Brassinosteroiders roll i stimulering av tillväxt och stress tolerans hos växter efter priming med nyttiga bakterier

Brassinosteroids (BR) are plant hormones widely distributed throughout the plant kingdom in low concentrations and with structural homology to animal and insect steroids. BR are involved in numerous physiological processes, and they also fulfill an antagonistic role in anti-herbivory structure formation in tomato (Campos et al., 2009). In order to characterize the role of BR upon priming with B. amyloliquefasciens 5113, gene expression analysis of BR genes was assessed in Arabidopsis thaliana. BAK1, BRI1 and DWF1 expression down-regulates, while DET2 upregulates upon bacterial priming. CPD gene expression was not affected by priming. qPCR analysis of VSP2 and PR1 were performed on BR mutants upon priming with B. amyloliquefasciens 5113. Basal levels of PR1 were higher in det2, bak1 and dwf1 compared to primed samples. Primed bri1 displayed two-fold higher expression of PR1 compared to untreated bri1. VSP2 level goes up on det2, bak1 and bri1 upon priming. No changes of VSP2 expression were observed in dwf1 upon priming. Methyl jasmonate treatment up-regulates VSP2 level twofold in det2 and nine-fold in bak1. The role of BR genes in response to insect attack was examined. BR genes appear not to be responsive to herbivory by S. littoralis. However, S. littoralis larvae fed more on BR mutants compared to those that fed on Col-0 WT. In order to understand the role of BR in JA signaling pTRV-JAR1 and pTRV-LOX2 constructs were developed and virus induced gene silencing were performed on Col-0 and BR mutants bak1 and det2. Gene silencing was confirmed by qPCR analysis of the target genes in Col-0 and det2, but not in bak1. Further insect feeding experiments are required to elucidate if BR play a role in defense responses to herbivory when JA signaling pathway is compromised

Time-domain scars: resolving the spectral form factor in phase space

We study the relationship of the spectral form factor with quantum as well as classical probabilities to return. Defining a quantum return probability in phase space as a trace over the propagator of the Wigner function allows us to identify and resolve manifolds in phase space that contribute to the form factor. They can be associated to classical invariant manifolds such as periodic orbits, but also to non-classical structures like sets of midpoints between periodic points. By contrast to scars in wavefunctions, these features are not subject to the uncertainty relation and therefore need not show any smearing. They constitute important exceptions from a continuous convergence in the classical limit of the Wigner towards the Liouville propagator. We support our theory with numerical results for the quantum cat map and the harmonically driven quartic oscillator.Comment: 10 pages, 4 figure

Random Graphs Associated to some Discrete and Continuous Time Preferential Attachment Models

We give a common description of Simon, Barab\'asi--Albert, II-PA and Price growth models, by introducing suitable random graph processes with preferential attachment mechanisms. Through the II-PA model, we prove the conditions for which the asymptotic degree distribution of the Barab\'asi--Albert model coincides with the asymptotic in-degree distribution of the Simon model. Furthermore, we show that when the number of vertices in the Simon model (with parameter $\alpha$) goes to infinity, a portion of them behave as a Yule model with parameters $(\lambda,\beta) = (1-\alpha,1)$, and through this relation we explain why asymptotic properties of a random vertex in Simon model, coincide with the asymptotic properties of a random genus in Yule model. As a by-product of our analysis, we prove the explicit expression of the in-degree distribution for the II-PA model, given without proof in \cite{Newman2005}. References to traditional and recent applications of the these models are also discussed

Scale-free behavior of networks with the copresence of preferential and uniform attachment rules

Complex networks in different areas exhibit degree distributions with heavy upper tail. A preferential attachment mechanism in a growth process produces a graph with this feature. We herein investigate a variant of the simple preferential attachment model, whose modifications are interesting for two main reasons: to analyze more realistic models and to study the robustness of the scale free behavior of the degree distribution. We introduce and study a model which takes into account two different attachment rules: a preferential attachment mechanism (with probability 1-p) that stresses the rich get richer system, and a uniform choice (with probability p) for the most recent nodes. The latter highlights a trend to select one of the last added nodes when no information is available. The recent nodes can be either a given fixed number or a proportion (\alpha n) of the total number of existing nodes. In the first case, we prove that this model exhibits an asymptotically power-law degree distribution. The same result is then illustrated through simulations in the second case. When the window of recent nodes has constant size, we herein prove that the presence of the uniform rule delays the starting time from which the asymptotic regime starts to hold. The mean number of nodes of degree k and the asymptotic degree distribution are also determined analytically. Finally, a sensitivity analysis on the parameters of the model is performed