Hydrothermal crystallization kinetics of m-ZrO2 and t-ZrO2

1990 ◽  
Vol 5 (11) ◽  
pp. 2698-2705 ◽  
Author(s):  
Raymond P. Denkewicz ◽  
Kevor S. TenHuisen ◽  
James H. Adair
Keyword(s):  
Crystallization Kinetics ◽  
Low Ph ◽  
Formation Mechanisms ◽  
Gel Structure ◽  
Hydrothermal Conditions ◽  
High Ph ◽  
Ph Values ◽  
Ph Conditions ◽  
Apparent Activation Energies ◽  
Kinetics Of

The isothermal nucleation and crystallization kinetics of hydrothermally prepared monoclinic and tetragonal ZrO2 have been determined at various pH conditions. It is shown that monoclinic ZrO2 precipitates at low pH whereas at high pH tetragonal ZrO2 crystallizes from an amorphous zirconium (hydrous) oxide, Zr(OH)xOy, precursor. At intermediate pH conditions mixtures of the polymorphs are formed suggestive of kinetically competing particle formation mechanisms. The data are explained by the proposed existence of three controlling regimes for the formation of crystalline ZrO2: dissolution/precipitation at low pH, a solubility controlled regime at intermediate pH values, and a gel structure controlled regime at high pH. Apparent activation energies for the nucleation and crystallization of monoclinic and tetragonal ZrO2 formed under hydrothermal conditions are presented.

Expression patterns of two carbonic anhydrase genes, Na+/K+-ATPase and V-type H+-ATPase, in the freshwater crayfish, Cherax quadricarinatus, exposed to low pH and high pH

2017 ◽  
Vol 65 (1) ◽  
pp. 50 ◽  
Author(s):  
Muhammad Yousuf Ali ◽  
Ana Pavasovic ◽  
Peter B. Mather ◽  
Peter J. Prentis
Keyword(s):  
Carbonic Anhydrase ◽  
Expression Patterns ◽  
Maximum Level ◽  
Low Ph ◽  
Freshwater Crayfish ◽  
Α Subunit ◽  
Cherax Quadricarinatus ◽  
High Ph ◽  
Internal Ph ◽  
Ph Conditions

Carbonic anhydrase (CA), Na+/K+-ATPase (NKA) and Vacuolar-type H+-ATPase (HAT) play vital roles in osmoregulation and pH balance in decapod crustaceans. As variable pH levels have a significant impact on the physiology of crustaceans, it is crucial to understand the mechanisms by which an animal maintains its internal pH. We examined expression patterns of cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of freshwater crayfish, Cherax quadricarinatus, at three pH levels – 6.2, 7.2 (control) and 8.2 – over 24 h. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer. Expression increased at low pH after 12 h, and reached its maximum level by 24 h. CAg showed a significant increase in expression at 6 h after transfer at low pH. Expression of NKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated for up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h after transfer to low pH and remained significantly elevated throughout the experiment. Overall, CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish.

scholarly journals pH-jump studies at subzero temperatures on an intermediate in the reaction of xanthine oxidase with xanthine

1978 ◽  
Vol 175 (3) ◽  
pp. 879-885 ◽  
Author(s):  
A D Tsopanakis ◽  
S J Tanner ◽  
R C Bray
Keyword(s):  
Nitrate Reductase ◽  
Xanthine Oxidase ◽  
Low Ph ◽  
High Ph ◽  
Ph Values ◽  
Exchangeable Proton ◽  
Subzero Temperatures ◽  
Ph Jump ◽  
Unique Nature ◽  
Prototropic Equilibrium

Xanthine oxidase is stable and active in aqueous dimethyl sulphoxide solutions of up to at least 57% (w/w). Simple techniques are described for mixing the enzyme in this solvent at–82 degrees C, with its substrate, xanthine. When working at high pH values under such conditions, no reaction occurred, as judged by the absence of e.p.r. signals. On warming to–60 degrees C, for 10 min, however, the Very Rapid molybdenum(V) e.p.r. signal was obtained. This signal did not change on decreasing the pH, while maintaining the sample in liquid nitrate reductase, caused its molybdenum(V) e.p.r. signal to change from the high-pH to the low-pH form. These findings are not compatible with the conclusions of Edmondson, Ballou, Van Heuvelen, Palmer & Massey [J. Biol. Chem. (1973) 248, 6135-6144], that the Very Rapid signal is in prototropic equilibrium with the Rapid signal, and should be important in understanding the mechanism of action of the enzyme. They emphasize the unique nature of the intermediate represented by the Very Rapid e.p.r. signal. The possible value of the pK for loss of an exchangeable proton from the Rapid signal is discussed.

scholarly journals Expression patterns of two Carbonic anhydrase genes, Na+/K+-ATPase and V-type H+-ATPase in the freshwater crayfish, Cherax quadricarinatus, under different pH

2015 ◽  
Author(s):  
Muhammad Yousuf Ali ◽  
Ana Pavasovic ◽  
Peter B Mather ◽  
Peter J Prentis
Keyword(s):  
Carbonic Anhydrase ◽  
Expression Patterns ◽  
Low Ph ◽  
Freshwater Crayfish ◽  
Acid Base Balance ◽  
Acid Base ◽  
Expression Levels ◽  
High Ph ◽  
Base Balance ◽  
Ph Conditions

Osmoregulation and systemic acid-base balance in decapod crustaceans are largely controlled by a set of transport-related enzymes including carbonic anhydrase (CA), Na + /K + -ATPase (NKA) and V-type- H + -ATPase (HAT). Variable pH levels and changes in osmotic pressure can have a significant impact on the physiology and behaviour of crustaceans. Therefore, it is crucial to understand the mechanisms via which an animal can maintain its internal pH balance and regulate the movement of ions into and out of its cells. Here, we examined expression patterns of the cytoplasmic (CAc) and membrane-associated form (CAg) of CA, NKA α subunit and HAT subunit a in gills of the freshwater crayfish Cherax quadricarinatus. Expression levels of the genes were measured at three pH levels, pH 6.2, 7.2 (control) and 8.2 over a 24 hour period. All genes showed significant differences in expression levels, either among pH treatments or over time. Expression levels of CAc were significantly increased at low pH and decreased at high pH conditions 24 h after transfer to these treatments. Expression increased in low pH after 12 h, and reached their maximum level by 24 h. The membrane-associated form CAg showed changes in expression levels more quickly than CAc. Expression increased for CAg at 6 h post transfer at both low and high pH conditions, but expression remained elevated only at low pH (6.2) at the end of the experiment. Expression of CqNKA significantly increased at 6 h after transfer to pH 6.2 and remained elevated up to 24 h. Expression for HAT and NKA showed similar patterns, where expression significantly increased 6 h post transfer to the low pH conditions and remained significantly elevated throughout the experiment. The only difference in expression between the two genes was that HAT expression decreased significantly 24 h post transfer to high pH conditions. Overall, our data suggest that CAc, CAg, NKA and HAT gene expression is induced at low pH conditions in freshwater crayfish. Further research should examine the physiological underpinnings of these changes in expression to better understand systemic acid/base balance in freshwater crayfish.

Electronic and Raman spectroscopic studies of copper adrenalin complexes and copper induced compounds

1976 ◽  
Vol 54 (24) ◽  
pp. 3815-3823 ◽  
Author(s):  
Mohammed S. Rahaman ◽  
Stephen M. Korenkiewicz
Keyword(s):  
Free Radical ◽  
Hydrochloric Acid ◽  
Raman Spectra ◽  
Spectroscopic Studies ◽  
Low Ph ◽  
Basic Solution ◽  
High Ph ◽  
Raman Spectroscopic ◽  
Ph Values

Electronic and Raman spectra of adrenalin–copper(II) complexes and copper catalyzed compounds have been studied. Adrenalin reacts with copper(II) ion at pH 9.2 and higher to produce a very short lived violet free radical, a brown adrenochrome, a yellow conjugated salt, indolyl-indoquinone, and melanin. Results indicate that copper does not form complexes with adrenalin in basic solution. Between pH 6.5 and 8.5 adrenalin transforms into adrenochrome in presence of copper. The adrenochrome in 1.5 N hydrochloric acid produces the conjugate salt that is produced in the solution of high pH. At low pH values, between pH 4.0 to 5.5, adrenalin forms a brown complex with copper(II). Copper is entirely chelated to the phenolic groups of the amines. The complex in 1.5 N hydrochloric acid produces a black polymeric pigment.

Mossbauer spectroscopic evidence of a IVFe3+ intermediate in the oxidation of Fe(Oh)2 to α-FeOOH

Soil Research ◽  
1991 ◽  
Vol 29 (3) ◽  
pp. 399 ◽  
Author(s):  
CM Cardile ◽  
DG Lewis
Keyword(s):  
Alkaline Solution ◽  
Building Blocks ◽  
Spectral Parameters ◽  
Initial Oxidation ◽  
Spectroscopic Evidence ◽  
High Ph ◽  
Ph Values ◽  
Fe Species ◽  
Ph Conditions ◽  
Surrounding Liquid

Mossbauer spectroscopy was used to study the oxidation of Fe(OH)2 under high pH conditions with the aim of detecting the formation of Fe(OH)3. The Mossbauer spectral parameters indicated that a small IVFe3+ component was initially present in the Fe(OH)2. The Mossbauer spectra were recorded at 77 K, thus any Fe species in solution would also be observed in the frozen state. The small IVFe3+ component increased progressively with the oxidation of the Fe(OH)2, maximizing with the onset of �-FeOOH formation. As �-FeOOH formation increased, the IVFe3+ component decreased, with �-FeOOH being the final sole phase. It is suggested that the Mossbauer spectral parameters indicate that a component such as Fe(OH)2 may form at high pH values as used in this study. Furthermore, any Fe3+ produced by the initial oxidation of Fe(OH)2 is exsolved from the solid and at the high pH of the surrounding liquid produces Fe(OH)-4 until the formation of the more stable �-FeOOH begins. This suggests Fe(OH)2 could be the building blocks for �-FeOOH in alkaline solution. No apparent Fe(OH)3 phase was observed as anticipated.

scholarly journals pH Tolerance in Freshwater Bacterioplankton: Trait Variation of the Community as Measured by Leucine Incorporation

2015 ◽  
Vol 81 (21) ◽  
pp. 7411-7419 ◽  
Author(s):  
Erland Bååth ◽  
Emma Kritzberg
Keyword(s):  
Bacterial Growth ◽  
Low Ph ◽  
Tolerance Index ◽  
Response Curves ◽  
Trait Variation ◽  
High Ph ◽  
Ph Values ◽  
Ph Tolerance ◽  
Community Tolerance

ABSTRACTpH is an important factor determining bacterial community composition in soil and water. We have directly determined the community tolerance (trait variation) to pH in communities from 22 lakes and streams ranging in pH from 4 to 9 using a growth-based method not relying on distinguishing between individual populations. The pH in the water samples was altered to up to 16 pH values, coveringin situpH ± 2.5 U, and the tolerance was assessed by measuring bacterial growth (Leu incorporation) instantaneously after pH adjustment. The resulting unimodal response curves, reflecting community tolerance to pH, were well modeled with a double logistic equation (meanR2= 0.97). The optimal pH for growth (pHopt) among the bacterial communities was closely correlated within situpH, with a slope (0.89 ± 0.099) close to unity. The pH interval, in which growth was ≥90% of that at pHopt, was 1.1 to 3 pH units wide (mean 2.0 pH units). Tolerance response curves of communities originating from circum-neutral pH were symmetrical, whereas in high-pH (8.9) and especially in low-pH (<5.5) waters, asymmetric tolerance curves were found. In low-pH waters, decreasing pH was more detrimental for bacterial growth than increasing pH, with a tendency for the opposite for high-pH waters. A pH tolerance index, using the ratio of growth at only two pH values (pH 4 and 8), was closely related to pHopt(R2= 0.83), allowing for easy determination of pH tolerance during rapid changes in pH.

Effects of pH on Hg0 Re-Emission in WFGD

2014 ◽  
Vol 960-961 ◽  
pp. 462-468 ◽  
Author(s):  
Yong Qiu ◽  
Hui Wu ◽  
Guang Qian Luo ◽  
Hong Yao
Keyword(s):  
Flue Gas ◽  
Laboratory Experiments ◽  
Low Ph ◽  
Time Span ◽  
Flue Gas Desulfurization ◽  
Solution Theory ◽  
High Ph ◽  
Ph Values ◽  
Effects Of Ph ◽  
Conventional Solution

Gaseous oxidized mercury (Hg2+) in the flue gas is soluble in water and can be captured effectively by Wet flue gas desulfurization (WFGD) system. But in some extent Hg0re-emission happens due to the reduction of absorbed Hg2+, and the pH of slurry is an important factor affecting Hg0re-emission. In this study, the theoretical formulas of slurry pH were derived through the conventional solution theory and then were used to evaluate the factors determining the pH of slurry. A series of laboratory experiments were carried out under N2,CO2and O2/N2atmosphere to measure the Hg0re-emission tendency at different pH values. The results show that the higher the pH, the less Hg2+reduced by S(IV), resulting in the decrease of Hg0re-emission. Under N2atmosphere, the Hg0re-emission was mild at pH>4 while it was dramatic at pH<4. Under O2/N2atmosphere, the addition of O2extended the time span of Hg0re-emission at low pH and increased Hg0re-emission unexpectedly in the latter part of the experiments at high pH. CO2atmosphere almost did not affect Hg0re-emission because of its little effect on the slurry pH.

scholarly journals Structural Changes of Co Caused a Change of the Solution pH During Chemical Deposition

2020 ◽  
pp. 451-458
Author(s):  
Sergey A. Podorozhnyak ◽  
Anatoly V. Chzhan ◽  
Vadim K. Maltsev ◽  
Ivan N. Krayuhin ◽  
Gennady S. Patrin ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Crystal Lattice ◽  
Phase Transformations ◽  
Structural Changes ◽  
Chemical Deposition ◽  
Low Ph ◽  
Nanocrystalline State ◽  
Solution Ph ◽  
High Ph ◽  
Ph Values

The phase transformations of the Co lattice are discussed, which determine the anomalous changes in the magnetic properties of chemically deposited Co-P films obtained at various pH values. The coercivity of the Hc films obtained at low pH values exceeds 1 kOe and decreases to several units Oe in the films obtained at high pH values. It is shown that the observed changes in the magnetic properties of Co-P films are caused by the transition of the cobalt crystal lattice to the nanocrystalline state

THE EFFECT OF NITROGEN AND PHOSPHORUS NUTRITION ON pH OF TOMATO

1966 ◽  
Vol 46 (6) ◽  
pp. 681-684 ◽  
Author(s):  
J. S. Matthews ◽  
L. G. Denby
Keyword(s):  
Low Ph ◽  
The Other ◽  
Phosphorus Nutrition ◽  
Nitrogen And Phosphorus ◽  
Tomato Fruits ◽  
High Ph ◽  
Ph Values ◽  
Low Levels ◽  
Nutrient Solutions

Tomato fruits, grown under glass in inert media, and supplied with nutrient solutions containing high and low levels of N and P, varied in pH from 4.21 to 4.61. Fruits from plants receiving low levels of both nutrients consistently had low pH values. Those from plants fed high levels of P or N had high pH whenever the level of the other element was not limiting.

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