Optical emission from ultrafast laser filament-produced air plasmas in the multiple filament regime
- NSF-PAR ID:
- 10077898
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Express
- Volume:
- 26
- Issue:
- 22
- ISSN:
- 1094-4087; OPEXFF
- Page Range / eLocation ID:
- Article No. 29110
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
The structure of the axoneme in motile cilia and flagella is emerging with increasing detail from high-resolution imaging, but the mechanism by which the axoneme creates oscillatory, propulsive motion remains mysterious. It has recently been proposed that this motion may be caused by a dynamic ‘flutter’ instability that can occur under steady dynein loading, and not by switching or modulation of dynein motor activity (as commonly assumed). In the current work, we have built an improved multi-filament mathematical model of the axoneme and implemented it as a system of discrete equations using the finite-element method. The eigenvalues and eigenvectors of this model predict the emergence of oscillatory, wave-like solutions in the absence of dynein regulation and specify the associated frequencies and waveforms of beating. Time-domain simulations with this model illustrate the behaviour predicted by the system's eigenvalues. This model and analysis allow us to efficiently explore the potential effects of difficult to measure biophysical parameters, such as elasticity of radial spokes and inter-doublet links, on the ciliary waveform. These results support the idea that dynamic instability without dynamic dynein regulation is a plausible and robust mechanism for generating ciliary beating.more » « less
-
null (Ed.)Synopsis Many flying insects utilize a membranous structure for flight, which is known as a “wing.” However, some spiders use silk fibers for their aerial dispersal. It is well known that spiders can disperse over hundreds of kilometers and rise several kilometers above the ground in this way. However, little is known about the ballooning mechanisms of spiders, owing to the lack of quantitative data. Recently, Cho et al. discovered previously unknown information on the types and physical properties of spiders’ ballooning silks. According to the data, a crab spider weighing 20 mg spins 50–60 ballooning silks simultaneously, which are about 200 nm thick and 3.22 m long for their flight. Based on these physical dimensions of ballooning silks, the significance of these filament-like structures is explained by a theoretical analysis reviewing the fluid-dynamics of an anisotropic particle (like a filament or a high-slender body). (1) The filament-like structure is materially efficient geometry to produce (or harvest, in the case of passive flight) fluid-dynamic force in a low Reynolds number flow regime. (2) Multiple nanoscale fibers are the result of the physical characteristics of a thin fiber, the drag of which is proportional to its length but not to its diameter. Because of this nonlinear characteristic of a fiber, spinning multiple thin ballooning fibers is, for spiders, a better way to produce drag forces than spinning a single thick spider silk, because spiders can maximize their drag on the ballooning fibers using the same amount of silk dope. (3) The mean thickness of fibers, 200 nm, is constrained by the mechanical strength of the ballooning fibers and the rarefaction effect of air molecules on a nanoscale fiber, because the slip condition on a fiber could predominate if the thickness of the fiber becomes thinner than 100 nm.more » « less
-
The objective of this work is to identify and measure in situ the embedded features in parts manufactured with a fused filament fabrication (FFF) 3D printer. After implementing the monitoring system consisting of optical and thermal cameras, the efficiency of the system is determined in terms of efficacy for automated defect detection through data analysis. In contrast to our previous work, which involved the detection of a large number of randomly embedded sub-surface defects, this study identifies defects of various sizes, geometries, and depths printed in a rectangular strip. Temperature differences, or ΔT, between certain layers are evaluated to determine their significance to the detection of embedded features and internal voids. ΔT between the final layer of a void within the embedded feature and the subsequent layer was found to increase as void size decreased. ΔT between the formation layer and the subsequent layer decreased as void size decreased. Additionally, embedded feature geometries registered higher ΔT between formation layer and the subsequent layer when they consisted of 3-layer voids, which indicates that larger voids, or multilayer defects, within embedded features led to higher formation layer temperatures. Overall, real-time image acquisition, image processing, and data correlation was demonstrated to effectively detect abnormalities in large datasets.more » « less
