Due to the more powerful and miniaturized nature of modern devices, conventional heat-transfer working fluids are not capable of meeting the cooling needs of these systems. Therefore, it is necessary to improve the heat-transfer abilities of commonly used cooling fluids. Recently, nanoparticles with different characteristics have been introduced to base liquids to enhance the overall thermal conductivity. This paper studies the influence of various parameters, including base liquid, temperature, nanoparticle concentration, nanoparticle size, nanoparticle shape, nanoparticle material, and the addition of surfactant, on nanofluid thermal conductivity. The mechanisms of thermal conductivity enhancement by different parameters are discussed. The impact of nanoparticles on the enhanced thermal conductivity of nanofluids is clearly shown through plotting the thermal conductivities of nanofluids as a function of temperature and/or nanoparticle concentration on the same graphs as their respective base liquids. Additionally, the thermal conductivity of hybrid nanofluids, and the effects of the addition of carbon nanotubes on nanofluid thermal conductivity, are studied. Finally, modeling of nanofluid thermal conductivity is briefly reviewed.

Beginning with the work of Lohe [14,15] there have been a number of papers [3,5,8,9,11] that have generalized the Kuramoto model for phase-locking to a non-commuting situation. Here we propose and analyze another such model. We consider a collection of symmetric matrix-valued variables that evolve in such a way as to try to align their eigenvector frames. The phase-locked state is one where the eigenframes all align, and thus the matrices all commute. We analyze the stability of the phase-locked state and show that it is stable. We also analyze a dynamic analog of the twist states arising in the standard Kuramoto model, and show that these twist states are dynamically unstable.

Samples of Dreissena polymorpha were collected at several sites along the River Shannon navigation in Ireland, to determine the occurrence and distribution of their obligate host-specific commensalistic ciliate, Conchophthirus acuminatus, in this newly invaded region. Mussels collected by various methods were fixed immediately in 75% ethanol, in which they were later dissected under a stereoscopic microscope, beginning with thorough flushing of the mantle cavity and removal of the gills. One ml of sediment flushed from the mantle cavity and dissection residue of each mussel was examined under a compound light microscope using brightfield, phase-contrast, and differential-interference-contrast optics. Of 180 mussels examined, 125 (69.44%) harbored C. acuminatus. The ciliates were invariably well fixed and easily identifiable in all preparations. Mean sampling intensity for infected mussels was 8.47 ciliates per ml of sediment. Both prevalence and sampling intensity varied between sites, but no pattern was discernible. The present results are consistent with other reports of C. acuminatus being the most widespread and abundant symbiont of D. polymorpha throughout Europe, often occurring where no other symbionts occur. Its occurrence in Ireland indicates introduction of the mussels as adults, since planktonic veliger larvae are not known to harbor ciliates. Following similar reasoning, it is possible that the earlier North American invasion by D. polymorpha included only veligers, since C. acuminatus has not been found on that continent. Using these simple and quick methods, the ciliates could be easily identified and counted to give general comparative data among sites regarding intensity and prevalence. Thus, this method has promise for future efforts to obtain basic information rapidly in newly invaded systems.

No abstract