4,731 research outputs found
Wavelet domain style transfer for an effective perception-distortion tradeoff in single image super-resolution
In single image super-resolution (SISR), given a low-resolution (LR) image, one wishes to find a high-resolution (HR) version of it which is both accurate and photorealistic. Recently, it has been shown that there exists a fundamental tradeoff between low distortion and high perceptual quality, and the generative adversarial network (GAN) is demonstrated to approach the perception-distortion (PD) bound effectively. In this paper, we propose a novel method based on wavelet domain style transfer (WDST), which achieves a better PD tradeoff than the GAN based methods. Specifically, we propose to use 2D stationary wavelet transform (SWT) to decompose one image into low-frequency and high-frequency sub-bands. For the low-frequency sub-band, we improve its objective quality through an enhancement network. For the high-frequency sub-band, we propose to use WDST to effectively improve its perceptual quality. By feat of the perfect reconstruction property of wavelets, these sub-bands can be re-combined to obtain an image which has simultaneously high objective and perceptual quality. The numerical results on various datasets show that our method achieves the best trade-off between the distortion and perceptual quality among the existing state-of-the-art SISR methods
Generalization Error in Deep Learning
Deep learning models have lately shown great performance in various fields
such as computer vision, speech recognition, speech translation, and natural
language processing. However, alongside their state-of-the-art performance, it
is still generally unclear what is the source of their generalization ability.
Thus, an important question is what makes deep neural networks able to
generalize well from the training set to new data. In this article, we provide
an overview of the existing theory and bounds for the characterization of the
generalization error of deep neural networks, combining both classical and more
recent theoretical and empirical results
Entanglement in coined quantum walks on regular graphs
Published versio
Achieving Stable Nitritation for Mainstream Deammonification by Combining Free Nitrous Acid-Based Sludge Treatment and Oxygen Limitation.
Stable nitritation is a critical bottleneck for achieving autotrophic nitrogen removal using the energy-saving mainstream deammonification process. Herein we report a new strategy to wash out both the Nitrospira sp. and Nitrobacter sp. from the treatment of domestic-strength wastewater. The strategy combines sludge treatment using free nitrous acid (FNA) with dissolved oxygen (DO) control in the nitritation reactor. Initially, the nitrifying reactor achieved full conversion of NH4(+) to NO3(-). Then, nitrite accumulation at ~60% was achieved in the reactor when 1/4 of the sludge was treated daily with FNA at 1.82 mg N/L in a side-stream unit for 24 h. Fluorescence in-situ hybridization (FISH) revealed FNA treatment substantially reduced the abundance of nitrite oxidizing bacteria (NOB) (from 23.0 ± 4.3 to 5.3 ± 1.9%), especially that of Nitrospira sp. (from 15.7 ± 3.9 to 0.4 ± 0.1%). Nitrite accumulation increased to ~80% when the DO concentration in the mainstream reactor was reduced from 2.5-3.0 to 0.3-0.8 mg/L. FISH revealed the DO limitation further reduced the abundance of NOB (to 2.1 ± 1.0%), especially that of Nitrobacter sp. (from 4.9 ± 1.2 to 1.8 ± 0.8%). The strategy developed removes a major barrier for deammonification in low-strength domestic wastewater
Evidence for Superfluidity of Ultracold Fermions in an Optical Lattice
The study of superfluid fermion pairs in a periodic potential has important
ramifications for understanding superconductivity in crystalline materials.
Using cold atomic gases, various condensed matter models can be studied in a
highly controllable environment. Weakly repulsive fermions in an optical
lattice could undergo d-wave pairing at low temperatures, a possible mechanism
for high temperature superconductivity in the cuprates. The lattice potential
could also strongly increase the critical temperature for s-wave superfluidity.
Recent experimental advances in the bulk include the observation of fermion
pair condensates and high-temperature superfluidity. Experiments with fermions
and bosonic bound pairs in optical lattices have been reported, but have not
yet addressed superfluid behavior. Here we show that when a condensate of
fermionic atom pairs was released from an optical lattice, distinct
interference peaks appear, implying long range order, a property of a
superfluid. Conceptually, this implies that strong s-wave pairing and
superfluidity have now been established in a lattice potential, where the
transport of atoms occurs by quantum mechanical tunneling and not by simple
propagation. These observations were made for unitarity limited interactions on
both sides of a Feshbach resonance. For larger lattice depths, the coherence
was lost in a reversible manner, possibly due to a superfluid to insulator
transition. Such strongly interacting fermions in an optical lattice can be
used to study a new class of Hamiltonians with interband and atom-molecule
couplings.Comment: accepted for publication in Natur
Reversals in nature and the nature of reversals
The asymmetric shape of reversals of the Earth's magnetic field indicates a
possible connection with relaxation oscillations as they were early discussed
by van der Pol. A simple mean-field dynamo model with a spherically symmetric
coefficient is analysed with view on this similarity, and a comparison
of the time series and the phase space trajectories with those of paleomagnetic
measurements is carried out. For highly supercritical dynamos a very good
agreement with the data is achieved. Deviations of numerical reversal sequences
from Poisson statistics are analysed and compared with paleomagnetic data. The
role of the inner core is discussed in a spectral theoretical context and
arguments and numerical evidence is compiled that the growth of the inner core
might be important for the long term changes of the reversal rate and the
occurrence of superchrons.Comment: 24 pages, 12 figure
Dual-gated bilayer graphene hot electron bolometer
Detection of infrared light is central to diverse applications in security,
medicine, astronomy, materials science, and biology. Often different materials
and detection mechanisms are employed to optimize performance in different
spectral ranges. Graphene is a unique material with strong, nearly
frequency-independent light-matter interaction from far infrared to
ultraviolet, with potential for broadband photonics applications. Moreover,
graphene's small electron-phonon coupling suggests that hot-electron effects
may be exploited at relatively high temperatures for fast and highly sensitive
detectors in which light energy heats only the small-specific-heat electronic
system. Here we demonstrate such a hot-electron bolometer using bilayer
graphene that is dual-gated to create a tunable bandgap and
electron-temperature-dependent conductivity. The measured large electron-phonon
heat resistance is in good agreement with theoretical estimates in magnitude
and temperature dependence, and enables our graphene bolometer operating at a
temperature of 5 K to have a low noise equivalent power (33 fW/Hz1/2). We
employ a pump-probe technique to directly measure the intrinsic speed of our
device, >1 GHz at 10 K.Comment: 5 figure
Optical detection of single non-absorbing molecules using the surface plasmon of a gold nanorod
Current optical detection schemes for single molecules require light
absorption, either to produce fluorescence or direct absorption signals. This
severely limits the range of molecules that can be detected, because most
molecules are purely refractive. Metal nanoparticles or dielectric resonators
detect non-absorbing molecules by a resonance shift in response to a local
perturbation of the refractive index, but neither has reached single-protein
sensitivity. The most sensitive plasmon sensors to date detect single molecules
only when the plasmon shift is amplified by a highly polarizable label or by a
localized precipitation reaction on the particle's surface. Without
amplification, the sensitivity only allows for the statistical detection of
single molecules. Here we demonstrate plasmonic detection of single molecules
in realtime, without the need for labeling or amplification. We monitor the
plasmon resonance of a single gold nanorod with a sensitive photothermal assay
and achieve a ~ 700-fold increase in sensitivity compared to state-of-the-art
plasmon sensors. We find that the sensitivity of the sensor is intrinsically
limited due to spectral diffusion of the SPR. We believe this is the first
optical technique that detects single molecules purely by their refractive
index, without any need for photon absorption by the molecule. The small size,
bio-compatibility and straightforward surface chemistry of gold nanorods may
open the way to the selective and local detection of purely refractive proteins
in live cells
PTEN transcript variants caused by illegitimate splicing in “aged” blood samples and EBV-transformed cell lines
PTEN is one of the most frequently mutated tumor suppressor genes in human cancers. Mutations occur in either heritable or sporadic fashion. Sequencing of cDNA from patients and normal individuals often reveals splicing variants (SVs) of PTEN, some of which are non-mutation related. To investigate whether these SVs were the result of illegitimate splicing (a general decrease of fidelity in splicing site selection in “aged” samples), we tested “aged” blood from individuals who had normal PTEN transcripts in their “fresh” mononuclear cells. Blood from 20 normal individuals was collected and split into two aliquots. Total RNA and DNA were extracted immediately (“fresh”) and 48 h later (“aged”), respectively. Using RT-PCR, subcloning and sequencing, we found seven types of SVs. No mutation was detected in the related intron–exon flanking region in genomic DNA in either “fresh” or “aged” samples. Some of the SVs were also consistently present in both the “fresh” and “aged” EBV-transformed lymphoblastoid cells from six normal individuals. Western blot data indicated that the PTEN protein level (in full length) was not altered in the “fresh” EBV-transformed lymphoblastoid cells with SVs. In conclusion, our data demonstrate that PTEN illegitimate splicing often occurs in “aged” blood and EBV-transformed lymphoblastoid cells. Therefore, it is critical to note the time point of RNA extraction when investigating for PTEN aberrant transcripts. We hope that our data will increase awareness about the sample status, because gene expression data may be potentially flawed from “aged” samples, particularly when dealing with clinical samples
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