scholarly journals Coherent Scattering of Ultraviolet Light by Avian Feather Barbs

The Auk ◽  
2003 ◽  
Vol 120 (1) ◽  
pp. 163-170 ◽  
Author(s):  
Richard O. Prum ◽  
Staffan Andersson ◽  
Rodolfo H. Torres
Keyword(s):  
Rayleigh Scattering ◽  
Power Spectra ◽  
Coherent Scattering ◽  
Mie Scattering ◽  
Two Dimensional ◽  
Structural Colors ◽  
Physical Mechanisms ◽  
Spatial Frequencies ◽  
Transmission Electron ◽  
Alternative Hypotheses

Abstract Ultraviolet (UV) structural colors of avian feathers are produced by the spongy medullary keratin of feather barbs, but various physical mechanisms have been hypothesized to produce those colors, including Rayleigh scattering, Mie scattering, and coherent scattering (i.e. constructive interference). We used two-dimensional Fourier analysis of transmission electron micrographs of the medullary keratin of UV-colored feather barbs of the Blue Whistling Thrush (Myiophonus caeruleus) (Turdidae) to test the alternative hypotheses for production of those UV structural hues. The two-dimensional Fourier power spectra of the tissue reveal a ring-like distribution of peak periodicity at intermediate spatial frequencies (∼0.078 nm −1), which documents that Myiophonus medullary keratin is substantially nanostructured and equivalently ordered in all directions. This nanoscale spatial order falsifies a basic assumption of both the Rayleigh scattering and Mie scattering. A predicted reflectance spectrum based on the Fourier power spectra matches hue of the measured reflectance spectra of the feathers (345 nm). These results demonstrate that the Myiophonus medullary keratin is ordered at the appropriately nanoscale to produce the observed UV hues by coherent scattering.

scholarly journals Coherent light scattering by nanostructured collagen arrays in the caruncles of the malagasy asities (Eurylaimidae: aves)

1999 ◽  
Vol 202 (24) ◽  
pp. 3507-3522 ◽  
Author(s):  
R.O. Prum ◽  
R. Torres ◽  
C. Kovach ◽  
S. Williamson ◽  
S.M. Goodman
Keyword(s):  
Power Spectra ◽  
Coherent Scattering ◽  
Reflectance Spectra ◽  
Two Dimensional ◽  
Collagen Fibres ◽  
Discrete Fourier Analysis ◽  
Near Ultraviolet ◽  
Avian Communication ◽  
Dark Blue ◽  
Prominent Peak

We investigated the anatomy, nanostructure and biophysics of the structurally coloured facial caruncles of three species in a clade of birds endemic to Madagascar (Philepittinae, Eurylaimidae: Aves). Caruncle tissues of all species had reflectance spectra with prominent, peak hues between 403 and 528 nm. Dark blue Neodrepanis tissues had substantial reflectance in the near ultraviolet (320–400 nm), which is visible to birds but not to humans, providing the first evidence of ultraviolet skin colours in birds and the first indications of the possible function of ultraviolet skin colours in avian communication. These structural colours are produced by coherent scattering from arrays of parallel collagen fibres in the dermis. Tissues of Philepitta castanea were organized into hexagonal, crystal-like arrays, whereas Neodrepanis tissues were quasiordered. Predictions of the peak hues of reflectance (λ (max)) using Bragg's law were relatively accurate, but Bragg's law requires physical assumptions that are obviously violated by these structures. A two-dimensional discrete Fourier analysis of the spatial variation in refractive index within the tissues documented that all the tissues are substantially nanostructured at the appropriate spatial scale to scatter visible light coherently. Predicted reflectance spectra based on the two-dimensional Fourier power spectra are relatively accurate at predicting the hue and shape of the reflectance spectra of the tissues. These results confirm that the nanostructure of the collagen arrays determines the colours that are coherently scattered by these tissues. The evolution of the anatomy and nanostructure of asity caruncles is discussed.

A linearity test for thick specimens imaged by HVEM over a 180° angular range

1991 ◽  
Vol 49 ◽  
pp. 552-553
Author(s):  
Yu Liu
Keyword(s):  
Phase Contrast ◽  
Three Dimensional ◽  
Angular Range ◽  
Two Dimensional ◽  
Back Projection ◽  
Line Integral ◽  
Exponential Law ◽  
Transmission Electron ◽  
Absorption Law ◽  
Linearity Test

The image obtained in a transmission electron microscope is the two-dimensional projection of a three-dimensional (3D) object. The 3D reconstruction of the object can be calculated from a series of projections by back-projection, but this algorithm assumes that the image is linearly related to a line integral of the object function. However, there are two kinds of contrast in electron microscopy, scattering and phase contrast, of which only the latter is linear with the optical density (OD) in the micrograph. Therefore the OD can be used as a measure of the projection only for thin specimens where phase contrast dominates the image. For thick specimens, where scattering contrast predominates, an exponential absorption law holds, and a logarithm of OD must be used. However, for large thicknesses, the simple exponential law might break down due to multiple and inelastic scattering.

Strain analysis with nanometer resolution using a conventional transmission electron microsopy technique: electron diffraction contrast imaging revisited

1995 ◽  
Vol 53 ◽  
pp. 168-169
Author(s):  
Koenraad G F Janssens ◽  
Omer Van der Biest ◽  
Jan Vanhellemont ◽  
Herman E Maes ◽  
Robert Hull
Keyword(s):  
Electron Diffraction ◽  
Strain Field ◽  
Elastic Strain ◽  
Strain Analysis ◽  
Local Strain ◽  
Contrast Imaging ◽  
Strain Characterization ◽  
Physical Mechanisms ◽  
Diffraction Contrast ◽  
Transmission Electron

There is a growing need for elastic strain characterization techniques with submicrometer resolution in several engineering technologies. In advanced material science and engineering the quantitative knowledge of elastic strain, e.g. at small particles or fibers in reinforced composite materials, can lead to a better understanding of the underlying physical mechanisms and thus to an optimization of material production processes. In advanced semiconductor processing and technology, the current size of micro-electronic devices requires an increasing effort in the analysis and characterization of localized strain. More than 30 years have passed since electron diffraction contrast imaging (EDCI) was used for the first time to analyse the local strain field in and around small coherent precipitates1. In later stages the same technique was used to identify straight dislocations by simulating the EDCI contrast resulting from the strain field of a dislocation and comparing it with experimental observations. Since then the technique was developed further by a small number of researchers, most of whom programmed their own dedicated algorithms to solve the problem of EDCI image simulation for the particular problem they were studying at the time.

One Step Synthesis and Characterization of Zirconia-Graphene Composites

2012 ◽  
Vol 600 ◽  
pp. 174-177 ◽  
Author(s):  
Jian Fei Xia ◽  
Zong Hua Wang ◽  
Yan Zhi Xia ◽  
Fei Fei Zhang ◽  
Fu Qiang Zhu ◽  
...  
Keyword(s):  
Synthesis And Characterization ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
X Ray ◽  
Graphene Composite ◽  
Transmission Electron ◽  
One Step ◽  
Ft Ir ◽  
Xrd Techniques

Zirconia-graphene composite (ZrO2-G) has been successfully synthesized via decomposition of ZrOCl2•6H2O in a water-isopropanol system with dispersed graphene oxide (GO) utilizing Na2S as a precursor could enable the occurrence of the deposition of Zr4+ and the deoxygenation of GO at the same time. Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) techniques were used to characterize the samples. It was found that graphene were fully coated with ZrO2, and the ZrO2 existing in tetragonal phase, which resulted in the formation of two-dimensional composite.

scholarly journals Low-Zpolymer sample supports for fixed-target serial femtosecond X-ray crystallography

2015 ◽  
Vol 48 (4) ◽  
pp. 1072-1079 ◽  
Author(s):  
Geoffrey K. Feld ◽  
Michael Heymann ◽  
W. Henry Benner ◽  
Tommaso Pardini ◽  
Ching-Ju Tsai ◽  
...  
Keyword(s):  
Protective Antigen ◽  
Three Dimensional ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Fixed Target ◽  
X Ray ◽  
X Ray Crystallography ◽  
Transmission Electron ◽  
Linac Coherent Light Source ◽  
Efficient Alternative

X-ray free-electron lasers (XFELs) offer a new avenue to the structural probing of complex materials, including biomolecules. Delivery of precious sample to the XFEL beam is a key consideration, as the sample of interest must be serially replaced after each destructive pulse. The fixed-target approach to sample delivery involves depositing samples on a thin-film support and subsequent serial introductionviaa translating stage. Some classes of biological materials, including two-dimensional protein crystals, must be introduced on fixed-target supports, as they require a flat surface to prevent sample wrinkling. A series of wafer and transmission electron microscopy (TEM)-style grid supports constructed of low-Zplastic have been custom-designed and produced. Aluminium TEM grid holders were engineered, capable of delivering up to 20 different conventional or plastic TEM grids using fixed-target stages available at the Linac Coherent Light Source (LCLS). As proof-of-principle, X-ray diffraction has been demonstrated from two-dimensional crystals of bacteriorhodopsin and three-dimensional crystals of anthrax toxin protective antigen mounted on these supports at the LCLS. The benefits and limitations of these low-Zfixed-target supports are discussed; it is the authors' belief that they represent a viable and efficient alternative to previously reported fixed-target supports for conducting diffraction studies with XFELs.

scholarly journals Simulation of earthquakes with cellular automata

1998 ◽  
Vol 2 (4) ◽  
pp. 267-279 ◽  
Author(s):  
P. G. Akishin ◽  
M. V. Altaisky ◽  
I. Antoniou ◽  
A. D. Budnik ◽  
V. V. Ivanov
Keyword(s):  
Cellular Automata ◽  
Analytical Method ◽  
Power Spectra ◽  
Two Dimensions ◽  
Seismic Events ◽  
Two Dimensional ◽  
Stress Release ◽  
Event Energy

The relation between cellular automata (CA) models of earthquakes and the Burridge–Knopoff (BK) model is studied. It is shown that the CA proposed by P. Bak and C. Tang,although they have rather realistic power spectra, do not correspond to the BK model. We present a modification of the CA which establishes the correspondence with the BK model.An analytical method of studying the evolution of the BK-like CA is proposed. By this method a functional quadratic in stress release, which can be regarded as an analog of the event energy, is constructed. The distribution of seismic events with respect to this “energy” shows rather realistic behavior, even in two dimensions. Special attention is paid to two-dimensional automata; the physical restrictions on compression and shear stiffnesses are imposed.

scholarly journals Two-dimensional inorganic molecular crystals

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Wei Han ◽  
Pu Huang ◽  
Liang Li ◽  
Fakun Wang ◽  
Peng Luo ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Electronic Devices ◽  
Molecular Crystals ◽  
High Energy ◽  
Two Dimensional ◽  
Β Phase ◽  
Α Phase ◽  
Growth Plane ◽  
Transmission Electron

Abstract Two-dimensional molecular crystals, consisting of zero-dimensional molecules, are very appealing due to their novel physical properties. However, they are mostly limited to organic molecules. The synthesis of inorganic version of two-dimensional molecular crystals is still a challenge due to the difficulties in controlling the crystal phase and growth plane. Here, we design a passivator-assisted vapor deposition method for the growth of two-dimensional Sb2O3 inorganic molecular crystals as thin as monolayer. The passivator can prevent the heterophase nucleation and suppress the growth of low-energy planes, and enable the molecule-by-molecule lateral growth along high-energy planes. Using Raman spectroscopy and in situ transmission electron microscopy, we show that the insulating α-phase of Sb2O3 flakes can be transformed into semiconducting β-phase under heat and electron-beam irradiation. Our findings can be extended to the controlled growth of other two-dimensional inorganic molecular crystals and open up opportunities for potential molecular electronic devices.

scholarly journals Trap-Assisted Charge Injection into Large Bandgap Polymer Semiconductors

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2427 ◽  
Author(s):  
Dongdong Wang ◽  
Michael Fina ◽  
Suhan Kim ◽  
Chunmei Zhang ◽  
Ting Zhang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Charge Injection ◽  
Model Systems ◽  
Light Emitting ◽  
Physical Mechanisms ◽  
Polymer Semiconductors ◽  
Transmission Electron ◽  
Polymer Light Emitting Diodes

The trap-assisted charge injection in polyfluorene-poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) model systems with an Al or Al/LiF cathode is investigated. We find that inserting 1.3 nm LiF increases electron and hole injections simultaneously and the increase of holes is greater than electrons. The evolution of internal interfaces within polymer light-emitting diodes is observed by transmission electron microscopy, which reveals that the introduction of LiF improves the interface stability at both the cathode (cathode/polymer) and the anode (indium tin oxide (ITO)/PEDOT:PSS). Above-mentioned experimental results have been compared to the numerical simulations with a revised Davids model and potential physical mechanisms for the trap-assisted charge injection are discussed.

The Polarization Properties Research of Atmospheric Based on Actual Weather Conditions

2014 ◽  
Vol 556-562 ◽  
pp. 933-936
Author(s):  
Fei Zhang ◽  
Xiao Ping Du ◽  
Shen Wang
Keyword(s):  
Rayleigh Scattering ◽  
Weather Conditions ◽  
Mie Scattering ◽  
New Method ◽  
Degree Of Polarization ◽  
Scattering Angle ◽  
Polarization Characteristics ◽  
Simulation Results

A new method to calculate the polarization properties of the atmosphere by combining the Rayleigh scattering and Mie scattering is proposed in this paper. We inversed the values of the required data by experiment and simulated of the atmosphere polarization characteristics under the same conditions. The simulation results show that the proposed method can accurately describe the variation of the atmosphere polarization properties. Besides, the results show such variation: in the same weather conditions, the degree of polarization is gradually increased while scattering angle is gradually increased as 90°; in the same detect conditions, the degree of polarization decreases with the deteriorating weather conditions.

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