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The Tobin tax is an often discussed method to tame speculation and get a source of income. The discussion is especially heated when the financial markets are in crisis. In this article we refer to the foreign exchange markets. The Tobin tax should be a small international tax affecting all currency transactions and thus consequently reducing destabilizing speculations. In this way this tax should take over a control function. By including the Tobin tax in the microscopic model of Cont and Bouchaud one finds that this tax could be the right method to control foreign exchange operations and to get a good source of income.

Software maintenance is the task of modifying a running product previously delivered to the client, in order to correct defects, improve performance or adapt it to the environment. This task is a crucial activity for enterprises. Without it, existing systems would become rapidly out-of-date and inefficient. The purpose of this paper is to present a software maintenance approach used in small and medium-sized business (SMB) organizations in Brazil. Currently, these organizations represent 95.5% of the software companies in the country. The approach presented here indicates how SMB IT companies have improved their software maintenance processes. Multiple case studies were performed to validate this approach. The outcomes showed that strategies associated with managing users’ knowledge and development/maintenance teams are relevant to increase the maintenance process effectiveness. This approach involves three aspects: users’ knowledge management, maintenance team knowledge and the management and maintenance process. This improvement includes reducing time and also minimizing the number of tickets. The response time for tickets resolution to the end user has been reduced. In addition, IT organizations have minimized the effects associated with both staff and client turnovers.

In a large information system, the amount of cache space available to store read-only replicas of data may be limited. Since acquiring these data from their sources may be an expensive and time-consuming operation, it is essential to make efficient use of the available cache space. This cache space may be unevenly distributed over a large number of loosely coupled sites. An intelligent caching strategy is needed to insure that replicas are created often enough that they can be inexpensively reached when necessary, but not so often that important data are forced out to make room. We present such a strategy, which we have developed for use in ALIBI, a networked resource discovery and information retrieval system. The TCF Strategy, as it is called, allows individual sites to adjust their level of cache turnover to provide better overall performance. This novel approach could no doubt be beneficially applied in other distributed systems which use caching. We include discussion and simulation results supporting the efficiency of the TCF Strategy.

A community composition island biogeography model was developed to explain and predict two community patterns (beta diversity and endemism) with the consideration of speciation, extinction and dispersal processes. Results showed that rate of speciation is positively and linearly associated with beta diversity and endemism, that is, increasing species rates typically could increase the percentage of both endemism and beta diversity. The influences of immigration and extinction rates on beta diversity and endemism are nonlinear, but with numerical simulation, I could observe that increasing extinction rates would lead to decreasing percentage of endemism and beta diversity. The role of immigration rate is very similar to that of speciation rate, having a positive relationship with beta diversity and endemism. Finally, I found that beta diversity is closely related to the percentage of endemism. The slope of this positive relationship is determined jointly by different combinations of speciation, extinction and immigration rates.

Most of life maintains itself through turnover, namely cell proliferation, movement and elimination. Hydra’s cells, for example, disappear continuously from the ends of tentacles, but these cells are replenished by cell proliferation within the body. Inspired by such a biological fact, and together with various operations of polynomials, I here propose polynomial-life model toward analysis of some phenomena in multicellular organisms. Polynomial life consists of multicells that are expressed as multivariable polynomials. A cell is expressed as a term of polynomial, in which point $(m,n)$ is described as a term $x^m{y}^n$ and the condition is described as its coefficient. Starting with a single term and following reductions by set of polynomials, I simulate the development from a cell to a multicell. In order to confirm uniqueness of the eventual multicell-pattern, Gröbner base can be used, which has been conventionally used to ensure uniqueness of normal form in the mathematical context. In this framework, I present various patterns through the polynomial-life model and discuss patterns maintained through turnover. Cell elimination seems to play an important role in turnover, which may shed some light on cancer or regenerative medicine.

Because CEO turnover events provide the board of directors with a unique opportunity to potentially completely restructure CEO compensation packages, changes to CEO compensation following a turnover event could prove to inform the ongoing debate regarding CEO compensation. This paper investigates what happens to CEO compensation when a turnover event occurs. Specifically, I examine CEO compensation levels and pay-performance sensitivity for incoming and outgoing CEOs involved in turnover events at public companies in the United States. My main findings are as follows: (1) incoming CEOs are paid as much as or more than those they replace, (2) outsider replacements are paid more than their predecessors even after controlling for education and skills, and (3) CEOs who are forced out are not paid differently from those who replace them, while CEOs who leave voluntarily are paid significantly less than their replacements. Further analysis reveals that proxies for managerial power including CEO tenure, CEO centrality, founder status, and high CEO ownership cannot explain these results. Overall, these findings are difficult to reconcile with the view that managerial power is the primary determinant of CEO compensation.

Issuing activity does not result in superior post-issue liquidity. New issues are just as liquid as their peer non-issuers. Even the kinds of new issues that are supposed to be more liquid than others (initial public offerings (IPOs) backed by venture capital, new issues with high-prestige underwriters, severely underpriced IPOs) have the same liquidity as other similar issuers. The paper thus refutes the existing liquidity-based explanations of the new issues puzzle. The paper also shows that the low-minus-high turnover factor seems to explain the new issues puzzle and related anomalies only because it picks up volatility risk.