439 research outputs found

    Measuring Ethnic Fractionalization in Africa

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    Kenya's New Constitution

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    On 4 August 2010, Kenyans voted to adopt a new constitution, culminating a process that began as part of a resolution to the violent conflict that followed the December 2007 elections. By reducing executive power, devolving authority, and guaranteeing rights to women, minorities, and marginalized communities, the constitution has the potential to transform Kenyan politics. Political and logistical obstacles will, however, pose a challenge to implementation. Yet that the constitution has been adopted amidst a broader trend toward the institutionalization of political power in Africa—a context in which formal constitutional rules are increasingly consequential—provides cause for cautious optimism

    RuleMonkey: software for stochastic simulation of rule-based models

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    <p>Abstract</p> <p>Background</p> <p>The system-level dynamics of many molecular interactions, particularly protein-protein interactions, can be conveniently represented using reaction rules, which can be specified using model-specification languages, such as the BioNetGen language (BNGL). A set of rules implicitly defines a (bio)chemical reaction network. The reaction network implied by a set of rules is often very large, and as a result, generation of the network implied by rules tends to be computationally expensive. Moreover, the cost of many commonly used methods for simulating network dynamics is a function of network size. Together these factors have limited application of the rule-based modeling approach. Recently, several methods for simulating rule-based models have been developed that avoid the expensive step of network generation. The cost of these "network-free" simulation methods is independent of the number of reactions implied by rules. Software implementing such methods is now needed for the simulation and analysis of rule-based models of biochemical systems.</p> <p>Results</p> <p>Here, we present a software tool called RuleMonkey, which implements a network-free method for simulation of rule-based models that is similar to Gillespie's method. The method is suitable for rule-based models that can be encoded in BNGL, including models with rules that have global application conditions, such as rules for intramolecular association reactions. In addition, the method is rejection free, unlike other network-free methods that introduce null events, i.e., steps in the simulation procedure that do not change the state of the reaction system being simulated. We verify that RuleMonkey produces correct simulation results, and we compare its performance against DYNSTOC, another BNGL-compliant tool for network-free simulation of rule-based models. We also compare RuleMonkey against problem-specific codes implementing network-free simulation methods.</p> <p>Conclusions</p> <p>RuleMonkey enables the simulation of rule-based models for which the underlying reaction networks are large. It is typically faster than DYNSTOC for benchmark problems that we have examined. RuleMonkey is freely available as a stand-alone application <url>http://public.tgen.org/rulemonkey</url>. It is also available as a simulation engine within GetBonNie, a web-based environment for building, analyzing and sharing rule-based models.</p

    Market innovation as framing, productive friction and bricolage: an exploration of the personal data market

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    This paper explores the possibilities offered by recent Science and Technology Studies (STS) research on markets for engaging with market innovation. Although there exist few reflections on how innovation happens in markets, market innovation has not been singularly theorized in STS-inspired market studies. In this paper, we explore the potential analytic utility of different sets of ideas in the field of market studies, such as ‘framing’ [Callon, M. (1998) ‘Introduction: the embeddedness of economic markets in economics’, in The Laws of Markets, ed. M. Callon, Blackwell, Oxford, pp. 1–57; Callon, M. (2007) ‘An essay on the growing contribution of economic markets to the proliferation of the social’, Theory, Culture & Society, vol. 24, no. 7–8, pp. 136–163], ‘productive friction’ [Stark, D. (2009) The Sense of Dissonance: Accounts of Worth in Economic Life, Princeton University Press, Princeton, NJ] and ‘bricolage’ [MacKenzie, D. & Pardo-Guerra, J. P. (2014) ‘Insurgent capitalism: Island, bricolage and the re-making of finance’, Economy and Society, vol. 43, no. 2, pp. 153–182]. Drawing on our research into the online personal data industry and start-ups developing personal data control products, we put together five sensibilities that we think are of use for broader considerations of market innovation

    National estimates for maternal mortality: an analysis based on the WHO systematic review of maternal mortality and morbidity

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    BACKGROUND: Despite the worldwide commitment to improving maternal health, measuring, monitoring and comparing maternal mortality estimates remain a challenge. Due to lack of data, international agencies have to rely on mathematical models to assess its global burden. In order to assist in mapping the burden of reproductive ill-health, we conducted a systematic review of incidence/prevalence of maternal mortality and morbidity. METHODS: We followed the standard methodology for systematic reviews. This manuscript presents nationally representative estimates of maternal mortality derived from the systematic review. Using regression models, relationships between study-specific and country-specific variables with the maternal mortality estimates are explored in order to assist further modelling to predict maternal mortality. RESULTS: Maternal mortality estimates included 141 countries and represent 78.1% of the live births worldwide. As expected, large variability between countries, and within regions and subregions, is identified. Analysis of variability according to study characteristics did not yield useful results given the high correlation with each other, with development status and region. A regression model including selected country-specific variables was able to explain 90% of the variability of the maternal mortality estimates. Among all country-specific variables selected for the analysis, three had the strongest relationships with maternal mortality: proportion of deliveries assisted by a skilled birth attendant, infant mortality rate and health expenditure per capita. CONCLUSION: With the exception of developed countries, variability of national maternal mortality estimates is large even within subregions. It seems more appropriate to study such variation through differentials in other national and subnational characteristics. Other than region, study of country-specific variables suggests infant mortality rate, skilled birth attendant at delivery and health expenditure per capita are key variables to predict maternal mortality at national level

    STAT1 Pathway Mediates Amplification of Metastatic Potential and Resistance to Therapy

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    BACKGROUND: Traditionally IFN/STAT1 signaling is connected with an anti-viral response and pro-apoptotic tumor-suppressor functions. Emerging functions of a constitutively activated IFN/STAT1 pathway suggest an association with an aggressive tumor phenotype. We hypothesized that tumor clones that constitutively overexpress this pathway are preferentially selected by the host microenvironment due to a resistance to STAT1-dependent cytotoxicity and demonstrate increased metastatic ability combined with increased resistance to genotoxic stress. METHODOLOGY/PRINCIPAL FINDINGS: Here we report that clones of B16F1 tumors grown in the lungs of syngeneic C57BL/6 mice demonstrate variable transcriptional levels of IFN/STAT1 pathway expression. Tumor cells that constitutively overexpress the IFN/STAT1 pathway (STAT1(H) genotype) are selected by the lung microenvironment. STAT1(H) tumor cells also demonstrate resistance to IFN-gamma (IFNgamma), ionizing radiation (IR), and doxorubicin relative to parental B16F1 and low expressors of the IFN/STAT1 pathway (STAT1(L) genotype). Stable knockdown of STAT1 reversed the aggressive phenotype and decreased both lung colonization and resistance to genotoxic stress. CONCLUSIONS: Our results identify a pathway activated by tumor-stromal interactions thereby selecting for pro-metastatic and therapy-resistant tumor clones. New therapies targeted against the IFN/STAT1 signaling pathway may provide an effective strategy to treat or sensitize aggressive tumor clones to conventional cancer therapies and potentially prevent distant organ colonization

    Indefinitely Renewable Copyright

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    Class Actions: Aggregation, Amplification, and Distortion

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