Killing Range: Explaining Lethality Variance Within a Terrorist Organization

This paper presents an analysis of the Provisional Irish Republican Army's (PIRA) brigade level behavior during the Northern Ireland Conflict (1970-1998) and identifies the organizational factors that impact a brigade's lethality as measured via terrorist attacks. Key independent variables include levels of technical expertise, cadre age, counter-terrorism policies experienced, brigade size, and IED components and delivery methods. We find that technical expertise within a brigade allows for careful IED usage, which significantly minimizes civilian casualties (a specific strategic goal of PIRA) while increasing the ability to kill more high value targets with IEDs. Lethal counter-terrorism events also significantly affect a brigade's likelihood of killing both civilians and high-value targets but in different ways. Killing PIRA members significantly decreases IED fatalities but also significantly decreases the possibility of zero civilian IED-related deaths in a given year. Killing innocent Catholics in a Brigade's county significantly increases total and civilian IED fatalities. Together the results suggest the necessity to analyze dynamic situational variables that impact terrorist group behavior at the sub-unit level

Lethal Connections: The Determinants of Network Connections in the Provisional Irish Republican Army, 1970-1998

Using stochastic methods we illustrate that the Provisional Irish Republican Army's (PIRA) network is clustered along three primary dimensions: (a) brigade affiliation, (b) whether the member participated in violent activities, and (c) task/role within PIRA. While most brigades tended to foster connections within the brigade (that is, “closure”), the tendency to do so varied across the organization. Members who engaged with violent activities were far more likely to connect with each other; in later periods there is polarization into those who engage in violent activities and those who do not. Across brigades, those who engage in a particular task and role (improvised explosive device [IED] constructor, IED planter, gunman, robber/kidnapper/drug smuggler/hijacker) are more likely to connect with others who do the same task or play the same role than with other members who fulfill other roles. Standard forms of homophily (that is, the tendency to make connections with people who are similar in terms of demography or status) play a very weak role in explaining which members interact with one another. Finally, our analysis illustrates clear patterns of relational change that correspond to changes in the formal structures that PIRA's leadership promoted

Selective preservation of organic matter in marine environments; processes and impact on the sedimentary record

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 483-511, doi: 10.5194/bg-7-483-2010The present paper is the result of a workshop sponsored by the DFG Research Center/Cluster of Excellence MARUM "The Ocean in the Earth System", the International Graduate College EUROPROX, and the Alfred Wegener Institute for Polar and Marine Research. The workshop brought together specialists on organic matter degradation and on proxy-based environmental reconstruction. The paper deals with the main theme of the workshop, understanding the impact of selective degradation/preservation of organic matter (OM) in marine sediments on the interpretation of the fossil record. Special attention is paid to (A) the influence of the molecular composition of OM in relation to the biological and physical depositional environment, including new methods for determining complex organic biomolecules, (B) the impact of selective OM preservation on the interpretation of proxies for marine palaeoceanographic and palaeoclimatic reconstruction, and (C) past marine productivity and selective preservation in sediments. It appears that most of the factors influencing OM preservation have been identified, but many of the mechanisms by which they operate are partly, or even fragmentarily, understood. Some factors have not even been taken carefully into consideration. This incomplete understanding of OM breakdown hampers proper assessment of the present and past carbon cycle as well as the interpretation of OM based proxies and proxies affected by OM breakdown. To arrive at better proxy-based reconstructions "deformation functions" are needed, taking into account the transport and diagenesis-related molecular and atomic modifications following proxy formation. Some emerging proxies for OM degradation may shed light on such deformation functions. The use of palynomorph concentrations and selective changes in assemblage composition as models for production and preservation of OM may correct for bias due to selective degradation. Such quantitative assessment of OM degradation may lead to more accurate reconstruction of past productivity and bottom water oxygenation. Given the cost and effort associated with programs to recover sediment cores for paleoclimatological studies, as well as with generating proxy records, it would seem wise to develop a detailed sedimentological and diagenetic context for interpretation of these records. With respect to the latter, parallel acquisition of data that inform on the fidelity of the proxy signatures and reveal potential diagenetic biases would be of clear value.We acknowledge generous financial support by the DFG Research Center/Cluster of Excellence MARUM “The Ocean in the Earth System”, the International Graduate College EUROPROX and the Alfred Wegener Institute for Polar and Marine Research enabling the realisation of the “Workshop on Selective Preservation of Organic Matter: Processes and Impact on the Fossil Record” which formed the basis of this paper. GJMV acknowledges support by the German Science Foundation (DFG grant VE486/2)

Microbial methane cycling in sediments of Arctic thermokarst lagoons

Thermokarst lagoons represent the transition state from a freshwater lacustrine to a marine environment, and receive little attention regarding their role for greenhouse gas production and release in Arctic permafrost landscapes. We studied the fate of methane (CH4) in sediments of a thermokarst lagoon in comparison to two thermokarst lakes on the Bykovsky Peninsula in northeastern Siberia through the analysis of sediment CH4 concentrations and isotopic signature, methane-cycling microbial taxa, sediment geochemistry, lipid biomarkers, and network analysis. We assessed how differences in geochemistry between thermokarst lakes and thermokarst lagoons, caused by the infiltration of sulfate-rich marine water, altered the microbial methane-cycling community. Anaerobic sulfate-reducing ANME-2a/2b methanotrophs dominated the sulfate-rich sediments of the lagoon despite its known seasonal alternation between brackish and freshwater inflow and low sulfate concentrations compared to the usual marine ANME habitat. Non-competitive methylotrophic methanogens dominated the methanogenic community of the lakes and the lagoon, independent of differences in porewater chemistry and depth. This potentially contributed to the high CH4 concentrations observed in all sulfate-poor sediments. CH4 concentrations in the freshwater-influenced sediments averaged 1.34 ± 0.98 μmol g−1, with highly depleted δ13C-CH4 values ranging from −89‰ to −70‰. In contrast, the sulfate-affected upper 300 cm of the lagoon exhibited low average CH4 concentrations of 0.011 ± 0.005 μmol g−1 with comparatively enriched δ13C-CH4 values of −54‰ to −37‰ pointing to substantial methane oxidation. Our study shows that lagoon formation specifically supports methane oxidizers and methane oxidation through changes in pore water chemistry, especially sulfate, while methanogens are similar to lake conditions

Carrots, Sticks, and Insurgent Targeting of Civilians

How do conciliatory and coercive counterinsurgency tactics affect militant group violence against civilians? Scholars of civil war increasingly seek to understand intentional civilian targeting, often referred to as terrorism. Extant research emphasizes group weakness, or general state attributes such as regime type. We focus on terrorism as violent communication and as a response to government actions. State tactics toward groups, carrots and sticks, should be important for explaining insurgent terror. We test the argument using new data on terrorism by insurgent groups, with many time-varying variables, covering 1998 through 2012. Results suggest government coercion against a group is associated with subsequent terrorism by that group. However, this is only the case for larger insurgent groups, which raises questions about the notion of terrorism as a weapon of the weak. Carrots are often negatively related to group terrorism. Other factors associated with insurgent terrorism include holding territory, ethnic motivation, and social service provision