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Electrostatically assembled wound dressings deliver pro-angiogenic anti-miRs preferentially to endothelial cells
No full textChronic non-healing wounds occur frequently in individuals affected by diabetes, yet standard-of-care treatment leaves many patients inadequately treated or with recurring wounds. MicroRNA (miR) expression is dysregulated in diabetic wounds and drives an anti-angiogenic phenotype, but miRs can be inhibited with short, chemically-modified RNA oligonucleotides (anti-miRs). Clinical translation of anti-miRs is hindered by delivery challenges such as rapid clearance and uptake by off-target cells, requiring repeated injections, excessively large doses, and bolus dosing mismatched to the dynamics of the wound healing process. To address these limitations, we engineered electrostatically assembled wound dressings that locally release anti-miR-92a, as miR-92a is implicated in angiogenesis and wound repair. In vitro, anti-miR-92a released from these dressings was taken up by cells and inhibited its target. An in vivo cellular biodistribution study in murine diabetic wounds revealed that endothelial cells, which play a critical role in angiogenesis, exhibit higher uptake of anti-miR eluted from coated dressings than other cell types involved in the wound healing process. In a proof-of-concept efficacy study in the same wound model, anti-miR targeting anti-angiogenic miR-92a de-repressed target genes, increased gross wound closure, and induced a sex-dependent increase in vascularization. Overall, this proof-of-concept study demonstrates a facile, translational materials approach for modulating gene expression in ulcer endothelial cells to promote angiogenesis and wound healing. Furthermore, we highlight the importance of probing cellular interactions between the drug delivery system and the target cells to drive therapeutic efficacy
The D-equivalence conjecture for hyper-Kähler varieties via hyperholomorphic bundles
No full textWe show that birational hyper-Kähler varieties of K 3 [ n ] -type are derived equivalent, establishing the D -equivalence conjecture in these cases. The Fourier–Mukai kernels of our derived equivalences are constructed from projectively hyperholomorphic bundles, following ideas of Markman. Our method also proves a stronger version of the D -equivalence conjecture for hyper-Kähler varieties of K 3 [ n ] -type with Brauer classes
Essays on Technology and Trade
No full textThis thesis consists of essays on technology and trade. In Chapter 1, I study how technology in the 21st century has changed the pattern of trade. I document that skill-abundant countries no longer have a comparative advantage in skill-intensive sectors. While this empirical relationship was strong in the 1980s, it weakened in the 1990s and disappeared by the 2000s. The decline is more pronounced in countries and sectors with higher automation. I find no such heterogeneous effects among countries and sectors more exposed to offshoring. Using a quantitative trade model incorporating automation and offshoring, I confirm that the observed changes in automation can account for the evolution of comparative advantage while observed changes in offshoring cannot. I conclude by revisiting the relationships between globalization, technology, and inequality through this model. Automation increases skill premia in developed countries with high automation and also raises welfare globally, whereas offshoring leads to smaller, more evenly distributed welfare gains.
In Chapter 2 (joint with Daniel G. O'Connor), we turn to the geographic consequences of technology and trade by analyzing the role of granularity—the dominance of a few large firms in local labor markets. We propose a new economic geography model featuring granular firms subject to idiosyncratic shocks. We show that average wages increase in the size of the local labor market due to that granularity, and provide a sufficient statistic for the contribution of our mechanism. We further prove that too few firms enter in equilibrium. Using Japanese administrative data on manufacturing, we provide evidence consistent with our mechanism and quantify it. Our mechanism implies that markets with around 2 firms per sector have an elasticity of wages to population of 0.05 and firms capture only 85% of their contribution to production in profits. In large markets like Tokyo, the elasticity is around 0.001, and firm entry is approximately efficient. Enacting optimal place-based industrial policy would increase the number of firms in modest-sized cities by more than 30% and actually decrease the number of firms and people in Tokyo.
In Chapter 3 (joint with Sagiri Kitao), we study the distributional consequences of technological and trade-induced polarization—wage and employment losses of middle-class workers relative to low- and high-skill groups. We build a model of overlapping generations who choose consumption, savings, labor supply, and occupations over their life-cycles, and accumulate human capital. We simulate a wage shift observed since the early 1980s and investigate individuals' responses. Polarization improves welfare of young individuals that are high-skilled, while it hurts low-skilled individuals across all ages and especially younger ones. The gain of the high-skilled is larger for generations entering in later periods, who can fully exploit the rising skill premium.Ph.D
ObjecTier: Non-Invasively Boosting Memory Tiering Performance
No full textICPE Companion ’25, Toronto, ON, CanadaRecent research has developed page-based memory-tiering systems that place hot pages in fast tiers and cold pages in slower, more capacious tiers. However, applications place many objects together within pages, and most pages contain some objects that are hot and some that are cold. Our simulations of a key-value workload confirm this; even the hottest pages in the fast tier can contain 50% cold data.
To improve fast tier utilization, we describe the design of a new framework, ObjecTier, that uses application knowledge to efficiently consolidate hot data and cold data. This allows ObjecTier-enabled applications to boost fast tier hit rates and improve performance regardless of which underlying memory tiering system they use underneath, even if that system is page based.
With simulations, we show that ObjecTier may improve average memory access time (AMAT) by 2× without adding any memory space overhead for our simulated key-value store workload. We conclude by outlining the next steps to make the ObjecTier framework a reality for easy adaptation of applications like key-value stores and other indexed databases
Measurement of the 40Ar(e,e′) elastic scattering cross section with a novel gas-jet target
No full textWe report on a measurement of elastic electron scattering on argon performed with a novel cryogenic gas-jet target at the Mainz Microtron accelerator MAMI. The luminosity is estimated with the thermodynamical parameters of the target and by comparison to a calculation in distorted-wave Born approximation. The cross section, measured at new momentum transfers of 1.24 fm - 1 and 1.55 fm - 1 is in agreement with previous experiments performed with a traditional high-pressure gas target, as well as with modern ab-initio calculations employing state-of-the-art nuclear forces from chiral effective field theory. The nearly background-free measurement highlights the optimal properties of the gas-jet target for elements heavier than hydrogen, enabling new applications in hadron and nuclear physics
Exotic phases in finite-density ℤ3 theories
No full textLattice ℤ3 theories with complex actions share many key features with finite- density QCD including a sign problem and CK symmetry. Complex ℤ3 spin and gauge models exhibit a generalized Kramers-Wannier duality mapping them onto chiral ℤ3 spin and gauge models, which are simulatable with standard lattice methods in large regions of parameter space. The Migdal-Kadanoff real-space renormalization group (RG) preserves this duality, and we use it to compute the approximate phase diagram of both spin and gauge ℤ3 models in dimensions one through four. Chiral ℤ3 spin models are known to exhibit a Devil’s Flower phase structure, with inhomogeneous phases that can be thought of as ℤ3 analogues of chiral spirals. Out of the large class of models we study, we find that only chiral spin models and their duals have a Devil’s Flower structure with an infinite set of inhomogeneous phases, a result we attribute to Elitzur’s theorem. We also find that different forms of the Migdal-Kadanoff RG produce different numbers of phases, a violation of the expectation for universal behavior from a real-space RG. We discuss extensions of our work to ℤN models, SU(N) models and nonzero temperature
Concavity for elliptic and parabolic equations in locally symmetric spaces with nonnegative curvature
No full textWe establish a concavity principle for solutions to elliptic and parabolic equations on locally symmetric spaces with nonnegative sectional curvature, extending the results of Langford and Scheuer (Commun Partial Differ Equ 46(6):1005–1016, 2021). To the best of our knowledge, this is the first general concavity principle established on spaces with non-constant sectional curvature
Report to the President year ending June 30, 2025, Institute for Soldier Nanotechnologies
No full textThis report contains the following sections: ISN Headquarters Team; U.S. Army Program Management Team; Principal Investigators; Core Research Portfolio; Non-core Research; Funding; Collaborations; Transitioning; A Sample of ISN Research Accomplishments Between July 1, 2024, and June 30, 2025; Outreach Activities; Contributions to the MIT Community; Special Programs; and Future Plans
Induced Gradients in Steady, Two-Dimensional Heat Conduction? Yes, But…
No full textA two-dimensional object conducts heat steadily between isothermal segments of its boundary that are at two different temperatures, with the heat flow occurring either through the object or through the region surrounding it. In classical potential theory, the isothermal surfaces are represented by source distributions, and the adiabatic surfaces that separate them are represented by dipole distributions. Sources or dipoles at one location can induce a temperature gradient at another location on an isothermal surface. This induced gradient adds to the gradient produced by a source at that location. In this paper, induced gradients are shown to produce zero net power in objects that have appropriate geometrical symmetry but not in objects that lack symmetry. Further, unpowered conductors within the domain (so-called floating conductors) are shown to have a nonzero induced source density that integrates to zero over the surface of the conductor. These results differ from those of a previous study of such configurations
Electrochemical direct air capture of CO2 using neutral red as reversible redox-active material
No full textDirect air capture of carbon dioxide is a viable option for the mitigation of CO2
emissions and their impact on global climate change. Conventional processes
for carbon capture from ambient air require 230 to 800 kJ thermal per mole of
CO2, which accounts for most of the total cost of capture. Here, we demonstrate electrochemical direct air capture using neutral red as a redox-active
material in an aqueous solution enabled by the inclusion of nicotinamide as a
hydrotropic solubilizing agent. The electrochemical system demonstrates a
high electron utilization of 0.71 in a continuous flow cell with an estimated
minimum work of 35 kJe per mole of CO2 from 15% CO2. Further exploration
using ambient air (410 ppm CO2 in the presence of 20% oxygen) as a feed gas
shows electron utilization of 0.38 in a continuous flow cell to provide an
estimated minimum work of 65 kJe per mole of CO2