Search results for " Scanning"
showing 10 items of 988 documents
Silencing and enhancement of second-harmonic generation in optical gap antennas
2012
International audience; Amplifying local electromagnetic fields by engineering optical interactions between individual constituents of an optical antenna is considered fundamental for efficient nonlinear wavelength conversion in nanometer-scale devices. In contrast to this general statement we show that high field enhancement does not necessarily lead to an optimized nonlinear activity. In particular, we demonstrate that second-harmonic responses generated at strongly interacting optical gap antennas can be significantly suppressed. Numerical simulations are confirming silencing of second-harmonic in these coupled systems despite the existence of local field amplification. We then propose a…
Computation of the field diffracted by a local surface defect: application to tip–sample interaction in the photon scanning tunneling microscope
1996
We use a method based on the Fourier transform of the electromagnetic field to compute the field diffracted by a local deformation of a plane boundary surface. We give a complete development of each step of the technique. To show the interaction that exists between the probe of a near-field optical microscope and the observed sample, we use the model of a truncated cone-shaped tip above a rectangular surface defect. We compute the electrical intensity along a line located between the tip and the local surface defect. We show the influence of the polarization of the incident wave and the effect of the position of the tip with respect to the position of the surface defect.
Uncovering the metastable γ-Ag2WO4 phase: a joint experimental and theoretical study
2017
The synthesis of metastable solid phases is a pivotal starting point for innovative materials research. Here, we report the synthesis by means of a precipitation method of the metastable cubic γ-Ag2WO4 phase under ambient conditions. Different experimental techniques such as X-ray diffraction (XRD) with Rietveld refinement, field emission scanning electron microscopy (FE-SEM), micro-Raman/ultraviolet-visible (UV-vis) diffuse reflectance, photoluminescence spectroscopies, and differential scanning calorimetry (DSC) were employed. To complement the experimental data, the geometry, morphology, vibrational and electronic structure of γ-Ag2WO4 were characterized and evaluated using first-princip…
Carbon nanotubes as electrodes for dielectrophoresis of DNA
2006
Dielectrophoresis can potentially be used as an efficient trapping tool in the fabrication of molecular devices. For nanoscale objects, however, the Brownian motion poses a challenge. We show that the use of carbon nanotube electrodes makes it possible to apply relatively low trapping voltages and still achieve high enough field gradients for trapping nanoscale objects, e.g., single molecules. We compare the efficiency and other characteristics of dielectrophoresis between carbon nanotube electrodes and lithographically fabricated metallic electrodes, in the case of trapping nanoscale DNA molecules. The results are analyzed using finite element method simulations and reveal information abou…
Novel molluskan biomineralization proteins retrieved from proteomics: a case study with upsalin.
2012
12 pages; International audience; The formation of the molluskan shell is regulated by an array of extracellular proteins secreted by the calcifying epithelial cells of the mantle. These proteins remain occluded within the recently formed biominerals. To date, many shell proteins have been retrieved, but only a few of them, such as nacreins, have clearly identified functions. In this particular case, by combining molecular biology and biochemical approaches, we performed the molecular characterization of a novel protein that we named Upsalin, associated with the nacreous shell of the freshwater mussel Unio pictorum. The full sequence of the upsalin transcript was obtained by RT-PCR and 5'/3…
Confocal microscopy study of the distribution, content and activity of mitochondria during Paracentrotus lividus development
2007
Summary In the present paper we applied confocal microscopy andfluorescence technologies for studying the distribution andthe oxidative activity of sea urchin ( Paracentrotus lividus )mitochondria during development, by in vivo incubating eggsand embryos with cell-permeant MitoTracker probes. Wecalculated, by a mathematical model, the intensity values, the variations of intensity, and the variation index of incorporatedfluorochromes. Data demonstrate that mitochondrial massdoes not change during development, whereas mitochondrialrespirationincreases.Inaddition,startingfrom16blastomeresstage, some regions of the embryo contain organelles moreactive in oxygen consumption. Introduction The con…
The pia mater at the site of the entry of blood vessels into the central nervous system
1982
The entry of blood vessels into the central nervous system (CNS) has been studied at the surface of the brain stem and the spinal cord of two cats and two rabbits. The study was carried out by scanning electron microscopy (SEM). The results obtained by SEM concerning the layers of the pia mater corresponded to those obtained by other authors who used transmission electron microscopy. Between the basal lamina of the superficial glial membrane of the CNS and the cells lining the subarachnoid space, a pial connective tissue space could be clearly recognized. The blood vessles crossing the subarachnoid space were also covered by leptomeningeal lining cells. At the site of entry of these blood v…
Face-selective adhesion of calcium oxalate dihydrate crystals to renal epithelial cells
1996
The interaction between the most common urinary crystal, calcium oxalate dihydrate (COD) and the surface of monkey renal epithelial cells of the BSC-1 line was investigated. The [100] face of exogenous COD crystals bound selectively and rapidly to the kidney cell surface. Cellular processes extended preferentially over the [100] face initially, and then progressively covered the crystal so that by 24 hours some crystals were observed beneath the plasma membrane. When nucleated from solution onto the surface of the cell monolayer, COD crystals oriented preferentially so that their [100] faces were in direct contact with the cell surface. In contrast, when siliconized glass was used as a subs…
Characterization of the Etna volcanic emissions through an active biomonitoring technique (moss-bags): Part 2 – Morphological and mineralogical featu…
2013
Volcanic emissions were studied at Mount Etna (Italy) by using moss-bags technique. Mosses were exposed around the volcano at different distances from the active vents to evaluate the impact of volcanic emissions in the atmosphere. Morphology and mineralogy of volcanic particulate intercepted by mosses were investigated using scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS). Particles emitted during passive degassing activity from the two active vents, Bocca Nuova and North East Crater (BNC and NEC), were identified as silicates, sulfates and halide compounds. In addition to volcanic particles, we found evidences also of geogenic, anthropogenic and marin…
Building 3D Geometric and Kinematic Models of Five-Axis Machine-Tools for Manufacturing Prosthetic Devices
2015
The paper presents the process of building and testing a geometric and kinematic model of a five-axis machining center, which can be used for accurate cutting processes simulation of complex parts. After building the model, it was be tested by simulating the machining process of a hip joint prosthetic device. The prosthetic device was chosen because of its complex shape and because it was obtained by a 3D scanning process, which means that the part was reconstructed using meshes, instead of surfaces, which makes the toolpath control more difficult.