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FRB 20240619D: a study of the hyperactivity, rotation measure evolution, and searches for a persistent radio source
Get PDFThis paper presents a comprehensive wideband study of FRB 20240619D focusing on its hyperactivity, rotation measure evolution, and the search for an associated persistent radio source. Using data from the MeerKAT, Murriyang, and Lovell telescopes, we analysed the spectral, temporal, and polarimetric properties of 1539 bursts. Our observations reveal a remarkably high burst rate of 161 bursts per hour in early August above a fluence value of 1.6 Jy ms as well as significant secular variations in rotation measure and diverse polarization characteristics, including high linear polarization fractions and occasional circular polarization. The burst activity also showed frequency dependence with approximately 61 per cent of the total number of bursts detected between 1300 and 1800 MHz. The burst activity of FRB 20240619D ceased abruptly after a period of intense activity lasting approximately 80 d, suggesting an episodic behaviour. Follow-up observations with MeerKAT and Australia Telescope Compact Array did not reveal an associated compact persistent radio source. Altogether, our results highlight the importance of continued long-term monitoring and multiwavelength observations in understanding the emission mechanisms and diversity of progenitor populations of fast radio bursts
Thirsty forests and expansive droughts: the environmental impacts of data centers in Latin America
No full textGiven the vast resources required to operate data centers today, their environmental impacts have gained increasing attention. As awareness grows, this industry is facing mounting pressure and has begun announcing mitigation strategies aimed at strengthening its environmental and social responsibility. However, are these strategies effectively addressing local environmental impacts and benefiting communities?
To answer this question, this paper proposes a ‘feral’ approach by weaving ‘feral patches’. That is to elucidate how nonhuman beings are affected by the impacts of large-scale data centers. To do so, we present two Latin American case studies situated in Quilicura (Chile) and Queretaro (Mexico). Both sites are emerging as key data center hubs exposing signs of ferality: thirsty forests and expansive droughts. This paper contends that shifting from ‘global’ or ‘planetary’ scales to ‘local’ and ‘patchy’ approaches reveals the contradiction of mitigation strategies to deliver promised benefits. Instead, these compensations are increasingly entangled in the feral effects within the Anthropocene
Can AI-Predicted Complexes Teach Machine Learning to Compute Drug Binding Affinity?
Get PDFWe evaluate the feasibility of using co-folding models for synthetic data augmentation in training machine learning-based scoring functions (MLSFs) for binding affinity prediction. Our results show that performance gains depend critically on the structural quality of augmented data. In light of this, we established simple heuristics for identifying high-quality co-folding predictions without reference structures, enabling them to substitute for experimental structures in MLSF training. Our study informs future data augmentation strategies based on co-folding models
Spatio-temporal eco-evolutionary dynamics of prey-predator systems with defended and undefended prey
Get PDFThe dynamic interplay between evolutionary adaptations and ecological processes has emerged as a key focus for understanding biodiversity and species interactions. In predator-prey dynamics, spatial heterogeneity and eco-evolutionary feedback regulate species co-existence, shaping population stability and persistence. This study emphasizes the importance of integrating ecological and evolutionary perspectives to understand biodiversity maintenance, predator-prey coexistence, and long-term stability of structured ecosystems. We propose a spatial eco-evolutionary mathematical model for the interactions between undefended prey, toxicity-induced aposematic prey, and predators to explore their collective impact on species persistence and spatial organization. In particular, we focus on the roles of free space and the toxicity of defended prey (foraging efficiency). Most previous work neglects these factors and the spatial structure of the interacting species. We begin by conducting a linear stability analysis of the diffusion-free model and then perform a Turing analysis to determine the conditions for diffusion-driven pattern formation. Numerical simulations reveal the emergence of a range of spatio-temporal patterns and demonstrate how these patterns change as ecological and evolutionary factors vary, while also confirming the stability conditions derived analytically. Through this work, we highlight the roles of ecological and evolutionary factors in understanding the spatio-temporal dynamics of eco-evolutionary processes
Synthesis and Characterization of Unusual S =1 Fe(0)‐Silyl Complexes Supported by Styrene Ligands
Get PDFIn this research we report unprecedented high‐spin (S = 1) Fe(0)‐silyl complexes stabilized by simple styrene ligands. Access to these novel complexes follows a straightforward route through previously reported Fe(0)‐alkyl complexes paired with a range of aryl silanes to promote the protonation of the alkyl substituent and subsequent coordination of the silicon moiety. Spectroscopic and structural analyses (SC‐XRD, Evans Method, 80 K 57Fe Mössbauer) established their unique electronic and structural configuration while DFT calculations further probed electronic structure and bonding effects of the styrene to Fe(0) centres, identifying essential electronic stability. By uncovering the first high‐spin (S = 1), alkene stabilized Fe(0)‐silyl complexes, this work offers further fundamental insights into Fe–Si bonding that can contribute to future insights into reactivity
Warm and Cold Molecular Gas in the Cluster Center of MACS 1931−26 with JWST and ALMA
Get PDFWe perform one of the first spatially resolved studies of warm (>100 K) and cold (10–100 K) molecular gas in the circumgalactic medium (CGM), focusing on the brightest cluster galaxy (BCG) of a cool-core galaxy cluster, MACS 1931−26, at z = 0.35. This galaxy has a massive H2 reservoir and a radio-loud active galactic nucleus and is undergoing a starburst event. We present new JWST observations of this system, revealing warm H2 gas that is cospatial with the cold molecular gas traced by CO, extending over 30 kpc around the BCG in a tail-like structure reaching into the CGM of this galaxy. Analysis of the mid-infrared pure H2 rotational lines H2 S(1), H2 S(5), and H2 S(9) indicate warm gas temperatures of 515.6 ± 0.8 and 535.2 ± 1.9 K in the BCG and tail regions, respectively. We compare the cold gas traced by the CO(3–2) observed with the Atacama Large Millimeter/submillimeter Array to the warm gas traced by JWST. The warm-to-cold molecular gas fraction is comparable in the BCG (1.4% ± 0.2%) and the CGM tail (1.9% ± 0.3%). Our analysis suggests that the dissipation of the kinetic energy of the H2-emitting gas is sufficient to lead to the formation of the CO gas. This observation provides new insights into the molecular gas distribution and its potential role in the interplay between the central galaxy and its circumgalactic environment
Does stochastic gradient really succeed for bandits?
Get PDFRecent works of Mei et al. (2023, 2024) have deepened the theoretical understanding of the Stochastic Gradient Bandit (SGB) policy, showing that using a constant learning rate guarantees asymptotic convergence to the optimal policy, and that sufficiently small learning rates can yield logarithmic regret. However, whether logarithmic regret holds beyond small learning rates remains unclear. In this work, we take a step towards characterizing the regret regimes of SGB as a function of its learning rate. For two-armed bandits, we identify a sharp threshold, scaling with the sub-optimality gap ∆, below which SGB achieves logarithmic regret on all instances, and above which it can incur polynomial regret on some instances. This result highlights the necessity of knowing (or estimating) ∆ to ensure logarithmic regret with a constant learning rate. For general K-armed bandits, we further show the learning rate must scale inversely with K to avoid polynomial regret. We introduce novel techniques to derive regret upper bounds for SGB, laying the groundwork for future advances in the theory of gradient-based bandit algorithms
Sphingosine-1-phosphate receptor modulators in ulcerative colitis - a narrative review of current evidence and practical considerations
Get PDFUlcerative colitis (UC) is a chronic inflammatory bowel disorder with a relapsing and remitting course often necessitating the use of advanced therapy to maintain disease control. Sphingosine-1-phosphate receptor modulators (S1PRMs) represent a new class of oral small molecules approved for the management of moderate-to-severe UC. Evidence from pivotal trials shows promising results for the induction and maintenance of remission in UC. This comprehensive review of S1PRMs explores their mechanism of action, key clinical trial data, real-world insights, and an overview of their safety, including considerations for special populations and comparative effectiveness. S1PRMs offer distinct advantages, including oral administration and a lack of immunogenicity, positioning them as valuable additions to the UC treatment landscape. However, future research will be required to understand their position in the evolving UC treatment paradigms
The impact of pain on memory: a study in chronic low back pain and migraine patients
Get PDFPatients with chronic pain often complain of cognitive difficulties, such as ‘poor memory’. Both acute and chronic pain are thought to impair cognitive performance by demanding attentional and cognitive resources to the detriment of cognitive functioning. However, systematic experimental investigations in patients, as well as deeper understanding of factors that modulate these effects remain lacking. This study investigated whether patients with chronic migraine or patients with chronic low back pain are more susceptible to the disruptive effects of pain on memory as compared to pain-free healthy controls. Two groups of individuals with chronic pain (n = 55 patients with chronic migraine, n = 59 patients with chronic back pain) and n = 59 age-matched healthy controls, underwent experimental pain stimulation at either the back or head while performing a visual categorization and a subsequent recognition task. Pain-related cognitions and clinical parameters were assessed to explore their influence on pain-cognition interference. This large-scale experimental study revealed encouraging results regarding the impact of experimental pain on memory for the pain disorders studied here. Contrary to our hypothesis, patients with chronic migraine or chronic back pain showed no greater effects of experimental pain on recognition memory than healthy participants. Furthermore, the study showed no effect of stimulation site (i.e. head or lower back) or interaction with type of chronic pain. Pain-related cognitions, psychological variables and clinical parameters only had a marginal effect on pain-induced impairment of recognition memory in pain patients. Future research should focus on identifying cognitive and neural predictors associated with susceptibility or resilience to the disruptive effects of pain. Furthermore, larger and more diverse samples could enable person-centred methods to investigate how cognitive, clinical, and situational factors interact in shaping cognitive performance under pain. Such insights are crucial for the development of targeted, individualized therapeutic approaches in the management of chronic pain syndromes
Early Cretaceous insects from East Asia: palaeodiversity, palaeobiogeography and palaeoecology (title page)
Get PDFTitle page for this special issue which is a contribution to the National Key Research and Development Program China (2024YFF0807601): Terrestrial Ecosystem Evolution Across the Mesozoic-Cenozoic Transition