Phase Transitions and superuniversality in the dynamics of a self-driven particle

We study an active random walker model in which a particle's motion is determined by a self-generated field. The field encodes information about the particle's path history. This leads to either self-attractive or self-repelling behavior. For self-repelling behavior, we find a phase transition in the dynamics: when the coupling between the field and the walker exceeds a critical value, the particle's behavior changes from renormalized diffusion to one characterized by a diverging diffusion coefficient. The dynamical behavior for all cases is surprisingly independent of dimension and of the noise amplitude.Comment: 14 pages, 4 figure

Multiscale modeling in biology

The 1966 science-fction film Fantastic Voyage captured the public imagination with a clever idea: what fantastic things might we see and do if we could minaturize ourselves and travel through the bloodstream as corpuscles do? (This being Hollywood, the answer was that we'd save a fellow scientist from evildoers.

Analytical study of non Gaussian fluctuations in a stochastic scheme of autocatalytic reactions

A stochastic model of autocatalytic chemical reactions is studied both numerically and analytically. The van Kampen perturbative scheme is implemented, beyond the second order approximation, so to capture the non Gaussianity traits as displayed by the simulations. The method is targeted to the characterization of the third moments of the distribution of fluctuations, originating from a system of four populations in mutual interaction. The theory predictions agree well with the simulations, pointing to the validity of the van Kampen expansion beyond the conventional Gaussian solution.Comment: 15 pages, 8 figures, submitted to Phys. Rev.

The PRIMO FORTE framework for good governance in public, private and civic organisations : an analysis on small EU states

Purpose: In this article we lay out and discuss a framework proposed by the Public Risk Management Organisation (PRIMO) (https://www.primo-europe.eu/) of which the authors are board members and the results of a test on public and private entities of EU small jurisdictions, specifically Malta, Slovenia, Luxembourg, Lithuania, Latvia, Estonia and Cyprus. These are countries within the EU having less than 3 million people population. Design/methodology/approach: We collected our primary data by using a semi-structured questionnaire and administering it to participants who are working directly or indirectly with entities within these EU states. The questionnaire was structured using the FORTETM acronym as themes, ‘Financial and compliant design’, ‘Object orientation and delivery’, ‘Responsibility and stewardship’, ‘Tools and processes for creation’ and ‘Environmental awareness and interaction’, with 5 statements under each theme to which participants were required to answer using a 5-point Likert-scale ranging from “Strongly Disagree” to “Strongly Agree”. We, however, allowed the participants to open up and discuss each statement and recorded these comments. Some demographic data was also collected as to the type of entity the participants are working with, the level of expertise on governance of the participant and the size of the entity. The quantitative data was subjected to statistical analysis while the results from the open ended question was analysed using the Thematic approach. Findings: Factor analysis provided support for the FORTE Good Governance model for both the Private and Public entities, no-matter if they are small or large. Originality/value: The study provides a better understanding and supports the FORTE Model established by PRIMO-Europe, after approximately 15 years of collecting data on public risks and for the first time tests it on both Private and Public entities, in large and small firms in small EU Jurisdictions. Moreover, this model contributed to the vast literature on models of risk management within organisations, but was not validated empirically for reliability of the factors, and on small jurisdictions. Therefore, the significance and importance of such a study lies firstly on the premise that testing on small countries, can be deemed as small laboratories for more complex politics, regulations and policies of larger countries.peer-reviewe

The 5′-3′ exoribonuclease Pacman is required for normal male fertility and is dynamically localized in cytoplasmic particles in Drosophila testis cells

The exoribonuclease Xrn1 is widely recognised as a key component in the 5'-3' RNA degradation pathway. This enzyme is highly conserved between yeast and humans and is known to be involved in RNA interference and degradation of microRNAs as well as RNA turnover. In yeast and human tissue culture cells, Xrn1 has been shown to be a component of P-bodies (processing bodies), dynamic cytoplasmic granules where RNA degradation can take place. In this paper we show for the first time that Pacman, the Drosophila homologue of Xrn1, is localized in cytoplasmic particles in Drosophila testis cells. These particles are present in both the mitotically dividing spermatogonia derived from primordial stem cells and in the transcriptionally active spermatocytes. Pacman is co-localized with the decapping activator dDcp1 and the helicase Me31B (a Dhh1 homologue) in these particles, although this co-localization is not completely overlapping, suggesting that there are different compartments within these granules. Particles containing Pacman respond to stress and depletion of 5'-3' decay factors in the same way as yeast P-bodies, and therefore are likely to be sites of mRNA degradation or storage. Pacman is shown to be required for normal Drosophila spermatogenesis, suggesting that control of mRNA stability is crucial in the testis differentiation pathway

Low serum phosphate levels are related to increased cardiovascular risk in HIV-1 infected patients

Purpose of the study Hypophosphatemia may contribute directly to the devel- opment of obesity, hypertension and dyslipidemia. Hyperglycemia, insulin resistance, hyperlipidemia and hypertension, which are components of metabolic syn- drome, are also recognized as strong risk factors for car- diovascular disease [1]. This study was performed to determine whether serum phosphate levels are asso- ciated with increased risk for cardiovascular events. Methods We enrolled 125 consecutive HIV-1-infected patients in a cross-sectional study. All patients were receiving highly active antiretroviral therapy (HAART) for more than six months. Fasting phosphate, lipids (cholesterol, HDL, triglycerides), Homeostasis Model Assessment (HOMA), blood pressure were evaluated. Framingham 10 years risk of general cardiovascular disease was used to assess three cardiovascular risk (CVR) categories (low CVR 20%). Summary of results We observed a statistically significant decrease in serum phosphate levels in the three different CVR groups (low risk: 3.5 mg/dl; medium risk: 3.3 mg/dl; high risk: 2.9 mg/dl; p=0.001). There was a strong negative correlation between Framingham score and phosphate levels (r:- 0.37, p<0.0001). Figure 1 Multiple regression analysis, including age, months of HAART, CD4 cells count, cholesterol, HDL, HOMA, systolic pressure, months of Tenofovir use, showed that only HOMA (r:-0.30, p<0.01) and age (r:-0.3, p<0.01) were the most important determinants of serum phos- phate values. Conclusions We found that lower phosphate level is correlated with cardiovascular risk and insulin resistance. Therefore, when serum phosphate levels are too low the patients is at risk for cardiovascular events and/or metabolic syndrome

Investigation of Measuring Wall Friction on a Large Scale Wall Friction Tester and the Jenike Direct Shear Tester

The interaction of a granular material with boundary materials is one of the most important factors to consider when designing mass flow hoppers, chutes, feeders and other equipment where flow is expected to occur. Numerous properties of a bulk material and wall surface influence the measurement of wall friction angles (e.g. particle size and distribution, particle shape, particle and boundary asperities and moisture content) which can be difficult to thoroughly investigate on a standard Jenike direct shear tester. Often the Jenike direct shear tester is limited to small particle sizes, wall sample materials, shear rates and displacements.This paper presents the design and commissioning of a new large scale wall friction tester (LSWFT) to measure the wall friction angles of dry and wet bulk materials with a wide particle size distribution using a large shear cell. Factors which are examined on the LSWFT include particle size, moisture content, wall sample material conditions (i.e. effects of joints and edges between tiled materials) and shear cell size to improve the understanding of granular material interaction withboundaries to enhance infrastructure performance. The wall yield loci and kinematic angles of wall friction measured from the LSWFT are compared to the Jenike direct shear tester to examine the difference between the two measuring techniques and evaluate the performance of the LSWFT. The results presented in this paper are preliminary and are not intended to show any particle or shear cell scaling effects but to rather demonstrate the potential usefulness of the LSWFT and limitations of the Jenike tester

Sampling bias in systems with structural heterogeneity and limited internal diffusion

Complex systems research is becomingly increasingly data-driven, particularly in the social and biological domains. Many of the systems from which sample data are collected feature structural heterogeneity at the mesoscopic scale (i.e. communities) and limited inter-community diffusion. Here we show that the interplay between these two features can yield a significant bias in the global characteristics inferred from the data. We present a general framework to quantify this bias, and derive an explicit corrective factor for a wide class of systems. Applying our analysis to a recent high-profile survey of conflict mortality in Iraq suggests a significant overestimate of deaths

Liquid filled canyons on Titan

In May 2013 the Cassini RADAR altimeter observed channels in Vid Flumina, a drainage network connected to Titan’s second largest hydrocarbon sea, Ligeia Mare. Analysis of these altimeter echoes shows that the channels are located in deep (up to ~570 m), steep-sided, canyons and have strong specular surface reflections that indicate they are currently liquid filled. Elevations of the liquid in these channels are at the same level as Ligeia Mare to within a vertical precision of about 0.7 m, consistent with the interpretation of drowned river valleys. Specular reflections are also observed in lower order tributaries elevated above the level of Ligeia Mare, consistent with drainage feeding into the main channel system