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Kinematic Representations of Viscoelastic Postseismic Deformation
Full text linkAbstract Following large earthquakes, viscoelastic stress relaxation may contribute to postseismic deformation observed at Earth\u27s surface. Mechanical representations of viscoelastic deformation require a constitutive relationship for the lower crust/upper mantle material where stresses are diffused and, for non‐linear rheologies, knowledge of absolute stress level. Here, we describe a kinematic approach to representinggeodetically observed postseismic motions that does not require an assumed viscoelastic rheology. The core idea is to use observed surface motions to constrain time‐dependent displacement boundary conditions applied at the base of the elastic upper crust by viscoelastic motions in the lower crust/upper mantle, approximatingthese displacements as slip on a set of dislocation elements. Using three‐dimensional forward models of viscoelastically modulated postseismic deformation in a thrust fault setting, we show how this approach can accurately represent surface motions and recover predicted displacements at the base of the elastic layer. Applied to the 1999 Chi‐Chi (Taiwan) earthquake, this kinematic approach can reproduce geodetically observed displacements and estimates of the partitioning between correlated postseismic deformation mechanisms. Specifically, we simultaneously estimate afterslip on the earthquake source fault that is similar to previous estimates, along with slip on dislocations at the base of the elastic layer that mimic predictions from viscousstress dissipation models in which viscosity is inferred to vary three‐dimensionally. A use case for the dislocation approach to modeling viscoelastic deformation is the estimation of spatiotemporally variable fault slip processes, including across sequential interseismic phases of the earthquake cycle, without assuming alower crust/upper mantle rheology.
Plain Language Summary: After large earthquakes, Earth\u27s surface can be deformed by relaxation of stress in the lower crust and upper mantle. This postseismic relaxation process is often modeled as viscous flow. Here we present an alternate representation, using displacements at the base of the crust to mimic the stresschange imposed by flow. We compare our displacement‐based approach to models considering viscous flow, finding that our approach can reproduce postseismic motion at Earth\u27s surface. We apply our method to infer mechanisms that may be responsible for observed postseismic deformation following the 1999 Chi‐Chi (Taiwan) earthquake, finding that a combination of displacement at the base of the crust and continued slip on the fault that hosted the earthquake can explain motion measured geodetically at Earth\u27s surface
Quantification of Changes with Combined Shape Mode Analysis and Swimming Simulations
Full text linkMany different microswimmers propel themselves using flagella that beat periodically. The shape of the flagellar beat and swimming speed have been observed to change with fluid rheology. We quantify changes in the flagellar waveforms of Chlamydomonas reinhardtii in response to changes in fluid viscosity using (i) shape mode analysis and (ii) a full swimmer simulation to analyse how shape changes affect the swimming speed and to explore the dimensionality of the shape space. By decomposing the gait into the time‑independent mean shape and the time‑varying stroke, we find that the flagellar mean shape substantially changes in response to viscosity, while the changes in the time‑varying stroke are more subtle. Using the swimmer simulation, we quantify how the swimming speed is affected by the dimensionality of the flagellar shape reconstruction, and we show that the observedchange in swimming speed with viscosity is explained by the variations in mean flagellar shape and beat frequency, while the changes in swimming speed fromthe different time‑varying strokes are on the scale of variation between cells.This article is part of the theme issue ‘Biological fluid microorganism locomotion, dynamics: emerging directions’
The Making of Immigrant Labor: Inequality, Digital Capitalism, and Racialized Enforcement
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Offers a critique of the economic model of immigration. Most understandings of migration to the US focus on two primary factors. Either there was trouble in the home country, such as political unrest or famine, that pushed people out, or there was a general yearning for “a better life” or “more opportunity,” often conceptualized as the American Dream. Although many contemporary migrants in the United States have been driven by economic interests, the processes of immigration and integration are shaped also by the intersection of a range of noneconomic factors in both sending and receiving countries. The contributors to Beyond Economic Migration offer a nuanced look at a range of issues affecting motives to migrate and outcomes of integration, including US immigration policy and the visa system, labor market incorporation, employment precarity, identity and belonging, and transnationalism relating to female migrants, student migrants, and temporary foreign workers. Beyond Economic Migration argues that, for the dream of fair and equitable migration to be realized, analyses of cross-border movements, resettlement, and integration must pay attention to how migrants’ individual attributes interact with institutional mechanisms and social processes.https://scholarworks.smith.edu/soc_books/1023/thumbnail.jp
Sensory Integration Processes Characterize Concussed Athletes with Balance Deficits
Full text linkImpaired postural control constitutes a major symptom after mild traumatic brain injuries (mTBI/sport-related concussions (SRC)). In order to uphold cognition and behavior during pathological situations, individuals may be characterized by neuronal upregulation. Because postural control necessitates the integration of sensory information within somatosensory (/parietal) cortices, we investigated the hypothesis that athletes with ongoing symptoms after SRC are characterized by increased brain activation within these areas in order to compensate for postural deficits. Sixty-six athletes (27 ± 13 years; 50 men, 16 women) participated in the study. Twenty-two concussed athletes reported high post-concussion symptoms (PCS; symptomatic group), and 22 concussed athletes reported low PCS (asymptomatic group). Twenty-two healthy non-concussed athletes served as a control group. Postural control was assessed by a pressure distribution measuring plate during four balance conditions with eyes closed/open whilst either standing on a stable/unstable surface. Brain oxygenation was collected during postural control tasks by functional near-infrared spectroscopy (fNIRS) above pre- and postcentral cortices of both hemispheres. Increased postural sway was found in symptomatic athletes when compared to control athletes’ overall conditions as well as during unstable surface conditions. Symptomatic athletes were characterized by increased brain activation within the parietal cortex overall balance conditions and when compared to asymptomatic athletes. Increased brain activation within somatosensory and parietal cortices during postural control indicates that sensory integration processes are upregulated in concussed athletes with persisting symptoms. However, such potentially compensatory processes seem to constitute an ineffective neuronal mechanism as affected athletes cannot countervail post-concussion balance deficits
Considering Climate Contexts: Examining Promotive and Punitive School Characteristics Among Diverse High School Students
No full textSchools are a critical developmental context for adolescents that can, depending on certain characteristics, do a better or worse job at promoting student resilience and well- being. In working to meet student needs and respond to student behaviors, schools can exhibit more punitive characteristics, like exclusionary discipline practices, or more promotive characteristics, including restorative practices and marshaling of mental health resources. While punitive factors have been associated with more negative outcomes, especially for marginalized students, and promotive factors have been associated with more positive outcomes for students, these factors have rarely been considered together. We conducted an online survey of students from high schools in the Midwest. Students rated their experiences of various promotive and punitive characteristics at their schools, as well as their sense of the school climate – perceived safety, fairness, and belonging. Promotive factors uniquely and positively predicted climate outcomes, eclipsing any effect of punitive factors. Further, while main effects indicated differences across racial groups in perceptions of school climate, there were no racial group differences in the impact of promotive factors on these climate perceptions. When exploring different promotive elements, support from teachers and staff, as well as available resources and mental health resources had the largest predictive effects on climate outcomes for students. We discuss implications for how educators and policy makers can leverage such promotive characteristics to create equitable, inclusive contexts for all students
Syrian Regime Resilience and State Power Through Contracting Stateness: The Cases of al-Hasakeh and Aleppo
Full text linkThis chapter challenges the concepts of state weakness and state fragility that treat territorial control and control over the means of violence as key indicators of state strength in the context of civil war. We demonstrate that during the years of civil war in Syria, including periods when its survival was most precarious, the Assad regime’scapacity to manage processes of state contraction and state reassertion played a critical role in its endurance.https://scholarworks.smith.edu/mes_books/1002/thumbnail.jp
Assessing the Potential of Biochar in Northampton’s Urban Design
No full textThis paper aims to investigate the potential of biochar as a climate mitigation strategy in urban areas, as these are vulnerable to symptoms of climate change such as flooding and temperature rise. Biochar is an organic material capable of sequestering carbon and absorbing excess water and has historically been used in agricultural settings to improve crop yields. Through literature review, interviews, and spatial analysis, our study builds on the limited research on the urban usage of biochar, specifically in the context of the downtown urban forest of Northampton, Massachusetts. We conclude that the utilization of biochar on urban trees via the “Stockholm” solution has the potential to improve urban tree cover in the downtown area; however, more research is needed in order to determine the possibility of Northampton producing its own biochar. Our study provides a foundation for future research on urban biochar usage that could eventually help with local mitigation of climate change related stresse
Towards a 16S rRNA Sequence Analysis Pipeline: Exploring Statistical Methods for Taxonomic Assignment
No full textUsing 16S rRNA gene sequencing data is a fast, inexpensive method of performing taxonomic classification on prokaryotes. Many statistical methods have been developed to do such classifications. However, no existing tools for 16S analysis are geared towards long-read data. Long-read data is becoming increasingly accessible, and makes getting full-length 16S gene data significantly more feasible. We explore statistical methods in taxonomic assignment towards the development of a 16S analysis pipeline focused on long-read, full-gene data. We focus on the RDP Classifier, Bayesian Lowest Common Ancestor (BLCA), and Hidden Markov Model-based Utra-Fast OTU tools and assess their effectiveness on a testing set of Proteobacteria. We find that, when using continuous assignment, BLCA performs very similarly to RDP Classifier when using either bootstrap confidence scores or posterior probabilities to perform assignment. We conclude that BLCA’s novel Bayesian method shows great promise for growth and potential inclusion in a long-read, full-gene 16S analysis pipeline