5,980 research outputs found
The progenitors of Type Ia supernovae with long delay times
The nature of the progenitors of Type Ia supernovae (SNe Ia) is still
unclear. In this paper, by considering the effect of the instability of
accretion disk on the evolution of white dwarf (WD) binaries, we performed
binary evolution calculations for about 2400 close WD binaries, in which a
carbon--oxygen WD accretes material from a main-sequence star or a slightly
evolved subgiant star (WD + MS channel), or a red-giant star (WD + RG channel)
to increase its mass to the Chandrasekhar (Ch) mass limit. According to these
calculations, we mapped out the initial parameters for SNe Ia in the orbital
period--secondary mass () plane for various WD
masses for these two channels, respectively. We confirm that WDs in the WD + MS
channel with a mass as low as can accrete efficiently and reach
the Ch limit, while the lowest WD mass for the WD + RG channel is . We have implemented these results in a binary population synthesis
study to obtain the SN Ia birthrates and the evolution of SN Ia birthrates with
time for both a constant star formation rate and a single starburst. We find
that the Galactic SN Ia birthrate from the WD + MS channel is according to our standard model, which is higher than
previous results. However, similar to previous studies, the birthrate from the
WD + RG channel is still low (). We also
find that about one third of SNe Ia from the WD + MS channel and all SNe Ia
from the WD + RG channel can contribute to the old populations (\ga1 Gyr) of
SN Ia progenitors.Comment: 11 pages, 9 figures, 1 table, accepted for publication in MNRA
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Tissue factor in tumor microenvironment: a systematic review
The aberrant hemostasis is a common manifestation of cancer, and venous thromboembolism (VTE) is the second leading cause of cancer patients’ mortality. Tissue factor (TF), comprising of a 47-kDa transmembrane protein that presents in subendothelial tissues and leukocytes and a soluble isoform, have distinct roles in the initiation of extrinsic coagulation cascade and thrombosis. Laboratory and clinical evidence showed the deviant expression of TF in several cancer systems and its tumor-promoting effects. TF contributes to myeloid cell recruitment in tumor stroma, thereby remodeling of tumor microenvironment. Additionally, the number of TF-positive-microparticles (TF+MP) from tumor origins correlates with the VTE rates in cancer patients. In this review, we summarize our current understanding of the TF regulation and roles in tumor progression and clinical complications
Deterministic versus probabilistic quantum information masking
We investigate quantum information masking for arbitrary dimensional quantum
states. We show that mutually orthogonal quantum states can always be served
for deterministic masking of quantum information. We further construct a
probabilistic masking machine for linearly independent states. It is shown that
a set of d dimensional states, , , can be probabilistically masked by a general
unitary-reduction operation if they are linearly independent. The maximal
successful probability of probabilistic masking is analyzed and derived for the
case of two initial states.Comment: 5 pages, 1 figure
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