Evolution of Rotating Accreting White Dwarfs and the Diversity of Type Ia Supernovae

Type Ia supernovae (SNe Ia) have relatively uniform light curves and spectral evolution, which make SNe Ia useful standard candles to determine cosmological parameters. However, the peak brightness is not completely uniform, and the origin of the diversity has not been clear. We examine whether the rotation of progenitor white dwarfs (WDs) can be the important source of the diversity of the brightness of SNe Ia. We calculate the structure of rotating WDs with an axisymmetric hydrostatic code. The diversity of the mass induced by the rotation is ~0.08 Msun and is not enough to explain the diversity of luminosity. However, we found the following relation between the initial mass of the WDs and their final state; i.e., a WD of smaller initial mass will rotate more rapidly before the supernova explosion than that of larger initial mass. This result might explain the dependence of SNe Ia on their host galaxies.Comment: 7 pages, 6 figure

Extended x-ray-absorption fine-structure studies of heat-treated fcc-Fe_50Cu_50 powders processed via high-energy ball milling

The local structure and chemistry of a ferromagnetic fcc-Fe_50Cu_50 solid solution obtained through high-energy ball milling were measured before and after heat-treatment-induced decomposition using extended x-ray-absorption fine-structure measurements. The decomposition is first evident with the phase separation of a-Fe after a heat treatment at 523 K. Analysis of the residual fee component revealed that the Fe atoms were predominantly surrounded by other Fe atoms, suggesting that the Fe has coalesced within the fee structure. The Fe atoms within the fee phase likely exist in low-spin clusters which provide an explanation for the reduced values of low-temperature magnetization previously measured in annealed samples [P. Crespo et aZ., Phys. Rev. B 48, 7134 (1993)]

Type Ia Supernovae: Progenitors and Diversities

A key question for supernova cosmology is whether the peak luminosities of Type Ia supernovae (SNe Ia) are sufficiently free from the effects of cosmic and galactic evolution. To answer this question, we review the currently popular scenario of SN Ia progenitors, i.e., the single degenerate scenario for the Chandrasekhar mass white dwarf (WD) models. We identify the progenitor's evolution with two channels: (1) the WD+RG (red-giant) and (2) the WD+MS (near main-sequence He-rich star) channels. The strong wind from accreting WDs plays a key role, which yields important age and metallicity effects on the evolution. We suggest that the variation of the carbon mass fraction $X$(C) in the C+O WD (or the variation of the initial WD mass) causes the diversity of SN Ia brightness. This model can explain the observed dependence of SNe Ia brightness on the galaxy types. We then predict how SN Ia brightness evolves along the redshift (with changing metallicity and age) for elliptical and spiral galaxies. Such evolutionary effects along the redshift can be corrected as has been made for local SNe Ia. We also touch on several related issues: (1) the abundance pattern of stars in dwarf spheroidal galaxies in relation to the metallicity effect on SNe Ia, (2) effects of angular momentum brought into the WD in relation to the diversities and the fate of double degenerates, and (3) possible presence of helium in the peculiar SN Ia 2000cx in relation to the sub-Chandrasekhar mass model.Comment: 13 pages. Invited Review published in "From Twilight to Highlight: The Physics of Supernovae," eds. W. Hillebrandt & B. Leibundgut, ESO/Springer Series "ESO Astrophysics Symposia" (Berlin: Springer) p.115--127 (2003

Polymorphisms in pattern recognition receptors and their relationship to infectious disease susceptibility in pigs

<p>Abstract</p> <p>Background</p> <p>Pattern recognition receptors (PRRs), including Toll-like receptors (TLRs), are censoring receptors for molecules derived from bacteria, viruses, and fungi. The PRR system is a prerequisite for proper responses to pathogens, for example by cytokine production, resulting in pathogen eradication. Many cases of polymorphisms in PRR genes affecting the immune response and disease susceptibility are known in humans and mice.</p> <p>Methods</p> <p>We surveyed polymorphisms in pig genes encoding PRRs and investigated the relationship between some of the detected polymorphisms and molecular function or disease onset.</p> <p>Results</p> <p>Nonsynonymous polymorphisms abounded in pig TLR genes, particularly in the region corresponding to the ectodomains of TLRs expressed on the cell surface. Intracellular TLRs such as TLR3, TLR7, and TLR8, and other intracellular PRRs, such as the peptidoglycan receptor NOD2 and viral RNA receptors RIG-I and MDA5, also possessed nonsynonymous polymorphisms. Several of the polymorphisms influenced molecular functions such as ligand recognition. Polymorphisms in the PRR genes may be related to disease susceptibility in pigs: pigs with a particular allele of <it>TLR2</it> showed an increased tendency to contract pneumonia.</p> <p>Conclusions</p> <p>We propose the possibility of pig breeding aimed at disease resistance by the selection of PRR gene alleles that affect pathogen recognition.</p

Subaru and Keck Observations of the Peculiar Type Ia Supernova 2006gz at Late Phases

Recently, a few peculiar Type Ia supernovae (SNe) that show exceptionally large peak luminosity have been discovered. Their luminosity requires more than 1 Msun of 56Ni ejected during the explosion, suggesting that they might have originated from super-Chandrasekhar mass white dwarfs. However, the nature of these objects is not yet well understood. In particular, no data have been taken at late phases, about one year after the explosion. We report on Subaru and Keck optical spectroscopic and photometric observations of the SN Ia 2006gz, which had been classified as being one of these "overluminous" SNe Ia. The late-time behavior is distinctly different from that of normal SNe Ia, reinforcing the argument that SN 2006gz belongs to a different subclass than normal SNe Ia. However, the peculiar features found at late times are not readily connected to a large amount of 56Ni; the SN is faint, and it lacks [Fe II] and [Fe III] emission. If the bulk of the radioactive energy escapes the SN ejecta as visual light, as is the case in normal SNe Ia, the mass of 56Ni does not exceed ~ 0.3 Msun. We discuss several possibilities to remedy the problem. With the limited observations, however, we are unable to conclusively identify which process is responsible. An interesting possibility is that the bulk of the emission might be shifted to longer wavelengths, unlike the case in other SNe Ia, which might be related to dense C-rich regions as indicated by the early-phase data. Alternatively, it might be the case that SN 2006gz, though peculiar, was actually not substantially overluminous at early times.Comment: 8 pages, 6 figures, 4 tables. Accepted for publication in The Astrophysical Journa

Formation and Degradation of Beta-casomorphins in Dairy Processing

Milk proteins including casein are sources of peptides with bioactivity. One of these peptides is beta-casomorphin (BCM) which belongs to a group of opioid peptides formed from b-casein variants. Beta-casomorphin 7 (BCM7) has been demonstrated to be enzymatically released from the A1 or B b-casein variant. Epidemiological evidence suggests the peptide BCM 7 is a risk factor for development of human diseases, including increased risk of type 1 diabetes and cardiovascular diseases but this has not been thoroughly substantiated by research studies. High performance liquid chromatography coupled to UV-Vis and mass spectrometry detection as well as enzyme–linked immunosorbent assay (ELISA) has been used to analyze BCMs in dairy products. BCMs have been detected in raw cow’s milk and human milk and a variety of commercial cheeses, but their presence has yet to be confirmed in commercial yoghurts. The finding that BCMs are present in cheese suggests they could also form in yoghurt, but be degraded during yoghurt processing. Whether BCMs do form in yoghurt and the amount of BCM forming or degrading at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process used, but it remains an intriguing unknown