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Agregação de cadeias de acetatos de celulose em LiCl/DMAc: avaliação via viscosimetria; Aggregation of chains of cellulose acetates in LiCl/DMAc: evaluation via viscometry

MORGADO, Daniella L.; MARTINS, Virginia da C. A.; PLEPIS, Ana M. de G.; FROLLINI, Elisabete
Fonte: Associação Brasileira de Polímeros Publicador: Associação Brasileira de Polímeros
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
455.49594%
Celulose de linter foi acetilada, visando obter acetatos de celulose com diferentes Graus de Substituição (GS) em meio homogêneo, usando cloreto de lítio/N,N-dimetilacetamida (LiCl/DMAc) como sistema de solvente, e anidrido acético como reagente acetilante. A agregação entre cadeias de celulose ou acetatos de celulose (GS 0,8, 1,5 e 2,0) em solução foi avaliada através de medidas viscosimétricas. Os resultados mostraram que a formação de agregados no sistema de solvente utilizado (LiCl/DMAc) é diferente para celulose e acetatos, e dependente da temperatura e do GS, no caso dos acetatos. Este trabalho corresponde à primeira etapa de um estudo em que se pretende preparar filmes de acetatos, assim como de acetatos reforçados com celulose, diretamente a partir de soluções destes em LiCl/DMAc. Os resultados apresentados permitem uma escolha melhor embasada do intervalo de concentração mais adequado para preparação de filmes, a partir de soluções de acetatos e celulose nesse sistema de solvente.; Linters cellulose was acetylated to obtain cellulose acetates with different degrees of substitution (DS) in homogeneous medium, using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) as solvent system, and acetic anhydride as acetylating agent. The aggregation among chains of cellulose or cellulose acetates (DS 0.8...

Design, construction and evaluation of a simple pressurized solvent extraction system

PINTO, J. S. S.; LANÇAS, F. M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
373.3316%
This work describes the construction and testing of a simple pressurized solvent extraction (PSE) system. A mixture of acetone:water (80:20), 80 ºC and 103.5 bar, was used to extract two herbicides (Diuron and Bromacil) from a sample of polluted soil, followed by identification and quantification by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The system was also used to extract soybean oil (70 ºC and 69 bar) using pentane. The extracted oil was weighed and characterized through the fatty acid methyl ester analysis (myristic (< 0.3%), palmitic (16.3%), stearic (2.8%), oleic (24.5%), linoleic (46.3%), linolenic (9.6%), araquidic (0.3%), gadoleic (< 0.3%), and behenic (0.3%) acids) using high-resolution gas chromatography with flame ionization detection (HRGC-FID). PSE results were compared with those obtained using classical procedures: Soxhlet extraction for the soybean oil and solid-liquid extraction followed by solid-phase extraction (SLE-SPE) for the herbicides. The results showed: 21.25 ± 0.36% (m/m) of oil in the soybeans using the PSE system and 21.55 ± 0.65% (m/m) using the soxhlet extraction system; extraction efficiency (recovery) of herbicides Diuron and Bromacil of 88.7 ± 4.5% and 106.6 ± 8.1%...

Sisal, sugarcane bagasse and microcrystalline celluloses: Influence of the composition of the solvent system N,N-dimethylacetamide/lithium chloride on the solubility and acetylation of these polysaccharides

CIACCO, Gabriela T.; ASS, Beatriz A. P.; RAMOS, Ludmila A.; FROLLINI, Elisabete
Fonte: EUROPEAN POLYMER FEDERATION Publicador: EUROPEAN POLYMER FEDERATION
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
463.4239%
The present work describes an investigation concerning the acetylation of celluloses extracted from short-life-cycle plant sources (i.e. sugarcane bagasse and sisal fiber) as well as microcrystalline cellulose. The acetylation was carried out under homogeneous conditions using the solvent system N,N-dimethylacetamide/lithium chloride. The celluloses were characterized, and the characterizations included an evaluation of the amount of hemicellulose present in the materials obtained from lignocellulosics sources (sugarcane and sisal). The amount of LiCl was varied and its influence on the degree of acetate substitution was analyzed. It was found that the solvent system composition and the nature of the cellulose influenced both the state of chain dissolution and the product characteristics. The obtained results demonstrated the importance of developing specific studies on the dissolution process as well as on the derivatization of celluloses from various sources.

Distinct conformational properties determined by implicit and explicit representation of protein-solvent interactions. An analytical and computer simulation study

ROCHA, L. F. O.; SILVA, I. R.; CALIRI, A.
Fonte: ELSEVIER SCIENCE BV Publicador: ELSEVIER SCIENCE BV
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
468.30527%
In the protein folding problem, solvent-mediated forces are commonly represented by intra-chain pairwise contact energy. Although this approximation has proven to be useful in several circumstances, it is limited in some other aspects of the problem. Here we show that it is possible to achieve two models to represent the chain-solvent system. one of them with implicit and other with explicit solvent, such that both reproduce the same thermodynamic results. Firstly, lattice models treated by analytical methods, were used to show that the implicit and explicitly representation of solvent effects can be energetically equivalent only if local solvent properties are time and spatially invariant. Following, applying the same reasoning Used for the lattice models, two inter-consistent Monte Carlo off-lattice models for implicit and explicit solvent are constructed, being that now in the latter the solvent properties are allowed to fluctuate. Then, it is shown that the chain configurational evolution as well as the globule equilibrium conformation are significantly distinct for implicit and explicit solvent systems. Actually, strongly contrasting with the implicit solvent version, the explicit solvent model predicts: (i) a malleable globule...

Bond Strength of Epiphany Sealer Prepared with Resinous Solvent

RACHED-JUNIOR, Fuad Jacob Abi; SOUZA-GABRIEL, Aline Evangelista; ALFREDO, Edson; MIRANDA, Carlos Eduardo Saraiva; SILVA-SOUSA, Yara Teresinha Correa; SOUSA-NETO, Manoel Damiao
Fonte: ELSEVIER SCIENCE INC Publicador: ELSEVIER SCIENCE INC
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
371.99227%
This study evaluated in vitro the bond strength of Epiphany sealer prepared with resinous solvent of Epiphany system (Thinning resin) by using a push-out test. Forty maxillary canines were sectioned transversally below the cementoenamel junction to provide 4-mm-thick dentin disks that were centered in aluminum rings and embedded in acrylic resin. Root canals were prepared with tapered diamond bur. Intraradicular dentin was treated with 1% NaOCl for 30 minutes, 17% ethylenediaminetetraacetic acid for 5 minutes, and flushed with distilled water for 1 minute. The specimens were randomly distributed into 4 groups (n = 10) according to the filling material: GI, Epiphany without photoactivation; GII, Epiphany prepared with solvent without photoactivation; Gill, Epiphany followed by photoactivation; and GIV, Epiphany prepared with solvent followed by photoactivation. After the setting time, the specimens were submitted to the push-out test. The highest mean value (14.91 +/- 2.82 MPa) was obtained with Epiphany prepared with solvent followed by photoactivation (GIV), which was statistically different (P < .01) from the other groups. Groups I (8.15 +/- 2.47 MPa), II (9.46 +/- 2.38 MPa), and III (9.80 +/- 2.51 MPa) had inferior bond strength values and were statistically similar among themselves (P > .01). The resinous solvent of Epiphany system increased the bond strength of Epiphany sealer to dentin walls when followed by photoactivation. (J Endod 2009;35: 251-255)

Biobased films prepared from NaOH/thiourea aqueous solution of chitosan and linter cellulose

MORGADO, D. L.; FROLLINI, E.; CASTELLAN, A.; ROSA, D. S.; COMA, V.
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
460.98504%
In the present study, films based on linter cellulose and chitosan were prepared using an aqueous solution of sodium hydroxide (NaOH)/thiourea as the solvent system. The dissolution process of cellulose and chitosan in NaOH/thiourea aqueous solution was followed by the partial chain depolymerization of both biopolymers, which facilitates their solubilization. Biobased films with different chitosan/cellulose ratios were then elaborated by a casting method and subsequent solvent evaporation. They were characterized by X-ray analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), thermal analysis, and tests related to tensile strength and biodegradation properties. The SEM images of the biofilms with 50/50 and 60/40 ratio of chitosan/cellulose showed surfaces more wrinkled than the others. The AFM images indicated that higher the content of chitosan in the biobased composite film, higher is the average roughness value. It was inferred through thermal analysis that the thermal stability was affected by the presence of chitosan in the films; the initial temperature of decomposition was shifted to lower levels in the presence of chitosan. Results from the tests for tensile strength indicated that the blending of cellulose and chitosan improved the mechanical properties of the films and that an increase in chitosan content led to production of films with higher tensile strength and percentage of elongation. The degradation study in a simulated soil showed that the higher the crystallinity...

Influência dos parâmetros de solvente sobre a eficiência de quimi-excitação do sistema peróxi-oxalato; Influence of solvent parameters on the chemiexcitation efficiency of the peroxyoxalate system.

Souza Júnior, Sergio Pereira de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 11/06/2014 PT
Relevância na Pesquisa
373.75637%
Como intuito de contribuir para a elucidação do mecanismo de quimi-excitação da reação peroxi-oxalato, a transformação quimiluminescente mais eficiente conhecida que envolve a versão intermolecular do mecanismo "Chemically Initiated Electron Exchange Luminescence" - CIEEL, foram efetuados estudos cinéticos e determinados os rendimentos quânticos de quimi-excitação desta reação em diferentes solventes e misturas de solventes. A cinética da reação de oxalato de bis-2,4,6-triclorofenila com peróxido de hidrogênio, catalisada por imidazol foi estudada na presença de 9,10-difenilantraceno como ativador (ACT) em diferentes solventes. O comportamento das constantes de velocidade observados em função da polaridade e viscosidade dos solventes indica que o mecanismo dos passos iniciais desta transformação até a formação do intermediário de alta energia (IAE) não sofre modificações drásticas em função das propriedades de solventes, permitindo a escolha de solventes e misturas de solventes adequados para o estudo do mecanismo de quimi-excitação do sistema. A influência da viscosidade sobre os rendimentos quânticos singlete (Φs) e os rendimentos quânticos singlete na concentração infinita do ACT (Φs∞ - obtidos de gráficos duplo recíprocos entre os (Φs) e a [ACT]) foi estudada em misturas entre acetato de etila e ftalato dimetilico (que possuem viscosidades diferentes e parâmetros de polaridade similares...

Study of the effect of the peptide loading and solvent system in SPPS by HRMAS-NMR

Valente, A. P.; Almeida, FCL; Nakaie, C. R.; Schreier, S.; Crusca, E.; Cilli, Eduardo Maffud
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 556-563
ENG
Relevância na Pesquisa
460.98504%
The SPPS methodology has continuously been investigated as a valuable model to monitor the solvation properties of polymeric materials. In this connection, the present work applied HRMAS-NMR spectroscopy to examine the dynamics of an aggregating peptide sequence attached to a resin core with varying peptide loading (up to 80%) and solvent system. Low and high substituted BHAR were used for assembling the VQAAIDYING sequence and some of its minor fragments. The HRMAS-NMR results were in agreement with the swelling of each resin, i.e. there was an improved resolution of resonance peaks in the better solvated conditions. Moreover, the peptide loading and the attached peptide sequence also affected the spectra. Strong peptide chain aggregation was observed mainly in highly peptide loaded resins when solvated in CDCl3. Conversely, due to the better swelling of these highly loaded resins in DMSO, improved NMR spectra were acquired in this polar aprotic solvent, thus enabling the detection of relevant sequence-dependent conformational alterations. The more prominent aggregation was displayed by the VQAAIDYING segment and not by any of its intermediary fragments and these findings were also corroborated by EPR studies of these peptide-resins labelled properly with an amino acid-type spin probe. Copyright (c) 2005 European Peptide Society and John Wiley & Sons...

Evaluation of different solvent on paprika oleoresin extraction

Lemos, ALDC; Rusig, O.; Carvalho, PRN
Fonte: Inst Tecnologia Parana Publicador: Inst Tecnologia Parana
Tipo: Artigo de Revista Científica Formato: 659-667
POR
Relevância na Pesquisa
459.7069%
The best solvent for paprika oleoresin extraction was determined by comparison with a commercial oleoresin. Pigment composition was determined by HPLC. The solvent system hexane/acetone/isopropilic alcohol (3:2:1) shown to be the best for extraction of the oleoresin, giving the best yield and colour value and a chromatographic pattern identical to that of the commercial oleoresin.

Otimização multivariada para determinação direta de Ni utilizando voltametria de redissolução anodica em um sistema homogeneo de solventes; Multivariate optimization for the direct determination of Ni using anodic stripping voltammetry in a homogeneous solvent system

Gyda Marie May
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 28/06/2006 PT
Relevância na Pesquisa
459.43562%
A busca por alternativas práticas para a análise de amostras de controle de efluentes industriais resultou na modelagem e otimização de um sistema ternário homogêneo de solventes (STHS), composto por N,N-dimetilformamida (DMF), etanol e água, para a determinação de Ni por voltametria de varredura anódica com pulso diferencial (DPASV), usando acetato de amônio e HCI como eletrólitos de suporte. Como o Ni apresenta sinais DPASV nulos ou quase nulos em soluções aquosas e em misturas binárias etanol-água, foi necessário modelar e otimizar o sistema de análise como um todo, usando o planejamento estatístico multivariado "split-plot". Com a adição de N,N-dimetilformamida à mistura, observou-se um pico voltamétrico bem definido para o níquel em 250 mV. Por esses estudos, o sistema de mistura mais favorável para a determinação de níquel é composto por 80% m/m DMF, 10% m/m etanol e 10% m/m água. Sob essas condições, obteve-se uma faixa linear de resposta para a concentração entre 30 e 1000 mg L de íons níquel, com um limite de detecção calculado de 4,0 mg L, e limite de quantificação de 40 mg L. Estudos univariados adicionais mostraram que apenas cobalto e cobre interferem de maneira significativa na determinação de níquel por DPASV-STHS...

Influence of commercially available polyimide and formation conditions on the performance and structure of asymmetric polyimide organic solvent nanofiltration membranes

Lopes, Mafalda Pessoa
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2009 ENG
Relevância na Pesquisa
372.2436%
Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para a obtenção do grau de Mestre em Engenharia Química e Bioquímica; This work covers experimental and theoretical research related to the impact of the polymer structure of commercially available polyimide and polyetherimides as well as the formation conditions on the performance and structure of polyimide Organic Solvent Nanofiltration membranes. The influence in some membrane formation parameters such as polymer choice, solvent system composition, chemical crosslinking, solubility, humidity and coagulation bath temperature on the performance of PI membranes was investigated. A series of integrally skinned asymmetric membranes were prepared using different polyimide polymers, like Lenzing P84, P84 HT, Matrimid 5218 polyimide membranes and also polyetherimides membrane Ultem 1000. Non-crosslinked membranes were used to evaluate the influence of the polyimide choice and solvent system choice- DMF/1,4-Dioxane, NMP/THF and DMSO/Acetone in terms of performance and morphology. Non chemically modified membranes in DMF/1,4-Dioxane solvent system demonstrated low reproducibility. Polyimide P84 was found to generate tighter membranes with better rejection and higher flux performance than the other polyimides in study. Calculations were made to test the hypothesis that solubility parameters interaction can be a useful tool in theoretical predictions of PI OSN membranes performance and structure. Membrane formation conditions influenced membrane performance...

Design, construction and evaluation of a simple pressurized solvent extraction system

Pinto,J. S. S.; Lanças,F. M.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2009 EN
Relevância na Pesquisa
373.3316%
This work describes the construction and testing of a simple pressurized solvent extraction (PSE) system. A mixture of acetone:water (80:20), 80 ºC and 103.5 bar, was used to extract two herbicides (Diuron and Bromacil) from a sample of polluted soil, followed by identification and quantification by high-performance liquid chromatography coupled with diode array detector (HPLC-DAD). The system was also used to extract soybean oil (70 ºC and 69 bar) using pentane. The extracted oil was weighed and characterized through the fatty acid methyl ester analysis (myristic (< 0.3%), palmitic (16.3%), stearic (2.8%), oleic (24.5%), linoleic (46.3%), linolenic (9.6%), araquidic (0.3%), gadoleic (< 0.3%), and behenic (0.3%) acids) using high-resolution gas chromatography with flame ionization detection (HRGC-FID). PSE results were compared with those obtained using classical procedures: Soxhlet extraction for the soybean oil and solid-liquid extraction followed by solid-phase extraction (SLE-SPE) for the herbicides. The results showed: 21.25 ± 0.36% (m/m) of oil in the soybeans using the PSE system and 21.55 ± 0.65% (m/m) using the soxhlet extraction system; extraction efficiency (recovery) of herbicides Diuron and Bromacil of 88.7 ± 4.5% and 106.6 ± 8.1%...

A meanfield approach to the thermodynamics of a protein-solvent system with application to the oligomerization of the tumor suppressor p53

Noolandi, J.; Davison, T. S.; Völkel, A. R.; Nie, X.-F.; Kay, C.; Arrowsmith, C. H.
Fonte: The National Academy of Sciences Publicador: The National Academy of Sciences
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
455.49594%
The thermodynamic stability and oligomerization status of the tumor suppressor p53 tetramerization domain have been studied experimentally and theoretically. A series of hydrophilic mutations at Met-340 and Leu-344 of human p53 were designed to disrupt the hydrophobic dimer–dimer interface of the tetrameric oligomerization domain of p53 (residues 325–355). Meanfield calculations of the free energy of the solvated mutants as a function of interdimer distance were compared with experimental data on the thermal stability and oligomeric state (tetramer, dimer, or equilibrium mixture of both) of each mutant. The calculations predicted a decreasing stability and oligomeric state for the following amino acids at residue 340: Met (tetramer) > Ser Asp, His, Gln, > Glu, Lys (dimer), whereas the experimental results showed the following order: Met (tetramer) > Ser > Gln > His, Lys > Asp, Glu (dimers). For residue 344, the calculated trend was Leu (tetramer) > Ala > Arg, Gln, Lys (dimer), and the experimental trend was Leu (tetramer) > Ala, Arg, Gln, Lys (dimer). The discrepancy for the lysine side chain at residue 340 is attributed to the dual nature of lysine, both hydrophobic and charged. The incorrect prediction of stability of the mutant with Asp at residue 340 is attributed to the fact that within the meanfield approach...

Solubility enhancement of cox-2 inhibitors using various solvent systems

Seedher, Neelam; Bhatia, Sonu
Fonte: Springer-Verlag Publicador: Springer-Verlag
Tipo: Artigo de Revista Científica
Publicado em 05/06/2003 EN
Relevância na Pesquisa
371.3175%
This study examined the solubility enhancement of 4 cox-2 inhibitors, celecoxib, rofecoxib, meloxicam, and nimesulide, using a series of pure solvents and solvent mixtures. Water, alcohols, glycols, glycerol, and polyethylene glycol 400 (PEG 400) were used as solvents and water-ethanol, glycerol-ethanol, and polyethylene glycol-ethanol were used as mixed-solvent systems. A pH-solubility profile of drugs was obtained in the pH range 7.0 to 10.9 using 0.05M glycine-sodium hydroxide buffer solutions. Lower alcohols, higher glycols, and PEG 400 were found to be good solvents for these drugs. The aqueous solubility of celecoxib, rofecoxib, and nimesulide could be enhanced significantly by using ethanol as the second solvent. Among the mixed-solvent systems, PEG 400-ethanol system had highest solubilization potential. In the case of meloxicam and nimesulide, solubility increased significantly with increase in pH value. Physico-chemical properties of the solvent such as polarity, intermolecular interactions, and the ability of the solvent to form a hydrogen bond with the drug molecules were found to be the major factors involved in the dissolution of drugs by pure solvents. The greater the difference in the polarity of the 2 solvents in a given mixed solvent...

Composition Optimization and Stability Testing of a Parenteral Antifungal Solution based on a Ternary Solvent System

Kovács, Kristóf; Antal, István; Stampf, György; Klebovich, Imre; Ludányi, Krisztina
Fonte: Springer US Publicador: Springer US
Tipo: Artigo de Revista Científica
Publicado em 24/02/2010 EN
Relevância na Pesquisa
470.59094%
An intravenous solution is a dosage forms intended for administration into the bloodstream. This route is the most rapid and the most bioavailable method of getting drugs into systemic circulation, and therefore it is also the most liable to cause adverse effects. In order to reduce the possibility of side effects and to ensure adequate clinical dosage of the formulation, the primarily formulated composition should be optimized. It is also important that the composition should retain its therapeutic effectiveness and safety throughout the shelf-life of the product. This paper focuses on the optimization and stability testing of a parenteral solution containing miconazole and ketoconazole solubilized with a ternary solvent system as model drugs. Optimization of the solvent system was performed based on assessing the risk/benefit ratio of the composition and its properties upon dilution. Stability tests were conducted based on the EMEA (European Medicines Agency) “guideline on stability testing: stability testing of existing active substances and related finished products”. Experiments show that both the amount of co-solvent and surface active agent of the solvent system could substantially be reduced, while still maintaining adequate solubilizing power. It is also shown that the choice of various containers affects the stability of the compositions. It was concluded that by assessing the risk/benefit ratio of solubilizing power versus toxicity...

Counter-current chromatographic separation of nucleic acid constituents with an extremely hydrophilic solvent system

Shibusawa, Yoichi; Shoji, Atsushi; Suzuka, Chihiro; Yanagida, Akio; Ito, Yoichiro
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
455.49594%
Nucleic acid constituents such as nucleobases, nucleosides and nucleotides were separated by counter-current chromatography using a type J coil planet centrifuge. The separation was performed with an extremely hydrophilic solvent system composed of 1-propanol/800 mM potassium phosphate buffer (pH 7.4) (1 : 1) by eluting the lower aqueous phase at a flow-rate of 0.5 ml/min. Eight kinds of nucleic acid constituents, including UMP, AMP, deoxyAMP, uridine, urasile, 2’ deoxy uridine, adenosine and adenine were well resolved within 170 min.

Organic high ionic strength aqueous two-phase solvent system series for separation of ultra-polar compounds by spiral high-speed counter-current chromatography

Zeng, Yun; Liu, Gang; Ma, Ying; Chen, Xiaoyuan; Ito, Yoichiro
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
473.26027%
Existing two-phase solvent systems for high-speed countercurrent chromatography cover the separation of hydrophobic to moderately polar compounds, but often fail to provide suitable partition coefficient values for highly polar compounds such as sulfonic acids, catecholamines and zwitter ions. The present paper introduces a new solvent series which can be applied for the separation of these polar compounds. It is composed of 1-butanol, ethanol, saturated ammonium sulfate and water at various volume ratios and consists of a series of 10 steps which are arranged according to the polarity of the solvent system so that the two-phase solvent system with suitable K values for the target compound(s) can be found in a few steps. Each solvent system gives proper volume ratio and high density difference between the two phases to provide a satisfactory level of retention of the stationary phase in the spiral column assembly. The method is validated by partition coefficient measurement of four typical polar compounds including methyl green (basic dye), tartrazine (sulfonic acid), tyrosine (zwitter ion) and epinephrine (a catecholamine), all of which show low partition coefficient values in the polar 1-butanol-water system. The capability of the method is demonstrated by separation of three catecholamines.

Development of Suitable Solvent System for Downstream Processing of Biopolymer Pullulan Using Response Surface Methodology

Choudhury, Anirban Roy; Bhattacharjee, Paramita; Prasad, Gandham S.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 15/10/2013 EN
Relevância na Pesquisa
455.49594%
Downstream processing is an important aspect of all biotechnological processes and has significant implications on quality and yield of the final product. Several solvents were examined for their efficacy on pullulan precipitation from fermentation broth. Interactions among four selected solvents and their effect on pullulan yield were studied using response surface methodology. A polynomial model was developed using D-optimal design and three contour plots were generated by performing 20 different experiments and the model was validated by performing optimization experiments. The results indicated that lower concentration of ethanol in combination with the other three solvents has resulted in higher yield of polymer from fermentation broth and the optimized solvent system was able to recover 1.44 times more pullulan as compared to the conventional ethanolic precipitation method. These observations may help in enhancing efficiency of pullulan recovery from fermentation broth and also result in reduced cost of production for the final product.

Tailoring the grooved texture of electrospun polystyrene nanofibers by controlling the solvent system and relative humidity

Liu, Wanjun; Huang, Chen; Jin, Xiangyu
Fonte: Springer Publicador: Springer
Tipo: Artigo de Revista Científica
Publicado em 14/07/2014 EN
Relevância na Pesquisa
460.98504%
In this study, we have successfully fabricated electrospun polystyrene (PS) nanofibers having a diameter of 326 ± 50 nm with a parallel grooved texture using a mixed solvent of tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). We discovered that solvent system, solution concentration, and relative humidity were the three key factors to the formation of grooved texture and the diameter of nanofibers. We demonstrated that grooved nanofibers with desired properties (e.g., different numbers of grooves, widths between two adjacent grooves, and depths of grooves) could be electrospun under certain conditions. When THF/DMF ratio was higher than 2:1, the formation mechanism of single grooved texture should be attributed to the formation of voids on the jet surface at the early stage of electrospinning and subsequent elongation and solidification of the voids into a line surface structure. When THF/DMF ratio was 1:1, the formation mechanism of grooved texture should be ascribed to the formation of wrinkled surface on the jet surface at the early stage of electrospinning and subsequent elongation into a grooved texture. Such findings can serve as guidelines for the preparation of grooved nanofibers with desired secondary morphology.

Crystal growth of hexagonal boron nitride (hBN) from Mg-B-N solvent system under high pressure

Zhigadlo, N. D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
459.43562%
Transparent and colorless hexagonal boron nitride (hBN) single crystals were grown from the Mg-B-N system using high-pressure high-temperature cubic anvil technique. By varying the synthesis conditions we could determine the sequence of phase transformations occurring in the Mg-B-N system, construct the pressure-temperature (P-T) phase diagram and discuss the possible growth mechanism. The largest plate-like-shaped hBN crystals with sizes up to 2.5 mm in length and up to 10 (micro)m in thickness were grown at 30 kbar and 1900-2100 {\deg}C. The hBN crystals exhibited strong, narrow diffraction peaks typical of well-ordered stacking crystal planes, with the c-axis perpendicular to the crystal face. A characteristic Raman peak observed at 1367 cm-1 with a full width at half maximum of 8 cm-1 corresponds to the E2g vibration mode and indicates the high purity and order of hBN crystals grown by this method. From the practical point of view this work can stimulate further explorations of the Mg-B-N solvent system to obtain isotopically-enriched h10BN crystals, which can act as a key element in solid-state neutron detector devices.; Comment: 15 pages, 5 figures