Omar M. Barukab

Fault-tree modelling of computer system security

Quantitative assessment of the effect of security breaches on a computer system can be based on the following: specification of all foreseeable types of basic events and estimation of their probabilities of occurrence over a stated period of time; observation of the various types of security measures employed by the system; definition of the undesired top events resulting from security breaches, and estimation of the system’s vulnerability to each of these events as the cost incurred by the system if that event took place; mathematical modelling of the logical relations between the aforementioned entities. In this paper we adapt the fault-tree methodology of reliability engineering to the quantification of security exposure of computer systems. In this new context, a fault tree can be described as a logic diagram whose input represents breach events at various system levels, and whose vertices represent logic operations or gates. The root or output of the fault tree can be any of the undesired top events. We briefly survey algorithms for converting the switching (Boolean) expression of the indicator variable for the top event into a probability expression. Once the top event probability is determined, it can be multiplied by the system’s vulnerability to that event to yield a quantified value of the system’s exposure to it. We also handle the doubly stochastic problem of estimating the uncertainty in the top event probability by using an analytic exact formula relating the variance of the top event probability to the variances of the basic event probabilities. An example of a typical computer system is presented wherein numerical estimates are obtained for the top event probabilities and their variances and for the importance ranking of the various breach events.

A purely map procedure for two-level multiple-output logic minimization

A pedagogical treatment of two-level multiple-output logic minimization is presented through a compact exposition of a novel manual fast procedure. This procedure is a purely map technique which generalizes the map procedure for single-output minimization. It requires neither the generation of the set of all paramount prime implicants, nor the construction of a cover matrix. Instead, it utilizes certain visual interactions between various groups of maps placed at distinct levels of a Hasse diagram, which is conveniently drawn in a Karnaugh map layout so that any parent map is easily visualized as adjacent to all its children maps. The present exposition is believed to enhance what is currently available in undergraduate texts, and is intended as a supplement to, rather than a replacement of, automated computational experience. An illustrative example demonstrates the proposed procedure for the dual cases of AND–OR and OR–AND minimizations.

A versatile mathematical work-flow to explore how Cancer Stem Cell fate influences tumor progression

BackgroundNowadays multidisciplinary approaches combining mathematical models with experimental assays are becoming relevant for the study of biological systems. Indeed, in cancer research multidisciplinary approaches are successfully used to understand the crucial aspects implicated in tumor growth. In particular, the Cancer Stem Cell (CSC) biology represents an area particularly suited to be studied through multidisciplinary approaches, and modeling has significantly contributed to pinpoint the crucial aspects implicated in this theory.More generally, to acquire new insights on a biological system it is necessary to have an accurate description of the phenomenon, such that making accurate predictions on its future behaviors becomes more likely. In this context, the identification of the parameters influencing model dynamics can be advantageous to increase model accuracy and to provide hints in designing wet experiments. Different techniques, ranging from statistical methods to analytical studies, have been developed. Their applications depend on case-specific aspects, such as the availability and quality of experimental data, and the dimension of the parameter space.ResultsThe study of a new model on the CSC-based tumor progression has been the motivation to design a new work-flow that helps to characterize possible system dynamics and to identify those parameters influencing such behaviors. In detail, we extended our recent model on CSC-dynamics creating a new system capable of describing tumor growth during the different stages of cancer progression. Indeed, tumor cells appear to progress through lineage stages like those of normal tissues, being their division auto-regulated by internal feedback mechanisms. These new features have introduced some non-linearities in the model, making it more difficult to be studied by solely analytical techniques. Our new work-flow, based on statistical methods, was used to identify the parameters which influence the tumor growth. The effectiveness of the presented work-flow was firstly verified on two well known models and then applied to investigate our extended CSC model.ConclusionsWe propose a new work-flow to study in a practical and informative way complex systems, allowing an easy identification, interpretation, and visualization of the key model parameters. Our methodology is useful to investigate possible model behaviors and to establish factors driving model dynamics.Analyzing our new CSC model guided by the proposed work-flow, we found that the deregulation of CSC asymmetric proliferation contributes to cancer initiation, in accordance with several experimental evidences. Specifically, model results indicated that the probability of CSC symmetric proliferation is responsible of a switching-like behavior which discriminates between tumorigenesis and unsustainable tumor growth.

Two-Level Multiple-Output Logic Minimization Using A Single Function

A new method for obtaining a two-level collective minimal cover for a set of incompletely-specified switching functions

A Traffic Congestion Framework for Smart Riyadh City based on IoT Services

S=\{f_1,f_2,\ldots,f_n\}

Use of Flow Equivalent Servers in the Transient Analysis of Product Form Queuing Networks

is presented. The method relies on the introduction of a single auxiliary function F whose subfunctions (restrictions) with respect to some additional auxiliary variables

Identification of hub genes and their SNP analysis in West Nile virus infection for designing therapeutic methodologies using RNA-Seq data

y_1,y_2,\ldots,y_{n-1}

Constructing Matrix Exponential Distributions by Moments and Behavior around Zero

are certain members of S . The complete sum of F has full information on the multiple-output prime implicants (MOPIs) of the set of functions S . A particularly constrained minimal cover for F contains only labeled versions of some paramount prime implicants (PPIs) of S and can be used to construct a multiple-output minimal cover for S . The present method can proceed by map, algebraic or tabular techniques, though only the map version is presented herein. This version employs a single map whose construction avoids the ANDing operations needed in the classical method, and whose size is almost one half the total size of the maps used by the classical method, and whose entries can be variable as well as constant. The minimization process is a direct two-step technique that avoids constructing the set of all PPIs as it produces only these PPIs needed in the minimal cover. Details of the method are carefully explained and illustrated via a typical example.

In silico analysis of detrimental mutation in EPHB2 gene causing Alzheimer’s disease

Internet of Things (IoT) has become one of the most challenging issues in many researches to connect physical things through the internet by creating a virtual identity for everything. Traffic congestion in Riyadh city is chosen due to the proliferation in the number of vehicles on Riyadh roads that is resulting in grumbling by citizens. Currently, there is no reliable service offered to Riyadh citizens from the traffic department enabling them to access traffic information. A new traffic congestion framework for Riyadh is proposed so that it can help the development of traffic congestion services. This framework aims to benefit from the current Riyadh road infrastructure and apply the IoT paradigm for detecting traffic congestion. Sensing devices are used to identify the congestion of the traffic flow through providing multiple proposed services to the citizens such as a vehicle counting, live streaming video and rerouting services. Citizens are able to access all the services by using proposed mobile application connected to the internet, as all those services are integrated with public map Service. By using the services, the citizens are able to identify the exact location where congestion occurs and an alternate solution can be provided easily. To achieve this, Business Process Execution Language (BPEL) is embedded in one of the framework layers. Due to the effectiveness of BPEL, workflows are built to combine the proposed services with the legacy Riyadh services. This approach clearly defines how the services are executed through BPEL models.

An Exposition of the Modern Syllogistic Method of Propositional Logic

In this paper we deal with approximate transient analysis of Product Form Queuing Networks. In particular, we exploit the idea of flow equivalence to reduce the size of the model. It is well-known that flow equivalent servers lead to exact steady state solution in many cases. Our goal is to investigate the applicability of flow equivalence to transient analysis. We show that exact results can be obtained even in the transient phase, but the definition of the equivalent server requires the analysis of the whole original network. We propose thus to use approximate aggregate servers whose characterization demands much less computation. Specifically, the characterization corresponds to the steady state equivalent server of the stations that we aim to aggregate and thus can be achieved by analyzing the involved stations in isolation. This way, approximations can be derived for any queuing network, but the precision of the results depends heavily on the topology and on the parameters of the model. We illustrate the approach on numerical examples and briefly discuss a set of criteria to identify the cases when it leads to satisfactory approximation.