scholarly journals Catenary optics for achromatic generation of perfect optical angular momentum

2015 ◽  
Vol 1 (9) ◽  
pp. e1500396 ◽  
Author(s):  
Mingbo Pu ◽  
Xiong Li ◽  
Xiaoliang Ma ◽  
Yanqin Wang ◽  
Zeyu Zhao ◽  
...  
Keyword(s):  
Angular Momentum ◽  
State Of The Art ◽  
Incident Light ◽  
Optical Devices ◽  
Linear Phase ◽  
Robert Hooke ◽  
Complete Control ◽  
Broadband Spectrum ◽  
Hanging Chain ◽  
Topological Characteristics

The catenary is the curve that a free-hanging chain assumes under its own weight, and thought to be a “true mathematical and mechanical form” in architecture by Robert Hooke in the 1670s, with nevertheless no significant phenomena observed in optics. We show that the optical catenary can serve as a unique building block of metasurfaces to produce continuous and linear phase shift covering [0, 2π], a mission that is extremely difficult if not impossible for state-of-the-art technology. Via catenary arrays, planar optical devices are designed and experimentally characterized to generate various kinds of beams carrying orbital angular momentum (OAM). These devices can operate in an ultra-broadband spectrum because the anisotropic modes associated with the spin-orbit interaction are almost independent of the incident light frequency. By combining the optical and topological characteristics, our approach would allow the complete control of photons within a single nanometric layer.

scholarly journals Colour Constancy for Image of Non-Uniformly Lit Scenes

Sensors ◽  
2019 ◽  
Vol 19 (10) ◽  
pp. 2242
Author(s):  
Md Akmol Hussain ◽  
Akbar Sheikh-Akbari ◽  
Iosif Mporas
Keyword(s):  
Light Source ◽  
State Of The Art ◽  
Incident Light ◽  
Digital Camera ◽  
Input Image ◽  
Absolute Difference ◽  
Light Sources ◽  
Colour Constancy ◽  
Adjustment Factors ◽  
Camera Sensors

Digital camera sensors are designed to record all incident light from a captured scene, but they are unable to distinguish between the colour of the light source and the true colour of objects. The resulting captured image exhibits a colour cast toward the colour of light source. This paper presents a colour constancy algorithm for images of scenes lit by non-uniform light sources. The proposed algorithm uses a histogram-based algorithm to determine the number of colour regions. It then applies the K-means++ algorithm on the input image, dividing the image into its segments. The proposed algorithm computes the Normalized Average Absolute Difference (NAAD) for each segment and uses it as a measure to determine if the segment has sufficient colour variations. The initial colour constancy adjustment factors for each segment with sufficient colour variation is calculated. The Colour Constancy Adjustment Weighting Factors (CCAWF) for each pixel of the image are determined by fusing the CCAWFs of the segments, weighted by their normalized Euclidian distance of the pixel from the center of the segments. Results show that the proposed method outperforms the statistical techniques and its images exhibit significantly higher subjective quality to those of the learning-based methods. In addition, the execution time of the proposed algorithm is comparable to statistical-based techniques and is much lower than those of the state-of-the-art learning-based methods.

scholarly journals Photonic Materials for Optical Communications

MRS Bulletin ◽  
2003 ◽  
Vol 28 (5) ◽  
pp. 340-344 ◽  
Author(s):  
Hartmut Hillmer ◽  
Roland Germann
Keyword(s):  
Optical Communications ◽  
System Performance ◽  
State Of The Art ◽  
Optical Devices ◽  
Photonic Materials ◽  
Materials Properties

AbstractAn overview of key materials for optical communications, including semiconductors, dielectrics, glasses, and organics, is presented in this issue of MRS Bulletin. Materials quality is in all cases crucial for advanced device and system performance. Materials properties and important problems are reviewed, and their impact on the performance of state-of-the-art optical devices is assessed and demonstrated by means of selected examples.

Hooke's cubico–parabolical conoid

1998 ◽  
Vol 52 (1) ◽  
pp. 39-50 ◽  
Author(s):  
J. Heyman
Keyword(s):  
Royal Society ◽  
Three Dimensional ◽  
Not Given ◽  
Dimensional Problem ◽  
Masonry Arch ◽  
Robert Hooke ◽  
Correct Form ◽  
Hanging Chain ◽  
Catenary Curve ◽  
Leading Term

In 1675 Robert Hooke published, as one of his ‘Inventions’, a Latin anagram concerning the ‘true...form of all manner of arches for building’. His discovery was that the shape of a light flexible cord subjected to specified loads would, when inverted, give the required shape of the perfect (masonry) arch to carry those same loads. Hooke knew that the catenary curve was not given by the parabola y = ax 2 , but he was unable to solve the problem mathematically, and the decipherment of the anagram was not published until after his death. Four years earlier Hooke had stated to the Royal Society that the solution to the corresponding three–dimensional problem, that of the shape of the perfect dome, was the cubico–parabolical conoid; that is, the dome was formed by rotating the cubic parabola y = ax 3 about the y –axis. It is shown that the correct form of dome may be evaluated in terms of the integrals erf( t ) and erg( t ). Moreover, an alternative solution as a power series is rapidly convergent, and has a leading term in x 3 followed by a much smaller term in x 7 . Wren's design for the dome of St Paul's Cathedral made use of the idea of Hooke's ‘hanging chain’.

scholarly journals Asteroseismology and spectropolarimetry: opening new windows on the internal dynamics of massive stars

2014 ◽  
Vol 9 (S307) ◽  
pp. 420-425 ◽  
Author(s):  
S. Mathis ◽  
C. Neiner
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Massive Star ◽  
State Of The Art ◽  
Massive Stars ◽  
The State ◽  
Internal Dynamics ◽  
Dynamical Processes ◽  
Internal Mixing ◽  
Mixing And Transport

AbstractIn this article, we show how asteroseismology and spectropolarimetry allow to probe dynamical processes in massive star interiors. First, we give a summary of the state-of-the-art. Second, we recall the MHD mechanisms that take place in massive stars. Next, we show how asteroseismology gives strong constraints on the internal mixing and transport of angular momentum while spectropolarimetry allows to unravel the role played by magnetic fields.

STEREO PHOTOGRAPHY OF ATOMIC ARRANGEMENT AND ATOMIC-ORBITAL ANALYSIS BY TWO-DIMENSIONAL PHOTOELECTRON SPECTROSCOPY

2007 ◽  
Vol 14 (04) ◽  
pp. 637-643 ◽  
Author(s):  
FUMIHIKO MATSUI ◽  
TOMOHIRO MATSUSHITA ◽  
FANG ZHUN GUO ◽  
HIROSHI DAIMON
Keyword(s):  
Angular Momentum ◽  
Valence Band ◽  
Orbital Angular Momentum ◽  
Photoelectron Spectroscopy ◽  
Atomic Orbital ◽  
Incident Light ◽  
Atomic Orbitals ◽  
Angular Momentum Quantum Number ◽  
The Difference ◽  
Orbital Analysis

The circular dichroism of photoelectron forward focusing peak rotation around the incident-light axis reflects the orbital angular momentum of the excited core level and is inversely proportional to the distance between the emitter and scatterer atoms. This is the basis for the stereo photograph of the atomic arrangements. These rotations are also found in the case of the valence band excitation. The rotation for the 2pxy band of graphite was about twice those from 2s and 2pz bands, corresponding to the difference in the orbital angular momentum quantum number of each band. Simultaneously, photoelectron intensity from the bottom of the 2s band was observed at the Γ point of every other Brillouin zone reflecting the photoelectron structure factor that corresponds to the interference of photoelectron waves from 2s atomic orbitals within a unit cell. The origin of the dual behavior that appeared in the observation of a local angular momentum from a delocalized valence band is discussed.

Synthesis of Zero-Birefringence Polymers Based on Positive and Negative Birefringence Polymer

2010 ◽  
Vol 428-429 ◽  
pp. 111-116
Author(s):  
Wen Jun Yang ◽  
Guo Zhu Liu ◽  
Ji Min Wang ◽  
Du Ling Xia
Keyword(s):  
High Performance ◽  
Incident Light ◽  
Polarization State ◽  
Polarized Light ◽  
Optical Devices ◽  
Polymer Chains ◽  
Optical Polymers ◽  
Orientation Degree ◽  
Chain Orientation ◽  
Extrusion Processing

Birefringence of a polymer is caused by polymer chain orientation during an injection-molding, extrusion processing or heat drawing. Birefringence of polymers degrades the performance of optical devices that require focusing by lenses or maintaining the polarization state of incident light. Optical polymers which exhibit no birefringence with any orientation of polymer chains are desirable to realize high performance optical devices that handle polarized light. In this study we demonstrate the random copolymerization method for synthesizing the zero-birefringence polymers in which positive and negative birefringence homopolymer are blended. We synthesize a polymer that exhibits no orientational birefringence with any orientation degree in a system that is composed of Methyl methacrylate/Styrene/Benzyl methacrylate.

scholarly journals COVID-19 vaccination of pregnant women: state-of-the-art

2021 ◽  
Vol 5 (11) ◽  
pp. 768-772
Author(s):  
A.A. Girina ◽  
◽  
A.L. Zaplatnikov ◽  
V.I. Svintsitskaya ◽  
S.D. Izhogina ◽  
...  
Keyword(s):  
Pregnant Women ◽  
State Of The Art ◽  
Severe Disease ◽  
Perinatal Outcomes ◽  
Professional Associations ◽  
Disease Course ◽  
Complete Control ◽  
Outcome Monitoring ◽  
Coronavirus Infection ◽  
Novel Coronavirus

Despite efforts made by the world community to battle the novel coronavirus infection, we are still unable to take complete control of virus spread. One of the causes of this issue is inadequate coverage of vaccination. Meanwhile, disease course in specific populations is associated with the risks of severe complications and lethal outcome. Infection of pregnant women is of particular concern. This paper addresses recent data on vaccination against the COVID-19 infection in pregnant women, including those with risk of severe disease course and unfavorable outcome. Monitoring the health of women infected with SARS-CoV-2 during gestation demonstrates unfavorable effects of the COVID-19 infection on the course and outcome of pregnancy. On the other hand, observational programs have demonstrated that vaccination has no effects on pregnancy course and perinatal outcomes. A view of the WHO and professional associations on the vaccination of pregnant women, particularly those from risk groups of severe COVID-19 course, is discussed. The importance of a personalized and balanced approach to COVID-19 vaccination of pregnant women involving the assessment of risks and benefits for the mother and child is emphasized. KEYWORDS: novel coronavirus infection, COVID-19, vaccination, immunization, pregnant women, risk group. FOR CITATION: Girina A.A., Zaplatnikov A.L., Svintsitskaya V.I., Izhogina S.D. COVID-19 vaccination of pregnant women: state-of-the-art. Russian Medical Inquiry. 2021;5(11):768–772 (in Russ.). DOI: 10.32364/2587-6821-2021-5-11-768-772.

scholarly journals Optical Pulling Using Chiral Metalens as a Photonic Probe

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3376
Author(s):  
Miao Peng ◽  
Hui Luo ◽  
Zhaojian Zhang ◽  
Tengfang Kuang ◽  
Dingbo Chen ◽  
...  
Keyword(s):  
Incident Light ◽  
Longitudinal Optical ◽  
Optical Force ◽  
Optical Manipulation ◽  
Maximum Value ◽  
Broadband Spectrum ◽  
Course Control ◽  
Pulling Forces ◽  
Potential Applications ◽  
Pulling Force

Optical pulling forces, which can pull objects in the source direction, have emerged as an intensively explored field in recent years. Conventionally, optical pulling forces exerted on objects can be achieved by tailoring the properties of an electromagnetic field, the surrounding environment, or the particles themselves. Recently, the idea of applying conventional lenses or prisms as photonic probes has been proposed to realize an optical pulling force. However, their sizes are far beyond the scope of optical manipulation. Here, we design a chiral metalens as the photonic probe to generate a robust optical pulling force. The induced pulling force exerted on the metalens, characterized by a broadband spectrum over 0.6 μm (from 1.517 to 2.117 μm) bandwidth, reached a maximum value of −83.76 pN/W. Moreover, under the illumination of incident light with different circular polarization states, the longitudinal optical force acting on the metalens showed a circular dichroism response. This means that the longitudinal optical force can be flexibly tuned from a pulling force to a pushing force by controlling the polarization of the incident light. This work could pave the way for a new advanced optical manipulation technique, with potential applications ranging from contactless wafer-scale fabrication to cell assembly and even course control for spacecraft.

scholarly journals Fabrication and testing of high-performance all-metal neutron guides and axisymmetric mirrors by electrochemical replication

MRS Advances ◽  
2020 ◽  
Vol 5 (29-30) ◽  
pp. 1513-1528
Author(s):  
B. Khaykovich ◽  
S. Romaine ◽  
A. Ames ◽  
R. Bruni ◽  
H. A. Ambaye ◽  
...  
Keyword(s):  
Neutron Scattering ◽  
High Performance ◽  
State Of The Art ◽  
Neutron Transport ◽  
Optical Devices ◽  
High Fidelity ◽  
Single Piece ◽  
Critical Components ◽  
Structure Of Matter ◽  
Neutron Guides

ABSTRACTNeutron scattering is one of the most useful methods of studying the structure of matter, with applications to biomedical, structural, magnetic and energy-related materials. Neutron-scattering instruments are installed around research reactors or accelerator-based neutron sources, and neutron guides are critical components of these facilities. They are neutron-transport optical devices consisting of state-of-the-art mirrors often tens of meters long. Here we demonstrate a novel fabrication method of all-metallic neutron guides and axisymmetric mirrors by electroplating from precision mandrels. The process allows for the fabrication of single-piece all-metal guides of prismatic and axisymmetric shapes. We also demonstrate supermirror guides and axisymmetric focusing supermirrors produced with the same technology. We present the fabrication and tests of the multilayer-coated replicated guides and optic and show that the mandrel is reproduced with high fidelity and reliability. Such supermirror optics will provide game-changing improvements in neutron techniques.

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