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The glass ceiling effect has been defined in a recent US Federal Commission report as "the unseen, yet unbreakable barrier that keeps minorities and women from rising to the upper rungs of the corporate ladder, regardless of their qualifications or achievements". It is well documented that many societies and organizations exhibit a glass ceiling. In this paper we formally define and study the glass ceiling effect in social networks and propose a natural mathematical model, called the biased preferential attachment model, that partially explains the causes of the glass ceiling effect. This model consists of a network composed of two types of vertices, representing two sub-populations, and accommodates three well known social phenomena: (i) the "rich get richer" mechanism, (ii) a minority-majority partition, and (iii) homophily. We prove that our model exhibits a strong moment glass ceiling effect and that all three conditions are necessary, i.e., removing any one of them will prevent the appearance of a glass ceiling effect. Additionally, we present empirical evidence taken from a mentor-student network of researchers (derived from the DBLP database) that exhibits both a glass ceiling effect and the above three phenomena.

This article presents an outline of historical and situational arguments which suggest a focus on deconversion, an outline of conversion research and its consequences for deconversion, and a discussion of extant empirical research on deconversion. The discussion then focuses on the conceptualization of deconversion and compiles the features from which a comprehensive concept of deconversion may emerge. The core features of the deconversion concept which is suggested in this article are complemented by dimensions of diversity which also include a developmental perspective (from the religious styles perspective). This has implications for future research. Developments in Research on Conversion and DeconversionConversion has been a prominent focus of theorizing and research in the psychology of religion from its early days on. Deconversion has not. Searching for 'deconversion' in electronic data bases results in a relatively small number of books, articles or dissertations. Various names which may be regarded as referring to the same core phenomenon, may also point to its complexity: apostasy, defection, disaffiliation, falling from the faith; exit etc. The name 'deconversion' is rather new, and, because of its potential to structure the discussion in an evolving research field, we work towards a clarification.We will outline in this text perspectives for a conceptualization of deconversion-in its common features and in its diversity. Conceptual clarification structures empirical research and has to stand the test of empirical research; therefore we strive to show the merit of the

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The amount of messenger RNA (mRNA) for polypeptides of the chlorophyll a/bprotein complex of thylakoid membranes in etiolated and greening cells of Chlamydomonas reinhardtii y-1 was examined by immunoprecipitation and electrophoresis of products of in vitro translation to determine at which stage production of these polypeptides is regulated. Cells grown 4 d in the dark at 25°C contained small amounts of translatable mRNA for the major membrane polypeptides. Exposure of these etiolated cells to light, under conditions in which the membrane polypeptides accumulated, resulted in a significant increase in the quantity of the mRNA. In contrast, when etiolated cells were incubated for 1-2 h in the dark at 38°C, translation assays indicated that mRNA for the membrane polypeptides became abundant. Moreover, the quantity of the mRNA did not increase when these cells subsequently were exposed to light. Therefore, at 38°C the cellular level of the polypeptides is not regulated by synthesis of mRNA. The in vitro synthesized polypeptides, which were precipitated with antibodies prepared against the purified thylakoid polypeptides, had apparent molecular weights of 31,500 and 30,000. The corresponding immunoprecipitated polypeptides made in vivo had apparent molecular weights of 29,500 and 26,000. Thus, the membrane polypeptides are made as precursors.No net accumulation of the polypeptides occurred in cells in the dark at 38°C, but immunoreactive polypeptides the size of the mature membrane components were labeled during incubation of cells with [14C]acetate in the dark. These results indicated that the mRNA was translated in the dark, but since the polypeptides did not accumulate, the products of translation were probably degraded. We conclude from our experiments that at 25°C production of the polypeptides is regulated by the level of translatable mRNA in the cells. At 38°C, however, the accumulation of the polypeptides is controlled by posttranslational processes.

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