scholarly journals Microscopic origin of the chiroptical response of optical media

2019 ◽  
Vol 5 (10) ◽  
pp. eaav8262 ◽  
Author(s):  
Matthew S. Davis ◽  
Wenqi Zhu ◽  
Jay K. Lee ◽  
Henri J. Lezec ◽  
Amit Agrawal
Keyword(s):  
Optical Activity ◽  
Electromagnetic Coupling ◽  
Spectroscopic Techniques ◽  
Optical Fields ◽  
Model Framework ◽  
Optical Elements ◽  
Optical Media ◽  
Model Predictions ◽  
Generalized Framework ◽  
Order Of Magnitude

The potential for enhancing the optical activity of natural chiral media using engineered nanophotonic components has been central in the quest toward developing next-generation circular-dichroism spectroscopic techniques. Through confinement and manipulation of optical fields at the nanoscale, ultrathin optical elements have enabled a path toward achieving order-of-magnitude enhancements in the chiroptical response. Here, we develop a model framework to describe the underlying physics governing the origin of the chiroptical response in optical media. The model identifies optical activity to originate from electromagnetic coupling to the hybridized eigenstates of a coupled electron-oscillator system, whereas differential absorption of opposite handedness light, though resulting in a far-field chiroptical response, is shown to have incorrectly been identified as optical activity. We validate the model predictions using experimental measurements and show them to also be consistent with observations in the literature. The work provides a generalized framework for the design and study of chiroptical systems.

Near-field scanning optical microscopy

1986 ◽  
Vol 44 ◽  
pp. 642-643
Author(s):  
E. Betzig ◽  
A. Harootunian ◽  
M. Isaacson ◽  
A. Lewis
Keyword(s):  
Near Field ◽  
Optical Microscope ◽  
Visible Radiation ◽  
Field Methods ◽  
Optical Elements ◽  
Optical Region ◽  
Order Of Magnitude ◽  
Nondestructive Imaging ◽  
Scanning Optical Microscopy ◽  
Near Field Scanning

In general, conventional methods of optical imaging are limited in spatial resolution by either the wavelength of the radiation used or by the aberrations of the optical elements. This is true whether one uses a scanning probe or a fixed beam method. The reason for the wavelength limit of resolution is due to the far field methods of producing or detecting the radiation. If one resorts to restricting our probes to the near field optical region, then the possibility exists of obtaining spatial resolutions more than an order of magnitude smaller than the optical wavelength of the radiation used. In this paper, we will describe the principles underlying such "near field" imaging and present some preliminary results from a near field scanning optical microscope (NS0M) that uses visible radiation and is capable of resolutions comparable to an SEM. The advantage of such a technique is the possibility of completely nondestructive imaging in air at spatial resolutions of about 50nm.

scholarly journals Deformation Behavior and Fracture Patterns of Laminated PEEK- and PI-Based Composites with Various Carbon-Fiber Reinforcement

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2268
Author(s):  
Pavel V Kosmachev ◽  
Vladislav O Alexenko ◽  
Svetlana A Bochkareva ◽  
Sergey V Panin
Keyword(s):  
Carbon Fiber ◽  
Flexural Strength ◽  
Laminated Composites ◽  
Flexural Modulus ◽  
Strength Properties ◽  
Fe Model ◽  
Carbon Fabric ◽  
Model Framework ◽  
Order Of Magnitude ◽  
Stress States

Laminated composites based on polyetheretherketone (PEEK) and polyimide (PI) matrices were fabricated by hot compression. Reinforcing materials (unidirectional carbon-fiber (CF) tapes or carbon fabric) and their layout patterns were varied. Stress–strain diagrams after three-point flexural tests were analyzed, and both lateral faces of the fractured specimens and fractured surfaces (obtained by optical and scanning electron microscopy, respectively) were studied. It was shown that the laminated composites possessed the maximum mechanical properties (flexural elastic modulus and strength) in the case of the unidirectional CF (0°/0°) layout. These composites were also not subjected to catastrophic failure during the tests. The PEEK-based composites showed twice the flexural strength of the PI-based ones (0.4 and 0.2 GPa, respectively), while the flexural modulus was four times higher (60 and 15 GPa, correspondently). The reason was associated with different melt flowability of the used polymer matrices and varied inter- (intra)layer adhesion levels. The effect of adhesion was additionally studied by computer simulation using a developed two-dimensional FE-model. It considered initial defects between the binder and CF, as well as subsequent delamination and failure under loads. Based on the developed FE-model, the influence of defects and delamination on the strength properties of the composites was shown at different stress states, and the corresponding quantitative estimates were reported. Moreover, another model was developed to determine the three-point flexural properties of the composites reinforced with CF and carbon fabric, taking into account different fiber layouts. It was shown within this model framework that the flexural strength of the studied composites could be increased by an order of magnitude by enhancing the adhesion level (considered through the contact area between CF and the binder).

scholarly journals Traversal Caches: A Framework for FPGA Acceleration of Pointer Data Structures

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
James Coole ◽  
Greg Stitt
Keyword(s):  
Data Structures ◽  
Reconfigurable Computing ◽  
Application Development ◽  
Sequential Memory ◽  
Generalized Framework ◽  
Field Programmable ◽  
Order Of Magnitude ◽  
Programmable Gate Arrays ◽  
Irregular Data ◽  
Access Patterns

Field-programmable gate arrays (FPGAs) and other reconfigurable computing (RC) devices have been widely shown to have numerous advantages including order of magnitude performance and power improvements compared to microprocessors for some applications. Unfortunately, FPGA usage has largely been limited to applications exhibiting sequential memory access patterns, thereby prohibiting acceleration of important applications with irregular patterns (e.g., pointer-based data structures). In this paper, we present a design pattern for RC application development that serializes irregular data structure traversals online into a traversal cache, which allows the corresponding data to be efficiently streamed to the FPGA. The paper presents a generalized framework that benefits applications with repeated traversals, which we show can achieve between 7x and 29x speedup over pointer-based software. For applications without strictly repeated traversals, we present application-specialized extensions that benefit applications with highly similar traversals by exploiting similarity to improve memory bandwidth and execute multiple traversals in parallel. We show that these extensions can achieve a speedup between 11x and 70x on a Virtex4 LX100 for Barnes-Hut n-body simulation.

On the syntheses and the optical properties of optically active 2-pyrazoline compounds

1979 ◽  
Vol 57 (3) ◽  
pp. 360-366 ◽  
Author(s):  
Makoto Mukai ◽  
Takashi Miura ◽  
Masahiro Nanbu ◽  
Toshinobu Yoneda ◽  
Yohji Shindo
Keyword(s):  
Optical Properties ◽  
Optical Activity ◽  
Optically Active ◽  
Spectroscopic Techniques ◽  
Considerable Influence ◽  
Pyrazoline Ring

Optically active 2-pyrazolines were synthesized and their optical properties were studied using various spectroscopic techniques to investigate the effects of substituents at the 3 and 5 positions of the 2-pyrazoline ring on their optical activity. It was found that in the case of 5-substituted-1,3-diphenyl-2-pyrazoline derivatives, the substituent at the 5 position has considerable influence on the optical activity, whereas in 3-substituted-1,5-diphenyl-2-pyrazoline derivatives, the substituent at the 3 position has no such influence.

scholarly journals Обнаружение высокочастотных альфвеновских колебаний в омических разрядах сферического токамака Глобус-М2

2021 ◽  
Vol 47 (12) ◽  
pp. 17
Author(s):  
И.М. Балаченков ◽  
Ю.В. Петров ◽  
В.К. Гусев ◽  
Н.Н. Бахарев ◽  
В.И. Варфоломеев ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Standing Wave ◽  
High Frequency ◽  
Low Density ◽  
Frequency Range ◽  
High Frequency Oscillations ◽  
Model Predictions ◽  
Mode Excitation ◽  
Order Of Magnitude ◽  
Frequency Chirping

In Globus-M2 ohmic discharges with low density, by means of Mirnov coils array, magnetic field oscillations with frequencies in 1 MHz range were detected. Frequency range of these oscillations significantly exceed the range of TAE and RSAE frequencies, which were previously observed on Globus-M and Globus-M2 tokamaks, and their amplitude, contrary, turned out to be up to an order of magnitude lower. It was found that high frequency oscillations are interrelated with suprathermal electron fraction. At the same time the observed instability seems to have Alfvenic nature, since its frequency correlates well with Alfven frequency scaling. It was also found that magnetic perturbation always forms standing wave with predominantly low toroidal wavenumbers, including n = 0 structure, which makes gap (e.g. TAE) mode excitation impossible. Frequency chirping during single bursts with δω ~ √t is consistent with hole-clump model predictions.

scholarly journals Controlling three-dimensional optical fields via inverse Mie scattering

2019 ◽  
Vol 5 (10) ◽  
pp. eaax4769 ◽  
Author(s):  
Alan Zhan ◽  
Ricky Gibson ◽  
James Whitehead ◽  
Evan Smith ◽  
Joshua R. Hendrickson ◽  
...  
Keyword(s):  
Design Method ◽  
Scattering Problem ◽  
Three Dimensional ◽  
Mie Scattering ◽  
Three Dimensions ◽  
Inverse Design ◽  
Optical Fields ◽  
Optical Elements ◽  
Space Optics ◽  
Inverse Design Method

Controlling the propagation of optical fields in three dimensions using arrays of discrete dielectric scatterers is an active area of research. These arrays can create optical elements with functionalities unrealizable in conventional optics. Here, we present an inverse design method based on the inverse Mie scattering problem for producing three-dimensional optical field patterns. Using this method, we demonstrate a device that focuses 1.55-μm light into a depth-variant discrete helical pattern. The reported device is fabricated using two-photon lithography and has a footprint of 144 μm by 144 μm, the largest of any inverse-designed photonic structure to date. This inverse design method constitutes an important step toward designer free-space optics, where unique optical elements are produced for user-specified functionalities.

scholarly journals Relating foam and interfacial rheological properties of β-lactoglobulin solutions

Soft Matter ◽  
2014 ◽  
Vol 10 (48) ◽  
pp. 9626-9636 ◽  
Author(s):  
M. Lexis ◽  
N. Willenbacher
Keyword(s):  
Rheological Properties ◽  
Yield Stress ◽  
Volume Fraction ◽  
Laplace Pressure ◽  
Model Predictions ◽  
Order Of Magnitude ◽  
Gas Volume Fraction ◽  
Gas Volume ◽  
Β Lactoglobulin

Interfacial elasticity can strongly increase the modulus and yield stress of protein foams by more than an order of magnitude compared to widely accepted model predictions only including contributions from Laplace pressure and gas volume fraction.

scholarly journals Coherent parity violation

1976 ◽  
Vol 54 (5) ◽  
pp. 568-574 ◽  
Author(s):  
Gabriel Karl
Keyword(s):  
Optical Activity ◽  
Parity Violation ◽  
Rotatory Power ◽  
Forward Scattering ◽  
Elementary Level ◽  
Neutron Beams ◽  
Massive Particles ◽  
Order Of Magnitude ◽  
Magnitude Estimates

Recent theoretical speculations about parity violating effects in the forward scattering of massless and massive particles are reviewed at an elementary level. These phenomena are analogous to optical activity, whose history is also briefly reviewed. Order of magnitude estimates for the rotatory power are presented, and the feasibility of experiments with neutron beams is discussed.

scholarly journals Forecasting Solar Energetic Particle Fluence with Multi-Spacecraft Observations

2017 ◽  
Vol 13 (S335) ◽  
pp. 298-300 ◽  
Author(s):  
T. Laitinen ◽  
S. Dalla ◽  
M. Battarbee ◽  
M. S. Marsh
Keyword(s):  
Particle Transport ◽  
Energetic Particle ◽  
Transport Model ◽  
Solar Energetic Particle ◽  
Time Estimates ◽  
Single Location ◽  
Model Predictions ◽  
Solar Eruptions ◽  
Order Of Magnitude ◽  
Particle Transport Model

AbstractForecasting Solar Energetic Particle (SEP) fluence, as integrated over an SEP event, is an important element when estimating the effect of solar eruptions on humans and technology in space. Current real-time estimates are based on SEP measurements at a single location in space. However, the interplanetary magnetic field corotates with the Sun approximately 13° each day with respect to Earth, thus in 4 days a near-Earth spacecraft will have changed their connection about 60° from the original SEP source. We estimate the effect of the corotation on particle fluence using a simple particle transport model, and show that ignoring corotation can cause up to an order of magnitude error in fluence estimations, depending on the interplanetary particle transport conditions. We compare the model predictions with STEREO observations of SEP events.

Photomechanics of Light-Activated Shape Memory Polymers

2008 ◽  
Author(s):  
Kevin N. Long ◽  
Timothy F. Scott ◽  
H. Jerry Qi ◽  
Martin L. Dunn
Keyword(s):  
Shape Memory ◽  
Mechanical Response ◽  
Irradiation Time ◽  
Shape Memory Polymer ◽  
Polymer System ◽  
Shape Memory Polymers ◽  
Model Parameters ◽  
Model Framework ◽  
Mechanical Coupling ◽  
Model Predictions

Photomechanical shape memory polymers are an exciting class of materials that are able to store a temporary shape and recover their original shape when stimulated by light. In this work we develop a model to simulate the photomechanical behavior of light-activated shape memory polymers. To the best of our knowledge this is the first theoretical model developed to describe this exciting class of active materials. Our model incorporates the interplay among four aspects of the underlying physical phenomena: light propagation, photo-chemistry, chemical-mechanical coupling, and mechanical response. The model framework is applied to a recently developed photo-induced shape memory polymer system [1, 2]. We describe a suite of experiments used to guide the modeling efforts, calibrate the model parameters, and then validate model predictions. Regarding the latter, we measure and then simulate the photo-induced bending behavior of shape memory polymer samples; model predictions are in good agreement with measurements. We use the model to then explore the effect of important photomechanical parameters (applied strain magnitude, irradiation time and intensity, and photoabsorber concentration) on material response with a view toward the design of novel actuator materials and structures.

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