NCBI's Conserved Domain Database (CDD) is a resource for the annotation of protein sequences with the location of conserved domain footprints, and functional sites inferred from these footprints. CDD ...includes manually curated domain models that make use of protein 3D structure to refine domain models and provide insights into sequence/structure/function relationships. Manually curated models are organized hierarchically if they describe domain families that are clearly related by common descent. As CDD also imports domain family models from a variety of external sources, it is a partially redundant collection. To simplify protein annotation, redundant models and models describing homologous families are clustered into superfamilies. By default, domain footprints are annotated with the corresponding superfamily designation, on top of which specific annotation may indicate high-confidence assignment of family membership. Pre-computed domain annotation is available for proteins in the Entrez/Protein dataset, and a novel interface, Batch CD-Search, allows the computation and download of annotation for large sets of protein queries. CDD can be accessed via http://www.ncbi.nlm.nih.gov/Structure/cdd/cdd.shtml.
The technique of mutual approximations accurately gives the central instant of the maximum apparent approximation of two moving natural satellites in the plane of the sky. This can be used in ...ephemeris fitting to infer the relative positions of satellites with high precision. Only mutual phenomena-occultations and eclipses-can achieve better results. However, mutual phenomena only occur every six years in the case of Jupiter. Mutual approximations do not have this restriction and can be observed at any time in the year as long as the satellites are visible. In this work, we present 104 central instants determined from the observations of 66 mutual approximations between the Galilean moons carried out at different sites in Brazil and France during the period 2016-2018. For 28 events, we have at least two independent observations. All telescopes were equipped with a narrow-band filter centred at 889 nm with a width of 15 nm to eliminate the scattered light from Jupiter. The telescope apertures ranged between 25 and 120 cm. For comparison, the precision of the positions obtained with classical CCD astrometry is about 100 mas, for mutual phenomena it can be 10 mas or less, and the average internal precision obtained with mutual approximations is 11.3 mas. This new type of simple, yet accurate, observations can significantly improve the orbits and ephemeris of Galilean satellites and thus it can be very useful for the planning of future space missions to the Jovian system.
The Conserved Domain Database (CDD) is the protein classification component of NCBI's Entrez query and retrieval system. CDD is linked to other Entrez databases such as Proteins, Taxonomy and ...PubMed®, and can be accessed at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=cdd. CD-Search, which is available at http://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi, is a fast, interactive tool to identify conserved domains in new protein sequences. CD-Search results for protein sequences in Entrez are pre-computed to provide links between proteins and domain models, and computational annotation visible upon request. Protein–protein queries submitted to NCBI's BLAST search service at http://www.ncbi.nlm.nih.gov/BLAST are scanned for the presence of conserved domains by default. While CDD started out as essentially a mirror of publicly available domain alignment collections, such as SMART, Pfam and COG, we have continued an effort to update, and in some cases replace these models with domain hierarchies curated at the NCBI. Here, we report on the progress of the curation effort and associated improvements in the functionality of the CDD information retrieval system.
Samples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed 17 Ryugu samples measuring 1 to 8 millimeters. Carbon dioxide–bearing water inclusions are ...present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and calcium- and aluminum-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed through aqueous alteration reactions at low temperature, high pH, and water/rock ratios of <1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate that Ryugu’s parent body formed ~2 million years after the beginning of Solar System formation.
INTRODUCTION
Observations of asteroid Ryugu by the Hayabusa2 spacecraft found that it is a rubble pile, formed from fragments of a parent asteroid. Samples retrieved from Ryugu by the spacecraft were expected to contain a record of this history, including the formation and early evolution of the parent body, the subsequent impact destruction and partial reaccretion, and later space weathering. The composition of Ryugu was expected to be similar to that of Ivuna-type carbonaceous chondrite meteorites (CI chondrites).
RATIONALE
We investigated the formation history of Ryugu through laboratory analysis of the samples. Specifically, we sought to determine (i) when and where in the Solar System the parent asteroid formed; (ii) the original mineralogy, elemental abundances as a whole, and chemical compositions of the accreted materials, including their ice content; (iii) how these materials evolved through chemical reactions; and (iv) how the material was ejected from the parent body in an impact. To address these issues, we analyzed 17 Ryugu particles of 1 to ~8 mm in size.
RESULTS
We found carbon dioxide (CO
2
)–bearing water in an iron-nickel (Fe–Ni) sulfide crystal, indicating that the parent body formed in the outer Solar System. Remanent magnetization was detected, implying that the solar nebula might still have been present when magnetite crystals formed on the parent body.
We used muon analysis to determine the abundances of light elements, including carbon (C), nitrogen (N), sodium (Na), and magnesium (Mg), whose abundances relative to silicon (Si) are similar to those in CI chondrites, whereas oxygen (O) is deficient compared with that in CI chondrites. X-ray computed tomography analysis shows that all our Ryugu samples consist of fine-grained material. There are only rare objects of high-temperature origin, such as melted silicate-rich particles, all being smaller than 100 μm.
Electron microscope observations showed that the samples are breccias, assemblies of numerous small rock fragments with different compositions, mineralogies, and histories. The most common mineralogy contains Mg-rich hydrous silicates, MgCa and MgFe carbonates, hydroxyapatite, Fe sulfides, and Fe oxides. The mineralogy of this major lithology is consistent with classification as a CI chondrite. It also indicates widespread aqueous alteration (reactions with liquid water) on the parent body.
Some Ryugu fragments have a different mineralogy, containing anhydrous silicates (olivine and pyroxene), amorphous silicates, Ca carbonate, phosphides, Fe–Ni sulfide, Fe oxide, and poorly crystalline phyllosilicates. Some small objects (<~30 μm) that formed at high temperatures were also found. This mineralogy suggests that these fragments experienced less aqueous alteration.
We measured mechanical and thermal properties from the Ryugu samples. We found that they are similar, but not identical, to hydrated CI chondrites. Numerical simulations of the thermal history and impact disruption processes of the Ryugu parent asteroid were performed by incorporating the physical and mineralogical properties and appropriate water/rock ratios.
CONCLUSION
We propose that Ryugu’s parent asteroid formed ~1.8 million to 2.9 million years after the beginning of Solar System formation, in the outer Solar System, where water and CO
2
were present as ice. It acquired a water ice/rock mass ratio in the range of 0.2 to 0.9. In this region, material formed at low temperatures is dominant, whereas material of high temperature origin is rare. In the interior of the parent asteroid, radioactive heating caused the water ice to melt at ~3 million years; water-rock reactions then gradually changed the initial anhydrous mineralogy to a largely hydrous mineralogy. At shallow depths, the original material was less altered, at a low water/rock ratio of <0.2. At ~5 million years, all material in the parent asteroid experienced its peak temperature, and aqueous alteration continued. An impact occurred ~1 billion years ago, disrupting the parent asteroid. Some fragments, originating away from the impact point, then reassembled to form Ryugu.
Proposed model of Ryugu’s formation history.
(1) A parent body asteroid forms in the outer Solar System, containing abundant ice. (2 and 3) Radioactive heating causes the ice to melt, which modifies the mineralogy through aqueous alteration reactions. (4 and 5) An impact then disrupts the parent body but does not cause widespread heating. (6) Ryugu formed from reaccumulation of ejected material that originated away from the impact point. All times were measured from the start of Solar System formation. Colors indicate estimated temperatures from our thermal interior and impact models.
The Conserved Domain Database (CDD) is now indexed as a separate database within the Entrez system and linked to other Entrez databases such as MEDLINE®. This allows users to search for domain types ...by name, for example, or to view the domain architecture of any protein in Entrez's sequence database. CDD can be accessed on the WorldWideWeb at http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=cdd. Users may also employ the CD-Search service to identify conserved domains in new sequences, at http://www.ncbi.nlm.nih.gov/Structure/cdd/wrpsb.cgi. CD-Search results, and pre-computed links from Entrez's protein database, are calculated using the RPS-BLAST algorithm and Position Specific Score Matrices (PSSMs) derived from CDD alignments. CD-Searches are also run by default for protein–protein queries submitted to BLAST® at http://www.ncbi.nlm.nih.gov/BLAST. CDD mirrors the publicly available domain alignment collections SMART and PFAM, and now also contains alignment models curated at NCBI. Structure information is used to identify the core substructure likely to be present in all family members, and to produce sequence alignments consistent with structure conservation. This alignment model allows NCBI curators to annotate ‘columns’ corresponding to functional sites conserved among family members.
Context.
The Centaur (10199) Chariklo has the first ring system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow sizes and shapes ...to be determined with kilometre accuracy, and provide the characteristics of the occulting object and its vicinity.
Aims.
Using stellar occultations observed between 2017 and 2020, our aim is to constrain the physical parameters of Chariklo and its rings. We also determine the structure of the rings, and obtain precise astrometrical positions of Chariklo.
Methods.
We predicted and organised several observational campaigns of stellar occultations by Chariklo. Occultation light curves were measured from the datasets, from which ingress and egress times, and the ring widths and opacity values were obtained. These measurements, combined with results from previous works, allow us to obtain significant constraints on Chariklo’s shape and ring structure.
Results.
We characterise Chariklo’s ring system (C1R and C2R), and obtain radii and pole orientations that are consistent with, but more accurate than, results from previous occultations. We confirm the detection of W-shaped structures within C1R and an evident variation in radial width. The observed width ranges between 4.8 and 9.1 km with a mean value of 6.5 km. One dual observation (visible and red) does not reveal any differences in the C1R opacity profiles, indicating a ring particle size larger than a few microns. The C1R ring eccentricity is found to be smaller than 0.022 (3
σ
), and its width variations may indicate an eccentricity higher than ~0.005. We fit a tri-axial shape to Chariklo’s detections over 11 occultations, and determine that Chariklo is consistent with an ellipsoid with semi-axes of 143.8
−1.5
+1.4
, 135.2
−2.8
+1.4
, and 99.1
−2.7
+5.4
km. Ultimately, we provided seven astrometric positions at a milliarcsecond accuracy level, based on
Gaia
EDR3, and use it to improve Chariklo’s ephemeris.
Six existing minimally invasive techniques for the treatment of primary and secondary malignant hepatic tumors--radio-frequency ablation, microwave ablation, laser ablation, cryoablation, ethanol ...ablation, and chemoembolization--are reviewed and debated by noted authorities from six institutions from around the world. All of the authors currently believe that surgery remains the treatment of choice for patients with resectable hepatic tumors. However, the clinical results of each of the minimally invasive techniques presented have exceeded those obtained with conventional chemotherapy or radiation therapy. Thus, for nonsurgical patients, these techniques are becoming standard independent or adjuvant therapies. In addition, with continued improvement in technology and increasing clinical experience, one or more of these minimally invasive techniques may soon challenge surgical resection as the treatment of choice for patients with limited hepatic tumor.
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