The two rings of (50000) Quaoar Pereira, C. L.; Sicardy, B.; Morgado, B. E. ...
Astronomy and astrophysics (Berlin),
05/2023, Volume:
673
Journal Article
Peer reviewed
Open access
Context.
Quaoar is a classical trans-Neptunian object (TNO) with an area-equivalent diameter of 1100 km and an orbital semi-major axis of 43.3 astronomical units. Based on stellar occultations ...observed between 2018 and 2021, an inhomogeneous ring (Q1R, i.e., Quaoar’s first ring) has been detected around this body.
Aims.
A new stellar occultation by Quaoar was observed on August 9, 2022, with the aim of improving Quaoar’s shape models and the physical parameters of Q1R, while searching for additional material around the body.
Methods.
The occultation provided nine effective chords across Quaoar, pinning down its size, shape, and astrometric position. Large facilities, such as Gemini North and the Canada-France-Hawaii Telescope (CFHT), were used to obtain high acquisition rates and signal-to-noise ratios. The light curves were also used to characterize the Q1R ring (radial profiles and orbital elements).
Results.
Quaoar’s elliptical fit to the occultation chords yields the limb with an apparent semi-major axis of 579.5 ± 4.0 km, apparent oblateness of 0.12 ± 0.01, and area-equivalent radius of 543 ± 2 km. Quaoar’s limb orientation is consistent with Q1R and Weywot orbiting in Quaoar’s equatorial plane. The orbital radius of Q1R is refined to a value of 4057 ± 6 km. The radial opacity profile of the more opaque ring profile follows a Lorentzian shape that extends over 60 km, with a full width at half maximum (FWHM) of ∼5 km and a peak normal optical depth of 0.4. Besides the secondary events related to the already reported rings, new secondary events detected during the August 2022 occultation in three different data sets are consistent with another ring around Quaoar with a radius of 2520 ± 20 km, assuming the ring is circular and co-planar with Q1R. This new ring has a typical width of 10 km and a normal optical depth of ∼0.004. Just as Q1R, it also lies outside Quaoar’s classical Roche limit.
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Ultra-precision machining (UPM) is capable of manufacturing a high quality surface at a nanometric surface roughness. For such high quality surface in a UPM process, due to the machining complexity ...any variable would be possible to deteriorate surface quality, consequently receiving much attention and interest. The general factors are summarized as machine tool, cutting conditions, tool geometry, environmental conditions, material property, chip formation, tool wear, vibration etc. This paper aims to review the current state of the art in studying the surface roughness formation and the factors influencing surface roughness in UPM. Firstly, the surface roughness characteristics in UPM is introduced. Then in UPM, a wide variety of factors for surface roughness are then reviewed in detail and the mechanism of surface roughness formation is concluded thoroughly. Finally, the challenges and opportunities faced by industry and academia are discussed and several principle conclusions are drawn.
Display omitted
•The surface roughness characteristics in UPM is elaborated.•The factors and mechanism of surface roughness formation are reviewed in detail.•The challenges and opportunities faced by industry and academia are discussed.•The key issues are drawn to surface roughness formation in UPM.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The insecticidal and repellent activities of the essential oil extracted from Zingiber purpureum Roscoe rhizomes were evaluated against Tribolium castaneum (Herbst) and Lasioderma serricorne (L.) ...adults. During our screening program for agrochemicals from Chinese medicinal herbs and wild plants, the essential oil of Z. purpureum rhizomes was found to possess strong contact toxicity against T. castaneum and L. serricorne adults, with LD50 values of 39.0 and 16.3 µg per adult, respectively, and also showed strong fumigant toxicity against the two grain storage insects with LC50 values of 13.6 and 9.3 mg/liter of air, respectively. The essential oil obtained by hydrodistillation was investigated by gas chromatography-mass spectrometry. The main components of the essential oil were identified to be sabinene (48.1%), terpinen-4-ol (25.1%), and γ-terpinene (6.7%), followed by α-terpinene (4.3%), β-thujene (3.4%), and α-phellandrene (2.7%). Sabinene, terpinen-4-ol, and γ-terpinene were separated and purified by silica gel column chromatography and preparative thin-layer chromatography. Terpinen-4-ol showed the strongest contact toxicity against T. castaneum and L. serricorne (LD50 = 19.7 and 5.4 µg per adult, respectively) and also the strongest fumigant toxicity against T. castaneum and L. serricorne (LC50 = 3.7 and 1.3 mg/liter of air, respectively). Otherwise, sabinene and terpinen-4-ol were strongly repellent against T. castaneum as well as the essential oil, while γ-terpinene exhibited weaker repellency against T. castaneum compared with the positive control, DEET (N, N-diethyl-3-methylbenzamide). Moreover, only the essential oil exhibited strong repellency against L. serricorne, the three compounds exhibited weaker repellency against L. serricorne relative to DEET.
Summary
We performed a GWAS of trochanter and intertrochanter bone mineral density (BMD) in the Framingham Heart Study and replicated in three independent studies. Our results identified one novel ...locus around the associated variations at chromosomal region 3q13.32 and replicated two loci at chromosomal regions 3p21 and 8q24. Our findings provide useful insights that enhance our understanding of bone development, osteoporosis, and fracture pathogenesis.
Introduction
Hip trochanter (TRO) and intertrochanter (INT) subregions have important clinical relevance to subtrochanteric and intertrochanteric fractures but have rarely been studied by genome-wide association studies (GWASs).
Methods
Aiming to identify genomic loci associated with BMD variation at TRO and INT regions, we performed a GWAS utilizing the Framingham Heart Study (FHS,
N
= 6,912) as discovery sample and utilized the Women’s Health Initiative (WHI) African-American subsample (
N
= 845), WHI Hispanic subsample (
N
= 446), and Omaha osteoporosis study (
N
= 971), for replication.
Results
Combining the evidence from both the discovery and the replication samples, we identified one novel locus around the associated variations at chromosomal region 3q13.32 (
rs1949542
, discovery
p
= 6.16 × 10
−8
, replication
p
= 2.86 × 10
−4
for INT-BMD; discovery
p
= 1.35 × 10
−7
, replication
p
= 4.16 × 10
−4
for TRO-BMD, closest gene
RP11-384F7.1
). We also replicated two loci at chromosomal regions 3p21 (
rs148725943
, discovery
p
= 6.61 × 10
−7
, replication
p
= 5.22 × 10
−4
for TRO-BMD, closest gene
CTNNB1
) and 8q24 (
rs7839059
, discovery
p
= 2.28 × 10
−7
, replication
p
= 1.55 × 10
−3
for TRO-BMD, closest gene
TNFRSF11B
) that were reported previously. We demonstrated that the effects at both 3q13.32 and 3p21 were specific to the TRO, but not to the femoral neck and spine. In contrast, the effect at 8q24 was common to all the sites.
Conclusion
Our findings provide useful insights that enhance our understanding of bone development, osteoporosis, and fracture pathogenesis.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Phase change material slurries (PCS) can serve as both the heat transfer fluids and energy storage media, consequently, they are potentially applicable to the thermal systems, e.g., the secondary ...refrigeration and air conditioning loops, so as to improve the energy efficiency and to reduce the quantity of refrigerant used in the system. The design of the system using PCS needs the quantitative information about the thermal and fluidic behaviors of PCS. Here we provide an overview of the characteristics of two big groups of PCS, namely microencapsulated phase change material slurry (MPCS) and semi-clathrate hydrate slurry (CHS). The focuses are placed on the flow and heat transfer features and thermal properties, such as specific heat, viscosity and thermal conductivity. The suitable materials for making PCS are also discussed and compared based on the available data in the literature, and some examples of the applications of PCS are summarized as well.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
There is an increasing demand for ultrahigh-strength ferritic steels strengthened by nanoprecipitates. Improvement of the precipitation strengthening response requires an understanding of the ...nanoscale precipitation mechanisms. In this study, the synergistic effects of Cu and Ni on nanoscale precipitation and mechanical properties of ferritic steels were thoroughly investigated, and new steels with ultrahigh strength and high ductility have been developed. Our results indicate that Ni effectively increases the number density of Cu-rich nanoprecipitates by more than an order of magnitude, leading to a substantial increase in yield strength. It appears that Ni decreases both the strain energy for nucleation and the interfacial energy between the nucleus and the matrix, thereby decreasing the critical energy for nucleation of Cu-rich nanoprecipitates. Cu and Ni are also found to be beneficial to grain-size refinement, resulting from lowering the austenite-to-ferrite transformation temperature, as determined from thermodynamic calculations. In addition, the strengthening mechanisms of Cu and Ni were quantitatively evaluated in terms of precipitation strengthening, grain refinement strengthening and solid-solution strengthening. The current findings shed light on the composition–microstructure–property relationships in nanoprecipitate-strengthened ferritic steels.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Upsetting-extrusion (UE) process effectively prepared high-strength ZK61 magnesium alloy rods with tension/compression symmetry. The influence of upsetting-extrusion temperature and upsetting ratio ...on microstructure was studied. Microstructure evolution in the UE process included two stages: {10–12} tensile twinning significantly divided and refined the coarse grains in upsetting stage, forming a //ED (extrusion direction) texture component; grain refinement suppressed the inverse occurrence of {10–12} tensile twinning during extrusion stage, promoting multi-slip deformation and dynamic recrystallization (DRX) and leading to the diffused {0001}//ED texture. Lowering temperature and increasing upsetting ratio played positive roles in twinning division and DRX refinement. Both of them were beneficial to basal texture weakening which could effectively inhibit the activation of tensile twinning during compression, and promote basal slip contribution during tension, thus improving tension/compression asymmetry. The relationship between microstructure and tension/compression yield strengths was analyzed by texture-dependent Hall-Petch relationship composed of slip and twinning deformation mechanisms. Only slight weakening of the extruded fiber texture was required for tension/compression symmetry for fine-grained structure; but it was the opposite for coarse-grained structure. Correspondingly, only smaller critical upsetting ratio was needed at lower upsetting temperature.
•Tension/compression symmetry achieved by upsetting-extrusion process.•Twinning division in upsetting aided grain refinement and basal texture weakening.•Dominant deformation mechanisms investigated from strain hardening and Schmidt factor.•Texture-dependent Hall-Petch relationship including slip and twinning was established.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The magnetic skyrmion is a topologically stable spin texture in which the constituent spins point to all the directions wrapping a sphere. Generation and control of nanometric magnetic skyrmions have ...large potential, for example, reduced power consumption, in spintronics device applications. Here we show the real-space observation of a biskyrmion, as defined by a molecular form of two bound skyrmions with the total topological charge of 2, realized under magnetic field applied normal to a thin plate of a bilayered manganite with centrosymmetric structure. In terms of a Lorentz transmission electron microscopy (TEM), we have observed a distorted-triangle lattice of biskyrmion crystal, each composed of two bound skyrmions with oppositely swirling spins (magnetic helicities). Furthermore, we demonstrate that these biskyrmions can be electrically driven with orders of magnitude lower current density (<10(8) A m(-2)) than that for the conventional ferromagnetic domain walls.
Dark septate endophytes (DSE) are ubiquitous and abundant in stressful environments including heavy metal (HM) stress. However, our knowledge about the roles of DSE in improving HM tolerance of their ...host plants is poor. In this study, maize (
Zea mays L.) was inoculated with a HM tolerant DSE strain
Exophiala pisciphila H93 in lead (Pb), zinc (Zn), and cadmium (Cd) contaminated soils.
E. pisciphila H93 successfully colonized and formed typical DSE structures in the inoculated maize roots. Colonization of
E. pisciphila H93 alleviated the deleterious effects of excessive HM supplements and promoted the growth of maize (roots and shoots) under HM stress conditions, though it significantly decreased the biomass of inoculated maize under no HM stress. Further analysis showed that the colonization of
E. pisciphila H93 improved the tolerance of maize to HM by restricting the translocation of HM ions from roots to shoots. This study demonstrated that under higher HM stress, such a mutual symbiosis between
E. pisciphila and its host (maize) may be an efficient strategy to survive in the stressful environments.
►Effect of DSE (
E. pisciphila) on heavy metal tolerance of maize host was studied. ►DSE alleviated the deleterious effect of excessive heavy metals on maize. ►DSE restricted the transfer of heavy metals from the roots to shoots in maize. ►DSE colonization improved the tolerance of their host plants to heavy metals.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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