ARISTOTELES: A European approach for an Earth gravity field recovery mission

Under contract of the European Space Agency a system study for a spaceborne gravity field recovery mission was performed, covering as a secondary mission objective geodetic point positioning in the cm range as well. It was demonstrated that under the given programmatic constraints including dual launch and a very tight development schedule, a six months gravity field mission in a 200 km near polar, dawn-dusk orbit is adequate to determine gravity anomalies to better than 5 mgal with a spatial resolution of 100 x 100 km half wavelength. This will enable scientists to determine improved spherical harmonic coefficients of the Earth gravity field equation to the order and degree of 180 or better

The corpulent phenotype—how the brain maximizes survival in stressful environments

The reactivity of the stress system may change during the life course. In many—but not all—humans the stress reactivity decreases, once the individual is chronically exposed to a stressful and unsafe environment (e.g., poverty, work with high demands, unhappy martial relationship). Such an adaptation is referred to as habituation. Stress habituation allows alleviating the burden of chronic stress, particularly cardiovascular morbidity and mortality. Interestingly, two recent experiments demonstrated low stress reactivity during a mental or psychosocial challenge in subjects with a high body mass. In this focused review we attempt to integrate these experimental findings in a larger context. Are these data compatible with data sets showing a prolonged life expectancy in corpulent people? From the perspective of neuroenergetics, we here raise the question whether “obesity” is unhealthy at all. Is the corpulent phenotype possibly the result of “adaptive phenotypic plasticity” allowing optimized survival in stressful environments

Multivariate Anisotropic Interpolation on the Torus

We investigate the error of periodic interpolation, when sampling a function on an arbitrary pattern on the torus. We generalize the periodic Strang-Fix conditions to an anisotropic setting and provide an upper bound for the error of interpolation. These conditions and the investigation of the error especially take different levels of smoothness along certain directions into account

Expand-contract plasticity on the real line

The article deals with plastic and non-plastic sub-spaces $A$ of the real line ${\mathbb{R}}$ with the usual Euclidean metric $d$. It investigates non-expansive bijections, proves properties of such maps and demonstrates their relevance by hands of examples. Finally, it is shown that the plasticity property of a sub-space $A$ contains at least two complementary questions, a purely geometric and a topological one. Both contribute essential aspects to the plasticity property and get more critical in higher dimensions and more abstract metric spaces

Longterm existence of solutions of a reaction diffusion system with non-local terms modeling an immune response

This paper shows the global existence and boundedness of solutions of a reaction diffusion system modeling liver infections. Non-local effects in the dynamics between the virus and the cells of the immune system lead to an integro-partial differential equation with homogeneous Neumann boundary conditions. Depending on the chosen model parameters, the system shows two types of solutions which are interpreted as different infection courses. Apart from solutions decaying to zero, there are solutions with a tendency towards a stationary and spatially inhomogeneous state. By proving the boundedness of the solution in the $L^1(\Omega)$- and the $L^2(\Omega)$-norms, it is possible to show the global boundedness of the solution. The proof uses the opposite mechanisms in the reaction terms. The gained rough estimates for showing the boundedness in the $L^1(\Omega)$- and the $L^2(\Omega)$-norms are compared numerically with the norms of the solutions.Comment: 19 pages, 7 figure

Total Syntheses of (+)-Ricinelaidic Acid Lactone and of (−)-Gloeosporone Based on Transition-Metal-Catalyzed C−C Bond Formations

Total syntheses of the macrolides (R)-(+)-ricinelaidic acid lactone (6) and (−)-gloeosporone (7), a fungal germination self-inhibitor, are presented, which are distinctly shorter and more efficient than any of the previous approaches to these targets reported in the literature. Both of them benefit from the remarkable ease of macrocyclization of 1,ω-dienes by means of ring-closing olefin metathesis (RCM) using the ruthenium carbene 1a as catalyst precursor. The diene substrates are readily formed via the enantioselective addition of dialkylzinc reagents to aldehydes in the presence of catalytic amounts of Ti(OiPr)4 and bis-triflamide 18 and/or the stereoselective allylation of aldehydes developed by Keck et al. using allyltributylstannane in combination with a catalyst formed from Ti(OiPr)4 and (S)-(−)-1,1‘-bi-2-naphthol. Comparative studies show this latter procedure to be more practical than the stoichiometric allylation reaction employing the allyltitanium−α,α,α‘,α‘-tetraaryl-1,3-dioxolane-4,5-dimethanol complex 3b. Finally, a method for the efficient ring closure of 4-pentenoic acid esters by RCM is presented that relies on the joint use of 1a and Ti(OiPr)4 as a binary catalyst system. These results not only expand the scope of RCM to previously unreactive substrates but also provide additional evidence for the important role of ligation of the evolving ruthenium carbene center to a polar relay substituent on the substrate which constitutes the necessary internal bias for the RCM-based macrocyclization process

Stress and eating behavior

How stress, the stress response, and the adaptation of the stress response influence our eating behavior is a central question in brain research and medicine. In this report, we highlight recent advances showing the close links between eating behavior, the stress system, and neurometabolism

Build-Ups in the Supply Chain of the Brain: on the Neuroenergetic Cause of Obesity and Type 2 Diabetes Mellitus

Obesity and type 2 diabetes have become the major health problems in many industrialized countries. A few theoretical frameworks have been set up to derive the possible determinative cause of obesity. One concept views that food availability determines food intake, i.e. that obesity is the result of an external energy “push” into the body. Another one views that the energy milieu within the human organism determines food intake, i.e. that obesity is due to an excessive “pull” from inside the organism. Here we present the unconventional concept that a healthy organism is maintained by a “competent brain-pull” which serves systemic homeostasis, and that the underlying cause of obesity is “incompetent brain-pull”, i.e. that the brain is unable to properly demand glucose from the body. We describe the energy fluxes from the environment, through the body, towards the brain with a mathematical “supply chain” model and test whether its predictions fit medical and experimental data sets from our and other research groups. In this way, we show data-based support of our hypothesis, which states that under conditions of food abundance incompetent brain-pull will lead to build-ups in the supply chain culminating in obesity and type 2 diabetes. In the same way, we demonstrate support of the related hypothesis, which states that under conditions of food deprivation a competent brain-pull mechanism is indispensable for the continuance of the brain´s high energy level. In conclusion, we took the viewpoint of integrative physiology and provided evidence for the necessity of brain-pull mechanisms for the benefit of health. Along these lines, our work supports recent molecular findings from the field of neuroenergetics and continues the work on the “Selfish Brain” theory dealing with the maintenance of the cerebral and peripheral energy homeostasis

Qualitative properties of solutions to a nonlinear transmission problem for an elastic Bresse beam

We consider a nonlinear transmission problem for a Bresse beam, which consists of two parts, damped and undamped. The mechanical damping in the damped part is present in the shear angle equation only, and the damped part may be of arbitrary positive length. We prove well-posedness of the corresponding PDE system in energy space and establish existence of a regular global attractor under certain conditions on nonlinearities and coefficients of the damped part only. Moreover, we study singular limits of the problem when $l\to 0$ or $l\to 0$ simultaneously with $k_i\to +\infty$ and perform numerical modelling for these processes