Data Reduction And Error Analysis For The Physical Sciences

Over the last few years arrays of evanescently coupled waveguides have been brought into focus as a particular representation of functionalized optical materials, in which the dispersion and diffraction of propagating light can be specifically tuned Moreover, it turns out that the light evolution in these systems shares fundamental similarities to the quantum evolution of particle wavefunctions, so that waveguide arrays can act as a model system for emulating quantum mechanics Recently, a novel technique was developed with which waveguides can be directly 'written' into various optical bulk materials using femtosecond laser pulses, which allows for the realization of a variety of innovative concepts which are not feasible using other fabrication methods The aim of this tutorial is to give an introduction to this topic

https://iopscience.iop.org/article/10.1088/0953-4075/43/16/163001/pdf

Discrete optics in femtosecond-laser-written photonic structures

Nanotechnology offers the food industry a number of new approaches for improving the quality, shelf life, safety, and healthiness of foods. Nevertheless, there is concern from consumers, regulatory agencies, and the food industry about potential adverse effects (toxicity) associated with the application of nanotechnology in foods. In particular, there is concern about the direct incorporation of engineered nanoparticles into foods, such as those used as delivery systems for colors, flavors, preservatives, nutrients, and nutraceuticals, or those used to modify the optical, rheological, or flow properties of foods or food packaging. This review article summarizes the application of both inorganic (silver, iron oxide, titanium dioxide, silicon dioxide, and zinc oxide) and organic (lipid, protein, and carbohydrate) nanoparticles in foods, highlights the most important nanoparticle characteristics that influence their behavior, discusses the importance of food matrix and gastrointestinal tract effects on nanoparticle properties, emphasizes potential toxicity mechanisms of different food-grade nanoparticles, and stresses important areas where research is still needed. The authors note that nanoparticles are already present in many natural and processed foods, and that new kinds of nanoparticles may be utilized as functional ingredients by the food industry in the future. Many of these nanoparticles are unlikely to have adverse affects on human health, but there is evidence that some of them could have harmful effects and that future studies are required.

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Is nano safe in foods? Establishing the factors impacting the gastrointestinal fate and toxicity of organic and inorganic food-grade nanoparticles

An appropriate cellular response to implanted surfaces is essential for tissue regeneration and integration. It is well described that implanted materials are immediately coated with proteins from blood and interstitial fluids, and it is through this adsorbed layer that cells sense foreign surfaces. Hence, it is the adsorbed proteins, rather than the surface itself, to which cells initially respond. Diverse studies using a range of materials have demonstrated the pivotal role of extracellular adhesion proteins—fibronectin and vitronectin in particular—in cell adhesion, morphology, and migration. These events underlie the subsequent responses required for tissue repair, with the nature of cell surface interactions contributing to survival, growth, and differentiation. The pattern in which adhesion proteins and other bioactive molecules adsorb thus elicits cellular reactions specific to the underlying physicochemical properties of the material. Accordingly, in vitro studies generally demonstrate favorable cell responses to charged, hydrophilic surfaces, corresponding to superior adsorption and bioactivity of adhesion proteins. This review illustrates the mediation of cell responses to biomaterials by adsorbed proteins, in the context of osteoblasts and selected materials used in orthopedic implants and bone tissue engineering. It is recognized, however, that the periimplant environment in vivo will differ substantially from the cell–biomaterial interface in vitro. Hence, one of the key issues yet to be resolved is that of the interface composition actually encountered by osteoblasts within the sequence of inflammation and bone regeneration.

Mediation of biomaterial-cell interactions by adsorbed proteins: A review

Recent progress in the development of polyethylene/metal-oxide nanocomposites for extruded high-voltage direct-current (HVDC) cables with ultrahigh electric insulation properties is presented. This is a promising technology with the potential of raising the upper voltage limit in today's underground/submarine cables, based on pristine polyethylene, to levels where the loss of energy during electric power transmission becomes low enough to ensure intercontinental electric power transmission. The development of HVDC insulating materials together with the impact of the interface between the particles and the polymer on the nanocomposites electric properties are shown. Important parameters from the atomic to the microlevel, such as interfacial chemistry, interfacial area, and degree of particle dispersion/aggregation, are discussed. This work is placed in perspective with important work by others, and suggested mechanisms for improved insulation using nanoparticles, such as increased charge trap density, adsorption of impurities/ions, and induced particle dipole moments are considered. The effects of the nanoparticles and of their interfacial structures on the mechanical properties and the implications of cavitation on the electric properties are also discussed. Although the main interest in improving the properties of insulating polymers has been on the use of nanoparticles, leading to nanodielectrics, it is pointed out here that larger microscopic hierarchical metal-oxide particles with high surface porosity also impart good insulation properties. The impact of the type of particle and its inherent properties (purity and conductivity) on the nanocomposite dielectric and insulating properties are also discussed based on data obtained by a newly developed technique to directly observe the charge distribution on a nanometer scale in the nanocomposite.

The Role of Interfaces in Polyethylene/Metal-Oxide Nanocomposites for Ultrahigh-Voltage Insulating Materials.

A review on recent development in self-consistent description of high-frequency discharges is presented. The discussions are based on fluid models of travelling-wave-sustained plasmas and results for the axial structure of discharges in different gases. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Guided-wave-produced plasmas

The modeling of microwave-sustained discharges at atmospheric pressure is much less advanced than at reduced pressure (<10 Torr) because of the greater complexity of the mechanisms involved. In particular, discharge contraction, a characteristic feature of high-pressure discharges, is not well understood. To describe adequately this phenomenon, one needs to consider that the charged-particle balance in atmospheric-pressure discharges relies on the kinetics of molecular ions, including their dissociation through electron impact. Nonuniform gas heating plays a key role in the radial distribution of the density of molecular ions. The onset of contraction is shown to depend only on radially nonuniform gas heating. The radial nonuniformity of the electric field intensity also plays an important role allowing one, for instance, to explain the lower degree of contraction observed in microwave discharges compared to dc discharges. We present a numerical fluid-plasma model that aims to bring into relief the main features of discharge contraction in rare gases. It calls for surface-wave discharges because of their wide range of operating conditions, enabling a closer check between theory and experiment.

Modeling of microwave-sustained plasmas at atmospheric pressure with application to discharge contraction.

Multi-dipolar plasmas are sustained in large-volume chambers by a network of antennas located at the wall. Each antenna consists of a permanent magnet, trapping electrons in an axisymmetric dipole field, and a microwave applicator, heating the trapped electrons by cyclotron resonance (ECR). This paper presents a two-dimensional self-consistent model of a plasma sustained by one such antenna. The microwave fields and power absorption are calculated from the Maxwell equations coupled with a local electron momentum equation by an adaptation of the finite difference time domain method. The plasma is described by fluid equations for magnetized electrons and inertial ions, where quasi-neutrality is imposed through a semi-implicit numerical method based on Poisson's equation, which also yields the sheath potentials. Steady-state model results for argon show that below the critical plasma density (7.4×1016 m−3) the microwave power is absorbed in a narrow region all along the ECR surface around the end of the antenna; beyond this density the main absorption occurs near the plasma edge. Although the electron temperature varies considerably across the magnetic field lines, the plasma potential is nearly uniform all around the antenna and is controlled by the maximum electron temperature.

https://iopscience.iop.org/article/10.1088/0022-3727/42/19/194019/pdf

Modelling of a dipolar microwave plasma sustained by electron cyclotron resonance

A numerical model of surface-wave-produced plasmas in a diffusion-controlled regime is presented in this study. With the wide gas-pressure range (p=0.05–5 Torr) considered in a combination with a frequency (f=144 MHz) in the rf-range, the model covers discharge maintenance under different conditions with respect to mechanisms of electron heating and discharge self-consistency. The precise description of the wave dispersion properties and field distribution in inhomogeneous collisional plasmas included in the electrodynamical part of the model and the specification of the discharge kinetics in its gas-discharge part provide the quantitative description of the discharge production. The model results in the self-consistent structure of the discharge composed by interrelated variations, along the discharge, of wave number, damping rate, field distribution, power absorbed in average by an electron, plasma density, electron temperature, and Joule heating. The total absorbed power finally obtained in its relation to the discharge length is the power which should be externally applied for the discharge maintenance.

Surface-wave-produced plasmas in a diffusion-controlled regime

The aim of this work is to limit charge injection from a semi-conducting electrode into low density polyethylene (LDPE) under dc field by tailoring the polymer surface using a silver nanoparticles-containing layer. The layer is composed of a plane of silver nanoparticles embedded in a semi-insulating organosilicon matrix deposited on the polyethylene surface by a plasma process. Size, density and surface coverage of the nanoparticles are controlled through the plasma process. Space charge distribution in 300 μm thick LDPE samples is measured by the pulsed-electroacoustic technique following a short term (step-wise voltage increase up to 50 kV mm−1, 20 min in duration each, followed by a polarity inversion) and a longer term (up to 12 h under 40 kV mm−1) protocols for voltage application. A comparative study of space charge distribution between a reference polyethylene sample and the tailored samples is presented. It is shown that the barrier effect depends on the size distribution and the surface area covered by the nanoparticles: 15 nm (average size) silver nanoparticles with a high surface density but still not percolating form an efficient barrier layer that suppress charge injection. It is worthy to note that charge injection is detected for samples tailored with (i) percolating nanoparticles embedded in organosilicon layer; (ii) with organosilicon layer only, without nanoparticles and (iii) with smaller size silver particles (<10 nm) embedded in organosilicon layer. The amount of injected charges in the tailored samples increases gradually in the samples ranking given above. The mechanism of charge injection mitigation is discussed on the basis of complementary experiments carried out on the nanocomposite layer such as surface potential measurements. The ability of silver clusters to stabilize electrical charges close to the electrode thereby counterbalancing the applied field appears to be a key factor in explaining the charge injection mitigation effect.

http://iopscience.iop.org/article/10.1088/0022-3727/49/1/015304/pdf

Kremena Makasheva

Papers

Guided-wave-produced plasmas

Modeling of microwave-sustained plasmas at atmospheric pressure with application to discharge contraction.

Modelling of a dipolar microwave plasma sustained by electron cyclotron resonance

Surface-wave-produced plasmas in a diffusion-controlled regime

Silver nanoparticles as a key feature of a plasma polymer composite layer in mitigation of charge injection into polyethylene under dc stress