17,842 research outputs found
Measurement of the separation between atoms beyond diffraction limit
Precision measurement of small separations between two atoms or molecules has
been of interest since the early days of science. Here, we discuss a scheme
which yields spatial information on a system of two identical atoms placed in a
standing wave laser field. The information is extracted from the collective
resonance fluorescence spectrum, relying entirely on far-field imaging
techniques. Both the interatomic separation and the positions of the two
particles can be measured with fractional-wavelength precision over a wide
range of distances from bout lambda/550 to lambda/2.Comment: v2: Revised version for publicatio
Minimalist AdaBoost for blemish identification in potatoes
We present a multi-class solution based on minimalist Ad-
aBoost for identifying blemishes present in visual images of potatoes.
Using training examples we use Real AdaBoost to rst reduce the fea-
ture set by selecting ve features for each class, then train binary clas-
siers for each class, classifying each testing example according to the
binary classier with the highest certainty. Against hand-drawn ground
truth data we achieve a pixel match of 83% accuracy in white potatoes
and 82% in red potatoes. For the task of identifying which blemishes
are present in each potato within typical industry dened criteria (10%
coverage) we achieve accuracy rates of 93% and 94%, respectively
Zero-shot keyword spotting for visual speech recognition in-the-wild
Visual keyword spotting (KWS) is the problem of estimating whether a text
query occurs in a given recording using only video information. This paper
focuses on visual KWS for words unseen during training, a real-world, practical
setting which so far has received no attention by the community. To this end,
we devise an end-to-end architecture comprising (a) a state-of-the-art visual
feature extractor based on spatiotemporal Residual Networks, (b) a
grapheme-to-phoneme model based on sequence-to-sequence neural networks, and
(c) a stack of recurrent neural networks which learn how to correlate visual
features with the keyword representation. Different to prior works on KWS,
which try to learn word representations merely from sequences of graphemes
(i.e. letters), we propose the use of a grapheme-to-phoneme encoder-decoder
model which learns how to map words to their pronunciation. We demonstrate that
our system obtains very promising visual-only KWS results on the challenging
LRS2 database, for keywords unseen during training. We also show that our
system outperforms a baseline which addresses KWS via automatic speech
recognition (ASR), while it drastically improves over other recently proposed
ASR-free KWS methods.Comment: Accepted at ECCV-201
The anti-cancer effect of retinoic acid signaling in CRC occurs via decreased growth of ALDH+ colon cancer stem cells and increased differentiation of stem cells
Background: Tumorigenesis is driven by stem cell (SC) overpopulation. BecauseALDH is both a marker for SCs in many tissues and a key enzyme in retinoid acid (RA)signaling, we studied RA signaling in normal and malignant colonic SCs.Hypothesis: RA signaling regulates growth and differentiation of ALDH+ colonicSCs dysregulation of RA signaling contributes to SC overpopulation and colorectalcancer (CRC) development.Methods: We analyzed normal and malignant colonic tissues and CRC cell linesto see if retinoid receptors (RXR &RAR) are exclusively expressed in ALDH+ SCs,and if RA signaling changes during CRC development. We determined whether RAsignaling regulates cancer SC (CSC) proliferation, differentiation, sphere formation,and population size.Results: RXR &RAR were expressed in ALDH+ colonic SCs, but not in MCM2+proliferative cells. Western blotting/immunostaining of CRCs revealed that RAsignaling components become overexpressed in parallel with ALDH overexpression,which coincides with the known overpopulation of ALDH+ SCs that occurs during,and drives, CRC development. Treatment of SCs with all-trans retinoic acid (ATRA)decreased proliferation, sphere formation and ALDH+ SC population size, and induceddifferentiation along the neuroendocrine cell (NEC) lineage.Conclusions: Retinoid signaling, by regulating ALDH+ colonic CSCs, decreases SCproliferation, sphere formation, and population size, and increases SC differentiation toNECs. Dysregulation of RA signaling in colonic SCs likely contributes to overpopulationof ALDH+ SCs and CRC growth.Implications: That retinoid receptors RXR and RAR are selectively expressed inALDH+ SCs indicates RA signaling mainly occurs via ALDH+ SCs, which provides amechanism to selectively target CSCs. © 2018 Impact Journals LLC. All rights reserved
Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging
A size-dependent strain relaxation and its effects on the optical properties of InGaN/GaN multiple quantum wells (QWs) in micro-pillars have been investigated through a combination of high spatial resolution cathodoluminescence (CL) hyperspectral imaging and numerical modeling. The pillars have diameters (d) ranging from 2 to 150 μm and were fabricated from a III-nitride light-emitting diode (LED) structure optimized for yellow-green emission at ∼560 nm. The CL mapping enables us to investigate strain relaxation in these pillars on a sub-micron scale and to confirm for the first time that a narrow (≤2 μm) edge blue-shift occurs even for the large InGaN/GaN pillars (d > 10 μm). The observed maximum blue-shift at the pillar edge exceeds 7 nm with respect to the pillar centre for the pillars with diameters in the 2–16 μm range. For the smallest pillar (d = 2 μm), the total blue-shift at the edge is 17.5 nm including an 8.2 nm “global” blue-shift at the pillar centre in comparison with the unetched wafer. By using a finite element method with a boundary condition taking account of a strained GaN buffer layer which was neglected in previous simulation works, the strain distribution in the QWs of these pillars was simulated as a function of pillar diameter. The blue-shift in the QWs emission wavelength was then calculated from the strain-dependent changes in piezoelectric field, and the consequent modification of transition energy in the QWs. The simulation and experimental results agree well, confirming the necessity for considering the strained buffer layer in the strain simulation. These results provide not only significant insights into the mechanism of strain relaxation in these micro-pillars but also practical guidance for design of micro/nano LEDs
Superconductivity induced by Ni doping in BaFeAs
A series of 122 phase BaFeNiAs ( = 0, 0.055, 0.096, 0.18,
0.23) single crystals were grown by self flux method and a dome-like Ni doping
dependence of superconducting transition temperature is discovered. The
transition temperature reaches a maximum of 20.5 K at = 0.096,
and it drops to below 4 K as 0.23. The negative thermopower in the
normal state indicates that electron-like charge carrier indeed dominates in
this system. This Ni-doped system provides another example of superconductivity
induced by electron doping in the 122 phase.Comment: 7 pages, 5 figures, revised version, added EDX result, accepted for
special issue of NJ
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