Abstract
We present the second release of value-added catalogues of the LAMOST Spectroscopic Survey of the Galactic Anticentre (LSS-GAC DR2). The catalogues present values of radial velocity Vr, ...atmospheric parameters – effective temperature Teff, surface gravity log g, metallicity Fe/H, α-element to iron (metal) abundance ratio α/Fe (α/M), elemental abundances C/H and N/H and absolute magnitudes MV and $M_{K_{\rm s}}$ deduced from 1.8 million spectra of 1.4 million unique stars targeted by the LSS-GAC since 2011 September until 2014 June. The catalogues also give values of interstellar reddening, distance and orbital parameters determined with a variety of techniques, as well as proper motions and multiband photometry from the far-UV to the mid-IR collected from the literature and various surveys. Accuracies of radial velocities reach 5 km s−1 for the late-type stars, and those of distance estimates range between 10 and 30 per cent, depending on the spectral signal-to-noise ratios. Precisions of Fe/H, C/H and N/H estimates reach 0.1 dex, and those of α/Fe and α/M reach 0.05 dex. The large number of stars, the contiguous sky coverage, the simple yet non-trivial target selection function and the robust estimates of stellar radial velocities and atmospheric parameters, distances and elemental abundances make the catalogues a valuable data set to study the structure and evolution of the Galaxy, especially the solar-neighbourhood and the outer disc.
Abstract
Understanding the sources of lunar water is crucial for studying the history of lunar evolution, as well as the interaction of solar wind with the Moon and other airless bodies. Recent ...orbital spectral observations revealed that the solar wind is a significant exogenous driver of lunar surficial hydration. However, the solar wind is shielded over a period of 3–5 days per month as the Moon passes through the Earth’s magnetosphere, during which a significant loss of hydration is expected. Here we report the temporal and spatial distribution of polar surficial OH/H
2
O abundance, using Chandrayaan-1 Moon Mineralogy Mapper (
M
3
) data, which covers the regions inside/outside the Earth’s magnetosphere. The data shows that polar surficial OH/H
2
O abundance increases with latitude, and that the probability of polar surficial OH/H
2
O abundance remains at the same level when in the solar wind and in the magnetosphere by controlling latitude, composition, and lunar local time. This indicates that the OH/H
2
O abundance in the polar regions may be saturated, or supplemented from other possible sources, such as Earth wind (particles from the magnetosphere, distinct from the solar wind), which may compensate for thermal diffusion losses while the Moon lies within the Earth’s magnetosphere. This work provides some clues for studies of planet–moon systems, whereby the planetary wind serves as a bridge connecting the planet with its moons.
Acoustic coherent perfect absorbers Song, J Z; Bai, P; Hang, Z H ...
New journal of physics,
03/2014, Letnik:
16, Številka:
3
Journal Article
Recenzirano
Odprti dostop
In this paper, we explore the possibility of achieving acoustic coherent perfect absorbers. Through numerical simulations in two dimensions, we demonstrate that the energy of coherent acoustic waves ...can be totally absorbed by a fluid absorber with specific complex mass density or bulk modulus. The robustness of such absorbing systems is investigated under small perturbations of the absorber parameters. We find that when the resonance order is the lowest and the size of the absorber is comparable to the wavelength in the background, the phenomenon of perfect absorption is most stable. When the wavelength inside both the background and the absorber is much larger than the size of the absorber, perfect absorption is possible when the mass density of the absorber approaches the negative value of the background mass density. Finally, we show that by using suitable dispersive acoustic metamaterials, broadband acoustic perfect absorption may be achieved.
We presented and demonstrated both n-and p-type vertical C-shaped-channel nanosheet field-effect transistors (VCNFETs) featured with precise control of both channel thickness and gate length. The ...VCNFETs were fabricated by high-quality Si/SiGe epitaxy and atomic layer deposition to obtain nanometer-scale process control and self-aligned high-<inline-formula> <tex-math notation="LaTeX">\textit{k}</tex-math> </inline-formula> metal gate (HKMG). The integration flow is compatible with the process used in the mainstream industry and it can be easily extended to vertically stacked devices. Both the gate length and the channel thickness of the VCNFETs are mainly determined by the thicknesses of Si/SiGe films grown by epitaxy, instead of lithography and etch techniques. Perfect subthreshold swing (SS), small drain-induced barrier lowering (DIBL), and large <inline-formula> <tex-math notation="LaTeX">\textit{I}_{\biosc{on}}</tex-math> </inline-formula>/<inline-formula> <tex-math notation="LaTeX">\textit{I}_{\biosc{off}}</tex-math> </inline-formula> ratio were achieved for both n-and p-VCNFETs due to the crystalline silicon channel and the well-defined doping profiles. The device performance and optimization were also investigated and discussed. Used as access transistors in dynamic random access memory (DRAM) array, VCNFETs were also demonstrated for the potential applications to 10-nm DRAM and beyond.
Abstract
As a novel X-ray focusing technology, lobster-eye micropore optics (MPO) feature both a wide observing field of view and true imaging capability, promising sky monitoring with significantly ...improved sensitivity and spatial resolution in soft X-rays. Since first proposed by Angel, the optics have been extensively studied, developed and trialed over the past decades. In this Letter, we report on the first-light results from a flight experiment of the Lobster Eye Imager for Astronomy, a pathfinder of the wide-field X-ray telescope of the Einstein Probe mission. The piggyback imager, launched in 2022 July, has a mostly unvignetted field of view of 18.°6 × 18.°6. Its spatial resolution is in the range of 4′–7′ in FWHM and the focal spot effective area is 2–3 cm
2
, both showing only mild fluctuations across the field of view. We present images of the Galactic center region, Sco X-1, and the diffuse Cygnus Loop nebular taken in snapshot observations over 0.5–4 keV. These are truly wide-field X-ray images of celestial bodies observed, for the first time, by a focusing imaging telescope. Initial analyses of the in-flight data show excellent agreement between the observed images and the on-ground calibration and simulations. The instrument and its characterization are briefly described, as well as the flight experiment. The results provide a solid basis for the development of the present and proposed wide-field X-ray missions using lobster-eye MPO.
Main conclusion
CgVPE1 is important in the differentiation of TE cells in
C. grandis
‘Tomentosa’ fruits as it may directly affects secondary cell wall construction while participating in PCD.
The ...vacuolar processing enzyme (VPE) plays an important role in both developmental and environmentally inducible programmed cell death (PCD); it was originally identified as a cysteine protease localized in the vacuole to activate and mature vacuolar proteins in plants. Interestingly, we found a VPE called CgVPE1 to be associated with deposition of the secondary cell wall in tracheary element (TE) cells in the pericarp of
Citrus grandis
‘Tomentosa’ fruits. We then used ultrathin sections and the TUNEL assay to verify that PCD is involved in TE development. Furthermore,
CgVPE1
was found to be mainly expressed in secretory cavities and TEs in the pericarp of
Citrus grandis
‘Tomentosa’ fruits. Immunolocalization of CgVPE1 in the pericarp indicated that CgVPE1 is mainly distributed in the central large vacuole, endoplasmic reticulum, Golgi vesicles, cytosol, and secondary wall before TE maturation. CgVPE1 appeared earlier in the endoplasmic reticulum and Golgi vesicles of TEs cells. The vesicles containing CgVPE1 near the large central vacuole and secondary wall were observed, respectively. CgVPE1 proteins content in the cytoplasm decreased sharply, while the CgVPE1 content in the secondary cell wall did not change significantly after vacuole rupture. CgVPE1 protein contents in the secondary cell wall were significantly reduced until the TE cells developed into hollow thick-walled cells. Furthermore, labeling of VPE homologues in
Arabidopsis thaliana
using immunoelectron microscopy with anti-CgVPE1 antibody revealed that VPE homologues were specifically distributed in the secondary cell wall of stem TEs. Overall, these results suggested that CgVPE1 is not only involved PCD during TE cell development; furthermore, it may directly participate in the construction of plant secondary cell walls.
The back-streaming neutrons (back-n) is a white neutron experimental facility at the China spallation neutron source (CSNS). The time structure of the primary proton beam makes it fully applicable to ...use the time-of-flight (TOF) method for neutron energy measuring. We implemented the electronics of TOF measurement on the general-purpose readout electronics designed for all the seven detectors in back-n. The electronics are based on the peripheral component interconnect express eXtensions for instrumentation (PXIe) platform, which is composed of field digitizer modules (FDM), trigger and clock modules (TCM), and signal conditioning modules. The T0 signal synchronous to the CSNS accelerator represents the neutron emission from the target. It is the start of the time stamp. The TCM receives, synchronizes, and distributes the T0 signal to each FDM based on the PXIe backplane bus. Meanwhile, the detector signals, after being conditioned, are fed into FDMs for waveform digitizing. The first sample point of the signal waveform is the stop of the time stamp. According to the time stamp and the time of the signal over the threshold, the total TOF can be obtained. The time-to-digital converter (TDC) based on field-programmable gate array (FPGA) is implemented on the TCM to accurately acquire the time interval between the asynchronous T0 signal and the global synchronous clock phase. There is also an FPGA-based TDC on the FDM to accurately acquire the time interval between the T0 signal arriving at the FDM and the first sample point of the signal waveform. The over-threshold time of signal is obtained offline. This method for TOF measurement is efficient and not needed for additional modules. Test results showed that the accuracy of TOF is subnanosecond and can meet the requirement for back-n at the CSNS.
TiNi/Ti2Ni-based composite coatings reinforced by TiC and TiB2 were produced on Ti6Al4V by laser cladding the mixture of a Ni-based alloy and different contents of B4C (0wt%, 5wt%, 15wt%, and 25wt%). ...The macromorphologies and microstructures of the coatings were examined through optical microscopy, X-ray diffractometry, scanning electron microscopy, and energy dispersive spectrometry. The microhardness, fracture toughness, and wear behaviors of the coatings were also investigated by using a microhardness tester and an ultra-functional wear testing machine. Results showed that the coatings were mainly composed of TiNi/Ti2Ni and TiC/TiB2 as the matrix and reinforcement particles, respectively. The phase constituents of the coatings were not influenced by addition of different contents of B4C. The microstructure of the reinforcements in the coatings presented the following evolution: hypereutectic consisting of blocky (TiC+TiB2)e eutectic and primary TiCp cellular dendrites (0wt% B4C), mixture of hypereutectic and willow-shaped (TiB2+TiC)p pseudoeutectic (5wt% B4C), and pseudoeutectic (15 and 25wt% B4C). With increasing B4C content, the volume fraction and size of the pseudoeutectic structures as well as the average microhardness of the coatings (850, 889, 969, and 1002HV0.2) were increased. By contrast, the average fracture toughness of the coatings was gradually decreased (4.47, 4.21, 4.06, and 3.85Mpam1/2) along with their wear volumes (0wt%, 5wt%, and 15wt% B4C). The increase in B4C content to 25wt% did not further reduce wear loss. The wear mechanism transformed from micro-cutting (0wt% B4C) into a combination of micro-cutting and brittle debonding (5wt% B4C) and finally led to brittle debonding (15wt% and 25wt% B4C). Coatings with suitable contents of B4C (less than 15wt%) showed excellent comprehensive mechanical properties.
•TiC+TiB2 reinforced TiNi/Ti2Ni matrix coatings were fabricated by laser cladding.•The microstructural evolution of the reinforcements was analyzed.•The changes of microhardness and fracture toughness were studied.•Wear behaviors were investigated by wear tests.•The transformation of wear mechanism of the coatings was revealed.
Emerging evidence has indicated that serum exosomal microRNAs (miRNAs) have promising diagnostic and prognostic value for colorectal cancer (CRC). This study aimed to detect serum exosomal miR-874 ...expression in CRC patients and assess its potential clinical significance.
Blood samples were collected from 125 CRC patients, 45 cases with benign adenomas (AD) and 70 healthy individuals. Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) was performed to examine serum exosomal miR-874 levels.
The results showed that serum exosomal miR-874 levels were significantly downregulated in CRC patients compared to AD cases and healthy controls. Receiver operating characteristic (ROC) curve analysis revealed that serum exosomal miR-874 expression could discriminate CRC patients from healthy controls, as well as patients with AD. In addition, low serum exosomal miR-874 expression was associated with positive distant metastasis, positive lymph node metastasis, poor differentiation, and advanced TNM stage. Moreover, serum exosomal miR-874 expression was identified as a statistically significant independent prognostic factor for overall survival of CRC patients.
Collectively, serum exosomal miR-874 expression might serve as a reliable marker for CRC diagnosis and prognosis prediction.
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