146 research outputs found
Few-shot Learning with Multi-scale Self-supervision
Learning concepts from the limited number of datapoints is a challenging task
usually addressed by the so-called one- or few-shot learning. Recently, an
application of second-order pooling in few-shot learning demonstrated its
superior performance due to the aggregation step handling varying image
resolutions without the need of modifying CNNs to fit to specific image sizes,
yet capturing highly descriptive co-occurrences. However, using a single
resolution per image (even if the resolution varies across a dataset) is
suboptimal as the importance of image contents varies across the coarse-to-fine
levels depending on the object and its class label e. g., generic objects and
scenes rely on their global appearance while fine-grained objects rely more on
their localized texture patterns. Multi-scale representations are popular in
image deblurring, super-resolution and image recognition but they have not been
investigated in few-shot learning due to its relational nature complicating the
use of standard techniques. In this paper, we propose a novel multi-scale
relation network based on the properties of second-order pooling to estimate
image relations in few-shot setting. To optimize the model, we leverage a scale
selector to re-weight scale-wise representations based on their second-order
features. Furthermore, we propose to a apply self-supervised scale prediction.
Specifically, we leverage an extra discriminator to predict the scale labels
and the scale discrepancy between pairs of images. Our model achieves
state-of-the-art results on standard few-shot learning datasets
Rethinking Class Relations: Absolute-relative Supervised and Unsupervised Few-shot Learning
The majority of existing few-shot learning methods describe image relations
with binary labels. However, such binary relations are insufficient to teach
the network complicated real-world relations, due to the lack of decision
smoothness. Furthermore, current few-shot learning models capture only the
similarity via relation labels, but they are not exposed to class concepts
associated with objects, which is likely detrimental to the classification
performance due to underutilization of the available class labels. To
paraphrase, children learn the concept of tiger from a few of actual examples
as well as from comparisons of tiger to other animals. Thus, we hypothesize
that in fact both similarity and class concept learning must be occurring
simultaneously. With these observations at hand, we study the fundamental
problem of simplistic class modeling in current few-shot learning methods. We
rethink the relations between class concepts, and propose a novel
Absolute-relative Learning paradigm to fully take advantage of label
information to refine the image representations and correct the relation
understanding in both supervised and unsupervised scenarios. Our proposed
paradigm improves the performance of several the state-of-the-art models on
publicly available datasets.Comment: IEEE/CVF Conference on Computer Vision and Pattern Recognition 202
Hydrogen Clouds before Reionization: a Lognormal Model Approach
We study the baryonic gas clouds (the IGM) in the universe before the
reionization with the lognormal model which is shown to be dynamcially
legitimate in describing the fluctuation evolution in quasilinear as well as
nonlinear regimes in recent years. The probability distribution function of the
mass field in the LN model is long tailed and so plays an important role in
rare events, such as the formation of the first generation of baryonic objects.
We calculate density and velocity distributions of the IGM at very high spatial
resolutions, and simulate the distributions at resolution of 0.15 kpc from z=7
to 15 in the LCDM cosmological model. We performed a statistics of the hydrogen
clouds including column densities, clumping factors, sizes, masses, and spatial
number density etc. One of our goals is to identify which hydrogen clouds are
going to collapse. By inspecting the mass density profile and the velocity
profile of clouds, we found that the velocity outflow significantly postpones
the collapsing process in less massive clouds, in spite of their masses are
larger than the Jeans mass. Consequently, only massive (> 10^5 M_sun) clouds
can form objects at higher redshift, and less massive (10^4-10^5) collapsed
objects are formed later. For example, although the mass fraction in clouds
with sizes larger than the Jeans length is already larger than 1 at z=15, there
is only a tiny fraction of mass (10^{-8}) in the clouds which are collapsed at
that time. If all the ionizing photons, and the 10^{-2} metallicity observed at
low redshift are produced by the first 1% mass of collapsed baryonic clouds,
the majority of those first generation objects would not happen until z=10.Comment: Paper in AAStex, 12 figure
111In-Labeled Cystine-Knot Peptides Based on the Agouti-Related Protein for Targeting Tumor Angiogenesis
Agouti-related protein (AgRP) is a 4-kDa cystine-knot peptide of human origin with four disulfide bonds and four solvent-exposed loops. The cell adhesion receptor integrin Ī±vĪ²3 is an important tumor angiogenesis factor that determines the invasiveness and metastatic ability of many malignant tumors. AgRP mutants have been engineered to bind to integrin Ī±vĪ²3 with high affinity and specificity using directed evolution. Here, AgRP mutants 7C and 6E were radiolabeled with 111In and evaluated for in vivo targeting of tumor integrin Ī±vĪ²3 receptors. AgRP peptides were conjugated to the metal chelator 1, 4, 7, 10-tetra-azacyclododecane- N, Nā², Nā³, Nā“-tetraacetic acid (DOTA) and radiolabeled with 111In. The stability of the radiopeptides 111In-DOTA-AgRP-7C and 111In-DOTA-AgRP-6E was tested in phosphate-buffered saline (PBS) and mouse serum, respectively. Cell uptake assays of the radiolabeled peptides were performed in U87MG cell lines. Biodistribution studies were performed to evaluate the in vivo performance of the two resulting probes using mice bearing integrin-expressing U87MG xenograft tumors. Both AgRP peptides were easily labeled with 111In in high yield and radiochemical purity (>99%). The two probes exhibited high stability in phosphate-buffered saline and mouse serum. Compared with 111In-DOTA-AgRP-6E, 111In-DOTA-AgRP-7C showed increased U87MG tumor uptake and longer tumor retention (5.74 Ā± 1.60 and 1.29 Ā± 0.02%ID/g at 0.5 and 24āh, resp.), which was consistent with measurements of cell uptake. Moreover, the tumor uptake of 111In-DOTA-AgRP-7C was specifically inhibited by coinjection with an excess of the integrin-binding peptidomimetic c(RGDyK). Thus, 111In-DOTA-AgRP-7C is a promising probe for targeting integrin Ī±vĪ²3 positive tumors in living subjects
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Epigenetic memory in induced pluripotent stem cells.
Somatic cell nuclear transfer and transcription-factor-based reprogramming revert adult cells to an embryonic state, and yield pluripotent stem cells that can generate all tissues. Through different mechanisms and kinetics, these two reprogramming methods reset genomic methylation, an epigenetic modification of DNA that influences gene expression, leading us to hypothesize that the resulting pluripotent stem cells might have different properties. Here we observe that low-passage induced pluripotent stem cells (iPSCs) derived by factor-based reprogramming of adult murine tissues harbour residual DNA methylation signatures characteristic of their somatic tissue of origin, which favours their differentiation along lineages related to the donor cell, while restricting alternative cell fates. Such an 'epigenetic memory' of the donor tissue could be reset by differentiation and serial reprogramming, or by treatment of iPSCs with chromatin-modifying drugs. In contrast, the differentiation and methylation of nuclear-transfer-derived pluripotent stem cells were more similar to classical embryonic stem cells than were iPSCs. Our data indicate that nuclear transfer is more effective at establishing the ground state of pluripotency than factor-based reprogramming, which can leave an epigenetic memory of the tissue of origin that may influence efforts at directed differentiation for applications in disease modelling or treatment
A narrow line Seyfert 1--blazar composite nucleus in 2MASX J0324+3410
We report the identification of 2MASX J032441.19+341045.9 (hereafter 2MASX
J0324+3410) with an appealing object which shows the dual properties of both a
narrow line Seyfert 1 galaxy (NLS1) and a blazar. Its optical spectrum, which
has a H\beta line width about 1600 km s^-1 (FWHM), an [OIII] to H\beta line
ratio ~0.12, and strong FeII emission, clearly fulfills the conventional
definition of NLS1s. On the other hand, 2MASX J0324+3410 also exhibits some
behavior which is characteristic of blazars, including a flat radio spectrum
above 1 GHz, a compact core plus a one-sided jet structure on mas-scale at 8.4
GHz, highly variable fluxes in the radio, optical, and X-ray bands, and a
possible detection of TeV gamma-ray emission. On its optical image, obtained
with the HST WFPC2, the active nucleus is displaced from the center of the host
galaxy, which exhibits an apparent one-armed spiral structure extended to 16
kpc. The remarkable hybrid behavior of this object presents a challenge to
current models of NLS1 galaxies and -ray blazars.Comment: 12 pages, 2 figures. Accepted to ApJ
Treatment outcomes of fixed-dose combination versus separate tablet regimens in pulmonary tuberculosis patients with or without diabetes in Qatar
Background: Tuberculosis is considered the second most common cause of death due to infectious agent. The
currently preferred regimen for treatment of pulmonary tuberculosis (PTB) is isoniazid, rifampin, pyrazinamide, and
ethambutol, which has been used either as separate tablets (ST) or as fixed-dose combination (FDC). To date, no
studies have compared both regimens in Qatar. We aim to evaluate the safety and effectiveness of FDC and ST
regimen for treating PTB, in addition to comparing safety and efficacy of FDC and ST regimens in patients with
diabetes treated for TB.
Methods: A retrospective observational study was conducted in two general hospitals in Qatar. Patients diagnosed
with PTB received anti-tuberculosis medications (either as FDC or ST) administered by the nurse. Sputum smears
were tested weekly. We assessed the time to negative sputum smear and incidence of adverse events among FDC
and ST groups.
Results: The study included 148 patients. FDC was used in 90 patients (61%). Effectiveness was not different
between FDC and ST regimens as shown by mean time to sputum conversion (29.9 Ā± 18.3 vs. 35.6 Ā± 23 days, p = 0.12).
Similarly, there was no difference in the incidence of adverse events, except for visual one that was higher in ST group.
Among the 33 diabetic patients, 19 received the FDC and had faster sputum conversion compared to those who
received ST (31 Ā± 12 vs. 49.4 Ā± 30.9 days, p = 0.05). Overall, diabetic patients needed longer time for sputum conversion
and had more hepatotoxic and gastric adverse events compared to non-diabetics.
Conclusion: ST group had higher visual side effects compared to FDC. FDC may be more effective in diabetic patients;
however, further studies are required to confirm such finding.PublishedN/
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