The Large sky Area Multi-Object Spectroscopic Telescope (LAMOST) General Survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of stars, galaxies and QSOs. Objects both i
n the pilot survey and the first year general survey are included in the LAMOST First Data Release (DR1). The pilot survey started in October 2011 and ended in June 2012, and the data have been released to the public as the LAMOST Pilot Data Release in August 2012. The general survey started in September 2012, and completed its first year of operation in June 2013. The LAMOST DR1 includes a total of 1202 plates containing 2,955,336 spectra, of which 1,790,879 spectra have observed signal-to-noise S/N >10. All data with S/N>2 are formally released as LAMOST DR1 under the LAMOST data policy. This data release contains a total of 2,204,696 spectra, of which 1,944,329 are stellar spectra, 12,082 are galaxy spectra and 5,017 are quasars. The DR1 includes not only spectra, but also three stellar catalogues with measured parameters: AFGK-type stars with high quality spectra (1,061,918 entries), A-type stars (100,073 entries), and M stars (121,522 entries). This paper introduces the survey design, the observational and instrumental limitations, data reduction and analysis, and some caveats. Description of the FITS structure of spectral files and parameter catalogues is also provided.
We present a spectroscopically identified catalogue of 72 DA white dwarfs from the LAMOST pilot survey. 35 are found to be new identifications after cross-correlation with the Eisenstein et al. and Villanova catalogues. The effective temperature and
gravity of these white dwarfs are estimated by Balmer lines fitting. Most of them are hot white dwarfs. The cooling times and masses of these white dwarfs are estimated by interpolation in theoretical evolution tracks. The peak of mass distribution is found to be $sim$ 0.6 $M_odot$ which is consistent with prior work in the literature. The distances of these white dwarfs are estimated using the method of Synthetic Spectral Distances. All of these WDs are found to be in the Galactic disk from our analysis of space motions. Our sample supports the expectation white dwarfs with high mass are concentrated near the plane of Galactic disk
We present the design and implementation of a trapped ion cavity QED system. A single ytterbium ion is confined by a micron-scale ion trap inside a 2 mm optical cavity. The ion is coherently pumped by near resonant laser light while the cavity output
is monitored as a function of pump intensity and cavity detuning. We observe a Purcell enhancement of scattered light into the solid angle subtended by the optical cavity, as well as a three-peak structure arising from strongly driving the atom. This system can be integrated into existing atom{photon quantum network protocols and is a pathway towards an efficient atom{photon quantum interface.
The structural evolution of the strain-driven morphotropic phase boundary (MPB) in BiFeO3 films has been investigated using synchrotron x-ray diffractometry in conjunction with scanning probe microscopy. Our results demonstrate the existence of mixed
-phase regions that are mainly made up of two heavily tilted ferroelectric triclinic phases. Analysis of first-principles computations suggests that these two triclinic phases originate from a phase separation of a single monoclinic state accompanied by elastic matching between the phase-separated states. These first-principle calculations further reveal that the intrinsic piezoelectric response of these two low-symmetry triclinic phases is not significantly large, which thus implies that the ease of phase transition between these two energetically close triclinic phases is likely responsible for the large piezoelectric response found in the BiFeO3 films near its MPB. These findings not only enrich the understandings of the lattice and domain structure of epitaxial BiFeO3 films but may also shed some light on the origin of enhanced piezoelectric response near MPB.
The AC susceptibility at zero DC magnetic field of a polycrystalline sample of LaFeAsO_{0.94}F_{0.06} (T_c = 24 K) has been investigated as a function of the temperature, the amplitude of the AC magnetic field (in the range Hac = 0.003 - 4 Oe) and th
e frequency (in the range f = 10 kHz - 100 kHz). The temperature dependence of the AC susceptibility exhibits the typical two-step transition arising from the combined response of superconduncting grains and intergranular weak-coupled medium. The intergranular part of the susceptibility strongly depends on both the amplitude and the frequency of the AC driving field, from few Kelvin below T_c down to T = 4.2 K. Our results show that, in the investigated sample, the intergrain critical current is not determined by pinning of Josephson vortices but by Josephson critical current across neighboring grains.
Quantum networks based on atomic qubits and scattered photons provide a promising way to build a large-scale quantum information processor. We review quantum protocols for generating entanglement and operating gates between two distant atomic qubits,
which can be used for constructing scalable atom--photon quantum networks. We emphasize the crucial role of collecting light from atomic qubits for large-scale networking and describe two techniques to enhance light collection using reflective optics or optical cavities. A brief survey of some applications for scalable and efficient atom--photon networks is also provided.
Specific heat, resistivity, susceptibility and Hall coefficient measurements were performed on high-quality single crystalline Na$_{1-delta}$FeAs. This compound is found to undergo three successive phase transitions at around 52, 41, and 23 K, which
correspond to structural, magnetic and superconducting transitions, respectively. The Hall effect result indicates the development of energy gap at low temperature due to the occurrence of spin-density-wave instability. Our results provide direct experimental evidence of the magnetic ordering in the nearly stoichiometric NaFeAs.
