20,799 research outputs found
Suppressed star formation in circumnuclear regions in Seyfert galaxies
Feedback from black hole activity is widely believed to play a key role in
regulating star formation and black hole growth. A long-standing issue is the
relation between the star formation and fueling the supermassive black holes in
active galactic nuclei (AGNs). We compile a sample of 57 Seyfert galaxies to
tackle this issue. We estimate the surface densities of gas and star formation
rates in circumnuclear regions (CNRs). Comparing with the well-known
Kennicutt-Schmidt (K-S) law, we find that the star formation rates in CNRs of
most Seyfert galaxies are suppressed in this sample. Feedback is suggested to
explain the suppressed star formation rates.Comment: 1 color figure and 1 table. ApJ Letters in pres
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Sensitization of Human Pancreatic Cancer Cells Harboring Mutated K-ras to Apoptosis
Pancreatic cancer is a devastating human malignancy and gain of functional mutations in K-ras oncogene is observed in 75%–90% of the patients. Studies have shown that oncogenic ras is not only able to promote cell growth or survival, but also apoptosis, depending upon circumstances. Using pancreatic cancer cell lines with or without expressing mutated K-ras, we demonstrated that the inhibition of endogenous PKC activity sensitized human pancreatic cancer cells (MIA and PANC-1) expressing mutated K-ras to apoptosis, which had no apoptotic effect on BxPC-3 pancreatic cancer cells that contain a normal Ras as well as human lung epithelial BAES-2B cells. In this apoptotic process, the level of ROS was increased and PUMA was upregulated in a p73-dependent fashion in MIA and PANC-1 cells. Subsequently, caspase-3 was cleaved. A full induction of apoptosis required the activation of both ROS- and p73-mediated pathways. The data suggest that PKC is a crucial factor that copes with aberrant K-ras to maintain the homeostasis of the pancreatic cancer cells harboring mutated K-ras. However, the suppression or loss of PKC disrupts the balance and initiates an apoptotic crisis, in which ROS and p73 appear the potential, key targets
Unsupervised Hierarchical Domain Adaptation for Adverse Weather Optical Flow
Optical flow estimation has made great progress, but usually suffers from
degradation under adverse weather. Although semi/full-supervised methods have
made good attempts, the domain shift between the synthetic and real adverse
weather images would deteriorate their performance. To alleviate this issue,
our start point is to unsupervisedly transfer the knowledge from source clean
domain to target degraded domain. Our key insight is that adverse weather does
not change the intrinsic optical flow of the scene, but causes a significant
difference for the warp error between clean and degraded images. In this work,
we propose the first unsupervised framework for adverse weather optical flow
via hierarchical motion-boundary adaptation. Specifically, we first employ
image translation to construct the transformation relationship between clean
and degraded domains. In motion adaptation, we utilize the flow consistency
knowledge to align the cross-domain optical flows into a motion-invariance
common space, where the optical flow from clean weather is used as the
guidance-knowledge to obtain a preliminary optical flow for adverse weather.
Furthermore, we leverage the warp error inconsistency which measures the motion
misalignment of the boundary between the clean and degraded domains, and
propose a joint intra- and inter-scene boundary contrastive adaptation to
refine the motion boundary. The hierarchical motion and boundary adaptation
jointly promotes optical flow in a unified framework. Extensive quantitative
and qualitative experiments have been performed to verify the superiority of
the proposed method
Byod Approach To Blended Learning In Developing Nations
Businesses are adopting Bring Your Own Device (BYOD) policies in their organisations to allow employees to bring personal mobile devices to work. This approach can be adopted in education to address the educational divide between developing and developed nations. A BYOD approach to education could entail the use of cheap tablets to deliver educational content but would require an appropriate blended learning approach for learning to be effective. Consequently, the objective of this paper is to investigate the effectiveness of different blended learning approaches with tablets as an instructional medium. A conceptual model for blended learning was constructed from learning theories in the literature. Subsequently, experiments were conducted to investigate the impact of media richness, collaborative work and performance feedback on learner performance, engagement and satisfaction. The results have implications on educators who plan to design tablet-based blended learning arrangements
Quantum dynamics of topological strings in a frustrated Ising antiferromagnet
We investigate the quantum dynamics of the transverse field Ising model on
the triangular lattice through large-scale quantum Monte Carlo simulations and
stochastic analytic continuation. At weak transverse field, we capture for the
first time the excitations related to topological quantum strings, which
exhibits continuum features described by XY chain along the strings and those
in accord with "Luttinger string liquid" in the perpendicular direction. The
continuum features can be well understood from the perspective of topological
strings. Furthermore, we identify the contribution of strings from the
excitation spectrum. Our study provides characteristic features for the
experimental search for string-related excitations and proposes a new
theoretical method to pinpoint topological excitations in the experimental
spectra.Comment: 10 pages, 9 figures, comments are welcome and more information at
http://cqutp.org/users/xfzhang
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