Estimation of the parameters of symmetric stable ARMA and ARMA–GARCH models

In this article, we first propose the modified Hannan–Rissanen Method for estimating the parameters of autoregressive moving average (ARMA) process with symmetric stable noise and symmetric stable generalized autoregressive conditional heteroskedastic (GARCH) noise. Next, we propose the modified empirical characteristic function method for the estimation of GARCH parameters with symmetric stable noise. Further, we show the efficiency, accuracy and simplicity of our methods with Monte-Carlo simulation. Finally, we apply our proposed methods to model the financial data.     

Computer incompetents in the cross-hairs.

Human Resources managers are distressingly aware that more than half the middle and senior managers (40- and 50-year-olds) in their organizations are technologically incompetent. Having spent millions on technology, most corporate CEOs, many of whom can't use a computer either, are drawing a bead on middle managers who are passively resisting the computer revolution. Physician executives are no exception. Given the current shortage of physician managers with good track records and people skills, can middle managers skirt technology issues until retirement if they dance slowly enough? It's doubtful. Organizations are using new tactics to bar technically challenged managers from their ranks: They will only interview candidates with mastery of specific software and they're posting job opportunities on their web sites. Those who still believe they can ride out the computer revolution may want to rethink that strategy.     

Contractors and their Psychological Contracts

It is commonly assumed that contractors are largely calculative, instrumental and self-interested in their relationship with organizations and interface with them accordingly (e.g. low corporate interest and emotional investment). This paper describes a survey involving 117 contractors (62 on 'permanent' agency contracts and 55 on 'temporary' agency contracts) and a comparable (age, job level/grade, years of work experience) group of 86 direct employees (on fixed-term contracts). The survey comprised measures of the psychological contract, of organizational identification, social (corporate) attraction, team spirit and intention to leave. The findings show that contractors are not inevitably 'emotionally' detached from their place of work, in some cases investing in it as much as direct company employees. While transactional (e.g. financial gain, instrumentality) exchange considerations were more salient among contractors than employees, this did not appear to preclude the development of a relational (e.g. corporate integration and long-term investment) contractual orientation. 'Team spirit' and 'organizational identification' predicted the development of relational contracts over and above contractual status. The findings and their management implications are discussed in terms of 'strategic partnership'.     

From Resources to Value and Back: Competition Between and Within Organizations

Examining the relationship between the competitive processes between and within organizations, we use selection system theory to link resource value to product value. We identify three dimensions (in‐selection, before‐selection and after‐selection) that facilitate determining the value of resources based on the functions they serve in the competitive process between organizations in the product market, i.e. the external selection system. Subsequently, we use these dimensions to explore the competitive process among resource providers within organizations, i.e. the internal selection system. This leads us to formulate three propositions that link the competitive process within organizations to the competitive process between organizations. First, we posit that if resources that individually score highly along only one of the three dimensions are bundled, it is more likely that organizational performance can be sustained. Second, we argue that providers of resources scoring highly along multiple dimensions will enjoy stronger means of appropriation in comparison with providers of resources scoring highly along only one of the three dimensions. Third, we contend that the extent to which an organization endeavours to remunerate its resource providers based on their perceived contribution to the organization's competitive position has a curvilinear (inverted U‐shaped) relationship with organizational performance.     

Cancer risk estimation for mixtures of coal tars and benzo(a)pyrene.

Two-year chronic bioassays were conducted by using B6C3F1 female mice fed several concentrations of two different mixtures of coal tars from manufactured gas waste sites or benzo(a)pyrene (BaP). The purpose of the study was to obtain estimates of cancer potency of coal tar mixtures, by using conventional regulatory methods, for use in manufactured gas waste site remediation. A secondary purpose was to investigate the validity of using the concentration of a single potent carcinogen, in this case benzo(a)pyrene, to estimate the relative risk for a coal tar mixture. The study has shown that BaP dominates the cancer risk when its concentration is greater than 6,300 ppm in the coal tar mixture. In this case the most sensitive tissue site is the forestomach. Using low-dose linear extrapolation, the lifetime cancer risk for humans is estimated to be: Risk < 1.03 x 10(-4) (ppm coal tar in total diet) + 240 x 10(-4) (ppm BaP in total diet), based on forestomach tumors. If the BaP concentration in the coal tar mixture is less than 6,300 ppm, the more likely case, then lung tumors provide the largest estimated upper limit of risk, Risk < 2.55 x 10(-4) (ppm coal tar in total diet), with no contribution of BaP to lung tumors. The upper limit of the cancer potency (slope factor) for lifetime oral exposure to benzo(a)pyrene is 1.2 x 10(-3) per microgram per kg body weight per day from this Good Laboratory Practice (GLP) study compared with the current value of 7.3 x 10(-3) per microgram per kg body weight per day listed in the U.S. EPA Integrated Risk Information System.     

Improving Cancer Dose–Response Characterization by Using Physiologically Based Pharmacokinetic Modeling: An Analysis of Pooled Data for Acrylonitrile-Induced Brain Tumors to Assess Cancer Potency in the Rat

Historically, U.S. regulators have derived cancer slope factors by using applied dose and tumor response data from a single key bioassay or by averaging the cancer slope factors of several key bioassays. Recent changes in U.S. Environmental Protection Agency (EPA) guidelines for cancer risk assessment have acknowledged the value of better use of mechanistic data and better dose–response characterization. However, agency guidelines may benefit from additional considerations presented in this paper. An exploratory study was conducted by using rat brain tumor data for acrylonitrile (AN) to investigate the use of physiologically based pharmacokinetic (PBPK) modeling along with pooling of dose–response data across routes of exposure as a means for improving carcinogen risk assessment methods. In this study, two contrasting assessments were conducted for AN-induced brain tumors in the rat on the basis of (1) the EPA's approach, the dose–response relationship was characterized by using administered dose/concentration for each of the key studies assessed individually; and (2) an analysis of the pooled data, the dose–response relationship was characterized by using PBPK-derived internal dose measures for a combined database of ten bioassays. The cancer potencies predicted for AN by the contrasting assessments are remarkably different (i.e., risk-specific doses differ by as much as two to four orders of magnitude), with the pooled data assessments yielding lower values. This result suggests that current carcinogen risk assessment practices overestimate AN cancer potency. This methodology should be equally applicable to other data-rich chemicals in identifying (1) a useful dose measure, (2) an appropriate dose–response model, (3) an acceptable point of departure, and (4) an appropriate method of extrapolation from the range of observation to the range of prediction when a chemical's mode of action remains uncertain.     

Red unions and bourgeois democracy: A quantitative-historical analysis of worker militancy and socialist electoral power

This paper investigates how workers’ “economic struggle” determines the “democratic class struggle,” and extends socialist electoral constituency. This paper argues that political outcomes, namely, electoral behavior, may not be understood independently of the labor process, especially its most militant manifestation, strikes. Rather than follow the customary conceptual dichotomy between the sphere of production and the political sphere, it is suggested that both strike activity and electoral participation are compatible political strategies that, under specific historical circumstances, may jointly determine the fate of the Socialist party. The leading question is how did the wave of strikes in post World War I Italy affect the electoral power of the Italian Socialist party, in comparison with another mass party, the Popular Catholic Party. Hierarchical Linear Modeling (HLM) is employed to analyze census, strike, and electoral data. It is found that strike activity and electoral democracy increased the electoral power of the Socialist party, whereas they had little effect on the power of the Catholic party. It is suggested that this was due to the Catholic non-revolutionary program which was ambivalent about the political role of strikes. It is concluded that the socialists’ political success was determined by their dual political strategy in both spheres, electoral participation, and organizing strikes.     

Collecting text messages from college students: Evaluating a novel methodology

Social interaction, particularly in older adolescents, increasingly involves computer‐mediated communication. Although studies of public computer‐mediated communication are increasingly common, studies of private text messaging remain rare. As approaches for obtaining such data evolve with technological advances, developmental scientists need designs in which to use such approaches that reduce sampling biases in both participants and text messages. In this study (n = 854; 46% male; 22% African American, 60% European American), we examined selection biases in the participant sample (i.e., factors associated with actual participation), procedural biases in the participant sample (i.e., factors related to failed data capture due to technological or procedural issues), and selection biases in the sample of text messages (i.e., based on self‐reported reasons for texting). Findings from our study suggest that studying human interaction directly through analysis of text message data is not only feasible, but also may be successfully undertaken with minimal biases regarding sample selection and text message selection among those who are engaged in research and engaged in text messaging outside of the study context. However, biases may occur depending on the type of platform (iPhone vs. Android) used by participants for texting.