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Experimental measurement and modelling of KBr solubility in water, methanol, ethanol, and its binary mixed solvents at different temperatures

Pinho, Simão; Macedo, Eugénia A.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
482.4949%
A simple and accurate apparatus has been designed to measure the solubilities of potassium bromide by an analytical method. Salt solubility data have been measured in water, methanol, ethanol, (water + methanol), (water + ethanol), and (methanol + ethanol) solvents in the temperature range between 298.15 K and 353.15 K. A new formulation is presented for the calculation of salt solubility in pure and mixed solvents as a function of the temperature and solvent composition. This formulation is based on the symmetric convention for the normalization of the activity coefficients for all species in solution, and makes possible direct access to the solubility product of the salt in terms of its thermodynamic properties. The new solubility data measured in this work, as well as experimental information from the open literature, are used to estimate the interaction parameters of the two models proposed here. One model combines the original Universal Quasi Chemical (UNIQUAC) equation with a Pitzer–Debye–Huckel expression to take into account the long-range interaction forces; the other model only considers the short-range forces through the UNIQUAC equation with linear temperature dependent salt/solvent interaction parameters. Both models correlate satisfactorily the solubility data...

Multicomponent complex formation between vinpocetine, cyclodextrins, tartaric acid and water-soluble polymers monitored by NMR and solubility studies

Ribeiro, Laura; Carvalho, Rui A.; Ferreira, Domingos C.; Veiga, Francisco J. B.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
Relevância na Pesquisa
483.45742%
This work deals with multicomponent complex formation of vinpocetine (VP) with [beta]-cyclodextrin ([beta]CD), sulfobutyl ether [beta]-cyclodextrin (SBE[beta]CD) and tartaric acid (TA), in the presence or absence of water-soluble polymers, in aqueous solution. Complexation was monitored by phase-solubility and proton nuclear magnetic resonance (1H NMR) studies. TA demonstrated a synergistic effect on VP solubility, and in the complexation efficiency of [beta]CD and SBE[beta]CD. Additionally, water-soluble polymers increased even more the complexation efficiency of the CDs that was reflected by a 2.1-2.5 increase on KC values for VP-CD-TA-polymer multicomponent complexes. SBE[beta]CD was more effective in VP solubilization, as KC values of VP-SBE[beta]CD-TA multicomponent complexes were notably higher than in corresponding [beta]CD complexes. The large chemical shift displacements from protons located in the interior of the hydrophobic CD cavities (i.e., H-3 and H-5) coupled with significant chemical shift displacements of VP aromatic protons suggested that this moiety was included in the cavity of both [beta]CD and SBE[beta]CD. Two-dimensional rotating frame nuclear Overhauser effect spectroscopy (ROESY) experiments were carried out in order to obtain information about the multicomponent complex geometry in solution. Inspection of ROESY spectra allowed the establishment of spatial proximities between all aromatic protons of VP and the internal protons of the CDs...

Bovine serum albumin displays luciferase-like activity in presence of luciferyl adenylate: Insights on the origin of protoluciferase activity and bioluminescence colours

Viviani, Vadim R.; Ohmiya, Y.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 262-267
ENG
Relevância na Pesquisa
554.60234%
Luciferyl adenylate, the key intermediate in beetle bioluminescence, is produced through adenylation of D-luciferin by beetle luciferases and also by mealworm luciferase-like enzymes which produce a weak red chemiluminescence. However, luciferyl adenylate is only weakly chemiluminescent in water at physiological pH and it is unclear how efficient bioluminescence evolved from its weak chemiluminescent properties. We found that bovine serum albumin (BSA) and neutral detergents enhance luciferyl adenylate chemiluminescence by three orders of magnitude, simulating the mealworm luciferase-like enzyme chemiluminescence properties. These results suggest that the beetle protoluciferase activity arose as an enhanced luciferyl adenylate chemiluminescence in the protein environment of the ancestral AMP-ligase. The predominance of luciferyl adenylate chemiluminescence in the red region under most conditions suggests that red luminescence is a more primitive condition that characterized the original stages of protobioluminescence, whereas yellow-green bioluminescence may have evolved later through the development of a more structured and hydrophobic active site. Copyright © 2006 John Wiley & Sons, Ltd.

Effect of light curing tip distance and immersion media on the degree of conversion, sorption and solubility of methacrylate and silorane-based composites = : Efeito da distância de fotoativação e meios de imersão sobre o grau de conversão, sorção e solubilidade de compósitos à base de metacrilato e silorano; Efeito da distância de fotoativação e meios de imersão sobre o grau de conversão, sorção e solubilidade de compósitos à base de metacrilato e silorano

Diogo de Azevêdo Miranda
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 17/01/2013 PT
Relevância na Pesquisa
476.9135%
O objetivo deste estudo foi avaliar o efeito de três distâncias de fotoativação (0mm, 3mm e 6mm) e quatro meios de imersão (saliva artificial - AS, Plax FreshMint - PFM, Plax Sem álcool - PAF e Plax Whitening - PW) sobre a sorção e solubilidade de compósitos à base de metacrilato (Filtek Z350) e silorano (Filtek P90). Os espécimes foram confeccionados a partir de uma matriz de teflon de 6mm de diâmetro por 1mm de profundidade, onde o compósito foi inserido em incremento único e fotoativado por 20 segundos. Para controlar as distâncias de fotoativação, foi utilizado um dispositivo acoplado a um paquímetro digital. Para o teste de grau de conversão (GC) foram confeccionadas 30 amostras (n=5), de acordo com o tipo de resina e a distância de fotoativação. A leitura dos espectros foi realizada por um espectrômetro de raios infravermelhos transformado de Fourier (FTIR). Para os testes de sorção e solubilidade foram confeccionados 120 espécimes (n=5), de acordo com as variáveis compósitos, distâncias de fotoativação e meios de imersão. As amostras foram armazenadas em um dissecador com sílica em gel até a obtenção de uma massa inicial estável (m1). Após estabilização da massa inicial, o diâmetro e a espessura foram aferidos em quatro pontos equidistantes utilizando paquímetro digital. Durante 30 dias...

Inclusion complex of the antiviral drug acyclovir with cyclodextrin in aqueous solution and in solid phase

Rossel,Carlos von Plessing; Sepúlveda Carreño,Jacqueline; Rodríguez-Baeza,Mario; Alderete,Joel Bernabé
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2000 EN
Relevância na Pesquisa
483.0931%
Complexation between acyclovir (ACV), an antiviral drug used for the treatment of herpes simplex virus infection, and beta-cyclodextrin (beta-CD) was studied in solution and in solid states. Complexation in solution was evaluated using solubility studies and nuclear magnetic resonance spectroscopy (¹H-NMR). In the solid state, X-ray diffraction, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and dissolution studies were used. Solubility studies suggested the existence of a 1:1 complex between ACV and beta-CD. ¹H-NMR spectroscopy studies showed that the complex formed occurs with a stoichiometry ratio of 1:1. Powder X-ray diffraction indicated that ACV exists in a semicrystalline state in the complexed form with beta-CD. DSC studies showed the existence of a complex of ACV with beta-CD. The TGA studies confirmed the DSC results of the complex. Solubility of ACV in solid complexes was studied by the dissolution method and it was found to be much more soluble than the uncomplexed drug.

Solution thermodynamics of methocarbamol in some ethanol + water mixtures

Mercado,Katia C.; Rodríguez,Gerson A.; Delgado,Daniel R.; Martínez,Fleming; Romdhani,Asma
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
482.6468%
Apparent thermodynamic functions, Gibbs energy, enthalpy and entropy of solution and mixing, for methocarbamol in ethanol + water mixtures, were evaluated from solubility data determined at temperatures from 293.15 K to 313.15 K and from calorimetric values of drug fusion. The drug solubility was greatest in the mixtures with 0.70 or 0.80 mass fraction of ethanol and lowest in neat water across all temperatures studied. Non-linear enthalpy-entropy compensation was found for the dissolution processes. Accordingly, solution enthalpy drives the respective processes in almost all the solvent systems analyzed.

Temperature and curing time affect composite sorption and solubility

Castro,Fabricio Luscino Alves de; Campos,Bruno Barbosa; Bruno,Kely Firmino; Reges,Rogerio Vieira
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2013 EN
Relevância na Pesquisa
482.7755%
Objective: This study evaluated the effect of temperature and curing time on composite sorption and solubility. Material and Methods: Seventy five specimens (8×2 mm) were prepared using a commercial composite resin (ICE, SDI). Three temperatures (10°C, 25°C and 60°C) and five curing times (5 s, 10 s, 20 s, 40 s and 60 s) were evaluated. The specimens were weighed on an analytical balance three times: A: before storage (M1); B: 7 days after storage (M2); C: 7 days after storage plus 1 day of drying (M3). The storage solution consisted of 75% alcohol/25% water. Sorption and solubility were calculated using these three weights and specimen dimensions. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U Tests (α=5%). Results: The results showed that time, temperature and their interaction influenced the sorption and solubility of the composite (p<0.05). At 60°C, the composite sorption showed an inverse relationship with the curing time (p<0.05). The composite cured for 5 s showed higher sorption for the 40 s or 60 s curing times when compared with all temperatures (p<0.05). Curing times of 20 s and 40 s showed similar sorption data for all temperatures (p>0.05). The 60°C composite temperature led to lower values of sorption for all curing times when compared with the 10°C temperature (p<0.05). The same results were found when comparing 10°C and 25°C (p<0.05)...

Role of dissolution rate and solubility in biodegradation of aromatic compounds.

Stucki, G; Alexander, M
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /02/1987 EN
Relevância na Pesquisa
473.4222%
Strains of Moraxella sp., Pseudomonas sp., and Flavobacterium sp. able to grow on biphenyl were isolated from sewage. The bacteria produced 2.3 to 4.5 g of protein per mol of biphenyl carbon, and similar protein yields were obtained when the isolates were grown on succinate. Mineralization of biphenyl was exponential during the phase of exponential growth of Moraxella sp. and Pseudomonas sp. In biphenyl-supplemented media, Flavobacterium sp. had one exponential phase of growth apparently at the expense of contaminating dissolved carbon in the solution and a second exponential phase during which it mineralized the hydrocarbon. Phase-contrast microscopy did not show significant numbers of cells of these three species on the surface of the solid substrate as it underwent decomposition. Pseudomonas sp. did not form products that affected the solubility of biphenyl, although its excretions did increase the dissolution rate. It was calculated that Pseudomonas sp. consumed 29 nmol of biphenyl per ml in the 1 h after the end of the exponential phase of growth, but 32 nmol of substrate per ml went into solution in that period when the growth rate had declined. In a medium with anthracene as the sole added carbon source, Flavobacterium sp. converted 90% of the substrate to water-soluble products...

Effect of glycerol on the interactions and solubility of bovine pancreatic trypsin inhibitor.

Farnum, M; Zukoski, C
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1999 EN
Relevância na Pesquisa
489.05953%
The effects of additives used to stabilize protein structure during crystallization on protein solution phase behavior are poorly understood. Here we investigate the effect of glycerol and ionic strength on the solubility and strength of interactions of the bovine pancreatic trypsin inhibitor. These two variables are found to have opposite effects on the intermolecular forces; attractions increase with [NaCl], whereas repulsions increase with glycerol concentration. These changes are mirrored in bovine pancreatic trypsin inhibitor solubility where the typical salting out behavior for NaCl is observed with higher solubility found in buffers containing glycerol. The increased repulsions induced by glycerol can be explained by a number of possible mechanisms, all of which require small changes in the protein or the solvent in its immediate vicinity. Bovine pancreatic trypsin inhibitor follows the same general phase behavior as other globular macromolecules where a robust correlation between protein solution second virial coefficient and solubility has been developed. This study extends previous reports of this correlation to solution conditions involving nonelectrolyte additives.

Polyelectrolyte multilayers incorporating photocrosslinking polymers for controlling 2- and 3-dimensional structure; PEMs incorporating photocrosslinking polymers for controlling 2- and 3-dimensional structure

Olugebefola, Solar Candido Ademola
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 155 p.
ENG
Relevância na Pesquisa
561.96695%
Polyelectrolyte multilayer (PEM) assembly is a technology for building thin films with a number of useful and novel functionalities. PEMs interact favorably with proteins and other biomolecules making them potentially valuable as biomaterials. Many systems of polymers have been studied for use in PEMs, including weak polyelectrolytes such as those containing poly(acrylic acid) (PAA) and poly(allyamine hydrochloride) (PAH), which exhibit pH-dependent behavior. Properties such as thickness, swellability, mechanical stiffness, porosity (and by extention optical properties), and ability to adsorb small molecules are all controlled by the charge density of these polymers in the film and their resultant binding state. Patterning covalent binding through photo-crosslinking in addition to electrostatic binding, can locally override the native tendency to change structure with changes in pH. To achieve this, poly(acrylic acid) was chemically modified through a halide esterification reaction to incorporate photo-crosslinkable vinylbenzyl side groups, making poly(acrylic acid-ran-vinylbenzyl acrylate) (PAArVBA). The chemical modification was characterized by nuclear magnetic resonance spectroscopy (NMR) and light spectroscopy.; (cont.) NMR revealed that up to 6% of vinylbenzyl groups could be appended to PAA while maintaining the viability of the crosslinking group and the solubility of PAA in aqueous solution. Light spectroscopy indicated the location of the absorbance peak of the vinylbenzyl groups at 254 nm and the generation of crosslinking radicals was achieved with a quantum yield of 0.013. These parameters allow the polymer to be used in PEM films and to be crosslinked with a standard UV lamp...

Alquilação redutiva da quitosana a partir do glutaraldeído e 3-amino-1-pr; Reductive alkylation of chitosan by glutaraldehyde and 3-amino-1-propanol

Alves, Keila dos Santos
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
491.04758%
Chitosan derivatives were prepared by reductive alkylation using glutaraldehyde and 3-amino-1-propanol. The reducing agent used was the sodium borohydride. Tests of solubility, stability and viscosity were performed in order to evaluate these parameters effects in the reaction conditions (molar ratio of the reactants and presence of nitrogen in the reaction system). The molecular structure of commercial chitosan was determined by infrared (IR) and hydrogen nuclear magnetic resonance spectroscopy (1H NMR). The intrinsic viscosity and average molecular weight of the chitosan were determined by viscosimetry in 0.3 M acetic acid aqueous solution 0.2 M sodium acetate at 25 ºC. The derivatives of chitosan soluble in aqueous acidic medium were characterized by 1H NMR. The rheological behavior of the chitosan and of the derivative of chitosan (sample QV), which presented the largest viscosity, were studied as a function of polymer concentration, temperature and ionic strength of the medium. The results of characterization of the commercial chitosan (the degree of deacetylation obtained equal 78.45 %) used in this work confirmed a sample of low molar weight (Mv = 3.57 x 104 g/mol) and low viscosity (intrinsic viscosity = 213.56 mL/g). The chemical modification of the chitosan resulted in derivatives with thickening action. The spectra of 1H NMR of the soluble derivatives in acid aqueous medium suggested the presence of hydrophobic groups grafted into chitosan in function of the chemical modification. The solubility of the derivatives of chitosan in 0.25 M acetic acid aqueous solution decreased with increase of the molar ratio of the glutaraldehyde and 3-amino-1-propanol in relation to the chitosan. The presence of nitrogen and larger amount of reducing agent in reaction system contributed to the increase of the solubility...

Crystal transformations and crystallisation methodologies: polymorphic transformations of piracetam

Maher, Anthony
Fonte: Univeristy of Limerick Publicador: Univeristy of Limerick
Tipo: info:eu-repo/semantics/doctoralThesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations
ENG
Relevância na Pesquisa
493.9541%
peer-reviewed; The Ph.D project detailed in this thesis investigated the phenomena of crystallisation and polymorphism, focusing on 2-oxo-1-pyrrolidine acetamide (piracetam) as the model compound. The three polymorphs of practical relevance were isolated via different methods, and characterised using numerous analytical techniques. Solubility data was obtained between 5 and 50 °C for Form II and Form III in organic solvents. It was found that the solubility values correlated positively with solvent polar characteristics from a qualitative point of view; an increase in solubility was observed with increasing solvent polarity and solvent acidity. The metastable Form II has a slightly higher solubility than the stable Form III. A thorough investigation of the polymorphic transformations of the system was carried out, employing a combination of off-line and in-situ techniques. The solution mediated polymorphic transformation from Form II to Form III was investigated by monitoring the solution and solid phases. The effect of factors such as solvent, temperature, agitation, excess solid mass and specific surface area of the solid phase were examined. Solvent, temperature and agitation were all found to alter the transformation rate significantly due to their impact on the kinetics of the system. Increases in temperature and agitation increased the rate of the transformation. Indirectly...

Effect of chloride in soil solution on the plant availability of biosolid-borne cadmium

Weggler-Beaton, K.; McLaughlin, M.; Graham, R.
Fonte: Amer Soc Agronomy Publicador: Amer Soc Agronomy
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
490.92242%
Increasing chloride (Cl) concentration in soil solution has been shown to increase cadmium (Cd) concentration in soil solution and Cd uptake by plants, when grown in phosphate fertilizer– or biosolid-amended soils. However, previous experiments did not distinguish between the effect of Cl on biosolid-borne Cd compared with soil-borne Cd inherited from previous fertilizer history. A factorial pot experiment was conducted with biosolid application rates of 0, 20, 40, and 80 g biosolids kg–1 and Cl concentration in soil solution ranging from 1 to 160 mM Cl. The Cd uptake of wheat (Triticum aestivum L. cv. Halberd) was measured and major cations and anions in soil solution were determined. Cadmium speciation in soil solution was calculated using GEOCHEM-PC. The Cd concentration in plant shoots and soil solution increased with biosolid application rates up to 40 g kg–1, but decreased slightly in the 80 g kg–1 biosolid treatment. Across biosolid application rates, the Cd concentration in soil solution and plant shoots was positively correlated with the Cl concentration in soil solution. This suggests that biosolid-borne Cd is also mobilized by chloride ligands in soil solution. The soil solution CdCl+ activity correlated best with the Cd uptake of plants...

Montagem e desenvolvimento experimental de uma unidade de ozonização; Assembly and experimental development of an ozonation unit

Vanessa Trevizan Mochi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 12/03/2010 PT
Relevância na Pesquisa
493.8909%
A busca de tecnologias apropriadas para tratamento de água potável ou efluente tem sido direcionada para o desenvolvimento de novos métodos ou aprimoramento de métodos já existentes. Uma técnica que tem se mostrado bastante promissora é a ozonização. Diante desse contexto, a presente Tese de Doutorado visou montar e desenvolver uma unidade experimental de ozonização. Primeiramente, dimensionou-se e montou-se a unidade com o reator semicontínuo para estudo da solubilidade de ozônio em líquidos. Em seguida, determinou-se a solubilidade do ozônio em água destilada a 21oC e pH 7 pelo método convencional (isocrático). Diante dos resultados, optou-se por propor um novo método para determinação da solubilidade do ozônio em água destilada a 21oC e pH 7, denominado método por gradiente em etapas.Com esse método, obteve-se uma única curva com seis degraus, onde cada degrau está relacionado com uma concentração de ozônio na fase gasosa. Para a condição avaliada, o novo método reduziu a quantidade de experimentos de seis para um experimento, quando comparado com o método convencional (isocrático). A redução do número de experimentos resultou numa redução do tempo de 36 % e o método proposto apresentou o mesmo resultado que o método tradicional de determinação de solubilidade de ozônio em líquido.O valor da constante de Henry obtida também foi corroborado pelos valores encontrados na literatura para a solubilidade de ozônio em água a 21 °C e pH 7...

The donor ability of the chelated carbonate ligand: protonation and metallation of [(L)Co(O2CO)]+ complexes in aqueous solution

McClintock, Lisa F.; Cavigliasso, German; Stranger, Robert; Blackman, Allan G.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
560.96438%
The syntheses and X-ray structures of [Co(Me-tpa)O2COZnCl 3], [Co(pmea)O2COZnCl3]•H2O [Co(trpyn)O2COZn(OH2)4OCO2Co(trpyn)] (ZnCl4)2•H2O, [Co(trpyn)(O 2COH)]ZnCl4•3H2O and [Co(trpyn)(O 2CO)]ClO4 are reported (Me-tpa = [(6-methyl-2-pyridyl) methyl]bis

Temperature and curing time affect composite sorption and solubility

Castro, Fabricio Luscino Alves de; Campos, Bruno Barbosa; Bruno, Kely Firmino; Reges, Rogerio Vieira
Fonte: Universidade de São Paulo. Faculdade de Odontologia de Bauru Publicador: Universidade de São Paulo. Faculdade de Odontologia de Bauru
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; ; Formato: application/pdf
Publicado em 01/04/2013 ENG
Relevância na Pesquisa
476.74023%
Objective: This study evaluated the effect of temperature and curing time on composite sorption and solubility. Material and Methods: Seventy five specimens (8×2 mm) were prepared using a commercial composite resin (ICE, SDI). Three temperatures (10°C, 25°C and 60°C) and five curing times (5 s, 10 s, 20 s, 40 s and 60 s) were evaluated. The specimens were weighed on an analytical balance three times: A: before storage (M1); B: 7 days after storage (M2); C: 7 days after storage plus 1 day of drying (M3). The storage solution consisted of 75% alcohol/25% water. Sorption and solubility were calculated using these three weights and specimen dimensions. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U Tests (α=5%). Results: The results showed that time, temperature and their interaction influenced the sorption and solubility of the composite (p

The Effect of Silicic Acid in the Fountain Solution

Ajibade, Kayode
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
484.54055%
Silicic acid is a water soluble colloidal resin which can be obtained commercially. The effect of silicic acid as a desensitizer in fountain solution was studied. The resin of this colloidal solution was compared to gum arabic solution. The study included the investigation of the physical properties of the solution at different concentrations as well as press performance. Comparisons were drawn regarding wettability, viscosity, surface tension, dot size change, minimum dampening rate to clean-up the non-image areas, resolution, resistance to scum, blinding of image areas, rate of de-inking over- run non-image areas, performance distinction between lithium silicate and sodium silicate, and changes with aging in solubility properties of silicates in fountain solutions. The experiments were carried out under carefully controlled conditions; the only variable present was one ingredient of the fountain solution. The concentration of the necessary solution was determined. The effect of concentration was discussed and reported. A considerable number of the results were statistically analyzed by the two factor analysis of variance. The effectiveness of silicic acid solution as a substitute for gum arabic solution varied. Silicic acid is comparable in regard to the ability of the solution to clean the plate with minimum number of sheets...

Characterization of novel vanadium(III)/acetate clusters formed in aqueous solution

Fry, Fiona; Dougan, Brenda; McCann, Nichola; Zeigler, Christopher; Brasch, Nicola
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
567.53902%
We report the first structures of simple acetate complexes of vanadium(III) formed in aqueous solution. Paramagnetic 1H NMR spectroscopy titration experiments indicate the formation of two major V(III)/acetate complexes in acidic aqueous solution for acetate/V(III) ≤4, pD 3.50. A novel tetranuclear cluster and a trinuclear cluster have been characterized by X-ray diffraction studies. Mass spectrometry measurements show these clusters retain their integrity in solution.

Near-infrared chemiluminescence from the oxidation of ammonia in aqueous alkaline solution

Francis, Paul; Barnett, Neil; Smith, Trevor; Spizzirri, Paul; Wang, Xue Qin; Krausz, Elmars
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
564.2842%
The chemiluminescent oxidation of ammonia with hypobromite in aqueous alkaline solution evokes a broadly distributed emission in the near-infrared region, with intensity maxima at 1055 nm and 1270 nm.

Influence of gadolinium on the microstructure and mechanical properties of steel and stainless steel

Khan,Z
Fonte: Journal of the Southern African Institute of Mining and Metallurgy Publicador: Journal of the Southern African Institute of Mining and Metallurgy
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2012 EN
Relevância na Pesquisa
473.79234%
Iron, in the form of steel and stainless steel, is the most commonly used metal in the world. Plain steels corrode and oxidize easily, while stainless steels exhibit improved corrosion and oxidation resistance. It has been found that rare earth metal (REM) additions, such as cerium and erbium, result in the improvement of the abovementioned properties in iron-containing compounds. Gadolinium is a REM, however, there is very little information available on the influence of gadolinium on the microstructure and mechanical properties of iron-containing compounds. Thus, the purpose of this research project was to determine the influence of gadolinium additions on the microstructure and mechanical properties of mild steel and 316 stainless steel. Ten alloys were produced for the purposes of this research. Five of the alloys had a base composition of mild steel while the remaining five had base composition of 316 stainless steel. The alloys for each of the base composition contained gadolinium additions of 0.1, 0.5, 1.2, and 5 weight per cent. The as-cast and the cold-rolled alloys were analysed. The alloys responded well to the cold-rolling with the exception of the 5 weight per cent gadolinium mild steel and stainless steel alloys. These alloys were extremely brittle and underwent a significant amount of cracking during the cold rolling process. A microstructural analysis of the alloys was conducted using a light optical microscope...