Relaxation of finite perturbations: Beyond the Fluctuation-Response relation

We study the response of dynamical systems to finite amplitude perturbation. A generalized Fluctuation-Response relation is derived, which links the average relaxation toward equilibrium to the invariant measure of the system and points out the relevance of the amplitude of the initial perturbation. Numerical computations on systems with many characteristic times show the relevance of the above relation in realistic cases.Comment: 7 pages, 5 figure

Power-Law Distributions in a Two-sided Market and Net Neutrality

"Net neutrality" often refers to the policy dictating that an Internet service provider (ISP) cannot charge content providers (CPs) for delivering their content to consumers. Many past quantitative models designed to determine whether net neutrality is a good idea have been rather equivocal in their conclusions. Here we propose a very simple two-sided market model, in which the types of the consumers and the CPs are {\em power-law distributed} --- a kind of distribution known to often arise precisely in connection with Internet-related phenomena. We derive mostly analytical, closed-form results for several regimes: (a) Net neutrality, (b) social optimum, (c) maximum revenue by the ISP, or (d) maximum ISP revenue under quality differentiation. One unexpected conclusion is that (a) and (b) will differ significantly, unless average CP productivity is very high

Lagrangian Statistics and Temporal Intermittency in a Shell Model of Turbulence

We study the statistics of single particle Lagrangian velocity in a shell model of turbulence. We show that the small scale velocity fluctuations are intermittent, with scaling exponents connected to the Eulerian structure function scaling exponents. The observed reduced scaling range is interpreted as a manifestation of the intermediate dissipative range, as it disappears in a Gaussian model of turbulence.Comment: 4 pages, 5 figure

Protein folding mediated by solvation: water expelling and formation of the hydrophobic core occurs after the structure collapse

The interplay between structure-search of the native structure and desolvation in protein folding has been explored using a minimalist model. These results support a folding mechanism where most of the structural formation of the protein is achieved before water is expelled from the hydrophobic core. This view integrates water expulsion effects into the funnel energy landscape theory of protein folding. Comparisons to experimental results are shown for the SH3 protein. After the folding transition, a near-native intermediate with partially solvated hydrophobic core is found. This transition is followed by a final step that cooperatively squeezes out water molecules from the partially hydrated protein core.Comment: Proceedings of the National Academy of Science, 2002, Vol.99. 685-69

Upper mantle velocity-temperature conversion and composition determined from seismic refraction and heat flow

International audience[1] We compile upper mantle P n velocities from seismic refraction/wide-angle reflection surveys in the southern Superior Province of the Canadian Shield and compare them with temperatures at the Moho deduced from heat flow data. Calculated Moho temperatures and P n velocities correlate well, showing that in this area, P n depends primarily on temperature. The obtained values of @V(P n)/@T depend weakly on the assumed value of Moho heat flow and are on the order of À6.0 Â 10 À4 ± 10% km s À1 K À1 , within the range of temperature derivatives obtained in laboratory studies of ultramafic rocks. Comparison between observed P n velocities and predicted values for several mineralogical models at Moho temperatures allows constraints on both the Moho heat flow and the shallow mantle composition. For all Moho heat flows, undepleted (clinopyroxene-rich) mantle compositions do not allow a good fit to the data. For depleted mantle compositions, temperatures consistent with the observed P n velocities correspond to values of Moho heat flow larger than 12 mW m À2. For our preferred Moho heat flow of 15 mW m À2 , the best fit mantle composition is slightly less depleted than models for average Archean subcontinental lithospheric mantle. This may be due to rejuvenation by melt-related metasomatism during the Keweenawan rifting event. The similarity in P n À T conversion factors estimated from this empirical large-scale geophysical study and those from laboratory data provides confidence in the absolute temperature values deduced from heat flow measurements and seismic studies. Citation: Perry, H. K. C., C. Jaupart, J.-C. Mareschal, and N. M. Shapiro (2006), Upper mantle velocity-temperature conversion and composition determined from seismic refraction and heat flow

A protocol to communicate seismic risk in schools: design, test and assessment in Italy

The best chance to achieve a future disaster-resilient society is through risk education in School: it has a great potential to strengthen capacity of communities to mitigate risks. The KnowRISK (Know your city, Reduce seISmic risK through non-structural elements) project took this opportunity and implemented a risk communication campaign for schools in Portugal, Italy, and Iceland. The idea was that suitably changes in people’s knowledge and attitude can trigger best practices. Crucial to reach such target is the raise of awareness on meaningful issues. The main challenge of the campaign was how to effectively address the mitigation of the vulnerability to earthquakes of non-structural elements, which is an issue considered to be of low priority even in the building regulations of many countries around the world. The campaign stood on a communication strategy that was systematized within a protocol, for 13- 15 years old students, that specifies goals, contents, learning strategy, support material, and relies on face-to-face intervention of scientists in the classroom. This protocol had training sessions bounded by assessment sessions, ex-ante and ex-post, that allowed to validate its efficacy. The training made large use of flipped learning and Episode of Situated Learning (EAS) strategy to raise student’s motivation and increase achievements. To ensure its replicability, the protocol was tested in zones matching a wide range of seismic hazard in Italy. The assessment showed the protocol be effective and ready for a wide dissemination

Patient-derived mutations within the N-terminal domains of p85α impact PTEN or Rab5 binding and regulation

The p85α protein regulates flux through the PI3K/PTEN signaling pathway, and also controls receptor trafficking via regulation of Rab-family GTPases. In this report, we determined the impact of several cancer patient-derived p85α mutations located within the N-terminal domains of p85α previously shown to bind PTEN and Rab5, and regulate their respective functions. One p85α mutation, L30F, significantly reduced the steady state binding to PTEN, yet enhanced the stimulation of PTEN lipid phosphatase activity. Three other p85α mutations (E137K, K288Q, E297K) also altered the regulation of PTEN catalytic activity. In contrast, many p85α mutations reduced the binding to Rab5 (L30F, I69L, I82F, I177N, E217K), and several impacted the GAP activity of p85α towards Rab5 (E137K, I177N, E217K, E297K). We determined the crystal structure of several of these p85α BH domain mutants (E137K, E217K, R262T E297K) for bovine p85α BH and found that the mutations did not alter the overall domain structure. Thus, several p85α mutations found in human cancers may deregulate PTEN and/or Rab5 regulated pathways to contribute to oncogenesis. We also engineered several experimental mutations within the p85α BH domain and identified L191 and V263 as important for both binding and regulation of Rab5 activit

Seismic disasters and the demographic perspective: 1968, Belice and 1980, Irpinia-Basilicata (southern Italy) case studies

One of the challenges on disasters’ understanding is the assessment of impact from a more global perspective, adding to their scenario of injuries, deaths, homeless and economic losses, those effects that are mostly widespread and could last for a long period of time, driving to a serious disruption of a community or a society. Seismic disasters are not just the results of the energy released by the earthquake or buildings’ vulnerability: social, demographic, cultural parameters may instead play a crucial, yet underestimated, role. We carried out a pilot study to investigate the demographic perspective of the impact of 1968 Belice and 1980 Irpinia-Basilicata earthquakes on local communities. The macroseismic MCS intensities were used as a primary parameter upon which the demographic scenario was derived. Population annual growth rates, the ageing index, the child- woman ratio, and the Gini index from the demographic data census of the period 1951-2011 were analyzed to assess population dynamics, age structure evolution and its level of spatial concentration within the disasters’ areas. Demographic data were then matched to macroseismic intensities to outline a new, original analysis which describes the impact of the two seismic disasters with a broad multi-parameter perspective. The results highlight also the existence of a general marginality of most affected areas with respect to the processes of population growth, ageing and fertility, as well as for distribution of the regional population, occurring already before the disasters stroke. This marginality might have enhanced the impact of disasters by significantly increasing vulnerability

Aneuploidy in pluripotent stem cells and implications for cancerous transformation

Owing to a unique set of attributes, human pluripotent stem cells (hPSCs) have emerged as a promising cell source for regenerative medicine, disease modeling and drug discovery. Assurance of genetic stability over long term maintenance of hPSCs is pivotal in this endeavor, but hPSCs can adapt to life in culture by acquiring non-random genetic changes that render them more robust and easier to grow. In separate studies between 12.5% and 34% of hPSC lines were found to acquire chromosome abnormalities over time, with the incidence increasing with passage number. The predominant genetic changes found in hPSC lines involve changes in chromosome number and structure (particularly of chromosomes 1, 12, 17 and 20), reminiscent of the changes observed in cancer cells. In this review, we summarize current knowledge on the causes and consequences of aneuploidy in hPSCs and highlight the potential links with genetic changes observed in human cancers and early embryos. We point to the need for comprehensive characterization of mechanisms underpinning both the acquisition of chromosomal abnormalities and selection pressures, which allow mutations to persist in hPSC cultures. Elucidation of these mechanisms will help to design culture conditions that minimize the appearance of aneuploid hPSCs. Moreover, aneuploidy in hPSCs may provide a unique platform to analyse the driving forces behind the genome evolution that may eventually lead to cancerous transformation

Impact of Ownership Types on R&D Intensity and Innovation Performance - Evidence from Transitional China

This paper examines the effects of ownership types on firms’ R&D intensity and innovation performance, using a sample of 357,857 Chinese firms from 2005-2007. This study finds considerable divergence among Chinese domestic enterprises in terms of R&D intensity and innovation performance. We find that firms owned by the central government are the key drivers for firms’ R&D activities, while local government, private and foreign ownerships are negatively related to both R&D intensity and innovation performance. This paper finds significant divergence within government ownership category and argue China’s institutional changes generate varied government ownership groups with different levels of resource endowment, which in turn influence firms’ R&D activities. Publisher Statement: This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made