We investigate the effect of hydrodynamic interactions (HIs) on the crystal nucleation of hard-sphere colloids for varying supersaturations. We use molecular dynamics and stochastic rotation dynamics techniques to account for the HIs. For high supersaturation values, we perform brute force simulations and compute the nucleation rate, obtaining good agreement with previous studies where HIs were neglected. In order to access low supersaturation values, we use a seeding approach method and perform simulations with and without HIs. We compute the nucleation rates for the two cases and surprisingly find good agreement between them. The nucleation rate in both cases follows the trend of the previous numerical results, thereby corroborating the discrepancy between experiments and simulations. Furthermore, we investigate the amount of fivefold symmetric clusters (FSCs) in a supersaturated fluid under different physical conditions, following the idea that FSCs compete against nucleation. To this end, we explore the role of the softness of the pair interactions, different solvent viscosities, and different sedimentation rates in simulations that include HIs. We do not find significant variations in the amount of FSCs, which might reflect the irrelevance of these three features on the nucleation process.

Anterior skull base defects with encephalocele in adults are quite rare and can be a cause of spontaneous rhinoliquorrhea; however, cerebrospinal fluid (CSF) fistula can be not rarely misdiagnosed for several months or years. Five adult patients affected by ethmoidal encephalocele with CSF fistula were treated in our institute from 2006 through to 2011. Onset of clinical history was represented by rhinoliquorrhea, which was precociously recognized in only 1 patient; in the other 4, it was misdiagnosed for a period ranging from 11 months to 5 years. After clinical diagnosis of CSF fistula and after brain magnetic resonance imaging, ethmoidal encephalocele was evident in all patients; preoperative study was completed by spiral computed tomography scan, to clearly identify the skull base bone defect. All patients were operated on by transsphenoidal endonasal endoscope-assisted microsurgical approach through 1 nostril. The herniated brain was coagulated and removed, and reconstruction of cranial base was performed. Postoperative rhinoliquorrhea or other complications did not occur in any patient at short and late follow-up. All patients were discharged after a few days. Endonasal endoscope-assisted microsurgical approach was effective in exposing and repairing the ethmoidal bone defect; tridimensional vision and wide lateral and superior exposition of the operative field were possible in each patient, thanks to the use of microscope and angulated endoscope.

Small Brownian particles, asymmetric in shape, display self-alignment in Hele-Shaw flow in nanofluidic channels.

We perform non-equilibrium Brownian dynamics simulations to investigate the out-of-equilibrium phase behavior of a suspension of charged colloids under external oscillatory shear. We independently vary the frequency f and the maximum strain amplitude γmax of the oscillations and map out an out-of-equilibrium phase diagram in the f–γmax plane. Similar to what has been observed in earlier studies on colloidal hard spheres, we find the formation of a twinned face-centered-cubic phase in a specific range of γmax, which displays a martensitic transition to a body-centered-cubic crystal within half of the oscillation cycle. We provide a comprehensive analysis of these structures and show how the system transforms from one to the other. We also report evidence of a sliding layer phase and a string phase.

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