Neutral-cluster implantation in polymers by computer experiments

In this work we perform atomistic model potential molecular dynamics simulations by means of state-of-the art force-fields to study the implantation of a single Au nanocluster on a Polydimethylsiloxane substrate. All the simulations have ben performed on realistic substrate models containing up to 4.6 millions of atoms having depths up to 90 nm and lateral dimensions up to 25 nm. We consider both entangled-melt and cross-linked Polydimethylsiloxane amorphous structures. We show that even a single cluster impact on the Polydimethylsiloxane substrate remarkably changes the polymer local temperature and pressure. Moreover we observe the presence of craters created on the polymer surface having lateral dimensions comparable to the cluster radius and depths strongly dependent on the implantation energy. Present simulations suggest that the substrate morphology is largely affected by the cluster impact and that most-likely such modifications favor the the penetration of the next impinging clusters

Dark Matter, Dark Energy and the solution of the strong CP problem

The strong CP problem was solved by Peccei & Quinn by introducing axions, a viable candidate for Dark Matter (DM). Here the PQ approach is modified so to yield also Dark Energy (DE). DM and DE arise, in fai proportions, from a single scalar field, without tuning any extra parameter. In the present epoch, they are weakly coupled. Fluctuations have a fair evolution. The model is also fitted to the WMAP1 release, using a Markov Chain Monte Carlo technique, and performs as well as $\Lambda$CDM, coupled or uncoupled DE. Best--fit cosmological parameters for different models are mostly within 2--$\sigma$ level. Here, the main peculiarity of the model is to favor high values of the Hubble parameter.Comment: Proceeding of the workshop dsu2006, "The Dark Side of th Universe", Madrid, June 20-24, 200

Surgical Strategy in Midline Tumours of the Anterior Cranial Fossa

Midline tumors of the anterior cranial fossa (ACF) are mostly represented by olfactory groove menigiomas (OGM). There are many different approaches to this complex anatomical area but only a few that allow from the beginning dural implant removal: purely endoscopic transnasal (EA), transcranial/transfrontal sinus (TFA), and combined EA-TFA (CA) approach. Despite the improvement of EA, the optimal treatment strategy for the surgical treatment of OGM is still a matter of debate. The most advocate advantages of the EA are the absence of cerebral retraction and the possibility to resect the dural implant of the tumor, thus reducing its vascularization. On the other hand, it presents several limits: an important sinonasal morbidity, the loss of olfaction as default, increased risk of postoperative CSF leakage (5-10% in referral centers), especially in anteriorly located tumors. Moreover, the EA is contraindicated in case of lateral (above the orbital floor) or anterior extension (posterior wall of frontal sinus), cerebral parenchima involvment, or in case of major nerves or artery encasement. Consequently, only little tumors extended to the tuberculum sellae or planum sphenoidalis could be safely resected through a purely EA. The TFA is performed by a bicoronal incision, creating a craniotomy on the anterior wall of the frontal sinus and drilling the posterior wall of the frontal sinus. It gives direct access to the dural attachment of the tumor and avoids any cerebral retraction. In case of bulky or far posterior tumors, the interhemispheric route is usually very effective. The TFA permits to remove OGM of any dimension, to deal with nerves of vessel encasement, and to respect meningohypophyseal arteries. The incidence of postoperative CSF leakage is minimal since the closure with the galea is of the utmost effectiveness (0% in our experience). In case of sinonasal involvement, a CA is usually preferred

Surgical Strategy in Midline Tumours of the Anterior Cranial Fossa

Midline tumors of the anterior cranial fossa (ACF) are mostly represented by olfactory groove menigiomas (OGM). There are many different approaches to this complex anatomical area but only a few that allow from the beginning dural implant removal: purely endoscopic transnasal (EA), transcranial/transfrontal sinus (TFA), and combined EA-TFA (CA) approach. Despite the improvement of EA, the optimal treatment strategy for the surgical treatment of OGM is still a matter of debate. The most advocate advantages of the EA are the absence of cerebral retraction and the possibility to resect the dural implant of the tumor, thus reducing its vascularization. On the other hand, it presents several limits: an important sinonasal morbidity, the loss of olfaction as default, increased risk of postoperative CSF leakage (5-10% in referral centers), especially in anteriorly located tumors. Moreover, the EA is contraindicated in case of lateral (above the orbital floor) or anterior extension (posterior wall of frontal sinus), cerebral parenchima involvment, or in case of major nerves or artery encasement. Consequently, only little tumors extended to the tuberculum sellae or planum sphenoidalis could be safely resected through a purely EA. The TFA is performed by a bicoronal incision, creating a craniotomy on the anterior wall of the frontal sinus and drilling the posterior wall of the frontal sinus. It gives direct access to the dural attachment of the tumor and avoids any cerebral retraction. In case of bulky or far posterior tumors, the interhemispheric route is usually very effective. The TFA permits to remove OGM of any dimension, to deal with nerves of vessel encasement, and to respect meningohypophyseal arteries. The incidence of postoperative CSF leakage is minimal since the closure with the galea is of the utmost effectiveness (0% in our experience). In case of sinonasal involvement, a CA is usually preferred

The multimode covering location problem

In this paper we introduce the Multimode Covering Location Problem. This is a generalization of the Maximal Covering Location Problem that consists in locating a given number of facilities of different types with a limitation on the number of facilities sharing the same site. The problem is challenging and intrinsically much harder than its basic version. Nevertheless, it admits a constant factor approximation guarantee, which can be achieved combining two greedy algorithms. To improve the greedy solutions, we have developed a Variable Neighborhood Search approach, based on an exponential-size neighborhood. This algorithm computes good quality solutions in short computational time. The viability of the approach here proposed is also corroborated by a comparison with a Heuristic Concentration algorithm, which is presently the most effective approach to solve large instances of the Maximal Covering Location Problem

Sulla storia degli studi di frattura in Italia

History of studies of fracture is inherently intermingled with the history of technology developments. In the beginning very little was written about. We must credit Leonardo and Galileo as the first ones that wrote about the problem and on how to measure and foresee rupture loads. Later, nineteenth century italian scientists distinguished themselves in attempting to establish material laws and multiple stresses rupture criteria. A review of the works of past centuries italian scientists is presented, along with a critical comparison with the work of other past european scientists

Development of a Systems Architecture for Robot-Aided Telerehabilitation

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