2,469 research outputs found
Interference Effects Due to Commensurate Electron Trajectories and Topological Crossovers in (TMTSF)2ClO4
We report angle-dependent magnetoresistance measurements on (TMTSF)2ClO4 that
provide strong support for a new macroscopic quantum phenomenon, the
interference commensurate (IC) effect, in quasi-one dimensional metals. In
addition to observing rich magnetoresistance oscillations, and fitting them
with one-electron calculations, we observe a clear demarcation of
field-dependent behavior at local resistance minima and maxima (versus field
angle). Anticipated by a theoretical treatment of the IC effect in terms of
Bragg reflections in the extended Brillouin zone, this behavior results from
1D-2D topological crossovers of electron wave functions as a function of field
orientation.Comment: 14 page
Interference Commensurate Oscillations in Q1D Conductors
We suggest an analytical theory to describe angular magnetic oscillations
recently discovered in quasi-one-dimensional conductor (TMTSF)2PF6 [see Phys.
Rev. B, 57, 7423 (1998)] and define the positions of the oscillation minima.
The origin of these oscillations is related to interference effects resulting
from an interplay of quasi-periodic and periodic ("commensurate") electron
trajectories in an inclined magnetic field. We reproduce via calculations
existing experimental data and predict some novel effects.Comment: 10 pages, 2 figure
Direct-write, focused ion beam-deposited,7 K superconducting C-Ga-O nanowire
We have fabricated C-Ga-O nanowires by gallium focused ion beam-induced
deposition from the carbon-based precursor phenanthrene. The electrical
conductivity of the nanowires is weakly temperature dependent below 300 K, and
indicates a transition to a superconducting state below Tc = 7 K. We have
measured the temperature dependence of the upper critical field Hc2(T), and
estimate a zero temperature critical field of 8.8 T. The Tc of this material is
approximately 40% higher than that of any other direct write nanowire, such as
those based on C-W-Ga, expanding the possibility of fabricating direct-write
nanostructures that superconduct above liquid helium temperaturesComment: Accepted for AP
Segmentation and three-dimensional visualisation of digital in-line holographic microscopy data
This paper demonstrates that transmissive or partially
transmissive scenes imaged by digital in-line holographic
microscopy (DIHM) can be reconstructed as a threedimensional
(3-D) model of the imaged volume from a single
capture. This process entails numerical reconstruction,
segmentation and polygonisation. Numerical reconstruction
of a digital hologram captured using a DIHM set up
is performed at equally spaced depths within a range. In
the case of intensity modulating objects, segmentation of
each of the reconstructed intensity images produces a contour
slice of the scene by applying an adaptive threshold
and border following. These slices are visualised in 3-D by
polygonising the data using the marching cubes algorithm.
We present experimental results for a real world DIHM capture
of a partially transmissive scene that demonstrates the
steps in this process
Introducing secure modes of operation for optical encryption
We analyze optical encryption systems using the techniques of conventional cryptography. All conventional
block encryption algorithms are vulnerable to attack, and often they employ secure modes of operation as one
way to increase security. We introduce the concept of conventional secure modes to optical encryption and analyze
the results in the context of known conventional and optical attacks. We consider only the optical system
“double random phase encoding,” which forms the basis for a large number of optical encryption, watermarking,
and multiplexing systems. We consider all attacks proposed to date in one particular scenario. We analyze
only the mathematical algorithms themselves and do not consider the additional security that arises from employing
these algorithms in physical optical systems
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