University of Delaware
  • Newark, Delaware, United States
Recent publications
Experiences of poverty and racism in early childhood can overburden physiological systems that respond to stress with implications for the development of the prefrontal cortex and related executive functioning. The present study is unique in its examination of basal cortisol output across the preschool day in relation to teacher ratings of executive functioning. Participants were 310 children attending Head Start preschool in the United States, a majority of whom were Black, Hispanic, or Asian Heritage. Salivary cortisol was sampled in duplicate at 4 times across 2 days near the beginning of the school year, resulting in a total of 16 samples per child. Several weeks later, the BRIEF-P teacher rating scale assessed various components of executive functioning. Zero-order correlations suggested that basal cortisol output across the preschool day related to each assessed component of executive functioning, as well as to composite scores. Results of hierarchical linear modeling indicated that higher cortisol across the preschool day related to greater difficulties in overall teacher-reported executive functioning, controlling for child age, birth-assigned sex, race/ethnicity, and family income. Implications concern understanding the impact of stress on executive functioning in the preschool classroom and promoting positive outcomes for children facing adversity.
Mangrove wetlands play an essential role as blue carbon ecosystems. However, worldwide they also face imminent threats caused by anthropogenic activities and climate change. Mangroves in the semiarid region of the Gulf of California are highly vulnerable to both threats. In this study, we present eddy covariance measurements of net ecosystem exchange of CO2 (NEE), gross primary productivity (GPP), and ecosystem respiration (Reco) at a preserved mangrove (Estero El Sargento) and a site influenced by anthropogenic activities (Bahia del Tobari) located in northwest Mexico. Both sites were net annual carbon sinks but had different dynamics. The net annual carbon gain for Estero El Sargento was −717 g C m⁻² y⁻¹ while for Bahia deTobari was −247 g C m⁻² y⁻¹. Over the studied year, Estero El Sargento had lower Reco(329 g C m⁻²) during the winter-spring months and an overall lower annual Reco/GPP (0.42) than Bahia de Tobari. The Reco was notably high during the winter-spring period at Bahia de Tobari when agriculture drainage from the intensive food production activities at the Yaqui Valley reaches the bay. The contrasting NEE patterns and magnitude between both mangrove sites suggest that anthropogenic activities influencing coastal ecosystems exert an important control on the CO2 sink potential.
To successfully generate creative solutions, teams must reconcile inconsistent perspectives and integrate competing task demands. We suggest that adopting a paradoxical frame - a mental template that promotes recognizing and embracing the simultaneous existence of seemingly contradictory elements - helps teams navigate this process to produce creative ideas, if team members are epistemically motivated. Our results from two laboratory studies (N = 950) suggest that teams that adopt paradoxical frames and have high epistemic motivation develop more creative solutions than teams with paradoxical frames and low epistemic motivation or epistemically motivated teams with frames that only encourage information sharing. Teams with paradoxical frames and high epistemic motivation are more creative because they engage in idea elaboration – they exchange, consider, and integrate diverse ideas and perspectives. By contrast, other teams settle on suboptimal middle-way solutions that do not address task demands. Our research advances knowledge of why and when paradoxical frames benefit team creativity, by unpacking the processes that enable teams to leverage task and team tensions. We show that when teams collectively work through their tensions and elaborate their diverse ideas they become more creative.
Inflammatory breast cancer (IBC) is an aggressive disease for which the spectrum of preclinical models was rather limited in the past. More recently, novel cell lines and xenografts have been developed. This study evaluates the transcriptome of an extended series of IBC preclinical models and performed a comparative analysis with patient samples to determine the extent to which the current models recapitulate the molecular characteristics of IBC observed clinically. We demonstrate that the IBC preclinical models are exclusively estrogen receptor (ER)-negative and of the basal-like subtype, which reflects to some extent the predominance of these subtypes in patient samples. The IBC-specific 79-signature we previously reported was retrained and discriminated between IBC and non-IBC preclinical models, but with a relatively high rate of false positive predictions. Further analyses of gene expression profiles revealed important roles for cell proliferation, MYC transcriptional activity, and TNFɑ/NFκB in the biology of IBC. Patterns of MYC expression and transcriptional activity were further explored in patient samples, which revealed interactions with ESR1 expression that are contrasting in IBC and nIBC and notable given the comparatively poor outcomes of ER+ IBC. Our analyses also suggest important roles for NMYC, MXD3, MAX, and MLX in shaping MYC signaling in IBC. Overall, we demonstrate that the IBC preclinical models can be used to unravel cancer cell intrinsic molecular features, and thus constitute valuable research tools. Nevertheless, the current lack of ER-positive IBC models remains a major hurdle, particularly since interactions with the ER pathway appear to be relevant for IBC.
Background Previous research shows kinematic and kinetic coupling between the metatarsophalangeal (MTP) and midtarsal joints during gait. Studying the effects of MTP position as well as foot structure on this coupling may help determine to what extent foot coupling during dynamic and active movement is due to the windlass mechanism. This study’s purpose was to investigate the kinematic and kinetic foot coupling during controlled passive, active, and dynamic movements. Methods After arch height and flexibility were measured, participants performed four conditions: Seated Passive MTP Extension, Seated Active MTP Extension, Standing Passive MTP Extension, and Standing Active MTP Extension. Next, participants performed three heel raise conditions that manipulated the starting position of the MTP joint: Neutral, Toe Extension, and Toe Flexion. A multisegment foot model was created in Visual 3D and used to calculate ankle, midtarsal, and MTP joint kinematics and kinetics. Results Kinematic coupling (ratio of midtarsal to MTP angular displacement) was approximately six times greater in Neutral heel raises compared to Seated Passive MTP Extension, suggesting that the windlass only plays a small kinematic role in dynamic tasks. As the starting position of the MTP joint became increasingly extended during heel raises, the amount of negative work at the MTP joint and positive work at the midtarsal joint increased proportionally, while distal-to-hindfoot work remained unchanged. Correlations suggest that there is not a strong relationship between static arch height/flexibility and kinematic foot coupling. Conclusions Our results show that there is kinematic and kinetic coupling within the distal foot, but this coupling is attributed only in small measure to the windlass mechanism. Additional sources of coupling include foot muscles and elastic energy storage and return within ligaments and tendons. Furthermore, our results suggest that the plantar aponeurosis does not function as a rigid cable but likely has extensibility that affects the effectiveness of the windlass mechanism. Arch structure did not affect foot coupling, suggesting that static arch height or arch flexibility alone may not be adequate predictors of dynamic foot function.
Background Police shootings are unevenly spatially distributed, with substantive spikes throughout the USA. While minorities are disproportionately the victims of police force, social or structural factors associated with this distribution are not well understood. The objective of this work was to evaluate police shootings in relation to victim race or ethnicity and residential segregation and racial diversity. Methods Validated crowdsourced data from the Washington Post’s Fatal Force (2015–2020) were linked with census tract-level data from the American Community Survey. Residential minority dissimilarity, interaction, and a racial and ethnic diversity metric were calculated in order to assess the potentially variant importance of evenness in distribution, exposure likelihood, and general representation. Logistic and multinomial regression was used to model associations between segregation and diversity, adjusted for other ecological characteristics. Analyses were stratified by victim race or ethnicity (Black, Asian, or Hispanic). Results Across all races combined, the odds of a police shooting in a particular census tract were associated with non-Hispanic Black dissimilarity (OR = 0.98, 95% CI 0.97, 0.99) and racial and ethnic diversity (1.046, 95% CI 1.044, 1.060). Areas with higher racial diversity had a higher likelihood of having a police shooting event with Black victims (OR = 1.092, 95% CI 1.064, 1.120) or Asian victims (OR = 1.188, 1.051, 1.343) than less diverse areas. Higher non-Hispanic Black interaction was associated with a lower likelihood of having a police shooting event with Black victims (OR = 0.914, 95% CI 0.833, 0.946) than lower interaction areas. Higher Hispanic dissimilarity was associated with a lower likelihood of having a police shooting event with a Hispanic victim (OR = 0.398, 95% CI 0.324, 0.489) than lower dissimilarity areas. Conclusions The variant effects of residential segregation are only seen when victims are analyzed separately by race. There appears to be a protective effect for Hispanic populations in Hispanic communities, while the reverse is true of Black individuals. We urge law enforcement responsible for locations with segregated communities to monitor individual interactions that police have with residents as well as the patterns of frequency and context of those interactions.
The detection of variations of fundamental constants of the Standard Model would provide us with compelling evidence of new physics, and could lift the veil on the nature of dark matter and dark energy. In this work, we discuss how a network of atomic and molecular clocks can be used to look for such variations with unprecedented sensitivity over a wide range of time scales. This is precisely the goal of the recently launched QSNET project: A network of clocks for measuring the stability of fundamental constants. QSNET will include state-of-the-art atomic clocks, but will also develop next-generation molecular and highly charged ion clocks with enhanced sensitivity to variations of fundamental constants. We describe the technological and scientific aims of QSNET and evaluate its expected performance. We show that in the range of parameters probed by QSNET, either we will discover new physics, or we will impose new constraints on violations of fundamental symmetries and a range of theories beyond the Standard Model, including dark matter and dark energy models.
Background Boxwood blight disease caused by Calonectria henricotiae and C. pseudonaviculata is of ecological and economic significance in cultivated and native ecosystems worldwide. Prior research has focused on understanding the population genetic and genomic diversity of C. henricotiae and C. pseudonaviculata , but gene family evolution in the context of host adaptation, plant pathogenesis, and trophic lifestyle is poorly understood. This study applied bioinformatic and phylogenetic methods to examine gene family evolution in C. henricotiae , C. pseudonaviculata and 22 related fungi in the Nectriaceae that vary in pathogenic and saprobic (apathogenic) lifestyles. Results A total of 19,750 gene families were identified in the 24 genomes, of which 422 were rapidly evolving. Among the six Calonectria species, C. henricotiae and C. pseudonaviculata were the only species to experience high levels of rapid contraction of pathogenesis-related gene families (89% and 78%, respectively). In contrast, saprobic species Calonectria multiphialidica and C. naviculata , two of the closest known relatives of C. henricotiae and C. pseudonaviculata , showed rapid expansion of pathogenesis-related gene families. Conclusions Our results provide novel insight into gene family evolution within C. henricotiae and C. pseudonaviculata and suggest gene family contraction may have contributed to limited host-range expansion of these pathogens within the plant family Buxaceae.
Almost four billion people worldwide use social media platforms. For some individuals, the social rewards obtained on these sites can lead to problematic social media use (PSMU). Research attempting to understand social media use in general has found relationships with various types of social comparison, but no study has yet investigated PSMU with respect to specific platforms and type of social comparison. To address this, we conducted an online survey (n = 601) to assess how three different trait constructs of social comparison (comparison of abilities, comparison of opinions, comparison directionality) relate to the problematic use of five social media platforms (Facebook, Instagram, Snapchat, TikTok, and Twitter). While controlling for demographic characteristics and total number of social media platforms used, linear regression models revealed different associations between problematic use of each platform depending on trait social comparison type. Overall, comparison of abilities was positively related with PSMU of all five platforms, whereas comparison of opinions was negatively related with PSMU of only Facebook, Instagram, and Snapchat. However, social comparison directionality was not significantly related with PSMU. Results, limitations, and future directions are discussed.
Plasma processing can be one of the drivers of low-carbon footprint chemical manufacturing using renewable electricity. Several established commercial processes already rely on this technology in different production sectors, such as metallurgy, waste-to-energy, olefin production, and ozone production. Emerging plasma applications such as activation of stable small molecules (e.g. CO2, CH4, and N2) can greatly outperform their thermo(catalytic) counterparts at mild operating conditions and low CO2 emissions. Nonetheless, a series of scientific and technical hurdles must be overcome to scale-up plasma processes without compromising energy efficiency and economics, thus enabling widespread implementation of plasma technology at industrial level.
The mechanical environment of the myocardium has a potent effect on cardiomyocyte form and function, yet an understanding of the cardiomyocyte responses to extracellular stiffening remains incomplete. We therefore employed a cell culture substrate with tunable stiffness to define the cardiomyocyte responses to clinically relevant stiffness increments in the absence of cell–cell interactions. When cultured on substrates magnetically actuated to mimic the stiffness of diseased myocardium, isolated rat adult cardiomyocytes exhibited a time-dependent reduction of sarcomere shortening, characterized by slowed contraction and relaxation velocity, and alterations of the calcium transient. Cardiomyocytes cultured on stiff substrates developed increases in viscoelasticity and microtubule detyrosination in association with early increases in the α-tubulin detyrosinating enzyme vasohibin-2 (Vash2). We found that knockdown of Vash2 was sufficient to preserve contractile performance as well as calcium transient properties in the presence of extracellular substrate stiffening. Orthogonal prevention of detyrosination by overexpression of tubulin tyrosine ligase (TTL) was also able to preserve contractility and calcium homeostasis. These data demonstrate that a pathologic increment of extracellular stiffness induces early, cell-autonomous remodeling of adult cardiomyocytes that is dependent on detyrosination of α-tubulin.
Appearance-related social media consciousness (ASMC) is the persistent awareness of one’s attractiveness on social media. The ASMC Scale, recently developed for use with adolescents (Choukas-Bradley et al., 2020), provides a promising tool for systematically examining ASMC and associations with mental health. The current study examined the psychometric properties of the ASMC Scale among emerging adult men and women. Participants for Study 1 were 428 emerging adults (M age = 21.9) from five Anglophone, industrialized countries (U.S., U.K., Canada, Australia, New Zealand). Results from Study 1 provide evidence that the 13-item ASMC Scale has a unidimensional structure, strong internal consistency, measurement invariance across gender, and convergent validity (i.e., associations with related offline appearance concerns and cognitions) and incremental validity (i.e., associations with depressive symptoms and disordered eating, above and beyond time spent on social media). Participants from Study 2 were 296 U.S. college students (M age = 18.6). Results from Study 2 confirmed the factor structure and further demonstrated the convergent and incremental validity (above and beyond both time spent on social media and offline appearance concerns) of the ASMC Scale. Findings suggest that the ASMC Scale can be used among emerging adults, aiding future research investigating social media experiences and mental health.
Legacy phosphorus (P) soils have received excessive P inputs from historic manure and fertilizer applications and present unique management challenges for protecting water quality. Soil P saturation increases soluble P (measured as water-extractable P, WEP) long after cessation of P application. We used P K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the dominant P minerals in four representative legacy P soils under conventional till and no-till management in Maryland, USA. The dominant P minerals may indicate the potential of legacy P soils to contribute to soluble P losses. Linear combination fits of XANES spectra identified the presence of four phosphate mineral groups, consisting predominately of (i) calcium-phosphate minerals (11-59%) in the form of fluorapatite, β-tricalcium phosphate, and brushite, followed by (ii) iron-phosphate minerals (12-49%) in the form of ludlamite, heterosite, P sorbed to ferrihydrite, and amorphous iron phosphates, (iii) aluminum-phosphate minerals (15-33%) in the form of wavellite and P sorbed to aluminum hydroxide, and (iv) other phosphate minerals (5-35%) in the form of copper-phosphate mineral (cornetite, 5-18%) and manganese-phosphate mineral (hureaulite, 25-35%). Extractable measures of soil P, including WEP (20.6-54.1 mg kg-1 at 1:10 ratio; 52.7-132.2 mg kg-1 at 1:100 ratio), Mehlich 3-P (693-1139 mg kg-1), and P saturation ratio (0.54-1.37), were above the environmental threshold values in soils. Organic P consisting of phytic acid was identified in most soils (13-24%) and was more pronounced in the surface layer of no-till (21-24%) than in tilled (16%) fields. Of the P forms identified with XANES, we conclude that P sorbed to Fe and Al, and Ca-P in the form of brushite and β-tricalcium phosphate will likely contribute to the soil WEP pool as the soil solution P is depleted by crop uptake.
This paper examines the “V-Matrix” and provides a wave theory life cycle model of organizations’ adoption of big data. The V-Matrix is based on the big data five “V’s”: Volume, Velocity, Variety, Veracity, and Value and captures and enumerates the different potential states that an organization can go through as part of its adoption and evolution towards big data. We extend the V-Matrix to a state space approach in order to provide a characterization of the adoption of big data technologies in an organization. We develop and use a wave theory of implementation to accommodate a firm’s movement through the V-Matrix. Accordingly, the V-Matrix provides a life cycle model of organizational use of the different aspects of big data. In addition, the model can help organizations’ plan for decision-making use of big data as they anticipate movement from one state to another, as they add big data capabilities. As part of this analysis, the paper examines some of the issues that occur in the different states, including synergies and other issues associated with co-occurrence of different V’s with each other. Finally, this paper integrates the V-Matrix with other data analytic life cycles and examines some of the implications of those models.
Explicit racism in political campaigns is on the rise. Some research suggests policy threat and government discrimination are correlated with increased political participation, while others find evidence of alienation and withdrawal. However, little direct causal evidence exists on the effects of inflammatory campaign rhetoric on marginalized groups. Using a survey experiment of Latinx Americans, we investigate how exposure to racist political attacks shapes a targeted group’s political engagement. We find that randomized exposure to a stylized campaign video critical of immigrants or Latinx people increases vote intention and enthusiasm, but does not affect other political actions, such as donating and protesting. Increased participation effects are concentrated among respondents who report strong Latino identity and low political interest. These findings highlight the resilience of minority communities who respond to political attacks with political mobilization, not avoidance. Together, this causal evidence complements previous observational work and shows that mobilization can result not just from policy threat and state action, but also from campaign rhetoric.
Providing students opportunities to engage in problem posing activities is advocated in the mathematics curriculum standards of many countries — for instance, China and the United States. This paper synthesizes research from the last two years that addresses how to integrate problem posing into the classroom so that students can gain more problem posing learning opportunities. We summarize current ideas about this topic from three closely related factors: textbooks and teaching materials, teachers, and students. We then propose future directions for research about integrating problem posing into the classroom based on these research findings. This review contributes to realizing the educational goals of effectively integrating problem posing into the classroom, promoting the development of problem posing tasks in textbooks and teaching materials, and expanding strategies to teach mathematics through problem posing.
According to the research literature, services at academic libraries and institutions of higher education do not adequately address the support needed to help autistic students thrive in college. We surveyed academic librarians about library services for autistic students at their libraries to better understand the relevant library services provided for this population. At the institutions surveyed, 37 % (n = 22) of libraries have a person responsible for accessibility issues, and 63 % (n = 37) do not have a person responsible for accessibility. Additionally, we found that 78 % (n = 47) of academic libraries provide services for disabled students and only 22 % do not (n = 13). Most pertinent to our research, 34 % of libraries (n = 20) provide services for autistic students and 66 % (n = 39) do not provide services for autistic students.
Signal analysis on graphs relies heavily on the graph Fourier transform, which is defined as the projection of a signal onto an eigenbasis of the associated shift operator. Large graphs of similar structure may be represented by a graphon. Theoretically, graphons are limit objects of converging sequences of graphs. Our work extends previous research proposing a common scheme for signal analysis of graphs that are similar in structure to a graphon. We extend a previous definition of graphon Fourier transform, and show that the graph Fourier transforms of graphs in a converging graph sequence converge to the graphon Fourier transform of the limiting graphon. We then apply this convergence result to signal processing on Cayley graphons. We show that Fourier analysis of the underlying group enables the construction of a suitable eigen-decomposition for the graphon, which can be used as a common framework for signal processing on graphs converging to the graphon.
Introduction Depression may influence treatment participation and outcomes of people with post-stroke aphasia, yet its prevalence and associated characteristics in aphasia are poorly understood. Using retrospective data from an overarching experimental study, we examined depressive symptoms and their relationship to demographic and language characteristics in people with chronic aphasia. As a secondary objective, we compared prevalence of depressive symptoms among the overarching study's included and excluded participants. Methods We examined retrospective data from 121 individuals with chronic aphasia including depression scale scores, demographic information (sex, age, time post onset of stroke, education, race/ethnicity, and Veteran status), and scores on assessments of general and modality-specific language impairments. Results Approximately 50% of participants reported symptoms indicative of depressive disorders: 23% indicative of major depression and 27% indicative of mild depression. Sex (males) and comparatively younger age emerged as statistically significant variables associated with depressive symptoms; naming ability was minimally associated with depressive symptoms. Time post onset of stroke, education level, race/ethnicity, Veteran status, and aphasia severity were not significantly associated with depressive symptoms. Depression-scale scores were significantly higher for individuals excluded from the overarching study compared to those who were included. Conclusions The rate of depressive disorders in this sample was higher than rates of depression reported in the general stroke literature. Participant sex, age, and naming ability emerged as factors associated with depressive symptoms, though these links appear complex, especially given variable reports from prior research. Importantly, depressive symptoms do not appear to diminish over time for individuals with chronic aphasia. Given these results and the relatively limited documentation of depression in aphasia literature, depression remains a pressing concern for aphasia research and routine clinical care.
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7,948 members
Olga Dmitrenko
  • Department of Chemistry and Biochemistry
Louis Rossi
  • Department of Mathematical Sciences
Cecil Dybowski
  • Department of Chemistry and Biochemistry
19716, Newark, Delaware, United States
Head of institution
Dr. Dennis Assanis, President