ASU Scholarship Showcase

2H–13C HETCOR MAS NMR is performed on 2H/13C/15N-Pro enriched A. aurantia dragline silk. Proline dynamics are extracted from 2H NMR line shapes and T1 in a site-specific manner to elucidate the backbone and side chain molecular dynamics for the MaSp2 GPGXX β-turn regions for spider dragline silk in the dry and wet, supercontracted states.

Our knowledge of magma dynamics would be improved if geophysical data could be used to infer rheological constraints in melt-bearing zones. Geophysical images of the Earth's interior provide frozen snapshots of a dynamical system. However, knowledge of a rheological parameter such as viscosity would constrain the time-dependent dynamics of melt bearing zones. We propose a model that relates melt viscosity to electrical conductivity for naturally occurring melt compositions (including H2O) and temperature. Based on laboratory measurements of melt conductivity and viscosity, our model provides a rheological dimension to the interpretation of electromagnetic anomalies caused by melt and partially molten rocks (melt fraction ~ >0.7).

Attention deficit/hyperactivity disorder (ADHD) is a risk factor for tobacco use and dependence. This study examines the responsiveness to nicotine of an adolescent model of ADHD, the spontaneously hypertensive rat (SHR). The conditioned place preference (CPP) procedure was used to assess nicotine-induced locomotion and conditioned reward in SHR and the Wistar Kyoto (WKY) control strain over a range of nicotine doses (0.0, 0.1, 0.3 and 0.6 mg/kg). Prior to conditioning, SHRs were more active and less biased toward one side of the CPP chamber than WKY rats. Following conditioning, SHRs developed CPP to the highest dose of nicotine (0.6 mg/kg), whereas WKYs did not develop CPP to any nicotine dose tested. During conditioning, SHRs displayed greater locomotor activity in the nicotine-paired compartment than in the saline-paired compartment across conditioning trials. SHRs that received nicotine (0.1, 0.3, 0.6 mg/kg) in the nicotine-paired compartment showed an increase in locomotor activity between conditioning trials. Nicotine did not significantly affect WKY locomotor activity. These findings suggest that the SHR strain is a suitable model for studying ADHD-related nicotine use and dependence, but highlights potential limitations of the WKY control strain and the CPP procedure for modeling ADHD-related nicotine reward.

How do states decide to extend or withhold international recognition in cases of contested sovereignty? We focus on how religion shapes the incentives of states in making this decision, both at the domestic level through religious institutions and at the international level through religious affinities. States with transnational religious ties to the contested territory are more likely to extend recognition. At the domestic level, states that heavily regulate religion are less likely to extend international recognition. We test these conjectures, and examine others in the literature, with two new data sets on the international recognition of both Palestine and Israel and voting on the United Nations resolution to admit Palestine as a non-member state observer, combined with global data on religious regulation and religious affinities. In cases of contested sovereignty, the results provide support for these two mechanisms through which religion shapes foreign policy decisions about international recognition.

Objective: The literature on indiscriminate violence has emphasized how information shapes state capacity and determines whether and where the government employs collective targeting. This article investigates the conditions that influence the government's ability to obtain intelligence in counterinsurgencies. Specifically, it suggests that the government is more likely to use indiscriminate violence in areas characterized by indigenous ethnic homogeneity and forested terrain. These features increase the cost of acquiring information about the insurgents, and reduce state capacity, thereby increasing the likelihood of indiscriminate violence.

Method: We examine district-level data on the Russian government's use of indiscriminate violence and disaggregated data on ethnicity and terrain across the North Caucasus from 2000 to 2011.

Results: The results indicate that ethnically homogeneous and forested areas are significantly more likely targets of indiscriminate violence, and that the effect of ethnicity is markedly stronger when the district is densely forested.

Conclusion: This finding expands on previous studies by testing the observable implications of theories linking information to indiscriminate violence, and by providing new micro-level evidence for important human and physical constraints on counterinsurgencies.

It is commonly thought that human genetic diversity in non-African populations was shaped primarily by an out-of-Africa dispersal 50–100 thousand yr ago (kya). Here, we present a study of 456 geographically diverse high-coverage Y chromosome sequences, including 299 newly reported samples. Applying ancient DNA calibration, we date the Y-chromosomal most recent common ancestor (MRCA) in Africa at 254 (95% CI 192–307) kya and detect a cluster of major non-African founder haplogroups in a narrow time interval at 47–52 kya, consistent with a rapid initial colonization model of Eurasia and Oceania after the out-of-Africa bottleneck. In contrast to demographic reconstructions based on mtDNA, we infer a second strong bottleneck in Y-chromosome lineages dating to the last 10 ky. We hypothesize that this bottleneck is caused by cultural changes affecting variance of reproductive success among males.

Premise of the Study: The earliest eukaryotes were likely flagellates with a centriole that nucleates the centrosome, the microtubule-organizing center (MTOC) for nuclear division. The MTOC in higher fungi, which lack flagella, is the spindle pole body (SPB). Can we detect stages in centrosome evolution leading to the diversity of SPB forms observed in terrestrial fungi? Zygomycetous fungi, which consist of saprobes, symbionts, and parasites of animals and plants, are critical in answering the question, but nuclear division has been studied in only two of six clades.

Methods: Ultrastructure of mitosis was studied in Coemansia reversa (Kickxellomycotina) germlings using cryofixation or chemical fixation. Character evolution was assessed by parsimony analysis, using a phylogenetic tree assembled from multigene analyses.

Key results: At interphase the SPB consisted of two components: a cytoplasmic, electron-dense sphere containing a cylindrical structure with microtubules oriented nearly perpendicular to the nucleus and an intranuclear component appressed to the nuclear envelope. Markham’s rotation was used to reinforce the image of the cylindrical structure and determine the probable number of microtubules as nine. The SPB duplicated early in mitosis and separated on the intact nuclear envelope. Nuclear division appears to be intranuclear with spindle and kinetochore microtubules interspersed with condensed chromatin.

Conclusions: This is the sixth type of zygomycetous SPB, and the third type that suggests a modified centriolar component. Coemansia reversa retains SPB character states from an ancestral centriole intermediate between those of fungi with motile cells and other zygomycetous fungi and Dikarya.

Childhood trauma is associated with premature declines in health in midlife and old age. Pathways that have been implicated, but less studied include social-emotional regulation, biological programming, and habitual patterns of thought and action. In this study we focused on childhood trauma’s influence via alterations in social-emotional regulation to everyday life events, a pathway that has been linked to subsequent health effects. Data from a 30-day daily diary of community residents who participated in a study of resilience in Midlife (n = 191, Mage = 54, SD = 7.50, 54% women) was used to examine whether self-reports of childhood trauma were associated with daily well-being, as well as reported and emotional reactivity to daily negative and positive events. Childhood trauma reports were associated with reporting lower overall levels of and greater variability in daily well-being. Childhood trauma was linked to greater reports of daily negative events, but not to positive events. Focusing on emotional reactivity to daily events, residents who reported higher levels of childhood trauma showed stronger decreases in well-being when experiencing negative events and also stronger increases in well-being with positive events. For those reporting childhood trauma, higher levels of mastery were associated with stronger decreases in well-being with negative events and stronger increases in well-being with positive events, suggesting that mastery increases sensitivity to daily negative and positive events. Our results suggest that childhood trauma may lead to poorer health in midlife through disturbances in the patterns of everyday life events and responses to those events. Further, our findings indicate that mastery may have a different meaning for those who experienced childhood trauma. We discuss social-emotional regulation as one pathway linking childhood trauma to health, and psychosocial resources to consider when building resilience-promoting interventions for mitigating the detrimental health effects of childhood trauma.

Osteosarcoma is the most common bone cancer in children and adolescents. Although 70% of patients with localized disease are cured with chemotherapy and surgical resection, patients with metastatic osteosarcoma are typically refractory to treatment. Numerous lines of evidence suggest that cytotoxic T lymphocytes (CTLs) limit the development of metastatic osteosarcoma. We have investigated the role of PD-1, an inhibitory TNFR family protein expressed on CTLs, in limiting the efficacy of immune-mediated control of metastatic osteosarcoma. We show that human metastatic, but not primary, osteosarcoma tumors express a ligand for PD-1 (PD-L1) and that tumor-infiltrating CTLs express PD-1, suggesting this pathway may limit CTLs control of metastatic osteosarcoma in patients. PD-L1 is also expressed on the K7M2 osteosarcoma tumor cell line that establishes metastases in mice, and PD-1 is expressed on tumor-infiltrating CTLs during disease progression. Blockade of PD-1/PD-L1 interactions dramatically improves the function of osteosarcoma-reactive CTLs in vitro and in vivo, and results in decreased tumor burden and increased survival in the K7M2 mouse model of metastatic osteosarcoma. Our results suggest that blockade of PD-1/PD-L1 interactions in patients with metastatic osteosarcoma should be pursued as a therapeutic strategy.

Biological Soil Crusts (BSCs) are organosedimentary assemblages comprised of microbes and minerals in topsoil of terrestrial environments. BSCs strongly impact soil quality in dryland ecosystems (e.g., soil structure and nutrient yields) due to pioneer species such as Microcoleus vaginatus; phototrophs that produce filaments that bind the soil together, and support an array of heterotrophic microorganisms. These microorganisms in turn contribute to soil stability and biogeochemistry of BSCs. Non-cyanobacterial populations of BSCs are less well known than cyanobacterial populations. Therefore, we attempted to isolate a broad range of numerically significant and phylogenetically representative BSC aerobic heterotrophs. Combining simple pre-treatments (hydration of BSCs under dark and light) and isolation strategies (media with varying nutrient availability and protection from oxidative stress) we recovered 402 bacterial and one fungal isolate in axenic culture, which comprised 116 phylotypes (at 97% 16S rRNA gene sequence homology), 115 bacterial and one fungal. Each medium enriched a mostly distinct subset of phylotypes, and cultivated phylotypes varied due to the BSC pre-treatment. The fraction of the total phylotype diversity isolated, weighted by relative abundance in the community, was determined by the overlap between isolate sequences and OTUs reconstructed from metagenome or metatranscriptome reads. Together, more than 8% of relative abundance of OTUs in the metagenome was represented by our isolates, a cultivation efficiency much larger than typically expected from most soils. We conclude that simple cultivation procedures combined with specific pre-treatment of samples afford a significant reduction in the culturability gap, enabling physiological and metabolic assays that rely on ecologically relevant axenic cultures.