The active centaur 2020 MK4 C. de la Fuente Marcos; R. de la Fuente Marcos; Licandro, J ...
Astronomy and astrophysics (Berlin),
05/2021, Letnik:
649
Journal Article
Recenzirano
Odprti dostop
Context. Centaurs go around the Sun between the orbits of Jupiter and Neptune. Only a fraction of the known centaurs have been found to display comet-like features. Comet 29P/Schwassmann-Wachmann 1 ...is the most remarkable active centaur. It orbits the Sun just beyond Jupiter in a nearly circular path. Only a handful of known objects follow similar trajectories. Aims. We present photometric observations of 2020 MK4, a recently found centaur with an orbit not too different from that of 29P, and we perform a preliminary exploration of its dynamical evolution. Methods. We analyzed broadband Cousins R and Sloan g′, r′, and i′ images of 2020 MK4 acquired with the Jacobus Kapteyn Telescope and the IAC80 telescope to search for cometary-like activity and to derive its surface colors and size. Its orbital evolution was studied using direct N-body simulations. Results. Centaur 2020 MK4 is neutral-gray in color and has a faint, compact cometary-like coma. The values of its color indexes, (g′− r′) = 0.42 ± 0.04 and (r′− i′) = 0.17 ± 0.04, are similar to the solar ones. A lower limit for the absolute magnitude of the nucleus is Hg = 11.30 ± 0.03 mag which, for an albedo in the range of 0.1–0.04, gives an upper limit for its size in the interval (23, 37) km. Its orbital evolution is very chaotic and 2020 MK4 may be ejected from the Solar System during the next 200 kyr. Comet 29P experienced relatively close flybys with 2020 MK4 in the past, sometimes when they were temporary Jovian satellites. Conclusions. Based on the analysis of visible CCD images of 2020 MK4, we confirm the presence of a coma of material around a central nucleus. Its surface colors place this centaur among the most extreme members of the gray group. Although the past, present, and future dynamical evolution of 2020 MK4 resembles that of 29P, more data are required to confirm or reject a possible connection between the two objects and perhaps others.
Acute myeloid leukaemia (AML) is a haematological malignancy characterized by clonal stem cell proliferation and aberrant block in differentiation. Dysfunction of epigenetic modifiers contributes ...significantly to the pathogenesis of AML. One frequently mutated gene involved in epigenetic modification is DNMT3A (DNA methyltransferase-3-alpha), a DNA methyltransferase that alters gene expression by de novo methylation of cytosine bases at CpG dinucleotides. Approximately 22% of AML and 36% of cytogenetically normal AML cases carry DNMT3A mutations and around 60% of these mutations affect the R882 codon. These mutations have been associated with poor prognosis and adverse survival outcomes for AML patients. Advances in whole-exome sequencing techniques have recently identified a large number of DNMT3A mutations present in clonal cells in normal elderly individuals with no features of haematological malignancy. Categorically distinct from other preleukaemic conditions, this disorder has been termed clonal haematopoiesis of indeterminate potential (CHIP). Further insight into the mutational landscape of CHIP may illustrate the consequence of particular mutations found in DNMT3A and identify specific “founder” mutations responsible for clonal expansion that may contribute to leukaemogenesis. This review will focus on current research and understanding of DNMT3A mutations in both AML and CHIP.
. Objective: The mechanisms of renewal of skin and mucosal epithelia in vivo are associated with hierarchies of stem and amplifying cells organized in distinct spatial patterns. Stem and amplifying ...characteristics persist after isolation and growth of human keratinocytes in vitro but the pattern for murine keratinocytes has been less clear. Materials and Methods: Murine keratinocytes were grown in low calcium media and examined for their patterns of colony morphologies. Results: We consistently identified three types of colonies, one of which contains concentric zones of amplifying and differentiated cells surrounding a central zone of cells that have patterns of expression and behavioural characteristic of stem cells. This zonal organization facilitated analysis of stem cell formation and loss. Cells in the central stem cell zone undergo rapid symmetric divisions but expansion of this population is partially limited by their peripheral transition into amplifying cells. A striking feature of central zone cells is their enhanced apoptotic susceptibility and stem cell expansion limited by consistently high background rates of apoptosis. This occasionally reaches catastrophic levels with elimination of the entire central zone. Conclusion: In vitro amplification of stem cells for the generation of engineered tissue has tended to focus on control of asymmetric division but these findings suggest that development of mechanisms protecting stem cells from apoptotic changes are also likely to be of particular value.
The active centaur 2020 MK 4 de la Fuente Marcos, C.; de la Fuente Marcos, R.; Licandro, J. ...
Astronomy and astrophysics (Berlin),
5/2021, Letnik:
649
Journal Article
Recenzirano
Context.
Centaurs go around the Sun between the orbits of Jupiter and Neptune. Only a fraction of the known centaurs have been found to display comet-like features. Comet 29P/Schwassmann-Wachmann 1 ...is the most remarkable active centaur. It orbits the Sun just beyond Jupiter in a nearly circular path. Only a handful of known objects follow similar trajectories.
Aims.
We present photometric observations of 2020 MK
4
, a recently found centaur with an orbit not too different from that of 29P, and we perform a preliminary exploration of its dynamical evolution.
Methods.
We analyzed broadband Cousins
R
and Sloan
g
′,
r
′, and
i
′ images of 2020 MK
4
acquired with the
Jacobus Kapteyn
Telescope and the IAC80 telescope to search for cometary-like activity and to derive its surface colors and size. Its orbital evolution was studied using direct
N
-body simulations.
Results.
Centaur 2020 MK
4
is neutral-gray in color and has a faint, compact cometary-like coma. The values of its color indexes, (
g
′−
r
′) = 0.42 ± 0.04 and (
r
′−
i
′) = 0.17 ± 0.04, are similar to the solar ones. A lower limit for the absolute magnitude of the nucleus is
H
g
= 11.30 ± 0.03 mag which, for an albedo in the range of 0.1–0.04, gives an upper limit for its size in the interval (23, 37) km. Its orbital evolution is very chaotic and 2020 MK
4
may be ejected from the Solar System during the next 200 kyr. Comet 29P experienced relatively close flybys with 2020 MK
4
in the past, sometimes when they were temporary Jovian satellites.
Conclusions.
Based on the analysis of visible CCD images of 2020 MK
4
, we confirm the presence of a coma of material around a central nucleus. Its surface colors place this centaur among the most extreme members of the gray group. Although the past, present, and future dynamical evolution of 2020 MK
4
resembles that of 29P, more data are required to confirm or reject a possible connection between the two objects and perhaps others.
There is considerable interest in the bioavailability of flavonoids and phenolic components of the diet and their bioactivity in vivo. However, little is known of pre-absorption events in the gastric ...lumen. The effects of the acidic environment, as found in the gastric milieu, on procyanidin oligomers of catechin polyphenols has been investigated. The results show that under these conditions the procyanidin oligomers (trimer to hexamer) are hydrolysed to mixtures of epicatechin monomer and dimer, thus enhancing the potential for their absorption in the small intestine.
Marine seismic surveys are performed to establish and investigate geological structures associated with hydrocarbon deposits in the seabed. Air gun arrays are the most common energy source used in ...marine seismic surveys. These air gun arrays are known to emit a frequency that overlaps with the vocalisation ranges of a number of marine mammals. National and international legislation exists that prohibits the disturbance of marine mammals. In the UK, the Joint Nature Conservation Committee (JNCC) issued a set of guidelines for minimising acoustic disturbance to marine mammals from seismic surveys.
The active centaur 2020 MK4 C de la Fuente Marcos; R de la Fuente Marcos; Licandro, J ...
arXiv.org,
04/2021
Paper, Journal Article
Odprti dostop
Context. Centaurs go around the Sun between the orbits of Jupiter and Neptune. Only a fraction of the known centaurs have been found to display comet-like features. Comet 29P/Schwassmann-Wachmann 1 ...is the most remarkable active centaur. It orbits the Sun just beyond Jupiter in a nearly circular path. Only a handful of known objects follow similar trajectories. Aims. We present photometric observations of 2020 MK4, a recently found centaur with an orbit not too different from that of 29P, and we perform a preliminary exploration of its dynamical evolution. Methods. We analyzed broadband Cousins R and Sloan g', r', and i' images of 2020 MK4 acquired with the Jacobus Kapteyn Telescope and the IAC80 telescope to search for cometary-like activity, and to derive its surface colors and size. Its orbital evolution was studied using direct N-body simulations. Results. Centaur 2020 MK4 is neutral-gray in color and has a faint, compact cometary-like coma. The values of its color indexes, (g'-r')=0.42+/-0.04 and (r'-i')=0.17+/-0.04, are similar to the solar ones. A lower limit for the absolute magnitude of the nucleus is Hg=11.30+/-0.03 mag which, for an albedo in the range of 0.1-0.04, gives an upper limit for its size in the interval (23, 37) km. Its orbital evolution is very chaotic and 2020 MK4 may be ejected from the Solar System during the next 200 kyr. Comet 29P experienced relatively close flybys with 2020 MK4 in the past, sometimes when they were temporary Jovian satellites. Conclusions. We confirm the presence of a coma of material around a central nucleus. Its surface colors place this centaur among the most extreme members of the gray group. Although its past, present, and future dynamical evolution resembles that of 29P, more data are required to confirm or reject a possible connection between the two objects and perhaps others.
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