48 research outputs found
The Customary International Law Game
Structural realists in political science and some rationalist legal scholars argue that customary international law cannot affect state behavior: that it is âepiphenomenal.â This article develops a game theoretic model of a multilateral prisonerâs dilemma in the customary international law context that shows that it is plausible that states would comply with customary international law under certain circumstances. Our model shows that these circumstances relate to: (i) the relative value of cooperation versus defection, (ii) the number of states effectively involved, (iii) the extent to which increasing the number of states involved increases the value of cooperation or the detriments of defection, including whether the particular issue has characteristics of a commons problem, a public good, or a network good, (iv) the information available to the states involved regarding compliance and defection, (v) the relative patience of states in valuing the benefits of long-term cooperation compared to short-term defection, (vi) the expected duration of interaction, (vii) the frequency of interaction, and (viii) whether there are also bilateral relationships or other multilateral relationships between the involved states.
This model shows that customary international law is plausible in the sense that it may well affect state behavior where certain conditions are met. It shows what types of contexts, including malleable institutional features, may affect the ability of states to produce and comply with customary international law. This article identifies a number of empirical strategies that may be used to test the model
A Historiometric Examination of Machiavellianism and a New Taxonomy of Leadership
Although researchers have extensively examined the relationship between charismatic leadership and Machiavellianism (Deluga, 2001; Gardner & Avolio, 1995; House & Howell, 1992), there has been a lack of investigation of Machiavellianism in relation to alternative forms of outstanding leadership. Thus, the purpose of this investigation was to examine the relationship between Machiavellianism and a new taxonomy of outstanding leadership comprised of charismatic, ideological, and pragmatic leaders. Using an historiometric approach, raters assessed Machiavellianism via the communications of 120 outstanding leaders in organizations across the domains of business, political, military, and religious institutions. Academic biographies were used to assess twelve general performance measures as well as twelve general controls and five communication specific controls. The results indicated that differing levels of Machiavellianism is evidenced across the differing leader types as well as differing leader orientation. Additionally, Machiavellianism appears negatively related to performance, though less so when type and orientation are taken into account.Yeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
26th Annual Computational Neuroscience Meeting (CNS*2017): Part 3 - Meeting Abstracts - Antwerp, Belgium. 15â20 July 2017
This work was produced as part of the activities of FAPESP Research,\ud
Disseminations and Innovation Center for Neuromathematics (grant\ud
2013/07699-0, S. Paulo Research Foundation). NLK is supported by a\ud
FAPESP postdoctoral fellowship (grant 2016/03855-5). ACR is partially\ud
supported by a CNPq fellowship (grant 306251/2014-0)
Mimicking Micro-networks: Design, Methods, and Techniques for Particle Flow and Deposition
In vivo imaging and morphogenesis of butterfly scale development
During metamorphosis, the wings of a butterfly sprout hundreds of thousands of scales with intricate micro- and nanostructures that determine the wings' optical appearance, wetting characteristics, thermodynamic properties, and aerodynamic behavior. This strategyâof enabling multifunctionality by controlling material structure across relevant length scalesâcan be emulated in bioinspired materials. However, the range of structural length scales that are integrated in biological materials exceeds that of their synthetic counterparts, due in large part to our limited understanding of the processes that biology employs in their formation. Key to gaining deeper insights into these processes is the visualization of material structures as they form within the living organism.
In this thesis, I present an approach for studying structure formation in wing scales of live butterflies with high temporal and spatial resolution. To gain a comprehensive perspective of scale formation, I developed pupal surgery techniques and adapted quantitative phase microscopy methods to achieve label-free, in vivo visualization of scale cell growth in Vanessa cardui pupae throughout pupal development. This continuous visualization of scale cells establishes a clear phenomenological timeline of scale morphogenesis that was previously limited by the discrete nature of ex vivo studies of fixed cells. Moreover, by capturing time-resolved volumetric tissue data together with nanoscale surface height information, we gain quantitative insights into the underlying processes involved in scale cell patterning and growth.
The quantitative data from live imaging informs a continuum mechanics model of the growth of the scales' ridge structures and allows examination of the structural requirements for proper ridge formation. Live imaging of structure formation also leads to unique broader impacts, including approaches for exploiting human perception of color to visualize overlapping structures in volumetric data, and hands-on learning activities in the classroom and laboratory centered around bio-optics, structure formation in nature, and butterfly surgery. In vivo visualization of butterfly scale cell morphogenesis offers a rich foundation for deciphering biological processes and biomechanical principles involved in the formation of functional materials and for engaging broader audiences.Ph.D
Modeling oxygen requirements in ischemic cardiomyocytes
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 36-40).Ischemic heart disease remains a leading cause of death globally and in the US. The most common ischemic event is a heart attack, where one or more arteries are obstructed and the cardiac muscle is deprived of oxygen. Although removing the blockage and allowing reperfusion can prevent death, at the same time it can cause significant damage through "reperfusion injury." To date, there are limited methods to predict the viability of the myocardial muscle cell (myocyte) and its quantitative conditions during ischemia. Here, we explore the viability of heart cells using a model for cellular metabolism. We use this model to predict conditions that will sustain viable concentrations of adenosine triphosphate (ATP) and compare these conditions to baseline energy consumption rates. Glycolytic metabolism is modeled using a system of coupled ordinary differential equations that describe the individual metabolic reactions that occur within the cardiac myocyte and its surrounding tissue. Over 200 conditions were simulated to characterize a range of reduced oxygen levels and ATP consumption rates. These conditions were organized according to their steady-state level of [ATP], and reveal a distinct transition region between low levels of ATP that are sustainable and depleted ATP levels that lead to cell death. Our simulations and analysis illustrate how very low concentrations of oxygen in the extracellular tissue allow the cells to perform essential survival functions. The model contains 58 of the molecular species within the cell, so that the conditions of the cell at the time of reperfusion can be predicted. We find the oxygen level required for viability increases roughly linearly with the ATP consumption rate, and is smaller than one would have expected based on previous results. An external tissue level 02 concentration of around 0.007 mM is sufficient to sustain cardiomyocyte viability in the absence of beating. This level of oxygen could be achieved through collateral circulation. This model of ischemia will also provide future investigations of the reperfusion process to proceed from a known metabolic and molecular state of the cardiomyocytes preceding re-oxygenation.by Anthony Drew McDougal.S.M
Biological growth and synthetic fabrication of structurally colored materials
Nature's light manipulation strategies - in particular those at the origin of bright iridescent colors - have fascinated humans for centuries. In recent decades, insights into the fundamental concepts and physics underlying biological light-matter interactions have enabled a cascade of attempts to copy nature's optical strategies in synthetic structurally colored materials. However, despite rapid advances in bioinspired materials that emulate and exceed nature's light manipulation abilities, we tend to create these materials via methods that have little in common with the processes used by biology. In this review, we compare the processes that enable the formation of biological photonic structures with the procedures employed by scientists and engineers to fabricate biologically inspired photonic materials. This comparison allows us to reflect upon the broader strategies employed in synthetic processes and to identify biological strategies which, if incorporated into the human palette of fabrication approaches, could significantly advance our abilities to control material structure in three dimensions across all relevant length scales
In vivo visualization of butterfly scale cell morphogenesis in Vanessa cardui
During metamorphosis, the wings of a butterfly sprout hundreds of thousands of scales with intricate microstructures and nano-structures that determine the wingsâ optical appearance, wetting characteristics, thermodynamic properties, and aerodynamic behavior. Although the functional characteristics of scales are well known and prove desirable in various applications, the dynamic processes and temporal coordination required to sculpt the scalesâ many structural features remain poorly understood. Current knowledge of scale growth is primarily gained from ex vivo studies of fixed scale cells at discrete time points; to fully understand scale formation, it is critical to characterize the time-dependent morphological changes throughout their development. Here, we report the continuous, in vivo, label-free imaging of growing scale cells of Vanessa cardui using speckle-correlation reflection phase microscopy. By capturing time-resolved volumetric tissue data together with nanoscale surface height information, we establish a morphological timeline of wing scale formation and gain quantitative insights into the underlying processes involved in scale cell patterning and growth. We identify early differences in the patterning of cover and ground scales on the young wing and quantify geometrical parameters of growing scale features, which suggest that surface growth is critical to structure formation. Our quantitative, time-resolved in vivo imaging of butterfly scale development provides the foundation for decoding the processes and biomechanical principles involved in the formation of functional structures in biological materials.NSF (DMREF-1922321)NSF CBET program (Grant 1804241)NIH Grant (P41EB015871)NIH Grant (R21GM140613)NIH Grant (R01HL158102)NIH Grant (R01DA045549)Grant U01CA202177DOE (DE-FOA-0002359
A computational model of cardiomyocyte metabolism predicts unique reperfusion protocols capable of reducing cell damage during ischemia/reperfusion
If a coronary blood vessel is occluded and the neighboring cardiomyocytes deprived of oxygen, subsequent reperfusion of the ischemic tissue can lead to oxidative damage due to excessive generation of reactive oxygen species. Car-diomyocytes and their mitochondria are the main energy producers and consumers of the heart, and their metabolic changes during ischemia seem to be a key driver of reperfusion injury. Here, we hypothesized that tracking changes in cardiomyocyte metabolism, such as oxygen and ATP concentrations, would help in identifying points of metabolic failure during ischemia and reperfusion. To track some of these changes continuously from the onset of ischemia through reperfusion, we developed a system of differential equations representing the chemical reactions involved in the production and consumption of 67 molecular species. This model was validated and used to identify conditions present during periods of critical transition in ischemia and reperfusion that could lead to oxidative damage. These simulations identified a range of oxygen concentrations that lead to reverse mitochondrial electron transport at complex I of the respiratory chain and a spike in mitochondrial membrane potential, which are key suspects in the generation of reactive oxygen species at the onset of reperfusion. Our model predicts that a short initial reperfusion treatment with reduced oxygen content (5% of physiological levels) could reduce the cellular damage from both of these mechanisms. This model should serve as an open-source platform to test ideas for treatment of the ischemia reperfusion process by following the temporal evolution of molecular concentrations in the cardiomyocyte.ISSN:0021-9258ISSN:1083-351