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Abstract Given a $$k$$-uniform hypergraph $$H$$ on $$n$$ vertices, an even cover in $$H$$ is a collection of hyperedges that touch each vertex an even number of times. Even covers are a generalization of cycles in graphs and are equivalent to linearly dependent subsets of a system of linear equations modulo $$2$$. As a result, they arise naturally in the context of well-studied questions in coding theory and refuting unsatisfiable $$k$$-SAT formulas. Analogous to the irregular Moore bound of Alon, Hoory, and Linial [3], Feige conjectured [8] an extremal trade-off between the number of hyperedges and the length of the smallest even cover in a $$k$$-uniform hypergraph. This conjecture was recently settled up to a multiplicative logarithmic factor in the number of hyperedges [12, 13]. These works introduce the new technique that relates hypergraph even covers to cycles in the associated Kikuchi graphs. Their analysis of these Kikuchi graphs, especially for odd $$k$$, is rather involved and relies on matrix concentration inequalities. In this work, we give a simple and purely combinatorial argument that recovers the best-known bound for Feige’s conjecture for even $$k$$. We also introduce a novel variant of a Kikuchi graph which together with this argument improves the logarithmic factor in the best-known bounds for odd $$k$$. As an application of our ideas, we also give a purely combinatorial proof of the improved lower bounds [4] on 3-query binary linear locally decodable codes. 

This article advances geographic scholarship about conservation and protected areas (PAs) through a focuson biocultural geographies. Biocultural geographies derive from relationships between heterogenousIndigenous stewardship practices, biological diversity, and trans-scalar multidimensional social, political, andecological processes. The concept brings together insights from political ecology and biocultural conservationto address the interplay between environmental governance, cultural change, and biodiversity. We drawfrom collaborative, transdisciplinary research with Siona, Siekopai, and Cofan Indigenous communities inthe northern Ecuadorian Amazon, a site of global importance for its biodiversity and cultural heritage. Thisis also a region of rapid and extensive social-ecological change driven by expanding agricultural frontiers,intensifying extractive industries, and new infrastructure development for regional integration. It is from thiscontext that we call for a timely and critical conversation between human–environment geographers and thefield of biocultural conservation, two approaches that have reshaped thinking about PAs and the role ofIndigenous stewardship in an era of accelerating global challenges to social-ecological well-being. Data forour analysis derive from a multiyear study that investigates strategies used to ensure social-ecological well-being in the face of change. Our findings show that Siona, Siekopai, and Cofan stewardship sustains thebiological diversity that characterizes many Amazonian PAs through locally adapted institutions based onknowledge, innovation, and practices they collectively hold. Such stewardship advances self-determinationthat challenges conventional conservation and PA models by centering Indigenous territorial governance. 

Abstract Impaired organelle-specific protein import triggers a variety of cellular stress responses, including adaptive pathways to balance protein homeostasis. Most of the previous studies focus on the cellular stress response triggered by misfolded proteins or defective protein import in the endoplasmic reticulum or mitochondria. However, little is known about the cellular stress response to impaired protein import in the peroxisome, an understudied organelle that has recently emerged as a key signaling hub for cellular and metabolic homeostasis. To uncover evolutionarily conserved cellular responses upon defective peroxisomal import, we carried out a comparative transcriptomic analysis on fruit flies with tissue-specific peroxin knockdown and human HEK293 cells expressing dominant-negative PEX5C11A. Our RNA-seq results reveal that defective peroxisomal import upregulates integrated stress response (ISR) and downregulates ribosome biogenesis in both flies and human cells. Functional analyses confirm that impaired peroxisomal import induces eIF2α phosphorylation and ATF4 expression. Loss of ATF4 exaggerates cellular damage upon peroxisomal import defects, suggesting that ATF4 activation serves as a cellular cytoprotective mechanism upon peroxisomal import stress. Intriguingly, we show that peroxisomal import stress decreases the expression of rRNA processing genes and inhibits early pre-rRNA processing, which leads to the accumulation of 47S precursor rRNA and reduction of downstream rRNA intermediates. Taken together, we identify ISR activation and ribosome biogenesis inhibition as conserved adaptive stress responses to defective peroxisomal import and uncover a novel link between peroxisomal dysfunction and rRNA processing. 

Ecologists seek to understand the intermediary ecological processes through which changes in one attribute in a system affect other attributes. Yet, quantifying the causal effects of these mediating processes in ecological systems is challenging. Researchers must define what they mean by a “mediated effect”, determine what assumptions are required to estimate mediation effects without bias, and assess whether these assumptions are credible for a study. To address these challenges, scholars in fields outside of ecology have made significant advances in mediation analysis over the past three decades. Here, we bring these advances to the attention of ecologists, for whom understanding mediating processes and deriving causal inferences are important for testing theory and developing resource management and conservation strategies. To illustrate both the challenges and the advances in quantifying mediation effects, we use a hypothetical ecological study. With this study, we show how common research designs used in ecology to detect and quantify mediation effects may have biases and how these biases can be addressed through alternative designs. Throughout the review, we highlight how causal claims rely on causal assumptions, and we illustrate how different designs or definitions of mediation effects can relax some of these assumptions. In contrast to statistical assumptions, causal assumptions are not verifiable from data, so we also describe procedures that researchers can use to assess the sensitivity of a study’s results to potential violations of its causal assumptions. The advances in causal mediation analyses reviewed herein will provide ecological researchers with approaches to clearly communicate the causal assumptions necessary for valid inferences and examine potential violations to these assumptions, which will enable rigorous and reproducible explanations of intermediary processes in ecology. 

The phenomenon known as strong thermal emission velocity enhancement (STEVE) is a narrow optical structure that may extend longitudinally for thousands of kilometers. Initially observed by amateur photographers, it has recently garnered researchers’ attention. STEVE has been associated with a rapid westward flow of ions in the ionosphere, known as subauroral ion drift (SAID). In this work, we investigate three occurrences of STEVE, using data from one of the Time History of Events and Macroscale Interactions during Substorms (THEMIS) ground-based all-sky imagers (ASIs) located at Pinawa, Manitoba, and from the Super Dual Auroral Radar Network (SuperDARN). This approach allows us to verify the correlation between STEVE and SAID, as well as analyze the temporal variation of SAID observed during STEVE events. Our results suggest that the SAID activity starts before the STEVE, and the magnitude of the westward flow decreases as the STEVE progresses toward the end of its optical manifestation.