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Imaging the kinetics of anisotropic dissolution of bimetallic core–shell nanocubes using graphene liquid cells
No full textChemical design of multicomponent nanocrystals requires atomic-level understanding of reaction kinetics. Here, we apply single-particle imaging coupled with atomistic simulation to study reaction pathways and rates of Pd@Au and Cu@Au core-shell nanocubes undergoing oxidative dissolution. Quantitative analysis of etching kinetics using in situ transmission electron microscopy (TEM) imaging reveals that the dissolution mechanism changes from predominantly edge-selective to layer-by-layer removal of Au atoms as the reaction progresses. Dissolution of the Au shell slows down when both metals are exposed, which we attribute to galvanic corrosion protection. Morphological transformations are determined by intrinsic anisotropy due to coordination-number-dependent atom removal rates and extrinsic anisotropy induced by the graphene window. Our work demonstrates that bimetallic core-shell nanocrystals are excellent probes for the local physicochemical conditions inside TEM liquid cells. Furthermore, single-particle TEM imaging and atomistic simulation of reaction trajectories can inform future design strategies for compositionally and architecturally sophisticated nanocrystals
A Cyclin A—Myb-MuvB—Aurora B network regulates the choice between mitotic cycles and polyploid endoreplication cycles
No full textEndoreplication is a cell cycle variant that entails cell growth and periodic genome duplication without cell division, and results in large, polyploid cells. Cells switch from mitotic cycles to endoreplication cycles during development, and also in response to conditional stimuli during wound healing, regeneration, aging, and cancer. In this study, we use integrated approaches in Drosophila to determine how mitotic cycles are remodeled into endoreplication cycles, and how similar this remodeling is between induced and developmental endoreplicating cells (iECs and devECs). Our evidence suggests that Cyclin A/CDK directly activates the Myb-MuvB (MMB) complex to induce transcription of a battery of genes required for mitosis, and that repression of CDK activity dampens this MMB mitotic transcriptome to promote endoreplication in both iECs and devECs. iECs and devECs differed, however, in that devECs had reduced expression of E2F1-dependent genes that function in S phase, whereas repression of the MMB transcriptome in iECs was sufficient to induce endoreplication without a reduction in S phase gene expression. Among the MMB regulated genes, knockdown of AurB protein and other subunits of the chromosomal passenger complex (CPC) induced endoreplication, as did knockdown of CPC-regulated cytokinetic, but not kinetochore, proteins. Together, our results indicate that the status of a CycA—Myb-MuvB—AurB network determines the decision to commit to mitosis or switch to endoreplication in both iECs and devECs, and suggest that regulation of different steps of this network may explain the known diversity of polyploid cycle types in development and disease
Back to the future: A time-calibrated theory of entrepreneurial action
Get PDFTime is a defining feature of human activity but is under-examined in theories of entrepreneurial action. This is perplexing given that entrepreneurial action is oriented toward novel creations that unfold under conditions of uncertainty, where temporal concerns may be especially impactful. This paper addresses this lacuna by introducing a framework that articulates the key dimensions of time entrepreneurs consider. We advance that entrepreneurs organize and shape their visions of entrepreneurial endeavors by constructing time-calibrated internal narratives. These narratives address the dimensions of initialization (i.e., timing of action), pace (i.e., time from action to outcome) and chronology (i.e., sequencing of action). Our theoretical model identifies how variations in these dimensions affect the likelihood of entrepreneurial action. We further specify that narrative vigilance and externalization moderate these effects with hyper levels of each reversing the relationships. Together, our conceptualizations reveal how entrepreneurial time-calibrations are themselves an essential lever for action. We discuss the implications of these insights for a range of perspectives on the ways entrepreneurs engage their craft, with special attention toward dynamic process-centered frameworks
Performance optimization, modeling and analysis of sparse matrix-matrix products on multi-core and many-core processors
Get PDFTetela Amulets: Re-Interpreting a Medical Anthropology Collection as a Fashion Benchmark
Get PDFIn the 1920s and 30s, missionaries and colonial officials in equatorial Africa collected thousands of amulets—devices worn on the body that were made locally for protection and healing (spiritual and/or physical). One of these collections—assembled in the 1920s by an American pseudo-missionary, Major John White—is now held at the Mathers Museum of World Cultures at Indiana University, which accepted the amulets and other artefacts used by the Tetela people as an example of ‘medical anthropology.’ Although they were not made as ‘fashion’ (or even as art), I argue that they can be viewed as a style of dress specific to a time and place and thus as fashion. Like fashions in clothing, individual amulets can be shown to have similarities in their form and symbolic meaning, which can be expected to change over time. I propose looking at this collection of amulets as a ‘fashion benchmark’ in the history of Tetela dress, calling for further research and seeking to push the boundaries on our conception of fashion, making it less focused on the ‘fashion industry’ and more inclusive of slower-changing styles of dress, minority cultures, and non-Western cultures
Borderline Personality Disorder symptom comorbidity within a high externalizing sample: Relationship to the internalizing-externalizing dimensional structure of psychopathology
No full textBackground: Borderline personality disorder (BPD) is highly comorbid with both internalizing and externalizing psychopathology. The current study replicates previous findings (Eaton et al. 2011) that indicate that BPD symptomatology is best conceptualized at the intersection of the distress subfactor of the internalizing dimension and the externalizing dimension of psychopathology. Methods: Confirmatory factor analysis of the covariance among continuous measures of lifetime alcohol problems, marijuana problems, other drug problems, antisocial behavior, and conduct problems, and measures of depression, trait-anxiety, neuroticism, and BPD symptoms assessed in 837 young adults. The sample was recruited to obtain a roughly normal distribution of externalizing problems ranging from no problems to individuals of high externalizing severity leading to an overrepresentation of externalizing problems in the current sample. Results: Results indicated BPD symptoms were associated with both the externalizing dimension and the distress subfactor of the internalizing dimension and lay at the intersection of the two dimensions. Interestingly, in the current study BPD had a stronger association with the externalizing dimension than was observed in previous studies. Conclusions: The results replicated earlier findings that BPD symptoms lie at the intersection of the externalizing and internalizing-distress dimensions while using different and more dimensional measures of the pathology assessed. Current findings indicate that perhaps BPD is more heavily influenced by the externalizing dimension of psychopathology within a high externalizing sample, such as those presenting for treatment for alcohol use disorder or substance use disorder
Ion-Ion Interactions in Charge Detection Mass Spectrometry
No full textCharge detection mass spectrometry (CDMS) is a single-particle technique where the masses of individual ions are determined by simultaneously measuring their mass-to-charge ratio (m/z) and charge. Ions are usually trapped inside an electrostatic linear ion trap (ELIT) where they oscillate back and forth through a detection cylinder, generating a periodic signal that is analyzed by fast Fourier transforms. The oscillation frequency is related to the ion's m/z, and the magnitude is related to the ion's charge. In early work, multiple ion trapping events were discarded because there was a question about whether ion-ion interactions affected the results. Here, we report trajectory calculations performed to assess the influence of ion-ion interactions when multiple highly charged ions are simultaneously trapped in an ELIT. Ion-ion interactions cause trajectory and energy fluctuations that lead to variations in the oscillation frequencies that in turn degrade the precision and accuracy of the m/z measurements. The peak shapes acquire substantial high and low m/z tails, and the average m/z shifts to a higher value as the number of trapped ions increases. The effects of the ion-ion interactions are proportional to the product of the charges and the square root of the number of trapped ions and depend on the ions' m/z distribution. For the ELIT design examined here, ion-ion interactions limit the m/z resolving power to several hundred for a typical homogeneous ion population
Assessing Historical Discussion
Get PDFDiscussion can be a valuable element of history classrooms, and assessing participation can provide an important means of improving students’ engagement in this valuable form of communication. Doing so requires that teachers identify the specific skills of historical discussion that they want students to master; teach those skills systematically; and develop practical procedures for collecting information on students’ participation. This article suggests guidelines for teachers to consider in preparing for each of these tasks
Smart Factories, Dumb Policy? Managing Cybersecurity and Data Privacy Risks in the Industrial Internet of Things
No full textInterest is booming in the so-called Internet of Things (IoT). The Industrial Internet of Things (IIoT) is one application of this trend and involves the use of smart technologies in a manufac- turing context. Even though these applications hold the promise to revolutionize manufacturing, there are a number of outstand- ing cybersecurity and data privacy issues impacting the realiza- tion of the myriad benefits promised by IIoT proponents. This ar- ticle analyzes some of these pressing issues, focusing on: (1) critical infrastructure protection and cybersecurity due diligence, (2) trends in transatlantic data privacy protections, and (3) the regulation of new technologies like artificial intelligence (AI) and blockchain. The aticle concludes with a list of recommendations for state and federal policymakers to consider in an effort to harden the IIoT along with the supply chains critical to the con- tinued development of smart factories
What Happens Next? A Qualitative Study of Founder Succession in Social Enterprises
No full textIn the organizational context of social enterprises, the viability of the primary social mission is put to the test when the founder leaves the organization. Yet the literature has remained silent on this important stage in the life of a social enterprise. We address this gap by conducting in-depth case studies in the unexplored setting of India. Based on multiple interviews, field observations and archival data, we develop insights into the significance of “social entrepreneur centrality” in social enterprise founder succession, discuss its consequences, and review the effects of contextual influences. Contributions to social entrepreneurship research and practice are discussed