scholarly journals Binary asteroid (31) Euphrosyne: ice-rich and nearly spherical

2020 ◽  
Vol 641 ◽  
pp. A80
Author(s):  
B. Yang ◽  
J. Hanuš ◽  
B. Carry ◽  
P. Vernazza ◽  
M. Brož ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Family Formation ◽  
Large Fraction ◽  
Imaging Study ◽  
Spherical Shape ◽  
Hydrostatic Equilibrium ◽  
Main Belt ◽  
Binary Asteroid ◽  
Water Ice ◽  
The Impact

Aims. Asteroid (31) Euphrosyne is one of the biggest objects in the asteroid main belt and it is also the largest member of its namesake family. The Euphrosyne family occupies a highly inclined region in the outer main belt and contains a remarkably large number of members, which is interpreted as an outcome of a disruptive cratering event. Methods. The goals of this adaptive-optics imaging study are threefold: to characterize the shape of Euphrosyne, to constrain its density, and to search for the large craters that may be associated with the family formation event. Results. We obtained disk-resolved images of Euphrosyne using SPHERE/ZIMPOL at the ESO 8.2 m VLT as part of our large program (ID: 199.C-0074, PI: Vernazza). We reconstructed its 3D shape via the ADAM shape modeling algorithm based on the SPHERE images and the available light curves of this asteroid. We analyzed the dynamics of the satellite with the Genoid meta-heuristic algorithm. Finally, we studied the shape of Euphrosyne using hydrostatic equilibrium models. Conclusions. Our SPHERE observations show that Euphrosyne has a nearly spherical shape with the sphericity index of 0.9888 and its surface lacks large impact craters. Euphrosyne’s diameter is 268 ± 6 km, making it one of the top ten largest main belt asteroids. We detected a satellite of Euphrosyne – S/2019 (31) 1 – that is about 4 km across, on a circular orbit. The mass determined from the orbit of the satellite together with the volume computed from the shape model imply a density of 1665 ± 242 kg m−3, suggesting that Euphrosyne probably contains a large fraction of water ice in its interior. We find that the spherical shape of Euphrosyne is a result of the reaccumulation process following the impact, as in the case of (10) Hygiea. However, our shape analysis reveals that, contrary to Hygiea, the axis ratios of Euphrosyne significantly differ from those suggested by fluid hydrostatic equilibrium following reaccumulation.

scholarly journals The impact crater at the origin of the Julia family detected with VLT/SPHERE?

2018 ◽  
Vol 618 ◽  
pp. A154 ◽  
Author(s):  
P. Vernazza ◽  
M. Brož ◽  
A. Drouard ◽  
J. Hanuš ◽  
M. Viikinkoski ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Adaptive Optics ◽  
Impact Crater ◽  
Large Fraction ◽  
Family Studies ◽  
High Angular Resolution ◽  
Main Belt ◽  
3D Shape ◽  
The Family ◽  
The Impact

Context. The vast majority of the geophysical and geological constraints (e.g., internal structure, cratering history) for main-belt asteroids have so far been obtained via dedicated interplanetary missions (e.g., ESA Rosetta, NASA Dawn). The high angular resolution of SPHERE/ZIMPOL, the new-generation visible adaptive-optics camera at ESO VLT, implies that these science objectives can now be investigated from the ground for a large fraction of D ≥ 100 km main-belt asteroids. The sharp images acquired by this instrument can be used to accurately constrain the shape and thus volume of these bodies (hence density when combined with mass estimates) and to characterize the distribution and topography of D ≥ 30 km craters across their surfaces. Aims. Here, via several complementary approaches, we evaluated the recently proposed hypothesis that the S-type asteroid (89) Julia is the parent body of a small compact asteroid family that formed via a cratering collisional event. Methods. We observed (89) Julia with VLT/SPHERE/ZIMPOL throughout its rotation, derived its 3D shape, and performed a reconnaissance and characterization of the largest craters. We also performed numerical simulations to first confirm the existence of the Julia family and to determine its age and the size of the impact crater at its origin. Finally, we utilized the images/3D shape in an attempt to identify the origin location of the small collisional family. Results. On the one hand, our VLT/SPHERE observations reveal the presence of a large crater (D ~ 75 km) in Julia’s southern hemisphere. On the other hand, our numerical simulations suggest that (89) Julia was impacted 30–120 Myrs ago by a D ~ 8 km asteroid, thereby creating a D ≥ 60 km impact crater at the surface of Julia. Given the small size of the impactor, the obliquity of Julia and the particular orientation of the family in the (a,i) space, the imaged impact crater is likely to be the origin of the family. Conclusions. New doors into ground-based asteroid exploration, namely, geophysics and geology, are being opened thanks to the unique capabilities of VLT/SPHERE. Also, the present work may represent the beginning of a new era of asteroid-family studies. In the fields of geophysics, geology, and asteroid family studies, the future will only get brighter with the forthcoming arrival of 30–40 m class telescopes like ELT, TMT, and GMT.

scholarly journals Triggering Comet-Like Activity of Main Belt Comets

2015 ◽  
Vol 10 (S318) ◽  
pp. 135-141
Author(s):  
N. Haghighipour ◽  
T. I. Maindl ◽  
C. Schäfer ◽  
R. Speith ◽  
R. Dvorak
Keyword(s):  
Impact Angle ◽  
Material Strength ◽  
Main Belt ◽  
Water Ice ◽  
New Class ◽  
Energy Impact ◽  
Particle Hydrodynamics ◽  
Fracture Models ◽  
The Impact

AbstractMain Belt Comets (MBCs) have attracted a great deal of interest since their identification as a new class of bodies by Hsieh and Jewitt in 2006. Much of this interest is due to the implication that MBC activity is driven by the sublimation of volatile material (presumed to be water-ice) presenting these bodies as probable candidates for the delivery of a significant fraction of Earth's water. Results of the studies of the dynamics of MBCs suggest that these objects might have formed in-situ as the remnants of the break-up of large icy asteroids. Simulations also show that collisions among MBCs and small objects could have played an important role in triggering the cometary activity of these bodies. Such collisions might have exposed sub-surface water-ice which sublimated and created thin atmospheres and tails around MBCs. In order to drive the effort of understanding the nature of the activation of MBCs, we have investigated these collision processes by simulating the impacts in detail using a smooth particle hydrodynamics (SPH) approach that includes material strength and fracture models. We have carried out simulations for a range of impact velocities and angles, allowing m-sized impactors to erode enough of an MBC's surface to expose volatiles and trigger its activation. Impact velocities were varied between 0.5 km/s and 5.3 km/s, and the projectile radius was chosen to be 1 m. As expected, we observe significantly different crater depths depending on the impact energy, impact angle, and MBC's material strength. Results show that for all values of impact velocity and angle, crater depths are only a few meters, implying that if the activity of MBCs is due to the sublimation of water-ice, ice has to exist in no deeper than a few meters from the surface. We present details of our simulations and discuss the implications of their results.

scholarly journals Size-resolved characterization of organic aerosol in the North China Plain: new insights from high resolution spectral analysis

2021 ◽  
Author(s):  
Weiqi Xu ◽  
Chun Chen ◽  
Yanmei Qiu ◽  
Conghui Xie ◽  
Yunle Chen ◽  
...  
Keyword(s):  
Radiative Forcing ◽  
North China Plain ◽  
North China ◽  
Fine Particles ◽  
Large Fraction ◽  
Organic Aerosol ◽  
Size Distributions ◽  
The North ◽  
The Impact

Organic aerosol (OA), a large fraction of fine particles, has a large impact on climate radiative forcing and human health, and the impact depends strongly on size distributions. Here we...

The impact of depression on Veterans with PTSD and traumatic brain injury: A diffusion tensor imaging study

2015 ◽  
Vol 105 ◽  
pp. 20-28 ◽  
Author(s):  
Linda Isaac ◽  
Keith L. Main ◽  
Salil Soman ◽  
Ian H. Gotlib ◽  
Ansgar J. Furst ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Diffusion Tensor Imaging ◽  
Brain Injury ◽  
Diffusion Tensor ◽  
Imaging Study ◽  
The Impact ◽  
Diffusion Tensor Imaging Study

scholarly journals Nonsynonymous single nucleotide polymorphisms of NHE3 differentially decrease NHE3 transporter activity

2015 ◽  
Vol 308 (9) ◽  
pp. C758-C766 ◽  
Author(s):  
Xinjun Cindy Zhu ◽  
Rafiquel Sarker ◽  
John R. Horton ◽  
Molee Chakraborty ◽  
Tian-E Chen ◽  
...  
Keyword(s):  
Single Nucleotide Polymorphisms ◽  
Large Fraction ◽  
Regulatory Protein ◽  
Nucleotide Polymorphisms ◽  
Genetic Determinants ◽  
Single Nucleotide ◽  
Mutant Proteins ◽  
Homologous Protein ◽  
Genetic Abnormalities ◽  
The Impact

Genetic determinants appear to play a role in susceptibility to chronic diarrhea, but the genetic abnormalities involved have only been identified in a few conditions. The Na+/H+ exchanger 3 (NHE3) accounts for a large fraction of physiologic intestinal Na+ absorption. It is highly regulated through effects on its intracellular COOH-terminal regulatory domain. The impact of genetic variation in the NHE3 gene, such as single nucleotide polymorphisms (SNPs), on transporter activity remains unexplored. From a total of 458 SNPs identified in the entire NHE3 gene, we identified three nonsynonymous mutations (R474Q, V567M, and R799C), which were all in the protein's intracellular COOH-terminal domain. Here we evaluated whether these SNPs affect NHE3 activity by expressing them in a mammalian cell line that is null for all plasma membrane NHEs. These variants significantly reduced basal NHE3 transporter activity through a reduction in intrinsic NHE3 function in variant R474Q, abnormal trafficking in variant V567M, or defects in both intrinsic NHE3 function and trafficking in variant R799C. In addition, variants NHE3 R474Q and R799C failed to respond to acute dexamethasone stimulation, suggesting cells with these mutant proteins might be defective in NHE3 function during postprandial stimulation and perhaps under stressful conditions. Finally, variant R474Q was shown to exhibit an aberrant interaction with calcineurin B homologous protein (CHP), an NHE3 regulatory protein required for basal NHE3 activity. Taken together, these results demonstrate decreased transport activity in three SNPs of NHE3 and provide mechanistic insight into how these SNPs impact NHE3 function.

scholarly journals ICE PROPULSION ABILITY OF VESSELS WITH NONTRADITIONAL FORM

2020 ◽  
pp. 143-156
Author(s):  
Vasily A. Lobanov
Keyword(s):  
Experimental Data ◽  
Statistical Analysis ◽  
Empirical Equation ◽  
Main Attention ◽  
Resistance Level ◽  
Water Ice ◽  
Ship Hulls ◽  
The Impact ◽  
Ice Resistance ◽  
Different Thickness

In article the fact related to the significant increase in structure of the ice category fleet internal and mixed a river sea operation with non-traditional ship hulls forms is stated. With the CAE technologies use such vessels interaction nature with ice cakes and small ice cakes of different thickness and concentration in the ice channel is studied and analyzed. The main attention is paid to a research concerning the influence of different forms bulbous fore ends on change of the vessel ice resistance level. Qualitative features of such bulbous vessels contact with the water ice environment are noted. The statistical analysis concerning the obtained experimental data on the impact assessment related to constructive, dynamic and ice factors on ice propulsion ability of vessels with non-traditional forms is carried out. The quantitative forecast of such influence in the form of the multifactorial regression empirical equation is given.

scholarly journals Impact of extreme drought and incentive programs on flooded agriculture and wetlands in California’s Central Valley

2018 ◽  
Author(s):  
Matthew E Reiter ◽  
Nathan Elliott ◽  
Dennis Jongsomjit ◽  
Gregory H Golet ◽  
Mark D Reynolds
Keyword(s):  
Surface Water ◽  
Large Fraction ◽  
Central Valley ◽  
Open Water ◽  
Extreme Drought ◽  
Freshwater Wetland ◽  
Post Harvest ◽  
Incentive Programs ◽  
Managed Wetlands ◽  
The Impact

Between 2013 and 2015 a large part of the western United States, including the Central Valley of California, sustained an extreme drought. The Central Valley is recognized as a region of hemispheric importance for waterbirds which use flooded agriculture and wetlands as habitat. Thus, the impact of drought on the distribution of surface water needed to be assessed to understand the effects on waterbird habitat availability. We used satellites to quantify the impact the recent extreme drought on the timing and extent of available waterbird habitat during the non-breeding season (July – May) by examining flooding in agriculture (rice, corn, and other crops) and managed wetlands across the Central Valley. We assessed the influence of habitat incentive programs, particularly The Nature Conservancy’s BirdReturns and the Natural Resources Conservation Service’s Waterbird Habitat Enhancement Program (WHEP), at offsetting waterbird habitat loss related to drought. Overall, we found significant declines in open water in post-harvest agriculture (20 – 80% declines) and in managed wetlands (47 – 59% declines) during the 2013 – 2015 drought compared to non-drought years 2000 – 2011. Crops associated with the San Joaquin Valley, specifically corn, as well as wetlands in that part of the Central Valley exhibited larger reductions in open water than rice and wetlands in the Sacramento Valley. However, seasonal wetlands on protected lands had a marginally significant (P<0.10) higher amount of open water in the drought years than those on non-protected lands. A large fraction of the daily open water in rice during certain times of the year, particularly in the fall for BirdReturns (64%) and the winter for WHEP (100%), may have been provided through incentive programs underscoring the contribution of these programs. However, further assessment is needed to know how much the incentive programs directly offset the impact of drought in post-harvest rice or simply supplemented funding for activities that might have been done regardless. Our, first of its kind, landscape analysis documents the significant impacts of the drought on freshwater wetland habitats in the Central Valley and highlights the value of using satellite data to track surface water and waterbird habitats. More research is needed to understand subsequent impacts on the freshwater dependent species that rely on these systems and how incentive programs can most strategically support vulnerable species during future drought.

scholarly journals ADAPTIVE OPTICS OBSERVATIONS OF 3 μm WATER ICE IN SILHOUETTE DISKS IN THE ORION NEBULA CLUSTER AND M43

2012 ◽  
Vol 144 (6) ◽  
pp. 175 ◽  
Author(s):  
Hiroshi Terada ◽  
Alan T. Tokunaga ◽  
Tae-Soo Pyo ◽  
Yosuke Minowa ◽  
Yutaka Hayano ◽  
...  
Keyword(s):  
Adaptive Optics ◽  
Orion Nebula ◽  
Water Ice

The Impact of Military Spending on Economic Development

2018 ◽  
pp. 182-191
Author(s):  
Saptarshi Chakraborty
Keyword(s):  
Economic Growth ◽  
Causal Effect ◽  
Large Fraction ◽  
Military Spending ◽  
Military Expenditure ◽  
Policy Debate ◽  
External Threats ◽  
The Cost ◽  
The Military ◽  
The Impact

Some countries spend a relatively large percentage of GDP on their militaries in order to preserve or secure their status as global powers. Others do so because they are ruled by military governments or aggressive regimes that pose a military threat to their neighbors or their own populations. It is debatable whether there is a causal relationship between military spending and economic growth in the economy. It is again a policy debate how much to allocate funds for civilian and how much for military expenditure. Under these puzzling results of the impact of military expenditure on economic growth which is frequently found to be non-significant or negative, yet most countries spend a large fraction of their GDP on defense and the military. The chapter tries to investigate the relationship between military spending and economic growth in India. It also sees whether external threats, corruption, and other relevant controls have any causal effect. This chapter obtains that additional expenditure on Indian military in the presence of additional threat is significantly detrimental to growth implying that India cannot afford to fight or demonstrate power at the cost of its development.

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