3,240 research outputs found
Entanglement and quantum phase transition in the one-dimensional anisotropic XY model
In this paper the entanglement and quantum phase transition of the
anisotropic s=1/2 XY model are studied by using the quantum renormalization
group method. By solving the renormalization equations, we get the trivial
fixed point and the untrivial fixed point which correspond to the phase of the
system and the critical point, respectively. Then the concurrence between two
blocks are calculated and it is found that when the number of the iterations of
the renormalziation trends infinity, the concurrence develops two staturated
values which are associated with two different phases, i.e., Ising-like and
spin-fluid phases. We also investigate the first derivative of the concurrence,
and find that there exists non-analytic behaviors at the quantum critical
point, which directly associate with the divergence of the correlation length.
Further insight, the scaling behaviors of the system are analyzed, it is shown
that how the maximum value of the first derivative of the concurrence reaches
the infinity and how the critical point is touched as the size of the system
becomes large.Comment: 10 pages, 5 figure
Cultural-based visual expression: Emotional analysis of human face via Peking Opera Painted Faces (POPF)
© 2015 The Author(s) Peking Opera as a branch of Chinese traditional cultures and arts has a very distinct colourful facial make-up for all actors in the stage performance. Such make-up is stylised in nonverbal symbolic semantics which all combined together to form the painted faces to describe and symbolise the background, the characteristic and the emotional status of specific roles. A study of Peking Opera Painted Faces (POPF) was taken as an example to see how information and meanings can be effectively expressed through the change of facial expressions based on the facial motion within natural and emotional aspects. The study found that POPF provides exaggerated features of facial motion through images, and the symbolic semantics of POPF provides a high-level expression of human facial information. The study has presented and proved a creative structure of information analysis and expression based on POPF to improve the understanding of human facial motion and emotion
Relation between flux formation and pairing in doped antiferromagnets
We demonstrate that patterns formed by the current-current correlation
function are landmarks which indicate that spin bipolarons form in doped
antiferromagnets. Holes which constitute a spin bipolaron reside at opposite
ends of a line (string) formed by the defects in the antiferromagnetic spin
background. The string is relatively highly mobile, because the motion of a
hole at its end does not raise extensively the number of defects, provided that
the hole at the other end of the line follows along the same track. Appropriate
coherent combinations of string states realize some irreducible representations
of the point group C_4v. Creep of strings favors d- and p-wave states. Some
more subtle processes decide the symmetry of pairing. The pattern of the
current correlation function, that defines the structure of flux, emerges from
motion of holes at string ends and coherence factors with which string states
appear in the wave function of the bound state. Condensation of bipolarons and
phase coherence between them puts to infinity the correlation length of the
current correlation function and establishes the flux in the system.Comment: 5 pages, 6 figure
A topological Dirac insulator in a quantum spin Hall phase : Experimental observation of first strong topological insulator
When electrons are subject to a large external magnetic field, the
conventional charge quantum Hall effect \cite{Klitzing,Tsui} dictates that an
electronic excitation gap is generated in the sample bulk, but metallic
conduction is permitted at the boundary. Recent theoretical models suggest that
certain bulk insulators with large spin-orbit interactions may also naturally
support conducting topological boundary states in the extreme quantum limit,
which opens up the possibility for studying unusual quantum Hall-like phenomena
in zero external magnetic field. Bulk BiSb single crystals are
expected to be prime candidates for one such unusual Hall phase of matter known
as the topological insulator. The hallmark of a topological insulator is the
existence of metallic surface states that are higher dimensional analogues of
the edge states that characterize a spin Hall insulator. In addition to its
interesting boundary states, the bulk of BiSb is predicted to
exhibit three-dimensional Dirac particles, another topic of heightened current
interest. Here, using incident-photon-energy-modulated (IPEM-ARPES), we report
the first direct observation of massive Dirac particles in the bulk of
BiSb, locate the Kramers' points at the sample's boundary and
provide a comprehensive mapping of the topological Dirac insulator's gapless
surface modes. These findings taken together suggest that the observed surface
state on the boundary of the bulk insulator is a realization of the much sought
exotic "topological metal". They also suggest that this material has potential
application in developing next-generation quantum computing devices.Comment: 16 pages, 3 Figures. Submitted to NATURE on 25th November(2007
Isomeric Effects of Solution Processed Ladderâ Type Nonâ Fullerene Electron Acceptors
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138922/1/solr201700107_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138922/2/solr201700107-sup-0001-SuppData-S1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138922/3/solr201700107.pd
The A-rich RNA sequences of HIV-1 pol are important for the synthesis of viral cDNA
The bias of A-rich codons in HIV-1 pol is thought to be a record of hypermutations in viral genomes that lack biological functions. Bioinformatic analysis predicted that A-rich sequences are generally associated with minimal local RNA structures. Using codon modifications to reduce the amount of A-rich sequences within HIV-1 genomes, we have reduced the flexibility of RNA sequences in pol to analyze the functional significance of these A-rich ‘structurally poor’ RNA elements in HIV-1 pol. Our data showed that codon modification of HIV-1 sequences led to a suppression of virus infectivity by 5–100-fold, and this defect does not correlate with, viral entry, viral protein expression levels, viral protein profiles or virion packaging of genomic RNA. Codon modification of HIV-1 pol correlated with an enhanced dimer stability of the viral RNA genome, which was associated with a reduction of viral cDNA synthesis both during HIV-1 infection and in a cell free reverse transcription assay. Our data provided direct evidence that the HIV-1 A-rich pol sequence is not merely an evolutionary artifact of enzyme-induced hypermutations, and that HIV-1 has adapted to rely on A-rich RNA sequences to support the synthesis of viral cDNA during reverse transcription, highlighting the utility of using ‘structurally poor’ RNA domains in regulating biological process
Extension of ELM suppression window using n=4 RMPs in EAST
The q95 window for Type-I Edge Localized Modes (ELMs) suppression using n=4
even parity Resonant Magnetic Perturbations (RMPs) has been significantly
expanded to a range from 3.9 to 4.8, which is demonstrated to be reliable and
repeatable in EAST over the last two years. This window is significantly wider
than the previous one, which is around q95=3.7pm0.1, and is achieved using n=4
odd parity RMPs. Here, n represents the toroidal mode number of the applied
RMPs and q95 is the safety factor at the 95% normalized poloidal magnetic flux.
During ELM suppression, there is only a slight drop in the stored energy
(<=10%). The comparison of pedestal density profiles suggests that ELM
suppression is achieved when the pedestal gradient is kept lower than a
threshold. This wide q95 window for ELM suppression is consistent with the
prediction made by MARS-F modeling prior to the experiment, in which it is
located at one of the resonant q95 windows for plasma response. The Chirikov
parameter taking into account plasma response near the pedestal top, which
measures the plasma edge stochasticity, significantly increases when q95
exceeds 4, mainly due to denser neighboring rational surfaces. Modeling of
plasma response by the MARS-F code shows a strong coupling between resonant and
non-resonant components across the pedestal region, which is characteristic of
the kink-peeling like response observed during RMP-ELM suppression in previous
studies on EAST. These promising results show the reliability of ELM
suppression using the n=4 RMPs and expand the physical understanding on ELM
suppression mechanism.Comment: 25 pages, 11 figure
Functional Diversity and Structural Disorder in the Human Ubiquitination Pathway
The ubiquitin-proteasome system plays a central role in cellular regulation and protein quality control (PQC). The system is built as a pyramid of increasing complexity, with two E1 (ubiquitin activating), few dozen E2 (ubiquitin conjugating) and several hundred E3 (ubiquitin ligase) enzymes. By collecting and analyzing E3 sequences from the KEGG BRITE database and literature, we assembled a coherent dataset of 563 human E3s and analyzed their various physical features. We found an increase in structural disorder of the system with multiple disorder predictors (IUPred - E1: 5.97%, E2: 17.74%, E3: 20.03%). E3s that can bind E2 and substrate simultaneously (single subunit E3, ssE3) have significantly higher disorder (22.98%) than E3s in which E2 binding (multi RING-finger, mRF, 0.62%), scaffolding (6.01%) and substrate binding (adaptor/substrate recognition subunits, 17.33%) functions are separated. In ssE3s, the disorder was localized in the substrate/adaptor binding domains, whereas the E2-binding RING/HECT-domains were structured. To demonstrate the involvement of disorder in E3 function, we applied normal modes and molecular dynamics analyses to show how a disordered and highly flexible linker in human CBL (an E3 that acts as a regulator of several tyrosine kinase-mediated signalling pathways) facilitates long-range conformational changes bringing substrate and E2-binding domains towards each other and thus assisting in ubiquitin transfer. E3s with multiple interaction partners (as evidenced by data in STRING) also possess elevated levels of disorder (hubs, 22.90% vs. non-hubs, 18.36%). Furthermore, a search in PDB uncovered 21 distinct human E3 interactions, in 7 of which the disordered region of E3s undergoes induced folding (or mutual induced folding) in the presence of the partner. In conclusion, our data highlights the primary role of structural disorder in the functions of E3 ligases that manifests itself in the substrate/adaptor binding functions as well as the mechanism of ubiquitin transfer by long-range conformational transitions. © 2013 Bhowmick et al
Polarized epithelium-sperm co-culture system reveals stimulatory factors for the secretion of mouse epididymal quiescin sulfhydryl oxidase 1
Spermatozoa acquire fertilization ability through post-translational modifications. These membrane surface alterations occur in various segments of the epididymis. Quiescin sulfhydryl oxidases, which catalyze thioloxidation reactions, are involved in disulfide bond formation, which is essential for sperm maturation, upon transition and migration in the epididymis. Using castration and azoospermia transgenic mouse models, in the present study, we showed that quiescin sulfhydryl oxidase 1 (QSOX1) protein expression and secretion are positively correlated with the presence of testosterone and sperm cells. A two-dimensional in vitro epithelium-sperm co-culture system provided further evidence in support of the notion that both testosterone and its dominant metabolite, 5 alpha-dihydrotestosterone, promote epididymal QSOX1 secretion. We also demonstrated that immature caput spermatozoa, but not mature cauda sperm cells, exhibited great potential to stimulate QSOX1 secretion in vitro, suggesting that sperm maturation is a key regulatory factor for mouse epididymal QSOX1 secretion. Proteomic analysis identified 582 secretory proteins from the co-culture supernatant, of which 258 were sperm-specific and 154 were of epididymal epitheliumorigin. Gene Ontology analysis indicated that these secreted proteins exhibit functions known to facilitate sperm membrane organization, cellular activity, and sperm-egg recognition. Taken together, our data demonstrated that testosterone and sperm maturation status are key regulators of mouse epididymal QSOX1 protein expression and secretion.</p
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