The Anatomy of Large Scale Systems

Many theoretical analyses of systems emphasize their behavior. In this paper we shall emphasize the role of organizational structure in influencing certain aspects of the behavior of systems, rather than the full behavior of the systems. There are several historical examples where structure was analyzed early on in order to gain a better understanding of systems. In medicine, for example, anatomy was studied well before we had a deep understanding of the role and behavior of subsystems or infrastructures of the body, such as the liver and blood flow. Different generic structures or architectures provide different advantages and disadvantages in coping with changes in the overall environment in which an evolving system is expected to operate during its lifetime. We shall discuss some of these advantages and disadvantages for various generic structures or architectures. One difficulty in discussing systems issues is the lack of a relatively precise language and concepts for dealing with such issues. We propose that abstract algebra has at least some of the needed concepts

Macsyma: A personal history

AbstractThe Macsyma system arose out of research on mathematical software in the AI group at MIT in the 1960s. Algorithm development in symbolic integration and simplification arose out of the interest of people, such as the author, who were also mathematics students. The later development of algorithms for the GCD of sparse polynomials, for example, arose out of the needs of our user community. During various times in the 1970s the computer on which Macsyma ran was one of the most popular nodes on the ARPANET. We discuss the attempts in the late 70s and the 80s to develop Macsyma systems that ran on popular computer architectures. Finally, we discuss the impact of the fundamental ideas in Macsyma on the author’s current research on large scale engineering and socio-technical systems

Analogies Between Complex Systems and Phases of Matter

The behavior of a complex system in a changing environment is strongly affected by the system's architecture. We present an analogy between the major phases of matter (solid, liquid, gas) and three major generic architectures of complex systems: tree structures, layered structures and grid networks. This analogy is realized using a graph-based formalism, with nodes and edges in a given configuration. Solid materials are akin to tree structures, especially when we consider that most solids actually have cracks. Solids with cracks between their components can be modeled by nodes (representing each component) and their interconnection, leading to a tree structured hierarchy. Gases made up of molecules can be modeled by nodes (the molecules) with local interconnections representing nearby molecules in space, thus forming a grid network. Liquids can form layers as in a mixture of oil and water. We represent this by connections that are densely horizontal within layers as well as sparsely vertical between layers. A key issue for complex systems is the ease by which they may be changed, which we call the system’s flexibility. Our definition of flexibility indicates that tree structures, like solids, are relatively inflexible and that grid networks, like gases, are extremely flexible, possibly leading to loss of control and chaotic behavior. Like liquids, layered systems are intermediate in flexibility and controllability. Solids, even with cracks, are relatively difficult to modify, whereas gases change internal form so quickly that they can only be constrained; not controlled. Liquids are intermediate in their ability to change form internally. Just as heating solids can lead to liquids, and heating liquids can result in gases, we shall present transformations in the interconnection structure of systems, analogous to heating, that change tree structures into layered ones and layered structures into networks

Flexibility, Complexity, and Controllability in Large Scale Systems

System structure is a key determinant of system behavior. There is a particularly strong link between a system’s structure and its flexibility – it’s capacity to respond to changes. Often, adding flexibility entails adding complexity. In this paper, we propose measures for a system’s complexity that are complementary to existing flexibility measures. Furthermore, flexibility often comes at the cost of some measure of control over the system’s behavior. We therefore propose a metric for system controllability that is complementary to our flexibility metric

Estimating Namibias Equilibrium Real Exchange Rate

This paper estimates the equilibrium real exchange rate for Namibia for the post independence period (1998 to 2012) using quarterly data. Increases in the ratio of investment to GDP and resource balance are associated with an appreciation of the real exchange rate. The terms of trade causes the real exchange rate to depreciate, which suggests that the substitution effect was dominant over the income effect. The real exchange rate adjusts to equilibrium rate while the speed of adjustment indicates that it takes about 4.4 quarters or 1.1 years for 50 percent of the deviation from the equilibrium to be corrected. There were periods of undervaluation and overvaluation of the real exchange, which means that the real exchange rate experienced misalignment

Situation analysis of healthcare service delivery using geographically weighted regression: (A case study of Sironko District, Eastern Uganda)

Geography plays an important role in planning and allocation of healthcare resources for an effective and efficient health system. Lack of statistical information analyzed using geostatistical tools then becomes a major bottleneck to proper planning and policy formulation in healthcare delivery. This study sought to compare existing health staffing, funding and medical supplies data given minimal national healthcare package, spatially explore the relationship between health service utilization and gaps in resource allocation, and to develop propositions to support the health policy. Facility survey and secondary data collection from the District Health Office and the Ministry of Health were utilized. Geographically Weighted Regression was used to spatially explore the relationships between Out-patient department attendance and gaps in health funding, staffing and stock-out days for essential drugs in health facilities. Global Moran’s I test was performed on the standard residuals to statistically test for their randomness. The analysis yielded local parameter estimates which were mapped to reveal the spatial variation of the relationships. There was strong influence of facility allocation gap in the North West diminishing towards South East, Strong negative influence of the staffing gap in the South West diminishing eastwards, and High influence of Stock-Out days in the South compared to the South West. Basing on the observations, the study proposed increased health vote while revising allocation based more on need other than solely on budgetary allocation of funds, increased staffing and providence of incentives for disadvantaged areas, and monitoring of drug supply and dispensing at health centres

Financial stress spillover across Asian Countries.

This paper uses fractional integration techniques to explore the stochastic properties of the Financial Stress Indices (FSIs) of 10 Asian countries, further investigating the bilateral linkages between them to ascertain how financial stress spreads among countries in the region. For the FSIs of each country, the results show that all the estimated orders of integration are in the interval (0, 1) implying fractional integration and a long memory pattern. Thus, shocks will have transitory though long‐lasting effects. For the cross‐country spillovers of the FSIs, we find that convergence is satisfied in all cases with values of the differencing parameter around 0 and thus showing short memory behavior. It is worth noting that for the larger economies in the region, Japan and China, financial stress transmission between Japan and the smaller economies was faster than with respect to China. Overall, the results provide valuable information on the financial market activity of the countries in the region. To check for the robustness of the baseline results we also use systemic risk measures for these countries, CoVaR with the results showing evidence of fractional integration for the individual series, with all values of the differencing parameter in the range (0, 1). For convergence, there is a substantial reduction in the degree of integration, though the results are not as clear as with the FSIs.pre-print412 K

Mycobacterium tuberculosis spoligotypes and drug susceptibility pattern of isolates from tuberculosis patients in South-Western Uganda

BACKGROUND: Determination of the prevalence and drug susceptibility of the M. tuberculosis strains is important in tuberculosis control. We determined the genetic diversity and susceptibility profiles of mycobacteria isolated from tuberculosis patients in Mbarara, South Western Uganda. METHODS: We enrolled, consecutively; all newly diagnosed and previously treated smear-positive TB patients aged ≥ 18 years. The isolates were characterized using regions of difference (RD) analysis and spoligotyping. Drug resistance against rifampicin and isoniazid were tested using the Genotype(® )MDRTBplus assay and the indirect proportion method on Lowenstein-Jensen media. HIV-1 testing was performed using two rapid HIV tests. RESULTS: A total of 125 isolates from 167 TB suspects (60% males) with a mean age 33.7 years and HIV prevalence of 67.9% (55/81) were analyzed. Majority (92.8%) were new cases while only 7.2% were retreatment cases. All the 125 isolates were identified as M. tuberculosis strict sense with the majority (92.8%) of the isolates being modern strains while seven (7.2%) isolates were ancestral strains. Spoligotyping revealed 79 spoligotype patterns, with an overall diversity of 63.2%. Sixty two (49.6%) of the isolates formed 16 clusters consisting of 2-15 isolates each. A majority (59.2%) of the isolates belong to the Uganda genotype group of strains. The major shared spoligotypes in our sample were SIT 135 (T2-Uganda) with 15 isolates and SIT 128 (T2) with 3 isolates. Sixty nine (87%) of the 79 patterns had not yet been defined in the SpolDB4.0.database. Resistance mutations to either RIF or INH were detected in 6.4% of the isolates. Multidrug resistance, INH and RIF resistance was 1.6%, 3.2% and 4.8%, respectively. The rpoβ gene mutations seen in the sample were D516V, S531L, H526Y H526D and D516V, while one strain had a Δ1 mutation in the wild type probes. There were three strains with katG (codon 315) gene mutations only while one strain showed the inhA promoter gene mutation. CONCLUSION: The present study shows that the TB epidemic in Mbarara is caused by modern M. tuberculosis strains mainly belonging to the Uganda genotype and anti-TB drug resistance rate in the region is low