PACS photometer calibration block analysis

The absolute stability of the PACS bolometer response over the entire mission lifetime without applying any corrections is about 0.5% (standard deviation) or about 8% peak-to-peak. This fantastic stability allows us to calibrate all scientific measurements by a fixed and time-independent response file, without using any information from the PACS internal calibration sources. However, the analysis of calibration block observations revealed clear correlations of the internal source signals with the evaporator temperature and a signal drift during the first half hour after the cooler recycling. These effects are small, but can be seen in repeated measurements of standard stars. From our analysis we established corrections for both effects which push the stability of the PACS bolometer response to about 0.2% (stdev) or 2% in the blue, 3% in the green and 5% in the red channel (peak-to-peak). After both corrections we still see a correlation of the signals with PACS FPU temperatures, possibly caused by parasitic heat influences via the Kevlar wires which connect the bolometers with the PACS Focal Plane Unit. No aging effect or degradation of the photometric system during the mission lifetime has been found.Comment: 15 pages, accepted for publication in Experimental Astronom

Dynamic control of modern, network-based epidemic models

In this paper we make the first steps to bridge the gap between classic control theory and modern, network-based epidemic models. In particular, we apply nonlinear model predictive control (NMPC) to a pairwise ODE model which we use to model a susceptible-infectious-susceptible (SIS) epidemic on nontrivial contact structures. While classic control of epidemics concentrates on aspects such as vaccination, quarantine, and fast diagnosis, our novel setup allows us to deliver control by altering the contact network within the population. Moreover, the ideal outcome of control is to eradicate the disease while keeping the network well connected. The paper gives a thorough and detailed numerical investigation of the impact and interaction of system and control parameters on the controllability of the system. For a certain combination of parameters, we used our method to identify the critical control bounds above which the system is controllable. We foresee that our approach can be extended to even more realistic or simulation-based models with the aim of applying these to real-world situations

Effects of constant electric fields on the buoyant stability of reaction fronts

The effects that applying constant electric fields have on the buoyant instability of reaction fronts propagating vertically in a Hele-Shaw cell are investigated for a range of electric field strengths and fluid parameters. The reaction produces a decrease in density across the front such that upwards propagating fronts are buoyantly unstable in the field-free situation. The reaction kinetics are modeled by cubic autocatalysis. A linear stability analysis reveals that a positive electric field increases the stability of a reaction front and can stabilize an otherwise unstable front. A negative field has the opposite effect, making the reaction front more unstable. Numerical simulations of the full nonlinear problem confirm these predictions and show the development of cellular fingers on unstable fronts. These simulations show that the electric field effects on the reaction within the front can alter the fluid density so as to give the possibility of destabilizing an otherwise stable downward propagating front

Towards the Sustainable Food Consumption in Central Europe: Stochastic Relationship Between Water Footprint and Nutrition

Sustainable nutrition (SN) considers the environmental impact of food production. This study aims to analyse the relationship between nutrient density and water footprint (WF) of the most consumed food items in Hungary and to create a classification of nutrients. Based on a comprehensive analysis of literature and different data sources, the authors analysed the stochastic relationship between WF and nutrient density of different food items by Spearman's rank correlation. The analysis proved significant (P<0.05) relationship between nutrient density and WF of the most relevant food items in Hungary. Based on the classification, there are nutrients that are overconsumed among the Hungarian population and positively correlate with WF (e.g., cholesterol) and there are nutrients that are under-consumed among the Hungarian population and negatively correlate with WF (e.g., dietary fibres). In general, it can be concluded that the re-structuration of food consumption patterns in Hungary is an important and urgent task, which serves both the public health and ecologic goals. These efforts should be based on a complex evaluation of the problem. This study was one initial step to analyse SN focused on Hungary and further studies are definitely needed

From Markovian to pairwise epidemic models and the performance of moment closure approximations

Many if not all models of disease transmission on networks can be linked to the exact state-based Markovian formulation. However the large number of equations for any system of realistic size limits their applicability to small populations. As a result, most modelling work relies on simulation and pairwise models. In this paper, for a simple SIS dynamics on an arbitrary network, we formalise the link between a well known pairwise model and the exact Markovian formulation. This involves the rigorous derivation of the exact ODE model at the level of pairs in terms of the expected number of pairs and triples. The exact system is then closed using two different closures, one well established and one that has been recently proposed. A new interpretation of both closures is presented, which explains several of their previously observed properties. The closed dynamical systems are solved numerically and the results are compared to output from individual-based stochastic simulations. This is done for a range of networks with the same average degree and clustering coefficient but generated using different algorithms. It is shown that the ability of the pairwise system to accurately model an epidemic is fundamentally dependent on the underlying large-scale network structure. We show that the existing pairwise models are a good fit for certain types of network but have to be used with caution as higher-order network structures may compromise their effectiveness

The 106Cd(α, α)106Cd elastic scattering in a wide energy range for γ process studies

Date of Acceptance: 15/04/2015Alpha elastic scattering angular distributions of the 106Cd(α, α)106Cd reaction were measured at three energies around the Coulomb barrier to provide a sensitive test for the α + nucleus optical potential parameter sets. Furthermore, the new high precision angular distributions, together with the data available from the literature were used to study the energy dependence of the locally optimized α + nucleus optical potential in a wide energy region ranging from ELab=27.0MeV down to 16.1 MeV.The potentials under study are a basic prerequisite for the prediction of α-induced reaction cross sections and thus, for the calculation of stellar reaction rates used for the astrophysical γ process. Therefore, statistical model predictions using as input the optical potentials discussed in the present work are compared to the available 106Cd + alpha cross section data.Peer reviewe

Rapid convergence of time-averaged frequency in phase synchronized systems

Numerical and experimental evidence is presented to show that many phase synchronized systems of non-identical chaotic oscillators, where the chaotic state is reached through a period-doubling cascade, show rapid convergence of the time-averaged frequency. The speed of convergence toward the natural frequency scales as the inverse of the measurement period. The results also suggest an explanation for why such chaotic oscillators can be phase synchronized.Comment: 6 pages, 9 figure

Synchronization and oscillator death in oscillatory media with stirring

The effect of stirring in an inhomogeneous oscillatory medium is investigated. We show that the stirring rate can control the macroscopic behavior of the system producing collective oscillations (synchronization) or complete quenching of the oscillations (oscillator death). We interpret the homogenization rate due to mixing as a measure of global coupling and compare the phase diagrams of stirred oscillatory media and of populations of globally coupled oscillators.Comment: to appear in Phys. Rev. Let

Investigation of alpha-nuclear potential families from elastic scattering experiments

In this work we present the continuation of the reported analysis [1] of the experimentally measured angular distributions of the reaction Cd-106(alpha, alpha)Cd-106 at several different energies around the Coulomb barrier. The difficulties that arise in the study of Cd-106-alpha-nuclear potential and the so called Family Problem are addressed