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Soil flushing of cresols contaminated soil: application of nonionic and ionic surfactants under different pH and concentrations

Gitipour, Saeid; Narenjkar, Khadijeh; Sanati Farvash, Emad; Asghari, Hossein
Fonte: BioMed Central Publicador: BioMed Central
Tipo: Artigo de Revista Científica
Publicado em 11/11/2014 EN
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In this study, the viability of soil flushing on the removal of cresols (meta-, ortho-, and para-cresols) from contaminated soil has been investigated. High production and distribution of cresols in the environment indicate their potential for a widespread exposure to humans. The presence of these compounds in soil could cause a significant threat to environment, as they are toxic and refractory in nature. Cresols are persistent chemicals which are classified by the United State Environmental Protection Agency (U.S.EPA) as Group C, possible human carcinogens. Soil flushing is one of the soil remediation technologies which could by applied for treatment of hydrocarbon contaminated soil. Flushing of the contaminated soil samples was carried out by using sodium dodecyl sulfate (SDS) and Triton X-100 surfactant solutions at the concentrations of 0.1%, 0.2%, 0.3%, and 0.4% (W/W). Three acidic, neutral, and alkaline environments were utilized by adjusting pH of the washing solutions at 3, 7 and 12 to evaluate the effect of washing environment in removing cresols. The results of this research denote that the highest removal efficiencies of 79.6% and 83.51% were achieved for m-cresol and total o- and p-cresols, respectively, under the alkaline environment of pH12 at 0.4% (W/W) SDS concentration. Regarding performance of Triton X-100...

Polyelectrolyte multilayers : nanofabricated architectures for bio-interface materials

Mendelsohn, Jonas Daniel, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 135 p.; 14268994 bytes; 14268753 bytes; application/pdf; application/pdf
ENG
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The layer-by-layer process, whereby aqueous solutions of oppositely charged polymers are alternately and repeatedly deposited onto a substrate, has emerged in recent years as a promising approach for creating thin films with nanoscale control of structure, composition, and surface properties. Applications ranging from surface modification to optical and electronic devices have arisen from the versatility of this nanocomposite fabrication technique. The additional ability to assemble into films a wide variety of biological entities, such as enzymes and DNA, has expanded the use of polyelectrolyte multilayers for biosensor and other biomaterials applications. This thesis further explores the rationale of using multilayers as biomaterials, with particularly emphasis on the importance of the underlying molecular architecture. Many of the results presented here concern films assembled from weak polyions, i.e., ones with pH-dependent charge densities, including poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH). Using weak polyions enables the creation of thin films with chemical and structural properties controlled with nanoscale precision by simply adjusting the pH of the polymer solutions. Under certain assembly conditions...

Anisotropic and tunable characteristics of the colloidal behavior of metal oxide surfaces

Bullard, Joseph Warren, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 128 p.
ENG
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The electroosmotic behavior of the rutile polymorph of titanium dioxide was explored as a function of crystallographic orientation. Atomic force microscopy (AFM) was employed to make high-resolution force spectroscopy measurements between a silica sphere attached to a traditional, contact-mode AFM cantilever and TiO2 (110), (100), and (001) surfaces in aqueous solutions. Measurements were taken in a variety of solution conditions across a broad range of pH values, and the resultant force-distance curves were used to deduce relative behaviors of each orientation of rutile, with particular interest in changes of the isoelectric point (iep). Differences in iep as a function of orientation are explained in terms of differences in both the coordination number and density of (Lewis) acidic and basic sites on the surface. The results were supported by angle-resolved X-ray photoelectron spectroscopy (XPS) measurements of a nominal monolayer of palladium metal deposited on each of the three orientations studied. The palladium monolayer served as a means of probing the relative electron affinities of the three surfaces studied, which was exhibited in shifts of the palladium XPS peak that corresponded to differences in binding energy as a function of substrate orientation.; (cont.) The correlation between rutile orientation and shift in palladium binding energy corresponded directly to the relationship between isoelectric point and orientation...

Obtenção de polímeros graftizados de quitosana e estudo das propriedades físico-químicas para aplicação na indústria do petróleo

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: Tese de Doutorado Formato: application/pdf
POR
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Chitosan is a biopolymer derived from the shells of crustaceans, biodegradable, inexpensive and renewable with important physical and chemical properties. Moreover, the different modifications possible in its chemical structure generate new properties, making it an attractive polysaccharide owing to its range of potential applications. Polymers have been used in oil production operations. However, growing concern over environmental constraints has prompted oil industry to search for environmentally sustainable materials. As such, this study sought to obtain chitosan derivatives grafted with hydrophilic (poly(ethylene glycol), mPEG) and/or hydrophobic groups (n-dodecyl) via a simple (one-pot) method and evaluate their physicochemical properties as a function of varying pH using rheology, small-angle Xray scattering (SAXS), dynamic light scattering (DLS) and zeta potential. The chitosan derivatives were prepared using reductive alkylation under mild reaction conditions and the chemical structure of the polymers was characterized by nuclear magnetic resonance (1H NMR) and CHN elemental analysis. Considering a constant mPEG/Chitosan molar ratio on modification of chitosan, the solubility of the polymer across a wide pH range (acidic, neutral and basic) could only be improved when some of the amino groups were submitted to reacetylation using the one-pot method. Under these conditions...

Adsor??o de cromo (VI) por carv?o ativado granular de solu??es dilu?das utilizando um sistema batelada sob pH controlado

SOUZA, Renata dos Santos; CARVALHO, Samira Maria Le?o de; GARCIA J?NIOR, M?rcio Ronald de Lima; SENA, Rafael dos Santos Fernandes
Fonte: Universidade Federal do Pará Publicador: Universidade Federal do Pará
Tipo: Artigo de Revista Científica
POR
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Na Amaz?nia o cromo ? empregado principalmente na ind?stria de couro e de madeira, sendo respons?vel por v?rios problemas de sa?de porque ? t?xico para os seres vivos. A remo??o de cromo de efluentes industriais ? feita por meio de diversos processos como a adsor??o. Este trabalho mostra os resultados da adsor??o de Cr(VI) por carv?o ativado granular comercial (CAG) como adsorvente de solu??es dilu?das empregando um sistema de adsor??o batelada com controle de pH. Os grupos funcionais da superf?cie do CAG foram determinados pelo m?todo de Boehm. Al?m disso, o efeito do pH na adsor??o de Cr(VI), o equil?brio e a cin?tica de adsor??o foram estudados nas condi??es experimentais (pH = 6, MA = 6g, tempo de adsor??o 90min.). Na superf?cie do CAG, os grupos carbox?licos foram determinados em maior concentra??o (MAS=0,43 mmol/gCAG), estes, presentes em concentra??es elevadas aumentam a adsor??o do metal, principalmente em valores de pH ?cidos. A capacidade de adsor??o ? dependente do pH da solu??o, devido a sua influ?ncia nas propriedades de superf?cie do CAG e nas diferentes formas i?nicas das solu??es de Cr(VI). Os dados de equil?brio da adsor??o foram ajustados satisfatoriamente pela isoterma de Langmuir (R2=0,988), tipo favor?vel. A partir da cin?tica de adsor??o a 5mg/L e 20mg/L...

Surface roughness of orthodontic band cements with different compositions

Sande, Fran??oise H??l??ne van de; Silva, Adriana Fernandes da; Michelon, Douver; Piva, Evandro; Cenci, Maximiliano S??rgio; Demarco, Fl??vio Fernando
Fonte: Journal of Applied Oral Science/Scielo Publicador: Journal of Applied Oral Science/Scielo
Tipo: Artigo de Revista Científica
EN_US
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Objectives: The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions. Material and Methods: Eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP), compomer (C), resin-modified glass ionomer cement (RMGIC) and resin cement (RC). Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0) or 0.1 M lactic acid solution (pH 4.0) for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200) before and after the storage period. Data were analyzed by two-way ANOVA and Tukey???s test (comparison among cements and storage solutions) or paired t-test (comparison before and after the storage period) at 5% significance level. Results: The values for average surface roughness were statistically different (p<0.001) among cements at both baseline and after storage. The roughness values of cements in a decreasing order were ZP>RMGIC>C>R (p<0.001). After 15 days, immersion in lactic acid solution resulted in the highest surface roughness for all cements (p<0.05), except for the RC group (p>0.05). Compared to the current threshold (0.2 ??m) related to biofilm accumulation, both RC and C remained below the threshold...

Mesure de la concentration en métaux traces dans la solution de sol par microlysimétrie

Duquette, Marie-Claude
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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La présente étude porte sur l’évaluation d’une méthode d’acquisition de la solution de sol présente à l’interface sol-racine, dans la rhizosphère. Cette interface constitue le lieu privilégié de prise en charge par les plantes des contaminants, tels que les métaux traces. Comme les plantes acquièrent ces éléments à partir de la phase liquide, la solution de sol de la rhizosphère est une composante clé pour déterminer la fraction de métaux traces biodisponibles. La microlysimétrie est la méthode in situ la plus appropriée pour aborder les difficultés liées à l’échelle microscopique de la rhizosphère. Ainsi, dans les études sur la biodisponibilité des métaux traces au niveau de la rhizosphère, les microlysimètres (Rhizon©) gagnent en popularité sans, toutefois, avoir fait l’objet d’études exhaustives. L’objectif de cette étude est donc d’évaluer la capacité de ces microlysimètres à préserver l’intégrité chimique de la solution, tout en optimisant leur utilisation. Pour ce faire, les microlysimètres ont été soumis à une série d’expériences en présence de solutions et de sols, où la quantité de solution prélevée et le comportement des métaux traces (Cd, Cu, Ni...

Lanthanide Complexes of Bifunctional Chelates as pH and Ca2+ Sensitive Contrast Agents for MR Imaging. Design, Synthesis and Characterization; Lanthanoidkomplexe von funktionalisierten Chelaten als pH- und Ca2+- abhängige Kontrastmittel für die Magnetresonanz-Bildgebung. Design, Synthese und Charakterisierung

Mammadov, Ilgar
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
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A series of gadolinium based complexes have been designed, synthesized and characterized. Finally in vivo investigations of the compounds have been preformed by combined electrophysiological and fMRI methods. Acyclic bifunctional chelating agents were synthesized by two different ways starting from the dimethylester of nitro- or aminoisophtalic acid. Complexes with gadolinium and europium were obtained and relaxivities were measured at 300 MHz and 25oC. The very poor solubility of the complexes in water and most organic solvents indicate the formation of di- or polymer chains upon the complexation. This makes the complexes useless for further investigations as MRI contrast agents. Although the amino derivative can be modified and used as a building blocks in the syntheses of the specific chelators. The second set of compounds was designed to be sensitive to changes of pH. Protected and unprotected phosphonates were used to study the effect of the charge and acidity of the complexes on the relaxivity. Thermodynamic investigations of the ligands have been performed using glass-electrode potentiometric titrations and protonation constants of the phosphonates as well as stability constants of the ligand-calcium(II) complexes (as model for the stability of gadolinium(III) complexes) have been determined. pK values of the phosphonic functional groups increase with increase of the chain length of the pendant arm. The reverse behavior was observed for the second protonation constant of the nitrogen atom of the cyclen rim. Relaxometric measurements of the gadolinium(III) complexes have been performed at various magnetic fields (20...

The determination of sinigrin in Brassica, and investigations into the use of allyl-isothiocyanate as a nematicide

Zawadzki, Michael A.
Fonte: Brock University Publicador: Brock University
Tipo: Electronic Thesis or Dissertation
ENG
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The goal of this thesis was to study factors related to the development of Brassica juncea as a sustainable nematicide. Brassica juncea is characterized by the glycoside (glucosinolate) sinigrin. Various methods were developed for the determination of sinigrin in Brassica juncea tissue extracts. Sinigrin concentrations in plant tissues at various stages of growth were monitored. Sinigrin enzymatically breaks down into allylisothiocyanate (AITC). AITC is unstable in aqueous solution and degradation was studied in water and in soil. Finally, the toxicity of AITC against the root-lesion nematode (Pratylenchus penetrans) was determined. A method was developed to extract sinigrin from whole Brassica j uncea tissues. The optimal time of extraction wi th boiling phosphate buffer (0.7mM, pH=6.38) and methanol/water (70:30 v/v) solutions were both 25 minutes. Methanol/water extracted 13% greater amount of sinigrin than phosphate buffer solution. Degradation of sinigrin in boiling phosphate buffer solution (0.13%/minute) was similar to the loss of sinigrin during the extraction procedure. The loss of sinigrin from boiling methanol/water was estimated to be O.Ol%/minute. Brassica juncea extract clean up was accomplished by an ion-pair solid phase extraction (SPE) method. The recovery of sinigrin was 92.6% and coextractive impurities were not detected in the cleaned up extract. Several high performance liquid chromatography (HPLC) methods were developed for the determination of sinigrin. All the developed methods employed an isocratic mobile phase system wi th a low concentration of phosphate buffer solution...

Acetilacetona, diacetamida e N-(2-piridil)-acetamida imobilizadas na superficie de silica gel - preparação, caracterização, adsorção, termoquimica e espectroscopia de complexos suportados

Edesio Fernandes da Costa Alcantara
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 31/12/1993 PT
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Os ligantes acetilacetona(ac), diacetamida(da) e N-(2-piridil)acetamida(pa) foram imobilizados sobre a superfície da sílica gel obtendo-se os produtos Si-ac, Si-da e Sipa, respectivamente. Estes materiais foram caracterizados por análise elementar, espectroscopia no infravermelho, medida de área superficial, RMN-C no estado sólido, termogravimetria e calorimetria exploratória diferencial. As análises elementares indicaram a presença de 0,616; 0,286 e 0,345 mmol de ac, da e pa ligados por grama de sílica. Os materiais funcionalizados foram equilibrados com soluções de cloretos divalentes Co, Cu, Ni, Zn, Cd e Hg em etanol e acetona e Cr(VI) em meio ácido à 298K. A adsorção destes íons seguem o modelo da Equação de Langmuir, a qual foi usada para determinar a capacidade máxima(N)(molg) e a intensidade de adsorção(K' )(lmol). Os valores de N mostraram que para um determinado cátion metálico, a adsorção em acetona foi sempre maior que em etanol, como mostram as sequências: Si-da: Cu>Co>Zn em acetona e Cd>Hg>Zn>Ni>Co>Cu em etanol; Si-pa: Cu>Co>Zn em acetona e HgCdZn>Co>Cu>Ni em etanol; Si-ac: Cu>Co>Zn em acetona e Hg>Cd>Cu>Co>Zn>Ni em etanol. A adsorção de Cr(VI) nas três superfícies segue a ordem de funcionalização. As titulações calorimétricas das suspensões das superfícies funcionallizadas com as soluções catiônicas em etanol e acetona resultaram em isotermas que obedecem à Equação de Langmuir modificada. A linearização destas isotermas possibilitou a determinação dos parâmetros termoquímicos Ke...

Decolorization of aqueous effluents using agro waste

Apostol, L.; Pereira, Luciana; Alves, M. M.; Gavrilescu, Maria
Fonte: Institutul Politehnic din Iasi Publicador: Institutul Politehnic din Iasi
Tipo: Artigo de Revista Científica
Publicado em /03/2012 ENG
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In this study, the potential of agrowaste for a food dye sequestration from aqueous effluents was investigated. Initially, four local agrowaste waste namely pumpkin seed hull, bean null, oat straw and nut shells, were tested in natural condition. Bean hull (BH) revealed the best uptake capacity for Food Red 14 (FR14). The agro waste was characterised before and after dye sorption process using SEM and FTIR techniques. Those analyses were conducted in order to identify the principal connections contributing to the sorption process. The point of zero charge of BH surface, pHpzc was assessed at 4.6, which indicated a mostly acidic surface, favorable for dye adsorption at pH<6, when the sorbent is positively charged. The dye removal efficiency of the adsorbent has been established in relation to some factors, such as: pH, amount of adsorbent, dye initial concentration, contact time and temperature. In order to make the sorption process predictable, four empirical isotherms and four kinetics models were applied to the experimental data so as to enact the nature of the sorption process. Attempts have also been made for sorbent viability by testing different solvents for FR14 desorption. FTIR spectra reveal the main bands in FR14 sorption process: that at 1450 cm-1 corresponding to C=C bond from the aromatic ring appears greatly diminished for FR14-BH after the sorption process and suggests a horizontal orientation of the molecules. The movement of the band at 3442 cm-1...

Preparation of solid dispersions of nonsteroidal anti-inflammatory drugs with acrylic polymers and studies on mechanisms of drug-polymer interactions

Pignatello, Rosario; Ferro, Marinella; Puglisi, Giovanni
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em 20/03/2002 EN
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This work studied the mechanisms of interaction between Eudragit RS100 (RS) and RL100 (RL) polymers with 3 nonsteroidal anti-inflammatory drugs: diflunisal (DIF), flurbiprofen (FLU), and piroxicam (PIR). Solid dispersions of polymers and drugs at different weight ratios were prepared by coevaporation of their ethanol solutions. The resulting coevaporates were characterized in the solid state (Fourier-transformed infrared spectroscopy (FT-IR) IR, differential scanning calorimetry, powder-x-ray diffractometry) as well as by studying the in vitro drug release in a gastroenteric environment. Absorption tests from drug solutions to the solid polymers were also performed to better explain the mechanism of interactions between them. The preparative conditions did not induce changes in the crystalline state of the drugs (amorphization or polymorphic change). Drugs strongly interacted with the ammonium groups present in polymers, giving an electrostatic interaction that reinforced the mere physical dispersion of drug molecules within polymer networks. Such interactions are related to the chemical structure of the drugs and to their dissociated or undissociated state. The dispersion of drugs in the polymer matrices strongly influenced their dissolution rate...

Bicarbonate conductance and pH regulatory capability of cystic fibrosis transmembrane conductance regulator.

Poulsen, J H; Fischer, H; Illek, B; Machen, T E
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 07/06/1994 EN
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The cystic fibrosis transmembrane conductance regulator (CFTR) is an epithelial Cl- channel regulated by protein kinase A. The most common mutation in cystic fibrosis (CF), deletion of Phe-508 (delta F508-CFTR), reduces Cl- secretion, but the fatal consequences of CF have been difficult to rationalize solely in terms of this defect. The aim of this study was to determine the role of CFTR in HCO3- transport across cell membranes. HCO3- permeability was assessed from measurements of intracellular pH [pHi; from spectrofluorimetry of the pH-sensitive dye 2',7'-bis(2-carboxyethyl)-5-(and -6)carboxyfluorescein] and of channel activity (patch clamp; cell attached and isolated, inside-out patches) on NIH 3T3 fibroblasts and C127 mammary epithelial cells transfected with wild-type CFTR (WT-CFTR) or delta F508-CFTR, and also on mock-transfected cells. When WT-CFTR-transfected cells were acidified (pulsed with NH4Cl) and incubated in Na(+)-free (N-methyl-D-glucamine substitution) solutions (to block Na(+)-dependent pHi regulatory mechanisms), pHi remained acidic (pH approximately 6.5) until the cells were treated with 20 microM forskolin (increases cellular [cAMP]); pHi then increased toward (but not completely to) control level (pHi 7.2) at a rate of 0.055 pH unit/min. Forskolin had no effect on rate of pHi recovery in delta F508 and mock-transfected cells. This Na(+)-independent...

SOME PHYSICOCHEMICAL PROPERTIES OF DISSOCIATED SPONGE CELLS

Galtsoff, P. S.; Pertzoff, Vladimir
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 20/11/1926 EN
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1. The activity of the hydrogen ion, in a system containing 0.00280 mols of NaAc, 0.520 mols of NaCl per liter, and varied amounts of HCl or NaOH has been investigated. The average value of pK' for acetic add in this system is about 4.37. 2. The effect of the addition of various amounts of HCl and NaOH to a system containing 0.00280 mols of NaAc, 0.520 mols of NaCl, and a known number of cells of either Microciona prolifera or Cliona celata was then studied. It was found that in weak acid solutions Microciona behaves as a stronger base than Cliona, the former being practically saturated with base at a pH of 7.5. Similar behavior is shown by suspensions of cells to which no acid or base was added: the cells of Cliona are more acidic than the cells of Microciona. 3. The microscopic examinations of the cells subjected to the treatment with acid or base indicate that the cells of Microciona remain alive down to pH 4.50; the cells of Cliona sustain greater acidity,— a,t pH 3.7 they exhibit no signs of cytolysis. Tests for aggregation of these cells showed that this phenomenon is greatly inhibited even by slightly acid solutions. 4. The conclusion is drawn that the concentration of cells being equal, the suspensions of cells of Microciona and Cliona differ from each other in their physicochemical properties...

The Effect of Different Storage Conditions on the Physical Properties of Pigmented Medical Grade I Silicone Maxillofacial Material

Al-Dharrab, Ayman A.; Tayel, Seham B.; Abodaya, Mona H.
Fonte: Hindawi Publishing Corporation Publicador: Hindawi Publishing Corporation
Tipo: Artigo de Revista Científica
Publicado em 28/03/2013 EN
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Objective. This study aimed to evaluate the effect of different storage solutions that simulate acidic, alkaline, and sebum conditiions on the physical properties of pigmented (colorant elastomer) cosmesil M511 maxillofacial prosthetic material. Materials and Methods. Sixty specimens were prepared according to the manufacturer's instructions and were tested before and after immersion of different storage conditions for six months at 37 °C. The following tests were performed: color changes (group I), solution absorption (group II), surface roughness (group III), and scanning electron microscopy (group IV). Results. There were no significant changes observed in the color and solution absorption tests while surface roughness revealed significant difference between control group and other testing storage medium groups, and this result was supported by SEM analysis that revealed limited surface changes. Conclusions. Cosmaseil material is an acceptable cross-linked formulation that withstands storage in different solutions with variable pH. The addition of pigment cannot vary the physical properties of these materials. Surface roughness test as well as SEM microscopic study showed moderate changes indicating a limited effect on the surface of the material.

Surface roughness of orthodontic band cements with different compositions

Sande,Françoise Hélène van de; Silva,Adriana Fernandes da; Michelon,Douver; Piva,Evandro; Cenci,Maximiliano Sérgio; Demarco,Flávio Fernando
Fonte: Faculdade De Odontologia De Bauru - USP Publicador: Faculdade De Odontologia De Bauru - USP
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2011 EN
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OBJECTIVES: The present study evaluated comparatively the surface roughness of four orthodontic band cements after storage in various solutions. MATERIAL AND METHODS: Eight standardized cylinders were made from 4 materials: zinc phosphate cement (ZP), compomer (C), resin-modified glass ionomer cement (RMGIC) and resin cement (RC). Specimens were stored for 24 h in deionized water and immersed in saline (pH 7.0) or 0.1 M lactic acid solution (pH 4.0) for 15 days. Surface roughness readings were taken with a profilometer (Surfcorder SE1200) before and after the storage period. Data were analyzed by two-way ANOVA and Tukey's test (comparison among cements and storage solutions) or paired t-test (comparison before and after the storage period) at 5% significance level. RESULTS: The values for average surface roughness were statistically different (p<0.001) among cements at both baseline and after storage. The roughness values of cements in a decreasing order were ZP>RMGIC>C>R (p<0.001). After 15 days, immersion in lactic acid solution resulted in the highest surface roughness for all cements (p<0.05), except for the RC group (p>0.05). Compared to the current threshold (0.2 µm) related to biofilm accumulation, both RC and C remained below the threshold...

Adsorción de Cu(II) y Zn(II) desde soluciones acuosas ácidas mediante silicatos de calcio y magnesio nano-estructurados y microcápsulas poliméricas contenedoras de extractantes no-específicos

Yáñez Bellido, Sebastián Andrés
Fonte: Universidad de Chile Publicador: Universidad de Chile
Tipo: Tesis
ES
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Memoria para optar al título de Químico; En la presente Memoria de Titulo se desarrolló el estudio de la remoción de los metales pesados Cu(II) y Zn(II) desde soluciones acuosas que simulan aguas ácidas de minas, mediante dos metodologías distintas de adsorción, la microencapsulación de extractantes orgánicos no-específicos y el uso de los silicatos de calcio y magnesio nanoestructurados. La síntesis de las microcápsulas se desarrollo mediante el método de polimerización radicalaria in situ empleando como monómeros estireno y etilenglicol-dimeta-acrilato y como extractantes los compuestos PC-88A (un ácido alquilfosfónico) y LIX-860 N-IC (una hidroxioxima quelante). Los silicatos de calcio y magnesio nanoestructurados se sintetizaron siguiendo una ruta sencilla y económica en base a la reacción de una solución de silicato de sodio y los hidróxidos de calcio y magnesio, respectivamente. Ambos tipos de adsorbentes fueron caracterizados física y químicamente, empleando diferentes metodologías, entre ellas, las de microscopía electrónica de barrido, análisis de porosimetría, tamaño de partículas, difracción de rayos X y la determinación de los contenidos de extractantes en las microcápsulas. Posteriormente se realizaron diversos experimentos de adsorción de los iones metálicos Cu(II) y Zn(II) desde soluciones acuosas con ambos tipos de adsorbentes...

Estudio de Remoción y/o Recuperación de Cobre y Cinc desde Soluciones Acuosas Ácidas Mediante Microencapsulación de Extractantes no Específicos Mediante Polimerización Radicalaria in Situ

Canales Vera, Juan Patricio
Fonte: Universidad de Chile; Programa Cybertesis Publicador: Universidad de Chile; Programa Cybertesis
Tipo: Tesis
ES
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Memoria para optar al título de Químico; En esta Memoria de Título se estudió la recuperación de cobre y cinc desde soluciones acuosas ácidas que simulan drenajes ácidos de mina y aguas residuales industriales, mediante la metodología de microencapsulación de extractantes no específicos. Las microcápsulas se prepararon mediante polimerización in situ en suspensión vía radicales libres, empleando en la conformación de la matriz polimérica una proporción de divinilbenceno-estireno previamente establecida. Se inmovilizó en ellas distintos tipos de extractantes incluyendo los compuestos de tipo ácido-fosforados PC-88A y D2EHPA, el compuesto quelante LIX 84-I, los extractantes básicos intercambiadores de aniones Aliquat 336, Alamine 336 y TOA y los compuestos neutros solvatantes TOPO y TBP. El estudio se dividió en dos partes: 1) Microencapsulación del extractante PC-88A, cuya síntesis resultó ser sencilla y de alta eficiencia, aumentando el rendimiento a medida que se incrementa el contenido de extractante. Se observó además que al aumentar la velocidad de agitación en el reactor se reducía el tamaño de las microesferas obtenidas. La determinación del extractante encapsulado fue efectuada por titulación potenciométrica y la caracterización física de las microesferas se realizó...

Desordem de spins, anisotropia magnética e magneto-ótica de nanopartículas de ferrita; Desordre de spins, anisotrope magnetique et magneto-optique de nanoparticules de ferrites

Sousa, Eduardo Carvalho
Fonte: Universidade de Brasília Publicador: Universidade de Brasília
Tipo: Tese
POR
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Tese (doutorado)—Universidade de Brasília, Instituto de Física, 2007.; Investigamos neste trabalho a desordem de spins, a anisotropia magnética e magneto-ótica de nanopartículas de ferrita utilizadas na elaboração de líquidos magnéticos. As nanopartículas de ferrita obtidas por síntese química hidrotérmica em meio alcalino são peptizadas em meio aquoso ácido graças a uma estratégia do tipo núcleo-superficie, que previne a dissolução das partículas. Entretanto a sua composição química não é homogênea e pode ser descrita como um núcleo de ferrita estequiométrica envolto por uma camade de superfície de composição media Fe3O4. A fração volumétrica em partículas e a espessura da camada superficial foram determinadas a partir das dosagens químicas. Medidas a temperatura ambiente de magnetização, birrefringência magneto-ótica e rotação Faraday foram utilizadas para caracterizar a distribuição em tamanhos das partículas. Medidas de magnetização em função da temperatura permitiram distinguir entre o núcleo monodomínio magneticamente organizado e uma camada superficial cujos spins congelam a muito baixa temperatura em uma estrutura do tipo vidro de spin. Medidas de espectroscopia Mössbauer em presença de campo aplicado mostraram...

Sulfur-bearing phases detected by evolved gas analysis of the Rocknest aeolian deposit, Gale Crater, Mars

McAdam, Amy C.; Franz, Heather B.; Sutter, Brad; Archer, Paul D., Jr.; Freissinet, Caroline; Eigenbrode, Jennifer L.; Ming, Douglas W.; Atreya, Sushil K.; Bish, David L.; Blake, David F.; Bower, Hannah E.; Brunner, Anna; Buch, Arnaud; Glavin, Daniel P.; G
Fonte: American Geophysical Union Publicador: American Geophysical Union
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /02/2014
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The Sample Analysis at Mars (SAM) instrument suite detected SO_2, H_(2)S, OCS, and CS_2 from ~450 to 800°C during evolved gas analysis (EGA) of materials from the Rocknest aeolian deposit in Gale Crater, Mars. This was the first detection of evolved sulfur species from a Martian surface sample during in situ EGA. SO_2 (~3–22 µmol) is consistent with the thermal decomposition of Fe sulfates or Ca sulfites, or evolution/desorption from sulfur-bearing amorphous phases. Reactions between reduced sulfur phases such as sulfides and evolved O_2 or H_(2)O in the SAM oven are another candidate SO_2 source. H_(2)S (~41–109 nmol) is consistent with interactions of H_(2)O, H_2 and/or HCl with reduced sulfur phases and/or SO2 in the SAM oven. OCS (~1–5 nmol) and CS2 (~0.2–1 nmol) are likely derived from reactions between carbon-bearing compounds and reduced sulfur. Sulfates and sulfites indicate some aqueous interactions, although not necessarily at the Rocknest site; Fe sulfates imply interaction with acid solutions whereas Ca sulfites can form from acidic to near-neutral solutions. Sulfides in the Rocknest materials suggest input from materials originally deposited in a reducing environment or from detrital sulfides from an igneous source. The presence of sulfides also suggests that the materials have not been extensively altered by oxidative aqueous weathering. The possibility of both reduced and oxidized sulfur compounds in the deposit indicates a nonequilibrium assemblage. Understanding the sulfur mineralogy in Rocknest materials...