Near-field calibration of an objective spectrophotometer to NIST radiometric standards for the creation and maintenance of standard stars for ground- and space-based applications

This paper reports the development of an apparatus, technique, and method for calibrating the field emission phenomena’s dependence on both the voltage applied between the anode and cathode and the electrodes gap. A precise knowledge of the electrodes gap is required for calibrating field emitters. The I-V characteristic of isolated carbon nanotube field emitter is a strong function of the electrodes gap distance. A consolidated IV curve is obtained by calculating the current density and the local electric field with the field enhancement factor taken into consideration. The field enhancement factor and emitting area are unique for each electrodes gap distance. We also found that the turn-on voltage decreases as the electrodes gap distance decreases.

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Characterization of Polydioxanone in Near-Field Electrospinning

Polymers ◽

10.3390/polym12010001 ◽

2019 ◽

Vol 12 (1) ◽

pp. 1

Author(s):

William E. King ◽

Yvonne Gillespie ◽

Keaton Gilbert ◽

Gary L. Bowlin

Keyword(s):

Applied Voltage ◽

Biomedical Applications ◽

Near Field ◽

Deposition Velocity ◽

Polymer Concentration ◽

Air Gap ◽

Translational Velocity ◽

Individual Fiber ◽

The Creation ◽

Fiber Deposition

Electrospinning is a popular method for creating random, non-woven fibrous templates for biomedical applications, and a subtype technique termed near-field electrospinning (NFES) was devised by reducing the air gap distance to millimeters. This decreased working distance paired with precise translational motion between the fiber source and collector allows for the direct writing of fibers. We demonstrate a near-field electrospinning device designed from a MakerFarm Prusa i3v three-dimensional (3D) printer to write polydioxanone (PDO) microfibers. PDO fiber diameters were characterized over the processing parameters: Air gap, polymer concentration, translational velocity, needle gauge, and applied voltage. Fiber crystallinity and individual fiber uniformity were evaluated for the polymer concentration and translational fiber deposition velocity. Fiber stacking was evaluated for the creation of 3D templates to guide the alignment of human gingival fibroblasts. The fiber diameters correlated positively with polymer concentration, applied voltage, and needle gauge; and inversely correlated with translational velocity and air gap distance. Individual fiber diameter variability decreases, and crystallinity increases with increasing translational fiber deposition velocity. These data resulted in the creation of tailored PDO 3D templates, which guided the alignment of primary human fibroblast cells. Together, these results suggest that NFES of PDO can be scaled to create precise geometries with tailored fiber diameters for biomedical applications.

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Single-reference near-field calibration procedure for step-frequency ground penetrating radar

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.2002.808060 ◽

2003 ◽

Vol 41 (1) ◽

pp. 75-80 ◽

Cited By ~ 18

Author(s):

V.A. Mikhnev ◽

P. Vainikainen

Keyword(s):

Ground Penetrating Radar ◽

Near Field ◽

Calibration Procedure ◽

Step Frequency ◽

Field Calibration ◽

Ground Penetrating

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Near-Field Electrospinning and Melt Electrowriting of Biomedical Polymers—Progress and Limitations

Polymers ◽

10.3390/polym13071097 ◽

2021 ◽

Vol 13 (7) ◽

pp. 1097

Author(s):

William E. King ◽

Gary L. Bowlin

Keyword(s):

Electric Field ◽

Relative Motion ◽

Biomedical Applications ◽

Near Field ◽

Biomedical Polymers ◽

The Creation

Near-field electrospinning (NFES) and melt electrowriting (MEW) are the process of extruding a fiber due to the force exerted by an electric field and collecting the fiber before bending instabilities occur. When paired with precise relative motion between the polymer source and the collector, a fiber can be directly written as dictated by preprogrammed geometry. As a result, this precise fiber control results in another dimension of scaffold tailorability for biomedical applications. In this review, biomedically relevant polymers that to date have manufactured fibers by NFES/MEW are explored and the present limitations in direct fiber writing of standardization in published setup details, fiber write throughput, and increased ease in the creation of complex scaffold geometries are discussed.

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