Regional Archives in the People\u27s Republic of China: A Case Study of the Chongqing Municipal Archives and the Yunnan Provincial Archives

The emergence of China as an active member of the international community and the growing number of exchange programs between archival institutions in China and the United States have fostered broader professional contacts between American archivists and their counterparts in China. Consequently, American archivists have become increasingly curious about the professional practices of their Chinese colleagues. The following description and analysis offers a case study of the structure, function, and use of Chinese regional archives

A Novel Scheme to Search for Fractional Charge Particles in Low Energy Accelerator Experiments

In the Standard Model of particle physics, the quarks and anti-quarks have fractional charge equal to $\pm1/3$ or $\pm2/3$ of the electron's charge. There has been a large number of experiments searching for fractional charge, isolatable, elementary particles using a variety of methods, including $e^+e^-$ collisions using dE/dx ionization energy loss measurements, but no evidence has been found to confirm existence of free fractional charge particles, which leads to the quark confinement theory. In this paper, a proposal to search for this kind particles is presented, which is based on the conservation law of four-momentum. Thanks to the CLEOc and BESIII detectors' large coverage, good particle identification, precision measurements of tracks' momenta and their large recorded data samples, these features make the scheme feasible in practice. The advantage of the scheme is independent of any theoretical models and sensitive for a small fraction of the quarks transitioning to the unconfinement phase from the confinement phase.Comment: 9 page

Enantiomerically pure β-phenylalanine analogues from α–β-phenylalanine mixtures in a single reactive extraction step

An efficient and selective method for the extraction of α-amino acids in preference over their β-isomers using PdCl2(PPh3)2 was discovered, which enables the separation of product mixtures obtained in the enantioselective enzymatic formation of β-amino acids.

Strategies and reaction systems for solar-driven CO2 reduction by water

Solar driven CO2 conversion into high-value-added chemicals and energy-rich fuels is one of the promising strategies to tackle global warming and to address the energy-supply crisis. Even though enormous effort has been devoted to exploring all sorts of homogeneous and heterogeneous photocatalysts, the current efficiency and more importantly selectivity to valuable chemicals are still rather moderate, thus it is desired to develop high-efficiency photocatalytic system toward CO2 reduction with excellent selectivity. In this review, fundamental aspects of photocatalytic CO2 reduction by pure water, the reaction systems and the reliable method for detection of the products are firstly described. Thereafter the recent advances of the main strategy for improving the photocatalytic CO2 reduction from the perspective of promoting the CO2 adsorption and activation, accelerating the kinetics of water oxidation, and modulating charge separation are overviewed. The prospects and challenges on precise designing heterogeneous catalysts for CO2 photoreduction are proposed at the end, indicating the significance for the further development of photocatalytic systems with high CO2 conversion efficiency and product selectivity

A comparison of the local spiral structure from Gaia DR2 and VLBI maser parallaxes

Context. The Gaia mission has released the second data set (Gaia DR2), which contains parallaxes and proper motions for a large number of massive, young stars. Aims. We investigate the spiral structure in the solar neighborhood revealed by Gaia DR2 and compare it with that depicted by VLBI maser parallaxes. Methods. We examined three samples with different constraints on parallax uncertainty and distance errors and stellar spectral types: (1) all OB stars with parallax errors of less than 10%; (2) only O-type stars with 0.1 mas errors imposed and with parallax distance errors of less than 0.2 kpc; and (3) only O-type stars with 0.05 mas errors imposed and with parallax distance errors of less than 0.3 kpc. Results. In spite of the significant distance uncertainties for stars in DR2 beyond 1.4 kpc, the spiral structure in the solar neighborhood demonstrated by Gaia agrees well with that illustrated by VLBI maser results. The O-type stars available from DR2 extend the spiral arm models determined from VLBI maser parallaxes into the fourth Galactic quadrant, and suggest the existence of a new spur between the Local and Sagittarius arms.Comment: 4 pages, 3 figures, 1 table, accepted for publication in A&

The Host Galaxy and Central Engine of the Dwarf AGN POX 52

We present new multi-wavelength observations of the dwarf Seyfert 1 galaxy POX 52 in order to investigate the properties of the host galaxy and the active nucleus, and to examine the mass of its black hole, previously estimated to be ~ 10^5 M_sun. Hubble Space Telescope ACS/HRC images show that the host galaxy has a dwarf elliptical morphology (M_I = -18.4 mag, Sersic index n = 4.3) with no detected disk component or spiral structure, confirming previous results from ground-based imaging. X-ray observations from both Chandra and XMM show strong (factor of 2) variability over timescales as short as 500 s, as well as a dramatic decrease in the absorbing column density over a 9 month period. We attribute this change to a partial covering absorber, with a 94% covering fraction and N_H = 58^{+8.4}_{-9.2} * 10^21 cm^-2, that moved out of the line of sight in between the XMM and Chandra observations. Combining these data with observations from the VLA, Spitzer, and archival data from 2MASS and GALEX, we examine the spectral energy distribution (SED) of the active nucleus. Its shape is broadly similar to typical radio-quiet quasar SEDs, despite the very low bolometric luminosity of L_bol = 1.3 * 10^43 ergs/s. Finally, we compare black hole mass estimators including methods based on X-ray variability, and optical scaling relations using the broad H-beta line width and AGN continuum luminosity, finding a range of black hole mass from all methods to be M_bh = (2.2-4.2) * 10^5 M_sun, with an Eddington ratio of L_bol/L_edd = 0.2-0.5.Comment: 19 pages, 16 figures, accepted for publication in Ap

Synthesis of Silicate-Bridged Heterojunctional SnO2/BiVO4 Nanoplates as Efficient Photocatalysts to Convert CO2 and Degrade 2,4-Dichlorophenol

Bismuth vanadate (BiVO4) is a promising visible‐light responsive photocatalyst, whose photocatalytic activity can be significantly improved by increasing its surface area and utilizing its high‐energy‐level photogenerated electrons effectively. In this work, 2D BiVO4 nanoplates with large specific surface area are successfully fabricated by hydrothermal conversion with the pre‐prepared BiOCl nanosheets as precursors. To improve the photogenerated charge separation, resulted BiVO4 nanoplates are further coupled with nanocrystalline SnO2 to construct heterojunctions, then silicate bridges are introduced between the interfaces of BiVO4 and SnO2. The amount‐optimized silicate‐bridged SnO2/BiVO4 nanocomposite exhibit exceptional visible‐light photocatalytic activities, by ≈7‐time and 4‐time enhancements for CO2 conversion to CH4 and for 2,4‐dichlorophenol degradation, respectively, compared to bare BiVO4 nanoparticles. The significantly enhanced charge separation is verified by steady‐state and time‐resolved surface photovoltage responses and produced hydroxyl radical amounts. Moreover, it is deduced through designed photo‐electrochemical experiments that the introduced SnO2 acts as a proper‐energy platform capable of accepting the photogenerated electrons of BiVO4 nanoplates, and the constructed silicate bridges further facilitate the electron transfer between BiVO4 and SnO2. This work opens up a feasible route to synthesize visible‐light‐driven 2D bismuth‐based nano‐photocatalysts with high photocatalytic activities for efficient fuel production and environmental remediation

Spitzer IRS Spectra of Optically Faint Infrared Sources with Weak Spectral Features

Spectra have been obtained with the low-resolution modules of the Infrared Spectrograph (IRS) on the Spitzer Space Telescope (Spitzer) for 58 sources having f$_{\nu}$(24 micron) > 0.75 mJy. Sources were chosen from a survey of 8.2 deg$^{2}$ within the NOAO Deep Wide-Field Survey region in Bootes (NDWFS) using the Multiband Imaging Photometer (MIPS) on the Spitzer Space Telescope. Most sources are optically very faint (I > 24mag). Redshifts have previously been determined for 34 sources, based primarily on the presence of a deep 9.7 micron silicate absorption feature, with a median z of 2.2. Spectra are presented for the remaining 24 sources for which we were previously unable to determine a confident redshift because the IRS spectra show no strong features. Optical photometry from the NDWFS and infrared photometry with MIPS and the Infrared Array Camera on the Spitzer Space Telescope (IRAC) are given, with K photometry from the Keck I telescope for some objects. The sources without strong spectral features have overall spectral energy distributions (SEDs) and distributions among optical and infrared fluxes which are similar to those for the sources with strong absorption features. Nine of the 24 sources are found to have feasible redshift determinations based on fits of a weak silicate absorption feature. Results confirm that the "1 mJy" population of 24 micron Spitzer sources which are optically faint is dominated by dusty sources with spectroscopic indicators of an obscured AGN rather than a starburst. There remain 14 of the 58 sources observed in Bootes for which no redshift could be estimated, and 5 of these sources are invisible at all optical wavelengths.Comment: Accepted by Ap