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Absorption Cross-sections (absorption + cross-section)
Selected AbstractsDIEL VARIATIONS IN OPTICAL PROPERTIES OF IMANTONIA ROTUNDA (HAPTOPHYCEAE) AND THALASSIOSIRA PSEUDONANA (BACILLARIOPHYCEAE) EXPOSED TO DIFFERENT IRRADIANCE LEVELS,JOURNAL OF PHYCOLOGY, Issue 3 2008Sébastien Mas Diel variations of cellular optical properties were examined for cultures of the haptophyte Imantonia rotunda N. Reynolds and the diatom Thalassiosira pseudonana (Hust.) Hasle et Heimdal grown under a 14:10 light:dark (L:D) cycle and transferred from 100 ,mol photons · m,2 · s,1 to higher irradiances of 250 and 500 ,mol photons · m,2 · s,1. Cell volume and abundance, phytoplankton absorption coefficients, flow-cytometric light scattering and chl fluorescence, and pigment composition were measured every 2 h over a 24 h period. Results showed that cell division was more synchronous for I. rotunda than for T. pseudonana. Several variables exhibited diel variability with an amplitude >100%, notably mean cell volume for the haptophyte and photoprotective carotenoids for both species, while optical properties such as flow-cytometric scattering and chl a,specific phytoplankton absorption generally showed <50% diel variability. Increased irradiance induced changes in pigments (both species) and mean cell volume (for the diatom) and amplified diel variability for most variables. This increase in amplitude is larger for pigments (factor of 2 or more, notably for cellular photoprotective carotenoid content in I. rotunda and for photosynthetic pigments in T. pseudonana) than for optical properties (a factor of 1.5 for chl a,specific absorption, at 440 nm, in I. rotunda and a factor of 2 for the absorption cross-section and the chl a,specific scattering in T. pseudonana). Consequently, diel changes in optical properties and pigmentation associated with the L:D cycle and amplified by concurrent changes in irradiance likely contribute significantly to the variability in optical properties observed in biooptical field studies. [source] Two-Photon Absorption-Related Properties of Functionalized BODIPY Dyes in the Infrared Range up to Telecommunication WavelengthsADVANCED MATERIALS, Issue 10-11 2009Pierre-Antoine Bouit Aza boron-dipyrromethene dyes functionalized by extended donor-,-conjugated moieties present high potentialities for nonlinear applications in the telecommunication spectral range (1300,1500,nm). Their significant two-photon absorption cross-sections (,2,>,600 GM) over this entire spectral range, combined with their high stability and solubility, allow nonlinear transmission experiments. [source] Gold Nanocages for Biomedical Applications,ADVANCED MATERIALS, Issue 20 2007E. Skrabalak Abstract Nanostructured materials provide a promising platform for early cancer detection and treatment. Here we highlight recent advances in the synthesis and use of Au nanocages for such biomedical applications. Gold nanocages represent a novel class of nanostructures, which can be prepared via a remarkably simple route based on the galvanic replacement reaction between Ag nanocubes and HAuCl4. The Au nanocages have a tunable surface plasmon resonance peak that extends into the near-infrared, where the optical attenuation caused by blood and soft tissue is essentially negligible. They are also biocompatible and present a well-established surface for easy functionalization. We have tailored the scattering and absorption cross-sections of Au nanocages for use in optical coherence tomography and photothermal treatment, respectively. Our preliminary studies show greatly improved spectroscopic image contrast for tissue phantoms containing Au nanocages. Our most recent results also demonstrate the photothermal destruction of breast cancer cells in vitro by using immuno-targeted Au nanocages as an effective photo-thermal transducer. These experiments suggest that Au nanocages may be a new class of nanometer-sized agents for cancer diagnosis and therapy. [source] Radiative transitions of the helium atom in highly magnetized neutron star atmospheresMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 1 2008Z. Medin ABSTRACT Recent observations of thermally emitting isolated neutron stars revealed spectral features that could be interpreted as radiative transitions of He in a magnetized neutron star atmosphere. We present Hartree,Fock calculations of the polarization-dependent photoionization cross-sections of the He atom in strong magnetic fields ranging from 1012 to 1014 G. Convenient fitting formulae for the cross-sections are given along with the related oscillator strengths for various bound,bound transitions. The effects of finite nucleus mass on the radiative absorption cross-sections are examined using perturbation theory. [source] In Situ Monitoring of Silicon Plasma Etching Using a Quantum Cascade Laser Arrangement,CHEMICAL VAPOR DEPOSITION, Issue 6-7 2007D. Stancu Abstract In etch plasmas used for semiconductor processing, concentrations of the precursor gas NF3 and of the etch product SiF4 are measured online and in situ using a new diagnostic arrangement, the Q-MACS Etch system, which is based on quantum cascade laser absorption spectroscopy (QCLAS). In addition, the etch rates of SiO2 layers and of the silicon wafer are monitored including plasma-etching endpoint detection. For this purpose the Q-MACS Etch system is working as an interferometer arrangement. The experiments are performed in an industrial, dual-frequency, capacitively coupled, magnetically enhanced, reactive ion etcher (MERIE), which is a plasma reactor developed for dynamic random access memory (DRAM) technologies. In the spectral range 1028 ± 0.3 cm,1, the absorption cross-sections of SiF4 and NF3 are determined to be ,,=,(7.7 ± 0.7) × 10,18 cm2 molecule,1 and ,,=,(8.7 ± 0.8) × 10,20 cm2 molecule,1, respectively. [source] Pyrrolopyrrole Cyanine Dyes: A New Class of Near-Infrared Dyes and FluorophoresCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2009Georg Abstract NIRer there: Pyrrolopyrrole cyanine (PPCys) dyes, a new class of near-infrared (NIR) fluorophores, are obtained by condensation of heteroarylacetonitrile and diketopyrrolopyrrole compounds (see picture). Complexation with BF2 or BPh2 yields strongly fluorescent, photostable NIR dyes that show high absorption cross-sections and fluorescence quantum yields. Furthermore, alteration of the heterocycle can tune the main absorption between ,,=,684 and 864,nm. Pyrrolopyrrole cyanine (PPCy) dyes are presented as a novel class of near-infrared (NIR) chromophores, which are synthesized in a condensation reaction of diketopyrrolopyrrole with heteroarylacetonitrile compounds. Their optical properties are marked by strong and narrow-band NIR absorptions. Complexation products with BF2 and BPh2 show strong NIR fluorescence and hardly any absorption in the visible range. We synthesized a series of new PPCys that differ only in the heterocyclic peripheral groups of the chromophore. With this strategy, the absorption spectra can be tuned between 684 and 864,nm, while high fluorescence quantum yields are maintained. The influence of the heterocycle on the optical properties of the dyes is discussed. [source] Two-Photon Absorption Cross-Sections of Reference Dyes: A Critical ExaminationCHEMPHYSCHEM, Issue 1 2008Prakash Chandra Jha Dr. Abstract The electronic structure and one- and two-photon absorption spectra of four fluorophores, p -bis(o -methoxystyryl)benzene (Bis-MSB), coumarin 307, fluorescein and rhodamine B, commonly used as reference compounds for two-photon absorption spectra, have been theoretically calculated and compared with available experimental data. The possible reasons for the wide discrepancies in two-photon absorption cross-sections reported in the literature are discussed on the basis of the theoretical findings. The role of a solvent environment on the electronic one- and two-photon absorption spectra is also studied. We highlight some necessary precautions that one needs to take when comparing literature results of two-photon absorption cross-sections. [source] | |||||||||||||