Probing intrinsic transport properties of single metal nanowires: Direct-write contact formation using a focused ion beam

The transport characteristics of 70-nm-diameter platinum nanowires (NWs), fabricated using a pore-templated electrodeposition process and individually contacted using a focused ion beam (FIB) method, are reported. This approach yields nanowire devices with low contact resistances (similar to400 Omega) and linear current-voltage characteristics for current densities up to 65 kA/cm(2). The intrinsic nanowire resistivity (33+/-5 muOmega cm) indicates significant contributions from surface- and grain-boundary scattering mechanisms. Fits to the temperature dependence of the intrinsic NW resistance confirm that grain-boundary scattering dominates surface scattering (by more than a factor of 2) at all temperatures. Our results demonstrate that FIB presents a rapid and flexible method for the formation of low-resistance ohmic contacts to individual metal nanowires, allowing intrinsic nanowire transport properties to be probed

Fabricação aditiva de suportes 3D porosos de um vidro bioativo isento de alcalinos para aplicações médicas

Tissue Engineering is a multidisciplinary field of study based on the techniques, methods and knowledge of biology, medicine and engineering. The aim is to produce artificial devices able to act as temporary substitutes of damaged tissues: the structure realized must serve as supports for cell attachment and proliferation as well as the production of extracellular matrix, ideally until the same device degrades. The great issues related to this approach are therefore implementing a suitable scaffold material produced with an adequate technique in order to satisfy the above requirements. In this Thesis project, an alkali-free bioactive glass composition in the binary system of Diopside-Tricalcium Phosphate that has already shown promising properties for tissue engineering and bone regeneration was selected. The robocasting technique was adopted for manufacturing 3D porous scaffolds with adequate structures and porosities designed by CAD. The work included different steps such as: (i) preparation and characterization of glass powders with different particle size distributions to enhance the packing ability; (ii) preparation of concentrated suspensions and investigate the dependence of their rheological properties on solid loading and the content of CMC selected as the single processing additive; (iii) production of the scaffold with different porosity; (iv) characterization of the printed structures before and after sintering process. The results obtained demonstrated that a 1:1 mixture of glass powders having mean particle diameters of 1 m and 45 m enables preparing suitable suspensions by playing with the contents of CMC and solid loading. The printed scaffolds present well-defined geometry and good shape retention. The work carried out could be considered as a very promising starting point for further studies aiming at obtaining further improvementsA Engenharia de tecidos é um campo de estudo multidisciplinar baseado nas técnicas, métodos e conhecimentos derivados das áreas da biologia, medicina e engenharia. O objetivo é produzir dispositivos artificiais capazes de atuar como substitutos temporários de tecidos danificados: a estrutura obtida deve servir de suporte para a fixação e proliferação de células, bem como para a produção de matriz extracelular, idealmente até o mesmo dispositivo se degradar. Os grandes problemas relacionados a esta abordagem requerem a selecção adequada de um material e de uma técnica de processamento das estruturas de suporte. Neste projeto de tese foi selecionada uma composição de vidro bioativo isento de álcalis no sistema binário de Diópsido - Fostato Tricálcico que já mostrou propriedades promissoras para engenharia de tecidos e regeneração óssea. A técnica de robocasting foi adotada para fabricação de andaimes porosos 3D com estruturas e porosidades projetadas por CAD e adequados para as funções almejadas. O trabalho incluiu diferentes etapas, tais como: (i) preparação e caracterização de pós de vidro com diferentes distribuições granulométricas como forma de aumentar a capacidade de empacotamento; (ii) preparação de suspensões concentradas e estudo da dependência das suas propriedades reológicas do teor de sólidos e da quantidade adicionada de CMC, selecionado como único aditivo de processamento; (iii) produção dos scaffolds com diferentes porosidades; (iv) caracterização das estruturas impressas antes e após o processo de sinterização. Os resultados obtidos demonstraram que uma mistura 1:1 de pós de vidro com diâmetros médios de partículas de 1 m e de 4 a 5 m permite a preparação de suspensões adequadas, alterando com o conteúdo de CMC e com a carga de sólidos. Os scaffolds impressos apresentam geometrias bem definidas e boa retenção da forma. O trabalho realizado pode ser considerado um ponto de partida muito interessante para estudos futuros com vista a obter melhorias adicionaisMestrado em Engenharia de Materiai

Magnetic resonance tumor regression grade (MR-TRG) to assess pathological complete response following neoadjuvant radiochemotherapy in locally advanced rectal cancer

This study aims to evaluate the feasibility of a magnetic resonance (MR) automatic method for quantitative assessment of the percentage of fibrosis developed within locally advanced rectal cancers (LARC) after neoadjuvant radiochemotherapy (RCT). A total of 65 patients were enrolled in the study and MR studies were performed on 3.0 Tesla scanner; patients were followed-up for 30 months. The percentage of fibrosis was quantified on T2-weighted images, using automatic K-Means clustering algorithm. According to the percentage of fibrosis, an optimal cut-off point for separating patients into favorable and unfavorable pathologic response groups was identified by ROC analysis and tumor regression grade (MR-TRG) classes were determined and compared to histopathologic TRG. An optimal cut-off point of 81% of fibrosis was identified to differentiate between favorable and unfavorable pathologic response groups resulting in a sensitivity of 78.26% and a specificity of 97.62% for the identification of complete responders (CRs). Interobserver agreement was good (0.85). The agreement between P-TRG and MR-TRG was excellent (0.923). Significant differences in terms of overall survival (OS) and disease free survival (DFS) were found between favorable and unfavorable pathologic response groups. The automatic quantification of fibrosis determined by MR is feasible and reproducible

Skeletal anomalies in dusky grouper Epinephelus marginatus (Lowe 1834) juveniles reared with different methodologies and larval densities

The first attempts to reproduce dusky grouper (Epinephelus marginatus, Lowe 1834) under controlled conditions started in 1995, but the egg and larvae quality was very low. Mass production is still encountering many difficulties, mainly concentrated in the larval period when very high mortality rates are observed, confirming what has been observed in the rearing of other grouper species. The main bottlenecks have been identified as the difficulty to properly nourish the larvae, stress shock syndrome, and the high deformation rates. We analysed 633 dusky grouper larvae and juveniles (0.2–7.2 cm total length, TL), sampled during two larval rearing cycles carried out in 2001 and 2002 in Italy. The specimens at different development stages were stained in toto for bone and cartilage and examined for skeletal anomalies during dusky grouper ontogenesis. The incidence of anomalies in groupers hatched from the same egg batch but reared using two different methods (green waters and semi-intensive rearing) and three stocking densities (8, 16 and 28 larvae/l) was compared, with a view to providing tools for identifying the most appropriate larval rearing method in order to at least limit the onset of skeletal anomalies. Our results suggest that during development no particular skeletal anomaly patterns (or fate) can be clearly identified as a high variability was observed in malformation typologies and the regions affected. No significant differences in the morphological quality between groupers reared using semi-intensive (LV02 lot) and green water (GW02-01 lot) methodologies were observed, whilst groupers reared at the highest stocking density (28 larvae/l) showed the highest frequency of deformed individuals (75.8%), the highest malformation charge (average of 5.5 anomalies per deformed individual), the largest range of anomaly typologies (38), and the highest incidence of individuals with at least one severe anomaly (30.9%). Whilst in green waters no evident effects of larvae density were observed on survival rates, the survival rate in large volume reared individuals (17.5%) was considerably higher with respect to those reared in green waters (0.2%) at 7–8 larvae/l. This indicates that the semi-intensive methodology should be considered more effective in enhancing the survival rate of dusky grouper larvae

Detection and Reinforcement of Celiac Communities on Twitter Argentina

Social Networks have shown great growth relating the number of their users and generated content. For example, Twitter is used asa means to gather support, express ideas and opinions on various topicsor interact with users with similar interests. In the latter case, the ideaof community formation appears, that is, groups of users that are moreclosely related to each other than the rest of the nodes in the network.In this work we propose the detection of the community of users ofArgentina interested in the celiac disease. We apply a series of techniques to detect and characterize them. In addition, we propose anduse a methodology for the detection of more influential and active nodes(users), showing how the community can be reinforced by the recommendation of some particular links. The results show that with only a lowpercentage of accepted recommendation the network becomes denser andaverage distance between two users decreases quickly, thus improving thespread of information.Fil: Giordano, Luis Andres. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Banchero, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: Cerny, Natacha. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; ArgentinaFil: de Marzi, Mauricio Cesar. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Tolosa, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Luján. Departamento de Ciencias Básicas; Argentin

Complete resolution of non-necrotizing lung granuloma and pyoderma gangrenosum after restorative proctocolectomy in a woman with severe ulcerative colitis and cytomegalovirus infection

Here, we report the unusual case of an ulcerative colitis female patient presenting together with cytomegalovirus infection, pyoderma gangrenosum and a noncaseating lung granuloma, both resistant to immunomodulatory drugs which dramatically obtained a clinical stable remission after restorative proctocolectomy

Pareto-Optimization of HTS CICC for High-Current Applications in Self-Field

The ENEA superconductivity laboratory developed a novel design for Cable-in-Conduit Conductors (CICCs) comprised of stacks of 2nd-generation REBCO coated conductors. In its original version, the cable was made up of 150 HTS tapes distributed in five slots, twisted along an aluminum core. In this work, taking advantage of a 2D finite element model, able to estimate the cable's current distribution in the cross-section, a multiobjective optimization procedure was implemented. The aim of optimization was to simultaneously maximize both engineering current density and total current flowing inside the tapes when operating in self-field, by varying the cross-section layout. Since the optimization process involved both integer and real geometrical variables, the choice of an evolutionary search algorithm was strictly necessary. The use of an evolutionary algorithm in the frame of a multiple objective optimization made it an obliged choice to numerically approach the problem using a nonstandard fast-converging optimization algorithm. By means of this algorithm, the Pareto frontiers for the different configurations were calculated, providing a powerful tool for the designer to achieve the desired preliminary operating conditions in terms of engineering current density and/or total current, depending on the specific application field, that is, power transmission cable and bus bar systems

Charge transport in a CoPt3 nanocrystal microwire

The electrical characteristics of single CoPt3 nanocrystal microwires formed by magnetic field-directed growth from colloidal solutions are presented. The wires comprise disordered assemblies of discrete nanocrystals, separated from each other by protective organic ligand shells. Electrical data indicate that the activated charge transport properties of the wires are determined by the nanocrystal charging energy, governed by the size and capacitance of the individual nanocrystals. Focused ion beam-assisted deposition of Pt metal at the wire-electrode junctions is employed to optimize the wire-electrode contacts, whilst maintaining the nanocrystal-dominated transport characteristics of these one-dimensional nanocrystal structures. (C) 2004 American Institute of Physics. (DOI:10.1063/1.1830684