Community Structures in Bipartite Networks: A Dual-Projection Approach

Identifying communities or clusters in networked systems has received much attention across the physical and social sciences. Most of this work focuses on single layer or one-mode networks, including social networks between people or hyperlinks between websites. Multilayer or multi-mode networks, such as affiliation networks linking people to organizations, receive much less attention in this literature. Common strategies for discovering the community structure of multi-mode networks identify the communities of each mode simultaneously. Here I show that this combined approach is ineffective at discovering community structures when there are an unequal number of communities between the modes of a multi-mode network. I propose a dual-projection alternative for detecting communities in multi-mode networks that overcomes this shortcoming. The evaluation of synthetic networks with known community structures reveals that the dualprojection approach outperforms the combined approach when there are a different number of communities in the various modes. At the same time, results show that the dual-projection approach is as effective as the combined strategy when the number of communities is the same between the modes

Investigating The Role Of Signaling Pathways In Adult Stem Cells Governed By Population Asymmetry

Adult stem cells are vital to animal biology, tasked with replenishing cells in a variety of tissue types. Historically, there have been two contrasting models of stem cell behavior, “single-cell asymmetry,” where each stem cell is generally long lived and is responsible for perpetual daughter (non-stem) cell production, and “population asymmetry,” where a group of stem cells maintain population numbers while producing non-stem cell daughters, but individual stem cells undergo stochastic competition leading to frequent loss or amplification of individual lineages. Our work examines Drosophila ovarian Follicle Stem Cells (FSCs), which are somatic adult stem cells organized as a population of 14-16 cells within each germarium. FSCs are responsible for the production of two distinct somatic daughter cell types at opposite borders of the stem cell population. The FSCs are arranged in three anteroposterior layers; posterior “layer 1” FSCs divide faster and directly produce Follicle Cells (FCs), while anterior “layer 2 and 3” FSCs divide more slowly and give rise to Escort Cells (ECs). We have examined how signaling pathways contribute individually to FSC behavior, using clonal analysis to manipulate individual FSC genotypes and subsequently determine how autonomous FSC properties and competition among FSCs is affected. Our data indicate that Janus Kinase/Signal Transducers and Activators of Transcription (JAK-STAT) and Wnt pathways are primarily responsible for regulating location, proliferation and differentiation in FSCs. The activities of Hedgehog (Hh), Hippo (Hpo), and Phosphoinositide 3-kinase (PI3K) pathways are also shown to be important for FSC competition

DROPOUT, EARLY TERMINATION AND DETACHMENT FROM A PUBLIC PSYCHIATRIC CLINIC

Background: Dropout from an outpatient clinic is the loss of a patient to scheduled follow-up. Due to movement of mental health care to the community, adherence to ambulatory care is crucial to maintain stability among individuals with mental disorders. We hypothesized that patients drop out from ambulatory psychiatric care when regardless of the therapist\u27s evaluation, they feel that they have recovered, or because they are dissatisfied with treatment. The aim was to examine the phenomenon of premature termination of treatment in a public community-based ambulatory psychiatric clinic serving a catchment area with a population of 200,000. Subjects and methods: The study sample was drawn from patients who had at least one ambulatory therapy session during the previous five years, immediately or shortly following initial treatment and who were subsequently lost to follow-up. Participants completed a questionnaire that evaluated their satisfaction with treatment and described their reasons for early termination of treatment. Results: The sample included eighty-two patients. Eighty percent of the responders (N=65) terminated therapy on their own, and twenty percent (N=17) decided to end treatment together with their therapists. Discussion: Increased involvement of patients in treatment planning, duration and end of therapy, may improve attendance in ambulatory mental health care settings. Conclusions: Though dropouts generally reported satisfaction with the ambulatory service, some explained early termination of treatment as being due to dissatisfaction with the therapist, the type of treatment or because of therapist turnover. Others terminated treatment because they felt their problems were solved or their conditions had improved, though therapists had determined otherwise

The Robustness of Reciprocity: Experimental Evidence that Each Form of Reciprocity is Robust to the Presence of Other Forms of Reciprocity

Prosocial behavior is paradoxical because it often entails a cost to one’s own welfare to benefit others. Theoretical models suggest that prosociality is driven by several forms of reciprocity. Although we know a great deal about how each of these forms operates in isolation, they are rarely isolated in the real world. Rather, the topological features of human social networks are such that people are often confronted with multiple types of reciprocity simultaneously. Does our current understanding of human prosociality break down if we account for the fact that the various forms of reciprocity tend to co-occur in nature? Results of a large experiment show that each basis of human reciprocity is remarkably robust to the presence of other bases. This lends strong support to existing models of prosociality and puts theory and research on firmer ground in explaining the high levels of prosociality observed in human social networks

Division-independent differentiation mandates proliferative competition among stem cells.

Cancer-initiating gatekeeper mutations that arise in stem cells would be especially potent if they stabilize and expand an affected stem cell lineage. It is therefore important to understand how different stem cell organization strategies promote or prevent variant stem cell amplification in response to different types of mutation, including those that activate proliferation. Stem cell numbers can be maintained constant while producing differentiated products through individually asymmetrical division outcomes or by population asymmetry strategies in which individual stem cell lineages necessarily compete for niche space. We considered alternative mechanisms underlying population asymmetry and used quantitative modeling to predict starkly different consequences of altering proliferation rate: A variant, faster proliferating mutant stem cell should compete better only when stem cell division and differentiation are independent processes. For most types of stem cells, it has not been possible to ascertain experimentally whether division and differentiation are coupled. However,Drosophilafollicle stem cells (FSCs) provided a favorable system with which to investigate population asymmetry mechanisms and also for measuring the impact of altered proliferation on competition. We found from detailed cell lineage studies that division and differentiation of an individual FSC are not coupled. We also found that FSC representation, reflecting maintenance and amplification, was highly responsive to genetic changes that altered only the rate of FSC proliferation. The FSC paradigm therefore provides definitive experimental evidence for the general principle that relative proliferation rate will always be a major determinant of competition among stem cells specifically when stem cell division and differentiation are independent.This work was supported by NIH Grant R01 GM079351 (to D.K.), and D.M. was supported, in part, by an NIH training grant

Developmental Regulation of B Lymphocyte Immune Tolerance Compartmentalizes Clonal Selection from Receptor Selection

AbstractB lymphocyte development is a highly ordered process that involves immunoglobulin gene rearrangements, antigen receptor expression, and a learning process that minimizes the development of cells with reactivity to self tissue. Two distinct mechanisms for immune tolerance have been defined that operate during early bone marrow stages of B cell development: apoptosis, which eliminates clones of cells, and receptor editing, which spares the cells but genetically reprograms their autoreactive antigen receptors through nested immunoglobulin L chain gene rearrangements. We show here that sensitivity to antigen-induced apoptosis arises relatively late in B cell development and is preceded by a functionally distinct developmental stage capable of receptor editing. This regulation compartmentalizes clonal selection from receptor selection

A Europa face contra à ameaça do radicalismo religioso do estado Islâmico

The main objective of this article is to present a critical analysis on how the emergence and the rise of the Islamic State, its proclamation of a new caliphate and its violent religious radicalism pose a serious threat to international security, especially in Europe. The Islamic State has now become the most notorious jihadist organisation. Its territorial expansion, its extremist ideology, its operational capacity and its foreign fighter recruitment strategy make this organisation an enormous menace to the European continent, due to its geographical proximity and to its traditional influence on the Middle East and to the isolation and marginalisation inflicted on a large part of the Muslim population in the region. Europe is facing a complex scenario in which religious extremism could generate violence and terror acts. That is the reason why European liberal societies must come to an understanding of how to deal with this particular threat.El objetivo principal del presente artículo es presentar un análisis crítico acerca de cómo la emergencia y el auge del Estado Islámico, su proclamación de un nuevo califato y su radicalismo religioso violento representan una grave amenaza para la seguridad internacional, especialmente en Europa. En la actualidad, el Estado Islámico se ha convertido en la organización yihadista más notoria. Su expansión territorial, su ideología extremista, su capacidad operacional y su estrategia de reclutamiento de combatientes extranjeros hacen de esta organización una gran amenaza para el continente europeo, debido a su proximidad geográfica y a su influencia tradicional en Medio Oriente, y al aislamiento y la marginalización infligidos a gran parte de la población musulmana en la región. Europa se enfrenta a un escenario complejo en el cual el extremismo religioso podría generar violencia y actos de terrorismo. Es por esta razón que las sociedades europeas liberales deben llegar a un entendimiento acerca de cómo lidiar con esta amenaza en concreto.O objetivo principal deste artigo é apresentar uma análise crítica sobre como a emergência e o auge do Estado Islâmico, sua proclamação de um novo califado e seu radicalismo religioso representam uma séria ameaça para a segurança internacional, especialmente na Europa. Na atualidade, o Estado Islâmico converteu-se na organização jihadista mais notória. Sua expansão territorial, sua ideologia extremista, sua capacidade operacional e sua estratégia de recrutamento de combatentes estrangeiros fazem desta organização uma grande ameaça para o continente europeu, devido a sua proximidade geográfica e sua influência tradicional no Médio Oriente, e ao isolamento e a marginalização infligida a grande parte da população muçulmana na região. A Europa enfrenta um cenário complexo no qual o extremismo religioso poderia gerar violência e atos de terrorismo. É por esta razão que as sociedades europeias liberais devem chegar a um entendimento sobre como lidar com esta ameaça em concreto

Del conflicto al posconflicto en el contexto colombiano

Colombia es desde hace décadas el epicentro de uno los conflictos armados de mayor complejidad evidenciados en el hemisferio occidental y que ha sido caracterizado por la diversidad de actores armados que han tomado un papel de relevancia a lo largo de su historia. Pese a que aún el contexto de violencia producto de esta coyuntura no ha sido resuelto en su totalidad, sí ha evidenciado la desmovilización, desarme y reintegración a la vida civil de muchos grupos armados ilegales a lo largo de las últimas décadas. El presente análisis muestra un recuento de los principales antecedentes históricos frente a esta materia y resalta los mayores desafíos que aún existen frente a iniciativas de concertación pacifica encaminadas a la consecución de un escenario real de posconflicto en el contexto colombiano