Micellar Aggregates of Gemini Surfactants: Monte Carlo Simulation of a Microscopic Model

We propose a "microscopic" model of gemini surfactants in aqueous solution. Carrying out extensive Monte Carlo simulations, we study the variation of the critical micellar concentration (CMC) of these model gemini surfactants with the variation of the (a) length of the spacer connecting the two hydrophilic heads, (b) length of the hydrophobic tail and (c) the bending rigidity of the hydrocarbon chains forming the spacer and the tail; some of the trends of variation are counter-intuitive but are in excellent agreement with the available experimental results. Our simulations also elucidate the dependence of the shapes of the micellar aggregates and the magnitude of the CMC on the geometrical shape and size of the surfactant molecules and the electrical charge on the hydrophilic heads

Vertebral artery dissection presenting as a Brown-Séquard syndrome: a case report

<p>Abstract</p> <p>Introduction</p> <p>Vertebral artery dissection has become increasingly recognized as an important cause of stroke. It usually presents with posterior headache or neck pain followed within hours or days by signs of posterior circulation stroke. To the best of our knowledge, the clinical presentation of a Brown-Séquard syndrome with a vertebral artery dissection has been reported only once before.</p> <p>Case presentation</p> <p>An otherwise healthy 35-year-old man presented with acute left-sided weakness. He had experienced left-sided posterior neck pain after a 4-hour flight 4 weeks previously. Physical examination was consistent with a left Brown-Séquard syndrome. Magnetic resonance angiography showed evidence of left vertebral artery dissection. He improved after therapy with anticoagulants.</p> <p>Conclusion</p> <p>We report a case of an unusual presentation of a relatively uncommon condition. This diagnosis should be considered early in relatively young patients with stroke-like symptoms or unexplained neck pain, because missing a dissection can result in adverse outcomes.</p