196,345 research outputs found
Traffic Offloading/Onloading in Multi-RAT Cellular Networks
No full textWe analyze next generation cellular networks, offering connectivity to mobile users through multiple radio access technologies (RATs), namely LTE and WiFi. We develop a framework based on the Markovian agent formalism, which can model several aspects of the system, including user traffic dynamics and radio resource allocation. In particular, through a mean-field solution, we show the ability of our framework to capture the system behavior in flash-crowd scenarios, i.e., when a burst of traffic requests takes place in some parts of the network service area. We consider a distributed strategy for the user RAT selection, which aims at ensuring high user throughput, and investigate its performance under different resource allocation scheme
IN VITRO ANTIVIRAL ACTIVITY OF A CRANBERRY VACCINIUM MACROCARPON EXTRACT AGAINST EBOLA VIRUS AND RABIES VIRUS
No full textEmerging and reemerging viral infections represent a major concern for human and veterinary public health and there is an urgent need for the development of broad-spectrum antivirals. We have recently observed that a cranberry (Vaccinium macrocarpon) extract, which contains high levels of A2-type proanthocyanidins (PAC-A2), inhibits influenza A and B viruses
[1], herpes simplex virus type 1 and 2 [2], and Crimean-Congo Hemorrhagic Fever Virus [3] in vitro replication by interfering with the adhesion/internalization stage of the viral life cycle. In this work, we have evaluated the antiviral activity of the cranberry extract against two highly pathogenic viruses, such as Ebola Virus (EBOV) and Rabies Virus (RABV).
To evaluate the antiviral activity of the cranberry extract, a recombinant Vesicular Stomatitis Virus (pVSV) vector expressing the luciferase reporter was adopted. The pVSV was pseudotyped either with the EBOV or RABV glycoproteins. Time-of-addition, viral attachment,and entry assays were performed on Vero CCL-81 in the presence of different concentrations of the cranberry extract. Finally, experiments with infectious EBOV and RABV were performed to validate the results obtained with pseudovirus. The cranberry extract showed an inhibitory activity against both the pVSV-EBOV and pVSV-RABV infection. Treating target cells or the pseudovirus with the compound before or during the infection phase determined a significant reduction of viral infectivity. In contrast, only a modest inhibition was detected when cells were treated with the extract after
virus internalization. The antiviral activity of the cranberry extract was confirmed against the live EBOV, while experiments are ongoing for RABV. In Conclusions: - The cranberry extract inhibits EBOV and RABV infection acting at the early stages of
their replicative cycles. - This broad-spectrum antiviral activity suggests this cranberry extract (or its components)
as a promising antiviral candidate against emerging and re-emerging viral infections.
References
1. Luganini, A., Terlizzi, M. E., Catucci, G., Gilardi, G., Maffei, M. E., & Gribaudo, G. The Cranberry Extract Oximacro
® Exerts in vitro Virucidal Activity Against Influenza Virus by Interfering With Hemagglutinin. Front
Microbiol. 2018, 9, 1826. https://doi.org/10.3389/fmicb.2018.01826.
2. Terlizzi, M. E., Occhipinti, A., Luganini, A., Maffei, M. E., & Gribaudo, G. Inhibition of herpes simplex type 1 and
type 2 infections by Oximacro®, a cranberry extract with a high content of A-type proanthocyanidins (PACs-
A). Antiviral Res. 2016, 132, 154–164. https://doi.org/10.1016/j.antiviral.2016.06.006.
3. Mirandola, M., Salvati, M.V., Rodigari, C., Appelberg, K. S., Mirazimi, A., Maffei, M. E., Gribaudo, G., Salata, C.
Cranberry (Vaccinium macrocarpon) Extract Impairs Nairovirus Infection by Inhibiting the Attachment to
Tar-get Cells. Pathogens. 2021 Aug 13;10(8):1025. https://doi.org/10.3390/pathogens10081025
An Efficient Algorithm for the Transient Analysis of a Class of Deterministic Stochastic Petri Nets
No full textIn this paper a new algorithm for the transient solution of a sub-class of Deterministic Stochastic Petri Nets (DSPN) is proposed. The technique can be applied to DSPNs comprising only deterministic and immediate transitions and such that in each tangible marking only one deterministic transition is enabled. The algorithm does not require any additional restriction on the deterministic transition delays that can have any positive real value. Most of the optimized algorithms presented in the literature are based on an efficient solution of the equations governing the stochastic process associated with the DSPN; the new algorithm we propose is based on an efficient combinatorial analysis of the paths within the state space underlying the DSPN, instead
Performance Modeling And Analysis Of An Autonomic Router
No full textModern networking is moving towards exploitation of autonomic features into networks to reduce management effort and compensate the increasing complexity of network infrastructures, e.g. in large computing facilities such the data centers that support cloud services delivery. Autonomicity provides the possibility of reacting to anomalies in network traffic by recognizing them and applying administrator defined reactions without the need for human intervention, obtaining a quicker response and easier adaptation to network dynamics, and letting administrators focus on general system-wide policies, rather than on each component of the infrastructure. The process of defining proper policies may benefit from adopting model-based design cycles, to get an estimation of their effects. In this paper we propose a model-based analysis approach of a simple autonomic router, using Stochastic Petri Nets, to evaluate the behavior of given policies designed to react to traffic workloads. The approach allows a detailed analysis of the dynamics of the policy and is suitable to be used in the preliminary phases of the design cycle for a Software Defined Networks compliant router control plane
Theory and application of multi-formalism modeling
No full textWith complex systems and complex requirements being a challenge that designers must face to reach quality results, multi-formalism modeling offers tools and methods that allow modelers to exploit the benefits of different techniques in a general framework intended to address these challenges. Theory and Application of Multi-Formalism Modeling boldly explores the importance of this topic by gathering experiences, theories, applications, and solutions from diverse perspectives of those involved with multi-formalism modeling. Professionals, researchers, academics, and students in this field will be able to critically evaluate the latest developments and future directions of multi-formalism research
Element Based Semantics in Multi Formalism Performance Models
No full textThe design and the requirements of modern computer-based systems have reached a complexity level that calls for the use of models for the verification of non functional requirements since the beginning of their design cycle. Such systems are however too complex to be modeled directly in a simple unstructured formal language like Queueing Networks or Petri Nets. SIMTHESys (Structured Infrastructure for Multiformalism modeling and Testing of Heterogeneous formalisms and Extensions for SYStems) is a novel approach to multiformalism compositional modeling, that is based on the possibility of freely specifying the dynamics of the elements of a formal modeling language in an open framework. This is obtained by the application of consolidated metamodeling foundations to the description of models, together with the concept of behavior as a bridge between formalism dynamics and solution techniques. In this paper the main concepts of the SIMTHESys approach are presented, together with a running example of how SIMTHESys copes with performance evaluation of multiformalism models
Analysis of Television and Cinema Productions using Mean Field Models
No full textTelevision and cinema productions have a critical influence in today's economy, but performance evaluation techniques are rarely used in these contexts. Both kind of productions share a similar key feature: the spectator. It is in fact the final user who determines the success of a production by deciding to spend his or her money for it. In this paper we use Mean Field techniques to model the behavior of the users, of the production and of the distribution. We use Generalized Stochastic Petri Nets as an upper level formalism to simplify the description of the proposed models. Finally we present comparisons with real data (where available) to prove the validity of the Mean Field approach. © 2010 Elsevier B.V. All rights reserved
On the use of structural Petri net analysis for studying product form equilibrium distributions of queueing networks with blocking
No full textIn this paper we investigate some relations between the Petri net formalism and the queueing networks with blocking. This type of queueing network models are used to represent systems with finite capacity resource constraints, such as production, communication and computer systems. Various blocking mechanisms have been defined in the literature to represent the different behaviours of real systems with limited resources. We show that the representation of these queueing networks by means of Generalized Stochastic Petri Nets offers the possibility of using results developed within the Petri net framework. In particular, we investigate product form equilibrium distributions for queueing networks with blocking by means of structural Petri net results. More precisely, we use the notion of implicit places. With this concept we characterise a class of queueing networks with blocking having interesting properties. For each queueing network of this class there exists another model with the same performance measures and exhibiting product form equilibrium distribution
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