1,720,952 research outputs found
BDC-Decomposition for global influence analysis
No full textIn biochemical networks, the steady-state input-output influence is the sign of the output steady-state variation due to a persistent positive input perturbation; if the sign does not depend on the value of the strictly positive system parameters, the influence is structural. As recently shown for small perturbations, when the linearized system approximation is valid, steady-state input-output influences can be structurally assessed, for biochemical networks with m unknown parameters, by means of a vertex algorithm with complexity 2m. This letter shows that the structural input-output influence of a biochemical network is a global property, which does not require any small-perturbation assumption. It also shows that, using a new algorithm, the complexity can be reduced down to 2m-n , where n is the system order, thus drastically reducing the computation time. Finally, when the uncertain parameters belong to known intervals, non-conservative bounds are given for the steady-state ratio between output and input, allowing for sensitivity analysis.Accepted Author ManuscriptTeam Tamas Keviczk
The Trial of Giordano Bruno
Full text linkIn 1600, Giordano Bruno, one of the leading intellectuals of the Renaissance, was burned at the stake on the charge of heresy by the Roman Inquisition. He is remembered primarily for his cosmological theories, particularly that the universe was infinite with the Earth not being at its centre. Today, he has become a symbol of the struggle for religious and philosophical tolerance.
The Trial of Giordano Bruno, originally published in Italian in 2018, provides English audiences with a complete and updated reconstruction of the inquisitorial trial by analysing the accusations, witnesses, and legal proceedings in detail. The author also gives a detailed profile of Bruno as well as the body which arrested and accused him – the Inquisition.
This book will appeal to all those interested in the life and death of Giordano Bruno, as well as those interested in Early Modern legal proceedings, the Roman Inquisition, and the history of religious and philosophical tolerance
Benign epithelial lesions of the cervix, which can be mistaken as epithelial neoplastic malignancies: Morphological and immunohistochemical analysis
Full text linkIn this paper the Author describes the morphological and the immunohistochemical features of the most common lesions of the cervix, which can be mistaken for neoplastic malignancies (pseudoneoplastic lesions), on microscopic examination.The lesions discussed in this paper represent physiological changes and benign reactive lesions that are the consequences of hormone stimulation or inflammation, which occur in the cervix.
In the cervix there are many lesions which can mimic epithelial malignancies adn here the Author demonstrates that morphological, clinical data and immunohistochemical features are all useful for an accurate differential pathological diagnosi
Non neoplastic lesions that may mimic epithelial malignancies of the endometrium: Morphological and immunohistochemical analysis
No full textIn this paper the author describes the morphological and immunohistochemical features of the most common benign epithelial lesions of
the endometrium, which can be mistaken for neoplastic malignancies (pseudoneoplastic lesions). In addition, here it was demonstrated that both
morphologic clinical data and immunohistochemical features are useful for an accurate differential pathological diagnosis from non-neoplastic
lesions and epithelial malignancies
Can Clinical and Surgical Parameters Be Combined to Predict How Long It Will Take a Tibia Fracture to Heal? A Prospective Multicentre Observational Study: The FRACTING Study
Full text linkHealing of tibia fractures occurs over a wide time range of months, with a number of risk factors contributing to prolonged healing. In this prospective, multicentre, observational study, we investigated the capability of FRACTING (tibia FRACTure prediction healING days) score, calculated soon after tibia fracture treatment, to predict healing time.
Methods:
The study included 363 patients. Information on patient health, fracture morphology, and surgical treatment adopted were combined to calculate the FRACTING score. Fractures were considered healed when the patient was able to fully weight-bear without pain.
Results:
319 fractures (88%) healed within 12 months from treatment. Forty-four fractures healed after 12 months or underwent a second surgery. FRACTING score positively correlated with days to healing: r = 0.63 (p < 0.0001). Average score value was 7.3 ± 2.5; ROC analysis showed strong reliability of the score in separating patients healing before versus after 6 months: AUC = 0.823.
Conclusions:
This study shows that the FRACTING score can be employed both to predict months needed for fracture healing and to identify immediately after treatment patients at risk of prolonged healing. In patients with high score values, new pharmacological and nonpharmacological treatments to enhance osteogenesis could be tested selectively, which may finally result in reduced disability time and health cost savings
Polyhedral Lyapunov functions structurally ensure global asymptotic stability of dynamical networks iff the Jacobian is non-singular
No full textFor a vast class of dynamical networks, including chemical reaction networks (CRNs) with monotonic reaction rates, the existence of a polyhedral Lyapunov function (PLF) implies structural (i.e., parameter-free) local stability. Global structural stability is ensured under the additional assumption that each of the variables (chemical species concentrations in CRNs) is subject to a spontaneous infinitesimal dissipation. This paper solves the open problem of global structural stability in the absence of the infinitesimal dissipation, showing that the existence of a PLF structurally ensures global convergence if and only if the system Jacobian passes a structural non-singularity test. It is also shown that, if the Jacobian is structurally non-singular, under positivity assumptions for the system partial derivatives, the existence of an equilibrium is guaranteed. For systems subject to positivity constraints, it is shown that, if the system admits a PLF, under structural non-singularity assumptions, global convergence within the positive orthant is structurally ensured, while the existence of an equilibrium can be proven by means of a linear programming test and the computation of a piecewise-linear-in-rate Lyapunov function
Analysis of coupled genetic oscillators with delayed positive feedback interconnections
No full textGenetic oscillators have a fundamental role in the regulation not only of intracellular, but also of intercellular functions: for instance, in the segmentation clock, the synchronised oscillation of neighbouring cells generates spatial travelling waves that induce segmentation of precursors of the vertebral column. To investigate this type of phenomena, we consider the behaviour of two genetic negative feedback oscillators, each operating in a different cell, coupled by an intercellular positive-feedback interconnection with delays. The two coupled systems are nominally identical, but can be different due to noise and cell-to-cell variability. When they can be different in general, we study the effect of positive-feedback and of delay in inducing an oscillatory behaviour. When they are identical, we study how the intercellular feedback delay affects the phase difference between the two oscillators
Control-theoretic methods for biological networks
No full textFeedback is both a pillar of control theory and a pervasive principle of nature. For this reason, control-theoretic methods are powerful to analyse the dynamic behaviour of biological systems and mathematically explain their properties, as well as to engineer biological systems so that they perform a specific task by design. This paper illustrates the relevance of control-theoretic methods for biological systems. The first part gives an overview of biological control and of the versatile ways in which cells use feedback. By employing control-theoretic methods, the complexity of interlaced feedback loops in the cell can be revealed and explained, and layered feedback loops can be designed in the cell to induce the desired behaviours, such as oscillations, multi-stability and activity regulation. The second part is mainly devoted to modelling uncertainty in biology and understanding the robustness of biological phenomena due to their inherent structure. Important control-theoretic tools used in systems biology are surveyed. The third part is focused on tools for model discrimination in systems biology. A deeper understanding of molecular pathways and feedback loops, as well as qualitative information on biological networks, can be achieved by studying the “dynamic response phenotypes” that appear in temporal responses. Several applications to the analysis of biological systems are showcased.Accepted Author ManuscriptTeam Tamas Keviczk
Fair and Sparse Solutions in Network-Decentralized Flow Control
No full textWe proposed network-decentralized control strategies, in which each actuator can exclusively rely on local information, without knowing the network topology and the external input, ensuring that the flow asymptotically converges to the optimal one with respect to the p -norm. For 1 < p < ∞ , the flow converges to a unique constant optimal up∗. We show that the state converges to the optimal Lagrange multiplier of the optimization problem. Then, we consider networks where the flows are affected by unknown spontaneous dynamics and the buffers need to be driven exactly to a desired set-point. We propose a network-decentralized proportional-integral controller that achieves this goal along with asymptotic flow optimality; now it is the integral variable that converges to the optimal Lagrange multiplier. The extreme cases p=1 and p=∞ are of some interest since the former encourages sparsity of the solution while the latter promotes fairness. Unfortunately, for p=1 or p=∞ these strategies become discontinuous and lead to chattering of the flow, hence no optimality is achieved. We then show how to approximately achieve the goal as the limit for p 1 or p ∞.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Tamas Keviczk
A bounded complementary sensitivity function ensures topology-independent stability of homogeneous dynamical networks
No full textThis paper investigates the topology-independent stability of homogeneous dynamical networks, composed of interconnected equal systems. Precisely, dynamical systems with identical nominal transfer function F(s) are associated with the nodes of a directed graph whose arcs account for their dynamic interactions, described by a common nominal transfer function G(s). It is shown that topology-independent stability is guaranteed for all possible interconnections with interaction degree (defined as the maximum number of arcs leaving a node) equal at most to N if the infinity-norm of the complementary sensitivity function NF(s)G(s)/[1+NF(s)G(s)] is less than 1. This bound is non-conservative. When nodes and arcs transferences are affected by uncertainties with norm bound K>0, topology-independent stability is robustly ensured if the infinity-norm is less than 1/(1+2NK). For symmetric systems, stability is guaranteed for all topologies with interaction degree at most N if the Nyquist plot of NF(s)G(s) does not intersect the real axis to the left of -1/2. The proposed results are applied to fluid networks and platoon formation
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