Microbiota, Oral Microbiome, and Pancreatic Cancer

Only 30% of patients diagnosed with pancreatic cancer survive one year post-diagnosis. Progress in understanding the causes of pancreatic cancer has been made, including solidifying the associations with obesity and diabetes, and a proportion of cases should be preventable through lifestyle modifications. Unfortunately, identifying reliable biomarkers of early pancreatic cancer has been extremely challenging, and no effective screening modality is currently available for this devastating form of cancer. Recent data suggest the microbiota may play a role in the disease process, but many questions remain. Future studies focusing on the human microbiome, both etiologically and as a marker of disease susceptibility, should shed light on how to better tackle prevention, early detection, and treatment of this highly fatal disease

The Betti numbers of forests

This paper produces a recursive formula of the Betti numbers of certain Stanley-Reisner ideals (graph ideals associated to forests). This gives a purely combinatorial definition of the projective dimension of these ideals, which turns out to be a new numerical invariant of forests. Finally, we propose a possible extension of this invariant to general graphs

The Betti numbers of forests

This paper produces a recursive formula of the Betti numbers of certain Stanley-Reisner ideals (graph ideals associated to forests). This gives a purely combinatorial definition of the projective dimension of these ideals, which turns out to be a new numerical invariant of forests. Finally, we propose a possible extension of this invariant to general graphs

Modelling resonances and orbital chaos in disk galaxies. Application to a Milky Way spiral model

Context: Resonances in the stellar orbital motion under perturbations from spiral arms structure play an important role in the evolution of the disks of spiral galaxies. The epicyclic approximation allows the determination of the corresponding resonant radii on the equatorial plane (for nearly circular orbits), but is not suitable in general. Aims: We expand the study of resonant orbits by analysing stellar motions perturbed by spiral arms with Gaussian-shaped profiles without any restriction on the stellar orbital configurations, and we expand the concept of Lindblad (epicyclic) resonances for orbits with large radial excursions. Methods: We define a representative plane of initial conditions, which covers the whole phase space of the system. Dynamical maps on representative planes are constructed numerically, in order to characterize the phase-space structure and identify the precise location of resonances. The study is complemented by the construction of dynamical power spectra, which provide the identification of fundamental oscillatory patterns in the stellar motion. Results: Our approach allows a precise description of the resonance chains in the whole phase space, giving a broader view of the dynamics of the system when compared to the classical epicyclic approach, even for objects in retrograde motion. The analysis of the solar neighbourhood shows that, depending on the current azimuthal phase of the Sun with respect to the spiral arms, a star with solar kinematic parameters may evolve either inside the stable co-rotation resonance or in a chaotic zone. Conclusions: Our approach contributes to quantifying the domains of resonant orbits and the degree of chaos in the whole Galactic phase-space structure. It may serve as a starting point to apply these techniques to the investigation of clumps in the distribution of stars in the Galaxy, such as kinematic moving groups.Comment: 17 pages, 15 figures. Matches accepted version in A&

Piracy on the internet: Accommodate it or fight it? A dynamic approach

This paper uses a dynamic stochastic model to solve for the optimal pricing policy of themusic recording companies in the presence of P2P file-sharing networks eroding their CDsales. We employ a policy iteration algorithm on a discretized state space to numericallycompute the optimal price policy. The realistically calibrated model reflects the real-worldfigures we observe and provides estimates of figures we can not observe, such as changesin total welfare. The results suggest that, thanks to the existence of P2P networks, totalwelfare in 2008 in the U.S. is about $25.6 billion more per annum than in 1999 before P2Pwas introduced. Moreover, the results predict that the current trend of decreasing CDsales will continue until around the year 2020 when it will stabilize at around 231.2 millioncopies per year, comparing to the industry all-time high of 938.9 million in 1999. Thecomparative static analysis shows that full enforcement of intellectual property rights,although helpful for the industrial profit, may have adverse effect on total welfare.microeconomics ;

Gesunder Boden - gesunde Pflanzen

Obwohl viele ältere Biobetriebe kleinere Nährstoffgehalte im Boden aufwiesen, waren diese noch nicht ertragsbegrenzend. Die abnehmenden Nährstoffgehalte im Boden und den Pflanzen zeigen, dass regelmässige Bodenanalysen auf dem Biobetrieb nötig sind. Die Suppressivität der Böden hing nicht direkt von den Biojahren ab. Durch die Gestaltung der Fruchtfolge und den Hofdüngereinsatz lässt sie sich aber steigern. Der Zusammenhang zwischen Bewirtschaftung Bodeneigenschaften und der Suppressivität muss genauer untersucht werden

Ripples in Tapped or Blown Powder

We observe ripples forming on the surface of a granular powder in a container submitted from below to a series of brief and distinct shocks. After a few taps, the pattern turns out to be stable against any further shock of the same amplitude. We find experimentally that the characteristic wavelength of the pattern is proportional to the amplitude of the shocks. Starting from consideration involving Darcy's law for air flow through the porous granulate and avalanche properties, we build up a semi-quantitative model which fits satisfactorily the set of experimental observations as well as a couple of additional experiments.Comment: 7 pages, four postscript figures, submitted PRL 11/19/9