Advances in Colloid and Interface Science (v.191-192, #C)

Chain formation and aging process in biocompatible polydisperse ferrofluids: Experimental investigation and Monte Carlo simulations by Andris Figueiroa Bakuzis; Luis César Branquinho; Leonardo Luiz e Castro; Marcos Tiago de Amaral e Eloi; Ronei Miotto (1-21).
We review the use of Monte Carlo simulations in the description of magnetic nanoparticles dispersed in a liquid carrier. Our main focus is the use of theory and simulation as tools for the description of the properties of ferrofluids. In particular, we report on the influence of polydispersity and short-range interaction on the self-organization of nanoparticles. Such contributions are shown to be extremely important for systems characterized by particles with diameters smaller than 10 nm. A new 3D polydisperse Monte Carlo implementation for biocompatible magnetic colloids is proposed. As an example, theoretical and simulation results for an ionic-surfacted ferrofluid dispersed in a NaCl solution are directly compared to experimental data (transmission electron microscopy — TEM, magneto-transmissivity, and electron magnetic resonance — EMR). Our combined theoretical and experimental results suggest that during the aging process two possible mechanisms are likely to be observed: the nanoparticle's grafting decreases due to aggregate formation and the Hamaker constant increases due to oxidation. In addition, we also briefly discuss theoretical agglomerate formation models and compare them to experimental data.Display Omitted► Critical review of the use of Monte Carlo methods in the description of magnetic nanoparticles. ► Theoretical agglomerate formation models are discussed and compared to simulations and experimental data. ► Use of EMR to extract the agglomerate's chain size. ► New procedure to model the ionic-surfacted layer relating the intensity of steric and ionic repulsions. ► Aging process explained through modifications of grafting (because of chain formation) or Hamaker constant (due to oxidation).
Keywords: Superparamagnetic iron oxide nanoparticles; Monte Carlo simulations; Interparticle interactions; Aggregate formation; Magneto-optical properties; Biomedical applications;

A critical review of physiological bubble formation in hyperbaric decompression by Virginie Papadopoulou; Robert J. Eckersley; Costantino Balestra; Thodoris D. Karapantsios; Meng-Xing Tang (22-30).
Bubbles are known to form in the body after scuba dives, even those done well within the decompression model limits. These can sometimes trigger decompression sickness and the dive protocols should therefore aim to limit bubble formation and growth from hyperbaric decompression. Understanding these processes physiologically has been a challenge for decades and there are a number of questions still unanswered. The physics and historical background of this field of study is presented and the latest studies and current developments reviewed. Heterogeneous nucleation is shown to remain the prime candidate for bubble formation in this context. The two main theories to account for micronuclei stability are then to consider hydrophobicity of surfaces or tissue elasticity, both of which could also explain some physiological observations. Finally the modeling relevance of the bubble formation process is discussed, together with that of bubble growth as well as multiple bubble behavior.Display Omitted
Keywords: Scuba; Diving; Decompression sickness; Decompression; Bubble; Micronuclei;