Search results for "light"
showing 10 items of 3575 documents
Photoemission time-of-flight spectromicroscopy of Ag nanoparticle films on Si(111)
2004
Abstract Time-of-flight photoemission electron microscopy was used to measure spatially resolved energy distribution curves of electrons emitted from Ag nanoparticle films with different mass thicknesses. Two-photon photoemission (2PPE) was induced by femtosecond laser pulse excitation with 3.1 eV photon energy and 200 fs pulse width. Regions of Ag nanoparticles with different average sizes and one region with a continuous 100 nm thick Ag film were deposited as a stepped wedge on a Si(1 1 1) substrate. Upon laser excitation the nanoparticle films exhibit a very high electron emission yield in the images, whereas the uncovered Si surface and the continuous Ag film are dark. The time-of-fligh…
Factors affecting the amount and the mode of merocyanine 540 binding to the membrane of human erythrocytes. A comparison with the binding to leukemia…
1995
Abstract In the presence of albumin Merocyanine 540 (MC540) exhibits a very limited binding to the outer surface of the membrane of normal erythrocytes, whereas pronounced binding is observed to leukemia cells. To find out whether this difference is due to differences in the composition or structural organization of the cell membrane we analyzed effects of a number of covalent and non-covalent perturbations of the red cell membrane on the binding and fluorescence characteristics of membrane-bound MC540. It is shown that exposure of the cells to cationic chlorpromazine, neuraminidase or photodynamic treatment with AlPcS 4 as sensitizer caused a limited increase (30–50%) of MC540 binding, tog…
Les Temps modernes et le tournant transcendantal. Blumenberg, Kant et la question du monde
2012
International audience; Blumenberg’s phenomenology of the history of concepts couldn’t overlook Kantian inventions to escape the dead ends of metaphysics. Kant constitutes a decisive help in mapping the ruptures of Modern Age. On the one hand, the cosmogonical essays of the precritical period illustrate reason’s typically modern self-assertion. On the other hand, the transcendental turn stands for a radicalization of Modern Age towards the Enlightenment. But Blumenberg also pays attention to what, in Kant, disturbs the modern project of reason’s self-authorization. Transcendental philosophy always calls for a new beginning, because it anticipates its possible failure.
Optical rogue-wave-like extreme value fluctuations in fiber Raman amplifiers
2008
International audience; We report experimental observation and characterization of rogue wave-like extreme value statistics arising from pump-signal noise transfer in a fiber Raman amplifier. Specifically, by exploiting Raman amplification with an incoherent pump, the amplified signal is shown to develop a series of temporal intensity spikes whose peak power follows a power-law probability distribution. The results are interpreted using a numerical model of the Raman gain process using coupled nonlinear Schrödinger equations, and the numerical model predicts results in good agreement with experiment.
Raman Scattering Applied to Materials Science
2015
Abstract One of the most powerful techniques to extract physical and chemical information of a material is the light scattering. Opposite to x-ray scattering for instance, where an average of the sample properties is obtained, Raman scattering is a local probe which can be used to detect inhomogeneities, local strain, lack of crystallinity, anharmonicities or information on the electronic structure by means of resonant Raman scattering. In this work, we will analyze the main contributions of Raman scattering in Materials Sciences. After a brief introduction of the technique and the equipment needed for the physical measurements, we will give practical examples of Raman scattering measuremen…
Colloidal electro-phoresis in the presence of symmetric and asymmetric electro-osmotic flow
2018
We characterize the electro-phoretic motion of charged sphere suspensions in the presence of substantial electro-osmotic flow using a recently introduced small angle super-heterodyne dynamic light scattering instrument (ISASH-LDV). Operation in integral mode gives access to the particle velocity distribution over the complete cell cross-section. Obtained Doppler spectra are evaluated for electro-phoretic mobility, wall electro-osmotic mobility and particle diffusion coefficient. Simultaneous measurements of differing electro-osmotic mobilities leading to asymmetric solvent flow are demonstrated in a custom made electro-kinetic cell fitting standard microscopy slides as exchangeable sidewall…
UV light energy storage and thermoluminescence in AlN ceramics
2007
AlN ceramics, untreated and subjected to oxygen ion implantation, are studied for potential application in TL dosimetry of UV light. Based on photoluminescence and thermoluminescence measurements there are shown advantages of the selection of the 480 emission band for TL signal recording instead of the previously used 400 nm band: higher intensity of the TL signal, lower fading rate of the accumulated TL signal, excitation region (270-340 nm) corresponding to UV-B range, monitoring of which is actual in UV dosimetry. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanoparticles Size Distribution Assessment During Early Synthesis Stages
2021
Nanotechnology, an innovative field of material science, designs and produces nanostructures materials with unique properties that make them suited for various bioengineering applications. The shape and the dimension are the main variables depending on the method of synthesis or chemical precursors. Silver nanoparticles obtained through chemical synthesis exhibit as strong antibacterial effect if their size lays in a well-defined range. However, a small size of such particles, in the range of nanometers to several tens of nanometers, requires specific techniques as Dynamic Light Scattering or Transmission Electron Microscopy, both being affected by certain assumptions or by the high cost an…
Compact Method for Proton Range Verification Based on Coaxial Prompt Gamma-Ray Monitoring: a Theoretical Study
2020
Range uncertainties in proton therapy hamper treatment precision. Prompt gamma-rays were suggested 16 years ago for real-time range verification, and have already shown promising results in clinical studies with collimated cameras. Simultaneously, alternative imaging concepts without collimation are investigated to reduce the footprint and price of current prototypes. In this manuscript, a compact range verification method is presented. It monitors prompt gamma-rays with a single scintillation detector positioned coaxially to the beam and behind the patient. Thanks to the solid angle effect, proton range deviations can be derived from changes in the number of gamma-rays detected per proton,…
Autonomic Stress Response and Perceived Effort Jointly Inform on Dual Tasking in Aging
2019
The study investigated, through neuroendocrinological, subjective and behavioral assessments, how aging individuals cope with locomotor-cognitive dual-tasking and whether physical activity habits influence the acute response to locomotor-cognitive performance. Seventy-nine healthy participants aged 55&ndash