Pion-pion phase shifts from covariant perturbation theory for a chiral invariant field theoretic model

The Lehmann model for pion -pion scattering consists of a low-energy expansion of the scattering amplitude to fourth order in the momenta on the basis of the chiral-invariant pion-nucleon Lagrangian. Because of the non-renormalizability of the pion Lagrangian two parameters remain undetermined in the pion-loop contribution. Using covariant perturbation theory and superpropagator methods, we calculate these two parameters independently of the choice of the pion field coordinates. The resulting phase shifts are shown to be in very good agreement with the data.     

Influence of nuclear deformation on the correlation of protons emitted from compound nuclei

The angular correlations of protons evaporated from the compound nucleus¹²⁴Ce exhibit strong anisotropies which are inconsistent with the emission from a spherical source. The data can be explained by an enhanced emission probability due to a lower Coulomb barrier perpendicular to the spin axis of strongly deformed nuclei.     

Influence of different copolymer sequences in low band gap polymers on their performance in organic solar cells

The chemical design of a polymer can be tailored by a random or a block sequence of the comonomers in order to influence the properties of the final material. In this work, two sequences, PCPDTBT and F8BT (F8), were polymerized to form a block or a random copolymer. Differences between the various polymers were examined by exploring the surface topography and charge carrier mobility. A distinct surface texture and a higher charge carrier mobility was found for the block copolymer with respect to the other materials. Solar cells were prepared with polymer:PC₇₁BM blend active layers and the best performance of up to 2% was found for the block copolymer, which was a direct result of the fill factor. Overall, the sequences of different copolymers for solar cell applications were varied and a positive impact on efficiency was found when the block copolymer structure was utilized. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Intensive care unit occupancy predictions in the COVID-19 pandemic based on age-structured modelling and differential flatness

The COVID-19 pandemic confronts governments and their health systems with great challenges for disease management. In many countries, hospitalization and in particular ICU occupancy is the primary measure for policy makers to decide on possible non-pharmaceutical interventions. In this paper a combined methodology for the prediction of COVID-19 case numbers, case-specific hospitalization and ICU admission rates as well as hospital and ICU occupancies is proposed. To this end, we employ differential flatness to provide estimates of the states of an epidemiological compartmental model and estimates of the unknown exogenous inputs driving its nonlinear dynamics. A main advantage of this method is that it requires the reported infection cases as the only data source. As vaccination rates and case-specific ICU rates are both strongly age-dependent, specifically an age-structured compartmental model is proposed to estimate and predict the spread of the epidemic across different age groups. By utilizing these predictions, case-specific hospitalization and case-specific ICU rates are subsequently estimated using deconvolution techniques. In an analysis of various countries we demonstrate how the methodology is able to produce real-time state estimates and hospital/ICU occupancy predictions for several weeks thus providing a sound basis for policy makers.

     

A numerical investigation of rank-two ellipsoid algorithms for nonlinear programming

We study the performance of some rank-two ellipsoid algorithms when used to solve nonlinear programming problems. Experiments are reported which show that the rank-two algorithms studied are slightly less efficient than the usual rank-one (center-cut) algorithm. Some results are also presented concerning the growth of ellipsoid asphericity in rank-one and rank-two algorithms.     

Electromotive Force and Dissipation in the Plasma-Induced Arc

A joint treatment of cathode spot, main plasma and anode sheath of the plasma induced are is given which shows an additional electromotive force in the plasma and accounts for the upper limit of the electron temperature. The plasma-emf may be substantially larger than that of the sheath. The reduction effect of the dissipation is comparatively small. As a result existence limitations for the electron temperature and the neutral density are given which are quite different from those derived simply from the floating potential.     

On Computing an Initial Efficient Extreme Point

In this note we provide a counter example to a proposed method of finding an initial efficient extreme point for multiple objective linear programs. We also show that the existing method of Ecker and Kouada for finding an initial efficient point can be used to find an efficient extreme point easily.