45,092 research outputs found
Comparing Image Quality in Phase Contrast sub X-Ray Tomography -- A Round-Robin Study
How to evaluate and compare image quality from different sub-micrometer
(sub) CT scans? A simple test phantom made of polymer microbeads is used
for recording projection images as well as 13 CT scans in a number of
commercial and non-commercial scanners. From the resulting CT images, signal
and noise power spectra are modeled for estimating volume signal-to-noise
ratios (3D SNR spectra). Using the same CT images, a time- and
shape-independent transfer function (MTF) is computed for each scan, including
phase contrast effects and image blur (). The SNR spectra
and MTF of the CT scans are compared to 2D SNR spectra of the projection
images. In contrary to 2D SNR, volume SNR can be normalized with respect to the
object's power spectrum, yielding detection effectiveness (DE) a new measure
which reveals how technical differences as well as operator-choices strongly
influence scan quality for a given measurement time. Using DE, both
source-based and detector-based sub CT scanners can be studied and their
scan quality can be compared. Future application of this work requires a
particular scan acquisition scheme which will allow for measuring 3D
signal-to-noise ratios, making the model fit for 3D noise power spectra
obsolete
Robust particle outline extraction and its application to digital on-line holography
Peer reviewedPostprin
A novel method for the injection and manipulation of magnetic charge states in nanostructures
Realising the promise of next-generation magnetic nanotechnologies is
contingent on the development of novel methods for controlling magnetic states
at the nanoscale. There is currently demand for simple and flexible techniques
to access exotic magnetisation states without convoluted fabrication and
application processes. 360 degree domain walls (metastable twists in
magnetisation separating two domains with parallel magnetisation) are one such
state, which is currently of great interest in data storage and magnonics.
Here, we demonstrate a straightforward and powerful process whereby a moving
magnetic charge, provided experimentally by a magnetic force microscope tip,
can write and manipulate magnetic charge states in ferromagnetic nanowires. The
method is applicable to a wide range of nanowire architectures with
considerable benefits over existing techniques. We confirm the method's
efficacy via the injection and spatial manipulation of 360 degree domain walls
in Py and Co nanowires. Experimental results are supported by micromagnetic
simulations of the tip-nanowire interaction.Comment: in Scientific Reports (2016
Project SLOPE - Study of Lunar Orbiter Photographic Evaluation Final report
Quantitative measurement methods for evaluating ability of Lunar Orbiter photographs to detect topographic feature
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