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Sainis SK Germain V Mejean CO Dufresne ER 《Langmuir : the ACS journal of surfaces and colloids》2008,24(4):1160-1164
We study the electrostatic and hydrodynamic interactions of colloidal particles in nonpolar solvents. Using blinking optical tweezers, we can extract the screening length, kappa-1, the effective surface potential, |ezeta*|, and the hydrodynamic radius, ah, in a single measurement. We apply this technique to suspensions of polystyrene and poly(methyl methacrylate) particles in hexadecane with soluble charge control agents, aerosol sodium di-2-ethylhexylsulfosuccinate (AOT) and polyisobutylene succinimide (OLOA-1200). We find that the electrostatic interactions of these particles depend sensitively on surface composition as well as on the concentration and chemistry of the charge control agent. 相似文献
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COŞKUN DENIZ 《Pramana》2017,88(1):20
Common recipe for the lengthening pendulum (LP) involves some change of variables to give a relationship with the Bessel’s equation. In this work, conventional semiclassical JWKB solution (named after Jeffreys, Wentzel, Kramers and Brillouin) of the LP is being obtained by first transforming the related Bessel’s equation into the normal form ‘via the suggested change of independent variable’. JWKB approximation of the first-order Bessel functions (ν=1) of both types along with their zeros are being obtained analytically with a very good accuracy as a result of the appropriately chosen associated initial values and they are extended to the neighbouring orders (ν=0 and 2) by the recursion relations. The required initial values are also being studied and a quantization rule regarding the experimental LP parameters is being determined. Although common numerical methods given in the literature require adiabatic LP systems where the lengthening rate is slow, JWKB solution presented here can safely be used for higher lengthening rates and a criterion for its validity is determined by the JWKB applicability criterion given in the literature. As a result, the semiclassical JWKB method which is normally used for the quantum mechanical and optical waveguide systems is applied to the classical LP system successfully. 相似文献
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In severe perinatal asphyxia, the prognostic value of apparent diffusion coefficient (ADC) measurements is still open to question. We hypothesized that temporal and anatomical changes of brain ADC values occurring early after the hypoxic-ischemic insult could predict the outcome at 36 months. To demonstrate this, mean ADC values were calculated for 16 brain structures in 59 term neonates who underwent an MR examination during the first month of life. Neonates were divided into two groups according to their 36-month outcome: unfavorable (death/severe disability) or favorable outcome. ADC values were plotted against age at scan.In neonates with favorable outcomes (n=32), ADC values were constant over the study period. In babies with unfavorable outcomes (n=27), ADCs exhibited two different patterns. In infratentorial structures, ADCs were constant and normal. In supratentorial areas, ADCs followed a biphasic temporal evolution: ADC values were at their lowest at day 2, showed a rapid increase until Days 5-7, and were thereafter similar to those of neonates with favorable outcomes. Using receiver operating characteristic analysis, during the first 3-5 days of life, all neonates with decreased ADC had an unfavorable outcome.These temporal and anatomical changes of ADC values imply that individual prognosis of asphyxiated neonates can only be predicted by measurement of ADC in supratentorial areas within the first 3-5 days of life. 相似文献
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Subramaniam AB Mejean C Abkarian M Stone HA 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):5986-5990
We report the behavior of particle-stabilized bubbles (armored bubbles) when exposed to various classes and concentrations of surfactants. The bubbles are nonspherical, which is a signature of the jamming of the particles on the interface, and are stable to dissolution prior to the addition of surfactant. Armored bubbles exposed to surfactants, dissolve, and exhibit distinct morphological, microstructural, and lifetime changes, which correlate with the concentration of surfactant employed. For low concentrations of surfactant, an armored bubble remains nonspherical while dissolving, whereas for concentrations close to and above the surfactant cmc a bubble reverts to a spherical shape before dissolving. We propose a microstructural interpretation, supported by our experimental observations of particle dynamics on the bubble interface, that recognizes the role of interfacial jamming and stresses in particle-stabilization and surfactant-mediated destabilization of armored bubbles. 相似文献
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