505 research outputs found

    Dynamical Computation on Coefficients of Electroweak Chiral Lagrangian from One-doublet and Topcolor-assisted Technicolor Models

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    Based on previous studies deriving the chiral Lagrangian for pseudo scalar mesons from the first principle of QCD, we derive the electroweak chiral Lagrangian and build up a formulation for computing its coefficients from one-doublet technicolor model and a schematic topcolor-assisted technicolor model. We find that the coefficients of the electroweak chiral Lagrangian for the topcolor-assisted technicolor model are divided into three parts: direct TC2 interaction part, TC1 and TC2 induced effective Z' particle contribution part, and ordinary quarks contribution part. The first two parts are computed in this paper and we show that the direct TC2 interaction part is the same as that in the one-doublet technicolor model, while effective Z' contributions are at least proportional to the p^2 order parameter \beta_1 in the electroweak chiral Lagrangian and typical features of topcolor-assisted technicolor model are that it only allows positive T and U parameters and the T parameter varies in the range 0\sim 1/(25\alpha), the upper bound of T parameter will decrease as long as Z' mass become large. The S parameter can be either positive or negative depending on whether the Z' mass is large or small. The Z' mass is also bounded above and the upper bound depend on value of T parameter. We obtain the values for all the coefficients of the electroweak chiral Lagrangian up to order of p^4.Comment: 52 pages, 15 figure

    Accurate Segmentation of CT Male Pelvic Organs via Regression-Based Deformable Models and Multi-Task Random Forests

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    Segmenting male pelvic organs from CT images is a prerequisite for prostate cancer radiotherapy. The efficacy of radiation treatment highly depends on segmentation accuracy. However, accurate segmentation of male pelvic organs is challenging due to low tissue contrast of CT images, as well as large variations of shape and appearance of the pelvic organs. Among existing segmentation methods, deformable models are the most popular, as shape prior can be easily incorporated to regularize the segmentation. Nonetheless, the sensitivity to initialization often limits their performance, especially for segmenting organs with large shape variations. In this paper, we propose a novel approach to guide deformable models, thus making them robust against arbitrary initializations. Specifically, we learn a displacement regressor, which predicts 3D displacement from any image voxel to the target organ boundary based on the local patch appearance. This regressor provides a nonlocal external force for each vertex of deformable model, thus overcoming the initialization problem suffered by the traditional deformable models. To learn a reliable displacement regressor, two strategies are particularly proposed. 1) A multi-task random forest is proposed to learn the displacement regressor jointly with the organ classifier; 2) an auto-context model is used to iteratively enforce structural information during voxel-wise prediction. Extensive experiments on 313 planning CT scans of 313 patients show that our method achieves better results than alternative classification or regression based methods, and also several other existing methods in CT pelvic organ segmentation

    The influence of net-quarks on the yields and rapidity spectra of identified hadrons

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    Within a quark combination model, we study systematically the yields and rapidity spectra of various hadrons in central Au+Au collisions at sNN=200\sqrt{s_{NN}}= 200 GeV. We find that considering the difference in rapidity between net-quarks and newborn quarks, the data of multiplicities, rapidity distributions for π±\pi^{\pm}, K±K^{\pm}, p(pˉ)p(\bar{p}) and, in particular the ratios of charged antihadron to hadron as a function of rapidity, can be well described. The effect of net-quarks on various hadrons is analysed, and the rapidity distributions for Ks0K^{0}_{s}, Λ(Λˉ)\Lambda(\bar{\Lambda}), Σ+(Σˉ)\Sigma^{+}(\bar{\Sigma}^{_-}), Ξ\mathrm{\Xi^{-}} (Ξˉ+\mathrm{\bar{\Xi}^{_+}}) and Ω(Ωˉ+)\mathrm{\Omega^{-}}(\mathrm{\bar{\Omega}}^{_+}) are predicted. We discuss the rapidity distribution of net-baryon, and find that it reflects exactly the energy loss of colliding nuclei.Comment: 8 pages, 7 figure

    Centrality dependence of pTp_{T} spectra for identified hadrons in Au+Au and Cu+Cu collisions at sNN=200\sqrt{s_{NN}}= 200 GeV

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    The centrality dependence of transverse momentum spectra for identified hadrons at midrapidity in Au+Au collisions at sNN=200\sqrt{s_{NN}}= 200 GeV is systematically studied in a quark combination model. The pT\mathrm{{p}_{T}} spectra of π±\pi^{\pm}, K±K^{\pm}, p(pˉ)p(\bar{p}) and Λ(Λˉ)\Lambda(\bar{\Lambda}) in different centrality bins and the nuclear modification factors (RCPR_{CP}) for these hadrons are calculated. The centrality dependence of the average collective transverse velocity for the hot and dense quark matter is obtained in Au+Au collisions, and it is applied to a relative smaller Cu+Cu collision system. The centrality dependence of pT\mathrm{{p}_{T}} spectra and the RCPR_{CP} for π0\pi^{0}, Ks0K_{s}^{0} and Λ\Lambda in Cu+Cu collisions at sNN=200\sqrt{s_{NN}}= 200 GeV are well described. The results show that <β(r)><\beta (r)> is only a function of the number of participants NpartN_{part} and it is independent of the collision system.Comment: 7 pages, 6 figure

    Rapidity dependence of hadron production in central Au+Au collisions at sNN=200\sqrt{s_{NN}}= 200 GeV

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    The rapidity and transverse momentum spectra for identified hadrons in central Au+Au collisions at sNN=200\sqrt{s_{NN}}= 200 GeV are computed in a quark combination model. The data of rapidity distributions for π±\pi^{\pm}, K±K^{\pm}, p(pˉ)p(\bar{p}) and net protons (ppˉ)(p-\bar{p}) are well described. We also predict rapidity distributions for Ks0K^{0}_{s}, Λ(Λˉ)\Lambda(\bar{\Lambda}), Ξ\mathrm{\Xi^{-}} (Ξˉ+\mathrm{\bar{\Xi}^{_+}}) and Ω+Ωˉ+\mathrm{\Omega^{-}}+\mathrm{\bar{\Omega}}^{_+}. The multiplicity ratios of charged antihadrons to hadrons as a function of rapidity are reproduced. The results for pT{p}_{T} spectra of π±\pi^{\pm}, K±K^{\pm}, p(pˉ)p(\bar{p}) and for the p/πp/\pi ratios in a broader pT{p}_{T} range agree well with the data. Finally the rapidity dependence of transverse momentum distributions for hadrons are given.Comment: 10 pages,11figures,3 table

    Prostate deformation from inflatable rectal probe cover and dosimetric effects in prostate seed implant brachytherapy: Deformation on prostate permanent brachytherapy dosimetry

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    Prostate brachytherapy is an important treatment technique for patients with localized prostate cancer. An inflatable rectal ultrasound probe cover is frequently utilized during the procedure to adjust for unfavorable prostate position relative to the implant grid. However, the inflated cover causes prostate deformation, which is not accounted for during dosimetric planning. Most of the therapeutic dose is delivered after the procedure when the prostate and surrounding organs-at-risk are less deformed. The aim of this study is to quantify the potential dosimetry changes between the initial plan (prostate deformed) and the more realistic dosimetry when the prostate is less deformed without the cover

    Self-Transforming Configuration Based on Atmospheric-Adaptive Materials for Solid Oxide Cells

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    Solid oxide cells (SOC) with a symmetrical configuration have been focused due to the practical benefits of such configurations, such as minimized compatibility issues, a simple fabrication process and reduced cost compared to SOCs with the asymmetrical configuration. However, the performance of SOCs using a single type of electrode material (symmetrical configuration) is lower than the performance of those using the dissimilar electrode materials (asymmetrical configuration). Therefore, to achieve a high-performance cell, we design a &apos;self-transforming cell&apos; with the asymmetric configuration using only materials of the single type, one based on atmospheric adaptive materials. Atmospheric-adaptive perovskite Pr0.5Ba0.5Mn0.85Co0.15O3-delta (PBMCo) was used for the so-called self-transforming cell electrodes, which changed to layered perovskite and metal in the fuel atmosphere and retained its original structure in the air atmosphere. In fuel cell mods, the self-transforming cell shows excellent electrochemical performance of 1.10Wcm(-2) at 800 degrees C and good stability for 100 h without any catalyst. In electrolysis mode, the moderate current densities of -0.42A cm(-2) for 3 vol.% H2O and -0.62 A cm(-2) for 10 vol.% H2O, respectively, were observed at a cell voltage of 1.3V at 800 degrees C. In the reversible cycling test, the transforming cell maintains the constant voltages for 30 h at +/- 0.2A cm(-2) under 10 vol. % H2O

    Search for W~1Z~2\widetilde{W}_1\widetilde{Z}_2 Production via Trilepton Final States in ppˉp\bar{p} collisions at s=1.8\sqrt{s}=1.8 TeV

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    We have searched for associated production of the lightest chargino, W~1\widetilde{W}_1, and next-to-lightest neutralino, Z~2\widetilde{Z}_2, of the Minimal Supersymmetric Standard Model in ppˉp\bar{p} collisions at \mbox{s\sqrt{s} = 1.8 TeV} using the \D0 detector at the Fermilab Tevatron collider. Data corresponding to an integrated luminosity of 12.5±0.7\pm 0.7 \ipb were examined for events containing three isolated leptons. No evidence for W~1Z~2\widetilde{W}_1\widetilde{Z}_2 pair production was found. Limits on σ(W~1Z~2)\sigma(\widetilde{W}_1\widetilde{Z}_2)Br(W~1lνZ~1)(\widetilde{W}_1\to l\nu\widetilde{Z}_1)Br(Z~2llˉZ~1)(\widetilde{Z}_2\to l\bar{l}\widetilde{Z}_1) are presented.Comment: 17 pages (13 + 1 page table + 3 pages figures). 3 PostScript figures will follow in a UUEncoded, gzip'd, tar file. Text in LaTex format. Submitted to Physical Review Letters. Replace comments - Had to resumbmit version with EPSF directive

    IDN2 and Its Paralogs Form a Complex Required for RNA–Directed DNA Methylation

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    IDN2/RDM12 has been previously identified as a component of the RNA–directed DNA methylation (RdDM) machinery in Arabidopsis thaliana, but how it functions in RdDM remains unknown. By affinity purification of IDN2, we co-purified two IDN2 paralogs IDP1 and IDP2 (IDN2 PARALOG 1 and 2). The coiled-coil domain between the XS and XH domains of IDN2 is essential for IDN2 homodimerization, whereas the IDN2 C-terminal XH domain but not the coiled-coil domain is required for IDN2 interaction with IDP1 and IDP2. By introducing the wild-type IDN2 sequence and its mutated derivatives into the idn2 mutant for complementation testing, we demonstrated that the previously uncharacterized IDN2 XH domain is required for the IDN2-IDP1/IDP2 complex formation as well as for IDN2 function. IDP1 is required for de novo DNA methylation, siRNA accumulation, and transcriptional gene silencing, whereas IDP2 has partially overlapping roles with IDP1. Unlike IDN2, IDP1 and IDP2 are incapable of binding double-stranded RNA, suggesting that the roles of IDP1 and IDP2 are different from those of IDN2 in the IDN2-IDP1/IDP2 complex and that IDP1 and IDP2 are essential for the functioning of the complex in RdDM

    Challenges in QCD matter physics - The Compressed Baryonic Matter experiment at FAIR

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    Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.Comment: 15 pages, 11 figures. Published in European Physical Journal
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