15064 research outputs found
Sort by
Star trails at Magellan
No full textAs a part of the Field Course in Astrophysics, I was privileged to visit Chile for an observing run at the Magellan Telescopes atop the Andean foothills of the Atacama desert. The primary objective of this expedition was to capture light from elusive strong gravitational lenses, which present images of distant galaxies gravitationally magnified and distorted into ring-like shapes. The twin Magellan Telescopes, perched on a peak in the arid Chilean desert, offer some of the best astronomical observing conditions on the planet, allowing us a spectacular view of the universe. The image you see is a testament to this journey: it captures the ethereal streaks of the Milky Way, a testament to the vastness of the universe; as well as the silhouette of the Walter Baade Magellan Telescope, a symbol of our relentless pursuit of knowledge. This single, 250-second exposure encapsulates the intersection of our scholarly curiosity, the awe-inspiring beauty of the night sky, and UChicago’s ongoing quest in the field of Astrophysics
Fishing the Divide: Water and Industry – Field Work Along the Little Calumet River
No full textMy photo captures Daniel Arad fishing under the Major Taylor Trail Bridge in Whistler Woods Forest Preserve on the Little Calumet River to collect specimens of Micropterus salmoides (Largemouth Bass). My research project investigates the concentration of heavy metals in fish tissue from the Calumet region over time. The Calumet region encompasses the southern tip of Lake Michigan, spanning southeast Chicago and northwest Indiana, and is marked by a biodiverse marsh ecosystem alongside extensive industrial development since the 1870s. Tissue samples from museum specimens (1910s–2010s) and contemporary fieldwork specimens from the Calumet watershed will be analyzed with an ICP-MS spectrometer to measure element concentration. Additionally, I am digitizing historic USGS and Sanborn maps and incorporating Landsat satellite data to track shifts in hydrology and industrial land ownership over time. By quantifying the increased presence of industry over time and the temporality of biomagnification of metals in fish tissue, I hope to identify a correlation between polluting industries and impacts on aquatic ecosystems, as water quality was largely undocumented before the late 20th century
Genomic divergence across the tree of life
Get PDFNucleotide sequence data are being harnessed to identify species, even in cases in which organisms themselves are neither in hand nor witnessed. But how genome-wide sequence divergence maps to species status is far from clear. While gene sequence divergence is commonly used to delineate bacterial species, its correspondence to established species boundaries has yet to be explored across eukaryotic taxa. Because the processes underlying gene flow differ fundamentally between prokaryotes and eukaryotes, these domains are likely to differ in the relationship between reproductive isolation and genome-wide sequence divergence. In prokaryotes, homologous recombination, the basis of gene flow, depends directly on the degree of genomic sequence divergence, whereas in sexually reproducing eukaryotes, reproductive incompatibility can stem from changes in very few genes. Guided by measures of genome-wide sequence divergence in bacteria, we gauge how genomic criteria correspond to species boundaries in eukaryotes. In recognized species of eukaryotes, levels of gene sequence divergence within species are typically very small, averaging 1% genome-wide sequence divergence are likely separate species, whereas prokaryotic populations with 1% divergence are still able to recombine and thus can be considered the same species
HCN4 channels sense temperature and determine heart rate responses to heat
Get PDFThe hyperpolarization-activated cyclic nucleotide-gated ion channel 4 (HCN4) current increases due to cAMP binding and is well-recognized to contribute to adrenergically driven heart rate acceleration. HCN4 current also increases with heat by an unknown mechanism(s). We use thermodynamical and homology computational modeling, site-directed mutagenesis, and mouse models to identify a concise motif on the S4-S5 linker of HCN4 channels (M407/Y409) that determines HCN4 current (If) responses to heat. This motif is required for heat-triggered rate acceleration in cardiac pacemaker cells, isolated hearts and in vivo. Surprisingly, a loss of function M407/Y409 motif mutation prevented not only normal heat but also cAMP responses, suggesting that the heat-sensing machinery within the S4-S5 linker is essential for operating the cAMP allosteric pathway and is central to HCN4 gating modulation. The M407/Y409 motif is conserved across all HCN family members suggesting that HCN channels participate broadly in coupling heat to changes in cell membrane excitability
Introduction
Get PDFAn introduction to the volume in tribute to Professor Reuven Amitai upon his retirement from teaching
Some Reflections on Timur’s Invasion of Mamluk Syria
Get PDFThe Central Asian conqueror Timur-i lang entered the Mamluk dominions at the head of a formidable army in the autumn of 803/1400. I do not intend here to provide a narrative of the Syrian campaign. Instead I shall focus upon a number of incidents during the course of the invasion that may shed light upon the conqueror’s character, outlook, and methods, and on his indebtedness to Mongol tradition. Timur proved himself to be highly resourceful in his ideological and diplomatic maneuvers, and one premise of this article is that his confrontation with the Mamluk regime involved various motives and aspirations that are specific to the Syrian theatre
Khiḍr and Rasputin: On the Potentials and Limits of Charismatic Advisors at Court
Get PDFThe stories of the sufi shaykh Khiḍr (d. 676/1277), who was sultan Baybarsʼ spiritual advisor, and Grigory Rasputin (1869–1916), the notorious spiritual advisor to the last Czar of Russia, Nicholas II (1868–1918), and especially to the latterʼs spouse, Alexandra (1872–1918), have much in common, and pairing them in a discussion about the possible influence of saintly characters at rulersʼ courts could be instructive. This short essay will thus examine the influence a charismatic advisor was able to wield at court but also consider how crossing certain boundaries might lead to a clash with other, more traditional or bureaucratic, authorities. Focusing on Khiḍr and the Mamluk context, Rasputin will serve as a point of comparison, which will help shed new light on Khiḍr and the phenomenon he represented at large. By doing so, the article will propose insights into the nature of relations between the Mamluk ruling elite and Sufi shaykhs, or other saintly figures, while situating them within a broader context
Federal Dataset: Center for Disease Control (CDC) Guidelines, Resources and Reports for Vulnerable Populations
No full textGuidelines, Clinical Guidelines, Reports, and User Guides for Vulnerable Population
The Natural Variability of a Dexterous Motor Skill Is Stably Encoded in the Cortex of Freely Behaving Mice
Get PDFThe nervous system enables precise, skilled movements across diverse contexts, consistently performed day after day. However, the extent to which the brain's neural activity patterns are specific to each instance of a movement or behavior, and how similar these patterns are across days, remains unclear. To address this, we record calcium fluorescence activity in the motor cortex of freely moving mice performing a self-initiated, skilled reach-to-grasp task. The high trial counts and single-trial variability in this task allow for a rigorous statistical analysis of moment-to-moment movement encoding across matched behavioral sets over five days. We found that single neurons in motor cortex encode the single trial (reach-to-reach) details of paw, digit, and head movements, and this encoding is stable over days. This suggests that the stable contribution of individual cells in the motor circuit underlies the generation of skilled movements, even in complex sensory-driven tasks like reach-to-grasp
Gene Family Phylogeography Expands Insights Into Microbial Ecology Beyond Genome Collections
Get PDFAdvances in metagenomics and genome recovery from diverse habitats have dramatically ex- panded the availability of microbial genomes, unlocking unprecedented insights into microbial ecology and evolution. These discoveries are paving the way for transformative biotechnolog- ical and biomedical innovations. Despite this progress, final genome collections often provide an incomplete picture of microbial diversity, limiting our understanding of genome variation and excluding certain gene family orthologs. In contrast, metagenomic assemblies offer a more comprehensive view of microbial genomic diversity, capturing gene families lost during genome recovery and revealing broader ecological and variation of orthologs. This thesis in- troduces the EcoPhylo workflow, an open-source computational framework designed to track the phylogeography of gene families across environments. By leveraging single-copy core genes, such as ribosomal protein gene families, EcoPhylo enables benchmarking of genome recovery rates across environments, taxa, and recovery methods, providing a powerful tool for evaluating microbial genome datasets. Using this workflow, I benchmarked genome re- covery rates in the human oral cavity and gut, uncovering variation across taxa and biomes, and offering valuable guidance for optimizing genome recovery strategies in future studies. The scalability of EcoPhylo is further demonstrated through its application to a biome-level genome collection from the global surface ocean, highlighting its ability to analyze large-scale datasets. Additionally, I applied EcoPhylo to investigate the evolutionary landscape of anaero- bic flavin respiratory reductases across hundreds of gut microbes, illustrating its broader utility for exploring gene family phylogenetics and functional diversity. Overall, the EcoPhylo work- flow provides a platform for linking microbial genomes and gene families across environmental metagenomics datasets and offers a new avenue for benchmarking genome recovery efforts and advancing our understanding of microbial ecology