459 research outputs found
Effect of cooling rate on microstructure of B2-NiSc intermetallics
Ni-50at%Sc alloy was prepared by centrifugal
casting method. Volume fraction, the actual
content of B2-NiSc and second phase Ni2Sc in
alloy were analyzed with an Image-Pro Plus
software. The cooling rates for the solidified thin
plate with thickness of 2.65mm, 1.2mm, 0.75mm
and 0.35 mm are 1164, 2570, 4112 and 8811 K·s-
1, respectively. It is found that d=0.5 mm was an
critical dimension which corresponds to an abrupt
change in the solidification rate. It is also found
that (Ni2Sc+NiSc)eutectic was dispersed at grain
boundary or between dendritic arms due to the loss
of Sc element during melting. While d> 0.5mm
(corresponding to the thin plate with thickness of
0.75mm, 1.20mm and 2.65 mm), the solidification
structure consists of primary phase B2-NiSc and
(Ni2Sc+NiSc)eutectic. While d < 0.5mm
(corresponding to the thin plate with thickness of
0.35 mm), the solidification structure is composed
of fine globular B2-NiSc and relatively small
amounts of (Ni2Sc+NiSc)eutectic. Based on the phase
volumetric analyzing of the microstructure with an
Image-Pro Plus software, the loss of Sc element
during melting was about 3.01~3.10 at%. The
eutectic NiSc in the lamellar eutectic structure
together with the primary phase B2-NiSc form a
larger single phase NiSc, while Ni2Sc with the form
of particles is distributed on the grain boundaries
after (970 ℃, 72 h) homogenization heat
treatment
Photometry of Variable Stars from THU-NAOC Transient Survey I: The First 2 Years
In this paper, we report the detections of stellar variabilities from the
first 2-year observations of sky area of about 1300 square degrees from the
Tsinghua University-NAOC Transient Survey (TNTS). A total of 1237 variable
stars (including 299 new ones) were detected with brightness < 18.0 mag and
magnitude variation >= 0.1 mag on a timescale from a few hours to few hundred
days. Among such detections, we tentatively identified 661 RR Lyrae stars, 431
binaries, 72 Semiregular pulsators, 29 Mira stars, 11 slow irregular variables,
11 RS Canum Venaticorum stars, 7 Gamma Doradus stars, 5 long period variables,
3 W Virginis stars, 3 Delta Scuti stars, 2 Anomalous Cepheids, 1 Cepheid, and 1
nove-like star based on their time-series variability index Js and their phased
diagrams. Moreover, we found that 14 RR Lyrae stars show the Blazhko effect and
67 contact eclipsing binaries exhibit the O'Connell effect. Since the period
and amplitude of light variations of RR Lyrae variables depend on their
chemical compositions, their photometric observations can be used to
investigate distribution of metallicity along the direction perpendicular to
the Galactic disk. We find that the metallicity of RR Lyrae stars shows large
scatter at regions closer to the Galactic plane (e.g., -3.0 < [Fe/H] < 0) but
tends to converge at [Fe/H]~ -1.7 at larger Galactic latitudes. This variation
may be related to that the RRAB Lyrae stars in the Galactic halo come from
globular clusters with different metallicity and vertical distances, i.e. OoI
and OoII populations, favoring for the dual-halo model.Comment: 18 pages, 19 figures, published in AJ, 150, 10
A Computational Drug-Target Network for Yuanhu Zhitong Prescription
Yuanhu Zhitong prescription (YZP) is a typical and relatively simple traditional Chinese medicine (TCM), widely used in the clinical treatment of headache, gastralgia, and dysmenorrhea. However, the underlying molecular mechanism of action of YZP is not clear. In this study, based on the previous chemical and metabolite analysis, a complex approach including the prediction of the structure of metabolite, high-throughput in silico screening, and network reconstruction and analysis was developed to obtain a computational drug-target network for YZP. This was followed by a functional and pathway analysis by ClueGO to determine some of the pharmacologic activities. Further, two new pharmacologic actions, antidepressant and antianxiety, of YZP were validated by animal experiments using zebrafish and mice models. The forced swimming test and the tail suspension test demonstrated that YZP at the doses of 4 mg/kg and 8 mg/kg had better antidepressive activity when compared with the control group. The anxiolytic activity experiment showed that YZP at the doses of 100 mg/L, 150 mg/L, and 200 mg/L had significant decrease in diving compared to controls. These results not only shed light on the better understanding of the molecular mechanisms of YZP for curing diseases, but also provide some evidence for exploring the classic TCM formulas for new clinical application
Acute small bowel obstruction: a rare initial presentation for the metastasis of the large-cell carcinoma of the lung
We present one case with symptom of paroxysmal abdominal pain for over 20 days. Abdominal computerized tomography (CT) scan revealed intestinal obstruction and a mass of 6.0 cm × 6.0 cm in size located at the left adrenal. Chest CT scan showed a lobulated mass of 2.7 cm × 2.7 cm in size at the upper left lung. Core needle biopsy of the lung mass confirmed the diagnosis of large cell carcinoma. The patient underwent an emergency abdominal laparotomy and received a chemotherapy regimen that consisted of pemetrexed and cisplatin postoperatively. In addition, we made a review of the literature of the occurrence, diagnosis and outcome of this manifestation
A Shape-Based Method for Continuous Low-Thrust Trajectory Design between Circular Coplanar Orbits
The shape-based method can provide suitable initial guesses for trajectory optimization, which are useful for quickly converging a more accurate trajectory. Combined with the optimal control theory, an optimized shape-based method using the finite Fourier series is proposed in this paper. Taking the flight time-fixed case and the time-free case into account, respectively, the optimized shape-based method, which considers the first-order optimal necessary conditions, can guarantee that not only an orbit designed during the preliminary phase is optimal, but also the thrust direction is not constrained to be tangential. Besides, the traditional shape-based method using the finite Fourier series, in which the thrust direction is constrained to be tangential, is developed for the time-free case in this paper. The Earth-Mars case and the LEO-GEO case are used to verify the optimized shape-based method’s feasibility for time-fixed and time-free continuous low-thrust trajectory design between circular coplanar orbits, respectively. The optimized shaped-based method can design a lower cost trajectory
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