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Journal articles on the topic 'Acidity'

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Author: Grafiati
Published: 4 June 2021
Last updated: 25 May 2024

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1

Zhang, Wen Lin, Wei Du, Xiao Wen Wang, Nan Meng, Yong Jun Shao, and Chun Li Li. "Progress in Adjustment of Ionic Liquids Acidity Based on the Alkylation." Advanced Materials Research 634-638 (January 2013): 581–86. http://dx.doi.org/10.4028/www.scientific.net/amr.634-638.581.

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Acidity is a very important character of ionic liquids, which determines the application of ionic liquids in catalysis. In some cases, the adjustment of ionic liquids acidity becomes important and necessary. Focusing on acidic ionic liquids, researches on determination of acidity, application of acidic ionic liquids in alkylation, acidic adjustment methods and novel acidic ionic liquids were reviewed. Finally the development of acidic ionic liquids is discussed.
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2

Lim, Sung-Chul, Hyoin Hwang, and Song Iy Han. "Ellagic Acid Inhibits Extracellular Acidity-Induced Invasiveness and Expression of COX1, COX2, Snail, Twist 1, and c-myc in Gastric Carcinoma Cells." Nutrients 11, no. 12 (December 10, 2019): 3023. http://dx.doi.org/10.3390/nu11123023.

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Extracellular acidity has been implicated in enhanced malignancy and metastatic features in various cancer cells. Gastric cancer cell lines (AGS and SNU601) maintained in an acidic medium have increased motility and invasiveness. In this study, we investigated the effect of ellagic acid, a plant-derived phenolic compound, on the acidity-promoted migration and invasion of gastric cancer cells. Treating cells maintained in acidic medium with ellagic acid inhibited acidity-mediated migration and invasion, and reduced the expression of MMP7 and MMP9. Examining regulatory factors contributing to the acidity-mediated invasiveness, we found that an acidic pH increased the expression of COX1 and COX2; importantly, expression decreased under the ellagic acid treatment. The general COX inhibitor, sulindac, also decreased acidity-mediated invasion and expression of MMP7 and MMP9. In addition, acidity increased the mRNA protein expression of transcription factors snail, twist1, and c-myc; these were also reduced by ellagic acid. Together, these results suggest that ellagic acid suppresses acidity-enhanced migration and invasion of gastric cancer cells via inhibition of the expression of multiple factors (COX1, COX2, snail, twist1, and c-myc); for this reason, it may be an effective agent for cancer treatment under acidosis.
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3

Chang, Jui-Cheng, Che-Hsuan Yang, I.-Wen Sun, Wen-Yueh Ho, and Tzi-Yi Wu. "Synthesis and Properties of Magnetic Aryl-Imidazolium Ionic Liquids with Dual Brønsted/Lewis Acidity." Materials 11, no. 12 (December 13, 2018): 2539. http://dx.doi.org/10.3390/ma11122539.

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A series of unique tunable aryl-imidazolium magnetic ionic liquids (MILs) with dual acidity that contain both Brønsted and Lewis acidic sites (abbreviated as B-L MILs) were synthesized and characterized using nuclear magnetic resonance and mass spectrometry. Physical properties, such as thermal properties, magnetic susceptibility, and Brønsted and Lewis acidity, were measured. These properties were found to depend on the cation structure. These B-L MILs had good solubility in many organic solvents, good thermal stability, and low melting points, and exhibited magnet-like behavior. For these B-L MILs, the Brønsted acidity was measured using ultraviolet-visible (UV-Vis), and the Lewis acidity was measured using Fourier transform infrared spectroscopy (FTIR). The results showed that B-L MILs with an electron-withdrawing group in the aryl-imidazolium moiety had higher Brønsted acidity, whereas those with an electron-donating group had higher Lewis acidity. This type of ionic liquid, with both Brønsted and Lewis acidic sites, is expected to be a useful solvent and catalyst for organic reactions.
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4

Devi, M. M., D. Bhattacharyya, K. N. Das, D. K. Patgiri, K. Kurmi, H. Saikia, and K. D. Devi. "Dynamics of Acidity Component of the Soils as Influenced by Liming in Upper Brahmaputra Valley Zone of Assam, India." Ecology, Environment and Conservation 29 (2023): 131–36. http://dx.doi.org/10.53550/eec.2023.v29i02s.025.

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An incubation study was conducted to investigate the effect of lime (CaCO3 )on the acidity components in Upper Brahmaputra Valley Zone (UBVZ) of Assam. Fourteen(14) geo-referenced soil samples were collected from Sibsagar and Jorhat districts of Assam. Soils were treated with 3 different doses of lime viz. 10 per cent Lime Requirement (LR10), 25 per cent Lime Requirement (LR25) and 50 per cent of Lime Requirement (LR50) and initial properties were recorded before liming. Samples were incubated in laboratory at different period of time viz. 15, 30, 60 and 90 days after liming (DAL) with moisture content at Field Capacity (0.33 bar). At four different intervals, soils were analysed for soil acidity components viz. total acidity, exchange acidity, exchangeable Al3+ and exchangeable H+. The soil of Upper Brahmaputra Valley Zone (UBVZ) of Assam were highly acidic to moderately acidic, sandy loam to silt loam in texture with high OC content ranged from 0.72 to 2.59%. The Cation Exchange Capacity (CEC) value ranged from 7.8 to 14.2 cmol (p+)/ kg. Application of lime brought about mark decreased in acidity components viz. total acidity, exchange acidity, exchangeable aluminium and exchangeable hydrogen. Soil acidity components recorded highest decreased at 90 DAL @ LR50 and decreased started from 15 days onwards. The findings of the investigation showed that liming @ LR10 was found effective in reducing soil acidity. The residual effect of lime was found persisting till 90 days. However, the magnitude of lime was increasing with increase in application of lime@ from LR10 to LR25 and to LR50.
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5

Abure, Tesfaye. "Status of Soil Acidity under Different Land Use Types and Soil Depths: The Case of Hojje Watershed of Gomibora District, Hadiya Zone, Southern Ethiopia." Applied and Environmental Soil Science 2022 (November 12, 2022): 1–13. http://dx.doi.org/10.1155/2022/7060766.

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In the humid regions of Ethiopia, soil productivity and fertility are significantly affected by soil acidity, which is connected to infertility and mineral toxicity. The study aimed to assess the status of soil acidity under different land use types and soil depths in Hojje watershed of Gomibora district, Hadiya Zone, Southern Ethiopia, in November 1, 2020. Soil samples (24 nos.) were collected using X-design format from four different land use typeshome garden, cultivated land, grazing land, and Eucalyptus plantation at two soil depths (0–20 cm and 20–40 cm). The soil samples were prepared, their physiochemical characteristics were examined, and statistical analysis was performed. The results indicated that the soil under cultivated land and Eucalyptus plantation were strongly acidic (pH 5.15 and 5.32) with mean values of exchangeable acidity (4.6, 4.59 cmol(+) kg−1) and acid saturation percentage (47.85, 46.96%), respectively. The grazing land was moderately acidic (pH 5.63) and home garden soil was slightly acidic (pH 6.67). The home garden soils had statistically significant ( p < 0.01 ) lower exchangeable acidity (0.64 cmol(+) kg−1) and acid saturation percentage (2.61%). Although, soil pH (H2O and KCl), exchangeable acidity, acid saturation percentage, exchangeable base, CEC, and base saturation are significantly ( p < 0.01 ) affected by both the main effect and interaction effects of the two factors. As a result, it is advised to apply lime to the cultivated land to reduce the acidity of the soil for profitable crop production as the amount of acidity is above the tolerance limit for the area’s locally produced crops.
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6

Shalaby, Khaled. "Effect of Olive Oil Acidity on Skin Delivery of Diclofenac: In Vitro Evaluation and Ex Vivo Skin Permeability Studies." Journal of Biomedical Nanotechnology 18, no. 1 (January 1, 2022): 234–42. http://dx.doi.org/10.1166/jbn.2022.3219.

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Olive oil is a vegetable oil which has been successfully used as a skin penetrating agent. Acidity of olive oil is considered as one of the characteristic properties of olive oil. Olive oil acidity was selected as a parameter under investigation for evaluation of skin permeability. The acidities of the three investigated olive oils are varying from 0.75±0.16 to 2±0.17. Olive oil with acidity equals 2.0 showed the highest skin permeation for 12 h and cutaneous deposition with significant difference compared to the permeation values of 0.75 and F1.4 acidities. Results of cutaneous secretion of cytokines suggested that higher penetration was accompanied higher cytokines’ secretions. Olive oil with acidity equals 2.0 also showed more prominent skin changes which suggested to be due to acidity and fatty acids’ content. These results suggest that olive oil might improve the epidermal permeability, which is more pronounced in highly acidic olive oil, through weakening of skin barriers followed by acting of cytokines on re-building effective barriers. Finally, based on the current study, highly acidic olive oil is more efficient skin permeation enhancer vehicle than less acidic ones and can be efficiently used in formulation of cutaneous drug delivery systems.
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7

KUMAR, MANOJ. "Rising levels of soil acidity in Meghalaya: Evidences and Imperatives." Annals of Plant and Soil Research 23, no. 3 (August 1, 2021): 297–303. http://dx.doi.org/10.47815/apsr.2021.10073.

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In order to examine the current status of soil acidity in Meghalaya, representative soil samples (n= 497) were collected (during 2015-2016) from across the state and analyzed for soil acidity and associated parameters. Averaged across the samples, pH of the soils was found to be very strongly acidic (4.94). Nearly 20 % of the soils had pH below 4.50, 59% below pH 5.0 and 80% below pH 5.50. Only 3.4% of the samples recorded pH more than 6.0. East Khasi Hills District had the maximum percentage (95.1%) of strongly acidic soils (pH ≤ 5.50) while Garo Hills had the least (50.2%). All other districts recorded more than 85% of the strongly acidic soils. Average exchangeable acidity, exchangeable Al and effective CEC were found to be 1.60, 1.27 and 3.86 meq/100g soil, respectively. Mean base saturation was recorded below 60%. Aluminium saturation (percentage of effective CEC being occupied by exch. Al) ranged from 1.5 to 79.7% with its mean value being as high as 33%. Principal component analysis provided three PCs with Eigen values >1 and together they explained 83.2 % of the variance in total dataset. The soil acidity in Meghalaya is on rise, with 80.2% of its soils being strongly acidic (pH ≤ 5.50) in contrast to the previous reports of 53% soils being strongly acidic. This calls for widespread adoption of soil acidity ameliorative measures in agriculture of Meghalaya, Northeast India.
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8

He, Zhaoshuai, Yajie Chou, Hanxin Zhou, Han Zhang, Tanyu Cheng, and Guohua Liu. "A nitroreductase and acidity detecting dual functional ratiometric fluorescent probe for selectively imaging tumor cells." Organic & Biomolecular Chemistry 16, no. 17 (2018): 3266–72. http://dx.doi.org/10.1039/c8ob00670a.

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A dual functional ratiometric fluorescent probe can obviously distinguish acidity, nitroreductase, and nitroreductase in an acidic environment. Confocal fluorescence imaging of A549 cells indicates the probe can detect acidity and expressed nitroreductase in living cells.
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9

Tilgner, Andreas, Thomas Schaefer, Becky Alexander, Mary Barth, Jeffrey L. Collett Jr., Kathleen M. Fahey, Athanasios Nenes, Havala O. T. Pye, Hartmut Herrmann, and V. Faye McNeill. "Acidity and the multiphase chemistry of atmospheric aqueous particles and clouds." Atmospheric Chemistry and Physics 21, no. 17 (September 10, 2021): 13483–536. http://dx.doi.org/10.5194/acp-21-13483-2021.

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Abstract. The acidity of aqueous atmospheric solutions is a key parameter driving both the partitioning of semi-volatile acidic and basic trace gases and their aqueous-phase chemistry. In addition, the acidity of atmospheric aqueous phases, e.g., deliquesced aerosol particles, cloud, and fog droplets, is also dictated by aqueous-phase chemistry. These feedbacks between acidity and chemistry have crucial implications for the tropospheric lifetime of air pollutants, atmospheric composition, deposition to terrestrial and oceanic ecosystems, visibility, climate, and human health. Atmospheric research has made substantial progress in understanding feedbacks between acidity and multiphase chemistry during recent decades. This paper reviews the current state of knowledge on these feedbacks with a focus on aerosol and cloud systems, which involve both inorganic and organic aqueous-phase chemistry. Here, we describe the impacts of acidity on the phase partitioning of acidic and basic gases and buffering phenomena. Next, we review feedbacks of different acidity regimes on key chemical reaction mechanisms and kinetics, as well as uncertainties and chemical subsystems with incomplete information. Finally, we discuss atmospheric implications and highlight the need for future investigations, particularly with respect to reducing emissions of key acid precursors in a changing world, and the need for advancements in field and laboratory measurements and model tools.
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10

Das, Dhrubajyoti, E. Veerashekhar Goud, Suresh Annam, S. Jayalakshmi, Gopinadhanpillai Gopakumar, C. V. S. Brahmmananda Rao, N. Sivaraman, Akella Sivaramakrishna, and Kari Vijayakrishna. "Experimental and theoretical studies on extraction behavior of di-n-alkyl phosphine oxides towards actinides." RSC Advances 5, no. 130 (2015): 107421–29. http://dx.doi.org/10.1039/c5ra19090h.

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The extraction behavior of U(vi) & Am(iii) with di-n-alkyl phosphine oxides (DAPOs) was investigated. DAPO behaves like an acidic extractant at low acidity and at higher acidity they extracted via cation exchange mechanism.
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11

Han, Yuemei, Craig A. Stroud, John Liggio, and Shao-Meng Li. "The effect of particle acidity on secondary organic aerosol formation from <i>α</i>-pinene photooxidation under atmospherically relevant conditions." Atmospheric Chemistry and Physics 16, no. 21 (November 11, 2016): 13929–44. http://dx.doi.org/10.5194/acp-16-13929-2016.

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Abstract. Secondary organic aerosol (SOA) formation from photooxidation of α-pinene has been investigated in a photochemical reaction chamber under varied inorganic seed particle acidity levels at moderate relative humidity. The effect of particle acidity on SOA yield and chemical composition was examined under high- and low-NOx conditions. The SOA yield (4.2–7.6 %) increased nearly linearly with the increase in particle acidity under high-NOx conditions. In contrast, the SOA yield (28.6–36.3 %) was substantially higher under low-NOx conditions, but its dependency on particle acidity was insignificant. A relatively strong increase in SOA yield (up to 220 %) was observed in the first hour of α-pinene photooxidation under high-NOx conditions, suggesting that SOA formation was more effective for early α-pinene oxidation products in the presence of fresh acidic particles. The SOA yield decreased gradually with the increase in organic mass in the initial stage (approximately 0–1 h) under high-NOx conditions, which is likely due to the inaccessibility to the acidity over time with the coating of α-pinene SOA, assuming a slow particle-phase diffusion of organic molecules into the inorganic seeds. The formation of later-generation SOA was enhanced by particle acidity even under low-NOx conditions when introducing acidic seed particles after α-pinene photooxidation, suggesting a different acidity effect exists for α-pinene SOA derived from later oxidation stages. This effect could be important in the atmosphere under conditions where α-pinene oxidation products in the gas-phase originating in forested areas (with low NOx and SOx) are transported to regions abundant in acidic aerosols such as power plant plumes or urban regions. The fraction of oxygen-containing organic fragments (CxHyO1+ 33–35 % and CxHyO2+ 16–17 %) in the total organics and the O ∕ C ratio (0.52–0.56) of α-pinene SOA were lower under high-NOx conditions than those under low-NOx conditions (39–40, 17–19, and 0.61–0.64 %), suggesting that α-pinene SOA was less oxygenated in the studied high-NOx conditions. The fraction of nitrogen-containing organic fragments (CxHyNz+ and CxHyOzNp+) in the total organics was enhanced with the increases in particle acidity under high-NOx conditions, indicating that organic nitrates may be formed heterogeneously through a mechanism catalyzed by particle acidity or that acidic conditions facilitate the partitioning of gas-phase organic nitrates into particle phase. The results of this study suggest that inorganic acidity has a significant role to play in determining various organic aerosol chemical properties such as mass yields, oxidation state, and organic nitrate content. The acidity effect being further dependent on the timescale of SOA formation is also an important parameter in the modeling of SOA.
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12

Buondonno, A., and A. Violante. "Titratable acidity of organo-mineral complexes as affected by mode of preparation, drying and stability of aggregates." Canadian Journal of Soil Science 71, no. 3 (August 1, 1991): 285–92. http://dx.doi.org/10.4141/cjss91-028.

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Hydroxy-aluminum-tannate-montomorillonite complexes, which were prepared at pH 4.5 by different addition sequences of hydroxy-Al, tannic acid and montomorillonite showed distinct differences in titratable acidity both before and after drying. Titratable acidity of the complexes depended on the feed rate of the base and on the presence and nature of neutral salts (KCl or CaCl2). The organo-mineral complexes showed acidity values in CaCl2 substantially higher than those determined in KCl or in water (in the order listed), probably because many weak acidic groups released H+ ions by complexation (tannate molecules) or adsorption (OH-Al-ions) of Ca2+ ions. The hydroxy-Al-tannate-montmorillonite complexes, which were washed differently (dialyzed or ultrafiltered) and dried (freeze-dried or air-dried) also showed remarkably different titratable acidity. All the complexes usually showed much lower acidity values when air-dried than when freeze-dried. After sonification the titratable acidity values of all the complexes increased, but some air-dried samples, even after four sonification treatments, showed titratable acidity lower than that of the same freeze-dried complexes before sonification. Key words: Organo-mineral complexes, aluminum, titratable acidity, potentiometric titrations
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13

He, K., Q. Zhao, Y. Ma, F. Duan, F. Yang, Z. Shi, and G. Chen. "Spatial and seasonal variability of PM<sub>2.5</sub> acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols." Atmospheric Chemistry and Physics 12, no. 3 (February 6, 2012): 1377–95. http://dx.doi.org/10.5194/acp-12-1377-2012.

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Abstract. Aerosol acidity is one of the most important parameters influencing atmospheric chemistry and physics. Based on continuous field observations from January 2005 to May 2006 and thermodynamic modeling, we investigated the spatial and seasonal variations in PM2.5 acidity in two megacities in China, Beijing and Chongqing. Spatially, PM2.5 was generally more acidic in Chongqing than in Beijing, but a reverse spatial pattern was found within the two cities, with more acidic PM2.5 at the urban site in Beijing whereas the rural site in Chongqing. Ionic compositions of PM2.5 revealed that it was the higher concentrations of NO3− at the urban site in Beijing and the lower concentrations of Ca2+ within the rural site in Chongqing that made their PM2.5 more acidic. Temporally, PM2.5 was more acidic in summer and fall than in winter, while in the spring of 2006, the acidity of PM2.5 was higher in Beijing but lower in Chongqing than that in 2005. These were attributed to the more efficient formation of nitrate relative to sulfate as a result of the influence of Asian desert dust in 2006 in Beijing and the greater wet deposition of ammonium compared to sulfate and nitrate in 2005 in Chongqing. Furthermore, simultaneous increase of PM2.5 acidity was observed from spring to early summer of 2005 in both cities. This synoptic-scale evolution of PM2.5 acidity was accompanied by the changes in air masses origins, which were influenced by the movements of a subtropical high over the northwestern Pacific in early summer. Finally, the correlations between [NO3−]/[SO42−] and [NH4+]/[SO42−] suggests that under conditions of high aerosol acidity, heterogeneous reactions became one of the major pathways for the formation of nitrate at both cities. These findings provided new insights in our understanding of the spatial and temporal variations in aerosol acidity in Beijing and Chongqing, as well as those reported in other cities in China.
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14

Deng, Yange, Satoshi Inomata, Kei Sato, Sathiyamurthi Ramasamy, Yu Morino, Shinichi Enami, and Hiroshi Tanimoto. "Temperature and acidity dependence of secondary organic aerosol formation from <i>α</i>-pinene ozonolysis with a compact chamber system." Atmospheric Chemistry and Physics 21, no. 8 (April 21, 2021): 5983–6003. http://dx.doi.org/10.5194/acp-21-5983-2021.

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Abstract. Secondary organic aerosols (SOAs) affect human health and climate change prediction; however, the factors (e.g., temperature, acidity of pre-existing particles, and oxidants) influencing their formation are not sufficiently resolved. Using a compact chamber, the temperature and acidity dependence of SOA yields and chemical components in SOA from α-pinene ozonolysis were systematically investigated under 278, 288, and 298 K temperatures using neutral ((NH4)2SO4) and acidic (H2SO4+((NH4)2SO4)) seed aerosols. SOA components with m/z less than 400 were analyzed using negative electrospray ionization liquid-chromatography time-of-flight mass spectrometry. Based on the slightly negative temperature dependence of the SOA yields, the enthalpies of vaporization under neutral and acidic seed conditions were estimated to be 25 and 44 kJ mol−1, respectively. In addition, SOA yields increased with an increase in the acidity of seed particles (solid/near-solid state) at low SOA mass loadings, when compared with the seed particle amounts. Acidity dependence analysis of the chemical formula, molecular mass, and O:C ratio of the detected compounds indicated the enhanced formation of multiple oligomers in the wide molecular mass range with a wide range of O:C ratios under acidic seed conditions. The peak abundances of some chemical compounds increased with an increase in the acidity of seed particles (e.g., m/z 197, 311, 313, 339, 355, and 383), while decreases in the peak abundances of some chemical compounds were observed (e.g., m/z 171, 185, 215, 343, and 357). The acidity dependence could be explained by acid-catalyzed heterogeneous reactions or acid-catalyzed decomposition of hydroperoxides. In addition, organosulfate (OS) formation was observed under acidic seed conditions. Six out of the 11 detected OSs were potentially formed via the aldehyde + HSO4- pathway.
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15

Schier, George A., and Roy L. Patton. "Damping-off disease of pine seedlings on soils treated with simulated acidic rain." Canadian Journal of Forest Research 25, no. 5 (May 1, 1995): 838–44. http://dx.doi.org/10.1139/x95-091.

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Damping-off during seed germination and early seedling growth of Pinusrigida Mill., Pinusechinata Mill., Pinustaeda L., and Pinusstrobus L. were observed for 28 days on three New Jersey (U.S.A.) Pine Barrens soils (Atsion, Downer, Lakewood) treated with simulated acidic rain solutions of pH 4.2, 3.5, or 3.0 (SO42−:Cl−:NO3−, 2.2:1.4:1.0). The soils were sandy, highly acidic, and deficient in mineral nutrients. Treatment with rain solution was started 53 days before planting the pine seeds and continued during germination. Seedling emergence and seedling mortality were affected significantly by solution pH, soils, and species. Seedling emergence of all pine species on Atsion and Lakewood soils decreased with increasing solution acidity. On Downer soil seedling emergence was unaffected by solution acidity probably because the buffering action of the soil decreased the acidity of the rain solution. Seedling mortality of all species increased with increasing treatment acidity on all soils and was significantly higher on Atsion (100% at pH 3.0) than on the other soils. Although solution acidity significantly increased the concentration of Al in the soil solution, there was no evidence of Al toxicity. Two isolated fungal species, a Trichoderma and a Penicillium, significantly reduced seedling emergence and increased seedling mortality of P. rigida in sterile, acid-washed quartz sand; however, neither seedling emergence nor seedling mortality was affected significantly by solution acidity.
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16

He, K., Q. Zhao, Y. Ma, F. Duan, and F. Yang. "Spatial and seasonal variability of PM<sub>2.5</sub> acidity at two Chinese megacities: insights into the formation of secondary inorganic aerosols." Atmospheric Chemistry and Physics Discussions 11, no. 9 (September 13, 2011): 25557–603. http://dx.doi.org/10.5194/acpd-11-25557-2011.

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Abstract. Aerosol acidity is one of the most important parameters influencing atmospheric chemistry and physics. Based on continuous field observation from January 2005 to May 2006, both spatial and seasonal variation in PM2.5 acidity was investigated at Beijing and Chongqing, two megacities in northern and southwestern China, respectively. PM2.5 was generally more acidic at urban and rural sites in Chongqing than Beijing, but a reverse spatial pattern was found within the two cities, with more acidic PM2.5 at urban Beijing and rural Chongqing comparing to their rural and urban sites, respectively. PM2.5 was more acidic in summer and fall than in winter, while large inter-annual variations were evident during the springs of 2005 and 2006, with Beijing and Chongqing exhibiting opposite trends, however. The higher acidity of PM2.5 in the spring of 2006 in Beijing was attributed to the influence of Asian desert dust which significantly enhanced the formation of nitrate relative to sulfate; in contrast, the more acidic aerosols found during the spring of 2005 in Chongqing was mainly due to the greater wet deposition of ammonium, and precipitation was probably one of the key factors that controlled the partition of ammonium in PM2.5 and rain water over the surrounding region. Meanwhile, PM2.5 became more acidic at both cities from spring into early summer of 2005. The synoptic-scale evolution of its acidity was found to be closely associated with the greater contribution of air masses from between the Northern China Plain to the south of Beijing, and from central China to the east of Chongqing, and was ended by the northward movement of a subtropical high over the northwestern Pacific, a major element of the Asian summer monsoon. Under conditions of high aerosol acidity, heterogeneous reactions may become one of the major pathways for the formation of nitrate at both cities. These findings may also explain the significant variation in inter-annual aerosol acidity observed during other seasons at Beijing, Chongqing and many other cities in China, as reported in previous studies.
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17

Sanaullah, A. F. M., M. Akhtaruzzaman, and M. A. Uddin. "Effect of Topography and Soil Depth on Clay Content, Organic Matter Content, Active Acidity, Reserve Acidity and Cation Exchange Capacity of Some Tea Soils of Bangladesh." Journal of Scientific Research 8, no. 2 (May 1, 2016): 229–35. http://dx.doi.org/10.3329/jsr.v8i2.26867.

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Soil samples were collected from M. R. Khan tea-estate area of Moulvibazar district, Bangladesh. Organic matter, active acidity, reserve acidity, cation exchange capacity, clay content and textural class of the collected soil samples for different topographic positions and depths were determined. The percentage of sand, silt and clay varied from 59.75 to 70.50, 12.50 to 20.00 and 14.50 to 22.75, respectively. Active acidity and reserve acidity of the soils varied from 4.13 to 5.82 and 3.46 to 4.84, respectively. Organic matter content varied from 0.37% to 1.93%. Cation exchange capacity (CEC) varied from 11.42 to 24.86 cmolKg-1. Soils were acidic in nature with considerably high reserve acidity. The measured parameters of the soil samples were plotted and analyzed with reference to topography and depth. The parameters have been found to vary with sampling sites, depths and topography.
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18

Louis, C., A. Bebba, and J. Bessiere. "Acidity level in concentrated mineral acid mixtures. Iso-acidic media." Canadian Journal of Chemistry 65, no. 6 (June 1, 1987): 1353–55. http://dx.doi.org/10.1139/v87-227.

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Assuming the relationship between the R0(H) acidity function and the water activity in mineral acid concentrated solutions, iso-acidic solutions are prepared by mixing in all proportion two or three of the acids: H3PO4, HCl, HClO4, H2SO4, H2SiF6. These solutions are characterized by an equal R0(H) acidity level and different redox and complexing properties. Their R0(H) acidity level is determined from potential measurements involving o-chloranil as an H+ indicating system and ferricinium/ferrocene as a comparison system.
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19

Barroso, Ana, Teresa Valente, Amélia Paula Marinho Reis, and Isabel Margarida H. R. Antunes. "A New Acidity-Based Approach for Estimating Total Dissolved Solids in Acidic Mining Influenced Water." Water 15, no. 16 (August 19, 2023): 2995. http://dx.doi.org/10.3390/w15162995.

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In natural waters, total dissolved solids (TDS) are usually estimated from electrical conductivity (EC) by applying a conversion factor (f). However, defining this conversion factor for mining influenced water is more complex since this type of water is highly mineralized and has complex chemical matrices. So, the present work aimed to establish a new conversion factor to estimate TDS from the classic parameters usually analyzed for the hydrochemical characterization of these contaminated waters. A total of 121 mining influenced water samples were collected in three mining areas representing pollution scenarios, such as acidic streams, acidic lagoons, and pit lakes. The parameters analyzed were pH, EC, sulfate, acidity, and TDS. The statistical analysis showed that TDS and acidity are related, with a high and significant correlation (r ≥ 0.964, ρ < 0.001), suggesting that this parameter could be an appropriate indicator to estimate the TDS. Moreover, although acidity analysis also involves laboratory work, the time and effort required are considerably less than the gravimetric determination of TDS. Hierarchical cluster analysis applied to these samples allowed the definition of seven classes, and their specific fmedian was calculated employing TDS/Acidity. Then, seven conversion factors were obtained for mining influenced water based on sulfate concentration and acidity degree.
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Devi, Manoharmayum Monica, Devajit Bhattacharyya, Kulendra Nath Das, and Keisham Dony Devi. "Distribution Study of the Different Forms of Soil Acidity and Available Nutrients in Upper Brahmaputra Valley Zone (UBVZ) of Assam." International Journal of Plant & Soil Science 35, no. 18 (July 21, 2023): 634–43. http://dx.doi.org/10.9734/ijpss/2023/v35i183328.

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Soil acidity is a major constraint that affect crop growth and production in larger aspect. The objective of the study is to characterize different forms of soil acidity components in relation to the soil properties. So, 14 georeferenced soil samples were collected from Jorhat and Sibsagar district of Assam. The soils of UBVZ of Assam were highly to moderately acidic (pH range 4.27 to 5.34) with sandy loam to silty clay loam in texture and high content of organic carbon ranged from 0.72 to 2.59%. The exchangeable Ca and Mg value ranged from 1.40-2.64 cmol(p+)/kg and 0.7-2.0 cmol(p+)/kg, respectively with CEC from 7.8 to 14.2 cmol(p+)/kg and BS from 25.03 to 43.76%. Correlation between soil physico-chemical properties and soil acidity components revealed that OC had positive correlation with total acidity (r = 0.638*) and exchange acidity (r = 0.551*) while BS% had negative significant correlation with total acidity (r = -0.540*). Exchangeable calcium was significantly correlated with total acidity (r = -0.751**), exchange acidity (r = -0.610*) and exchangeable H+ (r = -0.557*) while Ex Mg had significant negative correlation with exchangeable H+ (r=-0.596*). Deficiency of various nutrients in soil can hinder the yield productive prospects in future. So, we must think of the holistic approach to meet the present need of the nutrients.
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Shi, Zhi Cheng, Aline Auroux, and Younes Ben Taarit. "Calorimetric study of the acidity of Y-zeolites treated with silicon tetrachloride." Canadian Journal of Chemistry 66, no. 4 (April 1, 1988): 1013–17. http://dx.doi.org/10.1139/v88-168.

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The acidity of synthetic HY samples dealuminated with silicon tetrachloride vapour at various temperatures is investigated using microcalorimetry. The work covers sample preparation, characterization, and acidic properties. The differential heats of ammonia adsorption versus coverage and the acidity spectra are described. The catalytic performance is measured in the hydrogen transfer reaction.
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He, Lizhe, Xiaoling Liu, and Chris Rudd. "Additive-Manufactured Gyroid Scaffolds of Magnesium Oxide, Phosphate Glass Fiber and Polylactic Acid Composite for Bone Tissue Engineering." Polymers 13, no. 2 (January 15, 2021): 270. http://dx.doi.org/10.3390/polym13020270.

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Composites of biodegradable phosphate glass fiber and polylactic acid (PGF/PLA) show potential for bone tissue engineering scaffolds, due to their ability to release Ca, P, and Mg during degradation, thus promoting the bone repair. Nevertheless, glass degradation tends to acidify the surrounding aqueous environment, which may adversely affect the viability and bone-forming activities of osteoblasts. In this work, MgO was investigated as a neutralizing agent. Porous network-phase gyroid scaffolds were additive-manufactured using four different materials: PLA, MgO/PLA, PGF/PLA, and (MgO + PGF)/PLA. The addition of PGF enhanced compressive properties of scaffolds, and the resultant scaffolds were comparably strong and stiff with human trabecular bone. While the degradation of PGF/PLA composite induced considerable acidity in degradation media and intensified the degradation of PGF in return, the degradation media of (MgO + PGF)/PLA maintained a neutral pH close to a physiological environment. The experiment results indicated the possible mechanism of MgO as the neutralizing agent: the local acidity was buffered as the MgO reacted with the acidic degradation products thereby inhibiting the degradation of PGF from being intensified in an acidic environment. The (MgO + PGF)/PLA composite scaffold appears to be a candidate for bone tissue engineering.
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Vít, Zdeněk. "Effect of activation temperature on acidity of alumina, silica-alumina and cobalt-molybdenum-alumina catalysts." Collection of Czechoslovak Chemical Communications 50, no. 6 (1985): 1268–73. http://dx.doi.org/10.1135/cccc19851268.

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The effect of surface dehydration on the acidity of silica-alumina and cobalt-molybdenum-alumina catalysts has been studied and compared with alumina. The catalysts were characterized by surface hydroxyl groups concentrations, acid sites concentrations and by catalytic activities in paraldehyde depolymerisation and cumene cracking. It was found that the acidity of alumina and cobalt-molybdenum-alumina catalysts increases significantly with surface dehydration and attains maximum after activation at 500-550 °C. Silica-alumina is strongly acidic even in the hydrated state, the acidity being formed already at relatively low temperature around 100 °C.
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24

Yi, Fengping, Jie Gao, Lirong Zhang, and Xiaoyan Jiang. "New Brønsted-Lewis Acidic Quaternary Ammonium Ionic Liquids: Synthesis, Acidity Determination and Acidity-Catalytic Activity Relationship." Asian Journal of Chemistry 27, no. 4 (2015): 1260–64. http://dx.doi.org/10.14233/ajchem.2015.17494.

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25

AGUROVA, I. V., and D. V. SYSHCHYKOV. "ACIDITY OF DEGRADED SOILS OF AGRICULTURAL LANDS OF THE DONETSK PEOPLES REPUBLIC." Ser-17_2023-3 78, no. 3, 2023 (August 30, 2023): 125–30. http://dx.doi.org/10.55959/msu0137-0944-17-2023-78-3-125-131.

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The purpose of this work was to study the acidity of degraded agricultural soils. The main objectives of the research were to study the actual and potential soil acidity of agricultural lands of the Donetsk Peoples Republic on the example of agricultural farms in the northern part of the Shakhtyorsky district. It was established that the studied model sites are characterized by a slightly acidic, neutral or slightly alkaline medium reaction, which creates favorable conditions for the formation of crops and plant growth. When studying the exchangeable acidity of soils, the ambiguity of changes in its values was established, depending on the location of the model sites, the system of soil content in the crop rotation, the horizon, and other factors. Th e most exceeding the control values of the exchange acidity are characteristic of the slope surfaces of sites where the intensity of erosion processes reaches a maximum (exceeding the indicator compared to the control by average of 8,6%). In the future, increased values of exchangeable acidity may adversely affect the formation of crop yields. Changes in the values of hydrolytic acidity of soils follow the same regularity as the variation in the indices of exchangeable acidity. The most significant excess of the hydrolytic acidity index in comparison with the control was recorded on the slope sites of the fields (increase by 11-17%). The conducted studies confirm the need for constant agroecological monitoring of these lands with the regulation of mineral fertilizers to increase the absorption capacity of soils due to increased values of exchangeable and hydrolytic acidity.
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26

Kottyan, Leah C., Ann R. Collier, Khanh H. Cao, Kathryn A. Niese, Megan Hedgebeth, Caius G. Radu, Owen N. Witte, Gurjit K. Khurana Hershey, Marc E. Rothenberg, and Nives Zimmermann. "Eosinophil viability is increased by acidic pH in a cAMP- and GPR65-dependent manner." Blood 114, no. 13 (September 24, 2009): 2774–82. http://dx.doi.org/10.1182/blood-2009-05-220681.

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Abstract The microenvironment of the lung in asthma is acidic, yet the effect of acidity on inflammatory cells has not been well established. We now demonstrate that acidity inhibits eosinophil apoptosis and increases cellular viability in a dose-dependent manner between pH 7.5 and 6.0. Notably, acidity induced eosinophil cyclic adenosine 5′-monophosphate (cAMP) production and enhanced cellular viability in an adenylate cyclase–dependent manner. Furthermore, we identify G protein-coupled receptor 65 (GPR65) as the chief acid-sensing receptor expressed by eosinophils, as GPR65-deficient eosinophils were resistant to acid-induced eosinophil cAMP production and enhanced viability. Notably, GPR65−/− mice had attenuated airway eosinophilia and increased apoptosis in 2 distinct models of allergic airway disease. We conclude that eosinophil viability is increased in acidic microenvironments in a cAMP- and GPR65-dependent manner.
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Cui, Tao. "Analysis on Acidity and Alkalinity of Metallogenetic Environment in Penecontemporaneous Period on the Bauxite in WZD Area, Northern Guizhou, China." Advanced Materials Research 989-994 (July 2014): 1428–31. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.1428.

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Acidity and alkalinity of metallogenetic environment in penecontemporaneous period is very important for the informing of high grade bauxite. Through the research on migration regular of elements, the position of rare earth mineral and the qualitative alternation of bauxite we found that metallogenetic environment is acidic in penecontemporaneous period, from top to bottom of the profile acidity is decreased gradually. In the acidic condition, Si and Fe moved downward but Al is relative enrichment in the middle-upper part of profile.
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Tafech, Alaa, and Angélique Stéphanou. "On the Importance of Acidity in Cancer Cells and Therapy." Biology 13, no. 4 (March 29, 2024): 225. http://dx.doi.org/10.3390/biology13040225.

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Cancer cells are associated with high glycolytic activity, which results in acidification of the tumor microenvironment. The occurrence of this stressful condition fosters tumor aggressiveness, with the outcome of invasiveness and metastasis that are linked to a poor clinical prognosis. Acidosis can be both the cause or consequence of alterations in the functions and expressions of transporters involved in intracellular acidity regulation. This review aims to explore the origin of acidity in cancer cells and the various mechanisms existing in tumors to resist, survive, or thrive in the acidic environment. It highlights the difficulties in measuring the intracellular pH evolution that impedes our understanding of the many regulatory and feedback mechanisms. It finally presents the consequences of acidity on tumor development as well as the friend or foe role of acidity in therapy.
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29

&NA;. "Soil Acidity." Soil Science 153, no. 3 (March 1992): 259. http://dx.doi.org/10.1097/00010694-199203000-00011.

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TUTUIAN, R., P. KATZ, S. XUE, and D. CASTELL. "Percent time, integrated intragastric acidity or acidity index?" Gastroenterology 120, no. 5 (April 2001): A157. http://dx.doi.org/10.1016/s0016-5085(01)80777-0.

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31

Tutuian, Radu I., Philip O. Katz, Shuwen Xue, and Donald O. Castell. "Percent time, integrated intragastric acidity or acidity index?" Gastroenterology 120, no. 5 (April 2001): A157. http://dx.doi.org/10.1016/s0016-5085(08)80777-9.

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32

Sinkevich, O. V., M. B. Kopina, and T. A. Syrina. "INFLUENCE OF ACIDITY NUTRIENT ENVIRON ON CULTURAL CHARACTERISTICS OF STAGONOSPOROPSIS CHRYSANTHEMI ISOLATES." Chronos 6, no. 9(59) (September 13, 2021): 11–14. http://dx.doi.org/10.52013/2658-7556-59-9-3.

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The use of a nutrient medium (CHA) with different acidity for growing Stagonosporopsis chrysanthemi only influenced the growth rate of the colony, the acidic medium pH 4.6 inhibited growth, while in the case of a neutral reaction, the rotational speed was higher. At the same time, the acidity of the medium did not affect the cultural characteristics of the isolates.
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Pye, Havala O. T., Athanasios Nenes, Becky Alexander, Andrew P. Ault, Mary C. Barth, Simon L. Clegg, Jeffrey L. Collett Jr., et al. "The acidity of atmospheric particles and clouds." Atmospheric Chemistry and Physics 20, no. 8 (April 24, 2020): 4809–88. http://dx.doi.org/10.5194/acp-20-4809-2020.

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Abstract. Acidity, defined as pH, is a central component of aqueous chemistry. In the atmosphere, the acidity of condensed phases (aerosol particles, cloud water, and fog droplets) governs the phase partitioning of semivolatile gases such as HNO3, NH3, HCl, and organic acids and bases as well as chemical reaction rates. It has implications for the atmospheric lifetime of pollutants, deposition, and human health. Despite its fundamental role in atmospheric processes, only recently has this field seen a growth in the number of studies on particle acidity. Even with this growth, many fine-particle pH estimates must be based on thermodynamic model calculations since no operational techniques exist for direct measurements. Current information indicates acidic fine particles are ubiquitous, but observationally constrained pH estimates are limited in spatial and temporal coverage. Clouds and fogs are also generally acidic, but to a lesser degree than particles, and have a range of pH that is quite sensitive to anthropogenic emissions of sulfur and nitrogen oxides, as well as ambient ammonia. Historical measurements indicate that cloud and fog droplet pH has changed in recent decades in response to controls on anthropogenic emissions, while the limited trend data for aerosol particles indicate acidity may be relatively constant due to the semivolatile nature of the key acids and bases and buffering in particles. This paper reviews and synthesizes the current state of knowledge on the acidity of atmospheric condensed phases, specifically particles and cloud droplets. It includes recommendations for estimating acidity and pH, standard nomenclature, a synthesis of current pH estimates based on observations, and new model calculations on the local and global scale.
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Dejene, Matiyas, Girma Abera, and Temesgen Desalegn. "The Effect of Phosphorus Fertilizer Sources and Lime on Acidic Soil Properties of Mollic Rhodic Nitisol in Welmera District, Central Ethiopia." Applied and Environmental Soil Science 2023 (October 18, 2023): 1–14. http://dx.doi.org/10.1155/2023/7002816.

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The soil acidity problem is intensified by improper utilization of synthetic fertilizers in addition to other naturally existing causes; thus, it is important to consider effects on soil health beyond seasonal crop productivity. Most widely used sources of soluble phosphate fertilizers cannot perform effectively on acidic soil due to its fixation. Field experiments were conducted on the acidic nitisols of Welmera District in two locations to determine the effects of using lime and different phosphorus fertilizer sources on the soil acidity attributes and nutrient use efficiency of barley crops. Treatments include a factorial combination of 4 different phosphate fertilizer sources (PARP, MOHP, NPSB, and NAFAKA) with 2 application rates (34.5 kg P2O5 ha−1 and 69 kg P2O5 ha−1) and 2 lime application rates computed from soil exchangeable acidity result 404.25 kg·ha−1 and 563.9 kg·ha−1 for on-station and on-farm sites, respectively, with no lime application (1/4th of LR and 0 lime). Partially acidulated rock phosphate as a phosphorus fertilizer significantly improves soil acidity attributes such as exchangeable acidity, present acid saturation, and plant available phosphorus, and also another soil nutrient status is significantly affected by using different phosphorus sources with the lime application. Application of PARP phosphate sources significantly improves soil exchangeable acidity and present acid saturation by 42% and 41%, respectively, over the commonly used NPSB standard sources of phosphorus fertilizer. Using lime with alternative phosphate sources also contributes to more effective nutrient use efficiency and barely yields improvements with a productive acid soil amendment option. Maintaining soil health by using those integrated approaches improves the efficient utilization of scarce unrenewable resources on sustainable bases.
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35

Shafer, S. R., L. F. Grand, R. I. Bruck, and A. S. Heagle. "Formation of ectomycorrhizae on Pinustaeda seedlings exposed to simulated acidic rain." Canadian Journal of Forest Research 15, no. 1 (February 1, 1985): 66–71. http://dx.doi.org/10.1139/x85-012.

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Effects of simulated acidic rain on formation of ectomycorrhizae were studied with Pinustaeda seedlings grown in plastic trays in a greenhouse. Trays of ectomycorrhizal seedlings were exposed 37 times over 16 weeks to simulated rains adjusted to pH 5.6, 4.0, 3.2, or 2.4. After exposures, mean percentages of short roots that were mycorrhizal (%M) were greatest (62.2%) for seedlings exposed to rains of pH 2.4. Values of %M exhibited a quadratic relationship with rain acidity (%M = 146.49 − 48.96 (rain pH) + 5.68 (rain pH)2). Values of R/S (root/shoot ratio) were negatively correlated (P < 0.01) with %M. Responses of ecetomycorrhiza formation and associated shoot growth to acidity of simulated rains suggest that rains of intermediate acidity (pH 4.0 and 3.2) inhibited ectomycorrhiza formation, or that increased soil acidity or other factors induced by rains at pH 2.4 enhanced ectomycorrhiza formation.
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36

Echeverri-Giraldo, Luz Fanny, Valentina Osorio Pérez, Claudia Tabares Arboleda, Lady Juliet Vargas Gutiérrez, and Luis Carlos Imbachi Quinchua. "Content of Acidic Compounds in the Bean of Coffea arabica L., Produced in the Department of Cesar (Colombia), and Its Relationship with the Sensorial Attribute of Acidity." Separations 11, no. 2 (February 7, 2024): 52. http://dx.doi.org/10.3390/separations11020052.

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Cesar, a coffee-growing department in Colombia, has particular characteristics that favor the production of coffees differentiated by sensory profile, for which the acidity attribute stands out. The chemical composition and sensory quality of the coffee produced by 160 coffee growers during two production harvests (2021 and 2022) and processed by the wet method were evaluated to correlate the contents of the main acidic chemical compounds present in green coffee beans with the perceived acidity of the beverage. The chemical analysis of coffee samples utilized spectrophotometric methods and HPLC-DAD techniques. Lactic, 3,5-di-CQA and phosphoric acids were good discriminators of acidity classified as excellent; that is, with a score higher than 7.75 on the Specialty Coffee Association (SCA) scale, presenting the highest contents in the green coffee bean. There was a direct linear relationship between acidity and 3,5-di-CQA and 5-CQA and an inverse relationship between acidity and 3-CQA, 4-CQA and 4,5-CQA. These findings contribute to the understanding of the quality and chemistry of Colombian coffee.
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37

Green, Rosalind, T. David Waite, Michael D. Melville, and Ben C. T. Macdonald. "Characteristics of the Acidity in Acid Sulfate Soil Drainage Waters, McLeods Creek, Northeastern NSW, Australia." Environmental Chemistry 3, no. 3 (2006): 225. http://dx.doi.org/10.1071/en05055.

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Environmental Context. Acid sulfate soils are found in many low-lying coastal areas, but they can also be encountered in inland areas of Australia and other parts of the world. These soils typically contain iron sulfides, primarily pyrite (FeS2) and mackinawite (FeS), and the products that result from oxidation of these iron minerals. Acidic and metal-rich waters can be produced when the pyrite in soil is oxidized by natural means or accelerated when the soil is drained, which typically occurs when it is developed for agriculture or urban use. In general, acid sulfate soils become a problem when oxidation products are transported from the soil profile into nearby streams and estuaries, which can severely affect the ecology, biodiversity, economic development, and the aesthetics of adjacent waterways. The key contributors to acidity in drainage waters from the site examined are Al3+, AlSO4– and, under particular circumstances, Mn2+ and Fe2+, but the principal species contributing to acidity are strongly time variant and would be expected to vary from site to site. Abstract. Catchments that contain acid sulfate soils can discharge large quantities of acid and dissolved metals into waterways. At McLeods Creek in far northern NSW, Australia, the acidity from the hydrolysis of dissolved metal species, particularly aluminium and iron, contributes to greater than 70% of the total acidity. Therefore, a poor relationship exists between both calculated and titrated acidity and pH because of the dominant influence of these hydrolyzable metal species. Determination of the so-called ‘cold acidity’ by direct titration with NaOH yields results that are difficult to replicate because of the buffering effects of suspended solids, carbon dioxide ingassing, and/or MnII and FeII oxidation in the sample as the titration end-point is approached. Samples that are pre-treated with sulfuric acid and hydrogen peroxide produce results (of ‘hot acidity’) that can be easily replicated and are similar to calculated acidities based on elemental analysis and speciation calculations. The cold acidity values for titrations of 105 water samples from the chosen field site are often higher than hot acidity values as a result of the loss of carbonate acidity during pre-treatment of samples for hot acidity analysis.
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Huang, Juan, Wei Zhang, Yuelin Li, Senhao Wang, Jinhua Mao, Jiangming Mo, and Mianhai Zheng. "Long-term nitrogen deposition does not exacerbate soil acidification in tropical broadleaf plantations." Environmental Research Letters 16, no. 11 (November 1, 2021): 114042. http://dx.doi.org/10.1088/1748-9326/ac30bd.

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Abstract Nitrogen (N) deposition induces soil acidification in natural forests; however, whether it increases soil acidity in tropical plantations with simple tree structures compared with natural forests remains unclear. This study aimed to investigate the effects of N deposition on the soil acidity of tropical broadleaf plantations dominated by Acacia auriculiformis and Eucalyptus urophylla in South China, which has been enduring N deposition for over 30 years, and investigate the reasons for the changes in soil acidity. Long-term N addition did not affect soil acidity in the two plantations, with no significant changes in soil pH values, and exchangeable non-acidic and acidic cation concentrations. Long-term N deposition did not significantly affect the plant and total soil N concentrations, but significantly increased the soil nitrous oxide emission rates and total dissolved N concentrations in the soil solutions. Our findings indicate that most of the added N was lost via leaching and emissions, such that long-term N addition did not exacerbate soil acidification in broadleaf plantations, thereby providing novel insight into the effects of atmospheric N deposition on forest ecosystems. Overall, our study indicates that long-term N deposition does not always lead to soil acidification in tropical forests, as previously expected.
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Barboza Januário, Jaqueline Gilmara, Tailana Marin de Lima, Daiane Aparecida Camargo Portella, Caroline Barboza Januário, Suellen Jensen Klososki, and TATIANA COLOMBO PIMENTEL. "Development of Kefir beverages: Standardization of process parameters." Brazilian Journal of Food Research 7, no. 2 (September 1, 2016): 80. http://dx.doi.org/10.3895/rebrapa.v7n2.3630.

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This study aimed to characterize physico-chemically Kefir grains and standardize the process parameters of the beverages, in order to obtain an optimum product. Kefir grains consisted basically of water (85.61 ± 0.41%) and had an acidic pH (4.45) and low acidity (0.44 ± 0.09% lactic acid). To determine the process parameters, it was used a 23 factorial design with three replications at the central point, being evaluated the amount of grain (2-6%), amount of sugar (10-14%) and fermentation time (18-24 hours) at 25oC. The amount of sugar or grains had no influence on the pH and titratable acidity. A longer fermentation time (24 hours) resulted in products with pH and acidity within the recommended values, while fewer grains (2%) did not result in too firm beverages. The formulation with the best physicochemical and sensory characteristics had 2% grain, 10% sugar and 24 hours of fermentation, being described as creamy, slightly acidic and with intermediate sweetness.
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40

Boedtkjer, Ebbe, and Stine F. Pedersen. "The Acidic Tumor Microenvironment as a Driver of Cancer." Annual Review of Physiology 82, no. 1 (February 10, 2020): 103–26. http://dx.doi.org/10.1146/annurev-physiol-021119-034627.

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Acidic metabolic waste products accumulate in the tumor microenvironment because of high metabolic activity and insufficient perfusion. In tumors, the acidity of the interstitial space and the relatively well-maintained intracellular pH influence cancer and stromal cell function, their mutual interplay, and their interactions with the extracellular matrix. Tumor pH is spatially and temporally heterogeneous, and the fitness advantage of cancer cells adapted to extracellular acidity is likely particularly evident when they encounter less acidic tumor regions, for instance, during invasion. Through complex effects on genetic stability, epigenetics, cellular metabolism, proliferation, and survival, the compartmentalized pH microenvironment favors cancer development. Cellular selection exacerbates the malignant phenotype, which is further enhanced by acid-induced cell motility, extracellular matrix degradation, attenuated immune responses, and modified cellular and intercellular signaling. In this review, we discuss how the acidity of the tumor microenvironment influences each stage in cancer development, from dysplasia to full-blown metastatic disease.
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41

Reddy, A. Ramakrishna, A. Panasa Reddy, and M. Thirumala Chary. "Ruthenium(III) Catalyzed Oxidation of Hypoxanthine and Xanthine by Mn(VII) in Aqueous Brønsted Acid Solutions: A Kinetic and Mechanistic Study." Asian Journal of Chemistry 35, no. 5 (2023): 1074–78. http://dx.doi.org/10.14233/ajchem.2023.27618.

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Mn(VII) is broadly utilized as an oxidizing specialist, however it couldn’t oxidize hypoxanthine (HXAN) and xanthine (XAN) even in concentrated Brønsted acidic (HClO4, H2SO4) media and at raised temperatures. In any case, the responses went through flawlessly in presence of millimolar arrangements of ruthenium chloride (Ru(III) or RuCl3) in presence of fluid Brønsted acidic arrangements. Under synergist conditions, response complied with first request energy in [(Mn(VII)] and [Alkaloid] at steady causticity and temperature. Increase in [Ru(III)] dramatically sped up the reactions with a first order dependence on [catalyst] at constant acidity and temperature. The rate of oxidation was enhanced by an increase in the concentration of Brønsted acid (HClO4, H2SO4). The rate increases observed were examined using the acidity function criteria of Zucker-Hammett, Bunnett and Bunnett-Olsen. The most logical mechanism, involving the involvement of the water molecule in the slow step, has been proposed based on observed Bunnett-Olsen criteria of acidity functions (as proton transferring agent).
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42

Warke, Amanuel, and Tesfaye Wakgari. "A Review on the Impact of Soil Acidification on Plant Nutrient Availability, Crop Productivity, and Management Options in the Ethiopian Highlands." Agriculture, Forestry and Fisheries 13, no. 2 (April 2, 2024): 31–45. http://dx.doi.org/10.11648/j.aff.20241302.13.

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Soil acidity is a type of soil deterioration that has a negative impact on Ethiopia&apos;s overall and Western Oromia&apos;s specific sustainable agricultural production. Currently, soil acidity in highland portions of Western Oromia, including Gimbi, Nedjo, and surrounding areas, is a major problem that can impede agricultural productivity. Reviewing the mechanisms of soil acidification, which can affect soil nutrient availability and agricultural production, as well as management choices, were done in this context for this review topic. The main causes of acid soils are leaching of exchangeable basic cations and topsoil erosion caused by high temperatures and heavy rains, which promote the loss of organic matter the most. In most of Ethiopia&apos;s highland regions, the removal of agricultural waste and ongoing use of inorganic fertilizers that produce acidity are major factors in the development of soil acidity. Al and Mn toxicity are caused by acid soil, which also reduces nutrient availability. Furthermore, agricultural yield decreases due to acidity in the soil. The management options for acid soils include crop types resistant to Al toxicity, liming, and the use of organic materials as integrated forms of soil fertility control. Therefore, lime and organic fertilizers should be employed as crucial agricultural techniques for small-holder farmers in acidic soil locations in order to decrease the effects of soil acidity.
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43

VIDAL, Michael Gomes, Pedro Henrique Cabral de OLIVEIRA, Ynara Bosco de Oliveira LIMA-ARSATI, and José Augusto RODRIGUES. "The effect of dilution on the erosive potential of maltodextrin-containing sports drinks." Revista de Odontologia da UNESP 46, no. 1 (January 9, 2017): 28–32. http://dx.doi.org/10.1590/1807-2577.12316.

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Abstract Introduction The increasing consumption of maltodextrin-containing sports drinks, usually acidic, during physical activity may cause dental erosion. Objective To evaluate the effect of dilution on the erosive potential of maltodextrin-containing sports drinks. Methodology Five samples of five maltodextrin-containing sports drinks [Sports Nutrition (SN), Body Action (BA), New Millen (NM), Athletica Nutrition (AN), Integral Medica (IM)] were diluted with distilled water in three different proportions: as recommended by manufacturer (rec), with 20% more powder (20+) and with 20% less powder (20-) than recommended. Their pH and titratable acidity (volume of 1N NaOH necessary to raise pH to 5.5) were determined. Result The pH and titratable acidity differed among the products, and pH values differed among the dilutions. All sports drinks showed pH below the critical pH for dental enamel demineralization. There was a significant negative correlation between pH and titratable acidity (p <0.01; r = -0.795). Conclusion Changes in the dilution of maltodextrin-containing sports drinks affected their pH, but not their titratable acidity.
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García, Begoña, and José M. Leal. "Applicability of excess acidity functions in low-acidity media." Journal of Physical Organic Chemistry 4, no. 7 (July 1991): 413–19. http://dx.doi.org/10.1002/poc.610040704.

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45

Åhlund, Matti, Roland Börjesson, Eva Engblom, Mats O. G. Eriksson, Pär-Erik Lingdell, Kåre Ström, and Ingemar Åhlund. "Strömstaren Cinclus cinclus och försurningen: beståndsutveckling, häckningsresultat och födoval i sydvästra Sverige." Ornis Svecica 9, no. 1–2 (April 1, 1999): 47–58. http://dx.doi.org/10.34080/os.v9.22915.

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Breeding Dippers were surveyed at 45 streams in southwestern Sweden in 1974—1978 and in 1990—1992. Dippers bred at 37 streams (65 sites) in 1974—1978 and 38 streams (74 sites) in 1990—1992. The breeding frequency, and the change in breeding frequency from 1974—1978 to 1990—1992, did not differ between streams with different history of acidity. Also, clutch size and brood size were similar along neutral, formerly acidic, and acidic streams. We analysed by faeces the diet of adult Dippers in 30 breeding pairs in 1991. Their diet at neutral, formerly acidic and acidic streams showed no clear differences; preferred prey seemed to be available even on acidic streams. So, in contrast to studies in Scotland and Wales, we found no apparent effects of stream acidity on breeding Dippers in this pilot study.
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46

Kalkhoran, Sanaz Shoghi, David Pannell, Tas Thamo, Maksym Polyakov, and Benedict White. "Optimal lime rates for soil acidity mitigation: impacts of crop choice and nitrogen fertiliser in Western Australia." Crop and Pasture Science 71, no. 1 (2020): 36. http://dx.doi.org/10.1071/cp19101.

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Many agricultural soils are naturally acidic, and agricultural production can acidify soil through processes such as nitrogen (N) fixation by legumes and application of N fertiliser. This means that decisions about mitigation of soil acidity (e.g. through application of lime), crop rotation and N fertiliser application are interdependent. This paper presents a dynamic model to determine jointly the optimal lime application strategies and N application rates in a rainfed cropping system in Western Australia. The model accounts for two crop rotations (with and without a legume break crop), for the acid tolerance of different crop types, and for differences in the acidifying effect of different N fertilisers. Results show that liming is a profitable strategy to treat acidic soils in the study region, but that there are interactions between N and acidity management. Choice of fertiliser affects optimal lime rates substantially, with the use of a more acidifying ammonium-based fertiliser leading to higher lime rates. The optimal liming strategy is also sensitive to inclusion of a legume crop in the rotation, because its fixed N can be less acidifying than fertiliser, and it allows a reduction in fertiliser rates. Higher rainfall zones have greater N leaching, which contributes to a higher optimal rate of lime. We find that injection of lime into the subsoil increases profit. Optimal lime rates in the absence of subsoil incorporation are higher than usual current practice, although the economic gains from increasing rates are small.
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47

Gackowski, Mariusz, and Jerzy Datka. "Acid Properties of Hierarchical Zeolites Y." Molecules 25, no. 5 (February 26, 2020): 1044. http://dx.doi.org/10.3390/molecules25051044.

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The article reviews different strategies towards obtaining mesoporous zeolites Y: desilication; surfactant templating and assembly of zeolite crystals. The impact of those methods on physicochemical properties is covered, with a special focus on the acidity of the samples measured with infrared (IR) spectroscopy. The methods of characterization of acidity are presented. Quaternary ammonium cations used for desilication lead to obtaining crystalline; mesoporous and highly acidic zeolites. Si-OH-Al groups of extremely high acidity can be produced by calcination in a humid atmosphere. When the conditions are optimized, post-synthetic surfactant templating allows crystalline mesoporous zeolite to be obtained with no loss of material. All mesoporous zeolites Y proved to be active catalysts in liquid phase isomerization, catalytic cracking, and other reactions.
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48

Alvarez-Macho, María Piedad, and María Isabel Montequi-Martin. "Chromic oxidation of lactic acid in very strong acid media." Canadian Journal of Chemistry 68, no. 1 (January 1, 1990): 29–32. http://dx.doi.org/10.1139/v90-007.

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The oxidation of lactic acid by chromic acid was studied at high concentrations of HClO4, HNO3, and H2SO4. It was observed that the reaction rate depends not only on the acidity of the medium, but also on the nature of the mineral acid. The use of the Bunnett and Bunnett–Olsen criteria and the excess acidity concept allows us to propose a reaction mechanism of the A-2 type, the rate-determining step being a bimolecular process in which water participates as a nucleophile. The enthalpy and entropy of activation were determined; the decrease of the magnitude of these parameters when the acidity of the medium was increased suggests the existence of a compensation effect. Keywords: chromic acid, oxidation, lactic acid, acidic media.
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Suzuki, Shiori, Yuko Takeoka, Masahiro Rikukawa, and Masahiro Yoshizawa-Fujita. "Brønsted acidic ionic liquids for cellulose hydrolysis in an aqueous medium: structural effects on acidity and glucose yield." RSC Advances 8, no. 26 (2018): 14623–32. http://dx.doi.org/10.1039/c8ra01950a.

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Using Brønsted acidic ionic liquids with various structures, their acidic catalytic activity for cellulose hydrolysis assisted by microwave irradiation was assessed using the Hammett acidity function (H0) and theoretical calculations.
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50

Yau, C. C., V. N. L. Wong, and D. M. Kennedy. "Soil chemistry and acidification risk of acid sulfate soils on a temperate estuarine floodplain in southern Australia." Soil Research 54, no. 7 (2016): 787. http://dx.doi.org/10.1071/sr15174.

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The distribution and geochemical characterisation of coastal acid sulfate soils (CASS) in Victoria in southern Australia is relatively poorly understood. This study investigated and characterised CASS and sulfidic material at four sites (wetland (WE), swamp scrub (SS), woodland (WO) and coastal tussock saltmarsh (CTS)) on the estuarine floodplain of the Anglesea River in southern Australia. Shell material and seawater buffered acidity generated and provided acid-neutralising capacity (up to 10.65% CaCO3-equivalent) at the sites located on the lower estuarine floodplain (WO and CTS). The SS site, located on the upper estuarine floodplain, can potentially acidify soil and water due to high positive net acidity (>200molH+t–1) and a limited acid-neutralising capacity. High titratable actual acidity in the SS and WO profiles (>270molH+t–1) were the result of high organic matter in peat-like layers that can potentially contribute organic acids in addition to acidity formed from oxidation of sulfidic sediments. The results of the present study suggest that the environments and chemistry of acid sulfate soils in southern Australia are distinct from those located in eastern Australia; this may be related to differences in estuarine processes that affect formation of acid sulfate soils, as well as the geomorphology and geology of the catchment.
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