Abstract
KIC 9406652, one of the recently identified IW And-type dwarf novae, is the best target for studying the tilted disk in cataclysmic variable stars. In a previous paper by Kimura et al. ...(2020b, PASJ, 72, 94), we analyzed its Kepler light curves and found that its orbital light curves during the brightening stage were dominated by the reflection effect of the secondary star and varied with the orientation of the tilted disk; the amplitude was maximized at the minimum of the super-orbital signal and the phase of the light maximum shifted to an earlier one with the advance of the super-orbital phase. We argued in that work that this was direct evidence of the retrogradely precessing tilted disk as the secondary star acts like a reflecting object. In order to confirm this interpretation, we have performed numerical modeling of orbital light curves in this paper. We have succeeded in reproducing the main characteristics of the observed orbital light curves by a simple model in which the secondary star is irradiated by the tilted disk. We have also constrained the inclination angle, i, of the binary system and the tilt angle, θ, of the disk purely from photometric considerations. The best-fitting parameter set is found to be i ∼ 45° and $\theta \sim {2{_{.}^{\circ}}0}$, respectively. The orbital inclination thus estimated is consistent with that obtained from the spectroscopic considerations within the uncertainty limit. On the other hand, the tilt angle of the disk could be underestimated by using only the semi-amplitude of super-orbital signals.
Abstract
The prototype dwarf nova SS Cyg unexpectedly exhibited an anomalous event in its light curve in the early few months of 2021 in which regular dwarf nova-type outbursts stopped, and only ...small-amplitude fluctuations occurred. Inspired by this event, we have performed numerical simulations of light curves of SS Cyg by varying mass transfer rates and varying viscosity parameters in the cool disk. We have also studied the effect of gas-stream overflows beyond the outer disk edge in the light curve simulations. We have confirmed that the enhanced mass transfer is not likely to be responsible for the 2021 anomalous event or its forerunner. We have found that the enhancement of the viscosity in the disk may reproduce the forerunner of that event but may not be sufficient to explain the 2021 anomalous event, although the latter result might be particular to the thermal equilibrium curve we used. Within our simulations, a model of the gas-stream overflow with a slightly higher mass transfer rate than that of our standard model reproduces light curves similar to the 2021 anomalous event. We suggest that the gas-stream overflow is necessary to reproduce that event. The gas-stream overflow may also be responsible for the abnormally high X-ray flux during the normal quiescent state in SS Cyg.
Alternative splicing of pre‐mRNAs can regulate gene expression levels by coupling with nonsense‐mediated mRNA decay (NMD). In order to elucidate a repertoire of mRNAs regulated by alternative ...splicing coupled with NMD (AS‐NMD) in an organism, we performed long‐read RNA sequencing of poly(A)+ RNAs from an NMD‐deficient mutant strain of Caenorhabditis elegans, and obtained full‐length sequences for mRNA isoforms from 259 high‐confidence AS‐NMD genes. Among them are the S‐adenosyl‐L‐methionine (SAM) synthetase (sams) genes sams‐3 and sams‐4. SAM synthetase activity autoregulates sams gene expression through AS‐NMD in a negative feedback loop. We furthermore find that METT‐10, the orthologue of human U6 snRNA methyltransferase METTL16, is required for the splicing regulation in␣vivo, and specifically methylates the invariant AG dinucleotide at the distal 3′ splice site (3′SS) in␣vitro. Direct RNA sequencing coupled with machine learning confirms m6A modification of endogenous sams mRNAs. Overall, these results indicate that homeostasis of SAM synthetase in C. elegans is maintained by alternative splicing regulation through m6A modification at the 3′SS of the sams genes.
SYNOPSIS
Alternative splicing (AS) of pre‐mRNAs can regulate gene expression levels by coupling with nonsense‐mediated mRNA decay (NMD). Here, assessment of the organismal substrate repertoire of this process reveals SAM synthetase (sams) gene expression regulation via m6A modification in C. elegans.
Long‐read sequencing of poly(A)+ RNAs from an NMD‐deficient mutant strain reveals 259 high‐confidence AS‐NMD genes, including the SAM synthetase (sams) genes.
SAMS activity negatively autoregulates AS‐NMD of the sams genes in␣vivo.
Direct RNA sequencing coupled with machine learning reveals m6A modification of endogenous sams mRNAs at the distal 3′ splice sites.
Methyltransferase METT‐10 catalyzes m6A modification specifically at the distal 3′ splice site of sams pre‐mRNA in␣vitro.
METT‐10 regulates alternative splicing of the sams genes in␣vivo.
Full‐length sequences of natural NMD isoforms in C. elegans are elucidated by direct RNA sequencing. SAM synthetase homeostasis is regulated via pre‐mRNA splicing of the sams genes through m6A modification at the invariant AG of the distal 3′SS.
Abstract
KIC 9406652 is a cataclysmic variable, sub-classified as an “IW And-type” star, which shows repeated standstills with oscillatory variations terminated by brightening. This system shows ...negative superhumps, semi-periodic variations having periods slightly shorter than the ∼6 hr orbital period, and super-orbital signals having ∼4 d periods, both of which are believed to originate from a precessing, tilted accretion disk. We have re-examined its Kepler light curve over 1500 d. In accordance with a cycle of IW And-type light variation, the frequency of negative superhumps showed reproducible variation: a rapid drop during the brightening and a gradual increase during the standstill. This is interpreted as a drastic change in the radial mass distribution and the expansion of the tilted disk, which is not expected from the existing models of IW And stars. The constancy in flux amplitudes of the negative superhumps confirms that their light source is the bright spot sweeping across the surface of the tilted disk. The frequencies of the negative superhumps and super-orbital signals varied in unison on long timescales, suggesting their common origin: the tilted disk. The orbital signals at the brightening were dominated by the irradiation of the secondary star and varied with the orientation of the tilted disk; the amplitude was maximized at the minimum of the super-orbital signals, and the light maximum shifted to early orbital phases as the super-orbital phase advanced. This is the first direct evidence that the disk is tilted out of the binary orbital plane and is retrogradely precessing. The tilt angle of the disk inferred from semi-amplitudes of super-orbital signals was lower than 3°. The diversity in light curves of the negative superhumps supports this and suggests that part of the gas stream overflows the disk edge. This study thus offers rich information about the tilted disk in cataclysmic variables.
Abstract
IW And stars are a subgroup of dwarf novae characterized by repetition of the intermediate brightness state with oscillatory variations terminated by brightening. This group of dwarf novae ...is also known to exhibit a wide variety even within one system in long-term light curves, including the usual dwarf-nova outbursts, Z Cam-type standstills, and so on, besides the typical IW And-type variations mentioned above. Following recent observations suggesting that some IW And stars seem to have tilted disks, we have investigated how the thermal-viscous instability works in tilted accretion disks in dwarf novae and whether it could reproduce the essential features of the light curves in IW And stars. By adopting various simplifying assumptions for tilted disks, we have performed time-dependent one-dimensional numerical simulations of a viscous disk by taking into account various mass supply patterns to the disk; that is, the gas stream from the secondary star flows not only to the outer edge of the disk but also to the inner portions of the disk. We find that tilted disks can achieve a new kind of accretion cycle, in which the inner disk almost always stays in the hot state while the outer disk repeats outbursts, thereby reproducing alternating mid-brightness intervals with dips and brightening, which are quite reminiscent of the most characteristic observational light variations of IW And stars. Further, we have found that our simulations produce diverse light variations, depending on different mass supply patterns even without time variations in mass transfer rates. This could explain the wide variety in long-term light curves of IW And stars.
Abstract
We present timing and spectral analysis results of the NICER and NuSTAR observations of the dwarf nova MASTER OT J030227.28+191754.5 during the 2021–2022 outburst. The soft X-ray component ...was found to be dominated by blackbody radiation with a temperature of ∼30 eV and also showed prominent oxygen and neon emission lines. The blackbody luminosity exceeded 10
34
erg s
−1
, which is consistent with theoretical predictions, and then decreased more than an order of magnitude in 3.5 days. The inferred abundances of oxygen and neon in the optically thin coronal region surrounding the central white dwarf (WD) are several times higher than the respective solar values. Although inconclusive, the abundance enrichment may originate from the WD, indicating that it may be mainly composed of oxygen and neon. Assuming that the blackbody radiation comes from the belt-shaped boundary layer between the WD and the accretion disk, we estimated the WD radius to be (2.9 ± 1.1) × 10
8
cm, which corresponds to the WD mass range of 1.15–1.34
M
⊙
. If the accretion continues for another ∼1 Gyr, the WD may experience an accretion-induced collapse into a neutron star and form a so-called black widow pulsar system.
In the present study, for the discovery of uncharacterized glycan-binding receptors or lectin-like receptors in plants, we developed neoglycopolymers to which three types of N-glycopeptides are ...conjugated; the first with plant complex type N-glycan (M3FX), the second with high-mannose type N-glycan (M8), and the third with animal complex type N-glycan (NeuAc2Gal2GN2M3). Three types of Asn-oligosaccharide (Asn-M3FX, Asn-M8, or Asn-NeuAc2Gal2GN2M3) were prepared from storage glycoproteins of Ginkgo biloba seeds, Vigna angularis seeds, and egg yolk glycopeptides from actinase digests of each glycoproteins or glycopeptide. Neoglycopolymers were synthesized such that the α-amino groups of Asn-oligosaccharide were coupled to the carboxyl groups of poly-γ-L-glutamic acid (γ-L-PGA) with 4-(4,6-Dimethoxy-1,3,5-triazin-2-yl)-4-methylmorpholinium chloride n-hydrate (DMT-MM). The resulting neoglycopolymers were purified through a combination of gel-filtration and reverse-phase HPLC. The incorporation of N-glycans into γ-L-PGA (mol%) was estimated through amino acid composition analysis after acid hydrolysis. The incorporation rates of Asn-M3FX, Asn-M8, and Asn-NeuAc2Gal2GN2M3 into γ-L-PGA were 15.4%, 8.6%, and 11.1%, indicating that nearly 890, 500, and 640 molecules of N-glycans were conjugated with γ-L-PGA, respectively. Furthermore, we confirmed that the neoglycopolymer carrying the multivalent high-mannose type N-glycans is a useful tool for rapid purification of mannose-binding protein, Concanavalin A, from jack bean extract.
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•Stachyose treatment prevented allergic diarrhea.•Raffinose and stachyose suppressed the degranulation of intestinal mast cells.•The proportion of CD4+CD25+ T cells increased in ...stachyose-treated mice.•Increasing in B. fragilis of intestinal microbiota is related with the preventing food allergy.
Food allergy is a refractory condition for which there are no standard effective therapies. Prebiotic supplementation such as oligosaccharides in infants was found to be associated with decreased risk of allergic diseases. Raffinose and stachyose are the major oligosaccharides identified in beans; these oligosaccharides have properties of regulating homeostasis. In this study, we explored the use of oligosaccharides as a means to prevent food allergy using an ovalbumin (OVA) sensitization and challenge model in which reductions in body temperature and diarrhea were evaluated. Raffinose and stachyose were administered ad libitum in drinking water for five weeks from one week prior the first sensitization through the final oral administration of OVA. Among our findings, treatment with stachyose suppressed allergic diarrhea and prevented elevations in OVA-specific immunoglobulin (Ig)G1. We hypothesize that suppression of these responses was associated with the actions of regulatory T cells and promoted by utilization of the oligosaccharides by intestinal microbiota. Taken together, our findings suggest that daily ingestion of oligosaccharides might be effective for the prevention of food allergy.
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