2,198 research outputs found
Spontaneous Breaking of Flavor Symmetry and Naturalness of Nearly Degenerate Neutrino Masses and Bi-maximal Mixing
The gauge model with flavor symmetry and three Higgs triplets is
studied. We show how the intriguing nearly degenerate neutrino mass and
bi-maximal mixing scenario comes out naturally after spontaneous breaking of
the symmetry. The hierarchy between the neutrino mass-squared differences,
which is needed for reconciling both solar and atmospheric neutrino data, is
naturally resulted from an approximate permutation symmetry. The model can also
lead to interesting phenomena on lepton-flavor violations via the
gauge interactions.Comment: 13 pages, latex, no figures, the version appearing in SCIENCE IN
CHINA (Series A), Vol.35 No.9 (2000
Hawking Radiation as Quantum Tunneling in Rindler Coordinate
We substantiate the Hawking radiation as quantum tunneling of fields or
particles crossing the horizon by using the Rindler coordinate. The thermal
spectrum detected by an accelerated particle is interpreted as quantum
tunneling in the Rindler spacetime. Representing the spacetime near the horizon
locally as a Rindler spacetime, we find the emission rate by tunneling, which
is expressed as a contour integral and gives the correct Boltzmann factor. We
apply the method to non-extremal black holes such as a Schwarzschild black
hole, a non-extremal Reissner-Nordstr\"{o}m black hole, a charged Kerr black
hole, de Sitter space, and a Schwarzschild-anti de Sitter black hole.Comment: LaTex 19 pages, no figure; references added and replaced by the
version accepted in JHE
Ractopamine-induced changes in sarcoplasmic proteome profile of post-rigor pork semimembranosus muscle
Ractopamine is a beta-adrenergic agonist that increases leanness and carcass weight in finishing pigs. Our previous study observed that dietary ractopamine increased the abundance of several glycolytic enzymes in the sarcoplasmic proteome of post-rigor pork longissimus thoracis muscle. Pork semimembranosus is an economically important muscle and demonstrates differences in biochemistry compared with longissimus thoracis. Nonetheless, the effects of ractopamine on sarcoplasmic proteome of semimembranosus have not been evaluated yet. Therefore, this study examined the influence of ractopamine on sarcoplasmic proteome of post-rigor pork semimembranosus. Analyses of sarcoplasmic proteome of semimembranosus muscles from control (CON; diet without ractopamine) and ractopamine-fed (RAC; 7.4 mg/kg for 14 days followed by 10.0 mg/kg for 14 days) barrows revealed that haemoglobin subunit beta, alpha-crystallin B, and titin fragments were over-abundant in CON. In contrast, myosin light chain 1/3 and tripartite motif-containing protein 72 were over-abundant in RAC. The low abundance of haemoglobin subunit beta and alpha crystallin B in RAC could be attributed to fibre type shift (from oxidative to glycolytic) in response to ractopamine. The over-abundance of MLC 1/3 and tripartite motif-containing protein 72 in RAC could be due to the increased myofibrillar protein synthesis and muscle mass in ractopamine-fed pigs. Dietary ractopamine decreased the abundance of sarcoplasmic proteins involved in oxygen transport and chaperone activity, but increased the abundance of proteins involved in muscle contraction and plasma membrane repair in pork semimembranosus muscle.Keywords: Pork, ractopamine, sarcoplasmic proteome, semimembranosu
Covariant anomaly and Hawking radiation from the modified black hole in the rainbow gravity theory
Recently, Banerjee and Kulkarni (R. Banerjee, S. Kulkarni, arXiv:0707.2449
[hep-th]) suggested that it is conceptually clean and economical to use only
the covariant anomaly to derive Hawking radiation from a black hole. Based upon
this simplified formalism, we apply the covariant anomaly cancellation method
to investigate Hawking radiation from a modified Schwarzschild black hole in
the theory of rainbow gravity. Hawking temperature of the gravity's rainbow
black hole is derived from the energy-momentum flux by requiring it to cancel
the covariant gravitational anomaly at the horizon. We stress that this
temperature is exactly the same as that calculated by the method of cancelling
the consistent anomaly.Comment: 5 page
Topological B-Model on Weighted Projective Spaces and Self-Dual Models in Four Dimensions
It was recently shown by Witten on the basis of several examples that the
topological B-model whose target space is a Calabi-Yau (CY) supermanifold is
equivalent to holomorphic Chern-Simons (hCS) theory on the same supermanifold.
Moreover, for the supertwistor space CP^{3|4} as target space, it has been
demonstrated that hCS theory on CP^{3|4} is equivalent to self-dual N=4 super
Yang-Mills (SYM) theory in four dimensions. We consider as target spaces for
the B-model the weighted projective spaces WCP^{3|2}(1,1,1,1|p,q) with two
fermionic coordinates of weight p and q, respectively - which are CY
supermanifolds for p+q=4 - and discuss hCS theory on them. By using twistor
techniques, we obtain certain field theories in four dimensions which are
equivalent to hCS theory. These theories turn out to be self-dual truncations
of N=4 SYM theory or of its twisted (topological) version.Comment: 12 pages; v2: minor clarification, 3 references added, published
versio
Potent Trivalent Inhibitors of Thrombin through Hybridization of Salivary Sulfopeptides from Hematophagous Arthropods
Blood feeding arthropods, such as leeches, ticks, flies and mosquitoes, provide a privileged source of peptidic anticoagulant molecules. These primarily operate through inhibition of the central coagulation protease thrombin by binding to the active site and either exosite I or exosite II. Herein, we describe the rational design of a novel class of trivalent thrombin inhibitors that simultaneously block both exosites as well as the active site. These engineered hybrids were synthesized using tandem diselenide-selenoester ligation (DSL) and native chemical ligation (NCL) reactions in one-pot. The most potent trivalent inhibitors possessed femtomolar inhibition constants against alpha-thrombin and were selective over related coagulation proteases. A lead hybrid inhibitor possessed potent anticoagulant activity, blockade of both thrombin generation and platelet aggregation in vitro and efficacy in a murine thrombosis model at 1 mg kg(-1). The rational engineering approach described here lays the foundation for the development of potent and selective inhibitors for a range of other enzymatic targets that possess multiple sites for the disruption of protein-protein interactions, in addition to an active site
Prediction Space Weather Using an Asymmetric Cone Model for Halo CMEs
Halo coronal mass ejections (HCMEs) are responsible of the most severe
geomagnetic storms. A prediction of their geoeffectiveness and travel time to
Earth's vicinity is crucial to forecast space weather.
Unfortunately coronagraphic observations are subjected to projection effects
and do not provide true characteristics of CMEs. Recently, Michalek (2006, {\it
Solar Phys.}, {\bf237}, 101) developed an asymmetric cone model to obtain the
space speed, width and source location of HCMEs. We applied this technique to
obtain the parameters of all front-sided HCMEs observed by the SOHO/LASCO
experiment during a period from the beginning of 2001 until the end of 2002
(solar cycle 23). These parameters were applied for the space weather forecast.
Our study determined that the space speeds are strongly correlated with the
travel times of HCMEs within Earth's vicinity and with the magnitudes related
to geomagnetic disturbances
Rotating metrics admitting non-perfect fluids in General Relativity
In this paper, by applying Newman-Janis algorithm in spherical symmetric
metrics, a class of embedded rotating solutions of field equations is
presented. These solutions admit non-perfect fluidsComment: LaTex, 39 page
A hybrid semantic approach to building dynamic maps of research communities
In the last ten years, ontology-based recommender systems have been shown to be effective tools for predicting user preferences and suggesting items. There are however some issues associated with the ontologies adopted by these approaches, such as: 1) their crafting is not a cheap process, being time consuming and calling for specialist expertise; 2) they may not represent accurately the viewpoint of the targeted user community; 3) they tend to provide rather static models, which fail to keep track of evolving user perspectives. To address these issues, we propose Klink UM, an approach for extracting emergent semantics from user feedbacks, with the aim of tailoring the ontology to the users and improving the recommendations accuracy. Klink UM uses statistical and machine learning techniques for finding hierarchical and similarity relationships between keywords associated with rated items and can be used for: 1) building a conceptual taxonomy from scratch, 2) enriching and correcting an existing ontology, 3) providing a numerical estimate of the intensity of semantic relationships according to the users. The evaluation shows that Klink UM performs well with respect to handcrafted ontologies and can significantly increase the accuracy of suggestions in content-based recommender systems
Effects of anisotropic spin-exchange interactions in spin ladders
We investigate the effects of the Dzialoshinskii-Moriya (DM) and
Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) interactions on various
thermodynamic and magnetic properties of a spin 1/2 ladder. Using the Majorana
fermion representation, we derive the spectrum of low energy excitations for a
pure DM interaction and in presence of a superimposed KSEA interaction. We
calculate the various correlation functions for both cases and discuss how they
are modified with respect to the case of an isotropic ladder. We also discuss
the electron spin resonance (ESR) spectrum of the system and show that it is
strongly influenced by the orientation of the magnetic field with respect to
the Dzialoshinskii-Moriya vector. Implications of our calculations for NMR and
ESR experiments on ladder systems are discussed.Comment: 14 pages, 4 eps figures, corrected calculation of NMR rate (v3
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