scholarly journals Broadband Microwave Absorption by Logarithmic Spiral Metasurface

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Shubo Wang ◽  
Bo Hou ◽  
Che Ting Chan
Keyword(s):  
Electromagnetic Wave ◽  
Scale Invariance ◽  
Logarithmic Spiral ◽  
Unit Cell ◽  
Scale Invariant ◽  
Archimedean Spiral ◽  
Broadband Absorption ◽  
Fabry Perot ◽  
Classical Waves

Abstract Metamaterials have enabled the design of electromagnetic wave absorbers with unprecedented performance. Conventional metamaterial absorbers usually employ multiple structure components in one unit cell to achieve broadband absorption. Here, a simple metasurface microwave absorber is proposed that has one metal-backed logarithmic spiral resonator as the unit cell. It can absorb >95% of normally incident microwave energy within the frequency range of 6 GHz–37 GHz as a result of the scale invariant geometry and the Fabry-Perot-type resonances of the resonator. The thickness of the metasurface is 5 mm and approaches the Rozanov limit of an optimal absorber. The physics underlying the broadband absorption is discussed. A comparison with Archimedean spiral metasurface is conducted to uncover the crucial role of scale invariance. The study opens a new direction of electromagnetic wave absorption by employing the scale invariance of Maxwell equations and may also be applied to the absorption of other classical waves such as sound.

scholarly journals Scale Invariant Turbulence and Gibbs Free Energy in the Atmosphere

2022 ◽  
Author(s):  
Adrian F. Tuck
Keyword(s):  
Free Energy ◽  
Solar Radiation ◽  
Gibbs Free Energy ◽  
Open System ◽  
Scale Invariance ◽  
Aerosol Particles ◽  
Solar Radiation Management ◽  
Scale Invariant ◽  
Radiation Management

A method of calculating the Gibbs Free Energy (Exergy) for the Earth’s atmosphere using statistical multifractality — scale invariance - is described, and examples given of its application to the stratosphere, including a methodology for extension to aerosol particles. The role of organic molecules in determining the radiative transfer characteristics of aerosols is pointed out. These methods are discussed in the context of the atmosphere as an open system far from chemical and physical equilibrium, and used to urge caution in deploying “solar radiation management”.

The orientation of sickle hemoglobin fibers within fascicles

1988 ◽  
Vol 46 ◽  
pp. 400-401
Author(s):  
Christopher A. Miller ◽  
Bridget Carragher ◽  
William A. McDade ◽  
Robert Josephs
Keyword(s):  
Sickle Cell ◽  
Sickle Cell Anemia ◽  
Relative Orientation ◽  
Unit Cell ◽  
Red Cell ◽  
High Ph ◽  
Sickle Hemoglobin ◽  
Polar Crystal ◽  
Helical Configuration

Highly ordered bundles of deoxyhemoglobin S (HbS) fibers, termed fascicles, are intermediates in the high pH crystallization pathway of HbS. These fibers consist of 7 Wishner-Love double strands in a helical configuration. Since each double strand has a polarity, the odd number of double strands in the fiber imparts a net polarity to the structure. HbS crystals have a unit cell containing two double strands, one of each polarity, resulting in a net polarity of zero. Therefore a rearrangement of the double strands must occur to form a non-polar crystal from the polar fibers. To determine the role of fascicles as an intermediate in the crystallization pathway it is important to understand the relative orientation of fibers within fascicles. Furthermore, an understanding of fascicle structure may have implications for the design of potential sickling inhibitors, since it is bundles of fibers which cause the red cell distortion responsible for the vaso-occlusive complications characteristic of sickle cell anemia.

scholarly journals Ready Access to Molecular Rotors Based on Boron Dipyrromethene Dyes-Coumarin Dyads Featuring Broadband Absorption

Molecules ◽  
2020 ◽  
Vol 25 (4) ◽  
pp. 781
Author(s):  
Ernesto Enríquez-Palacios ◽  
Teresa Arbeloa ◽  
Jorge Bañuelos ◽  
Claudia I. Bautista-Hernández ◽  
José G. Becerra-González ◽  
...  
Keyword(s):  
Molecular Rotors ◽  
Fluorescence Signal ◽  
Access Method ◽  
Broadband Absorption ◽  
Boron Dipyrromethene ◽  
Conformational Freedom ◽  
Meso Position ◽  
Photophysical Study ◽  
Ready Access

Herein we report on a straightforward access method for boron dipyrromethene dyes (BODIPYs)-coumarin hybrids linked through their respective 8- and 6- positions, with wide functionalization of the coumarin fragment, using salicylaldehyde as a versatile building block. The computationally-assisted photophysical study unveils broadband absorption upon proper functionalization of the coumarin, as well as the key role of the conformational freedom of the coumarin appended at the meso position of the BODIPY. Such free motion almost suppresses the fluorescence signal, but enables us to apply these dyads as molecular rotors to monitor the surrounding microviscosity.

scholarly journals Broadband Absorption in Patterned Metal/Weakly-Absorbing-Spacer/Metal with Graded Photonic Super-Crystal

Photonics ◽  
2021 ◽  
Vol 8 (4) ◽  
pp. 114
Author(s):  
Steve Kamau ◽  
Safaa Hassan ◽  
Khadijah Alnasser ◽  
Hualiang Zhang ◽  
Jingbiao Cui ◽  
...  
Keyword(s):  
Surface Plasmon ◽  
Surface Plasmon Polariton ◽  
Near Infrared ◽  
Broadband Absorption ◽  
Au Film ◽  
Fabry Perot ◽  
Absorbing Material ◽  
Multiple Band ◽  
Band Absorption ◽  
Plasmon Polaritons

It is challenging to realize the complete broadband absorption of near-infrared in thin optical devices. In this paper, we studied high light absorption in two devices: a stack of Au-pattern/insulator/Au-film and a stack of Au-pattern/weakly-absorbing-material/Au-film where the Au-pattern was structured in graded photonic super-crystal. We observed multiple-band absorption, including one near 1500 nm, in a stack of Au-pattern/spacer/Au-film. The multiple-band absorption is due to the gap surface plasmon polariton when the spacer thickness is less than 30 nm. Broadband absorption appears in the near-infrared when the insulator spacer is replaced by a weakly absorbing material. E-field intensity was simulated and confirmed the formation of gap surface plasmon polaritons and their coupling with Fabry–Pérot resonance.

scholarly journals Low-coherence photonic method of electrochemical processes monitoring

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Monika Kosowska ◽  
Paweł Jakóbczyk ◽  
Michał Rycewicz ◽  
Alex Vitkin ◽  
Małgorzata Szczerska
Keyword(s):  
Electrochemical Process ◽  
Electrochemical Measurements ◽  
Boron Doped Diamond ◽  
Silica Substrate ◽  
Low Coherence ◽  
Optical Responses ◽  
Boron Doped ◽  
Fabry Perot ◽  
Hybrid Characterization

AbstractWe present an advanced multimodality characterization platform for simultaneous optical and electrochemical measurements of ferrocyanides. Specifically, we combined a fiber-optic Fabry–Perot interferometer with a three-electrode electrochemical setup to demonstrate a proof-of-principle of this hybrid characterization approach, and obtained feasibility data in its monitoring of electrochemical reactions in a boron-doped diamond film deposited on a silica substrate. The film plays the dual role of being the working electrode in the electrochemical reaction, as well as affording the reflectivity to enable the optical interferometry measurements. Optical responses during the redox reactions of the electrochemical process are presented. This work proves that simultaneous opto-electrochemical measurements of liquids are possible.

scholarly journals Scale Invariance, Horizons, and Inflation

2021 ◽  
Author(s):  
Andre Maeder ◽  
Vesselin G Gueorguiev
Keyword(s):  
Scalar Field ◽  
Scale Invariance ◽  
Maxwell Equations ◽  
High Redshift ◽  
Empty Space ◽  
Causal Connection ◽  
Cosmological Constant Problem ◽  
Scale Invariant ◽  
Starting Point ◽  
Final Answer

Abstract Maxwell equations and the equations of General Relativity are scale invariant in empty space. The presence of charge or currents in electromagnetism or the presence of matter in cosmology are preventing scale invariance. The question arises on how much matter within the horizon is necessary to kill scale invariance. The scale invariant field equation, first written by Dirac in 1973 and then revisited by Canuto et al. in 1977, provides the starting point to address this question. The resulting cosmological models show that, as soon as matter is present, the effects of scale invariance rapidly decline from ϱ = 0 to ϱc, and are forbidden for densities above ϱc. The absence of scale invariance in this case is consistent with considerations about causal connection. Below ϱc, scale invariance appears as an open possibility, which also depends on the occurrence of in the scale invariant context. In the present approach, we identify the scalar field of the empty space in the Scale Invariant Vacuum (SIV) context to the scalar field ϕ in the energy density $\varrho = \frac{1}{2} \dot{\varphi }^2 + V(\varphi )$ of the vacuum at inflation. This leads to some constraints on the potential. This identification also solves the so-called “cosmological constant problem”. In the framework of scale invariance, an inflation with a large number of e-foldings is also predicted. We conclude that scale invariance for models with densities below ϱc is an open possibility; the final answer may come from high redshift observations, where differences from the ΛCDM models appear.

The Role of Topology and Tissue Mechanics in Remora Attachment

2014 ◽  
Vol 1648 ◽  
Author(s):  
Michael Culler ◽  
Keri A. Ledford ◽  
Jason H. Nadler
Keyword(s):  
Finite Element ◽  
Material Properties ◽  
Tissue Mechanics ◽  
Unit Cell ◽  
Surface Topology ◽  
Finite Element Models ◽  
Cell Geometry ◽  
Critical Step ◽  
Tissue Material

ABSTRACTRemora fish are capable of fast, reversible and reliable adhesion to a wide variety of both natural and artificial marine hosts through a uniquely evolved dorsal pad. This adhesion is partially attributed to suction, which requires a robust seal between the pad interior and the ambient environment. Understanding the behavior of remora adhesion based on measurable surface parameters and material properties is a critical step when creating artificial, bio-inspired devices. In this work, structural and fluid finite element models (FEM) based on a simplified “unit cell” geometry were developed to predict the behavior of the seal with respect to host/remora surface topology and tissue material properties.

Electrostatic energy in ionic crystals

1981 ◽  
Vol 375 (1763) ◽  
pp. 475-505 ◽  
Keyword(s):  
Dipole Moment ◽  
Ionic Crystal ◽  
Unit Cell ◽  
Electrostatic Energy ◽  
Cubic Crystal ◽  
Simple Cubic ◽  
Dependent Part ◽  
Unit Cells ◽  
Cell Energy

The problem of calculating electrostatic energies in large, finite and arbitrarily shaped pieces of ionic crystal is analysed. The electrostatic energy of a unit cell of the crystal deep within the interior of the piece of crystal is shown to be composed of a shape-independent part depending on the structure of the crystal lattice concerned and the distribution of ions within a unit cell, and a shape-dependent part which depends on the shape of the piece of crystal and the dipole moment of a unit cell. The shape-dependent part is zero if this dipole moment is zero. The electrostatic energy of the whole piece of crystal is shown to be the unit cell energy multiplied by the number of unit cells in the piece of crystal, plus corrections proportional to the surface area of the piece of crystal. These surface corrections are calculated explicitly for a finite cube of simple cubic crystal. Different descriptions of the same crystal structure are shown to lead to different bulk energies. This disagreement is discussed for the CsCl lattice, and is shown to arise from the way the different descriptions of the lattice imply different surface structures on the surface of a cube of crystal. The energy of a test charge at the surface of a cube of simple cubic crystal, and then the energy of layers of charges on the surfaces of a cube of simple cubic crystal, are analysed. The analyses confirm the origin of the disagreement in bulk energies for the two descriptions of the CsCl lattice. The role of the energies of surface layers in the bulk electrostatic energy of a piece of ionic crystal, and the relation of this bulk energy to a shape-independent Madelung constant are discussed. Some conjectures on the role of bulk energies in surface reconstruction are also discussed.

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