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Search Results: 1 - 10 of 13572 matches for " acid "
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Comparative Study of the Kinetics of Dissolution of Laterite in some Acidic Media  [PDF]
Olushola S. AYANDA, Folahan A. ADEKOLA, Alafara A. BABA, Olalekan S. FATOKI, Bhekumusa J. XIMBA
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2011, DOI: 10.4236/jmmce.2011.1015113
Abstract: Studies on the kinetics of dissolution of a Nigerian lateritic soil in acids media including hydrochloric, nitric and sulphuric acids have been undertaken. The elemental and mineralogical characterization, loss of mass on ignition, moisture content and pH of the material suspension in water were determined. The effects of acid concentration, process temperature, stirring rate and particle size on the dissolution rate were investigated. Experimental results indicated that laterite dissolution was greatly influenced by hydrogen ion concentration and the leaching data fitted a diffusion model. The linear dependence of the rate constant k on 1/ro 2 supported the proposed kinetic model. Values of 60.23 kJmol-1, 64.31 kJmol-1 and 67.53 kJmol-1 were obtained for the activation energies of laterite dissolution in hydrochloric, nitric and sulphuric acids respectively; and the order of reaction was approximately one with respect to each of the three acids.
Reactions with Aminobenzoic Acids via Diazonium Salts Open New Routes to Bio-Derived Aromatics  [PDF]
Anthony Farlow, Jens Olaf Kr?mer
International Journal of Organic Chemistry (IJOC) , 2016, DOI: 10.4236/ijoc.2016.62010
Abstract: Aromatics have a broad application in our everyday life ranging from plastics, coatings and fibres, to food and pharmaceuticals. To date the bulk of these aromatics is derived from naphtha-based pet-rochemistry. However, recent progress in the fermentative production of metabolites using renew-able resources and engineered microbes has enabled the production of bio-precursors, such as 4-amino benzoic acid (pABA) and 2-amino benzoic acid (oABA). In this work we explored the feasibility of Sandmeyer reactions for the conversion of pABA to terephthalic and oABA salicylic acid, providing two very important platform chemicals for the chemical and pharmaceutical industries. We could demonstrate that both acids can be obtained from the amino benzoic acids derived from the shikimate pathway in microbes and plants. Good conversions could be achieved using Sandmeyer reactions at mild conditions with biodegradable reagents and without organic solvents.
The Effect of Chitosan Prepared in Different Solvents on the Quality Parameters of Brown Trout Fillets (Salmo trutta fario)  [PDF]
Gonca Alak
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.39172
Abstract: In this study, the use of chitosan prepared in different solvents (acetic acid, lactic acid) as a coating material was researched. The lowest mean pH, TBARS and TVB-N values among the treatment groups were observed in the acetic acid group. Similarly, the lowest growth of aerobic, lactic acid and Pseudomonas bacteria was recorded in this group. The growth of aerobic bacteria in the fillets that were packaged using chitosan film, was lower than the control group throughout the trial. The number of Pseudomonas and lactic acid bacteria was statistically higher in the fillets in the control groups compared to the groups with chitosan (p < 0.01). As a result, it is thought that the use of acetic acid in chitosan film coating is more convenient for the preservation of fish, compared to lactic acid.
Synergism Effect between Phenolic Metabolites and Endogenous Antioxidants in Terms of Antioxidant Activity  [PDF]
María Noguer, Ana B. Cerezo, M. Luisa Moyá, Ana M. Troncoso, M. Carmen García-Parrilla
Advances in Chemical Engineering and Science (ACES) , 2014, DOI: 10.4236/aces.2014.42029
Abstract:

Polyphenolic compounds, widely distributed in plant kingdom, have been exhaustively studied for their bioactive properties specially antioxidant activity. However, they are extensively metabolized by human organism and the resulting metabolites are largely responsible for their effects. Furthermore, they may interact with the endogenous antioxidant network being this possibility scarcely studied. Plasma antioxidant network encompasses antioxidant enzymes and other substances such as uric acid. In addition, ascorbic acid is the major compound representing water soluble compartment both in foods and human body. The interaction of this vitamin with phenolic compound is largely unexplored. This work aims to study if there is a synergic effect between phenolic metabolites and main antioxidants (uric and ascorbic acid). For this purpose, the antioxidant activity was evaluated in terms of ORAC (oxygen radical absorbance capacity) and FRAP (ferricreducing antioxidant power) as these tests involved either HAT (Hydrogen Atom Transfer) or SET (Single Electron Transfer) mechanisms. Additionally, a kinetic studied was developed to test if the rate constant presented a synergic effect. Protocatechuic acid, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylpropionic acid and 3-hydroxyphenylacetic acid were selected as they were metabolites of polyphenol compounds such as anthocyanins, quercetin, neohesperidin, chlorogenic acid and hesperetin present in wines, orange and strawberries. A synergic effect was proved for the combination of ascorbic acid with 3,4-dihydroxyphenylacetic acid, both in terms of antioxidant activity and potent increase of velocity of the antioxidant reaction that took place.

Effects of Various Foods Intakes on Plasma Levels of Trans Fatty Acids in Japanese Old Men  [PDF]
F. Shimizu, Y. Ishii, M. Ogawa, T. Takao, S. Koba, A. Takada
Food and Nutrition Sciences (FNS) , 2018, DOI: 10.4236/fns.2018.97059
Abstract: Background: Trans fatty acids are said to be formed by the partial hydrogenation of vegetable oils. Some amounts are produced in digestive organs of ruminants and present in dairy products or meat. In Japan, use of trans fatty acids in the foods is prohibited, thus trans fatty acids must come from foods or microbes in the digestive organs. Methods: Plasma levels of fatty acids including trans forms of healthy old men are measured by gas chromatography and correlations between various foods intakes and plasma levels of trans fatty acids such as palmitoelaidic, elaidic and linoelaidic acids are examined. Results: No correlations between various foods intakes and trans fatty acids were found except between intake of preference drinks such as tea or coffee and plasma levels of palmitoelaidic and linoelaidic acids. Conclusion: Since palmitoelaidic acid is cardioprotective, increase in plasma levels of palmitoelaidic acid may indicate that intakes of tea and coffee may be beneficial for heath by increasing palmitoelaidic acids.
Docosahexaenoic Acid in Breast Milk Reflects Maternal Fish Intake in Iranian Mothers  [PDF]
Beheshteh Olang, Majid Hajifaraji, Mohamed Atiya Ali, Sophie Hellstrand, Mohammad Palesh, Ebrahim Azadnyia, Zinat Kamali, Birgitta Strandvik, Agneta Yngve
Food and Nutrition Sciences (FNS) , 2012, DOI: 10.4236/fns.2012.34063
Abstract: To estimate essential fatty acid (FA) and long-chain polyunsaturated fatty acid (LCPUFA) concentrations in early breast milk (BM) in relation to habitual fish intake. BM was collected within 72-hours after delivery from consecutively included mothers, 60 in Guilan (coastal) and 60 in Kermanshah (inland) provinces. Mothers were interviewed to com-plete a food frequency questionnaire. The FA composition was measured with gas chromatography. Mothers in the coastal area had higher intake of fish/seafood. Consumption of saturated fat was higher in Kermanshah and olive intake was higher in Guilan. High fish/seafood intake was associated with higher docosahexaenoic acid (DHA) and lower arachidonic acid (AA)/DHA ratio in BM. There were no differences in linoleic and α-linolenic acid concentrations in BM between the provinces. N-3 FA and DHA concentration were significantly higher in Guilan than Kermanshah, but total n-6 FAs and AA did not differ and were high in both provinces. The ratios of total n-6/n-3 and AA/DHA in BM of mothers from Guilan were significantly lower than those in Kermanshah. The LCPUFA status in BM in two Iranian provinces was generally good and DHA was higher and the AA/DHA was significantly lower in mothers with high fish intake.
Fatty Acids and Autism Spectrum Disorders: The Rett Syndrome Conundrum  [PDF]
Claudio De Felice, Cinzia Signorini, Silvia Leoncini, Alessandra Pecorelli, Thierry Durand, Jean-Marie Galano, Valérie Bultel-Poncé, Alexandre Guy, Camille Oger, Gloria Zollo, Giuseppe Valacchi, Lucia Ciccoli, Joussef Hayek
Food and Nutrition Sciences (FNS) , 2013, DOI: 10.4236/fns.2013.49A1012
Abstract:

Autism spectrum disorders (ASDs) are epidemically explosive clinical entities, but their pathogenesis is still unclear and a definitive cure does not yet exist. Rett syndrome (RTT) is a rare genetically determined cause of autism linked to mutations in the X-linked MeCP2 gene or, more rarely, in CDKL5 or FOXG1. A wide phenotypical heterogeneity is a known feature of the disease. Although several studies have focused on the molecular genetics and possible protein changes at different levels, to date very little attention has been paid to fatty acids in this disease, which could be considered as a natural paradigm for the ASDs. To this regard, a quite enigmatic feature of the disease is the evidence in the affected patients of an extensive peroxidation of polyunsaturated fatty acids (arachidonic acid, AA, docosaexahenoic acid, DHA, adrenic acid, AdA and, to a lesser extent, eicosapentaenoic acid, EPA), in contrast with amelioration of the redox changes and phenotypical severity following the supplementation of some of those same fatty acids (DHA + EPA). Therefore, fatty acids may represent a kind of Janus Bifrons in the particular context of RTT. Here, we propose a rational explanation for this apparent “fatty acid paradox” in RTT. A better understanding of this paradox could also be of help to get a better insight into the complex mechanism of action for polyunsaturated fatty acids in health and disease.

Charged Amino Acid Frequencies of Proteins over Macroevolutionary Time Scale  [PDF]
Yu-Juan Zhang, Jian-Jun Li, You-Jin Hao, Bin Chen
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.510B086
Abstract:

Charged amino acids (AAs) are targets for selective forces in protein evolution. To fully explore the trend of charged AA frequencies evolution in macroevolutionary process from prokaryotes to eukaryotes, we extend the analysis of five charged AAs separately and total basic and acidic AAs in protein sequences of 158 prokaryotic and 63 eukaryotic predicted proteomes and 456 clusters of orthologous groups (COGs). Also, we eliminate the biases that may caused by extreme organisms in both predicted proteomes and COGs analyses. More basic AAs, His,Lysand Glu were found in eukaryotic proteins compared with prokaryotic proteins by predicted proteomes analysis. By COGs analysis, we found that basic AAs andLysfrequencies are higher in eukaryotic orthologous proteins than their prokaryotic companions, while the trend of Arg frequency is the opposite. We discussed the agreements and disagreements of two analyses and gained a more credible trend of charged AAs evolution in macroevolutionary time scale.

A Green, One-Pot Route to the Biphenyldicarboxylic Acids: Useful Intermediates in Polymer Synthesis  [PDF]
Richard S. Clary, Christopher D. Lee, William G. Monroe IV, David A. Vaughn, Ragy T. Ragheb, Jack W. Erter III, David M. Brown, David A. Schiraldi
International Journal of Organic Chemistry (IJOC) , 2013, DOI: 10.4236/ijoc.2013.32016
Abstract:

Isomeric biphenyldicarboxylic acids have been prepared from halobenzoic acids and aryl boronic acids using an inverse biphasic modification of the Suzuki coupling reaction. In this modification of the Suzuki coupling reaction, both reactants and products are contained in the aqueous phase, with palladium catalyst contained in the organic phase. A phase transfer catalyst is used to contact reactants and catalyst. Multiple cycles, in which the catalyst/organic solvent is contacted with fresh aqueous reactants, generating products with no loss of efficiency, are demonstrated. We believe that this is the first demonstration of Suzuki coupling to produce biphenyldicarboxylic acids, in this case useful as monomers for the production of condensation polymers.

Dissolution Kinetics and Leaching of Rutile Ore in Hydrochloric Acid  [PDF]
Alafara A. Baba, Folahan A. Adekola, Emmanuela E. Toye, Rafiu B. Bale
Journal of Minerals and Materials Characterization and Engineering (JMMCE) , 2009, DOI: 10.4236/jmmce.2009.810068
Abstract: Experiments on the dissolution kinetics and leaching of rutile ore by hydrochloric acid have been carried out. The influence of acid concentration, temperature, stirring speed and particle diameter on the leaching of the ore were examined. The dissolution rates were greatly influenced by the hydrogen ion concentration, temperature, stirring speed and particle diameter. Kinetic data analysis showed that the dissolution mechanism followed a diffusion controled shrinking core model with the surface chemical reaction as the rate controlling step. The study showed that with 4M HCl solution, about 82.3 % of 10g rutile ore per litre of leachant at 80oC was dissolved within 120min., using 0.045-0.075mm particle diameter at a stirring speed of 360rpm. The reaction order with respect to hydrogen ion concentration was found to be 1.0, while 42.28kJ/mol was calculated for the activation energy of the dissolution process. Finally, the Xray diffraction spectrum showed that the residual solid which amounted to 18% of the initial solid material contained silica (a-SiO2) and are formed around the shrinking core of the unreacted material.
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