The formation, morphology, and pH and ionic strength responses of cationic block copolymer micelles in aqueous solutions have been examined in detail to provide insight into the future development of cationic micelles...
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The formation, morphology, and pH and ionic strength responses of cationic block copolymer micelles in aqueous solutions have been examined in detail to provide insight into the future development of cationic micelles for complexation with polyanions such as DNA. Diblock polymers composed of a hydrophilic/cationic block of N,N-dimethylaminoethyl methacrylate (DMAEMA) and a hydrophobic/nonionic block of n-butyl methacrylate (BMA) were synthesized [denoted as DMAEMA-b-BMA (X-Y), where X = DMAEMA molecular weight and Y = molecular weight of BMA in kDa]. Four variants were created with block molecular weights of 14-13, 14-23, 27-14, 27-29 kDa and low dispersities less than 1.10. The amphiphilic polymers self-assembled in aqueous conditions into coreshell micelles that ranged in size from 25-80 nm. These cationic micelles were extensively characterized in terms of size and net charge in different buffers over a wide range of ionic strength (0.02-1 M) and pH (5-10) conditions. The micelle core is kinetically trapped, and the corona contracts with increasing pH and ionic strength, consistent with previous work on micelles with glassy polystyrene cores, indicating that the corona properties are independent of the dynamics of the micelle core. The contraction and extension of the corona scales with solution ionic strength and charge fraction of the amine groups. The aggregation numbers of the micelles were obtained by static light scattering, and the R-g/R-h ratios are close to that of a hard sphere. The zeta potentials of the micelles were positive up to two pH units above the corona pK(a), suggesting that applications relying on micelle charge for stability should be viable over a wide range of solution conditions.
This study utilized experimental methods involving high-speed cameras to observe the interaction between cavitation bubbles, generated by a low-voltage electric spark device, and particles near a rigid wall. The dynam...
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This study utilized experimental methods involving high-speed cameras to observe the interaction between cavitation bubbles, generated by a low-voltage electric spark device, and particles near a rigid wall. The dynamic characteristics of the particles were analyzed under varying conditions, including different cavitation bubble sizes, particle sizes, and distances between the cavitation bubble and the wall. Two characteristic parameters were introduced: chi for the particle and cavitation bubble sizes, and lambda for the cavitation bubble wall distance. Qualitative distinctions were made among types of particle-bubble interactions, and force analysis was conducted under conditions where chi exceeded the threshold chi(t). The findings reveal that when chi < chi(t), particle motion is primarily influenced by the jet effects produced by the cavitation bubble. Conversely, when chi > chi(t), particle motion is dominated by the radiation forces exerted by the cavitation bubble. Under jet-dominated conditions, particle trajectories were observed to be erratic and unpredictable. For cases where lambda < 0, the high-speed jet directly impacts the particle. Conversely, for lambda > 0, the jet's velocity decays rapidly upon reaching the particle. In scenarios dominated by radiation forces, the cavitation bubble drew particles away from the wall, followed by their free fall back toward it. The influence of gravity, buoyancy, bubble radiation force, fluid resistance, and virtual mass force on particles was studied when radiation forces prevailed. The acceleration formula for particles was derived through the application of the bubble dynamics equation and was refined based on experimental observations.
In lieu of an abstract, here is a brief excerpt of the content: Reviewed by: Europe's Physician: The Various Life of Sir Theodore de Mayerne Frederick Holmes, M.D. Hugh Trevor-Roper . Europe's Physician: The V...
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In lieu of an abstract, here is a brief excerpt of the content:
Reviewed by: Europe's Physician: The Various Life of Sir Theodore de Mayerne Frederick Holmes, M.D. Hugh Trevor-Roper . Europe's Physician: The Various Life of Sir Theodore de Mayerne. New Haven, Connecticut, Yale University Press, 2006. xii, 438 pp., illus. Using the life of the Huguenot physician, Sir Theodore de Mayerne, as a template, the author has presented the separate struggles of religion and medicine that consumed Europe in the seventeenth century. Apparently Trevor-Roper conceived, researched, and wrote most of this biography by 1979, occasionally revising and adding to it after his retirement in 1987, but never bringing it close to publication. After Trevor-Roper's death in 2003, Professor Blair Worden completed the manuscript and it was published in 2006. The amount of research that Trevor-Roper did to present de Mayerne's life in its entirety is impressive. The thoughtfulness and skill of Worden in getting the manuscript completed and edited are noteworthy. Born of a Geneva Huguenot family in 1573, the year following the St. Bartholomew's Day massacre of Huguenots in France, Theodore Turquet's life was shaped by the long fight of French Protestants to survive in France with a Roman Catholic Church of ever-increasing political power and ever-decreasing tolerance. Educated in Basel and Montpellier, he assumed a status above that of his birth and became de Mayerne, leaving his family surname, Turquet, behind. By 1598, he was practicing medicine in Paris, part of the Huguenot medical community, and clearly identified with the disciples of Paracelsus, physicians who believed in chemical treatment of disease, which was anathema to the reigning Galenist philosophy of the powerful Medical Faculty of Paris. Despite his relatively tender age, Huguenot identity, and keen interest in chemical treatments, Mayerne, as Trevor-Roper names him, was soon a popular consultant physician, even enjoying an
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