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141.
Kelley L. Spence Richard A. Venditti Orlando J. Rojas Youssef Habibi Joel J. Pawlak 《Cellulose (London, England)》2010,17(4):835-848
The interactions with water and the physical properties of microfibrillated celluloses (MFCs) and associated films generated from wood pulps of different yields (containing extractives, lignin, and hemicelluloses) have been investigated. MFCs were produced by combining mechanical refining and a high pressure treatment using a homogenizer. The produced MFCs were characterized by morphology analysis, water retention, hard-to-remove water content, and specific surface area. Regardless of chemical composition, processing to convert macrofibrils to microfibrils resulted in a decrease in water adsorption and water vapor transmission rate, both important properties for food packaging applications. After homogenization, MFCs with high lignin content had a higher water vapor transmission rate, even with a higher initial contact angle, hypothesized to be due to large hydrophobic pores in the film. A small amount of paraffin wax, less than 10%, reduced the WVTR to a similar value as low density polyethylene. Hard-to-remove water content correlated with specific surface area up to approximately 50 m2/g, but not with water retention value. The drying rate of the MFCs increased with the specific surface area. Hornified fibers from recycled paper also have the potential to be used as starting materials for MFC production as the physical and optical properties of the films were similar to the films from virgin fibers. In summary, the utilization of lignin containing MFCs resulted in unique properties and should reduce MFC production costs by reducing wood, chemical, and energy requirements. 相似文献
142.
143.
Maciel Juliana Villela Silva Tiago Almeida Dias Daiane Fatibello-Filho Orlando 《Journal of Solid State Electrochemistry》2018,22(7):2277-2285
Journal of Solid State Electrochemistry - The determination of eugenol employing voltammetry of immobilized microdroplets (VIM) is reported in this work. The construction of the electrode was based... 相似文献
144.
A flow injection potentiometric procedure for saccharin determination in dietary products is proposed. Saccharin is precipitated as mercurous saccharinate and the excess of the mercurous cation is potentiometrically measured using a silver wire coated with a mercury film as the working electrode. A filter unit is used to avoid contact between the precipitate and the electrode surface. With relocation in the flow manifold, the accumulated precipitate is removed on-line. Sucrose, glucose, aspartame, sodium cyclamate and sodium benzoate do not interfere when present in amounts similar to those observed in commercial products. Results are comparable with those obtained by UV-spectrophotometry and the correlation coefficient between methods is equal to 0.9930. A linear relationship between DeltaE (mV) and the logarithm of saccharin concentration was obtained in the saccharin concentration range 2 x 10(-3) - 1 x 10(-2)M. The sampling frequency is 60/hour and only 0.76 mg of Hg(2+)(2) is consumed in each determination. 相似文献
145.
L. Valenzano Y. Noël R. Orlando C. M. Zicovich-Wilson M. Ferrero R. Dovesi 《Theoretical chemistry accounts》2007,117(5-6):991-1000
The equilibrium geometry, the Raman and IR vibrational spectra at the Γ point, TO–LO splitting, IR intensities, Born and dielectric
tensors of magnesite MgCO3, dolomite MgCa(CO3)2 and calcite CaCO3 have been calculated with the periodic ab initio program CRYSTAL, by using an all-electron gaussian type basis set and the
B3LYP hamiltonian. LO (longitudinal-optical) modes are computed by correcting the dynamical matrix through Born charges and
high frequency dielectric tensors obtained from well localized Wannier functions and a saw-tooth computational scheme. The
mean absolute difference between calculated and experimental frequencies (IR TO and LO and RAMAN) is as small as 6.9 cm−1 for magnesite, 7.7 cm−1 for dolomite and 8.5 cm−1 for calcite. Calculated IR intensities are in semiquantitative agreement with experiment. The modes of the three compounds
are compared through graphical animation available on the CRYSTAL web-site. 相似文献
146.
147.
Kim EB Guzman O Grollau S Abbott NL de Pablo JJ 《The Journal of chemical physics》2004,121(4):1949-1961
Monte Carlo simulations and dynamic field theory (DyFT) are used to study the interactions between dilute spherical particles, dispersed in nematic and isotropic phases of a liquid crystal. A recently developed simulation method (expanded ensemble density of states) was used to determine the potential of mean force (PMF) between the two spheres as a function of their separation and size. The PMF was also calculated by a dynamic field theory that describes the evolution of the local tensor order parameter. Both methods reveal an overall attraction between the colloids in the nematic phase; in the isotropic phase, the overall attraction between the colloids is much weaker, whereas the repulsion at short range is stronger. In addition, both methods predict a new topology of the disclination lines, which arises when the particles approach each other. The theory is found to describe the results of simulations remarkably well, down to length scales comparable to the size of the molecules. At separations corresponding to the width of individual molecular layers on the particles' surface, the two methods yield different defect structures. We attribute this difference to the neglect of density inhomogeneities in the DyFT. We also investigate the effects of the size of spherical colloids on their interactions. 相似文献
148.
King D Lumpkin M Bergmann C Orlando R 《Rapid communications in mass spectrometry : RCM》2002,16(16):1569-1574
Protein-carbohydrate interactions play a significant role in biological processes. Presented here is the novel application of amide hydrogen/deuterium exchange mass spectrometry (amide exchange-MS) to the study of the interaction between a protein and its carbohydrate substrate. The degree of deuterium incorporation into hen egg lysozyme was monitored with and without substrate to verify that a carbohydrate can provide sufficiently stable protection of the amide hydrogen atoms in a protein's backbone from exchange with deuterated solvent. The substrate protected a number of amide hydrogens from exchange, implying that protein-carbohydrate binding systems will be compatible with amide exchange-MS. Endopolygalacturonase-II (EPG-II) from Aspergillus niger, a pectin-degrading enzyme, was chosen as the first carbohydrate-binding system to be extensively studied using quenched amide exchange-MS. Monitoring the changes in deuterium incorporation of EPG-II in the presence and absence of an oligomer of galacturonic acid implied the location of substrate binding. This study demonstrates the ability of amide exchange-MS to investigate protein-carbohydrate interactions. 相似文献
149.
An enzymatic reactor was constructed by the immobilization of polyphenol oxidase (PPO) from avocado (Persea americana) crude extract in an inorganic support of controlled pore silica (CPS), after a previous step of silanization. This inorganic support has been used as an excellent carrier to immobilize this enzyme and the enzymatic reactor was used in a flow injection system for the determination of isoproterenol in pharmaceutical products. The procedure is based on the oxidation reaction of this drug with immobilized PPO and the product obtained was monitored at 492 nm. This system presented an analytical curve from 1.23x10(-4) to 7.38x10(-4) mol l(-1) isoproterenol with a detection limit of 6.25x10(-5) mol l(-1). Recoveries of isoproterenol between 98.5 and 103.1%, a relative standard deviation (R.S.D.) less than 1% (n=10) and 36 determinations per h were obtained. 相似文献
150.
Stubenrauch C Rojas OJ Schlarmann J Claesson PM 《Langmuir : the ACS journal of surfaces and colloids》2004,20(12):4977-4988
The interactions between nonpolar surfaces coated with the nonionic surfactant hexaoxyethylene dodecyl ether C12E6 were investigated using two techniques and three different types of surfaces. As nonpolar surfaces, the air/water interface, silanated negatively charged glass, and thiolated uncharged gold surfaces were chosen. The interactions between the air/water interfaces were measured with a thin film pressure balance in terms of disjoining pressure as a function of film thickness. The interactions between the solid/liquid interfaces were determined using a bimorph surface force apparatus. The influence of the nature of the surface on the interaction forces was investigated at surfactant concentrations below and above the cmc. The adsorption of the nonionic surfactant on the uncharged thiolated surface does not, as expected, lead to any buildup of a surface charge. On the other hand, adsorption of C12E6 on the charged silanated glass and the charged air/water interface results in a lowering of the surface charge density. The reduction of the surface charge density on the silanated glass surfaces is rationalized by changes in the dielectric permittivity around the charged silanol groups. The reason for the surface charge observed at the air/water interface as well as its decrease with increasing surfactant concentration is discussed and a new mechanism for generation of OH- ions at this particular interface is proposed. 相似文献