Magnetic phase diagram of the spin-1 two-dimensional J1-J3 Heisenberg model on a triangular lattice

The spin-1 Heisenberg model on a triangular lattice with the ferromagnetic nearest, $J_1=-(1-p)J,$ $J>0$, and antiferromagnetic third-nearest-neighbor, $J_3=pJ$, exchange interactions is studied in the range of the parameter $0 \leqslant p \leqslant 1$. Mori's projection operator technique is used as a method, which retains the rotation symmetry of spin components and does not anticipate any magnetic ordering. For zero temperature several phase transitions are observed. At $p\approx 0.2$ the ground state is transformed from the ferromagnetic spin structure into a disordered state, which in its turn is changed to an antiferromagnetic long-range ordered state with the incommensurate ordering vector ${\bf Q = Q^\prime} \approx (1.16, 0)$ at $p\approx 0.31$. With the further growth of $p$ the ordering vector moves along the line ${\bf Q^\prime-Q_c}$ to the commensurate point ${\bf Q_c}=(\frac{2\pi}{3}, 0)$, which is reached at $p = 1$. The final state with an antiferromagnetic long-range order can be conceived as four interpenetrating sublattices with the $120^\circ$ spin structure on each of them. Obtained results are used for interpretation of the incommensurate magnetic ordering observed in NiGa$_2$S$_4$.Comment: 18 pages, 6 figures, accepted for publication in Physics Letters

Structural basis of template-boundary definition in Tetrahymena telomerase.

Telomerase is required to maintain repetitive G-rich telomeric DNA sequences at chromosome ends. To do so, the telomerase reverse transcriptase (TERT) subunit reiteratively uses a small region of the integral telomerase RNA (TER) as a template. An essential feature of telomerase catalysis is the strict definition of the template boundary to determine the precise TER nucleotides to be reverse transcribed by TERT. We report the 3-Å crystal structure of the Tetrahymena TERT RNA-binding domain (tTRBD) bound to the template boundary element (TBE) of TER. tTRBD is wedged into the base of the TBE RNA stem-loop, and each of the flanking RNA strands wraps around opposite sides of the protein domain. The structure illustrates how the tTRBD establishes the template boundary by positioning the TBE at the correct distance from the TERT active site to prohibit copying of nontemplate nucleotides

Use of emission spectroscopy for real-time assessment of relative wall erosion rate of BHT-200 hall thruster for various regimes of operation

Radiation emission due to Boron atoms sputtered from the Boron-Nitride ceramic walls of a BHT-200 Hall thruster was measured as a diagnostic for real time assessment of thruster wall erosion and to determine the e ects of various operation conditions on thruster lifetime. Boron neutral 249.677 and 249.773nm lines were measured using a high resolution spectrometer. Spectral measurement results and the accompanying analysis and discussion are presented in this study. From the spectral measurements it was observed that the Boron emission intensity significantly increases for increased discharge voltage pointing to a large increase in the thruster wall erosion rate. Additionally, the measurements show that for the nominal discharge voltage and the applied magnetic field intensity, there is an optimum propellant flow rate for minimum Boron emission, thus minimum wall erosion rate. The variation in the current to the magnet coils showed that the Boron emission intensity increases for increased magnetic field and the Boron emission intensity shows similar behavior to that of the Xenon single ion emission line intensity at 248.911nm. The findings of the study show that emission spectroscopy can be used in determining the optimum operational parameters for minimum wall erosion for SPT type Hall thrusters

Search for dark matter in the Sun with the ANTARES neutrino telescope in the CMSSM and mUED frameworks

ANTARES is the first neutrino telescope in the sea. It consists of a three-dimensional array of 885 photomultipliers to collect the Cherenkov light induced by relativistic muons produced in CC interactions of high energy neutrinos. One of the main scientific goals of the experiment is the search for dark matter. We present here the analysis of data taken during 2007 and 2008 to look for a WIMP signal in the Sun. WIMPs are one of the most popular scenarios to explain the dark matter content of the Universe. They would accumulate in massive objects like the Sun or the Galactic Center and their self-annihilation would produce (directly or indirectly) high energy neutrinos detectable by neutrino telescopes. Contrary to other indirect searches (like with gamma rays or positrons), the search for neutrinos in the Sun is free from other astrophysical contributions, so the interpretation of a potential signal in terms of dark matter is much more robust

Galactic rotation curves and brane world models

In the present investigation flat rotational curves of the galaxies are considered under the framework of brane-world models where the 4d effective Einstein equation has extra terms which arise from the embedding of the 3-brane in the $5d$ bulk. It has been shown here that these long range bulk gravitational degrees of freedom can act as a mechanism to yield the observed galactic rotation curves without the need for dark matter. The present model has the advantage that the observed rotation curves result solely from well-established non-local effects of gravitation, such as dark radiation and dark pressure under a direct use of the condition of flat rotation curves and does not invoke any exotic matter field.Comment: 7 Latex pages, 7 figures; Edited substantially with new figures and references; Accepted for Mon. Not. R. Astron. So

Propensity score estimation in the presence of length‐biased sampling: a non‐parametric adjustment approach

The pervasive use of prevalent cohort studies on disease duration increasingly calls for an appropriate methodology to account for the biases that invariably accompany samples formed by such data. It is well known, for example, that subjects with shorter lifetime are less likely to be present in such studies. Moreover, certain covariate values could be preferentially selected into the sample, being linked to the long‐term survivors. The existing methodology for estimating the propensity score using data collected on prevalent cases requires the correct conditional survival/hazard function given the treatment and covariates. This requirement can be alleviated if the disease under study has stationary incidence, the so‐called stationarity assumption. We propose a non‐parametric adjustment technique based on a weighted estimating equation for estimating the propensity score, which does not require modeling the conditional survival/hazard function when the stationarity assumption holds. The estimator's large‐sample properties are established, and its small‐sample behavior is studied via simulation. The estimated propensity score is utilized to estimate the survival curves. Copyright © 2014 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106732/1/sta446.pd

Reply to “Comment on ‘A Vertical Exposure of the 1999 Surface Rupture of the Chelungpu Fault at Wufeng, Western Taiwan: Structural and Paleoseismic Implications for an Active Thrust Fault,’ by Jian-Cheng Lee, Yue-Gau Chen, Kerry Sieh, Karl Mueller, Wen-Shan Chen, Hao-Tsu Chu, Yu-Chang Chan, Charles Rubin, and Robert Yeats,” by Yuan-Hsi Lee, Shih-Ting Lu, Tung-Sheng Shih, and Wei-Yu Wu

We welcome Y. H. Lee et al.'s interest in our article (Lee et al., 2001). We thank them for their comment, which provides a further opportunity for discussing the quantification of the slip amounts including horizontal and vertical components and the fault geometry for an earthquake thrust scarp in Wufeng, western Taiwan, during the 1999 M 7.6 earthquake. In their comment, Y. H. Lee et al. used restoration of deformed concrete fence across the 1999 scarp to estimate the slip vector of the main fault. The estimated slip amount, especially the horizontal component, is different (significantly less) from our results presented in the 2001 BSSA article. They then applied an “area-balance” technique to compare their results with ours. They showed that their area-balance method favored their estimates including the slip amounts and the fault dip angle. They concluded that their estimated slip amounts are more reasonable than ours. The fundamental questions in this issue, in our opinions, include the actual amounts of deformation (slip) and the associated deformation processes, as well as the limitation and uncertainty of the applied techniques on an earthquake-formed thrust scarp. Hereafter we attempt to answer these questions and clarify the related problems

Primate-specific Evolution of an LDLR Enhancer

Background: Sequence changes in regulatory regions have often been invoked to explain phenotypic divergence among species, but molecular examples of this have been difficult to obtain. Results: In this study we identified an anthropoid primate-specific sequence element that contributed to the regulatory evolution of the low-density lipoprotein receptor. Using a combination of close and distant species genomic sequence comparisons coupled with in vivo and in vitro studies, we found that a functional cholesterol-sensing sequence motif arose and was fixed within a pre-existing enhancer in the common ancestor of anthropoid primates. Conclusion: Our study demonstrates one molecular mechanism by which ancestral mammalian regulatory elements can evolve to perform new functions in the primate lineage leading to human

Candida albicans Yeast, Pseudohyphal, and Hyphal Morphogenesis Differentially Affects Immune Recognition

The authors thank Amy Whittington for preliminary experiments on in vitro induction of pseudohyphae and Mihai Netea for discussions. The authors also thank Michael Weig for the pga29 strains. Funding NG and AW were supported by the Wellcome Trust (086827, 075470, 097377, 101873, and 200208); the European Union ALLFUN (FP7/2007 2013, HEALTH-2010-260338), and the MRC Centre for Medical Mycology for funding (N006364/1). LM was supported by a SORSAS (Scottish Overseas Research Students Award Scheme) from the University of Aberdeen and Funding from the Rwandan Government.Peer reviewedPublisher PD