16,641 research outputs found

    Muon anomalous magnetic moment and lepton flavor violation in MSSM

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    We give a thorough analysis of the correlation between the muon anomalous magnetic moment and the radiative lepton flavor violating (LFV) processes within the minimal supersymmetric standard model. We find that in the case when the slepton mass eigenstates are nearly degenerate, δaμ\delta a_\mu, coming from SUSY contributions, hardly depends on the lepton flavor mixing and, thus, there is no direct relation between δaμ\delta a_\mu and the LFV processes. On the contrary, if the first two generations' sleptons are much heavier than the 3rd one, i.e., in the effective SUSY scenario, the two quantities are closely related. In the latter scenario, the SUSY parameter space to account for the experimental δaμ\delta a_\mu is quite different from the case of no lepton flavor mixing. Especially, the Higgsino mass parameter μ\mu can be either positive or negative.Comment: 22 pages, 9 figures; Some discussions are modifie

    Towards Quantitative Simulations of High Power Proton Cyclotrons

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    PSI operates a cyclotron based high intensity proton accelerator routinely at an average beam power of 1.3MW. With this power the facility is at the worldwide forefront of high intensity proton accelerators. The beam current is practically limited by losses at extraction and the resulting activation of accelerator components. Further intensity upgrades and new projects aiming at an even higher average beam power, are only possible if the relative losses can be lowered in proportion, thus keeping absolute losses at a constant level. Maintaining beam losses at levels allowing hands-on maintenance is a primary challenge in any high power proton machine design and operation. In consequence, predicting beam halo at these levels is a great challenge and will be addressed in this paper. High power hadron driver have being used in many disciplines of science and, a growing interest in the cyclotron technology for high power hadron drivers are being observed very recently. This report will briefly introduce OPAL, a tool for precise beam dynamics simulations including 3D space charge. One of OPAL's flavors (OPAL-cycl) is dedicated to high power cyclotron modeling and is explained in greater detail. We then explain how to obtain initial conditions for our PSI Ring cyclotron which still delivers the world record in beam power of 1.3 MW continuous wave (cw). Several crucial steps are explained necessary to be able to predict tails at the level of 3\sigma ... 4\sigma in the PSI Ring cyclotron. We compare our results at the extraction with measurements, obtained with a 1.18 MW cw production beam. Based on measurement data, we develop a simple linear model to predict beam sizes of the extracted beam as a function of intensities and confirm the model with simulations.Comment: Corrections and new figur

    A new taxol-producing fungus (Pestalotiopsis malicola) and evidence for taxol as a transient product in the culture

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    Fungal production of the anti-tumor taxol is an effective way of making this drug in industries. We reported here a new taxol-producing fungus, NK101, from plant debris in the soil. Based on the culture characteristics, conidia structure and molecular evidence, NK101 was classified as Pestalotiopsis malicola. Taxol was verified in both the culture and the mycelium in a high level (186 μg/L). The time course of yield suggests that taxol was present as a transient product in the fungus. This work may show the diversity of using fungi to produce taxol.Key words: Taxol, saprophyte, Pestalotiopsis

    ColorSketch: A Drawing Assistant for Generating Color Sketches from Photos

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    Ages and Masses of 0.64 million Red Giant Branch stars from the LAMOST Galactic Spectroscopic Survey

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    We present a catalog of stellar age and mass estimates for a sample of 640\,986 red giant branch (RGB) stars of the Galactic disk from the LAMOST Galactic Spectroscopic Survey (DR4). The RGB stars are distinguished from the red clump stars utilizing period spacing derived from the spectra with a machine learning method based on kernel principal component analysis (KPCA). Cross-validation suggests our method is capable of distinguishing RC from RGB stars with only 2 per cent contamination rate for stars with signal-to-noise ratio (SNR) higher than 50. The age and mass of these RGB stars are determined from their LAMOST spectra with KPCA method by taking the LAMOST - KeplerKepler giant stars having asteroseismic parameters and the LAMOST-TGAS sub-giant stars based on isochrones as training sets. Examinations suggest that the age and mass estimates of our RGB sample stars with SNR >> 30 have a median error of 30 per cent and 10 per cent, respectively. Stellar ages are found to exhibit positive vertical and negative radial gradients across the disk, and the age structure of the disk is strongly flared across the whole disk of 6<R<136<R<13\,kpc. The data set demonstrates good correlations among stellar age, [Fe/H] and [α\alpha/Fe]. There are two separate sequences in the [Fe/H] -- [α\alpha/Fe] plane: a high--α\alpha sequence with stars older than \sim\,8\,Gyr and a low--α\alpha sequence composed of stars with ages covering the whole range of possible ages of stars. We also examine relations between age and kinematic parameters derived from the Gaia DR2 parallax and proper motions. Both the median value and dispersion of the orbital eccentricity are found to increase with age. The vertical angular momentum is found to fairly smoothly decrease with age from 2 to 12\,Gyr, with a rate of about -50\,kpc\,km\,s1^{-1}\,Gyr1^{-1}. A full table of the catalog is public available online.Comment: 16 pages, 22 figures,accepted by MNRA

    Robustness and Enhancement of Neural Synchronization by Activity-Dependent Coupling

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    We study the synchronization of two model neurons coupled through a synapse having an activity-dependent strength. Our synapse follows the rules of Spike-Timing Dependent Plasticity (STDP). We show that this plasticity of the coupling between neurons produces enlarged frequency locking zones and results in synchronization that is more rapid and much more robust against noise than classical synchronization arising from connections with constant strength. We also present a simple discrete map model that demonstrates the generality of the phenomenon.Comment: 4 pages, accepted for publication in PR
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