An approximation to the convolution of gamma distributions

In general, the exact distribution of a convolution of independent gamma random variables is quite complicated and does not admit a closed form. Of all the distributions proposed, the gamma-series representation of Moschopoulos (1985 Moschopoulos, P. G. (1985). The distribution of the sum of independent gamma random variables. Annals of the Institute of Statistical Mathematics 37Part A:541–544. [Google Scholar]) is relatively simple to implement but for particular combinations of scale and/or shape parameters the computation of the weights of the series can result in complications with too much time consuming to allow a large-scale application. Recently, a compact random parameter representation of the convolution has been proposed by Vellaisamy and Upadhye (2009 Vellaisamy, P., Upadhye, N. S. (2009). On the sums of compound negative binomial and gamma random variables. Journal of Applied Probability 46:272–283.[Crossref], [Web of Science ®] , [Google Scholar]) and it allows to give an exact interpretation to the weights of the series. They describe an infinite discrete probability distribution. This result suggested to approximate Moschopoulos’s expression looking for an approximating theoretical discrete distribution for the weights of the series. More precisely, we propose a general negative binomial distribution. The result is an “excellent” approximation, fast and simple to implement for any parameter combination.     

A gradient-based deletion diagnostic measure for generalized linear mixed models

A gradient-statistic-based diagnostic measure is developed in the context of the generalized linear mixed models. Its performance is assessed by some real examples and simulation studies, in terms of ability in detecting influential data structures and of concordance with the most used influence measures.     

Cultural Attunement in Therapy With Mexican‐Heritage Couples: A Grounded Theory Analysis of Client and Therapist Experience

There is a need for culturally attuned approaches for couple therapy with Mexican/Mexican‐Americans. This qualitative grounded theory study utilized interviews with 11 client couples of Mexican heritage and 14 marital and family therapists to shed light on how Latino and non‐Latino therapists co‐construct positive experiences of cultural attunement with Mexican and Mexican‐American couple clients. Analysis identified a model of cultural connection through personal engagement with four interrelated phases: (a) mutual invitation, (b) shared engagement, (c) expanding personal connection, and (d) creating cultural connections. Clients in this study valued professionalism and expertise of the therapist, but felt attuned to and respected when therapists demonstrated humility, shared personal stories and emotion, and engaged in a collaborative process.     

Strengthening Purity: Moral Purity as a Mediator of Direct and Extended Cross-Group Friendships on Sexual Prejudice

The present research investigated whether enhanced perceptions of moral purity drive the effects of intergroup cross-group friendships on the intentions to interact with homosexuals. High-school students (N = 639) reported their direct and extended cross-group friendships with homosexuals as well as their beliefs regarding the moral character of the sexual minority. Participants further reported their desire to interact with homosexuals in the future. Results showed that both face-to-face encounters and extended contact with homosexuals increased their perceived moral purity, which in turn fostered more positive behavioral intentions. Results further revealed the specific role of moral purity in this sense, as differential perceptions along other moral domains (autonomy and community) had no mediation effects on behavioral tendencies toward homosexuals. The importance of these findings for improving intergroup relations is discussed, together with the importance of integrating research on intergroup contact and morality.     

“I Had to Go to the Streets to Get Love”: Pathways From Parental Rejection to HIV Risk Among Young Gay and Bisexual Men

Young, gay, and bisexual men (YGBM) are at increased risk of family rejection, which is related to HIV infection. What remains unknown is how family rejection leads to HIV risk. In this exploratory study, qualitative interviews were conducted with 21 HIV-positive YGBM aged 18 to 24. Most participants reported family rejection, which decreased instrumental and emotional support and resulted in participants using riskier ways to support themselves, such as engaging in survival sex. Conceptualizing the findings using a family systems framework, we present a tentative conceptual model to describe the potential relationships between family rejection and HIV risk for YGBM.     

The implementation of digital technologies for operations management: a case study for manufacturing apps

Abstract

Manufacturing applications address business to business (B2B) with highly customised applications developed for specific requirements, offering highly specialised solution-oriented and service-based software components, systems, and digital tools that aim at a fast and accurate decision-making support system. The purpose of this paper is to describe the implementation of digital technologies for operations management using manufacturing or engineering apps (eApps), for product design and manufacturing processes. In particular, starting from the specific needs of two companies from mature European industries as automotive and food, this work depicts how this kind of solutions can support companies and improve their operations. In particular, related benefits and challenges faced for the full implementation of the developed tools are highlighted. Moreover a business model to exploit the manufacturing apps is also proposed. The business model proposed for the exploitation of the eApps supports the commercialisation of all the revenue streams offered by this rapidly growing sector taking into account the specific needs of the concerned stakeholders through a diversified value proposition.     

Minority and majority private equity investments: firm performance and governance

This paper adds to the literature on the determinants of the effects of private equity (PE) investments. Using an original dataset of 191 target firms in Italy, we study the effects on performance and governance of the stakes acquired by the PE investor. We employ a difference-in-differences approach and compare target and control firms sharing similar characteristics and performance in the years preceding the deal. We find that PE investment has a positive effect on profitability, sales, and employment; these effects are larger for minority investments. We argue that this signals effective governance that follows from complementing rather than substituting incumbent managers in minority investments.     

Paneldaten in der Soziologie: Fixed Effects Paradigma und empirische Praxis in Panelregression und Ereignisanalyse

In sociology there is a growing body of literature discussing the ability of quantitative research methods to test causal inferences. This discourse introduces panel data as an important instrument to defend the interpretation of coefficients as effects: by focusing on what is going on within individuals, panel data allow for longitudinal empirical modelling, which reflects the inherent semantic of scientific hypotheses. As a consequence, unobserved heterogenity is absorbed and alternative explanations to the presumed causal mechanisms are largely ruled out. However, a within-, or rather Fixed Effects-estimator is needed to realize this potential of panel data. Consequently, such within-estimators are well established as standard in the methodological discourse on panel data. We explain this standard with references to the mechanics of within-estimators in panel-regression and event-history analysis. Finally, inspection of contributions to the two major German language journals for sociology shows that within-estimators are rarely used in empirical practice. We conclude that the potential of panel data to control for heterogeneity is largely underused in empirical practice. At the same time, our inspection of studies illustrates that the benefits of panel data are multidimensional and go beyond statistical virtues.     

Living in the shadow of occupation: Life satisfaction and positive emotion as protective factors in a group of Palestinian school children

Starting from perspectives on functioning and wellbeing, the aim of the present study was to investigate positive and negative affect, self-perceived life satisfaction and happiness in a group of 74 Palestinian children exposed to political violence. We hypothesized that the children in our sample would display generally satisfactory wellbeing and good functioning in terms of positive affect, life satisfaction and happiness, despite their negative life conditions. Both quantitative and qualitative analysis of the dimensions of participants' wellbeing was carried out. In particular, we explored the ecological dimensions affecting the wellbeing of Palestinian children through content analysis of narratives produced by the group of participants. Positive emotions were found to contribute to wellbeing and life satisfaction in children, acting as protective factors in dealing with daily violence. The children displayed a range of personal resources facilitated above all by the functioning community structure supporting them. Implications for clinical intervention are discussed.     

Cognitively automated assembly processes: a simulation based evaluation of performance

The numerical control of an experimental assembly cell with two robots--termed a cognitive control unit (CCU)--is able to simulate human information processing at a rule-based level of cognitive control. To enable the CCU to work on a large range of assembly tasks expected of a human operator, the cognitive architecture SOAR is used. The CCU can plan assembly processes autonomously and react to ad-hoc changes in assembly sequences effectively. Extensive simulation studies have shown that cognitive automation based on SOAR is especially suitable for random parts supply, which reduces planning effort in logistics. Conversely, a disproportional increase in processing time was observed for deterministic parts supply, especially for assemblies containing large numbers of identical parts. In this contribution, the effect of phase-shifts in deterministic part supply is investigated for assemblies containing maximal different parts. It can be shown that the concept of cognitive automation is as well suitable for these planning problems.