Stochastic models of systems for Nanotechnology: from micro to macro scale.

Computer modeling technique based on the theory of stochastic processes have been used in order to provide a realistic simulation of the behavior of nanoscopic systems, related in particular to plasma reactors in microelectronic device production. Basing on decades of experience, we show here, with new results, that the universality of such methods allows the development of codes with the highest reusability and versatility, crossing the barrier of scale. At the smallest scale, the quantum calculations of the potential energy surface of hydrogen species under nano-confinement conditions display the effects due to the dimension and the symmetry of the confining potential well. At a slightly larger scale, nanoparticles dispersed as aerosol in plasma feature strong fluctuations in temperature and charge which may affect the processing of silicon wafers. At the macroscopic scale, using a stochastic solution of transport equations, it is possible to describe laboratory or industrial systems for the production or treatment of nanomaterials, also exploiting the analogy between neutral particle transport and radiative transfer and information obtained by molecular simulations. These findings are relevant in the control of solid-particle contamination in the manufacture of electronic components and in other fields.

Hydrogen isotope fractionation in methane plasma.

The hydrogen isotope ratio (D/H) is commonly used to reconstruct the chemical processes at the origin of water and organic compounds in the early solar system. On the one hand, the large enrichments in deuterium of the insoluble organic matter (IOM) isolated from the carbonaceous meteorites are interpreted as a heritage of the interstellar medium or resulting from ion-molecule reactions taking place in the diffuse part of the protosolar nebula. On the other hand, the molecular structure of this IOM suggests that organic radicals have played a central role in a gas-phase organosynthesis. So as to reproduce this type of chemistry between organic radicals, experiments based on a microwave plasma of CH4 have been performed. They yielded a black organic residue in which ion microprobe analyses revealed hydrogen isotopic anomalies at a submicrometric spatial resolution. They likely reflect differences in the D/H ratios between the various CHx radicals whose polymerization is at the origin of the IOM. These isotopic heterogeneities, usually referred to as hot and cold spots, are commensurable with those observed in meteorite IOM. As a consequence, the appearance of organic radicals in the ionized regions of the disk surrounding the Sun during its formation may have triggered the formation of organic compounds.

Nanoparticles synthesis in microwave plasmas: peculiarities and comprehensive insight.

Low-pressure plasma processes are routinely used to grow, functionalize or etch materials, and thanks to some of its unique attributes, plasma has become a major player for some applications such as microelectronics. Plasma processes are however still at a research level when it comes to the synthesis and functionalization of nanoparticles. Yet plasma processes can offer a particularly suitable solution to produce nanoparticles having very peculiar features since they enable to: (i) reach particle with a variety of chemical compositions, (ii) tune the size and density of the particle cloud by acting on the transport dynamics of neutral or charged particles through a convenient setting of the thermal gradients or the electric field topology in the reactor chamber and (iii) manipulate nanoparticles and deposit them directly onto a substrate, or codeposit them along with a continuous film to produce nanocomposites or (iv) use them as a template to produce 1D materials. In this article, we present an experimental investigation of nanoparticles synthesis and dynamics in low-pressure microwave plasmas by combining time-resolved and in-situ laser extinction and scattering diagnostics, QCL absorption spectroscopy, mass spectrometry, optical emission spectroscopy and SEM along with a particle transport model. We showed for the first time the thermophoresis-driven dynamic of particle cloud in electrodless microwave plasmas. We showed that this effect is linked to particular fluctuations in the plasma composition and results in the formation of a void region in the bulk of the plasma surrounded by a particle cloud in the peripherical post-discharge. We also reveals and analyze the kinetics of precursor dissociation and molecular growth that result in the observed nanoparticle nucleation.

Metastatic ameloblastoma responding to combination chemotherapy: case report and review of the literature.

BACKGROUND: Ameloblastoma is a rare benign odontogenic tumor with locally aggressive behavior and a high recurrence rate. When metastases occur, which are uncommon, lungs constitute the most frequent site involved. Malignant ameloblastomas are different from ameloblastic carcinomas. Malignant ameloblastomas are tumors considered metastatic despite the appearance of well-differentiated or benign histology, while ameloblastic carcinomas are histologically malignant in both primary and metastatic sites. CASE PRESENTATION: A 24-year-old Moroccan man presented a malignant ameloblastoma of the mandible. The tumor was entirely resected. Five years later, a local recurrence occurred. Our patient was treated by exclusive radiotherapy with persistence of a residual disease. After two years he developed multiple lung metastases. Our patient received a combination chemotherapy using doxorubicin and cisplatin. CONCLUSION: Less than 50 cases of ameloblastoma with metastases have been reported. There is still no standard treatment for metastatic ameloblastoma. Only through continuous reporting of such cases will clinicians be able to draw an optimal strategy for management of this pathology.