U-shaped Pattern (u-shaped + pattern)

Distribution by Scientific Domains

Selected Abstracts


We investigate the relationship between corruption and political stability, from both theoretical and empirical perspectives. We propose a model of incumbent behavior that features the interplay of two effects: a horizon effect, whereby greater instability leads the incumbent to embezzle more during his short window of opportunity, and a demand effect, by which the private sector is more willing to bribe stable incumbents. The horizon effect dominates at low levels of stability, because firms are unwilling to pay high bribes and unstable incumbents have strong incentives to embezzle, whereas the demand effect gains salience in more stable regimes. Together, these two effects generate a non-monotonic, U-shaped relationship between total corruption and stability. On the empirical side, we find a robust U-shaped pattern between country indices of corruption perception and various measures of incumbent stability, including historically observed average tenures of chief executives and governing parties: regimes that are very stable or very unstable display higher levels of corruption when compared with those in an intermediate range of stability. These results suggest that minimizing corruption may require an electoral system that features some re-election incentives, but with an eventual term limit. [source]

Regulation of hippocampal cell adhesion molecules NCAM and L1 by contextual fear conditioning is dependent upon time and stressor intensity

J. Joaquín Merino
Abstract Cell adhesion molecules (CAMs) of the immunoglobulin superfamily, NCAM and L1, as well as the post-translational addition of ,-2,8-linked polysialic acid (PSA) homopolymers to NCAM (PSA,NCAM), have been implicated in the neural mechanisms underlying memory formation. Given that the degree of stress elicited by the training situation is one of the key factors that influence consolidation processes, this study questioned whether training rats under different stressor intensities (0.2, 0.4, or 1 mA shock intensity) in a contextual fear conditioning task might regulate subsequent expression of NCAM, PSA,NCAM and L1 in the hippocampus, as evaluated immediately after testing rats for conditioning at 12 and 24 h after training. Behavioural inhibition (evaluated as a ,freezing' index) at testing and post-testing plasma corticosterone levels were also assessed. The results showed that 12 h post-training, conditioned animals displayed reduced NCAM, but increased L1, expression. At this time point, the group trained at the highest shock intensity (1 mA) also presented decreased PSA,NCAM expression. Analyses performed 24 h post-training indicated that the 1 mA group exhibited increased NCAM and L1 expression, but decreased expression of PSA,NCAM levels. In addition, L1 values that presented a shock intensity-dependent U-shaped pattern were also increased in the group trained at the lowest shock condition (0.2 mA) and remained unchanged in the intermediate shock condition (0.4 mA). Freezing and corticosterone values at both testing times were positively related with shock intensity experienced at training. Therefore, our results show a complex regulation of CAMs of the immunoglobulin superfamily in the hippocampus that depends upon stressor intensity and time factors. In addition, the pattern of CAMs expression found in the 1 mA group (which is the one that shows higher post-training corticosterone levels and develops the stronger and longer-lasting levels of fear conditioning) supports the view that, after a first phase of synaptic de-adherence during consolidation, NCAM and L1 might participate in the stabilization of selected synapses underlying the establishment of long-term memory for contextual fear conditioning, and suggests that glucocorticoids might play a role in the observed regulation of CAMs. [source]

Intra Day Bid-Ask Spreads, Trading Volume and Volatility: Recent Empirical Evidence from the London Stock Exchange

Charlie X. Cai
With the benefit of very high frequency (25 million 1 minute observations) and recent data (2001) for the UK, this paper explores a number of intra day patterns of stock market behaviour. More specifically, a distinct reverse J shaped bid-ask spread pattern is noted for SETS securities, a declining bid-ask spread pattern for non-SETS securities, a two hump pattern for trading volume and a U-shaped pattern for returns volatility for all securities. In terms of complementing the existing literature, the paper shows that differences in trading systems may affect the bid-ask spread patterns, while differences in market environments (i.e. US and UK markets) seems to affect the trading volume pattern. The paper suggests avenues for future research, in particular, the need to consider what factors are significant in determining intra day patterns for different trading systems and the need for additional cross-market comparisons to identify how institutional factors affect the behaviour of investors on an intra day basis. [source]

International Patterns of Union Membership

David G. Blanchflower
This paper examines changes in unionization that have occurred over the last decade or so using individual level micro data on many countries, with particular emphasis on the United Kingdom, the United States and Canada. I document an empirical regularity not hitherto identified, namely the probability of being unionized follows an inverted U-shaped pattern in age, maximizing in the mid- to late 40s in 34 of the 38 countries I study. I consider the question of why union membership seems to follow a similar inverted U-shape pattern in age across countries with such diverse industrial relations systems. I find evidence that this arises in part because of cohort effects, but even when cohort effects are removed a U-shape remains. [source]