Radial Trends in IMF-Sensitive Absorption Features in Two Early-Type Galaxies: Evidence for Abundance-Driven Gradients

Samples of early-type galaxies show a correlation between stellar velocity dispersion and the stellar initial mass function (IMF) as inferred from gravity-sensitive absorption lines in the galaxies' central regions. To search for spatial variations in the IMF, we have observed two early-type galaxies with Keck/LRIS and measured radial gradients in the strengths of absorption features from 4000-5500 \AA $\,$ and 8000-10,000 \AA. We present spatially resolved measurements of the dwarf-sensitive spectral indices NaI (8190 \AA) and Wing-Ford FeH (9915 \AA), as well as indices for species of H, C$_2$, CN, Mg, Ca, TiO, and Fe. Our measurements show a metallicity gradient in both objects, and Mg/Fe consistent with a shallow gradient in \alpha-enhancement, matching widely observed trends for massive early-type galaxies. The NaI index and the CN$_1$ index at 4160 \AA $\,$ exhibit significantly steeper gradients, with a break at $r \sim 0.1 r_{\rm eff}$ ($r \sim 300$ pc). Inside this radius NaI strength increases sharply toward the galaxy center, consistent with a rapid central rise in [Na/Fe]. In contrast, the ratio of FeH to Fe index strength decreases toward the galaxy center. This behavior cannot be reproduced by a steepening IMF inside $0.1 r_{\rm eff}$ if the IMF is a single power law. While gradients in the mass function above $\sim 0.4 M_\odot$ may occur, exceptional care is required to disentangle these IMF variations from the extreme variations in individual element abundances near the galaxies' centers.Comment: Accepted for publication in ApJ. Updates from v1 include an expanded comparison of measured index strengths to SPS models. 20 page body + 7 page appendix + references. Includes 25 figure

From Heteroditopic to Multitopic Receptors for Ion-Pair Recognition: Advances in Receptor Design and Applications

Ion-pair recognition has emerged from cation and anion recognition and become a diverse and active field in its own right. The last decade has seen significant advances in receptor design in terms of the types of binding motifs, understanding of cooperativity and increase in complexity from heteroditopic to multitopic receptors. As a result, attention has turned to applying this knowledge to the rational design of ion-pair receptors for applications in salt solubilisation and extraction, membrane transport and sensing. This Review highlights recent progress and developments in the design and applications of heteroditopic and multitopic receptors for ion-pair recognition

Isomorphism of graph classes related to the circular-ones property

We give a linear-time algorithm that checks for isomorphism between two 0-1 matrices that obey the circular-ones property. This algorithm leads to linear-time isomorphism algorithms for related graph classes, including Helly circular-arc graphs, \Gamma-circular-arc graphs, proper circular-arc graphs and convex-round graphs.Comment: 25 pages, 9 figure

Još Hrvatska ni propala: [Still Croatia has not fallen]: examining the public face of memory in Croatia

This thesis examines the “public face of memory,” the visual elements of cultural memory going beyond the simple structure of a statue or a plaque to tell a story about the politics of remembrance. The structure of cultural memory is determined by ongoing struggles between social groups for power over memory itself (Müller 2009) to secure the power to endure (Hearn 2014), thus binding memory and identity over space and time. My study of the structures of power and memory in Croatia highlights the role of social responses to the past in determining local, national and supranational identities. Since the end of the Croatian War of Independence or “Homeland War” in 1995, much has been remembered and more forgotten for the sake of a united national identity. Monuments have been constructed to remind passers-by of the nation, its defenders and its victims, yet the meaning these concrete manifestations of memory impart depends on how a given audience interacts with them. This results in plural and contradictory iterations of cultural memory, contrary to the intent of those exercising power over memory to forge a unitary image of the nation. In this thesis, I address the following core research questions: • How is memory visualised in public spaces, and how does the construction of particular monuments or the commemoration of certain events reflect social behaviours toward the past? • How does Croatia’s visual culture of remembrance illustrate the relationships between power, violence, memory and identity? • How, and by whom, is memory constructed to perpetuate social divisions, based on nationality, ethnicity or religion? • Using a concept of “memory abuse” in post-conflict settings, what are the normative expectations of remembrance and what form does resistance to specific memorialisations take? • How do processes of social differentiation elevate or exclude specific historical narratives from commemorative processes? My point of departure is the construction of cultural memory, as described by Aleida Assmann (1999; 2006) and Jan Assmann (2000). I address the neglect and subsequent lack of development of Todorov’s term, “memory abuse” (1995). I find the transitions between forms of memory provide voids in which various actors exercise power over memory to mould narratives of the past to serve their vision of the present and future. These transitions and abuses are made visible through public memorials. Through my work on capturing its public display and performance, I advance a method for the documentation of memory. Through the case study of Croatia, this work highlights patterns of memorialisation that perpetuate violence and providesa template to identify memory abuse elsewhere. My key arguments are: • Memory can be “abused” when processes of memorialisation are manipulated in ways that result in violence; • Privileged groups (in this case, the ruling Croatian Democratic Union and veterans of the Homeland War) exercise power over memory to construct an exclusive narrative of national identity and belonging; this is represented in memorial spaces; • There is no singular “cultural memory,” rather cultures of memory intersect or align at key points in the mnemonic calendar, with groups seeking power over memory to ensure the persistence of their own identity; • The process of making “Croatian” identity shares similar characteristics with other national groups in that much of this identity is formed by the drawing of strict ethnic, political, religious or related boundaries through negation. In marking these boundaries, those with greater influence over the mnemonic landscape deny opportunities for some of those most affected by the violent destruction of Yugoslavia to contribute to the formation of shared cultural memory of the past at the level of the Republic of Croatia, ultimately, and a corresponding inclusive national identity

Using Statistics, Computational Modelling and Artificial Intelligence Methods to Study and Strengthen the Link between Kinematic Impacts and mTBIs

Mild traumatic brain injuries (mTBIs) are frequently occurring, yet poorly understood, injuries in sports (e.g., ice hockey) and other physical recreation activities where head impacts occur. Helmets are essential pieces of equipment used to protect participants’ heads from mTBIs. Evaluating the performance of helmets to prevent mTBIs using simulations on anatomically accurate computational head finite element models is critically important for advancing the development of safer helmets. Advancing the level of detail in, and access to, such models, and their continued validation through state-of-the-art brain imaging methods and traditional head injury assessment procedures, is also essential to improve safety. The significant research contributions in this thesis involve evaluating the decrease in blunt impact-induced brain axon fiber tract strains that various helmets provide by studying outputs of existing finite element brain models and implementing open-source artificial intelligence technology to create a novel pipeline for predicting such strains

COVID-19 pandemic: A process of recovery and renewal

Guest editoria

Giant interfacial spin-Hall angle from Rashba-Edelstein effect revealed by the spin-Hall Hanle processes

The Rashba-Edelstein effect (REE), which generates interfacial spin polarization and subsequent spin current, is a compelling spin-charge conversion mechanism for spintronics applications, since it is not limited by the elemental spin-orbit coupling. In this work, we demonstrate REE at Pt/ferroelectric interfaces using the recently elucidated spin-Hall Hanle effects (SHHE), in which a Larmor precession of spin polarization in a diffusion process from the interface manifest as magnetoresistance and Hall effect. We show that REE leads to a three-fold enhancement of the effective spin Hall angle in ferroelectric interface Pt/h-LuFeO3 compared to that of Pt /Al2O3, although the difference in the spin relaxation time is negligible. Modeling using SHHEs involving REE as an additional source of interfacial polarization suggests that REE can lead to an interfacial spin Hall angle (~0.3) that is one order of magnitude larger than the bulk value of Pt. Our results demonstrate that a ferroelectric interface can produce large spin-charge conversion and that SHHEs are a sensitive tool for characterizing interfacial spin transport properties