Implicit Network Research Articles

Spatial and Temporal Heterogeneity Explain Disease Dynamics in a Spatially Explicit Network Model

There is an increasing recognition that individual-level spatial and temporal heterogeneity may play an important role in metapopulation dynamics and persistence. In particular, the patterns of contact within and between aggregates (e.g., demes) at different spatial and temporal scales may reveal important mechanisms governing metapopulation dynamics. Using 7 years of data on the interaction between the anther smut fungus (Microbotryum violaceum) and fire pink (Silene virginica), we show how the application of spatially explicit and implicit network models can be used to make accurate predictions of infection dynamics in spatially structured populations. Explicit consideration of both spatial and temporal organization reveals the role of each in spreading risk for both the host and the pathogen. This work suggests that the application of spatially explicit network models can yield important insights into how heterogeneous structure can promote the persistence of species in natural landscapes.

Efficiency of a Two-Item Pre-Screen to Reduce the Burden of Depression Screening in Pregnancy and Postpartum: An IMPLICIT Network Study

Systems for efficient case finding of women with major depression during pregnancy and postpartum are needed. Here we assess the diagnostic accuracy of a modified 2-item patient health questionnaire (PHQ-2) as a pre-screen in assessing depression. Cross-sectional assessments at 15 weeks' gestation (n = 414), 30 weeks' gestation (n = 334), and 6 to 16 weeks postpartum (n = 193) among women from a diverse set of races/ethnicities, participating in the IMPLICIT maternal care quality improvement network. The Edinburgh Postnatal Depression Scale score (>or=13) was used as the criterion measure for the PHQ-2. A positive 2-item screen had sensitivity of 93%, 82%, and 80% and specificity of 75%, 80%, and 86% for Edinburgh Postnatal Depression Scale score of >or=13 for assessment at 15 and 30 weeks gestational age and postpartum, respectively. The positive/negative predictive values for the PHQ-2 were 44/98, 24/91, and 30/98 for each time point, respectively. Areas under the receiver operating characteristic curve analysis suggested that 2-item assessments at each time point had approximately equal diagnostic validity. Two questions were efficient to rule out depression and reduced the need for further screening of approximately 60% to 80% of women, depending on the point in pregnancy or postpartum. A diagnostic interview follow-up of women screening positive is still required.

Causal inference in biomolecular pathways using a Bayesian network approach and an Implicit method

We introduce here the concept of Implicit networks which provide, like Bayesian networks, a graphical modelling framework that encodes the joint probability distribution for a set of random variables within a directed acyclic graph. We show that Implicit networks, when used in conjunction with appropriate statistical techniques, are very attractive for their ability to understand and analyze biological data. Particularly, we consider here the use of Implicit networks for causal inference in biomolecular pathways. In such pathways, an Implicit network encodes dependencies among variables (proteins, genes), can be trained to learn causal relationships (regulation, interaction) between them and then used to predict the biological response given the status of some key proteins or genes in the network. We show that Implicit networks offer efficient methodologies for learning from observations without prior knowledge and thus provide a good alternative to classical inference in Bayesian networks when priors are missing. We illustrate our approach by an application to simulated data for a simplified signal transduction pathway of the epidermal growth factor receptor (EGFR) protein.

CONSTRUCTION OF BELIEF AND DECISION NETWORKS

We describe a representation and set of inference techniques for the dynamic construction of probabilistic and decision‐theoretic models expressed as networks. In contrast to probabilistic reasoning schemes that rely on fixed models, we develop a representation that implicitly encodes a large number of possible model structures. Based on a particular query and state of information, the system constructs a customized belief net for that particular situation. We develop an interpretation of the network construction process in terms of the implicit networks encoded in the database. A companion method for constructing belief networks with decisions and values (decision networks) is also developed that uses sensitivity analysis to focus the model building process. Finally, we discuss some issues of control of model construction and describe examples of constructing networks.

G-net: implicit token-passing bus LAN

An implicit token-passing bus local area network (LAN) that provides a reverse round robin service to the stations is presented. The network, named G-Net, consists of a unidirectional bus folded to create a topology similar to the letter G. The G-Net provides bounded delay, a feature that makes it suitable for voice traffic. The performance of the G-Net, is evaluated via simulation.

The Mindfulness of Anthropology

rest of the Frankfurt School, was reacting to the failure of Marxism during the First World War, then to the myth-laden symbolic power of Fascism. Disillusioned with mechanical Marxist views of history which proved to be too optimistic, Benjamin emphasized the importance of images and myth as fields of struggle in revolutionary practice. He wanted the left to enlist religion in its cause, to act in the dreamworld of popular imagination, a dreamworld which, by projecting images of the past into the future, was a 'sleeping giant' which could 'break history's mythic spell'. Taussig shows that shamanism also contains this slumbering power of the imagery of the dead'. But identifying shamanism as a form of liberation seems to romanticize its place in the Colombian social order. As the author acknowledges, the awe in which indigenous magic is held reinforces negative stereotypes of Indians. 'The more shamanic, mystic and wild the Indian becomes as a way of exploiting the exploiters,' he notes, 'the more tightly is the noose of ethnic magic and racism drawn'. Shamans are often perceived as charlatans owing to their fees and failures. Yage is a great liar, one of Taussig's informants says: by enabling sufferers to 'see' the supposed source of their problems, it can generate false accusations of witchcraft and justify homicide. As for power, these people have precious little except to cure each other, with the aforementioned mixed results. While Shamanism, Colonialism and the Wild Man is a fascinating exploration of popular iconography, that realm is a highly contradictory and ambiguous one, of what Taussig calls 'implicit networks, smoky trails, manifested but indirectly in the cracks, dreams, and jokes of everyday life'. 'Wherever you go', Taussig notes, 'the great brujos are elsewhere'. In a yage vision, an Indian shaman sees the Colombian army as golden, dancing, singing soldiers. When oppressor and oppressed see each other as curing images, it does not suggest that they will be rid of each other anytime soon.

Literary Representation and Social Legitimation: J. L. Burckhardt's Approach to “The Orient”

As a field of study, the Middle East, like its predecessor the “Orient”, continues to exist more concretely within a vast realm of Western texts, both artistic and ethnographic, than it does on the ground. This ingrained disparity between representation and social reality has motivated some scholars to examine this literature as the manifestation of physical or ideological domination. In Edward Said's Orientalism the interpretation of this literature becomes a search for determining social and political forces, the evidence of which, like the nineteenth-century anthropological notion of “survivals”, resides in each text as an implicit network of unconscious images and metaphors. Similarly, Abdelkebir Khatibi, investigating the historical and ethnographic texts of Jacques Berque, views this literature as determined by the requirements of an exigent and compelling, but inherently flawed, Western metaphysic; an “onto-tháologie” which, in confronting questions of essence and existence, must formulate an “other” to realize its “self”.