On a class of polynomial Lagrangians

In the framework of finite order variational sequences a new class of Lagrangians arises, namely, \emph{special} Lagrangians. These Lagrangians are the horizontalization of forms on a jet space of lower order. We describe their properties together with properties of related objects, such as Poincar\'e--Cartan and Euler--Lagrange forms, momenta and momenta of generating forms, a new geometric object arising in variational sequences. Finally, we provide a simple but important example of special Lagrangian, namely the Hilbert--Einstein Lagrangian.Comment: LaTeX2e, amsmath, diagrams, hyperref; 15 page

On the bi-Hamiltonian Geometry of WDVV Equations

We consider the WDVV associativity equations in the four dimensional case. These nonlinear equations of third order can be written as a pair of six component commuting two-dimensional non-diagonalizable hydrodynamic type systems. We prove that these systems possess a compatible pair of local homogeneous Hamiltonian structures of Dubrovin--Novikov type (of first and third order, respectively).Comment: 21 pages, revised published version; exposition substantially improve

Systems of conservation laws with third-order Hamiltonian structures

We investigate $n$-component systems of conservation laws that possess third-order Hamiltonian structures of differential-geometric type. The classification of such systems is reduced to the projective classification of linear congruences of lines in $\mathbb{P}^{n+2}$ satisfying additional geometric constraints. Algebraically, the problem can be reformulated as follows: for a vector space $W$ of dimension $n+2$, classify $n$-tuples of skew-symmetric 2-forms $A^{\alpha} \in \Lambda^2(W)$ such that $$\phi_{\beta \gamma}A^{\beta}\wedge A^{\gamma}=0,$$ for some non-degenerate symmetric $\phi$.Comment: 31 page

Accessing extremes of mid-latitudinal wave activity: methodology and application

A statistical methodology is proposed and tested for the analysis of extreme values of atmospheric wave activity at mid-latitudes. The adopted methods are the classical block-maximum and peak over threshold, respectively based on the generalized extreme value (GEV) distribution and the generalized Pareto distribution (GPD). Time-series of the ‘Wave Activity Index’ (WAI) and the ‘Baroclinic Activity Index’ (BAI) are computed from simulations of the General Circulation Model ECHAM4.6, which is run under perpetual January conditions. Both the GEV and the GPD analyses indicate that the extremes ofWAI and BAI areWeibull distributed, this corresponds to distributions with an upper bound. However, a remarkably large variability is found in the tails of such distributions; distinct simulations carried out under the same experimental setup provide sensibly different estimates of the 200-yr WAI return level. The consequences of this phenomenon in applications of the methodology to climate change studies are discussed. The atmospheric configurations characteristic of the maxima and minima of WAI and BAI are also examined

CO2 capture at high temperature and low concentration on Li4SiO4 based sorbents

Solid sorbents based on lithium orthosilicate (Li4SiO4) have shown promise for CO2 capture at high temperature. Improved sorption properties can be obtained by appropriate doping. In this study, different promoted Li4SiO4-based sorbents were prepared by addition of potassium carbonate and binary/ternary alkali (Li, K and Na) carbonate eutectic mixtures. The CO2 sorption properties of the sorbents were investigated by thermal gravimetric analysis (TGA) at different temperatures in the range between 500 and 600 °C and at low CO2 partial pressure (0.04 atm). The results showed that all the promoters used noticeably improved the CO2 sorption capacity in comparison to no-promoted Li4SiO4. At the optimum sorption temperature of 580 °C, Li4SiO4 with addition of 30 wt% of K2CO3 showed the best CO2 adsorption proprieties with sorption capacities of 230 mg CO2/g sorbent corresponding to a conversion of about 80 %. Besides this sample maintained its original capacity during multiple CO2 sorption/desorption cycles

Understanding the global burden of atrial fibrillation and regional variations: We need improvement

This editorial refers to 'Global variations in the prevalence, treatment, and impact of atrial fibrillation in a multinational cohort of 153,152middle-aged individuals' by P.G. Joseph et al., pp. 1523-1531