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21.
The phase behavior, microstructure, and emulsification of polyoxyethylene (20) sorbitan monooleate (Tween 80), water, and d-limonene (LM) or perfluoromethyldecalin (PFMD) has been studied by small-angle X-ray scattering and polarizing optical microscopy. In the Tween 80/water binary system, a micellar solution (L(1)), a hexagonal (H(1)) phase, and a water-swellable isotropic surfactant liquid (L(2)) phase are successively formed at 25 °C. LM can be solubilized into all of the phases formed by Tween 80/water mixtures, whereas no solubilization of PFMD occurs. The L(2) phase was found by small-angle neutron scattering to be bicontinuous with low interfacial curvature. Added water swells and amplifies the pre-existing amphiphilic structure. The stability of oil-in-H(1) complex emulsions is found to be sensitive to changes in structure that accompany solubilization. 相似文献
22.
Structural Chemistry - Tuberculosis (TB), an infectious remains a global health burden till date. Considering immense importance of theoretical tools in computer aided-drug designing, the current... 相似文献
23.
Phase behavior and surface tensions of amphiphilic fluorinated random copolymer aqueous solutions 总被引:2,自引:0,他引:2
Suraj Chandra Sharma Durga P. Acharya Miguel García-Roman Yasuo Itami Hironobu Kunieda 《Colloids and surfaces. A, Physicochemical and engineering aspects》2006,280(1-3):140-145
Phase behavior and surface tension of aqueous solutions of fluorinated random copolymers [perfluoroalkylacrylate]–[poly(ethyleneoxide)methacrylate], [CmRf-acrylate]-[EOn-methacrylate] with fluroalkyl carbon number m = 8, 6, 4, 2 and number of ethyleneoxide unit, n = 9 and 4.5 were investigated as a function of composition and different combinations of m and n. Isotropic solutions are formed at lower temperatures over wide concentration range of copolymer but at higher temperature phase separation occurs. The cloud point of copolymer decreases with decreasing n as well as m, and also with decreasing the number of poly(ethyleneoxide)methacrylate chain per perfluorinatedalkylacrylate chain, suggesting that the copolymers become more hydrophobic on decreasing m and n. Equilibrium and dynamic surface tension measurements show that copolymers become increasingly surface active as m as well as n decrease but the adsorption at the air–water interface is very slow due to bulkiness of the molecules. No clear evidence of the formation of micellar aggregates could be obtained from surface tension–composition curves. 相似文献
24.
The coordination chemistry of an extracellular siderophore produced by Mycobacterium smegmatis, exochelin MS (ExoMS), is reported along with its pK(a) values, Fe(III) and Fe(II) chelation constants, and aqueous solution speciation as determined by spectrophotometric and potentiometric titrations. Exochelin MS has three hydroxamic acid groups for Fe(III) chelation and has four additional acidic protons from a carboxylic acid group and three primary amine groups, on the backbone of the molecule. The pK(a) values for the three hydroxamic acid moieties, the carboxylic acid group and the alkylammonium groups on ExoMS, correspond well with the literature values for these moieties. Equilibrium constants for proton-dependent Fe(III)-ExoMS equilibria were determined using a model involving the sequential protonation of the Fe(III)-ExoMS complexes at the first and second coordination shells. The equilibrium constants (beta) for the overall formation of Fe(III)ExoMS(H(3))(2+) and Fe(II)ExoMS(H(3))(+) from Fe((aq))(3+) or Fe((aq))(2+) and the deprotonated hydroxamate coordinating group form of the siderophore, ExoMS(H(3))(-), are calculated as log beta(III) = 28.9 and log beta(II) = 10.1. A calculated pFe value of 25.0 is very similar to that of other linear trihydroxamic acid siderophores, and indicates that ExoMS is thermodynamically capable of removing Fe(III) from transferrin. The E(1/2) for the Fe(III)-ExoMS/Fe(II)-ExoMS couple was determined from quasi reversible cyclic voltammograms at pH = 6.5 and found to be -380 mV. 相似文献
25.
Suraj Chandra Sharma Lok Kumar Shrestha Kenichi Sakai Hideki Sakai Masahiko Abe 《Colloid and polymer science》2010,288(4):405-414
We have studied the rheology and structure of a mixed long polyoxyethylene chain phytosterol (PhyEO30) and monoglyceride (monolaurin (ML) or monopalmitin (MP)) surfactants in an aqueous system. Both ML and MP are insoluble
in 10 wt.% PhyEO30 solution at normal room temperature, but their solubility is found to increase with the rise of temperature and an isotropic
solution is formed at higher temperature. A maximum viscosity as a function of temperature appears as ML or MP is solubilized
in the micellar solution of PhyEO30. With increasing temperature, viscosity increases rapidly for higher monoglyceride content and forms viscoelastic solution.
The oscillatory rheological behavior of the viscoelastic solution can be described by Maxwell model at low-frequency region,
which is the typical pattern of entangled wormlike micelles. Upon successive increase in temperature, the viscosity decreases
and ultimately a phase separation occurs. Small-angle X-ray scattering measurements were performed to provide a supportive
structural evidence for the rheological data. 相似文献
26.
Pakorn Bovonsombat Rameez Ali Chiraphorn Khan Juthamard Leykajarakul Kawin Pla-on Suraj Aphimanchindakul Natchapon Pungcharoenpong Nisit Timsuea Anchalee Arunrat Napat Punpongjareorn 《Tetrahedron》2010,66(34):6928-181
para-Regioselective bromination of phenol and analogues, promoted by p-toluenesulfonic acid, is achieved in high to excellent yields at room temperature with N-bromosuccinimide. Chlorination with N-chlorosuccinimide and catalysed by p-toluenesulfonic acid also gives para-chlorinated phenol analogues in good yields at room temperature. 相似文献
27.
Suraj Ravindran Rajesh Langoju Abhijit Patil Pramod Rastogi 《Optics and Lasers in Engineering》2007,45(7):766-772
The effectiveness of phase-shifting interferometry (PSI) techniques employing piezoelectric device PZT in the estimation of phase depends largely on the accuracy with which the phase shifts are imparted to the device and the noise influencing the measurement. Several effective algorithms have been proposed to compute the phase shifts imparted to the device and subsequently obtain the phase using least-squares estimation technique. In this paper, we propose a generalized approach, which accurately estimates the phase shifts in the presence of noise. The method is based on the idea of linear prediction and explores the fact that sampling more data frames yields a reliable phase step estimate in a least-squares sense. We also compare our method with a commonly used generalized phase-shifting method based on histogram analysis and show that our proposed approach is highly effective. We also present simulation and experimental validations of our proposed method. 相似文献
28.
Nonlinear Dynamics - Analysis of electrostatic floating potential fluctuations associated with multiple anodic double layer revealed a complexity dynamic coexisting with chaotic behavior. These... 相似文献
29.
30.
Damped transient dynamic elasto-plastic analysis of plate is investigated. A finite element model based on a C
0 higher order shear deformation theory has been developed. Nine noded Lagrangian elements with five degrees of freedom per
node are used. Selective Gauss integration is used to evaluate energy terms so as to avoid shear locking and spurious mechanisms.
Von Mises and Tresca yield criteria are incorporated along with associated flow rules. Explicit central difference time stepping
scheme is employed to integrate temporal equations. The mass matrix is diagonalized by using the efficient proportional mass
lumping scheme. A program is developed for damped transient dynamic finite element analysis of elasto-plastic plate. Several
numerical examples are studied to unfold different facets of damping of elasto-plastic plates. 相似文献