Influence of pH value and chelating reagent on performance of Li_3V_2(PO_4)3/C cathode material

The Li3V2（PO4）3/C composite cathode material was synthesized via sol-gel method using three different chelating agents （citric acid, salicylic acid and polyacrylic acid） at pH value of 3 or 7. The crystal structure, morphology, specific surface area and electrochemical performance of the prepared samples were investigated by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, cyclic voltammetry （CV）, electrochemical impedance spectroscopy （EIS） and galvanostatic charge/discharge test. The results show that the effects of pH value on the performance of the prepared materials are greatly related to the chelating agents. With salicylic acid or polyacrylic acid as the chelating reagent, the structure, morphology and electrochemical performance of the samples are greatly influenced by the pH values. However, the structure of the materials with citric acid as the chelating agent does not change as pH value changes, and the materials own uniform particle size distribution and good electrochemical performance. It delivers an initial discharge capacity of 113.58 mA·h/g at 10C, remaining as high as 108.48 mA·h/g after 900 cycles, with a capacity retention of 95.51%.

Influence of pH Value on Photocatalytic Activity of Bi4Ti3O12 Crystals Obtained by Hydrothermal Method

Bi4Ti3O12 （BIT） crystals were controllably synthesized via a facile hydrothermal process without adding any surfactant or template. The morphologies of BIT with nanosphere, nanoplate, nanobelt, and nanosheet can be selectively obtained by adjusting the pH value of the reactant. The formation mechanisms of these distinctive morphologies were then discussed based on the structural analysis of samples obtained at different pH values. BIT sample prepared at pH=1 showed the highest photocatalytic activity under visible light irradiation. The photocatalytic activities difference for the BIT samples synthesized at different pH values was studied based on their shape, size, and the variation of local structure.

Adsorption Kinetics of NH_4^+ by Purple Soils with Different pH Values

Ammonium adsorption and desorption properties by purple soils with dif- ferent pH were studied. The results showed that the adsorption and desorption amounts of NH4＋ by purple soils increased with the increase of NH4＋ concentration, regardless of soil pH values; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 6.0 were 10.3 and 7.96 mg/g, respectively; the largest adsorp- tion and desorption amounts of NH4＋ by purple soil at pH 7.2 were 12.8 and 4.62 mg/g, respectively; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 8.0 were 13.5 and 2.23 mg/g, respectively. The isothermal adsorption ki- netics of NH4＋ by purple soils fits the Freundlich equation best （R〉0.95）. This study shows that the adsorption of NH4＋ by purple soils with different pH values is multi- molecular layer uneven surface adsorption.

Effect of pH values on extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans during chalcopyrite bioleaching

The effect of pH values on the extracellular protein and polysaccharide secretions of Acidithiobacillus ferrooxidans was comparatively investigated in different phases of bacterial growth during chalcopyrite bioleaching. The results indicate that the extracellular protein is always more than the extracellular polysaccharide secreted by attached cells on the chalcopyrite, on the contrary, and is always less than the extracellular polysaccharide secreted by free cells in the solution at bacterial adaptive phase, logarithmic phase and stationary phase whenever pH value is at 1.0, 1.5, 2.0 or 2.5; free cells are mainly through the secretion of extracellular polysaccharide rather than the extracellular protein to fight against disadvantageous solution environment, such as high concentration of metal ions and unsuitable pH solution; both amounts of polysaccharide and protein secreted by attached cells are mainly positively related to the solution acidity rather than the total concentration of soluble metal ions. The experimental results imply that bacteria are mainly through secreting more extracellular polysaccharide to fight against disadvantageous environment and the extracellular protein perhaps plays an important role in oxidation？reduction reactions in the bioleaching system.

Corrosion behaviour of die-cast AZ91D magnesium alloys in sodium sulphate solutions with different pH values

The corrosion behaviours of die-cast AZ91D magnesium alloys were investigated in 0.1 mol/L sodium sulphate （Na 2 SO 4 ） solutions with different pH values. The corrosion rates, morphologies, and compositions of the corrosion products were studied by means of scanning electron microscopy （SEM）, Fourier transform infrared spectroscopy （FTIR）, and X-ray diffractometry （XRD）. The results indicate that the order of corrosion rates in Na 2 SO 4 solutions with various pH values is pH 2pH 4pH 7pH 9pH 12. The corrosion rates in acidic solutions are higher than those in alkaline solutions, and the corrosion products are mainly magnesium hydroxide （Mg（OH） 2 ） and hydrated sulphate pickeringite （MgAl 2 （SO 4 ） 4 ·22H 2 O）. The results also indicate that the solution pH can influence the corrosion rate and morphology of corrosion products. Chloride ions and sulphate ions have different pitting initiation time.

The Distribution Characteristics of Soil pH Values of Tobacco-growing Areas in Dali City and Its Correlation with Soil Nutrients

[Objective] The aim was to study the distribution characteristics of soil pH values and its correlation with soil nutrients in tobacco-growing areas. [Method] Soil nutrients of 43 samples from tobacco-growing areas in Dali City were analyzed.[Results] The results showed that average pH value of tobacco-planting soil in Dali City was 6.52, soil samples which suited for flue-cured tobacco cultivation accounted for 72.09% of total soil samples. In four soil types of tobacco-growing areas, the pH values in a descending order were as follows： alluvial soil〉 paddy soil 〉purple soil〉 red soil. At the altitude range of 1 780-2 200 m, soil pH values showed a gradual decreasing trend. The average contents of soil organic matters were relatively abundant and generally suited for high-quality tobacco cultivation; the average contents of soil alkali-hydrolyzable nitrogen, available phosphorus, exchangeable calcium and exchangeable magnesium were generally at medium and abundant level, however,their rations under the medium level in some tobacco-growing areas were 6.98%,11.63%, 2.33% and 4.65%, respectively; moreover, soil with lower available potassium contents occupied a large proportion, namely 58.14%. [Conclusion] Soil pH values had significant correlation with exchangeable magnesium and exchangeable magnesium, however, they had no significant correlation with other soil nutrients.

Effects of temperatures and pH values on rheological properties of cemented paste backfill

In this study,different influence mechanisms associated with temperatures and pH values were investigated through cemented paste backfill(CPB)systems.CPB samples were prepared with temperatures ranging from 10 to 50℃ in 10℃ increments and pH values of 3,7,and 13.Then,the CPB mixture were subjected to rheological tests,thermogravimetric analysis(TG),derivative thermogravimetry analysis(DTG),Fourier-transform infrared spectroscopy(FT-IR),and scanning electron microscopy(SEM).Results demonstrated that the temperatures had significant effects on the rheological properties of CPB,whereas the effects of pH values were relatively unapparent.Higher temperatures(over 20℃)were prone to bring higher shear stress,yield stress,and apparent viscosity with the same pH value condition.However,an overly high temperature(50℃)cannot raise the apparent viscosity.Non-neutral conditions,for pH values of 3 and 13,could strengthen the shear stress and apparent viscosity at the same temperature.Two different yield stress curves could be discovered by uprising pH values,which also led to apparent viscosity of two various curves under the same temperatures(under 50℃).Microscopically,rheological properties of CPB were affected by temperatures and pH values which enhanced or reduced the cement hydration procedures,rates,products and space structures.

Correspondence between Susceptibility to SCC of 7050 Aluminum Alloy and Passive Film-induced Stress at Various pH Values

The passive film-induced stress and the susceptibility to SCC of 7050 aluminum alloy in 3.5%sodium chloride solution at various pH values were investigated by slow strain rate testing（SSRT） and flowing stress differential method.The results showed that the passive film-induced stress and the susceptibility to SCC decreased with increasing pH values when pH≤7,while they increased with increasing pH values when pH7.However,the corrosion type was interpreted as exfoliation corrosion when pH=l and 14,and there was no film formed on the surface of the specimens.The whole variation plots of film-induced stress and the SCC susceptibility with pH values were both presented as a valley shape.The symbol and amount of the film-induced stress were related to the compositions of the passive film,which were analyzed using X-ray photoelectron spectroscopy（XPS）.

Microstructure of nano precursors of La-Mg hydrogen storage alloy synthesized by sol-gel technology at different pH values

Sol-gel technology was employed to synthesize nanosized precursors of La-Mg hydrogen storage alloy at different pH values (0.5, 1.5, 8.0 and 9.0) of reaction solution. The effect of pH value on microstructure of the nano precursors of La-Mg hydrogen storage alloy was studied by infrared radiation (IR), thermo-gravimetric and differential thermal analysis (TG/DTA), X-ray diffraction analyzer (XRD) and transmission electron microscopy (TEM). IR results indicate that the chelating agent, citric acid, is not fully ionized, and carboxyl groups are not entirely used to complex metal ions in acidic solutions. The efficiency of complexing metal ions is enhanced in basic solutions. TG/DTA results show that the combustion may take place with low rate of the flame propagation that causes the longer combustion time when pH<1.5. On the contrary, the dry gel synthesized in basic solution combusts at low ignition temperature and combustion reaction is violent; it is easy to form fine particles. XRD and TEM results reveal that the precursor powders are mainly two-phase mixture of La 2 O 3 and MgO. The morphology of the particles is almost flake with the size of ~30 nm when pH is 8.0.

Effect of Cu and Ni on Growth, Mineral Uptake,Photosynthesis and Enzyme Activities of Chlorella vulgaris at Different pH Values

A pH dependent reduction in growth, Pigment, ATP content, O,' evolution, carbonfixation, Photosynthetic electron transport system, nutrient uptake (NO,' and NH4+),nitrate reductase, and ATPase activities and increase in K+ emux of Chlorella vulgaris wasnoticed following supplementation of Cu and Ni to the culture medium. PS II was foundto be more sensitive to both pH and metals than PS I. Though, nitrate reductase (NR) wasmore sensitive to both PH and metals, the ATPase was however, more sensitive t0 metalsbut less sensitive to acidic pH. Acid PH was found to dst the nutrient (NO,' and NH4+)uptake and nitrate reductase in a non-competitive manner. The inhibition Pnduced by thetest metals alone was of noncompetitive type for NO3' uptake, nitrate reductase andATPase and competitive for NH'+ uptake. Acidity not only inhibited the metabolicvariables directly but also through facilitated uptake of metals and increased membranepermeability. A very low sensitivity of ATPase to acidic pH seems to be resgnsible forthe survival of algae in acid environment.

Comparison of pH Value, TBA Value, Glycogen and Lactic Acid Content in Muscle of Landrace and Yorkshire under Different Storage Time and Conditions

In order to assess the meat quality under different storage time and conditions, the pH value, TBA value, glycogen and lactic acid content in muscle of Landrace and Yorkshire were measured. The results showed that within 10 h post slaughtering, post slaughtering time had extremely significant influence on pH value and lactic acid content of Landrace, but had no significant influence on glycogen content and TBA value. On the other hand, post slaughtering time had extremely significant influence on pH value of Yorkshire, but had no significant influence on glycogen, lactic acid content and TBA value. The pH values of Yorkshire at 3, 5 and 10 h post slaughtering were 5.21% （ P 〈 0.01 ）, 5.64% （ P 〈 0.05 ） and 5.59% （ P 〈 0.05 ） higher than those of Landrace, respectively ; the lactic acid content in muscle of Landrace at 10 h post slaughtering was 56.04% （P 〈0.05） higher than that of Yorkshire; the TBA value in muscle of Yorkshire at 10 h post slaughtering was 89. 19% （P 〈 0.01 ） higher than that of Landrace; there was no significant difference in glycogen content between Yorkshire and Landrace. When pork stored at 4℃, storage time had no significant influence on pH value and glycogen content in muscle of Landrace, but had significant influence on drip loss, lactic acid content and TBA value ; storage time had no significant influence on pH value, glycogen content and TBA value in muscle of Yorkshire, but extremely significant influence on drip loss and significant influence on lactic acid content. The pH value in muscle of Yorkshire at 24 h post storage at 4℃ was 6.56% （P 〈0.05） higher than that of Landrace; the glycogen contents in muscle of Landrace at 24, 48, 72, 96, 120 and 144 h post storage at 4℃ were 84.90% （P〈0.05）,78.40% （P〈0.01）, 101.87% （P〈0.05）, 83.80% （P〈0.05）, 83.59% （P〈 0.05）and67.25% （P〈0.01）higher than those of York-shire, respectively; the drip loss of Landrace at 72 h post storage and TBA value at 144 h post storage were 55.70% （ P 〈 0.05 ） and 141.33 % （ P 〈 0.01 ） higher than those of Yorkshire, respectively; there was no significant difference in glycogen content between Yorkshire and Landrace. When pork stored at -20℃, storage time had significant influence on TBA value in muscle of Landrace, but had no significant influence on pH value, thawing water loss rate, glycogen and lactic acid content; storage time had no significant impact on pH value, thawing water loss rate, glycogen content and TBA value in muscle of Yorkshire, and had significant influence on lactic acid content. The pH value in muscle of Yorkshire at 24 h post storage at - 20℃ was 5.43 % （ P 〈 0.05 ） higher than that of I.andrace ; the glycogen contents in muscle of Landrace at 24, 48, 72, 96, 120 h post storage at - 20℃ were 85.08% （ P 〈0. 05 ）, 108.66% （ P 〈 0.01 ）, 72.69% （ P 〈 0.05 ）, 90.31% （ P 〈 0.01 ）, 70.38% （ P 〉 0.05 ） higher than those of Yorkshire, respectively ; the thawing water loss rates of Landrace at 24 and 72 h were 160.14% （ P 〈 0.05 ） and 74.32% （ P 〈 0.05 ） higher than those of Yorkshire, respectively ; there was no significant difference in lactic acid content and TBA value at the same time point between Yorkshire and Landrace.

pH Value Effects in Shear Rheology of Concentrated Alumina Suspensions

The influence of pH on the rheological properties of concentrated alumina suspensions was investigated. At various pH values, the alumina exhibited pseudoplastic, near Bingham flow behaviors. The fully-deflocculated suspensions exhibited Newtonian flow behaviors, while the fully-flocculated suspensions demonstrated very high viscosity and shear yield stress.

Electrochemical Behavior of Steel Bar in Electrolytes:Influence of pH Value and Cations

Steel bar corrosion on electrolytes and the influence of cation were investigated. Three electrolytes of Ca（OH）2, NaOH and KOH with pH levels of 12.5, 11.5, 10.5, 9.5, 8.5 were prepared, meanwhile, the methods of free corrosion potential and electrochemical impedance spectra （EIS） were used to evaluate the influence of cations on the depassivation of the steel bar in electrolytes. The experimental results indicate that the initial corrosion pH value of the steel bar is influenced by the cation in electrolyte and the influence of K＋ in electrolyte is the most remarkable, followed by Na＋ and Ca2＋. The initial corrosion pH values are 10.5 in KOH electrolyte, 9.5 in NaOH electrolyte and lower than 8.5 in Ca（OH）2 electrolyte.

Relationship Between pH Value and Physical and Chemical Properties of Tobacco-growing Soil

[Objectives]This study was conducted to understand the relationship between soil pH and soil physical and chemical properties during tobacco planting.[Methods]Through a field experiment,the pH value of tobacco-growing soil,the contents of mineral nutrients(ammonium nitrogen,alkali-hydrolyzable nitrogen,available potassium,available phosphorus),soil bulk density and porosity were investigated.[Results]The pH value of the soil after tobacco planting increased,and the contents of ammonium nitrogen,alkali-hydrolyzable nitrogen,and available potassium were closely related to the change of pH value.The bulk density of the tobacco-planting soil decreased and the porosity increased.Planting flue-cured tobacco had certain impacts on soil pH,soil bulk density and other physical and chemical properties.[Conclusions]This study provides a theoretical basis for the investigation of the fertilization laws in the process of tobacco planting and the selection of subsequent crops.

Effects of Straw and Biochar Returned to the Soil on Soil Physical Properties and pH Value in Cold Rice Region

[Objectives]In order to explore the feasibility of using straw and biochar returned to the soil to improve soil physical properties and pH value in cold rice regions of China.[Methods]the effects of straw directly returned to the soil and charred straw(biochar)returned to the soil on soil bulk density,porosity,temperature and pH value of cold paddy soil were studied in this paper.[Results]The results showed that compared with conventional production,straw(6 t/ha),a small amount of biochar(2 t/ha)and a large amount of biochar(40 t/ha)returned to the soil reduced paddy soil bulk density at different growth stages by 6.02%-11.86%,2.69%-6.67%and 8.58%-11.32%,respectively,increased total porosity by 7.41%-14.93%,3.19%-8.38%and 9.81%-14.27%,respectively,and increased aeration porosity by 22.28%-192.11%,17.80%-92.11%and 52.44%-157.11%,respectively.Straw and a small amount of biochar returned to the soil had no significant effect on soil temperature and pH value of paddy field,but a large amount of biochar returned to the soil could significantly increase soil temperature by 5.13%-8.79%and pH value by 3.15%-5.96%in the later stage of rice growth.[Conclusions]The straw and biochar returned to the soil could reduce soil bulk density,increase total porosity and aeration porosity,and only a large amount of biochar returned to the soil could significantly increase soil temperature and pH value.

Effect of pH value and calcination temperature on synthesis and characteristics of Cu-Ni nano-alloys

Cu?Ni nano-alloys were prepared using precursors synthesized by the citrate-gel method. The effects of initial solution pH value and calcination temperature on the composition, crystalline structure, purity, morphology, homogeneity and grain size of Cu?Ni nanoparticles were investigated. Both the parameters significantly affect the crystalline structure, composition and grain size. Cu?Ni alloys prepared at pH value of 1 do not contain impurities, and their compositions are Cu0.42Ni0.58, Cu0.45Ni0.55 and Cu0.52Ni0.48 reduced at 300, 400 and 500 °C, respectively. The grain size grows with the increase of calcination temperature for the precursor prepared at pH values of 1.6 and 3. The Ni content of the alloys gradually increases with the increase of calcination temperature at pH value of 3.

Analyzing pH value, energy and phospholipid metabolism of various cerebral tumors and normal brain tissue with ^(31)P magnetic resonance spectroscopy

BACKGROUND： ^31p magnetic resonance spectroscopy （^31p MRS） can be used to non-injuredly and dynamicly detect vadous metabolites including phosphorus in organis and reflect changes of phospholipid metabolism and energy metabolism in tissue and pH value in cells. OBJECTIVE： To observe changes of pH value, phospholipid metabolism and energy metabolism of various cerebral tumors and normal brain tissue with sip MRS. DESIGN： Semi-quantitative contrast observation PARTICIPANTS ： A total of 44 patients with cerebral tumor diagnosed with surgery operation were selected from the Department of Magnetic Resonance, Central South Hospital, Wuhan University from September 2004 to June 2006. All the subjects had complete sip MRS data before steroid and operation. Among them, 16 patients had glioma of grade Ⅱ-Ⅲ, 12 spongioblastoma and 16 meningioma. The mean age was （45±6） years. Another 36 subjects without focus on cerebral MRI were regarded as normal group, including 19 males and 18 females, and the mean age was （41±4） years. Included subjects were consent. METHODS： Eclipse1.5T MRS （Philips Company） was used to collect wave spectrum; jMRUI（1.3） was used to analyze expenmental data and calculate pH value in voxel and ratios of phosphocreatine （PCr）/inorganic phosphate （Pi）, PCr/phosphodiesterase （PDE） and phosphomonoesterase （PME）/β-adenosine triphosphate （β-ATP） of vadous metabolites. ^31p MRS results were compared with t test between tumor patients and normal subjects. MAIN OUTCOME MEASURES： Changes of phospholipid metabolism （PME./PDE）, energy metabolism （PCr/ATP） and pH value of various cerebral tumors and normal brain tissues. RESULTS ： A total of 44 cases with cerebral tumor and 36 normal subjects were involved in the final analysis. pH value and semi-quantitative measurements of normal brain tissues and various cerebral tumors： ① pH value at top occipital region and temple occipital region of normal brain tissue was 7.04 ±0.02; PCr/β-ATP was 1.51 ±0.03; PCr/Pi was 2.85±0.20; PDE/β-ATP was 2.70±0.40; PME/β-ATP was 1.01 ±0.03. Giioma of grade Ⅱ - Ⅲ ： Tumor tissue was alkalized. The pH value was 7.09±0.01, which was higher than that in normal group （t=-1.823, P 〈 0.05）; PCr/β-ATP, PME/β-ATP and PCr/ Pi were 1.50±0.04, 1.04±0.07 and 2.49±0.21, respectively, which was close to that in normal group （P 〉 0.05）; PDE/β-ATP was 1.73±0.20, which was lower than that in normal group （t=-2.168, P 〈 0.05）. ③ Spongioblastoma： Tumor tissue was alkalized. The pH value was 7.12±0.02, which was higher than that in normal group （t=-2.170, P 〈 0.05）; PCr/β-ATP and PCr/Pi were 1.48±0.05 and 2.39±0.23, respectively, which was lower than that in normal group, but the difference was not significant （P 〉 0.05）; PDE/β-ATP was 1.61±0.25, which was lower than that in normal group （t=-3.582, P 〈 0.01）; PME/β-ATP was 1.64±0.05, which was higher than that in normal group （t=-3.930, P 〈 0.01）. ④ Meningioma： Tumor tissue was alkalized. The pH value was 7.16±0.03, which was higher than that in normal group （t=-2.978, P 〈 0.01）; PCr/β-ATP, PCr/Pi and PDE/β-ATP were 0.46±0.04, 1.08±0.16 and 0.82±0.10, respectively, which was lower than that in normal group （t=-3.132, 3.983, 3.985, P 〉 0.01）; PME/β-ATP was 2.05±0.03, which was higher than that in normal group （t=-3.007, P〈 0.01）. CONCLUSION： ^31p MRS can provide informations about pH value of cerebral tumor, phospholipid metabolism and energy metabolism. Changes of pH value, PCr, PME and PDE can reflect metabolic characteristics of various cerebral tumors.

X-ray absorption near-edge structure study on the configuration of Cu2＋/histidine complexes at different pH values

The local configurations around metal ions in metalloproteins are of great significance for understanding their biolog- ical functions. Cu2＋/histidine （His） is a typical complex existing in many metalloproteins and plays an important role in lots of physiological functions. The three-dimensional （3D） structural configurations of Cu2＋/His complexes at different pH values （2.5, 6.5, and 8.5） are quantitatively determined by x-ray absorption near-edge structure （XANES）. Generally Cu2＋/His complex keeps an octahedral configuration consisting of oxygen atoms from water molecules and oxygen or nitrogen atoms from histidine molecules coordinated around Cu2＋. It is proved in this work that the oxygen atoms from water molecules, when increasing the pH value from acid to basic value, are gradually substituted by the Ocarboxy1, Nam, and Nim from hisitidine molecules. Furthermore, the symmetries of Cu2＋/His complexes at pH 6.5 and pH 8.5 are found to be lower than at pH 2.5.

Capacitance Characterization of the Effect of pH Value on the Self-assembled Monolayers of Octadecanethiol

In this paper, the membrane capacitance (Cm), which was obtained from the electro- chemical impedance spectroscopy (EIS) method, was used to characterize the effect of pH value on the self-assembled monolayers (SAMs) of octadecanethiol(18SH) for the first time. The results not only strongly proved that inorganic ions could penetrate the SAMs of 18SH, but also ascertained that SAMs of 18SH were not an absolute of free of ion-penetration. Verifying the existence of pin-holes in the octadecanethiol SAMs was the main contribution of this paper, which coincided with the former conjecture very well.

Effect of pH Value on Nano-Al_2O_3/Ni+Co Gradient Bionic Composite Coating by Electrodeposition

The metal and nano-ceramic composite coatings were formed on gray cast iron surface by electrodepositon method.The Ni-Co was used as metal matrix,and the nano-Al2O3 was chosen as second-phase particulates.The gradient structure of biology material was the model to avoid bad interface bonding and stress distribution,therefore the gradient composite coating was prepared.The morphology of composite coatings was flatter and the microstructure was more com-pact than the pure Ni-Co coatings.Effect of pH value on surface morphology was analyzed,which some microcracks appeared when pH value was greater than 5.The content of codeposition na-no-Al2O3 reached a maximum value at pH value of 3-4,at the same time the properties including mi-crohardness and wear-resistance were analyzed.The result indicated that the mirohardness reached a maximum value and the wear loss volume was less at pH value 3-4.