Structurally robust biological networks

Background: The molecular circuitry of living organisms performs remarkably robust regulatory tasks, despite the often intrinsic variability of its components. A large body of research has in fact highlighted that robustness is often a structural property of biological systems. However, there are few systematic methods to mathematically model and describe structural robustness. With a few exceptions, numerical studies are often the preferred approach to this type of investigation. Results: In this paper, we propose a framework to analyze robust stability of equilibria in biological networks. We employ Lyapunov and invariant sets theory, focusing on the structure of ordinary differential equation models. Without resorting to extensive numerical simulations, often necessary to explore the behavior of a model in its parameter space, we provide rigorous proofs of robust stability of known bio-molecular networks. Our results are in line with existing literature. Conclusions: The impact of our results is twofold: on the one hand, we highlight that classical and simple control theory methods are extremely useful to characterize the behavior of biological networks analytically. On the other hand, we are able to demonstrate that some biological networks are robust thanks to their structure and some qualitative properties of the interactions, regardless of the specific values of their parameters

Phases of Cost Cutting: Downsizing is Dead; Long Live the Downsizing Phenomenon

This downsizing research article presents a phase typology of job cutting which includes three distinct phases and three levels of argument. Conceptually, the paper draws heavily upon the seminal work of Littler and Gandolfi (2008) seeking to expand and update their 2008 Academy of Management (AOM) Conference paper. The paper culminates with a contemporary discussion of current downsizing practices showcasing that the strategy of downsizing has remained a popular restructuring method on a global scale.downsizing; cost cutting; phase; strategy.

Field Theories on the Poincar\'e Disk

The massive scalar field theory and the chiral Schwinger model are quantized on a Poincar\'e disk of radius $\rho$. The amplitudes are derived in terms of hypergeometric functions. The behavior at long distances and near the boundary of some of the relevant correlation functions is studied. The exact computation of the chiral determinant appearing in the Schwinger model is obtained exploiting perturbation theory. This calculation poses interesting mathematical problems, as the Poincar\'e disk is a noncompact manifold with a metric tensor which diverges approaching the boundary. The results presented in this paper are very useful in view of possible extensions to general Riemann surfaces. Moreover, they could also shed some light in the quantization of field theories on manifolds with constant curvature scalars in higher dimensions.Comment: 22 pages, Plain TeX+harvma

Physical models from noncommutative causality

We introduced few years ago a new notion of causality for noncommutative spacetimes directly related to the Dirac operator and the concept of Lorentzian spectral triple. In this paper, we review in a non-technical way the noncommutative causal structure of many toy models as almost commutative spacetimes and the Moyal-Weyl spacetime. We show that those models present some unexpected physical interpretations as a geometrical explanation of the Zitterbewegung trembling motion of a fermion as well as some geometrical constraints on translations and energy jumps of wave packets on the Moyal spacetime.Comment: 10 pages, 4 figures, proceedings of ICNFP 201

Decorated Great Siege armours for the Hospitaller Knights at the Palace Armoury Museum, Valletta

The collection of arms and Armour at the Palace Armoury Museum in Valletta represents the Hospitallers' military adaptations during the path of warfare in history and their artistic tastes. Particularly interesting are the mid-sixteenth century Armours, frequently termed the "Great Siege Armours". The latter bear intricate designs of decorations that speak a Mannerist artistic language, inherited by the Italian Renaissance. This language, one may perhaps add, was international and spread from Northern Italy and Southern Germany throughout Europe, manifesting itself in the emergence of different schools of armourers and decorators. The present collection was first catalogued by Sir G. F. Laking in 1903. Laking categorised and attributed several pieces and harnesses, and he was to remain the only scholar to research these valuable items until 1969. In 1969 the UNESCO sent two Polish experts to study and inventory the arms and armours within the collection. Z. Zygulsky and A. Czerwinsky worked on an extensive and very important inventory between 25 January and 7 February 1969. Unfortunately, the work carried out by the Polish experts lost much ofits validity in 1975 when the armoury was moved to what were once the Palace's stables. The UNESCO experts had organised and catalogued each item, inventorizing portions, measurements and case numbers. Hence, the items had to be re-ordered. For a more academic study on the collection of arms and armour, and Hospitaller military organisation, the most recent study was that carried out by S. C. Spiteri in 2003. As for the decorations and methods of identification of Hospitaller Great Siege Armours, the most important work was recently carried out by K. Watts. The latter is the curator of Art and Armour at the Royal Armouries of Leeds.peer-reviewe

Towards a noncommutative version of Gravitation

Alain Connes' noncommutative theory led to an interesting model including both Standard Model of particle physics and Euclidean Gravity. Nevertheless, an hyperbolic version of the gravitational part would be necessary to make physical predictions, but it is still under research. We shall present the difficulties to generalize the model from Riemannian to Lorentzian Geometry and discuss key ideas and current attempts.Comment: 7 pages, to appear in the AIP proceedings of the "Invisible Universe International Conference", UNESCO-Paris, June 29-July 3, 200

Truth-value semantics and functional extensions for classical logic of partial terms based on equality

We develop a bottom-up approach to truth-value semantics for classical logic of partial terms based on equality and apply it to prove the conservativity of the addition of partial description and partial selection functions, independently of any strictness assumption.Comment: 15 pages, to appear in the Notre Dame Journal of Formal Logi