5,774 research outputs found
A generalized approach to computer synthesis of digital holograms
Hologram is constructed by taking number of digitized sample points and blending them together to form ''continuous'' picture. New system selects better set of sample points resulting in improved hologram from same amount of information
Spin Readout Techniques of the Nitrogen-Vacancy Center in Diamond
The diamond nitrogen-vacancy (NV) center is a leading platform for quantum
information science due to its optical addressability and room-temperature spin
coherence. However, measurements of the NV center's spin state typically
require averaging over many cycles to overcome noise. Here, we review several
approaches to improve the readout performance and highlight future avenues of
research that could enable single-shot electron-spin readout at room
temperature.Comment: 21 pages, 7 figure
Limiter Control of a Chaotic RF Transistor Oscillator
We report experimental control of chaos in an electronic circuit at 43.9 MHz,
which is the fastest chaos control reported in the literature to date. Limiter
control is used to stabilize a periodic orbit in a tuned collector transistor
oscillator modified to exhibit simply folded band chaos. The limiter is
implemented using a transistor to enable monitoring the relative magnitude of
the control perturbation. A plot of the relative control magnitude vs. limiter
level shows a local minimum at period-1 control, thereby providing strong
evidence that the controlled state is an unstable periodic orbit (UPO) of the
uncontrolled system
Creep fatigue of low-cobalt superalloys: Waspalloy, PM U 700 and wrought U 700
The influence of cobalt content on the high temperature creep fatigue crack initiation resistance of three primary alloys was evaluated. These were Waspalloy, Powder U 700, and Cast U 700, with cobalt contents ranging from 0 up to 17 percent. Waspalloy was studied at 538 C whereas the U 700 was studied at 760 C. Constraints of the program required investigation at a single strain range using diametral strain control. The approach was phenomenological, using standard low cycle fatigue tests involving continuous cycling tension hold cycling, compression hold cycling, and symmetric hold cycling. Cycling in the absence of or between holds was done at 0.5 Hz, whereas holds when introduced lasted 1 minute. The plan was to allocate two specimens to the continuous cycling, and one specimen to each of the hold time conditions. Data was taken to document the nature of the cracking process, the deformation response, and the resistance to cyclic loading to the formation of small cracks and to specimen separation. The influence of cobalt content on creep fatigue resistance was not judged to be very significant based on the results generated. Specific conclusions were that the hold time history dependence of the resistance is as significant as the influence of cobalt content and increased cobalt content does not produce increased creep fatigue resistance on a one to one basis
Co-ordinating retinal histogenesis: early cell cycle exit enhances early cell fate determination in the Xenopus retina
The laminar arrays of distinct cell types in the vertebrate retina are built by a histogenic process in which cell fate is correlated with birth order. To explore this co-ordination mechanistically, we altered the relative timing of cell cycle exit in the developing Xenopus retina and asked whether this affected the activity of neural determinants. We found that Xath5, a bHLH proneural gene that promotes retinal ganglion cell (RGC) fate, ( Kanekar, S., Perron, M., Dorsky, R., Harris, W. A., Jan, L. Y., Jan, Y. N. and Vetter, M. L. (1997) Neuron 19, 981-994), does not cause these cells to be born prematurely. To drive cells out of the cell cycle early, therefore, we misexpressed the cyclin kinase inhibitor, p27Xic1. We found that early cell cycle exit potentiates the ability of Xath5 to promote RGC fate. Conversely, the cell cycle activator, cyclin E1, which inhibits cell cycle exit, biases Xath5-expressing cells toward later neuronal fates. We found that Notch activation in this system caused cells to exit the cell cycle prematuely, and when it is misexpressed with Xath5, it also potentiates the induction of RGCs. The potentiation is counteracted by co-expression of cyclin E1. These results suggest a model of histogenesis in which the activity of factors that promote early cell cycle exit enhances the activity of factors that promote early cellular fates
Amplified Sensitivity of Nitrogen-Vacancy Spins in Nanodiamonds using All-Optical Charge Readout
Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile
platform for sensing applications spanning from nanomagnetism to in-vivo
monitoring of cellular processes. In many cases, however, weak optical signals
and poor contrast demand long acquisition times that prevent the measurement of
environmental dynamics. Here, we demonstrate the ability to perform fast,
high-contrast optical measurements of charge distributions in ensembles of NV
centers in nanodiamonds and use the technique to improve the spin readout
signal-to-noise ratio through spin-to-charge conversion. A study of 38
nanodiamonds, each hosting 10-15 NV centers with an average diameter of 40 nm,
uncovers complex, multiple-timescale dynamics due to radiative and
non-radiative ionization and recombination processes. Nonetheless, the
nanodiamonds universally exhibit charge-dependent photoluminescence contrasts
and the potential for enhanced spin readout using spin-to-charge conversion. We
use the technique to speed up a relaxometry measurement by a factor of
five.Comment: 13 pages, 14 figure
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