Dna studies: Latest spectroscopic and structural approaches

This review looks at the different approaches, techniques, and materials devoted to DNA studies. In the past few decades, DNA nanotechnology, micro-fabrication, imaging, and spectro-scopies have been tailored and combined for a broad range of medical-oriented applications. The continuous advancements in miniaturization of the devices, as well as the continuous need to study biological material structures and interactions, down to single molecules, have increase the interdisciplinarity of emerging technologies. In the following paragraphs, we will focus on recent sensing approaches, with a particular effort attributed to cutting-edge techniques for structural and mechanical studies of nucleic acids

Investigation of Radar Signal Interaction with Crossflow Turbine for Aviation Application

The increased adoption of wind energy is an important part of the push towards a net zero-emission economy. One obstacle that stands in the way of a higher rate of wind energy adoption is the interference that wind turbines cause to nearby radar installations. Wind turbines negatively affect the performance of nearby radar sites in a variety of different ways. Almost all types of radar are affected in at least one of these ways.In order to understand the degree to which an object such as a wind turbine interacts with radar, it is important to have detailed radar cross section (RCS) data for the object. In this work, a novel, low-cost, scale model radar cross section characterization system is presented with various advantages over traditional designs. This system was used to characterize the RCS of the novel Crossflow wind turbine. Additionally, work has been carried out on the characterization of metamaterial absorber coatings that can be applied to new and existing turbines for the purposes of reducing their radar cross section and the degree to which they cause radar inter-ference. The works presented can be leveraged to reduce concerns around radar interference from wind turbines, as well as to iteratively generate ge-ometries with lower radar cross sections for the aviation and infrastructure sectors, ultimately accelerating the pace of wind energy adoption and the move towards a net zero-emission economy

Development of the SHiP downstream muon detector

SHiP (Search for Hidden Particles) is a beam dump experiment proposed at CERN SPS, currently in the design stage. SHiP aims to observe long lived particles very weakly coupled with ordinary matter, as expected in a large number of Hidden Sector models, that are able do describe Dark matter, neutrino oscillation and the origins of the Barionic Asimmetry of universe. In this thesis the development of the SHiP Downstream Muon Detector is described. This subdetector aims to identify with high efficiency muons produced by signal processes and to distinguish them from neutrino- and beam-induced background ones. In order to effectively distinguish background events mistakenly reconstructed as signal vertexes due to their spatial overlapping, a time resolution better than 200 ps is mandatory. Therefore, it is extremely important that the detector components are optimized with respect to time resolution. The detector employs active layers made of plastic scintillator tiles, each coupled to silicon photomultipliers (SiPM). This thesis focuses on the development of tile prototypes that are able to meet the detector time resolution requirements, through the study of various aspects of the tile design. The improved design defined with the contribution of this thesis work has become the current baseline design and will be tested with a prototype in early 2020 at the Frascati INFN Laboratories

Light manipulation through periodic plasmonic corrugations

textCollective oscillations of free electrons localized in a small volume have drawn a lot of attention for the past decades. These so-called plasmons have special optical properties that can be used in many applications ranging from optical modulators to sensing of small quantities of molecules. Large numbers of extensive plasmonic applications are being based on the capability of light manipulation proposed by the periodic nanostructure and its optical response. By controlling over the way in which plasmonic modes interact with incident radiation, periodic corrugation opens up the possibility of developing new and exciting photonic devices. The goal of doctoral research presented herein is to investigate at a fundamental level of several corrugated metallic structures which may offer effective control of the optical response by coupling radiation to plasmonic modes. By controlling morphologies and material compositions, sophisticatedly engineered nanostructure may allow the coupling of electromagnetic waves into desired spectral/spatial modes in a way that an effective tuning of macroscopic optical properties in desired domain can be achieved. This dissertation is dedicated to answer the following question, if and how one can manipulate the optical responses by use of different nanostructures and various materials. Based on devised analytical models proposed for various corrugated nanostructures, we show that I. spatial and II. spectral manipulation of light can be realized. Specifically, we investigate how the grating array interacts with light. To understand those periodic nanostructures showing inherently dispersive nature, firstly the diffraction of light and accompanying effects are studied with the analytical models and numerical simulation. On this basis, we show the optical response is readily tunable, and efficiently controlled by the morphology and dielectric property of the corrugations. The outline of doctoral research is broadly categorized into (1) theoretical considerations on the topic of plasmonics, (2) specific insight in the analytical model of the various nanostructures, and (3) investigation of the plasmonic properties of the fabricated structures. Lastly, the discussion of outlook to possibilities and future experiments will close the dissertation.Electrical and Computer Engineerin

Transverse Beam Profiles

The performance and safe operation of a particle accelerator is closely connected to the transverse emittance of the beams it produces. For this reason many techniques have been developed over the years for monitoring the transverse distribution of particles along accelerator chains or over machine cycles. The definition of beam profiles is explained and the different techniques available for the detection of the particle distributions are explored. Examples of concrete applications of these techniques are given.Comment: 37 pages, 53 figure

Geometric optical metasurface for polarization control

Like amplitude and phase, polarization is one of the fundamental properties of light. Controlling polarization in a desirable manner is fundamental to science and technology. However, practical applications based on polarization manipulation are mainly hindered by the complexity of experimental system, bulky size and poor spatial resolution. In recent years, metasurfaces have drawn considerable attention in the scientific community due to their exotic electromagnetic properties and potential breakthrough for light manipulation. With the development of nanophotonics, the generation of arbitrary spatially-varying polarization from an input beam is achievable. The objective of this thesis is to develop metasurface approaches to control phase and polarization of light in subwavelength scale for novel applications, such as polarization-controlled hologram generation and structured beam generation. The emphasis of the thesis is placed on the polarization control using geometric plasmonic metasurfaces. We start by reviewing recent progress regarding novel planar optical components. After the introduction of mechanism of light-nanostructure interaction and the far-field scattering of metal nanostructure arrays based on Mie theory, we discuss the abrupt phase change emerging from rotated nanostrips and the generalized Snell’s law. To demonstrate the precise phase manipulation, we develop a metasurface approach for polarization-controlled hologram generation. Moreover, we propose and experimentally demonstrate a novel method to realise the superposition of orbital angular momentum states in multiple channels using a single device. Spring from the superposition of two opposite circular polarizations, two different approaches for polarization manipulation at nanoscale are developed and experimentally verified. Based on the first approach, a vector vortex beam with inhomogeneous polarization and phase distributions is demonstrated, which features the spin-rotation coupling and the superposition of two orthogonal circular components, i.e., the converted part with an additional phase pickup and the residual part without a phase change. The second approach is to control the phase of the two orthogonal circular components simultaneously to engineer the polarization profile. Furthermore, we adopt this approach to develop a compact metasurface device which can hide a high-resolution grayscale image in a laser beam. The compactness of metasurface approach in polarization manipulation renders this technology very attractive for diverse applications such as encryption, imaging, optical communications, quantum science, and fundamental physics

Anti-Reflective Dielectric Nanostructures for Solar Cells Analyzed from a Helicity Preservation Perspective

Continuing increase of carbon dioxide (CO$_2$) emissions and subsequent growth of the global average temperature pushes us towards a faster transition from fossil fuels to renewable energy sources. In this respect, photovoltaics (PV) may play a decisive role in achieving net zero CO$_2$ emissions within the desired time frame. While new PV technologies have been actively researched over recent years, silicon (Si) PV continues to dominate the world market. Despite the maturity of Si PV, there is still room for improvement. In particular, to keep up with the estimates for the global installed PV capacity for upcoming decades, one has to consider how much energy is actually used for manufacturing Si wafers. Thus, it is feasible to consider a transition to thinner Si absorbers. However, such transition requires adjustments of the industrially accepted processes used to negate optical losses since the standard approach employing random pyramidal textures is no longer feasible for rather thin wafers. Thus, alternative strategies have to be established. For this purpose, nanophotonic structures are of interest. In particular, dielectric scatterers supporting Mie resonances attracted attention from the research community over the last few years. In this thesis, we perform a holistic study of periodic and disordered anti-reflective (AR) dielectric nanostructures applied to crystalline silicon (c-Si) heterojunction (HJT) solar cells. We optimize the optical performance of these systems and show that the AR properties of the nanostructure arrays on top of solar cell stacks are related to two requirements: a sufficiently high degree of discrete rotational symmetry of an array and the ability to preserve helicity of the incident illumination. For a periodic system, the first condition can be readily met. The second condition generally requires the system to be made from materials with an equal electric permittivity and magnetic permeability. Since this is unfeasible with naturally available materials, this condition has to be relaxed. Indeed, similar effects can be achieved if only the electric and magnetic response from the photonic nanostructure is balanced. This balance is accomplished by tuning the geometrical parameters of scatterers made from high index materials. For a disordered system, the helicity preservation condition can be reduced similarly to a periodic system. However, in such a system, the first condition is not exactly applicable. Luckily, the disorder can be tailored such that it becomes stealthy hyperuniform, and large-scale density fluctuations are suppressed. Such tailored disordered patterns are fully isotropic, thus possessing effective continuous rotational symmetry. Therefore, the AR properties of these systems are also related to the requirements stated above. Furthermore, we fabricate solar cells coated with periodic and tailored disordered nanodisks based on the optimal designs. We characterize the optical and electrical properties of the samples and observe the improvement of the AR properties and subsequent positive influence on the short-circuit current density. A complementary analysis of the annual energy yield of the solar modules employing solar cells with nanodisk coatings shows that our designs can potentially be integrated into the module with their positive effect preserved

Multilayer homogeneous dielectric filler for electromagnetic invisibility

En los últimos años, la invisibilidad se ha convertido en un área de investigación de creciente interés debido a los avances en la ingeniería de materiales. Puede ser posible lograr la invisibilidad a través de dispositivos de camuflaje, recubriendo el cuerpo con una o más capas de materiales con las propiedades electromagnéticas adecuadas. Mediante el uso de técnicas asociadas al camuflaje plasmónico es posible obtener también la invisibilidad de pequeños objetos con varias capas de materiales homogéneos que trabajan desde el interior del objeto. Demostramos numéricamente que es, por lo tanto, posible lograr la invisibilidad a través de un sistema interno basado en técnicas de cancelación de la dispersión.In recent years, invisibility has become a research area of increasing interest due to the advances in material engineering. It may be possible to achieve invisibility through cloaking devices by coating the body using one or more layers of materials with the proper electromagnetic properties. By using techniques associated to plasmonic cloaking it is maybe possible to obtain also invisibility for small objects with several layers of homogeneous materials working from inside the object. We demonstrate numerically that it is, therefore, possible to achieve invisibility through an inner system based on scattering cancellation techniques.• Gobierno de España y Fondos Europeos de Desarrollo Regional. Proyecto TEC2017-85376-C2-X-R (I+D+i) • Ministerio de Educación, Cultura y Deportes. Proyecto FPU 00022/15peerReviewe