Fabrication and size control of gold nanoparticles by laser ablation ab 64.9 € als Taschenbuch: . Aus dem Bereich: Bücher, Wissenschaft, Physik,
Fabrication and size control of gold nanoparticles by laser ablation ab 64.9 EURO
Production of carbon nanomaterials particularly CNTs with good quality and high yield is a challenging task. Various methods used for the production of CNTs include laser ablation, arc discharge method and catalytic chemical vapor deposition (CCVD). CCVD method is the well-recognized method for a large-scale production of CNTs but this requires optimization of various parameters such as reactor size, catalyst amount, gas flow rates, time of reaction, etc. to multiply yield of CNTs. The present work aimed at developing a simple CCVD setup for the production of CNTs with high yield. A product of CCVD experiments was dispersed in an epoxy resin to produce corrosion protection coatings for stainless steels.
A finite-element model of a two-dimensional slice of human atrial tissue for the study of the electrograms and propagation of action potentials is presented. Action potential propagation is described by a reaction-diffusion model coupled with the complex Courtemanche et al. atrial cell model. The effects of recording electrode size and location on electrograms are presented. Action potential propagation as a result of atrial fibrillation ablation therapy is also modeled by defining a lesion area with decreased electrical conductivity. The effect of electrical conductivity and geometry of the lesion was also studied. It is shown that the success rate of atrial fibrillation ablation therapy is primarily correlated with the creation of continuous ablation lines and also the formation of fibrous tissue.
Various DLC films were prepared using four different type synthesis setups. Optical microscopy data showed that the film regions grown under excimer laser illumination were strongly interference colored ( E 3 eV) at certain energy densities of illumination. AFM studies indicated that lower deposition temperatures resulted in bigger grain size of the DLC film surface structures and that the DLC films grown under laser illumination conditions were smoother. Raman spectroscopy studies of films indicated that higher ablating laser beam intensity had positive influence on the sp3 hybridized carbon content in films and that the additional irradiation of the growing film between the ablation pulses is inevitable to create the individual diamond phase formation into DLC films. The existence of diamond clusters in these films was also confirmed using AFM method. The individual diamond phase forms only in a narrow window of irradiating laser beam energy density. The cyclic voltammetry and impedance data for the DLCE xM NaF+H2O interface show that this system is nearly ideally polarizable in the potential region 0.4 E 1.1 V [vs. AgCl Ag (sat. KCl in H2O)].
Radio frequency ablation (RFA) has become the most commonly used ablative therapy for selected group of patients with liver tumors. To understand the effectiveness of RFA it is important to understand the mechanism of injury to the liver caused by RFA. There is no large animal model to study hepatocellular cancer. This book details the animal experiments carried out by the author in an attempt to create a porcine model of hepatocellular cancer. This book also details the discovery of Transition zone following ablation of liver tissue. This zone lies beyond the zone of cell necrosis and can not be identified by the usual histological techniques. Transition zone lies between necrotic liver tissue and normal liver parenchyma in lesion produced by RFA. This zone has cells showing apoptosis and increased expression of Heat Shock Protein (HSP) suggestive of cellular injury which will eventually lead to cell death. Further research to find techniques to increase the size of "Transition zone" may help in ablating larger areas of liver tumors.
Radiofrequency ablation (RFA) is a procedure to treat tumors of the liver by passing current through a needle shaped applicator placed inside the tumor. The tissue gets heated up and tumor cells are destroyed. Careful planning of the applicator positioning is mandatory for a successful treatment. The desirability of a specific applicator positioning is measured by different criteria, rendering the RFA planning problem a multi-objective optimization problem. In our work we propose a deterministic vector optimization approach to solve the multi-objective RFA treatment planning problem.To allow for numerical optimization routines, feasibility must be expressed as a set of constraint functions. A difficult-to-treat aspect of feasibility is non-overlapping with critical structures such as organs and bones. We propose a modelling approach where the critical structures are approximated as a set of convex polytopes. Then it is a well-known fact that the non-overlapping condition is equivalent to the existence of a set of separating planes -- each plane separating the applicator from one of the polytopes. In this way we can express the non-overlapping condition as a set of analytical constraint functions.A vector optimization approach strives to represent or approximate the set of efficient solutions. In this work we develop the adapted hyperboxing algorithm as a specific sandwiching method for the approximation of a non-convex non-dominated set. As in similar approaches, the non-dominated set is enclosed by a set of boxes, whose size is reduced systematically in the course of the algorithm. The adapted hyperboxing algorithm differs from previous methods in the construction of these boxes, which are spanned by the set of all feasible combinations of a so-called inner and an outer knee point. For the bi-criteria case we prove an a-priori upper bound for the approximation quality achieved by this algorithm.We show with several examples that the developed method can be successfully applied to calculate the non-dominated set of real-data RFA planning problems.
The continuous drive to further miniaturization is one of the basic research and development goals in industry producing data processing and storage devices, for reasons of economy, performance and energy minimisation. Modern magnetic hard drives have storage densities of hundreds of GBits / in² , but future storage devices are required to reach values of over 1 TBits/ in². Ideally, a single domain magnetic nanoparticle could represent a single data bit. A main issue for reaching this is the thermal stability of magnetisation if the superparamagnetic limit is reached. The most promising material is the bimetallic alloy FePt which offers large magnetic anisotropy due the presence of the ordered face centered tetragonal phase. In the frame of this objective a synthesis process by means of the physical approach of evaporation and recondensation in the gas phase was developed and optimized. Thereby ns-Pulsed Laser Ablation was applied on a FePt rod inside a vacuum-tight facility. The FePt nanoparticles were size selected by means of a Differential Mobility Analyzer and annealed in order to obtain desired spherical shape and magnetic properties.
Hepatocellular carcinoma is a major health problem worldwide, with an estimated incidence ranging between 500,000 and 1,000,000 new cases annually. It is the fifth most common cancer in the world and the third most common cause of cancer-related deaths.For years, partial hepatectomy and liver transplantation have been considered as the main curative treatments. However, only 10% to 20% of HCC are resectable. Anatomic location, size or number of lesions, inadequate liver remnant, or co-morbid condition precludes surgery in the majority of patients. Currently, local ablative therapy competes with partial hepatectomy and liver transplantation as primary treatment for small HCC.Radiofrequency ablation (RFA) is considered a promising alternative to surgery. For irresectable tumors, RFA seems to be the most effective treatment among other locoregional therapies. The main advantages of RFA include low morbidity and mortality rates, effective tumor ablation and preservation of maximal normal liver parenchyma.However, despite the high complete necrosis rate of RFA, early tumor recurrence within one year, either local tumor recurrence or new tumor formation,remains a significant problem.