Prestack Data Enhancement with Phase Substitution and Phase Corrections Guided by Local Multidimensional Stacking

The goal of imaging the finest detail possible in biological specimens leads to contradictory requirements for the choice of an electron dose. The dose should be as low as possible to minimize object damage, yet as high as possible to optimize image statistics. For specimens that are protected by low temperatures or for which the low resolution associated with negative stain is acceptable, the first condition may be partially relaxed, allowing the use of (for example) 6 to 10 e/Å2. However, this medium dose is marginal for obtaining the contrast transfer function (CTF) of the microscope, which is necessary to allow phase corrections to the image. We have explored two parameters that affect the CTF under medium dose conditions.Figure 1 displays the CTF for carbon (C, row 1) and triafol plus carbon (T+C, row 2). For any column, the images to which the CTF correspond were from a carbon covered hole (C) and the adjacent triafol plus carbon support film (T+C), both recorded on the same micrograph; therefore the imaging parameters of defocus, illumination angle, and electron statistics were identical.

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Two-phase estimation of coverages with second-phase corrections

Environmetrics ◽

10.1002/env.647 ◽

2004 ◽

Vol 15 (4) ◽

pp. 357-368 ◽

Cited By ~ 18

Author(s):

L. Fattorini ◽

M. Marcheselli ◽

C. Pisani

Keyword(s):

Phase Estimation ◽

Second Phase ◽

Two Phase ◽

Phase Corrections

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Extension of forward modeling phase-screen code in isotropic and anisotropic media up to critical angle

Geophysics ◽

10.1190/1.2755945 ◽

2007 ◽

Vol 72 (5) ◽

pp. SM107-SM114 ◽

Cited By ~ 3

Author(s):

James C. White ◽

Richard W. Hobbs

Keyword(s):

Critical Angle ◽

Model Space ◽

Anisotropic Media ◽

Forward Modeling ◽

Phase Screen ◽

Computationally Efficient ◽

Reflection And Transmission ◽

Transmission Coefficients ◽

Phase Corrections ◽

Converted Phases

The computationally efficient phase-screen forward modeling technique is extended to allow investigation of nonnormal raypaths. The code is developed to accommodate all diffracted and converted phases up to critical angle, building on a geometric construction method. The new approach relies upon prescanning the model space to assess the complexity of each screen. The propagating wavefields are then divided as a function of horizontal wavenumber, and each subset is transformed to the spatial domain separately, carrying with it angular information. This allows both locally accurate 3D phase corrections and Zoeppritz reflection and transmission coefficients to be applied. The phase-screen code is further developed to handle simple anisotropic media. During phase-screen modeling, propagation is undertaken in the wavenumber domain where exact expressions for anisotropic phase velocities are available. Traveltimes and amplitude effects from a range of anisotropic shales are computed and compared with previous published results.

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Dynamically Focused Gaussian Beams for Seismic Imaging

International Journal of Geophysics ◽

10.1155/2011/316581 ◽

2011 ◽

Vol 2011 ◽

pp. 1-8 ◽

Cited By ~ 8

Author(s):

Robert L. Nowack

Keyword(s):

Seismic Imaging ◽

Initial Study ◽

Gaussian Beams ◽

Subsurface Scattering ◽

Local Data ◽

Quadratic Phase ◽

Phase Corrections ◽

Speed Up ◽

Data Windows ◽

Slant Stacking

An initial study is performed in which dynamically focused Gaussian beams are investigated for seismic imaging. Focused Gaussian beams away from the source and receiver plane allow the narrowest and planar portions of the beams to occur at the depth of a specific target structure. To match the seismic data, quadratic phase corrections are required for the local slant stacks of the surface data. To provide additional control of the imaging process, dynamic focusing is investigated where all subsurface points are specified to have the same planar beam fronts. This gives the effect of using nondiffracting beams, but actually results from the use of multiple focusing depths for each Gaussian beam. However, now different local slant stacks must be performed depending on the position of the subsurface scattering point. To speed up the process, slant stacking of the local data windows is varied to match the focusing depths along individual beams when tracked back into the medium. The approach is tested with a simple model of 5-point scatterers which are then imaged with the data, and then to the imaging of a single dynamically focused beam for one shot gather computed from the Sigsbee2A model.

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Phase corrections and their significance

Fourier Transform Spectrometry ◽

10.1016/b978-012042510-5/50007-x ◽

2001 ◽

pp. 101-117

Author(s):

Sumner P. Davis ◽

Mark C. Abrams ◽

James W. Brault

Keyword(s):

Phase Corrections

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Prestack data enhancement with phase corrections in time‐frequency domain guided by local multidimensional stacking

Geophysical Prospecting ◽

10.1111/1365-2478.12956 ◽

2020 ◽

Vol 68 (6) ◽

pp. 1811-1818

Author(s):

Andrey Bakulin ◽

Dmitri Neklyudov ◽

Ilya Silvestrov

Keyword(s):

Frequency Domain ◽

Time Frequency ◽

Phase Corrections

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Application of a Fluorescent Probe for the Online Measurement of PM-Bound Reactive Oxygen Species in Chamber and Ambient Studies

Sensors ◽

10.3390/s19204564 ◽

2019 ◽

Vol 19 (20) ◽

pp. 4564 ◽

Cited By ~ 1

Author(s):

Reece Brown ◽

Svetlana Stevanovic ◽

Zachary Brown ◽

Mingfu Cai ◽

Shengzhen Zhou ◽

...

Keyword(s):

Reactive Oxygen Species ◽

Cigarette Smoke ◽

High Efficiency ◽

Reactive Oxygen ◽

Organic Aerosol ◽

Oxygen Species ◽

Side Stream ◽

Chamber Study ◽

Phase Corrections ◽

Flow Through

This manuscript details the application of a profluorescent nitroxide (PFN) for the online quantification of radical concentrations on particulate matter (PM) using an improved Particle Into Nitroxide Quencher (PINQ). A miniature flow-through fluorimeter developed specifically for use with the 9,10-bis(phenylethynyl)anthracene-nitroxide (BPEAnit) probe was integrated into the PINQ, along with automated gas phase corrections through periodic high efficiency particle arrestor (HEPA) filtering. The resulting instrument is capable of unattended sampling and was operated with a minimum time resolution of 2.5 min. Details of the fluorimeter design and examples of data processing are provided, and results from a chamber study of side-stream cigarette smoke and ambient monitoring campaign in Guangzhou, China are presented. Primary cigarette smoke was shown to have both short-lived (t1/2 = 27 min) and long-lived (t1/2 = indefinite) PM-bound reactive oxygen species (ROS) components which had previously only been observed in secondary organic aerosol (SOA).

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