New discovery of the oldest maize weevils in the world from Jomon potteries, Japan

The maize weevil (_Sitophilus zeamais_) and rice weevil (_Sitophilus oryzae_) are two of the most damaging insects for stored grains, and are characteristic species of ancient Japan. Both species and the granary weevil (_Sitophilus granarius_) are common elsewhere in the world, but the natural distribution of maize and rice weevils is restricted to the Old World^1^. Japanese archaeological records contain a few maize weevil fossils after the Middle Yayoi period (ca. 2000 aBP)^2^. However, since evidence of weevils was discovered as impressions in Jomon potsherds in 2004^3^, many weevil impressions have been found. The oldest is from the Late Jomon (ca. 4000 to 3200 aBP). These findings and other archaeological evidence suggest that the maize weevil invaded Japan from Korea, accompanying the spread of rice cultivation^4^. However, in 2010 we discovered older weevil impressions dating to ca. 9000 aBP. These specimens are the oldest harmful insects discovered from archaeological sites around the world. The new discovery is valuable for future entomological research because such specimens are absent from the fossil record. It is also archaeologically and culturally interesting because this provides evidence of harmful insects living in Jomon villages. However, the new discovery raises the question of what these weevils infested: did cereal cultivation exist 9000 years ago? We have no persuasive answer, but hope one will be provided by future interdisciplinary collaborations among geneticists, entomologists, and archaeologists

Global boundedness of solutions to a parabolic-parabolic chemotaxis system with local sensing in higher dimensions

This paper deals with classical solutions to the parabolic-parabolic system \begin{align*} \begin{cases} u_t=\Delta (\gamma (v) u ) &\mathrm{in}\ \Omega\times(0,\infty), \\[1mm] v_t=\Delta v - v + u &\mathrm{in}\ \Omega\times(0,\infty), \\[1mm] \displaystyle \frac{\partial u}{\partial \nu} = \frac{\partial v}{\partial \nu} = 0 &\mathrm{on}\ \partial\Omega \times (0,\infty), \\[1mm] u(\cdot,0)=u_0, \ v(\cdot,0)=v_0 &\mathrm{in}\ \Omega, \end{cases} \end{align*} where $\Omega$ is a smooth bounded domain in $\mathbf{R}^n$($n \geq 3$), $\gamma (v)=v^{-k}$ ($k>0$) and the initial data $(u_0,v_0)$ is positive and regular. This system has striking features similar to those of the logarithmic Keller--Segel system. It is established that classical solutions of the system exist globally in time and remain uniformly bounded in time if $k \in (0,n/(n-2))$, independently the magnitude of mass. This constant $n/(n-2)$ is conjectured as the optimal range guaranteeing global existence and boundedness in the corresponding logarithmic Keller--Segel system. We will derive sufficient estimates for solutions through some single evolution equation that some auxiliary function satisfies. The cornerstone of the analysis is the refined comparison estimate for solutions, which enables us to control the nonlinearity of the auxiliary equation

Muonium addition reactions in the gas phase: Quantum tunneling in Mu + C2H4 and Mu + C2D4

Copyright © 1990 American Institute of Physics.The reaction kinetics for the addition of the muonium (Mu=μ+e−) atom to C2H4 and C2D4 have been measured over the temperature range 150–500 K at (N2) moderator pressures near 1 atm. A factor of about 8 variation in moderator pressure was carried out for C2H4, with no significant change seen in the apparent rate constant kapp, which is therefore taken to be at the high pressure limit, yielding the bimolecular rate constant kMu for the addition step. This is also expected from the nature of the μSR technique employed, which, in favorable cases, gives kapp=kMu at any pressure. Comparisons with the H atom data of Lightfoot and Pilling, and Sugawara et al. and the D atom data of Sugawara et al. reveal large isotope effects. Only at the highest temperatures, near 500 K, is kMu/kH given by its classical value of 2.9, from the mean velocity dependence of the collision rate but at the lowest temperatures kMu/kH≳30/1 is seen, reflecting the pronounced tunneling of the much lighter Mu atom (mμ=1/9 mp). The present Mu results should provide accurate tests of reaction theories on currently available ab initio surfaces.NSERC (Canada), the Canada Council for their awarding of a Killam Research Fellowship and the Meson Science Institute, Faculty of Science, University of Tokyo

Weak Solutions to a Parabolic-Elliptic System of Chemotaxis

AbstractWe study a parabolic-elliptic system of partial differential equations, which describes the chemotactic feature of slime molds. It is known that the blowup solution forms singularities such as delta functions, referred to as the collapses. Here, we study the case that the domain is a flat torus and show that the post-blowup continuation of the solution is possible only when those collapses are quantized with the mass 8π

Asymptotic behavior of type I blowup solutions to a parabolic-elliptic system of drift-diffusion type

A Cauchy problem for a parabolic-elliptic system of drift-di usion type is considered. The problem is formally of the form Ut = r (rU Ur( ) 1U): This system describes a mass-conserving aggregation phenomenon including gravitational collapse and bacterial chemotaxis. Our concern is the asymptotic behavior of blowup solutions when the blowup is type I in the sense that its blowup rate is the same as the corresponding ordinary di erential equation yt = y2 (up to a multiple constant). It is shown that all type I blowup is asymptotically (backward) self-similar provided that the solution is radial, nonnegative when the blowup set is a singleton and the space dimension is greater than or equal to three. 2000 Mathematics Subject Classi cation. 35K55, 35K57, 92C17.