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- 검색키워드
- 저자 : Amblard, A. (검색결과 4 건)
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How to better focus waves by considering symmetry and information loss
Lou, Kai,Granick, Steve,Amblard, Franç,ois National Academy of Sciences 2018 PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF Vol.115 No.26
<▼1><P><B>Significance</B></P><P>With applications from electromagnetic communications, to biological and astronomical imaging, to lithography and warfare, waves transmit information, and optimal wave focusing is essential. Here we demonstrate the need to amend the belief that spherical or cylindrical wavefronts necessarily focus at their center of curvature. Instead the effective focus shifts toward the source with decreasing apertures, producing astigmatism when, as increasingly shown for modern applications, the wavefronts are not axially symmetric. This leads to significant degradation of axial resolution in nonaxisymmetric light-focusing applications. These conclusions, derived from diffraction theory and validated by application to optical bioimaging, offer a general strategy to likewise improve the resolution of virtually any other wave-based application whose efficacy depends on focusing energy to points or lines.</P></▼1><▼2><P>We amend the general belief that waves with extended spherical wavefront focus at their center of curvature. Instead, when the spherical symmetry of waves is broken by propagating them through a finite aperture along an average direction, the forward/backward symmetry is broken and the focal volume shifts its center backward along that direction. The extent of this focal shift increases as smaller apertures are used, up to the point that the nominal focal plane is out of focus. Furthermore, the loss of axial symmetry with noncircular apertures causes distinct focal shifts in distinct axial planes, and the resulting astigmatism possibly degrades the axial focusing resolution. Using experiments and simulations, focal shift with noncircular apertures is described for classical and temporal focusing. The usefulness of these conclusions to improve imaging resolution is demonstrated in a high-resolution optical microscopy application, namely line-temporal focusing microscopy. These conclusions follow from fundamental symmetries of the wave geometry and matter for an increasing number of emerging optical techniques. This work offers a general framework and strategy to understand and improve virtually any wave-based application whose efficacy depends on optimal focusing and may be helpful when information is transmitted by waves in applications from electromagnetic communications, to biological and astronomical imaging, to lithography and even warfare.</P></▼2>
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Evolution of dust temperature of galaxies through cosmic time as seen by <i>Herschel</i><sup>★</sup>
Hwang, H. S.,Elbaz, D.,Magdis, G.,Daddi, E.,Symeonidis, M.,Altieri, B.,Amblard, A.,Andreani, P.,Arumugam, V.,Auld, R.,Aussel, H.,Babbedge, T.,Berta, S.,Blain, A.,Bock, J.,Bongiovanni, A.,Boselli, A.,B Blackwell Publishing Ltd 2010 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.409 No.1
<P>ABSTRACT</P><P>We study the dust properties of galaxies in the redshift range 0.1 ≲<I>z</I>≲ 2.8 observed by the <I>Herschel Space Observatory</I> in the field of the Great Observatories Origins Deep Survey-North as part of the PACS Extragalactic Probe (PEP) and <I>Herschel</I> Multi-tiered Extragalactic Survey (HerMES) key programmes. Infrared (IR) luminosity (<I>L</I><SUB>IR</SUB>) and dust temperature (<I>T</I><SUB>dust</SUB>) of galaxies are derived from the spectral energy distribution fit of the far-IR (FIR) flux densities obtained with the PACS and SPIRE instruments onboard <I>Herschel</I>. As a reference sample, we also obtain IR luminosities and dust temperatures of local galaxies at <I>z</I> < 0.1 using <I>AKARI</I> and <I>IRAS</I> data in the field of the Sloan Digital Sky Survey. We compare the <I>L</I><SUB>IR</SUB>–<I>T</I><SUB>dust</SUB> relation between the two samples and find that the median <I>T</I><SUB>dust</SUB> of <I>Herschel</I>-selected galaxies at <I>z</I>≳ 0.5 with <I>L</I><SUB>IR</SUB>≳ 5 × 10<SUP>10</SUP> L<SUB>⊙</SUB> appears to be 2–5 K colder than that of <I>AKARI</I>-selected local galaxies with similar luminosities, and the dispersion in <I>T</I><SUB>dust</SUB> for high-<I>z</I> galaxies increases with <I>L</I><SUB>IR</SUB> due to the existence of cold galaxies that are not seen among local galaxies. We show that this large dispersion of the <I>L</I><SUB>IR</SUB>−<I>T</I><SUB>dust</SUB> relation can bridge the gap between local star-forming galaxies and high-<I>z</I> submillimetre galaxies (SMGs). We also find that three SMGs with very low <I>T</I><SUB>dust</SUB> (≲20 K) covered in this study have close neighbouring sources with similar 24-μm brightness, which could lead to an overestimation of FIR/(sub)millimetre fluxes of the SMGs.</P>
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Substrate curvature affects the shape, orientation, and polarization of renal epithelial cells
Yu, Sun-Min,Oh, Jung Min,Lee, Junwon,Lee-Kwon, Whaseon,Jung, Woonggyu,Amblard, Franç,ois,Granick, Steve,Cho, Yoon-Kyoung Elsevier 2018 ACTA BIOMATERIALIA Vol.77 No.-
<P><B>Abstract</B></P> <P>The unique structure of kidney tubules is representative of their specialized function. Because maintaining tubular structure and controlled diameter is critical for kidney function, it is critical to understand how topographical cues, such as curvature, might alter cell morphology and biological characteristics. Here, we examined the effect of substrate curvature on the shape and phenotype of two kinds of renal epithelial cells (MDCK and HK-2) cultured on a microchannel with a broad range of principal curvature. We found that cellular architecture on curved substrates was closely related to the cell type-specific characteristics (stiffness, cell–cell adherence) of the cells and their density, as well as the sign and degree of curvature. As the curvature increased on convex channels, HK-2 cells, having lower cell stiffness and monolayer integrity than those of MDCK cells, aligned their in-plane axis perpendicular to the channel but did not significantly change in morphology. By contrast, MDCK cells showed minimal change in both morphology and alignment. However, on concave channels, both cell types were elongated and showed longitudinal directionality, although the changes in MDCK cells were more conservative. Moreover, substrate curvature contributed to cell polarization by enhancing the expression of apical and basolateral cell markers with height increase of the cells. Our study suggests curvature to be an important guiding principle for advanced tissue model developments, and that curved and geometrically ambiguous substrates can modulate the cellular morphology and phenotype.</P> <P><B>Statement of Significance</B></P> <P>In many tissues, such as renal tubules or intestinal villi, epithelial layers exist in naturally curved forms, a geometry that is not reproduced by flat cultures. Because maintaining tubular structure is critical for kidney function, it is important to understand how topographical cues, such as curvature, might alter cell morphology and biological characteristics. We found that cellular architecture on curved substrates was closely related to cell type and density, as well as the sign and degree of the curvature. Moreover, substrate curvature contributed to cell polarization by enhancing the expression of apical and basolateral cell markers with height increase. Our results suggested that substrate curvature might contribute to cellular architecture and enhance the polarization of kidney tubule cells.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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