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How Media Concentration in the Age of Radio Prefigured Today’s Big Tech Debate
No full textIn the 1930s, staffers at the newly established Federal Communications Commission devised a novel rationale for limiting network power in radio, telephony, and the press. While much has changed since the “age of radio,” the concerns they raised inform the present-day debate over the control that social media platforms exert over public discourse, writes Richard R. John.
This article is based on remarks that John gave at the 2025 Stigler Center Antitrust and Competition Conference this past April
Essays on Econometric Inference with High-Dimensional Factor Models
No full textMy dissertation consists of three chapters that develop new methods for estimation and inference in high-dimensional econometric models. A unifying theme across all chapters is the development of theoretically grounded, computationally efficient procedures for model evaluation, testing, and estimation in the presence of latent structures, sparsity, and heterogeneity.
The first chapter proposes a new approach to test conditional independence within the framework of high-dimensional factor models. A Cauchy-weighted measure is introduced to quantify the dependence between the idiosyncratic components and develop a corresponding conditional independence test. This measure, which ranges from 0 to 1, equals 0 if and only if conditional independence is true. It is robust to extreme values and computationally efficient. The proposed test is asymptotically distribution-free under the null hypothesis and capable of detecting nonlinear dependencies under the alternative hypothesis in high-dimensional scenarios. Furthermore, this chapter demonstrates that the approach of first directly estimating the factors using pooled data, followed by performing the test, is invalid when factors are unobserved. Instead, this chapter proposes to estimate the factors within the factor-augmented regression model framework and shows that the corresponding test remains valid. Extensive simulation studies and real data analysis are conducted to validate the effectiveness of this method, demonstrating its superior performance in high-dimensional scenarios.
The second chapter examines the adequacy of a simple, interpretable factor model that relies solely on the common factor component to capture the relationship between covariates and the response variable, compared to a more complex factor-augmented sparse regression model. Existing tests, based on maximum-type statistics or data-splitting projection methods, face notable limitations: the former lose power under moderate sparsity, while the latter introduce randomness and conservatism. This chapter proposes a new projection test with penalties that eliminates data splitting, improving reproducibility and efficiency. By leveraging a penalized projection pursuit framework, the proposed method enhances signal detection under alternatives while preserving validity under the null. The asymptotic null distribution of the proposed test statistic aligns with maximum-type approaches, yet it achieves superior power for moderately sparse signals. The effectiveness and robustness of the proposed test are validated through extensive numerical studies.
The third chapter proposes a new approach to instrumental variable (IV) estimation in high-dimensional settings using scaled principal component analysis (sPCA). While traditional principal component analysis (PCA) is commonly employed to extract latent factors from large panels of instruments for IV construction, it assigns equal weight to all variables and may perform poorly when many instruments are only weakly related to the endogenous regressor. To address this limitation, the chapter adapts sPCA—originally developed for forecasting—to the IV setting. By scaling each candidate instrument according to its relevance to the endogenous variable, sPCA emphasizes informative instruments while down-weighting irrelevant ones. Within a general factor model framework that accommodates heterogeneous factor strength, the chapter establishes the consistency and asymptotic normality of the resulting IV estimator. Simulation studies show that the sPCA-based IV estimator outperforms standard PCA-based IV, especially when only a small subset of instruments is strongly relevant. The proposed method offers a supervised and robust alternative for IV estimation in high-dimensional, data-rich environments
Urban Heat in Johannesburg and Ekurhuleni, South Africa: A Spatial Vulnerability Analysis
Full text linkDistinct spatial differences in the Urban Heat Island effect are observed, with greatest heat stress in areas with high building densities and low vegetation numbers. These areas are often characterized by lower socio-economic living conditions & poorer living conditions. The results of the case study can guide the design of climate-resilient urban planning strategies and improve living conditions in these city quarters
Modelling the Summertime Climate of Vienna
Full text linkThe urban climate model MUKLIMO_3 is used to simulate the historical, current and future heat load of Vienna, the capital city of Austria. The historical climate is based on land use and land cover data from 1985 and 2005. The future climate is based on EURO-CORDEX climate projections of temperature for the two emission scenarios RCP4.5 and RCP8.5. Land use and land cover changes are shown to result in changes of up to ±10 summer days per year, where the replacement of parks, water bodies, and other natural surfaces with roads, residential and industrial buildings leading to increases in the heat load and vice versa. Keeping the land use constant but including the effect of climate change shows that the greatest increase in the number of summer days is expected at the end of the 21st century for the RCP8.5 scenario
Disentangling tree growth and climate response of Andean-Amazon forests in Bolivia
No full textThe tropical Andes region of South America (~5º-24ºS) is one of the most unique and biodiverse regions of the world. It is under-sampled for dendrochronological studies, as most trees in this area lack defined annual rings and instead feature continuous growth in their wood due to a general lack of seasonality. However, annual growth rings can form in some tropical tree species in areas with seasonal precipitation, such as the low latitude Andes. Thus, they could be very valuable for understanding past climate variability in the region.
This dissertation describes newly developed tree-ring chronologies from wood samples collected in forests in the Andes-Amazon corridor of the Madidi National Park (MNP), a biodiversity hotspot in northern Bolivia. These are the first robust tree-ring chronologies developed for this region of Bolivia. They are part of a broader effort to increase the spatial coverage of forest and climate data in the tropics, where tree-ring records are short and sparse. The sites and species discussed herein are i.) a high elevation (4000-4400 m.a.s.l.) tropical treeline Polylepis pepei BB Simpson (Simpson, 1979) network, ii.) Juglans boliviana C. DC. Dode (Dode, 1906), a new species for dendrochronology, from a tropical wet forest (1100-1300 m.a.s.l.) and iii.) low elevation (895-1000 m.a.s.l.) Amburana cearensis Fr. Allem. (Smith, 1940) from a seasonally dry valley near the Tuichi River. Tree-ring anatomy, ring width (RW) and radiocarbon (14C) series were used to provide new information on growth dynamics and climate sensitivity for these tropical tree species. Results are highly relevant for determining the role that tropical forests will have as a carbon source and/or sink in this era of global warming.
Chapter 1 highlights the challenges inherent in traditional tree-ring cross-dating in one of the selected tree species, J. boliviana. These challenges include radial eccentricity in the stem, complex wood anatomy, and variable controls on tree growth. J. boliviana is a key indicator species of the humid lower montane Yungas that has not been previously studied for dendrochronology. Several methods for verifying annual periodicity (i.e. dendrochronology, histological slices, radiocarbon) and the building of robust chronologies for tropical tree-ring sites were employed. Tree growth, longevity, and dendroclimatic potential were assessed for this species, which is used structurally (e.g. for building of bridges) and medically (e.g. treatment of diabetes) by local indigenous communities. The RW chronology, which spans from 1814 to 2017, reflected patterns of low and high frequency variability and an increase in growth since 1979. Climate-growth analyses revealed J. boliviana RW is negatively impacted by maximum temperatures and positively correlated to mean precipitation during the dry months of the year (May-Oct). These results agree with other Juglans-related (J. australis and J. neotropica) dendroclimatic studies from Argentina and Peru and illustrate the importance of dry-season precipitation on tropical tree growth; a dynamic topic in recent literature.
Chapter 2 builds on the analyses in Chapter 1 by comparing the growth variability and climate sensitivity from the humid J. boliviana forest to the seasonally dry P. pepei, and A. cearensis sites. Despite the proximity of the forest sites in MNP (14°33´-14°43´ S, 68°41´-69°04´ W), the species inhabit distinct vegetation zones shaped by orography along the eastern Andean foothills. This chapter seeks to understand diverging trends in radial growth, land-use impacts, and climate-growth relationships in MNP using gridded climate products (CRU, CHIRPS) and tropical sea surface temperature (SST) indices (Hadley1 SST). Raw RW at the upper-montane P. pepei site, sensitive to summer (Nov-Jan) precipitation changes, has been declining since 1995, likely due to increasing minimum temperatures and decreasing spring (SON) precipitation in the central Andes. Conversely, A. cearensis RW, which is strongly linked to peak wet-season rainfall (Dec-Apr), has been growing exceptionally well since the late 1970s, at the same time that late-summer rainfall has increased. Flood events related to anomalously warm SST in the tropical Atlantic and/or colder (La Niña) conditions in the Pacific lead to higher growth in the lower montane sites (J. boliviana and A. cearensis), while El Nino-related droughts were associated with narrower RW overall. A. cearensis RW also recorded the strongest summer ENSO signal among the species, potentially due to the proximity of this site to the Tuichi River. These newly developed chronologies (1867-2018) provide long term, annually resolved RW information that may provide new insights into the future stability of these forests under the threats of deforestation and climate change.
Chapter 3 features a new annual (1950-2019) radiocarbon reconstruction for the Southern Hemisphere (SH) developed from a tree sample from the high elevation, remote P. pepei forest near the town of Keara. This is the first continuous post-1950 A.D. 14C bomb curve record for Bolivia and the lowest latitude site within the SH 14C radiocarbon Zone 1-2 (SH Zone 1-2). Radiocarbon variability both within and between individual trees of the same species was observed in several sites. This is particularly the case during the 1960s when atmospheric radiocarbon exponentially rose due to nuclear bomb testing in the Northern Hemisphere (NH). There is radiocarbon enrichment after 1973, as found for other tree-ring 14C chronologies from Brazilian Amazon forests. This may reflect the rate of carbon cycling in the Amazon Basin at this time and the influence of varying tropospheric circulation patterns within the tropical low-pressure belt (TLPB) and Intertropical Convergence Zone (ITCZ) boundaries. Air parcel backward trajectory models showed that most air masses arriving to the Keara forest during the wet season were derived from the Amazon Basin and Atlantic Ocean reservoirs. This finding confirms the influence of northern air masses on tree growth and isotopic variability in MNP and other forests of the Amazon-Andes ecotone in SH Zone 1-2.
These understudied forests play a critical role in the livelihoods of the local communities and their water supply from the Andes. These new results indicate significant progress in efforts to expand the South American tropical tree-ring network and improve our understanding of the causes of tree growth variability linked to climate and other environmental factors in the era of recent anthropogenic change
The Effect of the Speaker Immersion Protocol Across Categories and Exemplars on Verbal Communication for Preschoolers
No full textVerbal requests, or mands, are a crucial aspect of language development, as they enable children to appropriately express their wants and needs to others and use language appropriately in social contexts (Ninio & Snow, 2018; Owens, 2020). Speaker Immersion Protocol (SIP) is a mand training protocol that involves the manipulation of motivating operations to create intensive mand opportunities.
This method has been found as an effective approach for increasing the production of vocal verbal operants in both contrived and natural settings (Ross et al., 2006; Pistoljevic et al., 2010; Naresh et al., 2020; Naresh, 2022). In Experiment 1, the researcher evaluated the effects of SIP across categories of mands on verbal communication and peer interaction for three preschoolers with disabilities. The researcher provided 40 manding opportunities per day across four mand categories (i.e., mands for edibles, objects, activities, and social play) that includes different establishing operations and reinforcers.
The resulting data indicated that SIP produced contract reinforcement as evidenced by an increase in expanded mands emission across categories that were not directly targeted during intervention (i.e., during untaught mand probes). The results also indicated that SIP produced contact reinforcement as evidenced by an increased number of vocal verbal operant emissions in non-instructional settings; specifically, tacts, sequelics, and conversational units that are controlled by social reinforcement.
However, there was a limited effect on peer interaction. Experiment 2 extended Experiment 1 and evaluated the effect of SIP across and exemplars that was embedded within natural instructional routines on verbal communication. In Experiment 2, participants had no prior instructional history of SIP. Experiment 2 also included an assessment of the verbal function of self-talk emitted in non-instructional settings. As seen in Experiment 1, Experiment 2 resulting data showed an increase in expanded mand emissions towards untaught establishing operations along with an increase in vocal verbal operant emissions (e.g., tacts and sequelics) in non-instructional environments, while demonstrating a limited impact on peer interaction.
This dissertation extended the SIP literature by investigating the effect of SIP on establishing social contract and contact reinforcement, self-talk emission in non-instructional settings, and peer interaction
No Exceptional Man: Towards a Democratic Emergency Paradigm
No full textSocieties face exceptional circumstances, such as military attacks or pandemics, often framed as safety and security threats. In such situations, emergency powers are frequently invoked, leading to the centralization of power in the executive or an expert committee. Decisions are shielded from public discussion, and dissent is often neglected or delegitimized. This raises serious concerns about democratic resilience, as the frequent use of emergency powers have been linked to weakening democratic institutions. This dissertation make a case for confronting exceptional circumstances, while remaining committed to the democratic principles of political equality, majority rule, and respect for pluralism and opposition.
first put the problem of resorting to emergency powers in a historical perspective by reconstructing the arguments of Machiavelli, Locke, J.S. Mill, and Schmitt. I demonstrate that historically, opposing traditions that disagreed on core principles and institutions have all agreed on granting highly concentrated and discretionary decision-making powers to a single individual in exceptional circumstances. Machiavelli, a republican, advocated for a magistracy of dictatorship; Locke, a liberal, defended prerogative power; and Mill, a proponent of representative government, permitted temporary dictatorship. I argue that to preserve democracy during exceptional circumstances, a profound paradigm shift challenging predominant schools of thought is necessary.
Second, I conduct an interdisciplinary conceptual analysis of the notions of threat, security, and risk, drawing on constructivist international relations theories, challenging the prevailing attitude that security has primacy over democratic deliberation and dissent. I reject the notion that threat, security, and risk are apolitical concepts and can be approached from a neutral, objective standpoint, free from conflicting values, principles, and views of the common good. Instead, I argue that these ideas are inherently political and deeply intertwined with various value systems. Facts alone do not constitute threats; rather, threats are constructed through a process of normative evaluation of material conditions. A separatist rebellion can be seen primarily as a threat to territorial integrity and human lives for some. In contrast, some may not view it as a threat at all but rather as a just struggle for freedom. Similarly, the question of what security entails differs based on the different principles and priorities people uphold, looking different from a state-centered standpoint and human-centered or feminist standpoint. Moreover, identifying risks is, first and foremost, a speculative process where one anticipates an undesirable future and a portfolio of risks varies for people who have different priorities and conceptions of the good.
The later part, contributes to the core debates of democratic theory and emerging literature on political parties. Having previously established that responding to security threats isn't a technical problem with a fixed solution but involves conflicting values and priorities that generate constant disagreement, I argue that democracy is uniquely suited to fairly settle these disagreements amid pervasive conflict about the good and the right. Finally, I explore the role political parties can play when faced with exceptional circumstances. I argue that political parties, as value-based entities and as “ordinary loci of political creativity” (Rosenblum, 2008), have the tools to develop matters of facts into their political form and frame them as threats in relation to a particular conception of the common good. Political parties, therefore, render the exceptional phenomena amenable to political discussion, decision, and, ultimately, action.
The dissertation concludes that we have increasingly normalized the exceptional exercise of power by leaders in ordinary circumstances, leading to democratic decline, we should adhere to ordinary procedures even under exceptional circumstances to counter democratic erosion
Detecting Suicidal Thoughts and Behaviors: The Verbal and Nonverbal in Suicide Assessments with Adolescents and Young Adults
No full textSuicide is a leading cause of death among adolescents and young adults in the United States. Detecting suicidal thoughts and behaviors is an important component of suicide prevention. The current three-paper dissertation aimed to address limitations in the extant youth suicide assessment research through three empirical studies.
In Paper 1, we address the lack of research examining whether brief screeners adequately capture suicidal thinking by comparing single- and multi-item assessments of ideation in adolescents. In Paper 2, we seek to expand beyond verbal self-report by using the Facial Action Coding System (FACS) to conduct an in-depth examination of facial expressions exhibited by young adults and their clinical interviewers during a widely used suicide assessment. In Paper 3, we build upon this foundation by maximizing on advancements in affective computing to automatically extract a wider range of nonverbal behaviors associated with affective engagement, and test whether these behaviors predict suicidal thoughts and behaviors crosssectionally and prospectively.
Results across all three studies suggest that researchers and clinicians concerned with assessment would stand to benefit from expanding beyond just that which is said by the suicidal person, and into that which is registered and expressed verbally and nonverbally by both members of the interviewer-respondent dyad
Relational Power: Legal Authority and Particularized Power in Authoritarian China
No full textHow does an authoritarian state exercise its power and get commends obeyed? This dissertation looks at two challenging moments for an authoritarian state that correspond to two forms of power exercised by the authoritarian state: first, the promulgation of a new law that seeks to regulate a labor market previously dominated by an informal moral economy and replace it with formal-legal authority; and second, the eruption of crisis—such as labor unrest—where the state mobilizes informal, personalized connections to restore order. I argue that both legal-rational authority and particularistic, patron-clientelist power in authoritarian regimes rely on the construction of relational networks that establish network alliances.
In both cases, these networks serve as the infrastructure through which the state translates its interests into terms that align with the interests of its citizens. Yet this translation is bidirectional: citizens, in turn, use this same network to negotiate with the state, reinterpret alignment of interests, or voice dissent. While authoritarianism is often conceptualized as a system in which the state penetrates society, this dissertation shows that “society” also penetrates the state—not through institutionalized civil society, as in democracies, but through the very networks that the state itself assembles to implement its authority
Localization of Child-focused Rural Disaster Response in the United States: Findings from a formative qualitative study
No full textThe notion of strong local community partnerships remains a critical opportunity and ideal standard of practice for response organization engagement after a disaster. Strong relationships built upon contextual understanding, acknowledgment of local capacity, funding priorities, and cultural sensitivity can greatly improve response and recovery outcomes by promoting a shared understanding and vision. Localization is one approach for response organizations working with communities to acknowledge and work toward accomplishing these goals. How localization as a concept is applied, or is relevant, in domestic disaster response work has yet to be explored in depth. Using a hybrid of several localization frameworks, the research team conducted 17 semi-structured in-depth interviews across six states with rural community actors who have had, currently have, or will have a funding partnership with Save the Children USA. These interviews aimed to better understand the needs and expectations of local community members who serve children and/or families in rural areas. This report concludes with key quotes from respondents, ideal interactions between response organizations and local community organizations, and guiding questions to be asked introspectively by the response organization. Overall, the application of an adjusted localization framework for domestic disaster response has great utility. Findings suggest the addition of a new localization dimension of “rural context” to include social-cultural factors, physical environmental, historical and economic factors, and public health factors. This additional dimension will help promote contextually appropriate response decisions meant to support and bolster local capacity and capabilities