3,103 research outputs found
Bayesian Multiple Emitter Fitting using Reversible Jump Markov Chain Monte Carlo
In single molecule localization-based super-resolution imaging, high labeling density or the desire for greater data collection speed can lead to clusters of overlapping emitter images in the raw super-resolution image data. We describe a Bayesian inference approach to multiple-emitter fitting that uses Reversible Jump Markov Chain Monte Carlo to identify and localize the emitters in dense regions of data. This formalism can take advantage of any prior information, such as emitter intensity and density. The output is both a posterior probability distribution of emitter locations that includes uncertainty in the number of emitters and the background structure, and a set of coordinates and uncertainties from the most probable model
Dephasing due to Which Path Detector
We study dephasing of electrons induced by a which path detector and thus
verify Bohr's complementarity principle for fermions. We utilize a double path
interferometer with two slits, with one slit being replaced by a coherent
quantum dot (QD). A short one dimensional channel, in the form of a quantum
point contact (QPC), in close proximity to the QD, serves as a which path
detector. We find that by varying the properties of the QPC detector we affect
the visibility of the interference, inducing thus dephasing. We develop a
simple model to explain the dephasing due to the nearby detector and find good
agreement with the experiment.Comment: 8 pages, 3 figure
The origin of defects induced in ultra-pure germanium by Electron Beam Deposition
The creation of point defects in the crystal lattices of various
semiconductors by subthreshold events has been reported on by a number of
groups. These observations have been made in great detail using sensitive
electrical techniques but there is still much that needs to be clarified.
Experiments using Ge and Si were performed that demonstrate that energetic
particles, the products of collisions in the electron beam, were responsible
for the majority of electron-beam deposition (EBD) induced defects in a
two-step energy transfer process. Lowering the number of collisions of these
energetic particles with the semiconductor during metal deposition was
accomplished using a combination of static shields and superior vacuum
resulting in devices with defect concentrations lower than cm, the measurement limit of our deep level transient
spectroscopy (DLTS) system. High energy electrons and photons that samples are
typically exposed to were not influenced by the shields as most of these
particles originate at the metal target thus eliminating these particles as
possible damage causing agents. It remains unclear how packets of energy that
can sometimes be as small of 2eV travel up to a m into the material while
still retaining enough energy, that is, in the order of 1eV, to cause changes
in the crystal. The manipulation of this defect causing phenomenon may hold the
key to developing defect free material for future applications.Comment: 18 pages, 9 figure
Unraveling the Nature of Unidentified High Galactic Latitude Fermi/LAT Gamma-ray Sources with Suzaku
We report on the results of deep X-ray follow-up observations of four
unidentified Fermi/LAT gamma-ray sources at high Galactic latitudes using
Suzaku. The studied objects were detected with high significance during the
first 3 months of Fermi/LAT operation, and subsequently better localized in the
Fermi/LAT 1 year catalog (1FGL). Possible associations with pulsars and active
galaxies have subsequently been discussed, and our observations provide an
important contribution to this debate. In particular, an X-ray point source was
found within the 95% confidence error circle of 1FGL J1231.1-1410. X-ray
spectrum is well-fitted by a blackbody with an additional power-law. This
supports the recently claimed identification of this source with a millisecond
pulsar (MSP) PSR J1231-1411. Concerning 1FGL J1311.7-3429, two X-ray sources
were found within the LAT error circle. Even though the X-ray spectral and
variability properties were accessed, their nature and relationship with the
gamma-ray source remain uncertain. We found several weak X-ray sources in the
field of 1FGL J1333.2+5056, one coinciding with CLASS J1333+5057. We argue the
available data are consistent with the association between these two objects.
Finally, we have detected an X-ray source in the vicinity of 1FGL J2017.3+0603.
This object was recently suggested to be associated with a newly discovered MSP
PSR J2017+0603, because of the spatial-coincidence and the gamma-ray pulse
detection. We have only detected the X-ray counterpart of the CLASS J2017+0603,
while we determined an X-ray flux upper limit at the pulsar position. All in
all, our studies indicate while a significant fraction of unidentified high
Galactic latitude gamma-ray sources is related to the pulsar and blazar
phenomena, associations with other classes of astrophysical objects are still
valid options.Comment: Accepted for publication in the Ap
Spatial scales of interactions among bacteria and between bacteria and the leaf surface.
Microbial life on plant leaves is characterized by a multitude of interactions between leaf colonizers and their environment. While the existence of many of these interactions has been confirmed, their spatial scale or reach often remained unknown. In this study, we applied spatial point pattern analysis to 244 distribution patterns of Pantoea agglomerans and Pseudomonas syringae on bean leaves. The results showed that bacterial colonizers of leaves interact with their environment at different spatial scales. Interactions among bacteria were often confined to small spatial scales up to 5-20 μm, compared to interactions between bacteria and leaf surface structures such as trichomes which could be observed in excess of 100 μm. Spatial point-pattern analyses prove a comprehensive tool to determine the different spatial scales of bacterial interactions on plant leaves and will help microbiologists to better understand the interplay between these interactions
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