490 research outputs found
Surface State Magnetization and Chiral Edge States on Topological Insulators
We study the interaction between a ferromagnetically ordered medium and the surface states of a topological insulator with a general surface termination that were identified recently [F. Zhang et al.Phys. Rev. B 86 081303(R) (2012)]. This interaction is strongly crystal face dependent and can generate chiral states along edges between crystal facets even for a uniform magnetization. While magnetization parallel to quintuple layers shifts the momentum of the Dirac point, perpendicular magnetization lifts the Kramers degeneracy at any Dirac points except on the side face, where the spectrum remains gapless and the Hall conductivity switches sign. Chiral states can be found at any edge that reverses the projection of the surface normal to the stacking direction of quintuple layers. Magnetization also weakly hybridizes noncleavage surfaces
INTEGRATED ECOLOGICAL PLANNING IN SINGAPORE: NEOTIEWPIA ECO-VILLAGE IN BUSTLING METROPOLITAN
ABSTRACT :The Neotiewpia Eco-Village is located within the Lim Chu Kang district at the north of Singapore. The Eco-Village only comprised of 3.5 sq km. Meanwhile the area was
dominated by farms, chalets and Sungei Buloh Wetland Reserve. In 2006, National University of Singapore, School of Design and Environment (SDE), MSc. Environmental Management and Nature Society of Singapore initiated an ecological planning exercise within the Neotiewpia site
to reduce the environmental impact from the development while providing Eco-friendly Tourism and R&D activities that feasible in the site. We did participate in the exercise and we tried explaining the ecological process, the limitation and potential development for integrated
ecological planning framework in Developing Countries like Indonesia, Brazil, etc with high ecological-values ecosystems. The Vision of Neotiewpia was āA Model Eco-Village that Respects its Natural Heritage, Builds Strong Community Links and Promotes Economic Development on Natureās Premises." And Neotiewpia was successfully planned and designed with integrated ecological planning approach. It embraced the land evaluation and impact assessment. Further the plan was found feasible by the Singapore Government by earmarking the Lim Chu Kang and Kranji for Agri-tainment development in 2008 (although partially
implemented). The Neotiewpia or Lim Chu Kang area was found thriving with Green-Economy and Agro-Tourism. This integrated ecological planning could be translated to other areas in Developing Countries with agriculture potential and facing development pressures such as Neotiewpia. This concept would give alternate Green-Solution to the current economic crisis
Bacterial growth, detachment and cell size control on polyethylene terephthalate surfaces.
In medicine and food industry, bacterial colonisation on surfaces is a common cause of infections and severe illnesses. However, the detailed quantitative information about the dynamics and the mechanisms involved in bacterial proliferation on solid substrates is still lacking. In this study we investigated the adhesion and detachment, the individual growth and colonisation, and the cell size control of Escherichia coli (E. coli) MG1655 on polyethylene terephthalate (PET) surfaces. The results show that the bacterial growth curve on PET exhibits the distinct lag and log phases, but the generation time is more than twice longer than in bulk medium. Single cells in the lag phase are more likely to detach than clustered ones in the log phase; clustered bacteria in micro-colonies have stronger adhesive bonds with surfaces and their neighbours with the progressing colonisation. We show that the cell size is under the density-dependent pathway control: when the adherent cells are at low density, the culture medium is responsible for coordinating cell division and cell size; when the clustered cells are at high population density, we demonstrate that the effect of quorum sensing causes the cell size decrease as the cell density on surfaces increases.This is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/srep1515
Efficient variational approach to the Fermi polaron problem in two dimensions, both in and out of equilibrium
We develop a non-Gaussian variational approach that enables us to study both
equilibrium and far-from-equilibrium physics of the two-dimensional Fermi
polaron. This method provides an unbiased analysis of the polaron-to-molecule
phase transition without relying on truncations in the total number of
particle-hole excitations. Our results -- which include the ground state energy
and quasiparticle residue -- are in qualitative agreement with the known Monte
Carlo calculations. The main advantage of the non-Gaussian states compared to
conventional numerical methods is that they enable us to explore long-time
polaron evolution and, in particular, study various spectral properties
accessible to both solid-state and ultracold atom experiments. We design two
types of radiofrequency spectroscopies to measure polaronic and molecular
spectral functions. Depending on the parameter regime, we find that these
spectral functions and fermionic density profiles near the impurity display
either long-lived oscillations between the repulsive and attractive polaron
branches or exhibit fast relaxational dynamics to the molecular state.Comment: 12 pages, 7 figure
The First High Redshift Quasar from Pan-STARRS
We present the discovery of the first high redshift (z > 5.7) quasar from the
Panoramic Survey Telescope and Rapid Response System 1 (Pan-STARRS1 or PS1).
This quasar was initially detected as an i dropoutout in PS1, confirmed
photometrically with the SAO Widefield InfraRed Camera (SWIRC) at Arizona's
Multiple Mirror Telescope (MMT) and the Gamma-Ray Burst Optical/Near-Infrared
Detector (GROND) at the MPG 2.2 m telescope in La Silla. The quasar was
verified spectroscopically with the the MMT Spectrograph, Red Channel and the
Cassegrain Twin Spectrograph (TWIN) at the Calar Alto 3.5 m telescope. It has a
redshift of 5.73, an AB z magnitude of 19.4, a luminosity of 3.8 x 10^47 erg/s
and a black hole mass of 6.9 x 10^9 solar masses. It is a Broad Absorption Line
quasar with a prominent Ly-beta peak and a very blue continuum spectrum. This
quasar is the first result from the PS1 high redshift quasar search that is
projected to discover more than a hundred i dropout quasars, and could
potentially find more than 10 z dropout (z > 6.8) quasars.Comment: 8 pages, 7 figure
PPARs and the Cardiovascular System
Abstract Peroxisome proliferator-activated receptors (PPARs) belong to the nuclear hormone-receptor superfamily. Originally cloned in 1990, PPARs were found to be mediators of pharmacologic agents that induce hepatocyte peroxisome proliferation. PPARs also are expressed in cells of the cardiovascular system. PPARĪ³ appears to be highly expressed during atherosclerotic lesion formation, suggesting that increased PPARĪ³ expression may be a vascular compensatory response. Also, ligand-activated PPARĪ³ decreases the inflammatory response in cardiovascular cells, particularly in endothelial cells. PPARĪ±, similar to PPARĪ³, also has pleiotropic effects in the cardiovascular system, including antiinflammatory and antiatherosclerotic properties. PPARĪ± activation inhibits vascular smooth muscle proinflammatory responses, attenuating the development of atherosclerosis. However, PPARĪ“ overexpression may lead to elevated macrophage inflammation and atherosclerosis. Conversely, PPARĪ“ ligands are shown to attenuate the pathogenesis of atherosclerosis by improving endothelial cell proliferation and survival while decreasing endothelial cell inflammation and vascular smooth muscle cell proliferation. Furthermore, the administration of PPAR ligands in the form of TZDs and fibrates has been disappointing in terms of markedly reducing cardiovascular events in the clinical setting. Therefore, a better understanding of PPAR-dependent and -independent signaling will provide the foundation for future research on the role of PPARs in human cardiovascular biology. Antioxid. Redox Signal. 11, 1415-1452.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78115/1/ars.2008.2280.pd
Physically Explainable Deep Learning for Convective Initiation Nowcasting Using GOES-16 Satellite Observations
Convection initiation (CI) nowcasting remains a challenging problem for both
numerical weather prediction models and existing nowcasting algorithms. In this
study, object-based probabilistic deep learning models are developed to predict
CI based on multichannel infrared GOES-R satellite observations. The data come
from patches surrounding potential CI events identified in Multi-Radar
Multi-Sensor Doppler weather radar products over the Great Plains region from
June and July 2020 and June 2021. An objective radar-based approach is used to
identify these events. The deep learning models significantly outperform the
classical logistic model at lead times up to 1 hour, especially on the false
alarm ratio. Through case studies, the deep learning model exhibits the
dependence on the characteristics of clouds and moisture at multiple levels.
Model explanation further reveals the model's decision-making process with
different baselines. The explanation results highlight the importance of
moisture and cloud features at different levels depending on the choice of
baseline. Our study demonstrates the advantage of using different baselines in
further understanding model behavior and gaining scientific insights
Polymorphisms of the BCL2 gene associated with susceptibility to tuberculosis
Although tuberculosis (TB) is a serious public health concern, we still donāt understand why only 10% of people infected will develop the disease. Apoptosis plays a role in the interaction of Mycobacterium tuberculosis (Mtb) with the human host and it may be modified by subtle alterations in the B-cell lymphoma 2 (BCL2) gene, an anti-apoptotic regulatory element. Therefore, we investigated whether there is an association between BCL2 polymorphisms and susceptibility to TB by analyzing 130 TB cases, 108 subjects with latent TB infection (LTBI), and 163 healthy controls (HC). Logistic regression was used to calculate odds ratios (ORs) and 95% confidential intervals (95% CIs) for possible associations between single nucleotide polymorphisms (SNPs) in BCL2 and the risk of tuberculosis. We found that the G allele of rs80030866 (OR=0.62, 95%CI:0.42-0.91, P=0.015), and also the G allele of rs9955190 (OR=0.58, 95%CI:0.38-0.88, P=0.011) were less frequent in the TB group compared with the LTBI group. In addition, individuals with rs2551402 CC genotype were more likely to have LTBI than those with AA genotype (OR=2.166, 95%CI:1.046-4.484, P=0.037). Our study suggests that BCL2 gene polymorphisms may be correlated with susceptibility to both TB and LTBI
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