Oxygen and light sensitive field-effect transistors based on ZnO nanoparticles attached to individual double-wall carbon nanotubes

The attachment of semiconducting nanoparticles to carbon nanotubes is one of the most challenging subjects in nanotechnology. Successful high coverage attachment and control over the charge transfer mechanism and photo-current generation opens a wide field of new applications such as highly effective solar cells and fibre-enhanced polymers. In this work we study the charge transfer in individual double-wall carbon nanotubes highly covered with uniform ZnO nanoparticles. The synthetic colloidal procedure was chosen to avoid long-chained ligands at the nanoparticle-nanotube interface. The resulting composite material was used as conductive channel in a field effect transistor device and the electrical photo-response was analysed under various conditions. By means of the transfer characteristics we could elucidate the mechanism of charge transfer from non-covalently attached semiconducting nanoparticles to carbon nanotubes. The role of positive charges remaining on the nanoparticles is discussed in terms of a gating effect.Comment: 6 pages, 4 figure

The role of halogens in the synthesis of semiconductor nanocrystals

The presence of halogen compounds in the synthesis of semiconductor nanocrystals (NCs) produced by hot injection drastically influence their capping ligand sphere and/or chemical reactivity, allowing for the growth of hybrid systems, including composites combining NCs decorating carbon sp2 surfaces. As a result, the presence of halide anions on the surface of some NCs has proven to have a positive impact on the optical and electrical properties. In this work the effects that halogen co-solvents (including alkylchlorides, bromides, and iodides) induce in the synthesis of rod-like Wurtzite CdSe NCs generated by hot-injection will be reviewed. The proposed mechanism of the reaction as well as a detailed characterization of the capping ligand sphere by Nuclear Magnetic Resonance (NMR) and X-Ray photoelectron Spectroscopy (XPS) will be discussed. Correlated cyclic voltammetry (CV) and XPS studies have been performed to address the effect of the halide anions on the NCs surface. Finally an example of the effect of the addition of chlorine-containing co-solvents on the synthesis of PbS rock-salt NCs will be shownThe author thanks the Spanish Ministry of Economy and Competitiveness through MAT-2009-13488 and the Comunidad de Madrid through PHAMA_2.0 S2013/MIT-274

Renormalization Group Equations for the CKM matrix

We derive the one loop renormalization group equations for the Cabibbo-Kobayashi-Maskawa matrix for the Standard Model, its two Higgs extension and the minimal supersymmetric extension in a novel way. The derived equations depend only on a subset of the model parameters of the renormalization group equations for the quark Yukawa couplings so the CKM matrix evolution cannot fully test the renormalization group evolution of the quark Yukawa couplings. From the derived equations we obtain the invariant of the renormalization group evolution for three models which is the angle $\alpha$ of the unitarity triangle. For the special case of the Standard Model and its extensions with $v_{1}\approx v_{2}$ we demonstrate that also the shape of the unitarity triangle and the Buras-Wolfenstein parameters $\bar{\rho}=(1-{1/2}\lambda^{2})\rho$ and $\bar{\eta}=(1-{1/2}\lambda^{2})\eta$ are conserved. The invariance of the angles of the unitarity triangle means that it is not possible to find a model in which the CKM matrix might have a simple, special form at asymptotic energies.Comment: 9 page

Spin-Orbit Coupling and Ion Displacements in Multiferroic TbMnO3

The electronic and magnetic properties of TbMnO3 leading to its ferroelectric (FE) polarization were investigated on the basis of relativistic density functional theory (DFT) calculations. In agreement with experiment, we show that the spin-spiral plane of TbMnO3 can be either the bc- or ab-plane, but not the ac-plane. As for the mechanism of FE polarization, our work reveals that the "pure electronic" model by Katsura, Nagaosa and Balatsky (KNB) is inadequate in predicting the absolute direction of FE polarization. For the ab-plane spin-spiral state of TbMnO3, the direction of FE polarization predicted by the KNB model is opposite to that predicted by DFT calculations. In determining the magnitude and the absolute direction of FE polarization in spin-spiral states, it is found crucial to consider the displacements of the ions from their ecntrosymmetric positions

Microgels and nanoparticles: Where Micro and Nano Go Hand in Hand

The integration of different types of materials in a single hybrid system allows the combination of multiple functionalities, which can even be used in conjunction with each other. This strategy has been exploited in nanoscale systems for the creation of so-called smart nanomaterials. Within this category, the combination of inorganic nanoparticles with stimuli-responsive microgels is of very high interest because of the wide variety of potential applications. We present here a short overview of this type of materials in which the nano-and micro-scales get nicely integrated, with a great potential to expand the range of technological applications. We focus mainly on the integration of metal nanoparticles, either by themselves or in combination with semiconductor and magnetic nanoparticles. Various examples of the synergic properties that can be obtained are described, as well as the possibility to extract useful information when optical tweezers are used to manipulate single particles. We expect that this review will stimulate additional research in this fieldThis work was partly supported by the European Research Council (ERC Advanced Grant #267867 Plasmaquo

Graph Refinement based Airway Extraction using Mean-Field Networks and Graph Neural Networks

Graph refinement, or the task of obtaining subgraphs of interest from over-complete graphs, can have many varied applications. In this work, we extract trees or collection of sub-trees from image data by, first deriving a graph-based representation of the volumetric data and then, posing the tree extraction as a graph refinement task. We present two methods to perform graph refinement. First, we use mean-field approximation (MFA) to approximate the posterior density over the subgraphs from which the optimal subgraph of interest can be estimated. Mean field networks (MFNs) are used for inference based on the interpretation that iterations of MFA can be seen as feed-forward operations in a neural network. This allows us to learn the model parameters using gradient descent. Second, we present a supervised learning approach using graph neural networks (GNNs) which can be seen as generalisations of MFNs. Subgraphs are obtained by training a GNN-based graph refinement model to directly predict edge probabilities. We discuss connections between the two classes of methods and compare them for the task of extracting airways from 3D, low-dose, chest CT data. We show that both the MFN and GNN models show significant improvement when compared to one baseline method, that is similar to a top performing method in the EXACT'09 Challenge, and a 3D U-Net based airway segmentation model, in detecting more branches with fewer false positives.Comment: Accepted for publication at Medical Image Analysis. 14 page

Privacy Preserving Internet Browsers: Forensic Analysis of Browzar

With the advance of technology, Criminal Justice agencies are being confronted with an increased need to investigate crimes perpetuated partially or entirely over the Internet. These types of crime are known as cybercrimes. In order to conceal illegal online activity, criminals often use private browsing features or browsers designed to provide total browsing privacy. The use of private browsing is a common challenge faced in for example child exploitation investigations, which usually originate on the Internet. Although private browsing features are not designed specifically for criminal activity, they have become a valuable tool for criminals looking to conceal their online activity. As such, Technological Crime units often focus their forensic analysis on thoroughly examining the web history on a computer. Private browsing features and browsers often require a more in-depth, post mortem analysis. This often requires the use of multiple tools, as well as different forensic approaches to uncover incriminating evidence. This evidence may be required in a court of law, where analysts are often challenged both on their findings and on the tools and approaches used to recover evidence. However, there are very few research on evaluating of private browsing in terms of privacy preserving as well as forensic acquisition and analysis of privacy preserving internet browsers. Therefore in this chapter, we firstly review the private mode of popular internet browsers. Next, we describe the forensic acquisition and analysis of Browzar, a privacy preserving internet browser and compare it with other popular internet browser