Self-organization and optical response of silver nanoparticles dispersed in a dielectric matrix

Abstract. Double ion-beam sputtering has been used to fabricate nanocermet multilayers consisting of silver nanoparticles sandwiched between Si 3 N 4 dielectric layers. The organization of the nanoparticles has been studied in detail by quantitative analysis of transmission electronic microscopy and atomic force microscopy images. Our results show that the nanoparticles deposited on a plane surface present an isotropic macroscopic in-plane organization while their vertical arrangement displays a topology-induced self-organization. The use of faceted alumina substrates with periodic hill-and-valley structures results in the formation of linear chains of silver particles along the valleys. In that case, transmission optical measurements reveal in-plane anisotropy

Advances in multispectral and hyperspectral imaging for archaeology and art conservation

Multispectral imaging has been applied to the field of art conservation and art history since the early 1990s. It is attractive as a noninvasive imaging technique because it is fast and hence capable of imaging large areas of an object giving both spatial and spectral information. This paper gives an overview of the different instrumental designs, image processing techniques and various applications of multispectral and hyperspectral imaging to art conservation, art history and archaeology. Recent advances in the development of remote and versatile multispectral and hyperspectral imaging as well as techniques in pigment identification will be presented. Future prospects including combination of spectral imaging with other noninvasive imaging and analytical techniques will be discussed

Cardiac Hypertrophy Involves Both Myocyte Hypertrophy and Hyperplasia in Anemic Zebrafish

Background: An adult zebrafish heart possesses a high capacity of regeneration. However, it has been unclear whether and how myocyte hyperplasia contributes to cardiac remodeling in response to biomechanical stress and whether myocyte hypertrophy exists in the zebrafish. To address these questions, we characterized the zebrafish mutant tr265/tr265, whose Band 3 mutation disrupts erythrocyte formation and results in anemia. Although Band 3 does not express and function in the heart, the chronic anemia imposes a sequential biomechanical stress towards the heart. Methodology/principal findings: Hearts of the tr265/tr265 Danio rerio mutant become larger than those of the sibling by week 4 post fertilization and gradually exhibit characteristics of human cardiomyopathy, such as muscular disarray, re-activated fetal gene expression, and severe arrhythmia. At the cellular level, we found both increased individual cardiomyocyte size and increased myocyte proliferation can be detected in week 4 to week 12 tr265/tr265 fish. Interestingly, all tr265/tr265 fish that survive after week-12 have many more cardiomyocytes of smaller size than those in the sibling, suggesting that myocyte hyperplasia allows the long-term survival of these fish. We also show the cardiac hypertrophy process can be recapitulated in wild-type fish using the anemia-inducing drug phenylhydrazine (PHZ). Conclusions/significance: The anemia-induced cardiac hypertrophy models reported here are the first adult zebrafish cardiac hypertrophy models characterized. Unlike mammalian models, both cardiomyocyte hypertrophy and hyperplasia contribute to the cardiac remodeling process in these models, thus allowing the effects of cardiomyocyte hyperplasia on cardiac remodeling to be studied. However, since anemia can induce effects on the heart other than biomechanical, non-anemic zebrafish cardiac hypertrophy models shall be generated and characterized

The management of acute venous thromboembolism in clinical practice. Results from the European PREFER in VTE Registry

Venous thromboembolism (VTE) is a significant cause of morbidity and mortality in Europe. Data from real-world registries are necessary, as clinical trials do not represent the full spectrum of VTE patients seen in clinical practice. We aimed to document the epidemiology, management and outcomes of VTE using data from a large, observational database. PREFER in VTE was an international, non-interventional disease registry conducted between January 2013 and July 2015 in primary and secondary care across seven European countries. Consecutive patients with acute VTE were documented and followed up over 12 months. PREFER in VTE included 3,455 patients with a mean age of 60.8 ± 17.0 years. Overall, 53.0 % were male. The majority of patients were assessed in the hospital setting as inpatients or outpatients (78.5 %). The diagnosis was deep-vein thrombosis (DVT) in 59.5 % and pulmonary embolism (PE) in 40.5 %. The most common comorbidities were the various types of cardiovascular disease (excluding hypertension; 45.5 %), hypertension (42.3 %) and dyslipidaemia (21.1 %). Following the index VTE, a large proportion of patients received initial therapy with heparin (73.2 %), almost half received a vitamin K antagonist (48.7 %) and nearly a quarter received a DOAC (24.5 %). Almost a quarter of all presentations were for recurrent VTE, with >80 % of previous episodes having occurred more than 12 months prior to baseline. In conclusion, PREFER in VTE has provided contemporary insights into VTE patients and their real-world management, including their baseline characteristics, risk factors, disease history, symptoms and signs, initial therapy and outcomes

Advanced optical effective medium modeling for a single layer of polydisperse ellipsoidal nanoparticles embedded in a homogeneous dielectric medium: Surface plasmon resonances

We calculate, in the quasistatic coupled dipole approximation, the analytical expressions of the effective dielectric tensor of a single layer of polydisperse ellipsoidal nanoparticles with two of their principal axes in the layer's plane and embedded in a homogeneous dielectric medium. The organization (isotropic or anisotropic) and orientation (without or with a preferential in-plane orientation) of the nanoparticles is taken into account, together with their (possibly correlated) in-plane size, in-plane projected shape, and height distributions. In particular, we propose to describe the response of a layer of nanoparticles presenting a height distribution by using a vertically graded effective medium model. The expressions are tested in the case of finely characterized dielectric/silver/dielectric granular trilayers grown by means of vapor deposition in which the silver coalesced nanoparticles present correlated in-plane size and in-plane projected shape/height distributions and a moderate surface coverage of about 25%. A satisfactory quantitative agreement is obtained between the simulated and measured surface plasmon extinction bands of the metal nanoparticles. This agreement is permitted by the capability of the effective medium model of taking into account the ellipsoidal shape of the nanoparticles. The significant role of the size and shape distributions is also demonstrated. © 2012 American Physical Society.The authors would like to thank Philippe Guerin and ´ Marie-Franc¸oise Denanot for the preparation and TEM characterizations of the nanocomposite films, respectively. J.T. acknowledges financial support from the Spanish Ministry of Science and Innovation (Grant No. JCI2009-05098 and project MAT2009-14369-C02-02).Peer Reviewe

Separation between the different fluxes scattered by art glazes: explanation of the special color saturation

International audienceIn a previous paper, the special visual appearance of art glazes was explained using the auxiliary function method (AFM) for solving the radiative transfer equation. Glazes are made of low concentrated colored scattering centers embedded in a transparent medium and the artist modulates the color by varying the number of glaze layers. A simple model of glazes and the new solving method have both been validated by comparison between flux measurements and modeling. The color of art glazes is analyzed here, and the study shows a spectacular maximum of saturation (purity) of the color that is never reached, to the best of our knowledge, with other techniques, such as pigment mixtures. This phenomenon is explained once more using the AFM that allows separation of the different contributions to the scattered fluxes. It is then shown that, on the one hand, single scattering never induces a maximum of saturation. On the other hand, multiple scattering has a typical increasing and decreasing behavior with an increasing number of glaze layers and thus participates to the maximum of saturation, just as the scattering by the diffuse base layer. A comparison between glazes and pigment mixtures, where the proportion of colored pigments with white pigments varies instead of the number of layers, shows that this maximum of saturation is much smaller with the second technique. To the best of our knowledge, we present a new development of the AFM that allows separation of the different origins of light scattering. We also show that it is possible to determine the optical properties of the scattering centers and of the base layer to create the required visual effect of a scattering medium. (c) 2006 Optical Society of America

Self-organized growth and optical properties of silver nanoparticle chains and stripes

Self-organized chains and stripes of silver nanoparticles have been elaborated by ion-beam sputtering shadow deposition onto faceted alumina substrates. We show that the in-plane organization of the silver nanostructures can be controlled through the grazing-incidence conditions (angle and orientation of the atomic beam with respect to the nanostructured surface). Their optical properties are dominated by a surface-plasmon resonance whose spectral position depends on the polarization of the incident light (parallel or perpendicular to the facets of the alumina template) and that can be attributed to a strong electromagnetic coupling between individual nanoparticles

Ray scattering model for spherical transparent particles

By printing a variable number of droplets onto the same pixel location, ink jet printers produce pixels at variable dot-sizes yielding several darkness levels. Varying the number of printed droplets affects the ink volume deposited onto the substrate. In the present contribution, we explore the possibility of producing accurate spectral reflectance predictions at all pixel dot-sizes. For this purpose, we use a Clapper-Yule model, extended according to Beer's law,which accounts for ink thickness variations. This model expresses each colorant transmittance as a function of its constituent ink transmittances and their respective relative thicknesses. These relative thicknesses are initially computed when calibrating the model, at a given pixel dot-size, and can then be dynamically scaled according to the printed pixel dot-size. We first study the effect of varying pixel dot-sizes on the halftone's physical (mechanical) dot-gain. We then express the ink volume variations as a function of pixel dotsizes. Lastly, we show how, using the thickness extended Clapper-Yule model, we can effectively predict reflectances for different configurations of ink pixel dot-sizes