Can Superflares Occur on Our Sun?

Recent observations of solar type stars with the Kepler satellite by Maehara et al. have revealed the existence of superflares (with energy of 10^33 - 10^35 erg) on Sun-like stars, which are similar to our Sun in their surface temperature (5600 K - 6000 K) and slow rotation (rotational period > 10 days). From the statistical analysis of these superflares, it was found that superflares with energy 10^34 erg occur once in 800 years and superflares with 10^35 erg occur once in 5000 years on Sun-like stars. In this paper, we examine whether superflares with energy of 10^33 - 10^35 erg could occur on the present Sun through the use of simple order-of-magnitude estimates based on current ideas relating to the mechanisms of the solar dynamo.Comment: Accepted by Publ. Astron. Soc. Japan on Dec. 6, 2012 (to be published on PASJ vol. 65, No. 3, (2013) June 25

Scaling of impact fragmentation near the critical point

We investigated two-dimensional brittle fragmentation with a flat impact experimentally, focusing on the low impact energy region near the fragmentation-critical point. We found that the universality class of fragmentation transition disagreed with that of percolation. However, the weighted mean mass of the fragments could be scaled using the pseudo-control parameter multiplicity. The data for highly fragmented samples included a cumulative fragment mass distribution that clearly obeyed a power-law. The exponent of this power-law was 0.5 and it was independent of sample size. The fragment mass distributions in this regime seemed to collapse into a unified scaling function using weighted mean fragment mass scaling. We also examined the behavior of higher order moments of the fragment mass distributions, and obtained multi-scaling exponents that agreed with those of the simple biased cascade model.Comment: 6 pages, 6 figure

Spicule Dynamics over Plage Region

We studied spicular jets over a plage area and derived their dynamic characteristics using Hinode Solar Optical Telescope (SOT) high-resolution images. The target plage region was near the west limb of the solar disk. This location permitted us to study the dynamics of spicular jets without the overlapping effect of spicular structures along the line of sight. In this work, to increase the ease with which we can identify spicules on the disk, we applied the image processing method `MadMax' developed by Koutchmy et al. (1989). It enhances fine, slender structures (like jets), over a diffuse background. We identified 169 spicules over the target plage. This sample permits us to derive statistically reliable results regarding spicular dynamics. The properties of plage spicules can be summarized as follows: (1) In a plage area, we clearly identified spicular jet features. (2) They were shorter in length than the quiet region limb spicules, and followed ballistic motion under constant deceleration. (3) The majority (80%) of the plage spicules showed the cycle of rise and retreat, while 10% of them faded out without a complete retreat phase. (4) The deceleration of the spicule was proportional to the velocity of ejection (i.e. the initial velocity).Comment: 12 pages, 9 figures, accepted for publication in PAS

An interaction between Nrf2 polymorphisms and smoking status affects annual decline in FEV1: a longitudinal retrospective cohort study

<p>Abstract</p> <p>Background</p> <p>An Nrf2-dependent response is a central protective mechanism against oxidative stress. We propose that particular genetic variants of the <it>Nrf2 </it>gene may be associated with a rapid forced expiratory volume in one second (FEV₁) decline induced by cigarette smoking.</p> <p>Methods</p> <p>We conducted a retrospective cohort study of 915 Japanese from a general population. Values of annual decline in FEV₁were computed for each individual using a linear mixed-effect model. Multiple clinical characteristics were assessed to identify associations with annual FEV₁decline. Tag single-nucleotide polymorphisms (SNPs) in the <it>Nrf2 </it>gene (rs2001350, rs6726395, rs1962142, rs2364722) and one functional SNP (rs6721961) in the <it>Nrf2 </it>promoter region were genotyped to assess interactions between the <it>Nrf2 </it>polymorphisms and smoking status on annual FEV₁decline.</p> <p>Results</p> <p>Annual FEV₁decline was associated with smoking behavior and inversely correlated with FEV₁/FVC and FEV₁% predicted. The mean annual FEV₁declines in individuals with rs6726395 G/G, G/A, or A/A were 26.2, 22.3, and 20.8 mL/year, respectively, and differences in these means were statistically significant (p_corr= 0.016). We also found a significant interaction between rs6726395 genotype and smoking status on the FEV₁decline (p for interaction = 0.011). The haplotype rs2001350T/rs6726395A/rs1962142A/rs2364722A/rs6721961T was associated with lower annual decline in FEV₁(p = 0.004).</p> <p>Conclusions</p> <p>This study indicated that an Nrf2-dependent response to exogenous stimuli may affect annual FEV₁decline in the general population. It appears that the genetic influence of <it>Nrf2 </it>is modified by smoking status, suggesting the presence of a gene-environment interaction in accelerated decline in FEV₁.</p

Sour Taste Responses in Mice Lacking PKD Channels

The polycystic kidney disease-like ion channel PKD2L1 and its associated partner PKD1L3 are potential candidates for sour taste receptors. PKD2L1 is expressed in type III taste cells that respond to sour stimuli and genetic elimination of cells expressing PKD2L1 substantially reduces chorda tympani nerve responses to sour taste stimuli. However, the contribution of PKD2L1 and PKD1L3 to sour taste responses remains unclear.We made mice lacking PKD2L1 and/or PKD1L3 gene and investigated whole nerve responses to taste stimuli in the chorda tympani or the glossopharyngeal nerve and taste responses in type III taste cells. In mice lacking PKD2L1 gene, chorda tympani nerve responses to sour, but not sweet, salty, bitter, and umami tastants were reduced by 25–45% compared with those in wild type mice. In contrast, chorda tympani nerve responses in PKD1L3 knock-out mice and glossopharyngeal nerve responses in single- and double-knock-out mice were similar to those in wild type mice. Sour taste responses of type III fungiform taste cells (GAD67-expressing taste cells) were also reduced by 25–45% by elimination of PKD2L1.These findings suggest that PKD2L1 partly contributes to sour taste responses in mice and that receptors other than PKDs would be involved in sour detection