Why Leaves Turn Red in Autumn. The Role of Anthocyanins in Senescing Leaves of Red-Osier Dogwood

Why the leaves of many woody species accumulate anthocyanins prior to being shed has long puzzled biologists because it is unclear what effects anthocyanins may have on leaf function. Here, we provide evidence for red-osier dogwood (Cornus stolonifera) that anthocyanins form a pigment layer in the palisade mesophyll layer that decreases light capture by chloroplasts. Measurements of leaf absorbance demonstrated that red-senescing leaves absorbed more light of blue-green to orange wavelengths (495–644 nm) compared with yellow-senescing leaves. Using chlorophyll a fluorescence measurements, we observed that maximum photosystem II (PSII) photon yield of red-senescing leaves recovered from a high-light stress treatment, whereas yellow-senescing leaves failed to recover after 6 h of dark adaptation, which suggests photo-oxidative damage. Because no differences were observed in light response curves of effective PSII photon yield for red- and yellow-senescing leaves, differences between red- and yellow-senescing cannot be explained by differences in the capacities for photochemical and non-photochemical light energy dissipation. A role of anthocyanins as screening pigments was explored further by measuring the responses PSII photon yield to blue light, which is preferentially absorbed by anthocyanins, versus red light, which is poorly absorbed. We found that dark-adapted PSII photon yield of red-senescing leaves recovered rapidly following illumination with blue light. However, red light induced a similar, prolonged decrease in PSII photon yield in both red- and yellow-senescing leaves. We suggest that optical masking of chlorophyll by anthocyanins reduces risk of photo-oxidative damage to leaf cells as they senesce, which otherwise may lower the efficiency of nutrient retrieval from senescing autumn leaves.

The role of neighborhood organizations in the production of gentrifiable urban space: The case of Wynwood, Miami's Puerto Rican barrio

Partnerships between government and community-based actors and organizations are considered the hallmark of contemporary governance arrangements for the revitalization and gentrification of economically distressed, inner city areas. This dissertation uses historical, narrative analysis and ethnographic methods to examine the formation, evolution and operation of community-based governance partnerships in the production of gentrifiable urban space in the Wynwood neighborhood of Miami, FL between 1970 and 2010. This research is based on more than four years of participant observation, 60 in-depth interviews with respondents recruited through a purposive snowball sample, review of secondary and archival sources, and descriptive, statistical and GIS analysis. This study examines how different organizations formed in the neighborhood since the 1970s have facilitated the recent gentrification of Wynwood. It reveals specifically how partnerships between neighborhood-based government agencies, nonprofit organizations and real estate developers were constructed to be exclusionary and lead to inequitable economic development outcomes for Wynwood residents. The key factors conditioning these inequalities include both the rationalities of action of the organizations involved and the historical contexts in which their leaders’ thinking and actions were shaped. The historical contexts included the ethnic politics of organizational funding in the 1970s and the “entrepreneurial” turn of community-based economic development and Miami urban politics since the 1980s. Over time neighborhood organizations adopted highly pragmatic rationalities and repertoires of action. By the 2000s when Wynwood experienced unprecedented investment and redevelopment, the pragmatism of community-based organizations led them to become junior partners in governance arrangements and neighborhood activists were unable to directly challenge the inequitable processes and outcomes of gentrification.

Post-revolutionary post-modernism: Central American detective fiction by the turn of the 21st century

Contemporary Central American fiction has become a vital project of revision of the tragic events and the social conditions in the recent history of the countries from which they emerge. The literary projects of Sergio Ramirez (Nicaragua), Dante Liano (Guatemala), Horacio Castellanos Moya (El Salvador), and Ramon Fonseca Mora (Panama), are representative of the latest trends in Central American narrative. These trends conform to a new literary paradigm that consists of an amalgam of styles and discourses, which combine the testimonial, the historical, and the political with the mystery and suspense of noir thrillers. Contemporary Central American noir narrative depicts the persistent war against social injustice, violence, criminal activities, as well as the new technological advances and economic challenges of the post-war neo-liberal order that still prevails throughout the region. ^ Drawing on postmodernism theory proposed by Ihab Hassan, Linda Hutcheon and Brian MacHale, I argued that the new Central American literary paradigm exemplified by Sergio Ramirez's El cielo llora por mí, Dante Liano's El hombre de Montserrat, Horacio Castellanos Moya's El arma en el hombre and La diabla en el espejo , and Ramon Fonseca Mora's El desenterrador, are highly structured novels that display the characteristic marks of postmodern cultural expression through their ambivalence, which results from the coexistence of multiple styles and conflicting ideologies and narrative trends. The novels analyzed in this dissertation make use of a noir sensitivity in which corruption, decay and disillusionment are at their core to portray the events that shaped the modern history of the countries from which they emerge. The revolutionary armed struggle, the state of terror imposed by military regimes and the fight against drug trafficking and organized crime, are among the major themes of these contemporary works of fiction, which I have categorized as perfect examples of the post-revolutionary post-modernism Central American detective fiction at the turn of the 21st century.^

Why Most Biomedical Findings Echoed by Newspapers Turn Out to be False: The Case of Attention Deficit Hyperactivity Disorder

Context: Because positive biomedical observations are more often published than those reporting no effect, initial observations are often refuted or attenuated by subsequent studies. Objective: To determine whether newspapers preferentially report on initial findings and whether they also report on subsequent studies. Methods: We focused on attention deficit hyperactivity disorder (ADHD). Using Factiva and PubMed databases, we identified 47 scientific publications on ADHD published in the 1990s and soon echoed by 347 newspapers articles. We selected the ten most echoed publications and collected all their relevant subsequent studies until 2011. We checked whether findings reported in each ‘‘top 10’’ publication were consistent with previous and subsequent observations. We also compared the newspaper coverage of the ‘‘top 10’’ publications to that of their related scientific studies. Results: Seven of the ‘‘top 10’’ publications were initial studies and the conclusions in six of them were either refuted or strongly attenuated subsequently. The seventh was not confirmed or refuted, but its main conclusion appears unlikely. Among the three ‘‘top 10’’ that were not initial studies, two were confirmed subsequently and the third was attenuated. The newspaper coverage of the ‘‘top 10’’ publications (223 articles) was much larger than that of the 67 related studies (57 articles). Moreover, only one of the latter newspaper articles reported that the corresponding ‘‘top 10’’ finding had been attenuated. The average impact factor of the scientific journals publishing studies echoed by newspapers (17.1 n = 56) was higher (p,0.0001) than that corresponding to related publications that were not echoed (6.4 n = 56). Conclusion: Because newspapers preferentially echo initial ADHD findings appearing in prominent journals, they report on uncertain findings that are often refuted or attenuated by subsequent studies. If this media reporting bias generalizes to health sciences, it represents a major cause of distortion in health science communication.

Post-Revolutionary Post-Modernism: Central American Detective Fiction by the Turn of the 21st Century

Contemporary Central American fiction has become a vital project of revision of the tragic events and the social conditions in the recent history of the countries from which they emerge. The literary projects of Sergio Ramirez (Nicaragua), Dante Liano (Guatemala), Horacio Castellanos Moya (El Salvador), and Ramon Fonseca Mora (Panama), are representative of the latest trends in Central American narrative. These trends conform to a new literary paradigm that consists of an amalgam of styles and discourses, which combine the testimonial, the historical, and the political with the mystery and suspense of noir thrillers. Contemporary Central American noir narrative depicts the persistent war against social injustice, violence, criminal activities, as well as the new technological advances and economic challenges of the post-war neo-liberal order that still prevails throughout the region. Drawing on postmodernism theory proposed by Ihab Hassan, Linda Hutcheon and Brian MacHale, I argued that the new Central American literary paradigm exemplified by Sergio Ramirez’s El cielo llora por mí, Dante Liano’s El hombre de Montserrat, Horacio Castellanos Moya’s El arma en el hombre and La diabla en el espejo, and Ramon Fonseca Mora’s El desenterrador, are highly structured novels that display the characteristic marks of postmodern cultural expression through their ambivalence, which results from the coexistence of multiple styles and conflicting ideologies and narrative trends. The novels analyzed in this dissertation make use of a noir sensitivity in which corruption, decay and disillusionment are at their core to portray the events that shaped the modern history of the countries from which they emerge. The revolutionary armed struggle, the state of terror imposed by military regimes and the fight against drug trafficking and organized crime, are among the major themes of these contemporary works of fiction, which I have categorized as perfect examples of the post-revolutionary post-modernism Central American detective fiction at the turn of the 21st century.