Top Management Turnover and Organizational Performance: A Test of a Contingency Model

A crucial test of whether “management matters” is whether changes in the team at the top of an organization make a difference. Focusing on turnover in the collective senior team rather than successions of individual chief executives, this article argues that the impact of leadership succession is contingent upon prior organizational performance. The evidence on English local government shows that changes in the top management team lead to improvements when initial performance is bad, but result in deterioration when initial performance is good. The results support the view that high‐performing organizations should attempt to retain members of their senior management team, whereas low performers should seek to replace them.     

A New Twist on an Old Approach: A Random-Interaction Approach for Estimating Rates of Inter-Group Interaction

There are numerous instances in which researchers wish to measure the rate of intra- or inter-group interactions (whether positive or negative). When computing such measures as rates there is great uncertainty regarding the appropriate denominator: we analytically illustrate how the choice of the denominator when calculating such rates is not trivial and that some existing strategies create a built-in relationship between the computed rate and the group composition within the entity. Another strand of prior work only focused on the relative occurrence of intra- versus inter-group events, which does not account for the important theoretical possibility that both types of events might increase in certain social contexts. Our approach provides an advance over these earlier strategies as it allows one to take into account the relative frequency of interaction between members of different groups, but then translates this into per capita rates. We also provide an empirical example using data on inter- and intra-group robbery and aggravated assault events for block groups in a section of the city of Los Angeles to illustrate how our procedure works and to illustrate how other approaches can lead to dramatically different conclusions.     

Spatializing the Social Networks of Gangs to Explore Patterns of Violence

The majority of spatial studies of crime employ an inductive approach in both the modeling and interpretation of the mechanisms of influence thought to be responsible for the patterning of crime in space and time. In such studies, the spatial weights matrix is specified without regard to the theorized mechanisms of influence between the units of analysis. Recently, a more deductive approach has begun to gain traction in which the theory of influence is used to model influence in geographic space. Using data from Los Angeles, we model the spatial distribution of gang violence by considering both the relative location of the gangs in space while simultaneously capturing their position within an enmity network of gang rivalries. We find that the spatial distribution of gang violence is more strongly associated with the socio-spatial dimensions of gang rivalries than it is with adjacency-based measures of spatial autocorrelation.     

An Investigation of PCR Inhibition Using Plexor®‐Based Quantitative PCR and Short Tandem Repeat Amplification

A common problem in forensic DNA typing is PCR inhibition resulting in allele dropout and peak imbalance. In this paper, we have utilized the Plexor^® real‐time PCR quantification kit to evaluate PCR inhibition. This is performed by adding increasing concentrations of various inhibitors and evaluating changes in melt curves and PCR amplification efficiencies. Inhibitors examined included calcium, humic acid, collagen, phenol, tannic acid, hematin, melanin, urea, bile salts, EDTA, and guanidinium thiocyanate. Results were plotted and modeled using mathematical simulations. In general, we found that PCR inhibitors that bind DNA affect melt curves and C_T takeoff points while those that affect the Taq polymerase tend to affect the slope of the amplification curve. Mixed mode effects were also visible. Quantitative PCR results were then compared with subsequent STR amplification using the PowerPlex^® 16 HS System. The overall results demonstrate that real‐time PCR can be an effective method to evaluate PCR inhibition and predict its effects on subsequent STR amplifications.