Stochastic modelling of the effects of interdependencies between critical infrastructure

An approach to Quantitative Interdependency Analysis, in the context of Large Complex Critical Infrastructures, is presented in this paper. A Discrete state–space, Continuous–time, Stochastic Process models the operation of critical infrastructure, taking interdependencies into account. Of primary interest are the implications of both model detail (that is, level of model abstraction) and model parameterisation for the study of dependencies. Both of these factors are observed to affect the distribution of cascade–sizes within and across infrastructure

Teaching Social Studies from multicultural perspective: a practical approach to re-fashion African Studies for transformation

Currently, global education and global citizenship for social transformation addresses the issues of cordial and harmonious existence of our time. Africa is a multilingual and multicultural continent with about 3.000 ethnic groups and 2000 languages spoken; therefore, introduction of multicultural approach in teaching will ensure effective socialization and transformative education in Africa.  The roots to challenge bias, prejudice and creating classroom environment that reflects the learner’s culture for national unity lies in multicultural education. Multicultural education is a system of instruction which attempts to foster cultural pluralism and acknowledges the difference between race and culture in order to promote societal change and orderliness. This work examined a multicultural educational strategy which could be used in helping students from diverse racial, cultural, ethnic and language groups to experience academic success. Multicultural Concepts Knowledge Test (r=0.82), Multicultural Concept Attitude Scale (r= 0.86) were administered on 251 junior secondary school students from five secondary schools in the south-west region of Nigeria using the simple random technique. Two null hypotheses were formulated and tested at 0.05 level of significance. Data were analyzed using descriptive statistics, analysis of covariance. Treatment had significant main effect on students’ posttest knowledge scores in multicultural concepts (F (2,340) = 5.835; p<.05).  and attitude to multicultural concepts (F (2,340) = 34.055; P<.05). The MCA shows that the cooperative learning group had higher adjusted posttest knowledge score (x =10.14; Dev. =.83) In summary, findings of this study revealed that the cooperative multicultural learning strategy is effective for teaching multicultural classrooms. Therefore, this calls for improved approaches towards teaching by educators in order to bring us closer to the goal of multicultural education    

Effect of Concept Mapping Instructional Strategy on Junior Secondary School Student’s Knowledge of Multiculturalism in the Global 21st Century Social Studies Classroom

This ever-increasing diversity in today's classrooms is prompting teachers to incorporate a multicultural approach to lesson planning. The classroom in the 21st century is also more focused on a proactive learning environment rather than merely dispensing information. Hence, it is vital that teachers offer a rich and varied multicultural curriculum to accommodate the culturally diverse 21st century classroom. This article describes how concept mapping techniques were applied to evaluate the development of a solution-focused, public alternative school programme. Concept mapping appears to be a useful programme evaluation methodology for school workers to consider a valuable tool for examining complex problems and solutions within school organizations. A 30 item achievement test was administered on 50 junior secondary school students purposively selected from two secondary schools in the south-west region of Nigeria. Data were analysed using t- test. Three null hypotheses were raised and tested at 0.05 level of significance. The findings of this study revealed that there is a significant difference between pre and post test scores of the students when exposed to concept mapping instructional strategy (t=10.75;df=98;p<0.05). Therefore, this calls for improved approaches of teaching in culturally diverse 21st century Social Studies classroom. Key words: Concept mapping, Multiculturalism, Global, Century, Maps, teaching technique, students, Social Studies

Stochastic modeling for performance evaluation of database replication protocols

Performance is often the most important non-functional property for database systems and associated replication solutions. This is true at least in in-dustrial contexts. Evaluating performance using real systems, however, is com-putationally demanding and costly. In many cases, choosing between several competing replication protocols poses a difficulty in ranking these protocols meaningfully: the ranking is determined not so much by the quality of the com-peting protocols but, instead, by the quality of the available implementations. Addressing this difficulty requires a level of abstraction in which the impact on the comparison of the implementations is reduced, or entirely eliminated. We propose a stochastic model for performance evaluation of database replication protocols, paying particular attention to: i) empirical validation of a number of assumptions used in the stochastic model, and ii) empirical validation of model accuracy for a chosen replication protocol. For the empirical validations we used the TPC-C benchmark. Our implementation of the model is based on Stochastic Activity Networks (SAN), extended by bespoke code. The model may reduce the cost of performance evaluation in comparison with empirical measurements, while keeping the accuracy of the assessment to an acceptable level

Quantification of the Impact of Cyber Attack in Critical Infrastructures

In this paper we report on a recent study of the impact of cyber-attacks on the resilience of complex industrial systems. We describe our approach to building a hybrid model consisting of both the system under study and an Adversary, and we demonstrate its use on a complex case study - a reference power transmission network (NORDIC 32), enhanced with a detailed model of the computer and communication system used for monitoring, protection and control. We studied the resilience of the modelled system under different scenarios: i) a base-line scenario in which the modelled system operates in the presence of accidental failures without cyber-attacks; ii) scenarios in which cyber-attacks can occur. We discuss the usefulness of our findings and outline directions for further work

Traveling wave solutions for two species competitive chemotaxis systems

In this paper, we consider two species chemotaxis systems with Lotka–Volterra competition reaction terms. Under appropriate conditions on the parameters in such a system, we establish the existence of traveling wave solutions of the system connecting two spatially homogeneous equilibrium solutions with wave speed greater than some critical number c∗. We also show the non-existence of such traveling waves with speed less than some critical number c∗0 , which is independent of the chemotaxis. Moreover, under suitable hypotheses on the coefficients of the reaction terms, we obtain explicit range for the chemotaxis sensitivity coefficients ensuring c∗ = c∗0 , which implies that the minimum wave speed exists and is not affected by the chemoattractant

Competition-exclusion and coexistence in a two-strain SIS epidemic model in patchy environments

This work examines the dynamics of solutions of a two-strain SIS epidemic model in patchy environments. The basic reproduction number $\mathcal{R}_0$ is introduced, and sufficient conditions are provided to guarantee the global stability of the disease-free equilibrium (DFE). In particular, the DFE is globally stable when either: (i) $\mathcal{R}_0\le \frac{1}{k}$, where $k\ge 2$ is the total number of patches, or (ii) $\mathcal{R}_0<1$ and the dispersal rate of the susceptible population is large. Moreover, the questions of competition-exclusion and coexistence of the strains are investigated when the single-strain reproduction numbers are greater than one. In this direction, under some appropriate hypotheses, it is shown that the strain whose basic reproduction number and local reproduction function are the largest always drives the other strain to extinction in the long run. Furthermore, the asymptotic dynamics of the solutions are presented when either both strain's local reproduction functions are spatially homogeneous or the population dispersal rate is uniform. In the latter case, the invasion numbers are introduced and the existence of coexistence endemic equilibrium (EE) is proved when these invasion numbers are greater than one. Numerical simulations are provided to complement the theoretical results.Comment: 35 page

Effects of ficus exasperata vahl. (moraceae) leaf aqueous extract on the renal function of streptozotocin-treated rats

The present study was undertaken to evaluate the possible reno-protective effect of Ficus exasperata leaf aqueous extract (FEE) in a rat experimental paradigm of diabetes mellitus. Forty Wistar rats (weighing 200&#8211;230 g) were divided into four (A, B, C, and D) groups, each group consisting of 10 rats. Group A rats served as &#8216;control&#8217; animals and received citrate buffer (pH 6.3) solution in quantities equivalent to intraperitoneally-administered volumes of streptozotocin (STZ) and FEE. Diabetes mellitus was induced in Groups B and C rats by intraperitoneal injections of STZ (75 mg/kg). Group C rats were additionally treated with FEE (100 mg/kg/day, p.o.) 4 weeks post STZ injections, for 4 consecutive weeks. Group D rats received FEE (100 mg/kg/day p.o.) only for 4 weeks. Post-euthanisation, kidney tissues were excised for histopathological evaluation and processed for light microscopy. Plasma malondialdehyde and tissue nitric oxide were determined. Serum creatinine, blood urea nitrogen, nitrite, and albumin concentrations were measured for the evaluation of renal function. The diabetic rats significantly lost more weight and their blood glucose levels were significantly elevated as compared to the &#8216;control&#8217; group of animals. Renal dysfunction was evidenced by kidney hypertrophy, decreased renal blood flow, and increased serum creatinine and nitrite concentrations. Furthermore, vascular dysfunction, as evidenced by decreased carotid blood flow, was observed in the diabetic rats. FEE treatment positively ameliorated the alterations in the biochemical variables in the STZ + FEE-treated rats. In conclusion, our findings suggest that FEE treatment ameliorates STZ-induced nephrotoxicity

COVID-19 Experience: Taking the right steps at the right time to prevent avoidable morbidity and mortality in Nigeria and other nations of the world

The 2020 Coronavirus pandemic has caused countless governmental and societal challenges around the world. Nigeria, Africa’s most populous nation, has been exposed in recent years to a series of epidemics including Ebola and Lassa Fever. In this paper we document our perception of the national response to COVID-19 in Nigeria. The response to the pandemic is with a healthcare system that has changed as a result of previous infectious disease outbreaks but in the context of scarce resources typical of many low-middle income countries. We make recommendations regarding what measures should be in place for future epidemics