Hierarchical models for service-oriented systems

We present our approach to the denotation and representation of hierarchical graphs: a suitable algebra of hierarchical graphs and two domains of interpretations. Each domain of interpretation focuses on a particular perspective of the graph hierarchy: the top view (nested boxes) is based on a notion of embedded graphs while the side view (tree hierarchy) is based on gs-graphs. Our algebra can be understood as a high-level language for describing such graphical models, which are well suited for defining graphical representations of service-oriented systems where nesting (e.g. sessions, transactions, locations) and linking (e.g. shared channels, resources, names) are key aspects

Non-linear relativistic perturbation theory with two parameters

An underlying fundamental assumption in relativistic perturbation theory is the existence of a parametric family of spacetimes that can be Taylor expanded around a background. Since the choice of the latter is crucial, sometimes it is convenient to have a perturbative formalism based on two (or more) parameters. A good example is the study of rotating stars, where generic perturbations are constructed on top of an axisymmetric configuration built by using the slow rotation approximation. Here, we discuss the gauge dependence of non-linear perturbations depending on two parameters and how to derive explicit higher order gauge transformation rules.Comment: 5 pages, LaTeX2e. Contribution to the Spanish Relativity Meeting (ERE 2002), Mao, Menorca, Spain, 22-24.September.200

Analysis of flow cytometric aneuploid DNA histograms: validation of an automatic procedure against ad hoc experimental data

In this paper we present an improved version of a method for the automatic analysis of flow cytometric DNA histograms from samples containing a mixture of two cell populations. The procedure is tested against two sets of ad hoc experimental data, obtained by mixing cultures of cell lines in different known proportions. The potentialities of the method are enlightened and discussed with regard to its capability of recovering the population percentages, the DNA index and the G0/G1, S, G2+M phase fractions of each population. On the basis of the obtained results, the procedure appears to be a promising tool in the flow cytometric data analysis and, in particular, in problems of diagnosis and prognosis of tumor diseases

An Algebra of Hierarchical Graphs

We define an algebraic theory of hierarchical graphs, whose axioms characterise graph isomorphism: two terms are equated exactly when they represent the same graph. Our algebra can be understood as a high-level language for describing graphs with a node-sharing, embedding structure, and it is then well suited for defining graphical representations of software models where nesting and linking are key aspects

A molecular dynamics simulation of water confined in a cylindrical SiO2 pore

A molecular dynamics simulation of water confined in a silica pore is performed in order to compare it with recent experimental results on water confined in porous Vycor glass at room temperature. A cylindrical pore of 40 A is created inside a vitreous SiO2 cell, obtained by computer simulation. The resulting cavity offers to water a rough hydrophilic surface and its geometry and size are similar to those of a typical pore in porous Vycor glass. The site-site distribution functions of water inside the pore are evaluated and compared with bulk water results. We find that the modifications of the site-site distribution functions, induced by confinement, are in qualitative agreement with the recent neutron diffraction experiment, confirming that the disturbance to the microscopic structure of water mainly concerns orientational arrangement of neighbouring molecules. A layer analysis of MD results indicates that, while the geometrical constraint gives an almost constant density profile up to the layers closest to the interface, with an uniform average number of hydrogen bonds (HB), the hydrophilic interaction produces the wetting of the pore surface at the expenses of the adjacent water layers. Moreover the orientational disorder togheter with a reduction of the average number of HB persists in the layers close to the interface, while water molecules cluster in the middle of the pore at a density and with a coordination similar to bulk water.Comment: RevTex, 11 pages, 12 figures; to appear in June 15 issue of J. Chem. Phy

Unified Dark Matter scalar field models with fast transition

We investigate the general properties of Unified Dark Matter (UDM) scalar field models with Lagrangians with a non-canonical kinetic term, looking specifically for models that can produce a fast transition between an early Einstein-de Sitter CDM-like era and a later Dark Energy like phase, similarly to the barotropic fluid UDM models in JCAP1001(2010)014. However, while the background evolution can be very similar in the two cases, the perturbations are naturally adiabatic in fluid models, while in the scalar field case they are necessarily non-adiabatic. The new approach to building UDM Lagrangians proposed here allows to escape the common problem of the fine-tuning of the parameters which plague many UDM models. We analyse the properties of perturbations in our model, focusing on the the evolution of the effective speed of sound and that of the Jeans length. With this insight, we can set theoretical constraints on the parameters of the model, predicting sufficient conditions for the model to be viable. An interesting feature of our models is that what can be interpreted as w_{DE} can be <-1 without violating the null energy conditions.Comment: Slightly revised version accepted for publication in JCAP, with a few added references; 27 pages, 13 figure

Mitochondria: From physiology to pathology

Over the past decade, the role of mitochondria has extended beyond those tasks for which these organelles are historically known [...]

Integrating Dynamics and Wear Modelling to Predict Railway Wheel Profile Evolution

The aim of the work described was to predict wheel profile evolution by integrating multi-body dynamics simulations of a wheelset with a wear model. The wear modelling approach is based on a wear index commonly used in rail wear predictions. This assumes wear is proportional to Tγ, where T is tractive force and γ is slip at the wheel/rail interface. Twin disc testing of rail and wheel materials was carried out to generate wear coefficients for use in the model. The modelling code is interfaced with ADAMS/Rail, which produces multi-body dynamics simulations of a railway wheelset and contact conditions at the wheel/rail interface. Simplified theory of rolling contact is used to discretise the contact patches produced by ADAMS/Rail and calculate traction and slip within each. The wear model combines the simplified theory of rolling contact, ADAMS/Rail output and the wear coefficients to predict the wear and hence the change of wheel profile for given track layouts

From radio-quiet to radio-silent: low luminosity Seyfert radio cores

A strong effort has been devoted to understand the physical origin of radio emission from low-luminosity AGN (LLAGN), but a comprehensive picture is still missing. We used high-resolution ($\le$1 arcsec), multi-frequency (1.5, 5.5, 9 and 14 GHz) NSF's Karl G. Jansky Very Large Array (VLA) observations to characterise the state of the nuclear region of ten Seyfert nuclei, which are the faintest members of a complete, distance-limited sample of 28 sources. With the sensitivity and resolution guaranteed by the VLA-A configuration, we measured radio emission for six sources (NGC3185, NGC3941, NGC4477, NGC4639, NGC4698 and NGC4725), while for the remaining four (NGC0676, NGC1058, NGC2685 and NGC3486) we put upper limits at tens uJy/beam level, below the previous 0.12 mJy/beam level of Ho&Ulvestad (2001), corresponding to luminosities down to L$\le10^{19}$ W/Hz at 1.5 GHz for the highest RMS observation. Two sources, NGC4639 and NGC4698, exhibit spectral slopes compatible with inverted spectra ($\alpha\le$0, $S_{\nu}\,\propto\,{\nu}^{-\alpha}$), hint for radio emission from an optically-thick core, while NGC4477 exhibits a steep (+0.52$\pm$0.09) slope. The detected sources are mainly compact on scales $\le$ arcseconds, predominantly unresolved, except NGC3185 and NGC3941, in which the resolved radio emission could be associated to star-formation processes. A significant X-ray - radio luminosities correlation is extended down to very low luminosities, with slope consistent with inefficient accretion, expected at such low Eddington ratios. Such sources will be one of the dominant Square Kilometre Array (SKA) population, allowing a deeper understanding of the physics underlying such faint AGN.Comment: accepted for publication on MNRAS (19 pages, 26 figures