5,372 research outputs found
Noncommutative BTZ Black Hole in Polar Coordinates
Based on the equivalence between the three dimensional gravity and the
Chern-Simons theory, we obtain a noncommutative BTZ black hole solution as a
solution of noncommutative Chern-Simons theory using the
Seiberg-Witten map. The Seiberg-Witten map is carried out in a noncommutative
polar coordinates whose commutation relation is equivalent to the usual
canonical commutation relation in the rectangular coordinates up to first order
in the noncommutativity parameter . The solution exhibits a
characteristic of noncommutative polar coordinates in such a way that the
apparent horizon and the Killing horizon coincide only in the non-rotating
limit showing the effect of noncommutativity between the radial and angular
coordinates.Comment: 14 pages, V2: minor changes, v3: reduced for clarification, a
reference adde
Rotating Black Hole Entropy from Two Different Viewpoints
Using the brick-wall method, we study the entropy of Kerr-Newman black hole
from two different viewpoints, a rest observer at infinity and zero angular
momentum observer near horizon. We investigate this with scalar field in the
canonical quantization approach. An observer at infinity can take one of the
two possible frequency ranges; one is with positive frequencies only and the
other is with the whole range including negative frequencies. On the other
hand, a zero angular momentum observer near horizon can take positive
frequencies only. For the observer at infinity the superradiant modes appear in
either choice of the frequency ranges and the two results coincide. For the
zero angular momentum observer superradiant modes do not appear due to absence
of ergoregion. The resulting entropies from the two viewpoints turn out to be
the same.Comment: LaTeX 18 pages, 2 figures, Minor modifications in section 3(ZAMO
New Fe-based superconductors: properties relevant for applications
Less than two years after the discovery of high temperature superconductivity
in oxypnictide LaFeAs(O,F) several families of superconductors based on Fe
layers (1111, 122, 11, 111) are available. They share several characteristics
with cuprate superconductors that compromise easy applications, such as the
layered structure, the small coherence length, and unconventional pairing, On
the other hand the Fe-based superconductors have metallic parent compounds, and
their electronic anisotropy is generally smaller and does not strongly depend
on the level of doping, the supposed order parameter symmetry is s wave, thus
in principle not so detrimental to current transmission across grain
boundaries. From the application point of view, the main efforts are still
devoted to investigate the superconducting properties, to distinguish intrinsic
from extrinsic behaviours and to compare the different families in order to
identify which one is the fittest for the quest for better and more practical
superconductors. The 1111 family shows the highest Tc, huge but also the most
anisotropic upper critical field and in-field, fan-shaped resistive transitions
reminiscent of those of cuprates, while the 122 family is much less anisotropic
with sharper resistive transitions as in low temperature superconductors, but
with about half the Tc of the 1111 compounds. An overview of the main
superconducting properties relevant to applications will be presented. Upper
critical field, electronic anisotropy parameter, intragranular and
intergranular critical current density will be discussed and compared, where
possible, across the Fe-based superconductor families
The selective post-translational processing of transcription factor Nrf1 yields distinct isoforms that dictate its ability to differentially regulate gene expression
Upon translation, the N-terminal homology box 1 (NHB1) signal anchor sequence of Nrf1 integrates it within the endoplasmic reticulum (ER) whilst its transactivation domains [TADs, including acidic domain 1 (AD1), the flanking Asn/Ser/Thr-rich (NST) domain and AD2] are transiently translocated into the ER lumen, whereupon the NST domain is glycosylated to yield an inactive 120-kDa glycoprotein. Subsequently, these TADs are retrotranslocated into extra-luminal subcellular compartments, where Nrf1 is deglycosylated to yield an active 95-kDa isoform. Herein, we report that AD1 and AD2 are required for the stability of the 120-kDa Nrf1 glycoprotein, but not that of the non-glycosylated/de-glycosylated 95-kDa isoform. Degrons within AD1 do not promote proteolytic degradation of the 120-kDa Nrf1 glycoprotein. However, repositioning of AD2-adjoining degrons (i.e. DSGLS-containing SDS1 and PEST2 sequences) into the cyto/nucleoplasm enables selective topovectorial processing of Nrf1 by the proteasome and/or calpains to generate a cleaved active 85-kDa Nrf1 or a dominant-negative 36-kDa Nrf1γ. Production of Nrf1γ is abolished by removal of SDS1 or PEST2 degrons, whereas production of the cleaved 85-kDa Nrf1 is blocked by deletion of the ER luminal-anchoring NHB2 sequence (aa 81–106). Importantly, Nrf1 activity is positively and/or negatively regulated by distinct doses of proteasome and calpain inhibitors
Constituting Citizenship Through the Emotions: Singaporean Transmigrants in London
10.1080/00045600903102857Annals of the Association of American Geographers994788-80
Accreditation Standard Guideline Initiative for Tai Chi and Qigong Instructors and Training Institutions.
Evidence of the health and wellbeing benefits of Tai Chi and Qigong (TQ) have emerged in the past two decades, but TQ is underutilized in modern health care in Western countries due to lack of promotion and the availability of professionally qualified TQ instructors. To date, there are no government regulations for TQ instructors or for training institutions in China and Western countries, even though TQ is considered to be a part of Traditional Chinese medicine that has the potential to manage many chronic diseases. Based on an integrative health care approach, the accreditation standard guideline initiative for TQ instructors and training institutions was developed in collaboration with health professionals, integrative medicine academics, Tai Chi and Qigong master instructors and consumers including public safety officers from several countries, such as Australia, Canada, China, Germany, Italy, Korea, Sweden and USA. In this paper, the rationale for organizing the Medical Tai Chi and Qigong Association (MTQA) is discussed and the accreditation standard guideline for TQ instructors and training institutions developed by the committee members of MTQA is presented. The MTQA acknowledges that the proposed guidelines are broad, so that the diversity of TQ instructors and training institutions can be integrated with recognition that these guidelines can be developed with further refinement. Additionally, these guidelines face challenges in understanding the complexity of TQ associated with different principles, philosophies and schools of thought. Nonetheless, these guidelines represent a necessary first step as primary resource to serve and guide health care professionals and consumers, as well as the TQ community
Satellite Data-Based Phenological Evaluation of the Nationwide Reforestation of South Korea
Through the past 60 years, forests, now of various age classes, have been established in the southern part of the Korean Peninsula through nationwide efforts to reestablish forests since the Korean War (1950-53), during which more than 65% of the nation's forest was destroyed. Careful evaluation of long-term changes in vegetation growth after reforestation is one of the essential steps to ensuring sustainable forest management. This study investigated nationwide variations in vegetation phenology using satellite-based growing season estimates for 1982-2008. The start of the growing season calculated from the normalized difference vegetation index (NDVI) agrees reasonably with the ground-observed first flowering date both temporally (correlation coefficient, r = 0.54) and spatially (r = 0.64) at the 95% confidence level. Over the entire 27-year period, South Korea, on average, experienced a lengthening of the growing season of 4.5 days decade(-1), perhaps due to recent global warming. The lengthening of the growing season is attributed mostly to delays in the end of the growing season. The retrieved nationwide growing season data were used to compare the spatial variations in forest biomass carbon density with the time-averaged growing season length for 61 forests. Relatively higher forest biomass carbon density was observed over the regions having a longer growing season, especially for the regions dominated by young (<30 year) forests. These results imply that a lengthening of the growing season related to the ongoing global warming may have positive impacts on carbon sequestration, an important aspect of large-scale forest management for sustainable development.open2
Genome wide association mapping of grain arsenic, copper, molybdenum and zinc in rice (Oryza sativa L.) grown at four international field sites
Peer reviewedPublisher PD
Extremely strong coupling superconductivity in artificial two-dimensional Kondo lattices
When interacting electrons are confined to low-dimensions, the
electron-electron correlation effect is enhanced dramatically, which often
drives the system into exhibiting behaviors that are otherwise highly
improbable. Superconductivity with the strongest electron correlations is
achieved in heavy-fermion compounds, which contain a dense lattice of localized
magnetic moments interacting with a sea of conduction electrons to form a 3D
Kondo lattice. It had remained an unanswered question whether superconductivity
would persist upon effectively reducing the dimensionality of these materials
from three to two. Here we report on the observation of superconductivity in
such an ultimately strongly-correlated system of heavy electrons confined
within a 2D square-lattice of Ce-atoms (2D Kondo lattice), which was realized
by fabricating epitaxial superlattices built of alternating layers of
heavy-fermion CeCoIn5 and conventional metal YbCoIn5. The field-temperature
phase diagram of the superlattices exhibits highly unusual behaviors, including
a striking enhancement of the upper critical field relative to the transition
temperature. This implies that the force holding together the superconducting
electron-pairs takes on an extremely strong coupled nature as a result of
two-dimensionalization.Comment: A revised version has been accepted for publication in Nature Physic
Cortical Factor Feedback Model for Cellular Locomotion and Cytofission
Eukaryotic cells can move spontaneously without being guided by external
cues. For such spontaneous movements, a variety of different modes have been
observed, including the amoeboid-like locomotion with protrusion of multiple
pseudopods, the keratocyte-like locomotion with a widely spread lamellipodium,
cell division with two daughter cells crawling in opposite directions, and
fragmentations of a cell to multiple pieces. Mutagenesis studies have revealed
that cells exhibit these modes depending on which genes are deficient,
suggesting that seemingly different modes are the manifestation of a common
mechanism to regulate cell motion. In this paper, we propose a hypothesis that
the positive feedback mechanism working through the inhomogeneous distribution
of regulatory proteins underlies this variety of cell locomotion and
cytofission. In this hypothesis, a set of regulatory proteins, which we call
cortical factors, suppress actin polymerization. These suppressing factors are
diluted at the extending front and accumulated at the retracting rear of cell,
which establishes a cellular polarity and enhances the cell motility, leading
to the further accumulation of cortical factors at the rear. Stochastic
simulation of cell movement shows that the positive feedback mechanism of
cortical factors stabilizes or destabilizes modes of movement and determines
the cell migration pattern. The model predicts that the pattern is selected by
changing the rate of formation of the actin-filament network or the threshold
to initiate the network formation
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