50,492 research outputs found
Non-LTE analysis of copper abundances for the two distinct halo populations in the solar neighborhood
Two distinct halo populations were found in the solar neighborhood by a
series of works. They can be clearly separated by [alpha\Fe] and several other
elemental abundance ratios including [Cu/Fe]. Very recently, a non-local
thermodynamic equilibrium (non-LTE) study revealed that relatively large
departures exist between LTE and non-LTE results in copper abundance analysis.
We aim to derive the copper abundances for the stars from the sample of Nissen
et al (2010) with both LTE and non-LTE calculations. Based on our results, we
study the non-LTE effects of copper and investigate whether the high-alpha
population can still be distinguished from the low-alpha population in the
non-LTE [Cu/Fe] results. Our differential abundance ratios are derived from the
high-resolution spectra collected from VLT/UVES and NOT/FIES spectrographs.
Applying the MAFAGS opacity sampling atmospheric models and spectrum synthesis
method, we derive the non-LTE copper abundances based on the new atomic model
with current atomic data obtained from both laboratory and theoretical
calculations. The copper abundances determined from non-LTE calculations are
increased by 0.01 to 0.2 dex depending on the stellar parameters compared with
the LTE results. The non-LTE [Cu/Fe] trend is much flatter than the LTE one in
the metallicity range -1.6<[Fe/H]<-0.8. Taking non-LTE effects into
consideration, the high- and low-alpha stars still show distinguishable copper
abundances, which appear even more clear in a diagram of non-LTE [Cu/Fe] versus
[Fe/H]. The non-LTE effects are strong for copper, especially in metal-poor
stars. Our results confirmed that there are two distinct halo populations in
the solar neighborhood. The dichotomy in copper abundance is a peculiar feature
of each population, suggesting that they formed in different environments and
evolved obeying diverse scenarios.Comment: 9 pages, 7 figures, 2 table
Symmetric multiparty-controlled teleportation of an arbitrary two-particle entanglement
We present a way for symmetric multiparty-controlled teleportation of an
arbitrary two-particle entangled state based on Bell-basis measurements by
using two Greenberger-Horne-Zeilinger states, i.e., a sender transmits an
arbitrary two-particle entangled state to a distant receiver, an arbitrary one
of the agents via the control of the others in a network. It will be
shown that the outcomes in the cases that is odd or it is even are
different in principle as the receiver has to perform a controlled-not
operation on his particles for reconstructing the original arbitrary entangled
state in addition to some local unitary operations in the former. Also we
discuss the applications of this controlled teleporation for quantum secret
sharing of classical and quantum information. As all the instances can be used
to carry useful information, its efficiency for qubits approaches the maximal
value.Comment: 9 pages, 3 figures; the revised version published in Physical Review
A 72, 022338 (2005). The detail for setting up a GHZ-state quantum channel is
adde
Two Component Model of Dark Energy
We consider the possibility that the dark energy is made up of two or more
independent components, each having a different equation of state. We fit the
model with supernova and gamma-ray burst (GRB) data from resent observations,
and use the Markov Chain Monte Carlo (MCMC) technique to estimate the allowed
parameter regions. We also use various model selection criteria to compare the
two component model with the LCDM, one component dark energy model with static
or variable w(XCDM), and with other multi-component models. We find that the
two component models can give reasonably good fit to the current data. For some
data sets, and depending somewhat on the model selection criteria, the two
component model can give better fit to the data than XCDM with static w and
XCDM with variable w parameterized by w = w_0 + w_az/(1+z).Comment: 10 pages, 8 figures, 3 tables; Version accepted by PR
Collective Modes in the Loop Ordered Phase of Cuprates
We show that the two branches of collective modes discovered recently in
under-doped Cuprates with huge spectral weight are a necessary consequence of
the loop-current state. Such a state has been shown in earlier experiments to
be consistent with the symmetry of the order parameter competing with
superconductivity in four families of Cuprates. We also predict a third branch
of excitations and suggest techniques to discover it. Using parameters to fit
the observed modes, we show that the direction of the effective moments in the
ground state lies in a cone at an angle to the c-axis as observed in
experiments
Microflow valve control system design
A design synthesis for a microflow control system is presented based on the interrogation of an analytical model, testing, and observation. The key issues relating to controlling a microflow using a variable geometry flow channel are explored through the implementation and testing of open and closed-loop control systems. The reliance of closed-loop systems on accurate flow measurement and the need for an open-loop strategy are covered. A valve and control system capable of accurately controlling flowrates between 0.09 and 400 ml/h and with a range of 900:1 is demonstrated
Methods of Nature: Landscapes from the Gettysburg College Collection
Methods of Nature: Landscapes from the Gettysburg College Collection is the third annual exhibition curated by students enrolled in the Art History Methods course. The exhibition is an exciting academic endeavor and incredible opportunity for engaged learning, research, and curatorial experience. The five student curators are Molly Chason ’17, Leah Falk ’18, Shannon Gross ’17, Bailey Harper ’19 and Laura Waters ’19. The selection of artworks in this exhibition includes the depiction of landscape in the nineteenth- and twentieth-century French, American and East Asian cultural traditions in various art forms from traditional media of paintings and prints to utilitarian artifacts of porcelain and a paper folding fan. Landscape paintings in this exhibition are inspired by nature, specific locales and literature. Each object carries a distinctive characteristic, a mood, and an ambience. Collectively, they present a multifaceted view of the landscape in the heart and mind of the artists and intended viewers. [excerpt]https://cupola.gettysburg.edu/artcatalogs/1020/thumbnail.jp
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