chloride (SCl) channel from rabbit skeletal muscle on cytoplasmic pH (pHcis) and luminal pH (pHtrans) was investigated using the lipid bilayer-vesicle fusion technique. Low pHcis 6.75-4.28 modifies the operational mode of this multiconductance channel (conductance levels between 5 and 75 pS). At pHcis 7.26-7.37 the channel mode is dominated by the conductance and kinetics of the main conductance state (65-75 pS) whereas at low pHcis 6.75-4.28 the channel mode is dominated by the conductance and kinetics of subconductance states (5-40 pS). Similarly, low pHtrans 4.07, but not pHtrans 6.28, modified the activity of SCl channels. The effects of low pHcis are pronounced at 10(-3) and 10(-4) M [Ca2+]cis but are not apparent at 10(-5) M [Ca2+]cis, where the subconductances of the channel are already prominent. Low pHcis-induced mode shift in the SCl channel activity is due to modification of the channel proteins that cause the uncoupling of the subconductance states. The results in this study suggest that low pHcis can modify the functional properties of the skeletal SR ion channels and hence contribute, at least partly, to the malfunction in the contraction-relaxation mechanism in skeletal muscle under low cytoplasmic pH levels.

Scales and sources of pH and dissolved oxygen variability in a shallow, upwelling-driven ecosystem

NASA Astrophysics Data System (ADS)

Tanner, C. A.; Martz, T.; Levin, L. A.

2011-12-01

In the coastal zone extreme variability in carbonate chemistry and oxygen is driven by fluctuations in temperature, salinity, air-sea gas exchange, mixing processes, and biology. This variability appears to be magnified in upwelling-driven ecosystems where low oxygen and low pH waters intrude into shallow depths. The oxygen and carbon chemistry signal can be further confounded by highly productive ecosystems such as kelp beds where photosynthesis and respiration consume and release significant amounts of dissolved inorganic carbon and oxygen. This variability poses a challenge for scientists assessing the impacts of climate change on nearshore ecosystems. We deployed physical & biogeochemical sensors in order to observe these processes in situ. The "SeapHOx" instruments used in this study consist of a modified Honeywell Durafet° ISFET pH sensor, an Aanderra Optode Oxygen sensor, and a SBE-37 conductivity, temperature, pressure sensor. The instruments were deployed on and around the La Jolla Kelp Forest at a variety of depths. Our goals were to (a) characterize the link between pH and oxygen and identify the magnitude of pH and oxygen variability over a range of intra-annual time scales and (b) investigate spatial patterns of pH and oxygen variability associated with depth, proximity to shore, and presence of kelp. Results thus far reveal a strong relationship between oxygen and pH. Temporal variability is greatest at the semidiurnal frequency where pH (at 7 m) can range up to 0.3 units and oxygen can change 50% over 6 h. Diurnal variability is a combination of the diurnal tidal component and diel cycles of production and respiration. Event-scale dynamics associated with upwelling can maintain pH and oxygen below 7.8 units and 200 μmol kg-1, respectively, for multiple days. Frequent current reversals drive changes in the observed oxygen and pH variability. When alongshore currents are flowing southward, driven by upwelling-favorable winds, the magnitude of semidiurnal pH variability increases 5-fold relative to the magnitude of change during northward alongshore. Applying an empirically-determined alkalinity relationship, we conclude that changes in the carbonate chemistry parameters are largely driven by changes in total carbon. On small spatial scales, cross-shore differences exist in mean oxygen and pH but differences in alongshore mean oxygen and pH at a given depth appears to be negligible. Cross-shore differences can equate to a 0.05 pH unit decrease and 25 μmol kg-1 oxygen decrease over 1 km at a given depth. Strong spatial variability in pH and oxygen conditions exist over vertical gradients in the kelp forest, with mean pH at the surface (7m) being 0.2 pH units greater than at the bottom (17m) and mean oxygen being 104 μmol kg-1 greater. The observed range of pH (7.55-8.22) observed in this shallow environment during the course of a year is greater than open ocean predictions for a global mean pH reduction of 0.2-0.3 units predicted by the year 2100. These results suggest that organisms on exposed upwelling coasts may be adapted to a range of pH conditions and highlight the need for scientists to consider biological response to varying scales of pH change in order to develop more realistic predictions of the impacts of climate change for the coastal zone.

Spontaneous remodeling of HDL particles at acidic pH enhances their capacity to induce cholesterol efflux from human macrophage foam cells[S

PubMed Central

Nguyen, Su Duy; Öörni, Katariina; Lee-Rueckert, Miriam; Pihlajamaa, Tero; Metso, Jari; Jauhiainen, Matti; Kovanen, Petri T.

2012-01-01

HDL particles may enter atherosclerotic lesions having an acidic intimal fluid. Therefore, we investigated whether acidic pH would affect their structural and functional properties. For this purpose, HDL2 and HDL3 subfractions were incubated for various periods of time at different pH values ranging from 5.5 to 7.5, after which their protein and lipid compositions, size, structure, and cholesterol efflux capacity were analyzed. Incubation of either subfraction at acidic pH induced unfolding of apolipoproteins, which was followed by release of lipid-poor apoA-I and ensuing fusion of the HDL particles. The acidic pH-modified HDL particles exhibited an enhanced ability to promote cholesterol efflux from cholesterol-laden primary human macrophages. Importantly, treatment of the acidic pH-modified HDL with the mast cell-derived protease chymase completely depleted the newly generated lipid-poor apoA-I, and prevented the acidic pH-dependent increase in cholesterol efflux. The above-found pH-dependent structural and functional changes were stronger in HDL3 than in HDL2. Spontaneous acidic pH-induced remodeling of mature spherical HDL particles increases HDL-induced cholesterol efflux from macrophage foam cells, and therefore may have atheroprotective effects. PMID:22855736

The effect of excipients on the stability of levothyroxine sodium pentahydrate tablets.

PubMed

Patel, Himanshu; Stalcup, Apryll; Dansereau, Richard; Sakr, Adel

2003-10-02

Levothyroxine tablets, 50 microg, have been marketed for many decades but have had numerous recalls due to degradation and failure to meet potency. These experiments were devised to study the effects of various excipients on the stability of levothyroxine sodium pentahydrate in aqueous slurries and in formulated tablets. The active alone was found to be stable in the solid state for 6 months at 40 degrees C/75% RH whether stored in open or closed containers, and was found to be non-hygroscopic under normal processing conditions (>30% RH). In aqueous slurries with an excipient, the stability of the active improved as the pH of the slurry was increased from pH 3 to 11. Tablets manufactured with lactose anhydrous, starch, or microcrystalline cellulose failed to meet USP assay requirements at 3 months at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate or mannitol met USP assay requirements at 3, but not 6 months when stored at 40 degrees C/75% RH. Tablets manufactured with dibasic calcium phosphate and a basic pH modifier, such as sodium carbonate, sodium bicarbonate, or magnesium oxide, met the USP assay requirements at both 3 and 6 months. Thus, the use of basic pH modifiers is a potential technique for improving the stability of levothyroxine sodium pentahydrate tablets.

Utilization of a modified special-cubic design and an electronic tongue for bitterness masking formulation optimization.

PubMed

Li, Lianli; Naini, Venkatesh; Ahmed, Salah U

2007-10-01

A unique modification of simplex design was applied to an electronic tongue (E-Tongue) analysis in bitterness masking formulation optimization. Three formulation variables were evaluated in the simplex design, i.e. concentrations of two taste masking polymers, Amberlite and Carbopol, and pH of the granulating fluid. Response of the design was a bitterness distance measured using an E-Tongue by applying a principle component analysis, which represents taste masking efficiency of the formulation. The smaller the distance, the better the bitterness masking effect. Contour plots and polynomial equations of the bitterness distance response were generated as a function of formulation composition and pH. It was found that interactions between polymer and pH reduced the bitterness of the formulation, attributed to pH-dependent ionization and complexation properties of the ionic polymers, thus keeping the drug out of solution and unavailable to bitterness perception. At pH 4.9 and an Amberlite/Carbopol ratio of 1.4:1 (w/w), the optimal taste masking formulation was achieved and in agreement with human gustatory sensation study results. Therefore, adopting a modified simplex experimental design on response measured using an E-Tongue provided an efficient approach to taste masking formulation optimization using ionic binding polymers. (c) 2007 Wiley-Liss, Inc.

Measurement of net nitrogen and phosphorus mineralization in wetland soils using a modification of the resin-core technique

USGS Publications Warehouse

Noe, Gregory B.

2011-01-01

A modification of the resin-core method was developed and tested for measuring in situ soil N and P net mineralization rates in wetland soils where temporal variation in bidirectional vertical water movement and saturation can complicate measurement. The modified design includes three mixed-bed ion-exchange resin bags located above and three resin bags located below soil incubating inside a core tube. The two inner resin bags adjacent to the soil capture NH4+, NO3-, and soluble reactive phosphorus (SRP) transported out of the soil during incubation; the two outer resin bags remove inorganic nutrients transported into the modified resin core; and the two middle resin bags serve as quality-control checks on the function of the inner and outer resin bags. Modified resin cores were incubated monthly for a year along the hydrogeomorphic gradient through a floodplain wetland. Only small amounts of NH4+, NO3-, and SRP were found in the two middle resin bags, indicating that the modified resin-core design was effective. Soil moisture and pH inside the modified resin cores typically tracked changes in the surrounding soil abiotic environment. In contrast, use of the closed polyethylene bag method provided substantially different net P and N mineralization rates than modified resin cores and did not track changes in soil moisture or pH. Net ammonification, nitrifi cation, N mineralization, and P mineralization rates measured using modified resin cores varied through space and time associated with hydrologic, geomorphic, and climatic gradients in the floodplain wetland. The modified resin-core technique successfully characterized spatiotemporal variation of net mineralization fluxes in situ and is a viable technique for assessing soil nutrient availability and developing ecosystem budgets.

40 CFR 710.4 - Scope of the inventory.

Code of Federal Regulations, 2011 CFR

2011-07-01

... modifier, pH neutralizer, sequesterant, coagulant, flocculant, fire retardant, lubricant, chelating agent... upon use of curable plastic or rubber molding compounds, inks, drying oils, metal finishing compounds...

Theoretical and experimental adsorption studies of sulfamethoxazole and ketoprofen on synthesized ionic liquids modified CNTs.

PubMed

Lawal, Isiaka A; Lawal, Monsurat M; Akpotu, Samson O; Azeez, Mayowa A; Ndungu, Patrick; Moodley, Brenda

2018-06-18

The adsorption of sulfamethoxazole (SMZ) and ketoprofen (KET) using carbon nanotubes (CNTs) and CNTs modified with ionic liquids (ILs) was investigated. Two ionic liquids (1-benzyl, 3-hexyl imidazolium, IL1 and 1-benzyl, 3-decahexyl imidazolium, IL2) were synthesized, and characterized by nuclear magnetic resonance ( 1 H and 13 C NMR) and high resolution-mass spectrometry (HR-MS). CNTs and modified CNTs were characterized using FT-IR, X-ray diffraction (XRD), surface area and porosity analysis, thermal gravimetric analysis (TGA), Zeta potential, Raman and scanning electron microscopy (SEM). Kinetics, isotherm and computational studies were carried out to determine the efficiency and adsorption mechanism of SMZ and KET on modified CNTs. A density functional theory (DFT) method was applied to shed more light on the interactions between the pharmaceutical compounds and the adsorbents at the molecular level. The effects of adsorbent dosage, concentration, solution pH, energetics and contact time of SMZ and KET on the adsorption process were investigated. The adsorption of SMZ and KET on CNTs and modified CNTs were pH dependent, and adsorption was best described by pseudo-second-order kinetics and the Freundlich adsorption isotherm. Ionic liquid modified CNTs showed improved adsorption capacities compared to the unmodified ones for both SMZ and KET, which is in line with the computational results showing performance order; CNT+KET/SMZ < CNT-ILs+SMZ < CNT-ILs+KET. Copyright © 2018 Elsevier Inc. All rights reserved.

Effects of three low-molecular-weight organic acids (LMWOAs) and pH on the mobilization of arsenic and heavy metals (Cu, Pb, and Zn) from mine tailings.

PubMed

Wang, Suiling; Mulligan, Catherine N

2013-02-01

Natural organic acids may play an important role in influencing the mobility of toxic contaminants in the environment. The mobilization of arsenic (As) and heavy metals from an oxidized Pb-Zn mine tailings sample in the presence of three low-molecular-weight organic acids, aspartic acid, cysteine, and succinic acid, was investigated at a mass ratio of 10 mg organic additive/g mine tailings in this study. The effect of pH was also evaluated. The mine tailings sample, containing elevated levels of As (2,180 mg/kg), copper (Cu, 1,100 mg/kg), lead (Pb, 12,860 mg/kg), and zinc (Zn, 5,075 mg/kg), was collected from Bathurst, New Brunswick, Canada. It was found that the organic additives inhibited As and heavy metal mobilization under acidic conditions (at pH 3 or 5), but enhanced it under neutral to alkaline conditions (at pH above 7) through forming aqueous organic complexes. At pH 11, As, Cu, Pb, and Zn were mobilized mostly by the organic additives, 45, 46, 1,660, and 128 mg/kg by aspartic acid, 31, 28, 1,040, and 112 mg/kg by succinic acid, and 53, 38, 2,020, and 150 mg/kg by cysteine, respectively, whereas those by distilled water were 6, 16, 260, and 52 mg/kg, respectively. It was also found that the mobilization of As and the heavy metals was closely correlated, and both were closely correlated to Fe mobilization. Arsenic mobilization by the three LMWOAs was found to be consistent with the order of the stability of Fe-, Cu-, Pb-, and Zn-organic ligand complexes. The organic acids might be used potentially in the natural attenuation and remediation of As and heavy metal-contaminated sites.

Ancient Living Organisms Escaping from, or Imprisoned in, the Vents?

PubMed Central

Jackson, J. Baz

2017-01-01

We have recently criticised the natural pH gradient hypothesis which purports to explain how the difference in pH between fluid issuing from ancient alkali vents and the more acidic Hadean ocean could have driven molecular machines that catalyse reactions that are useful in prebiotic and autotrophic chemistry. In this article, we temporarily suspend our earlier criticism while we consider difficulties for primitive organisms to have managed their energy supply and to have left the vents and become free-living. We point out that it may have been impossible for organisms to have acquired membrane-located proton (or sodium ion) pumps to replace the natural pH gradient, and independently to have driven essential molecular machines such as the ATP synthase. The volumes of the ocean and of the vent fluids were too large for a membrane-located pump to have generated a significant ion concentration gradient. Our arguments apply to three of the four concurrent models employed by the proponents of the natural pH gradient hypothesis. A fourth model is exempt from these arguments but has other intrinsic difficulties that we briefly consider. We conclude that ancient organisms utilising a natural pH gradient would have been imprisoned in the vents, unable to escape and become free-living. PMID:28914790

How modifiable factors influence parental decision-making about organ donation.

PubMed

Luberda, Kamila; Cleaver, Karen

2017-11-07

A global shortage of organs from children and adults available for transplantation is compounded by the failure of next of kin to consent for organs to be donated after death. Non-modifiable and modifiable factors influence decision-making in this area. Modifiable factors are of interest when examining families' decision-making about the donation of organs from their deceased child. A scoping review was undertaken to determine how modifiable factors influence parental decision-making about organ donation. Thematic analysis identified two themes: interactions with healthcare professionals and pre-disposition to organ donation. Satisfaction with experiences of hospital care, the information provided and the way it was communicated, as well as interactions pertaining to emotional support were all found to be modifiable factors that influenced decision making. Likewise, a predisposition to organ donation and knowing the deceased's wishes were associated with the consent decision. Nurses working in critical care environments need to be able to support parents during this difficult time. This article aims to raise awareness of modifiable factors that influence parental decision-making, highlighting their relevance for children's nursing practice. ©2017 RCN Publishing Company Ltd. All rights reserved. Not to be copied, transmitted or recorded in any way, in whole or part, without prior permission of the publishers.

Changes in the level and activation state of the plasma membrane H(+)-ATPase during aging of red beet slices.

PubMed

Papini, R; De Michelis, M I

1997-07-01

The effect of aging on the plasma membrane (PM) H(+)-ATPase of red beet (Beta vulgaris L.) parenchyma discs was analyzed in PM purified by aqueous two-phase partitioning. Aging increased both the activity in the amount of immunodetectable H(+)-ATPase in the PM. The activity assayed at slightly alkaline pH values increased earlier and more strongly than that assayed at acidic pH values, so that the pH curve of the enzyme from aged beet discs was shifted toward more alkaline values. Aging decreased the stimulation of the PM H(+)-ATPase activity by controlled trypsin treatments or by lysophosphatidylcholine. After trypsin treatment the pH dependence of H(+)-ATPase from dormant or aged beet discs became equal. These results indicate that aging not only increases the level of H(+)-ATPase in the PM, but also determines its activation, most likely by modifying the interaction between the autoinhibitory carboxyl-terminal domain and the catalytic site. When the PM H(+)-ATPase activity was assayed at a slightly alkaline pH, the tyrosine modifier N-acetylimidazole inhibited the H(+)-ATPase in the PM from dormant beet discs much less than in the PM from aged discs, suggesting that modification of a tyrosine residue may be involved in the activation of the PM H(+)-ATPase induced by aging. The results are discussed with regard to aging-induced development of transmembrane transport activities.

Label-free silicon nanodots featured ratiometric fluorescent aptasensor for lysosomal imaging and pH measurement.

PubMed

Zhang, Yanan; Guo, Shan; Cheng, Shibo; Ji, Xinghu; He, Zhike

2017-08-15

The homeostasis of lysosomal pH is crucial in cell physiology. Developing small fluorescent nanosensors for lysosome imaging and ratiometric measurement of pH is highly demanded yet challenging. Herein, a pH-sensitive fluorescein tagged aptamer AS1411 has been utilized to covalently modify the label-free fluorescent silicon nanodots via a crosslinker for construction of a ratiometric pH biosensor. The established aptasensor exhibits the advantages of ultrasmall size, hypotoxicity, excellent pH reversibility and good photostability, which favors its application in an intracellular environment. Using human breast MCF-7 cancer cells and MCF-10A normal cells as the model, this aptasensor shows cell specificity for cancer cells and displays a wide pH response range of 4.5-8.0 in living cells. The results demonstrate that the pH of MCF-7 cells is 5.1, which is the expected value for acidic organelles. Lysosome imaging and accurate measurement of pH in MCF-7 cells have been successfully conducted based on this nanosensor via fluorescent microscopy and flow cytometry. Copyright © 2017 Elsevier B.V. All rights reserved.

Iridium oxide pH sensor for biomedical applications. Case urea-urease in real urine samples.

PubMed

Prats-Alfonso, Elisabet; Abad, Llibertat; Casañ-Pastor, Nieves; Gonzalo-Ruiz, Javier; Baldrich, Eva

2013-01-15

This work demonstrates the implementation of iridium oxide films (IROF) grown on silicon-based thin-film platinum microelectrodes, their utilization as a pH sensor, and their successful formatting into a urea pH sensor. In this context, Pt electrodes were fabricated on Silicon by using standard photolithography and lift-off procedures and IROF thin films were growth by a dynamic oxidation electrodeposition method (AEIROF). The AEIROF pH sensor reported showed a super-Nerstian (72.9±0.9mV/pH) response between pH 3 and 11, with residual standard deviation of both repeatability and reproducibility below 5%, and resolution of 0.03 pH units. For their application as urea pH sensors, AEIROF electrodes were reversibly modified with urease-coated magnetic microparticles (MP) using a magnet. The urea pH sensor provided fast detection of urea between 78μM and 20mM in saline solution, in sample volumes of just 50μL. The applicability to urea determination in real urine samples is discussed. Copyright © 2012 Elsevier B.V. All rights reserved.

An evaluation of the residual toxicity and chemistry of a sodium hydroxide-based ballast water treatment system for freshwater ships

USGS Publications Warehouse

Elskus, Adria; Ingersoll, Christopher G.; Kemble, Nile E.; Echols, Kathy R.; Brumbaugh, William G.; Henquinet, Jeffrey; Watten, Barnaby J.

2015-01-01

Nonnative organisms in the ballast water of freshwater ships must be killed to prevent the spread of invasive species. The ideal ballast water treatment system (BWTS) would kill 100% of ballast water organisms with minimal residual toxicity to organisms in receiving waters. In the present study, the residual toxicity and chemistry of a BWTS was evaluated. Sodium hydroxide was added to elevate pH to >11.5 to kill ballast water organisms, then reduced to pH <9 by sparging with wet-scrubbed diesel exhaust (the source of CO2). Cladocerans (Ceriodaphnia dubia), amphipods (Hyalella azteca), and fathead minnows (Pimephales promelas) were exposed for 2 d to BWTS water under an air atmosphere (pH drifted to ≥9) or a 2.5% CO2 atmosphere (pH 7.5–8.2), then transferred to control water for 5 d to assess potential delayed toxicity. Chemical concentrations in the BWTS water met vessel discharge guidelines with the exception of concentrations of copper. There was little to no residual toxicity to cladocerans or fish, but the BWTS water was toxic to amphipods. Maintaining a neutral pH and diluting BWTS water by 50% eliminated toxicity to the amphipods. The toxicity of BWTS water would likely be minimal because of rapid dilution in the receiving water, with subsurface release likely preventing pH rise. This BWTS has the potential to become a viable method for treating ballast water released into freshwater systems.

[Wastewater from the condensation and drying section of ABS was pretreated by microelectrolysis].

PubMed

Lai, Bo; Qin, Hong-Ke; Zhou, Yue-Xi; Song, Yu-Dong; Cheng, Jia-Yun; Sun, Li-Dong

2011-04-01

Wastewater from the condensation and drying section of acrylonitrile-butadiene-styrene (ABS) resin plant was pretreated by the microelectrolysis, and the effect of the influent pH value on the pollution removal efficiency of the microelectrolysis was mainly studied. In order to study the electrochemical action of the microelectrolysis for the degradation of toxic refractory organic pollutants, two control experiments of activated carbon and iron were set up. The results showed that the TOC removal efficiencies were all fluctuated between 40% and 60% under the condition of different influent pH values. The microelectrolysis can decompose and transform the toxic refractory organic pollutants and increase the BOD5/COD ratio from 0.32 to 0.60, which increased the biodegradability of ABS resin wastewater significantly. When the pH value of influent was 4.0, the BOD5/COD ratio of effluent reached 0.71. The result of UV-vis spectra indicates that the removal efficiency of the organic nitrile was the highest with influent pH was 4.0. Therefore, the best influent pH value of microelectrolysis was 4.0.

46 CFR 52.25-10 - Organic fluid vaporizer generators (modifies PVG-1 through PVG-12).

Code of Federal Regulations, 2011 CFR

2011-10-01

... 46 Shipping 2 2011-10-01 2011-10-01 false Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). 52.25-10 Section 52.25-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Other Boiler Types § 52.25-10 Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). (a) Organic...

46 CFR 52.25-10 - Organic fluid vaporizer generators (modifies PVG-1 through PVG-12).

Code of Federal Regulations, 2014 CFR

2014-10-01

... 46 Shipping 2 2014-10-01 2014-10-01 false Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). 52.25-10 Section 52.25-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Other Boiler Types § 52.25-10 Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). (a) Organic...

46 CFR 52.25-10 - Organic fluid vaporizer generators (modifies PVG-1 through PVG-12).

Code of Federal Regulations, 2013 CFR

2013-10-01

... 46 Shipping 2 2013-10-01 2013-10-01 false Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). 52.25-10 Section 52.25-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Other Boiler Types § 52.25-10 Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). (a) Organic...

46 CFR 52.25-10 - Organic fluid vaporizer generators (modifies PVG-1 through PVG-12).

Code of Federal Regulations, 2012 CFR

2012-10-01

... 46 Shipping 2 2012-10-01 2012-10-01 false Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). 52.25-10 Section 52.25-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Other Boiler Types § 52.25-10 Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). (a) Organic...

46 CFR 52.25-10 - Organic fluid vaporizer generators (modifies PVG-1 through PVG-12).

Code of Federal Regulations, 2010 CFR

2010-10-01

... 46 Shipping 2 2010-10-01 2010-10-01 false Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). 52.25-10 Section 52.25-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING POWER BOILERS Other Boiler Types § 52.25-10 Organic fluid vaporizer generators (modifies PVG-1 through PVG-12). (a) Organic...

Estimation of the toxicity of sulfadiazine to Daphnia magna using negligible depletion hollow-fiber liquid-phase microextraction independent of ambient pH

PubMed Central

Liu, Kailin; Xu, Shiji; Zhang, Minghuan; Kou, Yahong; Zhou, Xiaomao; Luo, Kun; Hu, Lifeng; Liu, Xiangying; Liu, Min; Bai, Lianyang

2016-01-01

The toxicity of ionizable organic compounds to organisms depends on the pH, which therefore affects risk assessments of these compounds. However, there is not a direct chemical method to predict the toxicity of ionizable organic compounds. To determine whether hollow-fiber liquid-phase microextraction (HF-LPME) is applicable for this purpose, a three-phase HF-LPME was used to measure sulfadiazine and estimate its toxicity to Daphnia magna in solutions of different pH. The result indicated that the sulfadiazine concentrations measured by HF-LPME decreased with increasing pH, which is consistent with the decreased toxicity. The concentration immobilize 50% of the daphnids (EC50) in 48 h calculated from nominal concentrations increased from 11.93 to 273.5 mg L−1 as the pH increased from 6.0 to 8.5, and the coefficient of variation (CV) of the EC50 values reached 104.6%. When calculated from the concentrations measured by HF-LPME (pH 12 acceptor phase), the EC50 ranged from 223.4 to 394.6 mg L−1, and the CV decreased to 27.60%, suggesting that the concentrations measured by HF-LPME can be used to estimate the toxicity of sulfadiazine irrespective of the solution pH. PMID:28004779

Curcumin modifies Apc(min) apoptosis resistance and inhibits 2-amino 1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) induced tumour formation in Apc(min) mice.

PubMed

Collett, G P; Robson, C N; Mathers, J C; Campbell, F C

2001-05-01

Curcumin, the active ingredient of the rhizome of Curcuma longa, promotes apoptosis and may have chemopreventive properties. This study investigates the effects of curcumin on apoptosis and tumorigenesis in male Apc(min) mice treated with the human dietary carcinogen, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). Intestinal epithelial apoptotic index in response to PhIP treatment was approximately twice as great in the wild-type C57BL/6 APC(+/+) strain than in Apc(min) mice (3.7% Apc(+/+) versus 1.9% Apc(min); P < 0.001). PhIP promoted tumour formation in Apc(min) proximal small intestine (4.6 tumours per mouse, PhIP treated versus 2.1 tumours per mouse, control untreated; P < 0.05). Curcumin enhanced PhIP-induced apoptosis (4.0% curcumin + PhIP versus 2.1% PhIP alone; P < 0.01) and inhibited PhIP-induced tumorigenesis in the proximal small intestine of Apc(min) mice (2.2 tumours per mouse, curcumin + PhIP versus 4.6 tumours per mouse PhIP alone; P < 0.05). This study shows that the Apc(min) genotype is associated with resistance to PhIP-induced apoptosis in intestinal epithelium. Curcumin attenuates Apc(min) resistance to PhIP-induced apoptosis and inhibits PhIP-induced tumorigenesis in proximal Apc(min) mouse small intestine.

40 CFR 720.30 - Chemicals not subject to notification requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... modifier, pH neutralizer, sequesterant, coagulant, flocculant, fire retardant, lubricant, chelating agent... plastic or rubber molding compounds, inks, drying oils, metal finishing compounds, adhesives, or paints...

Farmers prevailing perception profiles regarding GM crops: A classification proposal.

PubMed

Almeida, Carla; Massarani, Luisa

2018-04-01

Genetically modified organisms have been at the centre of a major public controversy, involving different interests and actors. While much attention has been devoted to consumer views on genetically modified food, there have been few attempts to understand the perceptions of genetically modified technology among farmers. By investigating perceptions of genetically modified organisms among Brazilian farmers, we intend to contribute towards filling this gap and thereby add the views of this stakeholder group to the genetically modified debate. A comparative analysis of our data and data from other studies indicate there is a complex variety of views on genetically modified organisms among farmers. Despite this diversity, we found variations in such views occur within limited parameters, concerned principally with expectations or concrete experiences regarding the advantages of genetically modified crops, perceptions of risks associated with them, and ethical questions they raise. We then propose a classification of prevailing profiles to represent the spectrum of perceptions of genetically modified organisms among farmers.

Dissolution kinetics of a lunar glass simulant at 25 degrees C: the effect of pH and organic acids

NASA Technical Reports Server (NTRS)

Eick, M. J.; Grossl, P. R.; Golden, D. C.; Sparks, D. L.; Ming, D. W.

1996-01-01

The dissolution kinetics of a simulated lunar glass were examined at pH 3, 5, and 7. Additionally, the pH 7 experiments were conducted in the presence of citric and oxalic acid at concentrations of 2 and 20 mM. The organic acids were buffered at pH 7 to examine the effect of each molecule in their dissociated form. At pH 3, 5, and 7, the dissolution of the synthetic lunar glass was observed to proceed via a two-stage process. The first stage involved the parabolic release of Ca, Mg, Al, and Fe, and the linear release of Si. Dissolution was incongruent, creating a leached layer rich in Si and Ti which was verified by transmission electron microscopy (TEM). During the second stage the release of Ca, Mg, Al, and Fe was linear. A coupled diffusion/surface dissolution model was proposed for dissolution of the simulated lunar glass at pH 3, 5, and 7. During the first stage the initial release of mobile cations (i.e., Ca, Mg, Al, Fe) was limited by diffusion through the surface leached layer of the glass (parabolic release), while Si release was controlled by the hydrolysis of the Si-O-Al bonds at the glass surface (linear release). As dissolution continued, the mobile cations diffused from greater depths within the glass surface. A steady-state was then reached where the diffusion rate across the increased path lengths equalled the Si release rate from the surface. In the presence of the organic acids, the dissolution of the synthetic lunar glass proceeded by a one stage process. The release of Ca, Mg, Al, and Fe followed a parabolic relationship, while the release of Si was linear. The relative reactivity of the organic acids used in the experiments was citrate > oxalate. A thinner leached layer rich in Si/Ti, as compared to the pH experiments, was observed using TEM. Rate data suggest that the chemisorption of the organic anion to the surface silanol groups was responsible for enhanced dissolution in the presence of the organic acids. It is proposed that the increased rate of Si release is responsible for the one stage parabolic release of mobile cations and the relatively thin leached layer compared to experiments at pH 3 and 5.

Aryl-modified graphene quantum dots with enhanced photoluminescence and improved pH tolerance

NASA Astrophysics Data System (ADS)

Luo, Peihui; Ji, Zhe; Li, Chun; Shi, Gaoquan

2013-07-01

Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed.Chemical modification is an important technique to modulate the chemical and optical properties of graphene quantum dots (GQDs). In this paper, we report a versatile diazonium chemistry method to graft aryl groups including phenyl, 4-carboxyphenyl, 4-sulfophenyl and 5-sulfonaphthyl to GQDs via Gomberg-Bachmann reaction. The aryl-modified GQDs are nanocrystals with lateral dimensions in the range of 2-4 nm and an average thickness lower than 1 nm. Upon chemical modification with aryl groups, the photoluminescence (PL) bands of GQDs were tuned in the range of 418 and 447 nm, and their fluorescence quantum yields (QYs) were increased for up to about 6 times. Furthermore, the aryl-modified GQDs exhibited stable PL (both intensity and peak position) in a wide pH window of 1-11. The mechanism of improving the PL properties of GQDs by aryl-modification was also discussed. Electronic supplementary information (ESI) available: Fluorescence quantum yield measurements, estimation of grafting ratio, TEM images, FTIR spectra, PL spectra and zeta potentials. See DOI: 10.1039/c3nr02156d

UPTAKE AND ELIMINATION OF IONIZABLE ORGANIC CHEMICALS AT FISH GILLS: PART I. MODEL FORMULATION, PARAMETERIZATION, AND BEHAVIOR

EPA Science Inventory

Effects of pH and alkalinity on uptake and elimination of ionizable organic chemicals at the gills of large rainbow trout were studied. Increased pH reduced uptake rates of weakly-acidic chlorinated phenols and increased that of weakly-basic 3,4-dichlorobenzylamine, indicating gr...

Psycho Educational Group Intervention for Women at Increased Risk for Breast Cancer

DTIC Science & Technology

1998-10-01

INVESTIGATOR: Kathryn M. Kash, Ph.D. CONTRACTING ORGANIZATION: Strang Cancer Prevention Center New York, New York 10021 REPORT DATE: October 1998 TYPE OF...M. Kash, Ph.D. 5. FUNDING NUMBERS DAMD17-94-J-4333 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Strang Cancer Prevention Center New York... New York 10021 E-MAIL: kmkash@earthlink.net 8. PERFORMING ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES

BRCA1 and BRCA2 Mutations in African Americans

DTIC Science & Technology

2000-10-01

BRCA2 Mutations in African Americans PRINCIPAL INVESTIGATOR: Carolyn W. Broome, Ph.D. CONTRACTING ORGANIZATION: Howard University Washington, DC 20059...DAMD17-98-1-8106 6. AUTHOR(S) Carolyn W. Broome, Ph.D. 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION Howard University REPORT... Howard University Women’s Health Institute, Washington DC, April, 1999. The Proceedings of Health Issues and Concerns of Women of Color: A Call to

Dynamics of aluminum speciation in forest-well drainage waters from the Rhode River watershed, Maryland.

PubMed

Bi, S P; An, S Q; Yang, M; Chen, T

2001-05-01

This paper reports an investigation of the dynamics of aluminum (Al) speciation in the forest-well waters from study site 110 of the Rhode River watershed, a representative sub-unit of Chesapeake Bay. Seasonal changes of Al speciation are evaluated by a modified MINEQL computer model using chemical equilibrium calculation. It was found that Al-F and Al-Org complexes were the dominate forms, whereas toxic forms of Al3+ and Al-OH were not significant. This indicates that Al toxicity is not very serious in the Rhode River area due to the high concentrations of fluoride and organic materials, even though sometimes pH is very low (approximately 4). Increased H+ or some other associated factors may be responsible for the decline in fish and amphibian population on the watershed.

Enantioseparations of amino acids by capillary array electrophoresis with 532 nm laser induced fluorescence detection.

PubMed

Liu, Kaiying; Wang, Li

2013-06-21

Capillary array electrophoresis (CAE) is a promising technique for multiple enantiomeric separations. Carboxytetramethylrhodamine succinimidyl ester (TAMRA SE), a rhodamine-core fluorescent probe, has rarely been applied as an original precolumn derivatization reagent for chiral amino acid (AA) analysis so far. For these purposes, high-throughput enantiomeric separations of 12 TAMRA SE-AAs by a home-made 532 nm CAE-LIF scanner are presented. The effect of cyclodextrins (CDs) and a variety of organic modifiers was quickly investigated. Baseline separations were achieved in 100 mM Tris-borate buffer (pH 10.0) containing 2 mM β-CD and 10 mM hexamethylenediamine (HDA). Multiple determination of the enantiomeric excess (ee) in non-racemic mixtures of alanine is successfully presented. Copyright © 2013 Elsevier B.V. All rights reserved.

Detoxification of zearalenone from corn oil by adsorption of functionalized GO systems

NASA Astrophysics Data System (ADS)

Bai, Xiaojuan; Sun, Changpo; Xu, Jing; Liu, Di; Han, Yangying; Wu, Songling; Luo, Xiaohong

2018-02-01

Graphene oxide (GO) and its functionalized systems have very unique structural advantages as excellent adsorbent or substrate material in the removal of organic contaminants. Herein, we reported a strategy to establish functionalized GO system (FGO) using amphiphilic molecules didodecyldimethylammonium bromide (DDAB) as a modifier for the detoxification of zearalenone (ZEN) from corn oil. The adsorption property for the removal of ZEN from edible corn oils under different experimental conditions such as pH, amphiphilic molecules, time and temperature was investigated in detail. The morphology structure, adsorption isotherm, adsorption kinetics and the recyclability of FGO systems have also been researched, systematically. The FGO systems exhibit a higher adsorption efficiency, recyclability and thermostability in comparison with the traditional adsorbent materials. It provides an insight into the detoxification of mycotoxin from edible oils by graphene-based new materials.

In Situ Determination of Bisphenol A in Beverage Using a Molybdenum Selenide/Reduced Graphene Oxide Nanoparticle Composite Modified Glassy Carbon Electrode.

PubMed

Shi, Rongguang; Liang, Jing; Zhao, Zongshan; Liu, Yi; Liu, Aifeng

2018-05-22

Due to the endocrine disturbing effects of bisphenol A (BPA) on organisms, rapid detection has become one of the most important techniques for monitoring its levels in the aqueous solutions associated with plastics and human beings. In this paper, a glassy carbon electrode (GCE) modified with molybdenum selenide/reduced graphene oxide (MoSe₂/rGO) was fabricated for in situ determination of bisphenol A in several beverages. The surface area of the electrode dramatically increases due to the existence of ultra-thin nanosheets in a flower-like structure of MoSe₂. Adding phosphotungstic acid in the electrolyte can significantly enhance the repeatability (RSD = 0.4%) and reproducibility (RSD = 2.2%) of the electrode. Under the optimized condition (pH = 6.5), the linear range of BPA was from 0.1 μM⁻100 μM and the detection limit was 0.015 μM (S/ N = 3). When using the as-prepared electrode for analyzing BPA in beverage samples without any pretreatments, the recoveries ranged from 98⁻107%, and the concentrations were from below the detection limit to 1.7 μM, indicating its potential prospect for routine analysis of BPA.

Cholic acid modified N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride for superoxide dismutase delivery.

PubMed

Cheng, Ye; Cai, Huanxin; Yin, Baoru; Yao, Ping

2013-09-15

A series of novel amphiphilic chitosan derivatives, cholic acid modified N-(2-hydroxy)-propyl-3-trimethylammonium chitosan chloride (HTCC-CA) with different quaternization degrees and cholic acid substitutions were synthesized in this study. HTCC-CA is biocompatible and forms particles in aqueous solution. The binding with superoxide dismutase (SOD) at pH 6.8 destroys the original aggregates of HTCC-CA and produces smaller SOD/HTCC-CA complex nanoparticles via electrostatic and hydrophobic interactions. The SOD loading efficiency and loading capacity of HTCC-CA can reach to more than 90% and 45%, respectively. Confocal laser scanning microscopy observation and flow cytometry analysis reveal that SOD/HTCC-CA complex nanoparticles greatly enhance the cellular internalization of the loaded SOD. The SOD activities and malonaldehyde concentrations in the serum and organs of the rats, administrated intravenously with free SOD, free HTCC-CA, and SOD/HTCC-CA nanoparticles, were assayed to evaluate the antioxidant efficiency in vivo. The results demonstrate that free HTCC-CA is effective to scavenge superoxide radicals in the blood circulation and SOD/HTCC-CA nanoparticles have better antioxidant efficiency than free SOD as well as free HTCC-CA. Copyright © 2013 Elsevier B.V. All rights reserved.

Dual-Emitting Fluorescent Metal-Organic Framework Nanocomposites as a Broad-Range pH Sensor for Fluorescence Imaging.

PubMed

Chen, Haiyong; Wang, Jing; Shan, Duoliang; Chen, Jing; Zhang, Shouting; Lu, Xiaoquan

2018-05-15

pH plays an important role in understanding physiological/pathologic processes, and abnormal pH is a symbol of many common diseases such as cancer, stroke, and Alzheimer's disease. In this work, an effective dual-emission fluorescent metal-organic framework nanocomposite probe (denoted as RB-PCN) has been constructed for sensitive and broad-range detection of pH. RB-PCN was prepared by encapsulating the DBI-PEG-NH 2 -functionalized Fe 3 O 4 into Zr-MOFs and then further reacting it with rhodamine B isothiocyanates (RBITC). In RB-PCN, RBITC is capable of sensing changes in pH in acidic solutions. Zr-MOFs not only enrich the target analyte but also exhibit a fluorescence response to pH changes in alkaline solutions. Based on the above structural and compositional features, RB-PCN could detect a wide range of pH changes. Importantly, such a nanoprobe could "see" the intracellular pH changes by fluorescence confocal imaging as well as "measure" the wider range of pH in actual samples by fluorescence spectroscopy. To the best of our knowledge, this is the first time a MOF-based dual-emitting fluorescent nanoprobe has been used for a wide range of pH detection.

Evaluation for rock phosphate solubilization in fermentation and soil-plant system using a stress-tolerant phosphate-solubilizing Aspergillus niger WHAK1.

PubMed

Xiao, Chunqiao; Zhang, Huaxiang; Fang, Yujuan; Chi, Ruan

2013-01-01

A strain WHAK1, identified as Aspergillus niger, was isolated from Yichang phosphate mines in Hubei province of China. The fungus developed a phosphate solubilization zone on modified National Botanical Research Institute's phosphate growth (NBRIP) agar medium, supplemented with tricalcium phosphate. The fungus was applied in a repeated-batch fermentation process in order to test its effect on solubilization of rock phosphate (RP). The results showed that A. niger WHAK1 could effectively solubilize RP in NBRIP liquid medium and released soluble phosphate in the broth, which can be illustrated by the observation of scanning electron microscope, energy-dispersive X-ray microanalysis, and Fourier transform infrared spectroscopy. Acidification of the broth seemed to be the major mechanism for RP solubilization by the fungus. Indeed, multiple organic acids (mainly gluconic acid) were detected in the broth by high-performance liquid chromatography analysis. These organic acids caused a significant drop of pH and an obvious rise of titratable acidity in the broth. The fungus also exhibited high levels of tolerance against temperature, pH, salinity, and desiccation stresses, although a significant decline in the fungal growth and release of soluble phosphate was marked under increasing intensity of stress parameters. Further, the fungus was introduced into the soil supplemented with RP to analyze its effect on plant growth and phosphate uptake of wheat plants. The result revealed that inoculation of A. niger WHAK1 significantly increased the growth and phosphate uptake of wheat plants in the RP-amended soil compared to the control soil.

Synthesis, characterization, and reactivity of cellulose modified nano zero-valent iron for dye discoloration

NASA Astrophysics Data System (ADS)

Wang, Xiangyu; Wang, Pei; Ma, Jun; Liu, Huiling; Ning, Ping

2015-08-01

Nano zero-valent iron (NZVI) was innovatively and successfully modified by using hydroxyethyl cellulose (HEC) and hydroxypropylmethyl cellulose (HPMC) as dispersants. The systematic characterization observations (including XRD, SEM and TEM) illustrate that, compared with bare nano zero-valent iron particles (BNZVI), the particle sizes of hydroxyethyl cellulose modified (ENZVI) and hydroxypropylmethyl cellulose modified (PNZVI) were decreased, while the dispersity and antioxidizability of ENZVI and PNZVI particles were increased. The discoloration efficiencies of ENZVI, PNZVI, and BNZVI were compared by using dyes (including orange II, methyl orange, methyl blue, and methylene blue) as target pollutant. The results show that both the discoloration efficiency and reaction rate of ENZVI and PNZVI are higher than that of BNZVI. In addition, effects of dispersant content, dye type, pH value, initial dye concentration, iron dosage, and reaction temperature on discoloration efficiencies were studied. The results show that discoloration efficiency was decreased by increasing initial pH value and dye concentration, and it was increased with the increase the iron dosage and reaction temperature. Under optimized NZVI addition of 0.7 g L-1, the discoloration efficiencies of ENZVI and PNZVI were increased to 96.33% and 98.62%, respectively. And the possible discoloration pathway and dispersant modification mechanism of NZVI were discussed. This study suggests hydroxyethyl cellulose and hydroxypropylmethyl cellulose dispersed NZVI can be utilized as a promising modified nano-material for degradation of dye wastewater.

In situ characterization of organo-modified and unmodified montmorillonite aqueous suspensions by UV-visible spectroscopy.

PubMed

Alin, Jonas; Rubino, Maria; Auras, Rafael

2015-10-15

UV-visible (UV-Vis) spectroscopy (Tyndall spectra) was applied and tested for its ability to measure organo-modified and unmodified montmorillonite (MMT) clays in aqueous suspensions. A full factorial design of experiments was used to study the influence of pH, NaCl and clay concentrations on the average particle size of the clay agglomerates. The methodology was evaluated by observing results that were consistent with previous research about the unmodified clay's behavior in aqueous suspensions. The results from this evaluation corresponded to accepted theories about the unmodified clay's behavior, indicating that the methodology is precise enough to distinguish the effects of the studied factors on these clay suspensions. The effect of clay concentration was related to the amount of ions per clay particle for the unmodified clay, but was not significant for the organo-modified MMT. The average particle size of the organo-modified MMT in suspension was significantly larger than that of the unmodified clay. Size of the organo-modified MMT agglomerates in suspension decreased in the presence of NaCl and at both high and low pH; this behavior was opposite to that of the unmodified clay. These results demonstrate that the UV-Vis methodology is well-suited for characterizing clay particle size in aqueous suspensions. The technique also is simple, rapid, and low-cost. Copyright © 2015 Elsevier Inc. All rights reserved.

Modification of chitosan by swelling and crosslinking using epichlorohydrin as heavy metal Cr (VI) adsorbent in batik industry wastes

NASA Astrophysics Data System (ADS)

Hastuti, B.; Masykur, A.; Hadi, S.

2016-02-01

Study on chitosan modification by swelling and crosslinking and its application as a selective adsorbent for heavy metals Cr (VI) in batik industry wastes was done. Swelling is intended to improve chitosan porosity, whereas crosslinking is to increase the resistance of chitosan against acid. Natural samples are generally acidic, thus limiting chitosan application as an adsorbent. Modification of chitosan by combining swelling and crosslinking is expected to increase its adsorption capacity in binding heavy metal ions in water. The modified chitosan was later contacted with Cr (VI) to test its adsorption capacity with a variation of pH and contact time. Finally, application of modified chitosan was done in batik industry waste containing Cr (IV). Based on the results, chitosan-ECH 25% (v/v) was the optimum concentration of crosslinker to adsorb Cr (VI) ions. Modified chitosan has a solubility resistance to acids, even though a strong acid. Modification of chitosan also improved its adsorption capacity to Cr (VI) from 74% (pure chitosan) to 89% with contact time 30 min at pH 3. On the application to the batik wastes, the modified chitosan were able to adsorb Cr (IV) up to the level of 5 ppm. Thus, the modified chitosan has a potential to be applied to as an adsorbent of Cr (VI) in batik industry wastes.

Bioavailability of classical and novel flame retardants: Effect of fullerene presence.

PubMed

Santín, Giselle; Eljarrat, Ethel; Barceló, Damià

2016-09-15

To understand the behavior of some emerging flame retardants (FRs) in the environment, a nonexhaustive extraction using Tenax was applied to study their behavior in aquatic ecosystems. Desorption of 8 polybrominated diphenyl ethers (PBDEs), 8 methoxylated PBDEs, 3 emerging brominated FRs and 6 halogenated norbornenes from sediments spiked in the laboratory was studied. Results showed that emerging FRs have a similar bioavailability than that of legacy FRs, already banned. In addition, some parameters such as sediment total organic carbon (TOC), aging or nanomaterial (NMs) presence in the sediment were modified in order to study their effects on the bioavailability of FRs. Bioavailability increases with a diminution of sediment TOC, while diminishes with an increase of aging. The study of effect of NM presence was performed at three different pH (acidic, neutral and basic), and for the three scenarios, FR bioavailability decreased with NM presence. The retention of pollutants in the sediment seems to be favoured by NM presence, minimizing their impact on living organisms. Copyright © 2016 Elsevier B.V. All rights reserved.

Organoclay nanocomposites of post-industrial waste poly(butylene terephthalate) from automotive parts.

PubMed

Quispe, Noe B; Fernandes, Elizabeth G; Zanata, Fernanda; Bartoli, Julio R; Souza, Diego H S; Ito, Edson N

2015-10-01

Polymeric nanocomposites are novel materials of huge interest owing to their favourable cost/performance ratio with low amount of nanofillers, improved thermal resistance, flame retardancy and mechanical properties in relation to their matrices. In this work, composites based on post-industrial waste or primary recycled poly(butylene terephthalate) and 5 wt.% of organic modified montmorillonite clays were melt compounded using a twin-screw extruder. A 2(2) factorial experimental design was used to study the compounding and processing variables: Organic modified montmorillonite with one or two hydrogenated tallow (initial basal spacing) and screw speed of the extruder. X-ray diffraction and transmission electron microscopy suggest that a partial exfoliation of the organoclay in the recycled poly(butylene terephthalate) matrix was achieved for organic modified montmorillonite with lower initial basal spacing. On the other hand, formulations containing organic modified montmorillonite with higher initial basal spacing showed only intercalated structure. The recycled poly(butylene terephthalate)-organic modified montmorillonite nanocomposites did not drip flaming material during burning tests. Storage of dynamic-mechanical, tensile and flexural moduli of the recycled poly(butylene terephthalate)-organic modified montmorillonite were improved when compared with both virgin and recycled poly(butylene terephthalate)s, mainly for nanocomposites formulated at a lower initial basal spacing organoclay. This could be related to a better diffusion of polymer into organic modified montmorillonite layers compared with the higher initial basal spacing organoclay. The improvements on the physical properties of recycled poly(butylene terephthalate) showed the feasibility to add value to primary recycled engineering thermoplastics with a very small amount of organic modified montmorillonite. © The Author(s) 2015.

Novel approach for modifying microporous filters for virus concentration from water.

PubMed Central

Preston, D R; Vasudevan, T V; Bitton, G; Farrah, S R; Morel, J L

1988-01-01

Electronegative microporous filters composed of epoxyfiberglass (Filterite) were treated with cationic polymers to enhance their virus-adsorbing properties. This novel and inexpensive approach to microporous filter modification entails soaking filters in an aqueous solution of a cationic polymer such as polyethyleneimine (PEI) for 2 h at room temperature and then allowing the filters to air dry overnight on absorbent paper towels. PEI-treated filters were evaluated for coliphage (MS2, T2, and phi X174) and enterovirus (poliovirus type 1 and coxsackievirus type B5) adsorption from buffer at pH 3.5 to 9.0 and for indigenous coliphages from unchlorinated secondary effluent at ambient pH. Adsorbed viruses were recovered with 3% beef extract (pH 9). Several other cationic polymers were used to modify epoxyfiberglass filters and were evaluated for their ability to concentrate viruses from water. Zeta potentials of disrupted filter material indicated that electronegative epoxyfiberglass filters were made more electropositive when treated with cationic polymers. In general, epoxyfiberglass filters treated with cationic polymers were found to adsorb a greater percentage of coliphages and enteroviruses than were untreated filters. PMID:2843091

Engineering birnessite-type MnO2 nanosheets on fiberglass for pH-dependent degradation of methylene blue

NASA Astrophysics Data System (ADS)

Xin Zhang, Yu; Long Guo, Xiao; Huang, Ming; Dong Hao, Xiao; Yuan, Yuan; Hua, Chao

2015-08-01

We construct hierarchical MnO2 nanosheets @ fiberglass nanostructures via one-pot hydrothermal method without any surfactants. The morphology and structure of MnO2-modified fiberglass composites are examined by focus ion beam scanning electron microscopy (FIB/SEM), X-Ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The birnessite-type MnO2 nanosheets are observed to grow vertically on the surface of fiberglass. Furthermore, the birnessite-type MnO2-fiberglass composites exhibit good ability for degradation of methylene blue (MB) in different pH levels. In neutral solution (pH 6.5-7.0), it achieves a high removal rate of 96.1% (2 h, at 60 °C) in the presence of H2O2; and in acidic environment (pH 1.5), 96.8% of MB solution (20 mg/L, 100 mL) is decomposed by oxidation within only 5 min. In principles, the rational design of MnO2 nanosheets-decorated fiberglass architectures demonstrated the suitability of the low-cost MnO2-modified fiberglass nanostructure for water treatment.

Net acidity indicates the whole effluent toxicity of pH and dissolved metals in metalliferous saline waters.

PubMed

Degens, Bradley P; Krassoi, Rick; Galvin, Lynette; Reynolds, Brad; Micevska, Tina

2018-05-01

Measurements of potential acidity in water are used to manage aquatic toxicity risks of discharge from acid sulfate soils or acid mine drainage. Net acidity calculated from pH, dissolved metals and alkalinity is a common measurement of potential acidity but the relevance of current risk thresholds to aquatic organisms are unclear. Aquatic toxicity testing was carried out using four halophytic organisms with water from four saline sources in southern Western Australia (3 acidic drains and one alkaline river; 39-40 g TDS/L) where acidity was varied by adjusting pH to 4.5-6.5. The test species were brine shrimps (Artemia salina), locally sourced ostracods (Platycypris baueri), microalgae (Dunaliella salina) and amphipods (Allorchestes compressa). Testing found the EC 10 and IC 10 of net acidity ranged from -7.8 to 10.5 mg CaCO 3 /L with no survival or growth of any species at >47 mg CaCO 3 /L. Reduced net acidity indicated reduced whole effluent toxicity more reliably than increased pH alone with organisms tolerating pH up to 1.1 units lower in the absence of dissolved metals. Variation in toxicity indicated by net acidity was mostly attributed to reduced concentrations of dissolved Al and Fe combined with higher pH and alkalinity and some changes in speciation of Al and Fe with pH. These results indicate that rapid in-field assessments of net acidity in acidic, Al dominated waters may be an indicator of potential acute and sub-chronic impacts on aquatic organisms. Crown Copyright © 2018. Published by Elsevier Ltd. All rights reserved.

The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH.

PubMed

Al-Reasi, Hassan A; Yusuf, Usman; Smith, D Scott; Wood, Chris M

2013-11-01

Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~5), to examine DOM effects on whole-body Na(+) concentration, unidirectional influx and efflux rates of Na(+), and ammonia and urea excretion rates in Daphnia magna. Whole-body Na(+) concentration, Na(+) influx, and Na(+) efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na(+) in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI). © 2013.

Analytical Method for Determining Tetrazene in Water.

DTIC Science & Technology

1987-12-01

8217-decanesulfonic acid sodium salt. The mobile phase pH was adjusted to 3 with glacial acetic acid. The modified mobile phase was optimal for separating of...modified with sodium tartrate, gave a well-defined reduction wave at the dropping mercury electrode. The height of the reduction wave was proportional to...anitmony trisulphide, nitrocellulose, PETN, powdered aluminum and calcium silicide . The primer samples were sequentially extracted, first with

Removal of 2,4-Dichlorophenolyxacetic acid (2,4-D) herbicide in the aqueous phase using modified granular activated carbon

PubMed Central

2014-01-01

Background Low cost 2,4-Dichlorophenolyxacetic acid (2,4-D) widely used in controlling broad-leafed weeds is frequently detected in water resources. The main objectives of this research were focused on evaluating the feasibility of using granular activated carbon modified with acid to remove 2,4-D from aqueous phase, determining its removal efficiency and assessing the adsorption kinetics. Results The present study was conducted at bench-scale method. The influence of different pH (3–9), the effect of contact time (3–90 min), the amount of adsorbent (0.1-0.4 g), and herbicide initial concentration (0.5-3 ppm) on 2,4-D removal efficiency by the granular activated carbon were investigated. Based on the data obtained in the present study, pH of 3 and contact time of 60 min is optimal for 2,4-D removal. 2,4-D reduction rate increased rapidly by the addition of the adsorbent and decreased by herbicide initial concentration (63%). The percent of 2,4-D reduction were significantly enhanced by decreasing pH and increasing the contact time. The adsorption of 2,4-D onto the granular activated carbon conformed to Langmuir and Freundlich models, but was best fitted to type II Langmuir model (R2 = 0.999). The second order kinetics was the best for the adsorption of 2,4-D by modified granular activated carbon with R2 > 0.99. Regression analysis showed that all of the variables in the process have been statistically significant effect (p < 0.001). Conclusions In conclusion, granular activated carbon modified with acid is an appropriate method for reducing the herbicide in the polluted water resources. PMID:24410737