Electrochemical Induced Calcium Phosphate Precipitation: Importance of Local pH

PubMed Central

2017-01-01

Phosphorus (P) is an essential nutrient for living organisms and cannot be replaced or substituted. In this paper, we present a simple yet efficient membrane free electrochemical system for P removal and recovery as calcium phosphate (CaP). This method relies on in situ formation of hydroxide ions by electro mediated water reduction at a titanium cathode surface. The in situ raised pH at the cathode provides a local environment where CaP will become highly supersaturated. Therefore, homogeneous and heterogeneous nucleation of CaP occurs near and at the cathode surface. Because of the local high pH, the P removal behavior is not sensitive to bulk solution pH and therefore, efficient P removal was observed in three studied bulk solutions with pH of 4.0 (56.1%), 8.2 (57.4%), and 10.0 (48.4%) after 24 h of reaction time. While P removal efficiencies are not generally affected by bulk solution pH, the chemical-physical properties of CaP solids collected on the cathode are still related to bulk solution pH, as confirmed by structure characterizations. High initial solution pH promotes the formation of more crystalline products with relatively high Ca/P molar ratio. The Ca/P molar ratio increases from 1.30 (pH 4.0) to 1.38 (pH 8.2) and further increases to 1.55 (pH 10.0). The formation of CaP precipitates was a typical crystallization process, with an amorphous phase formed at the initial stage which then transforms to the most stable crystal phase, hydroxyapatite, which is inferred from the increased Ca/P molar ratio from 1.38 (day 1) to the theoretical 1.76 (day 11) and by the formation of needle-like crystals. Finally, we demonstrated the efficiency of this system for real wastewater. This, together with the fact that the electrochemical method can work at low bulk pH, without dosing chemicals and a need for a separation process, highlights the potential application of the electrochemical method for P removal and recovery. PMID:28872838

Variation in bacterial ATP concentration during rapid changes in extracellular pH and implications for the activity of attached bacteria.

PubMed

Albert, Lynal S; Brown, Derick G

2015-08-01

In this study we investigated the relationship between a rapid change in extracellular pH and the alteration of bacterial ATP concentration. This relationship is a key component of a hypothesis indicating that bacterial bioenergetics - the creation of ATP from ADP via a proton gradient across the cytoplasmic membrane - can be altered by the physiochemical charge-regulation effect, which results in a pH shift at the bacteria's surface upon adhesion to another surface. The bacterial ATP concentration was measured during a rapid change in extracellular pH from a baseline pH of 7.2 to pH values between 3.5 and 10.5. Experiments were conducted with four neutrophilic bacterial strains, including the Gram-negative Escherichia coli and Pseudomonas putida and the Gram-positive Bacillus subtilis and Staphylococcus epidermidis. A change in bulk pH produced an immediate response in bacterial ATP, demonstrating a direct link between changes in extracellular pH and cellular bioenergetics. In general, the shifts in ATP were similar across the four bacterial strains, with results following an exponential relationship between the extracellular pH and cellular ATP concentration. One exception occurred with S. epidermidis, where there was no variation in cellular ATP at acidic pH values, and this finding is consistent with this species' ability to thrive under acidic conditions. These results provide insight into obtaining a desired bioenergetic response in bacteria through (i) the application of chemical treatments to vary the local pH and (ii) the selection and design of surfaces resulting in local pH modification of attached bacteria via the charge-regulation effect. Copyright © 2015 Elsevier B.V. All rights reserved.

Extraction and characterization of oil bodies from soy beans: a natural source of pre-emulsified soybean oil.

PubMed

Iwanaga, Daigo; Gray, David A; Fisk, Ian D; Decker, Eric Andrew; Weiss, Jochen; McClements, David Julian

2007-10-17

Soybeans contain oil bodies that are coated by a layer of oleosin proteins. In nature, this protein coating protects the oil bodies from environmental stresses and may be utilized by food manufacturers for the same purpose. In this study, oil bodies were extracted from soybean using an aqueous extraction method that involved blending, dispersion (pH 8.6), filtration, and centrifugation steps. The influence of NaCl (0-250 mM), thermal processing (30-90 degrees C, 20 min) and pH (2-8) on the properties and stability of the oil bodies was analyzed using zeta-potential, particle size, and creaming stability measurements. The extracted oil bodies were relatively small ( d 32 approximately 250 nm), and their zeta-potential went from around +12 mV to -20 mV as the pH was increased from 2 to 8, with an isoelectric point around pH 4. The oil bodies were stable to aggregation and creaming at low (pH = 2) and high (pH >/= 6) pH values but were unstable at intermediate values (3

Diffusion of Eu(III) in compacted bentonite-effect of pH, solution concentration and humic acid.

PubMed

Wang, Xiangke; Chen, Yixue; Wu, Yican

2004-06-01

The effect of pH, Eu(III) solution concentration and humic acid on the diffusion of Eu(III) in compacted bentonite (rho(b) = 1000 +/- 30 kg/m(3)) was studied with "in-diffusion" method at an ionic strength of 0.1M NaClO(4). The results (K(d) values from the first slice and theoretical calculation, apparent and effective diffusion coefficients) derived from the new capillary method are in good agreement with the literature data under similar conditions, and fit the Fick's second law very well. The results suggest that the diffusion of Eu(III) is dependent on pH values and independent on solution concentration in our experimental conditions. Humic acid forms precipitation/complexation with Eu(III) at the surface of compacted bentonite and thus deduces the diffusion/transport of Eu(III) in compacted bentonite. The K(d) values in compacted bentonite are in most cases lower than those in powdered bentonite obtained from batch experiments. The difference between the K(d) values from powdered and compacted bentonite is a strong function of the bulk density of the bentonite. The results suggest that the content of interlaminary space plays a very important role to the diffusion, sorption and migration of Eu(III) in compacted bentonite.

Effect of glycine on pH changes and protein stability during freeze-thawing in phosphate buffer systems.

PubMed

Pikal-Cleland, Katherine A; Cleland, Jeffrey L; Anchordoquy, Thomas J; Carpenter, John F

2002-09-01

Previous studies have established that the selective precipitation of a less soluble buffer component during freezing can induce a significant pH shift in the freeze concentrate. During freezing of sodium phosphate solutions, crystallization of the disodium salt can produce a pH decrease as great as 3 pH units which can dramatically affect protein stability. The objective of our study was to determine how the presence of glycine (0-500 mM), a commonly used bulking agent in pharmaceutical protein formulations, affects the pH changes normally observed during freezing in sodium phosphate buffer solutions and to determine whether these pH changes contribute to instability of model proteins in glycine/phosphate formulations. During freezing in sodium phosphate buffers, the presence of glycine significantly influenced the pH. Glycine at the lower concentrations (< or = 50 mM) suppressed the pH decrease normally observed during freezing in 10 and 100 mM sodium phosphate buffer, possibly by reducing the nucleation rate of salt and thereby decreasing the extent of buffer salt crystallization. The presence of glycine at higher concentration (> 100 mM) in the sodium phosphate buffer resulted in a more complete crystallization of the disodium salt as indicated by the frozen pH values closer to the equilibrium value (pH 3.6). Although high concentrations of glycine can facilitate more buffer salt crystallization and these pH shifts may prove to be potentially damaging to the protein, glycine, in its amorphous state, can also act to stabilize a protein via the preferential exclusion mechanism. Copyright 2002 Wiley-Liss Inc.

O(2)-dependent K(+) fluxes in trout red blood cells: the nature of O(2) sensing revealed by the O(2) affinity, cooperativity and pH dependence of transport.

PubMed

Berenbrink, M; Völkel, S; Heisler, N; Nikinmaa, M

2000-07-01

The effects of pH and O(2) tension on the isotonic ouabain-resistant K(+) (Rb+) flux pathway and on haemoglobin O2 binding were studied in trout red blood cells (RBCs) in order to test for a direct effect of haemoglobin O(2) saturation on K(+) transport across the RBC membrane. At pH values corresponding to in vivo control arterial plasma pH and higher, elevation of the O(2) partial pressure (PO(2)) from 7.8 to 157 mmHg increased unidirectional K(+) influx across the RBC membrane several-fold. At lower extracellular pH values, stimulation of K(+) influx by O(2) was depressed, exhibiting an apparent pK(a) (pK'(a)) for the process of 8.0. Under similar conditions the pK'(a) for acid-induced deoxygenation of haemoglobin (Hb) was 7.3. When trout RBCs were exposed to PO(2) values between 0 and 747 mmHg, O(2) equilibrium curves typical of Hb O(2) saturation were also obtained for K(+) influx and efflux. However, at pH 7.9, the PO(2) for half-maximal K(+) efflux and K(+) influx (P50) was about 8- to 12-fold higher than the P(50) for Hb-O(2) binding. While K(+) influx and efflux stimulation by O(2) was essentially non-cooperative, Hb-O(2) equilibrium curves were distinctly sigmoidal (Hill parameters close to 1 and 3, respectively). O(2)-stimulated K(+) influx and efflux were strongly pH dependent. When the definition of the Bohr factor for respiratory pigments (Phi = delta logP50 x delta pH(-1)) was extended to the effect of pH on O(2)-dependent K(+) influx and efflux, extracellular Bohr factors (Phi(o) of -2.00 and -2.06 were obtained, values much higher than that for Hb (Phi(o) = -0.49). The results of this study are consistent with an O(2) sensing mechanism differing markedly in affinity and cooperativity of O(2) binding, as well as in pH sensitivity, from bulk Hb.

Stochastic multicomponent reactive transport analysis of low quality drainage release from waste rock piles: Controls of the spatial distribution of acid generating and neutralizing minerals.

PubMed

Pedretti, Daniele; Mayer, K Ulrich; Beckie, Roger D

2017-06-01

In mining environmental applications, it is important to assess water quality from waste rock piles (WRPs) and estimate the likelihood of acid rock drainage (ARD) over time. The mineralogical heterogeneity of WRPs is a source of uncertainty in this assessment, undermining the reliability of traditional bulk indicators used in the industry. We focused in this work on the bulk neutralizing potential ratio (NPR), which is defined as the ratio of the content of non-acid-generating minerals (typically reactive carbonates such as calcite) to the content of potentially acid-generating minerals (typically sulfides such as pyrite). We used a streamtube-based Monte-Carlo method to show why and to what extent bulk NPR can be a poor indicator of ARD occurrence. We simulated ensembles of WRPs identical in their geometry and bulk NPR, which only differed in their initial distribution of the acid generating and acid neutralizing minerals that control NPR. All models simulated the same principal acid-producing, acid-neutralizing and secondary mineral forming processes. We show that small differences in the distribution of local NPR values or the number of flow paths that generate acidity strongly influence drainage pH. The results indicate that the likelihood of ARD (epitomized by the probability of occurrence of pH<4 in a mixing boundary) within the first 100years can be as high as 75% for a NPR=2 and 40% for NPR=4. The latter is traditionally considered as a "universally safe" threshold to ensure non-acidic waters in practical applications. Our results suggest that new methods that explicitly account for mineralogical heterogeneity must be sought when computing effective (upscaled) NPR values at the scale of the piles. Copyright © 2017 Elsevier B.V. All rights reserved.

Double-gated Si NW FET sensors: Low-frequency noise and photoelectric properties

NASA Astrophysics Data System (ADS)

Gasparyan, F.; Khondkaryan, H.; Arakelyan, A.; Zadorozhnyi, I.; Pud, S.; Vitusevich, S.

2016-08-01

The transport, noise, and photosensitivity properties of an array of silicon nanowire (NW) p+-p-p+ field-effect transistors (FETs) are investigated. The peculiarities of photosensitivity and detectivity are analyzed over a wide spectrum range. The absorbance of p-Si NW shifts to the short wavelength region compared with bulk Si. The photocurrent and photosensitivity reach increased values in the UV range of the spectrum at 300 K. It is shown that sensitivity values can be tuned by the drain-source voltage and may reach record values of up to 2-4 A/W at a wavelength of 300 nm at room temperature. Low-frequency noise studies allow calculating the photodetectivity values, which increase with decreasing wavelength down to 300 nm. We show that the drain current of Si NW biochemical sensors substantially depends on pH value and the signal-to-noise ratio reaches the high value of 105. Increasing pH sensitivity with gate voltage is revealed for certain source-drain currents of pH-sensors based on Si NW FETs. The noise characteristic index decreases from 1.1 to 0.7 with the growth of the liquid gate voltage. Noise behavior is successfully explained in the framework of the correlated number-mobility unified fluctuation model. pH sensitivity increases as a result of the increase in liquid gate voltage, thus giving the opportunity to measure very low proton concentrations in the electrolyte medium at certain values of the liquid gate voltage.

Characterization of Heat Treated Titanium-Based Implants by Nondestructive Eddy Current and Ultrasonic Tests

NASA Astrophysics Data System (ADS)

Mutlu, Ilven; Ekinci, Sinasi; Oktay, Enver

2014-06-01

This study presents nondestructive characterization of microstructure and mechanical properties of heat treated Ti, Ti-Cu, and Ti-6Al-4V titanium-based alloys and 17-4 PH stainless steel alloy for biomedical implant applications. Ti, Ti-Cu, and 17-4 PH stainless steel based implants were produced by powder metallurgy. Ti-6Al-4V alloy was investigated as bulk wrought specimens. Effects of sintering temperature, aging, and grain size on mechanical properties were investigated by nondestructive and destructive tests comparatively. Ultrasonic velocity in specimens was measured by using pulse-echo and transmission methods. Electrical conductivity of specimens was determined by eddy current tests. Determination of Young's modulus and strength is important in biomedical implants. Young's modulus of specimens was calculated by using ultrasonic velocities. Calculated Young's modulus values were compared and correlated with experimental values.

Luminescence and scintillation properties of liquid phase epitaxy grown Y2SiO5:Ce single crystalline films

NASA Astrophysics Data System (ADS)

Wantong, Kriangkrai; Yawai, Nattasuda; Chewpraditkul, Weerapong; Kucera, Miroslav; Hanus, Martin; Nikl, Martin

2017-06-01

Luminescence and scintillation properties of Y2SiO5:Ce single crystalline film (YSO:Ce-LPE) grown by the liquid phase epitaxy technique are investigated and compared to the bulk Czochralski-grown YSO:Ce single crystal (YSO:Ce-SC). The light yield (LY) and energy resolution are measured using an R6231 photomultiplier under excitation with α - and γ- rays. At 662 keV γ- rays, the LY value of 12,410 ph/MeV obtained for YSO:Ce -LPE is lower than that of 20,150 ph/MeV for YSO:Ce -SC whereas the comparable LY value and energy resolution are obtained under excitation with 5.5 MeV α- rays. The ratio of LY under excitation with α- and γ- rays (α/γ ratio) is determined. Dependence of LY on an amplifier shaping time (0.5-12 μs) is also measured.

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.

Comparison of wet-only and bulk deposition at Chiang Mai (Thailand) based on rainwater chemical composition

NASA Astrophysics Data System (ADS)

Chantara, Somporn; Chunsuk, Nawarut

The chemical composition of 122 rainwater samples collected daily from bulk and wet-only collectors in a sub-urban area of Chiang Mai (Thailand) during August 2005-July 2006 has been analyzed and compared to assess usability of a cheaper and less complex bulk collector over a sophisticated wet-only collector. Statistical analysis was performed on log-transformed daily rain amount and depositions of major ions for each collector type. The analysis of variance (ANOVA) test revealed that the amount of rainfall collected from a rain gauge, bulk collector and wet-only collector showed no significant difference ( ∝=0.05). The volume weight mean electro-conductivity (EC) values of bulk and wet-only samples were 0.69 and 0.65 mS/m, respectively. The average pH of the samples from both types of collectors was 5.5. Scatter plots between log-transformed depositions of specific ions obtained from bulk and wet-only samples showed high correlation ( r>0.91). Means of log-transformed bulk deposition were 14% (Na + and K +), 13% (Mg 2+), 7% (Ca 2+), 4% (NO 3-), 3% (SO 42- and Cl -) and 2% (NH 4+) higher than that of wet-only deposition. However, multivariate analysis of variance (MANOVA) revealed that ion depositions obtained from bulk and wet-only collectors were not significantly different ( ∝=0.05). Therefore, it was concluded that a bulk collector can be used instead of a wet-only collector in a sub-urban area.

Surface Chemical Studies on Pyrite in the Presence of Polysaccharide-Based Flotation Depressants.

PubMed

Rath; Subramanian; Pradeep

2000-09-01

The interaction of dextrin and guar gum with pyrite has been investigated through adsorption, flotation, and electrokinetic measurements. The adsorption densities of the polysaccharides onto pyrite reveal a region of higher adsorption density in the pH range 7.5-11, with a maximum around pH 10 for both polymers. The isotherms exhibit Langmuirian behavior. The adsorption density of guar gum onto pyrite is higher than that of dextrin. Electrokinetic measurements indicate a decrease in the electrophoretic mobility values in proportion to the concentration of the polymer added. Co-precipitation tests confirm polymer-ferric species interaction in the bulk solution, especially in the pH range 5.5-8.5. The pH range for higher adsorption, significant co-precipitation, and appreciable depression of pyrite encompass each other. XPS and FTIR spectroscopic studies provide evidence in support of chemical interaction between hydroxylated pyrite and the hydroxyl groups of the polymeric depressants. Copyright 2000 Academic Press.

Bioleached sludge composting drastically reducing ammonia volatilization as well as decreasing bulking agent dosage and improving compost quality: A case study.

PubMed

Hu, Weitong; Zheng, Guanyu; Fang, Di; Cui, Chunhong; Liang, Jianru; Zhou, Lixiang

2015-10-01

Sludge bioleaching technology with Acidithiobacillus species has been commercially adopted for improving advanced dewatering of sludge in China since 2010. However, up to now, little information on bioleached dewatered sludge (BS) composting is available. Here, we report the changes of physicochemical and biological properties in BS composting and evaluate compost product quality compared to conventional dewatered sludge (CS) composting in an engineering scale composting facility. The results showed that the amount of bulking agents required in BS composting was only about 10% of CS composting to obtain optimum moisture content, reducing about 700 kg bulking agents per ton fresh sludge. pH of BS composting mixture was slightly lower consistently by about 0.2-0.3 pH units than that in CS mixture in the first 30 days. Organic matter biodegradation in BS system mainly occurred in the first 9 days of composting. In spite of higher content of NH4(+)-N was found in BS mixture in related to CS mixture; unexpectedly the cumulative ammonia volatilization in the former was only 51% of the latter, indicating that BS composting drastically reduced nitrogen loss. Compared to CS composting system, the relative lower pH, the higher intensity of microbial assimilation, and the presence of water soluble Fe in BS system might jointly reduce ammonia volatilization. Consequently, BS compost product exhibited higher fertilizer values (N+P2O5+K2O=8.38%) as well as lower heavy metal levels due to the solubilization of sludge-borne heavy metals during bioleaching process. Therefore, composting of BS possesses more advantages over the CS composting process. Copyright © 2015 Elsevier Ltd. All rights reserved.

Flip-flop of hydroxy fatty acids across the membrane as monitored by proton-sensitive microelectrodes.

PubMed

Pohl, Elena E; Voltchenko, Anna M; Rupprecht, Anne

2008-05-01

Hydroxyl group-containing fatty acids play an important role in anti-inflammatory action, neuroprotection, bactericide and anti-cancer defense. However, the mechanism of long-chain hydroxy fatty acids (HFA) transport across plasma membranes is still disputed. Two main hypotheses have been suggested: firstly, that protonated HFAs traverse across the membranes spontaneously and, secondly, that the transport is facilitated by proteinaceous carriers. Here, we demonstrate that the protonated HFA are able to move across planar lipid bilayers without protein assistance. This transport step is accompanied by the acidification of the buffer in receiving compartment and the pH augmentation in the donating compartment. The latter contained liposomes doped with HFA. As revealed by scanning pH-sensitive microelectrodes, the pH shift occurred only in the immediate vicinity of the membrane, while bulk pH remained unchanged. In concurrence with the theoretical model of weak acid transport, the pH value at maximum proton flux was almost equal to the pK of the studied HFA. Intrinsic pKi values were calculated from the electrophoretic mobilities of HFA-containing liposomes and were 5.4, 6.5, 6.9 and 6.3 for 2-hydroxyhexadecanoic, 16-hydroxyhexadecanoic, 12-hydroxydodecanoic and 9,10,16-trihydroxyhexadecanoic acids, respectively.

On the kinetics of acid sodium caseinate gelation using particle tracking to probe the microrheology.

PubMed

Moschakis, Thomas; Murray, Brent S; Dickinson, Eric

2010-05-15

The sol-gel transition of a model dairy system (sodium caseinate solution) which undergoes gelation by acidification has been studied by conventional bulk rheology and particle tracking microrheology, via confocal microscopy. The Brownian diffusion of fluorescent microspheres (0.21, 0.32, 0.5, and 0.89 μm in diameter) with different surface coatings (polyethylene glycol, carboxylate groups and polystyrene) was used to probe spatial mechanical properties of the gels at the scale of microns. The microrheological results are compared with the macroscopic viscoelastic properties (storage and loss shear modulus) measured in a concentric cylinder rheometer (double gap, at shear strain of 0.005 and frequency of 1 Hz). At pH values close to pI of the caseins, where formation of a protein network, i.e., gelation, became obvious from the confocal microscopy and bulk rheological measurements, all the particles had a tendency to adhere to the network. In spite of this, the microrheological values of the moduli were only slightly lower than the macroscopically determined values and the gel points calculated via both techniques tended to be in good agreement. However, the particle tracking method has higher sensitivity and can detect changes in the structuring of the system before these are registered by the bulk rheological measurement. Copyright © 2010 Elsevier Inc. All rights reserved.

Double-gated Si NW FET sensors: Low-frequency noise and photoelectric properties

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

Gasparyan, F.; Forschungszentrum Jülich, Peter Grünberg Institute; Khondkaryan, H.

2016-08-14

The transport, noise, and photosensitivity properties of an array of silicon nanowire (NW) p{sup +}-p-p{sup +} field-effect transistors (FETs) are investigated. The peculiarities of photosensitivity and detectivity are analyzed over a wide spectrum range. The absorbance of p-Si NW shifts to the short wavelength region compared with bulk Si. The photocurrent and photosensitivity reach increased values in the UV range of the spectrum at 300 K. It is shown that sensitivity values can be tuned by the drain-source voltage and may reach record values of up to 2–4 A/W at a wavelength of 300 nm at room temperature. Low-frequency noise studies allow calculatingmore » the photodetectivity values, which increase with decreasing wavelength down to 300 nm. We show that the drain current of Si NW biochemical sensors substantially depends on pH value and the signal-to-noise ratio reaches the high value of 10{sup 5}. Increasing pH sensitivity with gate voltage is revealed for certain source-drain currents of pH-sensors based on Si NW FETs. The noise characteristic index decreases from 1.1 to 0.7 with the growth of the liquid gate voltage. Noise behavior is successfully explained in the framework of the correlated number-mobility unified fluctuation model. pH sensitivity increases as a result of the increase in liquid gate voltage, thus giving the opportunity to measure very low proton concentrations in the electrolyte medium at certain values of the liquid gate voltage.« less

Collection of Ni-bearing material from electroless plating waste by magnetic separation with HTS bulk magnet

NASA Astrophysics Data System (ADS)

Oka, T.; Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Tsujimura, M.; Yokoyama, K.

2014-01-01

The magnetic separation experiment to collect the Ni compounds from the waste liquid of electroless plating processes was conducted in the open-gradient magnetic separation process with the high temperature superconducting bulk magnet system. The magnetic pole containing Gd-based bulk superconductors was activated to 3.45 T at 35 K in the static magnetic field of 5 T with use of a superconducting solenoid magnet. The coarse Ni-sulfate crystals were formed by adding the concentrated sulfuric acid to the Ni-phosphite precipitates which yielded from the plating waste liquid by controlling the temperature and the pH value. The open-gradient magnetic separation technique was employed to separate the Ni-sulfate crystals from the mixture of the Ni-sulfate and Ni-phosphite compounds by the difference between their magnetic properties. And we succeeded in collecting Ni-sulfate crystals preferentially to the Ni-phosphite by attracting them to the magnetic pole soon after the Ni-sulfate crystals began to grow.

Interfacial properties of acidified skim milk.

PubMed

Cases, E; Rampini, C; Cayot, Ph

2005-02-01

The purpose of this study is to investigate the tension properties and dilatational viscoelastic modulus of various skim milk proteins (whole milk, EDTA-treated milk, beta-casein, and beta-lactoglobulin) at an oil/water interface at 20 degrees C. Measurements are performed using a dynamic drop tensiometer for 15,000 s. The aqueous bulk phase is a skim milk simulated ultrafiltrate containing 11 x 10(-3) g L(-1) milk protein. At pH 6.7, beta-casein appears as the best to decrease the interfacial tension, whereas beta-lactoglobulin leads to the highest interfacial viscoelastic modulus value. Whole milk was almost as surface-active as individual beta-casein in terms of the final (steady-state) lowering of the interfacial tension, but the rate of tension lowering was smaller. EDTA treatment improved the rate of tension lowering of whole milk. The acidification of milk, from previous measurements, would lead to the enhancement of surface activity. At t=15,000 s, the order of effectiveness is pH 4.3 > pH 5.3 = pH 5.6 > pH 6.7 whole milk, suggesting that pH 4.3 whole milk is the best surface active. As compared to pH 6.7 whole milk, the use of pH 5.3 and pH 5.6 milk as surface active would result in the use of milk containing more free beta-casein born of pH-dissociated casein micelles.

X-Ray Excited Luminescence Chemical Imaging of Bacterial Growth on Surfaces Implanted in Tissue.

PubMed

Wang, Fenglin; Raval, Yash; Tzeng, Tzuen-Rong J; Anker, Jeffrey N

2015-04-22

A pH sensor film is developed that can be coated on an implant surface and imaged using a combination of X-ray excitation and visible spectroscopy to monitor bacterial infection and treatment of implanted medical devices (IMDs) through tissue. X-ray scintillators in the pH sensor film generate light when an X-ray beam irradiates them. This light first passes through a layer containing pH indicator that alters the spectrum according to pH, then passes through and out of the tissue where it is detected by a spectrometer. A reference region on the film is used to account for spectral distortion from wavelength-dependent absorption and scattering in the tissue. pH images are acquired by moving the sample relative to the X-ray beam and collecting a spectrum at each location, with a spatial resolution limited by the X-ray beam width. Using this X-ray excited luminescence chemical imaging (XELCI) to map pH through ex vivo porcine tissue, a pH drop is detected during normal bacterial growth on the sensor surface, and a restoration of the pH to the bulk value during antibiotic treatment over the course of hours with milli-meter resolution. Overall, XELCI provides a novel approach to noninvasively image surface pH for studying implant infections and treatments. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Influence of pH, particle size and crystal form on dissolution behaviour of engineered nanomaterials.

PubMed

Avramescu, M-L; Rasmussen, P E; Chénier, M; Gardner, H D

2017-01-01

Solubility is a critical component of physicochemical characterisation of engineered nanomaterials (ENMs) and an important parameter in their risk assessments. Standard testing methodologies are needed to estimate the dissolution behaviour and biodurability (half-life) of ENMs in biological fluids. The effect of pH, particle size and crystal form on dissolution behaviour of zinc metal, ZnO and TiO 2 was investigated using a simple 2 h solubility assay at body temperature (37 °C) and two pH conditions (1.5 and 7) to approximately frame the pH range found in human body fluids. Time series dissolution experiments were then conducted to determine rate constants and half-lives. Dissolution characteristics of investigated ENMs were compared with those of their bulk analogues for both pH conditions. Two crystal forms of TiO 2 were considered: anatase and rutile. For all compounds studied, and at both pH conditions, the short solubility assays and the time series experiments consistently showed that biodurability of the bulk analogues was equal to or greater than biodurability of the corresponding nanomaterials. The results showed that particle size and crystal form of inorganic ENMs were important properties that influenced dissolution behaviour and biodurability. All ENMs and bulk analogues displayed significantly higher solubility at low pH than at neutral pH. In the context of classification and read-across approaches, the pH of the dissolution medium was the key parameter. The main implication is that pH and temperature should be specified in solubility testing when evaluating ENM dissolution in human body fluids, even for preliminary (tier 1) screening.

Mathematical model for internal pH control in immobilized enzyme particles

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

Liou, J.K.; Rousseau, I.

A mathematical model has been developed for the internal pH control in immobilized enzyme particles. This model describes the kinetics of a coupled system of two enzymes, immobilized in particles of either planar, cylindrical, or spherical shape. The enzyme kinetics are assumed to be of a mixed type, including Michaelis-Menten kinetics, uncompetitive substrate inhibition, and competitive and noncompetitive product inhibition. In a case study we have considered the enzyme combination urease and penicillin acylase, whose kinetics are coupled through the pH dependence of the kinetic parameters. The hydrolysis of urea by urease yields ammonia and carbon dioxide, whereas benzylpenicillin (Pen-G)more » is converted to 6-animo penicillanic acid and phenyl acetic acid by penicillin acylase. The production of acids by the latter enzyme will cause a decrease in pH. Because of the presence of the ammonia-carbon dioxide system, however, the pH may be kept under control. In order to obtain information about the optimum performance of this enzymatic pH controller, we have computed the effectiveness factor and the conversion in a CSTR at different enzyme loadings. The results of the computer simulations indicate that a high conversion of Pen-G may be achieved (80-90%) at bulk pH values of about 7.5 - 8. 27 references.« less

A Novel Technique that Enables Efficient Conduct of Simultaneous Isomerization and Fermentation (SIF) of Xylose

NASA Astrophysics Data System (ADS)

Rao, Kripa; Chelikani, Silpa; Relue, Patricia; Varanasi, Sasidhar

Of the sugars recovered from lignocellulose, D-glucose can be readily converted into ethanol by baker's or brewer's yeast (Saccharomyces cerevisiae). However, xylose that is obtained by the hydrolysis of the hemicellulosic portion is not fermentable by the same species of yeasts. Xylose fermentation by native yeasts can be achieved via isomerization of xylose to its ketose isomer, xylulose. Isomerization with exogenous xylose isomerase (XI) occurs optimally at a pH of 7-8, whereas subsequent fermentation of xylulose to ethanol occurs at a pH of 4-5. We present a novel scheme for efficient isomerization of xylose to xylulose at conditions suitable for the fermentation by using an immobilized enzyme system capable of sustaining two different pH microenvironments in a single vessel. The proof-of-concept of the two-enzyme pellet is presented, showing conversion of xylose to xylulose even when the immobilized enzyme pellets are suspended in a bulk solution whose pH is sub-optimal for XI activity. The co-immobilized enzyme pellets may prove extremely valuable in effectively conducting "simultaneous isomerization and fermentation" (SIF) of xylose. To help further shift the equilibrium in favor of xylulose formation, sodium tetraborate (borax) was added to the isomerization solution. Binding of tetrahydroxyborate ions to xylulose effectively reduces the concentration of xylulose and leads to increased xylose isomerization. The formation of tetrahydroxyborate ions and the enhancement in xylulose production resulting from the complexation was studied at two different bulk pH values. The addition of 0.05 M borax to the isomerization solution containing our co-immobilized enzyme pellets resulted in xylose to xylulose conversion as high as 86% under pH conditions that are suboptimal for XI activity. These initial findings, which can be optimized for industrial conditions, have significant potential for increasing the yield of ethanol from xylose in an SIF approach.

Effects of copper on the antioxidant activity of olive polyphenols in bulk oil and oil-in-water emulsions.

PubMed

Paiva-Martins, Fátima; Santos, Vera; Mangericão, Hugo; Gordon, Michael H

2006-05-17

The antioxidant activity and interactions with copper of four olive oil phenolic compounds, namely oleuropein, hydroxytyrosol, 3,4-dihydroxyphenylethanol-elenolic acid (1), and 3,4-dihydroxyphenylethanol-elenolic acid dialdehyde (2), in olive oil and oil-in-water emulsions stored at 60 degrees C were studied. All four phenolic compounds significantly extended the induction time of lipid oxidation in olive oil with the order of activity being hydroxytyrosol > compound 1 > compound 2 > oleuropein > alpha-tocopherol; but in the presence of Cu(ll), the stability of oil samples containing phenolic compounds decreased by at least 90%, and the antioxidant activity of hydroxytyrosol and compounds 1 and 2 became similar. In oil-in-water emulsions prepared from olive oil stripped of tocopherols, hydroxytyrosol enhanced the prooxidant effect of copper at pH 5.5 but not at pH 7.4. The stability of samples containing copper at pH 5.5 was not significantly different if oleuropein was present from that of the control. Oleuropein at pH 7.4, and compounds 1 and 2 at both pH values tested, reduced the prooxidant effect of copper. The lower stability and the higher reducing capacity of all compounds at pH 7.4 could not explain the higher stability of emulsions containing phenolic compounds at this pH value. However, mixtures containing hydroxytyrosol or oleuropein with copper showed higher 1,1-diphenyl-2-picrylhydrazyl radical scavenging activity at pH 7.4 than at pH 5.5. Moreover, the compound 2-copper complex showed higher radical scavenging activity then the uncomplexed compound at pH 5.5. It can be concluded that the formation of a copper complex with radical scavenging activity is a key step in the antioxidant action of the olive oil phenolic compounds in an emulsion containing copper ions.

Predicting the pKa and stability of organic acids and bases at an oil-water interface.

PubMed

Andersson, M P; Olsson, M H M; Stipp, S L S

2014-06-10

We have used density functional theory and the implicit solvent model, COSMO-RS, to investigate how the acidity constant, pKa, of organic acids and bases adsorbed at the organic compound-aqueous solution interface changes, compared to its value in the aqueous phase. The pKa determine the surface charge density of the molecules that accumulate at the fluid-fluid interface. We have estimated the pKa by comparing the stability of the protonated and unprotonated forms of a series of molecules in the bulk aqueous solution and at an interface where parts of each molecule reside in the hydrophobic phase and the rest remains in the hydrophilic phase. We found that the pKa for acids is shifted by ∼1 pH unit to higher values compared to the bulk water pKa, whereas they are shifted to lower values by a similar amount for bases. Because this pKa shift is similar in magnitude for each of the molecules studied, we propose that the pKa for molecules at a water-organic compound interface can easily be predicted by adding a small shift to the aqueous pKa. This shift is general and correlates with the functional group. We also found that the relative composition of molecules at the fluid-fluid interface is not the same as in the bulk. For example, species such as carboxylic acids are enriched at the interface, where they can dominate surface properties, even when they are a modest component in the bulk fluid. For high surface concentrations of carboxylic acid groups at an interface, such as a self-assembled monolayer, we have demonstrated that the pKa depends on the degree of deprotonation through direct hydrogen bonding between protonated and deprotonated acidic headgroups.

Predicting Soluble Nickel in Soils Using Soil Properties and Total Nickel

PubMed Central

Zhang, Xiaoqing; Li, Jumei; Wei, Dongpu; Li, Bo; Ma, Yibing

2015-01-01

Soil soluble nickel (Ni) concentration is very important for determining soil Ni toxicity. In the present study, the relationships between soil properties, total and soluble Ni concentrations in soils were developed in a wide range of soils with different properties and climate characteristics. The multiple regressions showed that soil pH and total soil Ni concentrations were the most significant parameters in predicting soluble Ni concentrations with the adjusted determination coefficients (Radj 2) values of 0.75 and 0.68 for soils spiked with soluble Ni salt and the spiked soils leached with artificial rainwater to mimic field conditions, respectively. However, when the soils were divided into three categories (pH < 7, 7–8 and > 8), they obtained better predictions with Radj 2 values of 0.78–0.90 and 0.79–0.94 for leached and unleached soils, respectively. Meanwhile, the other soil properties, such as amorphous Fe and Al oxides and clay, were also found to be important for determining soluble Ni concentrations, indicating that they were also presented as active adsorbent surfaces. Additionally, the whole soil speciation including bulk soil properties and total soils Ni concentrations were analyzed by mechanistic speciation models WHAM VI and Visual MINTEQ3.0. It was found that WHAM VI provided the best predictions for the soils with pH < 7, was relatively reasonable for pH 7 to 8, and gave an overestimation for pH > 8. The Visual MINTEQ3.0 could provide better estimation for pH < 8 and meanwhile quite reasonable results for pH > 8. These results indicated the possibility and applicability of these models to predict soil soluble Ni concentration by soil properties. PMID:26217951

Predicting Soluble Nickel in Soils Using Soil Properties and Total Nickel.

PubMed

Zhang, Xiaoqing; Li, Jumei; Wei, Dongpu; Li, Bo; Ma, Yibing

2015-01-01

Soil soluble nickel (Ni) concentration is very important for determining soil Ni toxicity. In the present study, the relationships between soil properties, total and soluble Ni concentrations in soils were developed in a wide range of soils with different properties and climate characteristics. The multiple regressions showed that soil pH and total soil Ni concentrations were the most significant parameters in predicting soluble Ni concentrations with the adjusted determination coefficients (Radj2) values of 0.75 and 0.68 for soils spiked with soluble Ni salt and the spiked soils leached with artificial rainwater to mimic field conditions, respectively. However, when the soils were divided into three categories (pH < 7, 7-8 and > 8), they obtained better predictions with Radj2 values of 0.78-0.90 and 0.79-0.94 for leached and unleached soils, respectively. Meanwhile, the other soil properties, such as amorphous Fe and Al oxides and clay, were also found to be important for determining soluble Ni concentrations, indicating that they were also presented as active adsorbent surfaces. Additionally, the whole soil speciation including bulk soil properties and total soils Ni concentrations were analyzed by mechanistic speciation models WHAM VI and Visual MINTEQ3.0. It was found that WHAM VI provided the best predictions for the soils with pH < 7, was relatively reasonable for pH 7 to 8, and gave an overestimation for pH > 8. The Visual MINTEQ3.0 could provide better estimation for pH < 8 and meanwhile quite reasonable results for pH > 8. These results indicated the possibility and applicability of these models to predict soil soluble Ni concentration by soil properties.

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

PubMed

Dulova, Niina; Trapido, Marina; Dulov, Aleksandr

2011-01-01

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

Inhibited phenol ionization in reverse micelles: confinement effect at the nanometer scale.

PubMed

Silva, O Fernando; Fernández, Mariana A; Silber, Juana J; de Rossi, Rita H; Correa, N Mariano

2012-01-16

We found that the absorption spectra of 2-acetylphenol (2-HAP), 4-acetylphenol (4-HAP), and p-nitrophenol (p-NPh) in water/sodium 1,4-bis(2-ethylhexyl)sulfosuccinate (AOT)/n-heptane reverse micelles (RMs) at various W(0) (W(0) = [H(2)O]/[surfactant]) values studied changed with time if (-)OH ions were present in the RM water pool. There is an evolution of ionized phenol (phenolate) bands to nonionized phenol absorption bands with time and this process is faster at low W(0) values and with phenols with higher bulk water pK(a) values. That is, in bulk water and at the hydroxide anion concentration used, only phenolate species are observed, whereas in AOT RMs at this fixed hydroxide anion concentration, ionized phenols convert into nonionized phenol species over time. Furthermore, we demonstrate that, independent of the (-)OH concentration used to prepare the AOT RMs, the nonionized phenols are the more stable species in the RM media. We explain our results by considering that strong hydrogen-bonding interactions between phenols and the AOT polar head groups result in the existence of only nonionized phenols at the AOT RM interface. The situation is quite different when the phenols are dissolved in cationic benzyl-n-hexadecyldimethylammonium chloride RMs. Therein, only phenolates species are present at the (-)OH concentrations used. The results clearly demonstrate that the classical definition of pH does not apply in a confined environment, such as in the interior of RMs and challenge the general idea that pH can be determined inside RMs. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RECOVERY OF THORIUM AND URANIUM VALUES FROM AQUEOUS SOLUTIONS

DOEpatents

Calkins, G.D.

1958-02-18

This patent deals with the separation and recovery of uranium from monazite sand. After initial treatment of the sand with sodium hydroxide, a precipitate is obtuined which contains the uranium, thorium, rare earths and some phosphorus. This precipitate is then dissolved in nitric acid. The bulk of the rare earths are removed from thls soiution by adding aa excess of alkali carbonate, causing precipitation of the rare earths together with part of the thorium present. The solution still contains a considerable amount of thorium, some rare earths, and practically all of the uranium originally present. Thorium and rare earth values are readily precipitated from such solution, and the uranium values thus isolated, by the addition of an excess hydrogen peroxide. The pH value of the solution is preferably adjusted to at least 9 prior to the addition of the peroxide.

Sorption of Sr, Co and Zn on illite: Batch experiments and modelling including Co in-diffusion measurements on compacted samples

NASA Astrophysics Data System (ADS)

Montoya, V.; Baeyens, B.; Glaus, M. A.; Kupcik, T.; Marques Fernandes, M.; Van Laer, L.; Bruggeman, C.; Maes, N.; Schäfer, T.

2018-02-01

Experimental investigations on the uptake of divalent cations (Sr, Co and Zn) onto illite (Illite du Puy, Le-Puy-en-Velay, France) were carried out by three different international research groups (Institute for Nuclear Waste Disposal, KIT (Germany), Group Waste & Disposal, SCK-CEN, (Belgium) and Laboratory for Waste Management, PSI (Switzerland)) in the framework of the European FP7 CatClay project. The dependence of solid-liquid distribution ratios (Rd values) on pH at trace metal conditions (sorption edges) and on the metal ion concentration (sorption isotherms) was determined in dilute suspensions of homo-ionic Na-illite (Na-IdP) under controlled N2 atmosphere. The experimental results were modelled using the 2 Site Protolysis Non Electrostatic Surface Complexation and Cation Exchange (2SPNE SC/CE) sorption model. The sorption of Sr depends strongly on ionic strength, while a rather weak pH dependence is observed in a pH range between 3 and 11. The data were modelled with cation exchange reactions, taking into account competition with H, K, Ca, Mg and Al, and surface complexation on weak amphotheric edge sites at higher pH values. The sorption of Co on Na-IdP, however, is strongly pH dependent. Cation exchange on the planar sites and surface complexation on strong and weak amphoteric edge sites were used to describe the Co sorption data. Rd values for Co derived from in-diffusion measurements on compacted Na-IdP samples (bulk-dry density of 1700 kg m-3) between pH 5.0 and 9.0 are in good agreement with the batch sorption data. The equivalence of both approaches to measure sorption was thus confirmed for the present test system. In addition, the results highlight the importance of both major and minor surface species for the diffusive transport behaviour of strongly sorbing metal cations. While surface complexes at the edge sites determine largely the Rd value, the diffusive flux may be governed by those species bound to the planar sites, even at low fractional occupancies. The pH dependent sorption determined for trace Zn concentrations showed large Rd values across the entire pH range with almost no dependence on the background electrolyte concentration. Additional sorption experiments carried out at substantial fractional Zn loadings demonstrated that the selectivity for the exchange of Na+ for Zn2+ at the planar sites could not explain the large Rd values measured at low pH and trace Zn concentrations. This suggests that another mechanism is ruling Zn uptake under these conditions.

Characterization of a backbone cleavage product of BMS-196854 (Oncostatin M), a recombinant anti-inflammatory cytokine.

PubMed

Zhao, F; Stein, D J; Paborji, M; Cash, P W; Root, B J; Wei, Z; Knupp, C J

2001-01-01

BMS-196843 (Oncostatin M) is a therapeutic recombinant protein in development. Scale-up process changes led to unexpected instability of the bulk drug substance solution during storage. A product with an apparent higher MW than the parent protein was observed by the size-exclusion chromatography (SEC). This study was aimed to fully characterize the product and to identify a solution to stabilize the protein. SEC, SDS-PAGE, tryptic mapping, and N-terminal sequencing were performed to characterize the unknown product. The effect of pH, temperature, bulk concentration, and immobilized trypsin inhibitor on the degradation rate was studied to elucidate the mechanism and to identify stabilization strategies. Despite the apparent high MW indicated initially by SEC, the unknown was characterized to be a degradation product resulted from a backbone cleavage between residues Arg145-Gly146. The resulting fragments from the backbone cleavage were, however, still linked through an intramolecular disulfide bond. Thus, the final product had a more open structure with an increased hydrodynamic radius compared to the parent protein, which explains the initial SEC results. The site-specific backbone cleavage was suspected to be catalyzed by trypsin-like protease impurities in the bulk solution. The bulk drug substance solution was subsequently treated with immobilized soybean trypsin inhibitor, and the degradation rate was significantly reduced. Furthermore, increasing the solution pH from 5 to 8 led to an increase in the degradation rate, which was consistent with the expected pH dependency of trypsin activity. In addition, the effect of bulk concentration also supported the involvement of protease impurities rather than a spontaneous peptide bond hydrolysis reaction. Trace trypsin-like protease impurities led to an unusual site-specific backbone cleavage of BMS-196854. The proteolytic degradation can be minimized by treating the bulk solution with immobilized soybean trypsin inhibitor and/or controlling the solution pH and storage temperature.

Sorption of perfluoroalkyl substances (PFASs) to an organic soil horizon - Effect of cation composition and pH.

PubMed

Campos Pereira, Hugo; Ullberg, Malin; Kleja, Dan Berggren; Gustafsson, Jon Petter; Ahrens, Lutz

2018-09-01

Accurate prediction of the sorption of perfluoroalkyl substances (PFASs) in soils is essential for environmental risk assessment. We investigated the effect of solution pH and calculated soil organic matter (SOM) net charge on the sorption of 14 PFASs onto an organic soil as a function of pH and added concentrations of Al 3+ , Ca 2+ and Na + . Often, the organic C-normalized partitioning coefficients (K OC ) showed a negative relationship to both pH (Δlog K OC /ΔpH = -0.32 ± 0.11 log units) and the SOM bulk net negative charge (Δlog K OC  = -1.41 ± 0.40 per log unit mol c g -1 ). Moreover, perfluorosulfonic acids (PFSAs) sorbed more strongly than perfluorocarboxylic acids (PFCAs) and the PFAS sorption increased with increasing perfluorocarbon chain length with 0.60 and 0.83 log K OC units per CF 2 moiety for C 3 -C 10 PFCAs and C 4 , C 6 , and C 8 PFSAs, respectively. The effects of cation treatment and SOM bulk net charge were evident for many PFASs with low to moderate sorption (C 5 -C 8 PFCAs and C 6 PFSA). However for the most strongly sorbing and most long-chained PFASs (C 9 -C 11 and C 13 PFCAs, C 8 PFSA and perfluorooctane sulfonamide (FOSA)), smaller effects of cations were seen, and instead sorption was more strongly related to the pH value. This suggests that the most long-chained PFASs, similar to other hydrophobic organic compounds, are preferentially sorbed to the highly condensed domains of the humin fraction, while shorter-chained PFASs are bound to a larger extent to humic and fulvic acid, where cation effects are significant. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

Chinese medicinal herbal residues as a bulking agent for food waste composting.

PubMed

Zhou, Ying; Selvam, Ammaiyappan; Wong, Jonathan W C

2018-02-01

This study aimed to co-compost Chinese medicinal herbal residues (CMHRs) as the bulking agent with food waste (FW) to develop a high value antipathogenic compost. The FW, sawdust (SD) and CMHRs were mixed at three different mixing ratios, 5:5:1, 2:2:1 and 1:1:1 on dry weight basis. Lime at 2.25% was added to the composting mix to buffer the pH during the composting. A control without lime addition was also included. The mixtures were composted in 20-L in-vessel composters for 56 days. A maximum of 67.2% organic decomposition was achieved with 1:1:1 mixing ratio within 8 weeks. The seed germination index was 157.2% in 1:1:1 mixing ratio, while other ratios showed <130.0% and the treatment without lime showed 40.3%. Therefore use of CMHRs as the bulking agent to compost food waste at the dry weight ratio of 1:1:1 (FW: SD: CMHRs) was recommended for FW-CMHRs composting. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of light Sphagnum peat on odour formation in the early stages of biowaste composting.

PubMed

Kurola, Jukka M; Arnold, Mona; Kontro, Merja H; Talves, Matti; Romantschuk, Martin

2010-05-01

In the present study, we investigated the effects of two bulking materials, Sphagnum peat and pine wood chips, on the early stages of biowaste composting in two pilot-scale processes. Emphasis was placed on studying the formation conditions of malodorous compost gases in the initial phases of the processes. The results showed that gas emission leaving an open windrow and a closed drum composting system contained elevated concentrations of fermentative microbial metabolites when acid Sphagnum peat (pH 3.2) was used as a bulking material. Moreover, the gas emission of the peat amended drum composter contained a high concentration of odour (up to 450,000oum(-3) of air). The highest odour values in the outlet gas of peat amended composts coincided with the elevated concentrations of volatile organic compounds such as acetoin and buthanedion. We conclude that the acidifying qualities of composting substrates or bulking material may intensify odour emission from biowaste composts and prolong the early stages of the composting process. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Pheromone discrimination by a pH-tuned polymorphism of the Bombyx mori pheromone-binding protein.

PubMed

Damberger, Fred F; Michel, Erich; Ishida, Yuko; Leal, Walter S; Wüthrich, Kurt

2013-11-12

The Bombyx mori pheromone-binding protein (BmorPBP) is known to adopt two different conformations. These are BmorPBP(A), where a regular helix formed by the C-terminal dodecapeptide segment, α7, occupies the ligand-binding cavity, and BmorPBP(B), where the binding site is free to accept ligands. NMR spectra of delipidated BmorPBP solutions at the physiological pH of the bulk sensillum lymph near pH 6.5 show only BmorPBP(A), and in mixtures, the two species are in slow exchange on the chemical shift frequency scale. This equilibrium has been monitored at variable pH and ligand concentrations, demonstrating that it is an intrinsic property of BmorPBP that is strongly affected by pH variation and ligand binding. This polymorphism tunes BmorPBP for optimal selective pheromone transport: Competition between α7 and lipophilic ligands for its binding cavity enables selective uptake of bombykol at the pore endings in the sensillum wall, whereas compounds with lower binding affinity can only be bound in the bulk sensillum lymph. After transport across the bulk sensillum lymph into the lower pH area near the dendritic membrane surface, bombykol is ejected near the receptor, whereas compounds with lower binding affinity are ejected before reaching the olfactory receptor, rendering them susceptible to degradation by enzymes present in the sensillum lymph.

The bulk composition and leaching properties of electroplating sludge prior/following the solidification/stabilization by calcium oxide.

PubMed

Orescanin, Visnja; Mikulic, Nenad; Mikelic, Ivanka Lovrencic; Posedi, Mario; Kampic, Stefica; Medunic, Gordana

2009-10-01

Eighteen samples of electroplating sludge were taken from three vertical profiles of waste storage pond of the zinc plating facility. Dry matter and organic matter content, pH value, bulk concentrations and leachate composition were determined. A sludge sample with the highest zinc value in the leachate was treated with calcium oxide (10% to 70%) and the obtained solidificate was repeatedly tested. There were found significant variations of all measured parameters among the profiles of untreated waste. Dry matter content varied from 125 to 455 mgg(-1), organic matter varied from 94.3 to 293.9 mgg(-1), and pH value varied from 3.42 to 5.90 (mean 4.34). Iron content ranged from 38.4 to 191.4 mgg(-1) (mean 136 mgg(-1); RSD 0.25), while zinc ranged from 10.9 to 58.2 mgg(-1) (mean 33.4 mgg(-1); RSD 0.38). According to its DIN38414-S4 leachate composition, this material was not suitable for landfilling of inert waste since zinc and nickel mean values were 10 and 1.5 times higher, respectively, and maximum values 27 and 2.5 times higher, respectively, compared to the upper permissible limit. Maximum values of Cr(VI), Fe, Ni, Cu, and Zn in the DIN38414-S4 leachate were 0.183 mgL(-1), 34.085 mgL(-1), 1.052 mgL(-1), 0.829 mgL(-1) and 107.475 mgL(-1)L, respectively. Following the solidification/stabilization procedure with CaO (sample/CaO = 90/10), concentrations of Cr(VI), Fe, Cu and Zn were reduced 92, 44, 66 and 57 times, respectively, compared to the untreated sample. The addition of 50% of CaO into the sludge reduced zinc and nickel concentrations 79 and 45 times, respectively, in the DIN38414-S4 leachate of the solidified waste compared to the original sludge, thereby converting an hazardous waste into the inert material suitable for landfilling or reuse in the construction processes.

Protein adsorption at charged surfaces: the role of electrostatic interactions and interfacial charge regulation.

PubMed

Hartvig, Rune A; van de Weert, Marco; Østergaard, Jesper; Jorgensen, Lene; Jensen, Henrik

2011-03-15

The understanding of protein adsorption at charged surfaces is important for a wide range of scientific disciplines including surface engineering, separation sciences and pharmaceutical sciences. Compared to chemical entities having a permanent charge, the adsorption of small ampholytes and proteins is more complicated as the pH near a charged surface can be significantly different from the value in bulk solution. In this work, we have developed a phenomenological adsorption model which takes into account the combined role of interfacial ion distribution, interfacial charge regulation of amino acids in the proximity of the surface, electroneutrality, and mass balance. The model is straightforward to apply to a given set of experimental conditions as most model parameters are obtained from bulk properties and therefore easy to estimate or are directly measurable. The model provides a detailed understanding of the importance of surface charge on adsorption and in particular of how changes in surface charge, concentration, and surface area may affect adsorption behavior. The model is successfully used to explain the experimental adsorption behavior of the two model proteins lysozyme and α-lactalbumin. It is demonstrated that it is possible to predict the pH and surface charge dependent adsorption behavior from experimental or theoretical estimates of a preferred orientation of a protein at a solid charged interface.

Facilitated fabrication of high strength silica aerogels using cellulose nanofibrils as scaffold.

PubMed

Fu, Jingjing; Wang, Siqun; He, Chunxia; Lu, Zexiang; Huang, Jingda; Chen, Zhilin

2016-08-20

Monolithic cellulose nanofibrils (CNF)-silica composite aerogels were successfully prepared by immersing CNF aerogels into a silica solution in a two-step sol-gel process (initial hydrolysis of tetraethyl orthosilicate (TEOS) followed by condensation of silica particles). Aerogels were characterized by SEM, BET surface area test, bulk density and silica content analysis, FTIR spectroscopy, and compression test. The form of SiO2 existing in the composite aerogel was the spherical individual particles coated on CNF fibrils. The pH value of condensation solution was found to have great influence on the properties of the composite aerogels. By varying the pH value of condensation atmosphere from 8 to 12, the bulk densities of composite aerogels were able to be linearly increased from 0.059gcm(-3) to 0.29gcm(-3)，and the silica content in the matrix sharply jumped from 3wt% to 79wt%. The porosities of the aerogels remained very high, between 85 and 96%, and the surface area of the composite aerogel reached up to 700.1m(2)g(-1). The compression properties of the composite aerogel improved greatly compared with those of the silica aerogel, about 8-30 times higher. Moreover, the compressive strength of the composite aerogel prepared in this work greatly exceeded the conventional insulation materials found in the recent commercial market, and without substantial increases in thermal conductivity. Hence, the findings of this research offer a promising application for composite aerogels and give a theoretical basis for developing new advanced materials. Copyright © 2016 Elsevier Ltd. All rights reserved.

Soil biochar amendments: type and dose effects

NASA Astrophysics Data System (ADS)

Ojeda, G.; Domene, X.; Mattana, S.; Sousa, J. P.; Ortiz, O.; Andres, P.; Alcañiz, J. M.

2012-04-01

Biochar is an organic material produced via the pyrolysis of C-based biomass, which is increasingly being recognized by scientists and policy makers for its potential role in carbon sequestration, reducing greenhouse gas emissions, waste mitigation, and as a soil amendment. Recent studies indicated that biochar improves soil fertility through its positive influence on physical-chemical properties, since not only improves water retention, aggregation and permeability, but its high charge density can also hold large amounts of nutrients, increasing crop production. However, it was observed that combustion temperature could affects the degree of aromaticity and the size of aromatic sheets, which in turns determine short-term mineralization rates. To reconcile the different decompasibility observations of biochar, it has sugested that physical protection and interactions with soil minerals play a significant part in biochar stability. In this context, it has initiated one pilot studies which aims to assess the effects of biochar application on physical and chemical properties of agricultural soil under Mediterranean conditions, such as changes in aggregate formation, intra-aggregate carbon sequestration and chemistry of soil water. In the present study, different clases of biochar produced from fast, slow and gasification pyrolisis of vegetal (pine, poplar) and dried sludge biomass, were applied at 1% of biochar-C to mesocosmos of an agricultural soil. Preliminary, it must be pointed out that slow and gasification pyrolisis changes the proportion of particles < 2 mm in diameter, from 10% (original materials) to almost 100%. In contrast, slow pyrolisis not modifies significantly biochar granulometry. As a consequence, bulk density of poplar and pine splinters decreases after fast pyrolisis. Regarding to organic carbon contents of biochar, all biochars obtained from plant biomass presented percentagens of total organic carbon (TOC) between 70 - 90%, while biochar obtained from dried sludge by slow pyrolisis has a TOC around of 22%. On the other hand, pH values of biochar depends of the type of pyrolisis as observed in the biochar obtained from poplar biomass, where pH of slow pyrolisis < fast pyrolisis < gasification pyrolisis. When soil aggregate stability was tested, it was observed that biochars from pine biomass obtained by slow and fast pyrolisis trend to increase the water-stable soil aggregates, while the biochars from poplar and thermally-dreid sludge obtained by slow pyrolisis and from pine biomass obtained by gasification trend to the contrary. These differences were not explained by TOC contents or bulk density of bichars, probably because specific resistence to slaking and wettability of each biochar. At least, when measuring pH values of water where soil aggregates were immersed during soil aggregate stability test, it was observed that biochars from thermally-dried sludge obtained by slow pyrolisis and from pine biomass obtained by gasification pyrolisis increased water pH, which corresponded with high pH values of both biochars. In general, increases in the percentage of water-stable soil aggregates corresponded with increases in water pH values, except in the case of biochar from pine biomass obtained by slow pyrolisis.

Potentiometric and Relaxometric Properties of a Gadolinium-based MRI Contrast Agent for Sensing Tissue pH

PubMed Central

Kálmán, Ferenc K.; Woods, Mark; Caravan, Peter; Jurek, Paul; Spiller, Marga; Tircsó, Gyula; Király, Róbert; Brücher, Ernő; Sherry, A. Dean

2008-01-01

The pH sensitive contrast agent, GdDOTA-4AmP (Gd1) has been successfully used to map tissue pH by MRI. Further studies now demonstrate that two distinct chemical forms of the complex can be prepared depending upon the pH at which Gd3+ is mixed with ligand 1. The desired pH sensitive form of this complex, referred to here as a Type II complex, is obtained as the exclusive product only when the complexation reaction is performed above pH 8. At lower pH values, a second complex is formed that, by analogy with an intermediate formed during preparation of GdDOTA, we tentatively assign this to a Type I complex where the Gd3+ is coordinated only by the appended side-chain arms of 1. The proportion of Type I complex formed is largely determined by the pH of the complexation reaction. The magnitude of pH dependent change in relaxivity of Gd1 was found to be less than earlier reported (S. Zhang, K. Wu, and A. D. Sherry, Angew. Chem., Int. Ed., 1999, 38, 3192), likely due to contamination of the earlier sample by an unknown amount of Type I complex. Examination of the NMRD and relaxivity temperature profiles, coupled with information from potentiometric titrations, shows that the amphoteric character of the phosphonate side-chains enables rapid prototropic exchange between the single bound water of the complex with those of the bulk water thereby giving Gd1 a unique pH dependent relaxivity that is quite useful for pH mapping of tissues by MRI. PMID:17539632

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

NASA Astrophysics Data System (ADS)

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

2014-12-01

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

Impact of drainage on wettability of fen peat-moorsh soils

NASA Astrophysics Data System (ADS)

Szajdak, L.; Szatyłowicz, J.; Brandyk, T.

2009-04-01

High water retention in peat is attributed to structural voids (macro-pores) due to the partial degradation of the structure of peat-forming plants, and molecular absorption sites (micro-pores) associated with the formation of humic substances. Water retention by the heterogeneously-structured system in peat organic matter depends on the chemical structure of solid surfaces. These naturally wet solids, if dried sufficiently, lose the ability to rewet quickly when immersed in water. The ability of peat surfaces to attract and hold water is attributed to hydrophilic functional groups which characterize the organic substances of peat. The investigations of chemical and physical properties were performed for three different peat-moorsh soils located in the Biebrza River Valley in Poland. All examined soils were used as meadow. Soil samples were taken from two depths: 5-10 cm (moorsh) and 50-80 cm (peat). Total organic carbon (TOC), dissolved organic carbon (DOC) and humic acids (HA) extracted from these samples were analysed. Also basic physical properties such as ash content and bulk density were measured. Wetting behavior of soils was quantified using water drop penetration time test (WDPT) and measured values of the soil-water contact angle using sessile drop method. The measurements were conducted on air-dry soil samples which volumetric moisture content was not exceeding 7%. The significant differences in the concentrations of TOC, DOC and properties of HA between two investigated depth of among peat and moorsh samples were observed. The measured concentrations of total organic carbon in the considered soils ranged from 37.2 to 45.6%. Generally, the decrease of total organic carbon concentration with depth of profiles was observed. The contents of dissolved organic carbon in the soils ranged from 5.3 to 19.4%. The quantities of dissolved organic carbon decreased simultaneously with E4/E6 values and with the depth of the soil profiles. For the investigated peat's, an increase of the depth is accompanied by the decrease in the degree of humification or an increase in chemical maturity of HA. The measured values of the contact angle for investigated soils were in the range from 81.4˚ to 114.3˚ what indicates their high water repellency. The WDPT was positively correlated with total organic carbon, organic matter and humic acids content while ash content, soil bulk density, pH and absorbance were correlated negatively. The highest value of correlation coefficient (statistically significant) was obtained for relation between WDPT and ash content. The soil water contact angle was less correlated with peat-moorsh soil properties in comparison with WDPT with one exception pH. The pH against the contact angle indicates tendency of increasing the contact angle with decreasing pH.

Influence of corrosive solutions on microhardness and chemistry of magnesium oxide /001/ surfaces

NASA Technical Reports Server (NTRS)

Ishigaki, H.; Miyoshi, K.; Buckley, D. H.

1982-01-01

X-ray photoelectron spectroscopy analyses and hardness experiments were conducted on cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved to specimen size along the /001/ surface, and indentations were made on the cleaved surface in corrosive solutions containing HCl, NaOH, or HNO3 and in water without exposing the specimen to any other environment. The results indicated that chloride (such as MgCl2) and sodium films are formed on the magnesium oxide surface as a result of interactions between an HCl-containing solution and a cleaved magnesium oxide surface. The chloride films soften the magnesium oxide surface. In this case microhardness is strongly influenced by the pH value of the solution. The lower the pH, the lower the microhardness. Sodium films, which are formed on the magnesium oxide surface exposed to an NaOH containing solution, do not soften the magnesium oxide surface.

Electrogenic steps of light-driven proton transport in ESR, a retinal protein from Exiguobacterium sibiricum.

PubMed

Siletsky, Sergey A; Mamedov, Mahir D; Lukashev, Evgeniy P; Balashov, Sergei P; Dolgikh, Dmitriy A; Rubin, Andrei B; Kirpichnikov, Mikhail P; Petrovskaya, Lada E

2016-11-01

A retinal protein from Exiguobacterium sibiricum (ESR) functions as a light-driven proton pump. Unlike other proton pumps, it contains Lys96 instead of a usual carboxylic residue in the internal proton donor site. Nevertheless, the reprotonation of the Schiff base occurs fast, indicating that Lys96 facilitates proton transfer from the bulk. In this study we examined kinetics of light-induced transmembrane electrical potential difference, ΔΨ, generated in proteoliposomes reconstituted with ESR. We show that total magnitude of ΔΨ is comparable to that produced by bacteriorhodopsin but its kinetic components and their pH dependence are substantially different. The results are in agreement with the earlier finding that proton uptake precedes reprotonation of the Schiff base in ESR, suggesting that Lys96 is unprotonated in the initial state and gains a proton transiently in the photocycle. The electrogenic phases and the photocycle transitions related to proton transfer from the bulk to the Schiff base are pH dependent. At neutral pH, they occur with τ 0.5ms and 4.5ms. At alkaline pH, the fast component ceases and Schiff base reprotonation slows. At pH8.4, a spectrally silent electrogenic component with τ 0.25ms is detected, which can be attributed to proton transfer from the bulk to Lys96. At pH5.1, the amplitude of ΔΨ decreases 10 fold, reflecting a decreased yield and rate of proton transfer, apparently from protonation of the acceptor (Asp85-His57 pair) in the initial state. The features of the photoelectric potential generation correlate with the ESR structure and proposed mechanism of proton transfer. Copyright © 2016 Elsevier B.V. All rights reserved.

[Correlations between standing trees trunk decay degree and soil physical-chemical properties in Korean pine-broadleaved mixed forest in Xiao Xing'an Mountains of Northeast China].

PubMed

Sun, Tian-Yong; Wang, Li-Hai; Sun, Mo-Long

2013-07-01

Standing trees decay often causes vast loss of timber resources. To investigate the correlations between the standing trees decay and the site conditions is of importance to scientifically and reasonably manage forests and to decrease wood resources loss. By using Resistograph and meter ruler, a measurement was made on the decay degree of the trunk near root and the diameter at breast height (DBH) of 15 mature Korean pine standing trees in a Korean pine-broadleaved mixed forest in Xiao Xing' an Mountains in May, 2011. In the meantime, soil samples were collected from the root zones of standing trees and the upslope and downslope 5 meters away from the trunks, respectively. Five physical-chemical properties including moisture content, bulk density, total porosity, pH value, and organic matter content of the soil samples were tested. The regression equations concerning the trunk decay degree of the standing trees, their DBH, and the 5 soil properties were established. The results showed that the trunk decay degree of the mature Korean pine standing trees had higher correlations with the bulk density, total porosity, pH value, and organic matter content (R = 0.687), and significant positive correlation with the moisture content (R = 0.507) of the soils at the root zones of standing trees, but less correlation with the 5 properties of the soils at both upslope and downslope 5 meters away from the trunks. The trunk decay degree was decreased when the soil moisture content was below 18.4%. No significant correlation was observed between the trunk decay degree of mature Korean pine standing trees and the tree age.

Economic characteristics of the peat deposits of Costa Rica: preliminary study

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

Cohen, A.D. Malavassi, L.; Raymond, R. Jr.; Mora, S.

1985-01-01

Recent field and laboratory studies have established the presence of numerous extensive peat deposits in Costa Rica. Three of these were selected for initial investigation: (1) the cloud-forest histosols of the Talamanca Mountain Range; (2) the Rio Medio Queso flood plain deposits near the northern Costa Rican border; and (3) a tropical jungle swamp deposit on the northeastern coastal plain. In the Talamanca area, 29 samples were collected from eight sites. Due to the high moisture and cool temperatures of the cloud forest, the peats in this area form blanket-like deposits (generally <1 meter thick) over a wide area (>150more » km/sup 2/). These peats are all highly decomposed (avg. 28% fiber), high in ash (avg. 21%), and extensively bioturbated. Relative to all other sites visited, these peats are lowest in moisture (avg. 84%), pH (avg. 4.4), fixed carbon (avg. 23%), and sulfur (avg. 0.2%). However, they have the highest bulk densities (avg. 0.22 g/cc), volatile matter contents (avg. 55%), and nitrogen. Their heating value averaged 7700 BTUs/lb., dry. In the Rio Medio Queso area, 28 samples were collected, representing one transect of the 70 km/sup 2/ flood plain. The peats here occurred in several layers (each <1-1/2 meters thick), interfingering with river flood plain sediments. These peats have the highest calorific values (avg. 8000 BTUs/lb., dry), fixed carbon (avg. 30%), and ash (avg. 22%) and have an average pH of 5.4 and a bulk density of 0.20 g/cc. These results represent only the first part of a long-term, extensive survey of Costa Rica's peat resources. However, they suggest that large, economically-significant peat deposits may be present in this country. 5 refs., 8 figs., 4 tabs.« less

Ions, metabolites, and cells: Water as a reporter of surface conditions during bacterial growth.

PubMed

Jarisz, Tasha A; Lane, Sarah; Gozdzialski, Lea; Hore, Dennis K

2018-06-14

Surface-specific nonlinear vibrational spectroscopy, combined with bulk solution measurements and imaging, is used to study the surface conditions during the growth of E. coli. As a result of the silica high surface charge density, the water structure at the silica-aqueous interface is known to be especially sensitive to pH and ionic strength, and surface concentration profiles develop that can be appreciably different from the bulk solution conditions. We illustrate that, in the presence of growing cells, a unique surface micro-environment is established as a result of metabolites accumulating on the silica surface. Even in the subsequent absence of the cells, this surface layer works to reduce the interfacial ionic strength as revealed by the enhanced signal from surface water molecules. In the presence of growing cells, an additional boost in surface water signal is attributed to a local pH that is higher than that of the bulk solution.

Ions, metabolites, and cells: Water as a reporter of surface conditions during bacterial growth

NASA Astrophysics Data System (ADS)

Jarisz, Tasha A.; Lane, Sarah; Gozdzialski, Lea; Hore, Dennis K.

2018-06-01

Surface-specific nonlinear vibrational spectroscopy, combined with bulk solution measurements and imaging, is used to study the surface conditions during the growth of E. coli. As a result of the silica high surface charge density, the water structure at the silica-aqueous interface is known to be especially sensitive to pH and ionic strength, and surface concentration profiles develop that can be appreciably different from the bulk solution conditions. We illustrate that, in the presence of growing cells, a unique surface micro-environment is established as a result of metabolites accumulating on the silica surface. Even in the subsequent absence of the cells, this surface layer works to reduce the interfacial ionic strength as revealed by the enhanced signal from surface water molecules. In the presence of growing cells, an additional boost in surface water signal is attributed to a local pH that is higher than that of the bulk solution.

Aromatic organic contaminant removal from an aqueous environment by p(4-VP)-based materials.

PubMed

Sahiner, Nurettin; Ozay, Ozgur; Aktas, Nahit

2011-10-01

p(4-vinylpyridine) (p(4-VP)) hydrogels were prepared in bulk (macro, 5 × 6 mm) and in nanosizes (370 nm) dimensions. The prepared hydrogels were used to remove organic aromatic contaminates such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), phenol (Ph) and nitrobenzene (NB) from an aqueous environment. Important parameters affecting the absorption phenomena, such as the initial concentration of the organic species and the absorbent, absorption rate, absorption capacity, pH and the temperature of the medium, were evaluated for both hydrogel sizes. The absorption capacity of bulk and microgels were found to be 4-NP>2-NP>Ph>NB. Furthermore, p(4-VP) microgels were embedded in poly(acrylamide) (p(AAm)) bulk hydrogel as a microgel-hydrogel interpenetrating polymer network and proved to be very practical in overcoming the difficulty of using the microgels in real applications. Moreover, it was demonstrated that separately prepared magnetic ferrite particles inserted inside p(4-VP) microgels during synthesis allowed for trouble-free removal of p(4-VP)-magnetic composite microgels from the aqueous environment by an externally applied magnetic field upon completion of their task. Copyright © 2011 Elsevier Ltd. All rights reserved.

Development of a Test Rig for Measuring Isentropic Bulk Modulus

DTIC Science & Technology

2013-01-01

Figure 4, was fabricated from 17 - 4PH heat-treated steel. The cell is a three-part design consisting of a top and bottom with a thermowell sandwiched in...Bulk Modulus, Speed-of-Sound, Fuel 16. SECURITY CLASSIFICATION OF: 17 . LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE

Bulk Dissolution Rates of Cadmium and Bismuth Tellurides As a Function of pH, Temperature and Dissolved Oxygen.

PubMed

Biver, Marc; Filella, Montserrat

2016-05-03

The toxicity of Cd being well established and that of Te suspected, the bulk, surface-normalized steady-state dissolution rates of two industrially important binary tellurides-polycrystalline cadmium and bismuth tellurides- were studied over the pH range 3-11, at various temperatures (25-70 °C) and dissolved oxygen concentrations (0-100% O2 in the gas phase). The behavior of both tellurides is strikingly different. The dissolution rates of CdTe monotonically decreased with increasing pH, the trend becoming more pronounced with increasing temperature. Activation energies were of the order of magnitude associated with surface controlled processes; they decreased with decreasing acidity. At pH 7, the CdTe dissolution rate increased linearly with dissolved oxygen. In anoxic solution, CdTe dissolved at a finite rate. In contrast, the dissolution rate of Bi2Te3 passed through a minimum at pH 5.3. The activation energy had a maximum in the rate minimum at pH 5.3 and fell below the threshold for diffusion control at pH 11. No oxygen dependence was detected. Bi2Te3 dissolves much more slowly than CdTe; from one to more than 3.5 orders of magnitude in the Bi2Te3 rate minimum. Both will readily dissolve under long-term landfill deposition conditions but comparatively slowly.

Femtosecond transient absorption dynamics of close-packed gold nanocrystal monolayer arrays*1

NASA Astrophysics Data System (ADS)

Eah, Sang-Kee; Jaeger, Heinrich M.; Scherer, Norbert F.; Lin, Xiao-Min; Wiederrecht, Gary P.

2004-03-01

Femtosecond transient absorption spectroscopy is used to investigate hot electron dynamics of close-packed 6 nm gold nanocrystal monolayers. Morphology changes of the monolayer caused by the laser pump pulse are monitored by transmission electron microscopy. At low pump power, the monolayer maintains its structural integrity. Hot electrons induced by the pump pulse decay through electron-phonon (e-ph) coupling inside the nanocrystals with a decay constant that is similar to the value for bulk films. At high pump power, irreversible particle aggregation and sintering occur in the nanocrystal monolayer, which cause damping and peak shifting of the transient bleach signal.

Persulfate enhanced photocatalytic degradation of bisphenol A by g-C3N4 nanosheets under visible light irradiation.

PubMed

Liu, Bochuan; Qiao, Meng; Wang, Yanbin; Wang, Lijuan; Gong, Yan; Guo, Tao; Zhao, Xu

2017-12-01

The enhancement of g-C 3 N 4 photocatalytic degradation of bisphenol A (BPA) via persulfate (PS) addition was investigated under visible light irradiation. The effects of various parameters on the BPA degradation were investigated, such as catalysts dosage, PS concentrations, initial pH value and BPA concentration. The results showed that g-C 3 N 4 nanosheets exhibited superior photocatalytic activity toward BPA degradation as compared with bulk g-C 3 N 4 . The addition of PS can further improve the g-C 3 N 4 photocatalytic performance for BPA degradation. With 5 mM PS, the degradation rate of BPA was increased from 72.5% to 100% at 90 min, and the corresponding first-order kinetic constants were increased from 0.0028 to 0.0140 min -1 . The removal efficiency of BPA increased with the decrease of solution pH value. The active radicals in the reaction system were tested by electron spin resonance (ESR) and radicals quenching experiments. Instead of persulfate radicals' oxidation, it was proposed that the main active radicals for BPA degradation were superoxide radicals and the photogenerated holes. Copyright © 2017. Published by Elsevier Ltd.

Towards pH-sensitive imaging of small animals with photon-counting difference diffuse fluorescence tomography

NASA Astrophysics Data System (ADS)

Li, Jiao; Wang, Xin; Yi, Xi; Zhang, Limin; Zhou, Zhongxing; Zhao, Huijuan; Gao, Feng

2012-09-01

The importance of cellular pH has been shown clearly in the study of cell activity, pathological feature, and drug metabolism. Monitoring pH changes of living cells and imaging the regions with abnormal pH-values, in vivo, could provide invaluable physiological and pathological information for the research of the cell biology, pharmacokinetics, diagnostics, and therapeutics of certain diseases such as cancer. Naturally, pH-sensitive fluorescence imaging of bulk tissues has been attracting great attentions from the realm of near infrared diffuse fluorescence tomography (DFT). Herein, the feasibility of quantifying pH-induced fluorescence changes in turbid medium is investigated using a continuous-wave difference-DFT technique that is based on the specifically designed computed tomography-analogous photon counting system and the Born normalized difference image reconstruction scheme. We have validated the methodology using two-dimensional imaging experiments on a small-animal-sized phantom, embedding an inclusion with varying pH-values. The results show that the proposed approach can accurately localize the target with a quantitative resolution to pH-sensitive variation of the fluorescent yield, and might provide a promising alternative method of pH-sensitive fluorescence imaging in addition to the fluorescence-lifetime imaging.

Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis

PubMed Central

Preiss, Laura; Hicks, David B.; Suzuki, Shino; Meier, Thomas; Krulwich, Terry Ann

2015-01-01

Alkaliphilic bacteria typically grow well at pH 9, with the most extremophilic strains growing up to pH values as high as pH 12–13. Interest in extreme alkaliphiles arises because they are sources of useful, stable enzymes, and the cells themselves can be used for biotechnological and other applications at high pH. In addition, alkaline hydrothermal vents represent an early evolutionary niche for alkaliphiles and novel extreme alkaliphiles have also recently been found in alkaline serpentinizing sites. A third focus of interest in alkaliphiles is the challenge raised by the use of proton-coupled ATP synthases for oxidative phosphorylation by non-fermentative alkaliphiles. This creates a problem with respect to tenets of the chemiosmotic model that remains the core model for the bioenergetics of oxidative phosphorylation. Each of these facets of alkaliphilic bacteria will be discussed with a focus on extremely alkaliphilic Bacillus strains. These alkaliphilic bacteria have provided a cogent experimental system to probe adaptations that enable their growth and oxidative phosphorylation at high pH. Adaptations are clearly needed to enable secreted or partially exposed enzymes or protein complexes to function at the high external pH. Also, alkaliphiles must maintain a cytoplasmic pH that is significantly lower than the pH of the outside medium. This protects cytoplasmic components from an external pH that is alkaline enough to impair their stability or function. However, the pH gradient across the cytoplasmic membrane, with its orientation of more acidic inside than outside, is in the reverse of the productive orientation for bioenergetic work. The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis. Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH. PMID:26090360

Alkaliphilic Bacteria with Impact on Industrial Applications, Concepts of Early Life Forms, and Bioenergetics of ATP Synthesis.

PubMed

Preiss, Laura; Hicks, David B; Suzuki, Shino; Meier, Thomas; Krulwich, Terry Ann

2015-01-01

Alkaliphilic bacteria typically grow well at pH 9, with the most extremophilic strains growing up to pH values as high as pH 12-13. Interest in extreme alkaliphiles arises because they are sources of useful, stable enzymes, and the cells themselves can be used for biotechnological and other applications at high pH. In addition, alkaline hydrothermal vents represent an early evolutionary niche for alkaliphiles and novel extreme alkaliphiles have also recently been found in alkaline serpentinizing sites. A third focus of interest in alkaliphiles is the challenge raised by the use of proton-coupled ATP synthases for oxidative phosphorylation by non-fermentative alkaliphiles. This creates a problem with respect to tenets of the chemiosmotic model that remains the core model for the bioenergetics of oxidative phosphorylation. Each of these facets of alkaliphilic bacteria will be discussed with a focus on extremely alkaliphilic Bacillus strains. These alkaliphilic bacteria have provided a cogent experimental system to probe adaptations that enable their growth and oxidative phosphorylation at high pH. Adaptations are clearly needed to enable secreted or partially exposed enzymes or protein complexes to function at the high external pH. Also, alkaliphiles must maintain a cytoplasmic pH that is significantly lower than the pH of the outside medium. This protects cytoplasmic components from an external pH that is alkaline enough to impair their stability or function. However, the pH gradient across the cytoplasmic membrane, with its orientation of more acidic inside than outside, is in the reverse of the productive orientation for bioenergetic work. The reversed gradient reduces the trans-membrane proton-motive force available to energize ATP synthesis. Multiple strategies are hypothesized to be involved in enabling alkaliphiles to circumvent the challenge of a low bulk proton-motive force energizing proton-coupled ATP synthesis at high pH.

Surface Protonation at the Rutile (110) Interface: Explicit Incorporation of Solvation Structure within the Refined MUSIC Model Framework

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

Machesky, Michael L.; Predota, M.; Wesolowski, David J

The detailed solvation structure at the (110) surface of rutile ({alpha}-TiO{sub 2}) in contact with bulk liquid water has been obtained primarily from experimentally verified classical molecular dynamics (CMD) simulations of the ab initio-optimized surface in contact with SPC/E water. The results are used to explicitly quantify H-bonding interactions, which are then used within the refined MUSIC model framework to predict surface oxygen protonation constants. Quantum mechanical molecular dynamics (QMD) simulations in the presence of freely dissociable water molecules produced H-bond distributions around deprotonated surface oxygens very similar to those obtained by CMD with nondissociable SPC/E water, thereby confirming thatmore » the less computationally intensive CMD simulations provide accurate H-bond information. Utilizing this H-bond information within the refined MUSIC model, along with manually adjusted Ti-O surface bond lengths that are nonetheless within 0.05 {angstrom} of those obtained from static density functional theory (DFT) calculations and measured in X-ray reflectivity experiments (as well as bulk crystal values), give surface protonation constants that result in a calculated zero net proton charge pH value (pHznpc) at 25 C that agrees quantitatively with the experimentally determined value (5.4 {+-} 0.2) for a specific rutile powder dominated by the (110) crystal face. Moreover, the predicted pH{sub znpc} values agree to within 0.1 pH unit with those measured at all temperatures between 10 and 250 C. A slightly smaller manual adjustment of the DFT-derived Ti-O surface bond lengths was sufficient to bring the predicted pH{sub znpc} value of the rutile (110) surface at 25 C into quantitative agreement with the experimental value (4.8 {+-} 0.3) obtained from a polished and annealed rutile (110) single crystal surface in contact with dilute sodium nitrate solutions using second harmonic generation (SHG) intensity measurements as a function of ionic strength. Additionally, the H-bond interactions between protolyzable surface oxygen groups and water were found to be stronger than those between bulk water molecules at all temperatures investigated in our CMD simulations (25, 150 and 250 C). Comparison with the protonation scheme previously determined for the (110) surface of isostructural cassiterite ({alpha}-SnO{sub 2}) reveals that the greater extent of H-bonding on the latter surface, and in particular between water and the terminal hydroxyl group (Sn-OH) results in the predicted protonation constant for that group being lower than for the bridged oxygen (Sn-O-Sn), while the reverse is true for the rutile (110) surface. These results demonstrate the importance of H-bond structure in dictating surface protonation behavior, and that explicit use of this solvation structure within the refined MUSIC model framework results in predicted surface protonation constants that are also consistent with a variety of other experimental and computational data.« less

Multivariate statistics as means of tracking atmospheric pollution trends in Western Poland.

PubMed

Astel, Aleksander M; Walna, Barbara; Simeonov, Vasil; Kurzyca, Iwona

2008-02-15

This study was carried out over a period of 4 years (2002-2005) at 2 sites located in western Poland differing as regards to human impact by analysis of chemical composition of bulk precipitation. The aim of the study was to determine the sources of pollutions and assess their quantitative contribution to the bulk precipitation composition and to analyse long term-changes in the chemical quality of precipitation. Based on this information the possible transboundary impacts of pollution were also determined. The samples were characterized by determining the values of pH, electrolytic conductivity and concentration levels of Cl(-), F(-), SO(4)(2-), NO(3)(-), Na(+), K(+), Mg(2+), Ca(2+) and NH(4)(+). Analytical measurements were connected with application of principal component regression (PCR) and time series analysis (TS). Based on PCR results three major sources of pollutants in central part of Poland have been identified and quantitatively assessed as follows: "combined" (Poznań - 31%, WNP - 32%), "soil-particulates" (Poznań - 2%, WNP - 26%), "anthropogenic-fossil fuels" (Poznań - 43%, WNP - 23%). Time series analysis enabled discovering 12-month time cycle for NO(3)(-), NH(4)(+), Cl(-), F(-) and SO(4)(2-) in average monthly concentration values in bulk precipitation collected in Wielkopolski National Park. Seasonal variation in the emission of precursors of NO(3)(-) and NH(4)(+) was caused by changes in intensity of fertilizer application in agriculture and automobile exhaust emissions. Decreasing trend was visible for sulphates, nitrates, chlorides and fluorides which is an important indication of the acid rain reduction in the ecologically protected area and in Poznań.

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

Sundaramurthi, Prakash; Suryanarayanan, Raj

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

Formation of Mg-aluminosilicates During Early Diagenesis of Carbonate Sediments in the Volcanic Crater Lake of Dziani Dzaha (Mayotte - Indian Ocean)

NASA Astrophysics Data System (ADS)

Milesi, V. P.; Jezequel, D.; Debure, M.; Marty, N.; Guyot, F. J.; Claret, F.; Virgone, A.; Gaucher, E.; Ader, M.

2017-12-01

Authigenic clays are increasingly reported in ancient carbonate rocks, but their origin remains poorly understood, strongly limiting paleoenvironmental interpretations. To tackle this issue, the carbonate sediments of the volcanic crater lake Dziani Dzaha are studied and reactive transport modeling is performed to assess the processes originating carbonate sediments associated with Mg-rich silicates during early diagenesis. The Dziani Dzaha is characterized by CO2-rich gases bubbling in three different locations, a high primary productivity leading to organic carbon contents of up to 30wt.% in the sediment, an alkalinity of 0.26 molal in the water column and pH values of 9 to 9.5. Characterization of bulk samples and clay fraction (<2µm) from the first meter of sediment with X-ray powder diffraction and X-ray fluorescence spectrometry indicates aragonite and hydromagnesite in surface sediment. The contents of hydromagnesite and organic matter decrease at depth while saponite, a Mg- and Al-rich trioctahedral smectite, accumulates to reach up to 25wt.% of mineral phases. Concurrently, chemical analyses of pore waters show a decrease of pH values from 9 to 8.3. Modeling of these diagenetic evolutions is performed with the reactive transport code Crunchflow, taking into account the sediment burial. High pH values combined with the alteration of alkaline feldspars and clinopyroxenes from the volcanic catchment allow supersaturation of lake waters relative to aragonite, hydromagnesite and saponite. Kinetic limitations in the formation of saponite explain its accumulation at depth. Production of CO2 associated with organic matter mineralization accounts for the pH decrease of pore waters, which induces hydromagnesite destabilisation leaving behind a saponite-aragonite mineral assemblage. The main driving force for the observed sequence is the intense primary productivity partly fueled by inputs of CO2-rich volcanic gases, which generates high pH, promoting the formation of saponite, aragonite and hydromagnesite, which precipitates at first before being destabilized at depth due to organic matter mineralization. The observed carbon cycle, influenced by volcanic gases, may thus play a key role in the development of carbonate rocks associated with Mg-silicates.

The removal of As(III) and As(V) from aqueous solutions by waste materials.

PubMed

Rahaman, M S; Basu, A; Islam, M R

2008-05-01

The use of different waste materials such as Atlantic Cod fish scale, chicken fat, coconut fibre and charcoal in removing arsenic [As(III) and As(V)] from aqueous solutions was investigated. Initial experimental runs, conducted for both As(III) and As(V) with the aforementioned materials, demonstrated the potential of using Atlantic Cod fish scale in removing both species of arsenic from aqueous streams. Therefore, the biosorbent fish scale was selected for further investigations and various parameters such as residence time, adsorbent dose, initial concentration of adsorbate, grain size of the adsorbent and pH of the bulk phase were studied to establish optimum conditions. The maximum adsorption capacity was observed at pH value 4.0. The equilibrium adsorption data were interpreted by using both Freundlich and Langmuir models. Rapid small-scale column tests (RSSCT) were also performed to determine the breakthrough characteristics of the arsenic species with respect to packed biosorbent columns.

Effect of biochars produced from solid organic municipal waste on soil quality parameters.

PubMed

Randolph, P; Bansode, R R; Hassan, O A; Rehrah, Dj; Ravella, R; Reddy, M R; Watts, D W; Novak, J M; Ahmedna, M

2017-05-01

New value-added uses for solid municipal waste are needed for environmental and economic sustainability. Fortunately, value-added biochars can be produced from mixed solid waste, thereby addressing solid waste management issues, and enabling long-term carbon sequestration. We hypothesize that soil deficiencies can be remedied by the application of municipal waste-based biochars. Select municipal organic wastes (newspaper, cardboard, woodchips and landscaping residues) individually or in a 25% blend of all four waste streams were used as feedstocks of biochars. Three sets of pyrolysis temperatures (350, 500, and 750 °C) and 3 sets of pyrolysis residence time (2, 4 and 6 h) were used for biochar preparation. The biochar yield was in the range of 21-62% across all feedstocks and pyrolysis conditions. We observed variations in key biochar properties such as pH, electrical conductivity, bulk density and surface area depending on the feedstocks and production conditions. Biochar increased soil pH and improved its electrical conductivity, aggregate stability, water retention and micronutrient contents. Similarly, leachate from the soil amended with biochar showed increased pH and electrical conductivity. Some elements such as Ca and Mg decreased while NO 3 -N increased in the leachates of soils incubated with biochars. Overall, solid waste-based biochar produced significant improvements to soil fertility parameters indicating that solid municipal wastes hold promising potential as feedstocks for manufacturing value-added biochars with varied physicochemical characteristics, allowing them to not only serve the needs for solid waste management and greenhouse gas mitigation, but also as a resource for improving the quality of depleted soils. Copyright © 2017 Elsevier Ltd. All rights reserved.

A mathematical model of the influence of salivary urea on the pH of fasted dental plaque and on the changes occurring during a cariogenic challenge.

PubMed

Dibdin, G H; Dawes, C

1998-01-01

Urea diffusing from saliva into dental plaque is converted to ammonia and carbon dioxide by bacterial ureases. The influence of normal salivary urea levels on the pH of fasted plaque and on the depth and duration of a Stephan curve is uncertain. A numerical model which simulates a cariogenic challenge (a 10% sucrose rinse alone or one followed by use of chewing-gum with or without sugar) was modified to include salivary urea levels from 0 to 30 mmol/l. It incorporated: site-dependent exchange between bulk saliva and plaque surfaces via a salivary film; sugar and urea diffusion into plaque; pH-dependent rates of acid formation and urea breakdown; diffusion and dissociation of end-products and other buffers (acetate, lactate, phosphate, ammonia and carbonate); diffusion of protons and other ions; equilibration with fixed and mobile buffers; and charge-coupling between ionic flows. The Km (2.12 mmol/l) and Vmax (0.11 micromol urea/min/mg dry weight) values for urease activity and the pH dependence of Vmax were taken from the literature. From the results, it is predicted that urea concentrations normally present in saliva (3-5 mmol/l) will increase the pH at the base of a 0.5-mm-thick fasted plaque by up to 1 pH unit, and raise the pH minimum after a sucrose rinse or sugar-containing chewing-gum by at least half a pH unit. The results suggest that plaque cariogenicity may be inversely related to salivary urea concentrations, not only when the latter are elevated because of disease, but even when they are in the normal range.

Vibrational spectroscopic study of pH dependent solvation at a Ge(100)-water interface during an electrode potential triggered surface termination transition

NASA Astrophysics Data System (ADS)

Niu, Fang; Rabe, Martin; Nayak, Simantini; Erbe, Andreas

2018-06-01

The charge-dependent structure of interfacial water at the n-Ge(100)-aqueous perchlorate interface was studied by controlling the electrode potential. Specifically, a joint attenuated total reflection infrared spectroscopy and electrochemical experiment was used in 0.1M NaClO4 at pH ≈ 1-10. The germanium surface transformation to an H-terminated surface followed the thermodynamic Nernstian pH dependence and was observed throughout the entire pH range. A singular value decomposition-based spectra deconvolution technique coupled to a sigmoidal transition model for the potential dependence of the main components in the spectra shows the surface transformation to be a two-stage process. The first stage was observed together with the first appearance of Ge-H stretching modes in the spectra and is attributed to the formation of a mixed surface termination. This transition was reversible. The second stage occurs at potentials ≈0.1-0.3 V negative of the first one, shows a hysteresis in potential, and is attributed to the formation of a surface with maximum Ge-H coverage. During the surface transformation, the surface becomes hydrophobic, and an effective desolvation layer, a "hydrophobic gap," developed with a thickness ≈1-3 Å. The largest thickness was observed near neutral pH. Interfacial water IR spectra show a loss of strongly hydrogen-bound water molecules compared to bulk water after the surface transformation, and the appearance of "free," non-hydrogen bound OH groups, throughout the entire pH range. Near neutral pH at negative electrode potentials, large changes at wavenumbers below 1000 cm-1 were observed. Librational modes of water contribute to the observed changes, indicating large changes in the water structure.

A validated chiral liquid chromatographic method for the enantiomeric separation of safinamide mesilate, a new anti-Parkinson drug.

PubMed

Zhang, Kai; Xue, Na; Shi, Xiaowei; Liu, Weina; Meng, Jing; Du, Yumin

2011-04-28

A enantioselective reversed-phase high performance liquid chromatographic method was developed for the enantiomeric resolution of safinamide mesilate, 2(S)-[4-(3-fluorobenzyloxy)benzylamino] propionamide methanesulfonate, a neuroprotectant with antiparkinsonian and anticonvulsant activity for the treatment of Parkinson disease. The enantiomers of safinamide mesilate were baseline resolved on a Chiralcel OD-RH (150mm×4.6mm, 5μm) column using a mobile phase system containing 300mM sodium di-hydrogen phosphate buffer (pH 3.0):methanol:acetonitrile (65:25:10, v/v/v). The resolution between the enantiomers was not less than 3.0. The pH value of buffer solution in the mobile phase has played a key role in enhancing chromatographic efficiency and resolution between the enantiomers. The developed method was validated and proved to be robust. The limit of detection and limit of quantification of (R)-enantiomer were found to be 15 and 50ng/mL, respectively, for 20μL injection volume. The percentage recovery of (R)-enantiomer was ranged from 94.2 to 103.7 in bulk drug samples of safinamide mesilate. The sample solution and mobile phase were found to be stable at least for 48h. The final optimized method was successfully applied to separate (R)-enantiomer from safinamide mesilate and was proven to be reproducible and accurate for the quantitative determination of (R)-enantiomer in bulk drugs. Copyright © 2010 Elsevier B.V. All rights reserved.

Towards predicting coral calcification responses to ocean acidification: A combined modeling and experimental approach

NASA Astrophysics Data System (ADS)

Mollica, N. R.; Guo, W.; Cohen, A. L.; Foster, G. L.; Barkley, H.

2016-02-01

Experiments show that ocean acidification is detrimental to coral calcification. Nevertheless, coral sensitivities to OA vary and the mechanism(s) underlying these variable responses are not fully understood. One hypothesis is that ocean acidification affects the ability of coral's to regulate the pH of fluid at the site of calcification. We developed a numerical model of coral calcification that simulates corals' pH regulation based on physiochemical principles and predicts the rate of calcification [1]. Here we apply this model to Palauan corals, and seek to test the model's efficacy by comparing the predicted coral calcification responses with experimental measurements. Four coral cores were collected from two sites of different pH (7.84 and 8.04 respectively). Their bulk annual calcification rates, quantified from average density and extension rate measurements, vary from .83 to 1.39 g cm-2 year-1 for the low pH site and from 0.75 to 1.21 g cm-2 year-1for the high pH site. The higher bulk calcification rates observed in corals from the low pH site contrasts the expected general decrease in calcification in low pH seawater, and differs from our model prediction. We suspect this apparent discrepancy arises because fast-calcifying corals in low pH water are able to modulate the pH of fluid at the site of calcification. We test this hypothesis using boron isotope measurements from each coral. In addition, a more accurate measurement of instantaneous calcification, considering the number of corallites per measured area and the exact surface area of each polyp's 3-dimensional calcification site is applied. [1] Guo, W. (2014). AGU Fall Meeting, Abstract B41B-0033.

Self-assembly and bilayer-micelle transition of fatty acids studied by replica-exchange constant pH molecular dynamics

PubMed Central

Morrow, Brian H.; Koenig, Peter H.; Shen, Jana K.

2014-01-01

Recent interest in the development of surfactant-based nano delivery systems targeting tumor sites has sparked our curiosity to understand the detailed mechanism of the self-assembly and phase transitions of pH-sensitive surfactants. Towards this goal we applied a state-of-the-art simulation technique, continuous constant pH molecular dynamics (CpHMD) with the hybrid-solvent scheme and pH-based replica-exchange protocol, to study de novo self-assembly of 30 and 40 lauric acids, a simple model titratable surfactant. We observed the formation of a gel-state bilayer at low and intermediate pH and a spherical micelle at high pH, with the phase transition starting at 20–30% ionization and completing at 50%. The degree of cooperativity for the transition increases from the 30-mer to the 40-mer. The calculated apparent or bulk pKa value is 7.0 for the 30-mer and 7.5 for the 40-mer. Congruent with experiment, these data demonstrate that CpHMD is capable of accurately modeling large conformational transitions of surfactant systems while allowing simultaneous proton titration of constituent molecules. We suggest that CpHMD simulations may become a useful tool to aid in the design and development of pH-sensitive nanocarriers for a variety of biomedical and technological applications. PMID:24215478

Importance of pH-regulated charge density on the electrophoresis of soft particles

NASA Astrophysics Data System (ADS)

Gopmandal, Partha P.; Ohshima, H.

2017-02-01

The present study deals with the electrophoresis of spherical soft particles consisting of an ion and liquid-penetrable but liquid-flow-impenetrable inner core surrounded by an ion and fluid-penetrable polyelectrolyte layer. The inner core is considered to be dielectric and bearing basic functional group coated with polyelectrolyte layer containing acidic functional group. An approximate expression for the electrophoretic mobility of such a particle is obtained under a low potential limit. The electrophoretic behaviour of the undertaken particle is investigated for a wide range of bulk pH values and electrolyte concentrations. Our study also indicates some remarkable features of the electrophoresis e.g., occurrence of zero mobility, mobility reversal etc.

Possibility of H2O2 decomposition in thin liquid films on Mars

NASA Astrophysics Data System (ADS)

Kereszturi, Akos; Gobi, Sandor

2014-11-01

In this work the pathways and possibilities of H2O2 decomposition on Mars in microscopic liquid interfacial water were analyzed by kinetic calculations. Thermal and photochemical driven decomposition, just like processes catalyzed by various metal oxides, is too slow compared to the annual duration while such microscopic liquid layers exist on Mars today, to produce substantial decomposition. The most effective analyzed process is catalyzed by Fe ions, which could decompose H2O2 under pH<4.5 with a half life of 1-2 days. This process might be important during volcanically influenced periods when sulfur release produces acidic pH, and rotational axis tilt change driven climatic changes also influence the volatile circulation and spatial occurrence just like the duration of thin liquid layer. Under current conditions, using the value of 200 K as the temperature in interfacial water (at the southern hemisphere), and applying Phoenix lander's wet chemistry laboratory results, the pH is not favorable for Fe mobility and this kind of decomposition. Despite current conditions (especially pH) being unfavorable for H2O2 decomposition, microscopic scale interfacial liquid water still might support the process. By the reaction called heterogeneous catalysis, without acidic pH and mobile Fe, but with minerals surfaces containing Fe decomposition of H2O2 with half life of 20 days can happen. This duration is still longer but not several orders than the existence of springtime interfacial liquid water on Mars today. This estimation is relevant for activation energy controlled reaction rates. The other main parameter that may influence the reaction rate is the diffusion speed. Although the available tests and theoretical calculations do not provide firm values for the diffusion speed in such a “2-dimensional” environment, using relevant estimations this parameter in the interfacial liquid layer is smaller than in bulk water. But the 20 days' duration mentioned above is still relevant, as the activation energy driven reaction rate is the main limiting factor in the decomposition and not the diffusion speed. The duration of dozen(s) days is still longer but not with orders of magnitude than the expected duration for the existence of springtime interfacial liquid water on Mars today. The results suggest such decomposition may happen today, however, because of our limited knowledge on chemical processes in thin interfacial liquid layers, this possibility waits for confirmation - and also points to the importance of conducting laboratory tests to validate the possible process. Although some tests were already realized for diffusion in an almost 2-dimensional liquid, the same is not true for activation energy, where only the value from the “normal” measurements was applied. Even if H2O2 decomposition is too slow today, the analysis of such a process is important, as under volcanic influence more effective decomposition might take place in thin interfacial liquids close to the climate of today if released sulfur produces pH<4.5. Large quantity and widespread occurrence of bulk liquid phase are not expected in the Amazonian period, but interfacial liquid water probably appeared regularly, and its locations, especially during volcanically active periods, might make certain sites than others more interesting for astrobiology with the lower concentration of oxidizing H2O2.

Surface protonation at the rutile (110) interface: explicit incorporation of solvation structure within the refined MUSIC model framework.

PubMed

Machesky, Michael L; Predota, Milan; Wesolowski, David J; Vlcek, Lukas; Cummings, Peter T; Rosenqvist, Jörgen; Ridley, Moira K; Kubicki, James D; Bandura, Andrei V; Kumar, Nitin; Sofo, Jorge O

2008-11-04

The detailed solvation structure at the (110) surface of rutile (alpha-TiO2) in contact with bulk liquid water has been obtained primarily from experimentally verified classical molecular dynamics (CMD) simulations of the ab initio-optimized surface in contact with SPC/E water. The results are used to explicitly quantify H-bonding interactions, which are then used within the refined MUSIC model framework to predict surface oxygen protonation constants. Quantum mechanical molecular dynamics (QMD) simulations in the presence of freely dissociable water molecules produced H-bond distributions around deprotonated surface oxygens very similar to those obtained by CMD with nondissociable SPC/E water, thereby confirming that the less computationally intensive CMD simulations provide accurate H-bond information. Utilizing this H-bond information within the refined MUSIC model, along with manually adjusted Ti-O surface bond lengths that are nonetheless within 0.05 A of those obtained from static density functional theory (DFT) calculations and measured in X-ray reflectivity experiments (as well as bulk crystal values), give surface protonation constants that result in a calculated zero net proton charge pH value (pHznpc) at 25 degrees C that agrees quantitatively with the experimentally determined value (5.4+/-0.2) for a specific rutile powder dominated by the (110) crystal face. Moreover, the predicted pHznpc values agree to within 0.1 pH unit with those measured at all temperatures between 10 and 250 degrees C. A slightly smaller manual adjustment of the DFT-derived Ti-O surface bond lengths was sufficient to bring the predicted pHznpcvalue of the rutile (110) surface at 25 degrees C into quantitative agreement with the experimental value (4.8+/-0.3) obtained from a polished and annealed rutile (110) single crystal surface in contact with dilute sodium nitrate solutions using second harmonic generation (SHG) intensity measurements as a function of ionic strength. Additionally, the H-bond interactions between protolyzable surface oxygen groups and water were found to be stronger than those between bulk water molecules at all temperatures investigated in our CMD simulations (25, 150 and 250 degrees C). Comparison with the protonation scheme previously determined for the (110) surface of isostructural cassiterite (alpha-SnO2) reveals that the greater extent of H-bonding on the latter surface, and in particular between water and the terminal hydroxyl group (Sn-OH) results in the predicted protonation constant for that group being lower than for the bridged oxygen (Sn-O-Sn), while the reverse is true for the rutile (110) surface. These results demonstrate the importance of H-bond structure in dictating surface protonation behavior, and that explicit use of this solvation structure within the refined MUSIC model framework results in predicted surface protonation constants that are also consistent with a variety of other experimental and computational data.

Decouple electronic and phononic transport in nanotwinned structures: a new strategy for enhancing the figure-of-merit of thermoelectrics.

PubMed

Zhou, Yanguang; Gong, Xiaojing; Xu, Ben; Hu, Ming

2017-07-20

Thermoelectric (TE) materials manifest themselves to enable direct conversion of temperature differences to electric power and vice versa. Though remarkable advances have been achieved in the past decades for various TE systems, the energy conversion efficiency of TE devices, which is characterized by a dimensionless figure-of-merit (ZT = S 2 σT/(κ el + κ ph )), generally remains a poor factor that severely limits TE devices' competitiveness and range of employment. The bottleneck for substantially boosting the ZT coefficient lies in the strong interdependence of the physical parameters involved in electronic (S and σ, and κ el ) and phononic (κ ph ) transport. Herein, we propose a new strategy of incorporating nanotwinned structures to decouple electronic and phononic transport. Combining the new concept of nanotwinned structures with the previously widely used nanocrystalline approach, the power factor of the nanotwin-nanocrystalline Si heterostructures is enhanced by 120% compared to that of bulk crystalline Si, while the lattice thermal conductivity is reduced to a level well below the amorphous limit, yielding a theoretical limit of 0.52 and 0.9 for ZT coefficient at room temperature and 1100 K, respectively. This value is almost two orders of magnitude larger than that for bulk Si and twice that for polycrystalline Si. Even for the experimentally obtained nanotwin-nanocrystalline heterostructures (e.g. grain size of 5 nm), the ZT coefficient can be as high as 0.26 at room temperature and 0.7 at 1100 K, which is the highest ZT value among all Si-based bulk nanostructures found thus far. Such substantial improvement stems from two aspects: (1) the improvement in the power factor is caused due to an increase in the Seebeck coefficient (degeneracy of the band valley) and the enhancement of electrical conductivity (the reduction of the effective band mass) and (2) the significant reduction of the lattice thermal conductivity is mainly caused due to the extremely strong phonon-grain boundary and phonon-twin boundary scattering. Our results suggest that nanotwinned structures are excellent building blocks for enhancing TE performance in diamond-like semiconductors, and our study provides a new strategy for the innovative development of other TE materials.

Facile Preparation of Light Emitting Organic Metal Halide Crystals with Near-Unity Quantum Efficiency

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

Zhou, Chenkun; Worku, Michael; Neu, Jennifer

Here, we report the synthesis and characterization of (Ph 4P) 2SbCl 5, a novel ionically bonded organic metal halide hybrid with a zero-dimensional (0D) structure at the molecular level. By cocrystallization of tetraphenylphosphonium (Ph 4P +) and antimony (Sb 3+) chloride salts, (Ph 4P) 2SbCl 5 bulk single crystals can be prepared in high yield, which exhibit a highly efficient broadband red emission peaked at 648 nm with a photoluminescence quantum efficiency (PLQE) of around 87%. Density functional theory (DFT) calculations reveal the origin of emission as phosphorescence from the excitons localized at SbCl 5 2– with strong excited-state structuralmore » distortion. Interestingly, (Ph 4P) 2SbCl 5 bulk crystals with a PLQE of around 100% can be prepared via a rapid crystal growth process within minutes, followed by a spontaneous structural transformation. It was found that the rapid growth process yielded a yellow emitting kinetically favored metastable product containing solvent molecules, which turned into the red emitting thermodynamically stable product slowly at room temperature or quickly upon thermal treatment.« less

Facile Preparation of Light Emitting Organic Metal Halide Crystals with Near-Unity Quantum Efficiency

DOE PAGES

Zhou, Chenkun; Worku, Michael; Neu, Jennifer; ...

2018-03-12

Here, we report the synthesis and characterization of (Ph 4P) 2SbCl 5, a novel ionically bonded organic metal halide hybrid with a zero-dimensional (0D) structure at the molecular level. By cocrystallization of tetraphenylphosphonium (Ph 4P +) and antimony (Sb 3+) chloride salts, (Ph 4P) 2SbCl 5 bulk single crystals can be prepared in high yield, which exhibit a highly efficient broadband red emission peaked at 648 nm with a photoluminescence quantum efficiency (PLQE) of around 87%. Density functional theory (DFT) calculations reveal the origin of emission as phosphorescence from the excitons localized at SbCl 5 2– with strong excited-state structuralmore » distortion. Interestingly, (Ph 4P) 2SbCl 5 bulk crystals with a PLQE of around 100% can be prepared via a rapid crystal growth process within minutes, followed by a spontaneous structural transformation. It was found that the rapid growth process yielded a yellow emitting kinetically favored metastable product containing solvent molecules, which turned into the red emitting thermodynamically stable product slowly at room temperature or quickly upon thermal treatment.« less

Characterization, sorption, and exhaustion of metal oxide nanoparticles as metal adsorbents

NASA Astrophysics Data System (ADS)

Engates, Karen Elizabeth

Safe drinking water is paramount to human survival. Current treatments do not adequately remove all metals from solution, are expensive, and use many resources. Metal oxide nanoparticles are ideal sorbents for metals due to their smaller size and increased surface area in comparison to bulk media. With increasing demand for fresh drinking water and recent environmental catastrophes to show how fragile water supplies are, new approaches to water conservation incorporating new technologies like metal oxide nanoparticles should be considered as an alternative method for metal contaminant adsorbents from typical treatment methods. This research evaluated the potential of manufactured iron, anatase, and aluminum nanoparticles (Al2O3, TiO2, Fe2O3) to remove metal contaminants (Pb, Cd, Cu, Ni, Zn) in lab-controlled and natural waters in comparison to their bulk counterparts by focusing on pH, contaminant and adsorbent concentrations, particle size, and exhaustive capabilities. Microscopy techniques (SEM, BET, EDX) were used to characterize the adsorbents. Adsorption experiments were performed using 0.01, 0.1, or 0.5 g/L nanoparticles in pH 8 solution. When results were normalized by mass, nanoparticles adsorbed more than bulk particles but when surface area normalized the opposite was observed. Adsorption was pH-dependent and increased with time and solid concentration. Aluminum oxide was found to be the least acceptable adsorbent for the metals tested, while titanium dioxide anatase (TiO2) and hematite (alpha-Fe2O3) showed great ability to remove individual and multiple metals from pH 8 and natural waters. Intraparticle diffusion was likely part of the complex kinetic process for all metals using Fe2O3 but not TiO 2 nanoparticles within the first hour of adsorption. Adsorption kinetics for all metals tested were described by a modified first order rate equation used to consider the diminishing equilibrium metal concentrations with increasing metal oxides, showing faster adsorption rates for nanoparticles compared to bulk particles. Isotherms were best fit with most correlations of r=0.99 or better using the Langmuir-Freundlich equation which describes a heterogeneous surface with monolayer adsorption. Calculated rate constants and distribution coefficients (Kd) showed TiO2 nanoparticles were very good sorbents and more rapid in removing metals than other nanoparticles studied here and reported in the literature. Desorption studies concluded Pb, Cd, and Zn appear to be irreversibly sorbed to TiO2 surfaces at pH 8. TiO2 and Fe2O3 nanoparticles were capable of multiple metal loadings, with exhaustion for both adsorbents at pH 6. Exhaustion studies at pH 8 showed hematite exhausted after four consecutive cycles while anatase showed no exhaustion after 8 cycles. Their bulk counterparts exhausted in earlier cycles indicating the lack of ability to adsorb much of the multiple metals in solution. The increased surface area of TiO2 and Fe 2O3 nanoparticles, coupled with strong adsorption at the pH of most natural waters and resistance to desorption of some metals, may offer a potential remediation method for removal of metals from water in the future.

High performance liquid chromatography for simultaneous determination of xipamide, triamterene and hydrochlorothiazide in bulk drug samples and dosage forms.

PubMed

Abd El-Hay, Soad S; Hashem, Hisham; Gouda, Ayman A

2016-03-01

A novel, simple and robust high-performance liquid chromatography (HPLC) method was developed and validated for simultaneous determination of xipamide (XIP), triamterene (TRI) and hydrochlorothiazide (HCT) in their bulk powders and dosage forms. Chromatographic separation was carried out in less than two minutes. The separation was performed on a RP C-18 stationary phase with an isocratic elution system consisting of 0.03 mol L(-1) orthophosphoric acid (pH 2.3) and acetonitrile (ACN) as the mobile phase in the ratio of 50:50, at 2.0 mL min(-1) flow rate at room temperature. Detection was performed at 220 nm. Validation was performed concerning system suitability, limits of detection and quantitation, accuracy, precision, linearity and robustness. Calibration curves were rectilinear over the range of 0.195-100 μg mL(-1) for all the drugs studied. Recovery values were 99.9, 99.6 and 99.0 % for XIP, TRI and HCT, respectively. The method was applied to simultaneous determination of the studied analytes in their pharmaceutical dosage forms.

Matching phosphate and maleate buffer systems for dissolution of weak acids: Equivalence in terms of buffer capacity of bulk solution or surface pH?

PubMed

Cristofoletti, Rodrigo; Dressman, Jennifer B

2016-06-01

The development of in vitro dissolution tests able to anticipate the in vivo fate of drug products has challenged pharmaceutical scientists over time, especially in the case of ionizable compounds. In the seminal model proposed by Mooney et al. thirty-five years ago, the pH at the solid-liquid interface (pH0) was identified as a key parameter in predicting dissolution rate. In the current work it is demonstrated that the in vitro dissolution of the weak acid ibuprofen in maleate and phosphate buffer systems is a function of the pH0, which in turn is affected by properties of the drug and the medium. The reported pH0 for ibuprofen dissolution in bicarbonate buffer, the predominant buffer species in the human small intestine under fasting conditions, can be achieved by reducing the phosphate buffer concentration to 5.0mM or the maleate buffer concentration to 2.2mM. Using this approach to identify the appropriate buffer/buffer capacity combination for in vitro experiments in FaSSIF-type media, it would be possible to increase the physiological relevance of this important biopharmaceutics tool. However, the necessity of monitoring and adjusting the bulk pH during the experiments carried out in 5.0mM phosphate or 2.2mM maleate buffers must also be taken into consideration. Copyright © 2016 Elsevier B.V. All rights reserved.

Physical and photoelectrochemical properties of spherical nanoparticles of α-AgBiS2

NASA Astrophysics Data System (ADS)

Bellal, B.; Berger, M. H.; Trari, M.

2017-10-01

We have investigated the physical and photo electrochemical properties of α-AgBiS2 (schapbachite), synthesized from Bi2S3 and Ag2S in evacuated Pyrex ampoule at 550 °C. The precursors are prepared by precipitation from nitrates in ethylene glycol using thiourea as complexing agent and sulfide source. AgBiS2 crystallizes in a rock salt structure (Fm-3m). The transmission electron micrograph shows spherical nanoparticles with an average size of 30 nm, a value very close to that obtained from the Williamson-Hall plot of the XRD powder pattern (33.06±1.28 nm). HRTEM gives inter reticular distance of 0.33 nm, a value in excellent agreement with that of the SAED analysis (d111=0.3276 nm). The diffuse reflectance spectrum indicates a direct optical transition of 0.89 eV. The thermal variation of the electrical conductivity is characteristic of semiconducting behavior with activation energy of 0.20 eV, electron mobility (μ300K) of 2.43 × 10-4 cm2 V-1 s-1 and an effective mass of 2.88 mo. The intensity-potential J(V) curve in alkaline medium (pH 10.2) shows a good electrochemical stability. The dark capacitance (C-2-V) exhibits a linear behavior, characteristic of n-type conduction (dC-2/dE>0), from which a flat band potential of 0.33 VSCE and an electrons density of 2.57 × 1021 cm-3 are determined. The valence band derives from S2-: 3p states while the conduction band is made up mainly of Ag+: 5 s orbital. The electrochemical impedance spectroscopy (EIS), measured in the dark and under illumination over the frequency range (10-3-105 Hz), indicates the contribution of both the bulk and grain boundaries. An equivalent electrical circuit was simulated from the Nyquist diagram at pH 10, indicating the bulk contribution in the transport mechanism.

A validated stability-indicating HPLC method for determination of varenicline in its bulk and tablets

PubMed Central

2011-01-01

A simple, sensitive and accurate stability-indicating HPLC method has been developed and validated for determination of varenicline (VRC) in its bulk form and pharmaceutical tablets. Chromatographic separation was achieved on a Zorbax Eclipse XDB-C8 column (150 mm × 4.6 mm i.d., particle size 5 μm, maintained at ambient temperature) by a mobile phase consisted of acetonitrile and 50 mM potassium dihydrogen phosphate buffer (10:90, v/v) with apparent pH of 3.5 ± 0.1 and a flow rate of 1.0 ml/min. The detection wavelength was set at 235 nm. VRC was subjected to different accelerated stress conditions. The degradation products, when any, were well resolved from the pure drug with significantly different retention time values. The method was linear (r = 0.9998) at a concentration range of 2 - 14 μg/ml. The limit of detection and limit of quantitation were 0.38 and 1.11 μg/ml, respectively. The intra- and inter-assay precisions were satisfactory; the relative standard deviations did not exceed 2%. The accuracy of the method was proved; the mean recovery of VRC was 100.10 ± 1.08%. The proposed method has high throughput as the analysis involved short run-time (~ 6 min). The method met the ICH/FDA regulatory requirements. The proposed method was successfully applied for the determination of VRC in bulk and tablets with acceptable accuracy and precisions; the label claim percentages were 99.65 ± 0.32%. The results demonstrated that the method would have a great value when applied in quality control and stability studies for VRC. PMID:21672253

Modelling of OPNMR phenomena using photon energy-dependent 〈Sz〉 in GaAs and InP.

PubMed

Wheeler, Dustin D; Willmering, Matthew M; Sesti, Erika L; Pan, Xingyuan; Saha, Dipta; Stanton, Christopher J; Hayes, Sophia E

2016-12-01

We have modified the model for optically-pumped NMR (OPNMR) to incorporate a revised expression for the expectation value of the z-projection of the electron spin, 〈S z 〉 and apply this model to both bulk GaAs and a new material, InP. This expression includes the photon energy dependence of the electron polarization when optically pumping direct-gap semiconductors in excess of the bandgap energy, E g . Rather than using a fixed value arising from coefficients (the matrix elements) for the optical transitions at the k=0 bandedge, we define a new parameter, S opt (E ph ). Incorporating this revised element into the expression for 〈S z 〉, we have simulated the photon energy dependence of the OPNMR signals from bulk semi-insulating GaAs and semi-insulating InP. In earlier work, we matched calculations of electron spin polarization (alone) to features in a plot of OPNMR signal intensity versus photon energy for optical pumping (Ramaswamy et al., 2010). By incorporating an electron spin polarization which varies with pump wavelength into the penetration depth model of OPNMR signal, we are able to model features in both III-V semiconductors. The agreement between the OPNMR data and the corresponding model demonstrates that fluctuations in the OPNMR intensity have particular sensitivity to light hole-to-conduction band transitions in bulk systems. We provide detailed plots of the theoretical predictions for optical pumping transition probabilities with circularly-polarized light for both helicities of light, broken down into illustrative plots of optical magnetoabsorption and spin polarization, shown separately for heavy-hole and light-hole transitions. These plots serve as an effective roadmap of transitions, which are helpful to other researchers investigating optical pumping effects. Copyright © 2016 Elsevier Inc. All rights reserved.

Investigating the behaviour of Mg isotopes during the formation of clay minerals

NASA Astrophysics Data System (ADS)

Wimpenny, Joshua; Colla, Christopher A.; Yin, Qing-Zhu; Rustad, James R.; Casey, William H.

2014-03-01

We present elemental and isotopic data detailing how the Mg isotope system behaves in natural and experimentally synthesized clay minerals. We show that the bulk Mg isotopic composition (δ26Mg) of a set of natural illite, montmorillonite and kaolinite spans a 2‰ range, and that their isotopic composition depends strongly on a balance between the relative proportions of structural and exchangeable Mg. After acid leaching, these natural clays become relatively enriched in isotopically heavy Mg by between 0.2‰ and 1.6‰. Results of exchange experiments indicate that the Mg that has adsorbed to interlayer spaces and surface charged sites is relatively enriched in isotopically light Mg compared to the residual clay. The isotopic composition of this exchangeable Mg (-1.49‰ to -2.03‰) is characteristic of the isotopic composition of Mg found in many natural waters. Further experiments with an isotopically characterized MgCl2 solution shows that the clay minerals adsorb this exchangeable Mg with little or no isotopic fractionation, although we cannot discount the possibility that the uptake of exchangeable Mg does so with a slight preference for 24Mg. To characterize the behaviour of Mg isotopes during clay mineral formation we synthesized brucite (Mg(OH)2), which we consider to be a good analogue for the incorporation of Mg into the octahedral sheet of Mg-rich clay minerals or into the brucitic layer of clays such as chlorite. In our experiment the brucite mineral becomes enriched in the heavy isotopes of Mg while the corresponding solution is always relatively enriched in isotopically light Mg. The system reaches a steady state after 10 days with a final fractionation factor (αsolid-solution) of 1.0005 at near-neutral pH. This result is consistent with the general consensus that secondary clay minerals preferentially take up isotopically heavy Mg during their formation. However our results also show that exchangeable Mg is an important component within bulk clay minerals and can have an important influence over the bulk clay δ26Mg value. Modeling shows that in certain soils or sediments where the percentage of exchangeable Mg is >30% and the isotopic composition of the exchangeable Mg is around -2‰, the generation of bulk δ26Mg values of <-0.5‰ is likely. On a broader scale, Mg-rich minerals such as smectite and illite are likely to impart a stronger control over the Mg budget in clay rich sediments, and their high structural Mg component is likely to result in bulk sediment δ26Mg values that are closer in composition to the UCC. Despite this, results of modeling, together with experimental observation suggests that the uptake of exchangeable Mg into these clay rich sediments could cause a decrease in the bulk δ26Mg value by up to ˜0.3-0.4‰. This should be accounted for when assessing the δ26Mg value of sediments on a crustal scale.

Development of soil quality along a chronosequence under natural succession in the Dragonja catchment, SW Slovenia

NASA Astrophysics Data System (ADS)

van Hall, Rutger; Cammeraat, Erik

2015-04-01

Agricultural fields have been increasingly abandoned in several regions in Southern Europe. In many cases this leads to natural vegetation succession which may have a direct impact on soil quality,biodiversity and hydrological connectivity. This research aims at getting insight on the effects of natural vegetation succession on the development of soil quality in the Sub-Mediterranean Dragonja catchment in SW Slovenia. This site was chosen due to its uniform geology, geomorphology and soil types. Four different stages of vegetation succession (i.e. field, abandoned field, young forest, semi-mature forest) were selected and sampled on both north-, and south-facing slopes, resulting in 8 treatments for which 6 representative sites were sampled. Samples were analysed on OC and TN content, EC, pH, bulk density, aggregate stability and grain size distribution. To get insight on the changes in biodiversity vegetation records were made distinguishing five different plant functional groups (i.e. juveniles, grasses, herbs, shrubs and trees). Age group (i.e. stage of vegetation succession) significantly influenced the OC and TN content, aggregate stability, bulk density and pH. Directly after abandonment, between age group 0 and 1, OC and TN content, aggregate stability and pH increased significantly and bulk density decreased significantly. OC content was most affected by age group and furthermore significantly correlated to TN content, aggregate stability, bulk density and pH. Regarding biodiversity, there was a significant increase in cover by trees between age group 1 and 2 and a significant decrease between age group 2 and 3. Cover by herbs decreased significantly between age group 1 and 2. The number of different trees and shrubs increased significantly between age group 0 and 1, and the number of different juveniles increased significantly between age group 2 and 3. Another factor significantly influencing the soil's quality is aspect. Although not found for each age group south-facing slopes generally had higher OC and TN content, and higher pH than north-facing slopes. On average OC content was 28% higher and TN content 25% higher on south facing slopes. Aspect did not have a significant influence on the biodiversity although on average vegetation cover is slightly (7%) higher and 16% mores species were found on north facing slopes.

Electroacoustic isoelectric point determinations of bauxite refinery residues: different neutralization techniques and minor mineral effects.

PubMed

Freire, Tiago S S; Clark, Malcolm W; Comarmond, M Josick; Payne, Timothy E; Reichelt-Brushett, Amanda J; Thorogood, Gordon J

2012-08-14

Bauxite refinery residue (BRR) is a highly caustic, iron hydroxide-rich byproduct from alumina production. Some chemical treatments of BRR reduce soluble alkalinity and lower residue pH (to values <10) and generate a modified BRR (MBRR). MBRR has excellent acid neutralizing (ANC) and trace-metal adsorption capacities, making it particularly useful in environmental remediation. However, soluble ANC makes standard acid-base isoelectric point (IEP) determination difficult. Consequently, the IEP of a BRR and five MBRR derivatives (sulfuric acid-, carbon dioxide-, seawater-, a hybrid neutralization, i.e, partial CO(2) neutralization followed by seawater, and an activated-seawater-neutralized MBRR) were determined using electroacoustic techniques. Residues showed three significantly different groups of IEPs (p < 0.05) based around the neutralization used. Where the primary mineral assemblage is effectively unchanged, the IEPs were not significantly different from BRR (pH 6.6-6.9). However, neutralizations generating neoformational minerals (alkalinity precipitation) significantly increased the IEP to pH 8.1, whereas activation (a removal of some primary mineralogy) significantly lowered the IEP to pH 6.2. Moreover, surface charging curves show that surfaces remain in the ±30 mV surface charge instability range, which provides an explanation as to why MBRRs remove trace metals and oxyanions over a broad pH range, often simultaneously. Importantly, this work shows that minor mineral components in complex mineral systems may have a disproportionate effect on the observable bulk IEP. Furthermore, this work shows the appropriateness of electroacoustic techniques in investigating samples with significant soluble mineral components (e.g., ANC).

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production.

PubMed

Reynal, Anna; Pastor, Ernest; Gross, Manuela A; Selim, Shababa; Reisner, Erwin; Durrant, James R

2015-08-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye ( RuP ) and a nickel bis(diphosphine) electrocatalyst ( NiP ) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H 2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP - NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP , which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP - NiP photocatalytic system, which can be widely applied to other photocatalytic systems.

Direct determination of protonation states and visualization of hydrogen bonding in a glycoside hydrolase with neutron crystallography

PubMed Central

Wan, Qun; Parks, Jerry M.; Hanson, B. Leif; Fisher, Suzanne Zoe; Ostermann, Andreas; Schrader, Tobias E.; Graham, David E.; Coates, Leighton; Langan, Paul; Kovalevsky, Andrey

2015-01-01

Glycoside hydrolase (GH) enzymes apply acid/base chemistry to catalyze the decomposition of complex carbohydrates. These ubiquitous enzymes accept protons from solvent and donate them to substrates at close to neutral pH by modulating the pKa values of key side chains during catalysis. However, it is not known how the catalytic acid residue acquires a proton and transfers it efficiently to the substrate. To better understand GH chemistry, we used macromolecular neutron crystallography to directly determine protonation and ionization states of the active site residues of a family 11 GH at multiple pD (pD = pH + 0.4) values. The general acid glutamate (Glu) cycles between two conformations, upward and downward, but is protonated only in the downward orientation. We performed continuum electrostatics calculations to estimate the pKa values of the catalytic Glu residues in both the apo- and substrate-bound states of the enzyme. The calculated pKa of the Glu increases substantially when the side chain moves down. The energy barrier required to rotate the catalytic Glu residue back to the upward conformation, where it can protonate the glycosidic oxygen of the substrate, is 4.3 kcal/mol according to free energy simulations. These findings shed light on the initial stage of the glycoside hydrolysis reaction in which molecular motion enables the general acid catalyst to obtain a proton from the bulk solvent and deliver it to the glycosidic oxygen. PMID:26392527

Direct determination of protonation states and visualization of hydrogen bonding in a glycoside hydrolase with neutron crystallography

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

Wan, Qun; Parks, Jerry M.; Hanson, B. Leif

Glycoside hydrolase (GH) enzymes apply acid/base chemistry to catalyze the decomposition of complex carbohydrates. These ubiquitous enzymes accept protons from solvent and donate them to substrates at close to neutral pH by modulating the pK a values of key side chains during catalysis. However, it is not known how the catalytic acid residue acquires a proton and transfers it efficiently to the substrate. To better understand GH chemistry, we used macromolecular neutron crystallography to directly determine protonation and ionization states of the active site residues of a family 11 GH at multiple pD (pD = pH + 0.4) values. Themore » general acid glutamate (Glu) cycles between two conformations, upward and downward, but is protonated only in the downward orientation. We performed continuum electrostatics calculations to estimate the pK a values of the catalytic Glu residues in both the apo- and substrate-bound states of the enzyme. The calculated pK a of the Glu increases substantially when the side chain moves down. The energy barrier required to rotate the catalytic Glu residue back to the upward conformation, where it can protonate the glycosidic oxygen of the substrate, is 4.3 kcal/mol according to free energy simulations. Lastly, these findings shed light on the initial stage of the glycoside hydrolysis reaction in which molecular motion enables the general acid catalyst to obtain a proton from the bulk solvent and deliver it to the glycosidic oxygen.« less

Direct determination of protonation states and visualization of hydrogen bonding in a glycoside hydrolase with neutron crystallography

DOE PAGES

Wan, Qun; Parks, Jerry M.; Hanson, B. Leif; ...

2015-09-21

Glycoside hydrolase (GH) enzymes apply acid/base chemistry to catalyze the decomposition of complex carbohydrates. These ubiquitous enzymes accept protons from solvent and donate them to substrates at close to neutral pH by modulating the pK a values of key side chains during catalysis. However, it is not known how the catalytic acid residue acquires a proton and transfers it efficiently to the substrate. To better understand GH chemistry, we used macromolecular neutron crystallography to directly determine protonation and ionization states of the active site residues of a family 11 GH at multiple pD (pD = pH + 0.4) values. Themore » general acid glutamate (Glu) cycles between two conformations, upward and downward, but is protonated only in the downward orientation. We performed continuum electrostatics calculations to estimate the pK a values of the catalytic Glu residues in both the apo- and substrate-bound states of the enzyme. The calculated pK a of the Glu increases substantially when the side chain moves down. The energy barrier required to rotate the catalytic Glu residue back to the upward conformation, where it can protonate the glycosidic oxygen of the substrate, is 4.3 kcal/mol according to free energy simulations. Lastly, these findings shed light on the initial stage of the glycoside hydrolysis reaction in which molecular motion enables the general acid catalyst to obtain a proton from the bulk solvent and deliver it to the glycosidic oxygen.« less

Application of 3-methylbenzothiazolin-2-one hydrazone for the quantitative spectrophotometric determination of oxcarbazepine in pharmaceuticals with cerium(IV) and periodate

NASA Astrophysics Data System (ADS)

Rajendraprasad, N.; Basavaiah, K.; Vinay, K. B.

2012-09-01

Two simple, sensitive, selective, accurate, and cost-effective spectrophotometric methods are described for the assay of oxcarbazepine (OXC) in bulk drug and in tablets. The methods are based on an oxidative coupling reaction involving OXC, 3-methylbenzothiazolin-2-one hydrazone (MBTH), and cerium(IV) sulfate at pH 4.28 ± 0.07 (method A) or sodium periodate at pH > 4.0 (method B) to form an orange colored product with an absorption maximum at 450 nm. Under optimized experimental conditions, the calibration graphs are linear over the ranges of 4-80 and 2-32 μg/ml for methods A and B, respectively, with correlation coefficient (r) values of 0.9984 and 0.9976. The apparent molar absorptivity values are 3.13ṡ103 and 9.13ṡ103 l/molṡcm for methods A and B, respectively. The other optical characteristics such as Sandell's sensitivity, limits of detection (LOD) and quantification (LOQ) values are also reported. The accuracy and precision of the methods were evaluated based on intra-day and inter-day variations. The proposed methods were successfully applied to the determination of OXC in tablets: the results were comparable with the published data obtained using the reference method. The reaction stoichiometry of OXC with MBTH (1:1 in method A and 1:2 in method B) was also evaluated using the limiting logarithmic method, and a possible reaction pathway is presented for the both methods.

Extractive Spectrophotometric Methods for the Determination of Zolmitriptan in Bulk Drug and Pharmaceutical Formulation Using Bromocresol Green

NASA Astrophysics Data System (ADS)

Prashanth, K. N.; Swamy, N.; Basavaiah, K.

2013-11-01

Considering the basic property of zolmitriptan (ZMT) to generate ion-pairs with sulfonephthalein dyes two methods have been developed for its assay in bulk drug and dosage form. The first method (method A) is based on the formation of a colored ion-pair complex (1:1 drug:dye) of ZMT with bromocresol green (BCG) at pH 4.20 ± 0.01 and extraction of the complex into chloroform followed by measurement of the yellow ion-pair complex at 435 nm. In the second method (method B), the drug-dye ion-pair complex was treated with ethanolic potassium hydroxide in ethanolic medium and the resulting base form of the dye was measured at 630 nm. Beer's law was obeyed in the concentration range of 0.8-18.0 and 0.08-1.4 μg/ml for method A and B, respectively, and the corresponding molar absorptivity values were 1.50ṡ104 and 1.52ṡ105 l/(molṡcm). The Sandell sensitivity values were 0.0191 and 0.0019 μg/cm2 for method A and method B, respectively. The stoichiometry of the ion-pair complex formed between the drug and dye (1:1) was determined by Job's continuous variation method and the stability constant of the complex was also calculated. The proposed method was successfully extended to dosage form (tablets).

Fertility status of cultivated floodplain soils in the Zambezi Valley, northern Zimbabwe

NASA Astrophysics Data System (ADS)

Chimweta, M.; Nyakudya, I. W.; Jimu, L.

2018-06-01

Flood-recession cropping improves smallholder farmers' household food security. The objective of this study was to determine the fertility status of cultivated Zambezi Valley floodplain soils, in northern Zimbabwe. The study was conducted at three sites, along tributaries of Musengezi River. Soil samples were taken at 0.20 m depth increments to 0.60 m from hydromorphologically stratified fields, during the cropping season. Sampling points were replicated twice in each stratum at points equidistant from river edges. Relative elevations of sampling points were measured using levelling equipment. Soil was analysed using: core method for bulk density, hydrometer method for texture, loss on ignition for soil organic carbon (SOC), Kjeldahl procedure for total nitrogen (N), 0.01 M CaCl2 for pH, and Inductively Coupled Plasma (ICP) for Mehlich 3 extractable elements. Data from soil analyses were subjected to One Way Analysis of Variance and Pearson's correlation analysis. Bulk density ranged from 1.2 to 1.4 g cm-3 and it was negatively related to distance from river; and positively related to elevation at two sites. Highest values for SOC and total N were 2.04% and 0.36% respectively. Soil pH ranged from 7.70 to 8.60. Soil organic carbon and N were positively related to distance from river but negatively related to elevation. Threshold concentrations for deficiency: < 12 ppm for K, and <39 ppm for Mg, were exceeded. Calcium, Na, and micronutrients in most cases exceeded concentrations reported for floodplains. Practices that slow down flowing water and fertilizer microdosing are among possible fertility management options.

Copper speciation in variably toxic sediments at the Ely Copper Mine, Vermont, United States

USGS Publications Warehouse

Kimball, Bryn E.; Foster, Andrea L.; Seal, Robert R.; Piatak, Nadine M.; Webb, Samuel M.; Hammarstrom, Jane M.

2016-01-01

At the Ely Copper Mine Superfund site, Cu concentrations exceed background values in both streamwater (160–1200 times) and sediments (15–79 times). Previously, these sediment samples were incubated with laboratory test organisms, and they exhibited variable toxicity for different stream sites. In this study we combined bulk- and microscale techniques to determine Cu speciation and distribution in these contaminated sediments on the basis of evidence from previous work that Cu was the most important stressor in this environment and that variable observed toxicity could have resulted from differences in Cu speciation. Copper speciation results were similar at microscopic and bulk scales. The major Cu species in the more toxic samples were sorbed or coprecipitated with secondary Mn (birnessite) and Fe minerals (jarosite and goethite), which together accounted for nearly 80% of the total Cu. The major Cu species in the less toxic samples were Cu sulfides (chalcopyrite and a covellite-like phase), making up about 80–95% of the total Cu, with minor amounts of Cu associated with jarosite or goethite. These Cu speciation results are consistent with the toxicity results, considering that Cu sorbed or coprecipitated with secondary phases at near-neutral pH is relatively less stable than Cu bound to sulfide at lower pH. The more toxic stream sediment sites were those that contained fewer detrital sulfides and were upstream of the major mine waste pile, suggesting that removal and consolidation of sulfide-bearing waste piles on site may not eliminate all sources of bioaccessible Cu.

In-situ identification of iron electrocoagulation speciation and application for natural organic matter (NOM) removal.

PubMed

Dubrawski, Kristian L; Mohseni, Madjid

2013-09-15

In this work, iron speciation in electrocoagulation (EC) was studied to determine the impact of operating parameters on natural organic matter (NOM) removal from natural water. Two electrochemical EC parameters, current density (i) and charge loading rate (CLR), were investigated. Variation of these parameters led to a near unity current efficiency (φ = 0.957 ± 0.03), at any combination of i in a range of 1-25 mA/cm(2) and CLR in a range of 12-300 C/L/min. Higher i and CLR led to a higher bulk pH and limited the amount of dissolved oxygen (DO) reduced at the cathode surface due to mass transfer limitations. A low i (1 mA/cm(2)) and intermediate CLR (60 C/L/min) resulted in low bulk DO (<2.5 mg/L), where green rust (GR) was identified by in-situ Raman spectroscopy as the primary crystalline electrochemical product. Longer electrolysis times at higher i led to magnetite (Fe3O4) formation. Both higher (300 C/L/min) and lower (12 C/L/min) CLR values led to increased DO and/or increased pH, with lepidocrocite (γ-FeOOH) as the only crystalline species observed. The NOM removal of the three identified species was compared, with conditions leading to GR formation showing the greatest dissolved organic carbon removal, and highest removal of the low apparent molecular weight (<550 Da) chromophoric NOM fraction, determined by high performance size exclusion chromatography. Copyright © 2013 Elsevier Ltd. All rights reserved.

Acid-base properties of Baltic Sea dissolved organic matter

NASA Astrophysics Data System (ADS)

Hammer, Karoline; Schneider, Bernd; Kuliński, Karol; Schulz-Bull, Detlef E.

2017-09-01

Calculations related to the marine CO2 system that are based on alkalinity data may be strongly biased if the contributions of organic compounds are ignored. In coastal seas, concentrations of dissolved organic matter (DOM) are frequently high and alkalinity from inorganic compounds is low. In this study, based on measurements of total alkalinity, total CO2, and pH, we determined the organic alkalinity, Aorg, in water from the central Baltic Sea. The maximum Aorg measured in the surface mixed layer during the spring bloom was > 50 μmol/kg-SW but the Aorg decreased with depth and approached zero below the permanent halocline. This behavior could be attributed to the decreased pH of deeper water layers. The data were used to calculate the bulk dissociation constant, KDOM, for marine DOM and the fraction f of dissolved organic carbon (DOC) that acts as a carrier for acid-base functional groups. The p KDOM (7.27) agreed well with the value (7.34) previously estimated in a preliminary study of organic alkalinity in the Baltic Sea. The fraction of carbon atoms carrying acid-base groups was 17% and was somewhat higher than previously reported (12%). Spike experiments performed using artificial seawater and three different humic/fulvic substances tested whether the acid-base properties of these substances explain the results of our field study. Specifically, Aorg was determined at different concentrations (DOC) of the added humic/fulvic substances. The relationship between Aorg and the DOC concentrations indicated that humic/fulvic substances are more acidic (p KDOM < 6.5) than the bulk DOC natural occurring in the Baltic Sea.

High-Resolution pH Imaging of Living Bacterial Cells To Detect Local pH Differences

PubMed Central

Morimoto, Yusuke V.; Kami-ike, Nobunori; Miyata, Tomoko; Kawamoto, Akihiro; Kato, Takayuki

2016-01-01

ABSTRACT Protons are utilized for various biological activities such as energy transduction and cell signaling. For construction of the bacterial flagellum, a type III export apparatus utilizes ATP and proton motive force to drive flagellar protein export, but the energy transduction mechanism remains unclear. Here, we have developed a high-resolution pH imaging system to measure local pH differences within living Salmonella enterica cells, especially in close proximity to the cytoplasmic membrane and the export apparatus. The local pH near the membrane was ca. 0.2 pH unit higher than the bulk cytoplasmic pH. However, the local pH near the export apparatus was ca. 0.1 pH unit lower than that near the membrane. This drop of local pH depended on the activities of both transmembrane export components and FliI ATPase. We propose that the export apparatus acts as an H+/protein antiporter to couple ATP hydrolysis with H+ flow to drive protein export. PMID:27923921

Combined effect of pH and heating conditions on the physical properties of Alaska pollock surimi gels.

PubMed

Lee, Myeong Gi; Yoon, Won Byong; Park, Jae W

2017-06-01

Physical properties of Alaska pollock surimi paste were investigated as affected by pH (4.0 and 6.0-10.0) and heating conditions (slow and fast). The highest values of gel strength and deformability, as shown by breaking force and penetration distance, were obtained at pH 7.5-8.0, while the lowest values were at pH 10.0 followed by pH 6.0 and pH 6.5, respectively. Two-step slow heating process increased the breaking strength value nearly two times higher than one-step fast heating. The effect of pH was strikingly high at pH 7.5 when gels were prepared using 2-step heating, indicating the pH dependence of endogenous transglutaminase. However, the highest gel strength was obtained at pH 8.0 when gels were prepared in fast heating. Whiteness value (L - 3b*) increased significantly (p < .05) as pH increased from 6.0 to 6.5, but thereafter decreased significantly (p < .05) as pH increased. L* value (lightness) and b* value (yellowness) continuously decreased as the pH is shifted from 6.0 to 10. Fast heated gels showed the lowest yellowness, resulting in whiter appearance, probably due to the effect of reduced browning reaction. The uniqueness of this study was to measure the combined effect of pH and heating conditions on the gel texture and color. There were various studies dealing with pH or heating conditions independently. As the primary character for surimi seafood is gel texture and color. The highest values of gel strength and deformability, as shown by breaking force and penetration distance, were obtained at pH 7.5-8.0, while the lowest values were at pH 10.0 followed by pH 6.0 and pH 6.5, respectively. Two-step slow heating process increased the breaking strength value nearly two times higher than one-step fast heating. Whiteness value (L - 3b*) increased significantly as pH increased from 6.0 to 6.5, but thereafter decreased significantly as pH increased. L* value (lightness) and b* value (yellowness) continuously decreased as the pH is shifted from 6.0 to 10. Fast heated gels showed the lowest yellowness, resulting in whiter appearance. © 2016 Wiley Periodicals, Inc.

Maintenance and regulation of the pH microclimate at the luminal surface of the distal colon of guinea-pig

PubMed Central

Genz, Anne-Katrin; v Engelhardt, Wolfgang; Busche, Roger

1999-01-01

The fluorescent dye 5-N-hexadecanoyl-aminofluorescein (HAF) was used to study the mechanisms involved in maintaining a relatively constant luminal surface pH (pHs) in the distal colon of the guinea-pig. The fatty acyl chain of the HAF molecule inserts into the apical membrane of epithelial cells. This allows a continuous measurement of the surface pH for several hours. The localization of HAF was confirmed by confocal laser-scanning microscopy and by using monoclonal antibodies against fluorescein. The insertion of HAF into the apical membrane of the colonocytes did not change the transepithelial conductance or the short-circuit current of the epithelium. With the HAF method a pH microclimate was confirmed at the colonic surface. Although the pH of the bulk luminal solution was decreased in bicarbonate-containing solution from 7.4 to 6.4 the pHs changed only in the range 7.54-6.98. In the absence of bicarbonate pHs almost followed changes of bulk luminal pH. In the presence of bicarbonate there was a decrease in pHs after removal of chloride from the luminal side and an increase in pHs after addition of butyrate to the luminal solution. This suggests the involvement of a bicarbonate-anion exchange in bicarbonate secretion: a Cl−-HCO3− as well as a short-chain fatty acid−-HCO3− exchange. The apical K+-H+-ATPase in the distal colon of guinea-pig has little influence on pHs in the presence of physiological buffer concentrations. Our findings indicate that bicarbonate plays a major role in maintaining the pH microclimate at the colonic surface. PMID:10332098

Hard X-ray Fluorescence Microscopy to Determine the Element Distribution of Soil Colloids in Aqueous Environment

NASA Astrophysics Data System (ADS)

Gleber, S.-C.; Vogt, S.; Niemeyer, J.; Finney, L.; McNulty, I.; Thieme, J.

2011-09-01

A prominent feature of soil colloids is their huge specific surface. It determines colloidal properties such as adsorption capacity or diffusion. The colloidal interactions differ significantly from the behavior of the same materials in a bulk system. Interactions in the colloidal regime are crucial, for example, for the transport and release of nutrients and toxicants in soils, which then influences directly the growth of plants. However, there is still a need for more analytical resources to study those interactions. To reveal the correlation of the particular trace elements and their distribution in correlation to colloidal interactions as well as changing pH values, experiments at the hard x-ray fluorescence microprobe at beamline 2-ID-E of the Advanced Photon Source (APS), were performed with colloidal clay and soil samples in an aqueous environment as naturally relevant. To obtain further spatial information, stereo imaging has been used. To study the dynamical behavior of these colloidal suspensions at changing pH, a wet sample chamber allowing in situ manipulation was developed and utilized.

Influences of the Tonga Subduction Zone on seafloor massive sulfide deposits along the Eastern Lau Spreading Center and Valu Fa Ridge

NASA Astrophysics Data System (ADS)

Evans, Guy N.; Tivey, Margaret K.; Seewald, Jeffrey S.; Wheat, C. Geoff

2017-10-01

This study investigates the morphology, mineralogy, and geochemistry of seafloor massive sulfide (SMS) deposits from six back-arc hydrothermal vent fields along the Eastern Lau Spreading Center (ELSC) and Valu Fa Ridge (VFR) in the context of endmember vent fluid chemistry and proximity to the Tonga Subduction Zone. To complement deposit geochemistry, vent fluid analyses of Cu, Zn, Ba, Pb and H2,(aq) were completed to supplement existing data and enable thermodynamic calculations of mineral saturation states at in situ conditions. Results document southward increases in the abundance of mantle-incompatible elements in hydrothermal fluids (Ba and Pb) and SMS deposits (Ba, Pb, As, and Sb), which is also expressed in the abundance of barite (BaSO4) and galena (PbS) in SMS deposits. These increases correspond to a decrease in distance between the ELSC/VFR and the Tonga Subduction Zone that correlates with a change in crustal lithology from back-arc basin basalt in the north to mixed andesite, rhyolite, and dacite in the south. Barite influences deposit morphology, contributing to the formation of horizontal flanges and squat terraces. Results are also consistent with a regional-scale lowering of hydrothermal reaction zone temperatures from north to south (except at the southernmost Mariner vent field) that leads to lower-temperature, higher-pH vent fluids relative to mid-ocean ridges of similar spreading rates (Mottl et al., 2011). These fluids are Cu- and Zn-poor and the deposits formed from these fluids are Cu-poor but Zn-rich. In contrast, at the Mariner vent field, higher-temperature and lower pH vent fluids are hypothesized to result from higher reaction zone temperatures and the localized addition of acidic magmatic volatiles (Mottl et al., 2011). The Mariner fluids are Cu- and Zn-rich and vent from SMS deposits that are rich in Cu but poor in Zn with moderate amounts of Pb. Thermodynamic calculations indicate that the contrasting metal contents of vent fluids and SMS deposits can be accounted for by vent fluid pH. Wurtzite/sphalerite ((Zn, Fe)S) and galena (PbS) are saturated at higher temperatures in higher-pH, Zn-, Cu-, and Pb-poor ELSC/VFR vent fluids, but are undersaturated at similar temperatures in low-pH, Zn-, Cu-, and Pb-rich vent fluids from the Mariner vent field. Indicators of pH in the ELSC and VFR SMS deposits include the presence of co-precipitated wurtzite and chalcopyrite along conduit linings in deposits formed from higher pH fluids, and different correlations between concentrations of Zn and Ag in bulk geochemical analyses. Significant positive bulk geochemical Zn:Ag correlations occur for deposits at vent fields where hydrothermal fluids have a minimum pH (at 25 °C) < 3.3, while correlations of Zn:Ag are weak or negative for deposits at vent fields where the minimum vent fluid pH (at 25 °C) > 3.6. Data show that the compositions of the mineral linings of open conduit chimneys (minerals present, mol% FeS in (Zn,Fe)S) that precipitate directly from hydrothermal fluids closely reflect the temperature and sulfur fugacity of sampled hydrothermal fluids. These mineral lining compositions thus can be used as indicators of hydrothermal fluid temperature and composition (pH, metal content, sulfur fugacity).

The use of refused tea as litter material for broiler chickens.

PubMed

Atapattu, N S B M; Wickramasinghe, K P

2007-05-01

A completely randomized design experiment was conducted to determine the suitability of refused tea (RT) as a litter material for broiler chickens. Physiochemical properties of RT were compared with paddy husk (PH). Subsequently, broilers were raised on RT- or PH-based litter to compare the performances and litter qualities. Twenty-day-old broiler chicks (n = 150) were randomly allocated into 6 deep litter pens so that each treatment had 3 replicates. Chicks received 0.8 ft(2) of floor spacing until d 28 and 1.3 ft(2) thereafter. Each cage had a feeder and a drinker. Litter materials and litter samples taken on 28, 35, and 39 d were analyzed for bulk density, moisture, ash, and N. Chick mortality was low (1.3%) and similar on 2 types of litters. Live weights on d 28, 35, 39, and weight gains, feed intakes, dressing percentages, and feed conversion ratios were not affected by the type of litter material. The bulk density, moisture level, and pH of the RT were comparable with PH. Even though the water-holding capacity of PH (213%) was significantly higher (P < 0.01) than RT (70%), the latter material had significantly higher (P < 0.01) water-releasing capacity compared with the former (17.9 vs. 13.6%). Throughout the experiment the RT litter had around 10% units higher moisture level than PH litter. By d 39, the moisture content of the RT litter was (48%) significantly higher (P = 0.05) than PH litter (37%). The N contents of RT litter were higher (P < 0.05) than those of PH on d 28, 35, and 39, being 8.1, 7.8, and 7% and 3.4, 3.6, and 3%, respectively. It was concluded that RT could be successfully used as an alternative litter material for broilers. A higher N content in RT-based spent broiler litter would make it be a better organic fertilizer and ruminant feed compared with PH-based litter.

Characterizing the variation in pH measurements with apheresis platelets.

PubMed

Moroff, Gary; Seetharaman, Shalini; Kurtz, James; Wagner, Stephen J

2011-11-01

pH measurements of platelet (PLT) components remain a key parameter when assessing how storage and shipping conditions influence the retention of PLT properties. Studies were conducted to characterize variations in pH measured with two pH meters and a blood gas analyzer. Samples were obtained from apheresis PLT units that were stored with or without continuous agitation to measure a range of pH values. pH values were determined with pH meters at room temperature (20-24°C) upon placing of samples in 5-mL sterile polypropylene tubes and with the blood gas analyzer at 37°C upon injection of identical samples, with conversion to 22°C. The calculated coefficient of variation (%CV) of pH measurements using pH meters (n = 10) was 0.43% or less. The %CV values were comparable with different samples having pH values ranging from 6.0 to 7.4. The %CV levels with the blood gas analyzer were comparable to those observed with the pH meters. The difference in the mean pH values for the two pH meters was no greater than 0.10 units, with 9 of 10 samples having differences in values of 0.05 or less; however, greater differences of values (0.1 to 0.2) were observed between pH measured using the blood gas analyzer and pH meters. Our data show good precision and comparability of pH measurements with two pH meters. Differences in pH values were greater on comparison of the blood gas analyzer with the pH meters. © 2011 American Association of Blood Banks.

Separation of no-carrier-added rhenium from bulk tantalum by the sodium malonate-PEG aqueous biphasic system.

PubMed

Dutta, Binita; Lahiri, Susanta; Tomar, B S

2014-02-01

The aqueous biphasic system (ABS) involving sodium malonate-polyethylene glycol (PEG) phases has been applied for the first time for separation of no-carrier-added (183)Re (T1/2=70 d) from α-particle irradiated bulk tantalum target. The various ABS conditions were applied for investigating the separation by varying pH, temperature, PEG-molecular weight, concentration of salt. The extraction pattern was hardly affected by change in pH and the molecular weight of PEG. One step separation of nca (183)Re from Ta was achieved at the optimal conditions of (i) 50% (w/w) PEG-4000-2 M sodium malonate, 40 °C and (ii) 50% (w/w) PEG-4000-3 M sodium malonate, room temperature (27 °C). © 2013 Published by Elsevier Ltd.

Effects of effluent organic matter characteristics on the removal of bulk organic matter and selected pharmaceutically active compounds during managed aquifer recharge: Column study

NASA Astrophysics Data System (ADS)

Maeng, Sung Kyu; Sharma, Saroj K.; Abel, Chol D. T.; Magic-Knezev, Aleksandra; Song, Kyung-Guen; Amy, Gary L.

2012-10-01

Soil column experiments were conducted to investigate the effects of effluent organic matter (EfOM) characteristics on the removal of bulk organic matter (OM) and pharmaceutically active compounds (PhACs) during managed aquifer recharge (MAR) treatment processes. The fate of bulk OM and PhACs during an MAR is important to assess post-treatment requirements. Biodegradable OM from EfOM, originating from biological wastewater treatment, was effectively removed during soil passage. Based on a fluorescence excitation-emission matrix (F-EEM) analysis of wastewater effluent-dominated (WWE-dom) surface water (SW), protein-like substances, i.e., biopolymers, were removed more favorably than fluorescent humic-like substances under oxic compared to anoxic conditions. However, there was no preferential removal of biopolymers or humic substances, determined as dissolved organic carbon (DOC) observed via liquid chromatography with online organic carbon detection (LC-OCD) analysis. Most of the selected PhACs exhibited removal efficiencies of greater than 90% in both SW and WWE-dom SW. However, the removal efficiencies of bezafibrate, diclofenac and gemfibrozil were relatively low in WWE-dom SW, which contained more biodegradable OM than did SW (copiotrophic metabolism). Based on this study, low biodegradable fractions such as humic substances in MR may have enhanced the degradation of diclofenac, gemfibrozil and bezafibrate by inducing an oligotrophic microbial community via long term starvation. Both carbamazepine and clofibric acid showed persistent behaviors and were not influenced by EfOM.

Physiological effects of pH gradients on Escherichia coli during plasmid DNA production.

PubMed

Cortés, José T; Flores, Noemí; Bolívar, Francisco; Lara, Alvaro R; Ramírez, Octavio T

2016-03-01

A two-compartment scale-down system was used to mimic pH heterogeneities that can occur in large-scale bioreactors. The system consisted of two interconnected stirred tank reactors (STRs) where one of them represented the conditions of the bulk of the fluid and the second one the zone of alkali addition for pH control. The working volumes ratio of the STRs was set to 20:1 in order to simulate the relative sizes of the bulk and alkali addition zones, respectively, in large-scale bioreactors. Residence times (tR ) in the alkali addition STR of 60, 120, 180, and 240 s were simulated during batch cultures of an engineered Escherichia coli strain that produced plasmid DNA (pDNA). pH gradients of up to 0.9 units, between the two compartments, were attained. The kinetic, stoichiometric, and pDNA topological changes due to the pH gradients were studied and compared to cultures at constant pH of 7.2 and 8.0. As the tR increased, the pDNA and biomass yields, as well as pDNA final titer decreased, whereas the accumulation of organic acids increased. Furthermore, the transcriptional response of 10 selected genes to alkaline stress (pH 8.0) and pH gradients was monitored at different stages of the cultures. The selected genes coded for ion transporters, amino acids catabolism enzymes, and transcriptional regulators. The transcriptional response of genes coding for amino acids catabolism, in terms of relative transcription level and stage of maximal expression, was different when the alkaline stress was constant or transient. This suggests the activation of different mechanisms by E. coli to cope with pH fluctuations compared to constant alkaline pH. Moreover, the transcriptional response of genes related to negative control of DNA synthesis did not correlate with the lower pDNA yields. This is the first study that reports the effects of pH gradients on pDNA production by E. coli cultures. The information presented can be useful for the design of better bioreactor scale-up strategies. © 2015 Wiley Periodicals, Inc.

Effect of humic acid & bacterial exudates on sorption-desorption interactions of 90Sr with brucite.

PubMed

Ashworth, Hollie; Abrahamsen-Mills, Liam; Bryan, Nick; Foster, Lynn; Lloyd, Jonathan R; Kellet, Simon; Heath, Sarah

2018-05-18

One of the nuclear fuel storage ponds at Sellafield (United Kingdom) is open to the air, and has contained a significant inventory of corroded magnox fuel and sludge for several decades. As a result, some fission products have also been released into solution. 90Sr is known to constitute a small mass of the radionuclides present in the pond, but due to its solubility and activity, it is at risk of challenging effluent discharge limits. The sludge is predominantly composed of brucite (Mg(OH)2), and organic molecules are known to be present in the pond liquor with occasional algal blooms restricting visibility. Understanding the chemical interactions of these components is important to inform ongoing sludge retrievals and effluent management. Additionally, interactions of radionuclides with organics at high pH will be an important consideration for the evolution of cementitious backfilled disposal sites in the UK. Batch sorption-desorption experiments were performed with brucite, 90Sr and natural organic matter (NOM) (humic acid (HA) and Pseudanabaena catenata cyanobacterial growth supernatant) in both binary and ternary systems at high pH. Ionic strength, pH and order of addition of components were varied. 90Sr was shown not to interact strongly with the bulk brucite surface in binary systems under pH conditions relevant to the pond. HA in both binary and ternary systems demonstrated a strong affinity for the brucite surface. Ternary systems containing HA demonstrated enhanced sorption of 90Sr at pH 11.5 and vice versa, likely via formation of strontium-humate complexes regardless of the order of addition of components. The distribution coefficients show HA sorption to be reversible at all pH values studied, and it appeared to control 90Sr behaviour at pH 11.5. Ternary systems containing cyanobacterial supernatant demonstrated a difference in 90Sr behaviour when the culture had been subjected to irradiation in the first stages of its growth.

In situ pH within particle beds of bioactive glasses.

PubMed

Zhang, Di; Hupa, Mikko; Hupa, Leena

2008-09-01

The in vitro behavior of three bioactive glasses with seven particle size distributions was studied by measuring the in situ pH inside the particle beds for 48h in simulated body fluid (SBF). After immersion, the surface of the particles was characterized with a field emission scanning electron microscope equipped with an energy-dispersive X-ray analyzer. In addition, the results were compared with the reactions of the same glasses formed as plates. A similar trend in pH as a function of immersion time was observed for all systems. However, the pH inside the particle beds was markedly higher than that in the bulk SBF of the plates. The pH decreased as power functions with increasing particle size, i.e. with decreasing surface area. The in vitro reactivity expressed as layer formation strongly depended on the particle size and glass composition. The average thickness of the total reaction layer decreased with the increase in sample surface area. Well-developed silica and calcium phosphate layers typically observed on glass plates could be detected only on some particles freely exposed to the solution. No distinct reaction layers were observed on the finest particles, possibly because the layers spread out on the large surface area. Differences in the properties of the bulk SBF and the solution inside the particle bed were negligible for particles larger than 800microm. The results enhance our understanding of the in vitro reactions of bioactive glasses in various product forms and sizes.

Innovative biocatalytic production of soil substrate from green waste compost as a sustainable peat substitute.

PubMed

Kazamias, Georgios; Roulia, Maria; Kapsimali, Ioanna; Chassapis, Konstantinos

2017-12-01

In the present work, a new simple and quick eco-friendly method is discussed to handle effectively the green wastes and produce a sustainable peat substitute of high quality on the large scale. Principal physicochemical parameters, i.e., temperature, moisture, specific weight, pH, electrical conductivity and, also, microorganisms, organic matter, humic substances, total Kjeldahl nitrogen and total organic carbon, C/N ratio, ash, metal content and phytotoxicity, were monitored systematically. Humic substances content values were interrelated to both C/N ratio and pH values and, similarly, bulk density, TOC, TKN, C/N, GI, ash and organic matter were found interconnected to each other. A novel biocatalyst, extremely rich in soil microorganisms, prepared from compost extracts and peaty lignite, accelerated the biotransformation. Zeolite was also employed. The compost does not demonstrate any phytotoxicity throughout the entire biotransformation process and has increased humic substances content. Both humic substances content and germination index can be employed as maturation indices of the compost. Addition of compost, processed for 60 days only, in cultivations of grass plants led to a significant increase in the stem mass and root size, annotating the significant contribution of the compost to both growth and germination. The product obtained is comparable to peat humus, useful as peat substitute and can be classified as a first class soil conditioner suitable for organic farming. Copyright © 2016 Elsevier Ltd. All rights reserved.

Questa baseline and pre-mining ground-water quality investigation. 19. Leaching characteristics of composited materials from mine waste-rock piles and naturally altered areas near Questa, New Mexico

USGS Publications Warehouse

Smith, Kathleen S.; Hageman, Philip L.; Briggs, Paul H.; Sutley, Stephen J.; McCleskey, R. Blaine; Livo, K. Eric; Verplanck, Philip L.; Adams, Monique G.; Gemery-Hill, Pamela A.

2007-01-01

The goal of this study is to compare and contrast the leachability of metals and the acidity from individual mine waste-rock piles and natural erosional scars in the study area near Questa, New Mexico. Surficial multi-increment (composite) samples less than 2 millimeters in diameter from five waste-rock piles, nine erosional-scar areas, a less-altered site, and a tailings slurry-pipe sample were analyzed for bulk chemistry and mineralogy and subjected to two back-to-back leaching procedures. The first leaching procedure, the U.S. Geological Survey Field Leach Test (FLT), is a short-duration leach (5-minute shaking and 10-minute settling) and is intended to leach readily soluble materials. The FLT was immediately followed by an 18-hour, end-over-end rotation leaching procedure. Comparison of results from the back-to-back leaching procedures can provide information about reactions that may take place upon migration of leachates through changing geochemical conditions (for example, pH changes), both within the waste-rock and scar materials and away from the source materials. For the scar leachates, the concentrations of leachable metals varied substantially between the scar areas sampled. The scar leachates have low pH (pH 3.2-4.1). Under these low-pH conditions, cationic metals are solubilized and mobile, but anionic species, such as molybdenum, are less soluble and less mobile. Generally, metal concentrations in the waste-rock leachates did not exceed the upper range of those metal concentrations in the erosional-scar leachates. One exception is molybdenum, which is notably higher in the waste-rock leachates compared with the scar leachates. Most of the waste-rock leachates were at least mildly acidic (pH 3.0-6.2). The pH values in the waste-rock leachates span a large pH range that includes some pH-dependent solubility and metal-attenuation reactions. An increase in pH with leaching time and agitation indicates that there is pH-buffering capacity in some of the waste-rock piles. As pH increased in the waste-pile leachates, concentrations of several metals decreased with increasing time and agitation. Similar pH-dependent reactions may take place upon migration of the leachates in the waste-rock piles. Bulk chemistry, mineralogy, and leachate sulfur-isotope data indicate that the Capulin and Sugar Shack West waste-rock piles are compositionally different from the younger Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles. The Capulin and Sugar Shack West piles have the lowest-pH leachates (pH 3.0-4.1) of the waste-pile samples, and the source material for the Capulin and Sugar Shack West piles appears to be similar to the source material for the erosional-scar areas. Calcite dissolution, in addition to gypsum dissolution, appears to produce the calcium and sulfate concentrations in leachates from the Sugar Shack South, Sugar Shack Middle, and Old Sulphur Gulch piles.

Aggregation of asbestos fibers in water: role of solution chemistry

NASA Astrophysics Data System (ADS)

Wu, L.; Ortiz, C. P.; Jerolmack, D. J.

2016-12-01

Aggregation kinetics and stability of colloidal particles have been extensively studied using bulk techniques such as dynamic light scattering; these techniques involve large ensembles of particles and interpretation of results is difficult when particles are non-spherical and poorly characterized, as is always the case with non-ideal natural hazardous materials such as asbestos fibers. These difficulties hinder greatly progress on fundamental understanding of whether the classic colloidal aggregation theories can be applied to natural materials and how the heterogeneity of particles (e.g., shape) affects the colloidal aggregation kinetics and structure. By using in-situ microscopy and particle tracking techniques, we were able to observe the particle-by-particle growth of aggregated formed by elongated particles (synthetic glass rods and natural asbestos fibers) and demonstrated the rod-shaped geometry induced novel structures and growth dynamics that challenge existing theory. In this study, we continue to use asbestos as model system of elongated colloidal contaminant, and investigate the effects of changing solution chemistry (e.g., ionic strength, pH, and natural organic matter (NOM)), on growth dynamics and aggregates structure. The results show that aggregate growth curves are self-similar with a characteristic timescale that increases with increasing pH. By varying ionic strength for fixed pH values, we determine that the ccc is sensitive to pH. Fractal dimension decreases slightly with increasing pH and decreasing ionic strength, indicating that stronger inter-particle repulsion create sparser aggregates; however, the magnitude of the solution chemistry effects is much smaller than that of colloid shape. In monovalent solutions, regardless of their concentration, HA drastically reduces the aggregation kinetics of asbestos fiber. This work may lead to enhanced prediction of the colloidal contaminants' mobility in the environment, bioavailability, and toxicity to organisms.

Unravelling the pH-dependence of a molecular photocatalytic system for hydrogen production† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5sc01349f Click here for additional data file.

PubMed Central

Pastor, Ernest; Gross, Manuela A.; Selim, Shababa

2015-01-01

Photocatalytic systems for the reduction of aqueous protons are strongly pH-dependent, but the origin of this dependency is still not fully understood. We have studied the effect of different degrees of acidity on the electron transfer dynamics and catalysis taking place in a homogeneous photocatalytic system composed of a phosphonated ruthenium tris(bipyridine) dye (RuP) and a nickel bis(diphosphine) electrocatalyst (NiP) in an aqueous ascorbic acid solution. Our approach is based on transient absorption spectroscopy studies of the efficiency of photo-reduction of RuP and NiP correlated with pH-dependent photocatalytic H2 production and the degree of catalyst protonation. The influence of these factors results in an observed optimum photoactivity at pH 4.5 for the RuP–NiP system. The electron transfer from photo-reduced RuP to NiP is efficient and independent of the pH value of the medium. At pH <4.5, the efficiency of the system is limited by the yield of RuP photo-reduction by the sacrificial electron donor, ascorbic acid. At pH >4.5, the efficiency of the system is limited by the poor protonation of NiP, which inhibits its ability to reduce protons to hydrogen. We have therefore developed a rational strategy utilising transient absorption spectroscopy combined with bulk pH titration, electrocatalytic and photocatalytic experiments to disentangle the complex pH-dependent activity of the homogenous RuP–NiP photocatalytic system, which can be widely applied to other photocatalytic systems. PMID:28717491

Materials Data on PH3 (SG:1) by Materials Project

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

Kristin Persson

2014-07-09

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

Low Temperature Annealed Zinc Oxide Nanostructured Thin Film-Based Transducers: Characterization for Sensing Applications

PubMed Central

Haarindraprasad, R.; Hashim, U.; Gopinath, Subash C. B.; Kashif, Mohd; Veeradasan, P.; Balakrishnan, S. R.; Foo, K. L.; Poopalan, P.

2015-01-01

The performance of sensing surfaces highly relies on nanostructures to enhance their sensitivity and specificity. Herein, nanostructured zinc oxide (ZnO) thin films of various thicknesses were coated on glass and p-type silicon substrates using a sol-gel spin-coating technique. The deposited films were characterized for morphological, structural, and optoelectronic properties by high-resolution measurements. X-ray diffraction analyses revealed that the deposited films have a c-axis orientation and display peaks that refer to ZnO, which exhibits a hexagonal structure with a preferable plane orientation (002). The thicknesses of ZnO thin films prepared using 1, 3, 5, and 7 cycles were measured to be 40, 60, 100, and 200 nm, respectively. The increment in grain size of the thin film from 21 to 52 nm was noticed, when its thickness was increased from 40 to 200 nm, whereas the band gap value decreased from 3.282 to 3.268 eV. Band gap value of ZnO thin film with thickness of 200 nm at pH ranging from 2 to 10 reduces from 3.263eV to 3.200 eV. Furthermore, to evaluate the transducing capacity of the ZnO nanostructure, the refractive index, optoelectric constant, and bulk modulus were analyzed and correlated. The highest thickness (200 nm) of ZnO film, embedded with an interdigitated electrode that behaves as a pH-sensing electrode, could sense pH variations in the range of 2-10. It showed a highly sensitive response of 444 μAmM-1cm-2 with a linear regression of R2 =0.9304. The measured sensitivity of the developed device for pH per unit is 3.72μA/pH. PMID:26167853

[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.

Source, transport and fate of soil organic matter inferred from microbial biomarker lipids on the East Siberian Arctic Shelf

NASA Astrophysics Data System (ADS)

Bischoff, Juliane; Sparkes, Robert B.; Doğrul Selver, Ayça; Spencer, Robert G. M.; Gustafsson, Örjan; Semiletov, Igor P.; Dudarev, Oleg V.; Wagner, Dirk; Rivkina, Elizaveta; van Dongen, Bart E.; Talbot, Helen M.

2016-09-01

The Siberian Arctic contains a globally significant pool of organic carbon (OC) vulnerable to enhanced warming and subsequent release by both fluvial and coastal erosion processes. However, the rate of release, its behaviour in the Arctic Ocean and vulnerability to remineralisation is poorly understood. Here we combine new measurements of microbial biohopanoids including adenosylhopane, a lipid associated with soil microbial communities, with published glycerol dialkyl glycerol tetraethers (GDGTs) and bulk δ13C measurements to improve knowledge of the fate of OC transported to the East Siberian Arctic Shelf (ESAS). The microbial hopanoid-based soil OC proxy R'soil ranges from 0.0 to 0.8 across the ESAS, with highest values nearshore and decreases offshore. Across the shelf R'soil displays a negative linear correlation with bulk δ13C measurements (r2 = -0.73, p = < 0.001). When compared to the GDGT-based OC proxy, the branched and isoprenoid tetraether (BIT) index, a decoupled (non-linear) behaviour on the shelf was observed, particularly in the Buor-Khaya Bay, where the R'soil shows limited variation, whereas the BIT index shows a rapid decline moving away from the Lena River outflow channels. This reflects a balance between delivery and removal of OC from different sources. The good correlation between the hopanoid and bulk terrestrial signal suggests a broad range of hopanoid sources, both fluvial and via coastal erosion, whilst GDGTs appear to be primarily sourced via fluvial transport. Analysis of ice complex deposits (ICDs) revealed an average R'soil of 0.5 for the Lena Delta, equivalent to that of the Buor-Khaya Bay sediments, whilst ICDs from further east showed higher values (0.6-0.85). Although R'soil correlates more closely with bulk OC than the BIT, our understanding of the endmembers of this system is clearly still incomplete, with variations between the different East Siberian Arctic regions potentially reflecting differences in environmental conditions (e.g. temperature, pH), but other physiological controls on microbial bacteriohopanepolyol (BHP) production under psychrophilic conditions are as yet unknown.

Evaluating the potential for quantitative monitoring of in situ chemical oxidation of aqueous-phase TCE using in-phase and quadrature electrical conductivity

NASA Astrophysics Data System (ADS)

Hort, R. D.; Revil, A.; Munakata-Marr, J.; Mao, D.

2015-07-01

Electrical resistivity measurements can potentially be used to remotely monitor fate and transport of ionic oxidants such as permanganate (MnO4-) during in situ chemical oxidation (ISCO) of contaminants like trichloroethene (TCE). Time-lapse two-dimensional bulk conductivity and induced polarization surveys conducted during a sand tank ISCO simulation demonstrated that MnO4- plume movement could be monitored in a qualitative manner using bulk conductivity tomograms, although chargeability was below sensitivity limits. We also examined changes to in-phase and quadrature electrical conductivity resulting from ion injection, MnO2 and Cl- production, and pH change during TCE and humate oxidation by MnO4- in homogeneous aqueous solutions and saturated porous media samples. Data from the homogeneous samples demonstrated that inversion of the sand tank resistivity data using a common Tikhonov regularization approach was insufficient to recover an accurate conductivity distribution within the tank. While changes to in-phase conductivity could be successfully modeled, quadrature conductivity values could not be directly related to TCE oxidation product or MnO4- concentrations at frequencies consistent with field induced polarization surveys, limiting the utility of quadrature conductivity for monitoring ISCO.

Injection efficiency of bound modes. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Egalon, Claudio Oliveira

1990-01-01

Previous work on efficiency of light injection into the core of a fiber from a thin film and a bulk distribution of sources in the cladding have used the fields of a weakly guiding fiber. This approximation simplifies the analysis of the power efficiency by introducing universal values for the eigenvalues of different fibers with the same V-number, but cannot predict accurately the behavior of the injected light into a fiber with arbitrary differences in indices of refraction. The exact field solution was used in the expressions of the power efficiency, p sub eff, and its behavior as a function of the fiber parameter was analyzed. Weakly guiding results obtained previously are confirmed. However, P sub eff does not always increase with the V-number but with the difference in the indices of refraction, eta sub core-eta sub clad. For the bulk distribution it was found that P sub eff increases with the wavelength, lambda, and decreases with the fiber core radius, a, i.e., it decreases with the V-number. However, for the thin film, the P sub eff remains almost constant with lambda and the fiber core radius.

The Interaction of Polycrystalline Copper Films with Dilute Aqueous Solutions of Cupric Chloride

DTIC Science & Technology

1989-10-01

to interconnect semiconductor devices and other computer components Electronic circuits are mass / produced to obtain poduct uniformity and lowestx...so one needs to determine what if any pH change is produced by this extraneous oxide film growth. Thus, in order to determine any interference which...diffusion type; bulk diffusion rates would lie between 10 - 1 3 and 6x10-12mol.h- 1cm-2 mixed grain -13 boundary and bulk diffusion would lie between 6x10

Enzymatic Processes to Unlock the Lignin Value

PubMed Central

Hämäläinen, Veera; Grönroos, Toni; Suonpää, Anu; Heikkilä, Matti Wilhem; Romein, Bastiaan; Ihalainen, Petri; Malandra, Sara; Birikh, Klara R.

2018-01-01

Main hurdles of lignin valorization are its diverse chemical composition, recalcitrance, and poor solubility due to high-molecular weight and branched structure. Controlled fragmentation of lignin could lead to its use in higher value products such as binders, coatings, fillers, etc. Oxidative enzymes (i.e., laccases and peroxidases) have long been proposed as a potentially promising tool in lignin depolymerization. However, their application was limited to ambient pH, where lignin is poorly soluble in water. A Finnish biotechnology company, MetGen Oy, that designs and supplies industrial enzymes, has developed and brought to market several lignin oxidizing enzymes, including an extremely alkaline lignin oxidase MetZyme® LIGNO™, a genetically engineered laccase of bacterial origin. This enzyme can function at pH values as high as 10–11 and at elevated temperatures, addressing lignin at its soluble state. In this article, main characteristics of this enzyme as well as its action on bulk lignin coming from an industrial process are demonstrated. Lignin modification by MetZyme® LIGNO™ was characterized by size exclusion chromatography, UV spectroscopy, and dynamic light scattering for monitoring particle size of solubilized lignin. Under highly alkaline conditions, laccase treatment not only decreased molecular weight of lignin but also increased its solubility in water and altered its dispersion properties. Importantly, organic solvent-free soluble lignin fragmentation allowed for robust industrially relevant membrane separation technologies to be applicable for product fractionation. These enzyme-based solutions open new opportunities for biorefinery lignin valorization thus paving the way for economically viable biorefinery business. PMID:29623274

Relative permittivity in the electrical double layer from nonlinear optics

NASA Astrophysics Data System (ADS)

Boamah, Mavis D.; Ohno, Paul E.; Geiger, Franz M.; Eisenthal, Kenneth B.

2018-06-01

Second harmonic generation (SHG) spectroscopy has been applied to probe the fused silica/water interface at pH 7 and the uncharged 11 ¯ 02 sapphire/water interface at pH 5.2 in contact with aqueous solutions of NaCl, NaBr, NaI, KCl, RbCl, and CsCl as low as several 10 μM. For ionic strengths up to about 0.1 mM, the SHG responses were observed to increase, reversibly for all salts surveyed, when compared to the condition of zero salt added. Further increases in the salt concentration led to monotonic decreases in the SHG response. The SHG increases followed by decreases are found to be consistent with recent reports of phase interference and phase matching in nonlinear optics. By varying the relative permittivity employed in common mean field theories used to describe electrical double layers and by comparing our results to available literature data, we find that models recapitulating the experimental observations are the ones in which (1) the relative permittivity of the diffuse layer is that of bulk water, with other possible values as low as 30, (2) the surface charge density varies with salt concentration, and (3) the charge in the Stern layer or its thickness varies with salt concentration. We also note that the experimental data exhibit sensitivity depending on whether the salt concentration is increased from low to high values or decreased from high to low values, which, however, is not borne out in the fits, at least within the current uncertainties associated with the model point estimates.

Functional properties of protein isolates extracted from stabilized rice bran by microwave, dry heat, and parboiling.

PubMed

Khan, Saima Hafeez; Butt, Masood Sadiq; Sharif, Mian Kamran; Sameen, Ayesha; Mumtaz, Semee; Sultan, Muhammad Tauseef

2011-03-23

Protein isolates extracted from differently stabilized rice bran were analyzed to work out the food use potential. Bulk density remained higher for isolates obtained from heat stabilized bran, the treatments were found to have positive impact on the oil absorption properties, while the water absorption was slightly impaired owing to some possible configurational changes. Surface hydrophobicity and emulsion properties were improved with bran stabilization. Isolates exhibited better foaming properties owing to the flexible nature of protein molecules, with less intensive disulfide bonding, that were slightly affected by the stabilization treatment. Nitrogen solubility index followed a curved pattern with the least value near isoelectric point that showed an increasing trend toward basic pH, and parboiled protein isolates exhibited better gelling properties among the isolates.

Alkaline Ammonia Electrolysis on Electrodeposited Platinum for Controllable Hydrogen Production.

PubMed

Gwak, Jieun; Choun, Myounghoon; Lee, Jaeyoung

2016-02-19

Ammonia is beginning to attract a great deal of attention as an alternative energy source carrier, because clean hydrogen can be produced through electrolytic processes without the emission of COx . In this study, we deposited various shapes of Pt catalysts under potentiostatic mode; the electrocatalytic oxidation behavior of ammonia using these catalysts was studied in alkaline media. The electrodeposited Pt was characterized by both qualitative and quantitative analysis. To discover the optimal structure and the effect of ammonia concentration, the bulk pH value, reaction temperature, and applied current of ammonia oxidation were investigated using potential sweep and galvanostatic methods. Finally, ammonia electrolysis was conducted using a zero-gap cell, producing highly pure hydrogen with an energy efficiency over 80 %. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Bulk C, H, O, and fatty acid C stable isotope analyses for purity assessment of vegetable oils from the southern and northern hemispheres.

PubMed

Spangenberg, Jorge E

2016-09-06

|The carbon, hydrogen and oxygen stable isotope composition (δ 13 C, δ 2 H, and δ 18 O values) of plants and their products is linked to photosynthetic fractionation, environmental factors and agricultural practices. Therefore, they contribute to determining the purity of commercial vegetable oils and may provide information on their geographical origin. Maize, olive, sunflower, groundnut, soybean and rice oils differing in sites of growth in the southern and northern hemispheres were characterized by bulk oil stable isotope ratios (δ 13 C bulk , δ 2 H bulk , and δ 18 O bulk values), fatty acids (FAs) concentrations and δ 13 C FA values using elemental analysis/isotope ratio mass spectrometry, gas chromatography/mass spectrometry, gas chromatography/flame ionization detection and gas chromatography/combustion/isotope ratio mass spectrometry. Principal component analysis was applied to examine the inherent structure of the data. The δ 13 C bulk values of maize oils (-18.4 to -14.9 ‰) are typical for C 4 plants, and those of olive (-30.2 to -28.2 ‰), sunflower (-30.2 to -29.2 ‰), groundnut (-29.3 ‰), soybean (-30.6 ‰), and rice (-34.5 ‰) oils are typical for C 3 plants. The δ 2 H bulk values vary from -161 to -132‰ for maize oils and -171 to -109 ‰ for C 3 oils. The δ 18 O bulk values of all oils vary between 15.2 and 38.9 ‰. The major δ 13 C FA differences (>5 ‰) within plant species render the inter-C 3 -species comparison difficult. These differences are explained in terms of variations in the lipid biosynthetic pathways and blend of vegetable oils of different FA composition and δ 13 C FA values. The samples from the southern hemisphere are generally enriched in 13 C compared with those from the northern hemisphere. Differences between the southern and northern hemispheres were observed in δ 2 H (p < 0.001) and δ 18 O bulk (p = 0.129) values for all C 3 oils, and in δ 13 C 18:1 (p = 0.026) and δ 18 O bulk (p = 0.160) values for maize oils. The results of this study show that combining bulk and molecular stable isotope ratios, fatty acid compositions and their statistical analysis helps the characterization of the geographic origin of oils. This methodology can be used to detect and source impurities in valuable vegetable oils commercialized worldwide. This article is protected by copyright. All rights reserved.

Low Medium pH Value Enhances Anthocyanin Accumulation in Malus Crabapple Leaves

PubMed Central

Tian, Ji; Jin, Kaina; Yao, Yuncong

2014-01-01

Anthocyanin is a critical factor involved in coloration of plant tissues, but the mechanism how medium pH values affect anthocyanin accumulation in woody plants is unknown. We analyzed anthocyanin composition and the expression of elements encoding anthocyanin and flavonols biosynthesis underlying different medium pH values by using three different leave color type cultivars. HPLC analysis demonstrated that high medium pH values treatment induced a dramatic decrease in the concentration of cyaniding in crabapple leaves. Conversely, the high medium pH values induced up-regulation of the content of flavones and flavonols, suggesting that low pH treatment-induced anthocyanin accumulation. Quantitative real time PCR experiment showed the expression level of anthocyanidin synthase (McANS) and uridine diphosphate glucose flavonoid 3-O-glucosyltransferase (McUFGT) was up-regulated by low pH values treatment, and high medium pH value treatment up-regulate the transcription level of flavonol synthase (McFLS). Meanwhile, several MYB TFs have been suggested in the regulation of pH responses. These results strongly indicate that the low pH treatment-induced anthocyanin accumulation is mediated by the variation of mRNA transcription of the anthocyanin biosynthetic genes. PMID:24914811

Treatment of cyanide wastewater by bulk liquid membrane using tricaprylamine as a carrier.

PubMed

Li, Guoping; Xue, Juanqin; Liu, Nina; Yu, Lihua

2016-01-01

The transport of cyanide from wastewater through a bulk liquid membrane (BLM) containing tricaprylamine (TOA) as a carrier was studied. The effect of cyanide concentration in the feed solution, TOA concentration in the organic phase, the stirring speed, NaOH concentration in the stripping solution and temperature on cyanide transport was determined through BLM. Mass transfer of cyanide through BLM was analyzed by following the kinetic laws of two consecutive irreversible first-order reactions, and the kinetic parameters (k(1), k(2), R(m)(max), t(max), J(a)(max), J(d)(max)) were also calculated. Apparently, increase in membrane entrance (k(1)) and exit rate (k(2)) constants was accompanied by a rise in temperature. The values of activation energies were obtained as 35.6 kJ/mol and 18.2 kJ/mol for removal and recovery, respectively. These values showed that both removal and recovery steps in cyanide transport is controlled by the rate of the chemical complexation reaction. The optimal reaction conditions were determined by BLM using trioctylamine as the carrier: feed phase: pH 4, carrier TOA possession ratio in organic phase: 2% (V/V), stripping phase concentration of NaOH: 1% (W/V), reaction time: 60 min, stirring speed: 250 r/min. Under the above conditions, the removal rate was up to 92.96%. The experiments demonstrated that TOA was a good carrier for cyanide transport through BLM in this study.

Development of Single-Seed Near-Infrared Spectroscopic Predictions of Corn and Soybeans Constituents Using Bulk Teference Values and Mean Spectra

USDA-ARS?s Scientific Manuscript database

Near-Infrared reflectance spectroscopic prediction models were developed for common constituents of corn and soybeans using bulk reference values and mean spectra from single-seeds. The bulk reference model and a true single-seed model for soybean protein were compared to determine how well the bul...

Comparative effect of ZnO NPs, ZnO bulk and ZnSO4 in the antioxidant defences of two plant species growing in two agricultural soils under greenhouse conditions.

PubMed

García-Gómez, Concepción; Obrador, Ana; González, Demetrio; Babín, Mar; Fernández, María Dolores

2017-07-01

The present study has investigated the toxicity of ZnO NPs to bean (Phaseolus vulgaris) and tomato (Solanum lycopersicon) crops grown to maturity under greenhouse conditions using an acidic (soil pH5.4) and a calcareous soil (soil pH8.3). The potentially available Zn in the soils and the Zn accumulation in the leaves from NPs applied to the soil (3, 20 and 225mgZnkg -1 ) and changes in the chlorophylls, carotenoids and oxidative stress biomarkers were measured at 15, 30, 60 and 90days and compared with those caused by bulk ZnO and ZnSO 4 . The available Zn in the soil and the leaf Zn content did not differ among the Zn chemical species, except in the acidic soil at the highest concentration of Zn applied as Zn ions, where the highest values of the two variables were found. The ZnO NPs showed comparable Zn toxicity or biostimulation to their bulk counterparts and Zn salts, irrespective of certain significant differences suggesting a higher activity of the Zn ion. The treatments altered the photosynthetic pigment concentration and induced oxidative stress in plants. ROS formation was observed at Zn plant concentrations ranging from 590 to 760mgkg -1 , but the effects on the rest of the parameters were highly dependent on the plant species, exposure time and especially soil type. In general, the effects were higher in the acidic soil than in the calcareous soil for the bean and the opposite for the tomato. The similar uptakes and toxicities of the different Zn forms suggest that the Zn ions derived from the ZnO NPs exerted a preferential toxicity in plants. However, several results obtained in soils treated with NPs at 3mgZnkg -1 soil indicated that may exist other underlying mechanisms related to the intrinsic nanoparticle properties, especially at low NP concentrations. Copyright © 2017 Elsevier B.V. All rights reserved.

Processes of zinc attenuation by biogenic manganese oxides forming in the hyporheic zone of Pinal Creek, Arizona

PubMed Central

Fuller, Christopher C.; Bargar, John R.

2014-01-01

The distribution and speciation of Zn sorbed to biogenic Mn oxides forming in the hyporheic zone of Pinal Creek, AZ, was investigated using micro-focused Extended X-ray Absorption Fine Structure (EXAFS) and X-ray fluorescence (μSXRF) mapping , bulk EXAFS, and chemical extraction. μSXRF and chemical extractions show that contaminant Zn co-varied with Mn in streambed sediment grain coatings. Bulk and micro-focused EXAFS spectra of Zn in the biogenic Mn oxides coating are indicative of Zn forming triple corner sharing inner-sphere complexes over octahedral vacancies in the Mn oxide sheet structure. Zn desorbed in response to decreasing in pH in batch experiments and resulted in near-equal dissolved Zn at each pH over a 10-fold range in solid to solution ratio. The geometry of sorbed Zn was unchanged after 50% desorption at pH 5, indicating desorption is not controlled by dissolution of secondary Zn phases. In sum, these findings support the idea that Zn attenuation in Pinal Creek is largely controlled by sorption to microbial Mn oxides forming in the streambed during hyporheic exchange. Sorption to biogenic Mn oxides is likely an important process in Zn attenuation in circum-neutral pH reaches of many acid-mine drainage contaminated streams when dissolved Mn is present. PMID:24460038

Polypeptide multilayer films on colloidal particles: an in situ electro-optical study.

PubMed

Radeva, Tsetska; Kamburova, Kamelia

2007-04-15

The buildup of poly(L-glutamic acid) (PGA) and poly(L-lysine) (PLL) multilayers on beta-FeOOH colloidal particles was investigated by means of electro-optics and electrophoresis. The films were built at different (acidic) pH in the absence of salt. We found that the thickness of the film grows linearly when the fully charged PLL (at pH 5.5) is combined with almost fully charged PGA (at pH 6.5), with a thickness of about 2 nm per single layer. When the fully charged PLL is combined with weakly charged PGA (at pH 4.5), the film thickness increases exponentially with the number of deposited layers. The thickness of the exponentially growing film increases to 300 nm after deposition of 16 layers. The exponential film growth is attributed to the ability of the PLL to diffuse "in" and "out" of the film bulk at each deposition step. The variation in the electrical polarizability of the film-coated particles was also monitored as a function of the number of adsorbed layers. The result reveals that the PLL chains, which can diffuse into the film bulk, have no measurable contribution to the electro-optical effect of the films terminated with PLL. It is only due to the polarization of counterions of the PLL adsorbed on the film surface.

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

NASA Astrophysics Data System (ADS)

Fu, Jingni; Zhang, Luning

2018-03-01

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

Recovery of gallium and vanadium from gasification fly ash.

PubMed

Font, Oriol; Querol, Xavier; Juan, Roberto; Casado, Raquel; Ruiz, Carmen R; López-Soler, Angel; Coca, Pilar; García Peña, Francisco

2007-01-31

The Puertollano Integrated Coal Gasification Combined Cycle (IGCC) Power Plant (Spain) fly ash is characterized by a relatively high content of Ga and V, which occurs mainly as Ga2O3 and as Ga3+ and V3+ substituting for Al3+ in the Al-Si fly ash glass matrix. Investigations focused on evaluating the potential recovery of Ga and V from these fly ashes. Several NaOH based extraction tests were performed on the IGCC fly ash, at different temperatures, NaOH/fly ash (NaOH/FA) ratios, NaOH concentrations and extraction times. The optimal Ga extraction conditions was determined as 25 degrees C, NaOH 0.7-1 M, NaOH/FA ratio of 5 L/kg and 6 h, attaining Ga extraction yields of 60-86%, equivalent to 197-275 mg of Ga/kg of fly ash. Re-circulation of leachates increased initial Ga concentrations (25-38 mg/L) to 188-215 mg/L, while reducing both content of impurities and NaOH consumption. Carbonation of concentrated Ga leachate demonstrated that 99% of the bulk Ga content in the leachate precipitates at pH 7.4. At pH 10.5 significant proportions of impurities, mainly Al (91%), co-precipitate while >98% of the bulk Ga remains in solution. A second carbonation of the remaining solution (at pH 7.5) recovers the 98.8% of the bulk Ga. Re-dissolution (at pH 0) of the precipitate increases Ga purity from 7 to 30%, this being a suitable Ga end product for further purification by electrolysis. This method produces higher recovery efficiency than currently applied for Ga on an industrial scale. In contrast, low V extraction yields (<64%) were obtained even when using extreme alkaline extraction conditions, which given the current marked price of this element, limits considerably the feasibility of V recovery from IGCC fly ash.

Materials Data on P(H3C)3 (SG:62) by Materials Project

DOE Data Explorer

Kristin Persson

2016-02-04

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

Materials Data on NaMgPH12O11 (SG:131) by Materials Project

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

Kristin Persson

2016-07-14

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

Photodimerisation of a coumarin-dipeptide gelator.

PubMed

Draper, Emily R; McDonald, Tom O; Adams, Dave J

2015-08-18

Here we report a coumarin based hydrogelator that can form bulk gels, or homogeneous thin gels via an electrochemical pH drop. The gel can then be strengthened by post-gelation photodimerisation of the coumarin groups by irradiating with UV light.

Characterization of active phosphorus surface sites at synthetic carbonate-free fluorapatite using single-pulse 1H, 31P, and 31P CP MAS NMR.

PubMed

Jarlbring, Mathias; Sandström, Dan E; Antzutkin, Oleg N; Forsling, Willis

2006-05-09

The chemically active phosphorus surface sites defined as PO(x), PO(x)H, and PO(x)H2, where x = 1, 2, or 3, and the bulk phosphorus groups of PO4(3-) at synthetic carbonate-free fluorapatite (Ca5(PO4)3F) have been studied by means of single-pulse 1H,31P, and 31P CP MAS NMR. The changes in composition and relative amounts of each surface species are evaluated as a function of pH. By combining spectra from single-pulse 1H and 31P MAS NMR and data from 31P CP MAS NMR experiments at varying contact times in the range 0.2-3.0 ms, it has been possible to distinguish between resonance lines in the NMR spectra originating from active surface sites and bulk phosphorus groups and also to assign the peaks in the NMR spectra to the specific phosphorus species. In the 31P CP MAS NMR experiments, the spinning frequency was set to 4.2 kHz; in the single-pulse 1H MAS NMR experiments, the spinning frequency was 10 kHz. The 31P CP MAS NMR spectrum of fluorapatite at pH 5.9 showed one dominating resonance line at 2.9 ppm assigned to originate from PO4(3-) groups and two weaker shoulder peaks at 5.4 and 0.8 ppm which were assigned to the unprotonated PO(x) (PO, PO2-, and PO3(2-)) and protonated PO(x)H (PO2H and PO3H-) surface sites. At pH 12.7, the intensity of the peak representing unprotonated PO(x) surface sites has increased 1.7% relative to the bulk peak, while the intensity of the peaks of the protonated species PO(x)H have decreased 1.4% relative to the bulk peak. At pH 3.5, a resonance peak at -4.5 ppm has appeared in the 31P CP MAS NMR spectrum assigned to the surface species PO(x)H2 (PO3H2). The results from the 1H MAS and 31P CP MAS NMR measurements indicated that H+, OH-, and physisorbed H2O at the surface were released during the drying process at 200 degrees C.

Fog and precipitation chemistry at a mid-land forest in central Taiwan.

PubMed

Liang, Yang-Ling; Lin, Teng-Chiu; Hwong, Jeen-Liang; Lin, Neng-Huei; Wang, Chiao-Ping

2009-01-01

We analyzed fog and bulk precipitation chemistry at a cloud forest in central Taiwan where mountain agriculture activities are highest. There were 320 foggy days (visibility <1000 m) recorded between April 2005 and March 2006. Fog was most frequent between April 2005 and July 2005 and in March 2006 (153/153 d) and least frequent in January 2006 (21/31 d). The total fog duration was 2415 h, representing 28% of the sampling period. Compared with bulk precipitation, fog was disproportionally enriched in NO(3)(-) and SO(4)(2-) relative to K(+), Ca(2+), Mg(2+), and NH(4)(+), resulting in higher a content of nitric acid and sulfuric acid than weak acids or neutral salts and, therefore, higher acidity (median pH, 4.9) in fog than in bulk precipitation (median and mean pH, 5.5). The very high input of NH(4)(+) (47 kg N ha(-1) yr(-1)) through bulk precipitation suggests that the use of fertilizer (ammonium sulfate and animal manure) associated with mountain agriculture has a major impact on atmospheric deposition at the surrounding forest ecosystems. The input of inorganic N reached 125 kg N ha(-1) yr(-1) and likely exceeded the biological demand of the forest ecosystem. Sulfate is the most abundant anion in fog at Chi-tou and in precipitation at various forests throughout Taiwan, suggesting that the emission and transport of large quantities of SO(2,) the precursor of SO(4)(2-), is an island-wide environmental issue.

Thermoelectric properties of Tl and I dual-doped Bi2Te3-based alloys

NASA Astrophysics Data System (ADS)

Wu, Fang; He, Qinglin; Tang, Mingsheng; Song, Hongzhang

2018-04-01

TlxBi2‑xTe3‑xIx (x = 0, 0.05, 0.1 and 0.2) flower-like nanopowders were prepared successfully by the hydrothermal method. Then, the synthesized nanoparticles were pressed into bulks by hot-pressing. The thermoelectric (TE) properties of the TlxBi2‑xTe3‑xIx bulk samples were investigated and discussed. The results showed that the influences of Tl doping on the electrical resistivity and Seebeck coefficients of the Bi2Te3 is over that of I doping. Thus, the power factors of the dual-doped bulks are all less than that of the Bi2Te3 bulk. The thermal conductivities of the TlxBi2‑xTe3‑xIx bulk samples also remain at lower values. As a result, the ZT value of the optimized doped bulk Tl0.1Bi1.9Te2.9I0.1 attains a value of 1.1 at 398 K.

Spatial distribution of soil properties on a landslide in Taiwan: effects of movement types and vegetation

NASA Astrophysics Data System (ADS)

Lee, Pei-Chen; Cheng, Chih-Hsin

2017-04-01

Landslides are critical natural disturbances in tropical and temperate areas and exert immense impacts on forest ecosystems and soil properties. The impacts of landslides on soil properties not only vary with their movement type, scale, or location but also have great spatial variation inside landslide. In this study, the effects of movement type (erosion and deposition) and succeeding vegetation on soil properties inside a landslide scar were evaluated. The study site was located in Chiufenernshan, central Taiwan. The landslide was triggered by the Chi-Chi Earthquake (Ritch magnitude 7.3) in 1999. A huge amount of waste debris (30 million m3) was moved along the sliding slope (with a tipping degree at 26o) and deposited in the lower parts. Total area size of landslide scar was 200 ha and about 30 - 50 m depth waste material was eroded/deposited in the upper/lower scar areas. After 17 years, the succeeding vegetation varied inside landslide scar. The erosion areas were covered with grass (Miscanthus floridulus) or left barren in some slopes. In contrast, a secondary forest, dominated with Trema orientalis, Lithocarpus konishii, Mallotus paniculatus, and Smilax bracteata, developed in the deposition areas. We collected soil samples in different landscape areas including (i) erosion areas without vegetation, (ii) erosion areas with grass vegetation, (iii) deposition areas, and (iv) adjacent undisturbed areas. Our results indicated that the erosion areas had higher bulk density, rock fragment and pH value, but less soil organic carbon, total nitrogen, total phosphorus and N-mineralization rate than both deposition and adjacent undisturbed areas. The soil properties without vegetation even showed the extreme end compared to the soils with grass vegetation. Soils at the deposition zone had similar rock fragment, bulk density, soil pH, soil organic carbon and N-mineralization rate values to the undisturbed site (p > 0.05). We speculate that movement types could determine the initial establishment of vegetation types and then influence soil properties under vegetation succession. Therefore, both waste movement types and vegetation and their interactions play important roles on soil properties.

Multiple oxygen and sulfur isotope compositions of secondary atmospheric sulfate in the city of Wuhan, central China

NASA Astrophysics Data System (ADS)

Li, X.; Bao, H.; Zhou, A.; Wang, D.

2012-12-01

Secondary atmospheric sulfate (SAS) is the oxidation product and sink for sulfur gases of biological, volcanic, and anthropogenic origins on Earth. SAS can be produced from gas-phase OH-radical oxidation and five aqueous-phase chemical reactions including aqueous-phase S (IV) oxidation reactions by H2O2, O3, oxygen catalyzed by Fe3+ and Mn2+, and methyle hydrogen peroxide and peroxyacetic acid. The tropospheric sulfur oxidation pathway is therefore determined by cloud-water pH, dissolved [Fe2+] or [Mn2+] content, S emission rate, meteorological condition, and other factors. The S isotope composition is a good tracer for the source while the O isotopes, especially the triple O isotope compositions are a good tracer for S oxidation pathway. Jerkins and Bao (2006) provided the first set of multiple stable isotope compositions (δ34S, δ18O and Δ17O) for SAS collected from bulk atmosphere in Baton Rouge in the relatively rural southern USA. Their study revealed a long-tern average Δ17O value of ~+0.7‰ for SAS, and speculated that much of the Earth mid-latitudes may have a similar average SAS Δ17O value. Additional sampling campaign at different sites is necessarily for constructing and testing models on sulfur oxidation and transport in the troposphere. A total of 33 sulfate samples were collected from bulk atmospheric deposition over a 950-day period from May 2009 to December 2011 in the city of Wuhan, Hubei Province, China. Differing from Baton Rouge, Wuhan is an industrial metropolis with a population of 9.8 million and a high particulate matter content (115 μg/m3). It also has a subtropical monsoon climate, with rainwater pH at ~5.3 year-around. The rainwater ion concentrations have seasonal variations, typically low in summer and high in winter. The anions are dominated by SO42-, at an average concentration of 8.5 mg/L. There is little sulfate contribution from sea-salt (SS) sulfate or dusts in Wuhan. The isotopic compositions for bulk atmospheric sulfate range from 0.00‰ to 1.02‰ for the Δ17O, 8.0‰ to 17.8‰ for the δ18O, and 2.1‰ to 24.1‰ for the δ34S. No apparent correlation is found among Δ17O, δ18O, or δ34S values. No significant temporal pattern exists for the Δ17O over the collection period. The positive Δ17O values for SAS have a time-weighted average of 0.52 ± 0.23‰, lower than the average in Baton Rouge, raising the possibility that the high particulate matter content in Wuhan may have played a role in promoting S oxidation via surface and/or Fe(III)-catalyzed pathways that do not generate positive 17O anomaly in product sulfate. The average Δ17O value also supports the assertion that the long-term average Δ17O value for SAS in the mid-latitude sites fall within a range (0.6~0.8‰) that is much lower than that in polar areas. The SAS δ18O values in Wuhan lie within the range reported for other sites (+5.0‰ to +19.6‰), with a time-weighted average value of 12.0 ± 2.3‰. Not counting three outlier (>13‰), the δ34S values are at a narrow range with a time-weighted average of +4.5 ±1.3‰ (n=30), which is higher than those from Baton Rouge but is typical for the heavily populated regions in China.

Packing Fraction of a Two-dimensional Eden Model with Random-Sized Particles

NASA Astrophysics Data System (ADS)

Kobayashi, Naoki; Yamazaki, Hiroshi

2018-01-01

We have performed a numerical simulation of a two-dimensional Eden model with random-size particles. In the present model, the particle radii are generated from a Gaussian distribution with mean μ and standard deviation σ. First, we have examined the bulk packing fraction for the Eden cluster and investigated the effects of the standard deviation and the total number of particles NT. We show that the bulk packing fraction depends on the number of particles and the standard deviation. In particular, for the dependence on the standard deviation, we have determined the asymptotic value of the bulk packing fraction in the limit of the dimensionless standard deviation. This value is larger than the packing fraction obtained in a previous study of the Eden model with uniform-size particles. Secondly, we have investigated the packing fraction of the entire Eden cluster including the effect of the interface fluctuation. We find that the entire packing fraction depends on the number of particles while it is independent of the standard deviation, in contrast to the bulk packing fraction. In a similar way to the bulk packing fraction, we have obtained the asymptotic value of the entire packing fraction in the limit NT → ∞. The obtained value of the entire packing fraction is smaller than that of the bulk value. This fact suggests that the interface fluctuation of the Eden cluster influences the packing fraction.

Materials Data on TaSi2PH18C6(NCl3)2 (SG:14) by Materials Project

DOE Data Explorer

Kristin Persson

2014-11-02

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

Vermiconversion of industrial sludge for recycling the nutrients.

PubMed

Sangwan, Pritam; Kaushik, C P; Garg, V K

2008-12-01

The aim of the present study was to investigate the transformation of sugar mill sludge (PM) amended with biogas plant slurry (BPS) into vermicompost employing an epigeic earthworm Eisenia fetida. To achieve the objectives experiments were conducted for 13 weeks under controlled environmental conditions. In all the waste mixtures, a decrease in pH, TOC, TK and C:N ratio, but increase in TKN and TP was recorded. Maximum worm biomass and growth rate was attained in 20% PM containing waste mixture. It was inferred from the study that addition of 30-50% of PM with BPS had no adverse effect on the fertilizer value of the vermicompost as well as growth of E. fetida. The results indicated that vermicomposting can be an alternate technology for the management and nutrient recovery from press mud if mixed with bulking agent in appropriate quantities.

Pilot study of Iopamidol-based quantitative pH imaging on a clinical 3T MR scanner.

PubMed

Müller-Lutz, Anja; Khalil, Nadia; Schmitt, Benjamin; Jellus, Vladimir; Pentang, Gael; Oeltzschner, Georg; Antoch, Gerald; Lanzman, Rotem S; Wittsack, Hans-Jörg

2014-12-01

The objective of this study was to show the feasibility to perform Iopamidol-based pH imaging via clinical 3T magnetic resonance imaging (MRI) using chemical exchange saturation transfer (CEST) imaging with pulse train presaturation. The pulse train presaturation scheme of a CEST sequence was investigated for Iopamidol-based pH measurements using a 3T magnetic resonance (MR) scanner. The CEST sequence was applied to eight tubes filled with 100-mM Iopamidol solutions with pH values ranging from 5.6 to 7.0. Calibration curves for pH quantification were determined. The dependence of pH values on the concentration of Iopamidol was investigated. An in vivo measurement was performed in one patient who had undergone a previous contrast-enhanced computed tomography (CT) scan with Iopamidol. The pH values of urine measured with CEST MRI and with a pH meter were compared. In the measured pH range, pH imaging using CEST imaging with pulse train presaturation was possible. Dependence between the pH value and the concentration of Iopamidol was not observed. In the in vivo investigation, the pH values in the human bladder measured by the Iopamidol CEST sequence and in urine were consistent. Our study shows the feasibility of using CEST imaging with Iopamidol for quantitative pH mapping in vitro and in vivo on a 3T MR scanner.

Mineralization, alteration, and hydrothermal metamorphism of the ophiolite-hosted Turner-Albright sulfide deposit, southwestern Oregon

USGS Publications Warehouse

Zierenberg, R.A.; Shanks, Wayne C.; Seyfried, W.E.; Koski, R.A.; Strickler, M.D.

1988-01-01

The Turner-Albright sulfide deposit, part of the Josephine ophiolite, formed on and below the seafloor during Late Jurassic volcanism at a back arc spreading center. Ore fluids were probably localized by faults which were active on the seafloor at the time of sulfide deposition. The uppermost massive sulfide formed on the seafloor at hydrothermal vents. The bulk of the sulfide mineralization formed below the seafloor within olivine basalt hyaloclastite erupted near the time of mineralization. Infiltration of hydrothermal fluid into the hyaloclastite altered the rock. The fluid responsible for the hydrothermal alteration was evolved seawater with low pH and Mg and high Fe. The average value of sulfide and the difference between sulfide and contemporaneous seawater sulfate values are similar to ophiolite-hosted sulfide deposits in Cyprus. Mudstone and clinopyroxene basalt above the sulfide horizons were not altered by the ore-transporting hydrothermal fluid, but these rocks were hydrothermally metamorphosed by altered seawater heated by deep circulation into hot oceanic crust. This subseafloor metamorphism produced a mineral assemblage typical of prehnite-pumpellyite facies metamorphism. Exchange with altered seawater increased the whole-rock ??18O of the basalts to values of 9.4-11.2%. -from Authors

The adsorption and thermal decomposition of PH 3 on Si(111)-(7 × 7)

NASA Astrophysics Data System (ADS)

Taylor, P. A.; Wallace, R. M.; Choyke, W. J.; Yates, J. T.

1990-11-01

The adsorption of PH 3, on Si(111)-(7 × 7) has been studied by Auger electron spectroscopy and temperature programmed desorption. PH 3 was found to exhibit two kinds of behavior on the surface. A small surface coverage of molecularly adsorbed PH 3 desorbs without any dissociative surface chemistry. For the majority of the adsorbed PH x species (3 ⩾ x ⩾ 1) dissociation occurs to form P(a) and H(a). At 120 K, PH 3 initially adsorbs as the reactive species with a sticking coefficient of S ≅ 1 up to ˜75% saturation. The reactive PH x species surface concentration saturates at (1.9 ± 0.3) × 10 14 PH x cm -2. Surface H(a), produc thermal decomposition, desorbs as H 2(g) at T > 700 K., and P(a) desorbs as P 2(g) at T > 900 K. Capping the Si-dangling bonds with atomic deuterium prevents PH 3 adsorption, indicating that the dangling bonds are the PH 3 adsorption sites. Isotopic studies involving Si-D surface species mixed with adsorbed PH x species indicate that PH 3 desorption does not occur through a recombination process. Finally, additional PH 3 may be adsorbed if the surface hydrogen produced by dissociation of PH 3 is removed. Evidence for P penetration into bulk Si(111) at 875 K is presented.

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

Predota, Milan; Machesky, Michael L.; Wesolowski, David J.

The zeta potential (ZP) is an oft-reported measure of the macroscopic charge state of solid surfaces and colloidal particles in contact with solvents. However, the origin of this readily measurable parameter has remained divorced from the molecular-level processes governing the underlying electrokinetic phenomena, which limits its usefulness. Here, we connect the macroscopic measure to the microscopic realm through nonequilibrium molecular dynamics simulations of electroosmotic flow between parallel slabs of the hydroxylated (110) rutile (TiO 2) surface. These simulations provided streaming mobilities, which were converted to ZP via the commonly used Helmholtz-Smoluchowski equation. A range of rutile surface charge densities (0.1more » to –0.4 C/m 2), corresponding to pH values between about 2.8 and 9.4, in RbCl, NaCl, and SrCl 2 aqueous solutions, were modeled and compared to experimental ZPs for TiO 2 particle suspensions. Simulated ZPs qualitatively agree with experiment and show that “anomalous” ZP values and inequalities between the point of zero charge derived from electrokinetic versus pH titration measurements both arise from differing co- and counterion sorption affinities. We show that at the molecular level the ZP arises from the delicate interplay of spatially varying dynamics, structure, and electrostatics in a narrow interfacial region within about 15 Å of the surface, even in dilute salt solutions. This contrasts fundamentally with continuum descriptions of such interfaces, which predict the ZP response region to be inversely related to ionic strength. In reality the properties of this interfacial region are dominated by relatively immobile and structured water. Furthermore, viscosity values are substantially greater than in the bulk, and electrostatic potential profiles are oscillatory in nature.« less

Modelling chemical depletion profiles in regolith

USGS Publications Warehouse

Brantley, S.L.; Bandstra, J.; Moore, J.; White, A.F.

2008-01-01

Chemical or mineralogical profiles in regolith display reaction fronts that document depletion of leachable elements or minerals. A generalized equation employing lumped parameters was derived to model such ubiquitously observed patterns:C = frac(C0, frac(C0 - Cx = 0, Cx = 0) exp (??ini ?? over(k, ??) ?? x) + 1)Here C, Cx = 0, and Co are the concentrations of an element at a given depth x, at the top of the reaction front, or in parent respectively. ??ini is the roughness of the dissolving mineral in the parent and k???? is a lumped kinetic parameter. This kinetic parameter is an inverse function of the porefluid advective velocity and a direct function of the dissolution rate constant times mineral surface area per unit volume regolith. This model equation fits profiles of concentration versus depth for albite in seven weathering systems and is consistent with the interpretation that the surface area (m2 mineral m- 3 bulk regolith) varies linearly with the concentration of the dissolving mineral across the front. Dissolution rate constants can be calculated from the lumped fit parameters for these profiles using observed values of weathering advance rate, the proton driving force, the geometric surface area per unit volume regolith and parent concentration of albite. These calculated values of the dissolution rate constant compare favorably to literature values. The model equation, useful for reaction fronts in both steady-state erosional and quasi-stationary non-erosional systems, incorporates the variation of reaction affinity using pH as a master variable. Use of this model equation to fit depletion fronts for soils highlights the importance of buffering of pH in the soil system. Furthermore, the equation should allow better understanding of the effects of important environmental variables on weathering rates. ?? 2008.

Molecular origins of the zeta potential

DOE PAGES

Predota, Milan; Machesky, Michael L.; Wesolowski, David J.

2016-09-19

The zeta potential (ZP) is an oft-reported measure of the macroscopic charge state of solid surfaces and colloidal particles in contact with solvents. However, the origin of this readily measurable parameter has remained divorced from the molecular-level processes governing the underlying electrokinetic phenomena, which limits its usefulness. Here, we connect the macroscopic measure to the microscopic realm through nonequilibrium molecular dynamics simulations of electroosmotic flow between parallel slabs of the hydroxylated (110) rutile (TiO 2) surface. These simulations provided streaming mobilities, which were converted to ZP via the commonly used Helmholtz-Smoluchowski equation. A range of rutile surface charge densities (0.1more » to –0.4 C/m 2), corresponding to pH values between about 2.8 and 9.4, in RbCl, NaCl, and SrCl 2 aqueous solutions, were modeled and compared to experimental ZPs for TiO 2 particle suspensions. Simulated ZPs qualitatively agree with experiment and show that “anomalous” ZP values and inequalities between the point of zero charge derived from electrokinetic versus pH titration measurements both arise from differing co- and counterion sorption affinities. We show that at the molecular level the ZP arises from the delicate interplay of spatially varying dynamics, structure, and electrostatics in a narrow interfacial region within about 15 Å of the surface, even in dilute salt solutions. This contrasts fundamentally with continuum descriptions of such interfaces, which predict the ZP response region to be inversely related to ionic strength. In reality the properties of this interfacial region are dominated by relatively immobile and structured water. Furthermore, viscosity values are substantially greater than in the bulk, and electrostatic potential profiles are oscillatory in nature.« less

Evaluation of Radiopacity of Bulk-fill Flowable Composites Using Digital Radiography.

PubMed

Tarcin, B; Gumru, B; Peker, S; Ovecoglu, H S

2016-01-01

New flowable composites that may be bulk-filled in layers up to 4 mm are indicated as a base beneath posterior composite restorations. Sufficient radiopacity is one of the several important requirements such materials should meet. The aim of this study was to evaluate the radiopacity of bulk-fill flowable composites and to provide a comparison with conventional flowable composites using digital imaging. Ten standard specimens (5 mm in diameter, 1 mm in thickness) were prepared from each of four different bulk-fill flowable composites and nine different conventional flowable composites. Radiographs of the specimens were taken together with 1-mm-thick tooth slices and an aluminum step wedge using a digital imaging system. For the radiographic exposures, a storage phosphor plate and a dental x-ray unit at 70 kVp and 8 mA were used. The object-to-focus distance was 30 cm, and the exposure time was 0.2 seconds. The gray values of the materials were measured using the histogram function of the software available with the system, and radiopacity was calculated as the equivalent thickness of aluminum. The data were analyzed statistically (p<0.05). All of the tested bulk-fill flowable composites showed significantly higher radiopacity values in comparison with those of enamel, dentin, and most of the conventional flowable composites (p<0.05). Venus Bulk Fill (Heraeus Kulzer) provided the highest radiopacity value, whereas Arabesk Flow (Voco) showed the lowest. The order of the radiopacity values for the bulk-fill flowable composites was as follows: Venus Bulk Fill (Heraeus Kulzer) ≥ X-tra Base (Voco) > SDR (Dentsply DeTrey) ≥ Filtek Bulk Fill (3M ESPE). To conclude, the bulk-fill flowable restorative materials, which were tested in this study using digital radiography, met the minimum standard of radiopacity specified by the International Standards Organization.

Estimation of the IC to CG Ratio Using JEM-GLIMS and Ground-based Lightning Network Data

NASA Astrophysics Data System (ADS)

Bandholnopparat, K.; Sato, M.; Takahashi, Y.; Adachi, T.; Ushio, T.

2017-12-01

The ratio between intracloud (IC) discharge and cloud-to-ground (CG) discharge, which is denoted by Z, is the important parameter for the studies on the climatological differences of thunderstorm structures and for the quantitative evaluation of lightning contributions to the global electric circuit. However, the latitudinal, regional, and seasonal dependences of Z-value are not fully clarified. The purposes of this study are (i) to develop new methods to identify IC and CG discharges using optical data obtained by the Global Lightning and Sprite Measurements on Japanese Experiment Module (JEM-GLIMS) from space and ground-based lightning data, (ii) to estimate Z-value and its latitudinal, regional, and seasonal dependences. As a first step, we compared the JEM-GLIMS data to the ground-based lightning data obtained by JLDN, NLDN, WWLLN, and GEON in order to distinguish the lightning discharge type detected by JEM-GLIMS. As a next step, we have calculated intensity ratios between the blue and red PH channels, that is, PH2(337 nm)/PH3(762 nm), PH5(316 nm)/PH3, PH6(392 nm)/PH3, PH2/PH4(599-900 nm), PH5/PH4, and PH6/PH4 for each lightning event. From these analyses, it is found that 447 and 454 of 8355 lightning events were identified to be CG and IC discharges, respectively. It is also found that the PH intensity ratio of IC discharges is clearly higher than that of CG discharges. In addition, the difference of the PH2/PH3, PH2/PH4, and PH6/PH4 ratio between IC and CG cases is relatively large, which means these three ratios are the useful proxy to classify the discharge types for other 7454 lightning events. Finally, the estimated Z-value varies from 0.18 - 0.84 from the equator to the higher latitude. The decrease of the Z-value from the equator to the higher latitude is confirmed both in the northern and the southern hemispheres. Although this latitudinal dependence of the Z-value is similar to previous studies, i.e., Boccippio et al. (2001), the estimated absolute Z-value is smaller than that in previous studies. The reason of the smaller absolute Z-value may be because JEM-GLIMS used the high threshold for the event triggering and missed many lightning events having lower optical energies. At the presentation, we will show the regional and seasonal dependences of the Z-value in detail.

Influence of indian mustard (Brassica juncea) on rhizosphere soil solution chemistry in long-term contaminated soils: a rhizobox study.

PubMed

Kim, Kwon-Rae; Owens, Gary; Kwon, Soon-lk

2010-01-01

This study investigated the influence of Indian mustard (Brassica juncea) root exudation on soil solution properties (pH, dissolved organic carbon (DOC), metal solubility) in the rhizosphere using a rhizobox. Measurement was conducted following the cultivation of Indian mustard in the rhizobox filled four different types of heavy metal contaminated soils (two alkaline soils and two acidic soils). The growth of Indian mustard resulted in a significant increase (by 0.6 pH units) in rhizosphere soil solution pH of acidic soils and only a slight increase (< 0.1 pH units) in alkaline soils. Furthermore, the DOC concentration increased by 17-156 mg/L in the rhizosphere regardless of soil type and the extent of contamination, demonstrating the exudation of DOC from root. Ion chromatographic determination showed a marked increase in the total dissolved organic acids (OAs) in rhizosphere. While root exudates were observed in all soils, the amount of DOC and OAs in soil solution varied considerably amongst different soils, resulting in significant changes to soil solution metals in the rhizosphere. For example, the soil solution Cd, Cu, Pb, and Zn concentrations increased in the rhizosphere of alkaline soils compared to bulk soil following plant cultivation. In contrast, the soluble concentrations of Cd, Pb, and Zn in acidic soils decreased in rhizosphere soil when compared to bulk soils. Besides the influence of pH and DOC on metal solubility, the increase of heavy metal concentration having high stability constant such as Cu and Pb resulted in a release of Cd and Zn from solid phase to liquid phase.

17 CFR 31.8 - Cover of leverage contracts.

Code of Federal Regulations, 2014 CFR

2014-04-01

... current market value of the commodity represented by each receipt. (ii) Warehouse receipts for gold bullion in the case of leverage contracts on bulk gold coins, bulk gold coins in the case of leverage contracts on gold bullion, silver bullion in the case of leverage contracts on bulk silver coins, bulk...

17 CFR 31.8 - Cover of leverage contracts.

Code of Federal Regulations, 2012 CFR

2012-04-01

... current market value of the commodity represented by each receipt. (ii) Warehouse receipts for gold bullion in the case of leverage contracts on bulk gold coins, bulk gold coins in the case of leverage contracts on gold bullion, silver bullion in the case of leverage contracts on bulk silver coins, bulk...

17 CFR 31.8 - Cover of leverage contracts.

Code of Federal Regulations, 2013 CFR

2013-04-01

... current market value of the commodity represented by each receipt. (ii) Warehouse receipts for gold bullion in the case of leverage contracts on bulk gold coins, bulk gold coins in the case of leverage contracts on gold bullion, silver bullion in the case of leverage contracts on bulk silver coins, bulk...

Immobilization of Bacillus sp. in mesoporous activated carbon for degradation of sulphonated phenolic compound in wastewater.

PubMed

Sekaran, G; Karthikeyan, S; Gupta, V K; Boopathy, R; Maharaja, P

2013-03-01

Xenobiotic compounds are used in considerable quantities in leather industries besides natural organic and inorganic compounds. These compounds resist biological degradation and thus they remain in the treated wastewater in the unaltered molecular configurations. Immobilization of organisms in carrier matrices protects them from shock load application and from the toxicity of chemicals in bulk liquid phase. Mesoporous activated carbon (MAC) has been considered in the present study as the carrier matrix for the immobilization of Bacillus sp. isolated from Effluent Treatment Plant (ETP) employed for the treatment of wastewater containing sulphonated phenolic (SP) compounds. Temperature, pH, concentration, particle size and mass of MAC were observed to influence the immobilization behavior of Bacillus sp. The percentage immobilization of Bacillus sp. was the maximum at pH 7.0, temperature 20 °C and at particle size 300 μm. Enthalpy, free energy and entropy of immobilization were -46.9 kJ mol(-1), -1.19 kJ mol(-1) and -161.36 JK(-1)mol(-1) respectively at pH 7.0, temperature 20 °C and particle size 300 μm. Higher values of ΔH(0) indicate the firm bonding of the Bacillus sp. in MAC. Degradation of aqueous sulphonated phenolic compound by Bacillus sp. immobilized in MAC followed pseudo first order rate kinetics with rate constant 1.12 × 10(-2) min(-1). Copyright © 2012 Elsevier B.V. All rights reserved.

SO 2 oxidation in an entraining cloud model with explicit microphysics

NASA Astrophysics Data System (ADS)

Bower, K. N.; Hill, T. A.; Coe, H.; Choularton, T. W.

A model of the chemical evolution of the droplets in a hill-cap cloud is presented. The chemistry of individual droplets forming on cloud condensation nuclei of differing size and chemical composition is considered, and the take-up of species from the gas phase by the droplets is treated explicity for the droplet population. Oxidation of S(IV) dissolved in cloud droplets is assumed to be dominated by hydrogen peroxide and ozone. Hydrogen peroxide is normally found to be the dominant oxidant for the oxidation of sulphur dioxide (except in the presence of substantial concentrations of ammonia gas, which increases droplet pH and the contribution made by the oxidant ozone). The entrainment of hydrogen peroxide from above the cloud top increases the amount of sulphate produced in conditions where the reaction is otherwise oxidant limited by the availability hydrogen peroxide. These conditions occur when there are high concentrations of sulphur dioxide accompanied by low cloudwater pH values. Within droplets formed on sodium chloride aerosol, reduced levels of acidity lead to an increase in sulphate production as a result of an enhanced reaction between SO 2 and the oxidant ozone. This results in an overall higher increase in cloudwater sulphate than would be expected assuming an even distribution of all reactants amongst the droplets. In addition, concentrations of the hydrogen sulphite ion predicted to occur in the cloudwater can be substantially in excess of those predicted from the bulk cloudwater pH. This is consistent with recent observations.

Radiation Fog in the US Mid-Atlantic Region: Chemical Composition, Trends, and Gas-Liquid Partitioning

NASA Astrophysics Data System (ADS)

Straub, D.

2016-12-01

The chemical composition of radiation fog has been studied at a rural site in central Pennsylvania over an eight year period extending through 2015. Bulk fog samples were collected with an automated Caltech Heated Rod Cloud Collector (CHRCC) and analyzed for pH, inorganic ions, organic acids, total organic carbon (TOC), and total nitrogen (TN). Over the duration of the project, 146 samples were collected and used to document chemical composition, evaluate changes over time, and to investigate partitioning between the gas and aqueous phases. Ammonium, sulfate, calcium, and nitrate were the most abundant inorganic ions while acetate and formate were the dominant organic acids. Organic acids contributed about 15% to TOC. Inorganic nitrogen accounted for the majority of TN, with only 18% of TN attributed to organic nitrogen. Overall, organic matter contributed 52% to the total mass loading of the fog samples, a value that is higher than reported for other radiation fog studies. Statistically significant decreasing trends were observed for sulfate, ammonium, chloride, nitrate, and pH. These trends coincide with reductions in emissions from fossil fuel combustion that have been documented over this time period. Seasonal trends were also detected for nitrate, ammonium, potassium, phosphate, acetate and formate which appear to be related to the agricultural growing season. Based on simultaneous measurements of gas phase ammonia and ammonium in the fog samples, significant deviations from equilibrium were found. In low pH samples, ammonium concentrations were much lower than equilibrium predicts, while the opposite occurred in high pH samples. Modeling suggested that mass transfer limitations contributed to the departure from equilibrium. Similarly, predictions of bicarbonate concentrations based on equilibrium with gas phase carbon dioxide appears to underestimate the actual amount of bicarbonate present in samples collected during this study.

Corrosion in low dielectric constant Si-O based thin films: Buffer concentration effects

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

Zeng, F. W.; Lane, M. W., E-mail: mlane@ehc.edu; Gates, S. M.

2014-05-15

Organosilicate glass (OSG) is often used as an interlayer dielectric (ILD) in high performance integrated circuits. OSG is a brittle material and prone to stress-corrosion cracking reminiscent of that observed in bulk glasses. Of particular concern are chemical-mechanical planarization techniques and wet cleans involving solvents commonly encountered in microelectronics fabrication where the organosilicate film is exposed to aqueous environments. Previous work has focused on the effect of pH, surfactant, and peroxide concentration on the subcritical crack growth of these films. However, little or no attention has focused on the effect of the conjugate acid/base concentration in a buffer. Accordingly, thismore » work examines the “strength” of the buffer solution in both acidic and basic environments. The concentration of the buffer components is varied keeping the ratio of acid/base and therefore pH constant. In addition, the pH was varied by altering the acid/base ratio to ascertain any additional effect of pH. Corrosion tests were conducted with double-cantilever beam fracture mechanics specimens and fracture paths were verified with ATR-FTIR. Shifts in the threshold fracture energy, the lowest energy required for bond rupture in the given environment, G{sub TH}, were found to shift to lower values as the concentration of the base in the buffer increased. This effect was found to be much larger than the effect of the hydroxide ion concentration in unbuffered solutions. The results are rationalized in terms of the salient chemical bond breaking process occurring at the crack tip and modeled in terms of the chemical potential of the reactive species.« less

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

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

Campos, A.; Morgan, B.

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

The effect of artificial bulk viscosity in simulations of forced compressible turbulence

DOE PAGES

Campos, A.; Morgan, B.

2018-05-17

The use of an artificial bulk viscosity for shock stabilization is a common approach employed in turbulence simulations with high-order numerics. The effect of the artificial bulk viscosity is analyzed in the context of large eddy simulations by using as a test case simulations of linearly-forced compressible homogeneous turbulence (Petersen and Livescu, 2010 [12]). This case is unique in that it allows for the specification of a priori target values for total dissipation and ratio of solenoidal to dilatational dissipation. A comparison between these target values and the true predicted levels of dissipation is thus used to investigate the performancemore » of the artificial bulk viscosity. Results show that the artificial bulk viscosity is effective at achieving stable solutions, but also leads to large values of artificial dissipation that outweigh the physical dissipation caused by fluid viscosity. An alternate approach, which employs the artificial thermal conductivity only, shows that the dissipation of dilatational modes is entirely due to the fluid viscosity. However, this method leads to unwanted Gibbs oscillations around the shocklets. The use of shock sensors that further localize the artificial bulk viscosity did not reduce the amount of artificial dissipation introduced by the artificial bulk viscosity. Finally, an improved forcing function that explicitly accounts for the role of the artificial bulk viscosity in the budget of turbulent kinetic energy was explored.« less

Effect of Fresh Poultry Litter and Compost on Soil Physical and Chemical Properties

NASA Technical Reports Server (NTRS)

Carr, Stacy; Tsegaye, Teferi; Coleman, Tommy

1998-01-01

Application of poultry litter and compost as a substitute for fertilizer not only uses unwanted waste and decreases expenditures for commercial fertilizer, it adds nutrients to soil for plant uptake. The properties of soil affected by poultry litter were analyzed to determine the positive and negative aspects of using this substitute fertilizer. This study focused on changes associated with saturated hydraulic conductivity, bulk density, nitrate concentrations, and pH after application of varying concentrations of poultry litter and compost. Soil samples from Tennessee Valley Substation in Alabama were analyzed in a laboratory at Alabama A&M University. As a result of the application of fresh poultry litter and compost, we found that the saturated hydraulic conductivity increased and the bulk density decreased, while the pH was generally not affected. Using poultry litter and compost as an alternative commercial fertilizers could be adapted by the farming community to protect the sustainability of our environment. Unwanted waste is used productively and soil is enriched for farming.

A comparison of freeze-drying and oven-drying preparation methods for bulk and compound-specific carbon stable isotope analyses: examples using the benthic macroinvertebrates Stenopsyche marmorata and Epeorus latifolium.

PubMed

Akamatsu, Fumikazu; Suzuki, Yaeko; Kato, Yoshikazu; Yoshimizu, Chikage; Tayasu, Ichiro

2016-01-15

Carbon stable isotope analysis of bulk samples and fatty acids is an established method for tracing carbon flow pathways and reconstructing trophic interactions, but there is no consensus on which sample drying method should be used for sample preparation. The aim of this study was to determine if freeze-drying and oven-drying treatments used to prepare samples of the benthic macroinvertebrates Stenopsyche marmorata and Epeorus latifolium for bulk and fatty-acid-specific carbon stable isotope analysis yield different isotopic ratio values. Five individuals each from two species were split in half; one half was freeze-dried and the other half was oven-dried. The samples were ground and the δ(13)C values of the bulk samples and eight fatty acids were measured following combustion using an isotope ratio mass spectrometer coupled to an elemental analyzer or gas chromatography system. The mean difference in the bulk and fatty acid δ(13)C values between freeze-dried and oven-dried samples was small (≤0.1‰ in both cases), although relatively large variations were observed in individual fatty-acid-specific δ(13)C values (maximum of ≤0.9 ‰). There were no significant differences in either bulk sample or fatty-acid-specific δ(13)C values between freeze-dried or oven-dried samples of the same species. Freeze-drying and oven-drying are equally acceptable methods for preparing freshly caught S. marmorata and E. latifolium samples for bulk and fatty-acid-specific carbon stable isotope analyses. Copyright © 2015 John Wiley & Sons, Ltd.

Yogurt made from milk heated at different pH values.

PubMed

Ozcan, Tulay; Horne, David S; Lucey, John A

2015-10-01

Milk for yogurt manufacture is subjected to high heat treatment to denature whey proteins. Low milk pH values (≤ 6.5) at heating result in most denatured whey proteins becoming associated with casein micelles, whereas high milk pH values (≥ 7.0) at heating result in the formation of mostly soluble (nonmicellar) denatured whey protein complexes. There are conflicting reports on the relative importance of soluble and casein-bound whey protein aggregates on the properties of acid gels. Prior studies investigating the effect of pH of milk at heating used model gels in which milk was acidified by glucono-δ-lactone; in this study, we prepared yogurt gels using commercial starter cultures. Model acid gels can have very different texture and physical properties from those made by fermentation with starter cultures. In this study, we investigated the effects of different pH values of milk at heating on the rheological, light backscatter, and microstructural properties of yogurt gels. Reconstituted skim milk was adjusted to pH values 6.2, 6.7, and 7.2 and heated at 85°C for 30 min. A portion of the heated milk samples was readjusted back to pH 6.7 after heating. Milks were inoculated with 3% (wt/wt) yogurt starter culture and incubated at 40°C until pH 4.6. Gel formation was monitored using dynamic oscillatory rheology, and parameters measured included the storage modulus (G') and loss tangent (LT) values. Light-backscattering properties, such as the backscatter ratio (R) and the first derivative of light backscatter ratio (R'), were also monitored during fermentation. Fluorescence microscopy was used to observe gel microstructure. The G' values at pH 4.6 were highest in gels made from milk heated at pH 6.7 and lowest in milk heated at pH 6.2, with or without pH adjustment after heating. The G' values at pH 4.6 were lower in samples after adjustment back to pH 6.7 after heating. No maximum in the LT parameter was observed during gelation for yogurts made from milk heated at pH 6.2; a maximum in LT was observed at pH ~4.8 for samples heated at pH 6.7 or 7.2, with or without pH adjustment after heating. Higher R-values were observed with an increase in pH of heating, with or without pH adjustment after heating. The sample heated at pH 6.2 had only one major peak in its R' profile during acidification, whereas samples heated at pH 6.7 and 7.2 had 2 large peaks. The lack of a maximum in LT parameter and the presence of a single peak in the R' profile for the samples heated at pH 6.2 were likely due to the partial solubilization of insoluble calcium phosphate when milk was acidified to this lower pH value. No clear differences were observed in the microstructures of gels between the different treatments. This study indicates that heating milk at the natural pH (~6.7) created an optimum balance of casein-bound and soluble denatured whey proteins, which resulted in yogurt with the highest gel stiffness. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

IKMTSL-PTE, a Phospholipid-Based EPR Probe for Surface Electrostatic Potential of Biological Interfaces at Neutral pH: Effects of Temperature and Effective Dielectric Constant of the Solvent.

PubMed

Voinov, Maxim A; Scheid, Christina T; Kirilyuk, Igor A; Trofimov, Dmitrii G; Smirnov, Alex I

2017-03-23

The synthesis and characterization of a lipidlike electrostatic spin probe, (S)-2,3-bis(palmitoyloxy)propyl 2-((4-(4-(dimethylamino)-2-ethyl-1-oxyl-5,5-dimethyl-2,5-dihydro-1H-imidazol-2-yl)benzyl)disulfanyl)ethyl phosphate (IKMTSL-PTE), are being reported. The intrinsic pK a 0 of IKMTSL-PTE was determined by X-band (9.5 GHz) electron paramagnetic resonance (EPR) titration of a water-soluble model compound, 4-(dimethylamino)-2-ethyl-2-(4-(((2-hydroxyethyl)disulfanyl)methyl)phenyl)-5,5-dimethyl-2,5-dihydro-1H-imidazol-1-oxyl (IKMTSL-ME), an adduct of methanethiosulfonate spin label IKMTSL and 2-mercaptoethanol. The pK a 0 of IKMTSL-ME in bulk aqueous solutions was found to be significantly higher than that of 4-(((2-hydroxyethyl)disulfanyl)methyl)-2,2,3,5,5-pentamethylimidazolidin-1-oxyl (IMTSL-ME), an adduct of the corresponding methanethiosulfonate spin label IMTSL and 2-mercaptoethanol (17 °C, pK a 0 = 6.16 ± 0.03 vs 20 °C, pK a 0 = 3.33 ± 0.03, respectively). A series of EPR titration experiments with IKMTSL-ME in aqueous solutions containing 0-60% v/v isopropanol have been carried out at 17 and 48 °C to determine the effects of temperature and bulk dielectric permittivity constant, ε, on the probe pK a . A linear relationship between the probe pK a and ε has been established and found to be essentially the same at 17 and 48 °C. The polarity term contributing to the pK a of IKMTSL-PTE at an uncharged lipidlike interface was determined by incorporating the probe into electrically neutral micelles formed from nonionic detergent Triton X-100, and it was found, similar to IMTSL-PTE, to be negative. In negatively charged DMPG lipid bilayers, IKMTSL-PTE exhibits ionization transitions with significantly higher pK a values than those previously reported for IMTSL-PTE (e.g., at 17 °C, pK a i = 7.80 ± 0.03 vs pK a 0 = 5.70 ± 0.05). The surface electrostatic potentials of DMPG lipid bilayers calculated using IKMTSL-PTE titration data were found to be somewhat lower than those calculated using IMTSL-PTE. The lower values measured by IKMTSL-PTE are the likely consequences of the structure of the linker that positions the reporter nitroxide further away from the bilayer plane into aqueous phase. Overall, the ionization transitions of IKMTSL-PTE with pK a values close to the neutral pH range make this lipidlike molecule a valuable spectroscopic EPR probe for studying the electrostatic phenomena at biological interfaces, including lipid bilayer/membrane protein systems, that could be unstable in the acidic pH range accessible by the previously available probes.

Particle characterization of poorly water-soluble drugs using a spray freeze drying technique.

PubMed

Kondo, Masahiro; Niwa, Toshiyuki; Okamoto, Hirokazu; Danjo, Kazumi

2009-07-01

A spray freeze drying (SFD) method was developed to prepare the composite particles of poorly water-soluble drug. The aqueous solution dissolved drug and the functional polymer was sprayed directly into liquid nitrogen. Then, the iced droplets were lyophilized with freeze-dryer to prepare solid particles. Tolbutamide (TBM) and hydroxypropylmethylcellulose (HPMC) were used as a model drug and water-soluble polymeric carrier in this study, respectively. The morphological observation of particles revealed that the spherical particles having porous structure could be obtained by optimizing the loading amount of drug and polymer in the spray solution. Especially, SFD method was characterized that the prepared particles had significantly larger specific surface area comparing with those prepared by the standard spray drying technique. The physicochemical properties of the resultant particles were found to be dependent on the concentration of spray solution. When the solution with high content of drug and polymer was used, the particle size of the resulting composite particles increased and they became spherical. The specific surface area of the particles also increased as a result of higher concentration of solution. The evaluation of spray solution indicated that these results were dependent on the viscosity of spray solution. In addition, when composite particles of TBM were prepared using the SFD method with HPMC as a carrier, the crystallinity of TBM decreased as the proportion of HPMC increased. When the TBM : HPMC ratio reached 1 : 5, the crystallinity of the particles completely disappeared. The dissolution tests showed that the release profiles of poorly water-soluble TBM from SFD composite particles were drastically improved compared to bulk TBM. The 70% release time T(70) of composite particles prepared by the SFD method in a solution of pH 1.2 was quite smaller than that of bulk TBM, while in a solution of pH 6.8, it was slightly lower. In addition, the release rates were faster than those of standard spray dried (SD) composite particles for solutions of pH 1.2 and 6.8, respectively. When composite particles were prepared from mixtures with various composition ratios, T(70) was found to decrease as the proportion of HPMC increased; the release rate was faster than that of bulk TBM in a solution of pH 6.8, as well as solution of pH 1.2.

Coral calcification and ocean acidification

USGS Publications Warehouse

Jokiel, Paul L.; Jury, Christopher P.; Kuffner, Ilsa B.

2016-01-01

Over 60 years ago, the discovery that light increased calcification in the coral plant-animal symbiosis triggered interest in explaining the phenomenon and understanding the mechanisms involved. Major findings along the way include the observation that carbon fixed by photosynthesis in the zooxanthellae is translocated to animal cells throughout the colony and that corals can therefore live as autotrophs in many situations. Recent research has focused on explaining the observed reduction in calcification rate with increasing ocean acidification (OA). Experiments have shown a direct correlation between declining ocean pH, declining aragonite saturation state (Ωarag), declining [CO32_] and coral calcification. Nearly all previous reports on OA identify Ωarag or its surrogate [CO32] as the factor driving coral calcification. However, the alternate “Proton Flux Hypothesis” stated that coral calcification is controlled by diffusion limitation of net H+ transport through the boundary layer in relation to availability of dissolved inorganic carbon (DIC). The “Two Compartment Proton Flux Model” expanded this explanation and synthesized diverse observations into a universal model that explains many paradoxes of coral metabolism, morphology and plasticity of growth form in addition to observed coral skeletal growth response to OA. It is now clear that irradiance is the main driver of net photosynthesis (Pnet), which in turn drives net calcification (Gnet), and alters pH in the bulk water surrounding the coral. Pnet controls [CO32] and thus Ωarag of the bulk water over the diel cycle. Changes in Ωarag and pH lag behind Gnet throughout the daily cycle by two or more hours. The flux rate Pnet, rather than concentration-based parameters (e.g., Ωarag, [CO3 2], pH and [DIC]:[H+] ratio) is the primary driver of Gnet. Daytime coral metabolism rapidly removes DIC from the bulk seawater. Photosynthesis increases the bulk seawater pH while providing the energy that drives calcification and increases in Gnet. These relationships result in a correlation between Gnet and Ωarag, with both parameters being variables dependent on Pnet. Consequently the correlation between Gnet and Ωarag varies widely between different locations and times depending on the relative metabolic contributions of various calcifying and photosynthesizing organisms and local rates of carbonate dissolution. High rates of H+ efflux continue for several hours following the mid-day Gnet peak suggesting that corals have difficulty in shedding waste protons as described by the Proton Flux Model. DIC flux (uptake) tracks Pnet and Gnet and drops off rapidly after the photosynthesis-calcification maxima, indicating that corals can cope more effectively with the problem of limited DIC supply compared to the problem of eliminating H+. Predictive models of future global changes in coral and coral reef growth based on oceanic Ωarag must include the influence of future changes in localized Pnet on Gnet as well as changes in rates of reef carbonate dissolution. The correlation between Ωarag and Gnet over the diel cycle is simply the result of increasing pH due to photosynthesis that shifts the CO2-carbonate system equilibria to increase [CO32] relative to the other DIC components of [HCO3] and [CO2]. Therefore Ωarag closely tracks pH as an effect of Pnet, which also drives changes in Gnet. Measurements of DIC flux and H+ flux are far more useful than concentrations in describing coral metabolism dynamics. Coral reefs are systems that exist in constant disequilibrium with the water column.

Isotopically enriched ammonium shows high nitrogen transformation in the pile top zone of dairy manure compost

NASA Astrophysics Data System (ADS)

Maeda, Koki; Toyoda, Sakae; Yano, Midori; Hattori, Shohei; Fukasawa, Makoto; Nakajima, Keiichi; Yoshida, Naohiro

2016-03-01

Nitrogen isotope ratios (δ15N) of NH4+ in dairy manure compost piles with and without bulking agent (10 % w/w) were compared to understand the effects of the use of bulking agent on nitrogen conversion during manure composting. The δ15N-NH4+ values in each of three pile zones (top, side and core) were also compared. At the end of the process, piles with bulking agent showed significantly higher δ15N values (17.7 ± 1.3 ‰) than piles without bulking agent (11.8 ± 0.9 ‰), reflecting the significantly higher nitrogen conversion and NH3 loss in the former. The samples from the top zone, especially in the piles with bulking agent, showed very high NH4+ concentrations with significantly high 15N (δ15N: 12.7-29.8 ‰) values, indicating that extremely high nitrogen conversion, nitrification-denitrification activity of the microbes and NH3 volatilization occurred in this zone.

Kinetic multi-layer model of the epithelial lining fluid (KM-ELF): Reactions of ozone and OH with antioxidants and surfactant molecules

NASA Astrophysics Data System (ADS)

Lakey, Pascale; Pöschl, Ulrich; Shiraiwa, Manabu

2015-04-01

Oxidants cause damage to biosurfaces such as the lung epithelium unless they are effectively scavenged. The respiratory tract is covered in a thin layer of fluid which extends from the nasal cavity to the alveoli and contain species that scavenge ozone and other incoming oxidants. The kinetic multi-layer model of the epithelial lining fluid (KM-ELF) has been developed in order to investigate the reactions of ozone and OH with antioxidants (ascorbate, uric acid, glutathione and α-tocopherol) and surfactant lipids and proteins within the epithelial lining fluid (ELF). The model incorporates different processes: gas phase diffusion, adsorption and desorption from the surface, bulk phase diffusion and known reactions at the surface and in the bulk. The ELF is split into many layers: a sorption layer, a surfactant layer, a near surface bulk layer and several bulk layers. Initial results using KM-ELF indicate that at ELF thicknesses of 80 nm and 1 × 10-4cm the ELF would become rapidly saturated with ozone with saturation occurring in less than a second. However, at an ELF thickness of 1 × 10-3cm concentration gradients were observed throughout the ELF and the presence of antioxidants reduced the O3 reaching the lung cells and tissues by 40% after 1 hour of exposure. In contrast, the antioxidants were efficient scavengers of OH radicals, although the large rate constants of OH reacting with the antioxidants resulted in the antioxidants decaying away rapidly. The chemical half-lives of the antioxidants and surface species were also calculated using KM-ELF as a function of O3 and OH concentration and ELF thickness. Finally, the pH dependence of the products of reactions between antioxidants and O3 were investigated. The KM-ELF model predicted that a harmful ascorbate ozonide product would increase from 1.4 × 1011cm-3at pH 7.4 to 1.1 × 1014 cm-3 at pH 4after 1 hour although a uric acid ozonide product would decrease from 2.0 × 1015cm-3to 5.9 × 1012cm-3.

Results From The Salt Disposition Project Next Generation Solvent Demonstration Plan

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

Peters, T. B.; Fondeur, F. F.; Taylor-Pashow, K. M.L.

2014-04-02

Strip Effluent Hold Tank (SEHT), Decontaminated Salt Solution Hold Tank (DSSHT), Caustic Wash Tank (CWT) and Solvent Hold Tank (SHT) samples were taken throughout the Next Generation Solvent (NGS) Demonstration Plan. These samples were analyzed and the results are reported. SHT: The solvent behaved as expected, with no bulk changes in the composition over time, with the exception of the TOA and TiDG. The TiDG depletion is higher than expected, and consideration must be taken on the required rate of replenishment. Monthly sampling of the SHT is warranted. If possible, additional SHT samples for TiDG analysis (only) would help SRNLmore » refine the TiDG degradation model. CWT: The CWT samples show the expected behavior in terms of bulk chemistry. The 137Cs deposited into the CWT varies somewhat, but generally appears to be lower than during operations with the BOBCalix solvent. While a few minor organic components were noted to be present in the Preliminary sample, at this time these are thought to be artifacts of the sample preparation or may be due to the preceding solvent superwash. DSSHT: The DSSHT samples show the predicted bulk chemistry, although they point towards significant dilution at the front end of the Demonstration. The 137Cs levels in the DSSHT are much lower than during the BOBCalix operations, which is the expected observation. SEHT: The SEHT samples represent the most different output of all four of the outputs from MCU. While the bulk chemistry is as expected, something is causing the pH of the SEHT to be higher than what would be predicted from a pure stream of 0.01 M boric acid. There are several possible different reasons for this, and SRNL is in the process of investigating. Other than the pH issue, the SEHT is as predicted. In summary, the NGS Demonstration Plan samples indicate that the MCU system, with the Blend Solvent, is operating as expected. The only issue of concern regards the pH of the SEHT, and SRNL is in the process of investigating this. SRNL results support the transition to routine operations.« less

Controlling mechanisms of metals release form cement-based waste form in acetic acid solution

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

Cheng, Kuang Ye.

1991-01-01

The purpose of this dissertation is to identify the individual leaching mechanisms of metals by knowing the pH profile within the leached specimen and the physical and chemical properties of the leached material. Leaching of cement-based waste form in acetic acid solutions with different acidic strengths has been investigated in this work. The pH profile along the acid penetration route in the cement-based waste form was identified by various pH color indicators. The pH in the surface altered layer varies from 5.0 to 6.0, which is very close to the pH in the bulk leachate. A reacting zone, where themore » pH abruptly changes from 6 to 12, sharply divides the altered surface layer from the remaining unleached waste form or kernel. Leaching of metals is controlled by the acidity available in the leachant. Dissolution of alkaline materials leaves a silica-rich layer on the surface of the cement-based waste form. This surface layer exhibits different properties than those of the unleached material. The surface layer has a higher water content, is lighter weight, and is soft and friable. Furthermore, the abundant silicate content on the solid surface detains portion of the leached metals, while they are moving through the leached layer into bulk solution. The leaching of metals is a consequence of acid penetration. The distance from the solid/solution interface to the front of the leaching boundary can be regarded as the depth of leaching zone, where the metals dissolve and diffuse out of the waste form. The metal ions diffuse through the leached layer may be retarded on the solid surface by the pH-dependent adsorption reactions. It is found that the leaching process through the leached layer is diffusion-controlled for calcium and cadmium, whereas diffusion and adsorption occur simultaneously in the leached layer for lead and arsenic.« less

Etude Spectroscopique des Surfaces des Couches Minces de Silicium Amorphe Hydrogene

NASA Astrophysics Data System (ADS)

Bekkay, Touhami

In this work, we have studied the surface of hydrogenated a-Si and phosphorous doped a-Si:H,P. Due to the presence of unstable dangling bonds, these films are oxidized in the air after their preparation. XPS and UPS have been used to study these oxidized surfaces before and after plasma sputtering and wet chemical cleaning. We used deconvolution technique for the analysis of the spectra. First, the composition of a-Si:H films, prepared by plasma deposition at various power levels, has been determined by XPS. It has been found that films deposited using 5 W power contain SiH_4 molecules. This is confirmed by IR measurements. These molecules have not been seen in films prepared with a plasma power above 5 W. The XPS spectra of the surface oxide, before and after 3 keV sputtering by argon show that is impossible to completely remove these surface oxide ions. During sputtering, some oxygen atoms are forward scattered into the silicon substrat and form new oxidation states. UPS has been used to study the valence bands of the oxidized surfaces before and after HF cleaning. Prior to a chemical etch, the valence band analysis of the native SiO_2 indicates the presence of three O(2p) orbitals, in agreement with theory. Two are non-bonding orbitals and the third is associated with weak bonding to Si(3p). Two other orbitals have been identified at 10 eV and 11.8 eV. They correspond to O(2p)-Si(3p) and O(2p)-Si(3s) bonds respectively. A residual film containing -SiH, -SiO, SiOH and non-bonding orbitals has been found, after HF cleaning. A series of a-Si:H films have been doped with phosphine (PH_3). Their corresponding XPS spectra around 130 eV are dominated by the surface and bulk plasmon peaks. Numerical filtering has been used to distinguish between the phosphorous P(2p) peak located at 129.5 eV and the phosphorous oxide peak located at 134 eV. The increase in the intensity of these peaks as the (PH_3) increases indicates that a certain proportion of phosphorous is incorporated into the Si matrix and that the rest is oxidized. The shifts of the bulk Fermi level, E_{rm F}, and the surface Fermi level, E _{rm FS}, vary linearly with (PH_3). The difference between these two straight lines give the potential responsible for the bulk band bending. Close to the surface, the band bending is deduced by varying the detection angle in XPS measurements; a maximum value of 0.2 eV has been found in a depth range of 38 A to 105 A.

From clusters to bulk: A relativistic density functional investigation on a series of gold clusters Aun, n=6,…,147

NASA Astrophysics Data System (ADS)

Häberlen, Oliver D.; Chung, Sai-Cheong; Stener, Mauro; Rösch, Notker

1997-03-01

A series of gold clusters spanning the size range from Au6 through Au147 (with diameters from 0.7 to 1.7 nm) in icosahedral, octahedral, and cuboctahedral structure has been theoretically investigated by means of a scalar relativistic all-electron density functional method. One of the main objectives of this work was to analyze the convergence of cluster properties toward the corresponding bulk metal values and to compare the results obtained for the local density approximation (LDA) to those for a generalized gradient approximation (GGA) to the exchange-correlation functional. The average gold-gold distance in the clusters increases with their nuclearity and correlates essentially linearly with the average coordination number in the clusters. An extrapolation to the bulk coordination of 12 yields a gold-gold distance of 289 pm in LDA, very close to the experimental bulk value of 288 pm, while the extrapolated GGA gold-gold distance is 297 pm. The cluster cohesive energy varies linearly with the inverse of the calculated cluster radius, indicating that the surface-to-volume ratio is the primary determinant of the convergence of this quantity toward bulk. The extrapolated LDA binding energy per atom, 4.7 eV, overestimates the experimental bulk value of 3.8 eV, while the GGA value, 3.2 eV, underestimates the experiment by almost the same amount. The calculated ionization potentials and electron affinities of the clusters may be related to the metallic droplet model, although deviations due to the electronic shell structure are noticeable. The GGA extrapolation to bulk values yields 4.8 and 4.9 eV for the ionization potential and the electron affinity, respectively, remarkably close to the experimental polycrystalline work function of bulk gold, 5.1 eV. Gold 4f core level binding energies were calculated for sites with bulk coordination and for different surface sites. The core level shifts for the surface sites are all positive and distinguish among the corner, edge, and face-centered sites; sites in the first subsurface layer show still small positive shifts.

Experimental measurements of U60 nanocluster stability in aqueous solution

NASA Astrophysics Data System (ADS)

Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

2015-05-01

In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the dissociation behavior of nanoclusters under a range of aqueous conditions.

A Stability Indicating HPLC Method for the Determination of Fluvoxamine in Pharmaceutical Dosage Forms.

PubMed

Souri, Effat; Donyayi, Hassan; Khaniha, Reza Ahmad; Barazandeh Tehrani, Maliheh

2015-01-01

Fluvoxamine maleate is a selective serotonin reuptake inhibitor, which is used for the treatment of different types of depressive disorders. In the present study, a stability indicating HPLC method was developed and validated for the determination of fluvoxamine maleate. The chromatographic separation was carried out using a Nova-Pak CN column and a mixture of K2HPO4 50 mM (pH 7.0) and acetonitrile (60: 40, v/v) as the mobile phase. Target compounds were detected using a UV detector set at 235 nm. The developed method was linear over the concentration range of 1-80 μg/ml with acceptable precision (CV values < 2.0%) and accuracy (error values < 1.6%). The degradation studies showed that fluvoxamine maleate is relatively unstable under acidic, basic and oxidative conditions and also when exposed to UV radiation. On the other hand, the bulk powder of fluvoxamine maleate was relatively stable when exposed to visible light or heat. The proposed method was successfully applied for the determination of active ingredient of fluvoxamine dosage form without any interference from tablet excipients.

Ellipsometric study of molecular orientations of Thermomyces lanuginosus lipase at the air-water interface by simultaneous determination of refractive index and thickness.

PubMed

Muth, Marco; Schmid, Reiner P; Schnitzlein, Klaus

2016-04-01

Ellipsometric studies of very thin organic films suffer from the low refractive index contrast between layer and bulk substrate. We demonstrate that null ellipsometry can not only provide detailed information about the adsorption kinetics and surface excess values, but in addition on layer thicknesses with submonolayer resolution of a lipase from Thermomyces lanuginosus at the air-water interface. While measuring very close to the Brewster angle, refractive indices and layer-thicknesses can both be determined with a precision that is sufficiently high to make conclusions on the density and orientation of the molecules at the interface. The orientation was found to be concentration- and pH value-dependent. At the isoelectric point, the lipase was almost vertically oriented with respect to the surface, while for pure distilled water and low lipase concentration a rather horizontal alignment was found. Further experiments, varying the size of the interfacial area in a Langmuir trough, confirm the different layer structures. Copyright © 2015 Elsevier B.V. All rights reserved.

Modeling the morphogenesis of brine channels in sea ice.

PubMed

Kutschan, B; Morawetz, K; Gemming, S

2010-03-01

Brine channels are formed in sea ice under certain constraints and represent a habitat of different microorganisms. The complex system depends on a number of various quantities as salinity, density, pH value, or temperature. Each quantity governs the process of brine channel formation. There exists a strong link between bulk salinity and the presence of brine drainage channels in growing ice with respect to both the horizontal and vertical planes. We develop a suitable phenomenological model for the formation of brine channels both referring to the Ginzburg-Landau theory of phase transitions as well as to the chemical basis of morphogenesis according to Turing. It is possible to conclude from the critical wave number on the size of the structure and the critical parameters. The theoretically deduced transition rates have the same magnitude as the experimental values. The model creates channels of similar size as observed experimentally. An extension of the model toward channels with different sizes is possible. The microstructure of ice determines the albedo feedback and plays therefore an important role for large-scale global circulation models.

Somatic cell counts in bulk milk and their importance for milk processing

NASA Astrophysics Data System (ADS)

Savić, N. R.; Mikulec, D. P.; Radovanović, R. S.

2017-09-01

Bulk tank milk somatic cell counts are the indicator of the mammary gland health in the dairy herds and may be regarded as an indirect measure of milk quality. Elevated somatic cell counts are correlated with changes in milk composition The aim of this study was to assess the somatic cell counts that significantly affect the quality of milk and dairy products. We examined the somatic cell counts in bulk tank milk samples from 38 farms during the period of 6 months, from December to the May of the next year. The flow cytometry, Fossomatic was used for determination of somatic cell counts. In the same samples content of total proteins and lactose was determined by Milcoscan. Our results showed that average values for bulk tank milk samples were 273,605/ml from morning milking and 292,895/ml from evening milking. The average values for total proteins content from morning and evening milking are 3,31 and 3,34%, respectively. The average values for lactose content from morning and evening milking are 4,56 and 4,63%, respectively. The highest somatic cell count (516,000/ml) was detected in bulk tank milk sample from evening milk in the Winter and the lowest content of lactose was 4,46%. Our results showed that obtained values for bulk tank milk somatic cell counts did not significantly affected the content of total proteins and lactose.

[Responses of rhizosphere nitrogen and phosphorus transformations to different acid rain intensities in a hilly red soil tea plantation].

PubMed

Chen, Xi; Chen, Fu-sheng; Ye, Su-qiong; Yu, Su-qin; Fang, Xiang-min; Hu, Xiao-fei

2015-01-01

Tea (Camellia sinensis) plantation in hilly red soil region has been long impacted by acid deposition, however its effects on nitrogen (N) and phosphorus (P) transformations in rhizosphere soils remain unclear. A 25-year old tea plantation in a typical hilly red soil region was selected for an in situ simulation experiment treated by pH 4.5, pH 3.5, pH 2.5 and control. Rhizosihere and bulk soils were collected in the third year from the simulated acid deposition experiment. Soil mineral N, available P contents and major enzyme activities were analyzed using the chemical extraction and biochemical methods, and N and P mineralization rates were estimated using the indoor aerobic incubation methods. Our results showed that compared to the control, the treatments of pH 4.5, pH 3.5 and pH 2.5, respectively decreased 7.1%, 42.1% and 49.9% NO3(-)-N, 6.4%, 35.9% and 40.3% mineral N, 10.5%, 41.1% and 46.9% available P, 18.7%, 30.1% and 44.7% ammonification rate, 3.6%, 12.7% and 38.8% net N-mineralization rate, and 31.5%, 41.8% and 63.0% P mineralization rate in rhizosphere soils; however, among the 4 treatments, rhizosphere soil nitrification rate was not significantly different, the rhizosphere soil urease and acid phosphatase activities generally increased with the increasing intensity of acid rain (P<0.05). In bulk soil, compared with the control, the treatments of pH 4.5, pH 3.5 and pH 2.5 did not cause significant changes in NO3(-)-N, mineral N, available P as well as in the rates of nitrification, ammonification, net N-mineralization and P mineralization. With increasing the acid intensity, the rhizosphere effects of NH4+-N, NO3(-)-N, mineral N, ammonification and net N-mineralization rates were altered from positive to negative effects, those of urease and acid phosphatease showed the opposite trends, those of available P and P mineralization were negative and that of nitrification was positive. In sum, prolonged elevated acid rain could reduce N and P transformation rates, decrease their availability, alter their rhizosphere effects, and have impact on nutrient cycling in tea plantation.

Nitration of pollen aeroallergens by nitrate ion in conditions simulating the liquid water phase of atmospheric particles.

PubMed

Ghiani, Alessandra; Bruschi, Maurizio; Citterio, Sandra; Bolzacchini, Ezio; Ferrero, Luca; Sangiorgi, Giorgia; Asero, Riccardo; Perrone, Maria Grazia

2016-12-15

Pollen aeroallergens are present in atmospheric particulate matter (PM) where they can be found in coarse biological particles such as pollen grains (aerodynamic diameter d ae >10μm), as well as fragments in the finest respirable particles (PM2.5; d ae <2.5μm). Nitration of tyrosine residues in pollen allergenic proteins can occur in polluted air, and inhalation and deposition of these nitrated proteins in the human respiratory tract may lead to adverse health effects by enhancing the allergic response in population. Previous studies investigated protein nitration by atmospheric gaseous pollutants such as nitrogen dioxide and ozone. In this work we report, for the first time, a study on protein nitration by nitrate ion in aqueous solution, at nitrate concentrations and pH conditions simulating those occurring in the atmospheric aerosol liquid water phase. Experiments have been carried out on the Bovine serum albumin (BSA) protein and the recombinant Phleum pratense allergen (Phl p 2) both in the dark and under UV-A irradiation (range 4-90Wm -2 ) to take into account thermal and/or photochemical nitration processes. For the latter protein, modifications in the allergic response after treatment with nitrate solutions have been evaluated by immunoblot analyses using sera from grass-allergic patients. Experimental results in bulk solutions showed that protein nitration in the dark occurs only in dilute nitrate solutions and under very acidic conditions (pH<3 for BSA; pH<2.2 for Phl p 2), while nitration is always observed (at pH0.5-5) under UV-A irradiation, both in dilute and concentrated nitrate solutions, being significantly enhanced at the lowest pH values. In some cases, protein nitration resulted in an increase of the allergic response. Copyright © 2016. Published by Elsevier B.V.

A magnetic, reversible pH-responsive nanogated ensemble based on Fe3O4 nanoparticles-capped mesoporous silica.

PubMed

Gan, Qi; Lu, Xunyu; Yuan, Yuan; Qian, Jiangchao; Zhou, Huanjun; Lu, Xun; Shi, Jianlin; Liu, Changsheng

2011-03-01

Stimuli-sensitive mesoporous silica nanoparticles (MSNs)-based hybrid "gate-like" ensembles capable of performing specific programmed release mode represent a new generation delivery system in recent years. In this paper, a magnetic and reversible pH-responsive, MSNs-based nanogated ensemble was fabricated by anchoring superparamagnetic Fe(3)O(4) nanoparticles on the pore outlet of MSNs via a reversible boronate esters linker. To achieve this, MSNs and Fe(3)O(4) nanoparticles were first synthesized and functionalized by polyalcohol derivative and boronic acid, respectively. The successful incorporation of Fe(3)O(4) nanoparticles onto the MSNs was confirmed by the results of XRD, TEM, XPS and N(2) adsorption-desorption method. The pH-driven "gate-like" effect was studied by in vitro release of an entrapped model dexamethasone from the pore voids into the bulk solution at different pH values. The results indicated that at pH 5-8, the pores of the MSNs were effectively capped with Fe(3)O(4) nanoparticles and the drug release was strongly inhibited. While at pH 2-4, the hydrolysis of the boroester bond took place and thus resulted in a rapid release of the entrapped drug. And by alternately changing the pH from 3 to 7, these Fe(3)O(4) cap gate could be switched "on" and "off" and thereby released the entrapped drug in a pulsinate manner (in small portions). Additionally, this nanogated release system exhibited good magnetic property, high cell biocompatibility and cellular uptake for MC3T3-E1 cells. The present data suggest that it is possible to obtain simple and very effective pH-driven pulsinate release using these Fe(3)O(4)-capped-MSNs, and this new platform represents a promising candidate in the formulation of in vivo targeted delivery of therapeutic agents to low pH tissues, such as tumors and inflammatory sites. Copyright © 2010 Elsevier Ltd. All rights reserved.

Effect of pH values on the extracellular polysaccharide secreted by Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

NASA Astrophysics Data System (ADS)

Yu, Run-lan; Liu, Jing; Tan, Jian-xi; Zeng, Wei-min; Shi, Li-juan; Gu, Guo-hua; Qin, Wen-qing; Qiu, Guan-zhou

2014-04-01

The pH value plays an important role in the bioleaching of sulphide minerals. The effect of pH values on the extracellular polysaccharide secreted by Acidithiobacillus ferrooxidans was investigated in different phases of bacterial growth during chalcopyrite bioleaching. It is found that extracellular polysaccharide secretion from the cells attached to chalcopyrite is more efficiently than that of the free cells in the bioleaching solution. Three factors, pH values, the concentration of soluble metal ions, and the bacterial growth and metabolism, affect extracellular polysaccharide secretion in the free cells, and are related to the bacterial growth phase. Extracellular polysaccharide secretion from the attached cells is mainly dependent on the pH value of the bacterial culture.

Low temperature reduction of free-standing graphene oxide papers with metal iodides for ultrahigh bulk conductivity.

PubMed

Liu, Chenyang; Hao, Feng; Zhao, Xiaochong; Zhao, Qiancheng; Luo, Songping; Lin, Hong

2014-02-05

Here we report a green and facile route for highly efficient reduction of free-standing graphene oxide (GO) papers with metal iodide aqueous solutions at low cost. The metal iodides (MgI2, AlI3, ZnI2, FeI2) were synthesized directly from metal and iodine powder with water as a catalyzer. An extremely high bulk conductivity of 55088 S/m for reduced graphene oxide (rGO) papers were obtained with FeI2 solution of which pH = 0 at 95°C for 6 hours. The catalytic effect of strong Lewis acid for the promotion of the nucleophilic substitution reaction is responsible for the greatly improved bulk conductivity. Furthermore, it was found that the layer-to-layer distance (dL) and the crystallinity of the rGO papers are regarded as two main factors affecting the bulk conductivity rather than C/O ratio and defect concentration.

Bulk-surface relationship of an electronic structure for high-throughput screening of metal oxide catalysts

NASA Astrophysics Data System (ADS)

Kweun, Joshua Minwoo; Li, Chenzhe; Zheng, Yongping; Cho, Maenghyo; Kim, Yoon Young; Cho, Kyeongjae

2016-05-01

Designing metal-oxides consisting of earth-abundant elements has been a crucial issue to replace precious metal catalysts. To achieve efficient screening of metal-oxide catalysts via bulk descriptors rather than surface descriptors, we investigated the relationship between the electronic structure of bulk and that of the surface for lanthanum-based perovskite oxides, LaMO3 (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu). Through density functional theory calculations, we examined the d-band occupancy of the bulk and surface transition-metal atoms (nBulk and nSurf) and the adsorption energy of an oxygen atom (Eads) on (001), (110), and (111) surfaces. For the (001) surface, we observed strong correlation between the nBulk and nSurf with an R-squared value over 94%, and the result was interpreted in terms of ligand field splitting and antibonding/bonding level splitting. Moreover, the Eads on the surfaces was highly correlated with the nBulk with an R-squared value of more than 94%, and different surface relaxations could be explained by the bulk electronic structure (e.g., LaMnO3 vs. LaTiO3). These results suggest that a bulk-derived descriptor such as nBulk can be used to screen metal-oxide catalysts.

Multiplexed flow cytometric sensing of blood electrolytes in physiological samples using fluorescent bulk optode microspheres.

PubMed

Xu, Chao; Wygladacz, Katarzyna; Retter, Robert; Bell, Michael; Bakker, Eric

2007-12-15

Polymeric bulk optode microsphere ion sensors in combination with suspension array technologies such as analytical flow cytometry may become a power tool for measuring electrolytes in physiological samples. In this work, the methodology for the direct measurement of common blood electrolytes in physiological samples using bulk optode microsphere sensors was explored. The simultaneous determination of Na(+), K(+), and Ca(2+) in diluted sheep blood plasma was demonstrated for the first time, using a random suspension array containing three types of mixed microsphere bulk optodes of similar size, fabricated from the same chromoionophore without additional labeling. Sodium ionophore X, potassium ionophore III, and grafted AU-1 in poly(butyl acrylate) were the ionophores used in the bulk optode microsphere ion sensors for Na(+), K(+), and Ca(2+), respectively, in combination with the cation-exchanger NaTFPB (sodium tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate) and the same concentration of the chromoionophore ETH 5294 (9-(di-ethylamino)-5-octadecanoylimino-5H-benzo[a]phen-oxazine) in plasticized poly(vinyl chloride). Excellent reproducibility was achieved for the sensing of potassium ions. The effect of sample pH was relatively small at near-physiological pH and followed theoretical predictions, yet the sample temperature was found to influence the sensor response to a larger extent. Multiplexed ion sensing was achieved by taking advantage of the chemical tunability of the sensor response, adjusting the sensor compositions so that the three types of ion sensors responded with distinct levels of protonation of the chromoionophore. Consequently, three well-resolved peaks were simultaneously observed in the single-channel histogram during the multiplexed calibration as well as in the subsequent measurement of the three cations in 10-fold-diluted sheep plasma. The assigned peak positions corresponded very well to the physiological range of the measured ions.

Effect of bulk modulus on deformation of the brain under rotational accelerations

NASA Astrophysics Data System (ADS)

Ganpule, S.; Daphalapurkar, N. P.; Cetingul, M. P.; Ramesh, K. T.

2018-01-01

Traumatic brain injury such as that developed as a consequence of blast is a complex injury with a broad range of symptoms and disabilities. Computational models of brain biomechanics hold promise for illuminating the mechanics of traumatic brain injury and for developing preventive devices. However, reliable material parameters are needed for models to be predictive. Unfortunately, the properties of human brain tissue are difficult to measure, and the bulk modulus of brain tissue in particular is not well characterized. Thus, a wide range of bulk modulus values are used in computational models of brain biomechanics, spanning up to three orders of magnitude in the differences between values. However, the sensitivity of these variations on computational predictions is not known. In this work, we study the sensitivity of a 3D computational human head model to various bulk modulus values. A subject-specific human head model was constructed from T1-weighted MRI images at 2-mm3 voxel resolution. Diffusion tensor imaging provided data on spatial distribution and orientation of axonal fiber bundles for modeling white matter anisotropy. Non-injurious, full-field brain deformations in a human volunteer were used to assess the simulated predictions. The comparison suggests that a bulk modulus value on the order of GPa gives the best agreement with experimentally measured in vivo deformations in the human brain. Further, simulations of injurious loading suggest that bulk modulus values on the order of GPa provide the closest match with the clinical findings in terms of predicated injured regions and extent of injury.

Birth asphyxia measured by the pH value of the umbilical cord blood may predict an increased risk of attention deficit hyperactivity disorder.

PubMed

Mikkelsen, Susanne Hvolgaard; Olsen, Jørn; Bech, Bodil Hammer; Wu, Chunsen; Liew, Zeyan; Gissler, Mika; Obel, Carsten; Arah, Onyebuchi

2017-06-01

Although birth asphyxia is a major risk factor for neonatal and childhood morbidity and mortality, it has not been investigated much in relation to attention deficit hyperactivity disorder (ADHD). We examined whether birth asphyxia measured by the pH of the blood in the umbilical artery cord was associated with childhood ADHD. A population-based cohort of 295 687 children born in Finland between 1991 and 2002 was followed until December 31, 2007. ADHD was identified by the International Classification of Diseases, 10th edition, as a diagnosis of hyperkinetic disorder. We examined the risk of ADHD with varying pH values using Cox regression, taking time trends into consideration. When compared to the reference group, a pH value below 7.10 was significantly associated with an increased risk of ADHD. The strongest risks were observed among children with a pH value <7.15 and a gestational age of <32 weeks. The pH value did not contribute much to the risk among children with an Apgar score of 0-3. Birth asphyxia, defined by low pH value, may predict an increased risk of ADHD in childhood. The association between the pH value and ADHD was homogenous when stratified by gestational age and the Apgar score. ©2017 Foundation Acta Paediatrica. Published by John Wiley & Sons Ltd.

A superhigh-frequency optoelectromechanical system based on a slotted photonic crystal cavity

NASA Astrophysics Data System (ADS)

Sun, Xiankai; Zhang, Xufeng; Poot, Menno; Xiong, Chi; Tang, Hong X.

2012-11-01

We develop an all-integrated optoelectromechanical system that operates in the superhigh frequency band. This system is based on an ultrahigh-Q slotted photonic crystal (PhC) nanocavity formed by two PhC membranes, one of which is patterned with electrode and capacitively driven. The strong simultaneous electromechanical and optomechanical interactions yield efficient electrical excitation and sensitive optical transduction of the bulk acoustic modes of the PhC membrane. These modes are identified up to a frequency of 4.20 GHz, with their mechanical Q factors ranging from 240 to 1730. Directly linking signals in microwave and optical domains, such optoelectromechanical systems will find applications in microwave photonics in addition to those that utilize the electromechanical and optomechanical interactions separately.

Lysozyme adsorption in pH-responsive hydrogel thin-films: the non-trivial role of acid-base equilibrium.

PubMed

Narambuena, Claudio F; Longo, Gabriel S; Szleifer, Igal

2015-09-07

We develop and apply a molecular theory to study the adsorption of lysozyme on weak polyacid hydrogel films. The theory explicitly accounts for the conformation of the network, the structure of the proteins, the size and shape of all the molecular species, their interactions as well as the chemical equilibrium of each titratable unit of both the protein and the polymer network. The driving forces for adsorption are the electrostatic attractions between the negatively charged network and the positively charged protein. The adsorption is a non-monotonic function of the solution pH, with a maximum in the region between pH 8 and 9 depending on the salt concentration of the solution. The non-monotonic adsorption is the result of increasing negative charge of the network with pH, while the positive charge of the protein decreases. At low pH the network is roughly electroneutral, while at sufficiently high pH the protein is negatively charged. Upon adsorption, the acid-base equilibrium of the different amino acids of the protein shifts in a nontrivial fashion that depends critically on the particular kind of residue and solution composition. Thus, the proteins regulate their charge and enhance adsorption under a wide range of conditions. In particular, adsorption is predicted above the protein isoelectric point where both the solution lysozyme and the polymer network are negatively charged. This behavior occurs because the pH in the interior of the gel is significantly lower than that in the bulk solution and it is also regulated by the adsorption of the protein in order to optimize protein-gel interactions. Under high pH conditions we predict that the protein changes its charge from negative in the solution to positive within the gel. The change occurs within a few nanometers at the interface of the hydrogel film. Our predictions show the non-trivial interplay between acid-base equilibrium, physical interactions and molecular organization under nanoconfined conditions, which leads to non-trivial adsorption behavior that is qualitatively different from what would be predicted from the state of the proteins in the bulk solution.

Effect of pH on rheotaxis of bull sperm using microfluidics.

PubMed

El-Sherry, T M; Abdel-Ghani, M A; Abou-Khalil, N S; Elsayed, M; Abdelgawad, M

2017-10-01

The aim of the present research is to study the effect of pH values on the sperm rheotaxis properties. Semen collected from bulls was diluted with SOF medium (1:10). pH of the medium was adjusted using a digital pH meter to the following pH values: 6.0, 6.2, 6.4, 6.4, 6.8, 7.0. All kinetic parameters of sperm (n = 3,385) were determined through a computer-assisted sperm analysis (CASA) system using microfluidic devices with controlled flow velocity. The following parameters were determined: total motility (TM%), positive rheotaxis (PR%), straightline velocity (VSL, μm/s), average path velocity (VAP, μm/s), linearity (LIN, as VSL/VCL, %), beat cross-frequency (BCF, Hz) and curvilinear velocity (VCL, μm/s). Nitric oxide, calcium and potassium were estimated in semen at different pH values. To confirm the effect of nitric oxide and K + , we used sodium nitroprusside (an NO donor) and KCL as (a K + donor) to see their effect on sperm PR%. The results showed no difference in TM% at pH (6-7). The PR% was the lowest at pH 6 and 7. The best parameters for the PR% were at pH 6.4-6.6. The concentration of Ca +2 did not change at different pH values. The mean NO values decreased with the increase of pH; however, the mean values of K + increased with the increase of pH. Addition of high concentration of NO and K + to the semen media at fixed pH level had a negative effect on TM% and PR%. In conclusion, the bull sperm had the best rheotaxis properties at pH 6.4-6.6 and sensitive to the change of seminal NO and K + . © 2017 Blackwell Verlag GmbH.

Proximate composition of Karkadeh (Hibiscus sabdariffa) seeds and some functional properties of seed protein isolate as influenced by pH and NaCl.

PubMed

Salah, E O Mahgoub; Hayat, Z E Elbashir

2009-05-01

Seeds of an inbred line (B-11-90) of Karkadeh (Hibiscus sabdariffa) were investigated for their proximate composition (AOAC methods), nitrogen solubility and protein isolate (Karkadeh seed protein isolates [KSPI]) functional properties (standard methods). The fat and protein contents of the seeds were 22.43% and 32.46%, respectively. Nitrogen solubility was good in both water and 1.0 M NaCl at alkaline pH rather than at acidic pH, with better solubility at higher pH levels in water than in 1.0 M NaCl. The functional properties of the KSPI were as follows: water absorption capacity, 181 ml/100 g; fat absorption capacity, 110 ml/100 g; bulk density, 0.77 g/ml; and apparent viscosity (at 20 degrees C), 13.42 cps. KSPI showed a maximum foaming capacity at pH 12 and 1.6 M NaCl, a maximum emulsification capacity at pH 11 and 1.8 M NaCl, and a weaker foam stability at neutral pH than at acidic or alkaline pH, with a better foam stability at alkaline pH. The foam stability was considerably improved by treatment with 1.6 M NaCl.

Atmospheric Processing of Volcanic Glass: Effects on Iron Solubility and Redox Speciation.

PubMed

Maters, Elena C; Delmelle, Pierre; Bonneville, Steeve

2016-05-17

Volcanic ash from explosive eruptions can provide iron (Fe) to oceanic regions where this micronutrient limits primary production. Controls on the soluble Fe fraction in ash remain poorly understood but Fe solubility is likely influenced during atmospheric transport by condensation-evaporation cycles which induce large pH fluctuations. Using glass powder as surrogate for ash, we experimentally simulate its atmospheric processing via cycles of pH 2 and 5 exposure. Glass fractional Fe solubility (maximum 0.4%) is governed by the pH 2 exposure duration rather than by the pH fluctuations, however; pH 5 exposure induces precipitation of Fe-bearing nanoparticles which (re)dissolve at pH 2. Glass leaching/dissolution release Fe(II) and Fe(III) which are differentially affected by changes in pH; the average dissolved Fe(II)/Fetot ratio is ∼0.09 at pH 2 versus ∼0.18 at pH 5. Iron release at pH 2 from glass with a relatively high bulk Fe(II)/Fetot ratio (0.5), limited aqueous Fe(II) oxidation at pH 5, and possibly glass-mediated aqueous Fe(III) reduction may render atmospherically processed ash a significant source of Fe(II) for phytoplankton. By providing new insight into the form(s) of Fe associated with ash as wet aerosol versus cloud droplet, we improve knowledge of atmospheric controls on volcanogenic Fe delivery to the ocean.

Utilization of turkey manure as granular activated carbon: physical, chemical and adsorptive properties.

PubMed

Lima, Isabel; Marshall, Wayne E

2005-01-01

The high availability of large quantities of turkey manure generated from turkey production makes it an attractive feedstock for carbon production. Pelletized samples of turkey litter and cake were converted to granular activated carbons (GACs) by steam activation. Water flow rate and activation time were changed to produce a range of activation conditions. The GACs were characterized for select physical (yield, surface area, bulk density, attrition), chemical (pH, surface charge) and adsorptive properties (copper ion uptake). Carbon physical and adsorptive properties were dependent on activation time and quantity of steam used as activant. Yields varied from 23% to 37%, surface area varied from 248 to 472 m(2)/g and copper ion adsorption varied from 0.72 to 1.86 mmol Cu(2+)/g carbon. Copper ion adsorption greatly exceeded the values for two commercial GACs. GACs from turkey litter and cake show considerable potential to remove metal ions from water.

A novel system for water soluble protein encapsulation with high efficiency: "micelles enhanced" polyelectrolyte capsules.

PubMed

Li, Xiaodong; Li, Xiaohui; Zhang, Jianxiang; Zhao, Shifang; Shen, Jiacong

2008-06-01

Novel "micelles enhanced" polyelectrolyte (PE) capsules based on functional templates of hybrid calcium carbonate were fabricated. Evidences suggested that the structure of capsule wall was different from that of conventional PE capsules, and the wall permeability of these PE capsules changed significantly. Lysozyme, a positively charged protein in neutral solution, was studied as a model protein to be encapsulated into the "micelles enhanced" PE capsules. Confocal laser scanning microscope was used to observe the entrapping process in real time, while UV-Vis spectroscope and scanning force microscope measurements suggested the high efficiency of encapsulation. In addition, the fluorescence recovery after photobleaching technique was employed to determine the existence form of deposited molecules. Further studies showed even negatively charged water-soluble peptides or proteins can be encapsulated into these hybrid capsules by modulating the pH value in bulk solution under its isoelectronic point as well. Copyright 2007 Wiley Periodicals, Inc.

Defect structure in electrodeposited nanocrystalline Ni layers with different Mo concentrations

NASA Astrophysics Data System (ADS)

Kapoor, Garima; Péter, László; Fekete, Éva; Gubicza, Jenő

2018-05-01

The effect of molybdenum (Mo) alloying on the lattice defect structure in electrodeposited nanocrystalline nickel (Ni) films was studied. The electrodeposited layers were prepared on copper substrate at room temperature, with a constant current density and pH value. The chemical composition of these layers was determined by EDS. In addition, X-ray diffraction line profile analysis was carried out to study the microstructural parameters such as the crystallite size, the dislocation density and the stacking fault probability. It was found that the higher Mo content yielded more than one order of magnitude larger dislocation density while the crystallite size was only slightly smaller. In addition, the twin boundary formation activity during deposition increased with increasing Mo concentration. The results obtained on electrodeposited layers were compared with previous research carried out on bulk nanocrystalline Ni-Mo materials with similar compositions but processed by severe plastic deformation.

Effects of dissolved oxygen and pH on nitrous oxide production rates in autotrophic partial nitrification granules.

PubMed

Rathnayake, Rathnayake M L D; Oshiki, Mamoru; Ishii, Satoshi; Segawa, Takahiro; Satoh, Hisashi; Okabe, Satoshi

2015-12-01

The effects of dissolved oxygen (DO) and pH on nitrous oxide (N2O) production rates and pathways in autotrophic partial nitrification (PN) granules were investigated at the granular level. N2O was primarily produced by betaproteobacterial ammonia-oxidizing bacteria, mainly Nitrosomonas europaea, in the oxic surface layer (<200μm) of the autotrophic PN granules. N2O production increased with increasing bulk DO concentration owing to activation of the ammonia (i.e., hydroxylamine) oxidation in this layer. The highest N2O emissions were observed at pH 7.5, although the ammonia oxidation rate was unchanged between pH 6.5 and 8.5. Overall, the results of this study suggest that in situ analyses of PN granules are essential to gaining insight into N2O emission mechanisms in a granule. Copyright © 2015 Elsevier Ltd. All rights reserved.

Seasonal atmospheric deposition variations of polychlorinated biphenyls (PCBs) and comparison of some deposition sampling techniques.

PubMed

Birgül, Askın; Tasdemir, Yücel

2011-03-01

Ambient air and bulk deposition samples were collected between June 2008 and June 2009. Eighty-three polychlorinated biphenyl (PCB) congeners were targeted in the samples. The average gas and particle PCB concentrations were found as 393 ± 278 and 70 ± 102 pg/m(3), respectively, and 85% of the atmospheric PCBs were in the gas phase. Bulk deposition samples were collected by using a sampler made of stainless steel. The average PCB bulk deposition flux value was determined as 6,020 ± 4,350 pg/m(2) day. The seasonal bulk deposition fluxes were not statistically different from each other, but the summer flux had higher values. Flux values differed depending on the precipitation levels. The average flux value in the rainy periods was 7,480 ± 4,080 pg/m(2) day while the average flux value in dry periods was 5,550 ± 4,420 pg/m(2) day. The obtained deposition values were lower than the reported values given for the urban and industrialized areas, yet close to the ones for the rural sites. The reported deposition values were also influenced by the type of the instruments used. The average dry deposition and total deposition velocity values calculated based on deposition and concentration values were found as 0.23 ± 0.21 and 0.13 ± 0.13 cm/s, respectively.

An intramolecular charge transfer process based fluorescent probe for monitoring subtle pH fluctuation in living cells.

PubMed

Sun, Mingtai; Du, Libo; Yu, Huan; Zhang, Kui; Liu, Yang; Wang, Suhua

2017-01-01

It is crucial to monitor intracellular pH values and their fluctuation since the organelles of cells have different pH distribution. Herein we construct a new small molecule fluorescent probe HBT-O for monitoring the subtle pH values within the scope of neutral to acid in living cells. The probe exhibited good water solubility, a marked turquoise to olivine emission color change in response to pH, and tremendous fluorescence hypochromatic shift of ∼50nm (1718cm -1 ) as well as the increased fluorescence intensity when the pH value changed from neutral to acid. Thus, the probe HBT-O can distinguish the subtle changes in the range of normal pH values from neutral to acid with significant fluorescence changes. These properties can be attributed to the intramolecular charge transfer (ICT) process of the probe upon protonation in buffer solutions at varied pH values. Moreover, the probe was reversible and nearly non-toxic for living cells. Then the probe was successfully used to detect pH fluctuation in living cells by exhibiting different fluorescence colors and intensity. These findings demonstrate that the probe will find useful applications in biology and biomedical research. Copyright © 2016 Elsevier B.V. All rights reserved.

Estimation of neonatal outcome artery pH value according to CTG interpretation of the last 60 min before delivery: a retrospective study. Can the outcome pH value be predicted?

PubMed

Kundu, S; Kuehnle, E; Schippert, C; von Ehr, J; Hillemanns, P; Staboulidou, Ismini

2017-11-01

The aim of this study was to analyze whether the umbilical artery pH value can be estimated throughout CTG assessment 60 min prior to delivery and if the estimated umbilical artery pH value correlates with the actual one. This includes analysis of correlation between CTG trace classification and actual umbilical artery pH value. Intra-and interobserver agreement and the impact of professional experience on visual analysis of fetal heart rate tracing were evaluated. This was a retrospective study. 300 CTG records of the last 60 min before delivery were picked randomly from the computer database with the following inclusion criteria; singleton pregnancy >37 weeks, no fetal anomalies, vaginal delivery either spontaneous or instrumental-assisted. Five obstetricians and two midwives of different professional experience classified 300 CTG traces according to the FIGO criteria and estimated the postnatal umbilical artery pH. The results showed a significant difference (p < 0.05) in estimated and actual pH value, independent of professional experience. Analysis and correlation of CTG assessment and actual umbilical artery pH value showed significantly (p < 0.05) diverging results. Intra- and interobserver variability was high. Intraobserver variability was significantly higher for the resident (p = 0.001). No significant differences were detected regarding interobserver variability. An estimation of the pH value and consequently of neonatal outcome on the basis of a present CTG seems to be difficult. Therefore, not only CTG training but also clinical experience and the collaboration and consultation within the whole team is important.

Influence of bath PH value on microstructure and corrosion resistance of phosphate chemical conversion coating on sintered Nd-Fe-B permanent magnets

NASA Astrophysics Data System (ADS)

Ding, Xia; Xue, Long-fei; Wang, Xiu-chun; Ding, Kai-hong; Cui, Sheng-li; Sun, Yong-cong; Li, Mu-sen

2016-10-01

The effect of bath PH value on formation, microstructure and corrosion resistance of the phosphate chemical conversion (PCC) coatings as well as the effect on the magnetic property of the magnets is investigated in this paper. The results show that the coating mass and thickness increase with the decrease of the bath PH value. Scanning electron microscopy observation demonstrates that the PCC coatings are in a blocky structure with different grain size. Transmission electron microscope and X-ray diffractometer tests reveal the coatings are polycomponent and are mainly composed of neodymium phosphate hydrate and praseodymium phosphate hydrate. The electrochemical analysis and static immersion corrosion test show the corrosion resistance of the PCC coatings prepared at bath PH value of 0.52 is worst. Afterwards the corrosion resistance increases first and then decreases with the increasing of the bath PH values. The magnetic properties of all the samples with PCC treatment are decreased. The biggest loss is occurred when the bath PH value is 0.52. Taken together, the optimum PH range of 1.00-1.50 for the phosphate solution has been determined.

Calcium Isotope (δ44/40Ca) Composition of Morozovella Velascoensis During the Paleocene Eocene Thermal Maximum Ocean Acidification Event

NASA Astrophysics Data System (ADS)

Kitch, G. D.; Jacobson, A. D.; Hurtgen, M.; Sageman, B. B.; Harper, D. T.; Zachos, J. C.

2017-12-01

Ocean acidification (OA) events are transient disruptions to the carbonate chemistry of seawater that involve decreases in pH, [CO32-] and carbonate mineral saturation states (Ω). Numerical modeling studies predict that the Ca isotope (δ44/40Ca) composition of primary marine carbonate should be sensitive to OA1, and recent evidence from the rock record may support this hypothesis2. Boron isotope (δ11B) data for the planktonic foraminifera Morozovella velascoensis indicate that the Paleocene-Eocene Thermal Maximum (PETM; 55 Mya) was an interval of pronounced OA3, although the Ca isotope composition of the bulk carbonate record appears to show post-burial diagenetic effects4. To further evaluate the Ca isotope proxy, we used a high-precision (2σSD=±0.04‰), double-spike (43Ca-42Ca) TIMS method5 to measure δ44/40Ca values of well-preserved M. velascoensis tests spanning the PETM. M. velascoensis tests (250-355 µm) were picked from samples recovered during ODP Leg 198, Site 1209 on Shatsky Rise in the equatorial Pacific. Five M. velascoensis tests were combined per sample, dissolved, spiked, and analyzed using a Triton TIMS. Repeat dissolutions of ten samples gave δ44/40Ca values within ±0.04‰ of the original measurements. Method and procedural blanks were negligible. δ44/40Ca values are elevated, even before the negative carbon isotope excursion (CIE) that marks the PETM. When δ11/10B values decrease during the CIE, δ44/40Ca values remain elevated, but then decrease by 0.10‰ as δ11B values return to pre-CIE levels. The apparent inverse correlation between δ44/40Ca and δ11B values suggests that Ca isotope fractionation by M. velascoensis was sensitive to OA. A decrease in pH indicated by lower δ11B values is consistent with higher δ44/40Ca values (decreased fractionation) due to elevated [Ca2+]/[CO32-] ratios and reduced W. The Ca isotope composition of pristine foraminiferal calcite may have potential for reconstructing [CO32-]. The current, preliminary dataset may indicate changes in [CO32-] prior to the CIE. 1Nielsen et al., 2012. 2Du Vivier et al., 2015. 3Penman et al., 2014. 4Griffith et al., 2015. 5Lehn et al., 2013.

Bulk viscosity of water in acoustic modal analysis and experiment

NASA Astrophysics Data System (ADS)

Kůrečka, Jan; Habán, Vladimír; Himr, Daniel

2018-06-01

Bulk viscosity is an important factor in the damping properties of fluid systems and exhibits frequency dependent behaviour. A comparison between modal analysis in ANSYS Acoustics, custom code and experimental data is presented in this paper. The measured system consists of closed ended water-filled steel pipes of different lengths. The influence of a pipe wall, flanges on both ends and longitudinal waves in the structural part were included in measurement evaluation. Therefore, the obtained values of sound speed and bulk viscosity are parameters of the fluid. A numerical simulation was carried out only using fluid volume in a range of bulk viscosity. Damping characteristics in this range were compared to measured values. The results show a significant influence of sound speed and subsequently, the use of sound speed value regressed from experimental data yields a better fit between the measurement and the computation.

Water transport by the bacterial channel alpha-hemolysin

NASA Technical Reports Server (NTRS)

Paula, S.; Akeson, M.; Deamer, D.

1999-01-01

This study is an investigation of the ability of the bacterial channel alpha-hemolysin to facilitate water permeation across biological membranes. alpha-Hemolysin channels were incorporated into rabbit erythrocyte ghosts at varying concentrations, and water permeation was induced by mixing the ghosts with hypertonic sucrose solutions. The resulting volume decrease of the ghosts was followed by time-resolved optical absorption at pH 5, 6, and 7. The average single-channel permeability coefficient of alpha-hemolysin for water ranged between 1.3x10-12 cm/s and 1.5x10-12 cm/s, depending on pH. The slightly increased single-channel permeability coefficient at lower pH-values was attributed to an increase in the effective pore size. The activation energy of water transport through the channel was low (Ea=5.4 kcal/mol), suggesting that the properties of water inside the alpha-hemolysin channel resemble those of bulk water. This conclusion was supported by calculations based on macroscopic hydrodynamic laws of laminar water flow. Using the known three-dimensional structure of the channel, the calculations accurately predicted the rate of water flow through the channel. The latter finding also indicated that water permeation data can provide a good estimate of the pore size for large channels.

Effect of pH and interaction between egg white protein and hydroxypropymethylcellulose in bulk aqueous medium on foaming properties.

PubMed

Sadahira, Mitie S; Lopes, Fernanda C Rezende; Rodrigues, Maria I; Yamada, Aureo T; Cunha, Rosiane L; Netto, Flavia M

2015-07-10

Egg white protein (EW) is used as surface-active ingredient in aerated food and hydroxypropylmethylcellulose (HPMC) is a polysaccharide that behaves as a surfactant. This study aimed at investigating the effects of process parameters biopolymer concentration (2.0-5.0%, w/w), EW:HPMC ratio (2:1-18:1), pH (3.0-6.0), and the influence of biopolymers' behavior in aqueous solution at different pH on the foaming properties (overrun, drainage, and bubble growth rate). Process parameters had effect on foaming properties. The pH was the major factor influencing the type of EW/HPMC interaction and affected the foaming properties of biopolymer mixture. At pH 3.0, EW and HPMC showed thermodynamic compatibility leading to better foaming properties, higher foaming capacity, and stability than without HPMC addition whereas at pH 4.5 and 6.0, EW and HPMC are incompatible that causes lower stability concerning the disproportionation comparing to foam without HPMC. At pH between 3.0 and 4.5, HPMC improves foaming properties of aerated products. Copyright © 2015 Elsevier Ltd. All rights reserved.

New proposal of mechanical reinforcement structures to annular REBaCuO bulk magnet for compact and cryogen-free NMR spectrometer

NASA Astrophysics Data System (ADS)

Fujishiro, H.; Takahashi, K.; Naito, T.; Yanagi, Y.; Itoh, Y.; Nakamura, T.

2018-07-01

We have proposed new reinforcement structures using an aluminum alloy ring to the annular REBaCuO bulks applicable to compact and cryogen-free 400 MHz (9.4 T) nuclear magnetic resonance (NMR) spectrometer using a numerical simulation of mechanical stress. The thermal compressive stress, σθcool, which was applied to the annular bulks during cooling due to the difference of thermal expansion coefficient between bulk and aluminum alloy, became fairly enhanced at the surface of the uppermost bulk for the new reinforcement structures, compared to the conventional reinforcement with the same height as the annular bulk, in which the compressive σθcool value was reduced. During field-cooled magnetization (FCM), the electromagnetic hoop stress, σθFCM, became the maximum at the innermost edge of the uppermost ring bulk at intermediate time step. The actual total hoop stress, σθ (= σθcool + σθFCM), due to both cooling and FCM processes was also analyzed and the new ring structures are fairly effective to reduce the σθ value and became lower than the fracture strength of the bulk. The new reinforcement structures have a possibility to avoid the fracture of the bulks and to realize a 400 MHz NMR spectrometer.

Development of Co-based bulk metallic glasses as potential biomaterials.

PubMed

Zhou, Zeyan; Wei, Qin; Li, Qiang; Jiang, Bingliang; Chen, You; Sun, Yanfei

2016-12-01

A new series of Co80-x-yCrxMoyP14B6 (x=5 y=5; x=5 y=10; x=10 y=10, all values in at.%) bulk metallic glasses (BMGs) with a maximum diameter of 1.5mm has been developed for using them as potential bio-implant materials by a combination of fluxing treatment and J-quenching technique. The performance of the present Co-based BMGs in biomedical implant applications was investigated as compared to the CoCrMo biomedical alloy (ASTM F75) and 316L stainless steel (316L SS). The corrosion behavior of the samples was investigated in both Hank's solution (pH=7.4) and artificial saliva solution (pH=6.3) at 37°C employing electrochemical measurements. The results indicate that the Co-based BMGs exhibit much higher corrosion resistance in the simulated body solutions than that of 316L SS. Compared with the corrosion resistance of ASTM F75, that of Co70Cr5Mo5P14B6 and Co65Cr5Mo10P14B6 BMGs is found to be lower and that of Co60Cr10Mo10P14B6 BMG is higher. The concentrations of Co, Cr, and Mo ions released into the simulated body solutions from our Co-based BMGs after potentiodynamic polarization are significantly lower than that released from ASTM F75. The biocompatibility of the specimens was evaluated using an in vitro test of NIH3T3 cell culture in the specimen extraction media for 1, 3, 5, and 7days, revealing the non-cytotoxicity of the Co-based BMGs towards NIH3T3 cells. Moreover, examinations on the cell adhesion and growth on the surface of the specimens indicate that the Co-based BMGs exhibit better cell viability compared to ASTM F75 and 316L SS biomedical alloys. Copyright © 2016 Elsevier B.V. All rights reserved.

Comparing WHAM 6 and MINEQL+ 4.5 for the chemical speciation of Cu2+ in the rhizosphere of forest soils.

PubMed

Cloutier-Hurteau, Benoît; Sauvé, Sébastien; Courchesne, François

2007-12-01

Metal speciation data calculated by modeling could give useful information regarding the fate of metals in the rhizospheric environment. However, no comparative study has evaluated the relative accuracy of speciation models in this microenvironment. Consequently, the present study evaluates the reliability of free Cu ion (Cu2+) activity modeled by WHAM 6 and MINEQL+ 4.5 for 18 bulk and 18 rhizospheric soil samples collected in two Canadian forested areas located near industrial facilities. The modeling of Cu speciation was performed on water extracts using pH, dissolved organic carbon (DOC), major ions, and total dissolved Al, Ca, Cu, Mg, and Zn concentrations as input data. Four scenarios representing the composition of dissolved organic substances using fulvic, humic, and acetic acids were derived from the literature and used in the modeling exercise. Different scenarios were used to contrast soil components (rhizosphere vs bulk) and soil pH levels (acidic vs neutral to alkaline). Reference Cu2+ activity values measured by an ion-selective electrode varied between 0.39 and 41 nM. The model MINEQL+ 4.5 provided good predictions of Cu2+ activities [root-mean-square residual (RMSR)= 0.37], while predictions from WHAM 6 were poor (RMSR = 1.74) because they overestimated Cu complexation with DOC. Modeling with WHAM 6 could be improved by adjusting the proportion of inert DOC and the composition of DOC (RMSR = 0.94), but it remained weaker than predictions with MINEQL+ 4.5. These results suggested that the discrepancies between speciation models were attributed to differences in the binding capacity of humic substances with Cu, where WHAM 6 appeared to be too aggressive. Therefore, we concluded that chemical interactions occurring between Cu and DOC were key factors for an accurate simulation of Cu speciation, especially in rhizospheric forest soils, where high variation of the DOC concentration and composition are observed.

Validation of a portable, waterproof blood pH analyser for elasmobranchs.

PubMed

Talwar, Brendan; Bouyoucos, Ian A; Shipley, Oliver; Rummer, Jodie L; Mandelman, John W; Brooks, Edward J; Grubbs, R Dean

2017-01-01

Quantifying changes in blood chemistry in elasmobranchs can provide insights into the physiological insults caused by anthropogenic stress, and can ultimately inform conservation and management strategies. Current methods for analysing elasmobranch blood chemistry in the field are often costly and logistically challenging. We compared blood pH values measured using a portable, waterproof pH meter (Hanna Instruments HI 99161) with blood pH values measured by an i-STAT system (CG4+ cartridges), which was previously validated for teleost and elasmobranch fishes, to gauge the accuracy of the pH meter in determining whole blood pH for the Cuban dogfish ( Squalus cubensis ) and lemon shark ( Negaprion brevirostris ). There was a significant linear relationship between values derived via the pH meter and the i-STAT for both species across a wide range of pH values and temperatures (Cuban dogfish: 6.8-7.1 pH 24-30°C; lemon sharks: 7.0-7.45 pH 25-31°C). The relative error in the pH meter's measurements was ~±2.7%. Using this device with appropriate correction factors and consideration of calibration temperatures can result in both a rapid and accurate assessment of whole blood pH, at least for the two elasmobranch species examined here. Additional species should be examined in the future across a wide range of temperatures to determine whether correction factors are universal.

Examining the freezing process of an intermediate bulk containing an industrially relevant protein

PubMed Central

Reinsch, Holger; Spadiut, Oliver; Heidingsfelder, Johannes; Herwig, Christoph

2015-01-01

Numerous biopharmaceuticals are produced in recombinant microorganisms in the controlled environment of a bioreactor, a process known as Upstream Process. To minimize product loss due to physico-chemical and enzymatic degradation, the Upstream Process should be directly followed by product purification, known as Downstream Process. However, the Downstream Process can be technologically complex and time-consuming which is why Upstream and Downstream Process usually have to be decoupled temporally and spatially. Consequently, the product obtained after the Upstream Process, known as intermediate bulk, has to be stored. In those circumstances, a freezing procedure is often performed to prevent product loss. However, the freezing process itself is inseparably linked to physico-chemical changes of the intermediate bulk which may in turn damage the product. The present study analysed the behaviour of a Tris-buffered intermediate bulk containing a biopharmaceutically relevant protein during a bottle freezing process. Major damaging mechanisms, like the spatiotemporal redistribution of ion concentrations and pH, and their influence on product stability were investigated. Summarizing, we show the complex events which happen in an intermediate bulk during freezing and explain the different causes for product loss. PMID:25765305

Elevated Air Humidity Changes Soil Bacterial Community Structure in the Silver Birch Stand.

PubMed

Truu, Marika; Ostonen, Ivika; Preem, Jens-Konrad; Lõhmus, Krista; Nõlvak, Hiie; Ligi, Teele; Rosenvald, Katrin; Parts, Kaarin; Kupper, Priit; Truu, Jaak

2017-01-01

Soil microbes play a fundamental role in forest ecosystems and respond rapidly to changes in the environment. Simultaneously with the temperature increase the climate change scenarios also predict an intensified hydrological cycle for the Baltic Sea runoff region. The aim of this study was to assess the effect of elevated air humidity on the top soil microbial community structure of a silver birch ( Betula pendula Roth.) stand by using a free air humidity manipulation facility (FAHM). The bacterial community structures of bulk soil and birch rhizosphere were analyzed using high-throughput sequencing of bacteria-specific16S rRNA gene fragments and quantification of denitrification related genes. The increased air humidity altered both bulk soil and rhizosphere bacterial community structures, and changes in the bacterial communities initiated by elevated air humidity were related to modified soil abiotic and biotic variables. Network analysis revealed that variation in soil bacterial community structural units is explained by altered abiotic conditions such as increased pH value in bulk soil, while in rhizosphere the change in absorptive root morphology had a higher effect. Among root morphological traits, the absorptive root diameter was strongest related to the bacterial community structure. The changes in bacterial community structures under elevated air humidity are associated with shifts in C, N, and P turnover as well as mineral weathering processes in soil. Increased air humidity decreased the nir and nosZ gene abundance in the rhizosphere bacterial community. The potential contribution of the denitrification to the N 2 O emission was not affected by the elevated air humidity in birch stand soil. In addition, the study revealed a strong link between the bacterial community structure, abundance of denitrification related genes, and birch absorptive root morphology in the ecosystem system adaptation to elevated air humidity.

Elevated Air Humidity Changes Soil Bacterial Community Structure in the Silver Birch Stand

PubMed Central

Truu, Marika; Ostonen, Ivika; Preem, Jens-Konrad; Lõhmus, Krista; Nõlvak, Hiie; Ligi, Teele; Rosenvald, Katrin; Parts, Kaarin; Kupper, Priit; Truu, Jaak

2017-01-01

Soil microbes play a fundamental role in forest ecosystems and respond rapidly to changes in the environment. Simultaneously with the temperature increase the climate change scenarios also predict an intensified hydrological cycle for the Baltic Sea runoff region. The aim of this study was to assess the effect of elevated air humidity on the top soil microbial community structure of a silver birch (Betula pendula Roth.) stand by using a free air humidity manipulation facility (FAHM). The bacterial community structures of bulk soil and birch rhizosphere were analyzed using high-throughput sequencing of bacteria-specific16S rRNA gene fragments and quantification of denitrification related genes. The increased air humidity altered both bulk soil and rhizosphere bacterial community structures, and changes in the bacterial communities initiated by elevated air humidity were related to modified soil abiotic and biotic variables. Network analysis revealed that variation in soil bacterial community structural units is explained by altered abiotic conditions such as increased pH value in bulk soil, while in rhizosphere the change in absorptive root morphology had a higher effect. Among root morphological traits, the absorptive root diameter was strongest related to the bacterial community structure. The changes in bacterial community structures under elevated air humidity are associated with shifts in C, N, and P turnover as well as mineral weathering processes in soil. Increased air humidity decreased the nir and nosZ gene abundance in the rhizosphere bacterial community. The potential contribution of the denitrification to the N2O emission was not affected by the elevated air humidity in birch stand soil. In addition, the study revealed a strong link between the bacterial community structure, abundance of denitrification related genes, and birch absorptive root morphology in the ecosystem system adaptation to elevated air humidity. PMID:28421053

Fluorescent probes and nanoparticles for intracellular sensing of pH values

NASA Astrophysics Data System (ADS)

Shi, Wen; Li, Xiaohua; Ma, Huimin

2014-12-01

Intracellular pH regulates a number of cell metabolism processes and its sensing is thus of great importance for cell studies. Among various methods, fluorescent probes have been widely used for sensing intracellular pH values because of their high sensitivity and spatiotemporal resolution capability. In this article, the development of fluorescent probes with good practicability in sensing intracellular pH values and pH variation during 2009 - 2014 is reviewed. These fluorescence probes are divided into two kinds: small molecules and nanoparticles. Photophysical properties, advantages/disadvantages and applications of the two kinds of probes are discussed in detail.

Wide-Field Imaging Using Nitrogen Vacancies

NASA Technical Reports Server (NTRS)

Englund, Dirk Robert (Inventor); Trusheim, Matthew Edwin (Inventor)

2017-01-01

Nitrogen vacancies in bulk diamonds and nanodiamonds can be used to sense temperature, pressure, electromagnetic fields, and pH. Unfortunately, conventional sensing techniques use gated detection and confocal imaging, limiting the measurement sensitivity and precluding wide-field imaging. Conversely, the present sensing techniques do not require gated detection or confocal imaging and can therefore be used to image temperature, pressure, electromagnetic fields, and pH over wide fields of view. In some cases, wide-field imaging supports spatial localization of the NVs to precisions at or below the diffraction limit. Moreover, the measurement range can extend over extremely wide dynamic range at very high sensitivity.

Electrostatics Control Actin Filament Nucleation and Elongation Kinetics*

PubMed Central

Crevenna, Alvaro H.; Naredi-Rainer, Nikolaus; Schönichen, André; Dzubiella, Joachim; Barber, Diane L.; Lamb, Don C.; Wedlich-Söldner, Roland

2013-01-01

The actin cytoskeleton is a central mediator of cellular morphogenesis, and rapid actin reorganization drives essential processes such as cell migration and cell division. Whereas several actin-binding proteins are known to be regulated by changes in intracellular pH, detailed information regarding the effect of pH on the actin dynamics itself is still lacking. Here, we combine bulk assays, total internal reflection fluorescence microscopy, fluorescence fluctuation spectroscopy techniques, and theory to comprehensively characterize the effect of pH on actin polymerization. We show that both nucleation and elongation are strongly enhanced at acidic pH, with a maximum close to the pI of actin. Monomer association rates are similarly affected by pH at both ends, although dissociation rates are differentially affected. This indicates that electrostatics control the diffusional encounter but not the dissociation rate, which is critical for the establishment of actin filament asymmetry. A generic model of protein-protein interaction, including electrostatics, explains the observed pH sensitivity as a consequence of charge repulsion. The observed pH effect on actin in vitro agrees with measurements of Listeria propulsion in pH-controlled cells. pH regulation should therefore be considered as a modulator of actin dynamics in a cellular environment. PMID:23486468

Cellulosic ethanol byproducts as a bulking agent

Treesearch

J.M. Considine; D. Coffin; J.Y. Zhu; D.H. Mann; X. Tang

2017-01-01

Financial enhancement of biomass value prior to pulping requires subsequent use of remaining materials; e.g., high value use of remaining stock material after cellulosic ethanol production would improve the economics for cellulosic ethanol. In this work, use of enzymatic hydrolysis residual solids (EHRS), a cellulosic ethanol byproduct, were investigated as a bulking...

The Simultaneous Determination of Muscle Cell pH Using a Weak Acid and Weak Base

PubMed Central

Adler, Sheldon

1972-01-01

Should significant pH heterogeneity exist within cells then the simultaneous calculation of intracellular pH from the distribution of a weak acid will give a value closest to the highest pH in the system, whereas calculation from the distribution of a weak base will give a value closer to the lowest pH. These two values should then differ significantly. Intact rat diaphragms were exposed in vitro to varying bicarbonate concentrations (pure metabolic) and CO2 tensions (pure respiratory), and steady-state cell pH was measured simultaneously either by distribution of the weak acid 5,5-dimethyloxazolidine-2,4-dione-14C (pH DMO) or by distribution of the weak base nicotine-14C (pH nicotine). The latter compound was found suitable to measure cell pH since it was neither metabolized nor bound by rat diaphragms. At an external pH of 7.40, pH DMO was 7.17 while pH nicotine was 6.69—a pH difference of 0.48 pH units (P < 0.001). In either respiratory or metabolic alkalosis both DMO and pH nicotine rose so that differences between them remained essentially constant. Metabolic acidosis induced a decrease in both values though they fell more slowly than did extracellular pH. In contradistinction, in respiratory acidosis, decreasing extracellular pH from 7.40 to 6.80 resulted in 0.35 pH unit drop in pH DMO while pH nicotine remained constant. In every experiment, under all external conditions, pH DMO exceeded pH nicotine. These results indicate that there is significant pH heterogeneity within diaphragm muscle, but the degree of heterogeneity may vary under different external conditions. The metabolic implications of these findings are discussed. In addition, the data show that true overall cell pH is between 6.69 and 7.17—a full pH higher than would be expected from thermodynamic considerations alone. This implies the presence of active processes to maintain cell pH. PMID:5009113

[Effects of ethanol extract of Rhizome Pinelliae Preparata on intracellular pH value of human gastric adenocarcinoma cells].

PubMed

Zhang, Ci-an; Wu, Feng; Mao, Zhu-jun; Wei, Zhen; Li, Yong-jin; Wei, Pin-kang

2011-08-01

To observe the effects of ethanol extract of Rhizome Pinelliae Preparata on the intracellular pH value of human gastric cancer SGC7901 cells. After coculturing SGC7901 cells with ethanol extract of Rhizome Pinelliae Preparata (1, 0.5, 0.25 and 0.125 mg/mL), cell viability was evaluated by chromatometry with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) staining. Intracellular pH value of SGC7901 cells was measured in the monolayer by using the pH-sensitive fluorescent probe 2,7-bis-(2-carboxyethyl)-5-carboxyfluorescein-acetoxymethyl ester. The extracellular pH value of culture medium was measured by a pH211 Calibration Check Microprocessor pH Meter. Half-inhibitory concentration (IC(50)) of ethanol extract culture to SGC7901 cells was decided by the MTT method and expressions of vacuolar-H(+)-ATPase (V-ATPase) and Na(+)/H(+) exchanger isoform 1 (NHE1) mRNAs were examined by the method of fluorescence quantitative-polymerase chain reaction after 72 h of drug treatment. Ethanol extract of Rhizome Pinelliae Preparata at different concentrations significantly inhibited the proliferation of SGC7901 cells, lowered the intracellular pH values and heightened the extracellular pH values. The IC(50) of 72 h culture was 0.5mg/mL and it inhibited the expressions of V-ATPase and NHE1 mRNAs. Ethanol extract of Rhizome Pinelliae Preparata can lower down the intracellular pH value of SGC7901 cells. The mechanism may be related to inhibiting the expressions of V-ATPase and NHE1 mRNAs.

Development of a larval diet for the South American fruit fly Anastrepha fraterculus (Diptera:Tephritidae)

USDA-ARS?s Scientific Manuscript database

Mass-rearing protocols must be developed. In particular, a cost-effective larval diet, to implement the sterile insect technique against Anastrepha fratercculus (Wiedemann). The key elements of this diet are the optimal nutrients and their concentrations, diet supports or bulking agents, and the pH ...

Sorption behavior of microamounts of zinc on titanium oxide from aqueous solutions

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

Hasany, S.M.; Ghaffar, A.; Chughtai, F.A.

1991-08-01

To correlate soil response toward zinc, it is necessary to study its adsorption in detail on soils or on their constituents. The adsorption of microamounts of zinc on titanium oxide, prepared and characterized in this laboratory, has been studied in detail. Zinc adsorption has been found to be dependent on the pH of the aqueous solution, amount of oxide, and zinc concentration. Maximum adsorption is from pH 10 buffer. EDTA and cyanide ions inhibit adsorption significantly. The adsorption of other elements under optimal conditions has also been measured on this oxide. Sc(III) and Cs(I) show almost negligible adsorption. Zinc adsorptionmore » follows the linear form of the Freundlich adsorption isotherm: log C{sub Ads} = log A + (1/n) log C{sub Bulk} with A = 0.48 mol/g and n = 1. Except at a very low bulk concentration (3 {times} 10{sup {minus}5} mol/dm{sup 3}), Langmuir adsorption isotherm is also linear for the entire zinc concentration investigated. The limiting adsorbed concentration is estimated to be 0.18 mol/g.« less

Low-voltage analog front-end processor design for ISFET-based sensor and H+ sensing applications

NASA Astrophysics Data System (ADS)

Chung, Wen-Yaw; Yang, Chung-Huang; Peng, Kang-Chu; Yeh, M. H.

2003-04-01

This paper presents a modular-based low-voltage analog-front-end processor design in a 0.5mm double-poly double-metal CMOS technology for Ion Sensitive Field Effect Transistor (ISFET)-based sensor and H+ sensing applications. To meet the potentiometric response of the ISFET that is proportional to various H+ concentrations, the constant-voltage and constant current (CVCS) testing configuration has been used. Low-voltage design skills such as bulk-driven input pair, folded-cascode amplifier, bootstrap switch control circuits have been designed and integrated for 1.5V supply and nearly rail-to-rail analog to digital signal processing. Core modules consist of an 8-bit two-step analog-digital converter and bulk-driven pre-amplifiers have been developed in this research. The experimental results show that the proposed circuitry has an acceptable linearity to 0.1 pH-H+ sensing conversions with the buffer solution in the range of pH2 to pH12. The processor has a potential usage in battery-operated and portable healthcare devices and environmental monitoring applications.

Power generation by a pH-regulated conical nanopore through reverse electrodialysis

NASA Astrophysics Data System (ADS)

Hsu, Jyh-Ping; Lin, Sheng-Chang; Lin, Chih-Yuan; Tseng, Shiojenn

2017-10-01

To assess the possibility of energy harvesting through reverse electrodialysis (RED), we consider the electrokinetic behavior of the ion transport in a pH-regulated conical nanopore connecting two large reservoirs having different bulk salt concentrations, taking account of the effect of osmotic flow. In particular, we examine the influence of the ion diffusion direction, the solution pH, and the bulk concentration ratio on that behavior in detail, and discuss the underlying mechanisms. We show that the geometrically asymmetric nature of the nanopore yields profound and interesting phenomena arising mainly from the distribution of ions in its interior. Assuming a single polymeric nanopore, a power density of 18.2 W/m2 can be generated. We show that the present system has the potential of serving as an ion-selective and a salinity gradient power generation device. The maximum power efficiency which is based on assuming a linear ionic distribution in nanopore can yield appreciable deviation, especially if pH deviates significantly from 7, where the presence of H+ and OH- needs be considered.

Study of a ternary blend system for bulk heterojunction thin film solar cells

NASA Astrophysics Data System (ADS)

Ahmad, Zubair; Touati, Farid; Shakoor, R. A.; Al-Thani, N. J.

2016-08-01

In this research, we report a bulk heterojunction (BHJ) solar cell consisting of a ternary blend system. Poly(3-hexylthiophene) P3HT is used as a donor and [6,6]-phenyl C61-butyric acid methylester (PCBM) plays the role of acceptor whereas vanadyl 2,9,16,23-tetraphenoxy-29H, 31H-phthalocyanine (VOPcPhO) is selected as an ambipolar transport material. The materials are selected and assembled in such a fashion that the generated charge carriers could efficiently be transported rightwards within the blend. The organic BHJ solar cells consist of ITO/PEDOT:PSS/ternary BHJ blend/Al structure. The power conversion efficiencies of the ITO/ PEDOT:PSS/P3HT:PCBM/Al and ITO/PEDOT:PSS/ P3HT:PCBM:VOPcPhO/Al solar cells are found to be 2.3% and 3.4%, respectively. This publication was made possible by PDRA (Grant No. PDRA1-0117-14109) from the Qatar National Research Fund (a member of Qatar Foundation). The findings achieved herein are solely the responsibility of the authors.

Bulk soil and rhizosphere bacterial community PCR-DGGE profiles and beta-galactosidase activity as indicators of biological quality in soils contaminated by heavy metals and cultivated with Silene vulgaris (Moench) Garcke.

PubMed

Martínez-Iñigo, M J; Pérez-Sanz, A; Ortiz, I; Alonso, J; Alarcón, R; García, P; Lobo, M C

2009-06-01

The biological quality of two heavy metal contaminated soils (soil C: Typic Calcixerept, pH 8.3 and soil H: Typic Haploxeraf, pH 7.3) was investigated after growing the metal-tolerant plant Silene vulgaris (Moench) Garcke for two vegetative periods. The activity of the enzyme beta-galactosidase, which is sensitive to the presence of contaminants in soil, and the polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) profiles of 16S rRNA gene fragments of culturable bacteria from bulk soil and rhizosphere were determined. The microbial enzymatic activity was higher in planted soils than in bare soils at the contamination level of 600 mg of total heavy metals kg(-1) soil. After growing S. vulgaris, beta-galactosidase activity was almost recovered in the calcareous soil. In this soil new bands appeared in the PCR-DGGE profiles of the rhizosphere bacterial community as a response to the exposure to heavy metals.

Correlation between ultrafiltration rate and phase angle measured by BIA in chronic kidney disease patients on regular hemodialysis

NASA Astrophysics Data System (ADS)

Nasution, B. R.; Lubis, A. R.

2018-03-01

Chronic Kidney Disease (CKD) patients with regular hemodialysis have high rates of morbidity and mortality that may be related to the hemodynamic effects of rapid UFR and low PhA value. In this study, we investigated whether high UFR is associated with a low value of PhA thus indirectly affect the risk of morbidity and mortality. UFR and Bioelectrical Impedance Analysis (BIA) examination on 92 subjects were recorded shortly after HD and analyzed by using Pearson correlation test. Multivariate analysis was also conducted to identify several factors that can affect the value of Phase angle. The number of HD regular CKD patients with PhA<4 based on the division of the UFR (cc/kg/h) <10, 10-13, ≥ 13, respectively were3, 10 and 6, whereas patients with ≥ 4 PhA <10, 10-13, ≥ 13respectively were 60, 11, and 2. The results showed a significant relationship between UFR with PhA. In CKD patients with regular HD, UFR has aninverse relationship with the value of PhA. After multivariate analysis, the UFR and the etiology of HD are still significantly affect the value of PhA. UFR optimal value in patients with CKD with regular HD is <10 cc/kg/h.

Salt Marsh Ecosystem Responses to Restored Tidal Connectivity across a 14y Chronosequence

NASA Astrophysics Data System (ADS)

Capooci, M.; Spivak, A. C.; Gosselin, K.

2016-02-01

Salt marshes support valuable ecosystem services. Yet, human activities negatively impact salt marsh function and contribute to their loss at a global scale. On Cape Cod, MA, culverts and impoundments under roads and railways restricted tidal exchange and resulted in salt marsh conversion to freshwater wetlands. Over the past 14 y, these structures have been removed or replaced, restoring tidal connectivity between marshes and a saltwater bay. We evaluated differences in plant community composition, sediment properties, and pore water chemistry in marshes where tidal connectivity was restored using a space-for-time, or chronosequence approach. Each restored marsh was paired with a nearby, natural salt marsh to control for variability between marshes. In each restored and natural salt marsh we evaluated the plant community by measuring species-specific percent cover and biomass and collected sediment cores for bulk density and pore water analyses. Plant communities responded rapidly: salt-tolerant species, such as Spartina alterniflora, became established while freshwater species, including Phragmites australis, were less abundant within 3 y of restoration. The number of plant species was generally greater in marshes restored within 10 y, compared to older and natural marshes. Sediment bulk density varied with depth and across sites. This likely reflects differences in site history and local conditions. Deeper horizons (24-30cm) generally had higher values in restored sites while surface values (0-3cm) were similar in restored and natural marshes. Porewater pH and sulfide were similar in restored and natural marshes, suggesting rapid microbial responses to seawater reintroduction. Overall, marsh properties and processes reflecting biological communities responded rapidly to tidal restoration. However, variability between study locations underscores the potential importance of site history, local hydrology, and geomorphology in shaping marsh biogeochemistry.

Ultra-fast grain boundary diffusion and its contribution to surface segregation on a martensitic steel. Experiments and modeling

NASA Astrophysics Data System (ADS)

Christien, F.; Le Gall, R.

2011-09-01

Phosphorus surface segregation was measured by Auger Electron Spectroscopy on a 17-4 PH martensitic stainless steel at 450, 550 and 600 °C. Surface segregation was shown to be much faster than expected which was attributed to a high contribution of phosphorus diffusion along the former austenitic grain boundaries. A model of surface segregation was developed following the Darken-du Plessis approach and taking account of both bulk and grain boundary solute diffusion. The phosphorus grain boundary diffusion coefficient in 17-4 PH was estimated: DGB< = 6.2 10 4 exp(- 157 kJ mol - 1 /RT)cm 2 s - 1 . It is found to be more than three orders of magnitude higher in 17-4 PH steel than in α-iron.

Continuous measurement of reticuloruminal pH values in dairy cows during the transition period from barn to pasture feeding using an indwelling wireless data transmitting unit.

PubMed

Gasteiner, J; Horn, M; Steinwidder, A

2015-04-01

This study was performed to investigate the effect of the transition from barn feeding to pasture on the pattern of reticuloruminal pH values in 8 multiparous dairy cows. A indwelling wireless data transmitting system for pH measurement was given to 8 multiparous cows orally. Reticuloruminal pH values were measured every 600 s over a period of 42 days. After 7 days of barn feeding (period 1), all of the animals were pastured with increasing grazing times from 2 to 7 h/day over 7 days (period 2). From day 15 to day 21 (period 3), the cows spent 7 h/day on pasture. Beginning on day 22, the animals had 20 h/day access to pasture (day and night grazing). To study reticuloruminal adaptation to pasture feeding, the phase of day and night grazing was subdivided into another 3 weekly periods (periods 4-6). Despite a mild transition period from barn feeding to pasture, significant effects on reticuloruminal pH values were observed. During barn feeding, the mean reticuloruminal pH value for all of the cows was 6.44 ± 0.14, and the pH values decreased significantly (p < 0.001) during period 2 and 3 to 6.24 ± 0.17 and 6.21 ± 0.19 respectively. During periods 4, 5 and 6, the reticuloruminal pH values increased again (pH 6.25 ± 0.22; pH 6.31 ± 0.17; pH 6.37 ± 0.16). Our results showed that the animals had significantly lowered reticuloruminal pH during the periods of feed transition from barn to pasture feeding. Despite these significant changes, the decrease was not harmful, as indicated by data of feed intake and milk production. Journal of Animal Physiology and Animal Nutrition © 2014 Blackwell Verlag GmbH.

Sampling and storage of blood for pH and blood gas analysis.

PubMed

Haskins, S C

1977-02-15

Techniques used in sampling and storage of a blood sample for pH and gas measurements can have an important effect on the measured values. Observation of these techniques and principles will minimize in vitro alteration of the pH and blood gas values. To consider that a significant change has occurred in a pH or blood gas measurement from previous values, the change must exceed 0.015 for pH, 3 mm Hg for PCO2, 5 mm Hg for PO2, and 2 mEq/L for [HCO-3] or base excess/deficit. In vitro dilution of the blood sample with anticoagulant should be avoided because it will alter the measured PCO2 and base excess/deficit values. Arterial samples should be collected for meaningful pH and blood gas values. Central venous and free-flowing capillary blood can be used for screening procedures in normal patients but are subject to considerable error. A blood sample can be stored for up to 30 minutes at room temperature without significant change in acid-base values but only up to 12 minutes before significant changes occur in PO2. A blood sample can be stored for up to 3.5 hours in an ice-water bath without significant change in pH and for 6 hours without significant change in PCO2 or PO2. Variations of body temperatures from normal will cause a measurable change in pH and blood gas values when the blood is exposed to the normal water bath temperatures of the analyzer.

Development of Hybrid pH sensor for long-term seawater pH monitoring.

NASA Astrophysics Data System (ADS)

Nakano, Y.; Egashira, T.; Miwa, T.; Kimoto, H.

2016-02-01

We have been developing the in situ pH sensor (Hybrid pH sensor: HpHS) for the long-term seawater pH monitoring. We are planning to provide the HpHS for researchers and environmental consultants for observation of the CCS (Carbon dioxide Capture and Storage) monitoring system, the coastal environment monitoring system (e.g. Blue Carbon) and ocean acidification. The HpHS has two types of pH sensors (i.e. potentiometric pH sensor and spectrophotometric pH sensor). The spectrophotometric pH sensor can measure pH correctly and stably, however it needs large power consumption and a lot of reagents in a long period of observation. The pH sensor used m-cresol purple (mCP) as an indicator of pH (Clayton and Byrne, 1993 and Liu et al., 2011). We can choose both coefficients before deployment. On the other hand, although the potentiometric pH sensor is low power consumption and high-speed response (within 10 seconds), drifts in the pH of the potentiometric measurements may possibly occur for a long-term observation. The HpHS can measure in situ pH correctly and stably combining advantage of both pH sensors. The HpHS consists of an aluminum pressure housing with optical cell (main unit) and an aluminum silicon-oil filled, pressure-compensated vessel containing pumps and valves (diaphragm pump and valve unit) and pressure-compensated reagents bags (pH indicator, pure water and Tris buffer or certified reference material: CRM) with an ability to resist water pressure to 3000m depth. The main unit holds system control boards, pump drivers, data storage (micro SD card), LED right source, photodiode, optical cell and pressure proof windows. The HpHS also has an aluminum pressure housing that holds a rechargeable lithium-ion battery or a lithium battery for the power supply (DC 24 V). The HpHS is correcting the value of the potentiometric pH sensor (measuring frequently) by the value of the spectrophotometric pH sensor (measuring less frequently). It is possible to calibrate in situ with Tris buffer or CRM on the spectrophotometric pH sensor. Therefore, the drifts in the value of potentiometric pH measurements can be compensated using the pH value obtained from the spectrophotometric pH measurements. Thereby, the sensor can measure accurately the value of pH over a long period of time with low power consumption.

Molecular binding mechanisms of aqueous cadmium and lead to siderophores, bacteria and mineral surfaces

NASA Astrophysics Data System (ADS)

Mishra, Bhoopesh

Recent studies have shown that diverse groups of bacteria adsorb metals to similar extents and uptake can be modeled using a universal adsorption model. In this study, XAFS has been used to resolve whether binding sites determined for single species systems are responsible for adsorption in more complex natural bacterial assemblages. Results obtained from a series of XAFS experiments on pure Gram positive and Gram negative bacterial strains and consortia of bacteria as a function of pH and Cd loading suggests that every bacterial strain has a complex physiology and they are all slightly different from each other. Nevertheless from the metal adsorption chemistry point of view, the main difference between them lies in the site ratio of three fundamental sites only - carboxyl, phosphoryl and sulfide. Two completely different consortia of bacteria (obtained from natural river water, and soil system with severe organic contamination) were successfully modeled in the pH range 3.4--7.8 using the EXAFS models developed for single species systems. Results thus obtained can potentially have very high impact on the modeling of the complex bacterial systems in realistic geological settings, leading to further refinement and development of robust remediation strategies for metal contamination at macroscopic level. In another study, solution speciation of Pb and Cd with DFO-B has been examined using a combination of techniques (ICP, TOC, thermodynamic modeling and XAFS). Results indicate that Pb does not complex with DFO-B at all until about pH 3.5, but forms a totally caged structure at pH 7.5. At intermediate pH conditions, mixture of species (one and two hydroxamate groups complexed) is formed. Cd on the other hand, does not complex until pH 5, forms intermediate complexes at pH 8 and is totally chelated at pH 9. Further studies were conducted for Pb sorption to mineral surface kaolinite with and without DFO-B. In the absence of DFO-B, results suggest outer sphere and inner sphere sorption of Pb on kaolinite surface at acidic and circumneutral pH conditions respectively. In the presence of DFO-B, bulk sorption studies indicated that Pb sorption is enhanced in the presence of DFO-B around pH 6 and inhibited above pH 6.5. This was confirmed by x-ray fluorescence measurements. Extended XAFS study clearly indicated unwrapping of DFO-B molecule at the surface. Our study has unambiguously recognized it as a "Type A" ternary complex ("Type A" complex means surface-metal-ligand type of interaction). Taken together, bulk adsorption measurements and XAFS experiments represent a powerful approach for determining and modeling metal speciation and adsorption.

Validation of a portable, waterproof blood pH analyser for elasmobranchs

PubMed Central

Bouyoucos, Ian A.; Shipley, Oliver; Rummer, Jodie L.; Mandelman, John W.; Brooks, Edward J.; Grubbs, R. Dean

2017-01-01

Abstract Quantifying changes in blood chemistry in elasmobranchs can provide insights into the physiological insults caused by anthropogenic stress, and can ultimately inform conservation and management strategies. Current methods for analysing elasmobranch blood chemistry in the field are often costly and logistically challenging. We compared blood pH values measured using a portable, waterproof pH meter (Hanna Instruments HI 99161) with blood pH values measured by an i-STAT system (CG4+ cartridges), which was previously validated for teleost and elasmobranch fishes, to gauge the accuracy of the pH meter in determining whole blood pH for the Cuban dogfish (Squalus cubensis) and lemon shark (Negaprion brevirostris). There was a significant linear relationship between values derived via the pH meter and the i-STAT for both species across a wide range of pH values and temperatures (Cuban dogfish: 6.8–7.1 pH 24–30°C; lemon sharks: 7.0–7.45 pH 25–31°C). The relative error in the pH meter's measurements was ~±2.7%. Using this device with appropriate correction factors and consideration of calibration temperatures can result in both a rapid and accurate assessment of whole blood pH, at least for the two elasmobranch species examined here. Additional species should be examined in the future across a wide range of temperatures to determine whether correction factors are universal. PMID:28616238

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).

CuO Nanoparticle Dissolution and Toxicity to Wheat ( Triticum aestivum) in Rhizosphere Soil.

PubMed

Gao, Xiaoyu; Avellan, Astrid; Laughton, Stephanie; Vaidya, Rucha; Rodrigues, Sónia M; Casman, Elizabeth A; Lowry, Gregory V

2018-03-06

It has been suggested, but not previously measured, that dissolution kinetics of soluble nanoparticles such as CuO nanoparticles (NPs) in soil affect their phytotoxicity. An added complexity is that such dissolution is also affected by the presence of plant roots. Here, we measured the rate of dissolution of CuO NPs in bulk soil, and in soil in which wheat plants ( Triticum aestivum) were grown under two soil NP dosing conditions: (a) freshly added CuO NPs (500 mg Cu/kg soil) and (b) CuO NPs aged for 28 d before planting. At the end of the plant growth period (14 d), available Cu was measured in three different soil compartments: bulk (not associated with roots), loosely attached to roots, and rhizosphere (soil firmly attached to roots). The labile Cu fraction increased from 17 mg/kg to 223 mg/kg in fresh treatments and from 283 mg/kg to 305 mg/kg in aged treatments over the growth period due to dissolution. Aging CuO NPs increased the toxicity to Triticum aestivum (reduction in root maximal length). The presence of roots in the soil had opposite and somewhat compensatory effects on NP dissolution, as measured in rhizosphere soil. pH increased 0.4 pH units for fresh NP treatments and 0.6 pH units for aged NPs. This lowered CuO NP dissolution in rhizosphere soil. Exudates from T. aestivum roots also increased soluble Cu in pore water. CaCl 2 extractable Cu concentrations increaed in rhizosphere soil compared to bulk soil, from 1.8 mg/kg to 6.2 mg/kg in fresh treatment and from 3.4 mg/kg to 5.4 mg/kg in aged treatments. Our study correlated CuO NP dissolution and the resulting Cu ion exposure profile to phytotoxicity, and showed that plant-induced changes in rhizosphere conditions should be considered when measuring the dissolution of CuO NPs near roots.

Mussel shells of Mytilus edulis as bioarchives of the distribution of rare earth elements and yttrium in seawater and the potential impact of pH and temperature on their partitioning behavior

NASA Astrophysics Data System (ADS)

Ponnurangam, A.; Bau, M.; Brenner, M.; Koschinsky, A.

2016-02-01

Mussel shells are potential bioarchives of proxies for changes in the physicochemical conditions in the bivalve's habitat. One such proxy is the distribution of rare earths and yttrium (REY) in seawater, as REY speciation in seawater is sensitive to pH and temperature variations, due to the impact of these parameters on the activity of CO32- in seawater. We present a new protocol for sample preparation and determination of ultratrace concentrations of REY in bulk bivalve shells (comprised of calcite and aragonite) that includes sample treatment with NaOCl followed by REY separation and preconcentration. The data obtained were used to calculate REY partition coefficients between bulk bimineralic shells of Mytilus edulis (calcite aragonite mix) and ambient seawater, and the results acquired were then used to investigate the potential effects of pH and temperature on REY partitioning.Shells of Mytilus edulis mussels from the North Sea show consistent shale-normalized (SN) REY patterns that increase from the light REY to the middle REY and decrease from the middle REY to the heavy REY. Despite being different from the general seawater REYSN pattern, the shells still display distinct REY features of seawater, such as a negative CeSN anomaly and small positive YSN and GdSN anomalies. Apparent REY partition coefficients between shells and seawater (appDTot.REYshell/seawater) are low and decrease strongly from the light REY (4.04 for La) to the heavy REY (0.34 for Lu). However, assuming that only the free REY3+ are incorporated into the shell, modDFreeREY3+shell/seawater values are higher and comparatively similar for all REY (102.46 for La; 113.44 for Lu) but show a slight maximum at Tb (199.18). Although the impact of vital effects, such as REY speciation in a mussel's extrapallial fluid from which the carbonate minerals precipitate, cannot be quantified yet, it appears that M. edulis shells are bioarchives of some REY features of seawater.We modeled the REYSN patterns of a hypothetical mussel shell at pH 8.2 and 7.6 and at temperatures of 25 and 5 °C, assuming that only free REY3+ are incorporated into the carbonate's crystal lattice and that vital effects do not obliterate the REY signal of the shells. The results suggest that with lower pH, REY concentrations in shells increase, but with little effect on the shape of the REYSN patterns, while a temperature change has an impact on the REYSN pattern but only minor effects on REY concentrations. Hence, after additional calibration studies, the REY systematics in mussel shells may become a valuable proxy for paleo-pH and ocean acidification.

Shear bond strength of bulk-fill and nano-restorative materials to dentin.

PubMed

Colak, Hakan; Ercan, Ertugrul; Hamidi, Mehmet Mustafa

2016-01-01

Bulk-fill composite materials are being developed for preparation depths of up to 4 mm in an effort to simplify and improve the placement of direct composite posterior restorations. The aim of our study was to compare shear-bond strength of bulk-fill and conventional posterior composite resins. In this study, 60 caries free extracted human molars were used and sectioned parallel to occlusal surface to expose midcoronal dentin. The specimens were randomly divided into four groups. Total-etch dentine bonding system (Adper Scotchbond 1XT, 3M ESPE) was applied to dentin surface in all the groups to reduce variability in results. Then, dentine surfaces covered by following materials. Group I: SonicFill Bulk-Fill, Group II: Tetric EvoCeram (TBF), Group III: Herculite XRV Ultra, and Group IV: TBF Bulk-Fill, 2 mm × 3 mm cylindrical restorations were prepared by using application apparatus. Shear bond testing was measured by using a universal testing machine. Kruskal-Wallis and Mann-Whitney U-tests were performed to evaluate the data. The highest value was observed in Group III (14.42 ± 4.34) and the lowest value was observed in Group IV (11.16 ± 2.76) and there is a statistically significant difference between these groups (P = 0.046). However, there is no statistically significant difference between the values of other groups. In this study, Group III was showed higher strength values. There is a need for future studies about long-term bond strength and clinical success of these adhesive and bulk-fill systems.

[Spatiotemporal variation of soil pH in Guangdong Province of China in past 30 years].

PubMed

Guo, Zhi-Xing; Wang, Jing; Chai, Min; Chen, Ze-Peng; Zhan, Zhen-Shou; Zheng, Wu-Ping; Wei, Xiu-Guo

2011-02-01

Based on the 1980s' soil inventory data and the 2002-2007 soil pH data of Guangdong Province, the spatiotemporal variation of soil pH in the Province in past 30 years was studied. In the study period, the spatial distribution pattern of soil pH in the Province had less change (mainly acidic), except that in Pearl River Delta and parts of Qingyuan and Shaoguan (weak alkaline). The overall variation of soil pH was represented as acidification, with the average pH value changed from 5.70 to 5.44. Among the soil types in the Province, alluvial soil had an increased pH, lateritic red soil, paddy soil, and red soil had a large decrement of pH value, and lime soil was most obvious in the decrease of pH value and its area percentage. The soil acidification was mainly induced by soil characteristics, some natural factors such as acid rain, and human factors such as unreasonable fertilization and urbanization. In addition, industrialization and mining increased the soil pH in some areas.

Effect of marination on CIE L* and pH values of chicken breast pectoralis major with different color lightness

USDA-ARS?s Scientific Manuscript database

Color lightness (CIE L* values) and pH are widely used as quality indicators for raw poultry breast fillets (pectoralis major). The objective of this study was to evaluate the effects of vacuum-tumbling marination on L* and pH values of raw chicken breast meat with different color lightness. Early d...

Effect of marination on CIE L* and pH values of chicken breast pectoralis major with different color lightness

USDA-ARS?s Scientific Manuscript database

Color lightness (CIE L* values) and pH are widely used as quality indicators for raw poultry breast fillets (pectoralis major). The objective of this study was to evaluate the effects of vacuum-tumbling marination on L* and pH values of raw chicken breast meat with different color lightness. Early ...

Surface and bulk modified high capacity layered oxide cathodes with low irreversible capacity loss

NASA Technical Reports Server (NTRS)

Manthiram, Arumugam (Inventor); Wu, Yan (Inventor)

2010-01-01

The present invention includes compositions, surface and bulk modifications, and methods of making of (1-x)Li[Li.sub.1/3Mn.sub.2/3]O.sub.2.xLi[Mn.sub.0.5-yNi.sub.0.5-yCo.sub.2- y]O.sub.2 cathode materials having an O3 crystal structure with a x value between 0 and 1 and y value between 0 and 0.5, reducing the irreversible capacity loss in the first cycle by surface modification with oxides and bulk modification with cationic and anionic substitutions, and increasing the reversible capacity to close to the theoretical value of insertion/extraction of one lithium per transition metal ion (250-300 mAh/g).

Surface and bulk modified high capacity layered oxide cathodes with low irreversible capacity loss

DOEpatents

Manthiram, Arumugam; Wu, Yan

2010-03-16

The present invention includes compositions, surface and bulk modifications, and methods of making of (1-x)Li[Li.sub.1/3Mn.sub.2/3]O.sub.2.xLi[Mn.sub.0.5-yNi.sub.0.5-yCo.sub.2- y]O.sub.2 cathode materials having an O3 crystal structure with a x value between 0 and 1 and y value between 0 and 0.5, reducing the irreversible capacity loss in the first cycle by surface modification with oxides and bulk modification with cationic and anionic substitutions, and increasing the reversible capacity to close to the theoretical value of insertion/extraction of one lithium per transition metal ion (250-300 mAh/g).

Stream Water Quality Modeling in the Great Smoky Mountains National Park

NASA Astrophysics Data System (ADS)

Barnett, T. W.; Robinson, R. B.

2003-12-01

The purpose of this study was to examine water quality in the acid-impacted Great Smoky Mountains National Park (GRSM). Water samples have been collected roughly quarterly at ninety sampling sites throughout the Park from October, 1993 to November, 2002.. These samples were analyzed for pH, acid neutralizing capacity (ANC), conductivity, major cations, and major anions. The trout fisheries of the GRSM are considered some of the best in the eastern United States. However, fisheries biologists at the GRSM believe that some of the streams that once supported trout populations twenty or thirty years ago, no longer do. This study outlines and quantifies surface water quality conditions that might be harmful to trout populations through a literature review. This study identifies 71 sites (79 percent of total sampling sites) that currently have a median pH of greater than 6.0, above which, is unlikely to be harmful to trout species unless a high runoff of acid, Al-rich water creates a mixing zone where Al(OH)3 precipitates. The precipitate can accumulate on the gills and impede normal diffusion of O2, CO2, and nutrients. There are 17 sites (18 percent) that have median pH values in the 5.0 to 6.0 range. This range of pH values is likely to be harmful to trout species when aluminum concentrations exceed about 0.2 mg/l. The lower end of this range is probably harmful to the eggs and fry of trout and also to non-acclimated trout especially when calcium, sodium, and chloride concentrations are low. Only two sampling sites have median pH values in the 4.5 to 5.0 range. This pH range is likely harmful to eggs, fry and adult trout, particularly in the soft water conditions prevalent in the GRSM. The mechanisms adversely affecting trout in these ranges are ionoregulatory dysfunction, respiratory stress, and circulatory stress. Currently, there are no sampling sites with median pH values less than 4.5, although pH values could be lowered by more than one pH unit during high-flow episodic events depending on the ANC in the stream. Stepwise multiple linear regression was used to model pH, ANC, nitrate and sulfate. This study incorporates basin characteristics, time, acid deposition data, USGS stream flow data as surrogate hydrologic data, and precipitation data, e.g., inches of rain on preceding days, to determine whether these variables are associated with water quality. Acid deposition data came from biweekly wet only and throughfall monitoring at the Noland Divide, which is a high elevation acid deposition monitoring site within the Park. Precipitation data is collected at five National Weather Service monitoring sites within the Park. Each of the above variables were found to be statistically significant (p<0.05) influencing factors to water quality, particularly pH. Water quality conditions were adversely (decreasing pH and ANC and increasing sulfate and nitrate) affected by increased stream flows, acid deposition and precipitation. Models for pH and ANC produced R-square values around 0.71 and 0.86, respectively. Nitrate and sulfate modeling produced R-square values around 0.30. This study also analyzes temporal trends in pH. Modeling reveals statistically significant decreasing trends in pH with time. If conditions remain the same and past trends continue, models suggest that 30.0 percent of the sampling sites will reach pH values less than 6.0 in less than 10 years, 63.3 percent of the sites will reach pH values less than 6.0 in less than 25 years, and 96.7 percent of the sites will reach pH values less than 6.0 in less than 50 years. The models used to predict future pH values explain around 70 percent of the variability in the data.

Comparison of different models for predicting soil bulk density. Case study - Slovakian agricultural soils

NASA Astrophysics Data System (ADS)

Makovníková, Jarmila; Širáň, Miloš; Houšková, Beata; Pálka, Boris; Jones, Arwyn

2017-10-01

Soil bulk density is one of the main direct indicators of soil health, and is an important aspect of models for determining agroecosystem services potential. By way of applying multi-regression methods, we have created a distributed prediction of soil bulk density used subsequently for topsoil carbon stock estimation. The soil data used for this study were from the Slovakian partial monitoring system-soil database. In our work, two models of soil bulk density in an equilibrium state, with different combinations of input parameters (soil particle size distribution and soil organic carbon content in %), have been created, and subsequently validated using a data set from 15 principal sampling sites of Slovakian partial monitoring system-soil, that were different from those used to generate the bulk density equations. We have made a comparison of measured bulk density data and data calculated by the pedotransfer equations against soil bulk density calculated according to equations recommended by Joint Research Centre Sustainable Resources for Europe. The differences between measured soil bulk density and the model values vary from -0.144 to 0.135 g cm-3 in the verification data set. Furthermore, all models based on pedotransfer functions give moderately lower values. The soil bulk density model was then applied to generate a first approximation of soil bulk density map for Slovakia using texture information from 17 523 sampling sites, and was subsequently utilised for topsoil organic carbon estimation.

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

PubMed

Xu, B; Li, Q; Wang, Y

2011-01-01

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

Effect of artificial saliva with different pH levels on the cytotoxicity of soft denture lining materials.

PubMed

Akay, Canan; Tanış, Merve Ç; Sevim, Handan

2017-10-13

The aim of this study was to evaluate the cytotoxic effects of 9 different soft denture liners on the viability of L-929 mouse fibroblast cells at different incubation periods by storing them in artificial saliva (AS) with different pH levels. 96 disk samples from each lining material were prepared and divided into 4 groups: GI: No treatment; GII: Stored in artificial saliva with pH 3 for 21 days; Group III: Stored in artificial saliva with pH 7 for 21 days; and Group IV: Stored in artificial saliva with pH 14 for 21 days. The cytotoxicity of the extracts to cultured mouse fibroblasts (L-929) was measured by MTT (tetrazolium salt 3-[4,5-dimethylthiazol-2-yl]-2,5-dipHnyltetrazolium bromide) assay. Data were analyzed using 1-way analysis of variation (ANOVA). It was found that for the pH 3 values of New Truliner, Trusoft, Mollosil Plus, Dentusil, TDV, and HydroCast®; for the pH 7 values of Ufi Gel P and Elite plus; and for the pH 14 values of HydroCast®, there was a noncytotoxic effect during both the 24-hour and 48-hour incubation periods. In the control group 48-hour incubation period, HydroCast®, TDV, Mollosil, 24-hour incubation period Elite plus, for pH 3 values; Elite Plus 24-hour incubation period, for pH 7 values Trusoft 48-hour incubation period there was a moderately cytotoxic effect. This in vitro study revealed that storage in artificial saliva with different pH levels can affect the cytotoxicity of soft lining materials.

Effect of pH on the rheological and structural properties of gels of water-washed chicken-breast muscle at physiological ionic strength.

PubMed

Feng, Y; Hultin, H O

2001-08-01

Adjustment of pH from 6.4 to neutrality improved gelling ability and water-holding capacity of twice water-washed, minced chicken-breast muscle significantly at physiological ionic strength, at which the majority of the myofibrillar proteins, including myosin, are not soluble. A strain value of 2.2 was obtained at neutral pH. Myofibrils were the main components of the gel network at both pH 6.4 and 7.0; however, the myofibrillar distribution varied with the pH value. At pH 6.4, myofibrils formed a network of localized aggregates leaving large voids between, whereas at neutral pH, an evenly distributed network of myofibrils was formed. In addition, at neutral pH, a network of fine strands was found within the network of myofibrils. The network was much less developed at pH 6.4. The thin and thick filaments within each myofibrillar structure were disorganized at both pH values. The intramyofibrillar spaces were larger at neutral pH than at pH 6.4. It was proposed that adjustment of pH to neutrality increased electrostatic repulsion leading to a more even distribution of the myofibrillar proteins, a key factor responsible for the improved gel strength and water-holding capacity.

Effects of pH and dose on nasal absorption of scopolamine hydrobromide in human subjects

NASA Technical Reports Server (NTRS)

Ahmed, S.; Sileno, A. P.; deMeireles, J. C.; Dua, R.; Pimplaskar, H. K.; Xia, W. J.; Marinaro, J.; Langenback, E.; Matos, F. J.; Putcha, L.;

Emulsification of algal oil with soy lecithin improved DHA bioaccessibility but did not change overall in vitro digestibility.

PubMed

Lin, Xinjie; Wang, Qi; Li, Weili; Wright, Amanda J

2014-11-01

Oil emulsification facilitates digestive lipolysis and subsequent lipid bioaccessibility. This study aimed to understand the effects of emulsification on DHA-rich algal oil digestion and bioaccessibility. An oil/water emulsion (50 : 44 : 6 oil-water-soy lecithin) was subjected to an in vitro digestion model with gastric pH 1.6 or 4.0 and particle size distributions, duodenal stage lipolysis and DHA bioaccessibility were determined. The emulsion was destabilized at gastric pH 1.6, with subsequent slow duodenal lipolysis. With gastric pH 4.0, the emulsion structure remained intact, initial lipolysis proceeded rapidly and DHA bioaccessibility was higher than for bulk oil, a mixture of oil, water and soy lecithin, and the gastric pH 1.6 destabilized emulsion (p < 0.05). However, the extent of lipolysis was not affected by emulsification or gastric pH. Therefore, the presence of an intact emulsion at the start of duodenal digestion, while not impacting the extent of lipolysis, did impact the initial lipolysis and DHA bioaccessibility.

Two-stage anaerobic digestion of sugar beet silage: The effect of the pH-value on process parameters and process efficiency.

PubMed

Kumanowska, Elzbieta; Uruñuela Saldaña, Mariana; Zielonka, Simon; Oechsner, Hans

2017-12-01

The study investigated the influence of the target pH-values 4.5, 5, 5.5 and 6 in the acidification reactor on process parameters, such as substrate-specific methane yield and the intermediates, in the two-stage anaerobic digestion of sugar beet silage. The total specific methane yield (Nlkg -1 CODd -1 ) increased with an increase in the pH (pH 4.5: 140.58±70.08, pH 5: 181.21±55.71, pH 5.5: 218.32±51.01, pH 6: 256.47±28.78). The pH-value also had an effect on the dominant intermediate in hydrolysate. At the pH-value of 4.5, almost no acidification and microbial activity was observed. At pH 5 and 5.5, butyric acid production dominated, guided by H 2 production. At pH 6 acetic acid was the main product. The absence of H 2 and the highest SMY makes it favorable under practical aspects. Copyright © 2017 Elsevier Ltd. All rights reserved.

Optical sensing properties of Au nanoparticle/hydrogel composite microbeads using droplet microfluidics

NASA Astrophysics Data System (ADS)

Li, Huilin; Men, Dandan; Sun, Yiqiang; Zhang, Tao; Hang, Lifeng; Liu, Dilong; Li, Cuncheng; Cai, Weiping; Li, Yue

2017-10-01

Uniform Au nanoparticle (NP)/poly (acrylamide-co-acrylic acid) [P(AAm-co-AA)] hydrogel microbeads were successfully prepared using droplet microfluidics technology. The microbeads exhibited a good stimuli-responsive behavior to pH value. Particularly in the pH value ranging from pH 2-pH 9, the composite microbead sizes gradually increased along with the increase of pH value. The homogeneous Au NPs, which were encapsulated in the P(AAm-co-AA) hydrogel microbeads, could transform the volume changes of hydrogel into optical signals by a tested single microbead with a microspectrometre system. The glucose was translated into gluconic acid by glucose oxidase. Thus, the Au NP/P(AAm-co-AA) hydrogel microbeads were used for detecting glucose based on pH effects on the composite microbeads. For this, the single Au NP/P(AAm-co-AA) hydrogel microbead could act as a good pH- or glucose-visualizing sensor.

Organelle-targeting surface-enhanced Raman scattering (SERS) nanosensors for subcellular pH sensing.

PubMed

Shen, Yanting; Liang, Lijia; Zhang, Shuqin; Huang, Dianshuai; Zhang, Jing; Xu, Shuping; Liang, Chongyang; Xu, Weiqing

2018-01-25

The pH value of subcellular organelles in living cells is a significant parameter in the physiological activities of cells. Its abnormal fluctuations are commonly believed to be associated with cancers and other diseases. Herein, a series of surface-enhanced Raman scattering (SERS) nanosensors with high sensitivity and targeting function was prepared for the quantification and monitoring of pH values in mitochondria, nucleus, and lysosome. The nanosensors were composed of gold nanorods (AuNRs) functionalized with a pH-responsive molecule (4-mercaptopyridine, MPy) and peptides that could specifically deliver the AuNRs to the targeting subcellular organelles. The localization of our prepared nanoprobes in specific organelles was confirmed by super-high resolution fluorescence imaging and bio-transmission electron microscopy (TEM) methods. By the targeting ability, the pH values of the specific organelles can be determined by monitoring the vibrational spectral changes of MPy with different pH values. Compared to the cases of reported lysosome and cytoplasm SERS pH sensors, more accurate pH values of mitochondria and nucleus, which could be two additional intracellular tracers for subcellular microenvironments, were disclosed by this SERS approach, further improving the accuracy of discrimination of related diseases. Our sensitive SERS strategy can also be employed to explore crucial physiological and biological processes that are related to subcellular pH fluctuations.

Effect of pH on whitening efficacy of 35% hydrogen peroxide and enamel microhardness.

PubMed

Jurema, Ana Luiza Barbosa; de Souza, Mauricio Yugo; Torres, Carlos Rocha Gomes; Borges, Alessandra Bühler; Caneppele, Taciana Marco Ferraz

2018-03-01

This study aimed to evaluate the effect of 35% hydrogen peroxide at different pH values and the degree of tooth staining on whitening efficacy and enamel microhardness. 90 enamel-dentin specimens were obtained from bovine incisors. They were randomly divided into 2 groups (n = 45), 1 group was immersed in a staining broth for 14 days, and another group was not stained and kept in distilled water at 37°C. Twenty-four hours after the staining procedure, each group was distributed into 3 subgroups that were whitened by 35% hydrogen peroxide with different pH values (5, 7, and 8.4) for 30 minutes. The color was measured at baseline and 7 days after whitening. Microhardness was measured at baseline, immediate, 24 hours, and 1 month after the whitening procedure. Data were submitted to 2-way analysis of variance (ANOVA) and the Tukey test for multiple comparisons for color analysis. Repeated measures ANOVA and the Tukey test were used to analyze microhardness data. The color change of the stained groups (ΔE 00  = 4.6) was significantly higher than that of the nonstained groups (ΔE 00  = 3.7). Microhardness value decreased significantly immediately after whitening for all subgroups and did not return to initial values. For each measurement time, microhardness was not significantly different among subgroups with different pH values. Despite the effectiveness of 35% hydrogen peroxide, changes on gel pH did not affect the whitening efficacy, and the enamel was superficially demineralized, regardless of pH values. Independently of the pH value of whitening gel, enamel undergoes superficial demineralization and with a reduction in superficial microhardness that does not return to the initial values. However, using hydrogen peroxide with different pH values does not alter the whitening effect. © 2018 Wiley Periodicals, Inc.

A new approximate sum rule for bulk alloy properties

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

A new, approximate sum rule is introduced for determining bulk properties of multicomponent systems, in terms of the pure components properties. This expression is applied for the study of lattice parameters, cohesive energies, and bulk moduli of binary alloys. The correct experimental trends (i.e., departure from average values) are predicted in all cases.

Shear bond strength of one-step self-etch adhesives: pH influence

PubMed Central

Poggio, Claudio; Beltrami, Riccardo; Scribante, Andrea; Colombo, Marco; Chiesa, Marco

2015-01-01

Background: The aim of this study was to compare the shear bond strength of four one-step self-etch adhesives with different pH values to enamel and dentin. Materials and Methods: In this in vitro study, 200 bovine permanent mandibular incisors were used. Four one-step self-etch adhesives with different pH values were tested both on enamel and on dentin: Adper™ Easy Bond Self-Etch Adhesive (pH = 0.8-1), Futurabond NR (pH=2), G-aenial Bond (pH = 1.5), Clearfil S3 Bond (pH = 2.7). After adhesive systems application, a nanohybrid composite resin was inserted into the bonded surface. The specimens were placed in a universal testing machine. The shear bond strength was performed at a cross-head speed of 1 mm/min until the sample rupture. The shear bond strength values (MPa) of the different groups were compared with analysis of variance after that Kolmogorov and Smirnov tests were applied to assess normality of distributions. P < 0.05 was considered as significant. Results: In enamel shear bond strength, the highest shear bond strength values were reported with Futurabond NR (P < 0.01); however, no significant differences were found with Clearfil S3 Bond. The others adhesive systems showed lower shear bond strength values with significant differences between them (P < 0.05). When comparing the dentin shear bond strength, the lowest shear bond strength values were reported with Clearfil S3 Bond (P < 0.05), while there were no significant differences among the other three products (P > 0.05). Conclusion: The pH values of adhesive systems did not influence significantly their shear bond strength to enamel or dentin. PMID:26005459

Selection harvests in Amazonian rainforests: long-term impacts on soil properties

Treesearch

K.L. McNabb; M.S. Miller; B.G. Lockaby; B.J. Stokes; R.G. Clawson; John A. Stanturf; J.N.M. Silva

1997-01-01

Surface soil properties were compared among disturbance classes associated with a single-tree selection harvest study installed in 1979 in the Brazilian Amazon. Response variables included pH, total N, total organic C, extractable P, exchangeable K, Ca, Mg, and bulk density. In general, concentrations of all elements displayed residual effects 16 years after harvests...

Host origin determines pH tolerance of Tritrichomonas foetus isolates from the feline gastrointestinal and bovine urogenital tracts.

PubMed

Morin-Adeline, Victoria; Fraser, Stuart T; Stack, Colin; Šlapeta, Jan

2015-10-01

The ability for protozoan parasites to tolerate pH fluctuations within their niche is critical for the establishment of infection and require the parasite to be capable of adapting to a distinct pH range. We used two host adapted Tritrichomonas foetus isolates, capable of infecting either the digestive tract (pH 5.3-6.6) of feline hosts or the reproductive tract (pH 7.4-7.8) of bovine hosts to address their adaptability to changing pH. Using flow cytometry, we investigated the pH tolerance of the bovine and feline T. foetus isolates over a range of physiologically relevant pH in vitro. Following exposure to mild acid stress (pH 6), the bovine T. foetus isolates showed a significant decrease in cell viability and increased cytoplasmic granularity (p-value < 0.003, p-value < 0.0002) compared to pH 7 and 8 (p-value > 0.7). In contrast, the feline genotype displayed an enhanced capacity to maintain cell morphology and viability (p-value > 0.05). Microscopic assessment revealed that following exposure to a weak acidic stress (pH 6), the bovine T. foetus transformed into rounded parasites with extended cell volumes and displays a decrease in viability. The higher tolerance for acidic extracellular environment of the feline isolate compared to the bovine isolate suggests that pH could be a critical factor in regulating T. foetus infections and host-specificity. Copyright © 2015 Elsevier Inc. All rights reserved.

Investigation of pH and Temperature Profiles in the GI Tract of Fasted Human Subjects Using the Intellicap(®) System.

PubMed

Koziolek, Mirko; Grimm, Michael; Becker, Dieter; Iordanov, Ventzeslav; Zou, Hans; Shimizu, Jeff; Wanke, Christoph; Garbacz, Grzegorz; Weitschies, Werner

2015-09-01

Gastrointestinal (GI) pH and temperature profiles under fasted-state conditions were investigated in two studies with each 10 healthy human subjects using the IntelliCap(®) system. This telemetric drug delivery device enabled the determination of gastric emptying time, small bowel transit time, and colon arrival time by significant pH and temperature changes. The study results revealed high variability of GI pH and transit times. The gastric transit of IntelliCap(®) was characterized by high fluctuations of the pH with mean values ranging from pH 1.7 to pH 4.7. Gastric emptying was observed after 7-202 min (median: 30 min). During small bowel transit, which had a duration of 67-532 min (median: 247 min), pH values increased slightly from pH 5.9-6.3 in proximal parts to pH 7.4-7.8 in distal parts. Colonic pH conditions were characterized by values fluctuating mainly between pH 5 and pH 8. The pH profiles and transit times described in this work are highly relevant for the comprehension of drug delivery of solid oral dosage forms comprising ionizable drugs and excipients with pH-dependent solubility. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Maxon and roton measurements in nanoconfined 4He

NASA Astrophysics Data System (ADS)

Bryan, M. S.; Sokol, P. E.

2018-05-01

We investigate the behavior of the collective excitations of adsorbed 4He in an ordered hexagonal mesopore, examining the crossover from a thin film to a confined fluid. Here, we present the inelastic scattering results as a function of filling at constant temperature. We find a monotonic transition of the maxon excitation as a function of filling. This has been interpreted as corresponding to an increasing density of the adsorbed helium, which approaches the bulk value as filling increases. The roton minimum exhibits a more complicated behavior that does not monotonically approach bulk values as filling increases. The full pore scattering resembles the bulk liquid accompanied by a layer mode. The maxon and roton scattering, taken together, at intermediate fillings does not correspond to a single bulk liquid dispersion at negative, low, or high pressure.

Processes affecting the response of sulfate concentrations to clearcutting in a northern hardwood forest, Catskill Mountains, New York, U.S.A.

USGS Publications Warehouse

Welsch, D.L.; Burns, Douglas A.; Murdoch, Peter S.

2004-01-01

The effects of disturbance on the biogeochemical processes that affect the sulfur (S) cycle in forested ecosystems are important, but have been studied in only a few locations. In this investigation, the mechanisms that caused large decreases in stream SO42- concentrations after clearcutting a small forested catchment in the Catskill Mountains of southeastern New York in 1997 were identified through an examination of pH and SO42- concentrations in soil solutions, bulk deposition of SO42- in throughfall collectors, adsorbed SO 42- concentrations in buried soil bags, and spatial variations in SO42- concentrations in shallow groundwater. The load of SO42- -S in stream water during the first 2 years after clearcutting was about 2 kg ha-1.year-1 less than the background value of 8-10 kg ha-1 year-1. The 10 and 19% decrease in net throughfall flux of SO42- -S during the 2nd and 3rd year after the clearcut, respectively, reflects reduced dry deposition of S after removal of the canopy, but this decrease accounts for 0 and 43%, respectively, of the decrease in SO42- load in streamflow for these 2 years. The pH of B-horizon soil water decreased from 4.5 to 4.0 within 8 months after the clearcut, and SO42- concentrations decreased from 45 ??mol L-1 to less than 20 ??mol L-1 during this time. A strong correlation between SO 42- concentrations and pH values (r2=0.71, p<0.01) in B-horizon soil water during the post-harvest period (1997-1999) reflects increased SO42- adsorption in response to soil acidification. Sulfate concentrations in groundwater from 21 spatially distributed wells were inversely related to a topographic index that served as a surrogate for soil wetness; thus, providing additional evidence that SO 42- adsorption was the dominant cause of the decreased SO42- concentrations in the stream after clearcutting. These results are consistent with those from a 1985 whole-tree harvest at the Hubbard Brook Experimental Forest in New Hampshire in which increased SO 42- adsorption resulting from decreased soil pH was the primary cause of decreased SO42- concentrations in stream water.

The use of functionalized monoalkyl phosphates and phosphonates in the colloidal processing of oxide ceramic powders

NASA Astrophysics Data System (ADS)

Radsick, Timothy Carl

The purpose of this study was to develop phosphorous-based chemicals that could be used to modify the interparticle pair potential of several oxide ceramic particles, thereby enabling their use in colloidal processing schemes. Several procedures for the synthesis of 11-12 carbon alpha,o-functionalized monoalkyl phosphates and phosphonates were developed. Because of its simplicity and its use of mild reagents, a procedure based on the Michaelis-Arbuzov rearrangement was selected to produce the bulk of the chemicals used in this study. Carboxyl- and hydroxyl-terminated monoalkyl phosphonates were adsorbed onto alumina and zirconia powders using either aqueous-based or solvent-based methods to produce a monolayer of "brushlike" steric molecules. In the aqueous-based methods, powders were processed at pH values below their isoelectric point in order to produce a positive charge on the powder, thereby attracting the negatively charged phosphate or phosphonate group onto the powder surface to form the steric monolayer. In solvent-based methods, powder was suspended in an acetone solution of the phosphonates, heated at reflux, washed, dried and heat treated at 120°C under vacuum. The zeta potential of the coated powders was measured to quantify the degree of steric layer adsorption and the shift in the isoelectric point. Slurries of coated alumina and zirconia were prepared having 20 vol % powder. Rheological behavior was studied by measuring viscosity as a function of shear rate for slurries of various pH values and counterion concentrations. Slurries with powder processed via the solvent method were the least sensitive to changes in slurry pH and were straightforward to prepare. It is thought that the solvent-based coating procedure produced a stronger, multi-dentate powder-phosphonate bond than that of the aqueous-based procedure. Dispersed and coagulated slurries were able to be prepared over a wide pH range, including at the isoelectric point of the uncoated powders where a flocculated slurry would typically occur. Slurries were consolidated using pressure filtration. Compressive stress-strain behavior and packing efficiencies were determined. Through consolidation, powder volume fraction was increased to a maximum of 56%, yet through vibration the slurry could be induced to flow, enabling its use in Colloidal Isopressing.

[Significance of identification of fungi in gastric juice of patients with artificial airway in intensive care unit].

PubMed

Feng, Yong-wen; Wu, Ming; Li, Ying; Zeng, Jing-jing; Li, Ming-li; He, Yun; Li, Dan-hui; Cui, Man-li

2012-02-01

To investigate the direct relationship and significance between the pH value of gastric juice and positive fungi in culture critical patients with artificial airway in intensive care unit (ICU) by analyzing and identifying the type of fungi and their sensitivity to antifungal therapy. A prospective study was conducted.One hundred and sixty patients (between December, 2008 and October, 2011) with artificial airway lasting longer than 48 hours were studied in the ICU at the First Affiliated Hospital of Shenzhen University. The gastric juice specimens were collected through a nasogastric tube, their pH values were measured using precise litmus paper. These samples were divided into six groups according to their pH values: pH ≤ 2.0, pH 2.1-3.0, pH 3.1-4.0, pH 4.1-5.0, pH 5.1-6.0 and pH 6.1-7.0, and then fungi were cultured in these specimens with different pH values. Susceptibility of different fungicide drugs were also investigated. The susceptibility of fungi to gastric juice with different pH values was also investigated. The relationship between 28-day survival rate and the presence of fungi in gastric juice was analyzed in order to analyze the relationship of the presence of fungi in gastric juice and clinical outcome. (1) No fungal growth was found in the gastric juice with pH value lower than 4.0, and the positive rate of fungal culture was significantly increased when the pH value of gastric juice raised. (2) The positive rate of fungal growth was 27.9% (55/197), in which, the positive rate of Candida and non-Candida fungi was 38.2% (21/55) and 61.8% (34/55) respectively, and the difference was significant statistically [χ(2) = 4.16, P < 0.05]. (3) The fungal positive rate was 40.0% (22/55) and 60.0% (33/55) respectively, in survivors (102 cases) and non-survivors (58 cases). The percentage of Candida infection and non-Candida infection was 54.5% (12/22) and 45.5% (10/22) respectively, in survivors, and it was 27.3% (9/33) and 72.7% (24/33), respectively, in non-survivors. The rate of resistance of Candida and non-Candida fungi was 4.7%-14.3% (mean 10.1%) and 0-60% (mean 28.5%) respectively. Positive fungus culture rate was higher in critical patients with artificial airway and higher gastric juice pH values. Non-Candida fungi were mainly found in gastric juice with increasing resistance rate. Candida was more commonly found in survivors, and non-Candida fungi were more commonly found in non-survivors.

Near-infrared noninvasive spectroscopic determination of pH

DOEpatents

Alam, Mary K.; Robinson, Mark R.

1998-08-11

Methods and apparatus for, preferably, determining noninvasively and in vitro pH in a human. The non-invasive method includes the steps of: generating light at three or more different wavelengths in the range of 1000 nm to 2500 nm; irradiating blood containing tissue; measuring the intensities of the wavelengths emerging from the blood containing tissue to obtain a set of at least three spectral intensities v. wavelengths; and determining the unknown values of pH. The determination of pH is made by using measured intensities at wavelengths that exhibit change in absorbance due to histidine titration. Histidine absorbance changes are due to titration by hydrogen ions. The determination of the unknown pH values is performed by at least one multivariate algorithm using two or more variables and at least one calibration model. The determined pH values are within the physiological ranges observed in blood containing tissue. The apparatus includes a tissue positioning device, a source, at least one detector, electronics, a microprocessor, memory, and apparatus for indicating the determined values.

Analysis of the sorption properties of different soils using water vapour adsorption and potentiometric titration methods

NASA Astrophysics Data System (ADS)

Skic, Kamil; Boguta, Patrycja; Sokołowska, Zofia

2016-07-01

Parameters of specific surface area as well as surface charge were used to determine and compare sorption properties of soils with different physicochemical characteristics. The gravimetric method was used to obtain water vapour isotherms and then specific surface areas, whereas surface charge was estimated from potentiometric titration curves. The specific surface area varied from 12.55 to 132.69 m2 g-1 for Haplic Cambisol and Mollic Gleysol soil, respectively, and generally decreased with pH (R=0.835; α = 0.05) and when bulk density (R=-0.736; α = 0.05) as well as ash content (R=-0.751; α = 0.05) increased. In the case of surface charge, the values ranged from 63.00 to 844.67 μmol g-1 Haplic Fluvisol and Mollic Gleysol, respecively. Organic matter gave significant contributions to the specific surface area and cation exchange capacity due to the large surface area and numerous surface functional groups, containing adsorption sites for water vapour molecules and for ions. The values of cation exchange capacity and specific surface area correlated linearly at the level of R=0.985; α = 0.05.

Experimental investigation of turbulent flow through a circular-to-rectangular transition duct. Ph.D. Thesis - Washington Univ.

NASA Technical Reports Server (NTRS)

Davis, David O.

1991-01-01

Steady, incompressible, turbulent, swirl-free flow through a circular-to-rectangular transition duck was studied experimentally. The cross-sectional area remains the same at the exit as at the inlet, but varies through the transition section to a maximum value approximately 15 percent above the inlet value. The cross-sectional geometry everywhere along the duct is defined by the equation of a superellipse. Mean and turbulence data were accumulated utilizing pressure and hot-wire instrumentation at five stations along the test section. Data are presented for operating bulk Reynolds numbers of 88,000 and 390,000. Measured quantities include total and static pressure, the three components of the mean velocity vector, and the six components of the Reynolds stress tensor. In addition to the transition duct measurements, a hot-wire technique which relies on the sequential use of single rotatable normal and slant-wire probes was proposed. The technique is applicable for measurement of the total mean velocity vector and the complete Reynolds stress tensor when the primary flow is arbitrarily skewed relative to a plane which lies normal to the probe axis of rotation.

Variation in pH optima of hydrolytic enzyme activities in tropical rain forest soils.

PubMed

Turner, Benjamin L

2010-10-01

Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β-glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates.

Research on dispose of wastewater from printing and dyeing by CWF combined with Iron-carbon Microelectrolysis

NASA Astrophysics Data System (ADS)

Chen, Xin; Ye, Tingjin; Xu, Zizhen; Chen, Xiaogang; Shi, Liang; He, Lingfeng; Zhang, Yongli

2018-03-01

The carboxymethylchitosan cladding coal ash (CWF) was oxidized by the high temperature using coal ash and sodium carboxymethyl chitosan as raw and processed material for treatment of simulated and actual printing and dyeing wastewater over iron-carbon micro-electrolysis. The results on pH and CWF dosage for effluent dispose were evaluated by the decolorization rate, COD removal efficiency and turbidity removal rate. The experimental results indicated that the decolorization rate was first augmented and then declined with the increase of pH, and attained a peak value when pH was at 5-6. The COD removal efficiency augmented with the augmented of pH, and attained a peak value when pH was 6-7. The turbidity removal rate was first increases and afterwards decreases with the augment of pH, and attained a peak value when pH was at 5-6. Furthermore, the optimum pH for the treatment of simulated dyeing wastewater was 6 over iron-carbon micro-electrolysis, which indicated that the appropriate pH can promote the degradation of wastewater.

Subunit interactions in horse spleen apoferritin. Dissociation by extremes of pH

PubMed Central

Crichton, Robert R.; Bryce, Charles F. A.

1973-01-01

1. The dissociation of horse spleen apoferritin as a function of pH was analysed by sedimentation-velocity techniques. The oligomer is stable in the range pH2.8–10.6. Between pH2.8 and 1.6 and 10.6 and 13.0 both oligomer and subunits can be detected. At pH values between 1.6 and 1.0 the subunit is the only species observed, although below pH1.0 aggregation of the subunits to a particle sedimenting much faster than the oligomer occurs. 2. When apoferritin is first dissociated into subunits at low pH values and then dialysed into buffers of pH1.5–5.0, the subunit reassociates to oligomer in the pH range 3.1–4.3. 3. U.v.-difference spectroscopy was used to study conformational changes occurring during the dissociation process. The difference spectrum in acid can be accounted for by the transfer of four to five tyrosine residues/subunit from the interior of the protein into the solvent. This process is reversed on reassociation, but shows the same hysteresis as found by sedimentation techniques. The difference spectrum in alkali is more complex, but is consistent with the deprotonation of tyrosine residues, which appear to have rather high pK values. 4. In addition to the involvement of tyrosine residues in the conformational change at low pH values, spectral evidence is presented that one tryptophan residue/subunit also changes its environment before dissociation and subsequent to reassociation. 5. Analysis of the dissociation and reassociation of apoferritin at low pH values suggests that this is a co-operative process involving protonation and deprotonation of at least two carboxyl functions of rather low intrinsic pK. The dissociation at alkaline pH values does not appear to be co-operative. 6. Of the five tyrosine residues/subunit only one can be nitrated with tetranitromethane. Guanidination of lysine residues results in the modification of seven out of a total of nine residues/subunit. Nine out of the ten arginine residues/subunit react with cyclohexanedione. PMID:4737425

Impact of preacidification of milk and fermentation time on the properties of yogurt.

PubMed

Peng, Y; Horne, D S; Lucey, J A

2009-07-01

Casein interactions play an important role in the textural properties of yogurt. The objective of this study was to investigate how the concentration of insoluble calcium phosphate (CCP) that is associated with casein particles and the length of fermentation time influence properties of yogurt gels. A central composite experimental design was used. The initial milk pH was varied by preacidification with glucono-delta-lactone (GDL), and fermentation time (time to reach pH 4.6 from the initial pH) was altered by varying the inoculum level. We hypothesized that by varying the initial milk pH value, the amount of CCP would be modified and that by varying the length of the fermentation time we would influence the rate and extent of solubilization of CCP during any subsequent gelation process. We believe that both of these factors could influence casein interactions and thereby alter gel properties. Milks were preacidified to pH values from 6.55 to 5.65 at 40 degrees C using GDL and equilibrated for 4 h before inoculation. Fermentation time was varied from 250 to 500 min by adding various amounts of culture at 40 degrees C. Gelation properties were monitored using dynamic oscillatory rheology, and microstructure was studied using fluorescence microscopy. Whey separation and permeability were analyzed at pH 4.6. The preacidification pH value significantly affected the solubilization of CCP. Storage modulus values at pH 4.6 were positively influenced by the preacidification pH value and negatively affected by fermentation time. The value for the loss tangent maximum during gelation was positively affected by the preacidification pH value. Fermentation time positively affected whey separation and significantly influenced the rate of CCP dissolution during fermentation, as CCP dissolution was a slow process. Longer fermentation times resulted in greater loss of CCP at the pH of gelation. At the end of fermentation (pH approximately 4.6), virtually all CCP was dissolved. Preacidification of milk increased the solubilization of CCP, increased the early loss of CCP crosslinks, and produced weak gels. Long fermentation times allowed more time for solubilization of CCP during the critical gelation stage of the process and increased the possibility of greater casein rearrangements; both could have contributed to the increase in whey separation.

Stable Ordering in Langmuir-Blodgett Films

NASA Astrophysics Data System (ADS)

Takamoto, Dawn Y.; Aydil, Eray; Zasadzinski, Joseph A.; Ivanova, Ani T.; Schwartz, Daniel K.; Yang, Tinglu; Cremer, Paul S.

2001-08-01

Defects in the layering of Langmuir-Blodgett (LB) films can be eliminated by depositing from the appropriate monolayer phase at the air-water interface. LB films deposited from the hexagonal phase of cadmium arachidate (CdA2) at pH 7 spontaneously transform into the bulk soap structure, a centrosymmetric bilayer with an orthorhombic herringbone packing. A large wavelength folding mechanism accelerates the conversion between the two structures, leading to a disruption of the desired layering. At pH > 8.5, though it is more difficult to draw LB films, almost perfect layering is obtained due to the inability to convert from the as-deposited structure to the equilibrium one.

Growth of 1.5-In Eu : SrI2 Single Crystal and Scintillation Properties

NASA Astrophysics Data System (ADS)

Yokota, Yuui; Ito, Tomoki; Yasuhiro, Shoji; Kurosawa, Shunsuke; Ohashi, Yuji; Kamada, Kei; Yoshikawa, Akira

2016-04-01

We grew 1.5-in Eu doped SrI2 (Eu : SrI2) bulk single crystal by a modified vertical Bridgman (VB) method using a removable chamber and high-frequency induction heating. Asgrown 1.5-in Eu : SrI2 bulk single crystal had no visible crack and inclusion in the crystal. In the transmittance and α-ray radioluminescence spectra, large absorption below 433 nm and emission peak at 433 nm were observed, respectively. Each polished Eu : SrI2 specimen indicated 56 000 62 000 ph/MeV light yield and 3.3 3.9% energy resolution. The decay times of the specimens were 0.61 0.67 μs.

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

NASA Astrophysics Data System (ADS)

Rodionov, A. K.

2011-07-01

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

Seawater pH at the advent of metazoan calcification

NASA Astrophysics Data System (ADS)

Ries, Justin; Gonzalez-Roubaud, Cécile; Douville, Eric; Montagna, Paolo

2016-04-01

The boron isotopic composition (δ11B) of bulk limestones provides a potentially powerful tool for reconstructing seawater pH deep into the geologic past (Kasemann et al., 2005; Paris et al., 2010; Ohnemueller et al., 2014). Here, we present δ11B of 35 calcitic limestones derived from a ca. 9 m.y. interval of the terminal Proterozoic Nama Group of southern Namibia. These units immediately precede the so-called Cambrian Radiation - the greatest diversification of metazoans in Earth history marked by the near-simultaneous advent of calcification across most animal phyla. The Nama Group represents one of the best preserved (average [Sr] = 1805 ppm; Mn/Sr < 2; δ18O > -10‰) and most continuous terminal Proterozoic limestone sequences known in the world. The carbonate units investigated here were deposited between ca. 552 and 543 Ma in a semi-divided foreland basin of the Kalahari Craton (Grotzinger and Miller, 2008). Depositional environments were shore-associated and ranged from upper shoreline/tidal flats to below-wave-base lower shoreface, and comprise calcisiltites, calcarenites, heterolithic interbeds, grainstones, and microbialites (Saylor et al., 1998; Grotzinger and Miller, 2008). The δ11B of the 35 sampled Nama Group carbonates were obtained via MC-ICP-MS. Samples were screened for contamination of the δ11B signal by clays (using [Al] as a proxy for clay content) (Paris et al., 2010) and by open-system meteoric diagenesis (δ11B-δ18O correlation). The δ11B values of the limestones ranged from 0.5 to 10.8‰ (avg. = 5.3‰), which is consistent with the previously observed increasing trend in carbonate δ11B (Paris et al., 2010) from the -6.2 to 2.7‰ values reported for Neoproterozoic cap carbonate dolostones (Kasemann et al., 2005) to the ca. 25‰ value reported for most modern marine carbonates. B/Ca ratios for the sampled limestones ranged from 3.4 to 24.0 ppm (avg. = 11.0). Assuming a seawater temperature of 25° C, a salinity of 35, a depth of 10 m, a seawater δ11B of 25‰ (based upon 380 Ma halites; Paris et al., 2010), and a boron isotope fractionation factor of 1.0272 (Klochko et al., 2006), the measured δ11B of the Nama Group carbonates suggests that seawater pH ranged from ca. 7.6 to 8.6 (avg. = 8.2) over the 9 My interval of Neoproterozoic time. Furthermore, seawater pH exhibited consistent oscillations of 0.6 to 1.0 units over relatively short timescales (200 ky to 1 my) between 552 to 545 Ma. Notably, seawater pH stabilized between 545 and 543 Ma - the 2 my interval immediately preceding the Cambrian Radiation of animal life. These results raise the possibility that it was the relative stabilization of seawater pH within carbonate shelf environments that fostered the polyphyletic advent of calcification within the animal kingdom during this remarkable period of Earth history.

PH-sensitive dispersion of carbon nanotubes by myoglobin

NASA Astrophysics Data System (ADS)

Nie, Haiyu; Shen, Ganni; Sun, Junlin; Zhang, Tao

2017-03-01

A facile and effective method of dispersion of double-walled carbon nanotubes (DWNTs) was developed. At appropriate pH value and sonication, myoglobin helps the solubilization of DWNTs. The product is a pH-sensitive dispersion, which remains in a highly dispersed state at pH<3.0 and pH>10.0. This approach can be used to disperse DWNTs in scale. A reversible conversion of the highly dispersed state to the aggregated state could be observed by changing the pH value. This feature holds great promise for the development of pH sensors.

Holocene soil pH changes and East Asian summer monsoon evolution derived from loess brGDGTs in the northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Duan, Y.; Sun, Q.; Zhao, H.

2017-12-01

GDGTs-based proxies have been used successfully to reconstruct paleo-temperature from loess-paleosol sequences during the past few years. However, the pH variations of loess sediments derived from GDGTs covering the geological history remain poorly constrained. Here we present two pH records spanning the last 12 ka (1ka=1000years) based on the modified cyclization ratio index (CBT') of the branched GDGTs using regional CBT'-pH empirical relationship from two well-dated loess-paleosol sections (YWY14 and SHD09) in the northeastern Tibetan Plateau. The results indicate that a slightly alkaline condition occurred during 12 8.5 ka with pH values ranging from 6.98 to 7.24, then CBT'-derived pH decreased from 8.5 to 6.5 ka with values from 7.19 to 6.49 and gradually increased thereafter. The reconstructed pH values from topmost samples can be well compared with instrumental pH values of the surrounding surface soil. The lowest intervals of CBT'-derived pH values during the mid-Holocene in our records are consistent with the results of highest tree pollen percentage from the adjacent lake sediments and regional weakest aeolian activities, which reveals that the moisture maximum during that period, but conflicted with previous results of the wettest early-Holocene inferred from speleothem or ostracod shell oxygen isotope (δ18O) values. Taking together, we conclude that Holocene humidity evolution (wettest middle Holocene) in response to the East Asian summer monsoon (EASM) changes exerts important control on pH variations of loess deposits in northeastern Tibetan Plateau. CBT'-derived pH variations can be potentially used as an indicator of EASM evolution reconstructions. In addition, we argue that speleothem or ostracod shell δ18O records are essentially a signal of the isotopic composition of precipitations rather than EASM intensity.

Evaluation of the pH- and Thermal Stability of the Recombinant Green Fluorescent Protein (GFP) in the Presence of Sodium Chloride

NASA Astrophysics Data System (ADS)

Ishii, Marina; Kunimura, Juliana Sayuri; Jeng, Hélio Tallon; Vessoni Penna, Thereza Christina; Cholewa, Olivia

The thermal stability of recombinant green fluorescent protein (GFP) in sodium chloride (NaCl) solutions at different concentrations, pH, and temperatures was evaluated by assaying the loss of fluorescence intensity as a measure of denaturation. GFP, extracted from Escherichia coli cells by the three-phase partitioning method and purified through a butyl hydrophobic interaction chromatography (HIC) column, was diluted in water for injection (WFI) (pH 6.0-7.0) and in 10 mM buffer solutions (acetate, pH 5.0; phosphate, pH 7.0; and Tris-EDTA, pH 8.0) with 0.9-30% NaCl or without and incubated at 80-95°C. The extent of protein denaturation was expressed as a percentage of the calculated decimal reduction time (D-value). In acetate buffer (pH 4.84 ±0.12), the mean D-values for 90% reduction in GFP fluorescence ranged from 2.3 to 3.6 min, independent of NaCl concentration and temperature. GFP thermal stability diluted in WFI (pH 5.94±0.60) was half that observed in phosphate buffer (pH 6.08±0.60); but in both systems, D-values decreased linearly with increasing NaCl concentration, with D-values (at 80°C) ranging from 3.44, min (WFI) to 6.1 min (phosphate buffer), both with 30% NaCl. However, D-values in Tris-EDTA (pH 7.65±0.17) were directly dependent on the NaCl concentration and 5-10 times higher than D-values for GFP in WFI at 80°C. GFP pH-and thermal stability can be easily monitored by the convenient measure of fluorescence intensity and potentially be used as an indicator to monitor that processing times and temperatures were attained.

Response of soil physico-chemical properties to restoration approaches and submergence in the water level fluctuation zone of the Danjiangkou Reservoir, China.

PubMed

Shu, Xiao; Zhang, KeRong; Zhang, QuanFa; Wang, WeiBo

2017-11-01

With the completion of the Danjiangkou Dam, the impoundment and drainage of dams can significantly alter shorelines, hydrological regime, and sediment and can result in the loss of soil and original riparian vegetation. Revegetation may affect soil properties and have broad important implications both for ecological services and soil recovery. In this work, we investigated the soil properties under different restoration approaches, and before and after submergence in the water level fluctuation zone (WLFZ) of the Danjiangkou Reservoir. Soil physical (bulk density and soil moisture), chemical (pH, soil organic carbon, nitrogen, phosphorus and potassium contents), and heavy metals were determined. This study reported that restoration approaches have impacts on soil moisture, pH, N, soil organic carbon, P, K and heavy metals in the WLFZ of the Danjiangkou Reservoir. Our results indicated that different restoration approaches could increase the soil moisture while decrease soil pH. Higher soil organic carbon in propagule banks transplantation (PBT) and shrubs restoration (SR) indicate that PBT and SR may provide soil organic matter more quickly than trees restoration (TR). SR and TR could significantly improve the soil total P and available P. PBT and SR could improve the soil total K and available K. SR and TR could significantly promote Cu and Zn adsorption, and Pb and Fe release by plant. Submergence could significantly affect the soil pH, NO 3 － -N, NH 4 ＋ -N, total P and available P. Submergence could promote NO 3 － -N and available P adsorption, and NH 4 ＋ -N and total P release by soil. The soil quality index (SQI) values implied that TR and PBT greatly improved soil quality. The present study suggests that PBT and TR could be effective for soil restoration in WLFZ of the Danjiangkou Reservoir. Copyright © 2017 Elsevier Inc. All rights reserved.

Distinct Redox Regulation in Sub-Cellular Compartments in Response to Various Stress Conditions in Saccharomyces cerevisiae

PubMed Central

Ayer, Anita; Sanwald, Julia; Pillay, Bethany A.; Meyer, Andreas J.; Perrone, Gabriel G.; Dawes, Ian W.

2013-01-01

Responses to many growth and stress conditions are assumed to act via changes to the cellular redox status. However, direct measurement of pH-adjusted redox state during growth and stress has never been carried out. Organellar redox state (E GSH) was measured using the fluorescent probes roGFP2 and pHluorin in Saccharomyces cerevisiae. In particular, we investigated changes in organellar redox state in response to various growth and stress conditions to better understand the relationship between redox-, oxidative- and environmental stress response systems. E GSH values of the cytosol, mitochondrial matrix and peroxisome were determined in exponential and stationary phase in various media. These values (−340 to −350 mV) were more reducing than previously reported. Interestingly, sub-cellular redox state remained unchanged when cells were challenged with stresses previously reported to affect redox homeostasis. Only hydrogen peroxide and heat stress significantly altered organellar redox state. Hydrogen peroxide stress altered the redox state of the glutathione disulfide/glutathione couple (GSSG, 2H+/2GSH) and pH. Recovery from moderate hydrogen peroxide stress was most rapid in the cytosol, followed by the mitochondrial matrix, with the peroxisome the least able to recover. Conversely, the bulk of the redox shift observed during heat stress resulted from alterations in pH and not the GSSG, 2H+/2GSH couple. This study presents the first direct measurement of pH-adjusted redox state in sub-cellular compartments during growth and stress conditions. Redox state is distinctly regulated in organelles and data presented challenge the notion that perturbation of redox state is central in the response to many stress conditions. PMID:23762325

Does dietary inulin affect biological activity of a grapefruit flavonoid-rich extract?

PubMed

Jurgoński, Adam; Juśkiewicz, Jerzy; Kowalska, Karolina; Zduńczyk, Zenon

2012-04-11

The aim of the study was to verify that the concomitant presence of grapefruit flavonoid extract with inulin in a Western-type diet may provide synergistic effects to the hindgut metabolism, as well as blood lipid and mineral profiles. Forty male Wistar rats were distributed into 4 groups and fed for 28 days with diets rich in fat, cholesterol and protein. A two-way repeated measures ANOVA was applied to assess the effects of inulin (v. sucrose, 5% of the diet), the addition of dietary grapefruit flavonoid extract (diets without or with 0.3% of an extract from hard parts of grapefruit) and the interaction between these two dietary factors. When compared to the control sucrose-containing diet, the diet enriched with inulin led to typical changes within the caecum, the main part of hindgut fermentation in rats, such as acidification of the digesta, support of bifidobacteria growth and increase of propionate and butyrate production. The dietary grapefruit flavonoid extract without inulin increased the bulk and pH value of caecal digesta, whereas short-chain fatty acid concentration and the bifidobacteria population were lowered compared to the extract-free diets. Simultaneous dietary addition of both tested components decreased slightly the pH value and increased somewhat the bifidobacteria number and the propionate concentration, however to the level observed with the control sucrose-containing diet. With regard to blood lipids, dietary grapefruit flavonoid extract decreased the triglyceride concentration regardless of the dietary carbohydrate type. Inulin does not provide any additional benefit to the blood lipid profile caused by the dietary application of grapefruit flavonoid extract and it does not counteract clearly detrimental effects of the extract in the hindgut. Adding grapefruit extract to the diet must be performed with caution due to possible adverse hindgut responses with overdoses.

Radiopharmaceutical development of a freeze-dried kit formulation for the preparation of [99mTc-EDDA-HYNIC-D-Phe1, Tyr3]-octreotide, a somatostatin analog for tumor diagnosis.

PubMed

Guggenberg, Elisabeth Von; Mikolajczak, Renata; Janota, Barbara; Riccabona, Georg; Decristoforo, Clemens

2004-10-01

[(99m)Tc-EDDA-HYNIC-D-Phe(1),Tyr(3)]-Octreotide ((99m)Tc-EDDA/HYNIC-TOC) is a promising new radiopharmaceutical with the potential to replace [(111)In-DTPA-D-Phe(1)]-Octreotide ((111)In-DTPA-OCT) as the radiopharmaceutical for somatostatin receptor scintigraphy due to the advantage of improved image quality, lower radiation dose for the patient, and daily availability. Here we describe the development of a freeze-dried kit formulation based on the Tricine/EDDA exchange labeling approach for the preparation of this radiopharmaceutical in a clinical setting. Three parameters were of major importance to achieve a suitable formulation with a radiochemical purity (RCP) >90%: addition of bulking agent, the pH of the freeze-drying solution, and the content of stannous chloride. The final formulation consisted of 20 mg Tricine, 10 mg EDDA, 50 mg Mannitol, 20 microg SnCl(2). 2H(2)O, and 20 microg [HYNIC-D-Phe(1), Tyr(3)]-Octreotide (HYNIC-TOC). Radiolabeling was performed by addition of 0.2 M Na(2)HPO(4) to adjust the pH to 6-7, followed by 0.5-2 GBq (99m)Tc sodium pertechnetate, in a total volume of 2 mL and incubation for 10 min in a boiling water bath. Mean RCP values of 10 batches showed values >90% over a storage period of up to 1 year, a high stability up to 24 h of the final preparation, and retained biological activity. The developed kit formulation forms the basis for further clinical evaluation of this promising new radiopharmaceutical. Copyright 2004 Wiley-Liss, Inc. and the American Pharmacists Association

Soil quality index for evaluation of reclaimed coal mine spoil.

PubMed

Mukhopadhyay, S; Masto, R E; Yadav, A; George, J; Ram, L C; Shukla, S P

2016-01-15

Success in the remediation of mine spoil depends largely on the selection of appropriate tree species. The impacts of remediation on mine soil quality cannot be sufficiently assessed by individual soil properties. However, combination of soil properties into an integrated soil quality index provides a more holistic status of reclamation potentials of tree species. Remediation potentials of four tree species (Acacia auriculiformis, Cassia siamea, Dalbergia sissoo, and Leucaena leucocephala) were studied on reclaimed coal mine overburden dumps of Jharia coalfield, Dhanbad, India. Soil samples were collected under the canopies of the tree species. Comparative studies on the properties of soils in the reclaimed and the reference sites showed improvements in soil quality parameters of the reclaimed site: coarse fraction (-20.4%), bulk density (-12.8%), water holding capacity (+0.92%), pH (+25.4%), EC (+2.9%), cation exchange capacity (+46.6%), organic carbon (+91.5%), N (+60.6%), P (+113%), K (+19.9%), Ca (+49.6%), Mg (+12.2%), Na (+19.6%), S (+46.7%), total polycyclic aromatic hydrocarbons (-71.4%), dehydrogenase activity (+197%), and microbial biomass carbon (+115%). Principal component analysis (PCA) was used to identify key mine soil quality indicators to develop a soil quality index (SQI). Selected indicators include: coarse fraction, pH, EC, soil organic carbon, P, Ca, S, and dehydrogenase activity. The indicator values were converted into a unitless score (0-1.00) and integrated into SQI. The calculated SQI was significantly (P<0.001) correlated with tree biomass and canopy cover. Reclaimed site has 52-93% higher SQI compared to the reference site. Higher SQI values were obtained for sites reclaimed with D.sissoo (+93.1%) and C.siamea (+86.4%). Copyright © 2015 Elsevier B.V. All rights reserved.

Evaluation of the efficacy of four weak acids as antifungal preservatives in low-acid intermediate moisture model food systems.

PubMed

Huang, Yang; Wilson, Mark; Chapman, Belinda; Hocking, Ailsa D

2010-02-01

The potential efficacy of four weak acids as preservatives in low-acid intermediate moisture foods was assessed using a glycerol based agar medium. The minimum inhibitory concentrations (MIC, % wt./wt.) of each acid was determined at two pH values (pH 5.0, pH 6.0) and two a(w) values (0.85, 0.90) for five food spoilage fungi, Eurotium herbariorum, Eurotium rubrum, Aspergillus niger, Aspergillus flavus and Penicillium roqueforti. Sorbic acid, a preservative commonly used to control fungal growth in low-acid intermediate moisture foods, was included as a reference. The MIC values of the four acids were lower at pH 5.0 than pH 6.0 at equivalent a(w) values, and lower at 0.85 a(w) than 0.90 a(w) at equivalent pH values. By comparison with the MIC values of sorbic acid, those of caprylic acid and dehydroacetic acid were generally lower, whereas those for caproic acid were generally higher. No general observation could be made in the case of capric acid. The antifungal activities of all five weak acids appeared related not only to the undissociated form, but also the dissociated form, of each acid.

Diurnal and seasonal variations of pH for a year in the western subarctic North Pacific observed by using a hybrid pH sensor

NASA Astrophysics Data System (ADS)

Nakano, Yoshiyuki; Fujiki, Tetsuichi; Kimoto, Katsunori; Miwa, Tetsuya

2017-04-01

Ocean acidification has many far reaching impacts on plankton community in the ocean. There is great need of quality instrumentation to assess and monitor the changing seawater pH. To meet the need, we have developed the in situ high accurate pH sensor (Hybrid pH sensor: HpHS) for the long-term seawater pH monitoring to participate the Wendy Schmidt Ocean health XPRIZE. The HpHS has two types of pH sensors (i.e. potentiometric pH sensor and spectrophotometric pH sensor). The spectrophotometric pH sensor can measure pH correctly and stably, however it needs large power consumption and a lot of reagents in a long period of observation. The pH sensor used m-cresol purple (mCP) as an indicator of pH. On the other hand, although the potentiometric pH sensor is low power consumption and high-speed response (within 10 seconds), drifts in the pH of the potentiometric measurements may possibly occur for a long-term observation. The HpHS can measure in situ pH correctly and stably combining advantage of both pH sensors. The HpHS is correcting the value of the potentiometric pH (measuring frequently) by the value of the spectrophotometric pH (measuring less frequently). It is possible to calibrate in situ with Tris buffer or CRM on the spectrophotometric pH sensor. Therefore, the drifts in the value of potentiometric pH measurements can be compensated using the pH value obtained from the spectrophotometric pH measurements. Thereby, the HpHS can measure accurately the value of pH over a long period of time with low power consumption. In order to understand the seasonal and inter-annual variabilities of biogeochemical cycles and ecosystems, ship-based studies have been carried out since 1997 at time-series station K2 (47oN, 160oE) in the subarctic western North Pacific, which is a region with progression of ocean acidification. However, the ship-based studies of the open ocean have been limited in their ability to conduct high-frequency observations for understanding the biogeochemical cycles and ecosystems. To overcome the problem, we developed a hybrid profiling buoy system. The HpHS was attached to a remote automatic water sampler (200m) in the buoy system in July 2015. We recovered the buoy system in June 2016 and succeeded in observing seawater pH every four hours for a year. Here, we show an overview of the diurnal and seasonal variations of pH for a year at station K2. In addition, we examine a relationship between the pH variations and marine calcifiers recovered by the sediment trap during the same period.

Phase angle assessment by bioelectrical impedance analysis and its predictive value for malnutrition risk in hospitalized geriatric patients.

PubMed

Varan, Hacer Dogan; Bolayir, Basak; Kara, Ozgur; Arik, Gunes; Kizilarslanoglu, Muhammet Cemal; Kilic, Mustafa Kemal; Sumer, Fatih; Kuyumcu, Mehmet Emin; Yesil, Yusuf; Yavuz, Burcu Balam; Halil, Meltem; Cankurtaran, Mustafa

2016-12-01

Phase angle (PhA) value determined by bioelectrical impedance analysis (BIA) is an indicator of cell membrane damage and body cell mass. Recent studies have shown that low PhA value is associated with increased nutritional risk in various group of patients. However, there have been only a few studies performed globally assessing the relationship between nutritional risk and PhA in hospitalized geriatric patients. The aim of the study is to evaluate the predictive value of the PhA for malnutrition risk in hospitalized geriatric patients. One hundred and twenty-two hospitalized geriatric patients were included in this cross-sectional study. Comprehensive geriatric assessment tests and BIA measurements were performed within the first 48 h after admission. Nutritional risk state of the patients was determined with NRS-2002. Phase angle values of the patients with malnutrition risk were compared with the patients that did not have the same risk. The independent variables for predicting malnutrition risk were determined. SPSS version 15 was utilized for the statistical analyzes. The patients with malnutrition risk had significantly lower phase angle values than the patients without malnutrition risk (p = 0.003). ROC curve analysis suggested that the optimum PhA cut-off point for malnutrition risk was 4.7° with 79.6 % sensitivity, 64.6 % specificity, 73.9 % positive predictive value, and 73.9 % negative predictive value. BMI, prealbumin, PhA, and Mini Mental State Examination Test scores were the independent variables for predicting malnutrition risk. PhA can be a useful, independent indicator for predicting malnutrition risk in hospitalized geriatric patients.

Axillary pH and influence of deodorants.

PubMed

Stenzaly-Achtert, S.; Schölermann, A.; Schreiber, J.; Diec, K. H.; Rippke, F.; Bielfeldt, S.

2000-05-01

BACKGROUND/AIMS: In moist intertriginous regions, such as the armpit, the pH value is physiologically higher than in other skin regions. The regulation of the axillary pH-value was examined in an open study with 48 subjects in three groups with n=16 each. METHODS: In the first 10 days (run-in) the subjects received a standard treatment in the axilla with shaving, cleansing and application of a pH-neutral deodorant. This was followed by a 5 day treatment period with the three test products (pH5 Eucerin(R) Deodorant Roll-on, Deodorant Balsam Spray, Deodorant Cream). The study was concluded by a wash-out period with procedures identical to the run-in phase. The pH was measured with a calibrated pH-meter. RESULTS: A significant pH reduction was shown during the treatment period when compared to the run-in phase. The Deodorant Roll-on induced a reduction of the mean pH values from 6.1 to 5.3, the Deodorant Balsam Spray from 6.5 to 5.7 and the Deodorant Cream from 6.2 to 5.3. During the wash-out period all pH values returned to baseline. CONCLUSION: All of the deodorants tested demonstrated a significant reduction in axillary pH. There is evidence that a high skin pH promotes the growth of several microorganisms that produce malodor. Therefore, the regulation of pH may contribute to the deodorant efficacy of the test products.

Effect of pH and lactose concentration on solvent production from whey permeate using Clostridium acetobutylicum

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

Ennis, B.M.; Maddox, I.S.

1987-02-20

A study was performed to optimize the production of solvents from whey permeate in batch fermentation using Clostridium acetobutylicum P262. Fermentations performed at relatively low pH values resulted in high solvent yields and productivities, but lactose utilization was incomplete. At higher pH values, lactose-utilization was improved but acid production dominated over solvent production. When operating at the higher pH values, an increase in the initial lactose concentration of the whey permeate resulted in lower rates of lactose utilization, and this was accompanied by increased solvent production and decreased acid production. Analysis of data from several experiments revealed a strong inversemore » relationship between solvent yield and lactose utilization rate. Thus, conditions which minimize the lactose utilization rate such as low culture pH values or high initial lactose concentrations, favor solventogenesis at the expense of acid production. 12 references.« less

Optimizing isothiocyanate formation during enzymatic glucosinolate breakdown by adjusting pH value, temperature and dilution in Brassica vegetables and Arabidopsis thaliana

NASA Astrophysics Data System (ADS)

Hanschen, Franziska S.; Klopsch, Rebecca; Oliviero, Teresa; Schreiner, Monika; Verkerk, Ruud; Dekker, Matthijs

2017-01-01

Consumption of glucosinolate-rich Brassicales vegetables is associated with a decreased risk of cancer with enzymatic hydrolysis of glucosinolates playing a key role. However, formation of health-promoting isothiocyanates is inhibited by the epithiospecifier protein in favour of nitriles and epithionitriles. Domestic processing conditions, such as changes in pH value, temperature or dilution, might also affect isothiocyanate formation. Therefore, the influences of these three factors were evaluated in accessions of Brassica rapa, Brassica oleracea, and Arabidopsis thaliana. Mathematical modelling was performed to determine optimal isothiocyanate formation conditions and to obtain knowledge on the kinetics of the reactions. At 22 °C and endogenous plant pH, nearly all investigated plants formed nitriles and epithionitriles instead of health-promoting isothiocyanates. Response surface models, however, clearly demonstrated that upon change in pH to domestic acidic (pH 4) or basic pH values (pH 8), isothiocyanate formation considerably increases. While temperature also affects this process, the pH value has the greatest impact. Further, a kinetic model showed that isothiocyanate formation strongly increases due to dilution. Finally, the results show that isothiocyanate intake can be strongly increased by optimizing the conditions of preparation of Brassicales vegetables.

An extension of ASM2d including pH calculation.

PubMed

Serralta, J; Ferrer, J; Borrás, L; Seco, A

2004-11-01

This paper presents an extension of the Activated Sludge Model No. 2d (ASM2d) including a chemical model able to calculate the pH value in biological processes. The developed chemical model incorporates the complete set of chemical species affecting the pH value to ASM2d describing non-equilibrium biochemical processes. It considers the system formed by one aqueous phase, in which biochemical processes take place, and one gaseous phase, and is based on the assumptions of instantaneous chemical equilibrium under liquid phase and kinetically governed mass transport between the liquid and gas phase. The ASM2d enlargement comprises the addition of every component affecting the pH value and an ion-balance for the calculation of the pH value and the dissociation species. The significant pH variations observed in a sequencing batch reactor operated for enhanced biological phosphorus removal were used to verify the capability of the extended model for predicting the dynamics of pH jointly with concentrations of acetic acid and phosphate. A pH inhibition function for polyphosphate accumulating bacteria has also been included in the model to simulate the behaviour observed. Experimental data obtained in four different experiments (with different sludge retention time and influent phosphorus concentrations) were accurately reproduced.

A review on the kinetics of microbially induced calcium carbonate precipitation by urea hydrolysis

NASA Astrophysics Data System (ADS)

van Paassen, L. A.

2017-12-01

In this study the kinetics of calcium carbonate precipitation induced by the ureolytic bacteria are reviewed based on experiments and mathematical modelling. The study shows how urea hydrolysis rate depends on the amount of bacteria and the conditions during growth, storage, hydrolysis and precipitation. The dynamics of Microbially Induced Carbonate Precipitation has been monitored in non-seeded liquid batch experiments. Results show that particulary for a fast hydrolysis of urea (>1 M-urea day-1) in a highly concentrated equimolar solution with calcium chloride (>0.25 M) the solubility product of CaCO3 is exceeded within a short period (less than 30 minutes), the supersaturation remains high for an exended period, resulting in prolonged periods of nucleation and crystal growth and extended growth of metastable precursor mineral phases. The pH, being a result of the speciation, quickly rises until critical supersaturation is reached and precipitation is initiated. Then pH drops (sometimes showing oscillating behaviour) to about neutral where it stays until all substrates are depleted. Higher hydrolysis rates lead to higher supersaturation and pH and relatively many small crystals, whereas higher concentrations of urea and calcium chloride mainly lead to lower pH values. The conversion can be reasonably monitored by electrical conductivity and reasonably predicted, using a simplified model based on a single reaction as long as the urea hydrolysis rate is known. Complex geochemical models, which include chemical speciciation through acid-base equilibria and kinetic equations to describe mineral precipitation, do not show significant difference from the simplified model regarding the bulk chemistry and the total amount of precipitates. However, experiments show that ureolytic MICP can result in a highly variable crystal morphologies with large variation in the affected hydraulic properties when applied in a porous medium. In order to calculate the number, size and type of crystals, use of these more complex models is essential. Quantitative prediction to a level at which the pH and conductivity are simulated accurately is not yet possible as experimental data regarding the interaction between existing mineral surfaces are the surface interaction between ions and micro-organisms is still lacking.

Effect of pH and glucose on cultured human peritoneal mesothelial cells.

PubMed

Shao, J C; Yorioka, N; Nishida, Y; Yamakido, M

1999-08-01

We investigated the effects of various pH and glucose concentrations on the growth of human peritoneal mesothelial cells and on coagulation and fibrinolytic factors. Cells were cultured at various pH values in Ham's F-12 medium containing 1.0% foetal calf serum and supplemented with D-glucose or D-mannitol at various concentrations. After 4-48 h, cell proliferation and 3H-thymidine incorporation were determined. Coagulation and fibrinolytic factors were measured after 48 h. Glucose caused concentration-dependent inhibition of cell growth at all pH values, but the deleterious effect of low pH on cell proliferation was faster and stronger than that of high glucose. At a similar osmolality, mannitol caused less inhibition of cell proliferation than glucose. There was a glucose concentration-dependent increase of thrombin-antithrombin III complex production at all pH values. At pH 5.2, tissue-type plasminogen activator production was far lower than at higher pH values, and production of the plasminogen activator inhibitor showed a glucose concentration-dependent increase. At pH 6.5 or 7.3, however, the plasminogen activator inhibitor production decreased and tissue-type plasminogen activator production increased in a glucose concentration-dependent manner. Low pH and/or high glucose culture medium had an inhibitory effect on peritoneal mesothelial cells, with the effect of high glucose being partially related to hyperosmolality. These cells may modulate peritoneal coagulant and fibrinolytic activity, with the balance between coagulation and fibrinolysis being disturbed by low pH and/or high glucose.

Uranium Adsorption on Ferrihydrite - Effects of Phosphate and Humic Acid

USGS Publications Warehouse

Payne, T.E.; Davis, J.A.; Waite, T.D.

1996-01-01

Uranium adsorption on ferrihydrite was studied as a function of pH in systems equilibrated with air, in the presence and absence of added phosphate and humic acid (HA). The objective was to determine the influence of PO43- and HA on uranium uptake. Below pH 7, the sorption of UO22+ typically increases with increasing pH (the 'low pH sorption edge'), with a sharp decrease in sorption above this pH value (the 'high pH edge'). The presence of ??PO43- of 10-4 mol/L moved the low pH edge to the left by approximately 0.8 pH units. The PO43- was strongly bound by the ferrihydrite surface, and the increased uptake of U was attributed to the formation of ternary surface complexes involving both UO22+ and PO43-. The addition of HA (9 mg/L) increased U uptake at pH values below 7, with little effect at higher pH values. The positions of the pH edges were also affected by the ionic strength and total U content. These experiments show that sorption interactions involving PO43 and HA must be considered in order to model the behavior of U in natural systems, in which these components are often present.

pH value promotes growth of Staphylococcus epidermidis in platelet concentrates.

PubMed

Störmer, Melanie; Kleesiek, Knut; Dreier, Jens

2008-05-01

The platelet (PLT) storage lesion is characterized metabolically by a pH value associated with lactic acid generation. PLT storage conditions support the growth of Staphylococcus epidermidis, the most common organism implicated in bacterial contamination of PLT concentrates (PCs). Here, different factors that influence bacterial growth in PCs are discussed and the relation between pH values of PCs and citrate plasma (CP) is studied, with emphasis on bacterial proliferation. The PLT lesion with regard to pH decrease and lactic acid production was monitored during storage and correlated to bacterial proliferation properties. A total of 115 coagulase-negative staphylococci, especially S. epidermidis isolates, were characterized for their proliferation in different blood components (CP, buffy coat-derived, and apheresis PCs). Furthermore, the influence of donor-specific, product-specific, species-specific, and strain-specific factors on bacterial proliferation was investigated. PCs showed a lower pH value in comparison to plasma during storage. Bacterial proliferation in PCs and the failure to grow in CP were determined with all organisms tested. No correlation to donor-specific, species-specific, or strain-specific factors was observed. Lowering the pH of CP resulted in bacterial proliferation, whereas a pH increase in the PC unit inhibited the proliferation of S. epidermidis. With emphasis on bacterial proliferation, the significant difference between PC and CP is the presence of metabolizing PLTs. The pH values of stored PLTs, but not those of stored plasma, support the growth of S. epidermidis.

Nanoparticle-based measurements of pH and O2 dynamics in the rhizosphere of Zostera marina L.: effects of temperature elevation and light-dark transitions.

PubMed

Elgetti Brodersen, Kasper; Koren, Klaus; Lichtenberg, Mads; Kühl, Michael

2016-07-01

Seagrasses can modulate the geochemical conditions in their immediate rhizosphere through the release of chemical compounds from their below-ground tissue. This is a vital chemical defence mechanism, whereby the plants detoxify the surrounding sediment. Using novel nanoparticle-based optical O2 and pH sensors incorporated in reduced and transparent artificial sediment, we investigated the spatio-temporal dynamics of pH and O2 within the entire rhizosphere of Zostera marina L. during experimental manipulations of light and temperature. We combined such measurements with O2 microsensor measurements of the photosynthetic productivity and respiration of seagrass leaves. We found pronounced pH and O2 microheterogeneity within the immediate rhizosphere of Z. marina, with higher below-ground tissue oxidation capability and rhizoplane pH levels during both light exposure of the leaf canopy and elevated temperature, where the temperature-mediated stimuli of biogeochemical processes seemed to predominate. Low rhizosphere pH microenvironments appeared to correlate with plant-derived oxic microzones stimulating local sulphide oxidation and thus driving local proton generation, although the rhizoplane pH levels generally where much higher than the bulk sediment pH. Our data show that Z. marina can actively alter its rhizosphere pH microenvironment alleviating the local H2 S toxicity and enhancing nutrient availability in the adjacent sediment via geochemical speciation shift. © 2016 John Wiley & Sons Ltd.

Competitive Adsorption between Nanoparticles and Surface Active Ions for the Oil-Water Interface.

PubMed

Hua, Xiaoqing; Bevan, Michael A; Frechette, Joelle

2018-04-24

Nanoparticles (NPs) can add functionality (e.g., catalytic, optical, rheological) to an oil-water interface. Adsorption of ∼10 nm NPs can be reversible; however, the mechanisms for adsorption and its effects on surface pressure remain poorly understood. Here we demonstrate how the competitive reversible adsorption of NPs and surfactants at fluid interfaces can lead to independent control of both the adsorbed amount and surface pressure. In contrast to prior work, both species investigated (NPs and surfactants) interact reversibly with the interface and without the surface active species binding to NPs. Independent measurements of the adsorption and surface pressure isotherms allow determination of the equation of state (EOS) of the interface under conditions where the NPs and surfactants are both in dynamic equilibrium with the bulk phase. The adsorption and surface pressure measurements are performed with gold NPs of two different sizes (5 and 10 nm), at two pH values, and across a wide concentration range of surfactant (tetrapentylammonium, TPeA + ) and NPs. We show that free surface active ions compete with NPs for the interface and give rise to larger surface pressures upon the adsorption of NPs. Through a competitive adsorption model, we decouple the contributions of NPs wetting at the interface and their surface activity on the measured surface pressure. We also demonstrate reversible control of adsorbed amount via changes in the surfactant concentration or the aqueous phase pH.

PH Tester Gauge Repeatability and Reproducibility Study for WO3 Nanostructure Hydrothermal Growth Process

NASA Astrophysics Data System (ADS)

Abd Rashid, Amirul; Hayati Saad, Nor; Bien Chia Sheng, Daniel; Yee, Lee Wai

2014-06-01

PH value is one of the important variables for tungsten trioxide (WO3) nanostructure hydrothermal synthesis process. The morphology of the synthesized nanostructure can be properly controlled by measuring and controlling the pH value of the solution used in this facile synthesis route. Therefore, it is very crucial to ensure the gauge used for pH measurement is reliable in order to achieve the expected result. In this study, gauge repeatability and reproducibility (GR&R) method was used to assess the repeatability and reproducibility of the pH tester. Based on ANOVA method, the design of experimental metrics as well as the result of the experiment was analyzed using Minitab software. It was found that the initial GR&R value for the tester was at 17.55 % which considered as acceptable. To further improve the GR&R level, a new pH measuring procedure was introduced. With the new procedure, the GR&R value was able to be reduced to 2.05%, which means the tester is statistically very ideal to measure the pH of the solution prepared for WO3 hydrothermal synthesis process.

Characterization of soil behavior using electromagnetic wave-based technique

NASA Astrophysics Data System (ADS)

Dong, Xiaobo

A 2.2 mm open-ended coaxial probe is selected to explore the broadband measurement of complex permittivity ranging from kHz up to GHz. The measurements are conducted in three different frequency ranges, i.e., high frequency (HF, 500 MHz ˜ 20 GHz), medium frequency (MF, 10 MHz ˜ 1 GHz), and low frequency (LF, 1 kHz ˜ 15 MHz), in view of pertinent aperture admittance models, feasible measurement principles, and required calibrations for system biases. These considerations are discussed and described in turn from the high frequency measurements to low frequency tests. Verification of the associated measurement techniques in the three operating frequency regimes is provided by experiments on pure ethanol and methanol liquids as well as on NaCl solutions of different concentrations. These testing techniques are also applied to measure the broadband dielectric spectrum of kaolinite slurry; simple analyses focusing on subtracting the influence of DC conductivity and multiple relaxations are presented. A complex permittivity spectrum from 1 kHz to 3 GHz is measured in kaolinite sediment of different structures using the slim-form open-ended coaxial probe. The sediment structure is manipulated by changing the pore-fluid pH. When the pH is below the isoelectrical point of the edge surface, IEPedge, the structure of face-to-edge (EF) flocculation is promoted in voluminous sediment (Group A samples). A higher dielectric constant due to bulk water polarization is measured because of the higher water content. As the pH is increased to greater than IEP edge, dense sediment with face-to-face (FF) aggregation is produced (Group B samples) and a lower dielectric constant is obtained. In bound water and spatial polarization, higher relaxation strength and longer relaxation time are observed in the Group B samples, which can be attributed to more negatively charged surfaces and denser packing. Fluid conductivity dominates the global conductivity of the sediment in the Group A samples so that the beta value, i.e., the ratio between the conductivities of the sediment and the fluid, is smaller than 1. The beta value is greater than 1 in the Group B samples owing to an overcompensation of surface conduction. Sedimentation behavior of two kaolinite samples with distinct fabric associations is characterized using mechanical and electromagnetic wave-based techniques. The two different fabric formations, the edge-to-face (EF) flocculated structure (i.e., sample A) and the dispersed and deflocculated structure (i.e., sample B), were regulated by changing the pH of the pore fluid and are produced. The anisotropy of shear wave velocity and DC conductivity was not observed in the sediment of sample A because of EF isotropic fabric associations but it was detected in sample B as a result of face-to-face (FF) aggregation. An open card-house structure of the sample A sediment results in a higher relaxation strength of the bulk water, Deltakappaw owing to a higher water content; the smaller Deltakappaw measured in the sample B sediment indicates denser packing. In both samples, sediment consolidation gives rise to a decrease in the bulk-water relaxation strength but an increase in the bound-water relaxation strength owing to increasing particle content. In response to sediment consolidation, the sediment conductivity of sample A continuously decreases because of the reduced contribution from the fluid conductivity. In sample B, the surface conduction via the overlapped double layer overcompensates such a decreased contribution so that the sediment conductivity increases with increasing particle content. The slim-form open-ended coaxial probe is also used to conduct a local dielectric measurement. The measured results, i.e. dielectric relaxation strength of bulk water, Deltakappaw, and the DC conductivity of the saturated sample, sigmamix, are jointly used to characterize the spatial variability of different specimens including glass beads, sand and mica samples, and kaolinte sediments with two different fabric associations. The pore distribution along the sample depth can be reflected from the measured Deltakappaw, and the local porosity can be estimated based on the mixing rules. The directional feature of the interconnected pores is captured in the totruosity which is derived from the measured sigmamix. In the kaolinite sediments, the ratio between the sediment and the pore-fluid conductivity not only reveals the spatial variability of the sediment packing but also the relative contribution of the fluid conductivity and surface conduction to the global sediment conductivity.

Influence of addition of degassed water on bulk nanobubbles.

PubMed

Tuziuti, Toru; Yasui, Kyuichi; Kanematsu, Wataru

2018-05-01

The effects of the addition of degassed water on bulk nanobubbles (ultrafine bubbles) of air in liquid water were investigated by measuring the volumetric concentration and size distribution at different dissolved air degree of saturation (DOS) values. The proportion of degassed water mixed with water containing bulk nanobubbles was increased to prepare samples having lower DOS values. It was found that the volumetric concentration of nanobubbles mostly decreased and the average nanobubble size became larger as the DOS was decreased. In our proposed mechanism, smaller nanobubbles are selectively dissolved into the surrounding liquid by Laplace pressure due to surface tension as the DOS is reduced. These results demonstrate that stable bulk nanobubbles are present even in water undersaturated with gas. The role of nanobubble under an ultrasound is also discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Use of thermal neutron reflection method for chemical analysis of bulk samples

NASA Astrophysics Data System (ADS)

Papp, A.; Csikai, J.

2014-09-01

Microscopic, σβ, and macroscopic, Σβ, reflection cross-sections of thermal neutrons averaged over bulk samples as a function of thickness (z) are given. The σβ values are additive even for bulk samples in the z=0.5-8 cm interval and so the σβmol(z) function could be given for hydrogenous substances, including some illicit drugs, explosives and hiding materials of ~1000 cm3 dimensions. The calculated excess counts agree with the measured R(z) values. For the identification of concealed objects and chemical analysis of bulky samples, different neutron methods need to be used simultaneously.

Temperature Dependent Electrical Properties of PZT Wafer

NASA Astrophysics Data System (ADS)

Basu, T.; Sen, S.; Seal, A.; Sen, A.

2016-04-01

The electrical and electromechanical properties of lead zirconate titanate (PZT) wafers were investigated and compared with PZT bulk. PZT wafers were prepared by tape casting technique. The transition temperature of both the PZT forms remained the same. The transition from an asymmetric to a symmetric shape was observed for PZT wafers at higher temperature. The piezoelectric coefficient (d 33) values obtained were 560 pc/N and 234 pc/N, and the electromechanical coupling coefficient (k p) values were 0.68 and 0.49 for bulk and wafer, respectively. The reduction in polarization after fatigue was only ~3% in case of PZT bulk and ~7% for PZT wafer.

Physical properties of pizza Mozzarella cheese manufactured under different cheese-making conditions.

PubMed

Banville, V; Morin, P; Pouliot, Y; Britten, M

2013-08-01

The effect of manufacturing factors on the shreddability and meltability of pizza Mozzarella cheese was studied. Four experimental cheeses were produced with 2 concentrations of denatured whey protein added to milk (0 or 0.25%) and 2 renneting pH values (6.4 or 6.5). The cheeses were aged 8, 22, or 36d before testing. Shreddability was assessed by the presence of fines, size of the shreds, and adhesion to the blade after shredding at 4, 13, or 22°C. A semi-empirical method was developed to measure the matting behavior of shreds by simulating industrial bulk packaging. Rheological measurements were performed on cheeses with and without a premelting treatment to assess melt and postmelt cheese physical properties. Lowering the pH of milk at renneting and aging the cheeses generally decreased the fines production during shredding. Adding whey protein to the cheeses also altered the fines production, but the effect varied depending on the renneting and aging conditions. The shred size distribution, adhesion to the blade, and matting behavior of the cheeses were adversely affected by increased temperature at shredding. The melting profiles obtained by rheological measurements showed that better meltability can be achieved by lowering the pH of milk at renneting or aging the cheese. The premelted cheeses were found to be softer at low temperatures (<40°C) and harder at high temperatures (>50°C) compared with the cheeses that had not undergone the premelting treatment. Understanding and controlling milk standardization, curd acidification, and cheese aging are essential for the production of Mozzarella cheese with desirable shreddability and meltability. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Ultramicroelectrode Studies of Self-Terminated Nickel Electrodeposition and Nickel Hydroxide Formation upon Water Reduction.

PubMed

Ritzert, Nicole L; Moffat, Thomas P

2016-12-08

The interaction between electrodeposition of Ni and electrolyte breakdown, namely the hydrogen evolution reaction (HER) via H 3 O + and H 2 O reduction, was investigated under well-defined mass transport conditions using ultramicroelectrodes (UME's) coupled with optical imaging, generation/collection scanning electrochemical microscopy (G/C-SECM), and preliminary microscale pH measurements. For 5 mmol/L NiCl 2 + 0.1 mol/L NaCl, pH 3.0, electrolytes, the voltammetric current at modest overpotentials, i.e. , between -0.6 V and -1.4 V vs. Ag/AgCl, was distributed between metal deposition and H 3 O + reduction, with both reactions reaching mass transport limited current values. At more negative potentials, an unusual sharp current spike appeared upon the onset of H 2 O reduction that was accompanied by a transient increase in H 2 production. The peak potential of the current spike was a function of both [Ni(H 2 O) 6 ] 2+ (aq) concentration and pH. The sharp rise in current was ascribed to the onset of autocatalytic H 2 O reduction, where electrochemically generated OH - species induce heterogeneous nucleation of Ni(OH) 2(ads) islands, the perimeter of which is reportedly active for H 2 O reduction. As the layer coalesces, further metal deposition is quenched while H 2 O reduction continues albeit at a decreased rate as fewer of the most reactive sites, e.g. , Ni/Ni(OH) 2 island edges, are available. At potentials below -1.5 V vs. Ag/AgCl, H 2 O reduction is accelerated, leading to homogeneous precipitation of bulk Ni(OH) 2 · x H 2 O within the nearly hemispherical diffusion layer of the UME.

Piezoelectric coefficients of bulk 3R transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Konabe, Satoru; Yamamoto, Takahiro

2017-09-01

The piezoelectric properties of bulk transition metal dichalcogenides (TMDCs) with a 3R structure were investigated using first-principles calculations based on density functional theory combined with the Berry phase treatment. Values for the elastic constant Cijkl , the piezoelectric coefficient eijk , and the piezoelectric coefficient dijk are given for bulk 3R-TMDCs (MoS2, MoSe2, WS2, and WSe2). The piezoelectric coefficients of bulk 3R-TMDCs are shown to be sufficiently large or comparable to those of conventional bulk piezoelectric materials such as α-quartz, wurtzite GaN, and wurtzite AlN.

Tailoring the structure of biphasic calcium phosphate via synthesis procedure

NASA Astrophysics Data System (ADS)

Mansour, S. F.; El-dek, S. I.; Ahmed, M. K.

2017-12-01

Nano calcium phosphate ceramics (CaPC) were synthesized using simple co-precipitation method at different preparation conditions. The selected Ca/P ratio with a variation of pH value lead to formation of dicalcium phosphate dihydrate (DCPD) at pH 5 and 6 while, hydroxyapatite (HAP) nano particles were formed at pH 9 and 12 at room temperature. The crystallite size was in the range of 15-55 nm depending on the obtained crystalline phase. The study displayed variation of decomposition depending on the annealing temperature. The significant note is the different transformation trend of each phase depending on the starting pH value. The HRTEM illustrated that the DCPD phase was formed as fibers with diameter around 4-6 nm, while HAP was formed in rod shape. The aspect ratio decreased from 6.6 at pH 9 to 4 at pH 12 which refer to the great influence of pH value on the morphology of calcium phosphates.

Structure and optical properties of ZnO produced from microwave hydrothermal hydrolysis of tris(ethylenediamine)zinc nitrate complex

NASA Astrophysics Data System (ADS)

Mostafa, Nasser Y.; Heiba, Zein K.; Ibrahim, Mohamed M.

2015-01-01

ZnO powders were synthesized using a solution microwave hydrothermal hydrolysis process and tris(ethylenediamine)zinc nitrate {[Zn(en)3](NO3)2} (en = ethylenediamine) as a precursor. Hydrolysis of the precursor complex at different pH produced zinc oxide with a diversity of well-defined morphologies. The effect of hydrolysis pH values on the structural and optical properties has been explored using XRD, SEM, and UV-visible diffuse reflectance spectroscopy (DRS). At pH = 7.0, randomly dispersed rods were formed. Whereas flower-like morphologies were obtained by treating the complex precursor in water at pH = 10.0 and 12.0. The ZnO4 tetrahedrons are greatly affected by the pH value. The band gap decreased sharply with increasing the pH value from 7.0 to 10.0, then slightly decreased with further increasing the pH to 12.0. The relationship between band gap and both structure and surface defects of the samples is also discussed.

Comparative kinetic and energetic modelling of phyllosemiquinone oxidation in Photosystem I.

PubMed

Santabarbara, Stefano; Zucchelli, Giuseppe

2016-04-14

The oxidation kinetics of phyllo(semi)quinone (PhQ), which acts as an electron transfer (ET) intermediate in the Photosystem I reaction centre, are described by a minimum of two exponential phases, characterised by lifetimes in the 10-30 ns and 150-300 ns ranges. The fastest phase is considered to be dominated by the oxidation of the PhQ molecule coordinated by the PsaB reaction centre subunit (PhQB), and the slowest phase is dominated by the oxidation of the PsaA coordinated PhQ (PhQA). Testing different energetic schemes within a unified theory-based kinetic modelling approach provides reliable limit-values for some of the physical-chemical parameters controlling these ET reactions: (i) the value of ΔG(0) associated with PhQA oxidation is smaller than ∼+30 meV; (ii) the value of the total reorganisation energy (λt) likely exceeds 0.7 eV; (iii) different mean nuclear modes are coupled to PhQB and PhQA oxidation, the former being larger, and both being ≥100 cm(-1).

Effect of pH value of probe molecule on the graphene oxide-based surface enhanced Raman scattering

NASA Astrophysics Data System (ADS)

Cui, Shao-li; Du, Xiao-qing; Zeng, Chao; Li, Lu; Bao, Jun

2017-06-01

The dependence of graphene oxide (GO)-based surface enhanced Raman scattering (SERS) on the pH value of probe molecule was investigated. Water-soluble copper phthalocyanine (TSCuPc) was used as probe molecule and its pH value was adjusted with HCl and NaOH solution. The Raman spectra of TSCuPc with pH equaling 3, 8, and 11 on GO base were tested, respectively. The results show that both Raman enhanced intensity and full width at half maximum (FWHM) of characteristic peaks vary with the pH value of TSCuPc. It is shown that there is no obvious spectral widening of TSCuPc characteristic peaks when TSCuPc is neutral or acidic, and the chemical enhancement intensity of neutral TSCuPc on GO is biggest. In contrast, when TSCuPc is alkaline, the characteristic Raman peaks between 1350 and 1600 cm-1 of TSCuPc on GO are much wider and the intensities of characteristic peaks decrease considerably. The reasons for the pH dependence of GO-based Raman spectra were explored by comparing the wettability of molecule droplet on GO and the absorbance of different pH-adjusted TSCuPc films. It is found that the effect of molecule's pH value on SERS can be contributed to the differences of concentration and distributions on GO surface for varied pH-treated molecule.

Chemical composition of bulk precipitation in the North-Central and Northeastern United States, December 1980 through February 1981

USGS Publications Warehouse

Peters, Norman E.; Bonelli, Joseph E.

1982-01-01

Samples of bulk precipitation were collected at 179 sites in the North-Central and Northeastern United States for 3 months during winter 1980-81 to provide data on the distribution of chemical constituents. Concentrations and average daily loads of 29 dissolved constituents were determined. Sodium and chloride deposition was relatively high in coastal areas and adjacent to some urban centers. Regional patterns of to daily loads of hydrogen ion, nitrate, lead, and iron correlate well with one another and form a concentric pattern around the center of high deposition in eastern Ohio and western Pennsylvania, suggesting an urban-industrial source. Samples from this area had low pH (5.7). The latter samples had high concentrations of calcium and total inorganic carbon, suggesting pH control by soil-derived carbonate minerals. Deposition patterns of ammonium, nitrate, and sulfate display regional highs in Illinois, Indiana, and southwestern Michigan, suggesting agricultural sources such as fertilizer. Median loads of zinc, iron, and lead were lower than reported in previous studies for North America. The apparent decrease in lead since 1950 throughout the area is attributed to reduced consumption of leaded fuels and lower deposition in winter.

Oxidative dissolution of silver nanoparticles: A new theoretical approach.

PubMed

Adamczyk, Zbigniew; Oćwieja, Magdalena; Mrowiec, Halina; Walas, Stanisław; Lupa, Dawid

2016-05-01

A general model of an oxidative dissolution of silver particle suspensions was developed that rigorously considers the bulk and surface solute transport. A two-step surface reaction scheme was proposed that comprises the formation of the silver oxide phase by direct oxidation and the acidic dissolution of this phase leading to silver ion release. By considering this, a complete set of equations is formulated describing oxygen and silver ion transport to and from particles' surfaces. These equations are solved in some limiting cases of nanoparticle dissolution in dilute suspensions. The obtained kinetic equations were used for the interpretation of experimental data pertinent to the dissolution kinetics of citrate-stabilized silver nanoparticles. In these kinetic measurements the role of pH and bulk suspension concentration was quantitatively evaluated by using the atomic absorption spectrometry (AAS). It was shown that the theoretical model adequately reflects the main features of the experimental results, especially the significant increase in the dissolution rate for lower pH. Also the presence of two kinetic regimes was quantitatively explained in terms of the decrease in the coverage of the fast dissolving oxide layer. The overall silver dissolution rate constants characterizing these two regimes were determined. Copyright © 2015 Elsevier Inc. All rights reserved.

Spectrophotometric determination of fluoxetine hydrochloride in bulk and in pharmaceutical formulations.

PubMed

Prabhakar, A H; Patel, V B; Giridhar, R

1999-07-01

Two new rapid, sensitive and economical spectrophotometric methods are described for the determination of fluoxetine hydrochloride in bulk and in pharmaceutical formulations. Both methods are based on the formation of a yellow ion-pair complex due to the action of methyl orange (MO) and thymol blue (TM) on fluoxetine in acidic (pH 4.0) and basic (pH 8.0) medium, respectively. Under optimised conditions they show an absorption maxima at 433 nm (MO) and 410 nm (TB), with molar absorptivities of 2.12 x 10(-4) and 4.207 x 10(-3) l mol(-1) cm(-1) and Sandell's Sensitivities of 1.64 x 10(-2) and 0.082 microg cm(-2) per 0.001 absorbance unit for MO and TB, respectively. The colour is stable for 5 min after extraction. In both cases Beer's Law is obeyed at 1-20 microg mol(-1) with MO and 4-24 microg mol(-1) with TB. The proposal method was successfully extended to pharmaceutical preparations capsules. The results obtained by both the agreement and E.P. (3rd edition) were in good agreement and statistical comparison by Student's t-test and variance ratio F-test showed no significant difference in the three methods.

Effect of nitro substituent on electrochemical oxidation of phenols at boron-doped diamond anodes.

PubMed

Jiang, Yi; Zhu, Xiuping; Li, Hongna; Ni, Jinren

2010-02-01

In order to investigate nitro-substitutent's effect on degradation of phenols at boron-doped diamond (BDD) anodes, cyclic voltammetries of three nitrophenol isomers: 2-nitrophenol (2NP), 3-nitrophenol (3NP) and 4-nitrophenol (4NP) were studied, and their bulk electrolysis results were compared with phenol's (Ph) under alkaline condition. The voltammetric study showed nitrophenols could be attacked by hydroxyl radicals and nitro-group was released from the aromatic ring. Results of bulk electrolysis showed degradation of all phenols were fit to a pseudo first-order equation and followed in this order: 2NP>4NP>3NP>Ph. Molecular structures, especially carbon atom charge, significantly influenced the electrochemical oxidation of these isomers. Intermediates were analyzed during the electrolysis process, and were mainly catechol, resorcinol, hydroquinone, and carboxylic acids, such as acetic acid and oxalic acid. A simple degradation pathway was proposed. Moreover, a linear increasing relationship between degradation rates and Hammett constants of the studied phenols was observed, which demonstrated that electrochemical oxidation of these phenols was mainly initiated by electrophilic attack of hydroxyl radicals at BDD anodes. Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Design of PH sensor signal acquisition and display system

NASA Astrophysics Data System (ADS)

Qian, Huifa; Zhang, Quanzhu; Deng, Yonghong

2017-06-01

With the continuous development of sensor manufacturing technology, how to better deal with the signal is particularly important. PH value of the sensor voltage generated by the signal as a signal, through the MCU acquisition A / D conversion, and ultimately through the digital display of its PH value. The system uses hardware and software to achieve the results obtained with the high-precision PH meter to strive to improve the accuracy and reduce error.

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

PubMed

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

2018-02-28

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

Studies on the Effects of Certain Soil Properties on the Biodegradation of Oils Determined by the Manometric Respirometric Method

PubMed Central

Kaakinen, Juhani; Vähäoja, Pekka; Kuokkanen, Toivo; Roppola, Katri

2007-01-01

The biodegradability of certain biofuels was studied in the case of forest soils using the manometric respirometric technique, which was proved to be very suitable for untreated, fertilized as well as pH adjusted soils. Experiments carried out in infertile sandy forest soil gave a BOD/ThOD value of 45.1% for a typical model substance, that is, sodium benzoate after a period of 30 days and mineral addition improved the BOD/ThOD value to a value of 76.2%. Rapeseed oil-based chain oil almost did not biodegrade at all in 30 days in nonprocessed soil, and when pH was adjusted to 8.0, the BOD/ThOD value increased slightly to a value of 7.4%. Mineral addition improved the BOD/ThOD value on average to 43.2% after 30 days. The combined mineral addition and pH adjustment together increased the BOD/ThOD value to 75.8% in 30 days. The observations were similar with a rapeseed oil-based lubricating oil: after 30 days, the BOD/ThOD value increased from 5.9% to an average value of 51.9%, when the pH and mineral concentrations of the soil were optimized. The mineral addition and pH adjustment also improved the precision of the measurements significantly. PMID:18273392

The temporal changes in saturated hydraulic conductivity of forest soils

NASA Astrophysics Data System (ADS)

Kornél Szegedi, Balázs

2015-04-01

I investigated the temporal variability of forest soils infiltration capacity through compaction. I performed the measurements of mine in The Botanical Garden of Sopron between 15.09.2014 - 15.10.2014. I performed the measurements in 50-50 cm areas those have been cleaned of vegetation, where I measured the bulk density and volume of soil hydraulic conductivity with Tension Disk Infiltrometer (TDI) in 3-3 repetitions. I took undisturbed 160 cm3 from the upper 5 cm layer of the cleaned soil surface for the bulk density measurements. Then I loosened the top 10-15 cm layer of the soil surface with spade. After the cultivation of the soil I measured the bulk density and volume of water conductivity also 3-3 repetitions. Later I performed the hydraulic conductivity (Ksat) using the TDI and bulk density measurements on undisturbed samples on a weekly basis in the study area. I illustrated the measured hydraulic conductivity and bulk density values as a function of cumulative rainfall by using simple graphical and statistical methods. The rate of the soil compaction pace was fast and smooth based on the change of the measured bulk density values. There was a steady downward trend in hydraulic conductivity parallel the compaction. The cultivation increased the hydraulic conductivity nearly fourfold compared to original, than decreased to half by 1 week. In the following the redeposition rate declined, but based on the literature data, almost 3-4 months enough to return the original state before cultivation of the soil hydraulic conductivity and bulk density values. This publication has been supported by AGRARKLIMA.2 VKSZ_12-1-2013-0034 project.

A renaissance of soaps? - How to make clear and stable solutions at neutral pH and room temperature.

PubMed

Wolfrum, Stefan; Marcus, Julien; Touraud, Didier; Kunz, Werner

2016-10-01

Soaps are the oldest and perhaps most natural surfactants. However, they lost much of their importance since "technical surfactants", usually based on sulfates or sulfonates, have been developed over the last fifty years. Indeed, soaps are pH- and salt-sensitive and they are irritant, especially to the eyes. In food emulsions, although authorized, they have a bad taste, and long-chain saturated soaps have a high Krafft temperature. We believe that most or perhaps all of these problems can be solved with modern formulation approaches. We start this paper with a short overview of our present knowledge of soaps and soap formulations. Then we focus on the problem of the lacking soap solubility at neutral pH values. For example, it is well known that with the food emulsifier sodium oleate (NaOl), clear and stable aqueous solutions can only be obtained at pH values higher than 10. A decrease in the pH value leads to turbid and unstable solutions. This effect is not compatible with the formulation of aqueous stable and drinkable formulations with neutral or even acidic pH values. However, the pH value/phase behavior of aqueous soap solutions can be altered by the addition of other surfactants. Such a surfactant can be Rebaudioside A (RebA), a steviol glycoside from the plant Stevia rebaudiana which is used as a natural food sweetener. In a recent paper, we showed the influence of RebA on the apKa value of sodium oleate in a beverage microemulsion and on its clearing temperature. In the present paper, we report on the effect of the edible bio-surfactant RebA, on the macroscopic and microscopic phase behavior of simple aqueous sodium oleate solutions at varying pH values. The macroscopic phase behavior is investigated by visual observation and turbidity measurements. The microscopic phase behavior is analyzed by acid-base titration curves, phase-contrast and electron microscopy. It turned out that even at neutral pH, aqueous NaOl/RebA solutions can be completely clear and stable for more than 50days at room temperature. This is for the first time that a long chain soap could be really solubilized in water at neutral pH at room temperature. At last, these findings were applied to prepare stable, highly translucent and drinkable aqueous solutions of omega-3-fatty acids at a pH value of 7.5. Copyright © 2016 Elsevier B.V. All rights reserved.

Pb and Cd binding to natural freshwater biofilms developed at different pH: the important role of culture pH.

PubMed

Hua, Xiuyi; Dong, Deming; Ding, Xiaoou; Yang, Fan; Jiang, Xu; Guo, Zhiyong

2013-01-01

The effects of solution pH on adsorption of trace metals to different types of natural aquatic solid materials have been studied extensively, but few studies have been carried out to investigate the effect of pH at which the solid materials were formed on the adsorption. The purpose of present study is to examine this effect of culture pH on metal adsorption to natural freshwater biofilms. The adsorption of Pb and Cd to biofilms which were developed at different culture pH values (ranging from 6.5 to 9.0) was measured at the same adsorption pH value (6.5). The culture pH had considerable effects on both composition and metal adsorption ability of the biofilms. Higher culture pH usually promoted the accumulation of organic material and Fe oxides in the biofilms. The culture pH also affected the quantity and species of algae in the biofilms. The adsorption of Pb and Cd to the biofilms generally increased with the increase of culture pH. This increase was minor at lower pH range and significant at higher pH range and was more remarkable for Cd adsorption than for Pb adsorption. The notable contribution of organic material to the adsorption at higher culture pH values was also observed. The profound impacts of culture pH on adsorption behavior of biofilms mainly resulted from the variation of total contents of the biofilm components and were also affected by the alteration of composition and properties of the components.

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.

XAFS studies of metal-ligand interactions at organic surfaces and in solution

NASA Astrophysics Data System (ADS)

Boyanov, Maxim I.

X-ray absorption fine structure spectroscopy (XAFS) was used as a structural probe to determine the mechanism of metal adsorption to organic surfaces. Two specific systems were investigated, Pb adsorption to heneicosanoic acid Langmuir monolayers (CH3(CH2)19COOH), and Cd adsorption to isolated cell walls of the Bacillus subtilis bacterium. Although the study of these systems is important for quite different reasons, the goal in both is metal binding site speciation and structural characterization of the surface complex. The adsorption of aqueous Cd to B. subtilis was studied as a function of pH by fluorescence mode bulk XAFS. Samples were prepared at six pH values in the range 3.4 to 7.8, and the bacterial functional groups responsible for the adsorption were identified under each condition. Under the experimental Cd and bacterial concentrations, the spectroscopy results indicate that Cd binds predominantly to protonated phosphoryl ligands below pH 4.4, while at higher pH adsorption to carboxyl groups becomes increasingly important. At pH 7.8 we observe the activation of an additional binding site, which we tentatively ascribe to deprotonated phosphoryl ligands. A quantitative Cd speciation diagram for the pH range is presented. Grazing-incidence Pb L3 edge XAFS was used in situ to determine the adsorption complex structure in the Pb-Langmuir monolayer study. The results indicate covalent binding of the Pb cations to the carboxyl headgroups, and the observed Pb-Pb coordination suggests that the metal is adsorbed as a hydrolysis polymer, rather than as individual Pb 2+ ions. The data suggest a bidentate binding mechanism and a one Pb atom to one carboxyl headgroup binding stoichiometry. We discuss how this adsorption model can explain the peculiarities observed with Pb in previous metal-Langmuir monolayer studies. A systematic study of the metal local environment in aqueous solutions was conducted and used in the above analyses. Perchlorate and acetate salt solutions of Cd, Pb, Mn, Cr, and Cu were characterized as standards of hydrated ions and metal-carboxyl complexes. The utility of XAFS in differentiating between the ionic, monodentate, bridging-bidentate, and bidentate metal-carboxyl complexes through C-C multiple scattering effects and XANES features is demonstrated.

Progress in Metabolic Engineering of Saccharomyces cerevisiae

PubMed Central

Nevoigt, Elke

2008-01-01

Summary: The traditional use of the yeast Saccharomyces cerevisiae in alcoholic fermentation has, over time, resulted in substantial accumulated knowledge concerning genetics, physiology, and biochemistry as well as genetic engineering and fermentation technologies. S. cerevisiae has become a platform organism for developing metabolic engineering strategies, methods, and tools. The current review discusses the relevance of several engineering strategies, such as rational and inverse metabolic engineering, evolutionary engineering, and global transcription machinery engineering, in yeast strain improvement. It also summarizes existing tools for fine-tuning and regulating enzyme activities and thus metabolic pathways. Recent examples of yeast metabolic engineering for food, beverage, and industrial biotechnology (bioethanol and bulk and fine chemicals) follow. S. cerevisiae currently enjoys increasing popularity as a production organism in industrial (“white”) biotechnology due to its inherent tolerance of low pH values and high ethanol and inhibitor concentrations and its ability to grow anaerobically. Attention is paid to utilizing lignocellulosic biomass as a potential substrate. PMID:18772282

Reuse of ultrafine mineral wool production waste in the manufacture of refractory concrete.

PubMed

Stonys, R; Kuznetsov, D; Krasnikovs, A; Škamat, J; Baltakys, K; Antonovič, V; Černašėjus, O

2016-07-01

The paper deals with the mineral wool production waste (cupola dust - CD), presents CD characterization and aims to reuse CD in production of refractory concrete with calcium aluminate cement. The study of CD covers its chemical, phase and thermal analyses along with the morphological study and determination of particles size distribution. Zeta-potential, electrical conductivity and pH values of CD suspension are presented in the paper as well. Commercial microsilica additive in refractory concrete has been replaced with cupola dust. Compositions of refractory concrete have been prepared by incorporating 1%, 2% and 3% of CD. The bulk density, ultrasonic wave velocity, cold crushing strength and thermal shock resistance of the created refractory concrete have been determined. Based on experimental results, it has been found that cupola dust may be used for the production of refractory concrete. The environmental impact related to the CD reuse in refractory concrete production has been evaluated as well. Copyright © 2016 Elsevier Ltd. All rights reserved.

Structural elucidation of potential impurities in Azilsartan bulk drug by HPLC.

PubMed

Zhou, Wentao; Zhou, Yuxia; Sun, Lili; Zou, Qiaogen; Wei, Ping; Ouyang, Pingkai

2014-01-01

During the synthesis of Azilsartan (AZS), it was speculated that 15 potential impurities would arise. This study investigated the possible mechanism for the formation of 14 of them, and their structures were characterized and confirmed by IR, NMR, and MS techniques. In addition, an efficient chromatographic method was developed to separate and quantify these impurities, using an Inertsil ODS-3 column (250 x 4.6 mm, 5 pm) in gradient mode with a mixture of acetonitrile and the potassium dihydrogen orthophosphate buffer (10 mM, pH adjusted to 3.0 with phosphoric acid). The HPLC method was validated for specificity, precision, accuracy, and sensitivity. LOQ of impurities were in the range of 1.04-2.20 ng. Correlation coefficient values of linearity were >0.9996 for AZS and its impurities. The mean recoveries of all impurities in AZS were between 93.0 and 109.7%. Thus, the validated HPLC method is suitable for the separation and quantification of all potential impurities in AZS.

African-Americans, Hispanic Americans, and non-Hispanic whites without GERD or reflux symptoms have equivalent 24-h pH esophageal acid exposure.

PubMed

Vega, Kenneth J; Langford, Tracy; Palacio, Carlos; Watts, Janet; Jamal, M Mazen

2013-12-01

Ambulatory esophageal pH monitoring is, currently, the recommended diagnostic exam for gastroesophageal reflux disease. Data are currently available for African-American (AA) and non-Hispanic white (nHw) volunteers among United States ethnic groups. The purpose of this study was to obtain normal values of 24-h esophageal pH by monitoring healthy adult Hispanic American (HA) volunteers and to compare these with values obtained from healthy AA and nHw volunteers to determine if ethnic variation exists in 24-h esophageal pH. 24-h Dual esophageal pH monitoring was performed for healthy AA, HA, and nHw. Values for total number of reflux episodes, episodes longer than 5 min, total reflux time, and longest reflux episode in the proximal and/or distal esophagus were obtained for all groups. Differences between groups were considered significant if p<0.05. One-hundred and thirty-six subjects volunteered and completed 24-h pH testing. Fifty-three were AA, 25 HA, and 58 nHw, with males accounting for 52, 47, and 47%, respectively, of each group. AA were older than nHw only and nHw had a lower body mass index than both AA and HA. Shorter study duration was observed for HA than for AA and nHw. No difference was observed between ethnic groups for any measured pH data in the proximal or distal esophagus. No difference exists in values obtained during esophageal pH monitoring among healthy AA, HA, and nHw. This indicates that currently accepted normal values of ambulatory esophageal pH monitoring can be used for all major United States ethnic groups without compromising diagnostic accuracy.

Computational Investigation of the pH Dependence of Loop Flexibility and Catalytic Function in Glycoside Hydrolases*

PubMed Central

Bu, Lintao; Crowley, Michael F.; Himmel, Michael E.; Beckham, Gregg T.

2013-01-01

Cellulase enzymes cleave glycosidic bonds in cellulose to produce cellobiose via either retaining or inverting hydrolysis mechanisms, which are significantly pH-dependent. Many fungal cellulases function optimally at pH ∼5, and their activities decrease dramatically at higher or lower pH. To understand the molecular-level implications of pH in cellulase structure, we use a hybrid, solvent-based, constant pH molecular dynamics method combined with pH-based replica exchange to determine the pKa values of titratable residues of a glycoside hydrolase (GH) family 6 cellobiohydrolase (Cel6A) and a GH family 7 cellobiohydrolase (Cel7A) from the fungus Hypocrea jecorina. For both enzymes, we demonstrate that a bound substrate significantly affects the pKa values of the acid residues at the catalytic center. The calculated pKa values of catalytic residues confirm their proposed roles from structural studies and are consistent with the experimentally measured apparent pKa values. Additionally, GHs are known to impart a strained pucker conformation in carbohydrate substrates in active sites for catalysis, and results from free energy calculations combined with constant pH molecular dynamics suggest that the correct ring pucker is stable near the optimal pH for both Cel6A and Cel7A. Much longer molecular dynamics simulations of Cel6A and Cel7A with fixed protonation states based on the calculated pKa values suggest that pH affects the flexibility of tunnel loops, which likely affects processivity and substrate complexation. Taken together, this work demonstrates several molecular-level effects of pH on GH enzymes important for cellulose turnover in the biosphere and relevant to biomass conversion processes. PMID:23504310

Cuspal Deflection of Premolars Restored with Bulk-Fill Composite Resins.

PubMed

Behery, Haytham; El-Mowafy, Omar; El-Badrawy, Wafa; Saleh, Belal; Nabih, Sameh

2016-01-01

This in vitro study compared cuspal deflection of premolars restored with three bulk-fill composite resins to that of incrementally-restored ones with a low-shrinkage silorane-based restorative material. Forty freshly-extracted intact human upper premolars were used. Reference points at buccal and palatal cusp tips were acid-etched and composite rods were horizontally bonded to them (TPH-Spectra-HV, Dentsply). Two acrylic resin guiding paths were made for each premolar to guide beaks of a digital micrometer used for cuspal deflection measurements. Standardized MOD cavities, 3 mm wide bucco-lingually and 3.5 mm deep, were prepared on each premolar. Prepared teeth were then equally divided into four groups (n = 10) and each group was assigned to one of four composite resin (QuiXX, Dentsply; X-tra fil, Voco; Tetric EvoCeram Bulk Fill, Ivoclar Vivadent; low-shrinkage Filtek LS, 3M/ESPE). Adper Single Bond-Plus, 3M/ESPE was used with all bulk-fill restoratives. LS-System Adhesive, 3M/ESPE was used with Filtek LS. For each prepared premolar, cuspal deflection was measured in microns as the difference between two readings between reference points before and after restoration completion. Means and SDs were calculated and data statistically-analyzed using One-way ANOVA and Tukey's test. Filtek LS showed the lowest mean cuspal deflection value 6.4(0.84)μm followed by Tetric EvoCeram Bulk Fill 10.1(1.2) μm and X-tra fil 12.4(1.35)μm, while QuiXX showed the highest mean 13(1.05)μm. ANOVA indicated significant difference among mean values of groups (p < 0.001). Tukey's test indicated no significant difference in mean values between QuiXX and X-tra fil (p = 0.637). Tetric EvoCeram Bulk Fill had significantly lower mean cuspal deflection compared with the two other bulk-fill composite resins tested. Filtek LS had the lowest significant mean cuspal deflection in comparison to all tested bulk-fill restoratives. The use of Tetric EvoCeram Bulk fill composite resin restorative for class II MOD cavities resulted in reduced cuspal deflection in comparison to the two other bulk-fill composite resins tested. The silorane-based Filtek LS restorative resulted in the least cuspal deflection in comparison to all tested bulk-fill composite restoratives. © 2016 Wiley Periodicals, Inc.

Effects of CO2 injection and Kerogen Maturation on Low-Field Nuclear Magnetic Resonance Response

NASA Astrophysics Data System (ADS)

Prasad, M.; Livo, K.

2017-12-01

Low-field Nuclear Magnetic Resonance (NMR) is commonly used in petrophysical analysis of petroleum reservoir rocks. NMR experiments record the relaxation and polarization of in-situ hydrogen protons present in gaseous phases such as free-gas intervals and solution gas fluids, bulk fluid phases such as oil and aquifer intervals, and immovable fractions of kerogen and bitumen. Analysis of NMR relaxation spectra is performed to record how fluid composition, maturity, and viscosity change NMR experimental results. We present T1-T2 maps as thermal maturity of a water-saturated, sub-mature Woodford shale is increased at temperatures from 125 to 400 degrees Celsius. Experiments with applied fluid pressure in paraffinic mineral oil and DI water with varying fluid pH have been performed to mimic reservoir conditions in analysis of the relaxation of bulk fluid phases. We have recorded NMR spectra, T1-T2 maps, and fluid diffusion coefficients using a low-field (2 MHz) MagritekTM NMR. CO2 was injected at a pressure of 900 psi in an in house developed NMR pressure vessel made of torlon plastic. Observable 2D NMR shifts in immature kerogen formations as thermal maturity is increased show generation of lighter oils with increased maturity. CO2 injection leads to a decrease in bulk fluid relaxation time that is attributed to viscosity modification with gas presence. pH variation with increased CO2 presence were shown to not effect NMR spectra. From this, fluid properties have been shown to greatly affect NMR readings and must be taken into account for more accurate NMR reservoir characterization.

Effect of Consuming Tea with Stevia on Salivary pH - An In Vivo Randomised Controlled Trial.

PubMed

Pallepati, Akhil; Yavagal, Puja; Veeresh, D J

To assess the effect of consuming tea with stevia on salivary pH. This randomised controlled trial employed a Latin square design. Twenty-four male students aged 20-23 years were randomly allocated to 4 different groups, 3 experimental with tea sweetened by sucrose, jaggery or stevia, and one unsweetened control. Salivary pH assessments were performed at baseline and 1 min, 20 and 60 min after consumption of the respective tea. One-way ANOVA and repeated measures ANOVA followed by Tukey's post-hoc tests were employed to analyse the data. One minute after tea consumption, the salivary pH of the sucrose group significantly decreased compared to the stevia group (p = 0.01). There was a significant difference between baseline mean salivary pH and post-interventional mean salivary pH values at all time intervals in the tea + sucrose, tea + jaggery, and plain tea groups (p < 0.01). One hour after consumption of tea, the salivary pH values reached the baseline pH in stevia and plain tea groups, but it remained lower in the sucrose and jaggery groups. The results of the present study, in which the salivary pH values returned to baseline pH 1 h after drinking stevia-sweetened tea, suggest stevia's potential as a non-cariogenic sweetener.

Quantitative Chemical Exchange Saturation Transfer MRI of Intervertebral Disc in a Porcine Model

PubMed Central

Zhou, Zhengwei; Bez, Maxim; Tawackoli, Wafa; Giaconi, Joseph; Sheyn, Dmitriy; de Mel, Sandra; Maya, Marcel M.; Pressman, Barry D.; Gazit, Zulma; Pelled, Gadi; Gazit, Dan; Li, Debiao

2017-01-01

Purpose Previous studies have associated low pH in interver-tebral discs (IVDs) with discogenic back pain. The purpose of this study was to determine whether quantitative CEST (qCEST) MRI can be used to detect pH changes in IVDs in vivo. Methods The exchange rate ksw between glycosaminoglycan (GAG) protons and water protons was determined from qCEST analysis. Its dependence on pH value was investigated in GAG phantoms with varying pH and concentrations. The relationship between ksw and pH was studied further in vivo in a porcine model on a 3T MR scanner and validated using a pH meter. Sodium lactate was injected into the IVDs to induce various pH values within the discs ranging from 5 to 7. Results Phantom and animal results revealed that ksw measured using qCEST MRI is highly correlated with pH level. In the animal studies, the relationship can be described as ksw =9.2 × 106 × 10−pH + 196.9, R2 = 0.7883. Conclusion The exchange rate between GAG and water protons determined from qCEST MRI is closely correlated with pH value. This technique has the potential to noninvasively measure pH in the IVDs of patients with discogenic pain. PMID:27670140

Effects of different annealing atmospheres on the properties of cadmium sulfide thin films

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

Yücel, E., E-mail: dr.ersinyucel@gmail.com; Kahraman, S.; Güder, H.S.

2015-08-15

Graphical abstract: The effects of different annealing atmospheres (air and sulfur) on the structural, morphological and optical properties of CdS thin films were studied at three different pH values. - Highlights: • Compactness and smoothness of the films were enhanced after sulfur annealing. • Micro-strain values of some films were improved after sulfur annealing. • Dislocation density values of some films were improved after sulfur annealing. • Band gap values of the films were improved after sulfur annealing. - Abstract: Cadmium sulfide (CdS) thin films were prepared on glass substrates by using chemical bath deposition (CBD) technique. The effects ofmore » different annealing atmospheres (air and sulfur) on the structural, morphological and optical properties of CdS thin films were studied at three different pH values. Compactness and smoothness of the films (especially for pH 10.5 and 11) enhanced after sulfur annealing. pH value of the precursor solution remarkably affected the roughness, uniformity and particle sizes of the films. Based on the analysis of X-ray diffraction (XRD) patterns of the films, micro-strain and dislocation density values of the sulfur-annealed films (pH 10.5 and 11) were found to be lower than those of air-annealed films. Air-annealed films (pH 10.5, 11 and 11.5) exhibited higher transmittance than sulfur-annealed films in the wavelength region of 550–800 nm. Optical band gap values of the films were found between 2.31 eV and 2.36 eV.« less

Secondary elements of blood pH variation can influence the effort effectiveness based on adaptive changes within a group of elite athletes.

PubMed

Martin, Ştefan Adrian; Tomescu, Valeriu; Voidăzan, Septimiu

2016-01-01

pH is the direct indicator of the body reaction following the activities performed. Establishing precise correlations between pH and blood biochemical parameters might support the balancing of values during periods of marked physical activity. We conducted a case study in a group of elite rowers. Twelve athletes were included in the study. Monitoring was carried out by collecting biological samples several times a day: in the morning, 80 minutes pre-workout, 12 hours after the last physical effort performed, at two different times, 10 days apart. Determinations were aimed at adapting the reported biochemical parameters depending on the effort performed. The following parameters were monitored: pH, HCO3, pCO2, pO2, BE, SBE, SBC, Ca++, Mg++, LDH, GPT, T-Pro, and Alb. The mean value of pH found in athletes was 7.41±0.024. The value obtained was significantly correlated to biochemical parameters such as BE (2.32±1.79), SBC (1.67±1.45), SBE (2.70±1.75). However, bicarbonate (HCO3) was statistically significantly related with SBE, SBC, SBE, and pO2, but did not present a strong association with the pH value (p=0.094). However, values such as Alb, Ca++, LDH, BE, SBC are related to pH value as a result of variations in the data submitted. The processed data evidence the fact that blood pH, in this case, is significantly influenced by a number of indices that correlate energy system activity, individual adaptation to effort, and the recovery process. The parameters under investigation (SBE, SBC, SBE, CPK, LDH) are associated with pH changes that could confirm the recovery efficiency of the athlete, along with a possible metabolic acidosis/alkalosis.

Coral-algae metabolism and diurnal changes in the CO2-carbonate system of bulk sea water.

PubMed

Jokiel, Paul L; Jury, Christopher P; Rodgers, Ku'ulei S

2014-01-01

Precise measurements were conducted in continuous flow seawater mesocosms located in full sunlight that compared metabolic response of coral, coral-macroalgae and macroalgae systems over a diurnal cycle. Irradiance controlled net photosynthesis (P net), which in turn drove net calcification (G net), and altered pH. P net exerted the dominant control on [CO3 (2-)] and aragonite saturation state (Ωarag) over the diel cycle. Dark calcification rate decreased after sunset, reaching zero near midnight followed by an increasing rate that peaked at 03:00 h. Changes in Ωarag and pH lagged behind G net throughout the daily cycle by two or more hours. The flux rate P net was the primary driver of calcification. Daytime coral metabolism rapidly removes dissolved inorganic carbon (DIC) from the bulk seawater and photosynthesis provides the energy that drives G net while increasing the bulk water pH. These relationships result in a correlation between G net and Ωarag, with Ωarag as the dependent variable. High rates of H(+) efflux continued for several hours following mid-day peak G net suggesting that corals have difficulty in shedding waste protons as described by the Proton Flux Hypothesis. DIC flux (uptake) followed P net and G net and dropped off rapidly following peak P net and peak G net indicating that corals can cope more effectively with the problem of limited DIC supply compared to the problem of eliminating H(+). Over a 24 h period the plot of total alkalinity (AT ) versus DIC as well as the plot of G net versus Ωarag revealed a circular hysteresis pattern over the diel cycle in the coral and coral-algae mesocosms, but not the macroalgae mesocosm. Presence of macroalgae did not change G net of the corals, but altered the relationship between Ωarag and G net. Predictive models of how future global changes will effect coral growth that are based on oceanic Ωarag must include the influence of future localized P net on G net and changes in rate of reef carbonate dissolution. The correlation between Ωarag and G net over the diel cycle is simply the response of the CO2-carbonate system to increased pH as photosynthesis shifts the equilibria and increases the [CO3 (2-)] relative to the other DIC components of [HCO3 (-)] and [CO2]. Therefore Ωarag closely tracked pH as an effect of changes in P net, which also drove changes in G net. Measurements of DIC flux and H(+) flux are far more useful than concentrations in describing coral metabolism dynamics. Coral reefs are systems that exist in constant disequilibrium with the water column.

Coral-algae metabolism and diurnal changes in the CO2-carbonate system of bulk sea water

PubMed Central

Jury, Christopher P.; Rodgers, Ku’ulei S.

2014-01-01

Precise measurements were conducted in continuous flow seawater mesocosms located in full sunlight that compared metabolic response of coral, coral-macroalgae and macroalgae systems over a diurnal cycle. Irradiance controlled net photosynthesis (Pnet), which in turn drove net calcification (Gnet), and altered pH. Pnet exerted the dominant control on [CO32−] and aragonite saturation state (Ωarag) over the diel cycle. Dark calcification rate decreased after sunset, reaching zero near midnight followed by an increasing rate that peaked at 03:00 h. Changes in Ωarag and pH lagged behind Gnet throughout the daily cycle by two or more hours. The flux rate Pnet was the primary driver of calcification. Daytime coral metabolism rapidly removes dissolved inorganic carbon (DIC) from the bulk seawater and photosynthesis provides the energy that drives Gnet while increasing the bulk water pH. These relationships result in a correlation between Gnet and Ωarag, with Ωarag as the dependent variable. High rates of H+ efflux continued for several hours following mid-day peak Gnet suggesting that corals have difficulty in shedding waste protons as described by the Proton Flux Hypothesis. DIC flux (uptake) followed Pnet and Gnet and dropped off rapidly following peak Pnet and peak Gnet indicating that corals can cope more effectively with the problem of limited DIC supply compared to the problem of eliminating H+. Over a 24 h period the plot of total alkalinity (AT) versus DIC as well as the plot of Gnet versus Ωarag revealed a circular hysteresis pattern over the diel cycle in the coral and coral-algae mesocosms, but not the macroalgae mesocosm. Presence of macroalgae did not change Gnet of the corals, but altered the relationship between Ωarag and Gnet. Predictive models of how future global changes will effect coral growth that are based on oceanic Ωarag must include the influence of future localized Pnet on Gnet and changes in rate of reef carbonate dissolution. The correlation between Ωarag and Gnet over the diel cycle is simply the response of the CO2-carbonate system to increased pH as photosynthesis shifts the equilibria and increases the [CO32−] relative to the other DIC components of [HCO3−] and [CO2]. Therefore Ωarag closely tracked pH as an effect of changes in Pnet, which also drove changes in Gnet. Measurements of DIC flux and H+ flux are far more useful than concentrations in describing coral metabolism dynamics. Coral reefs are systems that exist in constant disequilibrium with the water column. PMID:24883243

[Degradation kinetics of chlorogenic acid, cryptochlorogenic acid, and neochlorogenic acid at neutral and alkaline pH values].

PubMed

Zhu, Peng; Miao, Xiao-lei; Chen, Yong

2016-01-01

The degradation kinetics of chlorogenic acid (5-CQA), cryptochlorogenic acid (4-CQA), and neochlorogenic acid (3-CQA) in aqueous solution at 37 degrees C and different pH values (7.05, 7.96, 9.25) were investigated in the present work. The results indicated that 3-, 4- and 5-CQA tended to remain stable in acidic pH circumstance, and unstable in neutral and alkaline pH circumstance. With the increase of the alkalinity, the degradation of 3-, 4- and 5-CQA was increased leading to a less amount of total CQA and was satisfactorily described by the Weibull equation. Meanwhile, caffeic acid was not detected after the degradation of CQA. Moreover, the degradation of 3-CQA and 5-CQA tended to be converted to 4-CQA, and the degradation of 4-CQA tended to be converted to 3-CQA rather than 5-CQA. The comparison of the degradation kinetics parameters of 3-, 4- and 5-CQA at neutral and alkaline pH values showed that the orders of the rate constant (k) values were 4-CQA > 3-CQA > 5-CQA, while the orders of the degradation half life (t½) values were 4-CQA < 3-CQA < 5-CQA, indicating the orders of the stabilities of 3-, 4- and 5-CQA at 37 degrees C and neutral and alkaline pH values were 4-CQA < 3-CQA < 5-CQA.

Spectrophotometric analysis of flavonoid-DNA binding interactions at physiological conditions

NASA Astrophysics Data System (ADS)

Janjua, Naveed Kausar; Siddiqa, Asima; Yaqub, Azra; Sabahat, Sana; Qureshi, Rumana; Haque, Sayed ul

2009-12-01

Mode of interactions of three flavonoids [morin (M), quercetin (Q), and rutin (R)] with chicken blood ds.DNA (ck.DNA) has been investigated spectrophotometrically at different temperatures including body temperature (310 K) and at two physiological pH values, i.e. 7.4 (human blood pH) and 4.7 (stomach pH). The binding constants, Kf, evaluated using Benesi-Hildebrand equation showed that the flavonoids bind effectively through intercalation at both pH values and body temperature. Quercetin, somehow, showed greater binding capabilities with DNA. The free energies of flavonoid-DNA complexes indicated the spontaneity of their binding. The order of binding constants of three flavonoids at both pH values were found to be Kf(Q) > Kf(R) > Kf(M) and at 310 K.

Effect of increasing the colloidal calcium phosphate of milk on the texture and microstructure of yogurt.

PubMed

Ozcan, T; Horne, D; Lucey, J A

2011-11-01

The effect of increasing the colloidal calcium phosphate (CCP) content on the physical, rheological, and microstructural properties of yogurt was investigated. The CCP content of heated (85°C for 30 min) milk was increased by increasing the pH by the addition of alkali (NaOH). Alkalized milk was dialyzed against pasteurized skim milk at approximately 4°C for 72 h to attempt to restore the original pH and soluble Ca content. By adjustment of the milk to pH values 7.45, 8.84, 10.06, and 10.73, the CCP content was increased to approximately 107, 116, 123, and 128%, respectively, relative to the concentration in heated milk. During fermentation of milk, the storage modulus (G') and loss tangent values of yogurts were measured using dynamic oscillatory rheology. Large deformation rheological properties were also measured. The microstructure of yogurt was observed using fluorescence microscopy, and whey separation was determined. Acid-base titration was used to evaluate changes in the CCP content in milk. Total Ca and casein-bound Ca increased with an increase in the pH value of alkalization. During acidification, elevated buffering occurred in milk between pH values 6.7 to 5.2 with an increase in the pH of alkalization. When acidified milk was titrated with alkali, elevated buffering occurred in milk between pH values 5.6 to 6.4 with an increase in the pH of alkalization. The high residual pH of milk after dialysis could be responsible for the decreased contents of soluble Ca in these milks. The pH of gelation was higher in all dialyzed samples compared with the heated control milk, and the gelation pH was higher with an increase in CCP content. The sample with highest CCP content (128%) exhibited gelation at very high pH (6.3), which could be due to alkali-induced CN micellar disruption. The G' values at pH 4.6 were similar in gels with CCP levels up to 116%; at higher CCP levels, the G' values at pH 4.6 greatly decreased. Loss tangent values at pH 5.1 were similar in all samples except in gels with a CCP level of 128%. For dialyzed milk, the whey separation levels were similar in gels made from milk with up to 107% CCP but increased at higher CCP levels. Microstructure of yogurt gels made from milk with 100 to 107% CCP was similar but very large clusters were observed in gels made from milk with higher CCP levels. By dialyzing heated milk against pasteurized milk, we may have retained some heat-induced Ca phosphate on micelles that normally dissolves on cooling because, during dialysis, pasteurized milk provided soluble Ca ions to the heated milk system. Yogurt texture was significantly affected by increasing the casein-bound Ca (and total Ca) content of milk as well as by the alkalization procedure involved in that approach. Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Functional and rheological properties of proteins in frozen turkey breast meat with different ultimate pH.

PubMed

Chan, J T Y; Omana, D A; Betti, M

2011-05-01

Functional and rheological properties of proteins from frozen turkey breast meat with different ultimate pH at 24 h postmortem (pH(24)) have been studied. Sixteen breast fillets from Hybrid Tom turkeys were initially selected based on lightness (L*) values for each color group (pale, normal, and dark), with a total of 48 breast fillets. Further selection of 8 breast samples was made within each class of meat according to the pH(24). The average L* and pH values of the samples were within the following range: pale (L* >52; pH ≤5.7), normal (46 < L* < 52; 5.9 < pH <6.1), and dark (L* <46; pH ≥6.3), referred to as low, normal, and high pH meat, respectively. Ultimate pH did not cause major changes in the emulsifying and foaming properties of the extracted sarcoplasmic and myofibrillar proteins. An SDS-PAGE profile of proteins from low and normal pH meat was similar, which revealed that the extent of protein denaturation was the same. Low pH meat had the lowest water-holding capacity compared with normal and high pH meat as shown by the increase in cooking loss, which can be explained by factors other than protein denaturation. Gel strength analysis and folding test revealed that gel-forming ability was better for high pH meat compared with low and normal pH meat.Dynamic viscoelastic behavior showed that myosin denaturation temperature was independent of pH(24). Normal and high pH meat had similar hardness, springiness, and chewiness values as revealed by texture profile analysis. The results from this study indicate that high pH meat had similar or better functional properties than normal pH meat. Therefore, high pH meat is suitable for further processed products, whereas low pH meat may need additional treatment or ingredient formulations to improve its functionality.

The Effect of pH on Slurry Erosion-Corrosion of Tungsten Carbide Overlays Alloyed with Ru

NASA Astrophysics Data System (ADS)

Nelwalani, Ndivhuwo B.; van der Merwe, Josias W.

2018-02-01

The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion-corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion-corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion-corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

Protonation of carboxyl groups in EuDOTA-tetraamide complexes results in catalytic prototropic exchange and quenching of the CEST signal

NASA Astrophysics Data System (ADS)

Zhang, Lei; Evbuomwan, Osasere M.; Tieu, Michael; Zhao, Piyu; Martins, Andre F.; Sherry, A. Dean

2017-10-01

The CEST properties of EuDOTA-tetraamide complexes bearing pendant carboxylate and carboxyl ethyl esters were measured as a function of pH. The CEST signal from the Eu3+-bound water molecule decreased in intensity between pH 8.5 and 4.5 while the proton exchange rates (kex) increased over this same pH range. In comparison, the CEST signal in the corresponding carboxyl ester derivatives was nearly constant. Both observations are consistent with stepwise protonation of the four carboxylic acid groups over this same pH range. This indicates that negative charges on the carboxyl groups above pH 6 facilitate the formation of a strong hydrogen-bonding network in the coordination second sphere above the single Eu3+-bound water molecule, thereby decreasing prototropic exchange of protons on the bound water molecule with bulk water protons. The percentage of square antiprismatic versus twisted square antiprism coordination isomers also decreased as the appended carboxylic acid groups were positioned further away from the amide. The net effect of lowering the pH was an overall increase in kex and a quenching of the CEST signal. This article is part of the themed issue 'Challenges for chemistry in molecular imaging'.

Extracellular pH regulation in microdomains of colonic crypts: effects of short-chain fatty acids.

PubMed Central

Chu, S; Montrose, M H

1995-01-01

It has been suggested that transepithelial gradients of short-chain fatty acids (SCFAs; the major anions in the colonic lumen) generate pH gradients across the colonic epithelium. Quantitative confocal microscopy was used to study extracellular pH in mouse distal colon with intact epithelial architecture, by superfusing tissue with carboxy SNARF-1 (a pH-sensitive fluorescent dye). Results demonstrate extracellular pH regulation in two separate microdomains surrounding colonic crypts: the crypt lumen and the subepithelial tissue adjacent to crypt colonocytes. Apical superfusion with (i) a poorly metabolized SCFA (isobutyrate), (ii) an avidly metabolized SCFA (n-butyrate), or (iii) a physiologic mixture of acetate/propionate/n-butyrate produced similar results: alkalinization of the crypt lumen and acidification of subepithelial tissue. Effects were (i) dependent on the presence and orientation of a transepithelial SCFA gradient, (ii) not observed with gluconate substitution, and (iii) required activation of sustained vectorial acid/base transport by SCFAs. Results suggest that the crypt lumen functions as a pH microdomain due to slow mixing with bulk superfusates and that crypts contribute significant buffering capacity to the lumen. In conclusion, physiologic SCFA gradients cause polarized extracellular pH regulation because epithelial architecture and vectorial transport synergize to establish regulated microenvironments. Images Fig. 1 Fig. 3 PMID:7724557

Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete

NASA Astrophysics Data System (ADS)

Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

2015-12-01

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl-]/[OH-] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

Self-immunity microcapsules for corrosion protection of steel bar in reinforced concrete.

PubMed

Wang, Yanshuai; Fang, Guohao; Ding, Weijian; Han, Ningxu; Xing, Feng; Dong, Biqin

2015-12-17

A novel microcapsule-based self-immunity system for reinforced concrete is proposed. Its feasibility for hindering the corrosion of steel rebar by means of lifting the threshold value of [Cl(-)]/[OH(-)] is discussed. Precisely controlled release behavior enables corrosion protection in the case of depassivation. The release process is characterized over a designated range of pH values, and its release characteristics of the microcapsules, triggered by decreasing pH value, are captured by observing that the core crystals are released when exposed to a signal (stimulus). The aim of corrosion protection of steel bar is achieved through the constantly-stabilized passive film, and its stability is promoted using continuous calcium hydroxide released from the microcapsule, restoring alkaline conditions. The test results exhibited that the release process of the microcapsules is a function of time. Moreover, the release rate of core materials could interact with environmental pH value, in which the release rate is found to increase remarkably with decreasing pH value, but is inhibited by high pH levels.

Luminescence materials for pH and oxygen sensing in microbial cells - structures, optical properties, and biological applications.

PubMed

Zou, Xianshao; Pan, Tingting; Chen, Lei; Tian, Yanqing; Zhang, Weiwen

2017-09-01

Luminescence including fluorescence and phosphorescence sensors have been demonstrated to be important for studying cell metabolism, and diagnosing diseases and cancer. Various design principles have been employed for the development of sensors in different formats, such as organic molecules, polymers, polymeric hydrogels, and nanoparticles. The integration of the sensing with fluorescence imaging provides valuable tools for biomedical research and applications at not only bulk-cell level but also at single-cell level. In this article, we critically reviewed recent progresses on pH, oxygen, and dual pH and oxygen sensors specifically for their application in microbial cells. In addition, we focused not only on sensor materials with different chemical structures, but also on design and applications of sensors for better understanding cellular metabolism of microbial cells. Finally, we also provided an outlook for future materials design and key challenges in reaching broad applications in microbial cells.

Possibilities of new materials surface sensibility express determination based on ZnSe-CdS system by pH isoelectric state measurements of the surface state

NASA Astrophysics Data System (ADS)

Kirovskaya, I. A.; Mironova, E. V.; Ushakov, O. V.; Nor, P. E.; Yureva, A. V.; Matyash, Yu I.

2018-01-01

A method for determining the hydrogen index of the surfaces isoelectric state (pHiso) at various gases pressures -possible components of the surrounding and technological media has been developed. With its use, changes in pH of binary and more complex semiconductors-components of the new system-ZnSe-CdS under the influence of nitrogen dioxide-have been found. The limiting sensitivity of surfaces - minimum PNO2, causing a change in pH has been estimated. The most active components of ZnSe-CdS system, recommended as materials for measuring cells of NO2, have been revealed. The relationship between the changing patterns with the composition of surface (acid-base) and bulk (in particular, theoretical calculated crystal density) properties has been established, allowing to find the most effective materials for sensor technology and for semiconductor analysis.

The origin of organic matter in the Martian meteorite ALH84001.

PubMed

Becker, L; Popp, B; Rust, T; Bada, J L

1999-01-01

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common carbon sources on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars.

The origin of organic matter in the Martian meteorite ALH84001.

PubMed

Becker, L; Popp, B; Rust, T; Bada, J L

1999-03-30

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common sources of carbon on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery, of meteoritic or cometary debris to the surface of Mars.

Gallic Acid Grafted Chitosan Has Enhanced Oxidative Stability in Bulk Oils.

PubMed

Gim, Seo Yeong; Hong, Seungmi; Kim, Mi-Ja; Lee, JaeHwan

2017-07-01

Gallic acid (GA) was grafted in chitosan and the effects of GA grafted chitosan (GA-g-CS) on the oxidative stability in bulk oil was tested at 60 and 140 °C. To text oxidative stability in oils, headspace oxygen content, conjugated dienoic acid (CDA) value, p-anisidine value (p-AV), and acid value were determined. Chitosan itself did not show antioxidative or prooxidative effects in oils at 60 °C. However, GA-g-CS and GA acted as antioxidants at 60 °C. At 140 °C heating with moisture supplied condition, different results were observed. GA-g-CS acted as antioxidants based on the results of CDA and p-AV. However, chitosan showed the highest oxidative stability based on results of acid value and brown color formation at 140 °C. This could be due to reduction of moisture content by chitosan. GA was continuously released from GA-g-CS in bulk oil. This might have provided extra antioxidant activities to oils. © 2017 Institute of Food Technologists®.

Langasite, langanite, and langatate bulk-wave Y-cut resonators.

PubMed

Smythe, R C; Helmbold, R C; Hague, G E; Snow, K A

2000-01-01

Materials in the langasite family are of current interest for both bulk wave and surface wave devices. Piano-convex Y-cut bulk wave resonators have been built and tested on overtones 1 through 9 using LGS (langasite; La(3)Ga(5)SiO(14)), LGN (langanite; La(3)Ga(5.5)Nb(0.5)O(14)), and LGT (langatate; La(3)Ga(5.5)Ta(5.5)O(14)). Frequencies and motional inductances are compared with calculated values, with good agreement except for the motional inductance of LGT. For all three materials, frequency variation is an essentially parabolic function of temperature. For LGN and LGT, reported values of the Q-frequency product are significantly above the classical limit for AT-cut quartz. A maximum 4 f value of 25.6x10(6), where frequency is in megahertz;, was observed for an LGT resonator; for an unplated resonator, 29.2x10(6) was measured. Still higher values are believed possible.

Dipstick Spot urine pH does not accurately represent 24 hour urine PH measured by an electrode.

PubMed

Omar, Mohamed; Sarkissian, Carl; Jianbo, Li; Calle, Juan; Monga, Manoj

2016-01-01

To determine whether spot urine pH measured by dipstick is an accurate representation of 24 hours urine pH measured by an electrode. We retrospectively reviewed urine pH results of patients who presented to the urology stone clinic. For each patient we recorded the most recente pH result measured by dipstick from a spot urine sample that preceded the result of a 24-hour urine pH measured by the use of a pH electrode. Patients were excluded if there was a change in medications or dietary recommendations or if the two samples were more than 4 months apart. A difference of more than 0.5 pH was considered na inaccurate result. A total 600 patients were retrospectively reviewed for the pH results. The mean difference in pH between spot urine value and the 24 hours collection values was 0.52±0.45 pH. Higher pH was associated with lower accuracy (p<0.001). The accuracy of spot urine samples to predict 24-hour pH values of <5.5 was 68.9%, 68.2% for 5.5 to 6.5 and 35% for >6.5. Samples taken more than 75 days apart had only 49% the accuracy of more recent samples (p<0.002). The overall accuracy is lower than 80% (p<0.001). Influence of diurnal variation was not significant (p=0.588). Spot urine pH by dipstick is not an accurate method for evaluation of the patients with urolithiasis. Patients with alkaline urine are more prone to error with reliance on spot urine pH.

The influence of the kinetics of self-assembly on the properties of dipeptide hydrogels.

PubMed

Cardoso, Andre Zamith; Alvarez, Ana Estefania Alvarez; Cattoz, Beatrice N; Griffiths, Peter C; King, Stephen M; Frith, William J; Adams, Dave J

2013-01-01

We discuss the effect of the kinetics of pH change on the mechanical properties of dipeptide hydrogels. Data from other peptide-based low molecular weight gelator (LMWG) systems suggest that the rheological properties are often highly dependent on the assembly rate. To examine kinetics here, we have used the hydrolysis of glucono-8-lactone (GdL). The hydrolysis of GdL to gluconic acid results in a decrease in pH, the rate of which is temperature sensitive. Hence, we can adjust the rate of pH decrease, whilst achieving the same absolute final pH. Our data shows that at all temperatures the rheological profile is very similar, with an increase to a plateau, followed by a second increase in moduli, despite very different kinetics of assembly. Surprisingly, the final mechanical properties are very similar in all cases. We also show that the structures formed at the plateau can be accessed by adjusting the pH using CO2. By carefully balancing the pKa. of the gelator with the pH achievable using CO2, flexible hydrogel membranes can be formed as opposed to a bulk gel. The rheological characteristics of the membranes are typical of a highly entangled polymer network. These membranes can be rigidified by post-addition of GdL to further lower the pH.

Determination of Acidity in Donor Milk.

PubMed

Escuder-Vieco, Diana; Vázquez-Román, Sara; Sánchez-Pallás, Juan; Ureta-Velasco, Noelia; Mosqueda-Peña, Rocío; Pallás-Alonso, Carmen Rosa

2016-11-01

There is no uniformity among milk banks on milk acceptance criteria. The acidity obtained by the Dornic titration technique is a widely used quality control in donor milk. However, there are no comparative data with other acidity-measuring techniques, such as the pH meter. The objective of this study was to assess the correlation between the Dornic technique and the pH measure to determine the pH cutoff corresponding to the Dornic degree limit value used as a reference for donor milk quality control. Fifty-two human milk samples were obtained from 48 donors. Acidity was measured using the Dornic method and pH meter in triplicate. Statistical data analysis to estimate significant correlations between variables was carried out. The Dornic acidity value that led to rejecting donor milk was ≥ 8 Dornic degrees (°D). In the evaluated sample size, Dornic acidity measure and pH values showed a statistically significant negative correlation (τ = -0.780; P = .000). A pH value of 6.57 corresponds to 8°D and of 7.12 to 4°D. Donor milk with a pH over 6.57 may be accepted for subsequent processing in the milk bank. Moreover, the pH measurement seems to be more useful due to certain advantages over the Dornic method, such as objectivity, accuracy, standardization, the lack of chemical reagents required, and the fact that it does not destroy the milk sample.

Observations on the influence of water and soil pH on the persistence of insecticides.

PubMed

Chapman, R A; Cole, C M

1982-01-01

The pH-disappearance rate profiles were determined at ca. 25 degrees C for 24 insecticides at 4 or 5 pH values over the range 4.5 to 8.0 in sterile phosphate buffers prepared in water-ethanol (99:1 v/v). Half-lives measured at pH 8 were generally smaller than at lower pH values. Changes in half lives between pH 8.0 and 4.5 were largest (greater than 1000x) for the aryl carbamates, carbofuran and carbaryl, the oxime carbamate, oxamyl, and the organophosphorus insecticide, trichlorfon. In contrast, half lives of phorate, terbufos, heptachlor, fensulfothion and aldicarb were affected only slightly by pH changes. Under the experimental conditions described half lives at pH8 varied from 1-2 days for trichlorfon and oxamyl to greater than 1 year for fensulfothion and cypermethrin. Insecticide persistence on alumina (acid, neutral and basic), mineral soils amended with aluminum sulfate or calcium hydroxide to different pH values and four natural soils of different pH was examined. No correlation was observed between the measured pH of these solids and the rate of disappearance of selected insecticides applied to them. These observations demonstrate the difficulty of extrapolating the pH dependent disappearance behaviour observed in homogeneous solution to partially solid heterogeneous systems such as soil.

Evaluation of red cell distribution width in dogs with pulmonary hypertension.

PubMed

Swann, James W; Sudunagunta, Siddharth; Covey, Heather L; English, Kate; Hendricks, Anke; Connolly, David J

2014-12-01

To compare red cell distribution width (RDW) between dogs with different causes of pulmonary hypertension (PH) and a control dog population to determine whether RDW was correlated with severity of PH as measured by echocardiography. A further aim was to determine the prognostic significance of increased RDW for dogs with PH. Forty-four client-owned dogs with PH and 79 control dogs presented to a single tertiary referral institution. Signalment, clinical pathological and echocardiographic data were obtained retrospectively from the medical records of dogs with PH, and RDW measured on a Cell-Dyn 3500 was compared between dogs with pre- and post-capillary PH and a control population. Referring veterinary surgeons were contacted for follow-up information and Kaplan-Meier analysis was conducted to investigate differences in survival time between affected dogs with different RDW values. The RDW was significantly greater in dogs with pre-capillary PH compared to control dogs. There was no difference in median survival times between dogs with PH divided according to RDW values. The RDW was positively correlated with mean corpuscular volume and haematocrit in dogs with PH, but did not correlate with echocardiographic variables. An association was found between dogs with PH and increased RDW; however there was considerable overlap in values between control dogs and dogs with PH. The RDW was not associated with survival in this study. Copyright © 2014 Elsevier B.V. All rights reserved.

Magnetic precipitate separation for Ni plating waste liquid using HTS bulk magnets

NASA Astrophysics Data System (ADS)

Oka, T.; Kimura, T.; Mimura, D.; Fukazawa, H.; Fukui, S.; Ogawa, J.; Sato, T.; Ooizumi, M.; Yokoyama, K.; Tsujimura, M.; Terasawa, T.

2013-01-01

The magnetic separation experiment for recycling the nickel-bearing precipitates in the waste liquid from the electroless plating processes has been practically conducted under the high gradient magnetic separation technique with use of the face-to-face HTS bulk magnet system. A couple of facing magnetic poles containing Sm123 bulk superconductors were activated through the pulsed field magnetization process to 1.86 T at 38 K and 2.00 T at 37 K, respectively. The weakly magnetized metallic precipitates of Ni crystals and Ni-P compounds deposited from the waste solution after heating it and pH controlling. The high gradient magnetic separation technique was employed with the separation channels filled with the stainless steel balls with dimension of 1 and 3 mm in diameter, which periodically moved between and out of the facing magnetic poles. The Ni-bearing precipitates were effectively attracted to the magnetized ferromagnetic balls. We have succeeded in obtaining the separation ratios over 90% under the flow rates less than 1.35 L/min.

Co-composting of vegetable wastes and carton: Effect of carton composition and parameter variations.

PubMed

Rawoteea, Soonita Anjeena; Mudhoo, Ackmez; Kumar, Sunil

2017-03-01

The aim of the study was to investigate the effects of carton in the composting process of mixed vegetable wastes using an experimental composter of capacity 80L. Three different mixes were set-up (Mixes 1, 2 and 3) which consisted of vegetable wastes, 2.0kg paper and bulking agents, vegetable wastes, 1.5kg carton and bulking agents, vegetable wastes, 4.5kg carton and bulking agents, respectively. Temperature evolution, pH trends, moisture levels, respiration rates, percentage volatile solids and electrical conductivity were monitored for a period of 50days. The system remained under thermophilic conditions for a very short period due to the small size of the reactor. The three mixes did not exceed a temperature of 55°C, where sanitization takes place by the destruction of pathogens. The highest peak of CO 2 evolution was observed in Mix 2 indicating that maximum microbial degradation took place in that mix. Copyright © 2016. Published by Elsevier Ltd.

Improving the Accuracy of Satellite Sea Surface Temperature Measurements by Explicitly Accounting for the Bulk-Skin Temperature Difference

NASA Technical Reports Server (NTRS)

Castro, Sandra L.; Emery, William J.

2002-01-01

The focus of this research was to determine whether the accuracy of satellite measurements of sea surface temperature (SST) could be improved by explicitly accounting for the complex temperature gradients at the surface of the ocean associated with the cool skin and diurnal warm layers. To achieve this goal, work centered on the development and deployment of low-cost infrared radiometers to enable the direct validation of satellite measurements of skin temperature. During this one year grant, design and construction of an improved infrared radiometer was completed and testing was initiated. In addition, development of an improved parametric model for the bulk-skin temperature difference was completed using data from the previous version of the radiometer. This model will comprise a key component of an improved procedure for estimating the bulk SST from satellites. The results comprised a significant portion of the Ph.D. thesis completed by one graduate student and they are currently being converted into a journal publication.

Association of the anti-tuberculosis drug rifampicin with a PAMAM dendrimer.

PubMed

Bellini, Reinaldo G; Guimarães, Ana P; Pacheco, Marco A C; Dias, Douglas M; Furtado, Vanessa R; de Alencastro, Ricardo B; Horta, Bruno A C

2015-07-01

The association of the anti-tuberculosis drug rifampicin (RIF) with a 4th-generation poly(amidoamine) (G4-PAMAM) dendrimer was investigated by means of molecular dynamics simulations. The RIF load capacity was estimated to be around 20 RIF per G4-PAMAM at neutral pH. The complex formed by 20 RIF molecules and the dendrimer (RIF20-PAMAM) was subjected to 100 ns molecular dynamics (MD) simulations at two different pH conditions (neutral and acidic). The complex was found to be significantly more stable in the simulation at neutral pH compared to the simulation at low pH in which the RIF molecules were rapidly and almost simultaneously expelled to the solvent bulk. The high stability of the RIF-PAMAM complex under physiological pH and the rapid release of RIF molecules under acidic medium provide an interesting switch for drug targeting since the Mycobacterium resides within acidic domains of the macrophage. Altogether, these results suggest that, at least in terms of stability and pH-dependent release, PAMAM-like dendrimers may be considered suitable drug delivery systems for RIF and derivatives. Copyright © 2015 Elsevier Inc. All rights reserved.

Control of the microstructure and surface chemistry of graphene aerogels via pH and time manipulation by a hydrothermal method.

PubMed

García-Bordejé, E; Víctor-Román, S; Sanahuja-Parejo, O; Benito, A M; Maser, W K

2018-02-15

Three-dimensional graphene aerogels of controlled pore size have emerged as an important platform for several applications such as energy storage or oil-water separation. The aerogels of reduced graphene oxide are mouldable and light weight, with a porosity up to 99.9%, consisting mainly of macropores. Graphene aerogel preparation by self-assembly in the liquid phase is a promising strategy due to its tunability and sustainability. For graphene aerogels prepared by a hydrothermal method, it is known that the pH value has an impact on their properties but it is unclear how pH affects the auto-assembly process leading to the final properties. We have monitored the time evolution of the chemical and morphological properties of aerogels as a function of the initial pH value. In the hydrothermal treatment process, the hydrogel is precipitated earlier and with lower oxygen content for basic pH values (∼13 wt% O) than for acidic pH values (∼20 wt% O). Moreover, ∼7 wt% of nitrogen is incorporated on the graphene nanosheets at basic pH generated by NH 3 addition. To our knowledge, there is no precedent showing that the pH value affects the microstructure of graphene nanosheets, which become more twisted and bent for the more intensive deoxygenation occurring at basic pH. The bent nanosheets attained at pH = 11 reduce the stacking by the basal planes and they connect via the borders, hence leading eventually to higher pore volumes. In contrast, the flatter graphene nanosheets attained under acidic pH entail more stacking and higher oxygen content after a long hydrothermal treatment. The gravimetric absorption capacity of non-polar solvents scales directly with the pore volume. The aerogels have proved to be highly selective, recyclable and robust for the absorption of nonpolar solvents in water. The control of the porous structure and surface chemistry by manipulation of pH and time will also pave the way for other applications such as supercapacitors or batteries.

Intra-shell boron isotope ratios in the symbiont-bearing benthic foraminiferan Amphistegina lobifera: Implications for δ 11B vital effects and paleo-pH reconstructions

NASA Astrophysics Data System (ADS)

Rollion-Bard, C.; Erez, J.

2010-03-01

The boron isotope composition of marine carbonates is considered to be a seawater pH proxy. Nevertheless, the use of δ 11B has some limitations such as the knowledge of the fractionation factor ( α4-3) between boric acid and the borate ion and the amplitude of "vital effects" on this proxy that are not well constrained. Using secondary ion mass spectrometry (SIMS) we have examined the internal variability of the boron isotope ratio in the shallow water, symbionts bearing foraminiferan Amphistegina lobifera. Specimens were cultured at constant temperature (24 ± 0.1 °C) in seawater with pH ranging between 7.90 and 8.45. Intra-shell boron isotopes showed large variability with an upper limit value of ≈30‰. Our results suggest that the fractionation factor α4-3 of 0.97352 ( Klochko et al., 2006) is in better agreement with our experiments and with direct pH measurements in seawater vacuoles associated with the biomineralization process in these foraminifera. Despite the large variability of the skeletal pH values in each cultured specimen, it is possible to link the lowest calculated pH values to the experimental culture pH values while the upper pH limit is slightly below 9. This variability can be interpreted as follows: foraminifera variably increase the pH at the biomineralization site to about 9. This increase above ambient seawater pH leads to a range in δ 11B (Δ 11B) for each seawater pH. This Δ 11B is linearly correlated with the culture seawater pH with a slope of -13.1 per pH unit, and is independent of the fractionation factor α4-3, or the δ 11B sw through time. It may also be independent of the p KB (the dissociation constant of boric acid) value. Therefore, Δ 11B in foraminifera can potentially reconstruct paleo-pH of seawater.

Electrohydrodynamic properties of succinoglycan as probed by fluorescence correlation spectroscopy, potentiometric titration and capillary electrophoresis.

PubMed

Duval, Jérôme F L; Slaveykova, Vera I; Hosse, Monika; Buffle, Jacques; Wilkinson, Kevin J

2006-10-01

The electrostatic, hydrodynamic and conformational properties of aqueous solutions of succinoglycan have been analyzed by fluorescence correlation spectroscopy (FCS), proton titration, and capillary electrophoresis (CE) over a large range of pH values and electrolyte (NaCl) concentrations. Using the theoretical formalism developed previously for the electrokinetic properties of soft, permeable particles, a quantitative analysis for the electro-hydrodynamics of succinoglycan is performed by taking into account, in a self-consistent manner, the measured values of the diffusion coefficients, electric charge densities, and electrophoretic mobilities. For that purpose, two limiting conformations for the polysaccharide in solution are tested, i.e. succinoglycan behaves as (i) a spherical, random coil polymer or (ii) a rodlike particle with charged lateral chains. The results show that satisfactory modeling of the titration data for ionic strengths larger than 50 mM can be accomplished using both geometries over the entire range of pH values. Electrophoretic mobilities measured for sufficiently large pH values (pH > 5-6) are in line with predictions based on either model. The best manner to discriminate between these two conceptual models is briefly discussed. For low pH values (pH < 5), both models indicate aggregation, resulting in an increase of the hydrodynamic permeability and a decrease of the diffusion coefficient.

Voltammetry of naltrexone in commercial formulation and human body fluids: Quantification and pharmacokinetic studies.

PubMed

Ghoneim, Mohamed M; El-Desoky, Hanaa S; Abdel-Galeil, Mohamed M

2011-06-01

Naltrexone HCl (NAL.HCl) has been reduced at the mercury electrode in Britton-Robinson universal buffer of pH values 2-11 with a mechanism involving the quasi-reversible uptake of the first transferring electron followed by a rate-determining protonation step of its C=O double bond at position C-6. Simple, sensitive, selective and reliable linear-sweep and square-wave adsorptive cathodic stripping voltammetry methods have been described for trace quantitation of NAL.HCl in bulk form, commercial formulation and human body fluids without the necessity for sample pretreatment and/or time-consuming extraction steps prior to the analysis. Limits of quantitation of 6.0×10(-9)M and 8.0×10(-10)M NAL.HCl in bulk form or commercial formulation and of 9.0×10(-9) and 1.0×10(-9)M NAL.HCl in spiked human serum samples were achieved by the described linear and square-wave stripping voltammetry methods, respectively. Furthermore, pharmacokinetic parameters of the drug in human plasma samples of healthy volunteers following the administration of an oral single dose of 50mg NAL.HCl (one Revia(®) tablet) were estimated by means of the described square-wave stripping voltammetry method without interferences from the drug's metabolites and/or endogenous human plasma constituents. The estimated pharmacokinetic parameters were favorably compared with those reported in literature. Copyright © 2011 Elsevier B.V. All rights reserved.

Differential Models for B-Type Open-Closed Topological Landau-Ginzburg Theories

NASA Astrophysics Data System (ADS)

Babalic, Elena Mirela; Doryn, Dmitry; Lazaroiu, Calin Iuliu; Tavakol, Mehdi

2018-05-01

We propose a family of differential models for B-type open-closed topological Landau-Ginzburg theories defined by a pair (X,W), where X is any non-compact Calabi-Yau manifold and W is any holomorphic complex-valued function defined on X whose critical set is compact. The models are constructed at cochain level using smooth data, including the twisted Dolbeault algebra of polyvector-valued forms and a twisted Dolbeault category of holomorphic factorizations of W. We give explicit proposals for cochain level versions of the bulk and boundary traces and for the bulk-boundary and boundary-bulk maps of the Landau-Ginzburg theory. We prove that most of the axioms of an open-closed TFT (topological field theory) are satisfied on cohomology and conjecture that the remaining two axioms (namely non-degeneracy of bulk and boundary traces and the topological Cardy constraint) are also satisfied.

Thermal resistance parameters of acid-adapted and unadapted Escherichia coli O157:H7 in apple-carrot juice blends: effect of organic acids and pH.

PubMed

Usaga, Jessie; Worobo, Randy W; Padilla-Zakour, Olga I

2014-04-01

Numerous outbreaks involving fresh juices contaminated with Escherichia coli O157:H7 have occurred in the United States and around the world, raising concern for the safety of these products. Until now, only a few studies regarding the thermal tolerance of this pathogen in acidic juices over a wide range of pH values have been published. Therefore, the effect of varying the pH with different organic acids on the thermal inactivation of non-acid-adapted and acid-adapted E. coli O157:H7 (strain C7927) was determined. The decimal reduction times (D-values) and the change in temperature required for the thermal destruction curve to traverse 1 log cycle (z-values) were calculated for non-acid-adapted E. coli in an apple-carrot juice blend (80:20) adjusted to three pH values (3.3, 3.5, and 3.7) by the addition of lactic, malic, or acetic acid and at a pH of 4.5 adjusted with NaOH. Thermal parameters were also determined for acid-adapted cells in juices acidified with malic acid. The effect of the soluble solids content on the thermal tolerance was studied in samples with a pH of 3.7 at 9.4 to 11.5 °Brix. The D-values were determined at 54, 56, and 58 °C, and trials were conducted in triplicate. Non-acid-adapted E. coli exhibited the highest thermal tolerance at pH 4.5 (D-value at 54 °C [D54 °C] of 20 ± 4 min and z-value of 6.2 °C), although on average, the D-values increased significantly (P < 0.01) due to acid adaptation. In acidified juices, the highest tolerance was observed in acid-adapted E. coli in samples adjusted to pH 3.7 with malic acid (D54 °C of 9 ± 2 min and z-value of 5.4 °C) and the lowest in unadapted E. coli at pH 3.3 acidified with acetic acid (D58 °C of 0.03 ± 0.01 min and z-value of 10.4 °C). For juices acidified to the same endpoint pH with different acids, E. coli was found to be more tolerant in samples acidified with malic acid, followed by lactic and acetic acids. Increasing the soluble solids content from 9.4 to 11.5 °Brix showed no significant effect on the thermal tolerance of E. coli (P > 0.01). The data from this study will be useful for establishing critical limits for safe thermal processing of pH-controlled juices and similar products.

Inferring Phytoplankton, Terrestrial Plant and Bacteria Bulk δ¹³C Values from Compound Specific Analyses of Lipids and Fatty Acids

PubMed Central

Taipale, Sami J.; Peltomaa, Elina; Hiltunen, Minna; Jones, Roger I.; Hahn, Martin W.; Biasi, Christina; Brett, Michael T.

2015-01-01

Stable isotope mixing models in aquatic ecology require δ13C values for food web end members such as phytoplankton and bacteria, however it is rarely possible to measure these directly. Hence there is a critical need for improved methods for estimating the δ13C ratios of phytoplankton, bacteria and terrestrial detritus from within mixed seston. We determined the δ13C values of lipids, phospholipids and biomarker fatty acids and used these to calculate isotopic differences compared to the whole-cell δ13C values for eight phytoplankton classes, five bacterial taxa, and three types of terrestrial organic matter (two trees and one grass). The lipid content was higher amongst the phytoplankton (9.5±4.0%) than bacteria (7.3±0.8%) or terrestrial matter (3.9±1.7%). Our measurements revealed that the δ13C values of lipids followed phylogenetic classification among phytoplankton (78.2% of variance was explained by class), bacteria and terrestrial matter, and there was a strong correlation between the δ13C values of total lipids, phospholipids and individual fatty acids. Amongst the phytoplankton, the isotopic difference between biomarker fatty acids and bulk biomass averaged -10.7±1.1‰ for Chlorophyceae and Cyanophyceae, and -6.1±1.7‰ for Cryptophyceae, Chrysophyceae and Diatomophyceae. For heterotrophic bacteria and for type I and type II methane-oxidizing bacteria our results showed a -1.3±1.3‰, -8.0±4.4‰, and -3.4±1.4‰ δ13C difference, respectively, between biomarker fatty acids and bulk biomass. For terrestrial matter the isotopic difference averaged -6.6±1.2‰. Based on these results, the δ13C values of total lipids and biomarker fatty acids can be used to determine the δ13C values of bulk phytoplankton, bacteria or terrestrial matter with ± 1.4‰ uncertainty (i.e., the pooled SD of the isotopic difference for all samples). We conclude that when compound-specific stable isotope analyses become more widely available, the determination of δ13C values for selected biomarker fatty acids coupled with established isotopic differences, offers a promising way to determine taxa-specific bulk δ13C values for the phytoplankton, bacteria, and terrestrial detritus embedded within mixed seston. PMID:26208114

Evaporation Rates of Chemical Warfare Agents Measured Using 5 CM Wind Tunnels. 2. Munitions Grade Sulfur Mustard From Sand

DTIC Science & Technology

2009-07-01

micropores and the pH of 0.1 g sand in 2 mL water, measured after 24 hr using pH paper, was 6. The measured bulk and tapped densities of the sand...o oasr^^roryrgQcor-»infO KNceend’-ojnrS^’u:* ^ t\\i kO N © co uS oS - <- eg CM M (M n eft ^ eg ni r»i s rt...O cn o o 2 eft — cn co in ^ ^ iri — 3 *- t- — n vt rt CD £ 2 9 a H d a -i --’ p | E •i = ° 2r ^ A

Illumina sequencing-based analyses of bacterial communities during short-chain fatty-acid production from food waste and sewage sludge fermentation at different pH values.

PubMed

Cheng, Weixiao; Chen, Hong; Yan, ShuHai; Su, Jianqiang

2014-09-01

Short-chain fatty acids (SCFAs) can be produced by primary and waste activated sludge anaerobic fermentation. The yield and product spectrum distribution of SCFAs can be significantly affected by different initial pH values. However, most studies have focused on the physical and chemical aspects of SCFA production by waste activated sludge fermentation at different pH values. Information on the bacterial community structures during acidogenic fermentation is limited. In this study, comparisons of the bacterial communities during the co-substrate fermentation of food wastes and sewage sludge at different pH values were performed using the barcoded Illumina paired-end sequencing method. The results showed that different pH environments harbored a characteristic bacterial community, including sequences related to Lactobacillus, Prevotella, Mitsuokella, Treponema, Clostridium, and Ureibacillus. The most abundant bacterial operational taxonomic units in the different pH environments were those related to carbohydrate-degrading bacteria, which are associated with constituents of co-substrate fermentation. Further analyses showed that during organic matter fermentation, a core microbiota composed of Firmicutes, Proteobacteria, and Bacteroidetes existed. Comparison analyses revealed that the bacterial community during fermentation was significantly affected by the pH, and that the diverse product distribution was related to the shift in bacterial communities.

Synergistic effect of wire bending and salivary pH on surface properties and mechanical properties of orthodontic stainless steel archwires.

PubMed

Hobbelink, Marieke G; He, Yan; Xu, Jia; Xie, Huixu; Stoll, Richard; Ye, Qingsong

2015-01-01

The aim of this study was to investigate the corrosive behaviour of stainless steel archwires in a more clinically relevant way by bending and exposing to various pH. One hundred and twenty pieces of rectangular stainless steel wires (0.43 × 0.64 mm) were randomly assigned into four groups. In each group, there were 15 pieces of bent wires and 15 straight ones. Prior to measurements of the wires, as individual experimental groups (group 1, 2, and 3), the wires were exposed to artificial saliva for 4 weeks at pH 5.6, 6.6, and 7.6, respectively. A control group of wires (group 4) remained in air for the same period of time before sent for measurements. Surface roughness (Ra-value) was measured by a profilometer. Young's modulus and maximum force were determined by a four-point flexural test apparatus. Scanning electron microscopy was used to observe the surface morphology of straight wire. Differences between groups were examined using a two-way analysis of variance (ANOVA). Mean surface roughness values, flexural Young's moduli, and maximum force values of bent wires are significantly different from those of the straight wires, which was the main effect of wire bending, ignoring the influence of pH. A significant effect was found between Ra-values regarding the main effect of pH, ignoring the influence of shape. There was a significant interaction effect of bending and pH on flexural Young's moduli of stainless steel archwires, while pH did not show much impact on the maximum force values of those stainless steel wires. Bigger surface irregularities were seen on SEM images of straight wires immersed in artificial saliva at pH 5.6 compared to artificial saliva at other pH values. Surface depth (Rz) was more sensitive than Ra in revealing surface roughness, both measured from 3D reconstructed SEM images. Ra showed a comparable result of surface roughness to Ra-value measured by the profilometer. Bending has a significant influence on surface roughness and mechanical properties of rectangular SS archwires. pH plays a synergistic effect on the change of mechanical properties of stainless steel (SS) wires along with wire bending.

Effect of dextran and dextran sulfate on the structural and rheological properties of model acid milk gels.

PubMed

Pachekrepapol, U; Horne, D S; Lucey, J A

2015-05-01

Various types of polysaccharides are widely used in cultured dairy products. However, the interaction mechanisms, between milk proteins and these polysaccharides, are not entirely clear. To explore the interactions between uncharged and charged polysaccharides and the caseins, we used a model acid-milk-gel system, which allowed acidification to occur separately from gelation. The effect of adding uncharged dextran (DX; molecular weight ~2.0×10(6) Da) and negatively charged dextran sulfate (DS; molecular weight ~1.4×10(6) Da) to model acid milk gels was studied. Two concentrations (0.075 and 0.5%, wt/wt) of DX or DS were added to cold milk (~0°C) that had been acidified to pH values 4.4, 4.6, 4.8, or 4.9. Acidified milks containing DX or DS were then quiescently heated at the rate of 0.5°C/min to 30°C, which induced gelation, and gels were then held at 30°C for 17 h to facilitate gel development. Dynamic small-amplitude-oscillation rheology and large-deformation (shear) tests were performed. Microstructure of gels was examined by fluorescence microscopy. Gels made with a high concentration of DX gelled at a lower temperature, but after 17 h at 30°C, these gels exhibited lower storage moduli and lower yield-stress values. At pH 4.8 or 4.9 (pH values greater than the isoelectric point of caseins), addition of 0.5% DS to acidified milk resulted in lower gelation temperature. At pH 4.4 (pH values less than the isoelectric point of caseins), addition of 0.5% DS to acidified milk resulted in gels with very high stiffness values. Gels made at pH 4.8 or 4.9 with both concentrations of DS had much lower stiffness and yield-stress values than control gels. Microstructural analysis indicated that gels made at pH 4.4 with the addition of 0.5% DX exhibited large protein strands and pores, whereas gels made with 0.075% DX or the control gels had a finer protein matrix. At higher pH values (>4.4), gels made with 0.5% DX had a finer structure. At all pH values, gels made with 0.5% DS exhibited larger pores than the control gels. This study demonstrated that low concentrations of uncharged DX did not significantly affect the rheological properties of model acid milk gels; high concentrations of DX resulted in earlier gelation, possibly caused by depletion-induced attractions between casein particles, which altered the microstructure and created weaker gels. At pH values <4.6, negatively charged DS produced stiff casein gels, which might be due to attractive crosslinking by electrostatic interactions between DS and caseins at pH values below the isoelectric pH of casein (i.e., positively charged casein regions interacted with negatively charged DS molecules). Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

On the correct choice of equivalent circuit for fitting bulk impedance data of ionic/electronic conductors

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

Hernández, Miguel A.; Masó, Nahum; West, Anthony R.

Bulk conductivity data of ionically and electronically conducting solid electrolytes and electronic ceramics invariably show a frequency dependence that cannot be modelled by a single-valued resistor. To model this, common practice is to add a constant phase element (CPE) in parallel with the bulk resistance. To fit experimental data on a wide variety of materials, however, it is also essential to include the limiting, high frequency permittivity of the material in the equivalent circuit. Failure to do so can lead to incorrect values for the sample resistance and CPE parameters and to an inappropriate circuit for materials that are electricallymore » heterogeneous.« less

Soil pH on mobility of imazaquin in oxisols with positive balance of charges.

PubMed

Regitano, Jussara B; da Rocha, Wadson S D; Alleoni, Luís R F

2005-05-18

The influence of soil pH on the leaching potential of the ionizable herbicide imazaquin was assessed on the profile of two highly weathered soils having a net positive charge in the B horizon, in contrast to a soil having a net negative charge in the whole profile, using packed soil column experiments. Imazaquin leached to a large extent and faster at Kd values lower than 1.0 L kg(-1), a much more lenient limit than usually proposed for pesticides in the literature (Kd < 5.0 L kg(-1)). The amount of imazaquin leached increased with soil pH. As the soil pH increased, the percentage of imazaquin in the anionic forms, the negative surface potential of the soils, as well as imazaquin water solubility also increased, thus reducing sorption because of repulsive electrostatic forces (hydrophilic interactions). For all surface samples (0-0.2 m), imazaquin did not leach at soil pH values lower than pKa (3.8) and more than 80% of the applied amount was leached at pH values higher than 5.5. For subsurface samples from the acric soils, imazaquin only began to leach at soil pH values > zero point of salt effects (ZPSE > 5.7). In conclusion, the use of surface K(oc) values to predict the amount of imazaquin leached within soil profiles having a positive balance of charges may greatly overestimate its actual leaching potential.

Comparison of pH and refractometry index with calcium concentrations in preparturient mammary gland secretions of mares.

PubMed

Korosue, Kenji; Murase, Harutaka; Sato, Fumio; Ishimaru, Mutsuki; Kotoyori, Yasumitsu; Tsujimura, Koji; Nambo, Yasuo

2013-01-15

To test the usefulness of measuring pH and refractometry index, compared with measuring calcium carbonate concentration, of preparturient mammary gland secretions for predicting parturition in mares. Evaluation study. 27 pregnant Thoroughbred mares. Preparturient mammary gland secretion samples were obtained once or twice daily 10 days prior to foaling until parturition. The samples were analyzed for calcium carbonate concentration with a water hardness kit (151 samples), pH with pH test paper (222 samples), and refractometry index with a Brix refractometer (214 samples). The sensitivity, specificity, and positive and negative predictive values for each test were calculated for evaluation of predicting parturition. The PPV within 72 hours and the NPV within 24 hours for calcium carbonate concentration determination (standard value set to 400 μg/g) were 93.8% and 98.3%, respectively. The PPV within 72 hours and the NPV within 24 hours for the pH test (standard value set at 6.4) were 97.9% and 99.4%, respectively. The PPV within 72 hours and the NPV within 24 hours for the Brix test (standard value set to 20%) were 73.2% and 96.5%, respectively. Results suggested that the pH test with the standard value set at a pH of 6.4 would be useful in the management of preparturient mares by predicting when mares are not ready to foal. This was accomplished with equal effectiveness of measuring calcium carbonate concentration with a water hardness kit.

Effects of adding bulking agent, inorganic nutrient and microbial inocula on biopile treatment for oil-field drilling waste.

PubMed

Ma, Jie; Yang, Yongqi; Dai, Xiaoli; Chen, Yetong; Deng, Hanmei; Zhou, Huijun; Guo, Shaohui; Yan, Guangxu

2016-05-01

Contamination from oil-field drilling waste is a worldwide environmental problem. This study investigated the performance of four bench-scale biopiles in treating drilling waste: 1) direct biopile (DW), 2) biopile plus oil-degrading microbial consortium (DW + M), 3) biopile plus microbial consortium and bulking agents (saw dust) (DW + M + BA), 4) biopile plus microbial consortium, bulking agents, and inorganic nutrients (Urea and K2HPO4) (DW + M + BA + N). Ninety days of biopiling removed 41.0%, 44.0%, 55.7% and 87.4% of total petroleum hydrocarbon (TPH) in the pile "DW", "DW + M", "DW + M + BA", and "DW + M + BA + N" respectively. Addition of inorganic nutrient and bulking agents resulted in a 56.9% and 26.6% increase in TPH removal efficiency respectively. In contrast, inoculation of hydrocarbon-degrading microorganisms only slightly enhanced the contaminant removal (increased 7.3%). The biopile with stronger contaminant removal also had higher pile temperature and lower pile pH (e.g., in "DW + M + BA + N"). GC-MS analysis shows that biopiling significantly reduced the total number of detected contaminants and changed the chemical composition. Overall, this study shows that biopiling is an effective remediation technology for drilling waste. Adding inorganic nutrients and bulking agents can significantly improve biopile performance while addition of microbial inocula had minimal positive impacts on contaminant removal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Extensive ionic partitioning in interfaces that membranous and biomimetic surfaces form with electrolytes: Antitheses of the gold-electrolyte interface

NASA Astrophysics Data System (ADS)

Chilcott, Terry; Guo, Chuan; Coster, Hans

2013-04-01

Maxwell-Wagner modeling of electrical impedance measurements of tetradecane-electrolyte systems yielded three interfacial layers between the tetradecane layer and the bulk electrolytes of concentration ranging from 1-300 mM KCl whereas the gold-electrolyte system yielded only one layer. The conductivity and thickness for the surface layer were orders of magnitude different from that expected for the Gouy-Chapman layer and did not reflect dependencies of the Debye length on concentration. Conductivity values for the three layers were less than those of the bulk electrolyte but exhibited a dependency on concentration similar to that expected for the bulk. Thickness values for the layers indicate an interface extending ~106 Å into the bulk electrolyte, which contrasts with the gold-electrolyte interface that extended only 20-30 Å into the bulk. Maxwell-Wagner characterizations of both interfaces were consistent with spatial distributions of ionic partitioning arising from the Born energy as determined by the dielectric properties of the substrates and electrolyte. The distributions for the membranous and silicon interfaces were similar but the antitheses of that for the gold interface.

Experimental research on friction coefficient between grain bulk and bamboo clappers

NASA Astrophysics Data System (ADS)

Tang, Gan; Sun, Ping; Zhao, Yanqi; Yin, Lingfeng; Zhuang, Hong

2017-12-01

A silo is an important piece of storage equipment, especially in the grain industry. The internal friction angle and the friction coefficient between the grain and the silo wall are the main parameters needed for calculating the lateral pressure of the silo wall. Bamboo is used in silo walls, but there are no provisions about the friction coefficient between bulk grain and bamboo clappers in existing codes. In this paper, the material of the silo wall is bamboo. The internal friction of five types of grain and the friction coefficient between the grain and the bamboo clappers were measured with an equal-strain direct shear apparatus. By comparing the experimental result values with the code values, the friction coefficient between the grain bulk and bamboo clappers is lower than that between grain and steel wall and that between grain and concrete wall. The differences in value are 0.21 and 0.09, respectively.

AS SPECIATION AND EFFECTS OF PH AND PHOSPHATE ON THE MOBILIZATION OF AS IN SOILS FROM A LEAD SMELTING SITE. PUBLISHED IN ADVANCED PHOTON SOURCE ACTIVITY REPORT 2003.

EPA Science Inventory

Arsenic in soils from the Asarco lead smelter in East Helena, Montana was characterized by X-ray absorption spectroscopy (XAS). Arsenic oxidation state and mineralogy were analyzed as a function of depth and surface distribution using bulk and microprobe XAS. These results were c...

Tree species effects on soil properties and greenhouse gas fluxes in East-central Amazonia: comparison between monoculture and diverse forest

Treesearch

J. Van Haren; R.C. de Oliveira, Jr.; P.T. Beldini; P.B. de Camargo; M. Keller; S. Saleska

2013-01-01

Tropical plantations are considered a viable option to sequester carbon on abandoned agricultural lands, but implications of tree species selection for overall greenhouse gas budgets on plantations have been little studied. During three wet seasons, we investigated the influence of nine tree species on soil pH, temperature (ST), bulk density (BD), moisture content...

High titer and yield ethanol production from undetoxified whole slurry of Douglas-fir forest residue using pH profiling in SPORL

Treesearch

Jinlan Cheng; Shao-Yuan Leu; JY Zhu; Rolland Gleisner

2015-01-01

Forest residue is one of the most cost-effective feedstock for biofuel production. It has relatively high bulk density and can be harvested year round, advantageous for reducing transportation cost and eliminating onsite storage. However, forest residues, especially those from softwood species, are highly recalcitrant to biochemical conversion. A severe pretreatment...

Effect of heat, pH, ultrasonication and ethanol on the denaturation of whey protein isolate using a newly developed approach in the analysis of difference-UV spectra.

PubMed

Nikolaidis, Athanasios; Andreadis, Marios; Moschakis, Thomas

2017-10-01

A newly developed method of analysis of difference-UV spectra was successfully implemented in the study of the effect of heat, pH, ultrasonication and ethanol on the denaturation of whey protein isolate. It was found that whey proteins exhibit their highest stability against heat denaturation at pH 3.75. At very low pH values, i.e. 2.5, they exhibited considerable cold denaturation, while after heating at this pH value, the supplementary heat denaturation rate was lower compared to that at neutral pH. The highest heat denaturation rates were observed at pH values higher than neutral. High power sonication on whey proteins, previously heated at 90°C for 30min, resulted in a rather small reduction of the fraction of the heat denatured protein aggregates. Finally, when ethanol was used as a cosolvent in the concentration range 20-50%, a sharp increase in the degree of denaturation, compared to the native protein solution, was observed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Processed dairy beverages pH evaluation: consequences of temperature variation.

PubMed

Ferreira, Fabiana Vargas; Pozzobon, Roselaine Terezinha

2009-01-01

This study assessed the pH from processed dairy beverages as well as eventual consequences deriving from different ingestion temperatures. 50 adults who accompanied children attended to at the Dentistry School were randomly selected and they answered a questionnaire on beverages. The beverages were divided into 4 groups: yogurt (GI) fermented milk (GII), chocolate-based products (GIII) and fermented dairy beverages (GIV). They were asked which type, flavor and temperature. The most popular beverages were selected, and these made up the sample. A pH meter Quimis 400A device was used to verify pH. The average pH from each beverage was calculated and submitted to statistical analysis (Variance and Tukey test with a 5% significance level). for groups I, II and III beverages, type x temperature interaction was significant, showing the pH averages were influenced by temperature variation. At iced temperatures, they presented lower pH values, which were considered statistically significant when compared to the values found for the same beverages at room temperature. All dairy beverages, with the exception of the chocolate-based type presented pH below critical level for enamel and present corrosive potential; as to ingestion temperature, iced temperature influenced pH reducing its values, in vitro.

The origin of chromitic chondrules and the volatility of Cr under a range of nebular conditions

NASA Technical Reports Server (NTRS)

Krot, Alexander; Ivanova, Marina A.; Wasson, John T.

1993-01-01

We characterize ten chromatic chondrules, two spinelian chondrules andd one spinel-bearing chondrule and summarize data for 120 chromitic inclusions discovered in an extensive survey of ordinary chondrites. Compositional and petrographic evidence suggests that chromitic chondrules and inclusions are closely related. The Cr/(Cr + Al) ratios in the spinal of these objects range from 0.5 to 0.9 and bulk Al2O3 contents are uniformly high (greater than 10 wt%, except for one with 8 wt%). No other elements having comparable solar abundances are so stongly enriched, and alkali feldspar and merrillite are more common than in normal chondrules. The Cr/Mg ratios in chromitic chondrules are 180-750 times the ratios in the bulk chondrite. With the possible exception of magnetic clumping of chromite in the presolar cloud, mechanical processes cannot account for this enrichment. Examination of nebular equilibrium processes shows that 50%-condensation temperatures of Cr at pH2/pH2O of 1500 are several tens of degrees below those of Mg as Mg2SiO4; the condensation of Cr is primarily as MgCr2O4 dissolved in MgAl2O4 at nebular pressures of 10(exp -4) atm or below. At pH2 = 10(exp -3) atm condesation as Cr in Fe-Ni is favored. Making the nebula much more oxidizing reduces the difference in condensation temperatures but Mg remains more refractory. We conclude that nebular equilibrium processes are not responsible for the enhanced Cr/Mg ratios. We propose that both Cr and Al became enriched in residues formed by incomplete evaporation of presolar lumps. We suggest that spinals remained as solid phases when the bulk of the silicates were incorporated into the evaporating melt; vaporization of Al and Cr were inhibited by the slow kinetics of diffusion. Subsequent melting and crystallization of these residues fractionated Cr from Al. The resulting materials constituted major components in the precursors of chromitic chondrules. Our model implies that chromitic chondrules and inclusions preserve the Cr isotopic record of presolar sources.

Habitat management affects soil chemistry and allochthonous organic inputs mediating microbial structure and exo-enzyme activity in Wadden Sea salt-marsh soils

NASA Astrophysics Data System (ADS)

Mueller, Peter; Granse, Dirk; Thi Do, Hai; Weingartner, Magdalena; Nolte, Stefanie; Hoth, Stefan; Jensen, Kai

2016-04-01

The Wadden Sea (WS) region is Europe's largest wetland and home to approximately 20% of its salt marsh area. Mainland salt marshes of the WS are anthropogenically influenced systems and have traditionally been used for livestock grazing in wide parts. After foundation of WS National Parks in the late 1980s and early 1990s, artificial drainage has been abandoned; however, livestock grazing is still common in many areas of the National Parks and is under ongoing discussion as a habitat-management practice. While studies so far focused on effects of livestock grazing on biodiversity, little is known about how biogeochemical processes, element cycling, and particularly carbon sequestration are affected. Here, we present data from a recent field study focusing on grazing effects on soil properties, microbial exo-enzyme activity, microbial abundance and structure. Exo-enzyme activity was studied conducting digestive enzyme assays for various enzymes involved in C- and N cycling. Microbial abundance and structure was assessed measuring specific gene abundance of fungi and bacteria using quantitative PCR. Soil compaction induced by grazing led to higher bulk density and decreases in soil redox (Δ >100 mV). Soil pH was significantly lower in grazed parts. Further, the proportion of allochthonous organic matter (marine input) was significantly smaller in grazed vs. ungrazed sites, likely caused by a higher sediment trapping capacity of the taller vegetation in the ungrazed sites. Grazing induced changes in bulk density, pH and redox resulted in reduced activity of enzymes involved in microbial C acquisition; however, there was no grazing effect on enzymes involved in N acquisition. While changes in pH, bulk density or redox did not affect microbial abundance and structure, the relative amount of marine organic matter significantly reduced the relative abundance of fungi (F:B ratio). We conclude that livestock grazing directly affects microbial exo-enzyme activity, thus slowing down C turnover, and indirectly changes microbial structure, namely relative fungal abundance, by reducing high-quality marine organic matter inputs.

The pH dependent Raman spectroscopic study of caffeine

NASA Astrophysics Data System (ADS)

Kang, Jian; Gu, Huaimin; Zhong, Liang; Hu, Yongjun; Liu, Fang

2011-02-01

First of all the surface enhanced Raman spectroscopy (SERS) and normal Raman spectra of caffeine aqueous solution were obtained at different pH values. In order to obtain the detailed vibrational assignments of the Raman spectroscopy, the geometry of caffeine molecule was optimized by density functional theory (DFT) calculation. By comparing the SERS of caffeine with its normal spectra at different pH values; it is concluded that pH value can dramatically affect the SERS of caffeine, but barely affect the normal Raman spectrum of caffeine aqueous solution. It can essentially affect the reorientation of caffeine molecule to the Ag colloid surface, but cannot impact the vibration of functional groups and chemical bonds in caffeine molecule.

Capsule Design for Blue Light Therapy against Helicobacter pylori.

PubMed

Li, Zhangyong; Ren, Binbin; Tan, Haiyan; Liu, Shengrong; Wang, Wei; Pang, Yu; Lin, Jinzhao; Zeng, Chen

2016-01-01

A photo-medical capsule that emits blue light for Helicobacter pylori treatment was described in this paper. The system consists of modules for pH sensing and measuring, light-emitting diode driver circuit, radio communication and microcontroller, and power management. The system can differentiate locations by monitoring the pH values of the gastrointestinal tract, and turn on and off the blue light according to the preset range of pH values. Our experimental tests show that the capsule can operate in the effective light therapy mode for more than 32 minutes and the wireless communication module can reliably transmit the measured pH value to a receiver located outside the body.

Effect of initial soil properties on six-year growth of 15 tree species in tropical restoration plantings.

PubMed

Martínez-Garza, Cristina; Campo, Julio; Ricker, Martin; Tobón, Wolke

2016-12-01

In restoration plantings in degraded pastures, initial soil nutrient status may lead to differential growth of tropical tree species with diverse life history attributes and capacity for N 2 fixation. In 2006, we planted 1,440 seedlings of 15 native tree species in 16 fenced plots (30 × 30 m) in a 60-year-old pasture in Los Tuxtlas, Veracruz, Mexico, in two planting combinations. In the first year, we evaluated bulk density, pH, the concentration of organic carbon (C), total nitrogen (N), ammonia (NO3-), nitrate (NH4+), and total phosphorus (P) in the upper soil profile (0-20 cm in depth) of all plots. The first two axes of two principal component analyses explained more than 60% of the variation in soil variables: The axes were related to increasing bulk density, NO3-, NH4+, total N concentration, and pH. Average relative growth rates in diameter at the stem base of the juvenile trees after 6 years were higher for pioneer (45.7%) and N 2 -fixing species (47.6%) than for nonpioneer (34.7%) and nonfixing species (36.2%). Most N 2 -fixing species and those with the slowest growth rates did not respond to soil attributes. Tree species benefited from higher pH levels and existing litter biomass. The pioneers Ficus yoponensis , Cecropia obtusifolia , and Heliocarpus appendiculatus , and the N 2 -fixing nonpioneers Cojoba arborea , Inga sinacae , and Platymiscium dimorphandrum were promising for forest restoration on our site, given their high growth rates.

Challenges in Determining Intrinsic Viscosity Under Low Ionic Strength Solution Conditions.

PubMed

Pindrus, Mariya A; Shire, Steven J; Yadav, Sandeep; Kalonia, Devendra S

2017-04-01

To determine the intrinsic viscosity of several monoclonal antibodies (mAbs) under varying pH and ionic strength solution conditions. An online viscosity detector attached to HPLC (Viscotek®) was used to determine the intrinsic viscosity of mAbs. The Ross and Minton equation was used for viscosity prediction at high protein concentrations. Bulk viscosity was determined by a Cambridge viscometer. At 15 mM ionic strength, intrinsic viscosity of the mAbs determined by the single-point approach varied from 5.6 to 6.4 mL/g with changes in pH. High ionic strength did not significantly alter intrinsic viscosity, while a significant increase (up to 24.0 mL/g) was observed near zero mM. No difference in bulk viscosity of mAb3 was observed around pH 6 as a function of ionic strength. Data analysis revealed that near zero mM ionic strength limitations of the single-point technique result in erroneously high intrinsic viscosity. Intrinsic viscosity is a valuable tool that can be used to model baseline viscosity at higher protein concentrations. However, it is not predictive of solution non-ideality at higher protein concentrations. Furthermore, breakdown of numerous assumptions limits the applicability of experimental techniques near zero mM ionic strength conditions. For molecules and conditions studied, the single-point approach produced reliable intrinsic viscosity results at 15 mM. However, this approach must be used with caution near zero mM ionic strength. Data analysis can be used to reveal whether determined intrinsic viscosity is reliable or erroneously high.

Consumption of baked nuts or seeds reduces dental plaque acidogenicity after sucrose challenge.

PubMed

Wang, Xiaoling; Cheng, Chuoyue; Ge, Chunling; Wang, Bing; Gan, Ye-Hua

2016-06-01

To assess the acidogenic potential of eight different types of baked nuts or seeds eaten alone and after a sucrose challenge using in-dwelling electrode telemetry. Six participants wearing a mandibular partial prosthesis incorporated with a miniature glass pH electrode were enrolled. The plaque pH was measured after 5 or 6 days of plaque accumulation. To establish a control, the subjects were instructed to rinse with sucrose, without any subsequent treatment, at the first visit. At each subsequent test visit, the subjects were asked to chew sugar free xylitol gum or consume 10 g of baked (180 degrees C, 5 minutes) peanuts, walnuts, pistachios, cashews, almonds, sunflower seeds, pumpkin seeds, or watermelon seeds alone and 10 minutes after a sucrose rinse. The minimum plaque pH value and area of plaque pH curve under 5.7 (AUC5.7) during and after nut/seed consumption or gum chewing alone, the plaque pH value at 10 minutes after the sucrose rinse, the time required for the pH to return to >5.7 and AUC5.7 after the sucrose rinse with or without nut/seed consumption or gum chewing were calculated from the telemetric curves. The sucrose rinse induced a rapid decrease in the plaque pH to 4.32 +/- 0.17 at 10 minutes; this value remained below 5.7 for the measurement period. The AUC5.7 values were 34.58 +/- 7.27 and 63.55 +/- 15.17 for 40 and 60 minutes after the sucrose challenge, respectively. With the exception of cashews and pumpkin seeds (minimum pH, 5.42 and 5.63 respectively), the nuts or seeds did not decrease the plaque pH to below 5.7 when consumed alone, with the AUC5.7 values during and after consumption (total 40 minutes) ranging from 0.24 to 2.5 (8.44 for cashews), which were significantly lower than those after the sucrose challenge. Furthermore, nut/seed consumption or gum chewing after the sucrose challenge significantly reversed the sucrose-induced decrease in the plaque pH, and the time required for the pH to return to >5.7 and the AUC5.7 values for 60 minutes after the sucrose challenge were much less than that of the sucrose challenge without subsequent interference.

Characterization of callase (β-1,3-D-glucanase) activity during microsporogenesis in the sterile anthers of Allium sativum L. and the fertile anthers of A. atropurpureum.

PubMed

Winiarczyk, Krystyna; Jaroszuk-Ściseł, Jolanta; Kupisz, Kamila

2012-06-01

We examined callase activity in anthers of sterile Allium sativum (garlic) and fertile Allium atropurpureum. In A. sativum, a species that produces sterile pollen and propagates only vegetatively, callase was extracted from the thick walls of A. sativum microspore tetrads exhibited maximum activity at pH 4.8, and the corresponding in vivo values ranged from 4.5 to 5.0. Once microspores were released, in vitro callase activity peaked at three distinct pH values, reflecting the presence of three callase isoforms. One isoform, which was previously identified in the tetrad stage, displayed maximum activity at pH 4.8, and the remaining two isoforms, which were novel, were most active at pH 6.0 and 7.3. The corresponding in vivo values ranged from pH 4.75 to 6.0. In contrast, in A. atropurpureum, a sexually propagating species, three callase isoforms, active at pH 4.8-5.2, 6.1, and 7.3, were identified in samples of microsporangia that had released their microspores. The corresponding in vivo value for this plant was 5.9. The callose wall persists around A. sativum meiotic cells, whereas only one callase isoform, with an optimum activity of pH 4.8, is active in the acidic environment of the microsporangium. However, this isoform is degraded when the pH rises to 6.0 and two other callase isoforms, maximally active at pH 6.0 and 7.3, appear. Thus, factors that alter the pH of the microsporangium may indirectly affect the male gametophyte development by modulating the activity of callase and thereby regulating the degradation of the callose wall.

The effect of antacid on salivary pH in patients with and without dental erosion after multiple acid challenges.

PubMed

Dhuhair, Sarah; Dennison, Joseph B; Yaman, Peter; Neiva, Gisele F

2015-04-01

To evaluate the effect of antacid swish in the salivary pH values and to monitor the pH changes in subjects with and without dental erosion after multiple acid challenge tests. 20 subjects with tooth erosion were matched in age and gender with 20 healthy controls according to specific inclusion/exclusion criteria. Baseline measures were taken of salivary pH, buffering capacity and salivary flow rate using the Saliva Check System. Subjects swished with Diet Pepsi three times at 10-minute intervals. Changes in pH were monitored using a digital pH meter at 0-, 5-, and 10- minute intervals and at every 5 minutes after the third swish until pH resumed baseline value or 45 minutes relapse. Swishing regimen was repeated on a second visit, followed by swishing with sugar-free liquid antacid (Mylanta Supreme). Recovery times were also recorded. Data was analyzed using independent t-tests, repeated measures ANOVA, and Fisher's exact test (α= 0.05). Baseline buffering capacity and flow rate were not significantly different between groups (P= 0.542; P= 0.2831, respectively). Baseline salivary pH values were similar between groups (P= 0.721). No significant differences in salivary pH values were found between erosion and non-erosion groups in response to multiple acid challenges (P= 0.695) or antacid neutralization (P= 0.861). Analysis of salivary pH recovery time revealed no significant differences between groups after acid challenges (P= 0.091) or after the use of antacid (P= 0.118). There was a highly significant difference in the survival curves of the two groups on Day 2, with the non-erosion group resolving significantly faster than the erosion group (P= 0.0086).

Is Your Drinking Water Acidic? A Comparison of the Varied pH of Popular Bottled Waters.

PubMed

Wright, Kellie F

2015-06-01

Dental professionals continually educate patients on the dangers of consuming acidic foods and beverages due to their potential to contribute to dental erosion and tooth decay. Excess acid in the diet can also lead to acidosis, which causes negative systemic side effects. However, water is not typically categorized as acidic. The purpose of this in-vitro study was to investigate the pH levels of several popular brands of bottled water and compare them to various other acidic beverages. Two different brands of marketed alkaline water (with a pH of 8.8 or higher) were also studied, tested for acidity and described. A pilot in-vitro study was conducted to determine the pH levels of a convenience sample of popular brands of bottled water, tap water and other known acidic beverages in comparison with the pH values reported on the respective manufacturers' website. Each beverage was tested in a laboratory using a calibrated Corning pH meter model 240, and waters were compared to the corresponding company's testified pH value. Waters were also compared and contrasted based on their process of purification. The data was then compiled and analyzed descriptively. The pH values for the tested beverages and bottled waters were found to be predominantly acidic. Ten out of the 14 beverages tested were acidic (pH<7), 2 municipal (or "tap") waters were neutral (pH=7) and 2 bottled waters were alkaline (pH>7). The majority of waters tested had a more acidic pH when tested in the lab than the value listed in their water quality reports. It is beneficial for the health care provider to be aware of the potential acidity of popular bottled drinking waters and educate patients accordingly. Copyright © 2015 The American Dental Hygienists’ Association.

Neutralizing salivary pH by mouthwashes after an acidic challenge.

PubMed

Dehghan, Mojdeh; Tantbirojn, Daranee; Kymer-Davis, Emily; Stewart, Colette W; Zhang, Yanhui H; Versluis, Antheunis; Garcia-Godoy, Franklin

2017-05-01

The aim of the present study was to test the neutralizing effect of mouthwashes on salivary pH after an acidic challenge. Twelve participants were recruited for three visits, one morning per week. Resting saliva was collected at baseline and after 2-min swishing with 20 mL orange juice as an acidic challenge. Participants then rinsed their mouth for 30 s with 20 mL water (control), an over-the-counter mouthwash (Listerine), or a two-step mouthwash, randomly assigned for each visit. Saliva was collected immediately, 15, and 45 min after rinsing. The pH values of the collected saliva were measured and analyzed with anova, followed by Student-Newman-Keuls post-hoc test (significance level: 0.05). Orange juice significantly lowered salivary pH. Immediately after rinsing, Listerine and water brought pH back to baseline values, with the pH significantly higher in the Listerine group. The two-step mouthwash raised pH significantly higher than Listerine and water, and higher than the baseline value. Salivary pH returned to baseline and was not significantly different among groups at 15 and 45 min post-rinsing. Mouth rinsing after an acidic challenge increased salivary pH. The tested mouthwashes raised pH higher than water. Mouthwashes with a neutralizing effect can potentially reduce tooth erosion from acid exposure. © 2015 Wiley Publishing Asia Pty Ltd.

Safety of tomatillos and products containing tomatillos canned by the water-bath canning method.

PubMed

McKee, L H; Remmenga, M D; Bock, M A

1998-01-01

Three studies were conducted to evaluate the safety of tomatillos and products containing tomatillos canned by the water-bath processing method. In the first study, plain tomatillos were processed for 25, 37.5, 50 and 62.5 min. In the second study, five tomatillo/onion combinations were prepared while five tomatillo/green chile combinations were prepared in the third study. pH evaluations were conducted to determine safety in all studies using pH 4.2 as the cut-off value. No differences in the pH of plain tomatillos were detected due to processing time. All jars of plain tomatillos had pH values below 4.1. All combinations of tomatillos/onions and tomatillos/green chile containing more than 50% tomatillo had pH values below the 4.2 cut-off value. Results of the three studies indicate (1) acidification of plain tomatillos is probably unnecessary for canning by the water-bath processing method and (2) combinations of acidic tomatillos and low-acid onions or green chile must contain more than 50% tomatillos to have a pH low enough for safe water-bath processing.

Influence of pH, benzoic acid, glutathione, EDTA, 4-hexylresorcinol, and sodium chloride on the pressure inactivation kinetics of mushroom polyphenol oxidase.

PubMed

Weemaes, C A; Ludikhuyze, L R; Van den Broeck, I; Hendrickx, M E

1999-09-01

Pressure inactivation of mushroom PPO was studied for pH values ranging from 4 to 8, and the effect of some antibrowning agents on the pressure stability of mushroom PPO at pH 6.5 was evaluated. pH reduction below 6.5 resulted in a lowered inactivation threshold pressure and an increase of the absolute value of the activation volume (or a decrease of the z(p) value), the latter two parameters reflecting the pressure dependency of the inactivation rate constant. An increase in pH from 6.5 to 8, on the other hand, did only marginally affect the pressure stability of the enzyme. Mushroom PPO at pH 6.5 was markedly sensitized toward pressure by the presence of 2.5 mM 4-hexylresorcinol and slightly stabilized by the presence of 5 mM EDTA. The presence of 5 mM glutathione, sodium chloride, or benzoic acid caused no significant alteration of the enzyme pressure stability. Only in the presence of 4-hexylresorcinol, significant changes of the activation volume and z(p) value were noticed.

Boron Isotopic Composition Correlates with Ultra-Structure in a - Sea Coral Lophelia Pertusa: Implications for Biomineralization and - PH

NASA Astrophysics Data System (ADS)

Blamart, D.; Rollion-Bard, C.; Meibom, A.; Cuif, J.; Juillet-Leclerc, A.; Dauphin, Y.; Douarin, M.

2007-12-01

The geochemistry (stable isotopes and trace elements) of biogenic carbonates has been widely used for more than fifty years to reconstruct past climatic variability. During this time, the studies were mainly based on bulk sampling limiting sometimes the interpretations of the geochemical data as paleoclimatic proxies. Recently, high spatial resolution sampling techniques, such as micro-mill and SIMS, have been employed in the study of C, O and B isotopic compositions and trace elements (Mg, Sr) in the skeletons of a variety of (deep-sea) coral species. These studies have documented dramatic 'vital effects' and uncovered a systematic relationship between skeletal ultra-structure and stable isotopic composition. The formation of skeleton corals follows a universal two-step growth process. At the tips of the skeletal structures, the mineralizing cell layer produces centers of calcification (COC) or, equivalently, Early Mineralization Zone (EMZ). These EMZ are subsequently overgrown by fibrous aragonite(FA) consisting of cyclically added layers. The EMZ are characterized by systematically lighter C and O isotopic compositions compared with the adjacent FA. A number of geochemical models have been proposed, in which this systematic stable isotopic difference between EMZ and FA is ascribed to a biologically induced variation in the pH of a proposed Extra-cytoplasmic Calcifying Fluid (ECF) reservoir. In these models, relatively high pH conditions during the formation of EMZ result in relatively light C and O isotopic compositions compared with FA, which form under generally lower pH conditions. A direct test of such models would be possible if the Boron isotopic composition, which is pH sensitive, of EMZ and FA could be measured. We performed ion microprobe d11B measurements for EMZ and FA in Lophelia pertusa, a deep-sea coral common in the North-East Atlantic Ocean. We observe a systematic difference in B isotopic composition between the EMZ and FA skeleton. In EMZ, the measured δ11B values are consistently low. Fibrous aragonite is characterized by systematically higher d11B values, but also display B isotopic heterogeneity associated with specific growth bands in the calyx wall. The magnitude of the observed B isotopic variations cannot be explained by changes in environmental conditions and are likely caused by biological processes involved in the biomineralization of new skeleton; i.e. 'vital' effects. The observed B isotopic variations are opposite to the predictions of geochemical models for vital effects. Our data indicate that pH variations are not responsible for the observed stable isotopic fractionations. Geochemical models therefore do not provide an adequate framework within which to understand coral skeletal formation. Without a better understanding of these processes, which require experiments, the use of B isotopic composition to reconstruct paleo-pH variations in the oceans must be considered problematic - at least as far as Lophelia pertusa is concerned.

Transient kinetic studies of pH-dependent hydrolyses by exo-type carboxypeptidase P on a 27-MHz quartz crystal microbalance.

PubMed

Furusawa, Hiroyuki; Takano, Hiroki; Okahata, Yoshio

2008-02-15

pH-Dependent kinetic parameters (k(on), k(off), and k(cat)) of protein (myoglobin) hydrolyses catalyzed by exo-enzyme (carboxypeptidase P, CPP) were obtained by using a protein-immobilized quartz crystal microbalance (QCM) in acidic aqueous solutions. The formation of the enzyme-substrate (ES) complex (k(on)), the decay of the ES complex (k(off)), and the formation of the product (k(cat)) could be analyzed by transient kinetics as mass changes on the QCM plate. The Kd (k(off)/k(on)) value was different from the Michaelis constant Km calculated from (k(off) + k(cat))/k(on) due to k(cat) > k(off). The rate-determining step was the binding step (k(on), and the catalytic rate k(cat) was faster than other k(on) and k(off) values. In the range of pH 2.5-5.0, values of k(on) gradually increased with decreasing pH showing a maximum at pH 3.7, values of k(off) were independent of pH, and k(cat) increased gradually with decreasing pH. As a result, the apparent rate constant (k(cat)/Km) showed a maximum at pH 3.7 and gradually increased with decreasing pH. The optimum pH at 3.7 of k(on) is explained by the optimum binding ability of CPP to the COOH terminus of the substrate with hydrogen bonds. The increase of k(cat) at the lower pH correlated with the decrease of alpha-helix contents of the myoglobin substrate on the QCM.

Tessellated gold nanostructures from Au144(SCH2CH2Ph)60 molecular precursors and their use in organic solar cell enhancement

NASA Astrophysics Data System (ADS)

Bauld, Reg; Hesari, Mahdi; Workentin, Mark S.; Fanchini, Giovanni

2014-06-01

We report for the first time the fabrication of nanocomposite hole-blocking layers consisting of poly-3,4-ethylene-dioxythiophene:poly-styrene-sulfonate (PEDOT:PSS) thin films incorporating networks of gold nanoparticles assembled from Au144(SCH2CH2Ph)60, a molecular gold precursor. These thin films can be prepared reproducibly on indium tin oxide by spinning on it Au144(SCH2CH2Ph)60 solutions in chlorobenzene, annealing the resulting thin film at 400 °C, and subsequently spinning PEDOT:PSS on top. The use of our nanocomposite hole-blocking layers for enhancing the photoconversion efficiency of bulk heterojunction organic solar cells is demonstrated. By varying the concentration of Au144(SCH2CH2Ph)60 in the starting solution and the annealing time, different gold nanostructures were obtained ranging from individual gold nanoparticles (AuNPs) to tessellated networks of gold nanostructures (Tess-AuNPs). Improvement in organic solar cell efficiencies up to 10% relative to a reference cell is demonstrated with Tess-AuNPs embedded in PEDOT:PSS.

Emulsifying properties of succinylated arabinoxylan-protein gum produced from corn ethanol residuals

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

Xiang, Zhouyang; Runge, Troy

This study investigated the possibilities of making valuable products from corn ethanol byproducts and providing the beverage industries more variety of high quality emulsifiers other than gum arabic. An arabinoxylan-protein gum (APG) was extracted from distillers' grains (DG), a low-value corn ethanol byproduct, and modified through acylation with succinic anhydride. The effects of pH and degree of substitution (DS) on the emulsifying properties of succinylated APG, referred to as SAPG, were investigated. Emulsion particle size and stability of APG and gum arabic were comparable at pH 3.5–6.5. Succinylation could enhance the emulsifying properties of APG. Compared to gum arabic, atmore » pH < 5, SAPG emulsions had larger particle size but comparable stability, whereas at pH > 5, SAPG had much smaller particle size and better stability than gum arabic. The results suggested that SAPG, compared to gum arabic, could be a comparable emulsifier at low pH values and a better emulsifier at neutral pH values.« less

Emulsifying properties of succinylated arabinoxylan-protein gum produced from corn ethanol residuals

DOE PAGES

Xiang, Zhouyang; Runge, Troy

2015-07-21

This study investigated the possibilities of making valuable products from corn ethanol byproducts and providing the beverage industries more variety of high quality emulsifiers other than gum arabic. An arabinoxylan-protein gum (APG) was extracted from distillers' grains (DG), a low-value corn ethanol byproduct, and modified through acylation with succinic anhydride. The effects of pH and degree of substitution (DS) on the emulsifying properties of succinylated APG, referred to as SAPG, were investigated. Emulsion particle size and stability of APG and gum arabic were comparable at pH 3.5–6.5. Succinylation could enhance the emulsifying properties of APG. Compared to gum arabic, atmore » pH < 5, SAPG emulsions had larger particle size but comparable stability, whereas at pH > 5, SAPG had much smaller particle size and better stability than gum arabic. The results suggested that SAPG, compared to gum arabic, could be a comparable emulsifier at low pH values and a better emulsifier at neutral pH values.« less

Computer simulation of immobilized pH gradients at acidic and alkaline extremes - A quest for extended pH intervals

NASA Technical Reports Server (NTRS)

Mosher, Richard A.; Bier, Milan; Righetti, Pier Giorgio

1986-01-01

Computer simulations of the concentration profiles of simple biprotic ampholytes with Delta pKs 1, 2, and 3, on immobilized pH gradients (IPG) at extreme pH values (pH 3-4 and pH 10-11) show markedly skewed steady-state profiles with increasing kurtosis at higher Delta pK values. Across neutrality, all the peaks are symmetric irrespective of their Delta pK values, but they show very high contribution to the conductivity of the background gel and significant alteration of the local buffering capacity. The problems of skewness, due to the exponential conductivity profiles at low and high pHs, and of gel burning due to a strong electroosmotic flow generated by the net charges in the gel matrix, also at low and high pHs, are solved by incorporating in the IPG gel a strong viscosity gradient. This is generated by a gradient of linear polyacrylamide which is trapped in the gel by the polymerization process.

Batch and fed-batch production of butyric acid by Clostridium butyricum ZJUCB

PubMed Central

He, Guo-qing; Kong, Qing; Chen, Qi-he; Ruan, Hui

2005-01-01

The production of butyric acid by Clostridium butyricum ZJUCB at various pH values was investigated. In order to study the effect of pH on cell growth, butyric acid biosynthesis and reducing sugar consumption, different cultivation pH values ranging from 6.0 to 7.5 were evaluated in 5-L bioreactor. In controlled pH batch fermentation, the optimum pH for cell growth and butyric acid production was 6.5 with a cell yield of 3.65 g/L and butyric acid yield of 12.25 g/L. Based on these results, this study then compared batch and fed-batch fermentation of butyric acid production at pH 6.5. Maximum value (16.74 g/L) of butyric acid concentration was obtained in fed-batch fermentation compared to 12.25 g/L in batch fermentation. It was concluded that cultivation under fed-batch fermentation mode could enhance butyric acid production significantly (P<0.01) by C. butyricum ZJUCB. PMID:16252341

Sub-optimal pH Preadaptation Improves the Survival of Lactobacillus plantarum Strains and the Malic Acid Consumption in Wine-Like Medium

PubMed Central

Succi, Mariantonietta; Pannella, Gianfranco; Tremonte, Patrizio; Tipaldi, Luca; Coppola, Raffaele; Iorizzo, Massimo; Lombardi, Silvia Jane; Sorrentino, Elena

2017-01-01

Forty-two oenological strains of Lb. plantarum were assessed for their response to ethanol and pH values generally encountered in wines. Strains showed a higher variability in the survival when exposed to low pH (3.5 or 3.0) than when exposed to ethanol (10 or 14%). The study allowed to individuate the highest ethanol concentration (8%) and the lowest pH value (4.0) for the growth of strains, even if the maximum specific growth rate (μmax) resulted significantly reduced by these conditions. Two strains (GT1 and LT11) preadapted to 2% ethanol and cultured up to 14% of ethanol showed a higher growth than those non-preadapted when they were cultivated at 8% of ethanol. The evaluation of the same strains preadapted to low pH values (5.0 and 4.0) and then grown at pH 3.5 or 3.0 showed only for GT1 a sensitive μmax increment when it was cultivated in MRS at pH 3 after a preadaptation to pH 5.0. The survival of GT1 and LT11 was evaluated in Ringer's solution at 14% ethanol after a long-term adaptation in MRS with 2% ethanol or in MRS with 2% ethanol acidified at pH 5.0 (both conditions, BC). Analogously, the survival was evaluated at pH 3.5 after a long-term adaptation in MRS at pH 5.0 or in MRS BC. The impact of the physiologic state (exponential phase vs stationary phase) on the survival was also evaluated. Preadapted cells showed the same behavior of non-preadapted cells only when cultures were recovered in the stationary phase. Mathematical functions were individuated for the description of the survival of GT1 and LT11 in MRS at 14% ethanol or at pH 3.5. Finally, a synthetic wine (SW) was used to assess the behavior of Lb. plantarum GT1 and LT11 preadapted in MRS at 2% ethanol or at pH 5.0 or in BC. Only GT1 preadapted to pH 5.0 and collected in the stationary phase showed constant values of microbial counts after incubation for 15 days at 20°C. In addition, after 15 days the L-malic acid resulted completely degraded and the pH value increased of about 0.3 units. PMID:28382030

Net alkalinity and net acidity 2: Practical considerations

USGS Publications Warehouse

Kirby, C.S.; Cravotta, C.A.

2005-01-01

The pH, alkalinity, and acidity of mine drainage and associated waters can be misinterpreted because of the chemical instability of samples and possible misunderstandings of standard analytical method results. Synthetic and field samples of mine drainage having various initial pH values and concentrations of dissolved metals and alkalinity were titrated by several methods, and the results were compared to alkalinity and acidity calculated based on dissolved solutes. The pH, alkalinity, and acidity were compared between fresh, unoxidized and aged, oxidized samples. Data for Pennsylvania coal mine drainage indicates that the pH of fresh samples was predominantly acidic (pH 2.5-4) or near neutral (pH 6-7); ??? 25% of the samples had pH values between 5 and 6. Following oxidation, no samples had pH values between 5 and 6. The Standard Method Alkalinity titration is constrained to yield values >0. Most calculated and measured alkalinities for samples with positive alkalinities were in close agreement. However, for low-pH samples, the calculated alkalinity can be negative due to negative contributions by dissolved metals that may oxidize and hydrolyze. The Standard Method hot peroxide treatment titration for acidity determination (Hot Acidity) accurately indicates the potential for pH to decrease to acidic values after complete degassing of CO2 and oxidation of Fe and Mn, and it indicates either the excess alkalinity or that required for neutralization of the sample. The Hot Acidity directly measures net acidity (= -net alkalinity). Samples that had near-neutral pH after oxidation had negative Hot Acidity; samples that had pH < 6.3 after oxidation had positive Hot Acidity. Samples with similar pH values before oxidation had dissimilar Hot Acidities due to variations in their alkalinities and dissolved Fe, Mn, and Al concentrations. Hot Acidity was approximately equal to net acidity calculated based on initial pH and dissolved concentrations of Fe, Mn, and Al minus the initial alkalinity. Acidity calculated from the pH and dissolved metals concentrations, assuming equivalents of 2 per mole of Fe and Mn and 3 per mole of Al, was equivalent to that calculated based on complete aqueous speciation of FeII/FeIII. Despite changes in the pH, alkalinity, and metals concentrations, the Hot Acidities were comparable for fresh and most aged samples. A meaningful "net" acidity can be determined from a measured Hot Acidity or by calculation from the pH, alkalinity, and dissolved metals concentrations. The use of net alkalinity = (Alkalinitymeasured - Hot Aciditymeasured) to design mine drainage treatment can lead to systems with insufficient Alkalinity to neutralize metal and H+ acidity and is not recommended. The use of net alkalinity = -Hot Acidity titration is recommended for the planning of mine drainage treatment. The use of net alkalinity = (Alkalinitymeasured - Aciditycalculated) is recommended with some cautions. ?? 2005 Elsevier Ltd. All rights reserved.

Lower pH values of weakly acidic refluxes as determinants of heartburn perception in gastroesophageal reflux disease patients with normal esophageal acid exposure.

PubMed

de Bortoli, N; Martinucci, I; Savarino, E; Franchi, R; Bertani, L; Russo, S; Ceccarelli, L; Costa, F; Bellini, M; Blandizzi, C; Savarino, V; Marchi, S

2016-01-01

Multichannel impedance pH monitoring has shown that weakly acidic refluxes are able to generate heartburn. However, data on the role of different pH values, ranging between 4 and 7, in the generation of them are lacking. The aim of this study was to evaluate whether different pH values of weakly acidic refluxes play a differential role in provoking reflux symptoms in endoscopy-negative patients with physiological esophageal acid exposure time and positive symptom index and symptom association probability for weakly acidic refluxes. One hundred and forty-three consecutive patients with gastroesophageal reflux disease, nonresponders to proton pump inhibitors (PPIs), were allowed a washout from PPIs before undergoing: upper endoscopy, esophageal manometry, and multichannel impedance pH monitoring. In patients with both symptom index and symptom association probability positive for weakly acidic reflux, each weakly acidic reflux was evaluated considering exact pH value, extension, physical characteristics, and correlation with heartburn. Forty-five patients with normal acid exposure time and positive symptom association probability for weakly acidic reflux were identified. The number of refluxes not heartburn related was higher than those heartburn related. In all distal and proximal liquid refluxes, as well as in distal mixed refluxes, the mean pH value of reflux events associated with heartburn was significantly lower than that not associated. This condition was not confirmed for proximal mixed refluxes. Overall, a low pH of weakly acidic reflux represents a determinant factor in provoking heartburn. This observation contributes to better understand the pathophysiology of symptoms generated by weakly acidic refluxes, paving the way toward the search for different therapeutic approaches to this peculiar condition of esophageal hypersensitivity. © 2014 International Society for Diseases of the Esophagus.

A Quantitative Review and Meta-Models of the Variability and Factors Affecting Oral Drug Absorption-Part I: Gastrointestinal pH.

PubMed

Abuhelwa, Ahmad Y; Foster, David J R; Upton, Richard N

2016-09-01

This study aimed to conduct a quantitative meta-analysis for the values of, and variability in, gastrointestinal (GI) pH in the different GI segments; characterize the effect of food on the values and variability in these parameters; and present quantitative meta-models of distributions of GI pH to help inform models of oral drug absorption. The literature was systemically reviewed for the values of, and the variability in, GI pH under fed and fasted conditions. The GI tract was categorized into the following 10 distinct regions: stomach (proximal, mid-distal), duodenum (proximal, mid-distal), jejunum and ileum (proximal, mid, and distal small intestine), and colon (ascending, transverse, and descending colon). Meta-analysis used the "metafor" package of the R language. The time course of postprandial stomach pH was modeled using NONMEM. Food significantly influenced the estimated meta-mean stomach and duodenal pH but had no significant influence on small intestinal and colonic pH. The time course of postprandial pH was described using an exponential model. Increased meal caloric content increased the extent and duration of postprandial gastric pH buffering. The different parts of the small intestine had significantly different pH. Colonic pH was significantly different for descending but not for ascending and transverse colon. Knowledge of GI pH is important for the formulation design of the pH-dependent dosage forms and in understanding the dissolution and absorption of orally administered drugs. The meta-models of GI pH may also be used as part of semi-physiological pharmacokinetic models to characterize the effect of GI pH on the in vivo drug release and pharmacokinetics.

Application of the Oxidation-Reduction Potential (ORP) for Pre-grading Tuna Freshness On-board

NASA Astrophysics Data System (ADS)

Cheevaporanapivat, Mongkol; Sakai, Hisaharu; Mine, Yuuji; Watanabe, Manabu; Suzuki, Toru

Application of ORP as a rapid indicator for grading tuna's freshness on the ship was studied. The long line trawling process was used for catching the sample tuna in the South Pacific Ocean. All captured sample tuna were weighed, gender identified and investigated for their mortality, then measured ORP and K value. Three species of tuna were caught: blue marlin (Makaira mazara), yellow fin tuna (Thunnus albacares), and swordfish (Xiphia gladius). Most of the fish captured were male and they had been dead after picking onboard. The measured ORP values of blue marlin varied in the range of 0.295-0.362 Volt, with pH between 5.35-5.84. Both ORP and pH of swordfish was similar to that of blue marlin. But for yellow fin tuna, the ORP value was about the same as blue marlin while its pH was significantly higher. ORP value in all species tended to increase with pH of the fish meat decrease. It is interesting that ORP value of tuna increased in correlation with K value. These results suggested that ORP and pH change, which are measured in the short time, are the effective indicators for grading tuna's freshness on-board.

Stable Fe isotope fractionation during anaerobic microbial dissimilatory iron reduction at low pH

NASA Astrophysics Data System (ADS)

Chanda, P.; Amenabar, M. J.; Boyd, E. S.; Beard, B. L.; Johnson, C.

2017-12-01

In low-temperature anaerobic environments microbial dissimilatory iron reduction (DIR) plays an important role in Fe cycling. At neutral pH, sorption of aqueous Fe(II) (Fe(II)aq, produced by DIR) catalyzes isotopic exchange between Fe(II) and solid Fe(III), producing 56Fe/54Fe fractionations on the order of 3‰ during DIR[1,2,3]. At low pH, however, the absence of sorbed Fe(II) produces only limited abiologic isotopic exchange[4]. Here we investigated the scope of isotopic exchange between Fe(II)aq and ferric (hydr)oxides (ferrihydrite and goethite) and the associated stable Fe isotope fractionation during DIR by Acidianus strain DS80 at pH 3.0 and 80°C[5]. Over 19 days, 13% reduction of both minerals via microbial DIR was observed. The δ56Fe values of the fluid varied from -2.31 to -1.63‰ (ferrihydrite) and -0.45 to 0.02‰ (goethite). Partial leaching of bulk solid from each reactor with dilute HCl showed no sorption of Fe(II), and the surface layers of the solids were composed of Fe(III) with high δ56Fe values (ferrihydrite: 0.20 to 0.48‰ and goethite: 1.20 to 1.30‰). These results contrast with the lack of Fe isotope exchange in abiologic low-pH systems and indicate a key role for biology in catalyzing Fe isotope exchange between Fe(II)aq and Fe(III) solids, despite the absence of sorbed Fe(II). The estimated fractionation factor (ΔFeFe(III) -Fe(II)aq 2.6‰) from leaching of ferrihydrite is similar to the abiologic equilibrium fractionation factor ( 3.0‰)[3]. The fractionation factor (ΔFeFe(III) -Fe(II)aq 2.0‰) for goethite is higher than the abiologic fractionation factor ( 1.05‰)[2], but is consistent with the previously proposed "distorted surface layer" of goethite produced during the exchange with Fe(II)aq at neutral pH[1]. This study indicates that significant variations in Fe isotope compositions may be produced in low-pH environments where biological cycling of Fe occurs, in contrast to the expected lack of isotopic fractionation in low-pH abiologic systems, and such results bear on the search for biosignatures in Mars and Mars-analog settings. [1] Crosby et al., 2007 Geobiol. 5, 169-189 [2] Beard et al., 2010 Earth Planet. Sci. Lett. 295, 241-250 [3] Wu et al., 2011 Environ. Sci. Technol. 45, 1847-1852 [4] Reddy et al., 2015 Chem. Geol. 397, 118-127 [5] Amenabar et al., 2017 Nat. Geosci. In press

Investigating controls on boron isotope ratios in shallow marine carbonates

NASA Astrophysics Data System (ADS)

Zhang, Shuang; Henehan, Michael J.; Hull, Pincelli M.; Reid, R. Pamela; Hardisty, Dalton S.; Hood, Ashleigh v. S.; Planavsky, Noah J.

2017-01-01

The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects - physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally 'abiogenic' carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives. In addition, variability in δ11B based pH estimates provides additional support for the idea that photosynthetic CO2 uptake plays a significant role in driving carbonate precipitation in a wide range of shallow water carbonates.

Formation of positively charged gold nanoparticle monolayers on silica sensors.

PubMed

Oćwieja, Magdalena; Maciejewska-Prończuk, Julia; Adamczyk, Zbigniew; Roman, Maciej

2017-09-01

Formation of positively charged gold nanoparticle monolayers on the Si/SiO 2 was studied under in situ conditions using quartz microbalance (QCM). The gold nanoparticles were synthesized in a chemical reduction method using sodium borohydride as reducing agent. Cysteamine hydrochloride was applied to generate a positive surface charge of nanoparticles. The micrographs obtained from transmission electron microscopy (TEM) revealed that the average size of nanoparticles was equal to 12±3nm. The stability of nanoparticle suspensions under controlled pH and ionic strength was determined by dynamic light scattering (DLS). The electrophoretic mobility measurements showed that the zeta potential of nanoparticles was positive, decreasing with ionic strength and pH from 56mV at pH 4.2 and I=10 -4 M to 22mV at pH 8.3 and I=3×10 -3 M. The surface enhanced Raman spectroscopy (SERS) confirmed chemisorption of cysteamine on nanoparticles and the contribution of amine moieties in the generation of nanoparticle charge. The influence of suspension concentration, ionic strength and flow rate on the kinetics of nanoparticle deposition on the sensors was quantitatively determined. It was confirmed that the deposition for the low coverage regime is governed by the bulk mass transfer that results in a linear increase of the coverage with time. The significant increase in the maximum coverage of gold monolayers with ionic strength was interpreted as due to the decreasing range of the electrostatic interactions among deposited particles. Moreover, the hydratation of formed monolayers, their structure and the stability were determined by the comparison of the QCM results with those obtained by AFM and SEM. The experimental data were adequately interpreted in terms of the extended random sequential adsorption (eRSA) model that considers the bulk and surface transfer steps in a rigorous way. The obtained results are useful for a facile fabrication of gold nanoparticle-based biosensors capable to bind target molecules via available amine moieties. Copyright © 2017 Elsevier Inc. All rights reserved.

Numerical simulation of ozone concentration profile and flow characteristics in paddy bulks.

PubMed

Pandiselvam, Ravi; Chandrasekar, Veerapandian; Thirupathi, Venkatachalam

2017-08-01

Ozone has shown the potential to control stored product insect pests. The high reactivity of ozone leads to special problems when it passes though an organic medium such as stored grains. Thus, there is a need for a simulation study to understand the concentration profile and flow characteristics of ozone in stored paddy bulks as a function of time. Simulation of ozone concentration through the paddy grain bulks was explained by applying the principle of the law of conservation along with a continuity equation. A higher ozone concentration value was observed at regions near the ozone diffuser whereas a lower concentration value was observed at regions away from the ozone diffuser. The relative error between the experimental and predicted ozone concentration values for the entire bin geometry was less than 42.8%. The simulation model described a non-linear change of ozone concentration in stored paddy bulks. Results of this study provide a valuable source for estimating the parameters needed for effectively designing a storage bin for fumigation of paddy grains in a commercial scale continuous-flow ozone fumigation system. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Effect of pH on compressive strength of some modification of mineral trioxide aggregate

PubMed Central

Saghiri, Mohammad A.; Garcia-Godoy, Franklin; Asatourian, Armen; Lotfi, Mehrdad; Khezri-Boukani, Kaveh

2013-01-01

Objectives: Recently, it was shown that NanoMTA improved the setting time and promoted a better hydration process which prevents washout and the dislodgment of this novel biomaterial in comparison with WTMA. This study analyzed the compressive strength of ProRoot WMTA (Dentsply), a NanoWMTA (Kamal Asgar Research Center), and Bioaggregate (Innovative Bioceramix) after its exposure to a range of environmental pH conditions during hydration. Study Design: After mixing the cements under aseptic condition and based on the manufacturers` recommendations, the cements were condensed with moderate force using plugger into 9 × 6 mm split molds. Each type of cement was then randomly divided into three groups (n=10). Specimens were exposed to environments with pH values of 4.4, 7.4, or 10.4 for 3 days. Cement pellets were compressed by using an Instron testing machine. Values were recorded and compared. Data were analyzed by using one-way analysis of variance and a post hoc Tukey’s test. Results: After 3 days, the samples were solid when probed with an explorer before removing them from the molds. The greatest mean compressive strength 133.19±11.14 MPa was observed after exposure to a pH value of 10.4 for NanoWMTA. The values decreased to 111.41±8.26 MPa after exposure to a pH value of 4.4. Increasing of pH had a significant effect on the compressive strength of the groups (p<0.001). The mean compressive strength for the NanoWMTA was statistically higher than for ProRoot WMTA and Bioaggregate (p<0.001). Moreover, increasing of pH values had a significant effect on compressive strength of the experimental groups (p<0.001). Conclusion: The compressive strength of NanoWMTA was significantly higher than WMTA and Bioaggregate; the more acidic the environmental pH, the lower was the compressive strength. Key words:Compressive strength, mineral trioxide aggregate, Nano. PMID:23722137

TU-CD-BRB-04: Automated Radiomic Features Complement the Prognostic Value of VASARI in the TCGA-GBM Dataset

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

Velazquez, E Rios; Narayan, V; Grossmann, P

2015-06-15

Purpose: To compare the complementary prognostic value of automated Radiomic features to that of radiologist-annotated VASARI features in TCGA-GBM MRI dataset. Methods: For 96 GBM patients, pre-operative MRI images were obtained from The Cancer Imaging Archive. The abnormal tumor bulks were manually defined on post-contrast T1w images. The contrast-enhancing and necrotic regions were segmented using FAST. From these sub-volumes and the total abnormal tumor bulk, a set of Radiomic features quantifying phenotypic differences based on the tumor intensity, shape and texture, were extracted from the post-contrast T1w images. Minimum-redundancy-maximum-relevance (MRMR) was used to identify the most informative Radiomic, VASARI andmore » combined Radiomic-VASARI features in 70% of the dataset (training-set). Multivariate Cox-proportional hazards models were evaluated in 30% of the dataset (validation-set) using the C-index for OS. A bootstrap procedure was used to assess significance while comparing the C-Indices of the different models. Results: Overall, the Radiomic features showed a moderate correlation with the radiologist-annotated VASARI features (r = −0.37 – 0.49); however that correlation was stronger for the Tumor Diameter and Proportion of Necrosis VASARI features (r = −0.71 – 0.69). After MRMR feature selection, the best-performing Radiomic, VASARI, and Radiomic-VASARI Cox-PH models showed a validation C-index of 0.56 (p = NS), 0.58 (p = NS) and 0.65 (p = 0.01), respectively. The combined Radiomic-VASARI model C-index was significantly higher than that obtained from either the Radiomic or VASARI model alone (p = <0.001). Conclusion: Quantitative volumetric and textural Radiomic features complement the qualitative and semi-quantitative annotated VASARI feature set. The prognostic value of informative qualitative VASARI features such as Eloquent Brain and Multifocality is increased with the addition of quantitative volumetric and textural features from the contrast-enhancing and necrotic tumor regions. These results should be further evaluated in larger validation cohorts.« less

Sensitive detection of strong acidic condition by a novel rhodamine-based fluorescent pH chemosensor.

PubMed

Tan, Jia-Lian; Yang, Ting-Ting; Liu, Yu; Zhang, Xue; Cheng, Shu-Jin; Zuo, Hua; He, Huawei

2016-05-01

A novel rhodamine-based fluorescent pH probe responding to extremely low pH values has been synthesized and characterized. This probe showed an excellent photophysical response to pH on the basis that the colorless spirocyclic structure under basic conditions opened to a colored and highly fluorescent form under extreme acidity. The quantitative relationship between fluorescence intensity and pH value (1.75-2.62) was consistent with the equilibrium equation pH = pKa + log[(Imax - I)/(I - Imin)]. This sensitive pH probe was also characterized with good reversibility and no interaction with interfering metal ions, and was successfully applied to image Escherichia coli under strong acidity. Copyright © 2015 John Wiley & Sons, Ltd.

Functional photoacoustic microscopy of pH

NASA Astrophysics Data System (ADS)

Chatni, M. Rameez; Yao, Junjie; Danielli, Amos; Favazza, Christopher P.; Maslov, Konstantin I.; Wang, Lihong V.

2012-02-01

pH is a tightly regulated indicator of metabolic activity. In mammalian systems, imbalance of pH regulation may result from or result in serious illness. Even though the regulation system of pH is very robust, tissue pH can be altered in many diseases such as cancer, osteoporosis and diabetes mellitus. Traditional high-resolution optical imaging techniques, such as confocal microscopy, routinely image pH in cells and tissues using pH sensitive fluorescent dyes, which change their fluorescence properties with the surrounding pH. Since strong optical scattering in biological tissue blurs images at greater depths, high-resolution pH imaging is limited to penetration depths of 1mm. Here, we report photoacoustic microscopy (PAM) of commercially available pH-sensitive fluorescent dye in tissue phantoms. Using both opticalresolution photoacoustic microscopy (OR-PAM), and acoustic resolution photoacoustic microscopy (AR-PAM), we explored the possibility of recovering the pH values in tissue phantoms. In this paper, we demonstrate that PAM was capable of recovering pH values up to a depth of 2 mm, greater than possible with other forms of optical microscopy.

Evaluation of the relation between lipid coat, transepidermal water loss, and skin pH.

PubMed

Algiert-Zielińska, Barbara; Batory, Mirella; Skubalski, Janusz; Rotsztejn, Helena

2017-11-01

The epidermis is an epidermal barrier which accumulates lipid substances and participates in skin moisturizing. An evaluation of the epidermal barrier efficiency can be made, among others, by the measurement of the following values: the lipid coat, the transepidermal water loss (TEWL) index, and pH. The study involved 50 Caucasian, healthy women aged 19-35 years (mean 20.56). Measurements were made using Courage & Khazaka Multi Probe Adapter MPA 580: Tewameter TM 300, pH-Meter PH 905, Sebumeter SM 815. The areas of measurements included forehead, nose, left cheek, right cheek, chin, and thigh. In the T-zone, the lipid coat was in the range between 0 and 270 μg/cm 2 (mean 128 μg/cm 2 ), TEWL between 1 and 55 g/m 2 /h (mean 11.1 g/m 2 /h), and pH 4.0-5.6 (mean 5.39). Lower values of the lipid coat up to 100 μg/cm 2 were accompanied by TEWL greater than 30 g/m 2 /h and less acidic pH of 5.6-9.0. In the U-zone the range of lipid coat was up to 200 μg/cm 2 (mean 65.2 μg/cm 2 ), the skin pH remained 4.0-5.6 (mean 5.47), and TEWL was in the range between 1 and 20 g/m 2 /h (mean 8.7 g/m 2 /h). Lower values of the lipid coat up to 100 μg/cm 2 were accompanied by TEWL between 1 and 20 g/m 2 /h and less acidic pH of 5.6-9.0. High values of the lipid coat between 180 and 200 μg/cm 2 were connected with TEWL of 1-15 g/m 2 /h. On the skin of the thigh, we observed a very thin lipid coat - 35 μg/cm 2 (mean 5.6 μg/cm 2 ), pH (mean 5.37), and TEWL (mean 8.5 g/m 2 /h) were considered by us to be within regular limits. In the T-zone, a thinner lipid coat resulted in relatively high TEWL and pH levels changing toward alkaline. In the U-zone, thinner lipid coat was accompanied by lower TEWL and pH changing toward alkaline. We also observed that lower values of lipid coat up to 100 μg/cm 2 were associated with higher pH values ranging toward the basic character pH 5.6-9.0). © 2017 The International Society of Dermatology.

Development of a 500 GHz Optoelectronic Modulator Using Superconducting Transmission Lines

DTIC Science & Technology

1992-08-31

for operation in the multi- hundred-GHz regime, as well as high-power picosecond switching and the newly developed Semiconductor Optical, Temporal...bulk dielectric constants in the near infrared and millimeter-wave regimes that are essentially equal.J31 We have shown that encapsulating a...dielectric constant was found to be 11.60 (+/- 0.02). This value agrees remarkably well with the bulk value of GaAs at 1.3 4m, 11.62 [3]. The

High Sensitivity pH Sensor Based on Porous Silicon (PSi) Extended Gate Field-Effect Transistor

PubMed Central

Al-Hardan, Naif H.; Abdul Hamid, Muhammad Azmi; Ahmed, Naser M.; Jalar, Azman; Shamsudin, Roslinda; Othman, Norinsan Kamil; Kar Keng, Lim; Chiu, Weesiong; Al-Rawi, Hamzah N.

2016-01-01

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions. PMID:27338381

High Sensitivity pH Sensor Based on Porous Silicon (PSi) Extended Gate Field-Effect Transistor.

PubMed

Al-Hardan, Naif H; Abdul Hamid, Muhammad Azmi; Ahmed, Naser M; Jalar, Azman; Shamsudin, Roslinda; Othman, Norinsan Kamil; Kar Keng, Lim; Chiu, Weesiong; Al-Rawi, Hamzah N

2016-06-07

In this study, porous silicon (PSi) was prepared and tested as an extended gate field-effect transistor (EGFET) for pH sensing. The prepared PSi has pore sizes in the range of 500 to 750 nm with a depth of approximately 42 µm. The results of testing PSi for hydrogen ion sensing in different pH buffer solutions reveal that the PSi has a sensitivity value of 66 mV/pH that is considered a super Nernstian value. The sensor considers stability to be in the pH range of 2 to 12. The hysteresis values of the prepared PSi sensor were approximately 8.2 and 10.5 mV in the low and high pH loop, respectively. The result of this study reveals a promising application of PSi in the field for detecting hydrogen ions in different solutions.

Natural Oxidation of Bromide to Bromine in Evaporated Dead Sea Brines

NASA Astrophysics Data System (ADS)

Gavrieli, Ittai; Golan, Rotem; Lazar, Boaz; Baer, Gidi; Zakon, Yevgeni; Ganor, Jiwchar

2016-04-01

Highly evaporated Dead Sea brines are found in isolated sinkholes along the Dead Sea. Many of these brines reach densities of over 1.3 kg/L and pH<5 and are the product of evaporation of Dead Sea brine that drain into the sinkholes. The low pH and the reddish to brownish hue of these brines were an enigma until recently. Despite the rather high total alkalinity (TA) of the Dead Sea (3.826 mmol/kg) the pH of the Dead Sea brine is known to be slightly acidic with a value of ~6.3. In comparison, seawater with the same alkalinity would have a pH value well above 8.3, meaning that H+ activity is 100 fold lower than that of Dead Sea brine. In the present work we assess the apparent dissociation constant value of boric acid (K`B) for the Dead Sea brine and use it to explain the brine's low pH value. We then show that pH decreases further as the brine evaporates and salinity increases. Finally we explain the reddish hue of the hypersaline brines in the sinkholes as due to the presence of dissolved bromine. The latter is the product of oxidation of dissolved bromide, a process that is enabled by the low pH of the hypersaline brines and their high bromide concentration.

Atomic Physics with the Goddard High Resolution Spectrograph on the Hubble Space Telescope. III; Oscillator Strengths for Neutral Carbon

NASA Technical Reports Server (NTRS)

Zsargo, J.; Federman, S. R.; Cardelli, Jason A.

1997-01-01

High quality spectra of interstellar absorption from C I toward beta(sup 1) S(sub co), rho O(sub ph) A, and chi O(sub ph) were obtained with the Goddard High Resolution Spectrograph on HST. Many weak lines were detected within the observed wavelength intervals: 1150-1200 A for beta(sup 1) S(sub co) and 1250-1290 A for rho O(sub ph) A and chi O(sub ph). Curve-of-growth analyses were performed in order to extract accurate column densities and Doppler parameters from lines with precise laboratory-based f-values. These column densities and b-values were used to obtain a self-consistent set of f-values for all the observed C I lines. A particularly important constraint was the need to reproduce data for more than one line of sight. For about 50% of the lines, the derived f-values differ appreciably from the values quoted by Morton.

Effect of pH and nitrite concentration on nitrite oxidation rate.

PubMed

Jiménez, E; Giménez, J B; Ruano, M V; Ferrer, J; Serralta, J

2011-10-01

The effect of pH and nitrite concentration on the activity of the nitrite oxidizing bacteria (NOB) in an activated sludge reactor has been determined by means of laboratory batch experiments based on respirometric techniques. The bacterial activity was measured at different pH and at different total nitrite concentrations (TNO₂). The experimental results showed that the nitrite oxidation rate (NOR) depends on the TNO₂ concentration independently of the free nitrous acid (FNA) concentration, so FNA cannot be considered as the real substrate for NOB. NOB were strongly affected by low pH values (no activity was detected at pH 6.5) but no inhibition was observed at high pH values (activity was nearly the same for the pH range 7.5-9.95). A kinetic expression for nitrite oxidation process including switch functions to model the effect of TNO₂ concentration and pH inhibition is proposed. Substrate half saturation constant and pH inhibition constants have been obtained. Copyright © 2011 Elsevier Ltd. All rights reserved.

Fine-particle pH for Beijing winter haze as inferred from different thermodynamic equilibrium models

NASA Astrophysics Data System (ADS)

Song, Shaojie; Gao, Meng; Xu, Weiqi; Shao, Jingyuan; Shi, Guoliang; Wang, Shuxiao; Wang, Yuxuan; Sun, Yele; McElroy, Michael B.

2018-05-01

pH is an important property of aerosol particles but is difficult to measure directly. Several studies have estimated the pH values for fine particles in northern China winter haze using thermodynamic models (i.e., E-AIM and ISORROPIA) and ambient measurements. The reported pH values differ widely, ranging from close to 0 (highly acidic) to as high as 7 (neutral). In order to understand the reason for this discrepancy, we calculated pH values using these models with different assumptions with regard to model inputs and particle phase states. We find that the large discrepancy is due primarily to differences in the model assumptions adopted in previous studies. Calculations using only aerosol-phase composition as inputs (i.e., reverse mode) are sensitive to the measurement errors of ionic species, and inferred pH values exhibit a bimodal distribution, with peaks between -2 and 2 and between 7 and 10, depending on whether anions or cations are in excess. Calculations using total (gas plus aerosol phase) measurements as inputs (i.e., forward mode) are affected much less by these measurement errors. In future studies, the reverse mode should be avoided whereas the forward mode should be used. Forward-mode calculations in this and previous studies collectively indicate a moderately acidic condition (pH from about 4 to about 5) for fine particles in northern China winter haze, indicating further that ammonia plays an important role in determining this property. The assumed particle phase state, either stable (solid plus liquid) or metastable (only liquid), does not significantly impact pH predictions. The unrealistic pH values of about 7 in a few previous studies (using the standard ISORROPIA model and stable state assumption) resulted from coding errors in the model, which have been identified and fixed in this study.

Pnicogen bonds between X═PH3 (X = O, S, NH, CH2) and phosphorus and nitrogen bases.

PubMed

Alkorta, Ibon; Sánchez-Sanz, Goar; Elguero, José; Del Bene, Janet E

2014-02-27

Ab initio MP2/aug'-cc-pVTZ calculations have been carried out to investigate the pnicogen bonded complexes formed between the acids O═PH3, S═PH3, HN═PH3, and H2C═PH3 and the bases NH3, NCH, N2, PH3, and PCH. All nitrogen and phosphorus bases form complexes in which the bases are lone pair electron donors. The binding energies of complexes involving the stronger bases NH3, NCH, and PH3 differentiate among the acids, but the binding energies of complexes with the weaker bases do not. These complexes are stabilized by charge transfer from the lone pair orbital of N or P to the σ*P═A orbital of X═PH3, where A is the atom of X directly bonded to P. PCH also forms complexes with the X═PH3 acids as a π electron donor to the σ*P═A orbital. The binding energies and the charge-transfer energies of the π complexes are greater than those of the complexes in which PCH is a lone pair donor. Whether the positive charge on P increases, decreases, or remains the same upon complex formation, the chemical shieldings of (31)P decrease in the complexes relative to the corresponding monomers. (1p)J(P-N) and (1p)J(P-P) values correlate best with the corresponding P-N and P-P distances as a function of the nature of the base. (1)J(P-A) values do not correlate with P-A distances. Rather, the absolute values of (1)J(P-O), (1)J(P-S), and (1)J(P-N) decrease upon complexation. Decreasing (1)J(P-A) values correlate linearly with increasing complex binding energies. In contrast, (1)J(P-C) values increase upon complexation and correlate linearly with increasing binding energies.

A Hundred-Year-Old Experiment Re-evaluated: Accurate Ab-Initio Monte-Carlo Simulations of the Melting of Radon.

PubMed

Schwerdtfeger, Peter; Smits, Odile; Pahl, Elke; Jerabek, Paul

2018-06-12

State-of-the-art relativistic coupled-cluster theory is used to construct many-body potentials for the rare gas element radon in order to determine its bulk properties including the solid-to-liquid phase transition from parallel tempering Monte Carlo simulations through either direct sampling of the bulk or from a finite cluster approach. The calculated melting temperature are 201(3) K and 201(6) K from bulk simulations and from extrapolation of finite cluster values, respectively. This is in excellent agreement with the often debated (but widely cited) and only available value of 202 K, dating back to measurements by Gray and Ramsay in 1909. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Stratum corneum hydration and skin surface pH in patients with atopic dermatitis.

PubMed

Knor, Tanja; Meholjić-Fetahović, Ajša; Mehmedagić, Aida

2011-01-01

Atopic dermatitis (AD) is a chronically relapsing skin disease with genetic predisposition, which occurs most frequently in preschool children. It is considered that dryness and pruritus, which are always present in AD, are in correlation with degradation of the skin barrier function. Measurement of hydration and pH value of the stratum corneum is one of the noninvasive methods for evaluation of skin barrier function. The aim of the study was to assess skin barrier function by measuring stratum corneum hydration and skin surface pH of the skin with lesions, perilesional skin and uninvolved skin in AD patients, and skin in a healthy control group. Forty-two patients were included in the study: 21 young and adult AD patients and 21 age-matched healthy controls. Capacitance, which is correlated with hydration of stratum corneum and skin surface pH were measured on the forearm in the above areas by SM810/CM820/pH900 combined units (Courage AND Khazaka, Germany). The mean value of water capacitance measured in AD patients was 44.1 ± 11.6 AU (arbitrary units) on the lesions, 60.2 ± 12.4 AU on perilesional skin and 67.2 ± 8.8 AU on uninvolved skin. In healthy controls, the mean value was 74.1 ± 9.2 AU. The mean pH value measured in AD patients was 6.13 ± 0.52 on the lesions, 5.80 ± 0.41 on perilesional skin, and 5.54 ± 0.49 on uninvolved skin. In control group, the mean pH of the skin surface was 5.24 ± 0.40. The values of both parameters measured on lesional skin were significantly different (capacitance decreased and pH increased) from the values recorded on perilesional skin and uninvolved skin. The same held for the relation between perilesional and uninvolved skin. According to study results, the uninvolved skin of AD patients had significantly worse values of the measured parameters as compared with control group. The results of this study suggested the skin barrier function to be degraded in AD patients, which is specifically expressed in lesional skin.

Influence of the water molecules near surface of viral protein on virus activation process

NASA Astrophysics Data System (ADS)

Shepelenko, S. O.; Salnikov, A. S.; Rak, S. V.; Goncharova, E. P.; Ryzhikov, A. B.

2009-06-01

The infection of a cell with influenza virus comprises the stages of receptor binding to the cell membrane, endocytosis of virus particle, and fusion of the virus envelope and cell endosome membrane, which is determined by the conformational changes in hemagglutinin, a virus envelope protein, caused by pH decrease within the endosome. The pH value that induces conformation rearrangements of hemagglutinin molecule considerably varies for different influenza virus strains, first and foremost, due to the differences in amino acid structure of the corresponding proteins. The main goal of this study was to construct a model making it possible to assess the critical pH value characterizing the fusogenic activity of influenza virus hemagglutinin from the data on hemagglutinin structure and experimental verification of this model. Under this model, we assume that when the electrostatic force between interacting hemagglutinin molecules in the virus envelop exceeds a certain value, the hemagglutinin HA1 subunits are arranged so that they form a cavity sufficient for penetration of water molecules. This event leads to an irreversible hydration of the inner fragments of hemagglutinin molecule in a trimer and to the completion of conformational changes. The geometry of electrostatic field in hemagglutinin trimer was calculated taking into account the polarization effects near the interface of two dielectrics, aqueous medium and protein macromolecule. The critical pH values for the conformational changes in hemagglutinin were measured by the erythrocyte hemolysis induced by influenza virus particles when decreasing pH. The critical pH value conditionally separating the pH range into the regions with and without the conformational changes was calculated for several influenza virus H1N1 and H3N2 strains based on the data on the amino acid structure of the corresponding hemagglutinin molecules. Comparison of the theoretical and experimental values of critical pH values for influenza virus strains suggests that the proposed model of the interaction between water molecules and influenza virus envelope proteins has a high prediction efficiency.

Effect of sampling location on L* values and pH measurements and their relationship in broiler breast fillets

USDA-ARS?s Scientific Manuscript database

Lightness (CIELAB L*) and pH values are the most widely measured quality indicators for broiler breast fillets (pectoralis major). Measurement of L* values with a spectrophotometer can be done through Specular Component Included (SCI) or Specular Component Excluded (SCE) modes. The intra-fillet loca...

Pollution from the 2014-15 Bárðarbunga eruption monitored by snow cores from the Vatnajökull glacier, Iceland

NASA Astrophysics Data System (ADS)

Galeczka, Iwona; Eiriksdottir, Eydis Salome; Pálsson, Finnur; Oelkers, Eric; Lutz, Stefanie; Benning, Liane G.; Stefánsson, Andri; Kjartansdóttir, Ríkey; Gunnarsson-Robin, Jóhann; Ono, Shuhei; Ólafsdóttir, Rósa; Jónasdóttir, Elín Björk; Gislason, Sigurdur R.

2017-11-01

The chemical composition of Icelandic rain and snow is dominated by marine aerosols, however human and volcanic activity can also affect these compositions. The six month long 2014-15 Bárðarbunga volcanic eruption was the largest in Iceland for more than 200 years and it released into the atmosphere an average of 60 kt/day SO2, 30 kt/day CO2, 500 t/day HCl and 280 t/day HF. To study the effect of this eruption on the winter precipitation, snow cores were collected from the Vatnajökull glacier and the highlands northeast of the glacier. In addition to 29 bulk snow cores from that precipitated from September 2014 until March 2015, two cores were sampled in 21 and 44 increments to quantify the spatial and time evolution of the chemical composition of the snow. The pH and chemical compositions of melted snow samples indicate that snow has been affected by the volcanic gases emitted during the Bárðarbunga eruption. The pH of the melted bulk snow cores ranged from 4.41 to 5.64 with an average value of 5.01. This is four times greater H+ activity than pure water saturated with the atmospheric CO2. The highest concentrations of volatiles in the snow cores were found close to the eruption site as predicted from CALPUFF SO2 gas dispersion quality model. The anion concentrations (SO4, Cl, and F) were higher and the pH was lower compared to equivalent snow samples collected during 1997-2006 from the unpolluted Icelandic Langjökull glacier. Higher SO4 and Cl concentrations in the snow compared with the unpolluted rainwater of marine origin confirm the addition of a non-seawater SO4 and Cl. The δ34S isotopic composition confirms that the sulphur addition is of volcanic aerosol origin. The chemical evolution of the snow with depth reflects changes in the lava effusion and gas emission rates. Those rates were the highest at the early stage of the eruption. Snow that fell during that time, represented by samples from the deepest part of the snow cores, had the lowest pH and highest concentrations of SO4, F, Cl and metals, compared with snow that fell later in the winter. Also the Al concentration, did exceed World Health Organisation drinking water standard of 3.7 μmol/kg in the lower part of the snow core closest to the eruption site. Collected snow represents the precipitation that fell during the eruption period. Nevertheless, only minor environmental impacts are evident in the snow due to its interaction with the volcanic aerosol gases. In addition, the microbial communities identified in the snow that fell during the eruption were similar to those found in snow from other parts of the Arctic, confirming an insignificant impact of this eruption on the snow microecology.

Bulk vs. amino acid stable N isotope estimations of metabolic status and contributions of nitrogen fixation to size-fractionated zooplankton biomass in the subtropical N Atlantic

NASA Astrophysics Data System (ADS)

Mompeán, Carmen; Bode, Antonio; Gier, Elizabeth; McCarthy, Matthew D.

2016-08-01

A comparative analysis of natural abundance of stable N isotopes (δ15N) in individual amino acids and bulk organic matter of size-fractionated plankton revealed the differential impact of nitrogen fixation through the food web in a transect across the subtropical North Atlantic. All δ15N measurements showed low values in the central region, followed by the western zone, while maximum δ15N values were found in the eastern zone. These results were consistent with the prevalence of nitrogen fixation in the central and western zones, and the influence of the west Africa upwelling in the eastern zone. Use of compound-specific amino acid isotope data (CSI-AA) revealed relatively low variability in the impact of diazotrophic nitrogen within the different plankton size fractions, while δ15N of bulk organic matter showed high variability with size. Explicit CSI-AA trophic position estimates showed a small increase with mean plankton size class and varied in a relatively narrow range 1.8-2.5), with the lowest values in the central zone. High correlations between bulk plankton δ15N and individual amino acids (in particular Phe and Thr), as well as reconstructed total protein δ15N values, suggest a set of new relationships that may be important to tracing direct plankton contributions to nitrogen recycling in the ocean, including detrital organic nitrogen pools. Overall, these new results represent the most detailed investigation of CSI-AA data in plankton size classes to date, and indicated a greater importance of diazotrophic N than suggested by concurrent measurements of bulk δ15N, abundance of large nitrogen fixing organisms or nitrogen fixation rates.

Micro Electrochemical pH Sensor Applicable for Real-Time Ratiometric Monitoring of pH Values in Rat Brains.

PubMed

Zhou, Jie; Zhang, Limin; Tian, Yang

2016-02-16

To develop in vivo monitoring meter for pH measurements is still the bottleneck for understanding the role of pH plays in the brain diseases. In this work, a selective and sensitive electrochemical pH meter was developed for real-time ratiometric monitoring of pH in different regions of rat brains upon ischemia. First, 1,2-naphthoquinone (1,2-NQ) was employed and optimized as a selective pH recognition element to establish a 2H(+)/2e(-) approach over a wide range of pH from 5.8 to 8.0. The pH meter demonstrated remarkable selectivity toward pH detection against metal ions, amino acids, reactive oxygen species, and other biological species in the brain. Meanwhile, an inner reference, 6-(ferrocenyl)hexanethiol (FcHT), was selected as a built-in correction to avoid the environmental effect through coimmobilization with 1,2-NQ. In addition, three-dimensional gold nanoleaves were electrodeposited onto the electrode surface to amplify the signal by ∼4.0-fold and the measurement was achieved down to 0.07 pH. Finally, combined with the microelectrode technique, the microelectrochemical pH meter was directly implanted into brain regions including the striatum, hippocampus, and cortex and successfully applied in real-time monitoring of pH values in these regions of brain followed by global cerebral ischemia. The results demonstrated that pH values were estimated to 7.21 ± 0.05, 7.13 ± 0.09, and 7.27 ± 0.06 in the striatum, hippocampus, and cortex in the rat brains, respectively, in normal conditions. However, pH decreased to 6.75 ± 0.07 and 6.52 ± 0.03 in the striatum and hippocampus, upon global cerebral ischemia, while a negligible pH change was obtained in the cortex.

Effect of deposition parameters on the structural properties of ZnO nanopowders prepared by microwave-assisted hydrothermal synthesis.

PubMed

Caglar, Yasemin; Gorgun, Kamuran; Aksoy, Seval

2015-03-05

ZnO nanopowders were synthesized via microwave-assisted hydrothermal method at different deposition (microwave irradiation) times and pH values. The effects of pH and deposition (microwave irradiation) time on the crystalline structure and orientation of the ZnO nanopowders have been investigated by X-ray diffraction (XRD) study. XRD observations showed that the crystalline quality of ZnO nanopowders increased with increasing pH value. The crystallite size and texture coefficient values of ZnO nanopowders were calculated. The structural quality of ZnO nanopowder was improved by deposition parameters. Field emission scanning electron microscope (FESEM) was used to analyze the surface morphology of the ZnO nanopowders. Microwave irradiation time and pH value showed a significant effect on the surface morphology. Copyright © 2014 Elsevier B.V. All rights reserved.

Spectral investigation of somatotropin for different pH values

NASA Astrophysics Data System (ADS)

Otero de Joshi, Virginia; Gil, Herminia; Contreras, Silvia; Joshi, Narahari V.; Hernandez, Luis

1996-04-01

Spectral investigations of absorbance in deep ultra-violet region (from 200 nm to 350 nm) of (STM) was carried out for different pH values. On the high energy side the peak is located at 195 nm which is generally attributed to peptide bonds. This peak, as expected, does not show any shift with pH value (4.3 to 10.8). A rather broad peak is spread in the region from 200 nm to 240 nm which could be the superposition of the peaks corresponding to the absorption due to (alpha) helix and (beta) structure. This peak shows a red shift as pH value increases. The same hormone was glycated by a conventional method and the process was estimated with the absorption spectra. The results are discussed in the light of nonenzymatic glycation. It was found that glycation mucus somatotropin resistant towards the denaturation process.

Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation

PubMed Central

Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard N.

2017-01-01

Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 μM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 μm diameter; 84 ± 18 m s−1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets. PMID:29233214

Silver particle monolayers — Formation, stability, applications.

PubMed

Oćwieja, Magdalena; Adamczyk, Zbigniew; Morga, Maria; Kubiak, Katarzyna

2015-08-01

The formation of silver particle monolayers at solid substrates in self-assembly processes is thoroughly reviewed. Initially, various silver nanoparticle synthesis routes are discussed with the emphasis focused on the chemical reduction in aqueous media. Subsequently, the main experimental methods aimed at bulk suspension characterization are critically reviewed by pointing out their advantages and limitations. Also, various methods enabling the in situ studies of particle deposition and release kinetics, especially the streaming potential method are discussed. In the next section, experimental data are invoked illustrating the most important features of particle monolayer formation, in particular, the role of bulk suspension concentration, particle size, ionic strength, temperature and pH. Afterward, the stability of monolayers and particle release kinetics are extensively discussed. The results obtained by the ex situ AFM/SEM imaging of particles are compared with the in situ streaming potential measurements. An equivalency of both methods is demonstrated, especially in respect to the binding energy determination. It is shown that these experimental results can be adequately interpreted in terms of the hybrid theoretical approach that combines the bulk transport step with the surface blocking effects derived from the random sequential adsorption model. It is also concluded that the particle release kinetics is governed by the discrete electrostatic interactions among ion pairs on particle and substrate surfaces. The classical theories based on the mean-field (averaged) zeta potential concept proved inadequate. Using the ion pair concept the minor dependence of the binding energy on particle size, ionic strength, pH and temperature is properly explained. The final sections of this review are devoted to the application of silver nanoparticles and their monolayers in medicine, analytical chemistry and catalysis. Copyright © 2014 Elsevier B.V. All rights reserved.

Microdroplet fusion mass spectrometry: accelerated kinetics of acid-induced chlorophyll demetallation.

PubMed

Lee, Jae Kyoo; Nam, Hong Gil; Zare, Richard N

2017-01-01

Kinetics of acid-induced chlorophyll demetallation was recorded in microdroplets by fusing a stream of microdroplets containing 40 µM chlorophyll a or b dissolved in methanol with a stream of aqueous microdroplets containing 35 mM hydrochloric acid (pH = 1·46). The kinetics of the demetallation of chlorophyll in the fused microdroplets (14 ± 6 µm diameter; 84 ± 18 m s-1 velocity) was recorded by controlling the traveling distance of the fused microdroplets between the fusion region and the inlet of a mass spectrometer. The rate of acid-induced chlorophyll demetallation was about 960 ± 120 times faster in the charged microdroplets compared with that reported in bulk solution. If no voltage was applied to the sprayed microdroplets, then the acceleration factor was about 580 ± 90, suggesting that the applied voltage is not a major factor determining the acceleration. Chlorophyll a was more rapidly demetallated than chlorophyll b by a factor of ~26 in bulk solution and ~5 in charged microdroplets. The demetallation kinetics was second order in the H+ concentration, but the acceleration factor of microdroplets compared with bulk solution appeared to be unchanged in going from pH = 1·3 to 7·0. The water:methanol ratio of the fused microdroplets was varied from 7:3 to 3:7 causing an increase in the reaction rate of chlorophyll a demetallation by 20%. This observation demonstrates that the solvent composition, which has different evaporation rates, does not significantly affect the acceleration. We believe that a major portion of the acceleration can be attributed to confinement effects involving surface reactions rather than either to evaporation of solvents or to the introduction of charges to the microdroplets.

[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.

Effect of sonication on the colloidal stability of iron oxide nanoparticles

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

Sodipo, Bashiru Kayode; Aziz, Azlan Abdul

2015-04-24

Colloidal stability of superparamagnetic iron oxide nanoparticles’ (SPION) suspensions, ultrasonically irradiated at various pH was studied. Electrophoresis measurement of the sonicated SPION showed that the shock waves and other unique conditions generated from the acoustic cavitation process (formation, growth and collapse of bubbles) affect the zeta potential value of the suspension. In this work, stabled colloidal suspensions of SPION were prepared and their pH is varied between 3 and 5. Prior to ultrasonic irradiation of the suspensions, their initial zeta potential values were determined. After ultrasonic irradiation of the suspensions, we observed that the sonication process interacts with colloidal stabilitymore » of the nanoparticles. The results demonstrated that only suspensions with pH less 4 were found stable and able to retain more than 90% of its initial zeta potential value. However, at pH greater than 4, the suspensions were found unstable. The result implies that good zeta potential value of SPION can be sustained in sonochemical process as long as the pH of the mixture is kept below 4.« less

Stable and selective self-assembly of α-lipoic acid on Ge(001) for biomolecule immobilization

NASA Astrophysics Data System (ADS)

Kazmierczak, M.; Flesch, J.; Mitzloff, J.; Capellini, G.; Klesse, W. M.; Skibitzki, O.; You, C.; Bettenhausen, M.; Witzigmann, B.; Piehler, J.; Schroeder, T.; Guha, S.

2018-05-01

We demonstrate a novel method for the stable and selective surface functionalization of germanium (Ge) embedded in silicon dioxide. The Ge(001) surface is functionalized using α-lipoic acid (ALA), which can potentially be utilized for the immobilization of a wide range of biomolecules. We present a detailed pH-dependence study to establish the effect of the incubation pH value on the adsorption layer of the ALA molecules. A threshold pH value for functionalization is identified, dividing the examined pH range into two regions. Below a pH value of 7, the formation of a disordered ALA multilayer is observed, whereas a stable well-ordered ALA mono- to bi-layer on Ge(001) is achieved at higher pH values. Furthermore, we analyze the stability of the ALA layer under ambient conditions, revealing the most stable functionalized Ge(001) surface to effectively resist oxidation for up to one week. Our established functionalization method paves the way towards the successful immobilization of biomolecules in future Ge-based biosensors.

Effect of pH on particles size and gas sensing properties of In2O3 nanoparticles

NASA Astrophysics Data System (ADS)

Anand, Kanica; Thangaraj, Rengasamy; Singh, Ravi Chand

2016-05-01

In this work, indium oxide (In2O3) nanoparticles have been synthesized by co-precipitation method and the effect of pH on the structural and sensor response values of In2O3 nanoparticles has been reported. X-ray diffraction pattern (XRD) revealed the formation of cubic phase In2O3 nanoparticles. FESEM results indicate the formation of nearly spherical shape In2O3 nanoparticles. The band gap energy value changed with change in pH value and found to have highest value at pH 9. Indium oxide nanoparticles thus prepared were deposited as thick films on alumina substrates to act as gas sensors and their sensing response to ethanol vapors and LPG at 50 ppm was investigated at different operating temperatures. It has been observed that all sensors exhibited optimum response at 300°C towards ethanol and at 400°C towards LPG. In2O3 nanoparticles prepared at pH 9, being smallest in size as compared to other, exhibit highest sensor response (SR).

Electrochemical behavior of the antituberculosis drug isoniazid and its square-wave adsorptive stripping voltammetric estimation in bulk form, tablets and biological fluids at a mercury electrode.

PubMed

Ghoneim, M M; el-Baradie, K Y; Tawfik, A

2003-11-24

Isoniazid, pyridine-4-carboxylic acid hydrazide, is an antituberculosis-agent, which is used to prevent the development of clinical tuberculosis. A validated square-wave adsorptive cathodic stripping voltammetric procedure for the trace determination of the bulk drug at the hanging mercury drop electrode (HMDE) has been developed. Under the optimized conditions, (accumulation potential=-0.9 V, accumulation time=50-300 s, scan increment=8 mV, pulse-amplitude=25 mV, frequency=120 Hz and acetate buffer at pH 5.5) isoniazed generated two irreversible cathodic peaks. The first peak current showed a linear dependence with the drug concentration over the range 5 x 10(-10)-21 x 0(-6) M. The mean percentage recoveries, based on the average of five replicate measurements, for 7 x 10(-9) and 5 x 10(-8) M isoniazid were 97.71+/-2.93 and 99.76+/-0.77, respectively. The achieved limits of detection (LOD) and quantitation (LOQ) were 1.18 x 10(-10) and 3.93 x 10(-10) M isoniazid, respectively. The procedure was applied to the assay of the drug in tablets (Isocid and T.B. Zide), spiked human serum and urine with mean percentage recoveries of 97.81+/-1.49, 97.45+/-2.09, and 97.08+/-1.06, respectively. The limits of detection of 1.47 x 10(-9) and 2.4 x 10(-8) M, and quantitation of 4.9 x 10(-9) and 8 x 10(-8) M drug in human serum and urine, respectively, were achieved. The mean values of the various pharmackinetic parameters of isoniazid (C(max), T(max), t(1/2), AUC, and K(e)), estimated from analysis of plasma of two volunteers by means of the proposed procedure were similar to literature values.

Study of Vis/NIR spectroscopy measurement on acidity of yogurt

NASA Astrophysics Data System (ADS)

He, Yong; Feng, Shuijuan; Wu, Di; Li, Xiaoli

2006-09-01

A fast measurement of pH of yogurt using Vis/NIR-spectroscopy techniques was established in order to measuring the acidity of yogurt rapidly. 27 samples selected separately from five different brands of yogurt were measured by Vis/NIR-spectroscopy. The pH of yogurt on positions scanned by spectrum was measured by a pH meter. The mathematical model between pH and Vis/NIR spectral measurements was established and developed based on partial least squares (PLS) by using Unscramble V9.2. Then 25 unknown samples from 5 different brands were predicted based on the mathematical model. The result shows that The correlation coefficient of pH based on PLS model is more than 0.890, and standard error of calibration (SEC) is 0.037, standard error of prediction (SEP) is 0.043. Through predicting the pH of 25 samples of yogurt from 5 different brands, the correlation coefficient between predictive value and measured value of those samples is more than 0918. The results show the good to excellent prediction performances. The Vis/NIR spectroscopy technique had a significant greater accuracy for determining the value of pH. It was concluded that the VisINIRS measurement technique can be used to measure pH of yogurt fast and accurately, and a new method for the measurement of pH of yogurt was established.

Global Trophic Position Comparison of Two Dominant Mesopelagic Fish Families (Myctophidae, Stomiidae) Using Amino Acid Nitrogen Isotopic Analyses

PubMed Central

Choy, C. Anela; Davison, Peter C.; Drazen, Jeffrey C.; Flynn, Adrian; Gier, Elizabeth J.; Hoffman, Joel C.; McClain-Counts, Jennifer P.; Miller, Todd W.; Popp, Brian N.; Ross, Steve W.; Sutton, Tracey T.

2012-01-01

The δ15N values of organisms are commonly used across diverse ecosystems to estimate trophic position and infer trophic connectivity. We undertook a novel cross-basin comparison of trophic position in two ecologically well-characterized and different groups of dominant mid-water fish consumers using amino acid nitrogen isotope compositions. We found that trophic positions estimated from the δ15N values of individual amino acids are nearly uniform within both families of these fishes across five global regions despite great variability in bulk tissue δ15N values. Regional differences in the δ15N values of phenylalanine confirmed that bulk tissue δ15N values reflect region-specific water mass biogeochemistry controlling δ15N values at the base of the food web. Trophic positions calculated from amino acid isotopic analyses (AA-TP) for lanternfishes (family Myctophidae) (AA-TP ∼2.9) largely align with expectations from stomach content studies (TP ∼3.2), while AA-TPs for dragonfishes (family Stomiidae) (AA-TP ∼3.2) were lower than TPs derived from stomach content studies (TP∼4.1). We demonstrate that amino acid nitrogen isotope analysis can overcome shortcomings of bulk tissue isotope analysis across biogeochemically distinct systems to provide globally comparative information regarding marine food web structure. PMID:23209656

Global trophic position comparison of two dominant mesopelagic fish families (Myctophidae, Stomiidae) using amino acid nitrogen isotopic analyses

USGS Publications Warehouse

Choy, C. Anela; Davison, Peter C.; Drazen, Jeffrey C.; Flynn, Adrian; Gier, Elizabeth J.; Hoffman, Joel C.; McClain-Counts, Jennifer P.; Miller, Todd W.; Popp, Brian N.; Ross, Steve W.; Sutton, Tracey T.

2012-01-01

The δ15N values of organisms are commonly used across diverse ecosystems to estimate trophic position and infer trophic connectivity. We undertook a novel cross-basin comparison of trophic position in two ecologically well-characterized and different groups of dominant mid-water fish consumers using amino acid nitrogen isotope compositions. We found that trophic positions estimated from the δ15N values of individual amino acids are nearly uniform within both families of these fishes across five global regions despite great variability in bulk tissue δ15N values. Regional differences in the δ15N values of phenylalanine confirmed that bulk tissue δ15N values reflect region-specific water mass biogeochemistry controlling δ15N values at the base of the food web. Trophic positions calculated from amino acid isotopic analyses (AA-TP) for lanternfishes (family Myctophidae) (AA-TP ~2.9) largely align with expectations from stomach content studies (TP ~3.2), while AA-TPs for dragonfishes (family Stomiidae) (AA-TP ~3.2) were lower than TPs derived from stomach content studies (TP~4.1). We demonstrate that amino acid nitrogen isotope analysis can overcome shortcomings of bulk tissue isotope analysis across biogeochemically distinct systems to provide globally comparative information regarding marine food web structure.

In vitro activity of the novel echinocandin CD101 at pH 7 and 4 against Candida spp. isolates from patients with vulvovaginal candidiasis

PubMed Central

Boikov, Dina A.; James, Kenneth D.; Bartizal, Ken; Sobel, Jack D.

2017-01-01

Background: The novel echinocandin CD101 has stability properties amenable to topical formulation for use in the treatment of acute vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). CD101 has demonstrated potent antifungal activity at pH 7, but assessment of its activity at the physiological pH of the vaginal environment is needed. Objectives: To evaluate the antifungal activity of CD101 against clinical VVC isolates of Candida spp., including azole-resistant strains, at pH 4. Methods: MIC values of CD101 and comparators (fluconazole, itraconazole, micafungin, caspofungin and anidulafungin) were assessed via broth microdilution. MIC assays were conducted at pH 7 and 4 after 24 and 48 h against a 108 VVC isolate panel of Candida spp., including Candida albicans (n = 60), Candida glabrata (n = 21), Candida parapsilosis (n = 14) and Candida tropicalis (n = 13). Results: Overall, MIC values of all drugs were slightly higher at pH 4 versus 7 and at 48 versus 24 h of incubation. CD101 MIC values typically exhibited ∼4-fold shifts at pH 4 and were not affected by azole susceptibility. C. parapsilosis susceptibility was the least affected at pH 4 and did not increase for most drugs. Conclusions: CD101 had potent activity against all Candida isolates tested, including azole-resistant strains. Although there was some reduction in activity at pH 4 versus 7, the resulting MIC values were still well below the intravaginal CD101 drug concentrations anticipated to be present following topical administration. These results support continued development of topical CD101 for the treatment of VVC/RVVC. PMID:28158577

In vitro activity of the novel echinocandin CD101 at pH 7 and 4 against Candida spp. isolates from patients with vulvovaginal candidiasis.

PubMed

Boikov, Dina A; Locke, Jeffrey B; James, Kenneth D; Bartizal, Ken; Sobel, Jack D

2017-05-01

The novel echinocandin CD101 has stability properties amenable to topical formulation for use in the treatment of acute vulvovaginal candidiasis (VVC) and recurrent VVC (RVVC). CD101 has demonstrated potent antifungal activity at pH 7, but assessment of its activity at the physiological pH of the vaginal environment is needed. To evaluate the antifungal activity of CD101 against clinical VVC isolates of Candida spp., including azole-resistant strains, at pH 4. MIC values of CD101 and comparators (fluconazole, itraconazole, micafungin, caspofungin and anidulafungin) were assessed via broth microdilution. MIC assays were conducted at pH 7 and 4 after 24 and 48 h against a 108 VVC isolate panel of Candida spp., including Candida albicans ( n  =   60), Candida glabrata ( n  =   21), Candida parapsilosis ( n  =   14) and Candida tropicalis ( n  =   13). Overall, MIC values of all drugs were slightly higher at pH 4 versus 7 and at 48 versus 24 h of incubation. CD101 MIC values typically exhibited ∼4-fold shifts at pH 4 and were not affected by azole susceptibility. C. parapsilosis susceptibility was the least affected at pH 4 and did not increase for most drugs. CD101 had potent activity against all Candida isolates tested, including azole-resistant strains. Although there was some reduction in activity at pH 4 versus 7, the resulting MIC values were still well below the intravaginal CD101 drug concentrations anticipated to be present following topical administration. These results support continued development of topical CD101 for the treatment of VVC/RVVC. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy.

Engineering of acidic O/W emulsions with pectin.

PubMed

Alba, K; Sagis, L M C; Kontogiorgos, V

2016-09-01

Pectins with distinct molecular design were isolated by aqueous extraction at pH 2.0 or 6.0 and were examined in terms of their formation and stabilisation capacity of model n-alkane-in-water emulsions at acidic pH (pH 2.0). The properties and stability of the resulting emulsions were examined by means of droplet size distribution analysis, Lifshitz-Slyozov-Wagner modelling, bulk rheology, interfacial composition analysis, large-amplitude oscillatory surface dilatational rheology, electrokinetic analysis and fluorescence microscopy. Both pectin preparations were able to emulsify alkanes in water but exhibited distinct ageing characteristics. Emulsions prepared using pectin isolated at pH 6.0 were remarkably stable with respect to droplet growth after thirty days of ageing, while those prepared with pectin isolated at pH 2.0 destabilised rapidly. Examination of chemical composition of interfacial layers indicated multi-layered adsorption of pectins at the oil-water interface. The higher long-term stability of emulsions prepared with pectin isolated at high pH is attributed to mechanically stronger interfaces, the highly branched nature and the low hydrodynamic volume of the chains that result in effective steric stabilisation whereas acetyl and methyl contents do not contribute to the long-term stability. The present work shows that it is possible by tailoring the fine structure of pectin to engineer emulsions that operate in acidic environments. Copyright © 2016 Elsevier B.V. All rights reserved.

Examining the utility of bulk otolith δ13C to describe diet in wild-caught black rockfish Sebastes melanops

USGS Publications Warehouse

von Biela, Vanessa; Newsome, Seth D.; Zimmerman, Christian E.

2015-01-01

Otolith carbon isotope δ13C values may provide temporally resolved diet proxies in fish. If otolith δ13C values reflect diet, isotope values from recent otolith and muscle tissue should correlate and known ontogenetic diet shifts should be reflected in comparisons between otolith material deposited during different life history stages. We analyzed paired otolith and muscle samples for δ13C from black rockfish Sebastes melanops to examine the potential of otoliths to reflect diet in small (200-299 mm fork length) and large (≥300 mm) fish. We found a significant positive regression between δ13C values from recent (~12 mo) otolith material and muscle in large fish, but not in small fish. Within individual otoliths, δ13C values were enriched by ~3‰ in recent otolith edge material compared to age-0 otolith core material and were consistent with known nearshore-offshore gradients in δ13C values at the base of the food web. Bulk otolith δ13C appeared to provide a broad indicator of dietary carbon sources, but variation in metabolism and dissolved inorganic carbon δ13C among and within individuals likely influences otolith δ13C as well and limits precision. Nevertheless, the results are promising and bulk otolith δ13C may be an appropriate tool to examine large trophic and ecosystem level shifts that have occurred concurrently with changes in habitat, commercial fishing, invasive species, climate change, and other direct or indirect human impacts using historic or ancient otoliths. Future studies should continue to consider the utility of bulk otolith δ13C to describe diet in other marine fish using this simple approach.

Soil variation and sampling intensity under red pine and aspen in Minnesota.

Treesearch

David H. Alban

1974-01-01

In red pine or aspen stands only two soil samples were needed to estimate (+/- 10%, 95% confidence) pH, bulk density, or sand, but 25 to 60 samples were required to estimate N, P, K, Ca, Mg, available water, or silt + clay. To estimate most forest floor properties required 30 to 50 samples in red pine stands, but only about half as many in aspen stands.

Monitoring the Erosion of Hydrolytically-Degradable Nanogels via Multiangle Light Scattering Coupled to Asymmetrical Flow Field-Flow Fractionation

PubMed Central

Smith, Michael H.; South, Antoinette B.; Gaulding, Jeffrey C.; Lyon, L. Andrew

2009-01-01

We describe the synthesis and characterization of degradable nanogels that display bulk erosion under physiologic conditions (pH = 7.4, 37 °C). Erodible poly(N-isopropylmethacrylamide) nanogels were synthesized by copolymerization with N,O-(dimethacryloyl)hydroxylamine, a cross-linker previously used in the preparation of non-toxic and biodegradable bulk hydrogels. To monitor particle degradation, we employed multiangle light scattering and differential refractometry detection following asymmetrical flow field-flow fractionation. This approach allowed the detection of changes in nanogel molar mass and topology as a function of both temperature and pH. Particle erosion was evident from both an increase in nanogel swelling and a decrease in scattering intensity as a function of time. Following these analyses, the samples were recovered for subsequent characterization by direct particle tracking, which yields hydrodynamic size measurements and enables number density determination. Additionally, we confirmed the conservation of nanogel stimuli-responsivity through turbidity measurements. Thus, we have demonstrated the synthesis of degradable nanogels that erode under conditions and on timescales that are relevant for many drug delivery applications. The combined separation and light scattering detection method is demonstrated to be a versatile means to monitor erosion and should also find applicability in the characterization of other degradable particle constructs. PMID:20000662

Spatial boundary of urban ‘acid islands’ in southern China

PubMed Central

Du, E.; de Vries, W.; Liu, X.; Fang, J.; Galloway, J. N.; Jiang, Y.

2015-01-01

Elevated emissions of sulfur dioxide, nitrogen oxides and ammonia in China have resulted in high levels of sulfur and nitrogen deposition, being contributors to soil acidification, especially in and near large cities. However, knowledge gaps still exist in the way that large cities shape spatial patterns of acid deposition. Here, we assessed the patterns of pH, sulfate, nitrate and ammonium in bulk precipitation and throughfall in southern China’s forests by synthesizing data from published literature. Concentrations and fluxes of sulfate, nitrate and ammonium in bulk precipitation and throughfall exhibited a power-law increase with a closer distance to the nearest large cities, and accordingly pH showed a logarithmic decline. Our findings indicate the occurrence of urban ‘acid islands’ with a critical radius of approximately 70 km in southern China, receiving potential acid loads of more than 2 keq ha−1 yr−1. These urban acid islands covered an area of 0.70 million km2, accounting for nearly 30% of the land area in southern China. Despite a significant capacity to neutralize acids in precipitation, our analysis highlights a substantial contribution of ammonium to potential acid load. Our results suggest a joint control on emissions of multiple acid precursors from urban areas in southern China. PMID:26211880

Interrelationships among geotechnical and leaching properties of a cement-stabilized contaminated soil.

PubMed

Kogbara, Reginald B

2017-01-28

Relationships among selected performance properties have been established using experimental data from a cement-stabilized mixed contaminated soil. The sandy soil was spiked with 3,000 mg/kg each of Cd, Cu, Pb, Ni and Zn, and 10,000 mg/kg of diesel. It was then treated with 5%, 10%, 15%, and 20% dosages of Portland cement. Different water contents were considered for lower dosage mixes. Selected geotechnical and leaching properties were determined on 28-day old samples. These include unconfined compressive strength (UCS), bulk density, porosity, hydraulic conductivity, leachate pH and granular leachability of contaminants. Interrelationships among these properties were deduced using the most reasonable best fits determined by specialized curve fitting software. Strong quadratic and log-linear relationships exist between hydraulic conductivity and UCS, with increasing binder and water contents, respectively. However, the strength of interrelationships between hydraulic conductivity and porosity, UCS and porosity, and UCS and bulk density varies with binder and water contents. Leachate pH and granular leachability of contaminants are best related to UCS and hydraulic conductivity by a power law and an exponential function, respectively. These results suggest how the accuracy of not-easily-measurable performance properties may be constrained from simpler ones. Comparisons with some published performance properties data support this.

Spatial boundary of urban 'acid islands' in southern China.

PubMed

Du, E; de Vries, W; Liu, X; Fang, J; Galloway, J N; Jiang, Y

2015-07-27

Elevated emissions of sulfur dioxide, nitrogen oxides and ammonia in China have resulted in high levels of sulfur and nitrogen deposition, being contributors to soil acidification, especially in and near large cities. However, knowledge gaps still exist in the way that large cities shape spatial patterns of acid deposition. Here, we assessed the patterns of pH, sulfate, nitrate and ammonium in bulk precipitation and throughfall in southern China's forests by synthesizing data from published literature. Concentrations and fluxes of sulfate, nitrate and ammonium in bulk precipitation and throughfall exhibited a power-law increase with a closer distance to the nearest large cities, and accordingly pH showed a logarithmic decline. Our findings indicate the occurrence of urban 'acid islands' with a critical radius of approximately 70 km in southern China, receiving potential acid loads of more than 2 keq ha(-1) yr(-1). These urban acid islands covered an area of 0.70 million km(2), accounting for nearly 30% of the land area in southern China. Despite a significant capacity to neutralize acids in precipitation, our analysis highlights a substantial contribution of ammonium to potential acid load. Our results suggest a joint control on emissions of multiple acid precursors from urban areas in southern China.

Inorganic C-sources for Lemanea, Cladophora and Ranunculus in a fast-flowing stream: Measurements of gas exchange and of carbon isotope ratio and their ecological implications.

PubMed

Raven, John; Beardall, John; Griffiths, Howard

1982-04-01

CO 2 -and O 2 -exchange characteristics and δ 13 C values have been measured in a rhodophycean haptophyte (Lemanea mamillosa), a chlorophycean haptophyte (Cladophora glomerata) and a magnoliophyte rhizophyte (Ranunculus sp.) from a 5 m stretch of the Dichty Burn near Dundee. Light-and CO 2 -saturated rates of photosynthesis are greatest on a dry weight basis for Cladophora and lowest for Lemanea; the order is reversed on a surface area basis. The CO 2 concentration at pH 6.5 at which photosynthesis is half-saturated is 25-40 μM, with Lemanea rather lower than Cladophora or Ranunculus; these half-saturation values are similar to the free CO 2 concentration in the Burn water. Lemanea cannot use HCO 3 - in photosynthesis, while Cladophora and Ranunculus can. Despite being within a factor or two of saturation with free CO 2 in terms of the bulk water concentration, the growth habit of Cladophora and, particularly, Ranunculus means that the high water velocity in the Burn does not necessarily prevent C depletion effects around the plants, thus providing a possible role for HCO 3 - use by these plants. Lemanea lives in the fastest-growing parts of the Burn, and its growth habit insures that it is exposed to this high water velocity, thus minimising CO 2 depletion during photosynthesis despite the low surface/volume ratio for this plant. δ 13 C measurements on the inorganic C in the Burn water are consistent with at least part of its excess (above air-equilibrium) inorganic C levels coming from heterotrophic activity. Lemanea has the most negative δ 13 C value of the three plants, consistent with CO 2 use and small diffusion resistances. Ranunculus has the least negative δ 13 C value, consistent with some CO 2 depletion and/or HCO 3 - use in situ related to a high diffusion resistance in a rhizophyte which does not have to obtain all of its N and P from the bulk water but can obtain some from the sediments. Cladophora is intermediate, suggesting some CO 2 depletion and/or HCO 3 - use in this densely growing haptophyte.

Metastable and equilibrium phase diagrams of unconjugated bilirubin IXα as functions of pH in model bile systems: Implications for pigment gallstone formation.

PubMed

Berman, Marvin D; Carey, Martin C

2015-01-01

Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB. Copyright © 2015 the American Physiological Society.

Metastable and equilibrium phase diagrams of unconjugated bilirubin IXα as functions of pH in model bile systems: Implications for pigment gallstone formation

PubMed Central

Berman, Marvin D.

2014-01-01

Metastable and equilibrium phase diagrams for unconjugated bilirubin IXα (UCB) in bile are yet to be determined for understanding the physical chemistry of pigment gallstone formation. Also, UCB is a molecule of considerable biomedical importance because it is a potent antioxidant and an inhibitor of atherogenesis. We employed principally a titrimetric approach to obtain metastable and equilibrium UCB solubilities in model bile systems composed of taurine-conjugated bile salts, egg yolk lecithin (mixed long-chain phosphatidylcholines), and cholesterol as functions of total lipid concentration, biliary pH values, and CaCl2 plus NaCl concentrations. Metastable and equilibrium precipitation pH values were obtained, and average pKa values of the two carboxyl groups of UCB were calculated. Added lecithin and increased temperature decreased UCB solubility markedly, whereas increases in bile salt concentrations and molar levels of urea augmented solubility. A wide range of NaCl and cholesterol concentrations resulted in no specific effects, whereas added CaCl2 produced large decreases in UCB solubilities at alkaline pH values only. UV-visible absorption spectra were consistent with both hydrophobic and hydrophilic interactions between UCB and bile salts that were strongly influenced by pH. Reliable literature values for UCB compositions of native gallbladder biles revealed that biles from hemolytic mice and humans with black pigment gallstones are markedly supersaturated with UCB and exhibit more acidic pH values, whereas biles from nonstone control animals and patients with cholesterol gallstone are unsaturated with UCB. PMID:25359538

Sucrose synthase: A unique glycosyltransferase for biocatalytic glycosylation process development.

PubMed

Schmölzer, Katharina; Gutmann, Alexander; Diricks, Margo; Desmet, Tom; Nidetzky, Bernd

2016-01-01

Sucrose synthase (SuSy, EC 2.4.1.13) is a glycosyltransferase (GT) long known from plants and more recently discovered in bacteria. The enzyme catalyzes the reversible transfer of a glucosyl moiety between fructose and a nucleoside diphosphate (NDP) (sucrose+NDP↔NDP-glucose+fructose). The equilibrium for sucrose conversion is pH dependent, and pH values between 5.5 and 7.5 promote NDP-glucose formation. The conversion of a bulk chemical to high-priced NDP-glucose in a one-step reaction provides the key aspect for industrial interest. NDP-sugars are important as such and as key intermediates for glycosylation reactions by highly selective Leloir GTs. SuSy has gained renewed interest as industrially attractive biocatalyst, due to substantial scientific progresses achieved in the last few years. These include biochemical characterization of bacterial SuSys, overproduction of recombinant SuSys, structural information useful for design of tailor-made catalysts, and development of one-pot SuSy-GT cascade reactions for production of several relevant glycosides. These advances could pave the way for the application of Leloir GTs to be used in cost-effective processes. This review provides a framework for application requirements, focusing on catalytic properties, heterologous enzyme production and reaction engineering. The potential of SuSy biocatalysis will be presented based on various biotechnological applications: NDP-sugar synthesis; sucrose analog synthesis; glycoside synthesis by SuSy-GT cascade reactions. Copyright © 2015 Elsevier Inc. All rights reserved.

Iron oxide-mediated semiconductor photocatalysis vs. heterogeneous photo-Fenton treatment of viruses in wastewater. Impact of the oxide particle size.

PubMed

Giannakis, Stefanos; Liu, Siting; Carratalà, Anna; Rtimi, Sami; Talebi Amiri, Masoud; Bensimon, Michaël; Pulgarin, César

2017-10-05

The photo-Fenton process is recognized as a promising technique towards microorganism disinfection in wastewater, but its efficiency is hampered at near-neutral pH operating values. In this work, we overcome these obstacles by using the heterogeneous photo-Fenton process as the default disinfecting technique, targeting MS2 coliphage in wastewater. The use of low concentrations of iron oxides in wastewater without H 2 O 2 (wüstite, maghemite, magnetite) has demonstrated limited semiconductor-mediated MS2 inactivation. Changing the operational pH and the size of the oxide particles indicated that the isoelectric point of the iron oxides and the active surface area are crucial in the success of the process, and the possible underlying mechanisms are investigated. Furthermore, the addition of low amounts of Fe-oxides (1mgL -1 ) and H 2 O 2 in the system (1, 5 and 10mgL -1 ) greatly enhanced the inactivation process, leading to heterogeneous photo-Fenton processes on the surface of the magnetically separable oxides used. Additionally, photo-dissolution of iron in the bulk, lead to homogeneous photo-Fenton, further aided by the complexation by the dissolved organic matter in the solution. Finally, we assess the impact of the presence of the bacterial host and the difference caused by the different iron sources (salts, oxides) and the Fe-oxide size (normal, nano-sized). Copyright © 2017 Elsevier B.V. All rights reserved.

Environmental impacts of coal mine and thermal power plant to the surroundings of Barapukuria, Dinajpur, Bangladesh.

PubMed

Hossain, Md Nazir; Paul, Shitangsu Kumar; Hasan, Md Muyeed

2015-04-01

The study was carried out to analyse the environmental impacts of coal mine and coal-based thermal power plant to the surrounding environment of Barapukuria, Dinajpur. The analyses of coal, water, soil and fly ash were carried out using standard sample testing methods. This study found that coal mining industry and coal-based thermal power plant have brought some environmental and socio-economic challenges to the adjacent areas such as soil, water and air pollution, subsidence of agricultural land and livelihood insecurity of inhabitants. The pH values, heavy metal, organic carbon and exchangeable cations of coal water treated in the farmland soil suggest that coal mining deteriorated the surrounding water and soil quality. The SO4(2-) concentration in water samples was beyond the range of World Health Organisation standard. Some physico-chemical properties such as pH, conductivity, moisture content, bulk density, unburned carbon content, specific gravity, water holding capacity, liquid and plastic limit were investigated on coal fly ash of Barapukuria thermal power plant. Air quality data provided by the Barapukuria Coal Mining Company Limited were contradictory with the result of interview with the miners and local inhabitants. However, coal potentially contributes to the development of economy of Bangladesh but coal mining deteriorates the environment by polluting air, water and soil. In general, this study includes comprehensive baseline data for decision makers to evaluate the feasibility of coal power industry at Barapukuria and the coalmine itself.

Processing of MnBi bulk magnets with enhanced energy product

DOE PAGES

Poudyal, Narayan; Liu, Xubo; Wang, Wei; ...

2016-02-23

Here, we report magnetic properties and microstructure of high energy-product MnBi bulk magnets fabricated by low-temperature ball-milling and warm compaction technique. A maximum energy product (BH) max of 8.4 MGOe and a coercivity of 6.2 kOe were obtained in the bulk MnBi magnet at room temperature. Magnetic characterization at elevated temperatures showed an increase in coercivity to 16.2 kOe while (BH) max value decreased to 6.8 MGOe at 400 K. Microstructure characterization revealed that the bulk magnets consist of oriented uniform nanoscale grains with average size about 50 nm.

A novel FbFP-based biosensor toolbox for sensitive in vivo determination of intracellular pH.

PubMed

Rupprecht, Christian; Wingen, Marcus; Potzkei, Janko; Gensch, Thomas; Jaeger, Karl-Erich; Drepper, Thomas

2017-09-20

The intracellular pH is an important modulator of various bio(techno)logical processes such as enzymatic conversion of metabolites or transport across the cell membrane. Changes of intracellular pH due to altered proton distribution can thus cause dysfunction of cellular processes. Consequently, accurate monitoring of intracellular pH allows elucidating the pH-dependency of (patho)physiological and biotechnological processes. In this context, genetically encoded biosensors represent a powerful tool to determine intracellular pH values non-invasively and with high spatiotemporal resolution. We have constructed a toolbox of novel genetically encoded FRET-based pH biosensors (named Fluorescence Biosensors for pH or FluBpH) that utilizes the FMN-binding fluorescent protein EcFbFP as donor domain. In contrast to many fluorescent proteins of the GFP family, EcFbFP exhibits a remarkable tolerance towards acidic pH (pK a ∼3.2). To cover the broad range of physiologically relevant pH values, three EYFP variants exhibiting pK a values of 5.7, 6.1 and 7.5 were used as pH-sensing FRET acceptor domains. The resulting biosensors FluBpH 5.7, FluBpH 6.1 and FluBpH 7.5 were calibrated in vitro and in vivo to accurately evaluate their pH indicator properties. To demonstrate the in vivo applicability of FluBpH, changes of intracellular pH were ratiometrically measured in E. coli cells during acid stress. Copyright © 2017 Elsevier B.V. All rights reserved.

Complexation of sodium caseinate with gum tragacanth: Effect of various species and rheology of coacervates.

PubMed

Ghorbani Gorji, Sara; Ghorbani Gorji, Elham; Mohammadifar, Mohammad Amin; Zargaraan, Azizollaah

2014-06-01

We investigated complex coacervation of sodium caseinate/Astragalus rahensis (A.r) as a function of pH with light scattering, spectrophotometry, and viscosity measurements. Interestingly, sodium caseinate/A.r displayed five structural transitions; pH 7.00 to pH ∼5.40: no interaction occurred, pH ∼5.40 to pH ∼4.80: initiation of the formation of primary soluble complexes, pH ∼4.80 to ∼4.30: formation of interpolymer complexes, pH ∼4.30 to ∼4.02: optimum coacervation and pH ∼4.02 to ∼2.50: suppression of coacervation. In addition, rheological properties of sodium caseinate/A.r coacervates were studied at various pH values. A much higher storage modulus (G') than loss modulus (G″) for all sodium caseinate/A.r coacervates suggests the formation of highly interconnected gel-like network structures with mainly elastic behaviour. Moreover, sodium caseinate/A.r coacervates at all pH values exhibited a shear thinning behaviour across the entire shear rate range investigated. Effects of different species of gum tragacanth on the interactions with sodium caseinate have been scarcely studied. Our study showed that systems containing various species (A.r, soluble fraction of A.r and Astragalus gossypinus (A.g)) had different critical pH values and particle sizes during complex coacervation, which could be due to different ratio of soluble to insoluble fractions and uronic acid content of various species. Copyright © 2014 Elsevier B.V. All rights reserved.

Flexible modeling improves assessment of prognostic value of C-reactive protein in advanced non-small cell lung cancer.

PubMed

Gagnon, B; Abrahamowicz, M; Xiao, Y; Beauchamp, M-E; MacDonald, N; Kasymjanova, G; Kreisman, H; Small, D

2010-03-30

C-reactive protein (CRP) is gaining credibility as a prognostic factor in different cancers. Cox's proportional hazard (PH) model is usually used to assess prognostic factors. However, this model imposes a priori assumptions, which are rarely tested, that (1) the hazard ratio associated with each prognostic factor remains constant across the follow-up (PH assumption) and (2) the relationship between a continuous predictor and the logarithm of the mortality hazard is linear (linearity assumption). We tested these two assumptions of the Cox's PH model for CRP, using a flexible statistical model, while adjusting for other known prognostic factors, in a cohort of 269 patients newly diagnosed with non-small cell lung cancer (NSCLC). In the Cox's PH model, high CRP increased the risk of death (HR=1.11 per each doubling of CRP value, 95% CI: 1.03-1.20, P=0.008). However, both the PH assumption (P=0.033) and the linearity assumption (P=0.015) were rejected for CRP, measured at the initiation of chemotherapy, which kept its prognostic value for approximately 18 months. Our analysis shows that flexible modeling provides new insights regarding the value of CRP as a prognostic factor in NSCLC and that Cox's PH model underestimates early risks associated with high CRP.

Using eddy currents for noninvasive in vivo pH monitoring for bone tissue engineering.

PubMed

Beck-Broichsitter, Benedicta E; Daschner, Frank; Christofzik, David W; Knöchel, Reinhard; Wiltfang, Jörg; Becker, Stephan T

2015-03-01

The metabolic processes that regulate bone healing and bone induction in tissue engineering models are not fully understood. Eddy current excitation is widely used in technical approaches and in the food industry. The aim of this study was to establish eddy current excitation for monitoring metabolic processes during heterotopic osteoinduction in vivo. Hydroxyapatite scaffolds were implanted into the musculus latissimus dorsi of six rats. Bone morphogenetic protein 2 (BMP-2) was applied 1 and 2 weeks after implantation. Weekly eddy current excitation measurements were performed. Additionally, invasive pH measurements were obtained from the scaffolds using fiber optic detection devices. Correlations between the eddy current measurements and the metabolic values were calculated. The eddy current measurements and pH values decreased significantly in the first 2 weeks of the study, followed by a steady increase and stabilization at higher levels towards the end of the study. The measurement curves and statistical evaluations indicated a significant correlation between the resonance frequency values of the eddy current excitation measurements and the observed pH levels (p = 0.0041). This innovative technique was capable of noninvasively monitoring metabolic processes in living tissues according to pH values, showing a direct correlation between eddy current excitation and pH in an in vivo tissue engineering model.

Comparison of survival of diarrhoeagenic agents in two local weaning foods (ogi and koko).

PubMed

Bakare, S; Smith, S I; Olukoya, D K; Akpan, E

1998-12-01

The pH values of both cooked and uncooked ogi and koko samples were determined and the survival rate of four diarrhoeagenic agents, enteroinvasive Escherichia coli, Salmonella typhi, Shigella flexneri, and Vibrio cholerae were studied after they were seeded into cooked ogi and koko. Analysis of the pH of the cooked inoculated samples showed that there was a slight increase in pH (decrease in acidity) during storage for 48 h and 37 degrees C (from 3.5 to 3.7 for ogi and from 3.7 to 4.1 for koko). The study also showed that ogi had a slightly lower pH value than koko both before and after cooking. In both cases, the cooked samples had a slightly lower pH value than the uncooked samples. The pH value of ogi ranged from 3.0 to 3.6 and that of koko from 3.5 to 3.9. The survival experiment showed that the inoculated enteric pathogens were inhibited in cooked ogi and koko during storage for 24-48 h. The antibacterial effect of cooked koko was more pronounced, on the four enteric pathogens studied, than that of cooked ogi. Except for Shigella flexneri and E. coli in ogi, non of the other bacteria studied was recovered after 24 h.

Effects of Gold Salt Speciation and Structure of Human and Bovine Serum Albumins on the Synthesis and Stability of Gold Nanostructures

PubMed Central

Miranda, Érica G. A.; Tofanello, Aryane; Brito, Adrianne M. M.; Lopes, David M.; Albuquerque, Lindomar J. C.; de Castro, Carlos E.; Costa, Fanny N.; Giacomelli, Fernando C.; Ferreira, Fabio F.; Araújo-Chaves, Juliana C.; Nantes, Iseli L.

2016-01-01

The present study aimed to investigate the influence of albumin structure and gold speciation on the synthesis of gold nanoparticles (GNPs). The strategy of synthesis was the addition of HAuCl4 solutions at different pH values (3–12) to solutions of human and bovine serum albumins (HSA and BSA) at the same corresponding pH values. Different pH values influence the GNP synthesis due to gold speciation. Besides the inherent effect of pH on the native structure of albumins, the use N-ethylmaleimide (NEM)-treated and heat-denaturated forms of HSA and BSA provided additional insights about the influence of protein structure, net charge, and thiol group approachability on the GNP synthesis. NEM treatment, heating, and the extreme values of pH promoted loss of the native albumin structure. The formation of GNPs indicated by the appearance of surface plasmon resonance (SPR) bands became detectable from 15 days of the synthesis processes that were carried out with native, NEM-treated and heat-denaturated forms of HSA and BSA, exclusively at pH 6 and 7. After 2 months of incubation, SPR band was also detected for all synthesis carried out at pH 8.0. The mean values of the hydrodynamic radius (RH) were 24 and 34 nm for GNPs synthesized with native HSA and BSA, respectively. X-ray diffraction (XRD) revealed crystallites of 13 nm. RH, XRD, and zeta potential values were consistent with GNP capping by the albumins. However, the GNPs produced with NEM-treated and heat-denaturated albumins exhibited loss of protein capping by lowering the ionic strength. This result suggests a significant contribution of non-electrostatic interactions of albumins with the GNP surface, in these conditions. The denaturation of proteins exposes hydrophobic groups to the solvent, and these groups could interact with the gold surface. In these conditions, the thiol blockage or oxidation, the latter probably favored upon heating, impaired the formation of a stable capping by thiol coordination with the gold surface. Therefore, the cysteine side chain of albumins is important for the colloidal stabilization of GNPs rather than as the reducing agent for the synthesis. Despite the presence of more reactive gold species at more acidic pH values, i.e., below 6.0, in these conditions the loss of native albumin structure impaired GNP synthesis. Alkaline pH values (9–12) combined the unfavorable conditions of denaturated protein structure with less reactive gold species. Therefore, an optimal condition for the synthesis of GNPs using serum albumins involves more reactive gold salt species combined with a reducing and negatively charged form of the protein, all favored at pH 6–7. PMID:27066476

Heavy metals alter the electrokinetic properties of bacteria, yeasts, and clay minerals.

PubMed Central

Collins, Y E; Stotzky, G

1992-01-01

The electrokinetic patterns of four bacterial species (Bacillus subtilis, Bacillus megaterium, Pseudomonas aeruginosa, and Agrobacterium radiobacter), two yeasts (Saccharomyces cerevisiae and Candida albicans), and two clay minerals (montmorillonite and kaolinite) in the presence of the chloride salts of the heavy metals, Cd, Cr, Cu, Hg, Ni, Pb, and Zn, and of Na and Mg were determined by microelectrophoresis. The cells and kaolinite were net negatively charged at pH values above their isoelectric points (pI) in the presence of Na, Mg, Hg, and Pb at an ionic strength (mu) of 3 x 10(-4); montmorillonite has no pI and was net negatively charged at all pH values in the presence of these metals. However, the charge of some bacteria, S. cerevisiae, and kaolinite changed to a net positive charge (charge reversal) in the presence of Cd, Cr, Cu, Ni, and Zn at pH values above 5.0 (the pH at which charge reversal occurred differed with the metal) and then, at higher pH values, again became negative. The charge of the bacteria and S. cerevisiae also reversed in solutions of Cu and Ni with a mu of greater than 3 x 10(-4), whereas there was no reversal in solutions with a mu of less than 3 x 10(-4). The clays became net positively charged when the mu of Cu was greater than 3 x 10(-4) and that of Ni was greater than 1.5 x 10(-4). The charge of the cells and clays also reversed in solutions containing both Mg and Ni or both Cu and Ni (except montmorillonite) but not in solutions containing both Mg and Cu (except kaolinite) (mu = 3 x 10(-4)). The pIs of the cells in the presence of the heavy metals were at either higher or lower pH values than in the presence of Na and Mg. Exposure of the cells to the various metals at pH values from 2 to 9 for the short times (ca. 10 min) required to measure the electrophoretic mobility did not affect their viability. The specific adsorption on the cells and clays of the hydrolyzed species of some of the heavy metals that formed at higher pH values was probably responsible for the charge reversal. These results suggest that the toxicity of some heavy metals to microorganisms varies with pH because the hydrolyzed speciation forms of these metals, which occur at higher pH values, bind on the cell surface and alter the net charge of the cell.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:1622229

Displacement energy of the surface layers of tungsten

NASA Astrophysics Data System (ADS)

Han, Longtao; Krstic, Predrag

2015-11-01

A molecular dynamics study with BOP potential is used to calculate the threshold displacement energy (ED) of primary knock-on atoms in the surface layers of the tungsten bcc crystal lattice at 300 K and at various crystallographic directions. Depending on the direction, ED is 10% to 75% smaller from the bulk value at the first layer, interfacing vacuum, while it reaches close to the bulk value already at the third tungsten layer. Supported by IACS of SBU and LDRD of PPPL.

First-principles studies of electronic, transport and bulk properties of pyrite FeS2

NASA Astrophysics Data System (ADS)

Banjara, Dipendra; Malozovsky, Yuriy; Franklin, LaShounda; Bagayoko, Diola

2018-02-01

We present results from first principle, local density approximation (LDA) calculations of electronic, transport, and bulk properties of iron pyrite (FeS2). Our non-relativistic computations employed the Ceperley and Alder LDA potential and the linear combination of atomic orbitals (LCAO) formalism. The implementation of the LCAO formalism followed the Bagayoko, Zhao, and Williams (BZW) method, as enhanced by Ekuma and Franklin (BZW-EF). We discuss the electronic energy bands, total and partial densities of states, electron effective masses, and the bulk modulus. Our calculated indirect band gap of 0.959 eV (0.96), using an experimental lattice constant of 5.4166 Å, at room temperature, is in agreement with the measured indirect values, for bulk samples, ranging from 0.84 eV to 1.03 ± 0.05 eV. Our calculated bulk modulus of 147 GPa is practically in agreement with the experimental value of 145 GPa. The calculated, partial densities of states reproduced the splitting of the Fe d bands to constitute the dominant upper most valence and lower most conduction bands, separated by the generally accepted, indirect, experimental band gap of 0.95 eV.

The surface stability of Cr 2O 3 (0 0 0 1)

DOE PAGES

Cao, Shi; Wu, Ning; Echtenkamp, William; ...

2015-05-28

The surface of chromia (Cr 2O 3) has a surface electronic structure distinct from the bulk and a packing density distinct from the bulk. More than a demarcation between the solid and the vacuum, the surface differs from the bulk of chromia, not just because of a partial occupancy of chromium sites, but also because of an increased number of unoccupied surface oxygen sites (vacancy sites), evident in angle-resolved core level photoemission. In spite of the structural differences that exist at the surface, there is, as yet, no evidence that these complications affect the surface Debye temperature beyond the mostmore » simple of assumptions regarding the lower coordination of the surface. Using low-energy electron diffraction (LEED), the effective surface Debye temperature (similar to 490 K) is found to be lower than the bulk (similar to 645 K) Debye temperature of Cr 2O 3(0 0 0 1). This surface effective Debye temperature, indicative of vibrations along the surface normal, uncorrected for anharmonic effects, has a value reduced from the effective bulk Debye temperature yet close to the value root 2 expected from a simple mean field argument.« less

Narrow pH Range of Surface Water Bodies Receiving Pesticide Input in Europe.

PubMed

Bundschuh, Mirco; Weyers, Arnd; Ebeling, Markus; Elsaesser, David; Schulz, Ralf

2016-01-01

Fate and toxicity of the active ingredients (AI's) of plant protection products in surface waters is often influenced by pH. Although a general range of pH values is reported in literature, an evaluation targeting aquatic ecosystems with documented AI inputs is lacking at the larger scale. Results show 95% of European surface waters (n = 3075) with a documented history of AI exposure fall within a rather narrow pH range, between 7.0 and 8.5. Spatial and temporal variability in the data may at least be partly explained by the calcareous characteristics of parental rock material, the affiliation of the sampling site to a freshwater ecoregion, and the photosynthetic activity of macrophytes (i.e., higher pH values with photosynthesis). Nonetheless, the documented pH range fits well with the standard pH of most ecotoxicological test guidelines, confirming the fate and ecotoxicity of AIs are usually adequately addressed.

Fluorescent pH sensor based on Ag@SiO2 core-shell nanoparticle.

PubMed

Bai, Zhenhua; Chen, Rui; Si, Peng; Huang, Youju; Sun, Handong; Kim, Dong-Hwan

2013-06-26

We have demonstrated a novel method for the preparation of a fluorescence-based pH sensor by combining the plasmon resonance band of Ag core and pH sensitive dye (HPTS). A thickness-variable silica shell is placed between Ag core and HPTS dye to achieve the maximum fluorescence enhancement. At the shell thickness of 8 nm, the fluorescence intensity increases 4 and 9 times when the sensor is excited at 405 and 455 nm, respectively. At the same time, the fluorescence intensity shows a good sensitivity toward pH value in the range of 5-9, and the ratio of emission intensity at 513 nm excited at 455 nm to that excited at 405 nm versus the pH value in the range of 5-9 is determined. It is believed that the present pH sensor has the potential for determining pH real time in the biological sample.

Mapping Soil pH Buffering Capacity of Selected Fields

NASA Technical Reports Server (NTRS)

Weaver, A. R.; Kissel, D. E.; Chen, F.; West, L. T.; Adkins, W.; Rickman, D.; Luvall, J. C.

2003-01-01

Soil pH buffering capacity, since it varies spatially within crop production fields, may be used to define sampling zones to assess lime requirement, or for modeling changes in soil pH when acid forming fertilizers or manures are added to a field. Our objective was to develop a procedure to map this soil property. One hundred thirty six soil samples (0 to 15 cm depth) from three Georgia Coastal Plain fields were titrated with calcium hydroxide to characterize differences in pH buffering capacity of the soils. Since the relationship between soil pH and added calcium hydroxide was approximately linear for all samples up to pH 6.5, the slope values of these linear relationships for all soils were regressed on the organic C and clay contents of the 136 soil samples using multiple linear regression. The equation that fit the data best was b (slope of pH vs. lime added) = 0.00029 - 0.00003 * % clay + 0.00135 * % O/C, r(exp 2) = 0.68. This equation was applied within geographic information system (GIS) software to create maps of soil pH buffering capacity for the three fields. When the mapped values of the pH buffering capacity were compared with measured values for a total of 18 locations in the three fields, there was good general agreement. A regression of directly measured pH buffering capacities on mapped pH buffering capacities at the field locations for these samples gave an r(exp 2) of 0.88 with a slope of 1.04 for a group of soils that varied approximately tenfold in their pH buffering capacities.

Use of D(acid)-, D(bile)-, z(acid)-, and z(bile)-values in evaluating Bifidobacteria with regard to stomach pH and bile salt sensitivity.

PubMed

Jia, Li; Shigwedha, Nditange; Mwandemele, Osmund D

2010-01-01

The survival of bifidobacteria in simulated conditions of the gastrointestinal (GI) tract was studied based on the D- and z-value concept. Some Bifidobacterium spp. are probiotics that improve microbial balance in the human GI tract. Because they are sensitive to low pH and bile salt concentrations, their viability in the GI tract is limited. The D- and z-value approach was therefore adopted as a result of observing constant log-cell reduction (90%) when Bifidobacterium spp. were exposed to these 2 different stressing factors. Survivals of one strain each or 4 species of Bifidobacterium was studied at pH between 3.0 and 4.5 and in ox-bile between 0.15% and 0.60% for times up to 41 h. From the D(acid)- and D(bile)-values, the order of resistance to acid and bile was B. bifidum > B. infantis > B. longum > B. adolescentis. While the former 3 strains retained high cell viability at pH 3.5 (>5.5 log CFU/mL after 5 h) and at elevated bile salt concentration of 0.6% (>4.5 log CFU/mL after 3 h), B. adolescentis was less resistant (<3.4 log CFU/mL). The z(acid)- and z(bile)-values calculated from the D(acid)- and D(bile)-values ranged from 1.11 to 1.55 pH units and 0.40% to 0.49%, respectively. The results suggest that the D(acid)-, D(bile)-, z(acid)-, and z(bile)-value approach could be more appropriate than the screening and selection method in evaluating survival of probiotic bacteria, and in measuring their tolerance or resistance to gastric acidity and the associated bile salt concentration in the small intestine. The evaluation of the tolerance of bifidobacteria to bile salts and low pH has been made possible by use of D- and z-value concept. The calculated z(acid)- and z(bile)-values were all fairly similar for the strains used and suggest the effect of increasing the bile salt concentration or decreasing the pH on the D(acid)- and D(bile)-values. This approach would be useful for predicting the suitability of bifidobacteria and other lactic acid bacteria (LAB) as probiotics for use in real-life situations.

Obtention and characterization of dried gels prepared with whey proteins, honey and hydrocolloids mixture.

PubMed

Rodriguez, Ana C; Torrez Irigoyen, Martín R; Navarro, Alba S; Yamul, Diego K

2017-11-01

Large amounts of honey and liquid whey derived from the dairy industry are produced in Argentina. Honey is exported in bulk and whey is transformed into whey protein concentrates and isolates. The objective of this work was to investigate the effect of pH, composition and storage time on the properties of dried gels with honey, whey proteins and hydrocolloids. Color properties varied according to pH and composition. The fracture stress of dried gels prepared with corn starch was higher than that of gels prepared with guar gum in all conditions assayed. Young's modulus was higher at pH 7 for both compositions and increased with storage time. Rubbery characteristics were found in dried gels with guar gum, while both corn starch and guar gum made the microstructure rougher. Multivariate analysis showed that samples could be grouped by pH. Panelists preferred pH 7 products over acidic ones, and no significant differences in sensory properties were found using either corn starch or guar gum in the formulation. The results demonstrated that it is possible to generate a new product, which may open new applications for honey and whey in food formulations. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

Ultrafast excited-state dynamics of RNA and DNA C tracts

NASA Astrophysics Data System (ADS)

Cohen, Boiko; Larson, Matthew H.; Kohler, Bern

2008-06-01

The excited-state dynamics of the RNA homopolymer of cytosine and of the 18-mer (dC) 18 were studied by steady-state and time-resolved absorption and emission spectroscopy. At pH 6.8, excitation of poly(rC) by a femtosecond UV pump pulse produces excited states that decay up to one order of magnitude more slowly than the excited states formed in the mononucleotide cytidine 5'-monophosphate under the same conditions. Even slower relaxation is observed for the hemiprotonated, self-associated form of poly(rC), which is stable at acidic pH. Transient absorption and time-resolved fluorescence signals for (dC) 18 at pH 6.8 are similar to ones observed for poly(rC) near pH 4, indicating that hemiprotonated structures are found in DNA C tracts at neutral pH. In both systems, there is evidence for two kinds of emitting states with lifetimes of ˜100 ps and slightly more than 1 ns. The former states are responsible for the bulk of emission from the hemiprotonated structures. Evidence suggests that slow electronic relaxation in these self-complexes is the result of vertical base stacking. The similar signals from RNA and DNA C tracts suggest a common base-stacked structure, which may be identical with that of i-motif DNA.

Highly active and stable Ni-Fe bimetal prepared by ball milling for catalytic hydrodechlorination of 4-chlorophenol.

PubMed

Xu, Fuyuan; Deng, Shubo; Xu, Jie; Zhang, Wang; Wu, Min; Wang, Bin; Huang, Jun; Yu, Gang

2012-04-17

A novel Ni-Fe bimetal with high dechlorination activity for 4-chlorophenol (4-CP) was prepared by ball milling (BM) in this study. Increasing Ni content and milling time greatly enhanced the dechlorination activity, which was mainly attributed to the homogeneous distribution of Ni nanoparticles (50-100 nm) in bulk Fe visualized by scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS) with image mapping. In comparison with the Ni-Fe bimetal prepared by a chemical solution deposition (CSD) process, the ball milled Ni-Fe bimetal possessed high dechlorination activity and stability before being used up. Dechlorination kinetics indicated that the dechlorination rates of 4-CP increased with increasing Ni-Fe dose but decreased with increasing solution pH. Solution pH had a significant effect on the dechlorination of 4-CP and the passivation of the Ni-Fe bimetal. The enhanced pH during the dechlorination process significantly accelerated the formation of passivating film on the bimetallic surface. The Ni-Fe bimetal at the dose of 60 g/L was reused 10 times without losing dechlorination activity for 4-CP at initial pH less than 6.0, but the gradual passivation was observed at initial pH above 7.0.

Pre-incubation in soil improves the nitrogen fertiliser value of hair waste.

PubMed

Malepfane, N M; Muchaonyerwa, P

2018-01-25

Global generation of human hair waste and its disposal at landfills could contribute to the leaching of nitrates into ground water. High concentrations of nitrogen (N) and other elements suggest that the waste could be a source of plant nutrients and differences in ethnic hair types could affect nutrient release and fertiliser value. The objective of this study was to determine the effects of hair type, as an N source, and pre-incubation time on dry-matter yield, nutrient uptake by spinach (Spinacia oleracea L.) and residual soil nutrients. Salons in Pietermaritzburg provided bulk African and Caucasian hair waste, without distinguishing age, sex, health status or livelihood of the individuals. The hair waste was analysed for elemental composition. A pot experiment was set up under glasshouse conditions. The hair waste was incorporated (400 kg N ha -1 ) into a loamy oxisol and pre-incubated for 0, 28, 56 and 84 days before planting spinach. Potassium (K) and phosphorus (P) were corrected to the same level for all treatments. Spinach seedlings were then cultivated for 6 weeks. Shoot dry-matter and the uptake of all nutrients, except P, were increased by the pre-incubation of hair. African hair pre-incubated for 28 days resulted in greater dry-matter, N, K, Mn and S uptake than Caucasian hair. Increasing pre-incubation resulted in a decline in the residual soil pH and exchangeable K. The findings suggested that pre-incubation improves the N fertiliser value of hair and that African hair has greater value than Caucasian hair when pre-incubated for a short period.

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

PubMed

Suzuki, Yuji

2008-08-01

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

Intra-Shell boron isotope ratios in benthic foraminifera: Implications for paleo-pH reconstructions

NASA Astrophysics Data System (ADS)

Rollion-Bard, C.; Erez, J.

2009-12-01

The boron isotope composition of marine carbonates is considered to be a seawater pH proxy. Nevertheless, the use of δ11B has some limitations: 1) the knowledge of fractionation factor (α4-3) between the two boron dissolved species (boric acid and borate ion), 2) the δ11B of seawater may have varied with time and 3) the amplitude of the "vital effects" of this proxy. Using secondary ion mass spectrometry (SIMS), we looked at the internal variability in the boron isotope ratio of the shallow water, symbionts bearing foraminiferan Amphistegina lobifera. Specimens were cultured at constant temperature (24±0.1 °C) in seawater with pH ranging between 7.90 and 8.45. We performed 6 to 8 measurements of δ11B in each foraminifera. Intra-shell boron isotopes show large variability with an upper threshold value of pH ~ 9. The ranges of the skeletal calculated pH values in different cultured foraminifera, show strong correlation with the culture pH values and may thus serve as proxy for pH in the past ocean.

Improvement in trapped fields by stacking bulk superconductors

NASA Astrophysics Data System (ADS)

Suzuki, A.; Wongsatanawarid, A.; Seki, H.; Murakami, M.

2009-10-01

We studied the effects of stacking several bulk superconductor blocks on the field trapping properties. In order to avoid the detrimental effects of the bottom deteriorated parts, bulk Dy-Ba-Cu-O superconductors 45 mm in diameter and 10 mm in thickness were cut from the top parts of as-grown bulk blocks of 25 mm diameter. We stacked the superconductors and measured the field distribution as a function of the gap. The trapped field measurements were performed by field-cooling the samples inserted in between two permanent magnets with liquid nitrogen. It was found that the trapped field values are almost doubled when the number of stacked bulk superconductors increased from two to three. The present results clearly show that one can expect beneficial effects of increasing the ratio of the height to the diameter even in bulk high temperature superconductors.

Comparative study of the functional properties of three legume seed isolates: adzuki, pea and soy bean.

PubMed

Barac, Miroljub B; Pesic, Mirjana B; Stanojevic, Sladjana P; Kostic, Aleksandar Z; Bivolarevic, Vanja

2015-05-01

The aim of this work was to compare functional properties including solubility, emulsifying and foaming properties of native and thermally treated adzuki, soy and pea protein isolates prepared under the same conditions. These functional properties were tested at four pH values: pH 3.0, pH 5.0, pH 7.0 and pH 8.0. The lowest solubility at all pH values were obtained for isolate of adzuki whereas isolates of soybean had the highest values at almost all pHs. Thermal treatment reduced solubility of soy and pea isolates at all pH values, whereas solubility of adzuki isolate was unchanged, except at pH 8. Native isolate of adzuki had the best emulsifying properties at pH 7.0 whereas at the other pH values some of native pea and soybean protein isolates were superior. After thermal treatment, depending on tested pH and selected variety all of three species could be a good emulsifier. Native soy protein isolates formed the most stable foams at all pHs. Thermal treatment significantly improved foaming properties of adzuki isolate, whereas reduced foaming capacity of soy and pea isolates, but could improve foam stability of these isolates at specific pH. Appropriate selection of legume seed as well as variety could have great importance in achievement of desirable functional properties of final products. All three tested species could find specific application in wide range of food products.

Effect of ph Value and Calcination Temperature on Structure and Magnetic Properties of Strontium Hexaferrite Thin Film

NASA Astrophysics Data System (ADS)

Shanaghi, A.

2012-02-01

Strontium hexaferrite was widely used in the fabrication of commercial permanent magnets and certain microwave devices. In this study, the strontium hexaferrite nanoparticle coatings were prepared by sol-gel method and using spin coating process on silicon substrate, then the effect of pH value, such as 5, 7 and 9, and calcination temperatures, such as 600°C, 800°C, and 1000°C, on structural and magnetic properties of strontium hexaferrite thin films were investigated by XRD, SEM and VSM measurements. The maximum saturation magnetization value of 57.43 emu/g and coercivity value of 3908 Oe were achieved for the thin film with crystallite size approximately 41 nm, prepared at pH value of 7 and calcinations temperature of 800°C.

[Advances in the effects of pH value of micro-environment on wound healing].

PubMed

Tian, Ruirui; Li, Na; Wei, Li

2016-04-01

Wound healing is a complex regeneration process, which is affected by lots of endogenous and exogenous factors. Researches have confirmed that acid environment could prevent wound infection and accelerate wound healing by inhibiting bacteria proliferation, promoting oxygen release, affecting keratinocyte proliferation and migration, etc. In this article, we review the literature to identify the potential relationship between the pH value of wound micro-environment and the progress of wound healing, and summarize the clinical application of variation of pH value of micro-environment in wound healing, thereby to provide new treatment strategy for wound healing.

HDP for the Neutralized pH Value Control in the Clarifying Process of Sugar Cane Juice

NASA Astrophysics Data System (ADS)

Lin, Xiaofeng; Yang, Jiaran

2009-05-01

Neutralizing pH value of sugar cane juice is the important craft in the control process in the clarifying process of sugar cane juice, which is the important factor to influence output and the quality of white sugar. On the one hand, it is an important content to control the neutralized pH value within a required range, which has the vital significance for acquiring high quality purified juice, reducing energy consumption and raising sucrose recovery. On the other hand, it is a complicated physical-chemistry process, which has the characteristics of strong non-linearity, time-varying, large time-delay, and multi-input. Therefore, there has not been a very good solution to control the neutralized pH value. Firstly, in this chapter, a neural network model for the clarifying process of sugar juice is established based on gathering 1200 groups of real-time sample data in a sugar factory. Then, the HDP (Heuristic Dynamic Programming) method is used to optimize and control the neutralized pH value in the clarifying process of sugar juice. Simulation results indicate that this method has good control effect. This will build a good foundation for stabilizing the clarifying process and enhancing the quality of the purified juice and lastly enhancing the quality of white sugar.

How to examine soil sorption of ionizable organic compounds and avoid varying pH?

NASA Astrophysics Data System (ADS)

Borisover, Mikhail

2017-04-01

Multiple natural and anthropogenic organic compounds including new and emerging pollutants undergo ionization in aqueous solutions, and their sorption by soils and sediments is contributed by presence of both molecular and ionized species. Better understanding of environmental fate of organic chemicals requires taking into account interactions of molecular and ionized species with environmental sorbents. A "standard" (and undoubtedly important) procedure for differentiating contributions of molecular and ionized species into the overall soil sorption of an organic compound involves varying pH of solution in batch sorption experiments. However, varying pH is (1) often not possible, without destroying a sorbent, e.g., due to the buffer capacity of soils containing carbonates, (2) difficult for further interpretation, since it changes not only the ionization status of a solute in a solution but also the sorbent structure, e.g., a conformation of organic matter, and/or ionization of surface functional groups, (3) making difficult (or even impossible) to explicitly evaluate the role of dissolved species-bulk water interactions, directly affecting the affinity of a sorbate to distribute between water and a sorbent. Indeed, both molecular and ionized species undergo interactions with the solvent bulk and, at least in the case of the ionized ones, there was no a simple way to quantify organic ion-water interactions and their role in organic ion distribution between soil and water phases. This paper presents a "counter-intuitive" approach to examine sorption interactions of an ionizable compound, without experimenting with varied pH. The approach is based on an idea of replacing an initial state in sorption transfer of an ionizable compound from the solvent bulk to a solvated (hydrated) sorbed state: a traditional coefficient describing distribution of a partially ionized compound between a hydrated sorbent and a co-equilibrated aqueous phase is converted to the coefficient describing the transfer of the sorbing compound from its initial molecular (non-ionized) state (in a solution or in the gas phase) to the final hydrated sorbed state equilibrated with the actual aqueous solution of this ionizable compound. In this way, any contributions from the bulk solvent-organic ion interactions into the sorption transfer may be excluded; in addition, further any solute-solvent interactions may be taken out of the consideration. Therefore, compound's sorption characteristics "cleared" of solute-solvent interactions may be obtained, and a better understanding of relations between interactions in a sorbed phase and a molecular structure of organic sorbates can be reached. The approach is illustrated by examining sorption of variously ionized organic compounds, i.e., those belonging to the pharmaceuticals and personal care products (triclosan, gemfibrozil, galaxolide), and aliphatic organic acids on natural and organic amendment-enriched soils. Specifically, it is demonstrated how the greater H-donating ability of trifluoroacetic acid, as compared with acetic acid, strengthens the acid interactions in the soil phase. In another series of examples, it is shown how hydrophobic and non-ionizing galaxolide interacts weakly with soils, as compared with partially ionized triclosan and almost fully ionized gemfibrozil, i.e., leading to the conclusions not reachable based only on the direct comparison of experimentally measured distribution coefficients.

NASCAP-2K Version 4.2 Users Manual

DTIC Science & Technology

2014-10-31

the surface element is metal or dielectric coating , the conductivity and capacitance (if a coating ), and the electron emission stimulated by incident...film covering an underlying conductor in meters. It is ignored for conductors . Bulk conductivity . This property is the bulk conductivity of the...surface material in ohms-1 m-1. A negative value indicates that the material is a conductor . If the bulk conductivity is in excess of 10-4 Ω-1 m-1, the

Analytical Prediction of Motor Component Vibrations Driven by Acoustic Combustion Instability

DTIC Science & Technology

1976-02-01

27"V 1Sy 1 2 oiihedr41 Symmetry .. .. . ., . . C-28 3 SPCD Bulk Data Card Format ......... . . .. .- 29 4 CYJOIN Bulk Data Card Format...analysis, the loads, the values of enforced displacements, and the temperatures may vary from element to element. The SPCD bulk data card (Figure 3) is...Static loads for vech suhc’: -e are spcified with LOAD, ’TEMPERATURE (LOAD), or DE .-I, oiectic.-,!•. Enforced deformations may be specified on SPCD

Bulk Properties of Ni3Al(gamma') With Cu and Au Additions

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1995-01-01

The BFS method for alloys is applied to the study of 200 alloys obtained from adding Cu and Au impurities to a Ni3Al matrix. We analyze the trends in the bulk properties of these alloys (heat of formation, lattice parameter, and bulk modulus) and detect specific alloy compositions for which these quantities have particular values. A detailed analysis of the atomic interactions that lead to the preferred ordering patterns is presented.