Web調査における公募型モニターと非公募型モニターの回答傾向 : 変数間の関連に注目して

departmental bulletin pape

Observation of B+ → χc0K+

journal articl

Impact Sheet to IRME 2022

Impact Sheet</p

「刑法典理論モデル」(総則)についての覚書 : ソビエト刑法改正に関連して

application/pdfdepartmental bulletin pape

Population mixing promotes arms race host-parasite coevolution

The consequences of host-parasite coevolution are highly contingent on the qualitative coevolutionary dynamics: whether selection fluctuates (fluctuating selection dynamic; FSD), or is directional towards increasing infectivity/resistance (arms race dynamic; ARD). Both genetics and ecology can play an important role in determining whether coevolution follows FSD or ARD, but the ecological conditions under which FSD shifts to ARD, and vice versa, are not well understood. The degree of population mixing is thought to increase host exposure to parasites, hence selecting for greater resistance and infectivity ranges, and we hypothesize this promotes ARD. We tested this by coevolving bacteria and viruses in soil microcosms and found that population mixing shifted bacteria-virus coevolution from FSD to ARD. A simple theoretical model produced qualitatively similar results, showing that mechanisms that increase host exposure to parasites tend to push dynamics towards ARD. The shift from FSD to ARD with increased population mixing may help to explain variation in coevolutionary dynamics between different host-parasite systems, and more specifically the observed discrepancies between laboratory and field bacteria-virus coevolutionary studies

Open Access Documentary Production of the Spanish-Speaking Community in Mathematics Education for Middle School Education

Abstract We present results of a study which objective was the open access documental production characterization of the Spanish-speaking community in Mathematics Education for middle school. From a taxonomy of key terms specific to Mathematics Education, we made a semantic approach to the documentation content, which was produced by this community of teachers and researchers between 1986 and 2017. We defined the following study variables: educational level, document type, school mathematics, and curriculum. We crossed the educational level variable with the other variables and, with a normalization process, we identified the values of these variables in which the middle school is different from the other educational levels, since it has the highest or lowest percentage of documents published. In comparison with other educational levels, middle school is distinguished by having the highest or one of the highest production levels in activities. It stands out for addressing issues of probability, calculation, measurement and algebra, and classroom and learning.</p

The Impact of Resource Availability on Bacterial Resistance to Phages in Soil

<div><p>Resource availability can affect the coevolutionary dynamics between host and parasites, shaping communities and hence ecosystem function. A key finding from theoretical and <i>in vitro</i> studies is that host resistance evolves to greater levels with increased resources, but the relevance to natural communities is less clear. We took two complementary approaches to investigate the effect of resource availability on the evolution of bacterial resistance to phages in soil. First, we measured the resistance and infectivity of natural communities of soil bacteria and phage in the presence and absence of nutrient-providing plants. Second, we followed the real-time coevolution between defined bacteria and phage populations with resource availability manipulated by the addition or not of an artificial plant root exudate. Increased resource availability resulted in increases in bacterial resistance to phages, but without a concomitant increase in phage infectivity. These results suggest that phages may have a reduced impact on the control of bacterial densities and community composition in stable, high resource environments.</p></div

Proportion of infected bacteria clones.

<p>Bars represent the mean proportion (±SEM) of all bacteria clones isolated from non-plant associated (black bar) and plant-associated (white bar) soils that are susceptible to be infected by their non-plant and plant phage communities averaged across the three time points.</p

Bacterial and phage population dynamics in soil.

<p>Mean densities (±SEM) of (A) <i>P</i>. <i>fluorescens</i> SBW25 population (colony forming units·g^-1 soil) in absence (□) and presence (■) of phages, and (B) phage SBW25ø2 population (plaque forming units·g^-1 soil). Solid and dashed lines correspond to bacteria and phage population densities under nutrient addition or not, respectively.</p

Rates of bacterial resistance evolution.

<p>Proportion (±SEM) of <i>P</i>. <i>fluorescens</i> SBW25 resistant to (A) ancestral and (B) contemporary phages through time. Solid and dashed lines correspond to bacteria resistance under nutrient addition or not, respectively.</p